CN116250280A

CN116250280A - Methods, apparatus, and computer readable media for integrated access and backhaul communications

Info

Publication number: CN116250280A
Application number: CN202080105399.3A
Authority: CN
Inventors: I·凯斯基塔罗; D·科齐奥尔; 许翔; H·巴克; O·布拉克奇; O·布卢默
Original assignee: Nokia Shanghai Bell Co Ltd; Nokia Solutions and Networks Oy
Current assignee: Nokia Shanghai Bell Co Ltd; Nokia Solutions and Networks Oy
Priority date: 2020-09-25
Filing date: 2020-09-25
Publication date: 2023-06-09
Also published as: WO2022061780A1

Abstract

Embodiments of the present disclosure relate to methods, apparatuses, and computer-readable storage media for Integrated Access and Backhaul (IAB) communications. According to an embodiment of the present disclosure, a first IAB gives a master-slave second IAB donor to receive a reconfiguration message of a terminal device in a serving cell served by an IAB node. The IAB node migrates from a first cell in communication with a first IAB donor to a second cell in communication with a second IAB donor while leaving the cell identifier of the serving cell unchanged. The reconfiguration message instructs the terminal device to update the configuration of the second IAB donor. The first IAB donor encrypts the reconfiguration message based on the security parameters of the first IAB donor and provides the encrypted reconfiguration message to the IAB node. The solution enables the physical cell identifier of the cell provided by the IAB node to remain unchanged during the migration of the IAB node.

Description

Methods, apparatus, and computer readable media for integrated access and backhaul communications

Technical Field

Embodiments of the present disclosure relate generally to the field of telecommunications and, in particular, relate to methods, apparatuses, and computer-readable media for Integrated Access and Backhaul (IAB) communications.

Background

IAB has been introduced in release 16 of the 3GPP specifications (Rel-16) as a key driver for fast and cost-effective deployment. The IAB nodes use the same spectrum and air interface for access and backhaul, creating a hierarchical wireless multi-hop network between stations. Each hop eventually terminates with an IAB donor connected to the core network by means of a conventional fixed backhaul. The IAB node comprises a Mobile Terminal (MT) part acting as a User Equipment (UE) towards its parent IAB node and a Distributed Unit (DU) part acting as a base station towards the next hop IAB node. The IAB donor includes a Centralized Unit (CU) portion and a DU portion. The IAB DU may provide one or more cells to serve the UE. From the UE's point of view, the cell provided by the IAB DU may be considered a normal cell.

An IAB node may need to change its serving node, which may be located under the same or different IAB donor(s), due to a failure of the backhaul connection or a change in the IAB topology or IAB mobility. In the latter case, the Physical Cell Identifier (PCI) of the cell served by the IAB DU may have to be changed to avoid PCI collision due to the movement of the IAB node. If the PCI of the cell served by the IAB node changes during handover and connection to the new IAB donor, a handover or Radio Resource Control (RRC) reestablishment procedure will be performed in order to reconfigure the UE(s) connected to the IAB node. This may result in connection and service interruption at the UE connected to the IAB node.

Disclosure of Invention

In general, example embodiments of the present disclosure provide methods, apparatus, and computer-readable media for IAB communications.

In a first aspect, a method is provided. The method includes receiving, at the first device, a reconfiguration message from the second device for a fourth device in a serving cell served by a third device, the third device migrating from a first cell in communication with the first device to a second cell in communication with the second device while leaving a cell identifier of the serving cell unchanged, and the reconfiguration message indicating that the fourth device updates a configuration for the second device; encrypting the reconfiguration message based on the security parameters of the first device; and providing the encrypted reconfiguration message to the third device.

In a second aspect, a method is provided. The method includes generating, at the second device, a reconfiguration message for a fourth device in a serving cell served by a third device, the third device migrating from a first cell in communication with the first device to a second cell in communication with the second device while leaving a cell identifier of the serving cell unchanged, and the reconfiguration message indicating that the fourth device updates a configuration for the second device; and transmitting the reconfiguration message to the first device.

In a third aspect, a method is provided. The method includes receiving, at a third device, a reconfiguration message from the first device or the second device for a fourth device in a serving cell served by the third device, the third device migrating from a first cell in communication with the first device to a second cell in communication with the second device while leaving a cell identifier of the serving cell unchanged, and the reconfiguration message indicating that the fourth device updates a configuration for the second device; forwarding the reconfiguration message to the fourth device; and receiving a reconfiguration complete message from the fourth device.

In a fourth aspect, a method is provided. The method includes receiving, at a fourth device, a reconfiguration message from a third device, the third device providing a serving cell for serving the fourth device, the third device migrating from a first cell in communication with the first device to a second cell in communication with the second device while maintaining a cell identifier of the serving cell unchanged, and the reconfiguration message including a new configuration for the second device; updating the configuration used at the fourth device with the new configuration without performing the random access procedure; and transmitting a reconfiguration complete message to the third device.

In a fifth aspect, a first device is provided. The first device includes at least one processor and at least one memory including computer program code. The at least one memory and the computer program code are configured to, with the at least one processor, cause the first device to receive a reconfiguration message from the second device for a fourth device in a serving cell served by a third device, the third device migrating from the first cell in communication with the first device to a second cell in communication with the second device while leaving a cell identifier of the serving cell unchanged, and the reconfiguration message indicating that the fourth device updates a configuration for the second device; encrypting the reconfiguration message based on the security parameters of the first device; and providing the encrypted reconfiguration message to the third device.

In a sixth aspect, a second device is provided. The second device includes at least one processor and at least one memory including computer program code. The at least one memory and the computer program code are configured to, with the at least one processor, cause the second device to generate a reconfiguration message for a fourth device in a serving cell served by a third device, the third device migrating from a first cell in communication with the first device to a second cell in communication with the second device while leaving a cell identifier of the serving cell unchanged, and the reconfiguration message indicating that the fourth device updates a configuration for the second device; and transmitting the reconfiguration message to the first device.

In a seventh aspect, a third device is provided. The third device includes at least one processor and at least one memory including computer program code. The at least one memory and the computer program code are configured to, with the at least one processor, cause the third device to receive a reconfiguration message from the first device or the second device for a fourth device in a serving cell served by the third device, the third device migrating from the first cell in communication with the first device to a second cell in communication with the second device while leaving a cell identifier of the serving cell unchanged, and the reconfiguration message indicating that the fourth device updates the configuration for the second device; forwarding the reconfiguration message to the fourth device; and receiving a reconfiguration complete message from the fourth device.

In an eighth aspect, a fourth apparatus is provided. The fourth device comprises at least one processor and at least one memory including computer program code. The at least one memory and the computer program code are configured to, with the at least one processor, cause the fourth device to receive a reconfiguration message from a third device, the third device providing a serving cell for serving the fourth device, the third device migrating from a first cell in communication with the first device to a second cell in communication with the second device while maintaining a cell identifier of the serving cell unchanged, and the reconfiguration message including a new configuration for the second device; updating the configuration used at the fourth device with the new configuration without performing the random access procedure; and transmitting a reconfiguration complete message to the third device.

In a ninth aspect, an apparatus is provided. The apparatus includes means for receiving, from a second device, a reconfiguration message for a fourth device in a serving cell served by a third device, the third device migrating from a first cell in communication with the apparatus to a second cell in communication with the second device while leaving a cell identifier of the serving cell unchanged, and the reconfiguration message indicating that the fourth device updates a configuration for the second device; means for encrypting the reconfiguration message based on the security parameters of the apparatus; and means for providing the encrypted reconfiguration message to the third device.

In a tenth aspect, an apparatus is provided. The apparatus includes means for generating a reconfiguration message for a fourth device in a serving cell served by a third device, the third device migrating from a first cell in communication with the first device to a second cell in communication with the apparatus while leaving a cell identifier of the serving cell unchanged, and the reconfiguration message indicating that the fourth device updates a configuration for the apparatus; and means for transmitting the reconfiguration message to the first device.

In an eleventh aspect, an apparatus is provided. The apparatus includes means for receiving, from the first device or the second device, a reconfiguration message for a fourth device in a serving cell served by the apparatus, the third device migrating from the first cell in communication with the first device to a second cell in communication with the second device while leaving a cell identifier of the serving cell unchanged, and the reconfiguration message indicating that the fourth device updates a configuration for the second device; forwarding the reconfiguration message to the fourth device; and means for receiving a reconfiguration complete message from the fourth device.

In a twelfth aspect, an apparatus is provided. The apparatus includes means for receiving a reconfiguration message from a third device, the third device providing a serving cell for serving the apparatus, the third device migrating from a first cell in communication with the first device to a second cell in communication with the second device while maintaining a cell identifier of the serving cell unchanged, and the reconfiguration message including a new configuration for the second device; means for updating a configuration used at the apparatus with the new configuration without performing a random access procedure; and means for transmitting a reconfiguration complete message to the third device.

In a thirteenth aspect, a computer program product is provided, the computer program product being stored on a computer readable medium and comprising machine executable instructions. The machine executable instructions, when executed, cause a machine to perform a method according to the first, second, third or fourth aspects described above.

