Improved Signal Transmission through Randomization

Abstract

The transmission of energy and information is basic to science and engineering. A signal is transmitted from source to receiver by means of waves passing through a medium. A homogeneous medium transmits the direct wave only, and thus provides the best transmission. Transmission performance is less for a heterogeneous medium. Mathematically a continuously varying heterogeneous medium is difficult to handle, but it can be approximated by a finely divided layered system. A layered system is characterized by the sequence of fresnel reflection coefficients of the successive interfaces between layers. A layered system not only transmits the direct wave, but also transmits internal multiple reflections. The multiples degrade the transmission performance. Ideally the multiples should be kept small, so that most of the transmitted energy occurs in the direct wave. Transmission performance improves as the reflection coefficients become smaller in magnitude. Transmission performance can also be improved in another significant way. That way is randomization. high performance is achieved when, in addition to being small in magnitude, the reflection coefficients are a realization of random white stochastic process. Transmission though a layered system with small white reflection coefficients closely approximates the ideal transmission though a homogeneous medium.