System and method for detecting multiple direct sequence spread spectrum signals using a multi-mode searcher

• US 20040062299A1
• Filed: 08/28/2003
• Published: 04/01/2004
• Est. Priority Date: 10/01/2002
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Nambiar, Rajiv R., McDonough, John G., Abdulla, Karim, Jeong, Gibong
• Granted Patent: US 7,474,688 B2
• Time in Patent Office: Days
• US Class Current: 375/150
• CPC Class Codes: H04B 1/708 Parallel implementation
• CPC Class Codes: H04B 2201/70711 with modular structure
• CPC Class Codes: H04J 13/0044 OVSF [orthogonal variable spreading factor]
• CPC Class Codes: H04J 13/12 Generation of orthogonal codes

Abstract

System and method for detecting multiple direct sequence spread spectrum signals using a multi-mode searcher. A preferred embodiment comprises the specification of a hypothesis for a particular communications network. The hypothesis can then be used to generate a pseudo-random number (PN) sequence that is provided to a searcher. The searcher can then make adjustments to the PN sequence to bring the PN sequence to conformity with requirements of the particular communications network. The adjustment to the PN sequence permits the use of a multi-mode searcher to perform searches for signals of various communications networks with minimal hardware dedicated to each communications network.

Claims

1. A method for detecting direct sequence spread spectrum signals with a searcher comprising:

specifying a hypothesis for a direct sequence spread spectrum signal from a specific communications network;

generating a pseudo-random number (PN) sequence based on the hypothesis;

providing the PN sequence to the searcher to correlate with a received signal;

adjusting the PN sequence to conform to the specific communications network; and

correlating the adjusted PN sequence with a received signal.

2. The method of claim 1, further comprising after the using:

accumulating the correlation results of the adjusted PN sequence with the received signal; and

processing the accumulation result.

3. The method of claim 2, wherein the accumulating comprises coherent and non-coherent accumulation.

4. The method of claim 2, wherein the processing comprises:

comparing the accumulation result with a specified threshold; and

saving the accumulation result if it exceeds the specified threshold.

5. The method of claim 2 further comprising prior to the accumulating, despreading the received signal.

6. The method of claim 5, wherein the despreading removes an antenna diversity scheme.

7. The method of claim 1, wherein the specific communications network may be an Universal Mobile Telephony System (UMTS) compliant network or a Code-Division Multiple Access-2000 (CDMA2000) compliant network.

8. The method of claim 7, wherein a hypothesis for the direct sequence spread spectrum signal from a UMTS compliant communications network may be different from a hypothesis for the direct sequence spread spectrum signal from a CDMA2000 compliant communications network.

9. The method of claim 7, wherein the adjusting comprises wrapping around the PN sequence when the specific communications network is a CDMA2000 compliant communications network.

10. The method of claim 1, wherein the generating is further based on a timing reference.

11. The method of claim 10, wherein the timing reference is provided by the searcher.

12. The method of claim 11, wherein the timing reference is provided by a capture time unit.

13. A circuit comprising:

a memory to store information relevant to a hypothesis;

sequence generator coupled to the memory, the sequence generator containing circuitry to generate a pseudo-random number (PN) sequence based on the hypothesis;

a searcher coupled to the sequence generator, the searcher containing circuitry to correlate the PN sequence generated by the sequence generator with a received signal and to accumulate results from the correlation; and

a search controller coupled to the memory, the search controller containing circuitry to configure and control the operation of the searcher.

14. The circuit of claim 13, wherein the hypothesis is indexed in the memory by a reference number and the information relevant to the hypothesis can be accessed by the reference number.

15. The circuit of claim 13, wherein the sequence generator uses the hypothesis and a timing reference provided by the searcher to generate the PN sequence.

16. The circuit of claim 13, wherein the memory can store information for multiple hypotheses simultaneously.

17. The circuit of claim 16, wherein information relevant to each hypothesis can be referenced through the use of a unique reference number.

18. The circuit of claim 13, wherein the searcher contains a PN sequence adjust unit wherein differences between PN sequences for different communications networks can be accommodated.

19. The circuit of claim 18, wherein an adjustment made by the PN sequence adjust unit comprises changing a wraparound point for a PN sequence for use in CDMA2000 compliant communications network.

20. A wireless receiver comprising:

an analog front end coupled to an antenna, the analog front end containing circuitry to filter and amplify a received signal provided by the antenna;

an analog-to-digital converter (ADC), the ADC to convert an analog signal provided by the analog front end into a digital symbol stream; and

a digital signal processing section coupled to the ADC, the digital signal processing section containing circuitry to synchronize the wireless receiver with a communications network.

21. The wireless receiver of claim 20, wherein the digital signal processing section comprises:

a memory to store information relevant to a hypothesis;

sequence generator coupled to the memory, the sequence generator containing circuitry to generate a pseudo-random number (PN) sequence based on the hypothesis;

a searcher coupled to the sequence generator, the searcher containing circuitry to correlate the PN sequence generated by the sequence generator with a received signal and to accumulate results from the correlation; and

a search controller coupled to the memory, the search controller containing circuitry to configure and control the operation of the searcher.

22. The wireless receiver of claim 21, wherein the hypothesis is indexed in the memory by a reference number and the information relevant to the hypothesis can be accessed by the reference number.

23. The wireless receiver of claim 21, wherein the memory can store information for multiple hypotheses simultaneously.

24. The wireless receiver of claim 20, wherein the wireless receiver is part of a wireless device capable of operating in multiple communications networks.

25. The wireless receiver of claim 24, wherein the multiple communications networks are Universal Mobile Telephony System (UMTS) and CDMA2000 (Code-Division Multiple Access 2000) compliant communications networks.