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Adaptive modulation and coding (AMC) is widely employed in modern wirelesscommunication systems to improve the transmission efficiency by adjusting thetransmission rate according to the channel conditions. Thus, AMC can providevery efficient use of channel resources especially over fading channels.Quadrature Amplitude Modulation (QAM) is an ef- ficient and widely employeddigital modulation technique. It typically employs a rectangular signalconstellation. Therefore the decision regions of the constellation are squarepartitions of the two-dimensional signal space. However, it is well known thathexagons rather than squares provide the most compact regular tiling in twodimensions. A compact tiling means a dense packing of the constellation pointsand thus more energy efficient data transmission. Hexagonal modulation can bedifficult to implement because it does not fit well with the usual power-of-two symbol sizes employed with binary data. To overcome this problem,non-binary coding is combined with hexagonal modulation in this paper toprovide a system which is compatible with binary data. The feasibility andefficiency are evaluated using a software-defined radio (SDR) based prototype.Extensive simulation results are presented which show that this approach canprovide improved energy efficiency and spectrum utilization in wirelesscommunication systems.

Beyond Powers of Two: Hexagonal Modulation and Non-Binary Coding for Wireless Communication Systems