Download - WLAN Design for Location
CONFIDENTIAL
© Copyright 2014. Aruba Networks, Inc. All rights
reserved
WLAN Design for Location
Abhi Maras
June 2014
CONFIDENTIAL © Copyright 2014. Aruba Networks, Inc. All rights reserved
Agenda
• Analytics and Location Overview
• ALE System Overview
• Indoor Location Technology
• Probing
• Recommendations
• Summary
CONFIDENTIAL © Copyright 2014. Aruba Networks, Inc. All rights reserved
Agenda
• Design Guidelines for WiFi grade Location
• Design Guidelines for WiFi grade Voice
• Design Guidelines for WiFi grade Video
• QOS and Traffic Optimization
• Enterprise Diagnostics and Troubleshooting
Analytics & Location Overview
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Analytics & Location Ecosystem
Big DataAnalytics Partners
NetworkApplications
Cloud Applications
User Context(who, what, where, when)
Location Applications
(Wayfinding, etc)
Context:1. Location2. Applications3. Destinations4. Identity5. Device types
ALE (Context
Aggregation)
ALE System Overview
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Analytics and Location Engine (ALE) Overview
ALE
Unified context for
each user (user name, IP,
MAC, device type, App
visibility, etc.)
1
Seamless, secure
cloud connectivity4
Real time location
engine
2
Standard, high
performance northbound
APIs (publish/ subscribe,
polling)
3
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Data Collected & Provided by ALE
• Presence feed
• Events when a device is detected crossing a Geofence
• Device information
• User information from authentication to the network
• Applications used
• Destination URLs
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ALE Enabled Use Cases
ALE Use cases
People movement,
congested paths1
Way-finding (turn-
by-turn directions2
Way-finding (turn-
by-turn directions
Busy times by
location
Web
analytics
Energy
management
4
3
5
6
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ALE System Overview
LocalController
RemoteControllers
NETWORK
InstantAPs
Campus/Remote APs
VisualRF
SERVICES
Context aggregation, location engine
ALE VM
Location data forvisualization
on maps
APPLICATIONS
Context visualization, analytics
Northbound APIs:REST, Protobuf/OMQ
Context Data
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Understanding Probe Flow and Location
ALE
Client pulls its location from the
cloud every __ seconds?
Probes between few seconds to 10s of
minutes1
AP sends RSSI on a timer, default is 30 secs, can be set to 1 sec (6.3.1.1)(Future: Will be instantaneous)
2
Controller sends the data on a fixed timer of 10 seconds (Future: Will be instantaneous)
3
ALE calculates the location, latency varies based on the settings.
4
Indoor Location Technology
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Indoor Location Technology Overview
• Satellite-based GPS does not work indoors
• Two main approaches to indoor positioning technology: – Device-based scans of radio signals (software/hardware)
– Network-based scans of device radio signals (Wi-Fi)
• No standard indoor positioning solution exists today
• Indoor positioning (relative to the venue layout) requires indoor maps
• Layouts within locations often change
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Device vs Wi-Fi Network Based Location
Device-based software
The device performs signal scans ofnearby network signals to analyzes signal strengths to calculate position
Wi-Fi network based
The network APs perform signal scans of Wi-Fi traffic and analyzes the device’s Wi-Fi signal strength to calculate position
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Location Positioning Technology
How Information
is Transmitted
GPS Geofencing
Cell Phone
Triangulatio
n
Cell
Towers
How Info is Transmitted Hardware Required
Req
uir
es O
nsi
te Fingerprinting
BLE
LED Light Pulses
Sensor Fusion
Device-Based Signal Triangulation
RTLS Network-Based Wi-Fi Triangulation
Existing Wireless APs
LED Lights With Chips
Wi-Fi Hotspots
BLE Beacons or Nodes
Wi-Fi Hotspots
Audio QueueSound Emission Devices
Outside Venue
Inside Venue
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GPS –Triangulation from Satellites
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Indoor Location Positioning Technology
Network-Based Wi-Fi Positioning• Devices are constantly scanning for Wi-Fi
• The network does the work
• Analytics can be delivered without device app
• More battery efficient for mobile devices
• Can work with any device, including iPhones, Android, etc.
Wi-Fi must be turned on/enabled on the deviceUsed by:
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The Wi-Fi Location Puzzle
• Sparse samples
– Easier & better from infrastructure than from device– +/- 5dB inter-frame variation– Clients want to minimize radio activity > maximize battery life– Floor-level signal differs from ceiling-level– Absence of signal does not mean a device is absent
• Frame of reference for signal sources / sinks
– Where are the AP locations? Tx Pwr? Directional antennas? – ARM changes RF Plan
• Frame of reference – local or global (Lat/Long) or civic?
– Enterprise and indoor apps mostly use local maps– Google, Bing etc use Lat/Long
• Parametric or non-parametric?
