Multiple-access hybrid OFDM-CDMA system
First Claim
1. In a multiple-access OFDM-CDMA system, a method for recovering data transmitted over a wireless communication channel, comprising:
- processing a received signal to provide data samples;
transforming the data samples in accordance with a particular transformation to provide transformed samples;
despreading the transformed samples with one or more sets of despreading coefficients to provide despread samples, wherein each set of despreading coefficients is associated with a respective despreading code that corresponds to a spreading code used to spread data prior to transmission and selected from a set of available spreading codes;
combining the despread samples for each time interval to provide a demodulated symbol representative of a transmitted OFDM symbol; and
decoding demodulated symbols to provide decoded data.
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Accused Products
Abstract
In one aspect of a multiple-access OFDM-CDMA system, the data spreading is performed in the frequency domain by spreading each data stream with a respective spreading code selected from a set of available spreading codes. To support multiple access, system resources may be allocated and de-allocated to users (e.g., spreading codes may be assigned to users as needed, and transmit power may be allocated to users). Variable rate data for each user may be supported via a combination of spreading adjustment and transmit power scaling. Interference control techniques are also provided to improve system performance via power control of the downlink and/or uplink transmissions to achieve the desired level of performance while minimizing interference. A pilot may be transmitted by each transmitter unit to assist the receiver units perform acquisition, timing synchronization, carrier recovery, handoff, channel estimation, coherent data demodulation, and so on.
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Citations
20 Claims
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1. In a multiple-access OFDM-CDMA system, a method for recovering data transmitted over a wireless communication channel, comprising:
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processing a received signal to provide data samples;
transforming the data samples in accordance with a particular transformation to provide transformed samples;
despreading the transformed samples with one or more sets of despreading coefficients to provide despread samples, wherein each set of despreading coefficients is associated with a respective despreading code that corresponds to a spreading code used to spread data prior to transmission and selected from a set of available spreading codes;
combining the despread samples for each time interval to provide a demodulated symbol representative of a transmitted OFDM symbol; and
decoding demodulated symbols to provide decoded data. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. In a multiple-access OFDM-CDMA system, a method for recovering data transmitted over a wireless communication channel, comprising:
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processing a received signal to provide data samples;
decovering the data samples with a cover code to provide decovered samples;
transforming the decovered samples in accordance with a Fourier transform to provide transformed samples;
despreading the transformed samples with one or more sets of despreading coefficients to provide despread samples, wherein each set of despreading coefficients is associated with a respective despreading code that corresponds to a spreading code used to spread data prior to transmission and selected from a set of available spreading codes;
combining the despread samples for each time interval to provide a demodulated symbol representative of a transmitted OFDM symbol; and
decoding demodulated symbols to provide decoded data.
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13. A receiver unit in a multiple-access OFDM-CDMA system, comprising:
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a receiver operative to process a received signal to provide data samples;
a transformer operative to transform the data samples in accordance with a particular transformation to provide transformed samples;
a despreader operative to despread the transformed samples with one or more sets of despreading coefficients to provide despread samples, wherein each set of despreading coefficients is associated with a respective despreading code that corresponds to a spreading code used to spread data prior to transmission and selected from a set of available spreading codes;
a first summer operative to combine the despread samples for each time interval to provide a demodulated symbol representative of a transmitted OFDM symbol; and
a RX data processor operative to decode demodulated symbols to provide decoded data. - View Dependent Claims (14, 15, 16, 17, 18, 19)
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20. A receiver apparatus in a multiple-access OFDM-CDMA system, comprising:
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means for processing a received signal to provide data samples;
means for transforming the data samples in accordance with a particular transformation to provide transformed samples;
means for despreading the transformed samples with one or more sets of despreading coefficients to provide despread samples, wherein each set of despreading coefficients is associated with a respective despreading code that corresponds to a spreading code used to spread data prior to transmission and selected from a set of available spreading codes;
means for combining the despread samples for each time interval to provide a demodulated symbol representative of a transmitted OFDM symbol; and
means for decoding demodulated symbols to provide decoded data.
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Specification