KR101511905B1 - SYSTEM AND METHOD TO MITIGATE INTERFERENCE OF 3GPP LTE HetNet ACCORDING TO PRIORITY OF SERVICE USING COORDINATED MULTIPOINT TRANSMISSION AND RECEPTION - Google Patents

Abstract

A power control system and method for mitigating interference in a heterogeneous network is disclosed. A power control method for mitigating interference according to an exemplary embodiment includes receiving a link connection request from a femto terminal, transmitting an uplink signal when a link connection request is accepted, receiving information of a macro base station existing in the vicinity Controlling a power of an uplink signal when a High Interference Indicator (HII) report of the macro base station is received, receiving a HII report in a state where the power of the uplink signal is reduced to a predetermined power level, And controlling the power of the uplink signal based on the service priority while satisfying the constraint.

Description

TECHNICAL FIELD [0001] The present invention relates to a power control method and system for mitigating interference in a 3GPP LTE heterogeneous network according to the priority of a femtocell user service, and a power control method and system for mitigating interference in a 3GPP LTE heterogeneous network according to priority of a femtocell user service.

A method and system for mitigating interference of an LTE heterogeneous network (HetNet) composed of a femtocell and a macrocell by controlling power according to priority of a service is disclosed.

In order to improve the capacity of the wireless communication system, it is most efficient to place the transmitting end and the receiving end close to each other. Among them, the femtocell technique is a very efficient and cost effective method.

Femtocell technology has been applied to high-speed wireless communication systems because of its potential advantages in terms of improved area coverage, energy efficiency and cost. Also, the femtocell is adopted as one of the main functions of the LTE system, and the LTE femtocell has an advantage that all bands defined by 3GPP can be used and a dedicated frequency band is not required. For this reason, fatal co-channel interference may occur between a macro-cell and a femtocell.

Specifically, in a two-tier network, substantial interference problems may arise due to scalability, security, and limited availability of the backhaul bandwidth. In other words, it is more effective to use the macro cell base station and the femtocell base station in the same spectrum in the social communication base or spectral availability side, but there is a problem that serious interference may occur in the shared channel by sharing the channel between the two layers . In recent years, many methods have been proposed to solve the interference problem that may occur in a network in which such femtocell and macrocell coexist.

Meanwhile, an important requirement for a macro cell is that a user must be able to communicate without any additional device anytime, anywhere, and on the move, and a large number of users receive communication services from their respective macro cell base stations. Therefore, it is preferable that the communication capacity of the macrocell is higher than that of the femtocell. That is, even if inter-layer interference exists for the femtocell, the minimum target SINR of the macrocell user should be satisfied.

To do this, it is necessary to know how much power is to be reduced in the femtocell so that the macrocell user can satisfy the target SINR, the time required for processing the interference mitigation / elimination algorithm should be small and the latency to be minimized It is necessary to have an interference mitigation / removal scheme with a simple complexity. It should also be able to combine with other resource management such as power and subchannel allocation in performing interference mitigation / removal.

In this manner, the femtocell must be able to perform various measurements so that sufficient information is provided to the femtocell for interference mitigation / removal in the two-layer network, and at the same time, coverage of the femtocell can be maintained.

For example, the current LTE Technical Report proposes various options for information exchange between macrocells and femtocells. The macro cell and the femtocell are connected to each other by a macro cell base station through an X2 based interface which is a signaling protocol between a macro cell base station and a femtocell base station, A femtocell base station and a femtocell base station through an S1-based interface, which is a signaling protocol between a base station and a gateway, and an information exchange method between the femtocell base stations.

In this regard, Korean Patent Laid-Open No. 10-2009-0127908 (base station interference control method and apparatus) proposes an X2 interference control message used in an X2 interface to control interference occurring in a femtocell environment without an X2 interface, A method and apparatus for controlling the interference of a femtocell base station while using an existing X2 interference control message without newly defining an interference control message in the S1 interface by transmitting the signal through the S1 interface are proposed .

According to an exemplary embodiment, when the femto terminal receives the HII (High Interference Indicator) report of the macro base station in the heterogeneous network, it can control the transmission power of the femto terminal uplink signal.

According to an exemplary embodiment, the femto terminal may reduce transmission power of an uplink signal to mitigate interference to a macro terminal.

