WO2022041187A1

WO2022041187A1 - Degree selection schemes for rapid tornado (raptor) codes in multicast and broadcast services and in unicast services

Info

Publication number: WO2022041187A1
Application number: PCT/CN2020/112447
Authority: WO
Inventors: Kangqi LIU; Liangming WU; Changlong Xu; Hao Xu; Jian Li; Ruiming Zheng
Original assignee: Qualcomm Incorporated
Priority date: 2020-08-31
Filing date: 2020-08-31
Publication date: 2022-03-03

Abstract

Methods, systems, and devices for wireless communications are described. A transmitting device may use a fountain code to encode a set of source symbols for transmission. The transmitting device may encode the set of source symbols to obtain a set of systematic symbols. The transmitting device may transmit a first set of packets including the systematic symbols. In some cases, a receiving device may transmit a feedback message, for example, in response to the first set of packets. The transmitting device may further encode the source symbols to obtain a set of parity symbols based on a degree distribution (e.g., based on the feedback message). The transmitting device may order the parity symbols by decreasing degrees and may transmit a second set of packets including the parity symbols based on the ordering. The receiving device may decode the first and second sets of packets to recover the source symbols.

Description

DEGREE SELECTION SCHEMES FOR RAPID TORNADO (RAPTOR) CODES IN MULTICAST AND BROADCAST SERVICES AND IN UNICAST SERVICES

FIELD OF TECHNOLOGY

The following relates to wireless communications, including degree selection schemes for rapid tornado (Raptor) codes in multicast and broadcast services and in unicast services.

BACKGROUND

Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power) . Examples of such multiple-access systems include fourth generation (4G) systems such as Long Term Evolution (LTE) systems, LTE-Advanced (LTE-A) systems, or LTE-A Pro systems, and fifth generation (5G) systems which may be referred to as New Radio (NR) systems. These systems may employ technologies such as code division multiple access (CDMA) , time division multiple access (TDMA) , frequency division multiple access (FDMA) , orthogonal frequency division multiple access (OFDMA) , or discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-S-OFDM) . A wireless multiple-access communications system may include one or more base stations or one or more network access nodes, each simultaneously supporting communication for multiple communication devices, which may be otherwise known as user equipment (UE) .

Packets may be exchanged between network nodes (e.g., base stations, UEs, etc. ) to transmit information in wireless communications systems. A set of source symbols may be encoded according to a fountain code, such as a rapid tornado (Raptor) code, and the encoded symbols may be transmitted via the packets. In some systems (e.g., NR unicast or NR multicast/broadcast service (MBS) systems) , a transmitting device may precode the source symbols into a set of intermediate symbols, and the transmitting device may use a degree distribution to encode symbols based on the set of intermediate symbols. The transmitting device may transmit the encoded packets according to a random degree distribution, and a receiving device may receive each of the encoded packets to recover the source symbols. The process of using intermediate symbols and a random degree distribution may result in increased processing and latency overhead for devices receiving and decoding the packets.

SUMMARY

The described techniques relate to improved methods, systems, devices, and apparatuses that support degree selection schemes for rapid tornado (Raptor) codes in multicast and broadcast services and in unicast services. Generally, the described techniques provide for enabling a transmitting device (e.g., an encoding device, such as a base station) to encode a set of source symbols according to a fountain code to obtain a set of systematic symbols and a set of parity symbols. The transmitting device may encode the set of parity symbols according to a respective degree of each of the parity symbols, and the parity symbols may be ordered by decreasing degrees. Similarly, the described techniques may enable a receiving device (e.g., a decoding device, such as a user equipment (UE) ) to decode a set of systematic symbols and a set of parity symbols according to a fountain code to recover the set of source symbols based on the order that the receiving device receives the sets of systematic symbols and parity symbols. The receiving device may recover the source symbols from a first set of the parity symbols, and the receiving device may refrain from receiving the remaining parity symbols to reduce processing power.

In some examples, a receiving device may decode the set of systematic symbols transmitted by a transmitting device, and the receiving device may transmit a feedback message to the transmitting device based on a result of the decoding process. The transmitting device may determine a degree distribution for the sets of parity symbols based on the feedback message to improve the process of decoding at the receiving device. For example, by selecting a degree distribution according to the feedback message and by ordering the parity symbols by decreasing degrees, the process of recovering the source symbols at the one or more receiving devices may be improved, and the latency associated with communications may be decreased. Additionally or alternatively, in some examples, the transmitting device may encode the systematic symbols, the parity symbols, or both directly from the source symbols, and the receiving devices may refrain from decoding one or more intermediate symbols to reduce processing overhead at the receiving devices.

A method for wireless communications is described. The method may include encoding a set of source symbols according to a fountain code to obtain a set of systematic symbols and a set of parity symbols, where each systematic symbol of the set of systematic symbols is associated with a source symbol of the set of source symbols and each parity symbol of the set of parity symbols is associated with a number of source symbols of the set of source symbols according to a respective degree of each parity symbol based on a degree distribution for the set of parity symbols, transmitting a first set of packets including the set of systematic symbols, ordering the set of parity symbols by decreasing degrees based on the degree distribution for the set of parity symbols, and transmitting a second set of packets including the set of parity symbols based on the ordering.

An apparatus for wireless communications is described. The apparatus may include a processor, memory coupled with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to encode a set of source symbols according to a fountain code to obtain a set of systematic symbols and a set of parity symbols, where each systematic symbol of the set of systematic symbols is associated with a source symbol of the set of source symbols and each parity symbol of the set of parity symbols is associated with a number of source symbols of the set of source symbols according to a respective degree of each parity symbol based on a degree distribution for the set of parity symbols, transmit a first set of packets including the set of systematic symbols, order the set of parity symbols by decreasing degrees based on the degree distribution for the set of parity symbols, and transmit a second set of packets including the set of parity symbols based on the ordering.

Another apparatus for wireless communications is described. The apparatus may include means for encoding a set of source symbols according to a fountain code to obtain a set of systematic symbols and a set of parity symbols, where each systematic symbol of the set of systematic symbols is associated with a source symbol of the set of source symbols and each parity symbol of the set of parity symbols is associated with a number of source symbols of the set of source symbols according to a respective degree of each parity symbol based on a degree distribution for the set of parity symbols, transmitting a first set of packets including the set of systematic symbols, ordering the set of parity symbols by decreasing degrees based on the degree distribution for the set of parity symbols, and transmitting a second set of packets including the set of parity symbols based on the ordering.

A non-transitory computer-readable medium storing code for wireless communications is described. The code may include instructions executable by a processor to encode a set of source symbols according to a fountain code to obtain a set of systematic symbols and a set of parity symbols, where each systematic symbol of the set of systematic symbols is associated with a source symbol of the set of source symbols and each parity symbol of the set of parity symbols is associated with a number of source symbols of the set of source symbols according to a respective degree of each parity symbol based on a degree distribution for the set of parity symbols, transmit a first set of packets including the set of systematic symbols, order the set of parity symbols by decreasing degrees based on the degree distribution for the set of parity symbols, and transmit a second set of packets including the set of parity symbols based on the ordering.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving a feedback message indicating a feedback parameter, where encoding the set of source symbols according to the fountain code to obtain the set of parity symbols may be based on the feedback parameter.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining the degree distribution for the set of parity symbols based on the feedback parameter.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the feedback message may be received in response to the first set of packets, and the feedback parameter may include one or more positive acknowledgment (ACK) indicators for a number of systematic symbols of the set of systematic symbols successfully received by a UE, one or more negative acknowledgment (NACK) indicators for a number of systematic symbols of the set of systematic symbols unsuccessfully received by the UE, or a combination thereof.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the feedback parameter includes a channel quality indicator (CQI) value, a reference signal received power (RSRP) value, a reference signal received quality (RSRQ) value, a received signal strength indicator (RSSI) value, or a combination thereof.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for transmitting a message configuring a UE with a feedback schema, where the feedback parameter may be based on the feedback schema.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the message configuring the UE with the feedback schema includes a downlink control information (DCI) message, a medium access control (MAC) control element (CE) , a radio resource control (RRC) configuration message, or a combination thereof.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the encoding may include operations, features, means, or instructions for determining, at a first encoding stage, the set of systematic symbols directly from the set of source symbols and determining, at a second encoding stage, the set of parity symbols directly from the set of source symbols based on the feedback parameter satisfying an erasure threshold.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, determining the set of parity symbols may include operations, features, means, or instructions for selecting, for each parity symbol of the set of parity symbols, a degree from the degree distribution for the set of parity symbols, selecting, for each parity symbol of the set of parity symbols, a set of source symbols of the set of source symbols based on the selected degree, and combining, for each parity symbol of the set of parity symbols, the selected set of source symbols based on an exclusive OR (XOR) logic operation to determine each parity symbol of the set of parity symbols.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the encoding may include operations, features, means, or instructions for determining, at a first encoding stage, the set of systematic symbols directly from the set of source symbols and determining, at a second encoding stage, the set of parity symbols from a set of intermediate symbols based on the feedback parameter failing to satisfy an erasure threshold.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, determining the set of parity symbols may include operations, features, means, or instructions for mapping one or more source symbols of the set of source symbols to each intermediate symbol of the set of intermediate symbols, selecting, for each parity symbol of the set of parity symbols, a degree from the degree distribution for the set of parity symbols, selecting, for each parity symbol of the set of parity symbols, one or more intermediate symbols of the set of intermediate symbols based on the selected degree, and combining, for each parity symbol of the set of parity symbols, the selected one or more intermediate symbols based on an XOR logic operation to determine each parity symbol of the set of parity symbols.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the first set of packets and transmitting the second set of packets may further include operations, features, means, or instructions for broadcasting, to a set of UEs, the first set of packets and the second set of packets.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the second set of packets may include operations, features, means, or instructions for transmitting, in a first data block, a first one or more packets of the second set of packets including parity symbols with degrees greater than or equal to a threshold degree value based on the ordering and transmitting, in a second data block subsequent to the first data block, a second one or more packets of the second set of packets including parity symbols with degrees less than or equal to the threshold degree value based on the ordering.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the fountain code includes a Luby transform (LT) code, a Raptor code, or both.

A method for wireless communications is described. The method may include receiving a first set of packets including a set of systematic symbols, where each systematic symbol of the set of systematic symbols is associated with a source symbol of a set of source symbols, decoding the first set of packets according to a fountain code to recover a first subset of the set of source symbols, receiving a second set of packets including a set of parity symbols, where each parity symbol of the set of parity symbols is associated with a number of source symbols of the set of source symbols according to a respective degree of each parity symbol based on a degree distribution for the set of parity symbols, and where the second set of packets is received in an order according to decreasing degrees of parity symbols in each packet of the second set of packets, and decoding the second set of packets according to the fountain code to recover a second subset of the set of source symbols based on the recovered first subset of the set of source symbols, where the set of source symbols is recovered based on decoding the first set of packets and decoding the second set of packets.

An apparatus for wireless communications is described. The apparatus may include a processor, memory coupled with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to receive a first set of packets including a set of systematic symbols, where each systematic symbol of the set of systematic symbols is associated with a source symbol of a set of source symbols, decode the first set of packets according to a fountain code to recover a first subset of the set of source symbols, receive a second set of packets including a set of parity symbols, where each parity symbol of the set of parity symbols is associated with a number of source symbols of the set of source symbols according to a respective degree of each parity symbol based on a degree distribution for the set of parity symbols, and where the second set of packets is received in an order according to decreasing degrees of parity symbols in each packet of the second set of packets, and decode the second set of packets according to the fountain code to recover a second subset of the set of source symbols based on the recovered first subset of the set of source symbols, where the set of source symbols is recovered based on decoding the first set of packets and decoding the second set of packets.

Another apparatus for wireless communications is described. The apparatus may include means for receiving a first set of packets including a set of systematic symbols, where each systematic symbol of the set of systematic symbols is associated with a source symbol of a set of source symbols, decoding the first set of packets according to a fountain code to recover a first subset of the set of source symbols, receiving a second set of packets including a set of parity symbols, where each parity symbol of the set of parity symbols is associated with a number of source symbols of the set of source symbols according to a respective degree of each parity symbol based on a degree distribution for the set of parity symbols, and where the second set of packets is received in an order according to decreasing degrees of parity symbols in each packet of the second set of packets, and decoding the second set of packets according to the fountain code to recover a second subset of the set of source symbols based on the recovered first subset of the set of source symbols, where the set of source symbols is recovered based on decoding the first set of packets and decoding the second set of packets.

A non-transitory computer-readable medium storing code for wireless communications is described. The code may include instructions executable by a processor to receive a first set of packets including a set of systematic symbols, where each systematic symbol of the set of systematic symbols is associated with a source symbol of a set of source symbols, decode the first set of packets according to a fountain code to recover a first subset of the set of source symbols, receive a second set of packets including a set of parity symbols, where each parity symbol of the set of parity symbols is associated with a number of source symbols of the set of source symbols according to a respective degree of each parity symbol based on a degree distribution for the set of parity symbols, and where the second set of packets is received in an order according to decreasing degrees of parity symbols in each packet of the second set of packets, and decode the second set of packets according to the fountain code to recover a second subset of the set of source symbols based on the recovered first subset of the set of source symbols, where the set of source symbols is recovered based on decoding the first set of packets and decoding the second set of packets.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for transmitting a feedback message indicating a feedback parameter, where the degree distribution for the set of parity symbols may be based on the feedback parameter.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the feedback parameter may include one or more ACK indicators for the first subset of the set of source symbols successfully recovered from the first set of packets, one or more NACK indicators for the second subset of the set of source symbols unsuccessfully recovered from the first set of packets, or a combination thereof, and the feedback message may be transmitted in response to the first set of packets.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for performing a channel measurement procedure to determine the feedback parameter, where the feedback parameter includes a CQI value, an RSRP value, an RSRQ value, an RSSI value, or a combination thereof.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving a message configuring a feedback schema, where the feedback parameter may be based on the feedback schema.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the message configuring the feedback schema includes a DCI message, a MAC CE, an RRC configuration message, or a combination thereof.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the decoding the first set of packets may include operations, features, means, or instructions for determining, at a first decoding stage, the first subset of the set of source symbols directly from the set of systematic symbols, and the decoding the second set of packets may include operations, features, means, or instructions for determining, at a second decoding stage, the second subset of the set of source symbols directly from the set of parity symbols based on the feedback parameter satisfying an erasure threshold.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the decoding the first set of packets may include operations, features, means, or instructions for determining, at a first decoding stage, the first subset of the set of source symbols directly from the set of systematic symbols, and the decoding the second set of packets may include operations, features, means, or instructions for determining, at a second decoding stage, the second subset of the set of source symbols from the set of parity symbols via a set of intermediate symbols based on the feedback parameter failing to satisfy an erasure threshold.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for refraining from receiving at least one packet including additional parity symbols based on recovering the set of source symbols.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for entering a low power mode based on recovering the set of source symbols and prior to transmission of the at least one packet including additional parity symbols.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, receiving the second set of packets may include operations, features, means, or instructions for receiving, in a first data block, a first one or more packets of the second set of packets including parity symbols with degrees greater than or equal to a threshold degree value based on the order and receiving, in a second data block subsequent to the first data block, a second one or more packets of the second set of packets including parity symbols with degrees less than or equal to the threshold degree value based on the order.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the fountain code includes an LT code, a Raptor code, or both.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGs. 1 and 2 illustrate examples of wireless communications systems that support degree selection schemes for rapid tornado (Raptor) codes in multicast and broadcast services and in unicast services in accordance with aspects of the present disclosure.

FIG. 3 illustrates an example of an encoding scheme that supports degree selection schemes for Raptor codes in multicast and broadcast services and in unicast services in accordance with aspects of the present disclosure.

FIG. 4 illustrates an example of decoding procedures that support degree selection schemes for Raptor codes in multicast and broadcast services and in unicast services in accordance with aspects of the present disclosure.

FIG. 5 illustrates an example of a symbol allocation procedure that supports degree selection schemes for Raptor codes in multicast and broadcast services and in unicast services in accordance with aspects of the present disclosure.

FIG. 6 illustrates an example of a process flow that supports degree selection schemes for Raptor codes in multicast and broadcast services and in unicast services in accordance with aspects of the present disclosure.

FIGs. 7 and 8 show block diagrams of devices that support degree selection schemes for Raptor codes in multicast and broadcast services and in unicast services in accordance with aspects of the present disclosure.

FIG. 9 shows a block diagram of a communications manager that supports degree selection schemes for Raptor codes in multicast and broadcast services and in unicast services in accordance with aspects of the present disclosure.

FIG. 10 shows a diagram of a system including a device that supports degree selection schemes for Raptor codes in multicast and broadcast services and in unicast services in accordance with aspects of the present disclosure.

FIGs. 11 and 12 show block diagrams of devices that support degree selection schemes for Raptor codes in multicast and broadcast services and in unicast services in accordance with aspects of the present disclosure.

FIG. 13 shows a block diagram of a communications manager that supports degree selection schemes for Raptor codes in multicast and broadcast services and in unicast services in accordance with aspects of the present disclosure.

FIG. 14 shows a diagram of a system including a device that supports degree selection schemes for Raptor codes in multicast and broadcast services and in unicast services in accordance with aspects of the present disclosure.

FIGs. 15 through 18 show flowcharts illustrating methods that support degree selection schemes for Raptor codes in multicast and broadcast services and in unicast services in accordance with aspects of the present disclosure.

DETAILED DESCRIPTION

Some wireless communications systems, such as fifth generation (5G) systems-which may be referred to as New Radio (NR) systems-or other systems, may include network nodes that exchange packets via communications links. A network node, such as a user equipment (UE) , a base station, an integrated access and backhaul (IAB) relay node, or another wireless device, may encode packets before transmission to improve reliability of a destination node successfully receiving the transmitted information. In some cases, encoded packets may provide redundancy, which may be used to correct errors that result from the transmission environment (e.g., path loss, obstacles, etc. ) .

Some examples of encoding algorithms with error correcting codes include fountain codes, such as Luby transform (LT) codes or rapid tornado (Raptor) codes. A fountain code may be an example of a rateless code, where a set of source symbols (e.g., K symbols) may be encoded as any quantity of encoding symbols (e.g., a quantity of symbols greater than K symbols) . Encoding the source symbols may include combining one or more source symbols into each encoding symbol. In some examples, the encoding symbols may include a set of systematic symbols and a set of parity symbols. The encoding may involve using a degree distribution, where the degree distribution represents a probability mass function of a set of degrees d _i (e.g., d ₁, d ₂, d ₃, etc. ) . The probability of randomly selecting a degree d _i (i.e., a degree with index i) from the degree distribution may be represented by ρ (i) . In the encoding process, the degree d _i may represent the quantity of source symbols or intermediate symbols which may be combined into a given parity symbol.

The encoding symbols may be transmitted as a set of encoded packets from a transmitting device (e.g., a base station) to a receiving device (e.g., a UE) . In some examples, one or more encoded packets may be lost based on the transmission environment. The receiving device may receive a subset of the encoded packets. Based on the encoding and combining, the receiving device may decode the set of source symbols from the subset of encoded packets despite the packet loss.

To improve efficiency, the transmitting device may transmit a first set of encoded packets that may include systematic symbols (e.g., degree-one symbols determined from the source symbols) and a second set of encoded packets that may include parity symbols. The transmitting device may order the parity symbols by decreasing degrees to improve the efficiency of decoding the source symbols at the receiving device. For example, after transmitting the systematic symbols, the transmitting device may transmit the high-degree parity symbols first (e.g., parity symbols with degrees d _i greater than a threshold) , followed by the low-degree parity symbols (e.g., decreasing degrees until degree-two parity symbols are transmitted) . The receiving device may receive and decode the symbols as the packets are received to attempt to recover the source symbols. If the receiving device successfully recovers the source symbols before receiving each of the parity symbols, the receiving device may refrain from receiving and decoding the remaining packets of symbols (e.g., the receiving device may enter a low-power mode) .

