Back again

I promised to write a blog back at the beginning of July when I was in Cornwall. Right after that trip I pretty much lost dependable access to Internet for a long time. Now being back home finally, I am ready to get back to business.

Following figure is from Mario Amaya’s Master’s thesis I mentioned in an earlier post. It shows the progress of spectral efficiency. It is quite striking:

This shows a factor of 1 Billion over the last 100 years. Another figure from the FCC’s National Broadband Plan shows a similar picture for a much shorter time-span (covering the last 10-12 years) shows an efficiency growth of more than 30 times.

Spectrum Efficiency Changes

Looking at this most recent history, we can realize that this phenomenal growth is due to the following factors:

  • ability to implement higher order of modulation techniques via available chip/power real estate
  • better coding schema allowing the use of higher order modulation techniques (in larger portions of a given area)
  • antenna, code, phase diversity techniques that increase the robustness of the links

Ultimately all of these improvements are due to Moore’s law and they result in increasing the ratio between Signal and Noise in Shannon’s Law.

Before we conclude, we should recognize one rather obvious factor: Shannon’s law tells us that another way to increase that Signal/Noise ratio is to shorten the distances between the transmitter and receiver. Curiously FCC’s graph is missing a well-known technology: 802.11. Next post, let’s look at how WiFi plays a role in increasing the wireless capacity.

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