A method of communication using Orthogonal Frequency Division Multiplexing ("OFDM") comprises generating bit streams (b.sub.n.epsilon.(0,1),n=0,1, . . . ,K-1) and the corresponding sets of frequency domain carrier amplitudes (X.sub.O(k) to X.sub.N(k)), where k is the OFDM symbol number, modulated as OFDM symbols to be transmitted from a transmitter. Prefixes are inserted as guard intervals in the sample streams and the OFDM symbols are transmitted from the transmitter to a receiver. The receiver uses information from the prefixes to estimate the Channel Impulse Response (H.sup.(F).sub.D) of the transmission channels and uses the estimated Channel Impulse Response (H.sup.(F).sub.D) to demodulate the bit streams in the signals received. The prefixes (.alpha..sub.k.c.sub.o to .alpha..sub.k.c.sub.D-1) are deterministic and are known to the receiver as well as to the transmitter. Preferably, the prefixes (.alpha..sub.k.c.sub.o to .alpha..sub.k.c.sub.D-1) comprise a vector (P.sub.D) that is common to said symbols multiplied by at least one weighting factor (.alpha..sub.k). The weighting factor (.alpha..sub.k) preferably differs from one symbol to another but the elements of a given vector (P.sub.D) are multiplied by the same weighting factor. Preferably, the weighting factor (.alpha..sub.k) has a complex pseudo-random value.