The article focuses on emerging mobile and wireless networks. Mobile and wireless networks are experiencing significant progress in the form of wireless local area networks (WLAN), satellite-based networks, Wireless Local Loops, mobile Internet Protocol and wireless Asynchronous Transfer Mode. Wireless local area networks are designed to provide coverage in a small area. The main attraction is the flexibility and mobility supported by a wireless LAN. Unlike cellular networks where a frequency is allocated, users in WLAN have to share frequencies, which may lead to collisions. It is difficult to detect collisions in WLAN because the power levels of signals coming to a mobile user may be different and a station may not detect a potential competitor for the medium. Geosynchronous satellites are in wide use providing broadcasting services, long distance and international phone services, paging services, and data networking services. With advances in technologies, it is becoming possible to provide mobile services using satellites. Mobile and wireless networks present many challenges to application, hardware, software and network designers and implementers.