WO2016169473A1

WO2016169473A1 - Method and apparatus for facilitating communications

Info

Publication number: WO2016169473A1
Application number: PCT/CN2016/079718
Authority: WO
Inventors: Rui Fan; Jari Vikberg
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2015-04-24
Filing date: 2016-04-20
Publication date: 2016-10-27

Abstract

Embodiments of the present disclosure propose a method and an apparatus for facilitating communications in a wireless network comprising first tracking areas in which communications can be established with a core network via a first radio access technology and second tracking areas in which communications can be established with the core network via a second radio access technology. The method performed at a terminal device comprises receiving a message from the core network via the first radio access technology when the terminal device is located in one of the first tracking areas and acquiring, from the received message, first tracking area information indicating at least one of the first tracking areas available for the terminal device and second tracking area information indicating at least one of the second tracking areas available for the terminal device. Corresponding methods performed in a core network and at a base station are also provided.

Description

METHOD AND APPARATUS FOR FACILITATING COMMUNICATIONS

TECHNICAL FIELD

The non-limiting and exemplary embodiments of the present disclosure generally relate to the communications field， and specifically to a method， an apparatus， and a computer program for facilitating communications in a wireless network supporting communications using multiple different radio access technologies.

BACKGROUND

This section introduces aspects that may facilitate better understanding of the present disclosure. Accordingly， the statements of this section are to be read in this light and are not to be understood as admissions regarding what is in the prior art or what is not in the prior art.

The dynamic expansion of the communications market is accompanied by increasing diversity of technologies deployed in communications networks with a steady pace of new technological development. As a result， there is an immense heterogeneity of communications technologies， especially radio access technologies (RATs) ， such as Wideband Code Division Multiple Access (WCDMA) for the third generation (3G) networks， Long-Term Evolution (LTE) for the fourth generation (4G) networks， or a future RAT which is sometimes called NX for the next generation networks which may be called 5G networks. These access technologies have different characteristics， such as different radio coverage， different spectral efficiency， different cell capacity， and different peak data rates； they may support different services； and they differ in complexity and costs. For a network operator， different RATs may best be suited in different parts of a network， for example， depending on the radio environment， the expected traffic pattern， and the anticipated services. The dynamic selection of RAT according to communication requirements and network characteristics enable end users to be always appropriately served. Therefore， it is desirable to allow various RATs to be combined in a same network and to allow interworking of different access networks， even when they use different RATs.

Thus， integration of new RATs to legacy ones has always been an important feature in any wireless communications generation shift. For the transition from 4G to 5G， a tight integration is envisioned， which leads to architecture problems that have to be solved. The tight integration in this context means that common protocol layer (s) running on the top of RAT-specific protocol layers of LTE and for the new 5G air interface will be specified.

Base Station Split Architecture

In a Patent Cooperation Treaty (PCT) application No. PCT/SE2015/050166 with a title of “Flexible Assignment of Network Functions for Radio Access” and another PCT application No. PCT SE2015/050173 with a title of “Establishment of Ducal Connectivity” ， a Radio Access Network (RAN) functional split for tight multi-RAT integration is presented. In this functional split， RAN functions running at the network side can be classified into synchronous and asynchronous functions or function groups. The synchronous functions have requirements on processing timing which are strictly dependent on timing of a radio link used for communicating with a terminal device. The asynchronous functions have requirements on processing timing not strictly dependent on the timing of the radio link， or even independent on the timing of the radio link.

Synchronous functions may be deployed in the same network node (or logical network element) . This network node (or logical network element) may be called s-eNodeB (s-eNB or eNB-s) in the case of LTE， or s-NX-eNB (or NX-eNB-s) in the case of NX. Asynchronous functions typically have the flexibility to be placed in different network nodes (or logical network elements) ， being connected via an inter-node interface. In addition， the asynchronous functions at the network side have the flexibility to be deployed further from the air interface.

FIG. 1 shows an example of a functional split of an eNB in LTE， in which functions of the eNB in control plane is split into two parts running respectively on eNB-s and eNB-a in FIG. 1 (a) and likewise functions in user plane is also split into two parts running respectively on the eNB-s and the eNB-a in FIG. 1 (b) . As an example， synchronous functions in LTE may comprise “radio resources scheduling for downlink” at the Media Access Control (MAC) layer， “channel status information (CSI) reception” at the physical (PHY) layer and Service Data Units (SDUs) fragmentation/reassembly at the RLC layer. It is a typical deployment to place these synchronous functions in a same node and close to the air interface. As another example， asynchronous functions in LTE may comprises functions related to the Data Convergence Protocol (PDCP) ， Radio Resource Control (RRC) ， S1 Application Protocol (S1AP) ， Stream Control Transmission Protocol (SCTP) ， Internet Protocol (IP) ， User Datagram Protocol (UDP) ， and GPRS (General Packet Radio Service) Tunnelling Protocol for the user plane (GTP-U) . Obviously， with the technology development， various protocols and related functions may be split and added into the eNB-s and the eNB-a， which are represented with “New” in FIG. 1. The interface between the eNB-s and the eNB-a is a new interface. The other interfaces are the conventional 3GPP interfaces.

FIG. 2 shows an exemplary network architecture comprising an eNB split into two parts， i.e. an eNB-a and an eNB-s. The eNB-a is connected to the Mobility Management Entity (MME) over S1-MME interface and to the Serving Gateway (SGW) over S1-U interface and may also connect with other eNBs or eNB-a. The eNB-a is connected to the eNB-s via the new interface as illustrated in FIG. 1 and the eNB-s is connected to a user equipment (UE) via LTE-Uu interface.

FIG. 3 shows an exemplary network architecture enabling dual connectivity using the split solution as proposed in PCT application No. PCT SE2015/050166. The eNB-a can be a common point when the UE is connected via two or more different eNB-s. As shown in FIG. 3， the UE is connected via both eNB-s1 and eNB-s2 to eNB-a. The eNB-a contains in general the asynchronous functions e.g. the common protocols for both control plane (RRC and PDCP) and user plane (PDCP) .

The split of radio area network (RAN) functions on the network side into synchronous and asynchronous functions can also be considered for tight multi-RAT integration. One application context is 5G networks that are likely to include both LTE-compatible RAT and non-LTE-compatible RAT， i.e NX. Issues to consider in this context are for example to define a functional split for an integrated architecture of multiple air interfaces， air interface variants of different RATs， and features envisioned for 5G networks to enable seamless and/or lossless mobility between multiple RATs and control plane and user plane ultra-reliability. The non-LTE-compatible RAT in 5G context is very likely to have different lower layer protocols compared to LTE-compatible， e.g. due to high frequencies it is supposed to operate and/or new use cases it is required to address.

Assuming that a given UE is able to connect to multiple air interfaces (not necessarily at the same time) ， the previously mentioned functional split methodology can be extended so that a same instance of asynchronous functions is defined for these multiple air interfaces (where the UE can be connected at the same time or during the mobility procedure) and distinct synchronous functional groups are defined per air interface， e.g. LTE-compatible and non-LTE compatible parts in the 5G radio access. In this case， the eNB-a may contain common support for asynchronous functions in both control plane and user plane， and one or more eNB-s each may contain the RAT-specific synchronous functions. This case is shown in FIG. 4， where the common eNB-a is called “5G & LTE eNB-a” and two eNB-s corresponding to two RATs are called “LTE eNB-s1” and “5G eNB-s2” ， respectively.

