Dual mode code division multiple access communication system and method
First Claim
1. Apparatus for transmitting data signals in a CDMA spread spectrum transmission system comprising:
- a coherence interval channel encoder having an input and an output, the input being operable to receive an input data signal, wherein the coherence channel encoder is capable of processing an input data signal into encoded data blocks;
an orthogonal function encoder having an input and an output, the input being connected to the channel encoder output, wherein the orthogonal function encoder combines a data signal received at its input with a particular orthogonal function sequence to form a spread data signal which is provided to the output; and
a pseudo-noise (PN) channel modulator having an input and an output, the input being connected to the orthogonal function encoder output, wherein the PN channel modulator combines the spread signal with at least one PN sequence and modulates the resulting data signal, and wherein the generated encoded data blocks are of sufficiently short length to minimize phase shift of the transmitted modulated data signal at a receiver to enable the receiver to perform coherent detection of the data signal.
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Abstract
A CDMA communication system capable of operating at higher data rates with less bit errors and reduced cochannel interference facilitates coherent detection without the use of a pilot tracking signal. A transmitter in the communication system includes a coherence interval channel encoder, an orthogonal function encoder, such as a Walsh encoder, as well as a pseudo noise (PN) channel modulator. The channel encoder processes data sequences into sufficiently short encoded data blocks to minimize any phase shifts at a receiver in a high mobility environment due to a Doppler frequency shift. Depending on the application, several transmitters may be synchronized such that the corresponding transmitted information signals are orthogonal to one another. A receiver of the communication system includes a channel demodulator, matched filters and coherent decoder that generates weighted decoded signals, one of which is determined to be a proper coherent synchronous reading of the received information signals without the use of a pilot tracking signal. The communication system may be used as a forward and/or reverse communications link in a cellular telephone system.
193 Citations
48 Claims
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1. Apparatus for transmitting data signals in a CDMA spread spectrum transmission system comprising:
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a coherence interval channel encoder having an input and an output, the input being operable to receive an input data signal, wherein the coherence channel encoder is capable of processing an input data signal into encoded data blocks; an orthogonal function encoder having an input and an output, the input being connected to the channel encoder output, wherein the orthogonal function encoder combines a data signal received at its input with a particular orthogonal function sequence to form a spread data signal which is provided to the output; and a pseudo-noise (PN) channel modulator having an input and an output, the input being connected to the orthogonal function encoder output, wherein the PN channel modulator combines the spread signal with at least one PN sequence and modulates the resulting data signal, and wherein the generated encoded data blocks are of sufficiently short length to minimize phase shift of the transmitted modulated data signal at a receiver to enable the receiver to perform coherent detection of the data signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. Apparatus for receiving data signals in a CDMA spread spectrum communication system comprising:
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a channel demodulator having an input and in-phase and quadrature phase signal outputs, the input receiving an encoded modulated data signal; first and second matched filters connected to the demodulator in-phase and quadrature signal outputs, respectively; a PN sequence generator connected to the first and second matched filters; an orthogonal function sequence generator connected to the first and second matched filters, wherein each of the matched filters combine the orthogonal function sequence and the PN sequence with demodulated in-phase and quadrature phase data signals from the demodulator; first and second analog-to-digital (A/D) converters connected to the respective first and second match filters; and a weighted signal coherent decoder connected to the analog-to digital converters and having a decoded signal output. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20)
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21. Apparatus for receiving data signals using a plurality of antennas in a CDMA spread spectrum transmission system comprising:
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a plurality of channel demodulators, each demodulator having an input and in-phase and quadrature phase signal outputs, the input receiving an encoded modulated data signal from a respective antenna; a plurality of sets of first and second matched filters, each first and second matched filter in a set being connected to a respective demodulator in-phase and quadrature signal output, wherein each of the matched filters in a set combine an orthogonal function sequence and a PN sequence with demodulated but encoded in-phase and quadrature phase data signals from the respective demodulator; a plurality of first and second analog-to-digital (A/D) converters, each A/D converter being connected to a respective matched filters; and a weighted signal coherent decoder connected to the analog-to digital converters and having a decoded signal output, wherein the coherent decoder is capable of generating weighted signals based on respective digital sequences generated by the A/D converters for the in-phase and quadrature phase signals from the demodulators. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30)
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31. A method for transmitting CDMA spread spectrum signals in a transmission system comprising:
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channel encoding a data signal to be transmitted into encoded data blocks; combining the encoded data blocks with an orthogonal function sequence to form a spread signal; modulating the spread signal and combing the spread signal with at least one respective PN sequence; and transmitting the modulated data signals at a particular data rate, wherein the step of channel encoding produces sufficiently short encoded data blocks to minimize phase shift of the modulated signal at a receiver to enable the receiver to perform coherent detection of the modulated data signal. - View Dependent Claims (32, 33, 34, 35, 36, 37, 38)
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39. A method for receiving CDMA spread spectrum signals in a communication system comprising:
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channel demodulating a received modulated and encoded data signal into in-phase and quadrature phase demodulated signals; combining each of the in-phase and quadrature phase demodulated signals with respective PN sequences and orthogonal function sequences to produce processed in-phase and quadrature phase signals; converting the processed in-phase and quadrature phase signals into a digital signal; generating weighted decoded in-phase and quadrature phase signals based on the digital processed in-phase and quadrature phase signals; and selecting the weighted signals that correspond to synchronous reading of the modulated signal. - View Dependent Claims (40, 41, 42, 43)
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44. A method for receiving CDMA spread spectrum signals in a communication system using a plurality of antennas comprising:
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channel demodulating each modulated and encoded spread spectrum signal received from each respective antenna into corresponding in-phase and quadrature phase demodulated signals; combining each of the in-phase and quadrature phase demodulated signals with respective PN sequences and orthogonal function sequences to produce respective processed in-phase and quadrature phase signals; converting the respective processed in-phase and quadrature phase signals into corresponding digital signals; generating weighted decoded in-phase and quadrature phase signals based on the digital processed in-phase and quadrature phase signals; and selecting the weighted signals that correspond to synchronous reading of the modulated signal. - View Dependent Claims (45, 46, 47, 48)
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Specification