A method and apparatus for beam switching

Abstract

Embodiments of the present disclosure relate to beam switching. An apparatus, method, and computer program are described comprising: receiving, at a user equipment, a downlink reference signal from a communication node of a mobile communication system, wherein the downlink reference signal is received by one of a plurality of beams of a receiver of the user equipment in accordance with a configured beam alignment; determining, based at least in part on a signal power of the received downlink reference signal, whether a beam switch is to be initiated to reconfigure the beam alignment at the receiver; and in the event that the beam switch is to be initiated, determining whether to initiate a communication node assisted beam switch or a non-communication node assisted beam switch.

Description

TECHNICAL FIELD

[0001] This specification relates to beam switching, for example in mobile communication systems. BACKGROUND

[0002] A communication node (e.g. a base station) of a mobile communication system can comprise a plurality of beams which can be used to establish a communication link with a user equipment. Similarly, a user equipment can comprise a plurality of beams which can be used to establish a communication link with a base station or other communication node. Although beam switching in such systems has been developed, further development is desirable. SUMMARY

[0003] In a first aspect, this specification describes an apparatus comprising means for performing: receiving, at a user equipment, a downlink reference signal from a communication node (e.g. a base station or gNB) of a mobile communication system, wherein the downlink reference signal is received by one of a plurality of beams of a receiver of the user equipment in accordance with a configured beam alignment; determining, based at least in part on a signal power (e.g. RSRP) of the received downlink reference signal, whether a beam switch is to be initiated to reconfigure the beam alignment at the receiver; and in the event that the beam switch is to be initiated, determining whether to initiate a communication node assisted beam switch (e.g. a “non-adjacent” beam switch) or a non-communication node assisted beam switch (e.g. an “adjacent” beam switch).

[0004] Some example embodiments further comprise means for performing: in the event that it is determined that the communication node assisted beam switch is to be initiated, transmitting a signal to the communication node triggering communication node assistance.

[0005] Some example embodiments further comprise means for performing: in the event that it is determined that the non-communication node assisted beam switch is to be initiated, initiating an autonomous beam switch at the user equipment.

[0006] Some example embodiments further comprise means for performing: determining a signal power of the received downlink reference signal; and comparing the determined signal power to a threshold power level for use in determining whether the beam switch is to be initiated. For example, it can be determined whether the signal power has fallen below a relevant threshold power level.

[0007] Some example embodiments also include means for performing the following: identifying whether a channel between the communication node and the user equipment supports one or more available candidate links in addition to the first link for the configured beam alignment. For example, the available candidate links can provide another UE beam to the same serving communication node (e.g., serving gNB). The link can be “available” based on whether the signal level (e.g., RSRP) is above a threshold level and / or whether the corresponding beam is from a secondary angle group. The means for identifying whether a channel between the communication node and the user equipment supports one or more available candidate links in addition to the first link for the configured beam alignment can include analyzing a power delay profile (PDP) of the received downlink reference signals (e.g., determining whether any PDP signals are above a threshold level).

[0008] The apparatus can also include means for performing the following: determining whether a Doppler shift of the received downlink reference signals is above a threshold level; initiating a non-communication node assisted beam switch in the event that the beam switch is initiated, no available candidate links in addition to the first link are identified, and the Doppler shift of the received downlink reference signals is not above the threshold level; and not initiating a beam switch in the event that no available candidate links in addition to the first link are identified and the Doppler shift is above the threshold level. Alternatively or additionally, the apparatus can also include means for performing the following: initiating a communication node assisted beam switch in the event that the beam switch is initiated, one or more available candidate links in addition to the first link are identified, and the available candidate links include at least one link that is oriented in a different direction than the first link for the configured beam alignment and / or on a different receiver panel of the user equipment; and initiating a non-communication node assisted beam switch in the event that the beam switch is initiated, one or more available candidate links in addition to the first link are identified, and the available candidate links do not include any links that are oriented in a different direction than the first link.

[0009] The apparatus can include at least one processor; and at least one memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus to perform.

[0010] In a second aspect, the present specification describes a method comprising: receiving, at a user equipment, a downlink reference signal from a communication node of a mobile communication system, wherein the downlink reference signal is received by one of a plurality of beams of a receiver of the user equipment in accordance with a configured beam alignment; determining, based at least in part on a signal power of the received downlink reference signal, whether to initiate a beam switch to reconfigure the beam alignment at the receiver; and in a case where the beam switch is to be initiated, determining whether to initiate a communication node assisted beam switch or a non-communication node assisted beam switch.

[0011] The method can further comprise, in a case where it is determined that the communication node assisted beam switch is to be initiated, transmitting, to the communication node, a signal triggering communication node assistance.

[0012] The method can further comprise, in a case where it is determined that the non-communication node assisted beam switch is to be initiated, initiating, at the user equipment, an autonomous beam switch.

[0013] The method can further comprise one or more of: identifying whether a channel between the communication node and the user equipment supports one or more available candidate links other than a first link, the first link being used for the configured beam alignment; determining whether a Doppler shift of the received downlink reference signal is above a threshold level; in a case where the beam switch is initiated, no available candidate links other than the first link are identified, and the Doppler shift of the received downlink reference signal is not above the threshold level, initiating the non-communication node assisted beam switch; and in a case where no available candidate links other than the first link are identified, and the Doppler shift is above the threshold level, not initiating the beam switch. The method can further comprise, in a case where the beam switch is initiated, one or more available candidate links other than the first link are identified, and the available candidate links comprise at least one link that is directed in a different direction to the first link used for the configured beam alignment and / or on a different receiver panel of the user equipment, initiating the communication node assisted beam switch; and in a case where the beam switch is initiated, one or more available candidate links other than the first link are identified, and the available candidate links do not comprise any links that are directed in a different direction to the first link, initiating the non-communication node assisted beam switch.

[0014] In a third aspect, the present specification describes an apparatus configured to (at least) perform any method as described with reference to the second aspect.

[0015] In a fourth aspect, the present specification describes computer readable instructions which, when executed by a computing apparatus, cause the computing apparatus to (at least) perform any method as described with reference to the second aspect.

