Carlo Borgiattino, Claudio Casetti, Carla Fabiana Chiasserini, Yufeng Duan, Paolo Giaccone, Stefano Ordine, Marco Ricca

EuWIn workshop on “Experimental Research for the Future Internet”

Bologna, July 9th 2013

Investigating the efficiency of D2D communications

through the WiFi-Direct platform

Outline

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§  Device-to-device communications §  WiFi-Direct §  Our experimentation

Device-to-Device (D2D) communications

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§  Fast growth of mobile traffic –  challenging for wireless access network

•  infrastructure very expensive to upgrade §  D2D communications

–  possible solution, complementary to the standard wireless access network •  may improve the QoE for the end user

–  short range communications achieve higher speed •  may decrease the network congestion and improve the QoS provided by the

operator –  under discussion within 3GPP as alternative communication mode in LTE-

based networks –  will not be a panacea for all the application scenarios

•  beneficial only for some specific applications (e.g., viral contents) •  unclear business model

Applications leveraging D2D

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§  Content sharing with nearby devices –  music, photos, documents and games

•  music group play –  “coolest feature” in the new Samsung Galaxy S4

•  shared whiteboard within a large classroom

§  Cooperative content creation –  collaborative e-learning platform

§  Relay towards a network point of access §  Safety applications, when the infrastructure is partially functioning or

absent

Ad-hoc mode in standard WiFi @ Android

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§  Ad-hoc mode not supported in Android –  unless rooting the device

§  Famous “issue 82” since January 2008 –  e..g, #1721 paa...@gmail.com “This feature has been missing for years, and

has now become my top reason for wanting to root my phone.” [May 25, 2013] •  http://code.google.com/p/android/issues/detail?id=82

§  Possible reasons –  lack of security –  lack of efficient power saving –  lack of extented QoS capabilities

WiFi-Direct

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§  Enabling technology for D2D communications §  Exploiting traditional infrastructure-mode of WiFi

–  security, power control, QoS §  Multiplatform

–  available on new mobile devices with Android 4.2 (09/2012), Windows 8.1 (08/2013)

WiFi-Direct group

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§  WiFi-Direct devices communicate by establishing groups §  Devices can be:

–  Group Owner (GO): one device acts as AP within a group –  Client (CL): associates to the GO

•  many clients per group •  standard 802.11 clients do not formally belong to the group, but they simply see the

GO as a traditional AP

GO!CL! CL!

Group owner

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§  GO must: –  annunce itself through beacons –  support power saving services for its associated clients –  run a DHCP (Dynamic Host Configuration Protocol) server

§  WiFi-Direct does not allow the transfer of GO role within a group §  When the GO leaves the group, the group is turned down and has to

be re-established

GO!

Group formation

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Priority setting to elect GO!!

Possible alternative to GO negotiation/WPS: persistent_mode!![*] Camps-Mur, Garcia-Saavedra, Serrano, “Device to device communications with wifi direct: overview and experimentation”, !

IEEE Wireless Communications Magazine, 2012 !

(picture taken from [*])!

Within-one-group communications

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§  Point-to-point §  Multicast/broadcast §  Already available in WiFi-Direct enabled devices

GO!CL! CL!

Multi-group communications

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§  We implement bridging at application layer in three scenarios

GO!CL! GO! CL!

GO!CL! GO!CL! GO!CL!

GO! CL! GO!CL!

(TDM, persistent_mode)!

Group formation

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§  We are investigating smart group formation policies §  GO is responsible for traffic forwarding –  its central role should reflect

•  its centrality in the topology •  its forwarding/processing/power capability •  traffic demand

Resource discovery

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§  required for the group formation policies §  our resource advertisement protocol is based on flooding a JSON file

{"interfaces": [! {"type": "BT”,"available": false},! {"MAC": "30:85:a9:5f:af:5d”,"type": "wifi”,"address": "172.20.27.64”,! "netmask”:"255.255.254.0”},! {"MAC": "32:85:a9:5f:af:5d”,"type": "p2p”}],! "location": [ ! {"bearing": 0,"longitude": 7.6620661,"latitude": 45.0643902,"type": "Network”, ! "accuracy": 42.4370002746582,"speed": 0,"obsolete_time": 78816 }],! "system_info": [! {"ram_available": 429121536,"cpu_usage": 1.3881719496566802E-5,! "available_disk": 12469817344,"disk": 14341292032,"battery": 0.699999988079071}]!}!!

Current experimentation

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§  Standard laptop with Ubuntu 11.10 –  wpa_supplicant –  driver ath9k/mac80211 –  kernel >= 3.0

§  Raspberry PI with Raspbian optimised version of Debian –  25$ ARM-based single-board computer terminal –  Realtek Linux Wi-Fi Direct software

§  Nexus 7 tablet with Android 4.2

Conclusions

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§  Preliminary results show that multi-hop is feasible through the scenario –  tested so far only on Linux –  still under investigation on Android

§  We are currently evaluating the scalability of the performance when the number of nodes/groups becomes large

§  Open issues: how to implement smart group formation policies

GO!CL! GO!CL! GO!CL!