對於干擾受限的感知無線電網路以基於多根天線的頻譜偵測

Abstract

在下世代的感知無線電系統中，次要使用者(secondary user)在進行頻譜偵測(spectrum sensing)時，除了雜訊的影響外，外來的干擾訊號也會造成頻譜偵測的效能嚴重降低。因此，本論文針對在有干擾訊號且假設干擾訊號的子空間已知的情況下，在複數訊號空間中使用斜投影 (oblique-projection) 檢測與匹配子空間(matched-subspace)檢測來消除干擾訊號的影響，推導出準確檢測機率的公式，並藉由電腦模擬驗證之。另外，本論文也提出一個基於最小化輸出能量(minimal-output-power, MOP)原則的檢測演算法，並且進一步與斜投影檢測和匹配子空間檢測作效能的比較。此外，當干擾訊號的子空間無法得知的情況下，本論文提出另一個基於最小化輸出能量原則的檢測演算法，藉以改善傳統的能量檢測，並以電腦模擬驗證之。

Spectrum sensing in next-generation wireless cognitive systems, such as overlay femtocell net-works, performed at secondary users is indispensable. In a random access ad hoc network, the performance of spectrum sensing is further limited by interference. Thus, in the thesis we first investigate the performances of two interference-resistant detection schemes, namely, the oblique-projection based detector and matched-subspace detector, assuming that the interference subspace is complex-valued. The exact formulas for the detection and false-alarm probabilities are derived and corroborated via numerical simulations. In addition, we propose a minimal-output-power (MOP) based detection scheme. The performances of the three detectors are discussed. We also propose an MOP based detector with unstructured interference subspace. Computer simulation confirms the effectiveness of MOP based detector when compared with the traditional ED.