Developed at the University of Hawaii nearly 57 years ago, ALOHAnet pioneered the random access wireless protocols that enable your smart device’s Wi-Fi connection.
Cellular and satellite communications also owe a debt of gratitude to ALOHAnet.
The ALOHAnet project began in September 1968 at the University of Hawaii on the island of Oahu.
The university’s remote campuses on Maui, Hawaii Island, and Kauai faced the challenge of providing access to its central mainframe computer (IBM System/360 Model 65) located in Mānoa Valley, on Oahu.
In the late 1960s, students on these islands accessed the main campus computer through remote terminals linked by copper telephone lines.
They used devices like teletypes (TTYs), including the Model 33 and Model 35, which had keyboards and printed paper output, as well as early video display terminals such as the IBM 2260 and DEC VT05 to connect to the university’s central computer for processing.
The local telephone network, designed for analog voice communication, sometimes struggled with data transmissions from the terminal modems, which converted digital signals into analog for transmission.
The limitations of the telephone network drove the development of a radio-based system, which led to the development of ALOHAnet, as University of Hawaii professor Norman Abramson addressed in the Feb. 1, 1972, Honolulu Advertiser.
Another consideration was the expense of inter-island telephone calls, as terminal users sometimes needed seconds of computer time but were billed for three minutes.
Professors Norman Abramson and Franklin Kuo from the University of Hawaii developed ALOHAnet, a wireless data system using radio frequencies.
They introduced random access protocols that enabled multiple devices to share a single radio channel, laying the foundation for modern technologies.
ALOHAnet was developed as a proof-of-concept network to connect Oahu with other campuses in the Hawaiian Islands via wireless, radio frequency channels.
Both held doctorate degrees.
Abramson earned a bachelor’s and master’s in physics before obtaining his doctorate in electrical engineering from Stanford University.
Kuo received his BS, MS, and PhD degrees in electrical engineering from the University of Illinois Urbana-Champaign.
ALOHAnet transmitted data to Hawaiian schools through a radio channel linked to an IBM System/360 Model 65 mainframe.
An HP 2115A minicomputer, called the “Menehune,” acted as the central communication processor and network gateway.
According to Franklin Kuo’s 1981 system diagram, the Menehune managed data traffic across two 100 kHz (kilohertz) UHF (ultra-high-frequency) radio channels, 407.350 MHz (megahertz) and 413.475 MHz.
ALOHAnet’s design prioritized simplicity with direct packet bursts on fixed radio frequencies (channels).
In 1969, the team chose a cost-effective fixed-frequency approach over spread spectrum technology, which required complex and expensive hardware.
While spread spectrum would later become vital for military and commercial wireless, ALOHAnet’s fixed-frequency method made packet radio practical for academic use at the time.
The Menehune also functioned as a multiplexor/concentrator, similar to the interface message processors (IMPs) of ARPANET (Advanced Research Projects Agency Network), a pioneering packet-switching network and internet predecessor.
University of Hawaii engineering students gained hands-on experience by developing components for ALOHAnet, including its “communications modules,” or terminal control units (TCUs).
They connected their teletypes and video display terminals to these TCU modules.
These TCUs managed the wireless transmission of terminal data by applying ALOHAnet’s radio access protocols.
Dr. Abramson’s 1970 paper, “The ALOHA System,” described ALOHAnet as the first packet-radio network.
It detailed a 24,000 baud channel with 704-bit packets lasting 29 milliseconds and explained how terminal control units (TCUs) formatted these packets and managed re-transmissions.
ALOHAnet originally operated at 24,000 bits per second (bps), but speeds often dropped to 9,600 bps.
By June 1971, ALOHAnet was up and running with its random access protocol. Students on the islands were sending data packets via radio from their teletypes and CRT terminals.
If a data packet collided, the terminal would wait a random amount of time before re-transmitting until the data was successfully sent.
The Feb. 1, 1972, Honolulu Advertiser article explained that ALOHAnet could support more than 500 users on a single radio channel to the central computer.
ALOHAnet thus confirmed that multiple users could efficiently share a radio channel via simple, decentralized rules, eliminating the need for complex centralized management.
In December 1972, ALOHAnet became the first satellite node of ARPANET, linking the University of Hawaii to NASA’s Ames Research Center in California via a 50 kbps channel through the INTELSAT IV F-4 satellite.
This satellite connection, funded by ARPA, enabled ALOHAnet users to access ARPANET resources.
Today, the INTELSAT IV F-4 satellite is no longer operational, but it remains in orbit around Earth.
In the fall of 1976, ALOHAnet ceased operations when funding from the US government sponsors, primarily ARPA and NASA, ended.
The Institute of Electrical and Electronics Engineers (IEEE) hosted a virtually attended (due to COVID-19) event Oct. 13, 2020, from the University of Hawaii at Mānoa to commemorate ALOHAnet’s contributions to wireless communication.
Key speakers included IEEE leaders, Dr. Norman Abramson and Dr. Franklin Kuo.
Vint Cerf, acknowledged as “the father of the internet,” also spoke, recognizing ALOHAnet’s pioneering advancements.
Dr. Norman Manuel Abramson died Dec. 1, 2020, in San Francisco at the age of 88.
Dr. Franklin Kuo became a professor emeritus at the University of Hawaii in 2021 and is reportedly still with us at 91.
In June 2021, an IEEE commemorative plaque recognizing ALOHAnet was installed at the University of Hawaii’s Holmes Hall.
For more information on ALOHAnet, visit https://bit.ly/44LQ85a.
Aloha.
