Filter structure for iterative signal processing

Abstract

A method is for communicating by tracking time varying channels in a multiple access packet based communication network. Each packet includes a preamble portion including a data symbol, and a data portion including data symbols. The method may include initializing a channel estimate reference from an initial channel estimate based upon the data symbol in a preamble portion of a received packet, and updating the channel estimate reference based upon a channel estimate of a current data symbol and a previously received data symbol from the data symbols in a data portion of the received packet. The method may also include repeating the updating upon receipt of a subsequent data symbol from the data symbols in the data portion of the received packet.

The invention claimed is: 
     
       1. A method of communicating by tracking a plurality of time varying channels in a multiple access packet based communication network, each packet comprising a preamble portion including at least one data symbol, and a data portion including a plurality of data symbols, the method comprising:
 initializing a channel estimate reference from an initial channel estimate based upon the at least one data symbol in a preamble portion of a received packet; 
 updating the channel estimate reference based upon a channel estimate of a current data symbol and at least one previously received data symbol from the plurality of data symbols in a data portion of the received packet, the updating comprising:
 generating the channel estimate for the current data symbol, 
 updating the channel estimate reference based upon the channel estimate for the current data symbol, 
 decoding the current symbol based upon the channel estimate for the current data symbol, 
 updating a channel estimate for a data symbol directly preceding the current data symbol based upon time smoothing data and the channel estimate for the current data symbol, and 
 re-decoding the data symbol directly preceding the current data symbol based upon the updated channel estimate therefor; and 
 repeating the updating upon receipt of at least one subsequent data symbol from the plurality of data symbols in the data portion of the received packet; and 
 
 for each subsequent received data symbol, pipelining the steps of demodulating and modulating during the updating. 
 
     
     
       2. The method according to  claim 1  further comprising storing the channel estimate reference in a channel estimate database at a receiver device. 
     
     
       3. The method according to  claim 1  further comprising transforming the channel estimate to a frequency domain prior to updating the channel estimate reference to provide a time smoothed channel estimate reference. 
     
     
       4. The method according to  claim 1  further comprising:
 for each subsequent data symbol, during the updating, pipelining demodulating and modulating; and 
 updating the channel estimate reference by performing a forward error correction (FEC) decoding. 
 
     
     
       5. The method according to  claim 1  wherein the multiple access packet based communication network comprises an orthogonal frequency-division multiplexing (OFDM) wireless network. 
     
     
       6. The method according to  claim 5  wherein the updating of the channel estimate reference comprises calculations based upon at least one of a frequency domain statistic of a radio channel at an OFDM symbol rate, a time domain statistic of the radio channel across OFDM symbols, and outcomes of each decoded OFDM symbol. 
     
     
       7. The method according to  claim 1  wherein the updating is performed on a data symbol-by-data symbol basis. 
     
     
       8. The method according to  claim 1  wherein each previously received data symbol is decoded iteratively with each subsequent data symbol. 
     
     
       9. The method according to  claim 1  wherein the updating based upon the current and the at least one previously received data symbols is performed in parallel. 
     
     
       10. The method according to  claim 1  wherein the updating of the channel estimate reference is based upon the channel estimate of the current and all previously received data symbols. 
     
     
       11. A wireless communications device for communicating by tracking a plurality of time varying channels in a multiple access packet based communication network, each packet comprising a preamble portion including at least one data symbol, and a data portion including a plurality of data symbols, the wireless communications device comprising:
 a controller baseband receiver processor; and 
 a wireless transceiver cooperating with incorporating said controller baseband receiver processor for:
 initializing a channel estimate reference from an initial channel estimate based upon the at least one data symbol in a preamble portion of a received packet, 
 updating the channel estimate reference based upon a channel estimate of a current data symbol and at least one previously received data symbol from the plurality of data symbols in a data portion of the received packet, the updating comprising:
 generating the channel estimate for the current data symbol, 
 updating the channel estimate reference based upon the channel estimate for the current data symbol, 
 decoding the current symbol based upon the channel estimate for the current data symbol, 
 updating a channel estimate for a data symbol directly preceding the current data symbol based upon time smoothing data and the channel estimate for the current data symbol, and 
 re-decoding the data symbol directly preceding the current data symbol based upon the updated channel estimate therefor, and 
 
 repeating the updating upon receipt of at least one subsequent data symbol from the plurality of data symbols in the data portion of the received packet. 
 
 
     
     
       12. The wireless communications device according to  claim 11  wherein said controller and baseband receiver processor of the wireless transceiver are for storing stores the channel estimate reference in a channel estimate database at a receiver device. 
     
     
       13. The wireless communications device according to  claim 11  wherein said controller and baseband receiver processor of the wireless transceiver are for transforming transforms the channel estimate to a frequency domain prior to updating the channel estimate reference to provide a time smoothed channel estimate reference. 
     
     
       14. The wireless communications device according to  claim 11  wherein said controller and baseband receiver processor of the wireless transceiver, are for:
 for each subsequent data symbol during the updating, pipelining demodulating and modulating; and updating, updates the channel estimate reference by performing a forward error correction (FEC) decoding. 
 
     
     
       15. The wireless communications device according to  claim 11  wherein the multiple access packet based communication network comprises an orthogonal frequency-division multiplexing (OFDM) wireless network. 
     
