Understanding RF Fundamentals and the Radio Design of Wireless Networks

Understanding RF Fundamentals and the Radio Design of Wireless Networks Fred Niehaus Technical Marketing Engineer WNBU BRKEWN-3016

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© 2011 Cisco and/or its affiliates. All rights reserved.

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Session Abstract This advanced session focuses on the deep-dive understanding of the often overlooked Radio Frequency part of the design and deployment of 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. BRKEWN-3016


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Session Agenda – Objectives • • • • • • • •

What is radio how did we get here? Basic 802.11 Radio Hardware & Terminology 802.11 Antenna Basics – Single & Diversity Antennas Interpreting antenna patterns – Cisco Richfield Facility Diversity, Multipath, 802.11n RF characteristics DAS (Distributed Antenna Systems) overview Choosing the right Access Point Survey Tools

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What We Won’t Be Covering • Wireless Security • Clean-air (separate session for that)

• WIDS/WIPS (Wireless Intrusion Prevention Service) • High density deployments (separate session for that) • LBS (Location Base Services) • Walled garden, captive portals • WLAN management

• 802.11n beyond RF characteristics

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What Is Radio? How Did We End Up on These Frequencies?

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Basic Understanding of Radio…

AC Frequency 60 Hz or 60 CPS – Cycles Per Second

Battery is DC Direct Current

Typical home is AC Alternating Current

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 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) BRKEWN-3016


Waves travel back and forth so fast they leave the wire

Popular Radio Frequencies: AM Radio 1100 kHz (1.100 MHz) Shortwave 3-30 MHz FM Radio 88-108 MHz Weather Radio 162.40 MHz Cellular Phones 800-900 MHz Wi-Fi 802.11b/g 2.4 GHz Wi-Fi 802.11a 5 GHz Vintage RF Transmitter Cisco Public

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A Radio Needs a Proper Antenna As the frequency goes up the radiating element gets smaller

Cisco antennas are identified by color Blue indicates 5 GHz Black indicates 2.4 GHz

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 housing BRKEWN-3016


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

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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.

Example of 802.11n Modulation Coding Schemes

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

Generally speaking, the faster the data rate the more powerful signal needs to be at the receiver to be 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

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The Radio Spectrum in the US

Source US Department of Commerce http://www.ntia.doc.gov/osmhome/allochrt.PDF BRKEWN-3016


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Wi-Fi Radio Spectrum The first frequencies available for Wi-Fi use was in the 2.4 GHz range As Wi-Fi popularity and usage increased the FCC allocated additional spectrum in the 5 GHz band. 2.4 GHz

5 GHz

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. BRKEWN-3016


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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 and mechanisms are in place to co-exist with services such as radar 10

Wi-Fi Radio Spectrum

The 2.4 GHz spectrum has only 3 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

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 BRKEWN-3016


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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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Basic 802.11 RF Terminology Hardware Identification

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Common RF terms •

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

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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

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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.

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TxBF – Transmit beam forming the ability to transmit independent and separately encoded data signals, so-called streams, from each of the multiple transmit antennas

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Identifying RF Connectors

RP-TNC Connector

―RP-SMA‖ Connector

Used on most Cisco Access Points

Used on some Linksys Products

―N‖ Connector

―SMA‖ Connector

Used on the 1520 Mesh and 1400 Bridge

―Pig tail‖ type cable assemblies

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Identifying Different Cable Types

LMR- 400 Foil & shield LMR – 1200

Leaky Coax shield cut away on one side BRKEWN-3016

½ inch Heliax (Hardline)


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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 BRKEWN-3016


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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 BRKEWN-3016


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Antenna Cables – Plenum 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

If the cable is ORANGE in color it is usually Plenum Rated.

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Plenum cable is more expensive

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802.11 Antenna Basics

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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 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.

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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

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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). BRKEWN-3016


808 Ft Broadcast Monopole WSM 650 AM (erected in 1932) Cisco Public

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Antenna Theory (Dipole & Monopole)

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

9.5 dBi Patch, AIR-ANT5195-R BRKEWN-3016


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Antennas Identified by Color Black indicates 2.4 GHz Blue indicates 5 GHz Orange indicates 2.4 & 5 GHz

Orange indicates 2.4 & 5 GHz BRKEWN-3016


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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 BRKEWN-3016


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Most Common 5 GHz Antennas for Access Points (Single and Diversity) Antenna

