WO2022061780A1

WO2022061780A1 - Methods, apparatuses and computer readable media for integrated access and backhaul communication

Info

Publication number: WO2022061780A1
Application number: PCT/CN2020/117928
Authority: WO
Inventors: Ilkka Keskitalo; Dawid Koziol; Xiang Xu; Hajo Bakker; Omer BULAKCI; Oliver Blume
Original assignee: Nokia Shanghai Bell Co., Ltd.; Nokia Solutions And Networks Oy; Nokia Technologies Oy
Priority date: 2020-09-25
Filing date: 2020-09-25
Publication date: 2022-03-31
Also published as: CN116250280A

Abstract

Embodiments of the present disclosure relate to methods, apparatuses and computer readable storage media for integrated access and backhaul (IAB) communication. According to embodiments of the present disclosure, a first IAB donor receives, from a second IAB donor, a reconfiguration message for a terminal device in a serving cell served by an IAB node. The IAB node migrates from a first cell in communication with the first IAB donor to a second cell in communication with the second IAB donor while keeping a cell identifier of the serving cell unchanged. The reconfiguration message indicates the terminal device to update a configuration for the second IAB donor. The first IAB donor ciphers the reconfiguration message based on a security parameter of the first IAB donor and provides the ciphered reconfiguration message to the IAB node. The solution enables physical cell identifiers of the cells provided by an IAB node to remain unchanged during the migration of the IAB node.

Description

METHODS, APPARATUSES AND COMPUTER READABLE MEDIA FOR INTEGRATED ACCESS AND BACKHAUL COMMUNICATION

TECHNICAL FIELD

Embodiments of the present disclosure generally relate to the field of telecommunications, and in particular, to methods, apparatuses and computer readable media for integrated access and backhaul (IAB) communication.

BACKGROUND

IAB has been introduced in Release 16 (Rel-16) of 3GPP specifications as a key enabler for fast and cost-efficient deployments. IAB nodes use the same spectrum and air interface for access and backhaul, creating a hierarchical wireless multi-hop network between sites. The hops eventually terminate at an IAB donor that is connected by means of a conventional fixed backhaul to the core network. An IAB node contains a mobile termination (MT) part that acts as user equipment (UE) towards its parent IAB node and a distributed unit (DU) part that acts as a base station towards a next-hop IAB node. An IAB donor contains a centralized unit (CU) part and a DU part. An IAB DU can provide one or more cells to serve UEs. A cell provided by an IAB DU can be regarded as a normal cell from the UE perspective.

Due to possible failures on the backhaul connections or changes in the IAB topology or IAB mobility, an IAB node may need to change its serving node which can be under the same or different IAB donor (s) . 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 collisions due to the movement of the IAB node. If the PCI of the cell served by the IAB node is changed during the handover and connection to a new IAB donor, in order to reconfigure the UE (s) connected to the IAB node, a handover or a radio resource control (RRC) reestablishment procedure will be performed. This may result in an interruption of connections and services at the UEs connected to the IAB node.

SUMMARY

In general, example embodiments of the present disclosure provide methods, apparatuses and computer readable media for IAB communication.

In a first aspect, there is provided a method. The method comprises receiving, at a first device and 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 first device to a second cell in communication with the second device while keeping a cell identifier of the serving cell unchanged, and the reconfiguration message indicating the fourth device to update a configuration for the second device; ciphering the reconfiguration message based on a security parameter of the first device; and providing the ciphered reconfiguration message to the third device.

In a second aspect, there is provided a method. The method comprises generating, at 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 a first device to a second cell in communication with the second device while keeping a cell identifier of the serving cell unchanged, and the reconfiguration message indicating the fourth device to update a configuration for the second device; and transmitting the reconfiguration message to the first device.

In a third aspect, there is provided a method. The method comprises receiving, at a third device and from a first device or a second device, a reconfiguration message 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 keeping a cell identifier of the serving cell unchanged, and the reconfiguration message indicating the fourth device to update 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, there is provided a method. The method comprises receiving, at a fourth device, a reconfiguration message from a 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 keeping a cell identifier of the serving cell unchanged, and the reconfiguration message comprising 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.

In a fifth aspect, there is provided a first device. The first device comprises at least one processor and at least one memory including computer program codes. The at least one memory and the computer program codes are configured to, with the at least one processor, cause the first device to receive, 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 first device to a second cell in communication with the second device while keeping a cell identifier of the serving cell unchanged, and the reconfiguration message indicating the fourth device to update a configuration for the second device; cipher the reconfiguration message based on a security parameter of the first device; and provide the ciphered reconfiguration message to the third device.

In a sixth aspect, there is provided a second device. The second device comprises at least one processor and at least one memory including computer program codes. The at least one memory and the computer program codes 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 a first device to a second cell in communication with the second device while keeping a cell identifier of the serving cell unchanged, and the reconfiguration message indicating the fourth device to update a configuration for the second device; and transmit the reconfiguration message to the first device.

In a seventh aspect, there is provided a third device. The third device comprises at least one processor and at least one memory including computer program codes. The at least one memory and the computer program codes are configured to, with the at least one processor, cause the third device to receive, from a first device or a second device, a reconfiguration message 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 keeping a cell identifier of the serving cell unchanged, and the reconfiguration message indicating the fourth device to update a configuration for the second device; forward the reconfiguration message to the fourth device; and receive a reconfiguration complete message from the fourth device.

In an eighth aspect, there is provided a fourth device. The fourth device comprises at least one processor and at least one memory including computer program codes. The at least one memory and the computer program codes are configured to, with the at least one processor, cause the fourth device to receive a reconfiguration message from a 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 keeping a cell identifier of the serving cell unchanged, and the reconfiguration message comprising a new configuration for the second device; update a configuration used at the fourth device with the new security configuration without performing a random access procedure; and transmit a reconfiguration complete message to the third device.

In a ninth aspect, there is provided an apparatus. The apparatus comprises 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 keeping a cell identifier of the serving cell unchanged, and the reconfiguration message indicating the fourth device to update a configuration for the second device; means for ciphering the reconfiguration message based on a security parameter of the apparatus; and means for providing the ciphered reconfiguration message to the third device.

In a tenth aspect, there is provided an apparatus. The apparatus 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 a first device to a second cell in communication with the apparatus while keeping a cell identifier of the serving cell unchanged, and the reconfiguration message indicating the fourth device to update a configuration for the apparatus; and means for transmitting the reconfiguration message to the first device.

