Apparatus, method and computer program

Field

The present application relates to a method, apparatus, system and computer program and in particular but not exclusively to explicit time domain CSI reporting based on combined CIR.

Background

A communication system can be seen as a facility that enables communication sessions between two or more entities such as user terminals, base stations and/or other nodes by providing carriers between the various entities involved in the communications path. A communication system can be provided for example by means of a communication network and one or more compatible communication devices. The communication sessions may comprise, for example, communication of data for carrying communications such as voice, video, electronic mail (email), text message, multimedia and/or content data and so on. Non-limiting examples of services provided comprise two-way or multi-way calls, data communication or multimedia services and access to a data network system, such as the Internet.

In a wireless communication system at least a part of a communication session between at least two stations occurs over a wireless link. Examples of wireless systems comprise public land mobile networks (PLMN), satellite based communication systems and different wireless local networks, for example wireless local area networks (WLAN). The wireless systems can typically be divided into cells, and are therefore often referred to as cellular systems.

A user can access the communication system by means of an appropriate communication device or terminal. A communication device of a user may be referred to as user equipment (UE) or user device. A communication device is provided with an appropriate signal receiving and transmitting apparatus for enabling communications, for example enabling access to a communication network or communications directly with other users. The communication device may access a carrier provided by a station, for example a base station of a cell, and transmit and/or receive communications on the carrier. The communication system and associated devices typically operate in accordance with a given standard or specification which sets out what the various entities associated with the system are permitted to do and how that should be achieved. Communication protocols and/or parameters which shall be used for the connection are also typically defined. One example of a communications system is UTRAN (3G radio). Other examples of communication systems are the long-term evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio-access technology and so-called 5G or New Radio (NR) networks. NR is being standardized by the 3rd Generation Partnership Project (3GPP).

Summary

In a first aspect there is provided an apparatus, said apparatus comprising means for determining, at a user equipment, first channel state information for a first channel component having first parameters and second channel state information for at least one second channel component having second parameters, determining combined channel state information based on the first channel state information and the second channel state information and providing to a network an indication of the combined channel state information.

The first parameters and the second parameters may comprise multipath component parameters.

The first channel state information and the second channel state information may each comprise a channel impulse response. The combined channel state information may comprise a combined channel impulse response.

The indication of the combined channel state information may comprise taps, sub taps or multipath components of the combined channel impulse response.

The apparatus may comprise means for performing a time shift operation on the first channel state information and the second channel state information or performing a time shift operation on the combined channel state information.

The indication of the channel state information may be quantised based on predefined quantisation rules. The apparatus may comprise means for providing to the network an indication of an association between the first channel component and the first parameters and the at least one second channel component and the second parameters.

The means for providing the indication of the association between the first channel component and the first parameters and the at least one second channel component and the second parameters may comprise means for providing an indication of the channel state information for each channel component prior to providing the indication of the combined channel state information.

The apparatus may comprise means for receiving a control message from the network, the control message comprising an indication to provide an indication of the channel state information for each channel component prior to providing the indication of the combined channel state information.

The apparatus may comprise means for quantising the first and second parameters at the user equipment based on predefined quantisation rules.

The apparatus may comprise means for receiving a control message from the network, the control message comprising an indication of the number of channel components on which the combined channel state information is based.

In a second aspect there is provided an apparatus, said apparatus comprising means for receiving, from a user equipment, an indication of combined channel state information, wherein the combined channel state information is based on first channel state information for a first channel component having first parameters and second channel state information for at least one second channel component having second parameters.

The apparatus may comprise means for determining the first parameters and the second parameters based on the indication of combined channel state information.

The apparatus may comprise means for receiving from a user equipment network an indication of an association between the first channel component and the first parameters and the at least one second channel component and the second parameters.

The means for receiving the indication of the association between the first channel component and the first parameters and the at least one second channel component and the second parameters may comprise means for receiving an indication of the channel state information for each channel component prior to receiving the indication of the combined channel state information.

The apparatus may comprise means for providing a control message to the user equipment, the control message comprising an indication to provide an indication of the channel state information for each channel component prior to providing the indication of the combined channel state information.

The apparatus may comprise means for determining the first parameters and the second parameters based on the indication of combined channel state information and the indication of an association between the first channel component and the first parameters and the at least one second channel component and the second parameters.

The first parameters and the second parameters may comprise multipath component parameters.

The first channel state information and the second channel state information may each comprise a channel impulse response. The combined channel state information may comprise a combined channel impulse response.

