Patent ID: 7469022
Filing Date: 2008-12-23
Classification: H04L

Abstract:
1. A symmetrical phase-shift keying (SPSK) method for data modulation, wherein each symbol in a transmission signal carries n-bit information and is transmitted with one of 2 n+1 directions, 2 n directions among the 2 n+1 directions regarded as default directions and the other 2 n directions regarded as complementary directions, each default direction having a corresponding complementary direction with a phase difference of π and representing the same n-bit information as the default direction, the SPSK method comprising: retrieving one of the default direction corresponding to a current symbol of the transmission signal; determining whether a phase difference between the retrieved default direction and a previous direction of a previous symbol in the transmission signal is less than or equal to π/2; transmitting the current symbol according to the retrieved default direction if the phase difference is less than or equal to π/2; and transmitting the current symbol according to a complementary direction that corresponds to the retrieved default direction if the phase difference exceeds π/2.