KR102392917B1 - Apparatus And Method For Controlling Transmission Power In Wireless Communication System - Google Patents

Abstract

The present invention sets the target throughput according to one of the average requested throughput or the maximum required throughput of K IIoT terminals, calculates the target SINR according to the set target throughput, and obtains the calculated uplink SNR using the calculated target SINR And, if the obtained uplink SNR is an achievable uplink SNR, an uplink transmission power allocator and uplink transmission power that determine the uplink transmission power for data transmission from the K IIoT terminals to the base station according to the uplink SNR It is possible to determine energy-efficient uplink and downlink transmission power, including a downlink transmission power allocator that determines the downlink transmission power for data transmission from the base station to the K IIoT terminals based on It is possible to provide an apparatus and method for controlling transmission power of a wireless communication system that enables cost-effective communication without interruption of supply.

Description

Apparatus And Method For Controlling Transmission Power In Wireless Communication System

The present invention relates to an apparatus and method for controlling transmission power, and to an apparatus and method for controlling transmission power capable of improving transmission power energy efficiency of a wireless communication system.

In the past, a massive multiple-input multiple-output (Massive MIMO) technique has been mainly used in mobile communication networks. However, recently, research to apply large-scale MIMO to the Industrial Internet of Things (IIoT) is being conducted.

However, in the case of a mobile communication network, it is designed according to high reliability and speed requirements, and high cost can be afforded. On the other hand, IIoT requires high reliability, but speed may not be as important depending on the application or purpose. Also, in IIoT, reducing the possibility of power outages and reducing costs can be a major issue. Like terminals in mobile communication networks, in IIoT, a plurality of IIoT terminals mainly operate based on a battery with limited power, so it is important to control the uplink transmission power of the IIoT terminal. However, in IIoT, not only the amount of power that can be consumed in the downlink can be limited, but also control the downlink transmission power to reduce the cost caused by the large amount of power consumption caused by data transmission to multiple IIoT terminals. very important.

Korean Patent Registration No. 10-1642361 (Registered on July 19, 2016)

SUMMARY OF THE INVENTION It is an object of the present invention to provide a transmission power control apparatus and method capable of improving the transmission power energy efficiency of a wireless communication system.

Another object of the present invention is to provide an apparatus and method for controlling transmission power of a wireless communication system that enables cost-effective communication without interruption of power supply due to excessive use of power in a field in which available power is limited.

The transmission power control apparatus of the wireless communication system according to an embodiment of the present invention for achieving the above object is a target throughput according to one of the average required throughput (hereinafter ARTP) or the maximum required throughput (hereinafter MRTP) of K IIoT terminals. set, calculate a target signal-to-interference noise ratio (hereinafter referred to as target SINR) according to the set target throughput, and obtain a calculated uplink signal-to-noise ratio (hereinafter referred to as uplink SNR) using the calculated target SINR, and the calculated uplink SNR is an uplink transmission power allocator for determining an uplink transmission power for data transmission from the K IIoT terminals to the base station according to the calculated uplink SNR if it does not exceed the preset maximum allowable uplink SNR; and a downlink transmission power allocator for determining a downlink transmission power for data transmission from the base station to the K IIoT terminals based on the uplink transmission power.

The uplink transmission power allocator may include: a target throughput setting unit configured to set the target throughput; a target SINR determining unit for calculating and obtaining the target SINR using a preset downlink resource ratio and bandwidth, a coherence interval, and a reference signal transmission interval together with the target throughput; If the target SINR is determined to be an SINR reachable by the M antennas of the base station, an uplink SNR is calculated in a predetermined manner, and the target SINR is unreachable or the calculated uplink SNR is a predetermined maximum allowable uplink SNR if exceeded, an uplink SNR setting unit for setting the maximum allowable uplink SNR to the uplink SNR; and an uplink transmission power determining unit for calculating the uplink transmission power corresponding to the set uplink SNR in a predetermined manner.

When the target throughput setting unit sets the target throughput according to the ARTP, the target throughput is set at a predetermined ratio based on the cumulative distribution function (CDF) of the K IIoT terminals, and in the MRTP When setting the target throughput according to this, a reference SINR indicating a downlink SINR in which uplink transmission power and downlink transmission power are not taken into account is calculated, and a throughput corresponding to the calculated reference SINR is calculated and set as the target throughput. there is.

When the base station performs precoding according to a maximum-ratio (hereinafter referred to as MR) process, the reference SINR is obtained by the equation

(where 0.5 is a predetermined downlink resource ratio (ζ ^d ), B is a bandwidth, τ _c is a coherence interval, τ _p is a reference signal transmission interval, and Tput _t is a target throughput).

The target throughput is calculated from the reference SINR

(where 0.5 is a predetermined downlink resource ratio (ζ ^d ), B is a bandwidth, τ _c is a coherence interval, and τ _p is a reference signal transmission interval).

The target SINR determining unit calculates the target SINR (SINR _t ) using the target throughput, downlink resource ratio, bandwidth, coherence interval, and reference signal transmission interval.

(Where α ^t is a scaling vector preset to prevent power shortage of the base station, τ _c is a coherence interval, τ _p is a reference signal transmission interval. B is a bandwidth).

In the uplink SNR setting unit, the target SINR is an equation according to the number of antennas (M) of the base station

It is determined whether or not is satisfied, and if it is satisfied, the

(where β is a large-scale fading constant set equally between the base station and K terminals, L and J are the number of groups of K terminals grouped for reuse of the reference signal (RS) and the number of terminals per group, τ _p is is a reference signal transmission interval, ρ _u calculates the uplink SNR according to the calculated uplink SNR), the target SINR does not satisfy the equation according to the number of antennas (M) of the base station, or the calculated uplink SNR If this maximum allowable uplink SNR is exceeded, the maximum allowable uplink SNR calculated using the reference SINR may be set as the uplink SNR.

The uplink transmission power determining unit is expressed by the equation

(Where G _bs is the antenna gain of the base station, _Gue is the antenna gain of the terminal, N ₀ B is the noise power in a given bandwidth B, ω _bs is the noise figure of the base station (BS), p _u is Uplink transmission power can be calculated according to the uplink total loss power)).

The downlink transmission power allocator is

Accordingly, the downlink transmission power p _d may be calculated.

The transmission power control apparatus may be included in the base station, and the base station may transmit the uplink transmission power to the K terminals using a Transmission Power Control (TPC) command.