Tracking Area Handling in LTE

A new principle has been introduced for location registration in Evolved Packet Core (EPC) /Evolved Universal Terrestrial Radio Access Network (E-UTRAN) networks， i.e. Evolved Packet System (EPS) networks. This principle is based on a Tracking Area (TA) concept in a similar way as the Location Areas (LA) /Routing Areas (RA) concept in Global System for Mobile Communication (GSM) and WCDMA networks. Each E-UTRAN cell belongs normally to a single TA (if not considering RAN sharing deployments) and a Tracking Area Identity (TAI) is broadcasted as part of system information. The TAI consists of a Mobile Country Code (MCC) ， a Mobile Network Code (MNC) and a Tracking Area Code (TAG) .

The main difference from the LA/RA concept is that in EPC/E-UTRAN， a concept called multiple TAs or TAI List has been introduced. This means that the core network (CN) may return a TAI List to the UE as part of some EPS Mobility Management (EMM) procedures like Attach， Tracking Area Update (TAU) and Globally Unique Temporary Identification (GUTI) Reallocation. As long as a UE camps on a cell belonging to a TA whose TAI is included in the TAI List， the UE doesn’ t need to perform normal TAUs caused by TA change， although periodic TAUs are still performed， while the UE performs the normal TAU first when it moves to a cell that doesn’t belong to a TA in the TAI List. As part of this TAU， the UE will receive a new TAI List and the same procedure continues.

This concept is illustrated in FIG. 5 and FIG. 6. FIG. 5 shows the case when a UE has performed a TAU and has received a TAI List of {TA1， TA2， TA3} from the CN. This means that the UE can move within TA1， TA2 and TA3 without any TAU. The UE in FIG. 5 may also move towards TA4 that will be further described in FIG. 6.

In FIG. 6， the UE performs a TAU when it moves to a cell belonging to TA4. After the successful TAU in TA4， the UE receives a TAI List {TA2， TA3， TA4} from the CN. Now the UE can move within TA2， TA3 and TA4 without the need to perform a TAU.

Those skilled in the art shall appreciate that the terms TA1， TA2， etc. may be used to denote different tracking areas themselves or to denote identities of these tracking areas， depending on the context. For instance， when these terms are used in a TAI List， then TA1， TA2， etc. represent the identities， i.e. TAIs， of tracking area 1， tracking area 2， etc.， whereas when it is stated that the UE can move freely within TA1， TA2， etc.， the terms TA1， TA2， etc. represent the actual tracking Areas.

One purpose with the TAU is to provide information regarding the UE location to the network. This information can then be used e.g. for paging purposes for mobile terminating transactions， i.e. to locate the UE and to establish a signaling connection between the UE and the network. The main principle is that the network needs to page the UE on all the TAs represented by the whole TAI List， i.e. on all the cells belonging to any of the TAs whose TAIs are included in the TAI List. For example， considering the scenario in above FIG. 6， the network would need to page the UE on all cells belonging to TA2， TA3 or TA4.

Idle state Signaling Reduction (ISR) between GERAN/UTRAN and E-UTRAN

Idle state Signalling Reduction (ISR) is defined in 3rd Generation Partnership Project (3GPP) Technical Specification (TS) 23.401， which aims at reducing the frequency of TAU and RAU procedures caused by UEs reselecting between E-UTRAN and GSM EDGE Radio Access Network (GERAN) /UTRAN which are operated together. When ISR is activated， this means the UE is registered with both a MME and a Serving GPRS Support Node (SGSN) . Both the SGSN and the MME have a control connection with the SGW. The MME and SGSN are both registered at the Home Subscriber Server (HSS) . The UE stores Mobility Management (MM) parameters from the SGSN (e.g. Packet Temporary Mobile Subscription Identity (P-TMSI) and RA) and from MME (e.g. GUTI and TA (s) ) and the UE stores session management (bearer) contexts that are common to E-UTRAN and GERAN/UTRAN access. In idle state， the UE can reselect between E-UTRAN and GERAN/UTRAN within the registered RA and TAs without any need to perform TAU or RAU procedures with the network. The SGSN and MME store each other′s address when ISR is activated.

One example of ISR activation is shown in FIG. 7 that corresponds to Figure J. 3-1 in 3GPP TS 23.401. The process starts with an ordinary Attach procedure without requiring any special functionality for support of ISR， and ISR is deactivated for the UE. One important ISR concept is a ″Temporary Identity used in Next update″ (TIN) . The TIN is a parameter of the UE′s MM context， which identifies the UE identity to be indicated in the next RAU Request or TAU Request message. The TIN also identifies the status of ISR activation in the UE. With the Attach request message， the UE sets its TIN to ″GUTI″ . After attaching with the MME， the UE may perform any interactions via E-UTRAN without changing the ISR state i.e. ISR remains deactivated.

At the first time when the UE reselects GERAN or UTRAN， it initiates a Routing Area Update (step 4 in FIG. 7) . This represents an occasion to activate ISR. The TIN indicates ″GUTI″ ， so the UE indicates a P-TMSI mapped from a GUTI in the RAU Request. The SGSN gets contexts from the MME. When the MME sends the context to the SGSN， the MME includes the ISR supported indication only if the involved S-GW supports the ISR. After the ISR is activated， both CN nodes keep these contexts because ISR is being activated. The SGSN establishes a control relation with the Serving GW， which is active in parallel to the control connection between the MME and Serving GW (not shown in figure) . The RAU Accept indicates ISR activation to the UE. The UE keeps GUTI and P-TMSI as registered， which the UE memorizes by setting the TIN to ″RAT-related TMSI″ . The MME and the SGSN are registered in parallel with the HSS.

After the ISR activation， the UE may reselect between E-UTRAN and UTRAN/GERAN without any need for updating the network as long as the UE does not move out of the RA/TA (s) registered with the network. The ISR activation for a UE， which is already attached to GERAN/UTRAN， with a TAU procedure from E-UTRAN， works in a very similar way.

Problems

Currently， there are two solutions that a UE in idle mode executes TA update procedures in a network supporting communications using two different RATs.

The first solution is that the UE camps on one RAT and executes TA update procedures for that RAT only. The problem with this solution is that if the UE camps on a RAT with lower service performance， it may initiate a new session in this RAT even though another RAT with better service performance is available； while if the UE wants to use the other RAT for better service performance， a handover from the current RAT to the other RAT may have to be performed. This may result in either lower performance for the UE or higher signaling cost for the network that needs to handover the UE to the other RAT. On the other hand， if the UE camps on the RAT with better service performance which may be deployed in smaller areas， it would result in frequent measurements and cell reselection evaluations (leading to UE power drain) ， and a large number of tracking/location area update signaling messages as the UE move in and out of that RAT coverage (leading to high signalling load on the network) .

The second solution is that the UE camps on both RATs and executes TA update procedures for both RAT concurrently. The problem with this solution is that it results into too many location area update signaling as the UE has to do location update for two RATs concurrently.

SUMMARY

Various embodiments of the present disclosure mainly aim at providing an efficient solution for facilitating communications in a network integrating multiple different RATs， e.g. 5G networks. Other features and advantages of embodiments of the present disclosure will also be understood from the following description of specific embodiments when read in conjunction with the accompanying drawings， which exemplarily illustrate the principles of embodiments of the present disclosure.

