Cisco Systems 2700 User Manual
Cisco 2700 Series Wireless Location Appliance
Deployment Guide
This document provides configuration and deployment guidelines as well as troubleshooting tips and
answers to frequently asked technical questions for those adding the Cisco 2700 Series Wireless
Location Appliance (hereafter referred to as the location appliance) (Figure 1) to a Cisco wireless LAN
network. The existing installation and configuration guides for this appliance are available at the
following location:
http://www.cisco.com/en/US/products/ps6386/tsd_products_support_series_home.html
Note This document assumes an indoor installation of the location appliance, and any guidelines and
accuracies cited are consistent with that assumption.
Figure 1 Cisco 2700 Location Appliance
The location appliance tracks 802.11 devices directly from a wireless LAN infrastructure using
advanced RF fingerprinting technology. Additionally, the appliance records information so that you can
establish location trends and resolve problems regarding RF capacity.
By design, the location appliance is directly integrated into the wireless LAN infrastructure and is
configured through its command-line interface and then managed through WCS. The location appliance
tracks the physical location of wireless devices using wireless LAN controllers and Cisco Aironet
Corporate Headquarters:
Cisco Systems, Inc., 170 West Tasman Drive, San Jose, CA 95134-1706 USA
© 2005 Cisco Systems, Inc. All rights reserved.
lightweight access points. This appliance tracks any Wi-Fi device, including Wi-Fi clients,
standards-based Wi-Fi active RFID tags, rogue access points, and clients. It was designed with the
following requirements in mind:
• Manageability—The same browser-based interface that is used for the Cisco WCS is also used for
the appliance. Moreover, the location appliance integrates directly into the wireless LAN
architecture, providing one unified network to manage instead of multiple disparate wireless
networks.
• Scalability —The appliance was built to simultaneously track up to 1500 wireless devices. WCS can
manage multiple location appliances for greater scalability.
• Security—The controller, WCS, and the location appliance were separated to deliver the most secure
architecture possible. The appliance records historical location information that can be used for
audit trails and regulatory compliance.
• Open and standards based—The appliance has a SOAP/XML API that can be integrated by partners
with other business applications and can track any standards.
• Easy deployment of business applications—The appliance can be integrated with new business
applications such as asset tracking, inventory management, location-based security, or automated
workflow management.
Location Tracking
The location appliance calculates the location of tracked devices using RF fingerprinting. This technique
uses RF characteristics such as reflection, attenuation, and multi-path to impact signal strength readings
of devices in specific environments.
To detect the RF signal at each location in an enterprise, the system must first understand how the RF
interacts with an installation's environmental variables, such as building materials, walls, doors, and
furniture. As such, an RF calibration is required (post wireless LAN installation) to determine the
characteristics of that specific RF environment.
When an RF calibration is performed, the attenuation of walls and other building characteristics is taken
into account. The extent of RF reflection and multi-path is also calculated for every coordinate, or grid,
on a floor map in the management system for each access point. For a single point on the grid, many
different access points detect devices; however, each access point detects these devices at different signal
strengths.
At the conclusion of calibration, a database is populated inside of the management system. That database
contains each coordinate and how each access point views that coordinate from the standpoint of signal
strength.
When devices' locations are requested by the management system, each controller replies on behalf of
its access points with the signal strengths at which they detect them. The management system then
matches the information it gathers from the controllers against its database of location RF fingerprints.
Devices' locations are then plotted visually on a floor map.
Performing a Calibration
You can generate the location of coordinates of tracked devices by using prediction. The location
coordinates generated in this case are predicated from RF models that the engine already has in its
knowledge base. However, if the location resolution is not within specifications, it can be further tuned
using a technique known as calibration.
Cisco 2700 Series Wireless Location Appliance Deployment Guide
2
OL-8478-01
Calibration is the process whereby sample signal strength measurements are physically taken in the
actual environments in which you wish to perform location tracking as inputs to tune the location
tracking rather than using the canned or simulated environment’s inputs. Calibration is performed on a
per-floor basis with a wireless laptop using RSSI measurements.
The goal of the calibration process is to refine location accuracy to be within the specifications (10 m,
90%). The calibration is done by taking site specific measurements into account and narrowing the delta
between the actual and the predicted location coordinates of a tracked device. The calibration process is
complete when the actual and predicted location coordinates converge. On a per-floor basis, a wireless
laptop takes RSSI measurements. The calibration wizard, embedded in the WCS version of the product,
is launched from the laptop and guides the user through the calibration process.
Accuracy
Because location fidelity is statistical, the location coordinates can be either more or less accurate than
10 meters the other 10% of the time. The location coordinates that fall into this other 10% are known as
outliers. Making adjustments to the deployments of access points to provide more optimal placement, in
addition to performing a calibration, can sometimes yield more accurate results; however, the results are
very dependent on environment and deployment.