In an eleventh aspect, there is provided an apparatus. The apparatus comprises means for receiving, from a first device or a second device, a reconfiguration message for a fourth device in a serving cell served by 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 keeping a cell identifier of the serving cell unchanged, and the reconfiguration message indicating the fourth device to update a configuration for the second device; means for forwarding the reconfiguration message to the fourth device; and means for receiving a reconfiguration complete message from the fourth device.

In a twelfth aspect, there is provided an apparatus. The apparatus comprises means for receiving a reconfiguration message from a third device providing a serving cell for serving the apparatus, 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 keeping a cell identifier of the serving cell unchanged, and the reconfiguration message comprising 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, there is provided a computer program product that is stored on a computer readable medium and includes machine-executable instructions. The machine-executable instructions, when being executed, cause a machine to perform the method according to the above first, second, third or fourth aspect.

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

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

BRIEF DESCRIPTION OF THE DRAWINGS

Through the more detailed description of some example embodiments of the present disclosure in the accompanying drawings, the above and other objects, features and advantages of the present disclosure will become more apparent, wherein:

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

Fig. 2a and Fig. 2b illustrate an example mobile IAB environment in which embodiments of the present disclosure can 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 communication according to some example embodiments of the present disclosure;

Fig. 7 illustrates a flowchart of an example method for IAB communication according to some example embodiments of the present disclosure;

Fig. 8 illustrates a flowchart of an example method for IAB communication according to some example embodiments of the present disclosure;

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

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

Fig. 11 illustrates a block diagram of an example computer readable medium in accordance with some example embodiments of the present disclosure.

Throughout the drawings, the same or similar reference numerals represent the same or similar element.

DETAILED DESCRIPTION

Principle of the present disclosure will now be described with reference to some example embodiments. It is to be understood that these embodiments are described only for the purpose of illustration and help those skilled in the art to understand and implement the present disclosure, without suggesting any limitation as to the scope of the disclosure. The disclosure described herein can be implemented in various manners other than the ones 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 skills in the art to which this disclosure belongs.

References in the present disclosure to “one embodiment, ” “an embodiment, ” “an example embodiment, ” and the like indicate that the embodiment described may include a particular feature, structure, or characteristic, but it is not necessary that every embodiment includes the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an example embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

It shall 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. 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” , “having” , “includes” and/or “including” , when used herein, specify the presence of stated features, elements, and/or components etc., but do not preclude the presence or addition of one or more other features, elements, components and/or combinations thereof.

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

(a) hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry) and

(b) combinations of hardware circuits and software, such as (as applicable) :

(i) a combination of analog and/or digital hardware circuit (s) with software/firmware and

(ii) any portions of hardware processor (s) with software (including digital signal processor (s) ) , software, and memory (ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and

(c) hardware circuit (s) and or processor (s) , such as a microprocessor (s) or a portion of a microprocessor (s) , that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.

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

As used herein, the term “communication network” refers to a network following any suitable communication standards, such as Long Term Evolution (LTE) , LTE-Advanced (LTE-A) , Wideband Code Division Multiple Access (WCDMA) , High-Speed Packet Access (HSPA) , Narrow Band Internet of Things (NB-IoT) , New Radio (NR) and so on. Furthermore, the communications between a terminal device and a network device in the communication network may be performed according to any suitable generation communication protocols, including, but not limited to, the first generation (1G) , the second generation (2G) , 2.5G, 2.75G, the third generation (3G) , the fourth generation (4G) , 4.5G, the future fifth generation (5G) communication protocols, and/or any other protocols either currently known or to be developed in the future. Embodiments of the present disclosure may be applied in various communication systems. Given the rapid development in communications, there will of course also be future type communication technologies and systems with which the present disclosure may be embodied. It should not be seen as limiting the scope of the present disclosure to only the aforementioned system.

As used herein, the term “network device” refers to a node in a communication network via which a terminal device accesses the network and receives services therefrom. The network device may refer to a base station (BS) or an access point (AP) , for example, a node B (NodeB or NB) , an evolved NodeB (eNodeB or eNB) , a NR NB (also referred to 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, a pico, and so forth, depending on the applied terminology and technology. In the following description, the terms “network device” , “BS” , and “node” may be used interchangeably.

The term “terminal device” refers to any end device that may be capable of wireless communication. By way of example rather than limitation, a terminal device may also be referred to as a communication device, user equipment (UE) , a Subscriber Station (SS) , a Portable Subscriber Station, a Mobile Station (MS) , or an Access Terminal (AT) . The terminal device may include, but not limited to, a mobile phone, a cellular phone, a smart phone, voice over IP (VoIP) phones, wireless local loop phones, a tablet, a wearable terminal device, a personal digital assistant (PDA) , portable computers, desktop computer, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback appliances, vehicle-mounted wireless terminal devices, wireless endpoints, mobile stations, laptop-embedded equipment (LEE) , laptop-mounted equipment (LME) , USB dongles, smart devices, wireless customer-premises equipment (CPE) , an Internet of Things (loT) device, a watch or other wearable, a head-mounted display (HMD) , a vehicle, a drone, a medical device and applications (e.g., remote surgery) , an industrial device and applications (e.g., a robot and/or other wireless devices operating in an industrial and/or an automated processing chain contexts) , a consumer electronics device, a device 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.

Although functionalities described herein can be performed, in various example embodiments, in a fixed and/or a wireless network node may, in other example embodiments, functionalities may be implemented in a user equipment apparatus (such as a cell phone or tablet computer or laptop computer or desktop computer or mobile IOT device or fixed IOT device) . This user equipment apparatus can, for example, be furnished with corresponding capabilities as described in connection with the fixed and/or the wireless network node (s) , as appropriate. The user equipment apparatus may be the user equipment and/or or a control device, such as a chipset or processor, configured to control the user equipment when installed therein. Examples of such functionalities include the bootstrapping server function and/or the home subscriber server, which may be implemented in the user equipment apparatus by providing the user equipment apparatus with software configured to cause the user equipment apparatus to perform from the point of view of these functions/nodes.

Example embodiments of the present disclosure are directed to a radio access network with wireless backhaul of the access points. The backhaul links of the access nodes to the wired part of the network and the core network are dynamically reconfigured with little or no effect on terminal devices of users. The backhaul can be multi-hop or meshed. An important application of embodiments of the present disclosure is for IAB communication in a 3GPP IAB network with terminal devices, IAB nodes and wired IAB donor nodes. In the following, embodiments of the present disclosure will be described with reference to the 3GPP IAB network. It is to be understood that embodiments of the present disclosure may also be applied to any other network with wireless backhaul.

