More on Alex's research interests

Automated planning for Open Network Architectures (Panda, Conductor)

Open network architectures (ONA) allow dynamic deployment of services in the networks. The Internet would benefit from quick deployment of protocols that provide customized services to handle user data streams. ONA use increasingly abundant computational resources to relieve the often-limited resources of network communication channels. Complexities and dynamism of network conditions make it unreasonable to expect users and application writers to foresee and handle all possible problems. Having network systems automatically adjust to those problems would be a great improvement, but doing so clearly indicates a need for automated planning of services in ONA. We describe a planner implementation for ONA that automatically calculates properly ordered sequences of adaptations to increase throughput, reliability, and safety of communication channels. This planner addresses numerous problems of adaptation planning, such as feasibility and efficiency of a plan, composability of adaptations, and real-time limits. We demonstrate the feasibility of the approach with test results.


Mobile Computing Power-Saving Techniques

Recent research has demonstrated that portable computer users can save battery power by using wireless networks to migrate tasks to server machines. Making this technique useful in the general case requires considerable automation of the migration process. We describe a framework that automatically moves tasks from a portable computer over a wireless network to a server and migrates the results back. We present the framework's architecture, discuss key issues in creating the framework, and presents performance results that demonstrate that the framework is both useful and power-inexpensive.


Optimistic File Replication Systems (Rumor)

Rumor is a file replication system that can be used to keep multiple copies of files consistent. Rumor is especially useful for keeping replicated files on mobile computers. Maintaining multiple replicas of each file allows for higher availability. In particular, allowing mobile computers to store file replicas ensures that users will be able to access important data while disconnected, while still maintaining a single environment shared with workstation machines when connected. To further improve availability, Rumor uses an optimistic replication strategy. Optimistic replication permits any accessible replica to be updated, thus allowing disconnected portable computers to not only read, but also write, their local file replicas.



We present here individual content-based recommender system, which serves the profile of only one user. To measure content distances between texts we used time stamps and vocabilary statistics. No user explicit feedback is needed for the modification of the user profile just monitoring of his references. The system builds a user profile using the statistics of his reading interests and selects the list of new materials from some a pool of references that would correlate with his reading interests.

Secure Internet Voting System

We designed the system for secure voting on the Internet. The security of the system is based on 2-server scheme that allows the voting only to authorized personnel and, at the same time, completely protects the anonymity of ballots.


A common problem facing many organizations today is the multiple geterogenous information sources that include repositories, databases, object stores, knowledge bases, file systems, digital libraries, subsequent search engines, and electronic mail systems. The solution of the problem is in the design of wrappers and mediators. The wrapper system was designed that converts key words into the query on the language(s) of local databases and the Internet search systems (like AltaVista, Yahoo, and etc.) using CGI/Perl and Javascript. The system returns the result of the search as a list of text fragments of the found documents that contain the key words. Then the user chooses the interesting fragments for the complete document retrieval.

TDMA on CSMA protocol for wireless communications

CSMA protocol has some serious drawbacks for wireless communication. The conflicting radio packets cause back-offs and retransmissions that increase latency and battery power loss. We applied the time division scheme to the design of the WaveLAN card driver. The conflict avoiding technique is based on token division multiplexing, where each participant shares the channel keeping the correspondent part of the tokens. The combination of CSMA and TDMA protocols made the comunication even more effective; CSMA protocol was used to add a new participant that does not have tokens yet to the channel. The analysis of the driver performance shows that it can increase the fairness of channel division and some predictability of QoS in spite of the additional CPU processing of TDMA protocol that reduced the speed of the individual transmission. The combined CSMA/TDMA protocol should be deployed on the hardware of the WaveLAN card.

Administrating multicast teleconferencing

 The project is based on Mumble, the project that allows multiple people to have text-based conversations using multicast designed for the Special Interest Group for Computer Networking of the Student Chapter of the ACM at UIUC. Our part was to design a protocol that would allow the usage of Mumble for real-time text-mode teleconferencing. The protocol allowes to divide the responsibilites between chairman, and presenters. If a chairman or speaker disappears in the middle of the conference the protocol will resolve the "vacuum of power" and the conference will go on. The software was designed on C and curses library; the access to multicast capable routers and/or running mrouted on a workstation with more then one network interface is necessary.