WO2021028008A1

WO2021028008A1 - Communication system

Info

Publication number: WO2021028008A1
Application number: PCT/EP2019/071470
Authority: WO
Inventors: Zexian Li; Guillermo POCOVI
Original assignee: Nokia Technologies Oy
Priority date: 2019-08-09
Filing date: 2019-08-09
Publication date: 2021-02-18

Abstract

There is provided an apparatus comprising: means for determining a quality metric of a communication link over which multicast data is received from an apparatus, the multicast data being received using a first transmission scheme; means for selecting one of a first sequence and a second sequence in dependence on the quality metric, the first sequence being associated with more robust transmission schemes than the first modulation scheme and the second sequence being associated with less robust transmission schemes than the first transmission scheme; and means for transmitting the selected one of the first sequence and the second sequence to the apparatus.

Description

Title

COMMUNICATION SYSTEM

Field [0001] The present application relates to a method, apparatus, and computer program.

Background

[0002] A communication system can be seen as a facility that enables communication sessions between two or more entities such as user terminals, base stations/access points 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, 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.

Summary [0003] According to a first aspect, there is provided an apparatus comprising: means for determining a quality metric of a communication link over which multicast data is received from another apparatus, the multicast data being received using a first transmission scheme; means for selecting one of a first sequence and a second sequence in dependence on the quality metric, the first sequence being associated with more robust transmission schemes than the first modulation scheme and the second sequence being associated with less robust transmission schemes than the first transmission scheme; and means for transmitting the selected one of the first sequence and the second sequence to the another apparatus.

[0004] The means for transmitting may comprise means for transmitting the first sequence on a first physical resource and the second sequence on a second physical resource. [0005] The apparatus may further comprise receiving means for receiving from the another apparatus a communication that configures the first and second sequences in the apparatus.

[0006] The apparatus may further comprise receiving means for receiving a request from the another apparatus to provide relative feedback for multicast transmissions. The multicast transmissions may be downlink transmissions when the another apparatus is a network apparatus (e.g. an access point/a gNB). The multicast transmissions may be transmitted as part of device to device transmissions. In this case, the another apparatus may be operating as a master device for those multicast transmissions.

[0007] The first sequence may indicate that the reliability of the received multicast data is greater than a targeted level by a first threshold.

[0008] The second sequence may indicate that the reliability of the received multicast data is less than a targeted level by a second threshold. [0009] The transmission schemes may be modulation and coding schemes.

[0010] According to a second aspect, there is provided an apparatus comprising: means for transmitting multicast data over a communication link to a terminal, the multicast data being transmitted using a first transmission scheme; means for receiving one of a first sequence and a second sequence from the terminal, the first sequence being associated with more robust transmission schemes than the first modulation scheme and the second sequence being associated with less robust transmission schemes than the first transmission scheme; and means for determining whether or not to transmit multicast data to the terminal using a different transmission scheme compared to the first transmission scheme in dependence on the received sequence.

[0011] When first sequence is received, the means for determining may comprise means for determining to transmit multicast data at a more robust transmission scheme than the first transmission scheme, and the apparatus may further comprise means for using said more robust transmission scheme for transmitting the multicast data to the terminal and to any other terminals the multicast data is transmitted to. [0012] When the second sequence is received, the means for determining may comprise: means for transmitting a second transmission scheme to any other terminals the multicast data is transmitted to, the second transmission scheme being less robust than the first transmission scheme; means for determining from a response or lack of response to the transmitting of the second transmission scheme whether or not the any other terminals agrees to use the second transmission scheme for transmission of multicast data; and means for, when said any other terminals agrees, using the second transmission scheme for transmission of multicast data to the terminal and the any other terminals.

[0013] The apparatus may further comprise configuring means for configuring the first and second sequences to the terminal.

[0014] The apparatus may further comprise transmitting means for transmitting a request to the terminal to provide relative feedback for multicast transmissions. The multicast transmissions may be downlink transmissions when the apparatus is a network apparatus (e.g. an access point/a gNB). The multicast transmissions may be transmitted as part of device to device transmissions. In this case, the apparatus may be operating as a master device for those multicast transmissions. [0015] The apparatus may further comprise: determining means for determining that the multicast data is being transmitted to fewer than a predetermined number of terminals; and instructing means for, in response to said determining, transmitting an instruction to said terminal before said multicast transmission to provide feedback on the multicast transmission using one of the first and second sequences. [0016] The apparatus may further comprise: determining means for determining which terminals receiving the multicast data from the apparatus are the likeliest to experience poor channel quality; selecting means for selecting a fraction of the terminals that are the likeliest to experience poor channel quality, wherein the fraction is less than 1 ; and instructing means for transmitting instructions to said selected terminals to provide feedback on the multicast data before receiving one of the first and second sequences from said terminal.

[0017] The apparatus may further comprise transmitting means for transmitting a configuration communication to multiple terminals configured to receive the same multicast data, the configuration communication for configuring the first and second sequences in said multiple terminals.

[0018] The transmission schemes may be modulation and coding schemes.

[0019] According to a third aspect, there is provided a method for an apparatus, the method comprising: determining a quality metric of a communication link over which multicast data is received from another apparatus, the multicast data being received using a first transmission scheme; selecting one of a first sequence and a second sequence in dependence on the quality metric, the first sequence being associated with more robust transmission schemes than the first modulation scheme and the second sequence being associated with less robust transmission schemes than the first transmission scheme; and transmitting the selected one of the first sequence and the second sequence to the another apparatus.

[0020] The transmitting may comprise transmitting the first sequence on a first physical resource and the second sequence on a second physical resource. [0021] The method may further comprise receiving from the another apparatus a communication that configures the first and second sequences in the apparatus. [0022] The apparatus may further comprise receiving a request from the another apparatus to provide relative feedback for multicast transmissions. The multicast transmissions may be downlink transmissions when the another apparatus is a network apparatus (e.g. an access point/a gNB). The multicast transmissions may be transmitted as part of device to device transmissions. In this case, the another apparatus may be operating as a master device for those multicast transmissions. [0023] The first sequence may indicate that the reliability of the received multicast data is greater than a targeted level by a first threshold. [0024] The second sequence may indicate that the reliability of the received multicast data is less than a targeted level by a second threshold.

[0025] The transmission schemes may be modulation and coding schemes.

[0026] According to a fourth aspect, there is provided a method for an apparatus, the method comprising: transmitting multicast data over a communication link to a terminal, the multicast data being transmitted using a first transmission scheme; receiving one of a first sequence and a second sequence from the terminal, the first sequence being associated with more robust transmission schemes than the first modulation scheme and the second sequence being associated with less robust transmission schemes than the first transmission scheme; and determining whether or not to transmit multicast data to the terminal using a different transmission scheme compared to the first transmission scheme in dependence on the received sequence. [0027] When first sequence is received, the determining may comprise determining to transmit multicast data at a more robust transmission scheme than the first transmission scheme, and the method may further comprise using said more robust transmission scheme for transmitting the multicast data to the terminal and to any other terminals the multicast data is transmitted to.

[0028] When the second sequence is received, the determining may comprise: transmitting a second transmission scheme to any other terminals the multicast data is transmitted to, the second transmission scheme being less robust than the first transmission scheme; determining from a response or lack of response to the transmitting of the second transmission scheme whether or not the any other terminals agrees to use the second transmission scheme for transmission of multicast data; and, when said any other terminals agrees, using the second transmission scheme for transmission of multicast data to the terminal and the any other terminals.

[0029] The method may further comprise configuring the first and second sequences to the terminal.

[0030] The method may further comprise transmitting a request to the terminal to provide relative feedback for multicast transmissions. The multicast transmissions may be downlink transmissions when the apparatus performing the method is a network apparatus (e.g. an access point/a gNB). The multicast transmissions may be transmitted as part of device to device transmissions. In this case, the apparatus performing the method may be operating as a master device for those multicast transmissions.

