Signal shaping is vital to approach Shannon’s capacity, yet it is challenging to implement at very high speeds. For example, probabilistic shaping often requires arithmetic coding to realize the target distribution. Geometric shaping requires look-up tables to store the constellation points. In this letter, we propose a four-dimensional amplitude coding (4D-AC) geometrical shaper architecture. The proposed architecture can generate in real time geometrically shaped 4D formats via simple logic circuit operations and two conventional quadrature amplitude modulation (QAM) modulators. This letter describes the 4D-AC used in generating approximated versions of two recently proposed 4D orthant symmetric modulation formats with spectral efficiencies of 6 bit/4D-sym and 7 bit/4D-sym, respectively. Numerical results show losses below 0.05 dB when compared against the baseline formats.

中文翻译：

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通过幅度编码实现 4D 调制格式的低复杂度几何整形


信号整形对于接近香农的能力至关重要，但以非常高的速度实现具有挑战性。例如，概率整形常常需要算术编码来实现目标分布。几何整形需要查找表来存储星座点。在这封信中，我们提出了一种四维幅度编码（4D-AC）几何整形器架构。所提出的架构可以通过简单的逻辑电路运算和两个传统的正交幅度调制（QAM）调制器实时生成几何形状的 4D 格式。这封信描述了用于生成两种最近提出的 4D 正交对称调制格式的近似版本的 4D-AC，其频谱效率分别为 6 位/4D-sym 和 7 位/4D-sym。数值结果显示，与基线格式相比，损耗低于 0.05 dB。