Performance Analysis of Pilot Patterns for Channel Estimation for OFDM Systems in High-Speed Trains Scenarios

Abstract

In the last decade, different wireless technologies have been deployed in the railway infrastructure to support critical and non-critical services. Due to the tangible benefits that they have provided to both rail operators and users, different communication technologies are currently being designed or adapted to be deployed in this environment. In this sense, this paper proposes to adapt the IEEE802.11p protocol to be used in these environments, characterized by high speeds. It presents a comb-type pilot based channel estimation scheme adapted to the IEEE802.11p frame. In this proposal, the number of pilot carriers is increased (from four to six or eight) and distributed almost uniformly, without increasing the nominal bandwidth of the signal. In addition, different interpolation techniques are used to obtain the channel response for each OFDM transmitted symbol. The performance improvement is quantified through the effective bit rate and the BER (Bit Error Rate) in relation to the standard. The results show that the proposed estimation method has better performance than the standard estimation method for Doppler frequencies above 400 Hz (77 km/h). This enhancement is translated into a throughput gain in comparison to the standard, e.g 2.1 Mbps throughput gain for 600 Hz Doppler shift. Besides, its performance curves are more stable (lower fluctuation) at the increase of the Doppler shift.