WO2020164074A1

WO2020164074A1 - Msg3 transmission in unlicensed band

Info

Publication number: WO2020164074A1
Application number: PCT/CN2019/075119
Authority: WO
Inventors: Samuli Turtinen; Benoist Sebire; Chunli Wu
Original assignee: Nokia Shanghai Bell Co., Ltd.; Nokia Solutions And Networks Oy; Nokia Technologies Oy
Priority date: 2019-02-14
Filing date: 2019-02-14
Publication date: 2020-08-20
Also published as: CN113228786A; CN113228786B

Abstract

In accordance with some embodiments, an apparatus comprises at least one processor and at least one memory including computer program code. The at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus to detect at least one listen before talk failure associated with at least one initial transmission opportunity of a random access procedure message. The apparatus further designates at least one contention resolution as unsuccessful. The apparatus further in response to at least one contention resolution being designated as unsuccessful, initiates at least one random access resource selection procedure.

Description

MSG3 TRANSMISSION IN UNLICENSED BAND

BACKGROUND: Field:

Certain embodiments may relate to communication systems. For example, some embodiments may relate to random access procedures, in particular, msg3 transmissions for new radio operating in unlicensed spectrum.

Description of the Related Art:

3GPP technical report (TR) 38.889 describes a 4-step and 2-step random access channel (RACH) procedure, which are both meant to be supported under new radio for unlicensed spectrum (NR-U) . 2-step RACH refers to the procedure which can complete contention-based RACH (CBRA) in two steps as explained below. One example benefit of 2-step RACH is a minimized impact to LBT through its reduced number of messages. However, in order to alleviate the impact of LBT failures further, additional opportunities for the RACH messages may be introduced, for example, in time or frequency domain, for both 4-step and 2-step RACH. The additional opportunities for 4-step RACH may be applicable to both msg1 and msg3.

SUMMARY:

In accordance with some embodiments, a method may include detecting, at a user equipment, at least one listen before talk failure associated with at least one initial transmission opportunity of a random access procedure message. The method may further include designating, by the user equipment, at least one contention resolution as unsuccessful. The method may further include in response to at least one contention resolution being designated as unsuccessful, . initiating, by the user equipment, at least one random access resource selection procedure.

In accordance with some embodiments, an apparatus may include means for detecting at least one listen before talk failure associated with at least one initial transmission opportunity of a random access procedure message. The apparatus may further include means for designating at least one contention resolution as unsuccessful. The apparatus may further include means for in response to at least one contention resolution being designated as unsuccessful, initiating at least one random access resource selection procedure.

In accordance with some embodiments, an apparatus may include at least one processor and at least one memory including computer program code. The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to at least detect at least one listen before talk failure associated with at least one initial transmission opportunity of a random access procedure message. The at least one memory and the computer program code may be further configured to, with the at least one processor, cause the apparatus to at least designate at least one contention resolution as unsuccessful. The at least one memory and the computer program code may be further configured to, with the at least one processor, cause the apparatus to at least in response to at least one contention resolution being designated as unsuccessful, initiate at least one random access resource selection procedure.

In accordance with some embodiments, a non-transitory computer readable medium may be encoded with instructions that may, when executed in hardware, perform a method. The method may detect at least one listen before talk failure associated with at least one initial transmission opportunity of a random access procedure message. The method may further designate at least one contention resolution as unsuccessful. The method may further in response to at least one contention resolution being designated as unsuccessful, initiate at least one random access resource selection procedure.

In accordance with some embodiments, a computer program product may perform a method. The method may detect at least one listen before talk failure associated with at least one initial transmission opportunity of a random access procedure message. The method may further designate at least one contention resolution as unsuccessful. The method may further in response to at least one contention resolution being designated as unsuccessful, initiate at least one random access resource selection procedure.

In accordance with some embodiments, an apparatus may include circuitry configured to detect at least one listen before talk failure associated with at least one initial transmission opportunity of a random access procedure message. The circuitry may further designate at least one contention resolution as unsuccessful. The circuitry may further in response to at least one contention resolution being designated as unsuccessful, initiate at least one random access resource selection procedure.

