Survey on wireless technology trade-offs for the industrial internet of things

Aside from vast deployment cost reduction, Industrial Wireless Sensor and Actuator Networks (IWSAN) introduce a new level of industrial connectivity. Wireless connection of sensors and actuators in industrial environments not only enables wireless monitoring and actuation, it also enables coordination of production stages, connecting mobile robots and autonomous transport vehicles, as well as localization and tracking of assets. All these opportunities already inspired the development of many wireless technologies in an effort to fully enable Industry 4.0. However, different technologies significantly differ in performance and capabilities, none being capable of supporting all industrial use cases. When designing a network solution, one must be aware of the capabilities and the trade-offs that prospective technologies have. This paper evaluates the technologies potentially suitable for IWSAN solutions covering an entire industrial site with limited infrastructure cost and discusses their trade-offs in an effort to provide information for choosing the most suitable technology for the use case of interest. The comparative discussion presented in this paper aims to enable engineers to choose the most suitable wireless technology for their specific IWSAN deployment

Contributions to the routing of traffic flows in multi-hop IEEE 802.11 wireless networks

The IEEE 802.11 standard was not initially designed to provide multi-hop capabilities. Therefore, providing a proper traffic performance in Multi-Hop IEEE 802.11 Wireless Networks (MIWNs) becomes a significant challenge. The approach followed in this thesis has been focused on the routing layer in order to obtain applicable solutions not dependent on a specific hardware or driver. Nevertheless, as is the case of most of the research on this field, a cross-layer design has been adopted. Therefore, one of the first tasks of this work was devoted to the study of the phenomena which affect the performance of the flows in MIWNs. Different estimation methodologies and models are presented and analyzed. The first main contribution of this thesis is related to route creation procedures. First, FB-AODV is introduced, which creates routes and forwards packets according to the flows on the contrary to basic AODV which is destination-based. This enhancement permits to balance the load through the network and gives a finer granularity in the control and monitoring of the flows. Results showed that it clearly benefits the performance of the flows. Secondly, a novel routing metric called Weighted Contention and Interference routing Metric (WCIM) is presented. In all analyzed scenarios, WCIM outperformed the other analyzed state-of-the-art routing metrics due to a proper leveraging of the number of hops, the link quality and the suffered contention and interference. The second main contribution of this thesis is focused on route maintenance. Generally, route recovery procedures are devoted to the detection of link breaks due to mobility or fading. However, other phenomena like the arrival of new flows can degrade the performance of active flows. DEMON, which is designed as an enhancement of FB-AODV, allows the preemptive recovery of degraded routes by passively monitoring the performance of active flows. Results showed that DEMON obtains similar or better results than other published solutions in mobile scenarios, while it clearly outperforms the performance of default AODV under congestion Finally, the last chapter of this thesis deals with channel assignment in multi-radio solutions. The main challenge of this research area relies on the circular relationship between channel assignment and routing; channel assignment determines the routes that can be created, while the created routes decide the real channel diversity of the network and the level of interference between the links. Therefore, proposals which join routing and channel assignment are generally complex, centralized and based on traffic patterns, limiting their practical implementation. On the contrary, the mechanisms presented in this thesis are distributed and readily applicable. First, the Interference-based Dynamic Channel Assignment (IDCA) algorithm is introduced. IDCA is a distributed and dynamic channel assignment based on the interference caused by active flows which uses a common channel in order to assure connectivity. In general, IDCA leads to an interesting trade-off between connectivity preservation and channel diversity. Secondly, MR-DEMON is introduced as way of joining channel assignment and route maintenance. As DEMON, MR-DEMON monitors the performance of the active flows traversing the links, but, instead of alerting the source when noticing degradation, it permits reallocating the flows to less interfered channels. Joining route recovery instead of route creation simplifies its application, since traffic patterns are not needed and channel reassignments can be locally decided. The evaluation of MR-DEMON proved that it clearly benefits the performance of IDCA. Also, it improves DEMON functionality by decreasing the number of route recoveries from the source, leading to a lower overhead.El estándar IEEE 802.11 no fue diseñado inicialmente para soportar capacidades multi-salto. Debido a ello, proveer unas prestaciones adecuadas a los flujos de tráfico que atraviesan redes inalámbricas multi-salto IEEE 802.11 supone un reto significativo. La investigación desarrollada en esta tesis se ha centrado en la capa de encaminamiento con el objetivo de obtener soluciones aplicables y no dependientes de un hardware específico. Sin embargo, debido al gran impacto de fenómenos y parámetros relacionados con las capas físicas y de acceso al medio sobre las prestaciones de los tráficos de datos, se han adoptado soluciones de tipo cross-layer. Es por ello que las primeras tareas de la investigación, presentadas en los capítulos iniciales, se dedicaron al estudio y caracterización de estos fenómenos. La primera contribución principal de esta tesis se centra en mecanismos relacionados con la creación de las rutas. Primero, se introduce una mejora del protocolo AODV, que permite crear rutas y encaminar paquetes en base a los flujos de datos, en lugar de en base a los destinos como se da en el caso básico. Esto permite balacear la carga de la red y otorga un mayor control sobre los flujos activos y sus prestaciones, mejorando el rendimiento general de la red. Seguidamente, se presenta una métrica de encaminamiento sensible a la interferencia de la red y la calidad de los enlaces. Los resultados analizados, basados en la simulación de diferentes escenarios, demuestran que mejora significativamente las prestaciones de otras métricas del estado del arte. La segunda contribución está relacionada con el mantenimiento de las rutas activas. Generalmente, los mecanismos de mantenimiento se centran principalmente en la detección de enlaces rotos debido a la movilidad de los nodos o a la propagación inalámbrica. Sin embargo, otros fenómenos como la interferencia y congestión provocada por la llegada de nuevos flujos pueden degradar de forma significativa las prestaciones de los tráficos activos. En base a ello, se diseña un mecanismo de mantenimiento preventivo de rutas, que monitoriza las prestaciones de los flujos activos y permite su reencaminamiento en caso de detectar rutas degradadas. La evaluación de esta solución muestra una mejora significativa sobre el mantenimiento de rutas básico en escenarios congestionados, mientras que en escenarios con nodos móviles obtiene resultados similares o puntualmente mejores que otros mecanismos preventivos diseñados específicamente para casos con movilidad. Finalmente, el último capítulo de la tesis se centra en la asignación de canales en entornos multi-canal y multi-radio con el objetivo de minimizar la interferencia entre flujos activos. El reto principal en este campo es la dependencia circular que se da entre la asignación de canales y la creación de rutas: la asignación de canales determina los enlaces existentes la red y por ello las rutas que se podrán crear, pero son finalmente las rutas y los tráficos activos quienes determinan el nivel real de interferencia que se dará en la red. Es por ello que las soluciones que proponen unificar la asignación de canales y el encaminamiento de tráficos son generalmente complejas, centralizadas y basadas en patrones de tráfico, lo que limita su implementación en entornos reales. En cambio, en nuestro caso adoptamos una solución distribuida y con mayor aplicabilidad. Primero, se define un algoritmo de selección de canales dinámico basado en la interferencia de los flujos activos, que utiliza un canal común en todos los nodos para asegurar la conectividad de la red. A continuación, se introduce un mecanismo que unifica la asignación de canales con el mantenimiento preventivo de las rutas, permitiendo reasignar flujos degradados a otros canales disponibles en lugar de reencaminarlos completamente. Ambas soluciones demuestran ser beneficiosas en este tipo de entornos.Postprint (published version

