KR20050005992A - Apparatus for variable power hybrid arq in mobile communication system and method thereof - Google Patents

Abstract

PURPOSE: An HARQ(Hybrid Automatic Repeat Request) apparatus and a method for varying retransmission power in a mobile communication system are provided to reduce a repeat number and to minimize a power consumption by effectively controlling the retransmission power. CONSTITUTION: A mobile station(600) is used for a mobile communication system which repeats a transmission of packet data and related data when error generated in pre-transmitted packet data and combines the re-transmitted packet data with the pre-transmitted packet data to modulate the result. The mobile station retransmits required packet data. The mobile station includes an AMC(Adaptive Modulation and Coding) and retransmission power controller(619) and a power controller(621). The AMC and retransmission power controller calculates a required SNR(Signal to Noise Ratio), which is required for the retransmission, by using a target SNR, which is required for a frame error to have a predetermined value, and an SNR of the erroneous packet data which is calculated from a channel quality monitoring value from a terminal. The AMC and retransmission power controller further calculates retransmission power from the required SNR. The power controller controls the transmission power of a packet according to the retransmission power calculated at the AMC and retransmission power controller.

Description

Compound retransmission apparatus and method for varying transmission of retransmission power in mobile communication system {APPARATUS FOR VARIABLE POWER HYBRID ARQ IN MOBILE COMMUNICATION SYSTEM AND METHOD THEREOF}

The present invention relates to an apparatus and method for transmitting data in a mobile communication system, and more particularly, to an apparatus and method for retransmitting data having an error during transmission.

Today's mobile communication systems are evolving into high-speed, high-quality wireless data packet communication systems to provide data services and multimedia services beyond voice-oriented services. The standardization of High Speed Downlink Packet Access (HSDPA) and 1xEV-DV, which is currently being conducted around 3GPP and 3GPP2, is an effort to find a solution for a high speed, high quality wireless data packet transmission service of 2Mbps or higher in 3G mobile communication systems. This is a typical example. On the other hand, the fourth generation mobile communication system is based on the provision of more high-speed, high quality multimedia services.

In a mobile communication system performing such wireless communication, a factor that hinders high-speed and high-quality data service is largely due to a channel environment. In addition to the white noise, the channel for wireless communication is a change in the received signal power due to fading, shadowing, the Doppler effect caused by the movement of the terminal and the frequent speed change, interference by other users and multipath signals, etc. As a result, the channel environment changes frequently. Accordingly, in order to provide the high-speed wireless data packet service, other advanced technologies that can increase adaptability to channel changes are required in addition to the general technologies provided in the existing 2nd or 3rd generation mobile communication systems.

In order to improve the adaptability to the channel change in the high speed power control scheme adopted in the conventional mobile communication system, 3GPP and 3GPP2, which is in the process of standardizing the high speed data packet transmission system, have adopted the adaptive modulation / coding method (AMCS; Adaptive). Modulation & Coding Scheme (HARQ) and Hybrid Automatic Repeat Request (HARQ) are commonly mentioned.

The adaptive modulation / decoding (AMCS) method is a method of changing a modulation scheme and a code rate of a channel encoder according to downlink channel change. The channel quality information of the downlink can usually be obtained by measuring a signal-to-noise ratio (SNR) at the receiver of the terminal. On the other hand, the terminal transmits the channel quality information to the base station through the uplink. The base station predicts a downlink channel state based on the channel quality information provided from the terminal, and designates an appropriate modulation scheme and a code rate of a channel encoder based on the predicted value. Currently, QPSK, 8PSK, 16QAM and 64QAM are considered as modulation schemes discussed in HSDPA and 1X-EVDV, and 1/2 and 3/4 are considered as coding rates of the channel encoder.

Therefore, in the system using the adaptive modulation / decoding / coding technique (AMCS), the higher order modulation scheme (16QAM, 64QAM) and the higher code rate (UE) are used for terminals that typically use good quality channels such as terminals near the base station. 3/4) applies. However, low-order modulation schemes (8PSK, QPSK) and low code rates (1/2) are applied to terminals using channels of poor quality, such as terminals at cell boundary points.

As a result, the AMCS as described above improves the performance of the mobile communication system on average by reducing the interference signal compared to the conventional method that was dependent on the high-speed power control.

Meanwhile, when an error occurs in the initially transmitted data packet, the HARQ requires retransmission of the packet to compensate for the error packet, which means a link control technique used. The HARQ method includes Chase Combining (CC), Full Incremental Redundancy (FIR), and Partial Incremental Redundancy (hereinafter referred to as 'CC'). May be referred to as 'PIR'.

The CC simply transmits the same entire packet as the initial transmission during retransmission, and the receiving end combines the retransmitted packet and the initial transmission packet stored in the reception buffer by a predetermined method to encode bits inputted to the decoder. The performance gain of the overall mobile communication system can be obtained by improving the reliability. In this case, combining the same two packets has an effect similar to that of repetitive encoding, and thus an average performance gain of about 3 dB can be obtained.

The FIR is a method of improving the coding gain of a decoder at a receiver by retransmitting a packet including only the excess bits generated by the channel encoder instead of the same packet as the initial transmission packet. That is, when decoding, the decoder uses not only the information received during the initial transmission but also new excess bit information to increase the coding gain, thereby increasing the performance of the decoder.

In general, it is well known in the code theory that the performance gain due to low code rate is greater than the performance gain due to iterative coding. Therefore, considering only the performance gain, the FIR typically shows better performance than the CC.

Unlike the FIR, the PIR transmits a data packet including a combination of information bits and new surplus bits upon retransmission, by combining the information bits initially transmitted with respect to the information bits during decoding. The effect similar to that of CC is obtained. In addition, a similar effect to the IR is obtained by decoding using the surplus bits. In this case, the PIR has a higher code rate than the FIR, so that the PIR generally exhibits a moderate performance between the FIR and the CC.

However, the HARQ has many considerations in terms of the complexity of the system such as the buffer size and the signaling of the receiver in addition to the performance, so it is not easy to determine any one of them.

The adaptive modulation and coding / AMCS and HARQ techniques are independent techniques to improve the adaptability to channel changes, but the combination of the two schemes can greatly improve the performance of the system. have. That is, when the modulation scheme suitable for the downlink situation and the code rate of the channel encoder are determined by the adaptive modulation / decoding / coding scheme (AMCS), the corresponding data packet is transmitted.

Hereinafter, a complex retransmission method among the techniques applied to the wireless high speed packet data communication will be described in more detail.

In a typical wireless communication system, a channel decoding scheme mainly uses a linear block code such as convolutional codes or turbo codes to decode with a single decoder. As described above, in a wireless communication system for high-speed packet data communication, both an Error Correction Code (FEC) and an Automatic Repeat Request (ARQ) requesting retransmission of a data packet when an error is detected are used. The HARQ method used is applied.

The complex retransmission method is used in the wireless communication system to improve data transmission efficiency, that is, throughput and improve system performance by using a channel coding scheme. Here, the wireless communication system refers to a communication system collectively known as satellite system, ISDN, digital cellular, W-CDMA, UMTS, IMT-2000, and the like. In addition, convolutional codes, turbo codes, and the like are used as the FEC (Forward Error Correction).

