Robust channel estimation for broadband satellite communications

In this paper we study robust channel estimation techniques for supporting broadband satellite communications in OFDM (Orthogonal Frequency Division Multiplexing) based systems. The study considers the use of QPSK (Quadrature Phase-Shift Keying) digital modulation scheme. To achieve reliable coherent detection two different pilot symbols transmission methods are evaluated and compared: data multiplexed pilots and implicit pilots. The method of implicit pilots allows coherent detection at the receiver while avoiding spectral degradation associated with the data multiplexed pilots´ technique but results in mutual interference between pilots and data. Since the interference levels between data and pilots might be very high, we propose an iterative receiver.