In a fourteenth aspect, a computer readable storage medium is provided, the computer readable storage medium comprising program instructions stored thereon. The instructions, when executed by an apparatus, cause the apparatus to perform a method according to the first, second, third or fourth aspects described above.

It should be understood that the summary is not intended to identify key or essential features of the embodiments of the disclosure, nor is it intended to be used to limit the scope of the disclosure. Other features of the present disclosure will become apparent from the following description.

Drawings

The foregoing and other objects, features, and advantages of the disclosure will be apparent from the following more particular description of certain exemplary embodiments of the disclosure, as illustrated in the accompanying drawings in which:

FIG. 1 illustrates a block diagram of a system for IAB communication;

FIGS. 2a and 2b illustrate an example mobile IAB environment in which embodiments of the present disclosure may be implemented;

FIG. 3 illustrates a schematic diagram of interactions between devices according to some example embodiments of the present disclosure;

FIG. 4 illustrates a schematic diagram of interactions between devices according to some example embodiments of the present disclosure;

FIG. 5 illustrates a schematic diagram of interactions between devices according to some example embodiments of the present disclosure;

fig. 6 illustrates a flowchart of an example method for IAB communications, according to some example embodiments of the present disclosure;

fig. 7 illustrates a flowchart of an example method for IAB communications, according to some example embodiments of the present disclosure;

fig. 8 illustrates a flowchart of an example method for IAB communications, according to some example embodiments of the present disclosure;

Fig. 9 illustrates a flowchart of an example method for IAB communications, according to some example embodiments of the present disclosure;

FIG. 10 illustrates a simplified block diagram of an apparatus suitable for implementing embodiments of the present disclosure; and

fig. 11 illustrates a block diagram of an example computer-readable medium, according to some example embodiments of the present disclosure.

The same or similar reference numbers will be used throughout the drawings to refer to the same or like elements.

Detailed Description

Principles of the present disclosure will now be described with reference to some example embodiments. It should be understood that these embodiments are described merely for the purpose of illustrating and helping those skilled in the art understand and practice the present disclosure and are not meant to limit the scope of the present disclosure in any way. The disclosure described herein may be implemented in various other ways besides those described below.

In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

In this disclosure, references to "one embodiment," "an example embodiment," etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

It will be understood that, although the terms "first" and "second," etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term "and/or" includes any and all combinations of one or more of the listed terms.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises," "comprising," "has," "including," "includes" and/or "including" when used herein, specify the presence of stated features, elements, components, and/or groups thereof, but do not preclude the presence or addition of one or more other features, elements, components, and/or groups thereof.

As used in this application, the term "circuitry" may refer to one or more or all of the following:

(a) Pure hardware circuit implementations (such as implementations using only analog and/or digital circuitry), and

(b) A combination of hardware circuitry and software, such as (as applicable):

(i) Combination of analog and/or digital hardware circuit(s) and software/firmware, and

(ii) Any portion of the hardware processor(s) having software, including digital signal processor(s), software, and memory(s), which work together to cause a device, such as a mobile phone or server, to perform various functions, and

(c) Hardware circuit(s) and/or processor(s), such as microprocessor(s) or a portion of microprocessor(s), that require software (e.g., firmware)

The operation is performed, but the software may not exist when the operation is not required.

The definition of circuitry is applicable to all uses of that term in this application, including in any claims. As another example, as used in this application, the term circuitry also encompasses hardware-only circuitry or a processor (or multiple processors) or an implementation of a hardware circuit or portion of a processor and its accompanying software and/or firmware. For example, if applicable to the particular claim elements, the term circuitry also encompasses a baseband integrated circuit or processor integrated circuit for a mobile device, or a similar integrated circuit in a server, a cellular network device, or other computing or network device.

As used herein, the term "communication network" refers to a network that conforms to any suitable communication standard, such as Long Term Evolution (LTE), LTE-advanced (LTE-a), wideband Code Division Multiple Access (WCDMA), high Speed Packet Access (HSPA), narrowband internet of things (NB-IoT), new Radio (NR), and the like. Furthermore, the communication between the terminal device and the network device in the communication network may be performed according to any suitable generation communication protocol, including, but not limited to, first generation (1G), second generation (2G), 2.5G, 2.75G, third generation (3G), fourth generation (4G), 4.5G, future fifth generation (5G) communication protocols, and/or any other protocol currently known or to be developed in the future. Embodiments of the present disclosure may be applied to various communication systems. In view of the rapid development of communications, there are, of course, future types of communication techniques and systems that can embody the present disclosure. The scope of the present disclosure should not be limited to only the above-described systems.

As used herein, the term "network device" refers to a node in a communication network through which a terminal device accesses the network and receives services from the network. A network device may refer to a Base Station (BS) or an Access Point (AP), e.g., a node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), an NR NB (also known as a gNB), a Remote Radio Unit (RRU), a Radio Header (RH), a Remote Radio Head (RRH), a relay, a low power node (such as a femto, pico, etc.), depending on the terminology and technology applied. In the following description, the terms "network device", "BS" and "node" may be used interchangeably.

The term "terminal device" refers to any terminal device capable of wireless communication. By way of example, and not limitation, a terminal device may also be referred to as a communication device, user Equipment (UE), subscriber Station (SS), portable subscriber station, mobile Station (MS), or Access Terminal (AT). The terminal devices may include, but are not limited to, mobile phones, cellular phones, smart phones, voice over IP (VoIP) phones, wireless local loop phones, tablets, wearable terminal devices, personal Digital Assistants (PDAs), portable computers, desktop computers, image capture terminal devices (such as digital cameras), gaming terminal devices, music storage and playback devices, in-vehicle wireless terminal devices, wireless endpoints, mobile stations, laptop embedded devices (LEEs), laptop in-vehicle devices (LMEs), USB dongles, smart devices, wireless customer premise devices (CPE), internet of things (IoT) devices, watches or other wearable devices, head Mounted Displays (HMDs), vehicles, drones, medical devices and applications (e.g., tele-surgery), industrial devices and applications (e.g., robots and/or other wireless devices operating in the context of industrial and/or automated processing chains), consumer electronic devices, devices operating on commercial and/or industrial wireless networks, and the like. In the following description, the terms "terminal device", "communication device", "terminal", "user equipment" and "UE" may be used interchangeably.

While the functionality described herein may be performed in various example embodiments in fixed and/or wireless network nodes, in other example embodiments the functionality may be implemented in user equipment devices such as cell phones or tablets or laptops or desktops or mobile IOT devices or fixed IOT devices. For example, the user equipment device may be suitably equipped with corresponding capabilities as described in connection with the fixed and/or wireless network node(s). The user equipment device may be a user equipment and/or a control device, such as a chipset or a processor, configured to control the user equipment when installed in the user equipment. Examples of such functions include a bootstrapping server function and/or a home subscriber server, which may be implemented in a user equipment device by providing the user equipment device with software configured to cause the user equipment device to execute from the perspective of these functions/nodes.

Example embodiments of the present disclosure relate to a radio access network with a wireless backhaul of an access point. Backhaul links from the access nodes to the wired part of the network and the core network are dynamically reconfigured with little impact on the user's terminal equipment. The backhaul may be multi-hop or mesh. An important application of embodiments of the present disclosure is for IAB communication in a 3GPP IAB network having a terminal device, an IAB node and a wired IAB donor node. Hereinafter, embodiments of the present disclosure will be described with reference to a 3GPP IAB network. It should be understood that embodiments of the present disclosure may also be applied to any other network having a wireless backhaul.

Fig. 1 shows a block diagram of a system 100 for IAB communication. As shown in fig. 1, system 100 includes a core network 110, IAB donor 120, IAB nodes 130-1 and 130-2 (collectively referred to as "IAB nodes 130" or individually referred to as "IAB nodes 130"), a network device 140 (such as a gNB), and UEs 150-1, 150-2, and 150-3 (collectively referred to as "UE 150" or individually referred to as "UE 150"). The terms "IAB node" and "IAB device" may be used interchangeably herein. The terms "IAB donor node", "IAB donor" and "IAB donor device" may be used interchangeably.

The core network 110 may include many network entities providing different network functions, such as a Network Slice Selection Function (NSSF) 111, a unified data repository (UDM) 112, an access and mobility management function (AMF) 113, a Network Function (NF) repository function (NRF), a Session Management Function (SMF), a Policy Control Function (PCF), a Network Exposure Function (NEF), etc.

The IAB donor 120 may include a Centralized Unit (CU) 121 (also referred to as an "IAB donor CU 121") and a Distributed Unit (DU) 122 (also referred to as an "IAB donor DU 122"). IAB node 130-1 may include MT part 131-1 and DU 132-1.IAB node 130-2 may include MT portion 131-2 and DU 132-2.MT 131-1 and 131-2 are also collectively referred to as "IAB MT 131" or individually as "IAB MT 131". DUs 132-1 and 132-2 are also collectively referred to as "IAB DUs 132" or individually as "IAB DUs 132".

The or each IAB donor DU 122, 132 may provide one or more cells to serve the UE. For example, a cell provided by a DU may broadcast normal control signals such as a Synchronization Signal Block (SSB) for downlink synchronization, and system information. Thus, from the UE's point of view, the cell provided by the DU may be regarded as a normal cell. For example, as shown in FIG. 1, IAB donor DU 122 serves UE 150-1, IAB DU 132-1 serves UE 150-2, and IAB DU 132-2 serves UE 150-3.

