Polarization Shift Keying for Wireless Communication

This paper considers polarization shift keying (PolSK) modulation in wireless communication systems. The PolSK has previously been analyzed in additive white Gaussian noise (AWGN) for optical fiber and wireless communications. In our work, analytical results additionally focus on Rayleigh and Rician fading channels. It is shown that the dual-polarized signaling enjoys an ergodic capacity advantage over co-polarized signaling for a sufficiently large Rician K factor and signal-to-noise ratio. Specific PolSK constellations are formulated and analyzed in AWGN and Rayleigh fading channels. We examine the effect of the channel's polarization parameters on symbol error rates and achievable information. Also, considered are detection candidates to exploit statistical and instantaneous channel state information at the receiver. Over-the-air experiments were conducted to validate the principles. At higher modulation orders, uncoded PolSK shows an error rate advantage over unit symbol power constellations such as phase shift keying (PSK) and differential PSK with/without adverse carrier frequency offsets. The PolSK with dual-polarized antennas also outperforms the same modulation technique implemented with spatially separated co-polarized antenna elements in a line-of-sight (LoS) scenario. The proposed maximum likelihood PolSK detectors exploiting non-Gaussian statistics of the noise on the Poincaré sphere are validated to be superior to zero forcing and minimum mean square error equalization for a non-LoS scenario.