WO2024240380A1

WO2024240380A1 - Activation of tci states

Info

Publication number: WO2024240380A1
Application number: PCT/EP2024/055029
Authority: WO
Inventors: Smita SHETTY; Riikka Karoliina DIMNIK; Rafael Cauduro Dias De Paiva; Lars Dalsgaard
Original assignee: Nokia Technologies Oy
Current assignee: Nokia Technologies Oy
Priority date: 2023-05-22
Filing date: 2024-02-28
Publication date: 2024-11-28
Anticipated expiration: 2025-11-22

Abstract

Disclosed herein there is provided a method. The method involves defining, at a user equipment, an active transmission configuration indication (TCI) state list, comprising a first set of codepoints comprising quasi-co-located (QCL) information associated with a first set of reference signals. The method further involves receiving, at the user equipment from a network node, a medium access control control element (MAC-CE) command, wherein the MAC-CE command defines a target TCI state list, comprising a second set of codepoints comprising QCL information associated with a second set of reference signals. The method further involves comparing the QCL information of the first set of codepoints to the QCL information of the second set of codepoints. The method further involves determining a QCL relationship between the first set of codepoints and the second set of codepoints by identifying at least one common reference signal that is present in both the first set of reference signals and the second set of reference signals. The method further involves determining that no synchronization of synchronization signal blocks associated with the at least one common reference signal is required.

Description

Activation of TCI States

Field

Example embodiments may relate to systems, methods and computer programs for activation of transmission configuration indication (TCI) states. In particular, an apparatus is disclosed for fast activation of TCI states.

Background

Communication systems enable communication between two or more nodes or devices, such as fixed or mobile communication devices. Signals can be carried on wireless carriers.

An example of a cellular communication system is an architecture that is being standardized by the 3rd Generation Partnership Project (3GPP). A recent development in this field is often referred to as the long-term evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio-access technology. E-UTRA (evolved UMTS Terrestrial Radio Access) is the air interface of 3GPP's Long Term Evolution (LTE) upgrade path for mobile networks. In LTE, base stations, network nodes or access points, which are referred to as enhanced Node AP or Evolved Node B (eNBs), provide wireless access within a coverage area or cell. In LTE, mobile devices, or mobile stations are referred to as user equipment (UE). LTE has included a number of improvements or developments.

5G New Radio (NR) development is part of a continued mobile broadband evolution process to meet the requirements of 5G, similar to earlier evolution of 3G & 4G wireless networks. In addition, 5G is also targeted at the new emerging use cases in addition to mobile broadband. A goal of 5G is to provide significant improvement in wireless performance, which may include new levels of data rate, latency, reliability, and security. 5G NR may also scale to efficiently connect the massive Internet of Things (loT), and may offer new types of mission-critical services. Ultra-reliable and low-latency communications (URLLC) devices may require high reliability and very low latency.

Currently, TCI state switch radio resource management (RRM) requirements have only been defined for Single TRP. The present disclosure aims to address this. Furthermore, there is a requirement to reduce TCI active list update delay and TCI switching delays by avoiding need for a user equipment (UE) to synchronize to a synchronization signal block (SSB). Summary

The scope of protection sought for various embodiments of the invention is set out by the independent claims. The embodiments and features, if any, described in this specification that do not fall under the scope of the independent claims are to be interpreted as examples useful for understanding various embodiments of the invention.

According to a first aspect, there is described an apparatus comprising means for defining, at a user equipment, an active transmission configuration indication (TCI) state list, comprising a first set of codepoints comprising quasi-co-located (QCL) information associated with a first set of reference signals. The apparatus further comprises means for receiving, at the user equipment from a network node, a medium access control control element (MAC-CE) command, wherein the MAC-CE command defines a target TCI state list, comprising a second set of codepoints comprising QCL information associated with a second set of reference signals. The apparatus further comprises means for comparing the QCL information of the first set of codepoints to the QCL information of the second set of codepoints. The apparatus further comprises means for determining a QCL relationship between the first set of codepoints and the second set of codepoints by identifying at least one common reference signal that is present in both the first set of reference signals and the second set of reference signals. The apparatus further comprises means for determining that no synchronization of synchronization signal blocks associated with the at least one common reference signal is required.

In some embodiments, the MAC-CE command may be sent on a physical downlink shared channel, PDSCH.

In some embodiments, the apparatus may further comprise means for activating the target TCI state for PDSCH within a predetermined time interval.

In some embodiments, the apparatus may further comprise means for indicating the target TCI state for a physical downlink control channel, PDCCH, within a predetermined time interval.

In some embodiments, when the at least one common reference signal is identified, the predetermined time interval may be approximately equal to T-HARQ + 3 ms, wherein T-HARQ is the timing between a transmission of the MAC-CE command and a corresponding acknowledgement sent from the user equipment to the network node. In some embodiments, the first set of codepoints and second set of codepoints may comprise only one TCI state. In some embodiments, QCL information of the at least one common reference signal may be of QCL-D type.

In some alternative embodiments, the first set of codepoints and second set of codepoints each respectively may comprise a first TCI state and a second TCI state. In this case the apparatus further comprises means for comparing the QCL information of the first set of codepoints to the QCL information of the second set of codepoints for the first TCI state and means for comparing the QCL information of the first set of codepoints to the QCL information of the second set of codepoints for the second TCI state.

In some embodiments, the apparatus further may comprise means for determining a QCL relationship between the first set of codepoints and the second set of codepoints for the first TCI state, by identifying at least one common reference signal for the first TCI state that is present in both the first set of reference signals and the second set of reference signals. The apparatus further may comprise means for determining a QCL relationship between the first set of codepoints and the second set of codepoints for the second TCI state, by identifying at least one common reference signal for the second TCI state that is present in both the first set of reference signals and the second set of reference signals. The apparatus further may comprise means for determining that no synchronization of synchronization signal blocks associated with the at least one common reference signal in the first TCI state and at least one common reference signal in the second TCI state is required.

In some embodiments, the apparatus may further comprise means for determining a QCL relationship between the first set of codepoints and the second set of codepoints for the first TCI state, by identifying at least one common reference signal for the first TCI state that is present in both the first set of reference signals and the second set of reference signals. The apparatus further may comprise means for determining that no synchronization of synchronization signal blocks associated with the at least one common reference signal in the first TCI state is required. The apparatus further may comprise means for determining that no QCL relationship is found between the first set of codepoints and the second set of codepoints for the second TCI state, by establishing that no common reference signals are found for the second TCI state for the first set of reference signals and the second set of reference signals. The apparatus further may comprise means for determining that synchronization of synchronization signal blocks associated with the second TCI state for the second set of reference signals is required.

In some embodiments the QCL information of the at least one common reference signal may be of QCL-A, QCL-C or QCL-D type.

