TECHNICAL FIELD
[0001]
Embodiments of the present disclosure generally relate to the field of communication, and in particular, to methods, devices and computer readable media for beam failure recovery for a secondary cell.
BACKGROUND
[0002]
New radio access system, which is also called NR system or NR network, is the next generation communication system. It has been agreed that carrier aggregation (CA) which is used in Long Term Evolution (LTE) -Advanced to increase the bandwidth will be supported in the NR system. Each aggregated carrier is referred to as a component carrier (CC) . When CA is used, there are a number of serving cells, one for each CC. Generally, a primary cell (Pcell) corresponding to a primary CC and at least one secondary cell (Scell) corresponding to at least one secondary CC are provided.
[0003]
A beam failure may occur when the quality of beam pair (s) of a serving cell falls low enough (for example, comparison with a threshold or time-out of an associated timer) . Beam failure recovery is a mechanism for recovering beams when all or part of beams serving a terminal device has failed. In RAN2 #90 meeting for the 3GPP working group, it was already agreed that the beam failure recovery is supported in the same carrier case of CA. However, there still remain questions regarding the beam failure recovery for the Scell.
[0004]
SUMMARY
[0005]
In general, example embodiments of the present disclosure provide methods, devices and computer readable media for beam failure recovery for a secondary cell.
[0006]
In a first aspect, there is provided a method implemented in a terminal device. The method comprises in response to a beam failure on a Scell, transmitting a scheduling request to a network device; receiving, from the network device and on a Pcell, a response indicating a resource allocated to the terminal device; transmitting, to the network device and using the allocated resource, a beam failure recovery request comprising a beam index of a beam selected from available beams on the Scell by the terminal device, to recover communication between the terminal device and the network device via the selected beam on the Scell..
[0007]
In a second aspect, there is provided a method implemented in a terminal device. The method comprises in response to a beam failure on a Scell, determining a random access preamble to be transmitted, the random access preamble indicating a Scell index of the Scell; transmitting the random access preamble to a network device; receiving, from the network device and on a Pcell, downlink control information including a request for channel state information (CSI) reporting for the Scell; and transmitting, to the network device, a beam index of a beam selected from available beams on the Scell by the terminal device, to recover communication between the terminal device and the network device via the selected beam on the Scell.
[0008]
In a third aspect, there is provided a method implemented in a terminal device. The method comprises in response to a beam failure on a Scell, determining a random access preamble to be transmitted, the random access preamble indicating a beam index of a beam selected from available beams on the Scell by the terminal device; transmitting the random access preamble to a network device and on the Scell, to trigger communication between the terminal device and the network device via the selected beam on the Scell.
[0009]
In a fourth aspect, there is provided a method implemented in a terminal device. The method comprises in response to a beam failure on a Scell, determining an uplink control channel of a Pcell to be used, based on resources of the uplink control channel and uplink control information to be transmitted on the uplink control channel; and transmitting, to a network device and on the uplink control channel, a beam failure recovery request along with the uplink control information, the beam failure recovery request comprising a Scell index of the Scell and a beam index of a beam selected from available beams on the Scell by the terminal device, to recover communication between the terminal device and the network device via the selected beam on the Scell.
[0010]
In a fifth aspect, there is provided a method implemented in a network device. The method comprises receiving a scheduling request from a terminal device; transmitting, to the terminal device and on a Pcell, a response indicating a resource allocated to the terminal device; receiving, from the terminal device and using the allocated resource, a beam failure recovery request comprising a beam index of a beam selected from available beams on a Scell by the terminal device, to communicate with the terminal device via the selected beam on the Scell.
[0011]
In a sixth aspect, there is provided a method implemented in a network device. The method comprises receiving a random access preamble from a terminal device, the random access preamble indicating a Scell index of a Scell serving the terminal device; determining the Scell from the random access preamble; transmitting, to the terminal device and on a Pcell serving the terminal device, downlink control information including a request for CSI reporting for the Scell; and receiving, from the terminal device, a beam index of a beam selected from available beams on the Scell by the terminal device, to communicate with the terminal device via the selected beam on the Scell..
[0012]
In a seventh aspect, there is provided a method implemented in a network device. The method comprises receiving a random access preamble from a terminal device and on a Scell serving the terminal device, the random access preamble indicating a beam index of of a beam selected from available beams on the Scell by the terminal device; and determining the beam index from the random access preamble, to communicate with the terminal device via the selected beam on the Scell.
[0013]
In an eighth aspect, there is provided a method implemented in a network device. The method comprises receiving, from a terminal device and on an uplink control channel of a Pcell serving the terminal device, a beam failure recovery request along with uplink control information; and obtaining, from the beam failure recovery request, a Scell index of a Scell serving the terminal device and a beam index of a beam selected from available beams on the Scell by the terminal device, to communicate with the terminal device via the selected beam on the Scell..
[0014]
In a ninth aspect, there is provided a terminal device. The device includes a processor; and a memory coupled to the processing unit and storing instructions thereon, the instructions, when executed by the processing unit, causing the device to perform the method according to the first aspect.
[0015]
In a tenth aspect, there is provided a terminal device. The device includes a processor; and a memory coupled to the processing unit and storing instructions thereon, the instructions, when executed by the processing unit, causing the device to perform the method according to the second aspect.
[0016]
In a eleventh aspect, there is provided a terminal device. The device includes a processor; and a memory coupled to the processing unit and storing instructions thereon, the instructions, when executed by the processing umt, causing the device to perform the method according to the third aspect.