The indication of the combined channel state information may comprise taps, sub taps or multipath components of the combined channel impulse response.

The indication of the channel state information may be quantised based on predefined quantisation rules.

The apparatus may comprise means for providing a control message to the user equipment, the control message comprising an indication of the number of channel components on which the combined channel state information is based.

In a third aspect there is provided a method comprising determining, at a user equipment, first channel state information for a first channel component having first parameters and second channel state information for at least one second channel component having second parameters, determining combined channel state information based on the first channel state information and the second channel state information and providing to a network an indication of the combined channel state information. The first parameters and the second parameters may comprise multipath component parameters.

The first channel state information and the second channel state information may each comprise a channel impulse response. The combined channel state information may comprise a combined channel impulse response.

The indication of the combined channel state information may comprise taps, sub taps or multipath components of the combined channel impulse response.

The method may comprise performing a time shift operation on the first channel state information and the second channel state information or performing a time shift operation on the combined channel state information.

The indication of the channel state information may be quantised based on predefined quantisation rules.

The method may comprise providing to the network an indication of an association between the first channel component and the first parameters and the at least one second channel component and the second parameters.

Providing the indication of the association between the first channel component and the first parameters and the at least one second channel component and the second parameters may comprise providing an indication of the channel state information for each channel component prior to providing the indication of the combined channel state information.

The method may comprise receiving a control message from the network, the control message comprising an indication to provide an indication of the channel state information for each channel component prior to providing the indication of the combined channel state information.

The method may comprise quantising the first and second parameters at the user equipment based on predefined quantisation rules.

The method may comprise receiving a control message from the network, the control message comprising an indication of the number of channel components on which the combined channel state information is based. In a fourth aspect there is provided a method comprising receiving, from a user equipment, an indication of combined channel state information, wherein the combined channel state information is based on first channel state information for a first channel component having first parameters and second channel state information for at least one second channel component having second parameters.

The method may comprise determining the first parameters and the second parameters based on the indication of combined channel state information.

The method may comprise receiving from a user equipment network an indication of an association between the first channel component and the first parameters and the at least one second channel component and the second parameters.

Receiving the indication of the association between the first channel component and the first parameters and the at least one second channel component and the second parameters may comprise receiving an indication of the channel state information for each channel component prior to receiving the indication of the combined channel state information.

The method may comprise providing a control message to the user equipment, the control message comprising an indication to provide an indication of the channel state information for each channel component prior to providing the indication of the combined channel state information.

The method may comprise determining the first parameters and the second parameters based on the indication of combined channel state information and the indication of an association between the first channel component and the first parameters and the at least one second channel component and the second parameters.

The first parameters and the second parameters may comprise multipath component parameters.

The first channel state information and the second channel state information may each comprise a channel impulse response. The combined channel state information may comprise a combined channel impulse response.

The indication of the combined channel state information may comprise taps, sub taps or multipath components of the combined channel impulse response. The indication of the channel state information may be quantised based on predefined quantisation rules.

The method may comprise providing a control message to the user equipment, the control message comprising an indication of the number of channel components on which the combined channel state information is based.

In a fifth aspect there is provided an apparatus comprising at least one processor and at least one memory including a computer program code, the at least one memory and computer program code configured to, with the at least one processor, cause the apparatus at least to determine, at a user equipment, first channel state information for a first channel component having first parameters and second channel state information for at least one second channel component having second parameters, determine combined channel state information based on the first channel state information and the second channel state information and provide to a network an indication of the combined channel state information.

The first parameters and the second parameters may comprise multipath component parameters.

The first channel state information and the second channel state information may each comprise a channel impulse response. The combined channel state information may comprise a combined channel impulse response.

The indication of the combined channel state information may comprise taps, sub taps or multipath components of the combined channel impulse response.

The apparatus may be configured to perform a time shift operation on the first channel state information and the second channel state information or perform a time shift operation on the combined channel state information.

The indication of the channel state information may be quantised based on predefined quantisation rules.

The apparatus may be configured to provide to the network an indication of an association between the first channel component and the first parameters and the at least one second channel component and the second parameters. The apparatus may be configured to provide an indication of the channel state information for each channel component prior to providing the indication of the combined channel state information.

The apparatus may be configured to receive a control message from the network, the control message comprising an indication to provide an indication of the channel state information for each channel component prior to providing the indication of the combined channel state information.

