Effect of CSI Imperfection on Cognitive Underlay Transmission over Nakagami-m Fading Channel
This paper analyzes the performance of a cognitive underlay system over Nakagami-m fading channels, where maximal ratio combining (MRC) is employed at secondary destination and relay nodes. Under the condition of imperfect channel state information (CSI) of interfering channels, system performance metrics for the primary network and for the secondary network are formulated into exact and approximate expressions, which can be served as theoretical guidelines for system designs. To verify the performance analysis, several analytical and simulated results of the system performance are provided under various system and channel settings.
 L. Qian, R. Q. Hu, Q. Yi, and W. Geng, “Cooperative communications for wireless networks: techniques and applications in LTE-advanced systems,” IEEE Wirel. Commun., vol. 19, no. 2, Apr. 2012.
 T. Fujii and Y. Suzuki, “Ad-hoc cognitive radio - development to frequency sharing system by using multi-hop network,” in Proc. of The 2005 First IEEE International Symposium on New Frontiers in Dynamic Spectrum Access Networks (DySPAN 2005), 2005, pp. 589–592.
 Y. Youngjin, H. Murata, K. Yamamoto, and S. Yoshida, “Multihop cooperative sensing and transmit power control based on interference information for cognitive radio,” in Proc. of The IEEE 18th International Symposium on Personal, Indoor and Mobile Radio Communications 2007 (PIMRC’07), 2007, pp. 1–5.
 V. N. Q. Bao and D. H. Bac, “A unified framework for performance analysis of DF cognitive relay networks under interference constraints,” in Proc. of the International Conference on ICT Convergence 2011, 2011, pp. 537 – 542.
 D. T. Tran and V. N. Q. Bao, “Outage performance of cooperative multihop transmission in cognitive underlay networks,”in Proc. of The 2013 International Conference on Computing, Management and Telecommunications (ComManTel’13),, 2013, pp. 123–127.
 T. Q. Duong, D. Benevides da Costa, M. Elkashlan, and V. N. Q. Bao, “Cognitive amplify-and-forward relay networks over Nakagami-m fading,” IEEE Trans. Veh. Technol., vol. 6 1, no. 5, pp. 2368–2374, Jun. 2012.
 T.-T. Tran, V. N. Q. Bao, V. Dinh Thanh, and T. Q. Duong, “Performance analysis and optimal relay position of cognitive spectrum-sharing dual-hop decode-and-forward networks,” in Proc. of The 2013 International Conference on Computing, Management and Telecommunications (ComManTel’13), 2013, pp.
 V. N. Q. Bao, T. Q. Duong, D. Benevides da Costa, G. C. Alexandropoulos, and A. Nallanathan, “Cognitive amplifyand-forward relaying with best relay selection in nonidentical Rayleigh fading,” IEEE Commun. Lett., vol. 17, no. 3, pp. 475–478, Mar. 2013.
 Z. Xing, X. Jia, Y. Zhi, G. Yue, and W. Wenbo, “Outage performance study of cognitive relay networks with imperfect channel knowledge,” IEEE Commun. Lett., vol. 17, no. 1, pp. 27–30, Jan. 2013.
 Z. Bin, Z. Zhongshan, Z. Xu, W. Jun, and L. Keping, “Partial relay selection with fixed-gain relays and outdated CSI in underlay cognitive networks,” IEEE Trans. Veh. Technol., vol. 62, no. 9, pp. 4696–4701, May 2013.
 W. Qihui, Z. Zongsheng, and W. Jinlong, “Outage analysis of cognitive relay networks with relay selection under imperfect CSI environment,” IEEE Commun. Lett., vol. 17, no. 7, pp. 1297–1300, Jul. 2013.
 G. Nguyen Hong, V. N. Q. Bao, and N.-L. Hung, “Cognitive underlay communications with imperfect CSI: Network design and performance analysis,” in Proc. of the 2013 International Conference on Advanced Technologies for Communications (ATC’13), 2013, pp. 18–22.
 V. N. Q. Bao, T. Q. Duong, A. Nallanathan, and C. Tellambura, “Effect of imperfect channel state information on the performance of cognitive multihop relay networks,” in Proc. of Globecom 2013 - Signal Processing for Communications Symposium, 2013, pp. 3480–3485.
 V. N. Q. Bao, T. Q. Duong, and C. Tellambura, “On the performance of cognitive underlay multihop networks with imperfect channel state information,” IEEE Trans. Commun., vol. 61, no. 12, pp. 4864–4873, Dec. 2013.
 A. Goldsmith, S. A. Jafar, I. Maric, and S. Srinivasa, “Breaking spectrum gridlock with cognitive radios: An information theoretic perspective,” Proc. IEEE, vol. 97, no. 5, pp. 894–914, Apr. 2009.
 T. Q. Duong, V. N. Q. Bao, and H.-J. Zepernick, “Exact outage probability of cognitive AF relaying with underlay spectrum sharing,” Electro. Lett., vol. 47, no. 17, pp. 1001–1002, Sep. 2011.
 M. Schwartz, W. Bennett, and S. Stein, Communication systems and techniques. Wiley-IEEE Press, 1995.
 K. Seokjung, P. Sungsoo, and H. Daesik, “Performance analysis of opportunistic relaying scheme with outdated channel information,” IEEE Trans. Wireless Commun., vol. 12, no. 2, pp. 538–549, Feb. 2013.
 N. S. Ferdinand, N. Rajatheva, and M. Latva-aho, “Effects of feedback delay in partial relay selection over Nakagami-m fading channels,” IEEE Trans. Veh. Technol., vol. 61, no. 4, pp. 1620–1634, Sep. 2012.
 M. Abramowitz and I. A. Stegun, Handbook of mathematical functions with formulas, graphs, and mathematical tables, 10th ed.Washington: U.S. Govt. Print. Off., 1972. [Online]. Available: http://www.knovel.com/knovel2/Toc.jsp?BookID=528
 D. S. Michalopoulos, N. D. Chatzidiamantis, R. Schober, and G. K. Karagiannidis, “Relay selection with outdated channel estimates in Nakagami-m fading,” in Proc. of the 2011 IEEE International Conference on Communications (ICC’11), 2011, pp. 1–6.
 I. S. Gradshteyn, I. M. Ryzhik, A. Jeffrey, and D. Zwillinger, Table of integrals, series and products, 7th ed. Amsterdam ; Boston: Elsevier, 2007.
 A. Papoulis and S. U. Pillai, Probability, random variables, and stochastic processes, 4th ed. Boston: McGraw-Hill, 2002.
 M. O. Hasna and M.-S. Alouini, “Outage probability of multihop transmission over Nakagami fading channels,” IEEE Commun. Lett., vol. 7, no. 5, pp. 216–218, May 2003.
 V. N. Q. Bao and K. Hyung Yun, “Error probability performance for multi-hop decode-and-forward relaying over Rayleigh fading channels,” in Proc. of the 2009 11th International Conference on Advanced Communication Technology 2009 (ICACT’09), vol. 03, 2009, pp. 1512–1516.
 J. G. Proakis, Digital communications, 4th ed., ser. McGraw-Hill series in electrical and computer engineering. Boston: McGraw-Hill, 2001.
 H. Exton, Multiple hypergeometric functions and applications. E. Horwood, 1976. [Online]. Available: http://books.google.com.vn/books?id=hoYZAQAAIAAJ
 S. S. Ikki and S. Aissa, “Multihop wireless relaying systems in the presence of cochannel interferences: Performance analysis and design optimization,” IEEE Trans. Veh. Technol., vol. 61, no. 2, pp. 566–573, Feb. 2012.