« October 2004 | Main | March 2005 »



Overengineering 101: How to build a 900lb wireless network

A few colleagues of mine are in a similar line of work and as it turns out, work within a couple-hundred feet of my office. We thought it would be a great idea to to get networked to collaborate (and, of course, to stream each other's music)

We all had Macs and some networking devices, but as it oft is the case in NYC, the short distance between our macahines was littered with steel doors, microwave ovens, window cages, and more. The only way to get connected would be to:

(1) purchase hundreds of feet of Cat5 cable and find a way to get it across a hall, upstairs, and also across the alley into the building next door or
(2) wirelessly blast through and around the objects with brute force


We chose option number two. The below are images and descriptions of how we did it:

architecture.gif
An overhead view of our network Click to view full-sized image (941x600px)

survey_small.jpg
Our network from outside click to view full-sized image (1666x400px)

2_365_close-up.jpg2_369_close-up.jpg
Broadcasting antenna close-upReceiving antenna close-up


Now that we've got some hindsight we can say that the best way to go about building a powerful Mac network mesh like this would be to:
(1) Make a map like the image above
(2) Identify the parts and devices you will need to connect these machines
(3) Build the network out from the main base station to the end points starting with blank configs and using Apple's Airport Setup Utility


(1) Making a map:
You just need to identify where your network is going to be based and what remote points you will need to make to bounce your signal far enough to reach all of your workstations. We found our connection was not nearly as strong when using "relay" vs. setting up one Main Base station and one or more "remote" base stations.

Other considerations are angle, distance, and obstacles in the way. In our scenario the best way to bypass our obstacles was to use cable where we could, and antennas to broadcast/receive. In a residential suburban house I'd imagine you'd need half the equipment we ended up using.


(2) Our Parts list (pictures coming soon):


BASE STATION (EXTREME):
At first we were going to use my Airport "Snow" to broadcast. Thanks to our friends at vonwentzel.net we found out that the connections on the inside of this base station were MC so we knew what kind of adapter we had to get for the cable: N Male to MC.

After this was ordered we realized that we could *not* use the "Snow" base station as it did not support WDS (Wireless Distribution System), which was necessary in order to keep an all-Apple network.

So no problem - I'll get an Extreme *and* it will have an external antenna port so we'll just plug and play with our existing cables, right? Wrong. The Airport Extreme uses not just one, but TWO proprietary ports: "MC" on the inside and "MC-Card" on the outside.

No problem. We'll just drill a hole in the case like we were planning anyway and plug directly into the Extreme card inside...

The end-to-end connection looked like: Base Station --> MC Male to N Male pigtail --> LMR400 cable with female N on Base station end to N Male on antenna end --> Antenna with N female attachment

4_base_station.jpg
Broadcasting Base Station "Extreme"

4_pigtail_custom.jpg
Pigtail and bored hole close-up

WDS (WIRELESS DISTRIBUTION SYSTEM):
We quickly learned that this WDS thing, even though it was a completely obvious technology to us, is apparently a rather new feature in Apple wireless products. The first few generations of wireless network were one broadcaster and many receivers. With WDS you can rebroadcast and extend the range, or if you get all crazy like us, can blanket an area pretty effectively.

The trick here, being a newish Apple thing, is to make sure that *every single* network hub is new enough to do WDS. That means Airport Extreme and Express only.

WDS_1_snow.gif

WDS_2_extreme.gif


3/4 DRILL:
*specify type*. Good way to drill cleanly through the Airport Base station housing and not damage the internal components.


AIRPORT EXPRESS:
Cheap, small, and support WDS. A pretty good end point for a wireless network.


ALL-WEATHER ANTENNAS:
Broadcaster:
http://www.buffalotech.com/products/product-detail.php?productid=39&categoryid=8

Receiver:
http://www.buffalotech.com/products/product-detail.php?productid=40&categoryid=8


The most attractive looking (though a bit pricey for this use) antennas were definitely the ones from Buffallo. I've used their 54g PCI Airstation (with external antenna - no longer on the market) and instantly gained the highest respect for the company.

