Cell search method for inter-system handover in a mobile station

• US 7,409,214 B2
• Filed: 12/22/2003
• Issued: 08/05/2008
• Est. Priority Date: 08/18/2003
• Status: Expired due to Fees

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Lee, Jae-Hwan
• Primary Examiner(s): Nguyen; Tu
• Application Number:
  US10/740,896
• Publication Number:
  US 20050043046A1
• Time in Patent Office: 1,688 Days
• Field of Search: 455/436, 455/439, 455/442, 455/502, 455/432, 455/444, 455/522.1, 370/331, 370/324, 370/332, 370/335
• US Class Current: 455/436
• CPC Class Codes: H04B 1/7075 with code phase acquisition
• CPC Class Codes: H04B 2201/70702 Intercell-related aspects
• CPC Class Codes: H04W 36/0072 of resource information of target access point
• CPC Class Codes: H04W 36/14 Reselecting a network or an air interface

Abstract

A cell search method for handover between an asynchronous mobile communication system'"'"'s base station and a synchronous mobile communication system'"'"'s base station. A border base station, which is an asynchronous base station neighboring a synchronous mobile communication network, acquires information on a GPS satellite time, a reference time of the synchronous mobile communication network, generates base station frame number (BFN) synchronized to the satellite time and a system frame number (SFN) having a predetermined offset for the BFN for each cell, generates a system information block including a difference value between the BFN and the SFN, and transmits the system information block over a common channel along with the SFN. A dual-mode mobile station receives an SFN for each cell and a system information block from the border base station, acquires the satellite time synchronization, extracts a neighbor list of synchronous base stations, including PN offset information, from the system information block, searches a neighbor cell of a synchronous system at times when the PN offsets have elapsed from the satellite time synchronization, and reports the search result to the border base station. The cell search method contributes to rapid and efficient cell search during inter-system handover.

Claims

1. A method for providing timing information for inter-system handover by an asynchronous base station in a mobile communication system including an asynchronous mobile communication network associated with at least one asynchronous base station using independent synchronization, and a synchronous mobile communication network associated with at least one synchronous base station using synchronization matched with a satellite time, the method comprising:

acquiring information on the satellite time by the asynchronous base station, the asynchronous base station generating a base station frame number (BFN) synchronized to the satellite time and a system frame number (SFN) having a predetermined offset for the BFN for each cell;

generating a system information block including a difference value between the BFN and the SFN; and

transmitting the system information block over a common channel along with the SFN from the asynchronous base station.

2. The method of claim 1, wherein:

the BFN is generated so that the BFN becomes a multiple of 8 at a time when the satellite time becomes a multiple of 80 ms.

3. The method of claim 1, wherein:

the system information block is repeatedly transmitted at selected periods.

4. The method of claim 1, further comprising:

including a neighbor list containing frequency information and pseudo-random noise (PN) offset information of at least one neighbor synchronous base station in the system information block; and

transmitting the neighbor list-included system information block to a mobile station in an idle state over a common channel.

5. The method of claim 1, further comprising:

including a neighbor list containing frequency information and PN offset information of at least one neighbor synchronous base station in a measurement control message; and

transmitting the neighbor list-included measurement control message to a mobile station in an active state over a control channel.

6. The method according to claim 1, wherein:

the steps of acquiring information, generating a system information block and transmitting the system information block are performed by a border base station.

7. The method according to claim 6, wherein:

the border base station is an asynchronous border station.

8. A method for performing inter-system handover from an asynchronous base station to a synchronous base station by a mobile station in a mobile communication system including an asynchronous mobile communication network associated with at least one asynchronous base station using independent synchronization, and a synchronous mobile communication network associated with at least one synchronous base station using synchronization matched with a satellite time, the method comprising:

receiving a system frame number (SFN) of the asynchronous base station for each cell and a system information block from the asynchronous base station over a common channel;

extracting a difference value between a base station frame number (BFN) of the asynchronous base station and the SFN, from the system information block, the BFN being synchronized to the satellite time; and

acquiring frame synchronization of the base station synchronized to the satellite time by applying the difference value to the SFN.