The apparatus may be configured to quantise the first and second parameters at the user equipment based on predefined quantisation rules.

The apparatus may be configured to receive a control message from the network, the control message comprising an indication of the number of channel components on which the combined channel state information is based.

In a sixth aspect there is provided an apparatus comprising at least one processor and at least one memory including a computer program code, the at least one memory and computer program code configured to, with the at least one processor, cause the apparatus at least to receive, from a user equipment, an indication of combined channel state information, wherein the combined channel state information is based on first channel state information for a first channel component having first parameters and second channel state information for at least one second channel component having second parameters.

The apparatus may be configured to determine the first parameters and the second parameters based on the indication of combined channel state information.

The apparatus may be configured to receive from a user equipment network an indication of an association between the first channel component and the first parameters and the at least one second channel component and the second parameters.

The apparatus may be configured to receive an indication of the channel state information for each channel component prior to receiving the indication of the combined channel state information.

The apparatus may be configured to provide a control message to the user equipment, the control message comprising an indication to provide an indication of the channel state information for each channel component prior to providing the indication of the combined channel state information.

The apparatus may be configured to determine the first parameters and the second parameters based on the indication of combined channel state information and the indication of an association between the first channel component and the first parameters and the at least one second channel component and the second parameters.

The first parameters and the second parameters may comprise multipath component parameters.

The first channel state information and the second channel state information may each comprise a channel impulse response. The combined channel state information may comprise a combined channel impulse response.

The indication of the combined channel state information may comprise taps, sub taps or multipath components of the combined channel impulse response.

The indication of the channel state information may be quantised based on predefined quantisation rules.

The apparatus may be configured to provide a control message to the user equipment, the control message comprising an indication of the number of channel components on which the combined channel state information is based.

In a seventh aspect there is provided a computer readable medium comprising program instructions for causing an apparatus to perform at least the following determining, at a user equipment, first channel state information for a first channel component having first parameters and second channel state information for at least one second channel component having second parameters, determining combined channel state information based on the first channel state information and the second channel state information and providing to a network an indication of the combined channel state information.

The first parameters and the second parameters may comprise multipath component parameters. The first channel state information and the second channel state information may each comprise a channel impulse response. The combined channel state information may comprise a combined channel impulse response.

The indication of the combined channel state information may comprise taps, sub taps or multipath components of the combined channel impulse response.

The apparatus may be caused to perform a time shift operation on the first channel state information and the second channel state information or performing a time shift operation on the combined channel state information.

The indication of the channel state information may be quantised based on predefined quantisation rules.

The apparatus may be caused to perform providing to the network an indication of an association between the first channel component and the first parameters and the at least one second channel component and the second parameters.

Providing the indication of the association between the first channel component and the first parameters and the at least one second channel component and the second parameters may comprise providing an indication of the channel state information for each channel component prior to providing the indication of the combined channel state information.

The apparatus may be caused to perform receiving a control message from the network, the control message comprising an indication to provide an indication of the channel state information for each channel component prior to providing the indication of the combined channel state information.

The apparatus may be caused to perform quantising the first and second parameters at the user equipment based on predefined quantisation rules.

The apparatus may be caused to perform receiving a control message from the network, the control message comprising an indication of the number of channel components on which the combined channel state information is based.

In an eighth aspect there is provided a computer readable medium comprising program instructions for causing an apparatus to perform at least the following receiving, from a user equipment, an indication of combined channel state information, wherein the combined channel state information is based on first channel state information for a first channel component having first parameters and second channel state information for at least one second channel component having second parameters.

The apparatus may be caused to perform determining the first parameters and the second parameters based on the indication of combined channel state information.

The apparatus may be caused to perform receiving from a user equipment network an indication of an association between the first channel component and the first parameters and the at least one second channel component and the second parameters.

The apparatus may be caused to perform receiving an indication of the channel state information for each channel component prior to receiving the indication of the combined channel state information.

The apparatus may be caused to perform providing a control message to the user equipment, the control message comprising an indication to provide an indication of the channel state information for each channel component prior to providing the indication of the combined channel state information.

The apparatus may be caused to perform determining the first parameters and the second parameters based on the indication of combined channel state information and the indication of an association between the first channel component and the first parameters and the at least one second channel component and the second parameters.

The first parameters and the second parameters may comprise multipath component parameters.

The first channel state information and the second channel state information may each comprise a channel impulse response. The combined channel state information may comprise a combined channel impulse response.

