WO2022078614A1

WO2022078614A1 - Relaying in communication networks

Info

Publication number: WO2022078614A1
Application number: PCT/EP2020/079255
Authority: WO
Inventors: Vinh Van Phan; Ling Yu
Original assignee: Nokia Technologies Oy
Priority date: 2020-10-16
Filing date: 2020-10-16
Publication date: 2022-04-21

Abstract

According to an example aspect, there is provided a method comprising determining, by a first terminal device, a need to transmit data to at least one second terminal device via at least one third terminal device in a device-to-device communication based on a quality class of said data and/or a radio link condition; determining, by the first terminal device, at least one first relay identification configured for relaying data in the device-to-device communication; transmitting, by the first terminal device, said data to the at least one third terminal device with the at least one first relay identification and control information related to data relaying and/or data processing in the at least one third terminal device and/or in the at least one second terminal device; and monitoring, by the first terminal device, broadcast and/or multicast transmission of the at least one third terminal device for detecting the relaying of said data based on at least one second relay identification configured for relaying data in the device-to-device communication, wherein said broadcast and/or multicast transmission comprises said data and the at least one second relay identification.

Description

RELAYING IN COMMUNICATION NETWORKS

FIELD

[0001] Various example embodiments relate in general to communication networks and more specifically, to relaying in such networks.

BACKGROUND

[0002] Relaying may be used to enhance coverage, capacity and/or power savings by having a relay device between a transmitter device and a receiver device, thereby creating a multi-hop communication link. Relaying may be used, for example, in various communication networks, such as, in cellular communication networks operating according to 5G radio access technology. 5G radio access technology may also be referred to as new radio (NR) access technology. 3rd generation partnership project (3GPP) develops standards for 5G/NR and one of the topics in the 3GPP discussions is related to relaying. According to the discussions there is a need to provide improved methods, apparatuses and computer programs related to relaying. Such improvements may be exploited in other communication networks as well.

BRIEF DESCRIPTION

[0003] According to some aspects, there is provided the subject-matter of the independent claims. Some example embodiments are defined in the dependent claims.

[0004] The scope of protection sought for various example embodiments of the invention is set out by the independent claims. The example embodiments and features, if any, described in this specification that do not fall under the scope of the independent claims are to be interpreted as examples useful for understanding various example embodiments of the invention.

[0005] According to a first aspect, there is provided a method comprising determining, by a first terminal device, a need to transmit data to at least one second terminal device via at least one third terminal device in a device-to-device communication based on a quality class of said data and/or a radio link condition; determining, by the first terminal device, at least one first relay identification configured for relaying data in the device-to-device communication; transmitting, by the first terminal device, said data to the at least one third terminal device with the at least one first relay identification and control information related to data relaying and/or data processing in the at least one third terminal device and/or in the at least one second terminal device; and monitoring, by the first terminal device, broadcast and/or multicast transmission of the at least one third terminal device for detecting the relaying of said data based on at least one second relay identification configured for relaying data in the device-to-device communication, wherein said broadcast and/or multicast transmission comprises said data and the at least one second relay identification.

[0006] According to a second aspect, there is provided a method comprising receiving from at least one first terminal device, by a third terminal device, data with at least one first relay identification configured for relaying data in a device-to-device communication and control information related to data relaying and/or data processing in the third terminal device and/or in at least one second terminal device indicating a need to relay said data to the at least one second terminal device as a broadcast or a multicast in the device-to-device communication; determining, by the third terminal device, at least one second relay identification configured for relaying data in the device-to-device communication based on the at least one first relay identification and the control information received from the at least one first terminal device; and broadcasting or multicasting, by the third terminal device in the device-to-device communication, said data to the at least one second terminal device directly or via at least one fourth terminal device with the at least one second relay identification, said broadcasting or multicasting further comprising control information related to data relaying and/or data processing in the at least one fourth terminal device and/or in the at least one second terminal device.

[0007] According to a third aspect, there is provided an apparatus, comprising one or more processors, and memory storing instructions that, when executed by the one or more processors, cause the apparatus to perform perform a method according to the first aspect. The at least one memory and the computer program code may be configured to, with the at least one processing core, cause the apparatus at least to perform, determine, by a first terminal device, a need to transmit data to at least one second terminal device via at least one third terminal device in a device-to-device communication based on a quality class of said data and/or a radio link condition; determine, by the first terminal device, at least one first relay identification configured for relaying data in the device-to-device communication; transmit, by the first terminal device, said data to the at least one third terminal device with the at least one first relay identification and control information related to data relaying and/or data processing in the at least one third terminal device and/or in the at least one second terminal device; and monitor, by the first terminal device, broadcast and/or multicast transmission of the at least one third terminal device for detecting the relaying of said data based on at least one second relay identification configured for relaying data in the device-to-device communication, wherein said broadcast and/or multicast transmission comprises said data and the at least one second relay identification.

[0008] According to a fourth aspect, there is provided an apparatus, comprising one or more processors, and memory storing instructions that, when executed by the one or more processors, cause the apparatus to perform perform a method according to the second aspect. The at least one memory and the computer program code may be further configured to, with the at least one processing core, cause the apparatus at least to perform, receive from at least one first terminal device, by a third terminal device, data with at least one first relay identification configured for relaying data in the device-to-device communication and control information related to data relaying and/or data processing in the third terminal device and/or in at least one second terminal device indicating a need to relay said data to the at least one second terminal device as a broadcast or a multicast in a device-to-device communication; determine, by the third terminal device, at least one second relay identification configured for relaying data in the device-to-device communication based on the at least one first relay identification and the control information received from the at least one first terminal device; and broadcast or multicast, by the third terminal device in the device-to-device communication, said data to the at least one second terminal device directly or via at least one fourth terminal device with the at least one second relay identification, said broadcasting or multicasting further comprising control information related to data relaying and/or data processing in the at least one fourth terminal device and/or in the at least one second terminal device.

[0009] According to a fifth aspect, there is provided an apparatus, comprising means for performing a method according to the first aspect. The apparatus may comprise means for means for determining, by a first terminal device, a need to transmit data to at least one second terminal device via at least one third terminal device in a device-to-device communication based on a quality class of said data and/or a radio link condition; means for determining, by the first terminal device, at least one first relay identification configured for relaying data in the device-to-device communication; means for transmitting, by the first terminal device, said data to the at least one third terminal device with the at least one first relay identification and control information related to data relaying and/or data processing in the at least one third terminal device and/or in the at least one second terminal device; and means for monitoring, by the first terminal device, broadcast and/or multicast transmission of the at least one third terminal device for detecting the relaying of said data based on at least one second relay identification configured for relaying data in the device-to-device communication, wherein said broadcast and/or multicast transmission comprises said data and the at least one second relay identification.

[0010] According to a sixth aspect, there is provided an apparatus, comprising means for performing a method according to the second aspect. The apparatus may comprise means for receiving from at least one first terminal device, by a third terminal device, data with at least one first relay identification configured for relaying data in the device-to-device communication and control information related to data relaying and/or data processing in the third terminal device and/or in at least one second terminal device indicating a need to relay said data to the at least one second terminal device as a broadcast or a multicast in a device-to-device communication; means for determining, by the third terminal device, at least one second relay identification configured for relaying data in the device-to-device communication based on the at least one first relay identification and the control information received from the at least one first terminal device; and means for broadcasting or multicasting, by the third terminal device in the device-to-device communication, said data to the at least one second terminal device directly or via at least one fourth terminal device with the at least one second relay identification, said broadcasting or multicasting further comprising control information related to data relaying and/or data processing in the at least one fourth terminal device and/or in the at least one second terminal device.

[0011] According to a seventh aspect, there is provided non-transitory computer readable medium having stored thereon a set of computer readable instructions that, when executed by at least one processor, cause an apparatus to at least perform the method of the first aspect. According to an eighth aspect, there is provided non-transitory computer readable medium having stored thereon a set of computer readable instructions that, when executed by at least one processor, cause an apparatus to at least perform the method of the second aspect.

[0012] According to a ninth aspect, there is provided a computer program comprising instructions which, when the program is executed by an apparatus, cause the apparatus to carry out the method of the first aspect. According to a tenth aspect, there is provided a computer program comprising instructions which, when the program is executed by an apparatus, cause the apparatus to carry out the method of the second aspect.

BRIEF DESCRIPTION

[0013] FIGURE 1 illustrates an example system in accordance with at least some embodiments;

[0014] FIGURE 2 illustrates a flow graph of a first method in accordance with at least some example embodiments;

[0015] FIGURE 3 illustrates a flow graph of a second method in accordance with at least some example embodiments.

