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


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


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


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


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


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


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


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


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


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


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


GPS –Triangulation from Satellites


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:


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


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


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


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


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


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


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


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


AP Placement: Voice Overlay Design


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


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


ARM Features for Voice

• Interference Aware

• Band Steering

• Spectrum Load Balancing

• Voice/Video Aware Scanning


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


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


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)


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


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


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


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


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


QOS - Tunnel Mode (WMM Only)


AP



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


QOS - Tunnel Mode (Lync Heuristics for Voice)


AP



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


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


Voice Overlay Airwave


Airwave – Client Troubleshooting

#AirheadsLocal

wlan design for location

Technology

location ale client

polling3confidential

ale system overview

user user

monitoring dataplane

devicebased scans of

seconds future

wifi grade videoqos