CEN 4500C Fundamentals of Computer Communication Networks

R. E. Newman-Wolfe, University of Florida

Last modified 1/30/95.

Transmission

Physical Layer I - communicating over a single "wire"
  • The Spectral Efficiency is defined to be the number of bits of data transmitted per hertz, or 2 lg L.
  • In practice, Nyquist's formula must be modified according to how the signal is filtered. A useful measurement of performance of this filtering is r, where typically 0 < r < 1. Nyquist's theorem assumes that r = -1/2, and so, like Shannon's formula, is really a limit. The general equation for multilevel signaling relating bandwidth to data rate and number of levels used is:
  • While Nyquist's result (sort of a dual of the Sampling Theorem) states that at most two signal elements can be sent per cycle, in practice it is more like one signal element per one or two cycles.
  • transmission media and characteristics
  • Transmission - Once we are able to transmit and receive a signal, we wish to be able to encode data in that signal. While we have considered some fundamental limitations of transmission here, the next page considers the problem of encoding data in signals for transmission.
    This document is copyright 1995 by Richard E. Newman-Wolfe.
    Send comments to nemo@cis.ufl.edu