In Physical-Layer networkcoding (PNC), the symbol detected at the relay node in two-way relay channels (TWRC) is the superposition of the symbols transmitted by the sinks. We refer to these symbols as pnc-symbols. In...
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ISBN:
(纸本)9781424492688
In Physical-Layer networkcoding (PNC), the symbol detected at the relay node in two-way relay channels (TWRC) is the superposition of the symbols transmitted by the sinks. We refer to these symbols as pnc-symbols. In traditional modulation constellations such as Quadrature Amplitude Modulation (QAM) and Phase Shift Keying (PSK), the demodulator may fail to optimally identify pnc-symbols formed from pairs of central symmetrical symbols (CSS) because their superposition may yield to the same output point (i.e., to the same decision region) due to the presence of a central symmetry point. In order to avoid such ambiguity, we propose a non Central Symmetry constellation (CSC), called 4-TRAQAM, which is used by the sinks such that the decision regions of the output points are pair-wise disjoint. We show that the sinks in the PNC-based TWRC can be considered as a single transmitter using the same modulation with a higher order (10-TRAQAM). We further derive the average energy of pnc-symbols and the error probability of the derived PNC-based TWRC modulation, and we show that the 4-TRAQAM provides the best trade-off between the average energy and the disjointness of the decision regions, compared to other used QAM.
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