Low Complexity Iterative Carrier Synchronization Algorithms for Wireless Sensor Networks

Due to low power and low cost in wireless sensor networks, sensor node need to quicldy complete the carrier synchronization and decoding at very low signal-to-noise ratio. Iterative carrier synchronization algorithms with low rate error correction coding can operate at very low signal-to-noise ratio. However, they are often plagued by their high implementation complexity, especially those based on the maximum log-likelihood function (LLF). In this paper, a synchronization algorithm is proposed to reduce the implementation complexity. Its closed-form expressions are explicitly provided, which are derived by simplifying Maclaurin series of LLF. In order to further reduce the complexity of iterative synchronization, simplified soft information is also used in the proposed algorithms The performance of the proposed method is evaluated in practical systems by considering a joint pilot and code-aided synchronization scenario with large frequency and phase offsets. Simulation results obtained by employing LDPC-Hadamard codes with rate 1/12 indicate that at low signal-noise ratio (SNR) region, the performance of the proposed algorithms is only 0.1 dB away from the ideal synchronization.