Challenges in the design and implementation of Wireless Sensor Networks: A holistic approach-development and planning tools, middleware, power efficiency, interoperability

Wireless Sensor Networks (WSNs) constitute a networking area with promising impact in the environment, health, security, industrial applications and more. Each of these presents different requirements, regarding system performance and QoS, and involves a variety of mechanisms such as routing and MAC protocols, algorithms, scheduling policies, security, OS, all of which are residing over the HW, the sensors, actuators and the Radio Tx/Rx. Furthermore, they encompass special characteristics, such as constrained energy, CPU and memory resources, multi-hop communication, leading to a few steps higher the required special knowledge. Although the status of WSNs is nearing the stage of maturity and wide-spread use, the issue of their sustainability hinges upon the implementation of some features of paramount importance: Low power consumption to achieve long operational life-time for battery-powered unattended WSN nodes, joint optimization of connectivity and energy efficiency leading to best-effort utilization of constrained radios and minimum energy cost, self-calibration and self-healing to recover from failures and errors to which WSNs are prone, efficient data aggregation lessening the traffic load in constrained WSNs, programmable and reconfigurable stations allowing for long life-cycle development, system security enabling protection of data and system operation, short development time making more efficient the time-to-market process and simple installation and maintenance procedures for wider acceptance. Despite the considerable research and important advances in WSNs, large scale application of the technology is still hindered by technical, complexity and cost impediments. Ongoing R&D is addressing these shortcomings by focusing on energy harvesting, middleware, network intelligence, standardization, network reliability, adaptability and scalability. However, for efficient WSN development, deployment, testing, and maintenance, a holistic unified approach is n- cessary which will address the above WSN challenges by developing an integrated platform for smart environments with built-in user friendliness, practicality and efficiency. This platform will enable the user to evaluate his design by identifying critical features and application requirements, to verify by adopting design indicators and to ensure ease of development and long life cycle by incorporating flexibility, expandability and reusability. These design requirements can be accomplished to a significant extent via an integration tool that provides a multiple level framework of functionality composition and adaptation for a complex WSN environment consisting of heterogeneous platform technologies, establishing a software infrastructure which couples the different views and engineering disciplines involved in the development of such a complex system, by means of the accurate definition of all necessary rules and the design of the `glue-logic´ which will guarantee the correctness of composition of the various building blocks. Furthermore, to attain an enhanced efficiency, the design/development tool must facilitate consistency control as well as evaluate the selections made by the user and, based on specific criteria, provide feedback on errors concerning consistency and compatibility as well as warnings on potentially less optimal user selections. Finally, the WSN planning tool will provide answers to fundamental issues such as the number of nodes needed to meet overall system objectives, the deployment of these nodes to optimize network performance and the adjustment of network topology and sensor node placement in case of changes in data sources and network malfunctioning.