WO2020000429A1

WO2020000429A1 - Uplink skipping during random access procedure

Info

Publication number: WO2020000429A1
Application number: PCT/CN2018/093831
Authority: WO
Inventors: Samuli Turtinen; Benoist Sebire; Chunli Wu; Haitao Li
Original assignee: Nokia Shanghai Bell Co., Ltd.; Nokia Solutions And Networks Oy; Nokia Technologies Oy
Priority date: 2018-06-29
Filing date: 2018-06-29
Publication date: 2020-01-02
Also published as: CN112385282A

Abstract

Embodiments of the present disclosure relate to a method, device and computer readable storage medium for UL skipping during a random access procedure. In example embodiments, a terminal device transmits a random access request in a random access procedure to a network device. The terminal device is configured to skip uplink transmission for an uplink grant if there is no data available for the uplink transmission. In response to receiving, in the random access procedure, from the network device an uplink grant addressed to C-RNTI of the terminal device, the terminal device transmits a data unit is to the network device. In this way, the network device can know the feedback of the terminal device efficiently and the performance of the communication network can be improved.

Description

UPLINK SKIPPING DURING RANDOM ACCESS PROCEDURE

FIELD

Embodiments of the present disclosure generally relate to the field of communications, and in particular, to a method, device and computer readable storage medium for uplink (UL) skipping during a random access procedure.

BACKGROUND

UL skipping concept has been introduced in New Radio (NR) following the long term evolution (LTE) baseline where a terminal device, for example, user equipment (UE) , will skip UL grant (that is, not transmit data) when it has no data to transmit. This will both, save UE power consumption as well as reduce the inter-cell interference in UL.

In NR, a random access procedure, for example, a Beam Failure Recovery (BFR) procedure initiated by a UE due to beam failure, if the UE has no data in its buffers and the UL skipping has been configured, it will skip the UL grant that was given by a network device (for example, gNB) in response to a BFR random access request. This can be problematic as the UE will perform UL skipping and thus the gNB does not know if the grant went through or not and whether the beam is really recovered.

SUMMARY

In general, example embodiments of the present disclosure provide a method, device and computer readable storage medium for modulated symbol spreading.

In a first aspect, a method at a terminal device is provided. A random access request is transmitted in a random access procedure to a network device. The terminal device is configured to skip uplink transmission for an uplink grant if there is no data available for the uplink transmission. In response to receiving, in the random access procedure, from the network device an uplink grant addressed to Cell Radio Network Temporary Identifier (C-RNTI) of the terminal device, a data unit is transmitted to the network device.

In a second aspect, a method at a terminal device is provided. A random access request is transmitted in a random access procedure to a network device. In response to receiving, in the random access procedure, from the network device a downlink assignment addressed to C-RNTI of the terminal device, it is determined that the random access procedure is completed.

In a third aspect, a method at a network device is provided. A random access request in a random access procedure is received from a terminal device. In response to determining that the random access procedure is completed, a downlink assignment addressed to C-RNTI of the terminal device is transmitted to the terminal device to indicate completion of the random access procedure.

In a fourth aspect, there is provided a terminal device which comprises: at least one processor and a memory coupled to the at least one processor. The memory stores instructions therein, the instructions, when executed by the at least one processor, causing the terminal device to perform acts comprising: transmitting a random access request in a random access procedure to a network device, the terminal device being configured to skip uplink transmission for an uplink grant if there is no data available for the uplink transmission; and in response to receiving, in the random access procedure, from the network device an uplink grant addressed to C-RNTI of the terminal device, transmitting a data unit to the network device.

In a fifth aspect, there is provided a terminal device which comprises: at least one processor and a memory coupled to the at least one processor. The memory stores instructions therein, the instructions, when executed by the at least one processor, causing the terminal device to perform acts comprising: transmitting a random access request in a random access procedure to a network device; and in response to receiving, in the random access procedure, from the network device a downlink assignment addressed to C-RNTI of the terminal device, determining that the random access procedure is completed.

In a sixth aspect, there is provided a network device which comprises: at least one processor and a memory coupled to the at least one processor. The memory stores instructions therein, the instructions, when executed by the at least one processor, causing the network device to perform acts comprising: receiving a random access request in a random access procedure from a terminal device; and in response to determining that the random access procedure is completed, transmitting, to the terminal device, a downlink assignment addressed to C-RNTI of the terminal device to indicate completion of the random access procedure.

In a seventh aspect, there is provided a computer readable storage medium that stores a computer program thereon. The computer program, when executed by a processor, causes the processor to carry out the method according to the first aspect.

In an eighth aspect, there is provided a computer readable storage medium that stores a computer program thereon.The computer program, when executed by a processor, causes the processor to carry out the method according to the second aspect.

