Wi-Fi Location-Based Services—Design and Deployment Considerations Contents Executive Summary 3 Target Audience 3 Introduction 3 Overview 4 Objectives 4 Reference Publications 5 Hardware/Software 6 Location Tracking Approaches 6 Cell of Origin 7 Distance-Based (Lateration) Techniques 8 Angle-Based (Angulation) Techniques 14 Location Patterning (Pattern Recognition) Techniques 15 Cisco Location-Based Services Architecture 18 RF Fingerprinting 18 Overall Solution Architecture 20 Role of the Location Applian
Contents Rogue Access Points Rogue Clients 39 35 Installation and Configuration 41 Installing and Configuring the Location Appliance 41 Configuring the Wireless Control System for Location Tracking 41 Configuring Location Server History Parameters 41 Configuring Location Server Advanced Parameters 43 Configuring Location Server Location Parameters 45 Configuring Location Server Notification Parameters 46 Location Appliance Dual Ethernet Operation 47 Changing Default Passwords for the Location Appliance 4
Executive Summary Using Wi-Fi RFID Tags with the Cisco Location Appliance 94 Compatible RFID Tags 94 Using 802.11b Tags in an 802.
Overview It is not hard to understand why this is so. With integrated location tracking, enterprise wireless LANs become much more valuable as a corporate business asset.
Overview • Reviewing the procedures required to install and configure a Cisco LBS solution consisting of LWAPP-enabled access points, WLAN controllers, WCS, and the location appliance. Installation and Configuration, page 41, provides information that aids in competently installing the solution and responding to questions regarding some of the more unusual parameters used. • Describing best practices that should be followed in designing and deploying location-aware wireless LANs.
Location Tracking Approaches Note Other supported hardware or software can be found by referring to the information located at the following URL: http://www.cisco.com/en/US/products/ps6386/index.html. Table 1 Tested Hardware and Software Location Appliance AIR-LOC2700-L-K91 Location Appliance 2700 Series; software release 2.1.34.0 Wireless Control System (WCS) WCS-STANDARD-K9-4.0.66.0 Wireless Control System release 4.0.66.0 for Windows 2003 .exe Server2 WCS-STANDARD-K9-4.0.66.
Location Tracking Approaches to hear arguments supporting the case that a fifth category should exist to include those RTLS systems that sense and measure position using a combination of at least two of the four techniques mentioned above. Keep in mind that regardless of the underlying positioning technology, the “real-time” nature of an RTLS is only as real-time as the most current timestamps, signal strengths, or angle-of-incidence measurements.
Location Tracking Approaches Figure 2 Highest Signal Strength Technique Using this technique, the probability of selecting the true “nearest cell” is increased over that seen with pure cell of origin. Depending on the accuracy requirements of the underlying business application, performance may be more than sufficient for casual location of mobile clients using the highest signal strength technique.
Location Tracking Approaches • c = propagation speed of ~ 300 meters / microsecond • t = time in microseconds From distance ρ used as radii, a circular representation of the area around the receiving sensor can be constructed for which the location of the mobile device is highly probable. ToA information from two sensors resolves a mobile device position to two equally probable points.
Location Tracking Approaches The Global Positioning System (GPS) is a example of a well-known ToA system where precision timing is provided by atomic clocks. Time Difference of Arrival (TDoA) Time Difference of Arrival (TDoA) techniques use relative time measurements at each receiving sensor in place of absolute time measurements. Because of this, TDoA does not require coordination of received timestamps with a precision time source at the point of transmission to locate the mobile device.
Location Tracking Approaches Figure 4 Time Difference of Arrival (TDoA) TDOAC_A TDOAB_A X B C 190537 A A fourth receiving sensor and third hyperbola may be added as an enhancement to perform TDoA hyperbolic multi-lateration. This may be required to solve for cases where there may be more than one solution when using TDoA hyperbolic tri-lateration.
Location Tracking Approaches In close, confined indoor areas, both ToA and TDoA have traditionally suffered from less than optimal performance, especially in situations where the mobile station is likely to be surrounded by objects that promote multi-angular RF scattering and reflection. Interestingly, the effects experienced under such conditions appear to worsen with narrow-band implementations of TDoA versus wider band implementations such as WLANs.
Location Tracking Approaches • TxPWR represents the transmitter output power in dB. • LossTX represents the sum of all transmit-side cable and connector losses in dB. • GainTX represents the transmit-side antenna gain in dBi. • LossRX represents the sum of all receive-side cable and connector losses in dB. • GainRX represents the receive-side antenna gain in dBi. Solving for distance between the receiver and mobile device allows you to plot a circular area around the location of the receiver.
Location Tracking Approaches Pure RSS-based lateration techniques that do not take additional steps to account for attenuation and multipath in the environment rarely produce acceptable results except in very controlled situations. This includes those controlled situations where there is always established clear line-of-sight between the mobile device and the receiving sensors, with little attenuation with which to be concerned other than free-space path loss (FPL) and little to no concern of multipath.
Location Tracking Approaches “reverse beam-forming”, this technique involves directly measuring the arrival time of the signal at each element, computing the TDoA between array elements, and converting this information to an AoA measurement. This is made possible because of the fact that in beam-forming, the signal from each element is time-delayed (phase shifted) to “steer” the gain of the antenna array.
