Joint Channel and Doppler Spread Estimation over Time-Varying Flat-Fading Channels

Abstract

In time-varying flat-fading environments, time domain channel correlations are required for accurate channel estimation and interpolation. However, the correlation property, which depends on the Doppler spread, is hard to be extracted from corrupted channel responses within a short channel estimation interval. In this work, based on an approximate channel model via the Taylor expansion, we propose a joint channel and Doppler spread estimation scheme over timevarying flat-fading channels. It employs the expectationmaximization (EM) algorithm to iteratively attain the maximumlikelihood (ML) channel and Doppler spread estimates. Simulation results show that the proposed scheme achieves accurate performance of both channel estimation and Doppler spread estimation within a short estimation interval.

Low-complexity iterative Doppler spread and channel estimation over Rayleigh fading channels

“…As in [1]- [4], [10], we consider flat Rayleigh fading channels. Here, we mention that, if we adopt the tap-bytap channel estimation strategy in [8], the proposed approach can be readily extended to the case of frequency selective channels.…”

“…It has been revealed in [14] and [15] that α in (17) is not optimal for channel estimation in terms of mean square Doppler spread estimation only SC [4] O((L + 1)K) SML [1] O(K 2 ) ML [1] O(K 3 ) Joint channel and Doppler spread estimation Proposed O(20K) per iter EM in [11] O(17K) per iter EM in [10] O((N + 1) 2 K) per iter error (MSE). The work in [15] gave an approximated closedform expression for the optimal AR(1) model coefficient to minimize the MSE of channel estimation…”

“…The mutual dependence of Doppler spread estimation and channel estimation motivated joint Doppler spread and channel estimation to achieve better performance. To this end, an expectation-maximization (EM) based approach [10] was proposed by using a Taylor series expansion based channel model. However, the complexity of this approach can be a concern.…”

“…Alternatively, based on an autoregressive (AR) model for the fading channel, an EM based joint channel and AR model coefficients estimation scheme was proposed in [11] 1 , where the Doppler spread can be extracted from the estimated AR coefficients. The complexity of this approach is much lower than that of [10].…”

“…In addition, the Doppler spread estimate is used to optimize the AR(1) channel model coefficients to further enhance the channel estimation performance. Compared to the EM approach in [10], the proposed approach delivers similar or better performance with significantly lower complexity. Compared to the EM approach in [11], the proposed approach has similar complexity per iteration, but the convergence of the proposed approach is much faster than that in [11], and the performance of the proposed approach is better than that of [11].…”