WO2021142764A1

WO2021142764A1 - Avoiding erroneous discardment of downlink data in an unacknowledged mode (um)

Info

Publication number: WO2021142764A1
Application number: PCT/CN2020/072694
Authority: WO
Inventors: Hongjin GUO; Jintao HOU; Xiaochen Chen; Feng Chen; Zengyu Hao; Chunxia LI; Yi Qin; Haizhou LIU
Original assignee: Qualcomm Incorporated
Priority date: 2020-01-17
Filing date: 2020-01-17
Publication date: 2021-07-22

Abstract

Aspects of the present disclosure provide a method of wireless communication at a receiving device operating in an unacknowledged mode (UM). In some examples, the receiving device may be a user equipment, a vehicle-to-everything (V2X) device, or a cellular V2X (C-V2X) device. The receiving device receives an unacknowledged mode data (UMD) protocol data unit (PDU) and determines that an RLC sequence number of the UMD PDU is within a reordering window. The receiving device determines a first packet data convergence protocol (PDCP) sequence number included in the UMD PDU and determines whether the first PDCP sequence number is greater than a second PDCP sequence number in a last received UMD PDU when the RLC sequence number is within the reordering window. The receiving device stores the UMD PDU when the first PDCP sequence number is greater than the second PDCP sequence number.

Description

AVOIDING ERRONEOUS DISCARDMENT OF DOWNLINK DATA IN AN UNACKNOWLEDGED MODE (UM)

TECHNICAL FIELD

The technology discussed below relates generally to wireless communication systems, and more particularly, to avoiding erroneous discardment of downlink data in an unacknowledged mode (UM) .

INTRODUCTION

In 3rd Generation Partnership Project (3GPP) standards, the Radio Link Control (RLC) layer may operate in an unacknowledged mode (UM) . In the unacknowledged mode, the RLC layer implemented by a receiving device (e.g., a user equipment, a vehicle-to-everything (V2X) device, a cellular V2X (C-V2X) device) does not acknowledge reception of data packets to a transmitting device. For example, the receiving device operating in the unacknowledged mode (UM) may successfully receive a data packet and may not transmit an acknowledgement (ACK) to the transmitting device.

The receiving device operating in the unacknowledged mode (UM) may process incoming data packets (herein referred to as RLC unacknowledged mode data (UMD) protocol data units (PDUs) or more simply UMD PDUs) to ensure that the UMD PDUs are received in a proper sequence. For example, such processing may include the discarding of suspected duplicate UMD PDUs received at the RLC layer. However, in some scenarios, the RLC layer operating in the unacknowledged mode (UM) may erroneously discard UMD PDUs, which may lead to a data stall and degrade the user experience.

BRIEF SUMMARY OF SOME EXAMPLES

The following presents a simplified summary of one or more aspects of the present disclosure, in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated features of the disclosure, and is intended neither to identify key or critical elements of all aspects of the disclosure nor to delineate the scope of any or all aspects of the disclosure. Its sole purpose is to present some concepts of one or more aspects of the disclosure in a simplified form as a prelude to the more detailed description that is presented later.

In one example, a method of wireless communication at a user equipment operating in an unacknowledged mode (UM) is disclosed. The method includes receiving an unacknowledged mode data (UMD) protocol data unit (PDU) and determining that an RLC sequence number of the UMD PDU is within a reordering window. The method further includes determining a first packet data convergence protocol (PDCP) sequence number included in the UMD PDU, and determining whether the first PDCP sequence number in the UMD PDU is greater than a second PDCP sequence number in a last received UMD PDU when the RLC sequence number is within the reordering window. The method further includes storing the UMD PDU when the first PDCP sequence number is greater than the second PDCP sequence number. In some aspects of the disclosure, the method further includes discarding the UMD PDU when the first PDCP sequence number is less than the second PDCP sequence number.

Another example provides a user equipment operating in an unacknowledged mode (UM) in a wireless communication network. The user equipment includes a processor, a transceiver communicatively coupled to the processor, and a memory communicatively coupled to the processor. The processor is configured to receive a radio link control (RLC) unacknowledged mode data (UMD) protocol data unit (PDU) and determine that an RLC sequence number of the UMD PDU is within a reordering window. The processor is further configured to determine a first packet data convergence protocol (PDCP) sequence number included in the UMD PDU and determine whether the first PDCP sequence number in the RLC UMD PDU is greater than a second PDCP sequence number in a last received UMD PDU when the RLC sequence number is within the reordering window. The processor is further configured to store the UMD PDU when the first PDCP sequence number is greater than the second PDCP sequence number. In some aspects of the disclosure, the processor is further configured to discard the UMD PDU when the first PDCP sequence number is less than the second PDCP sequence number.

Another example provides a user equipment operating in an unacknowledged mode (UM) . The user equipment includes means for receiving a radio link control (RLC) unacknowledged mode data (UMD) protocol data unit (PDU) and means for determining that an RLC sequence number of the UMD PDU is within a reordering window. The user equipment further includes means for determining a first packet data convergence protocol (PDCP) sequence number included in the UMD PDU, and means for determining whether the first PDCP sequence number in the UMD PDU is greater than a second PDCP sequence number in a last received UMD PDU when the RLC sequence number is within the reordering window. The user equipment further includes means for storing the UMD PDU when the first PDCP sequence number is greater than the second PDCP sequence number.

Another example provides a non-transitory computer-readable medium storing computer-executable code, which includes code for causing a user equipment operating in an unacknowledged mode (UM) to receive a radio link control (RLC) unacknowledged mode data (UMD) protocol data unit (PDU) and determine that an RLC sequence number of the UMD PDU is within a reordering window. The code further causes the user equipment to determine a first packet data convergence protocol (PDCP) sequence number included in the UMD PDU and determine whether the first PDCP sequence number in the UMD PDU is greater than a second PDCP sequence number in a last received UMD PDU when the RLC sequence number is within the reordering window. The code further causes the user equipment to store the UMD PDU when the first PDCP sequence number is greater than the second PDCP sequence number. In some aspects, the code further causes the user equipment to discard the UMD PDU when the first PDCP sequence number is less than the second PDCP sequence number.

These and other aspects of the invention will become more fully understood upon a review of the detailed description, which follows. Other aspects, features, and embodiments of the present invention will become apparent to those of ordinary skill in the art, upon reviewing the following description of specific, exemplary embodiments of the present invention in conjunction with the accompanying figures. While features of the present invention may be discussed relative to certain embodiments and figures below, all embodiments of the present invention can include one or more of the advantageous features discussed herein. In other words, while one or more embodiments may be discussed as having certain advantageous features, one or more of such features may also be used in accordance with the various embodiments of the invention discussed herein. In similar fashion, while exemplary embodiments may be discussed below as device, system, or method embodiments it should be understood that such exemplary embodiments can be implemented in various devices, systems, and methods.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a wireless communication system.

FIG. 2 is a conceptual illustration of an example of a radio access network.

FIG. 3 illustrates an example of a vehicle-to-everything (V2X) wireless communication network.

FIG. 4 is a diagram illustrating an example of a radio protocol architecture for the user and control plane.

FIG. 5 is a diagram illustrating an example of a format of a Packet Data Convergence Protocol (PDCP) Protocol Data Unit (PDU) .

FIG. 6 is a diagram illustrating an example of a format of a Radio Link Control (RLC) Unacknowledged Mode Data (UMD) Protocol Data Unit (PDU) .

FIG. 7 illustrates an example format of a PDCP Data PDU for a sidelink radio bearer (SLRB) .

FIG. 8 illustrates an example format of an RLC unacknowledged mode data (UMD) protocol data unit (PDU) .

FIG. 9 illustrates an example format of a PDCP data PDU for a data radio bearer (DRB) .

FIG. 10 illustrates the contents of an example RLC UMD PDU.

FIG. 11 is a block diagram illustrating an example of a hardware implementation for a receiving device employing a processing system.

FIG. 12 is a flowchart illustrating a procedure for a receiving device operating in the unacknowledged mode (UM) .

FIG. 13 shows a sequence of UMD PDUs and their corresponding RLC sequence numbers

FIG. 14 is a flowchart illustrating a procedure for a receiving device operating in the unacknowledged mode in accordance with various aspects of the disclosure.

FIG. 15 is a flowchart illustrating a procedure for a receiving device operating in the unacknowledged mode in accordance with various aspects of the disclosure.

FIG. 16 is a flow chart of an exemplary method for receiving device operating in an unacknowledged mode (UM) according to various aspects of the present disclosure.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appended drawings is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well known structures and components are shown in block diagram form in order to avoid obscuring such concepts.

While aspects and embodiments are described in this application by illustration to some examples, those skilled in the art will understand that additional implementations and use cases may come about in many different arrangements and scenarios. Innovations described herein may be implemented across many differing platform types, devices, systems, shapes, sizes, packaging arrangements. For example, embodiments and/or uses may come about via integrated chip embodiments and other non-module-component based devices (e.g., end-user devices, vehicles, communication devices, computing devices, industrial equipment, retail/purchasing devices, medical devices, AI-enabled devices, etc. ) . While some examples may or may not be specifically directed to use cases or applications, a wide assortment of applicability of described innovations may occur. Implementations may range a spectrum from chip-level or modular components to non-modular, non-chip-level implementations and further to aggregate, distributed, or OEM devices or systems incorporating one or more aspects of the described innovations. In some practical settings, devices incorporating described aspects and features may also necessarily include additional components and features for implementation and practice of claimed and described embodiments. For example, transmission and reception of wireless signals necessarily includes a number of components for analog and digital purposes (e.g., hardware components including antenna, RF-chains, power amplifiers, modulators, buffer, processor (s) , interleaver, adders/summers, etc. ) . It is intended that innovations described herein may be practiced in a wide variety of devices, chip-level components, systems, distributed arrangements, end-user devices, etc. of varying sizes, shapes and constitution.

The various concepts presented throughout this disclosure may be implemented across a broad variety of telecommunication systems, network architectures, and communication standards. Referring now to FIG. 1, as an illustrative example without limitation, various aspects of the present disclosure are illustrated with reference to a wireless communication system 100. The wireless communication system 100 includes three interacting domains: a core network 102, a radio access network (RAN) 104, and a user equipment (UE) 106. By virtue of the wireless communication system 100, the UE 106 may be enabled to carry out data communication with an external data network 110, such as (but not limited to) the Internet.

