Projects and Selected Publications

1. Project "Offline Access to Mobile Online Social Networks": It usually takes long latency for mobile users to download videos/photos from Facebook (as well as other social networks) as they want to watch these media contents. With the current mobile apps, mobile users are even required to be online to watch the contents. This project aims to pre-download these contents to mobile devices automatically before mobile users really watch, which thus improves quality of experiences for users.

In the project, we develop a system which (i) recommends multimedia contents for pre-downloading, and (2) does the pre-downloads at right times and right places.

2. Project "Crowdsourcing for Mobile Access": The goal of the project is to develop incentive strategies motivating mobile devices to share data connections (e.g., 4G connections) to Internet (e.g., browsing, data download, data upload). The basic concept is mobile devices will share their last connections if they can resell unused quotas in their cellular data plans. Recent studies show that 49% of AT&T users with data plans do not use up quotas in their plans (80% of them have more than 100 MB left per month).

In this project, we build up a system that forms marketplaces for mobile users to share unused data quotas. The system should be able to support multiple applications varying from web browsing, email checking, to data upload and download. We employ Lyapunov optimization to address the optimization problem of maximizing revenue and maintaining system stability of sellers. We allow mobile devices to select multiple sellers for fast data upload and download. We also solve uncertainties caused by mobility, security issues, and legality concerns.

  • N. Do, C. Hsu, and N. Venkatasubramanian, "CrowdMAC: A Crowdsourcing System for Mobile Access", ACM/IFIP/USENIX Middleware 2012. [PDF]

  • N. Do, C. Hsu, and N. Venkatasubramanian, "Delay-guaranteed Mobile Internet Access with Crowdsourcing", Journal version, under submission.

3. Project "Massive Live Video Distribution using Hybrid Cellular and WiFi Peer-to-Peer Networks": This project addresses the problem of efficiently disseminating live videos (delay sensitive data) to mobile users by using multiple wireless network interfaces equipped on mobile devices, such as WiFi, WiFi Direct, Bluetooth, and Cellular. Videos are encoded using a layered coding standard H.264/SVC that scales well against bandwidth dynamics in wireless networks. We design a scheduler that streams video layers adaptively to wireless bandwidth, and two scheduling algorithms (optimal and practical solutions) for determining how to direct video layers to mobile devides.

  • N. Do, C. Hsu, and N. Venkatasubramanian, “Massive Live Video Distributed over Hybrid Cellular and Ad Hoc Networks", IEEE WoWMoM 2011. [PDF]

  • N. Do, C. Hsu, X. Huang, and N. Venkatasubramanian, “An Experimental Study on Scalable Video Streaming over Hybrid Cellular and Ad Hoc Networks", Poster ACM/IFIP/USENIX Middleware 2011. [PDF]

  • N. Do, C. Hsu, and N. Venkatasubramanian, “Live Video Streaming over Hybrid Cellular and Ad Hoc Networks", IEEE Transactions on Mobilie Computing 2014. [PDF]

4. Project "Rich Large Content Dissemination in Hybrid Networks": This project studies the problem of reliable and speedy dissemination of large rich content (non-delay sensitive data) to mobile devices. We propose a novel middleware system, called HybCast, for the above problem using two wireless network interfaces, Cellular and 802.11, equipped on mobile devices. In the system, we develop an approximation algorithm to address the NP-Hard problem of finding shortest forward paths between clusters in the structred hybrd network, which achieves a 1.2773-approximation factor. The middleware can be used in many applications where data is in need of being transferred fast and reliably to mobile devices.

  • N. Do, C. Hsu, and N. Venkatasubramanian, “Efficient Rich Content Dissemination in Hybrid Networks”, IEEE SRDS 2012. [PDF]

5. Project "Scalability Issues in Mobile Ad Hoc Networks": A stability of routing path is of a great importance for a reliable communication in mobile ad hoc networks. This project studies a novel source routing protocol that establishes a group path with virtual multiple paths to enable a robust communication. The entire mobile nodes form a disjoint set of clusters: Each has its clusterhead as a cluster leader and all the members in the same cluster are assigned an identical cluster label by its clusterhead. A group path is a sequence of cluster labels instead of nodes and the nodes with the same label collaborate to deliver packets to a node with next label on the group path. We prove by resorting to simulation that our proposed protocol outperforms the existing key routing protocols, even for a network with a high mobility of node and a high traffic.

  • H. Oh and N. Do, "Highly Scalable Group Dynamic Routing Protocol for Wireless Mobile Ad Hoc Networks", Proceedings of IEEE WCNC, 2008.

  • H. Oh and N. Do, "Group Source Routing Protocol with Selective Forwarding for Mobile Ad Hoc Networks", Proceedings of IFIP Home Networking, 2007.