A Robust MAI Constrained Adaptive Algorithm for Decision Feedback Equalizer for MIMO Communication Systems

Abstract

Abstract-Decision feedback equalizer uses prior sensor's decisions to mitigate damaging effects of intersymbol interference on the received symbols. Due to its inherent non linear nature, decision feedback equalizer outperforms the linear equalizer in case where the intersymbol interference is sever in a communication system. Equalization of multiple input multiple output fast fading channels is a daunting job as these equalizers should not only mitigate the intersymbol interference but also interstream interference. Various equalization methods have been suggested in the adaptive filtering literature for multiple input multiple output systems. In our paper, we have developed a novel algorithm for multiple input multiple output communication systems centered around constrained optimization technique. It is attained by reducing the mean squared error criteria with respect to known variance statistics of multiple access interference and white Gaussian noise. Novelty of our paper is that such a constrained method has not been used for scheme of multiple input multiple output decision feedback equalizer resulting in a constrained algorithm. Performance of the proposed algorithm is compared to the least mean squared as well as normalized least mean squared algorithms. Simulation results demonstrate that proposed algorithm outclasses competing multiple input multiple output decision feedback equalizer algorithms.Index Terms-Decision feedback equalizer, inter symbol interference, multiple access interference, Rayleigh fading, AWGN, adaptive algorithm I. INTRODUCTIONMultiple input multiple output (MIMO) is a diversifying technique for mobile communication systems which uses multiple antennas at the transmitting side and receiving side for an efficient channel gain capacity. Antennas installed at both side of a communication system are utilized in such a way as to reduce the errors and boost data speed resulting in an effective communication for the users. Due to its inherent performance drawbacks, single input, single output (SISO) technology, has given way to the MIMO technology. In SISO, an antenna is utilized at transmitter as well as at receiver that results in multi path phenomina. When electromagnetic field (EM) waves are blocked by barricades, mountains, tall buildings, poles etc, these waves are dispersed, and as such use numerous ways to reach the desired destination. The late arrival of disseminated waveforms (signals) results in problems such as fading, cut outs, or sporadic reception. Another drawback of SISO is observed in mobile Internet, in which it has not only reduced the data rate as but also enhanced error propagation. Utilization of MIMO technology where multiple antennas are used at both end of the channel has mitigated the multipath wave propagation problem.Equalization of MIMO fast fading channels is a daunting task as these equalizers should not only mitigate the intersymbol interference (ISI) but also interstream interference (ISI) and this led to the introduction of decesion feedback equlaizati...