27-01-2012, 02:17 PM
POWERPOINT PRESENTATION FOR G.P
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Bandwidth
In previous lectures, we briefly mentioned the concept of bandwidth. In this lecture, we will discuss more deeply what signal bandwidth is, what the meaning of channel bandwidth to a communications engineer is, and what the limitations on information rate are.
Shannon’s Theorem
Claude Shannon at Bell Labs figured out how much information a channel could theoretically carry:
Where I is Information Capacity in bits per second (bps)
B is the channel bandwidth in Hz
S/N is Signal-to-Noise ratio (SNR: unitless…don’t make into decibel: dB)
Signal-to-Noise Ratio
S/N is normally measured in dB (decibel). It is a relationship between the signal we want versus the noise that we do not want, which is in the medium.
It can be thought of as a fractional relationship (that is, before we take the logarithm):
