Patent Description:
A Content Delivery Network (CDN) is a network of servers and data centres that are utilised to distribute content to a number of users via a content delivery protocol. Content delivery protocols are typically optimised according to some performance parameters, such as high data throughput and/or minimal latency, which may involve storing particular content on CDN servers in a particular location. In conventional cellular telecommunications networks, CDNs are typically deployed in the core network using wired technology (e.g. optical fibre). However, in future cellular networks, it is expected that CDNs will be deployed in the access network, for example on small cell base stations or on relays. This highly distributed architecture of CDNs allows network operators to employ improved content delivery protocols in which content may be stored closer to the end user, thus improving customer experience by minimising latency, reducing congestion, and providing more reliable connections.

Future cellular networks are also expected to utilise mobile access nodes in which the backhaul connection (for example, from a small cell base station to the core network or from a relay node to a donor base station) is at least partially wireless. However, a problem arises when a CDN is deployed on a mobile access node having a wireless backhaul connection. That is, there is no standardised protocol for wireless communications between CDNs and other nodes in cellular telecommunication networks. Accordingly, wireless CDNs have to use dedicated radio links having proprietary IP-based protocols. This is undesirable and it is an aim of the present invention to alleviate these problems.

<NPL>discloses the market segments and verticals whose needs 3GPP should focus on meeting, and identifies groups of related use cases and requirements that the 3GPP eco-system would need to support in the future.

International Patent Application Publication No. <CIT> discloses an apparatus configured to receive a first signaling message comprising a first identifier of a first node and a second identifier of a second node, and responsive to the receiving initiate at least one policy action relating to at least one of the first node and the second node; and transmit a second signaling message to the first node, the second signaling message being configured to cause bearer establishment between the first node and the second node.

According to a first aspect of the invention, there is provided a method as claimed in Claim <NUM>.

The cellular telecommunications protocol may be a <NUM>rd Generation Partnership Project, 3GPP, protocol, and the identifier may be an International Mobile Subscriber Identifier, IMSI.

The content transaction request from the external node may be to store the content item, and the step of performing the transaction with the content store may include storing the content item in the content store together with the content identifier.

The content transaction request may be of a multicast/broadcast message.

The content transaction request from the external node may be to retrieve the content item, and the step of performing the transaction with the content store may include: identifying the content item based on the content identifier; and retrieving the content item from the content store.

According to a second aspect of the invention, there is provided a computer program product comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method of the first aspect of the invention. The computer program may be stored on a computer-readable data carrier.

According to a third aspect of the invention, there is provided a network node as claimed in Claim <NUM>.

The network node may be one of a group comprising: a relay node, and a small cell base station.

A first embodiment of a cellular telecommunications network <NUM> will now be described with reference to <FIG>. As shown in <FIG>, the cellular telecommunications network <NUM> includes a base station <NUM>, a relay node <NUM>, a User Equipment (UE) <NUM>, a core network <NUM>, and a core Content Delivery Network (CDN) server <NUM>. The base station <NUM>, core network <NUM> and core CDN server <NUM> are connected via respective wired links (e.g. optical fibre), whilst the base station <NUM>, relay node <NUM> and UE <NUM> are connected via respective wireless links.

The relay <NUM> is shown in more detail in <FIG> and <FIG>. As shown in <FIG>, the relay <NUM> includes a first communications interface <NUM>, a processor <NUM>, memory <NUM> (including a Subscriber Identity Module, SIM), an access CDN server <NUM> (including an access CDN processor 27a and an access content store 27b), and a second communications interface <NUM>, all connected via a data bus. The access CDN server <NUM> operates to store and retrieve one or more content items in the access content store 27b, wherein each content item is associated with a content item identifier. The first communications interface <NUM> is an antenna configured for wireless communications with the UE <NUM>. The second communications interface <NUM> is an antenna for a wireless backhaul connection towards the core network <NUM>, which, in this embodiment, is via a donor connection to the base station <NUM>. Accordingly, the relay <NUM> is a radio access node that supports both wireless access and wireless backhaul.

