| 摘要: | 近年來，為了服務越來越多的使用者及達到越來越好的收訊品質要求，造成能源消耗及電量供不應求，能量獵取技術(Energy Harvest)能夠藉由獵取周遭環境的能源，來維持小規模無線通訊裝置的使用時效，解決有限容量電池電量問題。在無線傳輸環境中，訊號會經歷複雜的反射、折射、散射、繞射、穿透、干擾等一系列複雜的過程，因此很難完美傳播，過去常用的解決方式著重在增強基地台和接收端的能力，而可重構智能板(Reconfigurable Intelligent Surface, RIS)技術則換了一種思路，直接在無線傳輸通道上做文章，且其元件能消耗極少的功率就能達到極佳的傳輸效能。可重構智能板是6G時代的突破性發明，它可部署在發射端和接收端之間任何地方，當作中繼站增強當前通訊網路性能。
在此篇論文中，吾人提出以太陽能能量獵取技術作為可充電電池之能量供應來源，並提供可重構智能板上之元件開關控制使用，模擬在單天線基地台與單天線用戶的無線傳輸環境中，以最大化系統通道容量為目標，聯合設計出可重構智能板上元件之相位偏移及開關模式，藉由先固定開關模式，推導出每個相位偏移都是獨立由相對應的通道來決定的，接著根據上述，制定出一非凸最佳化問題，並使用凸優化中連續凸逼近的遞迴式方法，求出最佳的開關模式，使整體傳輸速率最大。最後探討用戶所在位置不同、可重構智能板放置位置不同、可重構智能板元件數量不同、太陽能板數量多寡，以及三種通道：分別為可重構智能板加上直接路徑三條路徑、不包含可重構智能板的通道、不包含直接路徑的通道，造成通道容量的變化，以最佳化系統傳輸效能。由模擬結果可以證明使用凸優化中連續凸逼近(SCA)的遞迴式方法，可以獲得最好的可重構智能板的元件開關模式，且在無線傳輸環境使用可重構智能板的確能有效提升傳輸品質。;In recent years, in order to serve more and more users and achieve better and better reception quality requirements, resulting in energy consumption and power supply in short supply, energy harvesting technology can maintain small-scale wireless communication devices by harvesting energy from the surrounding environment. To maintain the operational use time of devices in small-scale wireless communication and solve the problem of limited battery capacity. In the wireless transmission environment, the signal will transmit through a complex environment such as complex, reflection, refraction, scattering, diffraction, penetration, interference, etc., so it is difficult to transmit perfectly. The commonly used solutions in the past focused on enhancing the base station and the receiver. However, while the Reconfigurable Intelligent Surface (RIS) technology changed a different way of thinking and made a fuss directly on the wireless transmission channel. RIS is a breakthrough invention in the 6G wireless networks. Unlike the transmitter and receiver, RIS can be deployed anywhere in between and used as a relay station to enhance the performance of the current communication network.
In this thesis, we propose to use solar energy harvesting technology as the energy supply source for rechargeable batteries and provide elements of the RIS to simulate the wireless transmission environment of base station is equipped with single-antenna and user is equipped with single-antenna. With the goal of maximizing the system channel capacity, the phase shift and switching mode of the elements of the RIS are jointly designed. By fixing the switching mode first, it is deduced that each phase shift is independent and corresponding. Then, according to the above, a non-convex optimization problem is formulated, and the recursive method of Successive Convex Approximation (SCA) is used to find the best switching mode to maximize the overall data rate. At last, we will discuss the number of configuration elements of the RIS, the placement position of the RIS, the location of the user′s movement, the amount of solar energy size, and three types of channels: first, BS directly to UE; second, BS to RIS and then RIS to UE; third, it is the combination of the former two types. All these resulting in the relationship among the change in channel capacity so as to optimize the system transmission efficiency.
The simulation results can prove that using the recursive method of Successive Convex Approximation (SCA) in convex optimization can obtain the optimal switching mode of elements of the RIS, and the use of RIS in wireless transmission environment can indeed effectively improve transmission quality. |
