Joint Synchronization and Channel Estimation in Near-Field Distributed Arrays

Near-field communication has attracted wide attention in recent years, where channel estimation is essential for various transmission and reception scheme design, e.g., near-field beam focusing. However, most of the existing research schemes consider the channel under the centralized antenna array, and assume that the clock of the entire array is synchronized. By contrast, the distributed array is capable to provide a comparably wide near-field coverage, while requires fewer antennas than its centralized counterpart, thus effectively reducing the layout cost and energy overhead. In this work, we shall consider the problem of near-field channel estimation in distributed arrays, and consider the practical situation that there may be sampling clock deviation between different arrays. In this case, the conventional least squares channel estimation algorithm fails in eliminating the clock misalignment. Therefore, a compressed sensing based estimation framework is first established where the parameterized channel representation allows channel and clock deviation to be extracted separately. Then, a joint synchronization and channel estimation algorithm is proposed with an iterative channel parameter estimation and clock deviation compensation involved. Simulation results support the effectiveness of the proposed method.