Factors affecting the speed and security of a digital data transmission system

THE MAXIMUM speed and security of a telecommunications system is limited by the bandwidth of the system. Bandwidth B is related to rise time tr of the received pulse by trB = K where K is a constant. As the bit duration tb decreases to within one or two multiples of tr, the security of any given binary threshold decreases or may cease to exist. Security of transmission under conditions of link perturbation and the closeness with which tb may be allowed to approach tr will be described in terms of the intrinsic security of the carrier methods and equipment, the intrinsic security of various binary decision criteria, and the error-detection and error-correction capabilities of a coding system.