Method and apparatus for communicating to UE an indication of available RS, based on MIMO mode settings

1. A method in a network node of a cellular communication network of enabling a user equipment (UE) to perform measurements, estimations or demodulations, the method comprising:

determining Multiple Input Multiple Output (MIMO) mode settings associated with the network node; and

transmitting, on a downlink common or shared channel, an indication of available reference signals based on the determined MIMO mode settings to the UE, wherein the indication of available reference signals explicitly or implicitly indicates common reference signals or dedicated reference signals available for said UE measurements, estimations or demodulations, wherein the indication of available reference signals further comprises an indication of reference signal availability based on MIMO modes used in at least one different network node in the cellular communication network operating a neighbor cell, and wherein the indication of available reference signals further indicates whether the available reference signals due to MIMO mode settings of the neighboring cell differ or not from the available reference signals due to MIMO mode settings of the network node.

2. The method of claim 1 , wherein the UE measurements, estimations or demodulations are selected from the group consisting of neighbor cell measurement, channel estimation, demodulation, and Channel Quality Indicator (CQI) estimation.

3. The method of claim 1 , wherein the indication of available reference signals indicates whether beamforming is used or not, and hence the relative availability of common reference signals.

4. The method of claim 1 , wherein the indication of available reference signals comprises an index of a reference signal pattern with the smallest number of available common reference signals.

5. The method of claim 1 , wherein the network node is the serving node for the UE.

6. The method of claim 5 , wherein the downlink common or shared channel is a Broadcast Channel (BCH).

7. The method of claim 5 , wherein the downlink common or shared channel is a Physical Downlink Shared Channel (PDSCH).

8. The method of claim 1 , wherein the network node is not the serving node for the UE.

9. The method of claim 1 , wherein the downlink common or shared channel is a Physical Broadcast Channel (PBCH).

10. The method of claim 8 , wherein the downlink common or shared channel is a Synchronization Channel (SCH).

11. The method of claim 1 , wherein said UE measurements comprise measurements of signals transmitted by a different network node in the cellular communication network operating a neighbor cell, and wherein the indication of available common reference signals to be used for neighbor cell measurements by the UE is transmitted via higher layer signaling.

12. A method in a user equipment (UE) of enabling the UE to perform measurements, estimations or demodulations, the method comprising:

receiving an indication, on a downlink common or shared channel, of available reference signals due to determined Multiple Input Multiple Output (MIMO) mode settings associated with a network node, wherein the indication of available reference signals explicitly or implicitly indicates available common reference signals or dedicated reference signals to be used for said UE measurements, estimations or demodulations,

further receiving an indication of reference signal availability based on the MIMO mode used in at least one different network node in the cellular communication network operating a neighbor cell, and wherein the indication of available reference signals further indicates whether the available reference signals due to MIMO mode settings of the neighboring cell differ or not from the available reference signals due to MIMO mode settings of the network node, and

performing measurements, estimations or demodulations based on said received indications.

13. The method of claim 12 , wherein the UE measurements, estimations or demodulations are selected from the group consisting of: neighbor cell measurement, channel estimation, demodulation and Channel Quality Indicator (CQI) estimation.

14. The method of claim 12 , wherein the indication of available reference signals indicates whether beamforming is used or not, and hence the relative availability of common reference signals.

15. The method of claim 12 , wherein the indication of available reference signals comprises an index of a reference signal pattern with the smallest number of available common reference signals.

16. A network node of a cellular communication network configured to enable a user equipment (UE) to perform measurements, estimations or demodulations, the network node comprising:

a controller configured to determine Multiple Input Multiple Output (MIMO) mode settings associated with the network node; and

a transmitter configured to transmit, on a downlink common or shared channel, an indication of available reference signals based on the determined MIMO mode settings to the UE;

wherein the indication of available reference signals explicitly or implicitly indicates available common reference signals or dedicated reference signals to be used for said UE measurements, estimations or demodulations, and wherein the transmitter is further configured to transmit to the UE an indication of reference signal availability based on the MIMO mode used in at least one other network node in the cellular communication network operating a neighbor cell, and wherein the indication of available reference signals further indicates whether the available reference signals due to MIMO mode settings of the neighboring cell differ or not from the available reference signals due to MIMO mode settings of the network node.

17. The network node of claim 16 , wherein the UE measurements, estimations or demodulations are selected from the group consisting of: neighbor cell measurement, channel estimation, demodulation and Channel Quality Indicator (CQI) estimation.

18. The network node of claim 16 , wherein the indication of available reference signals indicates whether beamforming is used or not, and hence the relative availability of common reference signals.

19. The network node of claim 16 , wherein the indication of available reference signals comprises an index of a reference signal pattern with the smallest number of available common reference signals.

20. The network node of claim 16 , wherein the downlink common or shared channel is a Broadcast Channel (BCH).

21. The network node of claim 16 , wherein the downlink common or shared channel is a Physical Downlink Shared Channel (PDSCH).

22. The network node of claim 16 , wherein the downlink common or shared channel is a Physical Broadcast Channel (PBCH).

23. The network node of claim 16 , wherein the downlink common or shared channel is a Synchronization Channel (SCH).

24. A user equipment (UE) operative to perform measurements, estimations or demodulations, comprising:

a receiver configured to receive an indication, on a downlink common or shared channel, of available reference signals due to determined Multiple Input Multiple Output (MIMO) mode settings associated with a network node, wherein the indication of available reference signals explicitly or implicitly indicates available common reference signals or dedicated reference signals available for said UE measurements, estimations or demodulations; wherein the receiver is further configured to receive an indication of reference signal availability based on the MIMO mode used in at least one different network node in the cellular communication network operating a neighbor cell, and wherein the indication of available reference signals further indicates whether the available reference signals due to MIMO mode settings of the neighboring cell differ or not from the available reference signals due to MIMO mode settings of the network node, and

a controller configured to perform measurements, estimations or demodulations based on said received indications.