Title of Invention

HPLMN SEARCH OPTIMIZATION BY MOBILE STATION IN WIRELESS SYSTEMS

Abstract

This is an improved method of HPLMN search/selection by MS. More particularly, when periodic HPLMN search timer expires or when MS is switched ON or on recovery from lack of coverage. If the operator does not have the HPLMN existing in one or more RATs, then the bits in EFHPLMNwAcT can be set accordingly to avoid unnecessary HPLMN search. Thus battery consumption can be reduced by doing minimal searches and the time required for selecting / searching a PLMN is reduced.

Full Text

VIELD OF THE INVENTION This invention in general relates to wireless networks and mobile communication devices. Further, this invention relates to an improved method of HPLMN search/selection by Mobile Station (MS) in a wireless network. More particularly, this invention relates to Home Public Land Mobile Network (HPLMN) search optimization by Mobile Station in wireless systems when periodic HPLMN search timer expires or when MS is switched ON or on recovery from lack of coverage. DESCRIPTION OF RELATED ART In any mobile network, when the mobile station (MS) logs on to a network while in national roaming, the MS always searches for HPLMN at periodic intervals as determined by periodic HPLMN search time written on SIM. If the SIM does not have any value for the HPLMN search time, then default of 60 minutes is considered. The MS searches for HPLMN in all the RATs (Radio Access Technology) it is capable of. At power ON or on recovery from lack of coverage, the MS searches for HPLMN if Registered Public Land Mobile Network (RPLMN) is not available. So when MS is in its home country i.e. currently camped Mobile Country Code (MCC) equals MCC of International Mobile Subscriber Identity (IMSI), HPLMN is given highest priority and MS prefers to get services from the HPLMN. The network selection procedure of MS forces to search for HPLMN in all the RATs the MS is capable of, starting from the RAT priority search order as given in EFHPLMNwAcT (HPLMN selector with Access Technology). With such an implementation, MS does not have any flexibility to limit its search for specific RATs, when searching for HPLMN. Secondly, if the operator wants to avoid the HPLMN selection due to network planning, it is not possible with the existing implementation. If the operator has HPLMN in only one RAT, in such a case, MS which supports more than one RAT will search for all the RATs it is capable of. This leads to excessive power consumption and consequently the battery gets drained. This problem can be seen in the following cases. a) At power ON or on recovery from lack of coverage At Power ON or on recovery from lack of coverage, if MS is unable to find RPLMN, MS starts the search for HPLMN in all the RATs it is capable of. If operator does not have HPLMN working in some/all the RATs, then MS drains the battery by doing unnecessary search. b) MS in national roaming The MS when in National roaming always searches for HPLMN or high priority PLMN periodically. The periodicity is given on SIM and if not available on SIM, the default value of 60 minutes is considered. During periodic search for HPLMN, the MS searches in all the RATs it is capable of. If HPLMN is not existent in any/all of those RATs then MS drains out the battery by doing useless search. SUMMARY OF THE INVENTION The primary object of the present invention is to provide a method for HPLMN search optimization by mobile station in wireless systems. It is a further object of this invention to invent a method for selecting/searching a PLMN by MS during power ON/on recovery from lack of coverage/periodic HPLMN search timer expiry that reduces the overall time spent in selecting a PLMN. is another object of the invention to provide a method for selecting/searching a PLMN by MS, wherein unnecessary searches for network are prevented and battery drainage is reduced. If the Operator does not have the HPLMN existing in one or more RATs, then the bits in EFHPLMNwAcT can be set accordingly to avoid unnecessary HPLMN search. This way o Battery consumption can be reduced by doing minimal searches. o The time required for selecting / searching