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.