Location Tracking Approaches Calibration Phase During the calibration phase, data is accumulated by performing a walk-around of the target environment with a mobile device and allowing multiple receiving sensors (access points in the case of 802.11 WLANs) to sample the signal strength of the mobile device (this refers to a “network-side” implementation of location patterning).
Location Tracking Approaches Operational Phase In the operational phase, a group of receiving sensors provide signal strength measurements pertaining to a tracked mobile device (network-side reporting implementation) and forwards that information to a location tracking server. The location server uses a complex positioning algorithm and the radio map database to estimate the location of the mobile device.
Cisco Location-Based Services Architecture minimum of three reporting receivers required to be in range of mobile devices at all times. Increased accuracy and performance (including exceeding 5 meters accuracy) is possible when six to ten receivers are in range of the mobile device. Location patterning applications perform well when there are sufficient array entries per location vector to allow individual locations to be readily distinguishable by the positioning application.
Cisco Location-Based Services Architecture pre-packaged models enable calibration-less deployment in common office environments, which is a significant advantage over approaches such as location patterning, especially in cases where easy and rapid deployment is the primary concern. In addition to the use of pre-packaged propagation models, RF Fingerprinting offers the ability to develop a customized propagation model that enhances the default path-loss models based on an on-site calibration phase.
Cisco Location-Based Services Architecture Cisco RF Fingerprinting offers several key advantages over traditional approaches: • Uses existing LWAPP-enabled Cisco Unified Networking Components—Unlike some other solutions, Cisco LBS with RF Fingerprinting is a 100 percent Wi-Fi RTLS without the need for specialized time-based receivers or other specialized hardware.
Cisco Location-Based Services Architecture Figure 8 Cisco Location-Based Services Solution Architecture Wireless Control System (WCS) Client Browser Third Party Location Applications HTTPS WCS Server SOAP/XML SOAP/XML SNMP TRAP W N S WLAN Location Appliance E Wireless LAN Controllers LWAPP LWAPP LWAPP AccessPoint AccessPoint 190331 AccessPoint Notifications EMAIL SYSLOG SOAP/XML SNMP TRAP Wi-Fi handsets, clients, rogues and Wi-Fi Tags Access points forward information to WLAN controlle
Cisco Location-Based Services Architecture Figure 9 Information Flow for Asset Tag RSSI Data Multicast Packet from Tag WLC Multicast packets sent to WLC LWAPP AP Tag information indexed by Tag MAC Address and Tag RSSI values reported by each AP SNMP Poll for Tag data Location Appliance Calculate location from raw RSSI information and store Asynchronous notifications Location Database WCS 190541 On-demand SOAP/XML Query Figure 9 summarizes the following events: 1.
Cisco Location-Based Services Architecture participating in location tracking during controller synchronization. Synchronization occurs either on-demand or as a scheduled task, the timing of which is determined by the Administration > Scheduled Tasks main menu option under the Cisco Wireless Control System (WCS). Location information is displayed to the end user using a location client application in conjunction with the Cisco Wireless Location Appliance.
Cisco Location-Based Services Architecture • Note SOAP/XML Location Application Programming Interface (API)—The Location Appliance API allows customers and partners to create customized location-based programs that interface with the Cisco Wireless Location Appliance.
Cisco Location-Based Services Architecture Accuracy and Precision of the Cisco LBS Solution With proper deployment according to the best practices outlined both in this white paper as well as those contained within the documents referenced in Reference Publications, page 5, the accuracy and precision of the Cisco LBS solution in indoor deployments is represented as follows: • Accuracy of less than or equal to 10 meters, with 90 percent precision • Accuracy of less than or equal to 5 meters, with 50 perc
Cisco Location-Based Services Architecture Figure 10 Enabling CCX Location Measurement Wireless LAN clients are displayed on the WCS location floor maps using a blue rectangle icon, as shown in Figure 11. To display WLAN clients on the WCS location floor map, ensure that the Show Clients view option is selected at the top of the floor map display, and click Reload in the left-hand column.
Cisco Location-Based Services Architecture Figure 11 WCS WLAN Client Location Map Note that beginning with Release 4.0 of WCS, it is possible to filter the location information displayed by WCS based on the age of the information. Thus, in Figure 11, WCS displays location server information that has aged up to 15 minutes. This value can be set to 2 or 5 minutes if you want to see location information that was received more recently or ½, 1, 3, 6, 12, or 24 hours for information that is even older.
Cisco Location-Based Services Architecture Figure 12 WCS WLAN Client Detailed Information Wi-Fi Location-Based Services—Design and Deployment Considerations 28 OL-11612-01
Cisco Location-Based Services Architecture Note that Figure 12 also includes a hyperlinked listing of location notifications as well as a miniature location map showing the client location. By enlarging the map and enabling the Location Debug parameter, WCS displays the last detected RSSI levels of each access point detecting the WLAN client, as shown in Figure 13.
Cisco Location-Based Services Architecture A graphical representation of the historical access point association history for the wireless client can be obtained by selecting AP Association History from the dropdown menu at the top right-hand corner of the screen shown in Figure 12 and clicking Go. Past access point association history stored within the location appliance is displayed in the screen format shown in Figure 14.
