  The spectrum is a scarce resource and must utilize efficiently, the cognitive
radio is a prospective solution for underutilized spectrum. The spectrum
sensing is a key functionality to alleviate interference of secondary user to
primary. The cognitive radios must detect the existence of the primary user and
vacate the band for the primary immediately if the primary user detected. In
cooperative sensing, every cognitive radio communicates their decision to
fusion center via reporting channel. The reporting channels are not error free,
which results corruption in the secondary's decision or information due to
multipath fading and shadowing. This paper investigates the distributed fuzzy
optimal cooperative spectrum sensing. The data and decision fusion with fuzzy
detection is investigated in this paper. The simulation result shows the
significant improvement in sensing performance over AND, OR and majority rules.
The optimality in spectrum sensing is achieved by the proposed method with 1/3
of total malicious secondary users. The proposed scheme outperforms in the
presence of malicious users.