[0017]
In a twelfth aspect, there is provided a terminal device. The device includes a processor; and a memory coupled to the processing unit and storing instructions thereon, the instructions, when executed by the processing unit, causing the device to perform the method according to the fourth aspect.
[0018]
In a thirteenth aspect, there is provided a network device. The device includes a processor; and a memory coupled to the processing unit and storing instructions thereon, the instructions, when executed by the processing umt, causing the device to perform the method according to the fifth aspect.
[0019]
In a fourteenth aspect, there is provided a network device. The device includes a processor; and a memory coupled to the processing unit and storing instructions thereon, the instructions, when executed by the processing unit, causing the device to perform the method according to the sixth aspect.
[0020]
In a fifteenth aspect, there is provided a network device. The device includes a processor; and a memory coupled to the processing unit and storing instructions thereon, the instructions, when executed by the processing unit, causing the device to perform the method according to the seventh aspect.
[0021]
In a sixteenth aspect, there is provided a network device. The device includes a processor; and a memory coupled to the processing unit and storing instructions thereon, the instructions, when executed by the processing unit, causing the device to perform the method according to the eighth aspect.
[0022]
In a seventeenth aspect, there is provided a computer readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to carry out the method according to the first aspect.
[0023]
In a eighteenth aspect, there is provided a computer readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to carry out the method according to the second aspect.
[0024]
In a nineteenth aspect, there is provided a computer readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to carry out the method according to the third aspect.
[0025]
In a twentieth aspect, there is provided a computer readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to carry out the method according to the fourth aspect.
[0026]
In a twenty-first aspect, there is provided a computer readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to carry out the method according to the fifth aspect.
[0027]
In a twenty-second aspect, there is provided a computer readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to carry out the method according to the sixth aspect.
[0028]
In a twenty-third aspect, there is provided a computer readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to carry out the method according to the seventh aspect.
[0029]
In a twenty-fourth aspect, there is provided a computer readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to carry out the method according to the eighth aspect.
[0030]
Other features of the present disclosure will become easily comprehensible through the following description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031]
Through the more detailed description of some embodiments of the present disclosure in the accompanying drawings, the above and other objects, features and advantages of the present disclosure will become more apparent, wherein:
[0032]
FIG. 1 is a schematic diagram of a communication environment in which embodiments of the present disclosure can be implemented;
[0033]
FIG. 2 illustrates a flowchart of a method in accordance with some embodiments of the present disclosure;
[0034]
FIG. 3 illustrates a flowchart of a method in accordance with some embodiments of the present disclosure;
[0035]
FIG. 4 illustrates a flowchart of a method in accordance with some embodiments of the present disclosure;
[0036]
FIG. 5 illustrates a flowchart of a method in accordance with some embodiments of the present disclosure;
[0037]
FIG. 6A and 6B are schematic diagrams illustrating padding beam failure request in a PUCCH according to some embodiments of the present disclosure;
[0038]
FIG. 7 illustrates a flowchart of a method in accordance with some embodiments of the present disclosure;
[0039]
FIG. 8 illustrates a flowchart of a method in accordance with some embodiments of the present disclosure;
[0040]
FIG. 9 illustrates a flowchart of a method in accordance with some embodiments of the present disclosure;
[0041]
FIG. 10 illustrates a flowchart of a method in accordance with some embodiments of the present disclosure;
[0042]
FIG. 11 is a flowchart illustrating a process according to some embodiments of the present disclosure;
[0043]
FIG. 12 is a flowchart illustrating a process according to some embodiments of the present disclosure;
[0044]
FIG. 13 is a flowchart illustrating a process according to some embodiments of the present disclosure;
[0045]
FIG. 14 is a schematic diagram illustrating a BFR-RA window for beam failure recovery according to some embodiments of the present disclosure;
[0046]
FIG. 15 is a flowchart illustrating a process according to some embodiments of the present disclosure;
[0047]
FIG. 16 is a flowchart illustrating a process according to some embodiments of the present disclosure;
[0048]
FIG. 17 is a flowchart illustrating a process according to some embodiments of the present disclosure; and
[0049]
FIG. 18 is a simplified block diagram of a device that is suitable for implementing embodiments of the present disclosure.
[0050]
Throughout the drawings, the same or similar reference numerals represent the same or similar element.
DETAILED DESCRIPTION
[0051]
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 limitations as to the scope of the disclosure. The disclosure described herein can be implemented in various manners other than the ones described below.
[0052]
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.
[0053]
As used herein, the term “network device” or “base station” (BS) refers to a device which is capable of providing or hosting a cell or coverage where terminal devices can communicate. Examples of a network device include, but not limited to, a Node B (NodeB or NB) , an Evolved NodeB (eNodeB or eNB) , a NodeB in new radio access (gNB) a Remote Radio Unit (RRU) , a radio head (RH) , a remote radio head (RRH) , a low power node such as a femto node, a pico node, and the like. For the purpose of discussion, in the following, some embodiments will be described with reference to gNB as examples of the network device.
[0054]
As used herein, the term “terminal device” refers to any device having wireless or wired communication capabilities. Examples of the terminal device include, but not limited to, user equipment (UE) , personal computers, desktops, mobile phones, cellular phones, smart phones, personal digital assistants (PDAs) , portable computers, image capture devices such as digital cameras, gaming devices, music storage and playback appliances, or Internet appliances enabling wireless or wired Internet access and browsing and the like.
