WO2020056737A1

WO2020056737A1 - User equipment identification in a random access response transmission

Info

Publication number: WO2020056737A1
Application number: PCT/CN2018/107026
Authority: WO
Inventors: Yiqing Cao; Wanshi Chen; Jing LEI
Original assignee: Qualcomm Incorporated
Priority date: 2018-09-21
Filing date: 2018-09-21
Publication date: 2020-03-26
Also published as: WO2020057319A1

Abstract

Methods, systems, and devices for wireless communications are described. Examples may include a user equipment (UE) transmitting a random access request that includes one or more random access channel (RACH) preamble parameters. In response to the random access request, a base station may transmit a random access response that is received by the UE. The random access response may uniquely identify the UE based on one or more RACH preamble parameters. In some cases, the random access response may include a modified radio access network temporary identifier (RA-RNTI) that includes a UE-specific parameter base on one or more or the RACH preamble parameters. The UE may determine that it is the intended recipient of the random access response based on identifying the UE-specific parameter and a communication connection may be established based on this exchange of messages.

Description

USER EQUIPMENT IDENTIFICATION IN A RANDOM ACCESS RESPONSE TRANSMISSION

BACKGROUND

The following relates generally to wireless communications, and more specifically to user equipment (UE) identification in a random access channel (RACH) response transmission.

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

Multiple UEs may attempt to initiate communications with a base station using a random access procedure. In some cases, in a contention-based procedure, multiple UEs may receive the same message from the base station indicating resources to use for establishing a connection with the base station. As such, there may be ambiguity regarding which UE was the intended recipient of the message from the base station. Techniques for resolving the contention between the competing UEs may include sending additional messages from the base station, which may increase the signaling overhead and latency for the random access procedure.

SUMMARY

The described techniques relate to improved methods, systems, devices, and apparatuses that support UE identification in a RACH response transmission. Generally, the described techniques provide for uniquely identifying a UE either explicitly or implicitly using a random access response message sent from a base station to the UE. The random access response message may identify the UE based on one or more RACH preamble parameters that were sent from the UE to the base station in a random access request message. For example, a random access response message may include a radio network temporary identifier that is modified to indicate a UE-specific parameter that is based on the one or more RACH preamble parameters. Additionally or alternatively, the random access response may uniquely identify a UE by indicating reference signals (e.g., demodulation reference signals (DMRS) ) that either explicitly or implicitly identify the UE. The random access response may also be scrambled with a UE-specific scrambling sequence.

A method of wireless communications is described. The method may include transmitting, from a UE, a random access request that includes one or more RACH preamble parameters, receiving a random access response in response to the random access request that uniquely identifies the UE based on at least one of the one or more RACH preamble parameters, and establishing a communication connection based on receiving the random access response.

An apparatus for wireless communications is described. The apparatus may include a processor, memory in electronic communication with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to transmit, from a UE, a random access request that includes one or more RACH preamble parameters, receive a random access response in response to the random access request that uniquely identifies the UE based on at least one of the one or more RACH preamble parameters, and establish a communication connection based on receiving the random access response.

Another apparatus for wireless communications is described. The apparatus may include means for transmitting, from a UE, a random access request that includes one or more RACH preamble parameters, receiving a random access response in response to the random access request that uniquely identifies the UE based on at least one of the one or more RACH preamble parameters, and establishing a communication connection based on receiving the random access response.

A non-transitory computer-readable medium storing code for wireless communications is described. The code may include instructions executable by a processor to transmit, from a UE, a random access request that includes one or more RACH preamble parameters, receive a random access response in response to the random access request that uniquely identifies the UE based on at least one of the one or more RACH preamble parameters, and establish a communication connection based on receiving the random access response.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving a modified random access radio network temporary identifier (RA-RNTI) in the random access response, where the modified RA-RNTI includes a UE-specific parameter, and where the UE-specific parameter may be based on at least one of the one or more RACH preamble parameters, identifying the UE-specific parameter included in the modified RA-RNTI and determining that the UE may be the intended recipient of the random access response based on identifying the UE-specific parameter.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the UE-specific parameter includes a preamble sequence that was indicated in the random access request.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the UE-specific parameter includes a product of a preamble sequence and a constant value, and where the preamble sequence, the constant value, or both were indicated in the random access request.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the UE-specific parameter includes a hashed value of a preamble sequence that was indicated in the random access request.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the UE-specific parameter includes a product of a hashed value of a preamble sequence and a constant value, and where the preamble sequence, the constant value, or both were indicated in the random access request.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the UE-specific parameter includes a demodulation reference signal (DMRS) sequence identifier, and where the DMRS sequence identifier may be based on an uplink (UL) DMRS that was indicated in the random access request.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the UE-specific parameter further includes a preamble sequence, a hashed value of the preamble sequence, a constant value, or a combination thereof, and where the preamble sequence, the constant value, or both were indicated in the random access request.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the UE-specific parameter includes a hashed DMRS sequence identifier, and where the hashed DMRS sequence identifier may be based on an UL DMRS that was indicated in the random access request.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving a downlink (DL) DMRS and determining that the UE may be the intended recipient of the random access response based on a mapping between the received DL DMRS and an UL DMRS that was indicated in the random access request.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for descrambling the random access response, where the random access response may be scrambled based on at least one of the one or more RACH preamble parameters indicated in the random access request and determining that the UE may be the intended recipient of the random access response based on descrambling the random access response.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the random access response may be scrambled based on a preamble sequence that was indicated in the random access request.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the random access response may be scrambled based on a scrambling sequence that may have a 1 to 1 mapping with a preamble sequence that was indicated in the random access request.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving the random access response on a set of resource blocks that indicates a preamble sequence identification.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the preamble sequence identification includes a resource block frequency index, a resource block frame index, or both.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the RACH preamble parameters include at least one of a RA-RNTI, a preamble sequence, a DMRS, or a combination thereof.

A method of wireless communications is described. The method may include receiving, from a UE, a random access request that includes one or more RACH preamble parameters, transmitting a random access response in response to the random access request that uniquely identifies the UE based on at least one of the one or more RACH preamble parameters, and establishing a communication connection based on transmitting the random access response.

An apparatus for wireless communications is described. The apparatus may include a processor, memory in electronic communication with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to receive, from a UE, a random access request that includes one or more RACH preamble parameters, transmit a random access response in response to the random access request that uniquely identifies the UE based on at least one of the one or more RACH preamble parameters, and establish a communication connection based on transmitting the random access response.

Another apparatus for wireless communications is described. The apparatus may include means for receiving, from a UE, a random access request that includes one or more RACH preamble parameters, transmitting a random access response in response to the random access request that uniquely identifies the UE based on at least one of the one or more RACH preamble parameters, and establishing a communication connection based on transmitting the random access response.

A non-transitory computer-readable medium storing code for wireless communications is described. The code may include instructions executable by a processor to receive, from a UE, a random access request that includes one or more RACH preamble parameters, transmit a random access response in response to the random access request that uniquely identifies the UE based on at least one of the one or more RACH preamble parameters, and establish a communication connection based on transmitting the random access response.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for transmitting a modified RA-RNTI in the random access response, where the modified RA-RNTI includes a UE-specific parameter indicating that the UE may be the intended recipient of the random access response, and where the UE-specific parameter may be based on at least one of the one or more RACH preamble parameters.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the UE-specific parameter includes a DMRS sequence identifier, and where the DMRS sequence identifier may be based on an UL DMRS that was indicated in the random access request.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for transmitting a DL DMRS indicating that the UE may be the intended recipient of the random access response based on a mapping between the received DL DMRS and an UL DMRS that was indicated in the random access request.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for scrambling the random access response, where the random access response may be scrambled based on at least one of the one or more RACH preamble parameters indicated in the random access request, and where the scrambling at least partially indicates that the UE may be the intended recipient of the random access response.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for transmitting the random access response on a set of resource blocks that indicates a preamble sequence identification.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a system for wireless communications that supports UE identification in a RACH response transmission in accordance with aspects of the present disclosure.

FIG. 2 illustrates an example of a system for wireless communications that supports UE identification in a RACH response transmission in accordance with aspects of the present disclosure.

FIG. 3 illustrates an example of a process flow that supports UE identification in a RACH response transmission in accordance with aspects of the present disclosure.

FIGs. 4 and 5 show block diagrams of devices that support UE identification in a RACH response transmission in accordance with aspects of the present disclosure.

FIG. 6 shows a block diagram of an identification module that supports UE identification in a RACH response transmission in accordance with aspects of the present disclosure.

FIG. 7 shows a diagram of a system including a device that supports UE identification in a RACH response transmission in accordance with aspects of the present disclosure.

FIGs. 8 and 9 show block diagrams of devices that support UE identification in a RACH response transmission in accordance with aspects of the present disclosure.

FIG. 10 shows a block diagram of an identification module that supports UE identification in a RACH response transmission in accordance with aspects of the present disclosure.

FIG. 11 shows a diagram of a system including a device that supports UE identification in a RACH response transmission in accordance with aspects of the present disclosure.

FIGs. 12 through 15 show flowcharts illustrating methods that support UE identification in a RACH response transmission in accordance with aspects of the present disclosure.

DETAILED DESCRIPTION

Aspects of the disclosure include a wireless communication system that supports UE identification in a RACH response transmission. The wireless communication system may include a base station and UE. The UE may transmit a first message such as a random access request to a base station to initiate a RACH procedure. In response, the base station may transmit a second response messages, such as a random access response. The random access response may uniquely identify the UE as the intended recipient of this second message. In some aspects, a communication connection may be established between the UE and the base station based on the UE receiving the random access response. The RACH procedure can be initiated in a variety of situations, for example, during establishment of a radio resource control (RRC) connection, during handover of a UE, if the UE has lost synchronization timing with a base station, or in other situations where the UE is initiating communication with a base station, but has not been assigned or does not have pre-determined resources to do so.

Aspects of the disclosure include the UE sending a random access request to a base station that includes one or more RACH preamble parameters, which may include a temporary identification parameter selected or generated by a UE. In some cases, the RACH preamble parameters may include a preamble sequence, a preamble ID derived from the preamble sequence (e.g., hashed value) , a RA-RNTI, preamble index, demodulation references signal (DMRS) , scrambling sequence, a set of specific resource blocks (RBs) , or the like. The base station may send a random access response that explicitly or implicitly identifies the UE as the intended recipient of the random access response. In some aspects, the UE may be explicitly identified by the random access response including a modified RA-RNTI, which may include a UE-specific parameter based on one or more of the RACH preamble parameters. In this regard, a UE may derive or identify the UE-specific parameter in the modified RA-RNTI as having been included in its random access request and thereby determine that it is the intended target of the random access response. In some aspects, the UE may be implicitly identified through scrambling the random access response according to, for example, the preamble sequence. As such, the UE being able to successfully decode the random access response based on the preamble sequence it included in the random access request, indicates that it is the intended recipient of the second message. Other examples of implicit identification include transmitting the random access response over specific resource blocks that indicate the preamble sequence, a preamble ID derived from the preamble sequence, or the like.

