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First Wireless Network
Norman Abramson (b. 1932), Robert Metcalfe (b. 1946)
By 1968 it was clear that the voice telephone network would not be adequate to serve the emerging requirements of networked computing. ALOHA was designed to explore the possibility of using wireless communications as a potentially superior alternative to wired.
A team of researchers at the University of Hawaii (UH), led by Norman Abramson, set out with the goal of linking computers on the main campus in Manoa Valley (near Honolulu) with terminals at a college in Hilo, Hawaii—and five community colleges on the islands of Oahu, Kauai, Maui, and Hawaii. If successful, the project would allow students at the schools to use the computers without having to travel to Hilo.
At the time, point-to-point microwave channels were well understood—and expensive. Such channels were also wasteful, because the nature of terminal communication was such that it was sporadic and frequently idle and could tolerate only small delays. Soon the group hit on the idea of sharing a single high-speed wireless channel between all the senders: if a sender didn’t get an acknowledgement, it would retransmit its packet until it did.
The first packet was transmitted in June 1971 from a terminal attached by an RS232 interface to a new device called a terminal control unit (TCU). With the TCU, the terminal could be used anywhere within 100 miles of the UH campus. Soon the group built more TCUs, networking the islands together with ALOHANET, the world’s first wireless computer network.
The ALOHANET system was interconnected to the ARPANET on December 17, 1972, over a single 56-kilobits-per-second satellite communications channel.
Electrical engineer Robert Metcalfe realized that the same broadcast architecture could be run over a piece of coaxial cable. He improved the basic protocol by having the radios listen for traffic before sending their packet, an approach called carrier sense multiple access (CSMA), and the Ethernet was born.
Versions of the ALOHANET protocol made their way into many other wireless networks, including early cellular systems. But the lasting contribution of the project was the impact on Ethernet protocols and, eventually, today’s Wi-Fi standards.
SEE ALSO IPv4 Flag Day (1983)
The campus at the University of Hawaii, Manoa, where computers were linked with terminals at other colleges throughout Hawaii.