Method and apparatus for open loop transmission in a multiple antenna wireless communication system

A radio transmitter configured to precode 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, and
• wherein the radio transmitter is configured to:
• apply a number, NUsed, of DM-RS:s, NUsed≦N, to the E allocated REs;
• precode 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;
• precode each of NUsed 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, use 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.

A user equipment adapted to receive a transmission from a radio transmitter 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, and
• wherein the user equipment is adapted to receive a precoded open loop transmission,
• wherein a number, NUsed, of DM-RS:s, NUsed≦N, is applied to the E allocated REs;
• wherein the data at each of the M REs within each RU is precoded with a precoding matrix and the same precoding matrix is used for all of the M REs within each RU;
• wherein each of NUsed DM-RSs over the E allocated REs within each RU is precoded with one column of the precoding matrix which is same as that used for precoding M data REs;
• and
• at least L≧2 different precoding matrices from a set of precoding matrices W are used 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.