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

1. A radio transmitter configured to transmit data in an open loop transmission in a wireless multiple antenna radio communications system, the radio transmitter comprising:

a computing device; and

a non-transitory computer-readable storage medium storing a program to be executed by the computing device;

wherein the wireless multiple antenna radio communications system is configured to:

provide for data transmission with a transmission rank r, wherein r is an integer and r≥1;

communicate resource units (RUs) containing resource elements (RUs);

provide N available Demodulation Reference Signals (DM-RS) for communication channel estimation in each of the RUs, wherein N is an integer and N≥1;

provide a number of M REs of the REs in each of the RUs for data transmission, wherein M is an integer and M≥1; and

provide a number of E REs of the REs in each of the RUs allocated for DM-RS transmission, wherein E is an integer and E≥1;

wherein the program includes instructions, which when executed by a processor, cause the processor to:

apply a number N Used of DM-RSes to the E allocated REs of the Res, where N Used >r and N Used ≤N, wherein each of the N Used DM-RSes in an RU defines one antenna port and there are N Used defined antenna ports, and wherein each of the M REs of the REs for data transmission is associated with r of N Used defined antenna ports; and

transmit data through the N Used defined antenna ports using the N Used DM-RSes and the E allocated REs of the REs.

2. The radio transmitter according to claim 1 , wherein the radio transmitter is further configured to use at least L≥2 different precoding matrices to precode the M REs of the REs in at least one RU of the RUs 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.

3. The radio transmitter according to claim 2 , wherein the number of used precoding matrices L is adapted to the transmission rank r and number N of available DM-RS.

4. The radio transmitter according to claim 1 , wherein the number N of available DM-RS depends on the number E of REs of the REs allocated for DM-RSes in an RU of the RUs and a length of code used for Code Division Multiplexing of DM-RSes over the E REs of the REs.

5. The radio transmitter according to claim 1 , wherein one resource unit is one Resource Block Pair in a Long Term Evolution mobile communications system.

6. The radio transmitter according to claim 1 , wherein:

E=12 REs of the REs are used in one RU of the RUs for DM-RS;

rank is chosen as either of 1 or 2;

a length of code-division multiplexing (CDM) code is 4 and there are N=4 CDM DM-RSes available; and

number L of used precoding matrices is a largest integer smaller than N/r.

7. The radio transmitter according to claim 1 , wherein:

E=24 REs of the REs are used in one RU of the RUs for DM-RS;

rank is chosen as either of 3 or 4;

a length of code-division multiplexing (CDM) code is 4 and there are N=8 CDM DM-RSes available; and

number L of used precoding matrices is a largest integer smaller than N/r.

8. The radio transmitter according to claim 1 , wherein:

the same number N of available DM-RSes are used for different rank r transmissions; and

a number of used precoding matrices is a largest integer smaller than N/r.

9. The radio transmitter according to claim 1 , wherein:

the number of available DM-RSes for different rank r transmissions is N r ;

the same number of L precoding matrices is used for each transmission rank r; and

the number N Used of used DM-RS≤N r available DM-RS for each rank r transmission is N Used =L*r.

10. The radio transmitter according to claim 9 , wherein the number of available DM-RSes N r for different rank r transmissions is the same.

11. The radio transmitter according to claim 1 , wherein the radio transmitter is further configured to use cycling of L≥2 precoding matrices in an RU of the RUs or in consecutive RUs of the RUs.

12. The radio transmitter according to claim 11 , wherein the radio transmitter is further configured to perform layer permutation by permuting columns of the L precoding matrices and then use the permuted precoding matrices for precoding.

13. The radio transmitter according to claim 1 , wherein each data transmission RE of the REs is associated with same antenna ports with different order.

14. The radio transmitter according to claim 1 , wherein the radio transmitter is further configured to signal a scheme of used L precoding matrices to a receiver of precoded REs U of the REs in the wireless multiple antenna radio communications system.

15. The radio transmitter according to claim 1 , wherein the radio transmitter is further configured to:

compute received channel coefficients using non precoded reference signals; and

extract precoding matrices used for received precoded reference signals using the computed received channel coefficients.

16. A user equipment configured to receive a transmission from a radio transmitter in a wireless multiple antenna radio communications system, the user equipment comprising:

a computing device; and

a non-transitory computer-readable storage medium storing a program to be executed by the computing device;

wherein the wireless multiple antenna radio communications system;

provide for data transmission with a transmission rank r, wherein r is an integer and r≥1;

communicate resource units (RUs) containing resource elements (Res);

provide N available Demodulation Reference Signals (DM-RSes) for communication channel estimation in each RU of the RUs, wherein N is an integer and N≥1,

provide a number of M REs of the REs in each RU of the RUs for data transmission, wherein M is an integer and M≥1; and

provide a number of E REs of the REs in each RU of the RUs allocated for DM-RS transmission, wherein E is an integer and E≥1;

wherein the program includes instructions, which when executed by a processor, cause the processor to:

receive a precoded data transmission transmitted through a number N Used of DM-RSes using a E allocated REs of the Res, wherein the DM-RSes are applied to the E allocated Res of the Res, wherein each of the N Used DM-RSes of the DM-REses defines one antenna port and there are N Used defined antenna ports, each of the M REs of the REs for data transmission being associated with r of N Used defined antenna ports, where N Used >r and N Used ≤N.

17. The user equipment according to claim 16 , wherein at least L≥2 different precoding matrices are used to precode the M REs of the REs in at least one RU for at least one certain rank r transmission such that REs of the REs precoded with a first precoding matrix are interleaved with REs of the REs precoded with at least one additional, a second different precoding matrix.

18. The user equipment according to claim 16 , wherein the number of used precoding matrices L is adapted to the transmission rank r and number N of available DM-RSes.

19. The user equipment according to claim 16 , wherein:

E=12 REs of the REs are used in one RU of the RUs for DM-RS;

rank is chosen as either of 1 or 2;

a length of code-division multiplexing (CDM) code is 4 and there are N=4 CDM DM-RSes available; and

number L of used precoding matrices is a largest integer smaller than N/r.

20. A method for data transmission in an open loop transmission in a wireless multiple antenna radio communications system that provides for data transmission with a transmission rank r (r is an integer and r≥1), communicates resource units (RUs) containing resource elements (REs), provides N available Demodulation Reference Signals (DM-RSes) for communication channel estimation in each RU, provides a number of M REs of the REs in each RU of the RUs for data transmission, and provides a number of E REs of the REs in each RU of the RUs allocated for DM-RS transmission, the method comprising:

applying a number N Used of DM-RSes to the E allocated Res of the REs, wherein each of the N Used DM-RSes defines one antenna port and there are N Used defined antenna ports, each of the M REs of the REs for data transmission being associated with r of N Used defined antenna ports, where N Used >r and N Used ≤N; and

transmitting data through the N Used defined antenna ports using the N Used DM-RSes and the E allocated REs of the REs.