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Understanding RF Fundamentals and the Radio Design of Wireless Networks

BRKEWN-2017

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Session Abstract

In this session we will focus on the fundamentals of Radio

Frequency (RF) and how we design wireless networks while keeping these in mind.

We will look at the impact of interference, both co-channel and external, and how we mitigate it's impact. We will also look at emerging approaches to deal with the challenges posed by RF.

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3

Session Agenda

– Objectives

What is radio and how did we get here?

Basic 802.11 Radio Hardware & Terminology

802.11 Antenna Basics

– Single, Diversity, Dual Band and MIMO

Antennas

Interpreting antenna patterns

– Cisco Radio Facilities

Diversity, Multipath, ClientLink Beamforming - 802.11n RF characteristics

Choosing the right Access Point

Placing the AP and the antennas properly

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4

What is Radio?

How Did We End Up on These

Frequencies?

Basic Understanding of Radio…

AC Frequency 60 Hz or 60

CPS – Cycles Per Second

Waves travel back and forth so fast they actually leave the wire

Battery is

D irect C

DC urrent

Typical home is AC

A lternating C urrent

How fast the AC current goes, is its “frequency”

AC is very low frequency 50-60 Hz (Cycles Per Second)

Radio waves are measured in kHz, MHz and GHz

The lower the frequency, the physically longer the radio wave – Higher frequencies have much shorter waves, and as such, it takes more power to move them greater distances. This is why 2.4 GHz goes further then

5 GHz (given same amount of RF power).

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Popular Radio Frequencies:

AM Radio 520-1610 KHz

Shortwave 3-30 MHz

FM Radio 88 to 108 MHz

Aviation 108-121 MHz

Weather Radio 162.40 MHz

GSM Phones 900 & 1800 MHz

DECT Phones 1900 MHz

Wi-Fi 802.11b/g/n 2.4 GHz

Wi-Fi 802.11a/n 5 GHz

Cisco Public

Vintage RF

Transmitter

6

The Radio Spectrum in Australia

5GHz

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2.4GHz

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Wi-Fi Radio Spectrum

2.4 GHz

5 GHz

Wi-Fi is an “unlicensed” service

It has beginnings in the ISM (industrial Scientific Medical) band where it was not desirable or profitable to license such short range devices.

The first frequencies available for

Wi-Fi use were in the 2.4 GHz range

As Wi-Fi popularity and usage increased, the regulatory bodies allocated additional spectrum in the

5 GHz band.

The spectrum we use today is also used by Amateur (Ham Radio) and other services such as radio location

(radar).

There is more bandwidth in 5 GHz with mechanisms in place to co-exist with licensed services such as radar using Dynamic Frequency Selection

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Wi-Fi Radio Spectrum 2.4 GHz

The 2.4 GHz spectrum in Australia has 3 non-overlapping channels

1, 6 and 11.

Even today, many portable devices in use are limited to 2.4 GHz only, including newer devices, but this is changing.

802.11b/g is 2.4 GHz

802.11a is 5 GHz

802.11n (can be either band) 2.4 or 5 GHz

There are plenty of channels in the

5 GHz spectrum and they do not overlap

2.4 GHz and 5 GHz are different portions of the radio band and usually require separate antennas

Most, if not all, 5 GHz devices also have support for 2.4 GHz - however there are still many 2.4 GHz only devices.

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Wi-Fi Radio Spectrum 2.4 GHz

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Wi-Fi Radio Spectrum 5 GHz Channels

Note: 5 GHz channels do not have the severe overlap that

2.4 GHz channels have but they use DFS to enable sharing of the band

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Dynamic Frequency Selection (DFS) 5 GHz

When Radar Signal is Present

Access Points detect radar activity and change channels so as not to cause interference with this licensed service.

This can result in lower available channels and loss of some UNII-2 and

UNII-2 extended bands.

UNII-1 and UNII-3 bands are outside of the weather radar and do not change.

