WO2019101343A1

WO2019101343A1 - Neighbor relation update for self-backhauling

Info

Publication number: WO2019101343A1
Application number: PCT/EP2017/080527
Authority: WO
Inventors: Ilkka Keskitalo; Esa Tiirola; Juha Korhonen
Original assignee: Nokia Technologies Oy
Current assignee: Nokia Technologies Oy
Priority date: 2017-11-27
Filing date: 2017-11-27
Publication date: 2019-05-31
Anticipated expiration: 2020-05-27

Abstract

According to an aspect, a method for establishing a neighbor relation for a relay node is provided. In the method, a relay node maintains a first list comprising information on network nodes with which the relay node is able to form a backhauling link. In response to receiving a first indication message comprising information on a second network node in a neighbor relation with the first network node from a serving network node of the relay node, the relay node performs measurements on pre-defined signals transmitted by the second network node to determine whether the second network node is usable for backhauling. In response to determining that the second network node is usable for backhauling, the relay node causes establishing a connection to the relay node. Upon establishing the connection, the relay node adds the information on the second network node to the first list.

Description

NEIGHBOR RELATION UPDATE FOR SELF-BACKHAULING

TECHN1CAL F1ELD

The invention relates to communications.

BACKGROUND

The following description of background art may include insights, dis coveries, understandings or disclosures, or associations together with disclosures not known to the relevant art prior to the present invention but provided by the invention. Some such contributions of the invention may be specifically pointed out below, whereas other such contributions of the invention will be apparent from their context.

The fifth generation cellular systems (5G) aim to improve the through put by a huge factor (even up to 1000 or more), which provides a multitude of challenges, especially considering the scarcity of spectrum at low frequency bands and the need for supporting a very diverse set of use cases ln order to reach this goal, it is important to exploit the higher frequencies such as millimeter wave frequencies in addition to the more conventional lower frequencies. To meet the demands of 5G systems, a new, globally standardized radio access tech nology known as New Radio (NR) has been proposed. One proposed feature of the New Radio technology is the support for wireless self-backhauling using relaying nodes (RN) enabling flexible and very dense deployment of cells without the need for densifying the transport network proportionately ln self-backhauling, the same carrier is used for backhaul connections and access links. As deterioration of any wireless self-backhauling link likely has a negative effect on the service quality of multiple user equipment, it is critical to make sure that at least one self- backhauling link providing high quality connection is available for backhauling at all times. A solution for this problem is needed before 5G New Radio systems may be deployed.

BRIEF DESCRIPTION

According to an aspect, there is provided the subject matter of the in dependent claims. Embodiments are defined in the dependent claims. One or more examples of implementations are set forth in more detail in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims.

BR1EF DESCRIPTION OF DRAW1NGS

ln the following, exemplary embodiments will be described with refer ence to the attached drawings, in which

Figures 1 and 2 illustrate wireless communication scenarios to which embodiments of the invention may be applied;

Figures 3 to 7 illustrate processes according to embodiments of the in vention; and

Figures 8 to 9 illustrate apparatuses according to embodiments of the invention.

DETA1LED DESCRIPTION OF SOME EMBOD1MENTS

The following embodiments are exemplary. Although the specification may refer to "an", "one", or "some" embodiment(s) in several locations, this does not necessarily mean that each such reference is to the same embodiment(s), or that the feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments.

Embodiments described may be implemented in a radio system, such as in at least one of the following: Worldwide lnteroperability for Microwave Ac cess (WiMAX), Global System for Mobile communications (GSM, 2G), GSM EDGE radio access Network (GERAN), General Packet Radio Service (GRPS), Universal Mobile Telecommunications System (UMTS, 3G) based on basic wideband-code division multiple access (W-CDMA), high-speed packet access (HSPA), Long Term Evolution (LTE), LTE-Advanced, a system based on 1EEE 802.11 specifications, a system based on 1EEE 802.15 specifications, and/or a fifth generation (5G), and beyond, mobile or cellular communication system.

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 commu nication systems provided with necessary properties. One example of a suitable communications system is the 5G system, as listed above. 5G has been envisaged to use multiple-input-multiple-output (MIMO) multi-antenna transmission tech niques, more base stations or nodes than the current network deployments of LTE, by using a so-called small cell concept including macro sites operating in co- operation with smaller local area access nodes and perhaps also employing a vari ety of radio technologies for better coverage and enhanced data rates. 5G will likely be comprised of more than one radio access technology (RAT), each opti mized for certain use cases and/or spectrum. 5G system may also incorporate both cellular (3GPP) and non-cellular (for example 1EEE) technologies. 5G mobile communications will have a wider range of use cases and related applications in cluding video streaming, augmented reality, different ways of data sharing and various forms of machine type applications, including vehicular safety, different sensors and real-time control. 5G is expected to have multiple radio interfaces, in cluding apart from earlier deployed frequencies below 6 GHz, also higher, that is cmWave and mmWave frequencies, and also being capable of integrating with ex isting legacy radio access technologies, such as the LTE. This is achieved by means of a scalable radio interface supporting variable numerologies based on power of two scaling of 15 kHz subcarrier spacing used in LTE. lntegration with the LTE may be implemented, at least in the early phase, as a system, where macro cover- age is provided by the LTE and 5G radio interface access comes from small cells by aggregation to the LTE. ln other words, 5G is planned to support both inter- RAT operability (such as LTE-5G) and inter-Rl operability (inter-radio interface operability, such as inter-Rl operability between cmWave and 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. Self-backhauling may be seen as one network slice in at least some foreseen scenarios.

lt should be appreciated that future networks will most probably uti- lize network functions virtualization (NFV) which is a network architecture con cept that proposes virtualizing network node functions into "building blocks" or entities that may be operationally connected or linked together to provide ser vices. A virtualized network function (VNF) may comprise, in addition to standard high-volume servers, switches and storage devices, one or more virtual machines running computer program codes using standard or general type servers instead of customized hardware. Cloud computing or cloud data storage may also be uti lized. ln radio communications, this may mean that node operations are carried out, at least partly, in a server, host or node operationally coupled to a remote ra dio head lt is also possible that node operations will be distributed among a plu rality of servers, nodes or hosts lt should also be understood that the distribution of labor between core network operations and base station operations may differ from that of the LTE or even be non-existent. Some other technology advance ments probably to be used are Software-Defined Networking (SDN), Big Data, and all-lP, which may change the way networks are being constructed and managed.

