Space-time coded modulation for high data rate wireless communications

This paper presents the theory and practice of a new advanced modem technology suitable for high data rate wireless communications and presents its performance over a frequency-flat Rayleigh fading channel. The new technology is based on space-time coded modulation (STCM) with multiple transmit and/or multiple receive antennas and orthogonal pilot sequence insertion (O-PSI). In this approach data is encoded by a space-time channel encoder and the output of the encoder is split into N streams to be simultaneously transmitted using N transmit antennas. The transmitter inserts periodic orthogonal pilot sequences in each of the simultaneously transmitted bursts. The receiver uses those pilot sequences to estimate the fading channel. When combined with an appropriately designed interpolation filter, accurate channel state information (CSI) can be estimated for the decoding process. Simulation results of the proposed modem as applied to the IS-136 cellular standard are presented. We present the frame error rate (FER) performance as a function of the signal to noise ratio (SNR) and Doppler spread in the presence of timing and frequency offset errors. Simulation results show that, for example, for 10% FER, data rates up to 54 kbps per a 30 kHz channel can be supported at a SNR of 11.7 dB and a Doppler spread of 180 Hz using a 32-state 8-PSK space-time code with 2 transmit and 2 receive antennas. Simulation results for other cases are also provided.