Santashil PalChaudhuri

Bio: Santashil PalChaudhuri is an academic researcher from Aruba Networks. The author has contributed to research in topics: Network Access Device & Networking hardware. The author has an hindex of 12, co-authored 42 publications receiving 785 citations. Previous affiliations of Santashil PalChaudhuri include Rice University.

Adaptive clock synchronization in sensor networks

Abstract: Recent advances in technology have made low cost, low power wireless sensors a reality. Clock synchronization is an important service in any distributed system, including sensor network systems. Applications of clock synchronization in sensor networks include data integration in sensors, sensor reading fusion, TDMA medium access scheduling, and power mode energy saving. However, for a number of reasons, standard clock synchronization protocols are unsuitable for direct application in sensor networks. In this paper, we introduce the concept of adaptive clock synchronization based on the need of the application and the resource constraint in the sensor networks. We describe a probabilistic method for clock synchronization that uses the higher precision of receiver-to-receiver synchronization, as described in Reference Broadcast Synchronization (RBS) protocol. This deterministic protocol is extended to provide a probabilistic bound on the accuracy of the clock synchronization, allowing for a tradeo between accuracy and resource requirement. Expressions to convert service specifications (maximum clock synchronization error and confidence probability) to actual protocol parameters (minimum number of messages and synchronization overhead) are derived. Further, we extend this protocol for maintaining clock synchronization in a multihop network.

Perfect Simulations for Random Trip Mobility Models

Abstract: The random trip model was recently proposed as a generic mobility model that contains many particular mobility models, including the widely-known random waypoint and random walks, and accommodates more realistic scenarios. The probability distribution of the movement of a mobile in all these models typically varies with time and converges to a "steady state" distribution (viz- stationary distribution), whenever the last exists. Protocol performance during this transient phase and in steady-state may differ significantly. This justifies the interest in perfect sampling of the initial node mobility state, so that the simulation of the node mobility is perfect, i.e. it is in steady state throughout a simulation. In this work, we describe implementation of the perfect sampling for some random trip models. Our tool produces a perfect sample of the node mobility state, which is then used as input to the widely-used ns-2 network simulator. We further show some simulation results for a particular random trip mobility model, based on a real-world road map. The performance metrics that we consider include various node communication properties and their evolution with time. The results demonstrate difference between transient and steady-state phases and that the transient phase can be long lasting (in the order of a typical simulation duration), if the initial state is drawn from a non steady-state distribution. The results give strong arguments in favor to running perfect simulations. Our perfect sampling tool is available to public at: http://www.cs.rice.edu//spl sim/santa/research/mobility.

Method and system for partitioning wireless local area network

Abstract: The present disclosure discloses a method and system for partitioning WLAN in order to separate network traffic from different WLANs. Specifically, a network device receives a packet from a client connected to a first network device on an access network. The network device then determines that the received packet is associated with a VLAN that is pre-configured on the first network device based on the access network to which the client is connected. Furthermore, the network device transmits the packet to a MAC layer switching device, which is not configured with the VLAN that is pre-configured on the network device. The packet includes one of a DHCP discovery message, an ARP request message, a unicast message, a multicast message, and a broadcast message. The unicast message will be transmitted to the second network device on the pre-configured VLAN prior to being transmitted to another network device outside the pre-configured VLAN.

Method and apparatus for computing priorities between conflicting rules for network services

Abstract: One embodiment of the present invention provides a system that resolves conflicts between rules for network services. During operation, the system receives a set of network service rules for network data traffic from multiple network services, wherein network service rules from different network services can possibly conflict. Next, the system identifies conflicts between pairs of network service rules in the set of network service rules. The system then determines a priority relationship between each pair of conflicting network service rules, and assigns priorities to the network service rules in a manner consistent with the determined priority relationships. This allows conflicts between network service rules to be subsequently resolved based on the assigned priorities.

Self-Organizing Hierarchical Routing for Scalable Ad Hoc Networking

Abstract: As devices with wireless networking become more pervasive, mobile ad hoc networks are becoming increasingly important, motivating the development of highly scalable ad hoc networking techniques. In this paper, we present the design and evaluation of a novel protocol for scalable routing in ad hoc networks as part of the Safari project. We develop a probabilistic, self-organizing network hierarchy formation protocol that recursively forms the nodes of the ad hoc network into an adaptive, proximity-based hierarchy of cells. We develop a hybrid routing protocol that uses this hierarchy and also develop an ondemand reactive routing protocol to scale to large numbers of nodes. The mapping of unique node identifiers to hierarchical addresses is done using a distributed hash table that leverages the hierarchical network structure. We evaluate this scalable routing protocol through analysis and simulations, showing individually as well as together the performance of the hierarchy formation protocol, the overhead of address mapping, and the performance of the routing protocol. As devices with wireless networking become more pervasive, mobile ad hoc networks are becoming increasingly important, motivating the development of highly scalable ad hoc networking techniques. In this paper, we present the design and evaluation of a novel protocol for scalable routing in ad hoc networks as part of the Safari project. We develop a probabilistic, self-organizing network hierarchy formation protocol that recursively forms the nodes of the ad hoc network into an adaptive, proximity-based hierarchy of cells. We develop a hybrid routing protocol that uses this hierarchy and also develop an on-demand reactive routing protocol to scale to large numbers of nodes. The mapping of unique node identifiers to hierarchical addresses is done using a distributed hash table that leverages the hierarchical network structure. We evaluate this scalable routing protocol through analysis and simulations, showing individually as well as together the performance of the hierarchy formation protocol, the overhead of address mapping, and the performance of the routing protocol.

Clock synchronization for wireless sensor networks: a survey

Abstract: Recent advances in micro-electromechanical (MEMS) technology have led to the development of small, low-cost, and low-power sensors Wireless sensor networks (WSNs) are large-scale networks of such sensors, dedicated to observing and monitoring various aspects of the physical world In such networks, data from each sensor is agglomerated using data fusion to form a single meaningful result, which makes time synchronization between sensors highly desirable This paper surveys and evaluates existing clock synchronization protocols based on a palette of factors like precision, accuracy, cost, and complexity The design considerations presented here can help developers either in choosing an existing synchronization protocol or in defining a new protocol that is best suited to the specific needs of a sensor-network application Finally, the survey provides a valuable framework by which designers can compare new and existing synchronization protocols

MANET simulation studies: the incredibles

Abstract: Simulation is the research tool of choice for a majority of the mobile ad hoc network (MANET) community. However, while the use of simulation has increased, the credibility of the simulation results has decreased. To determine the state of MANET simulation studies, we surveyed the 2000-2005 proceedings of the ACM International Symposium on Mobile Ad Hoc Networking and Computing (MobiHoc). From our survey, we found significant shortfalls. We present the results of our survey in this paper. We then summarize common simulation study pitfalls found in our survey. Finally, we discuss the tools available that aid the development of rigorous simulation studies. We offer these results to the community with the hope of improving the credibility of MANET simulation-based studies.

Mobile terminal and control method thereof

Abstract: A mobile terminal and a control method thereof, which can obtain an image, are provided. A mobile terminal (100) includes a camera unit (121), a pictogram extraction unit (182) and a controller (180). The camera unit (121) obtains image information corresponding to at least one of a still image and a moving image. The pictogram extraction unit (182) extracts at least one pictogram from the obtained image information. The controller (180) detects information related to the extracted pictogram, and displays the detected information to be overlapped with the obtained image information. In the mobile terminal, the controller (180) includes, as the detected information, at least one of previously recorded information and currently searched information related to the extracted pictogram.