System and method for generating signal waveforms in a CDMA cellular telephone system

• US 7,003,021 B2
• Filed: 02/05/2004
• Issued: 02/21/2006
• Est. Priority Date: 06/25/1990
• Status: Expired due to Fees

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Wheatley, Charles E. III, Gilhousen, Klein S., Padovani, Roberto, Jacobs, Irwin M., Viterbi, Andrew J., Weaver, Lindsay A. Jr.
• Primary Examiner(s): Tran, Khai
• Application Number:
  US10/772,490
• Publication Number:
  US 20040156427A1
• Time in Patent Office: 747 Days
• Field of Search: 375/150, 375/130, 375/140, 375/146, 375/147, 370/203, 370/204, 370/206, 370/208
• US Class Current: 375/150
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 1/70757 with increased resolution, i.e. higher than half a chip H04B1/70758 takes precedence
• CPC Class Codes: H04B 1/7115 Constructive combining of multi-path signals, i.e. RAKE receivers
• CPC Class Codes: H04B 2201/70701 featuring pilot assisted reception
• CPC Class Codes: H04B 2201/70703 using multiple or variable rates
• CPC Class Codes: H04B 7/2618 using hybrid code-time division multiple access [CDMA-TDMA]
• 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: H04B 7/2637 for logical channel control
• CPC Class Codes: H04J 13/0022 PN, e.g. Kronecker
• CPC Class Codes: H04J 13/0048 Walsh
• CPC Class Codes: H04J 13/12 Generation of orthogonal codes
• CPC Class Codes: H04J 3/02 Details electronic switching or gating H03K17/00
• CPC Class Codes: H04J 3/1688 the demands of the users being taken into account after redundancy removal, e.g. by predictive coding, by variable sampling reducing bandwidth of signals in general H04B1/66; in PCM-systems H04B14/046; removal of redundancy in telegraph communication H03M7/30
• CPC Class Codes: H04J 3/22 in which the sources have different rates or codes simultaneous speech and digital data or video transmission H04M11/06; see provisional also H04J3/16
• CPC Class Codes: H04L 1/0002 by adapting the transmission rate
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27
• CPC Class Codes: H04L 1/0072 Error control for data other than payload data, e.g. control data
• CPC Class Codes: H04L 1/06 using space diversity
• CPC Class Codes: H04L 1/08 by repeating transmission, e.g. Verdan system H04L1/1858 and H04L1/189 take precedence
• CPC Class Codes: H04L 23/02 adapted for orthogonal signalling
• CPC Class Codes: H04L 5/02 : Channels characterised by the type of signal
• CPC Class Codes: H04L 5/12 : the signals being represented by different phase modulations of a single carrier
• CPC Class Codes: H04W 52/08 : Closed loop power control
• CPC Class Codes: H04W 52/10 : Open loop power control
• CPC Class Codes: H04W 52/26 : using transmission rate or quality of service QoS [Quality of Service]

Abstract

A system and method for communicating information signals using spread spectrum communication techniques. PN sequences are constructed that provide orthogonality between the users so that mutual interference will be reduced, allowing higher capacity and better link performance. With orthogonal PN codes, the cross-correlation is zero over a predetermined time interval, resulting in no interference between the orthogonal codes, provided only that the code time frames are time aligned with each other. In an exemplary embodiment, signals are communicated between a cell-site and mobile units using direct sequence spread spectrum communication signals. In the cell-to-mobile link, pilot, sync, paging and voice channels are defined. Information communicated on the cell-to-mobile link channels are, in general, encoded, interleaved, bi-phase shift key (BPSK) modulated with orthogonal covering of each BPSK symbol along with quadrature phase shift key (QPSK) spreading of the covered symbols. In the mobile-to-cell link, access and voice channels are defined. Information communicated on the mobile-to-cell link channels are, in general, encoded, interleaved, orthogonal signaling along with QPSK spreading.

Claims

1. A spread-spectrum signal receiver comprising:

a PN sequence generator for generating a PN sequence;

a correlator coupled to the PN sequence generator and configured to produce a despread signal comprising a pilot signal by correlating the generated PN sequence and a received spread-spectrum signal; and

processing circuitry coupled to the correlator for processing the despread signal to extract time information from the pilot signal.

2. The receiver of claim 1, wherein the despread signal is synchronized to UTC time and the processing circuitry is configured to extract UTC time from the despread signal.

3. The receiver of claim 1 further comprising an RF receiver coupled to the signal input and configured to provide the spread-spectrum signal thereto, wherein the RF receiver comprises:

a first oscillator configured to generate a first reference frequency; and

a first mixer unit coupled to the first oscillator and connected between the antenna and the correlator, and configured to downconvert an RF signal from the antenna to an intermediate-frequency spread-spectrum signal.

4. The receiver of claim 1 further comprising an RF receiver coupled to the signal input and configured to provide the spread-spectrum signal thereto, wherein the RF receiver comprises:

a first oscillator configured to generate a first reference frequency;

a first mixer unit coupled to the first oscillator and connected between the antenna and the correlator, and configured to downconvert an RF signal from the antenna to an baseband spread-spectrum signal.

5. The receiver of claim 1, wherein the PN sequence generator is configured to generate a PN sequence with a length of 32,768 chips.

