Optimization Approaches in Wireless Sensor Networks

Abstract

Advancements in silicon technology, micro-electro-mechanical systems (MEMS), wireless communications, and digital electronics have led to the proliferation of wireless sensor networks (WSNs) in a wide variety of application domains including military, health, ecology, environment, industrial automation, civil engineering, and medical. This wide application diversity combined with complex sensor node architectures, functionality requirements, and highly constrained and harsh operating environments makes WSN design very challenging. One critical WSN design challenge involves meeting application requirements such as lifetime, reliability, throughput, delay (responsiveness), etc. for myriad of application domains. Furthermore, WSN applications tend to have competing requirements, which exacerbates design challenges. For example, a high priority security/defense system may have both high responsiveness and long lifetime requirements. The mechanisms needed for high responsiveness typically drain battery life quickly, thus making long lifetime difficult to achieve given limited energy reserves. Commercial off-the-shelf (COTS) sensor nodes have difficulty meeting application requirements due to the generic design traits necessary for wide application applicability. COTS sensor nodes are mass-produced to optimize cost and are not specialized for any particular application. Fortunately, COTS sensor nodes contain tunable parameters (e.g., processor voltage and frequency, sensing frequency, etc.) whose values can be specialized to meet application requirements. However, optimizing these tunable parameters is left to the application designer. Optimization techniques at different design levels (e.g., sensor node hardware and software, data link layer, routing, operating system (OS), etc.) assist designers in meeting application requirements. WSN optimization techniques can be generally categorized as static or dynamic. Static optimizations optimize a WSN at deployment time and remain fixed for the WSN’s lifetime. Whereas static optimizations are suitable for stable/predictable applications, static optimizations are inflexible and do not adapt to changing application requirements and environmental stimuli. Dynamic optimizations provide more flexibility by continuously optimizing a WSN/sensor node during runtime, providing better adaptation to changing application requirements and actual environmental stimuli. This chapter introduces WSNs from an optimization perspective and explores optimization strategies employed in WSNs at different design levels to meet application requirements 13