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AirMagnet Spectrum Analyzer

User’s Guide



© 2005 AirMagnet®, Inc. All rights reserved.

AirMagnet® Spectrum Analyzer User Guide.

The information contained in this user guide is subject to change withoutnotice.

AIRMAGNET®, INC. SHALL NOT BE HELD LIABLE FOR ERRORS OROMISSIONS CONTAINED HEREIN; NOR FOR INCIDENTAL ORCONSEQUENTIAL DAMAGES RESULTING FROM THE USE OF THISCONTENT.

AirMagnet® and AirWISE® are registered trademarks, and the AirMagnetlogo is a trademark, of AirMagnet, Inc. All the other product namesmentioned herein are trademarks or registered trademarks of their

respective companies.

AirMagnet, Inc.1325 Chesapeake TerraceSunnyvale, CA 94089USA

Compiled in the United States of America. July 12, 2005.



AirMagnet Spectrum Analyzer User's Guide

Table of Contents

1 Introduction........................................................................................................................... 1

1.1 Purpose........................................................................................................................... 1 1.2 System Requirements..................................................................................................... 1

1.3 The User's Guide and Online Help ................................................................................ 1 1.4 Conventions in This Manual .......................................................................................... 1

1.4.1 Screen Text................................................................................................................ 2 1.4.2 Menu Selections ........................................................................................................ 2 1.4.3 Screen Buttons........................................................................................................... 2 1.4.4 Keyboard Buttons ...................................................................................................... 2 1.4.5 Important Concepts.................................................................................................... 2 1.4.6 Spectrum Bands......................................................................................................... 2

2 Overview: AirMagnet Spectrum Analyzer........................................................................ 4

2.1 Intelligent Spectrum Analysis........................................................................................ 4

2.1.1 RF Visibility .............................................................................................................. 4 2.1.2 Mitigation and Performance Enhancement................................................................ 4

2.2 AirMagnet Spectrum Analyzer ...................................................................................... 5 2.3 Spectrum PC Card.......................................................................................................... 5 2.4 The Spectrum Analyzer Display .................................................................................... 6

2.4.1 AirMagnet Spectrum Analyzer Online Help ............................................................. 7 2.5 AirMagnet Spectrum Analyzer Operating Scenarios..................................................... 7

2.5.1 Firefighting Mode...................................................................................................... 7 2.5.2 RF Expert................................................................................................................... 8 2.5.3 Site Survey / Network Install and Initial Configuration............................................ 8

3 AirMagnet Spectrum Analyzer Setup............................................................................... 10 3.1 ASA Installation / Setup .............................................................................................. 10 3.2 Spectrum PC Card Installation..................................................................................... 11 3.3 Attaching an External Antenna.................................................................................... 12

3.3.1 Attaching the Omni-directional Antenna................................................................. 12 3.3.2 Attaching an optional Directional Antenna ............................................................. 13

3.3.2.1 Using the Directional Antenna.............................................................................. 13 3.4 Starting the AirMagnet Spectrum Analyzer for the First Time ................................... 14 3.5 Repairing A “Backwards” Installation......................................................................... 15

3.5.1 Automatic Hardware Recognition by Windows XP................................................ 15 3.5.2 Manual Driver Installation....................................................................................... 16

3.6 AirMagnet Spectrum Analyzer and Your PC’s 802.11 Operability ............................ 18 3.7 Upgrading the AirMagnet Spectrum Analyzer Software............................................. 18

4 The AirMagnet Spectrum Analyzer Display- An Overview ........................................... 20

4.1 Status Bar ..................................................................................................................... 20 4.2 Interferer List ............................................................................................................... 20 4.3 Menu Options............................................................................................................... 21

4.3.1 File Menu................................................................................................................. 21



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4.3.2 View Menu .............................................................................................................. 21 4.3.3 Plots Menu............................................................................................................... 22 4.3.4 Tools Menu.............................................................................................................. 22 4.3.5 Help ......................................................................................................................... 22

4.4 Tool Bar ....................................................................................................................... 23 4.5 Context-Sensitive (Right-Click) Menu Features.......................................................... 23

4.5.1 Spectrum Plots......................................................................................................... 23 4.5.2 Interferer List........................................................................................................... 23 4.6 What If I Do Not See Any Data? ................................................................................. 24

5 Spectrum Views................................................................................................................... 25

5.1 Using Spectrum View Graphs...................................................................................... 25 5.1.1 Entering Spectrum View Mode ............................................................................... 25 5.1.2 Creating A New Plot................................................................................................ 25 5.1.3 Multiple Plots .......................................................................................................... 26 5.1.4 Measurement Interval .............................................................................................. 26 5.1.5 Pause and Resume Plotting...................................................................................... 26

5.1.6 Saving and Restoring Spectrum View Layouts ....................................................... 27 5.1.7 Deleting A Spectrum View...................................................................................... 27 5.2 Plot Content ................................................................................................................. 27

5.2.1 Frequency-Based Plots ............................................................................................ 27 5.2.2 Time-Based Plots..................................................................................................... 27 5.2.3 Real-Time FFT Plot................................................................................................. 28 5.2.4 Power vs. Frequency................................................................................................ 28 5.2.5 FFT Duty Cycle....................................................................................................... 28 5.2.6 Swept Spectrogram.................................................................................................. 29 5.2.7 Air Quality............................................................................................................... 30 5.2.8 Power vs. Time........................................................................................................ 30 5.2.9 The Real-Time FFT Plot Compared with the Power vs. Frequency Plot ................ 30

5.3 Plot Controls ................................................................................................................ 32 5.3.1 Frequency and Bandwidth To Monitor.................................................................... 32 5.3.2 Amplitude ................................................................................................................ 32 5.3.3 Trace Settings .......................................................................................................... 33 5.3.4 Markers.................................................................................................................... 33 5.3.5 Channels .................................................................................................................. 34 5.3.6 Other Plot Control Panel Settings............................................................................ 34

5.3.6.1 Power vs. Time...................................................................................................... 34 5.3.6.2 Swept Spectrogram ...............................................................................................35 5.3.6.3 Air Quality ............................................................................................................36 5.3.6.4 FFT Duty Cycle Plot .............................................................................................36

6 Interferers............................................................................................................................ 37

6.1 Working with the Interferer List .................................................................................. 37 6.1.1 Setting the Time Interval ......................................................................................... 37 6.1.2 Showing and Hiding The List.................................................................................. 37 6.1.3 Docking and Undocking The List............................................................................ 37 6.1.4 Getting More Information On An Interferer............................................................ 38 6.1.5 Locating an Interferer .............................................................................................. 38

6.2 Interferer Data.............................................................................................................. 38



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6.3 Miscellaneous Interferer Issues.................................................................................... 39 6.3.1 Signal Bounce and Fading....................................................................................... 39 6.3.2 Device Detection Time............................................................................................ 39

7 Channel Summary .............................................................................................................. 40

7.1 Working with the Channel Summary........................................................................... 40

7.2 Channel Data................................................................................................................ 40 7.3 Miscellaneous Channel Summary Issues..................................................................... 41

7.3.1 802.11 Detection Sensitivity.................................................................................... 41 7.3.2 802.11 Device Types ............................................................................................... 41

8 Device Finder....................................................................................................................... 42

8.1 Overview...................................................................................................................... 42 8.2 Working with Device Finder........................................................................................ 43 8.3 Additional Device Finder Features .............................................................................. 44 8.4 “Divide and Conquer” Search Strategy........................................................................ 45

8.4.1 Omni-directional Antenna ....................................................................................... 45

8.4.2 Directional Antenna................................................................................................. 46 8.4.3 Detecting Narrowband Devices............................................................................... 48

9 Local Settings ...................................................................................................................... 49

9.1 Antennas ...................................................................................................................... 49 9.2 Display Settings ........................................................................................................... 50 9.3 Channel Settings .......................................................................................................... 51 9.4 Monitored Bands.......................................................................................................... 52

9.4.1 Follow 802.11 Channel Plan.................................................................................... 53 9.4.2 Pre-Defined Bands................................................................................................... 53 9.4.3 User-Defined Bands................................................................................................. 53

10 Glossary of Terms............................................................................................................... 54

11 Notices and Declarations.................................................................................................... 55

11.1 FCC Notices................................................................................................................. 55 11.2 Industry Canada's Interference Causing Equipment Standard for Digital Apparatus .. 55 11.3 Declaration of Conformity........................................................................................... 56

12 Limited Warranty............................................................................................................... 57



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List of Figures

Figure 2-1: ASA In Action............................................................................................................. 5

Figure 2-2: Spectrum Sensors (Mobile and Enterprise) .................................................................. 6

Figure 2-3: The Mobile Spectrum Management Console ............................................................... 6

Figure 3-1: Using The Directional Antenna.................................................................................. 13

Figure 3-2: Sensor Hardware Installation Error ........................................................................... 15

Figure 3-3: Successful Sensor Hardware Installation As Shown On Device Manager................ 16

Figure 3-4: Unsuccessful Sensor Hardware Installation As Shown On Device Manager............ 16

Figure 4-1: The Mobile Spectrum Management Console Display................................................ 20

Figure 5-1: Turning A Plot Trace On ............................................................................................ 25

Figure 5-2: Multiple Spectrum Plots ............................................................................................. 26

Figure 5-3: Paused Plot With "Paused" Indicator ......................................................................... 26

Figure 5-4: FFT, Power vs. Frequency, FFT Duty Cycle, and Swept Spectrogram ..................... 28

Figure 5-5: Understanding The Swept Spectrogram Plot.............................................................. 29

Figure 6-1: Interferer View ........................................................................................................... 37

Figure 6-2: Interferer List Time Selection..................................................................................... 37

Figure 7-1: Channel Summary ...................................................................................................... 40

Figure 9-1: Settings – Sensors and Antennas ................................................................................ 49

Figure 9-2: Settings - Console Settings ......................................................................................... 50

Figure 9-3: Settings – Channel Settings ........................................................................................ 51

Figure 9-4: Settings – Monitored Bands ....................................................................................... 52



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Page 1


1 INTRODUCTION

1.1 Purpose

AirMagnet Spectrum Analyzer monitors the RF spectrum used by 802.11 WLANs. For brevity,

the technology is referred to simply as “ASA”. ASA consists of hardware-based Spectrum PC card

and a GUI-based Spectrum Analyzer Software; together, these provide complete visibility of the

RF environment in which the WLAN operates.

ASA can identify virtually all sources of RF activity in the unlicensed bands that 802.11 networks

share with other devices (such as cordless phone and headsets, Bluetooth devices, and microwave

ovens). Based on this data, network engineers can take proactive steps to increase WLAN

performance and security in the face of interferers, network congestion, and security attacks.

This document provides all necessary information for network engineers to install ASA, including

information on how to install the Spectrum PC card in your notebook PC. This manual also

describes how to configure and operate AirMagnet Spectrum Analyzer software. Finally, themanual describes the comprehensive RF data displayed by ASA software.

1.2 System Requirements

The following are the hardware requirements for installing and running AirMagnet Spectrum

Analyzer:

• Notebook computer with Pentium series processor running at 1 GHz or faster

• At least 256 Meg of RAM

• Display resolution of 1024 x 768 or higher

• 30 Meg free disk space

• One available CardBus slot

1.3 The User's Guide and Online Help

This manual is intended primarily to provide an overview of ASA and its principal features.

Detailed operating instructions for many features may be found in the AirMagnet Spectrum

Analyzer Online Help System.

1.4 Conventions in This Manual

The following text conventions are used in this manual.



