Method and apparatus for performing radio-resource-management measurements

1. An apparatus, comprising:

at least one processor; and

at least one memory including computer program code,

wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus at least to

receive mapping information from at least one network node, wherein the mapping information indicates restrictions with respect to antenna ports to be used for measurements on each of one or more channel-state-information-reference-signal resources transmitted by the at least one network node;

transmit a message to a user equipment, wherein the message configures the user equipment to measure channel-state-information-reference-signal-received power from at least one of said one or more channel-state-information-reference-signal resources; and

receive a reporting from the user equipment,

wherein transmitting the message to the user equipment further comprises indicating, to the user equipment, the restrictions with respect to antenna ports to be used for measurements.

2. The apparatus according to claim 1 , wherein the restrictions define that:

all the antenna ports associated with the at least one channel-state-information-reference signal resource must be measured by the user equipment for channel-state-information-reference-signal-received power, or

only a subset of antenna ports associated with the said at least one channel-state-information-reference signal resource must be measured by the user equipment for channel-state-information-reference-signal-received power.

3. The apparatus according to claim 1 , wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus further to:

determine at least one of a serving cell and a beam to be used by the user equipment, wherein the determining is based on the received reporting; and

transmit results of the determining to the user equipment.

4. The apparatus according to claim 1 , wherein the receiving the reporting comprises receiving at least one of a channel-state-information-reference-signal-received-power and a reference-signal-received-power measurement report.

5. The apparatus according to claim 1 , wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus further to:

transmit timing information of discovery signals to the user equipment, for the user equipment to perform discovery signal measurements in accordance with the transmitted timing information.

6. The apparatus according to claim 1 , wherein the apparatus comprises a serving evolved Node B, and the network node comprises an evolved Node B that neighbors the serving evolved Node B.

7. The apparatus of claim 1 , wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus further to:

signal precoding codebook information for each configured channel-state-information-reference-signal resource to the user equipment, wherein the precoding codebook information further indicates associations between a subset of antenna ports of the one or more channel-state-information-reference-signal resources and a precoding codebook; and

configure the user equipment to measure a channel-state-information-reference-signal-received power of at least one combined channel from at least two antenna ports by using a selected codeword from the precoding codebook based on the received precoding codebook information.

8. A method, comprising: receiving, by a user equipment, a message from a first network node, wherein the message indicates restrictions with respect to antenna ports to be used for measurements on each of one or more channel-state-information-reference-signal resources transmitted by at least one second network node, and wherein the message configures the user equipment to measure channel-state-information-reference-signal-received power from at least one of said one or more channel-state-information-reference-signal resources; measuring channel-state-information-reference-signal-received-power based on the received message; and reporting the measurement results to the first network node.

9. The method according to claim 8 , wherein the restrictions define that:

all the antenna ports associated with the at least one channel-state-information-reference-signal resource must be measured by the user equipment for channel-state-information-reference-signal-received power, or

only a subset of antenna ports associated with the said at least one channel-state-information-reference signal resource must be measured by the user equipment for channel-state-information-reference-signal-received power.

10. The method according to claim 8 , further comprising:

receiving results of a determination performed by the first network node, the results indicating at least one of a serving cell and a beam; and

utilizing the at least one of a serving cell and a beam based on the received results.

11. The method according to claim 8 , wherein the reporting comprises transmitting at least one of a channel-state-information-reference-signal-received-power and a reference-signal-received-power report.

12. The method according to claim 8 , further comprising:

receiving timing information of discovery signals from the first network node; and

performing discovery signal measurement in accordance with the received timing information.

13. An apparatus, comprising:

at least one processor; and

at least one memory including computer program code,

wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause a user equipment at least to:

receive a message from a first network node, wherein the message indicates restrictions with respect to antenna ports to be used for measurements on each of one or more channel-state-information-reference-signal resources transmitted by at least one second network node, and wherein the message configures the user equipment to measure channel-state-information-reference-signal-received power from at least one of said one or more channel-state-information-reference-signal resources;

measure channel-state-information-reference-signal-received-power based on the received message; and

report the measurement results to the first network node.

14. The apparatus according to claim 13 , wherein the restrictions define that:

all the antenna ports associated with the at least one channel-state-information-reference signal resource must be measured by the user equipment for channel-state-information-reference-signal-received power, or

only a subset of antenna ports associated with the at least one channel-state-information-reference signal resource must be measured by the user equipment for channel-state-information-reference-signal-received power.

15. The apparatus according to claim 13 , wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the user equipment further:

receive results of a determination performed by the first network node, the results indicating at least one of a serving cell and a beam; and

utilize the at least one of a serving cell and a beam based on the received results.

16. The apparatus according to claim 13 , wherein the reporting comprises transmitting at least one of a channel-state-information-reference-signal-received-power and a reference-signal-received-power report.

17. The apparatus according to claim 13 , wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the user equipment further to:

receive timing information of discovery signals from the first network node; and

perform discovery signal measurement in accordance with the received timing information.

18. The apparatus according to claim 13 , wherein the apparatus comprises the user equipment, the first network node comprises a serving evolved Node B, and the at least one second network node comprises an evolved Node B that neighbors the serving evolved Node B.

19. The apparatus according to claim 13 , wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the user equipment further to:

receive precoding codebook information for each configured channel-state-information-reference-signal resource from the first network node, wherein the precoding codebook information further indicates associations between a subset of antenna ports of the one or more channel-state-information-reference-signal resources and a precoding codebook; and

measure a channel-state-information-reference-signal-received power of at least one combined channel from at least two antenna ports by using a selected codeword from the precoding codebook based on the received precoding codebook information.