Sanjay Kumar Madria

Sensor networks: an overview

Advances in hardware and wireless network technologies have created low-cost, low-power, multifunctional miniature sensor devices. These devices make up hundreds or thousands of ad hoc tiny sensor nodes spread across a geographical area. These sensor nodes collaborate among themselves to establish a sensing network. A sensor network can provide access to information anytime, anywhere by collecting, processing, analyzing and disseminating data. Thus, the network actively participates in creating a smart environment.

Research Issues in Web Data Mining

In this paper, we discuss mining with respect to web data referred here as web data mining. In particular, our focus is on web data mining research in context of our web warehousing project called WHOWEDA (Warehouse of Web Data). We have categorized web data mining into threes areas; web content mining, web structure mining and web usage mining. We have highlighted and discussed various research issues involved in each of these web data mining category. We believe that web data mining will be the topic of exploratory research in near future.

Sensor Cloud: A Cloud of Virtual Sensors

Newer models for interacting with wireless sensors such as Internet of Things and Sensor Cloud aim to overcome restricted resources and efficiency. The Missouri S&T (science and technology) sensor cloud enables different networks, spread in a huge geographical area, to connect together and be employed simultaneously by multiple users on demand. Virtual sensors, which are at the core of this sensor cloud architecture, assist in creating a multiuser environment on top of resource-constrained physical wireless sensors and can help in supporting multiple applications.

A secure hierarchical model for sensor network

In a distributed sensor network, large number of sensors deployed which communicate among themselves to self-organize a wireless ad hoc network. We propose an energy-efficient level-based hierarchical system. We compromise between the energy consumption and shortest path route by utilizing number of neighbors (NBR) of a sensor and its level in the hierarchical clustering. In addition, we design a Secure Routing Protocol for Sensor Networks (SRPSN) to safeguard the data packet passing on the sensor networks under different types of attacks. We build the secure route from the source node to sink node. The sink node is guaranteed to receive correct information using our SRPSN. We also propose a group key management scheme, which contains group communication policies, group membership requirements and an algorithm for generating a distributed group key for secure communication.

Mobile data and transaction management

Abstract Mobile computing paradigm has emerged due to advances in wireless or cellular networking technology. This rapidly expanding technology poses many challenging research problems in the area of mobile database systems. The mobile users can access information independent of their physical location through wireless connections. However, accessing and manipulating information without restricting users to specific locations complicates data processing activities. There are computing constraints that make mobile database processing different from the wired distributed database computing. In this paper, we survey the fundamental research challenges particular to mobile database computing, review some of the proposed solutions and identify some of the upcoming research challenges. We discuss interesting research areas, which include mobile location data management, transaction processing and broadcast, cache management and replication and query processing. We highlight new upcoming research directions in mobile digital library, mobile data warehousing, mobile workflow and mobile web and e-commerce.

A Model for XML Schema Integration

We define an object-oriented data model called XSDM (XML Schema Data Model) and present a graphical representation of XML Schema integration. The three layers included are, namely, pre-integration, comparison and integration. During pre-integration, the schema present in XML Schema notation is read and is converted into the XSDM notation. During the comparison phase of integration, correspondences as well as conflicts between elements are identified. During the integration phase, conflict resolution, restructuring and merging of the initial schemas take place to obtain the global schema.

A Transaction Model to Improve Data Availability in Mobile Computing

We incorporate a prewrite operation before a write operation in a mobile transaction to improve data availability. A prewrite operation does not update the state of a data object but only makes visible the future value that the data object will have after the final commit of the transaction. Once a transaction reads all the values and declares all the prewrites, it can pre-commit at mobile host (MH) (computer connected to unreliable mobile communication network). The remaining transactions execution (writes on database) is shifted to the mobile service station (MSS) (computer connected to the reliable fixed network). Writes on database consume time and resources and are therefore shifted to MSS and delayed. This reduces wireless network traffic congestion. Since the responsibility of expensive part of the transactions execution is shifted to the MSS, it also reduces the computing expenses at mobile host. A pre-committed transactions prewrite values are made visible both at mobile and at fixed database servers before the final commit of the transaction. Thus, it increases data availability during frequent disconnection common in mobile computing. Since a pre-committed transaction does not abort, no undo recovery needs to be performed in our model. A mobile host needs to cache only prewrite values of the data objects which take less memory, transmission time, energy and can be transmitted over low bandwidth. We have analysed various possible schedules of running transactions concurrently both at mobile and fixed database servers. We have discussed the concurrency control algorithm for our transaction model and proved that the concurrent execution of our transaction processing model produces only serializable schedules. Our performance study shows that our model increases throughput and decreases transaction-abort-ratio in comparison to other lock based schemes. We have briefly discussed the recovery issues and implementation of our model.