The transmission power control method of the wireless communication system according to another embodiment of the present invention for achieving the above object is a target throughput according to one of the average requested throughput (hereinafter ARTP) or the maximum required throughput (hereinafter MRTP) of K IIoT terminals. setting up; calculating a target signal-to-interference noise ratio (hereinafter referred to as target SINR) according to a set target throughput; obtaining an uplink signal-to-noise ratio (hereinafter referred to as uplink SNR) calculated using the calculated target SINR; If the calculated uplink SNR does not exceed the predetermined maximum allowable uplink SNR, determining an uplink transmission power for data transmission from the K IIoT terminals to the base station according to the calculated uplink SNR; and determining a downlink transmission power for data transmission from the base station to the K IIoT terminals based on the uplink transmission power.

Accordingly, the apparatus and method for controlling the transmission power of a wireless communication system according to an embodiment of the present invention is to achieve the target throughput by setting the target throughput corresponding to the data rate that a plurality of terminals should maintain on average or the maximum data rate under a given condition. Energy-efficient uplink and downlink transmission power can be determined by calculating the SINR for In addition, by introducing a scaling factor to prevent power wastage due to excessive transmission power determination, cost-effective communication is performed without power supply interruption due to excessive power use when applied to fields such as industrial IoT where available power is limited make it possible

1 shows a schematic structure of a wireless communication system according to an embodiment of the present invention.
FIG. 2 shows a schematic configuration of the base station of FIG. 1 .
FIG. 3 shows a detailed configuration of the transmission power control unit of FIG. 2 .
4 shows an example of a transmission power control method of a wireless communication system according to an embodiment of the present invention.
5 shows another example of a method for controlling transmission power of a wireless communication system according to an embodiment of the present invention.
6 shows a simulation result of the transmission power control method of the wireless communication system according to the present embodiment.

In order to fully understand the present invention, the operational advantages of the present invention, and the objects achieved by the practice of the present invention, reference should be made to the accompanying drawings illustrating preferred embodiments of the present invention and the contents described in the accompanying drawings.

Hereinafter, the present invention will be described in detail by describing preferred embodiments of the present invention with reference to the accompanying drawings. However, the present invention may be embodied in various different forms, and is not limited to the described embodiments. In addition, in order to clearly explain the present invention, parts irrelevant to the description are omitted, and the same reference numerals in the drawings indicate the same members.

Throughout the specification, when a part "includes" a certain component, it does not exclude other components, unless otherwise stated, meaning that other components may be further included. In addition, terms such as "...unit", "...group", "module", and "block" described in the specification mean a unit that processes at least one function or operation, which is hardware, software, or hardware. and a combination of software.

1 shows a schematic structure of a wireless communication system according to an embodiment of the present invention.

As shown in FIG. 1, the wireless communication system according to this embodiment may include a base station (BS) and K terminals (UE). Here, the K terminals (UEs) may be industrial Internet of Things (IIoT) terminals. That is, the wireless communication system according to the present embodiment may be an IIoT network. Since the service area is generally limited in the IIoT network, it has a simple cell structure to reduce design costs. Accordingly, in this embodiment, it is assumed that the wireless communication system is a single-cell IIoT network. Although it is a single cell, a large number of IIoT terminals (UEs) may be deployed in the IIoT network within the cell. In some cases, the K terminals (UE) may receive wireless power as well as perform data communication with the base station (BS).

FIG. 2 shows a schematic configuration of the base station of FIG. 1 .

Referring to FIG. 2 , the base station BS may include a baseband unit 100 , a plurality of RF chains 200 , a precoding unit 300 , a transmission power control unit 400 , and M antennas.

The baseband unit 100 receives data to be transmitted and converts it into transmission data corresponding to M antennas. In this case, the baseband unit 100 may convert the converted transmission data into an analog signal and output the converted data. The plurality of RF chains 200 receive an analog signal applied from the baseband unit 100 and uplink-convert it into a signal of a predetermined frequency band. The precoding unit 300 may include a plurality of power amplifiers and the like. The precoding unit 300 receives a signal output from each of the plurality of RF chains 200, and adjusts the power intensity according to the control of the transmission power control unit 400 to generate a power control precoded precoding signal, The generated precoding signal is transmitted to M antennas. The M antennas transmit a transmission signal to a plurality of IIoT terminals (UE) according to a signal transmitted from the precoding unit 300 .

Here, as an example, it has been described that only the analog-based precoder 300 operates as a precoder that adjusts the strength of signals transmitted to M antennas. It may be configured in the form of a hybrid precoder that performs digital precoding, and then the precoder 300 performs analog precoding.

Here, the transmit power control unit 400 operates as a transmit power control device according to the present embodiment to set a target data rate or a target throughput for uplink transmission, and set the target throughput under a constrained condition. Determine the uplink transmission power of a plurality of IIoT terminals (UE) that can satisfy And according to the determined uplink transmission power, the base station (BS) calculates the downlink transmission power so that the downlink transmission signal can be transmitted energy-efficiently to a plurality of IIoT terminals (UE) to control the precoding unit 300 .

At this time, the transmission power control unit 400 sets the target throughput according to the average required throughput (ARTP) of a plurality of IIoT terminals (UE), or the maximum required throughput of a plurality of IIoT terminals (UE) (Maximum Required Throughput: MRTP) can be set. And by determining the downlink transmission power using the uplink transmission power of a plurality of IIoT terminals (UE) determined according to the set target throughput, the power of the precoding signal to be transmitted from the precoding unit 300 to the M antennas adjust the

When a plurality of IIoT terminals (UE) transmit an uplink transmission signal to a base station (BS), the simplest way to determine the transmission power is to transmit an uplink transmission signal by a plurality of IIoT terminals (UE) with a predetermined fixed power. will be. However, when a plurality of IIoT terminals (UE) transmit an uplink transmission signal with the same fixed transmission power, the IIoT terminal (UE) adjacent to the base station (BS) performs communication at a high data rate, whereas IIoT at a long distance A terminal (UE) performs communication at a low data rate or is unable to perform communication. Also, as in the IIoT network, in a large-scale MIMO system, the number of IIoT terminals (UE) is very large, and this may cause a power shortage when the base station (BS) tries to transmit a downlink transmission signal.

