Methods and apparatus for facilitating multi TRP uplink communication

Abstract

Facilitating Multi-TRP uplink communication comprising means for: obtaining configuration information (by a UE); receiving, from the first communication network entity (first TRP), a first signal; rec

Description

Technical Field This specification describes systems, methods, and apparatus for facilitating multi TRP uplink communication in a wireless communication network. Background Wireless communication networks (such as cellular networks, including fifth generation (5G) wireless networks) may support multi-TRP communication. That is, such wireless communication networks may allow for a user equipment (UE) to be served by multiple transmission and reception points (TRPs) (such as macro-cells, small cells, pico cells, femto cells, remote radio heads, relay nodes, etc.) simultaneously. In some situations, the links to the multiple TRPs can be characterized by different propagation delays. To account for propagation delays and to reduce the possibility of interference between uplink (UL) transmission from different UEs, timing advances (TAs) can be provided to UEs (e.g., from a gNodeB (gNB)) to enable the UEs to adjust their uplink transmission timing such that the transmissions are received at the network (e.g., TRP(s), gNB, etc.) at the same time. A TA may be associated with a timing advance group (TAG). In some situations, based on the UE's capability, uplink (UL) transmission in the multi TRP scenario may only be performed when a transmit timing difference (TTD) between two UL transmissions (e.g., between two TAGs) is within a maximum transmit timing difference (MTTD). Summary In a first aspect, this specification relates to a method comprising: obtaining configuration information, the configuration information being usable to determine, when a signalling timing difference between a first communication network entity of a plurality of communication network entities and a second communication network entity of the plurality of communication network entities Is greater than a signalling timing difference threshold, which of the plurality of communication network entitles to stop uplink communication with and / or which of the plurality of communication network entities to continue uplink communication with; receiving, from the first communication network entity, a first signal; receiving, from the second communication network entity, a second signal; and in response to determining, based on the first signal and the second signal, that the signalling timing difference between the first communication network entity and the second communication network entity is greater than the signalling timing difference threshold: determining, based on the configuration information, which of the plurality of communication network entities to stop uplink communication with and / or which of the plurality of communication network entities to continue uplink communication with, and responsively: stopping, uplink communication with at least one communication network entity of the plurality of communication network entities. In a second aspect, this specification relates to a method comprising: determining configuration information, the configuration information being usable by a user equipment (UE) configured for multiple communication network entity uplink communication with a plurality of communication network entities to determine, when a signalling timing difference between a first communication network entity of the plurality of communication network entities and a second communication network entity of the plurality of communication network entities is greater than a signalling timing difference threshold, which of the plurality of communication network entities to stop uplink communication with and / or which of the plurality of communication network entities to continue uplink communication with; and receiving, via at least one communication network entity of the plurality of communication network entities with which the UE has continued uplink communication based on the configuration information, an uplink communication from the UE. In a third aspect, this specification relates to a method performed by a user equipment (UE) configured to perform multi transmission and reception point (TRP) uplink (UL) communications with a first TRP and a second TRP, comprising: receiving, from the first TRP and / or the second TRP, configuration information, the configuration information being usable to determine, when a signalling timing difference between the first TRP and the second TRP is greater than a signalling timing difference threshold, which one of the first TRP and the second TRP to stop uplink communication with and / or which one of the first TRP and the second TRP to continue uplink communication with; receiving, from the first TRP, a first signal; receiving, from the second TRP, a second signal; and in response to determining, based on the first signal and the second signal, that the signalling timing difference between the first TRP and the second TRP is greater than the signalling timing difference threshold: determining, based on the configuration information, which one of the first TRP and the second TRP to stop uplink communication with and / or which one of the first TRP and the second TRP to continue uplink communication with; and responsively: stopping uplink communication with one of the first TRP and the second TRP. In a fourth aspect, this specification relates to a method comprising: sending, to a user equipment, UE, configured for multi TRP communication with a first TRP and a second TRP, configuration information, the configuration information being usable by the UE to determine, when a signalling timing difference between the first TRP and the second TRP is greater than a signalling timing difference threshold, which one of the first TRP and the second TRP to stop uplink communication with and / or which one of the first TRP and the second TRP to continue uplink communication with; and receiving, via the one of the first TRP and the second TRP with which the UE has continued uplink communication based on the configuration information, a single-TRP uplink communication from the UE. In a fifth aspect, this specification relates to a method performed by a user equipment (UE) configured to perform multi transmission and reception point (TRP) uplink (UL) communications with a first TRP and a second TRP comprising: receiving, from the first TRP and / or the second TRP and during a muti-TRP UL communication session with the first TRP and the second TRP, configuration information, the configuration information being usable to determine, when a signalling timing difference between the first TRP and the second TRP is greater than a signalling timing difference threshold, which one of the first TRP and the second TRP to stop uplink communication with and / or which one of the first TRP and the second TRP to continue uplink communication with; receiving, from the first TRP, a first signal; receiving, from the second TRP, a second signal; and in response to determining, based on the first signal and the second signal, that the signalling timing difference between the first TRP and the second TRP is greater than the signalling timing difference threshold based on a transmit timing difference (TTD) being greater than a maximum transmit timing difference (MTTD) and / or a receive timing difference (RTD) being greater than a maximum receive timing difference (MRTD): determining, based on the configuration information, which one of the first TRP and the second TRP to stop uplink communication with and / or which one of the first TRP and the second TRP to continue uplink communication with; and responsively: stopping uplink communication with one of the first TRP and the second TRP. In a sixth aspect, this specification relates to a method, comprising: sending, to a user equipment (UE) configured for multi transmission and reception point (TRP) uplink (UL) communication with a first TRP and a second TRP, and during a multi TRP UL communication session with the first TRP and the second TRP, configuration information, the configuration information being usable by the UE to determine, when a signalling timing difference between the first TRP and the second TRP is greater than a signalling timing difference threshold based on a transmit timing difference (TTD) being greater than a maximum transmit timing difference (MTTD) and / or a receive timing difference (RTD) being greater than a maximum receive timing difference (MRTD), which one of the first TRP and the second TRP to stop uplink communication with and / or which one of the first TRP and the second TRP to continue uplink communication with; and receiving, via the one of the first TRP and the second TRP that with which the UE has continued uplink communication based on the configuration information, a single-TRP uplink communication from the UE. According to a further aspect of this specification, there is described an apparatus comprising means for performing the method of any of the preceding aspects. According to a further aspect of this specification, there is described an apparatus comprising at least one processor, and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to perform any of the methods described herein. According to a further aspect of this specification, there is described a computer program product / non-transitory computer readable medium storing computer-readable instructions that, when executed by a computer, cause the computer to perform any one or more of the methods described herein. Brief Description of the Drawings Example embodiments will now be described by way of non-limiting examples, with reference to the accompanying drawings, in which: FIG. 1 shows an example of a scenario in which a UE switches from multi TRP uplink communications to single TRP uplink communication; FIG. 2 shows an example flow chart of example methods of operating a UE in a communication network; FIG. 3 shows an example message flow sequence; FIGs. 4A and 4B show an example message flow sequence; FIGs. 5, 6, 7, 8, 9, and 10 show flow diagrams of example methods of operating various apparatus in a communication network; FIG. 11 shows an apparatus according to some example embodiments; and FIG. 12 shows a non-transitory media according to some embodiments. Detailed Description In the drawings and description below, like reference numerals refer to like elements throughout. When it is determined that a TTD exceeds a MTTD in a multi TRP scenario, it may be determined that a UE must stop uplink (UL) transmission. In order to avoid stopping all UL transmissions and unnecessarily increase UL interruption and decrease UL throughput, it may be determined that the UE should stop transmitting only towards some (e.g., one) of the multiple (e.g., two) TRPs. Hence, the UL transmission towards the other TRP(s) should not stop. One possible solution to determining which of the TRPs to stop UL transmission towards and which to continue could be to simply allow a UE to decide this based on some undefined implementation details. However, this approach may provide too much freedom to the UEs, allowing them to behave in ways which are detrimental to the overall performance of the communications network. In addition, it may be generally beneficial to clearly define the expected behaviour of each entity in a communications network. Implementations