One suggested feature of the future 5G communications systems is the so-called 5G New Radio. 5G New Radio refers to a new global 5G standard for an orthogonal frequency-division multiplexing (OFDM) -based air interface designed to fit the more stringent requirements of the 5G systems (for example, providing different types of services to a huge number of different types of devices operat ing over a wide frequency spectrum). The 5G New Radio shall be able to allow network deployment with minimized manual efforts and as automated self-con- figuration as possible. Especially on higher frequency bands the coverage will be an issue and specific capabilities are needed for New Radio to enable easy cover age extension with minimized/none requirements for network (re-)planning in a fast and cost-efficient manner. One of the features proposed for 5G New Radio in order to reach said requirements is wireless backhauling using relay links. The re lay links used for wireless backhauling may operate at different frequency bands compared to the access links of the network or at the same frequency band. The latter scenario, that is, backhauling using the same wireless channel or band as used by the access links, is called self-backhauling and has been specifically tar- geted for 5G systems. While self-backhauling has been proposed as one of the key technologies to enable small-cell densification in 5G systems, realizing a system utilizing self-backhauling at millimeter waves is challenging as complex schedul ing with fast switching is required between the access and backhauling links in order to avoid deterioration of the access and/or backhauling signal due to inter ference and to avoid short-term blocking, typical when using millimeter waves in handover scenarios. The considered self-backhauling scenarios include both fre quency division duplex (FDD) and time division duplex (TDD). However, is ex pected that TDD scenarios are more important in the commercial deployments. Another common assumption for relay nodes in TDD scenario is that a relay node cannot transmit and receive at the same time at least towards the same direction. This is called the half-duplex constraint. There are also relay scenarios following a full duplex assumption ln these cases, a relay node may transmit and receive at the same time on the same frequency band.

Figure 1 illustrates an example of a communications system 100 to which some embodiments of the invention may be applied. The communications system 100 may be a wireless communication system composed of one or more radio access networks of access nodes 110, 130, each providing and controlling a respective cell or cells 115, 135. From another point of view, the cell 115, 135 may define a coverage area or a service area of the access node. The Cells 115,

135 may comprise, for example, one or more macro cells and/or one or more small cells (micro, femto, or pico cells). The access nodes 110, 130 may be con nected via radio connections to the terminal devices 101. This link is called an ac cess link. Moreover, the access nodes 110, 130 may provide one or more terminal devices 101 (user equipment, UEs) with wireless access to other networks such as the lnternet, either directly or via a core network as illustrated by the connec- tion 151. Each access node 110, 130 may be connected to said other networks in a wired manner (e.g., using an optical fiber). The access node may equally be called a base station. The serving access node and the cell of the serving access node may be equivalently called a donor access node and a donor cell, respectively, when the serving node has a wired backhaul connection.

Each of the access nodes 110, 130 may be an evolved Node B (eNB) as in the LTE and LTE-A, a next generation node B (gNB), like in 5G, an access point of an 1EEE 802.11-based network (Wi-Fi or wireless local area network, WLAN), a radio network controller (RNC) as in the UMTS, a base station controller (BSC) as in the GSM/GERAN, Access Point (AP), or any other apparatus capable of control ling wireless communication and managing wireless resources within a cell. Typi- cally the wireless communication is radio communication. For 5G solutions, the implementation may be similar to LTE-A, as described above.

The system 100 may further comprise one or more relay nodes 120, 140 each providing and controlling a respective cell or cells 125, 145. The cells 125, 145 may defined similar to as discussed for the cells 115, 135 of the access nodes 110, 130. ln contrast to the access nodes 110, 130, while one or more ter minal devices 102, 103 may be able to establish communication links (access links) 152, 153 with one or more relay nodes 120, 140, the one or more relay nodes 120, 140 may not be able to provide access directly via a wired connection for said one or more terminal devices 101, 102 to the core network (i.e., enable backhauling). lnstead, the relay nodes 120, 140 have to relay the traffic (via back haul links) to one of the access nodes 110, 130 (so-called serving access node) in order to provide said access and further possible further access via the core net work to other networks such as the lnternet for any terminal devices 102, 103 within the cell of a relay node 120, 140. ln other words, the relay nodes 120, 140 may need to utilize wireless backhauling.

The wireless backhauling for a given relay nodes 120, 140 may be achieved with a single backhauling link, for example, using the backhauling link 154. On the other hand, in multi-hop deployment scenarios, two or more separate backhauling links or two or more "hops" (links 154, 156) may be needed in order to provide the access to network services for the terminal device. For example, the relay node 140 may be located in such a location that sufficiently high signal level for a backhauling link may not be achievable, at least in a dependable man ner, if only direct backhauling links between the relay node 140 and the access nodes 110, 130 are considered. Therefore, the best option for providing access for the terminal device 103 located within the cell of the relay node 140 may be to re lay the backhauling traffic via the relay node 120 (acting as serving relay node) to the access node 110 using the backhauling links 154, 156 and the radio access link 153.

The wireless backhauling may be transparent to the terminal device, that is, the terminal device 101, 102 may not be able to distinguish between an ac- cess node and a relay node ln such case, conventional radio resource manage ment (RRM) operations (e.g., mobility with handovers) may be applied and a sin gle relay node may form one or multiple cells. Transparent operation may also be achieved so that the relay node operates as a transmitter/receiver point (Tx/Rx point, TRP) within a cell of an access node. Moreover, the wireless backhauling using the relay nodes 120, 140 may be self-backhauling.

ln the communications system 100, the access nodes 110, 130 and the relay nodes 120, 140 may be connected to each other via links 154, 155, 156, 157. Specifically, in Figure 1 solid lines are used to denote active backhauling links 154, 156 and dashed line are used to denote available but currently non-active links 157 or links between two access nodes 155 (e.g., an Xn connection).

