Methods of and devices for enhancing communications that use spread spectrum technology by using variable power techniques

• US 6,044,073 A
• Filed: 08/06/1998
• Issued: 03/28/2000
• Est. Priority Date: 04/29/1994
• Status: Expired due to Term

• Current Assignee: Agere Systems Incorporated (Broadcom, Inc.)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Seshadri, Nambirajan, Sundberg, Carl-Erik Wilhelm
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): RAO, SEEMA SRINIVAS
• Application Number:
  US09/129,774
• Time in Patent Office: 600 Days
• Field of Search: 370/342, 370/345, 370/347, 370/465, 370/350, 375/200, 375/206, 714/746, 714/786, 714/787, 714/788, 714/789, 714/774, 714/762, 714/761, 714/752
• US Class Current: 370/342
• CPC Class Codes: H03M 13/35 Unequal or adaptive error protection, e.g. by providing a different level of protection according to significance of source information or by adapting the coding according to the change of transmission channel characteristics
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04L 1/0054 Maximum-likelihood or sequential decoding, e.g. Viterbi, Fano, ZJ algorithms
• CPC Class Codes: H04L 1/0059 Convolutional codes
• CPC Class Codes: H04L 1/007 Unequal error protection for format H04L1/0078; for codes per se H03M13/35
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27
• CPC Class Codes: H04L 1/0083 Formatting with frames or packets; Protocol or part of protocol for error control
• CPC Class Codes: H04L 2001/0096 Channel splitting in point-to-point links
• CPC Class Codes: H04L 2001/0098 Unequal error protection
• CPC Class Codes: H04L 25/4902 Pulse width modulation; Pulse position modulation

Abstract

We have invented methods of and devices for introducing unequal error protection into spread spectrum communication systems. One embodiment of the invention addresses certain inefficiencies of the standard known as IS-95 used, for example, in some mobile direct sequence code division multiple access ("DS-CDMA") phone systems. The invention allows for increased system capacity and/or improved quality. More specifically, spread spectrum multiple access ("SSMA") coding may be combined with the concept of unequal error protection ("UEP"), resulting in an UEP SSMA coding process. IS-95, in order to make significant portions of a signal highly immune to errors, has imposed the same high degree of error immunity on less significant portions of the signal (when, in fact, a lower degree would suffice) and, thus, wastes bandwidth. The present invention'"'"'s coding process (i.e., UEP SSMA) utilizes bandwidth in a closer to optimal manner than known methods.

Claims

1. A method of processing a signal comprising applying a spread spectrum coding process, the signal being a function of time, the improvement comprising:

modulating the signal to generate a modulated signal, the signal comprising a first segment a second segment, the first segment being more significant than the second segment and comprising a first time portion of the signal, the second segment comprising a second time portion of the signal, the modulating step increasing a duration of the first time portion relative to a duration of the second time portion.

2. The method of claim 1 further comprising spreading the modulated signal to generate a spread spectrum signal, the spreading comprising combining the modulated signal with a spreading signal.

3. The method of claim 2 wherein said spreading step comprises the use of an orthogonal spreading sequence.

4. The method of claim 1 further comprising:

(a) modulating a radio frequency carrier with a spread spectrum signal to generate a modulated radio frequency signal; and

(b) transmitting the modulated radio frequency signal.

5. The method of claim 1 wherein the signal is generated by:

(a) receiving an analog voice signal at a transmitter;

(b) coding the analog voice signal to generate a digitized voice signal;

(c) applying a forward error correction code to the digitized voice signal to generate an intermediate signal; and

(d) interleaving the intermediate signal to generate the signal.

6. The method of claim 5 wherein said interleaving step comprises interleaving the intermediate signal based upon a basic time unit of the signal.

7. The method of claim 1 wherein both the first segment and the second segment are modulated and wherein a duration increase in the first time portion is the same as a duration decrease in the second time portion.

8. The method of claim 1 wherein said applying the spread spectrum coding process step comprises applying a code division multiple access coding process.

9. The method of claim 8 wherein said applying the code division multiple access coding process step comprises applying a direct sequence code division multiple access coding process.

10. An apparatus for processing a signal including means for applying a spread spectrum coding process, the signal being a function of time, the improvement comprising:

means for modulating the signal to generate a modulated signal, the signal comprising a first segment and a second segment, the first segment being more significant than the second segment and comprising a first time portion of the signal, the second segment comprising a second time portion of the signal, the means for modulating comprising means for increasing a duration of the first time portion relative to a duration of the second time portion.

11. The apparatus of claim 10 further comprising means for spreading the modulated signal to generate a spread spectrum signal, the means for spreading comprising combining the modulated signal with a spreading signal.

12. The apparatus of claim 11 wherein the means for spreading comprises means for using an orthogonal spreading sequence.

13. The apparatus of claim 10 further comprising:

(a) means for modulating a radio frequency carrier with a spread spectrum signal to generate a modulated radio frequency signal; and

(b) means for transmitting the modulated radio frequency signal.

14. The apparatus of claim 10 wherein the signal is generated by:

(a) means for receiving an analog voice signal at a transmitter;

(b) means for coding the analog voice signal to generate a digitized voice signal;

(c) means for applying a forward error correction code to the digitized voice signal to generate an intermediate signal; and

(d) means for interleaving the intermediate signal to generate the signal.