described herein relate to operations of various apparatus in a communication network supporting multi TRP uplink transmissions. In particular, implementations described herein relate to providing configuration information (e.g., rules / prioritization information) to define which of the TRPs should be selected to stop (and / or keep) uplink communication with when a signalling timing difference (e.g., TTD or receive timing difference (RTD)) is greater than a signalling timing difference threshold (e.g., MTTD or maximum receive timing difference (MRTD)). In some implementations described herein, the configuration information is predefined and stored on the UE (e.g., based on a standards specification). In some implementations described herein, the configuration information is provided to the UE from the network (e.g., once when the multi-TRP uplink communications have been configured, or dynamically during the multi-TRP uplink communication session). Although, the multi TRP scenario is generally referred to as involving only two TRPs, it will be appreciated that the techniques described herein can be performed in a multi TRP scenario involving more than two TRPs. For instance, when there are more than two TRPs, the techniques described herein can be used to select which of the TRPs to keep and / or which to drop. As an example involving five TRPs, the techniques described herein can be used to determine which of the five TRPs should be dropped, and / or which of the five TRPs should be kept, and in some implementations how many should be kept or dropped (e.g., in some implementations four of the TRPs can be kept, and in some implementations only one of the TRPs should be kept). In addition, although the techniques are generally described in relation to TRPs, it will be appreciated that the techniques described herein can be used with any suitable communication network entity. In this way, techniques described herein allow the expected behaviour of each entity in a communications network to be defined, and known by all entities, allowing for the communications network to be configured accordingly. In addition, the UE can be caused to operate in a way which is not detrimental to the performance of the overall communications network. Furthermore, techniques described herein allow the UE to react more quickly in the event the MTTD (or MRTD) is violated. In addition, the techniques described herein may result in reduced signalling between the UE and the network when the MTTD (or MRTD) is violated (e.g., since it is not required to report RTD or TTD status changes to the network), resulting in reduced resources, capacity usage, and interference that would otherwise occur from the additional required signalling. Turning now to FIG. 1, an example of a scenario 100 in which a UE switches from multi TRP uplink communications to single TRP uplink communication is depicted. As depicted In FIG. 1, at a first time, the UE is at a first position 120, and is performing multi TRP uplink communications with both a first TRP 110 and a second TRP 112. Whilst the UE is at the first position 120, it may be determined that the TTD is lower than (or equal to) a MTTD. At a second time, the UE has moved to a second position 122. It may be determined that, at the second position 122, the TTD is greater than the MTTD. For instance, as depicted In FIG. 1, boundaries as to where the TTD will be greater than the MTTD are depicted as dashed lines around the first TRP 110 and the second TRP 112 respectively. Since the second position 122 of the UE has crossed this boundary, it can be expected that the TTD will be greater than the MTTD. As such, it may be determined that the UE can only perform single TRP UL transmission (e.g., with either the first TRP 110 or the second TRP 112). Although the techniques described herein are generally described in relation to determining whether the MTTD (or MRTD) is exceeded based on determining the TTD (or RTD), it will be appreciated that this can be performed in any suitable manner. For instance, in some implementations, a location of the UE can be used to determine whether the MTTD (or MRTD) is exceeded. For instance, the network can determine a location of the UE and predict that the MTTD is going to be violated based on the location of the UE (e.g., the network can determine that the UE has moved from position 120 to position 122). The TTD can be determined (e.g., by the UE) based on one or more of: a RTD from the two TRPs, a transmit alignment error (TAE), a TA value from the first TRP 110, and a TA value from the second TRP 112. The RTD can be determined (e.g., computed, monitored, estimated, etc.) at the UE (e.g., based on downlink (DL) signals received from the TRPs). The RTD may depend mainly on a propagation delay difference of the links toward the two TRPs. Since it is determined at the UE, the RTD is generally not known on the network side (e.g., at the gNB). The TAE may represent a transit timing misalignment between the TRPs. In some cases, it may be assumed that the RTD is the significant contributor to the TTD on the UE side. For instance, since the TTD is directly related to the RTD (e.g., as UL is transmitted relative to the DL reference timing), from the UE's perspective, the main contributor to the TTD may be the RTD. As such, in some cases, rather than the determination to stop multi TRP UL communications being based on the TTD being greater than the MTTD, it can additionally or alternatively be based on the RTD being greater than a MRTD. In this way, operations related to determining the TTD and comparing to the MTTD can be omitted, and the associated resource consumption can be avoided. Although the techniques described herein are generally described in relation to TTD and MTTD and / or RTD and MRTD, it will be appreciated that any suitable signalling timing difference and any suitable signalling timing difference threshold may additionally or alternatively be used for similar purposes. As mentioned, it can generally be assumed that the network (e.g., a gNB) cannot itself determine the RTD, and in turn, it can also be assumed that the network cannot determine the TTD. As such, it can also be assumed that the network cannot determine when the TTD exceeds (or is about to exceed) the MTTD (e.g., when the UE moves). As such, implementations described herein provide a mechanism by which, when the TTD exceeds the MTTD (and / or the RTD exceeds the MRTD), the UE can be caused to operate in a predictable and clearly defined manner according to configuration information available to the UE. In some implementations, the configuration information can be predefined and stored at the UE (e.g., ahead of the multi TRP session). For instance, the configuration information can be defined in a standard specification. In some implementations, the configuration information can be provided to the UE by the network. For instance, the configuration information can be provided once when the multi TRP session is initiated, and / or dynamically throughout the multi TRP session. For instance, when the TTD exceeds the MTTD (and / or the RTD exceeds the MRTD), implementations described herein can be used to provide certainty as to which of the TRPs should be selected to keep a UL link with, which entity (e.g., the UE, the network, a gNB, etc.) should make the decision, whether and how the decision can be dynamically updated, whether and how the other TRP (e.g., the TRP for which UL transmission has been stopped) and / or the network (e.g., a gNB) should be informed, etc. In some implementations, the configuration information can be indicative of one or more selection criteria. The one or more selection criteria can include one or more positive selection criteria and / or one or more negative selection criteria. When it is determined that one of the TRPs satisfies the one or more positive selection criteria, that TRP may be selected for keeping uplink communications with. When it is determined that one of the TRPs satisfies the one or more negative selection criteria, that TRP may be selected for stopping uplink communications with. In some implementations, one or more of the selection criteria may relate to an identifier associated with the TRPs and / or the associated TAG. For instance, the TRP associated with the TAG with a lower (e.g., the lowest) TAG index or ID may be selected. As another example, the TRP associated with the TAG with a higher (e.g., the highest) TAG index or ID may be selected. In some implementations, this TAG index or ID can be determined based on one or more transmission configuration indicator (TCI) states. In particular, a TCI state can be associated with a TAG Index or ID. In some Implementations, one or more of the selection criteria may relate to an index associated with a control resource set (e.g., a coresetPoolIndex). For instance, the TRP associated with a lower (e.g., the lowest) coresetPoolIndex value may be selected. As another example the TRP associated with a higher (e.g., the highest) coresetPoolIndex value may be selected. This control resource set index can be determined based on one or more transmission configuration indicator (TCI) states. In particular, a TCI state can be associated with a control resource set index, which In turn can be associated with a TRP. In some implementations, one or more of the selection criteria may relate to an estimated link quality of the link between the UE and a given TRP. The link quality may be determined based on a measurement report (e.g., a layer 1 measurement report, a layer 3 measurement report, etc.). For instance, the TRP with the highest link quality may be selected to be kept and / or the TRP with the lowest link quality may be selected to be stopped UL communication with. In some implementations, one or more of the selection criteria may relate to a UL transmit power used for each of the TRPs. For instance, it may be assumed that, when a lower UL power is used for one of the TRPs relative to the UL transmit power used for the other one of the TRPs, better channel conditions (e.g., in terms of UL signal to noise ratio (SNR), UL signal to interference and noise ratio (SINR), etc.) are available for the TRP associated with the lower UL power. As such, the TRP associated with the lower UL transmit power may be selected to be kept and / or the TRP with the higher UL transmit power may be selected to be stopped UL communication with. In some implementations, one or more of the selection criteria may relate to an available power headroom (PHR) for the TRPs. For instance, it may be assumed that, when a higher PHR is available for one of the TRPs relative to the PHR available for the other one of the TRPs, better channel conditions (e.g., in terms of UL signal to noise ratio (SNR), UL signal to interference and noise ratio (SINR), etc.) are available for the TRP associated with the higher PHR available. As such, the TRP associated with the higher PHR available may be selected to be kept and / or the TRP with the lower PHR available may be selected to be stopped UL communication with. In some implementations, one or more of the selection criteria may relate to a number of physical resource block (PRB) allocated (e.g., in the last slot where physical uplink shared channel (PUSCH) was scheduled). It may be assumed that a higher number of PRBs allocated for one of the TRPs is indicative of that TRP being less loaded than the other TRP (and vice versa). As such, the