Berta Carballido Villaverde

InRout - A QoS aware route selection algorithm for industrial wireless sensor networks

Wireless sensor networks are a key enabling technology for industrial monitoring applications where the use of wireless infrastructure allows high adaptivity and low cost in terms of installation and retrofitting. To facilitate the move from the current wired designs to wireless designs, concerns regarding reliability must be satisfied. Current standardization efforts for industrial wireless systems lack specification on efficient routing protocols that mitigate reliability concerns. Consequently, this work presents the InRout route selection algorithm, where local information is shared among neighbouring nodes to enable efficient, distributed route selection while satisfying industrial application requirements and considering sensor node resource limitations. Route selection is described as a multi-armed bandit task and uses Q-learning techniques to obtain the best available solution with low overhead. A performance comparison with existing approaches demonstrates the benefits of the InRout algorithm, which satisfies typical quality of service requirements for industrial monitoring applications while considering sensor node resources. Simulation results show that InRout can provide gains ranging from 4% to 60% in the number of successfully delivered packets when compared to current approaches with much lower control overhead.

Service Discovery Protocols for Constrained Machine-to-Machine Communications

An emerging trend in many applications is to use resource-constrained wireless devices for machine-to-machine (M2M) communications. The observed proliferation of wireless embedded systems is expected to have a significant impact on future M2M applications if the services provided can be automatically discovered and accessed at runtime. In order to realize the decoupling of M2M applications and services, energy efficient service discovery mechanisms must be designed so as to minimize human intervention during configuration and management phases. However, many traditional service discovery protocols cannot be applied to wireless constrained devices because they introduce too much overhead, fail in a duty-cycled environment or require significant memory resources. To address this, either new protocols are being proposed or existing ones are adapted to meet the requirements of constrained networks. In this article, we provide a comprehensive overview of service discovery protocols that have been recently proposed for constrained M2M communications by the Internet Engineering Task Force (IETF). Advantages, disadvantages, performance and challenges of the existing solutions for different M2M scenarios are also analyzed.

Constrained Application Protocol for Low Power Embedded Networks: A Survey

IPv6 will make it possible to provide Internet connectivity to any object embedding a communication device. In the same line, Web technologies will make managing, communicating and visualizing any information provided by these devices attractive to the end users and application developers. Most of the new devices connected to this Web of Things (WoT) will be embedded and wirelessly connected. However, current Web technologies have been developed with powerful devices in mind not being suited for this kind of constrained environment. In order to make the WoT a reality for low power embedded networks, specialised protocols that consider the energy, memory and processing constraints of wireless embedded devices must be designed. The IETF recently created the CoRE group whose first goal has been developing a Restful application layer protocol for communications within embedded wireless networks referred to as Constrained Application Protocol (CoAP). The year 2011 has seen a big push in the research community towards evaluating the performance and features of CoAP protocol, indicating a growing interest in the community towards Restful interactions in low power wireless embedded networks. This paper analyses those recent advances to provide a clear picture on what has been achieved so far in the evaluation and development of the Constrained Application Protocol.

Experimental Evaluation of Beacon Scheduling Mechanisms for Multihop IEEE 802.15.4 Wireless Sensor Networks

Recently, several scheduling techniques to enable multihop communications in the beacon enabled mode of the IEEE 802.15.4 standard have been proposed. Using the beacon enabled mode allows node synchronization and hence energy savings which is an important concern in wireless sensor networks (WSNs). However, and to the best of our knowledge, current available scheduling techniques have not been formally compared. This makes it difficult to decide which technique gives a better performance with regard to different WSN scenarios or applications. In this paper, we compare the two most popular methods for beacon enabled multihop IEEE 802.15.4 WSNs for different scenarios and performance parameters. Based on our findings, we propose recommendations for the use of each scheduling technique.

Multi-objective Cross-Layer Algorithm for Routing over Wireless Sensor Networks

With Wireless Sensor Networks popularity growth, numerous cross-layer routing protocols have been proposed. These proposals are mainly designed to address the limitations in energy resources of the sensor nodes. However, advances in technology have led to a wide variety of possible applications with many different requirements. The routing protocol should not only take into account the energy resources but it also should be able to adapt to different application requirements making different routing decisions. Here we present a flexible cross-layer algorithm based on a cost function to provide multi-objective adaptability to existing routing protocols that aims to balance the requirements of multiple applications and the resource constrained sensor network nodes. Computer simulations and real hardware experiments demonstrate that the cross layer algorithm applied over a collection protocol improves the performance for different application requirements and shows that energy resources are conserved through dynamic parameter tuning.

D-SeDGAM: A Dynamic Service Differentiation Based GTS Allocation Mechanism for IEEE 802.15.4 WSN

The plethora of applications for Wireless Sensor Networks (WSN) has experienced significant growth in recent years. Every application has a different set of requirements and it is highly desirable for all of them to share the available resources in an optimized way. The IEEE 802.15.4 standard for WSN includes guaranteed time slots (GTS) to schedule QoS demanding applications. However, the standard does not provide any type of QoS GTS scheduling mechanism and the authors are unaware of any other work that provides for service differentiation based GTS scheduling. We propose D-SeDGAM, a novel dynamic service based differentiation GTS allocation mechanism to provide QoS and service based differentiation for WSN applications. Our solution takes into account static and transient aspects of QoS provisioning in WSN to construct a dynamic scheduling method. This work demonstrates that D-SeDGAM provides significantly better performance in terms of QoS than the standard allocation method by simultaneously satisfying QoS and service differentiation demands.

Guaranteeing Reliable Communications in Mesh Beacon-Enabled IEEE802.15.4 WSN for Industrial Monitoring Applications

Wireless Sensor Networks (WSN) are a very promising solution for industrial monitoring applications in terms of safety, costs, efficiency and productivity. However, in order to move from the adopted manual/wired designs to wireless designs, certain guarantees must be assured, especially in terms of reliability, bandwidth and message transmission delays. Although quality of service (QoS) requirements can be satisfied in star based topologies using the Guaranteed Time Slots (GTS) feature of the IEEE802.15.4 standard, GTS communications in multihop scenarios are currently limited by IEEE802.15.4 beacon scheduling designs and peer-to-peer GTS allocation methods. This restricts applications to run over sensors that are within radio range of the network coordinator. In this work, we propose a distributed IEEE802.15.4 MAC modification to improve GTS usability and scalability in mesh networks. Also, we propose a reactive multihop GTS allocation technique based on our MAC modification to ensure reliable and latency aware end-to-end communications. Results show that our techniques improve greatly the reliability of multihop GTS communications.

Commissioning of low power embedded devices with IPv6/CoAP

The commissioning of sensors and actuators within a building is often carried out by an operator who manually gathers and later inserts configuration data into the building management system. Data sets collected can easily reach hundreds which makes this manual process a slow complex operation which in turn is prone to errors. In this paper, we present a client-server architecture for a simple web based commissioning application, based on the Constrained Application Protocol (CoAP), that allows an operator to easily discover and browse through newly installed devices in order to perform commissioning configurations onsite.