R. David Koilpillai

Doppler spread estimation in mobile radio systems

In this letter, Doppler spread estimation in digital mobile radio systems is described. A maximum-likelihood approach is derived, and used to develop suboptimal approaches with lower complexity. The proposed algorithms rely on periodic channel estimation and can be used in both TDMA and CDMA systems.

Doppler spread estimation for wireless mobile radio systems

In this paper, efficient and practical approaches for Doppler spread estimation in wireless mobile radio systems are described. A hypothesis-testing approach, given the channel autocorrelation estimate, is utilized for Doppler spread estimation. The channel autocorrelation is estimated slot-by-slot using the knowledge of the channel estimates over the known fields of a TDMA burst, and averaged over several slots to reduce the effect of noise. In practical systems, the Doppler spread must be estimated in the presence of frequency offsets between the transmitter and the receiver. Hence, an algorithm that decouples Doppler spread estimation from automatic frequency compensation (AFC) is also presented. In addition to the mean estimation error performance, the convergence and the tracking ability of the algorithms are evaluated via simulation using ANSI 136 Rev-B modulation and signal transmission format.

Optimal and suboptimal algorithms for Doppler spread estimation in mobile radio systems

Doppler spread estimation in digital mobile radio systems is described. An optimal approach (in the sense of maximum likelihood estimation) for Doppler spread estimation is derived. Suboptimal approaches, with trading off in performance and complexity, are developed from the optimal algorithm. In practical systems, the Doppler spread must be estimated in the presence of frequency offsets between the transmitter and the receiver. Hence, an algorithm that decouples Doppler estimation from automatic frequency compensation (AFC) is also presented. The proposed algorithms rely on channel estimation over the known fields of a TDMA burst. Such algorithms can be applied easily to systems with pilot symbols or a pilot channel.