In order to make reasonable use of the spectrum in ad hoc cognitive radio networks

the CR users must judge whether the primary user exists accurately to prevent the PUE attack launched by malicious attackers.The article presents an algorithm based on the DOA estimation with the condition of systematic errors existing.The simulation results show that the scheme can be good to do the judgment of users.The paper also presents a new collaborative weighted detection strategy when the channel environment is harsh and has a low SNR using the environmental factor.In the strategy

each of the CR users can make the final judgment of the primary user signal.It solves the problem of excessive concentration of power in previous collaboration strategies.