A Novel Pilot Expansion Approach for MIMO Channel Estimation and Tracking

Enabling high practical mobility of MIMO-OFDM systems requires accurate channel estimation under severe frequency and time selective fading channels. Conventional methods rely on non-realistic approximations or result in impractical complexities. In this paper, a new practical training-based MIMO channel estimation scheme is presented. The new pilot bits designed from the ´Paley-Hadamard´ matrix allows exploiting its orthogonal and ´Toeplitz-like´ structures for minimising its pilot length. Additionally, a novel pilot expansion technique is proposed to estimate the length of the channel impulse response, by flexibly extending its pilot length as required to capture the number of multipath existed within the MIMO channel. The proposed pilot expansion enables to deduce the initial channel variation and its Doppler rate, which can be subsequently applied for MIMO channel tracking using decision feedback Kalman filter during the data payload.