The Physics of WiFi

Now for the most important part the physics of how WiFi works! Now as we have learned from the history and what is section that WiFi is possible through radio waves. Radio waves are known as electromagnetic waves. These waves trasmit data by oscillating at different frequencies. These waves are vital in why WiFi works well."Electromagnetic waves have the same characteristic parts as mechanical waves (e.g., wavelength, amplitude, frequency, etc), but they behave very differently. Sound waves travel in air at a speed of approximately 344 meters/second, while electromagnetic waves travel at the speed of light"(kicp.uchicago.edu) These waves move at the speed of light which make data transfer fast. The only issue is how much data can be sent. While 915Mhz is great at going long distances it is moving so slow it is not capeable of transfering large amound of data in transmissions. While the stand 2.4 Ghz is oscillating at a much greater speed it allows for more data to be transfered. The major issues with radio waves is they refelct around. The faster the waves the easier they are reflected. So the new 5.0Ghz waves are more prone to being jumbled up and because of this they often only perform better in smaller areas.


Now we can get into the important qualities of radio waves and how they shape our world of WiFi "..different radio frequencies behave differently in different environments. The higher the frequency, the more easily radio waves are absorbed or reflected by things like ordinary building materials and vegetation. Visible light, though far higher up the electromagnetic spectrum, demonstrates the principle nicely. A sheet of typing paper will let some light through, but a ½ inch piece of plywood will block it entirely. Radio waves behave in a similar fashion. They have much better penetration than visible light, but you wouldn’t bother trying to pick up the Cubs game if you were working in a bank vault. Because higher frequencies are more easily reflected, they produce more multipath propagation, a phenomenon that occurs when transmitted signals bounce off an intervening object – even ordinary raindrops. The reflections cause different parts of the signal to arrive at the receiver at different times, and out of sequence. The worse the multipath propagation becomes, the more the signal begins to merge with the noise floor. " (automation.com) The issues with WiFi come down to the physics of radio waves. As the distance is added to the waves the faster they oscillate the more prone they are to what is called path loss. While with greater frequencies we are able to transfer greater amounds of data. That data can not travel as far. It is balance between amount of data and the range it needs to be transfered. In a a paper about radio waves in IEEE Transactions on Antennas and Propagation Vol. 66 "at 2.4 GHz could be expected to have greater range than Wi-Fi at 5 GHz. And 900 MHz could be expected to do even better. A 900 MHz GHz installation would have roughly 8.5 dB less path loss than a similar 2.4 GHz. installation. " While we are always looking to improve technolgy there are limitations by the physics. With greater speeds comes the lost of range due to the laws that bind electromagnetic waves. Have no fear in the end we have come up with mesh wireless networks to combat the loss of range by creating multiple sources of the signal to effectively cover an area with signal.

How Antennas work

image from infograph.venngage.com