On the Influence of the non-WSSUS Condition in the Performance of IEEE 802.11-Based Channel Estimators for Vehicular Communications

Measurement campaigns carried out in different propagation scenarios around the world have shown that the statistical properties of vehicular multipath radio channels are strongly non-stationary. However, in spite of its practical relevance, the impact of the channel's non-stationarities on the performance of the vehicular communication systems (VCS) has barely been investigated, and is therefore not fully understood. To increase the knowledge on such important subject, we present in this paper a comparative performance analysis of six channel estimation techniques for VCS based on the IEEE 802.11p Standard, namely, the Least Squares (LS), Spectral-Temporal Averaging (STA), Modified STA (MSTA), Constructed Data Pilots (CDP), Frequency Linear-Averaged Data Pilot (FLDP), and Time-Domain Reliable Frequency-Domain Interpolation (TRFI) estimation techniques. Using a novel simulation framework, we evaluate the estimators' performance in terms of their bit error rate (BER) for the case when the propagation channel fulfills the wide-sense stationary uncorrelated scattering (WSSUS) condition, and also for the case when such condition is not met. The obtained results show that the estimation techniques that apply a joint time-frequency interpolation (STA, FLDP, and TRFI) are considerably more sensible to the channel's non-stationarities than the techniques that only interpolate in the time domain (MSTA and CDP).