Fig. 1 illustrates a block diagram of a system 100 for IAB communication. As shown in Fig. 1, the system 100 comprises a core network 110, an IAB donor 120, IAB nodes 130-1 and 130-2 (collectively referred to as “IAB nodes 130” or individually referred to as “IAB node 130” ) , a network device 140 (such as, a gNB) , and UEs 150-1, 150-2 and 150-3 (collectively referred to as “UEs 150” or individually referred to as “UE 150” ) . In this text, the terms “IAB node” and “IAB device” can be used interchangeably. The terms “IAB donor node” , “IAB donor” and “IAB donor device” can be used interchangeably.

The core network 110 may comprise a lot of network entities that provide different network functions, for example, Network Slice Selection Function (NSSF) 111, Unified Data Repository (UDM) 112, Access and Mobility Management Function (AMF) 113, Network Function (NF) Repository Function (NRF) , Session Management Function (SMF) , Policy Control Function (PCF) , Network Exposure Function (NEF) and so on.

The IAB donor 120 may comprise a centralized unit (CU) 121 (also referred to as “IAB donor CU 121” ) and a distributed unit (DU) 122 (also referred to as “IAB donor DU 122” ) . The IAB node 130-1 may comprise a MT part 131-1 and a DU 132-1. The IAB node 130-2 may comprise a MT part 131-2 and a DU 132-2. The MTs 131-1 and 131-2 are also collectively referred to as “IAB MTs 131” or individually referred to as “IAB MT 131” . The DUs 132-1 and 132-2 are also collectively referred to as “IAB DUs 132” or individually referred to as “IAB DU 132” .

The IAB donor DU 122 or each IAB DU 132 can provide one or more cells to serve UEs. For example, a cell provided by a DU can broadcast normal control signals like Synchronization Signal Blocks (SSBs) for downlink synchronization and system information. Therefore, the cell provided by a DU can be regarded as a normal cell from a UE perspective. For example, as shown in Fig. 1, the IAB donor DU 122 serves the UE 150-1, the IAB DU 132-1 serves the UE 150-2 and the IAB DU 132-2 serves the UE 150-3.

The IAB MT 131 of an IAB node 130 may act as a UE towards its parent node. For example, the IAB MT 131-1 may act as a UE towards the IAB donor 120 (i.e., the IAB donor DU 122) and the IAB MT 131-2 may act as a UE towards the IAB node 130-1 (i.e., the IAB DU 132-1) . On the child links, the IAB DU 132 of an IAB node 130 may act as a network device (such as, gNB) towards its next-hop IAB node. For example, the IAB donor DU 122 may act as a gNB towards the IAB node 130-1 and the IAB DU 132-1 may act as a gNB towards the IAB node 130-2. On the access links, the IAB donor 120 and the IAB nodes 130 may act as normal gNBs, providing radio interfaces for the UEs 150 in their coverage areas, as described above.

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

Communications in the environment 100 may be implemented according to any proper communication protocol (s) , comprising, but not limited to, cellular communication protocols of the first generation (1G) , the second generation (2G) , the third generation (3G) , the fourth generation (4G) and the fifth generation (5G) and on the like, wireless local network communication protocols such as Institute for Electrical and Electronics Engineers (IEEE) 802.11 and the like, and/or any other protocols currently known or to be developed in the future. Moreover, the communication may utilize any proper wireless communication technology, comprising but not limited to: Code Divided Multiple Address (CDMA) , Frequency Divided Multiple Address (FDMA) , Time Divided Multiple Address (TDMA) , Frequency Divided Duplexer (FDD) , Time Divided Duplexer (TDD) , Multiple-Input Multiple-Output (MIMO) , Orthogonal Frequency Divided Multiple Access (OFDMA) and/or any other technologies currently known or to be developed in the future.

Due to possible failures on the backhaul (BH) connections or changes in the IAB topology or IAB mobility, an IAB node may need to change its serving node. Such change of the backhaul topology may involve the change of 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 for UEs 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. Such scenario will be relevant especially for mobile IAB nodes where the BH changes can be frequent and the IAB donor is likely to be changed at some point.

There can be different implementation options or mode of operations for the IAB nodes. For instance, an IAB node can be installed on fixed infrastructure, e.g., a lamp post or street furniture. Such IAB node may be referred to as a fixed IAB node. Depending on the channel conditions on the wireless backhaul, a fixed IAB node may be migrated from one donor IAB node to a neighbor donor IAB node. Another IAB node implementation can be the case where the IAB node is installed on a vehicle and the IAB node is active, (i.e., serving UEs) , when the IAB is static or slowly moving and serving UEs particularly outside the vehicle. For instance, the IAB node may serve the UEs outside the vehicle, when the vehicle is parked. 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 IAB nodes can be referred to as nomadic IAB nodes. Nomadic IAB nodes can be integrated into the vehicles, e.g., of a car sharing fleet or a taxi fleet. Nomadic IAB nodes can be used to provide coverage and/or capacity enhancement. Another concept of IAB, namely mobile IAB, has been proposed recently. A mobile IAB node is located on a moving object, e.g., vehicles or balloons or drones, and provides wireless access to UE (s) inside or outside the moving object. In some cases, the UEs may be physically attached to the movement of the mobile IAB node (e.g. inside a vehicle carrying the IAB node) . In this case, preferably the UEs stay connected to the moving IAB node.

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

The IAB donor 210 comprises a CU 211 (also referred to as “IAB donor CU 211” in the following) and a DU 212 (also referred to as “IAB donor DU 212” in the following) . The IAB donor 220 comprises a CU 221 (also referred to as “IAB donor CU 221” in the following) and a DU 222 (also referred to as “IAB donor DU 222” in the following) . The IAB node 230 comprises a MT 231 (also referred to as “IAB MT 231” in the following) and a DU 232 (also referred to as “IAB DU 232” in the following) . The IAB donor DU 212 may provide a cell 250-1 and the IAB donor DU 222 provides a cell 250-2. There is an Xn interface 270 between the IAB donor CU 211 and the IAB donor CU 221. In this text, the Xn interface 270 may also be referred to as a “third interface” .

