Luận Văn Modeling the Statistical Time and Angle of Arrival Characteristics of an Indoor Multipath Channel

Abstract

Most previously proposed statistical models for the indoor multipath channel include
only time of arrival characteristics. However, in order to use statistical models in
simulating or analyzing the performance of array processing or diversity combining, it also
necessary to know the statistics of the angle of arrival and its correlation with time of arrival.
In this paper, a system is described which was used to collect simultaneous time and angle
of arrival data at 7 GHz. Data processing methods are outlined, and results of data taken in
two different buildings are presented. Based on the results, a model is proposed that employs
the clustered “double Poisson” time of arrival model proposed by Saleh and Valenzuela [1].
The observed angular distribution is also clustered, with uniformly distributed clusters, and
arrivals within clusters that have a Laplacian distribution.

INTRODUCTION

Radio has recently become an increasingly viable option for indoor communications
applications. The availability of higher frequency bands in the 900 MHz and 2.4 GHz
range has made wireless an attractive option for high bandwidth digital communications applications
such as local area networks. Wireless networks can be particularly advantageous
for applications which require portability, or where installation of wiring is undesirable or
impractical.
Multipath interference, or interference due to the reception of multiple copies of a
signal due to reflections, is known to be a problem in many outdoor communication channels.
However, multipath can also be particularly problematic in an indoor environment. At UHF
and microwave frequencies, the presence of walls and large objects in rooms makes the indoor
multipath environment quite different from most outdoor scenarios. As a result, the study
of indoor propagation characteristics has become an area of increased study.
In order to analyze or simulate the performance of a communications system, some
kind of model for the channel is needed. One of the first statistical models for the indoor
multipath channel was proposed by Saleh and Valenzuela [1]. Their data showed multipath
arrivals which were grouped in clusters over time. The relative delay between clusters was
represented by a Poisson distribution, and the separation between elements within clusters
was modeled by a second Poisson distribution with a different delay parameter.
There have been many different approaches to overcoming the problem of multipath
interference, both in outdoor and indoor applications. Some of them include channel
equalization, directional antennas, and multiple antenna systems. Each of these tends to be
more particularly suited to different applications. This thesis will focus on multiple antenna
systems. The signals from different antennas can be combined in various ways, including diversity

combining, phased array processing, and adaptive array algorithms. Adaptive array
sytems are becoming increasingly feasible for high bandwidth applications with continuing
improvements in digital signal processors. The indoor multipath propagation model presented
in this thesis is intended as a tool to evaluate performance of these various multiple
antenna systems.