Samir R. Das

Bio: Samir R. Das is an academic researcher from Stony Brook University. The author has contributed to research in topics: Wireless network & Physics. The author has an hindex of 58, co-authored 186 publications receiving 29007 citations. Previous affiliations of Samir R. Das include University of Texas at San Antonio & University of Cincinnati.

A Self-Biased Low Modulation Index ASK Demodulator for Implantable Devices

Abstract: Free floating sub-mm and mm sized brain implants can communicate through a backscatter-based link in a presence of the EM field generated by the external coil. This link reduces the bandwidth requirement in the uplink communication of these implants to the external coil and enables a close-loop operation of the distributed implant system through reduced latency. The critical challenge in the link design stems from the low modulation index in the incident signal at the receiving coil. This calls for the design of the ASK demodulator that can resolve signals with low modulation index. We propose a demodulator design comprising a self-biased common-source based envelope detector that provides sufficient conversion gain and at the same time operates with a low power consumption. With 90 MHz carrier frequency and 50-kbps data rate, the ASK demodulator, implemented in 65 nm CMOS technology, resolves input RF signal with 1% modulation index consuming less than 100 nW when amplitude of the input RF signal is 200 mV.

Measurement of anti-3He nuclei absorption in matter and impact on their propagation in the Galaxy

Abstract: In our Galaxy, light antinuclei composed of antiprotons and antineutrons can be produced through high-energy cosmic-ray collisions with the interstellar medium or could also originate from the annihilation of dark-matter particles that have not yet been discovered. On Earth, the only way to produce and study antinuclei with high precision is to create them at high-energy particle accelerators. Although the properties of elementary antiparticles have been studied in detail, the knowledge of the interaction of light antinuclei with matter is limited. We determine the disappearance probability of $^{3}\overline{\rm He}$ when it encounters matter particles and annihilates or disintegrates within the ALICE detector at the Large Hadron Collider. We extract the inelastic interaction cross section, which is then used as input to calculations of the transparency of our Galaxy to the propagation of $^{3}\overline{\rm He}$ stemming from dark-matter annihilation and cosmic-ray interactions within the interstellar medium. For a specific dark-matter profile, we estimate a transparency of about 50%, whereas it varies with increasing $^{3}\overline{\rm He}$ momentum from 25% to 90% for cosmic-ray sources. The results indicate that $^{3}\overline{\rm He}$ nuclei can travel long distances in the Galaxy, and can be used to study cosmic-ray interactions and dark-matter annihilation.

Time-parallel algorithms for simulation of multiple access protocols

Abstract: We present time-parallel algorithms for parallel simulation of multiple access protocols for medium access-in particular slotted Aloha and slotted p-persistent CSMA. Two mechanisms are presented-regeneration point-based and fix up-based. Aloha is simulated using both mechanisms and CSMA is simulated using only the first mechanism. An analytical technique is developed to predict speedup for the regeneration point-based scheme for slotted Aloha. Speedup values obtained from the analytical technique are found to be in good agreement with those obtained from simulations. In general, it is observed that any mechanism that reduces the number of backlogged packets has good parallel performance regardless of the protocol simulated or the mechanism used to parallelize the simulation.

Performance of dead reckoning-based location service for mobile ad hoc networks: Research Articles

Abstract: A predictive model-based mobility tracking method, called dead reckoning, is developed for mobile ad hoc networks. It disseminates both location and movement models of mobile nodes in the network so that every node is able to predict or track the movement of every other node with a very low overhead. The basic technique is optimized to use ‘distance effect’, where distant nodes maintain less accurate tracking information to save overheads. The dead reckoning-based location service mechanism is evaluated against three known location dissemination service protocols: simple, distance routing effect algorithm for mobility (DREAM) and geographic region summary service (GRSS). The evaluation is done with geographic routing as an application. It is observed that dead reckoning significantly outperforms the other protocols in terms of packet delivery fraction. It also maintains low-control overhead. Its packet delivery performance is only marginally impacted by increasing speed or noise in the mobility model, that affects its predictive ability. Copyright © 2004 John Wiley & Sons, Ltd.

An application-specific protocol architecture for wireless microsensor networks

Abstract: Networking together hundreds or thousands of cheap microsensor nodes allows users to accurately monitor a remote environment by intelligently combining the data from the individual nodes. These networks require robust wireless communication protocols that are energy efficient and provide low latency. We develop and analyze low-energy adaptive clustering hierarchy (LEACH), a protocol architecture for microsensor networks that combines the ideas of energy-efficient cluster-based routing and media access together with application-specific data aggregation to achieve good performance in terms of system lifetime, latency, and application-perceived quality. LEACH includes a new, distributed cluster formation technique that enables self-organization of large numbers of nodes, algorithms for adapting clusters and rotating cluster head positions to evenly distribute the energy load among all the nodes, and techniques to enable distributed signal processing to save communication resources. Our results show that LEACH can improve system lifetime by an order of magnitude compared with general-purpose multihop approaches.

Directed diffusion: a scalable and robust communication paradigm for sensor networks

Abstract: Advances in processor, memory and radio technology will enable small and cheap nodes capable of sensing, communication and computation. Networks of such nodes can coordinate to perform distributed sensing of environmental phenomena. In this paper, we explore the directed diffusion paradigm for such coordination. Directed diffusion is datacentric in that all communication is for named data. All nodes in a directed diffusion-based network are application-aware. This enables diffusion to achieve energy savings by selecting empirically good paths and by caching and processing data in-network. We explore and evaluate the use of directed diffusion for a simple remote-surveillance sensor network.

Epidemic routing for partially-connected ad hoc networks

Abstract: Mobile ad hoc routing protocols allow nodes with wireless adaptors to communicate with one another without any pre-existing network infrastructure. Existing ad hoc routing protocols, while robust to rapidly changing network topology, assume the presence of a connected path from source to destination. Given power limitations, the advent of short-range wireless networks, and the wide physical conditions over which ad hoc networks must be deployed, in some scenarios it is likely that this assumption is invalid. In this work, we develop techniques to deliver messages in the case where there is never a connected path from source to destination or when a network partition exists at the time a message is originated. To this end, we introduce Epidemic Routing, where random pair-wise exchanges of messages among mobile hosts ensure eventual message delivery. The goals of Epidemic Routing are to: i) maximize message delivery rate, ii) minimize message latency, and iii) minimize the total resources consumed in message delivery. Through an implementation in the Monarch simulator, we show that Epidemic Routing achieves eventual delivery of 100% of messages with reasonable aggregate resource consumption in a number of interesting scenarios.