數位射頻干擾消除技術應用於超高速數位用戶迴路系統

Abstract

VDSL是利用大眾電話網路提供寬頻接取的服務。衍生出來的問題是此電話網路是使用無遮蔽效果的雙絞線，而且VDSL這項技術又與業餘無線電及AM廣播電台共享頻帶，如果在電話線路附近有一無線電發射端，則射頻訊號將會進入無遮蔽效果的雙絞線產生干擾，這種現象稱為射頻干擾(Radio Frequency Interference)。一般而言，業餘無線電對VDSL的訊號產生的干擾比AM廣播電台還嚴重，因此論文內容著重於處理業餘無線電對VDSL產生的干擾。關於RFI 演算法的模型，最簡單的模型是假設每個 Zipper VDSL字符時間中的RFI波封為常數[9]。但是在ETSI VDSL的系統中，每個字符時間比Zipper VDSL長數倍，所以RFI波封有時後並不為常數，因此使用此模型並不完全準確。我們提出一個較為準確的RFI演算法的模型來達到消除RFI的目地。模擬的結果可以證明我們演算法是可以有效消除RFI。

VDSL is a promising technology of unshielded twisted pairs in the public telephone network for the purpose of broadband access. A problem with this technology is that the frequency range used for VDSL signaling is shared with amateur radios and broadcast AM radios. A transmitter in the proximity of a wire will induce an electrical signal in the wire; this is called Radio Frequency Interference (RFI). In general, amateur radio (HAM) is more harmful than AM in VDSL. In this paper, we will focus on dealing with amateur radio. In regard to RFI model, the simplest model is zero-order with a constant RFI envelope in one Zipper VDSL symbol period [9]. But in ETSI VDSL systems, the symbol periods are several times longer than that of Zipper VDSL. The RFI envelop in one symbol may not be constant. Therefore, the use of such a model in digital RFI cancellation is not fully justified. We started with a more accurate RFI model and developed an improved way for RFI cancellation. Simulation results show support to our assumptions and the effectiveness of our algorithm.