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Title: Communication protocols for energy constrained networks
Keywords: energy constraints, wireless sensor networks, communication protocols
Issue Date: 4-Jan-2011
Source: TAN HWEE XIAN (2011-01-04). Communication protocols for energy constrained networks. ScholarBank@NUS Repository.
Abstract: The small wireless network devices in sensor and ad hoc networks can be deployed for a plethora of ubiquitous and collaborative applications, such as healthcare monitoring and tactical surveillance. However, these network elements are typically energy constrained as they have limited and/or irreplaceable battery supplies. This necessitates the design and development of energy efficient communication protocols in order to prolong the lifetimes of such networks. In this dissertation, we first identify the caveats of existing networking protocols for energy constrained networks. Three novel algorithms, viz. A^2-MAC, IQAR and IQDEA, are then proposed to provide better energy efficiency for both periodic monitoring as well as event driven sensor applications. A^2-MAC is an Adaptive, Anycast Medium Access Control protocol that effectively reduces energy expenditure in generic low-powered wireless sensor networks. It utilizes: (i) random wakeup schedules, such that each node can independently and randomly wakeup in each cycle without coordination and time synchronization; (ii) adaptive duty cycles based on network topology; and (iii) adaptive anycast forwarder selection, which allows each node to transmit to any member in its forwarding set. By allowing nodes to operate with different duty cycles and forwarding sets based on a given local delay performance objective and local network connectivity, A^2-MAC achieves better energy-delay tradeoffs and extends node lifetime substantially, while providing good end-to-end latency. Upon the presence of Phenomena of Interest (PoI) in event driven sensor networks, multiple sensors may be activated, leading to data implosion and redundancy. IQAR is an Information Quality Aware Routing protocol that finds the least-cost routing tree that satisfies a given information quality (IQ) constraint when a PoI occurs. As the optimal least-cost routing solution is a variation of the classical NP-hard Steiner tree problem in graphs, IQAR uses: (i) topology-aware histogram-based aggregation structure that encapsulates the cost of including the IQ contribution of each activated node in a compact and efficient way; and (ii) greedy heuristic to approximate and prune a least-cost aggregation routing path. Despite the existence of energy-delay tradeoffs, existing protocols tend to optimize only energy efficiency and overlook the significance of end-to-end delays. However, in mission critical applications such as intrusion detection and tsunami detection, faster detection of the PoI translates to earlier deployment of search-and-rescue operations and subsequently, significant reductions in casualties and infrastructural damages. IQDEA is an Information Quality aware Delay Efficient Aggregation scheme that minimizes PoI detection delays and transmission costs in duty cycled networks while satisfying application-level IQ requirements. Through the use of: (i) IQ-awareness; (ii) novel aggregation latency function for each node; and (iii) selection of forwarding nodes based on instantaneous expected end-to-end delays, IQDEA achieves a good balance between energy efficiency and delay efficiency. Performance evaluations of the proposed schemes show that they can achieve significant energy savings over existing protocols through the use of techniques such as adaptation to network conditions, anycast forwarding and information quality awareness. However, the design space for energy efficient communications remains very large, and continued research efforts are required to identify an integrated framework for the suite of these communication protocols.
Appears in Collections:Ph.D Theses (Open)

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