KR20090092496A - Apparatus and method for channel quality indication reporting for reducing overhead of uplink - Google Patents

Abstract

A CQI transmitting device for reducing the uplink overhead and a method thereof are provided to reduce the power loss and overhead which are caused in the uplink due to unnecessary CQI transmission. A CQI transmission period change information generator(220) performs the correlation operation between the previous CQI and current CQI, and then changes the CQI transmission period according to a result value of the operation. A CQI calculation/transmission unit(214) calculates the CQI and transmits the calculated CQI to a base station by the changed transmission period.

Description

Apparatus and method for transmitting channel quality indicator for reducing uplink overhead {APPARATUS AND METHOD FOR CHANNEL QUALITY INDICATION REPORTING FOR REDUCING OVERHEAD OF UPLINK}

The present invention relates to channel quality indicator (CQI), and more particularly, to an apparatus and method for transmitting CQI for reducing uplink overhead.

In the 802.16e system, the base station uses adaptive modulation and coding (hereinafter, referred to as 'AMC') to determine a modulation scheme and a coding rate according to a channel state by receiving channel information from a terminal. In other words, if the channel condition is not good, reduce the amount of data to be transmitted to adjust the reception error probability to the desired level. If the channel condition is good, increase the amount of data to be transmitted, and the reception error probability is adjusted to the desired level. To be transmitted.

 In order to transmit channel information to the base station, the terminal transmits the CQI to the base station at every channel quality indicator (hereinafter referred to as "CQI") transmission period predetermined by the base station. In this case, when the CQI transmission period is smaller than the change in the channel state, that is, when the CQI is frequently transmitted even though the change in the channel state is not large, power loss and frequency due to unnecessary transmission are repeatedly transmitted. And overhead such as waste of time and resources. On the other hand, when the CQI transmission period is larger than the change in the channel state, that is, when the CQI transmission is not frequently performed as compared with the rapidly changing channel state, AMC accuracy is lowered and system performance (Throughput) is reduced. .

An object of the present invention is to provide an apparatus and method for transmitting CQI for reducing power loss, overhead, and improving system performance.

Another object of the present invention is to determine the CQI transmission cycle adaptively to the channel state (adaptive), the terminal transmits the determined CQI transmission period to the base station using the CQI reporting period change (CPC) header Thereafter, an apparatus and method for transmitting a CQI to the base station in the determined CQI transmission period are provided.

In order to achieve the above object, according to an embodiment of the present invention, a method of transmitting a channel quality indicator (CQI) of a terminal includes performing a correlation operation between a previous CQI and a current CQI, and a result value of the correlation operation. And changing the CQI transmission period according to the present invention.

In order to achieve the above object, according to an embodiment of the present invention, a method for receiving a channel quality indicator (CQI) of a base station transmits an initial CQI transmission period to a terminal, and transmits a CQI to the initial CQI transmission period from the terminal. And receiving the CQI at the changed CQI transmission period from the terminal when the CQI transmission period change information is received from the terminal.

In order to achieve the above object, according to an embodiment of the present invention, a channel quality indicator (CQI) transmitting apparatus of a terminal performs a correlation operation between a previous CQI and a current CQI, and according to a result value of the correlation operation. A CQI transmission period change information generator for changing a CQI transmission period and transmitting CQI transmission period change information to a base station, a CQI calculation and transmitter for calculating a CQI and transmitting the calculated CQI to the base station in the changed CQI transmission period; It is characterized by including.

According to an exemplary embodiment of the present invention, a channel quality indicator (CQI) receiving apparatus of a base station includes: a MAP generating unit for generating a MAP including an initial CQI transmission period and transmitting the MAP to a terminal; A CQI receiver for receiving CQI in the initial CQI transmission period from the terminal and receiving CQI in a changed CQI transmission period from the terminal after receiving CQI transmission period change information from the terminal, and CQI transmission period change information from the terminal It characterized in that it comprises a CQI transmission period change information receiver for receiving the.

