KR101300854B1 - Apparatus and method for allocating resource in a ofdma wireless communicaion system - Google Patents

Abstract

The present invention relates to a method for allocating resources by a base station in a wireless communication system, the method comprising: determining whether to use subcarriers not used for transmission of control information from among subcarriers allocated for control information transmission for data transmission, and transmitting the control information. When it is determined that subcarriers not used in the data symbol transmission are to be used for transmitting the data symbol, the UE informs the terminal of the determination result and transmits the control information and the data using the subcarriers allocated for the control information transmission.

OFDMA, resource allocation, power allocation, control information.

Description

A resource allocation apparatus and method in an orthogonal frequency multiple access wireless communication system {APPARATUS AND METHOD FOR ALLOCATING RESOURCE IN A OFDMA WIRELESS COMMUNICAION SYSTEM}

1 is a view showing an example of the utilization of resources used in a conventional OFDMA system,

2 is a block diagram of a base station transmitter according to an embodiment of the present invention;

3 is an internal block diagram of a receiver of a terminal according to an embodiment of the present invention;

4 is a control flowchart of transmission of control information and data in a base station according to an embodiment of the present invention;

5 is a control flowchart of transmission of control information and data in a base station according to another embodiment of the present invention;

6 is a control flowchart when receiving control information and data in a terminal according to an exemplary embodiment of the present invention.

The present invention relates to an apparatus and method for allocating resources in a wireless communication system, and more particularly, to an apparatus and method for allocating a resource in an orthogonal frequency division multiplexing access (OFDMA) scheme. .

Typically, a wireless communication system is a communication system for ensuring the user's activity free from the distance constraints of the wire. This wireless communication system has been actively studied and used a communication system using a Code Division Multiplexing Access (hereinafter referred to as "CDMA") method. However, in CDMA, due to limited resources, it is difficult to provide more data services required by users at a low cost. Therefore, active discussions have been made on the OFDMA method that can provide more data. Reached.

The OFMDA method is a method based on Orthogonal Frequency Division Multiplexing (hereinafter referred to as " OFDM "), and transmits data using a multi-carrier. Accordingly, the OFDM scheme performs parallel conversion of serially input symbol strings and modulates each of them into a plurality of sub-carriers, that is, a plurality of sub-carrier channels. It is a kind of multi-carrier modulation (hereinafter referred to as "MCM") method to transmit by sending. The OFDMA system is a system that distinguishes multiple users through the plurality of subcarriers while taking the OFDM scheme as a basic transmission scheme, that is, a method of allocating different subcarriers to different users.

1 is a diagram illustrating an example of utilization of resources used in a conventional OFDMA system.

In FIG. 1, the horizontal axis represents a frequency axis which is an orthogonal frequency resource, and the vertical axis represents a time axis. One small square represents a unit in which one subcarrier is transmitted in one OFDM symbol. In FIG. 1, for convenience, only 36 subcarriers exist in a frequency axis. However, in actual systems, there may be much more subcarriers than this. The grids T ₁ to T ₄ of the grids hatched in FIG. 1 are pilot or reference signal symbols for transmit antenna 1, pilot symbols for transmit antenna 2, and transmit antenna 3. Pilot symbols for times and pilot symbols for transmit antenna 4 are shown. In addition, each grid that transmits pilot symbols is numbered according to antenna order.

Resource blocks (110, 120, 130) may be used as a unit of resource allocation. That is, the resource blocks 110, 120, and 130 determined by the reference numeral 140 and the reference numeral 150 are each composed of 12 subcarriers on the frequency axis and 14 OFDM symbols on the time axis. In FIG. 1, three resource blocks are shown for convenience. In FIG. 1, the gratings with dots not shown as T ₁ to T ₄ represent subcarriers used to transmit control information. In the conventional OFDMA system, the control information includes downlink resource allocation information, uplink resource allocation information, and uplink power control information. The detailed control information may vary slightly from system to system. Note that

On the other hand, the system shown in FIG. 1 is a system using time division multiplexing (hereinafter referred to as "TDM") in transmitting the control information. In general, when transmitting control information in an OFDMA system using a TDM scheme, control information is transmitted through N OFDM symbols at the foremost among resource blocks. That is, as indicated by reference numeral 160 in FIG. 1, the N OFDM symbols at the foremost of the resource blocks become resources for transmitting control information. This is referred to as "control information transmission subcarriers". In addition, the value of N typically depends on the amount of control information and the number of subcarriers used to transmit the control information. 1 illustrates a case where the N value is three. Note that not all subcarriers included in the 1 st to N th OFDM symbols are used for transmitting the control information.