[0016] In a fifth aspect, the present specification describes a computer readable medium (e.g. a non-transitory computer readable medium) comprising program instructions stored thereon for (at least) performing any of the methods described with reference to the second aspect.

[0017] In a sixth aspect, the present specification describes an apparatus comprising: at least one processor; and at least one memory including computer program code, the computer program code, when executed by the at least one processor, causing the apparatus (at least) to perform any of the methods described with reference to the second aspect.

[0018] In a seventh aspect, the present specification describes a computer program comprising instructions for causing an apparatus to perform at least the following: at a user equipment, receiving a downlink reference signal from a communication node of a mobile communication system, wherein the downlink reference signal is received by one of a plurality of beams of a receiver of the user equipment according to a configured beam alignment; determining, based at least in part on a signal power of the received downlink reference signal, whether a beam switch is to be initiated to reconfigure the beam alignment at the receiver; and in a case where the beam switch is to be initiated, determining whether to initiate a communication node assisted beam switch or a non-communication node assisted beam switch.

[0019] In an eighth aspect, the present specification describes an apparatus comprising: a receiver (or some other means) for receiving, at a user equipment, a downlink reference signal from a communication node of a mobile communication system, wherein the downlink reference signal is received by one of a plurality of beams of a receiver of the user equipment according to a configured beam alignment; a first control module (or some other means) for determining, based at least in part on a signal power of the received downlink reference signal, whether a beam switch is to be initiated to reconfigure the beam alignment at the receiver; and a second control module (or some other means) for determining, in a case where the beam switch is to be initiated, whether to initiate a communication node assisted beam switch or a non-communication node assisted beam switch. BRIEF DESCRIPTION OF DRAWINGS

[0020] Example embodiments will now be described, by way of non-limiting examples only, with reference to the accompanying schematic drawings in which:

[0021] Figure 1 is a block diagram of a system according to an example embodiment;

[0022] Figure 2 is a block diagram of a system according to an example embodiment;

[0023] Figure 3 is a flowchart illustrating an algorithm according to an example embodiment;

[0024] Figure 4A message sequence is shown in accordance with example embodiments;

[0025] Figure 5 is a flowchart showing an algorithm in accordance with example embodiments;

[0026] Figures 6 to 9 is a block diagram of a user equipment in accordance with example embodiments;

[0027] Figure 10 is a flowchart showing an algorithm in accordance with example embodiments;

[0028] Figures 11 to 13 is a block diagram of a system in accordance with example embodiments;

[0029] Figure 14 is a flowchart showing an algorithm in accordance with example embodiments;

[0030] Figure 15 is a block diagram of a user equipment in accordance with example embodiments;

[0031] Figure 16 is a block diagram of a user equipment in accordance with example embodiments;

[0032] Figures 17 to 20 is a plot showing a signal in accordance with example embodiments;

[0033] Figure 21 is a block diagram of components of a system in accordance with example embodiments; and

[0034] Figure 22A and Figure 22B respectively show tangible media storing computer readable code that, when executed by a computer, performs operations in accordance with example embodiments, respectively a removable non-volatile memory unit and a compact disc (CD). DETAILED DESCRIPTION

[0035] The scope of protection sought for various embodiments of the present invention is defined by the appended independent claims. The embodiments and features that are not part of the independent claims and that are described in the specification, if any, should be interpreted as examples useful for understanding the various embodiments of the present invention.

[0036] In the description and drawings, like numbers refer to like elements throughout.

[0037] Figure 1 is a block diagram of a system in accordance with example embodiments, generally indicated by the reference numeral 10. The system 10 comprises a mobile base station 12 (such as a next generation Node B (gNB)), a first user equipment 14 and a second user equipment 16. Bi-directional communication is provided between each user equipment and the base station 12.

[0038] Figure 2 is a block diagram of a system according to an example embodiment, the system being indicated generally by reference numeral 20. The system 20 comprises a node 21 of a mobile communications system, such as one of the base stations 12, or one of the user devices 14 and 16 described above. In use, the node 21 communicates with one or more other nodes of the communications system.

[0039] As shown in Figure 2 , the node 21 comprises a plurality of beams, such as a beam 22, which can be used to establish a communications link (e.g. between a base station and one or more user devices, between a user device and one or more base stations, or between one user device and another user device). As discussed in detail below, a beam selection algorithm can be provided to select one of the beams 22 for communication (e.g. by selecting the best or strongest available beam according to some metric such as received signal strength and / or signal to noise ratio).

[0040] Figure 3 is a flow chart illustrating an algorithm according to an example embodiment, the algorithm being indicated generally by reference numeral 30.

[0041] The algorithm 30 has a first phase, indicated generally by reference numeral 32, in which a transmission beam sweep is used to determine a best wide base station beam for transmissions between a base station, such as the base station 12 described above, and an associated user device, such as one of the user devices 14 and 16 described above. The first phase 32 can be implemented by the base station 12 by transmitting a first sequence of beams from the base station to the user device. The user device measures the reference signal received power (RSRP) or some other signal quality indicator, such as a channel quality indicator (CQI) or a rank indicator (RI), of the plurality of beams to determine a best (e.g. strongest) beam of the wide beams of the first phase.

[0042] The algorithm 30 has a second phase, indicated generally by reference numeral 34, in which a transmission beam sweep is used to determine a best narrower base station beam for transmissions between the base station and the associated user device. The second phase can be implemented by the base station by transmitting a second sequence of beams from the base station to the user device. The second sequence of beams is within a range identified in the operation 32 as a range of the best of the first sequence of beams.

[0043] In the second phase 34, the associated user device measures the RSRP (or some other signal quality indicator, such as a CQI or a RI) of the plurality of beams to determine a best beam of the narrower beams of the second phase. This best beam is selected for transmissions from the base station to the user device.