The IAB MT 131 of the IAB node 130 may act as a UE towards its parent node. For example, IAB MT 131-1 may act as a UE towards IAB donor node 120 (i.e., IAB donor DU 122), and IAB MT 131-2 may act as a UE towards IAB node 130-1 (i.e., IAB DU 132-1). On the sub-link, the IAB DU 132 of the IAB node 130 may act as a network device (such as a gNB) towards its next hop IAB node. For example, IAB donor DU 122 may act as a gNB towards IAB node 130-1 and IAB DU 132-1 may act as a gNB towards IAB node 130-2. On the access link, as described above, the IAB donor 120 and the IAB node 130 may act as a normal gcb to provide a wireless interface for UEs 150 in their coverage area.

In environment 100, each IAB MT 132 may have an RRC connection with an IAB donor CU 121 and a non-access stratum (NAS) connection with an AMF 113. Each IAB node 130 (i.e., IAB DU 132) maintains an F1 interface to an IAB donor 120 (i.e., IAB donor CU 121). It can thus be inferred that the IAB node 130 has both access node functionality (by means of the IAB DU 132 with the F1 interface to the IAB donor CU 121) and UE functionality (by means of the IAB MT 131 with the RRC connection to the IAB donor CU 121 and the NAS connection to the AMF 113).

Communication in environment 100 may be implemented in accordance with any suitable communication protocol(s), including but not limited to first generation (1G), second generation (2G), third generation (3G), fourth generation (4G), and fifth generation (5G) cellular communication protocols, wireless local network communication protocols such as Institute of Electrical and Electronics Engineers (IEEE) 802.11, and/or any other protocol currently known or to be developed in the future. Further, the communication may utilize any suitable wireless communication technology including, but not limited to: code Division Multiple Access (CDMA), frequency Division Multiple Access (FDMA), time Division Multiple Access (TDMA), frequency Division Duplex (FDD), time Division Duplex (TDD), multiple Input Multiple Output (MIMO), orthogonal Frequency Division Multiple Access (OFDMA), and/or any other technique currently known or developed in the future.

An IAB node may need to change its serving node due to a failure of the Backhaul (BH) connection or a change in the IAB topology or IAB mobility. Such a change in backhaul topology may involve a change in the parent IAB node of the IAB node or even the IAB donor. In the former case, the cell configuration is maintained and the change is transparent to the UE served by the IAB node. In the latter case, the cell configuration will be adapted by the new IAB donor, e.g. the security context may change. This is particularly true for mobile IAB nodes where BH changes frequently and IAB donors may change at some point in time.

The IAB node may have different implementation options or modes of operation. For example, the IAB node may be installed on a fixed infrastructure (e.g., a lamppost or street furniture). Such an IAB node may be referred to as a fixed IAB node. Depending on the channel conditions on the wireless backhaul, the fixed IAB node may migrate from one donor IAB node to a neighboring donor IAB node. Another IAB node implementation may be where the IAB node is installed on a vehicle and the IAB node is active (i.e., serving UE), at which time the IAB is static or slow moving, and in particular the serving UE outside the vehicle. For example, when the vehicle is parked, the IAB node may serve a UE external to the vehicle. When the nomadic IAB is not active (i.e., operational), it may enter an idle mode, e.g., similar to RRC idle or RRC inactive. Such an IAB node may be referred to as a nomadic IAB node. The nomadic IAB node may be integrated into a vehicle such as a car sharing fleet or a taxi fleet. Nomadic IAB nodes may be used to provide coverage and/or capacity enhancements. Another concept of IAB (i.e., mobile IAB) has recently been proposed. The mobile IAB node is located on a mobile object (e.g., a vehicle or balloon or drone) and provides wireless access to UE(s) inside or outside the mobile object. In some cases, the UE may be physically attached to a mobile (e.g., inside a vehicle carrying the IAB node) of the mobile IAB node. In this case, the UE preferably remains connected to the mobile IAB node.

Fig. 2a and 2b illustrate an example mobile IAB environment 200 in which embodiments of the present disclosure may be implemented. As shown in fig. 2a and 2b, environment 200 includes an IAB donor 210 (hereinafter also referred to as a "first IAB donor"), an IAB donor 220 (hereinafter also referred to as a "second IAB donor"), an IAB node 230, and UEs 240-1 and 240-2 (collectively referred to as "UE 240" or individually referred to as "UE 240").

The IAB donor 210 includes a CU 211 (hereinafter also referred to as "IAB donor CU 211") and a DU 212 (hereinafter also referred to as "IAB donor DU 212"). The IAB donor 220 includes a CU 221 (hereinafter also referred to as "IAB donor CU 221") and a DU 222 (hereinafter also referred to as "IAB donor DU 222"). The IAB node 230 includes an MT 231 (hereinafter also referred to as "IAB MT 231") and a DU 232 (hereinafter also referred to as "IAB DU 232"). The IAB donor DU 212 may provide cell 250-1 and the IAB donor DU 222 provides cell 250-2. An Xn interface 270 exists between IAB donor CU 211 and IAB donor CU 221. The Xn interface 270 may also be referred to herein as a "third interface".

Initially, as shown in fig. 2a, an IAB node 230 may be located in a cell 250-1 (hereinafter also referred to as a "first cell") and served by an IAB donor 210. The F1 interface 280 may be established between the IAB donor CU 211 and the IAB DU 232. The F1 interface 280 may also be referred to herein as a "first interface". The IAB DU 232 may provide cells 260-1 and 260-2 to serve the UE 240. For example, the PCI of cell 260-1 may be X and the PCI of cell 260-2 may be Y.

The IAB node 230 may then move out of the cell 250-1 and into the cell 250-2 (hereinafter also referred to as "second cell") as shown in fig. 2 b. This may trigger a BH change from the old cell 250-1 to the target cell 250-2 provided by the IAB donor DU 222.

Conventionally, in this case, the PCI of the cells 260-1 and 260-2 provided by the IAB DU 232 needs to be changed to avoid PCI collision due to the movement of the IAB node 230. However, if the PCI of cells 260-1 and 260-2 served by IAB DU 232 are changed during the handover and connection to IAB donor 220, then a handover or RRC reestablishment procedure will be used in order to reconfigure UE 240 connected to IAB node 230. This may result in connection and service interruption at the UE 240 connected to the IAB node 230.

Embodiments of the present disclosure provide a solution for IAB communications to address the above-described problems and one or more other potential problems. This solution enables the PCI of the cell provided by the migrating IAB node to remain unchanged. In this way, the solution can minimize the impact on UEs served by the migrating IAB node during inter-donor topology adaptation, since the RRC connection to the cell will be maintained and no connection interruption will occur at the UE. Furthermore, the solution may minimize the signalling required over the radio interface.

Specifically, as shown in fig. 2b, the target IAB donor CU (e.g., IAB donor CU 221) may generate an RRC reconfiguration message (with or without synchronization). The RRC reconfiguration message may be sent to UE 240 by the target donor CU (CU 221) or by the source IAB donor CU (e.g., IAB donor CU 211) via IAB DU 232. The reconfiguration message generated by the IAB donor CU 221 may include the new security configuration of the IAB donor CU 221 to be used after the reconfiguration.

If an RRC reconfiguration message is sent from the IAB donor CU 211 to the UE 240, the RRC reconfiguration message may be provided by the target donor CU 221 to the IAB donor CU 211 via the third interface 270 and encrypted by the IAB donor CU 211. An RRC message may then be sent from the IAB donor CU 211 to the IAB node 230 via the F1 interface 280 before the IAB node 230 changes the link of its MT 231.

If an RRC reconfiguration message is sent from the IAB donor CU 221 to the UE 240, the RRC reconfiguration message may be generated once the F1 interface 290 between the IAB DU 232 and the IAB donor CU 221 is established and the cells 260-1 and 260-2 are active operating under the IAB donor CU 221. The F1 interface 290 may also be referred to herein as a "second interface".

If an RRC reconfiguration message is sent from the IAB donor CU 221 to the UE 240, the IAB donor CU 221 may request that the IAB donor CU 211 encrypt the RRC reconfiguration message based on its security parameters and send the encrypted RRC reconfiguration message back to the IAB donor CU 221 so that the UE 240 will be able to decrypt the message. Once the RRC connection from the migrating IAB node 230 (i.e., IAB MT 231) to the IAB donor 220 is established and the F1 interface 290 between the IAB DU 232 and the IAB donor CU 221 is established, the IAB node 230 may send an RRC reconfiguration message to the UE 240 connected to the IAB node 230.

Even after reconfiguration, the UE240 connected to the IAB node 230 may remain connected to the same cells 260-1 and 260-2 of the IAB node 230 because the PCIs of the cells 260-1 and 260-2 have not changed. Since the UE240 is still synchronized with the same cell, the UE240 may not need a random access procedure. The IAB donor CUs 221 does not have to reserve (reserve) access resources (e.g., for contention-free random access procedures) for the cells of the IAB node 230. The HO procedure of the UE240 may not be performed during the migration of the IAB node 230. The UE240 may only need to change the security configuration, i.e., the security key, for use with the target IAB donor CU 221.