a PLMN is reduced. The solution is to limit the search (when MS is searching for HPLMN) to the RATs mentioned in EFHPLMNwAcT only. This can be done by using the unused bits of EFHPLMNwAcT. (a) Accordingly, the present invention comprises a method of HPLMN search / selection by Mobile Station (MS) in wireless systems, the said method comprising the steps of: a. limiting the HPLMN search for specified plurality of RATs by using unused bits of EFHPLMNwAcT; b. specifying the RATs for HPLMN, where search can be done using the Elementary File HPLMN selector with Access Technology (EFHPLMNwAcT); and c. specifying the Priority of a RAT search order using EFHPLMNwAcT, where the said search/selection is performed when periodic HPLMN search timer expires or when MS is switched ON or on recovery from lack of coverage These and other objects, features and advantages of the present invention will become more readily apparent from the detailed description taken in conjunction with the drawings and the claims. RIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS Figure 1 shows HPLMN selector with access technology data field containing the HPLMN code or codes together with the respective access technology in priority order. Figure 2 shows the coding of the two bytes 5n-1 and 5n of EFHPLMNwAct containing the RAT information. Figure 3 shows EFHPLMNwAcT byte structure when the bit b1 of 5n-1 is set. Figure 4 shows EFHPLMNwAcT byte structure when the bit b1 of 5n is set. Figure 5 shows EFHPLMNwAcT byte structure when HPLMN is present in UTRAN and GSM and bit b8 of 5n-1 is set to one and bit b8 of 5n is set to zero. Figure 6 shows EFHPLMNwAcT byte structure when HPLMN is present in UTRAN and GSM; and bit b8 of 5n is set to one and bit b8 of 5n-1 is set to zero. Figure 7 shows EFHPLMNwAcT byte structure when HPLMN is present in UTRAN and GSM and bit b8 of 5n and 5n-1 is set to zero. Figure 8 shows EFHPLMNwAcT byte structure when HPLMN is not present in UTRAN and GSM. Figure 9 shows EFHPLMNwAcT byte structure when HPLMN is present in UTRAN and GSM RAT and priority among the RATs is implementation dependent. Figure 10 shows EFHPLMNwAcT byte structure when HPLMN is present in UTRAN only and priority among the RATs is implementation dependent figure 11 shows EFHPLMNwAcT byte structure when HPLMN is present in GSM RAT only and priority among the RATs is implementation dependent Figure 12 shows EFHPLMNwAcT byte structure when HPLMN is not present in GSM and UTRAN and priority among the RATs is implementation dependent 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 on 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. In the preferred embodiment of the proposed invention, the EFHPLMNwAcT on SIM has the following structure. The bytes 5n-1 and 5n contain the RAT information. Currently these two bytes are coded as follows. MS shall use any of the unused bits b1 to b7 of 5n-1 to indicate whether the PLMN is present in the UTRAN. If the presence of HPLMN is indicated, then MS can search for HPLMN in UMTS RAT. MS shall use any of the unused bits b1 to b6 of 5n to indicate whether the PLMN is present in GSM. If the presence of HPLMN is indicated, then MS can search for PLMN in GSM RAT. • If the Operator does not have the HPLMN existing in one or more RATs, then the bits in EFHPLMNwAcT can be set accordingly to avoid unnecessary HPLMN search. • Battery consumption can be reduced by doing minimal searches. • The time required for selecting/searching a PLMN is reduced. In all the accompanying drawings, bit b1 of 5n-1 and 5n is used to indicate if the corresponding PLMN is present in that RAT. The bit settings of b8 (5n-1 and 5n) are considered only when b1 of 5n-1 and 5n are set to one. X means it can be zero or one (don't care condition). Figure 1 shows HPLMN selector with access technology data field containing the HPLMN code or codes together with the respective access technology in priority order. Refer [3GPP TS 31.102 version 3.11.0 Release 1999 sec 4.2.54 ] Figure 2 shows the coding of the two bytes,the bytes 5n-1 and 5n of EFHPLMNwAct containing the RAT information. The Access Technology of the HPLMN that the MS will assume when searching for