标题： 视差QAMA：用于具有简单接收器的MISO系统的新型下行链路多址接入 显示英文标题

标题： Parallax QAMA: Novel Downlink Multiple Access for MISO Systems with Simple Receivers

摘要： 在本文中，我们提出了一种新颖的下行链路多址系统，该系统具有多天线发射器和两个单天线接收器，其灵感来源于分层正交幅度调制（H-QAM）基于多址接入（QAMA）和空间分割多址接入（SDMA）的基本原理。 在所提出的方案中，来自两个用户的编码比特被分割并分配到一个共享符号和两个由不同波束承载的私有符号。 基于H-QAM星座图的联合符号映射和发射端相位对齐的预编码，每个接收器观察到一个不同的H-QAM星座图，采用Gray映射，这是一种现有方案未具备的独特视差特征。 除了避免连续干扰消除（SIC）外，每个用户还在独立的I和Q分支上解调其自身比特，计算基于闭式表达式。 因此，接收机复杂度与正交多址接入（OMA）相当，远低于其他竞争方案（如非正交多址接入（NOMA）和速率分割多址接入（RSMA））中的复杂度。 我们进行了系统优化并确定了可实现的速率区域。 数值结果表明，所提出的系统相对于不使用SIC的其他基准方案具有更大的速率区域，甚至在使用SIC接收器的基准方案中也实现了相当的速率区域。 显示英文摘要

摘要： In this paper, we propose a novel downlink multiple access system with a multi-antenna transmitter and two single-antenna receivers, inspired by the underlying principles of hierarchical quadrature amplitude modulation (H-QAM) based multiple access (QAMA) and space-division multiple access (SDMA). In the proposed scheme, coded bits from two users are split and assigned to one shared symbol and two private symbols carried by different beams. Based on joint symbol mapping of H-QAM constellations and phase-aligned precoding at the transmitter, each receiver observes a different H-QAM constellation with Gray mapping, a unique parallax feature not shared by existing schemes. In addition to avoiding successive interference cancellation (SIC), each user independently demodulates its own bits on separate I and Q branches with calculations based on closed-form expressions. Hence the receiver complexity is on par with that of orthogonal multiple access (OMA), which is much lower than that in other competing alternatives such as non-orthogonal multiple access (NOMA) and rate-splitting multiple access (RSMA). We carry out system optimization and determine the achievable rate region. Numerical results show that the proposed system has a larger rate region relative to other benchmark schemes with receivers not using SIC, and even achieves a comparable rate region to those benchmark schemes with SIC receivers.