802.11ac FAQ

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802.11ac Frequently Asked Questions

• 802.11ac Access Point Technology Overview
• 802.11ac Performance
• 802.11ac Deployment Considerations
• 802.11ac Security Implications
• 802.11ac Wave 1 and Wave 2

802.11ac Access Point Technology Overview

 

Is the C-75 integrated with the current cloud portal so it can be configured alongside the C-50 and C-55 APs?

The answer is yes. The thing to keep in mind is that each AP model will have its own device template. And just like with the C-55, with its own device template containing configuration specifics for C-55s, the C-75 will have its own device template, where configurations specific to C-75 would be made.

Does the C-75 require more power than the C-50 or C-55 due to extra antennas?

The C-75 is fully functional using 802.3af power. So there is no need to upgrade to PoE+.

Why don't you recommend factoring in the 2.4 GHz capacity?

Of course the recommendation is to provision SSIDs in both the 2.4 and 5 GHz bands, as they are still clients in use that do not support 5 GHz operation. However, the 2.4 GHz band at best offers only a fraction of what 5 GHz/11ac has to offer and at worst the 2.4 GHz band is so cluttered with interference from WiFi and non-WiFi interference that the capacity that it provides is unreliable and/or negligible. 

The AP Estimator tool presented today is useful in determining the estimated number of APs needed for a given interference region, for a given set of clients and SLA, etc. but I am also looking information on AP placement best practices.

During the next session in this series we will be covering 11ac deployment best practices. One of the topics covered will be AP placement recommendation. It should also be mentioned that AirTight Planner is a tool specifically designed to help with AP placement plans. This tool can factor in your requirements for coverage (e.g., link speed) or capacity (e.g., no. of simultaneous users, traffic load, VoIP calls, etc.). You can find out more about this application at the following link.

AirTight Planner

Don't forget the use of directional antennas in order to lower CCI when increasing the AP density.

Thank you for the recommendation. We will add this recommendation to the slide deck.

Is the AirTight Planner a 2D tool, or can it help with buildings with atriums?

AirTight Planner is currently a 2D tool.

802.11ac Performance

 

What about degradation of coverage by each AP when using only 5 GHz, or TCO (Total Cost of Ownership)?

Regarding your chat question about 5 GHz and signal degradation, it is true that if you design networks for 802.11ac, versus for 2.4 GHz, you will likely need more APs as 5 GHz signals do not propagate as far as 2.4 GHz signals do. From that perspective, the 802.11ac TCO will be somewhat higher than 2.4 GHz. But from a productivity standpoint, 802.11ac APs have the potential to enable more work to be done for a given period of time (compared to 802.11n/2.4 GHz). Something else I like to factor in.

Will APs with this standard be able to change the channel dynamically in order to have the best performance?

The answer is yes, the 802.11ac C-75, as well as other AirTight APs, can dynamically change channels to avoid interference from neighboring AirTight APs or non-AirTight APs.

We don't know the SLA, but we do know the applications in use. Can we do an AP estimation based off of applications?  

If applications have been identified we can look at the most demanding, in terms of throughput, for a given interference region of a network. We would also need to know the peak throughput, per client, that this most demanding application would require. We can use this peak throughput requirement in place of the per client throughput SLA to estimate the number of APs that would required.

The use cases that were presented during this webinar worked out AP estimations with the assumption that the channels to be used were free of interference but in reality it is likely that some, or all of the channels in use may have some level of interference present.

Very good point! The first version of the AP Estimator that was presented in today's session does not factor in external sources of interference. In the upcoming "11ac Channel Capacity Planning" session of this webinar series an updated version of the AP Estimator will be used. The latest AP Estimator will be able to consider external sources of interference and other factors that could impact channel capacity.

Can you do channel aggregation in 802.11ac?

If you are referring to the ability to use wider channels (e.g. 80 MHz) then the answer is yes.

With regards to the AP Estimator that was introduced during this webinar, if I know roughly the client density, but I don't know the types of clients, for example, the number spatial streams or 11ac vs. 11n, what do you recommend?

If we are talking about an 80 MHz channel plan, with some unknown mix of 11ac and 11n clients, the recommendation is to play it safe by assuming that the "average" client's maximum data rate is 300 Mbps, which is what it would be for a 2 spatial stream 11n client. For 40 MHz channel plans, the recommendation is to use 150 Mbps as the maximum data rate (for the average client).

802.11ac Deployment Considerations

 

If you deploy 802.11ac in a Greenfield environment, how do you support clients that only work in the 2.4 GHz band?

In 802.11ac Greenfield deployments, most 802.11ac APs (including the AirTight C-75) are dual radio, with support for 2.4 GHz/802.11n on one radio and support 5 GHz/802.11ac on the other radio. This allows WLANs (SSIDs) to be provisioned on both the 2.4 GHz and 5 GHz bands, ensuring that 2.4 GHz only devices will continue to have service.

5 Ghz devices are not allowed in Israel. What do you recommend?

There are only a handful of 5 GHz channels available for use in Israel. Here is a link to the list of Wi-Fi channels on Wikipedia for reference: http://en.wikipedia.org/wiki/List_of_WLAN_channels Considering the limited 5 GHz spectrum available in Israel, the recommendation for most networks installed there would be to use 20 MHz channels in order to limit the adverse effects of CCI (co-channel interference) and ACI (adjacent channel interference). We will be covering this topic in a future session of this 802.11ac webinar series (802.11ac Deployment Best Practices).

Is 802.11ac appropriate for an industrial application or utilities application?

802.11ac can have benefits even in industrial environments, where high throughput or high client density are not much of a concern. Lab testing and production network benchmarking have shown that even legacy and 802.11n devices tend to perform better with 802.11ac APs. This boost in performance can be up to 40%, using only legacy and 802.11n devices, compared to what 802.11n APs can provide. This gain is often attributed to better radios, DSPs, antennas, faster CPUs and more memory in the newer 802.11ac APs. And considering that there is little or no price difference (as is the case with the AirTight 802.11ac C-75), installing 802.11ac APs in industrial environments is a good way to go.

What is recommended if DFS channels are available but your clients may not support DFS?

In deployments where you need to use DFS channels in order to provision enough spectrum/throughput capacity to meet per client throughput SLAs and/or application performance metrics you may have to enable DFS channels and then take measures to ensure coverage for clients that do not support DFS channels. It is generally recommended that AP coverage be dense enough so clients can be serviced by a minimum of 3 APs. This way if 1 or 2 of the APs in a given area are using DFS channels then the non-DFS clients could join the WLAN via the 2nd or 3rd AP (in the 5 GHz band). The other suggestion is to be sure to provision SSIDs in both 5 and 2.4 GHz. This way if all 5 GHz channels for a given area are DFS channels then non-DFS clients can still connect via 2.4 GHz.

802.11ac Security Implications

 

How does the new 802.11ac standard effect the AirTight WIPS system?

The 802.11ac C-75 is able to detect and neutralize threats sourced by legacy (802.11a/b/g), 802.11n and 802.11ac devices. If C-75s are deployed, you have a comprehensive WIPS solution that can handle threats from all types of 802.11 devices.

802.11ac Wave 1 and Wave 2

 

Today I'm interested in 802.11r/k/v so maybe you'll cover that someday.

Great suggestion! All three of these standards show a lot of promise and it would be good to discuss how to implement them for optimal effect.