In some embodiments, the apparatus may be a user device.

In some embodiments, the network nodes may be radio access network, RAN, base stations.

In some embodiments, the means comprise: at least one processor; and at least one memory storing instructions that, when executed by the at least processor, cause the performance of the apparatus.

According to a second aspect, there is described a method comprising: defining, at a user equipment, an active transmission configuration indication (TCI) state list, comprising a first set of codepoints comprising quasi-co-located (QCL) information associated with a first set of reference signals. The method further comprises receiving, at the user equipment from a network node, a medium access control control element (MAC-CE) command, wherein the MAC-CE command defines a target TCI state list, comprising a second set of codepoints comprising QCL information associated with a second set of reference signals. The method further comprises comparing the QCL information of the first set of codepoints to the QCL information of the second set of codepoints. The method further comprises determining a QCL relationship between the first set of codepoints and the second set of codepoints by identifying at least one common reference signal that is present in both the first set of reference signals and the second set of reference signals. The method further comprises determining that no synchronization of synchronization signal blocks associated with the at least one common reference signal is required.

In some embodiments, the method may further comprise activating the target TCI state for PDSCH within a predetermined time interval.

In some embodiments, the method may further comprise indicating the target TCI state for a physical downlink control channel, PDCCH, within a predetermined time interval.

In some embodiments, when the at least one common reference signal is identified, the predetermined time interval may be approximately equal to T-HARQ + 3 ms, wherein T-HARQ is the timing between a transmission of the MAC-CE command and a corresponding acknowledgement sent from the user equipment to the network node.

In some embodiments, the first set of codepoints and second set of codepoints may comprise only one TCI state. In some embodiments, QCL information of the at least one common reference signal may be of QCL-D type.

In some alternative embodiments, the first set of codepoints and second set of codepoints each respectively may comprise a first TCI state and a second TCI state. In this case the method further comprises comparing the QCL information of the first set of codepoints to the QCL information of the second set of codepoints for the first TCI state and comparing the QCL information of the first set of codepoints to the QCL information of the second set of codepoints for the second TCI state.

In some embodiments, the method further may comprise determining a QCL relationship between the first set of codepoints and the second set of codepoints for the first TCI state, by identifying at least one common reference signal for the first TCI state that is present in both the first set of reference signals and the second set of reference signals. The method further may comprise determining a QCL relationship between the first set of codepoints and the second set of codepoints for the second TCI state, by identifying at least one common reference signal for the second TCI state that is present in both the first set of reference signals and the second set of reference signals. The method further may comprise determining that no synchronization of synchronization signal blocks associated with the at least one common reference signal in the first TCI state and at least one common reference signal in the second TCI state is required.

In some embodiments, the method may further comprise determining a QCL relationship between the first set of codepoints and the second set of codepoints for the first TCI state, by identifying at least one common reference signal for the first TCI state that is present in both the first set of reference signals and the second set of reference signals. The method further may comprise determining that no synchronization of synchronization signal blocks associated with the at least one common reference signal in the first TCI state is required. The method further may comprise determining that no QCL relationship is found between the first set of codepoints and the second set of codepoints for the second TCI state, by establishing that no common reference signals are found for the second TCI state for the first set of reference signals and the second set of reference signals. The method further may comprise determining that synchronization of synchronization signal blocks associated with the second TCI state for the second set of reference signals is required.

According to a third aspect, there is provided a computer program product comprising a set of instructions which, when executed on an apparatus, is configured to cause the apparatus to carry out the method of any preceding method definition.

According to a fourth aspect, there is provided a non-transitory computer readable medium comprising program instructions stored thereon for performing a method, comprising: defining, at a user equipment, an active transmission configuration indication (TCI) state list, comprising a first set of codepoints comprising quasi-co-located (QCL) information associated with a first set of reference signals. The method further comprises receiving, at the user equipment from a network node, a medium access control control element (MAC-CE) command, wherein the MAC-CE command defines a target TCI state list, comprising a second set of codepoints comprising QCL information associated with a second set of reference signals. The method further comprises comparing the QCL information of the first set of codepoints to the QCL information of the second set of codepoints. The method further comprises determining a QCL relationship between the first set of codepoints and the second set of codepoints by identifying at least one common reference signal that is present in both the first set of reference signals and the second set of reference signals. The method further comprises determining that no synchronization of synchronization signal blocks associated with the at least one common reference signal is required.

The program instructions of the fourth aspect may also perform operations according to any preceding method definition of the second aspect.

Brief Description of the Drawings

Example embodiments will now be described by way of non-limiting example, with reference to the accompanying drawings, in which:

Fig. 1 shows, by way of example, a network architecture of a communication system;

Fig. 2 shows, by way of example, a timeline from MAC-CE reception for TCI activation to PDSCH reception;

Fig. 3 shows, byway of example, a timeline of TCI state switching delay; Fig. 4 shows, by way of example, a flowchart of a method;

Fig. 5 shows, byway of example, a flow chart of a decision making process;

Fig. 6 shows, byway of example, a block diagram of an apparatus.

Detailed Description

Example embodiments may relate to an apparatus, method and/or computer program for managing TCI state activation.

Figure 1 shows, by way of an example, a network architecture of a communication system which is a radio access network (RAN). In the following, different exemplifying embodiments will be described using, as an example of an access architecture to which embodiments may be applied, a radio access architecture based on long term evolution advanced (LTE Advanced, LTE-A) or new radio (NR), also known as fifth generation (5G), without restricting the embodiments to such an architecture, however. Embodiments may also be applied to other kinds of communications networks having suitable means by adjusting parameters and procedures appropriately. Some examples of other options for suitable systems are the universal mobile telecommunications system = radio access network, long term evolution (LTE), wireless local area network (WLAN or WiFi), worldwide interoperability for microwave access (WiMAX), Bluetooth®, personal communications services (PCS), ZigBee®, wideband code division multiple access (WCDMA), systems using ultra-wideband (UWB) technology, sensor networks, mobile ad-hoc networks (MANETs) and Internet Protocol multimedia subsystems (IMS) or any combination thereof.

Figure 1 shows first and second user devices 100, 102 configured to be in a wireless connection on one or more communication channels in a cell with a network node, such as a network node 104 providing a cell. The physical link from a user device, e.g. the first user device 100, to the network node 104 is called the uplink (UL) or reverse link and the physical link from the network node to the user device is called the downlink (DL) or forward link. It should be appreciated that network nodes and their functionalities may be implemented by using any node, host, server or access point entity suitable for such a usage. A communications system typically comprises more than one network node in which case the network nodes may also be configured to communicate with one another over links, wired or wireless, designed for the purpose. These links may be used for signaling purposes. A network node is a computing device configured to control the radio resources of the communication system it is coupled to. A network node may also be referred to as a TRP, base station (BS), an access point or any other type of interfacing device including a relay station capable of operating in a wireless environment. A network node may include or is coupled to transceivers. From the transceivers of the network node 104, a connection may be provided to an antenna unit that establishes bidirectional radio links to user devices, such as the first and second user devices too, 102. The antenna unit may comprise a plurality of antennas or antenna elements, for example arranged as an antenna array. The network node 104 may further be connected to a core network 110.