[0044] The algorithm 30 has a third stage, generally indicated by reference numeral 36, in which receiver beam sweeping is used to determine the best user equipment beam for transmissions between the base station and the associated user equipment. The third stage can be implemented by the base station by transmitting a third beam sequence from the base station to the user equipment. The third beam sequence is transmitted with the beam identified in the second stage as the best transmission beam, and the user equipment performs beam sweeping to identify the best narrow RX beam for transmissions between the base station and the user equipment.

[0045] Thus, base station beam sweeping occurs in operations 32 and 34, and user equipment beam sweeping occurs in operation 36, in order to determine the best base station and user equipment beams for communication.

[0046] Figure 4 A message sequence according to an example embodiment is shown, generally indicated by reference numeral 40. The message sequence 40 in an example implementation of the algorithm 30 shows messages transmitted between a user equipment (UE) and a communication node (gNB). The message sequence 40 is a beam alignment procedure as specified in 5G New Radio (NR) Release 15 as described in 3GPP TR 38.802 Section 6.1.6 and TS 38.214 Section 5.2. In one example embodiment, the UE is an implementation of one of the user equipment 14 and 16, and the gNB is an implementation of the base station 12.

[0047] The message sequence 40 includes a first stage 43 (implementing the first stage 32 of the above-described algorithm 30), in which up to 64 synchronization signal beams (SSBs) are transmitted from the gNB to the UE, while assuming that the UE is configured with a wide Rx beam to receive signals from a wide angle. The best measured synchronization signal beam (e.g., based on RSRP or other quality indicator) is used to determine the random access beam. The UE reports the best SSB back to the gNB according to a relevance metric at the next allocated time instance (e.g., the next random access channel (RACH) group).

[0048] The message sequence 40 includes a second stage 44 (implementing the second stage 34 of the above-described algorithm 30), in which the gNB transmits refined downlink (DL) channel state information (CSI) beams, while assuming that the UE is still configured with a wide RX beam. The UE measures the RSRP (or some other quality metric) on the received CSI-RS and reports the best beam ID to the gNB. For example, as shown, the second stage 44 can be used to determine the best transmission beam of 8 narrower transmission beams from within the best wide transmission beam identified in the first stage 43. Figure 4

[0049] ​The message sequence 40 includes a third stage 45 (implementing the third stage 36 of the above-described algorithm 30), in which the gNB repeats the best CSI beam identified in the second stage 44, so that the UE can sweep its refined RX beam to align its narrow UE RX beam.

[0050] At the end of the third stage 45, the alignment between the best gNB TX beam and the best UE RX beam is achieved to realize the maximum directional gain and / or the minimum interference to other users in the serving cell and neighboring cells. Data communication can then take place, as shown by message 46.

[0051] In the message sequence 40, after the first stage 43, the UE is in RRC_Connected. The second and third stages are part of initial access, and can also be used for beam tracking and monitoring throughout the connection.

[0052] It should be noted that the algorithms 30 and 40 are provided as examples only, and that numerous variants are possible. For example, in some example embodiments, the second stage 34 or 44 can be omitted.

[0053] In the message sequence 40, the UE can rely on the reference signals associated with the NZP-CSI-RS-ResourceSet configured with the higher layer parameter repetition set to “ON” from the gNB in order to perform its beam alignment procedure in the third stage 45. The repetition parameter indicates to the UE that the NZP-CSI-RS-ResourceSet is transmitted using the same downlink spatial filter (see TS 38.214 section 5.1.6.1.2). The scheduling of such reference signals is controlled by the gNB and sent in an aperiodic manner. This means that the UE does not request the alignment reference signals from the gNB, and the UE is limited to waiting for the gNB to schedule such reference signals to align its Rx beam.

[0054] However, the gNB does not have all the knowledge of the UE’s internal beam and panel management, so the gNB can schedule the NZP-CSI-RS-ResourceSet in a suboptimal manner.

[0055] In order to seek to trigger the CSI-RS resources with repetition “ON” in an optimal manner, two types of beam switch are discussed in detail below, namely:

[0056] • Communication node assisted beam switch (or UE non-adjacent beam switch (N-ABS)); and

[0057] • Non-communication node assisted beam switch (or UE adjacent beam switch (ABS))

[0058] Figure 5is a flowchart illustrating an algorithm according to an example embodiment, the algorithm generally indicated by reference numeral 50.

[0059] The algorithm 50 starts at operation 52, where a downlink reference signal is received at a user equipment (UE) from a communication node (e.g., a base station or gNB) of a mobile communication system. The downlink reference signal can be received according to a configured beam alignment through one of a plurality of beams of a receiver of the user equipment.

[0060] At operation 54, a beam switch requirement is determined. Operation 54 has two parts, which can be implemented as a single step (as suggested in the message sequence 50) or two separate steps (as discussed further below).

[0061] First, it can be determined whether a beam switch is to be initiated to reconfigure the beam alignment at the above-mentioned receiver. This determination can be based at least in part on the strength (e.g., RSRP or some other metric) of the received downlink reference signal. If it is determined that no beam switch needs to be performed, the algorithm terminates at operation 58.

[0062] If it is determined that a beam switch is to be initiated, it is determined whether a communication node assisted beam switch (e.g., non-adjacent beam switch) or a non-communication node assisted beam switch (e.g., adjacent beam switch) is to be initiated.

[0063] If a communication node assisted beam switch is to be initiated, the algorithm 50 moves from operation 54 to operation 56, where a signal triggering communication node assistance is sent to the communication node (such as the third phase 45 of the above-mentioned message sequence 40). The algorithm 50 then terminates at operation 58.

[0064] If a non-communication node assisted beam switch is to be initiated, the algorithm 50 moves from operation 54 to operation 57, where an autonomous beam switch at the user equipment is triggered. The algorithm 50 then terminates at operation 58.

[0065] Figure 6 is a block diagram of a user equipment (UE) according to an example embodiment, the UE generally indicated by reference numeral 60. The user equipment 60 comprises a plurality of beams organized into three groups (provided by three panels). The first group comprises beams 1.1 to 1.7, the second group comprises beams 2.1 to 2.7, and the third group comprises beams 3.1 to 3.7. Thus, there are 21 beams available for receiving transmission signals, e.g., from a gNB. Figure 6 The illustrated signal channels are directional and comprise a single dominant angle power group (APG) with an angle of arrival (AoA) such that beam 2.4 represents the best beam for receiving transmission signals.