In an ninth aspect, there is provided a computer readable storage medium that stores a computer program thereon. The computer program, when executed by a processor, causes the processor to carry out the method according to the third aspect.

It is to be understood that the summary section is not intended to identify key or essential features of embodiments of the present disclosure, nor is it intended to be used to limit the scope of the present disclosure. Other features of the present disclosure will become easily comprehensible through the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

Some example embodiments will now be described with reference to the accompanying drawings, where:

FIG. 1 illustrates a communication network in which embodiments of the present disclosure can be implemented;

FIG. 2 illustrates a diagram of a random access procedure in accordance with some embodiments of the present disclosure;

FIG. 3 illustrates a flowchart of a method in accordance with some embodiments of the present disclosure;

FIG. 4 illustrates a flowchart of a method in accordance with some embodiments of the present disclosure;

FIG. 5 illustrates a flowchart of a method in accordance with some embodiments of the present disclosure; and

FIG. 6 illustrates a simplified block diagram of a device that is suitable for implementing embodiments of the present disclosure.

Throughout the drawings, the same or similar reference numerals represent the same or similar element.

DETAILED DESCRIPTION

Principle of the present disclosure will now be described with reference to some example embodiments. It is to be understood that these embodiments are described only for the purpose of illustration and help those skilled in the art to understand and implement the present disclosure, without suggesting any limitation as to the scope of the disclosure. The disclosure described herein can be implemented in various manners other than the ones described below.

In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skills in the art to which this disclosure belongs.

As used herein, the term “communication network” refers to a network that follows any suitable communication standards or protocols such as long term evolution (LTE) , LTE-Advanced (LTE-A) and 5G NR, and employs any suitable communication technologies, including, for example, Multiple-Input Multiple-Output (MIMO) , OFDM, time division multiplexing (TDM) , frequency division multiplexing (FDM) , code division multiplexing (CDM) , Bluetooth, ZigBee, machine type communication (MTC) , eMBB, mMTC and uRLLC technologies. For the purpose of discussion, in some embodiments, the LTE network, the LTE-A network, the 5G NR network or any combination thereof is taken as an example of the communication network.

As used herein, the term “network device” refers to any suitable device at a network side of a communication network. The network device may include any suitable device in an access network of the communication network, for example, including a base station (BS) , a relay, an access point (AP) , a node B (NodeB or NB) , an evolved NodeB (eNodeB or eNB) , a gigabit NodeB (gNB) , a Remote Radio Module (RRU) , a radio header (RH) , a remote radio head (RRH) , a low power node such as a femto, a pico, and the like. For the purpose of discussion, in some embodiments, the eNB is taken as an example of the network device.

The network device may also include any suitable device in a core network, for example, including multi-standard radio (MSR) radio equipment such as MSR BSs, network controllers such as radio network controllers (RNCs) or base station controllers (BSCs) , Multi-cell/multicast Coordination Entities (MCEs) , Mobile Switching Centers (MSCs) and MMEs, Operation and Management (O&M) nodes, Operation Support System (OSS) nodes, Self-Organization Network (SON) nodes, positioning nodes, such as Enhanced Serving Mobile Location Centers (E-SMLCs) , and/or Mobile Data Terminals (MDTs) .

As used herein, the term “terminal device” refers to a device capable of, configured for, arranged for, and/or operable for communications with a network device or a further terminal device in a communication network. The communications may involve transmitting and/or receiving wireless signals using electromagnetic signals, radio waves, infrared signals, and/or other types of signals suitable for conveying information over air. In some embodiments, the terminal device may be configured to transmit and/or receive information without direct human interaction. For example, the terminal device may transmit information to the network device on predetermined schedules, when triggered by an internal or external event, or in response to requests from the network side.

Examples of the terminal device include, but are not limited to, user equipment (UE) such as smart phones, wireless-enabled tablet computers, laptop-embedded equipment (LEE) , laptop-mounted equipment (LME) , and/or wireless customer-premises equipment (CPE) . For the purpose of discussion, in the following, some embodiments will be described with reference to UEs as examples of the terminal devices, and the terms “terminal device” and “user equipment” (UE) may be used interchangeably in the context of the present disclosure.

As used herein, the term “cell” refers to an area covered by radio signals transmitted by a network device. The terminal device within the cell may be served by the network device and access the communication network via the network device.

As used herein, the term “circuitry” may refer to one or more or all of the following:

(a) hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry) and

(b) combinations of hardware circuits and software, such as (as applicable) : (i) a combination of analog and/or digital hardware circuit (s) with software/firmware and (ii) any portions of hardware processor (s) with software (including digital signal processor (s) ) , software, and memory (ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and

(c) hardware circuit (s) and or processor (s) , such as a microprocessor (s) or a portion of a microprocessor (s) , that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.

