Articles written in Sadhana

    • κ–μ fading channels: a finite state Markov modelling approach


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      Finite state Markov channel (FSMC) is the automatic choice for accurate modelling of slow fading channels with memory. FSMC model for a κ–μ fading channel is investigated in this paper. Small-scale variations of the fading signal under Line-Of-Sight conditions are represented by κ–μ fading distributions. Here, FSMC is constructed by partitioning the fading amplitude into several regions. Each region corresponds to a particular state in the Markov model. The transition among these channel states characterizes the physical fading process. Performance measures such as steady-state probability, state-transition probability, level crossing rate and state-time duration corresponding to the κ–μ fading channel are derived, plotted and analysed. Finally,numerical results prove that FSMC modelling provides an effective way to reflect the nature of the κ–μ fading channel.

    • BER performance analysis of compound chaotic sequence (CCS)-based NR-DCSK system under multipath fading channel


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      This paper presents the performance analysis of compound chaotic sequence (CCS)-based noise reduction differential chaos shift keying (NR-DCSK) system under multipath Rayleigh fading channel conditions. The special characteristics of chaotic sequences are their deterministic randomness behaviour that adds security and multipath immunity to the data when used as a carrier in communication systems. In this paper, the chaotic sequences are generated by combining the outputs of chaotic maps, such as logistic map, Chebyshev map, Bernoullishift map, tent map, etc., leading to new complex sequences known as CCSs. This sequence possesses more randomness, overcomes severe interference levels encountered during transmission and provides higher multipath immunity compared with those of pseudo-noise (PN) codes. Since NR-DCSK is a spread spectrum technique, its performance in wireless multipath fading channels has important considerations. The CCS is used as a carrier in NR-DCSK systems, which leads to improved bit error rate (BER) performance. Comparisons of simulation results to theoretical BER expressions of additive white Gaussian noise (AWGN) and Rayleigh fading channels have been carried out to test the efficiency of the proposed CCS-based NR-DCSK system.

    • Improving bounds on outage probability in correlated Rayleigh fading environment


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      In this letter, we propose a limiting criterion to improve the bounds on outage probability for n-correlated Rayleigh fading channel. We use a threshold-based limiting distribution to yield explicit bounds on probability. This work takes into consideration the effect of correlated noise signal to the receiver, which is ageneralization based on the power and noise correlation vectors. The approach proposed in this paper is different from many other existing bounds and it provides strong information to improve the results for the bounds on the outage probability.

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