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Antennas and RF Considerations for Outdoor WLANs Chuck Lukaszewski, Director of Professional Services
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Page 1: Antennas and RF Considerations for Outdoor WLANstkb/94/1/AirHeads Rio...The Horizontal Range of the downtilt antenna is much less than the high gain antenna. A common mistake is to

Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved.

Antennas and RF Considerations for Outdoor WLANs Chuck Lukaszewski, Director of Professional Services

Page 2: Antennas and RF Considerations for Outdoor WLANstkb/94/1/AirHeads Rio...The Horizontal Range of the downtilt antenna is much less than the high gain antenna. A common mistake is to

Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved.

Agenda

1. The need for the Outdoor WLAN

2. Antenna Radiation Principles & Patterns

3. Mechanical Downtilt

4. 3D Visualization and Outdoor Coverage Strategies

5. Outdoor Physical Installation Basics

6. Case Study – Railyard

7. Case Study – University Campus

8. Case Study – Manufacturing Plant

Page 3: Antennas and RF Considerations for Outdoor WLANstkb/94/1/AirHeads Rio...The Horizontal Range of the downtilt antenna is much less than the high gain antenna. A common mistake is to

Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved.

Outdoor WLAN Examples

** Many photos from real Aruba deployments

Page 4: Antennas and RF Considerations for Outdoor WLANstkb/94/1/AirHeads Rio...The Horizontal Range of the downtilt antenna is much less than the high gain antenna. A common mistake is to

Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved.

Outdoor WLAN Examples

Page 5: Antennas and RF Considerations for Outdoor WLANstkb/94/1/AirHeads Rio...The Horizontal Range of the downtilt antenna is much less than the high gain antenna. A common mistake is to

Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved.

Aruba’s Outdoor Portfolio

5

ArubaOS Secure Mesh Software • Software module for

ArubaOS

• Turn any Aruba AP into a

wire-free mesh node

• Place APs anywhere

• Enterprise-grade security

Outdoor Access Systems

Outdoor Planning and Management Tools • Visualize outdoor coverage

in three dimensions

• Calculate path loss

automatically

• Pre-loaded with all Aruba

antenna types

• GIS integration

• AP-85 / AP175P for

centralized control and

management

• MSR2000 / MSR4000

standalone mesh routers

• Wide range of antennas

AP-85 AP175P Outdoor Antennas

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Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved.

ServiceEdge Partner Network Outdoor installations are labor intensive

and require experienced professional services

ServiceEdge includes partners with significant experience in outdoor design & installation using Aruba APs & antennas

ServiceEdge also includes partners with electrical engineering skills for solar/battery assist solutions

Online Directory Aruba Outdoor Design & Installation

Electrical Engineering

Page 7: Antennas and RF Considerations for Outdoor WLANstkb/94/1/AirHeads Rio...The Horizontal Range of the downtilt antenna is much less than the high gain antenna. A common mistake is to

Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved.

Agenda

1. The need for the Outdoor WLAN

2. Antenna Radiation Principles & Patterns

3. Mechanical Downtilt

4. 3D Visualization and Outdoor Coverage Strategies

5. Outdoor Physical Installation Basics

6. Case Study – Railyard

7. Case Study – University Campus

8. Case Study – Manufacturing Plant

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Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved. 3-8

Understanding Antenna Patterns

The Basic Antenna is the isotropic radiator This is an ideal concept and not a real antenna The isotropic radiator has Gain=1 (0 dBi) and

radiates in all directions equally (a sphere)

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Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved. 3-9

Understanding Antennas

Real antennas always distort the ideal isotropic pattern Antennas do not create or destroy power, but rather “focus”

energy into a tighter region of 3D space This focusing effect is called “Gain” The higher the gain, the more tightly focused the coverage

pattern of the antenn is in a particular direction This creates regions in space of

Higher power density (Gain >0 dBi) (i.e. “Gain”) But also regions of lower power density (Gain<0 dBi) (i.e. “Loss)

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Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved. 3-10

Beam-width and Patterns Half-power or 3 dB

beam-width in degrees Measure of how an

antenna directs the energy it radiates

Represented as a polar plot for horizontal (azimuth) and vertical (elevation)

Approx. 52 degrees

-3 dB

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Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved. 3-11

Reading Antenna Pattern Plots

Azimuth Elevation

Sector Antenna

-3 dB

-3 dB

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Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved. 3-12

Antennas – The Elevation Challenge AP on Pole @ 45m height

Mobile Client (Lifter @ 15m height)

Fixed Clients (View from

Crane @ 65m height)

Personnel ( Laptops @ 2m height)

Example : GROUND to 65m High Client Coverage is desired!

