Methods and apparatuses relating to wireless communication

Abstract

Methods and Apparatuses relating to Wireless Communication This specification describes a terminal device comprising: means for performing simultaneous uplink transmissions using a first transmission configuration indicator, TCI, state and a second TCI state; means for determining whether a transmit power imbalance between the first TCI state and the second TCI state exceeds a transmit power imbalance threshold; and means for, in a case that the transmit power imbalance threshold is exceeded, deactivating one of the first TCI state and the second TCI state.

Description

[0001] Methods and Apparatuses relating to Wireless Communication

[0002] Field

[0003] This specification relates generally to wireless communication.

[0004] Background

[0005] Terminal devices, sometimes referred to as 'user equipment' (UE), can communicate wirelessly with radio access nodes (e.g. base stations) of a network. Such communication may facilitate a variety of tasks.

[0006] Summary

[0007] In a first aspect, this specification describes a terminal device comprising: means for performing simultaneous uplink transmissions using a first transmission configuration indicator, TCI, state and a second TCI state; means for determining whether a transmit power imbalance between the first TCI state and the second TCI state exceeds a transmit power imbalance threshold; and means for, in a case that the transmit power imbalance threshold is exceeded, deactivating one of the first TCI state and the second TCI state. In some examples, the terminal device further comprises means for receiving, from a network node, configuration information indicative of the transmit power imbalance threshold. In addition or alternatively, the transmit power imbalance threshold may be pre-configured at the terminal device.

[0008] In some examples, the terminal device further comprises means for determining a first required transmit power reduction value for the first TCI state and a second required transmit power reduction value for the second TCI state for compliance with a maximum total radiated power value or a maximum effective isotropic radiated power value. In some such examples, the transmit power imbalance between the first TCI state and the second TCI state may be determined to exceed the transmit power imbalance threshold when a first transmit power value for the first TCI state resulting from application of the first required transmit power reduction value and a second transmit power value for the second TCI state resulting from application of the second required transmit power reduction value differ by at least the transmit power imbalance threshold.

[0009] In some examples, the terminal device further comprises means for, in a case that the transmit power imbalance threshold is exceeded, transmitting, to a network node, an indication that the transmit power imbalance threshold is exceeded. In some such examples, reception of the indication by the network node causes at least one network resource associated with uplink transmissions performed using the deactivated one of the first TCI state and the second TCI state to be released. In some examples, in a case that the transmit power imbalance threshold is exceeded, the one of the first TCI state and the second TCI state is deactivated based on quality metrics associated with the first TCI state and the second TCI state.

[0010] In some examples, the terminal device further comprises means for receiving, from a network node, information indicating which of the first TCI state and second TCI state to deactivate in a case that the transmit power imbalance threshold is exceeded. In addition or alternatively, the terminal device further comprises means for, in a case that the transmit power imbalance threshold is not exceeded, continuing performance of simultaneous uplink transmissions using the first TCI state and the second TCI state. In addition or alternatively, uplink transmissions performed using the first TCI state are associated with a first network node and uplink transmissions performed using the second TCI state are associated with a second network node.

[0011] In a second aspect, this specification describes a network node comprising: means for transmitting, to a terminal device, configuration information indicative of a transmit power imbalance threshold for use in determining whether to deactivate one of a first transmission configuration indicator, TCI, state and a second TCI state used for simultaneous uplink transmissions by the terminal device. In some examples, the network node further comprises means for receiving, from the terminal device, an indication that a power imbalance between the first TCI state and the second TCI state exceeds the transmit power imbalance threshold. In some such examples, the network node further comprises means for, responsive to the indication, releasing at least one network resource associated with uplink transmissions performed using a deactivated one of the first TCI state and the second TCI state.

[0012] In a third aspect, this specification describes a network node comprising: means for receiving, from a terminal device performing simultaneous uplink transmissions using a first transmission configuration indicator, TCI, state and a second TCI state, an indication that a power imbalance between the first TCI state and the second TCI state exceeds a transmit power imbalance threshold.

[0013] In a fourth aspect, this specification describes an apparatus (e.g. a terminal device) comprising at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to perform: performing simultaneous uplink transmissions using a first transmission configuration indicator, TCI, state and a second TCI state; determining whether a transmit power imbalance between the first TCI state and the second TCI state exceeds a transmit power imbalance threshold; and, in a case that the transmit power imbalance threshold is exceeded, deactivating one of the first TCI state and the second TCI state. In some examples, the instructions stored on the at least one memory of the apparatus of the fourth aspect, when executed by the at least one processor, may cause the apparatus at least to perform: receiving, from a network node, configuration information indicative of the transmit power imbalance threshold. In addition or alternatively, the transmit power imbalance threshold may be pre-configured at the terminal device.

[0014] In some examples, the instructions stored on the at least one memory of the apparatus of the fourth aspect, when executed by the at least one processor, may cause the apparatus at least to perform determining a first required transmit power reduction value for the first TCI state and a second required transmit power reduction value for the second TCI state for compliance with a maximum total radiated power value or a maximum effective isotropic radiated power value. In some such examples, the transmit power imbalance between the first TCI state and the second TCI state may be determined to exceed the transmit power imbalance threshold when a first transmit power value for the first TCI state resulting from application of the first required transmit power reduction value and a second transmit power value for the second TCI state resulting from application of the second required transmit power reduction value differ by at least the transmit power imbalance threshold.

[0015] In some examples, the instructions stored on the at least one memory of the apparatus of the fourth aspect, when executed by the at least one processor, may cause the apparatus at least to perform, in a case that the transmit power imbalance threshold is exceeded, transmitting, to a network node, an indication that the transmit power imbalance threshold is exceeded. In some such examples, reception of the indication by the network node causes at least one network resource associated with uplink transmissions performed using the deactivated one of the first TCI state and the second TCI state to be released. In some examples, in a case that the transmit power imbalance threshold is exceeded, the one of the first TCI state and the second TCI state is deactivated based on quality metrics associated with the first TCI state and the second TCI state.

[0016] In some examples, the instructions stored on the at least one memory of the apparatus of the fourth aspect, when executed by the at least one processor, may cause the apparatus at least to perform receiving, from a network node, information indicating which of the first TCI state and second TCI state to deactivate in a case that the transmit power imbalance threshold is exceeded. In addition or alternatively, the instructions stored on the at least one memory of the apparatus of the fourth aspect, when executed by the at least one processor, may cause the apparatus at least to perform, in a case that the transmit power imbalance threshold is not exceeded, continuing performance of simultaneous uplink transmissions using the first TCI state and the second TCI state. In addition or alternatively, uplink transmissions performed using the first TCI state are associated with a first network node and uplink transmissions performed using the second TCI state are associated with a second network node.

