|Title of Invention||
A METHOD OF BACKGROUND SCANNING FOR A HOME PUBLIC LAND MOBILE NETWORK (PLMN) IN OVER LAPPING SERVICE AREAS OF HOME PLMN AND A VISITED PLMN
|Abstract||A method for performing background scan for HPLMN in overlapping service areas of HPLMN and VPLMN in the case of International roaming is proposed which enables early reselection to HPLMN when coverage is available. Also, a method to do background scan for HPLMN and high priority PLMNs in the case of National roaming, only when the UE is camped in certain LAIs, identified by the operator, is proposed which would result in a longer battery time.|
|Full Text||FIELD OF INVENTION
The present invention relates to reselection of the HPLMN by the MS in an international roaming scenario and implements optimized HPLMN search to increase battery life in the case of national roaming. More particularly, the present invention relates to a method for background scanning for HPLMN/High Priority PLMNs in overlapping service areas of HPLMNS & VPLMNS.
DESCRIPTION OF RELATED ART
When the MS is in international roaming, the MS periodically attempts to obtain service only on higher priority PLMNs, if any, belonging to that particular country (PLMNs with MCC same as the MCC of the current serving VPLMN) and does not try for HPLMN until the MS loses the coverage of the VPLMN.
When the MS is in national roaming, the MS periodically attempts to obtain service on its HPLMN or higher priority PLMN listed in “user controlled PLMN selector” or “operator controlled PLMN selector” in the SIM card. This background scan is done at periodic intervals to ensure the MS is registered on HPLMN or Higher Priority PLMNs on the availability of the same.
in case of certain countries there is a possibility that the coverage area of a PLMN belonging to that country extends beyond the border and is present in the border area of the neighboring country. In such areas the current implementation of the high priority PLMN search may lead to a situation where the MS remains camped on the VPLMN of the neighboring country though HPLMN service is available in that location.
For the ease of demonstration let us consider the case of two countries i.e. Country A and Country B, as illustrated in Figure 1.
The regions encircled by the green line are two different location areas (LA) of the PLMN 1, which belongs to the Country A.
Similarly, the regions encircled by the red line are two different location areas of the PLMN 2 which belong to the Country B. Figure 2 is a zoomed image of the above border area.
Consider an MS belonging to a person from Country A who is registered with the PLMN 1 for mobile services. Let us examine the service state of the MS in different phases as the user travels from Country A to Country B and then back to Country A. The travel path under consideration is A4->A3->A2->A1->A2->A3->A4.
As illustrated above when the MS moves from Area A1 to Area A2 and then to Area A3 it does not reselect the HPLMN though the HPLMN coverage is available because when the MS is in international roaming it does not attempt to obtain service on any PLMN belonging to a different country.
The MS would not reselect the HPLMN until it loses the coverage of PLMN 2. So as long as the MS is in Area A3 it remains camped in the VPLMN, though the user is in
This Home Country and in an area with good HPLMN coverage, until the user manually selects the HPLMN using Manual Selection of Service.
Many of the operators do not have their PLMN coverage across the country they operate in. In similar lines of the previous illustration let us consider a hypothetical case of a particular operator operating in a single state of the country. The following diagram illustrates the case of a particular operator (PLMN1) operating in State A and has roaming agreements with operators of PLMN2 and PLMN3 for roaming in States B and C.
The background scan for HPLMN is always futile when it is done in an area with no HPLMN coverage. Since the service coverage of the PLMN 1 is available in only a single state of the country it is highly probable that background scan for HPLMN is unsuccessful in majority of the cases.
The result of the background scan when it is done in different LAIs is tabulated in the following table.
As can be seen from the above table the background scan for HPLMN is unsuccessful in most of the cases and results in lower battery life while in roaming.
SUMMARY OF THE INVENTION
The proposed solution is to maintain an operator controlled list of LAIs in a proprietary file in the SIM card which would be updated via OTA. Whenever the MS is in international roaming and camped in one of the LAIs present in proposed list, it attempts to obtain service on HPLMN and other high priority PLMNs belonging to the Home Country. A detailed description of the procedure and a file structure to store the LAIs is suggested in the following section.
As shown in the Fig. 4, the operator identifies the LAIs LAM, LAI2, LAI3, LAI4 etc. and builds a list of these LAIs. The length of the list and periodicity of updating would be implementation dependent.
When the MS is in international roaming, on the expiry of the HPLMN Search timer it verifies if the current serving LAI is present in list of LAIs in the above mentioned proprietary file of the SIM card. If present, the MS would attempt to obtain the service on HPLMN though the MCC of the current serving PLMN is different from the MCC of the HPLMN.
The solution is to restrict the background scan for HPLMN only to a particular set of LAIs in which the probability of finding the HPLMN is not equal to zero. In other words, the background scan for HPLMN is not done in areas where the coverage of HPLMN is definitely not present.
The list of LAIs in which the background scan is to be done is maintained in a proprietary file in the SIM card by the operator as described in the case of international roaming.
