Campus Best Practice (GN3+/NA3/T2) WLAN Network Planning · ... (know your layer 1) • Preparing...

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Campus Best Practice (GN3+/NA3/T2)

WLAN Network Planning

Anders Nilsson, SUNET

WLAN Network planning

Sofia, 19 June 2014



Agenda • Background (how did we get here?)

• Wi-Fi standards (a/b/g/n/ac...)

• RF Basics (know your layer 1)

• Preparing for a site survey

• Cell planning (size matters)

• Practical issues in placing access points

• General guide lines

• Planning and verification tools (demo time)

• Further reading

• Q&A open discussion



Is this what you are experiencing at your university now?



So how have WiFi evolved?

A walk down memory lane…..



Note!!

In theory 802.11n will reach

600Mbps with 4 spacial streams

running on 5GHz but 450Mbps is

the limit and for higher speeds go

for 802.11ac



The IEEE

standardization of

802.11n was a record

long 6 year journey.

802.11ac was much

faster. ;)



802.11n? Yes, but what flavor?

802.11n? Yes but

only on 2.4GHz



802.11ac builds on 802.11ac and removes some of the limitations

Note. 802.11ac wave 2 MU-MIMO is not yet proven and reises a lot of

question wether it will deliver a performance boost



Just because your

brand new

802.11ac AP

supports speeds

above 1 Gb/s

doesn’t mean that

all your devices

will benefit from

that.



Note in order for this to work you need to be able to use all your 802.11ac APs 80MHz

mode which might not be possible in a HD environment.



New accesspoints should be at least

802.11n based, managed and operating

on both 2.4 and 5 GHz band. Good

features to look for are Transmit

Beamforming and Bandselect

(Bandstearing). Higher capacity means

more room (Airtime) for clients and

more throughput. The faster jour

devices finish and can get off the air the

more capacity is left to others. Now

802.11ac APs are coming out with just

marginally higher price than 802.11n

based



Comparing 2.4 and 5GHz



Effect of bonding 5GHz channels in 802.11ac

In a real world campus deployment it’s very unlikely the 160MHz (or even 80MHz)

mode will be used. Note how we end up with the same issues as in 2.4GHz when

bonding channels in 5GHz. ETSI is working on freeing up more channels for 5GHz.



2.4GHz is limited to only 3 non-overlapping channels (1-6-11) and

is constantly filling up with other non-Wi-Fi devices competing for

the spectrum. The future is 5GHz where you have a least 20 non-

overlapping channels (varies between countries). Also note that only

5GHz will get you 300Mbps (channel bonding) with 802.11n.



Interference: The usual suspects. 2.4GHz getting crowed

Food for thoughts:

Do rouge APs create

interference and increase

the channel utilization?

(answer: YES! )



Always aim for the best

fuel at the gas station.

…and in the future go

ahead an fill your car

with 802.11ac if possible.



RF Basics (know your layer 1)



The dynamic nature of RF spectrum

• You are breathing the physical layer

• RF reflects off things

• RF is absorbed by things (walls, windows, furniture)

• It’s a shared medium (as such, not all RF is always yours)

• Not all RF is 802.11 traffic (especially true with 2.4GHz)

• In order to see what’s really going on you might need more than a

WiFi card.

• Things don’t stay the same, the only constant in the RF spectrum is

change.



And yes, other signals that the wifi chipset can’t recognize (Bluetooth,

Dect phones, Microwave Owens ) will be considered noise.



Cell size. Typical SNR versus speed values for 2.4GHz.

Note how much more efficient 802.11g with ODFM is, you get

12Mbps versus 5.5Mbps with the same SNR



Basic antenna types



Interference (problems and why MIMO might be your savior)



An 802.11n

accesspoint

improves

reception on older

abg-client.



Interference mitigation

Finding these evil polluters will need something better than an

ordinary WiFi card. A higher resolution RF-spectrum analyzer device

like Metageeks WiSpy ( www.metageek.net ) are the right tools for

this kind of job.

