Equalization and space diversity techniques in mobile environments

The development of high-quality digital mobile radio systems has become a major goal in the field of digital communications. The possibility of providing speech and data services free of wire constrictions in different environments is a very attractive proposition, supported by means of the personal communications network (PCN) concept. The aim of the present article is to analyze the behavior of different receiver structures for such systems in order to obtain some clues to be used in designing the next generation of mobile systems. These systems have to provide both low- and high-data-rate services (up to 1 Mb/s) and be efficient in environments where a high density of traffic is generated. Moreover, as the carrier frequencies will range between 1 and 4 GHz, and the vehicle speed can be as high as 400 km/hr (e.g., high-speed trains), large Doppler frequency values must be coped with. Under certain conditions, diversity techniques perform better than equalization techniques in typical mobile radio environments.