Title slide with picture
March, 2017
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#ATM16
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Understanding 802.11ac
Eric JohnsonDirector: Product Management@ArubaNetworks |
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AgendaAccess Point PortfolioWhat is Wave 211ac Data
RatesPractical CoverageAntennas11ac BeamformingMU MIMODirectional
AntennasRecap@ArubaNetworks |
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Access Point Portfolio
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Migrating from 802.11n to 802.11ac
220, 320, 330Series120 & 130Series110 Series90 &
100Series170Series200 Series
210 Series
270 Series
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#ATM16Christian Gilby (CG) - Added 330 Series since this is
being announced on March 8th.Comprehensive 802.11ac Portfolio 200
Series210 SeriesLecture Halls, Venues, Warehouses High Performance
& Density, Extended TempCarpeted SpaceHigh Performance,
Moderate DensityK-12, Hospitality & RetailModerate Performance
& DensityOutdoor EnvironmentsHigh Performance & Density
270 Series330, 320 & 220 Series
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#ATM16What is 11ac and Wave 2?
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802.11ac Technology Overview11n Introduced:2.4 and 5 GHz
supportedWider channels (40 MHz)Better modulation
(64-QAM)Additional streams (up to 4 streams)Beam forming (explicit
and implicit)Backwards compatibility with 11a/b/g11ac introduced:5
GHz onlyEven wider channels (160 MHz)Better modulation
(256-QAM)Additional streams (up to 8)Beam forming
(explicit)Backwards compatibility with 11a/b/g/nThink of 11ac as an
extension of 11n
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#ATM1611ac is an extension of 11n. Those of you who were around
for the 11n roll out will notice a lot of dj vu. The big difference
with 11ac is that end users care about wireless speeds now. Client
devices are differentiating themselves with 11ac support (HTC One,
Samsung GS4, MacBook Air)8
Wave 2 of 11acWhat does Wave 2 802.11ac offer?MU-MIMOUse AP MIMO
resources more effectivelyTransmit data to multiple devices
simultaneously: for example 4SS AP streaming data to 3 SS clients
simultaneously4x4:4SSBenefit of additional stream mostly for
MU-MIMONot anticipating any 4x4:4SS client devicesAdds 33% to max
data rate in SU-MIMOVHT160Doubles max dataratePractical problem:
only 2 VHT160 channels available in entire 5GHz band
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#ATM16IEEE ratified 11ac as a whole, including support up to 8
spatial streams. Wave 1 and Wave 2 are industry terms describing
the different feature sets of the APs. The Wi-Fi Alliance is
planning to certify Wave 2 11ac features in mid-2016. MU-MIMO, 4SS
and 160 MHz channels will be optional.
This is very much like the release of 3 stream 11n APs after 2
stream APs had gone mainstream. Just like then, we will see a range
of products from a manufacturer to meet all price/performance
points.
There will not be a single wave 2 product from manufacturers. In
general, it will be a portfolio of products. This will be very
similar to the release of 3 stream 11n products. When they released
they came out at flagship prices and represented the best
performance in wireless. Over time, 3 stream products dropped in
price and started to replace the previous mainstream 2 stream
products. Wave 2 will be the same thing. You will see them show up
as flagship APs at flagship prices. They will coexist with existing
11ac APs. Over time, they will drop in price and take over the
entire portfolio. 9
Channels
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#ATM16Potential Future 5GHz FCC Channel plan
23dBm30dBm30dBm36dBmTBD30dBm204080160NOTE: 160 MHz is actually
80 + 80
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#ATM16This is where we could end for spectrumThe 5.35 to 5.47
band is currently a restricted bandThe 5.85 to 5.925 band is
allocated for intelligent transportation systems and this is a
political issue of whether it will be reallocatedAPs that are being
developed now should be able to support the extra bandwidth through
SW changesNOTE: the 5.85 to 5.925 band has a different frequency
stability spec that may affect HW capability of supporting the
band. FCC will need to harmonize that with the other Wi-Fi bands to
avoid that impact
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Current 5GHz ETSI Channel plan
23dBm30dBm30dBm
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#ATM16Understanding 11ac Data Rates
Wave 1 and Wave 2
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#ATM16802.11 5 GHz Physical Layer Summary
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#ATM16This goes back to the original chart about the maximum
capability of the standard is.