Cisco Location-Based Services Architecture Figure 15 WCS WLAN Client Location History In many cases, it is desirable to graphically display the location history of a client device in sequential steps to better visualize and trace the movement of the client throughout the environment over time. This can be very useful, for example, in security and monitoring applications.
Cisco Location-Based Services Architecture Note Currently, each WLAN controller is capable of supporting up to 500 802.11 L2 active RFID tags. To display RFID asset tags on the WCS location floor map, ensure that the “Show 802.11 Tags” view option is selected at the top of the floor map display and then click Reload in the left-hand column. Note that it is assumed that all other components of the LBS system have been properly configured to collect asset tag information.
Cisco Location-Based Services Architecture Complete information on any displayed asset tag can be obtained by clicking on the yellow tag icon associated with the tag. WCS responds with the information shown in Figure 17, including asset tag vendor identifier, statistics, and tag properties (including battery status). Figure 17 WCS RFID Tag—Detailed Information Note that Figure 17 also includes a hyperlinked listing of location notifications as well as a miniature location map of the asset tags location.
Cisco Location-Based Services Architecture Figure 18 Asset Tag Detected RSSI Shown with Location Debug Asset tag location history may be displayed by selecting Location History from the dropdown menu at the top right-hand corner of the screen shown in Figure 17 and then clicking Go. Past location history stored within the location appliance is displayed for the asset tag, as shown in Figure 19.
Cisco Location-Based Services Architecture Figure 19 WCS RFID Location History In many cases, it is desirable to graphically display the location history of an asset tag in sequential order so as to better visualize and trace the movement of the RFID tag (and the attached asset) throughout the environment over time. This can be very useful, for example, in security and monitoring applications.
Cisco Location-Based Services Architecture These are all indicated on WCS location floor maps using a skull-and-crossbones within a black circle as shown in Figure 20. Rogue access points can be totally wireless, connected to the same wired infrastructure as the detecting WLAN, or connected to an entirely different wired infrastructure.
Cisco Location-Based Services Architecture Complete information on any displayed rogue access point can be obtained simply by left-clicking the cursor on the circular skull-and-crossbones icon representing the desired rogue access point on the floor map. Doing this yields a screen containing detailed information as shown in Figure 21. However, there is no RSSI information displayed for rogue access points when the location map is enlarged.
Cisco Location-Based Services Architecture Figure 22 WCS Rogue Access Point Event History Detecting APs (Figure 23) gives a tabular view of all access points detecting this rogue access point along with the RSSI/SNR at which the rogue was detected. Figure 23 WCS Rogue AP Detecting Access Points It is important to understand how localization of rogue access points and clients differs from that of WLAN clients and asset tags.
Cisco Location-Based Services Architecture the channels for which they are configured (which is why it is important to ensure that they are configured for the primary channels of all access points in your environment). Once again, these multicasts are quickly detected by access points operating on these channels in the vicinity of the asset tags.
Cisco Location-Based Services Architecture • Small icons (shown above) or regular sized icons can be selected. When using small icons, no text is displayed on the floor map for the rogue client except when a mouse-over is performed. When using regular size icons, an on-screen tag displays the rogue client’s MAC address. • Either all rogue clients can be displayed or filtering can be performed to select which rogue clients to display on the floor map.
Installation and Configuration Installation and Configuration Installing and Configuring the Location Appliance Detailed procedures for installing and configuring the Cisco Location Appliance can be found in the following documents: • Release Notes for Cisco Wireless Location Appliance— http://www.cisco.com/en/US/products/ps6386/prod_release_note09186a00806b5ec7.html • Cisco Wireless Location Appliance: Installation Guide— http://www.cisco.
Installation and Configuration History Archive Period The history archive period (shown as “Archive For”) specifies the number of days that the location appliance retains location history records for each enabled history collection category. The default archive period is 30 days.
Installation and Configuration more frequently and in advance of a low disk space situation. These aggressive data pruning intervals may need to be combined with a shorter history archive interval if the low disk free space situation is not addressed.
Installation and Configuration Note The df –H command is used here because it is a commonplace practice for most computer disk manufacturers to assume 1 GB = 1,000,000,000 bytes. The –H option displays output as powers of 1000 rather than 1024. Use df –h if your preference is for the contrary. The df display output shown here is for a location appliance containing a hard disk drive with an unformatted capacity of 80 GB.
Installation and Configuration Configuring Location Server Location Parameters The configuration of Location Server > Administration > Location Parameters is discussed in Cisco Wireless Location Appliance Configuration Guide: Editing Location Parameters at the following URL: http://www.cisco.com/en/US/products/ps6386/products_configuration_guide_chapter09186a00806b5b 10.html#wp1046431. Further clarification regarding some of these parameters is provided in subsequent sections.
Installation and Configuration RSSI Cutoff In addition to enforcing the aforementioned relative and absolute time constraints against received RSSI reports, the location appliance also applies a parameter known as the RSSI cutoff. Subject to the time constraints described in RSSI Discard Times, page 45, the location appliance retains the four highest signal strength reports plus any signal strength reports that meet or exceed the value specified for RSSI cutoff.