Figure 2 illustrates a communications system 200 comprising at least two access nodes 210, 230 and two relay nodes 220, 240 and interfaces between them. The communications system 200 may be the communications system 100 of Figure 1, the access node 210, 230 corresponding to the access nodes 110, 130 and the relay nodes 220, 240 corresponding to the relay nodes 120, 140. The ac cess nodes 210, 230 may comprise at least two units 211, 212, 231, 232, each con figured to provide different logical functionalities and corresponding to at least one interface 201, 202, 203, 204, 205. The functionality 211, 231 may, for exam ple, provide the access node 210, 230 connectivity with other access nodes 210, 1230 and relay nodes 220 over the network interface 203, 204, 205. The function ality 212, 232 may, for example, provide the access node 210, 230 over-the-air connectivity to terminal devices and relay nodes over the air interface 201, 202. ln other embodiments, the access node may comprise a single unit with at least all of the aforementioned functionalities and any other conventional access node functionalities. The relay node 220, 240 may comprise a relay unit 221, 241 config ured to take care of the communication with the donor cell (i.e., the donor access node) or another relay cell over the radio interface 201, 202 and an access unit 222, 242 having all access node functions for serving the terminal devices in the cell of the relay node and connecting to other relay or access nodes over the inter face 204, 205, 207. Though not explicitly shown in Figure 2, logical connections between the elements 242 and 211 as well as elements 242 and 231 may also ex ist. The relay unit 221, 241 may be, for example, configured to

• select and access the best cell (i.e., the best access node) and estab lish the backhauling connection and/or

• monitor the cell/beam(s) of the relay node and re-select the

cell/beam(s) if there is a change in the radio connections, i.e., per form beam measurements/selection, cell evaluation and triggering handovers.

ln Figure 2, the relay node 220 and specifically the relay unit 221 may have estab lished a backhauling link 202 with the access node 110. Further, the relay unit 220 may have detected also the access node 230 and determined it as a candidate for backhauling so that the relay unit 221 may switch to use the backhauling con nection 201 and the access node 230 if the backhauling connection 202 fails or deteriorates, for example, due to radio blocking (e.g., obstacles moving between the nodes and/or excessive interference). As discussed in relation to Figure 1, the relay node 240 may be using multi-hop backhauling via the relay node 220.

The access unit 222, 242 may be, for example, configured to

• perform relay node cell broadcasting such as transmitting synchro nization signals (SSB) and/or system information (Sl), and/or pag ing,

• control connections of the terminal devices in the cell of the relay node,

• act as a serving network node for the following relay node in case of multi-hop relaying (e.g., the access unit 242 acting as a serving network node for the relay node 220 for which no direct backhaul- ing link is available),

• communicate with the other access nodes and/or relay nodes over the non-backhauling interfaces 203, 204, 207 and/or

• connect to the core network (not shown in Figure 2).

The relay unit 221, 241 and the access unit 222, 242 of the same relay node 220, 240 may be connected to each other via at least one interface (not shown in Fig ure 2) so that information received by the access unit 222, 242 may be forwarded to the relay unit 221, 242 and vice versa.

ln some embodiments, the communications system 100 is a 5G com munications system, the one or more access nodes 210, 230 are gNBs (New Radio access nodes capable of interfacing with a 5G core network), the interfaces 203, 204, 205, 207 are Xn interfaces and the interfaces 201, 202 are Uu interfaces (UMTS air interfaces). The Xn interface 204 between the relay node 220 and the donor gNB 210, 230 or other relay nodes may go physically over the Uu interface among other data or signaling, but otherwise the same Xn signaling and proce dures between the relay nodes /gNBs may be supported ln some embodiments, one or more of the one or more access nodes 210, 230 may be eLTE eNBs

(evolved NodeBs capable of interfacing with the EPC and 5G core network) , in stead of gNBs.

The communications systems 100, 200 as illustrated in Figures 1 and 2 may be capable of self-backhauling using the one or more relay nodes 120, 140, 220, 240. ln order for the self-backhauling to be a dependable option for back- hauling, a control mechanism for the self-backhauling should be set up so that the relay node would react to any deterioration of the wireless backhauling link with out delay providing an alternative, working backhauling link. Such fast switching is especially critical in backhauling as the deterioration or failure of the backhaul ing link has an effect on the service quality of all terminal devices in the cell of the relay node as well as, in case of multi-hop deployment, the connection over an other backhaul hop to the following relay node ldeally, the relay node should at all times be connected to the best possible donor cell (or "upstream" relay node in multi-hop case) to maintain the normal operation in the cell of the relay node.

The relay node should have up-to-date information about alternative connections in case the active backhauling link(s) fail and the backhauling link should be switched to the best available backhauling link. As the relay nodes are stationary, the need for switching the backhauling link is predominantly due to changes in the environment, e.g., some obstacle(s) moving to block the line-of- sight (LOS) path of the backhauling link (so-called shadowing or shadow fading). The attenuation of the transmitted signal due to slow fading (including shadow fading) is often especially pronounced when operating at millimeter wave fre- quencies. Despite the static nature of the backhauling connections, the changes in the radio connection may be fast.

To be able to have fast recovery for any wireless backhauling connec tion failure, the relevant information about the candidate links (i.e., backhauling links available for a relay node) should be collected while the connection is good over a backhauling link. Network deployment may also change and new neigh bors, either access nodes (with wired connection) or other relay nodes, may emerge and old ones may be closed. The relay node should become aware of such changes with minimized efforts and impact on the backhauling and access link communication.

Figure 3 illustrates a process according to an embodiment for evaluat ing a newly deployed candidate access node for backhauling and thus providing means for maintaining information on candidate network nodes for backhauling. The illustrated process may be performed by the relay node 120, 220 or the relay node 140, 240 of Figure 1 or 2. lt is assumed that the relay node has in the begin- ning of the illustrated process already been powered-up for some time so that the initial power-up process has finished ln the initial power-up process, the relay node may have scanned frequencies to detect and select one or more suitable cells (network nodes) which to monitor for changes in the radio propagation en vironment or topology. Further, it is assumed that the relay node has already formed a neighbor relation at least with a first network node which acts as the serving network node for the relay node. Referring to Figure 3, a relay node in a communications system main tains, in block 301, a first list which comprises information on one or more net work nodes with which the relay node has established a neighbor relation and is thus able to form a backhauling link. The backhauling link may be a link between the relay node and an access node or a link between the relay node and another relay node in multi-hop backhauling. Moreover, the term "network node" as used here and in the following may comprise an access node or a relay node. The one or more network nodes in the first list may comprise at least a first network node acting as a serving network node for the relay node in a first backhauling link. The relay node receives, in block 302, a first indication message from the first network node. The first indication message may comprise at least information on a second network node in a neighbor relation with the first network node. The first indica tion message may be an existing message to which additional information con cerning the second network node has been added or it may be a new type of mes- sage, specific to this purpose. The information on the second network node may comprise relevant information about the cell, e.g., a physical cell identifier (PCI), and/or a global cell identifier (ID).

