On Constellations for Physical Layer Network Coded Two-Way Relaying
Modulation schemes for two-way bidirectional relay network employing two phases: Multiple Access (MA) phase and BroadCast (BC) phase and using physical layer network coding are currently studied intensively. Recently, adaptive modulation schemes using Latin Squares to obtain network coding maps with the denoise and forward protocol have been reported with good end-to-end performance. These schemes work based on avoiding the detrimental effects of distance shortening in the effective receive constellation at the end of the MA phase at the relay. The channel fade states that create such distance shortening called singular fade states, are effectively removed using appropriate Latin squares.