WO2021243685A1

WO2021243685A1 - Method to prune scheduling request (sr) failure

Info

Publication number: WO2021243685A1
Application number: PCT/CN2020/094575
Authority: WO
Inventors: Jinglin Zhang; Haojun WANG; Yi Liu; Zhenqing CUI; Hong Wei
Original assignee: Qualcomm Incorporated
Priority date: 2020-06-05
Filing date: 2020-06-05
Publication date: 2021-12-09

Abstract

Certain aspects of the subject matter described in this disclosure can be implemented in a method for wireless communication by a user equipment (UE). The method generally includes detecting that a random access procedure is ongoing when a quantity of scheduling request (SR) transmissions by the UE reaches a threshold; determining to forgo releasing a radio resource connection with a base station based on the detection; and after forgoing the release of the radio resource connection, continuing with the ongoing random access procedure by communicating one or more random access messages in accordance with the random access procedure.

Description

METHOD TO PRUNE SCHEDULING REQUEST (SR) FAILURE

BACKGROUND

Field of the Disclosure

Aspects of the present disclosure relate to wireless communications, and more particularly, to techniques for random access.

Description of Related Art

Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, broadcasts, etc. These wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, etc. ) . Examples of such multiple-access systems include 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) systems, LTE Advanced (LTE-A) systems, code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems, to name a few.

These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. New radio (e.g., 5G NR) is an example of an emerging telecommunication standard. NR is a set of enhancements to the LTE mobile standard promulgated by 3GPP. NR is designed to better support mobile broadband Internet access by improving spectral efficiency, lowering costs, improving services, making use of new spectrum, and better integrating with other open standards using OFDMA with a cyclic prefix (CP) on the downlink (DL) and on the uplink (UL) . To these ends, NR supports beamforming, multiple-input multiple-output (MIMO) antenna technology, and carrier aggregation.

However, as the demand for mobile broadband access continues to increase, there exists a need for further improvements in NR and LTE technology. Preferably, these improvements should be applicable to other multi-access technologies and the telecommunication standards that employ these technologies.

SUMMARY

The systems, methods, and devices of the disclosure each have several aspects, no single one of which is solely responsible for its desirable attributes. Without limiting the scope of this disclosure as expressed by the claims which follow, some features will now be discussed briefly. After considering this discussion, and particularly after reading the section entitled “Detailed Description” one will understand how the features of this disclosure provide advantages that include improved random access operations.

Certain aspects of the subject matter described in this disclosure can be implemented in a method for wireless communications by a user equipment (UE) . The method generally includes detecting that a random access procedure is ongoing when a quantity of scheduling request (SR) transmissions by the UE reaches a threshold; determining to forgo releasing a radio resource connection with a base station based on the detection; and after forgoing the release of the radio resource connection, continuing with the ongoing random access procedure by communicating one or more random access messages in accordance with the random access procedure.

Certain aspects of the subject matter described in this disclosure can be implemented in an apparatus for wireless communications by a user equipment (UE) . The apparatus generally includes means for detecting that a random access procedure is ongoing when a quantity of scheduling request (SR) transmissions by the UE reaches a threshold, means for determining to forgo releasing a radio resource connection with a base station based on the detection, and means for continuing with the ongoing random access procedure by communicating one or more random access messages in accordance with the random access procedure, wherein the continuation with the ongoing random access procedure occurs after forgoing the release of the radio resource connection.

Certain aspects of the subject matter described in this disclosure can be implemented in an apparatus for wireless communications by a user equipment (UE) . The apparatus generally includes a processing system configured to detect that a random access procedure is ongoing when a quantity of scheduling request (SR) transmissions by the UE reaches a threshold, determine to forgo releasing a radio resource connection with a base station based on the detection, and, after forgoing the release of the radio resource connection, continue with the ongoing random access procedure by communicating one or more random access messages in accordance with the random access procedure.

Certain aspects of the subject matter described in this disclosure can be implemented in a user equipment (UE) . The UE generally includes at least one antenna and a processing system configured to detect that a random access procedure is ongoing when a quantity of scheduling request (SR) transmissions by the UE reaches a threshold, determine to forgo releasing a radio resource connection with a base station based on the detection, and, after forgoing the release of the radio resource connection, continue with the ongoing random access procedure by communicating, via the at least one antenna, one or more random access messages in accordance with the random access procedure.

Certain aspects of the subject matter described in this disclosure can be implemented in a computer-readable medium for wireless communications by a user equipment (UE) . The computer-readable medium generally includes instructions executable to detect that a random access procedure is ongoing when a quantity of scheduling request (SR) transmissions by the UE reaches a threshold, determine to forgo releasing a radio resource connection with a base station based on the detection, and, after forgoing the release of the radio resource connection, continue with the ongoing random access procedure by communicating one or more random access messages in accordance with the random access procedure.

Aspects of the present disclosure provide means for, apparatus, processors, and computer-readable mediums for performing the methods described herein.

To the accomplishment of the foregoing and related ends, the one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the appended drawings set forth in detail certain illustrative features of the one or more aspects. These features are indicative, however, of but a few of the various ways in which the principles of various aspects may be employed.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the present disclosure can be understood in detail, a more particular description, briefly summarized above, may be had by reference to aspects, some of which are illustrated in the drawings. It is to be noted, however, that the appended drawings illustrate only certain typical aspects of this disclosure and are therefore not to be considered limiting of its scope, for the description may admit to other equally effective aspects.

FIG. 1 is a block diagram conceptually illustrating an example telecommunications system, in accordance with certain aspects of the present disclosure.

