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Move 4: Modulating Frequencies and Wifi

Bandwidth and data transfer rates

 

When transmitting information wirelessly via radio waves from a phone, television, or other device it takes up a certain amount of bandwidth. Bandwidth is generally the amount of sub-frequencies that data is transmitted over. Obviously, if certain things will take up more data than others. For instance, videos vs. FM radio (music), one requires much more data. With music, you only need to transmit a small amount of information per second, but with video you need to load many pictures per second. On standard is that all bands can carry the same amount of information, either one or a zero. When using a number of these bands more data can be transmitted, and the amount of bands necessary to communicate the necessary data is called the bandwidth. The bandwidth varies with the device, because as stated before the video will require more data than audio, so when watching a video online it will take a higher bandwidth than if you were listening to music. Most wireless routers have a maximum bit rate measured in bits per second, up to date wireless routers have a date transfer rate in the mega bits per second. Many current wifi routers range from about 5Mb/s to over 100Mb/s, depending on the location. Wifi routers usually broadcast with a carer frequency of about 2.4 GHz with a span of different bandwidths. All wifi routers fall under the standard of 802.11, this was created by the IEEE (Institute of Electrical and Electronics Engineers) in 1997. There are also different designations of 802.11, 802.11b, g, n, and ac.  Each designation marks a different advancement in router technology and enhances its range, strength, speed bandwidth.   

 

 

When observing the function of a modulated amplitude for example it is defined as f(x)=(1+m cos(mt))coscot. This defines what the frequency of the carrier frequency will be as well what is being modulated as the signal. As seen in the figure below the red function is the modulated signal that is superimposed on top of the carrier frequency, which is in blue.  This is what is actually being transmitted out of a wifi router, cellphone, etc, when you want to send information.  What is displayed below is basically a cos in the shape of a cos function, and what is actually transmitted is the red function. The blue function is there to show that the modulated signal forms a cos shape.

 

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