EP4397127A1

EP4397127A1 - Communications in an integrated access and backhaul network

Info

Publication number: EP4397127A1
Application number: EP21955385.6A
Authority: EP
Inventors: Xiang Xu; Ömer BULAKC; Oliver Blume
Original assignee: Nokia Solutions and Networks Oy
Current assignee: Nokia Solutions and Networks Oy
Priority date: 2021-08-31
Filing date: 2021-08-31
Publication date: 2024-07-10
Also published as: WO2023028810A1; CN118176824A; EP4397127A4

Abstract

Example embodiments of the present disclosure relate to devices, methods, apparatuses and computer readable storage media for communications in the IAB network. In this solution, a first device receives a first request for resuming a connection between a third device and a network via a second device. In particular, the third device is in the inactive state and a fourth device is the last serving device for the third device. Then, the first device transmits a second request for retrieving a context for the third device based on the migration history information of the second device and/or the information about whether the first device may communicate with the fourth device directly. In this way, the communications may be proceeded regardless of whether there is an interface between the first device and the fourth device.

Description

COMMUNICATIONS IN AN INTEGRATED ACCESS AND BACKHAUL NETWORK

FIELD

Embodiments of the present disclosure generally relate to the field of telecommunication and in particular, to devices, methods, apparatus and computer readable storage media for communications in an integrated access and backhaul (IAB) network.