In a first aspect of the disclosure， there is provided a method for facilitating communications in a wireless network comprising first tracking areas in which communications can be established with a core network via a first radio access technology and second tracking areas in which communications can be established with the core network via a second radio access technology. The method is performed at a terminal device located in one of the first tracking areas. The method comprises receiving a message from the core network via the first radio access technology when the terminal device is located in one of the first tracking areas and then acquiring， from the received message， first tracking area information indicating at least one of the first tracking areas available for the terminal device and second tracking area information indicating at least one of the second tracking areas available for the terminal device.

In an embodiment， the method may further comprise receiving a paging message via any of the first and second radio access technology based on the first and second tracking area information.

In another embodiment， the message may comprises the first tracking area information and information indicating a mapping relationship between the at least one of the first tracking areas and the at least one of the second tracking areas. In this embodiment， the second tracking area information may be acquired from the mapping relationship according to the first tracking area information.

In yet another embodiment， the message may be a tracking area update accept message received from the core network in response to sending a tracking area update request message to the core network or an attach accept message received from the core network in response to sending an attach request message to the core network.

In a second aspect of the disclosure， there is provided another method for facilitating communications in a wireless network comprising first tracking areas in which communications can be established with the core network via a first radio access technology and second tracking areas in which communications can be established with the core network via a second radio access technology. This method is performed in the core network， e.g. at MME. The method comprises generating a message including first tracking area information indicating at least one of the first tracking areas available for a terminal device located in one of the first tracking areas and second tracking area information indicating at least one of the second tracking areas available for the terminal device and sending the message to the terminal device for reception by the terminal device via the first radio access technology.

In an embodiment， the method may further comprise the following operations before generating the message： establishing a mapping relationship between the first tracking areas and the second tracking areas and obtaining the second tracking area information from the mapping relationship according to the first tracking area information.

In a further embodiment， the second tracking area information may comprise information indicating at least part of the mapping relationship.

In another embodiment， the message may be generated as a tracking area update accept message in response to reception of a tracking area update request message from the terminal device or generated as an attach accept message in response to reception of an attach request message from the terminal device.

In yet another embodiment， the method may further comprise sending a paging message that includes information indicating which of the first radio access technology and the second radio access technology will be used for transmitting the paging message.

In yet another embodiment， the method may further comprise sending a paging message that includes information indicating any of the following： a latency requirement preference for paging， service requirements related to downlink traffic that triggered the paging， or information regarding ongoing services for the terminal or subscription based information for the terminal device that is being paged.

In a third aspect of the disclosure， there is provided another method for facilitating communications in a wireless network comprising first tracking areas in which communications can be established with a core network via a first part of the base station associated with a first radio access technology and second tracking areas in which communications can be established with the core network via a second part of the base station associated with a second radio access technology. The method is performed at the base station， particularly at a common part of the base station shared by the first and second radio access technology. The method comprises receiving a message from the core network at the common part and then determining which of the first part and the second part of the base station will be used for transmitting the message. Once it is determined， the message will be transmitted via the determined corresponding part of the base station towards the terminal device. The common part and first and second parts may be embodies as three physically separate entities or network elements.

In an embodiment， the determining may be based on information included in the message indicating which of the first radio access technology and the second radio access technology will be used for transmitting the message.

In another embodiment， the determining may be based on information included in the message indicating any of the following： a latency requirement preference for paging， service requirements related to downlink traffic that triggered the paging， or information regarding ongoing services for the terminal or subscription based information for the terminal device that is being paged.

In a fourth aspect of the disclosure， there is provided an apparatus for facilitating communications in a wireless network comprising first tracking areas in which communications can be established with a core network via a first radio access technology and second tracking areas in which communications can be established with the core network via a second radio access technology. The apparatus may be embodied as a terminal device， a part thereof， or an independent apparatus. The apparatus comprises a receiving unit and an acquiring unit. The receiving unit is configured to receive a message from the core network via the first radio access technology when the terminal device is located in one of the first tracking areas. The acquiring unit is configured to acquire， from the received message， first tracking area information indicating at least one of the first tracking areas available for the terminal device and second tracking area information indicating at least one of the second tracking areas available for the terminal device.

In a fifth aspect of the disclosure， there is provided another apparatus for facilitating communications in a wireless network comprising first tracking areas in which communications can be established with a core network via a first radio access technology and second tracking areas in which communications can be established with the core network via a second radio access technology. The apparatus may be embodied in the core network， e.g. as an MME or a part thereof. The apparatus comprises a generating unit and a sending unit. The generating unit is configured to generate a message including first tracking area information indicating at least one of the first tracking areas available for a terminal device located in one of the first tracking areas and second tracking area information indicating at least one of the second tracking areas available for the terminal device. The sending unit is configured to send the message to the terminal device for reception by the terminal device via the first radio access technology.

In a sixth aspect of the disclosure， there is provided another apparatus for facilitating communications in a wireless network comprising first tracking areas in which communications can be established with a core network via a first radio access technology， particularly via a first part of the base station associated with the first radio access technology and second tracking areas in which communications can be established with the core network via a second radio access technology， particularly via a second part of the base station associated with the second radio access technology. The apparatus may be embodied as a common part of the base station shared by the first and second radio access technology or a part thereof. The apparatus comprises a receiving unit， a determining unit and a transmitting unit. The receiving unit is configured to receive a message from the core network at a common part of the base station shared by the first and second radio access technology. The determining unit is configured to determine which of the first part and the second part of the base station will be used for transmitting the message. The transmitting unit is configured to transmit the message via the determined corresponding part of the base station towards the terminal device. The apparatus may be embodied as an entity or network element physically separate from the first and second parts.

In a seventh aspect of the disclosure， there is provided an apparatus for facilitating communications in a wireless network comprising first tracking areas in which communications can be established with a core network via a first radio access technology and second tracking areas in which communications can be established with the core network via a second radio access technology. The apparatus comprises a processor and a memory. The memory containing instructions executable by the processor， whereby the apparatus is operative to perform the method according to the first， second， or third aspect.

In an eighth aspect of the disclosure， there is provided an apparatus for facilitating communications in a wireless network comprising first tracking areas in which can be established with a core network via a first radio access technology and second tracking areas in which communications can be established with the core network via a second radio access technology. The apparatus comprises processing means adapted to perform the method according to according to the first， second， or third aspect.

According to the various aspects and embodiments as mentioned above， an efficient solution is provided for facilitating communications in a network integrating multiple different RATs， e.g. 5G networks. According to this solution， it is not necessary for a terminal device to camp on two or more RATs in order to get better service performance， for example. Instead， the terminal device that camps on only one RAT may also acquire TA information related to another RAT so that the terminal device may have a possibility to receive paging messages and data traffic via the other RAT or more RATs， thereby possibly getting better service performance without handover between the RATs. Therefore， the tracking area update signaling messages due to the handover may be less than the normal case that the terminal device camps on one RAT and can receive paging messages via this RAT only. Since the terminal device only camps on one RAT， it needs to do the attach procedure or TA update procedure for this RAT only. Therefore， the signaling overhead during these procedures may be less than the case that the terminal device camps on more RATs and has to carry out these procedures for all RATs.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects， features， and benefits of various embodiments of the present disclosure will become more fully apparent， by way of example， from the following detailed description with reference to the accompanying drawings， in which like reference numerals or letters are used to designate like or equivalent elements：

FIG. 1 shows an example of a functional split of an eNB in LTE；

FIG. 2 shows an exemplary network architecture comprising an eNB split into two parts；

FIG. 3 shows an exemplary network architecture enabling dual connectivity using the existing split solution；

