Method for handoff between an asynchronous CDMA base station and a synchronous CDMA base station

• US 7,391,753 B2
• Filed: 10/08/2003
• Issued: 06/24/2008
• Est. Priority Date: 02/25/1999
• Status: Expired due to Fees

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Tiedemann, Edward G. Jr., Sarkar, Sandip, Terasawa, Daisuke
• Primary Examiner(s): Chan; Wing
• Assistant Examiner(s): JONES, PRENELL P
• Application Number:
  US10/682,046
• Publication Number:
  US 20040085938A1
• Time in Patent Office: 1,721 Days
• Field of Search: 370/331, 370/335, 370/342, 370/333, 370/328, 370/311, 370/332, 370/318, 370/252, 375/145, 375/141, 375/130, 375/148, 375/316, 375/224, 455436-439, 455/440, 455/443, 455/574, 455/9, 455/522, 342/457, 714/775
• US Class Current: 370/331
• CPC Class Codes: H04B 1/7075 with code phase acquisition
• CPC Class Codes: H04B 2201/70701 featuring pilot assisted reception
• CPC Class Codes: H04W 36/14 Reselecting a network or an air interface
• CPC Class Codes: H04W 36/142 over the same radio air interface technology

Abstract

An improved method for facilitating handoff between an asynchronous and a synchronous base station. A method for determining a pilot channel PN offset of a pilot channel transmitted by a wireless base station. In a first embodiment, the method includes correlating a PN sequence with a received pilot signal to acquire a PN frame timing, receiving at least one search code burst aligned with the PN frame timing, the at least one search code burst signifying the pilot channel PN offset, and comparing the at least one search code burst to a set of codewords, each codeword representing a predetermined PN offset. From the search code bursts, the mobile station is able to quickly determine the PN offset of the transmitting base station, and thereby identify it. Methods for transmitting a complementary set of forward link channels are also disclosed.

Claims

1. An apparatus in a wireless communication system, comprising:

means for correlating a PN sequence with a received pilot signal to acquire a PN frame timing;

means for receiving at least one search code burst aligned with said PN frame timing, said at least one search code burst signifying a pilot channel PN offset; and

means for comparing said at least one search code burst to a set of codewords, each codeword representing a predetermined PN offset.

2. The apparatus of claim 1, wherein said at least one search code burst comprises a plurality of search code bursts repeated a predetermined number of times per PN frame, and wherein said plurality of search code bursts signify said pilot channel PN offset and phase.

3. The apparatus of claim 1, wherein said at least one search code burst comprises a single search code burst repeated a predetermined number of times per PN frame, and wherein said single search code burst signifies said pilot channel PN offset and phase.

4. The apparatus of claim 3, wherein each of said single search code bursts is comprised of a predetermined number of fixed chip patterns or their complement.

5. The apparatus of claim 2, wherein said plurality of search code bursts are non-orthogonal to other received channels.

6. An apparatus in a wireless communication system, comprising:

means for searching for a primary search code to acquire a search code slot timing, said primary search code aligned with a system time frame;

means for correlating a PN sequence with a received pilot signal to acquire a PN frame timing using said search code slot timing;

means for searching for at least one secondary search code burst aligned with said PN frame timing, said at least one secondary search code burst signifying said pilot channel PN offset; and

means for comparing said at least one secondary search code burst to a set of codewords, each codeword representing a predetermined PN offset.

7. The apparatus of claim 6, wherein said secondary search code comprises a plurality of search code bursts repeated a predetermined number of times per PN frame, said plurality of search code bursts encoding said pilot channel PN offset and phase.

8. An apparatus in a wireless communication system, comprising:

means for searching for a primary search code to acquire a search code slot timing, said primary search code aligned with a system time frame;

means for searching for at least one secondary search code burst aligned with said search code slot timing;

means for comparing said at least one secondary search code burst to a set of codewords, each codeword representing a predetermined PN offset group; and

means for correlating a PN sequence with a received pilot signal at a plurality of PN offsets associated with said PN offset group to find said pilot channel PN offset and phase.

