Channel diagonalization through orthogonal space-time coding

Space-time block codes from orthogonal designs were proposed in Tarokh et al. (1999) for communication over fading channels with multiple transmit and receive antennas. These codes require no knowledge of the channel at the transmitter, and linear processing at the receiver achieves maximum-likelihood decoding. This paper presents an alternative approach to code design, where the code criterion is such that the transmitter and receiver operations essentially "diagonalize" any arbitrary matrix channel. Such diagonalization greatly simplifies decoding. The transmitter is assumed to have no knowledge of the channel. The desired properties of such a code are derived. It is shown that with some additional constraints, the resulting class of codes is identical to the codes introduced in Tarokh et al. Hence, an alternative interpretation of space-time block codes from orthogonal designs is given. The alternative code construction criteria that are derived may facilitate the design of more general classes of codes.