understanding rf fundamentals and the radio...

Session ID-BRKEWN-3016

Understanding RF Fundamentals and the Radio Design of Wireless Networks

© 2010 Cisco and/or its affiliates. All rights reserved. Cisco PublicPresentation_ID 2

Session Abstract

This advanced session focuses on the deep-dive understanding of the often overlooked Radio Frequency part of the designing and deploying a Wireless LAN Network. It discusses 802.11 Radio, MIMO, Access Points and antenna placements, when to use a DAS system, antenna patterns… It covers the main environments such as carpeted offices, campuses and conference centers, and it provides feedback based on lessons learned from challenging deployments such as outdoor/stadium/rail deployments and manufacturing areas.


Session Agenda - Objectives

What is radio how did we get here and what is frequency?

Basic 802.11 RF terminology and radio hardware identification

802.11 Antenna Basics – Single & Diversity Antennas

Interpreting antenna patterns – Cisco Richfield Facility

Diversity, Multipath, and the technical elements of 802.11n

DAS (Distributed Antenna Systems) overview – how used

Access Point Models and Features

802.11n design and deployment

Installations – above ceiling (plenum) – installations that went wrong

Antennas for Rugged Access Points – MIMO antennas for ceilings and walls


What We Won‘t Be Covering

Mesh deployments

Clean-Air (separate session for that)

Interference mitigation

Specific site survey utilities

LBS (Location Base Services)

FCC rules and regulations

WLAN management

802.11n beyond RF characteristics


What is radio? How did we get here and what is frequency?


Basic understanding of Radio…

How fast the AC current goes is its ―frequency‖

AC is very low frequency 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 as

such, they take more power to move them greater

distances. This is why 2.4 GHz goes further then 5 GHz

(given same amount of RF power)

Popular Radio Frequencies:AM Radio 650 kHz = WSM 650 AM

Shortwave 3-30 MHz

FM Radio 88-108 MHz

Weather Radio 162.40 MHz

Cellular Phones 800-900 MHz

WiFi 802.11a 5 GHz

WiFi 802.11b/g 2.4 GHz

Battery is DC

Direct CurrentTypical home is AC

Alternating Current

AC Frequency 60 Hz

or 60 CPS – Cycles

Per Second Waves travel back and forth

so fast they leave the wire

Vintage RF

Transmitter


Each Frequency or sets of

frequencies (channels) have different

services such as Shortwave, FM

radio, television, etc - Most of these

are licensed services however some

like ―Wi-Fi‖ are ―unlicensed‖

Rest assured your Federal

Government knows these

frequencies well…DC Light

Radio Spectrum goes almost from DC to LightYou just need a radio receiver to “tune them in”


The US Radio Spectrum (3kHz-300GHz)

Uncle Sam has allocated the entire usable RF spectrum from DC to Light Source: US Department of Commerce http://www.ntia.doc.gov/osmhome/allochrt.PDF

http://www.ntia.doc.gov/osmhome/allochrt.PDF


Wi-Fi Portion of the Radio Spectrum

Wi-Fi is ―unlicensed‖ so it doesn‘t show up in

the overall spectrum allocation as a service

But 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 was in the 900

MHz and 2.4 GHz range

As Wi-Fi popularity and usage

increased the FCC allocated

additional spectrum in the 5

GHz band for (unlicensed

usage)

Portions of the spectrum we

use today is licensed by

Amateur (Ham Radio) and

other services such as radio

location (weather radar)

There is more bandwidth in 5

GHz and mechanisms are in

place to co-exist with radio

location (radar) services

2.4 GHz 5 GHz


A radio needs a proper antenna

Cisco antennas are

identified by color

Blue indicates 5 GHz

Black indicates 2.4 GHz

As the frequency

goes up the radiating

element gets smaller

Antennas are custom made and have

frequency ranges and specifications

Omni-Directional antennas

like the one on the left,

radiate much like

a raw light bulb would

everywhere in all directions

Directional antennas like this

―Patch‖ antenna radiate

forward like placing tin foil

behind the light bulb or tilting

the lamp shade

Note: Same RF energy is

used but results in greater

range as its focused at the

cost of other coverage areas


Complex Modulation Schemes

Radio technology has a lot in

common with that old twisted pair

phone line that started out at 300

baud and then quickly increased

In order to get faster data rates,

(throughput) into the radio signal,

complex modulation schemes as

QPSK or 64 bit QAM is used.

Generally speaking, the faster the

data rate the more powerful the signal

needs to be (at the receiver) to be

successfully decoded.

Take-away here is that 802.11n is a

method of using special modulation

techniques and *not* specific to a

frequency like 2.4 or 5 GHz

802.11n can be used in either band

QAM or Quadrature Amplitude Modulation is one

of the fastest modulation types actually sending

two signals that are out of phase with each other

and then somehow ―putting all the pieces back

together‖ for even greater throughput.

