CN113228786A

CN113228786A - MSG3 transmission in unlicensed bands

Info

Publication number: CN113228786A
Application number: CN201980087551.7A
Authority: CN
Inventors: S·图尔蒂南; B·塞比尔; 吴春丽
Original assignee: Nokia Shanghai Bell Co Ltd; Nokia Networks Oy
Current assignee: Nokia Communications (Shanghai) Co., Ltd.; Nokia Solutions and Networks Oy
Priority date: 2019-02-14
Filing date: 2019-02-14
Publication date: 2021-08-06
Anticipated expiration: 2039-02-14
Also published as: WO2020164074A1; CN113228786B

Abstract

According to some embodiments, an apparatus includes 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 also indicates at least one contention resolution as unsuccessful. The apparatus also initiates at least one random access resource selection procedure in response to at least one contention resolution being designated as unsuccessful.

Description

MSG3 transmission in unlicensed bands

Technical Field

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

Background

The 3GPP Technical Report (TR)38.889 describes 4-and 2-step Random Access Channel (RACH) procedures, both of which will be supported under new radio of unlicensed spectrum (NR-U). The 2-step RACH refers to a procedure capable of completing a contention-based RACH (cbra) in two steps explained below. One example benefit of the 2-step RACH is to minimize the impact on LBT by reducing its number of messages. However, to mitigate the impact of LBT failure, it is further possible to introduce additional opportunities for RACH messages, e.g., in the time or frequency domain, for both 4-step RACH and 2-step RACH. The additional opportunity for 4-step RACH may apply to both msg1 and msg 3.

Disclosure of Invention

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

According to some examples, 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 also include means for designating at least one contention resolution scheme as unsuccessful. The apparatus may also include means for initiating at least one random access resource selection procedure in response to at least one contention resolution scheme being designated as unsuccessful.

According to 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 at least to 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 also be configured to, with the at least one processor, cause the apparatus at least to designate the at least one contention resolution as unsuccessful. The at least one memory and the computer program code may also be configured to, with the at least one processor, cause the apparatus at least to initiate at least one random access resource selection procedure in response to at least one contention resolution scheme being designated as unsuccessful.

According to some embodiments, a non-transitory computer readable medium may be encoded with instructions that, when executed in hardware, 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 also designate at least one contention resolution scheme as unsuccessful. The method may also initiate at least one random access resource selection procedure in response to at least one contention resolution scheme being designated as unsuccessful.

According to 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 also designate at least one contention resolution scheme as unsuccessful. The method may also initiate at least one random access resource selection procedure in response to at least one contention resolution scheme being designated as unsuccessful.

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 also designate the at least one contention resolution as unsuccessful. The circuitry may also initiate at least one random access resource selection procedure in response to the at least one contention resolution scheme being designated as unsuccessful.

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

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

According to some embodiments, an apparatus may comprise means for detecting at least one listen before talk failure associated with at least one retransmission random access channel transmission opportunity. The apparatus may also include means for designating at least one contention resolution scheme as unsuccessful based on the triggering condition. The apparatus may also include means for initiating at least one random access resource selection procedure in response to at least one contention resolution scheme being designated as unsuccessful.

According to some embodiments, an apparatus may comprise means for detecting at least one listen before talk failure associated with at least one retransmission random access channel transmission opportunity. The apparatus may also include means for restarting the at least one contention resolution timer. The apparatus may also include means for decoding at least one physical downlink control channel for further analysis.

According to 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 at least to detect at least one listen-before-talk failure associated with at least one retransmission random access channel transmission opportunity. The at least one memory and the computer program code may also be configured to, with the at least one processor, cause the apparatus at least to specify that the at least one contention resolution scheme is unsuccessful based on at least the trigger condition. The at least one memory and the computer program may also be configured to, with the at least one processor, cause the apparatus at least to initiate at least one random access resource selection procedure in response to at least one contention resolution scheme being designated as unsuccessful.

According to 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 at least to detect at least one listen-before-talk failure associated with at least one retransmission random access channel transmission opportunity. The at least one memory and the computer program code may also be configured to, with the at least one processor, cause the apparatus at least to restart the at least one contention resolution timer. The at least one memory and the computer program may also be configured, with the at least one processor, to cause the apparatus at least to decode at least one physical downlink control channel for further analysis.

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

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

According to 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 retransmission random access channel transmission opportunity. The method may also include designating at least one contention resolution scheme as unsuccessful based on the triggering condition. The method may also include initiating at least one random access resource selection procedure in response to at least one contention resolution scheme being designated as unsuccessful.

