Method, apparatuses and computer program products for transmission diversity

An apparatus, comprising:

• an estimator configured to make time-slot specific channel estimates for signals received from a first and at least one second transmission antenna or antenna group of a user device;
• a rotator configured to rotate a channel estimate made for a signal transmitted by the at least one second antenna or antenna group of the user device with at least one of antenna-specific, antenna group-specific, and data symbol-specific phases;
• and
• a determinator configured to determine a symbol-specific combined channel estimate by performing at least one of summing and averaging operations on the channel estimates.

An apparatus comprising:

• a controller configured to determine if data-symbol specific phases equal to an orthogonal sequence element used on a predetermined reference signal symbol are used;
• an estimator configured to make reference signal symbol specific channel estimates for signals received from a first and at least one second transmission antenna or antenna group of a user device;
• and
• a demodulator configured to use the channel estimates corresponding to the predetermined reference signal symbol in a coherent demodulation of a data symbol.

A method comprising:

• grouping antennas into antenna groups, if more antennas suitable for transmission are provided than pilot resources per a time slot;
• transmitting symbols using a first antenna or antenna group of a user device;
• and
• rotating selected symbols with at least one of antenna-specific, antenna group-specific, and data symbol-specific phases;
• and
• transmitting the rotated symbols using an at least one second antenna or antenna group of the user device.

A method comprising:

• making time-slot specific channel estimates for signals received from a first and at least one second transmission antenna or antenna group of a user device;
• rotating a channel estimate made for a signal transmitted by the at least one second antenna or antenna group of the user device with at least one of antenna-specific, antenna group-specific, and data symbol-specific phases;
• and
• determining a symbol-specific combined channel estimates by performing at least one of summing and averaging operations on the channel estimates.

A method comprising:

• determining if data-symbol specific phases equal to an orthogonal sequence element used on a predetermined reference signal symbol are used;
• making reference signal symbol specific channel estimates for signals received from a first and at least one second transmission antenna or antenna group of a user device;
• and
• using the channel estimates corresponding to the predetermined reference signal symbol in a coherent demodulation of a data symbol.