According to an embodiment, the femto terminal may reduce the transmission power of the uplink signal by a predetermined step.

According to one embodiment, the femto base station can control the transmission power according to the service priority so that the overall QoS is improved.

According to one embodiment, the femto base station receives a link connection request from a femto terminal, transmits an uplink signal when the link connection request is accepted, receives information of a macro terminal existing in the vicinity, When the HII report is received in a state in which the power of the uplink signal is reduced to a predetermined power level, a predetermined limit And controlling the power of the uplink signal based on a service priority while satisfying a condition of the uplink signal. The power control method for mitigating interference in a heterogeneous network may be provided.

According to another embodiment of the present invention, when the report of HII (High Interference Indicator) is received from the information of the macro base station, the step of controlling the power of the uplink signal comprises the steps of: A power control method for mitigating interference in a heterogeneous network including reducing the power of a signal can be provided.

According to another embodiment of the present invention, when the HII report is received while the power of the uplink signal is reduced to a predetermined power level, The step of controlling the power includes comparing the service priority of the macro terminal with the service priority of the femto terminal and decreasing the power of the uplink signal if the service priority of the macro terminal is higher than the service priority of the femto terminal A power control method for mitigating interference in a heterogeneous network may be provided.

According to another embodiment, when the service priority of the macro terminal is higher than the service priority of the femto terminal, decreasing the power of the uplink signal may include decreasing the power of the uplink signal by a predetermined second unit size A power control method for mitigating interference in a heterogeneous network may be provided.

According to another embodiment of the present invention, when the service priority of the macro terminal is higher than the service priority of the femto terminal, the step of decreasing the power of the downlink signal includes the step of increasing the downlink signal power by a predetermined second unit size, A power control method for mitigating interference in a heterogeneous network including reducing the power of the link signal can be provided.

According to another embodiment of the present invention, there is provided a power control method for mitigating interference in a heterogeneous network, further comprising increasing power of the uplink signal when a CQI (Channel Quality Indicator) value of the information of the macro terminal increases .

According to another embodiment of the present invention, when the HII report is received while the power of the uplink signal is reduced to a predetermined power level, The step of controlling the power may include a step of decreasing the power of the uplink signal until the SINR limiting condition of the predetermined constraint is satisfied, a power control method for mitigating interference in a heterogeneous network may be provided.

According to another embodiment of the present invention, the step of receiving the link connection request from the femto terminal comprises the step of allowing the link connection request when it is confirmed that the femto terminal is registered in the CSG (Closed Subscriber Group) A power control method for mitigating interference can be provided.

According to another embodiment of the present invention, the step of receiving the information of the macro terminal existing in the vicinity includes receiving the information of the macro terminal via the macro base station, and the power control method for mitigating interference in the heterogeneous network is provided .

According to an embodiment of the present invention, a macro base station transmitting information of a macro terminal to a femto base station, a macro terminal reporting a channel state of an uplink channel to the macro base station through a CQI, And transmits the uplink signal at a maximum power when the link connection request is granted, and when the HII report of the macro base station is received, the femto terminal receives power of the uplink signal based on the service priority, A power control system for mitigating interference in a heterogeneous network including a femto terminal for controlling interference can be provided.

According to another embodiment, the macro terminal transmits an HII report to the macro base station if interference by the femto base station is not less than a threshold value when the macro terminal is not registered in the CSG. Can be provided.

According to another embodiment, the femto base station may be provided with a power control system for reducing interference in a heterogeneous network, which reduces the power of the uplink signal if the service priority of the macro terminal is higher than the service priority of the femto terminal have.

According to another embodiment, the femto terminal may reduce the power of the uplink signal by a predetermined second unit size if the service priority of the macro terminal is higher than the service priority of the femto terminal, A power control system may be provided.

According to another embodiment, the femto terminal increases power of the uplink signal when a CQI (Channel Quality Indicator) value of the information of the macro terminal increases, and provides a power control system for mitigating interference in a heterogeneous network .

According to yet another embodiment, the femto terminal may be provided with a power control system for mitigating interference in a heterogeneous network, which reduces the power of the uplink signal until the SINR limiting condition among the predetermined conditions is satisfied have.

