Pseudo-random sequence padding in an OFDM modulation system

A method of estimating timing of at least one of the beginning and the end of a transmitted signal segment in the presence of time delay in a signal transmission channel in an OFDM system, the method comprising:

• providing a set of pseudo-random signal m-sequences PN(t;k) (k=1, . . . , K;
• K≧1) for which a convolution signal formed from any two sequences satisfies PN(t;i)*PN(t+Δt;j)=δ(Δt)·δ(i,j), where i and j are index numbers identifying the two sequences, t is a time variable, δ(Δt) is a modified delta function with infinitesimal width Δt1 (δ(Δt)=0 for |Δt|>Δt1) and δ(i,j)=0 unless i=j;
• appending a selected sequence PN(t;k) from the set of pseudo-random signal m-sequences PN(t;k) to at least one signal frame to be transmitted to form a padded signal frame;
• transmitting at least one padded signal frame as the transmitted signal through the signal transmission channel in which the transmitted signal may be received with an uncontrollable time delay Δt(delay);
• receiving a received signal Rc(t) of the transmitted signal associated with the at least one padded signal frame being transmitted and forming a composite signal, denoted as Rc(t;
• Δt;comp), given as:
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• where Δt is a selected time increment and k1 and k2 satisfy 1≦k1≦k2≦K;
• forming a remainder signal, denoted as Rc(t;rem), where Rc(t;rem)=Rc(t)−Rc(t;Δt;comp);
• and
• determining from the remainder signal at least one time at which said selected sequence PN(t;k) (k=k1, k1+1, . . . , k2) associated with said at least one padded signal frame begins in the received signal Rc(t).