[0031] The method may further comprise: determining that the multicast data is being transmitted to fewer than a predetermined number of terminals; and instructing, in response to said determining, transmitting an instruction to said terminal before said multicast transmission to provide feedback on the multicast transmission using one of the first and second sequences.

[0032] The method may further comprise: determining which terminals receiving the multicast data from the apparatus are the likeliest to experience poor channel quality; selecting a fraction of the terminals that are the likeliest to experience poor channel quality, wherein the fraction is less than 1 ; and instructing the transmittal of instructions to said selected terminals to provide feedback on the multicast data before receiving one of the first and second sequences from said terminal.

[0033] The method may further comprise transmitting a configuration communication to multiple terminals configured to receive the same multicast data, the configuration communication for configuring the first and second sequences in said multiple terminals.

[0034] The transmission schemes may be modulation and coding schemes.

[0035] According to a fifth aspect, there is provided an apparatus comprising at least one processor and at least one memory comprising code that, when run on the at least one processor, causes the apparatus to: determine a quality metric of a communication link over which multicast data is received from another apparatus, the multicast data being received using a first transmission scheme; select one of a first sequence and a second sequence in dependence on the quality metric, the first sequence being associated with more robust transmission schemes than the first modulation scheme and the second sequence being associated with less robust transmission schemes than the first transmission scheme; and transmit the selected one of the first sequence and the second sequence to the another apparatus.

[0036] The transmitting may comprise transmitting the first sequence on a first physical resource and the second sequence on a second physical resource.

[0037] The apparatus may further be caused to receive from the another apparatus a communication that configures the first and second sequences in the apparatus. [0038] The apparatus may further be caused to receive a request from the another apparatus to provide relative feedback for multicast transmissions. The multicast transmissions may be downlink transmissions when the another apparatus is a network apparatus (e.g. an access point/a gNB). The multicast transmissions may be transmitted as part of device to device transmissions. In this case, the another apparatus may be operating as a master device for those multicast transmissions. [0039] The first sequence may indicate that the reliability of the received multicast data is greater than a targeted level by a first threshold.

[0040] The second sequence may indicate that the reliability of the received multicast data is less than a targeted level by a second threshold.

[0041] The transmission schemes may be modulation and coding schemes.

[0042] According to a sixth aspect, there is provided an apparatus comprising at least one processor and at least one memory comprising code that, when run on the at least one processor, causes the apparatus to: transmit multicast data over a communication link to a terminal, the multicast data being transmitted using a first transmission scheme; receive one of a first sequence and a second sequence from the terminal, the first sequence being associated with more robust transmission schemes than the first modulation scheme and the second sequence being associated with less robust transmission schemes than the first transmission scheme; and determine whether or not to transmit multicast data to the terminal using a different transmission scheme compared to the first transmission scheme in dependence on the received sequence. [0043] When first sequence is received, the determining may comprise determining to transmit multicast data at a more robust transmission scheme than the first transmission scheme, and the apparatus may further be caused to use said more robust transmission scheme for transmitting the multicast data to the terminal and to any other terminals the multicast data is transmitted to.

[0044] When the second sequence is received, the determining may comprise: transmitting a second transmission scheme to any other terminals the multicast data is transmitted to, the second transmission scheme being less robust than the first transmission scheme; determining from a response or lack of response to the transmitting of the second transmission scheme whether or not the any other terminals agrees to use the second transmission scheme for transmission of multicast data; and when said any other terminals agrees, using the second transmission scheme for transmission of multicast data to the terminal and the any other terminals.

[0045] The apparatus may further be caused to configure the first and second sequences to the terminal.

[0046] The apparatus may further be caused to transmit a request to the terminal to provide relative feedback for multicast transmissions. The multicast transmissions may be downlink transmissions when the apparatus is a network apparatus (e.g. an access point/a gNB). The multicast transmissions may be transmitted as part of device to device transmissions. In this case, the apparatus may be operating as a master device for those multicast transmissions.

[0047] The apparatus may further be caused to: determine that the multicast data is being transmitted to fewer than a predetermined number of terminals; and instruct, in response to said determining, the transmitting of an instruction to said terminal before said multicast transmission to provide feedback on the multicast transmission using one of the first and second sequences.

[0048] The apparatus may further be caused to: determine which terminals receiving the multicast data from the apparatus are the likeliest to experience poor channel quality; select a fraction of the terminals that are the likeliest to experience poor channel quality, wherein the fraction is less than 1; and instruct the transmitting of instructions to said selected terminals to provide feedback on the multicast data before receiving one of the first and second sequences from said terminal. [0049] The apparatus may further be caused to transmit a configuration communication to multiple terminals configured to receive the same multicast data, the configuration communication for configuring the first and second sequences in said multiple terminals.

[0050] The transmission schemes may be modulation and coding schemes. [0051] According to a seventh aspect, there is provided an apparatus comprising: determining circuitry for determining a quality metric of a communication link over which multicast data is received from another apparatus, the multicast data being received using a first transmission scheme; selecting circuitry for selecting one of a first sequence and a second sequence in dependence on the quality metric, the first sequence being associated with more robust transmission schemes than the first modulation scheme and the second sequence being associated with less robust transmission schemes than the first transmission scheme; and transmitting circuitry for transmitting the selected one of the first sequence and the second sequence to the another apparatus. [0052] The transmitting circuitry may comprise transmitting circuitry for transmitting the first sequence on a first physical resource and the second sequence on a second physical resource.

[0053] The apparatus may further comprise receiving circuitry for receiving from the another apparatus a communication that configures the first and second sequences in the apparatus.

[0054] The apparatus may further comprise receiving circuitry for receiving a request from the another apparatus to provide relative feedback for multicast transmissions. The multicast transmissions may be downlink transmissions when the another apparatus is a network apparatus (e.g. an access point/a gNB). The multicast transmissions may be transmitted as part of device to device transmissions. In this case, the another apparatus may be operating as a master device for those multicast transmissions. [0055] The first sequence may indicate that the reliability of the received multicast data is greater than a targeted level by a first threshold.

[0056] The second sequence may indicate that the reliability of the received multicast data is less than a targeted level by a second threshold. [0057] The transmission schemes may be modulation and coding schemes.

[0058] According to an eighth aspect, there is provided an apparatus comprising: transmitting circuitry for transmitting multicast data over a communication link to a terminal, the multicast data being transmitted using a first transmission scheme; receiving circuitry for receiving one of a first sequence and a second sequence from the terminal, the first sequence being associated with more robust transmission schemes than the first modulation scheme and the second sequence being associated with less robust transmission schemes than the first transmission scheme; and determining circuitry for determining whether or not to transmit multicast data to the terminal using a different transmission scheme compared to the first transmission scheme in dependence on the received sequence.

[0059] When first sequence is received, the determining circuitry may comprise determining circuitry for determining to transmit multicast data at a more robust transmission scheme than the first transmission scheme, and the apparatus may further comprise using circuitry for using said more robust transmission scheme for transmitting the multicast data to the terminal and to any other terminals the multicast data is transmitted to.

[0060] When the second sequence is received, the means for determining may comprise: transmitting circuitry for transmitting a second transmission scheme to any other terminals the multicast data is transmitted to, the second transmission scheme being less robust than the first transmission scheme; determining circuitry for determining from a response or lack of response to the transmitting of the second transmission scheme whether or not the any other terminals agrees to use the second transmission scheme for transmission of multicast data; and using circuitry for, when said any other terminals agrees, using the second transmission scheme for transmission of multicast data to the terminal and the any other terminals.

[0061] The apparatus may further comprise configuring circuitry for configuring the first and second sequences to the terminal. [0062] The apparatus may further comprise transmitting circuitry for transmitting a request to the terminal to provide relative feedback for multicast transmissions. The multicast transmissions may be downlink transmissions when the apparatus is a network apparatus (e.g. an access point/a gNB). The multicast transmissions may be transmitted as part of device to device transmissions. In this case, the apparatus may be operating as a master device for those multicast transmissions.

