Joint frequency compensation and angle estimation for array processing and FHMA networks

A joint frequency compensation and angle estimation array processing technique is proposed to combat the broadband jammers and the performance drop during the hop-to-hop transient time in slow frequency hopping multiple access (FHMA) networks. We use the phase shifting technique, which is based on the direction of arrival (DOA) estimation, to modify the data matrices before the hop happens. A good beamforming weight is thus obtained during the transient period and also helps to find the arriving angle at the end of this hop. The DOA is obtained cheaply in the process of power iterations but as accurately as the costly subspace method. By using these techniques, we can rescue the data at the beginning of each dwell time and allow faster hopping to escape from following jammers. The method also has a good property: as the broadband jammers get closer to the desired signal in azimuth, which results in low received signal to interference and noise ratio (SINR), our proposed frequency compensation method works more efficiently in proportion. When jammers are away, the receiving signals will have high enough SINRs for low bit error rate decoding. Thus, we provide a robust approach in the most difficult communication situations.