A Survey on Higher-Order QAM Constellations: Technical Challenges, Recent Advances, and Future Trends

Communication system's performance is sensitive to bandwidth, power, cost etc. There have been various solutions improve the performance, out of them, one fundamental over years design optimum modulation schemes. As research on beyond 5G heats up, we survey and explore power bandwidth efficient schemes for next generation communication systems in details. In existing literature, initially square quadrature amplitude (SQAM) was considered. However, only constellations are not sufficient varying channel conditions rate requirements, thus, odd 2 were introduced. For constellations, rectangular QAM (RQAM) most commonly used. RQAM a good choice modified cross (XQAM) constellation preferred which provides improved efficiency due its energy two dimensional (2D) structure. The increasing demand high data-rates has further encouraged towards more compact 2D leads hexagonal lattice structure based (HQAM) constellations. this work, discussed detailed study star QAM, XQAM, HQAM presented. Generation, peak average energies, peak-to-average-power ratio, symbol-error-rate, decision boundaries, bit mapping, Gray code penalty, bit-error-rate different orders Finally, comparative presented justifies supremacy other wireless potential scheme future standards.