This is one of the advantages of 802.11n

Example of 802.11n Modulation Coding Schemes


Wi-Fi Radio Spectrum

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

The 2.4 GHz spectrum has only

(three non-overlapping channels

1,6 and 11 (US)

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

Note: There are still many

2.4 GHz only devices today

primarily because those

chipsets are less costly to

produce


Basic 802.11 RF terminology and Radio Hardware Identification


Common RF terms

Attenuation – a loss in force or intensity – As radio waves travel through objects or in media such as coaxial cable attenuationoccurs.

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


Identifying RF connectors

RP-TNC ConnectorUsed on most Cisco Access Points

―N‖ ConnectorUsed on the 1520 Mesh and 1400 Bridge

―SMA‖ Connector―Pig tail‖ type cable assemblies

―RP-SMA‖ ConnectorUsed on some Linksys Products


Identifying different cable types

LMR- 400 Foil & shield

LMR – 1200

½ inch solid copper cable sometimes

called ―hardline‖ or ―heliax‖ trade

names (side can be milled to be leaky)

Leaky Coax

shield cut away on one side


Antenna Cables – LMR Series

This is a chart depicting

different types of Times

Microwave LMR Series

coaxial cable.

Cisco uses Times

Microwave cable and has

standardized on two types:

Cisco Low Loss (LMR-400)

and Cisco 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 install


Antenna Cables

LMR-400 is 3/8 inch Cisco Low Loss

LMR-600 is ½ inch Cisco Ultra Low Loss

Trivia: LMR Stands for Land Mobile Radio


Antenna Cables - Plenum

If the cable is ORANGE in color it is usually

Plenum Rated.

Plenum is the air-handling

space that is found above

drop ceiling tiles or below

floors.

Because of fire

regulations this type of

cable must burn with low

smoke

The 3 Ft white cable

attached to most Cisco

antennas is plenum rated.

Our outdoor cable (black)

is not Plenum

Plenum cable is more

expensive


802.11 Antenna basics


Antenna basics

Antenna - a device which radiates and/or receives radio signals

Antennas are usually designed to operate at a specific frequency Wide-Band antennas can support additional frequencies but it‘s a trade-off and usually not with the same type of performance.

Antenna Gain is characterized using dBd or dBi

Antenna gain can be measured in decibels against a reference antenna called a dipole and the unit of measure is dBd (d for dipole)

Antenna gain can be measured in decibels against a computer modeled antenna called an ―isotropic‖ dipole <ideal antenna> and the unit of measure is dBi (i for isotropic dipole) (computer modeled ideal antenna)

WiFi antennas are typically rated in dBi.

dBi is a HIGHER value (marketing folks like higher numbers)

Conventional radio (Public safety) tend to use a dBd rating.

To convert dBd to dBi simply add 2.14 so a 3 dBd = 5.14 dBi

Again… dBd is decibel dipole, dBi is decibel isotropic.


How does a Omni-directional dipole radiate?

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


Antenna theory (Dipole & Monopole)

Dipole

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

Monopole

A Monopole requires a ground plane – (conductive surface)

808 Ft Broadcast Monopole WSM 650 AM - Grand Ole Opry (erected in 1932)


Antenna theory (dipole & monopole)

Monopoles were added to our antenna line primarily for aesthetics and require a metal surface to radiate


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)


Patch Antenna a look inside

9.5 dBi Patch, AIR-ANT5195-R

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


Antennas identified by color

Blue indicates 5 GHz

Black indicates 2.4 GHz


Most common 2.4 GHz antennas for Access Points (single and diversity)

Antenna Description

AIR-ANT4941

2.2 dBi Swivel-mount Dipole; most popular

mounts directly to radio, low gain, indoor

AIR-ANT5959

2 dBi Diversity Ceiling-mount Omni

AIR-ANT1729

6 dBi Wall-mount Patch

AIR-ANT1728

5.2 dBi Ceiling-mount Omni

AIR-ANT3549

9 dBi Wall-mount Patch


Most common 5 GHz antennas for Access Points (single and diversity)

Antenna Description

AIR-ANT5135D-R3.5 dBi Omni-directional Antenna; mounts directly to radio, low gain, indoor

AIR-ANT5145V-R4.5 dBi Omni-directional Diversity Antenna; unobtrusive, ceiling mount, low gain, indoor

AIR-ANT5160V-R6 dBi Omni-directional Antenna; ceiling or mast mount, indoor/outdoor

AIR-ANT5170P-R7 dBi Patch Diversity Antenna;directional, small profile, wall mount, indoor/outdoor

AIR-ANT5195-R9.5 dBi Patch Antenna;directional, small profile, wall mount, indoor/outdoor


Understanding and interpreting antenna patterns

A quick peek at the Cisco Richfield Facility


Understanding antenna patternsDipole (Omni-directional)

Low gain dipoles

radiate everywhere

think ―light bulb‖


Understanding antenna patternsMonopole (Omni-Directional) MIMO

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


Understanding antenna patternsPatch (Directional)

5 GHz Patch Antenna


Understanding antenna patternsPatch (Higher Gain Directional)

Four element Patch Array

Single Patch Antenna


Understanding antenna patternsSector (Higher Gain Directional)

AIR-ANT2414S-R

14 dBi Sector 2.4 GHz

Elevation plane has nulls due to high gain 14 dBi


Understanding antenna patternsSector (Higher Gain Directional)

AIR-ANT2414S-R

14 dBi Sector 2.4 GHz

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.


