Frequency offset compensation and carrier phase recovery for differentially encoded 16-qam vector signal in a 60-GHz RoF system

Abstract

Differentially encoding and frequency offset compensating for a 16-quadrature amplitude modulation (16-QAM) vector signal in 60-GHz millimeter-wave radio-over-fiber (RoF) systems are experimentally investigated. The fourfold phase ambiguity issue in a nondata-aided signal communication transmission system with conventional square 16-QAM constellations is successfully tackled based on the differentially encoding scheme. Experimental results show that frequency offset compensation and carrier phase recovery are simultaneously achieved by utilizing the decision-directed carrier phase recovery algorithm. Up to ∼±1.3 ×10-3 frequency offset times symbol rate product δf Ts is well compensated at the given bit-error-ratio (BER) value of ∼10-3. ©2013 IEEE.