air tight 11ac webinar series session 2 - 11ac feature deep dive - june 2014

© 2014 AirTight Networks, Inc. All rights reserved.

802.11ac Feature Deep Dive

MatthewSMullin

RAFerruolo Blog.airtightnetworks.com @MatthewSMullin

@RAFerruolo

http://www.linkedin.com/in/matthewsmullin/

http://www.linkedin.com/company/18640?trk=hp-feed-gorilla-suggestedsearch1-companytext

http://www.linkedin.com/in/raferruolo/

http://blog.airtightnetworks.com/

http://www.twitter.com/matthewsmullin

http://www.twitter.com/raferruolo


Agenda

• 11ac Feature/Benefit Review

• Dear FCC, etc. - More 5 GHz Channels Please

• What the heck is QAM?

• Beamforming Demystified

• Good Old Fashion MIMO

• MU-MIMO Magic

• Frame Aggregation Broken Down

• Forward Error Correction

• Tres Dynamic Channel Width

2

© 2014 AirTight Networks, Inc. All rights reserved. 3

11ac Features and Benefits

Feature Benefits 11ac

Channel Width Quadruple Throughput 20, 40, 80, 80+80, 160 MHz

QAM Encoding More Bits/MHz 16, 64, 256 QAM

Spatial Streams Double Throughput 8

Beamforming Higher Data Rates & Range (Standardized) Explicit

Multi User MIMO Switch-like Wi-Fi MU-MIMO

Frame Aggregation Greater MAC Efficiency A-MSDU size 11,426 Bytes

A-MPDU size 1,048,576 Bytes

Forward Error Correction

Signal Strength Gain

1 – 2 dB for LDPC

BCC

LDPC

Dynamic Channel Width Use Widest Channel Possible RTS/CTS Enhancements

Bands Supported More Channels & Less

Cluttered Spectrum 5 GHz Only


Dear FCC - More 5 GHz Channels Please

• Channels shown as red may become available in not too distant future.

Image source: http://www.samsung.com/global/business/enterprise-communications/news/latest-

news/upcoming-new-wi-fi-technologies-ieee802-11ac

http://www.samsung.com/global/business/enterprise-communications/news/latest-news/upcoming-new-wi-fi-technologies-ieee802-11ac




















Channel Width

Australia

& US

Brazil China Europe Japan Korea

20 MHz 9 17 12 4 8 25

40 MHz 4 8 5 2 4 12

80 MHz 2 4 2 1 1 6

160 or 80+80 MHz 1 2 1 0 0 3

Channel Availability without DFS Channels

Includes TDWR (Terminal Doppler Weather Radar) channels 120, 124 and 128.


Channel Width

Australia

& US

Brazil China Europe Japan Korea

20 MHz 25 28 16 19 23 25

40 MHz 12 14 8 9 11 12

80 MHz 6 7 3 4 5 6

160 or 80+80 MHz 3 3 1 2 2 3

Channel Availability with DFS Channels

Includes TDWR (Terminal Doppler Weather Radar) channels 120, 124 and 128.


Quadrature Amplitude Modulation

Source: Wikipedia - http://en.wikipedia.org/wiki/Quadrature_amplitude_modulation

7

Amplitude Modulation and Phase (Time) Shift

Constellation Diagram

http://en.wikipedia.org/wiki/Quadrature_amplitude_modulation


More Bits per MHz: 64-QAM vs. 256-QAM

As constellations become denser higher signal strength and SNR

are required to decode the data properly.

Constellation Diagrams


QAM Analogy

9

64-QAM

256-QAM

Phase and amplitude steer the dart.


Explicit Beamforming: Higher Client Data Rates

• Uses NDP (Null Data Packets) sounding

frames

• Clients respond with channel state

• Channel state includes DSP, antenna

and RF properties

• AP uses channel state to calculate

steering matrix

• Steering matrix is used to determine

amplitude and phase (time) parameters

of the transmission

• Single spatial stream is transmitted over

multiple antennas

• Objective is to create constructive

interference at the receiver

SNR


Explicit Beamforming: Potential Gains

Client type Spatial Streams Potential Gain

Phone

e.g. Galaxy S5 1 Up to 7 dB

Tablet

e.g. Galaxy Tab Pro 1 Up to 7 dB

Tablet

e.g. Surface Pro 3 2 Up to 3 dB

Laptop

e.g. MacBook Air 2 Up to 3 dB

Laptop

e.g. MacBook Pro 3 Negligible

Potential Gains for a 3 Spatial Stream AP


Beamforming Analogy

Waves crests combining

resulting in a stronger wave


Beamforming Oversimplified

Dark blue wave is transmitted at

the same time as the light blue

wave.

Dark blue wave is transmitted

before the light blue wave.

Antenna 2 Antenna 1 Antenna 1 Antenna 2


MIMO Example 1

• With an 80 MHz channel the max data rate is 1.733 Gbps, with

an expected max throughput rate of approximately 1 Gbps

• Puts all 4ss of the AP to good use

• Enables full capacity of the AP and channel


MIMO Example 2

• With an 80 MHz channel the max data rate is 433 Mbps, with an

expected max throughput rate of approximately 260 Mbps

• Uses only 1ss of the AP’s 4ss

• Effectively only use ¼ of the AP’s throughput potential


MU-MIMO: Efficient Use of AP Radio/Channel

• With an 80 MHz channel the aggregate max date rate is 1.733 Gbps

• However, the max aggregate throughput is expected to be somewhere

between 400 – 600 Mbps

• Enables AP to be used more efficiently and supports greater channel

capacity when clients support fewer spatial streams than the AP


MU-MIMO Magic

• Downstream only

• Supports up to 4 clients

simultaneously

• AP uses channel state from

individual beamformees to

calculate a composite steering

matrix

• Composite steering matrix is

used to determine amplitude and

phase parameters of the MU-

MIMO transmission

• Relies on APs ability to create

beams (constructive interference)

in combination with null beams

Null Beam

Beam


MU-MIMO Considerations

• AP transmit power is shared amongst the group in a MU-MIMO

transmission.

