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The term repeater comes from the early days of long
distance communication. The term describes the situation
when a person on one hill would repeat the signal that
was just received from the person on the previous hill.
The process would repeat until the message arrived at
its destination. Telegraph, telephone, microwave, and
optical communications use repeaters to strengthen
signals sent over long distances.
A repeater receives a signal, regenerates it, and passes
it on. It can regenerate and retime network signals at
the bit level to allow them to travel a longer distance
on the media. |
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One downside of repeaters, though, is that they reduce
throughput on the LAN. A repeater must receive and
retransmit each frame on the same RF channel, which
effectively doubles the number of frames that are sent.
This problem compounds when using multiple repeaters
because each repeater will duplicate the number of
frames sent. Thus, be sure to plan the use of repeaters
sparingly. The Four Repeater Rule for 10-Mbps Ethernet
should be used as a standard when extending LAN
segments. This rule states that no more than four
repeaters can be used between hosts on a LAN. This rule
is used to limit loss added to frame travel by each
repeater.
As a result, repeaters are an effective solution to
overcome signal impairments such as RF attenuation. For
example, repeaters provide connectivity to remote areas
that normally would not have wireless network access.
You may have one access point in a home or small office
that doesn't quite cover the entire area where users
need connectivity, such as a basement. The placement of
a repeater between the covered and uncovered areas,
however, will provide connectivity throughout the entire
space. The repeater fills holes in coverage, enabling
seamless roaming. |