The user device, or user equipment UE, typically refers to a portable computing device that includes wireless mobile communication devices operating with or without a subscriber identification module (SIM), including, but not limited to, the following types of devices: a mobile station (mobile phone), smartphone, personal digital assistant, handset, device using a wireless modem (alarm or measurement device, etc.), laptop and/or touch screen computer, tablet, game console, notebook, and multimedia device. It should be appreciated that a user device may also be a nearly exclusive uplink only device, of which an example is a camera or video camera loading images or video clips to a network. A user device may also be a device having capability to operate in Internet of Things (loT) network which is a scenario in which objects are provided with the ability to transfer data over a network without requiring human- to-human or human-to-computer interaction.

5G enables using multiple input and multiple output technology at both the UE and network node side, many more base stations or nodes than the LTE. 5G mobile communications supports a wide range of use cases and related applications including video streaming, augmented reality, different ways of data sharing and various forms of machine type applications, including vehicular safety, different sensors and real-time control. 5G is expected to have multiple radio interfaces, namely below 7GHz, cmWave and mmWave, and also being integratable with existing legacy radio access technologies, such as the LTE. Below 7GHz frequency range may be called as FRi, and above 24GHz (or more exactly 24- 52.6 GHz) as FR2, respectively. Integration with the LTE maybe implemented, at least in the early phase, as a system, where macro coverage is provided by the LTE and 5G radio interface access comes from small cells by aggregation to the LTE.

The communication system is also able to communicate with other networks, such as a public switched telephone network or the Internet 112, or utilize services provided by them. The communication network may also be able to support the usage of cloud services, for example at least part of core network operations may be carried out as a cloud service (this is depicted in Figure 1 by “cloud” 114). The communication system may also comprise a central control entity, or a like, providing facilities for networks of different operators to cooperate for example in spectrum sharing.

An edge cloud may be brought into radio access networks (RANs). Using an edge cloud may mean access node operations to be carried out, at least partly, in a server, host or node operationally coupled to a remote radio head or base station comprising radio parts. It is also possible that node operations will be distributed among a plurality of servers, nodes or hosts. Applications of cloud RAN architecture enables RAN real time functions being carried out at the RAN side (in a distributed unit, DU 104) and non-real time functions being carried out in a centralized manner (in a centralized unit, CU 108).

Beam management is applied during a random access channel (RACH) procedure, when the UE forms the initial connection with the network, and while the UE is in a connected state. In a connected state, transmitting beams and receiving beams may be refined.

Beam management may define a set of functionalities to assist the UE to set its reception (Rx) and transmission (Tx) beams for DL receptions and UL transmissions, respectively. The functionalities can be categorized roughly according to four groups.

In beam indication, the UE is assisted to set its Rx and Tx beam properly for the reception of the DL and the transmission of the UL, respectively.

Beam acquisition, measurements and reporting refer to procedures for providing the network node knowledge about feasible DL and UL beams for the UE.

Beam recoveiy refers to rapid link reconfiguration against sudden blockages, e.g. fast realignment of network node and UE beams.

Beam tracking and refinement refer to procedures for measuring and aligning network node and UE side beams, as well as to refine network node and UE side beams. The approach disclosed herein provides an improved method of beam alignment for network node and UE primary and secondary beams.

Regarding DL beam management and especially for beam acquisition, measurements and reporting, different beam management procedures, referred to as P-i, P-2 and P-3, are supported within one or multiple TRPs of the serving cell. P-i may be used to enable UE measurement on different TRP Tx beams to support selection of TRP Tx beams/UE Rx beam(s). For beamforming at a TRP, it typically includes an intra/inter-TRP Tx beam sweep from a set of different beams. For beamforming at a UE, it typically includes a UE Rx beam sweep from a set of different beams.

P-2 is used to enable UE measurement on different TRP Tx beams to possibly change inter/intra-TRP Tx beam(s). Measurements may be performed from a possibly smaller set of beams for beam refinement than in P-i. P-2 may be a special case of P-i.

P-3 is used to enable UE measurement on the same TRP Tx beam to change a UE Rx beam in the case UE uses beamforming.

Regarding DL beam indication, a quasi-colocation (QCL) indication functionality has been defined. The UE may be configured with, or the UE implicitly determines, a source reference signal (RS) that the UE has received and measured earlier and which defines how to set the Rx beam for the reception of the DL physical signal or channel to be received. To provide the UE with QCL characteristics for the target signal, that is the signal to be received, a transmission coordination indication (TCI) framework has been defined. By using the TCI framework, the UE may be configured with TCI state(s) to provide the UE with source RS(s) for determining QCL characteristics. Each TCI state includes one or two source RSs that provide UE QCL TypeA, TypeB, TypeC and/or TypeD parameters. Different types provide the parameters as follows:

QCL-TypeA: {Doppler shift, Doppler spread, average delay, delay spread}

QCL-TypeB: {Doppler shift, Doppler spread}

QCL-TypeC: {Doppler shift, average delay}

QCL-TypeD: {Spatial Rx parameter}

In the UL, the UE is provided a parameter called spatial relation information, providing a spatial source RS based on which the UE determines the UL transmit beam. The spatial source RS can be DL RS (synchronization signal block (SSB) or channel state information reference signal (CSI-RS)) or UL RS (such as sounding reference signal (SRS)). In case of DL RS as a spatial source RS, the UE sets its transmit beam to be the same or similar as was its receive beam to receive the spatial source RS. In the case of UL RS as a spatial source RS, the UE sets its transmit beam to be the same or similar as was its transmit beam to transmit the spatial source RS. The spatial source RS may also be the QCL-TypeD RS provided to the UE in a certain TCI state. For each physical UL control channel (PUCCH) and SRS resource, network node may provide explicitly a spatial source or TCI state while for physical UL shared channel (PUSCH) indirect indication maybe provided.

PUSCH may be scheduled using DL control information (DCI) format o_o and the spatial source maybe the same as with a certain PUCCH resource.

PUSCH maybe scheduled using DCI format o_i and the spatial source maybe the same as an indicated SRS resource(s). For example, the spatial source maybe one SRS resource indicated in a codebook based transmission scheme, or one or multiple SRS resources indicated in a non-codebook based transmission scheme.

