Patent ID: 8116278

Claim:
A method executed by a network access device comprising: transforming samples taken from a time domain signal to a frequency domain by a discrete Fourier transform; assigning the transformed samples to frequency subcarriers and thereafter transforming the samples to the time domain; and transmitting the samples that were transformed to the time domain in the assigned subcarriers; wherein: assigning the samples to the frequency subcarriers comprises assigning coefficients of the discrete Fourier transform to the sub-carriers which are orthogonal frequency division multiple access subcarriers on which the samples are transmitted; the samples taken from the time domain signal comprise N samples per symbol interval T seconds over an observation window of length JT that are represented as a sample vector of size JN on which the discrete Fourier transform is executed, where N and J are each positive integers greater than one and the coefficients are assigned to JN distinct subcarriers; and the transmitting comprises transmitting the samples in the JN distinct subcarriers to a first portable device operating in a cognitive radio environment and transmitting one of further samples or data to at least one other portable radio device in subcarriers other than the JN distinct subcarriers; the method further comprising, after assigning the coefficients, adding pilot symbols, converting the pilot symbols and the sample vector of size JN and the further samples or data to the time domain using an M-point inverse discrete Fourier transform, thereafter converting to analog, in which the transmitting comprises transmitting the analog signal over M subcarriers, wherein M is greater than JN.