本計畫藉由叢集化將CRAHNs 分為多個two-hop 叢集，以降低無線感知節點的競爭，進而降低資料傳輸的延遲；藉由控制訊息的交換來獲知相鄰SU 及PU 節點的狀況，以克服多重通道SU 及PU 隱藏節點及SU 暴露節點的問題，達到降低PU 干擾及提升SU 通道使用率來節省節點能量並提升系統輸出量的目的。新叢集方法將導入多重通道無線感知網路中MAC 協定設計，設計一個動態的共同控制通道MAC 協定。共同控制通道如果採取隨機式，將無法避免隱藏式節點問題，且剛開始傳輸資料時將浪費更多時間；如果採取固定式，必須要有特定的通道可供SU 使用，這將是一個冗長且成本高昂的建置過程，且固定的頻寬將失去擴展性。而本計畫之動態共同控制通道的選擇將透過對PU 空閒通道成功取得的機率、此空閒通道的穩定性及叢集成員間獲得此PU 空閒通道最大機率來決定。MAC 協定競爭視窗大小將依據系統資料流量及SU 競爭個數來動態的調整；以SU 傳送端優先權及所剩餘的能量多寡來決定是否持續佔有多個資料通道時槽，以提升系統輸出量。接下來透過模擬分析，將本研究方法與先前的方法比較，證明本計畫所提出來的方法，確實比先前的方法更能提升系統能源效率、系統輸出量及降低封包傳遞延遲。 In this proposal, the Cognitive Radio Ad Hoc Networks (CRAHNs) will divide into some two-hop SU clusters to reduce the probability of contention within SUs and then reduce the transmission delay. To obtain the status of SUs and PUs by the exchange of control messages overcome the hidden SU and PU terminal problems and exposed SU terminal problems. This will reduce the interference to PU and increase the channel spatial reuse, and then saving the system power and increase the system throughput. If a common control channel is in a random manner, this will be a time-consuming for SUs to start a data transmission. In addition, the random manner protocol does not consider the effects of hidden terminals . If a fixed licensed channel is selected as a common control channel. The licensing of such a channel is a long-winded and expensive process. The licensed channel has fixed bandwidth and is therefore limited in scalability. In this proposal, Cluster-based Dynamic common control channel MAC (CDMAC) protocol is proposed. The selection of common control channel is decided by the probability of success to get PU idle channels. We propose the dynamic length of contention window and permit the SU sender to reserve multiple data slots to solve the hidden and exposed terminal problems among PUs and SUs. We also compare our proposed scheme to existing MAC protocols for CRAHNs. We will show that CDMAC protocol has higher power efficiency, system throughput and lower transmission delay than previous MAC protocols.
