Cell searching apparatus and method in asynchronous mobile communication system

• US 7,453,863 B2
• Filed: 04/01/2003
• Issued: 11/18/2008
• Est. Priority Date: 04/04/2002
• Status: Expired due to Fees

• Current Assignee: LG Electronics, Inc. (LG Corporation)
• Original Assignee: LG Electronics, Inc. (LG Corporation)
• Inventors: Chung, Hee-Sok
• Primary Examiner(s): Milord; Marceau
• Application Number:
  US10/402,942
• Publication Number:
  US 20050259615A1
• Time in Patent Office: 2,058 Days
• Field of Search: 370/350, 370/329, 370/331, 370/341, 370/342, 370/347, 370/348, 370/324, 370/335, 455/502, 455/509, 375/368, 375/370
• US Class Current: 370/350
• CPC Class Codes: H04B 7/2684 Synchronisation of a mobile station with more than one base station
• CPC Class Codes: H04W 48/16 Discovering, processing access restriction or access information
• CPC Class Codes: H04W 48/20 Selecting an access point
• CPC Class Codes: H04W 56/00 Synchronisation arrangements

Abstract

A cell searching apparatus and method in an asynchronous mobile communication system allocates an adjacent SCG to each base station according to adjacent degrees. When a mobile terminal is powered on, the mobile terminal receives PSCs and SSCs from the base stations. Multiple searching of SSCs is then performed based on each slot synchronization followed by a frame synchronization and SCG detection through the first searched SSC. If the detected SCG is not an SCG of a base station to which the mobile terminal belongs, the cell searching apparatus detects an SCG with a large size among the adjacent SCGs and detects an SC by using the greatest SCG. Frame synchronization and SCG detection are therefore quickly performed in a cell searching, resulting in a quick search searching.

Claims

1. An asynchronous mobile communication system for searching a base station, comprising:

a plurality of base stations allocated in advance among at least two geographically adjacent scrambling code groups (SCGs); and

a mobile terminal which detects a first SCG based on first detected slot synchronization information and determines whether the first SCG corresponds to a second predetermined SCG, and if the first SCG does not correspond to said second predetermined SCG, the mobile terminal determines the first SCG to be geographically adjacent said second predetermined SCG.

2. The system of claim 1, wherein the mobile terminal includes a cell searching apparatus for:

serially detecting a plurality of slot synchronization information,

performing SCG detection using each slot synchronization information,

detecting one or more SCGs adjacent to the first SCG,

determining a suitable SCG among the detected adjacent SCGs, and

searching a base station to which the mobile terminal belongs using the determined SCG and a slot synchronization and a frame synchronization of the SCG, the determined SCG corresponding to said second predetermined SCG.

3. The system of claim 1, wherein the cell searching apparatus comprises:

a filter which removes a noise component in a reception radio frequency (RF) signal;

a slot synchronizer which serially performs a slot synchronization using primary synchronization codes (PSCs) that are repeatedly detected after a slot period among a plurality of PSCs outputted from the filter;

a processor which controls operations of slot synchronization, frame synchronization, and SCG detection;

a plurality of frame synchronizers connected in parallel to the slot synchronizer, each frame synchronization performing SCG detection using corresponding slot synchronization information serially outputted from the slot synchronizer and each SSC outputted from the filter and determining a desired SCG based on the detected SCG under the control of the processor; and

a scrambling code detector for detecting an SC based on said second predetermined SCG, a slot synchronization and a frame synchronization of the SCG.

4. The system of claim 3, wherein the plurality of frame synchronizers perform an SCG detection in parallel using the corresponding slot synchronization information and each SSC, wherein if the first detected SCG is not an SCG of a specific base station to which the mobile belongs, pertinent frame synchronizers among the plurality of frame synchronizers detect again adjacent SCGs of the detected SCG in order to detect an SCG of the specific base station.

5. The system of claim 1, further comprising a cell searching apparatus which comprises:

a filter which removes a noise component contained in a reception RF signal;

a slot synchronizer which serially performs slot synchronization using PSCs that are repeatedly detected after a slot period among a plurality of PSCs outputted from the filter;

a processor which controls a slot synchronization, a frame synchronization and an SCG detection operation;

a frame synchronizer which serially performs a frame synchronization and an SCG detection operation using each SSC outputted from the filter on each slot synchronization information received from the slot synchronizer, and determining a desired SCG based on the detected SCG under control of the processor; and

a scrambling code detector which detects an SC using the determined SCG and a slot synchronization and a frame synchronization of the SCG, the determined SCG corresponding to said second predetermined SCG.

6. The system of claim 1, wherein the second predetermined SCG includes a base station to which the mobile terminal belongs.

7. A cell searching apparatus in an asynchronous mobile communication system, comprising:

a filter which removes a noise component in an RF signal transmitted from base stations;

a slot synchronizer which serially performs slot synchronization using PSCs repeatedly detected after a slot period among a plurality of PSCs outputted from the filter;

a processor which controls a slot synchronization, frame synchronization, and SCG detecting operation;

a plurality of frame synchronizers which detect SCGs using each SSC outputted from the filter, and determines a desired SCG under control of the processor based on the first detected SCG; and

a scrambling code detector which detects an SC using the determined SCG, wherein, if the first detected SCG is an SCG detected based on the specific slot synchronization information, the processor selects the first detected SCG as a desired SCG, and

if the first detected SCG is not an SCG detected based on the specific slot synchronization information, the processor detects one or more SCGs adjacent to the first detected SCG and selects one of the adjacent SCGs as a desired SCG.

