KR100897059B1 - Method and apparatus for determining power allocation to each subchannel in uplink ofdma system for multi-user and multi-subchannel, and mobile terminal having the apparatus - Google Patents

Method and apparatus for determining power allocation to each subchannel in uplink ofdma system for multi-user and multi-subchannel, and mobile terminal having the apparatus Download PDF

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KR100897059B1
KR100897059B1 KR1020070138783A KR20070138783A KR100897059B1 KR 100897059 B1 KR100897059 B1 KR 100897059B1 KR 1020070138783 A KR1020070138783 A KR 1020070138783A KR 20070138783 A KR20070138783 A KR 20070138783A KR 100897059 B1 KR100897059 B1 KR 100897059B1
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subchannel
power
user terminal
allocated
channel gain
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Korean (ko)
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김성륜
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연세대학교 산학협력단
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
    • H04W52/04—TPC
    • H04W52/18—TPC being performed according to specific parameters
    • H04W52/24—TPC being performed according to specific parameters using SIR [Signal to Interference Ratio] or other wireless path parameters
    • H04W52/243—TPC being performed according to specific parameters using SIR [Signal to Interference Ratio] or other wireless path parameters taking into account interferences
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/04—Wireless resource allocation
    • H04W72/044—Wireless resource allocation based on the type of the allocated resource
    • H04W72/0473—Wireless resource allocation based on the type of the allocated resource the resource being transmission power

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  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

Disclosed are a method and a power control apparatus for determining power to be allocated to each subchannel of a user terminal in an uplink OFDMA system using multiple subchannels by multiple users, and a user terminal having the power control apparatus. In accordance with an aspect of the present invention, there is provided a method for determining power, comprising: measuring a noise power density of a user terminal and a channel gain of each subchannel, receiving a channel gain of each subchannel of another user terminal and power to be allocated to each subchannel And determining power to be allocated to each subchannel of the user terminal by a water filling method using the measured noise power density and the channel gain in consideration of the received channel gain and power. . According to the present invention, the total throughput of all user terminals can be maximized by considering interference with other user terminals in an uplink OFDMA system using multiple subchannels by multiple users.

Multiuser, Multiple Subchannels, OFDMA, Power Allocation

Description

A method and power control apparatus for determining power to be allocated to each subchannel of a user terminal in an uplink OPDMA system using multiple subchannels, and a user terminal having the power control apparatus. allocation to each subchannel in uplink OFDMA system for multi-user and multi-subchannel, and mobile terminal having the apparatus}

The present invention relates to a method and a power control apparatus for determining power to be allocated to each subchannel of a user terminal in an uplink OFDMA system, and in particular, each part of a user terminal in an uplink OFDMA system using multiple subchannels by multiple users. A method and a power control apparatus for determining power to be allocated to a channel.

In a wireless system in which multiple users use multiple subchannels, an important problem is how to allocate a carrier to each user terminal and transmit power. In such resource allocation, the main purpose is to maximize throughput and promote fairness among user terminals. In a downlink orthogonal frequency division multiple access (OFDMA) system, one carrier is allocated to one user terminal having an optimal channel gain for a corresponding carrier in order to maximize the total throughput. Therefore, in the downlink OFDMA system, the power allocation problem results in a convex optimization problem.

However, the throughput maximization problem in uplink OFDMA systems is more difficult to solve than in downlink OFDMA systems. This is because each user terminal has an independent power limit, and power not used in one user terminal cannot be switched to another user terminal.

Meanwhile, in the uplink OFDMA system, allowing a plurality of user terminals to share a given subchannel shows better throughput than a case in which one terminal occupies one subchannel despite interference between user terminals. It is known. Therefore, an uplink OFDMA system in which multiple users use multiple subchannels has been recently studied.

Conventionally, as a technique for determining power to be allocated to each subchannel of a user terminal in such an uplink OFDMA system, there is a method of performing a water-filling technique based on the following equation. Here, the water filling technique is a technique of allocating power using a difference between an arbitrary level (water level) and a reference value according to a frequency or a subchannel.

Figure 112007093850961-pat00001

In the above equation,

Figure 112007093850961-pat00002
N is the power to be allocated to the sub-channel m of the user terminal k, N 0 is the noise power density,
Figure 112007093850961-pat00003
Denotes a channel gain of the subchannel m of the user terminal k,
Figure 112007093850961-pat00004
Is
Figure 112007093850961-pat00005
Means.

However, in the above-described prior art, since interference with other user terminals is not considered, it is difficult to maximize the total throughput of all user terminals.

The technical problem to be achieved by the present invention is to maximize the total throughput of all user terminals by considering interference with other user terminals in an uplink OFDMA system in which multiple users use multiple subchannels. A method of determining a power to be allocated to a power control apparatus, a power control apparatus, a user terminal including the power control apparatus, and a computer-readable recording medium having recorded thereon a program for executing the power determination method.