This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and/or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

As used herein, the singular forms “a” , “an” , and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. The term “includes” and its variants are to be read as open terms that mean “includes, but is not limited to” . The term “based on” is to be read as “based at least in part on” . The term “one embodiment” and “an embodiment” are to be read as “at least one embodiment” . The term “another embodiment” is to be read as “at least one other embodiment” . Other definitions, explicit and implicit, may be included below.

FIG. 1 illustrates a communication network 100 in which embodiments of the present disclosure can be implemented. The communication network 100 may comply with any suitable protocol or standard that already exists or will be developed in the future. In some embodiments, the communication network 100 may be the LTE (or LTE-A) network, the NR network or combination thereof.

The communication network 100 comprises a network device 110. The network device 110 serves a terminal device 120 in a cell 111. It is to be understood that the numbers of network devices and terminal devices are shown only for the purpose of illustration without suggesting any limitation. The communication network 100 may include any suitable numbers of network devices and terminal devices. The communication between the network device 110 and the terminal device 120 may utilize any suitable technology that already exists or will be developed in the future.

The terminal device 120 may perform a random access procedure to obtain uplink resources required for uplink synchronization and/or communication. FIG. 2 illustrates a diagram of a random access procedure 200 in accordance with some embodiments of the present disclosure.

As shown in FIG. 2, when the terminal device 120 performs random access, it sends a random access request, that is, a random access preamble (RAP) 210 to the network device 110. The RAP 210 is also referred as “MESSAGE 1” or “Msg1” in the context of the present disclosure. The RAR is a signature code sequence which acts as an identifier for the terminal device 120. Upon detection of the detect the RAP 210 preamble from the terminal device 120, the network device 110 may respond to the random access request by transmitting a random access response (RAR) 220 (also referred as “MESSAGE 2” or “Msg2” in the context of the present disclosure) to the terminal device 120. The RAR 220 may be indicated on a physical downlink control channel (PDCCH) with a pointer address to the actual message in a physical downlink shared channel (PDSCH) .

Depending on whether the RAP is UE-specific, the random access procedure breaks down into a contention-free random access procedure and a contention-based random access procedure. In the contention-free random access procedure, in a non-contention based random access procedure, the terminal device 120 sends a dedicated RAP to the network device 110; and, if the terminal device 120 receives a RAR sent by the network device 110, the terminal device 120 determines success of the random access. If the terminal device 120 receives no RAR in a specified time window, the RAP may be sent again immediately or after a period for preamble re-attempt; and such actions are repeated until the random access of the terminal device 120 succeeds or until a preset maximum preamble transmission count is reached which triggers an action other than preamble re-attempt.

In the contention-free random access procedure, the network device 110 can also order the terminal device 120 through a PDCCH message to perform a contention-free random access. In the procedure of contention free random access initiated by PDCCH, similar to the contention-based random access, the Msg2 is transmitted in the downlink to the terminal device 120 and its corresponding PDCCH message CRC is scrambled with the RA-RNTI. The terminal device 120 considers the random access successfully completed after it has received Msg2 successfully. For the contention-free random access as for the contention-based random access, the Msg2 contain a timing alignment value. This enables the network device 110 to set the initial/updated timing according to the preamble transmitted by the terminal device 120.

In the contention-based random access procedure, after the terminal device 120 receives the RAR 220, the terminal device 120 may transmit a message 230 (also referred to as “MESSAGE 3” or “Msg3” ) on the physical uplink shared channel (PUSCH) to the network device 110. The Msg3 may convey Layer 2 and Layer 3 messages, such as a radio resource control connection request for initial access or C-RNTI Medium Access Control (MAC) Control Element (CE) for random access in connected mode, from the terminal device 120 to the network device 110. In response to receiving a Msg3 message, an eNB may transmit a contention resolution message 240 (also referred to as “MESSAGE 4” or “Msg4” ) . After transmitting the Msg3 on PUSCH, the terminal device 120 may start a contention resolution timer. The contention resolution timer may be stopped if the contention resolution message 240 is received from the network device 110 before the timer terminates. If the contention resolution timer expires, the terminal device 120 may preform preamble re-attempt.

Conventionally, the NR has implemented a concept of BFR which is used by the terminal device (for example, a UE) 120 to recover from a beam failure by informing the serving network device (for example, gNB) 110 of a new candidate beam to serve. The beam failure recovery uses the random access procedure performed by the MAC layer to indicate a new beam. When the random access procedure due to beam failure detection has been triggered, the UE-once it has transmitted a Contention Free Random Access (CFRA) preamble-will monitor Physical Downlink Control Channel (PDCCH) for its Cell Radio Network Temporary Identifier (C-RNTI) other than RA-RNTI as the UL time alignment is assumed to be the same and hence the response via Random Access Response (RAR) is not required. The RAR will only implement a Timing Advance Command (TAC) field which normally is used to set the initial UL timing alignment. With the above text, the gNB can respond to the UE’s beam failure recovery request via the CFRA preamble by UL grant or downlink (DL) assignment addressed to C-RNTI. Contention-based Random Access can be used for BFR as well when all the beams with dedicated PRACH/preamble provided are not above a configured threshold or in case gNB has not provided UE with dedicated PRACH/preamble resources. Contention-based Random Access for BFR follows the normal 4 steps as contention-based Random Access triggered by other occasions as described above.

