頻寬-空間-極化於寬頻多輸入多輸出無線電通道影響之研究

Abstract

為滿足下一代(B3G)無線通信系統的高傳輸速率需求，使用高頻寬並搭配多輸入多輸出(MIMO)天線技術是未來無線通信系統的發展趨勢，而其通道特性的掌握與適當模型的建構更是B3G無線通信系統發展之初的首要課題。 對寬頻MIMO通道而言，頻寬、天線間距及天線極化是影響其通道模型參數的主要因子。頻寬的增加代表系統時間解析度變好，多路徑延遲(multipath delay)及群聚(clustering)現象越明顯，窄頻之多路徑延遲模型必須修正以滿足寬頻系統通道之需求；而在多天線部份，除空間天線陣列架構外，極化天線的應用有助於在無線終端設備上實現多天線架構，因此，完整考量Space-Polarization相關性的MIMO通道模型，是MIMO技術設計發展所必需。 本論文完整探討Bandwidth-Space-Polarization對寬頻MIMO通道之影響，發展一創新之寬頻通道模型參數預估方法，可由窄頻通道模型參數預估寬頻通道參數模型。另外吾人也針對室內環境，發展三維空間幾何散射模型，該模型結合幾何圓模型與幾何橢圓模型之概念並將之拓展至三維空間，可用以模擬空間/極化陣列天線MIMO通道的相關性。除此，吾人也透過實測數據分析，探討UWB-MIMO於身域環境(BAN)之效能。本研究所發展之寬頻通道模型參數預估方法與MIMO通道相關性模型，皆經由實測數據分析獲得驗證，實測環境包含室外寬頻(120 MHz)、室內及身域環境之超寬頻(3-10 GHz頻段)通道量測，完全符合下一代無線通信系統之需求。

To achieve high data rate requirements of systems beyond 3rd generation (B3G), development and standardization of enhanced radio access technologies with wide bandwidth and multiple-input multiple-output (MIMO) antennas are sustained. In wireless communication systems, radio channels play an important role on system performance. Therefore, a through understanding of wideband MIMO channel characteristics is essential for B3G wireless systems developing and realization. Compared to traditional narrowband single-input single-output (SISO) channels, bandwidth, array spacing and antenna polarization effects should be taking into account in the models of wideband MIMO channels. For systems with larger bandwidth, it is possible to observe more multipath components, and therefore stronger clustering effects due to its better time resolution. For MIMO systems, in addition to spatial arrays, the utilization of polar arrays is of great interest recently due to its benefit to the device compactness. Therefore, a complete MIMO channel model should include the space factor as well as the polarization factors. In this research, effects of bandwidth-space-polarization on UWB/wideband MIMO channels are investigated. Here, a novel method for wideband model parameters estimation is developed. Through this method, the model parameters of a wideband signal can be determined from those of a narrowband signal. Furthermore, a three-dimensional Geometrically Based Single Bounce Model (3D GBSBM), is proposed for indoor wideband MIMO channel correlation modeling. This model is extended from a 2D model, which combines the concept of the Geometrically Based Single Bounce Circle Model (GBSBCM) and the Geometrically Based Single Bounce Ellipse Model (GBSBEM). In this model, the effect of 3D multipath on sub-channel correlation of the spatial/polar arrays is taken into account. Finally, the performance of UWB-MIMO for body area networks (BANs) is investigated through channel measurements. The newly developed method and models are validated by broadband channel (120-MHz bandwidth) measurements in outdoors as well as ultra-wideband channels (3-10 GHz) in indoors and BANs, which is agreeable to the requirements of B3G systems.