A signal modulation method performed at a communication device, the method comprising: receiving a first set of data symbols and a second set of data symbols defined with respect to a lattice in a two-dimensional information domain wherein the first set of data symbols is associated with a first user and the second set of data symbols is associated with a second user wherein the lattice is defined by sampling on a delay dimension of the two-dimensional information domain and by sampling on a Doppler dimension of the two-dimensional information domain; transforming and spreading the first set of data symbols onto a first set of grid points of a grid in a time-frequency domain by applying an OTFS transform to the first set of data symbols, thereby transforming the first set of data symbols into a first set of transformed symbols wherein the grid is defined by sampling a time axis in the time-frequency domain with sampling period T and sampling a frequency axis in the time-frequency domain with sampling period Δf and wherein the OTFS transform is given by; X n m = 1 MN W tr n m ∑ k = 0 N − 1 ∑ l = 0 M − 1 x l k b k, l n m; where x [ k,l] are data symbols, where X[n, m], n = 0,...,N - 1, m = 0,...,M - 1 are transformed symbols resulting from the data symbols, and where b k, l n m = e j 2 π ml M − nk N are a set of basis functions; where W tr [n, m] is a transmit windowing square summable function; transforming and spreading the second set of data symbols onto a second set of grid points of the grid in the time-frequency domain by applying the OTFS transform to the second set of data symbols, thereby transforming the second set of data symbols into a second set of transformed symbols; and mapping the first set of transformed symbols and the second set of transformed symbols to a transmitted waveform s(t) via a superposition of delay-and-modulate operations on a pulse waveform g tr (t), the transmitted waveform s(t) being defined by: s t = ∑ m = − M / 2 M / 2 − 1 ∑ n = 0 N − 1 X n m g tr t − nT e j 2 πm Δ f t − nT wherein X[n, m] are the first set of transformed symbols and the second set of transformed symbols; wherein the transmit pulse waveform g tr (t) satisfies the following bi-orthogonality property with a receive pulse waveform g r (t): g tr t, g r t − nT e j 2 πmΔf t − nT = ∫ g tr ∗ t g r t − nT e j 2 πmΔf t − nT dt = δ m δ n; wherein the first set of grid points are different from the second set of grid points. receiving a first set of data symbols and a second set of data symbols defined with respect to a lattice in a two-dimensional information domain wherein the first set of data symbols is associated with a first user and the second set of data symbols is associated with a second user wherein the lattice is defined by sampling on a delay dimension of the two-dimensional information domain and by sampling on a Doppler dimension of the two-dimensional information domain; transforming and spreading the first set of data symbols onto a first set of grid points of a grid in a time-frequency domain by applying an OTFS transform to the first set of data symbols, thereby transforming the first set of data symbols into a first set of transformed symbols wherein the grid is defined by sampling a time axis in the time-frequency domain with sampling period T and sampling a frequency axis in the time-frequency domain with sampling period Δf and wherein the OTFS transform is given by; X n m = 1 MN W tr n m ∑ k = 0 N − 1 ∑ l = 0 M − 1 x l k b k, l n m; where x [ k,l] are data symbols, where X[n, m], n = 0,...,N - 1, m = 0,...,M - 1 are transformed symbols resulting from the data symbols, and where b k, l n m = e j 2 π ml M − nk N are a set of basis functions; where W tr [n, m] is a transmit windowing square summable function; transforming and spreading the second set of data symbols onto a second set of grid points of the grid in the time-frequency domain by applying the OTFS transform to the second set of data symbols, thereby transforming the second set of data symbols into a second set of transformed symbols; and mapping the first set of transformed symbols and the second set of transformed symbols to a transmitted waveform s(t) via a superposition of delay-and-modulate operations on a pulse waveform g tr (t), the transmitted waveform s(t) being defined by: s t = ∑ m = − M / 2 M / 2 − 1 ∑ n = 0 N − 1 X n m g tr t − nT e j 2 πm Δ f t − nT wherein X[n, m] are the first set of transformed symbols and the second set of transformed symbols; wherein the transmit pulse waveform g tr (t) satisfies the following bi-orthogonality property with a receive pulse waveform g r (t): g tr t, g r t − nT e j 2 πmΔf t − nT = ∫ g tr ∗ t g r t − nT e j 2 πmΔf t − nT dt = δ m δ n; wherein the first set of grid points are different from the second set of grid points.