The indication of the combined channel state information may comprise taps, sub taps or multipath components of the combined channel impulse response.

The indication of the channel state information may be quantised based on predefined quantisation rules. The apparatus may be caused to perform providing a control message to the user equipment, the control message comprising an indication of the number of channel components on which the combined channel state information is based.

In a ninth aspect there is provided a non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least the method according to the third aspect or a method according to the fourth aspect.

In the above, many different embodiments have been described. It should be appreciated that further embodiments may be provided by the combination of any two or more of the embodiments described above.

Description of Figures

Embodiments will now be described, by way of example only, with reference to the accompanying Figures in which:

Figure 1 shows a schematic diagram of an example communication system comprising a base station and a plurality of communication devices;

Figure 2 shows a schematic diagram of an example mobile communication device;

Figure 3 shows a schematic diagram of an example control apparatus;

Figure 4 shows a flowchart of a method according to an example embodiment;

Figure 5 shows a flowchart of a method according to an example embodiment;

Figure 6 shows a schematic diagram of multi path components of three different channel components.

Detailed description

Before explaining in detail the examples, certain general principles of a wireless communication system and mobile communication devices are briefly explained with reference to Figures 1 to 3 to assist in understanding the technology underlying the described examples. In a wireless communication system 100, such as that shown in figure 1 , mobile communication devices or user equipment (UE) 102, 104, 105 are provided wireless access via at least one base station or similar wireless transmitting and/or receiving node or point. Base stations are typically controlled by at least one appropriate controller apparatus, so as to enable operation thereof and management of mobile communication devices in communication with the base stations. The controller apparatus may be located in a radio access network (e.g. wireless communication system 100) or in a core network (CN) (not shown) and may be implemented as one central apparatus or its functionality may be distributed over several apparatuses. The controller apparatus may be part of the base station and/or provided by a separate entity such as a Radio Network Controller. In Figure 1 control apparatus 108 and 109 are shown to control the respective macro level base stations 106 and 107. The control apparatus of a base station can be interconnected with other control entities. The control apparatus is typically provided with memory capacity and at least one data processor. The control apparatus and functions may be distributed between a plurality of control units. In some systems, the control apparatus may additionally or alternatively be provided in a radio network controller.

In Figure 1 base stations 106 and 107 are shown as connected to a wider communications network 1 13 via gateway 1 12. A further gateway function may be provided to connect to another network.

The smaller base stations 1 16, 1 18 and 120 may also be connected to the network 1 13, for example by a separate gateway function and/or via the controllers of the macro level stations. The base stations 1 16, 1 18 and 120 may be pico or femto level base stations or the like. In the example, stations 1 16 and 1 18 are connected via a gateway 1 1 1 whilst station 120 connects via the controller apparatus 108. In some embodiments, the smaller stations may not be provided. Smaller base stations 1 16, 1 18 and 120 may be part of a second network, for example WLAN and may be WLAN APs.

The communication devices 102, 104, 105 may access the communication system based on various access techniques, such as code division multiple access (CDMA), or wideband CDMA (WCDMA). Other non-limiting examples comprise time division multiple access (TDMA), frequency division multiple access (FDMA) and various schemes thereof such as the interleaved frequency division multiple access (IFDMA), single carrier frequency division multiple access (SC-FDMA) and orthogonal frequency division multiple access (OFDMA), space division multiple access (SDMA) and so on. An example of wireless communication systems are architectures standardized by the 3rd Generation Partnership Project (3GPP). A latest 3GPP based development is often referred to as the long term evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio-access technology. The various development stages of the 3GPP specifications are referred to as releases. More recent developments of the LTE are often referred to as LTE Advanced (LTE-A). The LTE (LTE-A) employs a radio mobile architecture known as the Evolved Universal Terrestrial Radio Access Network (E-UTRAN) and a core network known as the Evolved Packet Core (EPC). Base stations of such systems are known as evolved or enhanced Node Bs (eNBs) and provide E-UTRAN features such as user plane Packet Data Convergence/Radio Link Control/Medium Access Control/Physical layer protocol (PDCP/RLC/MAC/PHY) and control plane Radio Resource Control (RRC) protocol terminations towards the communication devices. Other examples of radio access system comprise those provided by base stations of systems that are based on technologies such as wireless local area network (WLAN) and/or WiMax (Worldwide Interoperability for Microwave Access). A base station can provide coverage for an entire cell or similar radio service area. Core network elements include Mobility Management Entity (MME), Serving Gateway (S-GW) and Packet Gateway (P-GW).