According to the present invention, the UE adaptively determines a CQI transmission period according to a channel state, transmits the determined CQI transmission period to a base station by using a CQI reporting period change (CPC) header, and then transmits the determined CQI transmission. By providing an apparatus and a method for transmitting CQI to the base station at periodic intervals, there is an advantage in that power loss and overhead in uplink caused by unnecessary CQI transmission can be reduced, and system throughput can be improved. In addition, since the terminal directly measures the channel state to determine the CQI transmission period accordingly, there is an advantage that the channel state sensitivity can be increased.

1 is a block diagram showing a configuration of a transceiver of a base station according to an embodiment of the present invention;

2 is a block diagram showing the configuration of a transmitting and receiving device of a terminal according to an embodiment of the present invention;

3 is a diagram illustrating a signal flow of a CQI transmission method for reducing uplink overhead according to an embodiment of the present invention;

4 is a flowchart illustrating a procedure of a CQI transmission method for reducing uplink overhead of a terminal according to an embodiment of the present invention;

5 is a flowchart illustrating a procedure of a CQI receiving method for reducing uplink overhead of a base station according to an embodiment of the present invention;

6 illustrates a CPC header in a data frame according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, when 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.

Hereinafter, the present invention will be described an apparatus and method for transmitting CQI for reducing uplink overhead.

1 is a block diagram showing a configuration of a transceiver of a base station according to an embodiment of the present invention.

As shown, the base station is a scheduler 100, MAP generator 102, code / modulator 104, resource mapper 106, OFDM modulator 108, DAC 110, RF (Radio Frequency) transmitter (112), CQI receiver 114, RF receiver 120, ADC 122, OFDM demodulator 124, resource demapper 126, decoder / modulator 128, CQI transmission period change information receiver 130 It is configured to include).

Referring to FIG. 1, first, resource (uplink / downlink resource) scheduling is performed, an MAP is generated and transmitted according to the scheduling result, and an operation for transmitting downlink data to a terminal to which downlink resource is allocated is performed. Let's take a look.

The scheduler 100 performs resource scheduling using a CQI, a request bandwidth, a service type, and the like for each terminal, and provides the scheduling result to the MAP generator 102. Here, in the initial terminal access, information about an initial CQI transmission period and a channel for CQI transmission is included in the scheduling result. The scheduler 100 controls overall transmission and reception operations of the base station according to the scheduling result.

The MAP generation unit 102 generates and outputs a MAP (DL-MAP / UL-MAP) using the scheduling result from the scheduler 100. The MAP includes resource allocation information transmitted to terminals. The code / modulator 104 codes and modulates downlink data and the MAP from the MAP generator 102 in a predetermined manner. The resource mapper 106 maps the data from the code / modulator 104 to a predetermined resource and outputs it.

The OFDM modulator 108 modulates the resource mapped data from the resource mapper 106 to generate an OFDM symbol. In this case, the OFDM modulation includes an Inverse Fast Fourier Transform (IFFT) operation, Cyclic Prefix (CP) insertion, and the like. The digital to analog converter (DAC) 110 converts the sample data from the OFDM modulator 108 into an analog signal and outputs the analog signal. The RF transmitter 112 converts the baseband signal from the DAC 110 into an RF signal and transmits it through an antenna.

The CQI receiver 114 receives the CQI from the terminal and outputs the CQI to the scheduler 100. In this case, the terminal access initially receives the CQI from the terminal in the initial CQI transmission period, after which the CQI from the terminal in the CQI transmission period changed according to the CQI transmission period change information received from the CQI transmission period change information receiver 130 Receive.

Next, the UEs receiving the MAP transmitted in this way receive downlink data from the base station according to the MAP, and transmit the uplink data to the base station. Hereinafter, an operation for receiving uplink data from a terminal allocated an uplink resource will be described.

The RF receiver 120 converts the RF signal received from the terminal into a baseband signal and outputs the baseband signal. The analog-to-digital converter (ADC) 122 converts the baseband analog signal from the RF receiver 120 into digital sample data and outputs the digital sample data. The OFDM demodulator 124 OFDM demodulates sample data from the ADC 122 and outputs subcarrier values. In this case, the OFDM demodulation means a CP removal, a Fast Fourier Transform (FFT) operation, or the like.

