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connect • communicate • collaborate
Campus Best Practice (GN3/NA3/T4)
WLAN Network Planning
Anders Nilsson, SUNET
Wireless Training Workshop
Belgrad, 12 September 2011
connect • communicate • collaborate
WLAN Network Planning
connect • communicate • collaborate
WLAN Network Planning
Agenda • Wi-Fi standards (a/b/g/n …….)
• RF Basics (know your layer 1)
• Preparing for a site survey
• Cell planning (size matters)
• Practical issues in placing accesspoints
• Planning and verification tools (demo time)
• Practical experience WCS demo from Umeå (if Murphy allows)
• Q&A open discussion
connect • communicate • collaborate
WLAN Network Planning
Yes,Wi-Fi is datacommuncation over radio.
connect • communicate • collaborate
WLAN Network Planning
Note!!
In theory 802.11n will might reach
600Mbps with 4 spacial streams
running on 5GHz but 450Mbps is
the limit right now.
connect • communicate • collaborate
WLAN Network Planning
Timeline of 802.11 standards.
802.11n is not the end of the development.
The standardization of 802.11n was a
record long 6 year journey.
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WLAN Network Planning
New installed accesspoints should be 802.11n based and operating
on both 2.4 and 5 GHz band. Higher capacity means more room
(Airtime) for clients and more throughput.
connect • communicate • collaborate
WLAN Network Planning
Comparing 2.4 and 5GHz
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WLAN Network Planning
802.11n? Yes, but what flavor?
802.11n? Yes but
only on 2.4GHz
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WLAN Network Planning
connect • communicate • collaborate
WLAN Network Planning
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.
connect • communicate • collaborate
WLAN Network Planning
Always aim for the best
fuel at the gas station.
connect • communicate • collaborate
WLAN Network Planning
connect • communicate • collaborate
WLAN Network Planning
RF Basics (know your layer 1)
connect • communicate • collaborate
WLAN Network Planning
The dynamic nature of 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.
connect • communicate • collaborate
WLAN Network Planning
About Decibels
Used to measure large dynamic ranges
• It is dimensionless
• A Decibel is a ratio
• Decibel is 1/10 of a Bel, but Bel is never used
connect • communicate • collaborate
WLAN Network Planning
connect • communicate • collaborate
WLAN Network Planning
connect • communicate • collaborate
WLAN Network Planning
connect • communicate • collaborate
WLAN Network Planning
connect • communicate • collaborate
WLAN Network Planning
Please note that
these 802.11b
threshold levels are
very depending on
your devices
antenna
performance and
the sensitivity of
the chipset (varies).
connect • communicate • collaborate
WLAN Network Planning
And yes, other signals that the wifi chipset can’t recognize (Bluetooth,
Dect phones, Microwave Owens ) will be considered noise.
connect • communicate • collaborate
WLAN Network Planning
connect • communicate • collaborate
WLAN Network Planning
Cell size. Typical SNR versus speed values for 2.4GHz.
Note how much more efficient 802.11g with ODFM is, you get
12Mbps versus 6Mbps with the same SNR
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WLAN Network Planning
connect • communicate • collaborate
WLAN Network Planning
Yes 5GHz loses more but normally also have a much lower noise floor
due to less co-channel interference
Please note:
Distances in feet
Attenuation in dB
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WLAN Network Planning
Basic antenna types
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WLAN Network Planning
connect • communicate • collaborate
WLAN Network Planning
Interference (problems and why MIMO might be your savior)
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WLAN Network Planning
connect • communicate • collaborate
WLAN Network Planning
connect • communicate • collaborate
WLAN Network Planning
An 802.11n
accesspoint
improves
reception on older
abg-client.
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WLAN Network Planning
connect • communicate • collaborate
WLAN Network Planning
connect • communicate • collaborate
WLAN Network Planning
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 (see demo later), Cisco’s Spectrum Expert or
similar products 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 (great but at an extra cost)
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.
connect • communicate • collaborate
WLAN Network Planning
connect • communicate • collaborate
WLAN Network Planning
Preparing for a site survey
connect • communicate • collaborate
WLAN Network Planning
connect • communicate • collaborate
WLAN Network Planning
connect • communicate • collaborate
WLAN NETWORK PLANNING
What type of WLAN are you building?
Three basic types WLAN design focuses:
• Coverage (as large area as possible) Outside coverage?