The relay node performs, in block 303, measurements on pre-defined signals transmitted by the second network node to determine whether the second network node is usable by the relay node for backhauling. lt may not only be de termined whether a backhauling link may be established, but also whether such a backhauling link meets certain criteria relating to, e.g., signal quality, signal strength and/or dependability. For example, the determining whether the second network node is usable by the relay node for backhauling may comprise deter- mining based on the measurements whether a metric for signal quality and/or signal strength exceeds a pre-defined threshold value for a link between the relay node and the second network node ln some embodiments, further information on the second network node may be received in the pre-defined signals.

The pre-defined signals transmitted by the second network node may be, for example, synchronization signal (SS) blocks. The SS blocks may contain in addition to primary and secondary synchronization signals, a physical broadcast channel (PBCH) which contains among other parameters, frequency and time lo cation of the control resource set used to schedule remaining minimum system information (RMSI) transmitted on physical downlink shared channel (PDSCH). The second network node may transmit SS burst sets with certain periodicity, where each burst set may consist of one or more SS blocks transmitted in the pre defined time domain positions within a certain time window (e.g., 5 ms). Alterna tively or in addition, the pre-defined signals may be beam-specific channel state information reference signals (CS1-RS). Moreover, the first indication message may comprise relevant parameters about the second network node and the corre- sponding cell which may be employed to speed up the measurement procedure. The parameters may include, e.g., the periodicity and time and frequency domain position of the pre-defined signals.

lf the second network node is determined, in block 304, to be usable for backhauling, the relay node causes, in block 305, establishing a connection to the second network node based on the information on the second network node. The connection may be, for example, a radio connection or a connection between access nodes such as an Xn connection. Consequently, the relay node adds, in block 306, the information on the second network node to the first list. Thus, a neighbor relation is established between the relay node and the second access node meaning that the relay node may consider the second network node as a candidate node for backhauling, in case the connection with the first network node is lost or can no longer provide sufficient connection quality.

Figure 4 illustrates a process according to an embodiment for inform ing a relay node of a candidate network node for backhauling. The illustrated pro- cess corresponds to a process performed by the first network node to initiate the process of Figure 3. The process may be performed, for example, by the access node 110, 220 or the access node 130, 230 serving the relay node 120, 220 or the relay node 120, 220 serving the relay node 140, 240 of Figure 1 or 2.

Referring to Figure 4, the first network node acting as a serving net- work node for a relay node in a first backhauling link in a communications system establishes, in block 401, a neighbor relation with a second network node. The neighbor relation may be established using any known automated neighbor rela tion (ANR) scheme ln response to the establishing, the first network node causes, in block 402, sending a first indication message to the relay node. The first indica tion message comprises at least information on the second network node. The in- formation on the second network node and further information comprised in the first indication message were described in detail in relation to Figure 3. The same discussion applies also here and will therefore not be repeated for brevity.

ln some embodiments where the first network node is a second relay node in multi-hop deployment, the establishing, in block 401, may be performed by performing the process illustrated in Figure 7. Said process will be discussed later in detail.

Figure 5 is a signaling diagram illustrating the process of setting up a new neighbor relation between a relay node and a second network node, said neighbor relation enabling future establishing of a backhauling connection be- tween the relay node and the second network node. The processes illustrated in Figure 5 are for the most part similar to processes of the embodiments illustrated in Figures 3 and 4 though some additional features are included in Figure 5. Most notably, the relay node is defined to comprise a relay unit and an access unit and processes and signaling are presented separately for the two units. The relay unit and the access unit may be defined as discussed in relation to Figure 2. The relay unit, the first network node (serving network node for the relay node) and the second network node (a newly deployed network node) of Figure 5 may corre spond to the relay node 120, 220, the access node 110, 210 and the access node 120, 220 of Figure 1 or 2, respectively. Furthermore, the signaling between the re- lay unit and the access unit of the relay node, the first network node and the sec ond network node may be achieved using the corresponding interfaces between given nodes/units as described in relation to Figure 2. The process is described in the following with an emphasis on the differences to the earlier embodiments.

Any definitions of processes and messages are to be assumed to correspond to the earlier embodiments unless otherwise stated.

Referring to Figure 5, the relay node maintains, in block 501, a first list similar to Figure 3, but in contrast to Figures 4, also the first network node main tains, in block 502, one or more lists ln the relay node, either the relay unit or the access unit or both the relay unit and the access unit may maintain the first list. The first list may be defined as discussed in relation to Figure 3. The one or more list of the first network node may, for example, comprise one or more first lists, each comprising information on one or more network nodes with which a relay node served by the first network node is able to form a backhauling link ln other words, the first network node may maintain lists corresponding to the first lists maintained by the relay nodes it is serving. Each of the one or more first lists may have been created when a corresponding backhauling link was established ln some embodiments, one or more first lists may also comprise first lists for relay nodes which have established a neighbor relation with the first network node but are not currently in a backhauling connection with the first network node. Fur thermore, the one or more lists of the first network node may comprise a second list. The second list is defined, for the first network node as comprising infor mation on one or more network nodes with which the first network node has es tablished a neighbor relation lnitially, the second list may comprise at least the relay node served by the first network node. A backhauling link (messages 503) is established between the relay unit of the relay node and the first network node. The data transfer via the backhauling link may occur during the execution of the process in parallel. The information for each network node stored to the first and second lists may comprise relevant information about the cell, e.g., a PC1, and/or a global cell 1D. The first and/or second lists may also comprise information on the type of network node (e.g., an access node or a relay node).

Similar to step 401 of Figure 4, a neighbor relation is established, in block 504, between the first network node and the second network node. The sec ond list maintained by the first network node may be updated, in block 505, by the first network node in response to the establishing or as a part of the establish ing process. The updating may comprise adding information on the network node with which the neighbor relation was established to the second list. Once the neighbor relation has been established, the first network node causes sending a first indication message (message 506) to the access unit of the relay node, simi lar to block 402 of Figure 4. Alternatively, the indication can be sent over Uu in terface, using, for example, radio resource control (RRC) signaling, to the relay unit (not shown in the Fig.5) including relevant information about the second net- work node. The indication may be, for example, in a form of a bitmap for the SSB blocks that the relay unit may measure where the bitmap may include SSB blocks sent by a new or newly detected network node.

