Resource allocation for beam failure recovery procedure

Abstract

To facilitate the initiation of a beam failure recovery procedure.SOLUTION: In a mobile communication system, mobile terminal UE includes a transceiver that receives a configuration of physical random access channel (PRACH) resources for transmitting a beam failure recovery signal, and a processor that detects a downlink beam failure event and initiates a beam failure recovery procedure in response thereto. The beam failure recovery procedure causes the transceiver to transmit the beam failure recovery signal using the PRACH resources. The configuration includes a timer indicating a time period during which the PRACH resources are valid and an indicator indicating the number of PRACH resources in a subset of a plurality of PRACH resources. The transceiver restricts the PRACH resources used for transmission to the subset of the plurality of PRACH resources allocated to the communication device by a base station gNB based on the indicator, and when the timer expires, the PRACH resources become unavailable.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to uplink resource allocation for a mobile terminal to transmit a beam failure recovery signal in response to detecting a downlink beam failure event while communicating with a base station in a mobile communication system.

Background Art

[0002] Currently, the 3rd Generation Partnership Project (3GPP (registered trademark)) is focusing on the next release (Release 15) of technical specifications for next-generation cellular technology, also known as 5th Generation (5G).

[0003] At the 3GPP Technical Specification Group (TSG) Radio Access Network (RAN) Meeting #71 (Joteborg, March 2016), the first 5G study item, "Study on New Radio Access Technology," including RAN1, RAN2, RAN3, and RAN4, was approved, which is expected to become the Release 15 work item (WI) that defines the first 5G standard.

[0004] One of the objectives of 5G New Radio (NR) is to provide a single technical framework that addresses all usage scenarios, requirements, and deployment scenarios defined in Non-Patent Document 1 (available at www.3gpp.org and incorporated herein by reference in its entirety), including at least enhanced mobile broadband (eMBB), ultra-reliable low-latency communication (URLLC), and massive machine type communication (mMTC).

[0005] For example, eMBB deployment scenarios may include indoor hotspots, dense urban areas, suburbs, wide urban areas, and highways. URLLC deployment scenarios may include industrial control systems, mobile healthcare (remote monitoring, diagnosis, and treatment), real-time vehicle control, and wide-area monitoring and control systems for smart grids. mMTC may include scenarios involving a large number of devices that use non-time-critical data transfer, such as smart wearables and sensor networks.

[0006] Another objective is forward compatibility that anticipates future use cases / deployment scenarios. Backward compatibility with Long Term Evolution (LTE) is not required, which facilitates a completely new system design and / or the introduction of new features.

[0007] As summarized in one of the technical reports on NR study items (Non-Patent Document 2), the basic physical layer signal waveform will be based on Orthogonal Frequency Division Multiplexing (OFDM). For both downlink and uplink, a Cyclic Prefix-Used OFDM (CP-OFDM)-based waveform is supported. For eMBB uplink up to at least 40 GHz, a Discrete Fourier Transform (DFT)-spread OFDM (DFT-S-OFDM)-based waveform is also supported as a supplement to the CP-OFDM waveform.

[0008] As summarized in another technical report on NR study items (Non-Patent Document 3), the multi-antenna method relies on a set of beam management procedures. With this procedure, the Transmit / Receive Point (TRP) and / or UE can acquire and maintain a set of beams that can be used for DL and UL transmission / reception, including beam determination, beam measurement, beam reporting, and beam sweeping.

[0009] One of the design targets in NR is to utilize the basic physical layer signal waveforms in communication while increasing the coverage by base stations that support single-user and multi-user MIMO in both the downlink and uplink. For this purpose, at the 3GPP TSG RAN1 WG1 meeting #89 (Hangzhou, People's Republic of China, May 15 - 19, 2017), it was agreed to adopt a beam management procedure including a beam failure recovery mechanism when a beam failure is detected. This mechanism is separate from the radio link failure procedure in the upper layer.

[0010] The term "downlink" refers to communication from a higher-level node to a lower-level node (e.g., from a base station to a relay node or a UE, from a relay node to a UE, etc.). The term "uplink" refers to communication from a lower-level node to a higher-level node (e.g., from a UE to a relay node or a base station, from a relay node to a base station, etc.). The term "sidelink" refers to communication between nodes at the same level (e.g., between two UEs, between two relay nodes, or between two base stations).

Prior Art Documents

Non-Patent Documents

[0011]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0012] One non - limiting and exemplary embodiment facilitates the initiation of a beam failure recovery procedure in a robust (reliable) manner, i.e., by more efficiently (situation - dependently) utilizing individual uplink radio resources.

Means for Solving the Problems

[0013] In one general aspect, the techniques disclosed herein feature a mobile terminal for communicating with a base station in a mobile communication system using at least one of a plurality of downlink beams and at least one of a plurality of uplink beams, wherein each of the downlink beam and the uplink beam has a different directivity and / or coverage. The mobile terminal, in operation, includes a transceiver that receives an allocation of individual uplink radio resources for transmitting a beam failure recovery signal for a beam failure recovery (BFR) procedure, and a processor that, in operation, detects a downlink beam failure event and initiates a beam failure recovery procedure in response thereto, the beam failure recovery procedure including the transceiver transmitting a beam failure recovery signal using the individual uplink radio resources from the allocation. The individual uplink radio resources restrict transmissions to a subset of the plurality of uplink beams that can be exclusively allocated to the mobile terminal by the base station.

[0014] Note that general or specific embodiments may be implemented as a system, a method, an integrated circuit, a computer program, a storage medium, or any optional combination thereof.

[0015] Additional benefits and advantages of the disclosed embodiments will be apparent from the present specification and the drawings. These benefits and / or advantages may be obtained individually by various embodiments and features of the present specification and the drawings, and it is not necessary that all embodiments and features be provided to obtain one or more of such benefits and / or advantages.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

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Figure 6

Figure 7a

Figure 7b

Modes for Carrying Out the Invention

[0017] In another general aspect, the techniques disclosed herein feature another mobile terminal for communicating with a base station in a mobile communication system using at least one of a plurality of downlink beams and at least one of a plurality of uplink beams, each of the downlink beam and the uplink beam having a different directivity. This mobile terminal, during operation, includes a transceiver that receives an allocation of individual uplink radio resources for transmitting a beam failure recovery signal for a beam failure recovery (BFR) procedure, and a processor that, during operation, detects a downlink beam failure event and initiates a beam failure recovery procedure in response thereto, the beam failure recovery procedure including the transceiver transmitting a beam failure recovery signal using the allocated individual uplink radio resources. The individual uplink radio resources restrict transmission to a subset of a plurality of uplink beams that can be non-exclusively allocated to the mobile terminal by the base station.

[0018] In yet another general aspect, the techniques disclosed herein feature a method for initiating a beam failure recovery procedure implemented by a mobile terminal configured to communicate with a base station in a mobile communication system using at least one of a plurality of downlink beams and at least one of a plurality of uplink beams, each of the downlink beam and the uplink beam having a different directivity and / or coverage. The method includes receiving an allocation of individual uplink radio resources for transmitting a beam failure recovery signal for a beam failure recovery (BFR) procedure, and detecting a downlink beam failure event and initiating a beam failure recovery procedure in response thereto, the beam failure recovery procedure including transmitting a beam failure recovery signal using the individual uplink radio resources from the allocation. The individual uplink radio resources restrict transmission to a subset of a plurality of uplink beams that can be exclusively allocated to the mobile terminal by the base station.

[0019] In yet another general aspect, the techniques disclosed herein feature another method for initiating a beam failure recovery procedure, which is implemented by a mobile terminal configured to communicate with a base station using at least one of a plurality of downlink beams and at least one of a plurality of uplink beams, wherein each of the uplink beam and the downlink beam has a different directivity. This method includes receiving an allocation of individual uplink radio resources for a beam failure recovery signal for a beam failure recovery (BFR) procedure, and detecting a downlink beam failure event and, in response, initiating a beam failure recovery procedure, the beam failure recovery procedure including transmitting a beam failure recovery signal using the allocated individual uplink radio resources. The individual uplink radio resources restrict transmission to a subset of a plurality of uplink beams that can be non-exclusively allocated to the mobile terminal by the base station.

[0020] As identified in TR38.913, the various use cases / deployment scenarios for NR have various requirements in terms of data rate, latency, and coverage. With these requirements in mind, NR should aim for even higher coverage compared to LTE.