the HPLMN, in priority order. Figure 3 shows EFHPLMNwAcT byte structure when the bit b1 of 5n-1 is set and hence MS can search for HPLMN in UTRAN Whenever necessary. But the bit b1 of 5n is set to zero, which indicates that MS shall never search for HPLMN in GSM RAT. Figure 4 shows EFHPLMNwAcT byte structure when the bit b1 of 5n is set and hence MS can search for HPLMN in GSM RAT Whenever necessary. But the bit b1 of 5n-1 is set to zero, which indicates that MS shall never search for HPLMN in UTRAN. Trigure 5 shows EFHPLMNwAcT byte structure when HPLMN is present in UTRAN and GSM; MS can search in both the RATs whenever necessary. Since bit b8 of 5n-1 is set to one and bit b8 of 5n is set to zero, UTRAN shall be given highest priority. Figure 6 shows EFHPLMNwAcT byte structure when HPLMN is present in UTRAN and GSM; MS can search in both the RATs whenever necessary. Since bit b8 of 5n is set to one and bit b8 of 5n-1 is set to zero, GSM shall be given highest priority. Figure 7 shows EFHPLMNwAcT byte structure when HPLMN is present in UTRAN and GSM; MS can search in both the RATs whenever necessary. Since bit b8 of 5n and 5n-1 is set to zero, the priority of the RAT search order is left to the implementation of MS. Figure 8 shows EFHPLMNwAcT byte structure when HPLMN is not present in UTRAN and GSM. MS shall never search for HPLMN in UTRAN and GSM RAT. If the priority among the RATs is implementation dependent for the PLMN(s) mentioned in EFHPLMNwAct, then MS can use only the bit 8 of byte 5n-1 and bits 7 and 8 of byte 5n. In this solution, MS need not use any of the unused bits of byte 5n-1 and 5n. Figure 9 shows EFHPLMNwAcT byte structure when HPLMN is present in UTRAN and GSM RAT and if priority among the RATs is implementation dependent. MS can search in both the RATs whenever necessary. The priority of the RAT search order is left to the implementation of MS. Figure 10 shows EFHPLMNwAcT byte structure when HPLMN is present in UTRAN only and if priority among the RATs is implementation dependent. MS shall search for HPLMN in UTRAN only. figure 11 shows EFHPLMNwAcT byte structure When HPLMN is present in GSM RAT only and if priority among the RATs is implementation dependent, MS shall search for HPLMN in GSM only. Figure 12 shows EFHPLMNwAcT byte structure When HPLMN is not present in GSM and UTRAN and if priority among the RATs is implementation dependent. MS shall never search for HPLMN. 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 below. It should also be noted that the host for storing the applications include but not limited to a computer, mobile handheld device, mobile network 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. GLOSSARY OF TERMS AND THEIR DEFINITIONS EFHPLMNwAcT: Elementary File HPLMN selector with Access Technology GSM: Global System for Mobile communication HPLMN: Home PLMN IMSI: International Mobile Subscriber Identity MCC: Mobile Country Code MS: Mobile Station PLMN: Public Land Mobile Network RAT: Radio Access Technology RPLMN: Registered PLMN UMTS: Universal Mobile Telecommunication System UTRAN: UMTS Terrestrial Radio Access Network VPLMN: Visited PLMN RFU: Reserved for Future Use WE CLAIM 1. A method of HPLMN search / selection by Mobile Station (MS) in wireless systems, the said method comprising the steps of: a. limiting the HPLMN search for specified plurality of RATs by using unused bits of EFHPLMNwAcT; b. specifying the RATs for HPLMN, where search can be done using the Elementary File HPLMN selector with Access Technology (EFHPLMNwAcT); and c. specifying the Priority of a RAT search order using EFHPLMNwAcT, where the said search/selection is performed when periodic HPLMN search timer expires or when MS is switched ON or on recovery from lack of coverage. 2. A method of HPLMN search/selection by MS in wireless systems as claimed in claim 1 wherein when the HPLMN exist in one or more RATs, the bits in EFHPLMNwAcT is set accordingly to avoid unnecessary HPLMN search. 3. A method of HPLMN search/selection by MS in wireless systems as claimed in claim 1 wherein the bytes 5n-1 and 5n of EFHPLMNwAcT contain the RAT information. 