In accordance with some embodiments, a method may include detecting, at a user equipment, at least one listen before talk failure associated with at least one re-transmission random access channel transmission opportunity. The method may further include designating at least one contention resolution as unsuccessful based on trigger condition. The method may further include in response to at least one contention resolution being designated as unsuccessful, initiating at least one random access resource selection procedure.

In accordance with some embodiments, a method may include detecting, at a user equipment, at least one listen before talk failure associated with at least one re-transmission random access channel transmission opportunity. The method may further include restarting, by the user equipment, at least one contention resolution timer. The method may further include decoding, by the user equipment, at least one physical downlink control channel for further analysis.

In accordance with some embodiments, an apparatus may include means for detecting at least one listen before talk failure associated with at least one re-transmission random access channel transmission opportunity. The apparatus may further include means for designating at least one contention resolution as unsuccessful based on trigger condition. The apparatus may further include means for in response to at least one contention resolution being designated as unsuccessful, initiating at least one random access resource selection procedure.

In accordance with some embodiments, an apparatus may include means for detecting at least one listen before talk failure associated with at least one re-transmission random access channel transmission opportunity. The apparatus may further include means for restarting at least one contention resolution timer. The apparatus may further include means for decoding at least one physical downlink control channel for further analysis.

In accordance with some embodiments, an apparatus may include at least one processor and at least one memory including computer program code. The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to at least detect at least one listen before talk failure associated with at least one re-transmission random access channel transmission opportunity. The at least one memory and the computer program code may be further configured to, with the at least one processor, cause the apparatus to at least designate at least one contention resolution as unsuccessful based on trigger condition. The at least one memory and the computer program code may be further configured to, with the at least one processor, cause the apparatus to at least in response to at least one contention resolution being designated as unsuccessful, initiating at least one random access resource selection procedure.

In accordance with some embodiments, an apparatus may include at least one processor and at least one memory including computer program code. The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to at least detect at least one listen before talk failure associated with at least one re-transmission random access channel transmission opportunity. The at least one memory and the computer program code may be further configured to, with the at least one processor, cause the apparatus to at least restart at least one contention resolution timer. The at least one memory and the computer program code may be further configured to, with the at least one processor, cause the apparatus to at least decode at least one physical downlink control channel for further analysis.

In accordance with some embodiments, a non-transitory computer readable medium may be encoded with instructions that may, when executed in hardware, perform a method. The method may detect at least one listen before talk failure associated with at least one re-transmission random access channel transmission opportunity. The method may further include designating at least one contention resolution as unsuccessful based on trigger condition. The method may further include in response to at least one contention resolution being designated as unsuccessful, initiating at least one random access resource selection procedure.

In accordance with some embodiments, a non-transitory computer readable medium may be encoded with instructions that may, when executed in hardware, perform a method. The method may detect at least one listen before talk failure associated with at least one re-transmission random access channel transmission opportunity. The method may further restart at least one contention resolution timer. The method may further decode at least one physical downlink control channel for further analysis.

In accordance with some embodiments, a computer program product may perform a method. The method may detect at least one listen before talk failure associated with at least one re-transmission random access channel transmission opportunity. The method may further include designating at least one contention resolution as unsuccessful based on trigger condition. The method may further include in response to at least one contention resolution being designated as unsuccessful, initiating at least one random access resource selection procedure.

In accordance with some embodiments, a computer program product may perform a method. The method may detect at least one listen before talk failure associated with at least one re-transmission random access channel transmission opportunity. The method may further restart at least one contention resolution timer. The method may further decode at least one physical downlink control channel for further analysis.

In accordance with some embodiments, an apparatus may include circuitry configured to detect at least one listen before talk failure associated with at least one re-transmission random access channel transmission opportunity. The circuitry may further designate at least one contention resolution as unsuccessful. The circuitry may further in response to at least one contention resolution being designated as unsuccessful, initiate at least one random access resource selection procedure.