An example of a suitable communications system is the 5G or NR concept. Network architecture in NR may be similar to that of LTE-advanced. Base stations of NR systems may be known as next generation Node Bs (gNBs). Changes to the network architecture may depend on the need to support various radio technologies and finer QoS support, and some on-demand requirements for e.g. QoS levels to support QoE of user point of view. Also network aware services and applications, and service and application aware networks may bring changes to the architecture. Those are related to Information Centric Network (ICN) and User-Centric Content Delivery Network (UC-CDN) approaches. NR may use multiple input - multiple output (MIMO) antennas, many more base stations or nodes than the LTE (a so-called small cell concept), including macro sites operating in co-operation with smaller stations and perhaps also employing a variety of radio technologies for better coverage and enhanced data rates.

Future networks may utilise network functions virtualization (NFV) which is a network architecture concept that proposes virtualizing network node functions into“building blocks” or entities that may be operationally connected or linked together to provide services. A virtualized network function (VNF) may comprise one or more virtual machines running computer program codes using standard or general type servers instead of customized hardware. Cloud computing or data storage may also be utilized. In radio communications this may mean node operations to be carried out, at least partly, in a server, host or node operationally coupled to a remote radio head. It is also possible that node operations will be distributed among a plurality of servers, nodes or hosts. It should also be understood that the distribution of labour between core network operations and base station operations may differ from that of the LTE or even be non-existent.

An example 5G core network (CN) comprises functional entities. The CN is connected to a UE via the radio access network (RAN). An UPF (User Plane Function) whose role is called PSA (PDU Session Anchor) may be responsible for forwarding frames back and forth between the DN (data network) and the tunnels established over the 5G towards the UE(s) exchanging traffic with the DN.

The UPF is controlled by an SMF (Session Management Function) that receives policies from a PCF (Policy Control Function). The CN may also include an AMF (Access & Mobility Function).

A possible mobile communication device will now be described in more detail with reference to Figure 2 showing a schematic, partially sectioned view of a communication device 200. Such a communication device is often referred to as user equipment (UE) or terminal. An appropriate mobile communication device may be provided by any device capable of sending and receiving radio signals. Non-limiting examples comprise a mobile station (MS) or mobile device such as a mobile phone or what is known as a’smart phone’, a computer provided with a wireless interface card or other wireless interface facility (e.g., USB dongle), personal data assistant (PDA) or a tablet provided with wireless communication capabilities, or any combinations of these or the like. A mobile communication device may provide, for example, communication of data for carrying communications such as voice, electronic mail (email), text message, multimedia and so on. Users may thus be offered and provided numerous services via their communication devices. Non-limiting examples of these services comprise two-way or multi-way calls, data communication or multimedia services or simply an access to a data communications network system, such as the Internet. Users may also be provided broadcast or multicast data. Non-limiting examples of the content comprise downloads, television and radio programs, videos, advertisements, various alerts and other information.

A mobile device is typically provided with at least one data processing entity 201 , at least one memory 202 and other possible components 203 for use in software and hardware aided execution of tasks it is designed to perform, including control of access to and communications with access systems and other communication devices. The data processing, storage and other relevant control apparatus can be provided on an appropriate circuit board and/or in chipsets. This feature is denoted by reference 204. The user may control the operation of the mobile device by means of a suitable user interface such as key pad 205, voice commands, touch sensitive screen or pad, combinations thereof or the like. A display 208, a speaker and a microphone can be also provided. Furthermore, a mobile communication device may comprise appropriate connectors (either wired or wireless) to other devices and/or for connecting external accessories, for example hands-free equipment, thereto.

The mobile device 200 may receive signals over an air or radio interface 207 via appropriate apparatus for receiving and may transmit signals via appropriate apparatus for transmitting radio signals. In Figure 2 transceiver apparatus is designated schematically by block 206. The transceiver apparatus 206 may be provided for example by means of a radio part and associated antenna arrangement. The antenna arrangement may be arranged internally or externally to the mobile device.

