On Mobility Management in Multi-Sink Sensor Networks for Geocasting of Queries

In order to efficiently deal with location dependent messages in multi-sink wireless sensor networks (WSNs), it is key that the network informs sinks what geographical area is covered by which sink. The sinks are then able to efficiently route messages which are only valid in particular regions of the deployment. In our previous work (see the 5th and 6th cited documents), we proposed a combined coverage area reporting and geographical routing protocol for location dependent messages, for example, queries that are injected by sinks. In this paper, we study the case where we have static sinks and mobile sensor nodes in the network. To provide up-to-date coverage areas to sinks, we focus on handling node mobility in the network. We discuss what is a better method for updating the routing structure (i.e., routing trees and coverage areas) to handle mobility efficiently: periodic global updates initiated from sinks or local updates triggered by mobile sensors. Simulation results show that local updating perform very well in terms of query delivery ratio. Local updating has a better scalability to increasing network size. It is also more energy efficient than ourpreviously proposed approach, where global updating in networks have medium mobility rate and speed

Data dissemination of emergency messages in mobile multi-sink wireless sensor networks

In wireless sensor networks (WSNs), data dissemination is generally performed from sensor nodes to a static sink. If the data under consideration is an emergency message such as a fire alarm, it must be transmitted as fast and reliably as possible towards the sink of WSN. In such mission critical applications, it may not be enough to have one static sink but there will be multiple and mobile sinks. Sinks can be associated to first responders such as firefighters, but also to unmanned aerial vehicles (UAVs). The existing approaches have a high communication cost and a high delivery latency, which makes them less suitable for emergency situations. As an alternative to existing protocols, we present Honeycomb Architecture and Hexagonal Tiling-Based Data Dissemination (HexDD) protocol for emergency message transmission in mobile multi-sink WSNs. Simulation results show that HexDD has a high data delivery ratio and a very low data delivery latency, which are major requirements for disaster management scenarios

Data dissemination of emergency messages in mobile multi-sink wireless sensor networks

In wireless sensor networks (WSNs), data dissemination is generally performed from sensor nodes to a static sink. If the data under consideration is an emergency message such as a fire alarm, it must be transmitted as fast and reliably as possible towards the sink of WSN. In such mission critical applications, it may not be enough to have one static sink but there will be multiple and mobile sinks. Sinks can be associated to first responders such as firefighters, but also to unmanned aerial vehicles (UAVs). The existing approaches have a high communication cost and a high delivery latency, which makes them less suitable for emergency situations. As an alternative to existing protocols, we present Honeycomb Architecture and Hexagonal Tiling-Based Data Dissemination (HexDD) protocol for emergency message transmission in mobile multi-sink WSNs. Simulation results show that HexDD has a high data delivery ratio and a very low data delivery latency, which are major requirements for disaster management scenarios

A Fault-Tolerant Data Dissemination Based on Honeycomb Architecture for Mobile Multi-Sink Wireless Sensor Networks

In mission critical applications of wireless sensor networks (WSNs), multiple sinks can be associated to first responders such as firefighters, but also to unmanned aerial vehicles (UAVs). In such scenarios, data dissemination of events towards mobile sinks should be performed reliably. In this paper we present Honeycomb Architecture which enables data dissemination considering dynamic conditions of multiple sinks and sources. Honeycomb Architecture exploits a virtual infrastructure called ‘highways’, which is an area where all event data are cached. The ‘highways’ act as rendezvous regions of the events and queries. Once a query is issued, it is sent to one of the ‘highways’ and searches relevant data stored in the ‘highway’. When the data is found, it is sent to the sink which has issued the query. Our data dissemination protocol is fault-tolerant, i.e., it can bypass holes in the network. We evaluate and compare the data delivery ratio and latency of our data dissemination protocol with previous approaches. We also analyze the hotspot regions in the network with different protocols. Simulation results show that our work significantly reduces overall energy consumption while maintaining comparably high data delivery ratio

A virtual infrastructure based on honeycomb tessellation for data dissemination in multi-sink mobile wireless sensor networks