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Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved. 3-13

Antennas – Horizontal Coverage Map AP85 with

AP-ANT-86

802.11A, 6 Mbit/s

Range appx 500m

What about higher

data rates?

Plan View

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Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved. 3-14

Antennas – Elevation Issue – Calculator Results

(5 GHz, 802.11A, AP-ANT-86)

802.11A Data Rates and Predicted Maximum Distances 6 18 36 54

Max Predicted Distance (m) 511.1 287.4 128.4 72.2

RSSI at Client (dB) 10.0 15.0 21.0 23.0RSSI at AP (dB) 4.0 9.0 16.0 21.0

Wireless Date Rate (Mbits/sec)

RSSI (dB)

0.0

5.0

10.0

15.0

20.0

25.0

0.0 100.0 200.0 300.0 400.0 500.0 600.0Distance (Meters)

ClientAP

Data Rate (Mbit/s)

6.0

18.0

36.0

54.0

0 100 200 300 400 500 600Distance (Meters)

6 Mbps at appx 500m Higher Rates Closer

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Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved. 3-15

What Really Happens ?

30m

72m

Try to improve by

walking closer, example

walk in to 51m

Signal increases

20log(72m/50m)= 3 dB

due to closer distance

But drops another -17

dB due to antenna

elevation (E-plane)

pattern!

Net is a 14 dB weaker

signal by moving closer!

In fact, with 30m

mounting height and this

antenna, you can walk

into the pole and will

never see -65 dBm/54

Mbps

Q: Why am I not getting a -65 dBm (54 Mbps) signal @ 72m?

A: Because client elevation is not aligned with direction of maximum gain.

51m

ELEVATION VIEW

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Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved.

High Gain Antenna 8 dBi

Vert BW: 14° Max Range: 481m

(AP-ANT-80)

Lower Gain Antenna 5 dBi

Vert BW 30° Max Range: 341m

(AP-ANT-8)

Down Tilt Antenna 3 dBi

Vert BW 60° Centered at -45°

Max Range 270m

Horizontal Vertical Antenna Comparison – Omnidirectional Antennas

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Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved.

Antenna Comparison (Plan View)

High Gain Omni (8 dBi) The Horizontal Range of the downtilt antenna is much less than the high gain antenna. A common mistake is to simply choose the higher gain antenna expecting more “coverage” and “overlap” for redundancy. Note that above plots are for two APs operating on the same channel, 54 Mbps coverage and at a reduced power setting (10 dBm)

Downtilt Omni (3 dBi)

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Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved.

Antenna Comparison (Elevation View)

High Gain Omni Downtilt Omni The Elevation View shows the vertical pattern of the same antennas when mounted at a 40 ft ceiling height. From this view it is clear that the high gain antennas will interfere with other APs on the same channel, but coverage does not reach the clients on the floor. The downtilt omni has coverage that reaches the floor and does not overlap at the AP height.

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Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved.

Direction of Maximum Gain at 0º, Gain=8 dBi

8dBi - 10dB = -2 dBi @ -20º

8dBi – 20dB = -12 dBi @ 80º

High Gain Omnidirectional (8 dBi, 2.4 GHz)

This way up

Highest gain is directed At next AP instead of clients!

Weakest signal is directed to clients!

Vertical Coverage: High Gain Omni

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Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved.

Vertical Coverage: Downtilt Omni

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Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved.

Beneficial Effect of Downtilt Antenna on AP-AP Interference

The Downtilt Pattern has maximum gain at 45 degrees down. This reduces the AP to AP signal by appx 11 dB below the signal seen by clients standing on the ground due to the pattern of the downtilt omnidirectional antenna.