Upon receiving, in block 507, the first indication message, the access unit forwards (or transfers or shares), in message 508, the information comprised in the first indication message to the relay unit of the relay node and the relay unit receives, in block 509, said information. The forwarding is not needed with the alternative where the indication is sent via RRC signaling directly to the relay unit of the relay node. The second network node causes sending pre-defined sig nals (messages 510, e.g., SSBs) which are measurable by the relay node. The word "measurable" should be understood here as meaning that the relay node is able to measure said pre-defined signals as long as the signal level is sufficiently high.

The relay unit of the relay node, then, performs, in block 511, measurements on the pre-defined signals lt is assumed in this example that the second network node is capable of providing a high-quality backhauling connection. Therefore, the relay unit of the relay node determines, in block 512, the second network node based on the measurements that the second network node is a suitable can didate for backhauling (as described in detail in relation to Figure 3). The relay unit forwards (or transfers or shares), in block 513, a second indication message that the second network node is usable for backhauling to the access unit which, then, causes sending, in message 514, a request for a neighbor relation. The re quest may comprise information on the relay node (e.g., a PC1 and/or a global cell 1D). Upon receiving, in block 515, the request, the second network node causes sending, in message 516, an acknowledgment which is received, in block 517, by the access unit of the relay node. The relay unit and/or the access unit also adds, in block 517, information on the second network node to the first list.

ln some embodiments, in order to provide up-to-date information also for the first network node, the access unit of the relay node may cause sending, in message 518, information on the new neighbor relation to the first network node. Upon receiving, in block 519, the information, the first network node may update, in block 519, the one or more lists based on the information. The first network node may update at least the first list relating to the relay node maintained in the first network node to match the first list maintained in the relay node itself ln other embodiments, said updating may be an independent process from the pro cess of Figure 5.

ln some embodiments, the first network node may, in response to the receiving the information in message 518, cause, in block 519, sending instruc tions to perform measurements on pre-defined signals to at least one relay node in the second list (excluding the relay node illustrated in Figure 5) to determine whether the second network node is usable by the at least one relay node for backhauling.

ln embodiments where the access unit of the relay node and the sec ond network node are connected using an Xn interface, the request message 514 and the acknowledgment message 516 may be XN SETUP REQUEST and XN SETUP RESPONSE messages, respectively.

Figure 6 illustrates an alternative process according to an embodiment for evaluating a newly deployed candidate access node for backhauling and thus providing means for maintaining information on candidate network nodes for backhauling. The illustrated process may be performed by the relay node 120,

220 or the relay node 140, 240 of Figure 1 or 2. The process is, for the most part, similar to the process of Figure 3. Namely, blocks 601, 602, 605, 606, 609 of Fig- ure 6 correspond to blocks 301, 302, 303, 304, 306of Figure 3. The discussion re lated to said blocks will, thus, not be repeated here for brevity.

Three additional features (illustrated by blocks 603, 604, 611) exist in the embodiment illustrated in Figure 6 not discussed in relation to the embodi ments illustrated Figure 3 and Figure 5. Firstly, once the first indication message is received, in block 602, the measurements of the pre-defined signals are not ini tiated directly lnstead, the relay node first establishes, in block 603, a connection between the relay node and the second network node. 6Consequently, in block 604, the relay node receives, in block 604, information about the pre-defined sig nal transmission for measurement by the relay node from the second network node via the connection ln embodiments where the relay node comprises a relay unit and an access unit, the connection may be established specifically between the access unit of the relay node and the second network node, for example, using an Xn interface. Finally, if it is determined, in block 606, that the second network node is not usable for backhauling or an acknowledgment is not received, in block 608, from the second network node (e.g., within a certain time frame) or a nega- tive acknowledgment is received, in block 608, from the second network node, the relay node (or specifically the access unit of the relay node) releases, in block 611, the connection lf no backhauling handovers are possible between the relay node and the second network node, such a connection is not necessary and may, thus, be released without consequences ln blocks 607 and 608, the relay node may confirm the connection to the second network node, if the connection was al ready established in block 603. Alternatively, if the block does not include a com plete signaling connection establishment, for example, Xn setup, the establish ment may be performed in blocks 607 and 608. ln a successful connection estab lishment with an acknowledgement received from the second node, the relay node and the second network node may update their lists of neighbor relations and the process may start again.

ln some alternative embodiments, features of embodiments of Figure 3, 5 and/or 6 may be combined. For example, in an embodiment blocks 603, 604 may be omitted (as in Figures 3 and 5), but the establishing the connection after the second network node is determined to be usable for backhauling (i.e., block 305) may be performed according to blocks 607, 608 of Figure 6. ln such an em bodiment, block 610 may also be omitted as no connection may have been estab lished at that point.

Once at least one network node other than the serving network node has been added to the first list (i.e., has established a neighbor relation with the relay node), the relay node is able to switch its serving network node if necessary, for example, in case the current backhauling connection fails. An exemplary pro cess according to an embodiment for said switching is illustrated in Figure 7. The illustrated process may be performed by, for example, the relay node 120, 220 or the relay node 140, 240 of Figure 1 or 2.

Referring to Figure 7, the illustrated exemplary process is initiated af ter performing block 306 of Figure 3 or block 609 of Figure 6, that is, after the first list is updated with a new network node (a second network node) capable of backhauling with the relay node. As in Figures 3 and 6 the relay node was already initially in a backhauling connection with another network node (first network node), the first list of the relay node comprises information on at least two net work nodes which the relay node may use for backhauling. lt should, however, be appreciated that the process of Figure 7 may also be performed before or after any of the other steps (blocks) in Figure 3 or 6 as long as there are multiple net work nodes comprised in the first list.

