應用動態差異演化法最佳化多輸入多輸出系統天線間距之通道容量研究

本研究提出應用動態型差異演化策略法（Dynamic Differential Evolution）於天線陣列排列在多輸入多輸出(multiple-input multiple-output )系統中。此最佳化方法有效提升平均的通道容量，這個問題也同樣探討最佳化選擇在發射端天線之間的天線間距。本研究中，亦探討多輸入多輸出窄頻系統通道容量的計算方法。本研究討論了使用在室內無線通道5千兆赫U-NII ( Unlicensed-National Information Infrastructure bands )頻道的通道容量，且提出在窄頻無線通訊系統中對發射端天線陣列中天線間距的一個最佳化的程序。藉由射線彈跳追蹤法 (Shooting and Bouncing Ray/Image techniques, SBR/Image Techniques )對應不同的頻率響應( frequency responses ) 的發射端與接收端天線陣列中天線間距來計算，並由得到的通道頻率響應，而進一步來計算相應的通道容量 (channel capacity) 。藉由使用動態型差異演化策略法來最佳化天線陣列中的天線間距進而最大化通道容量。發射器中天線陣列是在整個室內環境中心與接收器中天線每0.03公尺均勻間距且有150個接收器每0.25公尺間隔平均分怖在整個環境中所有木頭製的桌子上。探討發射器中4種不同的天線陣列排列(線性天線陣列、L型天線陣列、T型天線陣列、方型天線)於直接波與非直接波不同條件的三種不同辦公室環境中：（一）在此環境中有兩個辦公室隔版在發射端的兩側，高度皆為1公尺。（二）在此環境中有兩個辦公室隔版在發射端的兩側，高度皆為2公尺。（三）在此環境中有兩個鐵櫃在發射端的兩側，高度皆為2公尺。在發射端需求尋找更緊密天線陣列的排列及目的達到更高的系統通道容量，思考天線陣列不同的配置排列距離，探討考慮發射端天線陣列中天線非均勻間距二分之一波長距離到一個波長距離與均勻間距二分之一波長距離排列的幾何形狀做為比較。這是值得研究的課題，探討是否改變環境的複雜度與隔板材質和考慮更多的無線電波傳輸的多路徑可以有效地提升平均的通道容量。數值計算結果表明，該方法用於最佳化天線陣列中的天線間距而使平均通道容量增加是有效的。L型天線陣列具有最高的通道容量和方型天線陣列具有最高的改善比率。

關鍵字

多輸入多輸出系統；天線間距；通道容量；動態差異演化法則；最佳化

並列摘要

The geometrical shape of antenna arrays for maximizing the average channel capacity of the system in a multiple-input multiple-output (MIMO) link is investigated. The optimum element spacing of the transmitting antenna is also included. In this paper, channel capacity of multiple-input multiple-output narrowband system in indoor wireless channels at 5-GHz U-NII (Unlicensed-National Information Infrastructure) bands is calculated. An optimization procedure for the element spacing of the antenna transmitter in narrowband wireless communication system is presented. The frequency responses of different transceiver antenna element spacing are computed by shooting and bouncing ray/image (SBR/Image) techniques, and the channel frequency response is further used to calculate corresponding channel capacity. The transmitter is in the center of the indoor environment and the receivers are uniform intervals distribution, which 150 measurements with 0.25m intervals in the whole wooden table in indoor environment. And the inter-element separation of Receiver antennas (Rx) is 0.03m. Linear shaped array, L shaped array, T shaped array and rectangular shaped array geometries with non-uniform inter-element spacing are investigated for both line-of-sight (LOS) and non-LOS (NLOS) scenarios. The optimal element spacing of antenna for maximizing the channel capacity is searched by dynamic differential evolution (DDE). Numerical results have shown that our proposed method is effective for increasing average channel capacity. It is also found that L shaped array has the highest channel capacity and the improvement ratio for rectangular shaped array is largest.

並列關鍵字

DDE ； channel capacity ； narrowband ； SBR/Image

參考文獻

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應用動態差異演化法最佳化多輸入多輸出系統天線間距之通道容量研究

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