[0017] In a fifth aspect, this specification describes an apparatus (e.g. a network node) comprising at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to perform: transmitting, to a terminal device, configuration information indicative of a transmit power imbalance threshold for use in determining whether to deactivate one of a first transmission configuration indicator, TCI, state and a second TCI state used for simultaneous uplink transmissions by the terminal device. In some examples, the instructions stored on the at least one memory of the apparatus of the fifth aspect, when executed by the at least one processor, may cause the apparatus at least to perform: receiving, from the terminal device, an indication that a power imbalance between the first TCI state and the second TCI state exceeds the transmit power imbalance threshold. In some such examples, the instructions stored on the at least one memory of the apparatus of the fifth aspect, when executed by the at least one processor, may cause the apparatus at least to perform: responsive to the indication, releasing at least one network resource associated with uplink transmissions performed using a deactivated one of the first TCI state and the second TCI state.

[0018] In a sixth aspect, this specification describes an apparatus (e.g. a network node) comprising at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to perform receiving, from a terminal device performing simultaneous uplink transmissions using a first transmission configuration indicator, TCI, state and a second TCI state, an indication that a power imbalance between the first TCI state and the second TCI state exceeds a transmit power imbalance threshold. In a seventh aspect, this specification describes a method comprising: performing simultaneous uplink transmissions using a first transmission configuration indicator, TCI, state and a second TCI state; determining whether a transmit power imbalance between the first TCI state and the second TCI state exceeds a transmit power imbalance threshold; and in a case that the transmit power imbalance threshold is exceeded, deactivating one of the first TCI state and the second TCI state.

[0019] In some examples, the method further comprises receiving, from a network node, configuration information indicative of the transmit power imbalance threshold. In addition or alternatively, the transmit power imbalance threshold may be preconfigured at the terminal device.

[0020] In some examples, the method further comprises determining a first required transmit power reduction value for the first TCI state and a second required transmit power reduction value for the second TCI state for compliance with a maximum total radiated power value or a maximum effective isotropic radiated power value. In some such examples, the transmit power imbalance between the first TCI state and the second TCI state may be determined to exceed the transmit power imbalance threshold when a first transmit power value for the first TCI state resulting from application of the first required transmit power reduction value and a second transmit power value for the second TCI state resulting from application of the second required transmit power reduction value differ by at least the transmit power imbalance threshold.

[0021] In some examples, the method further comprises, in a case that the transmit power imbalance threshold is exceeded, transmitting, to a network node, an indication that the transmit power imbalance threshold is exceeded. In some such examples, reception of the indication by the network node causes at least one network resource associated with uplink transmissions performed using the deactivated one of the first TCI state and the second TCI state to be released. In some examples, in a case that the transmit power imbalance threshold is exceeded, the one of the first TCI state and the second TCI state is deactivated based on quality metrics associated with the first TCI state and the second TCI state.

[0022] In some examples, the method further comprises receiving, from a network node, information indicating which of the first TCI state and second TCI state to deactivate in a case that the transmit power imbalance threshold is exceeded. In addition or alternatively, the method further comprises, in a case that the transmit power imbalance threshold is not exceeded, continuing performance of simultaneous uplink transmissions using the first TCI state and the second TCI state. In addition or alternatively, uplink transmissions performed using the first TCI state are associated with a first network node and uplink transmissions performed using the second TCI state are associated with a second network node.

[0023] In an eighth aspect, this specification describes a method comprising: transmitting, to a terminal device, configuration information indicative of a transmit power imbalance threshold for use in determining whether to deactivate one of a first transmission configuration indicator, TCI, state and a second TCI state used for simultaneous uplink transmissions by the terminal device. In some examples, the method further comprises receiving, from the terminal device, an indication that a power imbalance between the first TCI state and the second TCI state exceeds the transmit power imbalance threshold. In some such examples, the method further comprises, responsive to the indication, releasing at least one network resource associated with uplink transmissions performed using a deactivated one of the first TCI state and the second TCI state.

[0024] In a ninth aspect, this specification describes a method comprising: receiving, from a terminal device performing simultaneous uplink transmissions using a first transmission configuration indicator, TCI, state and a second TCI state, an indication that a power imbalance between the first TCI state and the second TCI state exceeds a transmit power imbalance threshold.

[0025] In a tenth aspect, this specification describes a non-transitory computer readable medium comprising program instructions stored thereon for performing at least any of the operations described above with reference to the seventh to ninth aspects.

[0026] Brief Description of the Figs.

[0027] For a better understanding of the present application, reference will now be made by way of example to the accompanying drawings in which:

[0028] Fig. 1A is an example illustrating a terminal device in communication with a plurality of base stations;

[0029] Fig. IB is a graph illustrating constructive interference of overlapping transmit beams of a terminal device;

[0030] Fig. 2 is an example message flow sequence;

[0031] Figs. 3 and 4 are flowcharts illustrating various operations that may be performed in accordance with examples described herein; Fig. 5 is a schematic illustration of an example configuration of a computing device which may be configured to perform various operations described with reference to Figs. 1 to 4;

[0032] Fig. 6 is a schematic illustration of an example configuration of a base station which may be configured to perform various operations described with reference to Figs. 1 to 4; and

[0033] Fig. 7 is an illustration of a computer-readable medium upon which computer readable code may be stored.

[0034] Detailed Description

[0035] In the description and drawings, like reference numerals refer to like elements throughout.

[0036] In modern telecommunications networks (e.g. New Radio, NR, telecommunications networks), a terminal device may perform wireless communications using multiple antenna panels and / or beams simultaneously. For instance, the network may instruct the terminal device to perform uplink (UL) transmissions and / or receive downlink (DL) signals using a particular beam or antenna available to the terminal device. In NR networks, such beam management may be performed using a transmission configuration indication (TCI) signalling framework. Specifically, the network may provide the terminal device with an indication of one or more 'TCI states' for use in performing wireless communications.

