Channel state information reference signal resource mapping

1. A network node for serving a cell in a wireless network with at least one neighboring cell, the network node comprising processing circuitry configured to cause the network node to:

allocate at least one resource for Channel State Information Interference Measurement, CSI-IM, within a predetermined IM region of a Resource Block, RB, of the cell, the predetermined IM region encompassing a plurality of resources of the RB of the cell, the allocated at least one resource being selected from among the plurality of resources of the IM region to reduce a likelihood that the allocated at least one resource overlaps with at least one resource allocated for CSI-IM in a neighboring cell as compared to allocating a common set of resources for CSI-IM in each neighboring cell, the predetermined IM region at least partially overlapping with a respective predetermined IM region of a RB of the neighboring cell, and the predetermined IM region of the cell not overlapping resources allocated for Non-Zero Power Channel State Information Reference Signal, NZP CSI-RS, of the neighboring cell.

2. The network node according to claim 1 , wherein the processing circuitry is further configured to:

identify the at least one resource for the CSI-IM within the predetermined IM region of the RB of the cell based at least in part on an identifier of the cell.

3. The network node of claim 1 , wherein the processing circuitry is further configured to cause the network node to:

select at least one resource for Non-Zero Power, NZP, Channel State Information Reference Signal, CSI-RS, in a predetermined Reference Signal, RS, region of the RB of the cell, the predetermined RS region of the RB not overlapping with the predetermined IM region of the RB; and

transmit the NZP CSI-RS on the selected at least one resource.

4. The network node of claim 1 , wherein the predetermined IM region of the RB is a dedicated region for at least one CSI-IM resource, the dedicated region not comprising any NZP CSI-RS resources.

5. The network node of claim 1 , wherein the predetermined RS region is a region of the RB configured for at least one CSI-RS resource, the predetermined RS region not comprising any CSI-IM resources.

6. The network node of claim 1 , wherein the processing circuitry is further configured to cause the network node to:

determine a slot offset for the CSI-IM based on a cell identifier, ID, of the cell being served by the network node.

7. The network node of claim 1 , wherein the processing circuitry is further configured to cause the network node to:

determine a period for the CSI-IM, the period for the CSI-IM being common to a group of cells, the group of cells including at least the cell and the neighboring cell.

8. The network node of claim 7 , wherein the CSI-IM is mapped to the at least one resource of the predetermined IM region according to the determined period for the CSI-IM and the determined slot offset.

9. The network node of claim 1 , wherein the CSI-IM is mapped to the at least one resource of the predetermined IM region according to a random selection algorithm.

10. The network node of claim 1 , wherein the processing circuitry is further configured to cause the network node to:

allocate at least one resource for Non-Zero Power, NZP, Channel State Information Reference Signal, CSI-RS, to at least partially overlap with at least one NZP CSI-RS resource of the neighboring cell.

11. The network node of claim 10 , wherein the processing circuitry is further configured to cause the network node to:

determine a period and a slot offset for the at least one NZP CSI-RS that is the same as a period and a slot offset for the at least one NPZ CSI-RS associated with the neighboring cell.

12. The network node of claim 1 , wherein the processing circuitry is further configured to cause the network node to:

transmit at least one Tracking Reference Signal, TRS, to at least partially overlap with at least one TRS of the neighboring cell.

13. The network node of claim 1 , wherein the processing circuitry is further configured to cause the network node to:

determine a period and a slot offset for at least one Tracking Reference Signal, TRS, that is the same as a period and a slot offset for at least one TRS associated with the neighboring cell; and

transmit the at least one TRS according to the determined period and the determined slot offset.

14. The network node of claim 1 , wherein the processing circuitry is further configured to cause the network node to:

transmit at least one Tracking Reference Signal, TRS, in a fixed time domain location, the fixed time domain location being the same as a fixed time domain location of the neighboring cell.

15. The network node of claim 1 , wherein the processing circuitry is further configured to cause the network node to:

configure Tracking Reference Signal, TRS, resources in the RB of the cell by, for each TRS symbol in the RB, dividing a plurality of subcarriers into at least four sets of subcarriers, each of the at least four sets of subcarriers corresponding to a TRS power level that is different from a TRS power level of the other of the at least four sets of subcarriers; and

wherein the at least four sets of subcarriers comprise:

a first set of subcarriers that is assigned for transmitting TRS at a regular TRS power level;

a second set of subcarriers that is assigned for transmitting TRS at a power level that is 3 decibels, dB, higher than the regular TRS power level;

a third set of subcarriers that is assigned for transmitting TRS at a power level that is 4.8 dB higher than the regular TRS power level; and

a fourth set of subcarriers that is assigned for transmitting TRS at a power level that is 6 dB higher than the regular TRS power level.

16. The network node of claim 15 , wherein the processing circuitry is further configured to cause the network node to:

transmit at least one TRS on one of the at least four sets of subcarriers; and

if the at least one TRS is transmitted on one of the second set, the third set and the fourth set of subcarriers, transmit a Zero-Power, ZP, Channel State Information Reference Signal, CSI-RS, on at least the first set of subcarriers.

