Delay-Tolerant Networking @ TKK Comnet

Department of Communications and Networking

DT-Talkie is a DTN-based voice messaging application that enables mobile users to communicate over challenged environments in the walkie-talkie fashion. DT-Talkie is implemented for Maemo based Nokia Internet Tablet. We are porting DT-Talkie application to heterogeneous endpoints like smartphone, Linux and Mac based PC. In the current implementation, DT-Talkie supports both one-to-one and group communication.

The idea is that if User A wants to talk with User B, he presses a button (fullscreen hard button of Nokia Internet Tablet) and start talking. After finishing the talk, he presses the button again. Then DT-Talkie forwards his voice message over the DTN infrastructure destined to User B. On the other end, User B can hear the voice message as soon as it is received. User B communicates with User A using the aforementioned approach.

System Architecture

Audio C/P

• Captures voice from the audio source
• Saves encoded voice in a local file
• Plays the received voice message in the audio sink

Bundle S/R

• Encapsulates voice data in the DTN bundle
• Sends the bundle over DTN infrastructure
• Decapsulates the received bundle

GUI

• Creates the main window
• Draws several widgets over the window
• Handles interrupt of the hardkeys

dtnd

• Runs as a background process
• Provide the bundle protocol services to the application through dtnd APIs

Technologies

• GTK+, Hildon - Used for GUI
• GStreamer - To capture and playback voice messages
• DTN Reference Implementation (V 2.6.0) - To send and receive DTN bundles

DT-Talkie Screenshot

Contact List: list of endpoint identifiers (EID)

Pending List: list of voice messages which have not been played back yet

Current user: active user's EID

There is a text entry box beneath the contact list to input EID of a user that is not available in the list.

Installation

The DT-Talkie installation instructions are given for Nokia N810. The instructions are also applicable for Nokia N800 if OS2008 is flashed to the device. We consider that dtnd is already running in the system.

• Download DT-Talkie version 1.0 debian package to the system storage.
• Open a new terminal and type sudo gainroot to gain the root access.
• Navigate to the directory where you have stored the DT-Talkie debian package and type dpkg -i dttalkie_1.0_armel.deb to install the package.
• Open /media/mmc1/.dttalkie/account file and write your EID (e.g. dtn://Nokia-N810).
• In the terminal, type run-standalone.sh dttalkie to run the DT-Talkie application. It is also possible to launch the application from "Extras" menu.
• To uninstall the package, type dpkg -r dttalkie.

Demonstration Paper

DT-Talkie application was demonstrated in the ACM MobiCom 2008.

Md. Tarikul Islam: DT-Talkie: Push-to-talk in Challenged Networks. ACM MobiCom 2008. [PDF] [Poster]