Note that Ciscos latest APs with so called Clean Air capability

include an spectrum analyzer chip. Most others are also doing

spectrum analysis but in software.

Even though the source of the interference is located you might end

up having to keep the interferer. Removing Microwave Owens from

the kitchen may be a problem.

Depending on the type of interference you will end up with one or

more channels ending up unusable.

http://www.metageek.net/



Preparing for a site survey


WLAN NETWORK PLANNING

What type of WLAN are you building?

Four basic types WLAN design focuses:

• Coverage (as large area as possible) Where not capacity? ;)

• Capacity (density of user over a given area)

• High denisty ( requires carefull planning and special antennas)

• Location (the possibility to locate clients)

Because the cell size dictates the capacity there’s a tradeoff between Coverage and high

Capacity.

Location usually leads to even more APs required.

Get rid of older legacy protocols?

Disabling 802.11b will effectively almost double the capacity on 2.4GHz.

Disable at least 1 & 2 Mbps and consider 5,5 or 11Mbps if 802.11b is left.

What type of applications should run?

Given the density of clients some demanding applications will not be possible without HD

design (requires special antennas)

Wireless Voice over IP (VoWLAN) demands certain attention (not covered in this

presentation)



What type of clients do you have?

Are you sitting with older client not supporting 802.11n. Make sure all newer

clients support 802.11n on 5GHz also. Can we phase out old 802.11b ones?

Also take into account that different clients have different RF-performace and

hence you must find the “Vorst” client type and use that one as reference.

(see next slide)

How many SSIDs do we need?

There should never be more than 4 SSIDs per AP even though the AP itself

may support many more. (see separate Excel spreadsheet)

802.11u will hopefully solve this limitation in the future.

What are the roaming requirements?

Are we just building a single hotspot or do we need continuous coverage

Do you have a monopoly on setting up APs?

Finding yourself being the sole master is rare but if possible this definitly is an

advantage. Investigate if you can divide up RF between you and others.

Create a RF policy and get it signed.



Pracical maximum

speeds for different

types of clients



Not all devices have the same radio sensitivity

Don’t forget your tablets and smartphones



Perform an onsite site pre-survey

Try to get hold of the good drawings of the building. But after that it’s

very important to visit the location in person to understand if the

drawing is still current or if walls have moved or reinforced or

something similar.

Really ambitious people classify walls and the manually input that info

to their Wlan planning software (Ekahau and Airmagnet leads the

market). Anyway to know where thick walls and elevator shafts are and

maybe also look for modern high insulating windows (can reduce the

signal more than 12dB) is very important.



Spot check design

Rather than setting up all the APs at once simply select an area of you

building and set up 3-4 APs according to your design and then verify.

If your calculations seems to be right you can continue. Another method

is to bring up the APs one by one (time consuming) but my experience is

that you need to have 3-4 APs running and than after Cisco RRM has

done it’s magic se what the result became.

RRM = Radio Resource Management



Setting up APs

Make sure you read the instructions so that the accesspoint can work

with full performance. To put it short the AP needs “breathing space”

and to be mounted in the way the company manufacturing it intend.



The AP1130 was designed for the office environment. Easy mount

on a 3m ceiling and propagate the signal down and wide.



Even though MIMO based 802.11n APs are bit more “forgiving” try to avoid these

type of installations a much as possible.



Verify coverage

Here there are many schools on how to proceed

I personally prefer to use the Aircheck from Fluke (2000 euro)

NEWS!! There’s now a Aircheck for windows costing 1/3.

A free alternative is to combine inSSIDer and iperf to both test the

channel allocation and throughput.