Rel-16 introduced a default spatial relation for dedicated PUCCH/SRS (except SRS with usage = ‘beamManagement’ and SRS with usage = ‘nonCodeBook’ and configured with associated CSI-RS). If spatial relation is not configured in FR2, the UE may determine the spatial relation as follows: in the case when control resource set(s) (CORESET) are configured on the component carrier (CC), the spatial relation is the TCI state / QCL assumption of the CORESET with the lowest index or identity (ID); or in the case when any CORESETs are not configured on the CC, the spatial relation may be the activated TCI state with the lowest index or ID applicable to PDSCH in the active DL bandwidth part (DL-BWP) of the CC.

CORESET defines time and frequency resources on which the physical DL control channel (PDCCH) candidates may be transmitted to the UE.

Furthermore, Rel-16 introduced a default spatial relation for PUSCH scheduled by DCI format 0_0_o where UE determines spatial relation as follows: when there is no PUCCH, resources configured on the active UL BWP CC: the default spatial relation is the TCI state / QCL assumption of the CORESET with the lowest ID. The default pathloss RS is the QCL-TypeD RS of the same TCI state / QCL assumption of the CORESET with the lowest ID; when there is no PUCCH resources configured on the active UL BWP CC in FR2 and in RRC-connected mode: the default spatial relation is the TCI state / QCL assumption of the CORESET with the lowest ID. The default pathloss RS is the QCL-TypeD RS of the same TCI state / QCL assumption of the CORESET with the lowest ID.

The main tool for beam indication for downlink is a Transmission Configuration Indication (TCI) framework. A UE can be configured with up to 128 TCI states. A network node (e.g. gNB) configures the UE via RRC signaling with TCI states where each TCI states may have one or two source RSs that provide QCL parameters for the target RS - only one RS providing QCL type D per TCI state. A DL TCI chain consists of an SSB, and one or more CSI-RS resources, and the TCI state of each Reference Signal includes another Reference Signal in the same TCI chain, where the SSB can be associated with serving cell PCID or associated with a PCID different from serving cell PCID.

A TCI-state defines a QCL source and QCL type for a target reference signal and hence indicates a transmission configuration which includes QCL-relationships between the DL RSs in one RS set. DL and UL signals characterized by the TCI are received only by a subset of panels used by the UE and these panels receiving RSs characterized by TCI are active panels used in the actual DL and UL transmission. The RAN1 specification is also describing the RS grouping concept. DL signals received by the UE are said to be part of the same group if they are received by the same spatial filter (received beam) at the UE.

RANi has been working on improving the DCI based TCI state switching. The work involves enabling the use of DCI based TCI state switch for one or more channels simultaneously. As part of this work RANi is discussing introducing common beam management and unified beam management. Common and unified beam management enables the network to change the TCI state of more than 1 channel using one TCI command. Hence, with a single TCI state switch command the TCI state is changed for more than one channel. The channels can be either DL and/or UL channels including PDCCH, PDSCH, PUCCH and PUSCH. The work also includes enabling change of the PDCCH TCI state by use of DCI.

Within the unified TCI state framework, RANi is introducing the possibility to change both UL and DL independently or simultaneously. We assume that if the TCI state switch only includes switch of one TCI state (either UL or DL) existing TCI state switch delay requirements may still be readily re-usable. RAN4 discusses if new TCI state switch delay requirements would be needed in case both UL and DL TCI state is switched simultaneously. An FR2 4-layer connection can be configured by network with a single TCI-State or with 2 individual TCI-States (that are not QCL type D), depending on the selected beam configuration at the network node. Figure 2a shows a single-TCI scenario and Figure 2b shows a dual-TCI scenario.

In a single-TCI state the first set of DL RF signals and the second set of DL RF signals originate from a single primary reference signal. The first set of DL RF signals and the second set of DL RF signals are received at the user equipment from a single or multiple different angular directions.

In a dual-TCI state the first set of DL RF signals and the second set of DL RF signals originate from different reference signals from the network node. The first set of DL RF signals and the second set of DL RF signals are received at the user equipment from a single or multiple different angular directions. In dual-TCI scenario, the UE maybe configured with s-DCI or m- DCI, depending on the TRP’s cooperation.

Beam refinement implementation at the UE (P3) is not directly part of the current 3GPP specifications (Rel. 17), as this is considered UE implementation behavior, and the dedicated specified reference signal for P3 is aperiodic CSI-RS with repetition “ON”. The scheduling of this reference signal is fully controlled by the network node and the repetition feature is not mandatory, such that a UE might not be allocated aperiodic CSI-RS with repetition “ON” when needed e.g. due to load and/or resource overhead. The overhead of using aperiodic CSI-RS with repetition “ON” can be quite large, which is one reason the repetition feature is not mandatory, as the network node in principle will have to send that signal regularly for all connected UEs.

This resource overhead may be doubled for UEs supporting 4-layer DL and/or UL, as two different links must be monitored and maintained, to ensure optimal performance.

The required resource allocation of aperiodic CSI-RS with repetition “ON” for 4-Layer UE beam alignment is explained below for the cases of single and dual TCI-State configuration:

Dual TCI-State configuration: Each TCI-State must allocate its own set of aperiodic CSI-RS with repetition “ON”, which in theoiy will result in a doubling of the resource overhead. Therefore, there is a desire in dual TCI-state configuration to align both UE narrow beams to receive 4 layers with low correlation while minimizing resource utilization of the needed reference signals.

Single TCI-State configuration: Only a single TCI-State must be allocated with aperiodic CSI- RS with repetition “ON”, so in theory the same as for a 2-Layer connection. However, since the UE will have to maintain two aligned beams, it will require an increased periodicity of the aperiodic CSI-RS with repetition “ON”, also leading to doubling the resources spent on UE beam refinement. Therefore, there is a desire in single TCI-state configuration to reduce resource overhead for UE beam refinement, i.e. minimize or avoid scheduling aperiodic CSI- RS with repetition “ON”.

The UE may indicate to a network over which it will communicate wireless signals, for example to a network node of the network, whether a preferred secondary DL RS signal is detected. This allows for improved beam alignment by continuously searching for stronger DL RS signals.

TCI state switching delay requirements have been defined in RAN 4 for single TRP and the same is expected to be used as a baseline while defining RAN 4 requirements for dual TCI state switching in the Multi-TRP context. The current TCI state switching delay requirements for medium access control control element (MAC-CE) based TCI switch for PDCCH, DCI based TCI state switch delay and the active TCI state list update delay are given in specification TS 38.133 Section 8.10.

TCI state switch requirements for frequency range 2 (FR2) have currently only been defined for Rel-15 Single TRP and enhanced in Rel-16/ 17. So far there are no RAN4 requirements for TCI state switch in case of Multi-TRP. In 3GPP Rel-18, TCI state switch requirements will be defined for Multi-Rx chain UEs in the Multi-TRP scenario.