-8 dB

+3 dB

Side (elevation) View

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Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved. 3-22

Summary: Antenna Basics Higher Gain is always at the expense of coverage,

usually vertical coverage. Always think about the direction of gain relative to the

client locations. Clients should be within the -3 dB Area (horizontal and vertical) whenever possible.

For successful outdoor (or large indoor) planning, vertical coverage is usually a critical design requirement. Pay attention to the vertical pattern plots and the elevation of the clients relative to the proposed mounting heights.

For overhead installation, outdoor down tilt antenna (AP-ANT-90) helps considerably with very high mounting conditions (6m up to 50m) in some of the most challenging environments such as container facilities.

Page 23: Antennas and RF Considerations for Outdoor WLANstkb/94/1/AirHeads Rio...The Horizontal Range of the downtilt antenna is much less than the high gain antenna. A common mistake is to

Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved.

Agenda

1. Aruba Outdoor Products & Experience

2. Antenna Radiation Principles & Patterns

3. Mechanical Downtilt

4. 3D Visualization and Outdoor Coverage Strategies

5. Outdoor Physical Installation Basics

6. Case Study – Railyard

7. Case Study – University Campus

8. Case Study – Manufacturing Plant

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Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved. 3-24

Overhead/Plan View (No Downtilt)

AP-ANT-82 (12 dBi Sector) AP-ANT-83 (7 dBi Sector)

As expected, the higher gain antenna has much more range

and appears to have more coverage. The antenna mast at

this outdoor concert venue is 30m high.

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Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved. 3-25

Elevation/Side View (No Downtilt)

The side view shows that the 12 dBi sector coverage doesn’t reach the ground due to it’s narrow vertical beamwidth.

Some of the lower gain (7 dBi) sector reaches the ground.

How much can either be improved by some mechanical downtilt.

AP-ANT-82 (12 dBi) AP-ANT-83 (7 dBi)

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Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved. 3-26

High Gain Antenna with Downtilt

10 degree downtilt 15 degree downtilt 30 degree downtilt

Slight downtilt Severe downtilt

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Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved. 3-27

Low Gain Antenna with Downtilt

10 degree downtilt 15 degree downtilt

Slight downtilt

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Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved. 3-28

Summary: Mechanical Downtilt High-gain antennas have very narrow vertical

beamwidths Even relatively modest mounting heights (e.g. 10m-

15m) and small mechanical downtilts (e.g. 10-15 degrees) result in the “striping” effect on the ground which significantly reduces coverage

Mechanical downtilt is ineffective as a solution to compensate for narrow vertical beamwidth

Narrow vertical-beamwidth (i.e. high gain) antennas are best utilized for long-distance point-to-point links and not as client access antennas unless the elevation between the clients and the antennas is very carefully controlled, typically a maximum of 2m separation in elevation between clients and antennas is recommended for antennas with gain >5 dBi.

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Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved.

Agenda

1. Aruba Outdoor Products & Experience

2. Antenna Radiation Principles & Patterns

3. Mechanical Downtilt

4. 3D Visualization and Outdoor Coverage Strategies

5. Outdoor Physical Installation Basics

6. Case Study – Railyard

7. Case Study – University Campus

8. Case Study – Manufacturing Plant

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Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved.

Aruba Networks has developed a proprietary outdoor planning and mesh visualization tool

Uses Patent Pending process to render and display 3D coverage models from AP settings and coverage patterns of antennas used

Accounts for actual antenna mounting heights, downtilt and terrain effects

Model/Planning output is viewable in Google Earth and other GIS (kml compatible) systems

Aruba Networks Outdoor 3D Visualization

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Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved.

Aruba Networks Outdoor RF Coverage and Mesh Planning

Mesh and Coverage View

3D Coverage View

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Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved.

3D Models can also be included for Better Visualization

Coverage

Building Models Added

Aruba Networks Outdoor 3D Visualization

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Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved.

