在各項微波傳輸技術中，LMDS可以說是最受到注目的，因為它可以提 供雙向的語音、影像及數據傳輸的寬頻整合服務。LMDS能夠滿足各類型的 用戶分佈與應用，從住家到商業用途均能提供服務，因此更具有彈性及擴 充性。台灣在去年(2000)三月十九日發放固網執照，即使有線寬頻傳輸應 是其競爭的主軸，然而仍有業者藉助固定無線傳輸技術的應用，以提高其 競爭力。由此可窺知LMDS的發展潛力。 為了有效降低LMDS中細胞間干擾的問題，本論文提出一個新的細胞規 劃，可以獲得較少的細胞間干擾，相關的分析討論詳見第二章。第三章， 分析多模式分碼多重擷取的技術，以減少使用者受到的干擾。第四章則討 論雨衰的影響。由分析可知多模式分碼多重擷取的技術只適用於降雨率小 的情況；在大雨時可藉由縮小服務範圍及功率控制(預留所需的降雨衰落 餘裕)來維持系統的正常運作。第五章是結論及討論。 LMDS is the most obtrusive among mini-meter wave propagation techniques. Because it can provide wideband integrated services including two-way voice, video, and data transmission. The asymmetry between downstream and upstream is quite consistent with the normal data flow, particularly for residential applications. Of course the spectrum can also be used to provide symmetric traffic that would typically be required for business applications. In chapter 2, we propose a new cell planning, which suffers less inter-cell interference in comparison with the typical cell planning. Chapter 3 analyzes the technique of multi-mode CDMA scheme can reduce inter-cell interference effectively in clear air. Besides, high rainfall attenuation is a significant challenges associated with deploying systems at Ka band. Chapter 4 studies the multi-mode CDMA scheme is adequate in small rain rate condition. In large rain rate situation, we can maintain system performance by reducing cell size or by the process of power control. Finally, chapter 5 gives the conclusions.
