A critical aspect of wireless sensor networks is network lifetime. Power-constrained wireless sensor networks are usable as long as they can communicate sensed data to the base station. Multi-hop data gathering consumes increased energy, especially for data-intensive applications. In this paper we propose a UAV-enabled data gathering mechanism for wireless sensor networks which prolongs network lifetime compared to a traditional data gathering mechanism. Some of the aspects that we address are UAV path planning, scheduled and opportunistic data gathering, and integration of the data gathering with a node scheduling mechanism. Simulations using ns3 show that our algorithm is more efficient in terms of energy consumed and packet delivery ratio compared to traditional data gathering.

Routing in Delay-Tolerant Networks (DTNs) remains a challenging problem due to sporadic connectivity and high delays. To deal with this issue, researchers have investigated multi-copy schemes with predicting future contacts. However, most of the previous work has focused on the prediction of future contacts, without sufficiently considering contact times. This paper proposes McRTP, a multi- copy routing protocol with trajectory prediction for social DTNs. Based on estimating the probability distribution of future contact times, McRTP evaluates and selects multiple paths with the highest delivery probability for routing. Also, to control network traffic overhead, we develop a copy count assignment scheme limiting the number of message copies in networks. A simulation study shows that, with the estimation of both contact probability and contact times, and the path selection scheme, our McRTP outperforms traditional DTN multi-copy routing schemes, especially in sparse networks.

Inter-agency emergency response operations are sometimes hindered by a lack of common communication technology or by circumstances that render their networks unusable. We present a protocol architecture based on ubiquitous WiFi terminals (smartphones) that could be used for backup communications when everything else fails. If WLAN primary users (access points) are present, the channel selection mechanism selects alternate channels without the need of a common control channel. To deal with a sparse and disconnected topology, our mission-aware delay-tolerant routing algorithm uses short-term contact prediction and otherwise distributes packets to disconnected subnets without network-wide flooding.

Routing is one of the most challenging, open problems in disruption-tolerant networks (DTNs) because of the short-lived wireless connectivity environment. To deal with this issue, researchers have investigated routing based on the prediction of future contacts, taking advantage of nodes' mobility history. However, most of the previous work focused on the prediction of whether two nodes would have a contact, without considering the time of the contact. This paper proposes predict and relay (PER), an efficient routing algorithm for DTNs, where nodes determine the probability distribution of future contact times and choose a proper next-hop in order to improve the end-to-end delivery probability. The algorithm is based on two observations: one is that nodes usually move around a set of well-visited landmark points instead of moving randomly; the other is that node mobility behavior is semi-deterministic and could be predicted once there is sufficient mobility history information. Specifically, our approach employs a time-homogeneous semi-Markov process model that describes node mobility as transitions between landmarks. Then, we extend it to handle the scenario where we consider the transition time between two landmarks. A simulation study shows that this approach improves the delivery ratio and also reduces the delivery latency compared to traditional DTN routing schemes.

This paper presents a REST-compliant service oriented architecture of a web-based heterogeneous wireless sensor network monitoring system that has applicability in remote patient monitoring in healthcare. As smartphone and web-page technologies are ubiquitous nowadays, our architecture uses smartphone as a gateway between the data collected and the Internet. The system uses a heterogeneous WSN consisting of environmental sensors, medical sensors, and smartphone's internal sensors. To validate the system, a prototype experiment of the system is implemented using Android smartphone platform, Crossbow Micaz motes, and Alive Technology hart and activity monitor sensor.

In the United States, there has been a high incidence of hurricanes over the past decade. Before a hurricane makes landfall it is important, for safety, that people who live in potentially dangerous areas, such as along the coast, evacuate. Nursing homes have an even greater concern during an evacuation as the patients are primarily elderly or disabled, and require additional assistance. In this paper we investigate the characteristics and challenges associated with hurricane evacuation of health care centers, such as nursing homes. Then, we propose a patient centric hurricane evacuation management system that allow healthcare providers to continuously monitor and track patients. The hardware and software architecture, and the main operations are presented. The proposed system is able to operate in difficult conditions, such as lack of basic communication services such as cellular and Internet, temporary network partition, and scarce energy resources.