[0037] In the context of UL transmissions, a TCI state may identify one or more beams and / or antenna panels for use by the terminal device in transmitting signals to a network node. Beams, antenna panels, or TCI states can be used interchangeably. In some examples, a TCI state may be associated with an identifier (i.e. a TCI 'state id') which may be provided to the terminal device by the network to indicate that a particular TCI state should be used for transmissions. In addition or alternatively, the TCI state may include one or more channel parameters for use in configuring the terminal device for transmission via the indicated beam. For instance, the TCI state may include quasi co-location (QCL) information associated with one or more antenna ports of the terminal device. For instance, QCL information may include bandwidth part (BWP), and a reference signal ID (such as synchronization signal block, SSB, index or another resource indicator). In addition, the TCI state may include UL power parameters and / or a physical cell ID (PCI). Various other aspects of TCI states will be apparent to the skilled person. For physical uplink shared channel (PUSCH) transmission, a TCI state may identify a SSB index, a channel state information reference signal (CSI-RS) resource indicator (CRI), a sounding reference signal (SRS) resource indicator (SRI), or a path loss reference signal (PL-RS) resource indicator. The terminal device may then set its analogue beamforming coefficients for transmitting PUSCH signals based on the indicated resource. The unified TCI framework may be used for indicating the applicable UL and DL TCI states. Alternatively, the UL beams to use may be indicated using the spatial relation information framework.

[0038] A terminal device may perform transmissions using multiple TCI states simultaneously, such as when transmitting to multiple base stations concurrently. In some examples, simultaneous transmission is performed using multiple antenna panels (or antenna arrays) of the terminal device. Such transmission, which may be referred to as 'simultaneous transmission across multiple panels' (STxMP), is depicted in Fig. 1A. Alternatively, rather than transmitting from separate antenna panels, simultaneous transmission using multiple TCI states may be accomplished using different directional beams of a single antenna array.

[0039] As will be appreciated, simultaneous transmission of signals using multiple TCI states may cause constructive interference where concurrently transmitting beams overlap. For instance, beams may overlap when they are steered in the same direction or where their sidelobes overlap. As such, the maximum equivalent isotropic radiation power (EIRP) associated with a UE performing STxMP using two antenna panels, such as depicted in Fig. 1A, is achieved when the two panels are transmitting with maximum power (e.g. using a maximum power amplification, PA, configuration) and their directional transmit beams overlap, causing constructive interference. An example of constructive interference between overlapping transmit beams from separate antenna panels is depicted in the graph of Fig. IB. It will be apparent that the maximum EIRP is achieved when both beams / panels are pointing in the same direction or are closely aligned.

[0040] However, regulatory requirements specify limits on both maximum EIRP and maximum total radiated power (TRP) for terminal devices. Exceeding these limits may cause excessive interference with other networked devices and / or pose a health risk. As such, terminal devices must comply with maximum TRP and / or maximum EIRP limits to the greatest extent possible. Different maximum transmission power limits are specified for different types of devices, and are set out in 3GPP TS 38.101-2. For instance, 'power class 1' specifies a maximum TRP limit of 35 dBm and a maximum EIRP limit of 55 dBm in operating bands n257, n258, n260, n261 and n262, whilst 'power class 2' specifies a maximum TRP limit of 23 dBm and a maximum EIRP limit of 43 dBm in operating bands n257, n258, n260, n261 and n262. Power class 1 is intended for fixed wireless access (FWA) UEs, whilst power class 2 is intended for vehicular applications. It will be appreciated that the technology described herein may also be applicable to other power classes, provide the devices in question are capable of transmitting via multiple TCI states simultaneously. Output power limits are typically defined per UE rather than per panel.

[0041] The aforementioned interference between overlapping beams when transmitting using multiple TCI states simultaneously may cause the peak EIRP and / or TRP of the terminal device to exceed these limits. Put another way, constructive interference between concurrently used overlapping transmit beams may cause the terminal device's peak EIRP for certain directions to exceed a maximum allowed EIRP and / or may cause a TRP for the terminal device to exceed a maximum allowed TRP. To prevent the regulatory limits from being exceeded, the terminal device may reduce its power amplified (PA) output power. For instance, this may be achieved using power management maximum power reduction (P-MPR). As described in 3GPP TS 38.101-2, P-MPR allows the terminal device to reduce the maximum transmitted power for each of its transmitters so as to comply with the maximum EIRP and / or maximum TRP limits described above. For instance, a transmit power reduction value (sometimes referred to as a 'power management maximum output power reduction' value) for a given carrier f and serving cell c may be denoted MPRf c. P-MPR is applied by the terminal device autonomously and accordingly scales down the value PCAMy / t(the configured maximum terminal device output power for carrier f and serving cell c) when reporting power headroom to the network.

[0042] Although the terminal device may apply the same transmit power reduction value to each of the TCI states used for simultaneous transmission, thereby symmetrically reducing the output power, the terminal device may instead elect to reduce the transmission power associated with one of the TCI states more than that of another TCI state, giving an asymmetric reduction in output power. For instance, the terminal may reduce output power asymmetrically in the event of a radio frequency (RF) impairment, or to meet a transmission power limit as described above.

[0043] For a given maximum TRP limit, there are many different ways of asymmetrically reducing transmit power associated with a pair of TCI states so as to comply with the limit. For instance, the table below includes several asymmetric transmit power combinations that may be chosen by a terminal device for two UL TCI states (TCI A and TCI B) restricted by a maximum TRP limit of 35 dBm (e.g. corresponding to a power class 1 device):

[0044] In the table above, 'OFF' indicates that the TCI B state is switched off or deactivated.

[0045] As explained above, the P-MPR mechanism is autonomously performed by the terminal device without the knowledge or control of the network. However, asymmetric transmit power reduction between the simultaneous TCI states may cause degradation in UL performance or even lead to failures (e.g. radio link failures, RLF). For instance, a given base station (e.g. gNB) may only support a certain amount of power imbalance between TCI states. As will be appreciated, the extent to which a base station may support a power imbalance may depend on a variety of factors, such as at least one of: channel quality (e.g. roundtrip time, RTT, packet loss ratio, PLR etc.), multipath characteristics (e.g. whether signals arrive at the base station from the terminal device via a line of sight or non-line of sight path), a theoretical / measured / report rank indicator, base station instrument sensitivity, transmission type (e.g. redundant repetition of the same 2-layer or 4-layer data), the MIMO mode (e.g. single downlink control information, s-DCI, or multiple downlink control information, m-DCI), the gNB processing type (e.g. Maximum ratio combining, MRC, or others), and / or other factors.