[0016] FIGURE 4 illustrates a signalling example in accordance with at least some example embodiments;

[0017] FIGURE 5 illustrates an example apparatus capable of supporting at least some example embodiments.

EMBODIMENTS

[0018] At least some embodiments are related to relaying between terminal devices. In a multi-hop relaying scenario, a first terminal device may determine a need to transmit data to at least one second terminal device via at least one third terminal device. The first terminal device may also determine at least one first relay identification configured for relaying data in a Device-to-Device (D2D) communication. The first terminal device may then transmit said data with the at least one first relay identification to the at least one third terminal device and the at least one third terminal device may further broadcast or multicast said data with at least one second relay identification. The first terminal may determine the at least one second relay identification as well, and monitor broadcast and/or multicast transmissions of the at least one third terminal device to detect the relaying of said data based on the at least one second relay identification.

[0019] FIGURE 1 illustrates an example system in accordance with at least some embodiments. In the following, different exemplifying embodiments will be described using, as an example of an access architecture to which the embodiments may be applied, a radio access architecture based on long term evolution advanced (LTE Advanced, LTE-A) or new radio (NR), also known as fifth generation (5G), without restricting the embodiments to such an architecture, however. It is obvious for a person skilled in the art that the embodiments may also be applied to other kinds of communications networks having suitable means by adjusting parameters and procedures appropriately. Some examples of other options for suitable systems are the universal mobile telecommunications system (UMTS) radio access network (UTRAN or E-UTRAN), long term evolution (LTE, the same as E-UTRA), wireless local area network (WLAN or WiFi), worldwide interoperability for microwave access (WiMAX), Bluetooth®, personal communications services (PCS), ZigBee®, wideband code division multiple access (WCDMA), systems using ultra-wideband (UWB) technology, sensor networks, mobile ad-hoc networks (MANETs) and Internet Protocol multimedia subsystems (IMS) or any combination thereof.

[0020] FIGURE 1 depicts examples of simplified system architectures only showing some elements and functional entities, all being logical units, whose implementation may differ from what is shown. The connections shown in FIGURE 1 are logical connections; the actual physical connections may be different. It is apparent to a person skilled in the art that the system typically comprises also other functions and structures than those shown in FIGURE 1. The embodiments are not, however, restricted to the system given as an example but a person skilled in the art may apply the solution to other communication systems provided with necessary properties. Examples of such other communication systems include microwave links and optical fibers, for example. [0021] The example of FIGURE 1 shows a part of an exemplifying radio access network. FIGURE 1 shows terminal devices 100, 101 and 102 configured to be in a wireless connection on one or more communication channels in a cell with an access node (such as (e/g)NodeB) 104 providing the cell.

[0022] The physical link from a terminal device to a (e/g)NodeB is called uplink or reverse link and the physical link from the (e/g)NodeB to the terminal device is called downlink or forward link. It should be appreciated that (e/g)NodeBs or their functionalities may be implemented by using any node, host, server or access point etc. entity suitable for such a usage. A communications system typically comprises more than one (e/g)NodeB in which case the (e/g)NodeBs may also be configured to communicate with one another over links, wired or wireless, designed for the purpose. These links may be used for signalling purposes. The (e/g)NodeB is a computing device configured to control the radio resources of the communication system it is coupled to. The NodeB may also be referred to as a base station, an access point or any other type of interfacing device including a relay station such as distributed unit (DU) part of integrated access and backhaul (IAB) node capable of operating in a wireless environment. The DU part may facilitate the gNB functionalities of the IAB node. The (e/g)NodeB includes or is coupled to transceivers. From the transceivers of the (e/g)NodeB, a connection is provided to an antenna unit that establishes bi-directional radio links to terminal devices. The antenna unit may comprise a plurality of antennas or antenna elements. The (e/g)NodeB is further connected to core network 110 (CN or next generation core NGC). Depending on the system, the counterpart on the CN side can be a serving gateway (S-GW, routing and forwarding user data packets), packet data network gateway (P-GW), for providing connectivity of terminal devices (UEs) to external packet data networks, or mobile management entity (MME), etc.

[0023] The terminal device (also called UE, user equipment, user terminal, user device, etc.) illustrates one type of an apparatus to which resources on the air interface are allocated and assigned, and thus any feature described herein with a terminal device may be implemented with a corresponding apparatus, also including a relay node. An example of such scenario is MT (mobile termination) part of IAB node, which provides the backhaul connection for the IAB node.

[0024] Terminal devices 100, 101 and 102 may be configured to be in a wireless connection on one or more communication channels with each other, thereby creating D2D communication links. In some embodiments, terminal device 100 may be referred to as a transmitting, first terminal device, terminal device 101 may be referred to as a receiving, second terminal device and terminal device 102 may be referred to as a third, relay terminal device. The first terminal device 100 may transmit data to the third terminal device 102, wherein said data is to be relayed to the second terminal device 101. Thus, the third terminal device 102 may relay said data further to the second terminal device 101. A hop between the first terminal device 100 and the third terminal device 102 is denoted by 13 and a hop between the third terminal device 102 and the second terminal device 101 is denoted by 32. So if the first terminal device 100 transmits data to the second terminal device 101 via the third terminal device 102, the hop 13 would be an intermediate hop and hop 32 would be the last hop.

[0025] Embodiments may be applied for multi-hop relaying as well. In case of multi-hop relaying there may be multiple relays, such as the third, relay terminal device 102, between the transmitting, first terminal device 100 and the receiving, second terminal device 101. In such a case there may be multiple intermediate hops as well.

[0026] The terminal device, such as a user equipment, typically refers to a portable computing device that includes wireless mobile communication devices operating with or without a subscriber identification module (SIM), including, but not limited to, the following types of devices: a mobile station (mobile phone), smartphone, personal digital assistant (PDA), handset, device using a wireless modem (alarm or measurement device, etc.), laptop and/or touch screen computer, tablet, game console, notebook, and multimedia device. It should be appreciated that a terminal device may also be a nearly exclusive uplink only device, of which an example is a camera or video camera loading images or video clips to a network. The terminal device may also be a device having capability to operate in Internet of Things (loT) network which is a scenario in which objects are provided with the ability to transfer data over a network without requiring human-to- human or human-to-computer interaction.

[0027] Various techniques described herein may also be applied to a cyber-physical system (CPS) (a system of collaborating computational elements controlling physical entities). CPS may enable the implementation and exploitation of massive amounts of interconnected ICT devices (sensors, actuators, processors, microcontrollers, etc.) embedded in physical objects at different locations. Mobile cyber physical systems, in which the physical system in question has inherent mobility, are a subcategory of cyberphysical systems. Examples of mobile physical systems include mobile robotics and electronics transported by humans or animals.

[0028] Additionally, although the apparatuses have been depicted as single entities, different units, processors and/or memory units (not all shown in FIGURE 1) may be implemented inside these apparatuses, to enable the functioning thereof.

[0029] 5G enables using multiple input - multiple output (MIMO) antennas, many more base stations or nodes than the LTE (a so-called small cell concept), including macro sites operating in co-operation with smaller stations and employing a variety of radio technologies depending on service needs, use cases and/or spectrum available. 5G mobile communications supports a wide range of use cases and related applications including video streaming, augmented reality, different ways of data sharing and various forms of machine type applications (such as (massive) machine-type communications (mMTC), including vehicular safety, different sensors and real-time control. 5G is expected to have multiple radio interfaces, namely below 6GHz, cmWave and mmWave, and also being integratable with existing legacy radio access technologies, such as the LTE. Integration with the LTE may be implemented, at least in the early phase, as a system, where macro coverage is provided by the LTE and 5G radio interface access comes from small cells by aggregation to the LTE. In other words, 5G is planned to support both inter-RAT operability (such as LTE-5G) and inter-RI operability (inter-radio interface operability, such as below 6GHz - cmWave, below 6GHz - cmWave - mmWave). One of the concepts considered to be used in 5G networks is network slicing in which multiple independent and dedicated virtual sub-networks (network instances) may be created within the same infrastructure to run services that have different requirements on latency, reliability, throughput and mobility.

[0030] The current architecture in LTE networks is distributed in the radio and centralized in the core network. The low latency applications and services in 5G require to bring the content close to the radio which leads to local break out and multi-access edge computing (MEC). 5G enables analytics and knowledge generation to occur at the source of said data. This approach requires leveraging resources that may not be continuously connected to a network such as laptops, smartphones, tablets and sensors. MEC provides a distributed computing environment for application and service hosting. It also has the ability to store and process content in close proximity to cellular subscribers for faster response time. Edge computing covers a wide range of technologies such as wireless sensor networks, mobile data acquisition, mobile signature analysis, cooperative distributed peer-to-peer ad hoc networking and processing also classifiable as local cloud/fog computing and grid/mesh computing, dew computing, mobile edge computing, cloudlet, distributed data storage and retrieval, autonomic self-healing networks, remote cloud services, augmented and virtual reality, data caching, Internet of Things (massive connectivity and/or latency critical), critical communications (autonomous vehicles, traffic safety, real-time analytics, time-critical control, healthcare applications).