According to another embodiment, the femto base station may be provided with a power control system for mitigating interference in a heterogeneous network, which permits the link connection request when it is confirmed that the femto terminal is registered in a CSG (Closed Subscriber Group) have.

According to another embodiment, the femto terminal may be provided with a power control system for mitigating interference in a heterogeneous network, which reduces the power of the uplink signal by a predetermined first unit size when the HII report is received .

According to one embodiment, a computer readable storage medium storing one or more programs including instructions for causing a heterogeneous network to perform a power control method of mitigating interference may be provided.

According to an embodiment, uplink interference from neighboring femto terminals to neighboring macro terminals can be minimized, thereby maximizing the data yield of the entire system.

According to an exemplary embodiment, interference cancellation and QoS can be simultaneously guaranteed by using the priority of a service as a criterion in a power control procedure among SON (Self Organizing Network) functions in a femto base station.

In a specific case, the quality of service (QoS) of the entire system is sacrificed at the cost of a user terminal (UE, User Equipment) having a low priority of service among a macro terminal (MUE, Macro User Equipment) and a femto terminal ) Can be improved.

According to an embodiment, it is possible to minimize the interference occurring in the heterogeneous network by applying an effective power control procedure to various services having different priorities of services.

1 is a diagram illustrating interference in a 3GPP LTE heterogeneous network environment according to one embodiment.
FIG. 2 is a diagram illustrating an evolved packet system (EPS) bearer service structure according to an embodiment.
3 is a diagram illustrating QoS-based scheduling in an LTE uplink according to an embodiment.
4 is a functional block diagram of a 3GPP Policy and Charging Control (PCC) framework according to an exemplary embodiment of the present invention.
5 is a flowchart illustrating a method for mitigating interference in a heterogeneous network according to an embodiment.
6 is a diagram illustrating a system for mitigating interference in a heterogeneous network according to one embodiment.
7 is a diagram for explaining functions in a 3GPP Policy and Charging Control (PCC) framework according to an embodiment.

For the LTE (Long Term Evolution) system, a home femtocell that is currently installed in the home and an indoor femtocell for hotspot support in a building such as a conference room, coffee shop, -cell) can be developed and commercialized. In addition, by extending the coverage of the technology to street-level femtocells, it can cope with wireless data explosion in almost all hotspots.

Since femtocell technology is effective in improving cell yield and indoor coverage, energy efficiency, and cost, a femtocell can be adopted as one of the main network components in an LTE system. In particular, the femtocell can be commercialized in a more advanced form in the LTE-Advanced system, which is a fourth generation mobile communication system after the LTE system.

However, since the LTE femtocell is capable of using all the bands defined in 3GPP and does not require a dedicated femtocell frequency band, it is possible to prevent fatal equal channel interference (CCI) between a macro cell and a femtocell, , Co-Channel Interference).

For example, in a LTE environment, a femto base station is a macro terminal (MUE), in particular, in an uplink of a layer network in which a macro base station (eNB) and a femto base station (HeNB) The interference may occur. In addition, as the entire bandwidth is shared among the femtocells, when the same channel is reused between neighboring femtocells, interference may occur and the performance of the system may be degraded.

Therefore, in order to control co-channel interference in a network in which a femtocell is present, a technology capable of managing co-channel interference in terms of frequency classification, time division, and power allocation of resources is required.

A method and system for mitigating interference in HetNet (Heterogeneous Networks) according to an embodiment can be applied to all mobile communication systems composed of heterogeneous networks with different cell coverage. For example, in a LTE system, all services supported in a heterogeneous network formed of macrocells and femtocells, such as requirements for PER (Packet Error Rate) and latency, may be effective for various services have.

Specifically, the necessary information is collected in the L1 of the femto base station system, and a power control procedure, which is one of SON (Self Organizing Network) functions on the L2 and L3 software, can be implemented. In addition, power control procedures according to an embodiment can be used in all countries where LTE systems providing various services such as voice, video, real time, and best service are commercialized.

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings.

1 is a diagram illustrating interference 132 in a 3GPP LTE heterogeneous network 100 environment in accordance with one embodiment. Here, the interference situation in the heterogeneous network 100 environment composed of the macro base station 111, the femto base station 121, the macro terminal 112 and the FUE (FUE) equipment 122 in the 3GPP LTE can be shown have. According to one embodiment, the macro base station 111 and the macro terminal 112 may be connected by a wireless link 131.

