Tag Archives: Directional WiFi

Up to now, honestly, everything I have written about is equally applicable to anyone, rural or urban. But this is where that ends…

If you live in town, once you have a network that spans your house and yard, you’re pretty much done. You might want to put up cameras around the house or link in your watering system so you can control it over the internet, but, once you have the router set up, the network-building part is finished.

If you live in the country, though, you typically have a house, a garage, a workshop (or two), offices, barns, stables, and a wide variety of other possible outbuildings, as well as fields, storage facilities, waterways, etc.

Your $35 wireless router will not reach all these places, and a $200 router will only do slightly better. Nor is “hard-wiring” an option: Ethernet can only go 100 meters, and, although fiber cable can go farther, running cable is a difficult and prone to needing repair (critters seem to love cable, especially for lunch).

Wi-fi is the answer, but not the typical wi-fi router. A typical “consumer-grade” wi-fi router has an output power of 60 milliWatts (mW), or 0.06 watts, to a 2 deciBel omnidirectional antenna, which gives it an “Effective Isotropic Radiated Power” (EIRP) of about 100 mW or 0.1 Watts. If that doesn’t sound like much, that’s because it’s not – it is designed to provide a wi-fi signal inside a suburban house while not interfering with the house next door.

The Federal Communications Commission (FCC) and Industry Canada (IC), however, allow unlicensed “point-to-multipoint” stations on 2.4 GHz, like a wi-fi access point, to operate up to 1 Watt of power to a 6 dB antenna, for a total EIRP of 4 watts.

Now, 4 watts is going to go a lot further than 100 mW, and there is no restriction to how many of these higher-power devices you use. So we are faced with two problems:

1. Where do I find a device with a whole lot more power?
2. What do I do to get the most range out of it?

The first one is easy: there are a few companies out there building high-power, low-cost access points for the Wireless ISP (WISP) market. The second one, however, is a little tougher.

Wi-fi, at least the “b,” “g,” and “n” variants operate at 2.4 GHz (“n” can also operate simultaneously on 5.8 GHz), which is a very high radio frequency. For reference, cell phones operate at 0.8 GHz (sometimes at 1.9 GHz.), and FM radio operates at 0.1 GHz (100 MHz).

A friend of mine told me it’s best to think about it this way: the higher the frequency, the more radio waves behave like light. Lower-frequency radio waves will “bend” around or pass right through obstacles, but high-frequency radio waves will be weakened (“attenuated” is the technical term) by any solid objects. How much they are attenuated depends on the object, but, in general, the more solid, dense, and metallic the object, the more it will attenuate the signal. Metal is the worst – it is possible to build a structure with metallic mesh that you can see through but will stop almost all radio emissions from entering (called a “Faraday Cage“)

So, to get the best range from your wi-fi access point, you want to have it outside, so it doesn’t have to pass through the walls of your house.

However, the radio waves don’t all follow a completely straight line from transmitter to receiver – it turns out that they are distributed in the air in a football-shaped region between the transmitter and the receiver called the “Fresnel Zone.” For short distances, the Fresnel Zone is not that important, but, once you get out over 100 yards or so, it becomes increasingly important: for “good” radio transmission (constant contact with the source and a good rate of data transmission) you want to have the Fresnel Zone 80% open; to just have a fairly reliable connection, it needs to be at least 60% open.

What this means, for instance, is, even if you can see the antenna above a dense stand of trees, you may not be able to access the wi-fi access point from your computer because the trees are disrupting too much of the Fresnel Zone. Indeed, if you have the access point out in the open but only 4 feet off the ground, the ground will start to be more and more of an obstacle as you get further away.

The size of the Fresnel Zone increases as the distance between the transmitter and the receiver; for instance at 2.4 GHz and a distance of 1 mile, the Fresnel zone is approximately fifty feet across.

The keys, then, to getting the a wi-fi signal out to your garage, office, workshop, and stables are:

1. Getting a powerful wi-fi signal to start with; and
2. Removing as many obstacles as possible from the path between your wi-fi access point and your computer.

We’ll look at that first one in the next post.

So, in order to use the Internet from all over your property, you need something a little more powerful than your typical wifi router. But what, exactly?

If you’re like me, the first thing you do is go to Google and search for “high power wifi” or “long-distance wifi” or something like that, and you get back… almost nothing useful. The searches return (at least as of the time I am writing this) numerous pages of links to industrial-grade wi-fi systems (for tens of thousands of dollars), do-it-yourself projects (“build a wifi antenna out of cans and baling wire), high-power indoor wifi routers (e.g. Bountiful and others), and high-power wi-fi adapters for your laptop (so you can access the free wi-fi at the coffee shop from a block away).

A few of the ads are for things like “high-power AP & CPE” which, believe it or not, is what we’re looking for. These ads are aimed at Wireless Internet Service Providers, who use them (usually “tweaked” so they can’t be used for wi-fi access) as Access Points (AP) and Customer Premises Equipment (CPE) – the AP goes on a tower, and the CPE goes on the side of someone’s house to provide them with an internet connection. Because this equipment is meant for use by this rather demanding but low-margin business, they are tough, weatherproof (for mounting outside), and remarkably low-cost.

You’ll see, looking at those links, that there are two general kinds; most of them are directional, which means they have an antenna that “focuses” the radio energy in one particular direction, and some of them are omnidirectional (or don’t have an antenna at all), meaning they cast the radio energy in all directions around the unit.

The funny thing is that folks usually start with a directional unit because they are thinking of getting wi-fi to a specific place (e.g. a workshop) and a directional radio is the obvious way to do that. The problem comes later on when they realize that it’s also useful to have a link to some other place (e.g. a barn) or two (garage, storage building, stable, grain bin, etc.), or just to have internet access all around the house.

Some of these directional devices have external connectors that can be used with omnidirectional antennas. Good examples include the Ubiquiti NanoStation, the EnGenius EOC2611P, and the Deliberant AP-Solo. If you’re uncertain about how you want to proceed, these APs can provide flexibility. You can also start with one of them and simply add more in additional directions; 4-6 of them (depending on the directional gain of the antenna, pointed in various directions) create an omnidirectional signal.

However, best of all is to simply use an omnidirectional access point; my favorites are the Ubiquiti PicoStation 2 HP and the PicoStation M2; their cousins the Bullet 2 HP and Bullet M2 are similar, but comes without any antenna or power supply.

These Access Points are quite inexpensive, and they can be used up to half a mile away with a normal laptop. In addition, they have a function called “WDS” that allows you to set up additional APs as “repeaters.” This can allow you to cover a very large area with a WiFi signal, although my own testing shows that the practical limit is two repeaters. The WDS system creates a lot of network “overhead” traffic, and more than two repeaters seems to overload the network.

These high-power APs can broaden the distribution of your internet connection considerably, making a reliable WiFi signal available across your property.  But there is a lot more you can do…