TRP with the larger number of PRBs allocated may be selected to be kept and / or the TRP with the lower number of PRBs allocated may be selected to be stopped UL communication with. In some implementations, one or more of the selection criteria may relate to a modulation and coding scheme (MCS) index (e.g., in the last slot where PUSCH was scheduled). For instance, it can be assumed that the MCS index associated with a TRP is related to the UL SINR for that TRP. As such, it can be assumed that when a TRP has been allocated with a higher MCS index relative to the other TRP, a UL SINR towards that TRP may be better than the UL SINR towards the other TRP. As such, the TRP with the highest MCS index may be selected to be kept and / or the TRP with the lowest MCS index may be selected to be stopped UL communication with. In some implementations, one or more of the selection criteria may relate to whether physical uplink control channel (PUCCH) is scheduled for a given TRP. For instance, in a single downlink control information (DCI) setup, where the UE transmits PUSCH toward the TRPs (e.g., with time division multiplex (TDM)), if it is determined that PUCCH is transmitted toward one of the TRPs, that TRP may be selected to be kept and / or the other TRP may be selected to be stopped communication with. In some implementations, one or more of the selection criteria may relate to a number of received retransmission requests from the network for a given TRP. For instance, it may be assumed that a high number of transmission requests from the network for a given TRP indicates that the link with the TRP is not particularly reliable. As such, the TRP with the lower number of retransmission requests may be selected to be kept and / or the TRP with the higher number of retransmission requests may be selected to be stopped communication with. In some implementations, one or more of the selection criteria may relate to the TA value. For instance, the TRP associated with the TAG with the smaller TA value may be selected. As another example, the TRP associated with the TAG with the larger TA value may be selected. In some implementations, one or more of the selection criteria may relate to a time alignment timer. For instance, the TRP associated with the TAG with the smaller time alignment timer may be selected. As another example, the TRP associated with the TAG with the larger time alignment timer may be selected. In some Implementations, when the TTD violates the MTTD (and / or the RTD violates the MRTD), the UE can send a signalling message. The signalling message can be sent to inform the network that the UE has stopped or will stop UL transmission with one of the TRPs because of the MTTD (and / or MRTD) violation. For instance, the signalling message can be indicative of UL transmission with one of the TRPs being stopped, that the MTTD and / or MRTD has been violated, the TRP with which UL transmission will be stopped, etc. The UE may transmit the signalling message to the network via the TRP with which the UL transmission has not been stopped, when the MTTD (and / or MRTD) is violated. For instance, the signalling message can be sent via uplink control information (UCI) and / or medium access control - control element (MAC-CE). Additionally or alternatively, the UE can transmit the signalling message when the link with the TRP with which the UL transmission has been stopped is re-established (e.g., via either of the TRPs). Turning now to FIG. 2, an example flow chart 200 of example methods of operating a UE in a communication network according to a first example is depicted. In this example, the configuration information (which may represent e.g., rules or prioritization information, as described herein) can be predefined and is stored at the UE. For instance, the UE can store the configuration information ahead of the multi TRP session. For instance, the configuration information can be defined in a standard specification (such as the fifth generation technology standard for cellular networks (5G), 5G new radio (NR), etc.). For instance, as discussed herein, the configuration information could cause the UE to prioritise the TRPs based on link quality. For instance, the UE could determine to maintain UL transmissions with the TRP with the best UL or DL link quality (and / or determine to stop UL transmissions with the other TRP). In another example, the configuration information (to be implemented by the UE) could specify that: If a UE has indicated to be able to keep a single UL connection when MTTD is exceeded (e.g., if UE is configured with value SlngleTRPafterMTTDexceeded set to 'one'), and the UE is operating in a multi TRP mode (e.g., two TCI states are activated for CORESET, or associated with different values of coresetPoolIndex, by the activation command), when the TTD exceeds MTTD: if the configuration information is indicative of a particular TRP to keep (e.g., when the UE is provided with a specific TCI state to keep) in case of exceeded MTTD: UE keeps the indicated TRP (e.g., the UE applies the specific TCI state); else: the UE keeps the TRP according to the selection criteria indicated by the configuration information (e.g., the UE applies the TCI state indicated for the CORESET with the lowest CORESET ID). In this way, despite the configuration information being stored at the UE ahead of the multi TRP session, the network can be aware of (and be accordingly configured for) the decision making process for selecting the TRP to maintain a connection with and / or the TRP to stop UL transmissions with when the MTTD or MRTD is violated. In other words, the network can independently store the configuration information, without requiring this to be transmitted between the network and the UE. In this way, the advantages of a defined behaviour can be achieved without requiring additional communication or signalling between the UE and the network. As such, resources and network capacity usage that would otherwise be consumed by conducting additional signalling can be conserved. As depicted in FIG. 2, at operation 210, the UE is configured for multi TRP UL communications with a first TRP and a second TRP. At operation 220, the UE monitors the RTD between DL signals received from the first TRP and the second TRP. At operation 230, the UE determines TA values for each of the first TRP and the second TRP. The TA values can be updated when new signalling is received from the network. For instance, the TA values can be determined based on TA commands received from the network. At operation 240, the UE determines the TTD, as described herein. For instance, the UE can determine the TTD based on, at least, the RTD and the TA values for each of the TRPs. At operation 250, the UE determines whether the TTD is greater than the MTTD. If, at operation 250, the UE determines that the TTD does not exceed the MTTD, the UE proceeds to operation 260. If, at operation 250, the UE determines that the TTD exceeds the MTTD, the UE proceeds to operation 270. As described herein, other signalling timing differences can additionally or alternatively be used. For instance, the UE may instead determine whether the RTD is greater than a MRTD at operation 250. In this case, operations 230 and 240 can be bypassed. At operation 260, the UE continues to perform multi TRP UL transmissions to both the first TRP and the second TRP as scheduled by the network. At operation 270, the UE determines for which TRP UL transmission is to be kept or stopped according to the predefined configuration information. At operation 280, the UE is reconfigured for single TRP UL communication with the TRP determined to be kept (or the TRP for which UL transmission is to be stopped). In other words, UL communications with the TRP not determined to be kept (or the TRP for which UL transmission is to be stopped) can be stopped. Turning now to FIG. 3, an example message flow sequence 300 according to a second example is depicted. As depicted in FIG. 3, the message flow sequence 300 involves UE 310, a first TRP 320, a second TRP 330, and a network 340 (e.g., which may include, for instance, a gNB). In this example, the configuration information is provided to the UE by the network (e.g., using RRC signalling). This may be provided upon the UE being configured for multi TRP UL communications with the first TRP 320 and second TRP 330. In this way, additional flexibility can be provided as the network can configure different UEs in different ways, or even re-configure the same UE differently over time. As depicted in FIG. 3, at operation S3.1, the UE 310 is configured for multi TRP UL communications. At operation S3.2, the UE 310 Is provided with configuration information (e.g., TRP prioritization information in case of a MTTD violation). The configuration information can be received using an RRC message. The message may be sent by the network 340 (e.g., a gNB), for instance, via the first TRP 320 or the second TRP 330. The configuration information can, for instance, be indicative of one or more selection criteria usable to select the TRP for which UL transmission Is to be maintained or stopped In case of a MTTD (or MRTD) violation, as described herein. Additionally or alternatively, the configuration Information can provide an indication of the TRP for which UL transmission is to be maintained (or stopped) in case of a MTTD (or MRTD) violation. In other words, at operation S3.2, after initial access and with the UE 310 configured in UL with multi-TRP, the network 340 informs the UE (e.g., via RRC) about the configuration information (e.g., TRP prioritization / rule) in case TTD is greater than MTTD (or RTD being greater than MRTD). At operation S3.3, the UE 310 acknowledges the receipt of the configuration information (e.g., via the first TRP 320 and / or the second TRP 330). It will be appreciated that, in some implementations, this operation can be omitted. At operation S3.4, the UE 310 receives DL signals from both the first TRP 320 and the second TRP 330. At operation S3.5, the UE 310 determines the RTD. The estimation can be based on the DL signals received at operation 3.4. At operation S3.6, the UE 310 receives a further signal (e.g., from the first TRP 320) indicative of the timing advance for the first TRP 320. For instance, the further signal can be a TA command. At operation S3.7, the UE 310 receives a further signal (e.g., from the second TRP 330) indicative of the timing advance for the second TRP 330. For instance, the further signal can be a timing advance signal. At operation S3.8, the UE 310 determines the TTD. As described herein, the TTD can be determined based on, at least, the RTD, the TA for the first TRP 320 and the TA for the second TRP 330. The UE 310 can then determine whether the TTD exceeds the MTTD. It will be appreciated that, as described herein, any suitable signalling timing difference can additionally or alternatively be used. For instance, in some implementations, the UE 310 can Instead determine whether the RTD exceeds the MRTD. In this case, it will be appreciated that any one of operations S3.6, S3.7, and S3.8 can be omitted. At operation S3.9, the UE 310 determines that the TTD does not exceed the MTTD. As such, at operation S3.10, the UE 310 can continue performing multi-TRP UL communications (e.g., PUSCH) with both the first TRP 320 and the second TRP 330. At operation S3.11, the UE 310 determines that the TTD does exceed the MTTD. As such, at operation S3.12, the UE