Steps one and three W-CDMA and multi-mode searching

• US 20030147365A1
• Filed: 05/31/2002
• Published: 08/07/2003
• Est. Priority Date: 11/20/2001
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Liu, Hao, Terasawa, Daisuke, John, Deepu, Venkatesan, Sivarama Krishnan, Zou, Qiuzhen (Joe)
• Granted Patent: US 7,756,085 B2
• Time in Patent Office: Days
• US Class Current: 370/335
• CPC Class Codes: H04B 1/70735 Code identification H04B1/7083 takes precedence
• CPC Class Codes: H04B 2201/70707 Efficiency-related aspects
• CPC Class Codes: H04B 2201/7071 with dynamic control of receiver resources

Abstract

Techniques for efficient searching in asynchronous systems, such as W-CDMA, as well as multi-mode searching, are disclosed. In one aspect, step one and step three search are performed in a single search engine. In another aspect, a search engine is configurable to search the offsets of a slot in step one search, producing sequential hypothesis energies, and peak detecting and sorting those energies. In yet another aspect, the peak detector and sorter are configurable to perform step one searching or step three/multimode searching. Various other aspects of the invention are also presented. These aspects have the benefit of circuit area and search-time efficiency which translate into reduced costs, increased standby time, increased acquisition speed, higher quality signal transmission, increased data throughput, decreased power, and improved overall system capacity.

Claims

1. A single search engine operable in a first mode to detect a first pilot sequence transmitted during a portion of a slot, and operable in a second mode to detect a second pilot sequence transmitted continuously and used to scramble transmitted data, the detected first sequence being used for identifying slot timing, the detected second sequence being used for de-scrambling data.

2. In a system comprising a first pilot sequence transmitted during a portion of a slot, a second pilot sequence transmitted during a portion of each slot for a plurality of slots comprising a frame, and a third pilot transmitted continuously, a method of searching comprising:

detecting the first pilot sequence in a first search engine and identifying slot timing therefrom;

detecting the second pilot sequence in a second search engine, based on the identified slot timing, and identifying frame timing and base station group information therefrom; and

detecting the third pilot sequence in the first search engine, based on the identified frame timing and base station group information.

3. A method of searching a pilot sequence transmitted during a portion of a slot, comprising:

programming a plurality of sequence buffers with a plurality of sub-sequences of the pilot sequence;

selecting one of the plurality of sequence buffers at a time for correlation with input samples;

sequentially initiating coherent accumulation of correlation outputs for hypothesis offsets in a slot; and

coherently accumulating the correlation outputs for each hypothesis offset using each of the plurality of sequence buffers to produce coherent accumulation outputs sequentially for the hypothesis offsets in the slot.

4. The method of claim 3, further comprising:

calculating an energy value for each coherent accumulation output; and

non-coherently accumulating the energy values.

5. The method of claim 4, further comprising peak detecting the non-coherent accumulation outputs.

6. The method of claim 5, further comprising sorting the peak detector outputs.

7. A searcher, operable with a first system comprising a plurality of base stations, each base station transmitting a signal divided by frames, the frames comprising a plurality of slots, the signal having:

a first pilot sequence transmitted during a portion of each slot;

a second pilot sequence, the second pilot sequence being a concatenation of a subset of sequences drawn from a larger set of sequences, the subset identifying the base station group of the transmitting base station, each of the subset of sequences transmitted during the portion of a slot coincident with the transmission of the first pilot sequence; and

a third pilot sequence, continuously transmitted periodically with the frame, the third pilot sequence identifying the transmitting base station and used for communication therewith, the searcher comprising;

a first search engine for detecting the first pilot sequence, deriving slot timing therefrom, and for detecting the third pilot sequence using derived frame timing and base station group information; and

a second search engine for detecting the second pilot sequence and deriving frame timing and base station group information therefrom, the detection of the second pilot sequence using slot timing derived in the first search engine, and providing the derived frame timing and base station group information thereto.

8. The searcher of claim 7, further operable with a second system comprising a plurality of base stations, each of which transmits a fourth pilot sequence for identification therefrom, wherein the first search engine detects the fourth pilot sequence.

9. A searcher, operable with a pilot sequence, transmitted during a portion of a slot, comprising:

a time-shared correlator for correlating input samples with a plurality of sequences, each of the plurality of sequences correlated during a time slice;

a sequence generator for generating the plurality of sequences, each of which are sub-sequences of the pilot sequence; and

a coherent accumulator for accumulating the correlator output for a series of sequential offset hypotheses of the pilot sequence within a slot, the coherent accumulation for an offset hypothesis beginning during -each time slice, and the coherent accumulation for an offset hypothesis completing during each time slice subsequent to a coherent accumulation interval, each coherent accumulation result completing in sequential order of offset.

10. The searcher of claim 9, further comprising:

an energy calculator for receiving each coherent accumulator output and calculating an energy therefrom; and

a non-coherent accumulator for accumulating the output of the energy calculator for each of the series of sequential offset hypotheses, the non-coherent accumulation completed after a non-coherent accumulation interval, each non-coherent accumulation result completing in sequential order of offset.

11. The searcher of claim 10, further comprising a peak detector for detecting peaks within the sequence of non-coherent accumulation results.

