Accurate BCJR-based synchronization algorithm for single carrier channels with extremely high order modulations

Microwave transmission is a predominant technology in telecommunication networks. As capacity requirement for mobile networks rises every day, microwave backhauls links are forced to constantly improve their spectral efficiency over limited allocated bandwidths. Moving toward higher order modulation is a cost-efficient solution to increase capacity in bandwidth-limited channels. Complex higher order modulations may be practical if a well-defined, high performance, carrier synchronization algorithm is provided to detect and remove the phase noise from the desired signal. The importance of such a precise carrier recovery algorithm is stressed with the transition from legacy, GaAs VCO frequency sources, to integrated, low-cost CMOS based VCOs that suffer from a significantly elevated phase noise level. Contribution of this paper is proposing a novel carrier synchronization algorithm that handles phase noise challenges effectively and allows complicated extremely high QAMs at an acceptable complexity level. Our proposed algorithm is pilot-aided and employs a BCJR-based sequence estimator to detect fast-varying phase noise symbol-by-symbol. We verify and validate performance of our proposed algorithm on VC707 XILINX board and emulation results confirm zero BER performance for complex modulation orders as high as 4K-QAM.