My research interest is in mobile and wireless networked systems. I have worked on several interesting projects in wireless networking during my Ph.D. at Georgia Tech.
My research can be categorized into four broad areas: Spatial-Security, Smart WiFi, Long-lasting Wireless Sensor Networks and Novel Paradigms & Applications. I really like building practical systems and consequently, my works have a strong systems' component. I provide a description of my research below.
Spatial Security
The repeated failure of current wireless techniques is due primarily because current wireless security techniques have just been simple adaptations of those developed for wired networks. Researchers have shown how different security protocols for both wireless LANs ( WPA ) and cellular networks ( GSM-Nytimes) can be broken without significant effort. Given the increasing use of sensitive information over smartphones and other wireless enabled devices, securing wireless links is becoming critical. Spatial Security is a new approach to securing wireless networks where information access is limited at a spatial level using advanced communication and processing techniques. In this work, I use smart antennas and cooperation among access points to limit the information from eavesdroppers without relying on computational complexity. This approach is complementary to existing security techniques and can be applied to other problems such as privacy and denial of service attacks in wireless networks.
Smart WiFi
With the growing density of users and increasing bandwidth requirements of applications, wireless LANs cannot sustain the performance demands. Given the limited availability of spectrum,
multiple links in a given region must operate on the same frequency. Interfering links are typically not activated at the same time to avoid collisions. Hence approaches that can re-use the available spectrum and increase the concurrency of co-channel wireless links are central to improving the capacity problem. In this context, my work explores two distinct approaches to improving the concurrency and spatial reuse: coordinated beamforming and coordinated coding. My work first explores the spatial reuse available with directional antennas in indoor
wireless networks using experiments. In contrast to conventional wisdom, my experiments reveal that the spatial reuse benefits of directional antennas are quite limited due to the lack of flexible interference suppression. Hence strategies that achieve spatially controlled transmissions, and thereby suppress interference, are needed. In this context, I develop a light-weight spatial reuse algorithm LSR that leverages coordination among access point equipped with smart antennas.
Along the same vein, I developed a new cooperative coding approach called Symbiotic Coding to improve the spatial reuse of co-channel links in a wireless LAN. With a specific class of interference scenarios called asymmetric interference scenarios, interfering links can be coded appropriately so that each receiver is able to decode its intended reception successfully.
The performance of Symbiotic Coding scales with the number of interfering links achieving improvements of 33% to 167% over time sharing with two to four interfering links. I address fundamental challenges in realizing Symbiotic Coding including synchronization, coding algorithms, extensions to different modulations and also implement Symbiotic Coding on a testbed of software defined radios to demonstrate its practical achievability.
Long Lasting Sensor Networks
Wireless Sensor Networks are now garnering increased attention for many resource monitoring applications. One of the key challenges in such networks is to achieve high performance while maximizing the lifetime of the network, since the sensor nodes are typically battery powered and resource limited. The key contributions of this work are novel approaches to enhance the
sustainability and longevity of wireless sensor networks using cooperative transmission. I design an adaptive diversity routing protocol called Proteus that decides how physical layer cooperation can be leveraged to achieve the right rate and range improvements of wireless links. Inspired by recent interest in oil and gas exploration, I also explore the design of multi-radio wireless backhaul networks. My effort in this direction uses real-life experiments to identify the key considerations of using co-located IEEE 802.11n radios.
New Paradigms and Applications
Another line of my research explores new networking approaches.
Cue-based Networking
Cue-based networking is a new networking paradigm where networked applications use extraneous information about the user behaviour and the environment to make intelligent decisions. I use wireless sensors to generate cues about user behavior in homes and optimize the delivery of video over IP networks. Specifically, sensors in CBN provide additional information about the user such as his presence or channel switching to inform the video server in a proactive manner. Using such proactive feedback, video servers can prioritize content transmission preventing wastage of resources. This approach can be generalized to using sensors for other communication applications such as channel management in wireless LANs.
Nano-scale networking
The scale limitations of conventional silicon based systems and the potential benefits of nano-scale devices, have spurred significant interest in studying nano-scale
systems.Given the potential of nano-technology based systems to realize new advances in diverse application scenarios, communication and networking among these systems
will emerge as a critical requirement in the future. However, current communication and networking paradigms are based on electromagnetic propagation and become
inappropriate at nano-scales.
In this project, we intend to explore the design of networked nano-systems. We study biological networks where individual nano-machines or cells communicate
amongst themselves by the release of molecules into the medium or by physical transport of bacterial carriers. This study is expected to enhance the knowledge
about molecular nano-networks and contribute to improving the efficiency of biological networks. Additionally, it is also expected to provide benefits in nonbiological
application scenarios such as bio-films in industrial delivery lines and biosensors in securing against biological attacks.
