Performance Evaluation of NOMA-Based Cognitive Integrated Satellite Terrestrial Relay Networks With Primary Interference

Satellite communication has attracted great interests due to extensive coverage and no terrain restriction, which can make up for the shortcomings of terrestrial communication, especially in remote areas. Hence, integrated satellite-terrestrial relay network (ISTRN) is considered as a promising research direction. However, the shortage of spectrum resources is becoming the bottleneck of the future development of ISTRN because of the low utilization of spectrum. In this regard, non-orthogonal multiple access (NOMA) scheme and cognitive radio are considered as great ways to solve this problem. This paper investigates the performance of a NOMA-based ISTRN under spectrum sharing environment with primary interference. Particularly, the exact closed-form expressions of outage probability and ergodic capacity are derived to evaluate the system performance, where the interference constraint caused by the multiple primary users and the interference of primary transmitter have been considered. Furthermore, in order to reveal the impacts of key parameters on system performance at high signal-to-noise ratios efficiently, the asymptotic analysis of OP is also provided. After that, we obtain the relationship between system performance and the power allocation factor, the number of primary users, interference parameter or the channel environment, which will enlighten the research of NOMA-based cognitive ISTRN. At last, Monte Carlo results are provided to verify the effectiveness of our theoretical analysis.