With the improvement of the demand for multimedia data and huge data , people urgently need more great transfer ability, but the limited VBI resource is unfitted to transport the huge data.

• 现有的传输方式是利用电视频道的场逆程资源来传输数据，随着信息数据的增加，图像、音频等大容量、宽带数据的需求，迫切要求提供更大的容量数据传输能力。