Hereinafter, a typical complex retransmission method will be described with reference to FIGS. 1 to 3.

First, FIG. 1 is a diagram illustrating a packet retransmission process in a conventional complex retransmission method.

As shown in FIG. 1, the receiving end receives initial packet data initially transmitted from the transmitting end. (101) The receiving end checks whether an error occurs with respect to the received initial packet data. When the error occurrence of the initial packet data is detected by the error check, the receiving end transmits a retransmission request NAK having only packet identifier information (version number and sequence number) to the transmitting end (103). The retransmission request NAK is transmitted including a version number and a sequence number, which are packet identifier information, to notify the transmitter of the packet data to be retransmitted. Although not shown in FIG. 1, the ACK and packet identifier information are transmitted together with respect to packet data that has been successfully received without detecting an error.

On the other hand, when the transmitting end receives the retransmission request NAK, the packet data corresponding to the retransmission request is retransmitted to the receiving end. (105) The receiving end receiving the retransmitted packet data is re-received again. The packet data is checked for an error, and if an error is detected as a result of the check, the process as described above is repeatedly performed. (107 and 109)

Similarly, if no error is detected in the re-received packet data, the receiving end transmits an ACK having only packet identifier information (version number and sequence number) to the transmitting end.

As described above, the packet retransmission process in the conventional hybrid retransmission method is repeated until the decoding is successfully performed at the receiving end and the ACK is transmitted, or until a predetermined limited number of times. Here, the predetermined limited number of times refers to the number of retransmissions possible for the same packet data applied to the complex retransmission scheme. Therefore, in such a complex retransmission method, when an error occurs continuously in the transmitted packet data, that is, when the channel environment is poor, the time required to transmit the same packet data (t1-t0) is increased, thereby increasing the overall throughput. It will decrease sharply.

Meanwhile, in FIG. 1, only error packet data is described. However, since the complex retransmission method is operated by a selective repeat method, the transmitter continuously transmits the packet data regardless of the packet data in error. Therefore, when the transmitting end receives the packet identifier information, that is, the version number and the sequence number, of the packet data in error from the receiving end, the transmitter repeats the process of retransmitting only the specific packet data in error. .

2 is a diagram illustrating a receiving end packet data receiving process according to a conventional complex retransmission method. In particular, when an error occurs in initial packet data, packet data reception is always performed once retransmission is requested without considering channel environment. A diagram illustrating the process. In the packet data reception method shown in FIG. 2, the retransmission request is always performed in the same manner without considering the channel situation, that is, without considering the probability that an error occurs during packet data retransmission.

First, when receiving 201 initial packet data, the receiving end checks whether an error of the received initial packet data occurs (202). If no error is detected for the initial packet data as a result of the check, the terminal transfers initial packet data for which no error is detected to a higher layer and terminates (203).

On the other hand, if an error occurrence of the initial packet data is detected as a result of the check, the receiving end (NAK) including packet data identifier information including a version number and a sequence number for receiving the retransmitted initial error packet data 204 is transmitted to the transmitting end. After a predetermined time, the receiver re-receives 205 packet data retransmitted in response to the retransmission request. The receiving end checks again whether an error occurs in the re-received packet data (206). If an error is detected in the re-received packet data as a result of the check, the receiving end repeats the above-described retransmission request operation.

On the contrary, if no error is detected in the re-received packet data as a result of the inspection, the receiving end delivers the re-received packet data to the upper layer and terminates.

As described above, the receiving end may perform more effective decoding by combining the retransmitted packet data with the previously transmitted packet data.

3 is a diagram illustrating a packet data combining process of a receiver according to a conventional complex retransmission method. As shown in FIG. 3, the receiver makes a retransmission request due to an error in the packet data initially transmitted at the receiving end, and receives the retransmitted packet data according to the retransmission request (201).

At this time, the receiving end combines the initially transmitted packet data and the retransmitted packet data to decode 204.

On the other hand, the conventional complex retransmission method using the aforementioned Chassis Coupling (CC) does not discard an error even in the first transmitted packet data, but combines the retransmission signal with the maximum ratio combining with the retransmitted signal to detect only the current retransmission signal. It shows better transmission efficiency by reducing the average number of retransmissions than the scheme.

That is, when a plurality of packet data signals are combined, the signal to noise ratio (hereinafter, referred to as 'SNR') of the combined signal is given as the sum of the SNRs of the respective signals. As a result, the maximum ratio of more retransmission signals combined improves the SNR, and the probability of error becomes much smaller as the number of retransmissions increases.

Meanwhile, in the conventional complex retransmission scheme using the Chassis Coupling (CC), an additional resource (i.e., power) to be transmitted at the time of retransmission is predetermined or fixed in advance, and blindly only at the power specified in the current attempt. send.

Accordingly, there is a problem that the number of unnecessary retransmissions due to excess power may increase rapidly because it may not properly reflect the channel condition in the rapidly changing wireless communication environment. In addition, there is a disadvantage in that a sudden decrease in the transmission rate occurs due to the increase in the number of retransmissions.

Accordingly, an object of the present invention is to provide a method for efficiently setting the transmission power of retransmission packet data in case of combining a channel in a complex retransmission method in a mobile communication system.

Another object of the present invention is to provide an apparatus and method for efficiently setting and transmitting transmission power of retransmission packet data when performing a case combining in a complex retransmission method in a mobile communication system.

Another object of the present invention is to provide a transmission and reception apparatus for setting the transmission power of the retransmission packet data in consideration of the signal-to-noise ratio of the previously transmitted packet data and the current channel environment in case of the case combining in a complex retransmission method in a mobile communication system; In providing a method.

In order to achieve the above object, when an error occurs in the transmitted packet data, in a mobile communication system using a complex retransmission method of retransmitting the packet data associated with the packet data, combined with the previously transmitted packet data and demodulated In the method of determining the transmission power of the packet data to be retransmitted, the error occurs in the packet data transmitted from a predetermined base station to the terminal, so that the frame error of the predetermined received packet data has a predetermined value Calculating an additional required signal-to-noise ratio (Required SNR) during retransmission from the required target signal-to-noise ratio (Target SNR) and the signal-to-noise ratio (SNR) of the packet data in error; The process of calculating the transmit power required for retransmission from the signal-to-noise ratio It characterized by hamham.

In addition, in order to achieve the above object, when an error occurs in the transmitted packet data, mobile communication using a complex retransmission method of retransmitting the data related to the packet data, combined with the previously transmitted packet data and demodulated In a system, when an error occurs in a packet data transmitted from a predetermined base station to a terminal and requests retransmission, the method for retransmitting the packet data requiring retransmission to the terminal, the retransmission request message from the terminal and Receiving channel quality measurement (CQI) information, a target signal-to-noise ratio (Target SNR) required for the frame error of predetermined received packet data to have a preset value, and the error calculated by the received channel quality measurement; Is retransmitted from the signal-to-noise ratio (SNR) of the generated packet data. Calculating a required signal-to-noise ratio (Required SNR); and retransmitting the packet data to the terminal by calculating the transmit power required for retransmission from the signal-to-noise ratio additionally required for retransmission. It features.

