LLR-based hybrid relaying as a countermeasure against an impulsive noise jamming attack

A hybrid relaying protocol is proposed in this paper for cognitive radio networks (CRNs) under random jamming attacks of impulsive noise nature. The protocol switches between amplify-and-forward, decode-and-forward or a no-send state depending on the calculated value of the log-likelihood ratio (LLR) of the received signal at each of the randomly distributed cognitive radio (CR) nodes. A LLR-based spectrum sensing scheme is also proposed. Channel estimation is carried out using the sign algorithm (SA). Performance is evaluated in terms of BER and normalized mean squared (MSE) error curves.