For example, the femtocell 120 may use all the bands defined by the 3GPP and may not require the dedicated frequency band of the femtocell 120. [ This feature can lead to fatal co-channel interference between the macrocell 110 and the femtocell 120 and between the femtocell 120 and the femtocell 140. [

In addition, it can be assumed that the macro system and the femto system use the entire band instead of the partial band according to the frequency division. Here, by using the full-band frequency, the interference 132 that the femto terminal 122 transmits to the macro terminal 112 in the uplink can be reduced by using a power control method for mitigating the interference 132 in the heterogeneous network 100 according to an embodiment And through the system.

The femto terminal 122 registered in each femto base station 121 may be assumed to be a CSG (Closed Subscriber Group) that can use the femto base station 121 according to an embodiment. Therefore, the nearby macro terminal 112 that is not registered in each femto base station 121 can receive the uplink interference 132 from the neighbor femto terminal 122.

According to an exemplary embodiment, the femto base station 121 may include a downlink receiver that performs functions such as a Network Listen Mode (NLM), a Radio Environment Measurement (REM), and a HeNB Sniffer. The femto base station 121 can obtain control channel information broadcasted to the macro terminal 112 by the macro base station 111 through the downlink receiver.

According to one embodiment, the femto base station 121 may include an uplink receiver that receives information of the macro base station 111, such as a High Interference Indicator (HII) report.

FIG. 2 is a diagram illustrating an evolved packet system (EPS) bearer service structure according to an embodiment. Herein, the service priority of the user terminal can be defined by the macro base station referring to the bearer service structure shown in FIG. Also, defined service priorities can be used to distinguish services based on the QCI (QoS Class Identifier) as shown in Table 1 below.

3 is a diagram illustrating QoS-based scheduling in an LTE downlink according to one embodiment. Here, the macro base station may have information on the bearer model used by the user terminal by the QoS-aware MAC scheduler 310 in the macro base station shown in FIG.

4 is a functional block diagram of a 3GPP Policy and Charging Control (PCC) framework according to an exemplary embodiment of the present invention. According to an exemplary embodiment, the bearer service structure can distinguish traffic with different QoS requirements. Here, the Policy Control Resource Function (PCRF) 434 is a policy server in the EPC (Evolved Packet Core), and the policy and charging enforcement function (PCEF) policy decision. For example, the PDN-GW (Packet Data Network Gateway) 433 can perform the PCEF.

According to one embodiment, the macro base station (eNB) 410 and the femto base station (HeNB) 421 can be described in detail below. For example, a home user equipment (HUE) 422 may include a femto terminal and a macro base station 410 may broadcast information to a macro terminal (MUE) 412. Here, the gateway 431 may perform a general gateway function, and a serving gateway (S-GW) 432 may be used between the macro base station and the macro base station, between the 3GPP network and the E-UTRAN It is possible to perform an anchoring function for the movement.

5 is a flowchart illustrating a method for mitigating interference in a heterogeneous network according to an embodiment. Here, in order to mitigate the interference in the femto terminal heterogeneous network, the power can be controlled as follows.

In step 510, the femto base station may receive a link connection request from the femto terminal. Here, if the femto terminal that transmitted the link connection request exists in the CSG list, the femto terminal and the femto base station can be connected. For example, the femto base station may allow the link connection request if it is confirmed that the femto terminal is registered in the CSG.

If a link with the femto terminal is established in step 520, the uplink signal can be transmitted to the femto base station at the maximum power of the femto terminal. If a link connection request is allowed here, a link can be formed.

Each MAC terminal can report the channel state of the downlink to the CQI of the uplink and report it to the macro base station. Each of the macro terminals can generate a list of information about neighboring cells such as an active cell and a neighbor cell by measuring or maintain and update it by referring to a downlink control channel. If the specific macro terminal does not exist in the CSG list of the femto base station, the specific macro terminal can receive co-channel interference (CCI) from the neighboring femto base station.

