Delay-tolerant networking using Wi-Fi Direct was tested at a soccer stadium to improve mobile connectivity. The solution used smartphones to cache and share content, forming a pocket switched network. Trials showed median response times of 108 seconds over the delay-tolerant network. Future work includes optimizing the system for battery life and integrating with ticketing to deploy to thousands of users.

1. Delay-tolerantNetworking
UsingWi-FiDirect
Stephen Naicken
Visiting Research Fellow, Sussex University
Droidcon 2013

2. Outline
The Problem
The Solution
Wi-Fi Direct
Deployment in the AMEX Community Stadium, Falmer
Results
Future work and Conclusions
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Poor mobile data connectivity in stadia·
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Pocket Switched Network implementing a distributed cache with
idempotent HTTP POST
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Trials and tribultations·
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3. The Problem
Poor in-stadia mobile data connectivity

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

5. Project
EPSRC-funded research project to investigate the use of smartphones
to build new ways of communicating within stadiums
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6. In-stadia Mobile Data Experiences
Smartphones offer opportunities to improve the visitor experience
But poor connectivity in-stadia is a barrier to deployment of these
applications
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Live scores and league tables
Seat location service
Pie and pint ordering
Video highlights and goal-line replays
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7. The American Express Community Stadium
Opened in 2011
Capacity of 30750
Home to Brighton and Hove Albion Football Club
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Dominic Alves. http://www.flickr.com/photos/dominicspics/5606852371/

8. In-stadia Mobile Data Experiments
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9. Problem Statement
In a typical stadium, the concrete and steel construction and large
crowds combine to make mobile Internet access very unreliable
How can we improve connectivity so that fans can access matchday
services?
What are the possible solutions?
·
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Do nothing, but EPSRC would not be impressed
Invest in mobile network infrastructure to increase capacity
Wi-Fi
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10. Issues with Mobile Networks
Investment in mobile networks will not yield benefits to all fans unless
all major operators invest
Mobile network operators unlikely to be supportive of cash-stripped
clubs
A UK operator has invested approx. £1m to improve mobile data
connectivity at leading Premier League club's stadium
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Fans still complain of poor connectivity and the club accept that
video can still not be delivered to all fans
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11. Issues with Wi-Fi
Cost
Performance Issues
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Typically quoted cost to British clubs is around £500000
US market costs could be around $6m
Technology spend at British clubs is typically low
Many Football League clubs would struggle to justify costs (low ROI)
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It doesn't work too well
Low numbers of simulataneous users
User experience is typically poor - e.g. Gillette Stadium
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12. The Solution
Pocket Switched Networking

13. Technology Idea
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14. Technology Idea
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15. Technology Idea
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16. Technology Idea
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17. Supporting HTTP GET

18. Supporting HTTP GET

19. Supporting HTTP GET

20. Supporting HTTP GET

21. Supporting HTTP GET

22. Supporting HTTP GET

23. Supporting HTTP POST

24. Supporting HTTP POST

25. Supporting HTTP POST

26. Supporting HTTP POST

27. Supporting HTTP POST

28. Wi-Fi Direct
Trials and Tribulations

29. 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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30. Starting Wi-Fi Direct on ICS
WifiP2pManager p2pManager =
(WifiP2pManager) getSystemService(Context.WIFI_P2P_SERVICE);
// Wfd callbacks on a handler thread
channel = 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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31. Wi-Fi Protected Setup
WifiP2pConfig config = new WifiP2pConfig();
config.deviceAddress = device.deviceAddress;
JAVA
// Push-Button Configuration
config.wps.setup = WpsInfo.PBC;
JAVA
// Display pin on client, enter on GO
config.wps.setup = WpsInfo.DISPLAY;
JAVA
// Display pin on GO, enter on client
config.wps.setup = WpsInfo.KEYPAD;
JAVA
p2pManager.connect(channel, config, wfdActionListener) JAVA
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32. WPS without the dialog prompts - API 16-17
Automatic acceptance of WPS PBC dialogs is possible
Once again using reflection
API 16-17: WifiDirectAutoAccept.java (AllJoyn)
Interception of PBC dialogs only occurs when app is in foreground
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33. 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 GO
PBC supports only one connection attempt at a time
At supplicant, CTRL-EVENT-WPS-OVERLAP
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34. 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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35. Other Issues
Samsung devices will destroy the Wi-Fi Direct group when the last
remaining client disconnects
Samsung devices have supported simultaneous infrastructure Wi-FI
and Wi-Fi Direct connections since API 16
Samsung S4 persistent group passphrase will change when group is
destroyed and re-created
On some devices, it is possible to crash the Wi-Fi driver with many Wi-
Fi Direct operations
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36. Deployment
App Deployment, Fan Interaction & Feedback

37. User-centred Design Methodology
Built Fan Pilot group of Android users
Worked closely with key BHAFC staff to identify business-driven
services
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Focus groups
In-app user experience sampling
Observation and accompanied journeys
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38. Survey
1628 season ticket holders responded
95% smartphone users
Profile data e.g. Data usage, services used in stadium
Only 6% reported no connectivity issues
Sought participation consent in the survey
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47. Services: Matchday Statistics
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48. Services: Twitter
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49. Services: Traffic
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50. Battery and Data Limits
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51. Results
Installs, Round Trip Times, Data Transfered and More

52. Deployments
Brighton vs. Wolves - 4th May 2013
Brighton vs. Bolton - 21st September 2013
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Final game of the season
Brighton guaranteed place in Playoffs, but will their arch-rivals,
Crystal Palace join them
Although on a small scale, first successful deployment
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Largest deployment to date, 127 users
Comprehensive testing across a wide range of devices
Optimisation to applications' Wi-Fi Direct state machine
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53. Application Views (04/05/13)
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54. Round Trip Times on the DTN
Content is cached and replicated across the mobile phones
The time from sending HTTP GET request to receiving a response
Where the content is not available in the phone's cache and the phone
does not have a data connection
And the response is from either some other phone's cache or data
connection
Median RTT = 131s
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55. The app was a godsend on the final
day of the season. It’s hit-and-miss
as to whether you can get a signal at
the Amex, but the app meant I knew
the ever-changing scores and league
positions throughout the afternoon.
“
”

56. Connectivity Graph (21/09/13)
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57. Results (21/09/13)
338 installs and 127 in-stadium users
595 DTN Connections
1GB over DTN
60% of data over DTN
4006 requests from UI
Median delay 108s
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58. Future Work
And some conclusions

59. Conclusions
Successful deployments of a pocket-switched network using Wi-Fi
Direct
Positive user feedback from both club and fans
Fans have improved access to matchday services
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60. (Immediate) Future Work
Optimise battery management by optimising the protocols and code
Integrating the app with BHAFC's ticketing system
Distributing 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 digital
rights
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Aiming for in-stadium user numbers in the order of thousands
Target date: Brighton vs. Blackburn - 9th November
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61. Questions?
stephenn@sussex.ac.uk
twitter stephennaicken
www www.digitalstadium.mobi