In this embodiment, the cellular telecommunications operates according to the <NUM>th Generation (<NUM>) <NUM>rd Generation Partnership Project (3GPP) protocol. The relay <NUM> shall therefore be referred to as the Integrated Access Backhaul, IAB, node, and the base station <NUM> shall therefore be referred to as the IAB-donor.

<FIG> illustrates the functional elements of the IAB-node <NUM> implemented by its components. The IAB-node <NUM> implements an IAB Distributed Unit (DU) and IAB Mobile Termination (MT), which are discussed in 3GPP Technical Report (TR) <NUM>, which form connections with the UE <NUM> and IAB-donor <NUM> respectively. The IAB-DU and IAB-MT cooperate to implement an adaptation layer for routing data packets between the IAB-DU and IAB-MT. Accordingly, any data packet received at the IAB-MT destined for the UE <NUM> will be routed (by the adaptation layer) to the IAB-DU and onwards to the UE <NUM>. Similarly, any data packet received at the IAB-DU destined for the IAB-donor <NUM> or any node upstream of the IAB-donor <NUM> will be routed (by the adaptation layer) to the IAB-MT and onwards to the IAB-donor <NUM>.

<FIG> also illustrates a connection between the adaptation layer and the IAB-node's access CDN server <NUM> via an IAB-Line Break (IAB-LB). The IAB-node's access CDN server <NUM> is addressable by a CDN identifier that is recognised by each node in the cellular telecommunications network <NUM> as uniquely identifying the IAB-node's CDN server <NUM>. Accordingly, on receipt of a message from the UE <NUM> (via the first transceiver <NUM>) or a message from the IAB-donor <NUM> (via the second transceiver <NUM>) which includes the CDN identifier, the adaptation layer is configured to decode the message to retrieve the CDN identifier and process the CDN identifier to determine that the message relates to the IAB-node's access CDN server <NUM>. This message may, for example, include a content transaction request such as a request to store a content item in the access content store 27b, or a request to retrieve a content item from the access content store 27b, of the IAB-node's access CDN server <NUM>.

In this embodiment, the CDN identifier uses the same format as a UE identifier for identifying the UE <NUM>. As this embodiment is based on the <NUM> cellular protocol, the CDN identifier and UE identifier are both the International Mobile Subscriber Identifier (IMSI). This will now be explained in more detail with reference to <FIG>. The IMSI is composed of three parts: the Mobile Country Code (MCC) consisting of three digits and uniquely identifying the country of domicile of the mobile subscription; the Mobile Network Node (MNC) consisting of two or three digits and identifying the home network (i.e. the home Public Land Mobile Network, PLMN) of the mobile subscription; and the Mobile Subscriber Identification Number (MSIN) identifying the mobile subscription within the home network.

<FIG> also illustrates the MSIN being composed of two parts: MSIN - Special and MSIN - Current. MSIN - Current includes the unique identifier value, whereas MSIN - Special is a single digit that is utilised in this embodiment to indicate whether the identifier is being used to identify a UE or a CDN. In this example, the MSIN-Special digit uses the value <NUM> to indicate that the IMSI relates to a UE and uses the value <NUM> to indicate that the IMSI relates to a CDN.

In this embodiment, the IAB-node's SIM (in memory <NUM>) stores the IMSI of the IAB-node's access CDN server <NUM>. The MSIN of this IMSI therefore includes an MSIN-Current part containing the identifier value which uniquely identifies the access CDN server <NUM> from any other node in the cellular network, and a MSIN-Special part having value <NUM> to indicate that the IMSI is being used to identify a CDN. Furthermore, the UE <NUM> includes a SIM storing the UE's IMSI, which includes an MSIN-Current part containing the identifier value which uniquely identifies the UE <NUM> from any other node in the cellular network <NUM>, and a MSIN-Special part having value <NUM> to indicate that the IMSI is being used to identify a UE.

