Antoine B. Bagula

Energy Constrained Multipath Routing in Wireless Sensor Networks

This paper addresses the issue of Quality of Service (QoS) Routing to improve energy consumption in wireless sensor networks (WSNs). Building upon a previously proposed QoS provisioning benchmark model, we formulate the problem of routing sensed information in a WSN network as a path-based energy minimization problem subject to QoS routing constraints expressed in terms of reliability, delay and geo-spatial energy consumption. Using probabilistic approximations, we transform the path-based model into a link-based model and apply methods borrowed from the zero-one optimization framework to solve this problem. By comparing the performance achieved by its solution to the benchmark model, simulation results reveal that our model outperforms the benchmark model in terms of energy consumption and quality of paths used to route the sensed information.

Successful deployment of a Wireless Sensor Network for precision agriculture in Malawi

This paper demonstrates how an Irrigation Management System (IMS) can practically be implemented by successfully deploying a Wireless Sensor Network (WSN). Specifically, the paper describes an IMS which was set up in Manja Township, City of Blantyre based on an advanced irrigation scheduling technique. Since the system had to be self-sustained in terms of power, which is a challenge for deployment in rural areas of developing countries like Malawi where grid power supply is scarce, we used solar Photovoltaic (PV) and rechargeable batteries to power all electrical devices in this system. The system incorporated a remote monitoring mechanism through a General Packet Radio Service (GPRS) modem to report soil temperature, soil moisture, WSN link performance and PV power levels. Irrigation valves were activated to water the field. Our preliminary results have revealed engineering weakness of deploying such a system. Nevertheless, the paper shows that it is possible to develop a robust, fully-automated, solar powered, and low cost IMS to suit the socio-economic conditions of small scale farmers in developing countries.

On the Design of a Water Quality Wireless Sensor Network (WQWSN): An Application to Water Quality Monitoring in Malawi

More than one billion people lack access to safe drinking water in the world. Providing a way to measure automatically water quality will help tackle this problem. This paper presents the design of a water quality measuring system and proposes a prototype implementation of a water quality wireless sensor network (WQWSN) as a solution to this challenging problem. When applied to developing countries, the design and implementation of such a system must take into consideration the difficult environment in which it will operate. An application to water quality measurement in Malawi reveals the relevance of using our novel solution to mitigate two challenging issues: energy consumption of the system and the inter-networking problem.

On the design of smart parking networks in the smart cities: an optimal sensor placement model

Smart parking is a typical IoT application that can benefit from advances in sensor, actuator and RFID technologies to provide many services to its users and parking owners of a smart city. This paper considers a smart parking infrastructure where sensors are laid down on the parking spots to detect car presence and RFID readers are embedded into parking gates to identify cars and help in the billing of the smart parking. Both types of devices are endowed with wired and wireless communication capabilities for reporting to a gateway where the situation recognition is performed. The sensor devices are tasked to play one of the three roles: (1) slave sensor nodes located on the parking spot to detect car presence/absence; (2) master nodes located at one of the edges of a parking lot to detect presence and collect the sensor readings from the slave nodes; and (3) repeater sensor nodes, also called “anchor” nodes, located strategically at specific locations in the parking lot to increase the coverage and connectivity of the wireless sensor network. While slave and master nodes are placed based on geographic constraints, the optimal placement of the relay/anchor sensor nodes in smart parking is an important parameter upon which the cost and efficiency of the parking system depends. We formulate the optimal placement of sensors in smart parking as an integer linear programming multi-objective problem optimizing the sensor network engineering efficiency in terms of coverage and lifetime maximization, as well as its economic gain in terms of the number of sensors deployed for a specific coverage and lifetime. We propose an exact solution to the node placement problem using single-step and two-step solutions implemented in the Mosel language based on the Xpress-MPsuite of libraries. Experimental results reveal the relative efficiency of the single-step compared to the two-step model on different performance parameters. These results are consolidated by simulation results, which reveal that our solution outperforms a random placement in terms of both energy consumption, delay and throughput achieved by a smart parking network.