Radar signals may be present near airports, military bases or large cities

UNI 1

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UN 3

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12

A Radio Needs a Proper Antenna

As the frequency goes up, the radiating element gets smaller

Antennas are identified by colour

Blue indicates 5 GHz

Black indicates 2.4 GHz

Orange indicates Both

Omni-Directional antennas like the one on the left, radiate much like a raw light bulb would everywhere in all directions

Antennas are custom made for the frequency to be used. Some antennas have two elements to allow for both frequencies in one antenna enclosure. Cisco AP-3600 uses such antennas.

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Directional antennas like this

“Patch” antenna radiate forward like placing tin foil behind the light bulb or tilting and directing the lamp shade

Note: Same RF energy is used but results in greater range as it is focused towards one direction, at the cost of other coverage areas

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Basic 802.11 RF Terminology

Hardware Identification

Common RF Terms

For Your

Reference

Attenuation

– a loss in force or intensity – As radio waves travel in media such as coaxial cable attenuation occurs.

BER

– Bit Error Rate

- the fraction of bits transmitted that are received incorrectly.

Channel Bonding

– act of combining more than one channel for additional bandwidth dBd

– abbreviation for the gain of an antenna system relative to a dipole dBi

– abbreviation for the gain of an antenna system relative to an isotropic antenna dBm

– decibels milliwatt -- abbreviation for the power ratio in decibels (dB) of the measured power referenced to one milliwatt of transmitted RF power.

Isotropic antenna

– theoretical “ideal” antenna used as a reference for expressing power in logarithmic form.

MRC

– Maximal Ratio Combining a method that combines signals from multiple antennas taking into account factors such as signal to noise ratio to decode the signal with the best possible Bit Error Rate.

Multipath

– refers to a reflected signal that combines with a true signal resulting in a weaker or some cases a stronger signal. mW

– milliwatt a unit of power equal to one thousandth of a watt (usually converted to dBm)

Noise Floor

– The measure of the signal created from the sum of all the noise sources and unwanted signals appearing at the receiver.

This can be adjacent signals, weak signals in the background that don’t go away, electrical noise from electromechanical devices etc.

Receiver Sensitivity

– The minimum received power needed to successfully decode a radio signal with an acceptable BER. This is usually expressed in a negative number depending on the data rate. For example the AP-1140 Access Point requires an RF strength of at least negative -91 dBm at 1 MB and an even higher strength higher RF power -79 dBm to decode 54 MB

Receiver Noise Figure

– The internal noise present in the receiver with no antenna present (thermal noise).

SNR

– Signal to Noise Ratio – The ratio of the transmitted power from the AP to the ambient (noise floor) energy present.

TxBF

– Transmit beam forming the ability to transmit independent and separately encoded data signals, so-called

streams

, from each of the multiple transmit antennas changing the timing so the client can best decode the information. Sometimes called Cisco Client Link.

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Identifying RF Connectors

RP-TNC Connector

Used on most Cisco Access Points

“RP-SMA” Connector

Used on some Linksys Products

“N” Connector

Used on the 1520 and 1550 Mesh APs

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“SMA” Connector

“Pig tail” type cable assemblies

Cisco Public

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Antenna Cables

– LMR Series

This is a chart depicting different types of Microwave LMR Series coaxial cable.

Cisco uses Times Microwave cable and has standardised on two types:

Cisco Low Loss (LMR-400)

Ultra Low Loss (LMR-600).

LMR-600 is recommended when longer cable distances are required

Larger cables can be used but connectors are difficult to find and larger cable is harder to install

Trivia: LMR Stands for “Land Mobile Radio”

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Some Antenna Cables Characteristics

Foil shield and braid

LMR-400 3/8 inch

LMR-600 ½ inch

LMR type cable has a

Cisco P/N like this…

AIR-CAB-050-LL-R

AIR - Aironet

CAB – Cable

050 - Length

LL - Low Loss (LMR-400)

R - RP-TNC connector

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BRKEWN-2017

802.11 Antenna Basics

How Does a Omni-Directional Dipole

Radiate?