3GPP defined 5G NR Frequency Range 2 bands have huge bandwidths which can cater to 5G NR use cases requiring higher data rates. However, these bands are also subject to challenging propagating conditions such as high path loss, absorption from the environment, penetration losses to name a few. To overcome these, beam management procedures have been defined in 3GPP.

The TCI framework is used in NR and is particularly useful for beam indication in FR2 scenarios where beam management procedures are used. A UE can be configured via RRC signaling with up to 128 TCI states.

In a multi -TRP scenario, the UE can be configured to measure on a set of beams from different TRPs and reports the Li RSRP levels back to the network in the form of CSI report.

Based on the UE feedback, the network sends a MAC-CE indicating the TCI state for the PDCCH.

In case of PDSCH, a maximum of 8 TCI states or TCI state pairs (where each of the two TCI states is for PDSCH of different TRP in multi-TRP reception) can be activated for the UE. These are indicated by the network to the UE via MAC-CE signaling and will be a part of the codepoint table as the one in table 1 below:

Table 1: TCI codepoint table

After the update of the active TCI list in the table 1 above, the network may then send a DCI indicating which of the TCI states or TCI state pairs will be used for the reception of PDSCH.

The requirements for TCI state active list update delay are defined in RAN4 RRM requirements in 38.133 for single TRP. Figure 2 shows a timeline 200 from MAC-CE reception for TCI activation to PDSCH reception. The example shown in figure 2 applies to the existing RRM requirements defined for single TRP. A MAC-CE 201 is firstly received at the UE from a network node at time to 202. The MAC-CE may be either for TCI state indication for PDCCH or activation of TCI states for PDSCH. In the example of figure 2 a MAC-CE signal for PDSCH is shown.

After the UE has received the MAC-CE 201, the UE needs to first synchronize with the SSB after processing the MAC-CE and sending an acknowledgement, which in the current requirements in TS38.133 takes THARQ+3 ms. THARQ is the timing between a transmission of the MAC-CE from a network node and a corresponding acknowledgement sent from UE to a network node (as specified in TS 38.213). In an alternative embodiment the requirements for the time taken to for UE first synchronize with the SSB after processing the MAC-CE and sending an acknowledgement could be different (for example, THARQ+2 ms).

It is only after this synchronization with the SSB 203 is complete that depending on whether the MAC-CE received is for indicating the TCI state for PDCCH or TCI state activation for PDSCH, the UE is considered to be capable of using these target TCI states. The Synchronization Signal and PBCH block (SSB) consists of primary and secondary synchronization signals (PSS, SSS), each occupying 1 symbol and 127 subcarriers, and PBCH spanning across 3 OFDM symbols and 240 subcarriers

If we consider that the existing RAN 4 procedures defined today for single TRP TCI state switching will be used as a baseline for Multi-TRP scenarios, a multi-Rx UE will receive the MAC-CE with activation command for TCI states for PDSCH at time to 202 and will be able to switch the TCI state upon reception of DCI and receive the PDSCH at time instance ti 204 as shown in Error! Reference source not found.2.

Figure 2 considers the case where the active TCI state list is updated, and that one codepoint containing TCI#1 and TCI#2 from 2 TRPs is activated. In this example, SSB#1 is the first SSB transmission associated with TCI#1 after MAC-CE command 201 is decoded by the UE. Similarly, SSB#2 is the first SSB transmission associated with TCI#2 after MAC-CE command 201 is decoded by the UE. In both cases, the SSB shall be the QCL to target TCI states TCI#i and TCI#2. In this example the codepoint containing TCI#1 and TCI#2 is only activated after SSB#i and SSB#2 synchronization because the UE needs to detect the DL frame boundary related to TCI#i and TCI#2.

One challenge with this approach is that depending on when the MAC-CE command 203 is sent to the UE, there could be a further delay of one SSB period or more between THARQ+3 ms and the first SSB transmission SSB#i. The delay could be there could be a further delay or more than one SSB period depending on the SSB which arrives latest in time. Considering that THARQ is kUslot length, where Ki is indicated in PDSCH -to-HARQ-timing-indicator, which can be o to 15 slots, the MAC-CE activation delay could take theoretically about 4 ms if the first SSB would be sent immediately after THARQ+3ms. However, if we consider that the SSB periodicity can be up to 160 ms, this activation time can be extended to up to 164 ms. This problem is shown in Figure 3, where the time for the first SSB happens just before the THARQ+3 ms, and the UE has to wait for the next SSB transmission which happens only 160 ms after that time.

Therefore, figure 3 demonstrates that there may be a long time before the activation of the PDSCH.

The following invention describes a way to reduce TCI active list update delay and TCI switching delays by avoiding need for a UE to synchronize to an SSB. An apparatus and method for fast TCI state activation is proposed, in which the QCL relations with previously activated TCI states is considered for faster TCI activation and MAC-CE indication of PDCCH.

Figure 4 shows, by way of example, a flowchart of a method according to example embodiments. Each element of the flowchart may comprise one or more operations. The operations may be performed in hardware, software, firmware or a combination thereof. For example, the operations may be performed, individually or collectively, by a means, wherein the means may comprise at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the performance of the operations.

The method 400 may comprise a first operation 401 of defining, at a user equipment, an active TCI state list. The active TCI state list comprises a first set of codepoints comprising QCL information associated with a first set of reference signals.

The method 400 may comprise a second operation 402 of receiving, at the user equipment from a network node, a MAC-CE command. The MAC-CE command defines a target TCI state list. The target TCI state list comprises a second set of codepoints comprising QCL information associated with a second set of reference signals.

The first and second series of codepoints may be similar to those shown in table 1.

The method 400 comprises a third operation 403 of comparing the QCL information of the first set of codepoints to the QCL information of the second set of codepoints. The comparing may include reviewing each of the codepoints in first series of codepoints and reviewing each of the codepoints in the second series of codepoints. Each of the codepoints of the first series of codepoints may be compared in turn to each of the codepoints of the second series of codepoints. The method 400 comprises a fourth operation 404 of determining a QCL relationship between the first set of codepoints and the second set of codepoints by identifying at least one common reference signal that is present in both the first set of reference signals and the second set of reference signals. A common reference signal is a reference signal that is present in both the first series of codepoints and the second series of codepoints. The common reference signal maybe an SSB signal. When comparing each of the codepoints of the first series of codepoints in turn to each of the codepoints of the second series of codepoints, the method may identify that at least one of the codepoints is the same. A common codepoint is a codepoint that appears in both the first series of codepoints (i.e. in the active TCI list) and in the second series of codepoints (i.e. in the target TCI list). The synchronization of synchronization signal blocks can be also understood and referred to as reception of synchronization signal blocks or detection of synchronization signal blocks.

