KR102491936B1 - Method and apparatus for controlling uplink transmission power - Google Patents

Abstract

A method for a base station to control uplink transmission power of a mobile terminal is provided. The base station receives, from the mobile terminal, the available transmit power amount of the mobile terminal. The base station determines a target channel quality value corresponding to the current location of the mobile terminal based on the amount of available transmission power. The base station determines a reception channel quality value using an uplink data channel received from the mobile terminal. The base station determines transmit power control (TPC) by using a difference between the target channel quality value and the received channel quality value.

Description

Method and apparatus for controlling uplink transmission power {METHOD AND APPARATUS FOR CONTROLLING UPLINK TRANSMISSION POWER}

The present invention relates to a method and apparatus for controlling uplink transmission power of a mobile terminal in a small cell base station system based on long term evolution (LTE).

In a wireless communication system, uplink power control is a technique for optimally controlling transmission power of a mobile terminal. Uplink power control maintains a certain level of received channel quality (e.g., received signal-to-interference plus noise ratio (SINR), received signal to noise ratio (SNR), etc.) required by the base station, interference with neighboring base stations It is for minimizing interference and maximizing battery life of a mobile terminal. Uplink power control is a major element of radio resource management (RRM).

Such power control should be optimized in consideration of radio channel conditions including path loss and shadowing while minimizing interference to neighboring cells.

To this end, open-loop power control and closed-loop power control are defined for a physical uplink shared channel (PUSCH) and a physical uplink control channel (PUCCH) in LTE.

On the other hand, if the transmit power exceeds the maximum transmittable power of the mobile terminal, the base station's PUSCH reception performance deteriorates, and the battery consumption of the mobile terminal becomes severe along with the deterioration of uplink performance. Therefore, there is a need for a method of reducing battery consumption of a mobile terminal by preventing transmission power from exceeding the maximum transmittable power of the mobile terminal.

An object of the present invention is to provide a method and apparatus for controlling power so that battery consumption of a mobile terminal is minimized while maintaining reception power required by a base station.

In addition, the problem to be solved by the present invention is to provide a method and apparatus for controlling uplink transmission power in an LTE-based small cell base station system.

According to an embodiment of the present invention, a method for a base station to control uplink transmission power of a mobile terminal is provided. The control method of the base station may include receiving, from the mobile terminal, an available transmit power amount of the mobile terminal; determining a target channel quality value corresponding to a current location of the mobile terminal based on the amount of available transmission power; determining a reception channel quality value using an uplink data channel received from the mobile terminal; and determining a transmit power control (TPC) using a difference between the target channel quality value and the received channel quality value.

The receiving of the amount of available transmit power may include receiving a power headroom report (PHR) indicating the amount of available transmit power.

Determining the target channel quality value based on the amount of available transmission power may include using the PHR when a first value indicating how much to compensate for path loss corresponding to the current location of the mobile terminal is smaller than 1. inferring the path loss; and determining the target channel quality value according to the inferred path loss.

The determining of the received channel quality value may include smoothing a first channel quality value measured for the uplink data channel.

The flattening may include flattening the first channel quality value through an exponential filter that is a moving average filter.

In the step of flattening the first channel quality value through the exponential filter, the second channel quality value for the M3 message initially received by the base station for random access is used as the initial value for the exponential filter. steps may be included.

The determining of the TPC may include calculating a first difference between the target channel quality value and the received channel quality value determined during an update period for updating the TPC at a first time point; and determining a TPC command based on the first difference.

The update period may be changed according to the radio channel environment.

Determining the TPC command based on the first difference may include setting a difference between the target channel quality value and the received channel quality value to 0 from the first point in time until the next update period ends. steps may be included.

The control method of the base station may include determining a maximum number of resource blocks to be allocated to the mobile terminal based on the amount of available transmission power and the current location of the mobile terminal; and allocating a number of resource blocks smaller than the maximum number to the mobile terminal.

The base station may be a small cell base station.

The target channel quality value and the received channel quality value may be one of a signal-to-interference plus noise ratio (SINR) and a signal to noise ratio (SNR).

The uplink data channel may be a physical uplink shared channel (PUSCH).

Also, according to another embodiment of the present invention, a method for a mobile terminal to control uplink transmission power is provided. The control method of the mobile terminal may include transmitting, to a base station, an amount of available transmit power of the mobile terminal; Transmitting an uplink data channel to the base station; and transmission power control determined by a difference between a target channel quality value based on a first value indicating how much path loss of the mobile station is compensated for and the amount of available transmission power, and a reception channel quality value for the uplink data channel. and receiving (TPC: transmit power control) from the base station.

The method for controlling the mobile terminal may further include receiving, from the base station, a resource block that is smaller than the maximum number of resource blocks that can be allocated to the mobile terminal.

The maximum number may be determined based on the amount of available transmission power and the path loss of the mobile terminal.

