ABSTRACT
The deployment of cellular systems based on Global System for Mobile Communications and Time Division Multiple Access or Interim Standard is a worldwide success with the standards in operation in, for example, Europe, China, the United States, Australia, South Africa, and large parts of Asia as well as the current buildup of networks for Personal Communications Services services in the United States and most of the South American countries. Frequency hopping means that the carrier frequency is changed among a certain number of allowed frequencies at regular intervals. During a call, the terminals and the base station need to exchange large amounts of information, especially to prepare for the next handover to another cell. In adaptive antenna solutions aimed at increasing system capacity, the conventional sector antennas are replaced by one or several antenna arrays. Instead of transmitting information in the entire sector, the basic principle is to direct narrow beams from the base station toward the mobile station.