According to 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 retransmission random access channel transmission opportunity. The method may also restart at least one contention resolution timer. The method may also 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 retransmission random access channel transmission opportunity. The circuitry may also designate the at least one contention resolution as unsuccessful. The circuitry may also initiate at least one random access resource selection procedure in response to the at least one contention resolution scheme being designated as unsuccessful.

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 retransmission random access channel transmission opportunity. The circuitry may also restart at least one contention resolution timer. The circuitry may also decode at least one physical downlink control channel for further analysis.

Drawings

For a proper understanding of the present disclosure, reference should be made to the accompanying drawings, in which:

fig. 1 illustrates an example of a method performed by a user equipment, in accordance with some embodiments.

Fig. 2 illustrates another example of a method performed by a user equipment, in accordance with some embodiments.

FIG. 3 illustrates a system according to some embodiments.

Detailed Description

The NR-U may support contention-free RACH (cfra) and CBRD for both 2-and 4-step RACH procedures. With respect to secondary cells, CFRA may be supported as a baseline, while both CBRA and CFRA may be supported on SpCells. Time-ordered messages may be described as msg1, msg2, msg3, msg4 for a 4-step RACH procedure, and msgA and msgB for a 2-step RACH.

A single RACH procedure i may be used and thus multiple parallel RACH procedures may not be used to support NR-U. As a baseline, the random access response to msg1 may be on the SpCell, and it is assumed that msg3 uses a predetermined HARQ ID.

In a conventional RACH, the counters for preamble transmission and power ramping may be incremented with each attempt. In NR-U, no power ramping is applied when the preamble is not transmitted due to the possibility of LBT failure. Thus, this may require an indication from the physical layer to the MAC. In addition, ra-ResponseWindow may not be enabled when the preamble is not transmitted due to LBT failure. In addition, assume that the ra-ContentionResolutionTimer may need to be extended with a larger value to overcome any impact of LBT.

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

As a baseline, all triggers for 4-step RACH may be applied to a 2-step RACH procedure. However, further analysis may be required on one or more SI requests and BFRs, and how to obtain timing advance and grant for msgA. The contention resolution scheme in the 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.

Fallback from 2-step RACH procedures to 4-step RACH procedures may also be supported. Backoff after msgA transmission is only feasible if the UE is possible to detect without decoding the payload, and thus relies on such support at the physical layer. If the 2-step RACH procedure is used for initial access, the parameters of the 2-step RACH procedure include resources for msgA that can be broadcast. It should be noted that LBT may not be considered if a 2-step RACH procedure is applied for the admission operation. Thus, some data transmissions may fail when the channel is busy due to possible LBT failures. To do so, the MAC may receive an indication from L1 that an LBT failure occurred.

Under 3GPP TR 38.889, a mechanism may be used for SS/PBCH block transmission to transmit SS/PBCH blocks that are discarded due to LBT failure. When the specification is developed for a UE to determine frame timing and QCL hypotheses from detected SS/PBCH blocks, a mechanism may be defined. For SS/PBCH blocks that are part of the DRS, it may be beneficial to extend the maximum number of candidate SS/PBCH block locations within the DRS transmission window to Y (e.g., Y ≦ 64), where the selection of Y may depend on the numerology of the SS/PBCH block. The transmitted SS/PBCH blocks may not overlap, and the maximum number of SS/PBCH blocks transmitted may be represented as X within the DRS transmission window, where X ≦ 8. The time domain location of the actual transmitted SS/PBCH block may be selected from the set of Y candidate SS/PBCH block locations.

From the user equipment's perspective, when the preamble transmission (msg1) fails due to LBT, the preamble transmission can be retried without increasing the power ramp counter since no transmission occurs. However, when LBT fails, various techniques may occur with respect to retransmission by the UE (msg 3). In contrast, from the network entity's point of view, when msg3 is not received, the network entity does not know whether the failure was due to an LBT failure or due to a retransmission grant of RAR/msg3 that was not received by the UE. For example, the downlink preferred beam may change abruptly between preamble transmission and RAR reception, e.g., due to a sudden obstruction, and the DL scheduling (PDCCH) may not be decodable by the UE.

Certain embodiments described herein may support UE behavior for deterministic transmission of msg3 by the NW, and each failure to decode msg3 from the initial resources may be considered DTX by the NW. For example, it may know whether LBT failed or the RAR was not received by the UE, and/or the NW may know that the UE will reattempt transmission immediately. Thus, when the UE fails to receive the RAR, the network entity may avoid sending useless retransmission grants and/or may reduce latency for the RA procedure. Accordingly, certain embodiments are directed to improvements in computer-related techniques, particularly by preventing unnecessary retransmissions and allowing a UE to re-attempt a transmission immediately without waiting for a contention resolution timer to expire, e.g., in the event that a preferred beam indicated with a preamble of the transmission is blocked. Some embodiments may also preserve network resources by reducing redundant operations and reduce power consumption by network entities and/or user equipment located within the network.