Don’t forget to read through the document titled .

gn3-na3-t4-wlan-network-planning which can be found at

http://www.terena.org/activities/campus-bp/pdf/gn3-na3-t4-wlan-

network-planning.pdf

http://www.terena.org/activities/campus-bp/pdf/gn3-na3-t4-wlan-network-planning.pdf















My own view and recommendation on WLAN • Stop using 802.11b clients and disable it on you WLAN

• All new 802.11n clients should support 5GHz

• If possible no more than 20 active associated clients per AP (40 if 802.11ac)

• If you have more than 3 APs at one location you really need a managed WLAN

• If possible a 20% overlap of the cells is something to aim for (for good seamless

roaming)

• You should never have less than -65dBm signal strength in your coverage zone

• Closest AP on the same channel should be less than -80dBm

• RF utilization should never go above 65%. If it does you have an issue.

• Get RF-spectrum analysis tools for better understanding of what’s going on in your

environment.

• Remember to turn on Bandstearing and Transmit beamforming if possible

• Don’t forget to update your clients drivers (especially true on Windows with

802.11n cards)

• Remember that different devices have different RF-performance allways design and

veriyfy with the vorst device in mind.



My own view and recommendation on WLAN

• Always focus on the optimal placement of the AP. If needed stand your grounds

against architects and the “estetics police”. ;)

• CCI (Co-Channel Interference) is your enemy, Patch and directional antannas are

your friends, use as much as possible

• Don’t forget your wired infrastructure.

• Gigabit uplinks will be ok even with 802111.ac AP

• 802.3at PoE switches for newer AP 15.4W may not be enough

• CAT 6 or better cabling

• The world is 3d. Avoid if possible the long corridor multiple floor syndronme.

Spread out APs and/or use directional antennas.

• And finally always install managed WLAN infrastructure where some sort of

controller mechanism (RRM) manages channel and transmit level settings.

• Designing good work WLAN installations is a craft and requires skills and

experience.



Yes!!! We made it.



Further reading links :

http://www.arubanetworks.com/technology/reference-design-guides/

http://sharkfest.wireshark.org/sharkfest.11/presentations/B-7_Leutert-

Discovering_WLAN_802.11n_MIMO.pdf

http://www.wlanpros.com/

http://www.netcraftsmen.net/user-group/c-mug-archive/922-wireless-fundamentals.html

http://www.revolutionwifi.net/

http://www.cisco.com/web/strategy/docs/education/cisco_wlan_design_guide.pdf

http://www.7signal.com (Great blog)

http://www.ekahau.com/wifidesign/blog (another great blog)

http://www.ciscolive365.com/

Free access after registration, great mobile network presentations. If you only have time

for one link I highly recommend this one even if you don’t have Cisco equipment.






http://sharkfest.wireshark.org/sharkfest.11/presentations/B-7_Leutert-Discovering_WLAN_802.11n_MIMO.pdf






http://www.wlanpros.com/















http://www.cisco.com/web/strategy/docs/education/cisco_wlan_design_guide.pdf

http://www.7signal.com/

http://www.ekahau.com/wifidesign/blog



https://http//www.ciscolive365.com/





DEMO TIME!!!



Bonus slides



Professional site survey on a shoestring budget?

Of all the software I found I believe Wavedeploy from Veriwave (bought

just recently by IXIA). www.wavedeploy.com is the best. Unfortunately

the free version has been discontinued and the expert version is € 5000.

Of course this product is a bit expensive but if you want a product

where you can put your laptops and tablets on a trolley or just carry it

around and marking on your map and end up with a god coverage map.

This could be a shared resource between the universities.

http://www.wavedeploy.com/



Per-User Application Throughput examples



If you want really

good capacity in

your cubicle

landscape you may

have to install one

AP every 9th meter

but typically my

experience is 16-20

meters depending on

walls etc.



Large highly populated auditoriums need a different approach.



Typical settings on a Cisco WLAN controller with 802.11b disabled.

This will decrease the cell size and increase the performance.



Viewing neighbor APs frequency and signal strength on WLC



RF-Interferers show up on WLC with ver 7 software and Clean Air APs



Bad channel planning lead to co-channel interference

Actual measurements from my hotel yesterday



RF terms

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