GB2420937A

GB2420937A - A mobile radio communications device connecting to a network of a radio access technology (RAT)

Info

Publication number: GB2420937A
Application number: GB0422739A
Authority: GB
Inventors: Pierre-Jean Muller; Michael Roberts; Yannick Lair
Original assignee: NEC Technologies UK Ltd
Current assignee: NEC Technologies UK Ltd
Priority date: 2004-10-13
Filing date: 2004-10-13
Publication date: 2006-06-07
Anticipated expiration: 2024-10-13
Also published as: GB2420937B; GB0422739D0

Abstract

The invention provides a mobile radio communications device 10 arranged to operate in accordance with at least a first radio access technology (RAT) and a second radio access technology, for example, second generation (2G) and third generation (3G) RATs, and including memory means 18 for storing connection details for a previously visited network of the second radio access technology and control means 16 arranged, upon loss of connection to a network of the first radio access technology, to retrieve the connection details from the memory means 18 and attempt connection to the network of the second radio access technology. The connection details may be received by way of a PLMN (Public Land Mobile Network) selection function and may comprise one or more of the BA range, Broadcast Control Channel (BCCH) neighbour list and/or network parameters such as mobile network code (MNC) and mobile country code (MCC). Prior to retrieving the connection details, the mobile may attempt to reconnect to a network of the first radio access technology.

Description

* 2420937

MOBILE RADIO COMMUNICATIONS DEVICE AND METHOD OF

OPERATION

The present invention relates to a mobile radio communications device arranged for at least dual mode operation, and to a related method of operation.

Technical developments that have arisen with mobile radio communication devices such as cellular phones relate not only to the cellular phone handsets themselves, but also the networking technology adopted for facilitating communication in between such devices.

Different generations of technology have been developed, the most recent being identified as third-generation, i.e. 3G, technology.

However, it remains relevant for cellular phones to operate also in accordance with earlier, for example, 2G technologies, and dual-mode, and sometimes multi-mode cellular phone handsets have been developed allowing for operation in accordance with a Radio Access Technology (RAT) embodying 2G technology, and a RAT embodying 3G technology.

Due to the mobile nature of cellular phones, the likelihood of the cellular phone handset losing connectively with a network is always present.

Problems in particular arise when, for example a dual-mode handset is operating in a 3G only Public Land Mobile Network (PLMN). 3G specifications, such as those defined by way of the 3G Partnership Project (3GPP) do not readily adapt to the issues of priority of access technology for handsets operating in accordance with a single RAT PLMN when roaming to and from 2G coverage.

As outlined further below, this leads to unnecessarily complicated, time and power consuming, PLMN search and selection procedures.

In scenarios where a Home PLMN (HPLMN) and a partner PLMN do not readily coexist, national roaming agreements are generally reached allowing for search and selection amongst 2G and 3G networks should connectivity with the HPLMN be lost.

For example, when a cellular phone handset is leaving an area of 3G coverage, the standard 3GPP algorithm determines that the handset will then search for all PLMNs available in the current location to ultimately select the highest priority PLMN identified. This known procedure requires a time, and power-consuming, cell search on both the 2G and 3G RATs and this adversely affects battery life, related characteristics and, for example time to service, of the handset.

The present invention seeks to provide for a mobile radio communications device, and method of operation, having advantages over known such devices and methods.

According to a first aspect of the present invention there is provided a mobile radio communications device arranged to operate in accordance with at least a first and second radio access technology and including memory means for storing connection details for a previously visited network of the said second radio access technology, control means arranged upon loss of connection to a network of said first radio access technology to retrieve the said connection details from the said memory means and to attempt connection to the said network of the said second radio access technology.

The invention is advantageous in that it provides for identification and use of the details of the most recently registered PLMN associated with a different radio access technology and this advantageously avoids multiple, and unnecessary, full band searches that might otherwise be necessary.

Preferably, the said memory means comprises a non-volatile memory.

Preferably, the PLMN Selection function can be arranged to implement an algorithm to store, retrieve and use, parameters within the memory means when handling the said connection details.

Yet further, a personalisation flag can be included within the memory means serving to enable/disable the use of said connection details.

According to a particularly advantageous embodiment, the said connection details can comprise one or more of the BA range e.g. GSM ARFCN, FDD frequency list, the Broadcast Control Channel (BCCH) neighbour cell list, and network parameters such as the mobile network code (MNC) and the mobile country code (MCC).

It should be appreciated that the device can be arranged for operation wherein the network of the first and second radio access technologies each comprise a PLMN.

In particular, the network of the said first radio access technology in accordance with the operation defined above comprises the HPLMN.

Yet further, the control means can be arranged to attempt to reconnection to a network of the said first radio access technology, prior to retrieving the said connection details and attempting connection to the said network of the said second radio access technology.