In FIG. 1, it can be seen that only some subcarriers of the third OFDM symbols are used for transmission of control information. With the resource usage configuration for the control information transmission as described above, resource blocks transmitted during the time of transmitting three OFDM symbols for transmitting the control information in FIG. 1 are allocated to the terminals by a predetermined scheduling procedure. For example, the resource block 1 is assigned to the terminal 1, the resource block 2 is assigned to the terminal 2, the resource block 3 is assigned to the terminal 3. The resource block allocation is repeatedly performed through a predetermined period.

In the above example, look at the resource block 1 allocated to the terminal 1 in more detail. All of the remaining resources except for the resources used for transmitting the pilot and control information among all OFDM symbols, including the resource for transmitting control information in the resource block 1 (110), may be used for data transmission.

However, when all remaining OFDM symbols are used for data transmission except for resources used for transmission of control information among OFDM symbols, the following problem may occur. First, the power allocated to the control information transmission changes from time to time. Therefore, a problem occurs in data transmission due to a change in power allocated to control information transmission. This is because the power allocated to the control information transmission is typically controlled differently according to the channel environment of the terminal to receive the control information and the distance from the base station. For example, when the terminal to receive the control information is very far from the base station, the base station allocates a lot of power to the control information transmission, and vice versa. In this case, typically, the power that the base station can use to transmit one OFDM symbol is fixed. Accordingly, the available power available for data transmission in the third OFDM symbol of FIG. 1 is changed for transmission of control information. This means that the power allocated to the subcarriers used for data transmission of the fourth through 14th OFDM symbols among the data symbols of the resource block 1 may be different from the power allocated to data transmission in the third OFDM symbol. . In addition, due to the phenomenon in which data is transmitted at different powers, the data demodulation performance is deteriorated. Such a phenomenon may occur especially when the amount of power used to transmit control information included in the third OFDM symbol is very large.

Accordingly, the present invention provides a resource allocation apparatus and method capable of transmitting more data in an orthogonal frequency multiple access wireless communication system.

The present invention also provides an apparatus and method for allocating resources for improving data demodulation performance of a receiver in an orthogonal frequency multiple access wireless communication system.

The present invention also provides an apparatus and method for allocating resources capable of increasing the efficiency of data transmission in an orthogonal frequency multiple access wireless communication system.

The present invention also provides a receiving apparatus and method capable of extracting data using control information received in an orthogonal frequency multiple access wireless communication system.

A method according to an embodiment of the present invention comprises: A method of allocating resources by a base station in a wireless communication system, the method comprising: determining whether to use subcarriers, which are not used for transmission of control information, from among subcarriers allocated for transmission of control information, for data transmission; and When determining that the unused subcarriers are to be used for the data symbol transmission, informing the terminal of the determination result, and transmitting the control information and the data by using the subcarriers allocated for the control information transmission. .

An apparatus according to an embodiment of the present invention includes: An apparatus for allocating resources in a wireless communication system, comprising: determining whether to use subcarriers, which are not used for transmission of control information, for data transmission, from among subcarriers allocated for transmission of control information, and subcarriers not used for transmission of the control information. And a controller for informing the terminal of the determination result and generating a control signal including the determination result when determining that the data symbol is to be used for the data symbol transmission, a modem for encoding and modulating the control information and the data, and the control signal. A mapper for mapping the control information and the data to a corresponding subcarrier, an OFDM symbol configurator configured of orthogonal frequency division multiplexing (OFDM) symbols, and the OFDM symbol configuration To convert the signal of the signal to the transmission band It includes a wireless transmitter.