In step 530, the femto base station can receive the HII report of the macro terminal. More specifically, it is possible to receive information of a macro terminal existing in the vicinity. For example, information of the neighboring macro terminal can be received via the macro base station. According to an exemplary embodiment, if the co-channel interference is equal to or greater than a threshold value as in Equation (1), the macro terminal may report HII to the macro base station using the uplink to inform the macro base station of the interference situation. In this case, the femto base station can receive the HII report from the macro base station. Here, when the macro terminal reporting HII is not present around the femto terminal, the femto terminal can perform normal power control.

Equation 1

In the above-described Equation (1) and Equation

The interference caused by the kth macro cell base station from the femto terminal,

A predetermined interference level that the macro cell base station can withstand,

May represent a user terminal noise characteristic (UE noise figure).

According to an embodiment, the total amount of interference experienced from the F femto terminals existing in the vicinity of the kth macro terminal may be expressed by Equation (2).

Equation 2

In the above-described Equation 2 and the following Equation

May be the transmission power of the i < th > femto terminal out of F Femto terminals,

May be used to calculate the received SINR value of the user terminal as a path loss between the i-th femto BS and the k-th MAC terminal.

Then, in step 530, the femto terminal may control the power of the uplink signal when the HII report of the information of the macro base station is received. When the macro base station receives interference larger than the threshold given in Equation (1) from the femto terminal, it broadcasts HII. The HII report is generated at the macro base station and the femto base station receives the report through the X2 interface of the macro base station and the femto base station. Therefore, the femto terminal can use the same HII information as the femto base station. Based on the HII report, the femto terminal calculates its transmit power by using Equation (3) to maintain the user's QoS requirement,

. ≪ / RTI > In step 531, the femto terminal may decrease the transmission power. Specifically, according to Equation (3), the femto base station maintains the QoS (Quality-of-Service) of the femto terminal

It is possible to lower the transmission power of the femto terminal. For example, when the HII report is received, the power of the uplink signal may be reduced by a predetermined first unit size. Here, the predetermined first unit size is

Lt; / RTI >

Then, in step 532, the femto terminal determines whether the transmission power is higher than the requested power, and decreases the power of the uplink signal by the first unit size. Specifically, as shown in Equation (4), the transmission power can be lowered step by step until the transmission power of the femto terminal does not become smaller than the required power of the femto terminal.

Equation 3

Equation 4

In Equation (3), Equation (4) and Equation

The initial transmission power of the femto terminal,

The maximum transmit power of the femto terminal,

May represent the femto terminal transmit power at the lth iteration. Also,

A power control step according to the HII report,

May indicate the required power of the femto terminal.

In step 533, the femto terminal may allocate the transmission power not smaller than the required power. Specifically, when the transmission power in the l-th iteration is smaller than the required power, the transmission power in the (l-1) -th iteration can be allocated as the power of the uplink signal.

Subsequently, in step 540, the femto terminal may verify that the HII report is still received from the macro base station. Here, if the HII report is received while the power of the uplink signal is reduced to a predetermined power level, the femto terminal can control the power of the uplink signal based on the service priority while satisfying a predetermined constraint . At this time, if the HII report is not received, the power control procedure can be terminated.

More specifically, if the macro base station interfered by the femto terminal reports the HII from the macro base station even though the transmission power of the femto terminal is less than the required power due to the power control applied to the femto terminal, the femto terminal receives the service priority of the user terminal Based power control procedure.

According to an exemplary embodiment of the present invention, among the power control procedures for reducing the transmission power of the femto terminal, the restriction conditions predetermined for the macro terminal and the femto terminal may include constraints on interference, power, and SINR. For example, in the case of a femto terminal, a constraint condition for interference may be expressed by Equation (5).

Equation 5

In the above-described Equation 5 and the following equations

Interference between the nth femto terminal and the macro base station,

May represent the neighbor femto terminal interference to the jth femto terminal.

According to one embodiment, the interference of the femto terminal to the femto terminal may be expressed by Equation (6).

Equation 6

In the above-described equation (6) and the following equation

May represent a path loss between the i < th > femto BS and the j < th > femto BS, and may be used to calculate a received SINR value of the femto BS.

According to an exemplary embodiment, the interference from the neighboring femto terminal to the macro base station may be expressed by Equation (7).

Equation 7

In Equation (7) and Equation

May represent path loss between the nth macro base station and the jth femto terminal, and may be used to calculate the received SINR value of the femto terminal.