The resource demapper 126 extracts data corresponding to a resource allocated to the terminal from the data from the OFDM demodulator 124 and outputs the data to the decoder / demodulator 128. The decoder / demodulator 128 demodulates and decodes data from the resource demapper 126 according to a predetermined modulation level (Modulation and Coding Scheme (MCS) level). Restore uplink data.

The CQI transmission period change information receiver 130 extracts CQI transmission period change information from the decoded data.

2 is a block diagram showing the configuration of a transmitting and receiving device of a terminal according to an embodiment of the present invention.

As shown, the terminal is RF receiver 200, ADC 202, OFDM demodulator 204, resource demapper 206, decoder / demodulator 208, MAP decoder 210, CQI calculation and transmitter ( 214, the CQI transmission period change information generator 220, the code / modulator 222, the resource mapper 224, the OFDM modulator 226, the DAC 228, and the RF transmitter 230.

Referring to FIG. 2, first, an operation of receiving a MAP from a base station and receiving downlink data using a downlink resource allocated according to the MAP will be described.

The RF receiver 200 converts an RF signal received from a base station into a baseband signal and outputs the baseband signal. The ADC 202 converts the baseband analog signal from the RF processor 200 into digital sample data and outputs the digital sample data. The OFDM demodulator 204 OFDM demodulates sample data from the ADC 202 and outputs subcarrier values. In this case, the OFDM demodulation means a CP removal, a Fast Fourier Transform (FFT) operation, or the like.

The resource demapper 206 extracts MAP and downlink data received in a predetermined region within a frame from data from the OFDM demodulator 204 and outputs the data. The decoder / demodulator 208 demodulates and decodes the data from the resource demapper 206 in a predetermined manner to output MAP and downlink data.

The MAP decoder 210 decrypts the MAP from the decoder / demodulator 208 and controls the overall transmission and reception operations of the terminal according to the MAP. In the initial connection to the base station, an initial CQI transmission period is included in the MAP from the base station, and the MAP decoder 210 outputs the initial CQI transmission period to the CQI calculation and the transmitter 214.

The CQI calculation and transmitter 214 calculates the CQI using the OFDM demodulated signal by the OFDM demodulator 204, and feedback-transmits the calculated CQI to the base station according to the CQI transmission period. Here, in the initial connection to the base station, the CQI is transmitted using the initial CQI transmission period obtained through the MAP from the base station, and subsequently uses the changed CQI transmission period from the CQI transmission period change information generator 220 thereafter. To transmit the CQI. In addition, the CQI calculation and transmitter 214 outputs the calculated CQI to the CQI transmission period change information generator 220.

Next, an operation for transmitting uplink data using uplink resources allocated according to the MAP will be described.

The CQI transmission period change information generator 220 performs a correlation operation between an initial CQI and a current CQI using the CQI calculation and the CQI input from the transmitter 214, and transmits the CQI by comparing the result of the correlation operation with a reference value. After determining the increase or decrease of the period, the CQI transmission period change information is output together with the uplink data. In addition, the CQI transmission period changed according to the determination is output to the CQI calculation and the transmitter 214.

The code / modulator 222 codes and modulates the data from the CQI transmission period change information generator 220 at a predetermined modulation level (MCS level) and outputs the same. The resource mapper 224 maps data from the code / modulator 222 to resources allocated to the terminal and outputs the data.

The OFDM modulator 226 modulates and outputs the resource mapped data from the resource mapper 224. The DAC 228 converts the sample data from the OFDM modulator 226 into an analog signal and outputs the analog signal. The RF transmitter 230 converts the baseband signal from the DAC 228 into a radio frequency (RF) signal and transmits the baseband signal through the antenna.

3 is a diagram illustrating a signal flow of a CQI transmission method for reducing uplink overhead according to an embodiment of the present invention.

Referring to FIG. 3, the base station 300 schedules a CQI resource in step 301, and in step 302, the base station 300 transmits an initial CQI transmission period (eg, T0) and a channel for CQI transmission of the terminal 330 determined through the scheduling. An uplink MAP including information on the terminal is transmitted to the terminal 330. In this case, the terminal 330 calculates the CQI in step 303 and then transmits the calculated CQI to the base station 300 in step 304. Here, the process of calculating the CQI and transmitting the calculated CQI is repeatedly performed (steps 305 to 308) for a predetermined time in the received initial CQI transmission period (for example, T0).

