Energy and QoS Aware Management of Wireless Sensor Networks

In collaboration with:  Dr. Mohamed Younis (UMBC) and Dr. Phillip Regalia (CUA).

Recent advances in miniaturization and low-power design have led to active research in large-scale, highly distributed systems of small-size, wireless unattended sensors. Each sensor is capable of detecting ambient conditions such as temperature and sound. Over the last few years, the design of sensor networks has gained increasing importance due to their potential in a number of civil and military applications. A network of sensors can be used to gather meteorological variables such as temperature and pressure. These measurements can be used in preparing forecasts or detecting harsh natural phenomena. In disaster management situations such as earthquakes, sensor networks can be used to selectively map the affected regions directing emergency response units to survivors. In military situations, sensor networks can be used in surveillance missions and can be used to detect moving targets, chemical gases, or presence of micro-agents. Sensors in such environments are energy constrained and their batteries cannot be recharged. Therefore, designing energy-aware algorithms becomes an important factor for extending the lifetime of sensors.

Sensors are generally equipped with data processing and communication capabilities. The sensing circuit measures parameters from the environment surrounding the sensor and transforms them into an electric signal. Processing such a signal reveals some properties about objects located and/or events happening in the vicinity of the sensor. The sensor sends such sensed data, usually via radio transmitter, to a gateway (sink). The gateway can perform fusion of the sensed data in order to filter out erroneous data and anomalies and to draw conclusions from the reported data over a period of time. For example, in a reconnaissance-oriented sensor network, sensor data indicates detection of a target while fusion of multiple sensor reports can be used for tracking and identifying the detected target. Signal processing and communication activities are the main consumers of sensor's energy. Since sensors are battery-operated, keeping the sensor active all the time will limit battery’s lifetime. Therefore, optimal organization and management of the sensor network is crucial in order to perform the desired function with an acceptable level of quality and to maintain sufficient sensor energy for the required mission. Mission-oriented organization of the sensor network enables the appropriate selection of only a subset of the sensors to be turned on and thus avoids wasting the energy of sensors that do not have to be involved. Energy-aware network management will ensure a desired level of performance for the data transfer while extending the life of the network.

There has been an increasing interest in sensor’s applications that require certain performance guarantees such as end-to-end delay. For instance, transmission of imaging data in a disaster management setup requires careful handling in order to ensure that the end-to-end delay is within acceptable range and the images are received properly without any distortion. Other typical applications include real-time target tracking, emergent event triggering in monitoring applications and critical information relaying in battle environments. To support the desired Quality of Service (QoS) for the delivery of sensing data in these applications, new protocols need to be employed. Such protocols should not only ensure bounded response time but also strive to minimize energy consumption in data processing and communication. We pursue a comprehensive approach to handling QoS-constrained applications, at the physical, MAC, network and application layers.