於電話線上傳輸56kbps的數據機最近成爲熱門之話題，本研究根據Us Robotics[1]與Rockwell Semiconductor(RSS)[2]二家數據機的發展方法論，做一番探討，並朝類似方向嘗試設計一56kbps的數據機。我們知道傳統V.34 33.6kbps的傳輸方法與56kbps的方法不一樣，但56kbps傳輸只存在於下載，而上傳仍然33.6kbps傳輸所以本研究著重在下載的傳輸方法，也就是Trellis coding中的PAM傳輸。
The 56 kbps data transmission in telephone network has been a popular topic recently. In designing a 56kbps modem, the Trellis coded modulation plays an important role, This research emphasizes the encoder design for the 56 kbps modem based on the methodology used in the US Robotics [1] and Rockwell [2], the major two players in this competing market. A 256-PAM trellis encoder is designed followed by simulation test of the performance.
