WLAN Positioning Technology White Paper Issue 01 Date 2013-05-10 HUAWEI TECHNOLOGIES CO., LTD.
WLAN Positioning Technology White Paper
Issue 01
Date 2013-05-10
HUAWEI TECHNOLOGIES CO., LTD.
Issue 01 (2013-05-10) Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
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Copyright © Huawei Technologies Co., Ltd. 2013. All rights reserved.
No part of this document may be reproduced or transmitted in any form or by any means without prior
written consent of Huawei Technologies Co., Ltd.
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and other Huawei trademarks are trademarks of Huawei Technologies Co., Ltd.
All other trademarks and trade names mentioned in this document are the property of their respective
holders.
Notice
The purchased products, services and features are stipulated by the contract made between Huawei and
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within the purchase scope or the usage scope. Unless otherwise specified in the contract, all statements,
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The information in this document is subject to change without notice. Every effort has been made in the
preparation of this document to ensure accuracy of the contents, but all statements, information, and
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Huawei Technologies Co., Ltd.
Address: Huawei Industrial Base
Bantian, Longgang
Shenzhen 518129
People's Republic of China
Website: http://enterprise.huawei.com
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About This Document
Overview
This document describes WLAN positioning technology of Huawei wireless access device
V200R003C00. WLAN positioning technology helps locate rogue APs, terminals, and
interference devices, facilitating asset management, network optimization, and fault
rectification.
This document describes working principles, typical usage scenarios, and configuration notes
of WLAN positioning and provides WLAN positioning configuration examples.
Intended Audience
This document is intended for:
Data configuration engineers
Commissioning engineers
Network monitoring engineers
System maintenance engineers
Symbol Conventions
The symbols that may be found in this document are defined as follows:
Symbol Description
DANGER
Alerts you to a high risk hazard that could, if not avoided,
result in serious injury or death.
WARNING
Alerts you to a medium or low risk hazard that could, if not
avoided, result in moderate or minor injury.
CAUTION
Alerts you to a potentially hazardous situation that could, if not
avoided, result in equipment damage, data loss, performance
deterioration, or unanticipated results.
TIP Provides a tip that may help you solve a problem or save time.
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Symbol Description
NOTE Provides additional information to emphasize or supplement
important points in the main text.
Change History
Changes between document issues are cumulative. The latest document issue contains all the
changes made in earlier issues.
Changes in Issue 01 (2013-05-10)
This is the initial official release.
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WLAN Positioning Technical White Paper Contents
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Contents
About This Document .................................................................................................................... ii
1 WLAN Positioning ........................................................................................................................ 1
1.1 Introduction to WLAN Positioning .................................................................................................................. 1
1.2 Availability ....................................................................................................................................................... 2
1.3 Principle Description ........................................................................................................................................ 2
1.3.1 WLAN Positioning Overview ................................................................................................................. 2
1.3.2 WLAN Positioning Process .................................................................................................................... 4
2 WLAN Positioning Applications ............................................................................................... 6
2.1 Locating Rogue APs ......................................................................................................................................... 7
2.2 Locating Interference Sources .......................................................................................................................... 7
2.3 Locating Users ................................................................................................................................................. 8
3 Typical WLAN Positioning Configuration Examples ......................................................... 10
3.1 Networking Requirements .............................................................................................................................. 10
3.2 Configuration Roadmap ................................................................................................................................. 10
3.3 Configuration Procedure ................................................................................................................................ 11
3.4 Configuration Files ......................................................................................................................................... 12
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1 WLAN Positioning
About This Chapter
1.1 Introduction to WLAN Positioning
1.2 Availability
1.3 Principle Description
1.1 Introduction to WLAN Positioning
Definition
WLAN positioning technology uses wireless signals transmitted between a device and APs to
determine real-time location of the device.
Purpose
802.11 wireless technology has been widely used on home networks, SOHO, and enterprise
networks. Users can easily access the Internet over WLANs. In some scenarios, enterprises
must acquire device locations for asset management or rogue AP location. The GPS is precise
but costly, and not applicable to indoor scenarios. WLAN positioning makes use of existing
device resources to locate devices, saving investments on extra devices. A room-level
precision is achieved, meeting most indoor locating requirements.
Benefits
The deployed APs construct a wireless network and provide the device positioning function,
which simplifies asset management, network optimization, and fault rectification.
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1.2 Availability
Supported Product
Table 1-1 Products and versions
Device Model Product Version
AC AC6605 V200R003C00
AC6005 V200R003C00
AP AP6xxx
AP7xxx
V200R003C00
1.3 Principle Description
1.3.1 WLAN Positioning Overview
Working Principles
Huawei WLAN positioning system uses an RSSI-difference-based location algorithm. The
positioning process involves the offline phase and online phase.
In the offline phase, the following operations are involved:
Divide the whole network into multiple equal area grids.
Calculate the theoretical differences among RSSIs of a STA in the grid to all APs.