In accordance with some embodiments, an apparatus may include circuitry configured to detect at least one listen before talk failure associated with at least one re-transmission random access channel transmission opportunity. The circuitry may further restart at least one contention resolution timer. The circuitry may further decode at least one physical downlink control channel for further analysis.

BRIEF DESCRIPTION OF THE DRAWINGS:

For proper understanding of this disclosure, reference should be made to the accompanying drawings, wherein:

FIG. 1 illustrates an example of a method performed by a user equipment according to certain embodiments.

FIG. 2 illustrates another example of a method performed by a user equipment according to certain embodiments.

FIG. 3 illustrates a system according to certain embodiments.

DETAILED DESCRIPTION:

NR-U may support contention-free RACH (CFRA) and CBRA for both 2-step and 4-step RACH procedures. With respect to secondary cells, CFRA may be supported as a baseline, while both CBRA and CFRA are supported on SpCells. For 4-step RACH procedure, the messages in time order may be described as msg1, msg2, msg3, msg4, while for 2-step RACH, they are described as msgA and msgB.

A single RACH procedure i may be used, and thus multiple RACH procedures in parallel may not be supported for NR-U. As a baseline, the random-access response to msg 1 may be on SpCell, and msg3 is assumed to use a predetermined HARQ ID.

In legacy RACH, the counters for preamble transmission and power ramping may be increased with every attempt. In NR-U, power ramping is not applied when preamble is not transmitted due to the possibility of LBT failure. As a result, this may require an indication from the physical layer to the MAC. In addition, ra-ResponseWindow may not be started when the preamble is not transmitted due to LBT failure. In addition, it is assumed that ra-ContentionResolutionTimer may need to be extended with larger values to overcome any impact to LBT.

For 2-step RACH procedure, the msgA may be a signal to detect the UE and a payload, while the second message is for contention resolution for CBRA with a possible payload, msgA may at least include the information equivalent to the information transmitted in msg3 for 4-step RACH procedure.

As a baseline, all of the triggers for 4-step RACH procedure may be applicable to 2-step RACH procedure. However, further analysis may be needed on one or more SI requests and BFR, as well as how timing advance and grants may be obtained for msgA. The contention resolution in 2-step RACH procedure may include a UE identifier in the first message, which is then included in the second message. The type of UE identifier may include FFS.

Fall-back from 2-step RACH procedure to 4-step RACH procedure may also be supported. The fallback after msgA transmission may be feasible only if detection of the UE without the decoding of the payload is possible, and thus relies on such support at the physical layer. If 2-step RACH procedure is used for initial access, the parameters for 2-step RACH procedure including resources for msgA may be broadcasted. It is noted that 2-step RACH procedure, if applied to a licensed operation, may not take LBT into account. As a result, due to the possible LBT failures, some data transmissions may fail when the channel is busy. For this, MAC may receive an indication from L 1 about the occurrence of an LBT failure.

Under 3GPP TR 38.889, a mechanism may be used for SS/PBCH block transmission to transmit SS/PBCH blocks dropped due to LBT failure. A mechanism may also be defined when specifications are developed for UE to determine the frame timing and QCL assumptions from the detected SS/PBCH block. For SS/PBCH block transmissions as part of DRS, it may be beneficial to expand the maximum number of candidate SS/PBCH block positions within the DRS transmission window to Y, for example, Y ≤ 64, where the choice of Y may depend on the numerology of the SS/PBCH blocks. The transmitted SS/PBCH blocks may not overlap, and the maximum number of transmitted SS/PBCH blocks may be expressed as X within DRS transmission window, with X ≤ 8. The time-domain positions of the actually transmitted SS/PBCH blocks may be selected from a set of Y candidate SS/PBCH block positions.

From the viewpoint of the user equipment, when the preamble transmission (msg1) fails due to LBT failure, the preamble transmission may be reattempted without increasing power ramping counters since no transmission occurred. However, various techniques may occur with respect to the UE retransmission (msg3) when LBT failure occurs. In contrast, from the viewpoint of the network entity, when msg3 is not received, the network entity is unaware whether the failure is due to LBT failure or due to a RAR/msg3 re-transmission grant which could not be received by the UE. For example, the downlink preferred beam may change suddenly between the preamble transmission and RAR reception, for example, due to a sudden obstacle, and the DL scheduling (PDCCH) , may not be decoded by the UE.

