Apparatus And Method For Adaptive Wireless Channel Estimation

• US 20080159458A1
• Filed: 03/09/2007
• Published: 07/03/2008
• Est. Priority Date: 12/29/2006
• Status: Active Grant

• Current Assignee: Industrial Technology Research Institute
• Original Assignee: Industrial Technology Research Institute
• Inventors: Lu, Yi-Hung, Liu, Chia-Ling, Cheng, Yong-Hua
• Granted Patent: US 7,764,753 B2
• Time in Patent Office: Days
• US Class Current: 375/358
• CPC Class Codes: H04L 2025/03414 Multicarrier
• CPC Class Codes: H04L 25/0222 Estimation of channel variability, e.g. coherence bandwidth, coherence time, fading frequency
• CPC Class Codes: H04L 25/0232 by interpolation between sounding signals
• CPC Class Codes: H04L 25/025 using least-mean-square [LMS] method
• CPC Class Codes: H04L 25/03019 adaptive, i.e. capable of adjustment during data reception
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01

Abstract

Disclosed is an apparatus and method for adaptive wireless channel estimation. Once a packet is received, this invention analyzes channel interference index for a moving vehicle, and computes a first recursive parameter, a second recursive parameter and an interpolation number. Based on the first recursive parameter and the interpolation number, partial channel information is calculated for further channel estimation by using an interpolation. The parameter of an equalizer is also immediately updated. Cooperating with a decision feedback scheme and based on the second recursive parameter, channel tracking is performed. In order to achieve the adaptive channel estimation for wireless access on the time-variant vehicle environment, the parameter for the algorithm for performing the channel estimation is adjusted.

Claims

1. An apparatus for adaptive wireless channel estimation, applicable to a moving vehicle time-variant environment, said apparatus comprising:

an adaptive controller, for performing adaptive analysis when receiving a packet, and computing a first recursive parameter, a second recursive parameter, and an interpolation number;

a pilot-aided channel tracking module, for performing an interpolation to obtain update channel information based on said first recursive parameter and said interpolation number, and for adjusting an optimal channel information through said first recursive parameter; and

a decision feedback channel tracking unit, for performing decision feedback on a compensated information symbol, for performing channel tracking based on said second recursive parameter, for iteratively updating feedback information channel estimation information of previous time, and for providing said iteratively updated channel estimation information to a next information symbol.

2. The apparatus as claimed in claim 1, wherein said moving vehicle time-variant environment is a vehicle time-variant wireless access environment.

3. The apparatus as claimed in claim 1, wherein said apparatus is applicable to an orthogonal frequency division multiplexing (OFDM)-based system in a wireless access environment.

4. The apparatus as claimed in claim 1, wherein said adaptive controller performs adaptive analysis for one or more channel interference indexes.

5. The apparatus as claimed in claim 1, wherein said pilot-aided channel tracking module and said decision feedback channel tracking unit are connected to an equalizer.

6. The apparatus as claimed in claim 5, wherein said equalizer updates equalizer parameter based on said adjusted optimal channel information and said iteratively updated channel estimation.

7. The apparatus as claimed in claim 1, wherein said pilot-aided channel tracking module further comprises:

a pilot signal generator, for extracting at least a pilot signal from each information symbol;

a pilot-aided channel estimation unit, for performing multi-point channel estimation based on said at least a pilot signal;

a channel interpolation module, for performing said interpolation to obtain said updated channel information based on said interpolation number, said channel estimations of current information symbol from said channel estimation, and said channel information of previous time from said decision feedback channel tracking unit; and

a recursive computing unit, to adjust said optimal channel information based on said pilot-aided channel estimation information of two successive information symbols and said first recursive parameter.

8. A method for adaptive wireless channel estimation, applicable to a moving vehicle time-variant environment, said method comprising the steps of:

performing an adaptive analysis when receiving a packet, and computing a first recursive parameter, a second recursive parameter, and an interpolation number;

performing an interpolation to obtain update channel information based on said first recursive parameter and said interpolation number, and determining an optimal channel information through said first recursive parameter;

performing channel compensation on said information symbol;

performing decision feedback on a compensated information symbol, performing channel tracking based on said second recursive parameter, for iteratively updating feedback information channel estimation of previous time, and providing said iteratively updated channel estimation to a next information symbol; and

repeating the above steps until finishing all said information symbols in said packet.

9. The method as claimed in claim 8, wherein said interpolation is performed by using channel information and one or more pilot signals from long preamble of said packet.

10. The method as claimed in claim 8, wherein the step of said performing pilot-aided channel tracking on said information symbol further includes the step of:

performing an interpolation through a plurality of pilot-aided channel estimations and a plurality of feedback channel estimations at previous time, obtaining update channel information, and determining said optimal channel information through said first recursive parameter.

11. The method as claimed in claim 8, prior to said step of performing decision feedback to compensated information symbol, further including the step of:

providing said optimal channel information and said iteratively updated channel

estimation to an equalizer, updating parameter of said equalizer in real time, and said updated equalizer performing channel compensation to said information symbol.

12. The method as claimed in claim 8, wherein said first recursive parameter, said second recursive parameter, and said interpolation number are all adjustable.

13. The method as claimed in claim 8, wherein said adaptive analysis is performed on one or more channel interference indexes.

14. The method as claimed in claim 13, wherein said one ore more channel interference indexes are the speed and the environmental signal-to-noise ratio (SNR) of said moving vehicle.

15. The method as claimed in claim 8, wherein said method iteratively updates said channel estimation through a least mean square (LMS) algorithm, and said iterative update is performed on each said information symbol once.

16. The method as claimed in claim 8, wherein said optimal channel information is adjusted by using a least mean square algorithm.