Initially, as shown in Fig. 2a, the IAB node 230 may locate in the cell 250-1 (also referred to as “first cell” in the following) and be served by the IAB donor 210. An F1 interface 280 may be set up between the IAB donor CU 211 and the IAB DU 232. In this text, the F1 interface 280 may also be referred to as a “first interface” . The IAB DU 232 may provide cells 260-1 and 260-2 to serve the UEs 240. For example, the PCI of the cell 260-1 may be X and the PCI of the cell 260-2 may be Y.

Then, as shown in Fig. 2b, the IAB node 230 may move out of the cell 250-1 and enter into the cell 250-2 (also referred to as “second cell” in the following) . This may trigger a BH change from the old cell 250-1 towards the target cell 250-2 provided by the IAB donor DU 222.

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

Embodiments of the present disclosure provide a solution for IAB communication, so as to solve the above problem and one or more of other potential problems. This solution enables the PCIs of the cells provided by the migrating IAB node to remain unchanged. In this way, this solution can minimize the impacts on the UEs served by the migrating IAB node during an inter-donor topology adaptation, since the RRC connections to the cells will be maintained and no connection break will occur at the UEs. Moreover, this solution can minimize the required signaling over the radio interfaces.

Specifically, as shown in Fig. 2b, the target IAB donor CU (for example, the IAB donor CU 221) may generate a RRC reconfiguration message (with or without sync) . The RRC reconfiguration message may be sent to the UE 240 via the IAB DU 232 either by the target donor CU (CU 221) or by the source IAB donor CU (for example, the IAB donor CU 211) . The reconfiguration message generated by the IAB donor CU 221 may include a new security configuration for the IAB donor CU 221 to be used after the reconfiguration.

If the 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 cyphered by the IAB donor CU 211. Then, the RRC message may 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 the RRC reconfiguration message is sent from the IAB donor CU 221 to the UE 240, the RRC reconfiguration message may be generated once an F1 interface 290 between the IAB DU 232 and the IAB donor CU 221 is set up and the cells 260-1 and 260-2 are actively running under the IAB donor CU 221. In this text, the F1 interface 290 may also be referred to as a “second interface” .

If the RRC reconfiguration message is sent from the IAB donor CU 221 to the UE 240, the IAB donor CU 221 may request the IAB donor CU 211 to cipher the RRC reconfiguration message based on its security parameters and send the ciphered RRC reconfiguration message back to the IAB donor CU 221, such that the UE 240 will be able to de-cipher the message. Once a RRC connection from the migrating IAB node 230 (i.e., the 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 set up, the IAB node 230 may send the RRC reconfiguration message to the UE 240 connected to the IAB node 230.

The UEs 240 connected to the IAB node 230 may remain connected to the same cells 260-1 and 260-2 of the IAB node 230 even after the reconfiguration, since the PCIs of the cells 260-1 and 260-2 do not change. Since the UEs 240 are still synchronized with the same cells, random access procedures may not be required for the UEs 240. It is not mandatory for the IAB donor CU 221 to reserve access resources (e.g. for a contention-free random access procedure) for the cells of the IAB node 230. The HO procedure for the UEs 240 may not be performed during the migration of the IAB node 230. The UEs 240 may only need to change the security configuration, i.e. security keys, 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, the interactions 300 involve the UE 240 (such as, the UE 240-1 or 240-2) , the IAB node 230, the IAB donor 210 and the 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 can be triggered by the configured HO event indicating better connection quality on an alternative link to the IAB donor DU 222 under the IAB donor CU 221.

The IAB donor CU 211 decides 302 to hand-over the IAB node 230 (radio connection with the IAB MT 231) to the cell served by the IAB donor 220. The handover procedure can be any of a normal one or other mobility procedures like conditional handover (CHO) . It is to be understood that the scope of the present disclosure is not limited in the selection of the HO procedure for the IAB MT 231.

The IAB donor CU 211 transmits 303 a HO request to the IAB donor CU 221. The HO request may not only for the IAB MT 231 but also for the UE 240 connected to the IAB node 230 in the cell served by the IAB DU 232. It is to be understood that there may be also descendant/child nodes for the migrating IAB node 230 and the connections should be re-configured also for them during the migration procedure, which is not shown in Fig. 3. In some example embodiments, the HO request may comprise contexts for the F1 interface of the IAB donor CU 211 and for the UE 240. It is to be understood that the context transfer can also happen with other signaling (e.g., context fetch) than the HO request.

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

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

The IAB donor CU 211 transmits 306 the HO command to the IAB MT 231. Moreover, the IAB donor CU 211 transmits 307 the RRC reconfiguration message for the UE 240 to the IAB DU 232 via F1 Application Protocol (F1AP) signaling. In some example embodiments, the IAB donor CU 211 may also indicate that the F1 and UE contexts shall be maintained, even if a new F1 interface with the IAB donor CU 221 is set up. In some example embodiments, the IAB node 230 (i.e., the IAB DU 232) may store the RRC reconfiguration message for the UE 240. The IAB node 230 may also store current Cell-Radio Network Temporary Identifier (s) , C-RNTI (s) , since the UE 240 will continue monitoring the current C-RNTI (s) . After the migration of the IAB node 230, the C-RNTI (s) may change or remain unchanged.

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

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

A F1 setup procedure is initiated to establish 311 an F1 interface 290 between the IAB DU 232 and the IAB donor CU 221. In some example embodiments, the stored contexts (after 307) can be resumed. For example, there may be a separate indication for resuming the stored contexts either from the IAB DU 232 (which has the stored contexts) or from the IAB donor CU 221 if it wants to proceed with this new procedure.

Since the cell (s) served by the IAB DU 232 continue to be active, the IAB DU 232 transmits 312 the RRC reconfiguration message to the UE 240 using the C-RNTI (s) that the UE 240 are monitoring even after the F1 interface 290 with the IAB donor CU 221 is set up. Because the ciphering of the RRC reconfiguration message has been done by using the security parameters of the IAB donor CU 211, the UE 240 will be able to de-cipher 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 is to be noted that since the cell/PCI does not change, the change of the serving CU for the UE 240 is gradual as the reconfiguration message is sent to the UE 240.

The UE 240 transmits 313 a RRC reconfiguration complete message to the IAB DU 232 and the IAB DU 232 forwards 314 the RRC reconfiguration complete message via F1AP signaling after the UE 240 is controlled by the IAB donor CU 221. After successful completion of the procedure, the IAB donor CU 221 may release 315 the contexts in the IAB donor CU 211 and perform path switch for 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, the interactions 400 involve the UE 240 (such as, the UE 240-1 or 240-2) , the IAB node 230, the IAB donor 210 (also referred to as “source IAB donor” in the following) and the IAB donor 220 (also referred to as “target IAB donor” in the following) . The main difference between Fig. 3 and Fig. 4 is that the RRC reconfiguration message for 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 once the F1 interface between the IAB DU 232 and the IAB donor CU 221 is set up.