Fig. 3 illustrates a schematic diagram of interactions 300 between devices according to some example embodiments of the present disclosure. For example, interaction 300 involves UE240 (such as UE 240-1 or 240-2), IAB node 230, IAB donor 210, and IAB donor 220.

As shown in fig. 3, the IAB MT 231 transmits 301 a measurement report to the IAB donor CU 211, for example, via RRC signaling. In some example embodiments, the measurement report may be triggered by a configured HO event indicating better connection quality on an alternate link to the IAB donor DU 222 under the IAB donor CU 221.

The IAB donor CU 211 decides 302 to handover the IAB node 230 (radio connection with the IAB MT 231) to the cell served by the IAB donor 220. The handover procedure may be any of a normal one or other mobility procedures, such as Conditional Handover (CHO). It should be understood that the scope of the present disclosure is not limited to the selection of the HO procedure of the IAB MT 231.

The IAB donor CU 211 transmits 303 the HO request to the IAB donor CU 221. The HO request may be directed not only to the IAB MT 231 but also to the UE 240 connected to the IAB node 230 in the cell served by the IAB DU 232. It should be appreciated that the migrating IAB node 230 may also have descendants/child nodes and that during migration, the connection should also be reconfigured for it, which is not shown in fig. 3. In some example embodiments, the HO request may include the F1 interface of the IAB donor CU 211 and the context of the UE 240. It should be appreciated that the context transfer may also occur with other signaling than the HO request (e.g., context retrieval).

The IAB donor CU 221 performs 304 admission control by evaluating the likelihood of accommodating traffic moving with the IAB node 230. Here, it is assumed that the admission control of the IAB node 230 and the UE 240 is successful.

The IAB donor CU 221 transmits 305 to the IAB donor CU 211 an acknowledgement comprising the HO command of the IAB MT 231 and the RRC reconfiguration message of the UE 240. The RRC reconfiguration message may indicate a reconfiguration procedure without synchronization. That is, since the cell(s) served by the IAB DU 232 are not changed, the UE 240 will not acquire uplink synchronization by performing a random access procedure.

The IAB donor CU 211 transmits 306 the HO command to the IAB MT 231. Furthermore, IAB donor CU 211 transmits 307 an RRC reconfiguration message of ue 240 to IAB DU 232 via F1 application protocol (F1 AP) signaling. In some example embodiments, IAB donor CU 211 may also indicate that F1 and UE context should be maintained even if a new F1 interface with IAB donor CU 221 is established. In some example embodiments, the IAB node 230 (i.e., the IAB DU 232) may store the RRC reconfiguration message of the UE 240. The IAB node 230 may also store the current cell radio network temporary identifier(s) C-RNTI because the UE 240 will continue to monitor the current C-RNTI(s). The C-RNTI(s) may change or remain unchanged after the migration of the IAB node 230.

The IAB node 230 initiates 308HO execution to the target cell (i.e., the cell served by the IAB donor DU 222). In some example embodiments, the HO execution may immediately follow the HO command (i.e., normal HO procedure). Alternatively, if conditional HO is used, configured CHO triggers may be used to initiate HO execution.

The IAB MT 231 accesses 309 a target cell served by the IAB donor DU 222 and establishes an RRC connection to the IAB donor CU 221. The IAB MT 231 transmits 310 a HO complete message to the IAB donor CU 221.

An F1 setup procedure is initiated to establish 311 the F1 interface 290 between the IAB DU 232 and the IAB donor CU 221. In some example embodiments, the stored context may be restored (after 307). For example, there may be a separate indication from the IAB DU 232 (which has the stored context) or from the IAB donor CU 221 to restore the stored context if it wants to proceed with the new procedure.

Since the cell(s) served by the IAB DU 232 continue to be active, the IAB DU 232 transmits 312RRC reconfiguration messages to the UE 240 using the C-RNTI(s) that the UE 240 is monitoring, even after the F1 interface 290 with the IAB donor CU 221 is established. Because encryption of the RRC reconfiguration message has been completed using the security parameters of the IAB donor CU 211, the UE 240 will be able to decrypt and decode the message. The RRC reconfiguration message may include a new security configuration valid for the connection to the IAB donor CU 221. It should be noted that since the cell/PCI does not change, the change of the serving CU of the UE 240 is gradual (gradual) when a reconfiguration message is sent to the UE 240.

UE 240 transmits 313 an RRC reconfiguration complete message to IAB DU 232 and, after UE 240 is controlled by IAB donor CU 221, IAB DU 232 forwards 314 the RRC reconfiguration complete message via F1AP signaling. After successful completion of the procedure, IAB donor CU 221 can release 315 the context in IAB donor CU 211 and perform path switching on the traffic data.

Fig. 4 illustrates a schematic diagram of interactions 400 between devices according to some example embodiments of the present disclosure. For example, interaction 400 involves UE 240 (such as UE 240-1 or 240-2), IAB node 230, IAB donor 210 (hereinafter also referred to as "source IAB donor"), and IAB donor 220 (hereinafter also referred to as "target IAB donor"). The main difference between fig. 3 and fig. 4 is that once the F1 interface between the IAB DU 232 and the IAB donor CU 221 is established, the RRC reconfiguration message of the UE 240 is not sent via the IAB donor CU 211, but directly from the IAB donor CU 221 to the migrating IAB DU 232.

As shown in fig. 4, the IAB MT 231 transmits 401 a measurement report to the IAB donor CU 211, for example, via RRC signaling. In some example embodiments, the measurement report may be triggered by a configured HO event indicating better connection quality on an alternate link to the IAB donor DU 222 under the IAB donor CU 221.

The IAB donor CU 211 decides 402 to handover the IAB node 230 (radio connection with the IAB MT 231) to the cell served by the IAB donor 220. The handover procedure may be any of a normal one or other mobility procedures, such as Conditional Handover (CHO). It should be understood that the scope of the present disclosure is not limited to the selection of the HO procedure of the IAB MT 231.

The IAB donor CU 211 transmits 403 a HO request to the IAB donor CU 221. The HO request may be directed not only to the IAB MT 231 but also to the UE 240 connected to the IAB node 230 in the cell served by the IAB DU 232. It should be appreciated that the migrating IAB node 230 may also have descendants/child nodes and that during migration, the connection should also be reconfigured for it, which is not shown in fig. 4. In some example embodiments, the HO request may include the F1AP interface of the IAB donor CU 211 and the context of the UE 240. It should be appreciated that the context transfer may also occur with other signaling than the HO request (e.g., context retrieval).

The IAB donor CU 221 performs 404 admission control by evaluating the likelihood of adapting to traffic moving with the IAB node 230. Here, it is assumed that the admission control of the IAB node 230 and the UE 240 is successful.

The IAB donor CU 221 transmits 405 to the IAB donor CU 211 an acknowledgement comprising the HO command of the IAB MT 231 and the RRC reconfiguration message of the UE 240. In some embodiments, the HO command and RRC reconfiguration may be transmitted in separate messages at different times. The RRC reconfiguration message may indicate a reconfiguration procedure with or without synchronization. If the RRC reconfiguration message indicates a reconfiguration procedure without synchronization, the UE 240 will not acquire uplink synchronization by performing a random access procedure because the cell(s) served by the IAB DU 232 are not changed.

The IAB donor CU 211 transmits 406 the HO command to the IAB MT 231. In response to receiving 405 the acknowledgement from the IAB donor CU 221, the IAB donor CU 211 encrypts the RRC reconfiguration message with its own security parameters and transmits 407b the encrypted RRC reconfiguration message back to the IAB donor CU 221. The IAB donor CU 211 may also indicate 407a F1 and UE context to the IAB DU 232 via F1AP signaling that should be maintained even if a new F1 interface with the IAB donor CU 221 is established.

The IAB node 230 initiates 408HO execution to the target cell (i.e., the cell served by the IAB donor DU 222). In some example embodiments, the HO execution may immediately follow the HO command (i.e., normal HO procedure). Alternatively, if conditional HO is used, configured CHO triggers may be used to initiate HO execution.

The IAB MT 231 accesses 409 a target cell served by the IAB donor DU 222 and establishes an RRC connection to the IAB donor CU 221. The IAB MT 231 transmits 410 a HO complete message to the IAB donor CU 221.

An F1 setup procedure is initiated to establish 411 an F1 interface 290 between the IAB DU 232 and the IAB donor CU 221. Once the F1 interface 290 is established, the IAB donor CU 221 transmits 412 an RRC reconfiguration message directly to the IAB DU 232 via F1AP signaling over the established F1 interface 290.

Since the cell(s) served by the IAB DU 232 continue to be active, the IAB DU 232 transmits 413 an RRC reconfiguration message to the UE 240 using the C-RNTI(s) that the UE 240 is monitoring, even after the F1 interface 290 with the IAB donor CU 221 is established. Because encryption of the RRC reconfiguration message has been completed using the security parameters of the IAB donor CU 211, the UE 240 will be able to decrypt and decode the message. The RRC reconfiguration message may include a new security configuration valid for the connection to the IAB donor CU 221. It should be noted that since the cell/PCI is not changed, the change of the serving CU of the UE 240 is gradual when a reconfiguration message is sent to the UE 240.

