Neighbour cell quality measurement in a telecommunications system

1. A method, executed in a first network node of a wireless communication system, for measuring a quality of a neighbor cell for mobility purposes, the method comprising:

obtaining a cell-specific silent grid for measuring the quality of a neighbor cell, the cell-specific silent grid comprising resource elements having no data allocation;

measuring signal interference over said grid during a measurement period in one or more of the resource elements of said grid having no data allocation; and

estimating the quality of the neighbor cell based on the measured signal interference;

wherein the quality of the neighbour cell is calculated based on an inter-cell interference measured or estimated during the cell-specific silent grid by using signal strength and interference.

2. A method according to claim 1 , further comprising a step of reporting said estimated quality of the neighbor cell to a second network node.

3. A method according to claim 1 , wherein the inter-cell interference comprises noise and a received power from a data channel or a control channel, or a combination thereof.

4. A method according to claim 1 , further comprising calculating the quality of the neighbor cell as a Reference Symbol Received Quality (RSRQ) using the following equation:

RSRQ=RSRP/( I inter-cell +N 0 ),

where RSRP=Reference Symbol Received Power, I inter-cell =inter-cell interference measured during the silent resource element grid used in cell i, and N 0 =noise.

5. A method according to claim 1 , further comprising defining a position in the cell-specific silent grid of the resource elements having no data allocation, as a function of a cell ID of the cell corresponding to the cell-specific silent grid.

6. A method according to claim 1 , further comprising

deriving the cell-specific silent grid for the first network node, from a cell ID of the neighbor cell; and

making the cell-specific silent grid known to the first network node.

7. A method according to claim 1 , further comprising signaling or sending an index of the cell-specific silent grid, to the first network node, via at least one control channel.

8. A method according to claim 7 , wherein the at least one control channel is a broadcast channel mapped on, or sent via, a physical downlink shared channel (PDSCH).

9. An arrangement in a first network node, comprising a transceiver and a processor, said processor configured to:

obtaining a cell-specific silent grid to measure a quality of a neighbor cell, the cell-specific silent grid comprising data resource elements with no data allocation;

measure an inter-cell interference during said silent grid over a measurement period in one or more of the data resource elements of said silent grid with no data allocation; and

estimate the quality of the neighbor cell based on the measured signal interference;

wherein the quality of the neighbour cell is calculated as an inter-cell interference measured or estimated during the cell-specific silent grid by using signal strength and interference.

10. A arrangement according to claim 9 , further configured to report said estimated quality of the neighbor cell to a second network node.

11. An arrangement according to claim 9 , wherein the inter-cell interference comprises noise and a received power from a data channel or control channel, or a combination thereof.

12. An arrangement according to claim 9 , wherein the first arrangement is configured to estimate the quality of the neighbor cell based on calculating a Reference Symbol Received Quality (RSRQ) using the following equation:

RSRQ=RSRP/( I inter-cell +N 0 ),

where RSRP=Reference Symbol Received Power, I inter-cell =inter-cell interference measured during the cell-specific silent grid used in the neighbor cell and N 0 =noise.

13. An arrangement according to claim 9 , further configured to define the position in the cell-specific silent grid as a function of a cell ID of the neighbor cell.

14. An arrangement according to claim 9 , wherein:

the cell-specific silent grid is derived from a cell ID of the neighbor cell; and

the cell-specific silent grid is made known to the first network node.

15. An arrangement according to claim 9 , further configured to transmit an index of the cell-specific silent grid to the first network node, via one or more control channels.

16. An first arrangement according to claim 15 , wherein the arrangement is configured to transmit the index of the cell-specific silent grid via a secondary or a dedicated broadcast channel (D-BCH), or a physical downlink shared channel (PDSCH).