– Build a synthetic heatmap using RF propagation model– Or use AP-AP and other calibration and non-parametric curve-fitting (e.g. Gaussian
Process)
• Speed vs accuracy tradeoff
• Add Helpers
– GPS, celltower, Bluetooth beacons, BSSID surveys– On-board compass, accelerometers– Estimates for motion vectors and earlier position fixes– Knowledge of walls, doors and snap-to-grid tramlines
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Probing
• Again….location calculation today purely relies on client
probes
– NO PROBES…..NO LOCATION!!
• Unassociated devices will Probe more than associated
– If associated device is happily connected, it will not bother Probing.
• iOS devices Probe less than Android (battery life
considerations).
– Meridian and Aruba Utilities (mobile apps) can stimulate Probes
on Android.
– iOS does not expose any such API (to cause Wi0Fi scan)
• Going on Settings->Wifi on iOS will trigger Probes. If you want
to stimulate Probes on iOS, either unassociate, or
occasionally keep going to the Settings->Wifi page.
• A device must be heard by 3 or more
APs to calculate location
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RSSI Based Locationing
• The raw data for location estimation is the
received signal strength (RSSI) of Wi-Fi frames
received from client devices
– RSSI is inherently variable due to fluctuating RF conditions, the
geospatial
attitude of the mobile device
and its proximity and
relationship to human tissue
– We expect a variation of RSSI
in the order of 6dB even when
the person holding the device
is stationary
– As the distance from the AP
increases, the RSSI - distance
curve flattens
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Location: Accuracy & Latency
Accuracy
• Impacted by various factors:
– AP density, type, mounting type
– Physical Environments, enterprise, malls, warehouse, etc.
– RSSI variations
– Client probing behavior, device type, OS type
Latency
• Impacted by
– Client probe frequency (iOS vs Android)
– Network settings: AP/controller timers
– Engine smoothening algorithms
• Balance between accuracy and latency
ALE goal is to
be <10m 90%
of time on a
location grade
network
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Location Applications in PFE
• Location has different facets:– Presence (Inside a Store/Zone or outside)
• Useful for push notifications
– Wayfinding (“Blue Dot”)
• Useful in ultra large venues
• Most Location applications of practical value in PFE fall under “Presence” category
• Location Services are the not the only “PFE” applications– Guest Access, support for enterprise apps,
multimedia support, device onboarding, etc., are all applicable to PFE
Presence
Way-Finding
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Design Considerations for Locationing
• Start with a good understanding of commercial
requirements
• What is the key use case and “true” requirement?
– Self directed museum tour?
• In which case latency will not be an issue
– Ability to locate specific venue (conference room, restaurant, etc.)
within a large venue or a product with turn by turn directions?
– “Presence detection” in stores in a shopping mall?
• Knowledge of the use case is key to understanding
location accuracy, latency requirements
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AP Placement Guidelines (1)
• RSSI location uses triangulation techniques
– This needs at least three APs to receive a target’s transmissions at relatively short range to give a good location.
• Best indicator of location accuracy is AP spacing
• Studies and experience show that regularly spaced APs give the best overall location accuracy.
– Most WLAN planning tools produce a regular grid pattern of APs in the absence of local propagation information
• Our best advice is to take the output of such tools – or a wireless engineer’s design withregular AP spacing - and adjust the output to
take account of local knowledge:
• Areas that present special challenges or where accurate location is more important should receive special attention
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AP Placement Recommendation (2)
• Do:
– Place AP every 2500 sq. feet or 50 feet apart
– Cover the extremities!
– 65 dbm coverage (“Voice Grade)
– Ensure AP placement on floor plan is accurate
– Stagger AP placement in multi-floor buildings
• Do Not:
– Place AP in straight lines
– Design for coverage only & not enough density
• The standard topology is a ‘square’ grid pattern of APs,
but there is research indicating a hexagonal pattern
gives better results
• Aruba is testing this configuration
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AP Placement: Voice Overlay Design
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AP Placement Recommendations Summary
Recommendation Priority Comments
Voice Overlay 1
This is a must in all deployments to achieve
triangulation which is core requirement of
location calculation.
AP every 2500 sq. feet or 50
feet apart and cover the edges1
This is help achieve a good coverage
pattern and triangulation and is must for
most deployments.
Hexagonal pattern for AP layout 2
This is recommended but might be hard to
achieve in certain scenarios due to the
physical layout.
-65 dbm coverage2
This is strongly recommended but might be
hard to achieve in certain parts of a building.
In those cases, ensure that there is at least
a -75 dbm coverage in those areas.