[0031] The communication system is also able to communicate with other networks, such as a public switched telephone network or the Internet 112, or utilize services provided by them. The communication network may also be able to support the usage of cloud services, for example at least part of core network operations may be carried out as a cloud service (this is depicted in FIGURE 1 by “cloud” 114). The communication system may also comprise a central control entity, or a like, providing facilities for networks of different operators to cooperate for example in spectrum sharing.

[0032] Edge cloud may be brought into radio access network (RAN) by utilizing network function virtualization (NVF) and software defined networking (SDN). Using edge cloud may mean access node operations to be carried out, at least partly, in a server, host or node operationally coupled to a remote radio head or base station comprising radio parts. It is also possible that node operations will be distributed among a plurality of servers, nodes or hosts. Application of cloudRAN architecture enables RAN real time functions being carried out at the RAN side (in a distributed unit, DU 104) and non-real time functions being carried out in a centralized manner (in a centralized unit, CU 108).

[0033] It should also be understood that the distribution of labour between core network operations and base station operations may differ from that of the LTE or even be non-existent. Some other technology advancements, such as Big Data and all-IP, may change the way networks are being constructed and managed. 5G (or new radio, NR) networks are being designed to support multiple hierarchies, where MEC servers can be placed between the core and the base station or nodeB (gNB). It should be appreciated that MEC can be applied in 4G networks as well. [0034] 5G may also utilize satellite communication to enhance or complement the coverage of 5G service, for example by providing backhauling. Possible use cases are providing service continuity for machine-to-machine (M2M) or Internet of Things (loT) devices or for passengers on board of vehicles, or ensuring service availability for critical communications, and future railway/maritime/aeronautical communications. Satellite communication may utilise geostationary earth orbit (GEO) satellite systems, but also low earth orbit (LEO) satellite systems, in particular mega-constellations (systems in which hundreds of (nano)satellites are deployed). Each satellite 106 in the constellation may cover several satellite-enabled network entities that create on-ground cells. The on-ground cells may be created through an on-ground relay node 104 or by a gNB located on-ground or in a satellite.

[0035] It is obvious for a person skilled in the art that the depicted system is only an example of a part of a radio access system and in practice, the system may comprise a plurality of (e/g)NodeBs, the terminal device may have an access to a plurality of radio cells and the system may comprise also other apparatuses, such as physical layer relay nodes or other network elements, etc. A cellular radio system may be implemented as a multilayer network including several kinds of cells, such as macrocells, microcells and picocells, for example. Typically, in multilayer networks, one access node provides one kind of a cell or cells, and thus a plurality of (e/g)NodeBs are required to provide such a network structure.

[0036] Embodiments are related to relaying between terminal devices 100 - 102 in D2D communications, such as sidelink based UE-to-UE relaying discussed in the 3rd Generation Partnership Project (3 GPP) meetings. Sidelink is a direct communication link between UEs in a cellular communication network and UEs can communicate via a sidelink without going through a gNB. Multi-hop relaying is, or at least should be, possible as well.

[0037] Embodiments enable detection of relaying for avoiding unnecessary participation in relaying as well as for reassuring purposes. Alternatively, or in addition, relaying between terminal devices may be facilitated without a need of a connection setup for relaying. Some example embodiments are based on the one-to-many broadcast nature of the 3GPP sidelink (PC5 interface) as well as the existing packet data convergence protocol (PDCP) level duplication of the 3 GPP sidelink for both LTE and NR to avoid a significant change to the current PC5 protocols. Some embodiments also support the 3GPP sidelink for both in-coverage and out-of-coverage operations as well as multi-PLMN operation. These are with regards to individual UEs involved in transmitting, receiving or relaying for a SL based UE-to-UE relaying.

[0038] FIGURE 2 is a flow graph of a first method in accordance with at least some embodiments. The phases of the illustrated first method may be performed by the first, transmitting terminal device 100 shown in FIGURE 1, or by a control device configured to control the functioning thereof, possibly when installed therein.

[0039] The first method may comprise, at phase 210, determining by the first terminal device 100 a need to transmit data to at least one second terminal device 101 via at least one third terminal device 102 in a D2D communication based on a quality class of said data and/or a radio link condition. It should be noted that the first terminal device 100 may only determine the need to use at least one relay, but it does not need to know and select the at least one third terminal device 102 beforehand, i.e., discovery and connection setup are not needed. Said data to be relayed may be for example broadcasted or groupcasted to multiple relays.

[0040] Said determination at phase 210 may be based on various needs or conditions. For example, the first terminal device 100 may determine the need to transmit data to the second terminal device 101 via the third terminal device 102 if the first terminal device 100 needs to reduce transmit power or range towards the second terminal device 101 for power saving or for power redistribution for transmitting to other devices, if the first terminal device 100 detects a problem with the direct link towards the second terminal device 101 based on monitoring feedback from the second terminal device 101 and/or if the first terminal device 100 is configured to use the relay mode by default for the corresponding Quality of Service (QoS) ID of a QoS flow (of a PDCP packet for example) between the first terminal device 100 and the second terminal device 101.

[0041] The need to transmit data to the second terminal device 101 via the third terminal device 102 may be due to, for example, that the second terminal device 101 is out of direct reach or coverage of the first terminal device 100, or that the presence, reachability or location of the second terminal device 101 is not known to the first terminal device 100, or that the first terminal device 100 has a need to spread a groupcast or broadcast message to a group or all third terminal devices 102 within a certain range or service area. The communications between terminal devices may be direct, that is, said data does not traverse a base station en route, i.e., when transmitted, from the first terminal device 100 to the third terminal device 102, or en route from the third terminal device 102 to the second terminal device 101.

[0042] Moreover, the first method may also comprise, at phase 220, determining, by the first terminal device 100, at least one first relay identification configured for relaying data in the D2D communication. The at least one first relay identification may indicate an intermediate hop in a multi-hop relaying scenario of the D2D communication. In some embodiments, the at least one first relay identification may be a relay specific layer 2 (L2) identity (ID) corresponding to the hop 13 between the first terminal device 100 and the second terminal device 101. In general, the relay specific L2 ID corresponding to a hop may be a direct link identity, such as a sidelink identity. Due to one-to-many broadcast nature of the 3GPP sidelink, the direct link identity is identified by a couple of a L2 ID of the transmitting UE, also referred to as L2 source (SRC) ID, and a L2 ID of the receiving UE, also referred to as L2 destination (DST) ID. In this regard, the relay specific L2 ID corresponding to a hop is used as L2 DST ID by the transmitting UE to broadcast or multicast said data over SL for the hop.

[0043] Different hops may have the same or different relay identification. Thus, one relay identification may be associated with one or more hops. In other words, the relay identification of the hop 13 may be the same as the relay identification of a hop between the first terminal device 100 and some other terminal device in the proximity of the first terminal device 100. Alternatively, the relay identification of the hop 13 may be the same as the relay identification corresponding to a hop between the second terminal device 101 and some other terminal device in the proximity of the second terminal device 101. So the relay identification of the hop may be an identification for a set of hops, i.e., more than one hop.

[0044] In some embodiments, a relay identification may indicate at least one of the quality class of said data and an ordinal number of a hop in a multi-hop relaying scenario of the D2D communication. The ordinal number of the hop refers to a position of the hop in a list, such as the first, the second, the third, etc. In such a case, the first terminal device 100 may determine, based on the at least one of the quality class of said data and the ordinal number of the hop, the at least one first relay identification from a set of relay identifications.

[0045] The first method may also comprise, at phase 230, transmitting, by the first terminal device 100, said data to the at least one third terminal device 102 with the at least one first relay identification, the transmitting further comprising control information related to data relaying and/or data processing in the at least one third terminal device 102 and/or in the at least one second terminal device 101. Said transmitting takes place over the intermediate hop 13 between the first terminal device 100 and the third terminal device 102.

[0046] In some embodiments, said transmitting may further comprise transmitting the control information in a medium access control (MAC) control element (CE). The use of the MAC CE enables transmission of more control information related to relaying, thereby providing a flexible solution. In some embodiments, as an alternative optimization, said transmitting may further comprise transmitting the control information in a sidelink control information (SCI) message. The size of the SCI is limited though, and hence the MAC CE is a more flexible solution.

