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Ask the Expert: RF Matters in Mobility Design

Community Manager
Community Manager

Read the bioWith Flavien Richard

Welcome to the Cisco Support Community Ask the Expert conversation. This is an opportunity to learn and ask questions about 802.11 radio, MIMO, new APs, antennas and antenna placements, as well as outdoor requirements and Mesh with Cisco Expert Flavien Richard.  Enterprise Mobility requires planning, understanding of the evolving environment, and a good knowledge of the equipment that are installed to properly serve the needs of your workforce, contractors and visitors. This session focuses on understanding the often overlooked Radio Frequency part of designing and deploying a Wireless LAN Network including complex and challenging environments.

Flavien Richard is a technology solutions architect in the Borderless Networks team in France. He is an expert in wireless and mobility topics and servers as an escalation point of contact in the European theater. This gives him visibility over most of the biggest projects in EMEA. He is a technical interface between the Wireless business unit and Cisco customers, partners, and employees to help define and prioritize the new features and products for the mobility market. He is a frequent speaker and session manager at Cisco Live and other  Cisco events on mobility. He also was a contributor to the writing of the first Wireless CCIE exams.

Remember to use the rating system to let Flavien know if you have received an adequate response. 


Flavien might not be able to answer each question due to the volume expected during this event. Remember that you can continue the conversation on the Network Infrastructure  sub-community discussion forum shortly after the event. This event lasts through November 2nd, 2012. Visit this forum often to view responses to your questions and the questions of other community members.

12 Replies 12



How do I get a particular client to 'always' choose a particular AP? I have noticed that the client disassociates/associates multiple times during the day because they seem to be in the bermuda triangle of wireless ap coverage. There are 3 ap's nearby, but the client keeps bouncing around. I am using cisco wlan 4402-25 , and the ap's the client is flopping back and forth on are 1131ap and 1242 ap. Thanks---


First it is important to understand CLIENTs make the roaming decison. So with that being said:

1. What clients do you have

2. Are you on the latest driver

3. Are all devices behaving like this or just one

"Satisfaction does not come from knowing the solution, it comes from knowing why." - Rosalind Franklin
‎"I'm in a serious relationship with my Wi-Fi. You could say we have a connection."

"Satisfaction does not come from knowing the solution, it comes from knowing why." - Rosalind Franklin

Hi George,

Its an do I make sure this client has latest drivers? Yes, most devices, which as of now includes 2 users with iPhones, are complaining. I will bring my iPad over there to test connectivity. Thanks--

Ok a few things you might want to do. First do a client debug in the WLC for a iPhone and see what is going on. Feel free to post the capture here so we can take a peek.

Unfortunately, Apple locks down their devices and upgrading drivers arent an option had easily.

What codem controller and APs are you on ?

"Satisfaction does not come from knowing the solution, it comes from knowing why." - Rosalind Franklin
‎"I'm in a serious relationship with my Wi-Fi. You could say we have a connection."

"Satisfaction does not come from knowing the solution, it comes from knowing why." - Rosalind Franklin

Hi Misscat.

This is usually a client feature, more than a Wireless infrastructure feature. Here is, for instance, a picture from Intel ProSet utilities:

Quite a few clients supplicants let you do this on computers.

I am trying to look into a trick to make it potentially work from the Infrastructure, but so far, from the infrastructure, I don't have a quick knob to change in order to get this specifically to work as you want it.

Nevertheless, let's understand how a client decides to roam (handover) from one AP to the next.

[By now, I have read that the client is an iPhone, so, you cannot benefit from the previous recommendation]

A client decides to roam because there is a better signal at some point in the scanning result for the available APs on this SSID. The best way to (mostly) prevent a device to roam is to have a clear difference in favor of one AP signal strength over the others.

