10.1.1 Historical Review

The ultimate objective of communications is to enable anyone to communicate instantly with anyone else from anywhere. This can be achieved only by mobile radio communications. Mobile radio communications started with the early experiments of radio pioneers towards the end of the nineteenth century. A wellknown historical event that clearly showed the importance of mobile radio communications was the distress of the Titanic in 1912. In these early mobile radio communications, radio telegraph was dominant, in which Morse-coded on-off keying was used as the modulation scheme. It can, therefore, be seen that mobile radio communications started with digital technology. Radio telegraph was extensively used for ship-to-shore transmission during World War I. However, after World War I radio telephone, or analog voice transmission, began to play an important role along with radio telegraph, or digital data transmission.

This dichotomy of digital for telegraph and analog for telephone continued until the mid-1970s when digital voice transmission became more pervasive. Since the advent of mobile radio telegraph, various technological advances have brought the appearance of many other mobile radio communications systems, such as radio telephone, radio paging, emergency dispatch, navigation control, status reporting, and so on [Bowers, 10.1]. Demand for mobile radio communication services has steadily increased. Current mobile radio communication systems are limited to services for specialized groups...