The method 400 comprises a fifth operation 405 of determining that no synchronization of synchronization signal blocks associated with the at least one common reference signal is required. The fifth operation 405 is completed in response to the fourth operation 404, i.e. once it has been identified that there is a common codepoint in the first and second list. The Synchronization Signal and PBCH block (SSB) consists of primary and secondary synchronization signals (PSS, SSS). The UE uses this to obtain Physical cell id (PCI) during cell search, downlink frequency and time synchronization

The method 400 may be carried out by a computer program running on a computer.

In some embodiments, the MAC-CE command is sent on a physical downlink shared channel, PDSCH.

In some embodiments, the method 400 further involves activating the target TCI state for PDSCH within a predetermined time interval. Alternatively, the method 400 involves for indicating the target TCI state for a physical downlink control channel, PDCCH, within a predetermined time interval.

The pre-determined time interval maybe approximately equal to THARQ + 3 ms. Alternatively, the pre-determined time interval maybe approximately exactly to THARQ + 3 ms. This is based on the requirements of TS38.133 takes. However, the pre-determined time interval could be any time that is specified, for example THARQ + 2 ms should the requirements be updated in TS38.133 or otherwise updated in further iterations. THARQ is the timing between a transmission of the MAC-CE command and a corresponding acknowledgement sent from the user equipment to the network node. This time is shorted than the previously required time necessary for synchronization and therefore reduces the time needed to activated the target TCI state.

There are two example alternatives which have been considered herein. The first alternative relates to when the first set of codepoints and second set of codepoints contains only one TCI state. The second alternative relates to the first set of codepoints and second set of codepoints first TCI state and a second TCI state.

In the first alternative, when the first set of codepoints and second set of codepoints contains only one TCI state, the UE compares the second set of reference signals of the target TCI state with the first set reference signals of the TCI states in the previous list of active TCI states. If at least one of the active TCI states contains at least one common reference signal that is present in both the first set of reference signals and the second set of reference signals, the new TCI state can be considered activated/indicated after Tharq + 3ms without the need to wait for the first SSB (i.e. no delay is required as shown in figures 3 and 5). This therefore reduces the TCI active list update delay and TCI switching delays by avoiding need for a UE to synchronize to an SSB.

Instead, if no common codepoint were identified, the TCI switch/activation cannot be considered complete under a later stage (as shown in Figure 3). This would therefore take longer than when using the proposed approach.

In the first alternative, the QCL information of the at least one common reference signal is of QCL-D type.

An example of this approach is shown in the below table 2 and table 3.

Table 2: ‘Old’ Active TCI codepoint table

Table 3: ‘New’ Target TCI codepoint table

In this example the codepoint #3 is added to the new target TCI state list. This includes SSB#i as QCL-A source, which was already in the active TCI state list of codepoint #0, therefore, this TCI state can be considered active after Tharq + 3ms.

On the other hand, the new codepoint #4 includes SSB#1 for the first TCI, and SSB#8 for the second TCI. SSB#1 was already in the active TCI state list, but SSB#8 is not. Therefore, when activating the codepoint #4 the UE would have to wait Tharq + 3ms + Tfirst-SSB+TSSB-proc, where Tfirst-SSB is the time for the first occurrence of SSB#8.

In the second alternative, the first set of codepoints and second set of codepoints each respectively comprise a first TCI state and a second TCI state. The method 400 further includes comparing the QCL information of the first set of codepoints to the QCL information of the second set of codepoints for the first TCI state and also comparing the QCL information of the first set of codepoints to the QCL information of the second set of codepoints for the second TCI state. Furthermore, it not only possible for a first and second set of codepoints to comprise a first TCI state and a second TCI state but it is also possible that a codepoint of a first/second set of codepoint comprises a first TCI state and a second TCI state. In that situation a similar approach may apply.

When the first and second set of codepoints contains 2 TCI states, if the RS from both target TCI states also have a QCL relationship (i.e. common codepoint for the first TCI state and the second TCI state) with the RSs from any of the active TCI states, the new pair of TCI states can be considered to be active after Tharq + 3ms without the need to wait for the first SSB of either target TCI states. In this instance, the method 400 further comprises determining a QCL relationship between the first set of codepoints and the second set of codepoints for the first TCI state, by identifying at least one common reference signal for the first TCI state that is present in both the first set of reference signals and the second set of reference signals. The method 400 further comprises determining a QCL relationship between the first set of codepoints and the second set of codepoints for the second TCI state, by identifying at least one common reference signal for the second TCI state that is present in both the first set of reference signals and the second set of reference signals. Finally, the method further comprises determining that no synchronization of synchronization signal blocks associated with the at least one common reference signal in the first TCI state and at least one common reference signal in the second TCI state is required. This means that synchronization can be skipped for both of the first TCI state and the second TCI, therefore saving time.

Alternatively, if only one of the RSs from the target TCI states has a QCL relationship (i.e. common codepoint for the first TCI state and the second TCI state) with the RSs from any of the active TCI states, then a different scenario apply. Only the TCI states for which a common reference signal can be identified will the synchronization step be circumvented. In this instance, the method 400 further comprises determining a QCL relationship between the first set of codepoints and the second set of codepoints for the first TCI state, by identifying at least one common reference signal for the first TCI state that is present in both the first set of reference signals and the second set of reference signals. The method further comprises determining that no synchronization of synchronization signal blocks associated with the at least one common reference signal in the first TCI state is required. However, the method 400 also comprises determining that no QCL relationship is found between the first set of codepoints and the second set of codepoints for the second TCI state, by establishing that no common reference signals are found for the second TCI state for the first set of reference signals and the second set of reference signals. Finally, since no common reference signal can be found, the method comprises determining that synchronization of synchronization signal blocks associated with the second TCI state for the first set of reference signals and the second set of reference signals is required. Subsequent to this step the UE can proceed with the synchronization process for the second TCI state as per the usual procedure.

This therefore reduces the TCI active list update delay and TCI switching delays by avoiding need for a UE to synchronize to a SSB. Where two TCI states are present it is only necessary to perform the synchronization for the TCI states for which no prior relationship based on the a common reference signal can be found.

In this second alternative, the first reference signal and second reference signal may be QCL-A, QCL-C or QCL-D type. An example of this approach is shown in the below table 4 and table 5.

Table 4: ‘Old’ Active TCI codepoint table

Table 5: ‘New’ target active TCI codepoint table

In this example the codepoint #3 is added to the new target TCI state list of the first TCI state TCI#1. This includes SSB#1 as QCL-A source, which was already in the active TCI state list of codepoint #0, therefore, this TCI state can be considered active after Tharq + 3ms.

In another case, the new codepoint #5 includes SSB#1 for the first TCI and SSB#3 for the second TCI state. SSB#i and SSB#3 are already in the active TCI state list. Hence, the UE will not have to synchronize with the SSBs for either of the TCI states.