17. A method in a network node for serving a cell in a wireless network with at least one neighboring cell, the method comprising:

allocating at least one resource for Channel State Information Interference Measurement, CSI-IM, within a predetermined IM region of a Resource Block, RB, of the cell, the predetermined IM region encompassing a plurality of resources of the RB of the cell, the allocated at least one resource being selected from among the plurality of resources of the IM region to reduce a likelihood that the allocated at least one resource overlaps with at least one resource allocated for CSI-IM in a neighboring cell as compared to allocating a common set of resources for CSI-IM in each neighboring cell, the predetermined IM region at least partially overlapping with a respective predetermined IM region of a RB of the neighboring cell, and the predetermined IM region of the cell not overlapping resources allocated for Non-Zero Power Channel State Information Reference Signal, NZP CSI-RS, of the neighboring cell.

18. The method of claim 17 , further comprising:

identifying the at least one resource for the CSI-IM within the predetermined IM region of the RB of the cell based at least in part on an identifier of the cell.

19. The method of claim 17 , further comprising:

selecting at least one resource for Non-Zero Power, NZP, Channel State Information Reference Signal, CSI-RS, in a predetermined Reference Signal, RS, region of the RB of the cell, the predetermined RS region of the RB not overlapping with the predetermined IM region of the RB; and

transmitting the NZP CSI-RS on the selected at least one resource.

20. The method of claim 19 , wherein the predetermined RS region is a region of the RB of the cell configured for at least one CSI-RS resource, the predetermined RS region not comprising any CSI-IM resources.

21. The method of claim 17 , wherein the predetermined IM region of the RB of the cell is a dedicated region for at least one CSI-IM resource, the dedicated region not comprising any NZP CSI-RS resources.

22. The method of claim 17 , further comprising:

determining a slot offset for the CSI-IM based on a cell identifier, ID, of the cell being served by the network node.

23. The method of claim 17 , further comprising:

determining a period for the CSI-IM, the period for the CSI-IM being common to a group of cells, the group of cells including at least the cell and the neighboring cell.

24. The method of claim 23 , wherein the CSI-IM is mapped to the at least one resource of the predetermined IM region according to the determined period for the CSI-IM and the determined slot offset.

25. The method of claim 17 , wherein the CSI-IM is mapped to the at least one resource of the predetermined IM region according to a random selection algorithm.

26. The method of claim 17 , further comprising:

allocating at least one resource for Non-Zero Power, NZP, Channel State Information Reference Signal, CSI-RS, to at least partially overlap with at least one NZP CSI-RS resource of the neighboring cell.

27. The method of claim 26 , further comprising:

determining a period and a slot offset for the at least one NZP CSI-RS that is the same as a period and a slot offset for the at least one NPZ CSI-RS associated with the neighboring cell.

28. The method of claim 17 , further comprising:

transmitting at least one Tracking Reference Signal, TRS, to at least partially overlap with at least one TRS of the neighboring cell.

29. The method of claim 17 , further comprising:

determining a period and a slot offset for at least one Tracking Reference Signal, TRS, that is the same as a period and a slot offset for at least one TRS associated with the neighboring cell; and

transmitting the at least one TRS according to the determined period and the determined slot offset.

30. The method of claim 17 , further comprising:

transmitting at least one Tracking Reference Signal, TRS, in a fixed time domain location, the fixed time domain location being the same as a fixed time domain location of the neighboring cell.

31. The method of claim 17 , further comprising

configuring Tracking Reference Signal, TRS, resources in the RB of the cell by, for each TRS symbol in the RB, dividing a plurality of subcarriers into at least four sets of subcarriers, each of the at least four sets of subcarriers corresponding to a TRS power level that is different from a TRS power level of the other of the at least four sets of subcarriers; and

wherein the at least four sets of subcarriers comprise:

a first set of subcarriers that is assigned for transmitting TRS at a regular TRS power level,

a second set of subcarriers that is assigned for transmitting TRS at a power level that is 3 decibels, dB, higher than the regular TRS power level,

a third set of subcarriers that is assigned for transmitting TRS at a power level that is 4.8 dB higher than the regular TRS power level, and

a fourth set of subcarriers that is assigned for transmitting TRS at a power level that is 6 dB higher than the regular TRS power level.

32. The method of claim 31 , further comprising:

transmitting at least one TRS on one of the at least four sets of subcarriers; and

if the at least one TRS is transmitted on one of the second set, the third set and the fourth set of subcarriers, transmitting a Zero-Power, ZP, Channel State Information Reference Signal, CSI-RS, on at least the first set of subcarriers.

33. A computer readable storage medium comprising instructions which when executed on at least one processor of a network node perform a method for serving a cell in a wireless network with at least one neighboring cell, the method comprising:

allocating at least one resource for Channel State Information Interference Measurement, CSI-IM, within a predetermined IM region of a Resource Block, RB, of the cell, the predetermined IM region encompassing a plurality of resources of the RB of the cell, the allocated at least one resource being selected from among the plurality of resources of the IM region to reduce a likelihood that the allocated at least one resource overlaps with at least one resource allocated for CSI-IM in a neighboring cell as compared to allocating a common set of resources for CSI-IM in each neighboring cell, the predetermined IM region at least partially overlapping with a respective predetermined IM region of a RB of the neighboring cell, and the predetermined IM region of the cell not overlapping resources allocated for Non-Zero Power Channel State Information Reference Signal, NZP CSI-RS, of the neighboring cell.