FIG. 4 shows an exemplary network architecture comprising a common node supporting two different RATs and two RAT-specific nodes；

FIGs. 5 and 6 illustrate a TAI List concept in LTE；

FIG. 7 shows an example of ISR activation；

FIG. 8 illustrates example architecture of a NX and LTE integrated network into which embodiments of the present disclosure may be applied；

FIG. 9 illustrates a flowchart of a method at a terminal device according to embodiments of the present disclosure for facilitating communications in a wireless network integrating a first radio access technology and a second radio access technology；

FIG. 10 illustrates a flowchart of a method in a core network according to embodiments of the present disclosure for facilitating communications in a wireless network integrating a first radio access technology and a second radio access technology；

FIG. 11 illustrates a flowchart of a method at a base station according to an embodiment of the present disclosure for facilitating communications in a wireless network integrating a first radio access technology and a second radio access technology；

FIG. 12 illustrates a schematic block diagram of an apparatus according to some embodiments of the present disclosure for facilitating communications in a wireless network integrating a first radio access technology and a second radio access technology；

FIG. 13 illustrates a schematic block diagram of another apparatus according to some other embodiments of the present disclosure for facilitating communications in a wireless network integrating a first radio access technology and a second radio access technology；

FIG. 14 illustrates a schematic block diagram of another apparatus according to some other embodiments of the present disclosure for facilitating communications in a wireless network integrating a first radio access technology and a second radio access technology； and

FIG. 15 illustrates a schematic block diagram of another apparatus according to some other embodiments of the present disclosure for facilitating communications in a wireless network integrating a first radio access technology and a second radio access technology.

DETAILED DESCRIPTION

Hereinafter， the principle and spirit of the present disclosure will be described with reference to illustrative embodiments. It should be understood， all these embodiments are given merely for one skilled in the art to better understand and further practice the present disclosure， but not for limiting the scope of the present disclosure. For example， features illustrated or described as part of one embodiment may be used with another embodiment to yield still a further embodiment. In the interest of clarity， not all features of an actual implementation are described in this specification.

References in the specification to “an embodiment， ” “another embodiment， ” “a further embodiment， ” etc. indicate that the embodiment described may include a particular feature， structure， or characteristic， but every embodiment may not necessarily include the particular feature， structure， or characteristic. Further， when a particular feature， structure， or characteristic is described in connection with an embodiment， it is submitted that it is within the knowledge of one skilled in the art to affect such feature， structure， or characteristic in connection with other embodiments whether or not explicitly described.

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

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the 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” and the like， 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.

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. For example， the term “base station” (BS) ， used herein may be referred to as e.g. eNB， eNodeB， NodeB or base transceiver station (BTS) etc. depending on the technology and terminology used. Likewise， the term “terminal device” used herein may refer to a UE or any terminal having wireless communications capabilities， including but not limited to， mobile phones， cellular phones， smart phones， or personal digital assistants (PDAs) ， portable computers， image capture devices such as digital cameras， gaming devices， music storage and playback appliances and the like. The term “tracking area” or “TA” may refer to a minimum area that can be identified by a core network and in which a terminal device can freely move and communicate with the core network without a need for tracking area update. This term may be referred to as e.g. “routing area” or “RA” or “location area” or “LA” etc. depending on the technology and terminology used. In the following description， the terms “user equipment” or “UE” and “terminal device” may be used interchangeably. The terms “base station” and “eNB” may be used interchangeably.

For illustrative purposes， the concept and principle of several embodiments of the present disclosure will be described in the context of 5G networks as an example of tight integration of two different RATs， i.e. LTE and NX. Those skilled in the art will appreciate， however， that the concept and principle of the several embodiments of the present disclosure may be more generally applicable to any network in which multiple different RATs are integrated.

The LTE TAI list concept may also be applied for TA handling between LTE and NX radio access within 5G. This would require that the LTE TA/TAI/TAU concept is applied directly on NX. However， since LTE and NX are considered as different RATs， current researchers intend to design a different TA solution in NX compared to LTE. For example， The TA in NX may be identified by TACS (Tracking area code signature) which is a physical signature； and the TAI list in NX may be signaled in a different format etc. . Therefore， direct application of LTE TA solution into NX may not be feasible.

The ISR concept described in the Background section is used for signaling reduction between different RATs and could in principle be also applied for the idle mode mobility between LTE and NX. However， the ISR is based on different control plane core network nodes (i.e. SGSN and MME respectively) . When it comes to LTE and NX， a common core network node is instead assumed (for example an evolved MME) and therefore the ISR solution doesn’t apply in this context.

In order to solve at least some of the above and those mentioned problems in the Background section， embodiments of the present disclosure provide a novel solution for facilitating communications in a network that integrates multiple different RATs， e.g. LTE and NX in 5G networks， which will be detailed with reference to FIGs. 8-15.

FIG. 8 illustrates example architecture of a NX and LTE integrated network into which embodiments of the present disclosure may be applied. In this architecture， a base station is split into a common part shared by the NX and LTE and two independent parts. The common part of the base station is represented as 5G & LTE eNB-a； and the two independent parts are represented as LTE eNB-s1 and 5G eNB-s2 in FIG. 8. The common part 5G & LTE eNB-a may handle the synchronous functions having requirements on processing timing which are strictly dependent on timing of a radio link used for communicating with a UE， while the first independent part LTE eNB-s1 may handle the asynchronous functions associated with the first radio access technology and having requirements on processing timing not strictly dependent on the timing of the radio link， or even independent on the timing of the radio link and the second independent part 5G eNB-s2 may handle the asynchronous functions associated with the second radio access technology and having requirements on processing timing not strictly dependent on the timing of the radio link， or even independent on the timing of the radio link. The common part and the two independent parts may be embodied as physically separate network entities or nodes. The particular approaches for splitting the base station may follow the existing solutions as disclosed in PCT application No. PCT/SE2015/050166 and PCT application No. PCT/SE2015/050173 and thus will not be detailed herein for the sake of brevity.

For this NX and LTE integrated network， a common core is used. FIG. 8 exemplarily shows the common core as a management entity “MME” for the control plane of the common core network. The common core can know the deployment of both a radio access network using NX and another radio access network using LTE via the Operation and Management (O&M) system.

According to embodiments of the present disclosure， the common core， e.g. MME， may establish a mapping table of TAs for LTE and NX. In this mapping table， the NX TAs that have an inclusion relationship with the LTE TAs are listed. The inclusion relationship means that an NX TA is completely included in a LTE TA or vice versa， or the NX TA exactly overlaps with the LTE TA. This inclusion relationship will be referred to as a mapping relationship in the following description， which however only comprises exact overlapping relationship and uni-directional inclusion relationship， i.e. a TA of a RAT on which a UE is currently camping is completely included in another TA of a RAT that the UE is not camping. The term “camp on a RAT” used herein means that a UE can monitor system information and (in most cases) paging information via this RAT. It is assumed that LTE and NX use different area identifiers for the idle mode mobility management. LTE may continue using the LTE Tracking Area Concept and NX may use a new NX Tracking Area Concept. The identifiers used for NX TAs may follow the format used for LTE TAs， or may be based on a new format， as long as the NX TAIs may differentiate NX TAs from LTE TAs.

For a UE in the NX and LTE integrated network， in order to reduce the signaling overhead， the UE may only camp on a cell of a RAN using one RAT (which will be referred to as “camped RAT” ) ， either LTE or NX， and listen to system information and paging messages from this RAN so as to obtain TA information therefrom. The UE may send a TA update request message to the core network if necessary. When the RAN forwards the TA update request to the core network， an indication of the current TA identifier is also included， i.e. an LTE TAI or NX TAI， together with the current serving cell ID.

