ASK THE EXPERTS : High Density Wireless Deployments and CleanAir Technology

[ciscomoderator]

with

Welcome to the Cisco Support Community Ask the Expert conversation. This is an opportunity to get an update on High Density Wireless Deployments and CleanAir technology with Cisco expert Fred Niehaus. Fred is a technical marketing engineer for the Wireless Networking Business Unit at Cisco, where he is responsible for developing and marketing enterprise wireless solutions using Cisco wireless LAN products. In addition to his participation in major deployments, Fred has served as technical editor for several Cisco Press books including the "Cisco 802.11 Wireless Networking Reference Guide" and "The Business Case for Enterprise-Class Wireless LANs." Prior to joining Cisco with the acquisition of Aironet, Fred was a support engineer for Telxon Corporation, supporting some of the very first wireless implementations for major corporate customers. Fred has been in the data communications and networking industry for more than 20 years and holds a Radio Amateur (Ham) License "N8CPI."

Remember to use the rating system to let Fred know if you have received an adequate response.
 
Fred 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 shortly after the event. This event lasts through June 3, 2011. Visit this forum often to view responses to your questions and the questions of other community members.

[jogimercyaloysious]

Hello please help me ..

I have a big problem with my cisco wap4410n .. I have upgrade the firmware of this AP to

V2.0.3.3  for supporting multiple SSID after my upgradation is finished ..one time I can able to access the administration page

But when I connected to another system the same AP I cannot able to connect through ethernet .

The network connection in the system shows connected for one second and not connected for the next second its simultaneously repeating the same ..and still not connecting ..i changed my ip setting to default ie 192.168.1.xxxx and again to old config 192.169.3.xx any way the same instance is showing ..

  In the WAP the power led, wireless led , are connected good but the Ethernet led is blinking .. off on stage ..

I have many times hard reset the WAP but off no use the same happens .

Can any one please help me what may be the problem ..i could not able connect to WAP ..

This may be the worse case ever seen in wap4410n …

[fredn]

Take a look at the following URL http://www.cisco.com/en/US/products/ps10052/index.html

There is an area there to raise questions

[psmdhamodharan]

Hi

      Am planning to set up a CCNA lab in my home where users can able to access it from remote site. I have static IP. Am using cisco 877 for connecting to internet and 2611 as internal routers. From 877 i can able to connect to internet through my laptop. I dont know how to configure 2611. Now i need to access 2611 from remote site using telnet via 877. please help me to build this infrastructure.

[fredn]

While this question is out of the scope of WLAN deployments and clean air, you may find some information at the following URL

http://www.cisco.com/en/US/products/hw/routers/ps259/products_tech_note09186a0080094e92.shtml

I'm sorry but my expertise is limited to the forum topic.

Fred

[nomadicwifi]

Hi Fred,

With wireless becoming more of a critical service, the challenge now seems to be the high density of wireless deployments mainly on 802.11bg. Apart from the higher number of users wanting wireless service, each user now have multiple devices such as laptops, mobile phones and tablets. With only 3 non overlapping channels co-channel interference and high overlaps, deploying more access points becomes a problem.

Where do you think the balance is between co-channel interference and deploying a high amount of access points to support the high density? With Cisco's recommendation of roughly 20-25 clients and no more than 8 voice calls per access point, deploying more access points doesn't always fix the problem where too many access points will degrade the wireless quality. The solution often ends up with as much access point as possible that will still provide a good wireless service with minimal co-channel interference. This will of course limits the amount of wireless client on the wireless network. Is there a better way around this?

Thanks.

[fredn]

You are correct, between the higher numbers of users with multiple devices the bandwidth requirements keep increasing.

The limitation of three non-overlapping channels in the 2.4 GHz space is driving more customers to 5 GHz, it is important to have both bands when high density deployments are needed.  While many older devices only support 2.4 GHz, we are now seeing far more devices with 5 GHz as well.

