Browsing by Author "Kumar, Rajnish"

Now showing 1 - 5 of 5
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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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    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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    Secure implementation, network cost sharing and oligopolistic price discrimination
    (2010) Kumar, Rajnish; Moulin, Herve
    In chapter 1, we consider the possibility of Secure Implementation in Production Economies beyond the result provided in the Saijo et al. (2007) paper. We find a large class of SCFs to be securely implementable. The serial SCF and the widely studied Fixed Path SCFs which contains serial SCF as a special case are all special cases of our function. In chapter 2, which is a version of my work with Ruben Juarez, we consider the problem of sharing the cost of a network formed by choice of paths of agents to connect their demand nodes. Motivated by the inefficiency, instability and huge informational requirements of the widely used Shapley (Sh) cost sharing rules, we look for mechanisms in a setting of minimal informational requirement which overcome the said shortcoming. We characterize a class of such mechanisms under different notions of robust implementations. We also discover that voluntary participation is possible in this setup with no more inefficiency than that of Sh. In chapter 3, which is a version of my work with Levent Kutlu, we consider the aspect of price discrimination under oligopolistic setting. The environment has two stages of the game. In first stage the firms fight on the quantity they want to put in the market and then in the second stage they decide how to distribute that quantity among the buyers with different valuations. We characterize the unique NE of this game. The firms which ends up with higher quantity in the first stage sells to all the buyers whereas the smaller firm sells some of the high end buyers.
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    User-centric framework for device aggregation
    (2003) Kumar, Rajnish; Zwaenepoel, Willy
    As intelligent devices become affordable and wireless infrastructure becomes pervasive, the potential to combine, or aggregate, device functionality to provide a user with a better experience grows. Currently, the user must have a detailed understanding of the physical properties of the devices, the software services offered, and the dynamic behavior of the environment in order to form an appropriate aggregation. Even a small number of devices can be aggregated in many ways to perform a particular task effectively. This problem is more severe when the user is in an environment with unfamiliar devices, when a large number of devices are available, or when multiple tasks need to be performed simultaneously. This thesis presents the design and implementation of a system for the user-centric aggregation of device functionality in a dynamic environment. It supports the automated selection of device functionality for aggregation using predefined descriptions of devices and their services. It facilitates the selection of the aggregation that best matches a user's preferences using declarative policies, and it allows a user to express trade-offs between the quality of device attributes, user distraction, and aggregation stability. This approach enables a user to have a richer experience without having to constantly worry about device details and the aggregation of device functionality.