Bandwidth Efficiency Improvement for Differential Alamouti Space-Time Block Codes Using M-QAM

Abstract

We propose a technique that enhances the bandwidth efficiency of the two transmit antenna differential space-time block code (DSTBC) by use of space-time block code (STBC) expansion and trellis coding. STBC expansion is realized by expanding the conventional Alamouti STBC using unitary matrix transformation. This is followed by trellis code-aided mapping of additional bits to space-time codes of the expanded set. Trellis code-aided mapping of additional bits enhances the bandwidth efficiency of the proposed DSTBC scheme. The proposed scheme sends more information bits in each transmitted space-time code than the conventional differential detection-aided DSTBC (CDD-DSTBC) scheme, and yet retains the same error performance. For each additional bit sent with the transmitted space-time codeword, the proposed scheme using 16QAM achieves a 12.5% increase in bandwidth efficiency, while the scheme using 64QAM realises an 8.3% increase. Simulation results demonstrate that the error performance of the proposed scheme tightly matches that of CDD-DSTBC with improvement in bandwidth efficiency. The bandwidth efficiency is enhanced at the expense of a moderate increase of the computational complexity at the receiver.

Channel capacity and bit error rate analysis in wireless communication system over Rayleigh fading channel

“…There are many techniques included in MRC schemes such as 'Selection Combining (SC)', 'Equal-Gain Combining (EGC)' and 'Switch-and-Stay Combining (SSC)' available for combining received signals via different wireless links or diversity links (Duman and Ghrayeb, 2008). The Alamouti scheme employs diversity at the transmitter whereas the MRC scheme uses diversity at the receiver.…”

“…The individual capacity is computed for each realisation since inputs are still independent Gaussian. Finally, overall capacity is computed by taking an average of all the values (Duman and Ghrayeb, 2008;Choudhury and Gibson, 2007;Chen, 2012).…”

“…Data rates or throughput of the MIMO-OFDM system can be increased by transmitting several signals in parallel using several antennas at the transmitter. This is known as spatial multiplexing since several parallel information streams are multiplexed in space rather than time or frequency (Duman and Ghrayeb, 2008;Cho et al, 2010). The diversity gain is necessary for adequate error performance and the spatial multiplexing provides high 'Spectral Efficiency (SE)' but limited diversity gain.…”

“…Also, there is a trade-off between SE and diversity gain. So it is necessary to choose the proper algorithm to avoid this trade-off to achieve better error performance with considerable diversity gain (Duman and Ghrayeb, 2008). The concatenation of MIMO system with OFDM scheme referred to as MIMO-OFDM system efficiently fights against scarcity of bandwidth, power constraint, and various channel impairments and improves the data rates, QoS and trustworthiness of information over the wireless communication system.…”

“…The simulation results show e BER values of  and MRCche with 1 2  antenna system. Dlodlo et al (2018) employed differential STBC with trellis coding over Rayleigh fading channel for BER analysis and found the BER value of 2 4.0 10   at the SNR of 10 dB. Lee (2018) employed the MRC scheme over imperfect CSI to examine the ergodic capacity and outage capacity in a MIMO system.…”