In order to solve the above technical problem, according to the present invention, a method for determining power to be allocated to each sub-channel of a user terminal in an uplink OFDMA system using multiple sub-channels, (a) the noise of the user terminal Measuring power density and channel gain of each subchannel; (b) receiving a channel gain of each subchannel of another user terminal and power to be allocated to each subchannel; And (c) determining power to be allocated to each subchannel of the user terminal by a water filling technique using the measured noise power density and channel gain in consideration of the received channel gain and power. It features.

At this time, step (c), power to be allocated to the sub-channel m of the user terminal according to the following equation

Figure 112007093850961-pat00006
Can be obtained.

Figure 112007093850961-pat00007

Here, the subscript k denotes the user terminal,

Figure 112007093850961-pat00008
The Lagrange multiplier,
Figure 112007093850961-pat00009
Is a value considering the sum of SINRs of the other user terminals for the subchannel m calculated according to the received channel gain and power,
Figure 112007093850961-pat00010
Is the co-channel interference for the subchannel m, N 0 is the measured noise power density,
Figure 112007093850961-pat00011
Denotes the channel gain of the measured subchannel m,
Figure 112007093850961-pat00012
Is
Figure 112007093850961-pat00013
Means.

At this time, the

Figure 112007093850961-pat00014
May be calculated according to the following equation.

Figure 112007093850961-pat00015

Here, the subscript j represents the j th user terminal among the other user terminals,

Figure 112007093850961-pat00016
Is orthogonal constant,
Figure 112007093850961-pat00017
Is the co-channel interference for subchannel m,
Figure 112007093850961-pat00018
Is the channel gain of the received subchannel m,
Figure 112007093850961-pat00019
Denotes power to be allocated to the received subchannel m,
Figure 112007093850961-pat00020
to be.

Also, the

Figure 112007093850961-pat00021
May be calculated according to the following equation.

Figure 112007093850961-pat00022

here,

Figure 112007093850961-pat00023
Is orthogonal constant,
Figure 112007093850961-pat00024
Is the channel gain of the received subchannel m,
Figure 112007093850961-pat00025
Denotes power to be allocated to the received subchannel m.

The method may further include determining power to be allocated to each subchannel of the user terminal by repeating steps (b) and (c).

At this time, step (d), power to be allocated to the sub-channel m of the user terminal according to the following equation

Figure 112007093850961-pat00026
Can be obtained.

Figure 112007093850961-pat00027

Here, the subscript k denotes the user terminal, the superscript n (an integer of n≥1) denotes the number of repetitions,

Figure 112007093850961-pat00028
The Lagrange multiplier,
Figure 112007093850961-pat00029
Is a value considering the sum of SINRs of the other user terminals for the subchannel m calculated according to the received channel gain and power,
Figure 112007093850961-pat00030
Is the co-channel interference for the subchannel m, N 0 is the measured noise power density,
Figure 112007093850961-pat00031
Denotes the channel gain of the measured subchannel m,
Figure 112007093850961-pat00032
Is
Figure 112007093850961-pat00033
Means.

At this time, the

Figure 112007093850961-pat00034
May be calculated according to the following equation.

Figure 112007093850961-pat00035

Here, the subscript j is an identifier indicating the user terminal,

Figure 112007093850961-pat00036
Is orthogonal constant,
Figure 112007093850961-pat00037
Is the co-channel interference for subchannel m,
Figure 112007093850961-pat00038
Is the channel gain of the received subchannel m,
Figure 112007093850961-pat00039
Denotes power to be allocated to the received subchannel m,
Figure 112007093850961-pat00040
to be.

Also, the

Figure 112007093850961-pat00041
May be calculated according to the following equation.

Figure 112007093850961-pat00042

here,

Figure 112007093850961-pat00043
Is orthogonal constant, Is the channel gain of the received subchannel m,
Figure 112007093850961-pat00045
Denotes power to be allocated to the received subchannel m.

Also, in the step (d), if there is a subchannel to which no power is allocated in any of the user terminal and the other user terminal,

Figure 112007093850961-pat00046
May be determined to be a predetermined value other than 0 to apply the above equation. At this time, the predetermined value other than 0 is,
Figure 112007093850961-pat00047
It may be a value proportional to.

In order to solve the other technical problem, according to the present invention, in the uplink OFDMA system using multiple subchannels, a power control apparatus for determining the power to be allocated to each subchannel of the user terminal, A measuring unit measuring noise power density and channel gain of each subchannel; A receiver which receives the channel gain of each subchannel and power to be allocated to each subchannel of another user terminal; And a power determiner configured to determine power to be allocated to each subchannel of the user terminal by a water filling technique using the measured noise power density and the channel gain in consideration of the received channel gain and power. do.

In this case, the power determination unit, power to be allocated to the sub-channel m of the user terminal according to the following equation

Figure 112007093850961-pat00048
Can be obtained.