[0066] Figure 7 is a block diagram of a user equipment 60. In Figure 7 In the configuration shown, the user equipment 60 has rotated relative to the transmission signal (e.g., relative to the respective gNB) such that beam 2.5 now represents the best beam for receiving the transmission signal.

[0067] Adjacent beam switching (or non-communication node assisted beam switching) can be implemented at the user equipment 60 because the channel for transmission is directional and includes a single dominant angular power group (APG), and the user equipment is rotating or moving relative to the gNB. This scenario can be valid for a dominant radio channel cluster with a narrow angular spread (e.g., a LOS channel or a NLOS CDL-A channel model). Here, the user equipment 60 switches from beam 2.4 to adjacent beam 2.5 and within the same panel. However, the same scenario can result in a beam switch from beam 2.7 to adjacent beam 3.1 (i.e., between different panels) and still be considered an adjacent beam switch. If the user equipment knows which beam to switch to and when to switch (i.e., ensuring the required panel is active), the hardware and software procedures for performing beam switching at the user equipment can be similar for intra-panel adjacent beam switching and inter-panel adjacent beam switching.

[0068] Such adjacent beam switching can be implemented autonomously at the user equipment (i.e., without assistance from a communication node) because the user equipment can relatively easily predict the next best user equipment beam to switch to.

[0069] Figure 8 is a block diagram of a user equipment (UE) in accordance with example embodiments, indicated generally by the reference numeral 80. Like the user equipment 60, the user equipment 80 includes multiple beams organized into three groups (provided by three panels). The first group includes beams 1.1 through 1.7, the second group includes beams 2.1 through 2.7, and the third group includes beams 3.1 through 3.7. Figure 8 The signal channel shown is multi-directional and includes more than one dominant angular power group (APG) with angle of arrival (AoA) such that both beam 2.4 and beam 1.7 represent good candidates for receiving the transmission signal.

[0070] In Figure 8 beam 2.4 is used for transmission and is considered the first APG (beam 1.7 is the second APG). Figure 9 is a block diagram of the user equipment 80 in which beam 1.7 is used for transmission and is considered the first APG (beam 2.4 is the second APG).

[0071] When the channel is multi-directional and includes more than one dominant APG (e.g., CDL-B and CDL-C channel models), and the user equipment is rotating and / or moving relative to the gNB, a non-adjacent beam switch (or communication node assisted beam switch) can occur at the user equipment. However, such a switch can also occur for a static user equipment due to channel changes caused, for example, by blockage of the dominant APG (or dominant radio channel cluster).

[0072] Performing a non-adjacent beam switch can require assistance because the user equipment is likely not aware of the exact angular direction of the second APG (and can only know which panel to use). For example, the third phase 45 of the above message sequence 40 can be triggered.

[0073] Of course, the above configurations of user equipment 60 and 80 are provided by way of example only. In example embodiments, alternative user equipment having a different number of panels or a different number of beams for each panel can be used.

[0074] Figure 10 is a flowchart illustrating an algorithm according to example embodiments, generally indicated by the reference numeral 100.

[0075] The algorithm 100 begins at the above operation 52, in which a downlink reference signal is received at the user equipment from a communication node (e.g., a base station or gNB) of a mobile communication system. In operation 52, the downlink reference signal is received by one of a plurality of beams of a receiver of the user equipment according to a configured beam alignment (e.g., as illustrated by beam 2.4 in Figure 6 and Figure 8 The algorithm then moves to operation 101.

[0076] In operation 101, the signal power (e.g., RSRP or some other metric such as SNR, SINR, CQI, etc.) of the received downlink reference signal is determined and compared to a threshold power level to determine whether the signal power has dropped below the threshold. If so (indicating that a beam switch can be needed), the algorithm moves to operation 103. If not, the algorithm terminates at operation 102, in which no beam switch occurs.

[0077] In operation 103, it is determined whether the current properties of the channel between the above gNB and the above UE support a candidate link in addition to the first link used for the configured beam alignment. For example, Figure 6 and Figure 7 As illustrated by the channel properties in Figure 8 and Figure 9 the channel properties support a second link (referred to as an available candidate link).

[0078] A“usable candidate link” can be defined as an alternative link to the current serving link that has a sufficiently high signal strength (e.g., RSRP) to the relevant communication node. As discussed further below, the power delay profile (PDP) of the received signal can be analyzed to determine the presence of a usable candidate link, which is determined by the channel properties between the gNB and the UE.

[0079] If other usable candidate links are identified in operation 103, then the algorithm 100 moves to operation 105; otherwise, the algorithm 100 moves to operation 104.

[0080] In operation 104, it is determined whether the Doppler shift of the received downlink reference signal is above a threshold level. If so, the fact that only the first link (as determined in operation 103) has a high Doppler shift (as determined in operation 104) indicates that the user equipment is moving away from the connected communication node, and this is the likely source of the low power identified in operation 101. Therefore, no beam switch is required, and the algorithm 100 terminates at operation 102 without performing a beam switch.

[0081] If it is determined in operation 104 that the Doppler shift is not above the threshold level, this indicates that the user equipment can be rotating, rather than moving away from the connected communication node, or that there is some other cause of the low power signal. Therefore, a beam switch to a neighboring beam can be required, and so the algorithm 100 terminates at operation 106, where a non-communication node assisted beam switch (or neighboring beam switch) is performed.

[0082] Figure 11 is a block diagram of a system in accordance with example embodiments, which is indicated generally by the reference numeral 110. The system 110 illustrates the scenario described above, in which the user equipment 112 is moving away from the gNB 114, resulting in a reduction in signal power (identified in operation 101) and a high Doppler shift (identified in operation 104). As shown by the system 110, the current connected beam can still be the best beam to use, and therefore no beam switch is required.

