Reconfigurable Intelligent Surfaces based system design for future 6G wireless networks

• Autor(a) principal: Santos, Ana Rita Betencourt da Costa Rodrigues dos
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10071/27544
• topic: 6G; Terahertz (THz) communications; Channel modeling; Reconfigurable Intelligent Surfaces (RIS); Achievable rate; Ultra-Massive Multiple-Input Multiple-Output (UM-MIMO); Comunicações Terahertz (THz); Modelação de canais; Superfícies Inteligentes Reconfiguráveis (RIS); Taxa alcançável; Ultra-Massivo Múltiplas-Entradas Múltiplas-Saídas (UM-MIMO)

Future sixth generation (6G) wireless networks perceive the THz band as essential to support the high volume of wireless traffic data being generated in the network, thus enabling ultra high transmission rates. However, the behaviour of the THz frequency spectrum affects the propagation occurring in the wireless communication system due to high attenuation, leading to severe propagation losses. Reconfigurable intelligent surfaces (RIS) are a promising technology to overcome the limitations present in the THz waveband by reshaping the wave direction, thus enabling the signal to propagate towards its intended target. RIS have many applications in wireless systems, specifically in the optimization of the communication network performance when combined with ultra-massive multiple-input multiple-output antennas (UM-MIMO). UMMIMO systems are critical for implementing THz frequencies as the large number of antennas provides high directivity pencil like beams, thereby enabling easy data spread from the transmitter towards the receiver. To achieve low complexity whilst deploying UM-MIMO systems, hybrid precoders must be implemented. This dissertation aims to design and evaluate a RIS-assisted communication model for ultra-massive MIMO systems to extend coverage range and to improve the energy and spectral efficiency of 6G communications. To maximize the achievable rate of the structure, an algorithm will be developed to calculate the phase shifts of the individual RIS elements, and the implementation of various hybrid precoding structures. Several numerical results will be obtained through various simulations and analysed to give insight into which design is best suited for RIS-assisted THz communication system through the achievable rates obtained.