無線攜能通訊技術可以提供同時間的資訊與能量服務，傳統上被運用於單一層級的無線網路中，在本篇論文中，我們將無線攜能通訊技術運用於雙層級的無線網路。基於分時多工的概念，每個訊框被劃分成三個傳輸階段：通道估計階段、階段(I)和階段(II)。在階段(I)，第一層級將執行訊號傳輸，並提供第二層級作能量獵集。在階段(II)中，兩層級傳輸訊號給各自的使用者。為了保證系統的傳輸品質，我們探討兩個最佳化的問題，其一是最小化傳輸能量，此問題將受限於訊號吞吐量與能量獵集的需求，其二為最大化吞吐量問題，其須滿足總傳輸能量限制及能量獵集需求。為提升傳輸的效率，我們提出最佳化的資訊與能量波束設計，由於對應的最佳化為非凸問題，我們將運用半正定鬆弛技術解決兩個最佳化問題。此外，為更進一步改善第二層級因同通道干擾所造成的微弱吞吐量，我們將在兩個最佳化問題中，運用額外限制條件來保證吞吐量可滿足最低需求。最後，我們將透過模擬結果呈現最佳化問題的表現，並探討各系統參數對雙層級無線攜能網路效能的影響。

Simultaneous wireless information and power transfer (SWIPT) is an attractive technique to provide wireless data services and energy charging at the same time. Conventionally, it is applied to one-tier networks such as current cellular and WiFi networks where a central station is deployed to serve a number of users in the coverage. As the notion of heterogeneous network becomes emerging, it is of paramount importance to investigate effective SWIPT methods in the context of heterogeneous networks. In this thesis, we consider a two-tier heterogeneous network where the primary tier and the secondary tier are overlaid in the same geographical area. To enable SWIPT in such a heterogeneous network, we consider the time division multiple access (TDMA) and propose the frame structure. To guarantee the service quality in the system, we explore the optimal beamforming design based on two optimization formulations including the transmission power minimization subject to the requirement of data throughput and harvested energy, and the throughput maximization subject to the available transmission power and the harvested energy target. Since both the formulated problems are non-convex in nature, we obtain the optimal solution by applying the semidefinite relaxation (SDR) technique. We investigate the optimality of the SDR solutions and propose methods to improve the throughput of the secondary tier that may suffer severe co-channel interference from the primary tier. Numerical results are provided to evaluate the performance of the proposed optimal beamforming design and compare with some benchmark schemes.

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