近年來,協力式波束成型在細胞間干擾消除中之效果引起了許多人的關注,
為了能夠促進協力式波束成型的運作,在網路的反饋鏈路中,有效率的交換
通道狀態資訊是必要的。從文獻中,我們發現在許多反饋方法中,通常是假
設對通道狀態資訊使用均勻量化,然而,對於使用協力式波束成型消除細胞
間干擾來說,干擾主要源自於量化誤差,因此均勻量化在統計上並非最佳的
方式。在論文中,我們針對此問題提出非均勻量化方法,使用有限的反饋位
元,針對出現機率較高的通道狀態資訊使用較多的量化位階進行量化以降低
量化誤差,如此可以更精確的表示通道狀態資訊並降低細胞間的干擾。為了
驗證此方法,我們針對不同的反饋位元數所導致的干擾功率進行數學分析,我
們也透過模擬結果證明此方法在使用較少反饋位元的情況下,亦可達到較高
的傳輸速率。

In recent years, the coordinated beamforming (CBF) has attracted many attentions because of its effectiveness in the inter-cell interference (ICI) mitigation. In order to facilitate the operations of CBF, efficient channel state information (CSI) exchanges through backhaul links are necessary. From the literature, we find that uniform quantization of CSI was generally assumed in the feedback schemes. Statistically, however, uniform quantization may not be optimal from the viewpoint of the ICI in CBF, which is mainly caused by the quantization error (QE). In this paper, with a limited number of feedback bits, a non-uniform quantization method is proposed to apply more quantization levels to represent the feedback CSI with higher probability. This is because more accurate representation of frequent CSI can lead to lower QE so as to reduce the ICI level in most cases. To prove the effectiveness of the proposed scheme, the ICI in the considered two-cell CBF scenario is analyzed with various numbers of feedback bits. Also, higher transmission rate, especially in the cases with fewer feedback bits, is also proved by simulation results.

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