Cisco Cisco Wireless Site
Surveys
Call eTribeca at
888-219-0207 or e-mail us at
sales@etribeca.com
to discuss and schedule
wireless site surveys. We perform surveys both for end-users and as sub-contractors
to other organizations. We cover Domestic US.
The
Importance of a
Site Survey
For
radio LAN’s it is very important to perform a site-survey to determine
the effects of the facility on the propagated of radio waves.
This makes it possible to calculate the number of wireless Access
Points needed, as multiple cells will be necessary in a large building.
It is also important to test that there is no interference that may
present at some locations that may make the wireless network inoperable.
Part
of the wireless network design is to identify the location of these Access
Points to provide an interface to network resources located on the wired
network and adequate coverage for roaming users throughout the facility.
If
a wireless network were deployed in a completely open area, free from
walls, building components and furniture, radio waves from the wireless
devices would be able to maintain an omni directional radiation pattern,
making it simpler to predict the maximum operating range among all devices
and the location of the Access Points.
The construction of the facility offers radio waves through
flooring, for example, depends on the building methods present between the
floors. Range
is greatest if passing through plywood, fair if passing through concrete,
and very poor if going through metal.
eTribeca’s
engineers will conduct a detailed site survey of the building in
preparation for deployment of the wireless Ethernet equipment.
The only true method for optimum site performance is to test
empirically for proper placement of Access Points and type of antenna to
be employed.
There is no way to determine the distance that a signal will travel
without a survey.
Metal film on glass, leaded glass, steel studded walls, cement
floors and walls with steel reinforcement, foil backed insulated walls,
firewalls stairwells and elevator shafts are typical items that will
reduce range.
In a multi floor building, it is necessary to do a three
dimensional profile.
We
shall require a layout plan of the building for marking up.
If there is none available, eTribeca LLC will create one.
Site
Survey Methodology
A.
Overview of a Wireless Site Survey
To
simulate the operation of the wireless network as closely to future
operating conditions as possible, we will use two Cisco Aironet 802.11b
Access Points mounted at different locations, and two laptop computer
systems equipped with Cisco Aironet 802.11b series wireless LAN cards,
which can be used to roam throughout the facility. Theses tests will be
performed 1) to demonstrate the technology and 2) to determine the area
covered and quality of Wireless Connectivity. Both the wireless cards and
the 802.11b Access Points run at 11Mbps.
The
basic antenna that will be used is a 2.2dBi Dipole. If the topology of the
building demands it, we shall also survey with 3 dBi Omni or 8.5dBi patch
antennae, or such other antennae as our engineers consider to be
appropriate when they are on site.
The
test applications that will be used are “PING” and Cisco Aironet
“LinkScope” software. By varying the PING arguments (the number of
times to PING), we are able to monitor the connectivity of the wireless
link.
PING
Test: Each
laptop continuously PINGs two Access Points. The tester records statistics
on the minimum round-trip time, maximum round-trip time, average
round-trip time and percentage of no-response (packet losses).
Redundancy
Test: Redundancy
between Access Points is tested utilizing “LinkScope”, a testing
application from Cisco Aironet. This test shows the signal strength and
quality from the Wireless LAN Adapter to each Access Point.
Load
test: In
this test, creating a peer-to-peer environment simulates a LAN environment
between two computers, and file transfers are performed between the two.
This demonstrates the relationship between bandwidth and distance in the
wireless infrastructure.
B.
Explanation of PING test
PING
is a utility used to perform a connectivity test in a TCP/IP network. PING
works at the network layer. The protocol utilized is ICMP (Internet
Control Message Protocol), which is in the same layer as IP (Internet
Protocol). The program transmits a predetermined Ethernet packet
size
to a destination host, which is returned to the originating computer. PING
reports the round-trip time of the packet. By default, PING sends out four
requests and reports the statistics in the form of a maximum, minimum, and
average round-trip time. If there is no response within certain
A
typical PING test reply looks like the following:
Pinging
209.14.129.1 with 500 bytes of data:
Reply
from 209.14.129.1: bytes=500 time=12ms TTL=128
Reply
from 209.14.129.1: bytes=500 time=12ms TTL=128
Reply
from 209.14.129.1: bytes=500 time=14ms TTL=128
.
. . (omitted 94 lines, total 100 lines) . . .
Reply
from 209.14.129.1: bytes=500 time=16ms TTL=128
Reply
from 209.14.129.1: bytes=500 time=13ms TTL=128
Reply
from 209.14.129.1: bytes=500 time=16ms TTL=128
Ping
statistics for 209.14.129.1:
Packets:
Sent = 100, Received = 100, Lost = 0 (0% loss),
Approximate
round trip times in milli-seconds:
Minimum
= 11ms, Maximum = 62ms, Average = 15ms
C.
Explanation of LinkScope test.
LinkScope
is used to perform user level site surveys for the Cisco Cisco Wireless
LAN adapter card. It allows the user to view the current signal strength
and signal quality. This information can
be
used to assess the performance of the Radio Frequency (RF) link at various
locations covered
in
a wireless environment. The results of this test are used to determine the
RF network coverage, indicating the required number and placement of
Access Points within a specific area. It also identifies “dead spots”,
locations with low or no RF signal levels. Dead Spots are the result of RF
signal being attenuated by the environment or from multipath interference.
LinkScope
provides the following information:
Associated
Access Point
–While roaming from the coverage area of one access point to another,
Wireless adapters will automatically sense the signal and transparently
associate itself to the next Access Point without losing connectivity.
LinkScope will identify which Access Point an adapter
is
associated to.
Associated
Access Point MAC
– The MAC Address of the Access Point that your Aironet
Wireless
LAN Adapter is associated with.
Current
Signal Strength
– The Received Signal Strength Indicator (RSSI) for all received
packets. The range is from
0% - 100%.
Current
Signal Quality
– The Quality of received signal foe all received packets. The range is
from 0% - 100%.
Overall
Link Quality
– An indicator of the ability of the Cisco Wireless Adapter to
successfully communicate with an Access Point. Ratings are excellent,
Good, Fair, poor. It is derived from the Current Signal Strength and
Current Signal Quality. Excellent: value greater than 75%; Good:
value
greater than 40%; Fair: value greater than 20%; Poor: value less than 20%
Call eTribeca at 1-888-219-0207 or 1-212-219-0207
or e-mail sales@etribeca.com
for more information or to order.
|
