Analyze IEEE 802.11i standard and find deficiencies. See the course report and our published papers for more information.
Implement a secure chat room with Java (JCE and JSSE), supporting key exchange, data encryption, integrity check, user authentication, and certificates. [part1, part2]
This project studies the effects of security features on the per packet delay and loss rate of voice traffic over WLAN. We model the security features by adding packets and extending the length of each data packets. Different authentication and encryption schemes (WEP with Challenge-Response authentication and TKIP with a long term shared key and 4-way handshake) are investigated to represent the common secure WLAN implementations. Based on our simulation, when the traffic load is light in the network, adding security features does not decrease the performance, while the network performance will decrease more rapidly when the traffic load is getting higher and higher. That is because in 802.11 MAC, the frame body is transmitted in a higher rate (11Mbps) than the packet overhead, the number of packets transmitted over 802.11MAC dominates the performance in this case, instead of the length of the packets. [report]
Review and evaluate the security of 802.16e standard. [review]
RCP (Rate Control Protocol) is a rate-based congestion control algorithm, which can reduce the flow duration for small size files comparing with TCP slow start mechanism. Before transmission the sender and the routers will interact to achieve an optimal rate, in order to minimize the flow duration. We simulate and explore RCP in the networks with M/Pareto traffic. The result shows the optimal rate depends on the background traffic load and incoming traffic load of the bottleneck link. Furthermore, RCP works very well because some error in the optimal rate won't influence the flow duration greatly. Theoretically we work out the expression for queue size of a single queue with M/General traffic when the transmission rate is greater than the link capacity, and we describe a method to calculate the upper bound of the queue size when the transmission rate is less than the link capacity. Based on this, we explain the simulation results when M/General is specified as M/Pareto process. [report]
For video server, providing optimal service to highly diversified users is challenging because different users have different link conditions and different requirement of quality. Considering the low price of storage, we propose to store multiple video streams in different bit rate, different coding strategies and different formats for the same video sequences. Server can choose a certain video stream to transmit according to link condition. Multiple paths are used to increase the available bandwidth and resist single link loss. In this paper, we compare two coding approaches for multiple paths: Multiple Description Coding (MD) and Layered Coding (LC). Results show that MD is suitable for symmetrical links while LC is good in asymmetrical links with one of them in low loss rate to transmit base layer. Simulation results also support that if server can adapt its bit rate and coding strategies to diversified link condition and feedback, as much as 2dB improvement in video quality can be achieved. [report]
Network throughput and packet delay are the two most important parameters to evaluate the performance of wireless ad hoc networks. Generally it is difficult to achieve both high throughput and low packet delay. In this project, the objective is to achieve high throughput while keeping the packet delay under certain threshold. [report]