Delay-tolerant Networking using Wi-Fi Direct - Droidcon 2013

Delay-tolerant NetworkingUsing Wi-Fi DirectStephen NaickenVisiting Research Fellow, Sussex UniversityDroidcon 2013

Outline

The Problem

The Solution

Wi-Fi Direct

Deployment in the AMEX Community Stadium, FalmerResultsFuture work and Conclusions

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Poor mobile data connectivity in stadia·

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Pocket Switched Network implementing a distributed cache withidempotent HTTP POST

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Trials and tribultations·

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The ProblemPoor in-stadia mobile data connectivity

Dr. Ian Wakeman, Senior Lecturer at Sussex University. UEFA Champions League Final, 2012.

Project

EPSRC-funded research project to investigate the use of smartphonesto build new ways of communicating within stadiums

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In-stadia Mobile Data Experiences

Smartphones offer opportunities to improve the visitor experience

But poor connectivity in-stadia is a barrier to deployment of theseapplications

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Live scores and league tablesSeat location servicePie and pint orderingVideo highlights and goal-line replays

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The American Express Community Stadium

Opened in 2011Capacity of 30750Home to Brighton and Hove Albion Football Club

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Dominic Alves. http://www.flickr.com/photos/dominicspics/5606852371/

In-stadia Mobile Data Experiments

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Problem Statement

In a typical stadium, the concrete and steel construction and largecrowds combine to make mobile Internet access very unreliableHow can we improve connectivity so that fans can access matchdayservices?What are the possible solutions?

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Do nothing, but EPSRC would not be impressedInvest in mobile network infrastructure to increase capacityWi-Fi

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Issues with Mobile Networks

Investment in mobile networks will not yield benefits to all fans unlessall major operators investMobile network operators unlikely to be supportive of cash-strippedclubsA UK operator has invested approx. £1m to improve mobile dataconnectivity at leading Premier League club's stadium

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Fans still complain of poor connectivity and the club accept thatvideo can still not be delivered to all fans

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Issues with Wi-Fi

Cost

Performance Issues

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Typically quoted cost to British clubs is around £500000US market costs could be around $6mTechnology spend at British clubs is typically lowMany Football League clubs would struggle to justify costs (low ROI)

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It doesn't work too wellLow numbers of simulataneous usersUser experience is typically poor - e.g. Gillette Stadium

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The SolutionPocket Switched Networking

Technology Idea

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Technology Idea

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Technology Idea

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Technology Idea

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Supporting HTTP GET

Supporting HTTP GET

Supporting HTTP GET

Supporting HTTP GET

Supporting HTTP GET

Supporting HTTP GET

Supporting HTTP POST

Supporting HTTP POST

Supporting HTTP POST

Supporting HTTP POST

Supporting HTTP POST

Wi-Fi DirectTrials and Tribulations

Connectivity

Bluetooth

Tethering

Ad-hoc Wi-Fi

Wi-Fi Direct

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System dialog prompts·

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Unrestricted Internet access for all·

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Not part of the API and requires superuser·

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Only option open to us·

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Starting Wi-Fi Direct on ICS

WifiP2pManager p2pManager = (WifiP2pManager) getSystemService(Context.WIFI_P2P_SERVICE);// Wfd callbacks on a handler threadchannel = p2pManager.initialize(context, wfdHandler.getLooper(), channelListener);

if (!wifiManager.isWifiEnabled()) { // remember to handle exceptions gracefully Class p2pManagerClazz = Class.forName ("android.net.wifi.p2p.WifiP2pManager"); Method method = p2pManagerClazz.getMethod("enableP2p", new Class[]{WifiP2pManager.Channel.class}); method.setAccessible(true); method.invoke(p2pManager, channel); method.setAccessible(false);}

JAVA

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Wi-Fi Protected Setup

WifiP2pConfig config = new WifiP2pConfig();config.deviceAddress = device.deviceAddress;

JAVA

// Push-Button Configurationconfig.wps.setup = WpsInfo.PBC;

JAVA

// Display pin on client, enter on GOconfig.wps.setup = WpsInfo.DISPLAY;

JAVA

// Display pin on GO, enter on clientconfig.wps.setup = WpsInfo.KEYPAD;

JAVA

p2pManager.connect(channel, config, wfdActionListener) JAVA

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WPS without the dialog prompts - API 16-17

Automatic acceptance of WPS PBC dialogs is possibleOnce again using reflectionAPI 16-17: WifiDirectAutoAccept.java (AllJoyn)Interception of PBC dialogs only occurs when app is in foreground

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And API 18...