UE 240 transmits 414 an RRC reconfiguration complete message to IAB DU 232 and, after UE 240 is controlled by IAB donor CU 221, IAB DU 232 forwards 415 the RRC reconfiguration complete message via F1AP signaling. After successful completion of the procedure, IAB donor CU 221 may release 416 the context in IAB donor CU 211 and perform path switching on the traffic data.

Fig. 5 illustrates a schematic diagram of interactions 500 between devices according to some example embodiments of the present disclosure. For example, interaction 500 involves UE 240 (such as UE 240-1 or 240-2), IAB node 230, IAB donor 210 (hereinafter also referred to as "source IAB donor"), and IAB donor 220 (hereinafter also referred to as "target IAB donor"). The main difference between fig. 4 and fig. 5 is when RRC reconfiguration messages are exchanged between the IAB donor CU 211 and the IAB donor CU 221.

As shown in fig. 5, the IAB MT 231 transmits 501 a measurement report to the IAB donor CU 211, for example, via RRC signaling. In some example embodiments, the measurement report may be triggered by a configured HO event indicating better connection quality on an alternate link to the IAB donor DU 222 under the IAB donor CU 221.

The IAB donor CU 211 decides 502 to handover the IAB node 230 (radio connection with the IAB MT 231) to the cell served by the IAB donor 220. The handover procedure may be any of a normal one or other mobility procedures, such as Conditional Handover (CHO). It should be understood that the scope of the present disclosure is not limited to the selection of the HO procedure of the IAB MT 231.

The IAB donor CU 211 transmits 503 a HO request to the IAB donor CU 221. The HO request may be directed not only to the IAB MT 231 but also to the UE 240 connected to the IAB node 230 in the cell served by the IAB DU 232. It should be appreciated that the migrating IAB node 230 may also have descendants/child nodes and that during migration, the connection should also be reconfigured for it, which is not shown in fig. 4. In some example embodiments, the HO request may include the F1AP interface of the IAB donor CU 211 and the context of the UE 240. It should be appreciated that the context transfer may also occur with other signaling than the HO request (e.g., context retrieval).

The IAB donor CU 221 performs 504 admission control by evaluating the likelihood of adapting to traffic moving with the IAB node 230. Here, it is assumed that the admission control of the IAB node 230 and the UE 240 is successful.

The IAB donor CU 221 transmits 505 an acknowledgement to the IAB donor CU 211 including the HO command of the IAB MT 231. Unlike fig. 4, there is no RRC reconfiguration message of the UE 240 in the acknowledgement. However, the IAB donor CU 221 may indicate that the RRC reconfiguration message of the UE 240 will be sent later. The IAB donor CU 211 transmits 506 the HO command to the IAB MT 231.

The IAB donor CU 211 may indicate 507 via F1AP signaling to the IAB DU 232 that the F1 and UE context should be maintained even if a new F1 interface with the IAB donor CU 221 is established.

The IAB node 230 initiates 508HO execution to the target cell (i.e., the cell served by the IAB donor DU 222). In some example embodiments, the HO execution may immediately follow the HO command (i.e., normal HO procedure). Alternatively, if conditional HO is used, configured CHO triggers may be used to initiate HO execution.

The IAB MT 231 accesses 509 the target cell served by the IAB donor DU 222 and establishes an RRC connection to the IAB donor CU 221. The IAB MT 231 transmits 510 a HO complete message to the IAB donor CU 221.

An F1 setup procedure is initiated to establish 511F1 interface 290 between IAB DU 232 and IAB donor CU 221. Once the F1 interface 290 is established, the IAB donor CU 221 may generate an RRC reconfiguration message for the UE 240. The RRC reconfiguration message may indicate a reconfiguration procedure with or without synchronization. If the RRC reconfiguration message indicates a reconfiguration procedure without synchronization, the UE 240 will not acquire uplink synchronization by performing a random access procedure because the cell(s) served by the IAB DU 232 are not changed. The IAB donor CU 221 transmits 512 to the IAB donor CU 211 an acknowledgement of the RRC reconfiguration message including the UE 240. The RRC reconfiguration message may include the new security configuration valid for the connection to the IAB donor CU 221, as well as the target cell parameters. This delayed generation of the RRC reconfiguration message allows the IAB donor CU 221 to change the cell parameters of the IAB DU 232 (if needed).

The IAB donor CU 211 encrypts the RRC reconfiguration message with its own security parameters and transmits 513 the encrypted RRC reconfiguration message back to the IAB donor CU 221. The IAB donor CU 221 transmits 514 the RRC reconfiguration message directly to the IAB DU 232 via F1AP signaling through the established F1 interface 290.

Since the cell(s) served by the IAB DU 232 continue to be active, the IAB DU 232 transmits 515 an RRC reconfiguration message to the UE 240 using the C-RNTI(s) that the UE 240 is monitoring, even after the F1 interface 290 with the IAB donor CU 221 is established. Because encryption of the RRC reconfiguration message has been completed using the security parameters of the IAB donor CU 211, the UE 240 will be able to decrypt and decode the message. The RRC reconfiguration message may include a new security configuration valid for the connection to the IAB donor CU 221. It should be noted that since the cell/PCI is not changed, the change of the serving CU of the UE 240 is gradual when a reconfiguration message is sent to the UE 240.

UE 240 transmits 516 an RRC reconfiguration complete message to IAB DU 232 and, after UE 240 is controlled by IAB donor CU 221, IAB DU 232 forwards 517 the RRC reconfiguration complete message via F1AP signaling. After successful completion of the procedure, IAB donor CU 221 can release 518 the context in IAB donor CU 211 and perform path switching on the traffic data.

Fig. 6 illustrates a flowchart of an example method 600 for IAB communication, according to some example embodiments of the present disclosure. The method 600 may be implemented at the IAB donor 210 shown in fig. 2a and/or fig. 2 b. Hereinafter, the IAB donor 210 is also referred to as "first device", the IAB donor 220 is also referred to as "second device", the IAB node 230 is also referred to as "third device", and the UE 240 is also referred to as "fourth device". It should be understood that method 600 may include additional blocks not shown and/or that some of the blocks shown may be omitted, and the scope of the present disclosure is not limited in this respect.

At block 610, the first device receives a reconfiguration message from the second device for a fourth device in a serving cell served by a third device. The third device migrates from a first cell in communication with the first device to a second cell in communication with the second device while leaving the cell identifier of the serving cell unchanged. The reconfiguration message instructs the fourth device to update the configuration for the second device.

In some example embodiments, the reconfiguration message instructs the fourth device to update the configuration for the second device without performing the random access procedure.

In some example embodiments, the first device transmits a handover request to the second device, the handover request for a handover of the third device from the first cell to the second cell and for a reconfiguration of the fourth device. In response to the second device allowing the handover, the first device receives a handover confirmation from the second device, the handover confirmation including a handover command for the third device and a reconfiguration message for the fourth device.

In some example embodiments, the first device transmits a handover request to the second device, the handover request for a handover of the third device from the first cell to the second cell and for a reconfiguration of the fourth device. In response to the second device allowing the handover, the first device receives a handover acknowledgement from the second device, the handover acknowledgement including a handover command for the third device and an indication of the delayed transmission of the reconfiguration message. For example, if a HO acknowledgement is returned only for the third device, the indication of the delayed transmission may be implicit. The first device receives a reconfiguration message from the second device in response to establishment of the second interface between the third device and the second device.

In some example embodiments, the handover request includes context information of the fourth device and of the first interface between the third device and the first device.

At block 620, the first device encrypts the reconfiguration message based on the security parameters of the first device.

At block 630, the first device provides the encrypted reconfiguration message to the third device.

In some example embodiments, the first device transmits the encrypted reconfiguration message to the third device via a first interface between the third device and the first device.

In some example embodiments, the first device transmits the encrypted reconfiguration message to the second device via a third interface between the first device and the second device, such that the second device transmits the encrypted reconfiguration message to the third device via the second interface between the third device and the second device.

In some example embodiments, the first device transmits an indication to the third device via a first interface between the third device and the first device to reserve the context information of the first interface and the fourth device.

In some example embodiments, the first device is a first IAB donor (e.g., IAB donor 210), the second device is a second IAB donor (e.g., IAB donor 220), the third device is an IAB node (e.g., IAB node 230), and the fourth device is a terminal device (e.g., UE 240).

Fig. 7 illustrates a flowchart of an example method 700 for IAB communication, according to some example embodiments of the present disclosure. The method 700 may be implemented at the IAB donor 220 as shown in fig. 2a and/or fig. 2 b. Hereinafter, the IAB donor 210 is also referred to as "first device", the IAB donor 220 is also referred to as "second device", the IAB node 230 is also referred to as "third device", and the UE 240 is also referred to as "fourth device". It should be understood that method 700 may include additional blocks not shown and/or that some of the blocks shown may be omitted, and the scope of the present disclosure is not limited in this respect.

At block 710, the second donor generates a reconfiguration message for a fourth device in a serving cell served by a third device that migrates from a first cell in communication with the first device to a second cell in communication with the second device while leaving a cell identifier of the serving cell unchanged. The reconfiguration message instructs the fourth device to update the configuration for the second device.

