在載波聚合正交分頻多工系統下之通道估測方法

Abstract

在這篇論文中，我們會提出在載波聚合正交分頻多工下肢通道估測的方法。載波聚合LTE協定裡其中一種非常吸引人的特徵，他可以允許使用者聚合不同頻帶來達到所需求的頻寬，以提升所需的資料傳輸效率。不同頻帶的通道頻率響應事實上是非常不同的，但是所對應的通道脈衝響應其實是從相同的多路徑模型所推導出來，我們可以利用此特性去將不同的頻帶整合起來一起做通道估測，來達到更佳的通道估測效能。我們會在這篇論文利用載波聚合的特性，提出不同的通道估測方法。首先我們先提出子空間盲通道估測方法，新提出方法的效能優於前人提出的盲通道估測方法。接著我們提出利用一些已知的資料來估測通道的方法，叫做引導數據通道估測方法，模擬結果也顯示出我們提出的通道估測方法的效能都優於前人提出的方法。

In this thesis, we will investigate advances of signal processing techniques for subspace-based blind and pilot-assisted channel estimation in carrier aggregation (CA) orthogonal frequency division multiplexing (OFDM) systems. Carrier aggregation is one of the most distinct features of 4G systems including LTE Advanced, which is being standardized in 3GPP as part of LTE Release 10. This feature allows scalable expansion e ective bandwidth delivered to increase overall data rate. The channel frequency responses of individual component carriers are quiet di erent due to the nature of frequency selective channels induced from multipath environment. But these frequency responses can actually be derived from the same channel impulse response determined by multipath conditions. Based on this property, we propose to take advantage of the correlation present among di erent component carriers of the same physical link. For the initial step to explore this topic, we apply blind channel estimation, which have been largely studied due to high bandwidth e ciency. In communication systems employed with cyclic pre xes (CP), subspace-based (SS) methods are among the most popular categories of blind channel estimation schemes. Since existing blind channel estimation methods are only applied in single frequency band system, the idea of combining data from multiple frequency bands is proposed. Simulation results show that the proposed method outperforms all previously reported methods. Another important problem, namely the pilot-assisted channel estimation, is also studied in this thesis. Pilot-assisted channel estimation method can be divided into two methods: pure pilot-assisted method and semi-blind method. In all previously reported methods, pilot-assisted channel estimation methods are only applied in single component carrier system, we extend the estimation to multiple bands system. Simulation results show that the proposed method outperforms the previous pure pilot-assisted and semi-blind methods with the same number of pilot samples.