Alex Hills Chapter 27 Summary Communication engineer Alex Hills explains how the satellite communications systems he designed for rural Alaskans helped him develop WiFi system Because of tough terrain laying telephone wire was not feasible and shortwave radio signals often met interference ID: 620112
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Slide1
Riding the Waves
Alex Hills
Chapter 27Slide2
Summary
Communication engineer Alex Hills explains how the satellite communications systems he designed for rural Alaskans helped him develop Wi-Fi system. Because of tough terrain, laying telephone wire was not feasible, and shortwave radio signals often met interference from the Northern Lights. Alex helped devise a communications system using satellite technologies that allowed rural Alaskans to communicate across the tundra. Eventually, Hills was instrumental in linking the state’s university campuses together via satellite. The wireless network inspired Hills to develop the first Wi-Fi at Carnegie Mellon University in the 90’s.Slide3
Electro magnetic radiation
There are many types of electro magnetic radiation, including visible light, radio waves, microwaves, and gamma rays.
Electromagnetic radiation
is often described as a wave.Slide4
Wavelength and Frequency
Electromagnetic waves have associated wave lengths and frequencies.
The wavelength is a measure of the distance from one crest to the next of a wave.
Frequency refers to the number of complete wave cycles that occur in a unit of time.
Wave length and frequency are inversely related.
The unit for frequency is the Hertz (Hz).Slide5
Some other facts
Information can be encoded in radio wave signals.
Wireless communications systems can be established in locations where laying telephone lines is not practical.Slide6
How does Wi-Fi work?Slide7
In 70’s, why didn’t people in the Alaskan bush have telecommunications services?
The terrain was to rough and the distances between villages to o great for laying telephone lines to be cost effective.
Rural Alaskans could write letters or make radio broadcasts.Slide8
How did Alex draw on his earlier work in Alaska when developing Wi-Fi Technology?
He used radio waves to develop a communication system without wires.Slide9
Why wouldn’t shortwave radio solve the communications problem in rural Alaska?
Shortwave radio did not work because its signals were often distorted by the Aurora Borealis. The short wavelengths in Alaska bounce off a layer in the atmosphere called the ionosphere and come back to the earth. The Northern Lights interfere with this bounce.
Satellites solve this problem because the satellites have a much higher frequency, meaning that the wavelengths are extremely small – small enough to pass freely through the ionosphere to satellites and back to the people without
interferrence
.Slide10
What is the frequency of the broadcast by your favorite radio station?
94.5? The frequency is 94.5 megahertz.