Turning back to <FIG>, the IAB-node may therefore receive a message, at the IAB-DU or IAB-MT, which includes the IMSI of the access CDN server <NUM> as the destination of that message. The adaptation layer may then decode the MSIN-Special part of the IMSI to determine that the message is for a CDN, and decode the MSIN-Current to determine that the access CDN server <NUM> is the destination. In response, the adaptation layer forwards this message to the IAB-LB, which processes the message to determine the particular content transaction request (e.g. to identify a content item and to determine whether the transaction is to store or retrieve the content item).

By utilising the identifier used by the cellular protocol to identify UEs to further identify CDNs provides several advantages to this embodiment of the invention. That is, any external node may address a wireless CDN in the cellular network using the same hardware that is used for any other communication according to that cellular protocol, and may further utilise the same standardised processes for data transfer and mobility. This reduces the capital cost of deploying CDNs (as they may utilise the IAB-node's hardware for communication), and improves the quality of experience as the IAB-node may benefit from all processes of the cellular protocol (e.g. handover, multi-hop, etc.) without having a tailored software upgrade.

A first embodiment of a method of the present invention will now be described with reference to <FIG>. In this first embodiment, the IAB-node's access CDN server <NUM> is first established on the cellular network <NUM> by sending a connection request message to the core network (e.g. the Access and Mobility Management Function, AMF). The core network and IAB-node's access CDN server then exchange connection setup messages, and the credentials of the IAB-node's access CDN server (including its IMSI) are recorded in the core network.

Following connection setup, the core network sends data on the IAB-node's access CDN server <NUM> to all content providers in the cellular network (and any known content providers in external networks that the cellular network has onward connections to). This data includes the IMSI of the IAB-node's access CDN server <NUM>.

In this first embodiment, there is a determination by a content delivery protocol that a content item of the content provider should be stored in the IAB-node's access CDN server <NUM>. This determination may be based on data indicating a high probability that the content item will be requested by users in the geographical region of the IAB-node <NUM>, so that users in this geographical region retrieving the content item from the IAB-node's access CDN server <NUM> would experience improved quality of service (e.g. lower latency) compared to users in the same geographical region retrieving the content item from the core CDN server <NUM>. Furthermore, retrieval from the access CDN server <NUM>, instead of the core CDN server <NUM>, would reduce utilisation on any intermediate links between the IAB-node and the core CDN server.

Following this determination, the content provider sends a request message to the IAB-node's access CDN server <NUM> to establish a data bearer connection. As the IAB-node's access CDN server <NUM> is addressable as a UE (that is, using its IMSI), this may follow the same procedures for connection establishment as used in the cellular protocol for a UE.

Following establishment of the data bearer connection, the content provider sends the IAB-node's access CDN server <NUM> a content transaction request message. In this embodiment, the content transaction request includes: the CDN identifier uniquely identifying the access CDN server <NUM>, a content item (in this example, an operating system update file), a content item identifier uniquely identifying the content item, and a content transaction indicator indicating that the content transaction is to store the content item.

The processor <NUM> (implementing adaptation layer processes) decodes the constituent parts of the content transaction request message, and, in response, initiates storage of the content item in the access content store 27b together with the content item identifier.

A second embodiment of a method of present invention will now be described with reference to <FIG>. In this second embodiment, the UE <NUM> sends a request message to the content provider identifying a content item. The content provider responds to this request message by identifying the most suitable CDN server (either the core CDN server or access CDN server <NUM>) for the UE to retrieve the content item from. This identification step may include determining the quality of the connection between the UE and the core CDN server and of the connection between the UE and the access CDN server and/or by determining the geographical relationship between the UE and the core CDN server and between the UE and the access CDN server. In this example, the content provider determines that the UE should retrieve the content item from the IAB-node's access CDN server <NUM>. Accordingly, the content provider's response to the request message includes the IMSI of the access CDN server <NUM>.

