METHOD AND APPARATUS FOR ACCELERATED SUPER 3G CELL SEARCH

• US 20070091785A1
• Filed: 09/12/2006
• Published: 04/26/2007
• Est. Priority Date: 10/11/2005
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Lindoff, Bengt, Baldemair, Robert
• Granted Patent: US 7,656,850 B2
• Time in Patent Office: Days
• US Class Current: 370/203
• CPC Class Codes: H04J 11/0069 Cell search, i.e. determining cell identity [cell-ID] design of multiplexing codes H04J13/00; processing access restriction or access information H04W48/16; discovery of network devices for network data management H04W8/005; sounding signals for channel estimation H04L25/0226; structure of reference signals in multicarrier modulation systems H04L27/2613; frame, time or carrier synchronisation in multicarrier modulation systems H04L27/2655
• CPC Class Codes: H04L 27/2607 Cyclic extensions
• CPC Class Codes: H04W 56/0035 detecting errors in frequency or phase

Abstract

The method and system of a first aspect of the present invention is adapted to perform cell search on all possible bandwidths. In order to reduce the search time, the order in which the allowable BW is used in the search is based on information from history lists. These history lists include the BWs and frequency bands used. A second aspect of the present invention is a method and an OFDM cellular telecommunications system adapted to perform cell search and synchronization wherein the system has a certain number of bandwidth possibilities. The method comprises the steps of identifying at least one critical system parameter that reduces the set of possible synchronization signals; and performing cell search and synchronization over the limited number of different synchronization signals.

Claims

1. A method of performing a cell search in an OFDM cellular telecommunications system having a certain number of bandwidth (BW) possibilities and a certain number of cyclic prefix possibilities, comprising the steps of:

adapting a receiver front end in a mobile terminal/user equipment (UE) to a certain carrier frequency f₀ and BW, said BW including a certain number of BWs for the system;

commencing a cell search;

if slot timing found, performing a coarse frequency correction;

estimating a cyclic prefix length;

performing a frequency correction using the knowledge of the cyclic prefix;

detecting a cell ID; and

reading the broadcast channel.

2. The method of claim 1, wherein the search order over the different BWs is based on information from a history list.

3. The method of claim 1, wherein the search order over the different BWs is based on information about the current frequency band used.

4. The method of claim 3, wherein the frequency band is one selected from one on which the following standards is used:

Global System for Mobile Communications (GSM), Wideband Code Division Multiple Access (WCDMA) or IS-95.

5. The method of claim 1, wherein the step of estimating the cyclic prefix further comprises the step of correlating the received signal with a delayed version of the signal over at least two different sets (number) of samples, wherein the sets of samples over which the correlations are performed corresponds to the possible cyclic prefixes in the system and the estimated cyclic prefix length maximizes this correlation among all possible cyclic prefix lengths.

6. The method of claim 1, as implemented in a Super 3G mobile terminal.

7. A method for performing cell search and synchronization in an OFDM cellular telecommunications system having a certain number of bandwidth possibilities, comprising the steps of:

identifying at least one critical system parameter that reduces the set of possible synchronization signals; and

performing cell search and synchronization over the limited number of different synchronization signals.

8. The method of claim 7 wherein the reduced set of possible synchronization signals contains exactly one synchronization signal.

9. The method of claim 7 wherein one of the critical system parameters that reduces the number of possible synchronization signals is the system bandwidth (BW).

10. The method of claim 9 wherein the reduced set of possible synchronization signals contains exactly one synchronization signal.

11. The method of claim 7 wherein the critical system parameter that reduces the number of possible synchronization signals is the Fast Fourier Transform (FFT) size used to generate the transmitted signal.

12. The method of claim 11, wherein the reduced set of possible synchronization signals contains exactly one synchronization signal.

13. The method of claim 7, wherein the critical system parameter that reduces the number of possible synchronization signals is the length of the cyclic extension of the transmitted signal.

14. The method of claim 13, wherein the reduced set of possible synchronization signals contains exactly one synchronization signal.

15. An OFDM cellular telecommunications system, comprising means to facilitate a certain number of bandwidth possibilities and a certain number of cyclic prefix possibilities wherein information about cyclic prefix length for a specific cell is incorporated in a cell ID information.

16. An OFDM cellular telecommunications system having a certain number of bandwidth (BW) possibilities and a certain number of cyclic prefix possibilities, comprising:

a mobile terminal/user equipment (UE) operable at a certain carrier frequency f₀ and BW, said BW including a certain number of BWs for the system;

the mobile terminal/UE operable to commence a cell search;

if slot timing found, perform a coarse frequency correction;

estimate a cyclic prefix length;

perform a frequency correction using the knowledge of the cyclic prefix;

detect a cell ID; and

read the broadcast channel.

17. The OFDM cellular telecommunications system of claim 16, adapted to order the search over the different BWs is based on information from a history list.

18. The OFDM cellular telecommunications system of claim 16, adapted to order a search over the different BWs is based on information about the current frequency band used.

19. The OFDM cellular telecommunications system of claim 18, wherein the frequency band is one selected from one on which the following standards is used:

Global System for Mobile Communications (GSM), Wideband Code Division Multiple Access (WCDMA) or IS-95.

20. The OFDM cellular telecommunications system of claim 16, wherein the mobile terminal/UE, when estimating the cyclic prefix, is further adapted to correlate the received signal with a delayed version of the signal over at least two different sets (number) of samples, wherein the sets of samples over which the correlations are performed corresponds to the possible cyclic prefixes in the OFDM cellular telecommunications system and the estimated cyclic prefix length maximizes this correlation among all possible cyclic prefix lengths.

21. A mobile terminal/user equipment (UE) for use in an OFDM cellular telecommunications system having a means to facilitate a certain number of bandwidth possibilities and a certain number of cyclic prefix possibilities wherein information about cyclic prefix length for a specific cell is incorporated in a cell ID information, the mobile terminal/UE comprising a means adapted to utilize the cyclic prefix length information in the cell ID detected in to the cell search procedure for detecting CP for a specific cell.

22. An OFDM cellular telecommunications system operable to perform cell search and synchronization and having a certain number of bandwidth possibilities, comprising:

means for identifying at least one critical system parameter that reduces the set of possible synchronization signals; and

means for performing cell search and synchronization over the limited number of different synchronization signals.

23. The OFDM cellular telecommunications system of claim 22, wherein the reduced set of possible synchronization signals contains exactly one synchronization signal.

24. The OFDM cellular telecommunications system of claim 22, wherein one of the critical system parameters that reduces the number of possible synchronization signals is the system bandwidth (BW).

25. The OFDM cellular telecommunications system of claim 24, wherein the reduced set of possible synchronization signals contains exactly one synchronization signal.

26. The OFDM cellular telecommunications system of claim 22, wherein the critical system parameter that reduces the number of possible synchronization signals is the Fast Fourier Transform (FFT) size used to generate the transmitted signal.

27. The OFDM cellular telecommunications system of claim 26, wherein the reduced set of possible synchronization signals contains exactly one synchronization signal.

28. The OFDM cellular telecommunications system of claim 22, wherein the critical system parameter that reduces the number of possible synchronization signals is the length of the cyclic extension of the transmitted signal.

29. The OFDM cellular telecommunications system of claim 28, wherein the reduced set of possible synchronization signals contains exactly one synchronization signal.