[0021] In 3GPP RAN1#85, beam-based transmission was widely discussed for NR as an important technology to guarantee coverage. Regarding beam management, it was agreed that both intra-TRP and inter-TRP beamforming procedures would be considered, and the beamforming procedures would be considered according to the following potential use cases, i.e., UE mobility, UE rotation, beam blocking (change of beam at the TRP and the same beam at the UE, the same beam at the TRP and change of beam at the UE, or change of beam at the TRP and change of beam at the UE) with or without TRP beamforming / beam sweeping and with or without UE beamforming / beam sweeping, although other cases are not excluded. Furthermore, it was also agreed to consider beam (e.g., TRP beam and / or UE beam) management procedures (e.g., beam determination and change procedures), i.e., procedures for both data and control transmission / reception, with or without pre-acquired beam information. The procedures may be the same or different for data and control.

[0022] After that, in RAN1#88, the following agreement was reached. That is, a beam failure event occurs when the quality of the beam pair link of the related control channel degrades sufficiently (e.g., comparison with a threshold, expiration of a related timer). When a beam failure occurs, a mechanism for recovering from the beam failure is triggered. Note: The beam pair link is for convenience and may or may not be used in the specification. The following matters remained for further study (FFS). That is, whether the quality of the beam pair link related to NR-PDSCH can additionally include quality; when multiple Y beam pair links are configured, if X (≤Y) of the Y beam pair links fall below a certain threshold and meet the beam failure condition, a beam failure can be declared; the search space (UE-specific vs. common) of the related NR-PDCCH; what the signaling mechanism for NR-PDCCH is when the UE is configured to monitor multiple beam pair links for NR-PDCCH. Furthermore, the exact definition of such a threshold is FFS, and other conditions for triggering such a mechanism are not excluded.

[0023] It was also agreed that the following signals can be configured for the UE to detect beam blockage and to identify new potential beams, but the references to the signals are left for FFS. The signals are, for example, RS for beam management, RS for fine timing / frequency tracking, SS block, DM-RS of PDCCH (including group common PDCCH and / or UE-specific PDCCH), and DM-RS of PDSCH. Whether the UE provides a label to L3 and whether this label is linked to a radio link failure event if a beam blockage event occurs and no new potential beam is detected by the UE in the serving cell are left for FFS. Note: The criteria for declaring a radio link failure are determined by RAN2. Also, the need for such a label is left for FFS. NR supports configuring resources for sending recovery-purpose requests in symbols including RACH and / or FFS scheduling requests, or in other indicated symbols.

[0024] Then, in RAN1#88Bis, it was agreed that the UE beam blockage recovery mechanism includes the following aspects. That is, detection of beam blockage, identification of new candidate beams, and transmission of beam blockage recovery requests, and the UE monitors the gNB's response to the beam blockage recovery requests. In the detection of beam blockage, the UE monitors the beam blockage detection RS to evaluate whether the beam blockage trigger condition is met. The beam blockage detection RS includes at least the periodic CSI-RS for beam management, and if the sounding signal SS-block is also used in beam management, the SS-block in the serving cell can be considered. However, what the trigger conditions are for declaring a beam blockage are left for FFS.

[0025] Regarding the identification of new candidate beams, it was also agreed that the UE monitors beam identification RS to find new candidate beams. When the beam identification RS is configured by the NW, it includes periodic CSI-RS for beam management, and / or when SS-blocks are also used in beam management, it includes periodic CSI-RS and SS-blocks within the serving cell.

[0026] Regarding the transmission of beam failure recovery requests, it was also agreed that the information carried by the beam failure recovery request includes at least one of the following. That is, it is at least one of explicit / implicit information regarding identifying the UE and new gNB TX beam information, and explicit / implicit information regarding identifying the UE and whether there are new candidate beams. Information indicating UE beam failure and additional information, such as the quality of the new beam, were left for further study (FFS). The selection range limitation between channels for transmitting the beam failure recovery request was agreed to include PRACH, PUCCH, PRACH-like (for example, the preamble sequence parameters are different from those of PRACH). The beam failure recovery request resource / signal may additionally be used for scheduling requests.

[0027] In this regard, the UE monitors the control channel search space to receive the gNB's response to the beam failure recovery request, but whether the control channel search space may be the same as or different from the current control channel search space related to the serving BPL, and / or what further UE reaction there is if the gNB does not receive the beam failure recovery request transmission, is left for further study (FFS).

[0028] Thus, it can be concluded that the beam failure recovery procedure discussed above facilitates an efficient way to re - establish the connection between the UE and the gNB (i.e., the TRP) after a downlink beam failure event, i.e., a way to re - establish without the need to declare a radio link failure to the upper layer. However, it has been recognized that this beam failure recovery procedure will only work if the procedure provides a means for the UE to act quickly before a radio link failure event is triggered.

[0029] In other words, the concept of recovery after beam failure is based on a procedure where the UE indicates to the gNB alternative (i.e., candidate) downlink beams that can be used to resume communication between the gNB and the UE after the UE detects a beam failure for the downlink beam. Thus, this procedure relies on the UE still being able to indicate alternative (i.e., candidate) downlink beams to the gNB. However, this is only possible over a short time period after a downlink beam failure has occurred.

[0030] Therefore, one non - limiting exemplary embodiment of the present disclosure proposes a robust mechanism that enables the UE to respond to a beam failure detection event by starting the beam failure recovery procedure as soon as possible in order to avoid any degradation effects resulting from the inherent correspondence between the downlink beam and the uplink beam.

[0031] The proposed robust mechanism can be better understood when looking at the source or cause of the beam failure in the communication between the gNB and the UE. This understanding is generally based on, but not limited to, the 3GPP NR deployment scenario, i.e., the scenario where the concept of beams is introduced to improve directivity and / or coverage. This is particularly advantageous in view of the very high frequency bands (millimeter waves) assumed to be used by 3GPP NR.

[0032] As shown in FIGS. 7a and 7b, the gNB can be configured to communicate on a plurality of beams (e.g., beam #0 to beam #4). This is necessary for the initial access by the UE. After establishing the connection between the gNB and the UE, the gNB serves the UE using the downlink on a single beam (referred to as the "downlink serving beam" or "downlink beam"). However, it should be understood that a multi-beam scenario, i.e., a scenario where the gNB serves the UE using the downlink via two or more separate beams, for example, to increase capacity, is also possible.

[0033] Similarly, the UE can be configured to communicate on a plurality of beams (e.g., beam #0 to beam #4). This is equally necessary for the initial access by the UE. After establishing the connection, the UE also sends uplink traffic to the gNB using the uplink on a single beam (referred to as the "uplink serving beam" or "uplink beam"). However, this single uplink serving beam is not necessarily the same as the beam on which the downlink is served. Also in the uplink, a multi-beam scenario is possible, and thus, the present disclosure should be construed as not being limited in any way.

[0034] Generally, it can be assumed that the pair of downlink and uplink serving beams has characteristics suitable for downlink and uplink communication between the gNB and the UE. In many cases, it can be easily understood that there is a directional correspondence between the pair of downlink serving beam and uplink serving beam, i.e., the pair of downlink and uplink serving beams are beams having opposite directions and similar coverage.

[0035] In this context, it is to be noted that in 3GPP NR, a gNB is composed of one or more TRPs (Transmission / Reception Points, or Tx / Rx Points), and each TRP is linked to a downlink and / or uplink serving beam having a specific direction and specific coverage. Therefore, in a multi-beam configuration, the gNB will necessarily be composed of more than one TRP. That is, it will be configured to be able to transmit / receive beams having different directions and / or coverage.

[0036] Returning to the source or cause of beam obstruction, it can be immediately derived from the figure that one of the main causes of beam obstruction (see Figure 7a) is an obstacle that impedes the propagation of the serving beam between the gNB and the UE and vice versa. Another main cause of beam obstruction (see Figure 7b) is that the UE moves relative to the gNB, and as a result, the beam propagates in an inappropriate direction.

[0037] With this understanding, however, it can be recognized that these two main causes do not necessarily affect the downlink and uplink serving beam pairs in the same way. In other words, when downlink communication is served on a beam in a direction other than the direction of the beam serving the uplink communication, it is quite possible that only one of the downlink beam and the uplink beam is affected by beam obstruction.

[0038] Furthermore, there may be a case where the uplink serving beam is not affected by beam obstruction at a close distance, while the downlink serving beam is affected by beam obstruction at a farther distance when the distance between the obstacle and the UE is closer than the distance between the obstacle and the gNB.

[0039] Therefore, it is readily recognized that there is a need for a beam failure recovery procedure, i.e., this need exists in the situation where the downlink serving beam suffers a beam failure while the uplink serving beam still operates. In this situation, a beam failure recovery request indicating an alternative (i.e., candidate) downlink beam for serving downlink communication may be sent by the UE.

[0040] The present disclosure provides a robust mechanism that enables the UE to respond to the detection of a downlink beam failure event and reduces the amount of uplink radio resources blocked (allocated) for the start of the beam failure recovery procedure. This mechanism is particularly suitable for the proposed scenarios in 3GPP NR when the beam failure recovery procedure relies on contention-free physical random access channel (PRACH) resources or contention-free physical uplink control channel (PUCCH) resources.