At block 720, the second device transmits a reconfiguration message to the first device.

In some example embodiments, the second device receives a handover request from the first device for a handover of the third device from the first cell to the second cell and for a reconfiguration of the fourth device. The second device determines whether to allow the handover based on the handover request. In accordance with the determination that the handover is allowed, the second device generates a reconfiguration message and transmits a handover acknowledgement to the first device, the handover acknowledgement including a handover command for the third device and a reconfiguration message for the fourth device.

In some example embodiments, the second device receives a handover request from the first device for a handover of the third device from the first cell to the second cell and for a reconfiguration of the fourth device. The second device determines whether to allow the handover based on the handover request. In accordance with the determination that the handover is allowed, the second device transmits a handover acknowledgement to the first device, the handover acknowledgement including a handover command for the third device and an indication of the delayed transmission of the reconfiguration message. For example, if a HO acknowledgement is returned only for the third device, the indication of the delayed transmission may be implicit. In response to the second interface between the third device and the second device being established, the second device generates a reconfiguration message and transmits to the first device a further handover confirmation comprising the generated reconfiguration message.

In some example embodiments, the second device receives, from the first device via a third interface between the first device and the second device, a reconfiguration message encrypted based on the security parameters of the first device. In response to the second interface being established between the third device and the second device, the second device transmits a reconfiguration message to the third device via the second interface.

Fig. 8 illustrates a flowchart of an example method 800 for IAB communication, according to some example embodiments of the present disclosure. The method 800 may be implemented at the IAB node 230 shown in fig. 2a and/or fig. 2 b. Hereinafter, the IAB donor 210 is also referred to as "first device", the IAB donor 220 is also referred to as "second device", the IAB node 230 is also referred to as "third device", and the UE 240 is also referred to as "fourth device". It should be understood that method 800 may include additional blocks not shown and/or that some of the blocks shown may be omitted, and the scope of the present disclosure is not limited in this respect.

At block 810, the third device receives a reconfiguration message from the first device or the second device for a fourth device in a serving cell served by the third device. The third device migrates from a first cell in communication with the first device to a second cell in communication with the second device while leaving the cell identifier of the serving cell unchanged. The reconfiguration message instructs the fourth device to update the configuration for the second device.

At block 820, the third device forwards the reconfiguration message to the fourth device.

At block 830, the third device receives a reconfiguration complete message from the fourth device.

In some example embodiments, the third device receives a reconfiguration message from the first device via a first interface between the third device and the first device, the reconfiguration message being encrypted based on a security parameter of the first device. In some example embodiments, the third device stores the reconfiguration message at the third device. In response to a trigger for transmission of the reconfiguration message, the third device transmits the reconfiguration message to the fourth device by leaving the identifier of the serving cell unchanged. In some example embodiments, the trigger includes any one of the following: establishment of a second interface between an IAB anode (anode) and a second device; initiating, by the third device, a handover procedure; or the completion of the handover procedure by the third device.

In some example embodiments, the third device receives a reconfiguration message from the second device via a second interface between the third device and the second device, the reconfiguration message being encrypted based on the security parameters of the first device.

In some example embodiments, the third device receives, from the first device via a first interface between the third device and the first device, an indication to retain context information of the first interface and the fourth device; and storing the context information at the third device.

Fig. 9 illustrates a flowchart of an example method 900 for IAB communication, according to some example embodiments of the present disclosure. The method 900 may be implemented at the UE 240 as shown in fig. 2a and/or fig. 2 b. Hereinafter, the IAB donor 210 is also referred to as "first device", the IAB donor 220 is also referred to as "second device", the IAB node 230 is also referred to as "third device", and the UE 240 is also referred to as "fourth device". It is to be appreciated that method 900 may include additional blocks not shown and/or that some of the blocks shown may be omitted, and the scope of the present disclosure is not limited in this respect.

At block 910, the fourth device receives a reconfiguration message from a third device that provides a serving cell for serving the fourth device. The third device migrates from a first cell in communication with the first device to a second cell in communication with the second device while leaving the cell identifier of the serving cell unchanged. The reconfiguration message includes a new configuration for the second device.

At block 920, the fourth device updates the configuration used at the fourth device with the new configuration without performing the random access procedure.

At block 930, the fourth device transmits a reconfiguration complete message to the third device.

In some example embodiments, the reconfiguration message is encrypted based on security parameters of the first device. The fourth device decrypts the reconfiguration message based on the security parameters of the first device and decodes the reconfiguration message to obtain the configuration for the second device.

In some example embodiments, an apparatus capable of performing the method 600 may include means for performing the respective steps of the method 600. The component may be implemented in any suitable form. For example, the components may be implemented in circuitry or software modules.

In some example embodiments, an apparatus capable of performing the method 600 (e.g., IAB donor 210) includes: means for receiving a reconfiguration message from the second device for a fourth device in a serving cell served by a third device, the third device migrating from a first cell in communication with the apparatus to a second cell in communication with the second device while leaving a cell identifier of the serving cell unchanged, and the reconfiguration message indicating that the fourth device updates the configuration for the second device; means for encrypting the reconfiguration message based on the security parameters of the apparatus; and means for providing the encrypted reconfiguration message to the third device.

In some example embodiments, the means for receiving the reconfiguration message comprises: means for transmitting a handover request to the second device, the handover request being for a handover of the third device from the first cell to the second cell and for a reconfiguration of the fourth device; and means for receiving a handover confirmation from the second device in response to the second device allowing the handover, the handover confirmation comprising a handover command for the third device and a reconfiguration message for the fourth device.

In some example embodiments, the means for receiving the reconfiguration message comprises: means for transmitting a handover request to the second device, the handover request being for a handover of the third device from the first cell to the second cell and for a reconfiguration of the fourth device; means for receiving a handover acknowledgement from the second device in response to the second device allowing the handover, the handover acknowledgement comprising a handover command for the third device and an indication of a delayed transmission of the reconfiguration message; and means for receiving a reconfiguration message from the second device in response to a second interface between the third device and the second device being established.

In some example embodiments, the handover request includes context information of the fourth device and of the first interface between the third device and the apparatus.

In some example embodiments, the means for providing the encrypted reconfiguration message to the third device comprises: means for transmitting the encrypted reconfiguration message to the third device via a first interface between the third device and the apparatus.

In some example embodiments, the apparatus capable of performing the method 600 further comprises: means for transmitting an indication to the third device that context information of the first interface and the fourth device is preserved via the first interface between the third device and the apparatus.

In some example embodiments, the means for providing the encrypted reconfiguration message to the third device comprises: means for transmitting the encrypted reconfiguration message to the second device via a third interface between the apparatus and the second device, such that the second device transmits the encrypted reconfiguration message to the third device via the second interface between the third device and the second device.

In some example embodiments, the apparatus is a first IAB donor, the second device is a second IAB donor, the third device is an IAB node, and the fourth device is a terminal device.

In some example embodiments, an apparatus capable of performing the method 700 may include means for performing the respective steps of the method 700. The component may be implemented in any suitable form. For example, the components may be implemented in circuitry or software modules.

In some example embodiments, an apparatus (e.g., IAB donor 220) capable of performing method 700 comprises: means for generating a reconfiguration message for a fourth device in a serving cell served by a third device, the third device migrating from a first cell in communication with the first device to a second cell in communication with the apparatus while leaving a cell identifier of the serving cell unchanged, and the reconfiguration message indicating that the fourth device updates a configuration for the apparatus; and means for transmitting the reconfiguration message to the first device.

In some example embodiments, the reconfiguration message instructs the fourth device to update the configuration for the apparatus without performing the random access procedure.

In some example embodiments, the means for generating the reconfiguration message comprises: means for receiving a handover request from the first device, the handover request being for a handover of the third device from the first cell to the second cell and for a reconfiguration of the fourth device; means for determining whether to allow handover based on the handover request; and means for generating a reconfiguration message in accordance with the determination to allow handover. The means for transmitting the reconfiguration message to the first device comprises: means for transmitting a handover acknowledgement to the first device, the handover acknowledgement comprising a handover command for the third device and a reconfiguration message for the fourth device.

In some example embodiments, the means for generating the reconfiguration message comprises: means for receiving a handover request from the first device, the handover request being for a handover of the third device from the first cell to the second cell and for a reconfiguration of the fourth device; means for determining whether to allow handover based on the handover request; means for transmitting a handover acknowledgement to the first device in accordance with the determination that the handover is allowed, the handover acknowledgement comprising a handover command for the third device and an indication of the delayed transmission of the reconfiguration message; and means for generating a reconfiguration message in response to a second interface between the third apparatus and the device being established. The means for transmitting the reconfiguration message to the first device comprises: means for transmitting a further handover confirmation to the first device, the further handover confirmation comprising the generated reconfiguration message.

In some example embodiments, the apparatus capable of performing the method 700 further comprises: means for receiving, from the first device, a reconfiguration message encrypted based on the security parameters of the first device via a third interface between the first device and the apparatus; and means for transmitting a reconfiguration message to the third device via the second interface in response to the second interface between the third device and the apparatus being established.

