EM-based joint time delay and channel estimation for cooperative communications

In this paper, we study joint time delay and channel estimation for a cooperative communication system with amplify-and-forward (AF) relaying. The proposed joint estimator is based on Expectation-Maximization (EM) algorithm and presents a low-complexity solution for iterative maximum likelihood (ML) estimation. Our simulation results demonstrate that the performance of proposed cooperative system lies within 0.5dB of the genie bound (i.e., perfect knowledge of time delays and fading coefficients) at a target bit error rate of 10 -4 assuming the deployment of 4 pilot symbols and 3 iterations.