Near Field Communications for DMA-NOMA Networks
arxiv(2024)
摘要
A novel near-field transmission framework is proposed for dynamic metasurface
antenna (DMA)-enabled non-orthogonal multiple access (NOMA) networks. The base
station (BS) exploits the hybrid beamforming to communicate with multiple near
users (NUs) and far users (FUs) using the NOMA principle. Based on this
framework, two novel beamforming schemes are proposed. 1) For the case of the
grouped users distributed in the same direction, a beam-steering scheme is
developed. The metric of beam pattern error (BPE) is introduced for the
characterization of the gap between the hybrid beamformers and the desired
ideal beamformers, where a two-layer algorithm is proposed to minimize BPE by
optimizing hybrid beamformers. Then, the optimal power allocation strategy is
obtained to maximize the sum achievable rate of the network. 2) For the case of
users randomly distributed, a beam-splitting scheme is proposed, where two
sub-beamformers are extracted from the single beamformer to serve different
users in the same group. An alternating optimization (AO) algorithm is proposed
for hybrid beamformer optimization, and the optimal power allocation is also
derived. Numerical results validate that: 1) the proposed beamforming schemes
exhibit superior performance compared with the existing
imperfect-resolution-based beamforming scheme; 2) the communication rate of the
proposed transmission framework is sensitive to the imperfect distance
knowledge of NUs but not to that of FUs.
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