FIG. 2 is a block diagram conceptually illustrating a design of an example a base station (BS) and user equipment (UE) , in accordance with certain aspects of the present disclosure.

FIG. 3 is an example frame format for new radio (NR) , in accordance with certain aspects of the present disclosure.

FIG. 4 illustrates example operations for performing a random access procedure, in accordance with certain aspects of the present disclosure.

FIG. 5 is a flow diagram illustrating example operations for wireless communication by a UE, in accordance with certain aspects of the present disclosure.

FIG. 6 illustrates example operations for pruning a scheduling request (SR) failure, in accordance with certain aspects of the present disclosure.

FIG. 7 illustrates a communications device that may include various components configured to perform operations for the techniques disclosed herein in accordance with aspects of the present disclosure.

The attached APPENDIX includes details of certain aspects of the present disclosure.

To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one aspect may be beneficially utilized on other aspects without specific recitation.

DETAILED DESCRIPTION

Aspects of the present disclosure provide apparatus, methods, processing systems, and computer readable mediums for random access. The following description provides examples of random access in communication systems, and is not limiting of the scope, applicability, or examples set forth in the claims. Changes may be made in the function and arrangement of elements discussed without departing from the scope of the disclosure. Various examples may omit, substitute, or add various procedures or components as appropriate. For instance, the methods described may be performed in an order different from that described, and various steps may be added, omitted, or combined. Also, features described with respect to some examples may be combined in some other examples. For example, an apparatus may be implemented or a method may be practiced using any number of the aspects set forth herein. In addition, the scope of the disclosure is intended to cover such an apparatus or method which is practiced using other structure, functionality, or structure and functionality in addition to, or other than, the various aspects of the disclosure set forth herein. It should be understood that any aspect of the disclosure disclosed herein may be embodied by one or more elements of a claim. The word “exemplary” is used herein to mean “serving as an example, instance, or illustration. ” Any aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects.

In general, any number of wireless networks may be deployed in a given geographic area. Each wireless network may support a particular radio access technology (RAT) and may operate on one or more frequencies. A RAT may also be referred to as a radio technology, an air interface, etc. A frequency may also be referred to as a carrier, a subcarrier, a frequency channel, a tone, a subband, etc. Each frequency may support a single RAT in a given geographic area in order to avoid interference between wireless networks of different RATs.

The techniques described herein may be used for various wireless networks and radio technologies. While aspects may be described herein using terminology commonly associated with 3G, 4G, and/or new radio (e.g., 5G NR) wireless technologies, aspects of the present disclosure can be applied in other generation-based communication systems.

NR access may support various wireless communication services, such as enhanced mobile broadband (eMBB) targeting wide bandwidth (e.g., 80 MHz or beyond) , millimeter wave (mmW) targeting high carrier frequency (e.g., 25 GHz or beyond) , massive machine type communications MTC (mMTC) targeting non-backward compatible MTC techniques, and/or mission critical targeting ultra-reliable low-latency communications (URLLC) . These services may include latency and reliability requirements. These services may also have different transmission time intervals (TTI) to meet respective quality of service (QoS) requirements. In addition, these services may co-exist in the same subframe. NR supports beamforming and beam direction may be dynamically configured. MIMO transmissions with precoding may also be supported. MIMO configurations in the DL may support up to 8 transmit antennas with multi-layer DL transmissions up to 8 streams and up to 2 streams per UE. Multi-layer transmissions with up to 2 streams per UE may be supported. Aggregation of multiple cells may be supported with up to 8 serving cells.

FIG. 1 illustrates an example wireless communication network 100 in which aspects of the present disclosure may be performed. For example, the wireless communication network 100 may be an NR system (e.g., a 5G NR network) . As shown in FIG. 1, the wireless communication network 100 may be in communication with a core network 132. The core network 132 may in communication with one or more base station (BSs) 110 and/or user equipment (UE) 120 in the wireless communication network 100 via one or more interfaces.

As illustrated in FIG. 1, the wireless communication network 100 may include a number of BSs 110a-z (each also individually referred to herein as BS 110 or collectively as BSs 110) and other network entities. A BS 110 may provide communication coverage for a particular geographic area, sometimes referred to as a “cell” , which may be stationary or may move according to the location of a mobile BS 110. In some examples, the BSs 110 may be interconnected to one another and/or to one or more other BSs or network nodes (not shown) in wireless communication network 100 through various types of backhaul interfaces (e.g., a direct physical connection, a wireless connection, a virtual network, or the like) using any suitable transport network. In the example shown in FIG. 1, the

BSs

110a, 110b and 110c may be macro BSs for the

macro cells

102a, 102b and 102c, respectively. The BS 110x may be a pico BS for a pico cell 102x. The BSs 110y and 110z may be femto BSs for the

femto cells

102y and 102z, respectively. A BS may support one or multiple cells. A network controller 130 may couple to a set of BSs 110 and provide coordination and control for these BSs 110 (e.g., via a backhaul) .

The BSs 110 communicate with UEs 120a-y (each also individually referred to herein as UE 120 or collectively as UEs 120) in the wireless communication network 100. The UEs 120 (e.g., 120x, 120y, etc. ) may be dispersed throughout the wireless communication network 100, and each UE 120 may be stationary or mobile. Wireless communication network 100 may also include relay stations (e.g., relay station 110r) , also referred to as relays or the like, that receive a transmission of data and/or other information from an upstream station (e.g., a BS 110a or a UE 120r) and sends a transmission of the data and/or other information to a downstream station (e.g., a UE 120 or a BS 110) , or that relays transmissions between UEs 120, to facilitate communication between devices.