[0047] In general, the control information may comprise at least one of a destination identity of the second terminal device 101, like a L2 ID of the second terminal device 101 as the receiving UE, the quality class of said data, a maximum number of hops in a multihop relaying scenario of the D2D communication, an ordinal number of a hop in a multihop relaying scenario of the D2D communication, a logical channel identifier of said data and a data identifier of said data.

[0048] So there are 2 options for sending the control information: (1) using the SCI; or (2) using the MAC CE. In NR, the SCI is sent in 2 stages: the first stage is sent on a physical sidelink control channel (PSCCH) and the second stage is sent on a physical sidelink shared channel (PSSCH). Thus, the first-stage SCI may have capacity limitation on the size of control information, but the second-stage SCI may be flexible. Hence, overall, both of the option (1) and the option (2) may be flexible. Due to the introduction of the relay identification which is used as the L2 DST ID to be included at least in part in the SCI to transmit the said data for relaying but can be either hop specific or common to all possible hops, what and how to send the control information for relaying can be adapted to the relay identification used for sending/receiving the said data and control information. This comprises:

(i) The format of the SCI, the second stage at least, that is addressed to the L2 DST ID of the relay identification as used for relaying, can have different format compared to the format of the SCI when the L2 DST ID included in the SCI is other than the relay identification. The difference is due to a need for conveying the control information, at least a part of it.

(ii) The format of the SCI, the second stage at least, that is addressed to the L2 DST ID of the relay identification as used for relaying can be different regarding whether the relay identification is hop-specific or common to all possible hops. The difference is due to different control information (control info elements) needed regarding whether the relay identification is hop-specific or common to all possible hops.

(iii) The format of the MAC CE which is used for conveying the control information can be different regarding whether the relay identification is hopspecific or common to all possible hops, as in (ii).

[0049] Finally, at phase 240, the first terminal device 100 may monitor broadcast and/or multicast transmissions of the at least one third terminal device 102 for detecting the relaying of said data based on at least one second relay identification configured for relaying data in the D2D communication, wherein said broadcast and/or multicast transmission comprises said data and the at least one second relay identification. The first terminal device 100 may determine that said data has been relayed if a transmission comprising the at least one second relay identification is received during said monitoring.

[0050] The at least one second relay identification may be different compared to the at least one first relay identification when the at least one first relay identification is hopspecific in case of multi-hop relaying, the at least one second relay identification may be the same as the at least one first relay identification when the at least one first relay identification is common to all hops in case of multi-hop relaying or the at least one second relay identification may be the destination identity of the at least one second terminal device 101 when said transmission of the at least one third terminal device is for the last hop in in case of multi-hop relaying. [0051] FIGURE 3 is a flow graph of a second method in accordance with at least some embodiments. The phases of the illustrated second method may be performed by the third, relay terminal device 102 shown in FIGURE 1, or by a control device configured to control the functioning thereof, possibly when installed therein. It is noted that in case of multi -hop relaying the relay terminal device 102 acts as a receiving terminal device of the previous corresponding hop and as a transmitting terminal device of the next corresponding hop.

[0052] The second method may comprise, at phase 310, receiving from at least one first terminal device 100, by a third terminal device 102, data with at least one first relay identification and control information related to data relaying and/or data processing in the third terminal device 102 and/or in the at least one second terminal device 101 indicating a need to relay said data to the at least one second terminal device 101 as a broadcast or a multicast in a D2D communication, wherein the third terminal device 102 is configured to act as a relay.

[0053] Moreover, the second method may comprise, at phase 320, determining, by the third terminal device 102, at least one second relay identification based on the at least one first relay identification and the control information received from the at least one first terminal device 100. The third terminal device 102 may determine to act as a relay for the corresponding hop based on the control information. Said determining may thus comprise determining the at least one second relay identification for a hop for which the third terminal device 102 is acting as the transmitting terminal device. In case the determined hop is not the last hop, the third terminal device 102 may also need to update the control information and send it along with the relay data.

[0054] In some embodiments, said determination may be based on information the third terminal device 102 has about its neighbours. For example, if the second terminal device 101 is a neighbour of the third terminal device 102, the third terminal device 102 may determine that the at least one second relay identification should be a destination identity of the second terminal device 101 and relay said data directly to the second terminal device 101 via the last hop 32. However, if the second terminal device 101 is not a neighbour of the third terminal device 102, the third terminal device 102 has to relay said data via the intermediate hop. The information about the neighbours may be gathered, for example, based on measuring broadcasted transmissions of the other UEs, etc. This determination may override the determination based on the at least one first relay identification and the control information received from the at least one first terminal device 100.

[0055] Finally, the second method may comprise, at step 330, broadcasting or multicasting, by the third terminal device 102 in the D2D communication, said data to the at least one second terminal device 101 directly or via at least one fourth terminal device with the at least one second relay identification, said broadcasting or multicasting further comprising control information related to data relaying and/or data processing in the at least one second terminal device 101 and/or in the fourth terminal device. If needed, the at least one fourth terminal device may perform similar actions as the third terminal device 102 to relay said data further to the at least one second terminal 101.

[0056] FIGURE 4 illustrates a signalling example in accordance with at least some example embodiments. On the vertical axes are disposed, from the left to the right, the first terminal device 100, the third terminal device 102 and the second terminal device 101 of FIGURE 1. Time advances from the top towards the bottom. Even though relay specific L2 IDs are used as an example in connection with FIGURE 4, the signalling example may be applied for any relay identifications in general. Relay specific L2 IDs are particularly beneficial for sidelink UE-to-UE relays.

[0057] At step 402, terminal devices supporting relaying, such as the first 100 and the third terminal device 102, may be configured with one or more relay specific L2 IDs which are to be used as L2 IDs corresponding to intermediate hops of the relaying and/or QoS classes. In some embodiments, the terminal devices supporting relaying may be preconfigured or hard-coded with one or more relay specific L2 IDs. Pre-configuration may be provisioned to the terminal devices via an application server or stored in the SIM card of terminal device. The pre-configuration may be for supporting of out-of-coverage (OoC) or multi-PLMN operation. In some embodiments, the terminal devices supporting relaying may be configured with one or more relay specific L2 IDs from the network, such as 5G or LTE, or from the application server when terminal devices are in the network coverage. The (pre-)configured relay specific L2 ID(s) may also correspond to intermediate hops in case of multi-hop relaying. The (pre-)configured relay specific L2 ID(s) may be also application or service specific, e.g. for Public Safety or Road Safety applications. The relay specific L2 IDs may be unique as well. In some embodiments, the relay specific L2 IDs may be Proximity Service (ProSe) IDs.

[0058] In some embodiments, a maximum number of hops (NoH) may be predefined and configured to terminal devices for multi -hop relaying at step 402 as well. The maximum NoH may be predefined and configured by or along with configuring a corresponding number of relay specific L2 IDs. Based on the configured maximum NoH, the first terminal device 100 may be allowed to initially set the maximum NoH for the relaying to be initiated by the first terminal device 100 under the configured maximum NoH constraint. The set NoH is then indicated either via the relay specific L2 ID corresponding to the hop or in the control information sent along with the relay data. The specified maximum number of hops (NoH) may be pre-configured as per a quality class commonly to all terminal devices or set by the first terminal device as per a determined need for relaying of, said, data.

[0059] In some embodiments, the relay specific L2 IDs corresponding to hop(s) may correspond to Quality of Service (QoS) classes. That is to say, relay specific L2 ID may indicate a QoS class of data which is to be relayed. There may be a set of relay specific L2 IDs configured per a supported range of QoS classes, i.e., one relay specific L2 ID may indicate one QoS class (from the set of QoS classes) for said data to be relayed. Therefore, each relay specific L2 ID of the set may also indicate the corresponding QoS class or range.

[0060] Thus, for example the first terminal device 100 may determine, based on the QoS class of said data, the relay specific L2 ID corresponding to the hop 13 from a set of relay specific L2 IDs corresponding to the hop 13. So the QoS class of said data may be implicitly conveyed to the third terminal device 102 by selecting a certain relay specific L2 ID corresponding to the hop 13. Communication resources may be therefore saved while ensuring good overall service.

