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

• US 7,474,688 B2
• Filed: 08/28/2003
• Issued: 01/06/2009
• Est. Priority Date: 10/01/2002
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Abdulla, Karim, Nambiar, Rajiv R., McDonough, John G., Jeong, Gibong
• Primary Examiner(s): Odom; Curtis B
• Application Number:
  US10/651,282
• Publication Number:
  US 20040062299A1
• Time in Patent Office: 1,958 Days
• Field of Search: 375/130, 375136-137, 375141-144, 375147-150
• US Class Current: 375/147
• 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 first hypothesis for a direct sequence spread spectrum signal from a Universal Mobile Telephony System (UMTS) compliant network;

specifying a second hypothesis for a direct sequence spread spectrum signal from a Code-Division Multiple Access-2000 (CDMA2000) compliant network;

generating a pseudo-random number (PN) sequence based on the hypothesis associated with a selected one of the Universal Mobile Telephony System (UMTS) compliant and Code-Division Multiple Access-2000 (CDMA2000) compliant communications networks;

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

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

correlating the adjusted PN sequence with the 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 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.

8. The method of claim 1, wherein the adjusting comprises wrapping around the PN sequence when the specific communications network is a CDMA2000 compliant communications network.

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

10. The method of claim 9, wherein the timing reference is provided by the searcher.

11. The method of claim 10, wherein the timing reference is provided by a capture time unit.

12. A circuit comprising:

a memory to store information relevant to hypotheses associated with at least two incompatible communications networks;

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

a searcher coupled to the sequence generator, the searcher containing circuitry to correlate a PN sequence for a selected one of the communications networks 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.

13. The circuit of claim 12, wherein the hypotheses are indexed in the memory by a reference numbers and the information relevant to the hypotheses can be accessed by the reference numbers.

14. The circuit of claim 12, wherein the sequence generator uses one of the hypotheses and a timing reference provided by the searcher to generate the PN sequence.

15. The circuit of claim 12, wherein the memory can store information for multiple hypotheses simultaneously.

16. The circuit of claim 15, wherein information relevant to each hypothesis can be referenced through the use of a unique reference number.

17. The circuit of claim 12, wherein the searcher contains a PN sequence adjust unit wherein differences between PN sequences for different communications networks can be accommodated.

18. The circuit of claim 17, 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.

19. The circuit of claim 12, wherein the searcher comprises a despreader coupling a sample processor to a coherent/non-coherent accumulator.

20. The circuit of claim 19, further comprising a result processor coupled to the coherent/non-coherent accumulator.

21. 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, comprising;

a memory to store information relevant to a hypotheses associated with at least two incompatible communications networks;

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

a searcher coupled to the sequence generator, the searcher containing circuitry to correlate a PN sequence for a selected one of the communications networks 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 hypotheses are indexed in the memory by reference numbers and the information relevant to the hypotheses can be accessed by the reference numbers.

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

24. The wireless receiver of claim 21, 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.

26. The wireless receiver of claim 21, wherein the searcher comprises a despreader coupling a sample processor to a coherent/non-coherent accumulator.

27. The wireless receiver of claim 26, further comprising a result processor coupled to the coherent/non-coherent accumulator.

28. A method, comprising the steps of:

storing information relevant to hypotheses associated with at least two incompatible communications networks;

generating pseudo-random number (PN) sequences based on the hypotheses;

correlating a PN sequence for a selected one of the communications networks generated by a sequence generator with a received signal and accumulating results from the correlation; and

configuring and controlling the operation of a search controller coupled to a memory storing the relevant information.

29. A method, comprising the steps of:

providing 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;

providing 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

providing 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, comprising;

providing a memory to store information relevant to hypotheses associated with at least two incompatible communications networks;

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

providing a searcher coupled to the sequence generator, the searcher containing circuitry to correlate a PN sequence for a selected one of the communications networks generated by the sequence generator with a received signal and to accumulate results from the correlation; and

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

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

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

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

generating a pseudo-random number (PN) sequence based on the hypothesis associated with a selected one of the first and second communications networks, wherein a PN sequence for the first communications network is of a length different than the length of a PN sequence for the second communications network;

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

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

correlating the adjusted PN sequence with the received signal.

31. The method of claim 30, wherein the first PN sequence uses a Gold code and the second PN sequence uses a Walsh code.