According to certain aspects, the BSs 110 and UEs 120 may be configured for random access (RA) . As shown in FIG. 1, the UE 120a includes an RA manager 122. The RA manager 122 may be configured to detect that a random access procedure is ongoing when a quantity of scheduling request (SR) transmissions by the UE reaches a threshold; determine to forgo releasing a radio resource connection with a base station based on the detection; and after forgoing the release of the radio resource connection, continue with the ongoing random access procedure by communicating one or more random access messages, in accordance with the random access procedure, in accordance with aspects of the present disclosure.

FIG. 2 illustrates example components of BS 110a and UE 120a (e.g., in the wireless communication network 100 of FIG. 1) , which may be used to implement aspects of the present disclosure.

At the BS 110a, a transmit processor 220 may receive data from a data source 212 and control information from a controller/processor 240. The control information may be for the physical broadcast channel (PBCH) , physical control format indicator channel (PCFICH) , physical hybrid ARQ indicator channel (PHICH) , physical downlink control channel (PDCCH) , group common PDCCH (GC PDCCH) , etc. The data may be for the physical downlink shared channel (PDSCH) , etc. A medium access control (MAC) -control element (MAC-CE) is a MAC layer communication structure that may be used for control command exchange between wireless nodes. The MAC-CE may be carried in a shared channel such as a physical downlink shared channel (PDSCH) , a physical uplink shared channel (PUSCH) , or a physical sidelink shared channel (PSSCH) .

The processor 220 may process (e.g., encode and symbol map) the data and control information to obtain data symbols and control symbols, respectively. The transmit processor 220 may also generate reference symbols, such as for the primary synchronization signal (PSS) , secondary synchronization signal (SSS) , and channel state information reference signal (CSI-RS) . A transmit (TX) multiple-input multiple-output (MIMO) processor 230 may perform spatial processing (e.g., precoding) on the data symbols, the control symbols, and/or the reference symbols, if applicable, and may provide output symbol streams to the modulators (MODs) 232a-232t. Each modulator 232 may process a respective output symbol stream (e.g., for OFDM, etc. ) to obtain an output sample stream. Each modulator may further process (e.g., convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a downlink signal. Downlink signals from modulators 232a-232t may be transmitted via the antennas 234a-234t, respectively.

At the UE 120a, the antennas 252a-252r may receive the downlink signals from the BS 110a and may provide received signals to the demodulators (DEMODs) in transceivers 254a-254r, respectively. Each demodulator 254 may condition (e.g., filter, amplify, downconvert, and digitize) a respective received signal to obtain input samples. Each demodulator may further process the input samples (e.g., for OFDM, etc. ) to obtain received symbols. A MIMO detector 256 may obtain received symbols from all the demodulators 254a-254r, perform MIMO detection on the received symbols if applicable, and provide detected symbols. A receive processor 258 may process (e.g., demodulate, deinterleave, and decode) the detected symbols, provide decoded data for the UE 120a to a data sink 260, and provide decoded control information to a controller/processor 280.

On the uplink, at UE 120a, a transmit processor 264 may receive and process data (e.g., for the physical uplink shared channel (PUSCH) ) from a data source 262 and control information (e.g., for the physical uplink control channel (PUCCH) from the controller/processor 280. The transmit processor 264 may also generate reference symbols for a reference signal (e.g., for the sounding reference signal (SRS) ) . The symbols from the transmit processor 264 may be precoded by a TX MIMO processor 266 if applicable, further processed by the modulators in transceivers 254a-254r (e.g., for SC-FDM, etc. ) , and transmitted to the BS 110a. At the BS 110a, the uplink signals from the UE 120a may be received by the antennas 234, processed by the modulators 232, detected by a MIMO detector 236 if applicable, and further processed by a receive processor 238 to obtain decoded data and control information sent by the UE 120a. The receive processor 238 may provide the decoded data to a data sink 239 and the decoded control information to the controller/processor 240.

The

memories

242 and 282 may store data and program codes for BS 110a and UE 120a, respectively. A scheduler 244 may schedule UEs for data transmission on the downlink and/or uplink.

Antennas 252,

processors

266, 258, 264, and/or controller/processor 280 of the UE 120a and/or antennas 234,

processors

220, 230, 238, and/or controller/processor 240 of the BS 110a may be used to perform the various techniques and methods described herein. As shown in FIG. 2, the controller/processor 280 of the UE 120a has an RA manager 122, according to aspects described herein. Although shown at the controller/processor, other components of the UE 120a and BS 110a may be used to perform the operations described herein.

NR may utilize orthogonal frequency division multiplexing (OFDM) with a cyclic prefix (CP) on the uplink and downlink. NR may support half-duplex operation using time division duplexing (TDD) . OFDM and single-carrier frequency division multiplexing (SC-FDM) partition the system bandwidth into multiple orthogonal subcarriers, which are also commonly referred to as tones, bins, etc. Each subcarrier may be modulated with data. Modulation symbols may be sent in the frequency domain with OFDM and in the time domain with SC-FDM. The spacing between adjacent subcarriers may be fixed, and the total number of subcarriers may be dependent on the system bandwidth. The minimum resource allocation, called a resource block (RB) , may be 12 consecutive subcarriers. The system bandwidth may also be partitioned into subbands. For example, a subband may cover multiple RBs. NR may support a base subcarrier spacing (SCS) of 15 KHz and other SCS may be defined with respect to the base SCS (e.g., 30 kHz, 60 kHz, 120 kHz, 240 kHz, etc. ) .