[0041] As is apparent from this scenario, using contention-free PRACH or PUCCH resources for the beam failure recovery procedure has both advantages and disadvantages. Relying on contention-free resources on the uplink beam facilitates rapid access by the UE to signal to the gNB that a beam failure event has been detected for the downlink beam. However, since it is uncertain when and under which directional conditions a radio link failure will be detected, the UE will have to be allocated all potentially available combinations for the UE to successfully initiate the beam failure recovery procedure.

[0042] As a result of this uncertainty, each UE will block a large amount of individual uplink radio resources, especially in the case of proposed contention-free physical random access channel (PRACH) resources or contention-free physical uplink control channel (PUCCH) resources. In view of the large number of UEs that are expected to be served by each gNB, this results in a large overhead of individual uplink radio resources that cannot be used for other purposes. Therefore, this approach clearly conflicts with the existing design principle that resources (especially scarce resources) will only be allocated (and thus blocked) by the gNB if they are required and expected to be used in the UEs in the near future.

[0043] The present disclosure provides a solution for alleviating these drawbacks while still enabling the beam failure recovery procedure to be initiated in a robust (reliable) manner, i.e., by more efficiently (situationally) utilizing individual uplink radio resources.

[0044] In general, the present disclosure provides a device and method for initiating a beam failure recovery procedure using individual uplink radio resources for only the relevant constellations that are (actually) expected to be encountered when a beam failure is detected, rather than for all potentially available constellations. Since the relevant constellations can change over time, the individual uplink radio resources can be flexibly (re)allocated without incurring a large signaling overhead.

[0045] For this purpose, it is proposed that the gNB allocate uplink radio resources dedicated to the start of the beam failure recovery procedure to the UE in a restricted but efficient manner. That is, this is done by restricting the signaling of the beam failure recovery signal to only a subset of all potentially available uplink beams that can be allocated to the UE by the gNB, either exclusively or non-exclusively. After restricting the individual uplink radio resources to a subset, for example, one, two, or three uplink beams out of a maximum of 10 potentially available uplink beams, it is much less likely to impair the operation of the wireless communication system even if these individual uplink radio resources are blocked.

[0046] In particular, this is effectively in contrast to an alternative approach to the beam failure recovery procedure where the beam failure recovery signal is transmitted in a full beam sweeping manner (i.e., continuously using all potentially available uplink beams for the transmission of the beam failure recovery signal). This beam sweeping would require allocating (and thus blocking) individual uplink radio resources on all potentially available uplink beams.

[0047] In addition, it is proposed to adopt an efficient mechanism for (re)allocating these individual uplink radio resources that allows the gNB to reliably allocate only the most appropriate individual uplink radio resources to the UE. For each (actual) situation, the UE must still be able to initiate the beam failure recovery procedure upon detection of a downlink beam failure event. In this context, it may be advantageous to reduce blocking if the (re)allocation of individual uplink radio resources expires after a given time period or if the (re)allocation of individual uplink radio resources is updated periodically.

[0048] FIG. 1 illustrates a block diagram of a wireless communication system including a mobile terminal 110 and a base station 160 that communicate with each other using at least one of a plurality of downlink beams and at least one of a plurality of uplink beams. In other words, communication between the mobile terminal 110 and the base station 160 is performed on a pair 150 of (serving) downlink and uplink beams.

[0049] In the context of the present disclosure, the term beam is to be interpreted as having a specific (predetermined) directivity and / or coverage. Each uplink beam as well as each downlink beam has a different directivity and / or coverage, such that a transmitter can transmit a signal to a receiver at a different (spatial) location. In other words, each uplink beam as well as each downlink beam has different spatial parameters (e.g., gain and / or beamwidth).

[0050] The mobile terminal 110 includes a transceiver 120 that, during operation, receives from the base station 160 an allocation of individual uplink radio resources for sending a beam failure recovery signal for a beam failure recovery (BFR) procedure. Further, the mobile terminal 110 includes a processor 130 that, during operation, detects a downlink beam failure event and, in response, initiates a beam failure recovery procedure. The beam failure recovery procedure includes the transceiver 120 transmitting a beam failure recovery signal to the base station 160 using the individual uplink radio resources from the allocation.

[0051] In particular, the individual uplink radio resources allocated to the mobile terminal 110 limit transmission to a subset of a plurality of uplink beams that can be exclusively allocated by the base station 160. Thereby, only a subset and not all of the individual uplink radio resources are prevented from being used in an exclusive manner by another mobile terminal.

[0052] Alternatively, the individual uplink radio resources assigned to the mobile terminal 110 limit transmission to a subset of a plurality of uplink beams that can be non-exclusively assigned by the base station 160. As a result, here too, only a subset, rather than all, of the individual uplink radio resources will not be used in a non-exclusive manner by another mobile terminal.

[0053] In the context of the present disclosure, exclusive and non-exclusive allocations of individual uplink radio resources on an uplink beam are distinguished. Exclusive allocation should be interpreted to mean that the same individual uplink radio resources, including the same uplink beam, cannot be assigned to any other mobile terminal over the same time period. In contrast, non-exclusive allocation should be interpreted to mean that the same individual uplink radio resources, including the same uplink beam, can potentially be assigned to other mobile terminals over the same time period.

[0054] The base station 160 includes a transceiver 170, which, during operation, transmits to the mobile terminal 110 an allocation of individual uplink radio resources for the mobile terminal 110 to send a beam failure recovery signal for a beam failure recovery (BFR) procedure. Further, the base station 160 includes a processor 180, which, during operation, implements a beam failure recovery procedure in response to receiving from the mobile terminal 110 a beam failure recovery signal that uses the individual uplink radio resources from the allocation by the transceiver 170.

[0055] In particular, here too, the individual uplink radio resources assigned by the base station 160 limit transmission to a subset of a plurality of uplink beams that can be exclusively assigned to the mobile terminal 110. As a result, only a subset, rather than all, of the individual uplink radio resources will not be used in an exclusive manner by another mobile terminal.

[0056] Alternatively, the individual uplink radio resources allocated by base station 160 restrict transmission to a subset of a plurality of uplink beams that can be non-exclusively allocated to mobile terminal 110. Thus, again, only a subset, rather than all, of the individual uplink radio resources will not be used in a non-exclusive manner by another mobile terminal.

[0057] The start of the beam failure recovery procedure, particularly regarding the allocation of individual uplink radio resources, will be described in further detail with respect to FIG. 2. In particular, this figure represents the present disclosure in the context of an exemplary four-step beam failure recovery procedure. It should be understood that the present disclosure is not limited in any way.

[0058] In FIG. 2, mobile terminal 110 (also referred to as UE) and base station 160 (also referred to as gNB) are communicating in a wireless communication network using a pair of downlink and uplink (serving) beams 150. In particular, the pair of downlink and uplink beams is one of a plurality of downlink beams that can be configured by base station 160 in mobile terminal 110 and one of a plurality of uplink beams.

[0059] For the beam failure recovery procedure, individual uplink radio resources are allocated by base station 160 to mobile terminal 110 (FIG. 2 S01). As previously mentioned, the allocation of these uplink radio resources is dedicated to be used together with beam failure recovery signaling. In other words, by dedicating the uplink radio resources in this way, it is possible to prevent the uplink radio resources from being used in a different context. In any case, by dedicating the uplink radio resources, base station 160 can identify (recognize) and initiate the relevant functions (i.e., start the beam failure recovery procedure) when receiving beam failure recovery signaling on the individual uplink radio resources.

[0060] In addition, the allocation of individual uplink radio resources may include an instruction from the base station 160 instructing the mobile terminal 110 to include the identification information of the mobile terminal 110 (e.g., radio network terminal identifier (RNTI)) in subsequent messages of the beam failure recovery procedure for the purpose of the beam failure recovery procedure. This may be particularly advantageous when the individual uplink radio resources are allocated to the mobile terminal 110 non-exclusively rather than exclusively, which will be discussed further later.

[0061] Thereafter, the mobile terminal 110 detects a downlink (also referred to as DL) beam failure event, i.e., a beam failure for the downlink (serving) beam among the beam pairs 150 through which the base station 160 and the mobile terminal 110 communicate with each other. The two main causes of beam failure, i.e., obstacles and UE movement, have already been discussed above.

[0062] Furthermore, there are many methods for the mobile terminal 110 to detect a beam failure event for the downlink (serving) beam. For example, there is a method of measuring the reference signal received power RSRP or the reference signal received quality RSRQ on this (serving) downlink beam and determining that the measured value is below a given threshold. Another method for the mobile terminal 110 to detect a beam failure event for the downlink (serving) beam may include the expiration of a given (countdown) timer. That is, when periodic control data and / or user data are not received within the time period defined by a given (countdown) timer.

