Communications Technology Handbook, 2nd Edition

5 Codes and coding formats

With all forms of signal transmission, it is important to minimise the effects of noise, which is essentially an information destroyer. With analogue systems, this effect can be quantified by the signal to noise voltage, current or power ratio (see Noise, p. 232). In digital systems where the information is transmitted in binary digits or bits, of fundamental On/Off, mark/space or 1/0 elements, a similar concept can be applied. In this case the parameter is measured in terms of energy/bit per watt of noise power/hertz (E_b/N₀). If the noise power becomes comparable with the energy in each bit, then bit errors are produced. Thus the degradation of digital signal to noise ratio leads to a bit error rate. The Morse Code ...