12. The searcher of claim 11, further comprising a sorter for sorting the peaks detected in the peak detector.

13. The searcher of claim 9 wherein:

the time-shared correlator produces results eight times per pilot sequence chip;

the input samples are updated twice per pilot sequence chip;

the sequence generator comprises four buffers, identified as buffer 0, buffer 1, buffer 2, and buffer 3;

buffer 0 is programmed with the first quarter of the pilot sequence;

buffer 1 is programmed with the second quarter of the pilot sequence;

buffer 2 is programmed with the third quarter of the pilot sequence; and

buffer 3 is programmed with the fourth quarter of the pilot sequence.

14. The searcher of claim 13 wherein:

each sequential pilot sequence chip is identified by n;

each time slice is identified by chip×

8, a value increasing modulo 8 from 0 to 7 incrementing once each time slice; and

the number of the buffer selected for use in the time-shared correlator is identified by (n div 64−

chip×

8) mod 4.

15. The searcher of claim 9 wherein the coherent accumulator comprises:

a RAM for storing intermediate coherent accumulation results; and

an address generator for generating read and write addresses that increment by one each access.

16. The searcher of claim 15, wherein the address generator comprises an upcounter.

17. The searcher of claim 16, wherein the RAM is double-packed with coherent accumulation results for two hypotheses in each of 256 addresses.

18. The searcher of claim 10 wherein the non-coherent accumulator comprises:

a RAM for storing intermediate non-coherent accumulation results; and

an address generator for generating read and write addresses that increment by one each access.

19. The searcher of claim 18, wherein the address generator comprises an upcounter.

20. The searcher of claim 19, wherein the RAM is double-packed with non-coherent accumulation results for two hypotheses in each of 2,560 addresses.

21. A searcher operable with a first pilot sequence transmitted during a portion of a slot and operable with a second pilot sequence transmitted continuously, comprising:

a time-shared correlator for correlating input samples with a plurality of sequences, each of the plurality of sequences correlated during one of a plurality of time slices;

a sequence generator configurable for generating the plurality of sequences, in a first mode each of which are sub-sequences of the first pilot sequence, and in a second mode each of which are a plurality of independent sequences, offsets within the second pilot sequence, or a combination thereof; and

a coherent accumulator configurable for accumulating the correlator output;

in the first mode for a series of sequential offset hypotheses of the pilot sequence within a slot, the coherent accumulation for an offset hypothesis beginning during each time slice, and the coherent accumulation for an offset hypothesis completing during each time slice subsequent to a coherent accumulation interval, each coherent accumulation result completing in sequential order of offset; and

in the second mode for the plurality of sequential hypotheses corresponding to the plurality of time slices.

22. The searcher of claim 21, further comprising:

an energy calculator for receiving each coherent accumulator output and calculating an energy therefrom; and

a non-coherent accumulator for accumulating the output of the energy calculator;

in the first mode for each of the series of sequential offset hypotheses, the non-coherent accumulation completed after a non-coherent accumulation interval, each non-coherent accumulation result completing in sequential order of offset; and

in the second mode for each of the offset hypotheses corresponding to the time slices, the non-coherent accumulation completed after a non-coherent accumulation interval corresponding to each time slice.

23. The searcher of claim 22, further comprising a peak detector for detecting peaks within the sequence of non-coherent accumulation results.

24. The searcher of claim 23, further comprising a sorter for sorting the peaks detected in the peak detector.

25. The searcher of claim 22, further comprising a plurality of peak detectors, each corresponding to one of the plurality of time slices, configurable in the first mode to produce a single peak stream from the output of the non-coherent accumulator, and in the second mode to produce a plurality of peak streams corresponding to the plurality of time slices.

26. The searcher of claim 25, wherein the number of peak detectors is four.

27. The searcher of claim 25, wherein the sorter comprises:

a plurality of sorting components, each configurable in the first mode as part of larger single sorter and in the second mode for sorting one of the outputs of the plurality of peak detectors; and

an additional sorting component for sorting and integrating the results of the plurality of sorting components in the first mode to sort the single peak stream.

28. The searcher of claim 27, wherein:

the plurality of sorting components are four 7-bin sorters; and

the additional sorting component comprises three bins to produce a single 31-bin sorter in the first mode.

29. A subscriber unit including a searcher, operable with a pilot sequence, transmitted during a portion of a slot, comprising:

a time-shared correlator for correlating input samples with a plurality of sequences, each of the plurality of sequences correlated during a time slice;

a sequence generator for generating the plurality of sequences, each of which are sub-sequences of the pilot sequence; and

a coherent accumulator for accumulating the correlator output for a series of sequential offset hypotheses of the pilot sequence within a slot, the coherent accumulation for an offset hypothesis beginning during each time slice, and the coherent accumulation for an offset hypothesis completing during each time slice subsequent to a coherent accumulation interval, each coherent accumulation result completing in sequential order of offset.

30. A W-CDMA system including a searcher, operable with a pilot sequence, transmitted during a portion of a slot, comprising:

a time-shared correlator for correlating input samples with a plurality of sequences, each of the plurality of sequences correlated during a time slice;

a sequence generator for generating the plurality of sequences, each of which are sub-sequences of the pilot sequence; and

a coherent accumulator for accumulating the correlator output for a series of sequential offset hypotheses of the pilot sequence within a slot, the coherent accumulation for an offset hypothesis beginning during each time slice, and the coherent accumulation for an offset hypothesis completing during each time slice subsequent to a coherent accumulation interval, each coherent accumulation result completing in sequential order of offset.