According to another embodiment of the present invention, there is provided a method comprising: A method for receiving data by a terminal in a wireless communication system, the method comprising: detecting whether subcarriers not used for transmission of control information are used for data transmission among subcarriers allocated for transmission of control information; When detecting that the subcarriers not used for transmission are used for the data transmission, the method includes identifying a location of the subcarriers used for the data transmission and extracting data received at the identified location.

According to another embodiment of the present invention, there is provided an apparatus comprising: An apparatus for receiving data in a wireless communication system, comprising: a radio unit for converting a radio signal into a baseband signal and outputting the signal; an orthogonal frequency division multiple symbol receiver for converting the baseband signal into orthogonal frequency division multiple symbols; A demapper for separating control information and data from orthogonal frequency division multiple symbols, a modem for demodulating and decoding the control information and data, and subcarriers not used for transmitting the control information may be detected. And a control unit for identifying a location of a subcarrier used for the data transmission and extracting data received at the identified location.

The operation principle of the preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. The following terms are defined in consideration of the functions of the present invention, and may be changed according to the intentions or customs of the user, the operator, and the like. Therefore, the definition should be based on the contents throughout this specification.

First, after briefly reviewing the general contents of the present invention, a detailed apparatus and its operation will be described.

The present invention is first used in an OFDMA system having a structure for transmitting control information in a TDM manner. The base station determines whether or not to use the remaining subcarriers used for the transmission of the control information among the OFDM symbols including the control information for data transmission. The base station informs the terminal of the determined information. Through this, the terminal can check whether to extract data from the area for transmitting the control information. In addition, the terminal uses the information together when demodulating data to obtain the positions of subcarriers through which data is received.

In the present invention, whether or not to use the remaining subcarriers used for the transmission of control information among the OFDM symbols transmitted in the period during which the base station transmits the control information for data transmission or the amount of power allocated to the control information transmission or the control information transmission It is determined based on the amount of subcarriers used in. That is, the base station determines whether to transmit data using subcarriers for which control information is not actually transmitted in subcarriers used for control information transmission.

In addition, after determining whether to transmit the data, the base station can inform the terminal of the determined information using one of the following three methods.

(1) a method of explicitly signaling over a given broadcast channel

(2) a method of transmitting resource allocation information together with the terminal

(3) Predetermine whether or not the remaining subcarriers are used for data transmission according to the ratio of the remaining subcarriers used for transmission of control information in the last OFDM symbol or the number of subcarriers used for the transmission of control information to the total number of subcarriers. How to lose

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2 is a block diagram of a base station transmitter according to a preferred embodiment of the present invention. In FIG. 2, since the control information and the data are for explaining transmission, only portions related thereto are shown. Therefore, it should be noted that a general configuration other than the block configuration required for transmitting control information and data is omitted.

The control information is input to the control channel coding unit 202, and the control information is encoded to output encoded symbols. The control symbols encoded as described above are input to the control channel modulating unit 203. The control channel modulator 203 modulates the control symbols in a predetermined manner according to the system and outputs the modulated control symbols to the subcarrier mapper 206.

In addition, data to be transmitted to each user is input to the data channel encoder 204 and converted into data symbols. The data symbols are input to the data channel modulator 205 and modulated according to the modulation scheme assigned to each user, and the modulated data symbols are output to the subcarrier mapper 206. The reference numerals 202, 203, 204, and 205 may be configured as one modem.

The subcarrier mapper 206 receives pilot symbols 201 and the modulated control symbol and the modulated data symbol. The controller 211 maps each symbol to a corresponding subcarrier. In this mapping, the mapping of data symbols is determined under the control of the controller 211. First, the control unit 211 determines whether to transmit the data symbol to the remaining subcarriers (hereinafter referred to as "subcarrier except control information") except for the subcarriers used for transmission of control information among the OFDM symbols in the control information transmission period. .
When it is determined that data symbols are transmitted with the control information exclusion subcarriers, data symbols are mapped from the control information exclusion subcarriers to the subcarriers of other OFDM symbols of the resource block. If it is determined that data symbols are not transmitted on the subcarriers other than the control information, the data symbols are mapped from an OFDM symbol following a period in which the control information is transmitted in a resource block. Control by the control unit 211 will be described in more detail in the control flowchart described later.