[0063] The apparatus may further comprise: determining circuitry for determining that the multicast data is being transmitted to fewer than a predetermined number of terminals; and instructing circuitry for, in response to said determining, transmitting an instruction to said terminal before said multicast transmission to provide feedback on the multicast transmission using one of the first and second sequences.

[0064] The apparatus may further comprise: determining circuitry for determining which terminals receiving the multicast data from the apparatus are the likeliest to experience poor channel quality; selecting circuitry for selecting a fraction of the terminals that are the likeliest to experience poor channel quality, wherein the fraction is less than 1; and instructing circuitry for transmitting instructions to said selected terminals to provide feedback on the multicast data before receiving one of the first and second sequences from said terminal.

[0065] The apparatus may further comprise transmitting circuitry for transmitting a configuration communication to multiple terminals configured to receive the same multicast data, the configuration communication for configuring the first and second sequences in said multiple terminals.

[0066] The transmission schemes may be modulation and coding schemes.

[0067] According to a ninth aspect, there is provided a computer program comprising program instructions for causing a computer to perform any method as described above.

[0068] According to a tenth aspect, there is provided a computer program product stored on a medium may cause an apparatus to perform any method as described herein. [0069] According to an eleventh aspect, there is provided an electronic device that may comprise apparatus as described herein.

[0070] According to a twelfth aspect, there is provided a chipset that may comprise an apparatus as described herein. [0071] According to a thirteenth aspect, there is provided non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least the following: determine a quality metric of a communication link over which multicast data is received from another apparatus, the multicast data being received using a first transmission scheme; select one of a first sequence and a second sequence in dependence on the quality metric, the first sequence being associated with more robust transmission schemes than the first modulation scheme and the second sequence being associated with less robust transmission schemes than the first transmission scheme; and transmit the selected one of the first sequence and the second sequence to the another apparatus.

[0072] The transmitting may comprise transmitting the first sequence on a first physical resource and the second sequence on a second physical resource.

[0073] The apparatus may further be caused to receive from the another apparatus a communication that configures the first and second sequences in the apparatus. [0074] The apparatus may further be caused to receive a request from the another apparatus to provide relative feedback for multicast transmissions. The multicast transmissions may be downlink transmissions when the another apparatus is a network apparatus (e.g. an access point/a gNB). The multicast transmissions may be transmitted as part of device to device transmissions. In this case, the another apparatus may be operating as a master device for those multicast transmissions. [0075] The first sequence may indicate that the reliability of the received multicast data is greater than a targeted level by a first threshold.

[0076] The second sequence may indicate that the reliability of the received multicast data is less than a targeted level by a second threshold.

[0077] The transmission schemes may be modulation and coding schemes.

[0078] According to a fourteenth aspect, there is provided non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least the following: transmit multicast data over a communication link to a terminal, the multicast data being transmitted using a first transmission scheme; receive one of a first sequence and a second sequence from the terminal, the first sequence being associated with more robust transmission schemes than the first modulation scheme and the second sequence being associated with less robust transmission schemes than the first transmission scheme; and determine whether or not to transmit multicast data to the terminal using a different transmission scheme compared to the first transmission scheme in dependence on the received sequence.

[0079] When first sequence is received, the determining may comprise determining to transmit multicast data at a more robust transmission scheme than the first transmission scheme, and the apparatus may further be caused to use said more robust transmission scheme for transmitting the multicast data to the terminal and to any other terminals the multicast data is transmitted to.

[0080] When the second sequence is received, the determining may comprise: transmitting a second transmission scheme to any other terminals the multicast data is transmitted to, the second transmission scheme being less robust than the first transmission scheme; determining from a response or lack of response to the transmitting of the second transmission scheme whether or not the any other terminals agrees to use the second transmission scheme for transmission of multicast data; and when said any other terminals agrees, using the second transmission scheme for transmission of multicast data to the terminal and the any other terminals.

[0081] The apparatus may further be caused to configure the first and second sequences to the terminal.

[0082] The apparatus may further be caused to transmit a request to the terminal to provide relative feedback for multicast transmissions. The multicast transmissions may be downlink transmissions when the apparatus is a network apparatus (e.g. an access point/a gNB). The multicast transmissions may be transmitted as part of device to device transmissions. In this case, the apparatus may be operating as a master device for those multicast transmissions. The apparatus may further be caused to: determine that the multicast data is being transmitted to fewer than a predetermined number of terminals; and instruct, in response to said determining, the transmitting of an instruction to said terminal before said multicast transmission to provide feedback on the multicast transmission using one of the first and second sequences.

[0083] The apparatus may further be caused to: determine which terminals receiving the multicast data from the apparatus are the likeliest to experience poor channel quality; select a fraction of the terminals that are the likeliest to experience poor channel quality, wherein the fraction is less than 1; and instruct the transmitting of instructions to said selected terminals to provide feedback on the multicast data before receiving one of the first and second sequences from said terminal. [0084] The apparatus may further be caused to transmit a configuration communication to multiple terminals configured to receive the same multicast data, the configuration communication for configuring the first and second sequences in said multiple terminals. [0085] The transmission schemes may be modulation and coding schemes.

Description of Figures

[0086] Examples will now be described, by way of example only, with reference to the accompanying Figures in which: [0087] Figure 1 shows a schematic diagram of an example communication system comprising a plurality of base stations and a plurality of communication devices; [0088] Figure 2 shows a schematic diagram of an example mobile communication device;

[0089] Figure 3 shows a schematic diagram of an example network element; [0090] Figure 4 is a flow chart illustrating potential operations of a terminal;

[0091] Figure 5 is a flow chart illustrating potential operations of an apparatus;

[0092] Figure 6 is a schematic diagram of how feedback resources may be allocated; and

[0093] Figure 7 is a flowchart of potential operations of a terminal.

Detailed description

[0094] In general, the following disclosure relates to how to support multicast link adaption and focuses on efficient feedback mechanisms, such as channel state information (CSI) feedback mechanisms. [0095] In particular, a system is described in which a terminal determines whether or not a currently used transmission scheme for received multicast data provides an acceptable reliability/quality of service to the terminal. Depending on whether or not the currently used scheme is acceptable, and potentially a degree to which the currently used scheme is acceptable, the terminal selects between two sequences for indicating to an apparatus (such as an access point, and/or a device provide device- to-device transmissions) whether or not the transmission scheme needs to become more robust or may become less robust. This results in a system in which a terminal relatively indicates whether or not received communications has a reliability/quality of service that is above or below a target. The apparatus may use this provided relative information to adapt the transmission scheme used for the later transmission of multicast data.

[0096] By providing multicast feedback in relative terms, the communication system is able to use a wider variety of resource types to provide feedback information and can reduce overhead in the communication system for providing this feedback (as detailed further below). Further, the apparatus may configure only a subset of multicast users in a multicast group located within a cell to provide feedback on the quality of the received multicast data. In other words, not all of the multicast users within a multicast group located within a cell provide said feedback. This further reduces the overhead of the system. The subset may be selected based on certain criteria for example geographical locations of the UEs.

[0097] 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 2 to assist in understanding the technology underlying the described examples.

[0098] In a wireless communication system 100, such as that shown in figure 1 , mobile communication devices, user apparatus, or terminal 102, 104, 105 are provided wireless access via at least one base station or similar wireless transmitting and/or receiving node or point. A user can access the communication system by means of an appropriate communication device or terminal. A communication device of a user is often referred to as user equipment (UE) or as a user apparatus. Throughout the following, these terms will be used interchangeably. It is understood that the term “terminal” is used to cover communication devices that may access a network through an access point, and which may or may not have a user. Examples of such terminals without a user include devices that make machine-to-machine transmissions in a factory. 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 or access point, and transmit and/or receive communications on the carrier.

