RF  Fundamentals  and  the  Radio  Design  of  Wireless  Networks    

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•  Wi-Fi networks use radio technologies based on IEEE 802.11 standards to provide secure, reliable, fast wireless connectivity, typically within a limited area such as a home or campus.

•  A Wi-Fi network can connect electronic devices to each other, to the Internet, and to wired networks.

•  Wi-Fi networks operate primarily in the unlicensed 2.4 and 5 GHz radio bands, and most of the times in both bands (dual-band) now.

•  Unlicensed is good from the perspective that it is “free” spectrum and anyone can use it.

•  It is not good from the perspective that, due to its common shared use, the spectrum tends to be crowded, sometimes causing interference among devices.

What is Wi-Fi?

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Enterprise Wireless LAN Solutions

•  Allow companies to provide differentiated wireless access to: Employees Customers Students / Contractors Devices (M2M) Others, depending on the environment

•  Provide the ability for users to move about untethered to wired hardware: ROAMING •  Serve numerous verticals, with very different requirements, including SECURITY

Retail Manufacturing Finance Healthcare Energy Hospitality Education Transportation Sports

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What is 802.11? What is Wi-Fi? •  Wi-Fi products are designed to implement the IEEE-802.11 standard and be certified for

interoperability through the Wi-Fi Alliance to get the logo

•  The 802.11 technology has evolved over time, with new standard enhancements designated using a letter, e.g., 802.11a, 802.11b, etc.

•  Lower case letter denotes the specific technology standards enhancements to the original 802.11 standard

•  Five main 802.11 generations already, with the latest being 802.11ac, but still only half-duplex (like a hub was)

•  Each generation defines performance enhancements for devices operating in one or both 2.4 GHz and 5 GHz bands

•  Sixth generation will extend to other bands (3.5 GHz, 900 MHz, 60 Ghz etc.)

IEEE Wireless Standard Frequency Band(s) Bandwidth or

Maximum data rate 802.11b 2.4GHz 11 Mbps 802.11a 5GHz 54 Mbps 802.11g 2.4GHz 54 Mbps 802.11n 2.4GHz and 5GHz 450 Mbps 802.11ac 5 GHz 6900 Mbps

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Who Gets the Higher Transmission Priority?

1.  Access Point

2.  Wireless Client

3.  They all get equal access

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802.11 adopted CSMA/CA (Carrier Sense Multiple Access)/Collision Avoidance model where nodes (AP or clients) avoid collisions by transmitting only when the channel is sensed to be "idle”. Other channel access models have been proposed. These models allow the AP to organize channel access in a structured way, but these have never been widely adopted

1.  Legacy Point Coordination Function (PCF) 2.  802.11e Hybrid Controlled Channel Access (HCCA)

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Why is 802.11ac important today? 802.11ac comes in 2 waves: Wave-1 (now) et Wave-2 (mid-2015+)

Many 802.11ac equipements exist on the market today (tablets and smartphones). There is a big ask for more density and more performance from the end-users already.

Toshiba Excite Pro

Samsung Note 10.1 2014

IDENTIFY 802.11AC EXISTING CLIENTS here: https://wikidevi.com/wiki/List_of_802.11ac_Hardware#Mobile_general_purpose_computers_.28non-PC.29

Galaxy S5

iPad Air 2 iPhone 6/6+

Lumia 930

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At 11 mbps (802.11b)?

At 54 mbps (802.11a or g)?

At 300 mbps (802.11n5:2SS)?

At 866 mbps (802.11ac:2SS)?

How many packets can I transmit at that speed compared to the other speeds above?

Smasung Galaxy S5 supports MIMO 2x2:2SS 802.11ac for the first time on a smartphone (866 mbps)!

BASICS  OF  RF  

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Channel reuse scheme in the Network

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1

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Access Point

Neighboring APs use different channels to reduce interference.

