Electrical and Computer Engineering Ph.D. Public Defense

Automatic Creation and Maintenance of Dynamic WiFi Direct Networks

Utku Demir

Supervised by Professor Wendi Heinzelman and Professor Cristiano Tapparello

Wednesday, August 19, 2020
9 a.m.

Zoom Meeting ID: 959 7038 5695 Passcode: 100095

The wide diffusion of mobile devices that natively support ad hoc communication technologies has led to a number of protocols for enabling and optimizing Mobile Ad Hoc Networks (MANETs). Nevertheless, the actual utilization of MANETs in real life is still limited, in part due to the lack of protocols for the automatic creation and evolution of ad hoc networks. A novel ad hoc protocol named WiFi Direct has been proposed and standardized by the WiFi Alliance with the objective of facilitating the interconnection of nearby devices. WiFi Direct provides high performance direct communication among devices and includes different energy management mechanisms. However, the current WiFi Direct implementations require user interaction for setting up and maintaining the connection. Moreover, multi-group implementation is not defined in the specifications even though it is not restricted.

Overall, this thesis contributes new ideas for WiFi Direct network automation and maintenance for single-group networks, and extension to multi-group networks. For the single-group work, I pro- pose and analyze three practical schemes for creating self-organizing and self-healing WiFi Direct networks using Android OS devices. Experimental results show that our proposed approaches are feasible with different overhead in terms of prior knowledge about the network and coordination be- tween the devices. I also propose a proactive solution to unforeseen group owner failures in order to minimize the packet loss and network discontinuity time by setting up a redundant group on a second virtual network interface. Through emulation on Mininet-WiFi, I find that the proposed redundant scheme substantially decreases packet loss, providing almost continuous connectivity among nodes, which cannot be guaranteed through traditional WiFi Direct schemes. Additionally, I show the feasibility of my previously proposed protocols on real devices and validate the emulation results. The experiments have been conducted using a testbed of Raspberry Pi 3B single board computers. For the multi-group work, I implemented and evaluated distributed and centralized versions of previously proposed graph theory algorithms in MATLAB, mininet-wifi emualtor, and Raspberry Pis by adapting them for WiFi Direct standard for communication backbone construction. The results confirm the multi-group WiFi Direct feasibility in real devices and constitute network design insights by providing the number of GOs needed and average shortest paths within networks in various realistic scenarios.

Overall, my work in this thesis provides network design insights into WiFi Direct network automation both in single and multi-group networks through proposing new algorithms, adapting existing algorithms to WiFi Direct constraints, and network performance evaluation via simulations and real device implementations in various possible scenarios.