Abstract
Wireless communications has become an extremely important technology nowadays. Its landscape will continue to experience dramatic changes due to the emergence of new systems. Lately, there have been significant R&D activities in the development of a future (often referred to as 4G) wireless infrastructure. In February 2002, the FCC ruled that communications in the 3.1 to 10.6 GHz could be overlaid over existing systems if certain power constraints are met, thereby opening up a completely new approach to wireless communications known as ultrawideband (UWB). UWB has great potential to revolutionize traditional wireless technologies owing to its capability to resolve multipath distortion, its ability to penetrate through different materials, and its immunity to interference effects. UWB holds the promise of offering high-rate wireless broadband data access at low cost. Recent studies reveal that multipath fading, when appropriately exploited, can significantly increase the system capacity. Multiple input multiple output (MIMO) is one newly proposed wireless communication system to achieve such goal. In this project, we will focus on the channel characterization for UWB and MIMO systems. Statistical analysis of fast and slow fading will be carried out based on simulated signals using formal electromagnetics site-specific modeling and also measurements. Simulations will be conducted in both frequency and time domain using ray-tracing techniques with acceleration schemes, approximate analytic methods and fast solutions of Maxwell equations. For UWB studies, both single-band UWB system and multiband UWB system will be simulated. By analyzing the shape of time domain output signal, effects due to the distortion and the low-delay multipaths will be examined. The channel transfer matrix for MIMO applications will be calculated. The effects of coupling of antenna elements on the rank of the channel transfer matrix will be studied as well.

Contact Information
Mr H Y Wong
Director, Technology Transfer Office
City University of Hong Kong
83 Tat Chee Avenue
Kowloon, Hong Kong
Tel : (852) 2788 8428
Fax : (852) 2788 9119
Email : hy.wong@cityu.edu.hk

簡介
當前無線通訊已成為一種非常重要的技術。由於新的系統不斷湧現，它的應用前景將繼續發生巨大的變化。最近，在未來的無線底層結構研究（常稱為4G）中有許多重要的研發活動。在二零零二年二月，美國通信委員會規定，如果允許一定的功率制約，那麼在3.1到10.6GHz頻段的通信能在現有的系統疊加，於是將開創一個全新的，即稱作為超寬帶（UWB）的無線通信。基於超寬帶無線通信抗多徑失真能力、滲透到不同材料的能力和抗干擾能力，它將對傳統無線通信產生巨大的變革。超寬帶技術能以低成本傳輸高速率無線寬帶資料接入。最新研究表明，如果適當採用多徑衰落可大大提高系統容量。多輸入/輸出（MIMO）是一種達到這種目的的最新無線通信系統。在這種方案，我們關注超寬帶（UWB）和多輸入/輸出系統（MIMO）的通道特徵。利用電磁學特定場所模型和測量，基於仿真來實現快衰落和慢衰落的統計分析。利用具有加速功能的射線追蹤技術、近似分析方法和Maxwell方程組的快速解法在頻域和時域進行仿真。至於超寬帶研究，需要類比單頻段組和多頻段組兩種系統。通過分析時域輸出信號的波形，來檢測失真和低時延多徑的影響。計算多輸入/輸出（MIMO）的應用對通道傳輸矩陣的影響。同時分析天線單元的耦合對通道傳輸矩陣的秩的影響。

查詢
香港城市大學技術轉移處處長黃漢儀先生
地址 : 香港九龍達之路83號
電話 : (852) 2788 8428
傳真 : (852) 2788 9119
電郵 : hy.wong@cityu.edu.hk