We will take a look at how real products are going to stack up
against the above14
Sub-carriers52 subcarriers (48 usable) for a 20 MHz non-HT mode
(legacy 802.11a/g) channel
fc+10MHz-10MHz
26 carriers
26 carriers56 subcarriers (52 usable) for a 20 MHz HT mode
(802.11n) channelfc
28 carriers
28 carriers114 subcarriers (108 usable) for a 40 MHz HT mode
(802.11n) channel
fc+10MHz-20MHz
57 carriers
57 carriers+20MHz
-10MHz
242 subcarriers (234 usable) for a 80 MHz VHT mode (802.11ac)
channelAn 80+80MHz or 160MHz channel is exactly two 80MHz channels,
for 484 subcarriers (468 usable)
121 carriers
121 carriers
fc+10MHz-20MHz
+20MHz
-10MHz
-40MHz
-30MHz
+30MHz
+40MHz
OFDM subcarriers used in 802.11a, 802.11n and 802.11ac
+10MHz-10MHz
Guard Tones
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#ATM16TerminologyPropagation Channel: Everything that happens
between the transmitter and receiverRadio Channel: For Wi-Fi 20,
40, 80, or 160 MHz of spectrumTone/Sub-Carriers: OFDM is made up of
many tones. Symbol: Basic data element containing 1 to 8 bits of
information. Each symbol is mapped to a tone.Guard Band: Space
between channels. In these regions tones have a constant value of
zero amplitudeChannel to channel frequency spaceCyclic Extension:
technique used in OFDM to protect against multipath interferenceYou
need cyclic extension but it is dead air and consumes transmit
timePilot Tones: Used to train the receiver and estimate the
channelFEC: Forward Error Correction. Redundant information that is
sent to assist the receiver in decoding the bits.
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#ATM16BPSK and QPSK
Amplitude +1Amplitude -1Quadrature -1Quadrature +1BPSK
constellation1 bits/symbol
Amplitude +1Amplitude -1Quadrature -1Quadrature +1QPSK
constellation2 bits/symbol
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#ATM16QAM constellations
Amplitude +1Amplitude -1Quadrature -1Quadrature +1Amplitude
+1Amplitude -1Quadrature -1Quadrature +1Amplitude +1Amplitude
-1Quadrature -1Quadrature +116-QAM constellation64-QAM
constellation256-QAM constellationConstellation diagrams for 16-,
64-, 256-QAM
1024 QAM is 10 bits/symbol4 bits/symbol6 bits/symbol8
bits/symbol
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#ATM16How do I get to the data rate for a given MCS?Basic Symbol
RateBaud Rate = 312.5 KSpsBasic Symbol Durationt = 1/312500 = 3.2
ms = 3200 nsCyclic Extensiont/4 800 ns (Long Guard Interval)t/8 400
ns (Short Guard Interval)Bits Per ToneBPSK1QPSK216 QAM464 QAM6256
QAM8
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#ATM16Note, There are not additional modulation rates, or bits
per tone, with 11ac wave 2. This is important when planning
deployments. 19
Raw Data RatesExample: What is the raw data rate for a 20 MHz
channel supporting 16 QAMBaud Rate = 312.5 kSpsModulation Depth =
16 QAM = 4b/SNumber of sub carriers = 52
52 Subcarriers * 4b/S * 312.5 kSps = 65000 kbps = 65 Mbps
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#ATM16Correct for Cyclic Extension
-20 %-11 %-20 %-11 %-20 %-11 %-20 %-11 %
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#ATM16Apply FEC Coding
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#ATM16Useful TCP Throughput23
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#ATM16Sneak Peak
11ax
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#ATM16Some interesting features in 11ax discussionsDynamic
Sensitivity ControlClient and APs could alter their EDCA thresholds
to account for when they are close to their serving APDynamic
Transmit Power ControlClients back off their tx power when they
determine they are close to their serving APOFDMAService multiple
clients up and down in separate 20 MHz blocksDownlink is fairly
straight forward. Uplink is a bit more trickyDownlink MU
MIMOExploring ways to reduce sounding overheadUplink MU MIMONeed to
synchronize multiple clients. No BF at client is assumedNetwork
MIMOPossible coordination of transmissions from adjacent access
point
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#ATM16Practical Coverage
11n and 11ac
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Coverage Example: 40 MHz 11n360
405450Sample coverage for 3x3:3 11n AP (or 3x3:3 11ac AP with
11n clients) in HT40 mode
Coverage area showing MCS5 and up
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Coverage Example: 40 MHz with 11ac adding MCS 8 and 9
360
405450540600Upgrade to 3x3:3 11ac AP with 11ac clients, still
using 40MHz channels (VHT40)
Coverage area showing MCS5 and up
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Coverage Example: 40 and 80 MHz 11ac 3x3
780
87897511701300Coverage areas showing MCS5 and up
360
405450540600
3 dB40 MHz80 MHz
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802.11ac AP Spacing Impact30
Reducing the spacing between APs increases the interference
levels from adjacent devices on the same channel
MCS0MCS127 dB Difference
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#ATM16What about Wave 2 160 MHz coverage?Slightly complicated
