Social media platforms have become new battlegrounds for anti-social elements, with misinformation being the weapon of choice. Fact-checking organizations try to debunk as many claims as possible while staying true to their journalistic processes but cannot cope with its rapid dissemination. We believe that the solution lies in partial automation of the fact-checking life cycle, saving human time for tasks which require high cognition. We propose a new workflow for efficiently detecting previously fact-checked claims that uses abstractive summarization to generate crisp queries. These queries can then be executed on a general-purpose retrieval system associated with a collection of previously fact-checked claims. We curate an abstractive text summarization dataset comprising noisy claims from Twitter and their gold summaries. It is shown that retrieval performance improves 2x by using popular out-of-the-box summarization models and 3x by fine-tuning them on the accompanying dataset compared to verbatim querying. Our approach achieves Recall@5 and MRR of 35% and 0.3, compared to baseline values of 10% and 0.1, respectively. Our dataset, code, and models are available publicly: https://github.com/varadhbhatnagar/FC-Claim-Det/.

Considerable experimentation is happening in today's classrooms to handle large classes. In this paper, we present SAFE (Smart Authenticated Fast Exams), a tool that enables continuous assessment in the form of regular quizzes in classes. SAFE is based on a BYOD (bring your own device) model that leverages student smart-phones to conduct auto-graded, cheating-free exams in a proctored class room setting. SAFE has 3 components: a smart-phone app, a web server and WiFi infrastructure to enable app-server communication. SAFE support a rich set of features to handle various types of questions as well as instructor preferences. In the design of SAFE, we set to achieve 4 goals: easy setup, cheating-free operation, robustness and scale. Easy setup is achieved predominantly due to the BYOD model and online mode of exams. Cheating is prevented via locking the app for the intended purpose along with reporting to the server any user attempts at cheating. Robustness is handled via periodic syncing of messages and careful consideration of corner cases. Scale is handled by carefully tuning the WiFi as well as via application level scheduling.

In this paper, we present Esense, a new paradigm of communication between devices that have fundamentally different physical layers. Esense is based on sensing and interpreting energy profiles. While our ideas are generic enough to be applicable in a variety of contexts, we illustrate the usefulness of our ideas by presenting novel solutions to existing problems in three distinct research domains. As part of these solutions, we demonstrate the ability to communicate between devices that follow two different standards: IEEE 802.11 and 802.15.4. We consider two scenarios here: 1) where there is no background traffic and 2) where there is background 802.11 traffic. In each case, we build an "alphabet setâ: a set of signature packet sizes that can be used for Esense communication. Specifically for the second case, we take a measurement-based alphabet set construction by considering WiFi traces from actual deployments. Based on practical observations and experiments, we theoretically quantify the maximum achievable transmission rate when using Esense. With background traffic, we could potentially construct an alphabet of size as high as 100. Such a large alphabet size promises efficient Esense communication. We show via a prototype implementation that effective communication is indeed feasible even when both sides use different physical layers.

In this article, we consider the goal of achieving high throughput in a wireless sensor network. Our work is set in the context of those wireless sensor network applications which collect and transfer bulk data. We present PIP (Packets in Pipe), a MAC primitive for use by the transport module to achieve high throughput. PIP has a unique set of features: (a) it is a multihop connection-oriented primitive, (b) it is TDMA based, (c) it uses multiple radio channels, and (d) it is centrally controlled. This represents a significant shift from prior MAC protocols for bulk data transfer. PIP has several desirable properties: (a) its throughput degrades only slightly with increasing number of hops, (b) it is robust to variable wireless error rates, (c) it performs well even without any flow control, and (d) requires only small queue sizes to operate well. We substantiate these properties with a prototype implementation of PIP on the Tmote-Sky CC2420-based platform. PIP achieves about eleven times better throughput than the state-of-the-art prior work, over a network depth of 24 hops. We also show that PIP can be interagted with duty cycling, and that PIP can support streaming data from/to flash at little overhead.

