Estimation of the velocity of mobile units in micro-cellular systems using the instantaneous frequency of the received signals

Handover processes in micro-cellular systems are more involved than in cellular systems. In particular, micro-cellular systems suffer from the so-called corner effect where line-of-sight between the mobile station and the base station is suddenly lost when the mobile rounds a corner. As a result, the received signal drops rapidly below threshold level and the call can be lost. It has been shown that, if an accurate estimation of the velocity of the mobile unit is available, the call can be rescued by applying short temporal window averaging on the received signal. Current methods for estimating the velocity of mobile units in micro-cellular systems are based on the level crossing rate of the envelope of the received signals. This paper presents a new velocity estimator based on the instantaneous frequency of the received signal. The performance of the proposed estimator is shown to be superior to that of the level crossing rate method. The average relative error of the proposed estimator is down to below 8% whereas that of the LCR method reaches 14%.