Also according to another embodiment of the present invention, a base station is provided. The base station may include a memory; and a processor connected to the memory and determining a target channel quality value corresponding to a path loss of the mobile terminal based on a power headroom report (PHR) of the mobile terminal.

The processor performs a transmit power control (TPC) command for the mobile terminal using a difference between a received channel quality value determined through a physical uplink shared channel (PUSCH) of the mobile terminal and the target channel quality value. can decide

The processor determines the maximum number of resource blocks that can be allocated to the mobile terminal based on the PHR and the path loss of the mobile terminal, and assigns fewer resource blocks to the mobile terminal. can be assigned to

According to an embodiment of the present invention, uplink transmission power can be controlled in an LTE-based small cell base station system.

Also, according to an embodiment of the present invention, a reception target SNR (or reception target SINR) required by a base station may be determined based on a power headroom report (PHR) reported by a mobile terminal.

In addition, according to an embodiment of the present invention, the received SNR (or received SINR) can be determined by flattening the SNR (or SINR) of the PUSCH received from the mobile terminal.

In addition, according to an embodiment of the present invention, transmit power control (TPC) based on the difference between the target SNR (or target SINR) and the flattened received SNR (or flattened received SINR) through a periodically performed TCP mapper ) command can be determined.

In addition, according to an embodiment of the present invention, a physical resource block (PRB) that can be maximally allocated can be determined by estimating the current remaining power of the mobile terminal based on the PHR reported by the mobile terminal.

In addition, according to an embodiment of the present invention, by allocating a PRB less than the maximum PRB through an uplink scheduler, it is possible to minimize battery consumption of the mobile terminal while maintaining the received power required by the base station.

1 is a diagram illustrating the concept of open-loop power control.
2 is a diagram illustrating the concept of closed-loop power control.
3 is a diagram illustrating an uplink closed-loop power control method according to an embodiment of the present invention.
4 is a diagram illustrating a method of determining a target SINR (or target SNR) based on path loss of a mobile terminal according to an embodiment of the present invention.
5 is a diagram showing measured SNR when conventional power control is used.
6 is a diagram showing measured SNR when fractional power control is used.
7 is a diagram showing a wireless device (or communication node) according to an embodiment of the present invention.

Hereinafter, with reference to the accompanying drawings, embodiments of the present invention will be described in detail so that those skilled in the art can easily carry out the present invention. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. And in order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and similar reference numerals are attached to similar parts throughout the specification.

In this specification, redundant descriptions of the same components are omitted.

In addition, in this specification, when a component is referred to as being 'connected' or 'connected' to another component, it may be directly connected or connected to the other component, but another component in the middle It should be understood that may exist. On the other hand, in this specification, when a component is referred to as 'directly connected' or 'directly connected' to another component, it should be understood that no other component exists in the middle.

In addition, terms used in this specification are only used to describe specific embodiments and are not intended to limit the present invention.

Also, in this specification, a singular expression may include a plurality of expressions unless the context clearly indicates otherwise.

In addition, in this specification, terms such as 'include' or 'having' are only intended to designate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more It should be understood that the presence or addition of other features, numbers, steps, operations, components, parts, or combinations thereof is not precluded.

Also in this specification, the term 'and/or' includes a combination of a plurality of listed items or any item among a plurality of listed items. In this specification, 'A or B' may include 'A', 'B', or 'both A and B'.

In addition, in the present specification, a mobile terminal includes a terminal, a mobile station, an advanced mobile station, a high reliability mobile station, a subscriber station, It may also refer to a portable subscriber station, access terminal, user equipment (UE), etc., and may refer to a mobile terminal, terminal, mobile station, advanced mobile station, high reliability mobile station, subscriber station, portable It may include all or part of the functions of subscriber stations, access terminals, user equipment, etc.

In addition, in the present specification, a base station (BS) includes an advanced base station, a high reliability base station, a node B (NB), an advanced node B (evolved node B, eNodeB, eNB), access point, radio access station, base transceiver station, mobile multihop relay (MMR)-BS, relay station serving as a base station, base station It may refer to a high reliability relay station, repeater, macro cell base station, small cell base station, etc. It may include all or some functions of a station, a transceiver base station, an MMR-BS, a repeater, a high reliability repeater, a repeater, a macro cell base station, and a small cell base station.

1 is a diagram illustrating the concept of open-loop power control.

In the open loop power control method, a base station transmits a reference signal to a mobile terminal (S10).

The mobile terminal measures the received power of the reference signal transmitted by the base station (S11).

After the measurement, the mobile terminal calculates (estimates) a path loss (S12).

The mobile terminal determines (calculates) the transmission power based on the open-loop power control value configured in the mobile terminal (S13).

The mobile terminal transmits a message to the base station based on the determined transmit power (S14, S15). At this time, since the base station does not perform any feedback, such power control is referred to as open-loop power control.

