Performance of different interpolation strategies for an OFDM/MMSE smart antenna system in an indoor WLAN

This paper assesses the performance of different interpolation strategies for an OFDM/MMSE smart antenna serving multiple users through space division multiple access (SDMA) in a wireless LAN following the IEEE 802.11a/e or HIPERLAN/2 standards. The frequency dependence of the channel transfer matrix and the weights is studied in indoor environments of different dimensions and for different coherence bandwidths using a ray-tracing tool. Interpolation is proposed to reduce the complexity of calculating the smart antenna weights at every OFDM subcarrier. The performance of different interpolation strategies is investigated in terms of complexity and signal to interference plus noise ratio (SINR) degradation relative to the case where the weights are calculated at every subcarrier. Simulation results agree with the expected behaviour showing that FFT based interpolation generally outperforms linear interpolation when the span between calculated subcarriers is less than 16. Channel transfer matrix based interpolation outperforms weight matrix based interpolation at the cost of increased complexity.