As an example, it may be assumed that the uplink transmission power p _u of each of the plurality of IIoT terminals is fixed to 30 mW. This is relatively much less transmission power than 100 ~ 200mW, which is a general uplink transmission power of a terminal in a mobile communication system. Nevertheless, if the number (K) of the IIoT terminal (UE) is 1000, the downlink transmission power (p _d ) of the base station (BS) is the uplink transmission power (p _u ) and the number of IIoT terminals (UE) ( It is calculated as 300W by the product of K) (p _d = K o p _u ). Considering that the downlink transmission power is 80 W in a mobile communication system with a bandwidth (B) of 20 MHz in general, when a plurality of IIoT terminals (UE) have a fixed uplink transmission power in a large-scale MIMO system, the base station (BS) ) may increase in cost due to high downlink transmission power. Moreover, communication may be interrupted due to a power shortage of the base station (BS).

Accordingly, the transmit power control unit 400, which is the transmit power control device of this embodiment, is an IIoT terminal (UE) so that communication between a plurality of IIoT terminals (UE) and a base station (BS) can be maintained at low cost without interruption in a large-scale MIMO system Based on the average requested throughput (ARTP) or maximum requested throughput (MRTP) of

In this embodiment, the base station (BS) may include M antennas to transmit/receive data to and from K IIoT terminals (UE) while controlling interference according to a beamforming technique. And it is assumed that all K IIoT terminals (UEs) include one single antenna.

FIG. 3 shows a detailed configuration of the transmission power control unit of FIG. 2 .

Referring to FIG. 3 , the transmit power control unit 400 may include an uplink transmit power allocator 410 and a downlink transmit power allocator 420 . The uplink transmission power allocator 410 allocates the uplink transmission power through which the K IIoT terminals (UE) transmit a transmission signal to the base station (BS) according to the average requested throughput (ARTP) or the maximum requested throughput (MRTP).

And the downlink transmission power allocator 420 is a downlink transmission power for the base station (BS) to transmit a transmission signal to the K IIoT terminals (UE) according to the uplink transmission power determined by the uplink transmission power allocator 410. allocate

The uplink transmission power allocator 410 may include a target throughput setting unit 411 , a target SINR determining unit 412 , an uplink SNR setting unit 413 , and an uplink transmission power determining unit 414 .

First, the target throughput setting unit 411 sets the target throughput (Tput _t ) indicating the data transmission rate of the K IIoT terminals (UE). Here, the target throughput setting unit 411 may set the target throughput Tput _t based on the average requested throughput ARTP or the maximum requested throughput MRTP, as described above.

When based on the average requested throughput (ARTP), the target throughput setting unit 411 may set the data transmission rate that the K IIoT terminals (UE) should maintain on average as the target throughput (Tput _t ). On the other hand, when based on the maximum requested throughput (MRTP), the target throughput setting unit 411 may set the maximum data transfer rate that can be reached under a given environmental condition as the target throughput (Tput _t ). To this end, the target throughput setting unit 411 first calculates a maximum possible signal-to-interference and noise ratio (SINR) under a given condition, and sets the data rate according to the calculated maximum SINR to the target throughput (Tput _t ). ) can be set.

The target SINR determining unit 412 is a target signal-to-interference and noise ratio (SINR) that can satisfy the target throughput (Tput _t ) set by the target throughput setting unit 411 (SINR _t ) to decide

At this time, the target SINR determining unit 412 is configured to satisfy the target throughput Tput _t when the target throughput Tput _t is set based on the average requested throughput ARTP in the target throughput setting unit 411 , the target SINR that can satisfy the (SINR _t ) is determined.

However, when the target throughput Tput _t is set based on the maximum requested throughput MRTP in the target throughput setting unit 411, first, a scaling factor is weighted to the target throughput Tput _t , and the scaling factor factor) may determine a target SINR (SINR _t ) capable of satisfying the weighted target throughput (Tput _t ). Here, the target SINR determining unit 412 weights the scaling factor to the target throughput (Tput _t ) set based on the maximum requested throughput (MRTP) to prevent power wastage or power shortage that may occur due to excessive transmission power. .

In some cases, the target SINR determining unit 412 weights the scaling factor to the set target throughput (Tput _t ) even when the target throughput (Tput _t ) is set based on the average requested throughput (ARTP) to the target SINR (SINR _t ) may decide

Uplink SNR setting unit 413 is an uplink signal-to-noise ratio (SNR) estimated according to the target SINR (SINR _t ) determined by the target SINR determining unit 412 (SNR) (ρ _u ) is specified in advance. By determining which exceeds the maximum allowable uplink SNR(ρ _{u,max )} , if it exceeds the maximum allowable uplink SNR(ρ u,max ), the maximum allowable uplink SNR(ρ _u,max ) is calculated as the uplink SNR(ρ _u ).

The uplink transmission power determining unit 414 determines the uplink transmission power p _u according to the uplink SNR (ρ _u ) evaluated and set by the uplink SNR setting unit 413 , and the determined uplink transmission power p _u ) is transferred to the baseband unit 100 . Accordingly, the baseband unit 100 converts a Transmission Power Control (TPC) command corresponding to the uplink transmission power p _u determined by the uplink transmission power determination unit 414 into transmission data and outputs it. can That is, the base station (BS) may transmit the determined uplink transmission power (p _u ) to the K IIoT terminals (UE) as a TPC command, and the K IIoT terminals (UE) may transmit the determined uplink transmission power (p u) to the uplink transmission power (p) specified by the TPC command. _u ) may transmit the uplink transmission signal to the base station (BS) with a strength according to the.

On the other hand, the downlink transmission power allocator 420 calculates the downlink transmission power (p _d ) based on the uplink transmission power (p _u ) determined by the uplink transmission power allocator 410, and the calculated downlink transmission By controlling the precoding unit 300 according to the power (p _d ), the base station (BS) transmits a downlink transmission signal with a strength according to the calculated downlink transmission power (p _d ) to K IIoT terminals (UE) to do it

That is, the transmission power control apparatus according to the present embodiment sets a target throughput corresponding to a data transmission rate that a plurality of IIoT terminals (UE) must maintain on average or a maximum data transmission rate under a given condition, and a target SINR for achieving the set target throughput. , to determine an energy-efficient uplink transmission power, and determine the downlink transmission power according to the determined uplink transmission power. In addition, by introducing a scaling factor to prevent power wastage due to excessive transmission power determination, cost-effective communication without interruption of power supply due to excessive power use when applied to fields such as industrial IoT where available power is limited to be able to perform

Hereinafter, a technique in which the transmission power control unit 400 determines the uplink transmission power and the downlink transmission power will be described in detail.

First, the channel G between the base station (BS) having M antennas and the K IIoT terminals (UE) may be modeled as in Equation 1 as an M × K matrix (or vector).