Figure 112007093850961-pat00049

Here, the subscript k denotes the user terminal,

Figure 112007093850961-pat00050
The Lagrange multiplier,
Figure 112007093850961-pat00051
Is a value considering the sum of SINRs of the other user terminals for the subchannel m calculated according to the received channel gain and power,
Figure 112007093850961-pat00052
Is the co-channel interference for the subchannel m, N 0 is the measured noise power density,
Figure 112007093850961-pat00053
Denotes the channel gain of the measured subchannel m,
Figure 112007093850961-pat00054
Is
Figure 112007093850961-pat00055
Means.

In this case, the power determination unit is

Figure 112007093850961-pat00056
Can be calculated according to the following equation.

Figure 112007093850961-pat00057

Here, the subscript j is an identifier indicating the user terminal,

Figure 112007093850961-pat00058
Is orthogonal constant,
Figure 112007093850961-pat00059
Is the co-channel interference for subchannel m,
Figure 112007093850961-pat00060
Is the channel gain of the received subchannel m,
Figure 112007093850961-pat00061
Denotes power to be allocated to the received subchannel m,
Figure 112007093850961-pat00062
to be.

In addition, the power determination unit is

Figure 112007093850961-pat00063
Can be calculated according to the following equation.

Figure 112007093850961-pat00064

here,

Figure 112007093850961-pat00065
Is orthogonal constant,
Figure 112007093850961-pat00066
Is the channel gain of the received subchannel m,
Figure 112007093850961-pat00067
Denotes power to be allocated to the received subchannel m.

The receiver may repeatedly receive the channel gain and the power, and the power determiner may use the measured noise power density and the channel gain in consideration of the repeatedly received channel gain and power. Repeatedly, power to be allocated to each subchannel of the user terminal may be determined.

The power control device may further include a transmitter configured to transmit the measured channel gain and the determined power.

The present invention provides a user terminal for an uplink OFDMA system in which multiple users use multiple subchannels, which includes the power control apparatus according to the present invention.

In order to solve the above technical problem, a program for executing a method for determining power to be allocated to each subchannel of a user terminal in an uplink OFDMA system using multiple subchannels according to the present invention described above is provided. Provided is a computer readable recording medium having recorded thereon.

According to the present invention, the total throughput of all user terminals can be maximized by considering interference with other user terminals in an uplink OFDMA system in which multiple users use multiple subchannels.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description and the accompanying drawings, the substantially identical components are represented by the same reference numerals, and thus redundant description will be omitted. In addition, in the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

In order to solve the above technical problem, prior to describing the preferred embodiments of the present invention, a multi-user is required to determine the power to be allocated to each sub-channel of the user terminal in an uplink OFDMA system using multiple sub-channels Let's analyze the problem.

In the present embodiment, it is assumed that the number of user terminals is K and the number of subchannels is M. At this time, the channel gain of the subchannel m of the user terminal k (1≤k≤K)

Figure 112007093850961-pat00068
The power allocated to the subchannel m (1≤m≤M) of the user terminal k
Figure 112007093850961-pat00069
In this case, the signal-to-interference noise ratio (SINR) for the subchannel m of the user terminal k is obtained according to the following equation.

Figure 112007093850961-pat00070

here,

Figure 112007093850961-pat00071
Denotes cochannel interference in subchannel m of user terminal k, and N 0 denotes noise power density. In this case, the total throughput is calculated according to the following equation.

Figure 112007093850961-pat00072

Accordingly, a problem required for maximizing total throughput in determining power to be allocated to each subchannel of a user terminal in an uplink OFDMA system using multiple subchannels by multiple users may be defined as follows.

Figure 112007093850961-pat00073

here,

Figure 112007093850961-pat00074
Is the instantaneous maximum power that the user terminal can transmit, and co-channel interference in subchannel m
Figure 112007093850961-pat00075
Is obtained according to the following equation.

Figure 112007093850961-pat00076

here,

Figure 112007093850961-pat00077
Is an orthogonality factor, which is greater than 0 and less than or equal to 1.

Hereinafter, preferred embodiments of the present invention will be described in detail.

1 is a block diagram of an apparatus 300 for controlling power to be allocated to each subchannel of a user terminal in an uplink OFDMA system using multiple subchannels according to an embodiment of the present invention.

Referring to FIG. 1, the power control apparatus 300 according to the present exemplary embodiment includes a receiver 310, a power determiner 320, a measurer 330, and a transmitter 340. The power control apparatus 300 according to the present embodiment is provided in the user terminal 100 for an uplink OFDMA system in which multiple users use multiple subchannels. Hereinafter, 'other user terminals' means user terminals other than the user terminal 100 among a plurality of user terminals included in an uplink OFDMA system in which multiple users use multiple subchannels.

The measuring unit 330 measures the noise power density of the user terminal 100 and the channel gain of each subchannel, and the receiving unit 310 determines the channel gain of each subchannel of the other user terminals and the respective user terminals determined by the other user terminals. Receive information on power to be allocated to the subchannel.