The relay node determines, in block 701, whether the signal quality or the signal strength of the first backhauling link between the relay node and the first network node has fallen below a first pre-defined threshold level. The signal quality of the backhauling link may be evaluated using any known metric for sig nal quality, for example, signal-to-noise ratio or bit-error-rate. The signal strength of the backhauling link may, in turn, be evaluated, for example, simply using the magnitude or power of the received signal at the relay node as the metric for eval uation. lf the quality of the first backhauling link is determined to have fallen be low an acceptable level, the relay node selects, in block 702, another network node for backhauling from the first list and triggers, in block 703, a change of the backhauling connection from the first backhauling link to the second backhauling link between the relay node and a selected network node acting as the new serv ing network node. The new backhauling network node may be selected for the second backhauling link from the first list based on signal quality and/or signal strength (as defined above) lt should be noted that the metric for the determin- ing in block 701 and the metric for the selecting in 702 may, however, be differ ent. As the first list may comprise information on both access nodes and relay nodes, the selection may take the type of the network node also into account, for example, so that access nodes are always preferred in the selecting over the relay nodes. After block 703, the process of Figure 3 or 6 proceeds as usual, that is, the process restarts by going back to block 301 or 601.

ln some embodiments, the relay node may remove the first network node from the first list after the failure of the first backhauling link is detected (in block 701). The removing may be performed, for example, in block 703. ln other embodiments, a second pre-defined threshold level may be defined for the re moval of the first network node ln such embodiments, the relay node may deter- mine, in block 701, whether the signal quality or the signal strength of the first backhauling link between the relay node and the first network node has fallen be low a first pre-defined threshold level and whether it has fallen below a second pre-defined threshold level (preferably lower than the first pre-defined threshold level). The relay node may remove (e.g., in block 703) the first network node from the first list only if the signal quality or the signal strength has fallen below the second pre-defined threshold level.

As described above, the presented processes may be applied also in multi-hop relaying scenario (in multi-hop deployment) where, for example in re laying with two "hops", an access node acts as a serving access node for a first re- lay node which, in turn, acts as a serving relay node for a second relay node. For instance, the uplink backhauling traffic is, thus, relayed first from the second relay node to the first relay node and then from the first relay node to the access node which is able to connect directly (via a wired connection) to the core network. On the other hand, the downlink backhauling traffic from the core network is re- ceived via a wired connection in the access node and relayed first from the access node to the first relay node and then from the first relay node to the second relay node. Obviously, longer multi-hop chains are also possible ln principle, there is no limit to the number of "hops" though in practice the connection with the few est "hops" usually results in the best backhauling performance ln multi-hop sce- narios, the relay node may act as a relay node to be served (i.e., performing pro cesses of Figures 3, 6 and/or 7 and processes of the relay node in Figure 5), as a serving network node (i.e., performing a process of Figure 4 and processes of the first network node in Figure 5) and/or as a newly-deployed network node (i.e., performing processes of the second network node in Figure 5) simultaneously ln such a case, the first list of the relay node and the second list of the relay node (i.e., the first or second network node) as described above are the same and thus only one list may be maintained. Alternatively, two lists may be maintained so that the first list comprises information on backhauling-usable network nodes and the second list comprises information on all neighboring network nodes (even those unusable for backhauling). Moreover, the lists maintained by an ac- cess node or a relay node in multi-hop scenarios (i.e., multi-hop deployment) may also comprise information on the access nodes and/or relay nodes "up the chain" or "down the chain" from the access node or the relay node. Specifically, the first lists may comprise information on how many "hops" are needed for the backhaul ing. ln some embodiments, the relay node may be configured to select in block 702 primarily an access node, secondarily a one-hop relay node, tertiarily a two- hop relay node and so on. ln other embodiments, the selection may be based on both the number of hops and the signal quality and/or strength.

The blocks, related functions, and information exchanges described above by means of Figures 3 to 7 are in no absolute chronological order, and some of them may be performed simultaneously or in an order differing from the given one. ln some embodiments, some of the steps may be neglected, for example, if the relevant information is already available (e.g., stored to a memory).

Figure 8 illustrates an apparatus 801 configured to carry out the func tions described above in connection with any relay node (serving or being served) such as relay nodes 120, 140 indicated in Figure 1 or relay nodes 220,

240 indicated in Figure 2. The apparatus may be an electronic device comprising electronic circuitries. The apparatus may be a separate network entity or a plural ity of separate entities. The apparatus may comprise a communication control cir cuitry 820, such as at least one processor, and at least one memory 830 including a computer program code (software) 831 wherein the at least one memory and the computer program code (software) are configured, with the at least one pro cessor, to cause the apparatus to carry out any one of the embodiments of the re lay node described above.

The memory 830 may comprise a database 832 which may comprise at least one or more first lists and/or a second list, as described in previous em bodiments. The database 832 may further comprise a set of measurement results relating to measurements of pre-defined signal (as performed, e.g., in block 303 of Figure 3, block 511 of Figure 5 and block 605 of Figure 6) and/or one or more threshold values used, for example, for assessing usability of a candidate link for backhauling and deterioration of the current backhauling link. The memory 830 may also comprise other databases which may not be related to the described backhauling functionalities according to embodiments.

Referring to Figure 8, the communication control circuitry 820 may comprise access circuitry 821 and relay circuitry 822 which may have the func tionalities as described for the access unit and the relay unit in relation to Figure 2, respectively. Accordingly, the access circuitry 821 may be configured, for exam ple, to carry out at least some of blocks 302, 305 of Figure 3, block 507 and mes sages 508, 514, 518 of Figure 5 and/or blocks 602 to 604, 607, 608, 610 of Figure 6. For acting as a serving relay node, the access circuitry 821 may be further con figured, for example, to carry out at least some of block 402 of Figure 4, blocks/messages 504, 505, 506, 515, 516 of Figure 5 and/or blocks 702 to 709 of Figure 7. The relay circuitry 822 may be configured, for example, to carry out at least some of blocks 303, 304 of Figure 3, blocks 509, 511, 512 and message 513 of Figure 5, block 605, 606 of Figure 6 and blocks 701 to 703 of Figure 7. The blocks pertaining to the relay node not explicitly mentioned above may be per formed by either or both of the circuitry 821, 822.

Figure 9 illustrates an apparatus 901 configured to carry out the func tions described above in connection with an access node, such as the access nodes 110, 130 of Figure 1 or the access nodes 210, 230 of Figure 2. The apparatus may be an electronic device comprising electronic circuitries. The apparatus may be a separate network entity or a plurality of separate entities. The apparatus may comprise a communication control circuitry 920 such as at least one processor, and at least one memory 930 including a computer program code (software) 931 wherein the at least one memory and the computer program code (software) are configured, with the at least one processor, to cause the apparatus to carry out any one of the embodiments of the access node described above.

The memory 930 may comprise a database 932 which may comprise at least one or more first lists and/or a second list, as described in previous em bodiments. The memory 930 may also comprise other databases which may not be related to the functionalities of the access node according to any of presented embodiments such as any databases used by access nodes in conventional opera tion.

