New bounds on binary identifying codes

The original motivation for identifying codes comes from fault diagnosis in multiprocessor systems. Currently, the subject forms a topic of its own with several possible applications, for example, to sensor networks. In this paper, we concentrate on identification in binary Hamming spaces. We give a new lower bound on the cardinality of r-identifying codes when r>=2. Moreover, by a computational method, we show that M"1(6)=19. It is also shown, using a non-constructive approach, that there exist asymptotically good (r,@?@?)-identifying codes for fixed @?>=2. In order to construct (r,@?@?)-identifying codes, we prove that a direct sum of r codes that are (1,@?@?)-identifying is an (r,@?@?)-identifying code for @?>=2.