Rate-diversity tradeoff of space-time codes with fixed alphabet and optimal constructions for PSK modulation

In this correspondence, we show that for any (Q×M) space-time code S having a fixed, finite signal constellation, there is a tradeoff between the transmission rate R and the transmit diversity gain ν achieved by the code. The tradeoff is characterized by R ≤ Q−ν +1, where Q is the number of transmit antennas. When either BPSK or QPSK is used as the signal constellation, a systematic construction is presented to achieve the maximum possible rate for every possible value of transmit diversity gain. Keywords— Space-time codes, rate-diversity tradeoff.