CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority to Korean Patent Application No. 10-2019-0062539, filed May 28, 2019, the entire contents of which is incorporated herein for all purposes by this reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a power control method and apparatus in a wireless communication system. More particularly, the present invention relates to controlling power of an aggressor cell so as to reduce co-channel interference (CCI) in uplink transmission due to sharing the same frequency band between a femto user equipment (FUE) unit and a macro user equipment (MUE) unit. The appealing feature of the invention is that it considers the victim situation while controlling the user's power.

Description of the Related Art

Long term evolution (LTE) femto cells can use all available frequency bands defined in the 3rd Generation Partnership Project (3GPP), and serious co-channel interference occurs between a macro cell user and a femto cell user, and between a femto cell user and a femto cell user. In addition, a dedicated band for a femto cell is not present.

However, in a heterogeneous network, there are three major upload link interferences: interference in an uplink signal from a FUE unit to an MUE unit; interference in an uplink signal from an MUE unit to an FUE unit; and interference in an uplink signal from an FUE unit to a neighboring FUE unit within the same macro cell.

In order to reduce such co-channel interferences, exchanging user information between base stations by using a general X2 interface has to be performed, and this causes increases in loads for providing a feedback process. Accordingly, a conventional method of reducing co-channel interference by using an X2 interface cannot be applicable to a heterogeneous network with high density.

The foregoing is intended merely to aid in the understanding of the background of the present invention, and is not intended to mean that the present invention falls within the purview of the related art that is already known to those skilled in the art.

DOCUMENTS OF RELATED ART

(Patent Document 1) Korean Patent Application Publication No. 10-2013-0010128 “Semi-persistent scheduling grants in heterogeneous networks”;

(non-Patent Document 1) 3GPP, “FDD home eNode B (HeNB) radio frequency (RF) requirements analysis,” TR 36.921 version 15.0.1, Release 15;

(non-Patent Document 2) 3GPP TS 22.220: “Service requirements for home node B (HNB) and home eNode B (HeNB)”, v9.1.1;

(non-Patent Document 3) 3GPP, “Evolved universal terrestrial radio access (E-UTRA) and evolved universal terrestrial radio access network (E-UTRAN), Stage 2,” TS 36.300 version 15.0.2, Release 15; and

(non-Patent Document 4) 3GPP TR 36.922: “Evolved universal terrestrial radio access (E-UTRA); TDD home eNode B (HeNB) radio frequency (RF) requirements analysis”.

SUMMARY OF THE INVENTION

An objective of the present invention is to provide a power control apparatus and method in a wireless communication system, the apparatus and method being capable of controlling power of an FUE unit of an aggressor cell so as to decrease co-channel interference between a non-registered MUE unit and a FUE unit registered in a femto base station (FeNB) within a heterogeneous network environment.

Technical solutions obtainable from the present disclosure are not limited the above-mentioned technical solutions, and other unmentioned technical solutions can be clearly understood from the following description by those having ordinary skill in the technical field to which the present invention belongs to.

In order to achieve the above objective, according to one aspect of the present invention, there is provided a method of controlling a wireless communication system, wherein the system is configured with multiple femto base stations (FeNBs) in which one femto user equipment (FUE) unit is registered in each FeNB, and an evolved base station (eNB) including multiple macro user equipment (MUE) units; and, the method including: registering information on reference signal receive power (RSRP) of the registered FUE in the FeNB and the eNB; performing communication with the registered FUE unit and the MUE unit; and controlling power of the FUE unit in association with an aggressor cell by using RSRP information received from the eNB when co-channel interference occurs in uplink communication with the registered FUE unit and with an MUE unit that is not registered in the FeNB.

Preferably, the RSRP may be a linear average over power contributions of resource elements that carry cell-specific reference signals within a measurement frequency bandwidth.

Preferably, the controlling power of the FUE unit may include: calculating, by the MUE unit where the co-channel interference has occurred, a threshold interference value of a neighboring FUE unit by using a target signal-to-interference-plus-noise ratio (SINR); determining, by the FeNB, whether or not the registered FUE unit is in association with the aggressor cell on the basis of the received threshold interference value and the RSRP information registered in the FeNB; registering, by the FeNB, the FUE unit of the aggressor cell in an aggressor cell list when it is determined that the registered FUE unit is in association with the aggressor cell, and transferring the aggressor cell list to the eNB; performing, by the eNB, sorting for aggressor cell lists of multiple FeNBs so as to determine a worst FUE unit of the aggressor cell, and transferring information on downlink RSRP of the worst FUE unit of the aggressor cell to the FeNB in which the worst FUE unit of the aggressor cell is registered; and gradually decreasing, by the FeNB in which the worst FUE unit of the aggressor cell is registered, power of the worst FUE unit of the aggressor cell.