Referring to Figure 9, the communication control circuitry 920 may comprise access circuitry 921 configured to provide the access node functionali ties according to any of presented embodiments. The access circuitry 921 may be configured to carry out at least some of blocks in Figures 4 and/or blocks 502, 503, 504, 505, 515 and messages 506, 510, 516 of Figure 5.

The apparatuses 801, 901 described in relation to Figures 8 and 9 may further comprise communication interfaces (Tx/Rx) 810, 910 comprising hard ware and/or software for realizing communication connectivity according to one or more communication protocols. The communication interface may provide the apparatus with communication capabilities to communicate in the cellular com munication system and enable communication with other access nodes and ter minal devices, for example. Specifically, the communication interfaces (Tx/Rx) 810, 910 may comprise some or all of the interfaces illustrated in and discussed in relation to Figure 2 for the access nodes 210, 230 and the relay nodes 220, 240, respectively. The communication interface 810, 910 may comprise standard well- known components such as an amplifier, filter, frequency-converter, (de) modula tor, and encoder/decoder circuitries and one or more antennas. The communica tion interface 810, 910 may comprise radio interface components providing the apparatus with radio communication capability in the cell.

The memories of the apparatuses described in relation to Figures 8 and 9 may be implemented using any suitable data storage technology, such as semiconductor based memory devices, flash memory, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory.

As used in this application, the term 'circuitry' refers to all of the fol lowing: (a) hardware-only circuit implementations, such as implementations in only analog and/or digital circuitry, and (b) combinations of circuits and soft ware (and/or firmware), such as (as applicable): (i) a combination of proces sor^) or (ii) portions of processor(s)/software including digital signal proces sor^), software, and memory(ies) that work together to cause an apparatus to perform various functions, and (c) circuits, such as a microprocessor(s) or a por tion of a microprocessor(s), that require software or firmware for operation, even if the software or firmware is not physically present. This definition of 'circuitry' applies to all uses of this term in this application. As a further example, as used in this application, the term 'circuitry' would also cover an implementation of merely a processor (or multiple processors) or a portion of a processor and its (or their) accompanying software and/or firmware. The term 'circuitry' would also cover, for example and if applicable to the particular element, a baseband inte grated circuit or applications processor integrated circuit for a mobile phone or a similar integrated circuit in a server, a cellular network device, or another net work device.

ln an embodiment, at least some of the processes described in connec tion with Figures 3 to 7 may be carried out by an apparatus comprising corre sponding means for carrying out at least some of the described processes. Some example means for carrying out the processes may include at least one of the fol lowing: detector, processor (including dual-core and multiple-core processors), digital signal processor, controller, receiver, transmitter, encoder, decoder, memory, RAM, ROM, software, firmware, display, user interface, display circuitry, user interface circuitry, user interface software, display software, circuit, antenna, antenna circuitry, and circuitry ln an embodiment, the at least one processor, the memory, and the computer program code form processing means or comprises one or more computer program code portions for carrying out one or more oper ations according to any one of the embodiments of Figures 3 to 7 or operations thereof.

The techniques and methods described herein may be implemented by various means. For example, these techniques may be implemented in hardware (one or more devices), firmware (one or more devices), software (one or more modules), or combinations thereof. For a hardware implementation, the appa ratuses) of embodiments may be implemented within one or more application- specific integrated circuits (ASlCs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field program mable gate arrays (FPGAs), processors, controllers, micro-controllers, micropro cessors, other electronic units designed to perform the functions described herein, or a combination thereof. For firmware or software, the implementation can be carried out through modules of at least one chipset (procedures, functions, and so on) that perform the functions described herein. The software codes may be stored in a memory unit and executed by processors. The memory unit may be implemented within the processor or externally to the processor ln the latter case, it can be communicatively coupled to the processor via various means, as is known in the art. Additionally, the components of the systems described herein may be rearranged and/or complemented by additional components in order to facilitate the achievements of the various aspects, etc., described with regard thereto, and they are not limited to the precise configurations set forth in the given figures, as will be appreciated by one skilled in the art.

Embodiments as described may also be carried out in the form of a computer process defined by a computer program or portions thereof. Embodi ments of the methods described in connection with Figures 3 to 7 may be carried out by executing at least one portion of a computer program comprising corre sponding instructions. The computer program may be in source code form, object code form, or in some intermediate form, and it may be stored in some sort of car rier, which may be any entity or device capable of carrying the program. For ex ample, the computer program may be stored on a computer program distribution medium readable by a computer or a processor. The computer program medium may be, for example but not limited to, a record medium, computer memory, read-only memory, electrical carrier signal, telecommunications signal, and soft ware distribution package, for example. The computer program medium may be a non-transitory medium. Coding of software for carrying out the embodiments as shown and described is well within the scope of a person of ordinary skill in the art.

Even though the invention has been described above with reference to an example according to the accompanying drawings, it is clear that the invention is not restricted thereto but can be modified in several ways within the scope of the appended claims. Therefore, all words and expressions should be interpreted broadly and they are intended to illustrate, not to restrict, the embodiment lt will be obvious to a person skilled in the art that, as technology advances, the in ventive concept can be implemented in various ways. Further, it is clear to a per- son skilled in the art that the described embodiments may, but are not required to, be combined with other embodiments in various ways.

Claims

CLA1MS

1. A method comprising:

maintaining, in a relay node, a first list comprising information on one or more network nodes with which the relay node has established a neighbor re- lation and is able to form a backhauling link, the one or more network nodes com prising at least a first network node acting as a serving network node for the relay node in a first backhauling link;

receiving, in the relay node, a first indication message from the first network node, wherein the first indication message comprises information on a second network node in a neighbor relation with the first network node;

performing, by the relay node, measurements on pre-defined signals transmitted by the second network node to determine whether the second net work node is usable by the relay node for backhauling;

in response to determining that the second network node is usable for backhauling, causing, by the relay node, establishing a connection to the second network node based on the information on the second network node; and

in response to the establishing, adding, by the relay node, the infor mation on the second network node to the first list.

2. A method according to claim 1, wherein the establishing the connec tion comprises:

causing sending, by the relay node, a request for establishing a neigh bor relation to the second network node based on the information on the second network node; and

receiving, by the relay node, an acknowledgment from the second net work node indicating that the second network node accepts the neighbor relation.