Description AIR-ANT5135D-R 3.5 dBi Omni-directional Antenna; mounts directly to radio, low gain, indoor AIR-ANT5145V-R 4.5 dBi Omni-directional Diversity Antenna; unobtrusive, ceiling mount, low gain, indoor AIR-ANT5160V-R 6 dBi Omni-directional Antenna; ceiling or mast mount, indoor/outdoor AIR-ANT5170P-R 7 dBi Patch Diversity Antenna; directional, small profile, wall mount, indoor/outdoor AIR-ANT5195-R 9.5 dBi Patch Antenna; directional, small profile, wall mount, indoor/outdoor

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Understanding and Interpreting Antenna Patterns

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Understanding Antenna Patterns Dipole (Omni-Directional)

Low gain dipoles radiate everywhere think ―light bulb‖ BRKEWN-3016


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Understanding Antenna Patterns Monopole (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 BRKEWN-3016


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Understanding Antenna Patterns Patch (Directional)

Patch Antenna

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Understanding Antenna Patterns Patch (Higher Gain Directional)

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 AIR-ANT2414S-R 14 dBi Sector 2.4 GHz BRKEWN-3016


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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. BRKEWN-3016


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AIR-ANT2414S-R 14 dBi Sector 2.4 GHz 36

The Richfield Ohio (Aironet) Facility A Quick Peek Where Antennas Are Designed...

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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. BRKEWN-3016

Cisco Anechoic chamber using an 18-inch absorber all the way around 1-6 GHz Anechoic means ―without echo‖


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FCC Regulatory Compliance Testing Is Also Done at the Richfield Ohio Facility.

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Yes We Have Just a Few Access Points…

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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 fiber 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 and Diversity— 802.11n Characteristics

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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 BRKEWN-3016


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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 BRKEWN-3016


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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 47

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?

Never mount antennas near metal objects as it causes increased multipath and directionality BRKEWN-3016


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Understanding Diversity (SISO) 802.11a/b/g Diversity Has Just One Radio 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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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, socalled ―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 ―Me Moe‖

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Technical Elements of 802.11n MIMO

40Mhz Channels

Packet Aggregation

Backward Compatibility

MIMO

40Mhz Channels

Packet Aggregation


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Aspects of 802.11n MIMO

40Mhz Channels

Packet Aggregation


MIMO (Multiple Input, Multiple Output)

With Beam Forming Transmissions Arrive in Phase, Increasing Signal Strength

Without Beam Forming Transmissions Arrive out of Phase and signal is weaker

Performed by Transmitter (Talk Better)

Ensures Signal Received in Phase

Beam Forming BRKEWN-3016

Increases Receive Sensitivity

Maximal Ratio Combining


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Works with non-MIMO and MIMO Clients

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Aspects of 802.11n 40Mhz Channels

Packet Aggregation


MIMO (Multiple Input, Multiple Output) Without MRC Multiple Signals Sent; One Signal Chosen

With MRC Multiple Signals Sent and Combined at the Receiver Increasing Fidelity

MIMO AP Performance

Performed by Receiver (Hear Better)

Combines Multiple Received Signals


Increases Receive Sensitivity



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Works with non-MIMO and MIMO Clients


Aspects of 802.11n 40Mhz Channels

Packet Aggregation


MIMO (Multiple Input, Multiple Output) Information Is Split and Transmitted on Multiple Streams

stream 1

MIMO AP

stream 2 Performance

Transmitter and Receiver Participate


Concurrent Transmission on Same Channel

Increases Bandwidth



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Requires MIMO Client



40Mhz Channels

Packet Aggregation


MIMO (Multiple 40Mhz Input, Channels Multiple Output)

Moving from 2 to 4 Lanes

20-MHz Gained Space

40-MHz

20-MHz

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

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Packet Aggregation

40Mhz Channels

Packet 40MhzAggregation Channels

Carpooling Is More Efficient Than Driving Alone Without Packet Aggregation 802.11n Overhead

802.11n Overhead

Data Unit Packet

802.11n Overhead

Data Unit Packet

802.11n Overhead

Data Unit Packet

Data Unit Packet

Packet

Packet

With Packet Aggregation

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40Mhz Channels

Packet Aggregation


Backward Packet Aggregation Compatibility

2.4 GHz

5 GHz 11n Operates in Both Frequencies

802.11ABG Clients Interoperate with 11n AND Experience Performance Improvements

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Understanding MCS Rates and Channel Bonding 40MHz 802.11n channel 1

2

3

4

5

6

Channel Bonding: Wider channels means more bandwidth per AP

7

8

9

20 MHz channel

2.402 GHz

10

11

12

13

14

2.483 GHz

MCS rates 0-15 apply Regardless of channel Bonding.