In step 309, the terminal 330 performs a correlation operation between the previous CQI and the current CQI, and determines a change in the CQI transmission period according to whether the result of the correlation operation is larger or smaller than the reference value. If it is determined that the increase in the CQI transmission period, the UE 330 is increased to the base station 300 using a CQI reporting period change (hereinafter referred to as "CPC") header in step 310 The CQI transmission period (eg, T1) is transmitted, and in step 311, the base station 300 receives a response thereto. Thereafter, the terminal 330 calculates the CQI in step 312 and then transmits the calculated CQI to the base station 300 in step 313. Here, the process of calculating the CQI and transmitting the calculated CQI is repeatedly performed (steps 314 to 317) for a predetermined time with the increased CQI transmission period (eg, T1).

In step 318, the terminal 330 performs a correlation operation between the previous CQI and the current CQI, and determines a change in the CQI transmission period according to whether the result of the correlation operation is larger or smaller than the reference value. If it is determined that the decrease in the CQI transmission period, the terminal 330 transmits the reduced CQI transmission period (eg, T2) to the base station 300 by using the CPC header in step 319, and the step (320) Receive the response from the base station 300. Thereafter, the terminal 330 calculates the CQI in step 321 and then transmits the calculated CQI to the base station 300 in step 322. Here, the process of calculating the CQI and transmitting the calculated CQI is repeatedly performed (steps 323 to 326) for a predetermined time with the reduced CQI transmission period (eg, T2).

4 is a flowchart illustrating a procedure of a CQI transmission method for reducing uplink overhead of a terminal according to an embodiment of the present invention.

Referring to FIG. 4, the terminal checks whether an initial CQI transmission period is received from the base station in step 401. Here, the initial CQI transmission period is received through the uplink MAP, the uplink MAP also includes information on the channel for CQI transmission, the terminal can transmit the CQI to the base station using the corresponding CQI channel. . When the initial CQI transmission period is received, the terminal calculates the CQI in step 403 and then transmits the calculated CQI to the base station in the received initial CQI transmission period. Here, the process of calculating the CQI and transmitting the calculated CQI in the initial CQI transmission period is repeated for a predetermined time.

In step 405, the terminal performs a correlation operation between the previous CQI and the current CQI. In step 406, the terminal determines whether the result of the correlation operation is equal to the reference value. Here, the previous CQI means the average value of the CQI of the immediately previous time point or CQI values up to the previous time. When the result of the correlation operation is equal to the reference value, the UE calculates the CQI in step 419, transmits the calculated CQI to the base station in the current CQI transmission period, and returns to step 405 to repeat the following steps. do.

On the other hand, when the result value of the correlation operation is not equal to the reference value, the terminal checks whether the result value of the correlation operation is smaller than the reference value in step 407. When the result value of the correlation operation is smaller than the reference value, the terminal proceeds to step 409 to reduce the CQI transmission period. When the result value of the correlation operation is larger than the reference value, the terminal proceeds to step 411 and the CQI. Increase the transmission period Here, since the result of the correlation operation is smaller than the reference value means that the degree of channel state change is large and that the CQI changes rapidly, the UE can increase the AMC accuracy by reducing the CQI transmission period. In addition, since the result of the correlation operation is larger than the reference value means that the degree of channel state change is small and that the CQI is within a certain range, the UE increases the CQI transmission period to reduce unnecessary transmission and reduces overhead. Can be reduced.

In step 413, the terminal transmits CQI transmission period change information to the base station using the CPC header. In step 415, the terminal checks whether a response is received from the base station. Here, the CQI transmission period change information includes at least one of information on whether the CQI transmission period is changed or information on the changed CQI transmission period. In this case, the CPC header is transmitted using the remaining resources of the data frame, and if there is no remaining resource, it is determined whether the CQI transmission period should be changed drastically. The transmission of the link data is delayed to the next frame and the CQI transmission period change information is transmitted to the base station by using the remaining resources. If it is not necessary to change the CQI transmission period abruptly, it is recognized that it is not necessary to send the changed CQI transmission period right now, and transmits the CQI transmission period change information using the remaining resources in the next frame. Here, whether to change the CQI transmission period rapidly may be determined using whether the degree of change in the CQI transmission period is large. That is, when the degree of change in the CQI transmission period is large, it may be determined that the CQI transmission period should be changed abruptly. When the degree of change in the CQI transmission period is small, it may be determined that the CQI transmission period does not need to be abruptly changed.

