An Equalization Technique based on QR Decomposition for DSTBC-OFDM Systems with Distributed Carrier Frequency Offsets

In the distributed space-time block coded (DSTBC) orthogonal frequency division multiplexing (OFDM) system (DSTBC-OFDM), there may exist distributed carrier frequency offsets (CFOs) by sharing the transmission antennas belonging to different nodes. In this paper, the signal model of the DSTBC-OFDM system with distributed CFOs is presented. Then we propose a new equalization technique via the modification of the QR decomposition (MQRD) in order to eliminate ICI and ISI which are caused by CFOs. The proposed MQRD scheme guarantees transmit diversity gain. Several kinds of equalization techniques are introduced and compared in terms of bit error rate (BER) performance and transmit diversity order. Simulation results show that the proposed method outperforms conventional equalization techniques and achieves equal transmit diversity order with perfectly synchronized DSTBC-OFDM system.