Optimum Combining for Indoor Radio Systems with Multiple Users

Abstract

This paper studies the use of optimum combining to increase the capacity of narrow-band in-building radio communication systems with multiple users. We consider systems consisting of a base Station with numerous remotes in a Rayleigh fading environment and study the problem of more users requiring channels than the number of channels available. A system is described that, with multiple antennas at the base station but only one antenna at each remote, uses optimum combining to suppress interfering signals. We show that this system, with <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</tex> antennas at the base station, can achieve an <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</tex> -fold increase in the number of users or tolerate <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M - 1</tex> interferers from other systems. Thus, with optimum combining, radio communications can be used in high-density, multiple-user environments, such as within buildings, even when only limited bandwidth is available.