The symbols mapped to the subcarriers in the subcarrier mapper 206 are input to the OFDM symbol constructing unit 208 and configured as OFDM symbols. The OFDM symbol construction unit 208 is the same as a conventional OFDM symbol construction unit such as a Fast Fourier Transform (FFT) block, a cyclic prefix (CP) adder, and the like. When the OFDM symbol is configured as described above, the wireless transmission unit 209 converts the transmission frequency band and transmits the transmission to the corresponding user terminals through the antenna.

3 is a block diagram illustrating an internal receiver configuration of a terminal according to an exemplary embodiment of the present invention. In the terminal receiver of FIG. 3, only the necessary block configuration is illustrated in describing the present invention, and it should be noted that blocks that are considered unnecessary are omitted.

The signal received through the antenna is input to the wireless receiver 301. The wireless receiver 301 converts a signal of a transmission band into a baseband signal and outputs the signal to the OFDM symbol receiver 302. Then, the OFDM symbol receiver 302 outputs the received OFDM symbol by Inverse Fast Fourier Transform (IFFT). The OFDM symbol receiver 302 includes a CP remover, an IFFT block, and the like, like a typical OFDM receiver. The subcarrier demapper 303 divides the pilot symbol, the control symbol, and the data symbol under the control of the controller 311 and outputs the divided symbols.
According to an embodiment of the present invention, the controller 311 checks whether data symbols are transmitted using subcarriers other than control information among OFDM symbols in a period in which control information is transmitted. The test can be detected through control information output from the control channel decoding unit 307 when the signal is explicitly signaled through the control information. Alternatively, the control unit 311 may detect by an implicit method promised in advance. If it is determined that the data symbols are transmitted with subcarriers other than the control information among the OFDM symbols in the period in which the control information is transmitted, the controller 311 classifies and outputs the data symbols from the subcarriers except the control information. In the RB, data symbols are separated and output from the OFDM symbol following the interval in which the control information is transmitted. The operation of the control unit 311 will be described in more detail using a control flowchart to be described later.

The control channel demodulation unit 305 demodulates the symbols transmitted on the control channel and outputs the demodulated symbols to the control channel decoder 307. The control channel decoder 307 then decodes the demodulated symbol into control information. That is, a general decoding process is performed. The decoded information is input to the controller 311. The data symbol output from the subcarrier demapper 303 is demodulated by the data channel demodulator 306 and input to the data channel decoder 308. The data channel decoder 308 decodes the input symbol and outputs user data. The control channel demodulator 305, the control channel decoder 307, the data channel demodulator 306, and the data channel decoder 308 may be implemented by a modem.

4 is a control flowchart of transmission of control information and data in a base station according to an embodiment of the present invention. Hereinafter, a control process for transmitting control information and data according to an embodiment of the present invention will be described in detail with reference to FIGS. 2 and 4.

In step 400, the control unit 211 of the base station allocates resource blocks (RBs) to the user through predetermined scheduling. In this case, scheduling refers to a predetermined resource allocation decision process. In general, the operation of scheduling is based on the amount of data to be sent, the Quality of Service (QoS), and other criteria and procedures. In step 402, the controller 211 allocates resources to control symbols for transmitting resource allocation information and other control information including the resource block allocation result. In operation 402, the controller 211 allocates power to control symbols for transmitting the resource allocation information and other control information. In this case, the allocation of resources to control symbols means determining the amount and location of each OFDM symbol indicated by the control symbol in FIG. And allocating power means that the terminal to receive the control information determines the appropriate transmission power so as to correctly receive the control information.

In step 404, the controller 211 of the base station determines whether subcarriers of the remaining symbols except for the control symbols are used for data transmission among the subcarriers of the OFDM symbols including control symbols among the OFDM symbols in the allocated resource block. do. Herein, for the sake of convenience, the control symbols are defined. However, the control symbols may include symbols for other purposes other than the control symbols, that is, symbols other than data symbols. However, it should be noted that the present invention is limited to this as a control symbol for convenience. Whether the control information excluding subcarrier is used for data transmission may be determined according to the amount of power allocated to control symbols or the amount of subcarriers allocated to the control symbols.