Aspects of the disclosure also include the random access response identifying the UE based on a correspondence between an UL DMRS and a downlink DMRS. For example, a UE may receive a DL DMRS that is mapped to the UL DMRS that the UE previously transmitted to the base station. Accordingly, by receiving a random access response with the UE-specific DL DMRS, the UE can determine that it is the intended recipient of the random access response.

Aspects of the disclosure are initially described in the context of wireless communications systems. Aspects of the disclosure are then described in the context of a process flow diagram. Aspects of the disclosure are further illustrated by and described with reference to apparatus diagrams, system diagrams, and flowcharts that relate to UE identification in a RACH response transmission.

FIG. 1 illustrates an example of a wireless communications system 100 that supports UE identification in a RACH response transmission in accordance with aspects of the present disclosure. The wireless communications system 100 includes base stations 105, UEs 115, and a core network 130. In some examples, the wireless communications system 100 may be a Long Term Evolution (LTE) network, an LTE-Advanced (LTE-A) network, an LTE-A Pro network, or a New Radio (NR) network. In some cases, wireless communications system 100 may support enhanced broadband communications, ultra-reliable (e.g., mission critical) communications, low latency communications, or communications with low-cost and low-complexity devices.

Base stations 105 may wirelessly communicate with UEs 115 via one or more base station antennas. Base stations 105 described herein may include or may be referred to by those skilled in the art as a base transceiver station, a radio base station, an access point, a radio transceiver, a NodeB, an eNodeB (eNB) , a next-generation Node B or giga-nodeB (either of which may be referred to as a gNB) , a Home NodeB, a Home eNodeB, or some other suitable terminology. Wireless communications system 100 may include base stations 105 of different types (e.g., macro or small cell base stations) . The UEs 115 described herein may be able to communicate with various types of base stations 105 and network equipment including macro eNBs, small cell eNBs, gNBs, relay base stations, and the like.

Each base station 105 may be associated with a particular geographic coverage area 110 in which communications with various UEs 115 is supported. Each base station 105 may provide communication coverage for a respective geographic coverage area 110 via communication links 125, and communication links 125 between a base station 105 and a UE 115 may utilize one or more carriers. Communication links 125 shown in wireless communications system 100 may include uplink transmissions from a UE 115 to a base station 105, or downlink transmissions from a base station 105 to a UE 115. Downlink transmissions may also be called forward link transmissions while uplink transmissions may also be called reverse link transmissions.

The geographic coverage area 110 for a base station 105 may be divided into sectors making up only a portion of the geographic coverage area 110, and each sector may be associated with a cell. For example, each base station 105 may provide communication coverage for a macro cell, a small cell, a hot spot, or other types of cells, or various combinations thereof. In some examples, a base station 105 may be movable and therefore provide communication coverage for a moving geographic coverage area 110. In some examples, different geographic coverage areas 110 associated with different technologies may overlap, and overlapping geographic coverage areas 110 associated with different technologies may be supported by the same base station 105 or by different base stations 105. The wireless communications system 100 may include, for example, a heterogeneous LTE/LTE-A/LTE-A Pro or NR network in which different types of base stations 105 provide coverage for various geographic coverage areas 110.

The term “cell” refers to a logical communication entity used for communication with a base station 105 (e.g., over a carrier) , and may be associated with an identifier for distinguishing neighboring cells (e.g., a physical cell identifier (PCID) , a virtual cell identifier (VCID) ) operating via the same or a different carrier. In some examples, a carrier may support multiple cells, and different cells may be configured according to different protocol types (e.g., machine-type communication (MTC) , narrowband Internet-of-Things (NB-IoT) , enhanced mobile broadband (eMBB) , or others) that may provide access for different types of devices. In some cases, the term “cell” may refer to a portion of a geographic coverage area 110 (e.g., a sector) over which the logical entity operates.

UEs 115 may be dispersed throughout the wireless communications system 100, and each UE 115 may be stationary or mobile. A UE 115 may also be referred to as a mobile device, a wireless device, a remote device, a handheld device, or a subscriber device, or some other suitable terminology, where the “device” may also be referred to as a unit, a station, a terminal, or a client. A UE 115 may also be a personal electronic device such as a cellular phone, a personal digital assistant (PDA) , a tablet computer, a laptop computer, or a personal computer. In some examples, a UE 115 may also refer to a wireless local loop (WLL) station, an Internet of Things (IoT) device, an Internet of Everything (IoE) device, or an MTC device, or the like, which may be implemented in various articles such as appliances, vehicles, meters, or the like.

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

Some UEs 115 may be configured to employ operating modes that reduce power consumption, such as half-duplex communications (e.g., a mode that supports one-way communication via transmission or reception, but not transmission and reception simultaneously) . In some examples half-duplex communications may be performed at a reduced peak rate. Other power conservation techniques for UEs 115 include entering a power saving “deep sleep” mode when not engaging in active communications, or operating over a limited bandwidth (e.g., according to narrowband communications) . In some cases, UEs 115 may be designed to support critical functions (e.g., mission critical functions) , and a wireless communications system 100 may be configured to provide ultra-reliable communications for these functions.

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

Base stations 105 may communicate with the core network 130 and with one another. For example, base stations 105 may interface with the core network 130 through backhaul links 132 (e.g., via an S1, N2, N3, or other interface) . Base stations 105 may communicate with one another over backhaul links 134 (e.g., via an X2, Xn, or other interface) either directly (e.g., directly between base stations 105) or indirectly (e.g., via core network 130) .

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

At least some of the network devices, such as a base station 105, may include subcomponents such as an access network entity, which may be an example of an access node controller (ANC) . Each access network entity may communicate with UEs 115 through a number of other access network transmission entities, which may be referred to as a radio head, a smart radio head, or a transmission/reception point (TRP) . In some configurations, various functions of each access network entity or base station 105 may be distributed across various network devices (e.g., radio heads and access network controllers) or consolidated into a single network device (e.g., a base station 105) .

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

Wireless communications system 100 may also operate in a super high frequency (SHF) region using frequency bands from 3 GHz to 30 GHz, also known as the centimeter band. The SHF region includes bands such as the 5 GHz industrial, scientific, and medical (ISM) bands, which may be used opportunistically by devices that can tolerate interference from other users.

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

In some cases, wireless communications system 100 may utilize both licensed and unlicensed radio frequency spectrum bands. For example, wireless communications system 100 may employ License Assisted Access (LAA) , LTE-Unlicensed (LTE-U) radio access technology, or NR technology in an unlicensed band such as the 5 GHz ISM band. When operating in unlicensed radio frequency spectrum bands, wireless devices such as base stations 105 and UEs 115 may employ listen-before-talk (LBT) procedures to ensure a frequency channel is clear before transmitting data. In some cases, operations in unlicensed bands may be based on a CA configuration in conjunction with CCs operating in a licensed band (e.g., LAA) . Operations in unlicensed spectrum may include downlink transmissions, uplink transmissions, peer-to-peer transmissions, or a combination of these. Duplexing in unlicensed spectrum may be based on frequency division duplexing (FDD) , time division duplexing (TDD) , or a combination of both.

In some examples, base station 105 or UE 115 may be equipped with multiple antennas, which may be used to employ techniques such as transmit diversity, receive diversity, multiple-input multiple-output (MIMO) communications, or beamforming. For example, wireless communications system 100 may use a transmission scheme between a transmitting device (e.g., a base station 105) and a receiving device (e.g., a UE 115) , where the transmitting device is equipped with multiple antennas and the receiving devices are equipped with one or more antennas. MIMO communications may employ multipath signal propagation to increase the spectral efficiency by transmitting or receiving multiple signals via different spatial layers, which may be referred to as spatial multiplexing. The multiple signals may, for example, be transmitted by the transmitting device via different antennas or different combinations of antennas. Likewise, the multiple signals may be received by the receiving device via different antennas or different combinations of antennas. Each of the multiple signals may be referred to as a separate spatial stream, and may carry bits associated with the same data stream (e.g., the same codeword) or different data streams. Different spatial layers may be associated with different antenna ports used for channel measurement and reporting. MIMO techniques include single-user MIMO (SU-MIMO) where multiple spatial layers are transmitted to the same receiving device, and multiple-user MIMO (MU-MIMO) where multiple spatial layers are transmitted to multiple devices.

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

In one example, a base station 105 may use multiple antennas or antenna arrays to conduct beamforming operations for directional communications with a UE 115. For instance, some signals (e.g., synchronization signals, reference signals, beam selection signals, or other control signals) may be transmitted by a base station 105 multiple times in different directions, which may include a signal being transmitted according to different beamforming weight sets associated with different directions of transmission. Transmissions in different beam directions may be used to identify (e.g., by the base station 105 or a receiving device, such as a UE 115) a beam direction for subsequent transmission and/or reception by the base station 105. Some signals, such as data signals associated with a particular receiving device, may be transmitted by a base station 105 in a single beam direction (e.g., a direction associated with the receiving device, such as a UE 115) . In some examples, the beam direction associated with transmissions along a single beam direction may be determined based at least in in part on a signal that was transmitted in different beam directions. For example, a UE 115 may receive one or more of the signals transmitted by the base station 105 in different directions, and the UE 115 may report to the base station 105 an indication of the signal it received with a highest signal quality, or an otherwise acceptable signal quality. Although these techniques are described with reference to signals transmitted in one or more directions by a base station 105, a UE 115 may employ similar techniques for transmitting signals multiple times in different directions (e.g., for identifying a beam direction for subsequent transmission or reception by the UE 115) , or transmitting a signal in a single direction (e.g., for transmitting data to a receiving device) .

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

In some cases, the antennas of a base station 105 or UE 115 may be located within one or more antenna arrays, which may support MIMO operations, or transmit or receive beamforming. For example, one or more base station antennas or antenna arrays may be co-located at an antenna assembly, such as an antenna tower. In some cases, antennas or antenna arrays associated with a base station 105 may be located in diverse geographic locations. A base station 105 may have an antenna array with a number of rows and columns of antenna ports that the base station 105 may use to support beamforming of communications with a UE 115. Likewise, a UE 115 may have one or more antenna arrays that may support various MIMO or beamforming operations.