2 is a diagram illustrating the concept of closed-loop power control.

In the closed-loop power control method, a base station transmits a reference signal to a mobile terminal (S10).

The mobile terminal measures the received power of the reference signal transmitted by the base station (S21).

The mobile terminal calculates (estimates) the path loss (S22).

The mobile terminal determines (calculates) transmission power based on the closed-loop power control value set in the mobile terminal (S23).

The mobile terminal transmits a message to the base station based on the determined transmit power (S25 and S26).

Meanwhile, in the closed-loop power control method, unlike the open-loop power control method, when the base station receives a message from the mobile terminal, it commands the mobile terminal to adjust transmission power. Specifically, the base station may transmit a transmit power control (TPC) command to the mobile terminal in order to correct the difference between the received power and the target power required by the base station (S27).

When receiving the TPC command, the mobile terminal corrects the transmission power by a power offset indicated by the TPC command and determines the transmission power (S24).

The mobile terminal transmits a message to the base station based on the transmission power determined in step S24 (S25 and S26).

Through this, the base station can maintain the target reception power required by the base station.

In the closed-loop power control method, the base station cannot know the transmission power and path loss of the mobile station needed to determine the TPC command. Therefore, a method for efficiently determining the TPC command is needed.

Meanwhile, the PUSCH transmission power of the mobile terminal is determined as shown in Equation 1 below.

In Equation 1, P _CMAX represents the maximum power that the mobile terminal can transmit, has a value of 23±2 [dBm], and is set by the base station. In general, P _CMAX is set to 23[dBm].

In Equation 1, M _PUSCH represents the number of physical resource blocks (PRBs) transmitted through the PUSCH.

In Equation 1, P _{0_PUSCH is} a parameter representing a received power spectral density (PSD) required by the base station. P _{0 _ PUSCH} consists of P _{0_ nominal} and P _{0_UE} . That is, P _{0_ PUSCH} = P _{0_ nominal} +P _{0_ UE} to be.

_{P0_nominal _} has a cell-specific value and is equally applied to all mobile terminals within a cell.

P _{0_UE} is for compensating for an error caused by transmission power setting for each _mobile terminal and a path loss estimation error.

P _{0_ nominal} has a value of [-126, 24] dBm.

P _{0_ UE} has a value of [-8, 7] dB.

And P _{0_ PUSCH} is calculated as in Equation 2 below.

In Equation 2, α represents a compensation factor indicating the degree of signal transmission by compensating for path loss, and SINR ₀ is the target received SINR required by the base station when α = 1 Indicates, P _n represents noise power per PRB, P _CMAX represents the maximum transmission power of the mobile terminal, and M ₀ represents the number of reference transmission PRBs and can be generally set to 1.

In α·PL of Equation 1, PL represents the path loss estimated by the mobile terminal. α indicates whether to transmit a signal by compensating for all of the path loss or to transmit a signal by compensating for only a part of the path loss. Specifically, α may have one value among {0, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1} and may be set by the base station.

In Equation 1, Δ _TF is a parameter for responding to fast fading. Specifically, when a wireless device (eg, a mobile terminal) transmits a signal in a state where Δ _TF is set, transmission power may be additionally compensated according to an allocated modulation and coding scheme (MCS). Through this, the transmission PSD can be changed whenever the MCS is changed. Δ _TF is set to {disable, enable}, and a wireless device (eg, mobile terminal) can turn on/off transmission power compensation according to MCS according to the setting of Δ _TF .

In Equation 1, f(Δ _TPC ) is used to keep the received PSD constant. Specifically, when a wireless device (eg, base station) transmits downlink control information (DCI) by allocating resources to a mobile terminal or transmits DCI for the purpose of power control, the wireless device (eg, base station) previously received A TPC command may be generated based on a difference between the received power of the received PUSCH and the received target power required by the base station. In addition, the wireless device (eg, the base station) may correct the transmission power of the wireless device (eg, the mobile terminal) by including the generated TPC command in the corresponding DCI and transmitting the same.

The TPC command may be determined through an accumulated method or an absolute method. Specifically, the TPC command follows Table 1 (Mapping of TPC command field in DCI format 0/3/4) and Table 2 (Mapping of TPC command field in DCI format 3A) below. The cumulative method or the absolute method is set by the wireless device (eg base station). The accumulation method is a method of continuously accumulating a power value to be compensated for whenever a wireless device (eg, a mobile terminal) receives a TPC command. Unlike the accumulation method, the absolute method is a method in which a wireless device (eg, a mobile terminal) applies a compensation value to transmit power only once.

