Patent ID: 8787485

Claim:
A method for precoding in an open loop transmission in a wireless multiple antenna radio communications system, wherein the system: provides for rank adaptation for data transmission with selected transmission rank r being 1≦r≦R, where R is a maximum available transmission rank of the communication system, communicates resource units (RU) containing resource elements (RE), provides N available Demodulation Reference Signals (DM-RS) for communication channel estimation in each RU, provides a number of M REs in each RU for data transmission, and provides a number of E REs in each RU allocated for DM-RS transmission, wherein the method comprises: applying a number, N Used , of DM-RS:s, N Used ≦N, to the E allocated REs; precoding the data at each of the M REs within each RU with a precoding matrix and the same precoding matrix is used for all of the M REs within each RU; precoding each of N Used DM-RSs over the E allocated REs within each RU with one column of the precoding matrix which is same as that used for precoding M data REs; and when precoding, using at least L≧2 different precoding matrices from a set of precoding matrices W to precode the M REs and the E allocated REs in at least one RU for at least one certain rank r transmission such that REs precoded with a first precoding matrix are interleaved with REs precoded with at least one additional, a second different precoding matrix, and wherein the number of used precoding matrices L is adapted to the transmission rank r and number N of available DM-RS.