The radio signal leaves the centre wire using the ground wire (shield) as a counterpoise to radiate in a 360 degree pattern

Low gain Omni radiates much like a bulb “360”

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Antenna Theory (Dipole & Monopole)

Dipole

Monopole

A Monopole requires a ground plane – (conductive surface)

A dipole does not require a ground plane as the bottom half is the ground (counterpoise).

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808 Ft Broadcast Monopole

WSM 650 AM (erected in 1932)

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Antenna Theory (Dipole & Monopole)

Monopoles were added to our antenna line primarily for aesthetics

Monopoles are smaller and require a metal surface to properly radiate

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How Does a Directional Antenna Radiate?

Although you don’t get additional RF power with a directional antenna, it does concentrate the available energy into a given direction resulting in greater range, much like bringing a flashlight into focus.

Also a receive benefit - by listening in a given direction, this can limit the reception of unwanted signals (interference) from other directions for better performance.

A dipole called the “driven element” is placed in front of other elements.

This motivates the signal to go forward into a given direction for gain.

(Inside view of the Cisco AIR-ANT1949 - 13.5 dBi Yagi)

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Patch Antenna: a Look Inside

Patch antennas can have multiple radiating elements that combine for gain.

Sometimes, a metal plate is used behind the antenna as a reflector for more gain.

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The 9.5 dBi Patch called AIR-ANT5195-R

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Antennas Identified by Colour

Cisco Antenna

Colour Coding

Black indicates

2.4 GHz

Blue indicates

5 GHz

Orange indicates

2.4 & 5 GHz

(used on AP-3600)

Cisco antennas & cables are colour coded – Black or no markings indicate 2.4

GHz

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Guide to Antenna Part Numbers

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Most Common 802.11n Antennas

Indoor Access Points (1262 and 3502e)

Product ID Description Gain

AIR-ANT2451NV-R=

2.4 GHz 3 dBi/5 GHz 4 dBi 802.11n dual band omni antenna (6)

3 dbi / 4 dBi

AIR-ANT2460NP-R= 2.4 GHz 6 dBi 802.11n directional antenna (3) 6 dBi

AIR-ANT5160NP-R= 5 GHz 6 dBi 802.11n directional antenna (3) 6 dBi

AIR-ANT2422SDW-R=

AIR-ANT5135SDW-R=

2.4 GHz 2.2 dBi Short white dipole antenna (1)

5 GHz 3.5 dBi Short white dipole antenna (1)

2.2 dBi

3.5 dBi

AIR-ANT2450NV-R= 2.4 GHz 5 dBi 802.11n Omni wall mount antenna (3) 4 dBi

AIR-ANT5140NV-R= 5 GHz 4 dBi 802.11n Omni wall mount antenna (3) 4 dBi

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Dual Band Antennas for AP3600

Product ID

AIR-ANT2524DB-R

AIR-ANT2524DB-R=

Description

2.4 & 5 GHz -- Dual Band Dipole

Dipole Ant., Black, RP-TNC connector (1)

2.4 & 5 GHz

Dual Band Dipole

Dipole Ant., Gray, RP-TNC connector (1)

Gain

2 dBi (2.4 GHz)

4 dBi (5 GHz)

2 dBi (2.4 GHz)

4 dBi (5 GHz)

AIR-ANT2524DG-R

AIR-ANT2524DG-R=

AIR-ANT2524DW-R

AIR-ANT2524DW-R=

AIR-ANT2566P4W-R=

AIR-ANT2524V4C-R=

AIR-ANT2544V4M-R=

2.4 & 5 GHz

Dual Band Dipole

Dipole Ant., White, RP-TNC connector (1)

2.4 & 5 GHz

Dual Band Directional (Patch)

Directional Ant., RP-TNC connectors (4)

2.4 & 5 GHz

Dual Band Ceiling Mount

Ceiling Mount Omni Ant., RP-TNC connectors (4)