Figure 3 shows an example of a control apparatus for a communication system, for example to be coupled to and/or for controlling a station of an access system, such as a RAN node, e.g. a base station, eNB or gNB, a relay node or a core network node such as an MME or S-GW or P-GW, or a core network function such as AMF/SMF, or a server or host. The method may be implanted in a single control apparatus or across more than one control apparatus. The control apparatus may be integrated with or external to a node or module of a core network or RAN. In some embodiments, base stations comprise a separate control apparatus unit or module. In other embodiments, the control apparatus can be another network element such as a radio network controller or a spectrum controller. In some embodiments, each base station may have such a control apparatus as well as a control apparatus being provided in a radio network controller. The control apparatus 300 can be arranged to provide control on communications in the service area of the system. The control apparatus 300 comprises at least one memory 301 , at least one data processing unit 302, 303 and an input/output interface 304. Via the interface the control apparatus can be coupled to a receiver and a transmitter of the base station. The receiver and/or the transmitter may be implemented as a radio front end or a remote radio head.

The following may be applicable to multi transmission point (TRP) NR phase II systems.

FANTASTIC-5G interference mitigation based on joint transmission (JT) CoMP over a three site or nine cell cooperation area has been analysed. Such interference mitigation may provide large possible spectral efficiency gains, but may result in higher CSI reporting overhead. JT CoMP interference mitigation may involve accurate frequency selective CSI being provided to the cooperation area common JT CoMP precoder. Controlling the CSI reporting overhead while providing JT CoMP interference mitigation is desirable.

A flexible CSI estimation and reporting scheme including the fast adaptation by transmission configuration index (TCI) messages has been standardized for NR Release 15.

For more advanced CSI reporting, where a high number of relevant channel components are to be reported accurately and on a frequency selective basis, several further schemes have been developed. For example, Coded CSI RSs, which may be combined with subtiling, may enable accurate channel estimation in challenging multi cell and/or multi TRP scenarios.

Explicit time domain CSI reporting may provide performance gains compared to current NR Release 15 frequency domain CSI reporting. The basic idea for explicit time domain CSI reporting is to report relevant taps or multi path components (MPC) of the TD CIRs, which may be seen as special variants of a compressed sensing approach.

Related techniques are the so called profiling solution, which allows estimation of MPC parameters with high accuracy, and a time shift concept, which is a low complexity alternative to classical orthogonal matching pursuit (OMP) based compressed sensing techniques.

The MPCs have parameters such as delay T, amplitude a and phase cp. The MPC parameters may be estimated by a network, for example using the above mentioned profiling concept. Conventionally, for explicit time domain reporting, MPC parameters are reported from the UEs to the gNB, which can use these parameters to reconstruct the wideband and frequency selective channel transfer function (CTF).

With time shifting, the MPC parameters are not estimated at a UE. A compression is achieved by a time shift operation on the time domain CIR. For that purpose the according CTF for this CIR is multiplied by different phase slope vectors with different phase slope values so that the according CIR will be shifted several times by a certain sub tap time delay Dt. The CIR with the time shift leading to the lowest number of relevant taps will be selected and reported from the UE to the gNB.

Different proposals for efficient explicit time domain CSI reporting have been suggested. The proposed concepts rely on effective compressed sensing approaches, but the overhead may still be up to kbits per CSI report. For more simple NR single cell scenarios, a few hundreds of bits are being considered so far.

The relative larger overhead may be justified by significantly increased DL performance, but a higher degree of CSI feedback compression is of interest.

The following aims to provide a further level of CSI reporting compression in the multi TRP or JT CoMP case compared to state of the art solutions.

Figure 4 shows a flowchart of an example method of reporting of explicit time domain CSI.

In a first step, S1 , the method comprises determining, at a user equipment, first channel state information for a first channel component having first parameters and second channel state information for at least one second channel component having second parameters.

In a second step, S2, the method comprises determining combined channel state information based on the first channel state information and the second channel state information.

In a third step, S3, the method comprises providing an indication of the channel state information to a network.

Figure 5 shows a flowchart of an example method used in reporting of explicit time domain CSI. In a first step, T1 , the method comprises receiving, from a user equipment, an indication of combined channel state information, wherein the combined channel state information is based on first channel state information for a first channel component having first parameters and second channel state information for at least one second channel component having second parameters.

Determining channel state information may be based on CSI reference signals (RS) transmitted by the network (e.g. by gNBs).

The first and second parameters may comprise multipath component parameters.

The first channel state information and the second channel state information may comprise first and second CIRs, respectively.

The combined channel state information value may comprise a CIR. The first channel component and at least one second channel component are the UE’s relevant channel components. Relevant channel components may be those received at the UE above a certain power threshold.