However, if the UE initiates a BFR procedure due to failed beam and it has no data in its buffers when the UL skipping was configured, it will skip the UL grant that was given in response to the CFRA preamble transmission by the gNB. This can be problematic as the gNB does not know if the grant went through or not and whether the beam is really recovered.

Embodiments of the present disclosure provide a new scheme for UL skipping during a random access procedure. A terminal device is configured to skip uplink transmission for an uplink grant if there is no data available for the uplink transmission. In a random access procedure, the terminal device transmits a random access request to a network device. In response to receiving, in the random access procedure, from the network device an uplink grant addressed to C-RNTI of the terminal device, the terminal device transmits a data unit to the network device regardless of whether there is UL data in the terminal device’s buffer. In this way, undesired UL skipping can be avoided. As a result, the UL skipping scheme in a random access procedure can be improved.

More details will be discussed below in connection with embodiments of FIGs. 3 to 6. FIG. 3 illustrates a flowchart of a method 300 in accordance with some embodiments of the present disclosure. The method 300 can be implemented at the terminal device 120 as shown in FIG. 1. For the purpose of discussion, the method 300 will be described with reference to FIGs. 1 and 2.

At 310, the terminal device 120 transmits a random access request in a random access procedure to a network device 110. The terminal device 120 is configured to skip uplink transmission for an uplink grant if there is no data available for the uplink transmission.

At 320, in response to receiving in the random access procedure from the network device an uplink grant addressed to C-RNTI of the terminal device, the terminal device 120 transmits a data unit to the network device 110, regardless of whether there is data available for transmission in the uplink.

According to embodiments of the present disclosure, when a random access procedure (for example, for Beam Failure Recovery) is performed, the UL grant in response to the RA preamble transmission is not skipped regardless of the UL skipping configuration and the empty uplink buffer.

In some embodiments, the random access procedure is a contention-free random access (CFRA) procedure. In this case, the random access request comprises a contention-free random access preamble. The uplink grant addressed to the C-RNTI is comprised in a response to the random access request if the random access is triggered by BFR. For example, the random access request may be the RAP 210 (that is, Msgl) , and the response to the random access request may be the RAR 220 (that is, Msg2) .

In addition to CFRA procedure for beam failure recovery, 3GPP agreed that contention-based random access (CBRA) procedure can also be triggered in case there is no available candidate beam with CFRA resource and above the RSRP threshold, and thus contention resolution (i.e. Msg4) has the same issue as well. The solution is that, after transmitting C-RNTI MAC CE in Msg3, the terminal device 120 shall not perform UL skipping for the UL grant provided in the PDCCH addressed to the C-RNTI for contention resolution. Similar schemes for not skipping UL transmission can be adopted as the CFRA case.

In some embodiments where the random access procedure is a contention-based random access procedure, the random access request 210 may comprise a contention-based random access preamble. Upon receipt of the random access request 210 from the terminal device 120, the network device 110 may transmit a RAR 220 (Msg2) in response to the terminal device 120. The RAR 220 scheduled via PDCCH addressed to Random Access-Radio Network Temporary Identifier (RA-RNTI) comprises an uplink grant. Then, the terminal device 120 transmits a message 230 (Msg3) comprising the C-RNTI MAC CE to the network device 110. As a response to the message 230, the network device 110 transmits an uplink grant addressed to the C-RNTI in Msg4.

The random access procedure can be initiated in a variety of scenarios. In some embodiments, the random access procedure is performed for recovery from a beam failure. Upon detection of a beam failure, the terminal device 120 may transmits a random access request for beam failure recovery (BFR) to the network device.

In some embodiments, in response to a beam failure, the terminal device 120 transmits a BFR request to a network device 110. The BFR request may comprise a contention-free random access preamble (Msg1) for requesting recovery from the serving beam failure. In response to receiving from the network device 110 a response (Msg2) addressed to the C-RNTI of the terminal device 120, the terminal device 120 may transmit a data unit to the network device 110.

There may be several ways such that the UL grant is not skipped. In some embodiments, this can be achieved in the form of a new BSR or PHR trigger (from which PHR could be more meaningful to update the NW about the possibly changed UL power situation) . In some further embodiments, the BSR/PHR trigger may be enforced in the terminal device only in case the UL buffers are empty.

