Method, apparatuses and computer program products for transmission diversity

1. An apparatus comprising:

a grouper configured to group antennas into antenna groups, if more antennas suitable for transmission are provided than pilot resources per a time slot within a frame structure, wherein the time slot comprises symbols for at least control data and pilot resources;

a rotator configured to rotate selected symbols with at least one of antenna-specific, antenna group-specific, and data symbol-specific phases;

a transmitter configured to transmit signals to at least a receiver, wherein the transmitting signals comprises transmitting symbols using a first antenna or first antenna group of a user device and transmitting the rotated symbols using at least one second antenna or second antenna group of the user device, wherein time-slot specific channel estimates are made for the received signals; and

a multiplier configured to multiply, between time slots, half of the antennas within one of the antenna groups with a predetermined rotator.

2. The apparatus of claim 1 , wherein the transmitter is further configured to:

transmit reference signals from antennas of a user device, the reference signals being separated from each other with orthogonal sequences by multiplying each reference signal symbol in a time-slot with a corresponding orthogonal sequence element.

3. The apparatus of claim 1 , wherein the transmitter is further configured to transmit the rotated symbols also by the first antenna or antenna group.

4. The apparatus of claim 1 , wherein the data-symbol specific phases are equal to an orthogonal sequence element used on a predetermined reference signal symbol.

5. The apparatus of claim 1 , wherein the data-symbol specific phases used in a time-slot are uniformly distributed on a unit circle.

6. The apparatus of claim 1 , further comprising:

a re-orderer configured to re-order the antenna groups between time-slots.

7. The apparatus of claim 1 , further comprising:

a separator configured to separate a reference signal for different transmission antennas or antenna groups by spreading reference signal symbols block-wise with orthogonal sequences.

8. The apparatus of claim 1 , wherein the transmitter is further configured to transmit channel quality indicators on a physical uplink control channel.

9. A method comprising:

grouping antennas into antenna groups, if more antennas suitable for transmission are provided than pilot resources per a time slot within a frame structure, wherein the time slot comprises symbols for at least control data and pilot resources;

rotating selected symbols with at least one of antenna-specific, antenna group-specific, and data symbol-specific phases;

transmitting signals to at least a receiver, wherein the transmitting signals comprises transmitting symbols using a first antenna or first antenna group of a user device and transmitting the rotated symbols using at least one second antenna or second antenna group of the user device, wherein time-slot specific channel estimates are made for the received signals; and

multiplying half of the antennas, between time slots, within one of the antenna groups with a predetermined rotator.

10. The method of claim 9 , further comprising:

transmitting reference signals from antennas of a user device, the reference signals being separated from each other with orthogonal sequences by multiplying each reference signal symbol in a time-slot with a corresponding orthogonal sequence element.

11. The method of claim 9 , further comprising:

transmitting the rotated symbols also by the first antenna or antenna group.

12. The method of claim 9 , wherein the data-symbol specific phases are equal to an orthogonal sequence element used on a predetermined reference signal symbol.

13. The method of claim 9 , further comprising:

separating a reference signal for different transmission antennas or antenna groups by spreading reference signal symbols block-wise with orthogonal sequences.