{SearchText}Repeaters

The backbone of the network is the fast Internet backhaul down the valley into Sudbury, a distance of some 4.8 miles as the crow flies. Whilst this is not a problem for properly aligned and configured wireless equipment, we ran into problems getting a clear line of sight without using large masts and getting a clear Fresnel zone. The land around the Stour valley is not flat but undulating (those that live near mountains would consider our landscape flat!) In Sudbury the valley floor is 23 m above sea level and our highest repeater on the valley edge is just 65 m above sea level. This has the disadvantage that trees growing to around 20 - 30 m tall can block our signal due to them refracting it, imagine if they were made from translucent aluminium foil and you wanted to shine a light though some would get through but most would be bounced off.

In order to get around these obstructions we had to use repeater stations: a length of network cable was routed around the obstruction. The two microwave units (access points) are either connected back to back with a crossover cable or using a switch. The advantage of using the switch is that whoever is living in the house with the repeater equipment can tap into the network using ethernet cable. It is worth noting that in this configuration the network speed is not diminished too much, we still get a real throughput of around 4Mb/sec, the actual maximum speed of 802.11b. Since each AP is half duplex, it has to stop receiving in order to start transmitting, however ping times going through 3 repeater stations in series average around 10 ms round trip (beat that satellite Internet!), more than adequate.

ADSL==bridge- - - -bridge==client- - - -AP==client- - -AP- - -client==LAN

Key

== CAT5 Ethernet cable

- - - Air

This repeater comprises of two antennas, an omnidirectional and a parabolic directional antenna.

Last update Wednesday, March 14, 2007 2:24 PM