A method for initializing a scrambling sequence of a reference signal, for use by a base station to transmit subframes (22, 302, 304, 312) of data, the method comprising: calculating an initializing value according to at least a slot index, n s, of a radio frame for each subframe (22, 302, 304, 312) of data; generating a pseudo-random sequence according to the initializing value; generating the scrambling sequence of the reference signal based on the pseudo-random sequence, wherein the pseudo-random sequence is defined by the version 10.4.10 of the long term evolution, LTE, specification; and transmitting subframes (22, 302, 304, 312) of data comprising the scrambling sequence of the reference signal, wherein the reference signal is downlink, DL modulation reference signal, DMRS; the method being characterized in that the slot index, n s, is dynamically selected and informed to the UE on a subframe by subframe basis, according to: n s = { n s 0 = n s serving X = x 0 = N ID serving n s 1 = n s common X = x 1 = N ID common wherein: X is a virtual cell identifier which is dynamically selected from x 0 = N ID serving and x 1 = N ID common, n s common is a common slot number for a cooperating set of base stations, n s serving is a slot number of a serving cell, N ID cell is a cell identifier of the serving cell, and N ID common is a cell ID of the macro cell, and wherein, if X = x = N ID common, the slot index n s is signalled in form of a differential codebook entry Δ n s represented by two bits as follows: n s = n s serving + Δ Δ = 2Δ n s, Δ n s = [-3,-2,2,3], wherein Δ is a shift value such that n s = n s common. calculating an initializing value according to at least a slot index, n s, of a radio frame for each subframe (22, 302, 304, 312) of data; generating a pseudo-random sequence according to the initializing value; generating the scrambling sequence of the reference signal based on the pseudo-random sequence, wherein the pseudo-random sequence is defined by the version 10.4.10 of the long term evolution, LTE, specification; and transmitting subframes (22, 302, 304, 312) of data comprising the scrambling sequence of the reference signal, wherein the reference signal is downlink, DL modulation reference signal, DMRS; the method being characterized in that the slot index, n s, is dynamically selected and informed to the UE on a subframe by subframe basis, according to: n s = { n s 0 = n s serving X = x 0 = N ID serving n s 1 = n s common X = x 1 = N ID common wherein: X is a virtual cell identifier which is dynamically selected from x 0 = N ID serving and x 1 = N ID common, n s common is a common slot number for a cooperating set of base stations, n s serving is a slot number of a serving cell, N ID cell is a cell identifier of the serving cell, and N ID common is a cell ID of the macro cell, and wherein, if X = x = N ID common, the slot index n s is signalled in form of a differential codebook entry Δ n s represented by two bits as follows: n s = n s serving + Δ Δ = 2Δ n s, Δ n s = [-3,-2,2,3], wherein Δ is a shift value such that n s = n s common. wherein: X is a virtual cell identifier which is dynamically selected from x 0 = N ID serving and x 1 = N ID common, n s common is a common slot number for a cooperating set of base stations, n s serving is a slot number of a serving cell, N ID cell is a cell identifier of the serving cell, and N ID common is a cell ID of the macro cell,