The proliferation of connected embedded devices has driven wireless communications into commercial, military, industrial, and personal systems. It is unreasonable to expect privacy and security to be inherent in these networks given the spatial density of these devices, limited spectral resources, and the broadcast nature of wireless communications systems. Communications for these systems must have sufficient information capacity and secrecy capacity while typically maintaining small size, light weight, and minimized power consumption. With increasing crowding of the electromagnetic spectrum, interference must be leveraged as an available resource.
This work develops a new beamforming method for direction-dependent modulation that provides wireless communications devices with enhanced physical layer security and the ability to simultaneously communicate and harvest energy by exploiting co-channel interference. We propose a method that optimizes a set of time-varying array steering vectors to enable direction-dependent modulation, thus exploiting a new degree of freedom in the space-time-frequency paradigm. We formulate steering vector selection as a convex optimization problem for rapid computation given arbitrarily positioned array antenna elements.
We show that this method allows us to spectrally separate co-channel interference from an information-bearing signal in the analog domain, enabling the energy from the interference to be diverted for harvesting during the digitization and decoding of the information-bearing signal. We also show that this method provides wireless communications devices with not only enhanced information capacity, but also enhanced secrecy capacity in a broadcast channel. By using the proposed method, we can increase the overall channel capacity in a broadcast system beyond the current state-of-the-art for wireless broadcast channels, which is based on static coding techniques. Further, we also increase the overall secrecy capacity of the system by enabling secrecy for each user in the system. In practical terms, this results in higher-rate, confidential messages delivered to multiple devices in a broadcast channel for a given power constraint. Finally, we corroborate these claims with simulation and experimental results for the proposed method. / PHD / The proliferation of connected devices has driven wireless communications into commercial, military, industrial, and personal systems. It is unreasonable to expect privacy and security to be inherent in these networks given the spatial density of these devices, limited available resources, and the broadcast nature of wireless communications systems. Communications for these systems need not only sufficient information capacity, but also the assurance that the available information capacity remains confidential while typically maintaining small size, light weight, and minimized power consumption. With increasing crowding of the electromagnetic spectrum due to the numerous connected devices, interference between them must be leveraged as an available resource.
This work develops a new method for electrically steering an array of antennas to overlay or encode information onto a signal in a way that is direction-dependent and provides wireless communications devices with enhanced security and the ability to simultaneously communicate and harvest energy from interfering devices. We propose a method that optimizes a set of time-varying array steering vectors to enable direction-dependent modulation, thus exploiting a new degree of freedom in the traditional space-time-frequency paradigm. We formulate the selection of steering vectors as a convex optimization problem for rapid computation given arbitrarily positioned array antenna elements in three dimensions.
We show that this method allows us to separate interference from an information-bearing signal in the analog domain, enabling the energy from the interference to be diverted for harvesting during the digitization and decoding of the information-bearing signal. We also show that this method provides broadcast wireless communications devices with not only increased information capacity, but also assured secrecy. By using the proposed time-varying method, we can increase the overall channel capacity in a broadcast system beyond the current state-of-the-art, which is based on static encoding techniques. Further, we also increase the overall secrecy capacity of the system by ensuring that each user in the system receives separate and confidential signals. In practical terms, this results in higher-rate, confidential messages delivered to multiple devices in a broadcast channel for a given power constraint. Finally, we corroborate these claims with simulation and experimental results for the proposed method.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/88956 |
| Date | 20 October 2017 |
| Creators | Yamada, Randy Matthew |
| Contributors | Electrical Engineering, Mili, Lamine M., Steinhardt, Allan O., Buehrer, R. Michael, Clancy, Thomas Charles III, Gugercin, Serkan |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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