question160 is actually 80 + 80BUT the radio resources are divided
across each 80 MHz chunkThis reduces power per 80 MHz block by 3
dBAnd MRC (Maximal ratio combiner) in the receiver is using of the
antennas for each 80 MHz blockUplink and downlink are reduced by 3
dB.
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#ATM16Basic Beamforming
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#ATM16Antenna Basic PhysicsWhen the charges oscillate the waves
go up and down with the charges and radiate awayWith a single
element the energy leaves uniformly.Also known as
omni-directionally
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#ATM16Building Arrays: 2 ElementsBy introducing additional
antenna elements we can control the way that the energy radiates2
elements excited in phase
l/2
dB Plot
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Building Arrays: 4 ElementsBy introducing additional antenna
elements we can control the way that the energy radiates4 elements
excited in phaseEqual amplitude
dB Plot
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Building Arrays: 4 ElementsBy shaping the amplitude we can
control sidelobes4 elements excited in phase Amplitude 1, 3, 3,
1
dB Plot
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Building Arrays: 4 Elements PhaseBy altering phase we can alter
the direction that the energy travels4 elements excited with phase
slope Equal amplitude
dB Plot
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#ATM16Orthogonal Patterns
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#ATM162 Elements
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#ATM163 Elements
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#ATM164 Elements
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#ATM168 Elements
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#ATM16802.11ac BeamformingTheory43
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#ATM1611ac Beamforming: NotesWorks with clients that supports
11ac beamforming functionThis is at a minimum all 11ac client
devices using Broadcom chipsetsSupport will have to come to all
devices to compete with Broadcom offering11ac beamforming is
standards basedfirst standard that is doing this the right way11ac
beamforming represents the consensus view of the 1000s of
contributors to the standards process11ac beamforming is
implemented in baseband. It works with all antenna subsystemsThe
total number of beamforming combinations is effectively
infinite11ac actively tracks users so has a recent channel estimate
between the AP and client that is updated frequently
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#ATM16Background
11n/11ac MIMO1 StreamAll antenna elements send same data with
time delay (CDD/CSD)3 Streams1 Stream is sent on each antenna
11ac Beamforming1 StreamStream is spatially multiplexed across
the three antennasSame info but phase and amplitude differences3
StreamsAll three streams are spatially multiplexed across the three
antennas
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#ATM16Sounding process
AP
Explicit feedback for beamforming (802.11ac)(Beamformer / AP)
Heres a sounding frame(Beamformee / Client) Heres how I heard the
sounding frameNow I will pre-code to match how you heard me
sounding frames
Beamformed frames
feedback from soundingBeamformerBeamformee
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The MATRIX
Client Antennash11h21h31APClient
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#ATM16The Basic Model: Regular MIMO y = H xx is what is
transmitted from the APH is the propagation channely is what comes
out of each antenna at the receiving endWith 3 tx and 3 rx antennas
H is a 3x3 matrix, y and x are single vectorsIf you can determine
the inverse matrix of H you can calculateClient receiver estimates
this from preamble and pilot tonesx1x2x3
y1y2y3
h11h21h31h13
APClientyHx
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#ATM16BeamformingIf the client can send back the channel
estimate to the AP then beamforming can be executedThe signal from
each antenna then is a combination of the three streams
Non BeamformedStreamsBeamformedStreamsfrom the AP
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#ATM16802.11ac BeamformingPractical Examples50
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#ATM16Line of Sight3 stream APSmartphone1 Antenna/1 Stream
ClientAP
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#ATM16Simple ReflectionLets introduce two reflection surfaces
and look at the impact of one bounce on each side
ClientAP
AP Antenna PatternS1
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#ATM16Multi Stream ClientThe reflections allow beamforming to
send different streams with different antenna patterns through the
system
ClientAP
Stream 1Stream 2Stream 3
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#ATM16BeamformingStream 3 now appears on all three antennas on
the AP Here is how each transmitted component shows up at the
client
Now add them!