The Richfield Ohio (Aironet) facility A quick peek where antennas are designed...


The Richfield Ohio (Aironet) facility designs antennas and qualifies 3rd party antennas

Satimo software compatible with

Stargate-64 System. Basic

measurement tool is 8753ES

Network Analyzer.

Cisco Anechoic chamber using an 18-inch

absorber all the way around 1-6 GHz

Anechoic means ―without echo‖


FCC regulatory compliance testing is also done at the Richfield Ohio facility.


Yes we have just a few Access Points…


RF Screen rooms everywhereCopper shielding (Faraday Cage)


Cables are typically fiber and exit

through well shielded holes

Doors have copper fingers and

latch tight forming an RF seal

RF Screen rooms Copper shielding on top metal on bottom


RF Screen roomsCopper shielding (Faraday Cage)


Cisco Richfield Facility


Understanding multipath and diversity and the technical elements of 802.11n


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

Understanding MultipathMultipath can change signal strength

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


Understanding MultipathMultipath 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/n uses a type of modulation

based on symbols and is an improvement

over the older modulation types used with

802.11b clients

802.11n with more receivers can

use destructive interference

(multipath) as a benefit.

Tip: It is still best to reduce

multipath conditions whenever

possible – Keep antennas away

from metal objects


Antenna placement considerations

Never mount antennas near

metal objects as it causes

increased multipath and

directionality

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?


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

Understanding Diversity (SISO)802.11a/b/g diversity has just one radio


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

Understanding Diversity (MIMO)MRC Maximal Ratio Combining (three radios)

© 2010 Cisco and/or its affiliates. All rights reserved. Cisco PublicPresentation_ID 51Presentation_ID © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 51

Understanding 802.11 MIMO terminology

MIMO (Multiple-Input-Multiple-Output)

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-

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: Cisco 802.11n Access Points utilize two

transmitters and three receivers per radio module.

MIMO is pronounced ―My Moe‖ not to be confused with this Moe.


MIMO40Mhz

Channels

Packet

Aggregation

Backward

Compatibility

Technical Elements of 802.11n

MIMO 40Mhz ChannelsPacket

Aggregation

Backward

Compatibility


Aspects of 802.11n

Beam Forming Spatial MultiplexingMaximal Ratio Combining

MIMO (Multiple Input, Multiple Output)


Aggregation

Backward

Compatibility

Performed by

Transmitter

(Talk Better)

Ensures Signal

Received in

Phase

Increases

Receive

Sensitivity

Works with

non-MIMO and

MIMO Clients

Without Beam FormingTransmissions Arrive out of

Phase and signal is weaker

With Beam FormingTransmissions Arrive in Phase,

Increasing Signal Strength


Aspects of 802.11n



40Mhz ChannelsPacket

Aggregation

Backward

Compatibility

Performed by

Receiver

(Hear Better)

Combines

Multiple Received

Signals

Increases

Receive

Sensitivity

Works with

non-MIMO and

MIMO Clients

Performance

Multiple Signals Sent;

One Signal Chosen

Without MRC

Multiple Signals Sent and Combined

at the Receiver Increasing Fidelity

With MRC

MIMO AP


Aspects of 802.11n




Aggregation

Backward

Compatibility

Transmitter and

Receiver

Participate

Concurrent

Transmission on

Same Channel

Increases

Bandwidth

Requires MIMO

Client

Performance

stream 1

stream 2

Information Is Split and Transmitted on Multiple Streams

MIMO AP


20-MHz

20-MHz

40-MHzGained Space

MIMO (Multiple Input, Multiple Output)40Mhz Channels

Aspects of 802.11n


Aggregation

Backward

Compatibility

Moving from 2 to 4 Lanes

40-MHz = 2 aggregated 20-MHz channels—takes advantage of the

reserved channel space through bonding to gain more than double the

data rate of two 20-MHz channels


40Mhz Channels

Aspects of 802.11n

Packet Aggregation


AggregationMIMO

Backward

Compatibility

Carpooling Is More Efficient Than Driving Alone

Without Packet Aggregation

Data

Unit

Packet

802.11n

Overhead

Data

Unit

Packet

802.11n

Overhead

Data

Unit

Packet

802.11n

Overhead

With Packet Aggregation

Data Unit

Packet

802.11n

OverheadPacketPacket


Packet AggregationBackward Compatibility

Aspects of 802.11nPacket

Aggregation

Backward

CompatibilityMIMO 40Mhz Channels

2.4GHz 5GHz

802.11ABG Clients Interoperate with 11n AND

Experience Performance Improvements

11n Operates

in Both

Frequencies


1 2 6 113 4 5 7 8 9 12 13 1410

2.402 GHz 2.483 GHz

40MHz 802.11n channel

Channel Bonding:

Wider channels means more bandwidth per AP

Understanding MCS rates and Channel Bonding

20 MHz channel

MCS rates 0-15 apply

Regardless of channel

Bonding.