When the core network， e.g. MME， receives the TA update request message from the RAN using the camped RAT， it may know the area where UE is located in this RAN based on the indication from the RAN. Moreover， according to the TA mapping table， the core network can derive the TAIs for the UE in a RAN using another RAT (which will be referred to as “non-camped RAT” ) . In order to let the UE know its TA information in the RAN using the non-camped RAT as well， the core network may include the TA information of both RATs in the TA update accept message. The TAI information of a RAT may indicate the TAs available for the UE in which the UE can freely move and be paged without a need for TAU. In one example， the TA update accept message may contain a TA List information element that may comprise multiple LTE TAIs and multiple NX TAIs.

When the UE receives the TA update accept message from the core network， it may know the TAs corresponding to the non-camped RAT although it does not listen to the broadcast TA information from the RAN using this RAT.

Alternatively， the core network may include the TA information of both RATs in the Attach accept message during the Attach procedure initially started by the UE. In an example， the core network may not directly include the TA information of the non-camped RAT in the Attach accept message， instead including the TA mapping table in it. In this example， once the UE receives the Attach accept message， it may acquire the TA information of the camped RAT from the message first and then acquire the TA information of the non-camped on RAT from the mapping table according to the TA information of the camped RAT.

With the TA information ready， the UE may be prepared to receive the paging message from any of the RATs， for example performing measurement on a reference signal of the corresponding RAT.

When the core network wants to send a paging message toward the UE， it may decide which RAT should be used to send the paging message. The core network may include indication information comprising RAT preference that indicates paging via NX， paging via LTE or paging via both RATs， in the paging message to a common RAN node， i.e. the common part of the base station， 5G&LTE eNB-a as shown in FIG. 8.

The common RAN node may then send the paging message to the UE via the corresponding RAT indicated by the indication information included in the paging message. For example， if the paging message will be sent via LTE as indicated， the common RAN node 5G&LTE eNB-a may forward the paging information to the independent part of the base station， LTE eNB-s1， through which the paging message will be transmitted to the UE； while if the paging message will be sent via NX as indicated， the common RAN node 5G&LTE eNB-a may forward the paging information to the independent part of the base station， 5G eNB-s2， through which the paging message will be transmitted to the UE.

Alternatively， the core network may include some other indication information in the paging message. The common RAN node itself may determine based on the indication information that the paging message shall be transmitted via which RAT. The indication information may comprise： a latency requirement preference for the paging， service requirements related to the downlink traffic that triggered the paging， or information regarding ongoing services for the UE， or subscription based information for the UE that is being paged. Once the common RAN node determines the RAT for transmission of the paging message， it will forward the paging message to the corresponding independent part， e.g. LTE eNB-s1 or 5G eNB-s2 or both.

FIG. 9 illustrates a flowchart of a method 900 according to embodiments of the present disclosure， for facilitating communications in a wireless network comprising first tracking areas in which communications can be established with a core network via a first radio access technology， e.g. LTE， and second tracking areas in which communications can be established with the core network via a second radio access technology， e.g. NX. The method 900 is performed at a terminal device located in one of the first tracking areas.

The method 900 enters at block 910， in which a message is received at the terminal device from the core network via the first radio access technology when the terminal device is located in one of the first tracking areas. Then at block 920， the terminal device acquires， from the received message， first tracking area information indicating at least one of the first tracking areas available for the terminal device and second tracking area information indicating at least one of the second tracking areas available for the terminal device. The at least one of the first tracking areas available for the terminal device used herein refers to at least one first tracking area in which the terminal device can freely move and be paged via the first radio access technology without a need for tracking area update. The at least one of the second tracking areas available for the terminal device used herein refers to at least one second tracking area in which the terminal device can freely move and be paged via the second radio access technology without a need for tracking area update.

According to the first and second tracking area information， the terminal device may prepare for receiving a paging message from the core network via either or both of the first and second radio access technologies， for example performing measurement on reference signals over the corresponding RAT and then may receive the paging message from the core network via the corresponding RAT.

As discussed with reference to FIG. 8， the core network may establish a mapping table to indicate a mapping relationship between the first and the second tracking areas. Accordingly， the core network may acquire information directly indicating the at least one second tracking areas available for the terminal device from the mapping table according to the first tracking area information. This direct information is a form of the second tracking area information. Another form of the second tracking area information is indirect information indicating a mapping relationship between the at least one first tracking area and the at least one second tracking area， which may be regarded as information indirectly indicating the at least one second tracking area available for the terminal device. This indirect information may be a portion of the mapping table corresponding to the at least one second tracking area available for the terminal device. In an embodiment， the message from the core network may include the first tracking area information and the indirect information indicating the mapping relationship. Upon reception of the message， the terminal device may acquire the second tracking area information from the mapping relationship according to the first tracking area information.

In another embodiment， the message may be received during a tracking area update procedure initiated by the terminal device either periodically or due to movement of the terminal device. For example， the message may be a tracking area update accept message received from the core network in response to sending by the terminal device a tracking area update request message to the core network.

In another embodiment， the message may be received during a attach procedure when the terminal device initially attaches to the core network. For example， the message may be an attach accept message received from the core network in response to sending by the terminal device an attach request message to the core network.

According to this method， it is not necessary for a terminal device to camp on two or more RATs in order to get better service performance， for example. Instead， the terminal device that camps on only one RAT may also acquire TA information related to another RAT so that the terminal device may have a possibility to receive paging messages and data traffic via more RATs， thus possibly getting better service performance. Further， since the terminal device only camps on one RAT， it needs to do the attach procedure or TA update procedure for this RAT only. Therefore， the signaling overhead during these procedures may be less than the case that the terminal device camps on more RATs and has to carry out these procedures for all RATs.

FIG. 10 illustrates a flowchart of a method 1000 according to embodiments of the present disclosure for facilitating communications in a wireless network comprising first tracking areas in which communications can be established with a core network via a first radio access technology， e.g. LTE， and second tracking areas in which communications can be established with the core network via a second radio access technology， e.g. NX. The method 1000 is performed in a core network， e.g. at a MME.

The method 1000 enters at block 1010， in which a message including first tracking area information indicating at least one of the first tracking areas available for a terminal device located in one of the first tracking areas and second tracking area information indicating at least one of the second tracking areas available for the terminal device is generated. Then， at block 1020， the message is sent to the terminal device for reception by the terminal device via the first radio access technology.

As discussed above， when a terminal device is located in a tracking area of a RAT， e.g. one first tracking area， it may report its current location to the core network when it requests attach to the core network or requests TA update. Then， the core network may acquire the first tracking area information according to the current location that the terminal device is located. In an embodiment， a mapping relationship between the first tracking areas and the second tracking areas may be established first in the core network， e.g. at the MME， at block 1002. Then， the second tracking area information may be obtained at block 1004 from the mapping relationship according to the first tracking area information. In this sense， information indicating the mapping relationship may be regarded as a form of the second tracking area information， which indirectly indicates the at least one of the second tracking areas available for the terminal device. The mapping relationship may be presented in the form of a mapping table.

In an embodiment， therefore， the message from the core network may include the first tracking area information and information indicating at least part of the mapping relationship. For example， the information indicating the whole mapping relationship may be included in the message or the information indicating a portion of the mapping relationship corresponding to the at least one second tracking area may be included in the message. Upon reception of the message， the terminal device may acquire the second tracking area information from the mapping relationship according to the first tracking area information.

