112
Understanding RF Fundamentals and the Radio Design for 11ac
Wireless NetworksBrandon Johnson
Systems Engineer
Agenda
• Physics - RF Waves
• Antenna Selection
• Spectrum, Channels & Channel widths
• MIMO & Spatial Streams
• Cisco 802.11ac features
• Beyond 802.11ac
Electromagnetic Spectrum
• Radio waves
• Micro waves
• Infrared Radiation
• Visible Light
• Ultraviolet Radiation
• X-Rays
• Gamma Rays
Colour Frequency Wavelength
Violet 668-789 THz 380-450nm
Blue 606-668 THz 450-495nm
Green 526-606 THz 495-570nm
Yellow 508-526 THz 570-590nm
Orange 484-508 THz 590-620nm
Red 400-484 THz 620-750nm
Radio Frequency Fundamentals• Frequency and Wavelength
• f = c / λc = the speed of light in a vacuum
• 2.45GHz = 12.3cm
• 5.0GHz = 6cm
• Amplitude
• Phase *
A1
λ2λ1
A2
ϕ
Radio Frequency Fundamentals
• Signal Strength
• Gain and Amplification
• Loss and Attenuation
• Wave Propagation
– Attenuation and Free Space Loss
– Reflection and Absorption
– Wavelength
Physics of Waves
• In phase, reinforcement
• Out of phase, cancellation
RF Mathematics
• dB is a logarithmic ratio of values (voltages, power, gain, losses)
• We add gains
• We subtract losses
• dBm is a power measurement relative to 1mW
• dBi is the forward gain of an antenna compared to isotropic antenna
Now we know that …. How?
• Carrier sense, multiple access / open spectrum • (open, low-power ISM bands) no barrier to entry
• Energy detection must detect channel available – Clear Channel Assessment
• On collision, random back off timer before trying again.
• Clear channel is very important.
CSMA / CA – “Listen before talk”
Wireless Is Always A Two-Way Conversation
Interference and Signal to Noise Ratio
• Any RF signals other than what we want is interference
• SNR is a ratio
• The signal strength is a result of:
• Transmit power
• Receive sensitivity
• Increase the signal,or decrease the noise
Two way communication - Example
-120
-100
-80
-60
-40
-20
0
20
0 20 40 60 80 100 120
DistancePoint
A
Point
B
Antennas
Azimuth Elevation
Antenna FundamentalsOmni-Directional Antennas
Omnidirectional Antenna Radiation Pattern 3D
Not accurate or to scale; conceptual only
Azimuth Elevation
Antenna FundamentalsPatch Antennas
Panel Azimuth and Elevation in 3D
Not accurate or to scale; conceptual only
Panel EM field in 3D (Hypothetically)
Not accurate or to scale; conceptual only
Antenna FundamentalsInternal Antennas
Antenna FundamentalsHigh-Gain Antennas
Azimuth Elevation
Waveguide Azimuth and Elevation in 3D
Not accurate or to scale; conceptual only
Antenna FundamentalsHigh-Gain Antennas
First Null is “Filled In”
Second Null is
not as deep
Low signal regions occur close to tower
to minimise the impact
Low Signal Low Signal
Cisco 2.4GHz Antenna Combined 2.4 and 5GHz Antenna
Antenna Design
Direct
Multipath Propagation
Channels
2.4GHz Channels – really only 3; not used -11ac
• 5GHz only
• Channel Bonding
• 80 and 160MHz Channels
• Modulation
• 256-QAM
• Spatial Streams
• Support for up to 8
Understanding 802.11ac
• 80MHz Channel and 3 SS = 1.3Gbps
• 80MHz Channel and 2 SS = 866.6Mbps
• 80MHz Channel and 1 SS = 433.3Mbps
5GHz Channel Allocation
Channel widths
Resolution
20MHz – 1SS
80MHz – 1SS
Resolution
Modulation, SNR and Data Rates
SNR=6SNR=104-QAM
Rate vs Range and the Laws of Physics
4-QAM
64-QAM
16-QAM
Rate vs Range and the Laws of Physics
256-QAM
Rate vs Range and the Laws of Physics
Pop-Quiz
Multi In – Multi OutMIMO
