Spread spectrum receiver apparatus and method
View Patent ↗A receiver ( 200 ) incorporates in parallel an adaptive minimum mean square error (MMSE) equalizer stage ( 202 ) and a matched filter stage (RAKE) ( 204 ). A selector ( 206 ) is utilized to accept data from one of the two stages based upon an operating condition of the receiver. The receiver may incorporate a single MMSE equalizer ( 202 ) for all channels in a spread spectrum communication channel.
1. An apparatus comprising:
a shift register having a first input and a first output, the first input coupled to a received signal;
a minimum mean square equalizer having a second input and a second output, the second input coupled to the first output;
a matched filter having a third input and a third output, the third input coupled to the first output; and
a selector coupled to the second and third outputs, the selector having a first and second position and responsive to a selection criteria, wherein one of the second and third outputs is selected for further processing.
2. The apparatus of claim 1 wherein the first output comprises a matched filter coefficients output.
3. The apparatus of claim 1 wherein the minimum mean square equalizer comprising equalizer taps, the equalizer taps having an input coupled to an adaptive algorithm process and the equalizer taps having an equalizer coefficients output coupled to generate the second output of the minimum mean square equalizer.
4. The apparatus of claim 3 wherein the adaptive algorithm process comprises one of a least mean square process, a recursive least squares process, and a multi-stage Weiner filter.
5. The apparatus of claim 1 wherein the selector is operable based upon at least one of a frame error rate estimate, bit error rate estimate, cyclical redundancy check, signal-to-noise ratio, and Doppler frequency estimate of a channel fading process.
6. The apparatus of claim 1 wherein the minimum mean square error equalizer is coupled to a plurality of channel demodulators.
7. The apparatus of claim 6 , wherein at least one of the plurality of channel demodulators is a pilot channel demodulator.
8. A method for processing a received radio frequency signal that includes data, the method comprising:
coupling the radio frequency signal to an input of a shift register;
providing the data from an output of the shift register to a matched filter;
coupling the outputs of the minimum mean square equalizer to a selector, the selector having a first and a second position and responsive to a selection criteria, wherein one of the outputs of the minimum mean square equalizer and the matched filter responsive to said selection criteria is selected for decoding.
9. The method of claim 8 wherein the selecting the data for decoding comprises selecting the data for decoding based on one of a frame error rate estimate, bit error rate estimate, cyclical redundancy check, signal-to-noise ratio, and Doppler frequency estimate of a channel fading process.
10. The method of claim 8 further comprising means for adapting the minimum mean squared equalizer.