Searching methods for biometric identification systems: Fundamental limits

We study two-stage search procedures for biometric identification systems in an information-theoretical setting. Our main conclusion is that clustering based on vector-quantization achieves the optimum trade-off between the number of clusters (cluster rate) and the number of individuals within a cluster (refinement rate). The notion of excess rate is introduced, a parameter which relates to the amount of clusters to which the individuals belong. We demonstrate that noisier observation channels lead to larger excess rates.