Improved Doppler Mitigation Techniques for LTE Uplink Transmission

The third generation partnership project (3GPP) Long Term Evolution (LTE) uses Single-Carrier Frequency-Division Multiple Access (SC-FDMA) technology for uplink (UL) transmission. It has been shown that the SC-FDMA receivers are vulnerable to fast fading channels. In this paper, we first show that, although LTE UL system is based on OFDM, its performance is not sensitive to the inter-carrier-interference (ICI) due to Doppler effect in fast fading channels. The main challenge is to obtain accurate channel estimation with the limited number of time-domain pilot symbols. Next, we propose two improved channel estimation techniques: 1) pilot-aided cubic-Spline interpolator with time-domain noise filtering, 2) decision-directed channel estimation with time-domain noise filtering. We show by simulation that significant performance improvement is achieved by implementing the proposed techniques in both single-antenna LTE UL receivers and multiple-antenna receivers with diversity combining.