)은 k(k = 1, ..., K)번째 IIoT 단말(UE_k)에 대한 채널 벡터이다.where g _k (g _k ∈

) is a channel vector for the k (k = 1, ..., K)-th IIoT terminal (UE _k ).

And the downlink data channel can be modeled according to Equation (2).

)는 K개의 IIoT 단말(UE)에 수신된 수신 신호 벡터이고, ρ_d는 IIoT 단말의 잡음 전력이 반영된 정규화된 다운링크 SNR, T는 전치 행렬을 나타낸다. 그리고 x(x ∈

)는 기지국(BS)의 M개 안테나에 대해 전력 제어 프리코딩된 입력 벡터이고, w(w ∈

)는 잡음 벡터이다.where y (y ∈

) is the received signal vector received by K IIoT terminals (UE), ρ _d is the normalized downlink SNR in which the noise power of the IIoT terminal is reflected, and T represents the transposition matrix. and x(x ∈

) is the power control precoded input vector for the M antennas of the base station (BS), w(w ∈

) is the noise vector.

On the other hand, the power constraint for the downlink can be specified by Equation 3 based on the input vector (x), which is the power control precoded precoding signal applied to the M antennas from the precoding unit 300 of the base station (BS). there is.

where E[·] represents the expected value, and † represents the Hermitian matrix (or conjugate transpose matrix).

Among the channels (G) between the base station (BS) and the K IIoT terminals (UE), the channel vector (g _k ) between the k-th IIoT terminal (UE _k ) and the M antenna arrays of the base station (BS) is expressed in Equation 4 can be modeled.

)은 소규모 페이딩을 구성하는 원소이다. 이에 페이딩 채널 행렬(H)은

로 표현될 수 있으며, 소규모 페이딩 채널 행렬(H)은 독립 동일 분포(independent and identically distributed: i.i.d.)를 갖는 레일리 페이딩(Rayleigh fading)으로 모델링될 수 있다.where β _k is the large-scale fading coefficient for modeling geometric decay and lognormal shadow fading, and h _k (h _k ∈

) is an element constituting small-scale fading. Accordingly, the fading channel matrix (H) is

It may be expressed as , and the small fading channel matrix H may be modeled as Rayleigh fading having an independent and identically distributed (iid).

)이 0 평균(zero mean)과 단위 분산(unit variance)을 갖고, 비상관관계(uncorrelated)인 것으로 가정하면, 데이터 심볼(q)에 다른 다운링크에 대한 전력 제약은 수학식 5로 나타나고, 비상관 가우시안 잡음(uncorrelated Gaussian noise)(w ∈

)은 수학식 6으로 나타난다.Data symbol (q ∈) of IIoT terminal (UE)

) has zero mean and unit variance, and is assumed to be uncorrelated, the power constraint for downlinks other than the data symbol q is expressed by Equation 5, uncorrelated Gaussian noise (w ∈

) is represented by Equation (6).

Here, I _K represents a K-dimensional identity matrix.

According to Equation 4, the channel G between the base station (BS) having the M antennas of Equation 1 and the K IIoT terminals (UE) may be expressed by Equation 7.

As in the existing large-scale MIMO, in this embodiment, downlink precoding may be performed based on an uplink reference signal (RS).

)을 획득할 수 있다. 실제 페이딩 채널 행렬(H)을 직접 계산할 수 없으므로, 기지국(BS)은 MMSE에 기반하여 페이딩 채널 행렬(H)의 추정값(

)을 획득한다.K IIoT terminals (UE) transmit K reference signals (RS) to M antennas of the base station (BS) within a predetermined coherence interval (τ _c ), and the base station (BS) is transmitted Estimated value of fading channel matrix (H) by calculating Minimum Mean-Square Error (MMSE) of K reference signals (RS)

) can be obtained. Since the actual fading channel matrix (H) cannot be calculated directly, the base station (BS) calculates an estimate of the fading channel matrix (H) based on the MMSE (

) is obtained.

In general, in large-scale MIMO, precoding is performed according to a maximum-ratio (MR) process or a zero-forcing (ZF) process. In particular, it is known that the MR process is more suitable for precoding to support connection with large-scale IIoT (UE).

Accordingly, assuming that MR precoding is performed, the input vector (x), which is the precoding signal output from the precoding unit 300 , may be expressed by Equation (8).

,

)은 각각

,

이고, η = [η₁, …, η_K]^T 는 다운 링크 전력 제어 계수로, 다운 링크 전력 제어 계수(η)는 수학식 9의 총 전력 제약 조건을 만족해야만 한다.where two diagonal matrices (

,

) is each

,

and η = [η ₁ , ... , η _K ] ^T is a downlink power control coefficient, and the downlink power control coefficient η must satisfy the total power constraint condition of Equation (9).

Here, ||·| is the l1-norm function.

By substituting the input vector (x) of Equation (8) into Equation (2), the received signal vector (y) of Equation (2) can be expressed again by Equation (10).

And Equation 10 can be simplified to Equation 11 again.

을 나타낸다.where F _d ^mr is

indicates

On the other hand, K IIoT terminals (UE) can reuse the reference signal (RS) transmitted to the base station (BS) for resource efficiency, and in order to reuse the reference signal (RS), the K number of IIoT terminals (UE) are needs to be divided into groups of Here, as an example, it is assumed that K IIoT terminals (UEs) are divided into L groups. Therefore, each of the K IIoT terminals (UE) can be expressed as the j (l ∈ 1, ...., J)-th IIoT terminal (UE _j,l ) of the l (l ∈ 1, ...., L)-th group. And, according to the large-scale fading coefficient (β _j,l ) between each IIoT terminal (UE _j,l ) and the base station (BS), the large-scale fading matrix (Ω) can be expressed as in Equation 12.

In Equation 12, IIoT terminals (UE _j,1 , UE _j,2 , …, UE _j,L ) corresponding to each column, that is, IIoT terminals for each L groups use a reference signal (RS) orthogonal to each other, and each IIoT terminals corresponding to the row (UE _1,l , UE _2,l , ..., UE _J,l ) use the same reference signal (RS). In this case, as the number of groups L increases, the reuse of the reference signal increases.

Here, the number of IIoT terminals (UE) included in each group (L) may be different from each other, but in this case, the number of IIoT terminals (UE) in the group including the largest IIoT terminal (UE) among L groups (here, J ), the deficit of the large-scale fading coefficient β of the remaining group may be padded with 0. That is, the large-scale fading coefficient β may be filled with 0 so that the large-scale fading matrix Ω becomes a matrix having a size of K = J × L.

