Abstract
This letter proposes a novel improved differential space-time block code (DSTBC) scheme. By introducing a specific redundancy mechanism, the proposed DSTBC encoder behaves as a second-order discrete Markov process that we model by a multilevel trellis diagram. At the receiver side, the well-known Viterbi algorithm is applied without channel state information (CSI). The new scheme completely compensates for the 3-dB penalty, over wide SNR range, noticed in conventional DSTBC scheme and shows a closer performance to coherent STBC.