Wenjing Lou, assistant professor of electrical and computer engineering at Worcester Polytechnic Institute (WPI) has received a five-year, $450,000 CAREER award from the National Science Foundation (NSF).

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Lou’s research focuses on wireless networks and their security. The CAREER award will enable her to conduct a comprehensive study of a relatively new concept in wireless networking, one that takes better advantage of the broadcast nature of wireless communications. The aim of the research is to find ways to increase the efficiency, throughput, and reliability of wireless networks and to develop computer models and protocols that will enable designers to create more effective wireless technology.

The multihop networks Lou studies differ from the ones most wireless users encounter. In a home, office, or cellular network, a user with a laptop, cell phone, or other wireless device connects to a base station or access point (AP) in a single hop. The signal then travels over wires. Multihop networks (including sensor networks used in environmental monitoring, building security, and battlefield surveillance) are made up of hundreds or even thousands of individual wireless nodes. Signals from individual devices must hop wirelessly from node to node to reach their ultimate destination.

In a typical multihop network, a node that needs to send a packet of information selects from its neighboring nodes the one that appears to have the best chance to pass the signal along successfully and directs the packet to that node alone. However, intermittent channel fluctuations may prevent the packet from getting through. In opportunistic routing, the packet is sent to multiple neighbors and each one assesses its ability to forward the packet to its neighbors based on the instantaneous state of the network. The node with the highest probability of success passes the data along.

"Because wireless is a broadcast medium, all of the neighboring nodes will receive the packet. Opportunistic routing takes advantage of that fact, which significantly increases the odds of a successful transmission, said Lou."

While the basic idea behind opportunistic routing is simple, putting it into practice has proven difficult and little is currently known about how to design networks to take full advantage of the technique. Lou will conduct a comprehensive theoretical study of opportunistic routing that will, for the first time, produce a framework that will show the optimum way for nodes to share information, to determine the best path for a data packet, and so on. From this framework will grow models and protocols that will help network designers use opportunistic routing effectively.

"Ideally, we want to be able to make predictions about the end-to-end performance of a network using opportunistic routing," Lou noted. "With this knowledge, we can help create more reliable networks, where information gets through more quickly, with fewer retransmissions, added Lou."

In addition to studying multihop network routing, the NSF award will enable Lou to strengthen WPI’s academic program in wireless networking by developing a new wireless networking course for undergraduates and a new graduate course in wireless network security.

Lou has received two other NSF awards. One to develop a security architecture for wireless mesh networks and another to develop security protocols for sensor networks.

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