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ALOHA was a pioneering networking system developed at the University of Hawaii in 1971 as a first demonstration of wireless networks. It used a medium access method along with experimental UHF frequencies.
ALOHA served as the basis for the development of Ethernet and Wi-Fi networking.
This term is also known as ALOHAnet.
The concept of ALOHA emerged when frequency assignments for communications between computers were not available for commercial applications.
The initial version of ALOHA used two different frequencies in a hub configuration. The hub machines were used to broadcast packets to all outbound channels and to different client machines. Upon receiving error-free data at the hubs, an acknowledgment packet was sent to the clients. If no acknowledgments were received, data packets were retransmitted after a selected time interval. This mechanism detected and corrected collisions when two clients attempted to send packets at the same time.
All client nodes in ALOHA communicate with the hub using the same frequency. The shared use of a single medium for client transmissions was critical. A mechanism was used for controlling packet sending, resending and collisions. This was called pure ALOHA, or random access channel, and served as the basis for the development of Ethernet and Wi-Fi networks. It also was used for the outgoing hub channel, allowing broadcast packets to be sent to all clients on a second shared frequency where each client recipient has its own address.