Antenna Diversity
Diversity Combining
Multiple Input Multiple OutputMaximal Ratio Combining
3 Antennas Rx Signals
Combined Effect (Adding all Rx Paths)
Multiple Input Multiple OutputImplicit Transmit Beamforming
Multiple Input Multiple OutputImplicit Transmit Beamforming
Multiple Input Multiple OutputClientLink 4.0
1SS 1SS 2SS 3SS
802.11a/g/n/ac
Multiple Input Multiple OutputSpatial Multiplexing
TheData
The quick
brown fox
Data
The
quickData
The quick
brown fox
Data
The quick
Multiple Input Multiple OutputSpatial Multiplexing
TheData
The quick
brown fox
Data
The quick
brownData
The quick
brown fox
Data
The quick
brown fox
quick
fox
80MHz – 1SS
80MHz – 3SS
20-MHz
40-MHz
20-MHz
Gained Space
40-MHz
80-MHzGained Space
Channel Bonding
Gained Space
Gained Space
Channel Bonding
1SS 1SS 2SS 3SS
160-MHz
80-MHz
80-MHz
Gained Space
80-MHz
80-MHz
160-MHz
5GHz Channel Allocation
Engineer in a Can Features
Enhanced HDX
Cisco CleanAir® 80MHzMitigates interference and improves
channel capacity
Optimised RoamingIntelligently determines the
optimum time to roam
Turbo PerformanceImproves radio efficiency for higher
throughput and client density
Cisco ClientLink 3.0Improves legacy and 802.11ac
Client performance
Dynamic BW SelectionExtends DCA to automatically
select ideal channel widths
AirTime FairnessOptimises medium access as
allocation of airtime not bitrate
Cross-AP Management*Directs Wireless Signal for Better
Coverage
• iBeacons use Bluetooth Low-Energy to send advertising signals
• Smart phone applications using simple RSSI information figure out micro-location & apps then fetch relevant advertising content
• BLE /iBeacons can be used to improve the way finding experience
Spectrum IntelligenceCleanAir and iBeacon
Radio Resource Management
Dynamic Channel Assignment / Dynamic Bandwidth Selection
Transmit Power Control
Coverage Hole Detection and Mitigation … and more
• What It Does
• Dynamically balancesinfrastructure and mitigatechanges
• Monitor and maintaincoverage for all clients
• Provide the optimalthroughput under changingconditions
• What It Does NOT Do
• Substitute for a site survey
• Correct a poor design
• Manufacture spectrum orotherwise counteract the lawsof physics…
Optimised Roaming
DCA and 802.11ac – Channel Width
• Selection of 20 MHz – all AP’s set to 20 Mhz
• Selection of 40 MHz – All 40 MHz capable AP’s set to 40 MHz
• 20 MHz only AP’s will be left on 20 Mhz
• Selection to 80 MHz – all 80 MHz capable AP’s set to 80 MHz
• Others – 802.11n will be at 40 Mhz, and 802.11a at 20 Mhz
Wireless=>802.11a/b=>RRM=>DCA
802.11AC and the OBSS and Coexistence
• Using the example of an 80 MHz OBSS – (Overlapping BSS)
• AP-AC wins contention on my primary channel and will send data on that channel and 3 other bonded channels.
• The VHT header tells all 802.11AC stations that I’m using an 80 MHz OBSS and even tells what 20 MHz sub channels it’s using
• But What of the lowly 802.11a station, or the 802.11n (HT) station who don’t speak 802.11ac and it’s fancy VHT language?
802.11AC and the OBSS (Overlapping BSS)
• Never Fear – LBT (Listen before Talk) to the rescue – CCA! (Clear Carrier Assessment)
• CCA thresholds where adjusted in the 802.11ac specification to allow Overlapping BSS and IBSS stations coexist by adjusting the contention requirements for Sub Channels
• In the table above – you can see that all 3 protocols have equal contention on the primary.
