TRANSACTIONS ON EMERGING TELECOMMUNICATIONS TECHNOLOGIES Trans. Emerging Tel. Tech. 2012; 23:334–340 Published online 9 December 2011 in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/ett.1538 RESEARCH ARTICLE Average level crossing rate of microcellular mobile radio system with selection combining in the presence of arbitrary number of cochannel interferences Aleksandra Panajotovi´ c, Mihajlo Stefanovi ´ c, Dragan Draˇ ca and Nikola Sekulovi´ c* Faculty of Electronic Engineering, Telecommunications, Nis, Serbia ABSTRACT This paper provides an exact and rapidly converging infinite-series expression for the average level crossing rate of dual selection combining receiver in a communication system with a Rician desired signal affected by multiple Nakagami-m cochannel interferences. The branch selection is based on the desired signal power algorithm with input signals assumed to be correlated because of insufficient distance between diversity branches. The proposed mathematical analysis is com- plemented by various numerical results showing the effects of various system’s parameters. Copyright © 2011 John Wiley & Sons, Ltd. KEY WORDS cochannel interference; correlation; average level crossing rate; Rician fading; selection combining diversity *Correspondence Nikola Sekulovi´ c, Faculty of Electronic Engineering, Telecommunications, Nis, Serbia. E-mail: nikola.sekulovic@elfak.rs Received 11 August 2010; Revised 7 June 2011; Accepted 7 October 2011 1. INTRODUCTION System performance degraded by severe fading can be improved by increasing the transmitter power, bandwidth, antenna size, and height, etc., but these solutions are costly and sometimes impractical. Diversity techniques provide wireless link performance improvement at rel- atively low cost [1]. Among several types of diversity techniques, selection combining (SC) is the least com- plicated because processing is performed only on one of the diversity branches. Traditionally, the SC receiver chooses the branch with the highest signal-to-noise ratio (SNR), which corresponds to the strongest signal if equal noise power is assumed among the branches [2]. However, in interference-limited fading environment as in cellular communications system where the level of the cochannel interference (CCI) is sufficiently high compared with the thermal noise, three different decision algorithms can be applied: the desired signal power algorithm, the total sig- nal power algorithm, and the signal-to-interference power ratio (SIR) algorithm. In [3], Yang and Alouini compared the performance of different SC algorithms in the presence of CCI. They showed that of the three applied algorithms, the SIR algorithm provides the best performance for interference-limited systems in the sense of the outage probability (OP) and the average fade duration (AFD), but it almost provides the worst performance for the average level crossing rate (LCR), which is considered in this paper. Also, it is the most complex to implement. The desired sig- nal power algorithm requires identification and separation of the desired signal and the CCI (which can be achieved using different pilots with each of them [4]), and the total signal power algorithm is the most practical to implement. Furthermore, desired and total signal power algorithms have nearly the same performance for all three previously mentioned performance criteria [3, 5, 6]. For the purpose of analytical tractability, we adopted the desired signal power algorithm and reasonably assumed that obtained results may also closely indicate the performance of the total power algorithm [7]. Outage probability is commonly used as an impor- tant performance metric of various diversity techniques with/without CCI and over independent or correlated channels [3, 5, 6, 8, 9]. However, in certain applications such as in adaptive transmission, OP does not provide enough information for the overall system design and 334 Copyright © 2011 John Wiley & Sons, Ltd.