Method of searching for a bursty signal

• US 5,867,527 A
• Filed: 03/04/1997
• Issued: 02/02/1999
• Est. Priority Date: 09/30/1994
• Status: Expired due to Term

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Padovani, Roberto, Levin, Jeffrey A., Ziv, Noam A., Easton, Kenneth D.
• Primary Examiner(s): Pham, Chi H.
• Assistant Examiner(s): WEBSTER, BRYAN E
• Application Number:
  US08/810,744
• Time in Patent Office: 700 Days
• Field of Search: 375/200, 375/206, 375/208, 375/205, 375/347, 370/342, 370/320, 370/335, 370/209, 455/67.1, 455/226.2-226.4
• US Class Current: 375/147
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 1/70752 Partial correlation
• CPC Class Codes: H04B 1/70756 Jumping within the code, i.e. masking or slewing H04B1/70758 takes precedence
• CPC Class Codes: H04B 1/7113 Determination of path profile
• CPC Class Codes: H04B 1/7117 Selection, re-selection, allocation or re-allocation of paths to fingers, e.g. timing offset control of allocated fingers
• CPC Class Codes: H04B 2201/70703 using multiple or variable rates
• CPC Class Codes: H04B 7/2628 using code-division multiple access [CDMA] or spread spectrum multiple access [SSMA] H04B7/2618 takes precedence
• CPC Class Codes: H04J 13/0048 Walsh

Abstract

An integrated search processor used in a modem for a spread spectrum communications system buffers receive samples and utilizes a time sliced transform processor operating on successive offsets from the buffer. The search processor autonomously steps through a search as configured by a microprocessor specified search parameter set, which can include the group of antennas to search over, the starting offset and width of the search window to search over, and the number of Walsh symbols to accumulate results at each offset. The search processor calculates the correlation energy at each offset, and presents a summary report of the best paths found in the search to use for demodulation element reassignment. The search is done in a linear fashion independent of the probability that a signal being searched for was transmitted at any given time.

Claims

1. A method of receiving a signal comprised of a group of spread spectrum signals sharing a common frequency band and isolating a first signal from among said group of spread spectrum signals to determine a signal strength at a path delay time offset from a zero offset reference time of said first signal wherein said first signal comprises a series of symbols wherein a portion of said series of said symbols are grouped together in a symbol set wherein each symbol in a common symbol set is transmitted at a fixed power level wherein successive symbol sets may be transmitted at a variety of signal levels wherein said variety of signal levels includes a zero level wherein transmission of said first signal is gated off, said method comprising the steps of:

searching a first set of call signal samples corresponding to a first symbol set for said first signal at a first offset to produce a first power estimate thereof;

searching a second set of call signal samples corresponding to said first symbol set for said first signal at said first offset to produce a second power estimate thereof;

summing said first and second power estimates to produce a symbol set power level estimate at said first offset;

searching a third set of call signal samples corresponding to a second symbol set for said first signal at a second offset to produce a third power estimate thereof;

searching a fourth set of call signal samples corresponding to said second symbol set for said first signal at said second offset to produce a fourth power estimate thereof; and

summing said third and fourth power estimates to produce a symbol set power level estimate at said second offset;

wherein said first symbol set and said second symbol set correspond to time contiguous symbol sets and wherein said steps of searching are performed continually.

2. The method of claim 1 wherein said first set of call signal samples comprises two Walsh symbols.

3. The method of claim 2 wherein said second set of call signal samples comprises two Walsh symbols.

4. The method of claim 1 wherein said third set of call signal samples comprises two PN chips.

5. The method of claim 4 wherein said fourth set of call signal samples comprises two PN chips.

6. The method of claim 1 further comprising detection of at least one maximum demodulated energy value.