6. The receiver of claim 5, wherein the PN sequence generator is configured to generate the PN sequence at a chip rate between 1 Mchips/sec and 2.5 Mchips/sec.

7. The receiver of claim 5, wherein the PN sequence generator is configured to generate the PN sequence at a chip rate of 1.2288 Mchips/sec.

8. The receiver of claim 1, wherein:

the PN sequence generator modulates the PN sequence by a Walsh code comprising 32 binary ones followed by 32 binary zeroes from a set of length-64 Walsh codes; and

the PN sequence and the Walsh code each have a chip rate of 1.2288 Mchips/sec.

9. A spread-spectrum signal receiver comprising:

a PN sequence generator for generating a PN sequence;

a correlator coupled to the PN sequence generator and configured to produce a despread signal comprising a sync signal by correlating the generated PN sequence and a received spread-spectrum signal;

processing circuitry coupled to the correlator for processing the despread signal to extract time information from the sync signal; and

a Walsh-code generator coupled to the processing circuitry and configured to generate an orthogonal code stream comprising 32 binary ones followed by 32 binary zeroes; and

wherein the processing circuitry is configured to mix the despread signal with the orthogonal code stream to enable extraction of time information from the sync signal.

10. A method of extracting time information from a spread-spectrum signal, the method comprising:

generating a PN sequence;

correlating the generated PN sequence and a spread-spectrum signal to produce a despread signal comprising a pilot signal; and

processing the despread signal to extract time information from the pilot signal.

11. The method of claim 10, wherein the despread signal is synchronized to UTC time and the method comprises extracting UTC time from the despread signal.

12. The method of claim 10, wherein the PN sequence is generated with a length of 32,768 chips.

13. The method of claim 11, wherein the PN sequence is generated at a chip rate between 1 Mchips/sec and 2.5 Mchips/sec.

14. The method of claim 12, wherein the PN sequence is generated at a chip rate of 1.2288 Mchips/sec.

15. The method of claim 10, further comprising modulating the PN sequence by a Walsh code comprising 32 binary ones followed by 32 binary zeroes from a set of length-64 Walsh codes, and wherein the PN sequence and the Walsh code each have a chip rate of 1.2288 Mchips/sec.

16. A method of extracting time information from a spread-spectrum signal, the method comprising:

generating a PN sequence;

correlating the generated PN sequence and a spread-spectrum signal to produce a despread signal comprising a sync signal;

processing the despread signal to extract time information from the sync signal;

generating an orthogonal code stream comprising 32 binary ones followed by 32 binary zeroes; and

mixing the despread signal with the orthogonal code stream to enable extraction of time information from the sync signal.

17. A spread spectrum communication system comprising:

a plurality of base stations each operable for communication with at least one user unit;

two receiving systems each for receiving independently a user unit signal transmitted from a user unit as a direct sequence spread spectrum signal within which an information signal is modulated; and

a diversity combiner coupled to the two receiving system for combining signals received thereby to reconstruct the user unit signal.

18. The system of claim 17, wherein at least one of said base stations comprises said two receiving systems.

19. The system of claim 17, wherein one of said two receiving systems is provided in one of said plurality of base stations and the other of said two receiving systems is provided in another of said plurality of base stations.

20. A communications system comprising:

a first cell site unit configured to communicate through a direct-sequence spread-spectrum digital wireless link with at least one mobile unit; and

a second cell site unit configured to communicate through a direct-sequence spread-spectrum digital wireless link with at least one mobile unit, and wherein the first and second cell site units are synchronized to each other.

21. The communications system of claim 20, wherein the first and second cell site units are synchronized to each other by way of a common time reference.

22. The communications system of claim 20, wherein the first and second cell site units are synchronized to Universal Coordinated Time (UTC).

23. The communications system of claim 20, wherein the first and second cell site units each comprise a GPS receiver for receiving a GPS signal and wherein the first and second cell site units are synchronized to each other by way of the GPS signal.

24. The communications system of claim 20, wherein:

the first cell site is configured to generate a first spreading sequence for use in the direct-sequence spread-spectrum digital wireless link; and

the second cell site is configured to generate a second spreading sequence for use in the direct-sequence spread-spectrum digital wireless link, which second spreading sequence is a synchronized, time-shifted version of the first spreading sequence.

25. The communications system of claim 24, wherein:

the first cell site is configured to generate a pilot signal from the first spreading sequence; and

the second cell site is configured to generate a pilot signal from the second spreading sequence.

26. The communications system of claim 24, wherein:

the first cell site is configured to generate a sync signal from the first spreading sequence; and

the second cell site is configured to generate a sync signal from the second spreading sequence.

27. The communications system of claim 24, wherein:

the first cell site is configured to generate the first spreading sequence using a first code polynomial; and

the second cell site is configured to generate the second spreading sequence using the first code polynomial.

28. The communications system of claim 20, wherein the first and second cell site units each generate a synchronized PN sequence.

29. The communications system of claim 28, wherein the synchronized PN sequence generated by each cell site unit has a chip rate of 1.2288 Mchips/sec.

30. The communications system of claim 28, wherein the synchronized PN sequence generated by each cell site unit has a length of 32,768 chips.