Deployment Guide: Higher Education
Technical Guide
Site Survey
061808
2
Site Survey Guide
Table
of
Contents
Introduction .................................................................................................................................3
Types
of
Site
Surveys ....................................................................................................................3
Survey
Requirements....................................................................................................................5
Equipment
Required.....................................................................................................................7
Performing
the
Survey..................................................................................................................8
Getting
Started .............................................................................................................................9
Summary .................................................................................................................................... 11
Wi‐Fi
Tools.................................................................................................................................. 11
100508
2
Site Survey Guide
Introduction
The
purpose
of
this
guide
is
to
serve
as
an
introduction
and
education
on
the
basics,
the
values,
and
best
practices
associated
with
performing
Wi‐Fi
site
surveys.
We
will
describe
the
process
Xirrus
uses
for
site
surveys
and
demonstrate
how
these
same
processes
can
be
used
by
anyone
with
readily
available
tools.
Poorly
performed
site
surveys
can
result
in
not
only
coverage
gaps
and
reduced
performance,
but
also
increased
costs
associated
with
identifying
and
resolving
these
issues
after
the
fact.
The
goal
of
any
site
survey
is
to
determine
the
number
and
location
of
access
points
(APs)
required
to
meet
wireless
design
goals
(such
as
coverage,
performance
and
user
capacity).
Getting
the
site
survey
accurate
is
just
as
important
as
selecting
the
proper
hardware.
If
the
site
survey
is
too
optimistic
and
calls
for
too
few
access
points,
the
final
installation
will
yield
poor
coverage
and/or
performance.
This
in
turn
will
require
a
follow‐up
survey
to
determine
what
changes
may
be
required
to
the
number
or
location
of
deployed
APs.
The
end
result
will
be
increased
costs
not
only
in
additional
APs,
but
also
the
associated
costs
of
pulling
cable,
equipment,
contractors,
and
installation
effort.
Conversely,
if
the
survey
is
too
conservative,
more
access
points
than
are
needed
will
be
specified
and
again
money
is
wasted
on
unneeded
equipment
and
labor
charges.
Types of Site Surveys
Active vs. Predictive
There
are
two
primary
methods
in
which
site
surveys
can
be
performed:
Active
and
Predictive.
Active
site
surveys,
also
called
live
surveys
use
an
actively
transmitting
access
point
and
a
Wi‐Fi
enabled
laptop
or
other
tool
to
measure
Wi‐Fi
signal
strength
in
the
actual
environment
to
determine
how
many
and
where
access
points
are
required.
Predictive
site
surveys
use
software
packages
to
emulate
the
environment.
Floor
plans
of
the
site
are
imported
and
allow
the
user
to
assign
attenuation
values
(how
much
RF
energy
is
absorbed)
for
each
wall
and
object
in
the
building
(most
tools
typically
have
a
database
of
materials
to
choose
from),
the
application
will
then
predict
the
number
and
location
of
access
points
required
to
meet
the
desired
coverage
and
performance
goals.
Active site surveys
–
measures
the
real
performance
of
each
access
point
location
and
innately
takes
into
account
the
physical
characteristics
and
contents
of
the
building.
There
is
no
need
to
estimate
the
density
of
the
walls
or
floors.
An
active
site
survey
is
also
able
to
detect
any
sources
of
interference
and
apply
this
information
to
determine
SNR
(signal
to
noise
ratio).
This
type
of
survey
not
only
provides
the
most
accurate
performance
information
for
each
access
point,
it
also
allows
for
the
physical
inspection
of
the
site
to
assure
the
access
point
can
be
mounted
in
the
selected
location.
The
downside
of
this
type
of
survey
is
it
is
labor
intensive,
requires
physical
access
to
the
building
and
demands
a
higher
level
of
RF
knowledge
to
perform.
Predictive site surveys
–
may
take
less
time
but
still
require
“seat
time”
in
front
of
a
computer
program
versus
the
“leg
time”
needed
for
an
active
survey.
As
the
name
implies
the
software
performs
a
predictive
analysis
of
the
building,
once
floor
plans
are
imported
it
uses
industry
defined
attenuation
values
for
walls,
100508
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Site Survey Guide
doors,
windows,
etc.
