To implement a
wireless network with optimal coverage, you must first have a solid
understanding of the radio frequency operation in the field. Wireless site
surveys are the best way to obtain this information because they reveal areas
of channel interference and identify dead zones. It helps avoid problems when
building a network and prevents network users from being interrupted.
The main objective
of conducting a wireless site survey is to determine two things. First,
determine the feasibility of building a wireless network on your site. When
possible, you should determine the best location for the access point and other
equipment, such as antennas and cables. An On Site survey can also help you
determine the type of equipment you need, where to install it and how to
install it.
AP placement
WLAN access points
can potentially be located anywhere. Wireless site surveys can help identify
where APs should be implemented to avoid overlaps and interference.
Many networks
administrators simply install an additional Wi-Fi AP as a simple solution to
improve wireless coverage. But recently or nothing to solve the root of the
problem. In fact, having too many WiFi access points can increase the
likelihood of co-channel interference with other access points that are already
implemented. Surveys of wireless sites can help avoid this problem.
Surveys can also
help you find the AP around you. There are three non-overlapping channels that
can be used to implement wireless networks in the United States: 1, 6, and 11
for 2.4 GHz frequencies. These rules apply to everyone, not just the site.
Therefore, if your site is located at the facilities of other organizations
that have their own wireless network, you should coordinate with the APs of
those other organizations.
To implement a wireless network site survey, that does not overlap with other users in your area, you must know
nearby APs. In some cases, it may be more appropriate to use another WiFi
frequency, such as 5 GHz for 802.11 a / n / ac.
Channel interference
Channel interference
may indicate a problem with the wireless network and may be caused by a variety
of problems. Even when using the same radio frequency, even a microwave in the
dining room can cause network interruptions.
Humans can also
cause problems. The average human body is composed largely of water, and water
causes absorption, which can actually absorb radio signals and cause problems
to the network.
It is important to
keep these things in mind during a site survey. Sometimes we do a survey on the
site to determine where all APs should be implemented, but this is when people
really travel and work every day (and use the microwave) to discover that the
network does not work properly.
The best way to
avoid these problems is to use a wireless site survey to get a good
understanding of your site's RF. This is important to design and implement a
wireless network with optimal coverage.
Types of Site Surveys
There are three
types of surveys: Passive, Active, and Predictive.
Passive Survey
A passive survey is a survey conducted in listen-only mode.
Survey clients are not associated with an access point (AP). Such research can
be useful when looking for malicious devices or when the correct downlink RF
coverage gauge of infrastructure devices is needed.
This can be achieved with passive research:
· Identify fraud
· Find RF problem zones quickly
·Validate the final RF configuration
·Conduct an initial survey
The most important information losses in passive surveys are
uplink information, physical speed limits (PHY) and retransmissions. PHY rates
are generally based on RF signals and noise levels. Passive surveys only report
the propagation of the beacon signal measured by a particular customer. The PHY
rate can only be measured by the actual data sent to and from the AP.
Active Survey
Active surveys are performed on the survey client associated
with the AP used throughout the survey. When a client associates, it performs
all the tasks that a typical 802.11 client does. This includes changes in data
rate and retransmissions due to changing RF conditions. Active surveys are
commonly used in new WLAN implementations because they provide the most
detailed information on which to base the design.
There are two main
methods used in active surveys.
Basic Service Set
Identifier (BSSID) method: This method blocks the client to the wireless
MAC address of the AP and prevents the client from moving.
Service Set
Identifier (SSID) method: It is most commonly used in post-deployment
scenarios and is used to poll multiple APs. Survey clients can partner with an
SSID where the client roams between multiple APs.
Predictive Surveys
Predictive surveys are conducted in software programs. The
program uses information about the coverage area to perform AP placement based
on RF algorithms. These surveys are generally not valid for any type of field
measurement.
The best times to incorporate predictive research are:
- · When the deployment environment has not yet been created.
- · To obtain the budget environment for WLAN related hardware.
- · When roaming requirements are less strict.
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