The RAN 104 may implement any suitable radio access technology (RAT) or RATs to provide radio access to the UE 106. As one example, the RAN 104 may operate according to 3rd Generation Partnership Project (3GPP) New Radio (NR) specifications, often referred to as 5G. As another example, the RAN 104 may operate under a hybrid of 5G NR and Evolved Universal Terrestrial Radio Access Network (eUTRAN) standards, often referred to as LTE. The 3GPP refers to this hybrid RAN as a next-generation RAN, or NG-RAN. In another example, the RAN 104 may operate according to both the LTE and 5G NR standards. Of course, many other examples may be utilized within the scope of the present disclosure.

As illustrated, the RAN 104 includes a plurality of base stations 108. Broadly, a base station is a network element in a radio access network responsible for radio transmission and reception in one or more cells to or from a UE. In different technologies, standards, or contexts, a base station may variously be referred to by those skilled in the art as a base transceiver station (BTS) , a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS) , an extended service set (ESS) , an access point (AP) , a Node B (NB) , an eNode B (eNB) , a gNode B (gNB) , or some other suitable terminology. In examples where the RAN 104 operates according to both the LTE and 5G NR standards, one of the base stations 108 may be an LTE base station, while another base station may be a 5G NR base station.

The radio access network 104 is further illustrated supporting wireless communication for multiple mobile apparatuses. A mobile apparatus may be referred to as user equipment (UE) 106 in 3GPP standards, but may also be referred to by those skilled in the art as a mobile station (MS) , a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal (AT) , a mobile terminal, a wireless terminal, a remote terminal, a handset, a terminal, a user agent, a mobile client, a client, or some other suitable terminology. A UE 106 may be an apparatus that provides a user with access to network services.

Within the present document, a “mobile” apparatus need not necessarily have a capability to move, and may be stationary. The term mobile apparatus or mobile device broadly refers to a diverse array of devices and technologies. UEs may include a number of hardware structural components sized, shaped, and arranged to help in communication; such components can include antennas, antenna arrays, RF chains, amplifiers, one or more processors, etc. electrically coupled to each other. For example, some non-limiting examples of a mobile apparatus include a mobile, a cellular (cell) phone, a smart phone, a session initiation protocol (SIP) phone, a laptop, a personal computer (PC) , a notebook, a netbook, a smartbook, a tablet, a personal digital assistant (PDA) , and a broad array of embedded systems, e.g., corresponding to an “Internet of Things” (IoT) . A mobile apparatus may additionally be an automotive or other transportation vehicle, a remote sensor or actuator, a robot or robotics device, a satellite radio, a global positioning system (GPS) device, an object tracking device, a drone, a multi-copter, a quad-copter, a remote control device, a consumer and/or wearable device, such as eyewear, a wearable camera, a virtual reality device, a smart watch, a health or fitness tracker, a digital audio player (e.g., MP3 player) , a camera, a game console, etc. A mobile apparatus may additionally be a digital home or smart home device such as a home audio, video, and/or multimedia device, an appliance, a vending machine, intelligent lighting, a home security system, a smart meter, etc. A mobile apparatus may additionally be a smart energy device, a security device, a solar panel or solar array, a municipal infrastructure device controlling electric power (e.g., a smart grid) , lighting, water, etc.; an industrial automation and enterprise device; a logistics controller; agricultural equipment; military defense equipment, vehicles, aircraft, ships, and weaponry, etc. Still further, a mobile apparatus may provide for connected medicine or telemedicine support, i.e., health care at a distance. Telehealth devices may include telehealth monitoring devices and telehealth administration devices, whose communication may be given preferential treatment or prioritized access over other types of information, e.g., in terms of prioritized access for transport of critical service data, and/or relevant QoS for transport of critical service data.

Wireless communication between a RAN 104 and a UE 106 may be described as utilizing an air interface. Transmissions over the air interface from a base station (e.g., base station 108) to one or more UEs (e.g., UE 106) may be referred to as downlink (DL) transmission. In accordance with certain aspects of the present disclosure, the term downlink may refer to a point-to-multipoint transmission originating at a scheduling entity (described further below; e.g., base station 108) . Another way to describe this scheme may be to use the term broadcast channel multiplexing. Transmissions from a UE (e.g., UE 106) to a base station (e.g., base station 108) may be referred to as uplink (UL) transmissions. In accordance with further aspects of the present disclosure, the term uplink may refer to a point-to-point transmission originating at a scheduled entity (described further below; e.g., UE 106) .

In some examples, access to the air interface may be scheduled, wherein a scheduling entity (e.g., a base station 108) allocates resources for communication among some or all devices and equipment within its service area or cell. Within the present disclosure, as discussed further below, the scheduling entity may be responsible for scheduling, assigning, reconfiguring, and releasing resources for one or more scheduled entities. That is, for scheduled communication, UEs 106, which may be scheduled entities, may utilize resources allocated by the scheduling entity 108.

Base stations 108 are not the only entities that may function as scheduling entities. That is, in some examples, a UE may function as a scheduling entity, scheduling resources for one or more scheduled entities (e.g., one or more other UEs) .

As illustrated in FIG. 1, a scheduling entity 108 may broadcast downlink traffic 112 to one or more scheduled entities 106. Broadly, the scheduling entity 108 is a node or device responsible for scheduling traffic in a wireless communication network, including the downlink traffic 112 and, in some examples, uplink traffic 116 from one or more scheduled entities 106 to the scheduling entity 108. On the other hand, the scheduled entity 106 is a node or device that receives downlink control information 114, including but not limited to scheduling information (e.g., a grant) , synchronization or timing information, or other control information from another entity in the wireless communication network such as the scheduling entity 108.

In addition, the uplink and/or downlink control information and/or traffic information may be time-divided into frames, subframes, slots, and/or symbols. As used herein, a symbol may refer to a unit of time that, in an orthogonal frequency division multiplexed (OFDM) waveform, carries one resource element (RE) per sub-carrier. A slot may carry 7 or 14 OFDM symbols. A subframe may refer to a duration of 1ms. Multiple subframes or slots may be grouped together to form a single frame or radio frame. Of course, these definitions are not required, and any suitable scheme for organizing waveforms may be utilized, and various time divisions of the waveform may have any suitable duration.

In general, base stations 108 may include a backhaul interface for communication with a backhaul portion 120 of the wireless communication system. The backhaul 120 may provide a link between a base station 108 and the core network 102. Further, in some examples, a backhaul network may provide interconnection between the respective base stations 108. Various types of backhaul interfaces may be employed, such as a direct physical connection, a virtual network, or the like using any suitable transport network.

The core network 102 may be a part of the wireless communication system 100, and may be independent of the radio access technology used in the RAN 104. In some examples, the core network 102 may be configured according to 5G standards (e.g., 5GC) . In other examples, the core network 102 may be configured according to a 4G evolved packet core (EPC) , or any other suitable standard or configuration.

Referring now to FIG. 2, by way of example and without limitation, a schematic illustration of a RAN 200 is provided. In some examples, the RAN 200 may be the same as the RAN 104 described above and illustrated in FIG. 1. The geographic area covered by the RAN 200 may be divided into cellular regions (cells) that can be uniquely identified by a user equipment (UE) based on an identification broadcasted from one access point or base station. FIG. 2 illustrates

macrocells

202, 204, and 206, and a small cell 208, each of which may include one or more sectors (not shown) . A sector is a sub-area of a cell. All sectors within one cell are served by the same base station. A radio link within a sector can be identified by a single logical identification belonging to that sector. In a cell that is divided into sectors, the multiple sectors within a cell can be formed by groups of antennas with each antenna responsible for communication with UEs in a portion of the cell.

In FIG. 2, two base stations 210 and 212 are shown in

cells

202 and 204; and a third base station 214 is shown controlling a remote radio head (RRH) 216 in cell 206. That is, a base station can have an integrated antenna or can be connected to an antenna or RRH by feeder cables. In the illustrated example, the

cells

202, 204, and 126 may be referred to as macrocells, as the

base stations

210, 212, and 214 support cells having a large size. Further, a base station 218 is shown in the small cell 208 (e.g., a microcell, picocell, femtocell, home base station, home Node B, home eNode B, etc. ) which may overlap with one or more macrocells. In this example, the cell 208 may be referred to as a small cell, as the base station 218 supports a cell having a relatively small size. Cell sizing can be done according to system design as well as component constraints.

It is to be understood that the radio access network 200 may include any number of wireless base stations and cells. Further, a relay node may be deployed to extend the size or coverage area of a given cell. The

base stations

210, 212, 214, 218 provide wireless access points to a core network for any number of mobile apparatuses. In some examples, the

base stations

210, 212, 214, and/or 218 may be the same as the base station/scheduling entity 108 described above and illustrated in FIG. 1.

Within the RAN 200, the cells may include UEs that may be in communication with one or more sectors of each cell. Further, each

base station

210, 212, 214, and 218 may be configured to provide an access point to a core network 102 (see FIG. 1) for all the UEs in the respective cells. For example,

UEs

222 and 224 may be in communication with base station 210;

UEs

226 and 228 may be in communication with base station 212;

UEs

230 and 232 may be in communication with base station 214 by way of RRH 216; and UE 234 may be in communication with base station 218. In some examples, the

UEs

222, 224, 226, 228, 230, 232, 234, 238, 240, and/or 242 may be the same as the UE/scheduled entity 106 described above and illustrated in FIG. 1.

In some examples, an unmanned aerial vehicle (UAV) 220, which may be a drone or quadcopter, can be a mobile network node and may be configured to function as a UE. For example, the UAV 220 may operate within cell 202 by communicating with base station 210.