The
difficulty
here
is
the
common
GIGO
(Garbage
In‐Garbage
out)
problem
associated
with
trying
to
accurately
model
the
contents
and
makeup
of
the
building
(especially
ones
that
have
changed
or
remodeled
over
time).
Survey
Comparison
Active
(live)
Survey
Predictive
Survey
Survey
Effort
Higher
Potentially
Lower
Access
Point
Placement
Exact
Locations
chosen
Final
locations
still
need
be
chosen
Wireless
Coverage
Measured
/
Known
Predictive:
May
require
more
APs
Wireless
Performance
Measured
/
Known
Estimated:
May
require
more
APs
Cabling
and
Equipment
Typically
Accurate
May
require
cables
to
be
added
or
moved
Installation
Simplified
May
require
moving
APs
or
adding
more
APs
Remote
vs.
On‐Site
Survey
Although
the
following
discussion
goes
hand
in
hand
with
Active
vs.
Predictive
surveys,
it
is
important
to
identify
the
additional
value
beyond
RF
analysis
of
an
on‐site
active
survey
vs.
a
predictive
software
analysis.
The
key
point
is
to
understand
the
value
of
walking
the
facility
as
the
survey
is
performed
and
knowing
what
to
look
for.
The
active
survey
not
only
provides
the
most
accurate
performance
information
for
each
access
point,
it
also
allows
for
the
physical
inspection
of
the
site
to
assure
the
access
point
can
be
mounted
in
the
selected
location.
If
AP
placement
is
based
just
on
the
marking
on
a
floor
plan
the
actual
installers
may
find
the
location
unacceptable
for
installation,
as
it
may
not
be
physically
mountable
at
the
predicted
location.
A
physical
walkthrough
of
the
installation
site
enables
identification
and
addressing
of
the
following
types
of
issues
before
installation
day,
where
delays
can
be
costly:
Identifying AP locations – This
is
will
greatly
assist
those
pulling
data/power
cabling
and
avoid
costly
changes.
Physical restrictions
–
Are
there
mounting
issues
that
prevent
an
AP
being
installed
where
it
would
best
be
located,
such
as
lighting,
air
conditioning
ducts,
sprinklers,
appropriate
mounting
points,
etc.
It
also
allows
installers
to
identify
all
tools
and
any
special
mounting
hardware
required
for
the
install.
RF Interference issues
–
Are
there
nearby
non‐802.11
devices
that
emit
RF
energy
(microwave
ovens,
medical
equipment,
air
conditioning
units,
etc.)
that
may
interfere
with
the
proper
operation
of
the
AP?
In
addition,
what
other
Wi‐Fi
networks
are
located
in
the
environment?
If
other
5
GHz
networks
are
nearby
100508
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Site Survey Guide
there
is
typically
sufficient
available
channels
to
avoid
interference,
however
with
2.4
Ghz
(11b/g)
there
are
only
3
usable
channels
and
a
nearby
network
also
using
these
could
result
in
interference.
At
this
point
there
should
be
some
discussion
between
IT
staffs
to
set
channels
and
power
to
avoid
interference
that
could
degrade
both
networks
performance.
Aesthetic Issues
–
Are
there
corporate
policies
that
restrict
the
location,
color,
shape,
etc.,
of
the
Access
Point.
Regulations/Codes/Policies
–
Are
their
specific
rules
that
the
deployment
must
confirm
to,
such
as
AC
power
distribution,
cabling
runs,
RF
power
limits,
plenum
rating,
or
other
issues.
Arriving
on
site
with
inappropriate
components
can
add
expensive
delays.
Flexibility of environment
–
Many
environments
‐
especially
schools,
conference
centers,
warehouses,
manufacturing
facilities
–
can
be
very
physically
dynamic.
From
one
day
to
the
next,
walls
can
be
moved,
equipment
shuffled,
racks
rearranged,
etc.
A
visual
walkthrough
and
on‐site
discussion
can
identify
and
address
these
issues
prior
to
the
install
and
avoid
post
install
complications.
Bottom line
–
A
predictive
survey
is
often
easier
to
accomplish
but
has
the
potential
to
make
the
actual
install
more
complex
due
to
unknowns
that
could
be
encountered.
An
active
site
survey
that
includes
a
physical
walkthrough
is
more
complex,
however
will
make
the
install
go
smoother
by
identifying
potential
issues
up
front
and
ultimately
result
in
a
more
successful
deployment.