• Any primary operating within a secondary 20 or 40 will loose contention
• Any secondary 20 operating in a secondary 40 will win contention over other secondary's!
Protocol Primary Secondary 20 MHz Secondary 40 MHz
802.11a -82 dBm
802.11n -82 dBm -62 dBm (20 dB liberty)
802.11ac -82 dBm -72 dBm (10 dB liberty) -76 to -79 (3-6 dB liberty)
Awesome, so what?• More co-channel interference models to
worry about
• So What? It’s still fast – right?
• TCP downlink testing using 80 MHz channel width on channel 36. Interference AP set on channel 44 20 MHz – in the secondary 40 Mhz
If you had set an 802.11ac radio to 80 MHz, that radio will wait until all 80 MHz
is free before it will transmit
It will not roll back and use 40 MHz or 20 MHz
0
100
200
300
400
500
600
MBA MBA Interfereing MBA
Without With
TCP Down MBA
Enter Cisco Dynamic Bandwidth Selection
Radio Resource
Management (RRM)
selects channel only
Difficult to find non-
overlapping channels
80 MHz Channel
52/56/60/64
Interference impacts
80 MHz…what can
I use?
52
56
60
64
RRM selects channel
and channel width
Automatic detection
of non-overlapping
channels
Primary
20
Secondary
20
Secondary
40
• 80-MHz channel 52/56/60/64
• Interference is impacting only channel 60
• 3x20 MHz channels still available or
1x40 MHz and 1x20 MHz
52 56 60 64
AfterAutomatic and intelligent use of spectrum
BeforeComplex configuration and inefficient use of spectrum
52
56
60
64
Cisco Features (802.11ac)
Cisco Dynamic Bandwidth Selection
Radio Resource
Management (RRM)
selects channel only
Difficult to find non-
overlapping channels
80 MHz Channel
52/56/60/64
Interference impacts
80 MHz…what can
I use?
52
56
60
64
RRM selects channel
and channel width
Automatic detection
of non-overlapping
channels
Primary
20
Secondary
20
Secondary
40
• 80-MHz channel 52/56/60/64
• Interference is impacting only channel 60
• 3x20 MHz channels still available or
1x40 MHz and 1x20 MHz
52 56 60 64
AfterAutomatic and intelligent use of spectrum
BeforeComplex configuration and inefficient use of spectrum
52
56
60
64
Cisco CleanAir
AfterMitigated RF interference for improved
reliability and performance
BeforeRogue Wi-Fi interference decreases reliability and performance
until next dynamic channel assignment (DCA) cycle
Improved Client
Performance
Wi-Fi and
non-Wi-Fi
aware
Dynamic
mitigation
ED-RRM
Granular
spectrum
visibility and
control
Rogues seen as
security threat only
Non-Wi-Fi
interference
prioritized
Complete Automatic Interference Mitigation Solution for Rogues and Non-Wi-Fi Interference
Air Quality PerformanceAir Quality Performance
Cisco Air Time Fairness
AfterAir time is allocated per SSID, per realm, per client.
There is now better control over how air time is shared.
BeforeRate limiting can only specify a bit rate (throughput) limit.
There is no way to limit the duration that the bit rate will use.
