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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]

Orthogonal Frequency Division Multiplexing (OFDM) has emerged as the most reliable key technique in broadband wireless communication. As the technology is growing, the client demands are increasing, and there has been a growing demand for an advanced broadband wireless access system catering to a large variety of applications. The main objective of this paper is to present a survey of various OFDM-related modulation and access schemes enforced till date, and discuss the foremost challenges and open analysis problems with OFDM. [ABSTRACT FROM AUTHOR]

As the demand for high data rates continues to grow, advanced modulation formats must be adapted to support high data rates in optical communication system. Optical-Orthogonal Frequency Division Multiplexing (OFDM) is a promising technology providing support to high data rates and high tolerance to channel dispersion with high spectral efficiency. Further, advanced modulation techniques such as Quadrature Phase Shift Keying (QPSK) and 16-QAM have a greater effect on the performance of optical-OFDM system. QPSK modulation technique can be used to achieve high spectral efficiency, limited only by the noise level of the communication channel. M-Quadrature Amplitude Modulation (QAM) modulation techniques have high spectral efficiency in each subcarrier of the OFDM signal and this high spectral efficiency helps to support high data rate with the same low bandwidth optical components used at lower data rates. This paper presents an optical-OFDM system model for both QPSK and 16-QAM modulation techniques. The various performance parameters such as BER, Q factor, eye opening and jitter of optical-OFDM system are also analyzed for both modulation techniques. The effect of increase in modulation order M of M-QAM is also analyzed on the system data rate, while keeping the same data bandwidth. [ABSTRACT FROM AUTHOR]

Of late, there has been an exponential increase in demand on the wireless system for providing high speed data services. In the current scenario where spectrum is limited, the demand for high speed data degrades the quality of service. Therefore, Orthogonal Frequency Division Multiplexing (OFDM) system was proposed in the literature to overcome the problem of limited spectrum. Also, coupling OFDM system with MIMO (Multiple I/P and Multiple O/P) can further improve the performance of next-generation 4G wireless system. A number of antennas are used at transmitter as well as at receiver side in MIMO system which exploits spatial diversity. Therefore, MIMO-OFDM has been adopted as one of the most important techniques for 4G mobile wireless systems. However, there are certain design issues/challenges like antenna selection, synchronization, channel estimation and Peak to Average Power Ratio (PAPR), etc. which require due consideration. This paper provides a detailed overview of the history, evolution of OFDM and its related hybrid technique proposed in the literature till date. However, the main emphasis in this paper is on MIMO-OFDM. The design issues/challenges in the implementation of MIMO-OFDM system have been covered in great detail. Further, the simulation of MIMO-OFDM system has been carried out to evaluate certain performance parameters like PAPR, BER and channel capacity. [ABSTRACT FROM AUTHOR]

Multicarrier Code Division Multiple Access (CDMA) is one of the most promising candidates for radio access in next generation wireless systems. It is a combination of multicarrier modulation [Orthogonal Frequency-Division Multiplexing (OFDM)] and CDMA, which is very effective in combating severe multipath interference, and provides multiple access simultaneously. The objective of this paper is to highlight the challenges posed by the broadband services and the effectiveness of multicarrier CDMA in future generation mobile communication. It presents a comparative analysis of various types of multicarrier CDMA systems. Further, this paper examines the primary issues and problems in detail, providing various solutions to these problems. [ABSTRACT FROM AUTHOR]