The power determiner 320 considers the channel gain of each subchannel and the power corresponding to each subchannel of the other user terminals received by the receiver 310, and measures the noise power density and the channel gain measured by the measurer 330. The power to be allocated to each subchannel of the user terminal 100 by using a water-filling technique is determined.

Meanwhile, the transmitter 340 transmits the channel gains of the subchannels measured by the measurement unit 330 and the subchannels determined by the power determiner 320 so that other user terminals may determine power as in the user terminal 100. Transmit information about the power to be allocated.

Here, the information about the channel gain and power transmitted or received by the user terminal 100 may be transmitted to or received from other user terminals through the base station, or may be directly transmitted or received without passing through the base station. have.

Hereinafter, a detailed method of determining the power to be allocated to each subchannel of the user terminal 100 by considering the channel gain of each subchannel and power corresponding to each subchannel of other user terminals will be described. Let's do it. In the present embodiment, the power determiner 320 uses the Karrush-Kuhn condition (Karush-Kuhn) according to Equation 4 above to consider the channel gain of each subchannel and power corresponding to each subchannel of other user terminals. Use the optimal solution found by applying Tucker conditions. Karcykun Tucker conditions are necessary to solve the nonlinear optimization problem. Applying the Carcycun Tucker condition to Equation 4 above provides an optimized solution, such as the following equation.

Figure 112007093850961-pat00078

The power determiner 320 calculates power to be allocated to each subchannel of the user terminal 100 according to the above equation. In the above equation, the subscript k is an identifier indicating a user terminal, indicates the user terminal 100, m is an identifier indicating a subchannel,

Figure 112007093850961-pat00079
Lagrangian multiplier,
Figure 112007093850961-pat00080
Is a value considering the sum of the SINRs of other user terminals for the subchannel m calculated according to the channel gain and power received by the receiver 310,
Figure 112007093850961-pat00081
Is the co-channel interference for the sub-channel m, N 0 is the noise power density measured by the measuring unit 330,
Figure 112007093850961-pat00082
Denotes the channel gain of the subchannel m measured by the measurement unit 330,
Figure 112007093850961-pat00083
Is
Figure 112007093850961-pat00084
Means.

In the above equation

Figure 112007093850961-pat00085
and
Figure 112007093850961-pat00086
By considering the channel gain of each subchannel and the power corresponding to each subchannel of the other user terminal, it is possible to determine the power to be allocated to each subchannel in consideration of the interference with other user terminals.

Cochannel Interference for Subchannel m

Figure 112007093850961-pat00087
Is obtained according to Equation 5 described above,
Figure 112007093850961-pat00088
Is the power of the sub-channel m of the user terminal 100 k
Figure 112007093850961-pat00089
As this increase, it can be defined as the increase rate of the throughput of other user terminals sharing the sub-channel m,
Figure 112007093850961-pat00090
If this increases, the throughput of other user terminals decreases, so eventually
Figure 112007093850961-pat00091
Becomes negative. therefore
Figure 112007093850961-pat00092
Can be obtained according to the following equation.

Figure 112007093850961-pat00093

Here, the subscript j is an identifier indicating the user terminal,

Figure 112007093850961-pat00094
Is orthogonal constant,
Figure 112007093850961-pat00095
Co-channel interference for the sub-channel m in the user terminal j,
Figure 112007093850961-pat00096
The channel gain of the sub-channel m in the user terminal j,
Figure 112007093850961-pat00097
Denotes power to be allocated to subchannel m in user terminal j,
Figure 112007093850961-pat00098
to be. Referring to equation (7) above,
Figure 112007093850961-pat00099
Is a value considering the sum of signal-to-interference noise ratios (SINRs) of other user terminals with respect to the subchannel m, and is a value obtained by multiplying the channel gain-to-noise ratio of the user terminal 100 by the sum of the signal-to-interference noise ratios of other user terminals. Therefore, referring back to Equation 6,
Figure 112007093850961-pat00100
Considering the transmission power of the other user terminals by using. Specifically, in Equation 6 described above
Figure 112007093850961-pat00101
This water level, so (
Figure 112007093850961-pat00102
(Positive number) increases, that is, when the sum of SINRs of other user terminals increases, power to be allocated to the subchannel m by the user terminal 100 decreases. In addition, the equation cochannel interference
Figure 112007093850961-pat00103
As this increases, the power to allocate to subchannel m also decreases.

In addition, by analyzing the above equation (6), it can be seen that there is a feature according to the following equation.