Page 2 Section 1. Introduction


1.4.1 Screen Text

Any text which is displayed as part of an AirMagnet Spectrum Analyzer display screen—including

menu selections, text for options buttons and check boxes, list column headers, etc.—is quoted in

this manual using a bold, sans-serif font. For example, a discussion of choices for different antenna

options would be shown in this guide as:

Internal AntennaExternal Antenna

1.4.2 Menu Selections

Menu selections are displayed using an arrow to indicate successive levels of menu options. For

example, to select the Device Finder choice from the View menu, we write:

Select View Device Finder

Note that we simply indicate the option to be selected, not the method used. The user can use the

mouse to click on View, and then click on Device Finder; or the user could type <Alt+V>, <D>.

We assume you are familiar with standard MS Windows conventions. For example, an

underlined letter in a menu title indicates that the menu can be selected by pressing the

<Alt + letter> (e.g., <Alt + F> to select the File menu). Therefore, we do not specify the

speed keys (such as <Alt + F>) for quick access. We also do not indicate the underlined letters

in this documentation, since they are clearly visible on the Mobile Spectrum Management Console

display screens.

1.4.3 Screen Buttons

Buttons on screen (such as in dialog boxes) are indicated by enclosing the text in square brackets,

for example: [Add] [Cancel] [OK]

1.4.4 Keyboard Buttons

Keyboard buttons are indicated in angle brackets, and using a bold, mono-spaced font:<Shift> <Ctrl>

1.4.5 Important Concepts

Important terms and concepts —especially when used at the beginning of a paragraph to define

the subject of the discussion—are presented in boldface.

1.4.6 Spectrum Bands

ASA enables you to select various bands for spectrum monitoring. At points in this

documentation, we indicate that you can select the 2.4 GHz or 5 GHz bands, which are two bands

that are commonly monitored. 2.4 GHz refers to the 2.4 to 2.5 GHz band. When we say 5 GHz,

that is a shorthand way of referring to both the 5.1 to 5.4 GHz band, and the 5.7 to 5.9 GHz band.



Page 3


Note that depending on how you configure ASA, you may find that your menus (for example, for

the Spectrum Plots) display other band options.



Page 4 Section 2. Overview: AirMagnet Spectrum Analyzer


2 OVERVIEW: AIRMAGNET SPECTRUM ANALYZER

This section provides an overview of intelligent spectrum analysis technology implemented in

AirMagnet Spectrum Analyzer.

2.1 Intelligent Spectrum Analysis

AirMagnet Spectrum Analyzer conceived intelligent spectrum analysis to address several current

shortcomings in WLAN technology that are not fulfilled by traditional RF spectrum Analyzer.

These shortcomings fall into several inter-related categories.

2.1.1 RF Visibility

Currently, WLAN system administrators lack sufficient awareness of the RF environment in which

their access points and stations operate.

• Discovery – Current WLAN technologies are only aware of other network elements.

They have no way to discover other nearby sources emitting RF in the unlicensed bands.

• Performance – Because WLANs operate in the unregulated 2.4 GHz and 5 GHz frequency

bands, they are subject to interference from other devices operating in this same frequency

spectrum. These include microwave ovens, cordless phones and cordless headsets, wireless

surveillance cameras, garage door openers, Bluetooth technology, and other devices. There

can also be co-channel interference due to neighboring WLANs. These competing devices can

degrade 802.11 network performance, resulting in unacceptably slow data rates and excess

packet retransmissions.

• Troubleshooting – Current WLAN technologies are aware of network devices, so they can

determine if there is excess load on the network from network stations. But currenttechnologies cannot see the whole RF spectrum in the unlicensed band, and so cannot identify

sources of RF activity which can cause dropped network connections and other problems.

2.1.2 Mitigation and Performance Enhancement

Lacking full RF spectrum awareness, existing WLANs cannot apply appropriate, adaptive

responses to improve performance in the face of interferers and competing networks. ASA

includes sophisticated technology to detect and classify sources of RF activity. Using this data,

network engineers can take a variety of actions to enhance WLAN performance and reliability:

• Clean Channels – If a certain part of the frequency spectrum is in constant use by other

devices, the network engineer can program the WLAN to not transmit over those channels.Conversely, by deliberately searching for “clean” channels, the WLAN devices can be set to

broadcast over those channels.

• Setting Packet Size – ASA measures the duration of gaps between RF pulses. If the gaps are

very short, the network engineer can program the WLAN to decrease the size of packets to fit

within the available time gaps between pulses. This reduces the chances that single packets

will experience interference, and so reduces the need to retransmit WLAN packets. Of course,



Page 5


when the gaps between pulses become longer, the packet size can be increased again, resulting

in higher transmission speeds.

• Identifying, Locating, and Removing Interferers – ASA can identify the types of devices

which are introducing RF interference (such as microwave ovens or Bluetooth devices).

Again, the network engineer is alerted to the presence of these devices, and can take steps to

address the problem (including relocating or shutting off such devices).ASA can be used to identify interferers, and also be use as a lightweight homing device to track

down the precise location of the signal source.

• Device Specific Solutions – By knowing the ID of specific interfering devices, custom

solutions can also be tailored to specific technologies, and even specific brands of specific

technologies.

2.2 AirMagnet Spectrum Analyzer

ASA is a combined hardware and software component which implements the Spectrum Analysis

technology. ASA makes the 802.11 WLAN “spectrum savvy”, ensuring greatly increasedreliability and performance. ASA, the focus of this document, consists of two primary

components:

• Spectrum PC Card – AirMagnet’s Spectrum PC card provides the hardware foundations for

Intelligent Spectrum Analysis. It incorporates a powerful spectrum-analyzer-on-a-chip that

provides full visibility for the RF spectrum in the unlicensed band where WLANs operate.

ASA Smart Spectrum PC card is installed in a CardBus slot inside a laptop PC.

• ASA Spectrum Display – The ASA software analyzes data from the Spectrum PC card and

provides a GUI-based view of network and RF activity.

Figure 2-1: ASA in Action

2.3 Spectrum PC Card

As a first step in the intelligent spectrum analysis process, the ambient RF environment must be

scanned and analyzed to determine the sources of RF activity in the neighborhood of the network,

especially causes of interference or other problems.





Figure 2-2: Spectrum PC card

The essential internal components of a Spectrum PC card include:

• Radio – The radio transceiver detects the RF spectrum and feeds this data to Spectrum

Analysis Engine, SAgE.

• SAgE – Spectrum Analysis Engine performs a Fast Fourier Transform (FFT) of the RF

spectrum, and provides the feed of low-level data concerning the behavior of the RF spectrum.

Low-level data includes basic information on the power vs. frequency in the spectrum at agiven instant, and information on individual pulses in the RF spectrum. SAgE also performs

on-board statistical analysis of the spectrum, and statistical analysis of RF pulses (which

relieves CPUs of this processor intensive task).

• MCU – A programmable MicroController Unit (MCU), running proprietary software, provides

low-level analysis of the data stream. The analysis engines include:

Measurement Engine – Aggregates SAgE data, and normalizes it into meaningful units.

Classification Engine – Identifies specific types of interferers (Bluetooth devices,

microwave ovens, cordless phones and headsets, radar, etc.).

2.4 The Spectrum Analyzer Display

The AirMagnet Spectrum Analyzer Display runs under Windows XP (Service Pack 2 or later).

The display provides the interface—the GUI—which connects the network engineer with the

resources available from the Spectrum PC card:

• Spectrum Views – Provides graphs that offer a

direct view into the RF spectrum, including

measurements of RF power and RF pulse activity;

along with an overall Air Quality plot that can be

based on various criteria (average RF power,

maximum RF power, interferer RF power, etc.).

This view is especially useful to trained RFengineers. See Section 5 on page 25.

• Interferers –Displays interfering devices

(microwave ovens, cordless phone and headsets,

etc) in the network neighborhood. See Section 6

on page 37. Figure 2-3: AirMagnet Spectrum Analyzer

display



Page 7


• Channel Summary – Provides a statistical overview of RF activity (such as power levels and

number of interferers present) on a per-802.11-channel basis. This view gives you an instant

picture of which channels are subject to excess interference, and which channels have the best

potential for trouble-free 802.11 activity. See Section 7 on page 40.

• Device Finder – In Device Finder mode, ASA is a convenient, user-friendly RF “sniffer”,

optimized for displaying RF power data in a way that quickly enables the network engineer totrack down interfering devices. See Section 8 on page 42.

• Tools – Supports configuration of ASA. See Section 9 on page 49.

2.4.1 AirMagnet Spectrum Analyzer Online Help

Detailed reference information is found in ASA Online Help system, which can be accessed by

selecting <F1>, or selecting Help Help Topics.

2.5 AirMagnet Spectrum Analyzer Operating Scenarios

AIRMAGNET SPECTRUM ANALYZER can be used in several different ways, as described here.

2.5.1 Firefighting Mode

Critical Tasks:

• Identify problems in the RF environment

• Diagnose the problem as quickly as possible

• Resolve the problem

Centerpiece Applications:

• Air Quality Plots

• Interferers View

• Device Finder

• Channel Summary

Typically, the IT Administrator will have the AIRMAGNET SPECTRUM ANALYZER Display

up and running, with the Interferer List visible, along with either the Channel Summary or one or

more Spectrum Plots in view. The Air Quality plot, in particular, is an important resource for

detecting problems that may stress the network.

Once a problem occurs, the Administrator goes into action to determine the cause of the problem.

Through a combination of the Interferers List, Channel Summary, and the Device Finder, the

Administrator can pinpoint and isolate the source of the problem. If the solution is not obvious (for example, remove an interfering device), he may turn to the RF expert to help him arrive at a

solution. The key point is that the Administrator is notified before the problem has progressed too

far, so he can take proactive measures. This eliminates frustrated calls from management.

For example, in the Channel Summary the Administrator might notice two interfering devices

causing interference on channel 6. He might further observe a heavy Duty Cycle on channel 6, as

seen on the Air Quality plot. The Administrator can then use the Device Finder to track down the

location of the interfering devices, and then shut them off, relocate them, shield them, etc.





2.5.2 RF Expert

An RF expert is an individual with an advanced knowledge of radio frequency technology, and its

associated physics and electronics. He or she is an individual who is conversant with the use of

spectrum analyzers, as well as the inner workings of wireless network systems. Such an individual

is most likely to be at work at installations where the wireless system is considered mission critical.

Critical Tasks:

• Investigate reported ASA events at the raw RF level.

• Review raw RF data for cases that are unclassified by ASA.

• Confirm that recommended solutions have alleviated the problem

Centerpiece Application: Spectrum Analyzer Plots

The RF Expert primarily uses the detailed Spectrum Analyzer plotting capabilities of ASA’s

Spectrum Views mode. When he is called in on a problem, he uses the Spectrum Analyzer to

confirm and/or supplement the intelligence capabilities built into ASA.

For example, if ASA reports that a video interference signal is occurring, he may wish to view the

power vs. frequency plots to confirm that it is not some other type of device. In addition, there will

always be cases where ASA does not recognize the type of interference at work. In that case, the

human intelligence of the RF expert helps fill in the missing gaps.

Another critical use of the Spectrum Analyzer capabilities is to confirm when a problem has been

fixed by corrective action. When a fix has been attempted, the IT department can’t afford to wait

until the next day to see that no problem alerts re-surface. The RF expert can use the Spectrum

Analyzer functions to perform before-and-after comparisons that confirm that a fix (for example,

shielding was placed around an interference device) has indeed fixed the problem.

