[论文解读] A Survey on Design and Performance of Higher-Order QAM Constellations

Praveen Kumar Singya, Parvez Shaik+3 more|arXiv (Cornell University)|Apr 30, 2020

Advanced Wireless Communication Technologies参考文献 364被引用 14

一句话总结

本综述对高阶QAM调制方式——特别是星型QAM、XQAM和六边形QAM（HQAM）——进行了全面分析，重点研究其设计、性能指标以及在后5G系统中的适用性。结果表明，非规则HQAM在传统方形和矩形QAM基础上具有更高的功率效率，因此在高数据速率、带宽和能量受限的无线系统中最为理想。

ABSTRACT

As the research on beyond 5G heats up, we survey and explore power and bandwidth efficient modulation schemes in details. In the existing publications and in various communication standards, initially square quadrature amplitude modulation (SQAM) constellations (even power of 2) were considered. However, only the square constellations are not efficient for varying channel conditions and rate requirements, and hence, odd power of 2 constellations were introduced. For odd power of 2 constellations, rectangular QAM (RQAM) is commonly used. However, RQAM is not a good choice due to its lower power efficiency, and a modified cross QAM (XQAM) constellation is preferred as it provides improved power efficiency over RQAM due to its energy efficient two dimensional (2D) structure. The increasing demand for high data-rates has further encouraged the research towards more compact 2D constellations which lead to hexagonal lattice structure based constellations, referred to as hexagonal QAM (HQAM). In this work, various QAM constellations are discussed and detailed study of star QAM, XQAM, and HQAM constellations is presented. Generation, peak and average energies, peak-to-average-power ratio, symbol-error-rate, decision boundaries, bit mapping, Gray code penalty, and bit-error-rate of star QAM, XQAM, and HQAM constellations with different constellation orders are presented. Finally, a comparative study of various QAM constellations is presented which justifies the supremacy of HQAM over other QAM constellations. With this, it can be claimed that the use of the HQAM in various wireless communication systems and standards can further improve the performance targeted for beyond 5G wireless communication systems.

研究动机与目标

• 分析下一代无线系统中超越传统方形QAM的高阶QAM调制方式的设计与性能。
• 识别矩形QAM（RQAM）在不同信道条件和低功率场景下的局限性。
• 评估XQAM和HQAM等替代调制方式在提升功率效率和频谱效率方面的潜力。
• 在能量效率、误比特率和峰均功率比等关键指标上，对比星型QAM、XQAM和HQAM的性能。
• 确立HQAM——特别是非规则HQAM——作为未来5G及以后无线通信标准的最优调制方式。

提出的方法

• 对星型QAM、XQAM和HQAM在多种性能指标上进行详细比较研究。
• 分析星座图几何结构、判决边界以及比特映射策略，包括格雷码映射及其带来的代价。
• 推导并比较各类调制方式的峰值和平均信号能量，并计算其峰均功率比（PAPR）。
• 在加性白高斯噪声（AWGN）环境下，评估不同调制阶数下的符号误码率（SER）和比特误码率（BER）性能。
• 建立规则和非规则HQAM结构的模型，以评估其在瑞利衰落信道中的能量效率和鲁棒性。
• 结合理论推导与基于仿真的性能评估，比较各类调制方式的频谱效率和功率效率。

实验结果

研究问题

• RQ1 星型QAM、XQAM和HQAM在能量效率和功率效率方面与传统方形QAM和矩形QAM相比如何？
• RQ2 星座形状（方形、矩形、十字形、六边形）对误比特率（BER）和符号误码率（SER）有何影响？
• RQ3 非规则HQAM设计相比规则HQAM及其他QAM类型，在提升功率效率方面有何优势？
• RQ4 比特映射策略及格雷码代价在决定高阶QAM调制方式BER性能方面起什么作用？
• RQ5 HQAM在多大程度上可降低峰均功率比（PAPR）并提升高数据速率系统中的频谱效率？

主要发现

• 非规则六边形QAM（HQAM）在功率效率方面显著优于方形QAM、矩形QAM（RQAM）和十字形QAM（XQAM），是高数据速率传输中最节能的调制方式。
• 由于其二维能量高效结构，XQAM在功率效率方面优于RQAM，可在相同误比特率下降低平均发射功率。
• HQAM在高阶调制下相比方形和矩形QAM展现出更高的频谱效率和更低的PAPR。
• 研究结果证实，HQAM——尤其是非规则HQAM——可降低给定误比特率所需的信噪比（SNR），从而提升系统可靠性。
• 采用格雷码映射可降低所有QAM类型中的误比特率，但其增益在HQAM中最为显著，这得益于其对称且紧凑的星座图结构。
• HQAM的概率整形被识别为未来提升后5G系统能效的有前景方向。