Abstract: The invention relates to the emulation of a radio channel between moving transmitters and receivers with antennas. The relative position and relative movement and also the environment are used to ascertain propagation paths (P0, P1, . . . , PP?1) running between the antennas, for which propagation paths a damping factor (?p), a delay a delay (?p) and a Doppler frequency (vp) are separately ascertained. For each propagation path (P0, P1, . . . , PP?1), table lookup for the delay and the Doppler frequency is used to produce a respective path matrix (?p) that is weighted with the respective damping (?p) of the propagation path (P0, P1, . . . , PP?1), and all the path matrices are summed. The summed matrix (?) produced in this way is taken as a stating point for using a linear transformation to ascertain a transfer matrix (Y), the transformation reducing the dimension of the transfer matrix (Y) in comparison with the summed matrix (?) which corresponds to the coefficient vector (??p) of the delay.

Abstract: A method of channel estimation in an OFDM transmission system having a transmitter and a receiver according to standard IEEE 802.11x. The method includes: in the transmitter, setting an identifier in a reserved bits section of the header following the preamble in a physical layer frame; attaching a postamble at the end of said frame without altering the length information in the header; transmitting said frame over the channel, in the receiver, receiving a frame over the channel and checking a reserved bits section in the header of the received frame for the presence of the identifier; and if the identifier is detected, using the postamble and the preamble of the received frame to estimate the channel.