[0046] For instance, single DCI may refer to the case in which a common scheduler is used for both base stations and a single codeword is used for multi-layer transmission. In this situation, very similar power levels are required between the two links to yield throughput gain from the additional link (e.g. less than a 3 dB power difference between the links). This may be considered to be a 'true four-layer system'. On the other hand, multiple DCI may refer to the case in which independent schedulers are used for the different base stations with little coordination between the base stations (e.g. non-ideal backhaul). In this case, two codewords are used for a four-layer transmission and so the throughput is not as sensitive to the power difference between the links. Put another way, a larger UL power difference between the two links may be acceptable for the base station (e.g. gNB) to yield a gain. This may be considered to be more similar to a 'two-times two-layer system'. In this case, the Rx sensitivity level of the one base station may be relevant when the UL is no longer useful, independently of the other link to the other base station.

[0047] MRC may refer to a diversity combining technique which can yield gain by combining multiple links. It may also increase signal to noise ratio (SNR), to mitigate against fading. It will be appreciated that the closer the power levels of each of the links, the higher the gain of MRC. On the other hand, selection combining selects only the link with the highest SNR. Since only the 'best' link is selected, the power level different of the respective links is not relevant.

[0048] There therefore exists a need for a mechanism to dynamically control asymmetric power reduction for terminal device transmissions from the network side, thereby enabling compliance with TRP / EIRP limits whilst improving network performance and avoiding network failures or degradation. Various implementations of the technology described herein may fulfil this need.

[0049] In particular, implementations of the technology described herein relate to performing simultaneous uplink transmissions using a first TCI state and a second TCI state; determining whether a transmit power imbalance between the first TCI state and the second TCI state exceeds a transmit power imbalance threshold; and, in a case that the transmit power imbalance threshold is exceeded, deactivating one of the first TCI state and the second TCI state. Some example aspects relate to performing uplink transmissions using the other one of the first TCI state and the second TCI state that is not deactivated. Other example aspects relate to, in a case that the uplink power imbalance threshold is not exceeded, continuing performance of simultaneous uplink transmissions using the first TCI state and the second TCI state.

[0050] In some examples, the term 'terminal device' or 'user equipment' may refer to any device employed by a user to communicate. Whilst the terminal device of Fig. 1A is depicted schematically, it will of course be appreciated that terminal devices may comprise various devices, including, but not limited to smartphones, laptops, smartwatches, tablet computers and vehicle-based terminal devices, such as those mounted on cars, buses, uncrewed aerial vehicles (UAVs), aeroplanes, trains, or boats. Alternatively, mobile terminal devices may be carried by a user, or worn on their person.

[0051] Various methods and apparatuses are described in detail below, by way of example only, in the context of a cellular network, such as an Evolved Universal Terrestrial Radio Access (E-UTRA) network or a 5G network. However, it will be appreciated that the techniques may be applicable with communications networks of other types (e.g. but not limited to other types of cellular network). Cellular networks may comprise one or more base stations, sometimes referred to as transmit-receive points, network nodes, radio access nodes, or access points (e.g. but not limited to gNBs and / or eNBs). Whilst only two base stations are depicted in Fig. 1, a radio access network (RAN, NG-RAN) may typically comprise thousands of such base stations. Together, the base stations may provide cellular network coverage to one or more terminal devices over a wide geographical area.

[0052] Although by no means limited to such an implementation, the examples of the technology described herein may readily be integrated into any NR terminal device which performs STxMP communications.

[0053] In some implementations and, for instance, depending on the characteristics of the cellular network, the base stations and terminal devices within the network may be configured to communicate with one another, for instance, using an OFDM-based communication scheme, such as orthogonal frequency-division multiple access (OFDMA), single carrier frequency-division multiple access (SC-FDMA), and / or cyclic prefix orthogonal frequency-division multiple access (CP-OFDMA). For instance, in some non-limiting examples, OFDMA may be used for downlink (DL) communications, and SC-FDMA or OFDMA may be used for uplink (UL) communications.

[0054] Fig. 1A depicts a terminal device 100 in communication with first base station 150 and a second base station 160. In particular, terminal device 100 is depicted performing simultaneous uplink transmissions to both a first network node 150 using a first antenna panel 110 and a second network node 160 using a second antenna panel 120. As explained above, Fig. 1A therefore depicts an example of STxMP for multi-transmit- receive point (multi-TRP) operations. Whilst Fig. 1A depicts transmissions from multiple panels, it will be appreciated that transmissions may be performed from different beams of the same panel instead. In general, implementations of the technology described herein relate to performing simultaneous uplink transmissions using a first TCI state and a second TCI state, as described above. For simplicity, henceforth transmissions via antenna panel 110 will be referred to as being performed using the first TCI state, whilst transmissions via antenna panel 120 will be referred to as being performed using the second TCI state. However it will be appreciated that other mappings between TCI states and beams / antenna panels may be used.

[0055] Antenna panel 110 of terminal device 100 is associated with receive (Rx) chain 115 and transmit (Tx) chain 116, and has a plurality of beams llOa-c. Similarly, antenna panel 120 is associated with Rx chain 125 and Tx chain 126, and has a plurality of beams 120a-c. Wide angle beams for each of the antenna panels are also depicted. Although each antenna panel is depicted as having three directed beams, it will be appreciated that more or fewer beams may be associated with each antenna panel. Moreover, antenna panel 110 may be associated with a different number of beams compared to antenna panel 120.

[0056] As explained above, terminal device 100 may autonomously apply asymmetric power reduction. For instance, this may allow terminal device 100 to comply with a maximum TRP / EIRP threshold. In some examples, and as described below with reference to Fig. 2, asymmetric power reduction may be applied by terminal device 100 subsequent to UL power imbalance being authorised for use by the network.

[0057] During performance of uplink transmissions, terminal device 100 determines whether a transmit power imbalance between the first TCI state and the second TCI state exceeds a transmit power imbalance threshold. In some examples, this threshold is preconfigured at terminal device 100. In other examples, the threshold is received in configuration information (e.g. RRC reconfiguration information) from the network (e.g. via network node 150 or 160).

[0058] As explained above, there are many different asymmetric combinations of transmit power reduction values (P-MPR values) that may be used to achieve a given TRP threshold when performing simultaneous transmissions with two TCI states. Several example transmit power reduction values for UE power class 1, which has a maximum TRP limit of 35 dBm are given in the table below:

[0059] The transmit power imbalance threshold may be determined to be exceeded when the transmit power reduction values for the first and second TCI states differ by at least the threshold (or, equivalently, if the power values resulting from application of the P- MPR values differ by at least the threshold). For instance, if the threshold is 5 dBm, the first three rows of the table above would correspond to the threshold being exceeded (note that the first row, for which the second TCI state is deactivated entirely, could be considered to correspond to a P-MPR value of 35.00 dBm). By contrast, the last two rows (emphasised) would fall within the threshold.

