Link Adaptation and Channel Prediction in Wireless OFDM Systems


Antonio Forenza and Robert W. Heath Jr


to appear in Proc. of Midwest Symp. on Circ. and Sys., Tulsa, Oklahoma, Aug. 4-7, 2002.


Link adaptation algorithms enhance throughput in OFDM communication systems by adjusting various transmission parameters based on channel state information. In wireless OFDM systems, however, changes in the channel due to Doppler spread and limits on the reverse link bandwidth make it difficult to fully adapt to current channel conditions. Therefore in this paper we study link adaptation based on time-frequency blocks. We propose an algorithm that adapts the modulation scheme in a time-frequency block to maximize throughput while maintaining a target average block error rate. We describe a channel prediction algorithm and comment on the channel conditions where it improves performance. Simulations show that it is possible to optimize the size of the time-frequency block to maximize throughput given a fixed frequency of link adaptation control messages. 


OFDM, link adaptation, channel prediction, fading

This paper is available as a IEEE Xplore .