[0063] In this regard, the beam failure event can be understood as an event that can be detected directly (i.e., by measurement) or indirectly (i.e., by the expiration of a timer) in the mobile terminal 110.

[0064] In response to the detection of a downlink beam failure event, the mobile terminal 110 transmits a beam failure recovery signal to the base station 160 (Figure 2 S02). In particular, the beam failure recovery signal uses the assigned individual uplink radio resources described above. As previously mentioned, by using the individual uplink radio resources, the base station 160 can immediately identify (recognize) and initiate the relevant functions (i.e., initiate the beam failure recovery procedure).

[0065] If the number of uplink beams is greater than the number of uplink beams that form the subset used when the failure recovery signal is transmitted, the mobile terminal 110 may transmit this signal in a beam sweeping manner. However, this is less efficient than the beam failure recovery signal transmitted in a complete (not partial) beam sweeping manner due to the limitation to a subset of all available uplink beams that may be used.

[0066] Most importantly, the allocation of individual uplink radio resources restricts transmission to a subset of potentially available uplink beams. Restricting to such a subset of uplink beams is implemented regardless of whether the individual uplink radio resources are allocated to the mobile terminal 110 exclusively or non-exclusively by the base station 160. The individual uplink radio resources may be restricted to a subset, for example, one, two, or three uplink beams out of up to 10 potentially available uplink beams.

[0067] However, after receiving the beam failure recovery signal, the base station 160 is not yet in a state where it can complete the beam failure recovery procedure for the downlink beam in which the mobile terminal 110 detected the beam failure. As discussed previously, the beam failure recovery procedure also includes transmitting a message that enables the mobile terminal 110 to explicitly or implicitly indicate to the base station 160 alternative (candidate) downlink beams that can be used to recover from the beam failure.

[0068] For this purpose, the base station 160 transmits a beam failure recovery control signal to the mobile terminal 110 (Fig. 2 S03). This control signal most likely includes an uplink grant that enables the mobile terminal 110 to transmit an alternative (candidate) downlink beam. However, this control signal is not limited to only the uplink grant.

[0069] In addition, this control signal may also include an instruction from the base station 160 instructing the mobile terminal 110 to include the identification of the mobile terminal 110 (e.g., radio network terminal identifier (RNTI)) in subsequent messages of the beam failure recovery procedure for the purpose of the beam failure recovery procedure. This may be particularly advantageous when individual uplink radio resources are assigned to the mobile terminal 110 non-exclusively rather than exclusively, which will be discussed further later.

[0070] The mobile terminal 110 transmits a beam failure recovery request to the base station 160 with reference to the received uplink grant (Fig. 2 S04). This request includes at least one of explicit or implicit information regarding identifying the mobile terminal 110 and new downlink beam candidate information for the base station 160, and explicit or implicit information regarding identifying the mobile terminal 110 and whether there is a new downlink beam candidate.

[0071] Using this information, the base station 170 can recover from the beam failure on the downlink beam. That is, this can be done, for example, by reverting to one of the explicitly or implicitly indicated new downlink beam candidate information. This information regarding the new downlink candidate beam can be obtained, for example, from the downlink reference signals continuously transmitted by the base station 160 on all potentially available downlink beams. The mobile terminal 110 can identify new downlink beam candidates by measuring these downlink reference signals.

[0072] In response to the beam failure recovery request, the base station 160 transmits a beam failure recovery response to the mobile terminal 110 (Figure 2 S05). This response is a reply to the beam failure recovery request previously transmitted by the mobile terminal 110. In particular, only when this response is received by the mobile terminal 110 does the mobile terminal 110 know that the information indicating the new downlink beam candidate has been successfully received and put into execution.

[0073] In particular, successful beam failure recovery is possible even when the beam failure recovery request transmitted from the mobile terminal 110 to the base stations 160 and 170 does not include any new downlink beam candidate information for the base station 160 (instead, the request includes information that there is no new downlink beam candidate). In this case, a new downlink (serving) beam is determined by the base station 160 itself.

[0074] In particular, when the mobile terminal 110 does not propose any new downlink beam candidates, the base station 160 may instead determine which downlink beam to resume its communication with the mobile terminal 110 on. For this purpose, the base station may refer to the report on the measurement values of the downlink reference signal (e.g., CSI-RS in 3GPP NR terminology) obtained (previously) from the mobile terminal 110.

[0075] After determining the new downlink beam, the base station 160 must further notify the mobile station 110 of the new downlink beam. Only then can both the base station 160 and the mobile terminal 110 return to the same new pair of the new downlink (serving) beam and the current uplink (serving) beam. Therefore, after determining the new downlink beam, the base station 160 also includes information about this new downlink beam in the beam failure recovery response to the mobile terminal 110.

[0076] For example, the beam failure recovery response from base station 160 may mark the point in time when mobile terminal 110 switches communication to a new beam pair including a new downlink beam as the new downlink (serving) beam. In yet another example, if there is no beam failure response from base station 160 within a given time period, mobile terminal 110 will determine that the beam failure recovery procedure has not been successful, and thus will signal a radio link failure event to the upper layer.

[0077] In summary, a description of a 4-step beam failure recovery procedure is provided in the context of FIG. 2. That is, steps S02, S03, S04, and S05 in the figure resemble four individual steps of the procedure. In other words, step S01 in the figure is of a more preparatory nature and is not considered part of the 4-step beam failure recovery procedure in this sense.

[0078] Irrespective of this complete presentation of the beam failure recovery procedure, it is again emphasized that the present disclosure is focused on proposing a robust and efficient mechanism for starting (not ending) the beam failure recovery procedure. Due to this narrow focus, steps S03, S04, and S05 in the figure must be considered as options for achieving this effect. Whether the procedure is successfully completed or not does not make the start of the beam failure recovery procedure more robust or efficient, and is not relevant to the focus described herein.

[0079] Exclusive and non-exclusive allocations As described above, base station 160 can allocate individual uplink radio resources to mobile terminal 110 in an exclusive or non-exclusive manner. Although this may seem like a minor matter, it will have a significant impact on the beam failure recovery procedure, as will become apparent below.

[0080] Regarding exclusive allocation, after receiving the beam failure recovery signal at S02 in FIG. 2, the base station 160 accurately knows which mobile terminal it must send the control signal to at S03 in FIG. 2. Since the individual uplink radio resources are exclusively allocated to only one mobile terminal 110, the base station 160 can derive the mobile terminal 110 that was using this from the individual uplink radio resources. Therefore, the base station 160 can still send the subsequent control signal 110 to this mobile terminal 110.

[0081] Regarding non - exclusive allocation, after receiving the beam failure recovery signal at S02 in FIG. 2, the base station 160 does not (therefore) know which mobile terminal it must send the control signal to at S03 in FIG. 2. For this purpose, it is proposed that the base station 160 examines the context in which the beam failure recovery signal was received and tries to infer which mobile terminal the signal was received from. As will become apparent soon, if the individual uplink radio resources are allocated, even non - exclusively, to only a few mobile terminals, for example, only two mobile terminals, it becomes easier to identify which mobile terminal the signal was received from based on the context.

[0082] One possibility is associated with only a subset of all potentially available uplink beams being allocated to the base station as individual uplink radio resources for the beam failure recovery signal. For example, if one uplink beam, such as one, is allocated to each of two mobile terminals, etc., in a non - exclusive manner as a subset, this subset reduces the number of mobile terminals that could be the source of the signal.

[0083] However, with respect to this possibility, the base station still has to predict, based on context, e.g., based on the most recent beam status update, which of the reduced number of mobile terminals used the individually assigned uplink radio resources non-exclusively and which (actually) transmitted a beam failure recovery signal on that resource. Here it should already be understood that the subset also enables the base station to better identify the mobile terminal that is the source of the signal.

[0084] If the base station cannot or fails to predict with reasonable certainty which mobile terminal is the source of the signal, the base station can decide to send the beam failure recovery control signal of S02 in FIG. 2 to more than one mobile terminal. In the above example, it can be decided to send to two mobile terminals to which the same individual uplink radio resource is non-exclusively assigned to both.

[0085] In this case, as discussed before, it is advantageous if the mobile terminal is instructed to include its identification information in a subsequent message, namely the beam failure recovery request (i.e., of S04 in FIG. 2). From this identification information included in the beam failure recovery request, the base station can infer the correct mobile terminal for which the beam failure recovery procedure should be performed. For the other mobile terminals that were not correctly predicted, the base station will stop the beam failure recovery procedure.

[0086] Another possibility is associated with the fact that the beam failure recovery signal can be transmitted on the individually assigned uplink radio resources which themselves require the addition of additional control information. The base station can use this added control information to identify the mobile terminal as the source of the signal.

