本論文提出應用於頻譜異構之隨意式感知無線電網路下的多頻段能量偵測演算法，此演算法利用通道在空域、頻域與時域上的特性，來改善頻譜偵測效能。感知無線電下的次要使用者並無授權頻段的使用權，若其欲使用頻譜資源，必須在事前對頻譜進行週期性的偵測以確認頻譜空洞的存在，當發現頻譜空洞時，還須在不干擾主要使用者的前提之下，以機會性方式對頻譜資源進行存取。從次要使用者對頻譜進行使用的過程中可發現，頻譜偵測是感知無線電中最為重要的課題，其相關研究也將在本篇論文中繼續被探討。異構頻譜環境下不同的次要使用者會感受到相異的頻譜使用狀況，但部分次要使用者會因地理環境的緣故，而感受到相似的頻譜使用情形，這類有相似頻譜使用情況的環境又稱之為同構頻譜環境。為了使同構頻譜環境下的次要使用者們能彼此合作，利用插入權重定位演算法對主要使用者傳送端做定位，並根據次要使用者與主要使用者傳送端之間的距離來判斷次要使用者是否位在主要使用者傳送端的傳輸範圍內，進而推斷出次要使用者之間是異構還是同構的關係。同構頻譜環境的次要使用者們隨著所處的環境不同，將遭受不同程度的衰減。為了有效提高對頻譜的偵測能力，次要使用者們利用空間與時間上的多樣性，並透過馬可夫鏈的能量遞迴運算方式，使次要使用者與鄰居之間進行資訊交換，以提高資訊可信度；為了善用頻段之間的相關性，建議所有的次要使用者對頻譜進行寬頻頻譜偵測，SNR-based weighted wideband spectrum sensing便是利用頻段之間在使用上的關聯性對寬頻頻段偵測結果做權衡，以提升偵測精準度。 在硬體設計中，插入權重定位演算法與能量遞迴運算需要經過多次遞迴計算，將造成硬體成本的增加，但若採用以時間換取空間的方式，將資料回傳再運算，則可大大節省硬體面積。適當地插入管線不僅有助於排程，更能提高運算吞吐量。最終的硬體設計將以FPGA型號：Spartan6 XC6SLX150來做驗證，複雜的硬體僅使用9顆CORDIC除法器與8顆CORDIC絕對值器，綜觀而言，實屬一低複雜度的硬體設計。 ;In this paper, we propose an algorithm for heterogeneous spectrum sensing in cognitive radio ad-hoc network. This algorithm utilizes the spatial domain, frequency domain and time domain characteristics of the primary user occupancy to improve the spectrum sensing performance. In the heterogeneous spectrum environment, different secondary users may experience similar or dissimilar spectrum usage due to the geographical location. In the transmission range of the primary user, a similar spectrum occupancy appears. It is called the homogeneous spectrum environment. The weighted interpolation positioning algorithm (WIP) is used to locate the position of the primary transmitter and thus those secondary users can cooperate with each other when they are identified as nodes in the homogeneous environments. Given the assumption of the fixed transmitter of the primary user, tracking mechanism is used to enhance the accuracy of localization. On the other hand, the energy recursion algorithm based on Markov-chain to exchange information among neighboring secondary users can generate converged energy detection result after several iterations. In addition, wideband spectrum sensing is also adopted. Secondary users utilize the correlation of spectrum occupancy to detect the activity of the wide-band spectrum with SNR-based weighted wideband spectrum sensing technique. Thus, the network level detection performance can be improved with these algorithms that exploit the spatial, spectral, temporal properties to detection spectrum holes for opportunistic spectrum accesses of the secondary users. For the hardware design, the weighted interpolation positioning algorithm(WIP) and the energy recursive operation is calculated iteratively. With the time-sharing technique, the hardware complexity can be reduced. Only 9 CORDIC dividers and 8 CORDIC absoluters exist in the 8 parallel-processing wide-band spectrum sensing modules. Finally, the design is verified by FPGA, Spartan6 XC6SLX150.