Outdoor Planner - Mesh Planning

View coverage and Mesh Plans simultaneously

Page 34: Antennas and RF Considerations for Outdoor WLANstkb/94/1/AirHeads Rio...The Horizontal Range of the downtilt antenna is much less than the high gain antenna. A common mistake is to

Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved.

Agenda

1. Aruba Outdoor Products & Experience

2. Antenna Radiation Principles & Patterns

3. Mechanical Downtilt

4. 3D Visualization and Outdoor Coverage Strategies

5. Outdoor Physical Installation Basics

6. Case Study – Railyard

7. Case Study – University Campus

8. Case Study – Manufacturing Plant

Page 35: Antennas and RF Considerations for Outdoor WLANstkb/94/1/AirHeads Rio...The Horizontal Range of the downtilt antenna is much less than the high gain antenna. A common mistake is to

Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved. 3-35

Safety and Compliance

Aruba Access Points, antennas, and the AP-LAR-1 lightning arrestor are required to be installed by a professional installer

The professional installer is responsible for ensuring that grounding is available and it meets applicable local and national electrical codes

Do not work on an AP and do not connect or disconnect cables during periods of lightning activity

Never stand in front of any antenna system

Page 36: Antennas and RF Considerations for Outdoor WLANstkb/94/1/AirHeads Rio...The Horizontal Range of the downtilt antenna is much less than the high gain antenna. A common mistake is to

Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved.

AP Mounting Use Cases Most Enterprise outdoor deployments fall into 4

categories

Rooftop/Tower (Mast) Mount

Street Pole Mount

Rooftop/Perimeter Mount

High Mast Light Ring Mount

Page 37: Antennas and RF Considerations for Outdoor WLANstkb/94/1/AirHeads Rio...The Horizontal Range of the downtilt antenna is much less than the high gain antenna. A common mistake is to

Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved.

Your Basic Non-Penetrating Roof Mount

Non-Penetrating

Roof Mount (from

Tessco or Talley)

Cat5E and Ground to

Perimeter APs

Fiber backhaul to MDF

in Schedule 40 conduit

120VAC to main panel

in EMT conduit

Verified ground to

Building Steel

Protective Mat

underneath mount

Wind load ballast

(30lb cinder blocks)

Equipment Enclosure

with thermal control

(install-specific)

Two AP85TX clamped

to mast

Copper grounding

busbar (insulated

from mast)

Separate grounds to

each AP and LAR

(total of 5)

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Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved.

Rooftop Perimeter Coverage

Dual ANT-91 5dBi 120º Sector

View from ground level

AP85TX bolted

to Aruba wall-

mount bracket

Lightning arrestors on

EACH antenna lead

Copper grounding

busbar connected to

building steel

Cat5E in conduit

with hood

(ground strapped

to outside)

All

penetrations

sealed

AP

ground

lead

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Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved.

Mesh Point Installation on High Masts AP, antennas and Battery Assist system with battery

and charger may all be required.

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Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved.

Agenda

1. Aruba Outdoor Products & Experience

2. Antenna Radiation Principles & Patterns

3. Mechanical Downtilt

4. 3D Visualization and Outdoor Coverage Strategies

5. Outdoor Physical Installation Basics

6. Case Study – Railyard

7. Case Study – University Campus

8. Case Study – Manufacturing Plant

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Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved.

Outdoor Yard Coverage Strategies

There are three basic RF design strategies for large outdoor facilities:

1. Sparse Side Coverage 2. Dense Side Coverage 3. Dense Overhead Coverage

Definitions Coverage is sparse when a small number of locations cover

a large space with high-gain directional antennas Coverage is dense when many APs that are relatively

evenly spaced cover a large area with low-gain antennas Side coverage means that the main lobe of the antenna is

approximately the same elevation as the clients being served

Overhead coverage refers to the use of “squint” or downtilt antennas that face downwards but offer 360 degree pattern

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Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved.

Typical Sparse Side Coverage Limited mounting locations, re-using preexisting RF plan from

another frequency (e.g. 900MHz) High-gain antennas 15m AGL with mechanical downtilt Inconsistent cell overlap, static channel plan, cannot use ARM

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Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved.

