A novel view on modulus-preserving rate-one space-time block codes

In this paper, we first provide an alternative construction of full-diversity rate-one space-time block codes (STBCs) based on linear constellation precoding (LCP) and circular delay techniques. Through explicit unitary diagonal precoding on symbol blocks, and implicit FFT precoding via circularly shifted transmissions over multiple antennas, the proposed design preserves the modulus property of the information symbols. We then demonstrate that existing quasi-orthogonal STBCs can be constructed by embedding modulus-preserving LCP designs into orthogonal structures, and interestingly, they are also equivalent to the space-time-frequency (STF) block codes, which have been developed for multi-antenna OFDM systems, up to unitary transformations.