2.5.3 Site Survey / Network Install and Initial Configuration

AirMagnet ASA is an invaluable tool for supporting pre-installation WiFi site surveys, and also the

initial installation and configuration of a WLAN.

Critical Tasks:

• Set channel usage for APs

• Pre-emptive interference mitigation

• Deploy APs for effective coverage

Centerpiece Applications:

•

Spectrum Plots• Device Finder

• Channel Summary

• Interferer List

ASA can be used prior to deployment of a WLAN, to obtain information which is essential for

planning optimum deployment.



Page 9


• Band and Channel Allocations: ASA can determine which bands and/or channels have the

most RF activity. The APs can then be programmed to use other channels, resulting in higher

speed transmissions, and reduced packet retransmissions.

• Pre-emptive Interference Mitigation: Any interferers which are discovered to be

contributing significant RF activity can be moved, de-activated, or shielded, before putting the

WLAN into operation.

• AP Placement: As a lightweight, mobile RF probe, ASA can determine which general areas

have the highest level of RF activity—as determined by the Interferer List, the Device Finder,

and the Air Quality Plot —and therefore require the most APs for adequate network coverage.



Page 10 Section 3. AirMagnet Spectrum Analyzer Setup


3 AIRMAGNET SPECTRUM ANALYZER SETUP

The section discusses the physical setup of the ASA, along with software installation.

Be sure to install the ASA software before installing the Spectrum PC Card

into your computer.

3.1 ASA Installation / Setup

1. Insert the installation CD into your CD ROM drive.

2. The Installation Menu starts automatically.

If it does not, use Windows Explorer to find the

CD_Start.exe program on the CD, and double-click it

to start the program. From the Menu click on the

AirMagnet Spectrum Analyzer Installation Button

3. You will see a series of standard “Install Shield”

Wizard screens, culminating with a “Welcome”

screen. Click [Next].

4. The installation program presents a standard software

license agreement. Please review the agreement, and

if you concur, select “I accept the terms of the license

agreement”. Then select [Next].

5. Enter your User Name and Organization Name.

Then select one of the radio buttons to indicate if ASA

should be available to all users of the system, or only

the user running the installation program. Select[Next].

6. The next display indicates the default installation

directory. (To choose a different location, select

[Change…], and use the dialog box to indicate a

different folder.) When you are satisfied with the

installation location, select [Next].

7. On the next dialog box, click [Install]. InstallShield

then installs the ASA software.

8. Another dialog box will appear with an indicator bar,

showing the progress of the installation.

9. The final Screen will enable you to register your

product Select the “register product” option. Click

finish to complete the installation.



Page 11


3.2 Spectrum PC Card Installation

Be sure to install the ASA software before installing the Spectrum PC Card

into your computer. (See instructions on previous page.)

To install the Spectrum PC Card:

1. Identify an open CardBus slot (i.e., a PCMCIA slot) on your

computer.

2. Insert the ASA Spectrum PC card into the slot as shown.

The pins should go in first, and the LEDs on the card should

be face up.

3. Press the card gently but firmly into place.

4. You may see a screen which asks if you want Windows Update to create a device driver. Of the three available options, select [No, Not At This Time].

5. Windows XP will present a dialog box indicating that new

hardware has been found.

6. Normally, leave the default option (Install the software

automatically) selected, and select [Next].

7. Windows XP presents another dialog box, indicating thatdriver installation is in progress.

8. A final dialog box will indicate when installation is

complete. Select [Finish].





3.3 Attaching an External Antenna

The ASA Spectrum PC card has an internal antenna; however, you can obtain improved detection

sensitivity by using an external antenna. You can use the omni-directional antenna (included), or

the optional directional antenna. Refer to www.AirMagnet.com web site for the reference source of

supported external antennas.

The MMCX connector is limited to 500 connections. To prolong

the life of your MMCX connector, it is strongly recommended that, once

connected to the cardbus adapter, the antenna should not be disconnected unless it is

absolutely necessary. Frequently connecting and disconnecting the antenna may

increase the wear and tear, causing inadvertent damage to the connector.

3.3.1 Attaching the Omni-directional Antenna

1. Attach the antenna holder clip to the top of the display panel on the

computer, as shown here.

The clip has a round antenna holder. If you mount the clip as

shown, the antenna holder will be horizontal.

2. Slide the antenna vertically into the round, horizontal holder, so that

the antenna is held in place as shown at right.

3. A cable extends from the bottom of the antenna. The end of the

cable has a plug. Install the antenna plug into the external jack on

the Spectrum PC card.

You can mount the antenna and clip so that the antenna is in other

positions as well.



Page 13


3.3.2 Attaching an optional Directional Antenna

1. Mount the external antenna holder to the back of your PC.

(The holder has adhesive backing.)

2. Slide the antenna’s support staff into the slot on the holder.

3. A cable extends from the bottom of the antenna support staff.

The end of the cable has a plug. Install the antenna plug into

the external jack on the Spectrum PC card.

3.3.2.1 Using the Directional Antenna

The purpose of the directional antenna is to focus RF detection activity in a given direction.

This can be useful with all ASA features, but is especially useful with the Device Finder (seeSection 8 on page 42). The following diagram illustrates the directional sensitivity of the

directional antenna.

Figure 3-1: Using The Directional Antenna





3.4 Starting the AirMagnet Spectrum Analyzer for the First Time

Once the AirMagnet Spectrum Analyzer software is installed, and the Spectrum PC card is

installed, you can begin to use ASA to identify sources of interference in the neighborhood of your

WLAN.

NOTE: If your computer has an 802.11 card or built-in 802.11 capability, make sure it is not

transmitting when you use ASA. See Section 3.6 on page 18 for more information.

1. From the Start menu, select Programs AirMagnet AirMagnet Spectrum Analyzer.

2. When you first start the program—and depending on your

Windows XP security settings—you may see the security

warning shown at right. If you do, BE SURE TO SELECT

THE [Unblock] OPTION!

3. After seeing the ASA splash screen, a dialog box allows you to

choose the type of antenna to use. Select the appropriate

antenna selection (Internal or External).

4. If you expect to use these settings in the future, check the

Automatically Use These Settings Next Time box.

5. Select [OK],

You will now be presented with AirMagnet Startup View.

Depending on the country in which you are located, you may

need to change the Local Settings before you can make

effective use of ASA.

6. Select Tools Settings….

7. Select the Channel Settings button at left. For instructions on

using the Settings dialog, see Section 9 on page 49.

From here, you can use all the features of ASA. The followingsection provides an overview of the AirMagnet Spectrum Analyzer

and its features.



Page 15


3.5 Repairing A “Backwards” Installation

As indicated above, the ASA software should be installed before you insert the Spectrum PC card

into your PCMCIA slot. If you have installed the PC card hardware first, the software installation

process may not work correctly, and ASA may not recognize the PC card in your PC. This section

contains instructions on how to fix this situation, should it arise.

A little background information is helpful. The reason we ask you to install the ASA software first

is because the installation process automatically installs, on your PC, the software drivers required

by the Spectrum PC card. If you install the Spectrum PC card first, the necessary device drivers

are not present. You will then see a message such as this:

Figure 3-2: Spectrum PC card Hardware Installation Error

If you see such a message, first uncheck the box which says Don’t prompt me again to install the

software. Then select [Finish]. The next step is simply to go ahead and install the ASA software,

as per the instructions above (Section 3.1 on page 10).

After installing the software, one of two things will happen:

3.5.1 Automatic Hardware Recognition by Windows XP

Windows XP may automatically recognize that the necessary drivers are now present to support the

Spectrum PC Card. Windows XP will install the drivers for you, and you can go ahead and use

ASA.

One way to find this out is simply to start the ASA Software(Section 3.4 on page 14). If the

program starts successfully, this indicates it has found the Spectrum PC card, and you are all set.

Another way to check that the drivers are properly installed is to select:

• Start Settings Control Panel

• Double-click on the System icon.

• Select the Hardware tab.

• On the Hardware tab, select [Device Manager].

If the Spectrum PC card—with supporting software drivers—is properly installed, then there

will be an icon for ISMI Devices. Open that icon (double-click on it), and underneath you will





see listed the AirMagnet Spectrum Analyzer PC Card.

Figure 3-3: Successful Spectrum PC Card Hardware Installation As Shown On Device Manager

You can close the Device Manager, and get to work with the AirMagnet Spectrum Analyzer

Display.

3.5.2 Manual Driver Installation

If you first installed the Spectrum PC Card hardware; and then, installed the software; it is

possible that Windows XP may not automatically install the Spectrum PC Card . You can check

this by again visiting the Device Manager. (Same instructions almost the same as those above:

Select Start Settings Control Panel. Double-click on the System icon. Select the

Hardware tab.

On the Hardware tab, select [Device Manager]. Now double-click on Other Devices.)

In the event the driver is not installed, you will see:

Figure 3-4: Unsuccessful Spectrum PC Card Hardware Installation As Shown On Device Manager

This means that Windows XP knows the device is out there, but doesn’t have the necessary drivers

to fully support its functionality. To correct this problem:



Page 17


1. Right-click on PCI Data Acquisition and Signal Processing Controller.

2. Select Install Driver….

3. On the Found New Hardware Wizard select No, Not This Time.

4. Select [Next].

5. On the next screen, select Install From A List Or A Specific Location.

6. Select [Next].

At this point, make sure your ASA installation CD is installed in your CD drive.

7. The next dialog box will enable you to search the CD for a device driver. The ASA installation

CD has a Driver subdirectory. Select the device driver from this directory, or simply type in

the path to the directory.

8. Select [Next].

9. Windows XP will install the driver for the Spectrum PC Card.

You will now be able to use the AirMagnet Spectrum Analyzer software.





3.6 AirMagnet Spectrum Analyzer and Your PC’s 802.11Operability

If your PC has an 802.11 network card, or built-in 802.11 capability, ASA will not operate properly

if the 802.11 card is transmitting at the same time that ASA is making measurements. This means,

in practice, that your 802.11 card must be disabled with respect to transmitting while ASA is inuse.

However, it is acceptable for your 802.11 card to be receiving data while ASA is in operation at the

same time. For example, you can use AirMagnet Laptop WLAN Analyzer which is designed for

protocol-oriented monitoring of the 802.11 environment at the same time you use ASA to observe

the RF spectrum.

Because the software associated with your 802.11 card can vary depending on the particular

hardware in use, we can’t provide step-by-step instructions. In general, however, you need to makesure of the following:

• Your PC/802.11 hardware is not associated with an AP.

• Your PC/802.11 hardware is not associated with an adhoc network.

You can generally check your network associations—and change them, if necessary—using the

Network Connections settings on the Windows Control Panel (Start Settings Control

Panel Network Settings).

In some cases, your 802.11 hardware may also include software tools which enable you to set the

802.11 device for Rx mode only, with no Tx. See your 802.11 hardware documentation for more

information.

3.7 Upgrading the AirMagnet Spectrum Analyzer Software

From time-to-time, AirMagnet may release updates to the Spectrum Analyzer software.

In order to install the updates, you must reinstall the entire application from scratch:

10. First exit the AirMagnet Spectrum Analyzer application, if you are currently using it.

11. Remove the Spectrum PC Card from your PC.

12. Uninstall the AirMagnet Spectrum Analyzer software. You uninstall the software in the

standard way:

Select Start Settings Control Panel.

On the Control Panel, double-click on Add Or Remove Programs. Select AirMagnet Spectrum Analyzer.

Select [Remove].

Once AirMagnet Spectrum Analyzer software has been uninstalled, you can install the latest

version using the instruction in Section Error! Reference source not found. on page Error!

