Multicode direct sequence spread spectrum
DC CAFCFirst Claim
1. A transceiver for transmitting a first stream of data symbols, the transceiver comprising:
- a converter for converting the first stream of data symbols into plural sets of N data symbols each;
first computing means for operating on the plural sets of N data symbols to produce modulated data symbols corresponding to an invertible randomized spreading of the first stream of data symbols; and
means to combine the modulated data symbols for transmission.
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Abstract
In this patent, we present MultiCode Direct Sequence Spread Spectrum (MC-DSSS) which is a modulation scheme that assigns up to N DSSS codes to an individual user where N is the number of chips per DSSS code. When viewed as DSSS, MC-DSSS requires up to N correlators (or equivalently up to N Matched Filters) at the receiver with a complexity of the order of N2 operations. In addition, a non ideal communication channel can cause InterCode Interference (ICI), i.e., interference between the N DSSS codes. In this patent, we introduce new DSSS codes, which we refer to as the “MC” codes. Such codes allow the information in a MC-DSSS signal to be decoded in a sequence of low complexity parallel operations which reduce the ICI. In addition to low complexity decoding and reduced ICI. MC-DSSS using the MC codes has the following advantages: (1) it does not require the stringent synchronization DSSS requires, (2) it does not require the stringent carrier recovery DSSS requires and (3) it is spectrally efficient.
163 Citations
40 Claims
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1. A transceiver for transmitting a first stream of data symbols, the transceiver comprising:
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a converter for converting the first stream of data symbols into plural sets of N data symbols each;
first computing means for operating on the plural sets of N data symbols to produce modulated data symbols corresponding to an invertible randomized spreading of the first stream of data symbols; and
means to combine the modulated data symbols for transmission. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
a source of N more than one and up to M direct sequence spread spectrum code symbols codes, where M is the number of chips per direct sequence spread spectrum code; and
a modulator to modulate each ith data symbol from each set of N data symbols with the ith a code symbol from the N code symbol up to M direct sequence spread spectrum codes to generate N modulated data symbols, and thereby spread each ith data symbol set of data symbols over a separate code symbol .
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3. The transceiver of claim 2 in which the code symbols direct sequence spread spectrum codes are generated by operation of a non-trivial N point transform on a sequence of input signals.
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4. The transceiver of claim 1 in which the first computing means includes comprises:
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a transformer for operating on each set of N data symbols to generate N modulated data symbols as output, the N modulated data symbols corresponding to spreading of each ith data symbol over a separate code symbol selected from a set of more than one and up to M codes, where M is the number of chips per code; and
means to combine the modulated data symbols for transmission.
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5. The transceiver of claim 4 in which the transformer effectively applies a first transform selected from the group comprising consisting of a Fourier transform and a Walsh transform to the N data symbols.
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6. The transceiver of claim 5 in which the first transform is a Fourier transform and it is followed by a randomizing transform.
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7. The transceiver of claim 6 in which the first transform is a Fourier transform and it is followed by a randomizing transform and a second transform selected from the group comprising consisting of a Fourier transform and a Walsh transform.
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8. The transceiver of claim 4 in which the transformer effectively applies a first inverse transform selected from the group comprising consisting of a randomizer transform, a Fourier transform and a Walsh transform to the N data symbols, followed by a first equalizer and a second inverse transform selected from the group comprising consisting of a Fourier transform and a Walsh transform.
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9. The transceiver of claim 8 in which the second transform is followed by a second equalizer.
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10. The transceiver of claim 1 further including comprising:
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means for receiving a sequence of modulated data symbols, the modulated data symbols having been generated by invertible randomized spreading of a second stream of data symbols; and
second computing means for operating on the sequence of modulated data symbols to produce an estimate of the second stream of data symbols.
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11. The transceiver of claim 10 further including comprising means to apply diversity to the modulated data symbols before transmission, and means to combine received diversity signals.
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12. The transceiver of claim 10 in which the second computing means includes comprises:
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a correlator for correlating each ith modulated data symbol from the received sequence of modulated data symbols with the ith code symbol a code from the a set of N code symbols more than one and up to M codes, where M is the number of chips per code; and
a detector for detecting an estimate of the data symbols from output of the correlator.
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13. The transceiver of claim 10 in which the second computing means includes comprises an inverse transformer for regenerating an estimate of the N data symbols.
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14. The transceiver of claim 1 further including comprising a shaper for shaping the combined modulated data symbols for transmission.
