A high-performance MIMO-OFDM system with Walsh block coding

In this paper we present a multiple-input, multiple-output (MIMO)-orthogonal frequency division multiplexing (OFDM) system that uses orthogonal Walsh sequences for block coding. Two configurations, space-time block coding (STBC) and the Vertical Bell Laboratories Layered Space-Time (V-BLAST) architecture, are considered for the proposed system. A least-squares channel estimation with the fast Fourier transform method is utilized in the system to replicate real-life scenarios. The idea of employing block coding based on orthogonal Walsh sequences is inspired by the IS-95 standard and is attempted for the first time in MIMO-OFDM systems. A simulation study is carried out by considering different antenna configurations, code sizes, and channel delays. Computer simulations show that the proposed system achieves a significant performance improvement compared to MIMO-OFDM systems that do not use the proposed block coding scheme. It is also shown that the new system is superior to some previous systems in computational complexity.