Bookmark not defined.. (Note, however, that since you may not be installing from a CD, you will

need to run Setup.exe from wherever you have downloaded the installation program on your hard



Page 19


drive.) You can then install the Sensor and antenna, and start the application, as per the

instructions in sections Error! Reference source not found. through 3.4.



Page 20 Section 4. The AirMagnet Spectrum Analyzer Display- An Overview


4 THE AIRMAGNET SPECTRUM ANALYZER DISPLAY- AN OVERVIEW

NOTE: If your computer has an 802.11 card or built-in 802.11 capability, make sure it is not

transmitting when you are using ASA. See Section 3.6 on page 18.

Menu Workspace with Workspace with Workspace also displays the

Channel Summary Spectrum plot Device Finder (not shown)

Spectrum Interferer List Interferer List Time Control Plot Controls

(Can be undocked)

Figure 4-1: The AirMagnet Spectrum Analyzer Display

Detailed information on using the AirMagnet Spectrum Analyzer may be found in the ASA Online

Help system.

The AirMagnet Spectrum Analyzer display has the following basic features:

4.1 Status Bar

The ASA Display has a Status Bar at bottom, which may be toggled on and off usingView Status Bar. The Status Bar displays information about the Spectrum PC Card in use.

4.2 Interferer List

Interferers are any devices, such as microwave ovens and cordless phones, which may interfere

with the performance of your 802.11 network. The Interferers List, which is normally docked at

the bottom of the console window, displays all the interfering devices currently detected by the



Page 21


AirMagnet Spectrum Analyzer. Optionally, the list can display recently detected devices as well.

The list is toggled on and off by selecting View Interferers. See Section 6 on page 37.

4.3 Menu Options

The ASA Display has the following menu options:

4.3.1 File Menu

The File menu offers the following option:

• Exit – Closes the ASA application.

4.3.2 View Menu

This menu provides access to most of the main AirMagnet Spectrum Analyzer features. Some of these operations can also be accessed from the Tool Bar at left.

• Spectrum View – Enables you to create a variety of graphs or plots which provide real-time

views of RF activity. (The Air Quality plot provides recent historical information as well.)

See Section 5 on page 25.

• Channel Summary – This view shows RF activity—such as power levels, and the presence of

802.11 and interferer devices—on a channel-by-channel basis. See Section 7 on page 40.

• Device Finder – The Device Finder enables you to track down the location of interfering

devices. See Section 8 page 42.

• Spectrum Plot Controls – This option is only visible when the Spectrum View is active and

in the foreground.

Spectrum plots have controls which are used to configure the kinds of data shown in each plot.

The controls take up some space at the right of the display, which you may prefer to recover so

that the plots themselves are wider. Use this menu option to toggle the plot controls so that

they are visible/not visible. See Section 5 on page 25 for more information.

• Interferers – The Interferer List shows all interfering devices which are currently

broadcasting RF. It can also display recent interferer activity. However, the list does take up

space at the bottom of the display, which you may prefer to use for larger spectrum plots. Use

this menu option to toggle the list so that it is visible/not visible.

• Status Bar – The console Status Bar at the bottom of the console window provides various

system status information. Use this menu option to toggle the Status Bar display on or off.

Only one of the Spectrum View, Channel Summary, or Device Finder can be visible

at any given time. However, once you have activated any of these modes, it remains in operation

(in the background) even when not visible. For example, the Air Quality spectrum plot will

continue to record spectrum data, and update air quality information, even if you switch to the

Channel Summary mode. (When you return to the Spectrum View, the updated data will be

visible on screen.)





4.3.3 Plots Menu

This menu is only visible when the Spectrum View is active and in the foreground.

• Add New Plot – Adds one of the available plot types.

• Remove Selected Plot – Removes the currently selected plot from the display. (You must

first select a spectrum plot for this menu option to be active.)

• Pause Selected Plot – Freezes the display of data on the currently selected plot.

• Resume Selected Plot – Only shown if you first select a plot which was previously paused.

Resumes the real-time update of data for that plot.

• Pause All Plots – Freezes data display on all the currently open plots.

• Resume All Plots – Resumes the real-time update of data on all plots.

See Section 5 on page 25 for more information.

4.3.4 Tools MenuThis menu provides access to the Settings dialog. The Settings dialog, in turn, has four panels:

• Antennas – Selects internal or external antenna for spectrum data acquisition.

• Console Settings – Modifies date and time presentation on the AirMagnet Spectrum Analyzer

Display.

• 802.11 Channel Settings – Determines which channels are monitored for RF activity. You

can select channels based on regulatory domains (USA, Japan, etc.), or you can custom select

specific channels to monitor.

• Monitored Bands – This panel determines which RF bands are monitored and reported on by

ASA. The default setting is to monitor the channels indicated on the 802.11 Channel Settings panel. However, there are also options for other pre-defined bands, and two user-defined

bands as well.

See Section 9 on page 49 for more information.

4.3.5 Help

• Help Topics – Provides access to the AirMagnet Spectrum Analyzer Help system.

• About Spectrum Console… – Provides copyright and version information for the AirMagnet

Spectrum Analyzer software.

• Spectrum PC Card… – Provides technical data for the Spectrum PC Card currently in use.



Page 23


4.4 Tool Bar

The Tool Bar at the left side of the console provides access to three Console features:

• Spectrum View – Enables you to create a variety of graphs or plots which provide real-time

views of RF activity. See Section 5 on page 25.

• Channel Summary – This view shows RF activity—such as power levels, and the presence of

802.11 and interferer devices—on a channel-by-channel basis. See Section 7 on page 40.

• Device Finder – The Device Finder enables you to track down the location of interfering

devices. See Section 8 page 42.

4.5 Context-Sensitive (Right-Click) Menu Features

Many console features can be accessed by right-clicking on appropriate features (such as plots) to

bring up context-sensitive menus. The following is a partial list. (Other context sensitive features

are discussed—in context—in this manual.)

4.5.1 Spectrum Plots

When you right-click in the workspace for spectrum plots, you obtain the following options:

• Add New Plot – Adds one of the available plot types.

• Remove Selected Plot – Removes the currently selected plot from the display. (You must

first select a spectrum plot for this menu option to be active.)

• Pause Selected Plot – Freezes the display of data on the currently selected plot.

• Resume Selected Plot – Resumes the real-time update of data for the selected plot.

• Pause All Plots – Freezes data display on all the currently open plots.

• Resume All Plots – Resumes the real-time update of data on all plots.

The following three options are only available from the plots context menu:

• Open Spectrum View Configuration… – A spectrum view “configuration” is a group of

settings for one or more plots. This option opens a previously saved configuration.

• Save Spectrum View Configuration… – This saves the current configuration of spectrum

plots (it saves which plots are open, and what settings they have on the Control panel).

• New Spectrum View Configuration… – Clears (closes) all the plots currently on display, so

that you can open different plots, and create new plot settings.

4.5.2 Interferer List

The Interferer List has the following context-sensitive options:

• Find This Device – Activates the Device Finder for that interferer.

• What Is This? – Provides additional data on the device, if available.





4.6 What If I Do Not See Any Data?

It may happen that you are viewing one of the AirMagnet Spectrum Analyzer displays, such as a

spectrum plot, but you are not seeing any data; or data is missing for part of a plot. (For example,

some of the channels on the plot have spectrum data, and others do not.) Or, you may know

perfectly well that some kind of interfering device is present in the environment, but theInterferers List and/or Device Finder are not detecting it.

• One possible cause of this problem could be a complete lack of communication between the

Spectrum PC Card and the AirMagnet Spectrum Analyzer software. Normally, however, if

communication is lost with the Spectrum PC Card, the AirMagnet Spectrum Analyzer software

will present a warning message, and then shut down.

To resolve such problems, check to make sure that the Spectrum PC Card remains properly

seated in the CardBus slot.

• Another possibility is that, while you have set your spectrum plots to display certain channels

or bands, your configuration settings for ASA as a whole do not include those channels/bands.

To determine if this is the problem—and to rectify if—you need to check your Channel

Settings and Monitored Bands under the AirMagnet Spectrum Analyzer Display’s Settings

panel. SeeSection 9.3 on page 51 and Section 9.4 on page 52.

• A third possibility is that you may not currently using the antenna you think you are using.

You need to check your Antennas settings. See Section 9.1 on page 49.



Page 25


5 SPECTRUM VIEWS

The ASA Spectrum Views use graphical displays to provide detailed, low-level views of the RF

spectrum. The plots are based on data from the SAgE chip embedded in the Spectrum PC Card.

In this section we explain how to create a Spectrum View graph, and we explain the kinds of

information displayed in each graph.

5.1 Using Spectrum View Graphs

5.1.1 Entering Spectrum View Mode

To initiate or restore the Spectrum View, select the [Spectrum] button ( ) on the tool bar of

the AirMagnet Spectrum Analyzer Display. You can also select View Spectrum View.

5.1.2 Creating A New PlotTo add a new plot:

1. Make sure you are in Spectrum View mode (select the [Spectrum] button at the left side of

the console).

2. Right-click in the display area, and select Add Plot… from the pop-up menu; or select

Plot View Add Plot….

3. From the cascading menu which results, select one of the six plot types: Real-Time FFT, FFT

Duty Cycle, Swept Spectrogram, Air Quality, Power vs. Frequency, or Power vs. Time.

A description of each plot type is offered below, in Section 5.2 on page 27.

4. Use the Control Panel at the right of the display to set the parameters for the plot.

The particular parameters will vary depending on the type of plot. An overview of the

Control Panel is presented in Section 5.3 on page 32. Detailed descriptions of plot parameters

are contained in the Mobile Spectrum Management Console Online Help system.

Of particular importance – in order to see any data displayed at all, you need to

select the On button for at least one Trace. A “Trace” is the term we use to describe the line

of data shown on a plot. (By default, the Trace or Traces for a plot are set to Off.)

Figure 5-1: Turning a Plot Trace On



Page 26 Section 5. Spectrum Views


5.1.3 Multiple Plots

You can repeat the instructions immediately above (Section 5.1.2 on page 25) to place more than

one plot on display.

• If you are in Spectrum View mode, and the Control Panel is not showing, select

View Spectrum Plot Controls.

• To access the Control Panel for a particular plot, simply use the mouse to click on that plot.

(If you have more than one plot in view, then as you click on different plots, the Control Panel

will change to display the configuration options for the currently selected plot.)

Figure 5-2: Multiple Spectrum Plots

5.1.4 Measurement Interval

Unless you have paused a plot (discussed below), the AirMagnet Spectrum Analyzer Display

updates each plot with fresh data once per measurement interval, which is typically once every

second.

5.1.5 Pause and Resume Plotting

At times an event may occur in your network, such that you want to immediately capture the RF

environment at that moment for sustained study and review. You can pause and resume plots by

right-clicking in the spectrum plots workspace, and selecting the appropriate menu options, or by

selecting these options from the Plots menu (e.g., Plots Pause All Plots):

• Pause Selected Plot – Freezes the data displayed on the

currently selected plot. (Be sure you have right-clicked on

the appropriate plot when you bring up the context menu.)

• Resume Selected Plot – Resumes real-time data display for

the currently selected plot.

• Pause All Plots – Freezes data display on all plots.

• Resume All Plots – Resumes the real-time update of data on

all plots.

Figure 5-3: Paused Plot With

"Paused" Indicator



Page 27


5.1.6 Saving and Restoring Spectrum View Layouts

Other operations are available for working with plots. All these operations can be selected by

right-clicking on a plot, and selecting from the context menu that appear. (Remove Selected Plot

can also be selected from the Plots menu.)