RF Design Guidelines for Voice and Video
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Pervasive RF Coverage
• 100% coverage in all areas of Voice use
• Capacity based Wireless network design recommended
– Higher number APs operating with low TX Power
– Small Cell sizes, clients use higher data rates
Coverage design with 7.2 Mb/s cell edge Capacity design with 216.7 Mb/s cell edge
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ARM Features for Voice
• Interference Aware
• Band Steering
• Spectrum Load Balancing
• Voice/Video Aware Scanning
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Clientmatch
• Deterministic steering of clients based on the SNR and signal level information gathered from client's perspective
• Steering decision is based on the probes request from the client
• Periodic load balancing
• Resolves Sticky-client issue
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RF Design Best Practices for Voice
• Pervasive RF Coverage
• Distance between APs to not exceed 50 Ft
• Minimum RF signal (RSSI) levels of -65 dBm
• Minimum signal-to-noise ratio (SNR) of 25 dB
• Minimum and maximum AP power difference no greater than two steps
• Disable lower data rates
• In the Adaptive Radio Management™ (ARM) profile
– Enable voice/video aware scan
– ClientMatch™-enabled
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RF Design Best Practices for Voice (continued)
• Configure Supported Beacon rate to higher rate
• Enable WMM Traffic Management
– Give higher of bandwidth to Voice and Video
• Enable Fair access
– Provide high % of bandwidth to a VAP (For example, assign
higher % bandwidth to Corp VAP than Guest VAP)
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Best Practices for Video
• RF Best practices for Voice applies to Video as
well
• Best practices for Delivering multicast video
– Enable IGMP Snooping Or IGMP Proxy
– Enable Dynamic Multicast Optimization (DMO)
– Enable Decrypt-tunnel Dynamic Multicast Optimization (D-
DMO)
Designing a Roaming Network
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Designing a Roaming Network
• Difference in power levels on the deployed APs
should not be too high
• Airtime fairness is recommended in an
environment with mobile clients to avoid
slower clients taking too much airtime
• In a dot1x environment, enable EAPOL rate
optimization
• For faster roaming, use OKC and 802.11r
• Enable ClientMatch to help with sticky
client problem
• Match QoS markings that the devices are
using
Authentication / Encryption Guidelines
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Authentication/Encryption Guidelines
• 802.1x based authentication through radius
server may introduce delay during re-
association/roaming
• Use Opportunistic Key Caching
with 802.1x for faster roaming
• PSK works better for voice
devices (less delay), but not a
preferred method due to weak
security
• EAP-TLS provides the best security
and is preferred in enterprises rather
than EAP-PEAP
End-to-End QoS
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QoS Segments
LAN core LAN edge Wireless
Tagged DSCP, 802.1p Tagged DSCP, 802.1p WMM / strict queuing
Tagged DSCP, 802.1p Tagged DSCP, 802.1p WMM / SVP
Bandwidth management call admission control QoS
aware RF management
BandwidthManagement
Tagging
Upstream traffic
Downstream traffic
Deep Dive into DSCP and WMM AC
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QOS - Tunnel Mode Client No Tag (WMM Only)
ArubaMobility Controller
AP
Client-A, VO: DSCP 0
Client-B, VO: DSCP 0
DSCP 0WMM BE
DSCP 24WMM BE
DSCP 24
DSCP 24
VO: 46VI: 34BE: 24
Summary:• AP looks at L2 Priority and puts the DSCP as per DSCM-WMM mapping in controller• Controller decrypts the packet and uses L2 priority to assign DSCP mapping in
downstream direction
Controller decrypts the packet and retags as per
L2 priority
AP looks at L2 priority and puts DSCP as per DSCP to
WMM mapping
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QOS - Tunnel Mode (WMM Only)
ArubaMobility Controller
AP
Client-A, VO: DSCP 46
Client-B, VO: DSCP 46
DSCP 46WMM VI
DSCP 34WMM VI
DSCP 34
DSCP 34
Summary:• AP looks at L2 Priority and puts the DSCP as per DSCM-WMM mapping in controller• Controller decrypts the packet and uses L2 priority to assign DSCP mapping in
downstream direction
Controller decrypts the packet and retags as per
L2 priority
AP looks at L2 priority and puts DSCP as per DSCP to
WMM mapping
VO: 46VI: 34BE: 24
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QOS - Tunnel Mode (Lync Heuristics for Voice)
ArubaMobility Controller
AP
Client-A, VO: DSCP 46
Client-B, VO: DSCP 46
DSCP 46WMM VI
DSCP 46WMM VO
DSCP 46
DSCP 34
Summary:• AP looks at L2 priority and puts the DSCP as per DSCM-WMM mapping in controller• Lync heuristics determines the AC based on the codec. If the codec used is voice, it gives
DSCP value corresponding to voice.
Controller decrypts the packet and retags
as per traffic type
AP looks at L2 priority and puts DSCP as per DSCP
to WMM mapping
VO: 46VI: 34BE: 24
Troubleshooting and Diagnostics
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Troubleshooting Guidelines
• Are RF and other Configuration Best Practices in place?
• Does your Network have end-to-end QoS?
• Can you isolate if it is an RF Network issue Or Wired Network?
• If required, enable debugging at controller to get detail logs
• For example, if you are using Voice ALGs (Sip, Lync), enable the following command to troubleshoot voice issues:
– (SE_PFE_1) (config) #logging level debugging user process stm subcat voice
– (SE_PFE_1) (config) #show log user all
Troubleshooting and Diagnostics Demo
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Voice Overlay Airwave
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Airwave – Client Troubleshooting
#AirheadsLocal