In some example embodiments, the first device is a first IAB donor, the apparatus is a second IAB donor, the third device is an IAB node, and the fourth device is a terminal device.

In some example embodiments, an apparatus capable of performing the method 800 may include means for performing the respective steps of the method 800. The component may be implemented in any suitable form. For example, the components may be implemented in circuitry or software modules.

In some example embodiments, an apparatus (e.g., IAB node 230) capable of performing method 800 comprises: means for receiving a reconfiguration message from the first device or the second device for a fourth device in a serving cell served by the apparatus, the apparatus migrating from the first cell in communication with the first device to the second cell in communication with the second device while leaving a cell identifier of the serving cell unchanged, and the reconfiguration message indicating that the fourth device updates the configuration for the second device; forwarding the reconfiguration message to the fourth device; and means for receiving a reconfiguration complete message from the fourth device.

In some example embodiments, the means for receiving the reconfiguration message comprises: means for receiving a reconfiguration message from the first device via a first interface between the apparatus and the first device, the reconfiguration message being encrypted based on a security parameter of the first device.

In some example embodiments, the means for forwarding the reconfiguration message to the fourth device comprises: means for storing the reconfiguration message at the apparatus; and means for transmitting the reconfiguration message to the fourth device in response to a trigger for transmission of the reconfiguration message.

In some example embodiments, the trigger includes any one of the following: establishing a second interface between the device and a second apparatus; initiating a handover procedure by the apparatus; or by the device to complete the handover process.

In some example embodiments, the means for receiving the reconfiguration message comprises: means for receiving a reconfiguration message from the second device via a second interface between the apparatus and the second device, the reconfiguration message being encrypted based on the security parameters of the first device.

In some example embodiments, an apparatus capable of performing the method 800 further comprises: means for receiving, from the first device via a first interface between the apparatus and the first device, an indication to retain context information of the first interface and the fourth device; and means for storing the context information at the device.

In some example embodiments, the first device is a first IAB donor, the second device is a second IAB donor, the apparatus is an IAB node, and the fourth device is a terminal device.

In some example embodiments, an apparatus capable of performing the method 900 may include means for performing the respective steps of the method 900. The component may be implemented in any suitable form. For example, the components may be implemented in circuitry or software modules.

In some example embodiments, an apparatus (e.g., UE 240) capable of performing method 900 comprises: means for receiving a reconfiguration message from a third device serving the apparatus, the third device migrating from a first cell in communication with the first device to a second cell in communication with the second device while leaving a cell identifier of the serving cell unchanged, and the reconfiguration message including a new configuration for the second device; means for updating a configuration used at the apparatus with the new configuration without performing a random access procedure; and means for transmitting a reconfiguration complete message to the third device.

In some example embodiments, the reconfiguration message is encrypted based on security parameters of the first device. The apparatus capable of performing method 900 further comprises: means for decrypting the reconfiguration message based on the security parameters of the first device; and means for decoding the reconfiguration message to obtain a configuration for the second device.

In some example embodiments, the first device is a first IAB donor, the second device is a second IAB donor, the third device is an IAB node, and the apparatus is a terminal device.

In some example embodiments, in a multi-hop topology, the source serving node for migrating the IAB MT is another IAB node under the first IAB donor.

In some example embodiments, in the multi-hop topology, the target serving node for migrating the IAB MT is another IAB node under the second IAB donor.

Fig. 10 is a simplified block diagram of an apparatus 1000 suitable for implementing embodiments of the disclosure. For example, the IAB node 230, IAB donor 210, IAB donor 220, and/or UE 240 shown in fig. 2a and/or fig. 2b may be implemented by the device 1000. As shown, the device 1000 includes one or more processors 1010, one or more memories 1020 coupled to the processors 1010, and one or more communication modules 1040 coupled to the processors 1010.

The communication module 1040 is for bi-directional communication. The communication module 1040 has at least one antenna to facilitate communication. The communication interface may represent any interface necessary to communicate with other network elements.

The processor 1010 may be of any type suitable to the local technology network and may include, as non-limiting examples, one or more of the following: general purpose computers, special purpose computers, microprocessors, digital Signal Processors (DSPs), and processors based on a multi-core processor architecture. The device 1000 may have multiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock that is synchronized to the master processor.

Memory 1020 may include one or more non-volatile memories and one or more volatile memories. Examples of non-volatile memory include, but are not limited to, read-only memory (ROM) 1024, electrically programmable read-only memory (EPROM), flash memory, hard disks, compact Disks (CD), digital Video Disks (DVD), and other magnetic and/or optical storage. Examples of volatile memory include, but are not limited to, random Access Memory (RAM) 1022 and other volatile memory that does not persist during power failure.

The computer program 1030 includes computer-executable instructions that are executed by an associated processor 1010. Program 1030 may be stored in ROM 1024. Processor 1010 may perform any suitable actions and processes by loading program 1030 into RAM 1022.

Embodiments of the present disclosure may be implemented by program 1030 such that device 1000 may perform any of the processes of the present disclosure discussed with reference to fig. 3-9. Embodiments of the present disclosure may also be implemented in hardware or a combination of software and hardware.

In some example embodiments, program 1030 may be tangibly embodied in a computer-readable medium that may be included in device 1000 (such as in memory 1020) or other storage device that device 1000 may access. Device 1000 may load program 1030 from the computer readable medium into RAM 1022 for execution. The computer readable medium may include any type of tangible, non-volatile memory, such as ROM, EPROM, flash memory, hard disk, CD, DVD, etc. Fig. 11 shows an example of a computer readable medium 1100, which may be in the form of a CD or DVD. The computer-readable medium has stored thereon the program 1030.

It should be appreciated that future networks may utilize Network Function Virtualization (NFV), a network architecture concept that proposes to virtualize network node functions as "building blocks" or entities that may be operatively connected or linked together to provide services. A Virtualized Network Function (VNF) may comprise one or more virtual machines running computer program code using standard or generic type servers instead of custom hardware. Cloud computing or data storage may also be utilized. In radio communication, this may mean that node operations are performed at least in part in a central/centralized unit CU (e.g., server, host, or node) operatively coupled to distributed units DU (e.g., radio heads/nodes). Node operations may also be distributed among multiple servers, nodes, or hosts. It should also be appreciated that the allocation of work between core network operation and base station operation may vary from implementation to implementation.

In one embodiment, a server may generate a virtual network through which the server communicates with the distributed units. In general, virtual networks may involve a process of combining hardware and software network resources and network functions into a single software-based management entity (virtual network). Such virtual networks may provide a flexible distribution of operations between servers and radio heads/nodes. In practice, any digital signal processing task may be performed in a CU or DU, and the boundary at which responsibility is transferred between a CU and a DU may be chosen according to implementation.

Thus, in one embodiment, a CU-DU architecture is implemented. In this case, the device 1000 may be included in a central unit (e.g., control unit, edge cloud server, server) that is operatively coupled (e.g., via a wireless or wired network) to distributed units (e.g., remote radio heads/nodes). That is, the central unit (e.g., edge cloud server) and the distributed units may be independent devices that communicate with each other via a radio path or via a wired connection. Alternatively, they may be located in the same entity that communicates via a wired connection or the like. An edge cloud or edge cloud server may serve multiple distributed units or radio access networks. In one embodiment, at least some of the above-described processes may be performed by a central unit. In another embodiment, the device 1000 may instead be included in a distributed unit, and at least some of the processes described above may be performed by the distributed unit.

In one embodiment, execution of at least some of the functions of device 1000 may be shared between two physically separate devices (DU and CU) that form one operational entity. Thus, it can be seen that the apparatus depicts an operational entity comprising one or more physically separate devices for performing at least some of the processes described above. In one embodiment, such a CU-DU architecture may provide flexible allocation of operations between CUs and DUs. In practice, any digital signal processing task may be performed in a CU or DU, and the boundary at which responsibility is transferred between a CU and a DU may be chosen according to implementation. In one embodiment, the apparatus 1000 controls the execution of the above-described processes independent of the location of the above-described devices and also independent of where the above-described processes/functions are executed.

In general, the various embodiments of the disclosure may be implemented using hardware or special purpose circuits, software, logic or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. While various aspects of the embodiments of the disclosure are illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer-readable storage medium. The computer program product comprises computer executable instructions, such as instructions included in a program module, that are executed in a device on a target real or virtual processor to perform the method 600 described above with reference to fig. 6, the method 700 described above with reference to fig. 7, the method 800 described above with reference to fig. 8, and/or the method 900 described above with reference to fig. 9. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, etc. that perform particular tasks or implement particular abstract data types. In various embodiments, the functionality of the program modules may be combined or split between program modules as desired. Machine-executable instructions of program modules may be executed within local or distributed devices. In a distributed device, program modules may be located in both local and remote memory storage media.

Program code for carrying out the methods of the present disclosure may be written in any combination of one or more programming languages. These program code may be provided to a processor or controller of a general purpose computer, special purpose computer, or other programmable data processing apparatus such that the program code, when executed by the processor or controller, causes the functions/operations specified in the flowchart and/or block diagram to be implemented. The program code may execute entirely on the machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.

