Enhancing Circular USTLD Using Signal Space Diversity

Circular constellations have been widely studied for wireless communication systems, as they have a lower peak-to-average power ratio (PAPR) than their rectangular counterparts. This has led to their commercial adoption by standards such as the Digital Video Broadcasting satellite transmission standard DVB-S2X. This study explores the adoption of signal space diversity (SSD) to improve the link reliability of a recently-proposed next-generation transmission scheme, known as uncoded space-time labelling diversity (USTLD), for systems based on circular constellation designs. A theoretical average BER expression for the M-APSK USTLD-SSD system is presented and validated using simulation results. BER performance graphs show that the 16-APSK and 64-APSK USTLD-SSD systems discussed in the paper achieve gains of approximately 2.0 dB and 1.0 dB at a BER of 10
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when compared to their non-SSD variants. The results show that SSD holds comparable benefits for circular constellations as for rectangular constellations. An investigation into the optimization of the SSD rotation angle is also presented. Optimal angles of 47.3°for 16-APSK, and either 28.3°or 61.7 for 64APSK were identified.