[0055]
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. ” The terms “first, ” “second, ” and the like may refer to different or same objects. Other definitions, explicit and implicit, may be included below.
[0056]
In some examples, values, procedures, or apparatus are referred to as “best, ” “lowest, ” “highest, ” “minimum, ” “maximum, ” or the like. It will be appreciated that such descriptions are intended to indicate that a selection among many used functional alternatives can be made, and such selections need not be better, smaller, higher, or otherwise preferable to other selections.
[0057]
As mentioned above, a beam failure may occur when the quality of beam pair (s) of a serving cell falls low enough. A mechanism to recover from a beam failure may be triggered when the beam failure occurs. The beam failure recovery mechanism on terminal device side usually includes the following operations: beam failure detection, identification of a new beam, transmission of a beam failure recovery request and monitoring a response to the beam failure recovery request from a network device. In 3GPP specifications TS 38.214 and 38.321, the beam failure recovery (BFR) procedure for Pcell has been specified as follows:
[0058]
(a) the terminal device initiates a dedicated PRACH transmission in Pcell to the network device on contention-free physical random access channel (CFRA) as the BFR request, and the PRACH preamble index is associated with a new candidate beam index identified by the terminal device;
[0059]
(b) after receiving the PRACH transmission, the network device sends BFR request response on a dedicated control resource set (CORESET-BFR) to the terminal device, and the terminal device shall monitor CORESET-BFR for BFR request response.
[0060]
Herein, the PRACH preamble is also referred as random access preamble.
[0061]
However, this procedure does not work for beam failure recovery for Scell. Different from beam failure recovery for Pcell, media access control element (MAC CE) can be used in beam failure recovery for Scell since the link on Pcell can work when the beam fails in Scell. When MAC CE is used for beam failure recovery, there may be a problem of how to indicate the new beam if there is no physical uplink shared channel (PUSCH) resource to transmit MAC CE.
[0062]
Conventionally, buffer status report (BSR) is transmitted using the remaining bits (padding bits) of a PUSCH. A possible solution to the above problem is to use the physical uplink control channel (PUCCH) resources. There are several symbols for a PUCCH format and the PUCCH resources are determined by the size of uplink control information (UCI) and acknowledge resource indicator (ARI) . Thus, there may be remaining resources on the PUCCH which are not used to transmit the UCI. For example, if UE transmit the UCI using PUCCH format 1 or PUCCH format 3 in a PUCCH resource that includes physical resource blocks (PRB) , the UE determines a number of PRBs for the PUCCH transmission to be the minimum number of PRBs. Therefore, the remaining number of PRBs may be determined based on and The inventors of the present application have realized that the remaining resources on the PUCCH which are not used to transmit the UCI may be used for the beam failure recovery for the Scell.
[0063]
Embodiments of the present disclosure provide a solution for beam failure recovery. The solution for beam failure recovery in accordance with embodiments of the present disclosure can be adapted to the beam failure occurring on the Scell. Moreover, embodiments of the present disclosure specify the procedures for the beam failure recovery using MAC CE and can solve the above problem and one or more of other potential problems.
[0064]
Principle and implementations of the present disclosure will be described in detail below with reference to FIGs. 1-18.
[0065]
FIG. 1 shows an example communication network 100 in which embodiments of the present disclosure can be implemented. The network 100 includes a network device 110 and a terminal device 120 served by the network device 110. The network 100 may provide one or more serving cells 101, 102 to serve the terminal device 120, with each serving cell corresponding to a CC. It is to be understood that the number of network devices, terminal devices and serving cells is only for the purpose of illustration without suggesting any limitations. The network 100 may include any suitable number of network devices, terminal devices and serving cells adapted for implementing embodiments of the present disclosure.
[0066]
In the communication network 100, the network device 110 can communicate data and control information to the terminal device 120 and the terminal device 120 can also communication data and control information to the network device 110. A link from the network device 110 to the terminal device 120 is referred to as a downlink (DL) or a forward link, while a link from the terminal device 120 to the network device 110 is referred to as an uplink (UL) or a reverse link.
[0067]
Depending on the communication technologies, the network 100 may be a Code Division Multiple Access (CDMA) network, a Time Division Multiple Address (TDMA) network, a Frequency Division Multiple Access (FDMA) network, an Orthogonal Frequency-Division Multiple Access (OFDMA) network, a Single Carrier-Frequency Division Multiple Access (SC-FDMA) network or any others. Communications discussed in the network 100 may use conform to any suitable standards including, but not limited to, New Radio Access (NR) , Long Term Evolution (LTE) , LTE-Evolution, LTE-Advanced (LTE-A) , Wideband Code Division Multiple Access (WCDMA) , Code Division Multiple Access (CDMA) , cdma2000, and Global System for Mobile Communications (GSM) and the like. Furthermore, the communications may be performed according to any generation communication protocols either currently known or to be developed in the future. Examples of the communication protocols include, but not limited to, the first generation (1G) , the second generation (2G) , 2.5G, 2.75G, the third generation (3G) , the fourth generation (4G) , 4.5G, the fifth generation (5G) communication protocols. The techniques described herein may be used for the wireless networks and radio technologies mentioned above as well as other wireless networks and radio technologies. For clarity, certain aspects of the techniques are described below for LTE, and LTE terminology is used in much of the description below.
