Chai K. Toh

Chai K. Toh
Chai K. Toh
Associated organizations
University of London, UK, National Tsing Hua University, TAIWAN
Fields of study
Computer Science, Telecommunications, Wireless Networks, Mobile Ad Hoc Networks, ITS, Telematics, and IoT
IEEE Kiyo Tomiyasu Award,
IET Ambrose Fleming Medal


Dr. Chai Keong Toh, professor and chair in Communications Networks at the University of London in England, has been a trailblazer in the field of mobile ad hoc wireless networks. As former director of research in communications systems at TRW Tactical Systems Inc., (now Northrop Grumman Mission Systems Corporation) in Carson, California, and now as chair professor at the University of London, Dr. Toh has laid the critical foundation for a new type of next-generation mobile wireless communications, computing and networking.

He built the first practical wireless ad hoc network in 1998, using Lucent WaveLAN WiFi 802.11 2.4GHz radios, laptops running Linux OS, and his ad hoc routing protocol code. He demonstrated that realizing ad hoc networks is possible, and existing RPC/UDP/TCP/IP applications, such as FTP/TELNET/RLOGIN and HTTP web-based client-server multimedia applications can be supported transparently. He also worked to resolve power, media access, multicasting, TCP, and service discovery issues for wireless ad hoc networks.

In 1993, he invented associativity based routing, an on-demand routing approach that discovers route only when needed, selects stable mobile routes despite nodes' mobility and creates an ad hoc network that yields robust communications performance capable of relaying packets in a wireless hop-by-hop manner, without the need for any centralized control. It was a pioneering work that gained a U.S. patent and was subsequently licensed for defense use. Wireless ad hoc networks, also sometimes known as wireless mesh networks, is the precursor to Internet of Things, where devices could automatically connect to each other wirelessly. Wireless ad hoc networks have been widely used in smart phones (peer to peer chat without cellular), smart homes (Z-wave and ZigBee), smart street lights, disasters rescue operations during storms and earthquake, vehicular V2V communications for road safety, army tactical ad hoc mobile radios for soldiers in the battlefield, army explosive hopping mines, air force UAV (unmanned air vehicle) ad hoc networks, navy ship area ad hoc networks, etc.

A Fellow Member of IEEE, AAAS, and a pioneering creator of mobile ad hoc networks, Dr. Toh has devoted over two decades (since 1993 while at Cambridge University, England) in this field. For his pioneering contributions, he received the IEEE Kiyo Tomiyasu Award in 2005 and IET Sir John Ambrose Fleming Medal in 2009.