[0099] 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). An example of attempts to solve the problems associated with the increased demands for capacity is an architecture that is known as the long-term evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio access technology. The LTE standard is developed by the 3rd Generation Partnership Project (3GPP). LTE was first released in 2008 (known as LTE Release 8), and new enhancements (in form of releases) has been introduced since then. LTE Release 13 and onwards is also known as LTE Advanced Pro.

[00100] A base station is referred to as an eNodeB (eNB) in LTE, and may be referred to more generally as simply a network apparatus or a network access 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 apparatus. 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. In some systems, the control apparatus may additionally or alternatively be provided in a radio network controller. [00101] LTE systems may however be considered to have a so-called “flat” architecture, without the provision of RNCs; rather the (e)NB is in communication with a system architecture evolution gateway (SAE-GW) and a mobility management entity (MME), which entities may also be pooled meaning that a plurality of these nodes may serve a plurality (set) of (e)NBs. Each user apparatus is served by only one MME and/or S-GW at a time and the (e)NB keeps track of current association. SAE-GW is a “high-level” user plane core network element in LTE, which may comprise the S-GW and the P-GW (serving gateway and packet data network gateway, respectively). The functionalities of the S-GW and P-GW are separated and they are not required to be co-located. [00102] In an LTE system, radio resource control (RRC) is defined to be a sublayer of radio interface Layer 3 that exists in the control plane only, and which provides information transfer service to the non-access stratum (see 3GPP Technical Specification Group Services and System Aspects 21.905). RRC is a protocol layer between a user apparatus and an eNB, and is in charge of, for example, paging the user apparatus when traffic comes, establishing/maintaining or release of radio bearers (establishing an RRC connection between user apparatus and eNB), user apparatus mobility, user apparatus measurement configuration and user apparatus reporting configuration, etc. RRC is responsible for controlling the configuration of radio interface Layers 1 and 2.

[00103] In Figure 1 base stations 106 and 107 are shown as connected to a wider communications network 113 via gateway 112. A further gateway function may be provided to connect to another network.

[00104] The smaller base stations 116, 118 and 120 may also be connected to the network 113, for example by a separate gateway function and/or via the controllers of the macro level stations. The base stations 116, 118 and 120 may be pico orfemto level base stations or the like. In the example, base stations 116 and 118 are connected via a gateway 111 whilst station 120 connects via the controller apparatus 108. In some examples, the smaller stations may not be provided. [00105] 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 apparatus (terminal) 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. [00106] 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.

[00107] 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 communication devices 102, 104, 105 may access the communication system based on various access techniques.

[00108] 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 LTE Advanced Pro of the Universal Mobile Telecommunications System (UMTS) radio-access technology, or the 5th Generation (5G) New Radio (NR). 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.

[00109] An example network equipment for the 3GPP system is shown in Figure 3. Figure 3 shows an example of a control apparatus 300 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 or (g) node B, or a node of a core network such as an MME or Access and Mobility Management Function (AMF). 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 examples, base stations comprise a separate control apparatus unit or module. In other examples, the control apparatus can be another network element such as a radio network controller or a spectrum controller. In some examples, 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. For example the control apparatus 300 can be configured to execute an appropriate software code to provide the control functions. Control apparatus 300 may be included in a chipset or modem apparatus. A chipset or modem apparatus which includes apparatus 300 may be included in a control node such as an eNB. [00110] 5G NR is designed to accommodate a wide range of services on top of the traditional mobile broadband (MBB) communication. For example, ultra-reliable low-latency communications (URLLC) is one of the three main usage scenarios and is envisioned as enabling emerging new applications, for examplefrom industrial automations, autonomous driving, electric-power distribution to Programme Making and Special Events, and so on.

[00111] URLLC relates to minimising a delay for a communication device to successfully receive a communication from another device (i.e. reduce the latency of the communications and/or improve the reliability of the communications). [00112] For reliability, an operating communication protocol defines some level of how accurately and consistently communications are conducted. This may cover operations at both the transmitter (in preparing a communication for transmission and transmitting the communication) and at the receiver (in receiving the communication and in extracting data from the communication).

[00113] For latency, an operating communication protocol defines some level of delay for communicating data. For example, communications may be expected to be delivered within 0.5ms (it is understood that other values for a delay are possible, e.g. 1 ms, depending on the purpose behind the communications and any operating communication protocol). Longer delays than this defined level are considered to be unacceptable. When the delay is considered to be unacceptable or when it is predicted that the required delay is likely to exceed the defined level, the communication system may employ various techniques to act to reduce the delay or otherwise keep the delay below the defined level. Shorter delays than this defined level are considered to be acceptable. When the delay is considered to be acceptable, the communication system does not have to act to reduce the delay further, although it may choose to do so based on other factors.

[00114] Up to now, the 5G new radio (NR) Rel-15 and Rel-16 has introduced new features to provide URLLC for unicast data transmissions (current proposals are for a reliability corresponding to a block error rate (BLER) of 10^L(-5) or 10^L(-6) and up to 0.5 ms User-Plane latency, although this may be developed further in the future release). However, as discussed in TR 22.804 and also from current proposals for Rel-17 (e.g. TR 22.826), it may also be useful to define cases in which URLLC is provided for multicast transmissions, particularly for new application domains, e.g. industrial automation and remote driving, which are often referred to as vertical use cases or applications. One current use case in which such techniques would be useful would be Ethernet multicast, which is currently one widely used in the industry automation system. Another example use case is electric-power distribution, where the 5G system may support peer-to-peer layer-2 multicast message communication (such as the I EC 61850 Generic Object Oriented Substation Event protocol), with an end-to-end latency of less than 5 ms. More recently, multicast URLLC support is included in the Rel-17 studies including communication services for critical medical applications, audio-visual service production and other communication types. [00115] Multimedia Broadcast Multicast Services (MBMS) is a point to multipoint specification covering radio and upper layer protocol for 3GPP cellular networks. It has been defined in an evolving way in various 3GPP communication protocols, such as UMTS and LTE. MBMS defines both a multicast broadcast single frequency network (MBSFN) and single cell point-to-multipoint (SC-PTM) for LTE for supporting media delivery, vehicle to anything (V2X) communications, video broadcast, event venue experience, public/emergency safety services, etc. With SC-PTM, the overall concept is that one eNB can transmit the same data (identical data) to multiple terminals simultaneously. In some case, multiple eNBs can transmit the identical data simultaneously so that terminals can receive the same data from multiple eNBs, e.g. to support broadcast services over large geographical areas which can be referred as multi-cell point-to-multipoint (MC-PTM).

[00116] One important area for (reliable) multicast is related to uplink feedback, such as channel quality indication (CQI) reports for link adaptation and Hybrid Automatic Request (HARQ) Acknowledgement/Negative Acknowledgement (ACK/NACK) for retransmissions.

[00117] Reliable link adaptation in multicast may be conducted by adjusting a transmission scheme, such as a modulation and coding scheme (MCS), based on the worst CQI among those reported to the gNB (a 5G access point). For a large group of multicast users, the benefits of fast CQI feedback (and dynamic link adaptation, in general) are thus relatively small as there is quite a high probability that at least one terminal requires a low/relatively robust transmission scheme. However, some of the envisioned Rel-17 multicast use cases are directed towards multicast communications towards a relatively small group of users, e.g. 5-20 terminals. In such use cases, there may therefore be larger gains when dynamically adapting the link, in particular, when dynamically adapting the transmission scheme used on a link.

[00118] Currently, reporting feedback such as CQI feedback results in significantly high uplink control overhead, which may potentially result in insufficient uplink control resources for collecting CQI feedback from all of the terminals. That is one reason why, up to now, a majority of the existing multicast systems, e.g. eMBMS, run on a relative static link adaptation mode or a slow link adaption.

[00119] The following therefore relates to a problem of how to efficiently report feedback (such as CQI feedback) from multiple terminals to the gNB to enable link adaption for multicast transmission. Link adaptation in this case may have a target of achieving an optimal balance between spectral efficiency and a quality of service specified by a communication protocol. For the purpose of example only, the following mainly focuses on single cell point-to-multipoint transmissions, such as is discussed in the NR standard. However, it is understood that similar principles may be also applied to other multicast techniques, such as MC-PTM, or other wireless technologies, such as LTE.