[0083] Figure 12 is a block diagram of a system in accordance with example embodiments, which is indicated generally by the reference numeral 120. The system 120 illustrates the scenario described above, in which the user equipment 112 is rotating relative to the gNB 114, resulting in a reduction in signal power (identified in operation 101) but no Doppler shift (identified in operation 104). A neighboring beam can represent the best beam to use, and therefore a neighboring beam switch should be triggered.

[0084] At operation 105 of algorithm 100, having determined that other available links are available, it is determined whether the available candidate links include at least one direction that is different from the direction of the first link used for the configured beam alignment and / or on a different receiver panel of the user equipment. The available candidate links can be considered to have a "different" direction from the connecting link in many respects, e.g., if its direction differs from the direction of the connecting link by more than a threshold amount, or if it is received by a different panel.

[0085] If it is determined in operation 105 that there are no available candidate links from a direction different from the direction of the configured beam alignment, then algorithm 100 terminates at operation 106, where a neighbor beam switch is performed.

[0086] If it is determined in operation 105 that at least one of the available candidate links is from a direction different from the direction of the configured beam alignment and / or on a different receiver panel of the user equipment, then algorithm 100 terminates at operation 107, where a non-neighbor beam switch is performed.

[0087] In this way, algorithm 100 seeks to intelligently trigger a UE beam alignment request when needed, i.e., when the UE should perform a non-neighbor beam switch. This can prevent unnecessary CSI-RS signals from being sent from the gNB and processed at the UE, e.g., unnecessary third stage transmissions. For example, the user equipment can determine whether it should perform an autonomous neighbor beam switch or a gNB- assisted non-neighbor beam switch based on characteristics of the current channel conditions, e.g., the number of strong and available APGs, and then use a Doppler shift calculation to determine whether the APGs are arriving at different angular directions (see Section 6 for more detailed explanation).

[0088] Figure 13 is a block diagram of a system in accordance with example embodiments, generally indicated by reference numeral 130. System 130 illustrates an example scenario in which two different angular power groups (APGs) are received at a user equipment (UE) from similar angular directions but with different delays. In this case, an autonomous neighbor beam switch by the UE can be the best option for the user equipment, as the UE has some knowledge of the angular direction of the incoming signals.

[0089] Figure 14 is a flowchart illustrating an algorithm in accordance with example embodiments, generally indicated by reference numeral 140. Algorithm 140 is similar to algorithm 100 described above.

[0090] Algorithm 140 begins at step 1, which is a wait state. When a next received reference signal is received at the user equipment, algorithm 140 moves to step 2. Thus, step 1 is similar to operation 52 of algorithms 50 and 100 described above.

[0091] Step 2 determines whether the reference signal received in Step 1 is a Synchronization Signal Block (SSB) signal. If so, the algorithm 140 moves to Step 3; otherwise, the algorithm 140 moves to Step 4.

[0092] In Step 3, the Power Delay Profile (PDP) and Doppler shift of the SSB beams received at the user equipment in Step 1 on all panels are determined and stored. This can form part of a standard panel sweep procedure (as discussed above with reference to Figure 3 and Figure 4 ).

[0093] Step 4 starts from the determination (in Step 2) that the received signal is not an SSB beam. Step 4 determines whether the received signal is a Channel State Information Reference Signal (CSI-RS) with repetition “ON”. Such a signal can be transmitted as part of the third phase 45 of the message sequence 40 described above.

[0094] If the received signal is a CSI-RS signal with repetition “ON”, the algorithm moves to Step 5, in which beam alignment is performed at the user equipment with the help of the gNB, and a new reference RSRP value is measured and stored. The algorithm then returns to the waiting state (Step 1). Otherwise, the algorithm moves to Step 6, in which the RSRP and Doppler shift of the received signal are measured and stored. The algorithm then proceeds to Step 7. It is noted that RSRP is described here by way of example only; in some example embodiments, many other metrics (such as SNR, SINR, CQI, etc.) can be considered instead of or in addition to RSRP.

[0095] In Step 7, the RSRP value measured in Step 6 is compared to a threshold power level. This threshold power level is previously stored (for example, in a previous iteration of Step 5 discussed above or Step 10 discussed below). If the RSRP value is below the reference RSRP value (possibly with some error margin, such as 3dB), the algorithm 140 moves to Step 8. Otherwise, the algorithm returns to the waiting state (Step 1), so that no beam switch is performed.

[0096] With Step 8, it has been determined that the received downlink reference signal is neither an SSB signal nor a CSI-RS with repetition “ON”, and the RSRP is below the reference / threshold.

[0097] At step 8, if the channel contains more than one available angular power group (APG) from the corresponding SSB, the algorithm moves to step 12. Otherwise, the algorithm moves to step 9. An “available” APG can be one that has a good enough RSRP level for communication - a threshold level can be set for this. This can be determined by analyzing the power delay profile (PDP) of the received downlink reference signal, as discussed further below.

[0098] At step 9, if the Doppler shift (measured in step 6) is above a predetermined threshold (indicating that the user equipment is moving away from the gNB and no beam switch is needed), the algorithm enters step 10. If the Doppler shift is below this threshold (indicating that the user equipment is rotating and a beam switch is needed), then the algorithm moves to step 11. This step can be supplemented with other measurement data, e.g. using user equipment sensors such as GNSS, gyroscope, etc. (if available).

[0099] With step 10, it is determined that the received downlink reference signal is neither an SSB signal nor a CSI-RS with repetition “ON”, that the RSRP is below a reference / threshold, that the channel contains only one available angular power group (APG) from the corresponding SSB, and that the Doppler shift of the received downlink reference signal is above a threshold level. The result is that no beam switch is needed. Therefore, at step 10, a new RSRP measurement is made and stored as an updated reference for the user equipment, and the algorithm 140 returns to the waiting state (step 1).

