Saturday, September 17, 2005

Extending the Wireless

We recently installed a new pastor, who is interested in using technology as an aid to the work he is doing. Not only did he get a Tablet PC, I was able to help him install wireless networking in the parsonage so that he can use it anywhere in his house--not just in his office.

The first major stumbling block to his productivity, however, was that he wasn't able to connect to the Internet, and his email and research sites thereon, while in his office at church. One option, of course, would have been to arrange for a separate Internet connection in the church itself, but this would have meant paying twice for the same service for him, as he is generally the only one using it in either location. Since his house is directly across the street from the church, we figured that it might be feasible to wirelessly bridge his connection from his home office to his church office.

At my place of work we have a campus-wide wireless network. Most of this network rests on a backbone of fiber runs between the various buildings, but a few of the buildings aren't served by conduit runs that would allow us to pull fiber from a location with existing network connectivity. For those buildings we put in wireless bridges which send a focused beam of radio waves from one building to another. This works well as long as the signal is strong and there is a clear line of sight between the antennas on the two buildings being connected. It is a pricey solution, however, and using the same Cisco equipment we used there was financially out of the question at church.

Whereas a single such connection at work cost close to $1000, we were able to do the bridge at church for about $50. We could have done it for less than $10 if I had had more time (and gumption).

The first way that we saved money was through the donation of two Cisco AP350 wireless radios (called Access Points, or APs) from a local university that was replacing this aging equipment with newer equipment from a different manufacturer. We were very fortunate to receive these radios as Cisco radios are the ones I am most familiar with and have some experience setting up in this fashion. I haven't done significant research to find out what lower cost wireless units support repeater functionality, but the Netgear Model WG602 is one that claims to support this. There are probably others. I do know that the Cisco APs work very well in this regard.

A repeater, by the way, is an AP that gets its network signal wirelessly from another similar AP, then rebroadcasts it to extend the range of that signal.

In order to make this whole thing work, only a few things are needed: a router which is connected to the Internet, an AP connected to the router by an Ethernet cable, a long range directional antenna attached to that AP, and a second AP with regular omni-directional antennas located in such a way that it can receive the beamed signal from the long range antenna.

By stringing a long Ethernet cable from the router in the home office to an AP located by a window facing the church, we were able to position that AP properly for sending the signal to the church. We purchased a Wireless Garden Super Cantenna to use as our long range antenna. We could have mounted it outside the window on the side of the house, but New England winters being what they are and the antenna housing being on the fragile side we opted instead to use the included tripod mount and set it up inside the window. Connection to the AP was trivial and the antenna worked flawlessly right out of the box.

At this point, we had a 30 degree beam of radio waves pointed across the street at the door of the church located closest to the pastor's office. When I took my Tablet PC across the street, I had a very strong Internet connection standing inside that door. As I walked farther from the door the signal rapidly weakened and was lost just inside the church office.

Fortunately, there is a closet right inside that outer door which was well positioned for placing the repeater AP to receive that beamed signal. We set the repeater AP up at this location and turned it on. When it had booted, it picked up the signal from across the street and rebroadcast it, giving an excellent signal to the office. The signal was so strong, in fact, that we were able to get a decent Internet connection in the sanctuary and even in the pulpit at the far end of the church. (I haven't yet tried to see whether I can get it in my second floor Sunday School room, but that would be a nice benefit as we could use it this year in class.)

I would have preferred to beam the signal to a more central location in the church, but there are shrubs and trees around much of the building and foliage is a very effective blocker of radio signals. Bricks and some other construction materials can also hinder or block this. (We have one old building at work that has chicken wire in the plaster walls and we can't get a decent signal to broadcast anywhere in there.)

All in all, this appears to be an effective and inexpensive solution to our problem. We could have saved even more by building our own antenna, especially since the antenna is mounted inside and protected from the weather. There are several sites on the Internet that give instructions on building your own "cantenna" out of Pringle's potato chip cans. A few such sites are here, here, and here.

The last piece of the equation, and a critical one, is securing the wireless network. This needs to be done for a number of reasons. One of particular importance is the confidentiality of the information that a pastor will be dealing with. It is pretty trivial to sniff a wireless connection that isn't well encrypted and to read the packets that are being broadcast. Unscrupulous individuals could have access to some very personal and potentially embarrassing (or worse) information this way. If you decide to put wireless in, please take the time to secure it. Use the strongest encryption your AP and computers are capable of using. Open wireless networks are invitations for trouble.