A coding and modulation apparatus comprising - an encoder configured to encode input data into cell words, representing tuples of a codeword, according to a low density parity check code, LDPC, and - a modulator configured to modulate said cell words into constellation values of a non-uniform constellation and to assign bit combinations to constellation values of the used non-uniform constellation, wherein the coding and modulation apparatus is characterised in that said modulator is configured to use i) a non-uniform constellation, wherein - the constellation comprises 32, 64, 128 or 256 constellation points, - the constellation points in each quadrant of the constellation diagram either have a mirror constellation point in the same quadrant mirrored at the π/4 or -π/4 axis or lie on the π/4 or -π/4 axis, - the constellation points in each quadrant of the constellation diagram are symmetrical to the constellation points in all other quadrant, - at least one signal point within the signal points having same magnitude has an unequal angular distance to the neighbors in direct vicinity in angular domain, and - the Euclidean distance between two nearest neighboring constellation points in a quadrant is different for different pairs of nearest neighboring constellation points, or ii) a non-uniform constellation obtained from a constellation according to i) through rotation by an angle around the origin, through inversion of bit labels for all constellation points, through interchanging of bit positions and/or through predistortion for the constellation points, wherein said modulator is configured to use a non-uniform constellation, wherein in a quadrant there exists at least one constellation point lying on the π/4 or -π/4 axis and at least two constellation points with the same magnitude that is different from the magnitude of other constellation points in the same quadrant. - an encoder configured to encode input data into cell words, representing tuples of a codeword, according to a low density parity check code, LDPC, and - a modulator configured to modulate said cell words into constellation values of a non-uniform constellation and to assign bit combinations to constellation values of the used non-uniform constellation, wherein the coding and modulation apparatus is characterised in that said modulator is configured to use i) a non-uniform constellation, wherein - the constellation comprises 32, 64, 128 or 256 constellation points, - the constellation points in each quadrant of the constellation diagram either have a mirror constellation point in the same quadrant mirrored at the π/4 or -π/4 axis or lie on the π/4 or -π/4 axis, - the constellation points in each quadrant of the constellation diagram are symmetrical to the constellation points in all other quadrant, - at least one signal point within the signal points having same magnitude has an unequal angular distance to the neighbors in direct vicinity in angular domain, and - the Euclidean distance between two nearest neighboring constellation points in a quadrant is different for different pairs of nearest neighboring constellation points, or ii) a non-uniform constellation obtained from a constellation according to i) through rotation by an angle around the origin, through inversion of bit labels for all constellation points, through interchanging of bit positions and/or through predistortion for the constellation points, i) a non-uniform constellation, wherein - the constellation comprises 32, 64, 128 or 256 constellation points, - the constellation points in each quadrant of the constellation diagram either have a mirror constellation point in the same quadrant mirrored at the π/4 or -π/4 axis or lie on the π/4 or -π/4 axis, - the constellation points in each quadrant of the constellation diagram are symmetrical to the constellation points in all other quadrant, - at least one signal point within the signal points having same magnitude has an unequal angular distance to the neighbors in direct vicinity in angular domain, and - the Euclidean distance between two nearest neighboring constellation points in a quadrant is different for different pairs of nearest neighboring constellation points, or - the constellation comprises 32, 64, 128 or 256 constellation points, - the constellation points in each quadrant of the constellation diagram either have a mirror constellation point in the same quadrant mirrored at the π/4 or -π/4 axis or lie on the π/4 or -π/4 axis, - the constellation points in each quadrant of the constellation diagram are symmetrical to the constellation points in all other quadrant, - at least one signal point within the signal points having same magnitude has an unequal angular distance to the neighbors in direct vicinity in angular domain, and - the Euclidean distance between two nearest neighboring constellation points in a quadrant is different for different pairs of nearest neighboring constellation points, or ii) a non-uniform constellation obtained from a constellation according to i) through rotation by an angle around the origin, through inversion of bit labels for all constellation points, through interchanging of bit positions and/or through predistortion for the constellation points, wherein said modulator is configured to use a non-uniform constellation, wherein in a quadrant there exists at least one constellation point lying on the π/4 or -π/4 axis and at least two constellation points with the same magnitude that is different from the magnitude of other constellation points in the same quadrant.