[0061] Steps 404 and 406 correspond to phases 210 and 220 of the first method of FIGURE 2, respectively. At steps 408 and 410, which correspond to phase 230 of FIGURE 2, the first terminal device 100 may transmit said data to the at least one third terminal device 102 with the at least one first relay specific L2 ID, the transmitting further comprising the control information related to data relaying and/or data processing in the at least one third terminal device 102 and/or in the at least one second terminal device 101. [0062] At step 408, the first terminal device 100 may transmit a SCI to schedule for a transmission to follow at step 410, the SCI may comprise at least a part of the control information for relaying. Because SCI is sent on PSCCH (e.g., the whole SCI in LTE and 1 -stage SCI in NR) and addressed to a layer 1 (LI) ID, wherein the LI destination ID may comprise least significant bits of a L2 ID, the SCI may be used for transmitting and receiving a sidelink transmission. For example, L2 ID may have 24 bits and LI ID may have 8 or 16 bits. Embodiments introduce one or more relay specific L2 ID(s) used for corresponding relaying hop(s), e.g., corresponding to the hop 13, but not for the last hop 32 for which L2 destination ID may be a L2 ID of the second terminal device 101. So for optimization a SCI message may be addressed to a configured relay specific L2 ID by introducing a new format which corresponds to the configured relay specific L2 ID to convey at least a part of the control information for relaying, instead of or in addition to using the MAC CE.

[0063] According to the new format, the SCI may comprise, i.e., indicate (take over) some contents of a MAC CE such as the destination ID of the second terminal device 101, Packet ID, QoS ID, NoH, and/or source ID of the first terminal device 100 (e.g., from the header of PC5 MAC PDU). Therefore, the third terminal device 102 may be allowed, at least in case of a multi-hop relaying, to determine whether to relay or not only based on received SCI, and avoid unnecessary overhead without a need of receiving a transport block associated with the SCI. However, SCI, as LI signalling, is limited to bit-capacity of PSCCH. Therefore, the use of the MAC CE provides a more flexible alternative.

[0064] Alternatively, or additionally, the first terminal device 100 may transmit, at step 410, a MAC CE comprising the control information together with said data to be relayed to the second terminal device 101, for example in a transport block. The relay specific L2 ID corresponding to the hop 13 is used for transmitting said transport block.

[0065] Said MAC CE may be transmitted from the first terminal device 100 to the third terminal device 102 together with said data, such as a MAC PDU comprising at least one PDCP packet, in the same transport block for example. In some embodiments, the MAC CE may comprise for example at least one of a L2 destination ID of the second terminal device 101, QoS ID, and NoH which is initially set by the first terminal device 100 and updated by the third terminal device 102 for each hop, for said data, such as a PDCP packet, assuming that L2 source ID of the first terminal device 100 and logical channel ID (LCID) of said data is included in a header of the MAC PDU, as specified for current PC5, and no data multiplexing from different logical channels inside the transmission block just for an example.

[0066] In some embodiments, a format of the MAC CE may correspond to a relay specific L2 ID used for sending and receiving the MAC CE, e.g., over sidelink. For instance, with a certain relay specific L2 ID that indicates the corresponding hop and QoS ID of said data, the MAC CE may comprise only L2 destination ID of the second terminal device 101. In such a case, multiple specific L2 destination IDs may be configured and each relay specific destination ID may indicate a corresponding hop and QoS ID of the corresponding QoS flow. In addition, also the initial NoH may be preconfigured for the QoS ID to the involved terminal devices such as the first terminal device 100 and the third terminal device 102.

[0067] As another example, with a certain relay specific L2 ID, the MAC CE may comprise L2 destination ID of the second terminal device 101 and the NoH, initially set by the first terminal device 100. The relay specific L2 ID may indicate a corresponding hop and QoS ID of the corresponding QoS flow and the first terminal device 100 may be allowed to set the initial NoH.

[0068] As an additional example, assuming that a single relay specific L2 ID is configured for possible multi-hop relaying and data multiplexing from different logical channels is allowed, one or more individual MAC CEs may be generated and included in the same transport block. In such a case said one or more individual MAC CEs may comprise L2 destination ID of the second terminal device 101, NoH, QoS IDs, LCIDs, packet IDs of the corresponding PDCP packets which are included in the transport block. In this option, packet IDs may be needed to allow the third terminal device 102 to avoid relaying the same data for the same first terminal device 100 more than once.

[0069] Step 412 corresponds to step 310 of FIGURE 3. So at step 412, the third terminal device 102 may receive said data to be relayed to the second terminal device 101 for example with the SCI and/or the MAC CE, possibly in a transport block, from the first terminal device 100.

[0070] The SCI may include the information needed for reception of the transport block. That is, the second terminal device 101 or the third terminal device 102, needs to first receive the SCI. Based on the information derived from the SCI, the terminal device knows how and from which resources to receive the transport block (i.e. sidelink data).

[0071] If the third terminal device 102 received said data from the first terminal device 100 using the relay specific L2 ID corresponding to the hop 13, the third terminal device 102 may check the control information for relaying from the MAC CE received in the transport block based on the corresponding relay specific L2 ID and for example decode the MAC CE as well as map the PDCP packet from the MAC PDU. The third terminal device 102 may also preserve, e.g., store to its memory, a source ID and LCID of the first terminal device 100 and a destination ID of the second terminal device 101, to be used by the third terminal device 102 for relaying said data, such as the PDCP packet, assuming that the third terminal device 102 is configured to relay for one LCID of a paired source ID and destination ID at a time per a scheduled transport block from the third terminal device 102.

[0072] In some embodiments, the third terminal device 102 may determine whether it should relay said data to the second terminal device 101. In case the third terminal device 102 determines that it should not relay the received data further, for example because it detects that it has already relayed the same data or relayed for the same first terminal device 100 previously but on a different hop, within a preconfigured time interval. This time interval may be implemented with a timer starting from the instant the third terminal device 102 determined to relay for the first terminal device 100 previously. The third terminal device 102 may for example delete the preserved/stored contexts related to said data or the first terminal device 100 after expiry of the timer.

[0073] In some embodiments, the third terminal device 102 may determine, based on the relay specific L2 ID corresponding to the hop 13, the QoS class of said data. The QoS class of said data may be taken into account by the third terminal device 102 for example when it considers what should be relayed first. Hence good overall service can be provided by taking into account the implicitly indicated QoS class.

[0074] Step 414 corresponds to phase 320 of FIGURE 3. The third terminal device 102 may also determine whether it should relay said data to the second terminal device 101 via an intermediate hop or directly via a last hop, possibly upon determining that it should relay said data to the second terminal device 101. In case the third terminal device 102 determines that it is to relay for the last hop to reach the second terminal device 101 directly without any additional intermediate hops (e.g., based on the relay specific L2 ID on which said data, such as the PDCP packet, was received and/or NoH=l, as counted down from the set NoH for the first hop and 1 for the last hop, is set in the received MAC CE together with the PDCP packet), the third terminal device 102 may select as the second relay specific L2 ID the preserved/stored source ID of the first terminal device 100 and destination ID of the second terminal device 101 and possibly LCID set by the first terminal device 100 for the PDCP packet to send the PDCP packet to the second terminal device 101. No MAC CE is needed for the last hop, i.e., said data may be transmitted without the MAC CE.

[0075] However, in case the third terminal device 102 determines that it is to relay for the first terminal device 100, via the next intermediate hop towards the second terminal device 101 (i.e., the third terminal device 102 does not transmit directly to the second terminal device 101 via the last hop), the third terminal device 102 may act as a transmitting terminal device for the next intermediate hop using a relay specific L2 destination ID corresponding to the next hop between the second terminal device 101 and the third terminal device 102 as the second relay specific L2 ID.

[0076] It is not necessary to have another relay specific L2 ID for a different hop so the second specific L2 ID may be the same as the first relay specific L2 ID received from the first terminal device 100. There may be one relay specific L2 ID defined/configured while the other control information (e.g. no. of hops, QoS ID, etc.) for relaying may be carried in MAC CE or new format of SCI. In such a case the third terminal device 102 may set NoH=NoH-l in the MAC CE and send the MAC CE for the next intermediate hop. Other control information for further relaying may be inherited for example from the received MAC CE and MAC PDU and/or SCI of the previous hop. It is noted that it is flexible to use MAC CE generated by the third terminal device 102 to support, for example data multiplexing from different logical channels and/or different transmitting terminal devices for relaying.

[0077] Steps 416 and 418 corresponding to step 330 of FIGURE 3. Step 420 corresponds to step 240 of FIGURE 2. In case of 2-hop relay, the first terminal device 100 may overhear the relayed transmission of the third terminal device 102 to the second terminal device 101 for reassuring purposes. That is to say, the first terminal device 100 may monitor at least SCI transmissions from the third terminal device 102 addressed to the destination ID of the second terminal device 101 to determine that said data, such as the PDCP PDU, was received and relayed by the third terminal device 102 to the second terminal device 101 via the last hop.

