Souvik Basu

A human mobility based knowledge sharing approach for post disaster need assessment using DTN

In a post disaster scenario, assessment of resource needs is indeed challenging because needs are constantly changing and supplies trickle in at an uncertain rate. Moreover, information about resource needs of far-flung areas get rarely permeated owing to the disruption of cellular and other communication infrastructure, leading to a huge gap in perception about the actual needs in those areas. Therefore, a dynamic need assessment mechanism is essential to stay abreast of the actual situation. Movements of volunteers and relief workers are governed by two dominant characteristics of human mobility - spatial locality and spatial regularity. In this paper, we make use of such mobility characteristics to propose a knowledge sharing based approach for dynamic assessment of post disaster resource needs using a smart-phone based delay tolerant network (DTN). The proposed technique caters to the objective of bridging the gap in perception about actual resource needs.

A Global Reputation Estimation and Analysis Technique for detection of malicious nodes in a Post-Disaster Communication environment

Collection and analysis of situational data in a post disaster scenario is crucial for providing effective relief operation in the disaster stricken areas. However, malicious and selfish behavior of entities that forward such data pose to be a serious threat against transmission of sensitive situational data in a Post Disaster Communication Network. Due to the highly distributed nature of such a network and absence of trusted third party, one has to depend on attributes like trust and reputation of a node for evaluating it as honest and altruistic. However, a node cannot be expected to have knowledge about the global reputation of all other nodes in a distributed network. For this, we propose a scheme called GREAT (Global Reputation Estimation and Analysis Technique) that uses statistical estimation technique to estimate the global reputation of a node as a forwarder and as a rater from sample reputation values collected from a sample set of nodes in the network. GREAT eventually identifies selfish and malicious nodes in the network and excludes them to a great extent from future communication activities.

SAGE-PRoPHET: A Security Aided and Group Encounter based PRoPHET Routing Protocol for Dissemination of Post Disaster Situational Data

In this paper, we propose SAGE-PRoPHET, a security enhanced PRoPHET routing protocol that enables secure dissemination of post disaster situational messages using history of group encounters. Post disaster rescue and relief operations are essentially group based, where volunteers and rescue workers, belonging to different rescue groups, relay situational information relevant to their group to their respective relief camps, in multiple hops on a peer-to-peer basis. Now, it is evidently better to route situational information, destined for a relief camp of a particular group, through volunteers of that group or who has a history of encountering volunteers of that group frequently. Such history of encounters based routing resembles the PRoPHET routing protocol for delay tolerant networks that forwards messages intended to a particular receiver through those nodes that encounter that receiver frequently. However, to use PRoPHET for such group based routing of group specific messages the protocol needs to be tuned to use history of group encounters rather than individual encounters. On the other hand, PRoPHET assumes that nodes in the network are trusted and cooperate towards message forwarding. Such assumption turns out inaccurate in presence of malicious nodes that may severely impede the delivery, accuracy and timeliness of situational messages. Therefore, integrating proper security components with PRoPHET is extremely important. Our proposed protocol adapts PRoPHET for post disaster group encounter based routing and enhances it by incorporating certain security elements into it to provide full security against possible attacks by malicious nodes in the network. Simulation results show that our proposed protocol, in a disaster scenario, offers better performance in comparison to other well known routing protocols.

Developing a coherent global view for post disaster situation awareness using opportunistic network

Situational awareness is a critical component in a post-disaster recovery operation for assessment of needs and identification of available resources at different parts of a disaster-affected area. This information, in turn, may help the relief agencies to appropriately coordinate, manage and channelize their resources. A major hindrance in developing such global situational awareness is the non-uniform interaction pattern of relief workers. Volunteers in a particular region have much better knowledge of the local situation than those belonging to regions further away. This information asymmetry leads to deviation in perceptions of volunteers working in different regions, thereby affecting the resource distribution process. Thus, a unified global situational view of the entire disaster affected area is essential to bridge the perception gap of volunteers and to help them develop a common understanding of the actual scenario. In this paper, we propose a scheme for developing such a coherent global view of the post-disaster situation using local situational information in a smart-phone based delay tolerant peer-to-peer network environment.We focus on generating a comprehensive view which is consistent for all workers irrespective of their location or mobility. The proposed scheme takes into account the spatial locality and spatial regularity properties of human mobility and uses a concept of “opportunistic knowledge injection” to disseminate local situational knowledge to other remote areas without significant network overhead. The effectiveness of the proposal is evaluated on the ONE simulator.

Best-effort delivery of emergency messages in post-disaster scenario with content-based filtering and Priority-enhanced PRoPHET over DTN

Despite concerted efforts for relaying crucial situational information, disaster relief volunteers experience significant communication challenges owing to failures of critical infrastructure and longstanding power outages in disaster affected areas. Researchers have proposed the use of smartphones, working in delay tolerant (DTN) mode, for setting up a peer-to-peer network enabling post disaster communication. However, due to opportunistic contacts, intermittent connectivity and constrained resources (mainly battery) of mobile devices, not all messages get forwarded in such a network. As a result, several crucial messages, waiting in the buffer may get dropped and unimportant, extraneous (sentimental comments of victims, etc.) messages may get transmitted at the cost of expensive network resources. Therefore, filtering out such irrelevant messages (containing unrelated information and emotional expressions) and prioritizing relevant messages according to its importance becomes crucial so that messages which are critical for decision making receive the highest priority and get disseminated in the network at the minimum possible time. In this paper, our objective is to ensure best-effort delivery of emergency messages using a two-step approach, (i) segregation of high priority messages through natural language processing based filtering and (ii) dissemination of filtered messages over DTN using a Priority-enhanced PRoPHET routing protocol which is developed by adapting the popular PRoPHET routing protocol. The protocol successfully achieves on-the-fly message prioritization and ensures best effort delivery of such prioritized messages to their appropriate destinations. The proposed protocol is evaluated using the ONE simulator. Simulation results suggest that our protocol outperforms other well known DTN routing protocols like PRoPHET, Spray-And-Wait, MaxProp and Epidemic in terms of delivery ratio of prioritized messages and overhead ratio.