4. A method of HPLMN search/selection by MS in wireless systems as claimed in claim 1 wherein MS uses any of the unused bits b1 to b7 of 5n-1 to indicate whether the PLMN is present in the UTRAN. 5. A method of HPLMN search/selection by MS in wireless systems as claimed in claim 5 wherein when the presence of HPLMN is indicated, MS searches for HPLMN in UMTS RAT. is. A method of HPLMN search/selection by MS in wireless systems as claimed in claim 1 wherein MS uses any of the unused bits b1 to b6 of 5n to indicate whether the PLMN is present in GSM. 7. A method of HPLMN search/selection by MS in wireless systems as claimed in claim 6 wherein when the presence of HPLMN is indicated, MS searches for HPLMN in GSM RAT. 8. A method of HPLMN search/selection by MS in wireless systems as claimed in claim 1 wherein bit b1 of 5n-1 and 5n indicate the presence of PLMN in that RAT. 9. A method of HPLMN search/selection by MS in wireless systems as claimed in claim 1 wherein the bit settings of b8 for both 5n-1 and 5n are considered only when b1 of 5n-1 and 5n both are set to one. 10. A method as claimed in claim 8 wherein when b1 of 5n-1 and 5n both are not set to one, b8 setting is redundant. 11. A method of HPLMN search/selection by MS in wireless systems as claimed in claim 1 wherein when the bit b1 of 5n-1 is set to 1, MS searches for HPLMN in UTRAN and when the bit b1 of 5n is set to zero, MS never searches for HPLMN in GSM RAT. 12. A method of HPLMN search/selection by MS in wireless systems as claimed in claim 1 wherein when bit b1 of 5n is set to 1, MS searches for HPLMN in GSM RAT and when the bit b1 of 5n-1 is set to zero, MS never searches for HPLMN in UTRAN. 13. A method of HPLMN search/selection by MS in wireless systems as claimed in claim 1 wherein when HPLMN is present in UTRAN and GSM, MS searches in both the RATs and if bit b8 of 5n-1 is set to one and bit b8 of 5n is set to zero, UTRAN is given highest priority. 14. A method of HPLMN search/selection by MS in wireless systems as claimed in claim 1 wherein when HPLMN is present in UTRAN and GSM, MS searches in both the RATs and when bit b8 of 5n is set to one and bit b8 of 5n-1 is set to zero, GSM is given highest priority. 15. A method of HPLMN search/selection by MS in wireless systems as claimed in claim 1 wherein when HPLMN is present in UTRAN and GSM, MS searches in both the RATs and when bit b8 of 5n and 5n-1 is set to zero, the priority of the RAT search order is left to the implementation of MS. 16. A method of HPLMN search/selection by MS in wireless systems as claimed in claim 1 wherein when HPLMN is not present in UTRAN and GSM, MS does not search for HPLMN in UTRAN and GSM RAT. 17. A method of HPLMN search/selection by MS in wireless systems as claimed in claim 1 wherein the priority among the RATs is implementation dependent, then MS uses only the bit8 of byte 5n-1 and bits 7and8 of byte 5n. 18. A method of HPLMN search/selection by MS in wireless systems as claimed in claim 17 wherein when HPLMN is present in UTRAN and GSM RAT, MS searches in both the RATs and the priority of the RAT search order is left to the implementation of MS. 19. A method of HPLMN search/selection by MS in wireless systems as claimed in claim 17 wherein when HPLMN is present in UTRAN only, MS searches for HPLMN in UTRAN only. 20. A method of HPLMN search/selection by MS in wireless systems as claimed in claim 17 wherein when HPLMN is present in GSM RAT only, MS searches for HPLMN in GSM only. 21. A method of HPLMN search/selection by MS in wireless systems as claimed in claim 17 wherein when HPLMN is not present in GSM and UTRAN, MS does not search for HPLMN. 22. A method of HPLMN search/selection by MS in wireless systems, when periodic HPLMN search timer expires or when MS is switched ON or on recovery from lack of coverage such as substantially herein described particularly with reference to the accompanying drawings. Dated this 31st day of December 2004

Documents:

1487-che-2004-abstract.pdf

1487-che-2004-claims.pdf

1487-che-2004-correspondnece-others.pdf

1487-che-2004-correspondnece-po.pdf

1487-che-2004-description(complete).pdf

1487-che-2004-drawings.pdf

1487-che-2004-form 1.pdf

1487-che-2004-form 13.pdf

1487-che-2004-form 26.pdf