In some examples, the receiving device may transmit a feedback message (e.g., a hybrid automatic repeat request (HARQ) acknowledgment (ACK) or negative acknowledgment (NACK) ) to the transmitting device based on a result of decoding the systematic symbols (e.g., during unicast communications) . The feedback message may include one or more ACK indicators for a number of the systematic symbols that were successfully received and decoded by the receiving device, one or more NACK indicators for a number of the systematic symbols that were unsuccessfully received or decoded by the receiving device, or both. Additionally or alternatively, the feedback message may include a channel quality indicator (CQI) value, a reference signal received power (RSRP) value, a reference signal received quality (RSRQ) value, a received signal strength indicator (RSSI) value, or a combination thereof. In some cases, the transmitting device may transmit a message configuring the receiving device with a feedback schema, and the receiving device may determine the feedback to transmit based on the feedback schema. The transmitting device may determine a degree distribution for the parity symbols based on the feedback message. For example, the transmitting device may determine a number of each degree of parity symbols to transmit based on the feedback message. In some examples, if an erasure probability (e.g., based on the number of systematic symbols, k, successfully received out of the K transmitted systematic symbols) indicated by the feedback message fails to satisfy an erasure threshold, the transmitting device may determine to encode the set of parity symbols from a set of intermediate symbols. Additionally or alternatively, if the erasure probability satisfies the erasure threshold, the transmitting device may determine to encode the set of parity symbols directly from the source symbols.

Aspects of the disclosure are initially described in the context of wireless communications systems. Additional aspects are described with reference to encoding schemes, decoding processes, symbol allocations, and process flows. Aspects of the disclosure are further illustrated by and described with reference to apparatus diagrams, system diagrams, and flowcharts that relate to degree selection schemes for Raptor codes in multicast and broadcast services and in unicast services.

FIG. 1 illustrates an example of a wireless communications system 100 that supports degree selection schemes for Raptor codes in multicast and broadcast services and in unicast services in accordance with aspects of the present disclosure. The wireless communications system 100 may include one or more base stations 105, one or more UEs 115, and a core network 130. In some examples, the wireless communications system 100 may be a Long Term Evolution (LTE) network, an LTE-Advanced (LTE-A) network, an LTE-A Pro network, or a New Radio (NR) network. In some examples, the wireless communications system 100 may support enhanced broadband communications, ultra-reliable (e.g., mission critical) communications, low latency communications, communications with low-cost and low-complexity devices, or any combination thereof.

The base stations 105 may be dispersed throughout a geographic area to form the wireless communications system 100 and may be devices in different forms or having different capabilities. The base stations 105 and the UEs 115 may wirelessly communicate via one or more communication links 125. Each base station 105 may provide a coverage area 110 over which the UEs 115 and the base station 105 may establish one or more communication links 125. The coverage area 110 may be an example of a geographic area over which a base station 105 and a UE 115 may support the communication of signals according to one or more radio access technologies.

The UEs 115 may be dispersed throughout a coverage area 110 of the wireless communications system 100, and each UE 115 may be stationary, or mobile, or both at different times. The UEs 115 may be devices in different forms or having different capabilities. Some example UEs 115 are illustrated in FIG. 1. The UEs 115 described herein may be able to communicate with various types of devices, such as other UEs 115, the base stations 105, or network equipment (e.g., core network nodes, relay devices, integrated access and backhaul (IAB) nodes, or other network equipment) , as shown in FIG. 1.

The base stations 105 may communicate with the core network 130, or with one another, or both. For example, the base stations 105 may interface with the core network 130 through one or more backhaul links 120 (e.g., via an S1, N2, N3, or other interface) . The base stations 105 may communicate with one another over the backhaul links 120 (e.g., via an X2, Xn, or other interface) either directly (e.g., directly between base stations 105) , or indirectly (e.g., via core network 130) , or both. In some examples, the backhaul links 120 may be or include one or more wireless links.

One or more of the base stations 105 described herein may include or may be referred to by a person having ordinary skill in the art as a base transceiver station, a radio base station, an access point, a radio transceiver, a NodeB, an eNodeB (eNB) , a next-generation NodeB or a giga-NodeB (either of which may be referred to as a gNB) , a Home NodeB, a Home eNodeB, or other suitable terminology.

A UE 115 may include or may be referred to as a mobile device, a wireless device, a remote device, a handheld device, or a subscriber device, or some other suitable terminology, where the “device” may also be referred to as a unit, a station, a terminal, or a client, among other examples. A UE 115 may also include or may be referred to as a personal electronic device such as a cellular phone, a personal digital assistant (PDA) , a tablet computer, a laptop computer, or a personal computer. In some examples, a UE 115 may include or be referred to as a wireless local loop (WLL) station, an Internet of Things (IoT) device, an Internet of Everything (IoE) device, or a machine type communications (MTC) device, among other examples, which may be implemented in various objects such as appliances, or vehicles, meters, among other examples.

The UEs 115 described herein may be able to communicate with various types of devices, such as other UEs 115 that may sometimes act as relays as well as the base stations 105 and the network equipment including macro eNBs or gNBs, small cell eNBs or gNBs, or relay base stations, among other examples, as shown in FIG. 1.

The UEs 115 and the base stations 105 may wirelessly communicate with one another via one or more communication links 125 over one or more carriers. The term “carrier” may refer to a set of radio frequency spectrum resources having a defined physical layer structure for supporting the communication links 125. For example, a carrier used for a communication link 125 may include a portion of a radio frequency spectrum band (e.g., a bandwidth part (BWP) ) that is operated according to one or more physical layer channels for a given radio access technology (e.g., LTE, LTE-A, LTE-A Pro, NR) . Each physical layer channel may carry acquisition signaling (e.g., synchronization signals, system information) , control signaling that coordinates operation for the carrier, user data, or other signaling. The wireless communications system 100 may support communication with a UE 115 using carrier aggregation or multi-carrier operation. A UE 115 may be configured with multiple downlink component carriers and one or more uplink component carriers according to a carrier aggregation configuration. Carrier aggregation may be used with both frequency division duplexing (FDD) and time division duplexing (TDD) component carriers.

In some examples (e.g., in a carrier aggregation configuration) , a carrier may also have acquisition signaling or control signaling that coordinates operations for other carriers. A carrier may be associated with a frequency channel (e.g., an evolved universal mobile telecommunication system terrestrial radio access (E-UTRA) absolute radio frequency channel number (EARFCN) ) and may be positioned according to a channel raster for discovery by the UEs 115. A carrier may be operated in a standalone mode where initial acquisition and connection may be conducted by the UEs 115 via the carrier, or the carrier may be operated in a non-standalone mode where a connection is anchored using a different carrier (e.g., of the same or a different radio access technology) .

The communication links 125 shown in the wireless communications system 100 may include uplink transmissions from a UE 115 to a base station 105, or downlink transmissions from a base station 105 to a UE 115. Carriers may carry downlink or uplink communications (e.g., in an FDD mode) or may be configured to carry downlink and uplink communications (e.g., in a TDD mode) .

A carrier may be associated with a particular bandwidth of the radio frequency spectrum, and in some examples the carrier bandwidth may be referred to as a “system bandwidth” of the carrier or the wireless communications system 100. For example, the carrier bandwidth may be one of a number of determined bandwidths for carriers of a particular radio access technology (e.g., 1.4, 3, 5, 10, 15, 20, 40, or 80 megahertz (MHz) ) . Devices of the wireless communications system 100 (e.g., the base stations 105, the UEs 115, or both) may have hardware configurations that support communications over a particular carrier bandwidth or may be configurable to support communications over one of a set of carrier bandwidths. In some examples, the wireless communications system 100 may include base stations 105 or UEs 115 that support simultaneous communications via carriers associated with multiple carrier bandwidths. In some examples, each served UE 115 may be configured for operating over portions (e.g., a sub-band, a BWP) or all of a carrier bandwidth.

Signal waveforms transmitted over a carrier may be made up of multiple subcarriers (e.g., using multi-carrier modulation (MCM) techniques such as orthogonal frequency division multiplexing (OFDM) or DFT-S-OFDM) . In a system employing MCM techniques, a resource element may consist of one symbol period (e.g., a duration of one modulation symbol) and one subcarrier, where the symbol period and subcarrier spacing are inversely related. The number of bits carried by each resource element may depend on the modulation scheme (e.g., the order of the modulation scheme, the coding rate of the modulation scheme, or both) . Thus, the more resource elements that a UE 115 receives and the higher the order of the modulation scheme, the higher the data rate may be for the UE 115. A wireless communications resource may refer to a combination of a radio frequency spectrum resource, a time resource, and a spatial resource (e.g., spatial layers or beams) , and the use of multiple spatial layers may further increase the data rate or data integrity for communications with a UE 115.

One or more numerologies for a carrier may be supported, where a numerology may include a subcarrier spacing (Δf) and a cyclic prefix. A carrier may be divided into one or more BWPs having the same or different numerologies. In some examples, a UE 115 may be configured with multiple BWPs. In some examples, a single BWP for a carrier may be active at a given time and communications for the UE 115 may be restricted to one or more active BWPs.

The time intervals for the base stations 105 or the UEs 115 may be expressed in multiples of a basic time unit which may, for example, refer to a sampling period of T _s= 1/ (Δf _max·N _f) seconds, where Δf _max may represent the maximum supported subcarrier spacing, and N _f may represent the maximum supported discrete Fourier transform (DFT) size. Time intervals of a communications resource may be organized according to radio frames each having a specified duration (e.g., 10 milliseconds (ms) ) . Each radio frame may be identified by a system frame number (SFN) (e.g., ranging from 0 to 1023) .

Each frame may include multiple consecutively numbered subframes or slots, and each subframe or slot may have the same duration. In some examples, a frame may be divided (e.g., in the time domain) into subframes, and each subframe may be further divided into a number of slots. Alternatively, each frame may include a variable number of slots, and the number of slots may depend on subcarrier spacing. Each slot may include a number of symbol periods (e.g., depending on the length of the cyclic prefix prepended to each symbol period) . In some wireless communications systems 100, a slot may further be divided into multiple mini-slots containing one or more symbols. Excluding the cyclic prefix, each symbol period may contain one or more (e.g., N _f) sampling periods. The duration of a symbol period may depend on the subcarrier spacing or frequency band of operation.

A subframe, a slot, a mini-slot, or a symbol may be the smallest scheduling unit (e.g., in the time domain) of the wireless communications system 100 and may be referred to as a transmission time interval (TTI) . In some examples, the TTI duration (e.g., the number of symbol periods in a TTI) may be variable. Additionally or alternatively, the smallest scheduling unit of the wireless communications system 100 may be dynamically selected (e.g., in bursts of shortened TTIs (sTTIs) ) .

Physical channels may be multiplexed on a carrier according to various techniques. A physical control channel and a physical data channel may be multiplexed on a downlink carrier, for example, using one or more of time division multiplexing (TDM) techniques, frequency division multiplexing (FDM) techniques, or hybrid TDM-FDM techniques. A control region (e.g., a control resource set (CORESET) ) for a physical control channel may be defined by a number of symbol periods and may extend across the system bandwidth or a subset of the system bandwidth of the carrier. One or more control regions (e.g., CORESETs) may be configured for a set of the UEs 115. For example, one or more of the UEs 115 may monitor or search control regions for control information according to one or more search space sets, and each search space set may include one or multiple control channel candidates in one or more aggregation levels arranged in a cascaded manner. An aggregation level for a control channel candidate may refer to a number of control channel resources (e.g., control channel elements (CCEs) ) associated with encoded information for a control information format having a given payload size. Search space sets may include common search space sets configured for sending control information to multiple UEs 115 and UE-specific search space sets for sending control information to a specific UE 115.

Each base station 105 may provide communication coverage via one or more cells, for example a macro cell, a small cell, a hot spot, or other types of cells, or any combination thereof. The term “cell” may refer to a logical communication entity used for communication with a base station 105 (e.g., over a carrier) and may be associated with an identifier for distinguishing neighboring cells (e.g., a physical cell identifier (PCID) , a virtual cell identifier (VCID) , or others) . In some examples, a cell may also refer to a geographic coverage area 110 or a portion of a geographic coverage area 110 (e.g., a sector) over which the logical communication entity operates. Such cells may range from smaller areas (e.g., a structure, a subset of structure) to larger areas depending on various factors such as the capabilities of the base station 105. For example, a cell may be or include a building, a subset of a building, or exterior spaces between or overlapping with geographic coverage areas 110, among other examples.

A macro cell generally covers a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by the UEs 115 with service subscriptions with the network provider supporting the macro cell. A small cell may be associated with a lower-powered base station 105, as compared with a macro cell, and a small cell may operate in the same or different (e.g., licensed, unlicensed) frequency bands as macro cells. Small cells may provide unrestricted access to the UEs 115 with service subscriptions with the network provider or may provide restricted access to the UEs 115 having an association with the small cell (e.g., the UEs 115 in a closed subscriber group (CSG) , the UEs 115 associated with users in a home or office) . A base station 105 may support one or multiple cells and may also support communications over the one or more cells using one or multiple component carriers.

In some examples, a carrier may support multiple cells, and different cells may be configured according to different protocol types (e.g., MTC, narrowband IoT (NB-IoT) , enhanced mobile broadband (eMBB) ) that may provide access for different types of devices.

In some examples, a base station 105 may be movable and therefore provide communication coverage for a moving geographic coverage area 110. In some examples, different geographic coverage areas 110 associated with different technologies may overlap, but the different geographic coverage areas 110 may be supported by the same base station 105. In other examples, the overlapping geographic coverage areas 110 associated with different technologies may be supported by different base stations 105. The wireless communications system 100 may include, for example, a heterogeneous network in which different types of the base stations 105 provide coverage for various geographic coverage areas 110 using the same or different radio access technologies.

The wireless communications system 100 may support synchronous or asynchronous operation. For synchronous operation, the base stations 105 may have similar frame timings, and transmissions from different base stations 105 may be approximately aligned in time. For asynchronous operation, the base stations 105 may have different frame timings, and transmissions from different base stations 105 may, in some examples, not be aligned in time. The techniques described herein may be used for either synchronous or asynchronous operations.

Some UEs 115, such as MTC or IoT devices, may be low cost or low complexity devices and may provide for automated communication between machines (e.g., via Machine-to-Machine (M2M) communication) . M2M communication or MTC may refer to data communication technologies that allow devices to communicate with one another or a base station 105 without human intervention. In some examples, M2M communication or MTC may include communications from devices that integrate sensors or meters to measure or capture information and relay such information to a central server or application program that makes use of the information or presents the information to humans interacting with the application program. Some UEs 115 may be designed to collect information or enable automated behavior of machines or other devices. Examples of applications for MTC devices include smart metering, inventory monitoring, water level monitoring, equipment monitoring, healthcare monitoring, wildlife monitoring, weather and geological event monitoring, fleet management and tracking, remote security sensing, physical access control, and transaction-based business charging.

Some UEs 115 may be configured to employ operating modes that reduce power consumption, such as half-duplex communications (e.g., a mode that supports one-way communication via transmission or reception, but not transmission and reception simultaneously) . In some examples, half-duplex communications may be performed at a reduced peak rate. Other power conservation techniques for the UEs 115 include entering a power saving deep sleep mode when not engaging in active communications, operating over a limited bandwidth (e.g., according to narrowband communications) , or a combination of these techniques. For example, some UEs 115 may be configured for operation using a narrowband protocol type that is associated with a defined portion or range (e.g., set of subcarriers or resource blocks (RBs) ) within a carrier, within a guard-band of a carrier, or outside of a carrier.

The wireless communications system 100 may be configured to support ultra-reliable communications or low-latency communications, or various combinations thereof. For example, the wireless communications system 100 may be configured to support ultra-reliable low-latency communications (URLLC) or mission critical communications. The UEs 115 may be designed to support ultra-reliable, low-latency, or critical functions (e.g., mission critical functions) . Ultra-reliable communications may include private communication or group communication and may be supported by one or more mission critical services such as mission critical push-to-talk (MCPTT) , mission critical video (MCVideo) , or mission critical data (MCData) . Support for mission critical functions may include prioritization of services, and mission critical services may be used for public safety or general commercial applications. The terms ultra-reliable, low-latency, mission critical, and ultra-reliable low-latency may be used interchangeably herein.

In some examples, a UE 115 may also be able to communicate directly with other UEs 115 over a device-to-device (D2D) communication link 135 (e.g., using a peer-to-peer (P2P) or D2D protocol) . One or more UEs 115 utilizing D2D communications may be within the geographic coverage area 110 of a base station 105. Other UEs 115 in such a group may be outside the geographic coverage area 110 of a base station 105 or be otherwise unable to receive transmissions from a base station 105. In some examples, groups of the UEs 115 communicating via D2D communications may utilize a one-to-many (1: M) system in which each UE 115 transmits to every other UE 115 in the group. In some examples, a base station 105 facilitates the scheduling of resources for D2D communications. In other cases, D2D communications are carried out between the UEs 115 without the involvement of a base station 105.

In some systems, the D2D communication link 135 may be an example of a communication channel, such as a sidelink communication channel, between vehicles (e.g., UEs 115) . In some examples, vehicles may communicate using vehicle-to-everything (V2X) communications, vehicle-to-vehicle (V2V) communications, or some combination of these. A vehicle may signal information related to traffic conditions, signal scheduling, weather, safety, emergencies, or any other information relevant to a V2X system. In some examples, vehicles in a V2X system may communicate with roadside infrastructure, such as roadside units, or with the network via one or more network nodes (e.g., base stations 105) using vehicle-to-network (V2N) communications, or with both.

The core network 130 may provide user authentication, access authorization, tracking, Internet Protocol (IP) connectivity, and other access, routing, or mobility functions. The core network 130 may be an evolved packet core (EPC) or 5G core (5GC) , which may include at least one control plane entity that manages access and mobility (e.g., a mobility management entity (MME) , an access and mobility management function (AMF) ) and at least one user plane entity that routes packets or interconnects to external networks (e.g., a serving gateway (S-GW) , a Packet Data Network (PDN) gateway (P-GW) , or a user plane function (UPF) ) . The control plane entity may manage non-access stratum (NAS) functions such as mobility, authentication, and bearer management for the UEs 115 served by the base stations 105 associated with the core network 130. User IP packets may be transferred through the user plane entity, which may provide IP address allocation as well as other functions. The user plane entity may be connected to the network operators IP services 150. The network operators IP services 150 may include access to the Internet, Intranet (s) , an IP Multimedia Subsystem (IMS) , or a Packet-Switched Streaming Service.

Some of the network devices, such as a base station 105, may include subcomponents such as an access network entity 140, which may be an example of an access node controller (ANC) . Each access network entity 140 may communicate with the UEs 115 through one or more other access network transmission entities 145, which may be referred to as radio heads, smart radio heads, or transmission/reception points (TRPs) . Each access network transmission entity 145 may include one or more antenna panels. In some configurations, various functions of each access network entity 140 or base station 105 may be distributed across various network devices (e.g., radio heads and ANCs) or consolidated into a single network device (e.g., a base station 105) .

The wireless communications system 100 may operate using one or more frequency bands, typically in the range of 300 megahertz (MHz) to 300 gigahertz (GHz) . Generally, the region from 300 MHz to 3 GHz is known as the ultra-high frequency (UHF) region or decimeter band because the wavelengths range from approximately one decimeter to one meter in length. The UHF waves may be blocked or redirected by buildings and environmental features, but the waves may penetrate structures sufficiently for a macro cell to provide service to the UEs 115 located indoors. The transmission of UHF waves may be associated with smaller antennas and shorter ranges (e.g., less than 100 kilometers) compared to transmission using the smaller frequencies and longer waves of the high frequency (HF) or very high frequency (VHF) portion of the spectrum below 300 MHz.

The wireless communications system 100 may also operate in a super high frequency (SHF) region using frequency bands from 3 GHz to 30 GHz, also known as the centimeter band, or in an extremely high frequency (EHF) region of the spectrum (e.g., from 30 GHz to 300 GHz) , also known as the millimeter band. In some examples, the wireless communications system 100 may support millimeter wave (mmW) communications between the UEs 115 and the base stations 105, and EHF antennas of the respective devices may be smaller and more closely spaced than UHF antennas. In some examples, this may facilitate use of antenna arrays within a device. The propagation of EHF transmissions, however, may be subject to even greater atmospheric attenuation and shorter range than SHF or UHF transmissions. The techniques disclosed herein may be employed across transmissions that use one or more different frequency regions, and designated use of bands across these frequency regions may differ by country or regulating body.