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 can be triggered by the configured HO event indicating better connection quality on an alternative link to the IAB donor DU 222 under the IAB donor CU 221.

The IAB donor CU 211 decides 402 to hand-over the IAB node 230 (radio connection with the IAB MT 231) to the cell served by the IAB donor 220. The handover procedure can be any of a normal one or other mobility procedures like conditional handover (CHO) . It is to be understood that the scope of the present disclosure is not limited in the selection of the HO procedure for the IAB MT 231.

The IAB donor CU 211 transmits 403 a HO request to the IAB donor CU 221. The HO request may not only for the IAB MT 231 but also for the UE 240 connected to the IAB node 230 in the cell served by the IAB DU 232. It is to be understood that there may be also descendant/child nodes for the migrating IAB node 230 and the connections should be re-configured also for them during the migration procedure, which is not shown in Fig. 4. In some example embodiments, the HO request may comprise contexts for the F1AP interface of the IAB donor CU 211 and for the UE 240. It is to be understood that the context transfer can also happen with other signaling (e.g., context fetch) than the HO request.

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

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

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 ciphers the RRC reconfiguration message with its own security parameters and transmits 407b the ciphered RRC reconfiguration message back to the IAB donor CU 221. The IAB donor CU 211 may also indicate 407a, via F1AP signaling, to the IAB DU 232 that the F1 and UE contexts shall be maintained, even if a new F1 interface with the IAB donor CU 221 is set up.

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

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

A 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 the RRC reconfiguration message to the IAB DU 232 directly 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 the RRC reconfiguration message to the UE 240 using the C-RNTI (s) that the UE 240 are monitoring even after the F1 interface 290 with the IAB donor CU 221 is set up. Because the ciphering of the RRC reconfiguration message has been done by using the security parameters of the IAB donor CU 211, the UE 240 will be able to de-cipher 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 is to be noted that since the cell/PCI does not change, the change of the serving CU for the UE 240 is gradual as the reconfiguration message is sent to the UE 240.

The UE 240 transmits 414 a RRC reconfiguration complete message to the IAB DU 232 and the IAB DU 232 forwards 415 the RRC reconfiguration complete message via F1AP signaling after the UE 240 is controlled by the IAB donor CU 221. After successful completion of the procedure, the IAB donor CU 221 may release 416 the contexts in the IAB donor CU 211 and perform path switch for 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, the interactions 500 involve the UE 240 (such as, the UE 240-1 or 240-2) , the IAB node 230, the IAB donor 210 (also referred to as “source IAB donor” in the following) and the IAB donor 220 (also referred to as “target IAB donor” in the following) . The main difference between Fig. 4 and Fig. 5 is when the RRC reconfiguration message is 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 can be triggered by the configured HO event indicating better connection quality on an alternative link to the IAB donor DU 222 under the IAB donor CU 221.

The IAB donor CU 211 decides 502 to hand-over the IAB node 230 (radio connection with the IAB MT 231) to the cell served by the IAB donor 220. The handover procedure can be any of a normal one or other mobility procedures like conditional handover (CHO) . It is to be understood that the scope of the present disclosure is not limited in the selection of the HO procedure for the IAB MT 231.

The IAB donor CU 211 transmits 503 a HO request to the IAB donor CU 221. The HO request may not only for the IAB MT 231 but also for the UE 240 connected to the IAB node 230 in the cell served by the IAB DU 232. It is to be understood that there may be also descendant/child nodes for the migrating IAB node 230 and the connections should be re-configured also for them during the migration procedure, which is not shown in Fig. 4. In some example embodiments, the HO request may comprise contexts for the F1AP interface of the IAB donor CU 211 and for the UE 240. It is to be understood that the context transfer can also happen with other signaling (e.g., context fetch) than the HO request.

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

The IAB donor CU 221 transmits 505, to the IAB donor CU 211, an acknowledgement including a HO command for the IAB MT 231. Different from Fig. 4, there is no RRC reconfiguration message for the UE 240 in the acknowledgement. However, the IAB donor CU 221 may indicate that the RRC reconfiguration message for 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 contexts shall be maintained, even if a new F1 interface with the IAB donor CU 221 is set up.

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

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

A F1 setup procedure is initiated to establish 511 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 may generate the RRC reconfiguration message for the UE 240. The RRC reconfiguration message may indicate a reconfiguration procedure with or without sync. If the RRC reconfiguration message indicates a reconfiguration procedure without sync, the UE 240 will not obtain uplink synchronization by performing the random access procedure since the cell (s) served by the IAB DU 232 does not change. The IAB donor CU 221 transmits 512, to the IAB donor CU 211, an acknowledgement including the RRC reconfiguration message for the UE 240. The RRC reconfiguration message may include a new security configuration valid for the connection to the IAB donor CU 221 as well as target cell parameters. Such delayed generation of the RRC reconfiguration message allows the IAB donor CU 221 to change cell parameters for the IAB DU 232 (if needed) .

The IAB donor CU 211 ciphers the RRC reconfiguration message with its own security parameters and transmits 513 the ciphered RRC reconfiguration message back to the IAB donor CU 221. The IAB donor CU 221 transmits 514 the RRC reconfiguration message to the IAB DU 232 directly 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 515 the RRC reconfiguration message to the UE 240 using the C-RNTI (s) that the UE 240 are monitoring even after the F1 interface 290 with the IAB donor CU 221 is set up. Because the ciphering of the RRC reconfiguration message has been done by using the security parameters of the IAB donor CU 211, the UE 240 will be able to de-cipher 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 is to be noted that since the cell/PCI does not change, the change of the serving CU for the UE 240 is gradual as the reconfiguration message is sent to the UE 240.

The UE 240 transmits 516 a RRC reconfiguration complete message to the IAB DU 232 and the IAB DU 232 forwards 517 the RRC reconfiguration complete message via F1AP signaling after the UE 240 is controlled by the IAB donor CU 221. After successful completion of the procedure, the IAB donor CU 221 may release 518 the contexts in the IAB donor CU 211 and perform path switch for the traffic data.