The gNB and UE are aware of the following conditions while activating a codepoint with two TCI states TCI#A and TCI#B: A - If there exists a QCL relation between the RS of at least one of the already active TCI states and RS of one of the target TCI states TCI#A or TCI#B received in the MAC- CE command.

B - If there exists a QCL relation between the RS of the already active TCI states and RS for both of the TCI states TCI#A and TCI#B received in the MAC-CE command.

When the UE receives a MAC-CE command for TCI state activation or TCI state indication, UE compares which RS are common for the TCI states in the active list in comparison to the new active TCI state list. In case the RS of one of the TCI state received in the MAC-CE command for TCI activation is QCL A/ C with the RS of one of the indicated TCI states in the active TCI state list, then the UE will skip the synchronization with the first SSB associated with this TCI state and only synchronize with the first SSB transmission associated with the other TCI state (i.e. the TCI state that does not have QCL A/C relation to any of the active TCI states) after MAC-CE command is decoded by the UE (condition A). Additionally, if condition B is met, then the UE can reuse the synchronization information for both TCI states, and can conclude the TCI active state list update or TCI indication without monitoring SSB for TCI#A and TCI#B.

The method 400 may be performed by an apparatus such as a UE too of Figure 1, e.g. a mobile phone or a smart phone, or by a control device configured to control the functioning thereof, when installed therein. The UE too may be equipped with the antenna system. The antenna system may comprise an antenna array comprising a plurality of antenna elements or other known types of antenna. The antenna system may be configured to receive DL reference signals. Such antenna configurations can dynamically form and steer narrow transmission/reception beams, in a process known as UE-specific beamforming. Active antenna configurations can be used both at the network nodes and at the UE too to further enhance the beamforming potential. More than one beam can be received by each antenna array. The apparatus may also comprise at least one processor; and at least one memory storing instructions that, when executed by the at least processor, cause the performance of the apparatus.

In some embodiments, the network nodes are radio access network, RAN, base stations.

Figure 5 shows a flowchart 500 for a decision-making process. At box 502 the gNB receives a channel status information CSI report which includes an indication of the best beam pair from a UE. At box 504 the gNB sends a MAC-CE to the UE including TCI states. At box 506 the UE decodes the MAC-CE. At step 508 the UE checks the QCL relations between active TCI states and target TCI states (i.e. by comparing a first series of codepoints comprising QCL associated with a first reference signal and a second series of codepoints comprising QCL associated with a second reference signal).

At this stage there are three different options in the decision-making process. The first option 509 is taken when there exists a QCL relation between the RS of at least one of the already active TCI states and RS of one of the target TCI states TCI#A or TCI#B received in the MAC- CE command. In this instance, the next step 510 is to synchronize only with the SSB of the TCI state for which no QCL relation (i.e. common codepoint) is found. No synchronization is required for the TCI state where a QCL relation is found. Once this is complete the next step 512 is to activate all the target TCI states.

In further embodiments it is possible for there to be more than two TCI states. In this case, synchronization would only be required for the TCI states for which no QCL relation is found. The TCI states for which a QCL relation is found require no synchronization.

The second option 513 is taken when there exists a QCL relation between the RS of the already active TCI states and RS for both of the TCI states TCI# A and TCI#B received in the MAC-CE. In this instance, no further synchronization is required as shown in step 514 and the next stage 516 is to activate all the target TCI states.

The third option 517 is taken when there is no QCL relation found between the RS of the already active TCI states and RS for either of the TCI states TCI#A and TCI#B received in the MAC-CE. In this instance, the next step 518 is to synchronize with the SSB for all of the TCI state since no QCL relations were found. Only after this synchronization has taken place can all the target TCI states be activated 520.

This approach will enable faster target TCI state activation where a previous QCL relationship can be found. In particular, this is especially beneficial when two TCI states are activated simultaneously.

Figure 6 shows, by way of example, a block diagram of an apparatus capable of performing the method(s) as disclosed herein. Illustrated is device 600, which may comprise, for example, a mobile communication device such as mobile too of Figure 1. Comprised in device 600 is processor 610, which may comprise, for example, a single- or multi-core processor wherein a single-core processor comprises one processing core and a multi-core processor comprises more than one processing core. Processor 610 may comprise, in general, a control device. Processor 610 may comprise more than one processor. Processor 610 maybe a control device. A processing core may comprise, for example, a Cortex-A8 processing core manufactured by ARM Holdings or a Steamroller processing core designed by Advanced Micro Devices Corporation. Processor 610 may comprise at least one Qualcomm Snapdragon and/or Intel Atom processor. Processor 610 may comprise at least one application-specific integrated circuit, ASIC. Processor 610 may comprise at least one field-programmable gate array, FPGA. Processor 610 maybe means for performing method steps in device 600. Processor 610 may be configured, at least in part by computer instructions, to perform actions.

A processor may comprise circuitry, or be constituted as circuitry or circuitries, the circuitry or circuitries being configured to perform phases of methods in accordance with example embodiments described herein. As used in this application, the term “circuitry” may refer to one or more or all of the following: (a) hardware-only circuit implementations, such as implementations in only analog and/or digital circuitry, and (b) combinations of hardware circuits and software, such as, as applicable: (i) a combination of analog and/or digital hardware circuit(s) with software/firmware and (ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or a network node, to perform various functions) and (c) hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.

This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and/or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

Device 600 may comprise memory 620. Memory 620 may comprise random-access memory and/or permanent memory. Memory 620 may comprise at least one RAM chip. Memory 620 may comprise solid-state, magnetic, optical and/or holographic memory, for example. Memory 620 may be at least in part accessible to processor 610. Memory 620 may be at least in part comprised in processor 610. Memory 620 may be means for storing information. Memory 620 may comprise computer instructions that processor 610 is configured to execute. When computer instructions configured to cause processor 610 to perform certain actions are stored in memory 620, and device 600 overall is configured to run under the direction of processor 610 using computer instructions from memory 620, processor 610 and/ or its at least one processing core may be considered to be configured to perform said certain actions. Memory 620 may be at least in part external to device 600 but accessible to device 600.

Device 600 may comprise a transmitter 630. Device 600 may comprise a receiver 640. Transmitter 630 and receiver 640 may be configured to transmit and receive, respectively, information in accordance with at least one cellular or non-cellular standard. Transmitter 630 may comprise more than one transmitter. Receiver 640 may comprise more than one receiver. Transmitter 630 and/ or receiver 640 may be configured to operate in accordance with global system for mobile communication, GSM, wideband code division multiple access, WCDMA, 5G, long term evolution, LTE, IS-95, wireless local area network, WLAN, Ethernet and/or worldwide interoperability for microwave access, WiMAX, standards, for example.