This can be done by:

1) changing the AP location to a closer location, or to a place where you have clearer line of sight from the clients(sometimes, changing the AP placement to the middle of a corridor instead of at a corner, for instance, solves issues) or play with antenna orientation,

2) move to a 802.11n AP instead of 802.11a/g AP, because of Client explicit beamforming (otherwise known as ClientLink) like 1142 or 1262, which both work with your 4402-25 if you use 6.0.202 (MD) or 7.0 softwares,

3) dive into the RRM (Radio Resource Management) logs to see if the unwanted roaming is not happening at the same time as a recalculation of DCA and TPC events,

4) override some RRM parameters like setting the Transmit Power to a higher fixed number so that you have a clear differentiation of Signal Strength to a special AP (this should be the last resort option, but can be done if you cannot move the AP around) compared to the other APs in that neighborhood.

Hope this helps,


All great suggestions. I appreciate the input. I've checked user devices and found the iPhone is at 4.8 ios (not 5) and will have user upgrade, meanwhile I will try and move the AP to the corridor, which would be closer to this persons room. Will post results tomorrow. Thank you.

Sveta Prutikova

Hello Flavien,

I need to provide priority wireless service to a particular set of clients in my company. I have a 5508 controller with 11n in some places as well as non-11n APs in few remaining places. What can I do?

Privet Sveta,

With the latest 7.3 release comes an expanded feature for bi-directional rate limit. With this feature, there is a new ability to define per-user throughput limits with higher granularity, in allowing setting a priority service to a particular set of clients. Rate Limiting is done by expanding the existing rate-limiting feature of QoS profiling to AP, and is done through strict protocol matching. Real-time rate limits are applied to UDP traffic, while Data limits are applied to TCP Traffic (upstream and downstream). It can be set globally, or per WLAN.

Regarding your specific case, it is applied to the 11n APs (1040, 1140, 1250, 1260, 1600, 2600, 3500, 3600), but not to the non-11n APs, as well as Mesh APs or roles. It that case, the rate limit is equivalent to 7.2 code, which is "per user bandwidth contract" per "Global QoS profile" (bronze, silver, gold, platinum) for the downstream traffic only.

It is possible to mix both, although, as you can understand, it is preferred to consistently deploy 11n access points to benefit from this feature seamlessy in the network.

Thank you for the question.




This is a timely discussion for my particular issue.

We have a warehouse that has used since startup the 1231 series AP's. Several of the units have died recently and we are wondering what to do to replace them. We tried placing 1140 series on the 50 foot ceiling but unlike the current 1231's we cannot add directional anteneas. There is product floor to ceiling and the product movers are using RFguns to transmit data. We do not have a controler so we are relying on placement of the units for good service.


Hi John,

The best choice, today, would be to use the new replacement equipments for the 1231, which is the 2602e. This access point is sold with Autonomous IOS code under the reference: AIR-SAP2602E-x-K9

Be aware that you will have to:

- change the antennas that you are using today if you want to benefit from the dual-band capacity of this AP, and probably use the dual-band patch antenna AIR-ANT2566P4W-R (single antenna).

- or disable the 5GHz radio and buy 2 additional directional antennas per AP (same as the ones you are currently using) to benefit from full MIMO capacity of the 2602e, including ClientLink 2.0

- or disable the 5GHz and 2 of the 4 dual-band antenna connectors if you only want to replace the current APs without benefiting from the additional features and capacity of this 802.11n access point (but you will still be able to reactivate if needed later).

Best Regards,



hi john

i have a problem with a Cisco MSE, i upgrade to version 7.2 but i do not the sincroneze with NCS, in the MSE look this.


Server Config


Product name: Cisco Mobility Service Engine


Health Monitor Ip Address:

High Availability Role: 1

Hw Version: V01

Hw Product Identifier: AIR-MSE-3310-K9

Hw Serial Number: FTX1634M00Y

Use HTTP: false

Legacy HTTPS: false

Legacy Port: 8001

Log Modules: -1

Log Level: INFO

Days to keep events: 2

Session timeout in mins: 30

DB backup in days: 2

HTTP is no enable, in a forum instal a new certificate, with but in the second point

Import CA Certificate

the path is not valide,

can you help me for this part?



Sorry, I am not the expert. I was asking Flavien for his advice. I think you need to reply to him.

Best regards


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