A comparison of inner coding options for adaptive MIMO OFDM systems

Some novel results concerning adaptive space-time-frequency coding schemes for MIMO OFDM systems are illustrated. In the proposed concatenated schemes, a conventional convolutional encoder is followed by a bit-wise interleaver and an inner orthogonal space-time encoder in order to exploit the space/frequency diversity provided by the frequency selective MIMO channel. Adaptivity can be implemented by adjusting the constellation size on a subcarrier by subcarrier basis by means of standard bit/energy-loading algorithms for SISO channels. An extension of the transmit selection diversity (TSD) technique for the two transmit/receive antenna scenario is also considered as an alternative to the inner ST code.