•

Saving A Spectrum View – Enables you save the current configuration of open plots,including their specific display parameters. (The current data, however, is not saved.)

In the Save Spectrum View Configuration dialog, type in the name for your

configuration, or select the name of a previously defined configuration.

To make the current configuration be the default configuration, be sure to first select the

Set As Startup Default check box. If you select this, the current configuration will appear

every time you log into the AirMagnet Spectrum Analyzer Display.

Select [OK]

• Open A Saved Spectrum View – The dialog box for this operation will list all of your

currently saved spectrum views. Select one view, and then select [OK].

• New Spectrum View Configuration – This operation clears all currently displayed plots.

• Remove Selected Plot – This operation will close only the currently selected plot.

5.1.7 Deleting A Spectrum View

To delete a saved spectrum view, right-click the Plots workspace and select Save Spectrum View

Configuration…. In the Save Spectrum View Configuration dialog, select an existing view.

Then select [Remove Saved Configuration]. Select [OK] on the confirmation dialog box.

5.2 Plot Content

Spectrum View offers six different types of plots. We list all six plots here, and provide more

detailed discussion in the following pages. Further information is available in the Online Help.

5.2.1 Frequency-Based Plots

There are four plots which offer different views of RF power as a function of frequency. For these

plots, the entire plot is updated once per measurement interval (approximately once per second):

• Realtime FFT Plot

• Power vs. Frequency

• FFT Duty Cycle

• Swept Spectrogram – Combines a time- and frequency-based view of the RF spectrum.

5.2.2 Time-Based Plots

These plots show the variation of an RF metric over time.

• Air Quality – Plots data based on extended time intervals (10 minutes to 24 hours).

• Power vs. Time – Plots data based on short time intervals (milliseconds). Mainly used for

pulse detection.





5.2.3 Real-Time FFT Plot

An FFT Plot displays RF power as a function of frequency. The data in the plot is, in essence,

direct data from SAgE. The plot can provide three different views of the power readings from the

Spectrum PC Card: the average power (Avg) read during the most recent measurement interval;

the maximum power (Max) detected during the most recent measurement interval; or the

maximum power detected at any time since the plot began running (Max Hold, meaning the plotholds onto the maximum power up to now).

5.2.4 Power vs. Frequency

The Power vs. Frequency plot is also, in essence, a Fourier transform of the RF spectrum,

showing the amount of RF power detected at various frequencies. The different between this plot

and the Real-Time FFT plot is that the Power vs. Frequency plot is generated based on an

analysis of SAgE data. This means that data can be aggregated and combined in various ways that

are not possible with direct SAgE data, the basis for the Real-Time FFT plot.

Section 5.2.9 on page 30 compares the Real-Time FFT plot with the Power vs. Frequency plot.

5.2.5 FFT Duty Cycle

The FFT Duty Cycle plot displays the percentage of the time that the ambient RF signal is 20 dB

above the noise floor. (This is represented on a per-frequency bin basis.) The Duty Cycle for the

FFT Duty Cycle plot includes all RF energy, both from 802.11 devices and interferers.

Figure 5-4: FFT, Power vs. Frequency, FFT Duty Cycle, and Swept Spectrogram



Page 29


5.2.6 Swept Spectrogram

The Swept Spectrogram is a different presentation of the same data shown in the Real Time FFT

and FFT Duty Cycle plots. Each colored horizontal line in the Swept Spectrogram plot displays

the power or duty cycle in the RF spectrum as a function of frequency, as measured over the time

period of one sweep in time (typically one second). The power or duty cycle values in each sweep

are mapped to a range of colors, and displayed in a scrolling or "waterfall" display. This allowsyou to observe the FFT signals over historical time, and easily see signals with shifting frequencies

and various durations.

The color legend for the Swept Spectrogram is only displayed if there is enough room

on screen. Depending on your display resolution, and on how many plots you have open at once,

you may need to close some other plots in order to see the mapping of colors to power levels.

Figure 5-5: Understanding The Swept Spectrogram Plot





5.2.7 Air Quality

The Air Quality plot displays RF air quality as a function of time. Air quality is determined based

on a single spectrum measurement, selected by you (such as maximum RF power, average RF

power, pulse activity, duty cycle, interferer power, or other user-selectable criteria).

5.2.8 Power vs. Time

The Power vs. Time plot displays RF power as a function of time. The time frame is on the order

of milliseconds. The plot is used primarily to obtain a view of RF pulse activity.

5.2.9 The Real-Time FFT Plot Compared with the Power vs. Frequency Plot

Both the Real-Time FFT plot and the Power vs. Frequency plot show RF power as a function of

frequency, at a given moment in time. However, the two plots differ in important respects:

Property Real-Time FFT Plot Power vs. Frequency Plot

Data Source SAgE Hardware: Raw spectrum data iscollected on the SAgE chip inside the PC card,and statistical analysis is also performed directlyby SAgE’s onboard hardware. This provides forvery fast analysis of large quantities of spectrumdata, but with the limitation that the parametersof the analysis are hard-coded into the design ofthe SAgE chip.

SAgE plus Microprocessor Software:Raw spectrum data from SAgE is analyzedby software running on the local processorinside the PC card. (This PC Card’sprocessor is separate from the SAgE chip.)This provides greater flexibility in theanalysis, but with the trade-off that less datacan be analyzed in a given time frame.

Dwells For both plots, the FFT analysis is performed on only 20 MHz of the band at one time. Each 20MHz span is called a “dwell.” By measuring 5 or 10 successive, adjacent dwells, it is possible toconstruct a plot which is essentially a Fourier transform of the entire 2.4 GHz or 5 GHz band.

Bins and Bin Sizes Each 20 MHz dwell is divided into 128 bins,

where each bin is 156 KHz wide. A powermeasurement is provided for each bin.The number of bins, and the bandwidth of eachbin, is fixed.

The number of bins, and the bandwidth of

each bin, is user-definable. This enablesmuch finer granularity. A single bin can beas narrow as 9.77 KHz. You can also makea single bin as large as 1.25 MHz. The binsize is determined using the plot’sResolution Bandwidth setting.



Page 31


Property Real-Time FFT Plot Power vs. Frequency Plot

Number of FFTs PerPlot

The Real-Time FFT Plot is updated once persecond. Each plot is actually based on the 5000FFTs performed by SAgE during each dwell.

The software-based calculations generateonly a single FFT per second. That one FFTis shown in the Power vs. Frequency plot(which is updated nominally once persecond, to reflect the new FFT). If you have

set the plot to show an Average over allFFTs, the calculation is based on anaverage of several preceding FFTs; buteach successive second in real time onlycontributes one new FFT to that average.

(When you create the Power vs.Frequency plot, the very first plot shows asingle FFT. If the plot is in “Averaging”mode, the second plot adds one new FFT,and averages that with the FFT from the firstplot. Each second, one more FFT is addedto the average. But, the average is notperformed over all preceding FFTs, but onlyfor those included in a sliding time window.)

Max Mode? One of the plotting options is to display themaximum RF power seen during themeasurement interval (i.e., during one second).This is possible because the maximum powercan be selected from among the 5000 FFTs.

A maximum power plot cannot be created,because actual data is available for only oneFFT per second (rather than having data for5000 FFTs, as with the real-time plot).

Mode Summary

(selected using the“Type” parameterfor each Trace in theplot)

Average – Shows the average of all 5000 FFTsfrom a single measurement interval .

Max – Shows the maximum power seen in anyof the 5000 FFTs during the currentmeasurement interval.

So, in frequency bin 1, the max power may havebeen seen during FFT 27; in bin 2, the maxpower may have been seen during FFT 3057; inbin 3, the max power may have been seen

during FFT 1079. In each frequency bin, themaximum power from any of the 5000 FFTs isused to construct the plot of maximum power.

Technical Caveat: SAgE actually does just alittle bit of averaging, taking peak values from ahandful of FFTs.

Max Hold – Shows the maximum power seensince the plot was started, or since it was lastCleared.

Average – Shows a weighted average ofseveral FFTs including both the present measurement interval, and previous measurement intervals .

Normal – Shows the single FFT created (viasoftware analysis) during the currentmeasurement interval.

Max Hold – Shows the maximum powerseen since the plot was started, or since it

was last Cleared.

The Max power readings are useful for detecting (i) frequency hoppers and (ii) bursty devices.

The Average power readings are effective for detecting (i) continuous transmitters and(ii) devices with high duty cycles.

Advantage of UsingThis Plot Because the plot can show an average of all5000 FFT measurements made by SAgE in asecond, you are more likely to see spectrumresults from devices that are frequency hoppers,or bursty transmitters.

You can achieve much finer control over thegranularity of the spectra that you see.

Disadvantage ofUsing This Plot

You cannot control the granularity of thespectrum.

Since you only see one FFT for the entireone-second measurement interval, you areless likely to see either frequency hoppers orbursty devices.





5.3 Plot Controls

The plot Control Panel lets you fine-time the data presented by the plots. Each plot has its own

plot-appropriate controls. However, many of these controls are common to more than one plot.

We discuss the typical controls here. The Online Help fills in additional plot-specific details.

5.3.1 Frequency and Bandwidth To Monitor

Several plots provide measurements of RF power (average power, maximum power, etc.) as a

function of frequency. The RF frequencies are presented as a range across the horizontal axis.

Frequency settings enable you to establish the range of Y-axis. Even for the time-based plots,

however, you can still set the band and/or channel that ASA will monitor.

You can select the frequency to be monitored based on a Center Frequency and Span, or based ona Start/Stop frequency, or based on specific WiFi Channels. You then use the Band/Channel

drop-down menu to select a particular Band or Channel to monitor.

Once you have made a selection, the console automatically fills in default values for the Center

frequency and Span, or the Start and Stop frequency. However, you can edit these default values.

• If you change the default Center frequency and frequency Span, or the Start and Stop

frequencies, you may no longer be plotting entirely “in channel” or “in band.” However, ASA

will NOT permit you to set frequencies that are outside the hardware capabilities of the sensor

technology. In this sense, the technology is “error proof”.

• You can change the bands available here—that is, the bands or channels shown on the

Frequency menus—by changing the Monitored Bands settings (Tools Settings Monitored Bands). See Section 9.4, Monitored Bands on page 52 for more information.

Bandwidth – The Power vs. Frequency plot also has a

Bandwidth setting, which determines the size of each bin for RF

power measurements. See the Online Help for more information.

5.3.2 Amplitude

Amplitude settings enable you to set the scale for the vertical axis.

The exact measurements will depend on the type of measurement

being made. For example, RF power measurements are in dBm,while duty cycle measurements are in percentages (since the duty

cycle is typically defined as the percentage of time an RF signal is detected during the

measurement interval).

• Reference Level refers to the value at the top of the vertical axis.

• Vertical Scale refers to the change in value represented by each tic-mark on the vertical axis.



Page 33


In general, the bottom of the scale is

Reference Level – (10 * Vertical Scale).

Example: If the Reference Level is -20 dBm, and the

Vertical Scale is set to 7 dBm, then the top of the scale

is -20 dBm, while the bottom of the scale is

-20 dBm – (10 * 7 dBm) = -90 dBm.

AutoScale – If you select [AutoScale] the console

automatically selects the optimum calibration for the

vertical scale, based on recent power measurements.

5.3.3 Trace Settings

A “Trace” is the line which actually plots the RF data of interest.

• You must select the On radio button for at least one Trace, in

order to see any data at all.