When you bond a channel You have a control channel You have a data (extension) Channel Legacy clients use control Channel for communication BRKEWN-3016


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2.4 GHz, 40 MHz Bandwidths

Tip: Channel bonding in 2.4 GHz should be avoided in enterprise deployments use 5 GHz as there are no overlapping channels to worry about BRKEWN-3016


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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 BRKEWN-3016


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Channel Bonding – Subcarriers 802.11n uses both 20MHz and 40-MHz channels. The 40-MHz channels in 802.11n are two adjacent 20-MHz channels, bonded together.

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 BRKEWN-3016


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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. BRKEWN-3016

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


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MCS Index of 802.11n Rates NSD

NCBPS

GI = 800ns

GI = 400ns

Rate in

Rate in

Rate in

Rate in

40MHz

20MHz

40MHz

20MHz

40MHz

52

108

6.5

13.5

7 2/9

15

108

104

216

13

27

14 4/9

30

52

108

104

216

19.5

40.5

21 2/3

45

½

52

108

208

432

26

54

28 8/9

60

16-QAM

¾

52

108

208

432

39

81

43 1/3

90

1

64-QAM

2/3

52

108

312

648

52

108

57 7/9

120

6

1

64-QAM

¾

52

108

312

648

58.5

121.5

65

135

7

1

64-QAM

5/6

52

108

312

648

65

135

72 2/9

157.5

8

2

BPSK

½

52

108

104

216

13

27

14 4/9

30

9

2

QPSK

½

52

108

208

432

26

54

28 8/9

60

10

2

QPSK

¾

52

108

208

432

39

81

43 1/3

90

11

2

16-QAM

½

52

108

416

864

52

108

57 7/9

120

12

2

16-QAM

¾

52

108

416

864

78

162

86 2/3

180

13

2

64-QAM

2/3

52

108

624

1296

104

216

115 5/9

240

14

2

64-QAM

¾

52

108

624

1296

117

243

130

270

15

2

64-QAM

5/6

52

108

624

1296

130

270

144 4/9

300

MCS Index

Number of spatial streams

0

Modulation

Coding rate

20

40

20MHz

1

BPSK

½

52

108

1

1

QPSK

½

52

2

1

QPSK

¾

3

1

16-QAM

4

1

5

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So to Recap – 802.11n Operation Throughput improves when all things come together  MRC  TxBF  Spatial Multiplexing

 MRC  TxBF  Spatial Multiplexing

 MRC  TxBF 

802.11a/g AP (non-MIMO)

54

48 36 24 Mbps

802.11a/g client (non-MIMO)

802.11n AP (MIMO)

54 Mbps

802.11a/g client (non-MIMO)

802.11n AP (MIMO)

300 Mbps


Channel Bonding 802.11n client (MIMO)

Spatial Multiplexing

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Understanding DAS Antenna Systems (Very Brief Overview)

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Antenna Technologies ―DAS‖ Traditional DAS Deployments over Coaxial Cable •

DAS – Distributed Antenna System

•

Mostly seen in mining, healthcare and manufacturing

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Major benefits of DAS include: Carry multiple wireless signals simultaneously (cellular, paging, etc) Minimize work above ceiling Permits locations such as wiring closets where it is easier to replace

•

Disadvantages Usually one antenna per AP – Implementations vary among vendors Performance and/or support issues – Sometimes DAS requirement is not for Wi-Fi but for in-building cellular so WLAN cell sizes suffer Not a Cisco antenna – DAS antennas are not defined in Cisco’s Wireless Control System (WCS) must choose a ―close match‖

Reduced technology migration paths - 802.11n can be more difficult to support BRKEWN-3016


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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. Note: Cisco recommends using only discrete wideband antennas (one antenna per AP) as this prevents breaking key features like rogue AP detection and location.

Leaky ―radiating‖ coaxial cable

Bad for location based applications Wide-Band antenna BRKEWN-3016


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Leaky Coax DAS

Cable has shielding removed on one side – center radiates Leaky coaxial systems are sometimes used in mining applications and assembly lines (think above assembly work benches) To be effective, it needs to be installed in very close proximity to the actual WLAN users (distances are short typically 5-10 Ft) and will not work at higher 5 GHz frequencies. Limited to single channel - high potential for co-interference issues Note: Leaky coax is not recommended for advanced RF features such as voice or location BRKEWN-3016


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Traditional Coaxial DAS Solutions