[00120] In NR’s framework for reporting CQI feedback, the CQI is included in the Channel State Information (CSI) feedback to the gNB, together with a preferred precoding matrix indicator (PMI), rank indicator (Rl) and other terminal reports. The CQI feedback may be provided in the form of an index to a pre-configured transmission scheme table that both the network and the user equipment have access to. The CQI feedback indicates a maximum transmission scheme that the terminal can support without exceeding a certain block-error-rate constraint. A block error rate is a ratio of a number of erroneous blocks received to a total number of blocks transmitted. For NR, the block error rate target is either 10¹ or 10⁵, and may be implicitly derived from the higher-layer configured CQI table. Each table has 16 modulation and coding scheme entries, which the gNB may reference using an index. In other words, 4 bits of feedback are used under current NR specifications, which can be carried over the Physical Uplink Control Channel (PUCCH) or the Physical Uplink Shared Channel (PUSCH) depending on the final configuration and the availability of the resource. A terminal can be configured to report feedback on a periodic, semi-periodic or aperiodic manner. For the last two cases, the report may be triggered via a downlink control indicator (DCI) and/or via a media access control element (MAC CE). [00121] NR defines certain formats for resources on different channels. Given that 4 bits of feedback are used under current NR specifications, this means that CQI reporting on the PUCCH is restricted to only using PUCCH resource formats 2, 3 and 4, as these are the only formats that support more than 2 bits of feedback information. These PUCCH resources are configured by higher-layers of the gNB. PUCCH formats 3 and 4 are long in the time domain (4 to 14 OFDM symbols), whereas format 2 is short (1 or 2 symbols) but generally larger in the frequency domain to ensure the required capacity. Multiplexing multiple users on same time/frequency resources is supported on for example PUCCH format 4. Based on this, providing periodic CQI feedback (e.g. every 10 ms) from multiple terminals would require a significant amount of resources and would be restricted to certain resource formats (under current specifications).

[00122] At a higher level, the feedback channels can be classified as a dedicated feedback channel and a shared feedback channel. Both have their pros and cons from a resource usage and reliability point of view. For the following, the use of a shared feedback channel (i.e. shared time/frequency resource) for channel quality feedback reducing signalling overhead is assumed. It is, however, understood that the presently described techniques may also be applied to scenarios in which the feedback channel is a dedicated feedback channel.

[00123] For multicast transmission, there are several ways of how to more efficiently design the feedback for multicast transmission. For example, a timer-based feedback mechanism has been proposed in multicast communication for reducing the feedback overhead. Another proposal is for a terminal to transition to a certain state according to one of its own quality of service parameters, such as a frame error rate. In each state, a terminal decides to send either CQI feedback, or flag state indicator, or a joining request message. If a terminal determines that it satisfies an operating quality of service requirement, it will not send CQI feedback. This mechanism can be used to reduce feedback overhead.

[00124] As another example, a threshold-based feedback design may be used. As one example, in terms of a channel quality indicator (CQI), a base station broadcasting a channel quality threshold range to the mobile stations may use a channel quality threshold range to control the feedback of channel quality information. For example, the mobile stations determine their own mobile station-specific CQI and then generate CQI feedback information in response to a comparison between their own mobile station-specific CQI and the CQI threshold range.

[00125] The following proposes a different system to those discussed above. In particular, there is described a system in which a terminal determines whether or not a currently used transmission scheme provides an acceptable latency/quality of service to the terminal. Depending on whether or not the currently used scheme is acceptable, and potentially a degree to which the currently used scheme is acceptable, the terminal selects between two sequences for indicating to an access point whether or not a transmission scheme needs to become more robust or less robust. This results in a system in which a terminal indicates in a relative way whether or not received communications achieves a reliability/latency/quality of service that is above or below a target. For clarity and brevity, the following will primarily refer to reliability when discussing examples of how a quality metric may be used. However, it is understood that other quality metrics, such as latency, may be used instead.

[00126] Potential operations of a terminal operating in accordance with such a scheme is described in relation to Figure 4, which depicts a flowchart of operations by a terminal.

[00127] At 401 , the terminal determines a quality metric of a communication link over which multicast data is received from an apparatus, the multicast data being received using a first transmission scheme. The apparatus may be a network apparatus such as a gNB/an access point to the network. In this case, the communication link may be a downlink communication link. The apparatus may be another terminal. In this case, the communication link may be a device-to-device link between the two terminals. The quality metric may represent a reliability of the received multicast data. The quality metric may be determined irrespective of any data being transmitted over the communication link. The quality metric may represent a block error rate. The apparatus may be an access point to the network, such as a gNB in 5G. The quality metric may be made with reference to at least one threshold. For example, the quality metric may indicate that a determined reliability is more than a targeted reliability by a first amount. The quality metric may indicate that a reliability is less than a targeted reliability by a second amount. The first and second amounts may be the same. The first and second amounts may be different. The first and second amounts may be transmitted to the terminal by the apparatus. The first and second amounts may be preconfigured in the terminal according to an operating communication protocol.

[00128] At 402, the terminal selects one of a first sequence and a second sequence in dependence on the quality metric, the first sequence being associated with more robust transmission schemes than the first transmission scheme and the second sequence being associated with less robust transmission schemes than the first transmission scheme. The first and second sequences may have been previously configured to the terminal and stored by the terminal (i.e. prior to the determination of the quality metric being made at 401 ). [00129] The first and second sequences may be configured in the terminal following a communication from the apparatus to effect this. This may be achieved in a number of different ways. For example, the configuration may be achieved if the first and second sequences are received by the terminal from the apparatus. For example, the sequences may be received during a connection set up between the apparatus and the terminal. As another example the sequences may be received during multicast connection set up between the apparatus and the terminal. As another example, the method to generate the first and second sequences are specified in e.g. 3GPP specification and they will be used once the multicast service is activated. It is understood that the first and second sequences may be provided to the terminal via other mechanisms, and not necessarily through the apparatus. For example, they may be defined by an operating communication protocol, they may be pre-stored in the terminal during initial programming of the terminal. In such cases, the configuration communication may simply instruct a terminal to use the sequences. The configuration communication may indicate which sequences to use. For example, the configuration communication may provide an index by which at least one of the sequences is selected. It is understood that other mechanisms for configuring the terminal with the first and second sequences are possible.

[00130] At 403, the terminal transmits the selected one of the first sequence and the second sequence to the apparatus.

[00131] The terminal may be configured to transmit the first sequence on a first physical resource and to transmit the second sequence on a second physical resource. In other words, the terminal may be configured to transmit the first sequence on a different physical resource to the physical resource that the terminal is configured to transmit the second sequence on.

[00132] Other terminals in the multicast group may also be performing the steps of Figure 4. The other terminals may be performing these steps independently of each other. The other terminals may be configured with the same set of resources to transmit their corresponding sequences. Assuming that only multicast users are configured to use such resources, the apparatus may apply simple sequence- detection or power-detection techniques on those physical resources to determine if a transmission has been made on one of them or both. This may help to reduce the time taken to react to such relative feedback on the quality metric as compared to decoding a data payload. As the sequences are known in advance, the apparatus’ decoding procedure can be limited to just detecting whether a sequence is present on such resource (or if more than 1 sequence is present on a resource if multiple users are configured to use the same resource). This is faster and more reliable than transmitting a proper data payload, such as with CQI index as done for some LTE/5G systems. How the apparatus responds to such sequences will be discussed in more detail in relation to Figure 5.