• For some plots, you can have more than one Trace, and you canselect the type of data each trace displays (such as average RF

power, maximum RF power, max-hold RF power, etc.).

The Online Help describes these options in detail.

• Max Hold maintains a display of the highest RF power measured

since you began the current session. The [Clear] button deletes

the Max Hold Trace, and starts a new maximum power trace,

starting from the moment when [Clear] is selected.

5.3.4 Markers

A marker is a small icon on the plot which “rides” the graph at a particular point along the X-axis,

in other words, at a particular frequency. The marker moves up and down according to the

movement of the graph at that fixed point. The marker is the small red box riding the middle trace

in the plot shown here:

• On / Off – Indicates whether the marker

is on or off.

• Type – A Single marker is just that, one

marker that “rides” the trace. If you

select Delta, you will initially still see a

single marker on the plot. However—

with a quick “mouse hand”—you can

grab the marker with your mouse pointer (click and hold on the marker), and slide the marker

to a second location on the plot. You now have two markers riding the trace, so that you can

see the difference in behavior between two different frequencies.





• Value – Indicates where along the X-axis (the frequency axis) the marker should ride the plot.

Moving The Marker With The Mouse: You can indicate the frequency value using the

Value text box. However, once the marker is visible on screen, you can grab the marker (click

and hold the left mouse button), and drag the marker to a new location (a new frequency).

•

Trace – Use the drop-down list box to select which of the three traces the marker will ride.

5.3.5 Channels

Some of the spectrum plots use frequency values on the horizontal axis. On these plots you have,

as an option, the ability to superimpose bracketed indicators of channels, as illustrated here.

You can turn the display On or Off using the

Channels radio buttons. The channels shown will

be the ones appropriate for the band you arecurrently monitoring, taking into account any

Regulatory Domains you have selected under

Channel Settings (see Section 51 page 51).

Even if you turn Channels to On, they

will only be shown if the span of the plot is 200

MHz or less.

5.3.6 Other Plot Control Panel Settings

Certain plots have specialized settings, which are described in detail in the Online Help. We

mention them briefly here:

5.3.6.1 Power vs. Time

The Power Vs. Time plot is used to display short burst of RF activity, known as “pulses”. The plot

has a series of Trigger settings. Trigger criteria determine both what kinds of RF pulses are

displayed, and when the display is updated.

• Trigger Type – This determines when the plot is updated. Use the drop-down list box to select

one of the three options.

Free Run – RF energy (in your selected bandwidth) is sampled on a continuous basis, and

data is “dumped” to the screen as it is available. This means the display is updated on a

nearly constant basis, and data is shown whether or not any RF pulses are detected.

Single – This catches a single pulse only. The display is only updated when an RF pulse is

detected which matches your Trigger Threshold criteria (discussed below). (Of course, to

trigger the plot the pulse must also be within the bandwidth you have indicated, using the



Page 35


options above.) If you select Single, you must then click on [Arm], telling the Mobile

Spectrum Management Console to be on the lookout for a suitable RF pulse event.

Once such a pulse event is detected, it is displayed on the plot, and the plot is then frozen –

no further activity is displayed. To catch any further pulses, you click again on [Arm] (or

[Rearm]).

Continuous – The plot is only updated when ASA detects RF pulses which match your

Trigger Threshold criteria. However, after detecting a pulse, the plot automatically “re-

arms” itself, meaning every time a new pulse comes along, the plot is updated with new

data. (Once again, of course, the pulses are only shown if they also fall within the

bandwidth you have indicated, using the options above.)

• [Arm] – If you have selected a Trigger Type of Single, select [Arm] to tell the AirMagnet

Spectrum Analyzer Display to be on the lookout for the next pulse that comes along.

• Trigger Threshold – This indicates the minimum power that an RF pulse must attain in order

to register as a pulse, for purposes of this plot. Put another way: In order to be counted as a

pulse at all, for purposes of this plot, an RF pulse must exceed the amount of power you

indicate here. Units are in dBm, where 0 dBm is equivalent to 1 milliwatt.

For example, if you indicate -10 dBm, then a pulse which reaches -5 dBm will be displayed,

while a pulse whose maximum power is only -12 dBm will not be displayed.

• Trigger Delay – This feature lets you adjust the centering of a pulse on your display. The

default value for this parameter is 0, and with this setting the beginning of an RF pulse isalways centered on the midline of the time axis. If you set this to a positive value, the

beginning of the RF pulse is offset to the left. If you set this to a negative value, the beginning

of the pulse is offset to the right.

5.3.6.2 Swept Spectrogram

The Swept Spectrogram plot uses colors to represent RF power levels. The Color Scale options

enable you to map the “highest color” and “lowest color” to specific power levels.

Here, the color Blue has been mapped to -110 dBm, while Red has

been mapped to -30 dBm.

Values below the minimum value (-110 dBm, in this case) are

automatically mapped to Purple, while values above the maximum

value (-30 dBm here) are automatically mapped to White .

Color Scale Visibility: For the Swept Spectrogram, the color scale is only visible

when there is enough room to display it on screen. Depending on how many plots you have open,

and on your display monitor resolution, you may need to close some plots to see the Swept

Spectrogram color scale.

[Auto Scale] serves the same purpose as elsewhere – it chooses appropriate upper- and lower-

values based on recent power measurements.





5.3.6.3 Air Quality

The Air Quality plot has settings for:

• Metric – Determines what kind of measurement is used to evaluate the overall RF Air Quality.

Options include Average RF Power, Maximum RF Power, Interferer Power, and others.

• Interval – Indicates how far into the past the plot evaluates Air Quality. This can be as short as

the past ten minutes, or as long as twenty-four hours into the past.

5.3.6.4 FFT Duty Cycle Plot

For the FFT Duty Cycle plot, the scale of the Y-axis is based on a Maximum and Minimum, where

(typically) the Maximum would be 100%, and the Minimum would be 0%.



Page 37


6 INTERFERERS

ASA’s Interferer List enables you to see all interferers which were active, in the neighborhood of

your WLAN, during a time frame you indicate. An interferer is any non-802.11 RF device which

broadcasts in the same frequency bands as 802.11 devices, and which can cause disruption to your

802.11 network. Typical interferers include microwave ovens, cordless headphones and headsets,radar, and Bluetooth devices.

Figure 6-1: Interferer View

6.1 Working with the Interferer List

6.1.1 Setting the Time Interval

Use the drop-down list box at the right side of the display to indicate the time-interval of interest.

Figure 6-2: Interferer List Time Selection

For example, if you select a period of ten minutes, you will see a display of all interferers which

have been active during the preceding ten minutes (up to and included currently active interferers).

6.1.2 Showing and Hiding The List

If the Interferer List is not currently visible, select View Interferers.

Sometimes when the list is visible, you may choose to hide it in order to allow more room for the

spectrum plots. To hide the Interferer List, select View Interferers.

6.1.3 Docking and Undocking The List

The Interferer List can be undocked from the rest of the AirMagnet Spectrum Analyzer Display,

so that it is a standalone, free-floating window.



Page 38 Section 6. Interferers


• To undock the Interferer List, use the mouse to "grab" the title bar of the sub-window—that is,

left-click-and-hold on the title bar of the sub-window—and sweep the mouse up and away

from the main panel.

• To dock the Interferer List again, grab its title bar with the mouse, and sweep it back down

towards the lower part of your display screen, until the list is docked again.

You can also undock/dock the list by double-clicking on the top of the Interferer List window.

6.1.4 Getting More Information On An Interferer

The Interferer List displays various data about each interferer, as described below. To obtain

additional information on an interferer:

1. Right-click on the interferer.

2. From the pop-up menu, select What Is This?

The AirMagnet Spectrum Analyzer Display presents a dialog box with more detailed

information on the interferer, provided such information is available in the console’s database.

6.1.5 Locating an Interferer

The AirMagnet Spectrum Analyzer Display’s Device Finder mode enables you to use your PC as a

“sniffer” to track down a specific interfering device. Device Finder is discussed in detail in

Section 8 on page 42.

HINT: To get started, you can right-click on any interferer shown in the Interferer List.

Assuming the device is currently transmitting, you can select Find This Device from the pop-up

menu. This starts the Device Finder mode. If the selected device is not currently active, the Find

This Device option will be grayed out.

6.2 Interferer Data

The Interferer List displays the following information about each interfering devices:

• Start Time – The time that the interferer became active.

• End Time – When the interferer ceased being active. Currently active devices are listed as

Currently Active.

• Interferer – The type of interference device (for example, Microwave Oven, or Bluetooth).

• Sensor Name – The sensor which detected the device.

• Avg. Pulse Duration – Average duration of pulses emitted by the device (if applicable).

• Center Frequency – The center frequency of the radiation emitted by the device.

• Bandwidth – The bandwidth of the energy emitted by the device.

• Average Power – The average power emitted by the device.

• Channels Affected – The 802.11 channels that are impacted by this interferer, if any.



Page 39


6.3 Miscellaneous Interferer Issues

This section describes miscellaneous issues you need to be aware of when viewing or interpreting

data on the Interferer List.

6.3.1 Signal Bounce and Fading

Narrowband signals—such as signals from analog FM cordless phones or analog video cameras—

are prone to “fading.” Signals naturally fade (grow weaker) with increased distance from an RF

signal source. But as a technical term, “fading” refers to the fact that as a signal travels, it bounces

and reflects off of multiple surfaces. So, at some distance from a single source, that single source

of RF power results in multiple signals (all from the same source) crisscrossing each other.

When a single RF signal—reflected from multiple directions—crosses paths with itself, the result

is signal interference. Signal interference can be constructive (resulting in a stronger signal at a

given point), or destructive (resulting in a weaker signal, or even no signal, at a distance not at all

far from the original source).

The result is that, at a given receiving antenna, the signal can vary greatly in power when the

antenna is moved just a few inches in any direction. To further complicate matters: As people and

other objects in the environment move, the source signal is reflected differently. So even if the

receiving antenna stays in one place, signal strength can vary unpredictably over time.

As a result, when AirMagnet Spectrum Analyzer is detecting a narrowband interferer, the detection

status may toggle on and off due to fading. Fading occurs in most indoor environments, and the

fluctuations in received signal level are typically correlated to the rate of motion for nearby

people/objects.

The presence of strong signals may further impair the ability of the classification software to detect

weaker signals. This is the so-called near/far effect, which is caused when the strong and weak

signals use up the limited dynamic range of the receiver. (In other words, the receiver can only

handle so much signal strength, in total, at one time. So if the receiver is getting two signals, the

strong one can swamp the weaker one.)

Example: When you walk near one cordless phone while you are simultaneously listening to

another cordless phone that’s far away (e.g., at your next-door neighbor’s house), you may find that

you lose the weaker signal. When you turn off the near-by cordless phone, you may find that you

can detect the weaker signal again.

These effects cannot be removed by AirMagnet Spectrum Analyzer. The only thing we can do is

make you aware of them, so that you can understand why it is that certain interferers fade in andout of view at times.

6.3.2 Device Detection Time

In general, the time required for AirMagnet Spectrum Analyzer to detect and classify devices (andreclassify their status, if they go from being On to Off, will vary depending on RF environment and

location of devices relative to your ASA. In general most devices (other than 802.11) should take

on the order of 5 to 30 seconds. However, 802.11a/b/g devices and 802.11 frequency hoppers may

take as long as ten minutes to be detected.



Page 40 Section 7. Channel Summary


7 CHANNEL SUMMARY

The Channel Summary shows specific levels of RF activity, such as average power and maximum

power, and whether or not interferers are present, on a channel-by-channel basis. This information

is very helpful in determining whether channel reallocations might improve your network performance.

