WO2008146868A1

WO2008146868A1 - Signalling management in cellular mobile radio communications network

Info

Publication number: WO2008146868A1
Application number: PCT/JP2008/059859
Authority: WO
Inventors: Julie Teasdale; Iskren Ianev
Original assignee: Nec Corporation
Priority date: 2007-05-24
Filing date: 2008-05-22
Publication date: 2008-12-04
Also published as: GB2452691A; GB0709968D0

Abstract

A method of managing multi-cell signalling areas within a cellular mobile radio communications network. It comprises: determining if a mobile radio communications device is stationary within a first said signalling area, and assigning the said mobile radio communications device to a temporary signalling area responsive to a determination that the mobile radio communications device is stationary. The number of cells in the temporary signalling area may be less than the number within the first multi-cell signalling area. Particularly the temporary signalling area may comprise a single-cell Tracking Area.

Description

DES CRIPTION

SIGNALLING MANAGEMENT IN CELLULAR MOBILE RADIO

COMMUNICATIONS NETWORK

FIELD OF THE INVENTION

(REFERENCE TO RELATED APPLICATION)

The present application is claiming the priority o f the earlier GB patent application No . 0709968.2 filed on 24 May 2007 the entire disclo sure thereof being incorporated herein by reference thereto .

The present invention relates to a method for managing multi-cell signalling areas within a cellular mobile radio communications network. BACKGROUND In addition to the actual communications signals received at, and transmitted from, a mobile radio communications device such as a cellular phone handset, additional network signalling also arises in relation to call-management and, for example, in relation to paging procedures. To assist with the handling of such signalling, the cells of a network can be divided between different signalling areas.

Examples of known multi-cell signalling areas comprise

Tracking Areas (TA) defined for use in relation to Long Term

Evolution (LTE) networks, and Routing Areas (RA) and Location

Areas (LA) employed in relation to 3 G and 2G techno logy respectively. As a particular illustrative example relating to LTE network systems, paging procedures for contacting a cellular phone handset, for the purpo se for example, of handling incoming calls at the handset, employ multi-cell TAs determined by the network and which can be defined in broadcasts to the cellular phone handset within System Information (SI) data that is arranged to be received by the cellular phone handsets found within a particular cell forming part o f that TA.

The signalling received by the cellular phone handset can serve to confirm to the handset which TA it is located in and the handset is then paged via the eNodeB of every cell within that TA. SUMMARY OF THE DISCLOSURE

The management of signalling areas such as known TAs arising in relation to LTE systems exhibit particular characteristic s and, in some cases disadvantages and limitations. In particular, disadvantageous ping-pong signalling effects can arise due to the frequency TA updates required for cell changes that arise on TA boundaries and an increase in TA updates can arise if a relatively large population of cellular phone handsets requires near simultaneous registration, for example when a large number of network subscribers are travelling on a train through and between TAs.

Also it is now identified that the comparative requirements of fast-moving, as compared with slow-moving, or stationary, cellular phone handsets serve to focus, and in some cases emphasise, particular inefficiencies within TAs and, in some cases, an inappropriate choice of TA.

The present invention seeks to provide for a method o f signalling area management having advantages over known such methods. In particular, the invention seeks to provide for improved signalling area management in relation to cellular phone handsets that are found to be stationary.

As used herein, the term "stationary" is taken to imply that the handset's lo cation within a particular cell, or indeed within a particular signalling area, is considered to be constant for a particular period. Thus, the term stationary also implies that the cellular phone handset might be relatively slow-moving within a particular cell or particular signalling area.

According to a first aspect of the present invention there is provided a metho d of managing multi-cell signalling areas within a cellular mobile radio communications network, the metho d comprising the following steps : determining if a mobile radio communications device is stationary within a first signalling area, and assigning the mobile radio communications device to a temporary signalling area responsive to a determination that the mobile radio communications device is stationary. The arranging may be performed so that the number of cells in the temporary signalling area is less than the number within the first multi-cell signalling area. The meritorious effects of the present invention are summarized as fo llows.

The invention is particularly advantageous insofar as, with the aforementioned temporary signalling area, and responsive to the lack of movement of the cellular phone handset, it proves possible to limit the signalling that would otherwise arise within the signalling area so as, for example, to reduce the paging overhead arising within the system and also increase the over-the-air efficiency thereof.

Preferred modes may be briefly summarized as follows, however without limitative nature. Preferably, the method may also include the step of determining whether or not it is appropriate to establish the said temporary signalling area and/or, cancel the temporary signalling area.

The establishment or cancellation of the temporary signalling area can be made responsive to information provided from the mobile radio communications device (cellular phone handset) to the network.

Also , the aforementioned establishment/cancellation can be made responsive to factors such as network load and/or the number of stationary cellular phone handsets within for example, a particular cell.