[0078] At step 422, the second terminal device 101 may monitor the communication channel to receive said data, such as the PDCP PDU, for both IDs, L2 ID indicating an intermediate hop and its own destination ID, i.e., destination ID of the second terminal device 101. When said data is received along with the destination ID of the second terminal device 101, the second terminal device 101 may receive said data, such as the PDCP packet to be terminated by the second terminal device 101, from different relay terminal devices or from the first terminal device 100 on same or different hops and discard the redundant PDCP packets. When said data is received along with the second relay specific L2 ID, the second terminal device 101 may check the destination ID in the MAC CE received along with the received data. If the destination ID in the MAC CE is the same as destination ID of the second terminal device 101, the second terminal device 101 may regard the said data as valid, such as the PDCP packet to be terminated by the second terminal device 101. If redundant PDCP packets are identified, the redundant packets are discarded. In this case, the second terminal device 101 may broadcast or multicast over SL an indication to other terminal devices acting as relays in proximity of the second terminal device that it terminates the said data to cause other terminal devices to stop relaying the said data.

[0079] In some embodiments, support for relaying and therefore relay specific L2 ID indicating hops may be configured to targeted terminal devices or terminal device groups for targeted services so that only targeted terminal devices need to be involved in relaying. For example, the targeted terminal devices or terminal device groups may be for Public Safety. As another example, the targeted terminal devices or terminal device groups may be V2X terminal devices and the targeted services are for common road-safety applications. As a third example, the targeted terminal device groups or services may be limited to broadcast/multicast groups or services.

[0080] In some embodiments, said data in form of a transport block may be relayed in physical layer. In such a case, the MAC CE does not need to include LCID(s) of the PDCP packet(s). However, such a solution may not be flexible as a relaying terminal device needs to relay the transport block as such. Also, more changes may be required to physical layer and MAC layer due to, e.g., needs for transport block buffering for relay and transport block duplication detection and discarding.

[0081] In some embodiments, said data to be relayed is of a layer above PDCP such as service data application protocol (SDAP). In such a case there may be no need to preserve sidelink radio-bearer mapping context (LCID) but then more functions need to be introduced to SDAP such as duplication detection and in-order delivery causing functional redundancies and changes to the current standards.

[0082] FIGURE 5 illustrates an example apparatus capable of supporting at least some embodiments. Illustrated is device 500, which may comprise, for example, the first terminal device 100 or the third terminal device 102 or a device controlling functioning thereof. Comprised in device 500 is processor 510, which may comprise, for example, a single- or multi-core processor wherein a single-core processor comprises one processing core and a multi-core processor comprises more than one processing core. Processor 510 may comprise, in general, a control device. Processor 510 may comprise more than one processor. Processor 510 may be a control device. A processing core may comprise, for example, a Cortex-A8 processing core manufactured by ARM Holdings or a Steamroller processing core designed by Advanced Micro Devices Corporation. Processor 510 may comprise at least one Qualcomm Snapdragon and/or Intel Atom processor. Processor 510 may comprise at least one application-specific integrated circuit, ASIC. Processor 510 may comprise at least one field-programmable gate array, FPGA. Processor 510 may be means for performing method steps in device 500. Processor 510 may be configured, at least in part by computer instructions, to perform actions.

[0083] A processor may comprise circuitry, or be constituted as circuitry or circuitries, the circuitry or circuitries being configured to perform phases of methods in accordance with embodiments described herein. As used in this application, the term “circuitry” may refer to one or more or all of the following: (a) hardware-only circuit implementations, such as implementations in only analog and/or digital circuitry, and (b) combinations of hardware circuits and software, such as, as applicable: (i) a combination of analog and/or digital hardware circuit(s) with software/firmware and (ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and (c) hardware circuit(s) and or processor(s), such as a microprocessor s) or a portion of a microprocessor s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.

[0084] This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and/or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

[0085] Device 500 may comprise memory 520. Memory 520 may comprise randomaccess memory and/or permanent memory. Memory 520 may comprise at least one RAM chip. Memory 520 may comprise solid-state, magnetic, optical and/or holographic memory, for example. Memory 520 may be at least in part accessible to processor 510. Memory 520 may be at least in part comprised in processor 510. Memory 520 may be means for storing information. Memory 520 may comprise computer instructions that processor 510 is configured to execute. When computer instructions configured to cause processor 510 to perform certain actions are stored in memory 520, and device 500 overall is configured to run under the direction of processor 510 using computer instructions from memory 520, processor 510 and/or its at least one processing core may be considered to be configured to perform said certain actions. Memory 520 may be at least in part comprised in processor 510. Memory 520 may be at least in part external to device 500 but accessible to device 500.

[0086] Device 500 may comprise a transmitter 530. Device 500 may comprise a receiver 540. Transmitter 530 and receiver 540 may be configured to transmit and receive, respectively, information in accordance with at least one cellular or non-cellular standard. Transmitter 530 may comprise more than one transmitter. Receiver 540 may comprise more than one receiver. Transmitter 530 and/or receiver 540 may be configured to operate in accordance with global system for mobile communication, GSM, wideband code division multiple access, WCDMA, 5G, long term evolution, LTE, IS-95, wireless local area network, WLAN, Ethernet and/or worldwide interoperability for microwave access, WiMAX, standards, for example.

[0087] Device 500 may comprise a near-field communication, NFC, transceiver 550. NFC transceiver 550 may support at least one NFC technology, such as NFC, Bluetooth, Wibree or similar technologies.

[0088] Device 500 may comprise user interface, UI, 560. UI 560 may comprise at least one of a display, a keyboard, a touchscreen, a vibrator arranged to signal to a user by causing device 500 to vibrate, a speaker and a microphone. A user may be able to operate device 500 via UI 560, for example to accept incoming telephone calls, to originate telephone calls or video calls, to browse the Internet, to manage digital files stored in memory 520 or on a cloud accessible via transmitter 530 and receiver 540, or via NFC transceiver 550, and/or to play games.

[0089] Device 500 may comprise or be arranged to accept a user identity module 570. User identity module 570 may comprise, for example, a subscriber identity module, SIM, card installable in device 500. A user identity module 570 may comprise information identifying a subscription of a user of device 500. A user identity module 570 may comprise cryptographic information usable to verify the identity of a user of device 500 and/or to facilitate encryption of communicated information and billing of the user of device 500 for communication effected via device 500.

[0090] Processor 510 may be furnished with a transmitter arranged to output information from processor 510, via electrical leads internal to device 500, to other devices comprised in device 500. Such a transmitter may comprise a serial bus transmitter arranged to, for example, output information via at least one electrical lead to memory 520 for storage therein. Alternatively to a serial bus, the transmitter may comprise a parallel bus transmitter. Likewise processor 510 may comprise a receiver arranged to receive information in processor 510, via electrical leads internal to device 500, from other devices comprised in device 500. Such a receiver may comprise a serial bus receiver arranged to, for example, receive information via at least one electrical lead from receiver 540 for processing in processor 510. Alternatively to a serial bus, the receiver may comprise a parallel bus receiver. [0091] Device 500 may comprise further devices not illustrated in FIGURE 5. For example, where device 500 comprises a smartphone, it may comprise at least one digital camera. Some devices 500 may comprise a back-facing camera and a front-facing camera, wherein the back-facing camera may be intended for digital photography and the frontfacing camera for video telephony. Device 500 may comprise a fingerprint sensor arranged to authenticate, at least in part, a user of device 500. In some embodiments, device 500 lacks at least one device described above. For example, some devices 500 may lack a NFC transceiver 550 and/or user identity module 570.

[0092] Processor 510, memory 520, transmitter 530, receiver 540, NFC transceiver 550, UI 560 and/or user identity module 570 may be interconnected by electrical leads internal to device 500 in a multitude of different ways. For example, each of the aforementioned devices may be separately connected to a master bus internal to device 500, to allow for the devices to exchange information. However, as the skilled person will appreciate, this is only one example and depending on the embodiment various ways of interconnecting at least two of the aforementioned devices may be selected without departing from the scope.