In a further aspect of the RAN 200, sidelink signals may be used between UEs without necessarily relying on scheduling or control information from a base station. For example, two or more UEs (e.g., UEs 226 and 228) may communicate with each other using peer to peer (P2P) or sidelink signals 227 without relaying that communication through a base station (e.g., base station 212) . In a further example, UE 238 is illustrated communicating with

UEs

240 and 242. Here, the UE 238 may function as a scheduling entity or a primary sidelink device, and

UEs

240 and 242 may function as a scheduled entity or a non-primary (e.g., secondary) sidelink device. In still another example, a UE may function as a scheduling entity in a device-to-device (D2D) , peer-to-peer (P2P) , or vehicle-to-vehicle (V2V) network, and/or in a mesh network. In a mesh network example,

UEs

240 and 242 may optionally communicate directly with one another in addition to communicating with the scheduling entity 238. Thus, in a wireless communication system with scheduled access to time–frequency resources and having a cellular configuration, a P2P configuration, or a mesh configuration, a scheduling entity and one or more scheduled entities may communicate utilizing the scheduled resources. In some examples, the sidelink signals 227 include sidelink traffic and sidelink control. Sidelink control information may in some examples include a request signal, such as a request-to-send (RTS) , a source transmit signal (STS) , and/or a direction selection signal (DSS) . The request signal may provide for a scheduled entity to request a duration of time to keep a sidelink channel available for a sidelink signal. Sidelink control information may further include a response signal, such as a clear-to-send (CTS) and/or a destination receive signal (DRS) . The response signal may provide for the scheduled entity to indicate the availability of the sidelink channel, e.g., for a requested duration of time. An exchange of request and response signals (e.g., handshake) may enable different scheduled entities performing sidelink communications to negotiate the availability of the sidelink channel prior to communication of the sidelink traffic information.

In the radio access network 200, the ability for a UE to communicate while moving, independent of its location, is referred to as mobility. The various physical channels between the UE and the radio access network are generally set up, maintained, and released under the control of an access and mobility management function (AMF, not illustrated, part of the core network 102 in FIG. 1) , which may include a security context management function (SCMF) that manages the security context for both the control plane and the user plane functionality, and a security anchor function (SEAF) that performs authentication.

A radio access network 200 may utilize DL-based mobility or UL-based mobility to enable mobility and handovers (i.e., the transfer of a UE’s connection from one radio channel to another) . In a network configured for DL-based mobility, during a call with a scheduling entity, or at any other time, a UE may monitor various parameters of the signal from its serving cell as well as various parameters of neighboring cells. Depending on the quality of these parameters, the UE may maintain communication with one or more of the neighboring cells. During this time, if the UE moves from one cell to another, or if signal quality from a neighboring cell exceeds that from the serving cell for a given amount of time, the UE may undertake a handoff or handover from the serving cell to the neighboring (target) cell. For example, UE 224 (illustrated as a vehicle, although any suitable form of UE may be used) may move from the geographic area corresponding to its serving cell 202 to the geographic area corresponding to a neighbor cell 206. When the signal strength or quality from the neighbor cell 206 exceeds that of its serving cell 202 for a given amount of time, the UE 224 may transmit a reporting message to its serving base station 210 indicating this condition. In response, the UE 224 may receive a handover command, and the UE may undergo a handover to the cell 206.

In a network configured for UL-based mobility, UL reference signals from each UE may be utilized by the network to select a serving cell for each UE. In some examples, the

base stations

210, 212, and 214/216 may broadcast unified synchronization signals (e.g., unified Primary Synchronization Signals (PSSs) , unified Secondary Synchronization Signals (SSSs) and unified Physical Broadcast Channels (PBCH) ) . The

UEs

222, 224, 226, 228, 230, and 232 may receive the unified synchronization signals, derive the carrier frequency and slot timing from the synchronization signals, and in response to deriving timing, transmit an uplink pilot or reference signal. The uplink pilot signal transmitted by a UE (e.g., UE 224) may be concurrently received by two or more cells (e.g., base stations 210 and 214/216) within the radio access network 200. Each of the cells may measure a strength of the pilot signal, and the radio access network (e.g., one or more of the base stations 210 and 214/216 and/or a central node within the core network) may determine a serving cell for the UE 224. As the UE 224 moves through the radio access network 200, the network may continue to monitor the uplink pilot signal transmitted by the UE 224. When the signal strength or quality of the pilot signal measured by a neighboring cell exceeds that of the signal strength or quality measured by the serving cell, the network 200 may handover the UE 224 from the serving cell to the neighboring cell, with or without informing the UE 224.

Although the synchronization signal transmitted by the

base stations

210, 212, and 214/216 may be unified, the synchronization signal may not identify a particular cell, but rather may identify a zone of multiple cells operating on the same frequency and/or with the same timing. The use of zones in 5G networks or other next generation communication networks enables the uplink-based mobility framework and improves the efficiency of both the UE and the network, since the number of mobility messages that need to be exchanged between the UE and the network may be reduced.

In various implementations, the air interface in the radio access network 200 may utilize licensed spectrum, unlicensed spectrum, or shared spectrum. Licensed spectrum provides for exclusive use of a portion of the spectrum, generally by virtue of a mobile network operator purchasing a license from a government regulatory body. Unlicensed spectrum provides for shared use of a portion of the spectrum without need for a government-granted license. While compliance with some technical rules is generally still required to access unlicensed spectrum, generally, any operator or device may gain access. Shared spectrum may fall between licensed and unlicensed spectrum, wherein technical rules or limitations may be required to access the spectrum, but the spectrum may still be shared by multiple operators and/or multiple RATs. For example, the holder of a license for a portion of licensed spectrum may provide licensed shared access (LSA) to share that spectrum with other parties, e.g., with suitable licensee-determined conditions to gain access.

In order for transmissions over the radio access network 200 to obtain a low block error rate (BLER) while still achieving very high data rates, channel coding may be used. That is, wireless communication may generally utilize a suitable error correcting block code. In a typical block code, an information message or sequence is split up into code blocks (CBs) , and an encoder (e.g., a CODEC) at the transmitting device then mathematically adds redundancy to the information message. Exploitation of this redundancy in the encoded information message can improve the reliability of the message, enabling correction for any bit errors that may occur due to the noise.

In early 5G NR specifications, user data traffic is coded using quasi-cyclic low-density parity check (LDPC) with two different base graphs: one base graph is used for large code blocks and/or high code rates, while the other base graph is used otherwise. Control information and the physical broadcast channel (PBCH) are coded using Polar coding, based on nested sequences. For these channels, puncturing, shortening, and repetition are used for rate matching.

However, those of ordinary skill in the art will understand that aspects of the present disclosure may be implemented utilizing any suitable channel code. Various implementations of scheduling entities 108 and scheduled entities 106 may include suitable hardware and capabilities (e.g., an encoder, a decoder, and/or a CODEC) to utilize one or more of these channel codes for wireless communication.

The air interface in the radio access network 200 may utilize one or more multiplexing and multiple access algorithms to enable simultaneous communication of the various devices. For example, 5G NR specifications provide multiple access for UL transmissions from

UEs

222 and 224 to base station 210, and for multiplexing for DL transmissions from base station 210 to one or

more UEs

222 and 224, utilizing orthogonal frequency division multiplexing (OFDM) with a cyclic prefix (CP) . In addition, for UL transmissions, 5G NR specifications provide support for discrete Fourier transform-spread-OFDM (DFT-s-OFDM) with a CP (also referred to as single-carrier FDMA (SC-FDMA) ) . However, within the scope of the present disclosure, multiplexing and multiple access are not limited to the above schemes, and may be provided utilizing time division multiple access (TDMA) , code division multiple access (CDMA) , frequency division multiple access (FDMA) , sparse code multiple access (SCMA) , resource spread multiple access (RSMA) , or other suitable multiple access schemes. Further, multiplexing DL transmissions from the base station 210 to UEs 222 and 224 may be provided utilizing time division multiplexing (TDM) , code division multiplexing (CDM) , frequency division multiplexing (FDM) , orthogonal frequency division multiplexing (OFDM) , sparse code multiplexing (SCM) , or other suitable multiplexing schemes.

The air interface in the radio access network 200 may further utilize one or more duplexing algorithms. Duplex refers to a point-to-point communication link where both endpoints can communicate with one another in both directions. Full duplex means both endpoints can simultaneously communicate with one another. Half duplex means only one endpoint can send information to the other at a time. In a wireless link, a full duplex channel generally relies on physical isolation of a transmitter and receiver, and suitable interference cancellation technologies. Full duplex emulation is frequently implemented for wireless links by utilizing frequency division duplex (FDD) or time division duplex (TDD) . In FDD, transmissions in different directions operate at different carrier frequencies. In TDD, transmissions in different directions on a given channel are separated from one another using time division multiplexing. That is, at some times the channel is dedicated for transmissions in one direction, while at other times the channel is dedicated for transmissions in the other direction, where the direction may change very rapidly, e.g., several times per slot.

FIG. 3 illustrates an example of a vehicle-to-everything (V2X) wireless communication network 300. A V2X network can connect vehicles 302a–302d to each other (vehicle-to-vehicle (V2V) ) , to roadway infrastructure 304 (vehicle-to-infrastructure (V2I) ) , to pedestrians/cyclists 306 (vehicle-to-pedestrian (V2P) ) , and/or to the network 308 (vehicle-to-network (V2N)) .

A V2I transmission may be between a vehicle (e.g., vehicle 302a) and a roadside unit (RSU) 304, which may be coupled to various infrastructure, such as a traffic light, building, streetlight, traffic camera, tollbooth, or other stationary object. The RSU 304 may act as a base station enabling communication between vehicles 302a–302d, between vehicles 302a–302d and the RSU 304 and between vehicles 302a–302d and mobile devices 306 of pedestrians/cyclists. The RSU 304 may further exchange V2X data gathered from the surrounding environment, such as a connected traffic camera or traffic light controller, V2X connected vehicles 302a–302d, and mobile devices 306 of pedestrians/cyclists, with other RSUs 304 and distribute that V2X data to V2X connected vehicles 302a–302d and pedestrians 306. Examples of V2X data may include status information (e.g., position, speed, acceleration, trajectory, etc. ) or event information (e.g., traffic jam, icy road, fog, pedestrian crossing the road, collision, etc. ) , and may also include video data captured by a camera on a vehicle or coupled to an RSU 304.

