4,374 research outputs found
Trellis-Coded Non-Orthogonal Multiple Access
In this letter, we propose a trellis-coded non-orthogonal multiple access (NOMA) scheme. The signals for different users are produced by trellis coded modulation (TCM) and then superimposed on different power levels. By interpreting the encoding process via the tensor product of trellises, we introduce a joint detection method based on the Viterbi algorithm. Then, we determine the optimal power allocation between the two users by maximizing the free distance of the tensor product trellis. Finally, we manifest that the trellis-coded NOMA outperforms the uncoded NOMA at high signal-to-noise ratio (SNR)
Downlink Non-Orthogonal Multiple Access with Limited Feedback
In this paper, we analyze downlink non-orthogonal multiple access (NOMA)
networks with limited feedback. Our goal is to derive appropriate transmission
rates for rate adaptation and minimize outage probability of minimum rate for
the constant-rate data service, based on distributed channel feedback
information from receivers. We propose an efficient quantizer with
variable-length encoding that approaches the best performance of the case where
perfect channel state information is available everywhere. We prove that in the
typical application with two receivers, the losses in the minimum rate and
outage probability decay at least exponentially with the minimum feedback rate.
We analyze the diversity gain and provide a sufficient condition for the
quantizer to achieve the maximum diversity order. For NOMA with receivers
where , we solve the minimum rate maximization problem within an
accuracy of in time complexity of
, then, we apply the previously proposed
quantizers for to the case of . Numerical simulations are
presented to demonstrate the efficiency of our proposed quantizers and the
accuracy of the analytical results
Cooperative Non-Orthogonal Multiple Access in 5G Systems
Non-orthogonal multiple access (NOMA) has recently received considerable
attention as a promising candidate for 5G systems. A key feature of NOMA is
that users with better channel conditions have prior information about the
messages of the other users. This prior knowledge is fully exploited in this
paper, where a cooperative NOMA scheme is proposed. Outage probability and
diversity order achieved by this cooperative NOMA scheme are analyzed, and an
approach based on user pairing is also proposed to reduce system complexity in
practice
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