The recomendation of 20-25 clients and 8 voice calls on a given 2.4 GHz channel is still a good "rule of thumb" with actual customer data requirements driving those numbers higher or lower. You are right when you say "throwing Access Points" at the problem can degrade the wireless quality as co-channel interference and overall noise floor can rise with multiple Access Points that can all hear each other.

A better approach to the problem is to throw more spectrum at this issue (using 5 GHz channels) and elements of 802.11n (20 MHz) bandwidth on 2.4 GHz.

What we have been doing in high density deployments is to try to minimize the propagation of a cell and focus it in a given direction.  This can be done by

1. Managing the RF power of the radios (Access Points) and in some cases the client's power (using elements of CCX).

2. Using the right antennas to shape both Tx and Rx cell size to help isolate, we have recently introduced a new high gain antenna for stadiums that does this well.

3. Limit supported rates, obviously the higher the data rate the less sensitive the receiver is and the smaller the cell size becomes.

4. Enable 5 GHz (that adds far more channels for data throughput)

5. Limit the number of SSIDs in use as each requires a separate beacon (adding to RF utilization)

6. Co-locating access points with non-overlapping channels

There are some challenges, for example; many dual -band clients prefer to connect to 2.4 GHz, and 2.4 GHz is more likely to be busier and subject to interference, so we also enable Cisco "Band-Select" which basically "nudges" those clients off 2.4 GHz and pushes them to 5 GHz so as to free up the 2.4 GHz band when we can determine the client has 5 GHz capability.

So how is this done? well, we do this by listening to the clients and if we detect that the client is sending out probe requests on both bands we know the client can use 5 GHz so we essentially make the 5 GHz band "appear more attractive" to that client.

Note: Client load balancing and Band select are features in the Cisco Unified controller menu.

Also enabling client link (intelligent beam forming) helps direct the signal directly at the client and reduces same channel interference.

[Stephen Rodriguez]

Fred,

     Speaking of adding spectrum...  With MIMO there are power limitations to the UNI I band.  My understanding is that this has to do with not exceeding EIRP, and I was wondering if:

1.) that was true

2.) would this be a reason to not use UNI I?  Seeing as we would get less signal propagation.

Does Cisco have a stance on not using the lower channels with regards to the power limitations?

Cheers,

Steve

[fredn]

There are a lot of reasons for reducing power in the different UNII bands...

EIRP, exceeding out of band emissions and compliance with a fixed gain antenna are all items that play into power output along with FCC regulations .

We do a delicate balance act, because we want to have high power but also a decent gain on the AP antenna, however; there are lower power requirements in UNII-1 which is a band designed for indoors. Specifically FCC Part 15.407 General technical requirements with regards to power limits.

http://frwebgate.access.gpo.gov/cgi-bin/get-cfr.cgi?TITLE=47&PART=15&SECTION=407&YEAR=2000&TYPE=TEXT

I would likely design my network (site surveying) to include the UNII-1 power and use UNII-1 unless I were doing outdoor links where that's not recommended.

UNII-1 allows for additional channels also has an advantage of not requiring DFS for more on that see the following URL

http://www.cisco.com/en/US/prod/collateral/wireless/ps5679/ps5861/prod_white_paper0900aecd801c4a88_ps5279_Products_White_Paper.html

I don't think we have a stance or position simply because those frequencies have slightly less RF power.

Fred

[Leo Laohoo]

2. Using the right antennas to shape both Tx and Rx cell size to help isolate, we have recently introduced a new high gain antenna for stadiums that does this well.

Nice pointers Fred.  Can you tell me more information about this new high-gain antenna?  Can you point me to the direction of the data sheet?

[fredn]

Yes, take a look at the newly released AP-CAP-3502p  it is a professional install Access Point that permits the use of the "Stadium" type antenna.

The antenna is AIR-ANT25137NP-R both products should have datasheets posted externally - if not they will be soon as they are new products.  Fred

[Leo Laohoo]

Yes, take a look at the newly released AP-CAP-3502p  it is a professional install Access Point that permits the use of the "Stadium" type antenna.

