Patent ID: 8391403
Filing Date: 2013-03-05
Classification: H04L

Abstract:
1. A method for transmitting signals in a digital communication system, said method comprising: a) a first mapping step comprising mapping a first plurality of bits to a first modulation state according to a Gray mapping of bit sequences to modulation states; b) a transmission step comprising transmitting said first plurality of bits by modulating a carrier according to said first modulation state; c) at least one inverting step, each at least one inverting step comprising obtaining at least one further plurality of bits by inverting bits of one subset of said first plurality of bits and keeping bits not comprised within said subset unchanged; d) at least one further mapping step comprising mapping said at least one further plurality of bits to at least one further modulation state according to said Gray mapping of bit sequences to modulation states; and e) at least one re-transmission step comprising re-transmitting said first plurality of bits by modulating a carrier according to said at least one further modulation state; wherein in step c) each said inverting step inverts all bits comprised within said subset of said first plurality of bits such that a number of different vector sum results obtainable, for all combinations of bit values within said first plurality of bits, by adding vectors representing complex values of said first and said at least one further modulation states in a complex plane, is lower than a number of different modulation states within said Gray mapping of binary numbers to modulation states, wherein said Gray mapping defines modulation states of a mixed modulation comprising amplitude shift key modulation and phase shift key modulation, and said first plurality of bits comprises an amplitude shift key set defining an absolute value of a complex value of a modulation state associated with said plurality of bits within said Gray mapping and a phase shift key set defining a phase value of a complex value of a modulation state associated with said plurality of bits within said Gray mapping, step c) comprising: i. at least one first inverting sub-step, carried out on the amplitude shift key set, wherein in said at least one first inverting sub-step: said Gray mapping defines modulation states of the amplitude shift key modulation, and step c) inverts all bits comprised within one subset of said first plurality of bits, said subset consisting of a bit which has an identical value for half of all pluralities of bits which are mapped to modulation states having a lowest transmission power of all existing modulation states, or step c) inverts all bits comprised within one subset of said first plurality of bits, said subset consisting of a bit which has an identical value for half of all pluralities of bits which are mapped to modulation states having a highest transmission power of all existing modulation states, or ii. at least one second inverting sub-step, carried out on the phase shift key set, wherein in said at least one second inverting sub-step: each step c) inverts all bits comprised within a subset of said first plurality of bits, said subset being a subset of the set of combinations from one to all but one of said first plurality of bits.