Algorithms and protocols for multi-channel wireless networks

A wireless channel is shared by all devices, in the vicinity, that are tuned to the channel, and at any given time, only one of the devices can transmit information. One way to overcome this limitation, in throughput capacity, is to use multiple orthogonal channels for different devices, that want to transmit information at the same time. In this work, we consider the use of multiple orthogonal channels in wireless data networks. We explore algorithms and protocols for such multi-channel wireless networks under two broad categories of network-wide and link-level challenges. Towards handling the network-wide issues, we consider the channel assignment and routing issues in multi-channel wireless networks. We study both single radio and multi-radio multi-channel networks. For single radio multi-channel networks, we propose a new granularity for channel assignment, that we refer to as component level channel assignment. The strategy is relatively simple, and is characterized by several impressive practical advantages. For multi-radio multi-channel networks, we propose a joint routing and channel assignment protocol, known as Lattice Routing. The protocol manages channels of the radios, for the different nodes in the network, using information about current channel conditions, and adapts itself to varying traffic patterns, in order to efficiently use the multiple channels. Through ns2 based simulations, we show how both the protocols outperform other existing protocols for multi-channel networks under different network environments. Towards handling the link-level challenges, we identify the practical challenges in achieving a high data-rate wireless link across two devices using multiple off-the-shelf wireless radios. Given that the IEEE 802.11 a/g standards define 3 orthogonal wi-fi channels in the 2.4GHz band and 12 orthogonal wi-fi channels in the 5GHz band, we answer the following question: ``can a pair of devices each equipped with 15 wi-fi radios use all the available orthogonal channels to achieve a high data-rate link operating at 600Mbps?' Surprisingly, we find through experimental evaluation that the actual observed performance when using all fifteen orthogonal channels between two devices is a mere 91Mbps. We identify the reasons behind the low performance and present Glia, a software only solution that effectively exercises all available radios. We prototype Glia and show using experimental evaluations that Glia helps achieve close to 600Mbps data-rate when using all possible wi-fi channels.PhDCommittee Chair: Sivakumar, Raghupathy; Committee Member: Blough, Doug; Committee Member: Coyle, Edward; Committee Member: Eidenbenz, Stephan; Committee Member: Fekri, Faramar