The wireless communications system 100 may utilize both licensed and unlicensed radio frequency spectrum bands. For example, the wireless communications system 100 may employ License Assisted Access (LAA) , LTE-Unlicensed (LTE-U) radio access technology, or NR technology in an unlicensed band such as the 5 GHz industrial, scientific, and medical (ISM) band. When operating in unlicensed radio frequency spectrum bands, devices such as the base stations 105 and the UEs 115 may employ carrier sensing for collision detection and avoidance. In some examples, operations in unlicensed bands may be based on a carrier aggregation configuration in conjunction with component carriers operating in a licensed band (e.g., LAA) . Operations in unlicensed spectrum may include downlink transmissions, uplink transmissions, P2P transmissions, or D2D transmissions, among other examples.

A base station 105 or a UE 115 may be equipped with multiple antennas, which may be used to employ techniques such as transmit diversity, receive diversity, multiple-input multiple-output (MIMO) communications, or beamforming. The antennas of a base station 105 or a UE 115 may be located within one or more antenna arrays or antenna panels, which may support MIMO operations or transmit or receive beamforming. For example, one or more base station antennas or antenna arrays may be co-located at an antenna assembly, such as an antenna tower. In some examples, antennas or antenna arrays associated with a base station 105 may be located in diverse geographic locations. A base station 105 may have an antenna array with a number of rows and columns of antenna ports that the base station 105 may use to support beamforming of communications with a UE 115. Likewise, a UE 115 may have one or more antenna arrays that may support various MIMO or beamforming operations. Additionally or alternatively, an antenna panel may support radio frequency beamforming for a signal transmitted via an antenna port.

The base stations 105 or the UEs 115 may use MIMO communications to exploit multipath signal propagation and increase the spectral efficiency by transmitting or receiving multiple signals via different spatial layers. Such techniques may be referred to as spatial multiplexing. The multiple signals may, for example, be transmitted by the transmitting device via different antennas or different combinations of antennas. Likewise, the multiple signals may be received by the receiving device via different antennas or different combinations of antennas. Each of the multiple signals may be referred to as a separate spatial stream and may carry bits associated with the same data stream (e.g., the same codeword) or different data streams (e.g., different codewords) . Different spatial layers may be associated with different antenna ports used for channel measurement and reporting. MIMO techniques include single-user MIMO (SU-MIMO) , where multiple spatial layers are transmitted to the same receiving device, and multiple-user MIMO (MU-MIMO) , where multiple spatial layers are transmitted to multiple devices.

Beamforming, which may also be referred to as spatial filtering, directional transmission, or directional reception, is a signal processing technique that may be used at a transmitting device or a receiving device (e.g., a base station 105, a UE 115) to shape or steer an antenna beam (e.g., a transmit beam, a receive beam) along a spatial path between the transmitting device and the receiving device. Beamforming may be achieved by combining the signals communicated via antenna elements of an antenna array such that some signals propagating at particular orientations with respect to an antenna array experience constructive interference while others experience destructive interference. The adjustment of signals communicated via the antenna elements may include a transmitting device or a receiving device applying amplitude offsets, phase offsets, or both to signals carried via the antenna elements associated with the device. The adjustments associated with each of the antenna elements may be defined by a beamforming weight set associated with a particular orientation (e.g., with respect to the antenna array of the transmitting device or receiving device, or with respect to some other orientation) .

A base station 105 or a UE 115 may use beam sweeping techniques as part of beam forming operations. For example, a base station 105 may use multiple antennas or antenna arrays (e.g., antenna panels) to conduct beamforming operations for directional communications with a UE 115. Some signals (e.g., synchronization signals, reference signals, beam selection signals, or other control signals) may be transmitted by a base station 105 multiple times in different directions. For example, the base station 105 may transmit a signal according to different beamforming weight sets associated with different directions of transmission. Transmissions in different beam directions may be used to identify (e.g., by a transmitting device, such as a base station 105, or by a receiving device, such as a UE 115) a beam direction for later transmission or reception by the base station 105.

Some signals, such as data signals associated with a particular receiving device, may be transmitted by a base station 105 in a single beam direction (e.g., a direction associated with the receiving device, such as a UE 115) . In some examples, the beam direction associated with transmissions along a single beam direction may be determined based on a signal that was transmitted in one or more beam directions. For example, a UE 115 may receive one or more of the signals transmitted by the base station 105 in different directions and may report to the base station 105 an indication of the signal that the UE 115 received with a highest signal quality or an otherwise acceptable signal quality.

In some examples, transmissions by a device (e.g., by a base station 105 or a UE 115) may be performed using multiple beam directions, and the device may use a combination of digital precoding or radio frequency beamforming to generate a combined beam for transmission (e.g., from a base station 105 to a UE 115) . The UE 115 may report feedback that indicates precoding weights for one or more beam directions, and the feedback may correspond to a configured number of beams across a system bandwidth or one or more sub-bands. The base station 105 may transmit a reference signal (e.g., a cell-specific reference signal (CRS) , a channel state information reference signal (CSI-RS) ) , which may be precoded or unprecoded. The UE 115 may provide feedback for beam selection, which may be a precoding matrix indicator (PMI) or codebook-based feedback (e.g., a multi-panel type codebook, a linear combination type codebook, a port selection type codebook) . Although these techniques are described with reference to signals transmitted in one or more directions by a base station 105, a UE 115 may employ similar techniques for transmitting signals multiple times in different directions (e.g., for identifying a beam direction for subsequent transmission or reception by the UE 115) or for transmitting a signal in a single direction (e.g., for transmitting data to a receiving device) .

A receiving device (e.g., a UE 115) may try multiple receive configurations (e.g., directional listening) when receiving various signals from the base station 105, such as synchronization signals, reference signals, beam selection signals, or other control signals. For example, a receiving device may try multiple receive directions by receiving via different antenna subarrays, by processing received signals according to different antenna subarrays, by receiving according to different receive beamforming weight sets (e.g., different directional listening weight sets) applied to signals received at multiple antenna elements of an antenna array, or by processing received signals according to different receive beamforming weight sets applied to signals received at multiple antenna elements of an antenna array, any of which may be referred to as “listening” according to different receive configurations or receive directions. In some examples, a receiving device may use a single receive configuration to receive along a single beam direction (e.g., when receiving a data signal) . The single receive configuration may be aligned in a beam direction determined based on listening according to different receive configuration directions (e.g., a beam direction determined to have a highest signal strength, highest signal-to-noise ratio (SNR) , or otherwise acceptable signal quality based on listening according to multiple beam directions) .

The wireless communications system 100 may be a packet-based network that operates according to a layered protocol stack. In the user plane, communications at the bearer or Packet Data Convergence Protocol (PDCP) layer may be IP-based. A Radio Link Control (RLC) layer may perform packet segmentation and reassembly to communicate over logical channels. A Medium Access Control (MAC) layer may perform priority handling and multiplexing of logical channels into transport channels. The MAC layer may also use error detection techniques, error correction techniques, or both to support retransmissions at the MAC layer to improve link efficiency. In the control plane, the Radio Resource Control (RRC) protocol layer may provide establishment, configuration, and maintenance of an RRC connection between a UE 115 and a base station 105 or a core network 130 supporting radio bearers for user plane data. At the physical layer, transport channels may be mapped to physical channels.

The UEs 115 and the base stations 105 may support retransmissions of data to increase the likelihood that data is received successfully. HARQ feedback is one technique for increasing the likelihood that data is received correctly over a communication link 125. HARQ may include a combination of error detection (e.g., using a cyclic redundancy check (CRC) ) , forward error correction (FEC) , and retransmission (e.g., automatic repeat request (ARQ) ) . HARQ may improve throughput at the MAC layer in poor radio conditions (e.g., low signal-to-noise conditions) . In some examples, a device may support same-slot HARQ feedback, where the device may provide HARQ feedback in a specific slot for data received in a previous symbol in the slot. In other cases, the device may provide HARQ feedback in a subsequent slot, or according to some other time interval.

In some examples, a transmitting device (e.g., a base station 105 or a UE 115) may use a fountain code scheme (e.g., an LT or Raptor code scheme) to encode data for transmission to a receiving device (e.g., a UE 115 or a base station 105) . For example, the transmitting device may encode a set of source symbols into a set of systematic symbols and a set of parity symbols. The set of parity symbols may be encoded according to a respective degree of each of the parity symbols, and the parity symbols may be ordered by decreasing degrees. The transmitting device may transmit a first set of packets including the systematic symbols and a second set of packets including the parity symbols ordered by decreasing degrees. In some examples, the receiving device may decode the set of systematic symbols and the set of parity symbols according to a fountain code to recover the set of source symbols based on the order that the receiving device receives the sets of systematic symbols and parity symbols.

In some examples, a UE 115 may decode the set of systematic symbols transmitted by a base station 105, and the UE 115 may transmit a feedback message to the base station 105 based on a result of decoding the systematic symbols (e.g., indicating a number of systematic symbols successfully received, a number of systematic symbols unsuccessfully received, or a combination thereof) . The base station 105 may determine a degree distribution for the sets of parity symbols based on the feedback message. Additionally or alternatively, the base station 105 may transmit the systematic symbols and the parity symbols to a group of receiving devices (e.g., a group of UEs 115) , and the receiving devices may refrain from transmitting feedback messages. The base station 105 may transmit the systematic symbols in a first set of encoded packets and the base station 105 may order the remaining parity symbols by decreasing degrees. By ordering the parity symbols by decreasing degrees, the process of recovering the source symbols at the one or more receiving devices may be improved, and the latency associated with communications may be decreased. For example, if a UE 115 fails to recover a relatively small number of source symbols (e.g., one or two) , the UE 115 may use high-degree parity symbols to recover the small number of source symbols and may refrain from receiving the remaining parity symbols.

FIG. 2 illustrates an example of a wireless communications system 200 that supports degree selection schemes for Raptor codes in multicast and broadcast services and in unicast services in accordance with aspects of the present disclosure. In some examples, the wireless communications system 200 may implement aspects of the wireless communications system 100. For example, the wireless communications system 200 may include a first wireless device 205, a second wireless device 210, and a third wireless device 215, which may each be an example of a base station 105 or a UE 115 as described with reference to FIG. 1. The wireless communications system 200 may include features for improved data encoding, transmission, and decoding to reduce latency, among other benefits.

The first wireless device 205 (e.g., an encoder, a transmitting device, or both, such as a base station 105) may transmit one or more data transmissions to the second wireless device 210, the third wireless device 215, or both (e.g., decoders, receiving devices, or both, such as UEs 115) via channels 225-a and 225-b, respectively. In some examples, the data transmissions may be transmitted according to multicast or broadcast communications to the second wireless device 210, the third wireless device 215, and one or more other wireless devices. Additionally or alternatively, the data transmissions may be transmitted as part of a unicast transmission to one of the second wireless device 210 or the third wireless device 215.

The data transmissions may be transmitted as a set of one or more encoded packets (e.g., sets of encoded packets 220-a and 220-b) . Each encoded packet may include one or more encoding symbols encoded according to a fountain code (e.g., an LT code, a Raptor code, etc. ) . In some examples, one or more encoded packets may be lost based on the transmission environment. The second wireless device 210, the third wireless device 215, or both, may receive one or more sets of encoded packets 220. Based on the encoding and combining, the receiving device may decode the set of source symbols from the sets of encoded packets 220 despite the packet loss.

In some examples, the first wireless device 205 may use a precoding process that maps the set of source symbols to a set of intermediate symbols. Each intermediate symbol may be derived from one or more of the source symbols according to a precoding procedure. In some cases, the set of intermediate symbols may include one or more redundant symbols to improve decoding reliability. In some such examples, the first wireless device 205 may determine the encoded symbols from the set of intermediate symbols. In some other examples, the first wireless device 205 may refrain from performing the precoding process. For example, the first wireless device 205 may map the source symbols directly to the encoded symbols to reduce processing at the first wireless device 205 and the receiving device (s) .

The first wireless device 205 may perform a coding process, in which the first wireless device 205 may map the intermediate symbols, the source symbols, or both, to the encoding symbols. The coding process may follow the precoding process, or the coding process may occur instead of the precoding process. The coding process may employ a degree distribution (e.g., a Soliton distribution) , where the degree distribution represents a probability mass function of a set of degrees d _i (e.g., d ₁, d ₂, d ₃, etc. ) . In the coding process, the degree d _i of an i ^th encoding symbol may represent the quantity of intermediate symbols or source symbols which the first wireless device may combine into the i ^th encoding symbol. In some examples, a receiving device may decode the received encoding symbols based on the degrees of the symbols.

To reduce latency associated with the encoding and decoding, the first wireless device 205 may encode a set of source symbols according to a fountain code to obtain a set of systematic symbols and a set of parity symbols (e.g., the encoding symbols may be split into two or more subsets of encoding symbols) . Each systematic symbol may directly correspond to a source symbol-that is, the set of systematic symbols may match the set of source symbols. The set of parity symbols may support recovering any source symbols that a receiving device fails to recover from the set of systematic symbols. The second wireless device 210, the third wireless device 215, or both, may receive a first set of encoded packets 220-a that may include the set of systematic symbols and a second set of encoded packets 220-b that may include the set of parity symbols. Based on the encoding, the receiving device may decode the set of source symbols from the set of systematic symbols, the set of parity symbols, or both. In some examples, the systematic symbols may be referred to as “degree-one” symbols because the value for each systematic symbol is determined based on one source symbol.

As described herein, the first wireless device 205 may order the set of parity symbols within the second set of encoded packets 220-b to improve the process of recovering the source symbols. The parity symbols may be ordered by decreasing degrees based on a degree distribution for the set of parity symbols. For example, the first wireless device 205 may determine the set of parity symbols according to a random distribution of degrees and may re-order the resulting parity symbols by decreasing degrees. The first wireless device 205 may transmit a first set of encoded packets 220-a including the systematic symbols (e.g., degree-one symbols) , and the first wireless device 205 may subsequently transmit a second set of encoded packets 220-b including the parity symbols. The parity symbols with the highest degrees may be transmitted in a first encoded packet of the second set of encoded packets 220-b, and the parity symbols with the lowest degrees (e.g., degree-two) may be transmitted in a subsequent packet of the second set of encoded packets 220-b. It is to be understood that the second set of encoded packets 220-b may include any number of packets. Based on the transmitting device ordering the parity symbols, a receiving device may decode the source symbols from the parity symbols efficiently, and latency associated with the data transmissions may be reduced. For example, if the receiving device successfully recovers the source symbols from the high-degree parity symbols (e.g., in a first packet of the second set of encoded packets 220-b) , the receiving device may refrain from decoding the remaining parity symbols. In some cases, the receiving device may enter a low-power mode, significantly reducing the power consumption and latency involved in determining the set of source symbols.

In some examples, the second wireless device 210 or the third wireless device 215 may decode the respective data transmission and may transmit feedback message 230-a or feedback message 230-b (e.g., a HARQ message including one or more ACK or NACK indications) to the first wireless device 205 based on decoding a first set of encoded packets 220-a. For example, the second wireless device 210 may receive a data transmission from the first wireless device 205 that may be transmitted in a first set of encoded packets 220-a-1 including systematic symbols and a second set of encoded packets 220-b-1 including parity symbols. The second wireless device 210 may attempt to decode the first set of encoded packets 220-a-1, and the second wireless device 210 may transmit a feedback message 230-a to the first wireless device 205 based on decoding the systematic symbols of the first set of encoded packets 220-a-1. The first wireless device 205 may transmit a message to configure the second wireless device 210 with a feedback schema. The feedback schema may indicate one or more methods the second wireless device 210 may use for determining a feedback parameter. The configuration message may be transmitted as a downlink control information (DCI) message, a MAC control element (MAC CE) , an RRC configuration message, or a combination thereof.

The second wireless device 210 may determine the feedback parameter based on the feedback schema received from the first wireless device 205. For example, the feedback parameter may be determined based on a channel measurement procedure. The feedback parameter may include a CQI value, an RSRP value, an RSRQ value, an RSSI value, or a combination thereof. Additionally or alternatively, the feedback parameter may include one or more ACK indicators for the systematic symbols that were received and decoded successfully, one or more NACK indicators for the systematic symbols that were not received or decoded successfully, or some combination thereof. The feedback parameter may indicate an erasure probability (e.g., based on a number of successfully received systematic symbols, k, out of the K transmitted systematic symbols) . In some examples, the first wireless device 205 may estimate the erasure probability based on the channel measurement value (e.g., CQI or other measurement value) determined by the second wireless device 210, the number of ACK or NACK indicators, or both.

The first wireless device 205 may transmit the second set of encoded packets 220-b-1 including the parity symbols to the second wireless device 210 based on the feedback message 230-a. For example, the first wireless device 205 may determine a degree distribution for the set of parity symbols based on the feedback parameter. The degree distribution may be determined based on the estimated erasure probability indicated by the feedback parameter. In some examples (e.g., during unicast communications) , the first wireless device 205 may encode the source symbols such that the first wireless device 205 may determine the systematic symbols directly from the source symbols (e.g., the first wireless device 205 may refrain from mapping the source symbols to one or more intermediate symbols, and the first wireless device 205 may instead map the source symbols to the systematic symbols) . In such examples, if the erasure probability indicated by the feedback parameter satisfies an erasure threshold, the first wireless device may also determine the parity symbols directly from the source symbols. Additionally or alternatively, if the feedback parameter fails to satisfy the erasure threshold, the first wireless device 205 may determine to encode the parity symbols such that the parity symbols may be determined from a set of intermediate symbols.

In some examples, the second wireless device 210, the third wireless device 215, and one or more other wireless devices may receive a broadcast or multicast data transmission from the first wireless device 205. In some cases, the receiving wireless devices may refrain from transmitting a feedback message 230 in response to the data transmission (e.g., in broadcast or multicast scenarios) . The first wireless device 205 may order the parity symbols associated with the data transmission according to decreasing degrees such that the receiving wireless devices may efficiently recover the source symbols from the systematic symbols, the parity symbols, or both, without transmitting a feedback message 230. For example, the first wireless device 205 may transmit the first set of encoded packets 220-a-1 to the second wireless device 210 and the first set of encoded packets 220-a-2 to the third wireless device 215. The first sets of encoded packets 220-a may include systematic symbols broadcast to multiple wireless devices (e.g., UEs 115 in an NR MBS system) . The first wireless device 205 may subsequently transmit a second set of encoded packets 220-b-1 to the second wireless device 210 and the second set of encoded packets 220-b-2 to the third wireless device 215. The second sets of encoded packets 220-b-1 and 220-b-2 may include one or more parity symbols that may be ordered according to decreasing degrees. As such, the second wireless device 210 and the third wireless device 215 may attempt to recover the source symbols based on the highest degree parity symbols first. The receiving devices may thereby refrain from decoding the remaining parity symbols if the receiving devices successfully recover the source symbols from the highest degree parity symbols. For example, the second wireless device 210 may receive a first number of packets containing parity symbols in order to recover the source symbols, while the third wireless device 215 may receive a second number of packets containing parity symbols in order to recover the source symbols.

The operations performed by the first wireless device 205, the second wireless device 210, and the third wireless device 215 may support improvement to data encoding, transmission, and decoding operations and, in some examples, may promote improvements to data decoding processes to reduce latency and power requirements, among other benefits.

FIG. 3 illustrates an example of an encoding scheme 300 that supports degree selection schemes for Raptor codes in multicast and broadcast services and in unicast services in accordance with aspects of the present disclosure. In some examples, the encoding scheme 300 may implement aspects of

wireless communications systems

100 and 200. For example, the encoding scheme 300 may be associated with communications between a first wireless device (e.g., a transmitting device) , a second wireless device (e.g., a receiving device) , and in some examples, one or more other receiving devices, which may be examples of the corresponding devices described with reference to FIGs. 1 and 2. The encoding scheme 300 may illustrate features for improved degree selection schemes to improve reliability and reduce latency of communications, among other benefits.

