Jitender S. Deogun

Cost-effective implementation of multicasting in wavelength-routed networks

Multicasting in the optical domain has been recently shown to provide substantial savings in terms of the network-wide average packet hop distance and the total number of transceivers in the network. Current proposed multicasting architectures [e.g., splitter-and-delivery (SaD)] employ power splitting mechanisms which have the side effect of high fabrication cost due to the large number of splitters and the need for optical amplifiers. We propose a low-cost novel architecture called tap-and-continue (TaC) for realizing multicasting. This architecture provides a natural evolution from current unicast cross-connects and is based on tapping devices. We prove that any multicasting session can be feasibly realized in networks employing only TaC cross-connects, and the problem of finding the optimal multiple-destination minimum cost trail in such networks is NP-complete. Therefore, we develop a 4-approximation algorithm for multiple-destination routing. Simulation results demonstrate that the TaC cross-connect provides a realistic, cost-effective approach for implementing multicasting with negligible blocking degradation especially in multifiber networks.

Power-efficient design of multicast wavelength-routed networks

In this paper, we introduce the power-efficient design space for multicast wavelength-routed networks. The power-efficient design space is based on the impact of power on the overall design of wavelength-routed networks. Two cross-connect architectures on this design concept are investigated. One is an existing architecture called splitter-and-delivery (SaD). The other is a new architecture called multicast-only splitter-and-delivery (MOSaD). The MOSaD architecture uses power splitters for multicast connections only, allowing unicast connections to pass without enduring unnecessary power losses. Our cross-connect design provides a strictly nonblocking service for unicast connections while eliminating unnecessary power loss of the SaD cross-connect. Experimental results demonstrate that the MOSaD architecture provides substantial savings in cost and reduction in signal power loss with minimal effects on the blocking performance of the network.

Adaptive radio channel allocation for supporting coexistence of 802.15.4 and 802.11b

As the explosive growth of the ISM band usage continues, there are many scenarios where different systems operate in the same place at the same time. One of growing concerns is the coexistence of wireless systems [18]. For the successful deployment of mission-critical systems such as wireless sensor networks, it is required to provide a solution for the coexistence. In this paper, we propose a new scheme using multiple radio channels for the coexistence of 802.15.4 LRWPAN and 802.11b WLAN. To evaluate the effectiveness of the proposed scheme, measurement and simulation study are conducted. The simulation results show that the proposed scheme is effective in performance improvement for multi-hop largescale network of 802.15.4. Keywords-component; coexistence; interference; ISM band; 802.15.4; 802.11b

Sequential Association Rule Mining with Time Lags

This paper presents MOWCATL, an efficient method for mining frequent association rules from multiple sequential data sets. Our goal is to find patterns in one or more sequences that precede the occurrence of patterns in other sequences. Recent work has highlighted the importance of using constraints to focus the mining process on the association rules relevant to the user. To refine the data mining process, this approach introduces the use of separate antecedent and consequent inclusion constraints, in addition to the traditional frequency and support constraints in sequential data mining. Moreover, separate antecedent and consequent maximum window widths are used to specify the antecedent and consequent patterns that are separated by either a maximal width time lag or a fixed width time lag.Multiple time series drought risk management data are used to show that our approach can be effectively employed in real-life problems. This approach is compared to existing methods to show how they complement each other to discover associations in the drought risk management domain. The experimental results validate the superior performance of our method for efficiently finding relationships between global climatic episodes and local drought conditions. Both the maximal and fixed width time lags are shown to be useful when finding interesting associations.

Towards Missing Data Imputation: A Study of Fuzzy K-means Clustering Method

In this paper, we present a missing data imputation method based on one of the most popular techniques in Knowledge Discovery in Databases (KDD), i.e. clustering technique. We combine the clustering method with soft computing, which tends to be more tolerant of imprecision and uncertainty, and apply a fuzzy clustering algorithm to deal with incomplete data. Our experiments show that the fuzzy imputation algorithm presents better performance than the basic clustering algorithm.

Conceptual clustering in information retrieval

Clustering is used in information retrieval systems to enhance the efficiency and effectiveness of the retrieval process. Clustering is achieved by partitioning the documents in a collection into classes such that documents that are associated with each other are assigned to the same cluster. This association is generally determined by examining the index term representation of documents or by capturing user feedback on queries on the system. In cluster-oriented systems, the retrieval process can be enhanced by employing characterization of clusters. In this paper, we present the techniques to develop clusters and cluster characterizations by employing user viewpoint. The user viewpoint is elicited through a structured interview based on a knowledge acquisition technique, namely personal construct theory. It is demonstrated that the application of personal construct theory results in a cluster representation that can be used during query as well as to assign new documents to the appropriate clusters.

Sequencing Jobs with Unequal Ready Times to Minimize Mean Flow Time

This paper presents a procedure for sequencing a set of jobs on a single processor (machine) with the objective of minimizing the mean flow time, when the jobs may have unequal ready times. The procedure involves implicit enumeration with the branch and bound technique, coupled with some devices to improve the efficiency of the search. The devices include a sufficient optimality condition, a simple but tight lower bound and rules for tree pruning. The approach has potential applications to other sequencing problems.

Wireless optical communications: a survey

The demand for wireless broadband communications has been growing steadily for last several years. The congestion and the limitations on bandwidths of the radio spectrum have inhibited unrestricted growth of radio wireless systems. Wireless optical, however, holds the promise of delivering data rates that can meet the broadband requirements. As a result, wireless optical is believed to be a viable long term option for many applications of wireless communications. Nevertheless, the advantages of optical wireless have not yet been fully exploited. Basic and applied research is needed at the laboratory and commercial levels to bring the performance of real-life wireless optical systems into higher levels. The Gb/s level data rate has been validated in laboratory, however, available indoor systems only realize a data rate of 155Mb/s. Current research in wireless optical concentrates on increasing the communication capacity and improving the performance. In this paper, we survey the wireless optical discipline emphasizing major design, performance, and safety issues. Research directions that have the potential to close the gap between theory and practice, in wireless optical communications, are also presented.

TCP congestion avoidance algorithm identification

The Internet has recently been evolving from homogeneous congestion control to heterogeneous congestion control. Several years ago, Internet traffic was mainly controlled by the traditional AIMD algorithm, whereas Internet traffic is now controlled by many different TCP algorithms, such as AIMD, BIC, CUBIC, and CTCP. However, there is very little work on the performance and stability study of the Internet with heterogeneous congestion control. One fundamental reason is the lack of the deployment information of different TCP algorithms. In this paper, we first propose a tool called TCP Congestion Avoidance Algorithm Identification (CAAI) for actively identifying the TCP algorithm of a remote web server. CAAI can identify all default TCP algorithms (i.e., AIMD, BIC, CUBIC, and CTCP) and most non-default TCP algorithms of major operating system families. We then present, for the first time, the CAAI measurement result of the 5000 most popular web servers. Among the web servers with valid traces, we found that only 16.85~25.58\% of web servers still use the traditional AIMD, 44.51\% of web servers use BIC or CUBIC, and 10.27

Discovering Sequential Association Rules with Constraints and Time Lags in Multiple Sequences

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