Four ways to get the most from your 802.11n Wi-Fi

Four ways to get the most from your 802.11n Wi-Fi

Summary: 802.11n can give you really, really fast Wi-Fi... if it's set up right.

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The 802.11n Logo

The 802.11n Logo

In theory, 802.11n can zip by your 100Mbps Fast Ethernet at a real-world 160Mbps, but the practice it's usually much slower. No, the Wi-FI vendors aren't lying; the problem is that you have to set 802.11n up just right to really get fast performance.

First, you need to make sure that you're using up-to-date 802.11n hardware. Older 802.11n equipment, built before the 802.11n standard was finalized in late 2009, may not work and play well with your newer devices. There were many 802.11n draft access points (APs), network interface cards (NICs) and chipsets and each vendor used its own best guess on what the standard would eventually look like.

Thanks to all this older, not quite standard 802.11n hardware, we have two problems. The first is that some older hardware, unless the firmware can be upgraded, won't work at full 802.11n speeds with your newer standardized equipment. The other is that you can be almost certain that older APs, switches, or routers from one vendor won't work well with another vendor's equipment. Oh, it may look like it's working, but if you check you'll often find that your Wi-Fi's connection is only running at 802.11g's 54Mbps.

Of course, if your office is like most, you almost certainly still have a lot of 802.11g compatible laptops in work. You might think that since 802.11n is backwards compatible with 802.11g that you'll do just fine by replacing your 802.11g APs with 802.11n hardware. You'd be wrong.

802.11n AP will support 802.11g client hardware just fine, but letting 802.11n AP support 802.11g comes with a painful performance hit. While 802.11n devices working in the 2.4GHz band are backwards compatible with 802.11g, or even 802.11b, faster 802.11n equipment will lose about half its potential speed. So, instead of seeing say 100Mbps of throughput from 802.11n AP to the 802.11n laptops, you'll only see 50Mbps.

My fix for this is to keep 802.11g APs running until the last of the 802.11g PCs go to that big junk-pile in the Wi-Fi sky. It's worked well for me.

You also should use 802.11n's channel bonding to increase throughput. On your APs, you'll find this option labeled 'double-wide' channels. This in an ancient technique that's used to increase throughput by using two channels at once to deliver data. Then, as now, it works well.

There' a 'gotcha' though. A Wi-Fi's channel is required to be 20MHz. Thus, just like the name says, a 'double wide' takes up 40MHz of radio room instead of the usual 20MHz. The problem is that there's only room for three 20MHz channels in 802.11b/g/n's 2.4GHz radio spectrum. If you run out of Wi-Fi spectrum room, your overall network throughput will decline. Even if you're doing a good job of managing your network space, your available channels are likely to also be used by your next-door neighbors' Wi-Fi set-up.

The easiest way to dodge this potential problem, for now, is to use the higher 5GHz range. Far fewer people are currently using the 5GHz range. This will change as more people switch over to 802.11n, but for now it's the easiest way to use wide channels to increase your effective bandwidth without running into interference. The one downside is that 5GHz has less range than 2.4GHz.

That's why I prefer to use dual-band APs that support both 2.4GHz and 5GHz. Best of all is equipment that supports using both 2.4GHz and 5GHz at the same time for the maximum in flexibility, such as the Linksys Simultaneous Dual-N Band Wireless Router WRT610N. Older 802.11n hardware, such as the first generation of Apple's AirPort Extreme, as well as some entry-level APs, can only support 2.4GHz or 5GHz

High-performance 802.11n equipment also comes with a larger number of multiple-input, multiple-output (MIMO) antennas . 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 described in the technical specifications as 4x4, 3x3, and so on depending on the number of antennas. But, you can't tell just by looking, you have to check the documentation. Generally speaking the more antennas, the more simultaneous Wi-Fi connections the AP can handle, and the better the overall network performance.

It's not just how many antennas you have though. Higher-end APs use techniques like beam-forming to automatically work out the best use for those multiple antennas. In fact, 'smart antennas,' like D-Link's Xtreme N ANT24-0230 Antenna, will help compatible 802.11n APs perform better.

Last, but never least, the fastest 802.11n is only as fast as its slowest link . So, for instance, if your office is still using a T1 with its 1.544Mbps no one is likely to see any significant Internet speed increase when switching from 802.11g to 802.11n.

The bottom line: While it may look like simply adding 802.11n to your network may look like a cheap and easy way to expand and speed-up your network, it's really not. You still need to plan your network in detail, use higher-end network equipment. and possibly upgrade your Internet backbone to make the most out of 802.11n's potential for higher speeds.

Still, if you do your homework, you really can get a Wi-Fi network that will answer your in-house network expansion needs while still providing close to Fast Ethernet's 100Mbps speeds. Just as long as you keep in mind that 802.11n, by itself, isn't a silver bullet for your network speed needs, you'll do fine.

