[PDF][PDF] On the Application of Quasi-Degradation to Network NOMA in Downlink CoMP Systems

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N Network
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The application of network non-orthogonal multiple access (N-NOMA) technique to
coordinated multi-point (CoMP) systems has attracted significant attention due to its superior
capability to improve connectivity and maintain reliable transmission for CoMP users
simultaneously. Based on the concept of quasi-degraded channel for N-NOMA, this paper
studies the precoding design for downlink N-NOMA scenarios with two base stations (BSs)
equipped with multiple antennas. In specific, under quasi-degraded channels, simple linear …
Abstract
The application of network non-orthogonal multiple access (N-NOMA) technique to coordinated multi-point (CoMP) systems has attracted significant attention due to its superior capability to improve connectivity and maintain reliable transmission for CoMP users simultaneously. Based on the concept of quasi-degraded channel for N-NOMA, this paper studies the precoding design for downlink N-NOMA scenarios with two base stations (BSs) equipped with multiple antennas. In specific, under quasi-degraded channels, simple linear precoding based NNOMA can achieve the same minimal total transmission power as theoretically optimal but complicated dirty paper coding (DPC) scheme, when the users’ target rates and minimal transmission power of each BS are given. In this paper, the channel quasidegradation (QD) condition is first rigorously derived for the scenario with single CoMP user and two NOMA users. The closedform optimal precoders for N-NOMA under quasi-degraded channels are also provided. Then, based on QD condition, a novel hybrid N-NOMA (HN-NOMA) scheme is proposed, which is a mixture of N-NOMA and conventional zero-forcing beamforming (ZFBF) scheme. Further, for the scenarios with more users, a low-complexity QD based user pairing (QDUP) algorithm is proposed, which is then combined with HN-NOMA to make a novel scheme termed HN-NOMA/QDUP into being. Numerical results are presented to reveal the impact factors on QD channels, and also demonstrate the superior performance of the proposed HN-NOMA/QDUP scheme. It is shown that the proposed HNNOMA/QDUP scheme can effectively exploit the benefit of multi user diversity.
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