TPC command field in
DCI format 0/3/4 Accumulated δ_PUSCH,c [dB] Absolute δ_PUSCH,c [dB] only DCI format 0/4 0 -One -4 One 0 -One 2 One One 3 3 4

TPC command field in
DCI format 3A Accumulated δ_PUSCH,c [dB] 0 -One One One

를 나타낸다. 표 1 및 표 2에서,

는 TPC 커맨드 지시 인자에 따라 실제 보상되어야 하는 송신 전력을 나타낸다. 예를 들면, 0의 값을 가지는 TPC 커맨드는 송신 신호의 PSD를 -1dB 만큼 낮추라는 것을 의미한다.In Tables 1 and 2, δ_PUSCH,c is

indicates In Tables 1 and 2,

represents the transmission power to be actually compensated according to the TPC command indication factor. For example, a TPC command having a value of 0 means lowering the PSD of a transmission signal by -1dB.

Considering the PUSCH transmit power of the mobile terminal in Equation 1, a method for efficiently determining the TPC command is required. Through this, the received SNR (or received SINR) required by the base station can be matched even when the path loss at the current location of the mobile terminal is not known.

In addition, in order to reduce battery consumption of the mobile terminal, transmission power should not exceed P _CMAX . If the transmission power exceeds P _CMAX , the base station's PUSCH reception performance deteriorates, and eventually the uplink performance deteriorates and the mobile terminal's battery consumption becomes extreme.

Hereinafter, a method of performing uplink closed-loop power control in an LTE-based small cell base station system, that is, a method of controlling uplink transmission power, will be described.

A wireless device (eg, a small cell base station) receives a power headroom report (PHR) indicating an amount of available transmit power of the mobile terminal from the mobile terminal. And the wireless device (eg, small cell base station) determines a target SNR (or target SINR) required for the current location of the mobile terminal (corresponding to the current location or path loss of the mobile terminal) based on the received PHR . In this specification, an embodiment of the present invention will be described by taking a case in which the channel quality information is SNR or SINR as an example. In this specification, the contents described for the case in which the channel quality information is SNR may be equally or similarly applied to the case in which the channel quality information is SINR, and vice versa. However, this is just an example, and the embodiment of the present invention can be applied even when the channel quality information is not SNR or SINR.

A wireless device (eg, a small cell base station) receives an uplink data channel (eg, PUSCH) from a mobile terminal, and applies a filter to the received SNR (received SINR) measured through the received SNR (or smoothed) receive SINR).

The wireless device (eg, small cell base station) obtains the difference between the periodically determined target SNR (or target SINR) and the flattened received SNR (or flattened received SNR), and sends a TPC command based on the difference to the TPC mapper ) is determined through

A wireless device (eg, a small cell base station) receives a PHR from a mobile terminal and determines the maximum number of PRBs that can be allocated to the mobile terminal based on the PHR and the current location (or path loss) of the mobile terminal.

A wireless device (eg, a small cell base station) allocates a number of PRBs smaller than the maximum number of PRBs to the mobile terminal during scheduling by the uplink scheduler.

The wireless device (eg, the small cell base station) transmits the TPC command determined through the TPC mapper to the mobile terminal.

3 is a diagram illustrating an uplink closed-loop power control method according to an embodiment of the present invention.

As illustrated in FIG. 3, for uplink closed-loop power control, a procedure for determining a target SINR (or target SNR) (S100), a procedure for determining M _max (S110), and a SINR filter (or SNR filter) A procedure for determining an initial value for (S120), a procedure for using an SINR filter (or SNR filter) (S130), a procedure for determining a TPC command (S140), and a scheduling procedure (S150) are performed.

First, a procedure for determining a target SINR (or target SNR) (S100) will be described.

Whenever a wireless device (eg, a small cell base station) receives a PHR from a mobile terminal, it determines a target SINR (or target SNR) for the mobile terminal based on the received PHR value and the value of α.

The target SINR (or target SNR) depends on the value of α for determining how much to compensate for the path loss and the path loss of the mobile terminal. Here, the path loss of the mobile terminal may correspond to the current location of the mobile terminal.

When α = 1, the wireless device (eg, the small cell base station) receives a signal with constant reception power regardless of the path loss of the mobile terminal. That is, regardless of whether the mobile terminal is near or far from the base station, the base station receives signals with the same reception power. Such power control is referred to as conventional power control (CPC).

When α < 1, the received PSD varies according to the path loss of the mobile terminal. That is, the base station receives a signal with a high PSD for a mobile terminal that is close to the base station and has a small path loss, and receives a signal with a low PSD for a mobile terminal that is far from the base station and has a large path loss. Such power control is referred to as fractional power control (FPC).

P _{0_PUSCH} (received PSD requested by the base _station ) of conventional power control (CPC) has the same value for all mobile terminals regardless of the path loss of the mobile terminal, and can be obtained from Equation 2. When α = 1 is substituted into Equation 2, the following equation is obtained.

In the above equation, P _n represents noise power per PRB, and is calculated as in the following equation.

Therefore, when α = 1, the transmission (Tx) PSD of the mobile terminal is as follows.

Since the path loss is consumed before the signal reaches the base station, the reception (Rx) PSD at the base station is expressed by the following equation.