When the orthogonal reference signal (RS) is reused and the channel is estimated according to the MMSE, the mean square of the channel estimation for the j-th IIoT terminal (UE _j,l ) of the l-th group (Λ _i,j ) is expressed by Equation 13 can be calculated.

Here, γ _j, l is the reception SNR of the j-th IIoT terminal (UE _j,l ) of the l-th group, and τ _p represents the reference signal (RS) length.

And when the reference signal RS is reused in a single cell, since it is similar to the downlink SINR of multiple cells, the downlink SINR to which the MR precoding process and the ZF precoding process are applied can be expressed by Equations 14 and 15, respectively. .

Here, η _j,l is a power control coefficient for the j-th IIoT terminal (UE _j,l ) of the l-th group.

And each downlink transmission signal must satisfy the individual power constraint according to Equation (16).

That is, the power control coefficient (η _j,l ) for each of the K IIoT terminals (UE) must be 0 or more, and the sum of the power control coefficients (η _j,l ) for the entire K IIoT terminals (UE) is 1 or less should be

Meanwhile, in large-scale MIMO for estimating a downlink channel based on an uplink reference signal (RS), a time division duplex (TDD) mode is generally applied in order to reduce the overhead for the reference signal. Assuming that a reference signal transmission interval τ _p is allocated to the uplink reference signal RS among each coherence interval τ _c in the TDD mode, the interval for transmitting the data signal will be allocated as τ _c - τ _p . can Accordingly, the uplink reference signal overhead is calculated as τ _p /τ _c .

Accordingly, the downlink spectral efficiency (SE) can be calculated by Equation (17).

Here, SINR _i ^dl is the downlink SINR for the i-th IIoT terminal, and χ ^d is an adjustable factor indicating the number of IIoT terminals capable of simultaneous downlink transmission. And ζ ^d represents the downlink resource ratio allocated to the downlink for data transmission, ζ ^u represents the uplink resource ratio allocated to the uplink for data transmission, the downlink resource ratio (ζ ^d ) and the uplink The sum of the resource ratios (ζ ^u ) is 1 ( = ζ ^d + ζ ^u ). If it is assumed that the same resource is allocated to the uplink and the downlink, both the downlink resource ratio ζ ^d and the uplink resource ratio ζ ^u may be set to 0.5.

In this case, the throughput (Tput) of the K IIoT terminals (UE) may be calculated by Equation 18.

Here, SINR ^dl is a downlink SINR, and may be divided into SINR ^MR,dl or SINR ^ZF,dl according to the precoding process of the base station (BS), and may be expressed as B is the bandwidth.

First, looking at the case where the MR process is applied as the precoding process, the downlink transmit power is controlled to prevent the power shortage of the K IIoT terminals (UE), and the received SNR (γ _{i, j} ≡ γ) needs to be equal. In this case, it has the same effect as setting the large-scale fading coefficient (β _i,j ) to the same constant for each of the K IIoT terminals (UE). Therefore, all of the large-scale fading coefficients (β _i,j ) for each of the K IIoT terminals (UE) can be expressed as a large-scale fading constant (β) (β _i,j ≡ β).

Accordingly, the same received SNR (γ _i,j = γ) can be expressed by Equation (19).

Since the large-scale fading coefficient (β _i,j ) is the same as the large-scale fading constant (β) for all IIoT terminals (UE), the same power control coefficient (η _j ) so that the same SINR is reflected for the K IIoT terminals (UE). _,l ≡ 1/K) can be applied.

Therefore, the large-scale fading constant β can be obtained from Equation 14 to Equation 20.

)은 동일한 전력 제어 계수(η_j,l ≡ 1/K)와 수학식 19의 수신 SNR(γ)에 따라 수학식 21로 풀어질 수 있다.On the other hand, the downlink SINR to which the MR precoding process of Equation 14 is applied (

) can be solved by Equation 21 according to the same power control coefficient (η _j,l ≡ 1/K) and the received SNR (γ) in Equation 19.

And from Equation 18, the downlink SINR can be written as Equation 22.

In addition, when the large-scale fading constant β is greater than 0 (β > 0), the constraint on the downlink SINR can be derived from Equation 20 as Equation 23.

In order to minimize the overhead due to the reference signal (RS), the reference signal (RS) length (τ _p ) can be set (τ _p = J) according to the number of IIoT terminals (UE _j,l ) for each group (J) there is.

Accordingly, the large-scale fading constant β of Equation 20 can be expressed as Equation 24.

From Equations 21, 23 and 24, when the base station (BS) precodes according to the MR process, the downlink SINR(SINR ^MR,dl ) may be approximated as in Equation 25.

Since the approximate approximate downlink SINR (SINR ^MR,dl,appr ) of Equation 25 is independent of the transmit power p _u , p _d , the ideal maximum downlink SINR in which the transmit power p _u , p _d is not considered. , and this can be referred to as the reference SINR (SINR ₀ ).

In addition, the downlink transmission power (p _d ) of the base station (BS) may be set as the product (p _d = K o p _u ) of the uplink transmission power (p _u ) and the number (K) of the IIoT terminals (UE). , the large-scale fading constant β of Equation 24 can be summarized as Equation 26.

In Equation 26, it is assumed that the uplink resource ratio ζ ^u is set to 0.5 (ζ ^u = ζ ^d = 0.5).

Accordingly, the downlink SNR (ρ _d ) from Equation 26 can be obtained by Equation 27.

And when the base station BS precodes according to the MR process, the lower limit of the number of antennas M of the base station BS may be set by Equation 28.

In other words, when the number of antennas (M) of the base station (BS) is specified, the downlink SINR (SINR ^{MR, dl} ) means that Equation (28) must be satisfied.

Meanwhile, when the base station BS precodes according to the ZF process, the large-scale fading constant β from Equation 15 may be obtained from Equation 29.

The downlink SINR (SINR ^ZF,dl ) of Equation 30 can be obtained from Equation 29.

The downlink SINR(SINR ^ZF,dl ) of Equation 30 may be approximated as Equation 31 .

The approximated approximate downlink SINR(SINR ^ZF,dl,appr ) in Equation 31 may be referred to as the reference SINR(SINR ₀ ), which is the SINR in the ZF process.

