Method and apparatus for transmission of variable rate digital data

• US 5,581,575 A
• Filed: 10/05/1995
• Issued: 12/03/1996
• Est. Priority Date: 11/01/1993
• Status: Expired due to Term

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Zehavi, Ephraim, Viterbi, Andrew J.
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): GHEBRETINSAE, TEMESGHEN
• Application Number:
  US08/539,490
• Time in Patent Office: 425 Days
• Field of Search: 375/200-210, 375/281, 370/94.1, 370/18, 380/34
• US Class Current: 375/142
• CPC Class Codes: H03M 13/2707 Simple row-column interleaver, i.e. pure block interleaving
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04L 1/0013 Rate matching, e.g. puncturing or repetition of code symbols
• CPC Class Codes: H04L 1/0043 Realisations of complexity reduction techniques, e.g. use of look-up tables
• CPC Class Codes: H04L 1/0052 Realisations of complexity reduction techniques, e.g. pipelining or use of look-up tables
• CPC Class Codes: H04L 1/0065 Serial concatenated codes
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27
• CPC Class Codes: H04L 1/08 by repeating transmission, e.g. Verdan system H04L1/1858 and H04L1/189 take precedence
• CPC Class Codes: H04N 1/56 Processing of colour picture signals H04N1/52 takes precedence

Abstract

A communication system for transmitting variable rate data is disclosed wherein redundancy is added to the variable rate data to provide repetition symbols. The repetition symbol data is transmitted with symbol energy scaled in accordance to the rate of the variable rate data when the variable rate data is greater than or equal to a nominal data rate. When the variable rate data is less than the nominal data rate, the symbol data is transmitted at nominal symbol energy and redundancy is removed by transmission gating of a proportion of the transmission symbol data determined in accordance with the rate of the variable rate data. Furthermore, a receiver for receiving the variable rate data is disclosed which uses the redundancy in the transmitted data symbol stream to make a corrected estimate of the transmitted symbol data.

Claims

1. An apparatus for transmitting a variable rate data packet of data symbols, said apparatus comprising:

repetition generator means for receiving said packet and when the number of said data symbols in said packet is less than a first value generating duplicates of said data symbols and combining said data symbols and said duplicates of said data symbols in said packet; and

transmitter means for transmitting said packet from said repetition generator means, wherein when the number of data symbols in said packet equals said first value, transmitting said packet at a first energy level and when the number of data symbols in said packet is less than said first value and greater than a second value, transmitting said packet at a second energy level which is less than said first energy level, and when the number of data symbols in said packet is less than said second value gating ones of said data symbols and said duplicates of said data symbols and transmitting said packet at a third energy level.

2. The apparatus of claim 1 further comprising spreading means interposed between said repetition generator means and said transmitter means for receiving said packet and modulating said packet in accordance with a spread spectrum modulation format.

3. The apparatus of claim 2 wherein said spreading means comprises:

first PN generator means for generating a first pseudorandom noise sequence; and

first mixing means for receiving said packet and said first pseudorandom noise sequence and for spreading said packet in accordance with said first pseudorandom noise sequence to output a spread packet.

4. The apparatus of claim 3 wherein said spreading means further comprises:

second PN generator means for generating a second pseudorandom noise sequence;

second mixing means for receiving said spread packet and said second pseudorandom noise sequence and for digitally mixing said spread packet with said second pseudorandom noise sequence;

third PN generator means for generating a third pseudorandom noise sequence; and

third mixing means for receiving said spread packet and said third pseudorandom noise sequence and for digitally mixing said spread packet with said third pseudorandom noise sequence.

5. The apparatus of claim 4 further comprising offset quadrature phase shift keying (OQPSK) modulation means interposed between said spreading means and said transmitter means for receiving said spread packet and modulating said packet in accordance with an offset quadrature phase shift keying modulation format.

6. The apparatus of claim 1 wherein said transmitter means is further for reordering said data symbols and said duplicates of said data symbols in accordance with a pseudorandom reordering format when the number of data symbols in said packet is less than said second value.

7. The apparatus of claim 1 further comprising an encoder means preceding said repetition generator means for receiving said packet and for encoding said data symbols in accordance with an error correction encoding format.

8. The apparatus of claim 7 further comprising an interleaver means interposed between said encoder means and said repetition generator means for receiving said packet from said encoder means and for reordering said data symbols in said packet in accordance with an interleaving format.

9. The apparatus of claim 1 wherein said second energy level is one of a set of possible second energy levels and wherein said third energy level is the minimum energy level in said set of possible second energy levels.

10. The apparatus of claim 1 wherein the ratio between said second energy level and said first energy level equals the ratio between the said number of data symbols in said packet and said first value.