Therefore, the target SINR (or target SNR) of conventional power control (CPC) is as shown in Equation 3 below.

Meanwhile, in partial power control (FPC), the target SINR (or target SNR) varies according to the path loss of the mobile terminal, that is, the current location of the mobile terminal. Therefore, the transmission (Tx) PSD of the mobile terminal is as follows.

Since the path loss is consumed before the signal reaches the base station, the reception (Rx) PSD at the base station is shown in Equation 4 below.

As illustrated in Equation 4, path loss is an important factor in fractional power control (FPC). However, since the path loss for the mobile terminal is measured by the mobile terminal, the base station cannot directly know this. Therefore, the base station can indirectly infer the path loss of the mobile terminal through the PHR of the mobile terminal, and determine a target SINR (or target SNR) for the mobile terminal according to the inferred path loss. This will be described in detail with reference to FIG. 4 .

4 is a diagram illustrating a method of determining a target SINR (or target SNR) based on path loss of a mobile terminal according to an embodiment of the present invention. In Fig. 4, the horizontal axis represents the path loss and the vertical axis represents the received SINR. In Fig. 4, IN represents noise power.

As illustrated in Fig. 4, the target SINR (or target SNR) is obtained with a slope m along α. m is equal to Equation 5 below.

In Equation 5, ΔX and ΔY are as follows.

In the above equation, TargetSINR' represents a new target SINR according to the path loss of the mobile terminal, and TargetSINR represents the target SINR of Equation 3 for the case of α=1.

Further, PL and PL _max may be obtained (inferred) from Equation 1 based on PHR(P _h ) as in Equation 6 below.

In Equation 6, P _h represents the amount of available transmit power (i.e., power headroom) indicated by the PHR of the mobile terminal, P _CMAX represents the maximum transmit power of the mobile terminal, and M _PUSCH represents the PRB transmitted through the PUSCH. number, and PL _max represents the maximum path loss. Here, P _h is obtained based on the difference between the maximum transmission power of the mobile terminal and the current PUSCH transmission power. Specifically, P _h is reported through PHR in the form of indicators shown in Table 3 below. P _h represents the amount of available transmit power corresponding to the PHR indicator. Therefore, when P _h = 0, the amount of available transmit power is 0, and the path loss is maximized, so that PL _max can be obtained. Hereinafter, P _h may also be expressed as PHR(P _h ).

In Table 3, PH means P _h .

Through this, a new target SINR (Target SINR') according to the path loss of the mobile terminal can be obtained as shown in Equation 7 below.

In Equation 7, PH means P _h .

A target SINR (or target SNR) for the case where partial power control (FPC) is used may be determined through Equation 7.

Next, a procedure for determining M _max (S110) will be described.

As illustrated in Equation 1, the PUSCH transmit power is determined according to the path loss at the current location of the mobile terminal, the TPC command, and the number of allocated PRBs. In particular, in an environment in which path loss and shadowing of a mobile terminal do not change rapidly, such as in a small cell environment, the main factor for changing transmission power is the number of allocated PRBs. In this situation, in order to reduce battery consumption of the mobile terminal, the transmit power must be controlled so as not to exceed P _CMAX , which is the maximum transmit power of the mobile terminal.

Accordingly, the wireless device (eg, base station) can determine the maximum number of PRBs that can be currently allocated to the mobile terminal based on the number of PRBs allocated for PHR transmission whenever a PHR is received. In addition, the wireless device (eg, base station) may determine the number of PRBs to be allocated to the mobile terminal within a range not exceeding the maximum number of PRBs during scheduling by the scheduler.

M _max represents the maximum number of PRBs that can be allocated to a mobile terminal within a range not exceeding P _cmax . To find M _max , the current path loss state of the mobile terminal may be considered. Specifically, M _max can be obtained as follows based on PHR(P _h ).

The following equation can be derived from equation (6).

And from Equation 1 and Equation 1, Equation 8 below can be derived.

And P _CMAX according to M _max can be obtained as shown in Equation 9 below.

Therefore, M _max can be obtained as shown in Equation 10 below based on Equations 8 and 9.

Next, a procedure (S130) using the SINR filter (or SNR filter) will be described.

When a base station receives a PUSCH, a physical (PHY) layer of the base station measures a received SINR (or received SNR) for the PUSCH and reports it to the scheduler of the base station. Here, the measured received SINR (or received SNR) is not always an accurate value due to the state of the radio channel and the measurement error of the receiver. Accordingly, the base station may obtain a smoothed received SINR (or smoothed received SINR) by smoothing the received SINR (or received SNR) through an SINR filter (or SNR filter).

The base station may use an exponential filter, which is one of moving average filters, to flatten the SINR (or SNR) of the PUSCH received from the mobile terminal. At this time, since the use of a filter that is not too complex is required due to the hardware characteristics of the small cell, the base station may use a single step exponential filter as shown in Equation 11 below.