Here again, the downlink transmission power (p _d ) of the base station (BS) is the product (p _d = K·p _u ) of the uplink transmission power (p _u ) and the number (K) of the IIoT terminals (UE). , the large-scale fading constant β of Equation 29 can be summarized as Equation 32.

In Equation 32, it is assumed that the uplink resource ratio (ζ ^u ) is set to 0.5 (ζ ^u = ζ ^d = 0.5).

Accordingly, the downlink SNR (ρ _d ) from Equation 32 can be obtained by Equation 33.

And since the lower limit of the number of antennas M of the base station BS when the base station BS precodes according to the ZF process is set by Equation 34, the downlink SINR(SINR ^MR,dl ) satisfies Equation 34 Should be.

On the other hand, if the uplink SNR (ρ _u ) is known regardless of the precoding process, the uplink transmission power (p _u ) may be determined by Equation 35.

where G _bs is the antenna gain of the base station (BS), G _ue is the antenna gain of the IIoT terminal (UE), N ₀ B is the noise power in a given bandwidth (B), ω _bs is the noise figure of the base station (BS) figure). And it is assumed that the IIoT terminal noise figure (ω _ue ) is equal to the noise figure (ω _bs ) of the base station (BS).

Accordingly, the downlink transmission power p _d may be determined by Equation 36.

From Equations 35 and 36, when the uplink SNR (ρ _u ) is determined, the uplink transmission power (p _u ) can be determined, and when the uplink transmission power (p _u ) is determined, the downlink transmission power (p _d ) It can be seen that this can be determined.

4 shows an example of a transmission power control method of a wireless communication system according to an embodiment of the present invention, and FIG. 4 is an average requested throughput (ARTP) when the base station (BS) performs MR process-based precoding. A method of determining the uplink transmission power and the downlink transmission power in an energy-efficient manner is shown.

When the transmission power control method of the wireless communication system of FIG. 4 is described with reference to FIGS. 1 to 3 and the above equations, the target throughput setting unit 411 of the transmission power control unit 400 of FIG. 3 sets the average required throughput Based on (ARTP), the target throughput (Tput _t ) is set (S11). In this case, the target throughput Tput _t may be variously set according to the environment of large-scale MIMO. As an example, the target throughput Tput _t may be set to 50% based on a cumulative distribution function (CDF) of the throughput.

In this case, a scaling factor (α ^t ) for preventing a power shortage of the base station (BS) from occurring may be set together.

The target SINR determining unit 412 calculates the target SINR (SINR _t ) corresponding to the target throughput (Tput _t ) based on Equation 22 for calculating the downlink SINR according to the throughput (Tput) when the MR process is applied It can be obtained according to Equation 37 (S12).

In this case, the target SINR determining unit 412 may obtain by confirming the preset downlink resource ratio (ζ ^d ), the bandwidth (B), the coherence period (τ _c ), and the reference signal transmission period (τ _p ). .

And here too, it was assumed that the downlink resource ratio (ζ ^d ) was set to 0.5 (ζ ^u = ζ ^d = 0.5). In addition, the scaling factor (α ^t ) may be set, for example, to a value in the range of 0.95 ≤ α ^t < 1, but when the target throughput (Tput _t ) is set according to the average requested throughput (ARTP), the maximum required throughput (MRTP) Accordingly, since the target throughput Tput _t is set to be relatively lower than when the target throughput Tput _t is set, the scaling factor α ^t may be generally set to 1.

When the target SINR (SINR _t ) is obtained, the uplink SNR setting unit 413 evaluates the target SINR (SINR _t ) obtained by the target SINR determining unit 412 . First, assuming that the reference signal (RS) length (τ _p ) corresponds to the number (J) of IIoT terminals (UE _j,l ) for each group (τ _p = J), the uplink SNR setting unit 413 sets the target SINR It is determined whether (SINR _t ) satisfies the condition according to Equation 28 (S13). That is, it is determined whether the calculated target SINR (SINR _t ) can be achieved with the number of antennas (M) of the base station (BS) according to the set target throughput (Tput _t ).

When it is determined that the target SINR (SINR _t ) satisfies Equation 28, the uplink SNR setting unit 413 may obtain an uplink SNR (ρ _u ) from Equation 27 ( S14 ). And it is determined whether the obtained uplink SNR (ρ _u ) exceeds a predetermined maximum allowable uplink SNR (ρ _u.max ) (S15). If the uplink SNR (ρ _u ) exceeds the maximum allowable uplink SNR (ρ _u.max ), the uplink SNR setting unit 413 sets the maximum allowable uplink SNR (ρ _u.max ) to the uplink SNR (ρ) _u ) (S16).

However, if the uplink SNR setting unit 413 determines that the target SINR (SINR _t ) does not satisfy Equation 28, that is, the target SINR (SINR _t ) can reach the number of antennas (M) of the base station (BS). If it is determined that there is no, regardless of Equation 27, a predetermined maximum allowable uplink SNR (ρ _u.max ) is set as the uplink SNR (ρ _u ) (S16).

Here, the maximum allowable uplink SNR (ρ _u.max ) may be calculated and set according to Equation 27 from the reference SINR (SINR ₀ ) according to Equation 25.

The uplink transmission power determining unit 414 obtains the uplink transmission power p _u by substituting the uplink SNR (ρ _u ) set in the uplink SNR setting unit 413 into Equation 35 ( S17 ). And by transferring the obtained uplink transmission power (p _u ) to the baseband unit 100 , the uplink transmission power (p _u ) may be transmitted to the K IIoT terminals (UE) as a TPC command.

And the downlink transmission power allocator 420 obtains the downlink transmission power p _d by substituting the uplink transmission power p _u determined by the uplink transmission power allocator 410 into Equation 36 (S18). ). Accordingly, the precoder 300 may be controlled according to the acquired downlink transmission power p _d .

In the present embodiment, the target throughput (Tput _t ), the uplink transmission power (p _u ), and the downlink transmission power (p _d ) are not determined by a single operation, but may be obtained by repeatedly calculating a predetermined number of times.

5 shows another example of a method for controlling transmission power of a wireless communication system according to an embodiment of the present invention. It is also assumed in FIG. 5 that the base station (BS) performs MR process-based precoding. However, in FIG. 5 , a method in which the transmission power control unit 400 determines the uplink transmission power and the downlink transmission power according to the maximum requested throughput (MRTP) will be described.