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#ATM16Similarly Stream 1 and 2
Stream 1Stream 2
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#ATM16Sub-carriers52 subcarriers (48 usable) for a 20 MHz non-HT
mode (legacy 802.11a/g) channel
fc+10MHz-10MHz
26 carriers
26 carriers56 subcarriers (52 usable) for a 20 MHz HT mode
(802.11n) channelfc
28 carriers
28 carriers114 subcarriers (108 usable) for a 40 MHz HT mode
(802.11n) channel
fc+10MHz-20MHz
57 carriers
57 carriers+20MHz
-10MHz
242 subcarriers (234 usable) for a 80 MHz VHT mode (802.11ac)
channelAn 80+80MHz or 16MHz channel is exactly two 80MHz channels,
for 484 subcarriers (468 usable)
121 carriers
121 carriers
fc+10MHz-20MHz
+20MHz
-10MHz
-40MHz
-30MHz
+30MHz
+40MHz
OFDM subcarriers used in 802.11a, 802.11n and 802.11ac
+10MHz-10MHz
Guard Tones
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The standards based algorithm actually works out patterns for
each sub carrierBelow is the pattern for stream 1 at 5460, 5500,
5540 MHz
11ac Beamforming across an 80 MHz channel
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#ATM16802.11ac MU MIMO
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#ATM16The Basic Model: MU-MIMOy=HxH is the propagation channely
is what comes out of each antenna at each of the clientsThe channel
matrix is built from sounding each clientx1x2x3
y1y2y3
h11h21h31h13
With MU-MIMO each client sends a piece of the matrix
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3 Clients: 4x4 APRoom Width: 10mRoom Length: 10mRoom Height:
7m
AP Antenna Pattern
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Stream 1 to Client 1
Stream 1 Antenna Pattern
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#ATM16Stream 2 to Client 2
Stream 2 Antenna Pattern
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#ATM16Stream 3 to Client 3
Stream 3 Antenna Pattern
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802.11ac BeamformingImpact of Wall Loss and Directional
Antennas64
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#ATM161, 5, and 10 dB bounce losses
1 dB5 dB10 dB
20m x 20m x 7mAP
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#ATM16Directional Antennas With Drywall
20m x 20m x 7mAP
20m x 20m x 7m
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#ATM16802.11acExpectation and Reality of Wave 267
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#ATM16802.11 5 GHz Physical Layer Summary
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#ATM16This goes back to the original chart about the maximum
capability of the standard is.