Method m = wifiP2pManager.getClass().getMethod("startWps", channel.getClass(), WpsInfo.class, WifiP2pManager.ActionListener.class);WpsInfo wpsInfo = new WpsInfo();wpsInfo.setup = WpsInfo.PBC;m.invoke(wifiP2pManager, channel, wpsInfo, wfdActionListener);

JAVA

Starts a two minute WPS window at the Group Owner (GO)Execute WPS PBC on client to connect to GOPBC supports only one connection attempt at a timeAt supplicant, CTRL-EVENT-WPS-OVERLAP

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Wi-Fi Legacy Connections to GO

BroadcastReceiver receiver = new BroadcastReceiver() { @Override public void onReceive(Context context, Intent intent) { if(intent.getAction().equals (WifiP2pManager.WIFI_P2P_THIS_DEVICE_CHANGED_ACTION)){ wifiP2pManager.requestGroupInfo(channel, new WifiP2pManager.GroupInfoListener() { @Override public void onGroupInfoAvailable(WifiP2pGroup group) { if(group != null){ // clients require these String ssid = group.getNetworkName(), String passphrase = group.getPassphrase() } } }); } }};

registerReceiver(receiver, new IntentFilter (WifiP2pManager.WIFI_P2P_THIS_DEVICE_CHANGED_ACTION));

wifiP2pManager.createGroup(channel, wfdActionListener);

JAVA

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Other Issues

Samsung devices will destroy the Wi-Fi Direct group when the lastremaining client disconnectsSamsung devices have supported simultaneous infrastructure Wi-FIand Wi-Fi Direct connections since API 16Samsung S4 persistent group passphrase will change when group isdestroyed and re-createdOn some devices, it is possible to crash the Wi-Fi driver with many Wi-Fi Direct operations

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DeploymentApp Deployment, Fan Interaction & Feedback

User-centred Design Methodology

Built Fan Pilot group of Android users

Worked closely with key BHAFC staff to identify business-drivenservices

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Focus groupsIn-app user experience samplingObservation and accompanied journeys

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Survey

1628 season ticket holders responded95% smartphone usersProfile data e.g. Data usage, services used in stadiumOnly 6% reported no connectivity issuesSought participation consent in the survey

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Services: Matchday Statistics

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Services: Twitter

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Services: Traffic

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Battery and Data Limits

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ResultsInstalls, Round Trip Times, Data Transfered and More

Deployments

Brighton vs. Wolves - 4th May 2013

Brighton vs. Bolton - 21st September 2013

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Final game of the seasonBrighton guaranteed place in Playoffs, but will their arch-rivals,Crystal Palace join themAlthough on a small scale, first successful deployment

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Largest deployment to date, 127 usersComprehensive testing across a wide range of devicesOptimisation to applications' Wi-Fi Direct state machine

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Application Views (04/05/13)

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Round Trip Times on the DTN

Content is cached and replicated across the mobile phonesThe time from sending HTTP GET request to receiving a responseWhere the content is not available in the phone's cache and the phonedoes not have a data connectionAnd the response is from either some other phone's cache or dataconnectionMedian RTT = 131s

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The app was a godsend on the finalday of the season. It’s hit-and-missas to whether you can get a signal atthe Amex, but the app meant I knewthe ever-changing scores and leaguepositions throughout the afternoon.

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Connectivity Graph (21/09/13)

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Results (21/09/13)

338 installs and 127 in-stadium users595 DTN Connections1GB over DTN60% of data over DTN4006 requests from UIMedian delay 108s

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Future WorkAnd some conclusions

Conclusions

Successful deployments of a pocket-switched network using Wi-FiDirectPositive user feedback from both club and fansFans have improved access to matchday services

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(Immediate) Future Work

Optimise battery management by optimising the protocols and codeIntegrating the app with BHAFC's ticketing systemDistributing video replay in-stadia

Deploying stadium-wide through the Play store

Likely University Spin-off

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Self-destructs when you leave the stadium to comply with digitalrights

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Aiming for in-stadium user numbers in the order of thousandsTarget date: Brighton vs. Blackburn - 9th November

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Questions?stephenn@sussex.ac.uk

twitter stephennaickenwww www.digitalstadium.mobi