Certain embodiments described herein may enable UE behavior for deterministic transmission of msg3 for the NW, and every failure in decoding msg3 from the initial resources may be considered as DTX by NW. For example, it may be known whether it was a LBT failure, or RAR was not received by the UE, and/or the NW may know that the UE will immediately re-attempt transmission. As a result, the network entity may avoid sending useless re-transmission grants when the UE fails to receive the RAR, and/or may reduce latency for the RA procedure. Certain embodiments are, therefore, directed to improvements in computer-related technology, specifically, by preventing unnecessary retransmission, and allowing the UE to re-attempt transmission immediately without waiting for the contention resolution timer to expire, for example, in case the preferred beam indicated with the transmitted preamble is blocked. Certain embodiments may further conserve network resources and reduce power consumption of network entities and/or user equipment located within the network by reducing redundant operations.

FIG. 1 illustrates an example of a method performed by user equipment, such as user equipment 310 in FIG. 3. In step 101, the user equipment may detect at least one listen before talk failure associated with at least one initial transmission opportunity of a random access procedure message, such as msg3 of the 4-step RA procedure and/or msgA of the 2-step RA procedure. In step 103, the user equipment may designate at least one contention resolution as unsuccessful. In step 105, the user equipment may in response to at least one contention resolution being designated as unsuccessful, initiate at least one random access resource selection procedure. For example, the user equipment may immediately reattempt transmission of at least one preamble, such as msg1.

In some embodiments, the user equipment may have multiple transmission opportunities for the initial transmission of a random access procedure message, such as msg3 of the 4-step RA procedure and/or msgA of the 2-step RA procedure. For example, the multiple transmission opportunities may be received from at least one random access response (RAR) message sent by the network entity. In some examples, a RAR message may include at least one indication that the network entity will schedule further RAR messages configured to provide further transmission opportunities for the initial transmission of a random access procedure message.

In some embodiments, a power ramping counter may remain unchanged. Alternatively, the counter may be reduced by at least one offset, for example, the counter may be reduced by a fixed value, reduced by a value in a system information broadcast, and/or linked to a time elapsed between failure and new preamble transmission. In certain embodiments, the at least one offset may instead increase the power ramping counter, and/or may be a combination of at least one increasing offset and at least one decreasing offset. In certain embodiments, a contention resolution timer may be stopped, not started, and/or immediately considered as expired, which may lead to an increase of a preamble transmission counter. Alternatively, the preamble transmission counter may not be increased.

FIG. 2 illustrates an example of a method performed by user equipment, such as user equipment 310 in FIG. 3. In step 201, the user equipment may detect at least one listen before talk failure associated with at least one re-transmission opportunity of a random access procedure message. In step 203, the user equipment may designate at least one contention resolution as unsuccessful based on at least trigger condition. In one non-limiting example the user equipment may also restart at least one contention resolution timer. In step 205, the user equipment may in response to at least on contention resolution being designated as unsuccessful, initiate at least one random selection procedure. In one non-limiting example the user equipment may also decode at least one physical downlink control channel for further analysis. Same non-limiting examples as applied with FIG. 1 can be applied also to FIG. 2 when applicable.

In some embodiments, at least one trigger condition may be configured. In a sample embodiment, a network entity may configure the user equipment with the at least one trigger condition as maximum number of re-transmission attempts due to LBT failures after which the user equipment in response may designate at least one contention resolution as unsuccessful. In response to the at least one trigger condition occurring, the user equipment may initiate a new random access resource selection procedure. In another sample embodiment, the at least one trigger condition may be according to an indication in a re-transmission grant. For example, if a LBT fails during the re-transmission grant, the user equipment may initiate a new random access resource selection procedure. In certain embodiments, the re-transmission attempts associated with LBT failures may or may not be consecutive re-transmission attempts.

