An up-to-date and comprehensive text on the rapidly expanding field of fixed and mobile communications, including data networks and packet switched systems. The aim of the book is fourfold: (1) to develop the mathematical theory behind signal processing as used in modern digital communications systems, (2) to extend these theoretical signalling concepts into information links which are robust in the presence of noise and other impairment mechanisms, (3) to investigate how these transmission links can be developed into fixed and mobile data communications systems for voice and video transmission, and (4) to develop queuing theory techniques and explore their development in small and large scale data transmission networks such as ISDN. The material is set in an appropriate historical context, and a substantial number of numerical and practical examples are included in the text.