In some embodiments, upon detection of a beam failure, the terminal device 120 may trigger a Buffer Status Report (BSR) , for example, a regular BSR. As such, the condition for UL skipping is not satisfied. In this way, it can be ensured that the UL grant is not skipped when BFR happens.

Alternatively or in addition, in some embodiments, in response to a beam failure, the terminal device 120 may trigger a Power Headroom Report (PHR) . Since UL skipping does not apply when a PHR needs to be transmitted (i.e. when the MAC PDU does not include a BSR only) , the trigger of the PHR is simpler than the BSR. As such, the PHR can be triggered more efficiently and conveniently.

In some embodiments, multiplexing of the PHR is prioritized over the BSR as the BSR was to report empty buffers. Alternatively, the PHR is prioritized over BSR only in case the BSR would report empty UL buffers.

The data unit may be, for example, a Medium Access Control (MAC) protocol data unit (PDU) . In some embodiments, the data unit may comprise a BSR, a PHR, and/or other suitable information or data. For example, if there is no data available for the uplink transmission, in other words, if the uplink buffer is empty, the data unit may comprise padding data, for example zero MAC SDUs. In another example, the data unit may comprise padding BSR.

In some embodiments, a network device 110 implementation behavior is defined where aperiodic CSI (Channel State Information) is requested to be transmitted over PUSCH of the UL grant provided in the random access procedure addressed to the terminal device 120 C-RNTI. Since the UL skipping does not apply when aperiodic CSI is requested for an UL grant, the network device 110 may ensure by implementation the UL grant in the random access procedure is never skipped by the terminal device 120.

With embodiments of the present disclosure, confirmation about the successful beam failure recovery is always sent to the network device 110 even if there is no data in UL buffers of the terminal device 120. In this way, unnecessary polls to the terminal device 120 by the network device 110 about whether the BFR was successful can be avoided. As a result, the performance of the communication network can be improved.

Through the above embodiments, an MAC entity shall not generate a MAC PDU for the HARQ entity if the following conditions are satisfied:

- the MAC entity is configured with skipUplinkTxDynamic and the grant indicated to the HARQ entity was addressed to a C-RNTI, or the grant indicated to the HARQ entity is a configured uplink grant; and

- the grant indicated to the HARQ entity was addressed to C-RNTI is not received in response to transmission of contention-free Random Access Preamble for beam failure recovery request; and

- the grant indicated to the HARQ entity addressed to C-RNTI is not received in response to transmission of C-RNTI MAC CE during contention-based random access procedure for beam failure recovery; and

- there is no aperiodic CSI requested for this PUSCH transmission as specified in TS 38.212 [9] ; and

- the MAC PDU includes zero MAC SDUs; and

- the MAC PDU includes only the periodic BSR and there is no data available for any LCG, or the MAC PDU includes only the padding BSR.

Alternatively, or in addition, a BSR shall be triggered if Beam failure recovery procedure is triggered as specified in subclause 5.17 in 38.321, in which case the BSR is referred below to as ′Regular BSR′ .

Alternatively, or in addition, A PHR shall be triggered if Beam failure recovery procedure is triggered as specified in subclause 5.17 in 38.321.

In addition to the above, in some cases, by giving a DL grant, the terminal device 120 will send an ACK to uplink and hence the same issue does not occur. However, as the network device 110 cannot be sure if something else is happening in the terminal device 120 and as most likely it does not have anything to transmit in DL, it would usually give an UL grant. If the terminal device 120 is configured with UL skipping, this can be problematic as the network device 110 may not know if the UL grant went through or not and whether a beam failure is really recovered.

Embodiments of the present disclosure provide schemes to aid on this problem. According to embodiments of the present disclosure, it is proposed to restrict PDCCH terminating the CFRA triggered by BFR procedure for DL assignment to ensure the network always gets UL feedback from the UE side. This option may be applied to case where the UL skipping has been configured for the terminal device 120.

FIG. 4 illustrates a flowchart of a method 400 in accordance with some embodiments of the present disclosure. The method 400 can be implemented at the terminal device 120 as shown in FIG. 1. For the purpose of discussion, the method 400 will be described with reference to FIGs. 1 and 2.

At 410, the terminal device 120 transmits a random access request in a random access procedure to a network device. At 420, in response to receiving, in the random access procedure, from the network device a downlink assignment addressed to C-RNTI of the terminal device, determining that the random access procedure is completed.

In some embodiments, in response to receiving from the network device an uplink grant addressed to C-RNTI of the terminal device in the random access procedure, determining that the random access procedure is not completed.

In some embodiments, the terminal device 120 is configured to skip uplink transmission for an uplink grant if there is no data available for the uplink transmission.