     
       16. The wireless communications device according to  claim 15  wherein the updating of the channel estimate reference comprises calculations based upon at least one of a frequency domain statistic of a radio channel at an OFDM symbol rate, a time domain statistic of the radio channel across OFDM symbols, and outcomes of each decoded OFDM symbol. 
     
     
       17. The wireless communications device according to  claim 11  wherein the updating is performed on a data symbol-by-data symbol basis. 
     
     
       18. The wireless communications device according to  claim 11  wherein each previously received data symbol is decoded iteratively with each subsequent data symbol. 
     
     
       19. The wireless communications device according to  claim 11  wherein the updating based upon the current and the at least one previously received data symbols is performed in parallel. 
     
     
       20. The method according to  claim 1  wherein updating the channel estimate reference comprises error control based decoding. 
     
     
       21. The wireless communications device according to  claim 11  wherein updating the channel estimate reference comprises error control based decoding. 
     
     
       22. A method of communicating by tracking a plurality of time varying channels in a multiple access packet based communication network, each packet comprising a preamble portion included at least one data symbol, and a data portion including a plurality of data symbols, the method comprising:
 initializing a channel estimate reference from an initial channel estimate based upon the at least one data symbol in a preamble portion of a received packet; 
 updating the channel estimate reference based upon a channel estimate of a current data symbol and at least one previously received data symbol from the plurality of data symbols in a data portion of the received packet, the updating comprising:
 for each data symbol, demodulating the data symbol based upon the channel estimate, 
 decoding the data symbol, 
 generating training data by remodulating the decoded data symbol, 
 updating the a channel estimate database based upon the training data, and 
 generating the channel estimate for the data symbol based upon the updated channel estimate database; 
 
 repeating the updating upon receipt of at least one subsequent data symbol from the plurality of data symbols in the data portion of the received packet; and 
 storing the channel estimate reference in a the channel estimate database at a received device. 
 
     
     
       23. A wireless communications device for communicating by tracking a plurality of time varying channels in a multiple access packet based communication network, each packet comprising a preamble portion including at least one data symbol, and a data portion including a plurality of data symbols, the wireless communications device comprising:
 a controller baseband receiver processor; and 
 a wireless transceiver cooperating with incorporating said controller for initializing baseband receiver processor, the wireless transceiver initiating a channel estimate reference from an initial channel estimate based upon the at least one data symbol in a preamble portion of a received packet, 
 updating the channel estimate reference based upon a channel estimate of a current data symbol and at least one previously received data symbol from the plurality of data symbols in a data portion of the received packet, the updating comprising:
 for each data symbol, demodulating the data symbol based upon the channel estimate, 
 decoding the data symbol, 
 generating training data by remodulating the decoded data symbol, 
 updating the a channel estimate database based upon the training data, and 
 generating the channel estimate for the data symbol based upon the updated channel estimate database, 
 
 repeating the updating upon receipt of at least one subsequent data symbol from the plurality of data symbols in the data portion of the received packet, and 
 storing the channel estimate reference in a the channel estimate database at a receiver device. 
 
     
     
       24. A method of estimating one or more time varying channels in a multiple access packet based communication network, each packet comprising a preamble portion including at least one preamble symbol, and a data portion including a plurality of data symbols, the method comprising:
 initializing an initial channel estimate based upon the at least one preamble symbol in a preamble portion of a received packet;   updating the initial channel estimate to form updated channel estimates for a current data symbol and at least one previously received data symbol from the plurality of data symbols in a data portion of the received packet, the updating comprising:
 generating a first channel estimate for the current data symbol based upon the initial channel estimate, 
 decoding the current data symbol based upon the first channel estimate for the current data symbol to form decoder outcomes, and 
 generating a second channel estimate for a data symbol directly preceding the current data symbol based upon the decoder outcomes remodulated without re-encoding, the updated channel estimates including at least the second channel estimate; 
   repeating the updating upon receipt of at least one subsequent data symbol from the plurality of data symbols in the data portion of the received packet; and   for each subsequent received data symbol, pipelining the steps of demodulating and modulating during the updating.   
     
     
       25. A wireless communications device for estimating one or more of time varying channels in a multiple access packet based communication network, each packet comprising a preamble portion including at least one preamble symbol, and a data portion including a plurality of data symbols, the wireless communications device comprising:
 a baseband receiver processor; and   a wireless transceiver incorporating said baseband receiver processor and configured to perform:
 initializing an initial channel estimate based upon the at least one preamble symbol in a preamble portion of a received packet, 
 updating the initial channel estimate to form updated channel estimates for a current data symbol and at least one previously received data symbol from the plurality of data symbols in a data portion of the received packet, the updating comprising:
 generating a first channel estimate for the current data symbol based upon the initial channel estimate, 
 decoding the current data symbol based upon the first channel estimate for the current data symbol to form decoder outcomes, 
 generating a second channel estimate for a data symbol directly preceding the current data symbol based upon the decoder outcomes remodulated without re-encoding, the updated channel estimates including at least the second channel, and 
 
 repeating the updating upon receipt of at least one subsequent data symbol from the plurality of data symbols in the data portion of the received packet. 
   
     
     
       26. The method according to claim 1 further comprising:
 updating the channel estimate reference by performing a forward error correction (FEC) decoding.