According to an embodiment, a predetermined restriction condition in the femto terminal may be expressed by Equation (8).

Equation 8

According to an exemplary embodiment, the SINR for satisfying the QoS of the macro terminal and the femto terminal may be expressed by Equation (9) and Equation (10).

Equation 9

Equation 10

In Equation (9), Equation (10) and Equation (10), thr denotes a minimum required SINR at each user terminal,

Is the SINR of the k < th >

May represent the SINR of the j < th > femto terminal of the i < th > femto BS.

In step 541, the macro base station can compare the service priority of the macro terminal with the service priority of the femto terminal. Here, if the service priority of the macro terminal is not higher than the service priority of the femto terminal, the power control procedure of the uplink signal can be terminated.

According to an exemplary embodiment, a service priority of a user terminal can be defined by a macro base station with reference to the bearer model of FIG. In addition, the service priorities defined in Table 1 below can be used to distinguish services based on a QoS Class Identifier (QCI).

QCI Resource Type Priority Packet Delay Budget (ms) Packet Error Loss Rate Example Services One GBR 2 100 10 ^ -2 Conversation voice 2 GBR 4 150 10 ^ -3 Conversation video
(Live streaming) 3 GBR 5 300 10 ^ -6 Non-interactive video
(Buffer streaming) 4 GBR 3 50 10 ^ -3 Real-time games 5 Non-GBR One 100 10 ^ -6 IMS signal 6 Non-GBR 7 100 10 ^ -3 Audio, video (streaming),
Interactive Games 7 Non-GBR 6 300 10 ^ -6 Video (buffer streaming) 8 Non-GBR 8 300 12 ^ -6 TCP based (Internet), chat,
FTP, P2P file sharing,
Advanced Video and More 9 Non-GBR 9

According to an exemplary embodiment, the macro base station has information on a bearer model used by a user terminal and may be enabled by the QoS-aware MAC scheduler in the macro base station of FIG. FIG. 4 shows functional blocks in the 3GPP PCC framework. The bearer can distinguish traffic with different QoS requirements. Here, the PCRF is a policy server in the EPC, and the PCEF can make a policy decision according to the PCC rule. In addition, the power control method for mitigating interference in the heterogeneous network can be realized as one of SON (Self Organizing Network) functions on the L2 and L3 software by collecting necessary information in L1 of the femto base station system.

According to an exemplary embodiment, the macro base station can broadcast information on the service of the macro terminal on the downlink, and the femto base station can receive the information using the sniffer function in the femto base station. Here, the femto base station may already have information on the service of the femto terminal.

In step 542, if the service priority of the macro terminal is higher than the service priority of the femto terminal, the femto terminal may decrease the power of the uplink signal. Here, if the macro terminal has higher service priority than the femto terminal, the femto terminal can reduce the transmission power as shown in Equation (11). Specifically, the power of the uplink signal can be reduced by a predetermined second unit size. Here, the second unit size is expressed by the following equation (11)

.

Equation 11

In Equation (11)

Is the femto terminal transmit power in the lth iteration,

May represent the amount of power adjustment for each iteration. According to an embodiment, the femto terminal may reduce the power of the uplink signal by a predetermined second unit size which is equal to or smaller than a predetermined first unit size. for example

, The link of the femto terminal can be maintained as much as possible even if it receives a service that does not meet the priority of the service requested by the femto terminal.

In step 543, the femto terminal can confirm whether the macro terminal satisfies the SINR restriction condition. Here, the femto terminal may reduce the transmission power until the SINR restriction condition of Equation (12) is satisfied. The macro terminal satisfying Equation (12) may not report HII any more.

Equation 12

In Equation (12) and Equation

Is the reception SINR of the macro terminal,

May indicate the required SINR of the macro terminal.

Then, in step 544, the femto terminal can confirm whether the CQI (Channel Quality Indicator) of the macro terminal is improved.

In step 545, the femto terminal may increase the power of the uplink signal when the CQI value of the macro terminal information increases. For example, as the macro terminal in the interference condition from the femto terminal moves away from the femto base station, the CQI value reported to the uplink can be increased. In this case, the femto terminal may increase the transmission power as shown in Equation (13).