The encoding scheme 300 may use LT coding, Raptor coding, or both, to encode packets for transmission from a first wireless device to one or more second wireless devices. The first wireless device may encode a set of source symbols 305 (e.g., a quantity K of source symbols 305) into a set of encoded symbols 335. The set of encoded symbols 335 may include a set of systematic symbols 325, a set of parity symbols 330, or both. In some examples, the quantity of encoded symbols 335 may be greater than the quantity of source symbols 305 to improve a probability of successfully decoding the source symbols 305 at a second wireless device. Additionally or alternatively, the quantity of encoded symbols 335 may be the same as the quantity of source symbols 305 (e.g., in some examples, the set of encoded symbols 335 may not include the parity symbols 330) . In some examples, the encoding scheme 300 may be rateless, where the quantity of encoded symbols 335 may have no upper limit.

In some examples, the encoding scheme 300 may include a precoding process 310. In the precoding process 310, the first wireless device may map one or more source symbols 305 to each of a set of intermediate symbols 315. The first wireless device may generate a quantity of redundant intermediate symbols 340 (e.g., a quantity of intermediate symbols 315 in addition to a quantity K of intermediate symbols 315 directly mapped to the K source symbols 305) . In some examples, the redundant intermediate symbols 340 may include a quantity S of low-density parity-check (LDPC) symbols, where one or more copies (e.g., three copies) of each source symbol 305 may appear in each LDPC symbol. Additionally or alternatively, the redundant intermediate symbols 340 may include a quantity H of half symbols, where each half symbol may include ceil (H/2) source symbols 305, and where ceil (x) may represent a ceiling function mapping x to a least integer greater than or equal to x.

The encoding scheme 300 may include an LT coding process 320. In some examples, the LT coding process 320 may follow the precoding process 310. Additionally or alternatively, the LT coding process 320 may be performed instead of the precoding process 310. In the LT coding process 320, the first wireless device may map the intermediate symbols 315 or the source symbols 305 (e.g., if the LT coding process 320 replaces the precoding process 310) to the set of encoded symbols 335 (e.g., the set of systematic symbols 325, the set of parity symbols 330, or both) . The LT coding process 320 may employ a degree distribution Ω, where the degree distribution Ω represents a probability mass function of a set of degrees d _i (e.g., d ₁, d ₂, d ₃, etc. ) . The probability of randomly selecting a degree d _i (i.e., a degree with index i) from the degree distribution may be represented by ρ (i) . In the LT coding process 320, the degree d _i of an i ^th encoded symbol 335 may represent the quantity of intermediate symbols 315 or the quantity of source symbols 305 which the first wireless device may combine into the i ^th encoded symbol 335. For example, if the selected degree for a first parity symbol 330 is d ₁=2, two intermediate symbols 315 may be randomly selected and combined into the first parity symbol 330. Similarly, if the selected degree for a second parity symbol 330 is d ₂=1, a single intermediate symbol 315 may be combined into the second parity symbol 330. In some examples, the intermediate symbols 315 or source symbols 305 may be combined into the encoded symbols 335 using a logic operation such as a logical exclusive OR (XOR) operation. In some examples, each encoded symbol 335 may include information identifying the source symbols 305 or intermediate symbols 315 used to construct the encoded symbol 335. For example, the encoded symbol 335 may include indices (e.g., s ₁, s ₂, s ₃, s _K, etc. ) associated with the source symbols 305 used to construct the encoded symbol 335.

In some examples (e.g., in an ideal Soliton degree distribution) , the probability of randomly selecting a degree d _i (e.g., a degree with index i) from the degree distribution, ρ (d) , may be based on a number, K, of source packets, and a degree, d. The probability may be represented by:

Additionally or alternatively, the degree distribution may be determined to ensure that the expected number of degree-one symbols is a determined number, S (e.g.,

) , instead of a random number, and the degree distribution, τ (d) , may be represented by:

The encoded symbols 335 may be transmitted as a set of encoded packets from a first wireless device to a second wireless device. In some examples, the encoding scheme 300 may be represented by a generator matrix G. The source symbols 305 contained in the encoded symbols 335 of a given encoded packet may be represented by p _j, which may be defined by:

In some examples, one or more encoded packets may be lost based on the transmission environment. The second wireless device may receive a subset of encoded packets (e.g., a quantity N of encoded packets) via the multi-hop network. The source symbols 305 contained in encoded symbols 335 of a given encoded packet received by the second wireless device may be represented by r _k, which may be defined by:

Based on the encoding scheme 300, the second wireless device may recover all source symbols 305 in the set of source symbols 305 when the matrix G′ of the received packets is invertible. Additionally or alternatively, the second wireless device may recover all source symbols 305 in the set of source symbols 305 when the matrix G′ of the received packets has a rank K, where K is the quantity of source symbols 305 in the set of source symbols 305. To increase a probability of the second wireless device successfully recovering the set of source symbols 305, the encoding scheme 300 may be designed such that the representative generator matrix G′ is invertible for a minimum quantity N of received encoded packets.

The second wireless device may decode the received encoded symbols 335 to obtain the source symbols 305. In some examples, the second wireless device may begin a decoding process by identifying an encoded symbol 335 with an index t _j that is connected to a single source symbol 305 with an index s _i. The second wireless device may determine the encoded symbol 335 with index t _j is equivalent to the source symbol 305 with index s _i. The second wireless device may then apply an XOR operation to each other encoded symbol 335 connected to the source symbol 305 with index s _i, and remove all edges connected to the source symbol 305 with index s _i. The second wireless device may repeat this process to recover source symbols 305 from the received encoded symbols 335.

In some examples, the degree distribution may be designed based on the intermediate symbols 315. For example, the degrees represented by the degree distribution may represent the quantity of intermediate symbols 315 which the first wireless device may combine into the i ^th encoded symbol 335. The degree distribution may be designed to include a sufficient number of encoded symbols 335 that may be associated with a single intermediate symbol 315 (e.g., degree-one symbols) . However, the expected degree of an encoded symbol 335 may be:

As described herein, the degree distribution may be re-designed to encode the one or more parity symbols 330 based on a success rate of decoding the systematic symbols 325 (e.g., the parity symbols 330 may be encoded according to the systematic degree distribution instead of the Solution distribution directly) . For example, the first wireless device may encode the parity symbols 330 according to a degree distribution for the parity symbols 330, and the degree distribution may be determined based on feedback received from a second wireless device, an order of decreasing degrees of the parity symbols, or both. The first wireless device may determine the parity symbols 330 from the intermediate symbols 315 or directly from the source symbols 305 (e.g., based on feedback received from the second wireless device) . As such, the first wireless device may determine a degree distribution for encoding the parity symbols 330 to reduce latency of communications.

The systematic symbols 325 may be degree-one symbols, and the first wireless device may order the parity symbols 330 (e.g., symbols with a degree larger than one) by decreasing degrees. The second wireless device may receive a first set of packets including the systematic symbols 325 and a second set of packets including the parity symbols 330. In some examples, the second wireless device may decode the systematic symbols 325 and report a feedback message including a feedback parameter to the first wireless device, as described with reference to FIG. 2. Additionally or alternatively, the first wireless device may transmit the first and second sets of packets to the second wireless device and one or more other wireless devices, and the receiving devices may decode different numbers of packets based on a number of parity symbols 330 used to recover the set of source symbols 305.

If the first wireless device receives the feedback message from the second wireless device, the first wireless device may determine whether to encode the intermediate symbols 315 based on the feedback parameter included in the feedback message. For example, if the feedback parameter (e.g., a value, k, indicating a number of systematic symbols 325 successfully received by the second wireless device, or another parameter) satisfies an erasure threshold, the first wireless device may map the source symbols 305 to the parity symbols 330 directly (e.g., the first wireless device may refrain from using the intermediate symbols 315, and the parity symbols 330 may be mapped directly to the source symbols 305 during decoding) . If the feedback parameter fails to satisfy an erasure threshold, the first wireless device may map the source symbols 305 to the parity symbols 330 via the intermediate symbols 315 and, accordingly, the second wireless device may decode the source symbols 305 via the intermediate symbols 315. Mapping directly from the source symbols 305 to the encoded symbols 335 may reduce the processing overhead and latency associated with encoding and decoding, while mapping via the intermediate symbols 315 may improve the reliability of decoding.

FIG. 4 illustrates an example of decoding procedures 400-a and 400-b that support degree selection schemes for Raptor codes in multicast and broadcast services and in unicast services in accordance with aspects of the present disclosure. In some examples, decoding procedures 400-a and 400-b may implement aspects of the

wireless communications systems

100 and 200 and the encoding scheme 300. For example, decoding procedures 400-a and 400-b may be associated with communications between a first wireless device (e.g., a transmitting device) , a second wireless device (e.g., a receiving device) , and in some examples, one or more other receiving devices, which may be examples of the corresponding devices described with reference to FIGs. 1 and 2. Decoding procedures 400-a and 400-b may illustrate features for improved reliability and reduced latency for decoding source symbols during communications, among other benefits.

In some systems, a first wireless device may transmit information to a second wireless device using a fountain code (e.g., a Raptor code) . Decoding procedure 400-a may illustrate an example of a decoding procedure 400 performed by the second wireless device. In the example of decoding procedure 400-a, the second wireless device may attempt to recover one or more source symbols 415-a via two decoding processes 420. For example, decoding procedure 400-a may include a first decoding process 420-a and a second decoding process 420-b.

First decoding process 420-a (e.g., an LT decoding process) may include receiving one or more encoded symbols 405-a and decoding encoded symbols 405-a to obtain one or more of the intermediate symbols 410. Encoded symbols 405-a may include a set of systematic symbols and a set of parity symbols as described with reference to FIGs. 2 and 3. The second wireless device may receive a first set of packets that may include the one or more systematic symbols (e.g., degree-one symbols) and a second set of packets that may include the one or more parity symbols. The parity symbols may be ordered by decreasing degrees.

The second wireless device may perform first decoding process 420-a if the first wireless device performed a precoding procedure as described with reference to FIG. 3. For example, in the precoding procedure, the first wireless device may have encoded a set of source symbols 415-a by mapping source symbols 415-a to a set of intermediate symbols 410 according to a degree distribution. The degree distribution may be determined based on the intermediate symbols 410, and the degrees of each encoded symbol of encoded symbols 405-a may represent a number of the intermediate symbols 410 that may be combined into encoded symbols 405-a. The second wireless device may decode encoded symbols 405-a to obtain the intermediate symbols 410 based on the degree distribution and the respective degrees of each encoded symbol 405-a.

The second wireless device may decode the intermediate symbols 410 to recover source symbols 415-a during decoding process 420-b (e.g., an LDPC or half decoding process) . In one example, the second wireless device may use a number of LDPC symbols or a number of half symbols of the intermediate symbols 410 to recover source symbols 415-a. The decoding process 420-b may reverse a precoding procedure performed by the first wireless device.

As such, decoding procedure 400-a may illustrate a procedure for a receiving device to recover source symbols 415-a by performing a first decoding process 420-a (e.g., LT decoding) and a second decoding process 420-b (e.g., LDPC or half decoding) to obtain source symbols 415-a from the intermediate symbols 410 and encoded symbols 405-a.

Decoding procedure 400-b may represent a decoding procedure 400 that may reduce latency associated with recovering source symbols 415-b at the second wireless device. For example, decoding procedure 400-b may include one decoding process 420-c, which may be an example of an LT decoding process. By recovering source symbols 415-b according to decoding procedure 400-b, the second wireless device may refrain from decoding the intermediate symbols 410, thereby reducing processing overhead and latency at the second wireless device.

Decoding procedure 400-b may be performed by the second wireless device if the first wireless device maps a set of encoded symbols 405-b directly from a set of source symbols 415-b. For example, the first wireless device may map the set of systematic symbols within the set of encoded symbols 405-b to source symbols 415-b. The second wireless device may decode the set of systematic symbols successfully, and the second wireless device may thereby recover source symbols 415-b successfully via a single decoding process 420-c (e.g., LT decoding) .

Additionally or alternatively, the second wireless device may receive a first set of encoded packets that may include systematic symbols mapped directly to source symbols 415-b and a second set of encoded packets that may include parity symbols. In some examples, the parity symbols may be mapped directly to source symbols 415-b, and the second wireless device may decode the encoded symbols 405-b during two decoding stages (e.g., one decoding stage for each subset of packets) according to a single decoding process 420-c. For example, the second wireless device may decode the systematic symbols and transmit a feedback message to the first wireless device that may indicate an erasure probability associated with the systematic symbols. If the first wireless device determines that the erasure probability satisfies (e.g., is less than) an erasure threshold, the first wireless device may determine to map the parity symbols directly from source symbols 415-b. The second wireless device may decode the parity symbols and successfully recover source symbols 415-b from the parity symbols (e.g., without determining intermediate symbols) . Alternatively, the first wireless device may determine that the erasure probability fails to satisfy (e.g., is greater than) the erasure threshold and may determine to map the parity symbols via a set of intermediate symbols 410. The second wireless device may decode the parity symbols to determine a set of intermediate symbols and may use the intermediate symbols to successfully recover the source symbols.

As described herein, in some examples, a transmitting device may map a set of encoded symbols 405 directly from a set of source symbols 415, and a receiving device may recover the source symbols 415 in a single decoding process 420-c to reduce latency associated with the decoding procedure 400. Additionally or alternatively, the transmitting device may map the set of encoded symbols 405 from the source symbols 415 via a set of intermediate symbols 410, and the receiving device may recover the source symbols 415 via two or more decoding processes 420 (e.g., to improve decoding reliability, for example, if channel conditions are poor) .

FIG. 5 illustrates an example of a symbol transmission diagram 500 that supports degree selection schemes for Raptor codes in multicast and broadcast services and in unicast services in accordance with aspects of the present disclosure. In some examples, the symbol transmission diagram 500 may implement aspects of the

wireless communications systems

100 and 200, the encoding scheme 300, and the decoding procedures 400-a or 400-b. For example, the symbol transmission diagram 500 may be associated with communications between a first wireless device (e.g., a transmitting device) , a second wireless device (e.g., a receiving device) , and in some examples, one or more other receiving devices, which may be examples of the corresponding devices described with reference to FIGs. 1 and 2. The symbol transmission diagram 500 may include the sequence of encoded symbols 530, which may include features for improving reliability and reducing latency for encoding and decoding source symbols during communications, among other benefits.

The symbol transmission diagram 500 may illustrate an order of symbols transmitted by a first wireless device to a second wireless device over time. The symbol transmission diagram 500 may include sets of encoded packets 535-a, 535-b, 535-c, and 535-d, which may be examples of the encoded packets 220 as described with reference to FIG. 2. Each of the sets of encoded packets 535 may include one or more encoded packets, and each encoded packet may include one or more encoded symbols. The first wireless device may transmit the encoded packets 535 in an order based on a degree of the symbols included in the encoded packets 535 (e.g., starting with systematic-degree-one-symbols and then according to a decreasing degree) .

The first wireless device may transmit first encoded packets 535-a including a set of the systematic symbols 505. In some examples, the first wireless device may transmit one or more encoded packets 535 including a number, K, of the systematic symbols 505. The second wireless device may receive the systematic symbols 505, and the second wireless device may attempt to decode the systematic symbols 505 to recover a set of source symbols. In some examples, the systematic symbols 505 may be degree-one symbols. In one example, the first wireless device may map each symbol of a set of source symbols directly to each of the systematic symbols 505. In some cases, based on failing to receive one or more packets of the first encoded packets 535-a, the second wireless device may fail to recover all of the source symbols from the systematic symbols 505. The second wireless device may use parity symbols to recover the missing source symbols.

For example, the first wireless device may transmit parity symbols in the remaining encoded packets 535 in an order of decreasing degrees to improve efficiency of the decoding procedure at the receiving wireless devices. For example, the second wireless device may decode the encoded packets 535 starting with encoded packets 535-a. If the second wireless device fails to recover the source symbols from the systematic symbols 505 in encoded packets 535-a, the second wireless device may decode encoded packets 535-b. If the second wireless device successfully recovers each of the source symbols from the high- degree parity symbols 510 in encoded packets 535-b and the systematic symbols 505 in encoded packets 535-a, the second wireless device may refrain from decoding remaining encoded packets 535-c and 535-d (e.g., in some cases, the second wireless device may enter a low-power mode) . In this way, the second wireless device may continue to decode each of the encoded packets 535 including parity symbols with decreasing degrees until the second wireless device is able to successfully recover the source symbols. Thus, by transmitting the parity symbols in decreasing degree order, the first wireless device may allow for the second wireless device to recover the source symbols quickly and with few power requirements, and may thereby improve communications.

The number of encoded packets 535 that a receiving device may decode before recovering the source symbols may depend on the transmission environment (e.g., path loss, obstacles, etc. ) , a location of the receiving device, a capability of the receiving device, or some combination thereof. For example, a receiving device located in the center of a cell may receive more systematic symbols 505, successfully decode more of the systematic symbols 505, or both, than a cell-middle device or a cell-edge device (e.g., cell-center devices may receive K-1 systematic symbols, and cell-edge devices may receive some or no systematic symbols, or the cell-edge devices may decode the systematic symbols incorrectly) . In the example of multicast or broadcast transmissions, ordering the parity symbols by decreasing degrees may thereby allow some of the receiving devices (e.g., cell-center devices) to receive encoded packets 535-b including the high-degree symbols 510 and to refrain from decoding one or more of the later encoded packets 535 (e.g., the receiving devices may save power) if the receiving devices are able to successfully recover the source symbols based on the high-degree symbols 510.

A high-degree parity symbol may support recovering a number of different source symbols if a number of source symbols are already recovered. For example, a degree-six parity symbol includes information about six different source symbols. If the second wireless device has decoded any five of the six source symbols, the second wireless device may decode the sixth source symbol from the degree-six parity symbol. In contrast, low-degree parity symbols 515, including degree-two parity symbols 520, may support recovering a small number of source symbols, but may not rely on the second wireless device having already decoded a large number of source symbols. For example, a degree-two parity symbol includes information about two different source symbols. If the second wireless device has decoded one of the source symbols, the second wireless device may decode the other source symbol based on the degree-two parity symbol. In this way, a wireless device that has successfully decoded a large proportion of the source symbols may be able to successfully decode the remaining source symbols using high-degree parity symbols 510, while a wireless device that has failed to decode a large proportion of the source symbols may use a large number of parity symbols, including high-degree parity symbols 510, low-degree parity symbols 515, degree-two parity symbols 520, or a combination thereof to determine the full set of source symbols. As such, transmitting packets containing parity symbols with randomly distributed degrees may cause the receiving devices to receive all or a large portion of packets in order to recover the source symbols, even if a receiving device has decoded a large proportion of the source symbols based on the systematic symbols 505. By ordering the parity symbols by decreasing degrees, receiving devices that have successfully decoded a large proportion of the source symbols may receive enough information about a large number of source symbols (e.g., based on the high-degree parity symbols 510) from the first set of encoded packets 535-b to recover the remaining source symbols.

In some examples, cell-edge devices may decode each of the encoded packets 535-a, 535-b, 535-c, and 535-d to recover the original source symbols (e.g., the channel quality for the cell-edge devices may be reduced due to pathloss, distance, obstacles, or some other channel parameter) . In some examples, cell-middle devices may receive some of the systematic symbols 505, but the cell-middle devices may decode the systematic symbols 505 incorrectly. The cell-middle devices may thereby use the high-degree symbols 510, the low-degree parity symbols 515, one or more of the degree-two parity symbols 520, or a combination thereof for soft decoding (e.g., iterative Tanner Graph) .

In some examples (e.g., unicast communications) , the second wireless device may transmit a feedback message 525 including a feedback parameter to improve encoding of the parity symbols. In some cases, the feedback message 525 may be based on a channel measurement. As such, the second wireless device may transmit a feedback message 525-a (e.g., based on decoding a set of systematic symbols 505) or may transmit a feedback message 525-b (e.g., prior to decoding a set of systematic symbols 505) . If the first wireless device receives a feedback message 525-b, the first wireless device may encode the systematic symbols 505 and parity symbols based on the feedback information. Alternatively, if the first wireless device receives a feedback message 525-a, the first wireless device may encode the systematic symbols 505 independent of (e.g., prior to) the feedback and may encode the parity symbols based on the feedback information.