[0068]
CA can be supported in the network 100, in which two or more CCs are aggregated in order to support a broader bandwidth. In CA, the network device 110 may provide to the terminal device 120 a plurality of serving cells including one Pcell 101 and at least one SCell 102. The terminal device 120 can establish Radio Resource Control (RRC) connection with the network device 110 on the Pcell 101. The Scell 102 can provide additional radio resources once the RRC connection between the network device 110 and the terminal device 120 is established and the Scell 102 is activated via higher layer signaling.
[0069]
It is to be understood that the configuration of Pcell 101 and Scell 102 shown in FIG. 1 is only for the purpose of illustration without suggesting any limitations. Pcell 101 and Scell 102 may be in other configuration than that shown in FIG. 1.
[0070]
In some other scenarios, for example, the terminal device 120 may establish connections with two groups of CCs (not shown in FIG. 1) and thus can utilize more radio resources. The two groups of CCs may be respectively defined as a master group of CCs and a secondary group of CCs. The master group of CCs may provide a group of serving cells, which are also referred to as “Master Cell Group (MCG) ” . The secondary group of CCs may also provide a group of serving cells, which are also referred to as “Secondary Cell Group (SCG) ” . For dual connectivity operation, a term “Special Cell (SpCell) ” may refer to the Pcell of the MCG or the primary Scell (PScell) of the SCG depending on if the terminal device 120 is associated to the MCG or the SCG, respectively. In other cases than the dual connectivity operation, the term “SpCell” may also refer to the Pcell. Although Pcell is illustrated as examples, embodiments of the present disclosure may be also applicable to both groups of dual connectivity configuration.
[0071]
In embodiments, the network device 110 is configured to implement beamforming technique and transmit signals to the terminal device 120 via a plurality of beams. The terminal device 120 is configured to receive the signals transmitted by the network device 110 via the plurality of beams. There may be different beams associated with the Pcell 101 and the Scell 102. As shown in FIG. 1, DL beams 111 and 112 are associated with the Scell 102. It is to be understood that the Scell 102 may have more beams associated therewith. Although not shown, the Pcell 101 may also have beams associated therewith.
[0072]
As mentioned above, a beam failure may occur on the Scell 102. For example, the network device 110 may be configured to transmit a signal via the beam 112 and the terminal device 120 may detect a beam failure of the beam 112. Then, a beam failure recovery procedure may be initiated. Specifically, the terminal device 120 may identify a new beam for recovery from the beam failure. For example, the terminal device 120 may select a beam 111 from available beams on the Scell 102 as a new candidate beam, for example, based on the qualities of the available beams. For ease of discussion, the new beam identified by the terminal device 120 is hereinafter referred to as the selected beam 111.
[0073]
The terminal device 120 may include information on the selected beam 111 in a beam failure recovery request. The terminal device 120 may then transmit the beam failure recovery request to the network device 110, such that the network device 110 communicates with the terminal device 120 via the selected beam 111 of the Scell 120.
[0074]
Implementations of the present disclosure will be described in detail below with reference to FIGs. 2-17. FIGs. 2-6 illustrate example methods according to some embodiments of the present disclosure implemented at a terminal device. It is to be understood that the methods shown may include additional acts not shown and/or may omit some shown acts, and the scope of the present disclosure is not limited in this regard.
[0075]
FIG. 2 illustrates a flowchart of an example method 200 for beam failure recovery for a Scell in accordance with some embodiments of the present disclosure. The method 200 can be implemented at the terminal device 120 shown in FIGs. 1. For the purpose of discussion, the method 200 will be described with reference to FIG. 1.
[0076]
At 210, the terminal device 120 determines whether there is a beam failure on a Scell. If the terminal device 120 determines a beam failure on the Scell 102, the terminal device 120 at 220 transmits a scheduling request to a network device, for example, the network device 110.
[0077]
The scheduling request may be a PRACH transmission on PRACH channel of the Pcell 101 or the Scell 102. In such cases, the preamble of PRACH transmission may be based on CFRA or contention-based random access (CBRA) . Alternatively, the scheduling request may be a scheduling request (SR) transmitted on the PUCCH of the Pcell 101.
[0078]
At 230, the terminal device 120 receives from the network device 110 and on a Pcell (e.g. the Pcell 101) , a response indicating a uplink resource allocated to the terminal device 120. The response may be transmitted on physical downlink control channel (PDCCH) of the Pcell 101 and may comprise downlink control information (DCI) indicating a UL grant on physical uplink shared channel (PUSCH) . Depending on the type of the scheduling request transmitted at 220, the response may be scrambled by different types of Radio Network Temporary Identifier (RNTI) , such as random access-RNTI (RA-RNTI) determined by the PRACH transmission occasion or cell-RNTI (C-RNTI) allocated to terminal device.
[0079]
At 240, the terminal device 120 transmits, to the network device 110 and using the allocated resource, a beam failure recovery request comprising a beam index of a new beam selected from available beams on the Scell by the terminal device, to recover communication between the terminal device and the network device via the selected beam on the Scell. For example, the terminal device 120 may include the beam failure recovery request in MAC CE and transmit the MAC CE using the resource allocated by the network device 110, e.g. on the PUSCH.
[0080]
The beam failure recovery request may comprise the beam index of the selected beam 111 and the Scell index of the Scell 102. Accordingly, the structure of MAC CE can be designed as in show in Table 1. The field “LGID” indicates that the MAC CE is for beam failure recovery, the field “Serving Cell ID” indicates the Scell index with beam failure, and the field “RS ID” indicates the beam index of the new beam. It is to be noted that in the case where the scheduling request is transmitted on the Scell 102, the Scell index may be omitted. Although not shown, there may be reserved bits in the MAC-CE structure to align the length of MAC-CE information to an integer number of bytes.
