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Large scale multiuser multi-input multi-output (MU-MIMO) system is an emerging wireless technology, which can impart huge spectral efficiency, enhanced link reliability, and serves several users simultaneously in the same frequency-time resource. Pilot contamination (PC) is the major bottleneck in achieving the optimum performance of a multi-cell large MU-MIMO system. We propose a new multi-cell block diagonalization-QR-minimum mean square error (M-BD-QR-MMSE) precoding scheme to diminish the effects of pilot contamination in a multi-cell MIMO system. The reduced effects of Pilot contamination result in the enhancement of spectral efficiency for the multi-cell MU-MIMO system. The design of the proposed scheme utilizes block diagonalization (BD) in combination with MMSE precoding that obtains large null space using QR decomposition operation to reduce intercell and intracell interference much efficiently than conventional precoding schemes. The gain in spectral efficiency with the proposed scheme is enhanced through non-universal pilot reuse in contrast to single-cell schemes. Furthermore, the downlink spectral efficiency expression has been derived for a large scale MIMO system, and the same is computed using Monte Carlo simulations to analyze the results. The numerical results depict that the proposed M-BD-QR-MMSE provides a significant improvement in the spectral efficiency in comparison with traditional singlecell MMSE (S-MMSE), regularized zero-forcing (R-ZF), ZF, Maximum ratio transmission (MRT) and multi-cellMMSE(M-MMSE) schemes. The proposed precoding design provides the spectral enhancements of 32.19 and 50.13 bit/s/Hz/cell in comparison to conventional multi-cellMMSEand single-cell MMSE precoding schemes respectively. [ABSTRACT FROM AUTHOR]

The fiber nonlinearities are one of the main performance limiting factors in any optical communication system. There are several parameters that effectively contribute in mitigation of these fiber nonlinearities such as fiber dispersion, effective area of fiber core, etc. Here, we have investigated the four wave mixing (FWM) nonlinear impairments in 16-channel WDM system. The FWM crosstalk becomes very critical to handle for long haul transmission systems at high power levels. Here, 16 channels WDM is being implemented and its performance is evaluated in terms of bit error rate (BER), Q factor, etc. for distance transmission upto 500 km. [ABSTRACT FROM AUTHOR]

Large Scale Multiuser multiple input multiple output (LS-MU-MIMO) communication system is considered as an encouraging solution to attain greater spectral efficiency for the next-generation wireless communication system. In this paper, we propose an improved design of a precoding algorithm for LS-MU-MIMO communication system. The proposed precoding algorithm is based on Block diagonalization (BD) precoding which is a combination of QR decomposition and Zero forcing channel inversion (ZF-CI) operation named as QR-ZF-BD precoding algorithm. To enhance the performance of LS-MU-MIMO system, the proposed precoding algorithm utilizes ZF method and QR decomposition operation instead of more complex Singular value decomposition (SVD) operation as compared to the conventional Block diagonalization (BD) precoding technique. The proposed precoding algorithm is designed in two stages. In the first stage, the proposed QR-ZF-BD precoding algorithm first utilizes QR decomposition to diminish multiuser interference (MUI), the second stage utilizes ZF based channel inversion (ZFCI) and QR decomposition operation again to further enhance the spectral efficiency of a single cell downlink LSMU- MIMO system. The enhanced spectral efficiencies of values 334 bit/s/Hz and 388 bit/s/Hz are obtained with our proposed precoding algorithm design when LS-MU-MIMO system having 100 and 200 base station antennas respectively. The numerical results indicate that the proposed QR-ZF-BD precoding algorithm achieves the best spectral efficiency as compared to current LTE-A standard and other recently used conventional linear precoding algorithms. [ABSTRACT FROM AUTHOR]

The last decade witnessed an escalating growth in wireless devices. Because of the development of smart devices like mobiles, tablets and other data-intensive applications, wireless data traffic grows exponentially. In the present scenario and in the future, the wireless and fixed devices require high data throughput to support data-intensive applications such as video streaming to play online games, movies and real-time videos. The requirement of wireless throughput and number of wireless devices will be growing more in the near future. Moreover, the power consumption at Base Stations (BSs) is a growing concern for wireless communication systems. So the future wireless communication system has to fulfill the requirements of high throughput, less power consumption and serving many users simultaneously. To overcome the problems of increased data rates and power consumption at BSs, Large-Scale Multiuser Multiple Input Multiple Output (LS-MU-MIMO) is one of the solutions. LS-MIMO is new technology and has attracted considerable research attention recently. The paper provides information about theoretic concepts of MIMO starting from Single User MIMO (SUMIMO) to LS-MU-MIMO. It also discusses the benefits, survey of precoding and detection techniques and research issues and analyzes the LS-MU-MIMO system in terms of spectrum and power efficiencies by varying antennas at BS. [ABSTRACT FROM AUTHOR]