In step 406, the controller 211 of the base station transmits data through symbols available for data transmission in each RB. Here, the symbols available for data transmission include all subcarriers (except pilot symbols) of OFDM symbols not including the control symbols, and subcarriers except control information may or may not be included. At this time, the base station transmits whether to use the subcarrier other than the control information together with the resource block allocation information to the terminal. When this process is completed, the control unit 211 proceeds to step 400 again and repeats the above process.

5 is a control flowchart of transmission of control information and data in a base station according to another embodiment of the present invention. Hereinafter, a control process during data transmission and control information according to another embodiment of the present invention will be described in detail with reference to FIGS. 2 and 5.

In step 500, the control unit 211 of the base station determines the amount of symbols to be used for transmitting control information in one subframe. Herein, the subframe refers to a length of time corresponding to one of the resource blocks, that is, one of the reference numerals 110, 120, and 130 in FIG. 1. That is, the length of time corresponding to 14 OFDM symbols is shown. In step 502, the controller 211 determines whether to use the remaining symbols except for the control symbols in the OFDM symbols including the control symbols in one subframe for data transmission. This determination process may be determined based on the amount of control symbols included in the last OFDM symbols including the control symbols.

Next, the controller 211 proceeds to step 504 and transmits information on whether to use the subcarriers of the remaining symbols used for control information transmission, that is, the subcarriers other than the control information, for data transmission. The transmission of information on whether the remaining symbols are used for data transmission may be performed through a predetermined broadcast channel.

At this time, the base station may explicitly signal whether or not to use the control information subcarrier through a predetermined broadcast channel, but a predetermined threshold is promised between the base station and the terminal in advance, and the control information determined in step 500 is determined. A method of implicitly determining may be used according to the amount of control symbols for transmitting a. In addition, step 504 is indicated by a dotted line. The reason why the step 504 is indicated by the dotted line is that the step 504 may be omitted when using the implicit signaling method as described above.

In addition, when using the implicit method will be described how to put the threshold as described above. In the case of using the implicit method, if the amount of control symbols in the last OFDM symbol for transmitting the control symbol exceeds the threshold, the control information excluding subcarriers of the last OFDM symbol are not used for data transmission. On the contrary, when the amount of control symbols in the last OFDM symbol is less than or equal to the threshold, subcarriers other than control information of the last OFDM symbol are used for data transmission. For example, when the threshold is promised to be 50%, the amount of control symbols in the third OFDM symbol in FIG. 1 is 25% and therefore the control of the third OFDM symbol is because it is less than the threshold. Information-excluded subcarriers are used for data transmission.

This will be described with reference to FIG. 5 again. The control unit 211 of the base station allocates the RBs to the user through predetermined scheduling in every subframe in step 506. In operation 508, the controller 211 transmits data through symbols available for data transmission in each RB. As such, the control unit 211 of the base station repeats the steps 500 to 508. In this case, steps 500 to 504 may be repeated at a relatively longer period than steps 506 and 508. Therefore, if the period corresponds to the short period after step 508, the process proceeds to step 506 indicated by the solid line, and when the long period corresponds to the step 500 indicated by the dotted line.

6 is a control flowchart of receiving control information and data in a terminal according to an exemplary embodiment of the present invention. Hereinafter, a control process upon reception of control information and data in a terminal according to an exemplary embodiment of the present invention will be described in detail with reference to FIGS. 3 and 6.

In step 600, the control unit 311 of the terminal obtains information on whether remaining symbols except for control symbols are used for data transmission among OFDM symbols including control symbols in one subframe. The process of obtaining such information may be obtained through a predetermined broadcast channel as described with reference to FIGS. 4 and 5, or through the implicit signaling method described with reference to FIG. 5, or 406 of FIG. 4. The resource allocation information transmitted in the step may be received at the same time. In step 602, the control unit 311 of the terminal receives control information by a predetermined procedure every subframe to obtain information on whether a resource is allocated to itself. Thereafter, the controller 311 proceeds to step 604 and receives the data by a predetermined procedure when there is its own data in this subframe. At this time, the symbols used for data transmission are recognized by the allocated RB using the information obtained in step 600 together.

