| 摘要 |
Block coded digital data is communicated with associated overhead data in a data stream having a succession of coded blocks (106, 108 ... 110). Each block contains N symbols wherein M of the symbols (102) comprise information to be transmitted and the remaining N-M of the symbols (104) comprise error correcting data. The ratio M/N comprises a first information rate. The coded blocks (106, 108 ... 110) in the data stream are divided into a succession of frames (144, 146, 148, 150, 152, 154), each comprising F of the coded blocks. A frame overhead symbol (112) is added for each of the frames, to provide data necessary for a receiver function such as synchronization. The addition of the frame overhead symbols effectively lowers the first information rate to a second information rate M'/N', where M/N = (M' + b)/(N' + b) and b is an integer chosen to provide the second information rate at a desired value. N is less than 2<n> + 1, where n is the number of bits in each of the symbols. The number of coded blocks F in each frame is determined from the relationship F = M'P/(N-M)b. P is the smallest value integer that will render F an integer, and is also the number of overhead symbols added per frame. A plurality of X of the frames are formed into a superframe (100) containing FX coded blocks and PX frame overhead symbols. X is chosen to provide enough n-bit frame overhead symbols to implement the desired receiver function. <IMAGE> |
