  This paper considers a downlink (DL) system where non-orthogonal multiple
access (NOMA) beamforming and dynamic user pairing are jointly optimized to
maximize the minimum throughput of all DL users. The resulting problem belongs
to a class of mixed-integer non-convex optimization. To solve the problem, we
first relax the binary variables to continuous ones, and then devise an
iterative algorithm based on the inner approximation method which provides at
least a local optimal solution. Numerical results verify that the proposed
algorithm outperforms other ones, such as conventional beamforming, NOMA with
random-pairing and heuristic-search strategies.