BACKGROUND

Power consumption of a terminal device is a focus in current wireless communication system. In order to reduce power consumption of the terminal device, it is proposed that the terminal device may be configured in some power saving modes/states (such as, inactive/RRC_INACTIVE state) . When the terminal device is in the inactive state, the terminal device remains in Connection Management (CM) -CONNECTED and can move within an area (such as, a radio access network (RAN) -based notification area, RNA) configured by a next generation (NG) -RAN without notifying NG-RAN. Further, the last serving gNB for the terminal device keeps the context of the terminal device and the UE-associated NG connection with the serving access and mobility management function (AMF) and user plane function (UPF) .
Recently, the IAB network is utilized to support wireless relaying and backhauling for 5G New Radio (NR) . A relay node in the IAB architecture may be referred to as IAB, IAB device or IAB-node, which provides both access and backhaul by using a NR radio access. The network node terminating the wireless backhauling on the network side may be referred to as donor, donor device or donor node, which usually is a gNB with added functionalities to support IAB.
The terminal device connected with the IAB can also transition to RRC_INACTIVE while the IAB may migrate from one Donor to the next Donor, and to a further Donor, for example, when the IAB is installed on a high speed train. In this event, conventional technology for procedures (such as, resuming a connection between a terminal device and a network) would be infeasible due to the complicated scenario (such as, the last serving donor and the serving donor may not have an interface with each other) . Therefore, it is desirable to further discuss how to implement the communications (such as, resuming a connection between a terminal device and a network) in the IAB network.
SUMMARY
In general, example embodiments of the present disclosure provide a solution for communications in the IAB network. Various example embodiments of the present disclosure can relate to 5G mobile and wireless communications system and beyond 5G, e.g., 6G.
In a first aspect, there is provided 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: receive, from a third device via a second device, a first request for resuming a connection between the third device and a network, the first request comprising identity information of a fourth device being a last serving device in the network for the third device, wherein the third device is in an inactive state in the network and accesses the network via the second device and wherein the second device connects with the first device; and transmit a second request for retrieving a context of the third device to: a fifth device from which the second device migrated if an interface between the first device and the fourth device is not available, or the identity information of the fourth device is unknown to the first device, or a shortcut device of at least one device if the shortcut device is informed by the first device that the second device is connecting with the first device, wherein the second device connected with the at least one device prior to connecting with the fifth device from which the second device migrated.
In a second aspect, there is provided 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: transmit migration history information to a fifth device when the second device migrates from the fourth device to the fifth device; and receive a second request for retrieving a context of a third device being in an inactive state in a network and accessing the network via the second device from: a first device serving the third device if the fourth device is informed that the second device is connecting with the first device, or the fifth device.
In a third aspect, there is provided a fifth 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 fifth device to: receive, from a device of at least one device, a second request for retrieving a context of a third device accessing a network via a second device, wherein the second device migrated to the at least one device after the second device migrated to the fifth device; and forward, to a device from which the second device migrated, an updated second request based on the received second request.
In a fourth aspect, there is provided a method. The method comprises: receiving, at a first device from a third device via a second device, a first request for resuming a connection between the third device and a network, the first request comprising identity information of a fourth device being a last serving device in the network for the third device, wherein the third device is in an inactive state in the network and accesses the network via the second device and wherein the second device connects with the first device; and transmitting a second request for retrieving a context of the third device to: a fifth device from which the second device migrated if an interface between the first device and the fourth device is not available, or the identity information of the fourth device is unknown to the first device, or a shortcut device of at least one device if the shortcut device is informed by the first device that the second device is connecting with the first device, wherein the second device connected with the at least one device prior to connecting with the fifth device from which the second device migrated.
In a fifth aspect, there is provided a method. The method comprises: transmitting migration history information to a fifth device when the second device migrates from the fourth device to the fifth device; and receiving a second request for retrieving a context of a third device being in an inactive state in a network and accessing the network via the second device from: a first device serving the third device if the fourth device is informed that the second device is connecting with the first device, or the fifth device.
In a sixth aspect, there is provided a method. The method comprises: receiving, at a fifth device from a device of at least one device, a second request for retrieving a context of a third device accessing a network via a second device, wherein the second device migrated to the at least one device after the second device migrated to the fifth device; and forwarding, to a device from which the second device migrated, an updated second request based on the received second request.
In a seventh aspect, there is provided a first apparatus. The first apparatus comprises: means for means for receiving, from a third apparatus via a second apparatus, a first request for resuming a connection between the third apparatus and a network, the first request comprising identity information of a fourth apparatus being a last serving apparatus in the network for the third apparatus, wherein the third apparatus is in an inactive state in the network and accesses the network via the second apparatus and wherein the second apparatus connects with the first apparatus; and means for transmitting a second request for retrieving a context of the third apparatus to: a fifth apparatus from which the second apparatus migrated if an interface between the first apparatus and the fourth apparatus is not available, or the identity information of the fourth apparatus is unknown to the first apparatus, or a shortcut apparatus of at least one apparatus if the shortcut apparatus is informed by the first apparatus that the second apparatus is connecting with the first apparatus, wherein the second apparatus connected with the at least one apparatus prior to connecting with the fifth apparatus from which the second apparatus migrated.
In an eighth aspect, there is provided a fourth apparatus. The fourth apparatus comprises: means for transmitting migration history information to a fifth apparatus when the second apparatus migrates from the fourth apparatus to the fifth apparatus; and means for receiving a second request for retrieving a context of a third apparatus being in an inactive state in a network and accessing the network via the second apparatus from: a first apparatus if the fourth apparatus serving the third apparatus is informed that the second apparatus is connecting with the first apparatus, or the fifth apparatus
In a ninth aspect, there is provided a fifth apparatus. The fifth apparatus comprises: means for receiving, from an apparatus of at least one apparatus, a second request for retrieving a context of a third apparatus accessing a network via a second apparatus, wherein the second apparatus migrated to the at least one apparatus after the second apparatus migrated to the fifth apparatus; and means for forwarding, to an apparatus from which the second apparatus migrated, an updated second request based on the received second request.
In a tenth aspect, there is provided a computer readable medium having a computer program stored thereon which, when executed by at least one processor of a device, causes the device to carry out the method according to the fourth aspect.
In an eleventh aspect, there is provided a computer readable medium having a computer program stored thereon which, when executed by at least one processor of a device, causes the device to carry out the method according to the fifth aspect.
In a twelfth aspect, there is provided a computer readable medium having a computer program stored thereon which, when executed by at least one processor of a device, causes the device to carry out the method according to the sixth aspect.
Other features and advantages of the embodiments of the present disclosure will also be apparent from the following description of specific embodiments when read in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of embodiments of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the disclosure are presented in the sense of examples and their advantages are explained in greater detail below, with reference to the accompanying drawings, where;
Fig. 1 illustrates a conventional signaling flow of RNA updating procedure with UE context relocation;
Fig. 2A illustrates a conventional signaling flow of UE-triggered transition procedure from RRC_INACTIVE to RRC_CONNECTED;
Fig. 2B illustrates a conventional signaling flow of Network-triggered transition procedure from RRC_INACTIVE to RRC_CONNECTED;
Fig. 3 illustrates an example communication network architecture in which example embodiments of the present disclosure can be implemented;
Fig. 4 illustrates a signaling chart illustrating a method of communications in the IAB network without shortcut according to some example embodiments of the present disclosure;
Fig. 5 illustrates a signaling chart illustrating a method of communications in IAB network with shortcut according to some example embodiments of the present disclosure;
Fig. 6 illustrates block diagram of examples for shortcut transmission;
Fig. 7 illustrates a signaling chart illustrating a method centralized-based context maintaining according to some example embodiments of the present disclosure;
Fig. 8 illustrates a flowchart of an example method according to some example embodiments of the present disclosure;
Fig. 9 illustrates a flowchart of a further example method according to some example embodiments of the present disclosure;
Fig. 10 illustrates a flowchart of another example method according to some example embodiments of the present disclosure;
Fig. 11 shows a simplified block diagram of a device that is suitable for implementing example embodiments of the present disclosure; and
Fig. 12 shows a block diagram of an example computer readable medium in accordance with some 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 functionalities of various elements. 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 fifth generation (5G) systems, 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) 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) new radio (NR) 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 Next Generation NodeB (gNB) , a Remote Radio Unit (RRU) , a radio header (RH) , a remote radio head (RRH) , Integrated Access and Backhaul (IAB) node, a relay, a low power node such as a femto, a pico, and so forth, depending on the applied terminology and technology. The network device is allowed to be defined as part of a gNB such as for example in CU/DU split in which case the network device is defined to be either a gNB-CU or a gNB-DU.
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 (IoT) 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, 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.
As discussed above, when the terminal device is in the inactive state, the terminal device remains in CM-CONNECTED and can move within the RNA without notifying NG-RAN. In the conventional solution, the RNA for the terminal device may be configured by the last serving NG-RAN node, where the RNA can cover a single or multiple cells, and shall be contained within the core network (CN) registration area (RA) .
In addition, there are several different implements for configuring the RNA. In one implement, the RNA is indicated by a list of cells. Specifically, the terminal device is provided with an explicit list of cell (s) that constitute the RNA. In another implement, the RNA is indicated by a list of RAN areas. Specifically, the terminal device is provided with at least one RAN area identification (ID) , where a RAN area is a subset of a CN tracking area or equal to a CN tracking area. Further, a RAN area is specified by one RAN area ID, which consists of a tracking area code (TAC) and optionally a RAN area code (RANAC) . The network device broadcasts one or more RAN area IDs in the system information (SI) .
As for the terminal device, the terminal device determines whether it moves out of the RNA based on information, such as the cell identity (ID) , the tracking area identity (TAI) and RAN area ID. In case that the terminal device moves out of the RNA area or a periodic update timer (such as, T380 as stipulated by 3GPP standards) expiries, the terminal device initiates the RNA updating procedure. Reference is made to Fig. 1, which illustrates a conventional signaling flow 100 of RNA updating procedure with UE context relocation. As shown in Fig. 1, the UE in RRC_INACTIVE state initiates the RNA updating procedure by transmitting a RRC Resume Request to the gNB and the updating procedure involves the UE, the gNB, the last serving gNB and the AMF.
Further, both the terminal device (i.e., the UE) and the gNB may trigger the transition from the RRC_INACTIVE state to the RRC_CONNECTED state due to a newly-arrived data transmission. For example, if the UE detects that there is uplink data to be transmitted, the terminal device may trigger the transition from the RRC_INACTIVE state to the RRC_CONNECTED state. Fig. 2A illustrates a conventional signaling flow 200 of a UE-triggered transition procedure from the RRC_INACTIVE state to the RRC_CONNECTED state. Similarly, if the last serving gNB detects an event for triggering a paging procedure for the UE, the last serving gNB may trigger the transition from the RRC_INACTIVE state to the RRC_CONNECTED state. Fig. 2B illustrates a conventional signaling flow 250 Network-triggered transition procedure from RRC_INACTIVE to RRC_CONNECTED.
In addition, in the macro cell, the supported TAC/RANAC is semi-statically configured. The last serving gNB can know the TAC/RANAC supported by a neighbor gNB via Xn in advance, i.e., before assign RNA to a UE. Alternately, the network operator can configure different TAC/RANAC for the gNBs that have no Xn interface, such that it can be guaranteed that the RNA only includes the gNBs that are Xn connected. As a result, the scenario where an RNA includes the gNB that have no Xn interface with the last serving gNB may be avoided, and thus the above proposed solution may work well in macro cell.
Further, as discussed above, the IAB network is utilized to support wireless relaying and backhauling for 5G NR. In the IAB network, the IAB which functions as a distributed unit may inform the centralized unit (CU) about the supported TAC and RANAC via a F1AP interface. The CUs in the IAB network may exchange the information about the supported TAC and RANAC via the Xn interface among the CUs. Therefore, the CU can know the TAC and RANAC supported in the neighbouring CU.
Recently, it is proposed that the IAB may be deployed on a vehicle with high speed (such as, a train, a bus and so on) , which also referred to as mobile IAB. Some options for configuring the RNA are proposed as below
● Option 1: the RNA includes a list of cell IDs, for example, the list of cell IDs for the mobile IAB installed on the train.
The IAB’s cell ID is related to its Donor’s gNB ID. Whenever the mobile IAB migrates to target Donor, the mobile IAB changes the cell ID of system information block type 1 (SIB1) .
● Option 2: the RNA includes a list of {TAC, optional RAN area code} .
Option 2a: the RNA includes a list of {TAC, optional RAN area code} , the mobile IAB uses the TAC of the Donor. Whenever the mobile IAB migrates to the target donor, the mobile IAB changes the TAC of SIB1.
Option 2b: the RNA includes a list of {TAC} , and each mobile IAB uses a separate TAC. The mobile IAB’s TAC is not changed when the mobile IAB migrates to target Donor. The mobile IAB’s TAC is not shared with other mobile IABs or fixed cells (e.g. normal macro cell, pico cell, etc) . In case that the RNA only includes the mobile IAB’s TAC, there is no need to initiate RNA Update as long as the UE stays on the same train (i.e., stays in the RNA) except for the expiry of the periodic update timer (such as, T380) .
Option 2c: the RNA includes a list of {TAC, RAN area code} , and each mobile IAB uses a separate RAN area code while shares the same TAC with other mobile IAB(s) . The mobile IAB’s TAC and RAN area code are not changed when the mobile IAB migrates to target Donor. Further, the mobile IAB’s RANAC is not shared with other mobile IABs or fixed cells (for example, normal macro cell, pico cell and so on) . In case that the RNA only includes the mobile IAB’s TAC and RAN area code, there is no need to initiate RNA Update as long as the UE stays on the same train (i.e., stays in the RNA) except for the expiry of the periodic update timer (such as, T380) .
A UE connected with a mobile IAB also can transition to the RRC INACTIVE state. As a specific example, the UE is in the RRC INACTIVE state and accesses the network via the IAB installed on a train which may move at a high speed even up to 500 KM/H. At a first time point (for example, 10: 00 AM) , the UE transitions to the RRC_INACTIVE state when the mobile IAB connects with donor 1. Then, at a second time point (for example, 10: 30 AM) , the UE needs to transition to RRC_CONNECTED (for example, due to RNA updating procedure, or RRC connection resuming procedure) when the mobile IAB connects with a different Donor 2 which may not be a neighboring donor for donor 1.
In the above Options 2b and 2c, the mobile IAB may always use same TAC/RNAC and the UE on the train only need to perform RNA update upon the T380 expiry, or when the UE leaves the train. According to the conventional solution, the supported TAC/RANAC in the IAB’s serving CU (such as, donor 1 in the above specific example) dynamically changes when the mobile IAB comes or leaves, for example, when the mobile IAB connects with (or leaves) the IAB’s serving CU, the IAB’s serving CU will add (or remove) IAB’s TAC/RANAC in its supported list of TAC/RANAC. Further, when the IAB’s serving CU assigns the RNA to the UE, it does not know the CU (such as, donor 2 in the above specific example) that will serve the mobile IAB later.
Thus, the above conventional solution cannot guarantee that the serving donor and the last serving donor always have an interface with each other. Actually, in most cases, the serving donor and the last serving donor may not have an interface with each other in the mobile IAB network. Still refer to the above specific example, even if the serving donor (i.e., donor 2) and the last serving honor (i.e., donor 1) may connect with the same AMF, there still may be no Xn interface between the serving donor and the last serving donor. If so, the conventional procedures for RAN updating and resuming a connection between a terminal device and a network would be infeasible due to the complicated scenario (such as, the last serving donor and the serving may not have an interface with each other) . Therefore, the communications in the mobile IAB is desirable to further discussed.
In order to address at least some of the above problems and other potential problems, according to example embodiments of the present disclosure, there is proposed a solution for communications in the IAB network. In this solution, a first device (such as, a serving donor in the IAB network) receives a first request for resuming a connection between a third device (such as, a terminal device) and a network via a second device (such as, an IAB device) . In particular, the third device is in the inactive state and a fourth device is the last serving device for the third device. Then, the first device transmits a second request for retrieving a context for the third device based on the migration history information of the second device and/or the information about whether the first device may communicate with the devices on a migration chain of the second device. In this way, the communications (such as, procedures for RAN updating, resuming the connection and paging the third device) may be proceeded regardless of whether there is an interface between the first device and the fourth device.
Fig. 3 shows an example communication network 300 in which example embodiments of the present disclosure can be implemented. The communication network 300 includes a first device 310, a second device 320, a third device 330, a fourth device 340 and fifth devices 350-1 to 350-3 (hereinafter collectively referred to as the fifth devices 350 or individually referred to as a fifth device 350) . In the specific example of Fig. 3, the first device 310 may provide a serving cell 312, the fourth device 340 may provide a serving cell 342, and the fifth device 350-1 to 350-3 may provide respective serving cells 352-1 to 352-3.
Additionally, the communication network 300 also may comprise a sixth device 360, which may be a center data base, such as, aka RAN data storage function (DSF) . Further, the first device 310, the fourth device 340 and the fifth devices 350-1 to 350-3 may transmit/write information to the sixth device 360, or receive/read information from the sixth device 360.
As shown in Fig. 3, the third device 330 accesses the communication network 300 via the second device 320 which means that the third device 330 can communicate with the second device 320 via physical communication channels or links. Further, the second device 320 may connect with any of the first device 310, the fourth device 340 and the fifth devices 350. In addition, the second device 320 may move from one position to another location over time and migrates among the first device 310, the fourth device 340 and the fifth devices 350 accordingly.
In addition, the third device 330 may be in different in different states (such as, connected/RRC_CONNECTED state and inactive/RRC_INACTIVE state) . The third device 330 in the inactive state may transition to the connected state by resuming/establishing a RRC connection with the network. Such transition procedure may be initiated by either the third device 330 (such as, for updating RNA or resuming RRC connection) or the network (such as, for detecting an event for triggering a paging procedure for the third device 330) .
As one specific example, the communication network 300 may be an IAB network. In such example scenario, the first device 310, the fourth device 340 and the fifth device 350 may be donor devices. Further, the second device 320 may be an IAB device and additionally may be on deployed a vehicle with high speed (such as, a train, a bus and so on) . In addition, the third device 330 may be a terminal device.
As one specific scenario, when the second device 320 connects with the fourth device 340, the third device 330 transitions from the connected state to the inactive state. Then, the second device 320 is migrated to the fifth device 350-1 (and additional migrated to the fifth devices 350-2 and 350-3 orderly) , and then further migrated to the first device 310. When the second device 320 connects with the first device 310, the third device 330 needs to transition to the connected state. Communications in such specific scenario would be discussed in the following. In the following text, the first device 310 also may be referred to as a serving device, the fourth device 340 also may be referred to as a last serving device, and the fifth device (s) 350 also may be referred to as relay device (s) or intermediate device (s) .