can keep UL transmission (e.g., PUSCH) with one of the TRPs according to the configuration information (and stop communication with the other TRP), as described herein. In other words, the TRP switches to single TRP mode. Turning now to FIGs. 4A and 4B, an example message flow sequence 400 according to a third example is depicted. As depicted in FIG. 4, the message flow sequence 400 involves UE 410, a first TRP 420, a second TRP 430, and a network 440 (e.g., which may include, for instance, a gNB). In this example, the configuration information is provided to the UE by the network (e.g., using MAC-CE signalling). In some implementations, the configuration information can provide an indication of the TRP to keep (or drop) when the TTD exceeds the MTTD, based on the respective signal qualities. In some implementations, the configuration information can indicate one or more selection criteria, as described herein. In some implementations, the configuration information can be provided dynamically (or aperlodlcally) during the multi TRP session with the first TRP 420 and the second TRP 430. For instance, the configuration information can be provided based on a time varying quantity, which may not be known to the UE 410. For instance, the configuration information can be provided based on a signal quality of the UL communications received by the TRPs, such as a UL SINR. As an example, the network 440 can re-configure the UE 410 (e.g., in respect of the TRP to be kept when TTD will exceed MTTD) when the UL SINR of the currently weakest TRP becomes larger than a UL SINR threshold. The UL SINR threshold may be, for instance, the UL SINR of the currently strongest TRP. In some cases, an additional threshold factor can be applied such that the UL SINR threshold can be the UL SINR of the currently strongest TRP plus the additional threshold factor. This can be represented in the following equation, where TRP1 is the TRP that the UE 410 is configured to keep according to the previous configuration information, the network informs the UE 410 to keep TRP2 when: SINRul_TRP2 >SINRul_trp1 + TH where the TH is the threshold factor. The threshold factor can, for instance, be defined based on a standards specification, determined based on the particular implementation and / or vendor requirements, etc. In this way, a highly dynamic criteria can be implemented, based on time varying quantities. For example, as described herein, the network 440 can inform the UE 410 to keep the TRP with strongest UL SINR (which may not be known at the UE 410). In addition, by transmitting the configuration information in an aperiodic fashion, the signalling overhead from these techniques can be minimised. In some implementations, the UE 410 can also inform the network 440 of its preferred TRP to keep or to drop (e.g., based on one or more of the selection criteria previously described). This may also be performed dynamically, in a similar manner. This preference can be acknowledged (or not) by the network 440. As depicted in FIG. 4A, at operation S4.1, the UE 410 is configured for multi TRP UL communications. As such, at operation S4.2, the UE 410 performs multi-TRP UL communications (e.g., PUSCH) with both the first TRP 320 and the second TRP 330. At operation S4.3, the UL SINR Is determined for each of the first TRP 420 and the second TRP 430. The UL SINR can be determined by the network 440 (specifically, e.g., a gNB) based on information received from the TRPs. Additionally or alternatively, the TRPs can determine their respective UL SINRs and report this to the network 440. At operation S4.4, the UE 410 receives the configuration Information (e.g., the TRP prioritization when the MTTD is violated). The configuration information may be received from the network 440 (e.g., via the first TRP 420 and / or the second TRP 430). The configuration information may be received as a MAC-CE message. In some implementations, the configuration information may be transmitted (and thereby received by the UE 410) based on the UL SINR for the first TRP 420 and the second TRP 430. In other words, at operation S4.3, the network 440 can monitor the UL SINR toward each TRP and, at operation S4.4, dynamically re-configure the UE 410 to keep the TRP that is characterized, as an example, by the strongest UL SINR. It will be appreciated that, although UL SINR is generally the metric described as being utilised herein, any other suitable criteria (which may be, e.g., based on time-varying metrics), can be additionally or alternatively used to decide which TRP the UE 410 should keep or drop in case the MTTD is violated. For instance, the UE can be re-configured based on the UL SNR, the load of TRP (e.g., a number of UEs connected to the TRP), etc. At operation S4.5, the UE 410 can transmit a TRP prioritization suggestion to the network 440 (e.g., via the first TRP 420 or the second TRP 430). At operation S4.6, the UE 410 receives, from the network 440 (e.g., via the first TRP 420 or the second TRP 430), an acknowledgement of the TRP prioritization suggestion. For instance, the acknowledgement can be indicative of whether or not the prioritization suggestion will be adhered to when the next configuration information is provided. It will be appreciated that, in some implementations, one or both of operations S4.5 and S4.6 can be omitted. At operation S4.7, the UE 410 receives DL signals from both the first TRP 420 and the second TRP 430. At operation S4.8, the UE 410 determines the RTD. The determination can be based on the DL signals received at operation S4.7. At operation S4.9, the UE 410 receives a further signal (e.g., from the first TRP 420) indicative of the timing advance for the first TRP 420. For instance, the further signal can be a TA command. At operation S4.10, the UE 410 receives a further signal (e.g., from the second TRP 430) indicative of the timing advance for the second TRP 430. For instance, the further signal can be a timing advance signal. At operation S4.ll, the UE 410 determines the TTD. As described herein, the TTD can be determined based on, at least, the RTD, the TA for the first TRP 420 and the TA for the second TRP 430. The UE 410 can then determine whether the TTD exceeds the MTTD. It will be appreciated that, as described herein, any suitable signalling timing difference can additionally or alternatively be used. For instance, in some implementations, the UE 410 can instead determine whether the RTD exceeds the MRTD. In this case, it will be appreciated that any one of operations S4.9, S4.10, and S4.ll can be omitted. As depicted in FIG. 4B, at operation S4.12, the UE 410 determines that the TTD does not exceed the MTTD. As such, at operation S4.13, the UE 410 can continue performing multi-TRP UL communications (e.g., PUSCH) with both the first TRP 420 and the second TRP 430. As depicted in operations S4.14 to S4.20 (which correspond with operations S4.3 to S4.4 and S4.7 to S4.ll respectively) the network 440 can continue to monitor the UL SINR for the TRPs and update the configuration information at the UE 410 accordingly. In addition, the UE 410 can continue to monitor for the TTD violating the MTTD. At operation S4.21, the UE 410 determines that the TTD does exceed the MTTD. As such, at operation S4.22, the UE can keep UL transmission (e.g., PUSCH) with one of the TRPs according to the configuration information (and stop communication with the other TRP), as described herein. In other words, the TRP switches to single TRP mode. It will be appreciated that, although the first example (as described in relation to FIG. 2), the second example (as described in relation to FIG. 3), and the third example (as described In relation to FIGs. 4A and 4B) have generally been described in isolation, these examples are entirely compatible with one another, and any combination of the three examples is contemplated herein. Turning now to FIG. 5, a flow diagram of an example method of operating an apparatus (e.g., a UE) in a communication network is depicted. The apparatus may be initially configured to perform multi-communication network entity uplink communications with a plurality of communication network entities. At operation S5.1, the apparatus obtains configuration information. The configuration information can be as described throughout the description. For instance, the configuration information can be usable to determine, when a signalling timing difference between a first communication network entity (e.g., a TRP) of the plurality of communication network entities (e.g., that the apparatus is performing UL communication with) and a second communication network entity of the plurality of communication network entities is greater than a signalling timing difference threshold, which of the plurality of communication network entities to stop uplink communication with and / or which of the plurality of communication network entities to continue uplink communication with. In some implementations, the configuration information is indicative of one or more selection criteria. As such, determining which of the plurality of communication network entities to stop uplink communication with and / or which of the plurality of communication network entities to continue uplink communication can be based on determining which of the plurality of communication network entities satisfies the one or more selection criteria. In some of these implementations, the one or more selection criteria can be associated with link quality (e.g. the UL and / or DL link quality between the UE and a respective communication network entity). As such, determining which of the plurality of communication network entities to stop uplink communication with can include determining which of the plurality of communication network entities is associated with the lowest link quality (e.g., the communication network entity with the lowest link quality can be dropped). It will be appreciated that, when more than one communication network entities are to be dropped (e.g., N communication network entities are to be dropped), it may be determined to drop the N communication network entities with the lowest link qualities. Additionally or alternatively, determining which of the plurality of communication network entities to continue uplink communication may include determining which of the plurality of communication network entities is associated with the highest link quality (e.g., the communication network entity with the highest link quality can be kept). It will be appreciated that, when more than one communication network entities are to be kept (e.g., M communication network entities are to be kept), it may be determined to keep the M communication network entities with the highest link qualities. In additional or alternative implementations, the one or more selection criteria can be associated with a value of an identifier associated with the communication network entity. For instance, the identifier can be a TAG ID, a control resource set index, etc. As such, determining which of the plurality of communication network entities satisfies the one or more selection criteria can include determining which of the plurality of communication network entities is associated with the lowest identifier value and / or which of the plurality of communication network entities is associated with the highest identifier value. In some Implementations, the configuration information can be indicative of a particular communication network entity