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Definition
Wireless transmission of electromagnetic radiation (communication signals) has
become a popular method of transmitting RF signals such as cordless, wireless
and cellular telephone signals, paper signals, two way radio signals,video conferencing
signals and LAN signals indoors. Indoor wireless
transmission has the advantage that building in which transmission is taking place
does not have to be filled with wires or cables that are equipped to carry a multitude
of signals. Wires and signals are costly to install and may require expensive
upgrades when their capacity is exceeded or when new technologies require different
types of wires and cables than those already installed.
Traditional indoor wireless communication systems transmit and receive signals
through the use of a network of transmitters, receivers and antennas that are
placed through out the interior of a building. Devices must be located such that
signals must not be lost or signal strength may not get attenuated. Again a change
in the existing architecture also affects the wireless transmission. Another challenge
related to installation of wireless networks in buildings is the need to predict
the RF propagation and coverage in the presence of complex combinations of shapes
and materials in the buildings. In general,
the attenuation in buildings is larger than that in free space, requiring more
cells and higher power to obtain wider coverage. Despite of all these, placement
of antennas, receivers and antennas in an indoor environment is largely a process
of trial and error. Hence there is need for a method and a system for efficiently
transmitting RF and microwave signals indoors without having to install an extensive
system of wires and cables inside the buildings.
This paper suggests
an alternative method of distributing electromagnetic signals in buildings by
the recognition that every building is equipped with an RF wave guide distribution
system, the HVAC ducts. The use of HVAC ducts is also amenable to a systematic
design procedure but should be significantly less expensive than other approaches
since existing infrastructure is used and RF is distributed more efficiently.
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