Browsing by Author "PalChaudhuri, Santashil"

Now showing 1 - 9 of 9
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    A MAC protocol for Multi Frequency Physical Layer
    (2003-01-23) Kumar, Rajnish; PalChaudhuri, Santashil; Saha, Amit
    Existing MAC protocols for wireless LAN systems assume that a particular node can operate on only one frequency and that most/all of the nodes operate on the same frequency. We propose a MAC protocol for use in an ad hoc network of mobile nodes using a wireless LAN system that defines multiple independent frequency channels. Each node can switch quickly from one channel to another but can operate on one channel at a time. We simulate the proposed protocol by modifying the wireless extension. Our simulations show that the proposed protocol, though simple, is capable of much better performance in the presence of multiple independent channels than IEEE 802.11which assumes a single frequency channel for all nodes. As expected, the proposed protocol works as well as IEEE 802.11 in the presence of a single channel.
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    An adaptive sensor network architecture for multi-scale communication
    (2006) PalChaudhuri, Santashil; Johnson, David B.
    Sensor networking has emerged as a promising tool for monitoring and actuating the devices of the physical world, employing self-organizing networks of battery-powered wireless sensors that can sense, process, and communicate. Such networks can be rapidly deployed at low cost, enabling large-scale, on-demand monitoring and tracking over a wide area. Energy is the most crucial and scarce resource for such networks. However, since sensor network applications generally exhibit specific limited behaviors, there is both a need and an opportunity for adapting the network architecture to match the application in order to optimize resource utilization. Many applications-such as large-scale collaborative sensing, distributed signal processing, and distributed data assimilation-require sensor data to be available at multiple resolutions, or allow fidelity to be traded-off for energy efficiency. In this thesis, I develop an adaptive cross-layered sensor network architecture that enables multi-scale collaboration and communication. Analyzing the unique characteristics of sensor networks, I identify cross-layering and adaptability to applications as the primary design principles needed to build three closely coupled-protocols: (1) a self-organizing adaptive hierarchical data service for multi-scale communication, together with communication primitives to simplify application design; (2) a medium scheduling protocol tailored for this hierarchical data service, to take advantage of the communication and routing characteristics to achieve close to optimal latency and energy usage; and (3) an adaptive clock synchronization service, which provides an analytical framework for mapping clock synchronization requirements to actual protocol parameters, to provide required synchronization. I have analyzed as well as simulated the performance of these protocols to show optimized energy utilization.
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    Design and Performance of PRAN: A System for Physical Implementation ofAd Hoc Network Routing Protocols
    (2005-02-28) Du, Shu; Johnson, David B.; PalChaudhuri, Santashil; Saha, Amit Kumar; To, Khoa
    Simulation and physical implementation are both valuable tools in evaluating ad hoc network routing protocols, but neither alone is sufficient. In this paper, we present the design and performance of PRAN, a new system for implementation of ad hoc network routing protocols that merges these two types of evaluation tools. PRAN (Physical Realization of Ad Hoc Networks) allows existing simulation models of ad hoc network routing protocols to be used—without modification—to create a physical implementation of the same protocol. We have evaluated the simplicity and portability of our approach across multiple protocols and multiple operating systems through example implementations in PRAN of the DSR and AODV routing protocols in FreeBSD and Linux using the existing, unmodified ns-2 simulation models. We illustrate the ability of the resulting protocol implementations to handle real, demanding applications by describing a demonstration with this DSR implementation transmitting real-time video over a multi hop mobile ad hoc network; the demonstration features mobile robots being remotely operated based on the video stream transmitted over the network. We also present a detailed performance evaluation of PRAN to show the feasibility of our architecture.
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    Design of Adaptive Overlays for Multi-scale Communication in Sensor Networks
    (2005-06-01) PalChaudhuri, Santashil; Kumar, Rajnish; Baraniuk, Richard G.; Johnson, David B.; Digital Signal Processing (http://dsp.rice.edu/)
    In wireless sensor networks, energy and communication bandwidth are precious resources. Traditionally, layering has been used as a design principle for network stacks; hence routing protocols assume no knowledge of the application behavior in the sensor node. In resource-constrained sensor-nodes, there is simultaneously a need and an opportunity to optimize the protocol to match the application. In this paper, we design a network architecture that efficiently supports multi-scale communication and collaboration among sensors. The architecture complements the previously proposed Abstract Regions architecture for local communication and collaboration. We design a self-organizing hierarchical overlay that scales to a large number of sensors and enables multi-resolution collaboration. We design effective Network Programming Interfaces to simplify the development of applications on top of the architecture; these interfaces are efficiently implemented in the network layer. The overlay hierarchy can adapt to match the collaboration requirements of the application and data both temporally and spatially. We present an initial evaluation of our design under simulation to show that it leads to reduced communication overhead, thereby saving energy.We are currently building our architecture in the TinyOS environment to demonstrate its effectiveness.