Gain the Ability to
Meet SLAs
Time-
based
Automatic
calculation
on
availability
Ongoing
recalculation
Bandwidth
rate
unpredictable
Client-
dependent
fluctuation
Not time-
based
Improved Predictability and Performance
SSID 2
30%SSID 1
70%
SSID 2
48%
SSID 1
52%
Air Time Fairness Phase 1(ATF) 8.1 MR2
Total Air Quality(% usable time)
Wi-Fi Interference Non-Wi-Fi Interference(Bluetooth, Wireless phones)
Data Frames
Data (down)
Zero, one, multiple retries, abandoned, dropped
Data (up)
Discarded, error, duplicate
Management Frames
Beacons (down)
Probe Responses (up/down)
Control
Frames
CTS (down)
RTS (up)
ACKs
per AP Wi-Fi traffic
aggregrate (or individual)
Total airtime (data) Total airtime (mgmt) Total airtime (ctrl)
SSID #1
X% allocation
SSID #2
Y% allocationSSID #3
Z% allocation
Total “Air Time”8.1 MR2 Air Time Fairness
• Allocation is applied per SSID
• Applies to Downstream only
• Can be configured in WLC
GUI/CLI and PI
ATF Modes
• Disable
• Monitor Mode
• Enforce-Policy Mode
Can be applied to all APs on a
Network, AP Group, or AP
Supported on:
• AP1260, 1570, 1700, 2600,
2700, 3500, 3600, 3700
• Local and Flex-connect mode
X = A+B+C+D
Client #1
A% allocation
Client #2
B% allocation Client #3
C% allocation
Client #4
D%
allocation
Air Time Fairness Phase 2 (ATF)
Total Air Quality(% usable time)
Wi-Fi Interference Non-Wi-Fi Interference(Bluetooth, Wireless phones)
Data Frames
Data (down)
Zero, one, multiple retries, abandoned, dropped
Data (up)
Discarded, error, duplicate
Management Frames
Beacons (down)
Probe Responses (up/down)
Control
Frames
CTS (down)
RTS (up)
ACKs
per AP Wi-Fi traffic
aggregrate (or individual)
Total airtime (data) Total airtime (mgmt) Total airtime (ctrl)
SSID #1
X% allocation
SSID #2
Y%
allocation
SSID #3
Z% allocation
Total “Air Time”
8.2 Air Time Fairness
• Allocation is applied per
SSID Per Client w
• Applies to Downstream
only
• Can be configured in WLC
GUI/CLI and PI
8.2 code
X = A+A+A+A
Client #1
A% allocation
Client #2
A% allocation
Client #3
A% allocation
Client #4
A% allocation
Your Turn
Site SurveysAP and Antenna Placement
• Consider underlying requirements• Number of Users
• Application Types• Data• Voice• Video
• Location accuracy
• AP placement considerations• Consider environmentals
• Characterise the -67dBm edges
• For location a minimum of three AP should be able to hear the device with a a signal strength of -75dBm or higher
• Understand existing spectrum use• Interference mitigation
Planning ToolsAll models are wrongSome of them are useful
• A planning tool can be very useful for developing a preliminary design and solving deployment problems
• The model MUST be calibrated to ensure what you see is what you get
• These recommendations should be followed
• Always verify predicted coverage with an actual measurement
• Always remain conservative with power• Middle to lower end of the range should be selected
• Many tools default to high power and can be very misleading.
• Coverage and capacity should be balancedhttps://rftool.cisco.com
Channel Utilisation
• One simple change reduced the utilisation to 5%
• Remove the low rates
• Large cells = Low density
• More users spread across a larger area, connecting at lower data rates
• Small cells = High density
• Removing lower data rates constrains cell size
Wait a minute… Whats Next?
