Patent ID: 7965793

Claim:
A method for transmitting data in a digital communication system, the method comprising: a) selecting a subset of all available modulation states in a pre-determined modulation scheme, to be used for transmission; b) a first transmission step of transmitting a first symbol representing a first plurality of bits, the first symbol having a first modulation state comprised in said subset; and c) at least one further transmission step of transmitting further symbols representing the first plurality of bits, each of the further symbols having a further modulation state comprised in said subset, wherein addition, for each combination of bit values, of complex values associated with said first and said further modulation states, yields the same phase of a complex result for all combinations of values of the bits within the plurality of bits, and wherein: the first modulation state is obtained according to a first mapping of bit value combinations to modulation states; the at least one further transmission step comprises exactly one further transmission step; and the one further modulation state is obtained according to a second mapping of bit value combinations to modulation states; wherein the second mapping of bit value combinations to modulation states is obtained from the first mapping of bit value combinations to modulation states by: i. dividing a complex plane representing the first mapping of bit value combinations to modulation states into at least two non-overlapping adjacent sub-planes; ii. determining symmetry axes for at least a part of the sub-planes with respect to modulation states comprised within each of the part of the sub-planes; and iii. assigning to at least a part of the bit value combinations a complex value in said second mapping, having a position in the complex plane which is essentially mirrored from a position of a complex value assigned to said bit value combination according to a first assignment, with respect to a point on the symmetry axis of a sub-plane in which the complex value according to said first assignment is located; and wherein the subset of modulation states to be used for the transmissions comprises all modulation states within one of the at least two sub-planes.