Vinay Kumar Pamula

Multiuser detection for DS-CDMA systems over Nakagami-m fading channels using particle swarm optimization

This paper presents a robust multiuser detection technique for direct sequence-code division multiple access (DS-CDMA) systems over Nakgami-m fading channels in the presence of impulsive noise. Robust M-decorrelating detector to demodulate non-coherent DPSK signals is implemented by using the particle swarm optimization (PSO) algorithm. The PSO algorithm is used to obtain optimum M-estimates by minimizing an objective function, which is a sum of less rapidly increasing function of residuals. Simulation results are provided to show the evolutionary behavior and efficacy of the modified-Hampel based M-estimator in comparison with linear decorrelating detector, the Huber and the Hampel estimator based detectors.

Gaussian Q-function and Its Approximations

This paper presents some useful approximations to the Gaussian Q-function with an application to computation of bit error probability (BEP) of M-ary phase shift keying (MPSK) modulation scheme. Computational results are provided to compare various approximations to Gaussian Q-function.

Teaching-learning-based optimization with two-stage initialization

The teaching-learning-based optimization (TLBO) algorithm is an evolutionary algorithm based on simulated teaching-learning procedure in a class. This algorithm requires no controlling parameters and is moulded based on the effect of influence of teacher on the output of learners and hence can be implemented easily and also requires less computational memory compared to other evolutionary algorithms. This paper presents the (TLBO) algorithm with two-stage initialization (TSI). The TLBO with TSI (TLBO-TSI) is tested with the Rastrigin benchmark function and then used to minimize least-squares (LS), Huber (HU) and Hampel (HA) cost functions. Simulation results are presented to show the evolutionary behavior of the TLBO with TSI. Simulation results show that the TLBO-TSI performs better compared to existing TLBO.

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.

Differential evolution and particle swarm optimization algorithms with two stage initialization for PID controller tuning in coupled tank liquid level system

In this paper, a different type of initialization technique called the two stage initialization (TSI) is used for initializing the population vectors of differential evolution (DE) and particle swarm optimization (PSO). These two stage initialized optimization algorithms are then used to tune the PID controller for a coupled tank liquid level control system. In TSI, the population vector is randomly generated in two stages which would then go through the various phases involved in the algorithms. The PID controller is the most preferred controller in almost all process control industries due to its robustness and dynamic behavior. Hence it has been chosen for controlling the coupled tank liquid level system in this paper. Comparison of the application of four optimization algorithms out of which two are already existing ones and the other two are their TSI versions to PID-coupled tank liquid level system is also done. It can be found that TSI not only helps the existing optimization algorithms to start at a better optima but also to converge at a lesser minimum value of the objective function, which is often desirable.

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.

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.

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.

Performance analysis of decimal matrix code and modified decimal matrix code

This paper presents a method of increasing reliability of memory, so as not to make the data erroneous, and to make the data free from multiple cell upsets (MCUs). There are many methods to increase the reliability of memory, but in this paper a modification to decimal matrix code is proposed with reduced redundant bits. The error correction codes which are used to protect memories and to increase the reliability of memory are more complex, because of the shrinking of CMOS technology. The proposed technique increases error detection capability due to the use of decimal algorithm. In the existing decimal matrix code there are more number of redundant bits, which are required for the detection and correction of the data in the memory. In this paper same algorithm as that of decimal matrix code is used but, the number of redundant bits are reduced and it also has less area and power.