In some other cases, the first wireless device may transmit the feedback message 525 based on decoding the systematic symbols 505, as described with reference to FIG. 2. In some examples, the feedback parameter may include one or more ACK or NACK indications for a result of receiving and decoding each symbol of the set of systematic symbols 505. Additionally or alternatively, the feedback parameter may include a CQI value, a RSRP value, a RSRQ value, a RSSI value, or some combination thereof. The feedback parameter may indicate an erasure probability, which may be determined based on a number of the systematic symbols 505 that have been successfully decoded by the second wireless device (e.g., a number of ACK or NACK symbols) , a channel measurement value determined by the second wireless device, or both. For example, the erasure probability may be estimated based on a number, k, of the systematic symbols 505 that are received out of a number, K, of the systematic symbols 505 (e.g., degree-one symbols) that are transmitted. Additionally or alternatively, the erasure probability may be estimated based on the channel measurement (e.g., CQI) value indicated by the feedback parameter. The first wireless device may indicate which of the feedback schema should be used by the second wireless device via signaling (e.g., via DCI, MAC CE, RRC configuration, or some combination thereof) .

The first wireless device may determine a degree distribution for the parity symbols based on the feedback message 525 transmitted by the second wireless device. For example, if the number of the systematic symbols 505 that are successfully received by the second wireless device is relatively large (e.g., above a threshold) , the first wireless device may determine a degree distribution for the parity symbols that may include a greater proportion of high-degree parity symbols 510 (e.g., above a threshold proportion of the parity symbols) . If the feedback parameter indicates that the number of the systematic symbols 505 that are successfully received by the second wireless device is relatively small (e.g., below a threshold) , the first wireless device may determine a degree distribution for the parity symbols that may include a greater proportion of low-degree parity symbols 515 and degree-two parity symbols 520 (e.g., above a threshold proportion of the parity symbols) . Additionally or alternatively, if the CQI value indicated by the feedback parameter is relatively large (e.g., above a threshold) , the first wireless device may determine a degree distribution for the parity symbols that may include a large proportion of high-degree parity symbols 510. If the CQI value indicated by the feedback parameter is relatively small (e.g., below a threshold) , the first wireless device may determine a degree distribution for the parity symbols that may include a large proportion of low-degree parity symbols 515 and degree-two parity symbols 520. Such adjustments to the degree distributions may allow the encoder to dynamically select parity information that supports reliable decoding at the second wireless device based on a first decoding stage (e.g., for the systematic symbols 505) at the second wireless device.

For example, the first wireless device may determine a sequence (l _K, l _K-1, …, l ₂) , where l _i≥0 indicates the number of degree-i encoded symbols to be sent. The first wireless device may include a mapping (e.g., a table, look-up relationship, function, algorithm, or heuristic) for selecting the sequence based on a feedback message 525 (e.g., a value k, a CQI value, etc. ) . The sequence may define the degree distribution for the encoded symbols, the parity symbols, or both. Accordingly, dynamic degree distributions (e.g., based on dynamically determined sequences) may be used for fountain codes (e.g., Raptor codes, LT codes, etc. ) instead of ideal or robust Soliton distributions.

FIG. 6 illustrates an example of a process flow 600 that supports degree selection schemes for Raptor codes in multicast and broadcast services and in unicast services in accordance with aspects of the present disclosure. In some examples, the process flow 600 may implement various aspects of the present disclosure described with reference to FIGs. 1 through 5. For example, the process flow 600 may illustrate communications between a first wireless device (e.g., a transmitting device) and a second wireless device (e.g., a receiving device) , which may be examples of corresponding devices described with reference to FIGs. 1 through 5. For example, the first wireless device may be an example of a base station 105 and the second wireless device may be an example of a UE 115. In some examples, the first wireless device may transmit sets of encoded packets that may include systematic symbols, parity symbols, or both, that may be ordered by decreasing degrees to reduce latency and power requirements associated with the decoding procedure at the second wireless device. For example, the techniques described herein may support reduced encoding latency and reduced decoding latency. Alternative examples of the following may be implemented, where some steps are performed in a different order than described or are not performed at all. In some cases, a step may include additional features not mentioned below, or further steps may be added.

At 615, the first wireless device 605 may encode a set of source symbols according to a fountain code to obtain a set of systematic symbols, a set of parity symbols, or both. Each systematic symbol of the set of systematic symbols may be associated with a source symbol of the set of source symbols. Each parity symbol of the set of parity symbols may be associated with a number of source symbols of the set of source symbols. For example, the number of source symbols with which the parity symbols are associated may indicate a respective degree of each of the parity symbols. The degrees of the parity symbols may be determined based on a degree distribution for the set of parity symbols.

At 620, the first wireless device 605 may transmit a first set of packets to the second wireless device 610. The first set of packets may include the set of systematic symbols. The set of systematic symbols may be degree-one symbols. For example, each systematic symbol may be associated with a single source symbol. In some examples, the first wireless device 605 may transmit the first set of packets to the second wireless device 610 and one or more other devices (e.g., multicast or broadcast transmissions) .

At 625, the second wireless device 610 may decode the first set of packets according to a fountain code to recover a first subset of the set of source symbols. In some examples, the second wireless device 610 may decode the first set of packets according to an LT decoding scheme. For example, the second wireless device 610 may receive a number of the systematic symbols that may be less than or equal to a number of the systematic symbols that were transmitted, and the second wireless device 610 may decode each of the received systematic symbols. The second wireless device 610 may recover one or more of the source symbols based on decoding the systematic symbols. The source symbols may be recovered directly from the systematic symbols or via one or more intermediate symbols.

At 630, in some examples, the second wireless device 610 may transmit a feedback message to the first wireless device 605. The feedback message may indicate a feedback parameter. In some examples, the feedback parameter may indicate an erasure probability, which may be determined based on a number of systematic symbols that were successfully received by the second wireless device 610, a CQI value determined by the second wireless device 610, or both.

At 635, if the first wireless device 605 receives a feedback message, the first wireless device 605 may encode the set of source symbols according to a fountain code to obtain the set of parity symbols based on the feedback message. For example, the first wireless device 605 may determine a degree distribution for the parity symbols based on the feedback parameter. Additionally or alternatively, the first wireless device 605 may determine whether to use a set of intermediate symbols for encoding the parity symbols based on the feedback parameter. In some examples, the feedback parameter may satisfy an erasure threshold, and the first wireless device may determine the set of parity symbols directly from the set of source symbols. In some other examples, the feedback parameter may fail to satisfy the erasure threshold, and the first wireless device 605 may determine the set of parity symbols from a set of intermediate symbols.

At 640, the first wireless device 605 may order the parity symbols by decreasing degrees based on the degree distribution for the set of parity symbols. In some examples, the first wireless device 605 may determine or adjust the degree distribution for the set of parity symbols based on the feedback message that may be transmitted by the second wireless device 610.

At 645, the first wireless device 605 may transmit a second set of packets that may include the set of parity symbols. The second set of packets may be transmitted based on the ordering determined at 640. For example, the first wireless device 605 may transmit packets with high-degree parity symbols first and packets with low-degree parity symbols last.

At 650, the second wireless device 610 may decode the second set of packets according to a fountain code to recover a second subset of the source symbols. The second wireless device 610 may recover the second subset of source symbols based on decoding the second set of packets at 650 and the first set of packets at 625. In some examples, the second wireless device 610 may determine the second subset of the source symbols directly from the parity symbols. Additionally or alternatively, the second wireless device 610 may determine the second subset of the source symbols via a set of intermediate symbols. The second subset of the source symbols may be the remaining source symbols not decoded at 625.

FIG. 7 shows a block diagram 700 of a device 705 that supports degree selection schemes for Raptor codes in multicast and broadcast services and in unicast services in accordance with aspects of the present disclosure. The device 705 may be an example of aspects of a UE 115 as described herein. The device 705 may include a receiver 710, a communications manager 715, and a transmitter 720. The device 705 may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses) .

The receiver 710 may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to degree selection schemes for Raptor codes in multicast and broadcast services and in unicast services, etc. ) . Information may be passed on to other components of the device 705. The receiver 710 may be an example of aspects of the transceiver 1020 described with reference to FIG. 10. The receiver 710 may utilize a single antenna or a set of antennas.

The communications manager 715 may receive a first set of packets including a set of systematic symbols, where each systematic symbol of the set of systematic symbols is associated with a source symbol of a set of source symbols, and decode the first set of packets according to a fountain code to recover a first subset of the set of source symbols. The communications manager 715 may further receive a second set of packets including a set of parity symbols, where each parity symbol of the set of parity symbols is associated with a number of source symbols of the set of source symbols according to a respective degree of each parity symbol based on a degree distribution for the set of parity symbols, and where the second set of packets is received in an order according to decreasing degrees of parity symbols in each packet of the second set of packets, and decode the second set of packets according to the fountain code to recover a second subset of the set of source symbols based on the recovered first subset of the set of source symbols, where the set of source symbols is recovered based on decoding the first set of packets and decoding the second set of packets. The communications manager 715 may be an example of aspects of the communications manager 1010 described herein.

The communications manager 715, or its sub-components, may be implemented in hardware, code (e.g., software or firmware) executed by a processor, or any combination thereof. If implemented in code executed by a processor, the functions of the communications manager 715, or its sub-components may be executed by a general-purpose processor, a digital signal processor (DSP) , an application-specific integrated circuit (ASIC) , a field-programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described in the present disclosure.

The communications manager 715, or its sub-components, may be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations by one or more physical components. In some examples, the communications manager 715, or its sub-components, may be a separate and distinct component in accordance with various aspects of the present disclosure. In some examples, the communications manager 715, or its sub-components, may be combined with one or more other hardware components, including but not limited to an input/output (I/O) component, a transceiver, a network server, another computing device, one or more other components described in the present disclosure, or a combination thereof in accordance with various aspects of the present disclosure.

The transmitter 720 may transmit signals generated by other components of the device 705. In some examples, the transmitter 720 may be collocated with a receiver 710 in a transceiver module. For example, the transmitter 720 may be an example of aspects of the transceiver 1020 described with reference to FIG. 10. The transmitter 720 may utilize a single antenna or a set of antennas.

The communications manager 715 as described herein may be implemented to realize one or more potential advantages. One implementation may provide for reduced latency for encoding, decoding, and transmitting data messages using coding schemes. For example, the device 705 (e.g., a receiving device 705) may receive a set of the parity symbols in order of decreasing degrees, allowing the device 705 to decode the high-degree parity symbols first. If the receiving device 705 successfully recovers the source symbols from the high-degree parity symbols, the receiving device 705 may refrain from receiving and decoding each of the remaining parity symbols, which may thereby reduce latency associated with receiving and recovering a data transmission. In some examples, the receiving device 705 may enter a power saving mode if the device successfully recovers the source symbols, which may allow for reduced power consumption at the receiving device 705.

Additionally or alternatively, the receiving device 705 may recover the source symbols directly from the encoded symbols, and the receiving device 705 may reduce latency by refraining from decoding the encoded symbols and a set of intermediate symbols. In some examples, the receiving device 705 may transmit a feedback message to a transmitting device. The transmitting device may determine a degree distribution for transmitting the parity symbols based on the feedback message to improve a reliability associated with the communications and to reduce latency. For example, the transmitting device may select a greater number of high-degree parity symbols or a greater number of low-degree parity symbols based on the feedback message to allow for the receiving device 705 to recover the source symbols quickly and efficiently.

Based on receiving the packets including parity information in an order according to decreasing degrees of parity symbols, a processor of a UE 115 (e.g., a processor controlling the receiver 710, the communications manager 715, the transmitter 720, etc. ) may reduce processing resources used for communications. For example, by receiving high-degree parity symbols first, the UE 115 may recover the source symbols prior to receiving a number of packets. Once the source symbols are determined, the UE 115 may refrain from receiving any remaining packets and, in some cases, may enter a low power mode. Reducing the number of packets to receive and decode may reduce a number of times the processor ramps up processing power and turns on processing units to handle decoding for Raptor codes.

FIG. 8 shows a block diagram 800 of a device 805 that supports degree selection schemes for Raptor codes in multicast and broadcast services and in unicast services in accordance with aspects of the present disclosure. The device 805 may be an example of aspects of a device 705 or a UE 115 as described herein. The device 805 may include a receiver 810, a communications manager 815, and a transmitter 835. The device 805 may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses) .

The receiver 810 may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to degree selection schemes for Raptor codes in multicast and broadcast services and in unicast services, etc. ) . Information may be passed on to other components of the device 805. The receiver 810 may be an example of aspects of the transceiver 1020 described with reference to FIG. 10. The receiver 810 may utilize a single antenna or a set of antennas.

The communications manager 815 may be an example of aspects of the communications manager 715 as described herein. The communications manager 815 may include a systematic symbol component 820, a symbol decoder 825, and a parity symbol component 830. The communications manager 815 may be an example of aspects of the communications manager 1010 described herein.

The systematic symbol component 820 may receive a first set of packets including a set of systematic symbols, where each systematic symbol of the set of systematic symbols is associated with a source symbol of a set of source symbols. The symbol decoder 825 may decode the first set of packets according to a fountain code to recover a first subset of the set of source symbols.

The parity symbol component 830 may receive a second set of packets including a set of parity symbols, where each parity symbol of the set of parity symbols is associated with a number of source symbols of the set of source symbols according to a respective degree of each parity symbol based on a degree distribution for the set of parity symbols, and where the second set of packets is received in an order according to decreasing degrees of parity symbols in each packet of the second set of packets. The symbol decoder 825 may decode the second set of packets according to the fountain code to recover a second subset of the set of source symbols based on the recovered first subset of the set of source symbols, where the set of source symbols is recovered based on decoding the first set of packets and decoding the second set of packets.

The transmitter 835 may transmit signals generated by other components of the device 805. In some examples, the transmitter 835 may be collocated with a receiver 810 in a transceiver module. For example, the transmitter 835 may be an example of aspects of the transceiver 1020 described with reference to FIG. 10. The transmitter 835 may utilize a single antenna or a set of antennas.

FIG. 9 shows a block diagram 900 of a communications manager 905 that supports degree selection schemes for Raptor codes in multicast and broadcast services and in unicast services in accordance with aspects of the present disclosure. The communications manager 905 may be an example of aspects of a communications manager 715, a communications manager 815, or a communications manager 1010 described herein. The communications manager 905 may include a systematic symbol component 910, a symbol decoder 915, a parity symbol component 920, and a feedback component 925. Each of these components may communicate, directly or indirectly, with one another (e.g., via one or more buses) .

The systematic symbol component 910 may receive a first set of packets including a set of systematic symbols, where each systematic symbol of the set of systematic symbols is associated with a source symbol of a set of source symbols. The symbol decoder 915 may decode the first set of packets according to a fountain code to recover a first subset of the set of source symbols.

The parity symbol component 920 may receive a second set of packets including a set of parity symbols, where each parity symbol of the set of parity symbols is associated with a number of source symbols of the set of source symbols according to a respective degree of each parity symbol based on a degree distribution for the set of parity symbols, and where the second set of packets is received in an order according to decreasing degrees of parity symbols in each packet of the second set of packets. The symbol decoder 915 may decode the second set of packets according to the fountain code to recover a second subset of the set of source symbols based on the recovered first subset of the set of source symbols, where the set of source symbols is recovered based on decoding the first set of packets and decoding the second set of packets.

The feedback component 925 may transmit a feedback message indicating a feedback parameter, where the degree distribution for the set of parity symbols is based on the feedback parameter.

In some examples, the feedback parameter includes one or more ACK indicators for the first subset of the set of source symbols successfully recovered from the first set of packets, one or more NACK indicators for the second subset of the set of source symbols unsuccessfully recovered from the first set of packets, or a combination thereof, and the feedback message is transmitted in response to the first set of packets.

In some other examples, the feedback component 925 may perform a channel measurement procedure to determine the feedback parameter, where the feedback parameter includes a CQI value, an RSRP value, an RSRQ value, an RSSI value, or a combination thereof.

In some examples, the feedback component 925 may receive a message configuring a feedback schema, where the feedback parameter is based on the feedback schema. In some cases, the message configuring the feedback schema includes a DCI message, a MAC CE, an RRC configuration message, or a combination thereof.

In some examples, to decode the first set of packets, the symbol decoder 915 may determine, at a first decoding stage, the first subset of the set of source symbols directly from the set of systematic symbols. In some such examples, to decode the second set of packets, the symbol decoder 915 may determine, at a second decoding stage, the second subset of the set of source symbols directly from the set of parity symbols based on the feedback parameter satisfying an erasure threshold. In some other such examples, to decode the second set of packets, the symbol decoder 915 may determine, at a second decoding stage, the second subset of the set of source symbols from the set of parity symbols via a set of intermediate symbols based on the feedback parameter failing to satisfy an erasure threshold.

In some examples, the parity symbol component 920 may refrain from receiving at least one packet including additional parity symbols based on recovering the set of source symbols. In some such examples, the parity symbol component 920 may enter a low power mode based on recovering the set of source symbols and prior to transmission of the at least one packet including additional parity symbols.

In some examples, receiving the second set of packets may involve the parity symbol component 920 receiving, in a first data block, a first one or more packets of the second set of packets including parity symbols with degrees greater than or equal to a threshold degree value based on the order and receiving, in a second data block subsequent to the first data block, a second one or more packets of the second set of packets including parity symbols with degrees less than or equal to the threshold degree value based on the order.

In some cases, the fountain code may be an LT code, a Raptor code, or both.

FIG. 10 shows a diagram of a system 1000 including a device 1005 that supports degree selection schemes for Raptor codes in multicast and broadcast services and in unicast services in accordance with aspects of the present disclosure. The device 1005 may be an example of or include the components of a device 705, a device 805, or a UE 115 as described herein. The device 1005 may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including a communications manager 1010, an I/O controller 1015, a transceiver 1020, an antenna 1025, memory 1030, and a processor 1040. These components may be in electronic communication via one or more buses (e.g., bus 1045) .

The communications manager 1010 may receive a first set of packets including a set of systematic symbols, where each systematic symbol of the set of systematic symbols is associated with a source symbol of a set of source symbols, decode the first set of packets according to a fountain code to recover a first subset of the set of source symbols, receive a second set of packets including a set of parity symbols, where each parity symbol of the set of parity symbols is associated with a number of source symbols of the set of source symbols according to a respective degree of each parity symbol based on a degree distribution for the set of parity symbols, and where the second set of packets is received in an order according to decreasing degrees of parity symbols in each packet of the second set of packets, and decode the second set of packets according to the fountain code to recover a second subset of the set of source symbols based on the recovered first subset of the set of source symbols, where the set of source symbols is recovered based on decoding the first set of packets and decoding the second set of packets.

The I/O controller 1015 may manage input and output signals for the device 1005. The I/O controller 1015 may also manage peripherals not integrated into the device 1005. In some cases, the I/O controller 1015 may represent a physical connection or port to an external peripheral. In some cases, the I/O controller 1015 may utilize an operating system such as

or another known operating system. In other cases, the I/O controller 1015 may represent or interact with a modem, a keyboard, a mouse, a touchscreen, or a similar device. In some cases, the I/O controller 1015 may be implemented as part of a processor. In some cases, a user may interact with the device 1005 via the I/O controller 1015 or via hardware components controlled by the I/O controller 1015.

The transceiver 1020 may communicate bi-directionally, via one or more antennas, wired, or wireless links as described above. For example, the transceiver 1020 may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver. The transceiver 1020 may also include a modem to modulate the packets and provide the modulated packets to the antennas for transmission, and to demodulate packets received from the antennas.

In some cases, the wireless device may include a single antenna 1025. However, in some cases the device may have more than one antenna 1025, which may be capable of concurrently transmitting or receiving multiple wireless transmissions.