Figure 7-1: Channel Summary

7.1 Working with the Channel Summary

To access the Channel Summary:

• Select the [Channel Summary] button ( ) on the tool bar, or…

• Select View Channel Summary

Sorting the Display – You can sort the display by any of the columns, simply by clicking on the

column heading.

7.2 Channel Data

The following data is presented for each channel:

• 802.11 Channel – The channel number. (The display is sorted by channel number by default.)

• Center Frequency – The center frequency of the channel, in MHz.

• 802.11 Present? – A check mark (√) in this field indicates that ASA detected activity by an

802.11 device (a, b, or g) during the last measurement interval.

• Duty Cycle – The current duty cycle of RF activity in that channel. In this case, the Duty

Cycle is essentially the percentage of the time that some signal was present in the 802.11



Page 41


channel during the last measurement interval. The Duty Cycle includes all RF energy, both

from 802.11 devices and interferers.

• Avg. Power – The average power being measured in that channel, in dBm. More specifically,

this is actually the log of the average power in the 802.11 channel over the last measurement

interval.

• Max. Power – This is the maximum received PSD (power spectral density) in an 802.11channel over the last measurement interval, expressed in dBm.

• Interferers Present – This is the number of active interferers that were seen to be transmitting

in a particular 802.11 channel in the last measurement interval.

• Max. Interferer Power – This is the maximum power that was received in the 802.11 channel,

by a classified interferer (that is, a known interferer), during one of its transmit bursts over the

last measurement interval. It is expressed in dBm.

• Interferer Duty Cycle – The duty cycle for interferers only. This is the percentage of time that

one or more pulses belonging to a classified interferer overlapped with the 802.11 channel

during the last measurement interval. (By “classified interferer”, we mean an interfering

device which ASA can recognize as being a specific type, such as a Bluetooth device or amicrowave oven, etc.)

7.3 Miscellaneous Channel Summary Issues

7.3.1 802.11 Detection Sensitivity

The threshold for AirMagnet Spectrum Analyzer software to detect 802.11 devices is an RF power

of approximately -80 dBm. This detection sensitivity is commensurate to that of a reliable 54

Mbps connection, so the detection range is less than 150ft at 2.4GHz and less than 100ft at 5GHz

in an indoor environment. In a large environment users should take detection measurements atseveral representative locations to cover entire area 802.11.

Please see the AirMagnet Spectrum Analyzer software release notes for more information.

7.3.2 802.11 Device Types

When AirMagnet Spectrum Analyzer software indicates that an 802.11 a/b/g signal is present on a

channel, this may or may not indicate an AP or network in use. It could also be a zero config client

(a station not currently affiliated with a network) which is transmitting probes, as it seeks out a

network.



Page 42 Section 8. Device Finder


8 DEVICE FINDER

In Device Finder mode, ASA acts as a lightweight portable probe which enables you to quickly

track down the location of a specific interfering device. Essentially, your ASA-enabled PC acts as

a wireless “sniffer.”

8.1 Overview

Here we present a summary description of how to put Device Finder to work. Detailed

instructions are presented in the next subsection.

• From the Interferer list select the device that you wish to locate.

• Carry the ASA system to different locations in the WLAN environment.

• At each location, use ASA to measure the signal strength from the device of interest.

• Using these signal strength measurements, identify when you are closer to—and further

from—the device of interest. Essentially, the signal strengths indicate when you are “getting

warmer” or “getting colder” in terms of getting near to the signal source of interest.

Based on these measurements, you can then home in on the location of the intruding device.

• You can also use the Measurement Log to record RF signal strength levels at specific

locations. If the “hotter/colder” approach is proving problematic—which may happen if, for

example, the signal is intermittent—the log keeps a record of where different RF levels were

recorded. You can use this information, possibly with the help of a map of your network

space, to triangulate the location of the interfering device.



Page 43


8.2 Working with Device Finder

To use the Device Finder:

1. Select View Device Finder, or select the [Device Finder] button ( ) on the tool bar atleft.

2. In the Interferer List, select the device you wish to locate. Then right-click on the device

name, and select Find This Device from the pop-up menu.

3. The device is now listed in the Device Finder. If the device has more than one possible signal

(such as a portable phone base station vs. the handset), you can select the signal of interestfrom the drop-down list box.

4. The Signal Strength History graph shows a moving plot of the signal strength. (The plot does

not automatically reset if the signal is lost.) This plot makes it easy to visualize when you are

walking towards or walking away from the source of the signal.

The Rx Signal Strength meter also provides a real-time indicator of the signal strength from

the device of interest, and is an additional tool in determining whether you are “getting

warmer” or “getting colder” in terms of tracking down the interfering device.





At moments, you will record a signal of special interest. The signal may suddenly peak or drop

off; or you may be systematically recording the signal at carefully planned locations.

5. To maintain a record of the signal of interest, select the

[Record Signal] button, or simply press the

<Spacebar> on your keyboard.

ASA records the current signal strength, along with the

time, in the Measurement Log. For a Description,

ASA uses the device name as a default value.

6. Type in a description of where the measurement was taken. Press the <Enter> key on your

keyboard to confirm your description.

7. You can also edit the location information in the Measurement Log at a later time. Simply

double-click on the description, and then key in your new description; then press <Enter>.

(Pressing <Esc> cancels any changes you are making.)

8.3 Additional Device Finder Features

The Device Finder has the following additional features and capabilities:

• Stop Finding – You can stop tracking the interferer by selecting the [Stop Tracking] button.

It is a good idea to do this after you have found the interferer of interest, since it reduces the

drain on system processing resources.

• Clear Signal Strength History – Select the [Clear] button under the Rx Signal Strength

History plot to clear the plot.

•

Clear Measurement Log – You can clear the Measurement Log of all data by selecting the[Clear Log] button under the log.

• Delete A Single Log Entry – You can also delete an individual row from the Measurement

Log. Simply select the entry, and then press the <Del> key on your keyboard. Then select

[Yes] in the confirmation dialog box.

• Reset Maximum Signal Strength – If you select [Reset Max], AirMagnet Spectrum Analyzer

deletes the current value for the maximum signal strength; AirMagnet Spectrum Analyzer then

ascertains, starting from "now", the maximum interferer signal strength that is measured from

this time forward.

• [Reset Max] only clears the Max Strength text box, and the black rectangular box that appears

around the bar in the vertical signal meter to indicate the highest strength seen. Use the [Clear]

button (above) to clear the plot.

• Reset Signal Averaging – If you select the [Reset Signal Averaging] button, AirMagnet

Spectrum Analyzer no long uses prior signal values to calculate the average signal strength.

Instead, AirMagne t Spectrum Analyzer only calculates average signal strength from "now"

forward, where "now" is when you select [Reset Signal Averaging].

If you are moving around—or changing the orientation of a directional antenna—this command

will cause the signal averaging measurement to restart, so you don’t display data that may be

representative of the prior position/orientation. A lot of filtering is applied to provide accurate



Page 45


measures, and this can help AirMagnet Spectrum Analyzer to respond more quickly, and not be

biased from prior measurements.

8.4 “Divide and Conquer” Search Strategy

To minimize your effort, and maximize your chances of locating the interferer in question, we

recommend that you use a “divide and conquer” search strategy (also know as “rectangular

bisection”). We illustrate the strategy, first with the omni-directional antenna, and then using the

directional antenna. (See Section 3.3.2 on page 13 for more on the directional antenna.)

To use this process, you will greatly benefit from using a physical map of your network space.

8.4.1 Omni-directional Antenna

For purposes of simplicity, assume that your interfering device is located somewhere within a large

rectangular office space (which might measure, for example, 50’ by 150’).

1. Go to each of the far corners of the office space, and measure the signal strength from theinterfering device of interest. Take note of which corner of the office yields the highest signal

strength. (A printed map of your office space can be helpful for jotting down data.)

2. In the corner which has the largest signal strength, map out a rectangular sub-search area

comprising one quarter of the total office space.





3. Repeat this process, as necessary, to localize your measurement.

4. By repeating this process, you will be able to home in on the location of the interfering device.

8.4.2 Directional Antenna

The advantage of using the directional antenna is that is can save yourself a substantial amount of

walking, because four measurements at a time can be made from one central location.

1. Once again, assuming a rectangular office space, take your AirMagnet Spectrum Analyzer to

the center of the office space. Use the directional antenna, with Device Finder, to determine

the signal strength coming from your interferer, as measured in each of four directions. For

each measurement, the antenna should be pointed towards each of the four corners of the

office.



Page 47


2. Once again, for the corner which has the largest signal strength, map out a rectangular sub-search area comprising one quarter of the total office space.

3. Repeat, again making measurements in the quadrant with the highest power reading.

4. Once again, you will learn from experience whether the final measurements are best made by a

continued process of rectangular bisection, or whether the final measurements should be made

on a systematic grid of a local area.





8.4.3 Detecting Narrowband Devices

Interfering devices fall into two RF categories, narrowband and wideband. By the very nature of

wideband transmissions, the signal strength from a wideband device—as measured at any onelocation—tends to be consistent. (If the directional antenna is in use, the signal strength from a

wideband device will tend to be consistent, at a given measurement location, and for a given

direction in which you point the antenna.)

By contrast, narrowband devices have certain signal peculiarities. Small changes in the physical

environment—changes which have nothing to do with the device emitting the signal—can cause

large fluctuations in the signal strength. For example, the simple movement of people or furniture

can change the way a narrowband signal is reflected throughout the enterprise space, resulting in

changes in signal strength as measured from some distance away.

Fortunately, most interferers are wideband, which makes life easier for users of ASA. However,

there are some interferers, such as some FM phones and TDD phones, which are narrowband

devices. The signal from these devices can vary significantly over the space of just a few inches.As a result, there are some simple antenna tricks to use when searching for such devices:

• Omni-directional antenna: If you are using the omni-directional antenna (including the built-

in antenna on the ASA Spectrum Sensor), it can be helpful to slowly, physically sweep the

ASA PC in an arc along several inches, until you achieve the maximum signal strength.

• Directional antenna: If you are using the directional

antenna, a similar trick applies. With the PC resting in place

(such as on a cart), and with the antenna pointed in a desired

direction, you can then slowly sweep the antenna along an arc

of roughly 30 degrees to 45 degrees, centered on the primary

direction of interest, until you achieve the maximum signal

strength.



Page 49


9 LOCAL SETTINGS

There are a number of settings you can change to determine how ASA operates and presents data.

The available settings are for:

• Antennas – Determine the type of antenna in use.

• Console Settings – Use this to change the date formats seen on screen.

• Channel Settings – Determines which 802.11 channels will be monitored by ASA.

• Monitored Bands – Determines how wide a bandwidth is actually monitored by the Spectrum

PC Card.

9.1 Antennas

To modify which Spectrum PC Card antennas are used by ASA:

1. Select Tools Settings.

The Antenna Selection panel should be displayed by default. If it is not, select the [Antennas]

button on the tool bar at left.

Figure 9-1: Settings – Sensors and Antennas

2. Select the antenna combination of interest. Your choices are:

• Internal Antenna – Tells the AirMagnet Spectrum Analyzer Display to use the data stream

from the internal antenna of the Spectrum PC Card installed in one of the PCMCIA slots in

your PC.

• External Antenna – Tells the AirMagnet Spectrum Analyzer Display to use the data

stream from the internal antenna of the Spectrum PC Card installed in one of the PCMCIA

slots in your PC.