of the plurality of communication network entities to be kept. Additionally or alternatively, the configuration information can be indicative of a particular communication network entity of the plurality of communication network entities to be dropped. In some implementations, the configuration information can be predefined and stored at the apparatus. For instance, the configuration information can be stored at the apparatus prior to the apparatus being configured for multiple communication network entity uplink communications (e.g., by a manufacturer). The configuration information can be defined according to a standard specification. In some implementations, the configuration information can also be stored by the network (e.g., by one or more of the communication network entities, a gNB, etc.). The configuration information can be stored by the network independently of the UE (e.g., without the configuration information being transmitted between the UE and the gNB). In some implementations, the configuration information is received via at least one of the plurality of communication network entities. At operation S5.2, the apparatus receives, from the first communication network entity, a first signal. At operation S5.3, the apparatus receives, from the second communication network entity, a second signal. At operation S5.4, the apparatus determines, based on the first signal and the second signal, that the signalling timing difference between the first communication network entity and the second communication network entity is greater than the signalling timing difference threshold. In some implementations, the apparatus can determine, based on the first signal and the second signal, that the signalling timing difference between the first communication network entity and the second communication network entity Is not greater than the signalling timing difference threshold. As such, the apparatus can continue uplink communication with the plurality of communication network entities. In response to the determination at S5.4, at operation S5.5, the apparatus determines, based on the configuration information, which of the plurality of communication network entities to stop uplink communication with and / or which of the plurality of communication network entities to continue uplink communication with. In response to the determination at S5.5, at operation S5.6, the apparatus stops, uplink communication with at least one communication network entity of the plurality of communication network entities. The apparatus may also continue to perform uplink communication with at least one of the other communication network entities of the plurality of communication network entities (e.g., the communication network entities for which uplink communication was not stopped). In some implementations, the apparatus can inform the network (e.g., via at least one of the communication network entities) of the change in configuration. This can be performed by sending a message using UCI or MAC-CE. For instance, in some of these implementations, transmits, to at least one of the other communication network entities (e.g., for which uplink communication has not been stopped), a message indicating that the apparatus has stopped uplink communication with the at least one of the communication network entities and / or that the signalling timing difference between the first communication network entity and the second communication network entity is greater than the signalling timing difference threshold. In some additional or alternative implementations, the apparatus can determine that multi communication network entity uplink communication can resume. For instance, the apparatus can receive, from the first communication network entity, a subsequent first signal; receive, from the second communication network entity, a subsequent second signal; and in response to determining, based on the subsequent first signal and the subsequent second signal, that a subsequent signalling timing difference between the first communication network entity and the second communication network entity is not greater than the signalling timing difference threshold, resume uplink communication with the at least one communication network entity. The apparatus can then transmit, to the at least one communication network entity (e.g., the communication network entity(ies) that the UE had previously stopped communicating with), a message indicating that the apparatus stopped uplink communication with the at least one communication network entity and / or that the signalling timing difference between the first communication network entity and the second communication network entity was greater than the signalling timing difference threshold. Turning now to FIG. 6, a flow diagram of an example method of operating an apparatus (e.g., a radio base station, such as a gNB) in a communication network is depicted. At operation S6.1, the apparatus determines configuration information. The configuration information can be as described throughout the description, and for instance, as described in relation to FIG. 5. For instance, the configuration information can be usable by a UE configured for multiple communication network entity uplink communication with a plurality of communication network entities to determine, when a signalling timing difference between a first communication network entity of the plurality of communication network entities and a second communication network entity of the plurality of communication network entities is greater than a signalling timing difference threshold, which of the plurality of communication network entities to stop uplink communication with and / or which of the plurality of communication network entities to continue uplink communication with. In some implementations, the apparatus can store the configuration information independently of the UE (e.g., both the apparatus and the UE can store the configuration information without communicating the configuration information between one another). For instance, the configuration information may be defined in a standard specification. In some implementations, the apparatus can send, to the UE, the configuration information. At operation S6.2, the apparatus receives, via at least one communication network entity of the plurality of communication network entities with which the UE has continued uplink communication based on the configuration information, an uplink communication from the UE. The apparatus can also stop receiving, via at least one communication network entity of the plurality of communication network entitles with which the UE has stopped uplink communication based on the configuration information, uplink communications from the UE. In some implementations, the apparatus can determine which of the plurality of communication network entities the UE should stop uplink communication with and / or which of the plurality of communication network entities the UE should continue uplink communication with. This can be determined in the same or similar manner to that described in respect of the UE. For instance, this determination can be based on the configuration information, which may indicate one or more selection criteria and / or one or more particular communication network entity. In this way, the network and the UE can have common knowledge of the UE's behaviour. In some implementations, the apparatus can receive, via at least one of the communication network entities of the plurality of communication network entitles with which the UE has continued uplink communication based on the configuration information, a message indicating that the UE has stopped uplink communication with at least one of the communication network entities and / or that the signalling timing difference between the first communication network entity and the second communication network entity is greater than the signalling timing difference threshold. In some additional or alternative implementations, the apparatus can receive, at a subsequent time when multi communication network entity uplink communications between the UE and the plurality of communication network entities have resumed and via at least one communication network entity, a message indicating that the UE stopped uplink communication with the at least one communication network entity and / or that the signalling timing difference between the first communication network entity and the second communication network entity was greater than the signalling timing difference threshold. Turning now to FIG. 7, a flow diagram of an example method of operating an apparatus (e.g., a UE) in a communication network is depicted. The apparatus may be configured to perform multi transmission and reception point (TRP) uplink (UL) communications with a first TRP and a second TRP. At operation S7.1, the apparatus receives, from the first TRP and / or the second TRP, configuration information. The configuration information can be as described throughout the description. For instance, the configuration Information can be usable to determine, when a signalling timing difference between the first TRP and the second TRP is greater than a signalling timing difference threshold, which one of the first TRP and the second TRP to stop uplink communication with and / or which one of the first TRP and the second TRP to continue uplink communication with. In some Implementations, the configuration information can be received in the form of a radio resource control (RRC) message. In some implementations, the apparatus can receive, from the first TRP and / or the second TRP, updated configuration information. The apparatus can then overwrite the previously stored configuration information based on the updated received configuration Information. This may occur a number of times during the multi TRP communication session. In some implementations, the configuration information is indicative of one or more selection criteria. As such, the apparatus can determine which one of the first TRP and the second TRP to stop uplink communication with and / or which one of the first TRP and the second TRP to continue uplink communication with based on determining that one of the first TRP and the second TRP satisfies the one or more selection criteria. In some additional or alternative implementations, the configuration information may be indicative of a particular TRP of the first TRP and the second TRP to be kept and / or a particular TRP of the first TRP and the second TRP to be dropped. For instance, the configuration information may Indicate a specific TCI state to keep in case the signalling timing difference exceeds a signalling timing difference threshold. At operation S7.2, the apparatus can receive, from the first TRP, a first signal. At operation S7.3, the apparatus can receive, from the second TRP, a second signal. At operation S7.4, the apparatus can determine, based on the first signal and the second signal, that the signalling timing difference between the first TRP and the second TRP is greater than the signalling timing difference threshold. For instance, the apparatus can determine, based on the first signal and the second signal, a current receive timing difference (RTD). As such, the apparatus can determine that the signalling timing difference between the first TRP and the second TRP is greater than the signalling timing difference threshold when the current RTD is greater than a maximum RTD (MRTD). Additionally or alternatively, the apparatus can determine, based on a message received via the first TRP, a first timing advance (TA) associated with the first TRP, and, based on a message received via the second TRP, a second TA associated with the second TRP. The apparatus can thus determine, based at least on the current RTD, the first TA, and the second TA, a current transmit timing difference (TTD). As such, the apparatus can determine that the signalling timing difference between the first TRP and the second TRP is greater than the signalling timing difference threshold when the current TTD is greater than a maximum TTD (MTTD). In response to the determination at operation S7.4, at operation S7.5, the apparatus can determine, based on the configuration information, which one of the first TRP and the second TRP to stop uplink communication with and / or which one of the first TRP and the second TRP to continue uplink communication with. In response to the determination at operation S7.5, at operation S7.6, the apparatus can stop uplink communication with one of the first TRP and the second TRP. The apparatus can also perform single TRP uplink communications with the other one of the first TRP and the second TRP. In some implementations, stopping uplink communication with one of the first TRP and the second TRP comprises applying a transmission configuration indicator (TCI) state associated with the other one of the first TRP and the second TRP. In some implementations, the apparatus can determine that the apparatus is configured to keep a single UL connection when the signalling time difference exceeds the signalling time difference threshold. For instance, this can be based on a configuration setting associated with keeping a single UL connection when the signalling time difference exceeds the signalling time difference threshold value being set to a particular value. In some additional or alternative implementations, the apparatus can determine that the apparatus is currently operating In a multi TRP mode. For instance, this can be based on determining that two TCI states are activated for control resource set (CORESET) by an activation command and / or that the two TCI states are associated with different index values (e.g., control resource set index (e.g., coresetPooilndex), TAG ID, etc.). Turning now to FIG. 8, a flow diagram of an example method of operating an apparatus (e.g., radio base station such as a gNB) in a communication network is depicted. At operation S8.1, the apparatus can send, to a user equipment, UE, configured for multi TRP communication with a first TRP and a second TRP, configuration information. The configuration information can be as described throughout the description, and for instance, as described in relation to FIG. 7. For instance, the configuration information can be usable by the UE to determine, when a signalling timing difference between the first TRP and the second TRP is greater than a signalling timing difference threshold, which one of the first TRP and the second TRP to stop uplink communication with and / or which one of the first TRP and the second TRP to continue uplink communication with. In some implementations, the signalling timing difference between the first TRP and the second TRP is greater than the signalling timing difference threshold when a RTD is greater than a MRTD and / or a TTD is greater than a MTTD. In some implementations, the configuration information is sent in the form of a RRC message. In some implementations, the configuration information is sent in response to the UE being configured to perform multi TRP UL communications with the first TRP and the second TRP. In some additional or alternative implementations, the apparatus can send, to the UE, updated configuration information to cause the UE to overwrite the configuration information based on the updated received configuration information. In some implementations, the apparatus can send, to another UE configured for multi TRP UL communications, different configuration information. The different configuration information differs from the configuration information in at least one aspect (e.g., different selection criteria, a different particular TRP to keep or drop, etc.). At operation S8.2, the apparatus can receive, via the one of the first TRP and the second TRP with which the UE has continued uplink communication based on the configuration information, a single-TRP uplink communication from the UE. The apparatus can also stop receiving, via the one of the first TRP and the second TRP with which the UE has stopped uplink communication based on the configuration information, uplink communications from the UE. In some implementations, stopping uplink communication with the one of the first TRP and the second TRP comprises applying a transmission configuration indicator (TCI) state associated with the other one of the first TRP and the second TRP. In some implementations, the apparatus can determine that the UE is configured to keep a single UL connection when the signalling time difference exceeds the signalling time difference threshold. For instance, this can be based on a configuration setting associated with keeping a single UL connection when the signalling time difference exceeds the signalling time difference threshold value being set to a particular value for the UE. In some additional or alternative implementations, the apparatus can determine that the UE is currently operating in a multi TRP mode. For instance, this can be based on determining that two TCI states are activated for control resource set (CORESET) by an activation command and / or that the two TCI states are associated with different index values (e.g., control resource set index, TAG ID, etc.). Turning now to FIG. 9, a flow diagram of an example method of operating an apparatus (e.g., a UE) in a communication network is depicted. The apparatus may be configured to perform multi transmission and reception point (TRP) uplink (UL) communications with a first TRP and a second TRP. At operation S9.1, the apparatus receives, from the first TRP and / or the second TRP and during a muti-TRP UL communication session with the first TRP and the second TRP, configuration information. The configuration information can be as described throughout the description. For Instance, the configuration information can be usable to determine, when a signalling timing difference between the first TRP and the second TRP is greater than a signalling timing difference threshold, which one of the first TRP and the second TRP to stop uplink communication with and / or which one of the first TRP and the second TRP to continue uplink communication with. The configuration Information may be received in the form of a medium access control - control element (MAC-CE) message. In some implementations, the configuration information can be indicative of a particular one of the first TRP and the second TRP to be kept in case the signalling timing difference is greater than the signalling timing difference threshold, and / or a particular one of the first TRP and the second TRP to be dropped in case the signalling timing difference is greater than the signalling timing difference threshold. For instance, the configuration information can include an indication of a specific TCI state to keep in case the signalling timing difference exceeds a signalling timing difference threshold. In some Implementations, the configuration information may be received in response to a determination that the particular one of the first TRP and the second TRP is associated with a time varying metric (e.g., UL SINR, UL SNR, load of a TRP, etc.) that is greater than a first metric threshold and / or lower than a second metric threshold. For instance, the time varying metric may relate to an uplink connection quality (e.g., a signal to interference plus noise ratio (SINR)). As such, the configuration information can indicate that a TRP with an uplink connection quality above a first uplink connection quality threshold be kept and / or a TRP with an uplink connection quality below a second uplink connection quality threshold be dropped. The first uplink connection quality threshold and / or the second uplink connection quality threshold can be based, at least in part, on the uplink connection quality of the other one than the particular one of the first TRP and the second TRP. For instance, the first uplink connection quality threshold can be determined based on the uplink connection quality of the previously better connected TRP plus some threshold factor. As such, the configuration information can be received when the previously less well connected TRP has an uplink connection quality above the uplink connection quality of the other TRP plus the threshold factor. At operation S9.2, the apparatus receives, from the first TRP, a first signal. At operation S9.3, the apparatus receives, from the second TRP, a second signal. At operation S9.4, the apparatus determines, based on the first signal and the second signal, that the signalling timing difference between the first TRP and the second TRP is greater than the signalling timing difference threshold. This determination may, for instance, be based on a transmit timing difference (TTD) being greater than a maximum transmit timing difference (MTTD) and / or a receive timing difference (RTD) being greater than a maximum receive timing difference (MRTD). In response to the determination at operation S9.4, at operation S9.5, the apparatus determines, based on the configuration information, which one of the first TRP and the second TRP to stop uplink communication with and / or which one of the first TRP and the second TRP to continue uplink communication with. In response to the determination at operation S9.5, at operation S9.6, the apparatus stops uplink communication with one of the first TRP and the second TRP. The apparatus may perform single TRP uplink communication with the other one of the first TRP and the second TRP. In some implementations, stopping uplink communication with the one of the first TRP and the second TRP comprises applying a transmission configuration indicator (TCI) state associated with the other one of the first TRP and the second TRP. In some implementations, the apparatus can determine that the apparatus is configured to keep a single UL connection when the signalling time difference exceeds the signalling time difference threshold. For instance, this may be based on a configuration setting associated with keeping a single UL connection when the signalling time difference exceeds the signalling time difference threshold value being set to a particular value. Additionally or alternatively, the apparatus can determine that the apparatus is currently operating in a multi TRP mode. For instance, this can be based on determining that two TCI states are activated for control resource set (CORESET) by an activation command and / or that the two TCI states are associated with different index values (e.g., control resource set index, TAG ID, etc.). In some implementations, the apparatus can transmit a message indicating a preferred TRP of the first TRP and the second TRP to be kept and / or a preferred TRP of the first TRP and the second TRP to be dropped when the signalling timing difference between the first TRP and the second TRP exceeds the signalling timing difference threshold. The message may, for instance, be sent as a MAC-CE