[0100] With step 11, it is determined that the received downlink reference signal is neither an SSB signal nor a CSI-RS with repetition “ON”, that the RSRP is below a reference / threshold, that the channel contains only one available angular power group (APG) from the corresponding SSB, and that the Doppler shift of the received downlink reference signal is below a threshold level. The result is that a beam switch is needed. Therefore, at step 11, the user equipment performs an autonomous neighbor beam switch, and the algorithm returns to the waiting state (step 1).

[0101] As mentioned above, if more than one available APG is identified in step 8 above, the algorithm 140 moves to step 12. At step 12, it is determined whether the available APG is received on more than one panel. If yes, the algorithm moves to step 15; otherwise, the algorithm moves to step 13.

[0102] At step 13, the Doppler shift of the strongest APG is measured. Then, at operation 14, it is determined whether the APG is from a different angular direction (e.g. differs by more than a threshold amount of angle). If so, the algorithm moves to step 16 (where a communication node assisted beam switch is initiated). Otherwise, the algorithm moves to step 11, which performs a neighbour beam switch as described above.

[0103] At step 15, the number of panels receiving the available APG is determined. The algorithm then moves to step 16.

[0104] With step 16, it has been determined that a communication node assisted beam switch should be initiated. This can be achieved by the user equipment signalling to the gNB. For example, the user equipment can request transmission of a particular number of CSI-RS signals with repetition "ON", or indicate to the gNB that CSI-RS with repetition "ON" is no longer required when the gNB has completed its beam alignment.

[0105] Thus, the algorithm 140 (and the algorithms 50 and 100 described above) enables the user equipment to determine whether assistance from a gNB (or some other communication node) is required to perform beam alignment, and to signal this to the gNB. Thus, the gNB will only allocate CSI-RS with repetition "ON" when required.

[0106] As described above, Figures 6 to 9 are block diagrams of the user equipment 60 and 80. Figure 15 and Figure 16 are block diagrams of user equipment 150 and 160 respectively, in accordance with example embodiments. The user equipment 60, 80, 150 and 160 can be used in example implementations of the algorithms 50, 100 and 140.

[0107] The user equipment 60, 80, 150 and 160 comprises a plurality of panels, each panel having a plurality of beams that can be used for communication. As part of the general beam management procedure, each panel can periodically scan for SSB signals transmitted by a gNB. This scanning procedure can be performed simultaneously or sequentially, depending on the hardware capabilities of the UE. However, whether the scanning procedure can be completed within the coherence time of the channel is not so important for the present invention.

[0108] The user equipment used in the implementation of the algorithm 140 knows which SSB beam index contains the CSI beam it is currently connected to. The user equipment will measure the power delay profile (PDP) of this SSB beam index on all its panels while performing the general beam management procedure. The results obtained from the SSB#x measurement can fall into one of four possible outcomes, as follows:

[0109] • First effect: one panel receives one angular power group (APG) of SSB #x. This is the scenario shown in Figure 6 and Figure 7 In this scenario, no non-adjacent beam switch is needed; therefore, any beam switch is an adjacent beam switch.

[0110] • Second effect: one panel receives multiple APGs of SSB #x. This is the scenario shown in Figure 15 and In this scenario, adjacent or non-adjacent beam switch can be needed,

[0111] depending on the specifics.

[0112] • Third effect: multiple panels each receive one APG of SSB #x. This is the scenario shown in Figure 8 and Figure 9 In this scenario, non-adjacent beam switch can be needed.

[0113] • Fourth effect: multiple panels receive one or more APGs of SSB #x. This is the scenario shown in Figure 16 In this scenario, non-adjacent beam switch can be needed.

[0114] The user equipment (such as user equipment 60, 80, 150, and 160) can draw the following conclusions from the four different result effects discussed above.

[0115] The first result effect (one panel receives one angular power group (APG) of SSB #x) can occur in response to a negative answer to step 8 of algorithm 140. The first result effect has two variants, depending on the answer to step 9 (i.e., whether the Doppler shift is above a relevant threshold).

[0116] Result effect #1a (no in #8 and no in #9): only one panel receives an RSRP value of SSB #x that is above a certain threshold to characterize it as a usable strong APG and with a low Doppler shift. Therefore, the user equipment will perform an autonomous adjacent beam switch, as the decrease in RSRP is most likely caused by UE rotation and / or movement, and the adjacent beam will be the best new beam selection.

[0117] Result effect #1b (no in #8 and yes in #9): only one panel receives an RSRP value of SSB #x that is above a certain threshold to characterize it as a usable strong APG and with a high Doppler shift. Therefore, the user equipment will not perform a beam switch, as the decrease in RSRP is most likely caused by the UE moving away from the gNB. However, the UE will perform a new RSRP reference measurement.

[0118] A second resultant effect (one panel receives multiple angular power groups (APGs) of SSB #x) can occur in response to a negative answer to step 12 of algorithm 140. There are two variants of the second resultant effect, depending on the answer to step 14 (i.e., whether the APGs are from different angular directions.

[0119] Resultant effect #2a: (yes in #8, no in #12, and yes in #14): Multiple APGs of SSB #x are received at the UE at a single panel, with RSRP values exceeding a certain threshold and from different angular directions. The UE does not have angular direction knowledge (only power) of all the multiple APGs, and needs the assistance of the gNB to determine the best APG. Thus, the user equipment will request y CSI-RS signals with repetition “ON”, where y can equal the number of configurable beams on the array.

[0120] Resultant effect #2b: (yes in #8, no in #12, and no in #14): Multiple APGs of SSB #x are received at the UE on a single panel, with RSRP values exceeding a certain threshold but from the same angular direction (within the 3dB beamwidth of the intended aligned UE beam). Thus, the user equipment will perform an autonomous neighbor beam switch, since the reduction in RSRP is likely caused by UE rotation and / or movement, and the neighbor beam will be the best new beam selection.

[0121] A third resultant effect (multiple panels each receive one APG) can occur in response to a positive answer to step 12 of algorithm 140.

[0122] Resultant effect #3: (yes in #8 and yes in #12): A single APG of SSB #x is received at the user equipment on multiple panels. The user equipment can have some direction knowledge for the APG received on the panel currently connected with the gNB. However, the UE does not have direction knowledge from the other panels; thus, the user equipment will request z CSI-RS signals with repetition “ON”, where z can be the multiplication of:

[0123] • reduced scanning of the connected panels.

