Joint estimation of multipath parameters from OFDM signals in mobile channels

We study joint estimation of multipath parameters from orthogonal frequency division multiplex signals transmitted over doubly dispersive mobile radio channels. In particular, we study the joint estimation of the complex gain, delay and Doppler offset of each tap of the multipath channel impulse response. For such channels, the frequency domain channel coefficients for an entire packet can be expressed as the superimposition of two-dimensional complex sinusoids. The maximum likelihood estimate requires solution of a multidimensional non-linear least squares problem, which is computationally infeasible in practice. Therefore, we propose a low complexity suboptimal solution based on iterative successive and parallel cancellation. We demonstrate via Monte Carlo simulations that the root mean squared error statistics of our estimator are very close to the Cramer-Rao lower bound of a single two-dimensional sinusoid in Gaussian noise.