[0060] Alternatively, rather than specifying a limit on a difference between the P-MPR values for the first and second TCI states, the transmit power imbalance threshold may be determined to be exceeded when either of the first or second transmit power reduction values exceed the threshold. Again, in the table above the first three rows would correspond to the threshold being exceeded and the last two would fall within the threshold.

[0061] In the example of Fig. 1, in a case that the transmit power imbalance threshold is exceeded, terminal device 100 deactivates (possibly in response to a network instruction to do so, as described below with reference to operation 216 of Fig. 2) one of the first TCI state and the second TCI state, and performs uplink transmissions using the other one of the first TCI state and the second TCI state that has not been deactivated. In the example of the table above, the first row may be deemed to be a 'default option' in the event that the imbalance threshold is exceeded, and can be used in place of the other rows for which the threshold is exceeded (i.e. rows 2 and 3). Put another way, the threshold puts an upper limit on the transmit power imbalance. If the transmit power imbalance is above the threshold, the terminal device is required to switch off one of the TCI state, for instance the TCI state with the lower power.

[0062] In some examples, in a case that the uplink power imbalance threshold is not exceeded, terminal device 100 continues performance of simultaneous uplink transmissions using the first TCI state and the second TCI state, while applying the required power reduction values for the first and second TCI states if any. Various signalling aspects of the technology described herein are described below with reference to Fig. 2.

[0063] Fig. 2 is a message flow sequence, indicated generally by the reference numeral 2, in accordance with some aspects of the described technology. The message flow sequence 2 shows an example implementation within which aspects of a process, such as that described with reference to Fig. 1A, may be performed. In this example, a terminal device 100 is shown in communication with two access nodes of a network, base stations 150 and 160.

[0064] In general terms, the process depicted in Fig. 2 relates to the situation in which a terminal device is performing simultaneous uplink transmissions using a plurality of TCI states, such as the situation described with reference to Fig. 1A.

[0065] It will be appreciated that various operations and entities described with reference to Fig. 2 may correspond to operations and entities described with reference to the preceding Figs. It will be further appreciated that various operations described with reference to Fig. 2 may be performed by entities other than those expressly depicted. For instance, some or all of the operations attributed to base stations 150 and 160 may be performed by other network entities, such as another base station or a core network (CN) entity.

[0066] In operation 201, a radio resource control (RRC) connection is established between UE 100 and base station 150.

[0067] In operation 202, base station 150 determines a transmit power imbalance threshold for simultaneous uplink transmissions performed by terminal device 100. Put another way, base station 150 determines a maximum allowable threshold for UL power imbalance. In some examples, the transmit power imbalance threshold may be determined based on a sensitivity of an Rx antenna of base station 150 and / or a UL combining type (e.g. MRC vs selection combining, or s-DCI vs m-DCI configuration).

[0068] In addition or alternatively, the threshold may be determined based on measurements performed by terminal device 100 of signals received from the network, such as Ll- RSRP (reference signal received power) measurements of CSI-RS or SSB. In some such examples, measurements may be performed by the terminal device for each base station. In operation 203, TRP 150 determines which TCI state (e.g. from the first and second TCI states) should be deactivated in the event that the threshold determined in operation 202 is met or exceeded. For instance, TRP 150 may determine that transmissions using the first TCI state should continue to be performed, but that transmissions using the second TCI state should cease. Put another way, it may be determined that the second TCI state should be deactivated, whilst the first TCI state should remain active. Alternatively, TRP 150 may determine that the first TCI state should be deactivated in the event that the threshold is met, whilst the second TCI state should remain active.

[0069] As explained above, the UL TCI states of terminal device may correspond to base stations of the network. In this regard, rather than determining which TCI state should be deactivated in the event that the transmit power imbalance threshold is exceeded, TRP 150 may instead identify which of TRP 150 and TRP 160 the UL transmissions should be maintained for. For example, it may be determined that UL transmissions directed to TRP 150 should be maintained (which may, for instance, correspond to transmissions using the first TCI state), whilst UL transmissions directed to TRP 160 should cease (which may, for instance, correspond to transmissions using the second TCI state) (or vice versa).

[0070] In some examples, rather than determining which specific TCI state to identify, operation 203 may comprise determining a rule for the terminal device to follow when determining which TCI state to deselect / deactivate in the event that the transmit power imbalance threshold is exceeded. For instance, it may be determined to deactivate the TCI state associated with the lowest quality channel (e.g. as indicated by a lowest reference signal received power, RSRP, received signal strength indicator, RSSI measurements, channel quality indicator, CQI, or modulation coding scheme, MCS, value). Alternatively, TCI states associated with UL transmissions to more distant network nodes may be deactivated over those TCI states associated with UL transmissions to network nodes which are closer to the terminal device.

[0071] It will be appreciated that allowing the network to determine which TCI states should be maintained (e.g. based on channel quality measurements) may contribute to improvements in UL spectral efficiency.

[0072] In operation 204, base station 150 transmits configuration information (e.g. RRC reconfiguration information) including the transmit power imbalance threshold determined in operation 202 to terminal device 100. In some examples, the configuration information may further include an indication that UL power imbalance may be enabled at terminal device 100 when performing simultaneous uplink transmission. In addition or alternatively, the configuration information may include the TCI state determined, in operation 203, to be deactivated in the event that the transmit power imbalance threshold is met or exceeded by terminal device 100, or an indication of a rule for use in identifying the TCI state to deactivate.

[0073] In this way, the network may dynamically limit the allowable power imbalance between the two TCI states in use by the terminal device. In some examples, rather than using the R.RC reconfiguration mechanism, medium access control (MAC) signalling may be used. This may allow for greater flexibility in the event that the threshold needs to be changed regularly by the network.

[0074] As explained above with reference to Fig. 1A, the transmit power imbalance threshold may instead be preconfigured at the terminal device (e.g. 3 dB maximum power imbalance). This has the advantage that no R.RC signalling overhead is introduced, but is less flexible and so may lead to sub-optimal UL performance. Similarly, a rule for selecting which TCI state to deactivate in the event that the transmit power imbalance threshold is met may also be preconfigured at the terminal device. In some examples, a threshold or rule that is preconfigured at the device may be superseded by another rule or threshold (e.g. an updated version) that is provided by the network in the manner described above.

[0075] In operation 205, base station 150 transmits further configuration or control information to terminal device 100, thereby to configure terminal device 100 for performance of simultaneous uplink transmissions to base station 150 and base station 160. For instance, the further information may indicate the TCI states to be used for UL transmissions to each of base station 150 and station 160 (i.e. the first and second TCI states), for instance through downlink control information (DCI) or R.RC signalling (e.g. R.RC reconfiguration information).