A new category of intelligent sensor network applications emerges where motion is a fundamental characteristic of the system under consideration. In such applications, sensors are attached to vehicles, or people that move around large geographic areas. For instance, in mission critical applications of wireless sensor networks (WSNs), sinks can be associated to first responders. In such scenarios, reliable data dissemination of events is very important, as well as the efficiency in handling the mobility of both sinks and event sources. For this kind of applications, reliability means real-time data delivery with a high data delivery ratio. In this article, we propose a virtual infrastructure and a data dissemination protocol exploiting this infrastructure, which considers dynamic conditions of multiple sinks and sources. The architecture consists of `highways' in a honeycomb tessellation, which are the three main diagonals of the honeycomb where the data flow is directed and event data is cached. The highways act as rendezvous regions of the events and queries. Our protocol, namely hexagonal cell-based data dissemination (HexDD), is fault-tolerant, meaning it can bypass routing holes created by imperfect conditions of wireless communication in the network. We analytically evaluate the communication cost and hot region traffic cost of HexDD and compare it with other approaches. Additionally, with extensive simulations, we evaluate the performance of HexDD in terms of data delivery ratio, latency, and energy consumption. We also analyze the hot spot zones of HexDD and other virtual infrastructure based protocols. To overcome the hot region problem in HexDD, we propose to resize the hot regions and evaluate the performance of this method. Simulation results show that our study significantly reduces overall energy consumption while maintaining comparably high data delivery ratio and low latency

Ideas on Node Mobility Support in Schedule-based Medium Access

Typically, medium access control (MAC) protocols for wireless sensor networks implement synchronised periodic sleeping to conserve energy. We argue that (local) synchronisation between nodes is the main cause why MAC protocols do not efficiently support node mobility e.g. nodes waste valuable energy to resynchronise. In this paper, we present ideas on mobility support in schedule-based medium access control protocols for wireless sensor networks.The resulting MAC protocol is a hybrid protocol, which combines schedule-based access with contention-based access. The rationale is that the static part of the wireless sensor network can benefit from the high delivery ratio and support for high peak loads of schedule-based access, while mobile nodes can benefit from the natural self-organization of contention-based access. We try our protocol ideas by simulation and real-live experiments

Geo-casting of queries combined with coverage area reporting for wireless sensor networks

In order to efficiently deal with queries or other location dependent information, it is key that the wireless sensor network informs gateways what geographical area is serviced by which gateway. The gateways are then able to e.g. efficiently route queries which are only valid in particular regions of the deployment. The proposed algorithms combine coverage area reporting and geographical routing of queries which are injected by gateways. The combined solution is evaluated in terms of computational complexity and performance compared with existing geocasting protocols

Enabling Mobility in Heterogeneous Wireless Sensor Networks Cooperating with UAVs for Mission-Critical Management

Wireless sensor networks (WSNs) have the promise of revolutionizing the capture, processing, and communication of mission critical data for the use of first operational forces. Their low-cost, low-power, and size make it feasible to embed them into environment-monitoring tags in critical care regions, first responders uniform gear, and data collector sinks attached to unmanned aerial vehicles (UAVs). The ability to actively change the location of sensors can be used to mitigate some of the traditional problems associated with static sensor networks. On the other hand, sensor node mobility brings with it its own challenges. These include challenges associated with in-network aggregation of sensor data, routing, and activity monitoring of responders. Moreover, all different mobility patterns (e.g., sink mobility, sensor mobility, etc.) have their special properties, so that each mobile device class needs its own approach. In this article, we present a platform which benefits from both static and mobile sensors and addresses these challenges. The system integrates WSNs, UAVs, and actuators into a disaster response setting and provides facilities for event detection, autonomous network repair by UAVs, and quick response by integrated operational forces

Locality and Globality: Building a Comparative Analytical Framework in Migration and Urban Studies

One of the fundamental operations in sensor networks is convergecast which refers to the communication pattern in which data is collected from a set of sensor nodes and forwarded to a common end-point gateway, namely sink node, in the network. In case of multiple sinks within the network, the total load of the network has to be balanced among these sinks to minimize the problem of packet loss in the convergecast process in wireless sensor networks (WSNs) due to congestion and collisions near the sinks. In this paper, we present a novel cross-layered communication protocol for efficient data dissemination in multi-sink WSNs which is under consideration of SENSEI project. It basically combines network wide load balancing, clustering techniques and local routing optimizations with SENSEI architecture which make it efficient on both global and local level. The performance evaluation of the proposed technique shows how our routing protocol can balance the network load without additional control packets for routing tree maintenance