Cognitive Multi-Relay Transmission over Asymmetric Fading Channels with Imperfect CSI
Outage performance of a cognitive multi-relay system using imperfect channel state information (CSI) of interfering links is formulated in this paper. In the considered cognitive system, it is assumed that wireless channels in the secondary network (source-to-relay and relay-to-destination links) experience Rician fading whereas interfering channels between primary and secondary networks undergo Rayleigh fading. Under the assumption of asymmetric fading, an outage probability (OP) expression of the secondary network is approximately formulated. Analytical OP values are in good agreement with related empirical ones in low signal-to-noise ratio (SNR) regimes. As a result, the approximate OP expression can be used to quantify the effect of asymmetric fading channels and CSI imperfection on the performance of cognitive multi-relay systems in practical SNR ranges.
 A. Goldsmith, S. A. Jafar, I. Maric, and S. Srinivasa, “Breaking spectrum gridlock with cognitive radios: An information theoretic perspective,” Proc. IEEE, May 2009.
 Nguyen Hong Giang, Vo Nguyen Quoc Bao, and Hung Nguyen-Le, “Cognitive Underlay Communications with Imperfect CSI: Network Design and Performance Analysis,” Proc. The 2013 International Conference on Advanced Technologies for Communucations (ATC’13), pp. 18-22, Oct., 2013.
 T. Q. Duong, V. N. Q. Bao, and H.-J. Zepernick, “Exact outage probability of cognitive AF relaying with underlay spectrum sharing,” Electron. Lett., pp. 10011002, Aug. 2011.
 Z. Caijun, T. Ratnarajah, and W. Kai-Kit, “Outage analysis of decodeand-forward cognitive dual-hop systems with the interference constraint in Nakagami-m fading channels,” IEEE Trans. Veh. Technol., vol. 60, no. 6, pp. 28752879, Jun. 2011.
 J. Lee, H. Wang, J. G. Andrews, and D. Hong, “Outage probability of cognitive relay networks with interference constraints,” IEEE Trans. Wireless Commun., vol. 10, no. 2, pp. 390395, Feb. 2011.
 V. N. Q. Bao and D. Q. Trung, “Exact outage probability of cognitive underlay DF relay networks with best relay selection,”IEICE Trans. Commun., vol. E95B, no. 6, pp. 21692173, Jun. 2013.
 V. N. Q. Bao, T. T. Thanh, N. T. Duc, and V. D. Thanh, “Spectrum sharing-based multihop decode-and-forward relay networks under interference constraints: Performance analysis and relay position optimization,” J. Commun. Netw., vol. 15, no. 3, pp. 266275, Jun. 2013.
 T.-T. Tran, V. N. Q. Bao, V. Dinh Thanh, and T. Q. Duong, “Performance analysis and optimal relay position of cognitive spectrum-sharing dualhop decode-and-forward networks,” in Proc. 2013 International Conference on Computing, Management and Telecommunications (ComMan-Tel13), 2013, pp. 269273.
 Andrea Goldsmith, Wireless Communications, Cambridge University Press., 2005.
 T. Q. Duong, T. T. Duy, M. Matthaiou, T. Tsiftsis, G. K. Karagiannidis, ”Cognitive cooperative networks in dual-hop relaying asymmetric fading channels, ” Proc. IEEE Global Communications Conference (GLOBECOM), Atlanta, GA, December 2013.
 Karagiannidis, George K.; Kotsopoulos, Stavros A., ”On the distribution of the weighted sum of L independent Rician and Nakagami envelopes in the presence of AWGN,” Communications and Networks, Journal of , vol.3, no.2, pp.1,8, June 2001.
 M. K. Simon and M.-S. Alouini, Some New Results for Integrals Involving the Generalized Marcum Q- Function and their Application to Performance Evaluation over Fading Channels, IEEE Trans. Wireless Commun., vol. 2, no. 4, pp. 611615, 2003.
 Qihui Wu; Zongsheng Zhang; Jinlong Wang, ”Outage Analysis of Cognitive Relay Networks with Relay Selection under Imperfect CSI Environment,” Communications Letters, IEEE , vol.17, no.7, pp.1297,1300, July 2013.
 N. H. Giang, V. N. Q. Bao, and N. L. Hung, ”Receive Diversity in Cognitive Relay Transmission: Outage Analysis,” International Conference on Communications and Electronics (ICCE), 2014, to be published.
 Kyung-Seung Ahn; Heath, R.W., ”Performance analysis of maximum ratio combining with imperfect channel estimation in the presence of cochannel interferences,” Wireless Communications, IEEE Transactions on , vol.8, no.3, pp.1080,1085, March 2009.
 Nguyen Hong Giang; Vo Nguyen Quoc Bao; Hung Nguyen-Le, ”Cognitive underlay communications with imperfect CSI: Network design and performance analysis,” Advanced Technologies for Communications (ATC), 2013 International Conference on , vol., no., pp.18,22.
 Bocus, M.Z.; Dettmann, C.P.; Coon, J.P., ”An Approximation of the First Order Marcum Q-Function with Application to Network Connectivity Analysis,” Communications Letters, IEEE , vol.17, no.3, pp.499,502, March 2013.
 M. A. Chaudhry and S. M. Zubair, On a Class of Incomplete Gamma Functions with Applications. Boca Raton-London - New York-Washington, D.C. : Chapman and Hall/CRC, 2002.
 Ali, A.A.; Alkhudairi, K., ”BER for M-QAM with Space Diversity and MRC in Rician Fading Channels,” Mobile Computing and Wireless Communication International Conference, 2006. MCWC 2006. Proceedings of the First , vol., no., pp.67,72, 17-20 Sept. 2006.
 G.N. Watson, A Treatise on the Theory of Bessel Functions, Cambridge University Press, Cambridge, 1944.
 A. Nuttall, Some Integrals Involving the -Function, Naval Underwater Systems Center (NUSC) Technical Report, May 1974.
 I. Gradshteyn, I. Ryzhik, and A. Jeffrey, Table of Integrals, Series, and Products. Academic Press, 2007.