In some embodiments, the random access request comprises a contention-free random access preamble. The downlink assignment or the uplink grant may be comprised in a response to the random access request. That is, the downlink assignment or the uplink grant may be comprised in Msg2 of the random access procedure.

In some embodiments, the random access request comprises a contention-based random access preamble. In such a contention-based case, the terminal device 120, upon receipt of a response to the random access request (i.e., Msg2) comprising an uplink grant addressed to RA-RNTI from the network device 110, may transmit a message (i.e., Msg3) comprising the C-RNTI MAC CE to the network device 110. In this case, the downlink assignment or the uplink grant is comprised in a response to the message comprising the C-RNTI MAC CE, i.e., comprised in Msg4 of the random access procedure.

In some embodiments, the random access procedure is caused by beam failure recovery. The terminal device 120 may, in response to a beam failure, transmit the random access request (Msg1) for beam failure recovery to the network device 110.

In this way, only DL assignment, instead of the UL grant, is used for terminating the random access procedure. The terminal device 120 will know that the random access procedure is completed upon receipt of the DL assignment. Then, the terminal device 120 may send acknowledgment to the network device 110. Thus, the network device 110 may easily know if the DL assignment went through and whether a beam failure is really recovered.

FIG. 5 illustrates a flowchart of a method 500 in accordance with some embodiments of the present disclosure. The method 500 can be implemented at the terminal device 120 as shown in FIG. 1. For the purpose of discussion, the method 500 will be described with reference to FIGs. 1 and 2.

At 510, the network device 110 receives a random access request in a random access procedure from a terminal device. In some embodiments, the random access procedure may be caused by several factors, for example, in response to a beam failure. In this case, the random access request may be BFR request for recovery from the beam failure.

At 520, the network device 110 determines whether the random access procedure is completed. If so, at 530, the network device 110 transmits, to the terminal device 120, a downlink assignment addressed to C-RNTI of the terminal device 120 to indicate completion of the random access procedure.

In some embodiments, the random access request comprises a contention-free random access preamble. In this contention-free case, the downlink assignment may be comprised in a response to the random access request, that is, comprised in Msg2.

In some embodiments, the random access request comprises a contention-based random access preamble. In the contention-based case, the downlink assignment may be comprised in a response to a message comprising the C-RNTI received from the terminal device. In other words, the downlink assignment may be comprised in Msg4.

Through the above embodiments, if notification of a reception of a PDCCH transmission is received from lower layers; and if a downlink assignment has been received on the PDCCH addressed to the C-RNTI; and if the contention-free Random Access Preamble for beam failure recovery request was transmitted by the MAC entity: consider the Random Access procedure successfully completed.

Alternatively, or in addition, if notification of a reception of a PDCCH transmission is received from lower layers:

if the C-RNTI MAC CE was included in Msg3:

if the Random Access procedure was initiated by the MAC sublayer itself or by the RRC sublayer and the PDCCH transmission is addressed to the C-RNTI and contains a UL grant for a new transmission; or

if the Random Access procedure was initiated by a PDCCH order and the PDCCH transmission is addressed to the C-RNTI; or

if the Random Access procedure was initiated for beam failure recovery (as specified in subclause 5.17) and a downlink assignment has been received on the PDCCH transmission is addressed to the C-RNTI:

consider this Contention Resolution successful;

stop ra-ContentionResolutionTimer;

discard the TEMPORARY_C-RNTI;

consider this Random Access procedure successfully completed.

In some embodiments, an apparatus capable of performing the method 300 (for example, at the terminal device 120) may comprise means for performing the respective steps of the method 300. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

In some embodiments, the apparatus comprises: means for transmitting, at a terminal device, a random access request in a random access procedure to a network device, the terminal device being configured to skip uplink transmission for an uplink grant if there is no data available for the uplink transmission; and means for, in response to receiving, in the random access procedure, from the network device an uplink grant addressed to C-RNTI of the terminal device, transmitting a data unit to the network device.

In some embodiments, the random access request comprises a contention-free random access preamble, and the uplink grant addressed to the C-RNTI is comprised in a response to the random access request.

In some embodiments, the random access request comprises a contention-based random access preamble, and the apparatus further comprises: means for, in response to receiving a response to the random access request from the network device, transmitting to the network device a message comprising the C-RNTI MAC CE. The uplink grant addressed to the C-RNTI is comprised in a response to the message comprising the C-RNTI MAC CE.

In some embodiments, the means for transmitting the random access request comprises: means for, in response to a beam failure, transmitting the random access request for beam failure recovery to the network device.

In some embodiments, the data unit comprises at least one of: a BSR and a PHR.

In some embodiments, the apparatus may further comprise: means for, in response to a beam failure, triggering at least one of a BSR and a PHR.

