Covariance Based Listen Before Transmit for HF 3G-ALE

Listen before transmit(IBT) is one of key techniques in the third generation HF automatic link establishment(3G-ALE).Several signal detection methods are discussed taking account of the im-plement of LBT in HF communication systems.Then a detection method based on the sample covariance matrix of received signals is proposed.This method does not need any information of the signal,channel and noise power as a priori,and can be well applied to the LBT techniques which require parallel detec-tion of many different types of modulations as well as short observation period.Extensive computer simu-lations are given.Compare to the conventional method,the performance of detection is improved about 6 dB in the AWGN channel.