[0081]
Table 1 MAC CE for BFR
[0082]
[Table 0001]
LGID Serving Cell ID RS ID
[0083]
As mentioned above, the scheduling request may be a PRACH transmission or scheduling request on PUCCH. The embodiments where the scheduling request is a PRACH transmission and the embodiments where the scheduling request on PUCCH is a scheduling request will be described below with respect to FIGs. 11-13.
[0084]
In some embodiments, after transmitting the beam failure recovery request at 240, the terminal device 120 may monitor downlink control information in both PDCCH of the Pcell 101 and the Scell 102 during a timing window (also referred to as BFR-RA-window herein) for beam failure recovery request response. The terminal device 120 may initiate a timer for the BFR-RA-window, for example, several slots after transmitting the beam failure recovery request at 240, and the timer expires when the duration of BFR-RA-window ends. If a downlink control information in PDCCH for rescheduling the transmitted PUSCH which contains the beam failure recovery request in MAC CE is received from the network before the timer expires, then the terminal device 120 may retransmit the PUSCH containing the beam failure recovery request in MAC CE to the network device 110, and restart the timer for the BFR-RA-window to monitor beam failure recovery request response.
[0085]
The BFR-RA-window may have a predetermined duration. If the timer has expired or the BFR-RA-window ends, but no response to the beam failure recovery request has been received, then the terminal device 120 may terminate the beam failure recovery procedure, without retransmitting the beam failure request to the network device 110. The terminal device 120 may further indicate to the higher layer an unsuccessful beam failure recovery event.
[0086]
Alternatively, the BFR-RA-window may be initiated by receiving an acknowledge message from the network device 110. For example, the terminal device 120 may receive a message which explicitly acknowledges the reception of the PUSCH transmitted at 240. After that, the terminal device 120 may initiate or start the BFR-RA-window.
[0087]
In the embodiments described above, the scheduling request procedure may be a normal procedure which can be reused for other purpose, e.g., the PRACH transmission and the selected PRACH preamble can be used for uplink synchronization. In some embodiments, a dedicated procedure, such as a dedicated PRACH transmission, may be used only for the purpose of beam failure recovery, which will be described below with respect to FIGs. 3 and 4.
[0088]
FIG. 3 illustrates a flowchart of an example method 300 for beam failure recovery for a Scell in accordance with some embodiments of the present disclosure. The method 300 can be implemented at the terminal device 120 shown in FIGs. 1. For the purpose of discussion, the method 300 will be described with reference to FIG. 1.
[0089]
At 310, the terminal device 120 determines whether there is a beam failure on a Scell. If the terminal device 120 determines a beam failure on the Scell 102, the terminal device 120 at 320 determines a PRACH preamble to be transmitted, from a set of dedicated preambles. The PRACH preamble index indicates a Scell index of the Scell 102. For example, the terminal device 120 may determine the PRACH preamble based on a predefined mapping relation between the PRACH preamble indices and the at least one Scell provided by the network device 110. The PRACH preambles can be contention free based.
[0090]
At 330, the terminal device 120 transmits the PRACH preamble determined at 320 to a network device 110. For example, the terminal device 120 may initiate a dedicated PRACH transmission to the network device 110 with the PRACH preamble determined at 320. The terminal device 120 may transmit the preamble on PRACH channel of the Pcell 101.
[0091]
At 340, the terminal device 120 receives, from the network device 110 and on a Pcell, downlink control information including a request for CSI reporting for the Scell 102. The downlink control information may be scrambled with the C-RNTI of the terminal device and received on a CORESET-BFR which is a control resource set used dedicatedly for beam failure recovery.
[0092]
At 350, the terminal device 120 transmits, to the network device 110 and in response to the CSI request, a beam index of a beam selected from available beams on the Scell 102 by the terminal device 120, to recover communication between the terminal device 120 and the network device 110 via the selected beam on the Scell 102. For example, the terminal device 120 may include the beam index of the selected beam 111 in a CSI report and transmit the CSI report on the PUSCH of the Pcell 101 according to the CSI request.
[0093]
In such embodiments, the Scell index is implicitly indicated by the PRACH preamble index in a PRACH transmission and then the beam index is explicitly included in the CSI report. Therefore, the terminal device 120 may notify the network device 110 of the Scell on which a beam failure has occurred with the Scell index indicated by the PRACH preamble transmitted at 330, and notify the network device 110 of the candidate beam with the beam index of the selected beam 111 transmitted at 350.
[0094]
In some embodiments, the terminal device 120 may receive from the network device 110 a response to the beam failure recovery request (also referred to as BFR response) after the CSI report. The BFR response is for link reconfiguration of Scell based on the reported beam index, and may be received either on the Pcell 101 or on the Scell 102.
[0095]
In the embodiments described with respect to Fig. 3, the beam failure recovery procedure may utilize a PRACH preamble which is deliberately selected and thus indicates index information on the Scell. In this way, the explicit transmission of the Scell index may be omitted. Thus, the overhead for the beam failure recovery can be reduced.
[0096]
FIG. 4 illustrates a flowchart of an example method 400 for beam failure recovery for a Scell in accordance with some embodiments of the present disclosure. The method 400 can be implemented at the terminal device 120 shown in FIGs. 1. For the purpose of discussion, the method 400 will be described with reference to FIG. 1.
