Advances in Multiuser Detection

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OVERVIEW OF MULTIUSER DETECTION

Michael L. Honig

… But what is the use of counterpoint when, if played, one imagines that four different orchestras are playing at the same time four different tunes in four different keys and measures? A veritable nightmare!

—Music critic Arthur Bird, writing about R. Strauss's tonepoem Ein Heldenleben, May 1, 1899 [69, p. 186]

1.1 INTRODUCTION

One of the key challenges in designing multiuser communications systems is mitigating interference. This challenge is apparent for modern wireless networks, such as mobile cellular, and wireless local and metropolitan area networks, where achieving high spectral efficiencies requires aggressive frequency reuse. Interference also limits the performance of many wired channels, such as the digital subscriber line (DSL). Although each DSL is typically associated with a single user, capacitive coupling between pairs of DSLs in close physical proximity causes cross-talk interference, which degrades performance (e.g., see [72]).

Interference encompasses self-interference, due to reflections of the same signal, in addition to multi-user-interference associated with other signals sharing the same bandwidth. Self-interference arises from multipath in a wireless channel, a bridge tap in a Digital Subscriber Line (DSL), and bandwidth constraints, which cause intersymbol interference. Throughput this book, interference typically refers to signals from other users (or more generally, data streams) associated with the ...