| 摘要: | 本文主要研究超寬頻系統結合多輸入多輸出之通道容量研究，一方面，超寬頻系統本身即具有高通道容量的特性，另一方面，多輸入多輸出可以有效的用來增加通道容量，為了滿足未來高傳輸率的需求，合併此二者是可以預期的。根據理論，超寬頻系統結合多輸入多輸出可以明顯的提升系統容量，然而，當應用在真實的環境裡，某些問題是需要進一步克服的。因此，本文以此合併系統為基底，分析此系統通道容量在真實的環境裡計算的問題，並提出適合的解決方法。
藉由儀器測量去取得通道特性是最直接且有效的方法，但是，此方法往往耗時、昂貴且具有諸多限制，相較於此，藉由模擬可以解決此缺點。然而，模擬的準確性是必需的，因此，本文提出兩種模擬方法，並將之與某篇相關文獻中利用儀器測量的結果做比較，研究結果證明藉由此二模擬方法是否可以有效解決儀器測量的缺點，且具有良好的準確性。
本文藉由模擬去計算此合併系統在真實環境下之通道容量，首先計算對稱天線部署與非對稱天線部署對此系統之通道容量，以往多輸入多輸出大部分都是使用對稱天線部署，然而，在某些情況下，非對稱天線部署反而比對稱天線部署來的適合，研究結果將用來判定何種天線部署最適合此合併系統。
其次，在單一共通道干擾影響下，計算此合併系統的通道容量，對於蜂巢式系統而言，因為有大量的共通道干擾存在，所以此干擾可以假設成隨機變數，然而，此假設可能不適合此合併系統，因為此系統屬於無線個人區域網路且共通道干擾來源少，研究結果將用來判斷是否多輸入多輸出具有抵抗共通道干擾的能力，此外在共通道干擾下，不同天線陣列應用於此合併系統的影響也被量化呈現。
This dissertation focuses on the research of channel capacity of multiple-input multiple-output ultra-wide band (UWB) systems. On the one hand UWB systems possess a nature of high channel capacity, and on the other hand multiple-input multiple-out (MIMO) approach can be used to enhance channel capacity effectively. Thus, it is expectable that UWB systems can be combined with multiple-input multiple-output approach to fulfill the necessity of high transmission rate in the future. It is well-known that UWB systems combining multiple-input multiple-out approach can yield high data rates in theory. However, some problems must be overcome further in order for the combined system to work in the realistic environment. As a result, this dissertation analyzes the problems on channel capacity of the combined system in the realistic environment, and proposes a suitable method to tackle them.
By measurement is the most direct and useful method to predict channel characteristics of the realistic environment, but the method is often expensive, time-consuming and having a lot of natural restrictions. In contrast to measurement, the same process can be carried out through simulation to overcome these drawbacks as long as the accuracy of the simulation can be proven. Therefore, this dissertation proposes two simulation methods, and they are compared with the measured results given by related works in the literature. Our study results demonstrate that the simulation methods not only can eliminate the drawbacks of measurement but also yield good computation accuracy.
This dissertation calculates the channel capacity of the combined system by simulation in the realistic environment. First, the channel capacity affected by symmetric and asymmetric antenna deployment is calculated. Symmetric antenna deployment is used for multiple-input multiple-out in most researches. However, asymmetric antenna deployment is more suitable than symmetric antenna deployment in some scenarios. The study results are used to decide which deployment is suitable for the combined system.
Next, the channel capacity of the combined system with single co-channel interference is calculated. Since a lot of co-channel interferences exist for cellular systems, the interferences can be assumed as random variable. However, the assumption may be unsuitable for the combined system because the system belongs to wireless personal area network (WPAN) and just few co-channel interferences exist. The study results are used to decide whether MIMO can effectively reduce co-channel interference (CCI), and quantify the effects of applying different antenna arrays on the combined system. |
