在各項微波傳輸技術中，LMDS 可以說是最受到注目的，它是雙向數位蜂巣式通訊系統，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。但是，在LMDS系統中雨衰及細胞內干擾是影響服務品質之重要因素。因此為了減少LMDS系統中因為雨衰和細胞內干擾的問題，造成頻寬不必要的浪費。我們提出新的想法，利用LMDS系統分析的結果，建立模糊控制的歸屬函數與規則，來判斷通道品質的好壞來，決定碼率的使用，運用錯誤更正碼之LDPC碼改進LMDS系統的效能。根據系統的干擾環境影響下，減少冗餘碼的使用增加頻寬，來決定調整碼率， 在不損失誤碼率下，提升頻寬效益。 In every microwave transmission technology, LMDS can be said and receive the note purpose most. LMDS system is a two-way digital cellular system operating at 20-50 GHz. It offers the multiple services of the audio, video, multimedia and data transmission and can meet all kinds of users' demands. However, it is to influence the important factor in LMDS system which is rain attenuation and inter-cell interference (ICI). Therefore, LMDS is affected the interference problem by rain attenuation and inter-cell interference (ICI). Avoiding the band-width unnecessary waste, we proposed new idea that is the fuzzy-based rate compatible LDPC code for LMDS system. It utilized fuzzy control and according to the LMDS system channel quality to determine the code ate. We simulated the LMDS system interference factors such as rain attenuation, Cross-Polarization Discrimination (XPD) and beam-width. Those factors will be influence the LMDS system performance. The fuzzy membership function and fuzzy rule was defined by LMDS simulation results. And we implement the LDPC code of error correction coding to increasing the system performance and reduce the redundancy bit. Base on LMDS system does not loss Bit-Error-Rate and got the good spectrum efficiency.
