A Robust Transceiver for Narrow-Band Communications in Presence of Carrier Frequency Offset

We address narrow-band communications in presence of large and time-varying carrier frequency offset (CFO) at the receiver. This is a general assumption which includes the condition due to the Doppler effect where the transmitter and/or receiver are moving with a relative time-varying speed. A robust transceiver system is proposed to dynamically estimate and compensate the CFO. The proposed system is particulary attractive for low data-rate communications (e.g., voice service) where the CFO is significantly larger than the data bandwidth. A two-step carrier recovery scheme is developed with large acquisition range and fast frequency tracking. The proposed method provides accurate CFO estimation with affordable complexity. We also devise a robust frame synchronization scheme to provide accurate timing in presence of CFO. Furthermore, non-coherent detection with soft-decision decoding is employed to provide a low-complexity receiver with acceptable sensitivity. The proposed transceiver design is implemented on FPGA and real-time experiments are conducted on a Xilinx ZC706 evaluation base board along with AD-FMCOMMS3 daughterboard. After validating the experiments compared to the simulation results, the design was optimized for implementation on XC7Z020 and further integrated with the analog front-end on a board with smaller footprint.