Depending on the type of ―wide band antenna‖ DAS system, signals leave the Access Point antenna port and go through mechanical filters and/or bi-directional amplifier combiner circuitry. While this is much better then a leaky coaxial system, it is not a simple installation and requires specialized installers with experience cutting and terminating the unique low loss cable that is coaxial in nature but has a hard metal shield. Note: Unused antenna ports should be terminated to avoid adjacent cell interference BRKEWN-3016


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RP-TNC Terminator 70

New Approach DAS over CAT-5 Cisco has a Solutions Plus partnership with Mobile Access Which is offering an active DAS system over unshielded twisted pair

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Co-existence of Wi-Fi and Cellular Antenna Wi-Fi over Traditional DAS

Overlay

Shared Coax cabling APs in closet

No Wi-Fi limitations

In-building cellular

No Wi-Fi limitations Cheap UTP cables No Cisco RF Support Likely no MIMO, MRC or ClientLink, RRM, Poor roaming, Location

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Expensive cabling Duplicate cabling


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Co-existence with CUWN Wi-Fi

2 Cellular Bands or 1 MIMO Service POE Alt B

Cellular Controller

Switch

Access Pod

WLAN AP

New / Existing Cat-5/6 Ethernet GigE POE Alt A

BDA, BTS, Pico, Femto

Ethernet-LAN Traffic Passes Over 0 to ~100 MHz

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Cellular “Cell, PCS” MobileAccessVE Shifts Carrier to Intermediate Frequencies


Frequencies Starting at 140 MHz and Above

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WLAN “802.11n”

Shared Structured Cabling System is Passive to WLAN and Cellular

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Access Points and Features

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Introduction of New Access Points

Ruggedized

11abg

11n 1240

1250 1260

1140

3500e

3500i

Carpeted

1130

11n + CleanAir

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Aironet Indoor Access Point Comparison 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

802.3af

E-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

•802.3af fully powers single radio AP1250 or provides 1x3 performance on a dual radio 1250 BRKEWN-3016


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Integrated Antenna? – External Antenna? Carpeted areas

Integrated antenna versions are designed for mounting on a ceiling (carpeted areas) where aesthetics is a primary concern

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Rugged areas

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

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Rugged AP in ceiling enclosure

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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 Bridging distances • Recommend the AP-1240 if there is no requirement for 802.11n support or the infrastructure is older 10/100 ports • 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

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

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Coverage Comparison – 5GHz

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AP1140

AP1250

AP3500i

AP3500e


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Installation and Deployment Considerations

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Content Site Survey

Access Point Placement

Channel Strategy

Mixed Mode Environments Network Capacity & Scalability

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Site Survey Prepares for 802.11n • Recommended to optimize 11n deployment • Survey reveals effects of building characteristics on the wireless spectrum • Measure RF variations due to human activity and time of day

Metal Wall Furniture

• Survey with client types that you plan to implement (11n, 11abg, VoIP, location tags)

Elevator

Glass

• Spectrum intelligence to detect interference

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Access Point Placement ABG Access Point Placement 1 per 5,000 sq feet for data only ABG

1 per 3,000 sq feet for voice, location

ABG

Radio Resource Management Adaptive channel / power coverage Operational simplicity ABG ABG

Web Email

Several Supported Apps

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Access Point Placement .11n same 1 for 1 replacement Newer APs reuses existing Cisco AP bracket drill holes

ABG

Improved coverage at higher data rates

ABG

ERP Backup Video Voice Web Email

ABG ABG

Supported Apps

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Effective Frequency Use 5GHz - 2.4GHz Create a 5 GHz Strategy • 5 GHz Recommended for 802.11n More available spectrum—greater number of channels Benefits from 40MHz channels, although 20MHz still works well Many 11n devices only support 40MHz in 5GHz, although Cisco supports 40MHz in both 2.4GHz and 5GHz

• 2.4 GHz still benefits from MIMO and packet aggregation

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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 Available 40MHz Channels

Radar

No DFS Support

DFS Support

4

11

5 GHz Frequency UNI 1

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UNI 2

UNI 2 Ext.