MCS 0-7 is one Spatial Stream

When you bond a channel

You have a control channel and a

data (extension) Channel

Legacy ABG clients use control

channel for communication


2.4 GHz, 40 MHz Bandwidths

Tip: Channel bonding in 2.4 GHz should be avoided in enterprise deployments

Tip: Use 5 GHz as there are no overlapping channels to worry about


Example UNII-3 Channel Bonding

In 40-MHz you define the control channel this is the channel that

is used for communication by Legacy .11a clients.

The Extension channel is the bonded channel that High

Throughput ―HT‖ 802.11n clients use in addition to the control

channel for higher throughput as they send data on BOTH

channels


Channel Bonding - Subcarriers

When using the 40-MHz bonded channel, 802.11n takes advantage of the fact that each 20-MHz channel

has a small amount of the channel that is reserved at the top and bottom, to reduce interference in those

adjacent channels.

When using 40-MHz channels, the top of the lower channel and the bottom of the upper channel don't

have to be reserved to avoid interference. These small parts of the channel can now be used to carry

information. By using the two 20-MHz channels more efficiently in this way, 802.11n achieves slightly more

than doubling the data rate when moving from 20-MHz to 40-MHz channels

802.11n uses both 20-

MHz and 40-MHz

channels.

The 40-MHz channels

in 802.11n are two

adjacent 20-MHz

channels, bonded

together.


Understanding Guard Interval

The guard interval

that is part of each

OFDM symbol is a

period of time that is

used to minimize

inter-symbol

interference.

This type of

interference is

caused in multipath

environments when

the beginning of a

new symbol arrives

at the receiver before

the end of the last

symbol is done.Default mode for 802.11n is 800 nanoseconds

If you set a shorter interval it will go back to long

in the event retries occur


54 48 36 24 Mbps

54 Mbps MRC

TxBF

Spatial Multiplexing

802.11a/g AP

(non-MIMO)

802.11n AP

(MIMO)

802.11a/g client

(non-MIMO)

802.11a/g client

(non-MIMO)

300 Mbps802.11n AP

(MIMO)

802.11n client

(MIMO)

MRC

TxBF


MRC

TxBF


802.11n OperationThroughput improves when all things come together

Channel Bonding


MCS index of 802.11n rates


Understanding DAS Antenna SystemsOverview – How used


Antenna Technologies ―DAS‖Traditional DAS deployments over coaxial cable

DAS – Distributed Antenna System

Mostly seen in healthcare, higher education & hospitality

Major benefits of DAS include:

Carry multiple wireless signals simultaneously (cellular, paging, etc)

Consolidates work above ceiling – fewer cables

Aggregates majority of active components in closet for easy replacement

Disadvantages

Usually one antenna per AP – lack of MIMO and diversity support

Cisco TAC will not support RF signal when radio is separated from the antenna on non-Cisco equipment

Compromises the benefits of CUWN‘s advanced features including RRM, Location, VoFi, etc.

Reduced technology migration paths - 802.11n can be more difficult to support

Large solid copper cable once installed, is difficult to move if changes are later required (remodeling etc).


How does DAS work?

DAS works by placing multiple radio services on a common cable or antenna system using selective filters and/or a low gain multiband antenna.

Two methods are typically used ―Leaky coax‖ and ―discrete wideband antennas‖ or sometimes a combination of both.

Tip: Avoid daisy-chaining antennas as this breaks key features like location/voice based services – use only discrete wideband antennas (one antenna per AP) with this type of DAS

Leaky ―radiating‖ coaxial cable

Bad for location based applicationsWide-Band antenna


Leaky coax DAS

Leaky coaxial systems are sometimes used in mining applications and assembly lines (think above assembly work benches)

For leaky coax to be effective, it needs to be installed in very close proximity to the actual WLAN users (distances are short typically 5-20 Ft) and will not work reliably at higher 5 GHz

frequencies. Limited to single channel - high potential for co-interference issues

Note: Leaky coax should be used for only the most basic Wi-Fi scenarios, i.e. light connectivity for low bandwidth apps. Not recommended for features such as voice or location

Cable has shielding removed

on one side – center radiates


Traditional coaxial DAS solutions

Depending on the type of ―wide band antenna‖ DAS system used, signals leave the Access Point‘s antenna port and go through RF filters