Hi Fred,

Thanks for this (+5).  The only information I can gather with the new 3502P is a Getting Started Guide and I can't get any other information from the Data Sheet because it hasn't/wasn't updated.

The antenna is AIR-ANT25137NP-R both products should have datasheets posted externally

This information is still internal.  Can you point me to the correct information as I need information about these two products.

[tdennehy]

Fred,

Where I work, the design model in the distant past has been "throw an AP at it and they will come". That model doesn't work well and am trying to change that.

Moving from an "all 2.4 GHz" design model to a design focused on 5 GHz, there are a few things that I would like to ask.

We have 800+ 1242s on campus with only 2.4 GHz antennas on them. 5GHz is turned off. The other 400 APs are 1232s. We're going to do a phased rip and replace; with 15 buildings at a time. The first 15 buildings will be ripped out and replaced with 3502s. If there are 1242s in those buildings, they will be redeployed in other buildings where we can replace a 1232 with a 1242.

When we do this, we will attach 5GHz antennas on all of the 1242s in the building as we "refresh out" the 1232s. The 3502i APs will obviously have 5Ghz in them, and enabled as well.

We see that the highest maximum output power varies by model, channel and 20/40 MHz channel bonding.

Do you have any recommendations to design by?

Are there any best practices? We figured we would design down to the lowest maximum output power, which from what we can tell is 11 dBm.

We are also thinking we should use RRM only in the 2.4 GHz and statically set our 5GHz?

We cannot find a way to configure RRM to only allow our 1242s to use only channels 36-48,64 & 161 . Our 3502s would be allowed to use all channels since we plan on 40 MHz channels and want to take advantage of all the spectrum.

We're a large university and we have auditoriums with hundreds of seats in them. They're not packed full of wireless users yet, but we're headed that way. Average WLAN usage is 10k unique clients on campus per day.

Do you recommend allowing only 802.11n data rates in the 5GHz band, effectively turning off 802.11a? Is that even possible?

We're thinking of surveying for and trying to implement an AP for every other classroom - or possibly every third, so we would need to shrink our cell sizes down in the 5GHz band, and most likely disabling the 2.4 GHz radios on some of the 3502s to avoid CCI.

Do you have any deployment best practices (links) for having 1242s and 3502s in the same area? We're going to try to keep one model AP throughout each building, however we do have buildings that are adjacent to each other since we're a large public university.

Please feel free to hammer us with as many links to as many whitepapers/design guides as you would like.

Thanks in advance,

Tim

[fredn]

Yes, if you are going to use all the channels in 5 GHz, designing to the lowest maximum power is best as RRM can then turn up power on most APs.  I would use RRM on 5 GHz as well as 2.4 GHz. regarding the Q about allowing only .11n rates, we do require at least one legacy .11a rate must be enabled.  This is for compatibility and so as not to interfere with a neighboring system (but you can set that legacy rate to 54 Mbps).

Most of the publicly facing deployment guides can be found with simply searches, but we are working on a high density deployment guide, likely using the newer high gain antenna I mentioned previously.  Sometimes early deployment guides are posted internally (at first) so if you are looking for something new or beyond what you can find posted, check with your local account team who can then look internally or circle back with me or other TME's to see what's new.

[Matt Ankney]

Fred,

I was hoping you would be able to help out with a couple questions.  First, I had a customer ask if there is any way to fingerprint a device, e.g. an IPad or smartphone, and automatically reduce bandwidth.  They do not want seperate SSID's or credentials, nor do they want any appliance solution.  To my knowledge this function is not capable, within their requested limits, from a 5508 or WCS, but I'm hoping you can prove me wrong.

The other question was if you know of anyway easy way to detect, or possibly even notify, if a user is dual-homed on wired and wireless.  Such as when a user is wired into corporate while associated to a guest WLAN, thus opening a nice security hole.

Thanks for any kernels of wisdom!

Matt