In Equation 11, Y(t) represents an output value output from the SINR filter (or SNR filter) at time t, and Y(t-1) is output from the SINR filter (or SNR filter) at time t-1 represents an output value, and X(t) represents an input value input to the SINR filter (or SNR filter) at time t (ie, the SINR (or SNR) of the received PUSCH). In Equation 11, μ represents a SINR filter parameter (or SNR filter parameter), and 0≤μ≤1. μ can generally have a value of 0.7 to 0.9, and can be determined experimentally.

Next, a procedure for determining an initial value for the SINR filter (or SNR filter) (S120) will be described.

The base station may use the SINR value (or SNR value) obtained when receiving the M3 message as an initial value for using the SINR filter (or SNR filter). That is, the received SINR value (or received SNR value) of the M3 message may be used as an initial value for the SINR filter (or SNR filter). Here, the M3 message is a message first received by the base station in a random access procedure for the mobile terminal to access the base station. Power control for the M3 message is performed based on a received SINR value (or SNR value) of a physical random access channel (PRACH) preamble.

는 아래의 수학식 12와 같이 정의될 수 있다.for power control of M3 messages.

Can be defined as in Equation 12 below.

는 수신된 PRACH 프리앰블의 SINR(또는 SNR) 대비 M3 수신을 위해 필요한 전력 오프셋을 나타내며, 시스템 정보에 정의된다.In Equation 12, Received PRACH SINR represents the SINR (or SNR) of the received PRACH preamble. And,

Represents a power offset required for M3 reception compared to the SINR (or SNR) of the received PRACH preamble, and is defined in system information.

TPC commands for M3 (or M3 message) are shown in Table 4 below.

TPC command Value (in dB) 0 -6 One -4 2 -2 3 0 4 2 5 4 6 6 7 8

Next, a procedure for determining the TPC command (S140) will be described.

The TPC mapper is a function that determines a TPC command value based on a difference between a target SINR (or target SNR) and a filtered (flattened) received SINR (or received SNR).

If the TPC mapper determines the TPC command value whenever there is a difference between the target SINR (or target SNR) and the filtered (flattened) received SINR (or received SNR), even a temporary channel fluctuation can be reflected. and this may cause errors in power control. In order to prevent such a power control error, the TPC mapper may determine the TPC command based on the received SINR (or received SNR) determined through the SINR filter (or SNR filter) during a certain period (TPC command update period).

The TPC mapper of the base station may determine the TPC command using the following equation according to Tables 1 and 2.

는 타겟 SINR(또는 타겟 SNR)과 수신 SINR(또는 SNR) 간의 차이를 나타내고, ReceivedSINR은 필터링된(평탄화된) 수신 SINR(또는 SNR)을 나타낸다. 구체적으로 상기 수학식에서, ReceivedSINR은 TPC 커맨드 갱신 주기(update period) 동안에 필터링되어(평탄화되어) 결정된 수신 SINR(또는 SNR)을 나타낼 수 있다.In the above equation,

Represents the difference between the target SINR (or target SNR) and the received SINR (or SNR), ReceivedSINR represents the filtered (flattened) received SINR (or SNR). Specifically, in the above equation, ReceivedSINR may indicate a received SINR (or SNR) determined by being filtered (flattened) during a TPC command update period.

The TPC command update cycle may vary depending on the system installation environment or radio channel environment.

를 결정(계산)하여,

에 기초한 TPC 커맨드를 이동 단말에게 송신할 수 있다. 그리고 기지국은 그 이후부터 다음의 TPC 커맨드 갱신 주기까지(다음의 TPC 커맨드 갱신 주기가 종료되는 시점까지)는

=0 으로 설정하여,

에 기초한 TPC 커맨드를 이동 단말에게 송신할 수 있다. 그리고 기지국은 해당 TPC 커맨드 갱신 주기가 지난 후에

를 다시 결정하여,

에 기초한 TPC 커맨드를 이동 단말에게 송신할 수 있다.After the TPC command update period has elapsed, the base station

By determining (calculating),

A TPC command based on can be transmitted to the mobile terminal. And the base station from then until the next TPC command update cycle (until the next TPC command update cycle ends)

=0,

A TPC command based on can be transmitted to the mobile terminal. And the base station after the corresponding TPC command update period has passed

By re-determining

A TPC command based on can be transmitted to the mobile terminal.

Next, a scheduling procedure (S150) of the scheduler will be described.

The base station may allocate a number of PRBs smaller than the maximum number of PRBs to the mobile terminal and may transmit a TPC command to the mobile terminal. In FIG. 3, M of 'M/TPC' represents the number of PRBs allocated to a mobile terminal, and TPC of 'M/TPC' represents a TPC command transmitted to the mobile terminal.

