In recent years, we have witnessed a rapid evolution of wireless communication technologies to meet the ever increasing demand of diversified mobile services. It is expected that mobile traffic volume will continue to increase in the following years with a massive diffusion of connected devices and a wide range of quality of service requirements. This represents a challenge for future wireless systems, which shall guarantee high-quality and high-data rate services into limited spectrum. OFDMA femtocells have been pointed out by the industry as a good solution not only to overcome the indoor coverage problem but also to deal with the growth of traffic within macrocells. However, the deployment of a new femtocell layer may have an undesired impact on the performance of the macrocell layer. The resource allocation and the avoidance of electromagnetic interference are some of the more urgent challenges that operators face before femtocells become widely deployed. Following the primary/secondary paradigm, low power nodes shall have cognitive capabilities in order to monitor the network status and optimize their transmission reducing the interference to the primary licensed system. Otherwise, some types of coordination are often used to manage each transmission and to avoid that set of issues. This is possible when both systems are aware of the presence of the other transmission point and a control channel is available to each other. The use of multiple antennas for wireless communication systems has gained overwhelming interest during the last decade - both in academia and industry. Multiple antennas can be utilized in order to accomplish a multiplexing gain, a diversity gain, or an antenna gain, thus enhancing the bit rate, the error performance, or the signal-to-noise-plus-interference ratio of wireless systems, respectively. These techniques, and beamforming in particular, offer an extra degree of freedom to eliminate the interference in cognitive paradigm networks. This thesis recaps the works done throughout the Ph.D. course. Each chapters include parts and excerpts of publications. Chapter 1 provides a general introduction to the interference in wireless systems. Initially, a interference characterization is presented and then the interference management techniques in 4G and 5G systems are discussed. The need of heterogeneous scenarios leads to different issues and offers new solutions. In this context, the role and potentiality of the antenna arrays are treated. In the Chapter 2 primary/secondary paradigm is described in detail. In particular, the problem of interference management by a small-cell equipped with antenna array in an actual scenario is investigated. Then, the problems that arise both during the acquisition step of the angular information or during the antenna pattern modeling are discussed. In the last part, some resource allocation algorithms are proposed in order to improve the performance of secondary systems, keeping the interference on primary under control. In the Chapter 3, the interference management is approached from a coordinated point of view. Thus, macro-cell and small-cells cooperate to reduce the interference experienced by each user. Initially, the control link is exploited only to convey the network signaling information, useful to co-allocate users of each system on the same time-frequency elements and increase the total system efficiency. With regard to this, a resource management algorithm is proposed which exploits the knowledge of the angular distances among users by using an antenna array to shape the digital radio pattern. Subsequently, the behavior of the network is investigated when coordination increases. In this case, more transmission points can be used to convey information to users in order to increase the data-rate of the users at cell-edge and to relieve congestion of the more saturated cells. Finally, future directions and conclusions are drawn.

Interference Management in Next Generation Wireless Systems: Cognitive and Coordinated Approaches / Marco Pucci. - (2015).

Interference Management in Next Generation Wireless Systems: Cognitive and Coordinated Approaches

PUCCI, MARCO
2015

Abstract

In recent years, we have witnessed a rapid evolution of wireless communication technologies to meet the ever increasing demand of diversified mobile services. It is expected that mobile traffic volume will continue to increase in the following years with a massive diffusion of connected devices and a wide range of quality of service requirements. This represents a challenge for future wireless systems, which shall guarantee high-quality and high-data rate services into limited spectrum. OFDMA femtocells have been pointed out by the industry as a good solution not only to overcome the indoor coverage problem but also to deal with the growth of traffic within macrocells. However, the deployment of a new femtocell layer may have an undesired impact on the performance of the macrocell layer. The resource allocation and the avoidance of electromagnetic interference are some of the more urgent challenges that operators face before femtocells become widely deployed. Following the primary/secondary paradigm, low power nodes shall have cognitive capabilities in order to monitor the network status and optimize their transmission reducing the interference to the primary licensed system. Otherwise, some types of coordination are often used to manage each transmission and to avoid that set of issues. This is possible when both systems are aware of the presence of the other transmission point and a control channel is available to each other. The use of multiple antennas for wireless communication systems has gained overwhelming interest during the last decade - both in academia and industry. Multiple antennas can be utilized in order to accomplish a multiplexing gain, a diversity gain, or an antenna gain, thus enhancing the bit rate, the error performance, or the signal-to-noise-plus-interference ratio of wireless systems, respectively. These techniques, and beamforming in particular, offer an extra degree of freedom to eliminate the interference in cognitive paradigm networks. This thesis recaps the works done throughout the Ph.D. course. Each chapters include parts and excerpts of publications. Chapter 1 provides a general introduction to the interference in wireless systems. Initially, a interference characterization is presented and then the interference management techniques in 4G and 5G systems are discussed. The need of heterogeneous scenarios leads to different issues and offers new solutions. In this context, the role and potentiality of the antenna arrays are treated. In the Chapter 2 primary/secondary paradigm is described in detail. In particular, the problem of interference management by a small-cell equipped with antenna array in an actual scenario is investigated. Then, the problems that arise both during the acquisition step of the angular information or during the antenna pattern modeling are discussed. In the last part, some resource allocation algorithms are proposed in order to improve the performance of secondary systems, keeping the interference on primary under control. In the Chapter 3, the interference management is approached from a coordinated point of view. Thus, macro-cell and small-cells cooperate to reduce the interference experienced by each user. Initially, the control link is exploited only to convey the network signaling information, useful to co-allocate users of each system on the same time-frequency elements and increase the total system efficiency. With regard to this, a resource management algorithm is proposed which exploits the knowledge of the angular distances among users by using an antenna array to shape the digital radio pattern. Subsequently, the behavior of the network is investigated when coordination increases. In this case, more transmission points can be used to convey information to users in order to increase the data-rate of the users at cell-edge and to relieve congestion of the more saturated cells. Finally, future directions and conclusions are drawn.
2015
Romano Fantacci
ITALIA
Marco Pucci
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Utilizza questo identificatore per citare o creare un link a questa risorsa: https://hdl.handle.net/2158/980187
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