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

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

Time intervals in LTE or NR may be expressed in multiples of a basic time unit, which may, for example, refer to a sampling period of T _s = 1/30,720,000 seconds. Time intervals of a communications resource may be organized according to radio frames each having a duration of 10 milliseconds (ms) , where the frame period may be expressed as T _f = 307,200 T _s. The radio frames may be identified by a system frame number (SFN) ranging from 0 to 1023. Each frame may include 10 subframes numbered from 0 to 9, and each subframe may have a duration of 1 ms. A subframe may be further divided into 2 slots each having a duration of 0.5 ms, and each slot may contain 6 or 7 modulation symbol periods (e.g., depending on the length of the cyclic prefix prepended to each symbol period) . Excluding the cyclic prefix, each symbol period may contain 2048 sampling periods. In some cases, a subframe may be the smallest scheduling unit of the wireless communications system 100, and may be referred to as a transmission time interval (TTI) . In other cases, a smallest scheduling unit of the wireless communications system 100 may be shorter than a subframe or may be dynamically selected (e.g., in bursts of shortened TTIs (sTTIs) or in selected component carriers using sTTIs) .

In some wireless communications systems, a slot may further be divided into multiple mini-slots containing one or more symbols. In some instances, a symbol of a mini-slot or a mini-slot may be the smallest unit of scheduling. Each symbol may vary in duration depending on the subcarrier spacing or frequency band of operation, for example. Further, some wireless communications systems may implement slot aggregation in which multiple slots or mini-slots are aggregated together and used for communication between a UE 115 and a base station 105.

The term “carrier” refers to a set of radio frequency spectrum resources having a defined physical layer structure for supporting communications over a communication link 125. For example, a carrier of a communication link 125 may include a portion of a radio frequency spectrum band that is operated according to physical layer channels for a given radio access technology. Each physical layer channel may carry user data, control information, or other signaling. A carrier may be associated with a pre-defined frequency channel (e.g., an E-UTRA absolute radio frequency channel number (EARFCN) ) , and may be positioned according to a channel raster for discovery by UEs 115. Carriers may be downlink or uplink (e.g., in an FDD mode) , or be configured to carry downlink and uplink communications (e.g., in a TDD mode) . In some examples, signal waveforms transmitted over a carrier may be made up of multiple sub-carriers (e.g., using multi-carrier modulation (MCM) techniques such as OFDM or DFT-s-OFDM) .

The organizational structure of the carriers may be different for different radio access technologies (e.g., LTE, LTE-A, LTE-A Pro, NR, etc. ) . For example, communications over a carrier may be organized according to TTIs or slots, each of which may include user data as well as control information or signaling to support decoding the user data. A carrier may also include dedicated acquisition signaling (e.g., synchronization signals or system information, etc. ) and control signaling that coordinates operation for the carrier. In some examples (e.g., in a carrier aggregation configuration) , a carrier may also have acquisition signaling or control signaling that coordinates operations for other carriers.

Physical channels may be multiplexed on a carrier according to various techniques. A physical control channel and a physical data channel may be multiplexed on a downlink carrier, for example, using time division multiplexing (TDM) techniques, frequency division multiplexing (FDM) techniques, or hybrid TDM-FDM techniques. In some examples, control information transmitted in a physical control channel may be distributed between different control regions in a cascaded manner (e.g., between a common control region or common search space and one or more UE-specific control regions or UE-specific search spaces) .

A carrier may be associated with a particular bandwidth of the radio frequency spectrum, and in some examples the carrier bandwidth may be referred to as a “system bandwidth” of the carrier or the wireless communications system 100. For example, the carrier bandwidth may be one of a number of predetermined bandwidths for carriers of a particular radio access technology (e.g., 1.4, 3, 5, 10, 15, 20, 40, or 80 MHz) . In some examples, each served UE 115 may be configured for operating over portions or all of the carrier bandwidth. In other examples, some UEs 115 may be configured for operation using a narrowband protocol type that is associated with a predefined portion or range (e.g., set of subcarriers or RBs) within a carrier (e.g., “in-band” deployment of a narrowband protocol type) .

In a system employing MCM techniques, a resource element may consist of one symbol period (e.g., a duration of one modulation symbol) and one subcarrier, where the symbol period and subcarrier spacing are inversely related. The number of bits carried by each resource element may depend on the modulation scheme (e.g., the order of the modulation scheme) . Thus, the more resource elements that a UE 115 receives and the higher the order of the modulation scheme, the higher the data rate may be for the UE 115. In MIMO systems, a wireless communications resource may refer to a combination of a radio frequency spectrum resource, a time resource, and a spatial resource (e.g., spatial layers) , and the use of multiple spatial layers may further increase the data rate for communications with a UE 115.

Devices of the wireless communications system 100 (e.g., base stations 105 or UEs 115) may have a hardware configuration that supports communications over a particular carrier bandwidth, or may be configurable to support communications over one of a set of carrier bandwidths. In some examples, the wireless communications system 100 may include base stations 105 and/or UEs 115 that can support simultaneous communications via carriers associated with more than one different carrier bandwidth.

Wireless communications system 100 may support communication with a UE 115 on multiple cells or carriers, a feature which may be referred to as carrier aggregation (CA) or multi-carrier operation. A UE 115 may be configured with multiple downlink CCs and one or more uplink CCs according to a carrier aggregation configuration. Carrier aggregation may be used with both FDD and TDD component carriers.

In some cases, wireless communications system 100 may utilize enhanced component carriers (eCCs) . An eCC may be characterized by one or more features including wider carrier or frequency channel bandwidth, shorter symbol duration, shorter TTI duration, or modified control channel configuration. In some cases, an eCC may be associated with a carrier aggregation configuration or a dual connectivity configuration (e.g., when multiple serving cells have a suboptimal or non-ideal backhaul link) . An eCC may also be configured for use in unlicensed spectrum or shared spectrum (e.g., where more than one operator is allowed to use the spectrum) . An eCC characterized by wide carrier bandwidth may include one or more segments that may be utilized by UEs 115 that are not capable of monitoring the whole carrier bandwidth or are otherwise configured to use a limited carrier bandwidth (e.g., to conserve power) .

In some cases, an eCC may utilize a different symbol duration than other CCs, which may include use of a reduced symbol duration as compared with symbol durations of the other CCs. A shorter symbol duration may be associated with increased spacing between adjacent subcarriers. A device, such as a UE 115 or base station 105, utilizing eCCs may transmit wideband signals (e.g., according to frequency channel or carrier bandwidths of 20, 40, 60, 80 MHz, etc. ) at reduced symbol durations (e.g., 16.67 microseconds) . A TTI in eCC may consist of one or multiple symbol periods. In some cases, the TTI duration (that is, the number of symbol periods in a TTI) may be variable.

Wireless communications systems such as an NR system may utilize any combination of licensed, shared, and unlicensed spectrum bands, among others. The flexibility of eCC symbol duration and subcarrier spacing may allow for the use of eCC across multiple spectrums. In some examples, NR shared spectrum may increase spectrum utilization and spectral efficiency, specifically through dynamic vertical (e.g., across the frequency domain) and horizontal (e.g., across the time domain) sharing of resources.

To establish an initial connection or to re-establish a connection with a base station 105, a UE 115 may perform a four step RACH procedure that generally includes an exchange of four messages between a UE 115 and a base station 105. A UE 115 may initiate the RACH procedure by sending a first message to a base station 105. The first message may be referred to as a random access request and may include a RACH preamble, which may indicate a random access radio network temporary identification (RA-RNTI) , an indication for the layer 2/layer 3 (L2/L3) message size, or both. At this stage in the RACH procedure there may be a risk of contention or ambiguity between two UEs 115 if, for example, both UEs 115 transmit a random access request on the same resource blocks using the same preamble sequence.

A second message may be sent from base station 105 in response to receiving the RACH preamble from UE 115. For example, base station 105 may send a random access response that can include an UL grant, timing advance, the RA-RNTI from the random access request, or any combination of these factors. Using the UL grant, UE 115 may send a third message, which may include or be an example of a radio resource connection (RRC) connection request to base station 115. In some cases, a risk of contention or ambiguity between two UEs 115 may exist if both UEs 115 initiated the RACH procedure using the same resource blocks and preamble sequences. The RRC message sent by a first UE 115 and the other UE 115 may each include an identifier (e.g., S-TMSI or random number) that uniquely identifies the respective UE 115. In some case, the RRC transmission from UE 115 will be stronger and base station 105 will decode this transmission while the RRC transmission from the other UE 115 will only cause interference. Base station 105 may then send a fourth message that can resolve the contention between the two UEs 115, such as by transmitting the identifier (e.g., the random number) of the UE 115 that was indicated by that UE 115 in the RRC connection request. As a result, UE 115 and base station 105 can establish a communication connection.

As part of a random access procedure, a UE 115 may generate a RACH preamble based one or more resources that base station 105 has reserved for the physical random access channel (PRACH) . In some cases, the RACH preamble includes a RA-RNTI that is generated based on specific resources base station 105 has reserved for the PRACH. For example, the RA-RNTI can be generated according to the following calculation:

RA-RNTI = (1 + s_id) + (14 x t_id) + (14 x 80 x f_id) + (14 x 80 x 8 x ul_carrier_id)

In the above formula for generating the RA-RNTI: s_id is the index of the first orthogonal frequency division multiplex (OFDM) symbol of the specified PRACH, and in some cases may include a value between zero and 14; t_id is the index of the first slot of the specified PRACH in a system frame and may include a value between zero and 80; f_id is the index of the specified PRACH in the frequency domain and may include a value between 0 and 8; and ul_carrier_id id the UL carrier used for the random access request transmission and may include a value of 0 for NUL carrier and a value of 1 for SUL carrier.

In accordance with aspects of the present disclosure, contentions between competing UEs 115 can be resolved earlier in the RACH process by using a 2-step procedure. Such a 2-step RACH procedure may be used when a UE 115 is sending a relatively small data transmission (e.g., an mMTC communication) . A 2-step RACH process can reduce signaling overhead and latency of communications between bases station 105 and UE 115 as compared to a 4-step RACH process. For example, base station 105 can uniquely identify that a particular UE 115 is the intended recipient at the second message in the processes by sending a random access response that uniquely identifies UE 115. In this regard, UE 115 may transmit a random access request to a base station 105, and the base station 105 may transmit a random access response to the UE 115. The random access request may include one or more RACH preamble parameters. The RACH preamble parameters may include information used to establish a communication connect between UE 115 and base station 105. In some cases, the RACH preamble parameters contain information that is used to uniquely identify UE 115 among multiple UEs 115. For example, a base station 105 may use the RACH preamble parameters for the random access response. The random access response may uniquely identify the UE 115 that sent the random access request by explicitly identifying the target UE 115 using one or more of the RACH preamble parameters. Additionally or alternatively, the random access response may implicitly identify the UE 115 that sent the corresponding random access request.