Fig. 6 shows a flowchart of an example method 600 for IAB communication in accordance with some example embodiments of the present disclosure. The method 600 can be implemented at the IAB donor 210 shown in Fig. 2a and/or Fig. 2b. In the following, the IAB donor 210 is also referred to as a “first device” , the IAB donor 220 is also referred to as a “second device” , the IAB node 230 is also referred to as a “third device” and the UE 240 is also referred to as a “fourth device” . It is to be understood that the method 600 may include additional blocks not shown and/or may omit some shown blocks, and the scope of the present disclosure is not limited in this regard.

At block 610, the first device receives, from a second device, a reconfiguration message 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 keeping a cell identifier of the serving cell unchanged. The reconfiguration message indicates the fourth device to update a configuration for the second device.

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

In some example embodiments, the first device transmits, to the second device, a handover request for handover of the third device from the first cell to the second cell and for reconfiguration of the fourth device. In response to the handover being allowed by the second device, the first device receives, from the second device, a handover acknowledgement comprising a handover command for the third device and the reconfiguration message for the fourth device.

In some example embodiments, the first device transmits, to the second device, a handover request for handover of the third device from the first cell to the second cell and for reconfiguration of the fourth device. In response to the handover being allowed by the second device, the first device receives, from the second device, a handover acknowledgement comprising a handover command for the third device and an indication of late transmission of the reconfiguration message. The indication of late transmission can be implicit for example if only the HO acknowledgement for the third device is returned. In response to a second interface between the third device and the second device being setting up, the first device receives the reconfiguration message from the second device.

In some example embodiments, the handover request comprises context information for the fourth device and for a first interface between the third device and the first device.

At block 620, the first device ciphers the reconfiguration message based on a security parameter of the first device.

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

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

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

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

Fig. 7 shows a flowchart of an example method 700 for IAB communication in accordance with some example embodiments of the present disclosure. The method 700 can be implemented at the IAB donor 220 as shown in Fig. 2a and/or Fig. 2b. In the following, the IAB donor 210 is also referred to as a “first device” , the IAB donor 220 is also referred to as a “second device” , the IAB node 230 is also referred to as a “third device” and the UE 240 is also referred to as a “fourth device” . It is to be understood that the method 700 may include additional blocks not shown and/or may omit some shown blocks, and the scope of the present disclosure is not limited in this regard.

At block 710, the second donor generates 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 a first device to a second cell in communication with the second device while keeping a cell identifier of the serving cell unchanged. The reconfiguration message indicates the fourth device to update a configuration for the second device.

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

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

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

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

Fig. 8 shows a flowchart of an example method 800 for IAB communication in accordance with some example embodiments of the present disclosure. The method 800 can be implemented at the IAB node 230 shown in Fig. 2a and/or Fig. 2b. In the following, the IAB donor 210 is also referred to as a “first device” , the IAB donor 220 is also referred to as a “second device” , the IAB node 230 is also referred to as a “third device” and the UE 240 is also referred to as a “fourth device” . It is to be understood that the method 800 may include additional blocks not shown and/or may omit some shown blocks, and the scope of the present disclosure is not limited in this regard.

At block 810, the third device receives, from a first device or a second device, a reconfiguration message 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 keeping a cell identifier of the serving cell unchanged. The reconfiguration message indicating the fourth device to update a 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 the reconfiguration message from the first device via a first interface between the third device and the first device, the reconfiguration message ciphered 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 keeping an identifier of the serving cell unchanged. In some example embodiments, the trigger comprises any of the following: setting up of a second interface between the IAB anode and the second device; initiation of a handover procedure by the third device; or completion of the handover procedure by the third device.

In some example embodiments, the third device receives the reconfiguration message from the second device via a second interface between the third device and the second device, the reconfiguration message ciphered based on a security parameter 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 for retention of context information for the first interface and the fourth device; and stores the context information at the third device.

Fig. 9 shows a flowchart of an example method 900 for IAB communication in accordance with some example embodiments of the present disclosure. The method 900 can be implemented at the UE 240 as shown in Fig. 2a and/or Fig. 2b. In the following, the IAB donor 210 is also referred to as a “first device” , the IAB donor 220 is also referred to as a “second device” , the IAB node 230 is also referred to as a “third device” and the UE 240 is also referred to as a “fourth device” . It is to be understood that the method 900 may include additional blocks not shown and/or may omit some shown blocks, and the scope of the present disclosure is not limited in this regard.

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

At block 920, the fourth device updates a configuration used at the fourth device with the new configuration without performing a 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 ciphered based on a security parameter of the first device. The fourth device de-ciphers the reconfiguration message based on the security parameter 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 comprise means for performing the respective steps of the method 600. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

In some example embodiments, the apparatus capable of performing the method 600 (for example, the IAB donor 210) comprises: 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 keeping a cell identifier of the serving cell unchanged, and the reconfiguration message indicating the fourth device to update a configuration for the second device; means for ciphering the reconfiguration message based on a security parameter of the apparatus; and means for providing the ciphered reconfiguration message to the third device.

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

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

In some example embodiments, the handover request comprises context information for the fourth device and for a first interface between the third device and the apparatus.

In some example embodiments, the means for providing the ciphered reconfiguration message to the third device comprises: means for transmitting the ciphered 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, to the third device via a first interface between the third device and the apparatus, an indication for retention of context information for the first interface and the fourth device.

In some example embodiments, the means for providing the ciphered reconfiguration message to the third device comprises: means for transmitting the ciphered reconfiguration message to the second device via a third interface between the apparatus and the second device, such that the second device transmits the ciphered reconfiguration message to the third device via a 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 comprise means for performing the respective steps of the method 700. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

In some example embodiments, the apparatus capable of performing the method 700 (for example, the IAB donor 220) 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 a first device to a second cell in communication with the apparatus while keeping a cell identifier of the serving cell unchanged, and the reconfiguration message indicating the fourth device to update a configuration for the apparatus; and means for transmitting the reconfiguration message to the first device.

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

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

In some example embodiments, the means for generating the reconfiguration message comprises: means for receiving, from the first device, a handover request for handover of the third device from the first cell to the second cell and for reconfiguration of the fourth device; means for determining, based on the handover request, whether to allow the handover; means for in accordance with a determination to allow the handover, transmitting, to the first device, a handover acknowledgement comprising a handover command for the third device and an indication of late transmission of the reconfiguration message; and means for in response to a second interface between the third device and the apparatus being setting up, generating the reconfiguration message. The means for transmitting the reconfiguration message to the first device comprises: means for transmitting, to the first device, a further handover acknowledgement 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, the reconfiguration message ciphered based on a security parameter of the first device via a third interface between the first device and the apparatus; and means for in response to a second interface between the third device and the apparatus being setting up, transmitting the reconfiguration message to the third device via the second interface.