2.4 & 5GHz

Dual Band Wall Mount Omni

Wall Mount Omni Ant., RP-TNC connectors (4)

2 dBi (2.4 GHz)

4 dBi (5 GHz)

6 dBi (2.4 GHz)

6 dBi (5 GHz)

2 dBi (2.4 GHz)

4 dBi (5 GHz)

4 dBi (2.4 GHz)

4 dBi (5 GHz)

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Understanding and Interpreting

Antenna Patterns

Understanding Antenna Patterns

Dipole (Omni-Directional)

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Low gain dipoles radiate everywhere think “light bulb”

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Understanding Antenna Patterns

Monopole (Omni-Directional) MIMO

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When three monopoles are next to each other – the radiating elements interact slightly with each other – The higher gain 4 dBi also changes elevation more compared to the lower gain 2.2 dBi Dipole

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Understanding Antenna Patterns

Patch (Directional)

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Patch

Antenna

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Understanding Antenna Patterns

Patch (Higher Gain Directional)

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Four element

Patch Array

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Understanding Antenna Patterns

Patch (Higher Gain Directional)

Four element

Patch Array

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Understanding Antenna Patterns

Sector (Higher Gain Directional)

Elevation plane has nulls due to high gain 14 dBi

Cisco Public

AIR-ANT2414S-R

14 dBi Sector 2.4 GHz

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Understanding Antenna Patterns

Sector (Higher Gain Directional)

Elevation plane has nulls due to high gain 14 dBi but antenna was designed with “Null-Fill” meaning we scaled back the overall antenna gain so as to have less nulls or low signal spots on the ground.

AIR-ANT2414S-R

14 dBi Sector 2.4 GHz

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The Richfield Ohio (Aironet) Facility

A Quick Peek Where Antennas Are Designed...

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The Richfield Ohio (Aironet) Facility

Qualifying Cisco and 3rd Party Antennas

Satimo software compatible with

Stargate-64 System. Basic measurement tool is 8753ES

Network Analyzer.

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Cisco Anechoic chamber using an 45 cm absorber all the way, around 1-6 GHz

Anechoic means “without echo”

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The Richfield Ohio (Aironet) Facility

Regulatory Compliance Testing Done in this Chamber

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Yes We Have Just a Few Access Points

Running…

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RF Screen Rooms Everywhere

Copper Shielding (Faraday Cage)

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RF Screen Rooms

Copper Shielding on Top Metal on Bottom

Cables are typically fibre and exit through well shielded holes

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Doors have copper fingers and latch tight forming an RF seal

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RF Screen Rooms

Copper Shielding (Faraday Cage)

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Cisco Richfield Facility

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Understanding Multipath

Diversity and Beamforming

802.11n

Understanding Multipath

Multipath Can Change Signal Strength

As radio signals bounce off metal objects they often combine at the receiver

This often results in either an improvement

“constructive” or a

“destructive” type of interference

Note: Bluetooth type radios that “hop” across the entire band can reduce multipath interference by constantly changing the angles of multipath as the radio wave increases and decreases in size (as the frequency constantly changes) however throughput using these methods are very limited but multipath is less of a problem

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Understanding Multipath

Multipath Reflections Can Cause Distortion

As the radio waves bounce, they can arrive at slightly different times and angles causing signal distortion and potential signal strength fading

Different modulation schemes fair better –

802.11a/g uses a type of modulation based on symbols and is an improvement over the older modulation types used with 802.11b clients

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802.11n with more receivers can use destructive interference (multipath) as a benefit but it is best to reduce multipath conditions

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Understanding Diversity (SISO)

802.11a/b/g had just one radio per band diversity was limited

Non-802.11n diversity Access Points use two antennas sampling each antenna choosing the one with the least multi-path distortion

Cisco 802.11a/b/g Access Points start off favoring the right (primary antenna port) then if multi-path or packet retries occur it will sample the left port and switch to that antenna port if the signal is better.

