Relay-Satellite-Assisted LEO Constellation NOMA Communication System

This article proposes a relay satellite assisted low Earth orbit (LEO) constellation nonorthogonal multiple access combined beamforming (R-NOMA-BF) communication system, where multiple antenna LEO satellites deliver information to ground nonorthogonal users. To measure the service quality, we formulate a resource allocation problem to minimize the second-order difference between the achievable capacity and user request traffic. Based on the above problem, joint optimization for LEO satellite–cell assignment factor, NOMA power, and BF vector is taken into account. The optimization variables are analyzed with respect to feasibility and nonconvexity. In addition, we provide a pair of effective algorithms, i.e., Doppler-shift LEO satellite–cell-assisted monotonic programming of NOMA with BF vector (D-mNOMA-BF) and ant colony pathfinding-based NOMA exponential cone programming with BF vector (A-eNOMA-BF). Two compromise algorithms regarding the above are also presented. Numerical results show that: 1) D-mNOMA-BF and A-eNOMA-BF algorithms are superior to that of OMA-based BF and polarization multiplexing schemes; 2) with the increasing number of antennas and single satellite power, the R-NOMA-BF system is able to expand users satisfaction; and 3) by comparing various imperfect successive interference cancelation, the performance of A-mNOMA-BF algorithm exceeds D-mNOMA-BF.