(passive) and/or bi-directional amplifiers (active) circuitry

While better then a leaky coaxial system, it is not a simple installation and requires professional installers with experience cutting and terminating the expensive (solid copper shielded) cable. Connector termination can

be a point of failure and cable moves can be expensive

Note: Unused antenna ports should be terminated to avoid interference to Access Points that are co-located

RP-TNC

Terminator


New approach In-building cellular – CAT 5e/6/6a

Cisco has a Solutions Plus Resell partnership with Mobile AccessWhereas Cisco resells the MA branded and supported product

Mobile Access active indoor cellular over same UTP

cable that can be shared with Cisco Access Points


New approachIn-building cellular – CAT 5e/6/6a

Mobile Access Pod using one UTP cable from the cellular controller can filter the cellular signals from the cable and pass GigE PoE

to the Cisco Access Point

• Eliminates the need for expensive solid copper cabling and the complexities of same

• Enables quicker and cost effective deployment with common UTP cabling

• Allows MA solution & Wi-Fi to co-exist on one single UTP cable

• No modifications or wide band antennas, no terminators are required on the AP

Note: Cisco Access Points with integrated antennas can also be used with this solution.


Cellular and Wi-Fi sharing CAT-5e/6/6a

WLAN APSwitch

New / Existing Cat-5/6

Ethernet GigE

POE Alt A

WLAN

“802.11n”

Ethernet-LAN Traffic Passes

Over

0 to ~100 MHz

MobileAccessVE Shifts Carrier to

Intermediate Frequencies

Frequencies Starting at

140 MHz and Above

Shared Structured Cabling System is Passive to WLAN

and Cellular

Cellular

“Cell, PCS”

BDA, BTS,

Pico, Femto

Access

PodCellular

Controller

2 Cellular Bands

or 1 MIMO Service

POE Alt B


Co-existence of Wi-Fi and Cellular Antenna

Wi-Fi over Traditional DAS

Shared Coax cabling

APs in closet

No Cisco RF Support

Likely no MIMO, MRCor ClientLink, RRM,

Poor roaming, Location

Overlay

No Wi-Fi limitations

Expensive cabling

Duplicate cabling

Cellular over CAT5

No Wi-Fi limitations

Cheap UTP cables

RF signals limited by UTP cabling two for

CAT5 more with CAT6a


Access Point Models and Features


Ca

rpe

ted

R

ug

ge

diz

ed

11abg 11n + CleanAir11n

1130

12401260

3500e

3500i1140

Introduction of new Access Points

1250


AP 1130 AP 1140 AP 3500i AP 1240 AP 1250 1260 3500e

Integrated CleanAir No No Yes No No No Yes

Data Uplink (Mbps) 10/100 10/100/1000 10/100/1000 10/100 10/100/1000 10/100/1000 10/100/1000

Power Requirement 802.3af 802.3af 802.3af 802.3afE-PoE

802.3af*802.3af 802.3af

Installation Carpeted Carpeted Carpeted Rugged Rugged Rugged Rugged

Temp Range 0 to +40°C 0 to +40°C 0 to +40°C -20 to +55°C -20 to +55°C -20 to +55°C -20 to +55°C

Antennas Internal Internal Internal External External External External

Wi-Fi standards a/b/g a/b/g/n a/b/g/n a/b/g a/b/g/n a/b/g/n a/b/g/n

DRAM 32 MB 128 MB 128 MB 32 MB 64 MB 128 MB 128 MB

Flash 16 MB 32 MB 32 MB 16 MB 32 MB 32 MB 32 MB

Aironet Indoor Access Point Comparison

•802.3af fully powers single radio AP1250 or provides 1x3 performance on a dual radio 1250


Integrated antenna? – External antenna?

Integrated antenna versions

are designed for mounting

on a ceiling (carpeted areas)

where aesthetics is a

primary concern

Use for industrial applications

where external or directional

antennas are desired and or

applications requiring higher

temperature ranges

Carpeted areas Rugged areas


When to use integrated antennas

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

Areas such as enterprise carpeted office environments where aesthetics are important

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


When to use external antennas

Reasons to consider deploying a rugged AP

When directional ―focused‖ coverage is 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


When to use AP-1240 and AP-1250

Reasons to consider the AP-1240 or AP-1250

The AP-1240 and AP-1250 support higher gain antennas - a benefit only if a high gain antenna already exists or is required

Higher gain (up to 10 dBi) can improve WGB and outdoor Bridging distances

Recommend the AP-1240 if the infrastructure is older 10/100 ports and there is no interest in upgrading to 11n

AP-1240 will work with older Cisco PoE switches (Cisco proprietary power)

AP-1240 draws less power so better for solar applications

AP-1240 supports Cisco Fiber injectors

Tip: Higher than 10 dBi antenna gains are supported with the 1300 Series Bridge/AP


802.11n Design and Deployment


Phases of 802.11n deployment

Design Considerations

•Which AP to choose

•1:1 Replacement Strategy for Capacity

•5 GHz Strategy

•11n Clients

Planning

•WCS Planning Tool

•Infrastructure Considerations

Deployment

•Site Survey

Operation

•Configuration (40 MHz RRM, Data Rates, Security, etc.)

