Cellular telecommunications network

Abstract

The present invention relates to a method for operating an access point AP in a cellular telecommunications network, the cellular telecommunications network having a plurality of APs and a core network, wherein the AP is connected to a first subset of the plurality of APs via a wireless upstream connection towards the core network and is also connected to a second subset of the plurality of APs via a wireless downstream connection leaving the core network, the method comprising the steps of: receiving an inter-AP message in a first wireless communication from a first AP among the plurality of APs, the inter-AP message including a destination identifier; identifying a second adjacent AP among the plurality of APs based on the destination identifier of the inter-AP message; and sending the inter-AP message to the second adjacent AP in a second wireless communication via the wireless downstream connection.

Description

Technical Field

[0001] The present invention relates to cellular telecommunications networks. Background Art

[0002] In cellular telecommunications networks, overall capacity can be increased by increasing the density of base station deployments. However, there are associated cost expenditures in providing additional base station equipment and wired links ("backhaul") that connect the additional base stations to the core network. To reduce backhaul expenditures, access connections can be provided by relay nodes that utilize a wireless backhaul link to the core network (via a "donor" base station). Such relay nodes have become part of the 4G standard. One limitation of these 4G relay nodes is that there may be only a single relay node (i.e., "single-hop") between a user equipment (UE) and the donor base station.

[0003] In 5G, relay nodes are referred to as "Integrated Access and Backhaul" (IAB) nodes, and donor base stations are referred to as IAB donors. 5G networks can also employ a multi-hop architecture such that there can be multiple IAB nodes between a UE and an IAB donor.

[0004] In general, any form of networking node that can provide an access connection in a cellular telecommunications network can be referred to as an access point (AP). This term includes the above-mentioned base stations, donor base stations, relay nodes, IAB nodes, and IAB donors.

[0005] Cellular telecommunications networks also utilize AP-to-AP messaging protocols, such as X2 in 4G and Xn in 5G. These protocols allow connections (directly or indirectly) to be established between APs to exchange messages regarding mobility management, load management, and various configuration parameters. The donor base station in a 4G network or the IAB donor in a 5G network is responsible for routing AP-to-AP messages (or having a connection to a gateway node that provides such functionality), including AP-to-AP messages originating from any relay node or IAB node that they serve. Summary of the Invention

[0006] According to a first aspect of the present invention, there is provided a method of operating an access point AP in a cellular telecommunications network having a plurality of APs and a core network, wherein the AP is connected to a first subset of the plurality of APs via a wireless upstream connection towards the core network and is also connected to a second subset of the plurality of APs via a wireless downstream connection away from the core network, the method comprising the steps of: receiving an inter-AP message in a first wireless communication from a first AP in the second subset of the plurality of APs, the inter-AP message including a destination identifier; identifying a second AP in the second subset of the plurality of APs based on the destination identifier of the inter-AP message; and sending the inter-AP message to the second AP in the second subset of the plurality of APs in a second wireless communication via the wireless downstream connection.

[0007] The second adjacent AP may be the destination of the inter-AP message or a first neighbor of the second adjacent AP.

[0008] The method may further comprise the steps of: discovering the second adjacent AP; identifying a first neighbor of the second adjacent AP; recording an association between the second adjacent AP and the first neighbor of the second adjacent AP, wherein the step of identifying the second adjacent AP based on the destination of the inter-AP message utilizes the recorded association between the second adjacent AP and the first neighbor of the second adjacent AP.

[0009] The method may further comprise the steps of: detecting termination of an inter-AP connection between the second adjacent AP and a second neighbor of the second adjacent AP; and in response to the detection, updating the recorded association between the second adjacent AP and the second neighbor of the second adjacent AP.