The memory 1030 may include random-access memory (RAM) and read-only memory (ROM) . The memory 1030 may store computer-readable, computer-executable code 1035 including instructions that, when executed, cause the processor to perform various functions described herein. In some cases, the memory 1030 may contain, among other things, a basic I/O system (BIOS) which may control basic hardware or software operation such as the interaction with peripheral components or devices.

The processor 1040 may include an intelligent hardware device (e.g., a general-purpose processor, a DSP, a central processing unit (CPU) , a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof) . In some cases, the processor 1040 may be configured to operate a memory array using a memory controller. In other cases, a memory controller may be integrated into the processor 1040. The processor 1040 may be configured to execute computer-readable instructions stored in a memory (e.g., the memory 1030) to cause the device 1005 to perform various functions (e.g., functions or tasks supporting degree selection schemes for Raptor codes in multicast and broadcast services and in unicast services) .

The code 1035 may include instructions to implement aspects of the present disclosure, including instructions to support wireless communications. The code 1035 may be stored in a non-transitory computer-readable medium such as system memory or other type of memory. In some cases, the code 1035 may not be directly executable by the processor 1040 but may cause a computer (e.g., when compiled and executed) to perform functions described herein.

FIG. 11 shows a block diagram 1100 of a device 1105 that supports degree selection schemes for Raptor codes in multicast and broadcast services and in unicast services in accordance with aspects of the present disclosure. The device 1105 may be an example of aspects of a base station 105 as described herein. The device 1105 may include a receiver 1110, a communications manager 1115, and a transmitter 1120. The device 1105 may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses) .

The receiver 1110 may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to degree selection schemes for Raptor codes in multicast and broadcast services and in unicast services, etc. ) . Information may be passed on to other components of the device 1105. The receiver 1110 may be an example of aspects of the transceiver 1420 described with reference to FIG. 14. The receiver 1110 may utilize a single antenna or a set of antennas.

The communications manager 1115 may encode a set of source symbols according to a fountain code to obtain a set of systematic symbols and a set of parity symbols, where each systematic symbol of the set of systematic symbols is associated with a source symbol of the set of source symbols and each parity symbol of the set of parity symbols is associated with a number of source symbols of the set of source symbols according to a respective degree of each parity symbol based on a degree distribution for the set of parity symbols, transmit a first set of packets including the set of systematic symbols, order the set of parity symbols by decreasing degrees based on the degree distribution for the set of parity symbols, and transmit a second set of packets including the set of parity symbols based on the ordering. The communications manager 1115 may be an example of aspects of the communications manager 1410 described herein.

The communications manager 1115, or its sub-components, may be implemented in hardware, code (e.g., software or firmware) executed by a processor, or any combination thereof. If implemented in code executed by a processor, the functions of the communications manager 1115, or its sub-components may be executed by a general-purpose processor, a DSP, an ASIC, an FPGA or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described in the present disclosure.

The communications manager 1115, or its sub-components, may be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations by one or more physical components. In some examples, the communications manager 1115, or its sub-components, may be a separate and distinct component in accordance with various aspects of the present disclosure. In some examples, the communications manager 1115, or its sub-components, may be combined with one or more other hardware components, including but not limited to an I/O component, a transceiver, a network server, another computing device, one or more other components described in the present disclosure, or a combination thereof in accordance with various aspects of the present disclosure.

The transmitter 1120 may transmit signals generated by other components of the device 1105. In some examples, the transmitter 1120 may be collocated with a receiver 1110 in a transceiver module. For example, the transmitter 1120 may be an example of aspects of the transceiver 1420 described with reference to FIG. 14. The transmitter 1120 may utilize a single antenna or a set of antennas.

The communications manager 1115 as described herein may be implemented to realize one or more potential advantages. One implementation may provide for reduced latency for encoding, decoding, and transmitting data messages using coding schemes. For example, the device 1105 (e.g., a transmitting device 1105) may encode a set of parity symbols and the device 1105 may transmit the parity symbols in order of decreasing degrees. By ordering the parity symbols, the device 1105 may allow for a receiving device to receive and decode the high-degree parity symbols first. If the receiving device successfully recovers the source symbols from the high-degree parity symbols, the receiving device may refrain from receiving and decoding each of the remaining parity symbols, which may thereby reduce latency associated with receiving and recovering a data transmission.

In some examples, the transmitting device 1105 may encode a set of systematic symbols, a set of parity symbols, or both, by directly mapping the encoded systematic or parity symbols to a set of source symbols. The transmitting device 1105 may thereby refrain from encoding a set of intermediate symbols, which may reduce latency at the transmitting device. In some examples, the receiving device may transmit a feedback message to the transmitting device 1105. The transmitting device 1105 may determine a degree distribution for transmitting the parity symbols based on the feedback message to improve a reliability associated with the communications and to reduce latency.

FIG. 12 shows a block diagram 1200 of a device 1205 that supports degree selection schemes for Raptor codes in multicast and broadcast services and in unicast services in accordance with aspects of the present disclosure. The device 1205 may be an example of aspects of a device 1105 or a base station 105 as described herein. The device 1205 may include a receiver 1210, a communications manager 1215, and a transmitter 1235. The device 1205 may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses) .

The receiver 1210 may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to degree selection schemes for Raptor codes in multicast and broadcast services and in unicast services, etc. ) . Information may be passed on to other components of the device 1205. The receiver 1210 may be an example of aspects of the transceiver 1420 described with reference to FIG. 14. The receiver 1210 may utilize a single antenna or a set of antennas.

The communications manager 1215 may be an example of aspects of the communications manager 1115 as described herein. The communications manager 1215 may include a symbol encoder 1220, a packet transmitter 1225, and a degree distribution component 1230. The communications manager 1215 may be an example of aspects of the communications manager 1410 described herein.

The symbol encoder 1220 may encode a set of source symbols according to a fountain code to obtain a set of systematic symbols and a set of parity symbols, where each systematic symbol of the set of systematic symbols is associated with a source symbol of the set of source symbols and each parity symbol of the set of parity symbols is associated with a number of source symbols of the set of source symbols according to a respective degree of each parity symbol based on a degree distribution for the set of parity symbols. The packet transmitter 1225 may transmit a first set of packets including the set of systematic symbols. The degree distribution component 1230 may order the set of parity symbols by decreasing degrees based on the degree distribution for the set of parity symbols. The packet transmitter 1225 may transmit a second set of packets including the set of parity symbols based on the ordering.

The transmitter 1235 may transmit signals generated by other components of the device 1205. In some examples, the transmitter 1235 may be collocated with a receiver 1210 in a transceiver module. For example, the transmitter 1235 may be an example of aspects of the transceiver 1420 described with reference to FIG. 14. The transmitter 1235 may utilize a single antenna or a set of antennas.

FIG. 13 shows a block diagram 1300 of a communications manager 1305 that supports degree selection schemes for Raptor codes in multicast and broadcast services and in unicast services in accordance with aspects of the present disclosure. The communications manager 1305 may be an example of aspects of a communications manager 1115, a communications manager 1215, or a communications manager 1410 described herein. The communications manager 1305 may include a symbol encoder 1310, a packet transmitter 1315, a degree distribution component 1320, and a feedback component 1325. Each of these components may communicate, directly or indirectly, with one another (e.g., via one or more buses) .

The symbol encoder 1310 may encode a set of source symbols according to a fountain code to obtain a set of systematic symbols and a set of parity symbols, where each systematic symbol of the set of systematic symbols is associated with a source symbol of the set of source symbols and each parity symbol of the set of parity symbols is associated with a number of source symbols of the set of source symbols according to a respective degree of each parity symbol based on a degree distribution for the set of parity symbols.

The packet transmitter 1315 may transmit a first set of packets including the set of systematic symbols. The degree distribution component 1320 may order the set of parity symbols by decreasing degrees based on the degree distribution for the set of parity symbols. The packet transmitter 1315 may transmit a second set of packets including the set of parity symbols based on the ordering.

The feedback component 1325 may receive a feedback message indicating a feedback parameter, where encoding the set of source symbols according to the fountain code to obtain the set of parity symbols is based on the feedback parameter. In some examples, the degree distribution component 1320 may determine the degree distribution for the set of parity symbols based on the feedback parameter.

In some examples, the feedback message is received in response to the first set of packets, and the feedback parameter includes one or more ACK indicators for a number of systematic symbols of the set of systematic symbols successfully received by a UE, one or more NACK indicators for a number of systematic symbols of the set of systematic symbols unsuccessfully received by the UE, or a combination thereof.

In some other examples, the feedback parameter includes a CQI value, an RSRP value, an RSRQ value, an RSSI value, or a combination thereof.

In some examples, the feedback component 1325 may transmit a message configuring a UE with a feedback schema, where the feedback parameter is based on the feedback schema. In some cases, the message configuring the UE with the feedback schema includes a DCI message, a MAC CE, an RRC configuration message, or a combination thereof.

In some examples, the encoding may involve the symbol encoder 1310 determining, at a first encoding stage, the set of systematic symbols directly from the set of source symbols and determining, at a second encoding stage, the set of parity symbols directly from the set of source symbols based on the feedback parameter satisfying an erasure threshold. In some such examples, determining the set of parity symbols may involve the degree distribution component 1320 selecting, for each parity symbol of the set of parity symbols, a degree from the degree distribution for the set of parity symbols, the symbol encoder 1310 selecting, for each parity symbol of the set of parity symbols, a set of source symbols of the set of source symbols based on the selected degree, and the symbol encoder 1310 combining, for each parity symbol of the set of parity symbols, the selected set of source symbols based on an XOR logic operation to determine each parity symbol of the set of parity symbols.

In some other examples, the encoding may involve the symbol encoder 1310 determining, at a first encoding stage, the set of systematic symbols directly from the set of source symbols and determining, at a second encoding stage, the set of parity symbols from a set of intermediate symbols based on the feedback parameter failing to satisfy an erasure threshold. In some such examples, determining the set of parity symbols may involve the symbol encoder 1310 mapping one or more source symbols of the set of source symbols to each intermediate symbol of the set of intermediate symbols, the degree distribution component 1320 selecting, for each parity symbol of the set of parity symbols, a degree from the degree distribution for the set of parity symbols, the symbol encoder 1310 selecting, for each parity symbol of the set of parity symbols, one or more intermediate symbols of the set of intermediate symbols based on the selected degree, and the symbol encoder 1310 combining, for each parity symbol of the set of parity symbols, the selected one or more intermediate symbols based on an XOR logic operation to determine each parity symbol of the set of parity symbols.

In some examples, transmitting the first set of packets and transmitting the second set of packets may involve the packet transmitter 1315 broadcasting, to a set of UEs, the first set of packets and the second set of packets.

In some examples, transmitting the second set of packets may involve the packet transmitter 1315 transmitting, in a first data block, a first one or more packets of the second set of packets including parity symbols with degrees greater than or equal to a threshold degree value based on the ordering and transmitting, in a second data block subsequent to the first data block, a second one or more packets of the second set of packets including parity symbols with degrees less than or equal to the threshold degree value based on the ordering.

In some cases, the fountain code may be an example of an LT code, a Raptor code, or both.

FIG. 14 shows a diagram of a system 1400 including a device 1405 that supports degree selection schemes for Raptor codes in multicast and broadcast services and in unicast services in accordance with aspects of the present disclosure. The device 1405 may be an example of or include the components of a device 1105, a device 1205, or a base station 105 as described herein. The device 1405 may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including a communications manager 1410, a network communications manager 1415, a transceiver 1420, an antenna 1425, memory 1430, a processor 1440, and an inter-station communications manager 1445. These components may be in electronic communication via one or more buses (e.g., bus 1450) .

The communications manager 1410 may encode a set of source symbols according to a fountain code to obtain a set of systematic symbols and a set of parity symbols, where each systematic symbol of the set of systematic symbols is associated with a source symbol of the set of source symbols and each parity symbol of the set of parity symbols is associated with a number of source symbols of the set of source symbols according to a respective degree of each parity symbol based on a degree distribution for the set of parity symbols, transmit a first set of packets including the set of systematic symbols, order the set of parity symbols by decreasing degrees based on the degree distribution for the set of parity symbols, and transmit a second set of packets including the set of parity symbols based on the ordering.

The network communications manager 1415 may manage communications with the core network 130 (e.g., via one or more wired backhaul links) . For example, the network communications manager 1415 may manage the transfer of data communications for client devices, such as one or more UEs 115.

The transceiver 1420 may communicate bi-directionally, via one or more antennas, wired, or wireless links as described above. For example, the transceiver 1420 may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver. The transceiver 1420 may also include a modem to modulate the packets and provide the modulated packets to the antennas for transmission, and to demodulate packets received from the antennas.

In some cases, the wireless device may include a single antenna 1425. However, in some cases the device may have more than one antenna 1425, which may be capable of concurrently transmitting or receiving multiple wireless transmissions.

The memory 1430 may include RAM, ROM, or a combination thereof. The memory 1430 may store computer-readable code 1435 including instructions that, when executed by a processor (e.g., the processor 1440) cause the device to perform various functions described herein. In some cases, the memory 1430 may contain, among other things, a BIOS which may control basic hardware or software operation such as the interaction with peripheral components or devices.

The processor 1440 may include an intelligent hardware device (e.g., a general-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof) . In some cases, the processor 1440 may be configured to operate a memory array using a memory controller. In some cases, a memory controller may be integrated into processor 1440. The processor 1440 may be configured to execute computer-readable instructions stored in a memory (e.g., the memory 1430) to cause the device 1405 to perform various functions (e.g., functions or tasks supporting degree selection schemes for Raptor codes in multicast and broadcast services and in unicast services) .

The inter-station communications manager 1445 may manage communications with other base station 105, and may include a controller or scheduler for controlling communications with UEs 115 in cooperation with other base stations 105. For example, the inter-station communications manager 1445 may coordinate scheduling for transmissions to UEs 115 for various interference mitigation techniques such as beamforming or joint transmission. In some examples, the inter-station communications manager 1445 may provide an X2 interface within an LTE/LTE-A wireless communication network technology to provide communication between base stations 105.

The code 1435 may include instructions to implement aspects of the present disclosure, including instructions to support wireless communications. The code 1435 may be stored in a non-transitory computer-readable medium such as system memory or other type of memory. In some cases, the code 1435 may not be directly executable by the processor 1440 but may cause a computer (e.g., when compiled and executed) to perform functions described herein.

FIG. 15 shows a flowchart illustrating a method 1500 that supports degree selection schemes for Raptor codes in multicast and broadcast services and in unicast services in accordance with aspects of the present disclosure. The operations of method 1500 may be implemented by a base station 105 or its components as described herein. For example, the operations of method 1500 may be performed by a communications manager as described with reference to FIGs. 11 through 14. In some examples, a base station may execute a set of instructions to control the functional elements of the base station to perform the functions described below. Additionally or alternatively, a base station may perform aspects of the functions described below using special-purpose hardware.

At 1505, the base station may encode a set of source symbols according to a fountain code to obtain a set of systematic symbols and a set of parity symbols, where each systematic symbol of the set of systematic symbols is associated with a source symbol of the set of source symbols and each parity symbol of the set of parity symbols is associated with a number of source symbols of the set of source symbols according to a respective degree of each parity symbol based on a degree distribution for the set of parity symbols. The operations of 1505 may be performed according to the methods described herein. In some examples, aspects of the operations of 1505 may be performed by a symbol encoder as described with reference to FIGs. 11 through 14.

At 1510, the base station may transmit a first set of packets including the set of systematic symbols. The operations of 1510 may be performed according to the methods described herein. In some examples, aspects of the operations of 1510 may be performed by a packet transmitter as described with reference to FIGs. 11 through 14.

At 1515, the base station may order the set of parity symbols by decreasing degrees based on the degree distribution for the set of parity symbols. The operations of 1515 may be performed according to the methods described herein. In some examples, aspects of the operations of 1515 may be performed by a degree distribution component as described with reference to FIGs. 11 through 14.

At 1520, the base station may transmit a second set of packets including the set of parity symbols based on the ordering. The operations of 1520 may be performed according to the methods described herein. In some examples, aspects of the operations of 1520 may be performed by a packet transmitter as described with reference to FIGs. 11 through 14.

FIG. 16 shows a flowchart illustrating a method 1600 that supports degree selection schemes for Raptor codes in multicast and broadcast services and in unicast services in accordance with aspects of the present disclosure. The operations of method 1600 may be implemented by a base station 105 or its components as described herein. For example, the operations of method 1600 may be performed by a communications manager as described with reference to FIGs. 11 through 14. In some examples, a base station may execute a set of instructions to control the functional elements of the base station to perform the functions described below. Additionally or alternatively, a base station may perform aspects of the functions described below using special-purpose hardware.

At 1605, the base station may encode a set of source symbols according to a fountain code to obtain a set of systematic symbols, where each systematic symbol of the set of systematic symbols is associated with a source symbol of the set of source symbols. The operations of 1605 may be performed according to the methods described herein. In some examples, aspects of the operations of 1605 may be performed by a symbol encoder as described with reference to FIGs. 11 through 14.

At 1610, the base station may transmit a first set of packets including the set of systematic symbols. The operations of 1610 may be performed according to the methods described herein. In some examples, aspects of the operations of 1610 may be performed by a packet transmitter as described with reference to FIGs. 11 through 14.

At 1615, the base station may receive a feedback message indicating a feedback parameter. The operations of 1615 may be performed according to the methods described herein. In some examples, aspects of the operations of 1615 may be performed by a feedback component as described with reference to FIGs. 11 through 14.

At 1620, the base station may determine a degree distribution for a set of parity symbols based on the feedback parameter. The operations of 1620 may be performed according to the methods described herein. In some examples, aspects of the operations of 1620 may be performed by a degree distribution component as described with reference to FIGs. 11 through 14.

At 1625, the base station may encode the set of source symbols according to the fountain code to obtain the set of parity symbols, where each parity symbol of the set of parity symbols is associated with a number of source symbols of the set of source symbols according to a respective degree of each parity symbol based on the degree distribution for the set of parity symbols. The encoding the set of source symbols according to the fountain code to obtain the set of parity symbols may be based on the feedback parameter. The operations of 1625 may be performed according to the methods described herein. In some examples, aspects of the operations of 1625 may be performed by a symbol encoder as described with reference to FIGs. 11 through 14.

At 1630, the base station may order the set of parity symbols by decreasing degrees based on the degree distribution for the set of parity symbols. The operations of 1630 may be performed according to the methods described herein. In some examples, aspects of the operations of 1630 may be performed by a degree distribution component as described with reference to FIGs. 11 through 14.

At 1635, the base station may transmit a second set of packets including the set of parity symbols based on the ordering. The operations of 1635 may be performed according to the methods described herein. In some examples, aspects of the operations of 1635 may be performed by a packet transmitter as described with reference to FIGs. 11 through 14.

FIG. 17 shows a flowchart illustrating a method 1700 that supports degree selection schemes for Raptor codes in multicast and broadcast services and in unicast services in accordance with aspects of the present disclosure. The operations of method 1700 may be implemented by a UE 115 or its components as described herein. For example, the operations of method 1700 may be performed by a communications manager as described with reference to FIGs. 7 through 10. In some examples, a UE may execute a set of instructions to control the functional elements of the UE to perform the functions described below. Additionally or alternatively, a UE may perform aspects of the functions described below using special-purpose hardware.

At 1705, the UE may receive a first set of packets including a set of systematic symbols, where each systematic symbol of the set of systematic symbols is associated with a source symbol of a set of source symbols. The operations of 1705 may be performed according to the methods described herein. In some examples, aspects of the operations of 1705 may be performed by a systematic symbol component as described with reference to FIGs. 7 through 10.

At 1710, the UE may decode the first set of packets according to a fountain code to recover a first subset of the set of source symbols. The operations of 1710 may be performed according to the methods described herein. In some examples, aspects of the operations of 1710 may be performed by a symbol decoder as described with reference to FIGs. 7 through 10.

At 1715, the UE may receive a second set of packets including a set of parity symbols, where each parity symbol of the set of parity symbols is associated with a number of source symbols of the set of source symbols according to a respective degree of each parity symbol based on a degree distribution for the set of parity symbols, and where the second set of packets is received in an order according to decreasing degrees of parity symbols in each packet of the second set of packets. The operations of 1715 may be performed according to the methods described herein. In some examples, aspects of the operations of 1715 may be performed by a parity symbol component as described with reference to FIGs. 7 through 10.

