Four-dimensional signalling schemes - Application to satellite communications

In satellite communications both polarizations of an electromagnetic wave are used to transmit two separate signals. These two independent signals can be merged to form one dual-polarization, four-dimensional signal. The present article pursues this idea and proposes different signal constellations to be used for four-dimensional signalling in satellite links. Analytical methods and simulations predict an increased power efficiency of these constellations with respect to currently used transmission methods. The cost of this advantage is evaluated considering the limited applicability in non-linear channels. Four-dimensional signalling also implies simultaneous reception on both polarizations. Such a combined reception allows the precision of timing and carrier recovery loops to be doubled. This claim is derived analytically and illustrated by simulating an example case. An experimental transmitter/receiver pair was implemented and used to demonstrate a satellite transmission using a four-dimensional, bi-orthogonal signal in the dualpolarization channel. The experimental verification confirms the presented simulation results.