FIG. 3 is a diagram showing an example of a frame format 300 for NR. The transmission timeline for each of the downlink and uplink may be partitioned into units of radio frames. Each radio frame may have a predetermined duration (e.g., 10 ms) and may be partitioned into 10 subframes, each of 1 ms, with indices of 0 through 9. Each subframe may include a variable number of slots (e.g., 1, 2, 4, 8, 16, …slots) depending on the SCS. Each slot may include a variable number of symbol periods (e.g., 7 or 14 symbols) depending on the SCS. The symbol periods in each slot may be assigned indices. A mini-slot, which may be referred to as a sub-slot structure, refers to a transmit time interval having a duration less than a slot (e.g., 2, 3, or 4 symbols) . Each symbol in a slot may indicate a link direction (e.g., DL, UL, or flexible) for data transmission and the link direction for each subframe may be dynamically switched. The link directions may be based on the slot format. Each slot may include DL/UL data as well as DL/UL control information.

Example Techniques to Prune Scheduling Request (SR) Failure

In fifth-generation (5G) new radio (NR) , random access procedure may be used for uplink (UL) synchronization, and requesting UL grant. A random access procedure may be triggered by a user-equipment (UE) itself, or by the network, independently. Therefore, the network or the UE may trigger a random access procedure when there is already an ongoing random access procedure.

A random access procedure may be initiated by a physical downlink control channel (PDCCH) order, by a medium access control (MAC) entity, or by radio resource control (RRC) . PDCCH order is a mechanism by which a BS may attempt to force a UE to initiate the random access procedure. At any point in time, only a single random access procedure may be ongoing in a MAC entity. In some implementations, the random access procedure on a secondary cell (SCell) may only be initiated by a PDCCH order. If a new random access procedure is triggered while another is already ongoing in the MAC entity, either the ongoing procedure may be continued, or the new procedure (e.g. for a system information (SI) request) may be started, depending on UE implementation.

FIG. 4 illustrates example operations for performing a random access procedure, in accordance with certain aspects of the present disclosure. Certain aspect are directed to techniques for avoiding a radio resource mismatch between the network (NW) and a UE. For example, the UE may be connected with a NR cell (e.g., using non-standalone or stand-alone mode of operation) . At time 402, the UE may determine that the UE has UL data to send, and thus, may send a scheduling request (SR) 404 to the NW. However, the UE may not receive downlink control information (DCI) with an UL grant from the network. Thus, the UE may continue transmitting

SRs

406, 408, 410 to the NW. As illustrated, the UE may receive a PDCCH order command 412 to trigger CBRA (e.g., trigger a random access procedure) . For example, the BS may determine to send the PDCCH order command to the UE due to having downlink (DL) data to send to UE or determining that the UE is out-of-sync. As illustrated, the UE may begin Msg1 transmissions 414, 416 (e.g., transmissions of random access preambles) in response to the PDCCH order command 412. At time 418, the number of transmitted SRs may reach a threshold (sr-TransMax) , in response to which the UE may release radio resource configuration and trigger a CBRA for the SR failure.

For example, if an SR counter (SR_COUNTER) is less than an SR maximum transmission threshold (sr-TransMax) , the UE may increment SR_COUNTER by 1, instruct the physical layer to signal the SR on a valid physical uplink control channel (PUCCH) resource for SR, and starts a SR prohibit timer (sr-ProhibitTimer) . The UE starts the SR prohibit timer after transmitting an SR, and while the SR prohibit timer is running, the UE is not supposed to transmit SR. Once the SR counter reaches the sr-TransMax, the UE may notify the RRC layer of the UE to release PUCCH for all serving cells, notify the RRC layer to release sounding reference signal (SRS) for all serving cells, clear any configured downlink assignments and uplink grants, and clear any physical uplink shared channel (PUSCH) resources for semi-persistent CSI reporting. The UE may then initiate a random access procedure on a special cell (SpCell) and cancel all pending SRs. For example, the UE may select whether to perform a random access procedure by continuing the ongoing procedure (e.g., the CBRA triggered due to the SR transmissions reaching the threshold) , or by performing the PDCCH order triggered procedure in response to the PDCCH order command 412 from the BS.

The network may assume that the UE is performing CBRA for the PDCCH order triggered random access procedure, not realizing that the UE has already released radio resource. For example, the BS may assume that the

random access messages

440, 442, 444, 446 are associated with the PDCCH order command, when instead the UE may have released the radio resource and triggered another random access procedure in response to the SR failure. Thus, a radio resource mismatch may occur between the network and the UE. In other words, the UE may have released the radio resource, but the network may be under impression that the UE is in radio resource connected mode. In certain aspects of the present disclosure, a UE may forgo SR failure procedure if a PDCCH order CBRA is ongoing to avoid the radio resource mismatch between the network and the UE. In other words, at time 418, the UE may forgo releasing radio resource, as described in more detail herein.

FIG. 5 is a flow diagram illustrating example operations 500 for wireless communication, in accordance with certain aspects of the present disclosure. The operations 500 may be performed, for example, by UE (e.g., such as a UE 120a in the wireless communication network 100) .

Operations 500 may be implemented as software components that are executed and run on one or more processors (e.g., controller/processor 280 of FIG. 2) . Further, the transmission and reception of signals by the UE in operations 500 may be enabled, for example, by one or more antennas (e.g., antennas 252 of FIG. 2) . In certain aspects, the transmission and/or reception of signals by the UE may be implemented via a bus interface of one or more processors (e.g., controller/processor 280) obtaining and/or outputting signals.