So we're looking at the first antenna and I'm thinking it looks a lot like their indoor ones, but must be a little bigger, right? Wrong again, but we've taken a good-humored stance on the whole thing so this one can be laughed off; when my neighbor receives it by mail and walks over my jaw drops -- it's the size of a baseball bat (or missile launcher depending on your bend).


FOAM!:
Keep the heat in while letting the cable out your front window (from the top).


N TO MC-CARD PIGTAILS (ONE FOR EACH ANTENNA):
Our Buffallo antennas came with MC-Card to N Female pigtails so we knew our antenna-to-base-station cable would have to be "N".

http://nocat.net/connectors.html

"N: Threaded, larger connector common on many 2.4Ghz antennas. They perform quite well, although they are larger than some (but are perfect for thicker cable, like LMR-400)."


LENGTHS OF LMR-400 CABLE (N FEMALE TO N MALE):
Coaxial seems to be one of the standards for industrial use. Finding outdoor antennas to purchase was easy, but finding documentation on how to get them to work in non-industrial environments was a little more difficult (unless, I suppose, you're a professional network builder). As it turns out, LMR-400 is a shielded version of coaxial cable with less signal drop. This is important as you want your network signal to be as strong as possible from end to end and you can lose a few decibels before you even get to your antenna if the length is substantial. We used one 30' length and one 12' length.

We ordered from the saucy and obnoxious people at Pasadena Networks, LLC (800-259-5110). They will roll some cable off a spool and cut it to length and attach tips on the end for you. My guess is that they hated us because we weren't actually commercial vendors and that we ordered such a small amount of cable.

Anyway, if you can get the cable and connectors locally you can build it yourself:

http://www.qsl.net/n9zia/wireless/pics/n_install.png


ZIP TIES:
Keep your clusters of cables neat and professional looking.


TORX 7-8-9:
Not sure about the suburbs - but these are damned difficult to find in NYC. Many computer shops, but few computer tools - I guess they want to keep the repair business to themselves. We ended up finding a set at Sears (the Craftsman line)


(3) BUILDING THE NETWORK

Since we gave you most of the commentary when identifying the parts, you'll need only to get them, and assemble. The only special notes here are:

- If you're doing an all-Apple network* (*all apple networking gear - individual PCs are okay to have on network. If you're encrypted like we are you'll need to get them the "Network Password Equivalent" to type in as Apple is actually translating your human-readable password into some crazy garble that PC users are used to entering. To find this open the Airport Admin Utility and log into your base station and select the menu: Base Station/Equivalent Network Password...) you'll need to use the Airport Admin Utility.

Our broadcast arrangment is:
- network sharing (WDS)
- printer sharing
- external antenna

You'll want to set this up in order:
(1) configure base station to accept internet connection and share. connect from a computer and test.
(2) configure base station to printer share. connect from a computer and test.
(3) attach antenna. connect from a computer and test.
(4) bring Airport Express (or other extremes) into the room, plug in, do initial setup (name it, etc.) and use the Airport Admin Utility on the *main* base station to set up WDS "main base station". During this process you'll be asked to identify another base station to set up as a "remote" base station. It will log in and automatically configure it.

There are a few important parts here:

Once you've got one "remote" set up you should be able to unplug it, walk to where you're going to use it, plug it back in and go. Continue on with additional remote stations in the same way.


AFTERMATH "NETWORKS CAN BE DELICATE!":
I had a friend visiting from out of town that wanted to make some changes to my neighbor's 'Express (for better use with stereo).

From what we can determine, the 'Express config was changed and it tried to be "helpful" and update all the other WDS devices in the vecinity, botched it, and brought the entire network to the ground. We had to rebuild it from scratch using the steps above (manual config changes did nothing).

This is probably the biggest problem we ran into. Our advice: map out your network exactly as you envision it, then set it up, and NEVER TOUCH IT AGAIN. :-) It will be quite reliable that way (my "Snow" Base station worked for a few years with heavy daily traffic and *never* needed a reset - my DSL line did, however, have a few days worth of outages).

Posted by Aaron R. Deutsch on February 15, 2005 | Comments (0)