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 comprise means for performing the respective steps of the method 800. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

In some example embodiments, the apparatus capable of performing the method 800 (for example, the IAB node 230) comprises: means for receiving, from a first device or a second device, a reconfiguration message for a fourth device in a serving cell served by the apparatus, the apparatus migrating from a first cell in communication with the first device to a second cell in communication with the second device while keeping a cell identifier of the serving cell unchanged, and the reconfiguration message indicating the fourth device to update a configuration for the second device; means for 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 the reconfiguration message from the first device via a first interface between the apparatus and the first device, the reconfiguration message ciphered 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 in response to a trigger for transmission of the reconfiguration message, transmitting the reconfiguration message to the fourth device.

In some example embodiments, the trigger comprises any of the following: setting up of a second interface between the apparatus and the second device; initiation of a handover procedure by the apparatus; or completion of the handover procedure by the apparatus.

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

In some example embodiments, the 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 for retention of context information for the first interface and the fourth device; and means for storing the context information at the apparatus.

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 comprise means for performing the respective steps of the method 900. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

In some example embodiments, the apparatus capable of performing the method 900 (for example, the UE 240) 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 a first device to a second cell in communication with a second device while keeping a cell identifier of the serving cell unchanged, and the reconfiguration message comprising 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 ciphered based on a security parameter of the first device. The apparatus capable of performing the method 900 further comprises: means for de-ciphering the reconfiguration message based on the security parameter of the first device; and means for decoding the reconfiguration message to obtain the 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 the migrating IAB MT is another IAB node under the first IAB donor.

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

Fig. 10 is a simplified block diagram of a device 1000 that is suitable for implementing embodiments of the present disclosure. For example, the IAB node 230, the IAB donor 210, the IAB donor 220 and/or the UE 240 shown in Fig. 2a and/or Fig. 2b can 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 processor 1010, and one or more communication modules 1040 coupled to the processor 1010.

The communication module 1040 is for bidirectional communications. The communication module 1040 has at least one antenna to facilitate communication. The communication interface may represent any interface that is necessary for communication with other network elements.

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

The memory 1020 may include one or more non-volatile memories and one or more volatile memories. Examples of the non-volatile memories include, but are not limited to, a Read Only Memory (ROM) 1024, an electrically programmable read only memory (EPROM) , a flash memory, a hard disk, a compact disc (CD) , a digital video disk (DVD) , and other magnetic storage and/or optical storage. Examples of the volatile memories include, but are not limited to, a random access memory (RAM) 1022 and other volatile memories that will not last in the power-down duration.

A computer program 1030 includes computer executable instructions that are executed by the associated processor 1010. The program 1030 may be stored in the ROM 1024. The processor 1010 may perform any suitable actions and processing by loading the program 1030 into the RAM 1022.

The embodiments of the present disclosure may be implemented by means of the program 1030 so that the device 1000 may perform any process of the disclosure as discussed with reference to Figs. 3-9. The embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.

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

It should be appreciated that future networks may utilize network functions virtualization (NFV) which is a network architecture concept that proposes virtualizing network node functions into “building blocks” or entities that may be operationally connected or linked together to provide services. A virtualized network function (VNF) may comprise one or more virtual machines running computer program codes using standard or general type servers instead of customized hardware. Cloud computing or data storage may also be utilized. In radio communications, this may mean node operations to be carried out, at least partly, in a central/centralized unit, CU, (e.g. server, host or node) operationally coupled to distributed unit, DU, (e.g. a radio head/node) . It is also possible that node operations will be distributed among a plurality of servers, nodes or hosts. It should also be understood that the distribution of labour between core network operations and base station operations may vary depending on implementation.

In an embodiment, the server may generate a virtual network through which the server communicates with the distributed unit. In general, virtual networking may involve a process of combining hardware and software network resources and network functionality into a single, software-based administrative entity, a virtual network. Such virtual network may provide flexible distribution of operations between the server and the radio head/node. In practice, any digital signal processing task may be performed in either the CU or the DU and the boundary where the responsibility is shifted between the CU and the DU may be selected according to implementation.

Therefore, in an embodiment, a CU-DU architecture is implemented. In such case the device 1000 may be comprised in a central unit (e.g. a control unit, an edge cloud server, a server) operatively coupled (e.g. via a wireless or wired network) to a distributed unit (e.g. a remote radio head/node) . That is, the central unit (e.g. an edge cloud server) and the distributed unit may be stand-alone apparatuses communicating with each other via a radio path or via a wired connection. Alternatively, they may be in a same entity communicating via a wired connection, etc. The edge cloud or edge cloud server may serve a plurality of distributed units or a radio access networks. In an embodiment, at least some of the described processes may be performed by the central unit. In another embodiment, the device 1000 may be instead comprised in the distributed unit, and at least some of the described processes may be performed by the distributed unit.

In an embodiment, the execution of at least some of the functionalities of the device 1000 may be shared between two physically separate devices (DU and CU) forming one operational entity. Therefore, the apparatus may be seen to depict the operational entity comprising one or more physically separate devices for executing at least some of the described processes. In an embodiment, such CU-DU architecture may provide flexible distribution of operations between the CU and the DU. In practice, any digital signal processing task may be performed in either the CU or the DU and the boundary where the responsibility is shifted between the CU and the DU may be selected according to implementation. In an embodiment, the device 1000 controls the execution of the processes, regardless of the location of the apparatus and regardless of where the processes/functions are carried out.

Generally, various embodiments of the present disclosure may be implemented in 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 embodiments of the present disclosure are illustrated and described as block diagrams, flowcharts, or using some other pictorial representations, it is to be understood that the block, apparatus, system, technique or method 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 includes computer-executable instructions, such as those included in program modules, being executed in a device on a target real or virtual processor, to carry out the method 600 as described above with reference to Fig. 6, the method 700 as described above with reference to Fig. 7, the method 800 as described above with reference to Fig. 8 and/or the method 900 as described above with reference to Fig. 9. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, or the like that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or split between program modules as desired in various embodiments. Machine-executable instructions for program modules may be executed within a local or distributed device. In a distributed device, program modules may be located in both local and remote storage media.

