lton, England. References 9/19 Saxton, J.A.(Ed) (1964) Advances in radio research, Academic using the ionospheric transmission channel - Ionospheric Press, London. Communications Analysis and Prediction Program, Report 83- Smith, E.K. (1970) Electromagnetic probing of the upper atmos- 127, National Telecommunications and Information Adminis- phere, U.R.S.I. Working group, J. Atmosph. Terr. Phys. 32. 457. tration, Dept. of Commerce, Boulder, U.S.A. Smith, E.K. and Matsushita, S. (1962) Ionospheric sporadic- E. Titheridge, J.E. (1985) lonogram analysis with the generalised Macmillan, New York. program POLAN, Rep. UAG-93, Dept. of Commerce, Boulder, Stevens, E.E. (1968) The CHEC sounding system, in Ionospheric U.S.A. radio communications, ed. K. Kolkestad, Plenum, New York, URSI Commission F. Colloquium Proceedings; La Baule, France Stringer, F.S. (1969) Hyperbolic radionavigation systems, Wireless (CNET, Paris, 1977). Also at Lennoxville, Canada (Proceedings World 75. 353. edited by University of Bradford, England, 1980). Sugar, G.R. (1964) Radio propagation by reflection from meteor trails, Proc. IEEE 52. 116. Whalen, J.A., Buchau, J. and Wagner, R.A. (1971) Airborne ionos- Teters, L.R., Lloyd, J.L., Haydon, G.W. and Lucas, D.L. (1983) pheric and optical measurements of noontime aurora, J. At- Estimating the performance of telecommunication systems mosph. Terr. Phys. 33. 661. This page intentionally left blank Signals and noise John Price Northern Telecom Europe Terry Goble Northern Telecom Europe Contents Definition of a signal 10/3 Waveform and frequency 10/3 Digital signals 10/5 10.4 Examples of signals 10/5 10.5 Classification of signals 10/6 10.6 Signal representation 10/7 10.7 Distortion of signals 10/8 Types of noise 10/10 10.9 Noise units and measurements 10/11 10.10 Signal to noise ratio 10/13 10.11 Noise factor 10/13 10.12 Noise waveforms 10/14 10.13 Bibliography 10/15 This page intentionally left blank Definition of a signal 10/3 10.1 Definition of a signal 1. The strength and amplitude can easily be al