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

• US 5,416,797 A
• Filed: 01/24/1992
• Issued: 05/16/1995
• Est. Priority Date: 06/25/1990
• Status: Expired due to Term

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Gilhousen, Klein S., Padovani, Roberto, Jacobs, Irwin M., Viterbi, Andrew J., Weaver, Lindsay A. Jr.
• Primary Examiner(s): Gregory, Bernarr E.
• Application Number:
  US07/825,147
• Time in Patent Office: 1,208 Days
• Field of Search: 375/1, 375/68, 380/34, 370/18, 370/21, 370/22, 370/19, 379/59, 455/33.1, 455/54.1
• US Class Current: 370/209
• CPC Class Codes: H04B 1/3888 Arrangements for carrying or protecting transceivers
• 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 1/709 Correlator structure
• 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 13/10 Code generation
• CPC Class Codes: H04J 13/107 by concatenation
• CPC Class Codes: H04J 13/18 Allocation of orthogonal codes
• CPC Class Codes: H04L 1/0002 by adapting the transmission rate
• CPC Class Codes: H04L 1/0006 by adapting the transmission format
• CPC Class Codes: H04L 1/0046 Code rate detection or code type detection H04L1/0038 takes precedence; detection of the data rate H04L25/0262; for packet format H04L1/0091
• CPC Class Codes: H04L 1/0065 Serial concatenated codes
• CPC Class Codes: H04L 1/0068 by puncturing
• CPC Class Codes: H04L 1/0071 : Use of interleaving interleaving per se H03M13/27
• 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 52/26 : using transmission rate or quality of service QoS [Quality of Service]
• CPC Class Codes: Y02D 30/50 : in wire-line communication networks, e.g. low power modes or reduced link rate

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, hi-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 signalling along with QPSK spreading.

Claims

1. A spread spectrum modulator for modulating variable rate input digital data for transmission, said input digital data being provided in data frames of a predetermined time duration with each frame of input digital data having a number of data bits corresponding to one of several predetermined frame bit counts, said modulator comprising:

a convolutional encoder having an input receiving said frames of input digital data and an output;

a data interleaver having an input coupled to said convolutional encoder output and an output;

a Walsh function encoder having an input coupled to said interleaver output and an output;

a first pseudorandom noise (PN) code generator having an output;

a first exclusive-OR gate having a pair of inputs and an output, one of said first exclusive-OR gate inputs coupled to said first PN code generator output and another of said first exclusive-OR gate inputs coupled to said Walsh encoder output;

a second PN code generator having an output;

a third PN code generator having an output;

a second exclusive-OR gate having a pair of inputs and an output, one of said second exclusive-OR gate inputs coupled to said second PN code generator output and another of said second exclusive-OR gate inputs coupled to said first exclusive-OR gate output; and

a third exclusive-OR gate having a pair of inputs and an output, one of said third exclusive-OR gate inputs coupled to said third PN code generator output and another of said third exclusive-OR gate inputs coupled to said first exclusive-OR gate output.

2. The modulator of claim 1 wherein said data frames are of a duration of 20 msec. and wherein each data frame of said input digital data is at a data rate of 9.6 kbps, 4.8 kbps, 2.4 kbps and 1.2 kbps.

3. The modulator of claim 2 wherein said convolution encoder is a rate 1/3, convolution encoder.

4. The modulator of claim 3 wherein said convolutional encoder produces 3 symbols for each input data bit of each data frame of input data and said interleaver provides symbol repetition for symbols produced by said convolutional encoder for input digital data of data frames of said 4.8 kbps, 2.4 kbps and 1.2 kbps data rates, with said symbols repeated once for each 4.8 kbps data rate data frame of input digital data, twice for each 2.4 kbps data rate data frame of input digital data, and four times for each 1.2 kbps data rate data frame of input digital data.

5. The modulator of claim 4 wherein said Walsh function encoder converts each consecutive group of six symbols according to a binary value of each respective group into corresponding one of 64 Walsh function symbols wherein each Walsh function symbol is comprised of a different sequence of Walsh chips.

6. The modulator of claim 1 wherein said convolutional encoder is a rate 1/3, convolution encoder.

7. The modulator of claim 1 wherein said Walsh function encoder is a 64-ary orthogonal Walsh function generator.

8. The modulator of claim 1 wherein said first PN code generator is a augmented length maximal linear sequence generator.

9. A method for spread spectrum modulating a data signal comprising the steps of:

converting sequential portions of a digitized data signal into respective orthogonal function signal portions wherein each orthogonal function signal portion is representative of an orthogonal function selected from a plurality of orthogonal functions according to a value of a respective portion of said sequential portions;

generating a pseudorandom noise (PN) code; and

combining said orthogonal function signal portions with said PN code to produce a PN spread signal.

10. The method of claim 9 wherein said data signal is comprised of digital data bits and said step of converting comprises the steps of:

grouping a predetermined number of bits of said data signal into each one of said data signal portions;

determining from a binary value of said bits in each data signal portion a corresponding one of said orthogonal functions, wherein said orthogonal functions are Walsh functions; and

generating said respective orthogonal function signal portion corresponding to said determined orthogonal function.

11. The method of claim 10 further comprising the steps of:

generating at least one additional PN signal; and

combining said PN spread signal with each additional PN code to produce corresponding additional PN spread signals.

12. The method of claim 11 further comprising the steps of:

convolutional encoding an input digital signal to produce corresponding symbol data; and

organizing said symbol data according to a predetermined ordering format to provide said organized symbol data as said digitized data signal.

