Performance Evaluation of Ambient Backscattering Communication (AmBC) in Outdoor Environments
Biswas, Ritayan (2023)
Biswas, Ritayan
Tampere University
2023
Tieto- ja sähkötekniikan tohtoriohjelma - Doctoral Programme in Computing and Electrical Engineering
Informaatioteknologian ja viestinnän tiedekunta - Faculty of Information Technology and Communication Sciences
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Väitöspäivä
2023-12-01
Julkaisun pysyvä osoite on
https://urn.fi/URN:ISBN:978-952-03-3184-9
https://urn.fi/URN:ISBN:978-952-03-3184-9
Tiivistelmä
The demand for wireless communications surged in the past decade due to the massive number of devices requiring a connection to the internet. Although traditional wired communications provide a much more reliable connection, utilizing wires in specific deployment scenarios is improbable. The Internet of Things wireless communication is a concept where interrelated and interlinked devices and objects are connected to each other and the internet to collect information and respond intelligently to the end users. These “things” are deployed at a variety of locations with the objective of providing support for various use cases. Furthermore, the Internet of Things is envisioned to integrate everyday objects into the connected ecosystem. This has led to a significant increase in the amount of energy that will be required to power up these devices.
Modern battery technology involves the movement of electrons between the positive and negative electrodes. Thus, lithium-ion batteries need to be replaced as they degrade over time. However, different deployment scenarios of the Internet of Things render the regular maintenance of these devices impossible. Therefore, newer technologies need to be identified in order to provide energy and power to such devices.
Ambient backscattering communication utilizes ambient radio frequency signals to establish connection links between the transmitter, receiver, and backscatter devices. Radio frequency signals can originate from a variety of sources such as television and radio broadcasts, Wi-Fi signals, and cellular signals to name a few. Additionally, in ambient backscattering communication, the backscatter devices are able to harvest energy from the ambient signals and utilize them as the source of power for the backscatter devices.
This thesis focuses on the coverage, capacity, and interference aspects of ambient backscattering communication pertaining to different outdoor deployment scenarios. The main contributions to this thesis can be divided into three main parts.
Firstly, an analysis to determine the maximum coverage of ambient backscattering communication systems (operating in the mono-static and bi-static modes) was performed utilizing ambient FM radio signals. It was observed that in the bi-static mode of operation, about 44 dB (from the path loss) remained for the propagation of the signal between the backscatter device (located 30 km from the TX) and the RX. Additionally, in the mono-static mode of operation, the backscatter device could be located 14.5 km away utilizing the free space path loss equation. The achievable distance reduces with the decrease in the cross-section of the backscatter device.
Secondly, cellular signals were utilized to evaluate the achievable range of communication of mono-static ambient backscattering communication systems. It was observed that utilizing ambient Long-Term Evolution (LTE) signals (operating at a carrier frequency of 700MHz) a communication link between the TX/RX and the backscatter device located a few hundred meters apart could be established. Additionally, an analysis was carried out to determine the applicability of 5G signals for ambient backscattering communication systems in the outdoor macro cell and small cell environments. It was concluded that very short-range communication distances could be established between the TX/RX and the backscatter device at 5G frequencies, especially at the millimeter-wave carrier frequency of 26 GHz. The achievable range of communication was heavily dependent on the cross-section of the backscatter device and the additional loss. Furthermore, a study was carried out to determine the impact of the cell load and the adjacent cell interference on the coverage of mono-static ambient backscattering communication systems. It was observed that there was a 44 percent decrease in the coverage in a heavily loaded cellular network in comparison with an unloaded network.
Finally, bi-static AmBC systems were studied utilizing sub-1 GHz ambient signals. It was observed that only the carrier frequency of 200MHz was suitable for bi-static ambient backscattering communication. Subsequently, the need for the suppression of the direct path signal from the legacy source was studied and some interference suppression techniques were proposed. In addition, the impact caused by the presence of a second backscatter device in the environment was studied. It was observed that the second backscatter device caused the most interference when it was located close to the original backscatter device or the RX. The impact of the second backscatter device could be alleviated by positioning it one wavelength meter away from the first backscatter device or the RX.
Modern battery technology involves the movement of electrons between the positive and negative electrodes. Thus, lithium-ion batteries need to be replaced as they degrade over time. However, different deployment scenarios of the Internet of Things render the regular maintenance of these devices impossible. Therefore, newer technologies need to be identified in order to provide energy and power to such devices.
Ambient backscattering communication utilizes ambient radio frequency signals to establish connection links between the transmitter, receiver, and backscatter devices. Radio frequency signals can originate from a variety of sources such as television and radio broadcasts, Wi-Fi signals, and cellular signals to name a few. Additionally, in ambient backscattering communication, the backscatter devices are able to harvest energy from the ambient signals and utilize them as the source of power for the backscatter devices.
This thesis focuses on the coverage, capacity, and interference aspects of ambient backscattering communication pertaining to different outdoor deployment scenarios. The main contributions to this thesis can be divided into three main parts.
Firstly, an analysis to determine the maximum coverage of ambient backscattering communication systems (operating in the mono-static and bi-static modes) was performed utilizing ambient FM radio signals. It was observed that in the bi-static mode of operation, about 44 dB (from the path loss) remained for the propagation of the signal between the backscatter device (located 30 km from the TX) and the RX. Additionally, in the mono-static mode of operation, the backscatter device could be located 14.5 km away utilizing the free space path loss equation. The achievable distance reduces with the decrease in the cross-section of the backscatter device.
Secondly, cellular signals were utilized to evaluate the achievable range of communication of mono-static ambient backscattering communication systems. It was observed that utilizing ambient Long-Term Evolution (LTE) signals (operating at a carrier frequency of 700MHz) a communication link between the TX/RX and the backscatter device located a few hundred meters apart could be established. Additionally, an analysis was carried out to determine the applicability of 5G signals for ambient backscattering communication systems in the outdoor macro cell and small cell environments. It was concluded that very short-range communication distances could be established between the TX/RX and the backscatter device at 5G frequencies, especially at the millimeter-wave carrier frequency of 26 GHz. The achievable range of communication was heavily dependent on the cross-section of the backscatter device and the additional loss. Furthermore, a study was carried out to determine the impact of the cell load and the adjacent cell interference on the coverage of mono-static ambient backscattering communication systems. It was observed that there was a 44 percent decrease in the coverage in a heavily loaded cellular network in comparison with an unloaded network.
Finally, bi-static AmBC systems were studied utilizing sub-1 GHz ambient signals. It was observed that only the carrier frequency of 200MHz was suitable for bi-static ambient backscattering communication. Subsequently, the need for the suppression of the direct path signal from the legacy source was studied and some interference suppression techniques were proposed. In addition, the impact caused by the presence of a second backscatter device in the environment was studied. It was observed that the second backscatter device caused the most interference when it was located close to the original backscatter device or the RX. The impact of the second backscatter device could be alleviated by positioning it one wavelength meter away from the first backscatter device or the RX.
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