[0087] This is the case where, for example, the beam failure recovery signal is transmitted via the Physical Uplink Control Channel (PUCCH). The 3GPP NR specification for PUCCH stipulates that the mobile terminal not only transmits uplink control information (UCI) in a given format, but also adds a transmission demodulation reference signal DM-RS uniquely allocated to each mobile terminal thereto.

[0088] Therefore, when the base station receives the beam failure recovery signal in the UCI on the PUCCH, it can identify the mobile terminal that transmitted this signal from the DM-RS. Here too, the context serves as a determinant for the base station to identify the mobile terminal in order to send the subsequent beam failure recovery control signal to the correct mobile terminal at S03 in FIG. 2.

[0089] Next, in FIG. 3, a 3GPP NR deployment scenario is assumed. More specifically, this figure illustrates the start of the beam failure recovery procedure in the context of a 4-step beam failure recovery procedure in which the UE and the gNB communicate via a pair of a downlink beam and an uplink beam. Here too, the pair of the downlink and uplink (serving) beams is one of a plurality of downlink beams that can be configured in the UE by the gNB and one of the pairs of uplink beams.

[0090] For the beam failure recovery procedure, individual uplink radio resources are allocated by the gNB to the UE (FIG. 3 S11). As mentioned before, the allocation of uplink radio resources is dedicated to be used together with the beam failure recovery signaling. For this purpose, the gNB transmits a Radio Resource Configuration (RRC) connection reconfiguration message to the UE. Alternatively, an RRC connection setup message may be used for the purpose of allocation.

[0091] In another example, the individual uplink radio resources are allocated to the UE via a downlink media access control (MAC) control element (CE), downlink control information (DCI), and a control protocol data unit (PDU) of a packet data convergence protocol (PDCP). In particular, the PDCP control PDU also has the advantage of having slightly lower overhead compared to the RRC connection reconfiguration message. As a result, the signaling speed can be further increased.

[0092] Apart from the allocation via a single message, the allocation can also be achieved by a first message that configures the individual uplink radio resources and a second subsequent message that activates the configuration. In this case, the UE receives the configuration of the individual uplink radio resources from the gNB via an RRC connection setup or reconfiguration message and then receives the activation of the individual uplink radio resources from the configuration via one of the MAC CE, DCI, and PDCP control PDU.

[0093] This message may include a reference to an individual uplink radio resource of a physical random access channel (PRACH), i.e., a reference to one of the contention-free resources, preferably a reference to a contention-free preamble sequence having time and frequency references on the uplink beam.

[0094] Reference is made only to contention - free preamble sequences. This is because in 3GPP NR, the gNB (actively) allocates only these types of preamble sequences to the UE. In contrast, for non - contention - free (contention - based) preamble sequences, the gNB cannot distinguish whether these sequences are being used by the UE for the start of the beam failure recovery procedure or whether the (conventional) timing alignment procedure is being carried out. As a result, any use of non - contention - free (contention - based) preamble sequences as individual uplink radio resources for starting the beam failure recovery procedure is excluded.

[0095] For example, assuming the configuration shown in FIG. 5, the message may include a reference to a PRACH having a preamble sequence index S1, a time reference T1, and a frequency reference F1 on uplink beam #1. Thereby, individual uplink radio resources that the UE can use to start the beam failure recovery procedure are allocated to the UE. In this example, the time reference T1 will be understood as an offset indicating a slot that is time - shifted from each radio frame boundary. Additionally, the frequency reference F1 will be understood as an index of a resource block.

[0096] Alternatively, this message may also include a reference to an individual uplink radio resource of the physical uplink control channel (PUCCH), i.e., a reference to contention - free uplink control information (UCI) of a given format with time and frequency references on the uplink beam. For example, assuming the configuration shown in FIG. 6, the message may include a reference to a PUCCH having a time reference T1 and a frequency reference F1 on beam #1.

[0097] In both cases, i.e., contention-free PRACH or PUCCH, by dedicating the uplink radio resources, it is possible to prevent the uplink radio resources from being used in different contexts. In either case, by dedicating the uplink radio resources, when the gNB receives beam failure recovery signaling on an individual uplink radio resource, it can identify (recognize) and initiate the relevant functions (i.e., initiate the beam failure recovery procedure).

[0098] In response to detecting a beam failure event, the UE transmits a beam failure recovery signal to the gNB (S12 in Figure 3). In particular, the beam failure recovery signal uses a pre-allocated individual uplink radio resource, i.e., contention-free PRACH or PUCCH. As already mentioned before, by using individual uplink radio resources, the gNB can immediately identify (recognize) and initiate the relevant functions (i.e., initiate the beam failure recovery procedure). In particular, the PRACH resource implicitly indicates a scheduling request (SR), whereas the UCI of a given format may contain the SR either explicitly or implicitly.

[0099] Upon receiving an individual PRACH or PUCCH resource, the gNB initiates the beam failure recovery procedure. As part of this procedure, the gNB transmits physical downlink control channel (PDCCH) downlink control information (DCI) including an uplink grant (S13 in Figure 3). The DCI on the PDCCH also includes a cyclic redundancy check (CRC) field scrambled with the UE's radio network temporary identifier (RNTI). Thereby, the UE can detect whether the DCI for the UE is intended by the gNB to be used in the beam failure recovery procedure.

[0100] Assuming that the UE receives an uplink grant, the mobile terminal 110 transmits a beam failure recovery request to the gNB in the form of an uplink MAC control element (S14 in FIG. 3). This request includes at least one of explicit or implicit information regarding identifying the UE and new downlink beam candidate information for the gNB, and explicit or implicit information regarding identifying the UE and whether there are new downlink beam candidates.

[0101] Finally, in response to the beam failure recovery request, the gNB transmits a beam failure recovery response to the UE in the form of PDCCH DCI including an acknowledgement (e.g., an acknowledgement confirmation) (S15 in FIG. 3). This response is a response to the beam failure recovery request previously transmitted by the UE. In particular, only when this response is received by the UE does the UE know that the information indicating the new downlink beam candidate has been successfully received and put into execution.

[0102] Alternatively, when the mobile terminal does not propose any new downlink beam candidates, the gNB may include information regarding the new downlink beam in the beam failure recovery response to the UE. Depending on the number of potentially available downlink beams, this information may also be accommodated in the response in the form of PDCCH DCI. Also, both the gNB and the UE can then return to the same pair of the new downlink (serving) beam and the current uplink (serving) beam, thereby successfully completing the beam failure recovery procedure.

[0103] Next, in Figure 4, another 3GPP NR deployment scenario is assumed. More specifically, this figure depicts the start of the beam failure recovery procedure in the context of a two-step beam failure recovery procedure where the UE and the gNB communicate via a pair of (serving) beams for the downlink and uplink. Here too, the (serving) beams for the downlink and uplink are one of a plurality of downlink beams that can be configured by the gNB for the UE and one of a pair of uplink beams. In particular, the two-step beam failure recovery procedure is restricted to individual uplink radio resources from the Physical Uplink Control Channel (PUCCH).

[0104] This procedure is very similar to the four-step beam failure recovery procedure shown in the previous figure. The transmission between the UE and the gNB for the allocation of individual uplink resources (Figure 4 S21) and the transmission of the beam failure recovery response (Figure 4 S23) correspond to the respective steps in the previous procedure. Furthermore, the only difference lies in the format of the beam failure recovery signal (Figure 4 S22).

[0105] Here, it is utilized that the uplink control information (UCI) on the PUCCH depending on a given format can include a sufficient number of bits, for example, 1 or 2 bits in PUCCH format 1a / 1b, 20 coded bits in PUCCH format 2 / 2a / 2b, and even 48 coded bits in PUCCH format 3.

[0106] Therefore, in this example, it is proposed that the UE not only transmits UCI of the PUCCH similar to individual uplink radio resources as a beam failure recovery signal to the gNB, but also conveys at least one of the information of the beam failure recovery request, that is, explicit or implicit information regarding identifying the UE and new downlink beam candidate information for the gNB, and explicit or implicit information regarding identifying the UE and whether there are new downlink beam candidates.

[0107] Robust Allocation Mechanism As discussed previously, the present disclosure focuses on a robust mechanism that enables a base station to respond to the detection of a downlink beam obstruction event and reduces the amount of uplink radio resources that are blocked (allocated) for the initiation of a beam obstruction recovery procedure. However, reducing the amount of uplink radio resources requires, for example, the base station to carefully select the individual uplink radio resources to be allocated.

[0108] For this purpose, the base station may determine a subset of all potentially available uplink beams based on the most recent quality and / or power measurements. In this context, it may be advantageous to refer to reference signals signaled either on all potentially available downlink beams or on any of the uplink beams. From this, the base station can then select the subset with reference to the measured quality and / or power values.