It also should be appreciated that the numbers of first device, second device, third device, fourth device, fifth device, sixth device and serving cell are only for the purpose of illustration without suggesting any limitations. The communication environment 300 may include any suitable numbers of first device, second device, third device, fourth device, fifth device, sixth device and serving cell adapted for implementing embodiments of the present disclosure.
Principle and implementations of the present disclosure will be described in detail below with reference to Figs. 4-7. In the following text, although procedures (such as, migrations, resuming connection, paging the third device 350, and so on) may be discussed in one signalling chart, it is to be understood that the procedures may be performed separately or in any suitable sub-combination and any suitable order.
Reference is now made to Fig. 4, which shows example signaling chart 400 for the method of communications in the IAB network in accordance with some embodiments of the present disclosure. Only for the purpose of illustrations, the signaling chart 400 are described to be implemented between the first device 310, the second device 320, the third device 330, the fourth device 340, the fifth device 350 as shown in Fig. 3.
For ease of discussion, some terms used in the following description are listed as below:
● First duration (also referred to as “2nd gNB’s T380” or T380 of the 2 ^nd gNB sometimes) : a duration during which the first device 310 and the fifth device 350 keep context of the second device 320.
● Second duration (also referred to as “1st gNB’s T380” or T380 of the 1 ^st gNB sometimes) : a duration during which the fourth device 340 and the fifth device 350 keep context of the second device 320.
● Third duration: a duration during which the fifth device 350 and a device from which the second device 320 migrated keep context of the second device 320.
● Fourth duration: a duration during which the fifth device 350 and a device to which the second device 320 migrated keep a context of the second device 320.
Further, as clarified above, there may be more than one fifth device 350 are involved during the procedure that the second device 320 migrating from the last serving device (i.e., the fourth device 340) to the serving device (i.e., the first device 310) . In this event, when the second device 320 migrates from a source device to the fifth device 350, the source device may be the fourth device 340 or a further fifth device. Similarly, when the second device 320 migrates from the fifth device 350 to a target device, the target device may be the first device 310 or another fifth device.
In the following text, although some example embodiments are described for the scenario where merely one fifth device is involved, the example embodiments discussed herein also may be applied to other example embodiments where more than one fifth device 350 are involved during the procedure that the second device 320 migrates from the last serving device (i.e., the fourth device 340) to the serving device (i.e., the first device 310) . In this event, the described example embodiments may be adaptively adjusted and applied to the communications between the fifth device 350 and another fifth device and the communications between the further fifth device and the fifth device 350. Merely for brevity, the similar or some processes are omitted herein.
Further, in the following text, processes (such as, determining, transmitting/receiving, maintaining related gNB’s T380 and so on) associated with the first and second durations are described in detail as examples. It should be understood that the described example processes associated with the first and second durations may be adaptively adjusted and applied to the processes associated with the third and fourth durations. Merely for brevity, the similar or some processes are omitted herein. The correspondences between the third/fourth duration and the first/second duration are described as below.
Scenario where one fifth device is involved
In this event, as for the fifth device 350, the device from which the second device 320 migrated is the fourth device 340 and the device to which the second device 320 migrated is the first device 310. For this specific scenario, the third duration corresponds to the second duration, which is determined by the fourth device 340 and transmitted to the fifth device 350; the fourth duration corresponds to the first duration, which is determined by the fifth device 350 and transmitted to the first device 310.
Scenario where more than one fifth device is involved
In this event, as for the fifth device 350, the device from which the second device 320 migrated is the fourth device 340/afurther fifth device and the device to which the second device 320 migrated is the first device 310/another fifth device. For this specific scenario, if the device from which the second device 320 migrated is the fourth device 340, the third duration corresponds to the second duration, which is determined by the fourth device 340 and transmitted to the fifth device 350; if the device from which the second device 320 migrated is the further fifth device, the third duration corresponds to the first duration, which is determined by the further fifth device and transmitted to the fifth device 350; while the fourth duration corresponds to the first duration, which is determined by the fifth device 350 and transmitted to the first device 310/another fifth device.
As illustrated in Fig. 4, the second device 320 connects 405 with the fourth device 340 first. The third device 330 connects with the fourth device 340 via the second device 320. Then the third device 330 transitions 410 to the inactive state. Thus, the fourth device 340 is the last serving device for the third device 330, which means that the fourth device 340 should maintain/keep the context of the third device 330. Further, in some example embodiments, upon the transitioning of the third device 330, the fourth device 340 may start a timer (such as, a conventional T380) used for maintaining/keeping the context of the third device 330.
Example processes for migration from the fourth device 340 to the fifth device 350
In the following, the second device 320 migrates 415 from the fourth device 340 to a fifth device 350 (such as through an Xn handover procedure for the second device 320) . In some example embodiments, some migration history information which may be used for communication between the fourth device 340 and the fifth device 350 in the future may be exchanged during the migration procedure, for example, during the migration procedure for the second device 320.
One example of the migration history information is identity information of the second device 320 (such as, the UE XnAP ID of the second device 320) . The identity information of the second device 320 would be known to both the fourth device 340 and the fifth device 350. The identity information of the second device 320 may be determined by either the fourth device 340 or the fifth device 350 and then be transmitted to another device during the migration procedure. As one specific example, the identity information may be the Source NG-RAN node UE XnAP ID assigned by the fourth device 340 or the Target NG-RAN node UE XnAP ID assigned by the fifth device 350. The identity information of the second device 320 may be any other identity that can uniquely identify the second device in a receiver node. For example, when the fourth device 340 receive a further request related to the second device 320, the request should include the identity information of the second device 320 assigned by the fourth device 340, which can uniquely identify the second device 320 in the fourth device 340; when the fifth device 350 receive another further request related to the second device 320, the request should include the identity information of the second device 320 assigned by the fifth device 350, which can uniquely identify the second device 320 in the fifth device 350. Another example of the migration history information is identity information of the fourth device 340, for example, the Global NG-RAN Node ID of the fourth device 340. Additionally, the fourth device 340 may further indicate that the fourth device 340 is the last serving device for the third device 330.
A further example of the migration history information is information indicating a second duration (also referred to as “1 ^st gNB’s T380” ) for how long to keep context of the second device 320, for example, the identity information of the second device 320.
In some example embodiments, the second duration is determined by the fourth device 340. In one example, the fourth device 340 determines the second duration to be a default maximum value. Alternatively, in another example, the fourth device 340 determines the second duration based on at least one factor.
One example factor is remaining duration to keep context of at least one device including the third device 330, where the at least one device transitions to the inactive state via the second device 320 while the second device 320 is connecting with the fourth device 340. In one example, the fourth device 340 determines the second duration to be the maximum remaining value of T380 corresponding to the at least one device transitioning to the inactive state via the second device 320 while the second device 320 is connecting with the fourth device 340. Specifically, the fourth device 340 starts a respective T380 for each of the at least one device transitioning to the inactive state via the second device 320 while the second device 320 is connecting with the fourth device 340, and determines the second duration based on the maximum remaining value of all the started T380 (s) .
As one specific example, the T380 for the third device 330 expires at a first time point (such as, 10: 21 AM) . A further third device accessing the network via the second device 320 also transitions to the inactive state via the second device 320 while the second device 320 is connecting with the fourth device 340, and the T380 for the further third device expires at a second time point (such as, 10: 28 AM) . Then the fourth device 340 may use the second time point as the ending point of the second duration and indicate it to the fifth device 350. For example, the fourth device 340 may transmit the second time point as the 1 ^st gNB’s T380 to the fifth device 350.
Another example factor is the time required for migrating the second device 320 from the fourth device 340 to the fifth device 350.
It is to be understood that the above example factors for determining the second duration are only for the purpose of illustration without suggesting any limitations. In some other example embodiments, any suitable other factors may be applied for determining the second duration. Further, the above factors and the other factors may be applied separately or in any suitable sub-combination.
In some embodiments, the fourth device 340 discards/removes the context of the second device 320 beyond the second duration. In one example, the fourth device 340 discards/removes the context for the second device 320 upon the expiry of the 1 ^st gNB’s T380.
Similarly, in some example embodiments, the fifth device 350 performs the operations corresponding to the fourth device 340 after receiving the second duration. In one example, the fifth device 350 determines how long to keep the context of the second device 320, for example, the identity information of the second device 320 for communication over the interface (such as, an XnAP interface) between the fourth device 340 and the fifth device 350. Additionally, the fifth device 350 starts a timer based on the second duration and when the timer expiries (such as, at 10: 28: 01) , the fifth device 350 may discard/remove the context of the second device 320, for example, the identity information of the second device 320 for communication over the interface (such as, an XnAP interface) between the fourth device 340 and the fifth device 350.
A further example of the migration history information is an indication to indicate whether there is one or more terminal devices (for example, the third device 330) transition to the inactive state via the second device 320 while the second device 320 is connected with the fourth device 340.
It is to be understood that, the above illustrated examples of migration history information are only for the purpose of illustration without suggesting any limitations. In other example embodiments, the migration history information may be any suitable parameter (s) or information.
Further, the migration history information may be transmitted and represented in any suitable manner. For example, the migration history information may be transmitted in one information element (IE) as a set/list of parameter, or be transmitted separately in different IEs.
Example processes for migration from the fifth device 350 to the first device 310
In the specific example of Fig. 4, the second device 320 continues to migrate 420 from the fifth device 350 to a first device 310 (such through an Xn handover procedure for the second device 320) . Similar with the procedure discussed with regard to the migration from the fourth device 340 to the fifth device 350, some migration history information which may be used for communication between the fifth device 350 and the first device 310 in the future also may be exchanged during as discussed below, for example, during the migration procedure of the second device 320.
In some example embodiment, the migration history information transmitted by the fifth device 350 may merely comprise information about the fifth device 350.
Alternatively, in addition to the information about the fifth device 350, the migration history information further comprises information about at least one device, where the second device 320 connected with the at least one device prior to connecting with the fifth device 350. Specifically, the fifth device 350 receives migration history information from the device from which the second device 320 migrated, and transmits an updated migration history information to a device to which the second device 320 migrated by attaching the migration history information of the fifth device 350 to the received migration history information.
In the specific example of Fig. 4, when the fifth device 350 exchange the migration history information with the first device 310, the fifth device 350 may also include the migration history information received from the fourth device 340, for example, the fifth device 350 received it when the second device 230 migrates from the fourth device 340 to the fifth device 350.
One example of the migration history information is identity information of the second device 320 (such as, the UE XnAP ID of the second device 320) . The identity information of the second device 320 is known to both the fifth device 350 and the first device 310. The identity information of the second device 320 may be determined by either the fifth device 350 or the first device 310 and then be transmitted to another device during the migration procedure. For example, the identity information may be the Source NG-RAN node UE XnAP ID allocated by the fifth device 350 or the Target NG-RAN node UE XnAP ID allocated by the first device 310. The identity information of the second device 320 may be any other identity that can uniquely identify the second device in a receiver node. For example, when the fifth device 350 receive a further request related to the second device 320, the request should include the identity information of the second device 320 assigned by the fifth device 350, which can uniquely identify the second device 320 in the fifth device 350; when the first device 310 receive another further request related to the second device 320, the request should include the identity information of the second device 320 assigned by the first device 310, which can uniquely identify the second device 320 in the first device 310.
Another example of the migration history information is identity information of the fifth device 350, for example, the Global NG-RAN Node ID of the fifth device 350. For example, in some example embodiments, the fifth device 350 may transmit identify information of at least one device to the first device 310, where the second device 320 migrated from the at least one device orderly prior to connecting with the fifth device 350 and the identify information of the fifth device 350. In this way, the first device 310 may obtain about a migration history of the second device 320, such as, the identity information of the devices in a migration chain of the second device 320 (such as, identity information of the fourth device 340 and one or more fifth devices 350) . In another example, the migration history may be the mobility history or UE history information for the second device 320, which contains information about cells that the second device has been served by prior to the target cell. Further, in case that the above identity information of each of the devices is indicated following the migration order of the second device 320, the first device 310 may obtain a migration order/chain of the second device 320 accordingly.
In addition, in some example embodiments, the exchanged information is information indicating a first duration (also referred to as “2 ^nd gNB’s T380” ) for how long to keep context of the second device 320, for example, the identity information of the second device 320.
In some example embodiments, the first duration is determined by the fifth device 350. In one example, the fifth device 350 determines the first duration to be a default maximum value. Alternatively, in another example, the fifth device 350 determines the first duration based on at least one factor.
One example factor is remaining duration to keep context of at least one device, where the at least one terminal device transitions to the inactive state via the second device 320 while the second device 320 is connecting with the fifth device 350. The procedure for determining/obtaining the remaining duration is similar with that about how to determine the second duration as discussed above. For example, the fifth device 350 may start a respective T380 for each of the device (s) which is transitioned to the inactive state via the second device 320 while the second device 320 is connecting with the fifth device 350, and determines the remaining duration to be the maximum remaining value of all the started T380 (s) .
In addition to the above remaining duration, a further example of the factor is duration while the second device 320 is connecting with the fifth device 350. Alternatively, or in addition, another example factor is the time required for migrating the second device 320 from the fifth device 350 to the first device 310. Alternatively, or in addition, the other example factor is duration information indicating the second duration.
Two specific examples for determining the first duration are described below for better understanding.
In one specific example, when the second device 320 connects to the fifth device 350, at least one device (such as, two devices, which are referred to as device #1 and device #2 for ease description) accessing the network via the second device 320 transitions to the inactive state. The fifth device 350 starts respective T380 for each of the at least one device. For example, the T380 started for device #1 expires at a third time point (such as, 10:30AM) and the T380 started for device #2 expires at a fourth time point (such as, 10: 35AM) . Then, the fifth device 350 determines the fourth time point as the ending time point as the first duration. In other words, the fifth device 350 determines the first duration to be the maximum remaining value of T380 corresponding to the at least one device transitioning to the inactive state via the second device 320 while the second device 320 is connecting with the fifth device 350.
In another specific example, there is no device transitioning to the inactive state when the second device 320 connects to the fifth device 350. In this event, the fifth device may determine the first duration based on the received information about the second duration and the duration while the second device 320 is connecting with the fifth device. For example, the fifth device determines the first duration (i.e., 2 ^nd gNB’s T380) to be the remaining duration of the second duration (i.e., 1 ^st gNB’s T380) .
It is to be understood that the above example factors for determining the first duration are only for the purpose of illustration without suggesting any limitations. In some other example embodiments, any suitable other factors may be applied for determining the first duration. Further, the above factors and the other factors may be applied separately or in any suitable sub-combination.
In some embodiments, the fifth device 350 discards the context of the second device 320, for example, the identity information of the second device 320 for communication over an interface (such as, an XnAP interface) between the fourth device 340 and the fifth device 350 beyond the first duration. In one example, the fifth device 350 discards/removes the context for the second device 320 upon the expiry of the 2 ^nd gNB’s T380.
Similarly, in some example embodiments, the first device 310 performs the operations corresponding to the fifth device 350 after receiving the first duration. In one example, the first device 310 determines how long to keep the context of the second device 320, for example, the identity information of the second device 320 for communication over the interface (such as, an XnAP interface) between the fifth device 350 and the first device 310. Additionally, the first device 310 starts a timer based on the first duration and the when the timer expiries, the first device 310 may discard/remove the context of the second device 320, for example, the identity information of the second device 320 for communication over the interface (such as, an XnAP interface) between the fifth device 350 and the first device 310.
A further example of the migration history information is an indication to indicate whether there is at least one terminal device transition history to the inactive state via the second device 320 when the second device 320 is connected with the fifth device 350. In one example, when it indicates that there is at least one terminal device transition to the inactive state via the second device 320 while the second device 320 is connected with the fifth device 350, the fifth device 350 is the last serving device for the related terminal device (s) which transitioned to the inactive state via the second device 320 while the second device is connected with the fifth device 350.
As one specific example of the migration history information received by the first device 310, the migration history information comprises the following:
● identity information of the fifth device 350,
● duration information indicating a first duration during which the fifth device 350 keeps context of the second device 320, and
● identify information of the second device 320 being known to the fifth device 350, for example, an identity allocated for the second device 320 by the fifth device 350 or any other identity that can uniquely identify the second device 320 in the fifth device 350.
In another specific example of the migration history information received by the first device 310, the migration history information comprises the following:
● identity information of at least one device, wherein the second device 320 connected with the at least one device prior to connecting with the first device 350
● duration information indicating at least one duration during which the at least one device keeps context of the second device 320, and
● identify information of the second device 320 being known to the at least one device, for example, an identity allocated for the second device 320 by the at least one device or any other identity that can uniquely identify the second device 320 in the at least one device.
As discussed above, the migration history information may be transmitted and be represented in any suitable manner. As one example, the migration history information is represented in a list of parameter sets, where each parameter set comprises migration history information specific to one device. As one example, the parameter set may be in a manner of {identity information of the device, duration information indicating a duration during which the device keeps context of the second device 320, identity information of the second device 320 being known to the device} .
