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Unit 9: Wireless MAN Systems

same building but are normally in either adjacent buildings or with the proper antennas and line Notes
of sight bridges can even connect networks up to 30 miles apart. Wireless bridges connect to the
wired network through the Ethernet port and replicate that data to a remote network bridge or
access point via 802.11a/b/g wireless (Wi-Fi) protocol.
A point to Multipoint topology wirelessly connects multiple locations together allowing them
to share the same network resources. The bridge at the main, central, location is called the root
bridge or base station bridge and all data passing between the wireless bridge clients must pass
through the root bridge first. These point-to-multipoint networks are used in wireless internet
service providers (WISP), large corporate campuses, distribution facilities, school districts, public
safety applications and many others…
Point-to-multipoint bridging is when an access point talks directly to more than one access point:

Figure 9.3: Point-to-multipoint Bridging

What do I need to build a Point to Point Bridge Link?

Line of sight between the two locations. You may need to install a pole or tower on your roof top
in order to achieve this. A site survey is recommended before installation.
Select a Wireless Bridge: Here are some things to consider when selecting a wireless bridge
Distance: Distance will determine what gain antenna will be required and if you need an external
antenna or if an integrated antenna will be sufficient.
Wireless protocol: Do you want to use a bridge base on 802.11 standards so that you have
interoperability with other bridge manufacturers or would you like something with a protocol
proprietary to a particular vendor? There are some added security benefits when using a
proprietary over a standard protocol.

Frequency: Do you want to use a licensed or unlicensed (2.4, 5-5.8 GHz) band?
Indoor or Outdoor: Indoor wireless bridges are less expensive but you will have to buy quite
a bit of LMR-400 cable to connect to the outdoor antenna. This adds a great deal of signal loss
and in the end you will need a higher gain antenna to compensate. An outdoor bridge can be
placed right next to the antenna and therefore cuts down on the amount of cable you need to buy
as well as the amount of signal loss.

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