[0124] • full scanning of the remaining panels.

[0125] A fourth resultant effect (multiple panels each receive multiple APGs) can occur in response to a positive answer to step 12 of algorithm 140.

[0126] Result Effect #4: (Yes in #8 and Yes in #12): Multiple APGs of SSB #x are received at the UE on multiple panels. The user equipment does not have any directional knowledge of the APGs. Therefore, the user equipment will request v CSI-RS signals with repetition "ON", where v can be the product of full beam sweeping of all affected panels.

[0127] Figures 17 to 20 is a graph showing a signal according to an example embodiment, which is generally indicated by reference sign 170 to 200, respectively.

[0128] The difference in power delay profile (PDP) measurements for the above four result effects for two panels is explained in Figures 17 to 20 . Thus, plot 170 shows that the first panel receives one APG above a relevant threshold, plot 180 shows that the first panel receives multiple APGs above a relevant threshold, plot 190 shows that both the first panel and the second panel receive one APG above a relevant threshold, and plot 200 shows that both the first panel and the second panel receive multiple APGs above a relevant threshold.

[0129] Although PDP measurements are shown for only two panels, any number of panels can be used. Figures 17 to 20 PDP measurements are shown for only two panels, any number of panels can be used.

[0130] For completeness, Figure 21 is a schematic diagram of components of one or more of the foregoing example embodiments, which are hereinafter collectively referred to as processing system 300. The processing system 300 may, for example, be the apparatus referred to in the following claims.

[0131] The processing system 300 can have a processor 302, a memory 304 tightly coupled to the processor and comprising a RAM 314 and a ROM 312, and optionally a user input 310 and a display 318. The processing system 300 can comprise one or more network / device interfaces 308 for connecting to a network / apparatus, e.g. a modem which can be wired or wireless. The network / device interface 308 can also operate as a connection to other devices, such as devices / apparatuses which are not network-side apparatuses. Thus, a direct connection between devices / apparatuses without network involvement is possible.

[0132] The processor 302 is connected to each of the other components in order to control operation thereof.

[0133] The memory 304 can comprise a non-volatile memory such as a hard disk drive (HDD) or a solid state drive (SSD). The ROM 312 of the memory 304 stores, among other things, an operating system 315 and can store software applications 316. The RAM 314 of the memory 304 is used by the processor 302 for the temporary storage of data. The operating system 315 can contain code which, when executed by the processor, implements aspects of the above-described algorithms and message sequences 30, 40, 50, 100 and 140. Note that in the case of small devices / apparatuses, the memory can be most suitably of small size, i.e. a hard disk drive (HDD) or solid state drive (SSD) is not always used.

[0134] The processor 302 can take any suitable form. For example, it can be one microcontroller, a plurality of microcontrollers, one processor or a plurality of processors.

[0135] The processing system 300 can be a standalone computer, a server, a console or a network thereof. The processing system 300 and the required structural components can all be inside a device / apparatus, such as an loT device / apparatus, i.e. embedded to very small size.

[0136] In some example embodiments, the processing system 300 can also be associated with external software applications. These can be applications stored on a remote server device / apparatus and can be run partly or exclusively on the remote server device / apparatus. These applications can be referred to as cloud-hosted applications. The processing system 300 can communicate with the remote server device / apparatus in order to utilize the software applications stored there.

[0137] Figure 22A And Figure 22B A tangible medium storing computer readable code which, when run by a computer, can perform the methods according to the above example embodiments is shown, a removable memory unit 365 and an optical disc (CD) 368, respectively. The removable memory unit 365 can be a memory stick, e.g. a USB memory stick, which has an internal memory 366 storing the computer readable code. The internal memory 366 can be accessed by a computer system via a connector 367. The CD 368 can be a CD-ROM or a DVD or the like. Other forms of tangible storage media can be used. The tangible medium can be any device / apparatus which is capable of storing data / information which can be exchanged between devices / apparatuses / networks.

[0138] Embodiments of the application can be implemented in software, hardware, application logic or a combination of software, hardware and application logic. The software, application logic and / or hardware can reside on memory, a computer, or any computer medium. In an example embodiment, the application logic, software or an instruction set is maintained on any one of various conventional computer-readable media. In the context of this document, a "computer-readable medium" can be any non-transitory medium that can contain, store, communicate, propagate or transport the program for use by or in connection with the instruction execution system, apparatus, or device. Computer readable medium can be, for example but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device. More specific computer readable medium can include an electrical connection based on one or more wires, and / or based on the free-space interactions between particles, such as a carrier wave traveling through space, an optical fiber cable, and / or the like.

[0139] In relevant contexts, references to "computer-readable medium", "computer program product", "tangibly embodied computer program" etc., or a "processor" or "processing circuitry" etc. should be understood to encompass not only computers having differing architectures such as single / multi-processor architectures and sequencers / parallel architectures, but also specialized circuits such as FPGAs, ASICs, signal processing devices / apparatus and other devices / apparatus. References to computer program, instructions, code etc. should be understood to express software for a programmable processor, firmware such as, for example, the programmable content of a field programmable gate array (FPGA), or hardware description language (HDL) descriptions for an application specific integrated circuit (ASIC), and / or dedicated circuitry such as that for a signal processing device / apparatus.

[0140] If desired, the different functions discussed herein can be performed in a different order and / or concurrently with each other. Furthermore, if desired, one or more of the above-described functions can be optional or can be combined. Similarly, it will be appreciated that, Figure 3 , Figure 4 , Figure 5 , Figure 10 and Figure 14 The flow diagrams and message sequence charts of the various embodiments are examples only and it is understood that various operations depicted can be omitted, reordered and / or combined.

[0141] It is to be understood that the above-described example embodiments are purely illustrative and not limiting in any way to the scope of the present application. Numerous variations and modifications will be readily apparent to the skilled person upon reading the present description.

