|Collaborative beamforming with multiple frequency waveform interferometry in wireless sensor networks
|Tse, Michael (EIE)
|Wireless communication systems.
Sensor networks -- Design and construction.
Hong Kong Polytechnic University -- Dissertations
|Faculty of Engineering
|137 pages : illustrations ; 30 cm
|Collaborative Beamforming (CB) for distributed ad hoc wireless sensor networks (WSN) has been introduced as a scheme to achieve long distance communication. With phase synchronization, the process of coherent summation of all the signals improves the signal-to-noise ratio at the receiving end. This research proposes a new approach to avoiding the conventional phase synchronization process while achieving the required signal-to-noise ratio through constructive summation. We first discuss the development and applications of WSN. Emphasis is placed on the sensor power constraint and the practical implementations. We review the different research approaches conducted for achieving the phase synchronization among the sensors. Then, we present our approach of using the multiple frequency waveform interferometry technique to achieve the signal constructive summation. The last part of this thesis reports the co-operative research effort on the selection criteria of opportunistic relaying transmission method for the extension of the long-distance communication during the study period. We start the discussion with a pair of sensor nodes transmitting their carrier frequencies. The beat frequency is generated and constructive summation happens at the peaks of the amplitude. When the carriers of all the sensor nodes are constructively summed up, the result is equivalent to a synchronized beamformer. Instead of adjusting the phase of each sensor node, each sensor selects an appropriate and different carrier frequency according to the proposed algorithm so that the peaks of the beat frequencies will appear at the same time. Occurrence of the constructive summation can be controlled for efficient transmission.
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