Improved hard-decision fusion algorithm against SSDF in cognitive radio networks

In the existing cooperative spectrum sensing, fusion centers (FC) fuses these data received from cognitive users (CUs) without screening, which provides more opportunities for malicious users (MUs) hiding in the legal users to launch spectrum sensing data falsification (SSDF) attacks, SSDF easily mislead the FC to make incorrect decisions, resulting in reducing accuracy of spectrum detection. So, in order to deal with SSDF, an improved hard-decision fusion algorithm was proposed, which adopts the mechanism that FC just fuses parts of results reported by CUs preferentially and the remaining users take supplement for decision in order to reduce the opportunities for MUs to take participate in the cooperation. Besides, through comparing the CUs´ reputations updated according to their history behaviors, FC selects reliable users´ data to fuse with the object of ensuring the reliability of the data. Simulation also verified the effectiveness of the improved algorithm proposed on defending against SSDF attacks.