Going Beyond 802.11ac Wave 2
Cisco Aironet PortfolioPositioned to Capture the 802.11ac Wave 2 Transition
Enterprise Class Mission Critical Best in Class
1850
• 4x4:3SS 80Mhz; 1.7 Gbps
• Spectrum Analysis*
• Internal or External antenna
• Tx Beam Forming
• 2 GE Ports
• USB 2.0
• Centralized, FlexConnect and Mobility Express
2800
• 4x4:3SS 160 MHz; 5 Gbps
• 2.4, 5GHz or Dual 5GHz
• 2 GE Ports
• Internal or External antenna
• Smart Antenna Connector
• Enhanced Location* (External Antenna)
• CleanAir 160MHz
• ClientLink 4.0
• USB 2.0
• Centralized, FlexConnect and Mobility Express*
3800
• 4x4:3SS 160 MHz; 5 Gbps
• 2.4, 5GHz or Dual 5GHz
• 1 GE + 1 mGig (5G)
• Internal or External antenna
• Smart Antenna Connector
• Enhanced Location* (External Antenna)
• CleanAir 160 MHz
• ClientLink 4.0
• StadiumVision
• USB 2.0
• Modularity
• Centralized, FlexConnect and Mobility Express*
1810 Wall Plate• 2x2:2SS 80 MHz; 867 Mbps
• Tx Beam Forming
• 1 GE Port uplink
• 3 GE Local Ports, including 1 PoE out
• Local ports 802.1x ready
• Integrated BLE Gateway*
1830
• 3x3:2SS 80MHz; 867Mbps
• Spectrum Analysis*
• Internal antenna
• Tx Beam Forming
• 1 GE Port
• USB 2.0
• Centralized, FlexConnect and Mobility Express
1810 Teleworker• 2x2:2SS 80 MHz; 867 Mbps
• 3 GE Local Ports downlink, including 1 PoE out
• One or Two Local Ports can be tunneled back to corporate
* Future availability
Meet Any Wi-Fi Use CaseExpandability and Investment Protection
Future Wi-Fi
Standard
Video
Surveillance
Custom
Application
Using Linux
Adv. Security
and Spectrum
Analysis
3G and
LTE
Offload
Bluetooth
Beacon
Hyperlocation
Antenna
Directional
Antennas
Stadium
Panel
Antenna
SMART ANTENNA
PORT
MODULEPORT
Self-Discover /
Self-Configure
Other Other
Other
PRIMARY ANTENNAS
Potential Future
Expandability
Next-Generation Wave 2 802.11ac Access Points
Cisco Aironet® 3800 Series
* Planning
• Industry leading 4x4 MIMO:3 spatial streams (SS) Wave 2 802.11ac access points
• Dual radio, 802.11ac Wave 2, 160 MHz
• Combined Data Rate of 5.2Gbps
• 2 x 5 GHz: 4x4: 3SS supporting
- SU-MIMO / MU-MIMO
- Flexible Radio Assignment: 2.4GHz, Dual-5GHz, Wireless Security Monitoring, or Wireless Service Assurance
• Gigabit Ethernet and multi-Gigabit Ethernet (1G, 2.5G, 5G)
• HDX Technology
• USB 2.0
• Internal and external antenna models
• Smart Antenna Connector - 2nd Antenna Connector
• Modularity: Side Mount Modular
Gigabit Wi-Fi has fully arrived.
New
Next-Generation Wave 2 802.11ac Access Points
Cisco Aironet® 2800 Series
* Planning
• Industry leading 4x4 MIMO:3 spatial streams (SS) Wave 2 802.11ac access points
• Dual radio, 802.11ac Wave 2, 160 MHz
• Combined Data Rate of 5.2Gbps
• 2 x 5 GHz: 4x4: 3SS supporting
- SU-MIMO / MU-MIMO
- Flexible Radio Assignment: 2.4GHz, 5GHz, Wireless Security Monitoring, or Wireless Service Assurance
• 2 x Gigabit Ethernet
• HDX Technology
• USB 2.0
• Internal and external antenna models
• Smart Antenna Connector - 2nd Antenna Connector
Gigabit Wi-Fi has fully arrived.
New
Next-Generation Wave 2 802.11ac Wall Plate Access Point
Cisco Aironet® 1810w Series
• Simultaneous Wired and Wireless Access
• Dual Radio, Dual Band with 802.11ac Wave 2
• Integrated Bluetooth Low Energy radio*
• Designed for ease of mounting to numerous global wall junction
standards. Accessories available to mount directly on a wall or have
it desk mounted
• Sleek design in a small form factor: 165 x 114 x 41 mm (6.5 x 4.5 x
1.6 in)
• 3 x Local GigE Ethernet Ports + 1 x uplink GigE port + 1 x passive
pass-through RJ45
• Powered over Ethernet (PoE) or with AC Adapter
• PoE out on LAN 3 port, up to 803.af Class 0 (depending on
powering options)
* Future availability
Next-Generation Wave 2 802.11ac OfficeExtendAccess Point
Cisco Aironet® OEAP1810 Series
• Target for Teleworker or Micro-branch deployments, providing
wired and wireless corporate access to remote workers
• Simultaneous Dual Radio, Dual Band 2x2:2 with 802.11ac Wave
2, including MU-MIMO
• Vertical mount to optimize wireless coverage with integrated
antennas.