Survey Requirements
Before
starting
a
site
survey,
it
is
of
critical
importance
to
define
the
purpose
of
the
survey.
It
may
seem
very
basic
to
include
this
as
a
requirement,
however
it
is
amazing
how
many
surveys
are
conducted
with
the
focus
only
on
RF
coverage
and
no
consideration
given
to
the
reasons
for
installing
Wi‐Fi
in
the
first
place.
The
following
components
should
be
considered
before
selecting
a
vendor
or
performing
a
survey
as
they
will
help
determine
the
product
and
survey
requirements.
Business Requirements
–
What
is
the
purpose
of
adding/upgrading
the
Wi‐Fi
services?
Is
the
goal
to
just
add
Wi‐Fi
hotspots,
connectivity
in
the
conference
rooms,
or
is
it
a
building/campus‐wide
pervasive
Wi‐Fi
service
that
provides
seamless
coverage
and
roaming
throughout
the
enterprise.
The
answer
to
this
question
will
help
determine
the
vendors,
products
and
Wi‐Fi
architecture
you
select.
Application Requirements
–
Bandwidth
and
QoS
capabilities
define
the
products
purchased,
however
minimum
RF
signal
strength
must
also
be
considered
for
voice
over
Wi‐Fi
solutions.
The
majority
of
Wi‐Fi
phone
vendors
require
a
‐68
dBm
RSSI
(received
signal
strength
indicator)
or
stronger
signal.
Surveying
to
this
level
avoids
having
to
re‐survey
and
add
APs/cabling
at
a
later
time.
Security Requirements
–
Another
topic
often
overlooked
during
a
site
survey
is
security.
Controlling
the
amount
of
RF
energy
transmitted
beyond
the
enterprise
boundaries
(parking
lots,
etc.)
should
always
be
a
consideration.
With
proper
AP
placement,
power
levels,
and
use
of
directional
antennas,
RF
leakage
can
be
minimized.
To
clearly
define
the
edge
of
RF
coverage,
vary
power
levels
and
record
signal
strength
readings
on
inside
and
outside
walls
of
facility.
Directional
antenna
can
also
be
used
for
RF
shaping.
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Site Survey Guide
Coverage vs. Capacity
–
Most
vendors
offer
separate
survey
procedures
for
coverage
or
capacity
models.
Coverage
surveys
are
designed
to
generate
a
solution
with
the
minimum
number
of
APs
to
guarantee
client
association.
Capacity
surveys
are
designed
to
support
larger
numbers
of
stations
and
offer
higher
data
rates
to
clients;
these
typically
group
more
APs
in
a
single
area,
resulting
in
smaller
cells
and
with
more
radio
choices
for
clients.
The
result
is
typically
stronger
signal
strength
connections
for
clients,
which
results
in
higher
data
rates.
Cell Size Planning‐
Wi‐Fi
in
the
5GHz
band
(802.11a/n)
has
slightly
smaller
cells
than
Wi‐Fi
in
the
2.4GHz
band
(802.11b/g/n).
Design
for
5GHz
and
it
will
pretty
much
ensure
coverage
for
all
802.11a/b/g/n
clients.
Larger
cells
sizes
can
reduce
number
of
APs
required,
but
could
result
in
client
connectivity
problems.
Choosing Between 2.4 GHz or 5 GHz
–
Both
bands
are
commonly
deployed
in
Wi‐Fi
networks
today
and
it
is
strongly
recommended
to
perform
the
survey
for
both
bands.
Wireless Bridging (WDS) Requirements
–
Will
AP
to
AP
wireless
bridging
be
used?
This
question
may
come
up
in
outdoor
deployments,
in
warehouses
where
intra‐AP
distances
could
exceed
100
meters
or
even
building‐to‐building
links.
As
part
of
the
survey,
examine
point‐to‐point
path
loss.
Special
attention
should
be
paid
to
any
trees
or
foliage
in
the
path
as
seasonal
growth
could
impact
the
link.
Wired Infrastructure –
Don’t
overlook
the
existing
wired
infrastructure,
as
its
capabilities
or
lack
thereof
can
severely
impact
Wi‐Fi
performance.
For
example
if
deploying
802.11n
Wi‐Fi,
the
uplinks
will
require
Gigabit
links.