In addition, the base station apparatus for achieving the above object is calculated by the target signal-to-noise ratio (Target SNR) required to have a frame error of a predetermined received packet data has a predetermined value and the channel quality measurement received from the terminal. Calculate a required signal-to-noise ratio (SNR) additionally required for retransmission from the signal-to-noise ratio (SNR) of the packet data in error, and calculate a transmit power value required for retransmission from the additional signal-to-noise ratio required for retransmission. AMC and a retransmission power controller, and a power controller for controlling the transmission power of the retransmitted packet by the transmission power value required for the retransmission calculated from the AMC and the retransmission power controller.

In addition, a terminal apparatus for achieving the above object includes a channel quality measuring instrument for measuring channel quality information from received packet data, and a target signal to noise ratio required for a frame error of predetermined received packet data to have a preset value. Target SNR) and a signal-to-noise ratio (Required SNR) additionally required for retransmission from the signal-to-noise ratio (SNR) of the failed packet data calculated by the channel quality measurement measured by the channel quality measurer. And an AMC and a retransmission power controller for calculating a transmission power value required for retransmission from a signal-to-noise ratio additionally required.

Meanwhile, when an error occurs in the transmitted packet data in order to achieve the above another object, the mobile station uses a complex retransmission method of retransmitting packet data related to the packet data and combining and demodulating the previously transmitted packet data. In a communication system, an error occurs in packet data transmitted from a predetermined terminal to a base station, so that the base station determines the transmission power of the packet data retransmitted from the terminal. Calculating an additional required signal-to-noise ratio (Required SNR) upon retransmission from the target signal-to-noise ratio (Target SNR) required to have a preset value and the signal-to-noise ratio (SNR) of the packet data in error; Additional requirements for retransmission from the additionally required signal-to-noise ratio Characterized in that the process of calculating the transmission power.

Further, in order to achieve the above object, when an error occurs in the transmitted packet data, the mobile station uses a complex retransmission scheme of retransmitting data related to the packet data and combining and demodulating the previously transmitted packet data. In a communication system, when an error occurs in a packet data transmitted from a predetermined terminal to a base station and requests retransmission, the terminal retransmits the packet data required for retransmission to the base station. Additionally upon retransmission from the target signal-to-noise ratio (Target SNR) required to have a frame error of < RTI ID = 0.0 > and < / RTI > the signal-to-noise ratio (SNR) of the errored packet data calculated by the channel quality measurement measured from the received data. Calculate the required signal-to-noise ratio (Required SNR) and retransmit Receiving a transmission power value required for retransmission calculated from an additionally required signal-to-noise ratio, and retransmitting the packet data requested for retransmission to the base station based on the received transmission power value for retransmission Characterized in that it comprises a.

A base station apparatus for achieving the above object includes a channel quality meter for measuring channel quality information from received packet data, and a target signal-to-noise ratio (Target SNR) required for a frame error of predetermined received packet data to have a preset value. And an additional required signal-to-noise ratio (SNR) required for retransmission from the signal-to-noise ratio (SNR) of the erroneous packet data calculated by the channel quality measurement measured by the channel quality meter. And an AMC and a retransmission power controller for calculating a transmission power value required for retransmission from the signal to noise ratio.

1 is a diagram illustrating a packet retransmission process in a complex retransmission scheme in a typical mobile communication system.

2 is a diagram illustrating a packet data reception process of a receiver according to a complex retransmission scheme in a typical mobile communication system.

3 is a diagram illustrating a packet data combining process of a receiver according to a complex retransmission scheme in a typical mobile communication system.

4 is a graph illustrating a relationship between a signal-to-noise ratio and a frame error rate in a typical mobile communication system.

5 is a composite retransmission process flow diagram of a chasing combination that variably controls retransmission power in accordance with the present invention.

FIG. 6 is a block diagram showing the structure of a transceiver using complex retransmission of chasing combined to variably control retransmission power according to the first embodiment of the present invention. FIG.

7 is a flowchart illustrating a complex retransmission processing procedure of a Chassis combining that variably controls retransmission power according to the first embodiment of the present invention.

8 is a block diagram illustrating a structure of a transceiver using complex retransmission of a Chassis combining to variably control retransmission power according to a second embodiment of the present invention.

9 is a flowchart illustrating a complex retransmission processing procedure of a Chassis combining that variably controls retransmission power according to a second embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that in the following description, only parts necessary for understanding the operation according to the present invention will be described, and descriptions of other parts will be omitted without departing from the scope of the present invention.

The present invention is applicable to all wireless communication systems using a complex retransmission scheme, and particularly to any communication system that combines and decodes previously transmitted packet data and retransmitted packet data, such as chasing.

In addition, the present invention controls the transmit power of the retransmitted packet in consideration of the channel environment and the transmit power of the previously transmitted packet data, and effectively controls the transmit power of the retransmitted packet data to be decoded within the maximum allowable frame error required by the receiver. To control.

First, in describing the present invention, the following matters are assumed.

1. Channel state is fixed in one packet or slot.

2. The AMC level established in the initial transmission of a packet is fixed until the packet is successfully delivered, and only the transmission power varies in each attempt.

3. The receiving end periodically transmits a CQI (Channel Quality Indicator) to the transmitting end by measuring channel quality for each slot regardless of the presence or absence of a packet.

On the other hand, the above assumptions are not intended to limit the application of the present invention, but to clarify and facilitate the present invention.

Hereinafter, a power control method in a complex retransmission method using chaotic combining according to the present invention will be described.

In the complex retransmission method using the chaotic combining, a maximum ratio of all previously transmitted signals is detected. It is assumed that a packet data signal up to the current i th attempt is received, and when the SNR value of the signal obtained by maximally ratio combining the i separately received signals is β ⁽ⁱ⁾ , β ⁽ⁱ⁾ may be expressed as Equation 1 below.

Here, β _j is the SNR value at the j th trial, and a _j is the complex channel gain at the j th trial. In addition, P _j is the transmission signal power at the j th trial, and N ₀ is the noise power.

The channel estimation at the receiving end means an estimation of the reception SNR (ie β ₎ , and since the transmitting end already knows the transmission signal power (ie, P _j ), the estimated channel _j | a _j | Assume that ² / N ₀ is also known.

The occurrence factor of the channel estimation error may be due to an estimation error of noise power due to an unexpected interference signal, or a change in channel gain due to a round trip delay. Regardless of the cause, assuming that channel estimation error exists, two cases can be considered.

That is, it can be considered to divide into two cases where β ⁽ⁱ⁾ is smaller than the target SNR and larger. As can be easily predicted, the frame error is mainly caused by the former (i.e., when β ⁽ⁱ⁾ is less than the target SNR). Because the smaller the SNR of the transmitted signal, the lower the learning rate can distinguish the signal, the relatively higher the Frame Error Rate (hereinafter referred to as 'FER'). The relationship between SNR and FER as described above will be described with reference to FIG. 4.

