Invention of Spread Spectrum Technology for Wireless Communication

By Wentao Lin and Xiaoyi Wang,
PhD candidates at Polytechnique Montreal

Spread Spectrum Technology, a method of transmitting radio signals by rapidly switching a carrier among many frequency channels, was invented by Hedy Lamarr in 1941. Nowadays, the principle is incorporated into modern Wi-Fi (wireless fidelity), CDMA (code division multiple access) and Bluetooth technology, etc.

Hedy Lamarr is a famous actress recognized for her silver screen performances. But what’s interesting is that she’s also a pioneering inventor in the area of wireless communication. During the World War II, torpedoes were very important in the naval war to protect the radio signal. The radio-controlled torpedo was a vital subject. Hedy was stimulated by the sound of piano which changes the frequencies and came up with the idea of a frequency-hopping signal of torpedoes that could not be tracked or jammed easily. Ultimately, she synchronized a miniaturized player-piano mechanism with radio signals, to control a torpedo successfully.

By applying radio frequencies at irregular gap simultaneously between transmitting and receiving sides, the invention created encrypted modulating approaches to prevent classified messages from being intercepted by the enemies. Later after the World War II, the invention was soon implemented in radars on naval ships and subsequently applied in many other military applications. However, for some confidential reasons, the invention only worked on military applications and was not public.

Until 20 years ago with the development of commercial digital wireless communication systems, the invention of Spread Spectrum was finally made public and soon applied in the wireless communication system, leading to a boom of the 3rd Generation (3G) wireless communication system which directly changes the image that we used to connect with each other. Smartphones, WIFI, etc, were also booted to develop further.