Performance Comparison of Multi-Layer STBC OFDM and V-BLAST OFDM

We propose a multi-layer space-time block coded orthogonal frequency division multiplexing (multi-layer STBC OFDM) scheme. It combines the spatial diversity and spatial multiplexing in order to exploit the potentials of both techniques. The transmit antennas are divided into different layers and each layer is composed of a small number of antennas. These antennas transmit OFDM signals in order to deal with frequency- selective fading channels. In each layer, Alamouti´s space-time codes are applied at individual subcarriers to provide spatial diversity gain. Exhaustive simulations are conducted to compare the proposed scheme with the full-multiplexing V-BLAST OFDM under the same spectral efficiency condition. We find each scheme has its own prevailing area. When the receive diversity order is limited, the proposed Multi-Layer STBC OFDM has better performance since it embeds transmit diversity; as the receive diversity order increases, the performance gap between the two schemes shrinks and finally V-BLAST OFDM prevails in performance. Therefore, the proper choice depends on the system configuration, i.e., the numbers of transmit and receive antennas.