Methods of and devices for enhancing communications that use spread spectrum technology by using variable code techniques
DCFirst Claim
1. In a method of processing a signal, comprising the steps of applying a spread spectrum coding process, the signal being a function of time, the improvement comprising:
- (a) encoding a first segment of the signal with a first channel encoder operating at a first rate to generate a first encoded segment having more significant bits using a first error protection process; and
(b) encoding a second segment of the signal with a second channel encoder operating at a second rate to generate a second encoded segment having less significant bits using a second error protection process, the second rate being different from the first rate and the first error protection process providing a greater amount of error protection than the second error protection process.
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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.
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Citations
28 Claims
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1. In a method of processing a signal, comprising the steps of applying a spread spectrum coding process, the signal being a function of time, the improvement comprising:
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(a) encoding a first segment of the signal with a first channel encoder operating at a first rate to generate a first encoded segment having more significant bits using a first error protection process; and (b) encoding a second segment of the signal with a second channel encoder operating at a second rate to generate a second encoded segment having less significant bits using a second error protection process, the second rate being different from the first rate and the first error protection process providing a greater amount of error protection than the second error protection process. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. In a device for processing a signal comprising means for applying a spread spectrum coding process, the signal being a function of time, the improvement comprising:
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(a) first means for channel encoding a first segment of the signal to generate a first encoded segment having more significant bits using a first error protection process, the first means for channel encoding operating at a first rate; and (b) second means for channel encoding a second segment of the signal to generate a second encoded segment having less significant bits using a second error protection process, the second means for channel encoding operating at a second rate, the second rate being different from the first rate and the first error protection process providing a greater amount of error protection than the second error protection process. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. In a method of processing a signal comprising the steps of applying a spread spectrum multiple access decoding process, the signal being a function of time, the improvement comprising:
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(a) decoding a first received segment of the signal with a first channel decoder to generate a first decoded segment having more significant bits using a first error protection process, the first channel decoder operating at a first rate; and (b) decoding a second received segment of the signal with a second channel decoder to generate a second decoded segment having less significant bits using a second error protection process, the second channel decoder operating at a second rate, the second rate being different from the first rate and the first error protection process providing a greater amount of error protection than the second error protection process. - View Dependent Claims (18, 19, 20, 21, 22)
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23. In a device for processing a signal comprising means for applying a spread spectrum decoding process, the signal being a function of time, the improvement comprising:
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(a) means for decoding a first received segment of the signal with a first channel decoder to generate a first decoded segment having more significant bits using a first error protection process, the first channel decoder operating at a first rate; and (b) means for decoding a second received segment of the signal with a second channel decoder to generate a second decoded signal having less significant bits using a second error protection process, the second channel decoder operating at a second rate, the second rate being different from the first rate and the first error protection process providing a greater amount of error protection than the second error protection process. - View Dependent Claims (24, 25, 26, 27, 28)
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Specification