Title :
Decision-directed tracking for multi-user broadband mobile OFDM
Author :
Thomas, Timothy A. ; Vook, Frederick W.
Author_Institution :
Commun. Syst. Res. Lab., Motorola Inc., Schaumburg, IL, USA
Abstract :
This paper presents two new multi-user techniques that aid in the decision-directed tracking of a rapidly time-varying OFDM channel. The first is based on applying gradient optimization techniques to a least squares multi-user frequency-domain channel estimation problem. The second technique is based on a method for modeling a time-varying frequency response as a linear combination of a small number of time-invariant “Doppler channels.” This technique provides a formula for updating these Doppler channels, which greatly improves the performance of decision-directed tracking. These techniques are tested for different decision-directed methods in a simulated 6.0 MHz OFDM system with a 330 Hz maximum Doppler frequency and an 8.0 μsec maximum delay spread
Keywords :
Doppler effect; OFDM modulation; broadband networks; frequency response; frequency-domain analysis; gradient methods; land mobile radio; least squares approximations; multiuser channels; optimisation; parameter estimation; radio networks; radio tracking; time-varying channels; 330 Hz; 6.0 MHz; 8 mus; decision-directed tracking; frequency-domain channel estimation; gradient optimization techniques; least squares multi-user channel estimation; maximum Doppler frequency; maximum delay spread; multi-user broadband mobile OFDM; simulation; time-invariant Doppler channels; time-varying OFDM channel; time-varying frequency response modeling; Channel estimation; Delay; Frequency estimation; Frequency response; Laboratories; Least squares approximation; OFDM; Receiving antennas; System testing; Time varying systems;
Conference_Titel :
Wireless Communications and Networking Confernce, 2000. WCNC. 2000 IEEE
Conference_Location :
Chicago, IL
Print_ISBN :
0-7803-6596-8
DOI :
10.1109/WCNC.2000.903969
