IEEE 802.16e系統之通道估計及多用戶非同步干擾消除

Abstract

802.16e系統因為通道變化快速以及有限的嚮導信號，通道估計顯得是一個相當大的挑戰。在本論文的第一個部分，吾人即採用一個簡單有效之通道估計法來克服此難題。利用802.16e系統中群組的嚮導信號之特殊架構，在時間軸以線性內插通道響應，再將其以二次曲線方式在頻率軸內插出其他子載波通道響應。模擬結果顯示，吾人所提出之通道估計法，即使在行動端移動速度達到時速100公里，也能達到良好的效能！而本論文的第二個部分，吾人考慮像是在802.16e系統中多個存取資料的OFDM系統下多用戶非同步干擾，以結合決策回授符元干擾消除和環形重建等方法來處理此問題。模擬結果顯示，吾人所提出之演算法，能有效降低多用戶非同步干擾，以及增強系統效能。

Due to possible fast mobile scenarios and limited pilot tones, channel estimation in an IEEE 802.16e system has been a challenging problem. In this first part of the thesis, we develop a simple and effective channel estimation method to overcome the problem. Using the special pilot patterns defined in 802.16e clusters, we interpolate the channel response with a linear function in the time axis, and that with a quadratic function in the frequency axis. Simulations show that the proposed method can achieve good performance even with the mobile speed up to 100Km/hr. In the second part of the thesis, we consider the problem of multiuser asynchronous interference (MAI) mitigation, arising in an OFDM multiple access system such as 802.16e. We combine the decision feedback inter-symbol-interference (ISI) cancellation and cyclic reconstruction techniques to remedy this problem. Simulations show that the proposed algorithm can reduce the effect of MAI, and increase the overall system performance.