Chapter 1. Introduction to Wireless
Wireless networks use radio waves to move data
without wires and they have been around in one form or another for
decades. Teletype, or telex, systems were
established worldwide in the early 1920s. These systems used copper
lines to connect two or more teletype machines. Government
investments in military radios lead to innovations in radio;
teletype over radio (TOR), or
radioteletype,
replaced many teletype systems, particularly in third-world countries
that lacked copper-wire infrastructures. In many parts of the world,
TOR is still used as the primary communications medium for
governments. TOR uses the high
frequency (HF) radio band. We'll
cover the types of radio bands later in this chapter. In 1970, Norm Abramson, a professor of engineering at the
University of Hawaii, developed a radio-based communications system
known as ALOHANET. This was the world's
first wireless
packet-switched network, which allows multiple
devices to transmit and receive data simultaneously. The research
behind ALOHANET was
used by Bob Metcalfe to develop the
Ethernet standard for wired
networking. Presently, there are many types of wireless networks in use around
the world. The
802.11 protocol set, popularly
known as Wi-Fi, includes wireless network standards that allow data
transmission up to a theoretical 54 Mbps. The Global
Positioning System (GPS) uses a
wireless connection from a receiver to a series of satellites to fix
a location precisely on the planet. There are several wireless
networking standards in the mobile-phone world, including
General Packet Radio
Service (GPRS) and
Code Division
Multiple Access (CDMA) 1xRTT (1x Radio Transmission Technology).
Subsequent chapters will discuss all of these in detail. |