message. Turning now to FIG. 10, a flow diagram of an example method of operating an apparatus (e.g., a radio base station, such as a gNB) in a communication network is depicted. At operation S10.1, the apparatus sends, to a user equipment (UE) configured for multi transmission and reception point (TRP) uplink (UL) communication with a first TRP and a second TRP, and during a multi TRP UL communication session with the first TRP and the second TRP, configuration information. The configuration information may be as described throughout the description, and for instance, as described in relation to FIG. 9. For instance, the configuration information can be usable by the UE to determine, when a signalling timing difference between the first TRP and the second TRP is greater than a signalling timing difference threshold based on a transmit timing difference (TTD) being greater than a maximum transmit timing difference (MTTD) and / or a receive timing difference (RTD) being greater than a maximum receive timing difference (MRTD), which one of the first TRP and the second TRP to stop uplink communication with and / or which one of the first TRP and the second TRP to continue uplink communication with. The configuration information may, for instance, be sent in the form of a medium access control - control element (MAC-CE) message. The apparatus may send the configuration information in response to a determination that one of the first TRP and the second TRP is associated with a time varying metric (e.g., UL SINR, UL SNR, load of a TRP, etc.) that is greater than a first metric threshold and / or lower than a second metric threshold. For instance, the time varying metric may be an uplink connection quality (e.g., UL SINR). As such, the apparatus may send the configuration information in response to a determination that one of the first TRP and the second TRP Is associated with an uplink connection quality above a first uplink connection quality threshold (e.g., and be indicative that that TRP be kept) or below a second uplink connection quality threshold (e.g., and be indicative that that TRP be dropped). The first uplink connection quality threshold and / or the second uplink connection quality threshold can be based, at least in part, on the uplink connection quality of the other TRP (e.g., as described above in relation to FIG. 9). At operation S10.2, the apparatus receives, via the one of the first TRP and the second TRP with which the UE has continued uplink communication based on the configuration information, a single-TRP uplink communication from the UE. The apparatus can also stop receiving, via the one of the first TRP and the second TRP with which the UE has stopped uplink communication based on the configuration information, uplink communication from the UE. In some implementations, stopping uplink communication with one of the first TRP and the second TRP can comprise applying a transmission configuration indicator (TCI) state associated with the other one of the first TRP and the second TRP. In some implementations, the apparatus can receive a message (e.g., from the UE and via the first TRP and / or the second TRP) indicating a preferred TRP of the first TRP and the second TRP to be kept and / or a preferred TRP of the first TRP and the second TRP to be dropped when the signalling timing difference between the first TRP and the second TRP exceeds the signalling timing difference threshold. The message can be sent in the form of a MAC-CE message. In some implementations, the apparatus may subsequently send, to the UE, configuration information according to the message. For instance, this may be the case when a time varying metric corresponding to each of the TRPs is not conclusive as to which TRP to keep and / or drop (e.g., when the link connection quality is within a link connection quality difference threshold). FIG. 11 shows an apparatus 11 according to some example embodiments, which may form at least a part of a user equipment or network node. The apparatus 11 may comprise control apparatus 1100 which is configured to control operation of other components which form part of the apparatus 11 thereby to enable performance of various operations described herein. The control apparatus 1100 may comprise processing apparatus 1101 and memory 1102. Computer-readable code 1102-2A may be computer-readable code for any of the apparatus described herein and the computer-readable code 1102-2A may be stored on the memory 1102, which when executed by the processing apparatus 1101, causes the control apparatus 1100 to perform any of the operations described herein. In addition, the apparatus 11 may further include a network interface 1107 for communicating with other apparatuses 11. Some further details of components and features of the above-described entity / apparatus / device 11 and alternatives for them will now be described. The control apparatuses 1100 described above may comprise processing apparatus 1101 communicatively coupled with memory 1102. The memory 1102 has computer readable instructions 1102-2A stored thereon, which when executed by the processing apparatus 1101 causes the control apparatus 1100 to cause performance of various ones of the operations described with reference to Figs. 1 to 10. The control apparatus 1100 may in some instances be referred to, in general terms, as "apparatus". The processing apparatus 1101 may be of any suitable composition and may include one or more processors 1101A of any suitable type or suitable combination of types. Indeed, the term "processing apparatus" should be understood to encompass computers having differing architectures such as single / multi-processor architectures and sequencers / parallel architectures. For example, the processing apparatus 1101 may be a programmable processor that interprets computer program instructions 1102-2A and processes data. The processing apparatus 1101 may include plural programmable processors. Alternatively, the processing apparatus 1101 may be, for example, programmable hardware with embedded firmware. The processing apparatus 1101 may alternatively or additionally include one or more specialised circuit such as field programmable gate arrays FPGA, Application Specific Integrated Circuits (ASICs), signal processing devices etc. In some instances, processing apparatus 1101 may be referred to as computing apparatus or processing means. The processing apparatus 1101 is coupled to the memory 1102 and is operable to read / write data to / from the memory 1102. The memory 1102 may comprise a single memory unit or a plurality of memory units, upon which the computer readable instructions (or code) 1102-2A is stored. For example, the memory 1102 may comprise both volatile memory 1102-1 and non-volatile memory 1102-2. In such examples, the computer readable instructions / program code 1102-2A may be stored in the non-volatile memory 1102-2 and may be executed by the processing apparatus 1101 using the volatile memory 1102-1 for temporary storage of data or data and instructions. Examples of volatile memory include random-access memory (RAM), dynamic random-access memory (DRAM), and synchronous dynamic random-access memory (SDRAM) etc. Examples of non-volatile memory include read-only memory (ROM), programmable read-only memory (PROM), electronically erasable programmable read-only memory (EEPROM), flash memory, optical storage, magnetic storage, etc. The memory 1102 may be referred to as one or more non-transitory computer readable memory medium or one or more storage devices. Further, the term 'memory', in addition to covering memory comprising both one or more non-volatile memory and one or more volatile memory, may also cover one or more volatile memories only, one or more non-volatile memories only. In the context of this document, a "memory" or "computer-readable medium" may be any media or means that can contain, store, communicate, propagate or transport the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer. The computer readable instructions / program code 1102-2A may be pre-programmed into the control apparatus 1100. Alternatively, the computer readable instructions 1102-2A may arrive at the control apparatus via an electromagnetic carrier signal or may be copied from a physical entity 12 such as a computer program product, a memory device or a record medium such as a compact disc read-only memory (CD- ROM) or digital versatile disc (DVD) an example of which is illustrated in Fig. 12. The computer readable instructions 1102-2A may provide the logic and routines that enables the entity / device / apparatus 11 to perform the functionality described above. The combination of computer-readable instructions stored on memory (of any of the types described above) may be referred to as a computer program product. In general, references to computer program, instructions, code etc. should be understood to express software for a programmable processor firmware such as the programmable content of a hardware device as instructions for a processor or configured or configuration settings for a fixed function device, gate array, programmable logic device, etc. FIG. 12 shows a non-transitory media 12 according to some embodiments. The non-transitory media 12 is a computer readable storage medium. It may be e.g., a CD, a DVD, a USB stick, a blue ray disk, etc. The non-transitory media 12 stores instructions that, when executed by at least one processor, cause an apparatus to perform the method of any preceding process, for example as disclosed in relation to the flow diagrams and related features thereof. Names of network elements, protocols, and methods are based on current standards. In other versions or other technologies, the names of these network elements and / or protocols and / or methods may be different, as long as they provide a corresponding functionality. For example, embodiments may be deployed in 2G / 3G / 4G / 5G networks and further generations of 3GPP but also in non-3GPP radio networks such as WI-FI. A memory may be volatile or non-volatile. It may be e.g., a RAM, a SRAM, a flash memory, a FPGA block ram, a DCD, a CD, a USB stick, and a blue ray disk. If not otherwise stated or otherwise made clear from the context, the statement that two entities are different means that they perform different functions. It does not necessarily mean that they are based on different hardware. That is, each of the entities described in the present description may be based on a different hardware, or some or all of the entities may be based on the same hardware. It does not necessarily mean that they are based on different software. That is, each of the entities described in the present description may be based on different software, or some or all of the entities may be based on the same software. Each of the entities described in the present description may be embodied in the cloud. Implementations of any of the above-described blocks, apparatuses, systems, techniques or methods include, as non-limiting examples, Implementations as hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof. 5 Some embodiments may be implemented in the cloud. It is to be understood that what is described above is what is presently considered the preferred embodiments. However, it should be noted that the description of the preferred embodiments is given by way of example only and that various 10 modifications may be made without departing from the scope as defined by the appended claims.