[00133] The terminal may be further configured to receive a request from the apparatus to provide relative feedback for multicast downlink transmissions. In response to this request, the terminal may perform the above-described steps of Figure 4. However, it is understood that the steps of Figure 4 may be performed without the receipt of a request for this relative feedback from the access point. [00134] Figure 5 is a flow chart depicting potential operations of an apparatus, such as the apparatus interacting with the terminal of Figure 4. As per the above, the apparatus may be a network apparatus, such as a gNB/access point to a network. The communication link being considered may be a downlink communication link. The apparatus may be another terminal. In this case, the communication being considered may be a device-to-device link between two terminals.

[00135] At 501 , the apparatus transmits multicast data over a communication link to a terminal, the multicast data being transmitted using a first transmission scheme. The multicast data may be multicast data in that it relates to a multicast transmission. For example, the multicast data may be sent to terminals in a multicast group via a broadcast transmission. The multicast data may be sent to terminals via a multicast transmission. The multicast data may be sent to terminals via unicast transmissions. For all of these cases, the multicast data may comprise an indication of an initial transmission scheme to be used for multicast transmissions. The initial transmission scheme may be the first transmission scheme. As another example, the multicast data may be multicast to terminals in a multicast group.

[00136] At 502, the apparatus receives, in response to the transmitted multicast data, one of a first sequence and a second sequence is received from the terminal, the first sequence being associated with more robust transmission schemes than the first transmission scheme and the second sequence being associated with less robust transmission schemes than the first transmission scheme. Whether or not the first or second sequence is received may depend on a quality metric as determined by the terminal. This may be performed as described above with reference to Figure 4. [00137] At 503, the apparatus determines whether or not to transmit multicast data to the terminal using a different transmission scheme to the first transmission scheme in dependence on the received sequence. If a determination is made to use a different transmission scheme, multicast data is transmitted using the different transmission scheme. If a determination is made to not use a different transmission scheme, the apparatus continues to use the first transmission scheme.

[00138] It is understood that the apparatus may be transmitting the multicast data to multiple terminals that are in a multicast group, at least some of which may be performing similar actions to that described above in reference to Figure 4. Consequently, a sequence received at 502 from a single terminal may change the transmission scheme applied to all of the terminals in the multicast group. When both sequences are received (i.e. from separate terminals in the multicast group), the apparatus may prioritise changing the transmission scheme for multicast transmissions to a more robust transmission scheme. This helps to achieve a minimum reliability of multicast transmission for all of the terminals in the group. [00139] For example, when the first sequence is received, the apparatus may determine to transmit multicast data with a more robust transmission scheme than the first transmission scheme, and so may consequently transmit multicast data to all of the multicast group using said more robust transmission scheme. Transmitting data using a more robust transmission scheme increases the reliability of data reception. [00140] As an example, when the second sequence is received, the apparatus may determine to transmit multicast data using a second transmission scheme to all terminals receiving the multicast data. The second transmission scheme may be less robust than the first transmission scheme.

[00141] As an extension to this, the apparatus may be configured to transmit an indication of the second transmission scheme to the terminals receiving the multicast data. This indication may be transmitted using control signalling. The apparatus may determine from a response or lack of response to the transmitting of the indication whether or not the terminals agree to use the second transmission scheme for transmission of multicast data. For example, a terminal may be configured to respond to the transmitting of the indication when the terminal disagrees with the use of the second transmission scheme. The terminal may signal an agreement to use the second transmission scheme by abstaining from transmitting a response to the transmitting of the indication. As another example, that the terminal may signal an agreement to use the second transmission scheme by transmitting a response to the transmitting of the indication, and/or that terminal may signal a disagreement to use the second transmission scheme by abstaining from transmitting a response to the transmitting of the indication. As another example, the terminal may be configured to signal disagreement and agreement to use the second transmission scheme by transmitting a response to the transmitting of the indication, with the form of the response being indicative of whether an agreement or a disagreement is being signalled.

[00142] When all of said terminals agree to use the second transmission scheme for transmission of multicast data, the apparatus may use the second transmission scheme for transmission of multicast data to terminals in the multicast group (i.e. those terminals configured to receive the multicast data). The apparatus may use the second transmission scheme for transmission of multicast data to terminals in the multicast group.

[00143] When at least one terminal in the multicast group disagrees to use the second transmission scheme for transmission of multicast data, the apparatus may use the first transmission scheme for transmission of multicast data to terminals in the multicast group.

[00144] The above-described steps of Figures 4 and 5 may also apply in respect of initially configuring the multicast transmission. For example, before any multicast transmission is made at all, the network may be configured to select an initial transmission scheme for multicast transmission. This may be performed in dependence on feedback received from at least one of the terminals intended to form part of the multicast group (and potentially received from all of the terminals intended to form the multicast group). In this case, the apparatus may send the information indicating a proposed transmission scheme to terminals in the same multicast group. The information may be transmitted using the proposed transmission scheme. Terminals receiving the information may send their relative feedback as per the examples described herein, with the apparatus reacting to the received relative feedback as per the examples described herein. [00145] As per the example described above with respect to Figure 4, the apparatus may be configured to cause the first and second sequences to be configured to the terminal prior to performing steps 501 to 503. The apparatus may configure the first and second sequences to multiple terminals that are configured to receive the same multicast data. In other words, multiple terminals in the same multicast group may use the same sequences to indicate whether they would like the transmission scheme used for multicast transmission to be made more or less robust. As per the above discussion with respect to Figure 4, the configuration may be achieved by the apparatus transmitting a configuration communication prior to the steps of Figure 5 being performed. The configuration communication may be broadcast. The configuration communication may be multicast to the multicast group (i.e. a group of terminals configured to receive the multicast data). The configuration communication may be unicast. The configuration communication may simply instruct a terminal to use the sequences. The configuration communication may indicate which sequences to use. For example, the configuration communication may provide an index by which at least one of the sequences is selected. It is understood that other mechanisms for configuring the terminal with the first and second sequences are possible.

[00146] Also as per the example described above with respect to Figure 4, the apparatus may transmit a request to the terminal to provide relative feedback for multicast downlink transmissions. This request may be made before, during or subsequent to the multicast transmissions referred to in 501. Flowever, prior to the multicast transmission referred to in 501 is the most advantageous as it enables the apparatus to determine the appropriate transmission parameters before the actual multicast data transmission. The quality metric may represent a reliability of the received multicast data. The quality metric may represent a block error rate. The quality metric may be based on the outcome or information obtained during the decoding process. The quality metric may also be the actual outcome of the decoding process. [00147] The apparatus may further determine that the multicast data is being transmitted to fewer than a predetermined number of terminals. In response to this determining, the apparatus may transmit an instruction to said terminal to provide feedback on the multicast data before the step of 501. This step is useful as the feedback may then only be configured for relatively small numbers of terminals/user equipments, where the efficiency savings of the presently described system may be bigger. The predetermined number of terminals may be defined by a system designer, a network operator, a service provider, etc. The predetermined number of terminals may be dependent on the size of the cell being provided by the apparatus.

[00148] The apparatus may be configured to determine which terminals receiving the multicast data from the apparatus are the likeliest to experience interference or poor link quality in general. This may be performed in any number of ways. For example, the apparatus may consider those multicast members/terminals closest to the apparatus as being the least likely to experience poor channel quality. The apparatus may consider those multicast members/terminals furthest away/near a cell edge to be the most likely to experience poor channel quality. The apparatus may select a fraction of the terminals that are the likeliest to experience poor channel quality, wherein the fraction is less than 1. The value of the fraction may be set in any number of ways, including size of cell, deployment scenario, etc. The apparatus may transmit instructions to said selected terminals to provide feedback on the multicast data before receiving one of the first and second sequences from said terminal(s). [00149] In the following, a more specific example of the above-described mechanism is described in which the apparatus of Figure 5 is a network apparatus. It is understood that the principles illustrated through this example are not limited to network apparatuses, and may be applied to terminals operating device-to-device communications.

