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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.

i

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.

Trademarks and Permissions

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

the customer. All or part of the products, services and features described in this document may not be

within the purchase scope or the usage scope. Unless otherwise specified in the contract, all statements,

information, and recommendations in this document are provided "AS IS" without warranties, guarantees or

representations of any kind, either express or implied.

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

recommendations in this document do not constitute a warranty of any kind, express or implied.

Huawei Technologies Co., Ltd.

Address: Huawei Industrial Base

Bantian, Longgang

Shenzhen 518129

People's Republic of China

Website: http://enterprise.huawei.com

http://enterprise.huawei.com/

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WLAN Positioning Technical White Paper About This Document



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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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WLAN Positioning Technical White Paper 1 WLAN Positioning



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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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WLAN Positioning Technical White Paper 2 WLAN Positioning Applications



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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

#

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