The number of CIRs which might be combined into a combined CIR is variable. For example, in the case of CIRs with relatively lower number of MPCs per CIR a higher number of CIRs might be combined. That is, channel state information relating to a higher or lower number of channel components may be combined. The method may comprise receiving a control message from the network, the control message comprising an indication of the number of channel components on which the combined channel state information is based.

The method may comprise performing a time shift operation on the first channel state information and the second channel state information or performing a time shift operation on the combined channel state information. That is, a time shift operation may be applied per channel component. Alternatively, the UE may combine multiple CIRs into one single CIR value and apply the time shift component to the combined CIR. The time shift operation may provide the optimum compression of taps.

The combining may be performed in the frequency domain by adding up two or multiple frequency domain channel transfer functions of the according channel components.

The indication of the channel state information may comprise quantised combined CIR taps, subtaps or MPC parameters (delay T, amplitude a and phase cp).

A method as described with reference to Figure 5 may comprise determining the first parameters and the second parameters (parameter information) based on the indication of combined channel state information and optionally, an indication of an association between the first channel component and the first parameters and the at least one second channel component and the second parameter.

For example, the network, e.g. gNBs, estimates parameters for the combined CIR based on the indication of the combined channel state information and an indication of an association between the first channel component and the first parameters and the at least one second channel component and the second parameter, with the goal to estimate all relevant MPCs of the combined CIR (super resolution). This may be done, for example, by the profiling concept described above. The UEs may perform state of the art power window detection and phase and amplitude quantization per power class with the goal to minimize the reporting overhead for the quantized CIRs. The method may comprise quantising the first and second parameters at the user equipment based on predefined quantisation rules.

For example, parameter estimation at the gNB may be supported by specific quantization rules at the UE as well as additional information knowledge. For example, it may be useful to provide the network with the number of MPCs per CIR, which have been quantized into the combined CIR. Note, the quantized CIR is typically an artificial CIR, which will contain only the relevant MPCs, which have been estimated at the UE. Therefore, the UE might use only a limited set of quantization values for the amplitude, phase and delay values of the comprising MPCs. In case these quantization levels are relatively coarse then the gNB has an accordingly reduced search space for these parameters.

A method as described with reference to Figure 4 may comprise providing an indication to the network of an association between the first channel component and the first parameters and the at least one second channel component and the second parameters.

The indication of an association between the first channel component and the first parameters and the at least one second channel component and the second parameter may comprise a control message. For example, UEs may report the binding of MPCs to relevant channel components semi-statically. In this case, the gNB may reconstruct the CIR per channel component by distributing the MPC to its CIRs.

In the case the UEs report the MPC binding to CIRs, then the UEs would have to do a parameter estimation, e.g., profiling, which may result in a certain processing complexity. As an alternative embodiment, providing the indication of an association between the first channel component and the first parameters and the at least one second channel component and the second parameters may comprise providing an indication of the channel state information for each channel component prior to providing the indication of the combined channel state information. That is, for example, in an initial step all CIRs as single CIRs may be reported to the gNB by the UE so that the gNB can calculate the correct binding by itself.

The method may comprise receiving a control message from the network, the control message comprising an indication to provide an indication of the channel state information for each channel component prior to providing the indication of the combined channel state information. The indication of the channel state information for each channel component may comprise a CIR for each channel component. The gNB may estimate in an initial phase all CIRs without combining so that it knows the MPC parameters for each CIR. Note, here the assumption is that there is a periodic reporting, which allows to track the parameters of each MPC. Assuming the MPCs have a smooth evolution over time or UE location, from knowing the MPC parameters at one CSI reporting instance allows allocation of the MPCs to CIRs. The evolution of the MPC parameters may then be determined from the combined channel state information. The evolution comprises small changes compared to the initial reporting so that always a clear allocation of estimated parameters to MPCs is possible

In the method described above, the time shift operation per single channel component is extended to a reporting of time shifted combined CIR. As a result, the CIR information for multiple channel components is provided to the network by a single combined CIR.

Figure 6 shows the relevant multipath components of three different channel components. In the method described above according to an example, the MPCs of two or more CIRs are estimated and combined into a combined CIR as illustrated in Figure 6 by the bold line, where the three different line types indicate the MPCs from three different CIRs. Close MPCs may be combined, if useful.

After combining, a time shift operation is applied to minimize the number of relevant taps. The minimised number of relevant taps is then which are reported for the combined CIR from the UE to the gNB.

