Mobile WiMAX下行通道估測之研究

Downlink channel estimation for mobile WiMAX system

柯凱元(Kai-Yuan Ke)

指導教授 ： 尤信程

國立臺北科技大學/電資學院/資訊工程系研究所/碩士(2010年)

https://doi.org/10.6841/NTUT.2010.00027

摘要

本論文主要討論mobile WiMAX下行系統下的通道估測方法，由於WiMAX訊號在無線傳輸中遭受到雜訊以及周遭環境的多路干擾，為能正確解調變需要通道估測來估測訊號在通道中所受到的影響，並將通道影響加以補償。本論文以IEEE 802.16e-2005無線通訊協定為標準，以軟體實現mobile WiMAX下行系統實體層模擬平台，再依照國際電信聯盟無線電通信組(ITU-R)模擬車輛移動的通道環境來做為此實驗平台之通道。本論文實作了一階線性內插、二維線性內插、二維立方內插、ML估測法、LMMSE線性內插、MMSE內插、時間維度MMSE…等通道估測之方法，並在數種通道環境及車速條件下比較各種方法之優劣。經實驗過後，發現在mobile WiMAX下行系統中，LMMSE線性內插、MMSE內插、時間維度MMSE與ML等方法並無法比二維線性內插有更好的效果，唯一較好的方式是將二維線性內插後的所有子載波點做ML濾波。因此，以複雜度而言，二維線性內插是較好的選擇。

關鍵字

WiMAX ； 通道估測 ； MMSE

並列摘要

This thesis studies various channel estimation methods for mobile WiMAX downlink reception. Due to noise, and multi-path interference in the wireless communication environment, the WiMAX signal is faded. Therefore we need to perform the channel estimation to estimate the channel response, and then to compensate for its influence. The thesis uses the physical layer of the IEEE 802.16e-2005 standard as the transmission technique under study. The simulation of the experiments are carried out using software. The channel environment for the experiments is adopted from ITU-R 3GVA and 3GVB models. The thesis studies the relative performance, in terms of BER, for the following channel estimation methods: one-dimensional linear interpolation, two-dimensional linear interpolation, two-dimensional cubic-spline interpolation, maximum likelihood estimator, linear minimum mean square error (LMMSE), minimum mean square error interpolation, time domain MMSE … and so on. Throughout the experimental results we find that two-dimensional linear interpolation is more suitable than other methods in mobile WiMAX downlink system. One possible method to obtain better estimation performance is to perform filtering on all interpolated subcarrier response through FFT and IFFT, which is optimal in the sense of maximum likelihood (ML). For practical applications requiring low complexity algorithm, 2-D linear interpolation is good choice.

並列關鍵字

Channel Estimation ； MMSE ； WiMAX

參考文獻

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