Ergodic Capacity for the SIMO Nakagami- Channel
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Research Article Ergodic Capacity for the SIMO Nakagami-m Channel Efstathios D. Vagenas, Petros Karadimas, and Stavros A. Kotsopoulos Wireless Telecommunications Laboratory, Department of Electrical and Computer Engineering, University of Patras, 26500 Rio Patras, Greece Correspondence should be addressed to Efstathios D. Vagenas, [email protected] Received 10 February 2009; Revised 28 May 2009; Accepted 1 July 2009 Recommended by Gabor Fodor This paper presents closed-form expressions for the ergodic channel capacity of SIMO (single-input and multiple output) wireless systems operating in a Nakagami-m fading channel. As the performance of SIMO channel is closely related to the diversity combining techniques, we present closed-form expressions for the capacity of maximal ratio combining (MRC), equal gain combining (EGC), selection combining (SC), and switch and stay (SSC) diversity systems operating in Nakagami-m fading channels. Also, the ergodic capacity of a SIMO system in a Nakagami-m fading channel without any diversity technique is derived. The latter scenario is further investigated for a large amount of receive antennas. Finally, numerical results are presented for illustration. Copyright © 2009 Efstathios D. Vagenas et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
1. Introduction In recent years, the use of multiantenna systems provides large spectral efficiency for wireless communications in the presence of multipath fading environments. Multiple antennas can be used at the transmitter (MISO), the receiver (SIMO), or at both of them (MIMO). A SIMO system can be viewed as an antenna diversity scheme (diversity in space). Also, diversity combining is known to be a powerful technique to improve system performance in the presence of fading [1]. Several papers have been published regarding the capacity of SIMO systems operating in Nakagami environments. In [2], the channel capacity of a SIMO system in a Nakagamim fading channel is presented with the assumption that all links between transmit and receive antennas are independent and identically distributed (i.i.d.). In [3], capacity with MRC and optimal power and rate adaptation is presented while in [4] Shannon capacity with MRC is derived. In both of them, the assumption that all links are correlated and not identically distributed Nakagami holds. In [5], capacity of Nakagami-m multipath fading channels with MRC was studied for different power and rate adaptation policies. Also, simple capacity formulas for correlated SIMO Nakagami-m channels were derived in [6]. In [7], an analytical expression
for the capacity of SIMO systems over nonidentically independent Nakagami-m channels was derived. Significant work has been done in [8], where ergodic capacities of MRC, EGC, SC, and SSC of dual branch diversity systems are presented in closed-form expressions. The capacity expressions were ob
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