Herein, referring to FIG. 6, the format of the CPC header in the data frame is as follows. The data frame consists of a header 601, a payload 603, and a residual resource 605, and a CPC header 607 is transmitted using the residual resource 605. The CPC header 607 includes a CQI Reporting Period (CRP) channel indicator 609 and a CRP 611, wherein the CRP channel indicator 609 indicates whether a CQI transmission period is changed, and the CRP 611. ) Represents the changed CQI transmission period. Here, the header 601 of the data frame includes information on the presence or absence of the CPC header 607.

When the response is received, the terminal calculates the CQI in step 417, transmits the calculated CQI to the base station in the changed CQI transmission period, and returns to step 405 to repeat the following steps. Here, the process of calculating the CQI and transmitting the calculated CQI in the changed CQI transmission period is repeated for a predetermined time. On the other hand, when the response is not received, the terminal checks whether it is timed out in step 416, and when it times out, returns to step 413, and when it does not time out, returns to step 415 and repeats the following steps. To perform.

5 is a flowchart illustrating a procedure of a CQI receiving method for reducing uplink overhead of a base station according to an embodiment of the present invention.

Referring to FIG. 5, the base station transmits an initial CQI transmission period to the terminal in step 501. Here, the initial CQI transmission period is transmitted through the uplink MAP together with information about the channel for CQI transmission. Thereafter, the base station receives the CQI in the initial CQI transmission period for a predetermined time from the terminal in step 503.

In step 505, the base station determines whether CQI transmission period change information using a CPC header is received from the terminal. That is, the base station checks the header of the data frame to determine the presence of the CPC header, and when it is determined that the CPC header exists, the CQI transmission period change information using the CPC header transmitted through the remaining resources of the data frame Can be received. In this case, the base station may check whether the CQI transmission period has changed through the CRP channel indicator of the CPC header, and when it is confirmed that the CQI transmission period has been changed, the base station may check the changed CQI transmission period using the CRP of the CPC header. have.

 In step 507, the base station transmits a response to the reception of the CQI transmission period change information to the mobile station. In step 509, the base station receives the CQI in the changed CQI transmission period for a predetermined time from step 509. Go back and repeat the steps below.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the scope of the following claims, but also by the equivalents of the claims.

Claims (32)