In this paper, we consider the goal of achieving high throughput in a wireless sensor network. Our work is set in the context of those wireless sensor network applications which collect and transfer bulk data. We present PIP (Packets in Pipe), a MAC primitive for use by the transport module to achieve high throughput. PIP has a unique set of features: (a) it is a multi-hop connection oriented primitive, (b) it is TDMA-based, (c) it uses multiple radio channels, and (d) it is centrally controlled. This represents a significant shift from prior MAC protocols for bulk data transfer.

In this work, we consider the goal of enabling effective voice communication in a TDMA, multi-hop mesh network, using low cost and low power platforms. We consider two primary usage scenarios: (1) enabling a local voice communication within a village-like setting, in developing regions (2) supporting an on-site local communication among a team of users e.g. during emergency response systems.

In this paper, we present Esense: a new paradigm of communication between devices that have fundamentally different physical layers. The same communication framework also works between devices that have the same physical layer, which are out of communication range but within carrier-sense range. Esense is based on sensing and interpreting energy profiles. While our ideas are generic enough to be applicable in a variety of contexts, we illustrate the usefulness of our ideas by presenting novel solutions to existing problems in three distinct research domains. As part of these solutions, we demonstrate the ability to communicate between devices that follow two different standards: IEEE 802.11 and 802.15.4. We build an ``alphabet set'': a set of signature packet sizes which can be used for Esense. For this, we take a measurement based approach by considering WiFi traces from actual deployments. We then analyze the channel activity resulting from these traces and build an appropriate alphabet set for Esense communication. Our results show that we could potentially construct an alphabet of size as high as 100; such a large alphabet size promises efficient Esense communication. We also validate this alphabet set via a prototype implementation, and show that effective communication is indeed feasible even when both sides use different physical layers.

Outdoor community mesh networks based on 802.11 have seen tremendous growth in the recent past. The current understanding is that wireless link performance in these settings in inherently unpredictable, due to multipath delay spread. Consequently, researchers have focused on developing intelligent routing techniques to achieve the best possible performance. In this paper, we are specifically interested in mesh networks in rural locations. We first present detailed measurements to show that the PHY layer in these settings is indeed stable and predictable. There is a strong correlation between the error rate and the received signal strength. We show that interference, and not multipath fading, is the primary cause of unpredictable performance. This is in sharp contrast with current widespread knowledge from prior studies. Furthermore, we corroborate our view with a fresh analysis of data presented in these prior studies. Based on our results, we argue that outdoor rural mesh networks can indeed be built with the link abstraction being valid. This has several design implications, and opens up a fresh perspective on a wide range of technical issues in this domain.

Railway systems are critical in many regions, and can consist of several tens of thousands of bridges, being used over several decades. It is critical to have a system to monitor the health of these bridges and report when and where maintenance operations are needed. This paper presents BriMon, a wireless sensor network based system for such monitoring. The design of BriMon is driven by two important factors: application requirements, and detailed measurement studies of several pieces of the architecture. In comparison with prior bridge monitoring systems and sensor network prototypes, our contributions are three-fold. First, we have designed a novel event detection mechanism that triggers data collection in response to an oncoming train. Next, BriMon employs a simple yet effective multi-channel data transfer mechanism to transfer the collected data onto a sink located on the moving train. Third, the BriMon architecture is designed with careful consideration of the interaction between the multiple requisite functionalities such as time synchronization, event detection, routing, and data transfer. Based on a prototype implementation, this paper also presents several measurement studies to show that our design choices are indeed quite effective.

The use of 802.11 long-distance links is a cost-effective means of providing wireless connectivity to rural areas. Although deployments in this setting are increasing, a systematic study of the performance of 802.11 in these settings is lacking. The contributions of this paper are two-fold: (a)we present a detailed performance study of a set of long-distance 802.11b links at various layers of the network stack, and (b)we document the various non-obvious experiences during our study.Our study includes eight long-distance links, ranging from 1km to 37km in length. Unlike prior studies of outdoor 802.11 links, we find that the error rate as a function of the received signal strength behaves close to theory. Time correlation of any packet errors is negligible across a range of time-scales. We have observed at least one of the link to be robust to rain and fog. But any interference on the long-distance links can be detrimental to performance. Apart from this however, such long-distance links can be planned to work well with predictable performance. During our measurements, we have observed a few hardware/driver quirks as well as system bottlenecks apart from the wireless link itself. We believe that our measurements and the documentation of our experience will help future network planning as well as protocol design for these networks.

