Medium access control protocols for energy and delay efficient applications of wireless sensor networks
Pardeep Kumar · Universitätsbibliothek der FU Berlin Hochschulschriftenstelle u. Dokumentenserver · 2012
The swift evolution of computation and communication technologies has transferred low-power, low-cost, small-size, and self-organizing devices from obscurity into the complete reality via several hardware forms, each targeting specific applications and tasks. Wireless Sensor Networks (WSNs) are one of such emerging technologies being used in a wide spectrum of applications. However, in parallel to these advancements, WSNs pose design challenges due to the limited resources available to the sensor nodes. The most substantial challenge facing these networks is the requirement of significant reductions in energy consumption of the sensor nodes. A Medium Access Control (MAC) protocol for WSNs greatly influences the energy consumption of sensor nodes by controlling the functionalities of radio, which is the most power consuming component of a sensor node. Several WSN MAC protocols that have been proposed over the last years are, therefore, mainly tailored towards the single prime objective of energy efficiency. Due to the continuing proliferation of WSNs in many diverse applications, it becomes increasingly important to their communication protocols, particularly MAC protocols, not to restrain themselves with the energy efficiency objective. Considering the speedy achievements in producing ultra low power microprocessors and transceivers and in energy harvesting technologies, we conceive that in order to efficiently utilize sensor networks on a large scale for a long term and in a wide range of applications, energy efficiency, even though being the most critical metric, is not a sufficient challenge to address. This thesis mainly contributes towards the design of a novel WSN MAC protocol called AREA-MAC that considers, beside energy consumption, packet delay, packet delivery, redundancy, traffic adaptability, scalability, etc., for sensor nodes. The AREA-MAC protocol significantly reduces energy consumption of nodes through dealing with collision, idle listening, overhearing, over-emitting, and control overhead. At the same time, it substantially reduces packet delay by enabling the receiving node to respond early and adaptively to the sending node. The protocol efficiently reduces packet redundancy and enables nodes in adapting to the network and traffic conditions. The AREA-MAC protocol uses the channel polling scheme to access the channel, replaces long preambles with the short and smart ones, adds vital additional information to each of them, and employs several other novel approaches in order to achieve the required design goals. Moreover, unlike many other WSN MAC protocols, AREA-MAC does not need any sort of synchronization, time/frequency scheduling, and clustering among nodes, which greatly reduces overhead for nodes and helps a WSN to scale rather smoothly. Results that have been obtained from analytical, simulation, and real testbed experiments confirm the significant improvements of the AREA- MAC protocol over other state of the art protocols for several performance metrics. These results have been achieved under a wide range of experiments for several duty cycle values and with varying network scale, topology, and traffic conditions. The effect of cross-layering on the AREA-MAC nodes has also been analyzed. By using different optimization problems, the AREA-MAC has also achieved optimal duty cycle values for sensor nodes that could provide minimum energy consumption and minimum packet delay while keeping the packet delivery ratio above a threshold for a WSN. Similarly the evaluation results obtained from the testbed implementation establish a close match between both simulation and testbed platforms that verifies the acceptability and reliability of the used simulation models and parameter configuration. Additionally, the emerging IEEE 802.15.4 MAC protocol has been critically analyzed and its limitations, particularly related to energy, delay, and bandwidth have been explored. This manuscript also proposes a simple yet effective 802.15.4 BED scheme that looks into some vital enhancements to the 802.15.4 MAC protocol in order to make it compatible for energy, time, and bandwidth critical WSN applications.