[0010] According to a second aspect of the present invention, there is provided a method of operating an access point AP in a cellular telecommunications network having a plurality of APs and a core network, wherein the AP is connected to an adjacent AP among the plurality of APs via a wireless upstream connection towards the core network, the method comprising the steps of: storing data identifying the adjacent AP, a parent AP of the adjacent AP, and a child AP of the adjacent AP, wherein the adjacent AP is connected to the parent AP via a wireless upstream connection towards the core network and is connected to the child AP via a wireless downstream connection away from the core network; generating an inter-AP message having a destination of the child AP of the adjacent AP; determining that the child AP is a child AP of the adjacent AP; and, in response, sending the inter-AP message to the adjacent AP.

[0011] According to a third aspect of the present invention, there is provided a computer program comprising instructions which, when executed by a computer, cause the computer to perform the steps of the first aspect or the second aspect of the present invention. The computer program may be stored on a computer-readable carrier medium.

[0012] According to a fourth aspect of the present invention, there is provided an access point AP in a cellular telecommunications network, having a transceiver, a memory and a processor configured to cooperate to perform the steps of the first aspect or the second aspect of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] For a better understanding of the present invention, embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings, in which:

[0014] Figure 1 is a schematic diagram of an embodiment of the cellular telecommunications network of the present invention;

[0015] Figure 2 is Figure 1 a schematic diagram of the donor integrated access and backhaul (IAB) of the network;

[0016] Figure 3 is Figure 1 a schematic diagram of an IAB node of the network of;

[0017] Figure 4 is a flowchart showing the message passing process of an embodiment of the method of the present invention;

[0018] Figure 5 is after introducing a fifth IAB node Figure 1 a schematic diagram of the network; and

[0019] Figure 6 is a flowchart showing the routing table update process of an embodiment of the method of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] Now reference will be made to Figures 1 to 3 describe a first embodiment of the cellular telecommunications network 100 of the present invention. Figure 1 A cellular telecommunications network 100 is shown, which includes a plurality of user equipments (UEs) 110a... 110e, a plurality of integrated access and backhaul (IAB) nodes 120a... 120d, an IAB donor 130, and a core network 140, all of which operate according to the fifth-generation (5G) cellular telecommunications protocol standardized by the Third Generation Partnership Project (3GPP). The IAB nodes 120a... 120d are connected in a multi-hop relay architecture, enabling the first IAB node 120a and the second IAB node 120b to communicate with the IAB donor 130 via intermediate IAB nodes (the third IAB node 120c and the fourth IAB node 120d).

[0021] The IAB donor 130 is shown in more detail in Figure 2 . The IAB donor 130 includes a first communication interface 131 for wired communication (e.g., via optical fiber) with the core network 140, a processor 133, a memory 135, and a second communication interface 137 for wireless communication (e.g., via an antenna), all of which are connected via a bus 139. The second communication interface 137 is used to provide an access connection to one or more UEs (e.g., the fifth UE 110e among multiple UEs), and to provide a wireless backhaul connection to one or more IAB nodes (e.g., the fourth IAB node 120d). As Figure 2 shown, the processor 133 of the IAB donor 130 includes a centralized unit (CU) (providing radio resource control (RRC) and packet data convergence (PDC) functions) and a distributed unit (DU) (providing radio link control (RLC) and media access control (MAC) functions) for processing packets transmitted via the first communication interface 131 or the second communication interface 137.

[0022] The third IAB node 120c among multiple IAB nodes is shown in more detail in Figure 3 . The third IAB node 120c includes a first communication interface 121c for wireless communication (e.g., via an antenna), a processor 123c, a memory 125c, and a second communication interface 127c for wireless communication (e.g., via an antenna), all of which are connected via a bus 129c. The first communication interface 121c is used to provide a wireless backhaul connection to the fourth IAB node 120d. The second communication interface 127c is used to provide a wireless access connection to one or more UEs (e.g., the third UE 110c among multiple UEs), and to provide a wireless backhaul connection to the first IAB node 120a and the second IAB node 120b. Since both the first and second communication interfaces can be used for wireless backhaul connections, but in opposite directions, the first communication interface 121c for the wireless backhaul connection to the fourth IAB node 120d will be referred to hereinafter as the upstream wireless backhaul connection (as it is used for communication from the third IAB node 120c to an upstream network node such as the fourth IAB node 120d or the core network 140), and the second communication interface 127c for the wireless backhaul connection to the first IAB node 120a and the second IAB node 120ab will be referred to hereinafter as the downstream wireless backhaul connection (as it is used for communication from the third IAB node 120c to downstream network nodes such as the first IAB node 120a and the second IAB node 120b).