In an embodiment， the message may be generated during a tracking area update procedure initiated by the terminal device either periodically or due to movement of the terminal device. For example， the message may be a tracking area update accept message generated in response to reception of a tracking area update request message from the terminal device.

In another embodiment， the message may be generated during an attach procedure e.g. when the terminal first attaches to the core network. For example， the message may be an attach accept message generated in response to reception of an attach request message from the terminal device.

Subsequently， the core network may send a paging message at block 1006 towards the terminal device. In an embodiment， the paging message may include information indicating a RAT preference， i.e. whether the paging message is to be transmitted via the first radio access technology or the second radio access technology or via both. In another embodiment， the paging message may comprise indication information that may assist a common RAN node， e.g. 5G&LTE eNB-a of FIG. 8， to determine which RAT shall be selected for transmitting the paging message. The indication information may comprise any of the following： a latency requirement preference for the paging， service requirements related to the downlink traffic that triggered the paging， or information regarding ongoing services for the UE or subscription based information for the UE that is being paged， e.g whether the UE is a normal UE or a VIP UE.

According to this method 1000， the core network may provide TA information for more than one RAT to the terminal device that even though camps on only one RAT. Thus， the terminal device that camps on only one RAT may also acquire TA information related to another RAT so that the terminal device may have a possibility to receive paging messages and data traffic via more RATs， thereby possibly getting better service performance. Further， since the terminal device only camps on one RAT， it needs to do the attach procedure or TA update procedure for this RAT only. Therefore， the signaling overhead during these procedures may be less than the case that the terminal device camps on more RATs and has to carry out these procedures for all RATs.

FIG. 11 illustrates a flowchart of a method 1100 according to an embodiment of the present disclosure for facilitating communications in a wireless network comprising first tracking areas in which communications can be established with a core network via a first radio access technology， e.g. LTE， and second tracking areas in which communications can be established with the core network via a second radio access technology， e.g. NX. The method 1100 is performed at a base station.

The base station may be split according to various functions， e.g. synchronous functions and asynchronous functions， and comprise： a common part shared by the first radio access technology and the second radio access technology， a first part associated with the first radio access technology and a second part associated with a second radio access technology. The common part may handle the synchronous functions having requirements on processing timing which are strictly dependent on timing of a radio link used for communicating with the terminal device， while the first part may handle the asynchronous functions associated with the first radio access technology and having requirements on processing timing not strictly dependent on the timing of the radio link， or even independent on the timing of the radio link and the second part may handle the asynchronous functions associated with the second radio access technology and having requirements on processing timing not strictly dependent on the timing of the radio link， or even independent on the timing of the radio link. The particular approaches for splitting the base station may follow the existing solutions as disclosed in PCT application No. PCT/SE2015/050166 and PCT application No. PCT/SE2015/050173 and thus will not be detailed herein for the sake of brevity.

The method 1100 enters at block 1110， in which a message is received from the core network at the common part of the base station. Then at block 1120， the common part of the base station determines via which of the first part and the second part of the base station the message will be transmitted. Once it is determined， the common part will transmit the message via the determined corresponding part of the base station towards the terminal device. In some embodiments， the message may be a paging message from the core network.

In an embodiment that the message from the core network includes information indicating a RAT preference， i.e. whether the message is to be transmitted via the first radio access technology or the second radio access technology or both. The common part of the base station may directly determine based on this information which RAT (s) will be used for transmitting the message.

In another embodiment that the message from the core network includes indication information that may assist the common part to determine which RAT shall be selected for transmitting the message， the common part may determine based on this information via which of the first radio access technology and the second radio access technology to transmit the message. The indication information may comprise any of the following： a latency requirement preference for the paging， service requirements related to the downlink traffic that triggered the paging， or information regarding ongoing services for the terminal device or subscription based information for the terminal device that is being paged.

According to this method 1100， the base station may determine via which radio access technology (technologies) to transmit the message from the core network， e.g. a paging message， to the terminal device that camps on only one RAT. In this case， although the terminal device only camps on one RAT， it can have a possibility to receive paging messages and data traffic via more RATs， thereby possibly getting better service performance without handover between the RATs. Therefore， the signaling overhead during tracking area update procedures for the handover may be less than the case that the terminal device camps on one RAT and can receive messages via this RAT only.

FIG. 12 illustrates a schematic block diagram of an apparatus 1200 for facilitating communications in a wireless network comprising first tracking areas in which communications can be established with a core network via a first radio access technology， e.g. LTE， and second tracking areas in which communications can be established with the core network via a second radio access technology， e.g. NX. The apparatus 1200 may be embodied as a terminal device or a part thereof， or an apparatus independent of the terminal device.

Particularly， the apparatus 1200 comprises a receiving unit 1210 and an acquiring unit 1220. The receiving unit 1210 is configured to receive a message from the core network via the first radio access technology when the terminal device is located in one of the first tracking areas. The acquiring unit 1220 is configured to acquire， from the received message， first tracking area information indicating at least one of the first tracking areas available for the terminal device and second tracking area information indicating at least one of the second tracking areas available for the terminal device.

In an embodiment， the receiving unit 1210 may be further configured to receive a paging message via any of the first and second radio access technology based on the first and second tracking area information.

In an embodiment， the received message may comprise the first tracking area information and information indicating a mapping relationship between the at least one of the first tracking areas and the at least one of the second tracking areas. The acquiring unit may be configured to acquire the second tracking area information from the mapping relationship according to the first tracking area information.

In an embodiment， the message may be a tracking area update accept message received from the core network in response to sending a tracking area update request message to the core network.

In another embodiment， the message may be an attach accept message received from the core network in response to sending an attach request message to the core network.

The above units 1210-1220 may be configured to implement corresponding operations or steps of method 900 as described with reference to FIG. 9 and thus will not be detailed herein for the conciseness purpose.

FIG. 13 illustrates a schematic block diagram of an apparatus 1300 for facilitating communications in a wireless network comprising first tracking areas in which communications can be established with a core network via a first radio access technology， e.g. LTE， and second tracking areas in which communications can be established with the core network via a second radio access technology， e.g. NX. The apparatus 1300 may be embodied as an MME， a part thereof or an apparatus independent the MME.

Particularly， the apparatus 1300 comprises a generating unit 1310 and a sending unit 1320. The generating unit 1310 is configured to generate a message including first tracking area information indicating at least one of the first tracking areas available for a terminal device located in one of the first tracking areas and second tracking area information indicating at least one of the second tracking areas available for the terminal device. The sending unit 1320 is configured to send the message to the terminal device for reception by the terminal device via the first radio access technology.

In an embodiment， the apparatus 1300 may further comprise an establishing unit 1330 configured to establish a mapping relationship between the first tracking areas and the second tracking areas and an obtaining unit 1340 configured to obtain the second tracking area information from the mapping relationship according to the first tracking area information.

In an embodiment， the second tracking area information may comprise information indicating at least part of the mapping relationship.

In an embodiment， the message generated by the generating unit may be a tracking area update accept message generated in response to reception of a tracking area update request message from the terminal device or an attach accept message generated in response to reception of an attach request message from the terminal device.

In an embodiment， the sending unit 1320 may be further configured to send a paging message that includes information indicating which of the first radio access technology and the second radio access technology will be used to transmit the paging message to the terminal device.