[00150] In the following example, a network apparatus such as a gNB may flexibly control whether channel quality indicator (CQI) feedback for multicast is enabled or not depending on the deployment scenario. For example, the CQI feedback may be enabled and disable based on the number of members (e.g. user equipments/terminals) within the multicast group, the cell size of the gNB, and so on. This is useful as when there are a large number of members in a multicast group and/or when the cell size of the gNB is relatively large, it is likely that a very robust transmission scheme will be used for transmission to all of the members in the group. In such a case, the provision of CQI feedback from members has limited benefit, as there is less scope for adapting the transmission scheme to changing conditions (i.e. it is likely that at least one of the members will still require the more robust modulation and scheme).

[00151] The gNB may pre-configure members to enable and disable feedback of multicast data using radio resource control (RRC) signalling. [00152] The gNB may pre-configure members to enable and disable feedback of multicast data using a downlink control channel. For example, when multicast data is provided to members on a physical downlink shared channel (PDSCH), a physical downlink control channel (PDCCH) may be used to configure members of the multicast group for enabling/disabling feedback. The PDCCH may be common to the group of members. The PDCCH may be dedicated for a specific user equipment in the group of members. Combinations of these types of PDCCH may be used, depending on the particular deployment scenario being considered. Instead of using a PDCCH for configuring members of the multicast group, a physical broadcast channel (PBCH) may be used. The pre-configuring may be performed by broadcasting, multicasting and/or unicasting the transmission scheme information to be used before sending the coming multicast data packet transmission. The pre-configuring may be performed periodically. The pre-configuring may be performed aperiodically.

[00153] In both of these ways of pre-configuring multicast group members, the decision on whether or not CQI feedback is to be reported can be made per individual terminal, multiple terminals, or all terminals in the multicast group. In other words, the gNB may configure only a subset of a group of user equipments receiving multicast data with an instruction to report back on the quality of the received multicast data. The subset is a fraction of the total number in the multicast group. The fraction may have a value between 0 and 1. The fraction being less than one may be advantageous in reducing the amount of feedback being provided (and hence the overhead in receiving feedback).

[00154] For example, the gNB may be configured to disable feedback for those terminals who are determined to be likely to be experiencing a much higher signal to poor channel quality and noise ratio (SINR) than other terminals in the multicast group (e.g. to disable feedback from those terminals that are closer to the centre of the cell while enabling feedback from those terminals closer to the edge of the cell). In other words, the gNB may configure only those members that are likely to be experiencing the largest amount of poor channel quality and/or fading with an instruction to provide feedback on the quality of the received multicast data (i.e. the above-mentioned fraction is less than 1). Depending on the specific applications, the number of active group members may be fixed (which may be useful, for example, in a factory environment), or dynamically changed. A gNB may thus be configured to enable/disable multicast feedback in a more flexible way.

[00155] The terminals that are configured to provide CQI feedback may be configured to make quality-related measurements on received multicast data and to only transmit feedback in relation to these measurements if the difference between the applied CQI for multicast transmission and the terminal’s desired CQI is within a certain threshold.

[00156] In the present example, the gNB informs all multicast group member terminals about the transmission scheme information that will be applied to the coming multicast data packet. Such transmission scheme information may also provide a reference for the terminal with respect to the value of the CQI feedback (e.g. a threshold above which CQI feedback should be provided by the terminal). Transmission scheme information may be based on a specified transmission scheme table for unicast transmission or on a dedicated transmission scheme table for multicast transmission. The gNB may inform the multicast group member terminals about the transmission scheme by providing an index to a transmission scheme table, such as to a transmission scheme table used for unicast transmissions. The gNB may broadcast further instructions and/or requests to the terminals to report an absolute CQI value, and to report a relative CQI value, as described above and below with reference to use of different sequences.

[00157] The initial transmission scheme applied may be based on the feedback information from all group member terminals, or estimated based on the deployment, number of terminals, and so on.

[00158] As discussed above, there is a large overhead associated with multiple terminals providing absolute values of CQI feedback. This is particularly a problem on the physical uplink control channel (PUCCH). Consequently, the present application proposes the use of a relative CQI report.

[00159] To effect this, the gNB may be configured to schedule specific resources for reporting two cases, namely that a more robust transmission scheme should be used and that a less robust transmission scheme should be used. [00160] As described above, two separate physical sequences may be allocated for this purpose. A first sequence (“aggressive sequence”), for example S1, may be used to indicate a more robust MCS level may be used. A second, different sequence (“conservative sequence”), for example S2, may be used to indicate a less robust transmission scheme may be used. How to design the sequence is unimportant for present purposes and so will not be considered in detail. However, it is understood that similar sequences to those used in HARQ-ACK feedback design, sounding reference signals and demodulation reference signals may be extended for this purpose. The two sequences described above represent any mechanism that are usable to (and are used to) differentiate these two cases (i.e. to differentiate between a request for a more robust transmission scheme and a request for a less robust transmission scheme). For example, the sequences may be respective additional bits in a regular HARQ-ACK feedback design. The new added bits may be used to indicate the desired transmission scheme level for multicast data transmission. [00161] For example, the information about how to adjust the transmission scheme may be included in a multi-bit HARQ-ACK feedback. For example, if two extra bits were added to the current HARQ-ACK feedback format, then these may indicate the following relative feedback (although it is understood that this example is not limiting): 00: keep the same transmission scheme

11 : more robust transmission scheme 01 : less robust transmission scheme 10: reserved

[00162] The two different sequences may also be mapped to two different sets of time-frequency resources.

[00163] A way of potentially providing feedback as described above is illustrated with respect to Figure 6.

[00164] Figure 6 shows time-frequency resources, with time along the x-axis and frequency along the y-axis. In this particular example, the same frequency resource has been provided for S1 and S2, but a different time resource has been provided for S1 compared to S2. Therefore, by monitoring the same frequency resource over time, the gNB will be able to determine which sequence was transmitted. The sequences are shown in Figure 6 as being transmitted and their resource is indicated by a downlink control information (DCI) transmission. It is understood that this example is not limiting, as S1 and S2 may be assigned to different frequency resources to each other but the same time resource. S1 and S2 may be assigned to different frequency resources to each other and to different time resources to each other. It is also possible that the same physical resource is used in case the orthogonality between S1 and S2 is good enough. Further, the resource may be indicated other than by a DCI transmission, for example by pre-configured by dedicated RRC configuration or broadcasted to multiple terminals.

[00165] It is thus the case that multiple terminals in the same multicast group may be configured with the same set of sequences (i.e. with S1 and S2) and the same mapping, and the gNB may then apply simple sequence-detection techniques on those resources indicated by the mapping.

[00166] When a gNB detects a signal on one of those resources, the gNB will be able to determine whether there is terminal requesting to change the transmission scheme for the coming multicast transmission or not, and in what direction.

[00167] Faced with this received information, the gNB may select a transmission scheme for future multicast transmissions as follows.

[00168] When a conservative sequence (S2) is received, the gNB may apply a more robust MCS right away for the coming multicast packet to increase the possibility for successful reception. Based at least on the reliability and latency requirements of the multicast service being provided by the multicast transmissions, the gNB may select a new transmission scheme level. For example, in case the transmission scheme level for transmitting the multicast data was originally 16-Quadrature amplitude modulation (QAM) with a coding rate of 1/3, when the reliability/latency requirement is not so strict, the new transmission scheme level may be 16-QAM with a coding rate of 2/3. On the other hand, when the reliability/latency requirement is strict and 16-QAM with coding rate 1/3 is not sufficient to meet the requirement, the new transmission scheme level may be quadrature phase shift keying (QPSK) with a coding rate of 1/3. [00169] When an aggressive sequence (S1 ) is received, the gNB may apply the new MCS level right away, or apply a bit later for example first broadcast the intended MCS level to other members of the multicast group. In this latter case, the gNB may wait for the confirmation from all group members before applying a less robust transmission scheme than the one applied to the previously transmitted multicast data. [00170] Figure 7 is a flow chart illustrating potential operations of a terminal in accordance with this system. [00171] At 701, the terminal receives a configuration for providing multicast channel state information feedback. This may be as described above.

