The following document contains transcribed notes from Professor Gershenfeld's class lecture on 12/1/03

Shannon's Equation:

C=Df log (1+s/n)

where C is the channel capacity, f is the frequency, s is the energy or strength of the signal, and n is the noise or the energy put out by the item/medium the signal is being transmitted through.

The error rate while sending data through a channel can be zero (up to a certain point) with error correction. Even though a process is statistical does not mean that it is unreliable.

Complexity in Communications -

• Modulation - making your signal look different from anything else
  • AM (amplitude modulation), FM (frequency modulation), etc.
  • AM is easy, but natural noise is AM
  • AM, FM are also not too good because the modulation is one dimensional (are only modulating one thing)
  • Ideally, you want to increase the dimensionality of your signal modulation
• Codes generated are similar to the packing of spheres where the 'volume' of a 'sphere' is the the volume in which a signal can be received without purturbation/noise/etc. (I'm not too clear on this point)

Interdevice networking

• Internet zero - internet for everyday controllers
  • 802.11b or ethernet complexity comes from the bit that is being transfered being smaller than the conduit it is transfered through. This leads to relativistic effects? This why impedence matching is very important (otherwise reflections will occur upon the transfer of the information from one medium to another which is not good.)
  • When communicating in something the size of a building, 1Mb/s data transfer rates are possible with bigger bits.
  • This concept leads to some interesting devices/communication protocols that may be used in class. More to come on this later.