Advantageously, the method may include provision of a stationary indicator within signalling delivered from the cellular phone handset to the network. In particular, such a stationary indicator can be provided as part of the periodic update procedure.

Further details of the stationary indicator can be found in the applicants co-pending GB Patent Application No .0707455.2, the entire disclosure thereof being incorporated herein by reference thereto . To summarize, with regard to the criteria that can be employed to determine whether or not the mobile radio communications device is stationary, if no reselection procedures has occurred for a duration of the periodic TA update timer the mobile radio communications device can set a Stationary in Cell (SiC) flag ON. As soon as the mobile radio communications device re-selects, it can set the SiC flag OFF. As before, the periodic TA timer duration is network specific.

When the Stationary in Cell criteria has been fulfilled, the mobile radio communications device indicates to this network and, as noted, can include the SiC flag within the periodic TA update message and the state of that flag so as to indicate whether the mobile radio communications device has not moved from the cell for at least the time set by the periodic TA update timer. While other arrangements can of course be employed, the optional inclusion of the current cell identifier can also serve as an indication to the network that the mobile radio communications device has become stationary within a particular cell. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a signaling diagram illustrating the signaling flow between a mobile radio communication device and a network according to an example of the present invention. EXPLANATIONS OF NUMEROUS SYMBOLS

10: Tracking Area (TA)

10' : Sleeping TA 12, 14, 16: eNodeB (cell or LTE Base Station)

18 : Mobile Radio Communications UE Device (handset)

20: Network (NW)

24, 26, 50, 52: Tracking Area Update

28, 30, 32: Paging Signalling 34: Perio dic TA Update Signalling

38 : Periodic TA Confirmation Signalling

40, 42, 44, 46: Paging Signalling

PREFERRED MODES FOR CARRYING OUT THE INVENTION

According to a particularly advantageous exemplary embodiment of the present invention, the temporary signalling area is arranged to coincide with a single cell and thus comprises a single-cell temporary signalling area.

Use of such a single-cell temporary signalling area proves particularly advantageous in enhancing the improved efficiencies, in particular a reduction in signalling overhead and system load that can be achieved by way of the present invention.

As will be appreciated, the signalling managed by way of the present invention can comprise that arising in relation to paging procedures within the network. In one particular exemplary embodiment, the multi-cell signalling areas and the aforementioned temporary signalling area comprise respectively a multi-cell Tracking Area (TA) and a temporary Tracking Area (TA) .

The present invention therefore provides a particularly useful manner within a TA management environment of a LTE network system.

In particular, the metho d includes the step o f performing a TA update procedure should the cellular phone handset move to a cell that is within the same multi-cell TA but which is not of the temporary TA.

Such movement can serve to indicate that the cellular phone handset is no longer stationary.

The method can include the step o f managing a temporary TA list, in which cellular phone handsets are included when they are found to be stationary within a particular temporary TA.

Entry upon such a list can advantageously be employed to determine whether or not the cellular phone handset is paged by way of the base station o f the temporary TA or whether normal TA procedures are adopted via all o f the base stations associated with the multi-cell TA.

The method can further advantageously employ a periodic TA update confirm message so as to confirm for the cellular phone handset the nature of the TA within which the cellular phone handset is associated at any particular time. As noted above, the present invention is equally applicable to signalling areas associated with technologies other than LTE, for example 2G and 3 G routing and location areas noted above. The procedures then associated with the management o f such areas and which correspond to those outlined above in relation to an LTE system are thereby likewise applicable.

It should therefore be appreciated that, by way of the present invention, an improved efficiency in, for example, the paging o f mobile radio communication device handsets can be achieved through the reduced number of base stations that will be required for transmitting the paging information to those handsets that meet the " stationary" criteria. The existing TA update procedures can advantageously be employed so that the invention requires no increase in over-the-air signalling, although some additional parameters may be required within currently signalling. Also, the decision to create/use a temporary TA can be taken within the network rather than at the cellular phone handset, and so such TAs can advantageously be created and managed in accordance with overall system lo ad.

Also, the requirement for a temporary TA list in accordance with a particular exemplary embodiment of the present invention has relatively minor impact upon network operation. EXAMPLES

The invention is described further hereinafter, by way of example only, with reference to the accompanying drawing which comprises a signalling diagram illustrating the signalling between a mobile radio communications device operating within a network in accordance with an example of the present invention.

