Improved Spatial Modulation for High Spectral Efficiency

Spatial Modulation (SM) is a technique that can enhance the capacity of MIMO schemes by exploiting the index of transmit antenna to convey information bits. In this paper, we describe this technique, and present a new MIMO transmission scheme that combines SM and spatial multiplexing. In the basic form of SM, only one out of MT available antennas is selected for transmission in any given symbol interval. We propose to use more than one antenna to transmit several symbols simultaneously. This would increase the spectral efficiency. At the receiver, an optimal detector is employed to jointly estimate the transmitted symbols as well as the index of the active transmit antennas. In this paper we evaluate the performance of this scheme in an uncorrelated Rayleigh fading channel. The simulations results show that the proposed scheme outperforms the optimal SM and V-BLAST (Vertical Bell Laboratories Layered space-time at high signal-to-noise ratio (SNR). For example, if we seek a spectral efficiency of 8 bits/s/Hz at bit error rate (BER) of 10^-5, the proposed scheme provides 5dB and 7dB improvements over SM and V-BLAST, respectively.Comment: 7 pages, 4 figures, 1 table, International Journal of Distributed and Parallel Systems (IJDPS) Vol.3, No.2, March 201

MIMO signal processing in offset-QAM based filter bank multicarrier systems

Next-generation communication systems have to comply with very strict requirements for increased flexibility in heterogeneous environments, high spectral efficiency, and agility of carrier aggregation. This fact motivates research in advanced multicarrier modulation (MCM) schemes, such as filter bank-based multicarrier (FBMC) modulation. This paper focuses on the offset quadrature amplitude modulation (OQAM)-based FBMC variant, known as FBMC/OQAM, which presents outstanding spectral efficiency and confinement in a number of channels and applications. Its special nature, however, generates a number of new signal processing challenges that are not present in other MCM schemes, notably, in orthogonal-frequency-division multiplexing (OFDM). In multiple-input multiple-output (MIMO) architectures, which are expected to play a primary role in future communication systems, these challenges are intensified, creating new interesting research problems and calling for new ideas and methods that are adapted to the particularities of the MIMO-FBMC/OQAM system. The goal of this paper is to focus on these signal processing problems and provide a concise yet comprehensive overview of the recent advances in this area. Open problems and associated directions for future research are also discussed.Peer ReviewedPostprint (author's final draft