Vaskar Raychoudhury

Middleware for pervasive computing: A survey

The rapidly emerging area of pervasive computing faces many challenging research issues critical to application developers. Wide heterogeneity of hardware, software, and network resources pose veritable coordination problems and demand thorough knowledge of individual elements and technologies. In order to ease this problem and to aid application developers, different middleware platforms have been proposed by researchers. Though the existing middleware solutions are useful, they themselves have varied features and contribute partially, for context, data, or service management related application developments. There is no single middleware solution that can address a majority of pervasive computing application development issues, due to the diverse underlying challenges. In this survey paper, we identify different design dimensions of pervasive computing middleware and investigate their use in providing various system services. In-depth analysis of the system services have been carried out and middleware systems have been carefully studied. With a view to aid future middleware developers, we also identify some challenging open research issues that have received little or no attention in existing middleware solutions.

A survey of routing and data dissemination in Delay Tolerant Networks

Delay Tolerant Networks (DTNs) have practical applications in various fields. DTNs have been studied in-depth by many researchers and multiple high quality survey papers have been produced which analyzes DTN features, taxonomies, and applications. In recent years, interest in DTN research has rekindled as there are several emerging network-based application domains that require delay tolerance support and thus can use DTN specific routing and data dissemination techniques. Examples of such novel areas are Information Centric Network (ICN), Mobile ICN, Named Data Network (NDN), Internet of Things (IoT), etc. In this paper, we have surveyed those applications briefly and have proposed an alternate taxonomy for classifying existing DTN routing algorithms. The objective of this survey is to help future researchers to identify DTN specific properties in the new applications and to apply appropriate routing protocols whenever necessary. We have studied the relation between message replication and individual or group communication semantics of DTN routing protocols considering both social-based and opportunistic message forwarding techniques. We have also introduced an in-depth coverage of data dissemination protocols in DTN which can be adapted to content-centric networking domains. We conclude our survey by identifying a set of open challenges for future researchers.

An energy-efficient routing protocol using movement trends in vehicular ad hoc networks

Vehicular Ad hoc Networks (VANETs) are a killer application of Mobile Ad hoc Networks (MANETs), which exchange data among vehicles and vehicles to roadside infrastructures by routing. To save energy, various routing protocols for VANETs have been proposed in recent years. However, VANETs impose challenging issues to routing. These issues consist of dynamical road topology, various road obstacles, high vehicle movement and the fact that the vehicle movement is constrained on roads and traffic conditions. Moreover, the movement is significantly influenced by driving behaviors and vehicle categories. To this end, we incorporate them into routing and propose energy-efficient routing using movement trends (ERBA) for VANETs—an energy-efficient routing protocol. ERBA classifies vehicles into several categories, and then leverages vehicle movement trends to make routing recommendation. It predicts the movement trends by current directions and next directions after going through the road intersections. With the vehicular category information, the driving behavior patterns, the distance between the current sections and the next intersections, ERBA propagates information among vehicles with less energy consumption. The proposed scheme is validated by real urban scenarios extracted from ShanghaiGrid project. Experimental results show that ERBA outperforms the compared routing protocols with respect to the end-end delay, the packet delivery ratio and the path duration time.

A Dynamic Community Creation Mechanism in Opportunistic Mobile Social Networks

Web-based social networking services enable like-minded people to collaborate and socialize with each other. With rich sensing and communication capabilities, mobile phones provide new possibilities for enhancing face-to-face social interaction among people who are both socially and physically close to each other. Research challenges arise as how to exploit the characteristics of peoples mobility patterns and form a social community with a specific goal in the mobile environment. In this paper, we present SOCKER - a dynamic community creation mechanism based on social-aware broker selection strategies. SOCKER gradually forms a mobile social community by dynamically selecting a broker during each opportunistic encounter, and the selected broker disseminates community creation requests to the encountered users for match-making. Based on real human mobility traces, extensive evaluations are conducted showing that SOCKER achieves high community completion ratio as well as high user social satisfaction, while incurring a small overhead.

Top K-Leader Election in Wireless Ad Hoc Networks

In this paper, we propose a distributed algorithm to elect the top K leaders among the nodes in a wireless ad hoc network. Leader election is a fundamental distributed coordination problem arising from many applications, e.g. token regeneration, directory service. However, there is no deterministic algorithm proposed for electing k leaders. In our algorithm, election is based on the weight values of the nodes, which can represent any performance related attribute such as the nodes battery power, computational capabilities etc. To achieve message efficiency, coordinator nodes are first selected locally and then the coordinator nodes collect the weight information of other nodes using a diffusing computation approach. The coordinator nodes collaborate with each other to further reduce the message cost. Node failures are also considered in our design. The simulation results show that, compared with a naive solution, our proposed algorithm can elect top K leaders with much less message cost.