On 2.4 GHz, the “Reuse cluster” size is equal to 3 On 5 GHz, the “Reuse cluster” size varies depending on channel width:

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802.11 is the IEEE standard defining Wireless Access running in the Unlicensed Bands

•  802.11 b/g (1997 / 1999 / 2003) 11 Mb / 54 Mbps and runs in the 2.4 GHz frequency band 3 non-overlapping 20 MHz channels (1, 6, 11) – or 4? (1, 5 , 9, 13)? – Hint: it is an odd number

•  802.11 a (1999) 54 Mbps and runs in the 5 GHz frequency band (5.1 – 5.7 GHz) 16 non-overlapping 20 MHz channels in ETSI (864mbps) Shorter range than 802.11 b/g

•  802.11 n (2009) Backwards compatible to 802.11 a/b/g but adding the powerful MIMO technology 215 Mbps max data rate in 2.4 GHz, 450Mbps in 5 GHz band Either 20 MHz or 40 MHz wide channels in 5 GHz, up or 3.464 Gbps total with DFS Most useful running in the 5GHz band à Seven 40 MHz channels

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AFTER 5GHz capable clients are automatically

moved to cleaner 5GHz spectrum

2.4GHz

2.4GHz Capable Speed

5GHz

5GHz Capable Speed

5GHz

5GHz Capable Speed

Cisco BandSelect – Improves Reliability and Performance

Cisco BandSelect Technology Automatic band steering and selection for 5GHz capable devices

BEFORE All clients crowd the 2.4GHz

spectrum lowering performance

2.4GHz Capable Speed

2.4GHz

5GHz Capable Speed

5GHz Capable Speed

2.4GHz 2.4GHz

Wireless Client Performance

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Know the zones of potential problems

Microwave oven (2450 MHZ)

Metal cabinets

Stairwells (reinforced building areas)

Elevator Stairs Labs

Meeting room

Closed desks

Open desks President’s office

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What happens in the air? •  Path loss: attenuation due to distance

•  Fading (frequency dependent)

•  Shadowing

•  Reflection at large obstacles

•  Refraction depending on the density of a medium

•  Scattering at small obstacles

•  Diffraction at edges

reflection scattering diffraction shadowing refraction

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Common Sources of WLAN Interference

Bluetooth

Microwave ovens

Other Wi-Fi Networks

802.11FH

2.4/5 GHz cordless phones

radar

•  Older Microwave Links •  Game Controllers •  Wireless Headphones •  Wireless Video •  Mobile and Fixed Alarm Systems •  Motion Sensors •  Fluorescent Lights •  A Pinball Machine (really)

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Cisco ClientLink—Improves Predictability and Performance

Cisco CleanAir Technology Industry’s First and only Chip Level Proactive and Automatic Interference Protection

AFTER CleanAir mitigates RF interference

improving reliability and performance

Wireless Client Performance

BEFORE Wireless interference decreases

reliability and performance

AIR QUALITY PERFORMANCE AIR QUALITY PERFORMANCE

Fully available in 2600, 2700, 3500, 3600 and 3700 APs. CleanAir Express on 1600 and 1700

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CleanAir hardware visibility and resolution

•  Spectrum intelligence solution designed to proactively manage the challenges of a shared spectrum

•  Assess impact to Wi-Fi performance; proactively change channels when needed

•  CleanAir Radio ASIC: Only ASIC based solution can reliably detect interference sources

•  Best Practice: turn it on if supported by your APs (3500, 1600, 1700, 2600, 2700, 3600, 3700) CleanAir Express For more info: http://www.cisco.com/en/US/netsol/ns1070

•  32 times Wi-Fi chip’s visibility •  Accurate classification

•  Multiple device recognition

•  CleanAir •  Hardware based Solution

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RF Deployment Challenges •  Ensuring correct antenna installation

•  Managing the RF spectrum

•  Designing RF for capacity – not only coverage

•  Remembering that the wireless client devices dictate the cell size:

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Does all of this work magically? •  Site Survey

•  Site Survey

•  Site Survey

• Site Survey!

•  It is, most of the time, impossible to get a Bill of Material that is final in Wireless…

•  Experience is key, and a skilled partner is not optional for customers on voice and/or location deployments

802.11N  AND  802.11AC  

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Evolution to MIMO Technology •  Old Wi-Fi systems used Single Input Single Output (SISO) technology

Single transmit stream Single transmit antenna

Single receive antenna

Severely impacted by multipath signals Performance improved by diversity

Time

Received Signals

Combined Results Time

Single-input Single-output (SISO)

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Evolution to MIMO Technology (Cont.)