Such V2X data may enable autonomous driving and improve road safety and traffic efficiency. For example, the exchanged V2X data may be utilized by a V2X connected vehicle 302a–302d to provide in-vehicle collision warnings, road hazard warnings, approaching emergency vehicle warnings, pre-/post-crash warnings and information, emergency brake warnings, traffic jam ahead warnings, lane change warnings, intelligent navigation services, and other similar information. In addition, V2X data received by a V2X connected mobile device 306 of a pedestrian/cyclist may be utilized to trigger a warning sound, vibration, flashing light, etc., in case of imminent danger.

V2N communication may utilize traditional cellular links to provide cloud services to a V2X device (e.g., within a vehicle 302a–302d or RSU 304, or on a pedestrian 306) for latency-tolerant use cases. For example, V2N may enable a V2X network server to broadcast messages (e.g., weather, traffic, or other information) to V2X devices over a wide area network and may enable V2X devices to send unicast messages to the V2X network server. In addition, V2N communication may provide backhaul services for RSUs 304.

The radio protocol architecture for a radio access network, such as the radio access network 104 shown in FIG. 1 and/or the radio access network 200 shown in FIG. 2, may take on various forms depending on the particular application. An example for an LTE or NR radio access network will now be presented with reference to FIG. 4. FIG. 4 is a conceptual diagram illustrating an example of the radio protocol architecture for the user and control planes.

As illustrated in FIG. 4, the radio protocol architecture for a UE (e.g., a receiving device) and the base station includes three layers: Layer 1, Layer 2, and Layer 3. Layer 1 is the lowest layer and implements various physical layer signal processing functions. Layer 1 will be referred to herein as the physical layer 406. Layer 2 (L2 layer) 408 is above the physical layer 406 and is responsible for the link between the UE and base station over the physical layer 406.

In the user plane, the L2 layer 408 includes a media access control (MAC) sublayer 410, a radio link control (RLC) sublayer 412, and a packet data convergence protocol (PDCP) 414 sublayer, which are terminated at the base station on the network side. Although not shown, the UE may have several upper layers above the L2 layer 408 including a network layer (e.g., IP layer) that is terminated at the Packet Data Network (PDN) gateway on the network side, and an application layer that is terminated at the other end of the connection (e.g., far end UE, server, etc. ) .

The PDCP sublayer 414 provides multiplexing between different radio bearers and logical channels. The PDCP sublayer 414 also provides header compression for upper layer data packets to reduce radio transmission overhead, security by ciphering the data packets, and handover support for UEs between base stations. The RLC sublayer 412 provides segmentation and reassembly of upper layer data packets, retransmission of lost data packets, and reordering of data packets to compensate for out-of-order reception due to hybrid automatic repeat request (HARQ) and automatic repeat request (ARQ) . The MAC sublayer 410 provides multiplexing between logical and transport channels. The MAC sublayer 410 is also responsible for allocating the various radio resources (e.g., resource blocks) in one cell among the UEs. The MAC sublayer 410 is also responsible for HARQ operations. The physical layer 406 is responsible for transmitting and receiving data on physical channels (e.g., within slots) .

In the control plane, the radio protocol architecture for the UE and base station is substantially the same for the physical layer 406 and the L2 layer 408 with the exception that there is no header compression function for the control plane. The control plane also includes a radio resource control (RRC) sublayer 416 in Layer 3. The RRC sublayer 416 is responsible for obtaining radio resources (i.e., radio bearers) and for configuring the lower layers using RRC signaling between the base station and the UE.

In general, packets received by a sublayer from another sublayer may be referred to as Service Data Units (SDUs) , while packets output from a sublayer to another sublayer may be referred to as Protocol Data Units (PDUs) . For example, packets received by the PDCP sublayer 414 from an upper layer may be referred to as PDCP SDUs, and packets output from the PDCP sublayer 414 to the RLC sublayer may be referred to as PDCP PDUs or RLC SDUs.

An example of a PDCP protocol data unit (PDU) format is illustrated in FIG. 5. The PDCP PDU format 500 includes a header 502 and a body 504. The header 502 includes a D/C field 506 and SN field 508. The D/C field 506 is located within a first octet 512a and may include, for example, a single bit for indicating whether the PCDP PDU contains user plane data or control plane data. In the example shown in FIG. 5, the SN field 508 occupies the remainder of the first octet 512a, along with a second octet 512b. The SN field 508 contains the sequence number (SN) of the PDCP PDU. In some examples, the SN may contain 7 bits or 12 bits. The body 504 contains uncompressed or compressed user or control plane data 510 and may include one or more octets (only one octet 512c of which is shown for simplicity) .

An example format of an RLC unacknowledged mode data (UMD) protocol data unit (PDU) is illustrated in FIG. 6. In the present disclosure, an RLC UMD PDU may also be referred to simply as a UMD PDU. UMD PDUs may contain downlink data and may be used, for example, to transmit delay sensitive packets, such as VoIP packets. In the unacknowledged mode (UM) , the receiving device 1100 does not acknowledge reception of data packets to the transmitting device (e.g., the receiving device does not transmit ACK/NACK to the transmitting device) .

In the example shown in FIG. 6, the UMD PDU format 600 includes a header 602 and a body 604. The header 602 occupies a first octet 614a that includes a Framing Information (FI) field 606, Extension bit (E) field 608 and an SN field 610. The FI field 606 indicates whether the RLC PDU is segmented at the beginning and/or end of the data field. The E field 608 indicates whether a data field or a set of E field and Length Indicator (LI) fields follow the SN field 610. The SN field 610 occupies the remainder of the first octet 614a. The SN field 610 contains the sequence number (SN) of the RLC PDU. In some examples, the SN may contain 5 bits or 10 bits. When the SN contains 5 bits, the header 602 is one byte long, as shown in FIG. 6. However, when the SN contains 10 bits, the header 602 is two bytes long and the SN extends through the second octet 614b with the first three bits of the header 602 being reserved. The body 604 contains uncompressed or compressed user or control plane data 612 and may include one or more octets (e.g., the second octet 614b through the Nth octet 614c) .

FIG. 7 illustrates an example format of a PDCP Data PDU for a sidelink radio bearer (SLRB) . The SLRB PDCP Data PDU format 700 may be used for one-to-many communications. As shown in FIG. 7, the SLRB PDCP Data PDU format 700 includes a header 702 and a body 704. The header 702 includes an SDU type field 706, a ProSe Group Key (PGK) Index field 708, a ProSe Traffic Key (PTK) Identity field 710, and an SN field 712. The body 704 contains uncompressed or compressed user data or control plane data 714 and may include one or more octets (only one octet 716f of which is shown for simplicity) .

With reference to FIG. 7, the SDU type field 706 is located within a first octet 716a and may include, for example, three bits for indicating the type of the SDU (e.g., to indicate whether the SDU is based on an Internet Protocol (IP) , an address resolution protocol (ARP) protocol, or a PC5 signaling protocol) . The PGK index field 708 is located within the first octet 716a and may include, for example, five bits for indicating a PGK identity (ID) . If ciphering is not applied, the PGK Index may be set to 0. The PTK identity field 710 is located within the second and

third octets

716b, 716c and may include, for example, 16 bits for indicating the PTK identity. The PTK identity may be based on the PGK, the PGK identity (ID) , and the PDCP SN. In the example shown in FIG. 7, the SN field 712 is located in the fourth and

fifth octets

716d, 716e. The SN field 712 contains the sequence number (SN) of the PDCP SDU.

An example of an RLC unacknowledged mode data (UMD) protocol data unit (PDU) format (also referred to as a UMD PDU format) is illustrated in FIG. 8. In the example shown in FIG. 8, the UMD PDU format 800 includes a header 802 and a body 804. The header 802 occupies a first octet 812a that includes a Segment Information (SI) field 806 and an SN field 808. The SI field 806 indicates whether the data field (e.g., the data 810) includes all bytes of an RLC SDU, the first segment of an RLC SDU, the last segment of an RLC SDU, or neither the first nor last segment of an RLC SDU. The SN field 808 occupies the remainder of the first octet 812a. The SN field 808 contains a 6-bit sequence number (SN) of the RLC PDU. The body 804 contains uncompressed or compressed user or control plane data 810 and may include one or more octets (e.g., the second octet 812b through the Nth octet 812c) .

FIG. 9 illustrates an example format of a PDCP data PDU for a data radio bearer (DRB) . As shown in FIG. 9, the DRB PDCP data PDU format 900 includes a header 902, a body 904, and optionally, integrity protection information 906. The header 902 includes a D/C field 908, reserved bit fields 910, 913, 914, 916, and 918, and an SN field 920. The D/C field 908 is located within a first octet 912a and may include, for example, a single bit for indicating whether the PCDP PDU contains user plane data or control plane data. The SN field 920 occupies the remainder of the first octet 912a and the second and

third octets

912b, 912c. The SN field 920 contains an 18-bit sequence number (SN) of the RLC PDU. The body 904 contains uncompressed or compressed user or control plane data 922 and may include one or more octets (e.g., the fourth octet 912d) . The integrity protection information 906 may include a message authentication code integrity (MAC-I) field 924 and may include one or more octets (e.g., octet N-3 912e, octet N-2 912f, octet N-1 912g, octet N 912h) . The MAC-I field 924 may carry a message authentication code. In some examples, the integrity protection field 924 is present when the data radio bearer (DRB) is configured with integrity protection.

FIG. 10 illustrates the contents of an example UMD PDU. As shown in FIG. 10, when a transmitting device processes an IP packet 1006 for transmission, a PDCP layer (e.g., PDCP layer 414) may attach a PDCP header 1004 to the IP packet 1006 to form a PDCP PDU 1002. The PDCP layer may provide the PDCP PDU 1002 to an RLC layer (e.g., RLC layer 412) . The RLC layer may attach an RLC header 1010 to the PDCP PDU 1002 to form a UMD PDU 1008. In some examples, the PDCP header 1004 may include a PDCP sequence number (also abbreviated herein as SN _PDCP) and the RLC header 1010 may include an RLC sequence number (also abbreviated herein as SN _RLC) . In some examples, the SN _PDCP may be larger (e.g., a 16-bit value) than the SN _RLC (e.g., a 5-bit value or 6-bit value) .