In the channel quality indicator (CQI) transmission method of the terminal, Performing a correlation operation between the previous CQI and the current CQI, And changing a CQI transmission period according to a result value of the correlation operation. The method of claim 1, The CQI transmission period changing process may include: decreasing the CQI transmission period when the result of the correlation operation is smaller than a reference value and increasing the CQI transmission period when the result value of the correlation operation is larger than the reference value. Method characterized by that. The method of claim 2, Calculating a CQI when the result of the correlation operation is equal to a reference value, and transmitting the calculated CQI to a base station in a current CQI transmission period. The method of claim 1, Transmitting CQI transmission cycle change information to the base station; Calculating a CQI when the response is received from the base station, and transmitting the calculated CQI to the base station in the changed CQI transmission period. The method of claim 4, wherein The CQI transmission period change information includes at least one of information on whether the CQI transmission period changes and information on the changed CQI transmission period. The method of claim 4, wherein The CQI transmission period change information is transmitted using the remaining resources of the data frame. The method of claim 6, If the remaining resources do not exist, it is determined whether the degree of change in the CQI transmission period is large, and when the degree of change in the CQI transmission period is large, the transmission of uplink data is delayed and the CQI transmission is performed using the remaining resources. And transmits the CQI transmission period change information by using the remaining resources in the next frame, recognizing that it is not necessary to send the changed CQI transmission period right now if the CQI transmission period change degree is small. How to feature. The method of claim 6, The CQI transmission period change information is transmitted using a CQI reporting period change (CPCI) header in the remaining resource. The method of claim 8, The information on the presence or absence of the CPC header is included in the header of the data frame. The method of claim 1, Receiving an initial CQI transmission period from a base station, Calculating a CQI, and transmitting the calculated CQI to the base station in the received initial CQI transmission period. The method of claim 10, The initial CQI transmission period is characterized in that for receiving via uplink MAP. In the method for receiving a channel quality indicator (CQI) of the base station, Transmitting an initial CQI transmission period to a terminal and receiving a CQI in the initial CQI transmission period from the terminal; And receiving CQI at the changed CQI transmission period from the terminal when CQI transmission period change information is received from the terminal. The method of claim 12, The initial CQI transmission period is characterized in that for transmitting via uplink MAP. The method of claim 12, And when the CQI transmission period change information is received from the terminal, transmitting a response to the terminal. The method of claim 12, The CQI transmission period change information includes at least one of information on whether the CQI transmission period changes and information on the changed CQI transmission period. The method of claim 12, The CQI transmission period change information is received using the remaining resources of the data frame. The method of claim 16, The CQI transmission period change information is received using a CQI reporting period change (CPCI) header in the remaining resource. The method of claim 17, The information on the presence or absence of the CPC header is included in the header of the data frame. In the channel quality indicator (CQI) transmission apparatus of the terminal, A CQI transmission period change information generator for performing a correlation operation between a previous CQI and a current CQI, changing a CQI transmission period according to a result of the correlation operation, and transmitting CQI transmission period change information to a base station; A CQI calculation and transmitter for calculating a CQI and for transmitting the calculated CQI to the base station in the changed CQI transmission period. The method of claim 19, wherein the CQI transmission period change information generator, When the result value of the correlation operation is smaller than the reference value, the CQI transmission period is decreased, and when the result value of the correlation operation is larger than the reference value, the CQI transmission period is increased to change the CQI transmission period. Characterized in that the device. The method of claim 20, wherein the CQI calculation and transmitter, And calculating a CQI when the result of the correlation operation is equal to a reference value, and transmitting the calculated CQI to a base station in a current CQI transmission period. The method of claim 19, The CQI transmission period change information includes at least one of information on whether the CQI transmission period is changed and information on the changed CQI transmission period. The method of claim 19, The CQI transmission period change information is transmitted using the remaining resources of the data frame. The method of claim 23, If the remaining resources do not exist, it is determined whether the degree of change in the CQI transmission period is large, and when the degree of change in the CQI transmission period is large, the transmission of uplink data is delayed and the CQI transmission is performed using the remaining resources. And transmits the CQI transmission period change information by using the remaining resources in the next frame, recognizing that it is not necessary to send the changed CQI transmission period right now if the CQI transmission period change degree is small. Characterized in that the device. The method of claim 23, And transmitting the CQI transmission period change information by using a CQI reporting period change (CPC) header in the remaining resource. The method of claim 25, And information on the presence or absence of the CPC header is included in the header of the data frame. The method of claim 19, Further comprising a MAP decoder for decoding an MAP from a base station to receive an initial CQI transmission period, The CQI calculation and transmitter calculates a CQI and transmits the calculated CQI to the base station in the received initial CQI transmission period. In the channel quality indicator (CQI) receiving apparatus of the base station, A MAP generator for generating a MAP including an initial CQI transmission period and transmitting the MAP to a terminal; A CQI receiver for receiving CQI in the initial CQI transmission period from the terminal, and receiving CQI in a changed CQI transmission period from the terminal when receiving CQI transmission period change information from the terminal; And a CQI transmission period change information receiver for receiving CQI transmission period change information from the terminal. The method of claim 28, The CQI transmission period change information includes at least one of information on whether the CQI transmission period is changed and information on the changed CQI transmission period. The method of claim 28, The CQI transmission period change information is received using the remaining resources of the data frame (remained resource). The method of claim 30, The CQI transmission period change information is received using a CQI reporting period change (CPCI) header in the remaining resource. The method of claim 31, wherein And information on the presence or absence of the CPC header is included in the header of the data frame.