正交分頻多工傳輸上傳頻率同步

Abstract

本篇論文主要介紹IEEE802.16e正交分頻多工存取(OFDMA)的上傳頻率同步，在此主要討論為何要做同步、解決的演算法、以及模擬的結論等議題。在估測頻率偏移量時，估測效能會被多用戶干擾以及多路徑衰減(multi-path fading channel)通道嚴重影響估測效能，且要同時準確的估測多個用戶的頻率偏移量時是多維度的問題，所以是屬於高複雜度的運算，在實作系統上幾乎是無法實現的。在此利用EKF(Extended Kalman Filter)演算法將高維度的問題降低成為單一維度的遞迴式運算的問題，並且結合了IEEE 802.16e提供的兩個initial ranging symbol讓估測效能可以達到802.16e所規定的範圍內。由模擬可以看出我們所利用的估測方法可以有效的在正負1(經過正規化的頻率偏移量)範圍內的頻率偏移量可以有很好的估測效能，並且可以在802.16a以及802.16e上都適合利用此種方法來估測頻率偏移量。

This thesis introduces the frequency synchronization of IEEE 802.16e uplink OFDMA systems. We will discuss why we need to synchronize and algorithms and simulation results. Multi-path fading channel and multiple access interference will degrade the performance of carrier frequency offset estimation in IEEE 802.16e uplink OFDMA system seriously. The exact solution to estimate the carrier frequency offset turns out to be very complex because it is a search for a multidimensional domain. So it isn't suitable for practical system. This thesis will use the Extended Kalman Filter algorithm to estimation carrier frequency offset, this method replace above search with a recursion of one-dimensional search. We shall associate the two OFDMA symbols with EKF algorithm, it can increase our estimation performance inside the range of IEEE 802.16e defined. Simulation results show that it has a good estimation performance inside one (normalized carrier frequency offset), it is also suitable for the 802.16a system and the 802.16e system.