FIG. 11 is a conceptual diagram illustrating an example of a hardware implementation for an exemplary receiving device 1100 employing a processing system 1114. In the aspects described with reference to FIG. 11, the receiving device 1100 may be implemented as a user equipment (UE) , a vehicle-to-everything (V2X) device, a cellular V2X (C-V2X) device, or other suitable type of receiving device. For example, the receiving device 1100 may correspond to any of the UEs shown and described above in reference to FIGs. 1 and/or 2, or any of the vehicles 302a–302d shown and described above in reference to FIG. 3.

The receiving device 1100 may be implemented with a processing system 1114 that includes one or more processors 1104. Examples of processors 1104 include microprocessors, microcontrollers, digital signal processors (DSPs) , field programmable gate arrays (FPGAs) , programmable logic devices (PLDs) , state machines, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionality described throughout this disclosure. In various examples, the receiving device 1100 may be configured to perform any one or more of the functions described herein. That is, the processor 1104, as utilized in a receiving device 1100, may be used to implement any one or more of the processes described below and illustrated in FIGS. 14-16.

In this example, the processing system 1114 may be implemented with a bus architecture, represented generally by the bus 1102. The bus 1102 may include any number of interconnecting buses and bridges depending on the specific application of the processing system 1114 and the overall design constraints. The bus 1102 communicatively couples together various circuits including one or more processors (represented generally by the processor 1104) , a memory 1105, and computer-readable media (represented generally by the computer-readable medium 1106) . The bus 1102 may also link various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits, which are well known in the art, and therefore, will not be described any further. A bus interface 1108 provides an interface between the bus 1102 and a transceiver 1110. The transceiver 1110 provides a means for communicating with various other apparatus over a transmission medium (e.g., air) . Depending upon the nature of the apparatus, a user interface 1112 (e.g., keypad, display, speaker, microphone, joystick) may also be provided.

The processor 1104 is responsible for managing the bus 1102 and general processing, including the execution of software stored on the computer-readable medium 1106. The software, when executed by the processor 1104, causes the processing system 1114 to perform the various functions described below for any particular apparatus. The computer-readable medium 1106 and the memory 1105 may also be used for storing data that is manipulated by the processor 1104 when executing software. In some examples, the memory 1105 may include an RLC reception buffer 1115 and state variables 1118. In some aspects of the disclosure, the RLC reception buffer 1115 may be used for storing received UMD PDUs, which may later be processed for delivery to upper layers (e.g., a PDCP layer) . In some aspects of the disclosure, the state variables 1118 may include one or more state variables and/or values, such as VR (UH) , VR (UR) , RX_Next_Highest, RX_Next_Reassembly, a PDCP sequence number in a last received UMD PDU, and/or UM_Window_Size as described herein.

One or more processors 1104 in the processing system may execute software. Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. The software may reside on the computer-readable medium 1106.

The computer-readable medium 1106 may be a non-transitory computer-readable medium. A non-transitory computer-readable medium includes, by way of example, a magnetic storage device (e.g., hard disk, floppy disk, magnetic strip) , an optical disk (e.g., a compact disc (CD) or a digital versatile disc (DVD) ) , a smart card, a flash memory device (e.g., a card, a stick, or a key drive) , a random access memory (RAM) , a read only memory (ROM) , a programmable ROM (PROM) , an erasable PROM (EPROM) , an electrically erasable PROM (EEPROM) , a register, a removable disk, and any other suitable medium for storing software and/or instructions that may be accessed and read by a computer. The computer-readable medium 1106 may reside in the processing system 1114, external to the processing system 1114, or distributed across multiple entities including the processing system 1114. The computer-readable medium 1106 may be embodied in a computer program product. By way of example, a computer program product may include a computer-readable medium in packaging materials. Those skilled in the art will recognize how best to implement the described functionality presented throughout this disclosure depending on the particular application and the overall design constraints imposed on the overall system.

In some aspects of the disclosure, the processor 1104 may include circuitry configured for various functions. For example, the processor 1104 may include communication circuitry 1142. The communication circuitry 1142 may include one or more hardware components that provide the physical structure that performs various processes related to wireless communication (e.g., signal reception and/or signal transmission) as described herein. The communication circuitry 1142 may further be configured to execute communication software 1152 included on the computer-readable medium 1106 to implement one or more functions described herein. The processor 1104 may also include signal processing circuitry 1144. The signal processing circuitry 1144 may include one or more hardware components that provide the physical structure that performs various processes related to signal processing (e.g., processing a received signal and/or processing a signal for transmission) as described herein. The signal processing circuitry 1144 may further be configured to execute signal processing software 1154 included on the computer-readable medium 1106 to implement one or more functions described herein.

The processor 1104 may further include Radio Link Control (RLC) processing circuitry 1146 configured to provide an RLC sublayer in the radio protocol architecture. In some examples, the RLC processing circuitry 1146 may be configured to receive RLC Protocol Data Units (PDUs) , Packet Data Convergence Protocol (PDCP) PDUs and Internet Protocol (IP) packets from a lower layer in the radio protocol architecture and to process the received RLC PDUs.

In an aspect of the disclosure, the RLC processing circuitry 1146 may be configured to implement an unacknowledged mode (UM) of the receiving device 1100. For example, the RLC processing circuitry 1146 may receive an unacknowledged mode data (UMD) protocol data unit (PDU) and may determine that an RLC sequence number of the UMD PDU is within a reordering window. For example, the RLC processing circuitry 1146 may determine that the RLC sequence number of the UMD PDU is within the reordering window by determining that the RLC sequence number is less than a first state variable and greater than or equal to a difference between a second state variable and a window size. In some aspects of the disclosure, the first state variable (e.g., VR (UR) described with reference to FIG. 14) holds a value of a sequence number of an earliest UMD PDU that is considered for reordering, the second state variable (e.g., VR (UH) described with reference to FIG. 14) holds a value of a first sequence number following a second sequence number of a UMD PDU with a highest sequence number among received UMD PDUs. In these aspects, the window size may be set to a positive integer, such as 16. Therefore, the UE may determine that the RLC sequence number of the UMD PDU (e.g., SN _RLC = x) is within the reordering window if (VR (UH) –UM_Window_Size) <= x < VR (UR) .

In other aspects, the first state variable (e.g., RX_Next_Reassembly described with reference to FIG. 15) holds a value of an earliest sequence number that is considered for reassembly, the second state variable (e.g., RX_Next_Highest described with reference to FIG. 15) holds a value of a first sequence number following a second sequence number of a UMD PDU with a highest sequence number among received UMD PDUs. In these aspects, the window size may be set to a positive integer, such as 32.Therefore, the UE may determine that the RLC sequence number of the UMD PDU (e.g., SN _RLC) is within the reordering window if (RX_Next_Highest –UM_Window_Size) ≤ SN _RLC < RX_Next_Reassembly.

The RLC processing circuitry 1146 may determine a first packet data convergence protocol (PDCP) sequence number (abbreviated herein as SN _PDCP) included in the UMD PDU and may determine whether the first SN _PDCP in the UMD PDU is greater than a second SN _PDCP in a last received UMD PDU when the RLC sequence number is within the reordering window. In some examples, the SN _RLC is indicated with m bits and the SN _PDCP is indicated with n bits, wherein n is greater than m.For example, the SN _PDCP may be located in the PDCP header 1004 adjacent to the RLC header 1010 as shown in FIG. 10.

For example, the RLC processing circuitry 1146 may determine that the SN _RLC of the UMD PDU is within the reordering window by determining that the SN _RLC is less than a first state variable and greater than or equal to a difference between a second state variable and a window size. In one aspect, the first state variable holds a value of a sequence number of an earliest UMD PDU that is considered for reordering, the second state variable holds a value of a first sequence number following a second sequence number of a UMD PDU with a highest sequence number among received UMD PDUs. In another aspect, the first state variable holds a value of an earliest sequence number that is considered for reassembly, the second state variable holds a value of a first sequence number following a second sequence number of a UMD PDU with a highest sequence number among received UMD PDUs.

The RLC processing circuitry 1146 may store the UMD PDU when the first SN _PDCP is greater than the second SN _PDCP and may discard the UMD PDU when the first SN _PDCP is less than the second SN _PDCP. In some aspects, the RLC processing circuitry 1146 may store the UMD PDU by placing the UMD PDU in a reception buffer, such as the RLC reception buffer 1115.

The RLC processing circuitry 1146 may further be configured to execute RLC processing software 1156 included on the computer-readable medium 1106 to implement one or more functions described herein. The circuitry included in the processor 1104 is provided as non-limiting examples. Other means for carrying out the described functions exists and is included within various aspects of the present disclosure.

FIG. 12 is a flowchart illustrating a procedure 1200 for a receiving device operating in the unacknowledged mode (UM) . As shown in block 1202, the receiving device may receive an unacknowledged mode data (UMD) protocol data unit (PDU) (abbreviated herein as a UMD PDU) from a transmitting device. The UMD PDU may include a 5-bit RLC SN (also referred to as an SN _RLC) , which provides an SN _RLC space from 0 to 31. For example, when the transmitting device exhausts the SN _RLC space when transmitting a UMD PDU (e.g., when the SN _RLC of a UMD PDU is set to 31) , the SN _RLC space wraps around to zero (e.g., SN _RLC is set to 0) for a subsequent UMD PDU. With reference to block 1202, the SN _RLC of the received UMD PDU may be represented by the variable x.

The receiving device may maintain a reordering window according to one or more states variables as described herein. The reordering window may enable the receiving device to process any duplicate UMD PDUs or UMD PDUs that arrive out-of-order at the receiving device. For example, the receiving device may maintain the reordering window according to a state variable VR (UH) . The state variable VR (UH) holds the value of the SN _RLC following the SN _RLC of the UMD PDU with the highest SN _RLC among received UMD PDUs, and it serves as the higher edge of the reordering window. The receiving device also maintains a state variable VR (UR) , which holds the value of the SN _RLC of the earliest UMD PDU that is still considered for reordering. In some examples, the receiving device may initially set the state variables VR (UH) and VR (UR) to zero. In some examples, the receiving device may update the state variables VR (UH) and VR (UR) to the next expected SN _RLC. For example, if the receiving device receives a UMD PDU with SN _RLC = x and places the UMD PDU in the reception buffer, the receiving device may update VR (UH) and VR (UR) to be equal to x + 1.