5 is a diagram showing measured SNR when conventional power control is used. 6 is a diagram showing measured SNR when fractional power control is used. 5 and 6, OLPC represents open-loop power control and CLPC represents closed-loop power control. 5 and 6, P _{0 represents} P _{0_PUSCH} .

Specifically, in FIGS. 5 and 6, as the mobile terminal moves from the cell center to the cell edge, the PUSCH received by the small cell base station equipped with the power control method according to the embodiment of the present invention The results of measuring the SNR and M _max of are exemplified.

As illustrated in the measurement results of conventional power control (CPC) and fractional power control (FPC), the received SNR is greater than the target SNR when the closed-loop power control method is used than when the open-loop power control method is used. The transmit power of the mobile terminal is controlled without significantly departing.

And as illustrated in FIGS. 5 and 6 , as the mobile terminal moves toward the cell edge (to the right of the horizontal axis), the maximum number of PRBs (M _max ) that can be allocated to the mobile terminal is limited. Through this, the small cell base station can adaptively perform power control of the mobile terminal while reducing the battery consumption of the mobile terminal.

7 is a diagram showing a wireless device (or communication node) according to an embodiment of the present invention. The wireless device TN100 may be a base station or a terminal described in this specification, and may be a transmitter or receiver.

In the embodiment of FIG. 7 , the wireless device TN100 may include at least one processor TN110, a transmitting/receiving device TN120 connected to a network to perform communication, and a memory TN130. In addition, the wireless device TN100 may further include a storage device TN140, an input interface device TN150, and an output interface device TN160. Components included in the wireless device TN100 may communicate with each other by being connected by a bus TN170.

The processor TN110 may execute program commands stored in at least one of the memory TN130 and the storage device TN140. The processor TN110 may mean a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor on which methods according to embodiments of the present invention are performed. Processor TN110 may be configured to implement procedures, functions, and methods described in connection with embodiments of the present invention. The processor TN110 may control each component of the wireless device TN100.

Each of the memory TN130 and the storage device TN140 may store various information related to the operation of the processor TN110. Each of the memory TN130 and the storage device TN140 may include at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory TN130 may include at least one of read only memory (ROM) and random access memory (RAM).

The transmitting/receiving device TN120 may transmit or receive a wired signal or a wireless signal. Also, the wireless device TN100 may have a single antenna or multiple antennas.

Meanwhile, the embodiments of the present invention are not implemented only through the devices and/or methods described so far, and may be implemented through a program that realizes functions corresponding to the configuration of the embodiments of the present invention or a recording medium in which the program is recorded. And, such an implementation can be easily implemented by those skilled in the art from the description of the above-described embodiment.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims are also included in the scope of the present invention. that fall within the scope of the right.

Claims (22)

As a method for a base station to control uplink transmission power of a mobile terminal,
receiving, from the mobile terminal, an amount of available transmit power of the mobile terminal;
determining a target channel quality value corresponding to a current location of the mobile terminal based on the amount of available transmission power;
determining a reception channel quality value using an uplink data channel received from the mobile terminal; and
Determining transmit power control (TPC) using a difference between the target channel quality value and the received channel quality value
including,
Determining the received channel quality value,
Smoothing a first channel quality value measured for the uplink data channel through an exponential filter that is a moving average filter.
including,
The step of smoothing the first channel quality value measured for the uplink data channel through an exponential filter, which is a moving average filter,
Using, by the base station, a second channel quality value for the M3 message received from the mobile terminal in a random access procedure as an initial value for the exponential filter.
Including, the control method of the base station. According to claim 1,
Receiving the amount of available transmission power includes:
Receiving a power headroom report (PHR) indicating the amount of available transmit power;
Determining the target channel quality value based on the amount of available transmission power includes:
inferring the path loss using the PHR when a first value indicating how much to compensate for the path loss corresponding to the current location of the mobile terminal is less than 1; and
Determining the target channel quality value according to the inferred path loss
Base station control method. According to claim 2,
Determining the target channel quality value according to the inferred path loss,
Using Equation 1 below, determining the target channel quality value
Base station control method.
[Equation 1]

(target': the target channel quality value, α: the first value, P _h : the amount of available transmission power indicated by the PHR, target: target channel quality value for the case of α = 1) According to claim 1,
Determining the target channel quality value based on the amount of available transmission power includes:
Determining the target channel quality value using Equation 1 below when a first value indicating how much path loss corresponding to the current location of the mobile terminal is compensated for is 1
Base station control method.
[Equation 1]

(target: the target channel quality value, P _{0_CH} : received power spectral density (PSD) required by the base station) delete delete According to claim 1,
The flattening step is
Flattening the first channel quality value using a 1-step exponential filter defined by Equation 1 below
Base station control method.
[Equation 1]

