Equalizers in mobile communications: Tutorial 38

Modern cellular wireless systems would not be possible without high-performance equalizers. Signal impairments introduced by the wireless channel can only be compensated for by using such equalizers. This tutorial serves as an introduction to the challenging design of equalizers. By introducing a general framework based on the Bezout Theorem, we show that the most sophisticated equalizer concepts can be derived, thus allowing finite length solutions to be found. Based on a canonical receiver structure, we also show how equalizers improve the Signal-to-Interference and Noise Rat io (SINR) under different sources of interference such as temporal, spatial, code and multiuser. We furthermore address the challenges of adaptive equalizers as they are currently typical solutions for low-cost devices. Although research on equalizers has been performed for many decades, we finish the tutorial with some open issues that are still keeping the field alive.