Installation and Configuration Location Appliance Dual Ethernet Operation The Cisco Wireless Location Appliance is equipped with two 10/100/1000BASE-T Gigabit Ethernet ports that can be used to connect the location to two different IP networks such that it is easily accessible from either network. This makes it a simple affair, for example, to configure a location appliance for service on network A while affording it the capability to be managed out-of-band on network B if the need arises.
Installation and Configuration Figure 27 Default Location Application UserID This brings up the menu shown in Figure 28, which allows the password to be changed for the admin userid. Figure 28 Modifying the Admin Password Finally, change the value for the password used by WCS to access the location server application to the new value that was specified in Figure 28. This can be performed via Location Server > Administration > General Properties, as shown in Figure 29.
Installation and Configuration Figure 29 Specifying Location Server Application Login Credentials in WCS Location Appliance Time Synchronization With the advent of location notifications in Release 2.0 of the location appliance, ensuring proper time synchronization of the location appliances in your network has become an increasingly important issue.
Installation and Configuration providing the local time of the NOC, or simply the Coordinated Universal Time (UTC). By properly configuring the NTPD daemon on each location server, all notification messages appearing at configured destinations should arrive with a consistent time stamp. Complete guidance on configuring and activating the NTPD daemon on the location appliance can be found in Release Notes for Cisco Wireless Location Appliance at the following URL: http://www.cisco.
Deployment Best Practices Shutting down audit subsystem[ OK ] Starting killall: [ OK ] Sending all processes the TERM signal... Sending all processes the KILL signal... Syncing hardware clock to system time Turning off swap: Turning off quotas: Unmounting file systems: Halting system... md: stopping all md devices. flushing ide devices: Power down. Note that issuing the shutdown command from a remote SSH client results in your SSH session becoming disconnected.
Deployment Best Practices When performing a site survey of an area where clients or tags are tracked, the RSSI of representative devices should be verified to ensure compliance with the minimum number of recommended access points and the RSSI cutoff. This should be performed via one of two techniques: • Viewing detected RSSI for the client or asset tag using the show client detail or show rfid detail controller CLI command, as shown in Figure 31.
Deployment Best Practices In a similar fashion, the CLI command show rfid detail can be used to display detected RSSI information for an asset tag. This same information can be obtained graphically via the location map GUI by clicking on either a WLAN client icon (blue rectangle) or asset tag icon (yellow tag), enabling the location debug checkbox and then enlarging the miniature location map as stated in WLAN Clients, page 25 and shown in Figure 32 and Figure 33.
Deployment Best Practices Figure 33 Displaying Detected RSSI via the GUI Access Point Placement Considerations Proper placement and density of access points is critical to achieving the quoted performance of the Cisco location tracking solution. In many office wireless LANs, access points are distributed throughout interior spaces, providing service to the surrounding work areas.
Deployment Best Practices Figure 34 Location-Aware AP Deployment Access points are typically configured for primary channel operation on non-overlapping channels (that is, channels 1, 6, and 11 in 2.4 GHz, for example), either statically or more commonly via the Cisco Radio Resource Management (RRM) algorithm inherent in Cisco WLAN controllers.
Deployment Best Practices Figure 35 Location-Aware AP Placement Illustration WCS version 4.0 now includes new location planning capabilities that are accessible via Monitor > Maps > floormapname > Planning Mode. Whereas previous versions of the planning tool accounted for coverage and capacity planning only, the new version allows for location, data, and voice planning as well.
Deployment Best Practices Figure 36 Planning Tool Output for Location, Voice, and Data Determining Location Readiness Release 4.0 of WCS introduces a new feature known as Inspect Location Readiness that allows the network designer to perform a predictive analysis of the positioning performance expected for a particular floor access point layout.
Deployment Best Practices Figure 37 Example of 100 Percent Location Readiness A point is defined as being “location-ready” if the following are determined to be true: • At least four access points are deployed on the floor • At least three access points are within 70 feet of the point-in-question • At least one access point is found to be resident in each quadrant surrounding the point-in-question Figure 38 illustrates these three tenets of location readiness, where the green circles represent acce
Deployment Best Practices Figure 38 Definition of a “Location-Ready” Point < 70 ft. < 70 ft. < 70 ft. 190570 < 70 ft. Figure 39 shows an example of a floor deployment where some areas are predicted to have location accuracy below 10 m/90 percent. Although there are green areas toward the center of the figure, notice that red areas abound as you get beyond those access points located the furthest from the center of the floor.
Deployment Best Practices Once again, keep in mind that location readiness inspection is a distance-based predictive tool. As is the case with most predictive tools, it can be expected that some degree of variance naturally occurs between predicted and actual results. Cisco recommends that this location readiness should be used in conjunction with other best-practice techniques outlined in this document, including the new capability introduced with release 4.
Deployment Best Practices Additional information regarding deployment guidelines and best practices can be found in the Cisco Wireless Location Appliance: Deployment Guide at the following URL: http://www.cisco.com/en/US/products/ps6386/prod_technical_reference09186a008059ce31.html. Avoiding Location Display Jitter with Location Smoothing In release 4.0 of WCS and release 2.