• Shipping with included mounting cradle purposefully designed for
optimal mounting and cable management. Accessories available to
mount onto a junction box or directly on a wall
• 3 x GigE Ethernet Ports, 1 x uplink GigE port
• Up to 2 ports can be tunneled back to Wireless LAN Controller
• Powered over Ethernet (PoE) or with included AC Adapter
• PoE out on LAN 3 port, up to 803.af Class 0 (depending on
powering options)
Flexible Radio AssignmentAdjust Radio Bands to Better
Serve the Environment.
Innovations Only Cisco DeliversRadio Frequency Excellence for High-Density Environments
Optimized RoamingIntelligently Connects the Proper
Access Point as People Move
Turbo PerformanceScales to Support More Devices
Running High Bandwidth Apps.
Zero Impact AVCHardware Based Application Visibility
and Control without Impact to
Performance.
Cisco CleanAir®
Remediates Device
Impacting Interference
Cisco ClientLink Improves Performance of
Legacy and 802.11ac Devices.
Expandability Add Functionality Via Module, Smart
Antenna Port or USB Port
Multi-Gigabit UplinksFree Up Wireless With Faster
Wired Network Offload
Gb+
Flex Dynamic Frequency SelectionAutomatically Adjusts So Not to
Interfere With Other Radio Systems
The World’s Most Versatile Access Points All The Benefits of 802.11ac Wave 2
Higher
Data Rate
Wider
Channels
Simultaneous
Data Delivery
Better
Battery Life
Highest Wi-Fi Performance Ever Better End Device Efficiency
New Flexible Radio
Assignment
Improved
Modularity
Improved
CleanAir
Plus Cisco Innovations for High Density Environments
Improved
ClientLinkNew Multi-Gigabit
Uplinks
New Zero
Impact AVC
Turbo
Performance
Optimized
RoamingImproved
Enhanced Location*
Flexible Dynamic
Frequency Selection
Self-Optimizing Network Optimized Mobile User Experience
NEW: Cisco Aironet 2800 NEW: Cisco Aironet 3800
*Future
New Smart
Antenna
Connector
• 2.4 GHz and 5 GHz on the same silicon
• Allows serving of either 2.4 GHz or 5 GHz channel
• Allows Serial scanning of all 2.4 and 5 GHz channels
• Role selection is manual or Automatic – RRM
• Not new in production (WSSI/WSM modules)
What is an XOR Radio?
AP2800/3800 “I” series antenna system (cover removed)
Previously in the controller Access
Point radios were defined as…
Radio 0 = 2.4 GHz
Radio 1 = 5.0 GHz
Using “Flexible Radio Assignment”
Radio “0” can be configured as 2.4 GHz
(default) or as an additional 5 GHz radio.
If configured as a 5 GHz radio the 2.4 GHz
radio is disabled and the 5 GHz micro-cell
antennas are used.
