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  ______     ___                _____    ______   
 /_   _//   / _ \\    ____     |  ___|| |      \\ 
 `-| |,-   / //\ \\  |    \\   | ||__   |  --  // 
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   |_||   |_||  |_|| |  __//   |_____|| |______// 
   `-`'   `-`   `-`  |_|`-`    `-----`  `------`  
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發送短信 : LDPC code and PPM modulation in free space optical communication system