基於正交時頻空間調變設計最佳化功率頻譜密度以降低頻帶外發射

Abstract

本論文提出一個基於正交時頻調變(OTFS) 的新傳輸架構，及其收發機的最佳化設計。OTFS 是近年來被提出的一項新型傳輸方式，適用於高都普勒頻率偏移的環境下，具有高偵測信度(high detection reliability)，但在OTFS 中使用方波(rectangular pulse) 會導致頻帶外發射(OOBE) 過高，這項缺點會導致OTFS 在多使用者(multi-user) 的情境中不適用。本論文將OTFS 的譜密度(PSD) 函數導出，並為了解決OOBE 的問題我們設計了發射脈衝(transmitted pulse) 的最佳化問題，並且考慮接收端的雜訊增強損害（noise enhancement penalty）的情況下，最小化OOBE ，為了解決問題中的二階等式的限制，我們引進了Dattorro iterative algorithm。模擬結果顯示在高速的情境中，提出的方法在頻帶外發射(OOBE) 的表現會勝過使用方波，在位元錯誤率的表現會勝過Prolate Spheroidal Waveforms (PSW)。

A new transmit scheme based on Orthogonal Time Frequency Space modulation (OTFS) is proposed in this thesis. OTFS is a recently proposed waveform for reliable communication in high-speed vehicular communication scenarios. But using rectangular pulse shape in OTFS results in high out of band emission (OOBE), which is undesirable for multi-user scenarios. In this thesis, we formulated the power spectral density of OTFS. And to reduced the OOBE, we formulated a optimization problem of transmit pulse. In ordered to deal with the optimization problem we introduced the Dattorro iterative algorithm. Simulation results reveal that our propose method reduced the PSD compare with using rectangular pulse. And the BER performance is better than PSW waveform. Hence, we see trade of between of out of band emission and bit error rate of the OTFS system.