8. The apparatus of claim 7, wherein adjacent base stations use an adjacent SCGs.

9. The apparatus of claim 7, wherein the slot synchronizer informs the processor of detected specific slot synchronization information using a PSC with a most powerful reception strength.

10. A cell searching apparatus in an asynchronous mobile communication system, comprising:

a filter which removes a noise component in an RF signal transmitted from base stations;

a slot synchronizer which serially performs a slot synchronization using PSCs repeatedly detected after a slot period among a plurality of PSCs outputted from the filter;

a processor which controls a slot synchronization, frame synchronization and SCG detecting operation;

a frame synchronizer which serially performs frame synchronization and SCG detecting operation using each SSC outputted from the filter on each slot synchronization information, and determining a desired SCG under the control of the processor based on the first detected SCG; and

a scrambling code detector which detects an SC using the determined SCG, wherein if the first detected SCG is an SCG detected based on the specific slot synchronization information, the processor selects the first detected SCG as a desired SCG, and

if the first detected SCG is not an SCG detected based on the specific slot synchronization information, the processor detects SCGs adjacent to the first detected SCG and selects the adjacent SCGs as a desired SCG.

11. The apparatus of claim 10, wherein adjacent base stations use an adjacent SCGs.

12. The apparatus of claim 10, wherein the slot synchronizer informs the processor of detected specific slot synchronization information using a PSC with a most powerful reception strength.

13. An SCG allocating method in an asynchronous mobile communication system, comprising:

setting first one of a plurality of base stations as a reference base station and allocating a reference SCG thereto;

allocating an adjacent SCG of the reference SCG to at least a second one of the base stations adjacent to the first base station but not allocated to the reference SCG; and

determining whether a third one of the base stations is in a cell adjacent to the cell of the second base station base station but is not allocated to either of the reference SGG or the adjacent SGG; and

allocating an SGG different from the reference SGG and adjacent SGG to the third base station if the third base station is in a cell adjacent to the cell of the second base station but is not allocated to either of the reference SGG or the adjacent SGG.

14. A cell searching method in an asynchronous mobile communication system, comprising:

serially performing slot synchronization using PSCs received from a plurality of base stations;

performing multiple frame synchronization and SCG detection using SSCs received from the base stations based on each serially performed slot synchronization;

checking whether a first detected SCG is a desired one;

determining a suitable SCG among adjacent SCGs of the first detected SCG if the first detected SCG is not a desired one; and

completing a base station searching using the determined SCG,

wherein in determining a suitable SCG, if the first detected SCG is an SCG detected based on the slot synchronization information detected using the PSC with the most powerful reception strength among PSCs that are repeatedly detected after the slot period, the first detected SCG is determined as a suitable SCG.

15. The method of claim 14, wherein adjacent base stations use adjacent SCGs.

16. The method of claim 14, wherein, in the step of performing a slot synchronization, slot synchronization is performed using a PSC that is repeatedly detected after a slot period, and a slot synchronization is serially performed by using different PSCs that are repeatedly detected.

17. The method of claim 14, wherein, in the step of checking, it is checked whether the first detected SCG is an SCG detected based on the slot synchronization information detected by using the PSC with the most powerful reception strength among PSCs that are repeatedly detected after the slot period.

18. The method of claim 14 further comprising:

determining the first detected SCG as a suitable SCG if the first detected SCG is a desired SCG.

19. A cell searching method in an asynchronous mobile communication system, comprising:

serially performing slot synchronization using PSCs received from a plurality of base stations;

performing multiple frame synchronization and SCG detection using SSCs received from the base stations based on each serially performed slot synchronization;

checking whether a first detected SCG is a desired one;

determining a suitable SCG among adjacent SCGs of the first detected SCG if the first detected SCG is not a desired one; and

completing a base station searching using the determined SCG,

wherein determining a suitable SCG among adjacent SCGs comprises;

searching adjacent SSCs of an SSC used when the first detected SCG is detected based on the slot synchronization information detected using the PSC with a most powerful reception strength; and

detecting an SSC with a greatest value among the searched adjacent SSCs and performing a frame synchronization and SCG detection using the SSC.

20. A method for communicating information in a mobile communication system, comprising:

selecting a first base station from a plurality of base stations;

allocating a first scrambling code group to the selected base station;

selecting a second base station from the plurality of base stations;

determining whether the second base station is in a cell adjacent to a cell of the first base station and not included in the first scrambling code group; and

allocating a second scrambling code group to the second base station if the second base station is in a cell adjacent to the first base station but not in the first scrambling code group.

21. The method of claim 20, wherein the first scrambling code group and the second scrambling code group are related based on a predetermined pattern.

22. The method of claim 21, wherein in the predetermined pattern, the first scrambling code group and the second scrambling code group are sequentially related.

23. The method of claim 21, wherein the first scrambling code group and the second scrambling code group are adjacent code groups.

24. The method of claim 20, further comprising:

selecting a third base station from the plurality of base stations;

determining whether the third base station is in a cell adjacent the cell of the second base station but not include in either of the first or second scrambling code groups; and

allocating a third scrambling code to the third base station if the third base station is in a cell adjacent the cell of the second base station but not in either of the first or second scrambling code groups.

25. The method of claim 24, wherein the second scrambling code and the third scrambling code are adjacent scrambling codes.