Windowed orthogonal division multiplexing for spectrum agile radios

An orthogonal frequency division multiplex transmitter, comprising:

• a modulator (240, 410) adapted to provide P frequency carriers, to turn off M frequency carriers of the P frequency carriers, to receive data, and to modulate the data only onto a remaining, N≦P−M frequency carriers to produce N mutually orthogonal modulated frequency carriers;
• means (250, 440/450) for combining the N mutually orthogonal modulated frequency signals into an orthogonal frequency division multiplex signal;
• a transmission window (260, 460) adapted to apply a window function to the orthogonal frequency division multiplex signal to produce a windowed orthogonal frequency division multiplex signal;
• and a transmitter (270, 480) transmitting the windowed orthogonal frequency division multiplex signal, wherein the M turned-off frequency carriers are consecutively arranged within the frequency band so as to create a notch in the frequency spectrum of the windowed orthogonal frequency division multiplex signal.

A method of transmitting data, comprising:

• modulating data onto a plurality of frequency carriers to produce a plurality of mutually orthogonal modulated frequency signals;
• combining the mutually orthogonal modulated frequency signals into an orthogonal frequency division multiplex signal;
• multiplying the orthogonal frequency division multiplex signal by a transmission windowing function to produce a windowed orthogonal frequency division multiplex signal;
• and transmitting the windowed orthogonal frequency division multiplex signal, wherein the windowed orthogonal frequency division multiplex signal includes a first set of the frequency carriers uniformly spaced apart from each other in frequency by a spacing Δf, and a second set of the frequency carriers spaced apart from each other in frequency by the same spacing Δf, and there is a notch of at least 2Δf between the first set of frequency carriers and the second set of frequency carriers.