Abstract: The present invention relates to a distributed pilot scheme especially suited for single frequency networks used, for instance, for broadcasting digital TV. In current digital TV standards, e.g. DVB-T, the transmitters in the SFN transmit the exact same signal in the same frequency and at the same time. As a consequence the channel seen by the receiver is the channel created by the SFN characterized by a very long delay spread, which can be challenging to estimate. According to the present invention different, preferably orthogonal, pilot sequences are assigned to different transmitters in the same SFN so that the receiver can estimate the propagation channels from each transmitter to itself independently.

Abstract: A method of synchronizing multi-carrier systems is provided, wherein the method comprises inserting a predefined frequency domain signal into a signal on a transmitter side of a multi-carrier system and multi-carrier modulating the signal. Furthermore, the method comprises transmitting the multi-carrier modulated signal via a carrier channel to a receiving side of the multi-carrier system, and synchronizing the multi-carrier modulated signal by using the predefined frequency domain signal portion of the multi-carrier modulated signal.

Abstract: In a receiver for processing OFDM encoded signals, wherein the OFDM encoded digital signals are transmitted by means of a symbol in each of subcarrier frequency channels, with at least some of said subcarriers containing user data symbols, an initial estimate of a channel frequency response is formed from magnitudes of user data symbols received in those subcarriers. Then, a correlation function of a channel impulse response is estimated by performing an inverse Fourier transform on the initial estimate of the channel frequency response, and the length of the channel impulse response is estimated by examining peaks in the estimated correlation function of the channel impulse response.

Abstract: In an OFDM mobile communications system, an algorithm for forming a preliminary estimate of the channel on pilot subcarriers is carried out. Based on this preliminary estimate, a channel property is estimated. This channel property is then used to decide whether to enter a mobile receiver mode or a stationary receiver mode. For example, in the mobile mode channel estimation is performed using only pilot symbols from the current symbol period, while in the static mode channel estimation is performed using pilot symbols from the current symbol period and pilot symbols from other symbol periods.