Typical Dense Overhead Coverage Mount many APs to existing light poles 30m AGL with low-gain

downtilit antennas 5GHz mesh backhaul; Leverage existing towers for mesh

portals Overlapping cells for smooth roaming & redundancy; ARM

works

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Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved.

Measured vs. Predicted Coverage

Predicted 18Mbps (-76dBm) isocontour @ 6dB Margin

18Mbps coverage exceeded minimum requirements as measured at ground level.

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Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved.

HM45 – 18Mbps Predicted 18Mbps (-76dBm) isocontour @ 6dB Margin

18Mbps (SNR=9)

predicted to 360 feet

18Mbps (SNR=9)

measured to >700 feet uniformly

18Mbps (SNR=9)

measured to >1,400 feet down track

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Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved.

Agenda

1. Aruba Outdoor Products & Experience

2. Antenna Radiation Principles & Patterns

3. Mechanical Downtilt

4. 3D Visualization and Outdoor Coverage Strategies

5. Outdoor Physical Installation Basics

6. Case Study – Railyard

7. Case Study – University Campus

8. Case Study – Manufacturing Plant

Page 47: Antennas and RF Considerations for Outdoor WLANstkb/94/1/AirHeads Rio...The Horizontal Range of the downtilt antenna is much less than the high gain antenna. A common mistake is to

Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved.

University Campus

AP count is driven by Users/AP for dense areas and building locations (i.e. getting around them)

Design goal was 3-4 AP’s visible to users in dense areas, and 2 AP’s visible everywhere else

10 dB design margin is conservative but recommended due to trees/buildings/bodies

Above strategy results in 54 APs for the initial coverage shown, up to 70 APs are recommended to provide coverage of perimeter areas such as parking lots, etc. presently shown uncovered in following slides.

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Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved.

Desired Coverage Area

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Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved.

802.11G: 54 Mbps Coverage

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Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved.

802.11G:24 Mbps Coverage

Page 51: Antennas and RF Considerations for Outdoor WLANstkb/94/1/AirHeads Rio...The Horizontal Range of the downtilt antenna is much less than the high gain antenna. A common mistake is to

Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved.

Agenda

1. Aruba Outdoor Products & Experience

2. Antenna Radiation Principles & Patterns

3. Mechanical Downtilt

4. 3D Visualization and Outdoor Coverage Strategies

5. Outdoor Physical Installation Basics

6. Case Study – Railyard

7. Case Study – University Campus

8. Case Study – Manufacturing Plant

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Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved.

Coverage Requirement – Manufacturing Plant

5 Mesh Portals mounted to main plant providing backhaul on 5Ghz and client service on 2.4Ghz ANT-91 (5dBi dual-band) for both

2 Mesh Points mounted to Guard Building and Pump Building with 5Ghz backhaul only to provide local wireless service.

14 Mesh Points mounted to standard street lights powered via AC power tap with backhaul on 5Ghz and client service on 2.4Ghz

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Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved.

Predicted Coverage @ 54Mbps Predicted 54Mbps (-67dBm) isocontour @ 6dB Margin

54Mbps

(SNR=21) predicted to

220 feet from mesh portal on wall with ANT-91

54Mbps (SNR=21)

predicted to 100 feet

from mesh point on light pole

with ANT-90

Page 54: Antennas and RF Considerations for Outdoor WLANstkb/94/1/AirHeads Rio...The Horizontal Range of the downtilt antenna is much less than the high gain antenna. A common mistake is to

Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved.

Predicted Coverage @ 24Mbps Predicted 54Mbps (-67dBm) isocontour @ 6dB Margin

24Mbps

(SNR=12) predicted to

630 feet from mesh portal on wall with ANT-91

24Mbps (SNR=12)

predicted to 260 feet

from mesh point on light pole

with ANT-90

Page 55: Antennas and RF Considerations for Outdoor WLANstkb/94/1/AirHeads Rio...The Horizontal Range of the downtilt antenna is much less than the high gain antenna. A common mistake is to

Aruba Networks CONFIDENTIAL. © 2010 All Rights Reserved.

Thank You!


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