Increasing spectral efficiency by data multiplexing using antenna arrays

A novel data multiplexing scheme is presented. This technique uses an antenna array with K transmit antennas. In. total K information bits are multiplexed in an orthogonal fashion. The special property of the multiplexing technique is that, for each symbol duration, only one out of K antennas is transmitting using BPSK modulation. Furthermore, the symbol duration is equivalent to the bit-duration due to the parallelism introduced by the K antennas. The receiver is able to detect the transmitting antenna and by using this information the demultiplexing is carried out. It is demonstrated that the proposed method achieves about the same spectral efficiency as 8PSK, but with a relaxed bit-energy-to-noise ratio of about 2.5 dB. Furthermore, the linear channel capacity gain (error-free transmitted bits) over the single antenna BPSK transmission scheme is found to be in the range of 2.5-3.