[0076] As will be appreciated, in some examples, the information transmitted in operations 204 and 205 may be combined into a single message and / or divided into further portions for separate transmission to terminal device 100.

[0077] In operations 206 and 207, terminal device 100 performs simultaneous uplink transmissions using the first and second TCI states respectively. For instance, this may correspond to PUSCH transmission. In operation 208, terminal device 100 needs to apply asymmetrical power reduction to the simultaneous uplink transmissions. As described above with reference to Fig. 1A, there are many ways of selecting the transmit power reduction values for each of the first and second TCI states so as to meet a given TRP limit. For brevity, this discussion is not repeated here.

[0078] Subsequent to the determination in operation 206, the process either proceeds with the operations enclosed in box 250 or the operations enclosed in box 260. As will become apparent, whether the operations of box 250 or 260 are performed depends on the result of the determination in operation 206.

[0079] In box 250, at operation 209, it is determined that the transmit power imbalance of the terminal device is below the threshold. Put another way, the determination of operation 206 indicated that the transmit power imbalance threshold was not exceeded.

[0080] In operation 210, terminal device 100 readjusts the transmit power reduction values for the first and second TCI states based on the threshold. For instance, if a new threshold is received at operation 204, it may be necessary to adjust the P-MPR values to ensure UL performance is maintained. In some examples, terminal device determines a first required transmit power reduction value for the first TCI state and a second required transmit power reduction value for the second TCI state for compliance with a maximum total radiated power value or a maximum effective isotropic radiated power value.

[0081] In operations 211 and 212, terminal device 100 continues simultaneous uplink transmissions using the first and second TCI states respectively. As will be appreciated, these operations may correspond to operations 206 and 207 described above. However, for the transmissions of operations 211 and 212, the terminal device applies the transmit power reduction values for the first and second TCI states determined in operation 210 (if any).

[0082] In box 260, at operation 213, it is determined that the transmit power imbalance of the terminal device is at or above the threshold. Put another way, the determination of operation 206 indicated that the transmit power imbalance threshold was met or exceeded. As described above with reference to Fig. 1A, in a case that the transmit power imbalance threshold is met or exceeded, the terminal device deactivates one of the first TCI state and the second TCI state. The TCI state to be deactivated may be indicated explicitly by the network or determined based on a rule, as described with reference to operation 204 above.

[0083] In some examples, in the case that the power imbalance threshold is met or exceeded, the terminal device deactivates the one of the TCI state and the second TCI state responsive to determining that the transmit power imbalance is above the threshold. Put another way, the terminal device autonomously deactivates the relevant TCI state when it is determined that the threshold has been exceeded. In other examples, such as those described below with reference to operation 216, the terminal device deactivates the relevant TCI state responsive to instruction by the network (e.g. via base station 150 or 160).

[0084] In operation 214, in a case that the transmit power imbalance threshold is exceeded, the terminal device transmits, to the network (e.g. via base station 150), an indication that the transmit power imbalance threshold is exceeded.

[0085] In operation 215, reception of the indication by the network (e.g. at base station 150) causes at least one network resource associated with uplink transmissions performed using the deactivated (or to be deactivated) one of the first TCI state and the second TCI state to be released. For instance, the at least one resource could comprise at least one physical resource block (PRB). For instance, if it is determined that the second TCI state is to be deactivated, resources associated with the UL connection to base station 160 may be released. In the event that base stations 150 and 160 have separate schedulers (i.e. they do not share a common scheduler), base station 150 may signal (e.g. via an interface) to base station 160 that it should release resources associated with UL communications from the terminal device.

[0086] In operation 216, the network instructs the terminal device to deactivate the TCI state. For instance, base station 150 may transmit a signal to the terminal device indicating that one of the TCI states should be deactivated. The terminal device then deactivates the relevant TCI state responsive to receiving the instructions from the network. The network may provide the terminal device with a new indication of a TCI state to use for uplink transmission, where the TCI state indicated corresponds to the one of the first and second TCI states that is not selected for deactivation.

[0087] In some examples, the information transmitted in operation 216 may be transmitted using DCI or R.RC signalling. As will be appreciated, operation 216 is performed concurrently with, before or after operation 215. As will be further appreciated, operation 216 may not be performed in the case that the terminal device autonomously deactivates the relevant TCI state responsive to determination that the threshold has been exceeded.

[0088] In operation 216, terminal device 100 continues uplink transmissions using the remaining TCI state (i.e. the TCI state that was not deactivated). Similar to operation 206 above, this may correspond to PUSCH transmission. By way of example only, UL transmissions in Fig. 2 are depicted as continuing for base station 150 (i.e. the first TCI state) only, though it will be appreciated that they may continue for base station 160 (i.e. the second TCI state) only instead, depending on the configuration of the terminal device.

[0089] Fig. 3 is a flowchart depicting various operations which may be performed in accordance with various examples. For instance, the operations depicted in Fig. 3 may be executed by a terminal device (e.g. terminal device 100) or other suitable apparatus (such as described with reference to Fig. 5).

[0090] In some examples, operation S3.1 is performed, in which configuration information indicative of a transmit power imbalance threshold is received from a network node.

[0091] In some examples, operation S3.2 is performed, in which a first required transmit power reduction value for the first TCI state and a second required transmit power reduction value for the second TCI state are determined for compliance with a maximum total radiated power value or a maximum effective isotropic radiated power value.

[0092] In operation S3.3, simultaneous uplink transmissions are performed using a first TCI state and a second TCI state. In some examples, uplink transmissions performed using the first TCI state are associated with a first network node (e.g. TRP 150) and uplink transmissions performed using the second TCI state are associated with a second network node (e.g. TRP 160).

[0093] In operation S3.4, it is determined whether a transmit power imbalance between the first TCI state and the second TCI state exceeds a transmit power imbalance threshold. In some examples, the transmit power imbalance threshold is received from a network node (as described with reference to operation S3.1). In other examples, the transmit power imbalance threshold is pre-configured at the terminal device.

[0094] In examples in which operation S3.2 is performed, the transmit power imbalance between the first TCI state and the second TCI state is determined to exceed the transmit power imbalance threshold when a first transmit power value for the first TCI state resulting from application of the first required transmit power reduction value and a second transmit power value for the second TCI state resulting from application of the second required transmit power reduction value differ by at least the transmit power imbalance threshold, or alternatively when the first required transmit power reduction value and the second required transmit power reduction value differ by at least the transmit power imbalance threshold.