5, the target throughput setting unit 411 is the number of antennas (M) of the base station (BS) and the group number (L) of grouped IIoT terminals (UE) and the number of IIoT terminals (UE) in each group (J) ), a reference SINR (SINR ₀ ) may be obtained according to Equation 25 (S21). Here, the reference SINR (SINR ₀ ) may be calculated according to Equation 25 as the ideal maximum downlink SINR in which the transmission powers p _u and p _d are not considered. That is, from the number of antennas (M) of the base station (BS), the group number (L) of grouped IIoT terminals (UE), and the number of IIoT terminals (UE) in each group (J), the reference SINR (SINR ₀ ) to be obtained by calculating can

Then, the target throughput (Tput _t ) is calculated and obtained according to Equation (18) from the obtained reference SINR (SINR ₀ ) (S22). Since the reference SINR (SINR ₀ ) can be viewed as the ideal maximum downlink SINR in which the transmission power (p _u , p _d ) is not considered, the obtained target throughput (Tput _t ) can be viewed as the maximum achievable throughput.

The target SINR determining unit 412 obtains a target SINR (SINR _t ) corresponding to the target throughput Tput _t according to Equation 38 based on Equation 22 (S23).

In Equation 38, it is also assumed that the downlink resource ratio (ζ ^d ) is set to 0.5 (ζ ^u = ζ ^d = 0.5), and δ ^t is the available power to prevent the base station (BS) from running out of power. It is a scaling factor that can be adjusted by taking it into account. The scaling factor δ ^t may be set to a value in the range of 0.95 ≤ δ ^t <1, for example.

When the target SINR (SINR _t ) is obtained, the uplink SNR setting unit 413 performs an evaluation on the target SINR (SINR _t ) obtained by the target SINR determining unit 412 as in the average requested throughput (ARTP). , set the uplink SNR (ρ _u ).

Accordingly, similarly to the transmission power control method of FIG. 4 , the uplink SNR setting unit 413 determines whether the target SINR (SINR _t ) satisfies the condition according to Equation 28 (S24). Here again, it is assumed that the reference signal (RS) length (τ _p ) corresponds to the number (J) of IIoT terminals (UE _j,l ) for each group (τ _p = J).

And if it is determined that the target SINR (SINR _t ) satisfies Equation 28, an uplink SNR (ρ _u ) is obtained from Equation 27 ( S25 ). Thereafter, it is determined whether the obtained uplink SNR (ρ _u ) exceeds a predetermined maximum allowable uplink SNR (ρ _u.max ) ( S26 ). If it is determined that the uplink SNR (ρ _u ) exceeds the maximum allowable uplink SNR (ρ _u.max ), the uplink SNR setting unit 413 sets the maximum allowable uplink SNR (ρ _u.max ) to the uplink SNR(ρ _u ) is set (S27).

On the other hand, when it is determined that the target SINR (SINR _t ) does not satisfy Equation 28, the uplink SNR setting unit 413 sets the predetermined maximum allowable uplink SNR (ρ _u.max ) to the uplink SNR (ρ _u ). set (S27).

On the other hand, when the uplink SNR (ρ _u ) is set, by substituting the set uplink SNR (ρ _u ) in Equation 35, the uplink transmission power p _u is obtained and transmitted to the baseband unit 100 ( S28).

And the downlink transmission power allocator 420 obtains the downlink transmission power p _d by substituting the uplink transmission power p _u determined by the uplink transmission power allocator 410 into Equation 36 to precode The unit 300 is controlled (S29).

In the above, an algorithm for determining the uplink transmission power (p _u ) and the downlink transmission power (p _d ) when the base station (BS) performs MR process precoding has been described as an example, but this embodiment is based on the base station ( BS) may also be applied when performing ZF process precoding. However, in this case, Equations 27 and 28 applied in consideration of the MR process precoding may be replaced with Equations 33 and 34, respectively.

6 shows a simulation result of the transmission power control method of the wireless communication system according to the present embodiment.

6 shows the downlink spectrum efficiency (Downlink SE) according to the number of antennas (M) of the base station (BS) and the number of IIoT terminals (K) with 400 antennas (M). It shows the spectral efficiency when the coherence intervals (τ _c ) are 5 msec, 20 msec, and 50 msec and MR precoding is applied. The red O represents the simulation result, the blue line represents the SINR according to Equation 14, A yellow * indicates a reference SINR (SINR ₀ ) approximated according to Equation (25). It can be seen from FIG. 6 that the simulation result agrees well with the reference SINR (SINR ₀ ).

Although the present invention has been described with reference to the embodiment shown in the drawings, which is only exemplary, those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom.

Accordingly, the true technical protection scope of the present invention should be defined by the technical spirit of the appended claims.

BS: Base station UE: IIoT terminal
100: baseband part 200: RF chain
300: precoding unit 400: transmission power control unit
410: uplink transmission power allocation unit 420: downlink transmission power allocation unit
411: target throughput setting unit 412: target SINR determining unit
413: uplink SNR setting unit 414: uplink transmission power determining unit

Claims (20)

Set the target throughput according to either the average required throughput (hereinafter referred to as ARTP) or the maximum required throughput (hereinafter referred to as MRTP) of the K IIoT terminals, calculate the target signal-to-interference noise ratio (hereinafter referred to as the target SINR) according to the set target throughput, and calculate the calculated Obtain an uplink signal-to-noise ratio (hereinafter referred to as uplink SNR) calculated using the target SINR, and if the calculated uplink SNR does not exceed the preset maximum allowable uplink SNR, K IIoT terminals according to the calculated uplink SNR an uplink transmission power allocator for determining an uplink transmission power for data transmission from the to the base station; and
A downlink transmission power allocator for determining a downlink transmission power for data transmission from the base station to the K IIoT terminals based on the uplink transmission power,
The uplink transmission power allocator
a target throughput setting unit configured to set the target throughput;
a target SINR determining unit for calculating and obtaining the target SINR using a preset downlink resource ratio and bandwidth, a coherence interval, and a reference signal transmission interval together with the target throughput;
If the target SINR is determined to be an SINR reachable by the M antennas of the base station, an uplink SNR is calculated in a predetermined manner, and the target SINR is unreachable or the calculated uplink SNR exceeds the maximum allowable uplink SNR an uplink SNR setting unit configured to set the maximum allowable uplink SNR to an uplink SNR; and
an uplink transmission power determining unit for calculating the uplink transmission power corresponding to the set uplink SNR in a predetermined manner;
The uplink SNR setting unit
The target SINR is an equation according to the number of antennas (M) of the base station