Topics: Networking, Mobility, Wi-Fi

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31 comments
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  • My Wi Fi

    I have an "N" network. I can never get above 2.7 MB/s despite going through this (and all other) advice I have seen.
    avigdor6
    • RE: Four ways to get the most from your 802.11n Wi-Fi

      @avigdor6 try to find the option to make it a n only network, disable the wireless g/b backwards capibilities.
      m3kw9
    • RE: Four ways to get the most from your 802.11n Wi-Fi

      @avigdor6

      That's 21.6 Mb/s if you have your units correct. That's a decent broadband internet connection in the U.S. Have you tried copying from one computer to another on the same network?
      tkejlboom
    • Re: Can never get above 2.7MB/s

      @avigdor6,<br>2.7 MB (less than 24Mbit) is kinda slow, but are you absolutely, TOTALLY sure that your PC hardware isn't a limiting factor? (CPU power, disk read/write speeds, insufficient free memory).<br><br>If the endpoints can handle vastly more throughput, then I'll SWAG that you're using cheap antennas, going through walls/floors at a bad angle, or your AP doesn't have enough radio power, or your AP doesn't have enough CPU power. (The different price levels of DLink n-Routers/Access Points, for example, have different antennas, *and* different output power levels, *and* different processor chip speeds.)<br><br>Next, the angle at which the "middle" of the signal path goes through walls/floors is critical. For example, in my house, going straight through an interior wall is just one inch of sheet rock (two layers of 1/2" each), plus a 2" wide by 4" deep vertical strip every 16 inches (wooden studs). BTW, the signal doesn't travel as a thin string; it travels as a widening cone and somewhat "rebuilds" itself behind such obstacles).<br><br>Now, compare that with going almost parallel to the wall: The distance spent "inside" of gypsum board could easily reach 6, 8 , or 10 inches, and the entire "cone" of signal has to go through ALL of it. As the angle shifts away from "head-on" to the 2x4 studs, the distance goes down (the 4" distance of going straight through the wall was the longest possibility for one stud). But a wider proportion of the signal cone is facing into stud wood, and, as you become more and more parallel to the wall, you reach 100% wood blockage - and then you start going through MULTIPLE studs. :(( And metallic studs are worse, of course. They eat electromagnetic fields for breakfast <img border="0" src="http://www.cnet.com/i/mb/emoticons/wink.gif" alt="wink"><br><br>If your devices work fast when they're both RIGHT NEXT TO the Access Point/Router, then you're problem is radio strength: it needs more signal power; better antennas; multi-channel (and try DIFFERENT channels); or a layout which has more of the signal distances in free air (and less struggling through walls and floors). Or a combination of all these "solutions".<br><br>If it's NOT any faster when the distance is nearly zero, then either the Router/AP or one of the endpoint devices can't handle more traffic- even though the wireless network *is* capable. Money spent on new antennas, or anything else dealing purely with transmit/receive radio signal power, would accomplish nothing.<br><br>But, if your AP/Router is doing firewall work, or port-forwarding, then it could be getting CPU-bound. The extra work to inspecting TCP/IP port numbers and comparing them to various lists for blocking/re-mapping/re-routing could be leaving no CPU power left to handle additional traffic. (The packet transmission itself is "more difficult" over radio than it is over cat5/cat6 cable). In this case, replacing the AP to get a more powerful CPU would solve the problem.
      Rick S._z
      • RE: Four ways to get the most from your 802.11n Wi-Fi

        Further to the points @Rick S._z was making about walls...

        I lived in a full-brick house with concrete floors. My neighbour got better wi-fi reception (thru the window) than I did in the room next door or downstairs. Apparently, the chemical composition of concrete is 80-90% water which severely impacts radio signals at these frequencies
        martin.english
  • Proofread

    Info's good... but someone needs to proofread these before they get sent to thousands of people. Many typos, etc.
    islandbou
    • RE: Four ways to get the most from your 802.11n Wi-Fi

      @islandbou Yes, "Half." I've corrected it.

      I've love to have a copy-editor, but no, as you can tell, I don't have one.

      Darn it!

      Steven
      sjvn@...
  • faster 802.11n equipment will lose about its potential speed.

    Did you mean HALF???
    FiOS-Dave
  • RE: Four ways to get the most from your 802.11n Wi-Fi

    Apple, Cisco and Intel do not support 40MHz wide channels in the 2.4GHz band (even though Linksys, whose parent company is Cisco, DOES).

    Also, the bottom 4 non-overlapping channels in the 5GHz band are extremely-limited in regards to legal power levels here in the FCC zone... so switch to channel 52 or higher for 5x the legal power levels (30dBm vs. 23dBm) of the bottom 4 channels; channel 149 and higher can use up to 20x more power (36dBm) than the bottom 4 channels.