Fig. 1 illustrates an example of a method performed by a user device, such as user device 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 a 4-step RA procedure and/or msgA of a 2-step RA procedure. In step 103, the user equipment may designate at least one contention resolution scheme as unsuccessful. In step 105, the user equipment may initiate at least one random access resource selection procedure in response to at least one contention resolution scheme being designated as unsuccessful. For example, the user equipment may immediately reattempt transmission of at least one preamble, such as msg 1.

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

In some embodiments, the power ramp counter may remain unchanged. Alternatively, the counter may be decreased by at least one offset, e.g., the counter may be decreased by a fixed value, by a value in the system information broadcast, and/or linked to the elapsed time between the failure and the new preamble transmission. In some embodiments, the at least one offset may instead increment a power ramp counter, and/or may be a combination of at least one incremented offset and at least one decremented offset. In some embodiments, the contention resolution timer may be stopped, not started and/or immediately deemed to expire, which may cause the preamble transmission counter to increase. Alternatively, the preamble transmission counter may not be incremented.

Fig. 2 illustrates an example of a method performed by a 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 retransmission opportunity of the random access procedure message. In step 203, the user equipment may designate at least one contention resolution as unsuccessful based on at least one 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 initiate at least one random access resource selection procedure in response to at least one contention resolution scheme being designated as unsuccessful. In one non-limiting example, the user equipment may also decode at least one physical downlink control channel for further analysis. The same non-limiting example as applied in fig. 1 may be applied to fig. 2, where applicable.

In some embodiments, at least one trigger condition may be configured. In an exemplary embodiment, the network entity may configure the user equipment with at least one trigger condition that is a maximum number of retransmission attempts due to LBT failures, after which the user equipment designates at least one contention resolution scheme as unsuccessful in response. In response to 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 based on an indication in a retransmission grant. For example, if LBT fails during retransmission grant, the user equipment may initiate a new random access resource selection procedure. In some embodiments, the retransmission attempts associated with LBT failures may or may not be consecutive retransmission attempts.

In some embodiments, at least one preamble/power ramp counter may be incremented by one for each contention resolution failure (e.g., due to a collision). Alternatively or additionally, retransmitting the random access channel transmission opportunity may apply to at least one msg3 retransmission failure due to LBT, such as if the UE re-attempts transmission of the preamble immediately, regardless of whether there is a power ramp.

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

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

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

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

more transceivers

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

antennas

314 and 324 may be illustrated in any form of communication hardware, and are not limited to antennas.

The

transceivers

313 and 323 may each be a separate transmitter and receiver, or both, or may be configured as a unit or device for transmitting and receiving. For example, the transmitter and/or receiver (in the case of part of the radio) can also be implemented as a remote radio head, which is not located in the device itself, but in the mast. For example, operations and functions may be performed in different entities (e.g., nodes, hosts, or servers) in a flexible manner. In other words, the labor division may vary from case to case. One possible use is for network nodes to deliver local content. One or more functions may also be implemented as virtual application(s) in software that may run on a server.

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

Processors

311 and 321 may be implemented by any computing or data processing device, such as a Central Processing Unit (CPU), a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Programmable Logic Device (PLD), a Field Programmable Gate Array (FPGA), digital enhancement circuitry, or the like, or a combination thereof. The processor may be implemented as a single controller, or as multiple controllers or processors.

For firmware or software, an implementation may include modules or units of at least one chipset (e.g., 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 drive, random access memory, flash memory, or other suitable memory may be used. The memories may be combined on a single integrated circuit as a processor or may be separate therefrom. Furthermore, the computer program instructions may be stored in a memory, and the computer program instructions that may be processed by the processor may be in any suitable form of computer program code, such as 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 computer program instructions may be configured to, with the processor for a particular device, cause hardware devices such as user equipment 310 and/or network entity 320 to perform any of the processes described above (see, e.g., fig. 1-2). Thus, in certain embodiments, a non-transitory computer readable medium may be encoded with computer instructions or one or more computer programs (such as added or updated software routines, applets, or macros) that, when executed in hardware, may perform one of the processes such as those described herein. The computer program may be coded by a programming language, which may be a high-level programming language, such as object-oriented C, C, C + +, C #, Java, etc., or a low-level programming language, such as a machine language or an assembly language. Alternatively, some embodiments may be implemented entirely in hardware.