Equation 13

Then, in step 546, the femto terminal can check whether the HII report has been received after the power of the uplink signal has increased in step 545 described above. For example, after increasing the transmission power, the HII report and the CQI report from the corresponding macro terminal are continuously observed, and when the HII report starts again, the transmission power can be reduced as shown in Equation (11). For another example, if there is no HII report, the CQI may be observed, and if the CQI value is increased, the transmission power may be increased according to Equation (13).

If the CQI is not improved in step 548, the femto terminal may wait for the next CQI report while using the current transmission power. For example, it is possible to observe whether the next CQI is improved or decreased with the current transmission power.

Then, at step 547, if the femto terminal satisfies the SINR constraint according to Equation (14), it may terminate the power control procedure to mitigate interference in the heterogeneous network according to one embodiment. If it is not satisfied, it is possible to confirm whether the CQI is improved in step 544 described above. Or the power of the uplink signal may be reduced until the SINR limiting condition is satisfied among the predetermined limit conditions.

Equation 14

In Equation 14,

The reception SINR of the femto terminal,

May indicate the required SINR of the femto terminal.

In step 541, the macro base station may compare the service priority of the macro terminal with the service priority of the femto terminal.

If the service priority of the femto terminal is higher than the service priority of the macro terminal by comparing the priority of the macro terminal with the service priority of the femto terminal, the macro terminal reporting the HII does not satisfy the following condition (CoMP Cooperating Set) between non-active femto base stations (non-active HeNBs). Assistance means that a non-dynamic femto base station in a CoMP Cooperating Set provides a service to a macro terminal. In order to satisfy a required SNR when a priority of a macro terminal is low, It requires the assistance of the femto base station.

600: Power control system to mitigate interference in heterogeneous networks
610: macro base station
620: Macro terminal
630: femto terminal
640: femto base station

Claims (7)

Receiving a link connection request from a femto terminal;
Transmitting an uplink signal when the link connection request is accepted;
Receiving information of a macro base station existing in the vicinity;
Controlling a power of the uplink signal when a High Interference Indicator (HII) report is received from information of the macro base station; And
Controlling the power of the uplink signal based on the service priority while satisfying a predetermined constraint when the HII report is received while the power of the uplink signal is reduced to a predetermined power level
Wherein the power control method mitigates interference in a heterogeneous network. The method according to claim 1,
Wherein the step of controlling the power of the uplink signal when a High Interference Indicator (HII) report of the macro base station information is received comprises:
Reducing the power of the uplink signal by a predetermined first unit size when the HII report is received
Wherein the power control method mitigates interference in a heterogeneous network. The method according to claim 1,
Wherein controlling the power of the uplink signal based on the service priority while satisfying a predetermined constraint when the HII report is received in a state where the power of the uplink signal is reduced to a predetermined power level,
Comparing the service priority of the macro terminal with the service priority of the femto terminal; And
If the service priority of the macro terminal is higher than the service priority of the femto terminal, decreasing power of the uplink signal
Wherein the power control method mitigates interference in a heterogeneous network. The method of claim 3,
If the service priority of the macro terminal is higher than the service priority of the femto terminal, reducing the power of the uplink signal comprises:
Reducing the power of the uplink signal by a predetermined second unit size
Wherein the power control method mitigates interference in a heterogeneous network. 4. The method of claim 3, further comprising: configuring a confound common set between non-dynamic femto base stations;
Linking the non-dynamic femto base station and the macro terminal;
When the connection is completed, confirming whether the SINR constraint is satisfied;
If the condition is satisfied, disconnecting one of the femto base stations; And
Confirming whether the SINR constraint is satisfied
The method comprising the steps of: 6. The method of claim 5,
Reconnecting the disconnected femto base station;
Using UL CoMP JP between the macro base station and the femto base station;
The macro base station observing the macro terminal under an interference condition; And
Terminating the comp of the macro base station and the femto base station
The method comprising the steps of: A macro base station transmitting information of a macro terminal to a femto base station;
A macro terminal connected to the macro base station and reporting a channel state of an uplink to the macro base station via a CQI;
A femto terminal for transmitting a link connection request to a femto base station; And
And a control unit for controlling the power of the uplink signal based on the service priority while transmitting the uplink signal at the maximum power when the link connection request is granted and receiving the HII report from the macro base station, Base station
A power control system for mitigating interference in a heterogeneous network.

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