A further example of the migration history information received in the first device 310 may be a list of {ID of the previous connected device, ID of the second device, T380 of the previous connected device, an indication} . The ID of the previous connected device may be a Global NG-RAN Node ID, an IPv6 address, or any other ID that can uniquely identify the previous connected device. The ID of the second device 320 may be an ID allocated by the previous device (for example, a UE XnAP ID) , or a global unique ID of the second device 320, or any ID that can uniquely identify the second device 320 in the previous connected device. In the specific example of Fig. 4 (i.e., the second device 320 migrated from the fourth device 340 to the fifth device 350 then to the first device 310) , the first device 310 receives the migration history information including:
{ID of the fourth device 340, UE XnAP ID assigned for the second device 320 by the fourth device 340, second duration, an indication indicating whether one or more terminal device transition to inactive state via the second device 320 when the second device is connected with the fourth device 340}
{ID of the fifth device 350, UE XnAP ID assigned for the second device 320 by the fifth device 350, first duration, an indication indicating whether one or more terminal device transition to inactive state via the second device 320 when the second device is connected with the fifth device 350}
It is to be understood that the above specific examples of the migration history information are only for the purpose of illustration without suggesting any limitations.
Example processes for resuming a connection between the third device 330 and the network
As discussed above, the third device 330 may need to resume a connection with the network, such as, due to RNA update, receiving a paging message, detecting an uplink transmission and so on. In the specific example of Fig. 4, the second device 320 is connecting with the first device 310 and the third device 330 needs to resume the connection with the network via the second device 320.
As illustrated in Fig. 4, the third device 330 transmits 445 a request (referred to as a first request hereafter) for resuming a connection between the third device 330 and the network (such as, a RRC Resume Request) via the second device 320. The second device 320 forwards 450 the first request to the first device 310. In some example embodiments, the first request comprises identity information of the fourth device 340 (i.e., the last serving device for the third device 330) . As one example, the identity information of the fourth device 340 may be the included in the inactive radio network temporary identifier (I-RNTI) , which contains the NG-RAN node address index of the fourth device 340
After receiving the first request, the first device 310 may initiate a procedure to obtain the context of the third device 330 through a request (referred to as a second request hereafter) for retrieving a context of the third device 330 (such as, XnAP Retrieve UE Context Request) . According to example embodiments of the present disclosure, the second request may obtain the context of the third device 330 from the fourth device 340 based on the migration history information of the second device 320. Specifically, the migration path/chain of the second device 320 are consisting of a plurality of device, and at each device on the migration path/chain, the next device is determined based on the migration history information of the second device 320.
In some example embodiments, the first device 310 determines whether the fourth device 340 is addressable for the first device 310 based on the identity information received from the third device 330. In case that the fourth device 340 is un-addressable (for example, an interface between the first device 310 and the fourth device 340 is not available or the identity information of the fourth device 340 is unresolvable/unknown to the first device 310) for the first device 310, the first device 310 transmits 455 the second request to the fifth device 350 from which the second device 320 migrated, for example, based on the migration history information for the second device 320 received when the second device 320 migrated from the fifth device 350 to the first device 310. As one example, if the first device 310 cannot resolve the identity information of the fourth device 340 from an inactive radio network temporary identifier (I-RNTI) of the third device 330, the first device 310 may determine that the identity information of the fourth device 340 is unresolvable/unknown to the first device 310.
In some example embodiments, the second request comprises identity information of the second device 320 being known to both the first device 310 and fifth device 350. One example of the identity information is the identity information of the second device 320 allocated/determined by the first device 310 and the fifth device 350 when the second device 320 migrated from the fifth device 350 to the first device 310 as discussed above. In one example embodiment, the identity information of the second device 320 may be the UE XnAP ID assigned for the second device 320 by the fifth device 350. It is to be understood that the identity information of the second device 320 also may be any other suitable identity information that may be used for identifying the second device 320 at the fifth device 350.
In some example embodiments, if the fifth device 350 transmits the information indicating the first duration to the first device 310, the first device 310 transmits the second request to the fifth device 350 within the first duration. Additionally, in some example embodiments, if the first device 310 determines that the timer started for 2 ^nd gNB’s T380 is not expired, the first device 310 transmits the second request to the fifth device 350. In this way, it is guaranteed that the second request may be correctly handled by the fifth device 350.
After receiving the second request, the fifth device 350 forwards 460 an updated second request to a device from which the second device 320 migrated (may be the fourth device 340 or the further fifth device) .
In some example embodiments, the received second request comprises identity information of the second device 320 being known to both the fifth device 350 and the first device 310, and the updated second request comprises identity information of the second device 320 being known to both the fifth device 350 and the device from which the second device 320 migrated. One example of the identity information is the identity information of the second device 320 allocated/determined during the migration of the second device 320. In one example embodiment, the identity information of the second device 320 may be the UE XnAP ID assigned for the second device 320 by the previous connected device (for example, the fourth device 340) . It is to be understood that the identity information of the second device 320 also may be any other suitable identity information that may be used for identifying the second device 320 at the previous connected device.
In one example, the fifth device 350 maintains a mapping of different identity information of the second device 320 used for communicating with different devices. When the fifth device 350 receives the second request, the fifth device 350 replaces the identity information of the second device 320 comprised in the second request to be the identity information being known to both the fifth device 350 and the device from which the second device 320 migrated.
In some example embodiments, the fifth device 350 forwards the updated second request within a third duration during which both the fifth device 350 and the device from which the second device 320 migrated keep the context of the second device 320.
In the specific example of Fig. 4, if the fifth device 350 receives the information indicating the second duration from the fourth device 340, the fifth device 350 forwards the updated second request to the fourth device 340 within the second duration. Additionally, in some example embodiments, if the fifth device 350 determined that the timer started for 1 ^st gNB’s T380 is not expired, the fifth device 350 transmits the updated second request to the fourth device 340.
As one specific example, the fifth device 350 receives the second request for a third device and the third device 330 transitioned to inactive via the second device 320 while the second device 320 was connected to the fourth device. Then, the fifth device 350 does not have the context for the third device 330. The fifth device 350 knows that the second device 320 migrated from the fourth device 340. Then, if the timer (i.e., 1 ^st gNB’s T380) used for keeping the context of the second device 320 (for example, the identity information of the second device 320) is not expired, the fifth device 350 replaces the identity information of the second device 320 and forwards the updated second request to the fourth device 340.
Additionally, in some embodiments, for each fifth device on the migration path/chain, if there is at least one device which is transitioned to inactive state via the second device 320 while the second device 320 is connecting with the fifth device on the migration path/chain, the fifth device will store the context of the at least one device. In some example embodiments, if no UE context is stored at the fifth device on the migration path/chain, the fifth device may relay the second request to the related device by simply updating the identity information of the second device 320, without reading/resolving the whole content of the second request. Else, the device needs to read/resolve the content of the second request. This example embodiment especially benefits the scenario where there are multiple UE contexts that needed to be retrieved.
According to the above procedure, the second request may be forward along the migration path to the last serving device, even if the serving device does not have an interface with the last serving device.
As the fourth device 340 is the device responsible for maintaining the context of the third device 330, the fourth device 340 transmits 465 a response comprising the context of the third device 330 to the fifth device 350. In some example embodiments, the response comprises identity information of the second device 320 being known to both the fifth device 350 and the fourth device 340.
Upon the reception of the response from the fourth device 340, the fifth device 350 know that the response is to the second request, the fifth device 350 forwards 470 the response to the first device 310. In some example embodiments, the response comprises updated identity information of the second device 320 being known to both the fifth device 350 and the first device 310.
After obtaining the context of the third device 330, the first device 310 may reply to the first request. As illustrated in Fig. 4, the first device 310 transmits 475 a resume response (such as, RRC resume to the second device 320 and the second device 320 forward 480 the resume response to the third device 330. Therefore, the third device 330 may transition from the inactive state to the connected state.
In this way, the third device 330 can be resumed in the new serving 310 device which does not have an Xn interface with the last serving device 340.
Example processes for paging the third device 330
As discussed above, the resuming procedure also may be trigged by a paging procedure. In the following, the example processes for paging the third device 330 will be discussed in detail.
In conventional solution, a paging request (such as, XnAP RAN PAGING message) may include the RAN Paging Area which can be a list of cell IDs or RAN area IDs. However, the above conventional solution is not feasible for the mobile IAB network because the last serving device cannot know IAB’s cell ID when the IAB occurs more than one migration. According to example embodiments of the present disclosure, the paging request may be well handled.
As illustrated in Fig. 4, the fourth device 340 detects 425 an event for triggering a paging procedure for the third device 330. The fourth device 340 transmits 430 a request (referred to as a third request) for paging the third device 330 (such as, XnAP RAN PAGING message) to the fifth device 350 to which the second device 320 migrated. In some example embodiments, the third request comprises identity information of the second device 320 being known to both of the fourth device 340 and the fifth device 350.
Then, the fifth device 350 forward 435 an updated third request to the device to which the second device 320 migrated (such as, the first device 310 and another fifth device) . In some example embodiments, the updated third request comprises identity information of the second device 320 being known to both the fifth device 350 and the device to which the second device 320 migrated. In some example embodiments, the fifth device 350 replaces the identity information of the second device 320 and forwards the updated third request to the device which the second device 320 migrated.
Additionally, in some embodiments, the fifth device 350 forwards the updated third request within the fourth duration during which both the fifth device 350 and the device to which the second device 320 migrated keep the context of the second device 320.
In the specific example of Fig. 4, the fifth device 350 forward 435 the updated third request to the first device 310. After receiving the third request, the first device 310 may page 440 the third device 330.
As one specific example, when the fourth device 340 detects the event for triggering a paging procedure for the third device 330, the fourth device 340 knows that the second device 320 migrated to the fifth device 350. Then, the fourth device 340 transmits the third request to the fifth device 350, where the third request comprises the identity information of the second device 320 being known to the fourth device 340 and the fifth device 350. As for the fifth device 350, the fifth device 350 knows that the second device 320 migrated to the first device 310, and then forwards the third request to the first device 310 by replacing the identity information of the second device 320.
In this way, the paging procedure may be well handled in the IAB network.
Example processes for shortcut
For some scenarios, e.g., a long-distance high speed train, the migration chain may be quite long. In this event, forwarding messages (paging request or of retrieve context request/response) may create significant signalling load and signalling delay. On the other hand, the network operator may configure some of the donors along the track with direct interfaces even if they are not adjacent. As discusses above, some migration history information (such as, the identity information of the devices on the migration chain, duration information indicating the corresponding duration during which the devices keep the context of the second device 320, the identity information of the second device 320 being known to the devices and other migration history information) may be exchanged during the migration of the second device 320. With such information, when transmitting the following messages (such as, the second request, the response for the second request and the third request) , the following messages may not necessarily to be transmitted one by one strictly follow the migration chain/path. In other words, the first device 310 may bypass part of the devices on the migration chain/path to enable a shortcut transmission. For example, the first device 310 may determine an intermediate device (referred to as a shortcut device hereafter) based on the migration history information.
In some example embodiments, the migration history information may comprise the information about the last serving device (i.e., the fourth device 340) , for example, the identity information of the fourth device 340, the second duration and the identity information of the second device 320 being known to the fourth device 340. In this event, the first device 310 determines that if there is an interface with the fourth device 340. If so, the first device 310 determines the fourth device 340 as the shortcut device.
Alternatively, as discussed above, in some example embodiments, the first device 310 may receive migration history information from the fifth device 350, and the migration history information may comprise at least one of the following:
● identity information of at least one device, wherein the second device 320 connected with the at least one device prior to connecting with the first device 310,
● duration information indicating at least one duration during which the at least one device keeps context of the second device 320, and
● identify information of the second device 320 being known to the at least one device, for example, an identity allocated for the second device 320 by the at least one device or any other identity that can uniquely identify the second device 320 in the at least one device.
Example processes for determining the shortcut device based on the above migration history information are discussed below. In some example embodiments, the first device 310 determines whether there is an interface with a device based on the identity information of at least one device. If there is such device (s) and while the device (s) is not the fifth device from which the second device 320 migrated to the first device 310, it means that there is a shortcut device. That is, the shortcut device is the fourth device 340, or a fifth device from which the second device 320 migrated to a further fifth device.
Additional, in some example embodiments, the first device 310 may further determine whether the shortcut device still keeps the context of the second device 320 based on the duration information comprised in the migration history information. If the first device 310 determines that the shortcut device still keeps the context of the second device 320, the first device may inform the shortcut device by transmitting a message.
In some example embodiments, the message indicates to the shortcut device that the second device 320 is connecting to the first device 310. Further, the message comprises identity information of the second device 320 being known to the shortcut device which may be obtained from the migration history information, such that the shortcut device may identify the second device 320. Further, the message also may comprise identity information of the second device 320 being known to the first device 310, such that the short device may use the identity information of the second device 320 to communicate with the first device 310 in subsequent communication.
Some example processes about the above proposed solution will be discussed with reference to Figs. 5 and 6, where Fig. 5 illustrates a signaling chart illustrating a method 500 of communications in IAB network with shortcut according to some example embodiments of the present disclosure and Fig. 6 illustrates block diagram 600 of examples for shortcut transmission.
Only for the purpose of illustrations, the signaling chart 500 and block diagram 600 are described to be implemented between the first device 310, the second device 320, the third device 330, the fourth device 340, and the fifth devices 350-1 to 350-3 as shown in Fig. 3.
Further, in the specific example of Figs. 5 and 6, the second device 320 connects to the fourth device 340 first, and the migrates to the fifth device 350-1, the fifth device 350-2, the fifth device 350-3 and the first device 310 orderly.
Specific Example 1
In some embodiment, the information of the fourth device 340 (i.e., the last serving device) is transmitted during the transmission of the second device 320. In the Specific example of the Fig. 6, when the second device 320 migrates from the fourth device 340 to the fifth device 350-1 (such as, during the HO preparation for the second device 320) , the fourth device 340 transmits the identity information of the fourth device 340 (such as, a Global gNB ID of the fourth device 340) to the fifth device 350-1 and indicates that the fourth device 340 is the last serving device for one or more terminal devices transitioned to inactive state via the second device 320 when the second device 320 is connected with the fourth device 340. Similarly, during the following migrations, the fifth device 350-1 transmits the identity information of the fourth device 340 to the fifth device 350-2, the fifth device 350-2 transmits the identity information of the fourth device 340 to the fifth device 350-3 and the fifth device 350-3 transmits the identity information of the fourth device 340 to the first device 310, for example, as part of the migration history information for the second device 320. The migration history information also includes the identity information for other devices (for example, the fifth device 350-1, the fifth device 350-2 and the fifth device 350-3) of the migration chain.
In some example embodiments, in Fig. 5, the first device 310 determines 505 whether the first device 310 has an interface with the fourth device 340 based on the identity information of the fourth device 340. If the first device 310 has an interface with the fourth device 340, it means that there is a shortcut (the shortcut 610-1 as illustrated in Fig. 6) for transmitting the following messages (such as, the second request and the third request) .
In some example embodiments, if the first device 310 has an interface with the fourth device 340, the first device 310 transmits 510-1 a message to the fourth device 340. In some example embodiments, the message indicates to the fourth device 340 that the second device 320 is connecting with the first device 310. Alternatively, or in addition, in some example embodiments, the message indicates identity information of the second device 320 being known to the fourth device 340 (which may be obtained from the received migration history information) . Upon receiving the message, the fourth device 340 may update the context for the second device 320, for example, save the first device 310 as the serving device rather than the fifth device 350-1.
In this way, the fourth device 340 may be informed that there is an interface between the fourth device 340 and the first device 310, and if the fourth device 340 needs to transmit messages (such as, the third request) to the first device 310 in the following, it may transmit the messages to the first device 310 directly. Specifically, in some embodiments, the fourth device 340 transmit 525-1 the third request to the first device 310 in case that it has received the message (i.e., the fourth device is informed that the second device 320 is connecting with the first device 310, which implies that there is an interface between the fourth device 340 and the first device 310) . Additionally, in some example embodiments, the third request comprises identity information of the second device 320 being known to both the first device 310 and fourth device 340. For example, the identity information of the second device 320 may be obtained by the fourth device 340 from the message transmitted by the first device 310 when the first device 310 informing the fourth device 340 that the second device 320 is connecting with the first device 310.
Additionally, after transmitting the message to inform the fourth device 340 that the second device 320 is connecting with the first device 310, if the first device 310 needs to transmit messages (such as, the second request) to the fourth device 340 in the following, it may transmit the messages to the fourth device 340 directly. Specifically, in some embodiments, the first device 310 transmits 535-1 the second request to the fourth device 340 in case that the first device 310 has transmitted the message to inform the fourth device 340. Additionally, in some example embodiments, the second request comprises identity information of the second device 320 being known to both the first device 310 and fourth device 340.
In some example embodiments, the fifth device 350 comprises an indication in the migration history information, where the indication indicates that there is at least one terminal device transition to inactive state via the second device 320 when the second device connect with the fifth device.
Specific Example 2
