Ying Jian

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The loss of photochemical heating caused by gravity waves in the mesopause region

Journal of Atmospheric and Solar-terrestrial Physics, 2000

The in¯uence of gravity waves on photochemical heating in the mesopause region is studied in this... more The in¯uence of gravity waves on photochemical heating in the mesopause region is studied in this paper. The results indicate that gravity waves can cause a loss of photochemical heating in the region of the mesopause. The in¯uences of the variation of background temperature and of atomic oxygen density on the loss of photochemical heating induced by gravity waves are discussed. The results indicate that, as background temperature decreases, or as the background atomic oxygen density increases, the gravity wave induced loss of photochemical heating increases and the ratio between it and the background photochemical heating rate also increases. #

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Protecting Receiver-Location Privacy in Wireless Sensor Networks

Due to the open nature of a sensor network, it is relatively easy for an adversary to eavesdrop a... more Due to the open nature of a sensor network, it is relatively easy for an adversary to eavesdrop and trace packet movement in the network in order to capture the receiver physically. After studying the adversary's behavior patterns, we present countermeasures to this problem. We propose a locationprivacy routing protocol (LPR) that is easy to implement and provides path diversity. Combining with fake packet injection, LPR is able to minimize the traffic direction information that an adversary can retrieve from eavesdropping. By making the directions of both incoming and outgoing traffic at a sensor node uniformly distributed, the new defense system makes it very hard for an adversary to perform analysis on locally gathered information and infer the direction to which the receiver locates. We evaluate our defense system based on three criteria: delivery time, privacy protection strength, and energy cost. The simulation results show that LPR with fake packet injection is capable of providing strong protection for the receiver's location privacy. Under similar energy cost, the safe time of the receiver provided by LPR is much longer than other methods, including Phantom routing [1] and DEFP [2]. The performance of our system can be tuned through a couple of parameters that determine the tradeoff between energy cost and the strength of location-privacy protection.

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A novel scheme for protecting receiver's location privacy in wireless sensor networks

IEEE Transactions on Wireless Communications, 2008

... 1] and DEFP [2]. The performance of our system can be tuned through a few system parameters t... more

Can CSMA/CA networks be made fair

We demonstrate that CSMA/CA networks, including IEEE 802.11 networks, exhibit severe fairness pro... more We demonstrate that CSMA/CA networks, including IEEE 802.11 networks, exhibit severe fairness problem in many scenarios, where some hosts obtain most of the channel's bandwidth while others starve. Most existing solutions require nodes to overhear transmissions made by contending nodes and, based on the overheard information, adjust local rates to achieve fairness among all contending links. Their underlying assumption is that transmissions made by contending nodes can be overheard. However, this assumption holds only when the transmission range is equal to the carrier sensing range, which is not true in reality. As our study reveals, the overhearing-based solutions, as well as several non-overhearing AIMD solutions, cannot achieve MAC-layer fairness in various settings. We propose a new rate control protocol, called PISD (Proportional Increase Synchronized multiplicative Decrease). Without relying on overhearing, it provides fairness in CSMA/CA networks, particularly IEEE 802.11 networks, by using only local information and performing localized operations. It combines several novel rate control mechanisms, including synchronized multiplicative decrease, proportional increase, and background transmission. We prove that PISD converges and achieves (weighted) fairness.

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Ying Jian

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