Page 284 - Integrated Wireless Propagation Models

262 C h a p t e r F i v e

However, in the indoor environment, the boundary of coverage is well defined by the
geometry of the building, and the walls of the building itself will affect the propagation.
In addition to the frequency reuse on the same floor of a building, there is often a desire
to have frequency reuse between floors of the same building, adding a third dimension to
managing interference issues. Finally, in a very short range, particularly where millimeter
wave frequencies are used, small changes in the immediate environment of a radio path
may have substantial effects on the propagation characteristics. Because of the complex
nature of these factors, if the specific planning of an indoor radio system were under­
taken, the detailed knowledge of a particular site would be required, including geometry,
materials, furnture, and expected usage patterns. However, for an initial system planning,
it is necessary to estimate the number of base stations with their proper locations to pro­
vide coverage to the scattered mobile stations within the area and also to estimate poten­
tial interference to other wireless services or between systems. At the same time, the
model should not require a lot of input information by the user in order to carry out the
calculations.

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5 . 1 . 2 Propagation Impairments n d Measure f Quality in
I n door Radio Systems
Propagation impairments in an indoor radio channel are caused mainly by the following:
• Reflection from and diffraction around objects (including walls and floors)
within the rooms
• Transmission loss through walls, floors, and other obstacles
• Channeling of energy, especially in corridors at high frequencies
• Motion of persons and objects in the room, including possibly one or both ends
of the radio link, giving rise to impairments such as the following:
• Path loss-not only the free space loss but also additional loss due to obstacles
and transmission through building materials and possible mitigation of free
space loss by channeling
• Temporal and spatial variation of path loss
• Multi path effects from reflected and diffracted components of the wave
• Polarization of the radio wave mismatches due to random alignment of the
mobile terminal
This chapter presents mainly general site-independent models and the description
of propagation impairments encountered in the indoor radio environment. In many
cases, the available data on basic models were limited in either frequency ranges or test
environments; it is hoped that the accuracy of the models will be improved with more
available data and experience in their application.
It is useful to define which propagation characteristics of a channel are most appro­
priate in describing their significance for different applications, such as voice commu­
nications, data transfer at different speeds, and video services.

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5 . 1 . 3 The i ghlights of the Lee In-Building Model1·3
This section explains the features of newly constructed office buildings that influence the
radio-wave propagation between a transmitter and a receiver located on the same floor.