Pieter De Mil

Throughput and Delay Analysis of Unslotted IEEE 802.15.4

The IEEE 802.15.4 standard is designed as a low power and low data rate protocol offering high reliability. It defines a beaconed and unbeaconed version. In this work, we analyze the maximum throughput and minimum delay of the unbeaconed or unslotted version of the protocol. First, the most important features are described. Then the exact formula for the throughput and delay of a direct transmission between one sender and one receiver is given. This is done for the different frequency ranges and address structures used in IEEE 802.15.4. The analysis is limited to the unslotted version as this one experiences the lowest overhead. It is shown that the maximum throughput depends on the packet size. In the 2.4 GHz band, a bandwidth efficiency of 64.9% is reached when the maximum packet size is used. Further we describe the influence of the back off interval. A significant gain is found when the backs off parameters are altered. We have measured the throughput experimentally in order to compare the theoretical analysis with real-life examples.

Maximum throughput and minimum delay in IEEE 802.15.4

This paper investigates the maximum throughput and minimum delay of the new IEEE 802.15.4-standard. This standard was designed as a highly reliable and low-power protocol working at a low data rate and offers a beaconed and unbeaconed version. We will give the exact formulae for a transmission between one sender and one receiver for the unbeaconed version as this one has the least overhead. Further, the influence of the different address schemes, i.e. no addresses or the use of long and short addresses, is investigated. It is shown that the maximum throughput is not higher than 163 kbps when no addresses are used and that the maximum throughput drops when the other address schemes are used. Finally, we will measure the throughput experimentally in order to validate our theoretical analysis.

Design and implementation of a generic energy-harvesting framework applied to the evaluation of a large-scale electronic shelf-labeling wireless sensor network

Most wireless sensor networks (WSNs) consist of battery-powered nodes and are limited to hundreds of nodes. Battery replacement is a very costly operation and a key factor in limiting successful large-scale deployments. The recent advances in both energy harvesters and low-power communication systems hold promise for deploying large-scale wireless green-powered sensor networks (WGSNs). This will enable new applications and will eliminate environmentally unfriendly battery disposal. This paper explores the use of energy harvesters to scavenge power for nodes in a WSN. The design and implementation of a generic energy-harvesting framework, suited for a WSN simulator as well as a real-life testbed, are proposed. These frameworks are used to evaluate whether a carrier sense multiple access with collision avoidance scheme is sufficiently reliable for use in emerging large-scale energy harvesting electronic shelf label (EHESL) systems (i.e., 12000 labels in a star topology). Both the simulator and testbed experiments yielded an average success rate up to 92%, with an arrival rate of 40 transceive cycles per second. We have demonstrated that our generic energy-harvesting framework is useful for WGSN research because the simulator allowed us to verify the achieved results on the real-life testbed and vice versa.

Parking sensor network: Economic feasibility study of parking sensors in a city environment is well

Wireless sensor networks (WSNs) have a variety of purposes. They are mainly used for monitoring environmental factors, like CO2 concentrations, temperature and humidity. Other applications of sensor networks focus on detecting traffic parameters, e.g. passenger flows, damaged roads and traffic lights. This paper extends the current research with an economic feasibility of a real case, deploying a wireless parking sensor network in a city environment. After modeling the service adoption, the costs and revenues of the project are estimated. The static Net Present Value (NPV) case is already highly profitable. However, like most network projects, WSNs offer many flexibility options. A business case is extended with a Real Option Analysis (ROA), in order to quantify the value of the learning possibilities. We show that the built-in flexibility in the original project raises the attractiveness of the project.

Interconnecting Wireless Sensor and Wireless Mesh Networks: Challenges and Strategies

Wireless sensor networks consist of several hundredths of simple sensing devices, equipped with a radio. They are typically used for monitoring and automation purposes of large areas. Due to their simplicity, these networks quickly run out of energy, and often have problems regarding scalability and available bandwidth. To solve these issues, current research is mostly limited to the addition of extra sinks to the network, or the use of gateways to request sensor data over the Internet. In this paper, we explore how wireless sensor networks can be combined with wireless mesh networks to obtain a more optimized solution. The mesh network can be used to connect separate sensor networks, to connect sensor nodes with a monitoring platform, or as a scalable backbone for sensor to sensor communication. Additionally, we give an overview of the advantages and disadvantages of existing interconnection techniques between wireless and mesh networks, and propose several new interconnection strategies. Finally, we identify remaining challenges, upon which future research can be based.

PluralisMAC: a generic multi-MAC framework for heterogeneous, multiservice wireless networks, applied to smart containers

Developing energy-efficient MAC protocols for lightweight wireless systems has been a challenging task for decades because of the specific requirements of various applications and the varying environments in which wireless systems are deployed. Many MAC protocols for wireless networks have been proposed, often custom-made for a specific application. It is clear that one MAC does not fit all the requirements. So, how should a MAC layer deal with an application that has several modes (each with different requirements) or with the deployment of another application during the lifetime of the system? Especially in a mobile wireless system, like Smart Monitoring of Containers, we cannot know in advance the application state (empty container versus stuffed container). Dynamic switching between different energy-efficient MAC strategies is needed. Our architecture, called PluralisMAC, contains a generic multi-MAC framework and a generic neighbour monitoring and filtering framework. To validate the real-world feasibility of our architecture, we have implemented it in TinyOS and have done experiments on the TMote Sky nodes in the w-iLab.t testbed. Experimental results show that dynamic switching between MAC strategies is possible with minimal receive chain overhead, while meeting the various application requirements (reliability and low-energy consumption).

Definition and Evaluation of Local Path Recovery Mechanisms in Wireless Sensor and Actuator Networks

In Wireless Sensor and Actuator Networks nodes can fail and the link quality can fluctuate rapidly over time. With the start of the pervasive revolution, issues like scalability and mobility must be tackled in these low-power and lossy networks. We propose and evaluate two mechanisms,Path Resumption and Cost Based Multipath Routing, which can help existing or new local path recovery techniques to achieve a higher success rate. With Path Resumption we turn the network into several virtual mountain landscapes.This will help the search for new paths if necessary. Cost Based Multipath Routing enables the nodes to balance the load over a configured number of paths. The main objective is keeping suboptimal paths alive while keeping the maintenance overhead low. This way local recovery will achieve a higher success rate. The protocols are implemented in and simulated with ns-2 and evaluated by using WiNVis, anew wireless network visualisator. We have defined a new set of failure and mobility scenarios and we have compared the performance of both the protocols. Path Resumption has a lower complexity and is less suitable for mobile scenarios whereas Cost Based Multipath Routing offers more adjustable parameters and a better mobility support.