Figure 112007093850961-pat00104

Figure 112007093850961-pat00105

Referring to Equation 8, it can be seen that there is a limit in the power allocated to the subchannel. That is, no matter how much transmission power the user terminal has, the power to be allocated to each subchannel is

Figure 112007093850961-pat00106
(
Figure 112007093850961-pat00107
Since it is negative, it cannot be greater than the value of positive). Therefore, the larger the signal power of other user terminals using the same subchannel, the smaller the maximum power that can be allocated. Therefore, less power is allocated to the subchannels having the larger signal power of other users, thereby minimizing interference with other user terminals. can do.

In addition, referring to Equation 9, a second subchannel

Figure 112007093850961-pat00108
If the value is less than the inverse of the channel gain-to-interference noise ratio, no power is allocated to that subchannel. That is, when the channel gain of the user terminal 100 is not good when the signal strength of other user terminals is relatively good, the total throughput is maximized by not using the corresponding subchannel.

In addition, according to another embodiment of the present invention, in the power control apparatus 300 shown in FIG. 1, the receiver 310 repeatedly measures the channel gain of each subchannel and power to be allocated to each subchannel of other user terminals. In response to the channel gain and power being repeatedly received, the power determiner 320 repeatedly uses the noise power density and the channel gain measured by the measurement unit 330 in a waterfilling method. Determine the power to be allocated to each subchannel of). Furthermore, the measurement unit 330 also repeatedly measures the noise power density and the channel gain of the user terminal 100, and the transmitter 340 measures the noise power density and the channel gain and the power determined by the power determiner 320. Send information about repetitively.

The power control apparatus 300 according to the present embodiment is for a form in which each of user terminals determines power to be allocated to each subchannel in a distributed and repetitive manner. According to the present embodiment, in determining power to be allocated to each subchannel by each of the user terminals, since the channel gain and power to be allocated of each subchannel of other user terminals are not known at the present moment, each of the user terminals may be determined. Based on the channel gain of each subchannel of the other user terminals at the previous moment and the power to allocate

Figure 112007093850961-pat00109
and
Figure 112007093850961-pat00110
To calculate the power to be allocated to each sub-channel at the current moment, and to repeat this process, the power determined after a certain number of times repeated to allocate to each sub-channel.

2 is a flowchart of a method of determining, by the power control apparatus 300, power to be allocated to each subchannel in an uplink OFDMA system in which multiple users use multiple subchannels according to the present embodiment. According to the present embodiment, user terminals other than the user terminal 100 may also determine power to be allocated to each subchannel according to the description below, and other user terminals may repeatedly obtain channel gains of each subchannel as described below. The broadcast may be broadcast, but the power to be allocated to each subchannel may be determined once and allocated, and may not be repeatedly determined and allocated as described below.

First, the number of repetitions n is set to an initial value 0 in step 210.

In operation 215, the measurement unit 330 measures the noise power density and the channel gain of each subchannel.

In step 220, the power determiner 320 determines the power to be allocated to each subchannel by a water filling method using the noise power density and the channel gain measured in step 215. Here, the power determiner 320 determines the power to be allocated to each subchannel according to Equation 1 above, or according to the above Equation 6,

Figure 112007093850961-pat00111
and
Figure 112007093850961-pat00112
Is set to 0, and power to be allocated to each subchannel can be determined. This step is a step for determining an initial value of power to be allocated to each subchannel of the user terminal 100 because the channel gain of other user terminals and power to be allocated to each subchannel are not yet known.

In step 225, the transmitter 340 broadcasts the channel gain of each subchannel measured in step 215 and the power to be allocated to each subchannel determined in step 220. That is, it transmits so that other user terminals can know.

In operation 230, the receiver 310 receives the channel gain of each subchannel measured by other user terminals and power to be allocated to each subchannel determined by the other user terminals.

In step 240, the power determiner 320 uses the noise power density and the channel gain of each subchannel measured in step 215 in consideration of the channel gain and power of each subchannel of the other user terminals received in step 230. By using the water-filling technique to determine the power to be allocated to each subchannel.

In step 245, it is determined whether n is greater than a predetermined number of repetitions n ITER (n ITER ≥ 1). Since n is 0 at present, the process proceeds to step 250, n is increased by 1, and the process proceeds to step 225 again. Then, steps 225 to 240 are repeated until n is larger than n ITER . In the repeated step 230, the channel gain and the determined power measured in the other user terminals are received in the previous iteration number of the current iteration number, and thus, in the repeated 240, the channel gain and the determined power are measured in consideration of the channel gain measured in the other user terminals. The power to be allocated to each subchannel is determined.

If n is greater than n ITER , the UE proceeds to step 255 and the user terminal 100 transmits data by allocating power to each subchannel according to the power determined in step 240.

If there is no data to be transmitted in step 260, the procedure is terminated. If there is more data to be transmitted, the procedure proceeds to step 265 and n is initialized to 0. In step 270, the measurement unit 330 measures noise power density and channel gain of each subchannel. do. The process proceeds to step 225 again and repeats steps 225 to 240. At this time, of course, in step 240, the noise power density measured in step 270 and the channel gain of each subchannel are used.