Claims

1. An apparatus comprising:at least one processor;at least one memory storing instructions, wherein the instructions, when executed by the at least one processor, cause the apparatus to perform, at least:obtaining configuration information, the configuration information being usable to determine, when a signalling timing difference between a first communication network entity of a plurality of communication network entities and a second communication network entity of the plurality of communication network entities is greater than a signalling timing difference threshold, which of the plurality of communication network entities to stop uplink communication with and / or which of the plurality of communication network entities to continue uplink communication with;receiving, from the first communication network entity, a first signal;receiving, from the second communication network entity, a second signal; andin response to determining, based on the first signal and the second signal, that the signalling timing difference between the first communication network entity and the second communication network entity is greater than the signalling timing difference threshold:determining, based on the configuration information, which of the plurality of communication network entities to stop uplink communication with and / or which of the plurality of communication network entities to continue uplink communication with, and responsively:stopping uplink communication with at least one communication network entity of the plurality of communication network entities.

2. The apparatus of claim 1, wherein the instructions, when executed by the at least one processor, cause the apparatus to further perform:performing uplink communication with at least one of the other communication network entities of the plurality of communication network entities.

3. The apparatus of claim 1 or claim 2, wherein the configuration information is indicative of one or more selection criteria, wherein determining which of the plurality of communication network entities to stop uplink communication with and / or which of the plurality of communication network entities to continue uplink communication withis based on determining which of the plurality of communication network entities satisfies the one or more selection criteria.

4. The apparatus of claim 3, wherein the one or more selection criteria is associated with link quality and determining which of the plurality of communication network entities to stop uplink communication with comprises:determining which of the plurality of communication network entities is associated with the lowest link quality, and / orwherein determining which of the plurality of communication network entities to continue uplink communication with comprises:determining which of the plurality of communication network entities is associated with the highest link quality.

5. The apparatus of claim 3 or claim 4, wherein the one or more selection criteria is associated with a value of an identifier associated with the communication network entity and determining which of the plurality of communication network entities satisfies the one or more selection criteria comprises:determining which of the plurality of communication network entities is associated with the lowest identifier value and / or which of the plurality of communication network entities is associated with the highest identifier value.

6. The apparatus of any one of the preceding claims, wherein the configuration information is indicative of a particular communication network entity of the plurality of communication network entities to be kept and / or a particular communication network entity of the plurality of communication network entities to be dropped.

7. The apparatus of any one of the preceding claims, wherein the configuration information is predefined and is stored at the apparatus prior to the apparatus being configured for multiple communication network entity uplink communications.

8. The apparatus of any one of the preceding claims, wherein the configuration information is received via at least one of the plurality of communication network entities.

9. The apparatus of any one of the preceding claims, wherein the instructions, when executed by the at least one processor, cause the apparatus to further perform: transmitting, to at least one of the other communication network entities, a message indicating that the apparatus has stopped uplink communication with the atleast one of the communication network entities and / or that the signalling timing difference between the first communication network entity and the second communication network entity is greater than the signalling timing difference threshold.

10. The apparatus of any one of the preceding claims, wherein the instructions, when executed by the at least one processor, cause the apparatus to further perform:receiving, from the first communication network entity, a subsequent first signal;receiving, from the second communication network entity, a subsequent second signal; andIn response to determining, based on the subsequent first signal and the subsequent second signal, that a subsequent signalling timing difference between the first communication network entity and the second communication network entity is not greater than the signalling timing difference threshold:resuming uplink communication with the at least one communication network entity.

11. The apparatus of claim 10, wherein the instructions, when executed by the at least one processor, cause the apparatus to further perform:transmitting, to the at least one communication network entity, a message indicating that the apparatus stopped uplink communication with the at least one communication network entity and / or that the signalling timing difference between the first communication network entity and the second communication network entity was greater than the signalling timing difference threshold.

12. The apparatus of any one of the preceding claims, wherein the instructions, when executed by the at least one processor, cause the apparatus to further perform:In response to determining, based on the first signal and the second signal, that the signalling timing difference between the first communication network entity and the second communication network entity is not greater than the signalling timing difference threshold:continuing uplink communication with the plurality of communication network entities.

13. The apparatus of any one of the preceding claims, wherein the instructions, when executed by the at least one processor, cause the apparatus to further perform:initially configuring the apparatus to perform multi-communication network entity uplink communications with the plurality of communication network entitles.

14. An apparatus comprising:at least one processor;at least one memory storing instructions, wherein the instructions, when executed by the at least one processor, cause the apparatus to perform, at least: determining configuration information, the configuration informationbeing usable by a user equipment (UE) configured for multiple communication network entity uplink communication with a plurality of communication network entitles to determine, when a signalling timing difference between a first communication network entity of the plurality of communication network entities and a second communication network entity of the plurality of communication network entities is greater than a signalling timing difference threshold, which of the plurality of communication network entities to stop uplink communication with and / or which of the plurality of communication network entities to continue uplink communication with; andreceiving, via at least one communication network entity of the plurality of communication network entities with which the UE has continued uplink communication based on the configuration information, an uplink communication from the UE.

15. The apparatus of claim 14, wherein the instructions, when executed by the at least one processor, cause the apparatus to further perform:stopping receiving, via at least one communication network entity of the plurality of communication network entities with which the UE has stopped uplink communication based on the configuration information, uplink communications from the UE.

16. The apparatus of claim 14 or claim 15, wherein the configuration information is indicative of one or more selection criteria, and wherein the instructions, when executed by the at least one processor, cause the apparatus to further perform: determining which of the plurality of communication network entities to stop uplink communication with and / or which of the plurality of communication network entities to continue uplink communication with based on determining which of the plurality of communication network entities satisfies the one or more selection criteria.

17. The apparatus of claim 16, wherein the one or more selection criteria is associated with link quality and determining which of the plurality of communication network entities to stop uplink communication with comprises:determining which of the plurality of communication network entities is associated with the lowest link quality, and / orwherein determining which of the plurality of communication network entities to continue uplink communication with comprises:determining which of the plurality of communication network entities is associated with the highest link quality.

18. The apparatus of claims 16 or 17, wherein the one or more selection criteria is associated with value of an identifier associated with the communication network entity and determining which of the plurality of communication network entities satisfies the one or more selection criteria comprises:determining which of the plurality of communication network entities is associated with the lowest identifier value and / or which of the plurality of communication network entities is associated with the highest identifier value.

19. The apparatus of any one of claims 14 to 18, wherein the configuration information is indicative of a particular communication network entity of the plurality of communication network entities to be kept and / or a particular communication network entity of the plurality of communication network entities to be dropped.

20. The apparatus of any one of claims 14 to 19, wherein the instructions, when executed by the at least one processor, cause the apparatus to further perform:receiving, via at least one of the communication network entities of the plurality of communication network entities with which the UE has continued uplink communication based on the configuration information, a message indicating that the UE has stopped uplink communication with at least one of the communication network entities and / or that the signalling timing difference between the first communication network entity and the second communication network entity is greater than the signalling timing difference threshold.

21. The apparatus of any one of claims 14 to 20, wherein the instructions, when executed by the at least one processor, cause the apparatus to further perform:receiving, at a subsequent time when multi communication network entity uplink communications between the UE and the plurality of communication network entities have resumed and via at least one communication network entity, a messageindicating that the UE stopped uplink communication with the at least one communication network entity and / or that the signalling timing difference between the first communication network entity and the second communication network entity was greater than the signalling timing difference threshold.

22. The apparatus of any one of claims 14 to 21, wherein the instructions, when executed by the at least one processor, cause the apparatus to further perform:sending, to the UE, the configuration information.

23. A method performed by a user equipment, UE, comprising:obtaining configuration information, the configuration information being usable to determine, when a signalling timing difference between a first communication network entity of a plurality of communication network entities and a second communication network entity of the plurality of communication network entities is greater than a signalling timing difference threshold, which of the plurality of communication network entities to stop uplink communication with and / or which of the plurality of communication network entities to continue uplink communication with;receiving, from the first communication network entity, a first signal;receiving, from the second communication network entity, a second signal; and In response to determining, based on the first signal and the second signal, that the signalling timing difference between the first communication network entity and the second communication network entity is greater than the signalling timing difference threshold:determining, based on the configuration information, which of the plurality of communication network entities to stop uplink communication with and / or which of the plurality of communication network entities to continue uplink communication with, and responsively:stopping, uplink communication with at least one communication network entity of the plurality of communication network entities.

24. A method performed by a radio base station, comprising:determining configuration information, the configuration information being usable by a user equipment (UE) configured for multiple communication network entity uplink communication with a plurality of communication network entities to determine, when a signalling timing difference between a first communication network entity of the plurality of communication network entities and a second communication network entity of the plurality of communication network entities is greater than asignalling timing difference threshold, which of the plurality of communication network entities to stop uplink communication with and / or which of the plurality of communication network entities to continue uplink communication with; andreceiving, via at least one communication network entity of the plurality of5 communication network entities with which the UE has continued uplink communication based on the configuration information, an uplink communication from the UE.

25. A computer program comprising instructions which, when executed by an10 apparatus, cause the apparatus to perform the method of claim 23 or claim 24.

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