Coordinated multi-point transmission and reception method in overlaid cell environment

1. A method of performing coordinated multi-point (CoMP) transmission and reception in an overlaid cellular system in which a first base station and a second base station overlay each other, the method comprising:

performing a handover using a coordinated multi-point (CoMP) transmission and reception scheme based on Channel State Indicator-Reference Signal (CSI-RS) information of user equipment by the first and second base stations, wherein performing the handover comprises:

a coordinated multi-point add modification step for adding a third base station that is included in the first base station and that is a neighboring cell of the second base station while the coordinated multi-point transmission and reception is performed by the first and second base stations;

a coordinated multi-point exclude modification step of excluding the second base station while the coordinated multi-point transmission and reception is performed by the first, second, and third base stations; and

a termination step of terminating the coordinated multi-point transmission and reception by excluding the third base station from the coordinated multi-point transmission and reception attended by the first and third base stations.

2. The method of claim 1 , wherein performing the handover comprises:

preparing for performing coordinated multi-point transmission and reception based on the CSI-RS information of the user equipment by the first base station; and

initiating coordinated multi-point transmission and reception by the first and second base stations.

3. The method of claim 1 , wherein the first base station is a base station covering a macro cell, and the second base station is a neighboring cell covering a pico cell or a femto cell included in the macro cell covered by the first base station.

4. The method of claim 1 , wherein performing the handover comprises a basic packet transmission and reception step of transmitting and receiving downlink and uplink packets respectively using a PDSCH (Physical Downlink Shared Channel) and a PUSCH (Physical Uplink Shared Channel) by DL/UL grant information of CI (Control Information) information and a PDCCH (Physical Downlink Control Channel) by the user equipment accessing an RRH (Remote Radio Head) of the first base station.

5. The method of claim 2 , wherein the coordinated multi-point transmission and reception preparation step comprises:

controlling the measurement information configuration of the user equipment by a radio resource control (RRC) of the first base station using an RRC connection reconfiguration message;

preparing measurement by the user equipment according to a measurement control request of the RRC connection reconfiguration message and transmitting a measurement preparation complete message to the first base station; and

reporting a measurement report for the CSI-RS (Channel State Indicator-Reference Signal) to the first base station by the user equipment based on a measurement control determination reference and a reporting scheme provided from the first base station.

6. The method of claim 2 , wherein initiating the coordinated multi-point transmission and reception comprises:

analyzing the measurement report provided from the user equipment by the first base station, determining whether to include the second base station in the coordinated multi-point measurement set by the first base station, and transmitting configuration information for per-UE CSI feedback relating to the first and second base stations based on the determination to the user equipment;

preparing for CSI feedback according to a CSI feedback configuration request of the first RRC connection reconfiguration message by the user equipment, and when the preparation is complete, transmitting an RRC connection reconfiguration complete message to the first base station by the user equipment;

performing CSI feedback on a PUCCH or a PUSCH for the first and second base stations according to a CSI feedback configuration request by the user equipment; and

performing a JT (Joint Transmission) or a JR (Joint Reception) on a PDSCH or PUSCH of each of the first base station and the second base station using the PDCCH of the first base station.

7. The method of claim 1 , wherein the coordinated multi-point add modification step comprises:

analyzing the measurement report provided from the user equipment by the first base station, determining whether to include the third base station in a coordinated multi-point measurement set including the first and second base stations by the first base station, and transmitting a configuration information modification for per-UE CSI feedback relating to the first and second base stations to the user equipment through a second RRC connection reconfiguration message by the first base station;

preparing for CSI feedback according to a CSI feedback configuration modification request of the second RRC connection reconfiguration message by the user equipment, and when the preparation is complete, transmitting a second RRC connection reconfiguration complete message to the first base station by the user equipment;

performing CSI feedback on a PUCCH or PUSCH for the first base station, the second base station, and the third base station according to a CSI feedback configuration request of the second RRC connection reconfiguration message by the user equipment; and

performing a joint transmission or a joint reception on PDSCH or PUSCH of each of the first base station, the second base station, and the third base station using the PDCCH of the first base station.

8. The method of claim 1 , wherein the coordinated multi-point exclude modification step comprises:

analyzing a measurement report provided from the user equipment by the first base station, determining whether not to include the second base station in a coordinated multi-point measurement set including the first base station, the second base station, and the third base station, and if it is determined that coordinated multi-point transmission and reception is possible in the first base station and the third base station, transmitting a configuration information modification for per-UE CSI feedback relating to the first base station and the third base station to the user equipment through a third RRC connection reconfiguration message;

preparing for CSI feedback according to a CSI feedback configuration modification request of the third RRC connection reconfiguration message by the user equipment, and if the preparation is complete, transmitting a third RRC connection reconfiguration complete message to the first base station;

performing CSI feedback on a PUCCH or a PUSCH for the first base station and the third base station according to the CSI feedback configuration modification request of the third RRC connection reconfiguration message by the user equipment; and

performing a joint transmission or a joint reception on the PDSCH or PUSCH of each of the first base station and the third base station using the PDCCH of the first base station.

9. The method of claim 1 , wherein the coordinated multi-point transmission and reception terminating step comprises:

analyzing a measurement report provided from the user equipment by the first base station, determining whether to release the coordinated multi-point transmission and reception, and if the coordinated multi-point transmission and reception is determined to be released, transmitting a configuration information modification allowing CSI feedback associated with the coordinated multi-point transmission and reception not to be performed to the user equipment through a fourth RRC connection reconfiguration message by the first base station; and

if the modification is complete according to the CSI feedback configuration modification request of the fourth RRC connection reconfiguration message, transmitting a fourth RRC connection reconfiguration complete message to the first base station.