[0097]
At 410, the terminal device 120 determines whether there is a beam failure on a Scell. If the terminal device 120 determines a beam failure on the Scell 102, the terminal device 120 at 420 determines a PRACH preamble to be transmitted. The PRACH preamble index indicates a beam index of a beam selected from available beams on the Scell 102 by the terminal device 120. For example, the terminal device 120 may determine the PRACH preamble to be transmitted based on a predefined mapping relation between the PRACH preambles dedicated for beam failure recovery purpose and a plurality of beams associate with the Scell 102.
[0098]
At 430, the terminal device 120 transmits the PRACH preamble to a network device and on the Scell 102, to recover communication between the terminal device 120 and the network device 110 via the selected beam 111 on the Scell 102. For example, the terminal device 120 may initiate a dedicated PRACH transmission on the Scell 102 to a network device with PRACH preamble index determined at 410.
[0099]
In such embodiments, since the PRACH preamble is transmitted on the Scell 102, the terminal device 120 may not need to transmit with the information on the Scell index. Since the beam index is implicitly indicated by the PRACH preamble, the terminal device 120 also may not explicitly transmit the information on the beam index. Therefore, by transmitting the PRACH preamble on the Scell through a dedicated PRACH procedure, the terminal device 120 may notify the network device 110 of the beam failure recovery in only one message.
[0100]
In the embodiments described with respect to Fig. 4, the beam failure recovery procedure may utilize a PRACH transmission on the Scell and the PRACH preamble is deliberately selected and thus indicates information on the candidate beam. In this way, the explicit transmission of the Scell index and the beam index may be omitted. Thus, the overhead for the beam failure recovery can be further reduced.
[0101]
As mentioned above, there may be situation where no PUSCH is available for the transmission of MAC CE and thus the beam failure recovery request cannot be transmitted. When PUCCH transmission is available, the remaining resources of a PUCCH may be used for beam failure recovery request.
[0102]
Upon receiving data from the network device 110 and on a physical downlink shared channel (PDSCH) of the Pcell 101, the terminal device 120 may transmit to the network device 110 uplink control information (UCI) , such as hybrid automatic repeat request (HARQ) ACK/NACK. The PUCCH resources configured for the terminal device 120 to transmit the UCI may be more than that required by the UCI. Therefore, the remaining resources of the PUCCH may be utilized by the terminal device 120 to transmit the beam failure recovery request, i.e. to pad the beam failure recovery request in PUCCH.
[0103]
FIG. 5 illustrates a flowchart of an example method 500 for beam failure recovery for a Scell in accordance with some embodiments of the present disclosure. The method 500 can be implemented at the terminal device 120 shown in FIGs. 1. For the purpose of discussion, the method 500 will be described with reference to FIGs. 1 and 6A-6B.
[0104]
At 510, the terminal device 120 determines whether there is a beam failure on a Scell. If the terminal device 120 determines a beam failure on the Scell 102, the terminal device 120 at 520 determines an uplink control channel of a Pcell to be used, based on resources of the uplink control channel and uplink control information to be transmitted on the uplink control channel. The terminal deice 120 may determine a PUCCH of the Pcell 101 to be used.
[0105]
Refer to FIGs. 6A and 6B, which are schematic diagrams illustrating padding beam failure request in a PUCCH according to some embodiments of the present disclosure. Diagrams 601 and 602 show a long-PUCCH (L-PUCCH) 610 and a short-PUCCH (S-PUCCH) 620. As an example, the terminal device 120 may determine to use the L-PUCCH 610 to pad the beam failure recovery request. For example, a first potion 611 of the L-PUCCH 610 may be used to transmit the UCI and a second portion of the L-PUCCH 610 may be used to transmit the beam failure recovery request.
[0106]
In some embodiments, the terminal device 120 may determine the PUCCH to be used based on the remaining resource blocks. The terminal device 120 may first determine a first number of physical resource blocks (PRBs) that are allocated to the uplink control channel. For example, the terminal device 120 may determine the number of PRBs allocated to the L-PUCCH 610 to be The terminal device 120 may then determine a second number of PRBs to be used by the UCI. For example, the terminal device 120 may determine, based on information included in the UCI, the number of PRBs to be used by the UCI as That is, the number of PRBs corresponding to the first portion 611 is Then, a third number M r of PRBs that can be used to transmit the beam failure recovery request is determined by the following equation:
[0107]

[0108]
M r represents the number of PRBs corresponding to the second portion 612. If M r is determined to be equal to or greater than a threshold number, the terminal device 120 may determine the L-PUCCH 610 as a channel to transmit the beam failure recovery request. The threshold number may be predetermined based on the size of the beam failure recovery request.
[0109]
It is to be understood that other information such as CSI report may also be transmitted in the uplink control channel. In this event, the PRBs occupied by the other information should be considered into the determined Diagram 602 shows a S-PUCCH 602 along with its first portion 621 and second portion 622. The terminal device 120 may determine to use the second portion 622 to transmit the beam failure recovery request in a similar manner described with respect to the L-PUCCH 610.
[0110]
Still referring to FIG. 5, at 530, the terminal device 120 transmits, to a network device and on the uplink control channel, a beam failure recovery request along with the uplink control information. The terminal device 120 may transmit, to the network device 110, the beam failure recovery request in the second portion 612 or 622 and the UCI in the first portion 611 or 621. The beam failure recovery request comprises a Scell index of the Scell 102 and a beam index of a beam selected from available beams on the Scell 102 by the terminal device 120. The beam failure recovery request is transmitted to recover communication between the terminal device 120 and the network device 110 via the selected beam 111 on the Scell 102.