In some embodiments, at least one preamble/power ramping counter may be incremented by one for each contention resolution failure, for example, due to collision. Alternatively or additionally, the re-transmission random access channel transmission opportunity may apply to at least one msg3 re-transmission failure due to LBT, such as where the UE immediately re-attempts transmission of the preamble, with or without power ramping.

FIG. 3 illustrates a system according to certain embodiments. It should be understood that each signal or block in FIGS. 1-2 may be implemented by various means or their combinations, such as hardware, software, firmware, one or more processors and/or circuitry. In one embodiment, a system may include several devices, such as, for example, user equipment 310 and/or network entity 320. The system may include more than one user equipment 310 and more than one network entity 320.

User equipment 314 may be a mobile station (MS) such as a mobile phone or smart phone or multimedia device, an IoT cellular device, a computer, such as a tablet, provided with wireless communication capabilities, personal data or digital assistant (PDA) provided with wireless communication capabilities, portable media player, digital camera, pocket video camera, navigation unit provided with wireless communication capabilities or any combinations thereof.

Network entity 320 may be a CBSD, a base station, an access point, an access node, an eNB, a gNB, a server, a host, a MME, a S-GW, a P-GW, a PCRF, a P-CSCF, E/CSCF, or any other network entity that may communicate with user equipment 310.

Each of these devices may include at least one processor or control unit or module, respectively indicated as 311 and 321. At least one memory may be provided in each device, and indicated as 312 and 322, respectively. The memory may include computer program instructions or computer code contained therein. One or

more transceivers

313 and 323 may be provided, and each device may also include an antenna, respectively illustrated as 314 and 324. Although only one antenna each is shown, many antennas and multiple antenna elements may be provided to each of the devices. Other configurations of these devices, for example, may be provided. For example, user equipment 310 and/or network entity 320 may be additionally configured for wired communication, in addition to wireless communication, and in such a case,

antennas

314 and 324 may illustrate any form of communication hardware, without being limited to merely an antenna.

Transceivers

313 and 323 may each, independently, be a transmitter, a receiver, or both a transmitter and a receiver, or a unit or device that may be configured both for transmission and reception. The transmitter and/or receiver (as far as radio parts are concerned) may also be implemented as a remote radio head which is not located in the device itself, but in a mast, for example. The operations and functionalities may be performed in different entities, such as nodes, hosts or servers, in a flexible manner. In other words, division of labor may vary case by case. One possible use is to make a network node deliver local content. One or more functionalities may also be implemented as virtual application (s) in software that can run on a server.

In some embodiments, an apparatus, such as a user equipment or a network node, may include means for carrying out embodiments described above in relation to FIGS. 1-2. In certain embodiments, at least one memory including computer program code can be configured to, with the at least one processor, cause the apparatus at least to perform any of the processes described herein.

Processors

311 and 321 may be embodied by any computational or data processing device, such as a central processing unit (CPU) , digital signal processor (DSP) , application specific integrated circuit (ASIC) , programmable logic devices (PLDs) , field programmable gate arrays (FPGAs) , digitally enhanced circuits, or comparable device or a combination thereof. The processors may be implemented as a single controller, or a plurality of controllers or processors.

For firmware or software, the implementation may include modules or unit of at least one chip set (for example, procedures, functions, and so on) .

Memories

312 and 322 may independently be any suitable storage device, such as a non-transitory computer-readable medium. A hard disk drive (HDD) , random access memory (RAM) , flash memory, or other suitable memory may be used. The memories may be combined on a single integrated circuit as the processor, or may be separate therefrom. Furthermore, the computer program instructions may be stored in the memory and which may be processed by the processors can be any suitable form of computer program code, for example, a compiled or interpreted computer program written in any suitable programming language. The memory or data storage entity is typically internal but may also be external or a combination thereof, such as in the case when additional memory capacity is obtained from a service provider. The memory may be fixed or removable.