The operations 500 may begin, at block 505, by the UE detecting that a random access procedure is ongoing when a quantity of SR transmissions by the UE reaches a threshold. For example, the SR transmissions may include an initial SR transmission and one or more other SR transmissions, the one or more other SR transmissions being transmitted due to not receiving a response from the base station for the initial SR transmission.

At block 510, the UE determines to forgo releasing a radio resource connection with a base station based on the detection. In some aspects, determining to forgo releasing the radio resource connection may also include determining to forgo initiating another random access procedure in response to the quantity of the SR transmissions reaching the threshold. In some cases, the UE may also determine to forgo further SR transmissions in response to the quantity of the SR transmissions reaching the threshold.

At block 515, after forgoing the release of the radio resource connection, the UE continues with the ongoing random access procedure by communicating one or more random access messages in accordance with the random access procedure. In some cases, the UE may declare radio link failure (RLF) if the random access procedure fails. For instance, declaring the RLF may include triggering another random access procedure to obtain a grant of resources for communications with the base station.

For example, referring back to FIG. 4, if an SR_COUNTER is greater than or equal to sr-TransMax, and if PDCCH order CBRA is ongoing, the UE stops SR transmissions and prunes SR failure procedure (e.g., stops sending SR and does not release radio resource) . Otherwise, the UE may declare SR failure (e.g., release radio resource and trigger SR CBRA) . That is, at time 418 when the quantity of SR transmission reaches the SR transmission threshold, the UE may prune the SR failure. The UE then stops sending SRs, and does not release the radio resource and does not trigger CBRA for the SR failure. Instead, the UE may continue the random access procedure triggered in response to the PDCCH order. For example, the UE may transmit the random access message 440 (e.g., random access preamble) , receive the random access message 442 (e.g., random access response) , transmit the random access message 444 (e.g., contention request) , and receive the random access message 446 (e.g., contention resolution) . As such, at time 430, when the random access procedure is successful, there may be no radio resource mismatch between the network and the UE because the UE did not release the radio resource.

FIG. 6 illustrates example operations 600 for pruning an SR failure, in accordance with certain aspects of the present disclosure. As illustrated, at block 602, the UE may transmit SR, and at block 604, determine whether SR_COUNTER is greater than or equal to sr-TranMax. If not, the UE may continue transmitting SR. If so, the UE may determine whether PDCCH order CBRA is ongoing, at block 606. If not, the UE may declare SR failure, at block 608, as described herein. If so, the UE may stop SR transmissions, and prune the SR failure procedure, at block 610. In certain aspects, if PDCCH order CBRA fails, the UE may declare radio link failure (RLF) (e.g., with cause randomAccessProblem) . However, the CBRA is successful, the UE may receive an UL grant from Msg2, and declare SR success.

FIG. 7 illustrates a communications device 700 that may include various components (e.g., corresponding to means-plus-function components) configured to perform operations for the techniques disclosed herein, such as the operations illustrated in FIG. 5. The communications device 700 includes a processing system 702 coupled to a transceiver 708 (e.g., a transmitter and/or a receiver) . The transceiver 708 is configured to transmit and receive signals for the communications device 700 via an antenna 710, such as the various signals as described herein. The processing system 702 may be configured to perform processing functions for the communications device 700, including processing signals received and/or to be transmitted by the communications device 700.

The processing system 702 includes a processor 704 coupled to a computer-readable medium/memory 712 via a bus 706. In certain aspects, the computer-readable medium/memory 712 is configured to store instructions (e.g., computer-executable code) that when executed by the processor 704, cause the processor 704 to perform the operations illustrated in FIG. 5, or other operations for performing the various techniques discussed herein for SR failure pruning. In certain aspects, computer-readable medium/memory 712 stores code 714 for detecting that a random access procedure is ongoing when a quantity of SR transmissions reaches a threshold; code 716 for determining to forgo release a radio resource connection; code 718 for continuing a random access procedure by communicating one or more random access messages; and code 720 for declaring RLF. In certain aspects, the processor 704 has circuitry configured to implement the code stored in the computer-readable medium/memory 712. The processor 704 includes circuitry 722 for detecting that a random access procedure is ongoing when a quantity of SR transmissions reaches a threshold; circuitry 724 for determining to forgo release a radio resource connection; circuitry 726 for continuing a random access procedure by communicating one or more random access messages; and circuitry 728 for declaring RLF.

The techniques described herein may be used for various wireless communication technologies, such as NR (e.g., 5G NR) , 3GPP Long Term Evolution (LTE) , LTE-Advanced (LTE-A) , code division multiple access (CDMA) , time division multiple access (TDMA) , frequency division multiple access (FDMA) , orthogonal frequency division multiple access (OFDMA) , single-carrier frequency division multiple access (SC-FDMA) , time division synchronous code division multiple access (TD-SCDMA) , and other networks. The terms “network” and “system” are often used interchangeably. A CDMA network may implement a radio technology such as Universal Terrestrial Radio Access (UTRA) , cdma2000, etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. cdma2000 covers IS-2000, IS-95 and IS-856 standards. A TDMA network may implement a radio technology such as Global System for Mobile Communications (GSM) . An OFDMA network may implement a radio technology such as NR (e.g. 5G RA) , Evolved UTRA (E-UTRA) , Ultra Mobile Broadband (UMB) , IEEE 802.11 (Wi-Fi) , IEEE 802.16 (WiMAX) , IEEE 802.20, Flash-OFDMA, etc. UTRA and E-UTRA are part of Universal Mobile Telecommunication System (UMTS) . LTE and LTE-A are releases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A and GSM are described in documents from an organization named “3rd Generation Partnership Project” (3GPP) . cdma2000 and UMB are described in documents from an organization named “3rd Generation Partnership Project 2” (3GPP2) . NR is an emerging wireless communications technology under development.

