RF front-ends are nonlinear systems that have nonlinear frequency response and, hence, can impair receiver performance by harmful adjacent channel interference in non-intuitive ways. Next generation wireless networks will see unprecedented diversity across receiver and radio technologies accessing the same band of spectrum in spatio-temporal proximity. Ensuring adjacent channel co-existence is of prime importance for successful deployment and operations of next generation wireless networks. Vulnerabilities of receiver front-end can have a severe detrimental effect on network performance and spectrum co-existence. This dissertation addresses the technological challenges in understanding and accounting for receiver sensitivities in the design of next generation wireless networks. The dissertation has four major contributions.
In the first contribution, we seek to understand how receiver nonlinearity impacts performance. We propose a computationally efficient framework to evaluate the adjacent channel interference in a given radio/spectrum environment. We develop novel tractable representation of receiver front-end nonlinearity to specify the adjacent channel signals that contribute to the interference at the desired channel and the total adjacent channel interference power at a given desired channel.
In the second contribution, we seek to understand how the impact of receiver nonlinearity performance can be quantified. We quantify receiver performance in the presence of adjacent channel interference using information theoretic metrics. We evaluate the limits on achievable rate accounting for RF front-end nonlinearity and provide a framework to compare disparate receivers by forming generalized metrics.
In the third contribution, we seek to understand how the impact of receiver nonlinearity can be managed at the network level. We develop novel and comprehensive wireless network management frameworks that account for the RF nonlinearity, impairments, and diversity of heterogeneous wireless devices. We further develop computationally efficient algorithms to optimize the proposed framework and examine network level performance. We demonstrate through extensive network simulations that the proposed receiver-centric frameworks provide substantially high spectrum efficiency gains over receiver-agnostic spectrum access in dense and diverse next generation wireless networks.
In the fourth contribution, we seek to understand how scalable interference networks are with receiver nonlinearity. We propose practical achievable schemes for interference avoidance and assess the scalability of the next generation wireless networks with interference due to receiver nonlinearity. Further, we develop an algorithmic scheme to evaluate the upper bound on scalability of nonlinear interference networks. This provides valuable insights on scalability and schemes for nonlinear adjacent channel interference avoidance in next generation shared spectrum networks. / Ph. D. / There has been a dramatic increase in the demand for mobile data, since the introduction of smartphones. Over the air transmission of data utilizes a natural resource called radio frequency spectrum. The efficient utilization of the radio frequency spectrum and clever wireless network management is key for satisfying this demand. Besides improving the quality of wireless services, efficient spectrum utilization will also have profound economic benefits and spur growth. It has been shown that spectrum is most efficiently used when shared among various services rather than licensed to specific users and communication systems. This implies that next generation wireless networks will comprise of diverse types of wireless devices. Thus, network design and regulation should ensure their harmonious co-existence. However, the practicality of spectrum sharing technology and regulation is still in its infancy. In particular, the effect of radio receiver performance and vulnerabilities from signals in the spectral neighborhood on spectrum regulation and management is not well understood. A detailed study and analysis of this is of paramount importance spectrum sharing and regulation in next generation wireless networks. In this dissertation we develop the fundamentals, limitations, and management strategies on the impact of receiver performance on efficient spectrum access and co-existence. In addition, this key insights to maximize network efficiency in next generation wireless systems are presented. The outcome of this dissertation will aid in developing frameworks to increase social awareness about low-quality wireless devices and their implications on capacity. In summary, this dissertation provides a the necessary foundations to understand, design, and optimize the next generation wireless networks, which will have far reaching economic and social benefits.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/81958 |
| Date | 29 January 2018 |
| Creators | Padaki, Aditya V. |
| Contributors | Electrical Engineering, Reed, Jeffrey H., Marcus, Michael J., Beex, Aloysius A., Vullikanti, Anil Kumar S., Tandon, Ravi, Koh, Kwang-Jin |
| 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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