SecRout: a secure routing protocol for sensor networks

In this paper, we present a secure routing protocol for sensor networks (SecRout) to safeguard sensor networks under different types of attacks. The SecRout protocol uses the symmetric cryptography to secure messages, and uses a small cache in sensor nodes to record the partial routing path (previous and next nodes) to the destination. It guarantees that the destination will be able to identify and discard the tampered messages and ensure that the messages received are not tampered. Comparing the performance with non-secure routing protocol AODV (ad hoc on demand distance vector routing), the SecRout protocol only has a small byte overhead (less than 6%), but packet delivery ratio is almost same as AODV and packet latency is better than AODV after the route discovery.

SeRWA: A secure routing protocol against wormhole attacks in sensor networks

A wormhole attack is particularly harmful against routing in sensor networks where an attacker receives packets at one location in the network, tunnels and then replays them at another remote location in the network. A wormhole attack can be easily launched by an attacker without compromising any sensor nodes. Since most of the routing protocols do not have mechanisms to defend the network against wormhole attacks, the route request can be tunneled to the target area by the attacker through wormholes. Thus, the sensor nodes in the target area build the route through the attacker. Later, the attacker can tamper the data, messages, or selectively forward data messages to disrupt the functions of the sensor network. Researchers have used some special hardware such as the directional antenna and the precise synchronized clock to defend the sensor network against wormhole attacks during the neighbor discovery process. In this paper, we propose a Secure Routing protocol against wormhole attacks in sensor networks (SeRWA). SeRWA protocol avoids using any special hardware such as the directional antenna and the precise synchronized clock to detect a wormhole. Moreover, it provides a real secure route against the wormhole attack. Simulation results show that SeRWA protocol only has very small false positives for wormhole detection during the neighbor discovery process (less than 10%). The average energy usage at each node for SeRWA protocol during the neighbor discovery and route discovery is below 25mJ, which is much lower than the available energy (15kJ) at each node. The cost analysis shows that SeRWA protocol only needs small memory usage at each node (below 14kB if each node has 20 neighbors), which is suitable for the sensor network.

An XML Schema integration and query mechanism system

The availability of large amounts of heterogeneous distributed web data necessitates the integration of XML data from multiple XML sources for many reasons. For example, currently, there are many e-commerce companies, which offer similar products but use different XML Schemas with possibly different ontologies. When any two such companies merge, or make an effort to service customers in cooperation, there is a need for an integrated schema and query mechanism for the interoperability of applications. In applications like comparison-shopping, there is a need for an illusionary centralized homogeneous information system. In this paper, we propose XML Schema integration and querying methodology. We define an object-oriented data model called XSDM (XML Schema Data Model) and present a graphical representation of XML Schema for the purpose of schema integration. We use a three-layered architecture for XML Schema integration. The three layers included are namely pre-integration, comparison, and integration. The three layers can conceptually be regarded as three phases of the integration process. During pre-integration, the schemas present in XML Schema notation are read and converted into the XSDM notation. During the comparison phase of integration, correspondences as well as conflicts between elements are identified. During the integration phase, conflict resolution, restructuring and merging of the initial schemas takes place to obtain the global schema. We define integration policies for integrating element definitions as well as their datatypes and attributes. An integrated global schema forms the basis for querying a set of local XML documents. We discuss various strategies for rewriting the global query over the global schema into the sub-queries over local schemas. Their respective local schemas validate the sub-queries over the local XML documents. This requires the identification and use of mapping rules and relationships between the local schemas.