We will take a look at how real products are going to stack up
against the above68
Wave 2 On Air Data Rates
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#ATM163SS VHT80 is what we have in AP-225
4SS VHT 80 is what we have in AP-325
The 160 cases are shown as well but spectrum considerations make
this a poor choice in most enterprise environs,69
TCP Throughputs70% of on air data rate is best case throughput
for wireless TCP traffic.Throughput is lost to:TCP trafficSounding
PacketsManagement trafficAssuming best SNR and single client
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Wave 2 PracticalitiesWave 2 APs and chipsets continue to be
developed4x4 80 MHz support and MU MIMOSupports 3 MU MIMO
Clients4x4 160 MHz (80+80) and MU MIMOSupports 3 or 4 MU MIMO
Clients160 MHz operation splits the radio chains for 80 + 80 2x2160
MHz operation is not generally recommended due to limited spectrum
and resulting frequency reuse issues.MU MIMO is not 100% efficient3
single stream clients will get a total of 2x what can be delivered
to 1 single stream clientIndications are that we will not see any 4
stream client devicesAND, wave 2 may see the end of 3 stream
laptops
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#ATM16
Case 1: 4x4 80 MHz support and MU MIMO
No 4 Stream ClientsSU MIMOMU MIMO
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#ATM16These are best case lab condition test results with the
minimum number of clients required to do the testHigher client
counts increase contention and frequency reuse divide bandwidth
across APs that are sharing the channel72
What does that mean for 11ac wave 2?MU-MIMO allows the network
to reach higher throughputs much more oftenFCC opening up spectrum
is critical to realize the potential of 160 MHz channelsReal world
throughputs will be brought down from best case by:Client
capability mix (11n and non-MU-MIMO devices)Client location
distribution (weak SNR)Client count (air contention increases with
number of clients)
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#ATM16Do I need 2.5 Gbps for wireless?Short answer: No.
Long Answer:> 1gbps will likely be needed at some point, but
11ac will not get you thereReal world throughputs with 80 MHz
channels will not require >1 gbpsWired traffic is full duplex,
wireless is halfThere is a price, thermal and power consumption
premium for 2.5 Gbps interfaces
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#ATM16Limitations for 11ac features by environmentOutdoorMU-MIMO
will not function in most locations2x2 SU-MIMO will work if you use
dual polarized antennasTx BF will work with multiple single
polarized elementsIndoorConference Room and carpeted office
spaceAll 11ac features are expected to workAuditoriumsWill be
dependent on client location in the spaceUsing directional antennas
to improve reuse will decrease MU-MIMO and multi stream
operationDual pol antennas will give 2x2 to a single userLarge
Public VenuesMU-MIMO is not expected to work due to propagation
thru crowdsTxBF will work to increase signal to a single end user
for a single streamDual pol antennas will mostly defeat TxBF but
increase chance of multi stream
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#ATM16Resources11ac VRDs are the place to startRF and Roaming
Optimization for
11achttp://community.arubanetworks.com/aruba/attachments/aruba/ArubaVDRs/38/1/RF
and Roaming Optimization for Aruba 802.11ac Networks.pdf
Wave 2
Blogshttp://community.arubanetworks.com/t5/Technology-Blog/Wave-2-Antennas-in-the-spotlight/ba-p/228089
http://community.arubanetworks.com/t5/Technology-Blog/Wave-2-is-on-the-horizon-should-I-ride-it/ba-p/227096
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#ATM16Christian Gilby (CG [3]) - added the full link for the
first VRD
Join Arubas Titans of Tomorrow force in the fight against
network mayhem. Find out what your IT superpower is.
Share your results with friends and receive a free superpower
t-shirt.
www.arubatitans.com
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#ATM16Contest Overview - Aruba is running a marketing campaign
where we ask What is your IT superpower? - Go to arubatitans.com to
take a quick quiz to discover your superpower. - Share your results
with friends and encourage others to play the game- Once you share,
go to the Social and Community Hub, Gracia Commons, 3rd fl to pick
up your free superpower shirt.
FAQ 1. What do I have to do to get a shirt? Share your IT
superpower results with friends and encourage them to play the
game. Then come to the Social & Community Hub, 3rd Floor Gracia
Commons to pick up your shirt. We just need your name and badge for
verification. 2. Where do I get my shirt?Come to the #ATM16 Social
& Community hub located at Gracia Commons on the 3rd Floor3. Do
I have to be at the event to get the shirt?Yes. You have to be at
#ATM16 to get a shirt.4. Can I get my colleague a shirt? He/she is
in a session right now. Unfortunately not. We encourage your
colleague to participate so that they can win a shirt for
themselves. 5. Can I bring a shirt home for my colleague?
Unfortunately not. You have to be at #ATM16 to get a shirt. 6. You
dont have a shirt in my size, can you ship the right size to me
later? Unfortunately not. Please select the best size from our
inventory on site.
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Thank you
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#ATM16
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