Cooperative communication in near field magnetic induction communication systems
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Near-Field Magnetic Induction Communication (NFMIC) is a relatively new technology which has been proposed for short-range applications such as body-area networks. Since it uses a rapidly-decaying magnetic near-field instead of an electromagnetic wave as the signal transmission mechanism, it is ideal for situations in which limited transmission range is actually an advantage, such as where minimising internetwork interference or avoiding location disclosure are considered important. To date, little work has been done on multihop techniques specifically designed for NFMIC systems. Most existing applications, such as Radio Frequency Identification (RFID) and Near Field Communication (NFC) are strictly point-to-point. However, when each network node only needs to transmit occasionally, multihop relaying techniques have the potential to significantly reduce power consumption and overall levels of magnetic field egress. Cooperative retransmission strategies, where network nodes that are neither a transmission source nor sink can participate in relaying of frames at the physical layer, have been proposed as a solution for range-extension of conventional electromagnetic/radiofrequency networks. This thesis aims to propose, analyse and simulate a variety of strategies for cooperative relaying which are appropriate for the specific needs of multihop NFMIC networks. A link budget model for NFMIC is firstly developed and thoroughly analysed, for a variety of non-ideal channel conditions. Three relaying strategies are then proposed and evaluated using the link-budget model under a variety of channel conditions, varying from near-ideal to the pathological case, and a wide variety of source, destination and relay node placement configurations. Simulation results are used to identify the key factors which govern the performance of each technique and the conditions under which throughput can be maximised. A new link metric, which accurately captures these factors, is proposed and its benefits demonstrated through simulation. Finally, a number of opportunities for future study are identified.
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