[0109] Assuming a 3GPP NR deployment scenario, the base station may refer to all potentially available uplink reference signals, preferably sounding reference signals (SRS), transmitted by the mobile terminal on the potentially available or at least most relevant uplink beams for the determination of the subset of uplink beams.

[0110] The base station may also refer to reports (preferably channel state information (CSI) reports) created by the mobile terminal regarding measurements of downlink reference signals (preferably CSI-RS) transmitted by the base station on all potentially available downlink beams for this determination of the uplink beam subset.

[0111] In any case, it is possible to ensure that a subset of uplink resources is adapted for the purpose of enabling the mobile terminal to respond robustly to the detection of a downlink beam failure event (i.e., without the risk that the base station cannot receive the beam failure recovery signal).

[0112] Mobility state In an exemplary implementation, an efficient mechanism for allocating individual uplink radio resources on a subset of uplink beams is focused on. To achieve this, the base station varies the number of uplink beams that form the subset when individual uplink radio resources are allocated to the mobile terminal. In particular, by varying the number of uplink beams, the base station attempts to reflect the varying (actual) situation at the mobile terminal (e.g., a small or large number of position changes).

[0113] As can be seen from the above discussion, one of the main causes of beam failure is the mobility of the mobile terminal (i.e., the varying spatial position). If the mobile terminal changes its position at a high rate, it is difficult for the base station to predict which will be the most appropriate individual uplink radio resource in the event of a downlink beam failure. In other words, when the position of the mobile terminal changes drastically, it becomes difficult for the base station to allocate individual uplink radio resources on a subset of uplink beams that still meet the requirements of a reliable beam failure recovery procedure.

[0114] Taking these difficulties into account, the present disclosure proposes that the base station maintain a mobility state for each mobile terminal. The mobility state distinguishes, for each mobile terminal, between a small number of position changes and a large number of position changes during a given time period. In other words, based on the mobility state, the base station can ascertain whether position changes have occurred at a low rate or a high rate (in the past) for each mobile terminal.

[0115] Next, this mobility state is used by the base station to predict the number of uplink beams in the subset, thereby ensuring a reliable beam failure recovery procedure. Thus, the number of uplink beams forming a subset of all potentially available uplink beams may be determined by the base station corresponding to the mobility state of each mobile terminal.

[0116] In one example, that is, for a mobile terminal having a mobility state corresponding to a low position change rate, the base station may reasonably predict that the position of the mobile terminal will not change frequently in the future, and thus, it may be sufficient to allocate individual uplink radio resources on a small number of uplink beams (e.g., one or two uplink beams). In a different example, that is, for a mobile terminal having a mobility state corresponding to a high position change rate, the base station, in contrast, may reasonably predict that the position of the mobile terminal will change frequently in the future, and thus, it becomes necessary to allocate individual uplink radio resources on a large number of (e.g., three or more) uplink beams.

[0117] As an example, the mobility state and thus the position change rate can be determined by both the base station and the mobile terminal based on the number of reconfiguration commands (beam steering) for the downlink beam transmitted from the base station to the mobile terminal. Despite the downlink beam reconfiguration being performed at the base station, the mobile terminal will take this into account in the form of reconfiguration commands, that is, commands to the mobile terminal to reconfigure the beam pair of the mobile terminal to include a new downlink beam.

[0118] Also by way of example, the mobility state and thus the rate of position change can be determined based on the number of position changes, which is preferably determined from positioning measurements in the mobile terminal over a given time period and then signaled to the base station. In other words, the mobile terminal itself determines its rate of position change by performing positioning measurements, including for example checking whether there is a new downlink beam, and then signals this rate of position change to the base station.

[0119] In both cases, the mobility state facilitates the selection of a sufficient number of uplink beams for the mobile terminal to respond robustly to the detection of a downlink beam failure event (i.e., without the risk that the base station cannot receive a beam failure recovery signal).

[0120] Freshness of allocation In another exemplary implementation, an efficient mechanism for allocating individual uplink radio resources on a subset of uplink radio beams is again focused on. To achieve this, each allocation of an individual uplink radio resource to a mobile terminal has an expiration time. This can ensure the freshness of the allocation of individual uplink radio resources and that resources are blocked only for a limited amount of time.

[0121] As is clear from the above discussion, the base station that allocates individual uplink radio resources to a mobile station does not always succeed in coping well with the changing (actual) situation in the mobile terminal (e.g., position change). An allocation on a particular subset of uplink beams may be valid for a mobile terminal at one location but not for the same mobile terminal after it has moved to another location.

[0122] Accordingly, the present disclosure proposes that each allocation be valid for a given (short) time period and, exceptionally, only until a new (re)allocation is received. In other words, whether the mobile station receives an exclusive allocation or a non-exclusive allocation of individual uplink resources from the base station for the beam failure recovery procedure, these resources are blocked only for a limited amount of time.

[0123] This can be guaranteed by the base station 160 when transmitting to the mobile station 110 (see Figure 2 S01) an allocation indicating also the time period for which the individual uplink radio resources are valid. For example, both the base station and the mobile terminal can start a countdown timer together with the allocation of the individual uplink radio resources. When this timer expires, the base station as well as the mobile terminal know that the individual uplink radio resources are no longer available and thus can no longer be blocked.

[0124] However, to avoid the case of no allocation or only an expired allocation, the mobile terminal may send to the base station an indication for the base station to (re)start the allocation of individual uplink radio resources for the beam failure recovery procedure.

[0125] Assuming an NR deployment scenario, the indication for (re)starting the allocation of individual uplink radio resources is either a (non-explicit) channel state information (CSI) report signaling the quality or power of the serving downlink beam below a given threshold, or an individual transmission (preferably in the form of either an RRC message or an uplink MAC CE) signaling an explicit request to (re)start the allocation of individual uplink radio resources.

[0126] In summary, the invalidation of the allocation of individual uplink radio resources further improves the efficient use of these resources. The invalidation of the resource allocation not only promotes the timeliness necessary for the allocation to reflect the actual (current) situation of the mobile station, but also prevents the resources from being blocked, which is particularly advantageous when these resources are allocated in an exclusive manner.

[0127] The present disclosure can be implemented by software, hardware, or software cooperating with hardware. Each functional block used in the description of each of the above embodiments can be partially or entirely realized by an LSI such as an integrated circuit, and each process described in each embodiment can be partially or entirely controlled by the same LSI or a combination of LSIs. The LSI may be formed individually as a chip, or may be formed such that one chip includes some or all of the functional blocks. The LSI may include data inputs and outputs coupled thereto. Here, the LSI may be referred to as an IC, a system LSI, a super LSI, or an ultra LSI depending on the degree of integration. However, the technique for implementing the integrated circuit is not limited to the LSI, and may be realized using an application-specific circuit, a general-purpose processor, or a dedicated processor. In addition, an FPGA (field programmable gate array) that can be programmed after the manufacture of the LSI, or a reconfigurable processor in which the connection and setting of circuit cells arranged inside the LSI can be reconfigured may be used. The present disclosure can be realized as digital processing or analog processing. When future integrated circuit technology replaces the LSI as a result of the progress of semiconductor technology or other derivative technologies, the functional blocks may also be integrated using future integrated circuit technology. Biotechnology can also be applied.

[0128] According to a first aspect, a mobile terminal is proposed for communicating with a base station in a mobile communication system using at least one of a plurality of downlink beams and at least one of a plurality of uplink beams, each of the downlink beam and the uplink beam having different directivities and / or coverages. The mobile terminal includes, during operation, a transceiver that receives an allocation of individual uplink radio resources for transmitting a beam failure recovery signal for a beam failure recovery (BFR) procedure, and a processor that, during operation, detects a downlink beam failure event and initiates a beam failure recovery procedure in response thereto, the beam failure recovery procedure including the transceiver transmitting a beam failure recovery signal using the individual uplink radio resources from the allocation. The individual uplink radio resources restrict transmission to a subset of a plurality of uplink beams that can be exclusively allocated to the mobile terminal by the base station.

[0129] According to a second aspect that can be combined with the first aspect, a subset of a plurality of uplink beams is exclusively allocated to the mobile terminal based on uplink reference signals (preferably sounding reference signals (SRS)) transmitted on the plurality of uplink beams by the mobile terminal or based on a report (preferably channel state information (CSI) report) by the mobile terminal regarding measurements of downlink reference signals (preferably CSI-RS) transmitted on the plurality of downlink beams by the base station.

[0130] According to a third aspect that can be combined with the first or second aspect, the number of uplink beams forming a subset of a plurality of uplink beams corresponds to one, two, or three uplink beams.

[0131] According to a fourth aspect that can be combined with one of the first to third aspects, the number of uplink beams forming a subset of a plurality of uplink beams corresponds to the mobility state of the mobile terminal, which differentiates between a low-rate position change and a high-rate position change of the mobile terminal.

