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.

ProCSA: Protecting Privacy in Crowdsourced Spectrum Allocation

Abstract: Sharing a spectrum is an emerging paradigm to increase spectrum utilization and thus address the unabated increase in mobile data consumption. The paradigm allows the “unused” spectrum bands of licensed primary users to be shared with secondary users, as long as the allocated spectrum to the secondary users does not cause any harmful interference to the primary users. However, such shared spectrum paradigms pose serious privacy risks to the participating entities, e.g., the secondary users may be sensitive about their locations and usage patterns. This paper presents a privacy-preserving protocol for the shared spectrum allocation problem in a crowdsourced architecture, wherein spectrum allocation to secondary users is done based on real-time sensing reports from geographically distributed and crowdsourced spectrum sensors. Such an architecture is highly desirable since it obviates the need to assume a propagation model, and facilitates estimation based on real-time propagation conditions and high granularity data via inexpensive means.

Addressing Deafness and Hidden Terninal Problem in Directional Antenna based Wireless Multi-Hop Networks

Abstract: We address deafness and directional hidden terminal problem that occur when MAC protocols are designed for directional antenna based wireless multi-hop networks. Deafness occurs when the transmitter fails to communicate to its intended receiver, because the receiver's antenna is oriented in a different direction. The directional hidden terminal problem occurs when the transmitter fails to hear a prior RTS/CTS exchange between another pair of nodes and cause collision by initiating a transmission to the receiver of the ongoing communication. Though directional antennas offer better spatial reuse, these problems can have a serious impact on network performance. In this paper, we study various scenarios in which these problems can occur and design a MAC protocol that solves them comprehensively using only a single channel and single radio interface. Current solutions in literature either do not address these issues comprehensively or use more than one radio/channel to solve them. We evaluate our protocol using detailed simulation studies. Simulation results indicate that our protocol can effectively address deafness and directional hidden terminal problem and increase network performance.

Benchmarking resource usage for spectrum sensing on commodity mobile devices

Abstract: Effective management of various white space spectra may require spectrum sensing at finer spatial granularity than is feasible with expensive laboratory-grade spectrum sensors. To enable this, we envision a future where commodity mobile devices would be capable of spectrum sensing as needed, possibly via crowd-sourcing. However, since mobile devices are resource limited, understanding their resource usage in this set up is important, specifically in terms of overall latency and energy usage. In this work, we carry out a comprehensive performance benchmarking study using 4 different USB-powered software radios and 2 common smartphone/ embedded computers as mobile spectrum sensing platforms. The study evaluates latency and energy usage using a suite of commonly used sensing algorithms specifically targeting TV white space spectrum. The study shows that latency due to sensing and computation and related energy usage are both modest.

Cache placement in sensor networks under update cost constraint

Abstract: In this paper, we address an optimization problem that arises in context of cache placement in sensor networks. In particular, we consider the cache placement problem where the goal is to determine a set of nodes in the network to cache/store the given data item, such that the overall communication cost incurred in accessing the item is minimized, under the constraint that the total communication cost in updating the selected caches is less than a given constant. In our network model, there is a single server (containing the original copy of the data item) and multiple client nodes (that wish to access the data item). For various settings of the problem, we design optimal, near-optimal, heuristic-based, and distributed algorithms, and evaluate their performance through simulations on randomly generated sensor networks.

A framework for joint scheduling and diversity exploitation under physical interference in wireless mesh networks

Abstract: Recently, interest has arisen in use of realistic interference models for transmission scheduling in wireless multihop networks, particularly in mesh networks where throughput is a major concern. In this work, we use the SINR-based physical interference model and develop a uniform framework for transmission scheduling when diverse wireless resources can be exploited. The factors considered are multiple (possibly overlapped) channels, directional antennas, and transmit power control. We develop an efficient heuristic for computing a diversity exploiting schedule based on a new network saturation metric. We prove that, under uniform random node distributions, the schedule produced by our heuristic is within a poly-log factor from optimal with a probability that approaches one as network size increases. Through simulation, we demonstrate the ability of our algorithm to achieve up to a 10-fold throughput improvement with respect to networks without diversity. Our analysis also reveals a number of insights on the ability of diversity exploitation to reduce or eliminate interference.

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.