LMDS (Local Multi-point Distribution Service) 有釵h好處，例如：能提供寬頻的服務、架構建立較簡單、硬體設備花費較少等；而OFDM (Orthogonal Frequency Division Multiplexing) 對於ISI (Inter-symbol Interference) 、多路徑傳輸衰減有較大的抵抗能力。因此，本篇論文嘗試將兩者合併並加以模擬分析。 本篇論文首先設計傳送和接收端的模組，其中實體層的參數是參照IEEE 802.16所提供的標準[8]。通道模型是採用1999年在新加坡以LMDS為架構所測量而得的模型[6]，再加上兩種通道預測方法去模擬比較其效能。 論文中的模擬結果顯示： (1) 在LMDS的環境裡，OFDM對於多路徑傳輸衰減的抵抗力較傳統PSK、QAM的系統強。 (2) OFDM技術應用於LMDS系統，加上通道預測確實可以再提高其效能。 Local multipoint distribution service (LMDS) has three advantages: 1) large bandwidth 2) lower installation cost 3) ease of deployment [6]. Orthogonal frequency division multiplexing (OFDM) can solve some questions in communication systems, for example: inter-symbol interference, multi-path fading and so on. This thesis combines the OFDM technique with the LMDS system to simulate the OFDM-based LMDS system under the time-variant channel, which modeled by the measurement in Singapore [6]. And we use the two channel estimation methods, which one is linear interpolation method; the other is a novel method proposed in [3], to combat the interference of multi-path components. The simulation results show that 1) the performance of the OFDM system is better than of the traditional modulation systems in multi-path channel in LMDS environment 2) the channel estimation using pilot sub-carriers can improve the performance in the OFDM system.