13. The method of claim 9 further comprising the steps of:

generating at least one additional PN code; and

combining said PN spread signal with each additional PN code to produce corresponding additional PN spread signals.

14. The method of claim 9 further comprising the steps of:

convolutional encoding an input digital signal to produce corresponding symbol data; and

organizing said symbol data according to a predetermined ordering format to provide said organized symbol data as said digitized data signal.

15. A method for spread spectrum modulating digital data for transmission, comprising:

convolutional encoding digital data to produce symbol data in a first ordered sequence;

reordering said symbol data of said first ordered sequence to a second ordered sequence;

grouping symbols of said second ordered sequence of symbol data into corresponding symbol groups;

determining from a binary value formed by said symbol data in each symbol group a respective Walsh function symbol of a plurality of Walsh function symbols;

generating a first pseudorandom noise (PN) code; and

combining said Walsh function symbols with said first PN code to produce first PN spread data.

16. The method of claim 15 further comprising the steps of:

generating a second PN code;

generating a third PN code;

combining said second PN code with said first PN spread data to produce second PN spread data; and

combining said third PN code with said first PN spread data to produce third PN spread data.

17. The method of claim 16 wherein said digital data is variable rate data in data frames of a predetermined time duration with each frame of digital data having a number of data bits corresponding to a predetermined multiple of bits in a frame of a least number of bits and wherein:

said step of convolutional encoding said digital data produces three symbols for each data bit in each frame of digital data; and

said step of reordering said symbol data further comprises the step of repeating symbols of said first ordered sequence for frames of digital data having a lesser number of bits than a frame of digital data of a greatest number of bits so as to maintain a constant number of symbols in said second ordered sequence.

18. The method of claim 17 wherein:

in said step of grouping, six symbols are grouped to form said binary value;

in said step of determining, each binary value corresponds to one of 64 Walsh function symbols with each Walsh function symbol comprised of a sequence of 64 Walsh chips.

19. The modulator of claim 18 wherein said step of generating said first PN code, which is comprised of first PN code chips, said first PN code chips are generated at a multiple rate of said Walsh chips.

20. A system for modulating an information signal in a spread spectrum communication system comprising:

orthogonal function encoder means for receiving a digitized information signal and converting sequential portions of said digitized information signal into respective orthogonal function signals; and

spreading means connected to said orthogonal function encoder means for generating a pseudorandom noise (PN) code and combining said orthogonal function signals with said PN code to produce a PN spread signal.

21. The modulation system of claim 20 wherein said PN code is an augmented length maximal linear sequence PN code.

22. The modulation system of claim 20 further comprising additional spreading means for generating at least one additional PN code and combining said PN spread signal with each additional PN code.

23. The modulation system of claim 22 further comprising:

data encoder means for receiving digital user data and convolutional encoding said digital data to produce symbol data; and

interleaver means for organizing said symbol data according to a predetermined ordering format and providing said organized symbol data as said information signal.

24. The modulation system of claim 20 further comprising:

data encoder means for receiving and convolutional encoding said digital data to produce symbol data; and

interleaver means for organizing said symbol data according to a predetermined ordering format and providing said organized symbol data as said information signal.

25. The modulation system of claim 20 wherein said digitized information signal is comprised of variable data rate data frames of digital data wherein each data frame is of a predetermined time duration with a lowest rate data frame of a predetermined number of data bits and at least one higher rate data frame each of a respective greater number of data bits that said lowest rate data frame.

26. A modulator for spread spectrum modulating digital data for transmission, comprising:

convolutional encoder means for receiving and convolutional encoding digital data to produce symbol data in a first ordered sequence;

interleaver means for reordering said symbol data in a second ordered sequence;

orthogonal function encoder means for encoding said second ordered sequence symbol data into orthogonal function symbol data;

first generator means for generating a first pseudorandom noise (PN) code;

first combining means for combining said orthogonal function symbol data and said first PN code to produce a first PN spread data signal.

27. The modulator of claim 26 further comprising:

second and third generator means each for respectively generating second and third PN codes;

second combining means for combining said second PN code with said first PN spread data signal to produce a second PN spread data signal;

third combining means for combining said third PN code with said first PN spread data signal to produce a third PN spread data signal.

28. The modulator of claim 27 wherein said first PN code is of a first code length and said second and third PN codes are of a second code length, with said first code length being substantially greater in length than said second code length.

29. The modulator of claim 26 wherein each symbol of said orthogonal function symbol data is representative of a Walsh function.

30. The modulator of claim 26 wherein each symbol of said orthogonal function symbol data is a Walsh function symbol comprised of a sequence of Walsh chips.

31. The modulator of claim 30 wherein said convolutional encoder means generates symbol data using a rate 1/3 convolutional code.

32. The modulator of claim 30 wherein said digital data is variable rate data provided in data frames of a predetermined time duration with each frame of digital data having a number of data bits corresponding to a predetermined multiple of bits in a frame of a least number of bits, and said convolutional encoder means generating three symbols for each data bit in each frame of input digital data.

33. The modulator of claim 32 wherein said orthogonal function encoder means comprises a 64-ary Walsh function encoder.

34. The modulator of claim 32 wherein said orthogonal function encoder means converts consecutive six symbol groups of said second ordered sequence of symbol data according to a binary value of each respective group into a corresponding one of 64 Walsh function symbols wherein each Walsh function symbol is comprised of a different sequence of 64 Walsh chips.

35. The modulator of claim 34 wherein said first spreading means generates said first PN code, comprised of first PN code chips, at a multiple rate of said Walsh chips.;

36. The modulator of claim 35 wherein said first spreading means generates four of said first PN code chips for combining with each each Walsh chip.