車用網路抵抗載波間干擾的方法與模擬

Abstract

隨著車用網路經歷了快速的發展以及越來越多車輛用戶，高速公路上出現了車用管理以及無所不在的連接需求。由其是用戶需要從部屬在路邊的基地台下載越來越大量資訊的需求。但事實上在高速公路的情境中，高速移動造成了造成不穩定的連接以及不可靠的通道，常常會有不穩定的服務品質，這將會造成傳輸大量訊號的挑戰，在媒體存取控制層(Media Access Control Layer)有人已經提出車輛合作媒體存取控制(VC-MAC)協定，基地台和中繼站(Relay)合作利用空間多樣性(Spatial Diversity)以及用戶多樣性(User Diversity)克服不可靠的下鏈通道。 其中正交分頻多工(OFDM)傳輸技術在無線通訊的系統中非常普遍，正交分頻多工傳輸技術主要優點在於它的高頻譜使用效率以及能夠更有效地對抗多種路徑衰減效應，但正交分頻多工如果在快速變化的通道中會所生的載波間干擾，以及基地台與中繼站間干擾，使得錯誤率提高，造成系統效能降低。應該要消除和彌補如此的問題，使得接收到的資訊更可靠。 我們著重在頻率域等化方法的討論。在頻率域等化方法裡，最常見的就是圍繞著通道頻率響應矩陣去做估計、處理。而本篇論文將利用簡單的都普勒補償弦波來彌補大部分的載波間干擾，再利用簡單的方法去抵抗基地台與中繼站之間的干擾本篇論文的章節架構為: 第一章背景介紹與研究動機。第二章系統模型。第三章提出對抗載波間干擾的方法。第四章模擬結果。第五章結論與未來展望。

Vehicular networks are expected to experience rapid growth and evolution under the increasing demand of vehicular traffic management and ubiquitous network connectivity. In particular, the amount of information to be downloaded from the roadside deployed base station is dramatically increasing. Infected by high mobility, intermittent connectivity, and unreliability of the wireless channel, it is challenging to satisfy the need for reliable data transmission in vehicular networks. Vehicular cooperative media access control (VC-MAC) utilizes the concept of cooperative communication tailored for vehicular networks, particularly for base station downloading scenarios. The wireless communication systems that adopts Orthogonal Frequency-Division Multiplexing (OFDM) transmission scheme will experience rapid channel variations caused by high mobility. It is considered as a cause that induces inter-carrier interference (ICI) and BER performance degradation due to the orthogonality between subcarriers is destroyed in OFDM transmission systems. The most common technique to deal with the distortion causing by the ICI is focus on the channel frequency response (CFR) matrix. In this thesis we propose the ICI mitigation scheme methods by utilizing the compensation of high Doppler shifts and ICI cancellation. This thesis is organized as follows. Chapter1 will introduce background and motivations. Chapter2 gives an introduction of system model. Chapter3 will introduce the receiver algorithm. Chapter4 simulation results are shown and analyzed. Finally, the conclusion of this thesis will be provided in Chapter5.