Deployment Best Practices Table 2 Smoothing Factor Weight Assignments More smoothing (default) 75% 25% Maximum smoothing 90% 10% As the weight assigned to the previous position is increased in relation to the weight assigned to the new position, the more damping is applied to the movement of the device. This increased level of damping acts to retard visible device movement.
Deployment Best Practices When you understand the procedure used by the location appliance to assign mobile devices to floors, you can actively take steps to improve the location-aware designs to reduce the risk of floor misdetects. For example, a situation to avoid is the placement of access points in such a fashion that access points on floors directly above and below the mobile device are physically much closer than any access points located on the same floor as the mobile device (Figure 41).
Deployment Best Practices Figure 42 Facilitating Mobile Device Floor Assignment Using Multiple Location Appliances in Larger Designs As stated earlier, under release 2.1 a single Cisco Wireless Location Appliance can track up to 2500 devices, which includes WLAN clients, asset tags, rogue access points, and rogue clients. The location appliance allows for specific tracked device categories to be enabled via Location > Location Server > Administration > Polling Parameters.
Deployment Best Practices with a WCS governing it. The management chapter of the Cisco Unified Wireless Network Solutions Reference Design Guide contains additional considerations you should keep in mind for single and multiple management domain designs. Note Keep in mind that as of release 4.0.155.0, WLAN controllers each support a maximum of 500 L2 active 802.11 RFID tags. Each controller is capable of detecting the RSSI of each tracked device from a maximum of eight access points at any time.
Deployment Best Practices The subsections that follow examine how WCS and the location appliance can be combined beyond the standard deployment model in two common configurations that can be used to satisfy more demanding situations. Single Management Domain with Multiple Location Domains In this design, the WLAN network management needs of the enterprise WLAN are expected to be well within the capacity of a single WCS management domain.
Deployment Best Practices In this situation, one possible solution is to use WCS to create a campus location network design for the buildings and floors that comprise the headquarters location. The 140 access points that are registered to controller WiSM-1 are assigned to this network design, and an event notification group is created for the headquarters location.
Deployment Best Practices Figure 45 Multiple Management Domains with a Single Location Domain Each WCS-3 Headquarters 2710-1 W WCS-2 N S E 2710-2 W WCS-1 N S E 2710-3 W LWAPP WiSM N S E LWAPP LWAPP East Metro Locations West Metro Locations LWAPP LWAPP LWAPP LWAPP LWAPP LWAPP LWAPP LWAPP LWAPP LWAPP LWAPP LWAPP LWAPP LWAPP LWAPP LWAPP LWAPP LWAPP LWAPP LWAPP LWAPP LWAPP LWAPP LWAPP LWAPP LWAPP LWAPP LWAPP 190578 LWAPP LWAPP Three low-end WCS servers provide WL
Deployment Best Practices handles polling of controller WiSM-3 with regard to all tracked devices found in its location domain, which is shown by the green rectangle. Other than the fact that the three management/location domain pairs operate across a common Ethernet network and possess controllers that share a common physical residence with a Cat6500 chassis at headquarters, the three exist independently of each other.
Deployment Best Practices Figure 47 Example of Unequal Azimuth Propagation Patterns The orientation of the antenna, its gain, and its propagation characteristics are all taken into consideration when location calculations are performed.
Deployment Best Practices Note that WCS allows only for the adjustment of orientation in the horizontal (or azimuth) plane of the antenna. Vertical orientation is assumed to be as indicated in the antenna pictorial shown in WCS, which usually is vertical at 0° for omni-directional antennas and horizontal at 90° for directional and semi-directional antennas. There is no adjustment for either electrical or mechanical down tilt.
Deployment Best Practices Figure 49 Example of Suggested Calibration Locations To complete the calibration data collection and save the sample set, 150 client location to access point measurements must be recorded per band from 50 distinct locations in the target environment. In some cases, it may be noticed that although 150 client location to access point measurements have been collected, not all areas have been visited (white areas are present on the map).
Deployment Best Practices Detailed procedures covering the steps involved in performing a RF calibration can be found in the Cisco Wireless Location Appliance: Deployment Guide at the following URL: http://www.cisco.com/en/US/products/ps6386/prod_technical_reference09186a008059ce31.html.
Deployment Best Practices Tips for Successful Calibrations Number of Samples As stated earlier, the calibration application within WCS ensures that a sufficient number of location-to-access point measurements (no less than 150 per band) are collected before allowing the calibration user to move forward with calibrating the model and applying it to floors.
Deployment Best Practices Calibrating Under Representative Conditions As mentioned previously, the location appliance and the Cisco WCS use the information gathered during a site calibration to better understand the propagation characteristics present within the environment. This information is culled from the aggregate of all data collection performed during the calibration.
Deployment Best Practices When verifying whether RSSI cutoff thresholds have been met in production areas, use clients that are identical to the production clients if at all possible. If this is not possible, keep in mind that mobile devices with significantly higher default maximum transmitter output than devices regularly expected to be tracked should have their output power adjusted downward.