In some example embodiments, the migration history information comprises information for all the relevant devices on the migration chain (which is consisting of the fourth device 340, the first device 310 and one or more fifth device 350) . For example, for each device on the migration chain, the device receives migration history information from a previous device, attach migration history information about itself to the received migration history information to generated an updated migration history information, and forward the updated migration history information to the next device.
As one simplified example, the migrating second device 320 is following a less linear movement than a train on a track and it is possible that the new device in the migration chain has an interface to any of the earlier donors. In some example embodiments, identity information of the device on the migration chain is informed to the new device (such as, a donor) when the second device 320 migrates. Such identity information may comprise an ordered list of part or all of the IDs of the last serving device (i.e., the fourth device 340) and the previous connected devices along the migration path. As one specific example, the fifth device 350-3 transmits the identity information of the fourth device 340, the identity information of the fifth device 350-1, the identity information of the fifth device 350-2 and the identity information of itself to the first device 310.
As one specific example of the Fig. 6, when the second device 320 migrates from the fourth device 340 to the fifth device 350-1, the fourth device 340 transmits the migration history information including the identity information of the fourth device 340, the identity information of the second device 320 being known to the fourth device 340, the duration during which the fourth device keeps the context of the second device 320 and an optionally indication to the fifth device 350-1.
During the following migrations, the fifth device 350-1 transmits an updated migration history information to the fifth device 350-2, including: the migration history information received from the fourth device 340, the identity information of the fifth device 350-1, the identity information of the second device 320 being known to the fifth device 350-1, the duration during which the fifth device 350-1 keeps the context of the second device 320 and an optionally indication.
Similarly, the fifth device 350-2 transmits an updated migration history information to the fifth device 350-3, including: the migration history information received from the fifth device 350-1, the identity information of the fifth device 350-2, the identity information of the second device 320 being known to the fifth device 350-2, the duration during which the fifth device 350-2 keeps the context of the second device 320 and an optionally indication.
Finally, the fifth device 350-3 transmits an updated migration history information to the first device 310, including: the migration history information received form the fifth device 350-2, and the identity information of the fifth device 350-3, the identity information of the second device 320 being known to the fifth device 350-3, the duration during which the fifth device 350-3 keeps the context of the second device 320 and an optionally indication.
With the received migration history information, each newly involved/added device (such as, a donor) in the migration chain can check if the previous hop or hops in the chain can be shortcut, i.e., be removed from the context chain and keep the chain along a high speed track to the minimum length.
In some example embodiments, the first device 310 may determine whether there is a device rather than the last fifth device 350-3 in the migration chain having an interface with the first device 310 based on the migration history information.
In the specific example of Fig. 6, the first device 310 may obtain the identity information of the fourth device 340 and fifth devices 350-1 to 350-3. Further, the first device 310 knows that the second device 320 is migrated from the fifth device 350-3, and thus may know that the fifth device 350-3 is the last fifth device. Then, the first device 310 may determine whether there is interface between the first device 310 and the fourth device 340/the fifth device 350-1/fifth device 350-2. If so, it means that there is a short cut for the following transmission.
In the specific example of Fig. 6, the fifth device 350-1 has an interface with the first device 310, it means that there is a shortcut (the shortcut 610-2 as illustrated in Fig. 6) for transmitting the following messages (such as, the second request and the third request) .
Further, as discussed above, in case that the above identity information of each the devices is indicated following the migration order of the second device 320, the first device 310 may obtain a migration order/chain of the second device 320 accordingly. In this event, the first device 310 determines a fifth device 350-1 which is the first one having an interface with the first device 310 and in the migration chain.
In some embodiments, the first device 310 determines the first one from the at least one fifth device 350 based on migration history information of the second device 320, wherein the migration history information at least indicates an order of the at least one fifth device 350 during migration of the second device 320. Therefore, if there is more than one fifth device has an interface with first device 310, the first device 310 may determine which is the first one.
In the specific example of Fig. 6, assuming that both the fifth devices 350-1 and 350-2 have interface with the first device 310, and the first device 310 may determine that the fifth device 350-1 is the first one that has an interface with the first device 310 and in the migration chain. Thus, the shortcut 610-2 as illustrated in Fig. 6 is determined to be used for transmitting the following messages (such as, the second request and the third request) .
In some example embodiments, if the first device 310 determines that there is a shortcut between the first device 310 and a fifth device 350, the first device 310 transmits 510-2 a message to the determined shortcut device (such as, the fifth device 350-1 as illustrated in Fig. 5) . In some example embodiments, the message indicates to the shortcut device that the second device 320 is connecting with the first device 310. Alternatively, or in addition, in some example embodiments, the message comprises identity information of the second device 320 being known to the shortcut device (i.e., the fifth device 350-1 as illustrated in Fig. 5) , such that the shortcut device may identify the second device 320 in subsequent communication with the first device 310. Further, the message also comprises the identity information of the second device 320 being known to the first device 310, such that the shortcut device may use it to identify the second device 310 when communicating with first device 310. Upon receiving the message, the shortcut device may update the context for the second device 320, for example, save the first device 310 as the serving device rather than the fifth device 350-2.
In some embodiments, if the fifth device 350-1 is informed by the first device 310 that the second device 320 is connecting with the first device 310 (i.e., receiving the message from the first device 310) , the fifth device 350-1 forwards an updated third request to the first device 310 after receiving a third request. Additionally, in some example embodiments, the updated third request comprises identity information of the second device 320 being known to both the fifth device 350-1 and first device 310. As illustrated in Fig. 5, the fifth device 350-1 receives 525-2 a third request from the fourth device 340, and forwards 530-2 the updated third request to the first device 310.
Additionally, after transmitting the message to the shortcut device, if the first device 310 needs to transmit messages (such as, the second request) , it may transmit the messages to the determined fifth device 350. As illustrated in Fig. 5, the first device 310 transmits 535-2 the second request to the fifth device 350-1, then the fifth device 350-1 forwards 540-2 to the fourth device 340.
In this way, the serving device may determine whether there is a shortcut based on the migration history information, which enables the following transmission may be transmitted more quickly.
Example processes for centralized-based context maintaining
According to example embodiments of the present disclosure, there is proposed a solution for context maintaining in the IAB network. Reference is made to Fig. 7, which illustrates a signaling chart 700 illustrating a method for centralized-based context maintaining according to some example embodiments of the present disclosure. Only for the purpose of illustrations, the signaling chart 700 is described to be implemented between the first device 310, the second device 320, the third device 330, the fourth device 340, the sixth device 360 as shown in Fig. 3.
As illustrated in Fig. 7, the second device 320 connects 710 with the fourth device 340 first. The third device 330 connects with the fourth device 340 via the second device 320. Then the third device 330 transitions 720 to the inactive state. Upon the state transition (from the connected state to the inactive state) , the fourth device 340 transmits 730 the context of the third device 330 to the sixth device 360. In some example embodiments, the context of the third device 330 associates with an identity, for example, I-RNTI consisting of identity of the third device 330, and the identity of the second device 320. The sixth device 360 stores 740 the context of the third device 330, for example, an I-RNTI of the third device 330, and an ID of the second device 320, etc. In the following, the second device 320 connects 750 with the first device 310 (such as, via at least one migration procedure) . When the second device 320 is connecting with the first device 310, the first device 310 needs to retrieve the context of the third device 330 (such as, due to expiry of the T380, or resuming connection between the third device 330 and the network) , and the first device 310 transmits 760 a first request for retrieving the context of the third device 330 to the sixth device 360. The sixth device 360 transmits 770 a response comprising the context of the third device 330 to the first device 310.
In this way, the related context can be retrieved by the serving device from a central device (such as, RAN DSF) directly with a UE identity, for example, I-RNTI.
Various examples and embodiments described herein provide a solution that can be applied in the current RAN architecture with point-to-point (P2P) interfaces as well as in the service based-RAN (SB-RAN) architecture with service-based interface (SBI) .
In a service-based (SB) architecture, a consumer can inquire a network repository function (NRF) in order to discover an appropriate service producer entity. In order to discover and select the appropriate service entities, multiple filtering criteria may be applied by the NRF. The SBI can be based on the (Secure) Hypertext Transfer Protocol (“HTTP (S) ” ) . A Network Function (NF) service can be one type of capability exposed by an NF (NF service producer entity) to another authorized NF (NF service consumer entity) through an SBI. One NF may expose one or more NF services. NF services may communicate directly between NF service consumer entities and NF service producer entities, or indirectly via a Service Communication Proxy (SCP) . For example, for 5G, 5G core network (5GC) is defined as a SB architecture (SBA) [3GPP TS 23.501] , and the network management is also employing SBA principles, referred to as the SB management architecture (SBMA) [3GPP TS 28.533] .
However, the Access Network (AN) , e.g., RAN, and the associated interfaces, e.g., within the AN, among ANs and between the AN and CN are defined as legacy P2P interfaces in 5G.
In SB-RAN, herein, an entity can be, e.g., a logical entity, an access node, a base station, a part of an access node or base station, a protocol stack, a part of a protocol stack, a network function, a part of a network function, or the like.
It is to be noted that, in the present disclosure, a SB configuration, architecture or framework can encompass a microservice configuration, architecture or framework. That is, a SB (R) AN according to at least one exemplifying embodiment may be based on or comprise a microservice approach such that one or more network functions or one or more services within one or more network functions or one or more functionalities/mechanisms/processes of services of one or more network functions represent or comprise a set/collection of interacting microservices. Accordingly, in a SB (R)AN according to at least one exemplifying embodiment, a service may be produced or provided by any one of a NF, a microservice, a communication control entity or a cell.
Microservices can be understood as more modular services (as compared with services produced/provided by NFs) that come together to provide a meaningful service/application. In this scope, one can deploy and scale the small modules flexibly (e.g. within a NF or between various NFs) . For example, a NF provides a service, and a microservice can represent small modules that make up the service. When a service is clogged at a specific module, then one can scale the individual module (s) in microservice scope instead of the whole service as it would happen in network function scope. In microservice scope, energy saving according to at least one exemplifying embodiment would work the other way around, namely there is no need for a specific module to operate the service anymore, so the individual microservice would be shut down or deactivated.
Although some of the examples described herein depict and describe the RAN-DSF as a single NF, the AN-DSF may be implemented as part of a data storage architecture that may include one or more elements (e.g., functions or nodes) . For example, an RAN data storage architecture may include a RAN-DSF, a data repository, and/or a data management entity. Moreover, different deployment options may be implemented, where the elements may be collocated. Furthermore, the elements of the data storage architecture may perform storage and retrieval of data, such as UE context information.
In some example embodiments, there is provided a DSF having an SBI. In some example embodiments, the DSF is a (R) AN element (function, or node) , in which case it is referred to as a (R) AN-DSF. The (R) AN DSF may be used to retrieve (e.g., fetch) , store, and update a notification publish space. These operations may be performed by any authorized NF, such as a source gNB base station, a target gNB base station, open RAN (O-RAN) near-real-time RAN Intelligent Controller (Near-RT RIC) , and/or other network functions or entities in the (R) AN and/or core. The DSF may be accessed by an authorized central entity to create a notification publish space. Moreover, the notification publish space at the DSF may be accessed for updating in case of an event occurrence requiring an update on notification publish space or for retrieving in case of an event occurrence requiring the fetching of notification publish space. The DSF may provide notification publish space storage, update, fetch and any other operation that may provide efficient handling of monitoring and notifying the failure of a network entity in the network.
Fig. 8 shows a flowchart of an example method 800 implemented at a first device 310 in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 800 will be described from the perspective of the first device 310 with respect to Fig. 3.
At block 810, the first device 310 receives a first request for resuming a connection between the third device 330 and a network from a third device 330 via a second device 320. The first request comprises identity information of a fourth device 340 being a last serving device in the network for the third device 330. The third device 330 is in an inactive state in the network and accesses the network via the second device 320. The second device 320 connects with the first device 310.
At block 820, the first device 310 transmits a second request for retrieving a context of the third device 330 to: a fifth device 350 from which the second device 320 migrated if an interface between the first device 310 and the fourth device 340 is not available, or the identity information of the fourth device 340 is unknown to the first device 310, or a shortcut device of at least one device if the shortcut device is informed by the first device 310 that the second device 320 is connecting with the first device 310, wherein the second device 320 connected with the at least one device prior to connecting with the fifth device 350 from which the second device 320 migrated.
In some example embodiments, if the second request is transmitted to the fifth device 350 from which the second device 320 migrated, the second request comprises identity information of the second device 320 being known to both the first device 310 and the fifth device 350 from which the second device 320 migrated.
In some example embodiments, if the second request is transmitted to the shortcut device, the second request comprises identity information of the second device 320 being known to both the first and shortcut devices.
In some example embodiments, the first device 310 receives a third request for paging for the third device 330 from: the fifth device 350 from which the second device 320 migrated, or the shortcut device if the shortcut device is informed by the first device 310 that the second device 320 is connecting with the first device 310.
In some example embodiments, if the third request is received from the fifth device 350 from which the second device 320 migrated, the third request comprises identity information of the second device 320 being known to both the first device 310 and fifth device 350 from which the second device 320 migrated.
In some example embodiments, if the third request is received from the shortcut device, the third request comprises identity information of the second device 320 being known to both the first and shortcut devices.
In some example embodiments, the first device 310 receives migration history information from the fifth device 350 when the second device 320 migrated from the fifth device 350 to the first device 310. The migration history information comprises at least one of the following: identity information of the fifth device 350, duration information indicating a first duration during which the fifth device 350 keeps context of the second device 320, and identify information of the second device 320 being known to the fifth device 350.
In some example embodiments, the first device 310 transmits the second request to the fifth device 350 within the first duration.
In some example embodiments, the first device 310 receives migration history information from the fifth device 350 when the second device 320 migrated from the fifth device 350 to the first device 310. The migration history information comprises at least one of the following: identity information of at least one device, wherein the second device 320 connected with the at least one device prior to connecting with the first device 310, duration information indicating at least one duration during which the at least one device keeps context of the second device 320, and identify information of the second device 320 being known to the at least one device.
In some example embodiments, the first device 310 determines the shortcut device based on the migration history information. The shortcut device is the fourth device 340 if the interface between the first device 310 and the fourth device 340 is available, or a further fifth device 350 if an interface between the further fifth device 350 and the first device 310 is available, wherein the further fifth device 350 is one of the at least one device.
In some example embodiments, the first device 310 transmits to the shortcut device a message indicating at least one of the following: the second device 320 being connecting to the first device 310, identity information of the second device 320 being known to the shortcut device, and identity information of the second device 320 being known to the first device 310.
In some example embodiments, the first device 310 receives a response to the second request comprising the context of the third device 330 from the fifth device 350 from which the second device 320 migrated or the shortcut device.
In some example embodiments, if the response is received from the fifth device 350 from which the second device 320 migrated, the response comprises identity information of the second device 320 being known to both the first device 310 and fifth device 350 from which the second device 320 migrated.
In some example embodiments, if the response is received from the shortcut device, the response comprises identity information of the second device 320 being known to both the first and shortcut devices.
In some example embodiments, the first device 310, the fourth device 340 and the fifth device 350 are donor devices, the second device 320 is an integrated access and backhaul device and the third device 330 is a terminal device.
In some example embodiments, a first apparatus capable of performing any of the method 800 (for example, the first device 310) may comprise means for performing the respective operations 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. The first apparatus may be implemented as or included in the first device 310.
In some example embodiments, the first apparatus comprises: means for receiving, from a third apparatus via a second apparatus, a first request for resuming a connection between the third apparatus and a network, the first request comprising identity information of a fourth apparatus being a last serving apparatus in the network for the third apparatus, wherein the third apparatus is in an inactive state in the network and accesses the network via the second apparatus and wherein the second apparatus connects with the first apparatus; and means for transmitting a second request for retrieving a context of the third apparatus to: a fifth apparatus from which the second apparatus migrated if an interface between the first apparatus and the fourth apparatus is not available, or the identity information of the fourth apparatus is unknown to the first apparatus, or a shortcut apparatus of at least one apparatus if the shortcut apparatus is informed by the first apparatus that the second apparatus is connecting with the first apparatus, wherein the second apparatus connected with the at least one apparatus prior to connecting with the fifth apparatus from which the second apparatus migrated.
In some example embodiments, if the second request is transmitted to the fifth apparatus from which the second apparatus migrated, the second request comprises identity information of the second apparatus being known to both the first apparatus and the fifth apparatus from which the second apparatus migrated.
In some example embodiments, if the second request is transmitted to the shortcut apparatus, the second request comprises identity information of the second apparatus being known to both the first and shortcut apparatuses.
In some example embodiments, the first apparatus further comprises: means for receiving a third request for paging for the third apparatus from the fifth apparatus from which the second apparatus migrated, or the shortcut apparatus if the shortcut apparatus is informed by the first apparatus that the second apparatus is connecting with the first apparatus.
In some example embodiments, if the third request is received from the fifth apparatus from which the second apparatus migrated, the third request comprises identity information of the second apparatus being known to both the first apparatus and fifth apparatus from which the second apparatus migrated.
In some example embodiments, if the third request is received from the shortcut apparatus, the third request comprises identity information of the second apparatus being known to both the first and shortcut apparatuses.
In some example embodiments, the first apparatus further comprises: means for receiving migration history information from the fifth apparatus when the second apparatus migrated from the fifth apparatus to the first apparatus. The migration history information comprising at least one of the following: identity information of the fifth apparatus, duration information indicating a first duration during which the fifth apparatus keeps context of the second apparatus, and identify information of the second apparatus being known to the fifth apparatus.