Program code for carrying out methods of the present disclosure may be written in any combination of one or more programming languages. These program codes 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 codes, when executed by the processor or controller, cause the functions/operations specified in the flowcharts and/or block diagrams to be implemented. The program code may execute entirely on a 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 the present disclosure, the computer program codes or related data may be carried by any suitable carrier to enable the device, apparatus or processor to perform various processes and operations as described above. Examples of the carrier include a signal, computer readable medium, and the like.

The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable medium may include but 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 the 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 depicted in a particular order, this should not be understood 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 certain circumstances, multitasking and parallel processing may be advantageous. Likewise, while several specific implementation details are contained in the above discussions, these should not be construed as limitations on the scope of the present 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 may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable sub-combination.

Although the present disclosure has been described in languages specific to structural features and/or methodological acts, it is to be understood that the present 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

A method comprising:

receiving, at a first device and 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 first device to a second cell in communication with the second device while keeping a cell identifier of the serving cell unchanged, and the reconfiguration message indicating the fourth device to update a configuration for the second device;

ciphering the reconfiguration message based on a security parameter of the first device; and

providing the ciphered reconfiguration message to the third device.
The method of claim 1, wherein the reconfiguration message indicates the fourth device to update the configuration for the second device without performing a random access procedure.
The method of claim 1, wherein receiving the reconfiguration message comprises:

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

in response to the handover being allowed by the second device, receiving, from the second device, a handover acknowledgement comprising a handover command for the third device and the reconfiguration message for the fourth device.
The method of claim 1, wherein receiving the reconfiguration message comprises:

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

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

in response to a second interface between the third device and the second device being setting up, receiving the reconfiguration message from the second device.
The method of claim 3 or 4, wherein the handover request comprises context information for the fourth device and for a first interface between the third device and the first device.
The method of claim 1, wherein providing the ciphered reconfiguration message to the third device comprises:

transmitting the ciphered reconfiguration message to the third device via a first interface between the third device and the first device.
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 for retention of context information for the first interface and the fourth device.
The method of claim 1, wherein providing the ciphered reconfiguration message to the third device comprises:

transmitting the ciphered 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 ciphered reconfiguration message to the third device via a second interface between the third device and the second device.
The method of 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.
A method comprising:

generating, at 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 a first device to a second cell in communication with the second device while keeping a cell identifier of the serving cell unchanged, and the reconfiguration message indicating the fourth device to update a configuration for the second device; and

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

wherein generating the reconfiguration message comprises:

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

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

in accordance with a determination to allow the handover, generating the reconfiguration message; and wherein transmitting the reconfiguration message to the first device comprises:

transmitting, to the first device, a handover acknowledgement comprising a handover command for the third device and the generated reconfiguration message for the fourth device.
The method of claim 10,

wherein generating the reconfiguration message comprises:

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

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

in accordance with a determination to allow the handover, transmitting, to the first device, a handover acknowledgement comprising a handover command for the third device and an indication of late transmission of the reconfiguration message; and

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

wherein transmitting the reconfiguration message to the first device comprises:

transmitting, to the first device, a further handover acknowledgement comprising the generated reconfiguration message.
The method of claim 12 or 13, wherein the handover request comprises context information for the fourth device and for a first interface between the third device and the first device.
The method of claim 10, further comprising:

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

in response to a second interface between the third device and the second device being setting up, transmitting the reconfiguration message to the third device via the second interface.
The method of 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.
A method comprising:

receiving, at a third device and from a first device or a second device, a reconfiguration message 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 keeping a cell identifier of the serving cell unchanged, and the reconfiguration message indicating the fourth device to update a configuration for the second device;

forwarding the reconfiguration message to the fourth device; and

receiving a reconfiguration complete message from the fourth device.
The method of claim 17, wherein the reconfiguration message indicates the fourth device to update the configuration for the second device without performing a random access procedure.
The method of claim 17, wherein receiving the reconfiguration message comprises:

receiving the reconfiguration message from the first device via a first interface between the third device and the first device, the reconfiguration message ciphered based on a security parameter of the first device.
The method of claim 19, wherein forwarding the reconfiguration message to the fourth device comprises:

storing the reconfiguration message at the third device; and

in response to a trigger for transmission of the reconfiguration message, transmitting the reconfiguration message to the fourth device.
The method of claim 20, wherein the trigger comprises any of the following:

setting up of a second interface between the IAB anode and the second device;

initiation of a handover procedure by the third device; or

completion of the handover procedure by the third device.
The method of claim 17, wherein receiving the reconfiguration message comprises:

receiving the reconfiguration message from the second device via a second interface between the third device and the second device, the reconfiguration message ciphered based on a security parameter of the first device.
The method of claim 17, further comprising:

receiving, from the first device via a first interface between the third device and the first device, an indication for retention of context information for the first interface and the fourth device; and

storing the context information at the third device.
The method of 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.
A method comprising:

receiving, at a fourth device, a reconfiguration message from a 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 keeping a cell identifier of the serving cell unchanged, and the reconfiguration message comprising 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.
The method of claim 25, wherein the reconfiguration message is ciphered based on a security parameter of the first device, and the method further comprises:

de-ciphering the reconfiguration message based on the security parameter of the first device; and

decoding the reconfiguration message to obtain the configuration for the second device.
The method of 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.
A first device comprising:

at least one processor; and

at least one memory including computer program codes;

the at least one memory and the computer program codes are configured to, with the at least one processor, cause the first device to perform the method of any of claims 1-9.
A second device comprising:

at least one processor; and

at least one memory including computer program codes;

the at least one memory and the computer program codes are configured to, with the at least one processor, cause the second device to perform the method of any of claims 10-16.
A third device comprising:

at least one processor; and

at least one memory including computer program codes;

the at least one memory and the computer program codes are configured to, with the at least one processor, cause the third device to perform the method of any of claims 17-24.
A fourth device comprising:

at least one processor; and

at least one memory including computer program codes;

the at least one memory and the computer program codes are configured to, with the at least one processor, cause the fourth device to perform the method of any of claims 25-27.
An apparatus comprising means for performing the method of any of claims 1-9.
An apparatus comprising means for performing the method of any of claims 10-16.
An apparatus comprising means for performing the method of any of claims 17-24.
An apparatus comprising means for performing the method of any of claims 25-27.
A computer program product that is stored on a computer readable medium and includes machine-executable instructions, wherein the machine-executable instructions, when being executed, cause a machine to perform the method of any of claims 1-27.
A computer readable storage medium comprising program instructions stored thereon, the instructions, when executed by an apparatus, causing the apparatus to perform the method of any of claims 1-27.