The key differences between Dual Band and simultaneous Dual Band access points and why you should care?

 

WiFi

Simple Dual Band access points, the ones you generally find over the counter at your local big box stores, work by allowing one to connect to the wireless network utilizing multiple different wireless protocols.  They are an “either/or” when it comes to transmitting a signal.  In other words while it transmits a signal in one frequency range and/or using one specific protocol, it cannot transmit the other.  Simultaneous Dual Band access points will actually allow both signals to transmit concurrently which is ideal for connected devices of different types.  In this article I will concentrate on the two most used; 802.11g and 802.11n.  There are many access points that actually allow for dual  band or even tri band which would include 802.11a, 802.11b, 802.11g and 802.11n.  Please note that 802.11g is backwards compatible with the earlier and slower 802.11b protocol which has mostly been phased out yet you will sometimes find devices, such as some of the first generation Crestron TPMC-10X panels that still use this.  These play havoc with cheaper installations similar to what I will be explaining happens with 802.11g and 802.11n but not nearly as bad.

Speaking now specifically to the issues with dual band access points utilizing 802.11n and 802.11g I will explain why it is imperative to only use simultaneous dual band access points over their cheaper counterparts.  Throughout the years I’ve been contacted by people who seem to have unstable connections to their Wifi network with many different devices.  Sometimes the network will work flawlessly and then without word it just stops.  Probably the primary complaint I receive has to do with wireless printers.  Someone will be connecting to the printer over a wireless network to print a document and then all of a sudden the printer stops responding.  Normally the first thought is that it is the printer.  However after getting to know the infrastructure in place it eventually becomes clear what the real culprit is.

What’s happening is the client has a dual band wireless router or access point that is setup to transmit both 802.11g and 802.11n.  They are normally connecting to this printer with a newer laptop that has an 802.11n card installed.  The printer has an inferior 802.11g card.  Once the client laptop sends a print job the printer wakes up and in doing so now forces the AP to downgrade it’s wireless transmission to 802.11g.  In doing this the client laptop temporarily disconnects in the middle of spooling the print job as it is also now moving from 802.11n to 802.11g.  Now this doesn’t always happen and some printers and some laptop cards handle this better.  In a perfect world the devices would realize this has happened and resend the data.  Unfortunately that is not always the case and all too often the print job then hangs and never finishes the job.  This can be beyond frustrating for the client.

The solution for the issue above is to log into the AP or wireless router and turn off dual band mode.  Force all clients to connect using 802.11g and this problem goes away.  However, an even better solution is to replace the device in question with a simultaneous dual band AP that wouldn’t have this issue to begin with.   Just think, if this is happening to a simple print job then imagine what it can do to the performance of your wireless touch panels or other devices on the system.  What kind of aggravations are you setting your clients up to have by merely not spec’ing the right equipment or not correctly configuring the equipment you have spec’d?  Simultaneous dual band AP’s allow legacy devices to keep and hold a strong connection to the network while still allowing newer and faster devices to connect on their own “expressway” without having to slow down.  I like to think of it as adding a bike path for those annoying bikers that hog the road and force you to wait behind them until you have an opening to speed around them.  That way they can still ride their bikes without being a hindrance to the cars on the road.

My company never sells an access point that cannot simultaneously transmit both signals unless there is specifically no need for the other.  Generally the higher end products, and the only ones we sell, such as Cisco and Ruckus work this way.  There are some cheaper alternatives out there though.  The Apple AirPort Extreme is one, so is the Linksys WRT610.  D-Link and Netgear also have simultaneous dual band access points and/or routers such as the D-Link DAP-2553 or the Netgear WNDAP350.  However, for the best in wireless networking nothing can beat a controller based network.  This is still the way to go, however there may be some interesting changes in the air with companies such as Meraki, a new up and comer in the industry.  Meraki sells a cloud based controller system that allows you to forego purchasing an expensive hardware based solution.  This may appeal more to the pockets of your clients as you don’t have to try and find a way to convince them about the pluses of having a wireless LAN controller.  The only possible issue I see with that is how well the system manages its wireless traffic when the local network loses its connection to the cloud.  This remains to be seen but I will be testing this system in the coming weeks so I’ll be able to report back any good or bad news about it.

7 Comments

  1. Herb113 says:

    thanks that fixed my problem

  2. Bjørn Jensen says:

    Great! What was the problem?

  3. Nick says:

    Dual band had nothing to do with A B G or N protocols. It has to do with frequency. Dual band means the Access point(AP)/client transmits in the 2.4 Ghz band and the 5.8 Ghz band. Both radios can then transmit in any of the A B G N rates. Typically you will see 2.4 only use B, G & N. And 5.8 Typically only A & N. A is really only found in old point to point systems. Simultaneous dual band uses channel bonding to connect a client to the AP. This means that is uses both frequencies at the same time to transmit larger amounts of data at once. Regular dual band is basically two separate Access points running side by side working on different Frequencies. It allows entirely different clients to connect at different rates. If simultaneous dual band is used, then a client must be connected to be the 2.4 Ghz AP and the 5.8 Ghz AP with the same rates( A, B, G, or N) and will broadcast data on both frequencies at the exact same time.

    • Bjørn says:

      Hi there and thanks for posting! Anyway, I have to respectfully disagree. Regular Dual band devices are “selectable”, meaning you can select whether you would like to use the 5GHz band or the 2.4GHz band but cannot use them concurrently. Simultaneous dual band doesn’t have anything to do with channel bonding. It is an AP that can broadcast in both 2.4GHZ and 5GHz simultaneously (eg. the Ruckus ZoneFlex 7982). Channel bonding is used to aquire more bandwidth by utilizing multiple channels at once, as in the 5GHz 802.11n and the upcoming 802.11ac. It has nothing to do with dual band or simultaneous dual band.

    • Kees says:

      I agree with Nick, it is about frequency and has nothing to do with A B G N protocols. Simultaneous or not, bonding or not.. The whole article messes up protocols with frequency.

    • Bjørn says:

      Hi there Kees! Well I think for some reason you and your friend Nick are getting hung up on the fact that I tried to “dumb down” the article for a specific audience that may not be able to understand the difference between frequencies but are more familiar with the terms 802.11g or 802.11n. This article was also written some time ago when this first became something people needed to pay attention to. The idea behind focusing on the protocols rather than the frequencies was done in an effort to explain to people, in ways that they could more easily understand, why maybe they ran into the issues that they did when not using a simultaneous dual band AP.

      Please note that I specifically mention:
      “while it transmits a signal in one frequency range and/or using one specific protocol, it cannot transmit the other”

      I agree that I probably should have stressed the fact that the core difference is the frequency and not the protocol but the main goal was to make it as easy to understand as possible for the uninitiated. If you’d like to read something a lot more technical I suggest checking out the article I wrote featured in CEPro about 802.11ac here: http://www.whyreboot.com/2013/02/15/802-11ac-is-the-next-big-thing-in-wireless/ Anyway, thanks for posting and keeping me on my toes!

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