9. The method of claim 8, further comprising:

receiving a system information block including a neighbor list containing frequency information and pseudo-random noise (PN) offset information of at least one neighbor synchronous base station from the asynchronous system; and

searching the at least one neighbor synchronous base station at times when PN offsets in the neighbor list have elapsed from a time when the BFN becomes a multiple of 8.

10. The method of claim 9, further comprising:

performing idle-state handover to the synchronous base station if there is a synchronous base station satisfying a predetermined cell reselection criterion as a result of the search.

11. The method of claim 8, further comprising:

receiving a measurement control message including a neighbor list containing frequency information and pseudo-random noise (PN) offset information of a neighbor synchronous base station in an active state; and

searching at least the one neighbor synchronous base station at times when PN offsets in the neighbor list have elapsed from a time when the BFN becomes a multiple of 8, for an idle period of a frame based on a compressed mode.

12. The method of claim 11, further comprising

reporting the search result to the system, and upon receiving a handover direction to a synchronous base station from the system, performing active-state handover to the corresponding synchronous base station.

13. A mobile communication system including an asynchronous mobile communication network associated with at least one asynchronous base station using independent synchronization, and a synchronous mobile communication network associated with at least one synchronous base station using synchronization matched with a satellite time, the system comprising:

at least one border base station in the asynchronous mobile communication network, the border base station neighboring a service area of the synchronous mobile communication network, and using synchronization matched to the satellite time and providing timing information for the synchronization; and

a dual-mode mobile station capable of communicating with both the asynchronous mobile communication network and the synchronous mobile communication network, the dual-mode mobile station being synchronized to the timing information provided from the border base station,

wherein the timing information represents a base station frame number (BFN) that becomes a multiple of 8 at a time when the satellite time becomes a multiple of 80 ms.

14. The mobile communication system of claim 13, wherein the border base station acquires information on the satellite time, generates a base station frame number (BFN) synchronized to the satellite time and a system frame number (SFN) having a predetermined offset for the BFN for each cell, generates a system information block including a difference value between the BFN and the SFN, and transmits the system information block over a common channel along with the SFN.

15. The mobile communication system of claim 14, wherein the border base station includes a neighbor list containing frequency information and pseudo-random noise (PN) offset information of at least one neighbor synchronous base station in a system information block, transmits the neighbor list-included system information block to a mobile station in an idle state over a common channel, includes a neighbor list containing frequency information and PN offset information of at least one synchronous base station in a measurement control message, and transmits the neighbor list-included measurement control message to a mobile station in an active state over a control channel.

16. The mobile communication system of claim 13, wherein the dual-mode mobile station receives a system frame number (SFN) of the asynchronous base station for each cell and a system information block from the asynchronous base station over a common channel, extracts a neighbor list including a difference value between a base station frame number (BFN) of the asynchronous base station, synchronized to the satellite time, and the SFN, from the system information block, and acquires the BFN synchronized to the satellite time by applying the difference value to the SFN.

17. The mobile communication system of claim 16, wherein the dual-mode mobile station receives a system information block including a neighbor list containing frequency information and PN offset information of at least one neighbor synchronous base station from the asynchronous system, and searches the at least one neighbor synchronous base station at times when PN offsets in the neighbor list have elapsed from a time when the BFN becomes a multiple of 8.

18. The mobile communication system of claim 17, wherein the dual-mode mobile station performs idle-state handover to the synchronous base station, if there is a synchronous base station satisfying a predetermined cell reselection criterion as a result of the search.

19. The mobile communication system of claim 16, wherein the dual-mode mobile station receives a measurement control message including a neighbor list containing frequency information and PN (Pseudo-random Noise) offset information of a neighbor synchronous base station in an active state, and searches at least the one neighbor synchronous base station at times when PN offsets in the neighbor list have elapsed from a time when the BFN becomes a multiple of 8.

20. The mobile communication system of claim 19, wherein the dual-mode mobile station reports the search result to the system, and upon receiving a handover direction to a synchronous base station from the system, performs an active state handover to the corresponding synchronous base station.