Mobile speed estimation using diversity combining in fading channels

We consider the problem of mobile speed estimation using two common diversity schemes, selection combining (SC) and maximal ratio combining (MRC). We derive three new estimators, which rely on the inphase zero crossing rate, inphase rate of maxima, and the instantaneous frequency zero crossing rate of the output of SC. We also propose two estimators which work based on the level crossing rates of the envelopes at the output of SC and MRC. The performances of all these estimators are investigated in realistic noisy environments with different kinds of scattering and different numbers of diversity branches. Our simulation results reveal that a two-branch envelope level crossing rate estimator provides a performance gain. In terms of the implementation complexity, the SC-based estimator is superior to MRC, as it does not need channel estimation.