TEM Journal 4(3):292-296 Moments of Macrodiversity SC Receiver with Two Microdiversity EGC Receivers over Gamma Shadowed Rician Multipath Fading Channel Ilija Temelkovski 1 , Predrag Milačić 1 , Danijela Aleksić 2 , Danijel Đošić 3 , Stanislav Veljković 1 1 Faculty of Electronic Engineering, Aleksandra Medvedeva 14, 18000 Niš, Serbia 2 Faculty of Technical Sciences, Svetog Save 65, 32000 Čačak, Serbia 3 Faculty of Natural Science and Mathematics, Ive Lole Ribara 29, 38220 Kosovska Mitrovica, Serbia Abstract – SC macrodiversity system with dual EGC microdiversity receivers operating over shadowed multipath fading environment is considered. Received signal experiences correlated Gamma long term fading and Rician short term fading. SC macrodiversity receiver reduces Gamma large scale fading effects, while EGC microdiversity receivers mitigate short term fading effects on system performance. Closed form expressions for arbitrary order output moments of macrodiversity structure output signal is evaluated. Numerical results, obtained for arbitrary order output moments are presented graphically to show Gamma long term fading severity effect, correlation coefficient effects and Rician factor effect. Keywords – equal gain combining (EGC); Gamma shadowed; Rician fading; selection combining (SC). 1. Introduction Long term fading and short term fading degrade system performance and limit channel capacity. Reflections, refraction, diffraction and scattering cause short term fading and terrain profile deviation and large obstacles cause long term fading resulting in system performance degradation. It is important to determine how multipath fading and shadowing effect outage probability and bit error probability wireless communication system. There are more distribution that could be used to describe signal envelope variation depend on existence of line-of- sight (LOS) component, the number of clusters in propagation environments, nonlinearity of environment, inequality of quadrature components power and variation of signal envelope average power. The most frequently used statistical models to describe multipath fading are Rayleigh, Rician, Nakagami-m, Nakagami-q, Weibull and α-μ distribution [1], [2], [3]. Rayleigh distribution can be used to describe small scale signal envelope variation in linear, non line-of- sight multipath fading environment with on cluster. In line-of-sight multipath fading channels, signal envelope variation can be described by using Rician distribution. Nakagami-m distribution describes signal envelope variation in environment with two or more clusters. Nakagami-q distribution describes fading in environment where powers of in phase component and quadrature component are different [4], [5]. There are several combining techniques can be used the reduces multipath fading effects on system performance. The most frequently used combining techniques are maximum ratio combining (MRC), equal gain combining (EGC) and selection combining (SC). MRC combining enable the best performances. EGC technique processes all diversity branches and sums received equally-weighted replicas from each one to produce output statistics. EGC combining technique requires separate receiver chain for each branch of the diversity system, which increase its complexity [6]. Selection combining (SC) technique receiver is much simpler for practical realization (trade-off with obtained reception performances), in opposition to these combining techniques, since it processes one of the received signal replicas. However, this combining technique still requires the simultaneous and continuous monitoring of all the channels. Namely, in general, SC, assuming that noise power is equally distributed over branches, selects the branch with the highest signal-to-noise ratio (SNR), that is, the branch with the strongest signal [7], [8]. However, the usage of diversity techniques applied at single base station (micro-diversity combining) alleviates only influence of short-time fading. In order to combat with overall channel degradation, when shadowing (long-term fading) simultaneously occurs with multipath, combining between base stations (macro-diversity combining) has to be also applied. In that way is assured that different long- term fading is experienced, by signals received at two or more base stations (BS). In [9], macrodiversity SC receiver with two microdiversity MRC receivers operating over Gamma shadowed Nakagami-m multipath fading 292 TEM Journal – Volume 4 / Number 3 / 2015. www.temjournal.com