[0132] According to a fifth aspect that can be combined with the fourth aspect, the mobility state of the mobile terminal is determined based on the number of reconfiguration commands for the downlink beam transmitted by the base station to the mobile terminal over a time period, or is determined based on the number of position changes preferably determined from positioning measurements in the mobile terminal over a time period and signaled to the base station.

[0133] According to a sixth aspect that can be combined with one of the first to fifth aspects, during operation, the transceiver additionally receives, for the beam failure recovery procedure, an indication of the number of uplink beams in a subset of a plurality of uplink beams to be used in the beam failure recovery procedure.

[0134] According to a seventh aspect that can be combined with the first to sixth aspects, the indication of the number of uplink beams in a subset of a plurality of uplink beams to be used is received in a radio resource configuration (RRC) message, or a medium access control (MAC) control element (CE), or downlink control information (DCI).

[0135] According to an eighth aspect, another mobile terminal is proposed for communicating with a base station in a mobile communication system using at least one of a plurality of downlink beams and at least one of a plurality of uplink beams, each of the downlink beam and the uplink beam having a different directivity. This mobile terminal, during operation, includes a transceiver that receives an allocation of individual uplink radio resources for transmitting a beam failure recovery signal for a beam failure recovery (BFR) procedure, and a processor that, during operation, detects a downlink beam failure event and initiates a beam failure recovery procedure in response thereto, the beam failure recovery procedure including the transceiver transmitting a beam failure recovery signal using the allocated individual uplink radio resources. The individual uplink radio resources restrict transmission to a subset of a plurality of uplink beams that can be non-exclusively allocated to the mobile terminal by the base station.

[0136] According to a ninth aspect that can be combined with the eighth aspect, transmitting on a subset of a plurality of uplink beams where the beam failure recovery signal on the individual uplink radio resources is restricted enables the base station to identify the mobile terminal.

[0137] According to a tenth aspect that can be combined with the eighth or ninth aspect, when the individual uplink radio resources include a physical uplink control channel (PUCCH), transmitting a demodulation reference signal DM-RS together with the beam failure recovery signal in the PUCCH enables the base station to identify the mobile terminal.

[0138] According to an eleventh aspect that can be combined with one of the eighth to tenth aspects, the allocation of the individual uplink radio resources includes an instruction instructing the mobile terminal to include identification information of the mobile terminal in a subsequent message of the beam failure recovery procedure.

[0139] According to a twelfth aspect that can be combined with the first to eleventh aspects, the individual uplink radio resource corresponds to one of a contention-free resource of a physical random access channel (PRACH) (preferably, a contention-free preamble sequence including time and frequency references) and a contention-free resource of a physical uplink control channel (PUCCH) (preferably, uplink control information (UCI) including time and frequency references).

[0140] According to a thirteenth aspect that can be combined with one of the first to twelfth aspects, the allocation of the individual uplink radio resource is received via one of a radio resource configuration (RRC) connection reconfiguration or RRC connection setup message, a downlink media access control (MAC) control element (CE), downlink control information (DCI), and a control protocol data unit (PDU) of a packet data convergence protocol (PDCP).

[0141] According to a fourteenth aspect that can be combined with one of the first to twelfth aspects, the allocation of the individual uplink radio resource includes receiving, when the transceiver is operating, the configuration of the individual uplink radio resource via an RRC connection setup or reconfiguration message, and the activation of the individual uplink radio resource from the configuration via one of a MAC CE, DCI, and a PDCP control PDU.

[0142] According to a fifteenth aspect that can be combined with one of the first to fourteenth aspects, the allocation of the individual uplink radio resource is valid either over a time period or until a new allocation is received.

[0143] According to a sixteenth aspect that can be combined with one of the fifteenth aspects, the time period during which the allocation of the individual uplink resource is valid is indicated in the allocation.

[0144] According to a 17th aspect that can be combined with one of the 1st to 16th aspects, during operation, the transceiver transmits a signal indicating that the base station (re)starts the allocation of individual uplink radio resources for the beam failure recovery procedure.

[0145] According to an 18th aspect that can be combined with the 17th aspect, the signal indicating the (re)start of the allocation of individual uplink radio resources is channel state information (CSI) report signaling the quality or power of the serving downlink beam below a threshold, or an individual transmission (preferably in the form of either an RRC message or an uplink MAC CE) signaling an explicit request to (re)start the allocation of individual uplink radio resources.

[0146] According to a 19th aspect, a method for starting a beam failure recovery procedure is proposed, which is implemented by a mobile terminal configured to communicate with a base station in a mobile communication system using at least one of a plurality of downlink beams and at least one of a plurality of uplink beams, each of the downlink beam and the uplink beam having different directivities and / or coverages. The method includes receiving an allocation of individual uplink radio resources for transmitting a beam failure recovery signal for a beam failure recovery (BFR) procedure, detecting a downlink beam failure event, and in response, starting a beam failure recovery procedure, the beam failure recovery procedure including transmitting a beam failure recovery signal using the individual uplink radio resources from the allocation. The individual uplink radio resources limit transmission to a subset of a plurality of uplink beams that can be exclusively allocated to the mobile terminal by the base station.

[0147] According to a 20th aspect that can be combined with the 19th aspect, a subset of a plurality of uplink beams is exclusively assigned to a mobile terminal based on uplink reference signals (preferably sounding reference signals (SRS)) transmitted on the plurality of uplink beams by the mobile terminal, or based on a report (preferably a channel state information (CSI) report) by the mobile terminal regarding measurement values of downlink reference signals (preferably CSI-RS) transmitted on the plurality of downlink beams by the base station.

[0148] According to a 21st aspect that can be combined with the 19th or 20th aspect, the number of uplink beams forming a subset of the plurality of uplink beams corresponds to one, two, or three uplink beams.

[0149] According to a 22nd aspect that can be combined with one of the 19th to 21st aspects, the number of uplink beams forming a subset of the plurality of uplink beams corresponds to the mobility state of the mobile terminal, which distinguishes between low-rate and high-rate position changes of the mobile terminal.

[0150] According to a 23rd aspect that can be combined with one of the 19th to 22nd aspects, the mobility state of the mobile terminal is preferably determined based on the number of reconfiguration commands for downlink beams transmitted to the mobile terminal by the base station over a time period, or is determined based on the number of preferably position changes determined from positioning measurements in the mobile terminal over a time period and signaled to the base station.

[0151] According to a 24th aspect that can be combined with one of the 19th to 23rd aspects, the method includes the step of additionally receiving, for the beam failure recovery procedure, an indication of the number of uplink beams in a subset of the plurality of uplink beams that will be used in the beam failure recovery procedure.

[0152] According to a 25th aspect that can be combined with the 24th aspect, a sign indicating the number of uplink beams in a subset of a plurality of uplink beams to be used is received in a radio resource configuration (RRC) message, or a medium access control (MAC) control element (CE), or downlink control information (DCI).

[0153] According to a 26th aspect, another method for starting a beam failure recovery procedure is proposed, which is implemented by a mobile terminal configured to communicate with a base station using at least one of a plurality of downlink beams and at least one of a plurality of uplink beams, and each of the uplink beam and the downlink beam has different directivities. This method includes receiving an allocation of individual uplink radio resources for a beam failure recovery signal for a beam failure recovery (BFR) procedure, and detecting a downlink beam failure event and starting a beam failure recovery procedure in response thereto, and the beam failure recovery procedure includes transmitting a beam failure recovery signal using the allocated individual uplink radio resources. The individual uplink radio resources limit transmission to a subset of a plurality of uplink beams that can be non-exclusively allocated to the mobile terminal by the base station.

[0154] According to a 27th aspect that can be combined with the 26th aspect, transmitting on a subset of a plurality of uplink beams where a beam failure recovery signal on an individual uplink radio resource is restricted enables the base station to identify the mobile terminal.

[0155] According to a 28th aspect that can be combined with the 26th or 27th aspect, when an individual uplink radio resource includes a physical uplink control channel (PUCCH), transmitting a demodulation reference signal (DM-RS) together with a beam failure recovery signal in the PUCCH enables the base station to identify the mobile terminal.

[0156] According to a 29th aspect that can be combined with one of the 26th to 28th aspects, the allocation of individual uplink radio resources includes an instruction that orders the mobile terminal to include the identification information of the mobile terminal in a subsequent message of the beam failure recovery procedure.

[0157] According to a 30th aspect that can be combined with one of the 19th to 29th aspects, the individual uplink radio resource corresponds to one of the contention-free resources of the physical uplink control channel (PUCCH) (preferably, uplink control information (UCI) including time and frequency references).

