Abstract—The outage performance of multi-hop cooperative spectrum sharing systems with interference constraints over Nakagami-m fading is investigated. Employing a Decode-and-Forward (DF) relaying protocol, the closed-form analytic expression is derived for the Outage Probability (OP), which is validated through comparison with results from Monte-Carlo simulations. In addition, the corresponding asymptotic performance for the maximum transmit power is investigated as well. The obtained expressions provide useful insights on the behavior of the system performance under different operation parameters. Numerical results reveal that the system performance degrades as the number of relays increases, the relationship between the interference constraints and maximum transmits power leads to the emergence of the outage error floor. In addition, we compare the effectiveness of the interference link channel quality and the transmission link channel quality on the system performance improvement. Our results show that good performance of the system relies on the improvement of transmission links deeper than that of the interference links. However, the performance improvement of the overall system comes from good channel quality of all the links. Moreover, the presented results also demonstrate that underlay multi-hop cognitive networks depends on numerous factors and differs substantially from that of traditional multi-hop networks.

Index Terms—Cognitive relaying system, decode-and-forward, multi-hop communications, outage probability, Nakagami-m fading

Cite: Hui Guo, Shilong Ji, and Lihong Wang, “Outage Performance of Cognitive Multi-Hop Network under Interference Constraints over Nakagami-m Fading," Journal of Communications, vol. 11, no. 7, pp. 686-692, 2016. Doi: 10.12720/jcm.11.7.686-692