Energy-aware wireless multi-hop networks

Summary Wireless networks have provided us a variety of services which facilitate communication between people beyond the physical boundaries. Mobile telephony, mobile Internet access and high-de nition video calls are examples of services supported by modern networks nowadays. Beyond this, advances in wireless communication coupled with enhancements in processing capabilities of electronic devices have resulted in the emergence of devices which have high communication and processing capabilities. Small devices that we carry or miniaturized devices embedded in our surroundings can execute sophisticated communication protocols. This allows them to form distributed networks in which nodes communicate with each other to collaboratively o er services without the need for pre-established expensive infrastructures. Such networks are known as wireless multi-hop networks, where instead of powerful base stations, multi-hop communication connects all the devices that are outside the transmission range of each other. Each device may act as a router which relays packets on behalf of other devices. Ad hoc communication between laptops in a conference hall, multi-hop communication between personal devices at home, and collaborative communication between sensors distributed over a large area are example scenarios of multi-hop communication in wireless networks. This dissertation addresses the design of energy-aware wireless multi-hop networks, where energy is the key element in the design and analysis. Wireless multi-hop networks must be energy-aware for two reasons. First, devices in these networks usually run on batteries. Thus, reducing energy consumption can save scarce battery energy of devices and extend the autonomy of systems that are composed of. Second, vast deployment of these easy-to-establish networks can excessively increase energy consumption in the ICT sector. Energy-e cient and energy-aware communication protocols and mechanisms not only extend operational lifetime of devices but also reduce environmental impacts of these networks. The novelty of this dissertation is the proposal of a suite of new protocols which together form a platform for energy-aware and energy-e cient communication in wireless multi-hop networks. The proposed platform scans di erent layers of the communication stack taking into account cross-layer dependency between them from an energy-e ciency point of view. The energy e ciency across OSI Reference Architecture layers is addressed. Notably, the physical layer (Layer 1) to the transport layer (Layer 4) is covered. For the physical layer, we propose cooperative signal transmission techniques based on MIMO (Multi-Input Multi-Output) technology to reduce the transmission power of nodes without sacri cing link reliability. For the data link layer, we propose a network topology control algorithm which speci es a neighbor discovery policy to keep the maximum transmission power of nodes as low as required for network connectivity. For the network layer, we propose routing schemes for nding the most energy-e cient routes between any two nodes of the network taking into account the impact of the transmission control of the transport layer. Furthermore, we enhance these routing schemes with the capability to balance the tra c according to the available battery energy of nodes. We also analyze the expected duration that two nodes in a wireless multi-hop network with a random topology can communicate with each other (from transport layer point of view) through intermediate nodes between them. The proposed schemes in this dissertation together make the communication stack in wireless multi-hop networks more and more energy-e cient leading to green wireless multi-hop networks. This work is of a fundamental and theoretical nature supported by simulations. It could be continued by experimental studies using a testbed.