[0158] According to a 31st aspect that can be combined with one of the 19th to 30th aspects, the allocation of individual uplink radio resources is received via one of a radio resource configuration (RRC) connection reconfiguration or RRC connection setup message, a downlink medium access control (MAC) control element (CE), downlink control information (DCI), and a control protocol data unit (PDU) of a packet data convergence protocol (PDCP).

[0159] According to a 32nd aspect that can be combined with one of the 19th to 30th aspects, the allocation of individual uplink radio resources includes receiving the configuration of the individual uplink radio resources via an RRC connection establishment or reconfiguration message and the activation of the individual uplink radio resources from the configuration via one of a MAC CE, DCI, and PDCP control PDU.

[0160] According to a 33rd aspect that can be combined with one of the 19th to 32nd aspects, the allocation of individual uplink radio resources is valid either over a time period or until a new allocation is received.

[0161] According to a 34th aspect that can be combined with the 33rd aspect, the time period during which the allocation of individual uplink resources is valid is indicated in the allocation.

[0162] According to a 35th aspect that can be combined with one of the 19th to 34th aspects, the method includes a step in which a base station transmits a label for (re)starting the allocation of individual uplink radio resources for a beam failure recovery procedure.

[0163] According to a 36th aspect that can be combined with the 35th aspect, the label for (re)starting the allocation of individual uplink radio resources is either channel state information (CSI) report that signals the quality or power of a serving downlink beam below a threshold, or an individual transmission (preferably in the form of either an RRC message or an uplink MAC CE) that signals an explicit request to (re)start the allocation of individual uplink radio resources.

[0164] According to a 37th aspect, a base station for communicating with a mobile terminal in a mobile communication system using at least one of a plurality of downlink beams and at least one of a plurality of uplink beams is proposed, each of the downlink beam and the uplink beam having different directivities and / or coverages. The base station includes a processor that performs a beam failure recovery procedure during operation, and the beam failure recovery procedure includes a transceiver receiving a beam failure recovery signal from the mobile terminal using individual uplink radio resources from the allocation. The individual uplink radio resources limit transmission to a subset of a plurality of uplink beams that can be exclusively allocated to the mobile terminal by the base station.

[0165] According to the 38th aspect, another base station is proposed for communicating with a mobile terminal in a mobile communication system using at least one of a plurality of downlink beams and at least one of a plurality of uplink beams, each of the downlink beam and the uplink beam having different directivity and / or coverage. This base station includes a processor that starts a beam failure recovery procedure during operation, and the beam failure recovery procedure includes the transceiver receiving a beam failure recovery signal from the mobile terminal using individual uplink radio resources from the allocation. The individual uplink radio resources limit transmission to a subset of the plurality of uplink beams that can be non-exclusively allocated to the mobile terminal by the base station.

[0166] According to the 39th aspect, a method for starting a beam failure recovery procedure is proposed, which is implemented by a base station configured to communicate with a mobile terminal in a mobile communication system using at least one of a plurality of downlink beams and at least one of a plurality of uplink beams, each of the downlink beam and the uplink beam having different directivity and / or coverage. This method includes starting the beam failure recovery procedure in response to receiving a beam failure recovery signal from the mobile terminal using individual uplink radio resources from the allocation, and the individual uplink radio resources limit transmission to a subset of the plurality of uplink beams that can be exclusively allocated to the mobile terminal by the base station.

[0167] According to a 40th aspect, another method for initiating a beam failure recovery procedure is proposed, which is implemented by a base station configured to communicate with a mobile terminal in a mobile communication system using at least one of a plurality of downlink beams and at least one of a plurality of uplink beams, wherein each of the downlink beam and the uplink beam has a different directivity and / or coverage. This method includes the step of initiating a beam failure recovery procedure in response to receiving, from the mobile terminal, a beam failure recovery signal using an individual uplink radio resource from an allocation, where the individual uplink radio resource restricts transmission to a subset of a plurality of uplink beams that can be non-exclusively allocated to the mobile terminal by the base station.

Claims

1. A transceiver that receives a configuration of a Physical Random Access Channel (PRACH) resource for transmitting a beam failure recovery signal during operation; A processor that detects a downlink beam failure event during operation and initiates a beam failure recovery procedure (BFR) in response thereto, wherein the beam failure recovery procedure includes the transceiver transmitting the beam failure recovery signal using the PRACH resource; The configuration includes a timer indicating a time period during which the PRACH resource is valid, and a flag indicating the number of PRACH resources in a subset of a plurality of PRACH resources; During operation, the transceiver limits the PRACH resource used for the transmission to the subset based on the flag among the plurality of PRACH resources assigned to the communication device by a base station; When the timer expires, use of the PRACH resource is disabled; A communication device.

2. The configuration is valid until a new configuration is received; The communication device according to claim 1.

3. The number of PRACH resources forming the subset of the plurality of PRACH resources corresponds to one, two, or three PRACH resources; The communication device according to claim 1.

4. The flag is · Received in at least one of a Radio Resource Configuration (RRC) message; · A Medium Access Control (MAC) Control Element (CE); · Downlink Control Information (DCI); The communication device according to claim 1.

5. The configuration of the PRACH resource is · Received via one of a Radio Resource Configuration (RRC) connection reconfiguration or RRC connection setup message; · A downlink Medium Access Control (MAC) Control Element (CE); · Downlink Control Information (DCI); · A control protocol data unit (PDU) of a Packet Data Convergence Protocol (PDCP); Including being received via one of; The communication device according to claim 1.

6. Receiving a configuration of a Physical Random Access Channel (PRACH) resource for transmitting a beam failure recovery signal; ​ Detecting a downlink beam failure event and, in response, starting a beam failure recovery procedure (BFR), the beam failure recovery procedure including transmitting the beam failure recovery signal using the PRACH resource, The configuration includes a timer indicating a time period during which the PRACH resource is valid and an indication indicating the number of PRACH resources in a subset of a plurality of PRACH resources, Restricting the PRACH resource used for the transmission to the subset based on the indication among the plurality of PRACH resources allocated by the base station to the communication device, When the timer expires, the use of the PRACH resource becomes unavailable, Method. **Claim 7** A transceiver that transmits, during operation, a configuration of a physical random access channel (PRACH) resource for a communication device to transmit a beam failure recovery signal, and A processor that performs a beam failure recovery procedure (BFR) during operation, the beam failure recovery procedure including the transceiver receiving the beam failure recovery signal using the PRACH resource from the communication device, The configuration includes a timer indicating a time period during which the PRACH resource is valid and an indication indicating the number of PRACH resources in a subset of a plurality of PRACH resources, The PRACH resource is restricted to the subset based on the indication of the plurality of PRACH resources allocated by the base station to the communication device, When the timer expires, the use of the PRACH resource becomes unavailable, Base station. **Claim 8** During operation, transmitting a configuration of a physical random access channel (PRACH) resource for a communication device to transmit a beam failure recovery signal, and During operation, performing a beam failure recovery procedure (BFR), The beam failure recovery procedure includes receiving, from the communication device, the beam failure recovery signal using the PRACH resource, The configuration includes a timer indicating a time period during which the PRACH resource is valid and an indication indicating the number of PRACH resources in a subset of a plurality of PRACH resources, Among the plurality of PRACH resources allocated by the base station to the communication device, the PRACH resource is restricted to the subset based on the identifier. When the timer expires, the use of the PRACH resource becomes unavailable. Method.

9. An integrated circuit for controlling the processing of a communication device, wherein the processing, during operation, includes a process of receiving a configuration of a physical random access channel (PRACH) resource for transmitting a beam failure recovery signal, and a process of detecting a downlink beam failure event and starting a beam failure recovery procedure (BFR) in response thereto, wherein the beam failure recovery procedure includes transmitting the beam failure recovery signal using the PRACH resource. The configuration includes a timer indicating a time period during which the PRACH resource is valid, and an identifier indicating the number of PRACH resources in a subset of the plurality of PRACH resources. includes a process of restricting the PRACH resource to be used for the transmission to the subset based on the identifier among the plurality of PRACH resources allocated by the base station to the communication device. When the timer expires, the use of the PRACH resource becomes unavailable. Integrated circuit.

10. An integrated circuit for controlling the processing of a base station, wherein the processing, during operation, includes a process of transmitting a configuration of a physical random access channel (PRACH) resource for the communication device to transmit a beam failure recovery signal during operation, and a process of implementing a beam failure recovery procedure (BFR), wherein the beam failure recovery procedure includes receiving the beam failure recovery signal using the PRACH resource from the communication device. The configuration includes a timer indicating a time period during which the PRACH resource is valid, and an identifier indicating the number of PRACH resources in a subset of the plurality of PRACH resources. The PRACH resource is restricted to the subset based on the identifier among the plurality of PRACH resources allocated by the base station to the communication device. When the timer expires, the use of the PRACH resource becomes unavailable. Integrated circuit.

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