3. A method according to claim 1 or 2, further comprising: in response to signal strength or signal quality of the first backhauling link between the relay node and the first network node falling below a first pre defined threshold level, selecting, by the relay node, another network node for backhauling from the first list and triggering, by the relay node, a change of a backhaul connection from the first backhauling link to the second backhauling link between the relay node and a selected network node acting as the serving network node.

4. A method according to claim 3, further comprising:

in response to the signal strength or the signal quality of the first back hauling link between the relay node and the first network node falling below a second pre-defined threshold level, removing, by the relay node, the first network node from the first list.

5. A method according to claim 3 or 4, wherein the selected network node is selected from the first list based on signal quality and/or signal strength for the second backhauling link and/or type of the network node.

6. A method according to any preceding claim, wherein the determin ing whether the second network node is usable by the relay node for backhauling comprises:

determining, by the relay node, based on the measurements whether a metric for signal quality and/or signal strength exceeds a pre-defined threshold value for a link between the relay node and the second network node.

7. A method according to any preceding claim, further comprising: in response to the receiving the acknowledgment, causing, by the relay node, sending information of the neighbor relation to the first network node.

8. A method according to any preceding claim, further comprising: in response to the receiving the first indication message, establishing, by the relay node, a connection between the relay node and the second network node based on the information on the second network node and receiving, by the relay node, information on control signal transmission for measurement by the relay node from the second network node.

9. A method according to claim 8, further comprising:

in response to determining that the second network node is not usable for backhauling, releasing, by the relay node, the connection between the relay node and the second network node.

10. A method according to any of claims 1 to 7, wherein the relay node comprises a relay unit having a first interface and an access unit having a second interface, all backhauling links of the relay node being established and the meas urements and the determining being performed by the relay unit using the first interface, the acknowledgment being received and the request being sent by the access unit using the second interface and the first indication message being re ceived by the relay unit using the first interface or by the access unit using the second interface.

11. A method according to claim 8 or 9, wherein the relay node com prises a relay unit having a first interface and an access unit having a second in terface, all backhauling links of the relay node being established and the measure ments and the determining being performed by the relay unit using the first inter face, the acknowledgment being received, the request being sent, the connection being established and the information on the pre-defined signal transmission be ing received by the access unit using the second interface and the first indication message being received by the relay unit using the first interface or by the access unit using the second interface.

12. A method according to claim 10 or 11, wherein the first interface is an Uu interface and the second interface is an Xn interface.

13. A method according to any of claims 10 to 12, further comprising: in response to the receiving the first indication message using the sec ond interface, forwarding, by the access unit of the relay node, information com prised in the first indication message to the relay unit of the relay node and re ceiving, by the relay unit of the relay node, the first indication message; and/or in response to the determining that the second network node is usable for backhauling, before the sending the request, forwarding, by the relay unit of the relay node, a second indication message indicating whether the second net work node is usable for backhauling to the access unit of the relay node and re ceiving, by the access unit of the relay node, the second indication message.

14. A method according to any preceding claim, wherein the pre-de- fined signals comprise synchronization signal blocks, SSB, and/or beam-specific channel state information reference signals, CS1-RS.

15. A method comprising:

establishing, by a first network node acting as a serving network node for a relay node in a first backhauling link in a communications system, a neigh bor relation with a second network node; and

in response to the establishing, causing sending, by the first network node, a first indication message to the relay node, wherein the first indication message comprises information on the second network node.

16. A method according to claim 15, wherein the first indication is sent to the relay node via an Uu interface using radio resource control, RRC, signaling or via an Xn interface.

17. A method according to claim 15 or 16, further comprising:

maintaining, by the first network node, one or more first lists, each comprising information on one or more network nodes with which a relay node served or capable of being served by the first network node is able to form a back hauling link; and in response to receiving information on a new neighbor relation be tween the relay node served by the first network node and the second network node from the relay node, updating, by the first network node, a corresponding first list.

18. A method according to any of claims 15 to 17, further comprising: maintaining, by the first network node, a second list comprising infor mation on one or more network nodes with which the first network node has es tablished a neighbor relation, the one or more network nodes comprising, after the establishing the neighbor relation with the second network node, at least the second network node and the relay node.

19. A method according to claim 18, further comprising:

in response to the receiving the information, causing, by the first net- work node, sending instructions to perform measurements on pre-defined signals to at least one relay node in the second list to determine whether the second net work node is usable by the at least one relay node for backhauling.

20. A method according to any of claims 15 to 19, wherein if the first network node is a second relay node in multi-hop deployment, the backhauling is performed according to multi-hop deployment and the establishing is performed according to any of claims 3 to 5.

21. A method according to any of claims any preceding claim, wherein information on any network node comprises a physical cell identifier, PC1, and/or a global cell identifier of said network node.

22. A method according to any preceding claim, wherein each network node is either an access node or a relay node.

23. A method according to claim 22, wherein if the first network node is a second relay node, the backhauling is performed according to multi-hop de ployment.

24. A method according to any preceding claim, wherein any backhaul- ing links are self-backhauling links.

25. An apparatus comprising:

at least one processor; and

at least one memory comprising a computer program code, wherein the processor, the memory, and the computer program code are configured to cause the apparatus to perform a method according to any of claims 1 to 14.

26. An apparatus according to claim 25, wherein the processor, the memory, and the computer program code are further configured to cause the ap paratus to perform a method according to any of claims 15 to 24.

27. An apparatus comprising:

at least one processor; and

at least one memory comprising a computer program code, wherein the processor, the memory, and the computer program code are configured to cause the apparatus to perform a method according to any of claims 15 to 24.

28. An apparatus comprising means for carrying out the method ac- cording to any one of claims 1 to 24.

29. A non-transitory computer readable media having stored thereon instructions that, when executed by a computing device, cause the computing de vice to perform a method according to any of claims 1 to 24.

30. A computer program product comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method according to any of claims 1 to 24.

31. A system comprising:

one or more relay nodes configured to perform a method according to any of claims 1 to 14; and

one or more access nodes configured to act as serving network nodes for the one or more relay nodes by performing a method according to any of claims 15 to 20.

32. A system, wherein at least one of the one or more relay nodes is further configured act as a serving network node for a relay node of the one or more relay nodes in multi-hop deployment by performing a method according to any of claims 15 to 20.