Getting the most from 802.11n

With 802.11n finally here we can have really, really fast Wi-Fi ... if you know what you're doing.

Given a choice between fast, 802.11b; faster, 802.11g; and fastest, 802.11n, most people will pick the fastest every time. But, while the IEEE 802.11n Wi-Fi standard, with its up to 300Mbps burst speeds, is easily the fastest wireless networking protocol, until recently it's never been a standard. Thus, a Wi-Fi access point (AP) using a draft 802.11n protocol from one vendor was unlikely to deliver its full potential speed to a laptop with an 802.11n chipset from another maker.

It wasn't supposed to be that way. But, for years, the Wi-Fi hardware OEMs puppies fought over the 802.11n protocol like it was a chew toy. The result was that we've had to wait for over five-years before 802.11n finally became a real standard on September 11, 2009. The delay was never over the technology. The technical tricks that give 802.11n its 100Mbps to 140Mbps steady connection speeds have been well-known for years. The reason why is it's only recently that we're able to use 802.11n at its full potential.

So, you're ready to go with just buying a new 802.11n AP right? Not so fast tiger. While it's true that 802.11n can leave 802.11g at the starting line and even leave some older Ethernet routers eating its dust, it's still all too possible to set it up so that you can't get all the speed out of 802.11n you paid for.

How 802.11n Works

First, you need to know a little bit about how 802.11n works. Technically, 802.11n achieves its performance by adding multiple-in, multiple-out (MIMO) technology to the earlier 802.11g technology.

MIMO takes advantage of what has been one of radio's oldest problems: multipath interference. This occurs when transmitted signals reflect off objects and take multiple paths to their destination. With standard antennas, the signals arrive out of phase and then interfere with one another. You probably have heard this yourself on a radio as you approach the end of a tunnel and your favorite station's signal alternates getting stronger or weaker as you move towards the open air.

MIMO systems employ multiple antennas to use these reflected signals as additional simultaneous transmission channels. In short, MIMO knits the disparate signals together to produce a single, stronger signal.

802.11n devices can also take advantage of working not just in 802.11g's rather crowded 2.4GHz radio spectrum but the roomier 5GHz range as well. The net effect, if your equipment supports the 5Ghz range -- you'll know because your device will say that it's dual-band -- is faster throughput.

In addition, 802.11n uses channel bonding to increase its throughput. With this technique, an 802.11n device uses two separate non-overlapping channels at the same time to transmit data. Thus, customers can send and receive multiple data streams at the same time.

Speeding up 802.11n

Here's how this effects you. First, the more MIMO antennas hidden within your 802.11n router or network interface card (NIC) determines how fast potentially your devices can deliver the network to your computer. Generally speaking, the more expensive the equipment, the more MIMO antennas which gives you a stronger signal and a faster Internet experience.

The 802.11n standard allows for up to four antennas, which can handle up to 4 simultaneous data streams. Typically the number of antennas is advertised as 4x4, 3x3, and so on depending on the number of antennas. You can't tell though by looking at a device. Unlike the rabbit ears of old-fashioned, analog TVs, an 802.11n router might, or might not, have visible antennas.

It's more than just adding antennas though. Techniques such as beamforming are used to direct those multiple antennas to work out the most advantageous way to maximize signal strength and thus speed. In fact, you can even buy 'smart antennas' such as D-Link's Xtreme N ANT24-0230 Antenna that will help your 802.11n router maximize its potential.

However, if you want to try this you should keep in mind that you have to match the Antenna with the equipment. This isn't a case where simply adding a bigger antenna will noticeably boost your signal. You have to have just the right pairing before it will work efficiently.

Regardless of your antennas, you also need to make sure that you're using up-to-date 802.11n equipment. Older 802.11n equipment may, or may not, work well with your new hardware. 802.11n went through a miserably long standardization process and along the way a lot of 'somewhat' compatible equipment was made and sold. You really can't expect an 802.11n from say 2007 to work well with your 2010 802.11n AP. If the two devices are from different vendors that goes from being a very likely problem to being an almost lead pipe certainty that they won't work that well with each other.

