Cross layer network architecture for efficient packet forwarding in wireless networks

OF THE DISSERTATION Cross Layer Network Architecture for Efficient Packet Forwarding in Wireless Networks By SACHIN GANU Dissertation Director: Professor Dipankar Raychaudhuri With the evolution of 802.11-based wireless networks from hotspots to mesh networks, there has been a tremendous increase in the number of wireless users and density of deployments. Consequently, current wireless network face several problems due to interference, uncoordinated medium access, packet processing overheads at each hop and sub-optimal route selection. While radio technologies continue to improve speeds upto hundred megabits per second, the inadequacies of medium access and routing protocols severely impact the overall network capacity and end-user experience. In this thesis, we focus on improving the scalability and packet forwarding efficiency of multihop wireless networks. We introduce a self-organizing hierarchical ad-hoc network design (SOHAN) based on a threetier hierarchy with dedicated forwarding nodes to address the scalability of existing multihop networks. We focus on realistic system design considerations and develop a Linux-based system prototype including novel protocols for bootstrapping, discovery and topology control to enable hierarchical self-organization. Experimental and simulation-based evaluations indicate a ∼2.5 times ii performance improvement over flat network models. 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. A substantial contribution of this thesis also includes the design and development of the ORBIT wireless testbed with focus on cross-layer experimental framework to facilitate rapid prototyping of wireless protocols and experimental evaluations at scale.