• Capacity (high density of user over a given area)
• Location (the possibility to locate clients)
Because the cell size dictates the capacity there’s a tradeoff between high
Coverage and high Capacity. Location usually leads to more Aps required.
Can we 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 5,5Mbps if 802.11b is left.
What type of applications should run?
Wireless Voice over IP (VoWLAN) demands certain attention (not covered
in this presentation)
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WLAN NETWORK PLANNING
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.
How many SSIDs do we need?
There should never be more than 5 SSIDs per AP even though the AP itself
may support many more. 802.11u will 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 between you and others.
connect • communicate • collaborate
WLAN Network Planning
Perform an onsite site pre-survey
Try to get hold of the 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 (very time consuming). 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.
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WLAN Network Planning
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 the RRM has done
it’s magic se what the result became.
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WLAN Network Planning
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.
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WLAN Network Planning
connect • communicate • collaborate
WLAN Network Planning
The AP1130 was designed for the office environment. Easy mount
on a 3m ceiling and propagate the signal down and wide.
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WLAN Network Planning
Even though MIMO based 802.11n APs are bit more “forgiving” try to avoid these
type of installations a much as possible.
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WLAN Network Planning
Verify coverage
Here there are many schools on how to proceed
I personally prefer to use the Aircheck from Fluke (2000 euro)
A free alternative is to combine inSSIDer and iperf to both test the
channel allocation and throughput.
An interesting alternative is Wi-Fi inspector from Xirrus
http://www.xirrus.com/library/wifitools.php but this one is maybe better
for home users.
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
connect • communicate • collaborate
WLAN Network Planning
Semi professional site survey on a shoestring budget?
Of all the soft ware I found on the Internet I believe the free version of
Wavedeploy from Veriwave . www.wavedeploy.com
Ofcourse this product does not have all the bells and whistles as it’s full
blown commersial versions but if you want a product where you can put
your laptop on a trolley or just carry it around and marking on your map
and end up with a god coverage map. I’ve not tested it yet myself but
heard good reviews from colleagues in the
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WLAN Network Planning
connect • communicate • collaborate
WLAN Network Planning
connect • communicate • collaborate
WLAN Network Planning
Per-User Application Throughput examples
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WLAN Network Planning
connect • communicate • collaborate
WLAN Network Planning
connect • communicate • collaborate
WLAN Network Planning
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.
connect • communicate • collaborate
WLAN Network Planning
Large highly populated auditoriums need a different approach.
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WLAN Network Planning
connect • communicate • collaborate
WLAN Network Planning
connect • communicate • collaborate
WLAN Network Planning
Typical settings on Cisco controller with 802.11b disabled. This will
decrease the cell size and increase the performance.
connect • communicate • collaborate
WLAN Network Planning
connect • communicate • collaborate
WLAN Network Planning
connect • communicate • collaborate
WLAN Network Planning
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
• No more than 15 active associated clients per AP
• If possible a 20% overlap of the cells is something to aim for (for
good roaming)
• You should never have less than -65dBm signal strength in your
coverage zone
• Try to get RF-spectrum analysis tools for better understanding of
what’s going on in your environment.
connect • communicate • collaborate
WLAN Network Planning
Yes!!! We made it.
connect • communicate • collaborate
WLAN Network Planning
connect • communicate • collaborate
WLAN Network Planning
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.netcraftsmen.net/user-group/c-mug-archive/922-wireless-fundamentals.html
http://www.cisco.com/web/strategy/docs/education/cisco_wlan_design_guide.pdf
https://www.ciscolivevirtual.com/portal/login.ww
Free access after registration, great mobile network presentations. If you only have time
for one link I highly recommend this one.
connect • communicate • collaborate
WLAN Network Planning
Bonus slides
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WLAN Network Planning
Viewing neighbor APs frequency and signal strength on WLC
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WLAN Network Planning
RF-Interferers show up on WLC with ver 7 software and Clean Air APs
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WLAN Network Planning
connect • communicate • collaborate
WLAN Network Planning
connect • communicate • collaborate
WLAN Network Planning
Bad channel planning lead to co-channel interference
Actual measurements from my hotel yesterday
connect • communicate • collaborate
WLAN Network Planning
connect • communicate • collaborate
WLAN Network Planning
connect • communicate • collaborate
WLAN Network Planning
connect • communicate • collaborate
WLAN Network Planning