•Tracking and augmenting controller capacity


Which 802.11n Access Point is right?

AP-3500i and AP-3500e have the very latest Cisco features such as Clean Air Cisco‘s spectrum intelligence

AP-1140 and AP-1260 are of similar design less Cisco Clean Air features and can also run autonomous code (aIOS) for stand alone or Workgroup Bridge applications.

Note: 3500 Series does not support the older aIOS autonomous mode

All the Access Points were designed to have similar coverage for ease of deployment


AP1140 AP1250

AP3500i AP3500e

Coverage Comparison – 5GHz


1130 Access Point Placement

1130 Access Point Placement

1 per 5,000 sq feet for data only

1 per 3,000 sq feet for voice, location

Several

Supported Apps

Email

Web

Radio Resource Management

Adaptive channel / power coverage

Operational simplicity


1140, 3500i Access Point Placement

Improved coverage at

higher data rates

1 for 1 replacement

AP1140, 3500i reuses existing

AP1130 T-Rail Clip

More Applications Supported

at Any Given Location

Email

Web

Voice

Video

Backup

ERP

ABG

ABG

ABG

ABG


Access Points (Internal Antenna Models) Designed Primarily for ceiling (carpeted) Installations

Access Point has six integrated

802.11n MIMO antennas

4 dBi @ 2.4 GHz

3 dBi @ 5 GHz

Note: Metal chassis and

inverted ―F‖ antenna

elements were designed to

benefit ceiling installations as

the signal propagates

downward in a 360 degree

pattern for best performance

Antenna element


Antenna Patterns Azimuth and Elevation Patterns for 2.4 GHz & 5 GHz

2.4 GHz

Azimuth5 GHz

Azimuth

5 GHz

Elevation

2.4 GHz

Elevation


AP Placement – Wall Mounting

Wall mounting is acceptable

for small deployments such

as hotspots, kiosks, etc but

radiation is better on ceiling

Best for enterprise deployments as

coverage is more uniform

especially for advanced features

such as voice and location

AP-1140 and AP-3500i AP-1260 and AP-3500e


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

Locking enclosures and different

color plastic ―skins‖ available from

third party sources such as

www.oberonwireless.com

www.terrawave.com

http://www.oberonwireless.com/

http://www.terrawave.com/


AP Placement—Evaluate Problem Areas

Object in Signal Path

Plasterboard wall

Glass wall with metal frame

Cinder block wall

Office window

Metal door

Metal door in brick wall

Phone and Head position

3 dB

6 dB

4 dB

3 dB

6 dB

12 dB

6 dB

Signal

Attenuation


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

resolved 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


Effective Frequency Use—5GHz and 2.4GHzCreate a 5GHz Strategy

5GHz Recommended for 802.11n

• More available spectrum—greater number of channels

• Reduced interference (no Bluetooth, Microwave Ovens, etc.)

• Maximum throughput in a 40MHz channel

• Many 11n devices only support 40MHz in 5GHz

2.4GHz still benefits from MIMO and packet aggregation

1

6 11

2

1 3 5 7 9 11

4 6 8 10

5GHz 40MHz Channels2.4GHz 20MHz Channels


11n Client Adapters

Make sure adapter is 11n Draft 2.0 or better certified by WiFi Alliance - http://www.wi-fi.org

802.11n adapters have a major influence on performance levels that can be achieved

Built-in 11n adapters out perform add-on

• USB and PCMCIA 11n adapters have less than optimal antenna placement as those form factors have less then ideal antenna spacing

Not realistic to upgrade most older laptops with internal 11n adapters

• Need three antennas connectors

http://www.wi-fi.org/




11n Client Adapter Recommendations

Update 802.11n client drivers to the latest revision

Cisco-Intel relationship means that the Intel 11n adapter with Cisco‘s APs have had the most test time


WCS Planner1140 and 11n Support

Set AP type

Select ‗Enable 11n support‘

Select protocol ‗802.11a/n, b/g/n‘

Select optimize for HT

Select Voice & location if desired

Calculate/Apply/Add APs to Map


WCS PlannerData Rate Heat Map

Add APs to map

Set Heat Map type to Data Rates

Set Cutoff to desired minimum data rates


WCS PlannerProposal

Generate proposal

Use proposal for budgetary estimates

Use proposal with survey to create final install AP count and placement design

Recommend survey to validate and calibrate proposal results


Third Party Survey ToolsThere are many and I believe they are all good

Airmagnet

EDX

Ekahau

Helium Networks

Wireless Valley

… and many others

Tip: Survey and use Cisco antennas

If you contract this out, some companies use their

own antennas and then lock you into them saying

―that‘s what we surveyed with‖… if in doubt use

Cisco Advanced Services as they also perform

site surveys


Site SurveySite Survey Recommendations

Use ―Active Survey‖ tools

• Example - AirMagnet 6.0 uses Iperf to send traffic when surveying to measure actual data link speeds