9. The apparatus of claim 8, wherein said at least one secondary search code burst comprises a plurality of search code bursts repeated a predetermined number of times per system time frame.

10. The apparatus of claim 9, wherein said correlating step further comprises correlating said PN sequence at a plurality of PN shifts associated with said predetermined number of repeated search code bursts.

11. An apparatus in a wireless communication system, comprising:

means for correlating a PN sequence with a received pilot signal to acquire a PN frame timing;

means for searching for a primary search code using said PN frame timing to acquire a search code slot timing, said primary search code aligned with a system time frame;

means for determining a PN offset group and system frame timing from a difference between said PN frame timing and said search code slot timing;

means for searching for at least one secondary search code burst aligned with said search code slot timing; and

means for comparing said at least one secondary search code burst to a set of codewords, each codeword representing a predetermined pilot channel PN offset and phase.

12. The apparatus of claim 11, wherein said pilot signal, primary search code, and at least one secondary search code burst are each spread using the same PN sequence.

13. The apparatus of claim 12 wherein said pilot signal, primary search code, and at least one secondary search code burst are each covered with a different orthogonal Walsh sequence.

14. An apparatus in a wireless communication system, comprising:

means for transmitting a pilot channel having a repeating sequence of PN frames; and

means for transmitting at least one search code channel, said at least one search code channel comprising a repeating sequence of bursts, said at least one search code channel for providing a pilot channel PN offset of said pilot channel.

15. The apparatus of claim 14 wherein said at least one search code channel comprises a plurality of search code bursts repeated a predetermined number of times per PN frame, and wherein said plurality of search code bursts signify said pilot channel PN offset and phase.

16. The apparatus of claim 14 wherein said at least one search code channel comprises a single search code burst repeated a predetermined number of times per PN frame, and wherein said single search code burst signifies said pilot channel PN offset and phase.

17. The apparatus of claim 16 wherein each of said single search code bursts is comprised of a predetermined number of fixed chip patterns or their complement.

18. The apparatus of claim 15 wherein said plurality of search code bursts are non-orthogonal to other transmitted channels.

19. The apparatus of claim 14 wherein said at least one search code channel comprises a primary search code channel and a secondary search code channel.

20. The apparatus of claim 19 wherein said secondary search code channel comprises a plurality of search code bursts repeated a predetermined number of times per PN frame, said plurality of search code bursts encoding said pilot channel PN offset and phase.

21. The apparatus of claim 19 wherein said secondary search code channel comprises a plurality of search code bursts repeated a predetermined number of times per system time frame.

22. The apparatus of claim 19 wherein said pilot channel, primary search code channel, and secondary search code channel are each spread using the same PN sequence.

23. The apparatus of claim 22 wherein said pilot channel, primary search code channel, and secondary search code channel are each covered with a different orthogonal Walsh sequence.

24. A wireless communication system, comprising:

a base station; and

a mobile station in wireless communication with the base station, the mobile station configured to correlate a PN sequence with a received pilot signal to acquire a PN frame timing, receive at least one search code burst aligned with said PN frame timing, said at least one search code burst signifying a pilot channel PN offset, and compare said at least one search code burst to a set of codewords, each codeword representing a predetermined PN offset.

25. The wireless communication system of claim 24, wherein said at least one search code burst comprises a plurality of search code bursts repeated a predetermined number of times per PN frame, and wherein said plurality of search code bursts signify said pilot channel PN offset and phase.

26. The wireless communication system of claim 24, wherein said at least one search code burst comprises a single search code burst repeated a predetermined number of times per PN frame, and wherein said single search code burst signifies said pilot channel PN offset and phase.

27. The wireless communication system of claim 26, wherein each of said single search code bursts is comprised of a predetermined number of fixed chip patterns or their complement.

28. The wireless communication system of claim 25, wherein said plurality of search code bursts are non-orthogonal to other received channels.

