Performance evaluation of outage probability and BER for MIMO-femtocell system over spatial correlated channel q Joy Iong-Zong Chen a,⇑ , Lu-Tsou Yeh b , Chu-Hsing Lin c a Department of Communication Engineering, Dayeh University, 168 University Rd., Dacun, Chunghua 51505, Taiwan, ROC b Department of Electrical Engineering, Asia-Pacific Institute of Creativity, 110, XueFu Rd., Toufen, Miaoli 351, Taiwan, ROC c Department of Computer Science, Tunghai University, 181, Sec. 3, Taichung Port Rd., Taichung City 40704, Taiwan, ROC article info Article history: Available online 16 March 2013 abstract In this paper we investigate the channel correlation of a MIMO-femtocell (multiple-input multiple-output) system constructed with MIMO that is adapted to a tiered femtocellular network. The MIMO-femtocell system deployed with home BS (base station) in a single floor indoor environment is proposed. According to the analyses of both theoretical and simulation results, channel correlation definitely degrades the overall system performance of a MIMO-femtocell system, especially in indoor channels. Moreover, the coverage area of a MIMO-femtocell deployment is reduced because of channel correlation occurring in the propagation channel. Some analyses of closed forms are utilized to discuss the phenome- non of channel correlation that exists in MIMO-femtocell systems. Certainly, the analytical results match well with the experimental results obtained from the software package. Fur- thermore, some numerical results validate the performance of outage probability and the BER (bit error rate). It is noteworthy to remember that there is a degradation factor in the X1–X4 differences of the BS coverage area as the channel correlation phenomenon is not ignored in the performance evaluation of the MIMO-femtocell system and the Rayleigh sta- tistical model. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction The various channel correlations become very small, and can be assumed to equal zero, when the angular spreading of the energy and/or the antenna separation at both terminals of the transmission elements is sufficiently wide. The aforemen- tioned rules are hardly obeyed when the working area is indoors or in a constrained place. Accordingly, the results in Fig. 6 of [1] show significantly that the BER becomes degradation when the branch separation is increased. The correlation effect is mainly arisen from tightly space in distance between branches (antenna elements). Moreover, hence, according to [2] in which said that due to the limited resolution of the receiver, it is accumulated by scattering from the neighborhood of the receiver. In this paper, we aim to explore the correlation between the spatial diversity environments. The condition of the spatial channel correlation, which takes into account the coverage area calculation for TTFN (two-tiered femtocell networks), adapts to the MIMO (multiple-input multiple-output) channel environments. This is why TTFN is always used in the interiors of buildings and especially in inside rooms. The calculation of the coverage area for an f-AP (femtocell access point) hotspot within a TTFN has been made via the outage probability evaluation of a user communicating to an m-BS (macrocell base station). 0045-7906/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.compeleceng.2013.02.009 q Reviews processed and recommended for publication to Editor-in-Chief by Associate Editor Dr. Paul Cotae. ⇑ Corresponding author. Tel.: +886 4 8511888 2523; fax: +886 4 8511245. E-mail address: jchen@mail.dyu.edu.tw (J.I.-Z. Chen). Computers and Electrical Engineering 39 (2013) 1837–1845 Contents lists available at SciVerse ScienceDirect Computers and Electrical Engineering journal homepage: www.elsevier.com/locate/compeleceng