In another embodiment， the sending unit 1320 may be further configured to send a paging message that includes information indicating any of the following： a latency requirement preference for paging， service requirements related to downlink traffic that triggered the paging， or information regarding ongoing services for the terminal or subscription based information for the terminal device that is being paged.

The above units 1310-1340 may be configured to implement corresponding operations or steps of method 1000 as described with reference to FIG. 10 and thus will not be detailed herein for the conciseness purpose.

FIG. 14 illustrates a schematic block diagram of an apparatus 1400 for facilitating communications in a wireless network comprising first tracking areas in which communications can be established with a core network via a first radio access technology， particularly via a first part of a base station associated with the first radio access technology， and second tracking areas in which communications can be established with the core network via a second radio access technology， particularly via a second part of a base station associated with the second radio access technology. The apparatus 1400 may be embodied as a common part of the base station shared by the first and second radio access technology， or a part thereof.

Particularly， the apparatus 1400 comprises a receiving unit 1410， a determining unit 1420， and a transmitting unit 1430. The receiving unit 1410 is configured to receive a message from the core network at a common part of the base station shared by the first and second radio access technology. The determining unit 1420 is configured to determine which of the first part and the second part of the base station will be used for transmitting the message. The transmitting unit 1430 is configured to transmit the message via the determined corresponding part of the base station towards the terminal device.

In an embodiment， the determining unit 1420 may be further configured to determine which of the first part and the second part will be used for transmitting the message based on information included in the message indicating which of the first radio access technology and the second radio access technology will be used for transmitting the message.

In another embodiment， the determining unit 1420 may be further configured to determine which of the first part and the second part will be used for transmitting the message based on information included in the message indicating any of the following： a latency requirement preference for paging， service requirements related to downlink traffic that triggered the paging， or information regarding ongoing services for the terminal or subscription based information for the terminal device that is being paged.

The

above units

1410 and 1420 may be configured to implement corresponding operations or steps of method 1100 as described with reference to FIG. 11 and thus will not be detailed herein for the conciseness purpose.

FIG. 15 illustrates a schematic block diagram of an apparatus 1500 for facilitating communications in a wireless network comprising first tracking areas in which communications can be established with a core network via a first radio access technology， e.g. LTE， and second tracking areas in which communications can be established with the core network via a second radio access technology， e.g. NX.

Particularly， the apparatus 1500 comprises at least one processor 1510， such as a data processor (DP) and at least one memory (MEM) 1520 coupled to the processor 1510. The apparatus 1500 may further comprise a transmitter TX and receiver RX 1530 coupled to the processor 1510 for establishing communications with other apparatuses. The MEM 1520 stores a program (PROG) 1540. A combination of the at least one processor 1510 and the at least one MEM 1520 may form processing means 1550.

The apparatus 1500 may be embodied as a terminal device， a part thereof， or an independent apparatus. In an embodiment， the PROG 1540 may include instructions that， when executed on the associated processor 1510， enable the apparatus 1500 to operate in accordance with the embodiments of the present disclosure as described above with reference to FIG. 9， for example to perform method 900. In another embodiment， the processing means 1550 may be adapted to implement the embodiments of the present disclosure as described above with reference to FIG. 9.

The apparatus 1500 may be embodied as an MME， a part thereof， or an independent apparatus operating in the core network. In an embodiment， the PROG 1540 may include instructions that， when executed on the associated processor 1510， enable the apparatus 1500 to operate in accordance with the embodiments of the present disclosure as described above with reference to FIG. 10， for example to perform method 1000. In another embodiment， the processing means 1550 may be adapted to implement the embodiments of the present disclosure as described above with reference to FIG. 10.

The apparatus 1500 may be embodied as a common part of a base station that is shared by the first and second radio access technology， or a part thereof. In an embodiment， the PROG 1540 may include instructions that， when executed on the associated processor 1510， enable the apparatus 1500 to operate in accordance with the embodiments of the present disclosure as described above with reference to Fig. 11， for example to perform method 1100. In another embodiment， the processing means 1550 may be adapted to implement the embodiments of the present disclosure as described above with reference to FIG. 11.

The MEM 1520 may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology， such as semiconductor based memory devices， magnetic memory devices and systems， optical memory devices and systems， fixed memory and removable memory， as non-limiting examples.

The processor 1510 may be of any type suitable to the local technical environment， and may include one or more of general purpose computers， special purpose computers， microprocessors， digital signal processors (DSPs) and processors based on multicore processor architecture， as non-limiting examples.

In addition， the present disclosure may also provide a carrier containing the computer program as mentioned above， wherein the carrier is one of an electronic signal， optical signal， radio signal， or computer readable storage medium. The computer readable storage medium can be， for example， an optical compact disk or an electronic memory device like a RAM (random access memory) ， a ROM (read only memory) ， Flash memory， magnetic tape， CD-ROM， DVD， Blue-ray disc and the like.

The techniques described herein may be implemented by various means so that an apparatus implementing one or more functions of a corresponding apparatus described with an embodiment comprises not only prior art means， but also means for implementing the one or more functions of the corresponding apparatus described with the embodiment and it may comprise separate means for each separate function， or means that may be configured to perform two or more functions. For example， these techniques may be implemented in hardware (one or more apparatuses) ， firmware (one or more apparatuses) ， software (one or more modules) ， or combinations thereof. For a firmware or software， implementation may be made through modules (e.g.， procedures， functions， and so on) that perform the functions described herein.

Exemplary embodiments herein have been described above with reference to block diagrams and flowchart illustrations of methods and apparatuses. It will be understood that each block of the block diagrams and flowchart illustrations， and combinations of blocks in the block diagrams and flowchart illustrations， respectively， can be implemented by various means including computer program instructions. These computer program instructions may be loaded onto a general purpose computer， special purpose computer， or other programmable data processing apparatus to produce a machine， such that the instructions which execute on the computer or other programmable data processing apparatus create means for implementing the functions specified in the flowchart block or blocks.

While this specification contains many specific implementation details， these should not be construed as limitations on the scope of any implementation or of what may be claimed， but rather as descriptions of features that may be specific to particular embodiments of particular implementations. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely， various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable sub-combination. Moreover， although features may be described above as acting in certain combinations and even initially claimed as such， one or more features from a claimed combination can in some cases be excised from the combination， and the claimed combination may be directed to a sub-combination or variation of a sub-combination.

It will be obvious to a person skilled in the art that， as the technology advances， the inventive concept can be implemented in various ways. The above described embodiments are given for describing rather than limiting the disclosure， and it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the disclosure as those skilled in the art readily understand. Such modifications and variations are considered to be within the scope of the disclosure and the appended claims. The protection scope of the disclosure is defined by the accompanying claims.