At 1720, the UE may decode the second set of packets according to the fountain code to recover a second subset of the set of source symbols based on the recovered first subset of the set of source symbols, where the set of source symbols is recovered based on decoding the first set of packets and decoding the second set of packets. The operations of 1720 may be performed according to the methods described herein. In some examples, aspects of the operations of 1720 may be performed by a symbol decoder as described with reference to FIGs. 7 through 10.

FIG. 18 shows a flowchart illustrating a method 1800 that supports degree selection schemes for Raptor codes in multicast and broadcast services and in unicast services in accordance with aspects of the present disclosure. The operations of method 1800 may be implemented by a UE 115 or its components as described herein. For example, the operations of method 1800 may be performed by a communications manager as described with reference to FIGs. 7 through 10. In some examples, a UE may execute a set of instructions to control the functional elements of the UE to perform the functions described below. Additionally or alternatively, a UE may perform aspects of the functions described below using special-purpose hardware.

At 1805, the UE may receive a first set of packets including a set of systematic symbols, where each systematic symbol of the set of systematic symbols is associated with a source symbol of a set of source symbols. The operations of 1805 may be performed according to the methods described herein. In some examples, aspects of the operations of 1805 may be performed by a systematic symbol component as described with reference to FIGs. 7 through 10.

At 1810, the UE may decode the first set of packets according to a fountain code to recover a first subset of the set of source symbols. The operations of 1810 may be performed according to the methods described herein. In some examples, aspects of the operations of 1810 may be performed by a symbol decoder as described with reference to FIGs. 7 through 10.

At 1815, the UE may transmit a feedback message indicating a feedback parameter. The operations of 1815 may be performed according to the methods described herein. In some examples, aspects of the operations of 1815 may be performed by a feedback component as described with reference to FIGs. 7 through 10.

At 1820, the UE may receive a second set of packets including a set of parity symbols, where each parity symbol of the set of parity symbols is associated with a number of source symbols of the set of source symbols according to a respective degree of each parity symbol based on a degree distribution for the set of parity symbols, and where the second set of packets is received in an order according to decreasing degrees of parity symbols in each packet of the second set of packets. The degree distribution for the set of parity symbols may be based on the feedback parameter. The operations of 1820 may be performed according to the methods described herein. In some examples, aspects of the operations of 1820 may be performed by a parity symbol component as described with reference to FIGs. 7 through 10.

At 1825, the UE may decode the second set of packets according to the fountain code to recover a second subset of the set of source symbols based on the recovered first subset of the set of source symbols, where the set of source symbols is recovered based on decoding the first set of packets and decoding the second set of packets. The operations of 1825 may be performed according to the methods described herein. In some examples, aspects of the operations of 1825 may be performed by a symbol decoder as described with reference to FIGs. 7 through 10.

It should be noted that the methods described herein describe possible implementations, and that the operations and the steps may be rearranged or otherwise modified and that other implementations are possible. Further, aspects from two or more of the methods may be combined.

The following provides an overview of examples of the present disclosure:

Example 1: A method for wireless communications, comprising: encoding a set of source symbols according to a fountain code to obtain a set of systematic symbols and a set of parity symbols, wherein each systematic symbol of the set of systematic symbols is associated with a source symbol of the set of source symbols and each parity symbol of the set of parity symbols is associated with a number of source symbols of the set of source symbols according to a respective degree of each parity symbol based at least in part on a degree distribution for the set of parity symbols; transmitting a first set of packets comprising the set of systematic symbols; ordering the set of parity symbols by decreasing degrees based at least in part on the degree distribution for the set of parity symbols; and transmitting a second set of packets comprising the set of parity symbols based at least in part on the ordering.

Example 2: The method of example 1, further comprising: receiving a feedback message indicating a feedback parameter, wherein encoding the set of source symbols according to the fountain code to obtain the set of parity symbols is based at least in part on the feedback parameter.

Example 3: The method of example 2, further comprising: determining the degree distribution for the set of parity symbols based at least in part on the feedback parameter.

Example 4: The method of any one of examples 2 and 3, wherein: the feedback message is received in response to the first set of packets; and the feedback parameter comprises one or more ACK indicators for a number of systematic symbols of the set of systematic symbols successfully received by a UE, one or more NACK indicators for a number of systematic symbols of the set of systematic symbols unsuccessfully received by the UE, or a combination thereof.

Example 5: The method of any one of examples 2 through 4, wherein the feedback parameter comprises a CQI value, an RSRP value, an RSRQ value, an RSSI value, or a combination thereof.

Example 6: The method of any one of examples 2 through 5, further comprising: transmitting a message configuring a UE with a feedback schema, wherein the feedback parameter is based at least in part on the feedback schema.

Example 7: The method of example 6, wherein the message configuring the UE with the feedback schema comprises a DCI message, a MAC CE, an RRC configuration message, or a combination thereof.

Example 8: The method of any one of examples 2 through 7, wherein the encoding comprises: determining, at a first encoding stage, the set of systematic symbols directly from the set of source symbols; and determining, at a second encoding stage, the set of parity symbols directly from the set of source symbols based at least in part on the feedback parameter satisfying an erasure threshold.

Example 9: The method of example 8, wherein determining the set of parity symbols comprises: selecting, for each parity symbol of the set of parity symbols, a degree from the degree distribution for the set of parity symbols; selecting, for each parity symbol of the set of parity symbols, a plurality of source symbols of the set of source symbols based at least in part on the selected degree; and combining, for each parity symbol of the set of parity symbols, the selected plurality of source symbols based at least in part on an XOR logic operation to determine each parity symbol of the set of parity symbols.

Example 10: The method of any one of examples 2 through 7, wherein the encoding comprises: determining, at a first encoding stage, the set of systematic symbols directly from the set of source symbols; and determining, at a second encoding stage, the set of parity symbols from a set of intermediate symbols based at least in part on the feedback parameter failing to satisfy an erasure threshold.

Example 11: The method of example 10, wherein determining the set of parity symbols comprises: mapping one or more source symbols of the set of source symbols to each intermediate symbol of the set of intermediate symbols; selecting, for each parity symbol of the set of parity symbols, a degree from the degree distribution for the set of parity symbols; selecting, for each parity symbol of the set of parity symbols, one or more intermediate symbols of the set of intermediate symbols based at least in part on the selected degree; and combining, for each parity symbol of the set of parity symbols, the selected one or more intermediate symbols based at least in part on an XOR logic operation to determine each parity symbol of the set of parity symbols.

Example 12: The method of any one of examples 1 through 11, wherein transmitting the first set of packets and transmitting the second set of packets comprise: broadcasting, to a plurality of UEs, the first set of packets and the second set of packets.

Example 13: The method of any one of examples 1 through 12, wherein transmitting the second set of packets comprises: transmitting, in a first data block, a first one or more packets of the second set of packets comprising parity symbols with degrees greater than or equal to a threshold degree value based at least in part on the ordering; and transmitting, in a second data block subsequent to the first data block, a second one or more packets of the second set of packets comprising parity symbols with degrees less than or equal to the threshold degree value based at least in part on the ordering.

Example 14: The method of any one of examples 1 through 13, wherein the fountain code comprises an LT code, a Raptor code, or both.

Example 15: A method for wireless communications, comprising: receiving a first set of packets comprising a set of systematic symbols, wherein each systematic symbol of the set of systematic symbols is associated with a source symbol of a set of source symbols; decoding the first set of packets according to a fountain code to recover a first subset of the set of source symbols; receiving a second set of packets comprising a set of parity symbols, wherein each parity symbol of the set of parity symbols is associated with a number of source symbols of the set of source symbols according to a respective degree of each parity symbol based at least in part on a degree distribution for the set of parity symbols, and wherein the second set of packets is received in an order according to decreasing degrees of parity symbols in each packet of the second set of packets; and decoding the second set of packets according to the fountain code to recover a second subset of the set of source symbols based at least in part on the recovered first subset of the set of source symbols, wherein the set of source symbols is recovered based at least in part on decoding the first set of packets and decoding the second set of packets.

Example 16: The method of example 15, further comprising: transmitting a feedback message indicating a feedback parameter, wherein the degree distribution for the set of parity symbols is based at least in part on the feedback parameter.

Example 17: The method of example 16, wherein: the feedback parameter comprises one or more ACK indicators for the first subset of the set of source symbols successfully recovered from the first set of packets, one or more NACK indicators for the second subset of the set of source symbols unsuccessfully recovered from the first set of packets, or a combination thereof; and the feedback message is transmitted in response to the first set of packets.

Example 18: The method of any one of examples 16 and 17, further comprising: performing a channel measurement procedure to determine the feedback parameter, wherein the feedback parameter comprises a CQI value, an RSRP value, an RSRQ value, an RSSI value, or a combination thereof.

Example 19: The method of any one of examples 16 through 18, further comprising: receiving a message configuring a feedback schema, wherein the feedback parameter is based at least in part on the feedback schema.

Example 20: The method of example 19, wherein the message configuring the feedback schema comprises a DCI message, a MAC CE, an RRC configuration message, or a combination thereof.

Example 21: The method of any one of examples 16 through 20, wherein: the decoding the first set of packets comprises: determining, at a first decoding stage, the first subset of the set of source symbols directly from the set of systematic symbols; and the decoding the second set of packets comprises: determining, at a second decoding stage, the second subset of the set of source symbols directly from the set of parity symbols based at least in part on the feedback parameter satisfying an erasure threshold.

Example 22: The method of any one of examples 16 through 20, wherein: the decoding the first set of packets comprises: determining, at a first decoding stage, the first subset of the set of source symbols directly from the set of systematic symbols; and the decoding the second set of packets comprises: determining, at a second decoding stage, the second subset of the set of source symbols from the set of parity symbols via a set of intermediate symbols based at least in part on the feedback parameter failing to satisfy an erasure threshold.

Example 23: The method of any one of examples 15 through 22, further comprising: refraining from receiving at least one packet comprising additional parity symbols based at least in part on recovering the set of source symbols.

Example 24: The method of example 23, further comprising: entering a low power mode based at least in part on recovering the set of source symbols and prior to transmission of the at least one packet comprising additional parity symbols.

Example 25: The method of any one of examples 15 through 24, wherein receiving the second set of packets comprises: receiving, in a first data block, a first one or more packets of the second set of packets comprising parity symbols with degrees greater than or equal to a threshold degree value based at least in part on the order; and receiving, in a second data block subsequent to the first data block, a second one or more packets of the second set of packets comprising parity symbols with degrees less than or equal to the threshold degree value based at least in part on the order.

Example 26: The method of any one of examples 15 through 25, wherein the fountain code comprises an LT code, a Raptor code, or both.

Example 27: An apparatus for wireless communication comprising at least one means for performing a method of any one of examples 1 through 14.

Example 28: An apparatus for wireless communication comprising a processor, memory coupled with the processor, and instructions stored in the memory and executable by the processor to cause the apparatus to perform a method of any one of examples 1 through 14.

Example 29: A non-transitory computer-readable medium storing code for wireless communication, the code comprising instructions executable by a processor to perform a method of any one of examples 1 through 14.

Example 30: An apparatus for wireless communication comprising at least one means for performing a method of any one of examples 15 through 26.

Example 31: An apparatus for wireless communication comprising a processor, memory coupled with the processor, and instructions stored in the memory and executable by the processor to cause the apparatus to perform a method of any one of examples 15 through 26.

Example 32: A non-transitory computer-readable medium storing code for wireless communication, the code comprising instructions executable by a processor to perform a method of any one of examples 15 through 26.

Although aspects of an LTE, LTE-A, LTE-A Pro, or NR system may be described for purposes of example, and LTE, LTE-A, LTE-A Pro, or NR terminology may be used in much of the description, the techniques described herein are applicable beyond LTE, LTE-A, LTE-A Pro, or NR networks. For example, the described techniques may be applicable to various other wireless communications systems such as Ultra Mobile Broadband (UMB) , Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi) , IEEE 802.16 (WiMAX) , IEEE 802.20, Flash-OFDM, as well as other systems and radio technologies not explicitly mentioned herein.

Information and signals described herein may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

The various illustrative blocks and components described in connection with the disclosure herein may be implemented or performed with a general-purpose processor, a DSP, an ASIC, a CPU, an FPGA or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices (e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration) .

The functions described herein may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Other examples and implementations are within the scope of the disclosure and appended claims. For example, due to the nature of software, functions described herein may be implemented using software executed by a processor, hardware, firmware, hardwiring, or combinations of any of these. Features implementing functions may also be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations.

Computer-readable media includes both non-transitory computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A non-transitory storage medium may be any available medium that may be accessed by a general-purpose or special-purpose computer. By way of example, and not limitation, non-transitory computer-readable media may include RAM, ROM, electrically erasable programmable ROM (EEPROM) , flash memory, compact disk (CD) ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other non-transitory medium that may be used to carry or store desired program code means in the form of instructions or data structures and that may be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL) , or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of computer-readable medium. Disk and disc, as used herein, include CD, laser disc, optical disc, digital versatile disc (DVD) , floppy disk and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above are also included within the scope of computer-readable media.

As used herein, including in the claims, “or” as used in a list of items (e.g., a list of items prefaced by a phrase such as “at least one of” or “one or more of” ) indicates an inclusive list such that, for example, a list of at least one of A, B, or C means A or B or C or AB or AC or BC or ABC (i.e., A and B and C) . Also, as used herein, the phrase “based on” shall not be construed as a reference to a closed set of conditions. For example, an example step that is described as “based on condition A” may be based on both a condition A and a condition B without departing from the scope of the present disclosure. In other words, as used herein, the phrase “based on” shall be construed in the same manner as the phrase “based at least in part on. ”

In the appended figures, similar components or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a dash and a second label that distinguishes among the similar components. If just the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label, or other subsequent reference label.

The description set forth herein, in connection with the appended drawings, describes example configurations and does not represent all the examples that may be implemented or that are within the scope of the claims. The term “example” used herein means “serving as an example, instance, or illustration, ” and not “preferred” or “advantageous over other examples. ” The detailed description includes specific details for the purpose of providing an understanding of the described techniques. These techniques, however, may be practiced without these specific details. In some instances, known structures and devices are shown in block diagram form in order to avoid obscuring the concepts of the described examples.

The description herein is provided to enable a person having ordinary skill in the art to make or use the disclosure. Various modifications to the disclosure will be apparent to a person having ordinary skill in the art, and the generic principles defined herein may be applied to other variations without departing from the scope of the disclosure. Thus, the disclosure is not limited to the examples and designs described herein, but is to be accorded the broadest scope consistent with the principles and novel features disclosed herein.

Claims

A method for wireless communications, comprising:

encoding a set of source symbols according to a fountain code to obtain a set of systematic symbols and a set of parity symbols, wherein each systematic symbol of the set of systematic symbols is associated with a source symbol of the set of source symbols and each parity symbol of the set of parity symbols is associated with a number of source symbols of the set of source symbols according to a respective degree of each parity symbol based at least in part on a degree distribution for the set of parity symbols;

transmitting a first set of packets comprising the set of systematic symbols;

ordering the set of parity symbols by decreasing degrees based at least in part on the degree distribution for the set of parity symbols; and

transmitting a second set of packets comprising the set of parity symbols based at least in part on the ordering.
The method of claim 1, further comprising:

receiving a feedback message indicating a feedback parameter, wherein encoding the set of source symbols according to the fountain code to obtain the set of parity symbols is based at least in part on the feedback parameter.
The method of claim 2, further comprising:

determining the degree distribution for the set of parity symbols based at least in part on the feedback parameter.
The method of claim 2, wherein:

the feedback message is received in response to the first set of packets; and

the feedback parameter comprises one or more positive acknowledgment indicators for a number of systematic symbols of the set of systematic symbols successfully received by a user equipment (UE) , one or more negative acknowledgment indicators for a number of systematic symbols of the set of systematic symbols unsuccessfully received by the UE, or a combination thereof.
The method of claim 2, wherein the feedback parameter comprises a channel quality indicator value, a reference signal received power value, a reference signal received quality value, a received signal strength indicator value, or a combination thereof.
The method of claim 2, further comprising:

transmitting a message configuring a user equipment (UE) with a feedback schema, wherein the feedback parameter is based at least in part on the feedback schema.
The method of claim 6, wherein the message configuring the UE with the feedback schema comprises a downlink control information message, a medium access control control element, a radio resource control configuration message, or a combination thereof.
The method of claim 2, wherein the encoding comprises:

determining, at a first encoding stage, the set of systematic symbols directly from the set of source symbols; and

determining, at a second encoding stage, the set of parity symbols directly from the set of source symbols based at least in part on the feedback parameter satisfying an erasure threshold.
The method of claim 8, wherein determining the set of parity symbols comprises:

selecting, for each parity symbol of the set of parity symbols, a degree from the degree distribution for the set of parity symbols;

selecting, for each parity symbol of the set of parity symbols, a plurality of source symbols of the set of source symbols based at least in part on the selected degree; and

combining, for each parity symbol of the set of parity symbols, the selected plurality of source symbols based at least in part on an exclusive OR logic operation to determine each parity symbol of the set of parity symbols.
The method of claim 2, wherein the encoding comprises:

determining, at a first encoding stage, the set of systematic symbols directly from the set of source symbols; and

determining, at a second encoding stage, the set of parity symbols from a set of intermediate symbols based at least in part on the feedback parameter failing to satisfy an erasure threshold.
The method of claim 10, wherein determining the set of parity symbols comprises:

mapping one or more source symbols of the set of source symbols to each intermediate symbol of the set of intermediate symbols;

selecting, for each parity symbol of the set of parity symbols, a degree from the degree distribution for the set of parity symbols;

selecting, for each parity symbol of the set of parity symbols, one or more intermediate symbols of the set of intermediate symbols based at least in part on the selected degree; and

combining, for each parity symbol of the set of parity symbols, the selected one or more intermediate symbols based at least in part on an exclusive OR logic operation to determine each parity symbol of the set of parity symbols.
The method of claim 1, wherein transmitting the first set of packets and transmitting the second set of packets comprise:

broadcasting, to a plurality of user equipments (UEs) , the first set of packets and the second set of packets.
The method of claim 1, wherein transmitting the second set of packets comprises:

transmitting, in a first data block, a first one or more packets of the second set of packets comprising parity symbols with degrees greater than or equal to a threshold degree value based at least in part on the ordering; and

transmitting, in a second data block subsequent to the first data block, a second one or more packets of the second set of packets comprising parity symbols with degrees less than or equal to the threshold degree value based at least in part on the ordering.
The method of claim 1, wherein the fountain code comprises a Luby transform (LT) code, a rapid tornado (Raptor) code, or both.
A method for wireless communications, comprising:

receiving a first set of packets comprising a set of systematic symbols, wherein each systematic symbol of the set of systematic symbols is associated with a source symbol of a set of source symbols;

decoding the first set of packets according to a fountain code to recover a first subset of the set of source symbols;

receiving a second set of packets comprising a set of parity symbols, wherein each parity symbol of the set of parity symbols is associated with a number of source symbols of the set of source symbols according to a respective degree of each parity symbol based at least in part on a degree distribution for the set of parity symbols, and wherein the second set of packets is received in an order according to decreasing degrees of parity symbols in each packet of the second set of packets; and

decoding the second set of packets according to the fountain code to recover a second subset of the set of source symbols based at least in part on the recovered first subset of the set of source symbols, wherein the set of source symbols is recovered based at least in part on decoding the first set of packets and decoding the second set of packets.
The method of claim 15, further comprising:

transmitting a feedback message indicating a feedback parameter, wherein the degree distribution for the set of parity symbols is based at least in part on the feedback parameter.
The method of claim 16, wherein:

the feedback parameter comprises one or more positive acknowledgment indicators for the first subset of the set of source symbols successfully recovered from the first set of packets, one or more negative acknowledgment indicators for the second subset of the set of source symbols unsuccessfully recovered from the first set of packets, or a combination thereof; and