As will be appreciated, a particular concept of the present invention allows the network to optimize its paging procedures by creating a dynamic (temporary) single-cell Tracking Area referred to hereinafter as a " Sleeping Tracking Area" for stationary mobile radio communication device User Equipment (UE) within the cell. The decision to create/destroy the Sleeping Tracking Area is based on information provided to the network by the UE. The network chooses to create the Sleeping Tracking Area based on one or more of a variety of criteria, and then acts to assign the UE to that Sleeping Tracking Area. This way the UE is no longer tracked/paged in its normal multi-cell TA. Rather the network acts to track/page the UE in just this single cell Sleeping Tracking Area. The network continues to bro adcast the "normal" TAs within the System Information and so it should be appreciated that the Sleeping Tracking Area is considered a temporary TA, rather than "normal" TA.

This allows the network to page the stationary UE in only one cell and thereby reduces the paging overhead and increasing over-the-air efficiency of the system as mentioned above.

Any number of UEs can jo in the Sleeping Tracking Area and decisions relating to the establishment/disestablishment of such TAs, and assignment of UEs thereto can be taken in the network. The main criterion is the UE becoming stationary within a cell. The method can further be arranged such at, once the UE moves outside the cell (i. e. , moves from the Sleeping Tracking Area), the network will act to remove it from the S leeping Tracking Area, and it will be again paged in the "original" manner by way of the cells of the "normal" Tracking Area.

Turning now to the accompanying drawing, there is illustrated a multi-cell tracking area 10 which, in the illustrated example, comprises three cells o f which the respect eNodeBs 12, 14, 16 are illustrated. The accompanying drawing illustrates the signalling that arises within the tracking area 10 in accordance with an example o f the present invention and between a mobile radio communications UE device 18 such as a cellular phone handset, and its associated network 20. It is assumed that, as a first step, the handset 18 moves as indicated by arrow 22, into the cell o f eNodeB 12 within the tracking area 10 and that is new to the handset 18. This serves to establish a tracking area update procedure 24, 26 which will lead to the network 20 paging the handset 18 by way of each of the eNodeB s 12, 14, 16 of the tracking area 10 as indicated by signalling arrows 28, 30, 32.

Thus, although the handset 18 is located only within one 12 o f the three cells of the tracking area 10, paging signalling is transmitted from each of the three eNodeBs 12, 14, 16 of that tracking area 10. As is standard, periodic tracking area update signalling 34 arises and, in accordance with the present invention, such signalling, can include a stationary flag, serving to indicate to the network that the handset 18 is considered to be stationary within the cell associated with eNodeB 12. Responsive to such a stationary indication within the signalling 34, the network 20 establishes a temporary tracking area, hereinafter referred to as a Sleeping TA 10' as indicated by arrow 36 and, within the periodic tracking area confirmation signaling 38 , confirms to the handset 18 that it is now to be managed within the Sleeping TA 10'.

In order to enhance the advantages offered by the present invention, the Sleeping TA 10' is arranged to coincide with the cell associated with eNodeB 12 and thereby comprise a simple single-cell TA. As will be appreciated, the network 20 then knows only to page the handset 18 by way of the eNodeB 12 now associated with the Sleeping TA 10' as indicated by the signalling 40.

That is, only paging signalling 42 asso ciated with the eNodeB 12 is transmitted and the signalling 44, 46 previously arising in relation to the eNodeBs 14, 16 found within the original "normal" multi-cell tracking area 10 is no longer required.

As will be appreciated, this advantageously serves to limit paging overhead and increase the efficiency o f over-the-air signalling. Should it then be determined that the handset 18 is no longer stationary, the handset 18 moves to a new cell as illustrated by arrow 48, such movement is arranged to initiate a tracking area update procedure 50, 52 and the network 20 then adopts a procedure 54 to remove the handset 1 8 from the Sleeping TA 1 0'. Normal paging o f the handset 18 by way o f the three eNodeB s

12, 14, 16 is then re-established.

Whether or not the Sleeping TA 10' remains established, or is disestablished, depends generally upon whether other handsets are found to remain stationary within that Sleeping TA 10' or, having regard to general network load considerations.

The Sleeping TA 10 ' thus dynamically created/destroyed by the network.

As noted, the decision by the network to create/destroy the Sleeping TA 10' can be based on criteria such as the number o f sleeping UEs in the cell, and/or network lo ad etc.

Other non-stationary UEs within the cell will be paged in accordance with normal paging pro cedures.

The Sleeping TAs would typically be created in more densely populated areas such as in residential or commercial areas. Further the Sleeping TAs are likely to exist for long periods during user inactivity such as at night-time and again during normal office/school hours etc.

As noted, improved efficiency in the paging ofUEs is achieved due to a reduced number of eNodeB s (LTE Base Stations) that need to transmit paging info (information) for the stationary UEs. The following steps illustrate a typical basic scenario of the additional functionality introduced by an exemplary embodiment o f the present invention.

First, the UE (User's Equipment) enters a cell in a new TA and performs its usual TA Updates Procedures. The UE will be tracked/paged in all cells belonging to that new TA.