4 is a graph illustrating a relationship between a signal-to-noise ratio and a frame error rate.

Referring to FIG. 4, it can be seen that the higher the SNR of the received signal, the lower the FER.

In order for the received signal to maintain an appropriate level of FER, the SNR must be above a certain level. That is, in order to lower the FER below a setting value required for data transmission and reception, the transmission power must be made larger and transmitted.

4 illustrates a general form of the FER curve in which the target FER is expressed as a function of the SNR of the received signal, indicating that the target value of the FER required in the received signal, that is, the target FER is set to 0.01 (1%). At this time, the target SNR of the received signal required to maintain the target FER (that is, the frame error rate is 1%) is indicated as Required SNR.

In general, the target FER is set to 0.01, it is obvious that other values can be set.

The graph of FIG. 4 may vary depending on a modulation scheme and a coding rate. When the modulation scheme and coding rate are determined, the frame error is 0.01 which is a target FER when β ⁽ⁱ⁾ is larger than a target SNR. On the contrary, if β ⁽ⁱ⁾ is smaller than the target SNR (e.g., the noise power of the signal actually received due to unpredictable interference is much larger than the noise power based on the estimated value or the round trip delay If the channel gain of the received signal is much smaller than the channel gain based on the estimated value, the frame error probability is much greater than the target FER of interest.

Accordingly, in consideration of both cases described above, a method for allocating additional power required for retransmission according to the present invention can be set as follows.

First, when the SNR value additionally required through retransmission to maintain the specific target value (eg, 0.01) is β ⁽ⁱ⁾ _Req , the β ⁽ⁱ⁾ _Req is 2> can be defined.

Here, β _target is a target value of the SNR required to obtain a target value (eg, 0.01) of a frame error rate for a given AMC level, and β ^(i-1) is a signal received until the (i-1) th trial. SNR of the signal obtained by maximizing the maximum ratio combined.

As described above in Equation 1, the SNR of the maximum non-combined signal is equal to the sum of the SNRs of each received signal, so that the retransmission is performed in order to meet the target SNR required to maintain the target frame error rate. The SNR of the signal to be transmitted may be further transmitted by the difference between the β _Target which is the target SNR and β ^(i-1) which is the SNR of the previously transmitted signal. That is, in the related art, a signal transmitted during retransmission is transmitted at the same power as the transmission power of previous signals without considering the SNR of the previously received signal or the current channel environment, but according to the present invention, By transmitting at a power that satisfies the SNR as much as a difference from the target SNR capable of maintaining an appropriate FER according to the SNR, unnecessary power loss can be prevented and the number of additional retransmissions can be reduced.

On the other hand, when β ⁽ⁱ⁾ _Req , which is an additionally required SNR value through the retransmission, is obtained as in Equation 2, when P _i is the transmit power of the retransmission signal considering the current channel condition, P _i, May be defined as in Equations 3 and 4 below.

Equation 3 is a calculated value of the transmission power of the retransmission signal applicable when the β ⁽ⁱ⁾ _Req is positive as a result of the calculation of Equation 2, and Equation 4 is the β ⁽ⁱ⁾ _Req is a calculated transmit power value of the retransmission signal applicable when the number is not positive.

In general, when an error occurs in a received signal and needs to be retransmitted, the SNR (ie, β ^(i-1) ) of the received signal is less than the target SNR (ie, β _Target) . Therefore, Equation 3 is applied when retransmission occurs due to most errors, and Equation 4 may be applied when the defined condition is satisfied.

In Equations 3 and 4, a _i denotes a complex channel gain in the i th attempt (that is, at the i th retransmission), and N ₀ denotes a noise power.

That is, according to Equation 3, the transmission power of the retransmission signal can be effectively set to satisfy the finally required SNR by combining the retransmission signal and the previously received signal. The transmission power may be set in consideration of the channel environment at the present transmission time. As a result, Equation (3) allocates only the amount of power corresponding to the deficit when retransmitting, considering the current channel estimate and the additionally required SNR.

On the other hand, when β ⁽ⁱ⁾ _Req is not positive (i.e., when an error occurs even though the SNR value of the previously received signals exceeds the target SNR value), the power value of the retransmitted signal is equal to < It may be defined as shown in Equation 4>. Here, Δβ means a minimum additional SNR as a constant.

Referring to Equation 4, an error occurs in the received signal and causes retransmission not because the SNR of the received signal is smaller than the target SNR (that is, the transmission power is insufficient), but for another reason. Error caused by.

In the above case, if the SNR accumulated up to the (i-1) th attempt has already exceeded the target value, the transmission power is allocated such that only a minimum increase of the SNR (that is, Δβ) occurs. That is, it is desirable to retransmit with the minimum power (preset value) required for transmission.

Hereinafter, a process of transmitting and receiving data using the transmission power value of the retransmission signal determined by the above-described method will be described with reference to FIG. 5.

5 is a flowchart of a complex retransmission process of chasing combining variable retransmission power according to the present invention.

Referring to FIG. 5, the receiving side (terminal or base station) receives the packet data (502), and checks whether the packet data is new packet data (504). As a result of the check, in the case of new packet data, the received packet data is demodulated. If the received packet data is new packet data, a maximum ratio combined with the previously received packet is performed (506).

On the other hand, after decoding the received packet data as described above, and checks whether the error through the CRC bit added by the transmitting side (base station or terminal) (510).

As a result of the error checking, if there is no error, the packet data is regarded as normally received and transmitted to the upper layer, and the packet data stored in the memory is deleted (512). If an error occurs, the retransmission request for the packet data is transmitted to the transmitting side (base station or terminal).

In this case, according to the present invention, the transmission power of the retransmission packet transmitted from the transmission side is calculated in consideration of the SNR of the previously transmitted signals and the current channel environment, and the retransmission packet is transmitted according to the calculated transmission power of the retransmission packet. do.

In order to calculate the transmit power of the retransmission packet according to the present invention, first, the SNR of the currently received packet is measured (514). In this case, if the received packet data is new packet data, the SNR is measured only for the received packet data. However, if the received packet data is retransmitted packet data, the maximum ratio for all packet data retransmitted from the initially transmitted packet data is measured. The SNR of the signal obtained by combining must be obtained.

SNRs of the packets received to date may be calculated by Equation 1 described above. Then, an additional SNR required for retransmission is calculated 516. The additionally required SNR value becomes a difference between a target SNR value and an SNR value of packets received so far, and the additionally required SNR value may be calculated by Equation 2 described above.

In addition, the transmission power for the packet to be retransmitted is calculated 518 from the calculated additional required SNR value.

Finally, the retransmission packet is transmitted 520 based on the calculated transmission power value for the retransmission packet.

In the above process, the transmission power value for the retransmission packet can be calculated at the transmitting side or the receiving side (that is, the base station or the terminal), respectively, but to reduce the processing burden of the terminal and to efficiently manage radio resources. It is preferable to implement the calculation at the base station. That is, the transmission power calculation of the retransmission packet according to the present invention may be implemented in both the base station and the terminal, and in the following description of the embodiments to be described below, the calculation in the base station will be described as an example.