In 3GPP, the term “cell” can refer to a coverage area of a Node B (NB) and/or a NB subsystem serving this coverage area, depending on the context in which the term is used. In NR systems, the term “cell” and BS, next generation NodeB (gNB or gNodeB) , access point (AP) , distributed unit (DU) , carrier, or transmission reception point (TRP) may be used interchangeably. A BS may provide communication coverage for a macro cell, a pico cell, a femto cell, and/or other types of cells. A macro cell may cover a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs with service subscription. A pico cell may cover a relatively small geographic area and may allow unrestricted access by UEs with service subscription. A femto cell may cover a relatively small geographic area (e.g., a home) and may allow restricted access by UEs having an association with the femto cell (e.g., UEs in a Closed Subscriber Group (CSG) , UEs for users in the home, etc. ) . A BS for a macro cell may be referred to as a macro BS. A BS for a pico cell may be referred to as a pico BS.A BS for a femto cell may be referred to as a femto BS or a home BS.

A UE may also be referred to as a mobile station, a terminal, an access terminal, a subscriber unit, a station, a Customer Premises Equipment (CPE) , a cellular phone, a smart phone, a personal digital assistant (PDA) , a wireless modem, a wireless communication device, a handheld device, a laptop computer, a cordless phone, a wireless local loop (WLL) station, a tablet computer, a camera, a gaming device, a netbook, a smartbook, an ultrabook, an appliance, a medical device or medical equipment, a biometric sensor/device, a wearable device such as a smart watch, smart clothing, smart glasses, a smart wrist band, smart jewelry (e.g., a smart ring, a smart bracelet, etc. ) , an entertainment device (e.g., a music device, a video device, a satellite radio, etc. ) , a vehicular component or sensor, a smart meter/sensor, industrial manufacturing equipment, a global positioning system device, or any other suitable device that is configured to communicate via a wireless or wired medium. Some UEs may be considered machine-type communication (MTC) devices or evolved MTC (eMTC) devices. MTC and eMTC UEs include, for example, robots, drones, remote devices, sensors, meters, monitors, location tags, etc., that may communicate with a BS, another device (e.g., remote device) , or some other entity. A wireless node may provide, for example, connectivity for or to a network (e.g., a wide area network such as Internet or a cellular network) via a wired or wireless communication link. Some UEs may be considered Internet-of-Things (IoT) devices, which may be narrowband IoT (NB-IoT) devices.

In some examples, access to the air interface may be scheduled. A scheduling entity (e.g., a BS) allocates resources for communication among some or all devices and equipment within its service area or cell. The scheduling entity may be responsible for scheduling, assigning, reconfiguring, and releasing resources for one or more subordinate entities. That is, for scheduled communication, subordinate entities utilize resources allocated by the scheduling entity. Base stations are not the only entities that may function as a scheduling entity. In some examples, a UE may function as a scheduling entity and may schedule resources for one or more subordinate entities (e.g., one or more other UEs) , and the other UEs may utilize the resources scheduled by the UE for wireless communication. In some examples, a UE may function as a scheduling entity in a peer-to-peer (P2P) network, and/or in a mesh network. In a mesh network example, UEs may communicate directly with one another in addition to communicating with a scheduling entity.

The methods disclosed herein comprise one or more steps or actions for achieving the methods. The method steps and/or actions may be interchanged with one another without departing from the scope of the claims. In other words, unless a specific order of steps or actions is specified, the order and/or use of specific steps and/or actions may be modified without departing from the scope of the claims.

As used herein, a phrase referring to “at least one of” a list of items refers to any combination of those items, including single members. As an example, “at least one of: a, b, or c” is intended to cover a, b, c, a-b, a-c, b-c, and a-b-c, as well as any combination with multiples of the same element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b, b-b-b, b-b-c, c-c, and c-c-c or any other ordering of a, b, and c) .

As used herein, the term “determining” encompasses a wide variety of actions. For example, “determining” may include calculating, computing, processing, deriving, investigating, looking up (e.g., looking up in a table, a database or another data structure) , ascertaining and the like. Also, “determining” may include receiving (e.g., receiving information) , accessing (e.g., accessing data in a memory) and the like. Also, “determining” may include resolving, selecting, choosing, establishing and the like.

The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language of the claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more. ” Unless specifically stated otherwise, the term “some” refers to one or more. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 U.S.C. §112 (f) unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the element is recited using the phrase “step for. ”

The various operations of methods described above may be performed by any suitable means capable of performing the corresponding functions. The means may include various hardware and/or software component (s) and/or module (s) , including, but not limited to a circuit, an application specific integrated circuit (ASIC) , or processor. Generally, where there are operations illustrated in figures, those operations may have corresponding counterpart means-plus-function components with similar numbering.

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

If implemented in hardware, an example hardware configuration may comprise a processing system in a wireless node. The processing system may be implemented with a bus architecture. The bus may include any number of interconnecting buses and bridges depending on the specific application of the processing system and the overall design constraints. The bus may link together various circuits including a processor, machine-readable media, and a bus interface. The bus interface may be used to connect a network adapter, among other things, to the processing system via the bus. The network adapter may be used to implement the signal processing functions of the PHY layer. In the case of a user terminal (see FIG. 1) , a user interface (e.g., keypad, display, mouse, joystick, etc. ) may also be connected to the bus. The bus may also link various other circuits such as timing sources, peripherals, voltage regulators, power management circuits, and the like, which are well known in the art, and therefore, will not be described any further. The processor may be implemented with one or more general-purpose and/or special-purpose processors. Examples include microprocessors, microcontrollers, DSP processors, and other circuitry that can execute software. Those skilled in the art will recognize how best to implement the described functionality for the processing system depending on the particular application and the overall design constraints imposed on the overall system.