the feedback message is transmitted in response to the first set of packets.
The method of claim 16, further comprising:

performing a channel measurement procedure to determine the feedback parameter, wherein the feedback parameter comprises a channel quality indicator value, a reference signal received power value, a reference signal received quality value, a received signal strength indicator value, or a combination thereof.
The method of claim 16, further comprising:

receiving a message configuring a feedback schema, wherein the feedback parameter is based at least in part on the feedback schema.
The method of claim 19, wherein the message configuring the feedback schema comprises a downlink control information message, a medium access control control element, a radio resource control configuration message, or a combination thereof.
The method of claim 16, wherein:

the decoding the first set of packets comprises:

determining, at a first decoding stage, the first subset of the set of source symbols directly from the set of systematic symbols; and

the decoding the second set of packets comprises:

determining, at a second decoding stage, the second subset of the set of source symbols directly from the set of parity symbols based at least in part on the feedback parameter satisfying an erasure threshold.
The method of claim 16, wherein:

the decoding the first set of packets comprises:

determining, at a first decoding stage, the first subset of the set of source symbols directly from the set of systematic symbols; and

the decoding the second set of packets comprises:

determining, at a second decoding stage, the second subset of the set of source symbols from the set of parity symbols via a set of intermediate symbols based at least in part on the feedback parameter failing to satisfy an erasure threshold.
The method of claim 15, further comprising:

refraining from receiving at least one packet comprising additional parity symbols based at least in part on recovering the set of source symbols.
The method of claim 23, further comprising:

entering a low power mode based at least in part on recovering the set of source symbols and prior to transmission of the at least one packet comprising additional parity symbols.
The method of claim 15, wherein receiving the second set of packets comprises:

receiving, in a first data block, a first one or more packets of the second set of packets comprising parity symbols with degrees greater than or equal to a threshold degree value based at least in part on the order; and

receiving, in a second data block subsequent to the first data block, a second one or more packets of the second set of packets comprising parity symbols with degrees less than or equal to the threshold degree value based at least in part on the order.
The method of claim 15, wherein the fountain code comprises a Luby transform (LT) code, a rapid tornado (Raptor) code, or both.
An apparatus for wireless communications, comprising:

a processor;

memory coupled with the processor; and

instructions stored in the memory and executable by the processor to cause the apparatus to:

encode a set of source symbols according to a fountain code to obtain a set of systematic symbols and a set of parity symbols, wherein each systematic symbol of the set of systematic symbols is associated with a source symbol of the set of source symbols and each parity symbol of the set of parity symbols is associated with a number of source symbols of the set of source symbols according to a respective degree of each parity symbol based at least in part on a degree distribution for the set of parity symbols;

transmit a first set of packets comprising the set of systematic symbols;

order the set of parity symbols by decreasing degrees based at least in part on the degree distribution for the set of parity symbols; and

transmit a second set of packets comprising the set of parity symbols based at least in part on the ordering.
The apparatus of claim 27, wherein the instructions are further executable by the processor to cause the apparatus to:

receive a feedback message indicating a feedback parameter, wherein encoding the set of source symbols according to the fountain code to obtain the set of parity symbols is based at least in part on the feedback parameter.
The apparatus of claim 28, wherein the instructions are further executable by the processor to cause the apparatus to:

determine the degree distribution for the set of parity symbols based at least in part on the feedback parameter.
The apparatus of claim 28, wherein:

the feedback message is received in response to the first set of packets; and

the feedback parameter comprises one or more positive acknowledgment indicators for a number of systematic symbols of the set of systematic symbols successfully received by a user equipment (UE) , one or more negative acknowledgment indicators for a number of systematic symbols of the set of systematic symbols unsuccessfully received by the UE, or a combination thereof.
The apparatus of claim 28, wherein the feedback parameter comprises a channel quality indicator value, a reference signal received power value, a reference signal received quality value, a received signal strength indicator value, or a combination thereof.
The apparatus of claim 28, wherein the instructions are further executable by the processor to cause the apparatus to:

transmit a message configuring a user equipment (UE) with a feedback schema, wherein the feedback parameter is based at least in part on the feedback schema.
The apparatus of claim 32, wherein the message configuring the UE with the feedback schema comprises a downlink control information message, a medium access control control element, a radio resource control configuration message, or a combination thereof.
The apparatus of claim 28, wherein the instructions to encode are executable by the processor to cause the apparatus to:

determine, at a first encoding stage, the set of systematic symbols directly from the set of source symbols; and

determine, at a second encoding stage, the set of parity symbols directly from the set of source symbols based at least in part on the feedback parameter satisfying an erasure threshold.
The apparatus of claim 34, wherein the instructions to determine the set of parity symbols are executable by the processor to cause the apparatus to:

select, for each parity symbol of the set of parity symbols, a degree from the degree distribution for the set of parity symbols;

select, for each parity symbol of the set of parity symbols, a plurality of source symbols of the set of source symbols based at least in part on the selected degree; and

combine, for each parity symbol of the set of parity symbols, the selected plurality of source symbols based at least in part on an exclusive OR logic operation to determine each parity symbol of the set of parity symbols.
The apparatus of claim 28, wherein the instructions to encode are executable by the processor to cause the apparatus to:

determine, at a first encoding stage, the set of systematic symbols directly from the set of source symbols; and

determine, at a second encoding stage, the set of parity symbols from a set of intermediate symbols based at least in part on the feedback parameter failing to satisfy an erasure threshold.
The apparatus of claim 36, wherein the instructions to determine the set of parity symbols are executable by the processor to cause the apparatus to:

map one or more source symbols of the set of source symbols to each intermediate symbol of the set of intermediate symbols;

select, for each parity symbol of the set of parity symbols, a degree from the degree distribution for the set of parity symbols;

select, for each parity symbol of the set of parity symbols, one or more intermediate symbols of the set of intermediate symbols based at least in part on the selected degree; and

combine, for each parity symbol of the set of parity symbols, the selected one or more intermediate symbols based at least in part on an exclusive OR logic operation to determine each parity symbol of the set of parity symbols.
The apparatus of claim 27, wherein the instructions to transmit the first set of packets and transmit the second set of packets are executable by the processor to cause the apparatus to:

broadcast, to a plurality of user equipments (UEs) , the first set of packets and the second set of packets.
The apparatus of claim 27, wherein the instructions to transmit the second set of packets are executable by the processor to cause the apparatus to:

transmit, in a first data block, a first one or more packets of the second set of packets comprising parity symbols with degrees greater than or equal to a threshold degree value based at least in part on the ordering; and

transmit, in a second data block subsequent to the first data block, a second one or more packets of the second set of packets comprising parity symbols with degrees less than or equal to the threshold degree value based at least in part on the ordering.
The apparatus of claim 27, wherein the fountain code comprises a Luby transform (LT) code, a rapid tornado (Raptor) code, or both.
An apparatus for wireless communications, comprising:

a processor;

memory coupled with the processor; and

instructions stored in the memory and executable by the processor to cause the apparatus to:

receive a first set of packets comprising a set of systematic symbols, wherein each systematic symbol of the set of systematic symbols is associated with a source symbol of a set of source symbols;

decode the first set of packets according to a fountain code to recover a first subset of the set of source symbols;

receive a second set of packets comprising a set of parity symbols, wherein each parity symbol of the set of parity symbols is associated with a number of source symbols of the set of source symbols according to a respective degree of each parity symbol based at least in part on a degree distribution for the set of parity symbols, and wherein the second set of packets is received in an order according to decreasing degrees of parity symbols in each packet of the second set of packets; and

decode the second set of packets according to the fountain code to recover a second subset of the set of source symbols based at least in part on the recovered first subset of the set of source symbols, wherein the set of source symbols is recovered based at least in part on decoding the first set of packets and decoding the second set of packets.
The apparatus of claim 41, wherein the instructions are further executable by the processor to cause the apparatus to:

transmit a feedback message indicating a feedback parameter, wherein the degree distribution for the set of parity symbols is based at least in part on the feedback parameter.
The apparatus of claim 42, wherein:

the feedback parameter comprises one or more positive acknowledgment indicators for the first subset of the set of source symbols successfully recovered from the first set of packets, one or more negative acknowledgment indicators for the second subset of the set of source symbols unsuccessfully recovered from the first set of packets, or a combination thereof; and

the feedback message is transmitted in response to the first set of packets.
The apparatus of claim 42, wherein the instructions are further executable by the processor to cause the apparatus to:

perform a channel measurement procedure to determine the feedback parameter, wherein the feedback parameter comprises a channel quality indicator value, a reference signal received power value, a reference signal received quality value, a received signal strength indicator value, or a combination thereof.
The apparatus of claim 42, wherein the instructions are further executable by the processor to cause the apparatus to:

receive a message configuring a feedback schema, wherein the feedback parameter is based at least in part on the feedback schema.
The apparatus of claim 45, wherein the message configuring the feedback schema comprises a downlink control information message, a medium access control control element, a radio resource control configuration message, or a combination thereof.
The apparatus of claim 42, wherein:

the instructions to decode the first set of packets are executable by the processor to cause the apparatus to:

determine, at a first decoding stage, the first subset of the set of source symbols directly from the set of systematic symbols; and

the instructions to decode the second set of packets are executable by the processor to cause the apparatus to:

determine, at a second decoding stage, the second subset of the set of source symbols directly from the set of parity symbols based at least in part on the feedback parameter satisfying an erasure threshold.
The apparatus of claim 42, wherein:

the instructions to decode the first set of packets are executable by the processor to cause the apparatus to:

determine, at a first decoding stage, the first subset of the set of source symbols directly from the set of systematic symbols; and

the instructions to decode the second set of packets are executable by the processor to cause the apparatus to:

determine, at a second decoding stage, the second subset of the set of source symbols from the set of parity symbols via a set of intermediate symbols based at least in part on the feedback parameter failing to satisfy an erasure threshold.
The apparatus of claim 41, wherein the instructions are further executable by the processor to cause the apparatus to:

refrain from receiving at least one packet comprising additional parity symbols based at least in part on recovering the set of source symbols.
The apparatus of claim 49, wherein the instructions are further executable by the processor to cause the apparatus to:

enter a low power mode based at least in part on recovering the set of source symbols and prior to transmission of the at least one packet comprising additional parity symbols.
The apparatus of claim 41, wherein the instructions to receive the second set of packets are executable by the processor to cause the apparatus to:

receive, in a first data block, a first one or more packets of the second set of packets comprising parity symbols with degrees greater than or equal to a threshold degree value based at least in part on the order; and

receive, in a second data block subsequent to the first data block, a second one or more packets of the second set of packets comprising parity symbols with degrees less than or equal to the threshold degree value based at least in part on the order.
The apparatus of claim 41, wherein the fountain code comprises a Luby transform (LT) code, a rapid tornado (Raptor) code, or both.
An apparatus for wireless communications, comprising:

means for encoding a set of source symbols according to a fountain code to obtain a set of systematic symbols and a set of parity symbols, wherein each systematic symbol of the set of systematic symbols is associated with a source symbol of the set of source symbols and each parity symbol of the set of parity symbols is associated with a number of source symbols of the set of source symbols according to a respective degree of each parity symbol based at least in part on a degree distribution for the set of parity symbols;

means for transmitting a first set of packets comprising the set of systematic symbols;

means for ordering the set of parity symbols by decreasing degrees based at least in part on the degree distribution for the set of parity symbols; and

means for transmitting a second set of packets comprising the set of parity symbols based at least in part on the ordering.
The apparatus of claim 53, further comprising:

means for receiving a feedback message indicating a feedback parameter, wherein encoding the set of source symbols according to the fountain code to obtain the set of parity symbols is based at least in part on the feedback parameter.
The apparatus of claim 54, further comprising:

means for determining the degree distribution for the set of parity symbols based at least in part on the feedback parameter.
The apparatus of claim 54, wherein:

the feedback message is received in response to the first set of packets; and

the feedback parameter comprises one or more positive acknowledgment indicators for a number of systematic symbols of the set of systematic symbols successfully received by a user equipment (UE) , one or more negative acknowledgment indicators for a number of systematic symbols of the set of systematic symbols unsuccessfully received by the UE, or a combination thereof.
The apparatus of claim 54, wherein the feedback parameter comprises a channel quality indicator value, a reference signal received power value, a reference signal received quality value, a received signal strength indicator value, or a combination thereof.
The apparatus of claim 54, further comprising:

means for transmitting a message configuring a user equipment (UE) with a feedback schema, wherein the feedback parameter is based at least in part on the feedback schema.
The apparatus of claim 58, wherein the message configuring the UE with the feedback schema comprises a downlink control information message, a medium access control control element, a radio resource control configuration message, or a combination thereof.
The apparatus of claim 54, wherein the means for encoding comprise:

means for determining, at a first encoding stage, the set of systematic symbols directly from the set of source symbols; and

means for determining, at a second encoding stage, the set of parity symbols directly from the set of source symbols based at least in part on the feedback parameter satisfying an erasure threshold.
The apparatus of claim 60, wherein the means for determining the set of parity symbols comprise:

means for selecting, for each parity symbol of the set of parity symbols, a degree from the degree distribution for the set of parity symbols;

means for selecting, for each parity symbol of the set of parity symbols, a plurality of source symbols of the set of source symbols based at least in part on the selected degree; and

means for combining, for each parity symbol of the set of parity symbols, the selected plurality of source symbols based at least in part on an exclusive OR logic operation to determine each parity symbol of the set of parity symbols.
The apparatus of claim 54, wherein the means for encoding comprise:

means for determining, at a first encoding stage, the set of systematic symbols directly from the set of source symbols; and

means for determining, at a second encoding stage, the set of parity symbols from a set of intermediate symbols based at least in part on the feedback parameter failing to satisfy an erasure threshold.
The apparatus of claim 62, wherein the means for determining the set of parity symbols comprise:

means for mapping one or more source symbols of the set of source symbols to each intermediate symbol of the set of intermediate symbols;

means for selecting, for each parity symbol of the set of parity symbols, a degree from the degree distribution for the set of parity symbols;

means for selecting, for each parity symbol of the set of parity symbols, one or more intermediate symbols of the set of intermediate symbols based at least in part on the selected degree; and

means for combining, for each parity symbol of the set of parity symbols, the selected one or more intermediate symbols based at least in part on an exclusive OR logic operation to determine each parity symbol of the set of parity symbols.
The apparatus of claim 53, wherein the means for transmitting the first set of packets and transmitting the second set of packets comprise:

means for broadcasting, to a plurality of user equipments (UEs) , the first set of packets and the second set of packets.
The apparatus of claim 53, wherein the means for transmitting the second set of packets comprise:

means for transmitting, in a first data block, a first one or more packets of the second set of packets comprising parity symbols with degrees greater than or equal to a threshold degree value based at least in part on the ordering; and

means for transmitting, in a second data block subsequent to the first data block, a second one or more packets of the second set of packets comprising parity symbols with degrees less than or equal to the threshold degree value based at least in part on the ordering.
The apparatus of claim 53, wherein the fountain code comprises a Luby transform (LT) code, a rapid tornado (Raptor) code, or both.
An apparatus for wireless communications, comprising:

means for receiving a first set of packets comprising a set of systematic symbols, wherein each systematic symbol of the set of systematic symbols is associated with a source symbol of a set of source symbols;

means for decoding the first set of packets according to a fountain code to recover a first subset of the set of source symbols;

means for receiving a second set of packets comprising a set of parity symbols, wherein each parity symbol of the set of parity symbols is associated with a number of source symbols of the set of source symbols according to a respective degree of each parity symbol based at least in part on a degree distribution for the set of parity symbols, and wherein the second set of packets is received in an order according to decreasing degrees of parity symbols in each packet of the second set of packets; and

means for decoding the second set of packets according to the fountain code to recover a second subset of the set of source symbols based at least in part on the recovered first subset of the set of source symbols, wherein the set of source symbols is recovered based at least in part on decoding the first set of packets and decoding the second set of packets.
The apparatus of claim 67, further comprising:

means for transmitting a feedback message indicating a feedback parameter, wherein the degree distribution for the set of parity symbols is based at least in part on the feedback parameter.
The apparatus of claim 68, wherein:

the feedback parameter comprises one or more positive acknowledgment indicators for the first subset of the set of source symbols successfully recovered from the first set of packets, one or more negative acknowledgment indicators for the second subset of the set of source symbols unsuccessfully recovered from the first set of packets, or a combination thereof; and

the feedback message is transmitted in response to the first set of packets.
The apparatus of claim 68, further comprising:

means for performing a channel measurement procedure to determine the feedback parameter, wherein the feedback parameter comprises a channel quality indicator value, a reference signal received power value, a reference signal received quality value, a received signal strength indicator value, or a combination thereof.
The apparatus of claim 68, further comprising:

means for receiving a message configuring a feedback schema, wherein the feedback parameter is based at least in part on the feedback schema.
The apparatus of claim 71, wherein the message configuring the feedback schema comprises a downlink control information message, a medium access control control element, a radio resource control configuration message, or a combination thereof.
The apparatus of claim 68, wherein:

the means for decoding the first set of packets comprise:

means for determining, at a first decoding stage, the first subset of the set of source symbols directly from the set of systematic symbols; and

the means for decoding the second set of packets comprise:

means for determining, at a second decoding stage, the second subset of the set of source symbols directly from the set of parity symbols based at least in part on the feedback parameter satisfying an erasure threshold.
The apparatus of claim 68, wherein:

the means for decoding the first set of packets comprise:

means for determining, at a first decoding stage, the first subset of the set of source symbols directly from the set of systematic symbols; and

the means for decoding the second set of packets comprise:

means for determining, at a second decoding stage, the second subset of the set of source symbols from the set of parity symbols via a set of intermediate symbols based at least in part on the feedback parameter failing to satisfy an erasure threshold.
The apparatus of claim 67, further comprising:

means for refraining from receiving at least one packet comprising additional parity symbols based at least in part on recovering the set of source symbols.
The apparatus of claim 75, further comprising:

means for entering a low power mode based at least in part on recovering the set of source symbols and prior to transmission of the at least one packet comprising additional parity symbols.
The apparatus of claim 67, wherein the means for receiving the second set of packets comprise:

means for receiving, in a first data block, a first one or more packets of the second set of packets comprising parity symbols with degrees greater than or equal to a threshold degree value based at least in part on the order; and

means for receiving, in a second data block subsequent to the first data block, a second one or more packets of the second set of packets comprising parity symbols with degrees less than or equal to the threshold degree value based at least in part on the order.
The apparatus of claim 67, wherein the fountain code comprises a Luby transform (LT) code, a rapid tornado (Raptor) code, or both.
A non-transitory computer-readable medium storing code for wireless communications, the code comprising instructions executable by a processor to:

encode a set of source symbols according to a fountain code to obtain a set of systematic symbols and a set of parity symbols, wherein each systematic symbol of the set of systematic symbols is associated with a source symbol of the set of source symbols and each parity symbol of the set of parity symbols is associated with a number of source symbols of the set of source symbols according to a respective degree of each parity symbol based at least in part on a degree distribution for the set of parity symbols;

transmit a first set of packets comprising the set of systematic symbols;

order the set of parity symbols by decreasing degrees based at least in part on the degree distribution for the set of parity symbols; and

transmit a second set of packets comprising the set of parity symbols based at least in part on the ordering.
A non-transitory computer-readable medium storing code for wireless communications, the code comprising instructions executable by a processor to:

receive a first set of packets comprising a set of systematic symbols, wherein each systematic symbol of the set of systematic symbols is associated with a source symbol of a set of source symbols;

decode the first set of packets according to a fountain code to recover a first subset of the set of source symbols;

receive a second set of packets comprising a set of parity symbols, wherein each parity symbol of the set of parity symbols is associated with a number of source symbols of the set of source symbols according to a respective degree of each parity symbol based at least in part on a degree distribution for the set of parity symbols, and wherein the second set of packets is received in an order according to decreasing degrees of parity symbols in each packet of the second set of packets; and

decode the second set of packets according to the fountain code to recover a second subset of the set of source symbols based at least in part on the recovered first subset of the set of source symbols, wherein the set of source symbols is recovered based at least in part on decoding the first set of packets and decoding the second set of packets.