[0093] As an example, it is presented an apparatus comprising at least a processor 510, a memory 520, a transmitter 530 and a receiver 540, wherein the processor 510 is configured to determine 210, by a first terminal device 100, a need to transmit data to at least one second terminal device 101 via at least one third terminal device 102 in a device- to-device communication based on a quality class of said data and/or a radio link condition; the processor 510 and the memory 520 are configured to determine 220, by the first terminal device 100, at least one first relay identification configured for relaying data in the device-to-device communication; the transmitter 530 is configured to transmit 230 by the first terminal device 100, said data to the at least one third terminal device 102 with the at least one first relay identification and control information related to data relaying and/or data processing in the at least one third terminal device 102 and/or in the at least one second terminal device 101; and the receiver 540 is configured to monitor 240, by the first terminal device 100, broadcast and/or multicast transmission of the at least one third terminal device 102 for detecting the relaying of said data based on at least one second relay identification configured for relaying data in the device-to-device communication, wherein said broadcast and/or multicast transmission comprises said data and the at least one second relay identification. [0094] As another example, it is presented an apparatus comprising at least a processor 510, a memory 520, a transmitter 530 and a receiver 540, wherein the receiver 540 is configured to receive 310 from at least one first terminal device 100, by a third terminal device 102, data with at least one first relay identification configured for relaying data in the device-to-device communication and control information related to data relaying and/or data processing in the third terminal device 102 and/or in at least one second terminal device 101 indicating a need to relay said data to the at least one second terminal device 101 as a broadcast or a multicast in a device-to-device communication; the processor 510 and the memory are configured to determine 320, by the third terminal device 102, at least one second relay identification configured for relaying data in the device-to-device communication based on the at least one first relay identification and the control information received from the at least one first terminal device 100; and the transmitter 530 is configured to broadcast or multicast 330, by the third terminal device 102 in the device-to-device communication, said data to the at least one second terminal device 101 directly or via at least one fourth terminal device with the at least one second relay identification, said broadcasting or multicasting further comprising control information related to data relaying and/or data processing in the at least one fourth terminal device and/or in the at least one second terminal device 101.

[0095] As yet another example, it is presented an apparatus comprising means 510 for determining 210, by a first terminal device 100, a need to transmit data to at least one second terminal device 101 via at least one third terminal device 102 in a device-to-device communication based on a quality class of said data and/or a radio link condition; means 510, 520 for determining 220, by the first terminal device 100, at least one first relay identification configured for relaying data in the device-to-device communication; means 530 for transmitting 230, by the first terminal device 100, said data to the at least one third terminal device 102 with the at least one first relay identification and control information related to data relaying and/or data processing in the at least one third terminal device 102 and/or in the at least one second terminal device 101; and means 540 for monitoring 240, by the first terminal device 100, broadcast and/or multicast transmission of the at least one third terminal device 102 for detecting the relaying of said data based on at least one second relay identification configured for relaying data in the device-to-device communication, wherein said broadcast and/or multicast transmission comprises said data and the at least one second relay identification. [0096] As yet another example of an apparatus, it is presented an apparatus comprising means 540 for receiving 310 from at least one first terminal device 100, by a third terminal device 102, data with at least one first relay identification configured for relaying data in the device-to-device communication and control information related to data relaying and/or data processing in the third terminal device 102 and/or in at least one second terminal device 101 indicating a need to relay said data to the at least one second terminal device 101 as a broadcast or a multicast in a device-to-device communication; means 510, 520 for determining 320, by the third terminal device 102, at least one second relay identification configured for relaying data in the device-to-device communication based on the at least one first relay identification and the control information received from the at least one first terminal device 100; and means 530 for broadcasting or multicasting 330, by the third terminal device 102 in the device-to-device communication, said data to the at least one second terminal device 101 directly or via at least one fourth terminal device with the at least one second relay identification, said broadcasting or multicasting further comprising control information related to data relaying and/or data processing in the at least one fourth terminal device and/or in the at least one second terminal device 101.

[0097] It is to be understood that the embodiments disclosed are not limited to the particular structures, process steps, or materials disclosed herein, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting.

[0098] Reference throughout this specification to one embodiment or an embodiment means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Where reference is made to a numerical value using a term such as, for example, about or substantially, the exact numerical value is also disclosed.

[0099] As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and examples may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations.

[00100] An apparatus, such as, for example, the first terminal device 100 or the third terminal device 102, may comprise means for carrying out the embodiments described above and any combination thereof.

[00101] A computer program may be configured to cause a method in accordance with the embodiments described above and any combination thereof. A computer program product, embodied on a non-transitory computer readable medium, may be configured to control a processor to perform a process comprising the embodiments described above and any combination thereof.

[00102] An apparatus, such as, for example, the first terminal device 100 or the third terminal device 102, may comprise at least one processor, and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to perform the embodiments described above and any combination thereof.

[00103] Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the preceding description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.

[00104] While the forgoing examples are illustrative of the principles of the embodiments in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as by the claims set forth below.

[00105] The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of "a" or "an", that is, a singular form, throughout this document does not exclude a plurality.

Claims

32 CLAIMS:

1. A method, comprising:

- determining, by a first terminal device, a need to transmit data to at least one second terminal device via at least one third terminal device in a device-to-device communication based on a quality class of said data and/or a radio link condition;

- determining, by the first terminal device, at least one first relay identification configured for relaying data in the device-to-device communication;

- transmitting, by the first terminal device, said data to the at least one third terminal device with the at least one first relay identification and control information related to data relaying and/or data processing in the at least one third terminal device and/or in the at least one second terminal device; and

- monitoring, by the first terminal device, broadcast and/or multicast transmission of the at least one third terminal device for detecting the relaying of said data based on at least one second relay identification configured for relaying data in the device-to- device communication, wherein said broadcast and/or multicast transmission comprises said data and the at least one second relay identification.

2. A method according to claim 1, wherein the at least one first relay identification indicates an intermediate hop in a multi-hop relaying scenario of the device-to-device communication.

3. A method according to claim 1 or claim 2, wherein the at least one first relay identification indicates at least one of the quality class of said data and an ordinal number of a hop in a multi-hop relaying scenario of the device-to-device communication and the method further comprises:

- determining, based on the at least one of the quality class of said data and the ordinal number of the hop, the at least one first relay identification from a set of relay identifications.

4. A method according to any of the preceding claims, wherein the control information comprises at least one of a destination identity of the at least one second terminal device, 33 the quality class of said data, a maximum number of hops in a multi-hop relaying scenario of the device-to-device communication, an ordinal number of a hop in a multi-hop relaying scenario of the device-to-device communication, a logical channel identifier of said data and a data identifier of said data.

5. A method according to any of the preceding claims, wherein the at least one second relay identification is different compared to the at least one first relay identification when the at least one first relay identification is hop-specific in case of multi-hop relaying, the at least one second relay identification is the same as the at least one first relay identification when the at least one first relay identification is common to all hops in case of multi-hop relaying or the at least one second relay identification is a destination identity of the at least one second terminal device when said transmission of the at least one third terminal device is for the last hop in in case of multi-hop relaying.

6. A method, comprising:

- receiving from at least one first terminal device, by a third terminal device, data with at least one first relay identification configured for relaying data in a device- to-device communication and control information related to data relaying and/or data processing in the third terminal device and/or in at least one second terminal device indicating a need to relay said data to the at least one second terminal device as a broadcast or a multicast in the device-to-device communication;

- determining, by the third terminal device, at least one second relay identification configured for relaying data in the device-to-device communication based on the at least one first relay identification and the control information received from the at least one first terminal device; and

- broadcasting or multicasting, by the third terminal device in the device-to-device communication, said data to the at least one second terminal device directly or via at least one fourth terminal device with the at least one second relay identification, said broadcasting or multicasting further comprising control information related to data relaying and/or data processing in the at least one fourth terminal device and/or in the at least one second terminal device.

7. A method according to claim 6, wherein the at least one first relay identification indicates an intermediate hop in a multi-hop relaying scenario.

8. A method according to claim 6 or claim 7, wherein the at least one first relay identification indicates at least one of a quality class of said data and an ordinal number of a hop in a multi-hop relaying scenario, and the method further comprises:

- determining, based on the at least one first relay identification, the at least one of the quality class of said data and the ordinal number of the hop in the multi-hop relaying scenario.

9. A method according to any of claims 6 to 8, wherein the control information comprises at least one of a destination identity of the at least one second terminal device, the quality class of said data, a maximum number of hops in a multi-hop relaying scenario of the device-to-device communication, an ordinal number of a hop in a multi-hop relaying scenario of the device-to-device communication, a logical channel identifier of said data and a data identifier of said data.

10. A method according to any of claims 6 to 9, wherein the at least one second relay identification is different compared to the at least one first relay identification when the at least one first relay identification is hop-specific in case of multi-hop relaying, the at least one second relay identification is the same as the at least one first relay identification when the at least one first relay identification is common to all hops in case of multi-hop relaying or the at least one second relay identification is a destination identity of the at least one second terminal device when said broadcasting or multicasting is for the last hop in case of multi-hop relaying.

