Channel estimation for OFDM systems based on a time domain pilot averaging scheme

In modern wireless communications there is an increasing need for higher data rates. Modern Digital TV (DTV), like Digital Video Broadcasting Terrestrial (DVB-T/T2), DVB Handheld (DVB-H), Digital Audio Broadcasting (DAB), 4th Generation (4G) mobile telephony known as Long Term Evolution (LTE) and IEEE 802.11a/b/g/n for wireless LAN (WLAN) are typical applications where high data rates are needed. The adaptation of Orthogonal Division Multiplexing (OFDM), which is a multicarrier modulation, helped to achieve high data rates while the transmission system became more robust against multipath fading, which traditional single carrier systems failed to handle effectively. The OFDM system divides the available bandwidth into a large number of narrow band sub-channels, which have their own respective subcarrier and each one of them can considered as a flat fading channel. In order to have reliable reception of the transmitted data, the knowledge of the channel impulse response is important. In this paper we are focusing on pilot aided channel estimation. A novel channel estimator is proposed to eliminate multipath and noise effects assuming Additive White Gaussian Noise (AWGN) and considering that the channel suffers only from slow fading effects. In this case, the channel can be considered to be invariant in time over an interval of the few last OFDM received symbols. Averaging over the last received OFDM symbols leads to reduced noise at the receiver. The benefits of the proposed estimator are its very simple implementation, its good performance for slowly time-varying channels and its application in devices with limited available memory and computational capabilities. In addition, it can be used for battery saving in handheld devices, due to the reduced complexity.