區域多點分配服務系統（LMDS）為點對多點的固定式無線寬頻存取服務，是使用在 20-50GHz雙向數位式細胞系統，可提供高速服務，如雙向的語音、多媒體、數據傳輸及寬頻等，雨衰及細胞內干擾是影響LMDS系統服務品質的二個主要因素 。本篇論文針對影響LMDS系統效能的雨衰、波束寬、差級化等三個參數進行性能分析，發現雨衰影響最為明顯。 為了減少LMDS系統中雨衰之影響，本篇論文採用優異的通道編碼技術低密度同位元檢查碼，其錯誤更正能力可以接近shannon 的理論值，並提出相容碼率低密度同位元檢查碼方法，提供不同編碼率，用戶能根據通道品質選擇合適碼率，減少冗餘位元和改進傳輸率，通道品質好，則使用較高編碼率，通道品質差，則使用較低編碼率，至於通道品質之判斷，則採用適應性模糊推論系統塑造資料與自動創造模糊規則來判斷。模擬結果顯示提出基於適應性網路模糊推論系統相容碼率低密度同位元檢查碼方法方案較未使用相容碼率低密度同位元檢查碼獲得提升之傳輸率，但未損失其位元錯誤率。 Local Multipoint Distribution Service（LMDS）is the point to multi-point fixed wireless broadband access system and it is two-way digital cellular system operating in 20-50 GHz to provide high-speed service，such as broadband access 、data transmission、 two-way audio、 video、multimediaetc. Inter cell interference (ICI) and rain attenuation influence are the two major elements of Quality of Service (QoS) in LMDS system. In the thesis to analysis of performance to such three pieces of influence LMDS systems efficiency parameter as Beamwith ,rain attenuation, XPD, etc. and discover the rain attenuation is the major factors of definitive system performance in LMDS systems. In order to reduce the impacts on rain attenuation ， this thesis adopt mighty channel coding technologies Low Density Parity Check codes，Its error correction ability may approach shannon limit and propose Rate Compatible LDPC codes provide various coding rates and users can select suitable coding rates according to channel conditions, with respect to the rain attenuation to improve the performance of LMDS systems. The better the quality is, higher code rates are used to reduce the redundancy bit. As to the quality of channel conditions, we adopt ANFIS modeled the data with its own automatically created fuzzy rules to judge . Simulation results show that the proposed ANFIS-Based rate compatible LDPC code for LMDS systems compared with uncompatible LDPC code scheme leading improvement of Throughput. But not to loss the BER .