11. An apparatus comprising at least one processing core, at least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processing core, cause the apparatus at least to perform:

- determine, by a first terminal device, a need to transmit data to at least one second terminal device via at least one third terminal device in a device-to-device communication based on a quality class of said data and/or a radio link condition;

- determine, by the first terminal device, at least one first relay identification configured for relaying data in the device-to-device communication; - transmit, by the first terminal device, said data to the at least one third terminal device with the at least one first relay identification and control information related to data relaying and/or data processing in the at least one third terminal device and/or in the at least one second terminal device; and

- monitor, by the first terminal device, broadcast and/or multicast transmission of the at least one third terminal device for detecting the relaying of said data based on at least one second relay identification configured for relaying data in the device-to- device communication, wherein said broadcast and/or multicast transmission comprises said data and the at least one second relay identification.

12. An apparatus according to claim 11, wherein the at least one first relay identification indicates an intermediate hop in a multi-hop relaying scenario of the device-to-device communication.

13. An apparatus according to claim 11 or claim 12, wherein the at least one first relay identification indicates at least one of the quality class of said data and an ordinal number of a hop in a multi-hop relaying scenario of the device-to-device communication and the the at least one memory and the computer program code are further configured to, with the at least one processing core, cause the apparatus at least to perform:

- determine, based on the at least one of the quality class of said data and the ordinal number of the hop, the at least one first relay identification from a set of relay identifications.

14. An apparatus according to any of claims 11 to 13, wherein the control information comprises at least one of a destination identity of the at least one second terminal device, the quality class of said data, a maximum number of hops in a multi-hop relaying scenario of the device-to-device communication, an ordinal number of a hop in a multi-hop relaying scenario of the device-to-device communication, a logical channel identifier of said data and a data identifier of said data.

15. An apparatus according to any of claims 11 to 14, wherein the at least one second relay identification is different compared to the at least one first relay identification when the at least one first relay identification is hop-specific in case of multi-hop relaying, the at least one second relay identification is the same as the at least one first relay identification when 36 the at least one first relay identification is common to all hops in case of multi-hop relaying or the at least one second relay identification is a destination identity of the at least one second terminal device when said transmission of the at least one third terminal device is for the last hop in in case of multi-hop relaying.

16. An apparatus comprising at least one processing core, at least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processing core, cause the apparatus at least to perform:

- receive from at least one first terminal device, by a third terminal device, data with at least one first relay identification configured for relaying data in the device-to- device communication and control information related to data relaying and/or data processing in the third terminal device and/or in at least one second terminal device indicating a need to relay said data to the at least one second terminal device as a broadcast or a multicast in a device-to-device communication;

- determine, by the third terminal device, at least one second relay identification configured for relaying data in the device-to-device communication based on the at least one first relay identification and the control information received from the at least one first terminal device; and

- broadcast or multicast, by the third terminal device in the device-to-device communication, said data to the at least one second terminal device directly or via at least one fourth terminal device with the at least one second relay identification, said broadcasting or multicasting further comprising control information related to data relaying and/or data processing in the at least one fourth terminal device and/or in the at least one second terminal device.

17. An apparatus according to claim 16, wherein the at least one first relay identification indicates an intermediate hop in a multi-hop relaying scenario.

18. An apparatus according to claim 16 or claim 17, wherein the at least one first relay identification indicates at least one of a quality class of said data and an ordinal number of a hop in a multi-hop relaying scenario, and the the at least one memory and the computer program code are further configured to, with the at least one processing core, cause the apparatus at least to perform: 37

- determine, based on the at least one first relay identification, the at least one of the quality class of said data and the ordinal number of the hop in the multi-hop relaying scenario.

19. An apparatus according to any of claims 16 to 18, wherein the control information comprises at least one of a destination identity of the at least one second terminal device, the quality class of said data, a maximum number of hops in a multi-hop relaying scenario of the device-to-device communication, an ordinal number of a hop in a multi-hop relaying scenario of the device-to-device communication, a logical channel identifier of said data and a data identifier of said data.

20. An apparatus according to any of claims 16 to 19, wherein the at least one second relay identification is different compared to the at least one first relay identification when the at least one first relay identification is hop-specific in case of multi-hop relaying, the at least one second relay identification is the same as the at least one first relay identification when the at least one first relay identification is common to all hops in case of multi-hop relaying or the at least one second relay identification is a destination identity of the at least one second terminal device when said broadcasting or multicasting is for the last hop in case of multi-hop relaying.

21. An apparatus comprising:

- means for determining, by a first terminal device, a need to transmit data to at least one second terminal device via at least one third terminal device in a device-to- device communication based on a quality class of said data and/or a radio link condition;

- means for determining, by the first terminal device, at least one first relay identification configured for relaying data in the device-to-device communication;

- means for transmitting, by the first terminal device, said data to the at least one third terminal device with the at least one first relay identification and control information related to data relaying and/or data processing in the at least one third terminal device and/or in the at least one second terminal device; and

- means for monitoring, by the first terminal device, broadcast and/or multicast transmission of the at least one third terminal device for detecting the relaying of said data based on at least one second relay identification configured for relaying data in the device-to-device communication, wherein said broadcast and/or multicast transmission comprises said data and the at least one second relay identification.

22. An apparatus according to claim 21, wherein the at least one first relay identification indicates an intermediate hop in a multi-hop relaying scenario of the device-to-device communication.

23. An apparatus according to claim 21 or claim 22, wherein the at least one first relay identification indicates at least one of the quality class of said data and an ordinal number of a hop in a multi-hop relaying scenario of the device-to-device communication and the the apparatus further comprises:

- means for determining, based on the at least one of the quality class of said data and the ordinal number of the hop, the at least one first relay identification from a set of relay identifications.

24. An apparatus according to any of claims 21 to 23, wherein the control information comprises at least one of a destination identity of the at least one second terminal device, the quality class of said data, a maximum number of hops in a multi-hop relaying scenario of the device-to-device communication, an ordinal number of a hop in a multi-hop relaying scenario of the device-to-device communication, a logical channel identifier of said data and a data identifier of said data.

25. An apparatus according to any of claims 21 to 24, wherein the at least one second relay identification is different compared to the at least one first relay identification when the at least one first relay identification is hop-specific in case of multi-hop relaying, the at least one second relay identification is the same as the at least one first relay identification when the at least one first relay identification is common to all hops in case of multi-hop relaying or the at least one second relay identification is a destination identity of the at least one second terminal device when said transmission of the at least one third terminal device is for the last hop in in case of multi-hop relaying.

26. An apparatus comprising: 39

- means for receiving from at least one first terminal device, by a third terminal device, data with at least one first relay identification configured for relaying data in the device-to-device communication and control information related to data relaying and/or data processing in the third terminal device and/or in at least one second terminal device indicating a need to relay said data to the at least one second terminal device as a broadcast or a multicast in a device-to-device communication;

- means for determining, by the third terminal device, at least one second relay identification configured for relaying data in the device-to-device communication based on the at least one first relay identification and the control information received from the at least one first terminal device; and

- means for broadcasting or multicasting, by the third terminal device in the device- to-device communication, said data to the at least one second terminal device directly or via at least one fourth terminal device with the at least one second relay identification, said broadcasting or multicasting further comprising control information related to data relaying and/or data processing in the at least one fourth terminal device and/or in the at least one second terminal device.

27. An apparatus according to claim 26, wherein the at least one first relay identification indicates an intermediate hop in a multi-hop relaying scenario.

28. An apparatus according to claim 26 or claim 27, wherein the at least one first relay identification indicates at least one of a quality class of said data and an ordinal number of a hop in a multi-hop relaying scenario, and the apparatus further comprises:

- means for determining, based on the at least one first relay identification, the at least one of the quality class of said data and the ordinal number of the hop in the multi-hop relaying scenario.

29. An apparatus according to any of claims 26 to 28, wherein the control information comprises at least one of a destination identity of the at least one second terminal device, the quality class of said data, a maximum number of hops in a multi-hop relaying scenario of the device-to-device communication, an ordinal number of a hop in a multi-hop relaying 40 scenario of the device-to-device communication, a logical channel identifier of said data and a data identifier of said data.

30. An apparatus according to any of claims 26 to 29, wherein the at least one second relay identification is different compared to the at least one first relay identification when the at least one first relay identification is hop-specific in case of multi-hop relaying, the at least one second relay identification is the same as the at least one first relay identification when the at least one first relay identification is common to all hops in case of multi-hop relaying or the at least one second relay identification is a destination identity of the at least one second terminal device when said broadcasting or multicasting is for the last hop in case of multi-hop relaying.

31. A computer program comprising instructions which, when the program is executed by an apparatus, cause the apparatus to carry out the method of any previous claim 1 to 10.