Verify
the
cable
plant
and
switches
are
capable
of
Gigabit
Ethernet
or
if
a
wired
network
upgrade
will
be
required.
In
addition,
verify
AP
powering
options.
If
PoE
will
be
used,
verify
that
new
or
existing
PoE
products
provide
sufficient
power
(802.3af,
802.3at,
or
other)
for
the
Wi‐Fi
to
be
deployed
(for
example
802.11n
requires
increased
power).
The 802.11n Site Survey –
The
introduction
of
802.11n
has
added
some
confusion
and
caveats
to
the
traditional
site
survey.
802.11n
is
not
about
higher
transmit
power,
but
about
better
receiver
sensitivity
(ability
to
listen).
802.11n
range
improvements
require
11n
radios
at
both
ends
of
the
connection
‐
the
station
and
Access
Point.
The
majority
of
networks
deployments
will
include
a
mix
of
client
types
(802.11n
and
non‐802.11n)
and
cell
sizes
should
therefore
remain
the
same.
Some
recommendations
for
performing
11n
surveys
include:
• Always
survey
for
both
2.4/5
Ghz‐
This
is
the
same
as
for
802.11a/b/g
surveys
and
is
recommended
so
both
bands
will
be
properly
supported
• Use
an
802.11abg
adapter
for
site
survey
–
This
is
recommended
even
for
11n
APs
as
support
for
legacy
802.11a/b/g
devices
will
continue
for
some
time
• Use
an
802.11abgn
adapter
only
if
all
network
devices
will
be
11n
capable
–
Although
some
networks
may
meet
this
criteria,
the
vast
majority
of
Wi‐Fi
networks
will
be
mixed
11a/b/g/n
environments
for
some
time
100508
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Site Survey Guide
Equipment Required
This
section
identifies
specific
equipment,
tools,
and
software
Xirrus
recommends
for
performing
a
professional
quality
site
survey.
Array/APs/Radios:
Use
the
type
of
Array
or
AP
to
be
deployed.
All
surveys
should
be
performed
using
products
identical
to
those
that
will
be
installed;
this
approach
helps
to
guarantee
installed
coverage
matches
that
of
the
survey.
Using
different
products
for
survey
and
production
could
result
in
significant
variability
in
actual
coverage.
Support Equipment:
•
•
•
•
•
Multiple
copies
of
the
floor
plan
should
be
available
to
track
mounting
locations,
record
obstructions,
and
indicate
mounting
options
and
general
note
taking.
Surveys
should
be
conducted
with
Arrays/APs
located
as
close
as
possible
to
where
they
will
be
installed.
Xirrus
uses
tripods
to
locate
Arrays.
If
using
standard
APs,
it
is
recommend
to
pole
mount
them
for
easier
placement.
General
purpose
equipment
such
as
AC
extension
cords,
Ethernet
cabling,
console
cables,
ladders,
flashlights,
etc,
should
be
available
to
assist
on
the
survey.
A
camera
is
desirable
to
record
unique
mounting
obstacles
so
appropriate
mounts
can
be
defined.
Some
form
of
location
identifiers
(e.g.
stickers)
to
indicate
where
Array/APs
will
be
placed.
Software/Firmware Tools
A
laptop
with
the
following
tools
will
be
required
for
the
survey:
• RF
survey
tool,
for
example
AirMagnet
Survey
or
similar.
Alternatively
for
more
simple
surveys,
free
tools
that
read
Wi‐Fi
signal
strength
can
be
used.
The
Xirrus
Wi‐Fi
Monitor
gadget
is
a
free
tool
that
can
be
used
and
is
available
at
http://www.xirrus.com/library/wifitools.php.
• Optionally
some
form
of
RF
monitoring
tool
that
will
identify
nearby
APs
and
perform
Spectrum
Analysis
to
identify
potential
noise
sources.
The
Xirrus
Wi‐Fi
Array
has
these
capabilities
built‐in
and
can
be
leveraged
during
the
survey
process.
100508
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Site Survey Guide
Performing the Survey
This
section
describes
procedures
used
by
Xirrus
to
perform
a
site
survey.
Using
this
methodology
and
readily
available
Wi‐Fi
tools,
an
IT
administrator
with
a
moderate
degree
of
Wi‐Fi
knowledge
can
perform
a
reasonably
accurate
survey
of
their
own.