19. The method of claim 1 wherein said second energy level is one of a set of possible second energy levels and wherein said third energy level is the minimum energy level in said set of possible second energy levels.

11. A method for transmitting a variable rate data packet of data symbols, said method comprising the steps of:

receiving said packet;

when the number of said data symbols in said packet is less than a first value generating duplicates of said data symbols and combining said data symbols and said duplicates of said data symbols in said packet;

when the number of data symbols in said packet equals said first value, transmitting said packet at a first energy level;

when the number of data symbols in said packet is less than said first value and greater than a second value, transmitting said packet at a second energy level which is less than said first energy level; and

when the number of data symbols in said packet is less than said second value gating ones of said data symbols and said duplicates of said data symbols and transmitting said packet at a third energy level.

12. The method of claim 11 further comprising the step of modulating said packet in accordance with a spread spectrum modulation format.

13. The method of claim 12 wherein said step of modulating said packet in accordance with a spread spectrum modulation format comprises the steps of:

generating a first pseudorandom noise sequence; and

spreading said packet in accordance with said first pseudorandom noise sequence to output a spread packet.

14. The method of claim 13 wherein said step of modulating said packet in accordance with a spread spectrum modulation format further comprises the steps of:

generating a second pseudorandom noise sequence;

digitally mixing said spread packet with said second pseudorandom noise sequence;

generating a third pseudorandom noise sequence; and

digitally mixing said spread packet with said third pseudorandom noise sequence.

15. The method of claim 14 further comprising the step of modulating said packet in accordance with an offset quadrature phase shift keying (OQPSK) modulation format.

16. The method of claim 11 further comprising the step of reordering said data symbols and said duplicates of said data symbols in accordance with a pseudorandom reordering format when the number of data symbols in said packet is less than said second value.

17. The method of claim 11 further comprising the step of encoding said data symbols in accordance with an error correction encoding format.

18. The method of claim 17 further comprising the step of reordering said data symbols in said packet in accordance with an interleaving format.

20. The method of claim 11 wherein the ratio between said second energy level and said first energy level equals the ratio between the said number of data symbols in said packet and said first value.

21. A system for transmitting a variable rate data packet of data symbols, said system comprising:

a repetition generator having an input and having an output;

a transmitter having an input coupled to said repetition generator output and having an output;

a spread spectrum modulator interposed between said repetition generator and said transmitter having an input coupled to said repetition generator output and having an output coupled to said transmitter input, said spread spectrum modulator comprising;

a first PN generator having an output; and

a first mixer having a first input coupled to said repetition generator output and having a second input coupled to said first PN generator output and having an output.

22. The system of claim 21 wherein said spread spectrum modulator comprises:

a second PN generator having an output;

a second mixer having a first input coupled to said first mixer output and having a second input coupled to said second PN generator output;

a third PN generator having an output; and

third mixer having a first input coupled to said first mixer output and having a second input coupled to said third PN generator output.

23. The system of claim 21 further comprising an offset quadrature phase shift keying modulator having a first input coupled to said second mixer output and having a second input coupled to said third mixer output and having an output coupled to said transmitter input.

24. A system for transmitting a variable rate data packet of data symbols, said system comprising:

a repetition generator having an input connected to receive said packet of data symbols for generating duplicates of said data symbols when the number of data symbols in said packet is less than a first value and having an output at which a combination of said data symbols and said duplicates of said data symbols in said packet is provided as a data packet; and

a transmitter having an input connected to receive the output of said repetition generator and having an output from which data symbols received from said repetition generator are transmitted at a first energy level when the number of data symbols in said packet equals said first value, at a second energy level, which is less than said first energy level, when the number of data symbols in said packet is less than said first value.

25. The system of claim 24 wherein said transmitter transmits data symbols:

at said second energy level when the number of data symbols in said packet is less than said first value but greater than a second value, and

at a third energy level when the number of data symbols in said packet is less than said second value.

26. The system of claim 24 further comprising a spread spectrum modulator interposed between said repetition generator and said transmitter having an input coupled to said repetition generator output and having an output coupled to said transmitter input.

27. The system of claim 26 wherein said spread spectrum modulator comprises:

a first PN generator having an output; and

a first mixer having a first input coupled to said repetition generator output and having a second input coupled to said first PN generator output and having an output.

28. The system of claim 27 wherein said spread spectrum modulator comprises:

a second PN generator having an output;

a second mixer having a first input coupled to said first mixer output and having a second input coupled to said second PN generator output;

a third PN generator having an output; and

a third mixer having a first input coupled to said first mixer out-put and having a second input coupled to said third PN generator output.

29. The system of claim 27 further comprising an offset quadrature phase shift keying modulator having a first input coupled to said second mixer output and having a second input coupled to said third mixer output and having an output coupled to said transmitter input.