Anil Kumar Tipparti

Multiuser detection using comprehensive learning PSO over GK fading channels in impulsive noise

The direct sequence-code division multiple accesses (DS-CDMA) signals are transmitted over multipath channels that introduce fading and shadowing. Combined effect of multipath fading and shadowing along with multiple access interference (MAI) and inter-symbol interference (ISI) worsens the system performance. Further, experimental results have confirmed the presence of impulsive noise in wireless mobile communication channels. Hence, this paper presents a comprehensive learning particle swarm optimization (CLPSO) based multiuser detection technique for DS-CDMA systems over generalized-K (GK) fading channels in presence of impulsive noise. Maximal ratio combining (MRC) receive diversity is also incorporated to mitigate the effects of fading and shadowing. Performance of proposed M-decorrelator is studied by evaluating average error rate. Simulation results show that the proposed M-decorrelator performs better in the presence of fading, shadowing and heavy-tailed impulsive noise when compared to least squares, Huber and Hampel M-estimator based detectors.

Blind Multiuser Detection in Nakagami-m Fading Channels with Impulsive Noise

Experimental results have confirmed the presence of impulsive (heavy-tailed) noise in different wireless communication channels. In direct sequence-code division multiple accesses (DS-CDMA) systems, the signals are transmitted over multipath channels that introduce fading. Multipath fading along with multiple access interference (MAI) and inter-symbol interference (ISI) in impulsive noise environment degrades the system performance. This paper presents a technique for blind multiuser detection in DS-CDMA communication systems over Nakagami-m fading channels with impulsive non- Gaussian noise. Expression for average probability of error of an M-decorrelator is derived for the demodulation of BPSK signals over single-path Nakagami-m fading channel. A new M -- estimator is proposed for robustifying the detector and its performance is studied and analyzed by evaluating probability of error with the derived expression. Simulation results indicate that the proposed blind multiuser detector performs better in highly impulsive noise environment.

Robust blind multiuser detection in DS-CDMA systems over Nakagami-m fading channels with impulsive noise including MRC receive diversity

This paper presents robust blind multiuser detection in direct sequence-code division multiple access systems (DS-CDMA) over Nakagami-m fading channels with impulsive noise including maximal-ratio combining diversity. An M-estimator based structure for non-coherent demodulation of differentially phase shift keyed (DPSK) signals transmitted over a synchronous CDMA flat-fading Nakagami channels with impulsive noise is studied and analyzed. A new M-estimator is proposed for robustifying the detector and an approximate expression for average probability of error of non-coherent DPSK signals is derived using an approximation to generalized Marcum-Q function over single-path Nakagami-m fading channels. Simulation results are presented to evaluate the performance of the proposed robust blind multiuser detector in comparison with the linear decorrelating detector, Huber and Hampel estimator based detectors.

Multiuser detection over generalized-K fading channels using two-stage initialized teaching learning based optimization

A multiuser detection (MUD) technique for direct sequence-code division multiple access (DS-CDMA) systems over generalized-K (GK) fading channels using teaching learning based optimization algorithm (TLBO) with two-stage initialization (TSI) is proposed. In DS-CDMA systems, MUD techniques are applied to combat multiple access interference (MAI) and ambient noise. Empirical results proved that the ambient noise is non-Gaussian and impulse in nature which degrades the performance of the system substantially. The DS-CDMA signals are transmitted over channels that introduce impulsive noise, shadowing and fading. In this paper, we develop least-squares (LS), Huber and Hampel M-estimation based MUD technique for joint detection of DS-CDMA signals in the presence of MAI, impulsive noise, modeled by Laplace distribution, and channel fading, modeled by GK distribution. The TLBO with TSI (TLBO-TSI) algorithm is used to minimize a penalty function that is a less rapidly increasing function of residuals. Average bit error rate (BER) is computed to assess the performance of the TLBO-TSI based detector. Obtained results demonstrate that the proposed robust technique offer significant performance gains with increase in signal-to-noise ratio (SNR) and diversity order in the presence of heavy-tailed impulsive noise.