The operator surveys for LAIs of other PLMNs which overlap with the operator's PLMN service area and updates the SIM cards of the MSs whenever required through OTA as described in the case of international roaming. As shown in the
Fig.3 the operator selects the desired LAIs (LAI 6, LAI 7, LAI 2 etc.) and stores it as a list in the operator control proprietary file in the SIM card.
A single proprietary file can be used to store the LAIs, mentioned in the case of both National and International roaming. The background scan for HPLMN is done whenever the MS is registered in any of the LAIs present in the list. In all the other LAIs the background scan for HPLMN would be disabled.
Similarly, the required LAIs are identified for the PLMN entries which belong to UPLMN list and OPLMN list stored in the SIM, For each PLMN, a list of LAIs are identified which overlap with that particular PLMN. Only when the UE is camped in one of these LAIs, it would initiate the background search for the corresponding PLMN, if necessary. The LAIs for all the PLMNs can be stored in a single file in the SIM card. A file structure for the same is suggested in the following section.
Accordingly this invention explains a method for background scanning for HPLMN in overlapping service areas of HPLMNs & VPLMNs comprising the steps of:
(a) checking for the current serving LAI in the Background Search LAI List in the SIM Card of the MS if the HPLMN/High priority PLMN Search timer expires while camped on a roaming PLMN;
(b) retrieving all the PLMNs under which the said LAI is present in the list if the LAI is present in the list in the SIM Card;
(c) checking for the PLMNs with higher priority than that of the current camped
PLMN from the retrieved PLMNs;
(d) initiating the background scan for the said higher priority PLMNs;
(e) registering on HPLMN or any higher priority PLMN if available;
(f) stopping the HPLMN search timer if registered on HPLMN and if not restarting the timer;
(g) checking for any PLMNs without any LAI association if the current camped LAI is not present in the list in the SIM Card;
wherein if any PLMNs without any LAI association is found the said steps of (c) to (f) are performed and if not, the HPLMN search timer is restarted and waits for the expiry.
Accordingly, the present invention further comprises a method for background scanning for HPLMN in overlapping service areas of HPLMNs & VPLMNs comprising the steps of:
When MS in National Roaming:
(a) maintaining an operator controlled list of LAIs in a proprietary file in the SIM card which is updated via OTA;
(b) verifying if the current serving LAI is present in list of LAIs in the said proprietary file of the SIM card on the expiry of the HPLMN Search timer;
(c) attempting to obtain the service by MS on HPLMN/High Priority PLMNs under which the current LAI is present in the list;
(d) attempting to obtain the service by MS on those PLMNs in the list which do not have any LAI associated;
When MS in International Roaming:
(e) adding LAIs to the Background Search LAI List as they overlap with the HPLMN;
(f) performing background search for HPLMN if the HPLMN Search timer expires in one of the specified LAIs; and
(g) restarting the background search timer even if the MS is camped on the highest priority VPLMN.
LAIs of PLMNs which overlaps with the other PLMNs are surveyed and updated in the SIM cards of the MSs through OTA. A single proprietary file is used to store the LAIs, in both National and International roaming.
These and other objects, features and advantages of the present invention will become more apparent from the ensuing detailed description of the invention taken in conjunction with the accompanying drawings.
BREIF DESCRIPTION OF THE ACCOMPANYING DIAGRAMS
Figure 1 is an illustrative diagram to show the case of overlapping PLMN areas at international borders.
Figure 2 is a zoomed image of the border area shown Figure 1.
Figure 3 is a diagram showing specific LAI selection by the operator in the case of National Roaming.
Figure 4 is a diagram showing specific LAI selection by the operator in the case of
Figure 5 is a flowchart showing the behavior of the UE in the case of roaming when the current invention is implemented.
DETAILED DESCRIPTION OF THE INVENTION
The preferred embodiments of the present invention will now be explained with reference to the accompanying drawings. It should be understood however that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. The following description and drawings are not to be construed as limiting the invention and numerous specific details are described to provide a thorough understanding of the present invention, as the basis for the claims and as a basis for teaching one skilled in the art how to make and/or use the invention. However in certain instances, well-known or conventional details are not described in order not to unnecessarily obscure the present invention in detail.
Figure 1: An illustrative diagram to show the case of overlapping PLMN areas at international borders
The areas encircled in green are two different Location Areas of the HPLMN. Similarly the areas encircle in red are two different LAs of the VPLMN. The diagram is hypothetical and not to scale.
Figure 2: A zoomed image of the border area shown Figure 1
The areas A1, A2, A3 and A4 are marked for ease of demonstrating the state of the
UE while moving across the border.
Figure 3: A diagram showing specific LAI selection by the operator in the case of National Roaming
In the figure the LAIs of the HPLMN and two other VPLMNs are shown in different colors. The various LAIs have been marked to demonstrate how the operator selects a particular LAI for adding the same in the Background Search LAI List in the SIM card.
Assuming the two PLMNs other than the HPLMN are not preferred PLMNs the following LAIs will be added to the Background Search LAI List as they are overlapping with the HPLMN.
