Why 2.4 GHz is a dead end for Wi-Fi

Why 2.4 GHz is a dead end for Wi-Fi

Summary: If there is any doubt in anyone's mind that the channel-constrained 2.4 GHz band is a dead end for Wi-Fi, here are some charts that will put things in to perspective.

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TOPICS: Wi-Fi
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If there is any doubt in anyone's mind that the channel-constrained 2.4 GHz band is a dead end for Wi-Fi, here are some charts that will put things in to perspective.  The following is a power-level comparison between an Access Point, a Microwave oven, and normal background noise coming from the neighbors Wi-Fi gear.  All measurements were done with a Wi-Spy 2.4x review unit that I just got in the mail.  So far it's a very cool and useful product that any network engineer must have and I'll be doing a more formal review of it later.

802.11g Wi-Fi Access Point versus Microwave oven:

Background noise versus Microwave oven:

As you can see from the results, a Microwave oven (when in use) absolutely dwarfs the signal level of a typical consumer 802.11g Access Point.  Channel 6 (4-8) is absolutely murdered, half of channel 11 (9-13) is murdered, and the edge of channel 1 is severely degraded.  Microwave ovens do not interfere with the unlicensed 5 GHz band and it's no wonder that Microsoft will not give a "premium Vista certified logo" to a hardware device unless it supports the 5 GHz operation.  There is just no way you can reliably deliver HD video to your home theatre over 2.4 GHz when the Microwave is in operation.  The Ruckus smart antenna Access Points might stand a better chance operating on channel 1 but I wouldn't bet on 100% reliability.

There are only 3 non-overlapping channels in the 2.4 GHz unlicensed band for North America (even fewer in some countries) and these are channels 1, 6, and 11.  Every other channel in between like channel 3 is actually a part of channels 1, 6, or 11 so they can't really be counted as channels.  Since there are only 3 channels available, your neighbors (especially in urban and denser sub-urban environments) are often as much of a threat.  5 GHz on the other hand has 12 unique non-overlapping channels in North America and even 24 channels in some unique situations.

As I've written in my blog on 802.11n - The consequences of abandoning the 5 GHz frontier, consumers will get the short end of the stick with 802.11n.  Unfortunately consumers are paying a hefty premium buying up a lot of draft 802.11n devices which are almost always 2.4 GHz only devices.  Yes there are exceptions like the high-end Buffalo draft 802.11n dual-band wireless routers but this is the exception and not the norm.  Apple Airport Extreme wireless routers uses an either/or solution that either operates in 2.4 or 5 GHz but not both at the same time which means you're forced to use one or the other and that will often mean 2.4 if you have other wireless devices that are usually 2.4 only.

The fact that most draft 802.11n (even draft 2.0) routers eat up two of three channels and still fail to behave like good neighbors because the IEEE and Wi-Fi Alliance has no teeth in mandating good neighbor behavior means that 802.11n will likely be a huge debacle.  Only Intel (and their logo partners) follows the strict policy of not using dual-channels in the 2.4 GHz band and the Intel 4965agn PCI-Express mini card happens to be dual-band compliant.  At $49 is also one of the cheapest client adapters available.

The lesson here is that you should avoid any router that doesn't support simultaneous 2.4 AND 5 GHz operation and you avoid any client adapters that don't support 2.4 or 5 GHz operation.

Topic: Wi-Fi

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65 comments
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  • Good advice . . .

    but can you name me a dual-band router that works in both bands simultaneously and costs $120 or less? A list of dual-band routers would be nice since they are such a rare breed at this point in time.

    On a similar note didn't Draft 2.0 require dual-band routers or is this another case where the Wi-Fi Alliance felt that in the name of "peace" that idea won't be enforced until the final standard becomes ratified?
    n.stockwell@...
    • There is no such requirement, it's only optional

      There is no such requirement, it's only optional right now. Vista "premium" certified routers will be dual-band and I believe Microsoft has a list of these. Buffalo has dual-band 802.11n draft routers. Apple's Airport Extreme is either/or so that's no good. I'm going to look it up and post a list if I find it.
      georgeou
    • 802.11n does not mandate 5 GHz dual-band

      802.11n does not mandate 5 GHz dual-band. The standard says you're suppose to drop out of channel-bonding mode in 2.4 GHz if your neighbors use wireless but there is no enforcement mechanism to mandate this behavior. Wi-Fi Alliance says they'll crack down if another vendor complains but I don't put much faith in this. The problem is that the vendors want people to have trouble with their old gear getting jammed by the 802.11n gear so that they're forced to buy new gear.
      georgeou
      • You're right . . .

        my memory is at fault, but it's too bad they don't mandate it though because of the very issues you bring up in your article.

        Maybe if a bunch of Network Administrators, consultants, and others with buying power at least suggest to clients and network vendors that they would first prefer buying dual-band products vendors and chipset makers would actually continue to pursue making such products.

        We can't ignore 2.4 GHz only products because of the fact that they are cheap and they are many, but we should advocate consideration and purchase of dual-band products when appropriate.

        For instance, I'm currently consulting with business owner who wants to open up a private hotspot. After comparing prices I found out that a Linksys WRT55AG can be about the same price as a WRT54G. Prior to this discovery I thought dual-band routers would be out of consideration because of the price, but since there was little difference in price I will recommend the WRT55AG.
        n.stockwell@...
    • Did you leave the microwave door open?

      i can sit my powerbook or any of my friend's laptops directly next to my microwave
      oven and they work perfectly, no packet dropping or anything of that nature. I even
      stream high bit-rate mpeg 4 and h.264 video from my powermac to the powerbook
      and don't experience dropped frames or broken audio.

      btw, i've used wireless-A in a home before. it was limited to pretty much the same
      room as the router.
      nix_hed
      • doh!

        this should have been a new post
        nix_hed
      • No, I didn't. But did you use an unbuffered UDP stream?