[0111]
In some embodiments, after transmitting the beam failure recovery request on the uplink control channel, the terminal device 120 may initiate a timer for monitoring a response to the beam failure recovery request, i.e., start a BFR-RA-window. If the timer has expired or the BFR-RA-window ends but no response to the beam failure request has been received, the terminal device 120 may retransmit the beam failure recovery request to the network device 110.
[0112]
In some embodiments, the terminal device 120 may receive from the network device 110 a new data transmission associated with the same HARQ ID as the ACK/NACK transmitted at 530. In this case, the beam failure recovery request may be considered to have been received by the network device 110. Thus, the terminal device 120 may end up the BFR-RA-window, resulting in a reduced BFR-RA-window.
[0113]
In the embodiments described with respect to Fig. 5, the beam failure recovery procedure may utilize the remaining resources of a PUCCH which otherwise would be wasted. In this way, the transmission of the beam failure request may not require dedicated resources. Thus, the overhead for the beam failure recovery can be further reduced while improving the efficiency of the beam failure recovery.
[0114]
FIGs. 7-11 illustrate example methods for according to some embodiments of the present disclosure implemented at a network device. It is to be understood that the methods shown may include additional acts not shown and/or may omit some shown acts, and the scope of the present disclosure is not limited in this regard.
[0115]
FIG. 7 illustrates a flowchart of an example method 700 for beam failure recovery for a Scell in accordance with some embodiments of the present disclosure. The method 700 can be implemented at the network device 110 shown in FIG. 1. For the purpose of discussion, the method 700 will be described with reference to FIG. 1.
[0116]
At 710, the network device 110 receives a scheduling request from a terminal device, e.g. the terminal device 120. As described with respect to FIG. 2, the scheduling request may be a PRACH transmission received on the Pcell 101 or Scell 102. Alternatively, the scheduling request may be a scheduling request received on a PUCCH of the Pcell 101.

We Claims:

[Claim 1]
A method implemented in a terminal device, comprising: in response to a beam failure on a secondary cell (Scell) , transmitting a scheduling request to a network device; receiving, from the network device and on a primary cell (Pcell) , a response indicating a resource allocated to the terminal device; transmitting, to the network device and using the allocated resource, a beam failure recovery request comprising a beam index of a beam selected from available beams on the Scell by the terminal device, to recover communication between the terminal device and the network device via the selected beam on the Scell.
[Claim 2]
The method of claim 1, wherein transmitting the scheduling request comprises transmitting a random access preamble on the Pcell, wherein receiving the response comprises receiving downlink control information with an uplink grant, and wherein transmitting the beam failure recovery request comprises transmitting the beam index and a Scell index of the Scell in media access control (MAC) control element (CE) .
[Claim 3]
The method of claim 1, wherein transmitting the scheduling request comprises transmitting a random access preamble on the Scell, wherein receiving the response comprises receiving downlink control information with an uplink grant, and wherein transmitting the beam failure recovery request comprises transmitting the beam index in media access control (MAC) control element (CE) .
[Claim 4]
The method of claim 1, wherein transmitting the scheduling request comprises transmitting the scheduling request on an uplink control channel of the Pcell, wherein receiving the response comprises receiving downlink control information with an uplink grant, and wherein transmitting the beam failure recovery request comprises transmitting the beam index and a Scell index of the Scell in media access control (MAC) control element (CE) .
[Claim 5]
The method of claim 1, further comprising: in response to receiving from the network device downlink control information on reschedule of the beam failure recovery request, retransmitting the beam failure recovery request to the network device; and initiating a timer for monitoring a response to the beam failure recovery request.
[Claim 6]
A method implemented in a terminal device, comprising: in response to a beam failure on a secondary cell (Scell) , determining a random access preamble to be transmitted, the random access preamble indicating a Scell index of the Scell; transmitting the random access preamble to a network device; receiving, from the network device and on a primary cell (Pcell) , downlink control information including a request for channel state information (CSI) reporting for the Scell; and transmitting, to the network device, a beam index of a beam selected from available beams on the Scell by the terminal device, to recover communication between the terminal device and the network device via the selected beam on the Scell.
[Claim 7]
A method implemented in a terminal device, comprising: in response to a beam failure on a secondary cell (Scell) , determining a random access preamble to be transmitted, the random access preamble indicating a beam index of a beam selected from available beams on the Scell by the terminal device; transmitting the random access preamble to a network device and on the Scell, to recover communication between the terminal device and the network device via the selected beam on the Scell.
[Claim 8]
A method implemented in a terminal device, comprising: in response to a beam failure on a secondary cell (Scell) , determining an uplink control channel of a primary cell (Pcell) to be used, based on resources of the uplink control channel and uplink control information to be transmitted on the uplink control channel; and transmitting, to a network device and on the uplink control channel, a beam failure recovery request along with the uplink control information, the beam failure recovery request comprising a Scell index of the Scell and a beam index of a beam selected from available beams on the Scell by the terminal device, to recover communication between the terminal device and the network device via the selected beam on the Scell.
