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Internet of Things: Why GHz Matters


April 9, 2015 - 4 Comments

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Enterprise IT continues to play a critical role in the Internet of Things (IoT). A large part of IT’s role is understanding and anticipating what new device types will hit the network, when and how to optimally connect them. Beyond the obvious applications and services, an often-overlooked factor is the actual design of the thing. What spectrum does it use? And how will it impact your network?

Today Wi-Fi devices, including things such as sensors, connect using one of two spectrum bands – 2.4GHz or 5GHz. Conventional wisdom has been to advertise a common SSID for both 2.4GHz and 5GHz connectivity. But, with the rapid rise of more connected things, this has likely outlived its usefulness. Let me explain why this is my point of view.

2.4GHz, commonly called the junk band, has only three non-overlapping channels and has a practical upper limit of 216Mbps with 802.11n in terms of physical connection rate between the client device and the AP. While the 802.11n specification does support up to a theoretical 600Mbps with 40Mhz with 2.4GHz channels finding one of these would be akin to discovering rocking-horse droppings.

The practical limit of a 216Mbps data rate with 2.4GHz can rarely be attained partially due to proximity to the access-point; but and perhaps more importantly, data rates are impacted by co-channel interference from other Wi-Fi devices and the likes of Bluetooth and microwaves, which also operate in the 2.4GHz band.

Exasperating this is the difficulty in identifying those devices capable of both 2.4GHz and 5GHz. The 802.11b and 802.11g standards are 2.4GHz only, but 802.11n is available for both 2.4GHz and 5GHz. Device manufacturers often advertising 802.11n, but only supporting 2.4GHz. The Apple Watch is an excellent recent example of this, as is my recently purchased Amazon Kindle.

On the other hand, 5GHz has greater spectrum availability, more non-overlapping channels, and lower levels of interference. It has speeds today as fast as 1.3Gbps with 802.11ac Wave 1, 6.9Gbps with 802.11ac Wave 2, and even faster with future technologies such as 802.11ax.

So why advertise two Service Set Identifiers (SSIDs) or wireless networks?

  • SSID                                        2.4GHz only
  • SSID_ High_Speed                  5GHz only

The high speed SSID can be up to six times faster with 802.11ac Wave 1 and 30 times faster with 802.11ac Wave 2, assuming the theoretical maximums can be attained. Wouldn’t you want to know if you are on the interstate or single lane dirt track plagued by potholes?

Also, if you cannot see and therefore connect to the High_Speed network, you know the device does not support 5GHz and perhaps you should upgrade the device.

As you onboard more devices to the network, make sure you consider this for your next purchase: “I will not buy anything that only works in 2.4Ghz where a dual band 2.4 and 5GHz option is available.” This guideline won’t steer you wrong when navigating today’s IoT waters.

Other common questions:

Q         Isn’t advertising twice as many SSIDs supposed to be a bad idea?

A          There is still only a single network advertised in each band. So while some devices (those that are dual-band capable) will see two you are not consuming more bandwidth. In fact if the desired user behavior is achieved you will actually consume less.

Q         Is the network not supposed to optimize dual capable devices to the cleaner air on 5GHz?

A          While the network can assist in selecting the optimal band, the decision ultimately resides with the device itself. Even I can make the optimal choice when only one is available or you entice me with the promise of a faster network.

 

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4 Comments

  1. In reality, I can see both views and can't fault anyone for either way. I highly recommend choosing one of the methods though. I was forced to choose one for the pure reasons of standardization, realiabilify and support. Several years ago, after deploying wireless in a new building which housed over 700 laptops, I noticed that band select did not do what I hoped. I had laptop clients connecting on 802.11b/g/a /n. It was oddly enough about 150 clients on each one. The throughput difference was obviously all over the board. I had the clients managed by an MDM and decided to lock the configuration to 802.11 a/n. With the high AP density, I wish I had the choice to lock it to 802.11n only. So devices continued to connect to 802.11a. During an outage caused by a bug, it was simpler to have people change the client setting to change bands than it would of been to create and connect to another SSID. I also was told by the both client teams ( IT and Biomed) , that the one SSID was easier to remember and configure. I did have to add another SSID for clinical devices to enable segmentation. I can see adding a 5ghz SSID could remove the likelihood of misconfiguration of the client. End user experience and support teams are relying on wireless expertise to help them remove the client/band issue. The first few times you get a call about client disconnects and you see the ping pong effect between 2.4/5,you will decide the dual band feature is more of a support/reality nightmare than it is an advantage. Good luck !! Jim

  2. What would be swell is if the device manufacturers - (and I'm talking to android and IOS) would definitively decide to allow a user to control which band they connect to on a smart phone. in the meantime - this method of separating the ssid's worked extremely well at a tech conference - your mileage may vary.

    • I've been preaching this for 2 years. Separation of the two bands and don't let the clients select or be part of the decision making process, In other words an SSID with both 2.4/5 GHz enabled is not the future. The less you allow clients to meddle the less issues you will have. Also if you have vendors who only support 2.4 they go on the legacy SSID. In our AWO (All Wireless Office) we are doing exactly that. Good read thank you for sharing .. I'm glad someone else shares my thoughts ..

  3. Good artical and design arguements but going forward I think getting enterprise IT departments to recognize the value of device management when deploying devices would give more benefits. So to keep it intelligent control and know your devices NIC settings. Typically end-users are not keen on having to deal with settings and such and many times enterprise security policies do not want to hand over the control of which SSIDs users can connect to. Also in regards to latency sensitive applications enterprises would want to know how devices conway 802.11e during voice video and collaboration. A central tool for device NIC management would be handy mayby built into Cisco AnyConnect. Just a thought to a great discussion.