Deployment Best Practices Figure 52 Location Quality Inspection Results In Figure 52, you can see that the majority of the environment meets the expectation for coverage at 10 m with between 95–100 percent precision. Note that you can specify the band (2.4 GHz, 5GHz, or both) as well as the performance criteria to be used. A useful capability of location inspector is the ability to perform “what if” planning and to examine the limits of higher (or lower) levels of accuracy and precision.
Deployment Best Practices Figure 53 Location Inspection at 5 m Accuracy Correlating the colors seen on the floor map display to the legend located at the top right of the screen indicates that at the 5m accuracy level, the precision can be expected to degrade to about 80–85 percent, with some pockets showing 75 percent precision. Note that in both figures there are areas of pure white in proximity to the perimeter access points.
Deployment Best Practices Location Tracking Challenges Outdoor Environments Outdoor wireless deployments tend to be much different from the types of indoor deployments that have been described thus far. The deployment best practices described in this document do not readily lend themselves to easy deployment outdoors. The access point densities, inter-access point spacing, and antenna heights discussed, although acceptable for indoor deployments, tend to make outdoor location deployment less than optimal.
Deployment Best Practices concern. Although the overall path loss model may not be generally optimized, performance may still be acceptable, depending on the application requirements. Both these two options are fairly straightforward and follow the standard procedure for calibration and deployment. The third option offers the ability to calibrate for separate path loss models, each attuned to the individual floor areas and with that, the potential for improved location performance in each sub-floor area.
Deployment Best Practices • Minimize the amount of exposure to those “flattened” areas of the signal strength versus distance curve where there is little change in signal strength as distance increases Therefore, in general, Cisco recommends the following: • Antenna installation be performed at heights of 10 feet or less for optimum location fidelity. Antenna heights in this range have been found to be most conducive to good location fidelity. • Antenna installations above 20 feet be avoided.
Deployment Best Practices Figure 54 Enabling Location Server Polling on WCS Polling should never be arbitrarily enabled across all categories, especially in situations where controllers are deployed remotely across highly used or slow WAN links. Instead, enable polling only for devices that are truly of interest. When controllers must respond to unnecessary polling requests network bandwidth as well as controller and location appliance CPU cycles are wasted.
Deployment Best Practices number of received responses associated with a larger controller population. Use of a few centrally located large capacity WLAN controllers (such as the WiSM) would therefore appear to be advantageous over the use of many distributed smaller capacity WLAN controllers for the same number of tracked devices. The impact of these polling activities can be seen quantitatively by examining the protocol analysis shown in Appendix A—Polling Traffic 2700 <-> 4400 WLAN Controller, page 109.
Deployment Best Practices considered normal for the test environment (an internal WLAN development facility where there are many access points and clients being tested independently of one another), such an incredibly high level of rogue activity is certainly not what one would expect in a routine business environment.
RFID Tag Considerations Appendix C—Large Site Traffic Analysis, page 116 provides traffic information that provides an idea of what to expect when a network design synchronization is performed in a large-scale, active environment. In the large-scale test environment, the network design consists of a four floor building with 41 access points, without any obstacles or coverage areas defined and no calibration models beyond the included defaults.
RFID Tag Considerations Figure 55 Active and Passive RFID Comparison Within these basic categories of RFID tags can be found subcategories such as semi-passive, transponder active, and beaconing active RFID tags. Passive RFID Tags Passive RFID tags typically do not possess an onboard source of power. Instead, the passive RFID tag gets all its power from an energizing field that emanates from an RFID reader or interrogator.
RFID Tag Considerations Figure 56 Passive RFID Interrogators Passive RFID tags (shown in Figure 57) consist of a coil and a microcircuit that includes basic modulation circuitry, an antenna, and non-volatile memory. Figure 57 Passive RFID Tags Passive RFID tags can vary in how they communicate data to RFID readers and how they receive power from the RFID readers inductive or electromagnetic field.
RFID Tag Considerations Figure 58 Passive Tag Load Modulation Tag 190591 Reader Tag modulates inductive coupling Backscatter modulation and electromagnetic coupling—In this approach (shown in Figure 59), the RFID reader provides a medium-range electromagnetic field that the passive RFID tag uses for both power and as a communication medium. Via electromagnetic coupling, the passive RFID tag also draws energy from the electromagnetic field of the RFID reader to power the tag.
RFID Tag Considerations The passive RFID tag is available commercially packaged wide variety of designs, from mounting on a simple substrate to creating a classic “hard” tag sandwiched between adhesive and paper (commonly referred to as an RFID “smart” label). The form factor used depends primarily on the application intended for the passive RFID tag and can represent the bulk of the passive RFID tag cost. Passive RFID tags typically operate at low frequencies (125–135 kHz), high frequencies (13.
RFID Tag Considerations Figure 61 Semi-Passive RFID Tags Several varieties of semi-passive RFID tags exist, with and without onboard NVRAM, real time clocks, and various types of environmental sensors. Semi-passive RFID tags also support interfaces to tamper indicators, shock sensors, and so on.
RFID Tag Considerations Active tags can contain 512 KB of RAM (or more), which makes them ideal for access to telemetry systems of attached assets. This enables the active tag to store information from these devices for transmission at the next beacon interval or when polled by an active RFID reader. This large memory capacity also makes active RFID preferable to passive RFID in situations when the RFID tag cannot simply be used as a license plate for immediate lookup in a host database.