Note: Diversity Antennas should always cover the same cell area

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Understanding Diversity (MIMO)

MRC Maximal Ratio Combining (Three Radios)

Receiver benefit as each antenna has a radio section

MRC is done at Baseband using DSP techniques

Multiple antennas and multiple RF sections are used in parallel

The multiple copies of the received signal are corrected and combined at Baseband for maximum SNR (Signal to Noise) benefit

This is a significant benefit over traditional 802.11a/b/g diversity where only one radio is used

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MRC Effect on Received Signal

Maximal Ratio Combining

Combined Effect (Adding all Rx Paths)

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3 Antennas Rx Signals

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Understanding Client Link 1.0 & 2.0

Why You Want to Beamform to the Client

Beam-forming allows the signal to be best directed towards the client

(for illustration purposes – please do not place antennas like this

)

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Simple Example of Beamforming

Client Link doesn’t only help at the edge of the network but by pushing the signal at the client - it permits easier decoding maintaining higher data rate connectivity

(rate over range) on the downlink side

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Beamforming:

ClientLink 1.0 (Introduced in AP-1140)

The AP-1140/1260/3500 has dual band radio support using single band antennas.

Each radio band is separate allowing

Two transceivers (Tx/Rx) per band to be used at a time (2.4 or 5 GHz)

This two transceiver design allows for beam-forming to legacy clients

802.11a/g - this is called Client Link.

AP1140, 1260 and 3500 can beamform to legacy 802.11a/g clients. This is called

Client Link 1.0 and supports up to 15 clients per radio

Note: Client Link 1 & 2 works on the DOWNLINK (AP to CLIENT)

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AP-3600 Series with ClientLink 2.0

Client Link 2.0 is Client Link with Enhanced .11n Beam-forming

This new AP has four transceivers per band and all the antennas are used in the Client Link 2.0 beamforming process

More radios, less antennas, all 8 radios (4 per band) are

Transmit/Receive “Tx/Rx”

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Understanding Multipath and Beamforming

Why You Want More Receivers and Client Link 2.0

The picture above is an example of a 1-SS beam-form similar to what is done in Client Link 1.0 however – using client link 2.0 we can do this with multiple spatial streams.

3600 with multiple transceivers

ONE EXTRA RADIO PER BAND then the competition increases fidelity creating a more predictable and reliable 802.11n performance

The AP-3600 supports three spatial streams with four transceivers for even greater performance and then adds Client Link 2.0 enhancements

Client Link 2.0 benefits 802.11a/g/n 1-SS, 2-SS and 3-SS clients

Note: You need 4 radios to beam-form to 3-ss clients no one else has this

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Understanding ClientLink 2.0 Beamforming:

Full Picture

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Understanding 802.11 MIMO Terminology

MIMO ( M ultipleI nputM ultipleO utput)

Some RF components of 802.11n include:

MRC – Maximal Ratio Combining a method that combines signals from multiple antennas taking into account factors such as signal to noise ratio to decode the signal with the best possible Bit Error Rate.

TxBF – Transmit beam forming – The ability to transmit independent and separately encoded data signals, so-

For Your

Reference called “streams” from each of the multiple transmit antennas.

Channel Bonding – Use of more than one frequency or channel for more bandwidth.

Spatial Multiplexing – A technique for boosting wireless bandwidth and range by taking advantage of multiplexing which is the ability within the radio chipset to send out information over two or more transmitters known as “spatial streams”.

Note: Most Cisco 802.11n Access Points utilise two

MIMO is pronounced transmitters and three receivers per radio module

Note: The 3600 AP uses 4 Transmitters and 4 Receivers.

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“My Moe”

not

“Me Moe”

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Suggested Guidelines on Channel Bonding

20 MHz mode is suggested if…

‒ you have lots of voice clients.

