Trilinear Space-Time-Frequency Codes for broadband MIMO-OFDM systems

A new multi-antenna coding framework is proposed for space-time-frequency (STF) transmissions over broadband multiple input multiple output (MIMO) systems based on orthogonal frequency division multiplexing (OFDM). A tensor decomposition known as PARAFAC is used as the core of a multi- stream space-time-frequency coder that jointly multiplex and spreads several input streams over space (transmit antennas), time (symbol periods) and frequency (subcarriers). We coin the term trilinear STF codes since each input symbol is coded over a space-time-frequency grid by a triple product code: each trilinearly coded symbol is interpreted as an element of a third-order tensor, which can be decomposed using PAFAFAC analysis. Trilinear STF codes are designed for an arbitrary number of transmit and receive antennas. They afford a variable degree of multiplexing-spreading over each one of the three signal dimensions while providing full diversity gain for each multiplexed stream. At the receiver, a direct blind decoding based on a relatively simple linear processing is made possible thanks to the PARAFAC modeling of the received signal. Computer simulation results are provided for performance assessment of the proposed codes in a variety of configurations.