In the context of this disclosure, computer program code or related data may be carried by any suitable carrier to enable an apparatus, device or processor to perform the various processes and operations described above. Examples of carriers include signals, computer readable media, and the like.

The computer readable medium may be a computer readable signal medium or a computer readable storage medium. The computer readable medium may include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of a computer-readable storage medium would include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

Further, while operations are described in a particular order, this should not be construed as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In some cases, multitasking and parallel processing may be advantageous. Also, while several specific implementation details are included in the above discussion, these should not be construed as limitations on the scope of the disclosure, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination.

Although the disclosure has been described in language specific to structural features and/or methodological acts, it is to be understood that the disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

1. A method, comprising:

at a first device, receiving a reconfiguration message from a second device for a fourth device, the fourth device being in a serving cell served by a third device, the third device migrating from a first cell in communication with the first device to a second cell in communication with the second device while leaving a cell identifier of the serving cell unchanged, and the reconfiguration message indicating that the fourth device updates a configuration for the second device;

encrypting the reconfiguration message based on the security parameters of the first device; and

providing the encrypted reconfiguration message to the third device.

2. The method of claim 1, wherein the reconfiguration message instructs the fourth device to update the configuration for the second device without performing a random access procedure.

3. The method of claim 1, wherein receiving the reconfiguration message comprises:

transmitting a handover request to the second device, the handover request being for a handover of the third device from the first cell to the second cell and for a reconfiguration of the fourth device; and

a handover acknowledgement is received from the second device in response to the second device allowing the handover, the handover acknowledgement including a handover command for the third device and the reconfiguration message for the fourth device.

4. The method of claim 1, wherein receiving the reconfiguration message comprises:

transmitting a handover request to the second device, the handover request being for a handover of the third device from the first cell to the second cell and for a reconfiguration of the fourth device;

receiving a handover acknowledgement from the second device in response to the second device allowing the handover, the handover acknowledgement comprising a handover command for the third device and an indication of a delayed transmission of the reconfiguration message; and

the reconfiguration message is received from the second device in response to a second interface between the third device and the second device being established.

5. The method of claim 3 or 4, wherein the handover request includes context information of the fourth device and of a first interface between the third device and the first device.

6. The method of claim 1, wherein providing the encrypted reconfiguration message to the third device comprises:

the encrypted reconfiguration message is transmitted to the third device via a first interface between the third device and the first device.

7. The method of claim 1, further comprising:

transmitting, to the third device, via a first interface between the third device and the first device, an indication to retain context information of the first interface and the fourth device.

8. The method of claim 1, wherein providing the encrypted reconfiguration message to the third device comprises:

the encrypted reconfiguration message is transmitted to the second device via a third interface between the first device and the second device, such that the second device transmits the encrypted reconfiguration message to the third device via a second interface between the third device and the second device.

9. The method according to claim 1, wherein:

the first device is a first integrated access and backhaul donor;

the second device is a second integrated access and backhaul donor;

the third device is an integrated access and backhaul node; and

the fourth device is a terminal device.

10. A method, comprising:

generating, at a second device, a reconfiguration message for a fourth device, the fourth device being in a serving cell served by a third device, the third device migrating from a first cell in communication with a first device to a second cell in communication with the second device while leaving a cell identifier of the serving cell unchanged, and the reconfiguration message indicating that the fourth device updates a configuration for the second device; and

transmitting the reconfiguration message to the first device.

11. The method of claim 10, wherein the reconfiguration message instructs the fourth device to update the configuration for the second device without performing a random access procedure.

12. The method according to claim 10,

wherein generating the reconfiguration message comprises:

receiving a handover request from the first device, the handover request being for a handover of the third device from the first cell to the second cell and for a reconfiguration of the fourth device;

Determining whether to allow the handover based on the handover request; and

generating the reconfiguration message according to a determination that the handover is allowed; and wherein transmitting the reconfiguration message to the first device comprises:

transmitting a handover acknowledgement to the first device, the handover acknowledgement comprising a handover command for the third device and the generated reconfiguration message for the fourth device.

13. The method according to claim 10,

wherein generating the reconfiguration message comprises:

determining whether to allow the handover based on the handover request;

transmitting a handover acknowledgement to the first device in accordance with the determination that the handover is allowed, the handover acknowledgement including a handover command for the third device and an indication of delayed transmission of the reconfiguration message; and

generating the reconfiguration message in response to a second interface between the third device and the second device being established; and

Wherein transmitting the reconfiguration message to the first device includes:

transmitting a further handover acknowledgement to the first device, the further handover acknowledgement comprising the generated reconfiguration message.

14. The method of claim 12 or 13, wherein the handover request includes context information of the fourth device and of a first interface between the third device and the first device.

15. The method of claim 10, further comprising:

receiving, from the first device, the reconfiguration message encrypted based on the security parameters of the first device via a third interface between the first device and the second device; and

the reconfiguration message is transmitted to the third device via a second interface between the third device and the second device in response to the second interface being established.

16. The method according to claim 10, wherein:

the first device is a first integrated access and backhaul donor;

the second device is a second integrated access and backhaul donor;

the third device is an integrated access and backhaul node; and

the fourth device is a terminal device.

17. A method, comprising:

At a third device, receiving a reconfiguration message for a fourth device from a first device or a second device, the fourth device being in a serving cell served by the third device, the third device migrating from a first cell in communication with the first device to a second cell in communication with the second device while leaving a cell identifier of the serving cell unchanged, and the reconfiguration message indicating that the fourth device updates a configuration for the second device;

forwarding the reconfiguration message to the fourth device; and

a reconfiguration complete message is received from the fourth device.

18. The method of claim 17, wherein the reconfiguration message instructs the fourth device to update the configuration for the second device without performing a random access procedure.

19. The method of claim 17, wherein receiving the reconfiguration message comprises:

the reconfiguration message is received from the first device via a first interface between the third device and the first device, the reconfiguration message being encrypted based on a security parameter of the first device.

20. The method of claim 19, wherein forwarding the reconfiguration message to the fourth device comprises:

Storing the reconfiguration message at the third device; and

transmitting the reconfiguration message to the fourth device in response to a trigger for transmission of the reconfiguration message.

21. The method of claim 20, wherein the trigger comprises any one of:

establishment of a second interface between an IAB anode and the second device;

initiating, by the third device, a handover procedure; or alternatively

Completion of the handover procedure by the third device.

22. The method of claim 17, wherein receiving the reconfiguration message comprises:

the reconfiguration message is received from the second device via a second interface between the third device and the second device, the reconfiguration message being encrypted based on the security parameters of the first device.

23. The method of claim 17, further comprising:

receiving, from the first apparatus via a first interface between the third device and the first device, an indication to retain context information of the first interface and the fourth device; and

the context information is stored at the third device.

24. The method according to claim 17, wherein:

The first device is a first integrated access and backhaul donor;

the second device is a second integrated access and backhaul donor;

the third device is an integrated access and backhaul node; and

the fourth device is a terminal device.

25. A method, comprising:

at a fourth device, receiving a reconfiguration message from a third device, the third device providing a serving cell for serving the fourth device, the third device migrating from a first cell in communication with a first device to a second cell in communication with a second device while maintaining a cell identifier of the serving cell unchanged, and the reconfiguration message including a new configuration for the second device;

updating a configuration used at the fourth device with the new configuration without performing a random access procedure; and

transmitting a reconfiguration complete message to the third device.

26. The method of claim 25, wherein the reconfiguration message is encrypted based on a security parameter of the first device, and the method further comprises:

decrypting the reconfiguration message based on the security parameters of the first device; and

decoding the reconfiguration message to obtain the configuration of the second device.

27. The method according to claim 25, wherein:

the first device is a first integrated access and backhaul donor;

the second device is a second integrated access and backhaul donor;

the third device is an integrated access and backhaul node; and

the fourth device is a terminal device.

28. A first device, comprising:

at least one processor; and

at least one memory including computer program code;

the at least one memory and the computer program code are configured to, with the at least one processor, cause the first device to perform the method of any one of claims 1 to 9.

29. A second device, comprising:

at least one processor; and

at least one memory including computer program code;

the at least one memory and the computer program code are configured to, with the at least one processor, cause the second device to perform the method of any of claims 10 to 16.

30. A third device, comprising:

at least one processor; and

at least one memory including computer program code;

the at least one memory and the computer program code are configured to, with the at least one processor, cause the third device to perform the method of any of claims 17 to 24.

31. A fourth device, comprising:

at least one processor; and

at least one memory including computer program code;

the at least one memory and the computer program code are configured to, with the at least one processor, cause the fourth device to perform the method of any of claims 25-27.

32. An apparatus comprising means for performing the method of any one of claims 1 to 9.

33. An apparatus comprising means for performing the method of any one of claims 10 to 16.

34. An apparatus comprising means for performing the method of any one of claims 17 to 24.

35. An apparatus comprising means for performing the method of any one of claims 25 to 27.

36. A computer program product stored on a computer readable medium and comprising machine executable instructions, wherein the machine executable instructions when executed cause a machine to perform the method of any one of claims 1 to 27.

37. A computer readable storage medium comprising program instructions stored thereon, which when executed by an apparatus, cause the apparatus to perform the method of any of claims 1 to 27.