15. The apparatus of claim 14 wherein the means for interleaving comprises means for interleaving the intermediate signal based upon a basic time unit of the signal.

16. The apparatus of claim 10 wherein the means for modulating modulates both the first segment and the second segment and wherein a duration increase in the first time portion is the same as a duration decrease in the second time portion.

17. The apparatus of claim 10 wherein the means for applying the spread spectrum coding process comprises means for applying a code division multiple access coding process.

18. The apparatus of claim 17 wherein the means for applying the code division multiple access coding process comprises means for applying a direct sequence code division multiple access coding process.

19. A method including applying a spread spectrum decoding method to a signal, the signal being a function of time, the improvement comprising:

variable time demodulating the signal to generate a variable time demodulated signal, the signal comprising a first segment and a second segment, the first segment being more significant than the second segment and comprising a first time portion of the signal, the second segment comprising a second time portion of the signal, the variable time demodulating comprising increasing a duration of the second time portion relative to a duration of the first time portion.

20. The method of claim 19 wherein said variable time demodulating comprises:

(a) despreading the signal to generate a despread signal;

(b) deinterleaving the despread signal to generate a deinterleaved signal; and

(c) demultiplexing the deinterleaved signal to generate a first signal and a second signal.

21. The method of claim 20 further comprising:

(a) generating a first series of soft decision values based upon the first signal; and

(b) generating a second series of soft decision values based upon the second signal.

22. The method of claim 20 wherein said deinterleaving step comprises deinterleaving an intermediate signal based upon a basic time unit of the signal.

23. The method of claim 19 wherein said variable time demodulating demodulates both the first segment and the second segment and wherein a duration increase in the second time portion is the same as a duration decrease in the first time portion.

24. The method of claim 19 wherein said applying the spread spectrum decoding process step comprises applying a code division multiple access decoding process.

25. The method of claim 24 wherein said applying the code division multiple access decoding process step comprises applying a direct sequence code division multiple access decoding process.

26. An apparatus including means for applying a spread spectrum decoding method to a signal, the signal being a function of time, the improvement comprising:

means for variable time demodulating the signal to generate a variable time demodulated signal, the signal comprising a first segment and a second segment, the first segment being more significant than the second segment and comprising a first time portion of the signal, the second segment comprising a second time portion of the signal, the means for variable time demodulating comprising means for increasing a duration of the second time portion relative to a duration of the first time portion.

27. The apparatus of claim 26 wherein the means for variable time demodulating comprises:

(a) means for despreading the signal to generate a despread signal;

(b) means for deinterleaving the despread signal to generate a deinterleaved signal; and

(c) means for demultiplexing the deinterleaved signal to generate a first signal and a second signal.

28. The apparatus of claim 27 further comprising:

(a) means for generating a first series of soft decision values based upon the first signal; and

(b) means for generating a second series of soft decision values based upon the second signal.

29. The apparatus of claim 27 wherein the means for deinterleaving comprises means for deinterleaving an intermediate signal based upon a basic time unit of the signal.

30. The apparatus of claim 26 wherein the means for variable time demodulating demodulates both the first segment and the second segment and wherein a duration increase in the second time portion is the same as a duration decrease in the first time portion.

31. The apparatus of claim 26 wherein the means for applying the spread spectrum coding process comprises means for applying a code division multiple access coding process.

32. The apparatus of claim 31 wherein the means for applying the code division multiple access coding process comprises means for applying a direct sequence code division multiple access coding process.

33. An apparatus for processing a signal, the apparatus including means for applying a spread spectrum encoding process to the signal, the improvement comprising:

means for applying a first error protection process to at least one more significant portion of the signal, and a second error protection process to at least one less significant portion of the signal, wherein the first error protection process provides a greater amount of error protection than the second error protection process, the means for applying comprises means for applying a variable time modulator.

34. The apparatus of claim 33 wherein the means for applying the spread spectra encoding process comprises means for applying a code division multiple access coding process.

35. The apparatus of claim 34 wherein the means for applying the code division multiple access coding process comprises means for applying a direct sequence code division multiple access coding process.

36. The apparatus of claim 33, wherein the means for applying further comprises at least one of:

(a) means for applying a variable power modulator, and

(b) means for applying a variable rate coder.

37. A method of processing a signal that applies a spread spectrum encoding process to the signal, the improvement comprising:

applying a first error protection process to at least one more significant portion of the signal, and a second error protection process to at least one less significant portion of the signal, wherein the first error protection process provides a greater amount of error protection than the second error protection process, the step of applying comprises applying a variable time modulator to the signal to generate an intermediate modulated signal.

38. The method of claim 37 wherein the step of applying the spread spectrum encoding process comprises applying a code division multiple access coding process.

39. The method of claim 38 wherein the step of applying the code division multiple access coding process comprises applying a direct sequence code division multiple access coding process.

40. The method of claim 37, wherein the step of applying further comprises at least one of:

(a) applying a variable rate coder to the signal to generate an intermediate modulated signal; and

(b) applying a variable power modulator to the intermediate modulated signal.