In accordance with another aspect of the present invention there is provided a method of establishing connectivity with a second of two radio access technologies in an at least dual mode mobile radio communications device, and including the steps of retaining, in memory means of the said device, connection details of a previously visited network of the second radio access technology while connected to a network of the first radio access technology, monitoring for loss of connectivity to the said network of the said first radio access technology, and, on determining the said loss of connection, retrieving said connection details from the memory means and attempting to connect to the said network of the second radio access technology.

The mobile radio communications device to which the aforementioned method is applied advantageously includes the features such as defined above. In particular, the retained connection details can be stored within a nonvolatile memory.

Further, the method can include the step of adding a personalisation flag to the memory means for use in enabling/disabling the use of the connection details of the previously visited network.

Also, the device can be arranged to implement an algorithm to store, retrieve and use the connectivity parameters held within the memory means.

Again, the connectivity details retained within the memory means can comprise any one or more of the following, BA range, BCCH list, MCC and/or MNC.

Also, the method can include the step of attempting a reconnection to a network of the said first radio access technology before the said attempted connection to a network of the said second radio access technology on the basis of the connection details retrieved from the memory means.

Since in most cases, attempted connection to the HPLMN will be selected wherever it is thought possible, but that other PLMNs will be available, the present invention introduces a concept of an improved choice of Registered PLMN so as to increase time and power consumption, and increase efficiency when seeking to re-establish network connectivity.

The invention is described further hereinafter, by way of example only, with reference to the accompanying drawings in which: Fig. 1 is a schematic diagram of a cellular phone handset embodying the present invention; and Fig. 2 is a schematic flow diagram of operation within the handset of Fig. 1 and in accordance with an embodiment of the present invention.

Turning first to Fig. 1, there is illustrated in block diagram form, a mobile radio communications device in the form of a cellular phone handset 10 including receive/transmit radio circuitry 12 operatively connected to an antenna 14 for use of the handset 10 within a PLMN.

The illustrated view of the handset 10 also shows a processor 16 which, in addition to being operatively connected to the radio circuitry 12, is connected to storage means (18) is in the form of a non-volatile memory.

As is discussed further below, the non-volatile memory 18 is arranged to store parameters of a network which can be employed as a default network should connectivity to, for example, the HPLMN be lost.

The invention is described further with reference also to Fig. 2 which illustrates operation of the handset 10 in accordance with an embodiment of the present invention.

First however, a general case within the current state of the art is considered and which relates to a dual mode handset with 2G and 3G connectivity. When the handset is roaming within its home country, which can be identified by the MCC being similar to that provided by the International Mobile Subscriber Identifier (IMSI), the handset 10 will try as far as possible to remain camped on its home PLMN of the 3G radio access technology.

However, since 3G coverage is likely to be not as broad as 2G coverage, the handset 10 will from time to time lose its connectivity to the 3G network.

Generally, after an unsuccessful search for the 3G home PLMN, the handset will then attempt to recover connectivity by way of a 2G network where its home PLMN does not exist. That is, after a failed attempt to recover on the recently lost 3G network, as identified by information stored in the Universal Subscriber Identity Module (USIM), the handset will then search for all available 2G PLMNs and, subsequent to a full search, will select the highest priority PLMN identified which will become the visitor PLMN. It is noted that the highest priority visitor PLMN is likely to always be the same since 3G network operators quite often form partnerships with specific 2G operators whose details will generally be included in the preferred PLMN list in the highest visited 2G VPLMN.

Such a process for attempted connectivity to a 2G network is, as discussed previously, disadvantageously time and power consuming.

Within the present invention, and as compared with the above- mentioned specific example, when losing its 3G HPLMN coverage, the invention proposes that the handset introduce the previous registered PLMN associated with another RAT. These of the previously registered PLMN are stored within a non-volatile memory 18 of the handset 10, rather than in the USIM, so as to ensure handset portability.

The last previously registered 2G PLMN is identified by means of BA range data or the BCCH neighbour list if the BA range data is not available.

Thus, when recovering connectivity to a 2G network and if roaming within its home country, the handset 10 will search and select first the previous 2G registered PLMN using the associated BCCH carry information stored within the non-volatile memory 18 and this will prove particularly advantageous in avoiding the need for otherwise conducting multiple full band searches in order to achieve connectivity. The handset 10 can then advantageously ignore the USIM registered PLMN and USIM BCCH neighbour cell list.

Use of the present invention can advantageously improve the network search and selection procedure, by, for example, up to 10 seconds and if the 2G registered PLMN is present, and cell information for that 2G registered PLMN is available, the handset need not then conduct a full scan on both radio access technologies but will look only at known cells of the specified radio access technology.