Device 600 may comprise a near-field communication, NFC, transceiver 650. NFC transceiver 650 may support at least one NFC technology, such as NFC, Bluetooth, Wibree or similar technologies.

Device 600 may comprise user interface, UI, 660. UI 660 may comprise at least one of a display, a keyboard, a touchscreen, a vibrator arranged to signal to a user by causing device 600 to vibrate, a speaker and a microphone. A user may be able to operate device 600 via UI 660, for example to accept incoming telephone calls, to originate telephone calls or video calls, to browse the Internet, to manage digital files stored in memory 620 or on a cloud accessible via transmitter 630 and receiver 640, or via NFC transceiver 650, and/or to play games.

Device 600 may comprise or be arranged to accept a user identity module 670. User identity module 670 may comprise, for example, a subscriber identity module, SIM, card installable in device 600. A user identity module 670 may comprise information identifying a subscription of a user of device 600. A user identity module 670 may comprise cryptographic information usable to verify the identity of a user of device 600 and/or to facilitate encryption of communicated information and billing of the user of device 600 for communication effected via device 600. Processor 610 may be furnished with a transmitter arranged to output information from processor 610, via electrical leads internal to device 600, to other devices comprised in device 600. Such a transmitter may comprise a serial bus transmitter arranged to, for example, output information via at least one electrical lead to memory 620 for storage therein. Alternatively to a serial bus, the transmitter may comprise a parallel bus transmitter. Likewise processor 610 may comprise a receiver arranged to receive information in processor 610, via electrical leads internal to device 600, from other devices comprised in device 600. Such a receiver may comprise a serial bus receiver arranged to, for example, receive information via at least one electrical lead from receiver 640 for processing in processor 610. Alternatively to a serial bus, the receiver may comprise a parallel bus receiver.

Processor 610, memory 620, transmitter 630, receiver 640, NFC transceiver 650, UI 660 and/ or user identity module 670 may be interconnected by electrical leads internal to device 600 in a multitude of different ways. For example, each of the aforementioned devices maybe separately connected to a master bus internal to device 600, to allow for the devices to exchange information. However, as the skilled person will appreciate, this is only one example and depending on the embodiment various ways of interconnecting at least two of the aforementioned devices may be selected.

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. 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 modifications may be made without departing from the scope as defined by the appended claims.

Claims

1. An apparatus, comprising: means for defining, at a user equipment, an active transmission configuration indication (TCI) state list, comprising a first set of codepoints comprising quasi-co-located (QCL) information associated with a first set of reference signals; means for receiving, at the user equipment from a network node, a medium access control control element (MAC-CE) command, wherein the MAC-CE command defines a target TCI state list, comprising a second set of codepoints comprising QCL information associated with a second set of reference signals; means for comparing the QCL information of the first set of codepoints to the QCL information of the second set of codepoints; means for determining a QCL relationship between the first set of codepoints and the second set of codepoints by identifying at least one common reference signal that is present in both the first set of reference signals and the second set of reference signals; means for determining that no synchronization of synchronization signal blocks associated with the at least one common reference signal is required.

2. The apparatus of any preceding claim, wherein the MAC-CE command is sent on a physical downlink shared channel, PDSCH.

3. The apparatus of claims 1 or 2 further comprising: means for activating the target TCI state for PDSCH within a predetermined time interval.

4. The apparatus of claims 1 or 2 further comprising: means for indicating the target TCI state for a physical downlink control channel, PDCCH, within a predetermined time interval.

5. The apparatus of claims 3 or 4, wherein when the at least one common reference signal is identified, the pre-determined time interval is approximately equal to T-HARQ + 3 ms, wherein T-HARQ is the timing between a transmission of the MAC-CE command and a corresponding acknowledgement sent from the user equipment to the network node.

6. The apparatus of any preceding claim, wherein the first set of codepoints and second set of codepoints comprise only one TCI state.

7. The apparatus of claim 6, wherein QCL information of the at least one common reference signal is of QCL-D type.

8. The apparatus of any of claims 1 to 5, wherein the first set of codepoints and second set of codepoints each respectively comprise a first TCI state and a second TCI state; and the apparatus further comprises: means for comparing the QCL information of the first set of codepoints to the QCL information of the second set of codepoints for the first TCI state; means for comparing the QCL information of the first set of codepoints to the QCL information of the second set of codepoints for the second TCI state.

9. The apparatus of claim 8, further comprising: means for determining a QCL relationship between the first set of codepoints and the second set of codepoints for the first TCI state, by identifying at least one common reference signal for the first TCI state that is present in both the first set of reference signals and the second set of reference signals; means for determining a QCL relationship between the first set of codepoints and the second set of codepoints for the second TCI state, by identifying at least one common reference signal for the second TCI state that is present in both the first set of reference signals and the second set of reference signals; means for determining that no synchronization of synchronization signal blocks associated with the at least one common reference signal in the first TCI state and at least one common reference signal in the second TCI state is required.

10. The apparatus of claims 8, further comprising: means for determining a QCL relationship between the first set of codepoints and the second set of codepoints for the first TCI state, by identifying at least one common reference signal for the first TCI state that is present in both the first set of reference signals and the second set of reference signals; means for determining that no synchronization of synchronization signal blocks associated with the at least one common reference signal in the first TCI state is required; means for determining that no QCL relationship is found between the first set of codepoints and the second set of codepoints for the second TCI state, by establishing that no common reference signals are found for the second TCI state for the first set of reference signals and the second set of reference signals; means for determining that synchronization of synchronization signal blocks associated with the second TCI state for the second set of reference signals is required.

11. The apparatus of claims 8 to 10, wherein the QCL information of the at least one common reference signal is of QCL-A, QCL-C or QCL-D type.

12. The apparatus of any preceding claim, wherein the apparatus is a user device.

13. The apparatus of any preceding claim, wherein the network nodes are radio access network, RAN, base stations.

14. The apparatus of any preceding claim, wherein the means comprise: at least one processor; and at least one memory storing instructions that, when executed by the at least processor, cause the performance of the apparatus.

15. A method comprising: defining, at a user equipment, an active transmission configuration indication (TCI) state list, comprising a first set of codepoints comprising quasi-co-located (QCL) information associated with a first set of reference signals; receiving, at the user equipment from a network node, a medium access control control element (MAC-CE) command, wherein the MAC-CE command defines a target TCI state list, comprising a second set of codepoints comprising QCL information associated with a second set of reference signals; comparing the QCL information of the first set of codepoints to the QCL information of the second set of codepoints; determining a QCL relationship between the first set of codepoints and the second set of codepoints by identifying at least one common reference signal that is present in both the first set of reference signals and the second set of reference signals; determining that no synchronization of synchronization signal blocks associated with the at least one common reference signal is required.