中國地面數位電視廣播DMB-T/H目前已被ITU列為國際正式標準之一，採用時域同步正交分頻多工調變技術(TDS-OFDM)，其特點為利用保護區間放置PN序列實現快速同步與通道估測的能力，在資料部分有單載波以及多載波兩種調變模式，其中單載波調變並利用頻域等化方法(SC-FDE)在過去幾年中常被提出討論，此一傳統架構擁有較低的峰對峰值比(PAPR)和對相位誤差較不敏感等特點，適合拿來用作HDTV廣播系統或水下通訊等應用，但卻較無法對抗深度的頻率衰減通道。本論文針對單載波的規格訊號，使用PN595作為保護區間，探討通道估測與等化的課題。 TDS-OFDM主要依賴保護區間的PN序列來做通道估測，將其移除後系統等效為ZP-OFDM適用其相關等化演算法；本篇利用倍取樣的方式提高模擬精準度，考慮了通道延遲時間不在符元時間的整數點上時，取樣後看到的通道會包含因為濾波器產生的旁帶效應(sidelobe)，間接影響系統效能。因此參考比較不同的通道估測演算法，並針對傳統方法中使用臨界值濾除估測通道中雜訊的做法，探討其對於小數延遲時間產生之濾波器旁帶效應造成的影響；在等化方法中比較了線性和決定回授等化方法對於不同通道之優勢，目的是希望能針對特定的通道設計接收機，以電腦模擬並實際觀察細節，調整其中參數以達到降低複雜度和提高性能的效果。 ;Chinese Digital Terrestrial Multimedia Broadcast (DTMB), Previously known as DMB-T/H (Digital Multimedia Broadcast-Terrestrial/Handheld), has now been listed as one of the official international DTTB (Digital Terrestrial Television Broadcasting) Standard. Use time-domain synchronous orthogonal frequency division multiplexing modulation technique (TDS-OFDM), which is characterized by using PN sequence as guard interval, having the ability to achieve fast synchronization and channel estimation. In the frame body (FB) there are two kinds of modulation mode, single-carrier and multi-carrier in which a single carrier modulation and frequency domain equalization method (SC-FDE) has raised for discussion in the past few years, this traditional architecture has a lower peak-to-peak ratio (PAPR) and less sensitive to the phase error, which is suitable for applications such as HDTV broadcasting or underwater communications system, but it cannot be against the frequency doubly selective channel. In this paper, we discuss the channel estimation and equalization for the single-carrier specification signal, using PN595 as a guard interval. Channel estimation mainly dependent on the PN sequence, after its removed and the system is equivalent to the ZP-OFDM and compatible to its equalization algorithm. And we consider more practical situation to improve simulation accuracy by using upsampling, at the same time channel delay time is not on integer symbol period time, and there has sidelobe effect by the pulse-shaping filter which is resulting from the channel fractional delay after sampling at the receiver, will affect system performance. Therefore we compare different channel estimation and equalization algorithms for particular channel model represented different classic situation and design the receiver, using computer simulation and observation of details, hope to adjust the parameters to achieve the effect of reducing the complexity and improve performance.