FIG. 2 illustrates an example of a wireless communication system 200 that supports UE identification in a RACH response transmission in accordance with aspects of the present disclosure. In some examples, the wireless communication system 200 implements aspects of wireless communication system 100. The wireless communication system 200 may include a base station 105-a and a UE 115-a, which may be examples of a base station 105 or UE 115 described with reference to FIG. 1. The wireless communication system 200 illustrates an example of a RACH procedure where UE 115-a transmits a first message (e.g., random access request 205) to base station 105-a, and in response base station 105-a transmits a response message (e.g., random access response 210) to UE 115-a. A communication connection 215 may be established based on UE 115-a receiving a response message (e.g., random access response 210) from base station 105-a. The RACH procedure can be initiated in a variety of situations, for example, during the establishment of a radio resource control (RRC) connection, during handover of UE 115-a, if UE 115-a has lost synchronization timing with base station 105-a, or in other situations where the UE 115-a is initiating communication with base station 105-a, but has not been assigned or does not have pre-determined resources to do so.

To establish a communication connection 215 between UE 115-a and base station 105-a using a RACH procedure, base station 105-a and UE 105-a may exchange a series of messages. This exchange may occur on a physical access channel such as the physical random access channel (PRACH) . For example, UE 115-a may send a first messages to base station 105-a to initiate a RACH procedure with base-station 105-a. This first message may include information relevant to UE 115-a establishing a communication connection with base station 105-a. For example, this first communication may be a random access request 205 and include one or more RACH preamble parameters 220. In some examples, RACH preamble parameters 220 include a temporary identification parameter selected or generated by UE 115-a. For example, RACH preamble parameters 220 may include a preamble sequence that UE 115-a randomly selected from multiple possible preamble sequences. Further examples of an identification parameter included in RACH preamble parameters 220 are a RA-RNTI, preamble index, or the like. In other instances, RACH preamble parameters 220 may indicate resource or transmission parameters that UE 115-a and base station 105-a use to transmit RACH messages. For example, RACH preamble parameters 220 may include a DMRS, a scrambling sequence, specific resource blocks (RBs) , or the like.

Base station 105-a may send a second message to UE 115-a in response to the first message. The second message can be random access response 210, and can identify UE 115-a as the intended recipient of random access response 210. For example, random access response 210 can explicitly identify UE 115-a based on one or more RACH preamble parameters 220 that the UE 115-a sent in the random access request 205. That is, in some cases multiple UEs may be waiting to receive a response message such as a random access response 210 from base station 105-a. The multiple UEs may include UE 115-a as well as another UE, and both UE 115-a as well as the other UE can receive and decode the response messages (e.g., random access response 210) . However, random access response 210 may include a UE specific parameter 225 that identifies UE 115-a as the intended recipient of this second message (e.g., random access response 210) . In this regard, contention between UE 115-a and the other UE may be resolved at the second message, which may reduce the latency and signaling overhead related to uniquely identifying UE 115-a in a 2-step RACH procedure.

To explicitly identify UE 115-a as the intended recipient of the response message, random access response 210 may include a modified RA-RNTI, which may be based on one or more RACH preamble parameters 220. The modified RA-RNTI may indicate or be an example of a UE-specific parameter 225. In this regard, a modified RA-RNTI may be generated to include an additional parameter that may be used to identify UE 115-a as the sender of the random access request 205 and therefore the intended recipient of the random access response 210. In one example, a modified RA-RNTI may be generated to include a UE-specific parameter 225 in the calculation of the RA-RNTI shown above. The UE-specific parameter 225 may be derived or identified from random access request 205 to uniquely identify UE 115-a as having transmitted random access request 205. In some examples, the UE-specific parameter 225 may substantially uniquely identify UE 115-a such that some UE conflicts are possible, but this possibility may be decreased compared to two UEs transmitting on the same resource blocks and using the same preamble sequence. In some cases, the UE-specific parameter 225 includes a preamble identification (preamble_id) included in a modified RA-RNTI. For example, a modified RA-RNTI can be calculated as follows:

modified RA-RNTI = (1 + s_id) + (14 x t_id) + (14 x 80 x f_id) + (14 x 80 x 8 x ul_carrier_id) + preamble_id

The above equation is presented as one example of how the modified RA-RNTI can be calculated to include a UE-specific parameter. Accordingly, in other cases, the modified RA-RNTI can be calculated in various other ways that allow the UE-specific parameter (e.g., preamble_id) to be determined. For example, the preamble_id could be arithmetically applied into the modified RA-RNTI equation in other ways.

In this regard, preamble_id may be generated from one or more RACH preamble parameters 220. For example, the preamble_id can include the preamble sequence that was included in random access request 205. In some examples, the preamble_ID can include a product of a constant value and the preamble sequence that was included in random access request 205. The preamble_id may also be based on a shortened version of the preamble sequence. One example of this is the preamble_id including a hashed value of the preamble sequence included in random access request 205. In yet other cases, the preamble_id may include a combination of one or more of these examples.

Examples of the UE-specific parameter 225 may also include a DMRS identification (ID) based on a DMRS indicated in or derived from random access request 205. In some examples, the DMRS ID can include the DMRS from random access request 205. The DMRS ID may also be a shorter version of the DMRS, such as a hashed value of the DMRS. The DMRS ID may also be a product of a constant value and the DMRS from random access request 205. In some cases, the UE-specific parameter 225 can include one or more of the preamble ID, the DMRS ID, a hashed value of the preamble_id, a hashed value of the DMRS ID, or a combination thereof.

Alternatively or additionally, random access response 210 may implicitly identify UE 115-a based on how the random access response 210 is encoded or transmitted. For example, the random access response 210 may be scrambled based on a UE-specific sequence. In some cases, the scrambling sequence can be based on one or more of the RACH preamble parameters 220 that were transmitted in the random access request 205. For example, the scrambling sequence can have a 1-to-1 mapping with the preamble sequence. In this regard, UE 115-a receiving a scrambled random access response 210 may identify that it is the intended recipient of this message based on using the preamble sequence or preamble_id to correctly descramble the random access response 210. This 1-to-1 mapping may include the scrambling sequence having the same root sequence with fixed shifting. In some cases, the scrambling sequence is the same sequence indicated in the random access request 205. In this regard, UE 115-a may determine that it is the intended recipient of random access response 210 based on being able to correctly descramble random access response 210, for example, based on a sequence specific to UE 115-a.

UE 115-a may also be implicitly identified based on the transmission parameters of random access response 210. For example, random access response 210 may identify UE 115-a by using specific resource blocks (RBs) to indicate one or more RACH preamble parameters 220 included in random access request 205. In some cases, random access response 210 can indicate a preamble identification, which is derived from a RB index in the frequency domain or a RB index in a frame or sub-frame. In this regard, UE 115-a may determine that it is the intended recipient of random access response 210 based on receiving the random access response 210 on specific RBs, and then deriving a UE-specific identification based on which RBs the random access response 210 was on.

In some cases, correspondence between an UL and DL signal can be used to uniquely identify UE 115-a in random access response 210. For example, UE 115-a can receive a DL DMRS that is mapped to an UL DMRS that the UE 115-a previously transmitted to base station 105-a. In this regard, base station 105-a may set a 1-to-1 mapping between DL DMRS and UL DMRS, which creates a DL DMRS specific to UE 115-a. Accordingly, by receiving a random access response 210 with the UE specific DL DMRS, the UE 115-a can implicitly determine that it is the intended recipient of the random access response 210 based on the correspondence between the received DL DMRS and the previously-transmitted UL DMRS.

FIG. 3 illustrates an example of a process flow 300 that supports UE identification in a RACH response transmission in accordance with aspects of the present disclosure. In some examples, process flow 300 may implement one or more aspects of the

wireless communication systems

100 or 200 described with reference to FIGs. 1 and 2. The process flow 300 includes functions and communications implemented by base station 105-b and UE 115-b in the context of a RACH procedure, which may be examples of the base station 105 and UEs 115 described with reference to FIGs. 1 and 2.

At 305, UE 115-b may transmit a random access request to base station 105-b, and the random access request may include one or more RACH preamble parameters. In some cases, one or more of the RACH preamble parameters are used to initiate a RACH procedure with base station 105-b. For example, UE 115-b may randomly select a preamble sequence from multiple available preamble sequences at base station 105-b. The preamble sequence chosen by UE 115-b may be included in the RACH preamble parameters. Additionally or alternatively, UE 115-b may include a modified RA-RNTI, which may be generated according to the formula discussed in relation to FIG. 2. In some instances, RACH preamble parameters include a preamble_id, or a DMRS. In this regard, the RACH preamble parameters may include information that is both used to initiate communications with base station 105-b and be used by base station 105-b to uniquely identify UE 115-b. Such re-use of preamble information or using of resource information already present in random access request to also uniquely identify UE 115-b may reduce message overhead and decrease latency.

At 310, base station 105-b may scramble the random access response. The scrambling may be based on one or more of the RACH preamble parameters included in random access request. For example, the random access response may be scrambled based on a preamble sequence included in the random access request. In some cases, the scrambling sequence may have a 1-to-1 mapping with the preamble sequence that was indicated in the random access request. As will be discussed in more detail below, scrambling the random access response may be used by UE 115-b to determine that it is the intended recipient of the random access response (e.g., because UE 115-b will be able to descramble the random access response using a scrambling sequence unique to that UE 115-b) .

At 315, base station 105-b may transmit a DL DMRS. The DL DMRS may be mapped to an UL DMRS included in the random access request. As will be discussed in more detail below, the DL DMRS may be used by UE 115-b to determine that it is the intended recipient of the random access response. In some cases, base station 105-b may include the DL DMRS in the random access response.

At 320, base station 105-b may transmit a random access response. In some cases, random access response may explicitly include a modified RA-RNTI that is calculated using an RA-RNTI included in the RACH preamble parameters from random access request and a UE-specific parameter. The following equation provides an illustrative example:

modified RA-RNTI = (1 + s_id) + (14 x t_id) + (14 x 80 x f_id) + (14 x 80 x 8 x ul_carrier_id) + UE-specific parameter

In this regard, the UE-specific parameter may include a preamble sequence, a preamble ID, which may be derived from the preamble sequence, a constant value, a shortened version of the preamble ID, such as a hash, or a combination thereof. In some cases, the UE-specific parameter can be based on a DMRS from the random access request. For example, the UE-specific parameter may be the DMRS, a DMRS ID derived from the DMRS, a shortened version of the DMRS, such a hashed value of the DMRS or DMRS ID, a constant value, or a combination thereof.

At 320, base station 105-b may also transmit random access response on a set of (RBs) that indicates a preamble sequence or preamble ID. For example, random access response may be transmitted on frequency and frame/subframe RBs that correlate to a preamble ID. An example of this is illustrated using the following equation:

preamble ID = (a x RB_frquency) + (b x RB_time)

Where a and b are constants, RB_frequency is the RB index in frequency and RB_time is the RB index in frame/subframe. In this cases, random access response implicitly includes a unique identifier of base station 115-b.

At 325, UE 115-b may uniquely identify a UE-specific parameter included in the random access response and that is based at least in part on one or more RACH preamble parameters. Identifying one or more UE-specific parameter at 325 may include deriving or identifying the UE-specific parameter included in the modified RA-RNTI. In some examples this may include UE 115-b isolating the UE-specific parameter such as a preamble_id based on an RA-RNTI that UE 115-a included in random access request 105-b.

