Who Invented the Computer? Norman Abramson and ALOHAnet
Who Invented the Computer? This is the thirty-sixth installment in our ongoing series.
In 1968, Stanford engineering professor Norman Abramson (1932-2020) embarked on a transpacific airplane journey to an academic conference in Tokyo. Fortunately for the world, he was not on a direct flight — rather, Abramson had a two-day layover in Honolulu, Hawaii.
Instead of just sitting in his hotel room and fretting over the delay, Abramson went outside to experience the local culture. Like most island visitors, he headed to a local beach and, while there, sat watching surfers ride the waves.
Impressed by what he saw, Abramson put on some trunks, rented a board, had a quick lesson, and was soon hanging ten. His day was spent mostly wiping out, but amidst his minor successes, he fell in love with the activity.
Abramson enjoyed his experimental surfing escapade so much that he determined to return for more. During his brief stay, Abramson had also visited the engineering department at the University of Hawaii at Manoa (UHM). One year later, he was back in the Pineapple State working as a professor of engineering at UHM.
His first assignment at UHM was to work on the Aloha System, a project to connect the computer systems on Maui with the UHM computers via microwave radio waves instead of underwater phone lines. ALOHA awkwardly meant "Additive Links Online Hawaii Area."
Mainland computers were already being networked through existing telephone lines. In addition to the limited carrying capacity of these lines, however, they also often suffered from electrical interference, especially over long distances. Fortunately, mainland telephone lines consisted of hundreds of smaller lines enabling easy access to a free line.
UHM needed a wireless connection because its phone system was much more primitive than those on the mainland. There were far fewer lines that far more frequently suffered breakdowns and interference.
Under Abramson's leadership, ALOHA would evolve from a simple connection project into something much greater. His vision for ALOHA was a radio network able to transmit data to numerous locations and computers, enabling them all to communicate over a single microwave channel.
In June of 1971, Abramson's team succeeded in sending their first packet on the network. This small victory was not without setbacks.
The first problem the team wrestled with was solving the method of digital information transference through a radio channel. The process of digital data transmission hadn't changed since the electrical telegraph machines of the 1840s: Data travelled on a line from one point to another.
Unfortunately, much like a freight train engine pulling a number of cars behind it, the breakdown of a single car meant the entire train stopped. It was the same with digital streams travelling along radio waves: If a single piece of data was damaged in transit, the entire data stream had to be resent.
Trucking On Down the Information Highway
Abramson's solution was to establish protocols that broke data into small packets before transmission. Each packet contained bits of information of the entire message along with the digital address of a computer on the network. He described the procedure as similar to trucks travelling on a roadway:
The transmission was not like an entire message along a straight line between points as on a railroad. Rather, each packet acted as a truck, carrying a small piece of the entire message, along parallel lanes of traffic toward their designated destination.
The major advantage of breaking data into smaller packets was that if one packet became corrupted (a truck had an accident), only that packet (truck) had to be resent, not the entire data stream.
The microwave channel acted as the roadway for the digital information and the team set up a computer at each end of the connection that would direct the packets to the correct destinations by reading each packet's destination info. Since these computers rapidly performed their tasks unnoticed, they were referred to as Menehunes: the mythological race of island dwarves who built fish ponds, roads, canoes, and, houses at night when no one could see them.
After two years of prodigious effort, in June of 1971 Abramson's team successfully sent and received a digital packet through the world's first wireless network. Their celebration was cut short, however, as soon as ALOHAnet was fully implemented.
The new problem occurred when multiple computers would send messages simultaneously through the network. Messages would collide with one another resulting in garbled and unreadable content being received. If enough messages collided, they would pile up, resulting in a network shutdown.
To prevent packet collisions, UHM's team established ALOHA Random Access Protocols (RAP) that enabled network computers to set random time delays before sending any packets. RAP dramatically decreased the likelihood of packet collisions. Even ARPANET, which was under development at the time, decided to include ALOHA's protocols.
Abramson and his colleagues soon doubled ALOHAnet's efficiency, and made it even more reliable by implementing Slotted ALOHA: fixed-time slots with network-wide time synchronization. The ALOHA protocols worked so well that they were adopted by ARPANET.
'The surfing wouldn't have been as good'
Once ALOHAnet was operating smoothly, it was expanded even further to work through VHF satellite connections. In 1973, it was successfully connected to five universities on three different continents. This process, called PACnet, would open the door to vast new possibilities for radio and satellite communications.
ALOHAnet was a huge leap forward for wireless communication and it would become the foundation for modern day satellite communication largely through the efforts Abramson, his UHM colleagues, and the numerous graduate students who helped perfect it.
Fifty-one years later, ALOHAnet's protocols are widely used in nearly all forms of wireless communications such as cellular phone networks, Wi-Fi, Bluetooth, and global positioning systems, among other technologies.
Whenever we use our electronic devices to surf the Internet, place calls on cellular phones, purchase items on Amazon, apply for jobs, watch cat videos, play video games or just e-mail grandma, we can marvel that it all started with Norman Abramson's love of surfing.
Decades later, when an interviewer asked whether ALOHAnet could have been invented on the mainland, Abramson jokingly responded, "Definitely. Any mainland institution could have eventually come up with a similar system — but the surfing wouldn't have been as good."