Robust Multiuser Detection in Asynchronous DS-CDMA Systems over Nakagami-m Fading Channels

This paper presents a new M-estimator based robust multi-user detection technique in asynchronous direct sequence-code division multiple access systems over Nakagami-m fading channels with impulsive noise. A new M-estimator, which performs well in the heavy-tailed impulsive noise, is proposed and analyzed for robustifying the detector. Average probability of error is derived and the performance of the new M-estimator based multi-user detector is evaluated in comparison with the linear decor relating detector, Huber and Hampel estimator based detectors. Simulation results show that the proposed M-estimator based detector performs well with little attendant increase in computational-complexity. The proposed robust multi-user detection technique is also extended to blind version of asynchronous CDMA channels.

Outage performance analysis of basic receive diversity combining schemes in Nakagami-0.5 fading channel

This paper presents a study on the outage performance analysis of basic receive diversity combining schemes in terms of outage probability and average outage duration over Nakagami-0.5 fading channels. Recent attention has been given to Nakagami-0.5 fading channel as a special case of Nakakgami-m fading channel with m = 0.5 and as a worst-case (severe) fading scenario. Closed-form expressions for outage probability and average outage duration are derived for selection combining (SC), equal gain combining (EGC) and maximal-ratio combining (MRC) diversity schemes. The expressions derived are numerically evaluated to study the effect of diversity order and multipath intensity profile (MIP) on the system performance.

Improved performance of low complexity K-best sphere decoder algorithm

To achieve high data rates, reliable data rate transmission and near capacity performance for future wireless communication systems iterative processing has been widely considered. However, such an efficient receiver design has been made significant challenge. In this paper, multiple-input multiple output (MIMO) detection with channel decoding techniques has been investigated for achieve reliable data transmission, the performance and computation complexity of the receiver for MIMO system has been considered. First we studied and review the most MIMO detection algorithms based on the sphere decoding (SD), K-best decoding and interference cancellation. In consequence a low complexity K-best (LC-K-Best) based sphere decoder is proposed in order to substantially reduce the computation complexity without significant performance degradation.

Jaya optimization algorithm based multiuser detector over Generalized-K fading channels

Jaya optimization algorithm (JOA) based multiuser detector over generalized-K (GK) fading channels, in the presence of impulsive noise, is presented in this paper to eliminate multiple access interference (MAI) problem. The JOA is used to implement the M-decorrelator with least squares (LS), Huber (HU), Hampel (HA) and modified Hampel (MH) estimators by minimizing the corresponding penalty functions. An exact expression for average bit error rate (BER) is obtained to analyze the performance of M-decorrelator. Simulation results show the potency of MH based M-decorrelator.

Multiuser Detection Using Particle Swarm Optimization over Fading Channels with Impulsive Noise

—The direct sequence-code division multiple access (DS-CDMA) signals are transmitted over multipath channels that introduce fading and shadowing. Combined effect of multipath fading and shadowing along with Multiple Access Interference (MAI) and Inter-Symbol Interference (ISI) worsens the system performance. Further, experimental results have confirmed the presence of impulsive noise in wireless mobile communication channels. Hence, this paper presents a Particle Swarm Optimization (PSO) based multiuser detection technique for DS-CDMA systems over Rayleigh, Nakagami-n (Rice), Nakagami-m and Generalized-K (GK) fading channels in presence of impulsive noise. Impulsive noise is modeled by two-term Gaussian mixture noise and white Laplace noise. Maximal ratio combining (MRC) receive diversity is also incorporated to mitigate the effects of fading and shadowing. Performance of proposed M-estimator based detector is analyzed by evaluating average error rate. Simulation results show that the proposed M-estimator based detector performs better in the presence of fading, shadowing and heavy-tailed impulsive noise when compared to least squares, Huber and Hampel M-estimator based detectors.

Robust Frequency Estimation of Sampled Sinusoidal Signals with Impulsive Noise

This paper presents a robust method for estimating the signal frequency of sampled sinusoidal signals, which are corrupted by impulsive noise. Hampel estimator is proposed to robustify the frequency estimation. It was observed that the average frequency estimation error becomes zero when a (2/3)π phase interval was considered to calculate the signal difference. Numerical simulation results show that the frequency estimation error when impulsive noise is added to the input data approaches the Cramer-Rao bound. Further, the effect of harmonic components on the frequency estimation error minimization is also considered, when the phase interval is close to (2/3)π and the total number of data sample covers several signal periods or truncated close to an integer multiple of the signal period.