Differentially coded and guard pulse position modulation for communication networks

U.S. Patent Number: 5394410

Abstract: In a wireless infrared communications system, a technique for encoding data for serial transmission and the correlative technique for decoding the transmitted data. A data transmission period is divided into a plurality of slots. In a given pair of slots, the first slot comprises a gray code sequence of bits and a check bit, and the second slot comprises the same gray code sequence of bits and the complement of the check bit in the first slot. The last slot in a transmission time period comprises a guard slot to separate transmission time periods. A decoder receives the encoded data, and for a given slot derives calculated data for the slot from the gray code sequence of bits and the check bit. The check bit for the given slot is compared with a calculated check bit of the previous slot to determine if a predetermined relationship exists. If the predetermined relationship exists, the received encoded data is selected as the output of the decoder, and if the predetermined relationship does not exist, the calculated data is selected as the output of the decoder. The calculated check bit is derived from the output of the decoder for a slot, and is compared with the check bit of the encoded data for the following slot.

Inventors: Chen; Kwang-Cheng (Menlo Park, CA)

Assignee: International Business Machines Corporation (Armonk, NY)

Application Number: 07/968,726

Issued: 1995-02-28

Expired: 2007-02-28

Classes: 714/823

Field of search: 371/70,47.1,42 375/114,116 360/40

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