[0142] Furthermore, the disclosure of this application should be understood to include any novel features or any novel combination of features disclosed herein either explicitly or implicitly, and it should be understood that new claims can be formulated to claim any such features and / or combinations of features.

[0143] Although various aspects of the application are set forth in the independent claims, other aspects of the application include other combinations of features from the described example embodiments and / or dependent claims with the features of the independent claims, and not just the combinations explicitly set forth in the claims.

[0144] It is also noted herein that while the above describes example embodiments, these descriptions should not be viewed in terms of limitation. Rather, many changes and modifications can be made thereto without departing from the scope thereof as defined in the appended claims, and the scope thereof for the present application is by the appended claims.

Claims

1. An apparatus for communication, comprising means for: receiving (52), at a user equipment, a downlink reference signal from a communication node of a mobile communication system, wherein the downlink reference signal is received by one of a plurality of beams of a receiver of the user equipment in accordance with a configured beam alignment; determining (54), based at least in part on a signal power of the received downlink reference signal, whether to initiate a beam switch to reconfigure the beam alignment at the receiver; in a case where a beam switch is to be initiated, determining (54) whether to initiate a communication node assisted beam switch or a non-communication node assisted beam switch; and in a case where it is determined to initiate a non-communication node assisted beam switch, initiating (57), at the user equipment, an autonomous beam switch; wherein the apparatus further comprises means for: identifying whether a channel between the communication node and the user equipment supports one or more available candidate links in addition to a first link used for the configured beam alignment; determining whether a Doppler shift of the received downlink reference signal is above a threshold level; in a case where a beam switch is initiated, no available candidate links in addition to the first link are identified, and the Doppler shift of the received downlink reference signal is not above the threshold level, initiating a non-communication node assisted beam switch; and in a case where no available candidate links in addition to the first link are identified, and the Doppler shift is above the threshold level, not initiating a beam switch.

2. The apparatus of claim 1, further comprising means for: in a case where it is determined to initiate a communication node assisted beam switch, sending a signal to the communication node triggering communication node assistance.

3. The apparatus of claim 1 or 2, further comprising means for: determining the signal power of the received downlink reference signal; and comparing the determined signal power to a threshold power level for use in determining whether to initiate a beam switch.

4. The apparatus of claim 1, wherein the means for performing identifying whether the channel between the communication node and the user equipment supports one or more available candidate links for the receiver in addition to the first link for the configured beam alignment comprises: analyzing a power delay profile of the received downlink reference signal.

5. The apparatus of claim 1, further comprising means for: in a case where a beam switch is initiated, one or more available candidate links in addition to the first link are identified, and the available candidate links include at least one link that is oriented in a different direction than the first link used for the configured beam alignment and / or on a different receiver panel of the user equipment, initiating a communication node assisted beam switch; and in a case where a beam switch is initiated, one or more available candidate links in addition to the first link are identified, and the available candidate links do not include any links that are oriented in a different direction than the first link, initiating a non-communication node assisted beam switch.

6. The apparatus of claim 1 or 2, wherein the means comprise: at least one processor; and ​ at least one memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the performance of the apparatus.

7. A method for communication, comprising: receiving (52), at a user equipment, a downlink reference signal from a communication node of a mobile communication system, wherein the downlink reference signal is received by one of a plurality of beams of a receiver of the user equipment according to a configured beam alignment; determining (54), based at least in part on a signal power of the received downlink reference signal, whether to initiate a beam switch to reconfigure the beam alignment at the receiver; in case beam switch is to be initiated, determining (54) whether to initiate a communication node assisted beam switch or a non-communication node assisted beam switch; and in case it is determined to initiate a non-communication node assisted beam switch, initiating (57), at the user equipment, an autonomous beam switch; wherein the method further comprises: identifying (103) whether a channel between the communication node and the user equipment supports one or more available candidate links other than a first link, the first link being used for the configured beam alignment; determining (104) whether a Doppler shift of the received downlink reference signal is above a threshold level; in case beam switch is initiated, no available candidate links other than the first link are identified, and the Doppler shift of the received downlink reference signal is not above the threshold level, initiating a non-communication node assisted beam switch; and in case no available candidate links other than the first link are identified, and the Doppler shift is above the threshold level, not initiating a beam switch.

8. The method of claim 7, further comprising: in case it is determined to initiate a communication node assisted beam switch, sending a signal to the communication node triggering communication node assistance.

9. The method of claim 7, further comprising: in case beam switch is initiated, one or more available candidate links other than the first link are identified, and the available candidate links comprise at least one link that is oriented in a different direction than the first link used for the configured beam alignment and / or on a different receiver panel of the user equipment, initiating a communication node assisted beam switch; and in case beam switch is initiated, one or more available candidate links other than the first link are identified, and the available candidate links do not comprise any link that is oriented in a different direction than the first link, initiating a non-communication node assisted beam switch.

10. A machine-readable storage medium having stored thereon instructions for causing an apparatus to perform at least the following: receiving, at a user equipment, a downlink reference signal from a communication node of a mobile communication system, wherein the downlink reference signal is received by one of a plurality of beams of a receiver of the user equipment according to a configured beam alignment; ​ determining whether to initiate a beam switch to reconfigure the beam alignment at the receiver based at least in part on a signal power of the received downlink reference signal; in case a beam switch is to be initiated, determining whether to initiate a communication node assisted beam switch or a non-communication node assisted beam switch; and in case it is determined to initiate a non-communication node assisted beam switch, initiating (57) an autonomous beam switch at the user equipment; wherein the apparatus is further caused to perform: identifying (103) whether a channel between the communication node and the user equipment supports one or more available candidate links other than a first link, the first link being used for the configured beam alignment; determining (104) whether a Doppler shift of the received downlink reference signal is above a threshold level; in case a beam switch is initiated, no available candidate links other than the first link are identified, and the Doppler shift of the received downlink reference signal is not above the threshold level, initiating a non-communication node assisted beam switch; and in case no available candidate links other than the first link are identified, and the Doppler shift is above the threshold level, not initiating a beam switch.

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