10. A method of scheduling a per-UE (User Equipment) RS (Reference Signal) for coordinated multi-point (CoMP) transmission and reception by an HPN base station scheduler in an environment where an HPN (High Power Node) cell and an LPN (Low Power Node) cell co-exist, the method comprising:

allocating an RS RE (Reference Signal Resource Element) relating to a per-cell CSI-RS (Channel State Indicator-Reference Signal) for the HPN and LPN cells;

determining whether to apply coordinated multi-point transmission and reception based on entire quality information for a CSI-RS-related RE (Resource Element) during a constant period;

extracting a CSI-RS-related RE in an RB (Resource Block) allocated to a per-UE subframe by user equipment;

calculating an entire quality for the extracted CSI-RS-related RE during a constant period by the user equipment; and

determining whether to apply coordinated multi-point transmission and reception based on the calculated entire quality information by the HPN base station scheduler,

wherein the HPN base station scheduler allocates a CRS (Cell-specific Reference Signal) port to an RE corresponding to first and second rows and third, sixth, ninth, and twelfth columns of a PDCCH (Physical Downlink Control Channel) of a PRB (Physical Resource Block) and allocates a CSI-RS port to an RE corresponding to seventh and eighth rows and third, fourth, ninth, and tenth columns of the PRB not to overlap per base station.

11. A scheduling apparatus for scheduling a per-UE (User Equipment) RS (Reference Signal) for coordinated multi-point (CoMP) transmission and reception in an environment where an HPN (High Power Node) cell and an LPN (Low Power Node) cell co-exist, the scheduling apparatus comprising:

a scheduler in a base station configured to:

allocate an RS RE (Reference Signal Resource Element) relating to a per-cell CSI-RS (Channel State Indicator-Reference Signal) for the HPN and LPN cells;

extract a CSI-RS-related RE (Resource Element) in an RB (Resource Block) allocated to a per-UE subframe by user equipment;

calculate an entire quality for the extracted CSI-RS-related RE during a constant period by the user equipment; and

determine whether to apply coordinated multi-point transmission and reception based on the calculated entire quality information,

wherein the scheduling apparatus determines whether to apply coordinated multi-point transmission and reception based on entire quality information for a CSI-RS-related RE during a constant period, and

wherein the scheduling apparatus allocates a CRS (Cell-specific Reference Signal) port to an RE corresponding to first and second rows and third, sixth, ninth, and twelfth columns of a PDCCH (Physical Downlink Control Channel) of a PRB (Physical Resource Block) and allocates a CSI-RS port to an RE corresponding to seventh and eighth rows and third, fourth, ninth, and tenth columns of the PRB not to overlap per base station.

12. A downlink scheduling method for coordinated multi-point (CoMP) transmission and reception in an environment where an HPN (High Power Node) cell and an LPN (Low Power Node) cell co-exist, performed by a base station scheduler, the scheduling method comprises:

performing scheduling for the coordinated multi-point transmission and reception for a base station covering at least one LPN cell by anchoring a PDCCH (Physical Downlink Control Channel) channel of a base station covering the HPN cell,

extracting a CSI-RS (Channel State Indicator-Reference Signal) related RE (Resource Element) in an RB (Resource Block) allocated to a per-UE subframe by user equipment (UE);

calculating an entire quality for the extracted CSI-RS-related RE during a constant period by the user equipment; and

determining whether to apply coordinated multi-point transmission and reception based on the calculated entire quality information by the base station scheduler,

wherein only the PDCCH channel of the HPN cell is used for the scheduling of the at least one LPN cell, and

wherein the base station scheduler allocates a CRS (Cell-specific Reference Signal) port to an RE corresponding to first and second rows and third, sixth, ninth, and twelfth columns of a PDCCH of a PRB (Physical Resource Block) and allocates a CSI-RS port to an RE corresponding to seventh and eighth rows and third, fourth, ninth, and tenth columns of the PRB not to overlap per base station.

13. A scheduling apparatus for performing downlink scheduling for coordinated multi-point (CoMP) transmission and reception in an environment where an HPN (High Power Node) cell and an LPN (Low Power Node) cell co-exist, the scheduling apparatus comprising:

a scheduler in a base station configured to

perform scheduling for the coordinated multi-point transmission and reception for a base station covering at least one LPN cell by anchoring a PDCCH (Physical Downlink Control Channel) channel of a base station covering the HPN cell,

extract a CSI-RS-related RE (Resource Element) in an RB (Resource Block) allocated to a per-UE subframe by user equipment (UE);

calculate an entire quality for the extracted CSI-RS-related RE during a constant period by the user equipment; and

determine whether to apply coordinated multi-point transmission and reception based on the calculated entire quality information,

wherein only the PDCCH channel of the HPN cell is used for the scheduling of the at least one LPN cell, and

wherein the scheduling apparatus allocates a CRS (Cell-specific Reference Signal) port to an RE corresponding to first and second rows and third, sixth, ninth, and twelfth columns of a PDCCH of a PRB (Physical Resource Block) and allocates a CSI-RS port to an RE corresponding to seventh and eighth rows and third, fourth, ninth, and tenth columns of the PRB not to overlap per base station.