RFID Tag Considerations Figure 63 Transponder Active RFID Tag These RFID tags are usually mounted on the windshield or other unobstructed area of the vehicle. On approaching a tollbooth or choke point containing a tag exciter, the electromagnetic field of the exciter activates the RFID tag transmitter. The transponder active tag responds by beaconing its unique ID to the tag reader while the vehicle remains within range, as illustrated in Figure 64.
RFID Tag Considerations equipped with powered-on 802.11 Wi-Fi client radios can be tracked natively without the need to have an asset tag attached, other assets lacking an internal 802.11 Wi-Fi client radio can be tracked via a physically attached 802.11 active RFID tag. Configuring Asset Tags, page 98 examines two of the most popular 802.11 Wi-Fi active RFID tags in detail. Figure 65 802.
RFID Tag Considerations readers themselves is possible because of their use of industry standard 802.11 client radios. Because of this, these portable readers would be treated just as other WLAN clients and indicated on floor maps by a blue rectangular icon. Figure 66 Portable RFID Interrogators with Integrated Wi-Fi Uplink Using 802.11b Tags in an 802.11g Environment A common question that often arises has to do with the performance impact of an 802.
RFID Tag Considerations • Access points not on the same channel as the 802.11b asset tag or not RF-adjacent do not initiate protection mode. Some asset tags with motion detection can be configured to be almost completely RF silent when assets are not in motion. They associate and transmit information only when they have something to report (that is, movement); otherwise, they are “sleeping” for very long periods.
RFID Tag Considerations Enable Asset Tag RF Data Timeout The RFID Data Timeout parameter sets a static value of time (seconds) that must elapse without any access points on the controller detecting an asset tag before that asset tag is removed from the internal tables of the controller. Cisco recommends that this parameter be set to between 8 and 10 times the value that was specified in the asset tag for the beacon interval.
RFID Tag Considerations Polling Interval Polling cycle 300 330 Polling interval Polling cycle 630 660 Seconds 146189 Figure 68 Depending on asset movement, shorter polling intervals may increase the granularity of data collection. The polling interval value should be set keeping in mind its impact on network traffic between the location appliance and the controller (see Traffic Between the Location Appliance and WLAN Controllers, page 81).
RFID Tag Considerations Figure 70). When this is successfully performed, a yellow tag should appear under “View Filters” (as indicated in Figure 70), and yellow tags are then used on the floor map to denote the current location of any detected asset tags. Figure 70 Enabling Display of Asset Tags on WCS Configuring Asset Tags The Cisco LBS solution is based on IEEE 802.11 standards and can interoperate with a variety of 802.11-compatible clients and asset tags.
RFID Tag Considerations Figure 71 Tested 802.11 Wi-Fi Active RFID Tags AeroScout Asset Tags (Type 2) AeroScout Type 2 asset tags (http://www.aeroscout.com) are small 802.11 active RFID devices that can interact directly with the Cisco UWN. These tags use Layer 2 multicasts to communicate with the network and WCS displays their location on floor maps as a yellow-tag icon (see 802.11 Active RFID Tags (L2 Multicast), page 31). The small size of the AeroScout asset tag (2.44” x 1.57” x .
RFID Tag Considerations opening each tag casing and attaching a serial cable available from AeroScout. The tag activator is much easier to use and saves a tremendous amount of time by allowing up to 50 tags to be configured and activated simultaneously. The use of a tag activator eliminates disturbing the environmental seal of the tag casing for configuration modifications (a potential concern if the asset tag is used in harsh environments).
RFID Tag Considerations The AeroScout tag activator (shown in Figure 74) is an Ethernet 802.3af active RFID tag reader/interrogator (which can also be powered via an AC power adapter). The tag activator works in conjunction with AeroScout Tag Manager software to configure, program, activate, and deactivate up to 50 AeroScout asset tags simultaneously at a range of up to approximately three feet. The AeroScout tag activator may be powered directly from a Cisco 802.
RFID Tag Considerations PanGo Locator LAN Asset Tags PanGo version 1 Locator LAN asset tags (www.pangonetworks.com) are intelligent 802.11 active RFID devices that interact directly with the Cisco LBS solution as WLAN clients. These motion-sensitive asset tags are 3.5” x 2.6” x 1.1” in size and are powered by two commonly-available 1.5 volt “AA” size lithium batteries.
The SOAP/XML Application Programming Interface infrastructure without the use of the temporary access point or broadcaster application. The tags periodically receive updates from the PanOS server regarding any configuration profile updates that may have occurred. Version 1 Locator LAN asset tags are capable of sending a full complement of alert messages regarding their internal status and state of motion.
The SOAP/XML Application Programming Interface location and device statistical information. Location-based alarms and notifications can be triggered in applications through area boundary definitions, allowed areas, and distances. All these capabilities allow the SOAP/XML API interface to the Cisco Location Appliance to be used for integration with external software applications such as E911, asset management, enterprise-resource-planning (ERP) tools, and workflow automation systems.