3 is a flowchart of an exemplary embodiment of step 240 of FIG. 2 in more detail. Referring to FIG. 3, in step 241, the power determiner 320 uses the channel gain and power of each subchannel of other user terminals in the previous iteration number received by the receiver 310 for each subchannel. A value considering the sum of SINRs of other user terminals for each subchannel according to the equation

Figure 112007093850961-pat00113
And co-channel interference for each subchannel
Figure 112007093850961-pat00114
Calculate

Figure 112007093850961-pat00115

Figure 112007093850961-pat00116

Here, the subscript k denotes the user terminal 100, n denotes the number of repetitions, the subscript m is an identifier indicating a subchannel, and the subscript j is an identifier indicating the user terminal. N 0 is the noise power density measured in step 215 or 270.

Figure 112007093850961-pat00117
Is the channel gain of the subchannel m measured in step 215 or 270,
Figure 112007093850961-pat00118
Is orthogonal constant,
Figure 112007093850961-pat00119
Co-channel interference for the sub-channel m in the user terminal j,
Figure 112007093850961-pat00120
Is the channel gain of the sub-channel m of the user terminal j received by the receiver 310,
Figure 112007093850961-pat00121
Denotes power to be allocated to the subchannel m determined by the user terminal j,
Figure 112007093850961-pat00122
to be.

In operation 242, the power determination unit 320 may calculate the operation calculated in operation 241.

Figure 112007093850961-pat00123
and
Figure 112007093850961-pat00124
In consideration of the above, the power to be allocated to each subchannel is determined using a water-filling technique using the noise power density measured in step 215 or step 270 and the channel gain of each subchannel according to the following equation.

Figure 112007093850961-pat00125

Here, the symbols described in Equations 10 and 11 are similarly applied to the above equations,

Figure 112007093850961-pat00126
The Lagrange multiplier,
Figure 112007093850961-pat00127
Is
Figure 112007093850961-pat00128
Means.

A power value that step to step 240, 225 are repeated as described above, whereby the power value to be assigned to each sub-channel is determined is there is convergence to a constant value, and therefore the predetermined number of times, that is determined after n iterations ITER times according to this embodiment Therefore, in step 255, power is allocated to each subchannel and transmitted.

Other user terminals repeatedly broadcast the channel gain of each subchannel, but determine and allocate the power to be allocated to each subchannel once, and if not repeatedly determined and allocated as described above, the power to be allocated to each subchannel must be allocated. The value converges to a constant value. However, if the user terminals other than the user terminal 100 also repeatedly determine power to be allocated to each subchannel as described above, a case in which power values do not converge may vibrate. Because, in the process of determining power to be allocated to each subchannel, there may be a case in which a subchannel is not allocated power in any user terminal due to relatively poor channel gain or high noise.

Figure 112007093850961-pat00129
Since this becomes 0, a large number of user terminals allocate most of the power to the corresponding subchannel, and the subsequent iteration may result in distributing power to other subchannels other than the corresponding subchannel. .

4 is a flowchart illustrating another embodiment of step 240 of FIG. 2 in more detail. The present embodiment is an embodiment for preventing vibration of the power value. In the present embodiment, when there is a subchannel to which no power is allocated in any of the user terminal 100 and other user terminals, for a corresponding subchannel,

Figure 112007093850961-pat00130
Is determined to be a predetermined value other than 0 to apply Equation 12. Where the predetermined value is the value from the previous trial
Figure 112007093850961-pat00131
A value proportional to, for example
Figure 112007093850961-pat00132
It can be set to 1/2.

Referring to FIG. 4, in step 243, the power determination unit 320 includes the user terminal 100 to check whether there is a subchannel to which power is not allocated among the user terminals. To this end, the power control apparatus 300 may be implemented to transmit information on subchannels to which power is not allocated so that other user terminals may know.

If there is no subchannel to which no power is allocated in any of the user terminals, the flow proceeds to step 246. Since step 246 is the same as step 241 described with reference to FIG. 3, a description thereof will be omitted.

If there is a subchannel to which no power is allocated in any of the user terminals, the flow proceeds to step 244. In step 244, the power determiner 320 uses the channel gain and power of each subchannel of the other user terminals in the previous iteration number received by the receiver 310 for the corresponding subchannel in Equation 11 above. follow

Figure 112007093850961-pat00133
, And
Figure 112007093850961-pat00134
Determines a non-zero predetermined value. As described above, the value determined in the previous iteration is
Figure 112007093850961-pat00135
It can be determined by a value proportional to.

In operation 245, the power determiner 320 may perform the same operation on the other subchannels except for the corresponding subchannels as in step 241 described with reference to FIG. 3.

Figure 112007093850961-pat00136
and
Figure 112007093850961-pat00137
Calculate Proceed to step 247.

Next, the power determination unit 320 proceeds to step 247 and is calculated in step 246, or in steps 244 and 245.