[0023] The processor 123c of the third IAB node 120c includes a distributed unit (DU) (providing radio link control (RLC) and media access control (MAC) functions) for processing packets transmitted via the first communication interface 121c or the second communication interface 127c, and also includes a mobile terminal (MT) part for communicating via an upstream wireless backhaul connection (to the DU part of the fourth IAB node 120d).

[0024] The first IAB node 120a, the second IAB node 120b, and the fourth IAB node 120d are substantially the same as the third IAB node 120c, and the terms upstream / downstream wireless backhaul connection for these IAB nodes refer to the upstream / downstream direction from the perspective of each IAB node (i.e., the upstream wireless backhaul connection for the first IAB node 120a is towards the third IAB node 120c, the upstream wireless backhaul connection for the second IAB node 120b is towards the third IAB node 120c, the upstream wireless backhaul connection for the fourth IAB node 120d is towards the IAB donor 130, and the downstream wireless backhaul connection for the fourth IAB node 120d is towards the third IAB node 120c).

[0025] The IAB donor 130 and the IAB nodes 120a…120d are all configured to establish an inter-access point (AP - to - AP) connection (an Xn connection in this embodiment) with any other IAB donor or IAB node to which they can be (directly or indirectly) connected. In addition, the IAB donor 130 and each of the multiple IAB nodes 120a…120d store (in their respective memory modules) a routing table that lists each adjacent node having an established AP - to - AP connection (i.e., an established Xn connection) with it. For each of these adjacent nodes, the routing table also identifies the Internet Protocol (IP) address of the adjacent node, the identifier of the adjacent node's parent node, and the identifiers of each of the adjacent node's child nodes. In this context, the parent node is the IAB donor or IAB node to which the adjacent node is directly connected via its upstream wireless backhaul connection, and the child node is the IAB donor or IAB node to which the adjacent node is directly connected via its downstream wireless backhaul connection. The routing table update process will be described in more detail below.

[0026] Now, an embodiment of the method of the present invention will be described. The method includes multiple processes, including a message passing process and a routing table update process. Now, reference will be made to Figure 1 and Figure 4 to describe the message passing process.

[0027] The cellular telecommunications network 100 is initially in the state as Figure 1 shown, and Xn connections have been established between:

[0028] · The first IAB node 120a and the third IAB node 120c;

[0029] · The second IAB node 120b and the third IAB node 120c;

[0030] · The third IAB node 120c and the fourth IAB node 120d; and

[0031] · The fourth IAB node 120d and the IAB donor 130.

[0032] The routing table of the first IAB node 120a includes the following data (after the update process described below):

[0033]

[0034] Table 1: Routing table of the first IAB node 120a The routing table of the third IAB node 120c includes the following data (after the update process described below):

[0035]

[0036] Table 2: Routing table of the third IAB node 120c

[0037] In the first step (S201) of the message passing process, as Figure 4 shown in the flowchart of, the first IAB node 120a generates an Xn message with the destination being the second IAB node 120b. In step S203, the first IAB node 120a performs a lookup on its routing table to determine whether the first IAB node 120a has an established Xn connection with the second IAB node 120b (i.e., the second IAB node 120b is listed as an adjacent node in the routing table), or whether the second IAB node 120b is the parent or child node of an adjacent node listed in the routing table. In this embodiment, the first IAB node 120a does not have an established Xn connection with the second IAB node 120b, but the second IAB node 120b is identified as the child node of the third IAB node 120c. Responsively (in step S207), the first IAB node 120a sends the Xn message to the third IAB node 120c.