Software Requirements
Access points and controllers must be installed with a version of WCS using embedded location.
Table 1 WCS Versions
Part Number Description
AIR-LOC-2700-L-K9 Cisco wireless location appliances
AIR-WCS-LL-1.0-K9 Cisco WCS with location v1.0 with up to 50
AIR-WCS-WL-1.0-K9 Cisco WCS with location v1.0 with up to 50 Cisco Aironet 1000
Expansion licenses are available if greater scale is necessary. Visit the following location for more WCS
SKUs:
http://wwwincisco.com/dsw/wnbu/products/wlm/cwcs/
Hardware Requirements
Because the location appliance participates in a Lightweight Access Point Protocols (LWAPP)
architecture, this guide assumes the user already has or is in process of putting an LWAPP- capable
wireless LAN in place. Both an explanation of the various LWAPP components you can use to do
location tracking as well as a hardware compatibility matrix is provided to ensure all required
LWAPP-compatible infrastructure is in place to support location tracking.
Cisco Aironet 1000 series access points running Linux
series access points running Windows 2000/2003 server
OL-8478-01
Cisco 2700 Series Wireless Location Appliance Deployment Guide
3
The following Cisco wireless LAN controllers are available.
Table 2 Controllers
Part Number Description
AIR-WL C2006-K9 Cisco 2000 series wireless LAN controller for up to six Cisco
Aironet 1000 series lightweight access points
AIR-WL C4402-12-K9 4400 series WLAN controller for up to 12 Cisco Aironet 1000
series access points
AIR-WL C4402-25-K9 4400 series WLAN controller for up to 25 Cisco Aironet 1000
series access points
AIR-WL C4402-50-K9 4400 series WLAN controller for up to 50 Cisco Aironet 1000
series access points
AIR-WL C4404-100-K9 4400 series WLAN controller for up to 100 Cisco Aironet 1000
series access points
The following Cisco Aironet access points are available.
Table 3 Access Points
Part Number Description
AIR-AP1010-X-K9 1000 series 802.11 a/b/g access point with integrated antennas,
x=regulatory domain
AIR-AP1020-X-K9 1000 series 802.11 a/b/g access point with integrated antenna
and RP-TNC, x=regulatory domain
AIR-AP1030-X-K9 1000 series 802.11 a/b/g remote edge access point with
integrated antenna and RP-TNC, x=regulatory domain
AIR-LAP1131AG-x-K9 802.11 a/g Non-modular LWAPP AP: Integrated Antennas
AIR-LAP1232AG-x-K9 AIR-AP1210 platform with AIR-MP21G and AIR-RM22A
radio modules
AIR-LAP1242AG-x-K9 802.11 a/g Non-modular LWAPP AP
The Difference Between WCS with Location and the Location Appliance
WCS without the use of the location appliance supports on-demand or query-based location. This
version visually displays a single device's location at a time, placing each single device on the floor map
associated with the floor it is on. Location determination using this version of WCS with location is
captured in Figure 2 where the blue icon is the only visual presented of a Wi-Fi client device.
Cisco 2700 Series Wireless Location Appliance Deployment Guide
4
OL-8478-01
Figure 2 Location Determination
Note To add the location appliance, the WCS version with location must be installed. You cannot add the
location appliance to the WCS base version.
Additional Functionality with Location Appliance
Figure 3 illustrates the scale and variety of classes of devices that can be tracked by the location
appliance. You can narrow the search parameters if you are interested only in a subset of devices. For
example, a biomedical user may want to see only infusion pumps and EKG machines named with
friendly identifiers rather than rogue devices or devices with cryptic MAC or IP addresses.
OL-8478-01
Cisco 2700 Series Wireless Location Appliance Deployment Guide
5
System Architecture
Figure 3 Scale and Variety of Devices
System Architecture
The location appliance integrates with Cisco's centralized wireless LAN architecture. The appliance sits
out of the data path of the wireless LAN, working with both the WCS and the controllers to track device
locations (see Figure 4).
Cisco 2700 Series Wireless Location Appliance Deployment Guide
6
OL-8478-01
Figure 4 System Architecture
Location-Based Services Overview
Access points can detect devices both on the channels where they service clients and on all other
channels by periodically scanning, while still providing uninterrupted data access to their wireless
clients. The gathered raw location data is then forwarded from each access point upstream to its
controller. The location appliance polls controllers via SNMP for this raw location information.
To understand this gathered device information, the location appliance works with WCS to determine
access point and device locations, based on input network diagrams that consist of floor maps. The visual
front-end of the location appliance is provided through WCS where either a single device's location or
an entire floor's devices may be depicted simultaneously. All device details and specific historical
location information is accessed through WCS as well.
