Cross Layer Framework for efficient packet forwarding in multihop wireless networks (PhD thesis)

We address packet forwarding inefficiencies of existing techniques over multihop networks due to queuing, contention and reprocessing at each hop and propose an interface contained forwarding architecture (ICF) using a combination of cut-through MAC protocol and label-based forwarding to enable "atomic" channel access for downstream transmissions and reduce self-interference. Next, we design a cross layer enabled cut through architecture (CLEAR) that extends the ICF mechanism with novel airtime metric-based route selection to mitigate the interference between flows. We further outline a time-based coordination scheme using soft reservations during route discovery phase to coordinate multihop "burst" transfers amongst flows. This model can be adapted to support differentiated services and provide a "low-latency socket" for real-time traffic over multiple hops. Our work can be the basis for a switched multihop wireless network design that enables conflict-free transfers resulting in efficient utilization of channel capacity and providing a viable alternative to wired network deployments

Integrated Routing and MAC Scheduling (IRMA) for Wireless Networks

In parallel, we are also investigating an integrated approach to route selection and MAC scheduling based on an interference model that avoids the intra and inter flow interference problems associated with existing layered approaches. The IRMA approach is motivated by the fact that conventional contention-based MAC protocols such as 802.11 do not perform well in combination with independent ad hoc routing protocols such as DSR, DSDV or AODV due to interactions between neighboring nodes in the network. Joint routing and MAC eliminates contention between radio nodes and assigns traffic flows to alternate paths based on actual traffic demand, thereby providing significant increases in network capacity. Further details can be found in our publication in WiMesh 2006

Supporting open access multi-user wireless experimentation on the ORBIT Testbed

A substantial effort during my PhD also went into the design and deployment of the 400 node wireless experimental testbed (ORBIT). The multi-user facility currently hosted at the WINLAB facility in North Brunswick, NJ facilitates repeatable experimentation and evaluation of protocols and applications in real-world settings. Experiment management software allows script based deployment of experiments and supports run time measurement collection as well as visibility and access to several cross layer parameters such as Transmit Rate, Transmit Power, Frequencies, Signal Strengths etc. The testbed has been released for public use in Fall 2005 and currently has ~120 registered users who have conducted a total of over 4200 x 1-2 hr experiments on the testbed to date. It is also being used as a proof-of-concept prototyping platform for wireless aspects of GENI, the future Internet research infrastructure. Further details are available here

GENI: Methods for Wireless Virtualization and Wired-Wireless Testbed Integration

The GENI project aims to provide a flexible and programmable shared experimental infrastructure for future Internet protocols and software. In our project, we are addressing two important issues.

  • Virtualization of wireless network resource to simultaneously support multiple concurrent experiments on the same set of nodes or radios. Several alternative approaches for virtualizing the wireless grid resources at different layers of the stack such as PHY layer (frequency, time, space) and MAC layer (Virtual AP)
  • Integration of control and management framework across wired and wireless networks to provide with a single programming interface and experimental methodology for heterogeneous experiments

Self Organizing Hierarchical Ad-Hoc Networks (SOHAN): Design and Prototyping

The focus of this project is on improving the overall performance and scalability of multi-hop wireless networks. First, we propose a self-organizing hierarchical ad-hoc network architecture (SOHAN) that provides significant improvements in terms of capacity and performance as compared to a typical flat ad-hoc network. This architecture introduces a tier of dedicated forwarding nodes in order to extend the capacity and coverage of the network. We also focus on practical design aspects and protocol design for bootstrapping, discovery and routing and build a system prototype for performance evaluation in Linux. Initial results show 2.5 times improvement in terms of system throughput over traditional ad-hoc networks without hierarchy. More details available here

Location Estimation in Indoor Wireless Networks (Internship at Avaya)

This work focuses on fundamental system deployment aspects of location estimation in 802.11-based wireless networks. We concentrate on adaptable infrastructure-based approaches, where sniffers measure received signal strength from clients to locate them. Our implementation experience and experimental results show that sniffer-based location estimation is feasible and works well provided some important rules are followed. By studying data over a 6-month period, we observe that adaptation of models is necessary for good location estimation, and that our techniques enable location estimation with minimal profiling with median errors of ~6-10 feet.