Editing Packet radio (section)

=== Aloha and PRNET ===

Since radio [[Telecommunication circuit|circuits]] inherently possess a [[Broadcasting (computing)|broadcast]] [[network topology]] (i.e., many or all [[Node (networking)|nodes]] are connected to the [[Telecommunications network|network]] simultaneously), one of the first technical challenges faced in the implementation of packet radio networks was a means to control access to a shared [[communication channel]] to avoid collisions of signals. Professor [[Norman Abramson]] of the [[University of Hawaii]] led development of a packet radio network known as [[ALOHAnet]] and performed a number of experiments beginning in the 1970s to develop methods to arbitrate access to a shared radio channel by network nodes. This system operated on [[UHF]] frequencies at 9,600 baud. From this work the [[Aloha protocol|Aloha]] multiple access protocol was derived. Subsequent enhancements in channel access techniques made by [[Leonard Kleinrock]] ''et al.'' in 1975 would lead [[Robert Metcalfe]] to use [[carrier-sense multiple access]] (CSMA) protocols in the design of the now commonplace [[Ethernet]] [[local area network]] (LAN) technology.

Over 1973–76, [[DARPA]] created a packet radio network called [[PRNET]] in the [[San Francisco Bay]] area and conducted a series of experiments with [[SRI International|SRI]] to verify the use of [[ARPANET]] (a precursor to the [[Internet]]) [[Internet Protocol Suite|communications protocols]] (later known as [[Internet Protocol|IP]]) over packet radio links between mobile and fixed network nodes.<ref>Okin, J.R. (2005). ''The Internet Revolution: The Not-for-Dummies Guide to the History, Technology, and Use of the Internet'', p.81. Ironbound Press. {{ISBN|0-9763857-6-7}}.</ref> This system was quite advanced, as it made use of direct sequence [[spread spectrum]] (DSSS) modulation and forward error correction ([[Forward error correction|FEC]]) techniques to provide 100&nbsp;kbit/s and 400&nbsp;kbit/s data channels. These experiments were generally considered to be successful, and also marked the first demonstration of [[Internetworking]], as in these experiments data was routed between the ARPANET, PRNET, and [[SATNET]] (a satellite packet radio network) networks. Throughout the 1970s and 1980s, DARPA operated a number of terrestrial and satellite packet radio networks connected to the ARPANET at various military and government installations.