Iterative Multiuser Minimum Symbol Error Rate Beamforming Aided QAM Receiver

A novel iterative soft interference cancellation (SIC) aided beamforming receiver is developed for high-throughput quadrature amplitude modulation systems. The proposed SIC based minimum symbol error rate (MSER) multiuser detection scheme guarantees the direct and explicit minimization of the symbol error rate at the output of the detector. Adopting the extrinsic information transfer (EXIT) chart technique, we compare the EXIT characteristics of an iterative MSER multiuser detector (MUD) with those of the conventional minimum mean-squared error (MMSE) detector. As expected, the proposed SIC-MSER MUD outperforms the SIC-MMSE MUD. Index Terms—Beamforming, iterative multiuser detection, minimum symbol error rate, quadrature amplitude modulation

Performance Analysis of Linear and Non-Linear Equalizer in Rician Channel

AbstractIn this paper, equalization algorithms applying soft–decision feedback, designed for quaternary phase–shift keying (QPSK) and 8PSK (phase–shift keying) transmission are introduced. The method employed is a minimum mean– squared error (MMSE) in which each iteration is done in order to refine the data estimates. The rule for generating soft decisions is adapted continuously to the current state of the algorithm. We show that standard Decision Feedback Equalization (DFE-Non linear Equaliser) methods are clearly outperformed the minimum mean–squared error (MMSE linear Equaliser). We use the MATLAB to show that the MMSE-DFE provide better performance with the increasing value of SNR in scattering environment

Efficient joint maximum-likelihood channel estimation and signal detection

In wireless communication systems, channel state information is often assumed to be available at the receiver. Traditionally, a training sequence is used to obtain the estimate of the channel. Alternatively, the channel can be identified using known properties of the transmitted signal. However, the computational effort required to find the joint ML solution to the symbol detection and channel estimation problem increases exponentially with the dimension of the problem. To significantly reduce this computational effort, we formulate the joint ML estimation and detection as an integer least-squares problem, and show that for a wide range of signal-to-noise ratios (SNR) and problem dimensions it can be solved via sphere decoding with expected complexity comparable to the complexity of heuristic techniques

Iterative decoding for MIMO channels via modified sphere decoding

In recent years, soft iterative decoding techniques have been shown to greatly improve the bit error rate performance of various communication systems. For multiantenna systems employing space-time codes, however, it is not clear what is the best way to obtain the soft information required of the iterative scheme with low complexity. In this paper, we propose a modification of the Fincke-Pohst (sphere decoding) algorithm to estimate the maximum a posteriori probability of the received symbol sequence. The new algorithm solves a nonlinear integer least squares problem and, over a wide range of rates and signal-to-noise ratios, has polynomial-time complexity. Performance of the algorithm, combined with convolutional, turbo, and low-density parity check codes, is demonstrated on several multiantenna channels. The results for systems that employ space-time modulation schemes seem to indicate that the best performing schemes are those that support the highest mutual information between the transmitted and received signals, rather than the best diversity gain

Effect of Channel Equalization Schemes in Performance Evaluation of a Secured Convolutional Encoded DWT Based MIMO MC-CDMA System

In this research work, performance of different channel equalization techniques and various M-ary modulation schemes (MPSK, MQAM and DPSK) for DWT based MIMO Multi-Carrier Code Division Multiple Access (MC-CDMA) wireless communication system has been analyzed through simulation. We propose this system using convolutional coding scheme over AWGN and Rayleigh fading channel with implementation of Walsh Hadamard code as orthogonal spreading code. In this paper, we derive a generalized analytical framework to evaluate the Bit Error rate (BER) with respect to Signal-to Noise Ratio (SNR) and also use Electronic Codebook (ECB) mode as cryptographic algorithm to encrypt the actual data for security issues