多極化MIMO 無線室內通道量測與建構

Abstract

通訊系統為了提高傳輸速率，因而在發射端與接收端使用了多單元天線架構，稱之為多輸入多輸出系統，其系統容量比傳統的一對一天線要來的高。本論文採用頻域向量通道響應系統量測從一對一到四對四的多輸入多輸出系統;並且在發射跟接收端使用多極化天線，於國立交通大學工程四館及電資中心內進行量測與分析。並且建構了多極化MIMO的通道模型經實驗驗證,適用性良好;而在通道響應量側，發現下列幾個現象:(1) 通道容量會隨陣列間距增加而增加,當其間距到0.7 或0.8波長將會到達飽和而不再增加,非直接波的通道容量比直接波更容易看出間距的影響,原因為其多從路徑較多的關係;(2)多極化天線的使用,距離的增加跟非直視波的環境可以讓多極化的影響更明顯,並可讓間距的飽和長度縮短且獲得較高的通道容量;(3)通道頻率響應為隨機分布的情況,距離變化對其影響不大(4)環境內散射物的影響對通道容量有改善的效果

Multiple-input-multiple-output (MIMO) systems have the potential to achieve very high capacities, The use of multiple antennas offers extended range and higher throughputs than conventional Single-input-single-output (SISO) systems. In this paper, we use multi-polarization antenna at both transmitter and receiver sides to analysis and measure channel response at 4th Engineering Building and MISRC. We also create a multi-polarized (MIMO) channel model validated by the measurement results. Some phenomena are observed from the measurement results and are summarized as the following: (1) It seems that the capacity increases as the elements spacing increases, which is due to the increase of de-correlation effect as the spacing increases. It is noted that this incremental saturates asymptotically when the array spacing is larger than 0.7 λ or 0.8 λ. It is found that the array spacing has not much effect on the capacity in LOS situation especially when the number of array element is small. However, when the number of array element is large and the total array length is also large, the overall de-correlation effect due to array spacing is increased and the MIMO capacity is increased. The richness of multipath components in NLOS situations made all phenomena become more obvious. (2) It is found that polarization mismatch of array elements can increase the capacity. It is noted this effect may be enhanced by increasing the propagation distances. It is found that mismatch polarization can decrease the saturation length to 0.7 or 0.8 wavelengths. (3) The measurement results show that MIMO capacity frequency response is distributed randomly and changes slightly with propagation range. (4) The local scatterers around Tx/Rx array enhance MIMO capacity.