Secondly, it is determined whether or not the UE remains within the same cell. If the UE remains within the same cell for a particular time period, it will perform its normal Periodic Update Procedure.

During this Periodic Update, a " stationary indicator" will be passed to the network as an optional parameter responsive to a determination that the UE is stationary within the cell concerned.

Next, the network saves the stationary indicator parameter and decides whether to create a temporary Sleeping Tracking Area for that UE. This decision can also depend on the number of already existing sleeping UEs in that cell.

If the network decides to create a S leeping Tracking Area for the UE, it will indicate this to the UE in the Periodic TA Update Confirm Message and on receipt of the Periodic TA Update message noted above. The stationary UE will then be tracked/paged by way of that Sleeping TA only.

Then, if the UE moves to a cell that belongs to the original multi-cell TA (i. e., the TA broadcast in the System Information), the UE will perform a TA update procedure, which of course would not have occurred if the UE had not been allocated to the Sleeping TA.

With this TA update procedure, the UE indicates to the network that it is no longer stationary and restores the normal TA principles.

If UE moves to a cell that belongs to different TA the UE follows the existing procedure and performs TA update. Such TA update of course updates the existing procedure and inherently indicates to the NW that the UE is no longer stationary.

With an example in which the UE moves from cell the network will then act to remove the UE from a Sleeping TA UE list and will page the UE in accordance with "normal" TA procedures. The network will also indicate this decision to the UE in the subsequent

Periodic TA Update Confirm message so that the UE does not behave as if it is still in the Sleeping TA.

As new UEs join the cell and indicate to the network that they are now stationary via the Perio dic TA Update message, the network will indicate to the UE that it has jo ined the Sleeping TA using the

Periodic TA Update Confirm Message.

The network NW removes UEs from the Sleeping TA due to the network deleting S leeping Tracking Area, the network will indicate to any UEs in the S leeping TA that they should use the

"normal" TA and will indicate this in the next Periodic TA Update

Confirm Message on receipt of the next Periodic TA Update message from the UE, and if it decides to delete the Sleeping TA. As will therefore be appreciated, the present invention serves to optimize paging for mobile phone handsets that are stationary or at least remain within the same cell, or tracking area, for a sufficiently long period of time such as during the night or when a user is found at a constant location such as when at school or in the workplace, to be considered stationary.

It should be noted that other objects, features and aspects of the present invention will become apparent in the entire disclo sure and that modifications may be done without departing the gist and scope of the present invention as disclosed herein and claimed as appended herewith.

Also it should be noted that any combination of the disclo sed and/or claimed elements, matters and/or items may fall under the modifications aforementioned.

Claims

CLAIMS :

1 . A method of managing multi-cell signalling areas within a cellular mobile radio communications network, the method comprising: determining if a mobile radio communications device is stationary within a first signalling area; and assigning the mobile radio communications device to a temporary signalling area responsive to a determination that the mobile radio communications device is stationary.

2. A method as claimed in Claim 1 , further including: determining whether or not it is appropriate to establish the temporary signalling area and/or cancel the temporary signalling area.

3. A method as claimed in Claim 2, wherein the establishment or cancellation of the temporary signalling area is responsive to information provided from the mobile radio communications device to the network.

4. A method as claimed in Claim 2 or 3 , wherein the establishment or cancellation o f the temporary signalling area is responsive to at least one of network lo ad and the number of stationary mobile radio communication devices within a particular cell or signalling area.

5. A method as claimed in any one or more o f Claims 1 to 4, further including: providing o f a stationary indicator within signalling to be delivered from the mobile radio communications device to the network.

6. A method as claimed in Claim 5 , wherein the stationary indicator is provided as part of a periodic update procedure.

7. A method as claimed in any one or more of the preceding Claims 1 -6, wherein the temporary signalling area is defined as a single-cell temporary signalling area.

8. A metho d as claimed in any one or more of the preceding Claims 1 -7, wherein the metho d is arranged for managing paging signalling.

9. A method as claimed in any one or more of the preceding Claims 1 - 8, wherein the multi-cell signalling areas and the temporary signalling areas, comprise respectively a multi-cell Tracking Area and a single cell temporary Tracking Area.

10. A metho d as claimed in Claim 9, further including : performing a TA update procedure should the mobile radio communication device move to a cell that is within the same multi-cell tracking area but not of the temporary Tracking Area.

1 1. A metho d as claimed in Claim 9 or 10, further including: managing a temporary tracking area list within which mobile radio communications devices are included when they are found to be stationary within a particular temporary tracking area.

12. A metho d as claimed in any one or more o f the preceding Claims 1 - 1 1 , wherein a decision to create/use a temporary tracking area is taken within the network.

13. A method of managing multi-cell signalling areas within a mobile radio communications network and substantially as hereinbefore described with reference to, and as illustrated in the accompanying drawing.