Page 50 Section 9. Local Settings


3. Optionally, select the Ask When Program Starts check box. If you select this option, the

AirMagnet Spectrum Analyzer Display will present a dialog box each time the program starts,

asking you which Sensor to use.

If this check box is left unchecked, the AirMagnet Spectrum Analyzer Display will

“remember” your current setting, and assume it is the correct Sensor setting on start up.

4. Select [OK] to confirm your changes and close the dialog box. You can also select [Apply] to

apply your changes while leaving the dialog box open for further work.

9.2 Display Settings

This enables you to fine-tune how the AirMagnet Spectrum Analyzer displays data.

1. Select Tools Settings…,

2. From the tool bar on the left side of the dialog box, select Console Settings.

Figure 9-2: Settings - Console Settings

3. You can change the following settings using the drop-down list box:

Date Format Used In Interferer Log – This format is used wherever the date appears in the

Interferer List.





Page 51


9.3 Channel Settings

These settings allow you to customize the AirMagnet Spectrum Analyzer Display to use the

appropriate 802.11 channels for your current geographic region. In other words, ASA will only

monitor the channels you select here.

1. Select Tools Settings…,

2. From the tool bar on the left side of the dialog box, select Channel Settings.

Figure 9-3: Settings – Channel Settings

3. Select the channels to monitor for 802.11b/g, and select the channels to monitor for 802.11a.

Your options are:

Americas/Australia

EMEA/Asia/Pacific

Japan

All – Selects all available channels.

User Configure – If you select this radio button, you then need to check off individual

check boxes in the Channels list at right.

None – Deselects all channels.



Regulatory Domain channels are subject to change without notice, and may vary based

on:

• Whether the 802.11 devices are being used indoors or outdoors

• Protocol data rate and associated keying or modulation techniques



Page 52 Section 9. Local Settings


9.4 Monitored Bands

The Spectrum PC card is capable of monitoring up to 1 GHz of RF bandwidth at a time.

In practice, however, monitoring this much of the spectrum can result in some performance issues

for ASA. Moreover, for most practical applications, it is rarely necessary to monitor that much of

the spectrum at one time.

The Monitored Bands settings enable you to determine how much bandwidth is actually

monitored by the Spectrum PC Card. Monitoring only the bandwidth you need to monitor—rather

than trying to have the Spectrum PC Card scan its full potential range—will result in more

effective system performance.

• For Users-Defined Bands, ASA will only allow you to define bands which are consistent with

the monitoring capabilities of the Spectrum PC Card. Specifically, you bands must fall within

the ranges of 4.9 to 5.9 GHz and/or 2.4 to 2.5 GHz.

• If you change the settings for Monitored Bands, you must exit the application and restart the

AirMagnet Spectrum Analyzer Display before your settings will take effect.

• The bands you define here determine which Bands are available for selection on the spectrum plots. See the Section 5.3, Plot Controls on page 32, and in particular Section 5.3.1, Frequency

and Bandwidth To Monitor , on page 32, for more information.

• If you define two bands which are adjacent or which overlap (for example, 4.9 to 5.1 GHz, and

5.0 to 5.5 GHz), ASA will automatically consolidate the two bands into one band.

To define the bands you will monitor:

1. Select Tools Settings…

2. From the tool bar on the left side of the dialog box, select Monitored Bands.

Figure 9-4: Settings – Monitored Bands

3. Select one or more of the available check boxes. The options are described below.

4. Select [Apply] or [OK].



Page 53


9.4.1 Follow 802.11 Channel Plan

If you select the Follow 802.11 Channel Plan check box, all other options will be disabled.

Selecting this option tells ASA to only monitor the channels which are indicated on the Channel

Settings dialog (discussed immediately above, in Section 9.3 on page 51).

Example: If you select Follow 802.11 Channel Plan here; and on the Channel Settings dialogyou have selected Americas/Australia (the default setting); then the Mobile Spectrum Sensor will

only monitor channels 1 through 11 for 802.11 b/g, and the various appropriate channels for the

802.11a regulatory domain.

9.4.2 Pre-Defined Bands

You can select one or more of the Pre-Defined Bands, such as the 902 – 928 MHz band, the 2.4 to

2.5 GHz band, etc. Selecting all or most of the bands shown may result in reduced performance or

data quality, so we suggest that you select only those bands that are essential for your current

monitoring and testing needs.

9.4.3 User-Defined Bands

You can check the check boxes for one or both of the user-defined bands. You can also use the

radio buttons to determine how you will define the bands:

• Center Freq/Span – If you select this option, you can define your band(s) by entering the

central frequency for the band, and the total span. The band monitored will range from

CenterFrequency – Span/2 up to CenterFrequency + Span/2

• Start/Stop Freq – If you select this option, you can define your band(s) by a specific starting

frequency (at the low end), and a specific stop frequency (at the high end).



Page 54 Section 10. Glossary of Terms


10 GLOSSARY OF TERMS

Term Meaning

Fast Fourier Transform (FFT) A Fourier Transforms is a mathematical operation which takes a

waveform (such as RF waves), and determines the magnitude of the

different frequency components (sine waves and cosine waves) thatcomprise the wave. The numbers which give the magnitudes of the

sine and cosine waves can be thought of as a kind of RF “fingerprint”which distinctively identifies the wave. Waves which are very similar

to each other can be matched, because the numbers in their Fourier

Transforms will be very similar to each other.

A Fast Fourier Transform is a computational method which enables

Fourier Transforms to be performed very rapidly (on programmablechips, for instance), with some very minor imprecision.

Spectrum Analysis Engine (SAgE) The low-level hardware which provides for basic analysis of the RF

spectrum. SAgE feeds data to the MCU.

Wireless Local Area Network (WLAN) A computer network which uses wireless communication, such as

802.11 technology, and central Access Points (APs), to allow

computers to communicate without physical connecting wires.



Page 55


11 NOTICES AND DECLARATIONS

Note that this product is covered by several categories of regulation in a number of countries.

Changes or modifications not expressly approved by the manufacturer could void the user's

authority to operate the equipment in these regions.

11.1 FCC Notices

This equipment has been tested and found to comply with the limits for a Class B digital device,

pursuant to Part 15 of the FCC rules. These limits are designed to provide reasonable protection

against harmful interference when the equipment is operated in a residential installation. This

equipment generates, uses, and can radiate radio frequency energy and if not installed and used in

accordance with the instruction manual may cause harmful interference to radio communications.

However, there is no guarantee that interference will not occur in a particular installation. If this

equipment does cause harmful interference to radio or television reception, which can be

determined by turning the equipment off and on, the user is encouraged to try to correct the

interference by one or more of the following measures:

Reorient or relocate the receiving antenna.

Increase the separation distance between the equipment and the receiver.

Connect the equipment into an outlet on a circuit different from that to which the receiver

is connected.

Consult the dealer or an experienced radio TV technician for help.

11.2 Industry Canada's Interference Causing EquipmentStandard for Digital Apparatus

This Class B digital apparatus complies with Canadian ICES-003.

Cet appareil numérique de la Classe B est conforme à la norme NMB-003 du Canada.



Page 56 Section 11. Notices and Declarations


11.3 Declaration of Conformity

This equipment has been tested and conforms to the European Council Directive 89/336/EEC, StandardEN61326-1:1997/A2:2001 relating to Electromagnetic Compatibility for Laboratory Test Equipment.



Page 57


12 LIMITED WARRANTY

1. Products Warranty.

AirMagnet warrants that all Products (including associated firmware) sold by AirMagnet to

Customer under the terms of this Agreement will be free from defects in workmanship andmaterials and shall fully comply with: (i) the Product Specifications as published undernormal use and service, (ii) the End User documentation and (iii) all applicable UnitedStates laws, rules and regulations in effect at the time of Product shipment to Customerfor a period of one (1) year after shipment to Customer. If any Product, or part thereof,contains a defect in materials or workmanship, or otherwise fails to conform to theSpecifications, during the warranty period, AirMagnet shall, at its option and expense,correct any such defect by replacing, or repairing such defective Product.

2. Warranties Exclusive.

THE FOREGOING WARRANTIES, TERMS OR CONDITIONS ARE EXCLUSIVE ANDARE IN LIEU OF ALL OTHER WARRANTIES, TERMS OR CONDITIONS, EXPRESS OR

IMPLIED, EITHER IN FACT OR BY OPERATION OF LAW, STATUTORY OROTHERWISE, INCLUDING WARRANTIES, TERMS OR CONDITIONS OFMERCHANTABILITY, NON-INFRINGEMENT OF THIRD PARTY RIGHTS, ANDFITNESS FOR A PARTICULAR PURPOSE.

3. Warranty Exclusions.

AIRMAGNET SHALL NOT BE LIABLE UNDER THIS WARRANTY IF ITS TESTING AND

EXAMINATION DISCLOSES THAT THE ALLEGED DEFECT IN THE PRODUCT DOES

NOT EXIST OR WAS CAUSED BY CUSTOMER'S OR ITS END USER'S MISUSE,

NEGLECT, IMPROPER INSTALLATION OR TESTING, UNAUTHORIZED ATTEMPTS TO

REPAIR, OR BY ACCIDENT, FIRE, LIGHTNING OR OTHER HAZARD. AIRMAGNET

DOES NOT WARRANT THE ACCURACY OR COMPLETENESS OF THE INFORMATION,TEXT, GRAPHICS, LINKS OR OTHER ITEMS TRANSMITTED BY THE PRODUCTS.

4. Product Repairs.

AirMagnet will Repair a defective Product and forward the same back to Customer.AirMagnet will upgrade Repaired Product to the most recent engineering change level.Any Repaired Product shall be warranted for three (3) months or the remainder of theinitial warranty period, whichever is longer. This statement excludes Products that hasbeen damaged by accident, abuse or misuse. AirMagnet's obligation to Repair defectiveProducts under this section is subject to Customer's strict adherence to the RMAprocedures set forth in Section 5.

5. Return Material Authorization (RMA).

AirMagnet shall provide Customer with RMA procedures. The following procedure shallapply to AirMagnet’s Repair of Products.

(i) Management. AirMagnet will use its best efforts to provide Customer with an RMAnumber within three (3) business days after receipt of request. Customer will shipRMA returns to AirMagnet with enough information to allow AirMagnet to reproducethe problem promptly.



Page 58 Section 12. Limited Warranty


(ii) Turn-Around Time. AirMagnet will Repair any defective Product within which itcan reproduce the problem and forward the same back to Customer within five (5)business days after receipt. At Customer’s option, AirMagnet will provide advancedreplacement unit as in AirMagnet’s published price list.

(iii) Shipping charges. During the warranty period, Customer will pay transportation

charges and assume risk of loss for Products shipped to AirMagnet for Repair.AirMagnet will pay transportation charges by UPS ground or FedEx ground serviceand assume risk of loss for all Products returned to Customer during the warrantyperiod. Customer can request and pay for expedited service by providing Customer’sown UPS or FedEx number, or by credit card prepayment. After warranty expires,Customer shall pay all (round trip) shipping charges.

(iv) Packaging requirements. On all Products returned to Customer, AirMagnet willaffix label that identifies Product, including model number, serial number, currentrevision level, and RMA number.

6. Pricing and Out of Warranty Repairs.

There is no charge for in-warranty Repairs, except as provided in Section 3. For eachProduct purchased under this Agreement, AirMagnet agrees to make out of warrantyrepair services available to Customer for a period of three (3) years after the expirationof the one (1) year warranty period for such Product. Charges for out of warrantyrepair services, upgrade kits, and spare parts will be at AirMagnet’s published pricelist.

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