Orthogonal full diversity space-time block coding based on transmit channel state information for 4 Tx antennas

In this paper we consider the design of space-time block codes to benefit from multiple antennas at the emitter and possibly at the receiver. Theory of orthogonal designs has shown that such codes can not simultaneously be orthogonal, of rate 1, with full diversity order, for more than 2 transmit antennas. We propose in this paper to exploit channel state information available at the emitter to overcome this limitation and we describe a new rate 1 coding scheme with full diversity for 3 or 4 transmit antennas. This scheme is an orthogonal one thanks to transmit weights, which allow to use a simple linear receiver having optimal performance. The performance of the code is assessed by simulations in the 5 GHz OFDM-based WLAN environment (HIPERLAN/2). The practical interest of such approach is finally discussed