Filter structure for iterative signal processing

• US 8,964,865 B2
• Filed: 01/03/2013
• Issued: 02/24/2015
• Est. Priority Date: 05/02/2002
• Status: Active Grant

• Current Assignee: Cohda Wireless Pty Ltd.
• Original Assignee: Cohda Wireless Pty Ltd.
• Inventors: Alexander, Paul Dean, Grant, Alexander James, Rasmussen, Lars Kildehoj, Jakas, Stephen Peter
• Primary Examiner(s): NGUYEN, LEON VIET Q
• Application Number:
  US13/733,618
• Publication Number:
  US 20130201972A1
• Time in Patent Office: 782 Days
• Field of Search: None
• US Class Current: 375/260
• CPC Class Codes: H04L 25/0202 Channel estimation
• CPC Class Codes: H04L 25/0204 of multiple channels
• CPC Class Codes: H04L 25/03171 Arrangements involving maximum a posteriori probability [MAP] detection
• CPC Class Codes: H04L 27/2657 Carrier synchronisation
• CPC Class Codes: H04L 27/2662 Symbol synchronisation
• CPC Class Codes: H04L 27/2675 Pilot or known symbols

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.

Claims

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.

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.

20. The method according to claim 1 wherein updating the channel estimate reference comprises error control based decoding.

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; and

a wireless transceiver cooperating with said controller 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 wireless transceiver are for storing 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 wireless transceiver are for transforming 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 wireless transceiver are for:

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.

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.

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 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

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 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 channel estimate database at a receiver 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; and

a wireless transceiver cooperating with said controller 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

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 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 channel estimate database at a receiver device.