Preferably, the power of the worst FUE unit of the aggressor cell may be repeatedly decreased until an interference value Ivictimrecthe MUE unit that is in association with a victim cell becomes greater than a predefined threshold interference value Ivictimth, and a signal-to-interference-plus-noise ratio SINRaggressorof the FUE unit of the aggressor cell becomes equal to or greater than a target signal-to-interference-plus-noise ratio SINRaggressor.

Preferably, the controlling, by the FeNB, power of the FUE unit may be repeated until a relation between powers of the MUE unit of the victim cell and the FUE unit of the aggressor cell satisfies Equation 1 below,
PPUSCH,iFIMUE=PPUSCH,i−1FIMUE[Equation 1]

In order to achieve the above object, according to another aspect of the present invention, there is provided a wireless communication system, wherein the system is configured with multiple femto base stations (FeNBs) in which one femto user equipment (FUE) unit is registered in each FeNB, and an evolved base station (eNB) including multiple macro user equipment (MUE) units, wherein the FeNB in which one FUE unit is registered is configured to receive a threshold interference value from the MUE unit, and information on downlink RSRP of the eNB, determine whether or not the FUE unit is in association with an aggressor cell on the basis of the received threshold interference value and pre-registered RSRP information of the FUE unit, and when it is determined that the FUE unit is in association with the aggressor cell, add the FUE unit to an aggressor cell list and transfers the aggressor cell list to the eNB; the eNB is configured to perform sorting for the received aggressor cell list so as to determine a worst FUE unit of the aggressor cell, and transfer information on downlink RSRP of the worst FUE unit of the aggressor cell to the FeNB in which the worst FUE unit of the aggressor cell is registered; and the FeNB, in which the worst FUE unit of the aggressor cell is registered, is configured to repeatedly decrease power of the worst FUE unit of the aggressor cell until an interference value Ivictimrecof the MUE unit that is in association with a victim cell becomes greater than a predefined threshold interference value Ivictimth, and a signal-to-interference-plus-noise ratio SINRaggressorof the FUE unit of the aggressor cell becomes equal to or greater than a target signal-to-interference-plus-noise ratio SINRtargetaggressor.

In order to achieve the above object, according to still another aspect of the present invention, there is provided a power control apparatus in a wireless communication system, wherein the system is configured with multiple femto base stations (FeNBs) in which one femto user equipment (FUE) unit is registered in each FeNB, and an evolved base station (eNB) including multiple macro user equipment (MUE) units, the apparatus including: a calculation unit, calculating a threshold interference value of an adjacent FUE unit in an MUE unit of a victim cell receiving co-channel interference from the FUE by using a target SINR; a determination unit determining whether or not the registered FUE unit corresponds to an FUE unit of an aggressor cell on the basis of the threshold interference value received from the FeNB, and information on downlink RSRP of the FUE unit received from the eNB; an aggressor cell list transmission unit storing the registered FUE unit in an aggressor cell list of the FeNB when it is determined that the registered FUE unit corresponds to the FUE unit of the aggressor cell, and transferring the aggressor cell list to the eNB; a downlink RSRP transmission unit performing sorting for aggressor cell lists of multiple FeNBs received in the eNB so as to determine a worst FUE unit of the aggressor cell, and transferring information on downlink RSRP of the worst FUE unit of the aggressor cell to the FeNB in which the worst FUE unit of the aggressor cell is registered; and a power control unit gradually decreasing power of the worst FUE unit of the aggressor cell, wherein the power of the worst FUE unit of the aggressor cell is repeatedly decreased until an interference value Ivictimrecof the MUE unit that is in association with a victim cell becomes greater than a predefined threshold interference value Ivictimth, and a signal-to-interference-plus-noise ratio SINRaggressorof the FUE unit of the aggressor cell becomes equal to or greater than a target signal-to-interference-plus-noise ratio SINRtargetaggressor.

According to an embodiment, among FUE units neighboring to an MUE unit of a victim cell, an FUE unit of an aggressor cell can be derived on the basis of information on RSRP of the FUE unit that is pre-registered in the closed subscriber group (CSG), and a threshold interference value of the FUE unit. Subsequently, power of the derived FUE unit of the aggressor cell may be gradually decreased until an interference value of the MUE unit of the victim cell becomes greater than a predefined threshold interference value, and an SINR of the FUE unit of the aggressor cell becomes equal to or greater than a target SINR. Accordingly, co-channel interference can be reduced in a heterogeneous network environment, data transmission speed can be significantly improved, and latency time can be reduced by reducing conventional feedback time.

