Turbo channel estimation for OFDM systems
View Patent ↗A system and method for estimating a channel in a wireless receiver is disclosed. The method preferably applies to a communication system using the OFDM standard. The method comprises receiving a block of “n” transmitted symbols, the symbols including pilot symbols and “d” data symbols, estimating a channel using the pilot symbols to create a channel estimate, choosing a group of “m” strongest symbols from the “d” received symbols, compensating the “m” strongest symbols using the channel estimate to create a group of “m” compensated symbols, re-estimating the channel using the group of “m” compensated symbols and pilot symbols; and either (1) repeating the steps of choosing a group of “m” strongest symbols, compensating the group of “m” strongest symbols and re-estimating the channel, or (2) using a latest channel estimate to compensate all symbols within the block. The system comprises a wireless receiver having an estimator programmed, for example, using DSP or ASIC and imbedded into the wireless system design software for accomplishing the steps set forth according to the method.
1. A transceiver configured to estimate a channel in a communication system, the transceiver comprising:
a receiver portion for receiving a block of “n” transmitted symbols, the symbols including “p” pilot symbols and “d” data symbols, where “p” is an integer having a value greater than or equal to 1, “d” is an integer having a value greater than or equal to 2 and “n” is an integer having a value greater than or equal to 3;
an estimator for estimating a channel using the pilot symbols;
a processor for choosing a group of “m” strongest symbols from the “d” received data symbols, where “m” is an integer having a value less than or equal to d, and for compensating the group “m” strongest symbols using the channel estimate to create a group of “m” compensated symbols; and
wherein the estimator re-estimates the channel using the group of “m” compensated symbols and pilot symbols, and either:
the processor repeats choosing the group of “m” strongest symbols,
compensates the group of “m” strongest symbols to re-estimate the channel; or
the processor uses a latest channel estimate to compensate all symbols within the block.
2. The transceiver of claim 1 , wherein the communication system is an OFDM communication system.
3. The transceiver of claim 1 , wherein the “m” is less than “d.”
4. The transceiver of claim 1 , wherein “m” equals “d.”
5. The transceiver of claim 1 , wherein the communication system is associated with a multi-antenna receiver.
6. A transceiver for estimating a channel in a communication system, the transceiver comprising:
a receiver portion for receiving a block of “n” transmitted symbols, the symbols including “p” pilot symbols and “d” data symbols, where “p” is an integer having a value greater than or equal to 1, “d” is an integer having a value greater than or equal to 2 and “n” is an integer having a value greater than or equal to 3;
an estimator for estimating a channel using the pilot symbols to create a channel estimate;
a processor for choosing a group of “m” strongest symbols from the “d” received data symbols, where “m” is an integer having a value less than or equal to “d”;
a compensator for compensating the group of “m” strongest symbols using the channel estimate to create a group of “m” compensated symbols; and
wherein the estimator re-estimates the channel using the group of “m” compensated symbols and pilot symbols, and the transceiver either;
chooses a group of “x” strongest symbols, compensates the group of “x” strongest symbols and re-estimates the channel, where “x” is an integer having a value less than or equal to “m”; or
uses a latest channel estimate to compensate all symbols within the block.
7. The transceiver of claim 6 , wherein “m” is less than “d.”
8. The transceiver of claim 7 , wherein “x” is less than “m.”
9. The transceiver of claim 6 wherein “x” is less than “m.”
10. The transceiver of claim 6 wherein “d” equals “m” and “m” equals “x.”
11. The transceiver of claim 6 , wherein the communication system is associated with an OFDM protocol.
12. The transceiver of claim 6 wherein the communication system is associated with a multiple antenna receiver.
13. An apparatus for estimating a channel in a wireless receiver, the apparatus comprising:
means for receiving a block of “n” transmitted symbols, the block including “p” pilot symbols and “d” data symbols, where “p” is an integer having a value greater than or equal to 1, “d” is an integer having a value greater than or equal to 2 and “n” is an integer having a value greater than or equal to 3;
means for estimating a wireless channel using the pilot symbols to create a channel estimate;
means for choosing a group of “m” strongest data symbols from the “d” received data symbols, where “m” is an integer having a value less than or equal to “d”;
means for compensating the group of “m” strongest symbols using the channel estimate to create a group of “m” compensated symbols; and
means for re-estimating the wireless channel using the group of “m” compensated symbols and pilot symbols, and either:
repeating the steps of choosing the group of “x” strongest symbols, where “x” is an integer having a value less than or equal to “m”,
compensating the group of “x” strongest symbols and re-estimating the channel at least once; or
using a latest channel estimate to compensate all data symbols within the block.
14. The apparatus of claim 13 , wherein “m” equals “x.”
15. The apparatus of claim 13 , wherein “x” is less than “m.”
16. The apparatus of claim 13 , wherein “m” equals “d.”
17. The apparatus of claim 13 , wherein if the steps of choosing a group of “x” strongest symbols, compensating the group of “x” strongest symbols and re-estimating the channel at least once are repeated, the steps are repeated a plurality of times.
18. A method of estimating a channel in a communication system, the method comprising:
receiving a block of symbols comprising a plurality of data symbols;
estimating a channel using at least one of the symbols;
comparing the signal strengths of the plurality of data symbols;
choosing a group of data symbols from the received data symbols comprising the strongest symbols;
compensating the chosen group of data symbols using the channel estimate; and
re-estimating the channel using the group of compensated symbols and the at least one of the symbols.
19. The method of claim 18 , further comprising either:
repeating the steps of choosing a group of symbols, compensating the chosen group of data symbols and re-estimating the channel, or
using a latest channel estimate to compensate all symbols within the block.
20. The method of claim 18 , wherein the at least one of the symbols of the block of symbols is a pilot symbol.
21. The method of claim 18 wherein
comparing the signal strengths of a plurality of data symbols comprises one of maximum signal strength, average signal strength and using a strength of a first signal received.
22. The method of claim 18 wherein
the number of symbols in the group of received data symbols comprising the strongest symbols is less than the number of data symbols received in the block of symbols comprising data symbols.
23. The method of claim 18 wherein compensating data symbols comprises one of using diversity combining and beam forming.
24. A system of estimating a channel in a communication system, the system comprising:
a receiver for receiving a block of symbols;
an estimator for estimating a channel using at least one of the symbols;
a processing element for:
choosing a group of symbols from the received symbols, wherein the group of symbols chosen is chosen based on signal strength; and
compensating the group of symbols using the channel estimate; and
wherein the estimator re-estimates the channel using the group of compensated symbols and the at least one of the symbols.
25. The system of claim 24 , wherein the signal strength of the symbols chosen in the group is associated with predetermined criteria.
26. A processing unit for performing channel estimation associated with a wireless communication system, the wireless communication system receiving a block of symbols including pilot symbols and “d” data symbols, where “d” is an integer having a value greater than or equal to 1, the processing unit comprising:
a symbol selector element;
an initial channel estimator element;
a symbol compensator element; and
a channel estimator element, wherein the initial channel estimator element produces an initial channel estimate using the pilot symbols and the symbol selector element chooses a group of “m” strongest data symbols, where “m” is an integer having a value less than or equal to “d” and wherein the “m” strongest data symbols are compensated using the initial channel estimate and the channel estimator element re-estimates the channel using the compensated symbols and the pilot symbols.