Store <location coordinate, RSSI difference> to the database.
In the online phase, the following operations are involved:
APs report RSSIs to the positioning server after the APs receive signals of the device to
be located.
The positioning server computes differences among RSSIs received by the APs.
The positioning server compares the computing results with the information in the
database to obtain the location of the device.
This location algorithm allows the positioning system to compute device locations without
learning the transmit power of the terminals and interference sources and without performing
site surveys.
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Database
RSSI difference
algorithm
System Architecture
As shown in 0, the WLAN positioning system includes at least three APs, one AC, and one
eSight network management system.
Functions of each component are as follows:
AP
The APs collect wireless signals. Wireless signals can be collected in two modes: the
APs collect RSSI information of WLAN terminals and rogue APs and report the
information to the positioning server to locate WLAN terminals or rogue APs; the APs
scan spectrums and report fast Fourier transform (FFT) results of wireless signals to the
AC to identify and locate non-Wi-Fi interference sources.
RSSI information must contain AP identifiers, terminal identifiers, RSSIs, and channel
information. In Huawei prototype positioning system, APs report RSSI information of
WLAN terminals and rogue APs to the AC first. Then, the AC filters the RSSI
information and forwards the filtered information to the positioning server.
AC
The AC implements spectrum analysis on FFT data reported by the AP, identifies
non-Wi-Fi interference sources, calculates RSSIs of the interference sources, and reports
the RSSIs to the positioning server. In addition, the AC filters the RSSI information
received from the APs and sends the filtered RSSIs to the positioning server.
RSSI information of the interference sources must contain IDs of the APs that have
detected the interference sources, types and IDs of interference sources, and RSSIs.
eSight
eSight functions as the positioning server and display terminal in the positioning system.
The positioning server computes the signal transmission model according to locations of
APs and obstacles, and calculates locations of terminals, rogue APs, or non-Wi-Fi
interference sources based on the RSSI information collected by each AP.
The display terminal draws maps and displays locations of the devices on the map.
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Figure 1-1 WLAN positioning network topology
1.3.2 WLAN Positioning Process
The WLAN positioning process includes the offline phase and online phase.
Basic Steps in the Offline Phase
Basic steps in the offline phase are as follows:
Import building drawings or obstacle information into the NMS.
Obtain positions and attenuation values of the obstacles.
Mark APs on the building drawings.
A database is then generated based on the imported information for device locating in the
offline phase.
Radio wave attenuation in the air follows a pattern, which can be used by the AP to calculate
the theoretical RSSI value of a STA.
To calculate the theoretical RSSI value, you must also obtain AP positions and obstacle
information. Based on the attenuation pattern of radio waves and obtained information, RSSIs
of STAs in all positions received by each AP can be calculated. Then, store the information
<location coordinate, RSSI1, RSSI2… RSSIn> to the database for subsequent location
computation.
Basic Steps in the Online Phase
In the online phase, the APs must collect signals of the device to be located and report the
signals to the positioning server. The positioning server computes the location of the device
based on the RSSIs received by each AP.
The AC delivers RSSI collection configurations to the APs and enables the APs to
periodically switch channels and report RSSIs. If RSSI collection is disabled, the APs do
not report RSSIs and cannot locate devices.
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The positioning server calculates RSSIs. After receiving the reported RSSIs, the
positioning server computes the average RSSIs in a valid time. The valid time is
configurable and is 3 minutes by default.
The positioning server computes device locations.
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2 WLAN Positioning Applications
Figure 2-1 WLAN positioning
As shown in Figure 2-1, the WLAN positioning system is composed of at least three APs, one
AC, and one eSight network management system. The WLAN positioning system can locate
devices including authorized users, unauthorized users, rogue APs, and non-Wi-Fi
interference sources.
The following describes typical application scenarios.
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2.1 Locating Rogue APs
Figure 2-2 Locating rogue APs
Remove rogue APs
Start
The NMS detects rogue APs.
Is WLAN positioning enabled?
Yes
NoEnable WLAN
positioning
Locate rogue APs
Troubleshoot faults
End
Figure 2-2 shows the process for locating rogue APs. After users define characteristics of
rogue APs in the NMS and the NMS detects rogue AP data, the WLAN positioning system
helps locate rogue APs and troubleshoot the fault.
In this application scenario, rogue AP detection and location must be enabled.
2.2 Locating Interference Sources
If users complain about weak signals and IT operation and maintenance (O&M) personnel
have difficulty in locating the faults, enable spectrum analysis to identify and clear non-Wi-Fi
interference sources. If interference sources are detected through spectrum analysis, use the
WLAN positioning function to locate the interference sources.
Interference source locating depends on spectrum analysis. Therefore, spectrum analysis must
be enabled on the AC.
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Figure 2-3 Locating interference sources
Locate interference sources
Users complain about weak signals.
Enable spectrum analysis on APs
The NMS detects interference data.
Yes
NoEnable WLAN
positioningIs WLAN positioning
enabled?