(Y(t): output value output from the single-step exponential filter at time t, Y(t-1): output value output from the single-step exponential filter at time t-1, X(t): time t The first channel quality value input to the single-step exponential filter in, 0≤μ≤1) delete According to claim 1,
The step of determining the TPC,
calculating a first difference between the target channel quality value and the received channel quality value determined during an update period for updating the TPC at a first time point; and
determining a TPC command based on the first difference.
Base station control method. According to claim 9,
The update period is changed according to the radio channel environment.
Base station control method. According to claim 9,
Determining the TPC command based on the first difference comprises:
Setting a difference between the target channel quality value and the received channel quality value to 0 from the first time point until the next update period ends
Base station control method. According to claim 1,
determining the maximum number of resource blocks that can be allocated to the mobile terminal based on the amount of available transmission power and the current location of the mobile terminal; and
allocating a number of resource blocks smaller than the maximum number to the mobile terminal;
A control method of a base station further comprising a. According to claim 12,
Receiving the amount of available transmission power includes:
Receiving a power headroom report (PHR) indicating the amount of available transmit power;
Determining the maximum number of
Comprising the step of calculating the maximum number using Equation 1 below
Base station control method.
[Equation 1]

(M _max : the maximum number, M _PUSCH : the number of resource blocks transmitted through the uplink data channel, PHR (P _h ): available transmission power indicated by the PHR) According to claim 1,
The base station is a small cell base station,
The target channel quality value and the received channel quality value are one of a signal-to-interference plus noise ratio (SINR) and a signal to noise ratio (SNR),
The uplink data channel is a physical uplink shared channel (PUSCH).
Base station control method. As a method for a mobile terminal to control uplink transmission power,
transmitting, to a base station, an amount of available transmission power of the mobile terminal;
Transmitting an uplink data channel to the base station; and
Transmission power control determined by a difference between a target channel quality value based on a first value indicating how much to compensate for path loss of the mobile terminal and the amount of available transmission power and a reception channel quality value for the uplink data channel ( Receiving a transmit power control (TPC) from the base station
including,
The reception channel quality value for the uplink data channel is,
The first channel quality value measured for the uplink data channel is determined by smoothing through an exponential filter that is a moving average filter, and the initial value of the exponential filter is determined by the base station A method for controlling a mobile terminal, wherein a second channel quality value for an M3 message received from the mobile terminal is used in a random access procedure. According to claim 15,
Further comprising the step of allocating from the base station fewer resource blocks than the maximum number of resource blocks that can be allocated to the mobile terminal;
The maximum number is determined based on the amount of available transmission power and the path loss of the mobile terminal.
A control method of a mobile terminal. delete Memory; and
A processor connected to the memory and determining a target channel quality value corresponding to a path loss of the mobile terminal based on a power headroom report (PHR) of the mobile terminal;
the processor,
Determine a transmit power control (TPC) command for the mobile terminal using a difference between a received channel quality value determined through a physical uplink shared channel (PUSCH) of the mobile terminal and the target channel quality value,
The processor also
determining the maximum number of resource blocks that can be allocated to the mobile terminal based on the PHR and the path loss of the mobile terminal, and allocating resource blocks smaller than the maximum number to the mobile terminal;
The maximum number is determined by the processor using Equation 1 below.
[Equation 1]

(M _max : the maximum number, M _PUSCH : the number of resource blocks transmitted through the PUSCH, PHR (P _h ): available transmission power indicated by the PHR) delete delete As a method for a base station to control uplink transmission power of a mobile terminal,
receiving, from the mobile terminal, an amount of available transmit power of the mobile terminal;
determining a target channel quality value corresponding to a current location of the mobile terminal based on the amount of available transmission power;
determining a reception channel quality value using an uplink data channel received from the mobile terminal; and
Determining transmit power control (TPC) using a difference between the target channel quality value and the received channel quality value
including,
The step of determining the TPC,
calculating a first difference between the target channel quality value and the received channel quality value determined during an update period for updating the TPC at a first time point; and
determining a TPC command based on the first difference;
Including,
Determining the TPC command based on the first difference comprises:
Setting a difference between the target channel quality value and the received channel quality value to 0 from the first point in time until the next update period ends.
Including, the control method of the base station. As a method for a base station to control uplink transmission power of a mobile terminal,
receiving, from the mobile terminal, an amount of available transmit power of the mobile terminal;
determining a target channel quality value corresponding to a current location of the mobile terminal based on the amount of available transmission power;
determining a reception channel quality value using an uplink data channel received from the mobile terminal;
Determining transmit power control (TPC) using a difference between the target channel quality value and the received channel quality value
determining the maximum number of resource blocks that can be allocated to the mobile terminal based on the amount of available transmission power and the current location of the mobile terminal; and
allocating a number of resource blocks smaller than the maximum number to the mobile terminal;
Including more,
The maximum number is determined using Equation 1 below, the control method of the base station.
[Equation 1]

(M _max : the maximum number, M _PUSCH : the number of resource blocks transmitted through the PUSCH, PHR (P _h ): available transmission power indicated by the PHR)

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