If implemented in software, the functions may be stored or transmitted over as one or more instructions or code on a computer readable medium. Software shall be construed broadly to mean instructions, data, or any combination thereof, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. Computer-readable media include both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. The processor may be responsible for managing the bus and general processing, including the execution of software modules stored on the machine-readable storage media. A computer-readable storage medium may be coupled to a processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. By way of example, the machine-readable media may include a transmission line, a carrier wave modulated by data, and/or a computer readable storage medium with instructions stored thereon separate from the wireless node, all of which may be accessed by the processor through the bus interface. Alternatively, or in addition, the machine- readable media, or any portion thereof, may be integrated into the processor, such as the case may be with cache and/or general register files. Examples of machine-readable storage media may include, by way of example, RAM (Random Access Memory) , flash memory, ROM (Read Only Memory) , PROM (Programmable Read-Only Memory) , EPROM (Erasable Programmable Read-Only Memory) , EEPROM (Electrically Erasable Programmable Read-Only Memory) , registers, magnetic disks, optical disks, hard drives, or any other suitable storage medium, or any combination thereof. The machine-readable media may be embodied in a computer-program product.

A software module may comprise a single instruction, or many instructions, and may be distributed over several different code segments, among different programs, and across multiple storage media. The computer-readable media may comprise a number of software modules. The software modules include instructions that, when executed by an apparatus such as a processor, cause the processing system to perform various functions. The software modules may include a transmission module and a receiving module. Each software module may reside in a single storage device or be distributed across multiple storage devices. By way of example, a software module may be loaded into RAM from a hard drive when a triggering event occurs. During execution of the software module, the processor may load some of the instructions into cache to increase access speed. One or more cache lines may then be loaded into a general register file for execution by the processor. When referring to the functionality of a software module below, it will be understood that such functionality is implemented by the processor when executing instructions from that software module.

Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL) , or wireless technologies such as infrared (IR) , radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk and disc, as used herein, include compact disc (CD) , laser disc, optical disc, digital versatile disc (DVD) , floppy disk, and

disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Thus, in some aspects computer-readable media may comprise non-transitory computer-readable media (e.g., tangible media) . In addition, for other aspects computer-readable media may comprise transitory computer-readable media (e.g., a signal) . Combinations of the above should also be included within the scope of computer-readable media.

Thus, certain aspects may comprise a computer program product for performing the operations presented herein. For example, such a computer program product may comprise a computer-readable medium having instructions stored (and/or encoded) thereon, the instructions being executable by one or more processors to perform the operations described herein, for example, instructions for performing the operations described herein and illustrated in FIG. 5.

Further, it should be appreciated that modules and/or other appropriate means for performing the methods and techniques described herein can be downloaded and/or otherwise obtained by a user terminal and/or base station as applicable. For example, such a device can be coupled to a server to facilitate the transfer of means for performing the methods described herein. Alternatively, various methods described herein can be provided via storage means (e.g., RAM, ROM, a physical storage medium such as a compact disc (CD) or floppy disk, etc. ) , such that a user terminal and/or base station can obtain the various methods upon coupling or providing the storage means to the device. Moreover, any other suitable technique for providing the methods and techniques described herein to a device can be utilized.

It is to be understood that the claims are not limited to the precise configuration and components illustrated above. Various modifications, changes and variations may be made in the arrangement, operation and details of the methods and apparatus described above without departing from the scope of the claims.

APPENIDIX

In 5GNR, random access procedure can be used for UL synchronize, request UL grant etc. random access procedure can be triggered by UE self or network independently, therefore, another random access procedure may be triggered by network or UE when there already have one random access procedure ongoing.

According to spec 38.321,

5.1.1 Random Access procedure initialization

The Random Access procedure described in this subclause is initiated by a PDCCH order, by the MAC entity itself, or by RRC for the events in accordance with TS 38.300 [2] . There is only one Random Access procedure ongoing at any point in time in a MAC entity. The Random Access procedure on an SCell shall only be initiated by a PDCCH order with ra-PreambleIndex different from 0b000000.

NOTE 1: If a new Random Access procedure is triggered while another is already ongoing in the MAC entity, it is up to UE implementation whether to continue with the ongoing procedure or start with the new procedure (e.g. for SI request) .

Consider below scenario:

Figure 1 radio resource mismatch on multi random access procedure

1. An UE connected with a NR cell (under NSA or SA)

2. UL data arrival, UE send SR to network, but not receive UL DCI from network

3. UE receive PDCCH order command to trigger CBRA, trigger RACH (maybe due to DL data arrival, while network judge UL link is out-of-sync, so network send PDCCH order cmd to UE)

4. SR transmit reach sr-TransMax, UE release radio resource config and trigger a CBRA

5. UE select a random access procedure (ongoing procedure or pdcch order triggered procedure)

6. Network think this is a pdcch order triggered random access procedure, not realize UE already release radio resource

7. Radio resource mismatch between NW and UE

According to spec 38.321, after SR failure (i.e. SR_COUNT >= sr-TransMax)

3> if SR_COUNTER < sr-TransMax:

4> increment SR_COUNTER by 1;

4> instruct the physical layer to signal the SR on one valid PUCCH resource for SR;

4> start the sr-ProhibitTimer.