The UE <NUM> then sends a request message to the IAB-node's access CDN server <NUM> to establish a data bearer connection (utilising the access CDN server's IMSI). Again, as the IAB-node's access CDN server <NUM> is addressable as a UE (that is, using its IMSI), this may follow the same procedures for connection establishment as used in the cellular protocol for a UE. Following data bearer connection establishment, the UE <NUM> sends the IAB-node's access CDN server <NUM> a content transaction message. In this embodiment, the content transaction request includes: the CDN identifier uniquely identifying the access CDN server <NUM>, a content item identifier uniquely identifying the content item, and a content transaction indicator indicating that the content transaction is to retrieve the content item.

The processor <NUM> (implementing adaptation layer processes) decodes the constituent parts of the content transaction message and, in response, initiates retrieval of the content item from the access content store 27b, and further initiates the transfer of the content item to the UE <NUM> via the first transceiver <NUM>.

The above first and second embodiments of methods of the present invention illustrate how the new CDN identifier may be used to store and retrieve content items in a CDN where the CDN has a wireless backhaul connection. However, as noted above, there are further benefits to using a CDN identifier that takes the same form as the UE identifier, such as being able to utilise other standardised processes in the cellular protocol. These include, for example, multicast over the backhaul connection between the IAB-donor and a plurality of IAB-nodes each having access CDN servers. <FIG> illustrates such an example in which the IAB-donor forms a donor connection to a first, second and third IAB-node, having a first, second and third access CDN server respectively. In this scenario, the IAB-donor may use multicasting over the backhaul connections between the IAB-donor with each of the first, second and third IAB-nodes to efficiently transfer the same content item to all IAB-nodes (that is, by using a common part of the radio spectrum to transfer the content item to all IAB-nodes). This contrasts to the prior art scenario in which the content item would be transferred over unicast between the IAB-donor and all IAB-nodes in which the content item is transferred using distinct parts of the radio spectrum.

In the above embodiments, the IAB-node <NUM> includes the access CDN server. However, the skilled person will understand that it is not essential for the IAB-node and access CDN server to be part of the same infrastructure. In an alternative configuration, the IAB-node and access CDN server may be separate entities configured to communicate with each other. Furthermore, it is non-essential that the access CDN server is associated with an IAB-node. Instead, the access CDN server could be associated with any other access node which has a backhaul connection which is at least partially wireless, such as a small cell base station.

In the above embodiments, the cellular network operates according to the 3GPP <NUM> cellular networking protocol and uses the IMSI as the UE and CDN identifier. However, this is non-essential. That is, other identifiers that are used to identify a user or UE (e.g. the International Mobile Equipment Identity, IMEI) could also be used. The skilled person will understand that these are permanent forms of UE identifier. Furthermore, the cellular network may operate according to any other protocol and the CDN identifier would then have the form defined in that protocol for identifying the UE.

Furthermore, in the above embodiments, the MSIN of the IMSI is adapted to indicate whether or not the IMSI is being used to identify a CDN or a UE. This is non-essential, but it is preferential as it increases the number of unique identifiers that may be used.

Claim 1:
A method of operating a network node (<NUM>) in a cellular telecommunications network, the cellular telecommunications network including a User Equipment, UE, (<NUM>) wherein the UE (<NUM>) is identifiable in the cellular telecommunications network by an identifier having a form defined by a cellular telecommunications protocol, wherein the network node comprises a content store (27b), is one of a relay node and a small cell base station, and has a backhaul connection that is at least partially wireless, the method comprising:
receiving, at the network node (<NUM>), a content transaction request from another node in the cellular telecommunications network over a wireless connection, the content transaction request including a content store identifier for identifying the content store (27b) and further including a content identifier for identifying a content item; and
processing, at the network node (<NUM>), the content transaction request to perform a transaction with the identified content item in the identified content store (27b),
wherein the content store identifier has the form defined by the cellular telecommunications protocol for permanently identifying User Equipments.