•  MIMO requires at least 2 receivers or 2 transmitters per band Uses advanced signal processing to coordinate multiple simultaneous signals from multiple antennas

Improved link reliability

Time

Received Signals

Combined Results

Time

Transmitter Receiver The

Wireless Channel

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MIMO Uses Advanced Signal Techniques to improve link reliability and efficiency

Spatial multiplexing (SM) • Transmitter and receiver participate • Multiple antennas txmt concurrently on same channel

• Increases bandwidth • Requires MIMO client

Maximal ratio combining (MRC) • Performed by receiver • Combines multiple received signals • Increases receive sensitivity • Works with MIMO and non-MIMO clients

Transmit beam forming (TBF) • Performed by transmitter • Ensures signal received in phase • Increases receive sensitivity • Works with MIMO and non-MIMO clients

message

message message

message

message

message message

message

message

me ss

age

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Cisco’s ClientLink Technologies

Cisco ClientLink—Improves Predictability and Performance

Advanced Beam Forming Technologies Improve Wireless Client Performance

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Advanced Techniques Improve Data Rates for All Clients

(The same applies exactly to 802.11ac)

450 Mbps

54 Mbps

36 Mbps

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Bonding Channels Improves Data Rates •  802.11n supports 20- or 40-MHz wide channels, 802.11ac adds 80 and 160-MHz

Primary and secondary channel

40 MHz = 2.2 aggregated 20-MHz channels

Often referred to as an extension channel

Can be above or below the primary channel Protection provided for 20 MHz / 40 MHz client use

802.11n can bond up to 40 MHz Now we are on an 8 lane Highway

What  does  802.11ac  bring?  •  Even  Higher  Levels  of  Performance  •  Larger  channels  (up  to  160-­‐MHz),  more  spaSal  streams  (up  to  8)  •  Reduced  number  of  unused  opSons  in  802.11n  specificaSons  

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Client cell sizes similar between .11n and .11ac There are so many data-rates in .11ac

Using the internal .11n radio on the AP-3600i, we performed a quick cell size characterization with .11n rates using several .11n clients. When we switched to .11ac clients, and the .11ac radio module, it performed similar @40 MHz with clients having a cell size similar to the .11n clients. Take-away .11n/11ac are similar rate/range but of course @80 MHz and 256-QAM, you get a significant data-rate boost

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11ac client Dell E6430 with Broadcom 3-ss Vs. 11n client Apple 3-ss Macbook Pro

(Take-away) 802.11ac client @ 3-ss is able to get twice the speed than 802.11n

3 m 10 m 23 m

Any Rate over Range data? Comparing 802.11ac versus 802.11n using 3-SS clients

RF  RELATED    DEPLOYMENT  GUIDELINES  

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802.11n/ac Wireless Deployment Guidelines Capacity and Performance from Wireless

Data Only Applications Data and Voice

•  Casual wireless access (not primary access)

•  Low bandwidth data applications (email, web, file access)

•  Access Point installed every 25 meter

•  Always use dual radio Access Points (2.4GHz and 5GHz)

•  Location accuracy will be reduced

•  High density wireless access (primary access)

•  Simultaneous VoIP and data usage

•  Access Point installed every 18 meter

•  Always use dual radio Access Points (2.4GHz and 5GHz)

•  Location accuracy will be increased depending on placement

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Building example with few floors (capacity) •  4 floors building

•  45m x 40m per floor

•  1800 m2 per floor or a 7200 m2 building

§  Assuming 1.6 wireless devices per user soon to be the norm (voice and data) in Enterprise and SMB

•  Accepted metrics for employee density in an office building is 10 m² per employee (including all shared areas like lobby, restrooms, kitchen …) according to ILO estimates

•  Calculations:

For 7200m2, we have 720 employees

720 employees means 1152 wireless devices

45m

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Enterprise WLAN Design — Data

Generic guidelines for only data application - Coverage 465 m2 per AP (1 AP every 25 m)

7200 m2 of carpeted area may require 16 APs 10% overlap of coverage cells for roaming support

AP at 60% power for coverage redundancy

In case of AP failure

Average -75dBm at the edge of each cell

Can only be confirmed by site survey

Needs to be validated for capacity: 1152 devices on 16 APs = 72 devices per AP: too much!

Max recommended value is around 50 devices per AP Coverage vs capacity… 16 APs vs 24 APs (6 per floor) à evolution!

