Patent ID: 8761679

Claim:
A method of shaping signals intended for transmission via a plurality of antennas in a multi-carrier communications system, each signal having a respective frequency spectrum and being for transmission via a respective antenna, each said respective frequency spectrum comprising a plurality of subcarriers, the method comprising: defining, for each antenna, a plurality of possible interference-reducing signals, each interference-reducing signal having a respective plurality of tones, being such as to modify the plurality of subcarriers for the respective antenna, such that respective frequency notch is generated at an interference band in the frequency spectrum of the signals transmitted via the respective antenna, wherein each of said interference-reducing signals comprises at least one AIC edge tone, selecting, for each antenna, a respective interference-reducing signal, the selected signals together defining a group of interference-reducing signals; modifying the frequency spectrum of each antenna with its respective interference-reducing signal; wherein selection of the interference-reducing signal for each antenna is carried out jointly and comprises: minimising a cost function in order to find a group of interference-reducing signals that will together minimize the frequency notch for each antenna, subject to the constraint that the total power emission for the modified spectra at a predetermined frequency remains at or below a pre-determined level.