At 330, UE 115-b may determine that it is the intended recipient of the random access response. In some cases UE 115-b may determine that it is the intended recipient of the random access response based on identifying the UE-specific parameter. UE 115-b may implicitly determine that it is the intended recipient of the random access response by successfully receiving the random access response on a set of RBs that indicates the preamble sequence as described above in relation to 320. That is, UE 115-b may identify a preamble_id based on receiving the random access response on a specific frequency and frame/subframe RBs. In some cases UE 115-b may determine that it is the intended recipient of the random access response based on a mapping between the received DL DMRS and an UL DMRS that was indicated in the random access request described in relation to 315.

At 335, UE 115-b may also implicitly identify that it is the intended recipient of the random access response by successfully descrambling the random access response. In this regard, UE 115-b may only be able to successfully descramble the scrambled random access response as described at 310 if the random access response corresponds or maps to the random access request sent by UE 115-b.

At 340, a communication connection may be established between UE 115-a and base station 105-b based on receiving the random access response. For example, the communication connection may be established after UE 115-b determines that it is the intended recipient of the random access response.

FIG. 4 shows a block diagram 400 of a device 405 that supports UE identification in a RACH response transmission in accordance with aspects of the present disclosure. The device 405 may be an example of aspects of a UE 115 as described herein. The device 405 may include a receiver 410, an identification module 415, and a transmitter 420. The device 405 may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses) .

The receiver 410 may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to UE identification in a RACH response transmission, etc. ) . Information may be passed on to other components of the device 405. The receiver 410 may be an example of aspects of the transceiver 720 described with reference to FIG. 7. The receiver 410 may utilize a single antenna or a set of antennas.

The identification module 415 may transmit, from a UE, a random access request that includes one or more RACH preamble parameters, receive a random access response in response to the random access request that uniquely identifies the UE based on at least one of the one or more RACH preamble parameters, and establish a communication connection based on receiving the random access response. The identification module 415 may be an example of aspects of the identification module 710 described herein.

The identification module 415, or its sub-components, may be implemented in hardware, code (e.g., software or firmware) executed by a processor, or any combination thereof. If implemented in code executed by a processor, the functions of the identification module 415, or its sub-components may be executed by a general-purpose processor, a DSP, an application-specific integrated circuit (ASIC) , a FPGA or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described in the present disclosure.

The identification module 415, or its sub-components, may be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations by one or more physical components. In some examples, the identification module 415, or its sub-components, may be a separate and distinct component in accordance with various aspects of the present disclosure. In some examples, the identification module 415, or its sub-components, may be combined with one or more other hardware components, including but not limited to an input/output (I/O) component, a transceiver, a network server, another computing device, one or more other components described in the present disclosure, or a combination thereof in accordance with various aspects of the present disclosure.

The transmitter 420 may transmit signals generated by other components of the device 405. In some examples, the transmitter 420 may be collocated with a receiver 410 in a transceiver module. For example, the transmitter 420 may be an example of aspects of the transceiver 720 described with reference to FIG. 7. The transmitter 420 may utilize a single antenna or a set of antennas.

FIG. 5 shows a block diagram 500 of a device 505 that supports UE identification in a RACH response transmission in accordance with aspects of the present disclosure. The device 505 may be an example of aspects of a device 405, or a UE 115 as described herein. The device 505 may include a receiver 510, an identification module 515, and a transmitter 535. The device 505 may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses) .

The receiver 510 may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to UE identification in a RACH response transmission, etc. ) . Information may be passed on to other components of the device 505. The receiver 510 may be an example of aspects of the transceiver 720 described with reference to FIG. 7. The receiver 510 may utilize a single antenna or a set of antennas.

The identification module 515 may be an example of aspects of the identification module 415 as described herein. The identification module 515 may include a RACH request component 520, a RACH receive component 525, and an UE connection component 530. The identification module 515 may be an example of aspects of the identification module 710 described herein.

The RACH request component 520 may transmit, from a UE, a random access request that includes one or more RACH preamble parameters.

The RACH receive component 525 may receive a random access response in response to the random access request that uniquely identifies the UE based on at least one of the one or more RACH preamble parameters.

The UE connection component 530 may establish a communication connection based on receiving the random access response.

The transmitter 535 may transmit signals generated by other components of the device 505. In some examples, the transmitter 535 may be collocated with a receiver 510 in a transceiver module. For example, the transmitter 535 may be an example of aspects of the transceiver 720 described with reference to FIG. 7. The transmitter 535 may utilize a single antenna or a set of antennas.

FIG. 6 shows a block diagram 600 of a identification module 605 that supports UE identification in a RACH response transmission in accordance with aspects of the present disclosure. The identification module 605 may be an example of aspects of a identification module 415, a identification module 515, or a identification module 710 described herein. The identification module 605 may include a RACH request component 610, a RACH receive component 615, an UE connection component 620, an UE identification component 625, an UE determination component 630, and a RACH descrambling component 635. Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses) .

The RACH request component 610 may transmit, from a UE, a random access request that includes one or more RACH preamble parameters.

In some cases, the RACH preamble parameters include at least one of a RA-RNTI, a preamble sequence, a DMRS, or a combination thereof.

The RACH receive component 615 may receive a random access response in response to the random access request that uniquely identifies the UE based on at least one of the one or more RACH preamble parameters.

In some examples, receiving a modified RA-RNTI in the random access response, where the modified RA-RNTI includes a UE-specific parameter, and where the UE-specific parameter is based on at least one of the one or more RACH preamble parameters.

In some examples, the RACH receive component 615 may receive a DL DMRS.

In some examples, the RACH receive component 615 may receive the random access response on a set of resource blocks that indicates a preamble sequence identification.

In some cases, the preamble sequence identification includes a resource block frequency index, a resource block frame index, or both.

The UE connection component 620 may establish a communication connection based on receiving the random access response.

The UE identification component 625 may identify the UE-specific parameter included in the modified RA-RNTI.

The UE determination component 630 may determine that the UE is the intended recipient of the random access response based on identifying the UE-specific parameter.

In some examples, the UE determination component 630 may determine that the UE is the intended recipient of the random access response based on a mapping between the received DL DMRS and an UL DMRS that was indicated in the random access request.

In some examples, the UE determination component 630 may determine that the UE is the intended recipient of the random access response based on descrambling the random access response.

In some cases, the UE-specific parameter includes a preamble sequence that was indicated in the random access request.

In some cases, the UE-specific parameter includes a product of a preamble sequence and a constant value, and where the preamble sequence, the constant value, or both were indicated in the random access request.

In some cases, the UE-specific parameter includes a hashed value of a preamble sequence that was indicated in the random access request.

In some cases, the UE-specific parameter includes a product of a hashed value of a preamble sequence and a constant value, and where the preamble sequence, the constant value, or both were indicated in the random access request.

In some cases, the UE-specific parameter includes a DMRS sequence identifier, and where the DMRS sequence identifier is based on an UL DMRS that was indicated in the random access request.

In some cases, the UE-specific parameter further includes a preamble sequence, a hashed value of the preamble sequence, a constant value, or a combination thereof, and where the preamble sequence, the constant value, or both were indicated in the random access request.

In some cases, the UE-specific parameter includes a hashed DMRS sequence identifier, and where the hashed DMRS sequence identifier is based on an UL DMRS that was indicated in the random access request.

The RACH descrambling component 635 may descramble the random access response, where the random access response is scrambled based on at least one of the one or more RACH preamble parameters indicated in the random access request.

In some cases, the random access response is scrambled based on a preamble sequence that was indicated in the random access request.

In some cases, the random access response is scrambled based on a scrambling sequence that has a 1 to 1 mapping with a preamble sequence that was indicated in the random access request.

FIG. 7 shows a diagram of a system 700 including a device 705 that supports UE identification in a RACH response transmission in accordance with aspects of the present disclosure. The device 705 may be an example of or include the components of device 405, device 505, or a UE 115 as described herein. The device 705 may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including an identification module 710, an I/O controller 715, a transceiver 720, an antenna 725, memory 730, and a processor 740. These components may be in electronic communication via one or more buses (e.g., bus 745) .

The identification module 710 may transmit, from a UE, a random access request that includes one or more RACH preamble parameters, receive a random access response in response to the random access request that uniquely identifies the UE based on at least one of the one or more RACH preamble parameters, and establish a communication connection based on receiving the random access response.

The I/O controller 715 may manage input and output signals for the device 705. The I/O controller 715 may also manage peripherals not integrated into the device 705. In some cases, the I/O controller 715 may represent a physical connection or port to an external peripheral. In some cases, the I/O controller 715 may utilize an operating system such as

or another known operating system. In other cases, the I/O controller 715 may represent or interact with a modem, a keyboard, a mouse, a touchscreen, or a similar device. In some cases, the I/O controller 715 may be implemented as part of a processor. In some cases, a user may interact with the device 705 via the I/O controller 715 or via hardware components controlled by the I/O controller 715.

The transceiver 720 may communicate bi-directionally, via one or more antennas, wired, or wireless links as described above. For example, the transceiver 720 may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver. The transceiver 720 may also include a modem to modulate the packets and provide the modulated packets to the antennas for transmission, and to demodulate packets received from the antennas.

In some cases, the wireless device may include a single antenna 725. However, in some cases the device may have more than one antenna 725, which may be capable of concurrently transmitting or receiving multiple wireless transmissions.

The memory 730 may include RAM and ROM. The memory 730 may store computer-readable, computer-executable code 735 including instructions that, when executed, cause the processor to perform various functions described herein. In some cases, the memory 730 may contain, among other things, a BIOS which may control basic hardware or software operation such as the interaction with peripheral components or devices.

The processor 740 may include an intelligent hardware device, (e.g., a general-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof) . In some cases, the processor 740 may be configured to operate a memory array using a memory controller. In other cases, a memory controller may be integrated into the processor 740. The processor 740 may be configured to execute computer-readable instructions stored in a memory (e.g., the memory 730) to cause the device 705 to perform various functions (e.g., functions or tasks supporting UE identification in a RACH response transmission) .

The code 735 may include instructions to implement aspects of the present disclosure, including instructions to support wireless communications. The code 735 may be stored in a non-transitory computer-readable medium such as system memory or other type of memory. In some cases, the code 735 may not be directly executable by the processor 740 but may cause a computer (e.g., when compiled and executed) to perform functions described herein.

FIG. 8 shows a block diagram 800 of a device 805 that supports UE identification in a RACH response transmission in accordance with aspects of the present disclosure. The device 805 may be an example of aspects of a base station 105 as described herein. The device 805 may include a receiver 810, an identification module 815, and a transmitter 820. The device 805 may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses) .

