Coherent Detection of Non-Orthogonal Spectrally Efficient Multicarrier Signals Using a Decision Feedback Algorithm

Introduction. Spectrally efficient frequency division multiplexing (SEFDM) is a promising technology for improving spectral efficiency. Since SEFDM signals transmitted on subcarriers are not orthogonal, interchannel interference occurs due to the mutual influence of signals transmitted on adjacent subcarriers. Algorithms for receiving SEFDM signals can be distinguished into element-by-element coherent detection and maximum-likelihood sequence estimation (MLSE). The former method, although being simpler, is characterized by a low bit error rate performance. The latter method, although providing for a higher energy efficiency, is more complicated and does not allow high absolute message rates.Aim. To consider a trade-off solution to the problem of coherent detection of SEFDM signals under the condition of significant interchannel interference, namely, the use of an iterative algorithm of element-by-element processing with decision feedback at each subcarrier frequency.Materials and methods. Analytical expressions for the operation of a demodulator solver were derived. A simulation model for transmission of SEFDM signals was built in the MatLab environment, including element-by-element detection with decision feedback.Results. The simulation results confirmed the efficiency of the proposed algorithm. For error probabilities p =102…103, the energy gains reach values from 0.2 to 7.5 dB for different values of the non-orthogonal subcarrier spacing. At the same time, the efficiency of the detection algorithm with decision feedback turns out to be significantly lower than that when using the detection algorithm MLSE.Conclusion. The proposed detection algorithm can be used in future generations of mobile communications, which require high transmission rates. By reducing the computational complexity of the algorithm, it is possible to provide for a lower power consumption of mobile devices.

Performance Analysis of Spectrally Efficient Adaptive Spatial Modulation in MIMO System by using QAM

In this article, we proposed a multiple input multiple outputs (MIMO) technique such as spectrally efficient adaptive quadrature spatial modulation (SEAQSM) which is based on space modulation techniques (SMTs). SMTs are logarithmically proportional to transmitting antenna & this technique fulfills the requirement of high data rate in the MIMO system. The Spatial position of the transmitting antenna improves the performance of the MIMO system. In space modulation technique spectral efficiency is logarithmically proportional to transmit antenna, if we increase the antenna at the transmitter end then the bandwidth efficiency significantly improved. We have to improve the performance MIMO system, minimize the latency and low power consumption. The proposed technique performance is explored over Rayleigh fading channel for a particular MIMO. These techniques underestimate the transmit antennas with less RF chain. In this paper, we analyzed the performance of our proposed scheme with conventional SM and QSM by using MONTE CARLO Simulation in term of BER with distinct order of QAM symbol. SE acquired for varying SNR at a BER of 10−3are obtained for uncorrelated Rayleigh channel. Keywords: Spatial Modulation(SM), MIMO, Spectral efficiency, Energy efficiency, Quadrature Spatial Modulation (QAM), Maximum Likelihood (ML) detector.