Survey for lowest common client

• Once for 11a/g clients

• Once for 11n clients (optional)

Survey at intended AP power levels


11n Deployment ExpectationsData Services

Range

• 10-15% increase in maximum range versus a non-N AP

• Recommended 1:1 replacement of an 802.11a/g deployment

Coverage

• 10-20% increase in 802.11a/g high data rate coverage

• More uniform coverage and consistent coverage (MIMO)

Capacity

• Largest gain for 802.11n capable clients

• Maximum data rates of 144Mbps in 2.4GHz

• Maximum data rates of 300Mbps in 5GHz


1130 11G Survey

48 Mbps Coverage

86 Feet

1140 11G Survey

48 Mbps Coverage

102 Feet

Improved 802.11g Coverage1130 vs. 1140—11G Active Survey

18% Increase in 802.11g Coverage

Note the more uniform coverage of high (green) data rates


5GHz - Maximum Range

AP1130 – 5GHz AP1140 – 5GHz


802.11n DeploymentDesigning Around 5GHz 40MHz Channels

One AP

Data Rate vs. RSSIFull Deployment

Contiguous 5GHz Coverage


5 GHz Dynamic Frequency Selection

When Radar Is

Present

APs Shift

Channels—

Results in Lower

Available Channels

and Loss of UNI 2

and UNI 2e Bands Radar

Available

40MHz

Channels

No DFS

Support

DFS

Support

4 11

5 GHz Frequency

UNI 1 UNI 2 UNI 2 Ext. UNI 3UNI 2 UNI 2 Ext.


DFS and Available Bandwidth

Full DFS support is required forcomplete use of channels in 5GHz

Limited DFS support directlyimpacts available bandwidth

Limited bandwidth restrictsapplication support andnegates investment in 11n

Available Channels per Region Theoretical Cisco Meru/Aruba

United States

11n 5GHz

20MHz24 21 8

11n 5GHz

40MHz11 9 4

Europe

11n 5GHz

20MHz19 19 4

11n 5GHz

40MHz9 9 2

Available Bandwidth in 5GHz for 11n

0

150

300

450

600

750

900

1050

1200

1350

Meru/Aruba Meru/Aruba Cisco Cisco

* 40 MHz Channels in 5GHz

600Mbps

300Mbps

1350Mbps 1350Mbps

US Europe

US

Europe


Tuning RRM 5GHz Channel SelectionUNII-2 Extended Channel Considerations

Wireless ->802.11a/n -> DCA

Uncheck channels 100-140

(UNII2-Extended)

Some older clients cannot utilize UNII-2 Extended Channels

The 5GHz radio could be ‗invisible‘ to the client

If your clients do not support these channels they can be disabled see below


Utilizing 11n Wide Channels20MHz vs. 40MHz Considerations

The 40MHz mode of 802.11n provides the highest throughput with data rates of 300Mbps

• Should not be utilized in the 2.4GHz band

• Not enough channels for 40 MHz mode

The 5GHz band has enough spectrum to make 40MHz feasible

• Use 20MHz for 802.11a voice deployments

• Use 40MHz for maximum data throughput with 802.11n clients

Use RRM for 40MHz


Mixed Mode Performance

11n

300 Mb54 Mb

WLAN Controller

11n

11g

Mixed mode experiences slight

performance impact due to ABG

clients

11n clients still transmit at full

performance

PHY and MAC for 11n provides co-

existence and protection for ABG

clients

Move 11n clients to 5GHz, keep

legacy clients at 2.4GHz


Improving Mixed Mode PerformanceDisabling Unnecessary Data Rates

Benefit: Beacons and Broadcast traffic utilize less ―airtime‖

For 802.11b/g deploymentsDisable: 1, 2, 5.5, 6 and 9Mbps

For 802.11g-only deploymentsDisable: 1, 2, 5.5, 6, 9 and 11Mbps

For 802.11a deploymentsDisable: 6 and 9 Mbps

Higher rates can also be disabled (ex. 12, 18Mbps) – dependant on deployment

Tuned 802.11b/g Data Rates:


Installations – Above Ceiling (Plenum) When they must be invisible


AP Placement in Plenum 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


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.


Installation above the ceiling tiles Mount AP close to the tiles and away from objects

Installing Access Points

above the ceiling tiles

should be done only when

mounting below the ceiling

is not an option.