As
previously
discussed,
the
site
survey
is
one
of
the
most
crucial
steps
in
a
successful
Wi‐Fi
network
deployment.
With
many
techniques
commonly
used
for
Wi‐Fi
site
surveys
and
the
many
modes
of
802.11a/b/g/n,
ensuring
the
survey
is
done
right
is
more
important
than
ever.
A
poorly
performed
site
survey
does
not
only
impact
you
network
today,
it
can
result
in
a
costly
redesign
when
it’s
time
to
upgrade
to
802.11n.
Components
of
a
professional
site
survey
performed
by
vendor‐qualified
individuals
should
include:
• Complete
on‐site
survey
of
all
areas
to
be
covered,
using
same
products
that
will
be
deployed.
•
On‐site
RF
spectrum
analysis
to
identify
potential
interference
issues.
•
Post
survey
analysis
and
report
including
coverage
maps
and
RSSI
values.
•
Post
install
survey
to
confirm
installed
Wi‐Fi
equipment
meets
proposal
requirements.
Recommended Site Survey Parameters
•
•
•
Signal
Strength
‐70dBm
RSSI
(or
stronger)
in
all
areas
to
support
full
data
rates
Signal
Strength
‐68dBm
RSSI
(or
stronger)
in
all
areas
to
support
Wi‐Fi
voice
handsets
Client
should
be
able
to
see
at
least
2‐3
radios
at
every
location
these
signal
levels
Before Arriving On-site
•
•
•
Discuss
business
requirements
with
all
who
have
a
stake
in
the
Wi‐Fi
solution
Obtain
digital
floor
plans
of
facility
to
be
covered
(e.g.
.jpg,
.bmp,
.png)
Ensure
access
will
be
available
on
the
day
of
the
survey
to
all
area,
or
a
representative
subset
of
area,
that
is
to
be
covered
by
Wi‐Fi
Tips Before Starting
This
section
includes
a
number
of
tips
and
recommendations
to
help
ensure
a
successful
and
accurate
survey.
• It
is
a
good
idea
to
deploy
as
many
Arrays
as
reasonable,
as
this
will
simplify
the
survey
process
and
provide
superior
survey
measurements
vs.
just
using
just
one
Array
and
continually
moving
and
taking
measurements.
• Set
up
Tripod/Array
in
such
a
way
that
it
correctly
represents
how
the
Array
will
be
mounted
• For
each
Array
and
Array
location
during
the
survey,
use
a
separate
SSID
so
specific
coverage
of
each
Array
can
be
easily
distinguished.
• Set
Array
beacon
rate
to
20ms
‐
this
enables
the
survey
software
to
receive
many
more
beacons.
After
the
survey,
don’t
forget
to
reset
beacon
rate
to
default.
• Perform
surveys
under
worst‐case
usage
conditions
for
the
environment,
for
example
doors
closed,
curtains
drawn,
etc.
• Be
aware
that
each
client
(laptop/Wi‐Fi
card/driver)
will
have
slightly
different
readings.
This
is
a
good
reason
to
be
conservative
when
performing
Wi‐Fi
surveys.
100508
8
Site Survey Guide
•
•
•
•
•
•
•
•
Perform
the
survey
at
both
5GHz
and
2.4GHz.
Do
not
survey
for
802.11n
only
unless
you
are
100%
sure
no
legacy
(802.11a/b/g)
clients
will
be
supported
(not
common)
Take
measurements
where
users
will
be
located:
desks,
tables,
etc.
Take
multiple
readings
in
each
room
Consider
additional
signal
attenuation
if
Arrays/APs
will
be
placed
in
enclosures
or
above
ceilings.
In
multi‐floor
building,
check
for
floor‐to‐floor
bleed‐through.
If
significant,
plan
for
coverage
of
areas
from
Arrays/APs
placed
above/below
a
given
floor.
Stagger
the
final
placements
of
the
Arrays/APs
between
floors
to
account
for
this.
Constantly
consider
installation
concerns
when
surveying
and
prepare
accordingly
Don’t
rush!
Getting Started
This
section
demonstrates
a
process
that
Xirrus
has
found
to
be
successful
and
accurate.
1. Start
with
laptop
in
a
far
corner
of
the
facility
and
the
Array/AP
placed
nearby.