The memory and the computer program instructions may be configured, with the processor for the particular device, to cause a hardware apparatus such as user equipment 310 and/or network entity 320, to perform any of the processes described above (see, for example, FIGS. 1-2) . Therefore, in certain embodiments, a non-transitory computer-readable medium may be encoded with computer instructions or one or more computer program (such as added or updated software routine, applet or macro) that, when executed in hardware, may perform a process such as one of the processes described herein. Computer programs may be coded by a programming language, which may be a high-level programming language, such as objective-C, C, C++, C#, Java, etc., or a low-level programming language, such as a machine language, or assembler. Alternatively, certain embodiments may be performed entirely in hardware.

Furthermore, although FIG. 3 illustrates a system including a user equipment 310 and/or network entity 320, certain embodiments may be applicable to other configurations, and configurations involving additional elements, as illustrated and discussed herein. For example, multiple user equipment devices and multiple base stations may be present, or other nodes providing similar functionality, such as nodes that combine the functionality of a user equipment and a base station, such as a relay node. User equipment310 may likewise be provided with a variety of configurations for communication other than communicating with network entity 320. For example, user equipment 310 may be configured for device-to-device, machine-to-machine, or vehicle-to-vehicle communication.

As shown in FIG. 3,

transceivers

313 and 323 may be provided, and one or more devices may also include at least one antenna, respectively illustrated as 314 and 324. The device may have many antennas, such as an array of antennas configured for multiple input multiple output (MIMO) communications, or multiple antennas for multiple radio access technologies. Other configurations of these devices, for example, may be provided.

Transceivers

313 and 323 may be a transmitter, a receiver, or both a transmitter and a receiver, or a unit or device that may be configured both for transmission and reception.

Processors

311 and 321 may be embodied by any computational or data processing device, such as a central processing unit (CPU) , application specific integrated circuit (ASIC) , or comparable device. The processors may be implemented as a single controller, or a plurality of controllers or processors.

Memories

312 and 322 may independently be any suitable storage device, such as a non-transitory computer-readable medium. A hard disk drive (HDD) , random access memory (RAM) , flash memory, or other suitable memory may be used. The memories may be combined on a single integrated circuit as the processor, or may be separate from the one or more processors. Furthermore, the computer program instructions stored in the memory and which may be processed by the processors may be any suitable form of computer program code, for example, a compiled or interpreted computer program written in any suitable programming language. Memory may be removable or non-removable.

The memory and the computer program instructions may be configured, with the processor for the particular device, to cause a hardware apparatus such as user equipment to perform any of the processes described below (see, for example, FIGS. 1-2) . Therefore, in certain embodiments, a non-transitory computer-readable medium may be encoded with computer instructions that, when executed in hardware, perform a process such as one of the processes described herein. Alternatively, certain embodiments may be performed entirely in hardware.

In certain embodiments, an apparatus may include circuitry configured to perform any of the processes or functions illustrated in FIGS. 1-2. For example, circuitry may be hardware-only circuit implementations, such as analog and/or digital circuitry. In another example, circuitry may be a combination of hardware circuits and software, such as a combination of analog and/or digital hardware circuit (s) with software or firmware, and/or any portions of hardware processor (s) with software (including digital signal processor (s) ) , software, and at least one memory that work together to cause an apparatus to perform various processes or functions. In yet another example, circuitry may be hardware circuit (s) and or processor (s) , such as a microprocessor (s) or a portion of a microprocessor (s) , that include software, such as firmware for operation. Software in circuitry may not be present when it is not needed for the operation of the hardware.

The features, structures, or characteristics of certain embodiments described throughout this specification may be combined in any suitable manner in one or more embodiments. For example, the usage of the phrases “certain embodiments, ” “some embodiments, ” “other embodiments, ” or other similar language, throughout this specification refers to the fact that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the present invention. Thus, appearance of the phrases “in certain embodiments, ” “in some embodiments, ” “in other embodiments, ” or other similar language, throughout this specification does not necessarily refer to the same group of embodiments, and the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

One having ordinary skill in the art will readily understand that the invention as discussed above may be practiced with steps in a different order, and/or with hardware elements in configurations which are different than those wlfich are disclosed. Therefore, although the invention has been described based upon these preferred embodiments, it would be apparent to those of skill in the art that certain modifications, variations, and alternative constructions would be apparent, while remaining within the spirit and scope of the invention. The above embodiments may be applied to any communication network or wireless system. While many of the above embodiments refer to LTE or LTE-A, other embodiments may be used for 3GPP fifth generation (5G) technology, fourth generation (4G) technology, New Radio (NR) technology, and/or any wireless land access network (WLAN) .

