Thesis - Instituto de Telecomunicações

132 CHAPTER 6. APPLICATIONS AND RESULTSFigure 6.15: Histogram of feature vectors length for the ECG biometric system.n EER (in %) std1 4.8 0.23 3.4 0.35 2.4 0.47 2.2 0.39 1.7 0.2Table 6.3: Mean equal error rate and respective standard deviation for different numbersof training and testing samples n. Each sample corresponds to 10 heart beats.In the case of the ECG signal we decide on accepting or rejecting a user based on ascore function, computed as the minimum Euclidean distance of the testing sample to thetraining vector.When we have a sequence of testing samples we combine the individual result via thesum rule.6.3.3 Authentication ResultsWe observe the evolution of the sequential classifier EER in figure 6.16. The equal errorrate, is decreasing from a initial EER ≈ 4.8% to ≈ 1.7%. Table 6.3 presents some of theresults.