Claims

A method (900) at a terminal device for facilitating communications in a wireless network comprising first tracking areas in which communications can be established with a core network via a first radio access technology and second tracking areas in which communications can be established with the core network via a second radio access technology， comprising：

receiving (910) a message from the core network via the first radio access technology when the terminal device is located in one of the first tracking areas； and

acquiring (920) ， from the received message， first tracking area information indicating at least one of the first tracking areas available for the terminal device and second tracking area information indicating at least one of the second tracking areas available for the terminal device.
The method according to Claim 1， further comprising：

receiving (930) a paging message via any of the first and second radio access technology based on the first and second tracking area information.
The method according to Claim 1 or 2， wherein

said message comprises the first tracking area information and information indicating a mapping relationship between the at least one of the first tracking areas and the at least one of the second tracking areas； and

the second tracking area information is acquired from the mapping relationship according to the first tracking area information.
The method according to any of Claims 1-3， wherein

said message comprises a tracking area update accept message received from the core network in response to sending a tracking area update request message to the core network.
The method according to any of Claims 1-4， wherein

said message comprises an attach accept message received from the core network in response to sending an attach request message to the core network.
A method (1000) in a core network for facilitating communications in a wireless network comprising first tracking areas in which communications can be established with the core network via a first radio access technology and second tracking areas in which communications can be established with the core network via a second radio access technology， comprising：

generating (1010) a message including first tracking area information indicating at least one of the first tracking areas available for a terminal device located in one of the first tracking areas and second tracking area information indicating at least one of the second tracking areas available for the terminal device； and

sending (1020) the message to the terminal device for reception by the terminal device via the first radio access technology.
The method according to Claim 6， further comprising before generating the message：

establishing (1002) a mapping relationship between the first tracking areas and the second tracking areas； and

obtaining (1004) the second tracking area information from the mapping relationship according to the first tracking area information.
The method according to Claim 7， wherein

the second tracking area information comprises information indicating at least part of the mapping relationship.
The method according to any of Claims 6-8， wherein generating the message comprises：

generating a tracking area update accept message in response to reception of a tracking area update request message from the terminal device； or

generating an attach accept message in response to reception of an attach request message from the terminal device.
The method according to any of Claims 6-9， further comprising：

sending (1006) a paging message that includes information indicating which of the first radio access technology and the second radio access technology will be used for transmitting the paging message.
The method according to any of Claims 6-9， further comprising：

sending (1006) a paging message that includes information indicating any of the following： a latency requirement preference for paging， service requirements related to downlink traffic that triggered the paging， or information regarding ongoing services for the terminal or subscription based information for the terminal device that is being paged.
A method (1100) at a base station for facilitating communications in a wireless network comprising first tracking areas in which communications can be established with a core network via a first part of the base station associated with a first radio access technology and second tracking areas in which communications can be established with the core network via a second part of the base station associated with a second radio access technology， comprising：

receiving (1110) a message from the core network at a common part of the base station shared by the first and second radio access technology；

determining (1120) which of the first part and the second part of the base station will be used for transmitting the message； and

transmitting (1130) the message via the determined corresponding part of the base station towards the terminal device.
The method according to Claim 12， wherein

the determining is based on information included in the message indicating which of the first radio access technology and the second radio access technology will be used for transmitting the message.
The method according to Claim 12， wherein

the determining is based on information included in the message indicating any of the following： a latency requirement preference for paging， service requirements related to downlink traffic that triggered the paging， or information regarding ongoing services for the terminal or subscription based information for the terminal device that is being paged.
An apparatus (1200) at a terminal device for facilitating communications in a wireless network comprising first tracking areas in which communications can be established with a core network via a first radio access technology and second tracking areas in which communications can be established with the core network via a second radio access technology， comprising：

a receiving unit (1210) configured to receive a message from the core network via the first radio access technology when the terminal device is located in one of the first tracking areas； and

an acquiring unit (1220) configured to acquire， from the received message， first tracking area information indicating at least one of the first tracking areas available for the terminal device and second tracking area information indicating at least one of the second tracking areas available for the terminal device.
The apparatus according to Claim 15， wherein

the receiving unit (1210) is further configured to receive a paging message via any of the first and second radio access technology based on the first and second tracking area information.
The apparatus according to Claim 15 or 16， wherein

said message comprises the first tracking area information and information indicating a mapping relationship between the at least one of the first tracking areas and the at least one of the second tracking areas； and

the acquiring unit is configured to acquire the second tracking area information from the mapping relationship according to the first tracking area information.
The apparatus according to any of Claims 15-17， wherein

said message comprises a tracking area update accept message received from the core network in response to sending a tracking area update request message to the core network.
The apparatus according to any of Claims 15-18， wherein

said message comprises an attach accept message received from the core network in response to sending an attach request message to the core network.
An apparatus (1300) in a core network for facilitating communications in a wireless network comprising first tracking areas in which communications can be established with a core network via a first radio access technology and second tracking areas in which communications can be established with the core network via a second radio access technology， comprising：

a generating unit (1310) configured to generate a message including first tracking area information indicating at least one of the first tracking areas available for a terminal device located in one of the first tracking areas and second tracking area information indicating at least one of the second tracking areas available for the terminal device； and

a sending unit (1320) configured to send the message to the terminal device for reception by the terminal device via the first radio access technology.
The apparatus according to Claim 20， further comprising：

an establishing unit (1330) configured to establish a mapping relationship between the first tracking areas and the second tracking areas； and

an obtaining unit (1340) configured to obtain the second tracking area information from the mapping relationship according to the first tracking area information.
The apparatus according to Claim 21， wherein

the second tracking area information comprises information indicating at least part of the mapping relationship.
The apparatus according to any of Claims 20-22， wherein the message generated by the generating unit comprises：

a tracking area update accept message generated in response to reception of a tracking area update request message from the terminal device； or

an attach accept message generated in response to reception of an attach request message from the terminal device.
The apparatus according to any of Claims 20-23， wherein

the sending unit is further configured to send a paging message that includes information indicating which of the first radio access technology and the second radio access technology will be used for transmitting the paging message to the terminal device.
The apparatus according to any of Claims 20-23， wherein

the sending unit is further configured to send a paging message that includes infomation indicating any of the following： a latency requirement preference for paging， service requirements related to downlink traffic that triggered the paging， or information regarding ongoing services for the terminal or subscription based information for the terminal device that is being paged.
An apparatus (1400) at a base station for facilitating communications in a wireless network comprising first tracking areas in which communications can be established with a core network via a first part of the base station associated with a first radio access technology and second tracking areas in which communications can be established with the core network via a second part of the base station associated with a second radio access technology， comprising：

a receiving unit (1410) configured to receive a message from the core network at a common part of the base station shared by the first and second radio access technology；

a determining unit (1420) configured to determine which of the first part and the second part of the base station will be used for transmitting the message； and

a transmitting unit (1430) configured to transmit the message via the determined corresponding part of the base station towards the terminal device.
The apparatus according to Claim 26， wherein

the determining unit is further configured to determine which of the first part and the second part will be used for transmitting the message based on information included in the message indicating which of the first radio access technology and the second radio access technology will be used for transmitting the message.
The apparatus according to Claim 26， wherein

the determining unit is further configured to determine which of the first part and the second part will be used for transmitting the message based on information included in the message indicating any of the following： a latency requirement preference for paging， service requirements related to downlink traffic that triggered the paging， or information regarding ongoing services for the terminal or subscription based information for the terminal device that is being paged.
An apparatus (1500) for facilitating communications in a wireless network comprising first tracking areas in which communications can be established with a core network via a first radio access technology and second tracking areas in which communications can be established with the core network via a second radio access technology， the apparatus comprising a processor (1510) and a memory (1520) ， said memory containing instructions executable by said processor， whereby said apparatus is operative to perform the method according to any of Claims 1-5， any of Claims 6-11 or any of Claims 12-14.
An apparatus (1500) for facilitating communications in a wireless network comprising first tracking areas in which can be established with a core network via a first radio access technology and second tracking areas in which communications can be established with the core network via a second radio access technology， the apparatus comprising processing means (1550) adapted to perform the method according to any of Claims 1-5， any of Claims 6-11 or any of Claims 12-14.