[0095] In operation S3.5, in a case (e.g. responsive to a positive determination at operation S3.4) that the transmit power imbalance threshold is exceeded, one of the first TCI state and the second TCI state is deactivated. Uplink transmissions are then performed in operation S3.6 using the one of the first TCI state and the second TCI state that is not deactivated.

[0096] In some examples, in a case that the transmit power imbalance threshold is exceeded, an indication that the transmit power imbalance threshold is exceeded is transmitted to a network node (e.g. TRP 150). For instance, reception of the indication by the network node may cause at least one network resource associated with uplink transmissions performed using the deactivated (i.e. deselected) one of the first TCI state and the second TCI state to be released. Still for instance, reception of the indication by the network node may cause the network node to start scheduling new uplink transmissions using the remaining TCI state that is not deactivated.

[0097] In addition or alternatively, in a case that the transmit power imbalance threshold is exceeded, the one of the first TCI state and the second TCI state is deactivated based on quality metrics associated with the first TCI state and the second TCI state.

[0098] In operation S3.7, in a case (e.g. responsive to a negative determination at operation S3.4) that the transmit power imbalance threshold is not exceeded, simultaneous uplink transmissions are continued using the first TCI state and the second TCI state.

[0099] As will of course be appreciated, various operations illustrated in Fig. 3 may correspond to operations already described with reference to the preceding Figs. For instance, operation S3.1 may correspond to operation 204 in Fig. 2, operation S3.2 may correspond to operation 208 in Fig.2, operation S3.3 may correspond to operations 206 and 207 in Fig. 2, operation S3.4 may correspond to operations 209 and 213 in Fig. 2, operation S3.5 may correspond to operations 214 to 215 of Fig. 2, operation S3.6 may correspond to operation 217 of Fig. 2, and operation S3.7 may correspond to operations 210 to 212 of Fig. 2.

[0100] Fig. 4 is a flowchart depicting various operations which may be performed in accordance with various examples. For instance, the operations depicted in Fig. 4 may be executed by a network node (e.g. TRP 150) or other suitable apparatus, such as that described with reference to Fig. 6.

[0101] In operation S4.1, configuration information indicative of a transmit power imbalance threshold is transmitted to a terminal device for use in determining whether to deactivate one of a first TCI state and a second TCI state used for simultaneous uplink transmissions by the terminal device.

[0102] In some examples, operation S4.2 is performed, in which an indication that a power imbalance between the first TCI state and the second TCI state exceeds the transmit power imbalance threshold is received from the terminal device.

[0103] In some examples, operation S4.3 is performed, in which responsive to the indication, at least one network resource associated with uplink transmissions performed using the deactivated (or to be deactivated) one of the first TCI state and the second TCI state is released. As explained above with reference to the previous Figs., the one of the first TCI state and the second TCI state may either be deactivated autonomously by the terminal device or responsive to instruction by the network. In the latter case, the network may determine, based on the indication that the transmit power imbalance threshold is exceeded, that one of the first TCI state and the second TCI state is to be de-activated. The network may then instruct the terminal device accordingly (e.g. by only indicating one of the two TCI states).

[0104] As will of course be appreciated, various operations illustrated in Fig. 4 may correspond to operations already described with reference to the preceding Figs. For instance, operation S4.1 may correspond to operation 204 in Fig. 2, operation S4.2 may correspond to operation 214 in Fig. 2, and operation S4.3 may correspond to operation 215 in Fig. 2. Fig. 5 is a schematic illustration of an example configuration of a computing apparatus 5 which may be configured to perform various operations described with reference to Figs. 1 to 4. For instance, computing apparatus 5 may be configured to perform some or all of the operations described with reference to terminal device 100.

[0105] Computing apparatus may comprise control apparatus 500 which is configured to control operation of other components which form part of the computing apparatus 5 thereby to enable performance of various operations described with reference to Figs. 1 to 4. The computing apparatus 500 may comprise processing apparatus 501 and memory 502. Computer-readable code 502-2A may be stored on the memory 502, which when executed by the processing apparatus 501, causes the control apparatus 500 to perform any of the operations described herein.

[0106] In addition, computing apparatus may further include a display 503, user interactive interface (UII) 504, radio frequency interface 505 configured to interface radio frequency signals transmitted and received via a radio frequency antenna array 505A, and global navigation satellite system (GNSS) 506. In some examples, other satellite communications systems may be used instead of or in addition to GNSS 506.

[0107] Fig. 6 is a schematic illustration of an example configuration of a base station 6 which may be configured to perform various operations described with reference to Figs. 1 to 4. For instance, base station 6 may be configured to perform some or all of the operations described with reference to TRP / network nodes 150 and 160.

[0108] The base station 6, which may be referred to an eNB or access point (AP), comprises control apparatus 600 which is configured to control operation of other components which form part of the base station 6 thereby to enable transmission of signals to and receipt of signals from UEs in its coverage area vicinity. For example, the base station control apparatus 600 is configured to cause transmission of reference signals to UEs within its coverage area. Furthermore, in some examples, the control apparatus 600 may be configured to enable receipt of reference signal measurement data and / or location data from the UEs in its coverage area. The control apparatus 600 may also enable communication with other base stations and / or other network nodes. The control apparatus 600 may additionally be configured to cause performance of any other operations described herein with reference to the base station 6.

[0109] The base station 6 comprises a radio frequency antenna array 605 configured to receive and transmit radio frequency signals. Although the base station 6 in Fig. 6 is shown as having an array 605A of three antennas, this is illustrative only. The number of antennas may vary, for instance, from one to many hundreds.

[0110] The base station 6 further comprises a radio frequency interface 605 configured to interface the radio frequency signals received and transmitted by the antenna 605A and a control apparatus 60. The radio frequency interface 605 may also be known as a transmitter, receiver and / or transceiver. The base station 6 may also comprise an interface 607 via which, for example, it can communicate with other network elements such as other radio access network entities (such as the other base stations) and / or core network entities.

[0111] The base station control apparatus 600 may be configured to process signals from the radio frequency interface 605, to control the radio frequency interface 605 to generate suitable RF signals to communicate information to UEs via the wireless communications link, and also to exchange information with other base stations 5 and core network entities via the interface 607.

[0112] The control apparatus 600 may comprise processing apparatus 601 and memory 602. Computer-readable code 602-2A may be stored on the memory 602, which when executed by the processing apparatus 601, causes the control apparatus 600 to perform any of the operations described herein and attributed to the base station 6.