Micro-cell antenna is 7 dBi @ 5 GHz
Macro-cell antenna is 5 dBi @ 5 GHz
Conventional AP footprint
(Macro-Cell) uniform 360
degree coverage
Smaller AP footprint
(Micro-Cell) uniform 360
Degree but for smaller coverage
area (high density) deployments
By using spatially-efficient and
compact antenna design along with
different channels & Tx RF power –
BOTH radios can co-exist internally
Difference in antenna designs allow RF co-exist
• Default operating mode
• Serve Clients on both 2.4GHz and 5GHz
Flexible Radio Assignment
5GHz
Serving 2.4GHz
Serving
Wireless
Security
Monitor
Wireless
Service
Assurance*
• Dual 5GHz Support, both radios serving clients on 5GHz
• Maximum over the air data rate up to 5.2Gbps
• Wireless Security Monitoring
• Scan both 2.4GHz and 5GHz for security threats
• Serve Client of 5GHz
• Wireless Service Assurance*
• Proactively monitors the network performance
• Serve Client of 5GHz
* Denotes feature availability post-FCS
5GHz
Serving
5GHz
Serving
5GHz
Serving
5GHz
Serving
Enhanced
Location*
• Enhanced Location*
• Improves the client location accuracy
• Serve Client of 5GHz
5GHz
Serving
• Not new, implemented for years in Cellular
• Method for addressing Non Linear Traffic requirements
• Allows more bandwidth and efficiency to be applied to an area within a larger coverage cell
• Used in Wi-Fi today – i.e. Convention centers -Macro coverage of the whole floor area from Ceiling, while individual locations requiring more bandwidth/capacity may be covered by on the floor AP-700W
• 2800/3800 will support from single access point – it’s about Airtime Efficiency and Capacity
What is a Macro/Micro cell Architecture?
Self Optimizing Network Flexible Radio Assignment
2.4GHz
Serving
2.4-5GHz
Monitoring
5GHz.
Serving
5GHz.
Serving
CleanAIr
CleanAIr
!
2.4GHz
Serving
5GHz.
Serving
CleanAIr
Self Optimizing Network Flexible Radio Assignment
2.4GHz
Serving
2.4-5GHz
Monitoring
5GHz.
Serving
5GHz.
Serving
2.4GHz
Serving
5GHz.
Serving
5GHz
Serving
5Hz
Serving
2.4GHz
Serving
Self Optimizing Network Flexible Radio Assignment
5GHz
Serving
2.4GHz
Serving
5GHz.
Serving
5GHz.
Serving
5Hz
Serving
5GHz.
Serving
2.4GHz
Serving
2.4GHz
Serving
2.4-5GHz
Monitoring
Dual 5GHz – Improves Client Performance and Capacity
• Improves the Effective Spectrum Usage
of the Cell
• Micro-Radio
• 802.11ac Clients near the AP
• High Performance Wi-Fi Clients at
802.11ac data rates
• Excellent speed and performance
• Macro-Radio
• All legacy Clients join macro-cell
• Future of wireless
Users have a better overall experience on a Dual 5GHz Access Point
Micro Macro
Dual 5GHz – 2x the Coverage Area and Capacity
• Provide 2x the coverage area from
a single Access Point
• Improve the total Network
Performance
• Utilizes Smart Antenna Connector
• Mix and match all Cisco Supported
Antennas
• If you have designed a network for dense 5 GHz coverage, then you have too many 2.4 GHz radios
• 2.4 GHz has 1/7th the channels of 5 GHz spectrum in the –A regulatory and it propagates roughly 1.5x farther
• Prior to the 2800/3800 and 8.2 MRs release, your only option was to disable these radios. Disabling the radio provides no value other than making the 2.4 GHz spectrum manageable, but no location, rogue or other information is gathered.
• New in RRM is a redundant radio Identification algorithm to identify and manage locating redundant radios, and assign 1 of multiple roles it can play that and value to the equation.
