Low-Complexity Joint Time Synchronization and Channel Estimation for OFDM-Based PLC Systems

Orthogonal frequency division multiplexing (OFDM) plays an important role in powerline communications (PLC), due to its robustness to frequency-selective channels. Nevertheless, it also presents some persistent drawbacks over the years, some of them related to the synchronization and channel estimation and equalization, whose features are a key aspect in the global performance of the medium access technique. This work presents a novel timing synchronization and channel estimation method for OFDM under PLC conditions. Typical joint fine synchronization and channel estimation techniques for OFDM make use of the cross correlation from a transmitted pilot symbol with suitable correlation properties. However, these proposals often present the drawback of having a high computational load, sometimes reducing the feasibility of later practical implementations. Our proposal takes advantage of the properties of complementary pairs of sequences, as they provide good correlation properties, as well as efficient algorithms for generation and correlation. Furthermore, some practical thresholds for synchronization are derived, which adapt the system to the current signal-to-noise ratio and channel conditions. Finally, all the theoretical proposals have been validated by simulation, including an analysis of the performance achieved.