Cellular telephone systems 5 Mobile communication systems 3 Wireless communication systems 2 Broadband communication systems 1 Cell phones 1 Code division multiple access 1 Design and construction 1 Dissertations 1 Dissertations, Academic 1 Equipment and supplies 1 Gateways (Computer networks) 1 General Packet Radio Service 1 Global system for mobile communications 1 Instant messaging 1 Interface circuits 1 Network performance (Telecommunication) 1 Personal communication service systems 1 Public key infrastructure (Computer security) 1 Radio circuits 1 Security measures 1 Wireless Application Protocol (Computer network protocol) 1