In this paper, the composite Rayleigh-Gamma and Nakagami-Gamma distributions are considered. Multipath short-term fading and long-term fading (shadowing) affect wireless channels. A composite fading model was proposed for the modeling of shadowed channels, which resulted in a closed form solution for the probability density function (pdf). These composite Rayleigh-Gamma and Nakagami-Gamma are well-known as the K-distribution and KG-distribution, and are applied to cases where both micro- and macro-diversity schemes are implemented to mitigate short-term fading and shadowing, respectively. Thus, the composite pdf model offers significant improvement over approaches, which use lognormal pdf for shadowing. The results demonstrate the simplicity and usefulness of the composite pdf in the performance analyses of shadowed fading channels

Compression of highly correlated measurement signals is considered using DPCM/ADPCM (Difference Pulse Code Modulation/Adaptive Difference Pulse Code Modulation) technique. It is important since very often transmission and storage of measurement signals are needed. Theory is applied on ECG (Electrocardiogram) signal, as an example of highly correlated signals. Very good performances are achieved: high compression rate and high improvement of performances are obtained.

The complex SSC/MRC (Switch and Stay Combining/Maximal Ratio Combining) combiner is considered in this paper. The system in the presence of Rayleigh fading at the input, at two time instants, is observed. Both part of combiners, SSC as well as MRC, are dual-branches. The probability density function (PDF) at the output of the complex combiner is used for the ISSN 1943-3581 2012 www.macrothink.org/npa 36 bit error rate (BER), outage probability (P out ) and Amount of fading (AF) determination. Binary phase swift keying (BPSK) modulation is applied. Graphically presented results point out the gain of using this complex SSC/MRC combiner compared with classical MRC combiners and one channel receiver at one time instant. Network Protocols and Algorithms

In this paper wireless communication system with dual branch selection combining (SC) diversity receiver operating over k-? multipath fading environment is considered. Closed form expressions for average level crossing rate of SC receiver output signal envelope and average fade duration of proposed system are evaluated. Numerical results are presented graphically to show the influence of Rican factor k and fading severity ? on average level crossing rate and average fade duration.

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