At block 1204, the receiving device may determine whether VR (UR) < x <VR (UH) and whether a UMD PDU with SN _RLC = x has been received before. If VR (UR) < x < VR (UH) and a UMD PDU with SN _RLC = x has been received before, then at block 1206, the receiving device may discard the UMD PDU with SN _RLC = x. Otherwise, at block 1208, the receiving device may determine whether the SN _RLC of the received UMD PDU (e.g., the value of x) falls within the reordering window. The UMD PDU (e.g., the value of x) falls within the reordering window if (VR (UH) –UM_Window_Size) ≤ x < VR (UR) . For example, the UM_Window_Size may be 16 when a 5-bit SN _RLC is configured. If (VR (UH) –UM_Window_Size) ≤ x < VR (UR) , then at block 1206, the receiving device may discard the UMD PDU. Otherwise, if the UMD PDU (e.g., the value of x) does not fall within the reordering window 1208, then at block 1210, the receiving device may place the UMD PDU in a reception buffer of the receiving device.

An example scenario will be described with reference to the procedure 1200 in FIG. 12 and the sequence of RLC sequence numbers shown in FIG. 13. FIG. 13 shows a sequence of UMD PDUs and their corresponding RLC sequence numbers (e.g., UMD PDU 1304 with an SN _RLC set to zero) . In the example scenario of FIG. 13, the RLC sequence number included in each UMD PDU is a 5-bit sequence number (e.g., a 5-bit SN _RLC) , which may be included in an RLC header of each UMD PDU. Therefore, the SN _RLC space may begin at zero and end at 31. For example, as shown in FIG. 13, the first set of 32 UMD PDUs 1300 transmitted by the transmitting device may include the RLC sequence numbers 0 to 31. Thereafter, the SN _RLC space wraps around back to zero as indicated by the dotted arrow 1306. Accordingly, the second set of 32 UMD PDUs 1302 transmitted by the transmitting device may continue with the RLC sequence numbers 0 to 31.

In the example of FIG. 13, the receiving device may receive the UMD PDUs 1308 with SN _RLC = 0 to SN _RLC = 19 and may place these UMD PDUs in the reception buffer. As previously described, in some examples, if the receiving device receives a UMD PDU with SN _RLC = x and places this UMD PDU in the reception buffer, the receiving device may update the state variables VR (UH) and VR (UR) to be equal to x +1. Accordingly, in the scenario of FIG. 13, after receiving the UMD PDU with SN _RLC =19 and placing this UMD PDU in the reception buffer, the receiving device may set the state variables VR (UR) and VR (UH) to 20.

The transmitting device may proceed to transmit UMD PDUs with SN _RLC = 20 to SN _RLC = 31 and, due to the wrap around of RLC sequence numbers, subsequent UMD PDUs with SN _RLC = 0 to SN _RLC = 3 included in the second set of 32 UMD PDUs 1302. These 16 UMD PDUs (e.g., SN _RLC = 20 to SN _RLC = 31 and SN _RLC = 0 to SN _RLC = 3) may not be received by the receiving device for one or more reasons. For example, the receiving device may not be able to decode some or all of the 16 UMD PDUs and/or some or all of the transmissions carrying these 16 UMD PDUs may fail due to transmission conflicts.

The transmitting device may proceed to transmit UMD PDUs 1310 with SN _RLC = 4 to SN _RLC = 19 included in the second set of 32 UMD PDUs 1302. Although the receiving device may decode the UMD PDUs 1310, the receiving device may erroneously discard the UMD PDUs 1310. For example, with reference to block 1208 in the procedure 1200, the receiving device may set the state variables VR (UR) and VR (UH) to 20 after successfully receiving UMD PDU with SN _RLC = 19 and may set the UM_Window_Size to 16 as previously described. Since UMD PDUs with SN _RLC = x may be considered to fall within the reordering window if (VR (UH) –UM_Window_Size) ≤ x < VR (UR) as indicated in block 1208, and since VR (UR) = 20, VR (UH) = 20, and UM_Window_Size = 16, UMD PDUs with SN _RLC = x may be considered to fall within the reordering window if 4 ≤ x < 20. Therefore, when the receiving device processes the UMD PDUs 1310 according to block 1208, the receiving device will consider the UMD PDUs 1310 with SN _RLC = 4 to SN _RLC = 19 to be within the reordering window and will sequentially discard each of the UMD PDUs 1310.

It should be understood that the discarding of the UMD PDUs 1310 with SN _RLC = 4 to SN _RLC = 19 as required by

blocks

1208 and 1206 is erroneous because the UMD PDUs 1310 are fresh UMD PDUs with respect to the last received UMD PDU with SN _RLC = 19 (e.g., in the UMD PDUs 1308) . However, due to the failed transmissions of the 16 consecutive UMD PDUs (e.g., SN _RLC = 20 to SN _RLC = 31 and SN _RLC = 0 to SN _RLC = 3) and the wrap-around of the RLC sequence numbers in the 5-bit SN _RLC space, the conditions set in block 1208 require the receiving device to discard UMD PDUs (e.g., UMD PDUs 1310 with SN _RLC = 4 to SN _RLC = 19) until a UMD PDU with SN _RLC = 20 is received. Such erroneous discarding of UMD PDUs may lead to a data stall and, therefore, may degrade the user experience.

The transmitting device may proceed to transmit UMD PDUs with SN _RLC = 20 to SN _RLC = 31 included in the second set of 32 UMD PDUs 1302. Since the receiving device may consider UMD PDUs with SN _RLC = x to fall within the reordering window if 4 ≤ x < 20, the receiving device will consider the UMD PDU with SN _RLC = 20 to be outside of the reordering window and will place the UMD PDU with SN _RLC = 20 in the reception buffer. The subsequent UMD PDUs with SN _RLC = 21 to SN _RLC = 31 may also be considered to fall outside the reordering window and may also be placed in the reception buffer.

FIG. 14 is a flowchart illustrating a procedure 1400 for a receiving device operating in the unacknowledged mode (UM) in accordance with various aspects of the disclosure. As shown in block 1402, the receiving device (e.g., receiving device 1100 in FIG. 11) may receive a UMD PDU from a transmitting device. The UMD PDU may include a 5-bit RLC SN (also referred to as an SN _RLC) , which provides an SN _RLC space from 0 to 31. For example, when the transmitting device exhausts the SN _RLC space when transmitting a UMD PDU (e.g., when the SN _RLC of a UMD PDU is set to 31) , the SN _RLC space wraps around to zero (e.g., SN _RLC is set to 0) for a subsequent UMD PDU. With reference to block 1402, the SN _RLC of the received UMD PDU may be represented by the variable x.

The receiving device may maintain the state variables VR (UR) and VR (UH) , and may further maintain a reordering window according to one or more states variables (e.g., the state variable VR (UH) ) as previously described. In some examples, the receiving device may initially set the state variables VR (UH) and VR (UR) to zero. In some examples, the receiving device may update the state variables VR (UH) and VR (UR) to the next expected SN _RLC. For example, if the receiving device receives a UMD PDU with SN _RLC = x and places the UMD PDU in the reception buffer, the receiving device may update VR (UH) and VR (UR) to be equal to x + 1.

At block 1404, the receiving device may determine whether VR (UR) < x <VR (UH) and whether a UMD PDU with SN _RLC = x has been received before. If VR (UR) < x < VR (UH) and a UMD PDU with SN _RLC = x has been received before, then at block 1406, the receiving device may discard the UMD PDU with SN _RLC = x. Otherwise, at block 1408, the receiving device may determine whether the SN _RLC of the received UMD PDU (e.g., the value of x) falls within the reordering window. The UMD PDU (e.g., the value of x) falls within the reordering window if (VR (UH) –UM_Window_Size) ≤ x < VR (UR) . For example, the UM_Window_Size may be 16 when a 5-bit SN _RLC is configured. If (VR (UH) –UM_Window_Size) ≤ x < VR (UR) , then at block 1412, the receiving device may determine the packet data convergence protocol (PDCP) sequence number (e.g., the SN _PDCP in the PDCP header 1004) of the UMD PDU. Since the PDCP header including SN _PDCP may be located adjacent to the RLC header of the UMD PDU, the receiving device (e.g., the RLC layer of the receiving device) may determine the SN _PDCP without a significant amount of processing.

As previously described, the SN _PDCP in the UMD PDU (e.g., a 16-bit value) may be larger (e.g., more bits) than the SN _RLC (e.g., a 5-bit value) . Therefore, the SN _PDCP space may be significantly larger (e.g., 0 to 65535) than the SN _RLC space (e.g., 0 to 31) . As a result, the SN _PDCP may not wrap-around as frequently as the SN _RLC.

With reference to FIG. 14, at block 1414, the receiving device may determine whether the SN _PDCP in the UMD PDU with SN _RLC = x is greater than the SN _PDCP in a last received UMD PDU. If the SN _PDCP in the UMD PDU with SN _RLC = x is greater than the SN _PDCP in the last received UMD PDU, the receiving device may consider the UMD PDU with SN _RLC = x as a fresh UMD PDU and, at block 1410, may place the UMD PDU with SN _RLC = x in the reception buffer. Otherwise, if the SN _PDCP in the UMD PDU with SN _RLC = x is less than the SN _PDCP in a last received UMD PDU, the receiving device may consider the UMD PDU with SN _RLC = x as a stale UMD PDU and, at block 1406, may discard the UMD PDU with SN _RLC = x in the reception buffer.

Referring back to the example scenario in FIG. 13, when a receiving device applying the process 1400 receives and decodes the UMD PDUs 1310 with SN _RLC = 4 to SN _RLC = 19 included in the second set of 32 UMD PDUs 1302, the receiving device may not erroneously discard the UMD PDUs 1310. For example, with reference to block 1408 in the process 1400, the receiving device may set the state variables VR (UR) and VR (UH) to 20 after successfully receiving UMD PDU with SN _RLC = 19 and may set the UM_Window_Size to 16 as previously described. Since UMD PDUs with SN _RLC = x may be considered to fall within the reordering window if (VR (UH) –UM_Window_Size) ≤ x < VR (UR) as indicated in block 1408, and since VR (UR) = 20, VR (UH) = 20, and UM_Window_Size = 16, UMD PDUs with SN _RLC = x may be considered to fall within the reordering window if 4 ≤ x < 20. For example, when the receiving device processes the UMD PDU with SN _RLC = 4 (e.g., in the UMD PDUs 1310) according to block 1408, the receiving device may determine that the SN _RLC = 4 is within the reordering window if 4 ≤ x < 20 and may proceed to determine the SN _PDCP of the UMD PDU with SN _RLC = 4.