• Null beams raise the noise floor.

• Sustaining high per client data rate is more challenging with MU-

MIMO.

• Clients need to be spatially differentiated

• Channel state measurements consume airtime

• Unlikely the 256-QAM enabled MCS rates (MCS-8 and MCS-9) will

be used that often with MU-MIMO.


Frame Aggregation Broken Down

MAC Layer Aggregation

• Frame aggregation is a technique of combining multiple MPDUs or

MSDUs.

• Makes 802.11 more efficient by minimizing the time lost to 802.11

protocol overheads, such as:

• Contention process

• Interframe spacing

• PHY level headers (Preamble + PLCP)

• Acknowledgment frames

• A key difference between A-MSDU aggregation and A-MPDU

aggregation is that A-MPDU aggregation happens after the MAC

header encapsulation process.


A-MPDU Aggregation

Image source: EE Times - http://www.eetimes.com/document.asp?doc_id=1278239

A-MPDU - Aggregated MAC Protocol

Data Unit

• Multiple MPDUs into a single

aggregated MAC frame

• Uses block acknowledgements or

BlockAcks

• Retransmissions are limited to

specific subframes that were not

received.

• 802.11ac specifies that every

802.11ac transmission to be sent as

an A-MPDU aggregate.

http://www.eetimes.com/document.asp?doc_id=1278239


A-MSDU Aggregation

Image source: EE Times - http://www.eetimes.com/document.asp?doc_id=1278239

A-MSDU - Aggregated Multi Service

Data Unit

• Multiple MSDUs destined for the

same receiver are concatenated

in a single MPDU.

• Each original frame becomes a

subframe within the aggregated

MAC frame.

• Only MSDUs of the same Access

Class can be aggregated.

• Cannot be used for broadcast &

multicast.





Frame Aggregation Analogy

Without Aggregation

With Aggregation


Forward Error Correction

BCC - Binary Convolutional Code

• Required

LDPC – Low Density Parity Check

• Optional

• Potential Benefits:

• Effective gain of 1 – 2 dB over BCC

• Enable MCS-8 and MCS-9 (256-QAM rates) at greater distances

• Increase data rates

• Reduce transmission times

• Improve power savings

• Low density refers to the relatively fewer 1s, compared to 0s needed for

the parity check matrix.


Dynamic Channel Width

• Objective is to use widest possible channel to transmit.

• RTS/CTS is used to determine when channel bandwidth is clear.

• 802.11a transmissions (20 MHz) are replicated as needed (e.g. 80 MHz

channel would require 4 separate RTSs)

• Devices addressed by the RTSs respond with CTSs for the free/usable

20 MHz channels.


Staggered Primary Channels

20 MHz

Primary AP1

40 MHz 40 MHz

80 MHz 80 MHz

160 MHz

20 MHz

Primary AP2

AP1 AP2

Channels

100 104 108 112 116 120 124 128


Dynamic Bandwidth - Transmissions Over Time

40 40

40 40

80 80

20

20

80

20

20

t1 t2 t3 t4 t5 t6 t7 t8 t9 t10 t11 t12 t13

Ch. 40

Ch. 44

Primary

Ch. 48

Ch. 36

Primary

AP1

AP2


AirTight Networks 802.11ac APs

Dual radios

• Radio 1—802.11a/n/ac, 3x3:3, 5 GHz

• Radio 2—802.11b/g/n, 3x3:3, 2.4 GHz

Connectors

• LAN 1—GigE/802.3af PoE

• LAN 2—GigE/Wired Backhaul

• Power—12 VDC

• Console—RJ45

• Antenna—6 RSMA (Model C-75-E only)

Benefits

• Best price/performance

• Industry’s only 11ac WIPS solution

• Low power consumption (No feature sacrifice using 802.3af PoE)

• Uses existing infrastructure (No costly upgrades to 802.3at required)

Model C-75-E

External antennas

Model C-75

Internal antennas

27

#11acDeepDive


Additional Resources www.airtightnetworks.com/11ac

802.11ac Data Sheets

For C-75 and C-75-E Access

Points

802.11ac White Paper

Essential Considerations

802.11ac Migration

Qualifying and Planning Questions

28

http://www.airtightnetworks.com/11ac


Session 1: Intro to 11ac

Session 2: 11ac Feature Deep Dive

Session 3: Is 11ac Right for Your Network?

Session 4: 11ac Deployment Best Practices

Session 5: 11ac Channel Capacity Planning

Session 6: 11ac Network Optimization

11ac Webinar Series


Thank You!

Send inquiries to [email protected]

Next webinar: Tuesday, July 23rd, 8am & 6pm Pacific.

“Is 802.11ac Right for your Network.”

30

@AirTight AirTight Networks Blog.airtightnetworks.com

mailto:[email protected]?subject=Webinar: 802.11ac Essentials

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http://twitter.com/Airtight

http://twitter.com/Airtight

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air tight 11ac webinar series session 2 - 11ac feature deep dive - june 2014

Technology

airtight networks

channel state channel

channel availability

greater channel capacity

qam phase

max data rate

mimo example

mu mimo transmission