Figure 112007093850961-pat00138
and
Figure 112007093850961-pat00139
In consideration of the above, the power to be allocated to each subchannel is determined by a water-filling technique using the measured noise power density and the channel gain of each subchannel.

According to the present embodiment described with reference to FIG. 4, power to be allocated to each subchannel does not occur, and power to be allocated to each subchannel is converged to a predetermined value in all user terminals.

Meanwhile, the above-described embodiments of the present invention can be written as a program that can be executed in a computer, and can be implemented in a general-purpose digital computer that operates the program using a computer-readable recording medium. The computer-readable recording medium may be a magnetic storage medium (for example, a ROM, a floppy disk, a hard disk, etc.), an optical reading medium (for example, a CD-ROM, DVD, etc.) and a carrier wave (for example, the Internet). Storage medium).

So far I looked at the center of the preferred embodiment for the present invention. Those skilled in the art will appreciate that the present invention can be implemented in a modified form without departing from the essential features of the present invention. Therefore, the disclosed embodiments should be considered in descriptive sense only and not for purposes of limitation. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the scope will be construed as being included in the present invention.

1 is a block diagram of a power control apparatus according to an embodiment of the present invention.

2 is a flowchart of a power determination method according to an embodiment of the present invention.

3 is a flowchart of an exemplary embodiment of step 240 of FIG. 2 in more detail.

4 is a flowchart of another exemplary embodiment of step 240 of FIG. 2 in more detail.

Claims (18)