For example, when the terminal is configured to calculate the transmission power value for the retransmission packet in the transmission of the downlink signal, the terminal measures the SNR of the packet received so far, and further calculates the required SNR to retransmit the packet. The final transmission power for is calculated. Then, the transmission power value and the retransmission request message (eg, NACK message) for the calculated retransmission packet are transmitted to the base station, and the base station transmits the retransmission packet data by the received transmission power value.

In the transmission of the downlink signal, when the base station calculates a transmission power value for the retransmission packet, the terminal transmits a channel quality indicator and a retransmission request message to the base station. The base station receiving the retransmission request message calculates a transmission power for the retransmission packet through the received channel quality measurement value and the additionally required SNR value, and transmits the retransmission packet to the terminal based on the calculated value.

On the other hand, in the above-described transmission of the downlink signal, a method for calculating the transmission power for the retransmission packet in the terminal or the base station has been described, it is obvious that the same method can be applied to the transmission of the uplink signal.

As a result, when calculating the transmission power of the retransmission packet according to the present invention, a method of calculating at the transmitting side (ie, the base station) and a method of calculating at the receiving side (ie, the terminal) in the transmission of the downlink signal may be implemented. In the transmission of an uplink signal, a method of calculating at a transmitting side (ie, a terminal) and a method of calculating at a receiving side (ie, a base station) may be implemented.

Hereinafter, specific embodiments of the above-described methods will be described in detail by dividing downlink data transmission and uplink data transmission.

First Embodiment Power Control for Downlink Retransmission Packet Signal

Data transmission through the downlink means data transmission from the base station to the terminal. As described above, when an error occurs in the packet data received by the terminal, the terminal requests retransmission of the packet data to the base station, and the base station provides a method for calculating the transmission power of the retransmission packet according to the present invention. The retransmission packet is transmitted by the power value calculated accordingly.

In the following description, the base station calculates the transmission power of the retransmission packet data. However, as described above, the base station calculates the transmission power and transmits the transmission power to the base station.

6 and 7, power control on a downlink retransmission packet signal according to a first embodiment of the present invention will be described.

FIG. 6 is a block diagram illustrating a structure of a transceiver using complex retransmission of chasing in which a retransmission power is variably controlled according to the first embodiment of the present invention.

Referring to FIG. 6, a transmitter (ie, a base station because it is a downlink) 600 that variably controls retransmission power according to the first embodiment of the present invention includes a CRC generator 611, an encoder 613, and a modulator 615. ), A multiplier 617, an AMC and a retransmission power controller 619, and a power controller 621. In addition, the receiver (that is, the downlink terminal) 650 includes a demodulator 653, a decoder 655, a CRC checker 657, and a channel quality measurer 651.

Meanwhile, a signal transmitted from the base station 600 is transmitted to the terminal 650 through a downlink traffic channel, and the terminal 650 receives an error message of the received packet data through an uplink feedback channel 630. And data such as a channel quality indicator.

In more detail, cyclic redundancy check (CRC) information bits are added to the information data bits to be transmitted from the base station 600 through the CRC generator 611, and the CRC information bits are decoded at the receiving end. It is possible to check whether or not the normal reception of. Data output from the CRC generator 611 is encoded by the encoder 613, and the encoder 613 generally uses turbo coding or convolutional coding. According to the encoding method of the encoder 613, a coding rate may be set in various ways.

The data bits encoded by the encoder 613 are input to the modulator 615, modulated, and output as symbol data. In addition, the modulation method in the modulator 615 may be generally considered methods of QPSK, 8PSK, 16QAM and 64QAM in consideration of the channel conditions. On the other hand, it is possible to apply to the present invention using any other modulation method.

The symbol data modulated by the modulator 615 is amplified by the multiplier 617 according to the power control signal input from the power controller 621 and transmitted to the wireless environment through an antenna (not shown). The information data transmitted from the base station is generally transmitted through the downlink traffic channel 640.

Meanwhile, the transmitted information data is transmitted in packet units, and the receiving terminal 650 also processes the received data in packet units.

The terminal 650 receives information data transmitted through the downlink traffic channel 640 by an antenna (not shown) and demodulates the received data through a demodulator 653. Meanwhile, the demodulator 653 demodulates according to a method modulated by the modulator 615 of the base station 600.

The demodulated data from the demodulator 353 is decoded by the decoder 655. Similarly, the decoding method is also decoded according to the method encoded by the encoder 613 of the base station 600. The data decoded by the decoder 655 performs error checking by the CRC checker 357 and transmits a normal reception confirmation message (ie, an ACK or NACK message) through the uplink feedback channel 630.

If an error occurs as a result of the reception, the packet is stored in a memory. In addition, the terminal 650 transmits the NACK message to the base station 600, and the base station 600 receiving the NACK message retransmits the packet according to the NACK message.

Meanwhile, according to the present invention, when retransmitting packet data in the base station 600 as described above, the transmission power is variably set in consideration of the channel environment and SNR of the packet data transmitted up to now.

In FIG. 6, the AMC and the retransmission power controller 619 of the base station 600 are NACK signals transmitted from the CRC checker 657 of the terminal 650 and channel quality measurements (CQI) transmitted from the channel quality measurer 651. That is, it is determined to transmit the retransmission packet through the β _j value, and the transmission power of the retransmission packet is calculated as described above.

That is, the AMC and the retransmission power controller 619 calculates an additionally required SNR (that is, β ⁽ⁱ⁾ _Req ) through Equation 2 from the channel quality measurement received from the terminal 650. By using Equation 3 or Equation 4, the transmit power P _i value of the packet to be retransmitted is calculated. In addition, the power controller 621 outputs an appropriate power amplification value according to the calculated transmission power value and controls the retransmission packet to be transmitted at the calculated power value.

Hereinafter, a procedure according to the first embodiment of the present invention performed by the transmission and reception apparatus will be described in detail.

FIG. 7 is a flowchart illustrating a complex retransmission processing procedure of a chasing combination that variably controls retransmission power according to the first embodiment of the present invention.

Referring to FIG. 7, the CRC bit is added to the information data bit to be transmitted from the transmitting side (base station) by the CRC generator 611 (701), and the data to be transmitted by the encoder 613 is encoded (703). . If the data to be transmitted is the first data, an initial power level is set (705), and the data is transmitted (707) to a receiving side (terminal) according to the set initial power level. Meanwhile, the transmitted data is transmitted in packet units.

The receiving side (terminal) receives the received packet data (713), and checks whether the received packet data is new packet data (715). The identification of the new packet data is confirmed through a sequence number assigned to each packet for a complex retransmission scheme.

If the received packet data is retransmitted packet data instead of new packet data, a maximum ratio combined with the previously received packet data of the same serial number is performed 717 to demodulate 719. On the other hand, if the received packet data is new packet data, a demodulation procedure is performed without the maximum ratio combining process (719).

After demodulating the received data, the CRC checker 657 performs an error check. As a result of the error checking, if the signal is normally demodulated without any error, the demodulated data is transmitted to a higher layer, and the packet data stored in the memory is deleted (723).

