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 PDFInfo
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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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- 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
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- 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
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- 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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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
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.
In the above equation,
N is the power to be allocated to the sub-channel m of the user terminal k, N 0 is the noise power density, Denotes a channel gain of the subchannel m of the user terminal k, Is 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
Can be obtained.
Here, the subscript k denotes the user terminal,
The Lagrange multiplier, 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, Is the co-channel interference for the subchannel m, N 0 is the measured noise power density, Denotes the channel gain of the measured subchannel m, Is Means.At this time, the
May be calculated according to the following equation.
Here, the subscript j represents the j th user terminal among the other user terminals,
Is orthogonal constant, Is the co-channel interference for subchannel m, Is the channel gain of the received subchannel m, Denotes power to be allocated to the received subchannel m, to be.Also, the
May be calculated according to the following equation.
here,
Is orthogonal constant, Is the channel gain of the received subchannel m, 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
Can be obtained.
Here, the subscript k denotes the user terminal, the superscript n (an integer of n≥1) denotes the number of repetitions,
The Lagrange multiplier, 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, Is the co-channel interference for the subchannel m, N 0 is the measured noise power density, Denotes the channel gain of the measured subchannel m, Is Means.At this time, the
May be calculated according to the following equation.
Here, the subscript j is an identifier indicating the user terminal,
Is orthogonal constant, Is the co-channel interference for subchannel m, Is the channel gain of the received subchannel m, Denotes power to be allocated to the received subchannel m, to be.Also, the
May be calculated according to the following equation.
here,
Is orthogonal constant, Is the channel gain of the received subchannel m, 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,
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, 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
Can be obtained.
Here, the subscript k denotes the user terminal,
The Lagrange multiplier, 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, Is the co-channel interference for the subchannel m, N 0 is the measured noise power density, Denotes the channel gain of the measured subchannel m, Is Means.In this case, the power determination unit is
Can be calculated according to the following equation.
Here, the subscript j is an identifier indicating the user terminal,
Is orthogonal constant, Is the co-channel interference for subchannel m, Is the channel gain of the received subchannel m, Denotes power to be allocated to the received subchannel m, to be.In addition, the power determination unit is
Can be calculated according to the following equation.
here,
Is orthogonal constant, Is the channel gain of the received subchannel m, 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)
The power allocated to the subchannel m (1≤m≤M) of the user terminal k 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.
here,
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.
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.
here,
Is the instantaneous maximum power that the user terminal can transmit, and co-channel interference in subchannel m Is obtained according to the following equation.
here,
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
Referring to FIG. 1, the
The measuring
The
Meanwhile, the
Here, the information about the channel gain and power transmitted or received by the
Hereinafter, a detailed method of determining the power to be allocated to each subchannel of the
The
In the above equation
and 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
Is obtained according to Equation 5 described above, Is the power of the sub-channel m of the user terminal 100 k As this increase, it can be defined as the increase rate of the throughput of other user terminals sharing the sub-channel m, If this increases, the throughput of other user terminals decreases, so eventually Becomes negative. therefore Can be obtained according to the following equation.
Here, the subscript j is an identifier indicating the user terminal,
Is orthogonal constant, Co-channel interference for the sub-channel m in the user terminal j, The channel gain of the sub-channel m in the user terminal j, Denotes power to be allocated to subchannel m in user terminal j, to be. Referring to equation (7) above, 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 theIn addition, by analyzing the above equation (6), it can be seen that there is a feature according to the following equation.
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
( 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
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 theIn addition, according to another embodiment of the present invention, in the
The
2 is a flowchart of a method of determining, by the
First, the number of repetitions n is set to an
In
In
In
In
In
In
If n is greater than n ITER , the UE proceeds to step 255 and the
If there is no data to be transmitted in
3 is a flowchart of an exemplary embodiment of
Here, the subscript k denotes the
In
Here, the symbols described in Equations 10 and 11 are similarly applied to the above equations,
The Lagrange multiplier, Is 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
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
4 is a flowchart illustrating another embodiment of
Referring to FIG. 4, in
If there is no subchannel to which no power is allocated in any of the user terminals, the flow proceeds to step 246. Since
If there is a subchannel to which no power is allocated in any of the user terminals, the flow proceeds to step 244. In
In
Next, the
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
4 is a flowchart of another exemplary embodiment of
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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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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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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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