    While you did note that a T1 is only 1.54Mbps, you failed to mention that even premium cable speeds are rarely over 20Mbps, and a T3 is only 45Mbps (a T3 here in mid-michigan is about $2000/month, IF it's available at all), so even the reported 130Mbps connect speeds of 'narrow-channel' 802.11n provides enough bandwidth (about 60Mbps of true throughput) to saturate nearly any internet connection here in the USA.
    Darr247
    • RE: Four ways to get the most from your 802.11n Wi-Fi

      @Darr247

      Why do people so casually neglect the possibility that people will want to keep things in one place and access them from a different machine on the same broadcast network. Yes, internet connections in the U.S. are ridiculously poor, especially for the large amount of money we pay for them(though comcast and Verizon are both offering 50Mbps in select markets). We need not go out to the web ALL the time, though.
      tkejlboom
    • RE: Four ways to get the most from your 802.11n Wi-Fi

      @Darr247

      Lest you forget, though, some of us still use the local network for stuff and don't use the Internet for everything.

      -Not too long ago, I transferred 10 GB of information between two computers connected via gigabit ethernet with a router that also supported it. The speed was amazing.

      -I have installed on all of my PCs a file sync utility that uses the LAN when they are on the same network. It syncs much faster when they are on the same network.
      CobraA1
    • Thanks!

      @Darr,
      I didn't know about the increased power limits for higher channel numbers. Do you know of any "el-cheapo" AP and bridge vendors who already support higher power in their hardware, firmware, and user setup stuff, or is this strictly DIY via external power-boosters? (I know how antenna choice plays into it already, I'm wondering about "inside the box".)

      Thanks in advance, and thanks already. great post!
      Rick S._z
      • RE: Four ways to get the most from your 802.11n Wi-Fi

        @Rick S._z - some of the consumer-grade routers supported by DD-WRT allow adjustment of power levels, but I would not up it at all without considering extra cooling... stock power levels for Linksys is typically 70-75mW... if you up it to 100mW, I would at least enlarge the venting with a dremel; above 100mW consider radically altering the case, adding e.g. 80mm 5VDC fan, and possibly heat sinks to the hottest chips. Still, by the time you've spent that much time and effort on them, it might become cost effective to just drop a grand or so on a Cisco Aironet (see http://www.cisco.com/en/US/docs/wireless/access_point/channels/lwapp/reference/guide/lw_chp2.html for power levels).
        Darr247
    • RE: Four ways to get the most from your 802.11n Wi-Fi

      @Darr247 "Apple, Cisco and Intel do not support 40MHz wide channels in the 2.4GHz band (even though Linksys, whose parent company is Cisco, DOES)." True, and that's very perverse of them.

      That said, I can still overwhelm my 802.11n connection when I've got several people doing work at my office at once. That's one reason I'm not giving up my gigabit switch anytime soon.
      sjvn@...
  • great article, sjvn, thanks!

    I did some extensive research regarding N routers a little while ago which pretty clearly surfaced that the Linksys Simultaneous Dual-N Band Wireless Router WRT610N you mentioned did not perform as good as the Linksys WRT400N Simultaneous Dual-Band Wireless-N Router.

    Also accdg. to both, cnet AU http://tinyurl.com/22pvwa8 and smallnetbuilder http://tinyurl.com/27hbslo, Asus is cutting the edge right now with its RT-N13U (internal antennas) and the RT-N16 (3 swappable external high-gain antennas), both for a great price. They only cover the 2.4GHz range, but range ranks first for me anyway so I am not even interested in the 5GHz range ..
    leebinder
    • RE: Four ways to get the most from your 802.11n Wi-Fi

      @leebinder i'd get the buffulo for gigbit ethernet option as well.
      m3kw9
    • What is the MAXIMUM Range

      @leebinder Hi ! i m planning to use Single internet connection at my home for both home and office (250 meters and 10 walls apart). Is it possible by any means. please reply to me dramitjohari@gmail.com
      drjamit@...
  • RE: Four ways to get the most from your 802.11n Wi-Fi

    5ghz penetrates less walls than lower frequencies
    m3kw9
    • RE: Four ways to get the most from your 802.11n Wi-Fi

      @m3kw9 "5ghz penetrates less walls than lower frequencies." Aye, there's the rub, and why if you're doing a serious office Wi-Fi set-up you really need to sweat the details--and the walls.

      Steven
      sjvn@...
  • To bad public gets bad information

    I see a lot of cheaper routers claiming N compatibility. But of course its not quality N. What's sad is the fact that if you have one of these you really are stuck if you have any G hardware connecting to the router. It can be a much more expensive investment then just buying a new router. You have to look at the other end.
    jscott418-22447200638980614791982928182376