A novel symbol synchronization is presented with frame synchronization of PPM. On the basis of analyzing frame sync code pattern and length, a PPM frame scheme is designed.
The bits of each successive 4-ary output symbol are then interleaved, producing an output bit-stream which has global and interleaved run-length constraints.
然后交错每个连续四进位输出符号的位，从而产生具有全局且交错的连串长度约束的输出比特流。
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Otherwise, it should be checked from one known point to another with proportional anti-symbol allocation between closing error and the length of side.