[0113] Some further details of components and features of the above-described devices / entities / apparatuses 5, 6 and alternatives for them will now be described.

[0114] The control apparatuses described above 500, 600 may comprise processing apparatus 501, 601 communicatively coupled with memory 502, 602. The memory 502, 602 has computer readable instructions 502-2A, 602-2A stored thereon, which when executed by the processing apparatus 501, 601 causes the control apparatus 500, 600 to cause performance of various ones of the operations described with reference to Figs. 1 to 4. The control apparatus 500, 600 may in some instance be referred to, in general terms, as "apparatus".

[0115] The processing apparatus 501, 601 may be of any suitable composition and may include one or more processors 501A, 601A 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 501, 601 may be a programmable processor that interprets computer program instructions 502-2A, 602-2A and processes data. The processing apparatus 501, 601 may include plural programmable processors. Alternatively, the processing apparatus 501, 601 may be, for example, programmable hardware with embedded firmware. The processing apparatus 501, 601 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 501, 601 may be referred to as computing apparatus or processing means.

[0116] The processing apparatus 501, 601 is coupled to the memory 502, 602 and is operable to read / write data to / from the memory 502, 602. The memory 502, 602 may comprise a single memory unit or a plurality of memory units, upon which the computer readable instructions (or code) 502-2A, 602-2A is stored. For example, the memory 502, 602 may comprise both volatile memory 502-1, 602-1 and non-volatile memory 502-2, 602-2. In such examples, the computer readable instructions / program code 502-2A, 602-2A may be stored in the non-volatile memory 502-2, 602-2 and may be executed by the processing apparatus 501, 601 using the volatile memory 502-1, 602-1 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.

[0117] The memory 502, 602 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.

[0118] The computer readable instructions / program code 502-2A, 602-2A may be preprogrammed into the control apparatus 500, 600. Alternatively, the computer readable instructions 502-2A, 602-2A may arrive at the control apparatus via an electromagnetic carrier signal or may be copied from a physical entity 7 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. 5. The computer readable instructions 502-2A, 602-2A may provide the logic and routines that enables the entities devices / apparatuses 5, 6 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.

[0119] If desired, the different functions discussed herein may be performed in a different order and / or concurrently with each other. Furthermore, if desired, one or more of the above-described functions may be optional or may be combined. Similarly, it will also be appreciated that the flow diagrams of Figs. 5 and 6 are examples only and that various operations depicted therein may be omitted, reordered and / or combined.

[0120] Although the methods and apparatuses have been described in connection with an E- UTRA network, it will be appreciated that they are not limited to such networks and are applicable to radio networks of various different types.

[0121] Although various aspects of the methods and apparatuses described herein are set out in the independent claims, other aspects may comprise other combinations of features from the described embodiments and / or the dependent claims with the features of the independent claims, and not solely the combinations explicitly set out in the claims.

[0122] It is also noted herein that while various examples are described above, these descriptions should not be viewed in a limiting sense. Rather, there are several variations and modifications which may be made without departing from the scope of the present invention as defined in the appended claims.

Claims

Claims1. A terminal device comprising: means for performing simultaneous uplink transmissions using a first transmission configuration indicator, TCI, state and a second TCI state; means for determining whether a transmit power imbalance between the first TCI state and the second TCI state exceeds a transmit power imbalance threshold; and means for, in a case that the transmit power imbalance threshold is exceeded, deactivating one of the first TCI state and the second TCI state.

2. The terminal device of claim 1, further comprising: means for receiving, from a network node, configuration information indicative of the transmit power imbalance threshold.

3. The terminal device of claim 1, wherein the transmit power imbalance threshold is pre-configured at the terminal device.

4. The terminal device of any of the preceding claims, further comprising: means for determining a first required transmit power reduction value for the first TCI state and a second required transmit power reduction value for the second TCI state for compliance with a maximum total radiated power value or a maximum effective isotropic radiated power value.

5. The terminal device of claim 4, wherein the transmit power imbalance between the first TCI state and the second TCI state is determined to exceed the transmit power imbalance threshold when a first transmit power value for the first TCI state resulting from application of the first required transmit power reduction value and a second transmit power value for the second TCI state resulting from application of the second required transmit power reduction value differ by at least the transmit power imbalance threshold.

6. The terminal device of any preceding claim, further comprising: means for, in a case that the transmit power imbalance threshold is exceeded, transmitting, to a network node, an indication that the transmit power imbalance threshold is exceeded.

7. The terminal device of claim 6,wherein reception of the indication by the network node causes at least one network resource associated with uplink transmissions performed using the deactivated one of the first TCI state and the second TCI state to be released.

8. The terminal device of any preceding claim, wherein, in a case that the transmit power imbalance threshold is exceeded, the one of the first TCI state and the second TCI state is deactivated based on quality metrics associated with the first TCI state and the second TCI state.

9. The terminal device of any one of claims 1 to 8, further comprising: means for receiving, from a network node, information indicating which of the first TCI state and second TCI state to deactivate in a case that the transmit power imbalance threshold is exceeded.

10. The terminal device of any preceding claim, further comprising: means for, in a case that the transmit power imbalance threshold is not exceeded, continuing performance of simultaneous uplink transmissions using the first TCI state and the second TCI state.

11. The terminal device of any preceding claim, wherein uplink transmissions performed using the first TCI state are associated with a first network node and uplink transmissions performed using the second TCI state are associated with a second network node.

12. A network node comprising: means for transmitting, to a terminal device, configuration information indicative of a transmit power imbalance threshold for use in determining whether to deactivate one of a first transmission configuration indicator, TCI, state and a second TCI state used for simultaneous uplink transmissions by the terminal device.

13. The network node of claim 12, further comprising: means for receiving, from the terminal device, an indication that a power imbalance between the first TCI state and the second TCI state exceeds the transmit power imbalance threshold.

14. The network node of claim 13, further comprising:means for, responsive to the indication, releasing at least one network resource associated with uplink transmissions performed using a deactivated one of the first TCI state and the second TCI state.

15. A method comprising: performing simultaneous uplink transmissions using a first transmission configuration indicator, TCI, state and a second TCI state; determining whether a transmit power imbalance between the first TCI state and the second TCI state exceeds a transmit power imbalance threshold; and in a case that the transmit power imbalance threshold is exceeded, deactivating one of the first TCI state and the second TCI state.

16. A method comprising: transmitting, to a terminal device, configuration information indicative of a transmit power imbalance threshold for use in determining whether to deactivate one of a first transmission configuration indicator, TCI, state and a second TCI state used for simultaneous uplink transmissions by the terminal device.

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