As discussed, such operability can advantageously be enable/disabled by means of a flag within the non-volatile memory 18.

With specific reference to Fig. 2, an operation of an embodiment of the present application is now described.

At step 20, the handset 10 of Fig. 1 is first camped on a 30 HPLMN and a cell resejection process is conducted at step 22 by means of a trigger signal A and, assuming cell selection succeeds, as indicated by arrow B, the handset remains camped on the 3G HPLMN.

However, should the cell selection procedure at step 22 fail, the handset 10 identifies this at step 24 and this triggers step 26 which comprises a determination as to whether 2G registered PLMN information is available which of course relates to a previously visited 2G PLMN.

If, at step 26, it is determined that the 2G registered PLMN is available, the handset 10 is arranged to conduct a relatively fast PLMN selection at step 28 and, assuming this selection succeeds, the handset 10 then camps on the 2G registered PLMN at step 30.

A trigger then causes the handset to conduct periodic PLMN selection procedure at step 32 and, assuming the 2G registered PLMN currently camped on remains the highest 2G PLMN available, and as indicated by arrow C, the handset 10 remains camped on that 2G registered PLMN as indicated at step 30.

If, however, at step 32, a higher-ranking PLMN is identified, then the operation proceeds to step 34 where the handset camps on this higher identified PLMN.

Thus, on the basis of the 2G RPLMN identified at step 16, a relatively quick and efficient recovery procedure is employed in accordance with the present invention and which leads to the advantages discussed above.

Returning to step 16 however, should no 2G-registered PLMN be available, then the handset is arranged to conduct a full PLMN selection at step 36.

Likewise, should, at step 28, the relatively fast PLMN selection procedure fail, then, as indicated by arrow D, the full PLMN selection procedure at step 36 is initiated.

Thus, should the advantageous features of the present invention not, for some reason, be available, the handset can default to a 2G connection procedure in accordance with the prior-art.

It will therefore be appreciated that, in accordance with a particular aspect of the present invention, a network attached storage element is arranged to store within the non-volatile memory 18 within the handset 10 parameters of the 2G registered PLMN and including the MCC and MNC parameters, the associated BA range and/or or the BCCH neighbour cell list.

A personalisation flag can be included within the non-volatile memory 18 and can be arranged to be used for enabling/disabling the use of the most recent 2G registered PLMN parameters. Also, the PLMN selection function can be arranged to implement the algorithm to store, retrieve and use the parameters from the non-volatile memory 18 and the underlying layers namely Radio Resource Management is arranged to search and select the identified PLMN provided from the network attached storage, and the associated BA range and/or BCCH neighbour cell list.

In particular, and in accordance with current standards, the BCCH information employed may be derived by a variety of different methods. For example, the BA range information element may be employed which, if transmitted in the channel release message, serves to indicate range to the carriers which can include the BCCH carriers in use over a wide area or even over the whole PLMN. It should however be noted that the BCCH list might only contain carriers in use in the vicinity of the cell upon which it was broadcast and therefore might not be appropriate if the handset is switched off and moved to a new location. Nevertheless the device and method of the present invention lead to particular time and power savings, and thus improvements in efficiency as compared with currently available devices and operation methods.