A key challenge of message forwarding in delay tolerant networks (DTNs) is to increase delivery rate and decrease delay and cost. When information for future connectivity is not available, opportunistic routing is preferred in DTNs in which messages are forwarded opportunistic (non-deterministically) to nodes with higher delivery probabilities. Many real objects have non-deterministic but cyclic motions; however, few prior research work has investigated a multi-copy opportunistic message forwarding algorithm for DTNs with cyclic mobility patterns. Cyclic MobiSpace is a generalization of DTNs with cyclic mobility patterns. In this paper, we propose an optimal opportunistic multi-copy message forwarding algorithm in Cyclic MobiSpace. Specifically, we model a Cyclic MobiSpace as a state-space graph, and apply the optimal stopping rule to derive a delivery metric for each message state using the state-space graph. We perform simulations to compare our protocol, called Multi-copy Forwarding in Cyclic MobiSpace (MFC), against existing forwarding protocols using UMassDieselNet trace. Simulation results show that MFC delivers up to 100% more messages than the compared forwarding protocols under the same delay and forwarding cost.

Routing is one of the most challenging open problems in disruption-tolerant networks (DTNs) because of the short-lived wireless connectivity environment. To deal with this issue, researchers have investigated routing based on the prediction of future contacts, taking advantage of nodes' mobility history. However, most of the previous work focused on the prediction of whether two nodes would have a contact, without considering the time of the contact. This paper proposes predict and relay (PER), an efficient routing algorithm for DTNs, where nodes determine the probability distribution of future contact times and choose a proper next hop in order to improve the end-to-end delivery probability. The algorithm is based on two observations: one is that nodes usually move around a set of well-visited landmark points instead of moving randomly; the other is that node mobility behavior is semi-deterministic and could be predicted once there is sufficient mobility history information. Specifically, our approach employs a time-homogeneous semi-markov process model that describes node mobility as transitions between landmarks. Landmark transition and sojourn time probability distributions are determined from nodes' mobility history. A simulation study shows that this approach improves the delivery ratio and also reduces the delivery latency compared to traditional DTN routing schemes.

Mobile Optical Free Space networks are an emerg- ing technology that will offer low-delay and high speed con- nectivity using air-borne and ground wireless laser terminals. The time-variable link capacity and dynamic topology make Quality of Service provisioning a difficult problem. We present an architecture for end-to-end statistical delay guarantees. We describe a delay model that uses the concept of virtual traffic to accommodate link capacity variations and transient outages. A mechanism for deploying dependable TCP services is imple- mented in this QoS-enabled network. The primary-backup TCP replication mechanism is supported by the routing infrastructure and allows transparent server replication. We illustrate perfor- mance improvements with simulation results.

This paper considers a heterogeneous wireless sensor network that consists of several resource-rich supernodes used for data relaying and a large number of energy constrained wireless sensor nodes. Sensor nodes are deployed randomly to monitor a number of targets. Since targets are redundantly covered by more sensors, we organize the sensors in set covers that are activated successively to conserve energy. In this paper we introduce the Heterogeneous Connected Set Covers (HCSC) problem that has the objective to find a maximum number of set covers such that each set cover monitors all targets and each active sensor is connected to at least one supernode. A sensor can participate in multiple set covers, but the total energy spent in all sets is constrained by the battery capacity. In this paper we show that HCSC is NP-complete and we propose two algorithms for solving this problem, an Integer Programming approach and a distributed and localized protocol. Simulation results are presented to evaluate these solutions.

Mobile optical free space networks are an emerging architecture that can provide high speed connectivity between a ground-based backbone network and mobile users in challenging environments. In such a network traffic could be relayed by airborne or ground routers using wireless optical links. The variable nature of the wireless optical channel complicates support for real-time distributed applications demanding bounds on communication delay. In this paper we present an architecture for provisioning end-to-end statistical delay guarantees in MOFS networks. We describe a delay model that uses a concept of virtual traffic to accommodate link capacity variation. The link delay estimation is integrated with a population-insensitive utilization based flow admission control technique and IP differentiated services. The models and architecture for QoS are presented and the system performance is analyzed

The paper presents an innovative hierarchical feedback adaptation method that efficiently controls the dynamic QoS behavior of real time distributed data flow applications, such as sensor based data streams or mission-critical command and control applications. We applied this method in the context of the Real Time Adaptive Resource Management system, a middleware integrated services, developed at the Honeywell Technology Center. We present the analytical model for Automatic Target Recognition pipeline application and the impact of hierarchical feedback adaptation on the application behavior and its QoS parameters.