The gNB receives the combined CIR. In one example, the gNB applies the profiling concept as means for the parameter estimation of MPC parameter. The gNB is thus able to estimate parameters of all MPCs from all reported CIRs.

For the final reconstruction of the CIRs per reported channel component, the gNB uses additional information indicating which MPCs are associated with each CIR (i.e. an indication of an association between the first channel component and the first parameters and the at least one second channel component and the second parameters). The additional information may be sent semi statically as parallel information. Alternatively, or in addition, the additional information may be provided to the gNB in an initial phase, where each of the channel components is send as individual un-combined CIR from the UE. Due to the combined reporting of multiple channel components with one combined CIR it may be possible to report with a similar number of quantized taps for a single CIR the MPCs for multiple CIRs. For the reporting of two combined CIR the overhead may be roughly halved and in the case of four combined CIR the overhead may be reduced by 25%. Note, these are best case overhead reductions, some extra overhead may be required for robust estimates, e.g., in case two CIRs have almost same MPC delays.

At UE side the processing complexity may be kept low since it may just comprise adding the CTF signals of the multiple channel components, i.e., there is no need for the UE to estimate the MPCs itself.

The higher processing complexity is then at the gNB side by doing an accurate parameter estimation for the combined CIR. For advanced gNBs similar processing might be already available as means to support channel prediction. The above mentioned profiling concept has been proposed as one powerful alternative for super resolution, or parameter estimation, which is a robust solution.

The method may be implemented in a user equipment as described with reference to Figure 2 or a control apparatus as described with reference to figure 3. An apparatus may comprise means for determining, at a user equipment, first channel state information for a first channel component having first parameters and second channel state information for at least one second channel component having second parameters, determining combined channel state information based on the first channel state information and the second channel state information and providing to a network an indication of the combined channel state information.

Alternatively, or in addition, an apparatus may comprise means for receiving, from a user equipment, an indication of combined channel state information, wherein the combined channel state information is based on first channel state information for a first channel component having first parameters and second channel state information for at least one second channel component having second parameters.

It should be understood that the apparatuses may comprise or be coupled to other units or modules etc., such as radio parts or radio heads, used in or for transmission and/or reception. Although the apparatuses have been described as one entity, different modules and memory may be implemented in one or more physical or logical entities. It is noted that whilst embodiments have been described in relation to multi TRP phase II systems, similar principles can be applied in relation to other networks and communication systems where explicit time domain CSI reporting is used. Therefore, although certain embodiments were described above by way of example with reference to certain example architectures for wireless networks, technologies and standards, embodiments may be applied to any other suitable forms of communication systems than those illustrated and described herein.

It is also noted herein that while the above describes example embodiments, there are several variations and modifications which may be made to the disclosed solution without departing from the scope of the present invention.

In general, the various embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects of the invention may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the invention is not limited thereto. While various aspects of the invention may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

The embodiments of this invention may be implemented by computer software executable by a data processor of the mobile device, such as in the processor entity, or by hardware, or by a combination of software and hardware. Computer software or program, also called program product, including software routines, applets and/or macros, may be stored in any apparatus-readable data storage medium and they comprise program instructions to perform particular tasks. A computer program product may comprise one or more computer- executable components which, when the program is run, are configured to carry out embodiments. The one or more computer-executable components may be at least one software code or portions of it.

Further in this regard it should be noted that any blocks of the logic flow as in the Figures may represent program steps, or interconnected logic circuits, blocks and functions, or a combination of program steps and logic circuits, blocks and functions. The software may be stored on such physical media as memory chips, or memory blocks implemented within the processor, magnetic media such as hard disk or floppy disks, and optical media such as for example DVD and the data variants thereof, CD. The physical media is a non-transitory media.

The memory may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The data processors may be of any type suitable to the local technical environment, and may comprise one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASIC), FPGA, gate level circuits and processors based on multi core processor architecture, as non-limiting examples.

Embodiments of the inventions may be practiced in various components such as integrated circuit modules. The design of integrated circuits is by and large a highly automated process. Complex and powerful software tools are available for converting a logic level design into a semiconductor circuit design ready to be etched and formed on a semiconductor substrate.

The foregoing description has provided by way of non-limiting examples a full and informative description of the exemplary embodiment of this invention. However, various modifications and adaptations may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings and the appended claims. However, all such and similar modifications of the teachings of this invention will still fall within the scope of this invention as defined in the appended claims. Indeed, there is a further embodiment comprising a combination of one or more embodiments with any of the other embodiments previously discussed.