本篇論文探討在下鏈(Downlink)異質網路(Heterogeneous Network)系統之下，如何利用能量偵測法(Energy detection)搭配頻譜偵測(Spectrum Sensing)以達成最大傳輸效率。在異質網路環境中，主要基地台(Primary base station)與次要基地台(Secondary base station)之間共用同個頻帶，因此在傳輸過程中會產生同頻帶之間的干擾(Co-channel Interference)，這也是異質網路所面臨的一個重要問題。為了解決同頻帶之間的干擾，因此使用感知無線電(Cognitive Radio)的技術針對基地台之間傳輸時所產生的干擾問題進行優化與資源配置並達成傳輸效率的提升。 此論文探討次要使用者利用頻譜偵測技術及能量偵測法偵測異質網路主要使用者(Primary User)的使用情形，若當前頻段沒有主要使用者使用時，次要使用者(Secondary User)便可使用該頻段，否則需空出頻段給主要使用者。而頻譜偵測主要考慮兩種機率值，分別是正確偵測機率(Probability of Detection)值以及誤警報機率(Probability of False-alarm)值。正確偵測機率值越高或誤警報機率值越低，則次要使用者能夠占用頻帶的可能性就越高，也就更能利用頻帶，並利用偵測結果進行子載波配置以及利用拉格朗日乘數法進行功率配置。 此篇論文研究的感知無線電頻譜偵測搭配能量偵測技術，在模擬結果顯示出，相較於沒有考慮偵測機率的情形，更能增進次要使用者及總傳輸效率。;This thesis is about how to use spectrum sensing technology to improve the transmission capacity in downlink heterogeneous network systems. Heterogeneous network consists of primary and secondary base station. The major problem in heterogeneous network is the co-channel interference because it shares the same spectrum. Cognitive radio is the key technique to optimize the interference problem and allocate subcarriers and power among the base stations. The proposed scheme discusses that whether the spectrum is used by the primary user or not with the spectrum sensing technique. If the spectrum is detected to be idle, the secondary user can use the band. There are two main models of probability about spectrum sensing, probability of detection and probability of false-alarm. The higher detection probability or the lower false-alarm probability makes the secondary users to have more chances to occupy the spectrum. Based on the statement, using the sensing result to allocate the subcarrier, and using Lagrange multiplier method and Lagrange dual decomposition to allocate power lead to the simulation result reveals that the proposed scheme outperforms the other conditions which not consider the sensing probability.
