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

Bjørn Jensen 423 Views 6 Comments6 Comments

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 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.

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  1. Actually, it does. The article you posted says it does as well, unless I’m missing something there.

  2. Hi there! Well, first off the 802.11 wireless spec for 5GHz only touches the 5.8GHz frequency on the far upper channels, most channels are lower than that. I think you’re thinking of cordless phones that can be at 5.8GHz. So a dual band device COULD connect to an outdoor AP on 5.8GHz which would be somewhere between channels 161 and 165 but it could also connect to many channels below that.

    On to the rest of your question, I’m assuming you’re asking this because you have a 5GHz radio outside but inside you only have a single band 2.4GHz radio? If that’s the case then yes, a dual band wi-fi device will be able to switch between them just fine. If the devices are standalone (without a controller) then once they leave the range of the indoor APs they will disconnect from those and then have to re-authenticate with the outdoor AP making a slight break between connections. One thing a lot of people don’t realize is that you can put the same SSID (network name) on all of the APs within the same network. This way you don’t have to create multiple SSIDs and enter multiple passkeys on each device. The MOST IMPORTANT thing to do is manage your channels to ensure you minimize co-channel interference.

    I hope that helps. Make it a great day!

  3. Suppose I am using two bands together. How can I calculate the total throughput and the bandwidth that I can get?


  4. Hi there,
    I’m not aware you can use both bands simultaneously on a single client device, unless you have two separate wireless adapters installed. Bandwidth is also determined by what kind of client devices they are, how many streams they have, etc. This is also true for the AP you will be connecting to. Because it’s not accurate to go with what the max speed in a vacuum that is possible, we must go with real life scenarios. A great way to calculate actual bandwidth would be to have both connected and use JPerf to calculate the bandwidth you’re getting. I hope this helps!

  5. Aaaaahhh….my apologies. You are so very correct sir! I’m going to edit that unit out of the post. Thanks!

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