The main goals in developing new wireless communication systems are increasing the transmission capacity and improving the spectrum efficiency. In this paper, spectrum efficiency and capacity improving techniques, captured under the name space division multiplexing (SDM), are proposed. SDM algorithms exploit the richly scattered (indoor) wireless channel by transmitting different signals simultaneously on different transmit antennas at the same frequency and using multiple receive antennas for decoding. Among these algorithms, maximum likelihood decoding (MLD) is shown to have the best SNR performance.