In bridging the digital divide, two important criteria are cost-effectiveness, and power optimization. While 802.11 is cost-effective and is being used in several installations in the developing world, typical system configurations are not really power efficient. In this paper, we propose a novel "Wake-on-WLAN" mechanism for coarse-grained, on-demand power on/off of the networking equipment at a remote site. The novelty also lies in our implementation of a prototype system using low-power 802.15.4-based sensor motes. We describe the prototype, as well as its evaluation on field in a WiFi testbed. Preliminary estimates indicate that the proposed mechanism can save significant power in typical rural networking settings.

A variety of wireless interfaces are available for today's mobile user to access Internet content. When coverage areas of these different technologies overlap, a terminal equipped with multiple interfaces can use them simultaneously to improve the performance of its applications. In this paper, we motivate the advantages that can be had through simultaneous use of multiple interfaces and present a network layer architecture that enables diverse multiaccess services. In particular, we explore in depth one such service provided by the architecture: Bandwidth Aggregation (BAG) for real-time applications. An important aspect of the architecture when providing BAG services for real-time applications is the scheduling algorithm that partitions the traffic onto different interfaces such that the QoS requirements of the application are met. We propose one such algorithm Earliest Delivery Path First (EDPF), that ensures packets meet their playback deadlines by scheduling packets based on the estimated delivery time of the packets. We show through analysis that EDPF performs close to an idealized Aggregated Single Link (ASL) discipline, where the multiple interfaces are replaced by a single interface with same aggregated bandwidth. A prototype implementation and extensive simulations carried using video and delay traces show the performance improvement BAG with EDPF scheduling offers over using just the Highest Bandwidth Interface (HBI) and other scheduling approaches based on weighted round robin.

802.11 has been used well beyond its original intended use of WLANs. Of particular interest to us in this paper is its use in long-distance mesh networks being designed/used for low-cost rural connectivity. We describe in detail a new MAC protocol, called 2P, that is suited for such networks in terms of efficiency. A significant challenge here is the implementation of this protocol on top of off-the-shelf 802.11 hardware, to preserve the cost benefits. We show how this can be achieved, by exploiting the flexibilities available within Prism2-based chipsets. We then present the dependence of 2P on the network topology, and show that it is indeed possible to design in practice, network topologies compatible with 2P. We describe experimental as well as simulation-based evaluations of 2P, and show that 2P achieves significant performance improvement (as much as 20 times more throughput) over 802.11 CSMA/CA in long-distance mesh networks.

A mobile terminal equipped with multiple interfaces can achieve a much higher bandwidth by aggregating the bandwidth offered by the individual networks. This helps support demanding applications like interactive video. Often, in spite of bandwidth aggregation, the available bandwidth may be too small to avoid frame loss altogether. Under these circumstances, it may be necessary to selectively discard frames to minimize the effect of their loss on the overall video quality. In this paper, we consider different frame discard algorithms and study their performance in the presence of multiple interfaces. We show through trace driven simulations that attempting to transmit every frame results in severe performance degradation. In particular we show that our proposed algorithm MC-drop outperforms other algorithms in terms of suitably defined metrics that capture overall video quality.

With the emergence of different wireless technologies, a mobile terminal equipped with multiple interfaces can achieve a much higher bandwidth by aggregating the bandwidth offered by the individual networks. In this paper, we present a system based on Mobile IP that achieves the above objective. We discuss in detail the architectural requirements and algorithms that are needed to support the system.

In an effort to conserve energy, mobile hosts wake up periodically to serve incoming traffic. This gives rise to a trade-off between energy consumption and delay. However, the deterministic strategy of current systems might not yield the desired performance. We show that knowledge of the statistical characteristics of incoming traffic can be used to better meet the energy and delay requirements of the mobile node. We consider zero-buffer and buffered models. We propose some strategies to improve the energy efficiency and study the related trade-offs. We also introduce a new metric for energy efficiency and derive explicit expressions for the same. Our results prove that significant gains accrue by employing intelligent wake-up schemes.