        No, I didn't have the door open. But did you use an unbuffered UDP stream? That's the normal testing procedure. IPTV applications and wireless distribution systems have to use unbuffered video because people don't like delays on flipping channels.

        I use A too and I have no problems with it working throughout the home. It really depends on the model you use.
        georgeou
  • Friends don't let friends buy G-only devices

    "Only Intel (and their logo partners) follows the strict policy of not using dual-channels in the 2.4 GHz band"

    I may have mentioned this before. Apple 11n clients do not use wide channels in the 2.4GHz band.

    I also lament the continuing propagation of 2.4GHz-only products, but especially among 11n/11g clients. That's unforgivable these days. Let's focus our protests on these manufacturers.

    The routers, especially in retail, face a price pressure to get shelf space that is really non-negotiable - unfortunately. The "either/or" 2.4/5GHz solutions are to be commended in this perspective.

    I would say, don't buy 2.4GHz-only equipment, even if that means holding off on 11n altogether.
    GW Mahoney
    • LOL, good one

      Indeed, friends don't let friends do 2.4 GHz only devices and editors shouldn't let their readers do 2.4 GHz only devices.
      georgeou
  • The real answer is to use a wired .....

    .... solution using your existing premise wiring. Power Line, Cable or Twisted Pair solutions are available and have sufficient throughput to reliably stream HD.
    ShadeTree
  • George, did you test multiple microwave ovens?

    I'm sure some ovens are much worse than others in regards to emissions. So hopefully you aren't basing this whole premise on the output from one lousy oven.
    ejhonda
    • I've tested many others before and they're often worse

      I've tested many others before and they're often worse. I've also done far more in-depth analysys with performance over time tests. The graphs in this blog are for simplicity sakes to make a point.
      georgeou
    • Microwave Signatures

      Each microwave will generate it's own unique pattern. the same model will typicaly generate a similar pattern.
      bcolvin@...
  • Dual band

    Is the only way to go. I've got both and found that at my home (near an international airport) gets pulsed on an erratic basis by something in the mix. Both the 2.4 AND 5 GHz bands will get dropped sometimes as often as every 45 seconds but usually about every two minutes. At the office, the 5GHz band gets stepped on about the same but the office is in deep downtown Denver.

    I believe that certain military applications also use the 5GHz bands as well.

    I'd complain to the FCC but that 'unregulated' means just that. So consumer appliances that have high energy arcing (a broad band source of interference) will always whack wireless connections. Also I've seen that many of the newest wirelss phones use that 5GHz band too so the 802.11a gets whacked for sure by them too.

    Fact is, if I need a continuous reliable connection, I HAVE to use wire. Well that is unless I want to turn home and/or office into faraday cages with all sorts of shielding. But I hope that the concept of spread spectrum comes into the consumer world like it has been in the military for at least 25 years. Until then, we're just out of luck in most city areas.
    Technocrat@...
    • There's expensive window film and paint to block external signals

      There's expensive window film and paint to block external signals. The government uses a film that blocks 99% of RF energy; enough to protect against an EMP blast.

      If you use 5.8 GHz cordless phones like me, that won't interfere with the bottom 8 channels in the 5 GHz band which is somewhere around 5.2 to 5.3 GHz.
      georgeou
  • Another Misleading Expert

    Does this mean our highways & byways are also dead - congestion is a fact of life. Anyone that has their microwave running 7X24 should get checked. With advent of N technology,i.e. MIMO, the 5Ghz band will eventually become congested as well. Short term solution = buy WiFi devices with both frequencies and have some wiggle room. Ultimate solution = vendors move up into the 10 to 66 Ghz range where there lots of room and no congestion.
    Da Juicer
    • higher frequencies create different problems

      you can't just keep moving up in frequency in this particular application. higher frequencies are more seriously affected and attenuated when they pass through materials. they get "hit" far more by drywall, rock, wood, plaster, paint, than lower frequencies do. that equals far more power output or more access points to cover the same area.

      the ultimate solution is one i've used in my home on my 8 computer lan : run a wire.
      Valis
      Valis Keogh
      • Plus . . .

        at anything higher than 10 GHz the wavelength becomes smaller than 1 inch and rain for example signal loss. For my money I would stay where we are.
        n.stockwell@...
      • Have faith - None we can't overcome

        Remember we were told 10 Mhz over UTP Ethernet could never achieve fiber rates - well leave it to the guys in the labs and now we are now running 1 Ghz Ethernet over UTP - just had to get the correct number of turns/meter. Remember 802.11b (max speed 11 Mbps) became .11g (54 Mbps) and now 11n (540 Mbps). As long as the problem is a technology one, we can fix it. George's original RF scan shows a microwave oven nuking the entire house with potentially damaging RF waves (iononizing radiation). How come our brilliant legislators haven't passed some dumb law that limits microwave oven RF propagation to 40 milliwatts. All it requires is some RF shielding in the oven.
        Da Juicer
    • 5 GHz has 12 and possibly even 24 channels

      5 GHz has 12 and possibly even 24 channels. 2.4 GHz has 3 channels. Yes it's possible for 5 GHz to gt conjestion; but it's at least 4 times less likely to do so because it has 4-8 times the capacity.
      georgeou