[0038] When receiving an Xn message from the first IAB node 120a (step S202), the third IAB node 120c similarly performs step S203 to perform a lookup in its routing table to determine whether it has an established Xn connection with the second IAB node 120b or, if not, to determine whether the second IAB node 120b is the parent or child of an adjacent node listed in the routing table. When the third IAB node 120c has an established Xn connection with the second IAB node 120b, the third IAB node 120c responds by sending the Xn message to the second IAB node 120b (in step S205).

[0039] Accordingly, the second IAB node 120b receives the Xn message and processes the Xn message in its normal manner.

[0040] The above processing enables the IAB nodes to direct inter-AP messages to the destination of the inter-AP messages. In the absence of this functionality, the IAB node (the first IAB node 120a) that generates the Xn message must forward it to the IAB donor 130 so that the Xn message can be forwarded to the destination node (the second IAB node 120b). In this example, the Xn message would have to be forwarded via the constituent wireless backhaul connections between the first IAB node 120a and the IAB donor 130 (i.e., between the first IAB node 120a and the third IAB node 120c, between the third IAB node 120c and the fourth IAB node 120d, and between the fourth IAB node 120d and the IAB donor 130). However, by implementing the above process, the Xn message can be forwarded by the third IAB node 120c to the second IAB node 120b without any interaction from the fourth IAB node 120d or the IAB donor 130 and without using the corresponding wireless backhaul connections between the third IAB node 120c, the fourth IAB node 120d, and the IAB donor 130. Accordingly, the above processing frees up the capacity on these wireless backhaul connections that would otherwise be wasted to forward these Xn messages to the IAB donor 130. Additionally, since these multi-hop architectures result in a tree structure with additional IAB node branches (e.g., if the third IAB node 120c and / or the fourth IAB node 120d have one or more other child IAB nodes) and Xn messages initiated within these IAB node branches must also be forwarded up to the IAB donor 130, any wireless backhaul connections serving multiple IAB node branches will be significantly burdened. Accordingly, the above processing has a significant benefit for wireless backhaul connections serving multiple IAB node branches.

[0041] In another example of the above - described process of generating a message for a destination IAB node at the first IAB node 120a, if the destination IAB node is not identified in either the routing table of the first IAB node or the routing table of the third IAB node (as an adjacent node having an established Xn connection with the destination IAB node, or as a parent / child node of such an adjacent node), then the first IAB node 120a and the third IAB node 120c forward the Xn message towards the IAB donor 130 (step S209). If the routing table of the fourth IAB node identifies the destination IAB node, it can process the Xn message according to the steps of the above - described process. If not, the Xn message is ultimately received and processed by the IAB donor 130.

[0042] Now, a process of updating the routing table will be described with reference to Figure 1 、 Figure 5 and Figure 6 .

[0043] The cellular telecommunications network 100 is initially in the state as shown in Figure 1 . At a subsequent time, a fifth IAB node 120e is added to the network and is directly connected to the IAB donor 130, as shown in Figure 5 . The third UE 110c (connected to the third IAB node 120c) is within the coverage area of the fifth IAB node 120e. In the first step (S301) of this routing - table update process, the third IAB node 120c receives a measurement report from the third UE 110c identifying the fifth IAB node 120e. In step S303, the third IAB node 120c determines whether it has an established Xn connection with the fifth IAB node 120e by looking up its routing table. In this example, the third IAB node 120c and the fifth IAB node 120e do not have an established Xn connection. Responsively, the third IAB node 120c starts an Xn connection - establishment process with the fifth IAB node 120e (step S305). After establishment, the third IAB node 120c identifies the fifth IAB node 120e and receives the IP address of the fifth IAB node. Similarly, the fifth IAB node 120e has identified the third IAB node 120c and has received the IP address of the third IAB node.