In some example embodiments, the first apparatus further comprises: means for transmitting the second request to the fifth apparatus within the first duration.
In some example embodiments, the first apparatus further comprises: means for receiving migration history information when the second apparatus migrated from the fifth apparatus to the first apparatus from the fifth apparatus. The migration history information comprising at least one of the following: identity information of at least one apparatus, wherein the second apparatus connected with the at least one apparatus prior to connecting with the first apparatus, duration information indicating at least one duration during which the at least one apparatus keeps context of the second apparatus, and identify information of the second apparatus being known to the at least one apparatus.
In some example embodiments, the first apparatus further comprises: means for determining the shortcut apparatus based on the migration history information. The shortcut apparatus is one of the following: the fourth apparatus if the interface between the first apparatus and the fourth apparatus is available, or a further fifth apparatus if an interface between the further fifth apparatus and the first apparatus is available, wherein the further fifth apparatus is one of the at least one apparatus.
In some example embodiments, the first apparatus further comprises: means for transmitting a message to the shortcut apparatus. The message indicates at least one of the following: the second apparatus being connecting to the first apparatus, identity information of the second apparatus being known to the shortcut apparatus, and identity information of the second apparatus being known to the first apparatus.
In some example embodiments, the first apparatus further comprises: means for receiving a response to the second request comprising the context of the third apparatus from the fifth apparatus from which the second apparatus migrated or the shortcut apparatus.
In some example embodiments, if the response is received from the fifth apparatus from which the second apparatus migrated, the response comprises identity information of the second apparatus being known to both the first apparatus and fifth apparatus from which the second apparatus migrated.
In some example embodiments, if the response is received from the shortcut apparatus, the response comprises identity information of the second apparatus being known to both the first and shortcut apparatuses.
In some example embodiments, the first, fourth and fifth apparatuses are donor apparatuses, the second apparatus is an integrated access and backhaul apparatus and the third apparatus is a terminal apparatus.
Fig. 9 shows a flowchart of an example method 900 implemented at a fourth device 340 in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 900 will be described from the perspective of the fourth device 340 with respect to Fig. 3.
At block 910, the fourth device 340 transmits migration history information to a fifth device 350 when the second device 320 migrates from the fourth device 340 to the fifth device 350.
At block 920, the fourth device 340 receives a second request for retrieving a context of a third device 330 being in an inactive state in a network and accessing the network via the second device 320 from a first device 310 if the fourth device 340 is informed that the second device 320 is connecting with the first device 310, or the fifth device 350.
In some example embodiments, the fourth device 340 detects an event for triggering a paging procedure for the third device 330 and transmits a third request for paging the third device 330 to: the fifth device 350 within the second duration, or the first device 310 if the fourth device 340 is informed by the first device 310 that the second device 320 is connecting with the first device 310.
In some example embodiments, if the third request is transmitted to the fifth device 350, the third request comprises identity information of the second device 320 being known to both the fourth device 340 and the fifth device 350.
In some example embodiments, if the third request is transmitted to the first device 310, the third request comprises identity information of the second device 320 being known to both of the first device 310 and the fourth device 340.
In some example embodiments, the migration history information comprises at least one of the following: information indicating a second duration during which the fourth device 340 keeps context of the second device 320, identity information of the fourth device 340, and identify information of the second device 320 being known to the fourth device 340.
In some example embodiments, the fourth device 340 receives a message from the first device 310. The message indicates at least one of the following: the second device 320 being connecting with the first device 310, identity information of the second device 320 being known to the fourth device 340, and identity information of the second device 320 being known to the first device 310.
In some example embodiments, the fourth device 340 determines the second duration based on at least one of the following: remaining duration to keep context of at least one device including the third device 330, wherein the at least one device is transitioned to an inactive state in the network via the second device 320 while the second device 320 is connecting with the fourth device 340, and time required for migrating the second device 320 from the fourth device 340 to the fifth device 350.
In some example embodiments, the fourth device 340 discards the context of the second device 320 beyond the second duration.
In some example embodiments, the first device 310, the fourth device 340 and the fifth device 350 are donor devices are donor devices, the second device 320 is an integrated access and backhaul device and the third device 330 is a terminal device.
In some example embodiments, a fourth apparatus capable of performing any of the method 900 (for example, the fourth device 340) may comprise means for performing the respective operations 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. The fourth apparatus may be implemented as or included in the fourth device 340.
In some example embodiments, the fourth apparatus comprises: means for transmitting migration history information to a fifth apparatus when the second apparatus migrates from the fourth apparatus to the fifth apparatus; and means for receiving a second request for retrieving a context of a third apparatus being in an inactive state in a network and accessing the network via the second apparatus from: a first apparatus serving the third apparatus if the fourth apparatus is informed that the second apparatus is connecting with the first apparatus, or the fifth apparatus.
In some example embodiments, if the third request is transmitted to the fifth apparatus, the third request comprises identity information of the second apparatus being known to both the fourth apparatus and the fifth apparatus.
In some example embodiments, if the third request is transmitted to the first apparatus, the third request comprises identity information of the second apparatus being known to both of the first apparatus and the fourth apparatus.
In some example embodiments, the migration history information comprises at least one of the following: information indicating a second duration during which the fourth apparatus keeps context of the second apparatus, identity information of the fourth apparatus, and identify information of the second apparatus being known to the fourth apparatus.
In some example embodiments, the fourth apparatus further comprises: means for receiving a message from the first apparatus. The message indicates at least one of the following: the second apparatus being connecting with the first apparatus, identity information of the second apparatus being known to the fourth apparatus, and identity information of the second apparatus being known to the first apparatus.
In some example embodiments, the fourth apparatus further comprises: means for determining the second duration based on at least one of the following: remaining duration to keep context of at least one apparatus including the third apparatus, wherein the at least one apparatus is transitioned to an inactive state in the network via the second apparatus while the second apparatus is connecting with the fourth apparatus; and time required for migrating the second apparatus from the fourth apparatus to the fifth apparatus.
In some example embodiments, the fourth apparatus further comprises: means for discarding the context of the second apparatus beyond the second duration.
In some example embodiments, the first, fourth and fifth apparatuses are donor apparatuses, the second apparatus is an integrated access and backhaul apparatus and the third apparatus is a terminal apparatus.
Fig. 10 shows a flowchart of an example method 1000 implemented at a fifth device 350 in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 1000 will be described from the perspective of the fifth device 350 with respect to Fig. 3.
At block 1010, the fifth device 350 receives a second request for retrieving a context of a third device 330 accessing a network via a second device 320 from a device of at least one device. The second device 320 migrated to the at least one device after the second device 320 migrated to the fifth device 350
At block 1020, the fifth device 350 forward an updated second request based on the received second request to a device from which the second device 320 migrated.
In some example embodiments, the received second request comprises identity information of the second device 320 being known to both the fifth device 350 and the device of the at least one device.
In some example embodiments, the updated second request comprises identity information of the second device 320 being known to both the fifth device 350 and the device from which the second device 320 migrated.
In some example embodiments, the fifth device 350 receives a third request for paging the third device 330 from the device from which the second device 320 migrated, and further forwards an updated third request based on the received third request for paging to the device of the at least one device.
In some example embodiments, the received third request comprises identity information of the second device 320 being known to both the fifth device 350 and the device from which the second device 320 migrated.
In some example embodiments, the updated third request comprises identity information of the second device 320 being known to both the fifth device 350 and the device of the at least one device.
In some example embodiments, the fifth device 350 forwards the updated third request within a fourth duration during which both the fifth device 350 and the device of the at least one device keep context of the second device 320.
In some example embodiments, the fifth device 350 receives migration history information from the device from which the second device 320 migrated, when the second device 320 migrated to the fifth device 350. The migration history information comprises at least one of the following: identity information of the device from which the second device 320 migrated, duration information, the duration information indicating a third duration during which both the fifth device 350 and the device from which the second device 320 migrated keep context of the second device 320, and identify information of the second device 320 being known to the device from which the second device 320 migrated.
In some example embodiments, the fifth device 350 receives migration history information from the device from which the second device 320 migrated when the second device 320 migrated to the fifth device 350. The migration history information comprises at least one of the following: identity information of at least one device, wherein the second device 320 connected with the at least one device prior to connecting with the fifth device 350, duration information indicating at least one duration during which the at least one device keeps context of the second device 320, and identify information of the second device 320 being known to the at least one device.
In some example embodiments, the fifth device 350 forwards the updated second request within the third duration.
In some example embodiments, the fifth device 350 transmits migration history information to a device to which the second device 320 migrated when the second device 320 migrated from the fifth device 350. The migration history information comprises at least one of the following: duration information indicating a fourth duration during which both the fifth device 350 and the device to which the second device 320 migrated keep context of the second device 320, identify information of the fifth device 350, and identify information of the second device 320 being known to the fifth device 350.
In some example embodiments, when the second device 320 migrated from the fifth device 350, the fifth device 350 transmits an updated migration history information to a device to which the second device 320 migrated by attaching at least one of the following to the received migration history information: duration information indicating a fourth duration during which both the fifth device 350 and the device to which the second device 320 migrated keep context of the second device 320, identify information of the fifth device 350, and identify information of the second device 320 being known to the fifth device 350.
In some example embodiments, the fifth device 350 determines the fourth duration at least in part based on at least one of the following: remaining duration to keep context of at least one device which is transitioned to inactive state via the second device 320 while the second device 320 is connecting with the fifth device 350, duration information indicating a third duration during which both the fifth device 350 and the device from which the second device 320 migrated keep the context of the second device 320, time required for migrating the second device 320 from the fifth device 350, or a duration while the second device 320 is connecting with the fifth device 350.
In some example embodiments, the fifth device 350 discards the context of the second device 320 being known to both the fifth device 350 and the device to which the second device 320 migrated beyond the fourth duration.
In some example embodiments, the fifth device 350 receives a message from a first device 310 serving the second device 320. The message indicates at least one of the following: the second device 320 being connecting with the first device 310, identity information of the second device 320 being known to the fifth device, and identity information of the second device 320 being known to the first device 310.
In some example embodiments, the device of the at least one device is a further fifth device 350 to which the second device 320 migrated, or a first device 310 serving the third device 330 if the fifth device 350 is informed by the first device 310 that the second device 320 is connecting with the first device 310.
In some example embodiments, the fifth device 350 is donor device, the second device 320 is an integrated access and backhaul device and the third device 330 is a terminal device.
In some example embodiments, a fifth apparatus capable of performing any of the method 1000 (for example, the fifth device 350) may comprise means for performing the respective operations of the method 1000. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module. The fifth apparatus may be implemented as or included in the fifth device 350.
In some example embodiments, the fifth apparatus comprises: means for receiving, from an apparatus of at least one apparatus, a second request for retrieving a context of a third apparatus accessing a network via a second apparatus, wherein the second apparatus migrated to the at least one apparatus after the second apparatus migrated to the fifth apparatus; and means for forwarding, to an apparatus from which the second apparatus migrated, an updated second request based on the received second request.
In some example embodiments, the received second request comprises identity information of the second apparatus being known to both the fifth apparatus and the apparatus of the at least one apparatus, and the updated second request comprises identity information of the second apparatus being known to both the fifth apparatus and the apparatus from which the second apparatus migrated.
In some example embodiments, the fifth apparatus further comprises: means for: receiving, from the apparatus from which the second apparatus migrated, a third request for paging the third apparatus; and means for forwarding, to the apparatus of the at least one apparatus, an updated third request based on the received third request for paging.
In some example embodiments, the received third request comprises identity information of the second apparatus being known to both the fifth apparatus and the apparatus from which the second apparatus migrated, and the updated third request comprises identity information of the second apparatus being known to both the fifth apparatus and the apparatus of the at least one apparatus.
In some example embodiments, the fifth apparatus further comprises: means for forwarding the updated third request within a fourth duration during which both the fifth apparatus and the apparatus of the at least one apparatus keep context of the second apparatus.
In some example embodiments, the fifth apparatus further comprises: means for receiving migration history information from the apparatus from which the second apparatus migrated when the second apparatus migrated to the fifth apparatus. The migration history information comprising at least one of the following: identity information of the apparatus from which the second apparatus migrated, duration information, the duration information indicating a third duration during which both the fifth apparatus and the apparatus from which the second apparatus migrated keep context of the second apparatus, and identify information of the second apparatus being known to the apparatus from which the second apparatus migrated.
In some example embodiments, the fifth apparatus further comprises: means for receiving migration history information from the apparatus from which the second apparatus migrated when the second apparatus migrated to the fifth apparatus. The migration history information comprising at least one of the following: identity information of at least one apparatus, wherein the second apparatus connected with the at least one apparatus prior to connecting with the fifth apparatus, duration information indicating at least one duration during which the at least one apparatus keeps context of the second apparatus, and identify information of the second apparatus being known to the at least one apparatus.
In some example embodiments, the means for forwarding the updated second request comprises: means for forwarding the updated second request within the third duration.
In some example embodiments, the fifth apparatus further comprises: means for transmitting migration history information to an apparatus to which the second apparatus migrated when the second apparatus migrated from the fifth apparatus. The migration history information comprising at least one of the following: duration information indicating a fourth duration during which both the fifth apparatus and the apparatus to which the second apparatus migrated keep context of the second apparatus, identify information of the fifth apparatus, and identify information of the second apparatus being known to the fifth apparatus.
In some example embodiments, the fifth apparatus further comprises: means for when the second apparatus migrated from the fifth apparatus, transmitting an updated migration history information to an apparatus to which the second apparatus migrated by attaching at least one of the following to the received migration history information: duration information indicating a fourth duration during which both the fifth apparatus and the apparatus to which the second apparatus migrated keep context of the second apparatus, identify information of the fifth apparatus, and identify information of the second apparatus being known to the fifth apparatus.
In some example embodiments, the fifth apparatus further comprises: means for determining the fourth duration at least in part based on at least one of the following: remaining duration to keep context of at least one apparatus which is transitioned to inactive state via the second apparatus while the second apparatus is connecting with the fifth apparatus, duration information indicating a third duration during which both the fifth apparatus and the apparatus from which the second apparatus migrated keep the context of the second apparatus, time required for migrating the second apparatus from the fifth apparatus, or a duration while the second apparatus is connecting with the fifth apparatus.
In some example embodiments, the fifth apparatus further comprises: means for discarding the context of the second apparatus being known to both the fifth apparatus and the apparatus to which the second apparatus migrated beyond the fourth duration.
In some example embodiments, the fifth apparatus further comprises: means for receiving a message from a first apparatus serving the second apparatus. The message indicates at least one of the following: the second apparatus being connecting with the first apparatus, identity information of the second apparatus being known to the fifth apparatus, and identity information of the second apparatus being known to the first apparatuses.
In some example embodiments, the apparatus of the at least one apparatus is a further fifth apparatus to which the second apparatus migrated, or a first apparatus serving the third apparatus if the fifth apparatus is informed by the first apparatus that the second apparatus is connecting with the first apparatus.
In some example embodiments, the fifth apparatus is donor apparatus, the second apparatus is an integrated access and backhaul apparatus and the third apparatus is a terminal apparatus.
Fig. 11 is a simplified block diagram of a device 1100 that is suitable for implementing embodiments of the present disclosure. The device 1100 may be provided to implement the communication device, for example the first device 310, the fourth device 340 and the fifth device 350 as illustrated in Fig. 3. As shown, the device 1100 includes one or more processors 1110, one or more memories 1120 coupled to the processor 1110, and one or more transmitters and/or receivers (TX/RX) 1140 coupled to the processor 1110.
The TX/RX 1140 is for bidirectional communications. The TX/RX 1140 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 1110 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 800 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 1120 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) 1124, 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) 1122 and other volatile memories that will not last in the power-down duration.
A computer program 1130 includes computer executable instructions that are executed by the associated processor 1110. The program 1130 may be stored in the ROM 1120. The processor 1110 may perform any suitable actions and processing by loading the program 1130 into the RAM 1120.
The embodiments of the present disclosure may be implemented by means of the program 1130 so that the device 1100 may perform any process of the disclosure as discussed with reference to Figs. 3-10. The embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.
In some embodiments, the program 1130 may be tangibly contained in a computer readable medium which may be included in the device 1100 (such as in the memory 1120) or other storage devices that are accessible by the device 1100. The device 1100 may load the program 1130 from the computer readable medium to the RAM 1122 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. 12 shows an example of the computer readable medium 1200 in form of CD or DVD. The computer readable medium has the program 1130 stored thereon.
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, device, 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 methods 800-1000 as described above with reference to Fig. 8-10. 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 device, 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, device 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, device, 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 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:

receive, from a third device via a second device, a first request for resuming a connection between the third device and a network, the first request comprising identity information of a fourth device being a last serving device in the network for the third device, wherein the third device is in an inactive state in the network and accesses the network via the second device and wherein the second device connects with the first device; and

transmit a second request for retrieving a context of the third device to:

a fifth device from which the second device migrated if an interface between the first device and the fourth device is not available, or the identity information of the fourth device is unknown to the first device, or

a shortcut device of at least one device if the shortcut device is informed by the first device that the second device is connecting with the first device, wherein the second device connected with the at least one device prior to connecting with the fifth device from which the second device migrated.
The first device of claim 1, wherein if the second request is transmitted to the fifth device from which the second device migrated, the second request comprises identity information of the second device being known to both the first device and the fifth device from which the second device migrated; and

wherein if the second request is transmitted to the shortcut device, the second request comprises identity information of the second device being known to both the first and shortcut devices.
The first device of claim 1, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the first device to:

receive a third request for paging for the third device from:

the fifth device from which the second device migrated, or

the shortcut device if the shortcut device is informed by the first device that the second device is connecting with the first device.
The first device of claim 3, wherein if the third request is received from the fifth device from which the second device migrated, the third request comprises identity information of the second device being known to both the first device and fifth device from which the second device migrated; and

wherein if the third request is received from the shortcut device, the third request comprises identity information of the second device being known to both the first and shortcut devices.
The first device of claim 1, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the first device to:

receive, from the fifth device, migration history information when the second device migrated from the fifth device to the first device, the migration history information comprising at least one of the following:

identity information of the fifth device,

duration information indicating a first duration during which the fifth device keeps context of the second device, and

identify information of the second device being known to the fifth device.
The first device of claim 5, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the first device to transmit the second request by:

transmitting the second request to the fifth device within the first duration.
The first device of claim 1, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the first device to:

receive, from the fifth device, migration history information when the second device migrated from the fifth device to the first device, the migration history information comprising at least one of the following:

identity information of at least one device, wherein the second device connected with the at least one device prior to connecting with the first device,

duration information indicating at least one duration during which the at least one device keeps context of the second device, and

identify information of the second device being known to the at least one device.
The first device of claim 7, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the first device to:

determine the shortcut device based on the migration history information, wherein the shortcut device is one of the following:

the fourth device if the interface between the first device and the fourth device is available, or

a further fifth device if an interface between the further fifth device and the first device is available, wherein the further fifth device is one of the at least one device.
The first device of claim 8, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the first device to:

transmit to the shortcut device a message indicating at least one of the following:

the second device being connecting to the first device,

identity information of the second device being known to the shortcut device, and

identity information of the second device being known to the first device.
The first device of claim 1, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the first device to:

receive a response to the second request comprising the context of the third device from the fifth device from which the second device migrated or the shortcut device.
The first device of claim 10, wherein if the response is received from the fifth device from which the second device migrated, the response comprises identity information of the second device being known to both the first device and fifth device from which the second device migrated; and

wherein if the response is received from the shortcut device, the response comprises identity information of the second device being known to both the first and shortcut devices.
The first device of any one of claims 1-11, wherein the first, fourth and fifth devices are donor devices, the second device is an integrated access and backhaul device and the third device is a terminal device.
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:

transmit migration history information to a fifth device when the second device migrates from the fourth device to the fifth device; and

receive a second request for retrieving a context of a third device being in an inactive state in a network and accessing the network via the second device from:

a first device serving the third device if the fourth device is informed that the second device is connecting with the first device, or

the fifth device.
The fourth device of claim 13, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the fourth device to:

detect an event for triggering a paging procedure for the third device; and

transmit a third request for paging the third device to:

the fifth device within the second duration, or

the first device if the fourth device is informed by the first device that the second device is connecting with the first device.
The fourth device of claim 14, wherein if the third request is transmitted to the fifth device, the third request comprises identity information of the second device being known to both the fourth device and the fifth device; and

wherein if the third request is transmitted to the first device, the third request comprises identity information of the second device being known to both of the first device and the fourth device.
The fourth device of claim 13, wherein the migration history information comprises at least one of the following:

information indicating a second duration during which the fourth device keeps context of the second device,

identity information of the fourth device, and

identify information of the second device being known to the fourth device.
The fourth device of claim 13, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the fourth device to:

receive, from the first device, a message indicating at least one of the following:

the second device being connecting with the first device,

identity information of the second device being known to the fourth device, and

identity information of the second device being known to the first device.
The fourth device of claim 13, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the fourth device to:

determine the second duration based on at least one of the following:

remaining duration to keep context of at least one device including the third device, wherein the at least one device is transitioned to an inactive state in the network via the second device while the second device is connecting with the fourth device; and

time required for migrating the second device from the fourth device to the fifth device.
The fourth device of claim 13, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the fourth device to:

discard the context of the second device beyond the second duration.
The fourth device of any one of claims 13-19, wherein the first, fourth and fifth devices are donor devices, the second device is an integrated access and backhaul device and the third device is a terminal device.
A fifth 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 fifth device to:

receive, from a device of at least one device, a second request for retrieving a context of a third device accessing a network via a second device, wherein the second device migrated to the at least one device after the second device migrated to the fifth device; and

forward, to a device from which the second device migrated, an updated second request based on the received second request.
The fifth device of claim 21, wherein the received second request comprises identity information of the second device being known to both the fifth device and the device of the at least one device, and the updated second request comprises identity information of the second device being known to both the fifth device and the device from which the second device migrated.
The fifth device of claim 21, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the fifth device to:

receive, from the device from which the second device migrated, a third request for paging the third device; and

forward, to the device of the at least one device, an updated third request based on the received third request for paging.
The fifth device of claim 23, wherein the received third request comprises identity information of the second device being known to both the fifth device and the device from which the second device migrated, and the updated third request comprises identity information of the second device being known to both the fifth device and the device of the at least one device.
The fifth device of claim 23, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the fifth device to forward the updated third request by:

forwarding the updated third request within a fourth duration during which both the fifth device and the device of the at least one device keep context of the second device.
The fifth device of claim 21, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the fifth device to:

receive, from the device from which the second device migrated, migration history information when the second device migrated to the fifth device, the migration history information comprising at least one of the following:

identity information of the device from which the second device migrated,

duration information, the duration information indicating a third duration during which both the fifth device and the device from which the second device migrated keep context of the second device, and

identify information of the second device being known to the device from which the second device migrated.
The fifth device of claim 21, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the fifth device to:

receive, from the device from which the second device migrated, migration history information when the second device migrated to the fifth device, the migration history information comprising at least one of the following:

identity information of at least one device, wherein the second device connected with the at least one device prior to connecting with the fifth device,

duration information indicating at least one duration during which the at least one device keeps context of the second device, and

identify information of the second device being known to the at least one device.
The fifth device of claim 23, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the fifth device to forward the updated second request by:

forwarding the updated second request within the third duration.
The fifth device of claim 21, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the fifth device to:

transmit, migration history information to a device to which the second device migrated when the second device migrated from the fifth device, the migration history information comprising at least one of the following:

duration information indicating a fourth duration during which both the fifth device and the device to which the second device migrated keep context of the second device,

identify information of the fifth device, and

identify information of the second device being known to the fifth device.
The fifth device of claim 26 or 27, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the fifth device to:

when the second device migrated from the fifth device, transmit an updated migration history information to a device to which the second device migrated by attaching at least one of the following to the received migration history information:

duration information indicating a fourth duration during which both the fifth device and the device to which the second device migrated keep context of the second device,

identify information of the fifth device, and

identify information of the second device being known to the fifth device.
The fifth device of claim 29 or 30, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the fifth device to:

determine the fourth duration at least in part based on at least one of the following:

remaining duration to keep context of at least one device which is transitioned to inactive state via the second device while the second device is connecting with the fifth device,

duration information indicating a third duration during which both the fifth device and the device from which the second device migrated keep the context of the second device,

time required for migrating the second device from the fifth device, or

a duration while the second device is connecting with the fifth device.
The fifth device of claim 29 or 30, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the fifth device to:

discard the context of the second device being known to both the fifth device and the device to which the second device migrated beyond the fourth duration.
The fifth device of claim 21, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the fifth device to:

receive, from a first device serving the second device, a message indicating at least one of the following:

the second device being connecting with the first device,

identity information of the second device being known to the fifth device; and

identity information of the second device being known to the first device.
The fifth device of claim 21, wherein the device of the at least one device is one of the following:

a further fifth device to which the second device migrated, or

a first device serving the third device if the fifth device is informed by the first device that the second device is connecting with the first device.
The fifth device of any one of claims 21-34 wherein the fifth device is donor device, the second device is an integrated access and backhaul device and the third device is a terminal device.
A method comprising:

receiving, at a first device from a third device via a second device, a first request for resuming a connection between the third device and a network, the first request comprising identity information of a fourth device being a last serving device in the network for the third device, wherein the third device is in an inactive state in the network and accesses the network via the second device and wherein the second device connects with the first device; and

transmitting a second request for retrieving a context of the third device to:

a fifth device from which the second device migrated if an interface between the first device and the fourth device is not available, or the identity information of the fourth device is unknown to the first device, or

a shortcut device of at least one device if the shortcut device is informed by the first device that the second device is connecting with the first device, wherein the second device connected with the at least one device prior to connecting with the fifth device from which the second device migrated.
The method claim 36, wherein if the second request is transmitted to the fifth device from which the second device migrated, the second request comprises identity information of the second device being known to both the first device and the fifth device from which the second device migrated; and

wherein if the second request is transmitted to the shortcut device, the second request comprises identity information of the second device being known to both the first and shortcut devices.
The method of claim 36, further comprising:

receiving a third request for paging for the third device from:

the fifth device from which the second device migrated, or

the shortcut device if the shortcut device is informed by the first device that the second device is connecting with the first device.
The method of claim 38, wherein if the third request is received from the fifth device from which the second device migrated, the third request comprises identity information of the second device being known to both the first device and fifth device from which the second device migrated; and

wherein if the third request is received from the shortcut device, the third request comprises identity information of the second device being known to both the first and shortcut devices.
The method of claim 36, further comprising:

receiving, from the fifth device, migration history information when the second device migrated from the fifth device to the first device, the migration history information comprising at least one of the following:

identity information of the fifth device,

duration information indicating a first duration during which the fifth device keeps context of the second device, and

identify information of the second device being known to the fifth device.
The method of claim 40, wherein the transmitting the second request comprises:

transmitting the second request to the fifth device within the first duration.
The method of claim 36, further comprising:

receiving, from the fifth device, migration history information when the second device migrated from the fifth device to the first device, the migration history information comprising at least one of the following:

identity information of at least one device, wherein the second device connected with the at least one device prior to connecting with the first device,

duration information indicating at least one duration during which the at least one device keeps context of the second device, and

identify information of the second device being known to the at least one device.
The method of claim 42, further comprising:

determining the shortcut device based on the migration history information, wherein the shortcut device is one of the following:

the fourth device if the interface between the first device and the fourth device is available, or

a further fifth device if an interface between the further fifth device and the first device is available, wherein the further fifth device is one of the at least one device.
The method of claim 43, further comprising:

transmitting to the shortcut device a message indicating at least one of the following:

the second device being connecting to the first device,

identity information of the second device being known to the shortcut device, and

identity information of the second device being known to the first device.
The method of claim 36, further comprising:

receiving a response to the second request comprising the context of the third device from the fifth device from which the second device migrated or the shortcut device.
The method of claim 45, wherein if the response is received from the fifth device from which the second device migrated, the response comprises identity information of the second device being known to both the first device and fifth device from which the second device migrated; and

wherein if the response is received from the shortcut device, the response comprises identity information of the second device being known to both the first and shortcut devices.
The method of any one of claims 36-46, wherein the first, fourth and fifth devices are donor devices, the second device is an integrated access and backhaul device and the third device is a terminal device.
A method comprising:

transmitting, at a fourth device, migration history information to a fifth device when the second device migrates from the fourth device to the fifth device; and

receiving a second request for retrieving a context of a third device being in an inactive state in a network and accessing the network via the second device from:

a first device serving the third device if the fourth device is informed that the second device is connecting with the first device, or

the fifth device.
The method of claim 48, further comprising:

detecting an event for triggering a paging procedure for the third device; and

transmitting a third request for paging the third device to:

the fifth device within the second duration, or

the first device if the fourth device is informed by the first device that the second device is connecting with the first device.
The method of claim 49, wherein if the third request is transmitted to the fifth device, the third request comprises identity information of the second device being known to both the fourth device and the fifth device; and

wherein if the third request is transmitted to the first device, the third request comprises identity information of the second device being known to both of the first device and the fourth device.
The method of claim 48, wherein the migration history information comprises at least one of the following:

information indicating a second duration during which the fourth device keeps context of the second device,

identity information of the fourth device, and

identify information of the second device being known to the fourth device.
The method of claim 48, further comprising:

receiving, from the first device, a message indicating at least one of the following:

the second device being connecting with the first device,

identity information of the second device being known to the fourth device, and

identity information of the second device being known to the first device.
The method of claim 48, further comprising:

determining the second duration based on at least one of the following:

remaining duration to keep context of at least one device including the third device, wherein the at least one device is transitioned to an inactive state in the network via the second device while the second device is connecting with the fourth device; and

time required for migrating the second device from the fourth device to the fifth device.
The method of claim 48, further comprising:

discarding the context of the second device beyond the second duration.
The method of any one of claims 48-54, wherein the first, fourth and fifth devices are donor devices, the second device is an integrated access and backhaul device and the third device is a terminal device.
A method comprising:

receiving, at a fifth device from a device of at least one device, a second request for retrieving a context of a third device accessing a network via a second device, wherein the second device migrated to the at least one device after the second device migrated to the fifth device; and

forwarding, to a device from which the second device migrated, an updated second request based on the received second request.
The method of claim 56, wherein the received second request comprises identity information of the second device being known to both the fifth device and the device of the at least one device, and the updated second request comprises identity information of the second device being known to both the fifth device and the device from which the second device migrated.
The method of claim 56, further comprising:

receiving, from the device from which the second device migrated, a third request for paging the third device; and

forwarding, to the device of the at least one device, an updated third request based on the received third request for paging.
The method of claim 58, wherein the received third request comprises identity information of the second device being known to both the fifth device and the device from which the second device migrated, and the updated third request comprises identity information of the second device being known to both the fifth device and the device of the at least one device.
The method of claim 58, wherein the forwarding the updated third request comprises:

forwarding the updated third request within a fourth duration during which both the fifth device and the device of the at least one device keep context of the second device.
The method of claim 56, further comprising:

receiving, from the device from which the second device migrated, migration history information when the second device migrated to the fifth device, the migration history information comprising at least one of the following:

identity information of the device from which the second device migrated,

duration information, the duration information indicating a third duration during which both the fifth device and the device from which the second device migrated keep context of the second device, and

identify information of the second device being known to the device from which the second device migrated.
The method of claim 56, further comprising:

receiving, from the device from which the second device migrated, migration history information when the second device migrated to the fifth device, the migration history information comprising at least one of the following:

identity information of at least one device, wherein the second device connected with the at least one device prior to connecting with the fifth device,

duration information indicating at least one duration during which the at least one device keeps context of the second device, and

identify information of the second device being known to the at least one device.
The method of claim 58, wherein the forwarding the updated second request comprises:

forwarding the updated second request within the third duration.
The method of claim 56, further comprising:

transmitting, migration history information to a device to which the second device migrated when the second device migrated from the fifth device, the migration history information comprising at least one of the following:

duration information indicating a fourth duration during which both the fifth device and the device to which the second device migrated keep context of the second device,

identify information of the fifth device, and

identify information of the second device being known to the fifth device.
The method of claim 61 or 62, further comprising:

when the second device migrated from the fifth device, transmitting an updated migration history information to a device to which the second device migrated by attaching at least one of the following to the received migration history information:

duration information indicating a fourth duration during which both the fifth device and the device to which the second device migrated keep context of the second device,

identify information of the fifth device, and

identify information of the second device being known to the fifth device.
The method of claim 64 or 65, further comprising:

determining the fourth duration at least in part based on at least one of the following:

remaining duration to keep context of at least one device which is transitioned to inactive state via the second device while the second device is connecting with the fifth device,

duration information indicating a third duration during which both the fifth device and the device from which the second device migrated keep the context of the second device,

time required for migrating the second device from the fifth device, or

a duration while the second device is connecting with the fifth device.
The method of claim 64 or 65, further comprising:

discarding the context of the second device being known to both the fifth device and the device to which the second device migrated beyond the fourth duration.
The method of claim 56, further comprising:

receiving, from a first device serving the second device, a message indicating at least one of the following:

the second device being connecting with the first device,

identity information of the second device being known to the fifth device; and

identity information of the second device being known to the first device.
The method of claim 56, wherein the device of the at least one device is one of the following:

a further fifth device to which the second device migrated, or

a first device serving the third device if the fifth device is informed by the first device that the second device is connecting with the first device.
The method of any one of claims 56-69 wherein the fifth device is donor device, the second device is an integrated access and backhaul device and the third device is a terminal device.
A first apparatus comprising:

means for receiving, from a third apparatus via a second apparatus, a first request for resuming a connection between the third apparatus and a network, the first request comprising identity information of a fourth apparatus being a last serving apparatus in the network for the third apparatus, wherein the third apparatus is in an inactive state in the network and accesses the network via the second apparatus and wherein the second apparatus connects with the first apparatus; and

means for transmitting a second request for retrieving a context of the third apparatus to:

a fifth apparatus from which the second apparatus migrated if an interface between the first apparatus and the fourth apparatus is not available, or the identity information of the fourth apparatus is unknown to the first apparatus, or

a shortcut apparatus of at least one apparatus if the apparatus is informed by the first apparatus that the second apparatus is connecting with the first apparatus, wherein the second apparatus connected with the at least one apparatus prior to connecting with the fifth apparatus from which the second apparatus migrated.
A fourth apparatus comprising:

means for transmitting migration history information to a fifth apparatus when the second apparatus migrates from the fourth apparatus to the fifth apparatus; and

means for receiving a second request for retrieving a context of a third apparatus being in an inactive state in a network and accessing the network via the second apparatus from:

a first apparatus serving the third apparatus if the fourth apparatus is informed that the second apparatus is connecting with the first apparatus, or

the fifth apparatus.
A fifth apparatus comprising:

means for receiving, from an apparatus of at least one apparatus, a second request for retrieving a context of a third apparatus accessing a network via a second apparatus, wherein the second apparatus migrated to the at least one apparatus after the second apparatus migrated to the fifth apparatus; and

means for forwarding, to an apparatus from which the second apparatus migrated, an updated second request based on the received second request.
A computer readable medium comprising program instructions for causing an apparatus to perform any of the method of claims 36-70.