Opportunistic NOMA-based Low-Latency Uplink Transmissions
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In this paper, we study the application of opportunistic non-orthogonal multiple access (NOMA) mode to low-latency uplink transmissions with user's power control under a finite power budget. It is shown that opportunistic NOMA mode, which can transmit multiple packets per slot, can dramatically lower the outage probability when W packets are to be transmitted within Ws slots, where Ws >= W, compared to orthogonal multiple access (OMA) where at most one packet can be transmitted in each slot. From this, opportunistic NOMA mode can be seen as an attractive approach for low-latency uplink transmissions. We derive an upper-bound on the outage probability as a closed-form expression and also obtain a closed-form for the NOMA factor that shows the minimum possible ratio of the outage probability of opportunistic NOMA to that of OMA. Simulation results also confirm that opportunistic NOMA mode has a much lower outage probability than OMA and is suitable for low-latency uplink transmissions.
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