Руководство По Проектированию для Cisco Cisco Aironet 350 Mini-PCI Wireless LAN Client Adapter
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Enterprise Mobility 4.1 Design Guide
OL-14435-01
Chapter 13 Cisco Unified Wireless Location-Based Services
Deployment Best Practices
Deployment Best Practices
Location-Aware WLAN Design Considerations
In the past decade, the design best practices for enterprise-ready wireless LANs have evolved from
coverage-centric and minimum access point models to those where coverage uniformity and proper
cell-to-cell overlap are the predominant requirements. This has been driven by increased interest in
deploying new wireless applications that are typically not as tolerant as traditional data-only deployments
toward large amounts of dropped packets and roaming delays.
coverage-centric and minimum access point models to those where coverage uniformity and proper
cell-to-cell overlap are the predominant requirements. This has been driven by increased interest in
deploying new wireless applications that are typically not as tolerant as traditional data-only deployments
toward large amounts of dropped packets and roaming delays.
In a similar fashion, the deployment of location-aware WLAN applications requires modification to
traditional approaches. This includes the design of “greenfield” location-aware installations as well as
the augmentation or retrofitting of existing deployments. For location tracking to function optimally, the
correct number of access points along with proper access point placement is a key requirement.
traditional approaches. This includes the design of “greenfield” location-aware installations as well as
the augmentation or retrofitting of existing deployments. For location tracking to function optimally, the
correct number of access points along with proper access point placement is a key requirement.
The “Deployment Best Practices” section of Wi-Fi Location-Based Services: Design and Deployment
Considerations discusses in great detail several best-practice recommendations for location-aware
WLAN deployments, such as the following:
Considerations discusses in great detail several best-practice recommendations for location-aware
WLAN deployments, such as the following:
•
Minimum received signal thresholds—For mobile devices to be tracked properly, it is highly
recommended that access points report mobile device RSSI to their respective controllers at levels
meeting or exceeding the RSSI cutoff value that is configured in WCS. A minimum of three access
points (and preferably four or more for optimum accuracy) should be reporting this level of signal
strength or better for any device being localized. Mobile device RSSI reported below this level is
eligible for discard by the location appliance.
recommended that access points report mobile device RSSI to their respective controllers at levels
meeting or exceeding the RSSI cutoff value that is configured in WCS. A minimum of three access
points (and preferably four or more for optimum accuracy) should be reporting this level of signal
strength or better for any device being localized. Mobile device RSSI reported below this level is
eligible for discard by the location appliance.
•
Correct access point placement—Proper placement of access points is critical if the system is
expected to fully deliver on its performance potential. In many office wireless LANs, access points
are distributed throughout interior spaces, providing more than adequate coverage to surrounding
work areas. These locations are usually selected on the basis of coverage, WLAN bandwidth,
channel re-use, cell-to-cell overlap, security, aesthetics, and deployment feasibility. In a
location-aware WLAN design, however, access points must not be located based solely on these
criteria but must strike a balance between them and location placement requirements. Although
there is no single rule that consistently yields the proper access point density for every environment,
the signal threshold and placement suggestions made in the “Deployment Best Practices” section of
Wi-Fi Location-Based Services: Design and Deployment Considerations should be followed as a
starting point of any location-aware design. Among these recommendations is the adherence to an
inter-access point separation of 50 to 70 feet.
expected to fully deliver on its performance potential. In many office wireless LANs, access points
are distributed throughout interior spaces, providing more than adequate coverage to surrounding
work areas. These locations are usually selected on the basis of coverage, WLAN bandwidth,
channel re-use, cell-to-cell overlap, security, aesthetics, and deployment feasibility. In a
location-aware WLAN design, however, access points must not be located based solely on these
criteria but must strike a balance between them and location placement requirements. Although
there is no single rule that consistently yields the proper access point density for every environment,
the signal threshold and placement suggestions made in the “Deployment Best Practices” section of
Wi-Fi Location-Based Services: Design and Deployment Considerations should be followed as a
starting point of any location-aware design. Among these recommendations is the adherence to an
inter-access point separation of 50 to 70 feet.
•
Validating location performance—Although adherence to design and deployment best practices
provides the necessary foundation for success, tools that provide corrective feedback to the designer
(as well as the installer) play a major role in optimizing performance. The use of predictive tools
such as the Location Planning and the Location Readiness tools can identify performance
shortcomings early when they are most easily (and most cost-effectively) addressed.
Post-deployment tools such as Location Inspection can offer a comprehensive “reality-check” of an
entire calibration area by comparing known calibration positions to predictions and calculating the
degree of location error. When location accuracy does not conform to specifications, the location
debug feature can be enabled to allow for more in-depth investigation. This feature displays the
access points that contributed to the location calculations for a specific tracked device, the signal
strength of these devices, as well as a timestamp of when the signal strength measurement was last
received. Newly added in software Release 4.1 of the Cisco UWN, the use of location test points
allows for impromptu location accuracy checks to be performed by comparing predicted location
against the actual physical position of devices bearing selected MAC addresses.
provides the necessary foundation for success, tools that provide corrective feedback to the designer
(as well as the installer) play a major role in optimizing performance. The use of predictive tools
such as the Location Planning and the Location Readiness tools can identify performance
shortcomings early when they are most easily (and most cost-effectively) addressed.
Post-deployment tools such as Location Inspection can offer a comprehensive “reality-check” of an
entire calibration area by comparing known calibration positions to predictions and calculating the
degree of location error. When location accuracy does not conform to specifications, the location
debug feature can be enabled to allow for more in-depth investigation. This feature displays the
access points that contributed to the location calculations for a specific tracked device, the signal
strength of these devices, as well as a timestamp of when the signal strength measurement was last
received. Newly added in software Release 4.1 of the Cisco UWN, the use of location test points
allows for impromptu location accuracy checks to be performed by comparing predicted location
against the actual physical position of devices bearing selected MAC addresses.