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Enterprise WLAN Design — Data and Voice

Generic guidelines for voice and data applications - Coverage 270 m2 per AP (1 AP every 18 m)

7200 m2 of carpeted area may require 26 APs 15% overlap of coverage cells for roaming support

AP at 60% power for coverage redundancy in case of single AP failure

Average -67dBm at the edge of each cell

Can only be confirmed by site survey

Implement Cisco Centralized Key Management, 802.11r, OKC/PKC

Reduces latency associated with roaming

Do not implement Cisco Aggressive Load Balancing

Needs to be validated for capacity: 1152 devices on 26 APs = 44 devices per AP: better!

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Disable Lower data rates §  Disabled – not available to a client §  Supported – available to an associated

client §  Mandatory – Client must support in order

to associate §  Lowest mandatory rate is beacon rate §  Highest mandatory rate is default Mcast

rate Every SSID counts:

§  Each SSID requires a separate Beacon §  Each SSID will advertise at the minimum

mandatory data rate

ANTENNAS  AND  AP  PLACEMENT  

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A Radio Needs a Proper Antenna

Antennas are identified by color Blue indicates 5 GHz Black indicates 2.4 GHz Orange indicates Both

As the frequency goes up, the radiating element gets smaller

Antennas are custom made for the frequency to be used. Some antennas have two elements to allow for both frequencies in one antenna enclosure. Cisco AP-3700/3600/2700/2600/1700/1600 use such antennas.

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

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Antenna placement

•  Use the maximum number supported

•  Use all same type of antennas on an AP

•  Position all of them in the same orientation

•  Access points with internal antennas are designed to be mounted horizontally

•  Antenna spacing is always a compromise on effects Target for positioning antennas around ½ to 1 wave length apart*

*Results vary based on environment. Spacing on ½ wave length intervals has highest probability to provide best performance in multipath rich environment

For 2.4 GHz ½ wave length ~ 6.35 cm

For 5.2 GHz ½ wave length ~ 2.8 cm

receivers

transmitters

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Avoid Mounting AP Antennas Too High •  As a general rule, antenna heights of 3 meters or less are most

conducive to good coverage and consistent positioning accuracy when doing location.

•  As a general rule, antenna heights

of over 6 meters should be avoided.

•  If required, then tricks exist,

but you need to consult a specialist

•  It is important to understand the requirement for external antennas in cases like this, as the cost of a deployment will become significantly higher.

2.4 GHz

Cisco Confidential © 2014 Cisco and/or its affiliates. All rights reserved. 40

Antennas: use common sense Don’t assume because MIMO is so great that you should deploy

802.11n AP’s like this!

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Wall mounting APs (1600, 2x00, 3x00) Orientation of the dipoles if wall mounting

If using advanced features like location or voice, try to locate the AP on the ceiling, or when mounting the AP on a wall, orient the dipoles in this configuration. Because dipoles on a wall can easily get orientated wrong as people touch and move them. Better still might be to use a Patch antenna or use the Oberon wall bracket (see next). Be aware walls can add directional properties to the signal as they can have wiring, metal 2x4 construction and the wall attenuates the signal behind the AP limiting a nice 360 degree coverage. Note: The ceiling is usually higher and a better location for RF.

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Aironet 802.11n wall mount (style case) Third party wall mount option is available

This optional wall mount best positions the Access Point dipoles for optimum performance – Recommended for Voice applications, if you MUST mount the Access Point on a wall. Ceiling is a better location as the AP will not be disturbed or consider using patch antennas on wall installations

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INSTALLATIONS  THAT  WENT  WRONG…    

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NEVER EVER MIX ANTENNA TYPES Antennas should always cover the same RF cell watch polarity

Installations that Went Wrong

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Ceiling mounted AP on the wall, above false ceiling, up against water pipe (?poor coverage?)

Radio waves do not like metal cages…

Other installations that went Wrong

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Patch antenna shooting across a metal fence Multipath distortion causing severe retries

Installations that went Wrong

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GOOD INSTALL BAD INSTALL

Installations that Went Wrong - Mesh

Cisco  provides  well  engineered  Access  Points,  Antennas,  and  Radio  Resource  Management  features  in  the  controllers.  However,  you  need  to  understand  the  general  concepts  of  Radio,  otherwise  it  is  very  easy  to  end  up  implemen>ng  a  network  in  a  sub-­‐op>mal  way.  It  is  therefore  undeniable  that:  

Summary  

“RF  MaZers”  

Thank  you.