A Practical Approach to Joint Timing, Frequency Synchronization and Channel Estimation for Concurrent Transmissions in a MANET

In a mobile ad-hoc network (MANET), concurrent transmission enabled via interference alignment or transmit and receive beamforming between K transmitters and K receivers can result in a significant increase in the network's sum throughput. However, to achieve this high sum-throughput each of the K receivers must: 1) determine the presence of its desired transmitter; 2) correct the frequency and timing offset of the desired transmitter; 3) estimate the channel from the desired transmitter; and 4) estimate either the channel from each of the K - 1 interfering transmitters or the covariance matrix of the interferences. In this paper, we address the challenges associated with enabling concurrent links within a MANET. By exploiting the unique properties of Zadoff-Chu (ZC) sequences, we propose a practical mechanism for all receivers to achieve the required synchronization and channel estimations concurrently. We also propose a constant false alarm rate detection algorithm to detect the presence of the ZC sequences in a high-interference environment in the absence of frequency and timing lock. Simulation results verified the great performance of our approach in sequence detection, the carrier offset, timing offset, channel estimate and covariance estimates, in both frequency flat channels and frequency selective channels.