‒ you have lots of non-11n capable 5 GHz clients

‒ you will be deploying a transition of mixed 11a & 11n infrastructure:

40 MHz (Bonded channel) mode is suggested if…

‒ You have few voice clients (less than 10 per AP)

‒ You expect to have predominantly 11n clients that support 40 MHz operation.

‒ You are doing bandwidth-intensive file transfers such as video downloads,

wireless backups, etc.

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MCS Index of 802.11n Rates

AP-3600

Supports

3 Spatial

Stream

MCS Rates

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So to Recap: 802.11n Operation

Throughput Improves When All Things Come Together

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Access Points and Features

Integrated Antenna?

– External Antenna?

Carpeted areas

Rugged areas

Integrated antenna versions are designed for mounting on a ceiling

(carpeted areas) where aesthetics is a primary concern

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Use for industrial applications where external or directional antennas are desired and or applications requiring higher temperature ranges

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When to Use Integrated Antennas

When there is no requirement for directional antennas and the unit will ceiling mounted

Areas such as enterprise carpeted office environments where aesthetics are important

When the temperature range will not exceed 0 to +40C

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When to Use External Antennas

Reasons to consider deploying a rugged AP

When Omni-directional coverage is not desired or greater range is needed

The environment requires a more industrial strength

AP with a higher temperature rating of -20 to +55 C

(carpeted is 0 to +40 C)

The device is going to be placed in a NEMA enclosure and the antennas need to be extended

You have a desire to extend coverage in two different areas with each radio servicing an independent area - for example 2.4 GHz in the parking lot and 5 GHz indoors

Requirement for outdoor or greater range Bridging application (aIOS version)

Requirement for WGB or mobility application where the device is in the vehicle but antennas need to be mounted external

Rugged AP in ceiling enclosure

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Outdoor

–rated APs Used for Indoor

Applications

Harsh environmental conditions (e.g. refrigerated rooms, condensing humidity…)

12V DC powered or 100-480V AC

ATEX Class I Division 2 (potentially explosive areas)

Dual Band Omni

AIR-ANT2547V-N=

1552i (Integrated Ant)

1552e +

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Coverage Comparison

– 5GHz up to MCS15

AP 1140 AP 3600 (4 dBi)

AP 3500i AP 3500e (3.5 dBi)

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Installation and Deployment

Considerations

Site Survey Prepares for 802.11n

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Access Point Placement (Legacy a/b/g)

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Access Point Placement (802.11n)

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802.11n Support, Backward Compatibility and Co-existence

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Mixed Mode Performance

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Wall Mounting Access Point with Internal

Antennas

Wall mounting is acceptable for small deployments such as hotspots, kiosks, transportation or small coverage areas.

Coverage is always more uniform when installed on the ceiling tile or grid area

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Note: Wall mounting may create unwanted coverage areas on the floor above or below - This is not desirable for voice as it may cause excessive roams and is directional as metal is behind the antennas (backside).

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Access Points (Internal Antenna Models)

Designed Primarily for Ceiling (Carpeted) Installations

AP-3500 Access Point has six integrated 802.11n MIMO antennas

4 dBi @ 2.4 GHz

3 dBi @ 5 GHz

Note: Metal chassis and antennas were designed to benefit ceiling installations as the signal propagates downward in a 360 degree pattern for best performance

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Antenna Patterns

– Internal Access Points

Azimuth and Elevation Patterns for 2.4 GHz & 5 GHz

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Wall mounting AP-1260, 3500e & 3600e

Orientation of the Dipoles if Wall Mounting

Note: The ceiling is usually higher and a better location for RF.

If using advanced features like location or voice try to locate the AP on the ceiling, or when mounting the AP on a wall orient the dipoles in this configuration.

Because dipoles on a wall can easily get orientated wrong as people touch and move them. Better still might be to use a Patch antenna or use the Oberon wall bracket. Be aware walls can add directional properties to the signal as they can have wiring, metal 2x4 construction and the wall attenuates the signal behind the AP limiting a nice 360 degree coverage.