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    Network Stack Architecture for Future Sensors
    (2005-01-26) Johnson, David B.; Kumar, Rajnish; PalChaudhuri, Santashil; Ramachandran, Umakishore
    With wireless ad hoc sensor networks, there is simultaneously a need and an opportunity to optimize the protocol stack behavior to match the sensor-based applications. A general-purpose internet stack is neither appropriate nor sufficient to meet the needs of such applications. Motivated by this observation, we pose two related questions: (a) What is an appropriate layering of the protocol stack for future sensor networks? (b) How do we make the network stack tunable to a specific sensor application? We present the design of a new protocol stack, and we qualitatively argue that the new stack is more suitable to meet the demands of sensor network applications than traditional stacks.
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    Power Mode Scheduling for Ad Hoc Network Routing
    (2002-04-27) PalChaudhuri, Santashil
    An ad hoc network is a group of mobile wireless nodes that cooperatively form a network among themselves without any fixed infrastructure. Each node in the ad hoc network forwards packets for other nodes, to allow nodes not within direct wireless transmission range to communicate, using a routing protocol. Increasingly, power consumption within ad hoc networks is becoming a core issue for these low-power mobile devices. This thesis focuses on a novel approach for energy conservation within the ad hoc network routing protocol. I develop and evaluate two types of mechanisms for reducing this power consumption by the routing protocol in the network. The routing protocol uses information from packets received promiscuously to improve routing performance. The first part of this work is a strategy for reducing this use of promiscuous mode intelligently, thereby saving energy but retaining all the benefits of being in promiscuous mode. In addition, a wireless card in sleep mode expends an order of magnitude less power than in idle mode, but no packets can be sent or received while in sleep mode. In the second part of this work, I propose two algorithms for scheduling transition from idle mode to sleep mode. We apply probabilistic mechanisms as a useful tool, thereby trading energy for a minimal performance loss. Performance evaluation of these strategies show significant reduction in power usage, with only a slight decrease in performance.
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    Power mode scheduling for ad hoc network routing
    (2002) PalChaudhuri, Santashil; Johnson, David B.
    An ad hoc network is a group of mobile wireless nodes that cooperatively form a network among themselves without any fixed infrastructure. Each node in the ad hoc network forwards packets for other nodes, to allow nodes not within direct wireless transmission range to communicate, using a routing protocol. Increasingly, power consumption within ad hoc networks is becoming a core issue for these low-power mobile devices. This thesis focuses on a novel approach for energy conservation within the ad hoc network routing protocol. I develop and evaluate two types of mechanisms for reducing this power consumption by the routing protocol in the network. The routing protocol uses information from packets received promiscuously to improve routing performance. The first part of this work is a strategy for reducing this use of promiscuous mode intelligently, thereby saving energy but retaining all the benefits of being in promiscuous mode. In addition, a wireless network interface in sleep mode expends an order of magnitude less power than in idle mode, but no packets can be sent or received while in sleep mode. In the second part of this work, I propose two probabilistic algorithms for scheduling transition from idle mode to sleep mode. Performance evaluation of these strategies shows significant reduction in power usage, with only a slight decrease in performance.
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    Probabilistic Clock Synchronization Service in Sensor Networks
    (2003-04-16) Johnson, David B.; PalChaudhuri, Santashil; Saha, Amit
    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 describe a probabilistic service for clock synchronization that is based on the Reference Broadcast Synchronization protocol. In particular, we use the higher precision of receiver-to-receiver synchronization, as described in Reference Broadcast Synchronization protocol. We extend this deterministic protocol to provide a probabilistic bound on the accuracy of the clock synchronization service, allowing for a tradeoff between accuracy and resource requirement. We derive expressions to convert service specifications (maximum clock synchronization error and confidence probability) to actual protocol parameters(minimum number of messages and synchronization overhead). We also extend this protocol for maintaining clock synchronization in a multi hop network.
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    Self-Organizing Hierarchical Routing for Scalable Ad Hoc Networking
    (2005-02-08) Druschel, Peter; Du, Shu; Johnson, David B.; Khan, Muhammed; PalChaudhuri, Santashil; Post, Ansley; Riedi, Rudolf H.; Saha, Amit
    As wireless devices 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. Safari leverages and integrates research in both ad hoc networking and peer-to-peer networking. We develop a probabilistic, elf-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, with reactive and proactive routing, to scale to large number 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 design through analysis and simulations, under increasing network size, increasing fraction of mobile nodes, and increasing offered traffic load. Our analysis is well matched by our simulations, and our results demonstrate the protocol's scalability.