Claims

Claims 1. A mobile radio communications device arranged to operate in

accordance with at least a first and second radio access technology and including memory means for storing connection details for a previously visited network of the said second radio access technology, control means arranged upon loss of connection to a network of said first radio access technology to retrieve the said connection details from the said memory means and to attempt connection to the said network of the said second radio access technology.
2. A device as claimed in Claim 1, wherein the said memory means comprises a non-volatile memory.
3. A device as claimed in Claim 2, wherein the memory means is arranged to receive the said connection details from by way of a PLMN selection function.
4. A device as claimed in Claim 3, and arranged such that the PLMN selection function serves to implement an algorithm to store, retrieve and use parameters within the memory means when handling the said connection details.
5. A device as claimed in Claim 4, wherein the memory means can be arranged to include a personalisation flag arranged to enable/disable the use of said connection details.
6. A device as claimed in Claim 1, 2, 3, 4 or 5, wherein the said connection details comprise one or more of the BA range, the Broadcast Control Channel (BCCH) neighbour list, and/or network parameters.
7. A device as claimed in Claim 6, wherein the network parameters comprise mobile network code (MNC) and mobile country code (MCC).
8. A device as claimed in any one or more of Claims 1 to 7, wherein the control means is arranged to attempt reconnection to a network of the said first radio access technology, prior to retrieving the said connection details and attempting connection to the said network of the said second radio access technology.
9. A method of establishing connectivity with a second of two radio access technologies in an at least dual mode mobile radio communications device, and including the steps of retaining, in memory means of the said device, connection details of a previously visited network of the second radio access technology while connected to a network of the first radio access technology, monitoring for loss of connectivity to the said network of the said first radio access technology, and, on determining the said loss of connection, retrieving said connection details from the memory means and attempting to connect to the said network of the second radio access technology.
10. A method as claimed in Claim 9, wherein the said retained connection details are stored within non-volatile memory means.
11. A method as claimed in Claim 10, wherein the non-volatile memory means is arranged to receive data from a PLMN selection function arrangement.
12. A method as claimed in Claim 9, 10 or 11, and including the step of adding a personalisation flag to the memory means for use in enabling/disabling the use of the connection details of the previously visited network.
13. A method as claimed in Claim 9, 10, 11 or 12, wherein the connectivity details retained within the memory means can comprise any one or more of the following, BA range, BCCH neighbour list, MCC and MNC.
14. A method as claimed in any one or more of Claim 9 to 13, and including the step of attempting a reconnection to a network of the said first radio access technology before the said attempted connection to a network of the said second radio access technology on the basis of the connection details retrieved from the memory means.
15. A mobile radio communications device substantially as hereinbefore described with reference, and as illustrated in, Figs. 1 and 2 of the accompanying drawings.
16. A method of establishing connectivity within an at least dual mode mobile radio communications device substantially as hereinbefore described with reference to, and as illustrated in, Fig. 2 of the accompanying drawings.

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16. A method of establishing connectivity within an at least dual mode mobile radio communications device substantially as hereinbefore described with reference to, and as illustrated in, Fig. 2 of the accompanying drawings.

Amendment to the claims have been filed as follows Claims 1. A mobile radio communications device arranged to operate in accordance with at least a first and second radio access technology and including memory means for storing PLMN details for a previously visited network of the said second radio access technology, control means arranged upon loss of connection to a network of said first radio access technology to retrieve the said PLMN details from the said memory means and to attempt connection to the network identified by the PLMN details of the said second radio access technology.

2. A device as claimed in Claim 1, wherein the said memory means comprises a non-volatile memory.

3. A device as claimed in Claim 2, wherein the memory means is arranged to receive the said PLMN details from a network-attached storage element.

4. A device as claimed in Claim 3, and arranged such that the PLMN selection function serves to implement an algorithm to store, retrieve and use BA range parameters and/or a BCCH neighbour list within the memory means when handling the said PLMN details.

5. A device as claimed in Claim 4, wherein the memory means can be arranged to include a persona lisation flag arranged to enable/disable the use of said PLMN details.

6. A device as claimed in Claim 1, 2, 3, 4 or 5, wherein the said PLMN details comprise one or more of the BA range, the Broadcast Control Channel (BCCH) neighbour list, and/or network parameters. t ( & 11-I-

7. A device as claimed in Claim 6, wherein the network parameters comprise mobile network code (MNC) and mobile country code (MCC) 8. A device as claimed in any one or more of Claims 1 to 7, wherein upon loss of connection to a network of said first radio access technology said control means is arranged to attempt reconnection to the network of the said first radio access technology, prior to retrieving the said PLMN details and attempting connection to the network of the said second radio access technology.

9. A method of establishing connectivity with a second of two radio access technologies in an at least dual mode mobile radio communications device, and including the steps of retaining, in memory means of the said device, PLMN details of a previously visited network of the second radio access technology while connected to a network of the first radio access technology, monitoring for loss of connectivity to the said network of the said first radio access technology, and, on determining the said loss of connection, retrieving said PLMN details from the memory means and attempting to connect to the network identified by the PLMN details of the second radio access technology.

10. A method as claimed in Claim 9, wherein the said retained PLMN details are stored within non-volatile memory means.

11. A method as claimed in Claim 10, wherein the non-volatile memory means is arranged to receive data from a network-attached storage element.

12. A method as claimed in Claim 9, 10 or 11, and including the step of adding a personalisation flag to the memory means for use in enabling/disabling the use of the PLMN details of the previously visited network.

I I I 4 III I I I I C C * CI C C 1 C C C

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13. A method as claimed in Claim 9, 10, 11 0112, wherein the connectivity details retained within the memory means can comprise any one or more of the following, BA range, BCCH neighbour list, MCC and MNC.

14. A method as claimed in any one or more of Claim 9 to 13, and including the step of, upon loss of connection to the said network of the first radio access technology, attempting a reconnection to the network of the said first radio access technology before the said attempted connection to the network of the said second radio access technology on the basis of the PLMN details retrieved from the memory means.

15. A mobile radio communications device substantially as hereinbefore described with reference, and as illustrated in, Figs. 1 and 2 of the accompanying drawings.