LAI 2, LAI 6 and LAI 7: The background search for HPLMN would be done if the HPLMN Search timer expires in one of these LAIs.
Other LAIs: The other LAIs are not added to list because, the background search for HPLMN would fail if done in these LAIs
Figure 4: A diagram showing specific LAI selection by the operator in the case of international roaming.
In the figure the LAIs of the HPLMN and two international VPLMNs are shown in different colors. The different LAIs are marked to show the criterion for LAI selection by the operator.
The following LAIs would be added to the Background Search LAI List because these LAIs of the international VPLMNs are overlapping with the HPLMN.
LAM, LAI2, LAI3 and LAW: Whenever the background search timer expires in these LAIs the background search for HPLMN would be done though the MCC of the current camped PLMN is different from that of the HPLMN.
Figure 5: A flowchart showing the behavior of the UE in the case of roaming when the current invention is implemented.
The following steps outline the content of the flow chart.
1. While camped on a roaming PLMN, if the HPLMN/High priority PLMN Search timer expires check for the current serving LAI in the Background Search LAI List in the SIM Card.
2. If the LAI is present in the list in the SIM Card,
a. retrieve all the PLMNs under which this LAI is present in the list
b. From the retrieved PLMNs, check for the PLMNs with higher priority than that of the current camped PLMN
c. Initiate the background scan for these higher priority PLMNs
d. Register on the HPLMN or any higher priority PLMN if available.
e. If registered on HPLMN stop the HPLMN search timer. If not restart the timer.
3. If the current camped LAI is not present in the list in the SIM Card,
a. Check if there are any PLMNs without any LAI associated. If so, perform the steps 2b to 2e above.
b. If not, restart the HPLMN search timer and wait for expiry.
The SIM card provided by the operator contains a proprietary file in a format to store a list of LAIs. A survey of the Network coverage area of the HPLMN/High priority PLMN is done periodically and the overlapping LAIs of VPLMNs are identified. If a change in the overlapping LAIs is identified a new list of LAIs is created and the file in the corresponding SIM cards is updated via OTA. This ensures that the SIM card contains the latest list of the overlapping LAIs and thus the MS initiates the background scan only when camped in appropriate LAs of the VPLMN.
A suggested file structure for the proprietary file to store the list of LAIs in the SIM :card is as below.
The number of PLMNs M and the number of LAIs N to be stored for each PLMN is implementation dependent.
Henceforth this list would be referred as Background Search LAI List. Roaming case
In case of Roaming the following steps outline the MS behavior on the expiry of the background search timer.
1. Check for the current LAI in the Background Search LAI list.
2. Retrieve all the PLMNs under which” the current LAI is present in the list.
3. From the above retrieved PLMNs select only the PLMNs with higher priority than the currently camped PLMN.
4. Perform HPLMN/High Priority PLMN selection procedure on the PLMNs filtered in the previous step.
5. If registered PLMN is HPLMN, stop the background search timer.
6. If not, restart the timer.
The following things are to be achieved by the above mentioned behavior of the MS.
1. In the case of international roaming, the MS would search for HPLMN in those areas where the presence of HPLMN coverage is probable.
2. In the case of National Roaming, the UE would search for HPLMN or a high priority PLMN ONLY when the presence of such a PLMN is highly probable, as determined by the operator.
Let us now examine the service state of the MS in different phases as the user moves in the travel path under consideration A4->A3->A2->A1->A2->A3->A4.
The early reselection to HPLMN can be easily identified from the data in the table.
With the proposed implementation in the MS and the network let us analyze the scenario mentioned earlier in the case of National Roaming.
It can be observed from the above table, that in the case of National Roaming, background search is not performed wherever it is not required, as determined by the operator.
Although illustrative embodiments of the present invention have been described herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various other
Changes and modifications may be affected therein by one skilled in the art without departing from the scope or spirit of the invention.
It will also be obvious to those skilled in the art that other control methods and apparatuses can be derived from the combinations of the various methods and apparatuses of the present invention as taught by the description and the accompanying drawings and these shall also be considered within the scope of the present invention. Further, description of such combinations and variations is therefore omitted above. It should also be noted that the host for storing the applications include but not limited to a microchip, microprocessor, handheld communication device, computer, rendering device or a multi function device.
Although the present invention has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications are possible and are apparent to those skilled in the art. Such changes and modifications are to be understood as included within the scope of the present invention as defined by the appended claims unless they depart therefrom.
|Indian Patent Application Number||323/CHE/2006|
|PG Journal Number||15/2013|
|Date of Filing||24-Feb-2006|
|Name of Patentee||SAMSUNG INDIA SOFTWARE OPERATIONS PRIVATE LIMITED|
|Applicant Address||BAGMANE LAKEVIEW BLOCK 'B' NO. 66/1 BAGMANE TECH PARK, CV RAMAN NAGAR, BYRASANDRA BANGALORE - 560093, KARNATAKA, INDIA|
|PCT International Classification Number||H04Q 7/18|
|PCT International Application Number||N/A|
|PCT International Filing date|