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Publication in the conference proceedings of EUSIPCO, Tampere, Finland, 2000

Traditional Wireless Sensor Networks (WSN) rely on batteries with finite stored energy. In the future with billions of such devices, it will be difficult to replace and dispose their batteries, which can cause a huge environmental threat. Hence, research is being done to eliminate batteries from sensor devices and replace them with harvesters. These harvesters can power the sensor network nodes by extracting energy from ambient sources. Harvesters are already being implemented in many real-life applications like structural health monitoring, environment monitoring and body area networks. A sensor network of multiple energy harvesting enabled devices is known as Energy Harvesting based Wireless Sensor Network (EH-WSN). For uninterrupted operation of EH-WSN, radio protocols must consider the energy harvesting constraints; (i) energy harvesting process unpredictability and; (ii) energy harvesting rate variations in time and space. EH-WSN comes with unique traits which discourage the use of existing WSNs radio protocols, as most of existing protocols are focussed on decreasing the energy consumption and increasing the network lifetime. This thesis work focusses on modifying an existing energyefficient Multipath Rings (MPR) routing protocol for low-power and low-bandwidth EH-WSN and evaluating its performance through simulations. Firstly, the topology setup phase is revised by implementing a new ring formation scheme for better data reliability. Secondly, controlled flooding of data packets is used by enabling selective forwarding, which leads to decrease in network traffic and overall energy consumption. Lastly, every node is equipped with a neighbors’ table on-board which helps in making energy-related routing decisions in multi-hop networks. A periodic energy update packet transmission helps in keeping latest neighbor information. This modified version of MPR routing protocol is called Energy Harvesting based Multipath Rings (EH-MPR) routing. This work also provides a comprehensive survey on existing MAC and Routing protocols for energy efficient and energy harvesting based WSNs. Through this work, the main constraints on using existing energy-efficient protocols for EH-WSN are discussed and depicted with the help of network simulations. The effects of using fixed duty cycle for energy harvesting enabled sensor nodes are outlined by simulating T-MAC (adaptive duty cycle) against S-MAC (fixed duty cycle). For all evaluation metrics, T-MAC outperformed S-MAC. Using Castalia’s realistic wireless channel and radio model, EH-MPR is simulated for low-power, low-data rate and low bandwidth (1 MHz) networks where satisfactory results are obtained for sub-GHz frequencies (433 MHz and 868 MHz). Next, the modified EH-MPR protocol is compared with original MPR routing under practical deployment scenarios. The metrics in consideration are successful packet transmissions, energy consumption, energy harvested-to-consumed ratio and failed packets. After thorough simulations, it was concluded that although the packet success rate is approximately equal for both protocols, EH-MPR has advantages over original MPR routing protocol in terms of energy cost and uninterrupted operations.

The Digital Video Broadcasting (DVB) project has developed digital broadcasting system specifications which have been adapted worldwide. The family of DVB standards includes DVB-S for satellite, DVB-C for cable and DVB-T for terrestrial system. This DVB-T system has proven its capability and thus accepted as the standard for terrestrial system in most countries. DVB-T2 is the enhancement of DVB-T that will overcome the shortcomings of the previous standard and provide additional features. This thesis concentrates on synchronization performance in DVB-T2 systems. Synchronization is the most important task that the receiver has to perform in the beginning of its reception of the signal. DVB-T2 uses Orthogonal Frequency Division Multiplexing (OFDM) modulation method and has a special symbol, named P1 symbol, for performing initial synchronization tasks. This symbol is also used for detecting DVB-T2 signal, meaning that, if the receiver can detect the P1 symbol, then it can conclude that the channel contains DVB-T2 signal. Moreover, P1 symbol also transmits basic transmission parameters that the receiver needs in the first place in order to proceed for further processing. In this work, the DVB-T2 system model has been implemented including the P1 symbol and the performance of synchronization by P1 symbol has been analyzed extensively by simulations in different channel conditions. P1 symbol deals with the synchronization issues before performing Fast Fourier Transform (FFT). Therefore, P1 symbol based methods can achieve coarse timing synchronization and fine frequency synchronization. Also the detecting and decoding probabilities based on P1 symbol in different channels are presented in this thesis. /Kir09