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15. The transceiver of claim 1 further including comprising means to apply diversity to the combined modulated data symbols before transmission.
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16. The transceiver of claim 1 in which the N data symbols include a pilot frame and a number of data frames, and is preceded by a request frame, wherein the request frame is used to wake up receiving transceivers, synchronize reception of the N data symbols and convey protocol information.
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17. A transceiver for transmitting a first stream of data symbols and receiving a second stream of data symbols, the transceiver comprising:
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a converter for converting the first stream of data symbols into plural sets of N data symbols each;
first computing means for operating on the plural sets of N data symbols to produce sets of N modulated data symbols corresponding to an invertible randomized spreading of each set of N data symbols over N code symbols more than one and up to M direct sequence spread spectrum codes;
means to combine the modulated data symbols for transmission;
means for receiving a sequence of modulated data symbols, the modulated data symbols having been generated by an invertible randomized spreading of a second stream of data symbols over N code symbols more than one and up to M direct sequence spread spectrum codes;
second computing means for operating on the sequence of modulated data symbols to produce an estimate of the second stream of data symbols; and
means to combine output from the second computing means. - View Dependent Claims (18, 19, 20, 21, 22)
a source of N the direct sequence spread spectrum code symbols codes; and
a modulator to modulate each ith data symbol from each set of N data symbols with the ith code symbol a code from the N code symbol up to M direct sequence spread spectrum codes to generate N modulated data symbols, and thereby spread each ith data symbol over a separate direct sequence spread spectrum code symbol .
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19. The transceiver of claim 18 in which the code symbols direct sequence spread spectrum codes are generated by operation of plural non-trivial N point transforms on a random sequence of input signals.
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20. The transceiver of claim 17 in which the first computing means includes comprises:
a transformer for operating on each set of N data symbols to generate N modulated data symbols as output, the N modulated data symbols corresponding to spreading of each ith data symbol over a separate code symbol .
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21. The transceiver of claim 17 in which the second computing means includes comprises:
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a correlator for correlating each ith modulated data symbol from the received sequence of modulated data symbols with the ith code symbol a code from the set of N code symbols up to M direct sequence spread spectrum codes; and
a detector for detecting an estimate of the data symbols from the output of the correlator.
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22. The transceiver of claim 17 in which the second computing means includes comprises an inverse transformer for regenerating an estimate of the N data symbols.
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23. A method of exchanging data streams between a plurality of transceivers, the method comprising the steps of:
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converting a first stream of data symbols into plural sets of N data symbols each;
operating on the plural sets of N data symbols to produce modulated data symbols corresponding to a spreading of the first stream of data symbols over N code symbols more than one and up to M direct sequence spread spectrum codes;
combining the modulated data symbols for transmission; and
transmitting the modulated data symbols from a first transceiver at a time when no other of the plurality of transceivers is transmitting. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31, 32)
transforming, by application of a transform, each set of N data symbols to generate N modulated data symbols as output.
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26. The method of claim 25 in which transforming each set of N data symbols includes comprises applying to each set of N data symbols a randomizing transform and a transform selected from the group comprising consisting of a Fourier transform and a Walsh transform.
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27. The method of claim 25 in which transforming each set of N data symbols includes comprises applying to each set of N data symbols a Fourier transform, a randomizing transform and a transform selected from the group comprising consisting of a Fourier transform and a Walsh transform.
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28. The method of claim 25 in which transforming each set of N data symbols includes comprises applying to each set of N data symbols a first transform selected from the group comprising consisting of a Fourier transform and a Walsh transform, a randomizing transform and a second transform selected from the group comprising consisting of a Fourier transform and a Walsh transform.
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29. The method of claim 23 further including comprising the step of:
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receiving, at a transceiver distinct from the first transceiver, the sequence of modulated data symbols; and
operating on the sequence of modulated data symbols to produce an estimate of the first stream of data symbols.
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30. The method of claim 29 in which operating on the sequence of modulated data symbols includes comprises the steps of:
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correlating each ith modulated data symbol from the received sequence of modulated data symbols with the ith code symbol from the set of N code symbols a code from the up to M direct sequence spread spectrum codes; and
detecting an estimate of the first stream of data symbols from output of the correlator.
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31. The method of claim 23 further including comprising the step of shaping the modulated data symbols before transmission.
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32. The method of claim 23 further including comprising the step of applying diversity to the modulated data symbols before transmission.
- 33. A transceiver for transmitting a first stream of data symbols, the transceiver comprising:
Specification