An Efficient Collaborative Filtering Approach Using Smoothing and Fusing

Collaborative Filtering (CF) has achieved widespread success in recommender systems such as Amazon and Yahoo! music. However, CF usually suffers from two fundamental problems - data sparsity and limited scalability. Among the two broad classes of CF approaches, namely, memory-based and model-based, the former usually falls short of the system scalability demands, because these approaches predict user preferences over the entire item-user matrix. The latter often achieves unsatisfactory accuracy, because they cannot capture precisely the diversity in user rating styles. In this paper, we propose an efficient Collaborative Filtering approach using Smoothing and Fusing (CFSF) strategies. CFSF formulates the CF problem as a local prediction problem by mapping it from the entire large-scale item-user matrix to a locally reduced item-user matrix. Given an active item and a user, CFSF dynamically constructs a local item-user matrix as the basis of prediction. To alleviate data sparsity, CFSF presents a fusion strategy for the local item-user matrix that fuses ratings of the same user makes on similar items, and ratings of like-minded users make on the same and similar items. To eliminate diversity in user rating styles, CFSF uses a smoothing strategy that clusters users over the entire item-user matrix and then smoothes ratings within each user cluster. Empirical study shows that CFSF outperforms the state-of-the-art CF approaches in terms of both accuracy and scalability.

Mobile RFID with a High Identification Rate

An important category of mobile RFID systems is the RFID system with mobile RFID tags. The mobility of RFID tags poses new challenges to designing RFID anti-collision protocols. Existing RFID anti-collision protocols cannot support high tag moving speed and high identification rate simultaneously. These protocols do not distinguish the identification deadlines of moving tags. Also, when tags move fast, they cannot determine the number of unidentified tags in the interrogation area of an RFID reader. In this paper, we propose a schedule-based RFID anti-collision protocol which, given a high identification rate, achieves the maximal tag moving speed. The protocol, without the need to estimate the number of unidentified tags, schedules an optimal number of tags to compete for the channel according to their identification deadlines, so as to achieve the optimal identification performance. The simulation and experiment results show that our approach can increase the moving speed of tags significantly compared with existing approaches, while achieving a high identification rate.

CROWD-PAN-360: Crowdsourcing Based Context-Aware Panoramic Map Generation for Smartphone Users

Recent advances in smartphones and location-aware services necessitate identifying logical locations of users, in terms of their surroundings, instead of raw location coordinates. In this paper, we have proposed CROWD-PAN-360 (CP360), a novel smartphone-based system to generate 360-degree panoramic map of a querying user for his unfamiliar surrounding using crowd-sourced images. The objects (logical locations) appearing in the images are identified using manually or automatically generated tags. The system is context-aware and it intelligently associates user location coordinates with several smartphone contexts, like acceleration and orientation. CP360 can significantly reduce GPS positional errors for even cheap low-end smartphones and can identify the user surroundings very efficiently. We extensively tested the system in both indoor and outdoor environments of IIT Roorkee campus using Android smartphones over a dataset of more than 6,000 crowd-sourced images of nearly 70 objects (departments, hostels, cafeteria, etc.) and CP360 generates the panoramic map with an average accuracy of 92.2 percent.

Top K-leader election in mobile ad hoc networks

Many applications in mobile ad hoc networks (MANETs) require multiple nodes to act as leaders. Given the resource constraints of mobile nodes, it is desirable to elect resource-rich nodes with higher energy or computational capabilities as leaders. In this paper, we propose a novel distributed algorithm to elect top-K weighted leaders in MANETs where weight indicates available node resources. Frequent topology changes, limited energy supplies, and variable message delays in MANETs make the weight-based K leader election a non-trivial task. So far, there is no algorithm for weight-based K leader election in distributed or mobile environments. Moreover, existing single leader election algorithms for ad hoc networks are either unsuitable of extending to elect weight-based K leaders or they perform poorly under dynamic network conditions. In our proposed algorithm, initially few coordinator nodes are selected locally which collect the weights of other nodes using the diffusing computation approach. The coordinator nodes then collaborate together, so that, finally the highest weight coordinator collects weights of all the nodes in the network. Besides simulation we have also implemented our algorithm on a testbed and conducted experiments. The results prove that our proposed algorithm is scalable, reliable, message-efficient, and can handle dynamic topological changes in an efficient manner.

Radient: Scalable, memory efficient name lookup algorithm for named data networking

Named Data Networking (NDN) aims to discard the existing host-centric networking paradigm just to replace it with a more practical Content-Centric Networking (CCN) paradigm. CCN allows users to fetch and distribute contents directly using their names. NDN router stores all incoming content requests (׳/׳-delimited string components) in the Pending Interest Table (PIT) until they are satisfied. Multiple requests for the same content are merged in a single PIT entry and when the requested content is available, it is forwarded simultaneously to all the requesters. Although NDN has several benefits over the existing IP-based network, replacing IP addresses with names increases memory consumption and lookup cost. One possible way to restrict memory usage is to use name encoding, i.e., to encode identical components of a name with a unique integer. In this paper, we proposed a novel memory efficient name encoding scheme (called, Radient) for PIT and evaluated it extensively. Our results show that the Radient scheme can reduce memory consumption by 35.45% compared to the ENPT for 29 million names.