On the other hand, when an error occurs as a result of the error checking, by transmitting 725 a NACK signal to the transmitting side (base station), it is required to retransmit the received packet data. At this time, the receiving side (terminal) transmits the channel quality measurement (CQI information) together, and the transmitting side (base station) retransmits the corresponding packet data through the received NACK signal.

On the other hand, when the transmitting side (base station) receives the NACK signal (711) and retransmits the packet data, according to the present invention, the transmitting side (base station) newly sets the transmission power of the retransmitted packet.

The transmission power of the retransmission packet is calculated as described above. That is, an additionally required SNR value is calculated based on the SNR and the target SNR value of the error-transmitted previously transmitted packet data, and the transmission power of the packet data to be retransmitted is calculated through the calculated SNR value (709). do.

The transmitting side (base station) retransmits the corresponding packet data with the calculated transmission power of the retransmitted packet data (707).

Meanwhile, the channel quality measurement transmitted from the receiving side (terminal) to the transmitting side (base station) may be reported periodically to the transmitting side BS while the connection is maintained regardless of the packet error, or before and after packet transmission and reception. It may be reported.

For example, before the packet data is transmitted, it is transmitted to allocate an AMC level of the packet data to be transmitted, and after reception of the packet data, it is transmitted to inform the SNR of the received signal. Accordingly, the transmitting side allocates the power of the retransmitted packet data using the channel quality measurement CQI (ie, b _j ) and the above-described Equations 2 to 4 to perform retransmission.

Second Embodiment Power Control for Uplink Retransmission Packet Signal

Data transmission on the uplink means data transmission from the terminal to the base station. When an error occurs in the packet data received by the base station, the base station requests retransmission of the packet data to the terminal, and the terminal calculates a power value calculated according to the method of calculating the transmission power of the retransmission packet according to the present invention. The retransmission packet is transmitted by.

In the following description, the base station calculates and transmits the transmission power of the retransmission packet data to the terminal. However, as described above, the base station calculates the transmission power of the retransmission packet data and transmits the retransmission packet data to the base station as the calculated retransmission power. It is also possible to implement to transmit.

8 and 9, power control on an uplink retransmission packet signal according to a second embodiment of the present invention will be described.

FIG. 8 is a block diagram illustrating a structure of a transceiver using complex retransmission of chasing in which a retransmission power is variably controlled according to a second embodiment of the present invention.

Referring to FIG. 8, a receiver (ie, a base station because it is uplink) 800 which variably controls retransmission power according to the second embodiment of the present invention includes a CRC checker 811, a decoder 813, and a demodulator ( 815, AMC and retransmission power controller 817, and channel quality meter 819. In addition, the transmitter (ie, the uplink terminal) 850 includes a CRC generator 851, an encoder 853, a modulator 855, a multiplier 857, and a power controller 859.

Meanwhile, a signal transmitted from the terminal 850 is transmitted to the base station 800 through an uplink traffic channel 823, and the base station 800 receives the terminal 850 through a downlink control channel 821. Transmits the error message of the received packet data and the power allocation information of the retransmission packet data calculated by the base station 800. In this case, the power allocation information of the retransmission packet data may be calculated by the terminal 850. However, in terms of radio resource management, it is preferable to transmit only a retransmission transmit power value calculated by the base station 800 to the terminal 850. The retransmission transmit power value may be calculated by Equation 2 to Equation 4 described above.

In more detail, as described above in the first embodiment, the information data bits to be transmitted from the terminal 850 are added with Cyclic Redundancy Check (CRC) information bits through the CRC generator 851. The CRC information bits enable the receiving end to check whether data is normally received after decoding. Data output from the CRC generator 851 is encoded by an encoder 853, and the encoder 853 generally uses turbo coding or convolutional coding. According to the encoding method of the encoder 853, the coding rate can be set in various ways.

The data bits encoded by the encoder 853 are input to the modulator 855, and are modulated and output as symbol data. In addition, the modulation method in the modulator 855 may be generally considered methods of QPSK, 8PSK, 16QAM and 64QAM in consideration of the channel conditions. On the other hand, it is possible to apply to the present invention using any other modulation method.

The symbol data modulated by the modulator 855 is amplified by the multiplier 857 according to a power control signal input from the power controller 859 and transmitted to the wireless environment through an antenna (not shown). The information data transmitted from the terminal is generally transmitted through the uplink traffic channel 823.

Meanwhile, the transmitted information data is transmitted in packet units, and the receiving base station 800 processes the received data in packet units.

The base station 800 receives information data transmitted through the uplink traffic channel 823 by an antenna (not shown), and demodulates the received data through a demodulator 815. Meanwhile, the demodulator 815 demodulates according to a method modulated by the modulator 855 of the terminal 850.

The demodulated data from the demodulator 815 is decoded by the decoder 813. Similarly, the decoding method is also decoded according to the method encoded by the encoder 853 of the terminal 850. The data decoded by the decoder 813 performs error checking by the CRC checker 811 and transmits a normal reception confirmation message (ie, an ACK or NACK message) through the downlink control channel 821.

If an error occurs as a result of the reception, the packet data is stored in a memory. In addition, the base station 800 transmits the NACK message to the terminal 850, and the terminal 850 receiving the NACK message retransmits the packet according to the NACK message.

Meanwhile, according to the present invention, when retransmitting packet data in the terminal 850 as described above, the transmission power is variably set in consideration of the channel environment and the SNR of the packet data transmitted up to now.

In FIG. 8, the AMC and the retransmission power controller 817 of the base station 800 include the NACK signal confirmed by the CRC checker 811 of the base station 800 and the channel quality measurement CQI transmitted from the channel quality measurer 819. That is, it is determined to transmit the retransmission packet through the β _j value, and the transmission power of the retransmission packet is calculated as described above.

That is, the AMC and the retransmission power controller 817 is SNR (which is added to demand through the <Equation 2> from the channel quality measurement received from the channel quality estimator 819 of the BS 800, i.e., β ^{( i)} _Req ) is calculated, and the transmit power P _i value of the packet to be retransmitted is calculated by Equation 3 or 4 below.

Meanwhile, the base station 800 transmits the transmission power value of the NACK message and the calculated retransmission packet to the terminal 850 through a downlink control channel 821.

The terminal 850 receiving the NACK message from the base station 800 retransmits the corresponding packet, and the transmission power of the packet to be retransmitted is the transmission power value of the retransmission packet received from the base station 800. Set it.

That is, the power controller 859 of the terminal 850 outputs an appropriate power amplification value according to the transmission power value transmitted from the base station 800 and controls the retransmission packet to be transmitted at the calculated power value.

As described above, the transmission power of the retransmission packet is preferably implemented to be calculated by the base station 800, and may be implemented to be calculated by the terminal 850. That is, the base station 800 transmits the channel quality measurement measured by the channel quality measuring device 819 to the terminal 850 through the downlink control channel 821, and the terminal 850 receives the received channel quality. Through the measured values, the transmission power of the retransmission packet is calculated by the above-described Equations 2 to 4.

Hereinafter, the procedure according to the second embodiment of the present invention performed by the transmission and reception apparatus will be described in detail.

