KR20100059300A - Method of controlling power using dynamic step size - Google Patents

Abstract

PURPOSE: An external loop power control method using a dynamic step size is provided to perform power control efficiently by considering error/non-error count. CONSTITUTION: An error is identified in a received block. According to the error, a target reception quality value is up or down stepped. The up step size is changed by a previous consecutive error count. The previous consecutive error count is decided by a precious consecutive up-step count. The initial up-step size uses a default up-step size.

Description

Power control method using dynamic step size {METHOD OF CONTROLLING POWER USING DYNAMIC STEP SIZE}

The present invention relates to a power control method of a wireless communication system. More specifically, the present invention relates to an outer loop power control method of a wireless communication system.

Code Division Multiple Access (CDMA) uses the same frequency channel by multiple receivers and multiple transmitters simultaneously. Therefore, the interference between the simultaneous caller and the base station is caused, so that the proper operation of the system will operate smoothly.

For such control, CDMA uses a mixture of power control schemes. Power control allows transmission between the transmitting end and the receiving end with minimal power while satisfying the proper quality of the transmitted signal. Therefore, if the power control is properly performed, it is possible to reduce the interference due to the transmission power of each terminal and base station to maximize the system capacity. Responding to various fast channel changes is also an important challenge associated with power control of communication systems.

Uplink power control should perform power control in such a way as to overcome the problem of power intensity that may occur between the terminal far from the cell and the terminal near the base station. That is, the strength of all signals of each terminal received at the base station should have a constant average power. In the downlink power control, the interference that affects other cells is reduced to the maximum, and the power control that compensates the influence from the other cells should be provided to the terminal in the own cell. That is, each terminal should have sufficient signal strength to reduce interference with neighboring cells and compensate for interference from neighboring cells.

In a wireless communication system using Code Division Multiple Access (CDMA), power control is generally classified into open loop power control and closed loop power control. . The closed loop power control may be further divided into inner loop power control and outer loop power control.

Open loop power control is an operation that initially determines the transmit power at the beginning of a call connection. The basic principle is a simple principle that a terminal near a base station transmits a small output and a far terminal transmits a large output. In open loop power control, the terminal only determines the output based on the signal strength from the base station. That is, the terminal output reaching the base station can be minimized by reducing the terminal output when the reception power from the base station is large and increasing the terminal output when the reception power is small.

In the closed loop power control, the inner loop power control method compares the measured signal quality with the target signal quality determined by the outer loop power control, and transmits a transmit power control command (TPC command) to the transmitter according to the comparison result. do. As mentioned earlier, the outer loop power control scheme determines the target signal quality used for inner loop power control. After all, it is desirable to have a fast and efficient outer loop power control scheme because outer loop power control can directly affect the overall system capability, performance and coverage.

Existing outer loop power control schemes perform operations for each state in three states: initial state, acquisition state, and tracking state. 1 shows a flow diagram for state transition of outer loop power control in a code division multiple access scheme.

The initial state of the outer loop power control is a step of maintaining an initial value of the target reception quality for a predetermined time after the power control is started to ensure initial setup time of the transmitter and the receiver. The signal quality may be related to the signal to interference ratio. For example, the signal quality may be a signal to interference ratio (SIR). For convenience, the target signal quality is expressed as a target SIR or SIR _target . In acquisition state the block error occurs, or the operation to lower the predetermined value (Down_Step _START) as the SIR _target until it reaches the minimum _target SIR (SIR _{MIN_START_TARGET)} the SIR _target set by the state acquisition is performed. If a condition that satisfies the two conditions occurs, the transition to the tracking state. The acquisition state serves to quickly lower the SIR _target to a level deemed appropriate in the current channel situation. Therefore, in the acquisition state, a step size for lowering the SIR _target is set larger than the tracking state, which is the next step. The error of the block is determined by a cyclic redundancy check (CRC) of the received block, and is in a state of good (CRC OK) error and bad (CRC not OK) error. Classify.

The tracking state requires more granular power control than the acquisition state. 2 is a flowchart schematically showing the operation of the tracking state. In the tracking state, it is first determined whether there is a CRC. If the CRC exists, the CRC check process is performed. If the CRC does not exist, the existing SIR _target is maintained. In the CRC error checking process, the CRC determines whether the current block is good. In case of CRC failure, increase the SIR _target by the predetermined size (STEP _up ). If the CRC is good, the SIR _target is reduced by the size (STEP _down ) calculated by STEP _up and the target block error rate (BLER _TARGET , parameter signaled from higher layer). If the channel conditions are ideal, STEP _down to satisfy the BLER _TARGET can be determined by Equation 1 below.

Here, STEP _down is the down step size, STEP _up is the up step size, and BLER _TARGET is the target block error rate.

For example, if BLER _TARGET is 1%, STEP _up = 99 × STEP _down . Therefore, when the step down process is 99 times and the step up process is performed once, the SIR _target becomes the same as the initial value.

3 shows the change of the SIR _target over time in an ideal situation.

