Distance-vector routing protocol

A distance-vector routing protocol in data networks determines the best route for data packets based on distance. Distance-vector routing protocols measure the distance by the number of routers a packet has to pass; one router counts as one hop. Some distance-vector protocols also take into account network latency and other factors that influence traffic on a given route. To determine the best route across a network, routers using a distance-vector protocol exchange information with one another, usually routing tables plus hop counts for destination networks and possibly other traffic information. Distance-vector routing protocols also require that a router inform its neighbours of network topology changes periodically. Distance-vector routing protocols use the Bellman–Ford algorithm to calculate the best route. Another way of calculating the best route across a network is based on link cost, and is implemented through link-state routing protocols. The term distance vector refers t

Routing for Wireless Sensor Networks: From Collection to Event-Triggered Applications

Daniel Camilo Rojas Quirós

Wireless Sensor Networks (WSNs) are collections of sensing devices using wireless communication to exchange data. In the past decades, steep advancements in the areas of microelectronics and communication systems have driven an explosive growth in the deployment of WSNs. Novel WSN applications have penetrated multiple areas, from monitoring the structural stability of historic buildings, to tracking animals in order to understand their behavior, or monitoring humans' health. The need to convey data from increasingly complex applications in a reliable and cost-effective manner translates into stringent performance requirements for the underlying WSNs. In the frame of this thesis, we have focused on developing routing protocols for multi-hop WSNs, that significantly improve their reliability, energy consumption and latency. Acknowledging the need for application-specific trade-offs, we have split our contribution into two parts. Part 1 focuses on collection protocols, catering to applications with high reliability and energy efficiency constraints, while the protocols developed in part 2 are subject to an additional bounded latency constraint. The two mechanisms introduced in the first part, WiseNE and Rep, enable the use of composite metrics, and thus significantly improve the link estimation accuracy and transmission reliability, at an energy expense far lower than the one achieved in previous proposals. The novel beaconing scheme WiseNE enables the energy-efficient addition of the RSSI (Received Signal Strength Indication) and LQI (Link Quality Indication) metrics to the link quality estimate by decoupling the sampling and exploration periods of each mote. This decoupling allows the use of the Trickle Algorithm, a key driver of protocols' energy efficiency, in conjunction with composite metrics. WiseNE has been applied to the Triangle Metric and validated in an online deployment. The section continues by introducing Rep, a novel sampling mechanism that leverages the packet repetitions already present in low-power preamble-sampling MAC protocols in order to improve the WSN energy consumption by one order of magnitude. WiseNE, Rep and the novel PRSSI (Penalized RSSI, a combination of PRR and RSSI) composite metric have been validated in a real smart city deployment. Part 2 introduces two mechanisms that were developed in the frame of the WiseSkin project (an initiative aimed at designing highly sensitive artificial skin for human limb prostheses), and are generally applicable to the domain of cyber-physical systems. It starts with Glossy-W, a protocol that leverages the superior energy-latency trade-off of flooding schemes based on concurrent transmissions. Glossy-W ensures the stringent synchronization requirements necessary for robust flooding, irrespective of the number of motes simultaneously reporting an event. Part 2 also introduces SCS (Synchronized Channel Sampling), a novel mechanism capable of reducing the power required for periodic polling, while maintaining the event detection reliability, and enhancing the network coexistence. The testbed experiments performed show that SCS manages to reduce the energy consumption of the state-of-the-art protocol Back-to-Back Robust Flooding by over one third, while maintaining an equivalent reliability, and remaining compatible with simultaneous event detection. SCS' benefits can be extended to the entire family of state-of-the-art protocols relying on concurrent transmissions.

EPFL2018

Modeling and predicting mobility in wireless ad hoc networks

Jérôme Härri

Wireless Ad Hoc Networks are a particular paradigm where wireless devices communicate in a decentralized fashion, without any centralized infrastructure or decision. In order to avoid a situation where nodes chaotically try to communicate, distributed and localized structures (graphs, trees, etc.) need to be built. Mobility brings challenging issues to the maintenance and to the optimality of such structures. In conventional approaches, structures are adapted to the current topology by each node periodically sending beacon messages, which is a significant waste of network resources. If each node can obtain some a priori knowledge of future topology configurations, it could decide to send maintenance messages only when a change in the topology effectively requires updating the structure. In this Doctoral Thesis, we investigate this approach and define the Kinetic Graphs, a novel paradigm regrouping mobility predictions for a kinetic mobility management, and localized and distributed graph protocols to insure a high scalability. The Kinetic Graph framework is able to naturally capture the dynamics of mobile structures, and is composed of four steps: (i) a representation of the trajectories, (ii) a common message format for the posting of those trajectories, (iii) a time varying weight for building the kinetic structures, (iv) an aperiodic neighborhood maintenance. By following this framework, we show that any structure-based ad-hoc protocol may benefit from the kinetic approach. A significant challenge of Kinetic Graphs comes from prediction errors. In order to analyze them, we illustrate the relationship between the prediction model and the mobility model. We decompose the prediction errors into three metrics: the adequacy between the prediction and the mobility models, the predicability of the mobility model, and the mobility model's realism. Following the framework, we define a kinetic model for the modeling of the trajectories and then analyze the extents of the effects of each error metric and develop solutions in order to reduce them. We finally adapt the Multipoint Relaying (MPR) protocol, used by the Optimized Link State Routing protocol (OLSR), and show the significant improvements that may be obtained by using the Kinetic Graph Framework, even on the very challenging vehicular networks.

EPFL2007

Dynamic Routing for Flying Ad Hoc Networks

Dario Floreano, Grégoire Hilaire Marie Heitz, Karol Jacek Kruzelecki, Bixio Rimoldi, Stefano Rosati

This paper reports experimental results on self-organizing wireless networks carried by small flying robots. Flying ad hoc networks (FANETs) composed of small unmanned aerial vehicles (UAVs) are flexible, inexpensive and fast to deploy. This makes them a very attractive technology for many civilian and military applications. Due to the high mobility of the nodes, maintaining a communication link between the UAVs is a challenging task. The topology of these networks is more dynamic than that of typical mobile ad hoc networks (MANETs) and of typical vehicle ad hoc networks (VANETs). As a consequence, the existing routing protocols designed for MANETs partly fail in tracking network topology changes. In this work, we compare two different routing algorithms for ad hoc networks: optimized link-state routing (OLSR), and predictive-OLSR (P-OLSR). The latter is an OLSR extension that we designed for FANETs; it takes advantage of the GPS information available on board. To the best of our knowledge, P-OLSR is currently the only FANET-specific routing technique that has an available Linux implementation. We present results obtained by both Media Access Control (MAC) layer emulations and real-world experiments. In the experiments, we used a testbed composed of two autonomous fixed-wing UAVs and a node on the ground. Our experiments evaluate the link performance and the communication range, as well as the routing performance. Our emulation and experimental results show that P-OLSR significantly outperforms OLSR in routing in the presence of frequent network topology changes.