It is determined whether or not is satisfied, and if it is satisfied, the

(Where β is a large-scale fading constant set equally between the base station and K terminals, L and J are the number of groups of K terminals grouped for reuse of the reference signal (RS) and the number of terminals per group, τ _p is is the reference signal transmission interval, ρ _u is the calculated uplink SNR)
Calculate the uplink SNR according to
If the target SINR does not satisfy the equation according to the number of antennas (M) of the base station or the calculated uplink SNR exceeds the maximum allowable uplink SNR, the maximum allowable uplink SNR calculated using the reference SINR is Transmission power control device set by uplink SNR.
delete The method of claim 1, wherein the target throughput setting unit
When setting the target throughput according to the ARTP, setting the target throughput at a predetermined ratio based on a cumulative distribution function (CDF) of the K IIoT terminals,
When the target throughput is set according to the MRTP, the reference SINR indicating the downlink SINR in which the uplink transmission power and the downlink transmission power are not taken into consideration is calculated, and the throughput corresponding to the calculated reference SINR is calculated. Transmission power control device that sets the target throughput.
4. The method of claim 3, wherein the reference SINR is
When the base station performs precoding according to a maximum-ratio (hereinafter MR) process,
formula

(Where L and J are the number of K terminal groups grouped for reuse of the reference signal (RS) and the number of terminals for each group, SNIR ₀ is the reference SINR)
Transmission power control device calculated according to 5. The method of claim 4, wherein the target throughput is
Equation from the reference SINR

(where 0.5 is a predetermined downlink resource ratio (ζ ^d ), B is a bandwidth, τ _c is a coherence interval, τ _p is a reference signal transmission interval, and Tput _t is a target throughput)
Transmission power control device calculated according to The method of claim 4, wherein the target SINR determining unit
The target SINR is calculated using the target throughput, downlink resource ratio, bandwidth, coherence interval, and reference signal transmission interval.

(where α ^t is a scaling vector preset to prevent power shortage of the base station, τ _c is a coherence interval, τ _p is a reference signal transmission interval. B is a bandwidth)
Transmission power control device obtained by calculating according to delete The method of claim 6, wherein the uplink transmission power determining unit
formula

(where G _bs is the antenna gain of the base station, _Gue is the antenna gain of the terminal, N ₀ B is the noise power in a given bandwidth B, ω _bs is the noise figure of the base station (BS), p _u is an uplink transmission power), a transmission power control apparatus for calculating the uplink transmission power. The method of claim 8, wherein the downlink transmission power allocator
formula

Transmission power control device for calculating the downlink transmission power (p _d ) in accordance with. 10. The method of claim 9, wherein the transmission power control device
Transmission power control apparatus included in the base station, wherein the base station transmits the uplink transmission power to the K terminals using a Transmission Power Control (TPC) command. setting the target throughput according to one of the average requested throughput (hereinafter ARTP) or the maximum requested throughput (hereinafter MRTP) of the K IIoT terminals;
calculating a target signal-to-interference noise ratio (hereinafter referred to as a target SINR) according to a set target throughput;
obtaining an uplink signal-to-noise ratio (hereinafter referred to as uplink SNR) calculated using the calculated target SINR;
If the calculated uplink SNR does not exceed the predetermined maximum allowable uplink SNR, determining an uplink transmission power for data transmission from the K IIoT terminals to the base station according to the calculated uplink SNR; and
Comprising the step of determining a downlink transmission power for data transmission from the base station to the K IIoT terminals based on the uplink transmission power,
The step of determining the uplink transmission power
calculating an uplink SNR in a predetermined manner when the target SINR is determined to be an SINR reachable by the M antennas of the base station; and
If the target SINR is unreachable or the calculated uplink SNR exceeds a predetermined maximum allowed uplink SNR, setting the calculated maximum allowed uplink SNR using the reference SINR to the uplink SNR;
Calculating the uplink SNR comprises:
The target SINR is an equation according to the number of antennas (M) of the base station

determining whether it is satisfied; and
If the equation according to the number of antennas (M) is satisfied, the equation

(Where β is a large-scale fading constant set equally between the base station and K terminals, L and J are the number of groups of K terminals grouped for reuse of the reference signal (RS) and the number of terminals per group, τ _p is Reference signal transmission interval, ρ _u is the calculated uplink SNR)
A transmission power control method comprising calculating an uplink SNR according to
12. The method of claim 11, wherein setting the target throughput comprises:
When setting the target throughput according to the ARTP, setting the target throughput at a predetermined ratio based on the cumulative distribution function of the K IIoT terminals,
When the target throughput is set according to the MRTP, the reference SINR indicating the downlink SINR in which the uplink transmission power and the downlink transmission power are not taken into consideration is calculated, and the throughput corresponding to the calculated reference SINR is calculated. Transmission power control method set by target throughput. 13. The method of claim 12, wherein the reference SINR is
When the base station performs precoding according to a maximum-ratio (hereinafter MR) process,
formula

(Where L and J are the number of K terminal groups grouped for reuse of the reference signal (RS) and the number of terminals for each group, SNIR ₀ is the reference SINR)
Transmission power control method calculated according to 14. The method of claim 13, wherein the target throughput is
Equation from the reference SINR

(where 0.5 is a predetermined downlink resource ratio (ζ ^d ), B is a bandwidth, τ _c is a coherence interval, τ _p is a reference signal transmission interval, and Tput _t is a target throughput)
Transmission power control method calculated according to 14. The method of claim 13, wherein calculating the target SINR comprises:
The target SINR is calculated using the target throughput, downlink resource ratio, bandwidth, coherence interval, and reference signal transmission interval.

(where α ^t is a scaling vector preset to prevent power shortage of the base station, τ _c is a coherence interval, τ _p is a reference signal transmission interval. B is a bandwidth)
Transmission power control method obtained by calculating according to delete delete 16. The method of claim 15, wherein determining the uplink transmission power comprises:
formula

(Where G _bs is the antenna gain of the base station, _Gue is the antenna gain of the terminal, N ₀ B is the noise power in a given bandwidth B, ω _bs is the noise figure of the base station (BS), p _u A transmit power control method for calculating the uplink transmit power according to the uplink transmit power. 19. The method of claim 18, wherein determining the downlink transmission power comprises:
formula

(here, p _d is downlink transmission power)
A transmission power control method for calculating the downlink transmission power (p _d ) according to 20. The method of claim 19, wherein the transmission power control method comprises:
Transmitting, by the base station, the calculated uplink transmission power to the K terminals as a transmission power control command.

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