Move
the
Array/AP
away
from
the
laptop
until
signal
strength
drops
to,
but
not
under,
the
specified
RSSI
value
(e.g.
‐70)
100508
9
Site Survey Guide
2. Find
the
other
edge
of
coverage
area
by
moving
the
laptop
away
from
the
Array/AP
and
surveying
until
the
signal
strength
drops
to,
but
not
below,
the
specified
signal
strength
values.
3. This
defines
the
coverage
area
for
the
single
Array;
identify
the
location
by
recording
the
information
on
a
floor
plan
and
also
with
some
form
of
physical
tagging
(e.g.
stickers
on
the
ceiling)
to
identify
the
exact
location
where
the
Array
will
be
located.
4. Continue
to
repeat
this
process
as
you
move
across
the
building
until
the
complete
facility
has
been
surveyed.
If
surveying
a
multi‐story
facility,
make
sure
to
verify
floor‐to‐floor
coverage
before
turning
moving
the
Array.
5. Use
the
Array’s
RF
Monitor/Intrusion
Detection
function
(or
similar
tool)
to
find
other
APs
in
the
area.
All
detected
APs
should
be
identified
as
known
or
unknown
devices
and
considered
in
the
overall
survey.
6. Use
the
Array’s
RF
Monitor/Spectrum
Analyzer
function
(or
similar
tool)
to
identify
sources
of
interference,
either
802.11
co‐channel
interference
or
non‐802.11
noise.
Once
a
noise
source
is
identified,
define
a
plan
for
interference
avoidance.
In
some
cases,
discussions
with
neighboring
Wi‐
100508
10
Site Survey Guide
Fi
networks
IT
staff
should
be
set
up
to
arrange
for
channel
planning
and
power
setting
coordination.
7. Finally,
share
complete
survey
information
with
all
stakeholders.
Discuss
covered
areas,
RSSI
values,
weak
spots
and
indicate
how
many
radios
are
available
to
mobile
users
throughout
the
facility.
This
last
part
is
key
as
we
recommend
at
least
2‐3
strong
radios
to
all
clients
to
provide
resiliency
and
to
reduce
the
possibility
of
a
single
radio
failure
taking
down
any
area.
Example
of
‘Active’
Site
Survey
results
(using
AirMagnet
tool)
Summary
Predictive
site
surveys
may
be
acceptable
in
some
less
complex
Wi‐Fi
deployments,
however
the
larger
and
more
business
critical
your
Wi‐Fi
project
is,
the
more
essential
an
active
site
survey
becomes.
Rolling
out
Wi‐
Fi
for
a
large
office
building
or
campus
environment
mandates
an
accurate
site
survey.
With
large
projects,
even
being
off
by
a
small
percentage
could
result
in
unacceptable
additional
costs
associated
with
additional
equipment,
cabling,
and
manpower
requirements.
An
active,
on‐site
survey
using
tried
and
true
best
practice
methodologies
is
the
most
accurate
type
of
survey
and
Xirrus
strongly
recommends
it
be
made
a
requirement
of
any
Wi‐Fi
deployment.
Final
Thought
‐
You
are
betting
the
success
of
your
Wi‐Fi
network
on
the
survey,
and
maybe
your
job!
Wi-Fi Tools
•
•
Wi-Fi Basics FAQ – www.xirrus.com/library/faq.php
o Useful Wi-Fi FAQ for understanding the components, requirements and goals
associated with performing a site survey
Wi-Fi Tools – www.xirrus.com/library/wifitools.php
Xirrus
has
assembled
several
useful
Wi‐Fi
tools
found
to
be
of
great
value
in
planning,
deploying,
and
managing
Wi‐Fi
networks.
Xirrus Wi-Fi Reference Posters –
www.xirrus.com/posters
o Educational/reference
information on Wi-Fi
o
•
100508
11
Site Survey Guide
•
Xirrus Wi-Fi Widgets/Gadgets – www.xirrus.com/library/wifitools.php
o The Xirrus Wi-Fi Monitor provides detailed information about surrounding Wi-Fi
networks and your laptop’s current Wi-Fi connection, including SSID, signal
strength, IP address, MAC address, security level, vendor, and network type. This
free tool can be used to perform simple site surveys.
100508
12
Guide