29. A wireless communication system, comprising:

a base station; and

a mobile station in communication with the base station, the mobile station configured to search for a primary search code to acquire a search code slot timing, said primary search code aligned with a system time frame, correlate a PN sequence with a received pilot signal to acquire a PN frame timing using said search code slot timing, search for at least one secondary search code burst aligned with said PN frame timing, said at least one secondary search code burst signifying said pilot channel PN offset, and compare said at least one secondary search code burst to a set of codewords, each codeword representing a predetermined PN offset.

30. The wireless communication system of claim 29, wherein said secondary search code comprises a plurality of search code bursts repeated a predetermined number of times per PN frame, said plurality of search code bursts encoding said pilot channel PN offset and phase.

31. A wireless communication system, comprising:

a base station; and

a mobile station in communication with the base station, said mobile station configured to search for a primary search code to acquire a search code slot timing, said primary search code aligned with a system time frame, search for at least one secondary search code burst aligned with said search code slot timing, compare said at least one secondary search code burst to a set of codewords, each codeword representing a predetermined PN offset group, and correlate a PN sequence with a received pilot signal at a plurality of PN offsets associated with said PN offset group to find said pilot channel PN offset and phase.

32. The wireless communication system of claim 31, wherein said at least one secondary search code burst comprises a plurality of search code bursts repeated a predetermined number of times per system time frame.

33. The wireless communication system of claim 31, wherein said correlating step further comprises correlating said PN sequence at a plurality of PN shifts associated with said predetermined number of repeated search code bursts.

34. A wireless communication system, comprising:

a base station; and

a mobile station in wireless communication with the base station, said mobile station configured to correlate a PN sequence with a received pilot signal to acquire a PN frame timing, search for a primary search code using said PN frame timing to acquire a search code slot timing, said primary search code aligned with a system time frame, determine a PN offset group and system frame timing from a difference between said PN frame timing and said search code slot timing, search for at least one secondary search code burst aligned with said search code slot timing, and compare said at least one secondary search code burst to a set of codewords, each codeword representing a predetermined pilot channel PN offset and phase.

35. The wireless communication system of claim 34, wherein said pilot signal, primary search code, and at least one secondary search code burst are each spread using the same PN sequence.

36. The wireless communication system of claim 35 wherein said pilot signal, primary search code, and at least one secondary search code burst are each covered with a different orthogonal Walsh sequence.

37. A wireless communication system, comprising:

a base station, and a mobile station in communication with said base station, said mobile station configured to transmit a pilot channel having a repeating sequence of PN frames, and transmit at least one search code channel, said at least one search code channel comprising a repeating sequence of bursts, said at least one search code channel for providing a pilot channel PN offset of said pilot channel,

wherein said at least one search code channel comprises a single search code burst repeated a predetermined number of times per PN frame, wherein said single search code burst signifies said pilot channel PN offset and phase, and

wherein each of said single search code bursts is comprised of a predetermined number of fixed chip patterns or their complement.

38. A wireless communication system, comprising:

a base station, and a mobile station in communication with said base station, said mobile station configured to transmit a pilot channel having a repeating sequence of PN frames, and transmit at least one search code channel, said at least one search code channel comprising a repeating sequence of bursts, said at least one search code channel for providing a pilot channel PN offset of said pilot channel,

wherein said at least one search code channel comprises a primary search code channel and a secondary search code channel.

39. The wireless communication system of claim 38 wherein said secondary search code channel comprises a plurality of search code bursts repeated a predetermined number of times per PN frame, said plurality of search code bursts encoding said pilot channel PN offset and phase.

40. The wireless communication system of claim 38 wherein said secondary search code channel comprises a plurality of search code bursts repeated a predetermined number of times per system time frame.

41. The wireless communication system of claim 38 wherein said pilot channel, primary search code channel, and secondary search code channel are each spread using the same PN sequence.

42. The wireless communication system of claim 41 wherein said pilot channel, primary search code channel, and secondary search code channel are each covered with a different orthogonal Walsh sequence.