Transmit and Receive Beamforming for OFDMA/TDD System

It is well-known that mobile communication systems are usually limited in their performance and capacity by three major impairments, which are multi-path fading, delay spread and co-channel interference (CCI). OFDMA (OFDM-FDMA) system can cope with the multi-path fading and delay spread easily due to the beneficial properties of OFDM technology. Though OFDMA scheme avoids intra-cell interference using the orthogonality among subcarriers, the scheme contains difficulty of reducing co-channel interference. Therefore, in this paper, adaptive antenna techniques are deployed into OFDMA/TDD system to minimize the co-channel interference induced by adjacent cells and to enhance the uplink performance. For the improvement of downlink performance, we apply TxAA (Transmit Adaptive Array), a kind of transmit diversity technique, into OFDMA/TDD transmitter side. Simulation results show that the downlink and uplink performance under multi-path Rayleigh fading channel improved considerably compared with the case of single antenna system. Keyword : Transmit Beamforming, Receive Beamforming, OFDMA/TDD