Methods for determining a beam-forming gain parameter, user equipment, base station, computer programs and computer program products

1. A method performed in a user equipment for determining a beam-forming gain parameter, said user equipment configured for operation in a communication system comprising a base station serving the user equipment, the method comprising:

receiving a cell-specific reference signal and a dedicated reference signal from the base station,

measuring a received power, P RSRP , of the cell-specific reference signal and a received power, P DRSRP , of the dedicated reference signal,

determining a beam-forming gain parameter, G BF , based on the measured received power, P RSRP , of the cell-specific reference signal and on the measured received power, P DRSRP , of the dedicated reference signal, and

transmitting the determined beam-forming gain parameter, G BF , to the base station when the beam-forming gain parameter, G BF , is below a predetermined threshold value, G Thres .

2. The method of claim 1 , further comprising transmitting to the base station at least one of:

the measured received power, P DRSRP , of the dedicated reference signal;

the measured received power, P RSRP , of the cell-specific reference signal; and

the determined beam-forming gain parameter, G BF .

3. The method of claim 1 , wherein the determining of the beam-forming gain parameter, G BF , comprises calculating the beam-forming gain parameter, G BF , by:

G BF =P DRSRP −P′ DRSRP ,

wherein P DRSRP is the measured received power of the dedicated reference signal and P′ DRSRP is an estimation of received power of a dedicated reference signal when transmitted without use of beam-forming.

4. The method of claim 3 , wherein the estimation of received power, P′ DRSRP , of a dedicated reference signal transmitted without use of beam-forming is estimated by:

P′ DRSRP =P RSRP +10 lg(ρ)−10 lg(ρ′),

wherein P RSRP is the received power of the cell-specific reference signals, ρ is the ratio of energy per resource elements of a physical downlink shared channel and energy per resource element of the dedicated reference signal, and ρ′ is the ratio of energy per resource element for a physical downlink shared channel and the energy per resource element of the dedicated reference signal.

5. The method of claim 1 , wherein the received power, P DRSRP , of the dedicated reference signal comprises the linear average of resource elements carrying the dedicated reference signal within a predetermined measurement frequency bandwidth or the linear average of resource elements carrying the dedicated reference signal within a predetermined measurement frequency bandwidth for resource blocks upon which a corresponding physical downlink shared channel, P DSCH , is mapped.

6. A user equipment configured for operation in a communication system comprising a base station for serving the user equipment, the user equipment comprising:

a receiver adapted to receive a cell-specific reference signal and a dedicated reference signal from the base station;

a processing unit adapted to:

measure a received power, P RSRP , of the cell-specific reference signal and a received power, P DRSRP , of the dedicated reference signal, and

determine a beam-forming gain parameter, G BF , based on the measured received power, P RSRP , of the cell-specific reference signal and on the measured received power, P DRSRP , of the dedicated reference signal; and

a transmitter coupled to the processor and adapted to transmit the determined beam-forming gain parameter, G BF , to the base station when the beam-forming gain parameter, G BF , is below a predetermined threshold value, G Thres .

7. A non-transitory computer-readable medium storing a computer program for a user equipment configured for operation in a communication system comprising a base station for serving the user equipment, the computer program comprising computer program code which when executed by a processing circuit in the user equipment causes the user equipment to:

receive a cell-specific reference signal and a dedicated reference signal from the base station,

measure a received power, P RSRP , of the cell-specific reference signal and a received power, P DRSRP , of the dedicated reference signal,

determine a beam-forming gain parameter, G BF , based on the measured received power, P RSRP , of the cell-specific reference signal and on the measured received power, P DRSRP , of the dedicated reference signal, and

transmit the determined beam-forming gain parameter, G BF , to the base station when the beam-forming gain parameter, G BF , is below a predetermined threshold value, G Thres .

8. A method performed in a base station of a communication system, the base station serving one or more user equipments, the method comprising:

obtaining a beam-forming gain parameter, G SF , related to one of the user equipments;

determining based on the obtained beam-forming gain parameter, G BF , whether beam-forming is to be used for the user equipment; and

turnin on the beam-formin when a variance of an an le of arrival V AOA of a number of signals received from the user equipment is below a predetermined threshold value V AOA, Thres and when a set turn-on time period, T bon , has elapsed.

9. The method of claim 8 , wherein the obtaining of the beam-forming gain parameter, G BF , comprises receiving the beam-forming gain parameter, G BF , in a signal from the user equipment.

10. The method of claim 8 , wherein the obtaining of the beam-forming gain parameter, G BF , comprises:

transmitting a cell-specific reference signal and a dedicated reference signal;

receiving from the user equipment a measured received power, P RSRP , of the cell-specific reference signal and a measured received power, P DRSRP , of the dedicated reference signal; and

determining the beam-forming gain parameter, G BF , based on the measured received power, P DRSRP , of the dedicated reference signal and on the measured received power, P DRSRP , of the dedicated reference signal.

11. The method of claim 10 , wherein the determining of the beam-forming gain parameter, G BF , comprises calculating the beam-forming gain parameter, G BF , by:

G BF =P DRSRP− P′ DRSRP ,

wherein P DRSRP is the measured received power of the dedicated reference signal and P′ DRSRP is an estimation of received power of a dedicated reference signal transmitted without use of beamforming.

12. The method of claim 8 , wherein determining whether the beam-forming is to be used for the user equipment comprises:

comparing the beam-forming gain parameter, G BF , with a predetermined threshold value G Thres ;

calculating a variance of angle of arrival V AOA of a number of signals received from the user equipment;

comparing the calculated variance of angle of arrival V AOA with a predetermined threshold value V AOA, Thres ;

turning off the beam-forming for the user equipment if the beam-forming gain parameter, G BF , is below the predetermined threshold value G Thres ; if the calculated variance of angle of arrival V AOA , is above the predetermined threshold value V AOA, Thres , and if a set turn-off time period, T boff , has elapsed.

13. A base station of a communication system, the base station configured to serve one or more user equipments and comprising a processing unit adapted to:

obtain a beam-forming gain parameter, G BF , related to one of the user equipments;

determine based on the obtained beam-forming gain parameter, G BF , whether beam-forming is to be used for the user equipment; and

turn on the beam-formin when a variance of an angle of arrival V AOA of a number of signals received from the user equipment is below a predetermined threshold value V AOA,Thres and when a set turn-on time period, T bon , has elapsed.

14. A non-transitory computer-readable medium storing a computer program for a base station configured to serve one or more user equipments in a communication system, wherein the computer program comprises computer program code which, when executed by a processing circuit of the base station, causes the base station to:

obtain a beam-forming gain parameter, G BF , related to one of the user equipment,

determine based on the obtained beam-forming gain parameter, G BF , whether beam-forming is to be used for the user equipment, and

turn on the beam-formin when a variance of an an le of arrival V AOA of a number of signals received from the user equipment is below a predetermined threshold value V AOA, Thres and when a set turn-on time period, T bon , has elapsed.