Methods and devices for determining a transmission rank

A base station for determining a transmission rank, the base station comprising a processor for controlling two or more transmit antenna ports for supporting a multi-antenna transmission mode and for transmission of data on a channel for communication with a user equipment, the base station comprising:

• a receiver configured to receive a rank indicator from a user equipment, the rank indicator indicating the number of spatial multiplexing layers recommended by the user equipment, and
• a processor configured to determine, for a received rank indicator larger than 1, the transmission rank based on a channel imbalance factor CIF, wherein the channel imbalance factor CIF quantifies a difference in receive power of the two or more transmit antenna ports.

A computer program for a base station for determining a transmission rank, the base station controlling two or more transmit antenna ports for supporting a multi-antenna transmission mode and for transmission of data on a channel for communication with a user equipment, the computer program comprising computer program code, which, when run on the base station, causes the base station to perform the steps of:

• receiving a rank indicator from a user equipment, the rank indicator indicating the number of spatial multiplexing layers supported by the user equipment, and
• determining, for a received rank indicator larger than 1, the transmission rank based on a channel imbalance factor CIF, wherein the channel imbalance factor CIF quantifies a difference in receive power of the two or more transmit antenna ports.

A method in a user equipment for determining a rank indicator, the user equipment comprising two or more receive antennas for supporting a multi-antenna reception mode and for receiving data on a channel used in communication with a base station, the method comprising:

• performing channel measurements for determining a downlink channel matrix H, and
• determining the rank indicator based on a channel imbalance factor CIF, wherein the channel imbalance factor CIF quantifies a difference in receive power of the two or more receive antennas.

A user equipment for determining a rank indicator, the user equipment comprising two or more receive antennas for supporting a multi-antenna reception mode and for receiving data on a channel used in communication with a base station, the user equipment comprising a processor arranged to:

• perform channel measurements for determining a channel matrix H, and
• determine the rank indicator based on a channel imbalance factor (CIF), wherein the channel imbalance factor (CIF) quantifies a difference in receive power of the two or more receive antennas.

A computer program for a user equipment for determining a rank indicator, the user equipment comprising two or more receive antennas for supporting a multi-antenna reception mode and for receiving data on a channel used for communication with a base station, the computer program comprising computer program code, which, when run on the user equipment, causes the user equipment to perform the steps of:

• performing channel measurements for determining a channel matrix H, and
• determining the rank indicator based on a channel imbalance factor (CIF), wherein the channel imbalance factor (CIF) quantifies a difference in receive power of the two or more receive antennas.