In some embodiments, an apparatus capable of performing the method 400 (for example, at the terminal device 120) may comprise means for performing the respective steps of the method 400. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

In some embodiments, the apparatus comprises: means for transmitting, at a terminal device, a random access request in a random access procedure to a network device; and means for, in response to receiving, in the random access procedure, from the network device a downlink assignment addressed to C-RNTI of the terminal device, determining that the random access procedure is completed.

In some embodiments, the apparatus further comprises: means for, in response to receiving from the network device an uplink grant addressed to C-RNTI of the terminal device in the random access procedure, determining that the random access procedure is not completed.

In some embodiments, the terminal device is configured to skip uplink transmission for an uplink grant if there is no data available for the uplink transmission.

In some embodiments, the random access request comprises a contention-free random access preamble, and the downlink assignment or the uplink grant is comprised in a response to the random access request.

In some embodiments, the random access request comprises a contention-based random access preamble, and the apparatus may further comprise: means for, in response to receiving a response to the random access request from the network device, transmitting a message comprising C-RNTI MAC CE to the network device. The downlink assignment or the uplink grant is comprised in a response to the message comprising the C-RNTI MAC CE.

In some embodiments, an apparatus capable of performing the method 500 (for example, at the network device 110) may comprise means for performing the respective steps of the method 500. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

In some embodiments, the apparatus comprises: means for receiving, at a network device, a random access request in a random access procedure from a terminal device; and means for, in response to determining that the random access procedure is completed, transmitting, to the terminal device, a downlink assignment addressed to Cell Radio Network Temporary Identifier, C-RNTI, of the terminal device to indicate completion of the random access procedure.

In some embodiments, the random access request comprises a contention-free random access preamble, and the downlink assignment is comprised in a response to the random access request.

In some embodiments, the random access request comprises a contention-based random access preamble, and the downlink assignment is comprised in a response to a message comprising the C-RNTI received from the terminal device.

In some embodiments, the random access request is transmitted from the terminal device in response to a beam failure.

FIG. 6 is a simplified block diagram of a device 600 that is suitable for implementing embodiments of the present disclosure. The device 600 can be implemented at or as at least a part of the network device 110 or the terminal device 120as shown in FIG. 1.

As shown, the device 600 includes a processor 610, a memory 620 coupled to the processor 610, a communication module 640 coupled to the processor 610, and a communication interface (not shown) coupled to the communication module 640. The memory 620 stores at least a program 630. The communication module 640 is for bidirectional communications. The communication interface may represent any interface that is necessary for communication with other network elements, such as X2 interface for bidirectional communications between eNBs, S1 interface for communication between a Mobility Management Entity (MME) /Serving Gateway (S-GW) and the eNB, Un interface for communication between the eNB and a relay node (RN) , or Uu interface for communication between the eNB and a UE.

The program 630 is assumed to include program instructions that, when executed by the associated processor 610, enable the device 600 to operate in accordance with the embodiments of the present disclosure, as discussed herein with reference to FIGs. 3-5. The embodiments herein may be implemented by computer software executable by the processor 610 of the device 600, or by hardware, or by a combination of software and hardware. The processor 610 may be configured to implement various embodiments of the present disclosure.

The memory 620 may be of any type suitable to the local technical network and may be implemented using any suitable data storage technology, such as a non-transitory computer readable storage medium, semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory, as non-limiting examples. While only one memory 620 is shown in the device 600, there may be several physically distinct memory modules in the device 600. The processor 610 may be of any type suitable to the local technical network, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multicore processor architecture, as non-limiting examples. The device 600 may have multiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock which synchronizes the main processor.

Generally, various embodiments of the present disclosure may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. While various aspects of embodiments of the present disclosure are illustrated and described as block diagrams, flowcharts, or using some other pictorial representations, it is to be understood that the block, apparatus, system, technique or method described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer readable storage medium. The computer program product includes computer-executable instructions, such as those included in program modules, being executed in a device on a target real or virtual processor, to carry out the methods 300-500 as described above with reference to FIGs. 3-5. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, or the like that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or split between program modules as desired in various embodiments. Machine-executable instructions for program modules may be executed within a local or distributed device. In a distributed device, program modules may be located in both local and remote storage media.

Program code for carrying out methods of the present disclosure may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the program codes, when executed by the processor or controller, cause the functions/operations specified in the flowcharts and/or block diagrams to be implemented. The program code may execute entirely on a machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.

In the context of the present disclosure, the computer program codes or related data may be carried by any suitable carrier to enable the device, apparatus or processor to perform various processes and operations as described above. Examples of the carrier include a signal, computer readable media.

The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable medium may include but not limited to an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of the computer readable storage medium would include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM) , a read-only memory (ROM) , an erasable programmable read-only memory (EPROM or Flash memory) , an optical fiber, a portable compact disc read-only memory (CD-ROM) , an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

Further, while operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Likewise, while several specific implementation details are contained in the above discussions, these should not be construed as limitations on the scope of the present disclosure, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable sub-combination.

