感知無線電系統中，當主要使用者及次要使用者同時出現時，主要使用者的通信品質會受到干擾。本論文探討當GMSK訊號為主要使用者、OFDM為次要使用者的狀況下，要如何偵測主要使用者是否進行傳輸。因為大多數調變信號的自相關函數，在時間軸為週期函數，稱之具有循環穩態的統計特性，不同調變方式的信號會有不同的循環穩態性。本文即藉此統計特性探討GMSK訊號偵測問題，並針對下列通道模型進行模擬分析：（一）GMSK訊號無外界訊號干擾的環境。（二）當GMSK訊號經過有外界干擾訊號。（三）考慮都普勒效應的狀況。（四）多路徑通道。
合作式偵測技術是基地台端接收多個局部偵測器回傳的偵測結果，以此判斷偵測訊號是否出現，希望能提高系統的偵測效能。本篇假設基地台端可完美收到局部偵測器回傳的資訊，在基地台端使用多數決或卡方檢定的方式做決策。論文中比較使用合作式偵測及單一偵測器的效能。模擬結果顯示：在高訊雜比時，多數決會比無使用合作式通訊會有較好的效能，低訊雜比則反之；而使用卡方檢定的效能皆優於使用單一偵測器。

In cognitive radio systems, when the primary user and secondary user exist at the same time, the communication quality of primary user will be lowered. In the thesis, we assume that the GMSK signal is the primary user and the OFDM signal the secondary user; the main topic is about detecting whether the primary user is transmitting or not. We use the property that GMSK and OFDM signals exhibit distinct cyclostationary characteristics to detect the signal of interest. We investigate the detection problem of GMSK under the following cases: (1) in the absence of OFDM signal, (2) in the presence of OFDM signal (3) with Doppler effect, (4) with multi-path channel.
We then consider the cooperative detection problem, in which the case base station receives the decisions from each local detector, and make the final decision with these local decisions. In this thesis, we assume that the base station receives the local decisions perfectly. The majority vote or chi-square test is used at the base station to make the final decision. The simulation results show that, at the high and medium SINR (signal to interference and noise ratio) situation; the performance of chi-square test is better than the one without cooperation.

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