[00172] At 702, the terminal receives multicast information using a first transmission scheme.

[00173] At 703, the terminal compares the transmission scheme selected by the gNB for transmission of the multicast information with a transmission scheme level needed for correct reception of the multicast data at the terminal, and determines a suitable feedback sequence, as described above.

[00174] At 704, the terminal transmits the selected sequence on a resource that was allocated for this purpose during 701. [00175] Through use of the above-described mechanisms, sequences that are relatively short may be used to provide feedback on received multicast transmissions. For example, one symbol and one physical resource block may be sufficient for the two different sequences. This means that, in contrast to previous systems in which CQI information is carried over either PUCCFI (but only formats 2, 3, or 4, which support more than 2 bits of information) or PUSCFI, less resources are required for sending feedback. Under the presently described scheme, the same time-frequency may also be shared between different users when each user transmits using a different orthogonal sequence.

[00176] It is understood that references in the above to “transmission scheme” include references to a “modulation and coding scheme”, which is a type of transmission scheme. Consequently, references to a more robust transmission scheme also covers a more robust modulation and coding scheme. Similarly, references to a less robust transmission scheme also covers a less robust modulation and coding scheme. Other ways of making transmission scheme more or less robust are also covered by the present disclosure. For example, aside from changing the modulation and coding scheme to change the robustness of a transmission scheme, at least the following factors may also change the robustness of a transmission scheme: transmission power, multiple-input-multiple-output configuration and resource allocation. It is further understood that changing the robustness of a transmission scheme may be effected by changing only one of these parameters. It is further understood that changing the robustness of a transmission scheme may be effected by changing multiple of these parameters. [00177] It should be understood that each block of the flowchart of the Figures and any combination thereof may be implemented by various means or their combinations, such as hardware, software, firmware, one or more processors and/or circuitry.

[00178] It is noted that whilst examples have been described in relation to one example of a standalone 5G, similar principles maybe applied in relation to other examples of standalone 3G, LTE or 5G networks. It should be noted that other examples may be based on other cellular technology other than LTE or on variants of LTE. Therefore, although certain examples were described above by way of example with reference to certain example architectures for wireless networks, technologies and standards, examples may be applied to any other suitable forms of communication systems than those illustrated and described herein.

[00179] It is also noted herein that while the above describes example examples, there are several variations and modifications which may be made to the disclosed solution without departing from the scope of the present claims. [00180] 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. [00181] In general, the various examples may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects of the described 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 claimed is not limited thereto. While various aspects of the claimed 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.

[00182] The examples of this disclosure 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 examples. The one or more computer- executable components may be at least one software code or portions of it.

[00183] 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.

[00184] 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.

[00185] Examples of the above disclosures 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. [00186] The foregoing description has provided by way of non-limiting examples a full and informative description of the exemplary example of this disclosure. 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 disclosure will still fall within the scope of the appended claims.

Claims

1. An apparatus comprising: means for determining a quality metric of a communication link over which multicast data is received from another apparatus, the multicast data being received using a first transmission scheme; means for selecting one of a first sequence and a second sequence in dependence on the quality metric, the first sequence being associated with more robust transmission schemes than the first transmission scheme and the second sequence being associated with less robust transmission schemes than the first transmission scheme; and means for transmitting the selected one of the first sequence and the second sequence to the another apparatus.

2. An apparatus as claimed in claim 1, further comprising means for transmitting comprises means for transmitting the first sequence on a first physical resource and the second sequence on a second physical resource.

3. An apparatus as claimed in any preceding claim, further comprising receiving means for receiving from the another apparatus a communication that configures the first and second sequences in the apparatus.

4. An apparatus as claimed in any preceding claim, further comprising receiving means for receiving a request from the another apparatus to provide relative feedback for multicast downlink transmissions.

5. An apparatus as claimed in any preceding claim, wherein the first sequence indicates that the reliability of the received multicast data is greater than a targeted level by a first threshold.

6. An apparatus as claimed in any preceding claim, wherein the second sequence indicates that the reliability of the received multicast data is less than a targeted level by a second threshold.

7. An apparatus as claimed in any preceding claim, wherein the transmission schemes are modulation and coding schemes.

8. An apparatus comprising: means for transmitting multicast data over a communication link to a terminal, the multicast data being transmitted using a first transmission scheme; means for receiving one of a first sequence and a second sequence from the terminal, the first sequence being associated with more robust transmission schemes than the first transmission scheme and the second sequence being associated with less robust transmission schemes than the first transmission scheme; and means for determining whether or not to transmit multicast data to the terminal using a different transmission scheme compared to the first transmission scheme in dependence on the received sequence.

9. An apparatus as claimed in claim 8, wherein when the first sequence is received, the means for determining comprises determining to transmit multicast data at a more robust transmission scheme than the first transmission scheme, and further comprising: means for using said more robust transmission scheme for transmitting the multicast data to the terminal and to any other terminals the multicast data is transmitted to.

10. An apparatus as claimed in any of claims 8 to 9, wherein when the second sequence is received, the means for determining comprises: means for transmitting a second transmission scheme to any other terminals the multicast data is transmitted to, the second transmission scheme being less robust than the first transmission scheme; means for determining from a response or lack of response to the transmitting of the second transmission scheme whether or not the any other terminals agrees to use the second transmission scheme for transmission of multicast data; and means for, when said any other terminals agrees, using the second transmission scheme for transmission of multicast data to the terminal and the any other terminals.

11. An apparatus as claimed in any of claims 8 to 10, further comprising configuring means for configuring the first and second sequences to the terminal.

12. An apparatus as claimed in any of claims 8 to 11 , further comprising transmitting means for transmitting a request to the terminal to provide relative feedback for multicast downlink transmissions.

13. An apparatus as claimed in any of claims 8 to 12, further comprising: determining means for determining that the multicast data is being transmitted to fewer than a predetermined number of terminals; instructing means for, in response to said determining, transmitting an instruction to said terminal before said multicast transmission to provide feedback on the multicast transmission using one of the first and second sequences.

14. An apparatus as claimed in any of claims 8 to 13, further comprising: determining means for determining which terminals receiving the multicast data from the apparatus are the likeliest to experience poor channel quality; selecting means for selecting a fraction of the terminals that are the likeliest to experience poor channel quality, wherein the fraction is less than 1 ; and instructing means for transmitting instructions to said selected terminals before said multicast transmission to provide feedback on the multicast transmission using one of the first and second sequences.

15. An apparatus as claimed in any of claims 8 to 14, further comprising transmitting means for transmitting a configuration communication to multiple terminals configured to receive the same multicast data, the configuration communication for configuring the first and second sequences in said multiple terminals.

16. An apparatus as claimed in any of claims 8 to 15, wherein the transmission schemes are modulation and coding schemes.

17. A method for an apparatus, the method comprising: determining a quality metric of a communication link over which multicast data is received from an apparatus, the multicast data being received using a first transmission scheme; selecting one of a first sequence and a second sequence in dependence on the quality metric, the first sequence being associated with more robust transmission schemes than the first transmission scheme and the second sequence being associated with less robust transmission schemes than the first transmission scheme; and transmitting the selected one of the first sequence and the second sequence to the apparatus.

18. A method for an apparatus, the method comprising: transmitting multicast data over a communication link to a terminal, the multicast data being transmitted using a first transmission scheme; receiving one of a first sequence and a second sequence from the terminal, the first sequence being associated with more robust transmission schemes than the first transmission scheme and the second sequence being associated with less robust transmission schemes than the first transmission scheme; and determining whether or not to transmit multicast data to the terminal using a different transmission scheme compared to the first transmission scheme in dependence on the received sequence.

19. A computer program product comprising computer code that, when executed by at least one processor of an apparatus, causes the apparatus to perform the steps of claim 17.

20. A computer program product comprising computer code that, when executed by at least one processor of an apparatus, causes the apparatus to perform the steps of claim 18.