9 is a flowchart illustrating a complex retransmission processing procedure of a Chassis combining that variably controls retransmission power according to a second embodiment of the present invention.

Referring to FIG. 9, in the information data bit to be transmitted from the transmitter (terminal), the CRC generator 851 adds a CRC bit (901), and the data to be transmitted by the encoder 853 is encoded (903). . If the data to be transmitted is the first data, an initial power level is set (905), and the data is transmitted (907) to a receiving side (base station) according to the set initial power level. Meanwhile, the transmitted data is transmitted in packet units.

The receiving side (base station) receives the transmitted packet data (913), and checks whether the received packet data is new packet data (915). The identification of the new packet data is confirmed through a sequence number assigned to each packet for a complex retransmission scheme.

If the received packet data is retransmitted packet data instead of new packet data, a maximum ratio combined with the previously received packet data of the same serial number is performed 917 to demodulate 919. On the other hand, if the received packet data is new packet data, the demodulation procedure is performed without the maximum ratio combining process (919).

After demodulating the received data, an error check is performed by the CRC checker 811. As a result of the error checking, if the signal is normally demodulated without any abnormality, the demodulated data is transmitted to an upper layer, and the packet data stored in the memory is deleted (923).

On the other hand, when an error occurs as a result of the error checking, by transmitting (927) a NACK signal to the transmitting side (terminal), it is required to retransmit the received packet data. In this case, the receiving side (base station) measures the channel state through the received signal, and calculates additionally required SNR and transmission power of packet data to be retransmitted through the calculated channel quality measurement value (CQI information, β _i ). (925).

The transmission power of the retransmission packet is calculated as described above. That is, an additionally required SNR value is calculated through the SNR and the target SNR value of the error-transmitted previously transmitted packet data, and the transmission power of the packet data to be retransmitted is calculated through the calculated SNR value (925). do.

The receiving side (base station) transmits (927) the power control information of the calculated retransmission packet and the NACK message according to the error occurrence to the transmitting side (terminal).

On the other hand, when the transmitting side (terminal) receives the NACK signal (911) and retransmits the packet data, the transmitting side (terminal) sets the transmission power as the transmission power of the retransmission packet received from the receiving side (base station) (909). Retransmission (907).

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications may be made 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 defined not only by the scope of the following claims, but also by the equivalents of the claims.

The present invention as described above, in the HARQ method used in the high-speed packet data transmission method, by controlling the transmission power at the time of retransmission efficiently and variably, the number of average retransmissions can be reduced, and at the same time use of power There is an advantage that can be minimized.

In addition, in particular, when the present invention is applied to the uplink, it is possible to reduce battery consumption of the terminal, thereby effectively solving the problem of power usage, which is emerging as the biggest problem in the mobile communication system.

Claims (35)