Modelling and implementation of QoS in wireless sensor networks: a multiconstrained traffic engineering model

This paper revisits the problem of Quality of Service (QoS) provisioning to assess the relevance of using multipath routing to improve the reliability and packet delivery in wireless sensor networks while maintaining lower power consumption levels. Building upon a previous benchmark, we propose a traffic engineering model that relies on delay, reliability, and energy-constrained paths to achieve faster, reliable, and energy-efficient transmission of the information routed by a wireless sensor network. As a step forward into the implementation of the proposed QoS model, we describe the initial steps of its packet forwarding protocol and highlight the tradeoff between the complexity of the model and the ease of implementation. Using simulation, we demonstrate the relative efficiency of our proposed model compared to single path routing, disjoint path routing, and the previously proposed benchmarks. The results reveal that by achieving a good tradeoff between delay minimization, reliability maximization, and path set selection, our model outperforms the other models in terms of energy consumption and quality of paths used to route the information.

Long distance wireless sensor networks: simulation vs reality

Wireless sensor networks allow unprecedented abilities to observe and understand large-scale, real-world phenomena at a fine spatial-temporal resolution. Their application in Developing Countries is even more interesting: they can help solve problems that affect communities. One of the limitations of current wireless sensors is the communication range, with most devices having 100 meters as maximum limit. In contrast, many applications require long-range wireless sensor network where nodes are separated by large distances, giving the advantage of being able to monitor a vast geographic area. In this paper we will present the results of simulations and of experiments carried out using off-the-shelf equipment over distances ranging from 300m to 12km. The results show that long distance wireless sensor networks (LDWSN) are possible and that the quality of these links is high.

Design of a flexible and robust gateway to collect sensor data in intermittent power environments

The development of a Wireless Sensor Network (WSN) gateway is challenging for sites where limited infrastructures lead to frequent power shortages and network unreliability. In this paper, we present a low-power, low-cost 802.15.4 and 802.11 compatible solution which uses open source software to meet local conditions. Using the SunSPOT motes on a system which is mostly platform independent, our system is based on the Fox embedded Linux board and equipped with a USB flash drive and a USB WiFi adapter. The system can be solar powered, and the results of a solar system design are presented. All the hardware components are available off-the-shelf and are easy to assemble. We conclude that our system is preferred for applications in remote areas, where a stable power supply and a reliable network infrastructure are lacking. Furthermore, it can be used to extend the range of WSNs by layering a network of long-range motes above islands of low-range motes.

Experimental evaluation of temporal and energy characteristics of an outdoor sensor network

This paper revisits the link quality issue in Wireless Sensor Networks (WSN) by studying the temporal and energy characteristics of a 2, 4Ghz sensor network in an outdoor environment. Using different values of output power and sampling period, we analyze battery behavior in motes placed at different distances and show that farther motes have a shorter battery life. Our experimental results suggest that when deployed in real world deployments, the sampling periods of sensor networks be adjusted according to distance to normalize battery lifetime and a more accurate energy-aware routing protocol be developed.

A Survey of TV White Space Measurements

Unused spectrum in the television band (so-called TV white space) has the potential to provide new spectrum for access to information and communication services in developing countries. This claim has been subject to a variety of measurement studies. The purpose of this paper is to survey these studies to better characterize the spectrum that is provided by TV white space. We discuss some of the challenges to such studies and characterize the available TV white space spectrum in terms of the total volume that is available.

Planning and deploying long distance wireless sensor networks: the integration of simulation and experimentation

Wireless sensor networks allow unprecedented abilities to observe and understand large-scale, real-world phenomena at a fine spatial-temporal resolution. Their application in Developing Countries is even more interesting: they can help solve problems that affect communities. One of the limitations of current wireless sensors is the communication range, with most devices having 100 meters as maximum range. In contrast, many applications require long-range wireless sensor network where nodes are separated by large distances, giving the advantage of being able to monitor a large geographic area. In this paper we will present the results of an integrated approach combining a planning step using simulations and an experimental step carried out using off-the-shelf equipment over distances ranging from 600m to 12km. The results reveal that the simulation results agree with experimentation and show that long distance wireless sensor networks (LDWSN) are possible and that the quality of these links is high. Finally, we discuss the relative efficiency of our solution in terms of range compared to other wireless sensor networks.