• In the future - 5 GHz will also be crowded with Bonded channels as well -
Redundant Radio Identification
3 dB wall
5 GHz 8 dBm TX
268 Feet
3 dB wall
2.4 GHz 8 dBm TX
200 feet
400 Feet
200 feet
5GHz
Serving
2.4GHz
Serving
Redundant Radio IdentificationPer RF Neighborhood Coverage Analysis
• First and RF Neighborhood (different than an RF Group) is selected to solve
• Using reciprocal NDP messages, each AP is located relevant to one another another in RF Distance
• NDP operates at MAX power
• Coverage area is represented by a circle around each AP
• Then Overlap will be assessed based on multiple points within each AP’s coverage area
• In this way, the coverage of any Given AP can be evaluated for % of redundancy – or percentage of coverage another AP(s) could cover without it
• Current Power is evaluated, and AP’s with a high degree of redundancy are selected for other roles for the XOR radio to fill
5GHz
Serving
2.4GHz
Serving
Macro/Micro Dual 5 GHz cell Instant Capacity
5GHzServing
5GHzServing
• Cells must be isolated –• overlap in RF Frequency = shared
airtime = lost efficiency
• Begins in the Silicon design
• Extends to the AP/Antenna selections
• Frequency Diversity Critical• RRM knows and manages this
2800/3800 Dual Band
Channel Utilization = 60%
• The further a client is from the AP,
the lower the data rate will used
• Data Rate is a function of SNR
• The higher the SNR – The higher
the data Rate will be
• 1 x5 GHz cell has a finite amount of
Air Time available
• Capacity is the sum of all clients
within the cells Air Time
• You can’t get more than a second
out of 1s of Air time - period
-63 dBm
-60 dBm
-58 dBm
-68 dBm
-71 dBm
-73 dBm
-75 dBm
-51 dBm
-63 dBm = Client RSSI at AP
Single 5 GHz cell
5GHz
Serving
2.4GHz
Serving
2800/3800 Macro/MicroDual 5 GHz
CU Chnl 36= 20% !
CU Chnl 108=24% !
• Creating two RF diverse 5 GHz cells
– Doubles the Air Time available
• Optimizing Connections (Macro vs
Micro) keeps like performing clients
together, rather than have one drag
down the other
• RRM will optimize, based on received
RSSI only at FCS – Other
possibilities exist (protocol, SS
Capability)
-63 dBm
-60 dBm
-58 dBm
-68 dBm
-71 dBm
-73 dBm
-75 dBm
-51 dBm
-63 dBm = Client RSSI at AP
Macro/Micro
5 GHz cell
5GHz
Serving
5GHz
Serving
Intra-cell Roaming –Macro to Micro
Macro=Big
Micro=small
5GHz
Serving
5GHz
Serving
-51 dBm
-51 dBm
• The most likely scenario is a client will associate to the Macro cell first – since we have higher power and bigger footprint
• In this case, a client that has RSSI at the AP above the Micro cell threshold of -55 dBm will be moved into the Micro cell• -55 dBm default, configurable by user
• For an 802.11v client – on association we will send an 11v BSS Transition request with the Micro Cell BSSID as the only candidate
• For a non 11V client, we will send an 11K neighbor list and a disassociate
• Mechanism such as BandSelect is being investigated
Intra-cell Roaming –Macro to Micro
• If a client associates to the Micro cell first –less likely – but possible based on device scan and channels heard -
• In this case, a client that has RSSI at the AP below the Macro cell threshold of -65 dBm will be moved into the Micro cell• -65 dBm default, configurable by user
• For an 802.11v client – on association, we will send an 11v BSS Transition request with the Macro Cell BSSID as the only candidate
• For a non 11V client, we will send an 11K neighbor list and a disassociate
• Mechanism such as BandSelect is being investigated
Macro=Big
Micro=small
5GHz
Serving
5GHz
Serving
-65 dBm-65 dBm
Dual 5 GHz – “E” Model – Macro/Macro
• Using the DART connector on the E Model enables Dual 5 GHz cells with Discrete external antenna’s
• Doubles the effective coverage for the cost of one additional antenna
• mGIG provides throughput investment
• Existing conference centers Double capacity on existing cable plan
5GHz
Serving
5GHz
Serving
2 4 1
• BRKEWN-2670
• Best Practices for Configuring Cisco Wireless LAN Controllers
• BRKEWN-3010
• Improve Enterprise WLAN Spectrum Quality with Cisco's Advanced RF Capacities (RRM, CleanAir, ClientLink, etc)
Best Practices & Advanced RF Sessions
Q & A
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