Conventionally, various techniques regarding a method of coding data which is to be transmitted through a communication channel have been suggested. For example, Patent documents 1 and 2 disclose a coding method which is called a pulse position modulation (PPM) method. According to a PPM method, respective pieces of 2-bit data representing “00”, “01”, “10”, and “11” are converted into respective pieces of 4-bit data representing “1000”, “0100”, “0010”, and “0001”, for example.
On the other hand, Patent documents 3 and 4 disclose a coding method which is called a coded mark inversion (CMI) method. According to a CMI method, 1-bit data representing “1” is converted into alternately 2-bit data representing “11” and 2-bit data representing “00”, and 1-bit data representing “0” is converted into 2-bit data representing “01”.
Patent document 3 also discloses a technique for transmitting a frame sync signal by utilizing coding rule violation (CRV).
In the meantime, in a communications system, there is a need for a technique for regenerating a pulse signal which has been generated at a transmitting end, at a receiving end, in some cases. In an infrared communications system as described in Patent document 2, for example, binary data is transmitted from a transmitting end by causing infrared light to flash, and then, at a receiving end, the infrared light transmitted from the transmitting end is received and binary data is generated from a signal of the received infrared light. Since binary data can be regarded as a pulse signal, it is possible to obtain binary data transmitted from the transmitting end by regenerating the pulse signal which has been generated at the transmitting end, based on the signal of the received light at the receiving end.
Patent Document 1: Japanese Patent Application Laid-Open No. 2000-134186
Patent Document 2: Japanese Patent Application Laid-Open No. 2000-267771
Patent Document 3: Japanese Patent Application Laid-Open No. 8-18611
Patent Document 4: Japanese Patent Application Laid-Open No. 2002-94488