The receiver 810 may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to UE identification in a RACH response transmission, etc. ) . Information may be passed on to other components of the device 805. The receiver 810 may be an example of aspects of the transceiver 1120 described with reference to FIG. 11. The receiver 810 may utilize a single antenna or a set of antennas.

The identification module 815 may receive, from a UE, a random access request that includes one or more RACH preamble parameters, transmit a random access response in response to the random access request that uniquely identifies the UE based on at least one of the one or more RACH preamble parameters, and establish a communication connection based on transmitting the random access response. The identification module 815 may be an example of aspects of the identification module 1110 described herein.

The identification module 815, or its sub-components, may be implemented in hardware, code (e.g., software or firmware) executed by a processor, or any combination thereof. If implemented in code executed by a processor, the functions of the identification module 815, or its sub-components may be executed by a general-purpose processor, a DSP, an application-specific integrated circuit (ASIC) , a FPGA or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described in the present disclosure.

The identification module 815, or its sub-components, may be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations by one or more physical components. In some examples, the identification module 815, or its sub-components, may be a separate and distinct component in accordance with various aspects of the present disclosure. In some examples, the identification module 815, or its sub-components, may be combined with one or more other hardware components, including but not limited to an input/output (I/O) component, a transceiver, a network server, another computing device, one or more other components described in the present disclosure, or a combination thereof in accordance with various aspects of the present disclosure.

The transmitter 820 may transmit signals generated by other components of the device 805. In some examples, the transmitter 820 may be collocated with a receiver 810 in a transceiver module. For example, the transmitter 820 may be an example of aspects of the transceiver 1120 described with reference to FIG. 11. The transmitter 820 may utilize a single antenna or a set of antennas.

FIG. 9 shows a block diagram 900 of a device 905 that supports UE identification in a RACH response transmission in accordance with aspects of the present disclosure. The device 905 may be an example of aspects of a device 805, or a base station 105 as described herein. The device 905 may include a receiver 910, an identification module 915, and a transmitter 935. The device 905 may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses) .

The receiver 910 may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to UE identification in a RACH response transmission, etc. ) . Information may be passed on to other components of the device 905. The receiver 910 may be an example of aspects of the transceiver 1120 described with reference to FIG. 11. The receiver 910 may utilize a single antenna or a set of antennas.

The identification module 915 may be an example of aspects of the identification module 815 as described herein. The identification module 915 may include a BS receiving component 920, a BS transmitting component 925, and a BS connection component 930. The identification module 915 may be an example of aspects of the identification module 1110 described herein.

The BS receiving component 920 may receive, from a UE, a random access request that includes one or more RACH preamble parameters.

The BS transmitting component 925 may transmit a random access response in response to the random access request that uniquely identifies the UE based on at least one of the one or more RACH preamble parameters.

The BS connection component 930 may establish a communication connection based on transmitting the random access response.

The transmitter 935 may transmit signals generated by other components of the device 905. In some examples, the transmitter 935 may be collocated with a receiver 910 in a transceiver module. For example, the transmitter 935 may be an example of aspects of the transceiver 1120 described with reference to FIG. 11. The transmitter 935 may utilize a single antenna or a set of antennas.

FIG. 10 shows a block diagram 1000 of a identification module 1005 that supports UE identification in a RACH response transmission in accordance with aspects of the present disclosure. The identification module 1005 may be an example of aspects of a identification module 815, a identification module 915, or a identification module 1110 described herein. The identification module 1005 may include a BS receiving component 1010, a BS transmitting component 1015, a BS connection component 1020, and a BS scrambling component 1025. Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses) .

The BS receiving component 1010 may receive, from a UE, a random access request that includes one or more RACH preamble parameters.

The BS transmitting component 1015 may transmit a random access response in response to the random access request that uniquely identifies the UE based on at least one of the one or more RACH preamble parameters.

In some examples, transmitting a modified RA-RNTI in the random access response, where the modified RA-RNTI includes a UE-specific parameter indicating that the UE is the intended recipient of the random access response, and where the UE-specific parameter is based on at least one of the one or more RACH preamble parameters.

In some examples, the BS transmitting component 1015 may transmit a DL DMRS indicating that the UE is the intended recipient of the random access response based on a mapping between the received DL DMRS and an UL DMRS that was indicated in the random access request.

In some examples, the BS transmitting component 1015 may transmit the random access response on a set of resource blocks that indicates a preamble sequence identification.

The BS connection component 1020 may establish a communication connection based on transmitting the random access response.

The BS scrambling component 1025 may scramble the random access response, where the random access response is scrambled based on at least one of the one or more RACH preamble parameters indicated in the random access request, and where the scrambling at least partially indicates that the UE is the intended recipient of the random access response.

FIG. 11 shows a diagram of a system 1100 including a device 1105 that supports UE identification in a RACH response transmission in accordance with aspects of the present disclosure. The device 1105 may be an example of or include the components of device 805, device 905, or a base station 105 as described herein. The device 1105 may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including an identification module 1110, a network communications manager 1115, a transceiver 1120, an antenna 1125, memory 1130, a processor 1140, and an inter-station communications manager 1145. These components may be in electronic communication via one or more buses (e.g., bus 1150) .

The identification module 1110 may receive, from a UE, a random access request that includes one or more RACH preamble parameters, transmit a random access response in response to the random access request that uniquely identifies the UE based on at least one of the one or more RACH preamble parameters, and establish a communication connection based on transmitting the random access response.

The network communications manager 1115 may manage communications with the core network (e.g., via one or more wired backhaul links) . For example, the network communications manager 1115 may manage the transfer of data communications for client devices, such as one or more UEs 115.

The transceiver 1120 may communicate bi-directionally, via one or more antennas, wired, or wireless links as described above. For example, the transceiver 1120 may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver. The transceiver 1120 may also include a modem to modulate the packets and provide the modulated packets to the antennas for transmission, and to demodulate packets received from the antennas.

In some cases, the wireless device may include a single antenna 1125. However, in some cases the device may have more than one antenna 1125, which may be capable of concurrently transmitting or receiving multiple wireless transmissions.

The memory 1130 may include RAM, ROM, or a combination thereof. The memory 1130 may store computer-readable code 1135 including instructions that, when executed by a processor (e.g., the processor 1140) cause the device to perform various functions described herein. In some cases, the memory 1130 may contain, among other things, a BIOS which may control basic hardware or software operation such as the interaction with peripheral components or devices.

The processor 1140 may include an intelligent hardware device, (e.g., a general-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof) . In some cases, the processor 1140 may be configured to operate a memory array using a memory controller. In some cases, a memory controller may be integrated into processor 1140. The processor 1140 may be configured to execute computer-readable instructions stored in a memory (e.g., the memory 1130) to cause the device 1105 to perform various functions (e.g., functions or tasks supporting UE identification in a RACH response transmission) .

The inter-station communications manager 1145 may manage communications with other base station 105, and may include a controller or scheduler for controlling communications with UEs 115 in cooperation with other base stations 105. For example, the inter-station communications manager 1145 may coordinate scheduling for transmissions to UEs 115 for various interference mitigation techniques such as beamforming or joint transmission. In some examples, the inter-station communications manager 1145 may provide an X2 interface within an LTE/LTE-A wireless communication network technology to provide communication between base stations 105.

The code 1135 may include instructions to implement aspects of the present disclosure, including instructions to support wireless communications. The code 1135 may be stored in a non-transitory computer-readable medium such as system memory or other type of memory. In some cases, the code 1135 may not be directly executable by the processor 1140 but may cause a computer (e.g., when compiled and executed) to perform functions described herein.

FIG. 12 shows a flowchart illustrating a method 1200 that supports UE identification in a RACH response transmission in accordance with aspects of the present disclosure. The operations of method 1200 may be implemented by a UE 115 or its components as described herein. For example, the operations of method 1200 may be performed by a identification module as described with reference to FIGs. 4 through 7. In some examples, a UE may execute a set of instructions to control the functional elements of the UE to perform the functions described below. Additionally or alternatively, a UE may perform aspects of the functions described below using special-purpose hardware.

At 1205, the UE may transmit, from a UE, a random access request that includes one or more RACH preamble parameters. The operations of 1205 may be performed according to the methods described herein. In some examples, aspects of the operations of 1205 may be performed by a RACH request component as described with reference to FIGs. 4 through 7.

At 1210, the UE may receive a random access response in response to the random access request that uniquely identifies the UE based on at least one of the one or more RACH preamble parameters. The operations of 1210 may be performed according to the methods described herein. In some examples, aspects of the operations of 1210 may be performed by a RACH receive component as described with reference to FIGs. 4 through 7.

At 1215, the UE may establish a communication connection based on receiving the random access response. The operations of 1215 may be performed according to the methods described herein. In some examples, aspects of the operations of 1215 may be performed by an UE connection component as described with reference to FIGs. 4 through 7.

FIG. 13 shows a flowchart illustrating a method 1300 that supports UE identification in a RACH response transmission in accordance with aspects of the present disclosure. The operations of method 1300 may be implemented by a UE 115 or its components as described herein. For example, the operations of method 1300 may be performed by a identification module as described with reference to FIGs. 4 through 7. In some examples, a UE may execute a set of instructions to control the functional elements of the UE to perform the functions described below. Additionally or alternatively, a UE may perform aspects of the functions described below using special-purpose hardware.

At 1305, the UE may transmit, from a UE, a random access request that includes one or more RACH preamble parameters. The operations of 1305 may be performed according to the methods described herein. In some examples, aspects of the operations of 1305 may be performed by a RACH request component as described with reference to FIGs. 4 through 7.

At 1310, the UE may receive a random access response in response to the random access request that uniquely identifies the UE based on at least one of the one or more RACH preamble parameters. The operations of 1310 may be performed according to the methods described herein. In some examples, aspects of the operations of 1310 may be performed by a RACH receive component as described with reference to FIGs. 4 through 7.

At 1315, the UE may receive a modified RA-RNTI in the random access response, where the modified RA-RNTI includes a UE-specific parameter, and where the UE-specific parameter is based on at least one of the one or more RACH preamble parameters. The operations of 1315 may be performed according to the methods described herein. In some examples, aspects of the operations of 1315 may be performed by a RACH receive component as described with reference to FIGs. 4 through 7.

At 1320, the UE may identify the UE-specific parameter included in the modified RA-RNTI. The operations of 1320 may be performed according to the methods described herein. In some examples, aspects of the operations of 1320 may be performed by an UE identification component as described with reference to FIGs. 4 through 7.

At 1325, the UE may determine that the UE is the intended recipient of the random access response based on identifying the UE-specific parameter. The operations of 1325 may be performed according to the methods described herein. In some examples, aspects of the operations of 1325 may be performed by an UE determination component as described with reference to FIGs. 4 through 7.