Partial Glossary

3GPP 3rd Generation Partnership Project

5G 5th Generation Wireless System

BFR Beam Failure Recovery

CBRA Contention Based Random Access

CFRA Contention Free Random Access

CSI-RS Channel State Information Reference Signal

DRS Downlink Reference Signal

DTX Discontinuous Transmission

HO Handover

eNB evolved Node B

E-UTRAN Evolved Universal Mobile Telecommunications System Terrestrial Radio Access Network

gNB Next Generation Node B

LBT Listen Before Talk

LTE Long Term Evolution

MAC Medium Access Control

MIMO Multiple Input Multiple Output

NE Network Entity

NR New Radio

PBCH Physical Broadcast Channel

PRACH Physical Random Access Channel

QCL Quasi Co-Location

RA Random Access

RAR Random Access Response

RACH Random Access Channel

RO Random Access Channel Occasion

RS Reference Signal

RSRP Reference Signal Received Power

RSRQ Reference Signal Received Quality

RSSI Received Signal Strength Indicator

SINR Signal-to-Interference-plus-Noise Ratio

SS Synchronization Signal

SSB Synchronization Signal Block

UE User Equipment

UL Uplink

Claims

An apparatus, comprising:

at least one processor; and

at least one memory including computer program code,

wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus to:

detect at least one listen before talk failure associated with at least one initial transmission opportunity of a random access procedure message;

designate at least one contention resolution as unsuccessful; and

in response to at least one contention resolution being designated as unsuccessful, initiate at least one random access resource selection procedure.
The apparatus according to claim 1, wherein at least one power ramping counter remains unchanged.
The apparatus according to any of claims 1 and 2, wherein at least one power ramping counter is reduced by an offset.
The apparatus according to any of claims 1-3, wherein the at least one offset is reduced by a fixed value, reduced by a value in a system information broadcast, and/or linked to a time elapsed between failure and new preamble transmission.
The apparatus according to any of claims 1-4, wherein the designation is based on at least one trigger condition comprising at least one contention resolution timer stopping, not starting, and/or immediately being considered as expired.
The apparatus according to any of claims 1-5, wherein the random access procedure message is msg3 of the random access procedure.
An apparatus, comprising:

at least one processor; and

at least one memory including computer program code,

wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus to:

detect at least one listen before talk failure associated with at least one re-transmission opportunity of at least one random access procedure message;

designate at least one contention resolution as unsuccessful based on at least one trigger condition; and

in response to at least one contention resolution being designated as unsuccessful, initiate at least one random access resource selection procedure.
The apparatus according to claim 7, wherein at least one trigger condition comprises a maximum number of re-transmission attempts due to LBT failures.
The apparatus according to any of claims 7 and 8, wherein the at least one trigger condition is in a re-transmission grant and indicates that contention resolution is unsuccessful where at least one listen before talk failure is associate with the re-transmission opportunity.
The apparatus according to any of claims 7-9, wherein a preamble/power ramping counter is incremented by one for each contention resolution failure.
The apparatus according to any of claims 7-10, wherein the at least one trigger condition comprises at least one contention resolution timer stopping, not starting, and/or immediately being considered as expired.
A method according to any of claims 1-11.
A non-transitory computer-readable medium encoding instructions that, when executed in hardware, perform a process according to any of claims 1-11.
An apparatus comprising means for performing a process according to any of claims 1-11.
An apparatus comprising circuitry configured to cause the apparatus to perform a process according to any of claims 1-11.
A computer program product encoded with instructions for performing a process according to any of claims 1-11.