本論文是對IEEE 802.16標準之正交分頻多工(OFDM)工作模式，在通道估測及等化器做一探討。OFDM系統具有抵抗多重路徑干擾及頻譜使用效率高等優異特性，其中抵抗多重路徑干擾是藉由CP及多載波之特性以達到免除ISI及ICI，而頻譜使用效率高則是運用多載波正交特性達到的。在循環字首的保護下，多路徑通道對各載波的影響在於其振幅與相位的失真，因此在個子載波之通道等化只需一個複數係數(One-tap)以修正其失真，而其成功要件則在於各子載波之通道頻率響應估測。 本研究以實現複雜度許可之前提下，針對IEEE 802.16系統進行穩定通道之通道估測及等化演算法的模擬與設計實現。其中模擬實現結果亦有助於了解OFDM 傳收系統規格，如頻段、頻寬、子載波頻率間隔等與通道狀況對接收性能的影響。接收端利用最小平方估測法及內插運算求出每一個子載波通道頻率響應，正確的還原訊號。並以Verilog 語言撰寫所設計之系統，搭配Modelsim軟體進行模組驗證。 This thesis investigates on channel estimation and equalization in the Orthogonal Frequency division Multiple (OFDM) mode of the IEEE 802.16 standard. OFDM systems exhibit superior characteristics with simplicity in combating multi-path transmission and have efficiency in spectral utilization. The effects of ICI and ISI arise from the multi-path interference could be successfully eliminated by the insertion of cyclic-prefix. Furthermore, the advantage of spectral efficiency is achieved by the orthogonal property. Under the protection of cyclic-prefix, multi-path effect causes distortion of amplitude and phase only. In accordance with the exact channel estimation among sub-carriers, the distortion could be compensated by one-tap complex coefficients. With the consideration of hardware implementation, the algorithms of the channel estimation and equalization are investigated and simulated for static channels for IEEE 802.16 systems. Moreover, the dependence of the receiving performance upon relationships between channel conditions and system specifications, e.g. transmission band, bandwidth, sub-carrier spacing, etc. would be clarified from simulation results. In the receiver, channel frequency response is obtained by utilizing a least square method, and we use an interpolation method to get channel frequency response of subchannels. We implement the schemes with the Verilog language and verify the function of modules with the ModelSim software.
