Improving the Performance of Post-FFT Array Processing in OFDM Systems with Short Training Sequences

Three techniques were simultaneously applied to reduce the size of the training sequence of the antenna elements to improve the performance of post-FFT OFDM adaptive antenna arrays used for interference cancellation. These techniques are subcarrier training concatenation; frame training concatenation; and weight averaging. Using these simple and easily applicable techniques, the size of the training sequence can be reduced to only one symbol for a four-element antenna array. In addition, better performance is achieved with the same length of training sequence for training lengths less than four symbols. Further, this method has low cost and low complexity and is easily compatible with any weighting algorithm. As an example of an OFDM based WLAN link, a Matlab Simulink model of 802.11a is considered. To include the effect of the antennas in more detail, a vector channel model is utilized