On blind sequential detection of misbehaving relay

Consider a three-node cooperative system where the relay may misbehave for selfish or adversarial reasons. We propose a blind sequential detection to determine relay's misbehavior with the least number of observations under requirement of detection performance. The likelihood function conditioning on the detected data symbols is derived here for three types of misbehaviors. The destination accumulates log-likelihood ratio (LLR) of current received symbols, and completes detection until the probabilities of false alarm and miss are both guaranteed below required thresholds. Simulation results show that the proposed scheme demands only small number of received symbols at SNR greater than 10dB.