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Aironet 802.11n Wall Mount (Style Case)

Third Party Wall Mount Option is Available

This optional wall mount best positions the

Access Point dipoles for optimum performance –

Recommended for Voice applications If you

MUST mount the Access Point on a wall.

Ceiling is a better location as the AP will not be disturbed or consider using patch antennas on wall installations

Oberon model 1029-00 is a right angle mount works with “I” and “e” models http://www.oberonwireless.com/WebDocs/Model1029-00_Spec_Sheet.pdf

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What About Mounting Options?

Different Mounting Options for Ceiling APs

Cisco has options to mount to most ceiling rails and directly into the tile for a more elegant look

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Locking enclosures and different colour plastic

“skins” available from third party sources such as www.oberonwireless.com

www.terrawave.com

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Clips Adapt Rail to “T” Bracket.

Attaching to Fine Line Ceiling Rails

If the ceiling rail is not wide enough or too recessed for the

“T” rail this can be addressed using the optional clips

Part Number for ceiling clips is AIR-ACC-CLIP-20=

This item is packaged in 20 pieces for 10 Access Points

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Installation above the Ceiling Tiles

An Optional Rail Above the Tiles May Be Used

Note: The AP should be as close to the tile as practical

AP bracket supports this optional T-bar box hanger item 2

(not supplied) Such as the Erico Caddy 512 or B-Line BA12

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AP Placement Above False Ceiling Tiles

Areas

When placing the Access Point above the ceiling tiles (Plenum area) Cisco recommends using rugged

Access Points with antennas mounted below the

Plenum area whenever possible

Cisco antenna have cables that are plenum rated so the antenna can be placed below the Plenum with cable extending into the plenum

If there is a hard requirement to mount carpeted or rugged Access Points using dipoles above the ceiling

– This can be done however uniform RF coverage becomes more challenging, especially if there are metal obstructions in the ceiling

Tip: Try to use rugged Access Points and locate the antennas below the ceiling whenever possible

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Integrated Ceiling Mount

– Public Areas

Flush mount bracket part number is AIR-AP-BRACKET-3

This is a Cisco factory bracket that can be specified at time of order

Full strut on right provides support across two ceiling rails (earthquake areas)

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Antenna Placement Considerations

AP antennas need placements that are away from reflective surfaces for best performance

Avoid metal support beams, lighting and other obstructions.

When possible or practical to do so, always mount the Access Point (or remote antennas) as close to the actual users as you reasonably can

Avoid the temptation to hide the Access Point in crawl spaces or areas that compromise the ability to radiate well

Think of the Access Point as you would a light or sound source, would you really put a light there or a speaker there?

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Never mount antennas near metal objects as it causes increased multipath and directionality

Cisco Public

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Wall Mounting AP-1260e, 3500e & 3600e

Orientation of the Dipoles if Wall Mounting

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Wall Mounting AP-1260e, 3500e & 3600e

Orientation of the Dipoles if Wall Mounting

Dipoles pointing UP or Down are in vertical polarity

This is ideal for uniform coverage.

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Dipoles pointing sideways are in horizontal polarity.

Note: Cisco recommends transmitting antennas use vertical polarity

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Installations that went wrong…

Above ceiling installs that went wrong

Yes it Happens and When it Does it is Expensive to Fix and No One is Happy

When a dipole is mounted against a metal object you lose all Omnidirectional properties.

It is now essentially a directional patch suffering from acute multipath distortion problems.

Add to that the metal pipes and it is a wonder it works at all

Dipole antennas up against a metal box and large metal pipes create unwanted directionality and multipath distortion – This increases packet retries

Tip: Access Points like light sources should be in the clear and near the users

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Above Ceiling Installs that Went Wrong

Huh?? You Mean it Gets Worse?