A location based mobility prediction scheme for post disaster communication network using DTN

Selection of next hop forwarder plays a pivotal role in timely and accurate dissemination of post disaster situational data to a predetermined destination. Prior knowledge about the probability of future presence of a node near the destination eases this process significantly. In this paper, we propose a location based mobility prediction scheme that helps in selecting the appropriate forwarder by predicting the mobility pattern of nodes. Researchers, over a considerable period, have proposed the use of DTN in setting up a post disaster communication network. DTN specific user mobility involves both periodic and slightly chaotic patterns; chaotic behavior being attributed to the sudden causal events triggering instantaneous node mobility. In our approach, we approximate the periodicity of the DTN node mobility and use that knowledge to facilitate forwarding. Each mobile node in this approach is expected to periodically sample its own position in terms of time-location pair. This information is shared by other nodes upon contact. The sampled data, from other nodes, are extrapolated for future time instances to predict the possible locations of the mobile nodes for the next few points in time. So, the node having minimal distance around the vicinity of the destination, in some future time, qualify as the next forwarder. We compare the results, thus obtained, with real location of the nodes in future mentioned time instances and simulation results show that our scheme provides satisfactory results in predicting mobility of nodes to a great extent.

Wise-PRoPHET: A Watchdog supervised PRoPHET for reliable dissemination of post disaster situational information over smartphone based DTN

Abstract Delay tolerant network (DTN) has been successfully proposed for setting up emergency post disaster communication networks when normal communication infrastructure is typically incapacitated. These networks work on the basis of cooperation from participating nodes, which is cost-intensive in terms of battery life, computation, etc. Therefore, nodes can refuse to cooperate to save resources, giving rise to selfish nodes that hinder the transmission of sensitive post disaster situational messages. Another issue is the presence of malicious nodes that collude to either spoil the reputation of honest nodes or boost the reputation of selfish nodes. The existing DTN routing protocols, like PRoPHET, do not address these issues. In this paper, a trust based Watchdog technique is seamlessly integrated with PRoPHET so that situational messages are successfully delivered even in the presence of selfish and malicious nodes. The Watchdog monitors its neighbouring nodes to generate a local perception about their forwarding behaviour. This information is then disseminated in the network to build a global perception of forwarding behaviour for detection of selfish nodes. The local perception is further used to identify malicious nodes in the network. The proposed technique rationalizes self-trusting, a property of trust based data forwarding in opportunistic networks which reduces and delays message transfers, to further improve delivery ratio and delay. Results of extensive simulation, using ONE simulator, substantiate the efficiency of the proposed Watchdog enabled PRoPHET over state-of-the-art competing schemes, in terms of detection ratios, attraction ratio, etc. while not compromising standard network performance. Finally, it is claimed that the proposed technique, tolerates a reasonable percentage of selfish and malicious nodes to achieve a desirable level of network performance, in a post disaster communication scenario.

Hm2Sc: Human Movement Model for Post Disaster Scenario in Smart City

In this work, we propose a human movement model that characterizes the movement pattern of different stakeholders in a post-disaster scenario in smart city. Knowledge about such mobility pattern assists in designing fast deployable smartphone based delay-tolerant network for disseminating post-disaster crucial situational information in a smart city. To the best our knowledge, this model is a major step ahead in the arena of mobility models for a post-disaster scenario in a smart city environment specifically considering the rescue operations. We provide extensive analytical foundations to strengthen the proposed mobility model. Simulation results justify that routing protocols when applied with proposed movement model, optimize network performances in terms of delivery ratio, overhead ratio and average residual energy at the cost of tolerable latency.

Secured Categorization and Group Encounter Based Dissemination of Post Disaster Situational Data Using Peer-to-Peer Delay Tolerant Network

Despite concerted efforts for relaying crucial situational information, disaster relief volunteers experience significant communication challenges owing to failures of critical infrastructure and longstanding power outages in disaster affected areas. Researchers have proposed the use of smart-phones, working in delay tolerant mode, for setting up a peer-to-peer network enabling post disaster communication. In such a network, volunteers, belonging to different rescue groups, relay situational messages containing needs and requirements of different categories to their respective relief camps. Delivery of such messages containing heterogeneous requirements to appropriate relief camps calls for on-the-fly categorization of messages according to their content. But, due to possible presence of malicious and unscrupulous entities in the network, content of sensitive situational messages cannot be made accessible even if that helps in categorization. To address this issue, we, in this paper, propose a secured message categorization technique that enables forwarder nodes to categorize messages without compromising on their confidentiality. Moreover, due to group dynamics and interaction pattern among groups, volunteers of a particular group encounter other volunteers of their own group (or groups offering allied services) more often than volunteers of other groups. Therefore, we also propose a forwarding scheme that routes messages, destined to a particular relief camp, through volunteers of that group or who encounter members of that group most frequently. This expedites the delivery of categorized messages to their appropriate destinations.