As described above, when the present invention is applied, an error rate of data can be reduced in a receiver while using resources more efficiently in an OFDMA communication system, and there is an advantage that more resources can be used efficiently. This also has the advantage of increasing the throughput of the entire system.

Claims (14)

A method for a base station to allocate resources in a wireless communication system, Determining whether to use subcarriers not used for transmission of control information from among subcarriers allocated for transmission of control information for data transmission; Informing the UE of the determination result when determining that the subcarriers not used for the control information transmission are to be used for the data symbol transmission; And transmitting the control information and the data by using the subcarriers allocated for the control information transmission. The method of claim 1, The determining may include comparing the amount of power allocated to the control information transmission with a predetermined threshold value; When the amount of power allocated to the control information transmission is less than or equal to the predetermined threshold, determining that subcarriers not used for the control information transmission are to be used for the data symbol transmission. Assignment method. The method of claim 1, The determining may include comparing the amount of subcarriers used to transmit the control information with a predetermined threshold value; When the amount of subcarriers used for the control information transmission is less than or equal to the predetermined threshold, determining that subcarriers not used for the control information transmission are to be used for the data symbol transmission. Assignment method. The method of claim 1, The informing process further includes informing the terminal of the determination result through a predetermined broadcast channel. The method of claim 1, The notifying may include signaling the determination result along with the resource allocation information for the terminal to the terminal. The method of claim 1, Among subcarriers allocated for the control information transmission, whether to use subcarriers not used for the control information transmission for data transmission is determined in advance according to the amount of subcarriers not used for the control information transmission in the last orthogonal frequency division multiple symbol. Resource allocation method of the base station characterized in that. An apparatus for allocating resources in a wireless communication system, Determining whether to use subcarriers not used for control information transmission for data transmission among subcarriers allocated for control information transmission and determining that subcarriers not used for control information transmission are to be used for the data symbol transmission. A control unit for notifying the terminal of the determination result and generating a control signal including the determination result; A modem for encoding and modulating the control information and the data; A mapper for mapping the control information and the data to a corresponding subcarrier according to the control signal; An OFDM symbol configurator configured to configure orthogonal frequency division multiplexing (OFDM) symbols of the mapped control information and data; And a radio transmitter for converting a signal of the OFDM symbol configurator into a transmission band and transmitting the signal. 8. The control information of claim 7, wherein the controller compares an amount of power allocated to the control information transmission with a predetermined threshold value, and when the amount of power allocated to the control information transmission is equal to or less than the predetermined threshold value, the control information. And determining that subcarriers not used for transmission are to be used for the data symbol transmission. The control information of claim 7, wherein the control unit compares the amount of subcarriers used for the control information transmission with a predetermined threshold value, and when the amount of subcarriers used for the control information transmission is equal to or less than the predetermined threshold value, the control information. And determining that subcarriers not used for transmission are to be used for the data symbol transmission. The apparatus of claim 7, wherein the controller notifies the terminal of the determination result through a predetermined broadcast channel. The apparatus of claim 7, wherein the controller signals the determination result to the terminal together with the resource allocation information for the terminal. 8. The method of claim 7, wherein the control unit determines whether to use subcarriers not used for the transmission of the control information for data transmission among subcarriers allocated for the transmission of the control information in the last orthogonal frequency division multiple symbol. And determining in advance according to the amount of unused subcarriers. In a method of receiving data by a terminal in a wireless communication system, Detecting whether subcarriers not used for transmission of control information are used for data transmission among subcarriers allocated for transmission of control information; Determining the location of the subcarriers used for the data transmission when detecting that the subcarriers not used for the control information transmission have been used for the data transmission; And extracting data received at the identified location. An apparatus for receiving data in a wireless communication system, A wireless unit for converting and outputting a wireless signal into a baseband signal; An orthogonal frequency division multiple symbol receiver for converting the baseband signal into orthogonal frequency division multiple symbols and outputting the same; A demapper for separating control information and data from orthogonal frequency division multiple symbols; A modem for demodulating and decoding the control information and the data; When detecting that the subcarriers not used for the control information transmission is used for the data transmission, receiving a data including a control unit for checking the position of the subcarrier used for the data transmission, and extracts the data received at the identified position Device.

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