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Packet radio had its origins in ham radio in the 1970s. It was originated as a way to use radio frequencies to transmit digital data. Since its inception for radio applications, it has become indispensable for operation of some items, such as wireless routers, police and taxi radio systems, and analog cellular phone networks.
Early experiments with packet radio were attempts to arbitrate and control multiple users on a shared communications channel. By the mid-70s, these experiments had evolved into carrier sense multiple access (CSMA) protocols, which were the precursors to Local Area Network (LAN) Ethernet™ settings. By 1978, the Federal Communications Commission (FCC) and other agencies had given permission for ham radio operators to transmit American Standard Code for Information Interchange (ASCII) via radio. This led to early experiments using ham radio networks in the San Francisco area to verify packet data between mobile and fixed stations.
For the day, the technology was quite advanced, including direct sequence spread spectrum (DSSS) modulation and forward error control (FEC) technology to establish data channels. These experiments involved the Advanced Research Projects Agency Network (ARPANET), which was a United States Department of Defense predecessor to the Internet, and shuttled information between ARPANET, the packet radio network, and satellite packet systems for an early version of internetworking. Subsequently, these advances helped establish some of the technology behind modern Internet Protocols (IP).
A typical early packet radio setup for the ham operator would consist of a keyboard, terminal, modem, transceiver with antenna, and terminal node controller. The computer's role would be to control the radio channel, format and packet data, and manage network connections. Technological problems had to be overcome, since ham radio was designed for voice rather than data transmission. This primitive hybrid of the Internet and ham radio might also include a simple bulletin board messaging system or other functions. In modern times, packet radio via keyboard is more common than voice transmission for many ham operators.
From these roots, packet radio and packet switching technology evolved into the systems for cellular phones, digital walkie-talkies, wireless routers, and countless other devices. As it pertains to amateur radio, packet radio is still a key component of the Winlink 2000 (WL2K) system — a network put together by ham operators to deliver e-mail, text, weather info, and other data via radio frequency. Winlink has been invaluable in natural disasters and other events where conventional telecommunications were out of service.