[Claim 9]
The method of claim 8, wherein determining the uplink control channel to be used comprising: determining a first number of physical resource blocks that are allocated to the uplink control channel; determining a second number of physical resource blocks to be used by the uplink control information; based on the first number and the second number, determining a third number of physical resource blocks that can be used to transmit the beam failure recovery request; and in response to the third number being equate to or greater than a threshold number, determining the uplink control channel as a channel to transmit the beam failure recovery request.
[Claim 10]
The method of claim 8, further comprising: after transmitting the beam failure recovery request on the uplink control channel, initiating a timer for monitoring a response to the beam failure recovery request; in response to the timer having expired and no response to beam failure recovery request being received, retransmitting the beam failure recovery request.
[Claim 11]
A method implemented in a network device, comprising: receiving a scheduling request from a terminal device; transmitting, to the terminal device and on a primary cell (Pcell) , a response indicating a resource allocated to the terminal device; receiving, from the terminal device and using the allocated resource, a beam failure recovery request comprising a beam index of a beam selected from available beams on a Scell by the terminal device, to communicate with the terminal device via the selected beam on the Scell.
[Claim 12]
The method of claim 11, wherein receiving the scheduling request comprising receiving a random access preamble on the Pcell, wherein transmitting the response comprises transmitting downlink control information with an uplink grant, and wherein receiving the beam failure recovery request comprises receiving the beam index and a Scell index of the Scell in media access control (MAC) control element (CE) .
[Claim 13]
The method of claim 11, wherein receiving the scheduling request comprises receiving a random access preamble on the Scell, wherein transmitting the response comprises transmitting downlink control information with an uplink grant, and wherein receiving the beam failure recovery request comprises receiving the beam index in media access control (MAC) control element (CE) .
[Claim 14]
The method of claim 11, wherein receiving the scheduling request comprises receiving the scheduling request on an uplink control channel of the Pcell, wherein transmitting the response comprises transmitting downlink control information with an uplink grant, and wherein receiving the beam failure recovery request comprises receiving the beam index and a Scell index of the Scell in media access control (MAC) control element (CE) .
[Claim 15]
The method of claim 11, further comprising: transmitting, to the terminal device, a response to the beam failure recovery on the Scell.
[Claim 16]
A method implemented in a network device, comprising: receiving a random access preamble from a terminal device, the random access preamble indicating a secondary cell (Scell) index of a Scell serving the terminal device; determining the Scell from the random access preamble; transmitting, to the terminal device and on a primary cell (Pcell) serving the terminal device, downlink control information including a request for channel state information (CSI) reporting for the Scell; and receiving, from the terminal device, a beam index of a beam selected from available beams on the Scell by the terminal device, to communicate with the terminal device via the selected beam on the Scell.
[Claim 17]
A method implemented in a network device, comprising: receiving a random access preamble from a terminal device and on a secondary cell (Scell) serving the terminal device, the random access preamble indicating a beam index of of a beam selected from available beams on the Scell by the terminal device; and determining the beam index from the random access preamble, to communicate with the terminal device via the selected beam on the Scell.
[Claim 18]
A method implemented in a network device, comprising: receiving, from a terminal device and on an uplink control channel of a primary cell (Pcell) serving the terminal device, a beam failure recovery request along with uplink control information; and obtaining, from the beam failure recovery request, a Scell index of a secondary cell (Scell) serving the terminal device and a beam index of a beam selected from available beams on the Scell by the terminal device, to communicate with the terminal device via the selected beam on the Scell.
[Claim 19]
A terminal device, comprising: a processor; and a memory coupled to the processing unit and storing instructions thereon, the instructions, when executed by the processing unit, causing the device to perform the method according to any of claims 1-5.
[Claim 20]
A terminal device, comprising: a processor; and a memory coupled to the processing unit and storing instructions thereon, the instructions, when executed by the processing unit, causing the device to perform the method according to claim 6.
[Claim 21]
A terminal device, comprising: a processor; and a memory coupled to the processing unit and storing instructions thereon, the instructions, when executed by the processing unit, causing the device to perform the method according to claim 7.
[Claim 22]
A terminal device, comprising: a processor; and a memory coupled to the processing unit and storing instructions thereon, the instructions, when executed by the processing unit, causing the device to perform the method according to any of claims 8-10.
[Claim 23]
A network device, comprising: a processor; and a memory coupled to the processing unit and storing instructions thereon, the instructions, when executed by the processing unit, causing the device to perform the method according to any of claims 11-15.
[Claim 24]
A network device, comprising: a processor; and a memory coupled to the processing unit and storing instructions thereon, the instructions, when executed by the processing unit, causing the device to perform the method according to claim 16.
[Claim 25]
A network device, comprising: a processor; and a memory coupled to the processing unit and storing instructions thereon, the instructions, when executed by the processing unit, causing the device to perform the method according to claim 17.
[Claim 26]
A network device, comprising: a processor; and a memory coupled to the processing unit and storing instructions thereon, the instructions, when executed by the processing unit, causing the device to perform the method according to claim 18.
[Claim 27]
A computer readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to carry out the method according to any of claims 1-5.
[Claim 28]
A computer readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to carry out the method according to claim 6.
[Claim 29]
A computer readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to carry out the method according to claim 7.
[Claim 30]
A computer readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to carry out the method according to any of claims 8-10.
[Claim 31]
A computer readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to carry out the method according to any of claims 11-15.
[Claim 32]
A computer readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to carry out the method according to claim 16.
[Claim 33]
A computer readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to carry out the method according to claim 17.
[Claim 34]
A computer readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to carry out the method according to claim 18.