At block 1414, the receiving device may determine that the SN _PDCP of the UMD PDU with SN _RLC = 4 is larger than the SN _PDCP in a last received UMD PDU (e.g., the SN _PDCP of the UMD PDU with SN _RLC = 19 in the first set of 32 UMD PDUs 1300) and may place the UMD PDU with SN _RLC = 4 in the reception buffer. The receiving device may similarly process the UMD PDUs with SN _RLC = 5 to SN _RLC = 19 and may sequentially place the UMD PDUs with SN _RLC = 5 to SN _RLC = 19 in the reception buffer.

FIG. 15 is a flowchart illustrating a procedure 1500 for a receiving device operating in the unacknowledged mode (UM) in accordance with various aspects of the disclosure. As shown in block 1502, the receiving device may receive a UMD PDU from a transmitting device.

The receiving device may maintain the state variables RX_Next_Highest and RX_Next_Reassembly. The state variable RX_Next_Highest holds the value of the RLC sequence number (also referred to as SN _RLC) following the SN _RLC of the UMD PDU with the highest SN _RLC among received UMD PDUs. The state variable RX_Next_Reassembly holds the value of the earliest SN _RLC that is still considered for reassembly. In some examples, the receiving device may initially set the state variables RX_Next_Highest and RX_Next_Reassembly to zero. In some examples, the receiving device may update the state variables RX_Next_Highest and RX_Next_Reassembly to the next expected SN _RLC. For example, if the receiving device receives a UMD PDU with SN _RLC = x and places the UMD PDU in the reception buffer, the receiving device may update RX_Next_Highest and RX_Next_Reassembly to be equal to x + 1.

At block 1504, the receiving device may determine whether the UMD PDU includes an SN _RLC. For example, the SN _RLC may be a 6-bit SN _RLC, which provides an SN _RLC space from 0 to 63. For example, when the transmitting device exhausts the SN _RLC space when transmitting a UMD PDU (e.g., when the SN _RLC of a UMD PDU is set to 63) , the SN _RLC space wraps around to zero (e.g., SN _RLC is set to 0) for a subsequent UMD PDU.

If the UMD PDU does not include an SN _RLC, then at block 1506, the receiving device may remove the RLC header from the UMD PDU and may deliver the RLC SDU to an upper layer. Otherwise, if the UMD PDU includes an SN _RLC, then at block 1508, the receiving device may determine that the SN _RLC of the UMD PDU falls within the reordering window if (RX_Next_Highest –UM_Window_Size) ≤ SN _RLC <RX_Next_Reassembly. For example, the UM_Window_Size may be 32 when a 6-bit SN _RLC is configured. If (RX_Next_Highest –UM_Window_Size) ≤ SN _RLC <RX_Next_Reassembly, then at block 1512, the receiving device may determine the packet data convergence protocol (PDCP) sequence number (e.g., the SN _PDCP in the PDCP header 1004) of the UMD PDU. Since the PDCP header including SN _PDCP may be located adjacent to the RLC header of the UMD PDU, the receiving device may determine the SN _PDCP without a significant amount of processing.

As previously described, the SN _PDCP in the UMD PDU (e.g., a 16-bit value) may be larger (e.g., more bits) than the SN _RLC (e.g., a 6-bit value) . Therefore, the SN _PDCP space may be significantly larger (e.g., 0 to 65535) than the SN _RLC space (e.g., 0 to 63) . As a result, the SN _PDCP may not wrap-around as frequently as the SN _RLC.

With reference to FIG. 15, at block 1514, the receiving device may determine whether the SN _PDCP in the UMD PDU received at block 1502 is greater than the SN _PDCP in a last received UMD PDU. If the SN _PDCP in the UMD PDU is greater than the SN _PDCP in the last received UMD PDU, the receiving device may consider the UMD PDU received at block 1502 as a fresh UMD PDU and, at block 1510, may place the UMD PDU in the reception buffer. Otherwise, if the SN _PDCP in the UMD PDU received at block 1502 is less than the SN _PDCP in a last received UMD PDU, the receiving device may consider the UMD PDU as a stale UMD PDU and, at block 1516, may discard the UMD PDU received at block 1502 in the reception buffer.

FIG. 16 is a flow chart 1600 of an exemplary method for a receiving device operating in an unacknowledged mode (UM) according to some aspects of the present disclosure. As described below, some or all illustrated features may be omitted in a particular implementation within the scope of the present disclosure, and some illustrated features may not be required for implementation of all embodiments. In some examples, the method may be performed by the receiving device 1100, as described above and illustrated in FIG. 11, by a processor or processing system, or by any suitable means for carrying out the described functions.

At block 1602, the UE may receive a radio link control (RLC) unacknowledged mode data (UMD) protocol data unit (PDU) (e.g., the

UMD PDU

600, 800, 1008) . For example, the UMD PDU may include a 5-bit RLC sequence number (also referred to as an SN _RLC) , such as RLC SN 610, or a 6-bit RLC sequence number, such as RLC SN 808.

At block 1604, the receiving device may determine that the RLC sequence number of the UMD PDU is within a reordering window. In some aspects of the disclosure, the receiving device may determine that the RLC sequence number of the UMD PDU is within the reordering window by determining that the RLC sequence number is less than a first state variable and greater than or equal to a difference between a second state variable and a window size. In some aspects of the disclosure, the first state variable (e.g., VR (UR) described with reference to FIG. 14) holds a value of a sequence number of an earliest UMD PDU that is considered for reordering, the second state variable (e.g., VR (UH) described with reference to FIG. 14) holds a value of a first sequence number following a second sequence number of a UMD PDU with a highest sequence number among received UMD PDUs. In these aspects, the window size may be set to a positive integer, such as 16. Therefore, the receiving device may determine that the RLC sequence number of the UMD PDU (e.g., SN _RLC = x) is within the reordering window if (VR (UH) –UM_Window_Size) <= x < VR (UR) .

In other aspects, the first state variable (e.g., RX_Next_Reassembly described with reference to FIG. 15) holds a value of an earliest sequence number that is considered for reassembly, the second state variable (e.g., RX_Next_Highest described with reference to FIG. 15) holds a value of a first sequence number following a second sequence number of a UMD PDU with a highest sequence number among received UMD PDUs. In these aspects, the window size may be set to a positive integer, such as 32. Therefore, the receiving device may determine that the RLC sequence number of the UMD PDU (e.g., SN _RLC) is within the reordering window if (RX_Next_Highest –UM_Window_Size) ≤ SN _RLC < RX_Next_Reassembly.

At block 1606, the receiving device may determine a first packet data convergence protocol (PDCP) sequence number included in the UMD PDU. In some aspects, the PDCP sequence number (abbreviated herein as SN _PDCP) may be in a PDCP header located adjacent to the RLC header of the UMD PDU. For example, the SN _PDCP may be located in the PDCP header 1004 adjacent to the RLC header 1010 as shown in FIG. 10.

At block 1608, the receiving device may determine whether the first PDCP sequence number in the UMD PDU is greater than a second PDCP sequence number in a last received UMD PDU when the RLC sequence number is within the reordering window. In some examples, the RLC sequence number is indicated with m bits and the PDCP sequence number is indicated with n bits, wherein n is greater than m. In some examples, m may be a first positive integer, such as 5 or 6, and n may be a second positive integer, such as 16.

At block 1610, the receiving device may store the UMD PDU when the first PDCP sequence number is greater than the second PDCP sequence number. In some aspects of the disclosure, the receiving device may store the UMD PDU by placing the UMD PDU in a reception buffer (e.g., the RLC reception buffer 1115) .

At block 1612, the receiving device may discard the UMD PDU when the first PDCP sequence number is less than the second PDCP sequence number.

In one configuration, a receiving device operating in an unacknowledged mode (UM) includes means for receiving a radio link control (RLC) unacknowledged mode data (UMD) protocol data unit (PDU) , means for determining that an RLC sequence number of the UMD PDU is within a reordering window, means for determining a first packet data convergence protocol (PDCP) sequence number included in the UMD PDU, means for determining whether the first PDCP sequence number in the UMD PDU is greater than a second PDCP sequence number in a last received UMD PDU when the RLC sequence number is within the reordering window, means for storing the UMD PDU when the first PDCP sequence number is greater than the second PDCP sequence number, and means for discarding the UMD PDU when the first PDCP sequence number is less than the second PDCP sequence number.

In one aspect, the aforementioned means for receiving a radio link control (RLC) unacknowledged mode data (UMD) protocol data unit (PDU) , means for determining that an RLC sequence number of the UMD PDU is within a reordering window, means for determining a first packet data convergence protocol (PDCP) sequence number included in the UMD PDU, means for determining whether the first PDCP sequence number in the UMD PDU is greater than a second PDCP sequence number in a last received UMD PDU when the RLC sequence number is within the reordering window, means for storing the UMD PDU when the first PDCP sequence number is greater than the second PDCP sequence number, and means for discarding the UMD PDU when the first PDCP sequence number is less than the second PDCP sequence number may be the processor (s) 1104 shown in FIG. 11 configured to perform the functions recited by the aforementioned means. In another aspect, the aforementioned means may be a circuit or any apparatus configured to perform the functions recited by the aforementioned means.

For example, the aforementioned means for receiving a radio link control (RLC) unacknowledged mode data (UMD) protocol data unit (PDU) may include the communication circuitry 1142, the signal processing circuitry 1144, the RLC processing circuitry 1146, and the transceiver 1110. The aforementioned means for determining that an RLC sequence number of the UMD PDU is within a reordering window, means for determining a first packet data convergence protocol (PDCP) sequence number included in the UMD PDU, means for determining whether the first PDCP sequence number in the UMD PDU is greater than a second PDCP sequence number in a last received UMD PDU when the RLC sequence number is within the reordering window, means for storing the UMD PDU when the first PDCP sequence number is greater than the second PDCP sequence number, and means for discarding the UMD PDU when the first PDCP sequence number is less than the second PDCP sequence number may include the RLC processing circuitry 1146.