An efficient multichannel wireless sensor networks MAC protocol based on IEEE 802.11 distributed co-ordinated function.

This research aimed to create new knowledge and pioneer a path in the area relating to future trends in the WSN, by resolving some of the issues at the MAC layer in Wireless Sensor Networks. This work introduced a Multi-channel Distributed Coordinated Function (MC-DCF) which takes advantage of multi-channel assignment. The backoff algorithm of the IEEE 802.11 distributed coordination function (DCF) was modified to invoke channel switching, based on threshold criteria in order to improve the overall throughput for wireless sensor networks. This work commenced by surveying different protocols: contention-based MAC protocols, transport layer protocols, cross-layered design and multichannel multi-radio assignments. A number of existing protocols were analysed, each attempting to resolve one or more problems faced by the current layers. The 802.15.4 performed very poorly at high data rate and at long range. Therefore 802.15.4 is not suitable for sensor multimedia or surveillance system with streaming data for future multichannel multi-radio systems. A survey on 802.11 DCF - which was designed mainly for wireless networks –supports and confirm that it has a power saving mechanism which is used to synchronise nodes. However it uses a random back-off mechanism that cannot provide deterministic upper bounds on channel access delay and as such cannot support real-time traffic. The weaknesses identified by surveying this protocol form the backbone of this thesis The overall aim for this thesis was to introduce multichannel with single radio as a new paradigm for IEEE 802.11 Distributed Coordinated Function (DCF) in wireless sensor networks (WSNs) that is used in a wide range of applications, from military application, environmental monitoring, medical care, smart buildings and other industry and to extend WSNs with multimedia capability which sense for instance sounds or motion, video sensor which capture video events of interest. Traditionally WSNs do not need high data rate and throughput, since events are normally captured periodically. With the paradigm shift in technology, multimedia streaming has become more demanding than data sensing applications as such the need for high data rate protocol for WSN which is an emerging technology in this area. The IEEE 802.11 can support data rates up to 54Mbps and 802.11 DCF was designed specifically for use in wireless networks. This thesis focused on designing an algorithm that applied multichannel to IEEE 802.11 DCF back-off algorithm to reduce the waiting time of a node and increase throughput when attempting to access the medium. Data collection in WSN tends to suffer from heavy congestion especially nodes nearer to the sink node. Therefore, this thesis proposes a contention based MAC protocol to address this problem from the inspiration of the 802.11 DCF backoff algorithm resulting from a comparison of IEEE 802.11 and IEEE 802.15.4 for Future Green Multichannel Multi-radio Wireless Sensor Networks

Multi-Channel Multi-Radio Using 802.11 Based Media Access for Sink Nodes in Wireless Sensor Networks

The next generation surveillance and multimedia systems will become increasingly deployed as wireless sensor networks in order to monitor parks, public places and for business usage. The convergence of data and telecommunication over IP-based networks has paved the way for wireless networks. Functions are becoming more intertwined by the compelling force of innovation and technology. For example, many closed-circuit TV premises surveillance systems now rely on transmitting their images and data over IP networks instead of standalone video circuits. These systems will increase their reliability in the future on wireless networks and on IEEE 802.11 networks. However, due to limited non-overlapping channels, delay, and congestion there will be problems at sink nodes. In this paper we provide necessary conditions to verify the feasibility of round robin technique in these networks at the sink nodes by using a technique to regulate multi-radio multichannel assignment. We demonstrate through simulations that dynamic channel assignment scheme using multi-radio, and multichannel configuration at a single sink node can perform close to optimal on the average while multiple sink node assignment also performs well. The methods proposed in this paper can be a valuable tool for network designers in planning network deployment and for optimizing different performance objectives