[0044] In step S307, the third IAB node 120c sends a routing - table update message (encapsulated in an Xn message) to the fifth IAB node 120e. This routing - table update message identifies the parent node of the third IAB node 120c (in this example, the fourth IAB node 120d) and all the child nodes of the third IAB node 120c (in this example, the first IAB node 120a and the second IAB node 120b).

[0045] Upon reception, the fifth IAB node 120e stores the data in its routing table. Thus, the routing table of the fifth IAB node includes the following data:

[0046] The IP address of the neighboring node of the neighboring node's child node of the neighboring node's parent node

[0047]

[0048] Table 3: Routing table of the fifth IAB node 120e

[0049] The fifth IAB node 120e also sends a routing table update response message (encapsulated in an Xn message) to the third IAB node 120c, which identifies the parent node of the fifth IAB node 120e and all child nodes of the fifth IAB node 120e. In this example, the IAB donor 130 is the parent node of the fifth IAB node 120e, and there are no child nodes of the fifth IAB node 120e. Upon reception, in step S309, the third IAB node 130c stores the data in its routing table. Thus, the routing table of the third IAB node includes the following data:

[0050]

[0051] Table 4: Routing table of the third IAB node 120c

[0052] In addition, in step S311, the fifth IAB node 120e sends a routing table update message (encapsulated in an Xn message) to all other neighboring nodes identified in its routing table to identify any new parent / child relationships. In this example, there are no new relationships, so such a message is not required.

[0053] The above processing provides a mechanism for updating the routing table with information related to newly added IAB nodes, so that the newly added IAB nodes can be utilized in message passing processing. Additionally, the processing provides for updating the routing table from the network after the termination of the Xn connection between IAB nodes (e.g., if an IAB node is removed from the network, powered off, or the Xn connection is lost in some other way). After detecting the termination, the detected node sends a message to all other nodes identified in its routing table to notify the other nodes of the termination. The other nodes can then update their routing tables.

[0054] In the above embodiment, the inter-base station connection is an Xn connection. However, this is not necessary, and the above embodiment is applicable to other forms of AP - to - AP messages, such as X2 or S1.

[0055] Those skilled in the art will understand that any combination of features is possible within the scope of the claimed invention.

Claims

1. A method for operating an access point AP in a cellular telecommunications network, the cellular telecommunications network having a plurality of APs and a core network, wherein, The AP is connected to a first subset of the plurality of APs via a wireless upstream connection towards the core network and is also connected to a second subset of the plurality of APs via a wireless downstream connection away from the core network. The method includes the following steps: Receiving an inter-AP message from a first AP in the second subset of the plurality of APs in a first wireless communication, the inter-AP message including a destination identifier; Identifying a second AP in the second subset of the plurality of APs based on the destination identifier of the inter-AP message; and Sending the inter-AP message to the second AP in the second subset of the plurality of APs in a second wireless communication via the wireless downstream connection.

2. The method according to claim 1, wherein The second AP is the destination of the inter-AP message.

3. The method according to claim 1, wherein, The destination of the inter-AP message is a first neighbor of the second AP.

4. The method according to claim 3, the method further includes the following initial steps: Discovering the second AP; Identifying the first neighbor of the second AP; Recording the association between the second AP and the first neighbor of the second AP, Among them, The step of identifying the second AP based on the destination of the inter-AP message utilizes the recorded association between the second AP and the first neighbor of the second AP.

5. The method according to claim 1, the method further includes the following steps: Detecting the termination of an inter-AP connection between the second AP and a second neighbor of the second AP; And In response to the detection, updating the recorded association between the second AP and the second neighbor of the second AP.

6. A computer-readable carrier medium storing a computer program which, when executed by a computer, causes the computer to perform the method according to any one of claims 1 to 5.

7. An access point AP in a cellular telecommunications network, the access point AP having a transceiver, a memory and a processor, the transceiver, the memory and the processor being configured to cooperate to perform the steps of the method according to any one of claims 1 to 5.

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