A method for determining power to be allocated to each subchannel of a user terminal in an uplink OFDMA system using multiple subchannels by multiple users, (a) measuring the noise power density and the channel gain of each subchannel of the user terminal; (b) receiving a channel gain of each subchannel of another user terminal and power to be allocated to each subchannel; And (c) determining power to be allocated to each subchannel of the user terminal by a water filling technique using the measured noise power density and the channel gain in consideration of the received channel gain and power, In the step (c), power to be allocated to the subchannel m of the user terminal according to the following equation:
Figure 112009009024862-pat00140
Obtaining power characterized in that for obtaining.
Figure 112009009024862-pat00141
 Here, the subscript k denotes the user terminal,
Figure 112009009024862-pat00142
The Lagrange multiplier,
Figure 112009009024862-pat00143
Is a value considering the sum of SINRs of the other user terminals for the subchannel m calculated according to the received channel gain and power,
Figure 112009009024862-pat00144
Is the co-channel interference for the subchannel m, N 0 is the measured noise power density,
Figure 112009009024862-pat00145
Denotes the channel gain of the measured subchannel m,
Figure 112009009024862-pat00146
Is
Figure 112009009024862-pat00147
Means. delete The method of claim 1, remind
Figure 112009009024862-pat00148
Is determined according to the following equation.
Figure 112009009024862-pat00149
 Here, the subscript j represents the j th user terminal among the other user terminals,
Figure 112009009024862-pat00150
Is orthogonal constant,
Figure 112009009024862-pat00151
Is the co-channel interference for subchannel m,
Figure 112009009024862-pat00152
Is the channel gain of the received subchannel m,
Figure 112009009024862-pat00153
Denotes power to be allocated to the received subchannel m,
Figure 112009009024862-pat00154
to be. The method of claim 1, remind
Figure 112009009024862-pat00155
Is determined according to the following equation.
Figure 112009009024862-pat00156
 here,
Figure 112009009024862-pat00157
Is orthogonal constant,
Figure 112009009024862-pat00158
Is the channel gain of the received subchannel m,
Figure 112009009024862-pat00159
Denotes power to be allocated to the received subchannel m. The method of claim 1, and (d) determining power to be allocated to each subchannel of the user terminal by repeating steps (b) and (c). The method of claim 5, In step (d), power to be allocated to subchannel m of the user terminal according to the following equation:
Figure 112007093850961-pat00160
Obtaining power characterized in that for obtaining.
Figure 112007093850961-pat00161
 Here, the subscript k denotes the user terminal, the superscript n (an integer of n≥1) denotes the number of repetitions,
Figure 112007093850961-pat00162
The Lagrange multiplier,
Figure 112007093850961-pat00163
Is a value considering the sum of SINRs of the other user terminals for the subchannel m calculated according to the received channel gain and power,
Figure 112007093850961-pat00164
Is the co-channel interference for the subchannel m, N 0 is the measured noise power density,
Figure 112007093850961-pat00165
Denotes the channel gain of the measured subchannel m,
Figure 112007093850961-pat00166
Is
Figure 112007093850961-pat00167
Means. The method of claim 6, remind
Figure 112007093850961-pat00168
Is determined according to the following equation.
Figure 112007093850961-pat00169
 Here, the subscript j is an identifier indicating the user terminal,
Figure 112007093850961-pat00170
Is orthogonal constant,
Figure 112007093850961-pat00171
Is the co-channel interference for subchannel m,
Figure 112007093850961-pat00172
Is the channel gain of the received subchannel m,
Figure 112007093850961-pat00173
Denotes power to be allocated to the received subchannel m,
Figure 112007093850961-pat00174
to be. The method of claim 6, remind
Figure 112007093850961-pat00175
Is determined according to the following equation.
Figure 112007093850961-pat00176
 here,
Figure 112007093850961-pat00177
Is orthogonal constant,
Figure 112007093850961-pat00178
Is the channel gain of the received subchannel m,
Figure 112007093850961-pat00179
Denotes power to be allocated to the received subchannel m. The method of claim 6, In step (d), if there is a subchannel to which power is not allocated in any of the user terminal and the other user terminal, the subchannel may be generated.
Figure 112007093850961-pat00180
Is determined to be a predetermined value other than 0 to apply the above equation. The method of claim 9, The predetermined value other than 0 is
Figure 112009009024862-pat00181
And a value proportional to the power determining method. A computer-readable recording medium having recorded thereon a program for executing the power determination method according to any one of claims 1 and 3 to 10. A power control apparatus for determining power to be allocated to each subchannel of a user terminal in an uplink OFDMA system using multiple subchannels by multiple users, A measurement unit measuring noise power density and channel gain of each subchannel of the user terminal; A receiver which receives the channel gain of each subchannel and power to be allocated to each subchannel of another user terminal; And In consideration of the received channel gain and power, a power determination unit for determining the power to be allocated to each sub-channel of the user terminal by the water filling method using the measured noise power density and the channel gain, The power determiner, the power to be allocated to the sub-channel m of the user terminal according to the following equation
Figure 112009009024862-pat00182
Power control device, characterized in that for obtaining.
Figure 112009009024862-pat00183
 Here, the subscript k denotes the user terminal,
Figure 112009009024862-pat00184
The Lagrange multiplier,
Figure 112009009024862-pat00185
Is a value considering the sum of SINRs of the other user terminals for the subchannel m calculated according to the received channel gain and power,
Figure 112009009024862-pat00186
Is the co-channel interference for the subchannel m, N 0 is the measured noise power density,
Figure 112009009024862-pat00187
Denotes the channel gain of the measured subchannel m,
Figure 112009009024862-pat00188
Is
Figure 112009009024862-pat00189
Means. delete The method of claim 12, The power determiner is
Figure 112009009024862-pat00190
The power control device, characterized in that for calculating the following equation.
Figure 112009009024862-pat00191
 Here, the subscript j is an identifier indicating the user terminal,
Figure 112009009024862-pat00192
Is orthogonal constant,
Figure 112009009024862-pat00193
Is the co-channel interference for subchannel m,
Figure 112009009024862-pat00194
Is the channel gain of the received subchannel m,
Figure 112009009024862-pat00195
Denotes power to be allocated to the received subchannel m,
Figure 112009009024862-pat00196
to be. The method of claim 12, The power determiner is
Figure 112009009024862-pat00197
The power control device, characterized in that for calculating in accordance with the following equation.
Figure 112009009024862-pat00198
 here,
Figure 112009009024862-pat00199
Is orthogonal constant,
Figure 112009009024862-pat00200
Is the channel gain of the received subchannel m,
Figure 112009009024862-pat00201
Denotes power to be allocated to the received subchannel m. The method of claim 12, The receiving unit repeatedly receives the channel gain and the power, The power determiner may determine power to be allocated to each subchannel of the user terminal repeatedly by a water filling method using the measured noise power density and the channel gain in consideration of the repeatedly received channel gain and power. Power control device, characterized in that. The method of claim 12, And a transmitter configured to transmit the measured channel gain and the determined power. A user terminal for an uplink OFDMA system in which multiple users use multiple subchannels, comprising the power control device according to any one of claims 12 and 14-17.
KR1020070138783A 2007-12-27 2007-12-27 Method and apparatus for determining power allocation to each subchannel in uplink ofdma system for multi-user and multi-subchannel, and mobile terminal having the apparatus KR100897059B1 (en)

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KR101054738B1 (en) 2009-06-10 2011-08-05 성균관대학교산학협력단 Method for allocating transmit power to a plurality of subchannels and wireless communication device using same
KR101428919B1 (en) 2013-04-09 2014-08-11 한국과학기술원 Uplink multi radio access method and system in hetergeneous networks

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KR20050048357A (en) * 2003-11-19 2005-05-24 삼성전자주식회사 Apparatus for controlling transmission power selectively in a mobile communication system using orthogonal frequency division multiplexing and the method thereof

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Publication number Priority date Publication date Assignee Title
KR101054738B1 (en) 2009-06-10 2011-08-05 성균관대학교산학협력단 Method for allocating transmit power to a plurality of subchannels and wireless communication device using same
KR101428919B1 (en) 2013-04-09 2014-08-11 한국과학기술원 Uplink multi radio access method and system in hetergeneous networks

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