The SOAP/XML Application Programming Interface process solutions to enable location-based workflow optimization and better asset use. PanGo Locator recognizes industry-standard 802.11 active RFID tags and WLAN clients, but is especially optimized to take full advantage of the specialized features found in PanGo Locator LAN tags types 1 and 2. PanGo Locator is designed for business and operational asset owners and users whose main goal is to locate the assets they need quickly and efficiently.
The SOAP/XML Application Programming Interface • PanGo Locator Configuration—Define, configure, and manage assets, tags and spaces. • PanGo Locator Monitor—Visualize, search, and filter assets in maps/floorplans or tabular views. • PanGo Locator Notifier—Automatically send notifications and alerts based on user-defined, event-driven business rules, including asset location, presence/absence duration, and status.
Caveats Figure 78 Cisco Location-Based Services Solution with PanGo Location Client Location Client Browser PanGo Location Client HTTPS SOAP/XML Wireless Control System (WCS) Client Browser HTTPS WCS Server SOAP/XML SNMP TRAP W N S WLAN Location Appliance E Wireless LAN Controllers LWAPP AccessPoint LWAPP AccessPoint 190611 AccessPoint LWAPP Notifications EMAIL SYSLOG SOAP/XML SNMP TRAP Caveats The following caveats are in addition those already documented in these reference documents: •
Caveats CSCse14724—Degraded Location Accuracy with Monitor Mode APs Degraded accuracy has been observed in lab testing of monitor mode access points when compared to local mode. The use of monitor mode is not recommended in location-aware designs at this time. CSCse15237—Calibration Data Point Locations Mismatched with Cross-Hair Locations The calibration model is calibrated after taken all suggested samples at crosshair locations.
Appendix A—Polling Traffic 2700 <-> 4400 WLAN Controller Appendix A—Polling Traffic 2700 <-> 4400 WLAN Controller Figure 79 Polling Traffic 2700 <−> 4400 WLAN Controller (1) Wi-Fi Location-Based Services—Design and Deployment Considerations OL-11612-01 109
Appendix B—AeroScout Tag Manager Version 2.1 Figure 80 Polling Traffic 2700 <−> 4400 WLAN Controller (2) Appendix B—AeroScout Tag Manager Version 2.1 Version 2.1 of the AeroScout Tag Manager introduced a new “Advanced Configuration” sub-menu (Figure 81) under the Tag Configuration menu selection, with new asset tag programming capabilities that are not found in the previous version. Note The AeroScout Tag Manager is available from AeroScout Corporation at the following URL: http://www.aeroscout.
Appendix B—AeroScout Tag Manager Version 2.1 Figure 81 AeroScout Tag Manager v2.1 These new programming capabilities are categorized into four groups: general settings, data transmission mode, switch button activation, and map/cell ID. The enhancements that directly affect the use of AeroScout asset tags with the Cisco LBS solution are on the general settings submenu found at Configuration > Advanced > General Settings, as shown in Figure 82. Figure 82 AeroScout Tag Manager v2.
Appendix B—AeroScout Tag Manager Version 2.1 • Transmit Power (dBm)—T2 asset tags have an adjustable output power from +13dBm to +19dBm. Version 2.1 of the AeroScout Tag Manager exposes this via the GUI. • Data Frame Format—T2 asset tags are capable of transmitting probe requests in either the WDS or IBSS (Independent Basic Service Set or ad-hoc) frame formats. In the IBSS frame format, the “To DS” and “From DS” bits in the Frame Control Field of the 802.11 MAC header are both set to “0”.
Appendix B—AeroScout Tag Manager Version 2.1 This is because in v2.1 of Tag Manager, the default setting for data frame format is IBSS as was seen earlier in Figure 82. When an Apply is performed for all the options contained within the Advanced Configuration > General Settings submenu shown in Figure 84, all the general settings are programmed into the tag with the values indicated in Tag Manager 2.
Appendix B—AeroScout Tag Manager Version 2.1 Figure 85 Retrieving Existing AeroScout Tag Programming This displays the standard tag configuration options, as shown in Figure 86. Note that the tag hardware and software versions, the battery charge and activity status, the beacon transmission interval, and the beacon channels for which the tag is programmed can all be confirmed from this menu.
Appendix B—AeroScout Tag Manager Version 2.1 To display the Advanced Configuration > General Options values, click on the Advanced button icon shown above. This displays the values currently programmed into the selected tag (including the data frame format), as shown in Figure 87. Figure 87 AeroScout T2 Tag Advanced Status Display Further information regarding AeroScout Tag Manager v2.1 can be found in the AeroScout Tag Manager v2.1 User Guide, which is available from AeroScout Corporation.
Appendix C—Large Site Traffic Analysis Appendix C—Large Site Traffic Analysis Figure 88 Large Site Traffic Analysis (WLC Release 3.1.105.0, 2700 Release 1.2.20.
Appendix D—PanGo Locator LAN Tag Association and Signaling Appendix D—PanGo Locator LAN Tag Association and Signaling Figure 89 PanGo LAN Tag Association Sequence Wi-Fi Location-Based Services—Design and Deployment Considerations OL-11612-01 117
Appendix D—PanGo Locator LAN Tag Association and Signaling Wi-Fi Location-Based Services—Design and Deployment Considerations 118 OL-11612-01