Although the present disclosure has been described in languages specific to structural features and/or methodological acts, it is to be understood that the present disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

A method, comprising:

transmitting, at a terminal device, a random access request in a random access procedure to a network device, the terminal device being configured to skip uplink transmission for an uplink grant ifthere is no data available for the uplink transmission; and

in response to receiving, in the random access procedure, from the network device an uplink grant addressed to Cell Radio Network Temporary Identifier, C-RNTI, of the terminal device, transmitting a data unit to the network device.
The method of claim 1, wherein the random access request comprises a contention-free random access preamble, and

wherein the uplink grant addressed to the C-RNTI is comprised in a response to the random access request.
The method of claim l, wherein the random access request comprises a contention-based random access preamble,

wherein the method further comprises: in response to receiving a response to the random access request from the network device, transmitting to the network device a message comprising C-RNTI Medium Access Control, MAC, Control Element, CE, and

wherein the uplink grant addressed to the C-RNTI is comprised in a response to the message comprising the C-RNTI MAC CE.
The method of claim 1, wherein transmitting the random access request comprises:

in response to a beam failure, transmitting the random access request for beam failure recovery to the network device.
The method of claim 1, wherein the data unit comprises at least one of:

a Buffer Status Report, BSR; and

a Power Headroom Report, PHR.
The method of claim 1, further comprising:

in response to a beam failure, triggering at least one of a Buffer Status Report, BSR, and a Power Headroom Report, PHR.
A method, comprising:

transmitting, at a terminal device, a random access request in a random access procedure to a network device; and

in response to receiving, in the random access procedure, from the network device a downlink assignment addressed to Cell Radio Network Temporary Identifier, C-RNTI, of the terminal device, determining that the random access procedure is completed.
The method of claim 7, further comprising:

in response to receiving from the network device an uplink grant addressed to Cell Radio Network Temporary Identifier, C-RNTI, of the terminal device in the random access procedure, determining that the random access procedure is not completed.
The method of claim 7, wherein the terminal device is configured to skip uplink transmission for an uplink grant if there is no data available for the uplink transmission.
The method of claim 8, wherein the random access request comprises a contention-free random access preamble, and

wherein the downlink assignment or the uplink grant is comprised in a response to the random access request.
The method of claim 7, wherein the random access request comprises a contention-based random access preamble,

wherein the method further comprises: in response to receiving a response to the random access request from the network device, transmitting to the network device a message comprising C-RNTI Medium Access Control, MAC, Control Element, CE, and

wherein the downlink assignment or the uplink grant is comprised in a response to the message comprising the C-RNTI MAC CE.
The method of claim 7, wherein transmitting the random access request comprises:

in response to a beam failure, transmitting the random access request for beam failure recovery to the network device.
A method, comprising:

receiving, at a network device, a random access request in a random access procedure from a terminal device; and

in response to determining that the random access procedure is completed, transmitting, to the terminal device, a downlink assignment addressed to Cell Radio Network Temporary Identifier, C-RNTI, of the terminal device to indicate completion of the random access procedure.
The method of claim 13, wherein the terminal device is configured to skip uplink transmission for an uplink grant if there is no data available for the uplink transmission.
The method of claim 13, wherein the random access request comprises a contention-free random access preamble, and

wherein the downlink assignment is comprised in a response to the random access request.
The method of claim 13, wherein the random access request comprises a contention-based random access preamble, and

wherein the downlink assignment is comprised in a response to a message comprising the C-RNTI received from the terminal device.
The method of claim 13, wherein the random access request is transmitted from the terminal device in response to a beam failure.
A terminal device, comprising:

at least one processor; and

a memory coupled to the at least one processor, the memory storing instructions therein, the instructions, when executed by the at least one processor, causing the terminal device to perform the method according to any of claims 1 to 6.
A terminal device, comprising:

at least one processor; and

a memory coupled to the at least one processor, the memory storing instructions therein, the instructions, when executed by the at least one processor, causing the terminal device to perform the method according to any of claims 7 to 12.
A network device, comprising:

at least one processor; and

a memory coupled to the at least one processor, the memory storing instructions therein, the instructions, when executed by the at least one processor, causing the network device to perform the method according to any of claims 13 to 17.
A computer readable storage medium storing a computer program thereon, the computer program, when executed by a processor, causing the processor to carry out the method according to any of claims 1 to 6.
A computer readable storage medium storing a computer program thereon, the computer program, when executed by a processor, causing the processor to carry out the method according to any of claims 7 to 12.
A computer readable storage medium storing a computer program thereon, the computer program, when executed by a processor, causing the processor to carry out the method according to any of claims 13 to 17.