Indeed, unless your equipment was manufactured in 2010 even now I wouldn't count on getting maximum throughput by using say D-Link gear with Linksys equipment. While they should be able to talk to each, other minor technical incompatibilities will keep you from seeing the fastest possible speed.

No matter who made your equipment, you may want to continue to support your older 802.11g-only laptops and the like with your new 801.11n AP. While you can do that, this comes with a performance cost. While 802.11n devices working in the 2.4GHz band can also support 802.11g devices they do so at the cost of lowering 802.11n device connections speeds by half. So, for example, an 802.11n router capable of delivering 100Mbps of throughput if it were working only with 802.11n devices would deliver only about 50Mbps throughput to the 802.11n-based computer if it were also supporting 802.11g hardware.

In addition, 802.11n uses channel bonding to increase its throughput. With this technique, your 802.11n device uses two separate non-overlapping channels at the same time to transmit data. Thus, you end up sending and receiving multiple data streams at the same time. Your 802.11n AP probably calls this using 'double-wide' channels. A 'double wide' takes up 40MHz of radio space instead of the usual 20MHz.

That's great ... when it works. The problem with channel bonding is that, in the United States, there's really only room for three 20MHz channels in the 2.4GHz radio spectrum assigned to Wi-Fi. If you use a double wide, that means you're taking up most of the space. Now that may be fine, if you're out in the woods where your neighbors aren't also using Wi-Fi. If you're in an office building or a town there's a good chance you'll be interfering with a neighbor's Wi-Fi signal and vice-versa with double-wide.

I'm not saying don't do it. I am saying it probably won't give you as much of a boost as you thought it would due to interference problems.

The way to avoid this slowdown is to, once more, spend some additional money for a dual band 802.11n equipment such as the Linksys Simultaneous Dual-N Band Wireless Router WRT610N, which is what I use about my house. By using the far less crowded 5 GHz band for channel bonding I can easily run HD movies from my downstairs media center to my upstairs HDTV.

To get the most from channel bonding and its wider Wi-Fi channels you need a dual-band AP that can handle simultaneous signals. Some older dual-band equipment, like the first models of Apple's AirPort Extreme could do 2.4GHz or 5GHz but not both at the same time. To maximize your performance you want to avoid this kind of hardware.

Last, but not least, you should always keep in mind that even the fastest 802.11n set up in the world is only as fast as its slowest link. So, for example, if you only have a 3Mbps DSL connection to the Internet, all the 802.11n speed in the world isn't going to speed up downloading a new game.

Still, if you do have a fast Internet connection or an office where your servers are hooked up to a gigabit or faster LAN then taking steps to speed up you 802.11n network will reap you the benefits of truly faster wireless networking. Enjoy!

TABLE:

Slowest: 802.11: 1 to 2 Mbps. Established in 1997 and ran at the 2.4GHz the 2.4GHz frequency range. Now obsolete.

Slow: 802.11b: Maximum throughput: 11Mbps. Normal throughput in practice: 4Mbps. Made a standard in 1999 and runs on the 2.4GHz frequency range. Most Wi-Fi devices still support 802.11b.

Faster: 802.11a: Maximum throughput: 54Mbps. Normal throughput in practice: 20Mbps. Made a standard in 1999 at the same time as 802.11b, but regulatory slow-downs kept 802.11a off store shelves until 2002. 802.11a, which is still supported on some devices, runs on the 5GHz range.

Faster Still: 802.11g. Maximum throughput: 54Mbps. Normal throughput in practice: 20Mbps. Approved as an IEEE standard in 2003. Like 802.11b, it operates in the 2.4GHz range. While it has the same speed as 802.11a, it has a greater range inside buildings and so has become the most widely deployed Wi-Fi protocol.

Almost the Fastest: 802.11n: Maximum throughput: 450Mbps. Normal throughput in practice: 100Mbps+. Approved in 2009. It can operate on both the 2.4GHz or 5GHz.

Fastest: 802.11n with simultaneous 2.4GHz and 5GHz: Maximum throughput: 600Mbps. Normal throughput in practice: 125Mbps+. This requires the use of a dual band 802.11n routers and NICs and a 'clean' Wi-Fi environment with minimal interference from other Wi-Fi LANs.

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