UNI 3

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DFS and Available Bandwidth • Full DFS support is required for complete use of channels in 5GHz • Limited DFS support directly impacts available bandwidth • Limited bandwidth restricts application support and negates investment in 11n

Available Bandwidth in 5GHz for 11n 1350Mbps

1350

1350Mbps

1200 1050 900 750 600

US

600Mbps

Europe

450 300

300Mbps

US

Europe

150 0

Meru/Aruba

Meru/Aruba

Cisco

Cisco

* 40 MHz Channels in 5GHz

Available Channels per Region

United States

Europe

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Theoretical

Cisco

Meru/Aruba

11n 5GHz 20MHz

24

21

8

11n 5GHz 40MHz

11

9

4

11n 5GHz 20MHz

19

19

4

11n 5GHz 40MHz

9

9

2


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Backward Compatibility & Co-Existence • Co-existence of ABG/N APs • Benefits of 11n accrue to ABG clients MIMO benefits ABG clients on the AP receive side from MRC Backwards Compatibility

Co-Existence at Controller Level WLAN Controller 11g

WLAN Controller 11n

11g

11n

54 Mb 48 Mb 36 Mb 28 Mb

54 Mb

300 Mb

300 Mb

Roam

11g BRKEWN-3016

11n © 2011 Cisco and/or its affiliates. All rights reserved.

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Mixed Mode Performance

 3 Modes of operation supported

WLAN Controller Capacity 300mb

0

54 Mb

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Green Field Mixed

11n

11g

Legacy

300 Mb

 11n clients still transmit at full performance  PHY and MAC for 11n provides co-existence and protection for ABG clients

11n


 Mixed mode experiences slight performance impact due to ABG clients

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Wall Mounting Which Model to Choose?

AP-1140 and AP-3500i

Wall mounting is acceptable for small deployments such as hotspots, kiosks, etc but radiation is better on ceiling BRKEWN-3016

AP-1260 and AP-3500e

Best for enterprise deployments as coverage is more uniform especially for advanced features such as voice and location


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Aironet 1140 / 3500i (style case) Third party wall mount option is available

Oberon model 1029-00 is a right angle mount http://www.oberonwireless.com/WebDocs/Model1029-00_Spec_Sheet.pdf

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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 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 Azimuth and Elevation Patterns for 2.4 GHz & 5 GHz

2.4 GHz Azimuth

5 GHz Azimuth

2.4 GHz Elevation

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5 GHz Elevation


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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 BRKEWN-3016

Locking enclosures and different color 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 BRKEWN-3016


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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

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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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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)

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Tip: Mount antennas either below ceiling tile or the AP as close to the inside of the tile as possible

101

Plenum Installs That Went Wrong Yes 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.

Tip: Access Points like light Dipole antennas up against a metal box and sources should be near the users – Perhaps the AP is here large metal pipes Multipath everywhere for ―Pipe Fitter Connectivity‖?

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Plenum Installs That Went Wrong Huh?? You Mean It Gets Worse?

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Installations That Went Wrong

Ceiling mount AP up against pipe hmmm

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A little ICE to keep the packets cool

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Installations That Went Wrong

Patch antenna shooting across a metal fence

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Mount the box and antennas downward Please

105

Installations That Went Wrong Sure is a comfy nest glad the AP runs a bit on the warm side

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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 BRKEWN-3016


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Antennas for Rugged Access Points 802.11n Options for Ceilings and Walls

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Guide to Antenna Part Numbers

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MIMO Ceiling Antenna 2.4 GHz AIR-ANT2430V-R (3 dBi Ceiling Mount Omni)

Antenna has three monopole elements

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MIMO Ceiling Antenna 5 GHz AIR-ANT5140V-R (4 dBi Ceiling Mount Omni)

Antenna has three monopole elements

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AIR-ANT2451NV-R 2.4 GHz (2.5 dBi) & 5 GHz (3.5 dBi) Dual Band Ceiling Omni

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

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AIR-ANT2460NP-R 2.4 GHz 6 dBi Three Element Patch

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AIR-ANT5160NP-R 5 GHz 6 dBi Three Element Patch

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AIR-ANT2450NV-R= & AIR-ANT5140NR-R MIMO ―Multi-mount‖ Omni 2.4 GHz and 5 GHz

New 3 in 1 Antenna for 2.4 GHz and 5 GHz. Gain is 4 dBi Comes with articulating wall mount, can also be used on ceiling

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New Cisco Antenna Part Numbers

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Outdoor Weatherproofing Coax-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 BRKEWN-3016


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Complete Your Online Session Evaluation  Receive 25 Cisco Preferred Access points for each session evaluation you complete.  Give us your feedback and you could win fabulous prizes. Points are calculated on a daily basis. Winners will be notified by email after July 22nd.  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 and Networkers Virtual account for access to all session materials, communities, and on-demand and live activities throughout the year. Activate your account at any internet station or visit www.ciscolivevirtual.com.

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Visit the Cisco Store for Related Titles http://theciscostores.com

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Thank you.

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Understanding RF Fundamentals and the Radio Design of Wireless Networks

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