Cross layer design for energy conservation and capacity improvement over mobile ad hoc networks
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The layered architecture based on OSI model has been widely used in wired networks. Due to the dynamics of wireless medium and the node mobility, many special problems appear in wireless networks, which prevent the conventional layered architecture from functioning optimally in wireless environment. In this thesis, we study the wireless networks from different perspectives. Our objective is to systematically develop network protocols and architecture to address various limitations of wireless systems by assuming a cross-layer approach. Firstly, we develop an energy consumption model for wireless ad hoc networks. In existing work, transmission power is commonly used to represent energy consumption cost. In this study, we analyze possible energy consumptions in physical layer, MAC layer (such as signaling packets), and upper layers (such as end-to-end retransmission), and propose more accurate models to capture the energy consumption cost due to different factors. Secondly, based on the energy consumption model, we design an energy efficient routing protocol. The existing energy efficient routing protocols only focus on the search of the most energy efficient path. However, there are many problems in these protocols, including broadcast storm issue, long setup delay, and poor performance in mobility scenario. In this study, we propose an efficient method for estimating the accurate link cost, a quick path searching scheme to find the energy efficient path, and an efficient maintenance scheme to adjust the path according to the environment. Thirdly, we perform the cross-layer design for multiple-channel multiple-interface network to improve the throughput. Current MAC and routing protocols are mainly developed for only one channel and the existing wireless devices are equipped with only one wireless interface. In this study, we design a unified MAC and routing framework to exploit the benefits enabled by the multiple channels to improve the capacity of ad hoc networks. Our joint channel assignment and routing scheme searches for an efficient transmission path, while taking into account the limited number of channels/interfaces, local topology information, and link rate diversity. Our scheduling scheme at MAC layer coordinates transmissions within the vicinity over a short time scale to maximize channel usage and avoid collision among nodes sharing the same channel. The scheduling scheme complemented with prioritized transmitting will also coordinate interface switching to avoid unnecessary switching delay, support load balancing, reduce the broadcast delay and further improve throughput in a multi-channel multi-interface environment.