Mobile Applications

Wi-Vi: See Through Walls with Wi-Fi Signals

Wi-Vi is a new technology that enables seeing through walls using Wi-Fi signals. It allows us to track moving humans through walls and behind closed doors. Wi-Vi relies on capturing the reflections of its own transmitted signals off moving objects behind a wall in order to track them. Wi-Vi's operation does not require access to any device on the other side of the wall.

Alfalfa: real-time interactive protocols that work well over wireless networks

Alfalfa is an Internet videoconferencing protocol that works well over cellular wireless networks, where link speeds change dramatically with time, and current transport protocols build up lengthy in-network queues. Alfalfa does not use TCP-style reactive congestion control, but instead uses a stochastic model of the network path to forecast how many bytes are safe to send, while bounding the risk that its packets will be queued inside the network for too long.

Mosh: mobile shell

Remote terminal application that allows roaming, supports intermittent connectivity, and provides intelligent local echo and line editing of user keystrokes. Mosh is a replacement for SSH. It's more robust and responsive, especially over Wi-Fi, cellular, and long-distance links. Mosh is free software, available for GNU/Linux, FreeBSD, and Mac OS X.

Code In The Air - Simplifying Sensing and Coordination Tasks on Smartphones

Code in the Air (CITA), a system which simplifies the rapid development of tasking applications. It enables non-expert end users to easily express simple tasks on their phone, and more sophisticated developers to write code for complex tasks by writing purely server-side scripts. CITA provides a task execution framework to automatically distribute and coordinate tasks, energy-efficient modules to infer user activities and compose them, and a push communication service for mobile devices that overcomes some shortcomings in existing push services. 

Traffic-Aware Techniques to Reduce 3G/LTE Wireless Energy Consumption

The 3G/LTE wireless interface is a significant contributor to battery drain on mobile devices. A large portion of the energy is consumed by unnecessarily keeping the mobile device’s radio in its “Active” mode even when there is no traffic. This pproject aims to reduce this portion of energy consumption by learning the traffic patterns and predicting when a burst of traffic will start or end. We develop a technique to determine when to change the radio’s state to optimize energy efficiency.
 

SoftCast: A Cross-Layer Design for Scalable Mobile Video

In broadcast and mobile scenarios the bit rate supported by the channel differs across receivers and varies quickly over time. The conventional design however forces the source to pick a single bit rate and degrades sharply when the channel cannot not support the chosen bit rate. SoftCast is a clean-slate design for wireless video where the source transmits one video stream that each receiver decodes to a video quality commensurate with its specific instantaneous channel quality.

Aggregation in Dynamic Networks

CarSpeak: A Content-Centric Network for Autonomous Driving

We introduce CarSpeak, a communication system for autonomous driving. CarSpeak enables a car to query and access sensory information captured by other cars in a manner similar to how it accesses information from its local sensors. CarSpeak adopts a content-centric approach where information objects -- i.e., regions along the road -- are first class citizens. It names and accesses road regions using a multi-resolution system, which allows it to scale the amount of transmitted data with the available bandwidth.

Efficient and Reliable Backscatter Networks

There is a long-standing vision of embedding backscatter nodes like RFIDs into everyday objects to build ultralow power ubiquitous networks. A major problem that has challenged this vision is that backscatter communication is neither reliable nor efficient. Backscatter nodes cannot sense each other, and hence tend to suffer from colliding transmissions. Further, they are ineffective at adapting the bit rate to channel conditions, and thus miss opportunities to increase throughput, or transmit above capacity causing errors.

TIMO : Making 802.11n Robust to Cross-Technology Interference

Cross-technology interference is emerging as a major problem for 802.11 networks. Independent studies in 2010 by the Farpoint Group, BandSpeed, and Miercom all show that highpower interferers like baby monitors and cordless phones can cause 802.11n networks to experience a complete loss of connectivity. Other studies from Ofcom, Jupiter Research, and Cisco report that such interferers are responsible for more than half of the problems reported in customer networks.

802.11n+ : Random Access Heterogeneous MIMO Networks

This project presents the design and implementation of 802.11n+, a fully distributed random access protocol for MIMO networks. 802.11n+ allows nodes that differ in the number of antennas to contend not just for time, but also for the degrees of freedom provided by multiple antennas. We show that even when the medium is already occupied by some nodes, nodes with more antennas can transmit concurrently without harming the ongoing transmissions. Furthermore, such nodes can contend for the medium in a fully distributed way.

MegaMIMO: Scaling Wireless Capacity with User Demands

We present joint multi-user beamforming (JMB), a system that enables independent access points (APs) to beamform their signals, and communicate with their clients on the same channel as if they were one large MIMO transmitter. The key enabling technology behind JMB is a new low-overhead technique for synchronizing the phase of multiple transmitters in a distributed manner. The design allows a wireless LAN to scale its throughput by continually adding more APs on the same channel.