When an error occurs in the transmitted packet data, a mobile communication system using a complex retransmission method of retransmitting packet data related to the packet data and combining and demodulating the previously transmitted packet data is transmitted from a predetermined base station to a terminal. In the method that the error occurs in the packet data to be transmitted, the base station determines the transmission power of the retransmitted packet data, Target SNR required to have a predetermined frame error of received packet data has a preset value and a signal to noise ratio required additionally when retransmitted from the signal-to-noise ratio SNR of the packet data in which the error occurs. ), Calculating a transmission power required for retransmission from a signal-to-noise ratio additionally required for retransmission. The method of claim 1, If the retransmission is repeated two or more times, the additionally required signal-to-noise ratio is calculated from the combination of the target signal-to-noise ratio and the signal-to-noise ratio of previously transmitted error packet data. . The method of claim 1, The retransmitted packet data is the same packet data as previously transmitted packet data. The method of claim 1, When the target signal-to-noise ratio (Target SNR) is greater than the signal-to-noise ratio (SNR) of the error packet data, the transmission power required for the retransmission is the current channel to the additionally required signal-to-noise ratio (Required SNR) The method of claim 1, wherein the method is calculated in consideration of the estimated value. The method of claim 1, If the target signal-to-noise ratio (Target SNR) is less than the signal-to-noise ratio (SNR) of the errored packet data, the transmission power required for the retransmission takes the current channel estimate into a predetermined minimum additional signal-to-noise ratio (SNR). The method characterized in that the calculation. When an error occurs in the transmitted packet data, a mobile communication system using a complex retransmission method of retransmitting data related to the packet data and combining and demodulating the previously transmitted packet data is transmitted from a predetermined base station to a terminal. A method for retransmitting packet data for which retransmission is requested to the terminal when an error occurs in packet data and requesting retransmission, Receiving a retransmission request message and channel quality measurement (CQI) information from the terminal; Upon retransmission from the target signal-to-noise ratio (Target SNR) required for the frame error of a given received packet data to have a predetermined value and the signal-to-noise ratio (SNR) of the errored packet data calculated by the received channel quality measurement. Calculating a required signal-to-noise ratio (SNR); And retransmitting the packet data to the terminal by calculating a transmission power required for retransmission from a signal-to-noise ratio additionally required for the retransmission. The method of claim 6, If the retransmission is repeated two or more times, the additionally required signal-to-noise ratio is calculated from the combination of the target signal-to-noise ratio and the signal-to-noise ratio of previously transmitted error packet data. . The method of claim 6, The retransmitted packet data is the same packet data as previously transmitted packet data. The method of claim 6, When the target signal-to-noise ratio (Target SNR) is greater than the signal-to-noise ratio (SNR) of the error packet data, the transmission power required for the retransmission is the current channel to the additionally required signal-to-noise ratio (Required SNR) The method of claim 1, wherein the method is calculated in consideration of the estimated value. The method of claim 6, If the target signal-to-noise ratio (Target SNR) is less than the signal-to-noise ratio (SNR) of the errored packet data, the transmission power required for the retransmission takes the current channel estimate into a predetermined minimum additional signal-to-noise ratio (SNR). The method characterized in that the calculation. When an error occurs in the transmitted packet data, a mobile communication system using a complex retransmission method of retransmitting data related to the packet data and combining and demodulating the previously transmitted packet data is transmitted from a predetermined base station to a terminal. A base station apparatus for retransmitting the packet data for which the retransmission is requested when an error occurs in the packet data to request retransmission. From the target signal-to-noise ratio (Target SNR) required for the frame error of the predetermined received packet data to have a preset value and the signal-to-noise ratio (SNR) of the errored packet data calculated by the channel quality measurement received from the terminal. An AMC and a retransmission power controller for calculating a required signal-to-noise ratio (SNR) additionally required for retransmission and calculating a transmit power value for retransmission from the additionally required signal-to-noise ratio during retransmission; And a power controller for controlling the transmission power of the retransmitted packet by the transmission power value required for the retransmission calculated from the AMC and the retransmission power controller. The method of claim 11, If the retransmission is repeated two or more times, the additionally required signal-to-noise ratio is calculated from a combination of the target signal-to-noise ratio and the signal-to-noise ratio of previously transmitted error packet data. . The method of claim 11, The retransmitted packet data is the same packet data as the previously transmitted packet data. The method of claim 11, When the target signal-to-noise ratio (Target SNR) is greater than the signal-to-noise ratio (SNR) of the error packet data, the transmission power required for the retransmission is the current channel to the additionally required signal-to-noise ratio (Required SNR) And calculating the estimated value in consideration of the estimated value. The method of claim 11, If the target signal-to-noise ratio (Target SNR) is less than the signal-to-noise ratio (SNR) of the errored packet data, the transmission power required for the retransmission takes into account the current channel estimate at a predetermined minimum additional signal-to-noise ratio (SNR). The apparatus, characterized in that for calculating. When an error occurs in the transmitted packet data, a mobile communication system using a complex retransmission method of retransmitting data related to the packet data and combining and demodulating the previously transmitted packet data is transmitted from a predetermined base station to a terminal. In the terminal apparatus requesting the retransmission when an error occurs in the packet data and the retransmission is requested, A channel quality meter for measuring channel quality information from the received packet data; The target signal-to-noise ratio (Target SNR) required for the frame error of the predetermined received packet data to have a preset value and the signal-to-noise ratio (SNR) of the errored packet data calculated by the channel quality measurement measured by the channel quality meter. AMC and a retransmission power controller for calculating an additional required signal-to-noise ratio (SNR) required for retransmission and calculating a transmit power value required for retransmission from the additionally required signal-to-noise ratio for retransmission. The apparatus described above. The method of claim 16, If the retransmission is repeated two or more times, the additionally required signal-to-noise ratio is calculated from a combination of the target signal-to-noise ratio and the signal-to-noise ratio of previously transmitted error packet data. . The method of claim 16, The retransmitted packet data is the same packet data as the previously transmitted packet data. The method of claim 16, When the target signal-to-noise ratio (Target SNR) is greater than the signal-to-noise ratio (SNR) of the error packet data, the transmission power required for the retransmission is the current channel to the additionally required signal-to-noise ratio (Required SNR) And calculating the estimated value in consideration of the estimated value. The method of claim 16, If the target signal-to-noise ratio (Target SNR) is less than the signal-to-noise ratio (SNR) of the errored packet data, the transmission power required for the retransmission takes the current channel estimate into a predetermined minimum additional signal-to-noise ratio (SNR). The apparatus, characterized in that for calculating. When an error occurs in the transmitted packet data, a mobile communication system using a complex retransmission method of retransmitting packet data related to the packet data and combining and demodulating the transmitted packet data is transmitted from a predetermined terminal to a base station. A method for determining transmission power of packet data retransmitted from the terminal because an error occurs in packet data to be transmitted, Target SNR required to have a predetermined frame error of received packet data has a preset value and a signal to noise ratio required additionally when retransmitted from the signal-to-noise ratio SNR of the packet data in which the error occurs. ), Calculating a transmission power required for retransmission from a signal-to-noise ratio additionally required for retransmission. The method of claim 21, If the retransmission is repeated two or more times, the additionally required signal-to-noise ratio is calculated from the combination of the target signal-to-noise ratio and the signal-to-noise ratio of previously transmitted error packet data. . The method of claim 21, The retransmitted packet data is the same packet data as previously transmitted packet data. The method of claim 21, When the target signal-to-noise ratio (Target SNR) is greater than the signal-to-noise ratio (SNR) of the error packet data, the transmission power required for the retransmission is the current channel to the additionally required signal-to-noise ratio (Required SNR) The method of claim 1, wherein the method is calculated in consideration of the estimated value. The method of claim 21, If the target signal-to-noise ratio (Target SNR) is less than the signal-to-noise ratio (SNR) of the errored packet data, the transmission power required for the retransmission takes the current channel estimate into a predetermined minimum additional signal-to-noise ratio (SNR). The method characterized in that the calculation. When an error occurs in the transmitted packet data, a mobile communication system using a complex retransmission method of retransmitting data related to the packet data and combining and demodulating the transmitted packet data is transmitted from a predetermined terminal to a base station. A method for retransmitting packet data for which retransmission is requested to the base station when an error occurs in the packet data and requests retransmission, The target signal-to-noise ratio (Target SNR) required for the frame error of a given received packet data to have a preset value and the signal-to-noise ratio (SNR) of the errored packet data calculated by the channel quality measurement measured from the received data. Calculating a required signal-to-noise ratio (Required SNR) at the time of retransmission, and receiving a transmission power value required at the re-transmission calculated from the additionally required signal-to-noise ratio at the time of retransmission; And retransmitting the packet data for which the retransmission is requested to the base station by the transmission power value required for the received retransmission. The method of claim 26, If the retransmission is repeated two or more times, the additionally required signal-to-noise ratio is calculated from the combination of the target signal-to-noise ratio and the signal-to-noise ratio of previously transmitted error packet data. . The method of claim 26, The retransmitted packet data is the same packet data as previously transmitted packet data. The method of claim 26, When the target signal-to-noise ratio (Target SNR) is greater than the signal-to-noise ratio (SNR) of the error packet data, the transmission power required for the retransmission is the current channel to the additionally required signal-to-noise ratio (Required SNR) The method of claim 1, wherein the method is calculated in consideration of the estimated value. The method of claim 26, If the target signal-to-noise ratio (Target SNR) is less than the signal-to-noise ratio (SNR) of the errored packet data, the transmission power required for the retransmission takes the current channel estimate into a predetermined minimum additional signal-to-noise ratio (SNR). The method characterized in that the calculation. When an error occurs in the transmitted packet data, a mobile communication system using a complex retransmission method of retransmitting data related to the packet data and combining and demodulating the transmitted packet data is transmitted from a predetermined terminal to a base station. In the base station apparatus for transmitting information for retransmission when an error occurs in the packet data to request retransmission, A channel quality meter for measuring channel quality information from the received packet data; The target signal-to-noise ratio (Target SNR) required for the frame error of the predetermined received packet data to have a preset value and the signal-to-noise ratio (SNR) of the errored packet data calculated by the channel quality measurement measured by the channel quality meter. AMC and a retransmission power controller for calculating an additional required signal-to-noise ratio (SNR) required for retransmission and calculating a transmit power value required for retransmission from the additionally required signal-to-noise ratio for retransmission. The apparatus described above. The method of claim 31, wherein If the retransmission is repeated two or more times, the additionally required signal-to-noise ratio is calculated from a combination of the target signal-to-noise ratio and the signal-to-noise ratio of previously transmitted error packet data. . The method of claim 31, wherein The retransmitted packet data is the same packet data as the previously transmitted packet data. The method of claim 31, wherein When the target signal-to-noise ratio (Target SNR) is greater than the signal-to-noise ratio (SNR) of the error packet data, the transmission power required for the retransmission is the current channel to the additionally required signal-to-noise ratio (Required SNR) And calculating the estimated value in consideration of the estimated value. The method of claim 31, wherein If the target signal-to-noise ratio (Target SNR) is less than the signal-to-noise ratio (SNR) of the errored packet data, the transmission power required for the retransmission takes the current channel estimate into a predetermined minimum additional signal-to-noise ratio (SNR). The apparatus, characterized in that for calculating.