Check locations of interference sources
End
Troubleshot faults
2.3 Locating Users
IT personnel must know a user's location for network operation and maintenance. For
example, if a user reports an exception or a fault during Internet access, the IT personnel must
learn the area where the fault or exception occurs.
Figure 2-4 shows the process of locating a user.
Figure 2-4 Locating users
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Locating a user
Start
Users report a fault. Detect unauthorized actions of a user
The user sends a large number of packets.
Is WLAN positioning enabled?
No
Yes
Enable WLAN positioning
Check the user's location
End
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WLAN Positioning Technical White Paper 3 Typical WLAN Positioning Configuration Examples
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3 Typical WLAN Positioning Configuration Examples
3.1 Networking Requirements
3.2 Configuration Roadmap
After WLAN configurations are complete, APs report the collected RSSI data to the
positioning server in either of the following ways to implement the locating function.
APs report collected data to the AC. Then, the AC reports the data to the positioning
server.
When APs and the NMS are located on different networks, the APs must report the data
to the AC first.
The NMS requires only data information of authorized APs. Therefore, the AC must
identify authorized and rogue APs. Data is transmitted between the APs and the AC, and
between the AC and the positioning server through the UDP socket.
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The APs directly report the collected data to the positioning server.
If the network between the APs and positioning server is reachable, and the AC is not
required to identify unauthorized APs, configure the APs to directly send data to the
positioning server, which decreases CPU usage of the AC and reduces impacts of the
positioning function on services.
3.3 Configuration Procedure
Step 1 Configure the IP address and port for the APs to report data. In the system view, specify the
IP address or port for the APs to report the collected data. The IP address can be the IP
address of the AC or the NMS.
[AC-wlan-view] location ap report-server ac port 6002
Step 2 Specify the IP address and port for the AC to report data. In the system view, specify the
NMS's IP address and port to which the AC forwards the data reported by the APs.
[AC-wlan-view] location ac report-server ip-address 10.138.20.11 port 6001
Step 3 Enable WLAN positioning. You can enable or disable Wi-Fi device locating on a radio.
[AC-wlan-radio-0/0] location enable
Step 4 Enable channel switching. In the radio profile view, configure the radio that has WLAN
positioning enabled to scan channels and listen on signals. By default, the radio listens to only
local working channels. After channel switching is enabled, the APs periodically scan all
working channels and collect information about all channels.
[AC- wlan-radio-prof-test] channel scan-switch enable
Step 5 Set the interval for scanning channels. After the positioning function and channel switching
are enabled, the APs scan all working channels in turns to collect data. After the interval is
configured, an AP waits for the specified time to scan a new channel after the last channel is
scanned. The value ranges from 1 to 60, in seconds. The default value is 10s.
[AC- wlan-radio-prof-test] channel scan-frequency 30
Step 6 Set the time during which APs collect data in a channel. After the positioning function is
enabled, APs must collect signals in all channels. A longer duration indicates more collected
data. However, APs cannot provide services when collecting signals. If you set the value too
large, services may be affected. The value ranges from 1 to 200, in milliseconds. The default
value is 60 ms.
[AC- wlan-radio-prof-test] channel scan-time 60
Step 7 Specify the interval for reporting data. In the radio profile view, specify the interval for
reporting data to the NMS.
[AC-wlan-radio-prof-test] location report-frequency 11
Step 8 Query the IP address and port of the positioning server.
[AC] display wlan location server configuration
Location server configuration info:
--------------------------------------------------------------------------------
AP report-server IP address : 10.138.6.110 (AC)
AP report-server port : 6002
AC report-server IP address: 10.138.20.11
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AC report-server port : 6001
--------------------------------------------------------------------------------
----End
3.4 Configuration Files
#
vlan batch 88 100 to 104 300 to 301 1000 2000 4091
#
wlan ac-global country-code DE
#
dhcp enable
#
diffserv domain default
#
interface Wlan-Ess0
port hybrid pvid vlan 101
port hybrid untagged vlan 101
#
wlan
wlan ac source interface vlanif100
ap-auth-mode no-auth
ap id 4 type-id 17 mac cccc-8176-f040 sn 210235447410C9000028
wmm-profile name wp0 id 0
traffic-profile name tp0 id 0
security-profile name sp1 id 1
security-policy wpa2
wpa authentication-method psk pass-phrase cipher %$%$J]y1'xQ0CC5j^/ILvVdLy@Jl%
service-set name ss3 id 3
wlan-ess 0
ssid AC119-3
traffic-profile id 0
security-profile id 1
service-vlan 101
radio-profile name wpos-test id 0
wmm-profile id 0
location report-frequency 11
channel scan-frequency 30
channel scan-time 50
ap 4 radio 0
radio-profile id 0
service-set id 3 wlan 1
location enable
channel scan-switch enable
location ap report-server ac port 6002
location ac report-server ip-address 10.138.20.11 port 6011
#