We have been running a wireless network throughout the Karekare area (or more correctly the Waikarekare area), starting with an experimental network in 2004. The terrain is hilly and bush clad (Aerial Photo with network sites overlayed).

Step one was finding the antenna sites that maximise coverage and are handy to power sources. That involved lots of climbing on roofs with a laptop with an external antenna. The rule, "If you can see the remote site, everything will work", turned out to be mostly true. The reverse, "If you can't see it, it will not work", has always been true (except some trees are relatively transparent to 2.4GHz, while other are not. Damp ones are always a problem, unless the two routers are very close). The exceptions were sometimes baffling. We have had examples of sites with a perfectly clear path between the two wireless routers, and reasonably close at that, but the links have been marginal at best. Other, seemingly less optimal sites, have worked far better. We have put some of this down to reflections from the terrain, causing signal cancellation, and/or added noise. Some of it, we have put down to signal splatter off of trees off of the signal path. Large pine trees near the signal path, with needles about the length of an antenna, look to be adding to the received noise level. We assume that this is a similar effect to shining a light on to a tree full of tinsel. Raising the transmitter power, just increased the noise level.

We experimented with many antenna types, and still are (see Antenna ). We settled on single and double sided slotted wave guides as the antenna for our core network sites as they are high gain, have a low wind profile, good signal pattern, and are relatively easy to make. We have used bicircle antenna at the client end. These are small enough to put into the router enclosure, easy to make, and also have a good gain. A variant, with a small parabolic reflector, rather than a flat one, has worked well for long distance links. We are looking at circularly polarised antenna to see if these will help in some of the marginal signal areas, where reflections seem to be a problem.

We started by using LinkSys WRT54G and WRT54GS basestations (see router build), both in the core network and at client sites, with OpenWRT firmware using routed WDS links between the base stations. We have switched to Ubiquity Nanostations, as they are ready made for external use and have built in high gain antenna. These have proved very reliable. The core network backbone is now using Nanostation M5's, the newer clients use Nanostation 2's at the client end and we still have WRT54-GL's as distribution nodes for the clients to connect to.

Network Design