Patent ID: 7110479

Claim:
A method for determining the level of interferers and the level of a useful signal in a spectral window of a communications channel between a transmitting station and a receiving station comprising: generating a predefined baseband waveform with a frequency approximately equal to the Nyquist frequency of the spectral window at the transmitting station; upconverting and transmitting the waveform at the transmitting station; receiving, downconverting, and interpreting the waveform at the receiving station to determine the level of interferers; generating the useful signal at the transmitting station; upconverting and transmitting several repetitions of the useful signal; receiving, downconverting, and interpreting the useful signal at the receiving station to determine the level of the useful signal; wherein said waveform comprises at least one harmonic signal; wherein said harmonic signal comprises a predefined number of repetitions of a sine wave with predefined magnitude and frequency; wherein said frequency of the harmonic signal is approximately equal to the Nyquist frequency of the spectral window; wherein the magnitude of the harmonic signal is approximately equal to the magnitude of the useful signal; wherein the communications channel is characterized by a maximum delay; wherein said maximum delay is measured; wherein measuring said maximum delay comprises sending a pulse from the transmitting station to the receiving station; wherein establishing the duration of time intervals between successive harmonic signals in the waveform, wherein the duration is set not smaller than the maximum delay; wherein interpreting the waveform at the receiving station comprises: sampling and filtering the waveform; squaring the waveform and averaging the result of the squaring with a time window of a predefined size; determining the minimum of the result of the averaging over the total duration of the waveform; and equating the level of interferers to the value of the minimum; wherein the waveform comprises a sequence of harmonic signals with a frequency approximately equal to the Nyquist frequency of the spectral window and phase values evenly distributed in the interval (0, 2π) radians; wherein said waveform is determined in accordance with the following relationships: s ( t )= A *sin(π* f*t +(2*π* n/N )* int ( f*t/n )), where f represents the sampling rate; N represents the total number of samples in the waveform; n represents the number of samples in the time window used in the averaging plus the number of samples in a time interval equal to the maximum delay; A represents the amplitude of the waveform; int(x) is the maximum integer function to generate the maximum integer not exceeding a given real number x; and t represents the time.