Int. J. Electron. Commun. (AEÜ) 65 (2011) 413–418 Contents lists available at ScienceDirect International Journal of Electronics and Communications (AEÜ) journal homepage: www.elsevier.de/aeue Second-order statistics of SC macrodiversity system operating over Gamma shadowed Nakagami-m fading channels Duˇ san M. Stefanovi ´ c a , Stefan R. Pani ´ c b,∗ , Petar ´ C. Spalevi ´ c c a High Technical College, Aleksandra Medvedeva 20, 18000 Niˇ s, Serbia b Department of Telecommunications, Faculty of Electronic Engineering, University of Niˇ s, Aleksandra Medvedeva 14, 18000 Niˇ s, Serbia c Department of Telecommunications, Faculty of Technical Science, University of Priˇ stina, Knjaza Miloˇ sa 7, 40000 Kosovska Mitrovica, Serbia article info Article history: Received 11 January 2010 Received in revised form 28 April 2010 Accepted 25 May 2010 Keywords: Level crossing rate Average fade duration Shadowed fading channel Microdiversity Macrodiversity abstract This paper derives the second-order statistics of SC (selection combining) macrodiversity operating over the Gamma shadowed Nakagami-m fading channels. Macrodiversity system of SC type consists of two microdiversity systems and selection (switching) is based on their output signal power values. Each microdiversity system is of MRC (maximal ratio combining) type with arbitrary number of branches in the presence of correlative Nakagami-m fading. We have derived the infinite-series expressions for LCR (level crossing rate) and AFD (average fading duration) at the output of this system. Numerical results are also presented in order to show the influence of various parameters such as number of the diversity branches at the microcmbiners, fading severity and level of correlation between those branches on the system’s statistics, and then compared to the previously published results from this area. © 2010 Elsevier GmbH. All rights reserved. 1. Introduction Rapid growth of mobile communications as well as the emer- gence of wireless local area network (LAN) technologies has recently increased the interest in the wireless communications. Wireless channels are simultaneously affected by short-term fad- ing and long-term fading (shadowing) [1]. The short-term signal variation is described by several distributions such as Hoyt, Rayleigh, Rice, Nakagami-m, and Weibull. Nakagami-m fading describes multipath scattering with relatively large delay-time spreads, with different clusters of reflected waves [2]. It provides good fits to collected data in indoor and outdoor mobile–radio environments and is used in many wireless communications appli- cations. Various techniques for reducing short-term fading effect are used in wireless communication systems [3]. An efficient method for amelioration system’s quality of service (QoS) with using mul- tiple receiver antennas in is called space diversity. Upgrading transmission reliability without increasing transmission power and bandwidth while increasing channel capacity is the main goal of space diversity techniques. Several principal types of combin- ing techniques can be generally performed by their dependence on complexity restriction put on the communication system and ∗ Corresponding author. Tel.: +381 63 470 649. E-mail addresses: dusan.stefanovic@itcentar.co.rs (D.M. Stefanovi ´ c), stefanpnc@yahoo.com (S.R. Pani ´ c), petarspalevic@yahoo.com (P. ´ C. Spalevi ´ c). amount of channel state information available at the receiver. Com- bining techniques like maximal ratio combining (MRC) and equal gain combining (EGC) and require all or some of the amount of the channel state information of received signal, and separate receiver chain for each branch of the diversity system, which increases the complexity of system. In opposition to previous combining tech- niques, selection combining (SC) receiver processes only one of the diversity branches, and is much simpler and cheaper for practical realization. Generally, SC selects the branch with the highest signal-to-noise ratio (SNR), that is the branch with the strongest signal [1–3], assuming that noise power is equally distributed over branches. While short-term fading is mitigated through the use of diver- sity techniques typically at the single base station (microdiversity), use of such microdiversity approaches alone will not be sufficient to mitigate the overall channel degradation when shadowing is also concurrently present. In cellular networks, long-term fading known as shadowing can put a heavy limit on system performance. Shadowing is the result of the topographical elements and other structures in the transmission path such as trees, tall buildings. Now, we must simultaneously take short- and long-term fading conditions into account since they both coexist in wireless systems [4]. Macrodiversity is used to alleviate the effects of shadowing, where multiple signals are received at widely located base sta- tions, ensuring that different long-term fading is experienced by these signals [5]. The simultaneous use of multiple base stations and the processing of signals from these base stations will provide the framework for both macro- and microdiversity techniques to 1434-8411/$ – see front matter © 2010 Elsevier GmbH. All rights reserved. doi:10.1016/j.aeue.2010.05.001