正交分頻多工超寬頻系統之多重路徑效應及可適用位元分配

Abstract

在本篇論文中，根據電機電子工程師協會(IEEE)所制定的802.15.TG3a提案，我們實現了每秒200 Mega位元組的正交分頻多工超寬頻的系統。在正交分頻多工超寬頻的系統中所使用的通道模型是修改的SV通道模型。均等增益結合分集(Equal gain combining diversity)和選擇分集(Selection diversity)技術是被用來評估系統表現以達成較低的複雜度。 為了檢驗在正交分頻多工超寬頻的系統在多重路徑表現，我們利用超寬頻的天線去量測真實的通道響應環境。這些量測的通道響應是被用在我們所建構的正交分頻多工超寬頻系統中。根據這些通道量測以及模擬結果，正交分頻多工超寬頻系統的循環字首(cyclic prefix)長度似乎太短。 最後，可適用位元分配演算法也被採用在我們所建構的正交分頻多工超寬頻系統中。我們修改了Chow Cioffi和Bingham所提出的可適用位元分配演算法來降低正交分頻多工超寬頻系統的錯誤率。

In this thesis, we implement the multiband OFDM UWB with data rate of 200Mbps according to the proposal of IEEE 802.15.TG3a Working Group. The modified SV channel model is applied in the multiband OFDM UWB. To achieve lower complexity, the equal gain combining diversity and selection diversity techniques are adopted in the evaluation of the system performance. We measure the channel responses of the realistic environment by using “Ultra Wideband antennas” in order to examine the impact of multipath delay spread on the performance of the multiband OFDM UWB system. The measured channel responses are applied in the numerical simulation of the multiband OFDM UWB system. According to the result of channel measurement and numerical simulation, the cyclic prefix specified seems to be too short in multipband OFDM UWB systems. Finally, the bit loading algorithm is utilized in this system. We modified the Chow Cioffi and Bingham (CCB) bit loading algorithm and improve the BER performance of the multiband OFDM UWB systems by the adoption of the modified CCB bit loading algorithm. The simulation results support our claim.