  Non-orthogonal multiple access (NOMA) assisted semi-grant-free (SGF)
transmission has recently received much research attention, which can serve the
grant-free (GF) users with the grant-based (GB) users' spectrum. In this paper,
we first extend the SGF scheme with the best user scheduling (BU-SGF) to a more
practical randomly deployed users system. Then, a cumulative distribution
function (CDF)-based scheduling aided SGF (CS-SGF) scheme is proposed to ensure
fair admission probability for all GF users. Meanwhile, we analytically
demonstrate that, for both BU-SGF and CS-SGF schemes, full diversity orders can
be achieved only when the served users' data rate is capped. To address this
issue, we propose an efficient power control strategy to relax such data rate
constraint and further enhance the outage probability. In addition, after
applying the proposed power control strategy, both schemes' outage performances
are analyzed by utilizing stochastic geometry. Theoretic and simulation results
demonstrate that, with the proposed power control strategy both schemes can
achieve full diversity orders in all cases.