3> else:

4> notify RRC to release PUCCH for all Serving Cells;

4> notify RRC to release SRS for all Serving Cells;

4> clear any configured downlink assignments and uplink grants;

4> clear any PUSCH resources for semi-persistent CSI reporting;

4> initiate a Random Access procedure (see subclause 5.1) on the SpCell and cancel all pending SRs

This solution provides a UE controlled method that UE prune SR failure .

Figure 1 prune SR failure to avoid radio resource mismatch

If PDCCH order CBRA finally failure, UE will declare RLF with randomAccessProblem, if success, UE can get the UL grant from msg2, then declare SR success.

It can improve random access performance and avoid abnormal issue.

Claims

A method for wireless communications by a user-equipment (UE) , comprising:

detecting that a random access procedure is ongoing when a quantity of scheduling request (SR) transmissions by the UE reaches a threshold;

determining to forgo releasing a radio resource connection with a base station based on the detection; and

after forgoing the release of the radio resource connection, continuing with the ongoing random access procedure by communicating one or more random access messages in accordance with the random access procedure.
The method of claim 1, wherein the SR transmissions comprise an initial SR transmission and one or more other SR transmissions, the one or more other SR transmissions being transmitted due to not receiving a response from the base station for the initial SR transmission.
The method of claim 1, wherein the determination to forgo releasing the radio resource connection further comprises determining to forgo initiating another random access procedure in response to the quantity of the SR transmissions reaching the threshold.
The method of claim 1, further comprising determining to forgo further SR transmissions in response to the quantity of the SR transmissions reaching the threshold.
The method of claim 1, further comprising declaring radio link failure (RLF) if the random access procedure fails.
The method of claim 5, wherein the declaration of the RLF comprises triggering another random access procedure to obtain a grant of resources for communications with the base station.
The method of claim 1, wherein the communication of the one or more random access messages comprises transmitting a random access preamble, and receiving a random access response to the random access preamble.
An apparatus for wireless communications by a user-equipment (UE) , comprising:

means for detecting that a random access procedure is ongoing when a quantity of scheduling request (SR) transmissions by the UE reaches a threshold;

means for determining to forgo releasing a radio resource connection with a base station based on the detection; and

means for continuing with the ongoing random access procedure by communicating one or more random access messages in accordance with the random access procedure, wherein the continuation with the ongoing random access procedure occurs after forgoing the release of the radio resource connection.
The apparatus of claim 8, wherein the SR transmissions comprise an initial SR transmission and one or more other SR transmissions, the one or more other SR transmissions being transmitted due to not receiving a response from the base station for the initial SR transmission.
The apparatus of claim 8, wherein the means for determining to forgo releasing the radio resource connection further comprises means for determining to forgo initiating another random access procedure in response to the quantity of the SR transmissions reaching the threshold.
The apparatus of claim 8, further comprising means for determining to forgo further SR transmissions in response to the quantity of the SR transmissions reaching the threshold.
The apparatus of claim 8, further comprising means for declaring radio link failure (RLF) if the random access procedure fails.
The apparatus of claim 12, wherein the means for declaring the RLF comprises means for triggering another random access procedure to obtain a grant of resources for communications with the base station.
The apparatus of claim 8, wherein the communication of the one or more random access messages comprises transmitting a random access preamble, and receiving a random access response to the random access preamble.
An apparatus for wireless communications by a user-equipment (UE) , comprising:

a processing system configured to:

detect that a random access procedure is ongoing when a quantity of scheduling request (SR) transmissions by the UE reaches a threshold;

determine to forgo releasing a radio resource connection with a base station based on the detection; and

after forgoing the release of the radio resource connection, continue with the ongoing random access procedure by communicating one or more random access messages in accordance with the random access procedure.
The apparatus of claim 15, wherein the SR transmissions comprise an initial SR transmission and one or more other SR transmissions, the one or more other SR transmissions being transmitted due to not receiving a response from the base station for the initial SR transmission.
The apparatus of claim 15, wherein the determination to forgo releasing the radio resource connection further comprises determining to forgo initiating another random access procedure in response to the quantity of the SR transmissions reaching the threshold.
The apparatus of claim 15, wherein the processing system is further configured to determine to forgo further SR transmissions in response to the quantity of the SR transmissions reaching the threshold.
The apparatus of claim 15, wherein the processing system is further configured to declare radio link failure (RLF) if the random access procedure fails.
The apparatus of claim 19, wherein the declaration of the RLF comprises triggering another random access procedure to obtain a grant of resources for communications with the base station.
The apparatus of claim 15, wherein the communication of the one or more random access messages comprises transmitting a random access preamble, and receiving a random access response to the random access preamble.
A user-equipment (UE) , comprising:

at least one antenna; and

a processing system configured to:

detect that a random access procedure is ongoing when a quantity of scheduling request (SR) transmissions by the UE reaches a threshold;

determine to forgo releasing a radio resource connection with a base station based on the detection; and

after forgoing the release of the radio resource connection, continue with the ongoing random access procedure by communicating, via the at least one antenna, one or more random access messages in accordance with the random access procedure.
A computer-readable medium for wireless communications by a user-equipment (UE) , comprising instructions executable to:

detect that a random access procedure is ongoing when a quantity of scheduling request (SR) transmissions by the UE reaches a threshold;

determine to forgo releasing a radio resource connection with a base station based on the detection; and

after forgoing the release of the radio resource connection, continue with the ongoing random access procedure by communicating one or more random access messages in accordance with the random access procedure.