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Other Installations that Went Wrong

Ceiling mount AP mounted on the wall up against metal pipe (poor coverage)

Outdoor NEMA box not weatherised

(just keeping the packets on ice)

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Installations that Went Wrong

Patch antenna shooting across a metal fence

Multipath distortion causing severe retries

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Mount the box and the antennas in a downward fashion

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Installations that Went Wrong

Sure is a comfy nest - glad this model runs pretty warm

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Installations that Went Wrong - Mesh

GOOD INSTALL BAD INSTALL

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Installations that Went Wrong - Mesh

Building aesthetics matters – Antennas obstructed

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Minimise the Impact of Multipath

Temptation is to mount on beams or ceiling rails

This reflects transmitted as well as received packets

Dramatic reduction in SNR due to highstrength, multipath signals

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Try to minimise Reflections When Choosing Locations

© 2013 Cisco and/or its affiliates. All rights reserved. Cisco Public

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Summary

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RF Matters

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Recommended Reading

RF Matters

Also see the Cisco AP-3600 deployment guide at this URL http://www.cisco.com/en/US/products/ps11983/products_tech_note09186a0080bb9102.shtml

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Q & A

Complete Your Online Session

Evaluation

Give us your feedback and receive a Cisco Live 2013 Polo

Shirt!

Complete your Overall Event Survey and 5

Session Evaluations.

Directly from your mobile device on the

Cisco Live Mobile App

By visiting the Cisco Live Mobile Site www.ciscoliveaustralia.com/mobile

Visit any Cisco Live Internet Station located throughout the venue

Polo Shirts can be collected in the World of

Solutions on Friday 8 March 12:00pm-2:00pm

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Don

’t forget to activate your

Cisco Live 365 account for access to all session material, communities, and on-demand and live activities throughout the year. Log into your Cisco Live portal and click the

"Enter Cisco Live 365" button. www.ciscoliveaustralia.com/portal/login.ww

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Reference slides

Warehouse Design

As Stock Levels Change so Does Coverage

You can suspend an AP from the ceiling or use patch or Yagi on walls

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Warehouse Design

As Stock Levels Change so Does Coverage

Maximum Tx power Easy power

Patch or Yagi antennas

Null spots have to be corrected

Easy Ethernet drop

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Warehouse Design

As Stock Levels Change so Does Coverage

Reduced Tx power (RRM) More APs (+ power drops)

Omni directional antennas AP wire distance to nearest switch

More difficult to deploy

Placement of APs can be cumbersome

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Stadium and Sporting Venues

AIR-CAP3502P-x-K9 and AIR-ANT25137-R=

Program to release a new 3500e “style” of AP that is certified for use with a higher gain antenna

Program includes design and development of a new high gain antenna to go with the AP

• Aesthetically pleasing

• Single radome for both 2.4 and 5 GHz elements

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AIR-CAP3502P-x-K9

© 2013 Cisco and/or its affiliates. All rights reserved.

AIR-ANT25137-R=

Cisco Public

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Stadium Designs

Stadium Antenna is Cisco (AIR-ANT25137NP-R=)

Azimuth plane adjustment

+/- 20 degrees

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Cables exit from the back

Elevation Plane Adjustment,

+/- 60 degrees

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Was there a Need for this Antenna?

Yes, part of the problem was the 3500 Series was limited to antenna gains of 6 dBi so we needed a special model AP that could use higher gain antennas (AP-3502P)

Discrete antennas for 2.4 GHz and 5

GHz were unsightly and was labor intensive to mount and align.

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Similar performance designed into one housing that supports both 2.4 and 5 GHz

MIMO antennas

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High-Density Design - Bowl

Coverage area divided into cells to support anticipated number of users

Directional antennas create

WLAN cells within seating areas

Lower power, interference

Down-tilt to control the vertical

RF beam width

Lower interference

Design and install 2.4 GHz and 5 GHz

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Bowl Seating RF Cell Footprint

Overlapping cells should use non-overlapping channels (3 nonoverlapping channels in the 2.4 GHz domain)

Radio Resource Management

(RRM) automatically sets the

AP channel and power

Limitations on where APs can be mounted and pointed influences cell coverage

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