Rayleigh fading channels in mobile digital communication systems .1. Characterization

When the mechanisms of fading channels were first modeled in the 1950s and 1960s, the ideas were primarily applied to over-the-horizon communications covering a wide range of frequency bands. The 3-30 MHz high-frequency (HF) band is used for ionospheric communications, and the 300 MHz-3 GHz ultra-high-frequency (UHF) and 3-30 GHz super-high-frequency (SHF) bands are used for tropospheric scatter. Although the fading effects in a mobile radio system are somewhat different than those in ionospheric and tropospheric channels, the early models are still quite useful to help characterize fading effects in mobile digital communication systems. This tutorial addresses Rayleigh fading, primarily in the UHF band, that affects mobile systems such as cellular and personal communication systems (PCS). Part I of the tutorial itemizes the fundamental fading manifestations and types of degradation. Part II will focus on methods to mitigate the degradation.