1) What is Spread
Spread Spectrum is a special radio
frequency modulation technique that has been used for many years as
a solution to offering connectivity in point-to-point and
point-to-multi-point data communications applications. It was
developed by the military for secure communications.
2) What is the
operating range of Spread Spectrum radio systems?
That depends on many things. Indoor
propagation is affected by the type of construction of the walls and
floors. It depends on where in the building the radios are mounted.
A line of sight path has less loss and therefore greater range than
a path through walls. Metallic structures attenuate signals much
more than wood, cement or plaster. If the wave
must be propagated around corners by diffraction, the range can be
severely restricted. Typical spread spectrum systems have an indoor
range of up to 2,000 feet unobstructed, and up to 400 feet through
standard walls. Outdoor propagation depends on the factors mentioned
above as well as on heights of antennas, curvature of the earth,
distance between two systems, density of foliage, and size of any
buildings or obstructions in the path. Typically, spread spectrum
systems have an outdoor range of up to 25 miles under ideal
3) Can multiple
Spread Spectrum radio systems be operated in the same physical area?
Normally yes, depending on data rate
and frequency of the system. Spread Spectrum radios operate in
multiple frequencies, which at data rates up to 20 Mbps can be set
to allow from three to fifteen systems to operate in the same
vicinity. To assure maximum throughput, normal configuration should
be limited to no more than three systems in the same vicinity.
4) Can systems be
installed in a multi-point configuration?
Most bridge or bridge/router Spread
Spectrum systems can be configured as either point-to-point or
5) Can the actual
radio equipment be installed outside?
Yes, provided it is installed in
special water proof and climate-controlled enclosures. Radio units
typically function in the temperature range between -10F and +122F.
Outside of these temperature ranges, the performance of the systems
begin to degrade.
6) Am I allowed by
FCC rules to modify a manufacturer's packaged Spread Spectrum radio
No. FCC rules clearly state that a
manufacturer must certify a packaged system. This certification
specifies the type of radio, cables, connectors, antennas and
accessories that can be packaged for sale. These certified systems
cannot legally be modified in the U.S. by a manufacturer or an end
user. HOWEVER, AABroadband as a professional installer can legally
modify and customize a system, within certain limits.
7) How do I make
sure my communications are secure?
Much of today's technology for Spread
Spectrum radio was conceived for military applications with this
exact problem in mind. The unique spreading patterns in these
systems are difficult to decode for a receiver that doesn't know the
specific pattern. For 802.11 communications, implementation of
Dynamic WEP, EAP/LEAP, and RADIUS servers are required for complete
8) How much does a
typical Spread Spectrum radio system cost?
Systems vary in price depending on
the data rate, enhanced features and distance of the required link.
Cost per megabit of data rate decreases as the data rate of the
system increases. A typical 11 Mbps long distance point to point
link would cost about $6,000. A similar 45 Mbps would cost about
$20,000; a 100 Mbps link about $45,000
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