At 1330, the UE may establish a communication connection based on receiving the random access response. The operations of 1330 may be performed according to the methods described herein. In some examples, aspects of the operations of 1330 may be performed by an UE connection component as described with reference to FIGs. 4 through 7.

FIG. 14 shows a flowchart illustrating a method 1400 that supports UE identification in a RACH response transmission in accordance with aspects of the present disclosure. The operations of method 1400 may be implemented by a base station 105 or its components as described herein. For example, the operations of method 1400 may be performed by a identification module as described with reference to FIGs. 8 through 11. In some examples, a base station may execute a set of instructions to control the functional elements of the base station to perform the functions described below. Additionally or alternatively, a base station may perform aspects of the functions described below using special-purpose hardware.

At 1405, the base station may receive, from a UE, a random access request that includes one or more RACH preamble parameters. The operations of 1405 may be performed according to the methods described herein. In some examples, aspects of the operations of 1405 may be performed by a BS receiving component as described with reference to FIGs. 8 through 11.

At 1410, the base station may transmit a random access response in response to the random access request that uniquely identifies the UE based on at least one of the one or more RACH preamble parameters. The operations of 1410 may be performed according to the methods described herein. In some examples, aspects of the operations of 1410 may be performed by a BS transmitting component as described with reference to FIGs. 8 through 11.

At 1415, the base station may establish a communication connection based on transmitting the random access response. The operations of 1415 may be performed according to the methods described herein. In some examples, aspects of the operations of 1415 may be performed by a BS connection component as described with reference to FIGs. 8 through 11.

FIG. 15 shows a flowchart illustrating a method 1500 that supports UE identification in a RACH response transmission in accordance with aspects of the present disclosure. The operations of method 1500 may be implemented by a base station 105 or its components as described herein. For example, the operations of method 1500 may be performed by a identification module as described with reference to FIGs. 8 through 11. In some examples, a base station may execute a set of instructions to control the functional elements of the base station to perform the functions described below. Additionally or alternatively, a base station may perform aspects of the functions described below using special-purpose hardware.

At 1505, the base station may receive, from a UE, a random access request that includes one or more RACH preamble parameters. The operations of 1505 may be performed according to the methods described herein. In some examples, aspects of the operations of 1505 may be performed by a BS receiving component as described with reference to FIGs. 8 through 11.

At 1510, the base station may transmit a random access response in response to the random access request that uniquely identifies the UE based on at least one of the one or more RACH preamble parameters. The operations of 1510 may be performed according to the methods described herein. In some examples, aspects of the operations of 1510 may be performed by a BS transmitting component as described with reference to FIGs. 8 through 11.

At 1515, the base station may transmit a modified RA-RNTI in the random access response, where the modified RA-RNTI includes a UE-specific parameter indicating that the UE is the intended recipient of the random access response, and where the UE-specific parameter is based on at least one of the one or more RACH preamble parameters. The operations of 1515 may be performed according to the methods described herein. In some examples, aspects of the operations of 1515 may be performed by a BS transmitting component as described with reference to FIGs. 8 through 11.

At 1520, the base station may establish a communication connection based on transmitting the random access response. The operations of 1520 may be performed according to the methods described herein. In some examples, aspects of the operations of 1520 may be performed by a BS connection component as described with reference to FIGs. 8 through 11.

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

Techniques described herein may be used for various wireless communications systems such as code division multiple access (CDMA) , time division multiple access (TDMA) , frequency division multiple access (FDMA) , orthogonal frequency division multiple access (OFDMA) , single carrier frequency division multiple access (SC-FDMA) , and other systems. A CDMA system may implement a radio technology such as CDMA2000, Universal Terrestrial Radio Access (UTRA) , etc. CDMA2000 covers IS-2000, IS-95, and IS-856 standards. IS-2000 Releases may be commonly referred to as CDMA2000 1X, 1X, etc. IS-856 (TIA-856) is commonly referred to as CDMA2000 1xEV-DO, High Rate Packet Data (HRPD) , etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. A TDMA system may implement a radio technology such as Global System for Mobile Communications (GSM) .

An OFDMA system may implement a radio technology such as Ultra Mobile Broadband (UMB) , Evolved UTRA (E-UTRA) , Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi) , IEEE 802.16 (WiMAX) , IEEE 802.20, Flash-OFDM, etc. UTRA and E-UTRA are part of Universal Mobile Telecommunications System (UMTS) . LTE, LTE-A, and LTE-A Pro are releases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, LTE-A Pro, NR, and GSM are described in documents from the organization named “3rd Generation Partnership Project” (3GPP) . CDMA2000 and UMB are described in documents from an organization named “3rd Generation Partnership Project 2” (3GPP2) . The techniques described herein may be used for the systems and radio technologies mentioned herein as well as other systems and radio technologies. While aspects of an LTE, LTE-A, LTE-A Pro, or NR system may be described for purposes of example, and LTE, LTE-A, LTE-A Pro, or NR terminology may be used in much of the description, the techniques described herein are applicable beyond LTE, LTE-A, LTE-A Pro, or NR applications.

A macro cell generally covers a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs 115 with service subscriptions with the network provider. A small cell may be associated with a lower-powered base station 105, as compared with a macro cell, and a small cell may operate in the same or different (e.g., licensed, unlicensed, etc. ) frequency bands as macro cells. Small cells may include pico cells, femto cells, and micro cells according to various examples. A pico cell, for example, may cover a small geographic area and may allow unrestricted access by UEs 115 with service subscriptions with the network provider. A femto cell may also cover a small geographic area (e.g., a home) and may provide restricted access by UEs 115 having an association with the femto cell (e.g., UEs 115 in a closed subscriber group (CSG) , UEs 115 for users in the home, and the like) . An eNB for a macro cell may be referred to as a macro eNB. An eNB for a small cell may be referred to as a small cell eNB, a pico eNB, a femto eNB, or a home eNB. An eNB may support one or multiple (e.g., two, three, four, and the like) cells, and may also support communications using one or multiple component carriers.

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

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

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

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

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

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

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

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

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

Claims

A method for wireless communications, comprising:

transmitting, from a user equipment (UE) , a random access request that comprises one or more random access channel (RACH) preamble parameters;

receiving a random access response in response to the random access request that uniquely identifies the UE based at least in part on at least one of the one or more RACH preamble parameters; and

establishing a communication connection based at least in part on receiving the random access response.
The method of claim 1, further comprising:

receiving a modified random access radio network temporary identifier (RA-RNTI) in the random access response, wherein the modified RA-RNTI comprises a UE-specific parameter, and wherein the UE-specific parameter is based at least in part on at least one of the one or more RACH preamble parameters;

identifying the UE-specific parameter included in the modified RA-RNTI; and

determining that the UE is the intended recipient of the random access response based at least in part on identifying the UE-specific parameter.
The method of claim 2, wherein the UE-specific parameter comprises a preamble sequence that was indicated in the random access request.
The method of claim 2, wherein the UE-specific parameter comprises a product of a preamble sequence and a constant value, and wherein the preamble sequence, the constant value, or both were indicated in the random access request.
The method of claim 2, wherein the UE-specific parameter comprises a hashed value of a preamble sequence that was indicated in the random access request.
The method of claim 2, wherein the UE-specific parameter comprises a product of a hashed value of a preamble sequence and a constant value, and wherein the preamble sequence, the constant value, or both were indicated in the random access request.
The method of claim 2, wherein the UE-specific parameter comprises a demodulation reference signal (DMRS) sequence identifier, and wherein the DMRS sequence identifier is based at least in part on an uplink (UL) DMRS that was indicated in the random access request.
The method of claim 7, wherein the UE-specific parameter further comprises a preamble sequence, a hashed value of the preamble sequence, a constant value, or a combination thereof, and wherein the preamble sequence, the constant value, or both were indicated in the random access request.
The method of claim 2, wherein the UE-specific parameter comprises a hashed demodulation reference signal (DMRS) sequence identifier, and wherein the hashed DMRS sequence identifier is based at least in part on an uplink (UL) DMRS that was indicated in the random access request.
The method of claim 9, wherein the UE-specific parameter further comprises a preamble sequence, a hashed value of the preamble sequence, a constant value, or a combination thereof, and wherein the preamble sequence, the constant value, or both were indicated in the random access request.
The method of claim 1, further comprising:

receiving a downlink (DL) demodulation reference signal (DMRS) ; and

determining that the UE is the intended recipient of the random access response based at least in part on a mapping between the received DL DMRS and an uplink (UL) DMRS that was indicated in the random access request.
The method of claim 1, further comprising:

descrambling the random access response, wherein the random access response is scrambled based at least in part on at least one of the one or more RACH preamble parameters indicated in the random access request; and

determining that the UE is the intended recipient of the random access response based at least in part on descrambling the random access response.
The method of claim 12, wherein the random access response is scrambled based at least in part on a preamble sequence that was indicated in the random access request.
The method of claim 12, wherein the random access response is scrambled based at least in part on a scrambling sequence that has a 1 to 1 mapping with a preamble sequence that was indicated in the random access request.
The method of claim 1, further comprising:

receiving the random access response on a set of resource blocks that indicates a preamble sequence identification.
The method of claim 15, wherein the preamble sequence identification comprises a resource block frequency index, a resource block frame index, or both.
The method of claim 1, wherein the RACH preamble parameters comprise at least one of a random access radio network temporary identifier (RA-RNTI) , a preamble sequence, a demodulation reference signal (DMRS) , or a combination thereof.
A method for wireless communications, comprising:

receiving, from a user equipment (UE) , a random access request that comprises one or more random access channel (RACH) preamble parameters;

transmitting a random access response in response to the random access request that uniquely identifies the UE based at least in part on at least one of the one or more RACH preamble parameters; and

establishing a communication connection based at least in part on transmitting the random access response.
The method of claim 18, further comprising:

transmitting a modified random access radio network temporary identifier (RA-RNTI) in the random access response, wherein the modified RA-RNTI comprises a UE-specific parameter indicating that the UE is the intended recipient of the random access response, and wherein the UE-specific parameter is based at least in part on at least one of the one or more RACH preamble parameters.
The method of claim 19, wherein the UE-specific parameter comprises a preamble sequence that was indicated in the random access request.
The method of claim 19, wherein the UE-specific parameter comprises a product of a preamble sequence and a constant value, and wherein the preamble sequence, the constant value, or both were indicated in the random access request.
The method of claim 19, wherein the UE-specific parameter comprises a hashed value of a preamble sequence that was indicated in the random access request.
The method of claim 19, wherein the UE-specific parameter comprises a product of a hashed value of a preamble sequence and a constant value, and wherein the preamble sequence, the constant value, or both were indicated in the random access request.
The method of claim 19, wherein the UE-specific parameter comprises a demodulation reference signal (DMRS) sequence identifier, and wherein the DMRS sequence identifier is based at least in part on an uplink (UL) DMRS that was indicated in the random access request.
The method of claim 24, wherein the UE-specific parameter further comprises a preamble sequence, a hashed value of the preamble sequence, a constant value, or a combination thereof, and wherein the preamble sequence, the constant value, or both were indicated in the random access request.
The method of claim 19, wherein the UE-specific parameter comprises a hashed demodulation reference signal (DMRS) sequence identifier, and wherein the hashed DMRS sequence identifier is based at least in part on an uplink (UL) DMRS that was indicated in the random access request.
The method of claim 26, wherein the UE-specific parameter further comprises a preamble sequence, a hashed value of the preamble sequence, a constant value, or a combination thereof, and wherein the preamble sequence, the constant value, or both were indicated in the random access request.
The method of claim 18, further comprising:

transmitting a downlink (DL) demodulation reference signal (DMRS) indicating that the UE is the intended recipient of the random access response based at least in part on a mapping between the received DL DMRS and an uplink (UL) DMRS that was indicated in the random access request.
The method of claim 18, further comprising:

scrambling the random access response, wherein the random access response is scrambled based at least in part on at least one of the one or more RACH preamble parameters indicated in the random access request, and wherein the scrambling at least partially indicates that the UE is the intended recipient of the random access response.
The method of claim 29, wherein the random access response is scrambled based at least in part on a preamble sequence that was indicated in the random access request.
The method of claim 29, wherein the random access response is scrambled based at least in part on a scrambling sequence that has a 1 to 1 mapping with a preamble sequence that was indicated in the random access request.
The method of claim 18, further comprising:

transmitting the random access response on a set of resource blocks that indicates a preamble sequence identification.
The method of claim 32, wherein the preamble sequence identification comprises a resource block frequency index, a resource block frame index, or both.
The method of claim 18, wherein the RACH preamble parameters comprise at least one of a random access radio network temporary identifier (RA-RNTI) , a preamble sequence, a demodulation reference signal (DMRS) , or a combination thereof.
An apparatus for wireless communications, comprising:

a processor,

memory in electronic communication with the processor; and

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

transmit, from a user equipment (UE) , a random access request that comprises one or more random access channel (RACH) preamble parameters;

receive a random access response in response to the random access request that uniquely identifies the UE based at least in part on at least one of the one or more RACH preamble parameters; and

establish a communication connection based at least in part on receiving the random access response.
The apparatus of claim 35, wherein the instructions are further executable by the processor to cause the apparatus to:

receive a modified random access radio network temporary identifier (RA-RNTI) in the random access response, wherein the modified RA-RNTI comprises a UE-specific parameter, and wherein the UE-specific parameter is based at least in part on at least one of the one or more RACH preamble parameters;

identify the UE-specific parameter included in the modified RA-RNTI; and

determine that the UE is the intended recipient of the random access response based at least in part on identifying the UE-specific parameter.
The apparatus of claim 36, wherein the UE-specific parameter comprises a preamble sequence that was indicated in the random access request.
The apparatus of claim 36, wherein the UE-specific parameter comprises a product of a preamble sequence and a constant value, and wherein the preamble sequence, the constant value, or both were indicated in the random access request.
The apparatus of claim 36, wherein the UE-specific parameter comprises a hashed value of a preamble sequence that was indicated in the random access request.
The apparatus of claim 36, wherein the UE-specific parameter comprises a product of a hashed value of a preamble sequence and a constant value, and wherein the preamble sequence, the constant value, or both were indicated in the random access request.
The apparatus of claim 36, wherein the UE-specific parameter comprises a demodulation reference signal (DMRS) sequence identifier, and wherein the DMRS sequence identifier is based at least in part on an uplink (UL) DMRS that was indicated in the random access request.
The apparatus of claim 41, wherein the UE-specific parameter further comprises a preamble sequence, a hashed value of the preamble sequence, a constant value, or a combination thereof, and wherein the preamble sequence, the constant value, or both were indicated in the random access request.
The apparatus of claim 36, wherein the UE-specific parameter comprises a hashed demodulation reference signal (DMRS) sequence identifier, and wherein the hashed DMRS sequence identifier is based at least in part on an uplink (UL) DMRS that was indicated in the random access request.
The apparatus of claim 43, wherein the UE-specific parameter further comprises a preamble sequence, a hashed value of the preamble sequence, a constant value, or a combination thereof, and wherein the preamble sequence, the constant value, or both were indicated in the random access request.
The apparatus of claim 35, wherein the instructions are further executable by the processor to cause the apparatus to:

receive a downlink (DL) demodulation reference signal (DMRS) ; and

determine that the UE is the intended recipient of the random access response based at least in part on a mapping between the received DL DMRS and an uplink (UL) DMRS that was indicated in the random access request.
The apparatus of claim 35, wherein the instructions are further executable by the processor to cause the apparatus to:

descramble the random access response, wherein the random access response is scrambled based at least in part on at least one of the one or more RACH preamble parameters indicated in the random access request; and

determine that the UE is the intended recipient of the random access response based at least in part on descrambling the random access response.
The apparatus of claim 46, wherein the random access response is scrambled based at least in part on a preamble sequence that was indicated in the random access request.
The apparatus of claim 46, wherein the random access response is scrambled based at least in part on a scrambling sequence that has a 1 to 1 mapping with a preamble sequence that was indicated in the random access request.
The apparatus of claim 35, wherein the instructions are further executable by the processor to cause the apparatus to:

receive the random access response on a set of resource blocks that indicates a preamble sequence identification.
The apparatus of claim 49, wherein the preamble sequence identification comprises a resource block frequency index, a resource block frame index, or both.
The apparatus of claim 35, wherein the RACH preamble parameters comprise at least one of a random access radio network temporary identifier (RA-RNTI) , a preamble sequence, a demodulation reference signal (DMRS) , or a combination thereof.
An apparatus for wireless communications, comprising:

a processor,

memory in electronic communication with the processor; and

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

receive, from a user equipment (UE) , a random access request that comprises one or more random access channel (RACH) preamble parameters;

transmit a random access response in response to the random access request that uniquely identifies the UE based at least in part on at least one of the one or more RACH preamble parameters; and

establish a communication connection based at least in part on transmitting the random access response.
The apparatus of claim 52, wherein the instructions are further executable by the processor to cause the apparatus to:

transmit a modified random access radio network temporary identifier (RA-RNTI) in the random access response, wherein the modified RA-RNTI comprises a UE-specific parameter indicating that the UE is the intended recipient of the random access response, and wherein the UE-specific parameter is based at least in part on at least one of the one or more RACH preamble parameters.
The apparatus of claim 53, wherein the UE-specific parameter comprises a preamble sequence that was indicated in the random access request.
The apparatus of claim 53, wherein the UE-specific parameter comprises a product of a preamble sequence and a constant value, and wherein the preamble sequence, the constant value, or both were indicated in the random access request.
The apparatus of claim 53, wherein the UE-specific parameter comprises a hashed value of a preamble sequence that was indicated in the random access request.
The apparatus of claim 53, wherein the UE-specific parameter comprises a product of a hashed value of a preamble sequence and a constant value, and wherein the preamble sequence, the constant value, or both were indicated in the random access request.
The apparatus of claim 53, wherein the UE-specific parameter comprises a demodulation reference signal (DMRS) sequence identifier, and wherein the DMRS sequence identifier is based at least in part on an uplink (UL) DMRS that was indicated in the random access request.
The apparatus of claim 58, wherein the UE-specific parameter further comprises a preamble sequence, a hashed value of the preamble sequence, a constant value, or a combination thereof, and wherein the preamble sequence, the constant value, or both were indicated in the random access request.
The apparatus of claim 53, wherein the UE-specific parameter comprises a hashed demodulation reference signal (DMRS) sequence identifier, and wherein the hashed DMRS sequence identifier is based at least in part on an uplink (UL) DMRS that was indicated in the random access request.
The apparatus of claim 60, wherein the UE-specific parameter further comprises a preamble sequence, a hashed value of the preamble sequence, a constant value, or a combination thereof, and wherein the preamble sequence, the constant value, or both were indicated in the random access request.
The apparatus of claim 52, wherein the instructions are further executable by the processor to cause the apparatus to:

transmit a downlink (DL) demodulation reference signal (DMRS) indicating that the UE is the intended recipient of the random access response based at least in part on a mapping between the received DL DMRS and an uplink (UL) DMRS that was indicated in the random access request.
The apparatus of claim 52, wherein the instructions are further executable by the processor to cause the apparatus to:

scramble the random access response, wherein the random access response is scrambled based at least in part on at least one of the one or more RACH preamble parameters indicated in the random access request, and wherein the scrambling at least partially indicates that the UE is the intended recipient of the random access response.
The apparatus of claim 63, wherein the random access response is scrambled based at least in part on a preamble sequence that was indicated in the random access request.
The apparatus of claim 63, wherein the random access response is scrambled based at least in part on a scrambling sequence that has a 1 to 1 mapping with a preamble sequence that was indicated in the random access request.
The apparatus of claim 52, wherein the instructions are further executable by the processor to cause the apparatus to:

transmit the random access response on a set of resource blocks that indicates a preamble sequence identification.
The apparatus of claim 66, wherein the preamble sequence identification comprises a resource block frequency index, a resource block frame index, or both.
The apparatus of claim 52, wherein the RACH preamble parameters comprise at least one of a random access radio network temporary identifier (RA-RNTI) , a preamble sequence, a demodulation reference signal (DMRS) , or a combination thereof.
An apparatus for wireless communications, comprising:

means for transmitting, from a user equipment (UE) , a random access request that comprises one or more random access channel (RACH) preamble parameters;

means for receiving a random access response in response to the random access request that uniquely identifies the UE based at least in part on at least one of the one or more RACH preamble parameters; and

means for establishing a communication connection based at least in part on receiving the random access response.
An apparatus for wireless communications, comprising:

means for receiving, from a user equipment (UE) , a random access request that comprises one or more random access channel (RACH) preamble parameters;

means for transmitting a random access response in response to the random access request that uniquely identifies the UE based at least in part on at least one of the one or more RACH preamble parameters; and

means for establishing a communication connection based at least in part on transmitting the random access response.
A non-transitory computer-readable medium storing code for wireless communications, the code comprising instructions executable by a processor to:

transmit, from a user equipment (UE) , a random access request that comprises one or more random access channel (RACH) preamble parameters;

receive a random access response in response to the random access request that uniquely identifies the UE based at least in part on at least one of the one or more RACH preamble parameters; and

establish a communication connection based at least in part on receiving the random access response.
A non-transitory computer-readable medium storing code for wireless communications, the code comprising instructions executable by a processor to:

receive, from a user equipment (UE) , a random access request that comprises one or more random access channel (RACH) preamble parameters;

transmit a random access response in response to the random access request that uniquely identifies the UE based at least in part on at least one of the one or more RACH preamble parameters; and

establish a communication connection based at least in part on transmitting the random access response.