Such mounting methods

can be problematic for

advanced RF features

such as voice and location

as they depend on uniform

coverage

Try to find open ceiling areas away from

metal obstructions (use common sense)

Tip: Mount antennas either

below ceiling tile or the AP

as close to the inside of the

tile as possible


Plenum installs that went wrongYes it happens and when it does its bad…

When a dipole is mounted

against a metal object you

lose all Omni-directional

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 create a

patch like antenna - that plus metal pipes create

unwanted Multipath Destructive Interference

Tip: Try to get Access Points

close to the actual users – This

antenna is radiating forward

high in the ceiling where there

are no users - try to avoid these

types of installs


Plenum installs that went wrongHuh?? You mean it gets worse?

Antennas cannot radiate well with all this mess – someone went to a lot of

―trouble‖ to mount this -- just to encounter even more connectivity ―trouble‖.


Installations that went wrong

Ceiling mount AP up against pipe not good

Antennas are obstructedMetal duct blocking antenna causing

Multipath interference



Mount the box ―lid down‖ with

the antennas pointing

downward – Tip: Antennas do

not work well against metal

Patch antenna - Shooting across a metal

fence – Put it on a cross arm away from fence

or find a better location



Sure glad this particular model runs a

bit on the warm side --- ―Chirp Chirp‖

I guess most dry wall guys

are not radio engineers –

Exactly how did this happen?


Minimize 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 high-strength, multipath signals

Minimize Reflections When Choosing Locations


Antennas for Rugged Access Points802.11n options for ceilings and walls


Guide to Antenna part numbers


MIMO Ceiling Antenna 2.4 GHzAIR-ANT2430V-R (3 dBi ceiling mount Omni)

Antenna has three

monopole elements


MIMO Ceiling Antenna 5 GHzAIR-ANT5140V-R (4 dBi ceiling mount Omni)

Antenna has three

monopole elements


AIR-ANT2451NV-R2.4 GHz (2.5 dBi) & 5 GHz (3.5 dBi) dual band ceiling omni

Six leads - 5 GHz antennas have blue markings (shrink wrap)


AIR-ANT2460NP-R2.4 GHz 6 dBi Three Element Patch


AIR-ANT5160NP-R5 GHz 6 dBi Three Element Patch


AIR-ANT2450NV-R= & AIR-ANT5140NR-RMIMO “Multi-mount” Omni 2.4 GHz and 5 GHz

New 3 in 1 Antenna for 2.4 GHz and 5 GHz.

Gain should be 4 dBi for each antenna – but may be higher depending on how much gain we can achieve.


New Cisco Antenna part numbers


Outdoor weatherproofingCoax-Seal can be used with

or without electrical tape.

Taping first with a quality

electrical tape like Scotch 33+

vinyl allows the connection to

be taken apart easier.

Many people tape then use

Coax-Seal then tape again

this allows easy removal with

a razor blade.

Note: Always tape from the

bottom up so water runs over

the folds in the tape. Avoid

using RTV or other caustic

material.www.coaxseal.com


Links

Cisco Antenna Reference Guide http://www.cisco.com/en/US/prod/collateral/wireless/ps7183/ps469/product_data_sheet09186a008008883b.html

Antenna Product portfolio http://www.cisco.com/en/US/prod/collateral/wireless/ps7183/ps469/at_a_glance_c45-513837.pdf

New 3500 datasheets http://www.cisco.com/en/US/prod/collateral/wireless/ps5678/ps10981/data_sheet_c78-594630.html

Antenna Patterns and their meanings https://www.cisco.com/en/US/prod/collateral/wireless/ps7183/ps469/prod_white_paper0900aecd806a1a3e.html

http://www.cisco.com/en/US/prod/collateral/wireless/ps7183/ps469/product_data_sheet09186a008008883b.html

http://www.cisco.com/en/US/prod/collateral/wireless/ps7183/ps469/product_data_sheet09186a008008883b.html

http://www.cisco.com/en/US/prod/collateral/wireless/ps7183/ps469/at_a_glance_c45-513837.pdf




http://www.cisco.com/en/US/prod/collateral/wireless/ps5678/ps10981/data_sheet_c78-594630.html




https://www.cisco.com/en/US/prod/collateral/wireless/ps7183/ps469/prod_white_paper0900aecd806a1a3e.html

https://www.cisco.com/en/US/prod/collateral/wireless/ps7183/ps469/prod_white_paper0900aecd806a1a3e.html


Q and A


Complete Your Online Session Evaluation

Give us your feedback and you could win fabulous prizes. Winners announced daily.

Receive 20 Passport points for each session evaluation you complete.

Complete your session evaluation online now (open a browser through our wireless network to access our portal) or visit one of the Internet stations throughout the Convention Center.

Don‘t forget to activate your

Cisco Live Virtual account for access to

all session material, communities, and

on-demand and live activities throughout

the year. Activate your account at the

Cisco booth in the World of Solutions or visit

www.ciscolive.com.

http://www.ciscolive.com/

understanding rf fundamentals and the radio...

Documents