Several aspects of a wireless communication network have been presented with reference to an exemplary implementation. As those skilled in the art will readily appreciate, various aspects described throughout this disclosure may be extended to other telecommunication systems, network architectures and communication standards.

By way of example, various aspects may be implemented within other systems defined by 3GPP, such as Long-Term Evolution (LTE) , the Evolved Packet System (EPS) , the Universal Mobile Telecommunication System (UMTS) , and/or the Global System for Mobile (GSM) . Various aspects may also be extended to systems defined by the 3rd Generation Partnership Project 2 (3GPP2) , such as CDMA2000 and/or Evolution-Data Optimized (EV-DO) . Other examples may be implemented within systems employing IEEE 802.11 (Wi-Fi) , IEEE 802.16 (WiMAX) , IEEE 802.20, Ultra-Wideband (UWB) , Bluetooth, and/or other suitable systems. The actual telecommunication standard, network architecture, and/or communication standard employed will depend on the specific application and the overall design constraints imposed on the system.

Within the present disclosure, the word “exemplary” is used to mean “serving as an example, instance, or illustration. ” Any implementation or aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects of the disclosure. Likewise, the term “aspects” does not require that all aspects of the disclosure include the discussed feature, advantage or mode of operation. The term “coupled” is used herein to refer to the direct or indirect coupling between two objects. For example, if object A physically touches object B, and object B touches object C, then objects A and C may still be considered coupled to one another-even if they do not directly physically touch each other. For instance, a first object may be coupled to a second object even though the first object is never directly physically in contact with the second object. The terms “circuit” and “circuitry” are used broadly, and intended to include both hardware implementations of electrical devices and conductors that, when connected and configured, enable the performance of the functions described in the present disclosure, without limitation as to the type of electronic circuits, as well as software implementations of information and instructions that, when executed by a processor, enable the performance of the functions described in the present disclosure.

One or more of the components, steps, features and/or functions illustrated in FIGs. 1–16 may be rearranged and/or combined into a single component, step, feature or function or embodied in several components, steps, or functions. Additional elements, components, steps, and/or functions may also be added without departing from novel features disclosed herein. The apparatus, devices, and/or components illustrated in FIGs. 1, 2, 3, and 11 may be configured to perform one or more of the methods, features, or steps described herein. The novel algorithms described herein may also be efficiently implemented in software and/or embedded in hardware.

It is to be understood that the specific order or hierarchy of steps in the methods disclosed is an illustration of exemplary processes. Based upon design preferences, it is understood that the specific order or hierarchy of steps in the methods may be rearranged. The accompanying method claims present elements of the various steps in a sample order, and are not meant to be limited to the specific order or hierarchy presented unless specifically recited therein.

The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but are to be accorded the full scope consistent with the language of the claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more. ” Unless specifically stated otherwise, the term “some” refers to one or more. A phrase referring to “at least one of” a list of items refers to any combination of those items, including single members. As an example, “at least one of: a, b, or c” is intended to cover: a; b; c; a and b; a and c; b and c; and a, b and c. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims.

Claims

A method of wireless communication at a receiving device operating in an unacknowledged mode (UM) , the method comprising:

receiving an unacknowledged mode data (UMD) protocol data unit (PDU) ;

determining that an RLC sequence number of the UMD PDU is within a reordering window;

determining a first packet data convergence protocol (PDCP) sequence number included in the UMD PDU;

determining whether the first PDCP sequence number in the UMD PDU is greater than a second PDCP sequence number in a last received UMD PDU when the RLC sequence number is within the reordering window; and

storing the UMD PDU when the first PDCP sequence number is greater than the second PDCP sequence number.
The method of claim 1, further comprising:

discarding the UMD PDU when the first PDCP sequence number is less than the second PDCP sequence number.
The method of claim 1, wherein storing the UMD PDU comprises placing the UMD PDU in a reception buffer.
The method of claim 1, wherein the determining that the RLC sequence number of the UMD PDU is within the reordering window comprises determining that the RLC sequence number is less than a first state variable and greater than or equal to a difference between a second state variable and a window size.
The method of claim 4, wherein the first state variable holds a value of a sequence number of an earliest UMD PDU that is considered for reordering, the second state variable holds a value of a first sequence number following a second sequence number of a UMD PDU with a highest sequence number among received UMD PDUs.
The method of claim 4, wherein the first state variable holds a value of an earliest sequence number that is considered for reassembly, the second state variable holds a value of a first sequence number following a second sequence number of a UMD PDU with a highest sequence number among received UMD PDUs.
The method of claim 1, wherein the RLC sequence number is indicated with m bits and the PDCP sequence number is indicated with n bits, wherein n is greater than m.
A receiving device operating in an unacknowledged mode (UM) in a wireless communication network, comprising:

a processor;

a transceiver communicatively coupled to the processor; and

a memory communicatively coupled to the processor, wherein the processor is configured to:

receive a radio link control (RLC) unacknowledged mode data (UMD) protocol data unit (PDU) ;

determine that an RLC sequence number of the UMD PDU is within a reordering window;

determine a first packet data convergence protocol (PDCP) sequence number included in the UMD PDU;

determine whether the first PDCP sequence number in the RLC UMD PDU is greater than a second PDCP sequence number in a last received UMD PDU when the RLC sequence number is within the reordering window; and

store the UMD PDU when the first PDCP sequence number is greater than the second PDCP sequence number.
The receiving device of claim 8, wherein the processor is further configured to:

discard the UMD PDU when the first PDCP sequence number is less than the second PDCP sequence number.
The receiving device of claim 8, wherein the processor configured to store the UMD PDU is further configured to place the UMD PDU in a reception buffer.
The receiving device of claim 8, wherein the processor configured to determine that the RLC sequence number of the UMD PDU is within the reordering window is further configured to determine that the RLC sequence number is less than a first state variable and greater than or equal to a difference between a second state variable and a window size.
The receiving device of claim 11, wherein the first state variable holds a value of a sequence number of an earliest UMD PDU that is considered for reordering, the second state variable holds a value of a first sequence number following a second sequence number of a UMD PDU with a highest sequence number among received UMD PDUs.
The receiving device of claim 11, wherein the first state variable holds a value of an earliest sequence number that is considered for reassembly, the second state variable holds a value of a first sequence number following a second sequence number of a UMD PDU with a highest sequence number among received UMD PDUs.
The receiving device of claim 8, wherein the RLC sequence number is indicated with m bits and the PDCP sequence number is indicated with n bits, wherein n is greater than m.
A non-transitory computer-readable medium storing computer-executable code, comprising code for causing a receiving device operating in an unacknowledged mode to:

receive a radio link control (RLC) unacknowledged mode data (UMD) protocol data unit (PDU) ;

determine that an RLC sequence number of the UMD PDU is within a reordering window;

determine a first packet data convergence protocol (PDCP) sequence number included in the UMD PDU;

determine whether the first PDCP sequence number in the UMD PDU is greater than a second PDCP sequence number in a last received UMD PDU when the RLC sequence number is within the reordering window; and

store the UMD PDU when the first PDCP sequence number is greater than the second PDCP sequence number.
The non-transitory computer-readable medium of claim 15, wherein the code further causes the receiving device to:

discard the UMD PDU when the first PDCP sequence number is less than the second PDCP sequence number.
The non-transitory computer-readable medium of claim 15, wherein the code for causing the receiving device to store the UMD PDU causes the receiving device to:

place the UMD PDU in a reception buffer.
The non-transitory computer-readable medium of claim 15, wherein the code for causing the receiving device to determine that the RLC sequence number of the UMD PDU is within the reordering window causes the user equipment to:

determine that the RLC sequence number is less than a first state variable and greater than or equal to a difference between a second state variable and a window size.
The non-transitory computer-readable medium of claim 18, wherein the first state variable holds a value of a sequence number of an earliest UMD PDU that is considered for reordering, the second state variable holds a value of a first sequence number following a second sequence number of a UMD PDU with a highest sequence number among received UMD PDUs.
The non-transitory computer-readable medium of claim 18, wherein the first state variable holds a value of an earliest sequence number that is considered for reassembly, the second state variable holds a value of a first sequence number following a second sequence number of a UMD PDU with a highest sequence number among received UMD PDUs.
The non-transitory computer-readable medium of claim 15, wherein the RLC sequence number is indicated with m bits and the PDCP sequence number is indicated with n bits, wherein n is greater than m.
A receiving device operating in an unacknowledged mode (UM) , comprising:

means for receiving a radio link control (RLC) unacknowledged mode data (UMD) protocol data unit (PDU) ;

means for determining that an RLC sequence number of the UMD PDU is within a reordering window;

means for determining a first packet data convergence protocol (PDCP) sequence number included in the UMD PDU;

means for determining whether the first PDCP sequence number in the UMD PDU is greater than a second PDCP sequence number in a last received UMD PDU when the RLC sequence number is within the reordering window; and

means for storing the UMD PDU when the first PDCP sequence number is greater than the second PDCP sequence number.
The receiving device of claim 22, further comprising:

means for discarding the UMD PDU when the first PDCP sequence number is less than the second PDCP sequence number.
The receiving device of claim 22, wherein the means for storing the UMD PDU is configured to place the UMD PDU in a reception buffer.
The receiving device of claim 22, wherein the means for determining that the RLC sequence number of the UMD PDU is within the reordering window is configured to determine that the RLC sequence number is less than a first state variable and greater than or equal to a difference between a second state variable and a window size.
The receiving device of claim 25, wherein the first state variable holds a value of a sequence number of an earliest UMD PDU that is considered for reordering, the second state variable holds a value of a first sequence number following a second sequence number of a UMD PDU with a highest sequence number among received UMD PDUs.
The receiving device of claim 25, wherein the first state variable holds a value of an earliest sequence number that is considered for reassembly, the second state variable holds a value of a first sequence number following a second sequence number of a UMD PDU with a highest sequence number among received UMD PDUs.
The receiving device of claim 22, wherein the RLC sequence number is indicated with m bits and the PDCP sequence number is indicated with n bits, wherein n is greater than m.