Location-Based Services Overview
Using Cisco's Centralized wireless LAN architecture and location-based services, administrators can
determine the location of any 802.11-based device, as well as the specific type of each device. Clients,
rogue access points, rogue clients, and asset tags can all be identified and located by the system.
Clients are all devices associated with controller-based, lightweight access points on your network.
Rogue access point is any access point that is determined not to be part of the wireless LAN that detected
it. This consists of all non-system access points within earshot of lightweight access points, including
those on the wired network or those on another wired network (such as a neighbor's access point).
Because all lightweight access points hash a portion of the beacon frame with a special key, even spoofed
infrastructure access points are identified as rogue access points, rather than mistakenly indicated to be
legitimate access points flagged in WCS as spoof access points.
OL-8478-01
Cisco 2700 Series Wireless Location Appliance Deployment Guide
7
Deployment and Design Requirements
Rogue clients are simply all client devices that are associated to rogue access points.
Asset tags are any vendors' 802.11-based RF ID tags within range of infrastructure access points.
Deployment and Design Requirements
Consider the type of devices involved and how many devices will be tracked. Tracking of any of the four
device types can be configured. Determine the total number of devices and plan to deploy one location
appliance for every 1500 simultaneously tracked devices.
Depending on network requirements, placement of the location appliance in relation to WCS can be
adjusted to fit specific site needs. Where a single WCS is used for wireless LAN management, one or
more location appliances can be used to track 1500 or more devices. When multiple WCS are used to
manage separate wireless LANs, a single location appliance can be used by all WCSs to track each
device if the total number of tracked devices among them all does not exceed 1500.
Note If WCS and controllers are not physically co-located or have fast connections between them, deploy the
location appliance(s) as close as possible to WCS. Network diagrams (floor plan maps and the access
point locations on those maps) are synchronized between both devices.
Designing the Wireless LAN for Location
The Cisco Aironet 1000 series access points are supported by the Wireless LAN Controllers (2000-,
4100, and 4400-series controllers as well as Cisco Catalyst 6500 Series Wireless Services Module
(WiSM) which forward device information up to the location appliance. Antenna configuration on these
access points is important. The internal antenna of the Cisco Aironet 1000 series access point allows for
device location tracking, as do external antennas supported on both those access points. Select models
of the 1100 and 1200 series Cisco Aironet access points are also supported: Cisco Aironet 1240AG,
1230AG, 1200 series containing 802.11g such as AIR-MP21G-x-K9, second generation 802.11a radios
such as AIR-RM21A-x-K9 or AIR-RM22A-x-K9, and Aironet 1130AG.
Note WCS allows you to add non-Cisco antennas and their gain; however, no location or coverage maps are
generated for these non-Cisco antenna nor will they be TAC supported.
Below is the list of external Cisco antennas that conform to TAC supported configurations:
• AIR-ANT-4941
• AIR-ANT-1729
• AIR-ANT-1728
• AIR-20122410Y-R
• AIR-ANT-2506
• AIR-ANT-3213
• AIR-ANT-3549
• AIR-ANT-4941
• AIR-ANT-5959
• AIR-ANT-5135D-R
Cisco 2700 Series Wireless Location Appliance Deployment Guide
8
OL-8478-01
• AIR-ANT-5145V-R
• AIR-ANT-5160V-R
Access Point Placement
To determine the optimum location of all devices in the wireless LAN coverage areas, you need to
consider the access point density and location.
Ensure that no fewer than 3 access points, and preferably 4 or 5, provide coverage to every area where
device location is required. The more access points that detect a device, the better. This high level
guideline translates into the following best practices, ordered by priority:
1. Most importantly, access points should surround the desired location.
2. Roughly one access point should be placed every 50-70 linear feet (~17-20 meters). This translates
into one access point every 2,500 to 5000 square feet (~230-450 square meters).
Following these guidelines makes it more likely that access points will detect tracked devices. Rarely do
two physical environments have the same RF characteristics. Users may need to adjust those parameters
to their specific environment and requirements.
Deployment and Design Requirements
Note Devices must be detected at signals greater than -75 dBm for the controllers to forward information to
the location appliance. As such, no fewer than three access points should be able to detect any device at
signals below -75 dBm.
Meaningful placement of the access points is important for location information to the system.
Following a few basic rules contributes to location accuracy.
1. Focus on placing access points along the periphery of coverage areas to help locate devices close to
the exterior of rooms and buildings (see Figure 5). Access points placed in the center of these
coverage areas provide good data on devices that would otherwise appear equidistant from all other
access points.
Figure 5 Access Points Clustered Together Can Result in Poor Locationing
OL-8478-01
2. By increasing overall access point density and moving access points towards the perimeter of the
coverage area, location accuracy is greatly improved (see Figure 6).
Cisco 2700 Series Wireless Location Appliance Deployment Guide
9
Loading...