Further, although fig. 3 illustrates a system including user equipment 310 and/or network entity 320, certain embodiments may be applicable to other configurations and configurations including additional elements, as illustrated and discussed herein. For example, there may be multiple user equipment devices and multiple base stations, or other nodes providing similar functionality, such as nodes combining the functionality of user equipment and base stations, such as relay nodes. In addition to communicating with the network entity 320, the user equipment 310 may also be provided with various configurations for communication. For example, the user device 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, illustrated as 314 and 324, respectively. The device may have many antennas, such as an antenna array configured for multiple-input multiple-output (MIMO) communications, or multiple antennas for multiple radio access technologies. For example, other configurations of these devices may be provided.

The

transceivers

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

Processors

311 and 321 may be implemented by any computing or data processing device, such as a Central Processing Unit (CPU), Application Specific Integrated Circuit (ASIC), or the like. The processor may be implemented as a single controller, or as multiple 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 therefrom. Furthermore, the computer program instructions may be stored in a memory, and the computer program instructions that may be processed by the processor may be in any suitable form of computer program code, such as a compiled or interpreted computer program written in any suitable programming language. The memory may be fixed or removable.

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

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

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, use of the phrases "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 embodiments may be included in at least one embodiment of the present invention. Thus, appearances of the phrases "in certain embodiments," "in some embodiments," "in other embodiments," or other similar language throughout this specification are not necessarily referring 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.

Those of ordinary skill in the art will readily appreciate that the invention as discussed above may be practiced with steps in a different order, and/or with hardware elements in configurations other than those disclosed. Thus, while the invention has been described based upon these preferred embodiments, certain modifications, variations, and alternative constructions will be apparent to those skilled in the art 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 relate 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 terrestrial service network (WLAN).

Part glossary

3GPP third generation partnership project

5G fifth 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

Physical Random Access Channel (PRACH)

QCL quasi co-location

RA random access

RAR random access response

RACH random access channel

RO random access channel opportunity

RS reference signal

RSRP reference signal received power

RSRQ reference signal received quality

RSSI received signal strength indicator

SINR signal interference plus noise ratio

SS synchronization signal

SSB synchronization signal block

UE user equipment

UL uplink

Claims

1. 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:

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

designating at least one contention resolution scheme as unsuccessful; and

in response to at least one contention resolution scheme being designated as unsuccessful, at least one random access resource selection procedure is initiated.

2. The apparatus of claim 1, wherein at least one power ramp counter remains unchanged.

3. The apparatus of any of claims 1 and 2, wherein at least one power ramp counter is decremented by an offset.

4. The apparatus of any of claims 1 to 3, wherein at least one offset is reduced by a fixed value, by a value in a system information broadcast, and/or linked to an elapsed time between a failure and a new preamble transmission.

5. The apparatus according to any of claims 1 to 4, wherein the specifying is based on at least one trigger condition, the trigger condition comprising at least one contention resolution timer stopping, not starting, and/or being immediately deemed to be expired.

6. The apparatus according to any of claims 1-5, wherein the random access procedure message is msg3 of the random access procedure.

7. An apparatus, comprising:

at least one processor; and

at least one memory including computer program code;

detecting at least one listen-before-talk failure associated with at least one retransmission opportunity of at least one random access procedure message;

designating at least one contention resolution scheme as unsuccessful based on at least one triggering condition; and

8. The apparatus of claim 7, wherein at least one trigger condition comprises a maximum number of retransmission attempts due to LBT failure.

9. The apparatus according to any of claims 7 and 8, wherein the at least one trigger condition is in a retransmission grant and indicates that a contention resolution scheme was unsuccessful if at least one listen-before-talk failure is associated with the retransmission opportunity.

10. The apparatus of any of claims 7 to 9, wherein a preamble/power ramp counter is incremented by one for each contention resolution failure.

11. The apparatus according to any of claims 7 to 10, wherein the at least one trigger condition comprises at least one contention resolution timer stopping, not starting, and/or being immediately deemed to be expired.

12. A method according to any one of claims 1 to 11.

13. A non-transitory computer readable medium encoded with instructions that, when executed in hardware, perform a process according to any of claims 1 to 11.

14. An apparatus comprising means for performing a process according to any one of claims 1 to 11.

15. An apparatus comprising circuitry configured to cause the apparatus to perform the processes of any of claims 1-11.

16. A computer program product encoded with instructions for performing a process according to any of claims 1 to 11.