If an error is found during CRC error checking, windup is detected. Windup defines a kind of extreme situation. For example, this occurs when an error is continuously detected during the outer loop power control process and the SIR _target continues to increase. In addition, it occurs when the actual received SIR does not increase accordingly even if the inner loop power control stage continuously transmits the UP TPC to increase power to the transmitter. In general, if the number of slots for which the TPC is UP exceeds a predetermined value, the compression mode (measurement interval for handover) slot, or the average SIR is smaller than a predetermined value for windup detection, the current section is determined as the windup section. do. If it is determined to be windup, the SIR _target is maintained. If not, the SIR _target is increased by STEP _up . Here, STEP _up is a predetermined value based on experimental data.

In the related art, when a block error occurs consecutively due to a temporary deterioration of a channel condition, the SIR _target is constantly increased using a fixed interval (that is, an up step size) to a wind up point which is considered to be an extreme condition. Therefore, there is a disadvantage in that excessive power is required at the transmitting end, and power of a signal transmitted from the transmitting end to the corresponding terminal acts as interference to other users. In addition, when the channel condition improved and the increased SIR _target was lowered, it was constantly reduced to a fixed interval (ie, down step size), which is only a ratio of the BLER _TARGET of the up step size, regardless of the number of previous up steps. Therefore, it takes a long time to return to the proper SIR _target , resulting in power consumption and interference problems.

The present invention has been made to solve the problems of the prior art as described above, an object of the present invention is to provide a method for efficiently performing power control in a wireless communication system.

Another object of the present invention is to provide a method for efficiently performing power control in consideration of a previous consecutive error / non-error count in outer loop power control.

It is still another object of the present invention to provide a method for efficiently performing power control in consideration of the number of previous successive up / down steps in outer loop power control.

Technical problems to be achieved in the present invention are not limited to the above-mentioned technical problems, and other technical problems not mentioned above will be clearly understood by those skilled in the art from the following description. Could be.

In one aspect of the present invention, a method for controlling an outer loop power of a wireless communication system, the method comprising: determining whether an error occurs in a received block; A method of controlling an outer loop power is provided, including downstepping, wherein the upstep size is dynamically changed in accordance with a previous number of consecutive errors.

In another aspect of the present invention, there is provided a method for controlling an outer loop power of a wireless communication system, the method comprising: determining whether an error has occurred in a received block; A method of controlling an outer loop power is provided, the method comprising a step of down step, wherein the down step size is dynamically changed according to a previous number of consecutive errors or non-errors.

Here, the block may be a transport block or a code block. Preferably, the block is a transport block.

According to the embodiments of the present invention, the following effects are obtained.

First, power control can be efficiently performed in a wireless communication system.

Second, in the outer loop power control, the target reception quality can be returned and maintained at an appropriate level in consideration of the previous consecutive error / non-error count.

Third, in the outer loop power control, the target reception quality may be returned and maintained at an appropriate level in consideration of the previous consecutive up / down step number.

The effects obtainable in the present invention are not limited to the above-mentioned effects, and other effects not mentioned above may be clearly understood by those skilled in the art from the following description. will be.

The construction, operation, and other features of the present invention will be readily understood by the embodiments of the present invention described with reference to the accompanying drawings. The embodiments described below are examples in which technical features of the present invention are applied to a code division multiple access system.

4 is an operation flowchart of performing outer loop power control according to an embodiment of the present invention. 4 relates to a tracking state during outer loop power control.

Referring to FIG. 4, the receiver starts a tracking state operation (S410) and determines whether a cyclic redundancy check (CRC) exists in the received block (S420). If no CRC exists, the target reception quality SIR _TARGET remains the same. If a CRC exists, it is determined whether an error exists in the block (S430). The block may be a transport block. If a CRC error is detected in the block, a process for up-stepping the SIR _TARGET is performed (S440 to S470). On the other hand, if a CRC error is not detected in the block, a process for down stepping SIR _TARGET is performed (S480 to S490).

The basic up step and down step process is similar to the operation illustrated in FIG. However, in an embodiment of the present invention, in order to prevent excessive transmission power and return / maintain SIR _TARGET to an appropriate level, an _upstep size (parameter, which is a parameter used in outer loop power control, using a result of the previous outer loop power control) STEP _up ) and down step size (STEP _down ) can be changed dynamically. To this end, the embodiment of the present invention further includes updating the up step size (S440) and updating the down step size (S480). Preferably, the previous outer loop power control result is a previous continuous outer loop power control result. The previous continuous outer loop power control result may be a number of previous consecutive error occurrences. In other words, it may be the number of previous consecutive error occurrences or the number of previous consecutive non-errors. Further, the previous continuous outer loop power control result may be a previous consecutive up step number or a down step number.

Updating the up step size or the down step size using the previous continuous outer loop power control result may be performed as follows.

(Up step size update)

1. First up step size: Even if the previous result is a non-error or down step, the up step size for the newly occurring first error is always constant.

2. Second up step size:

   -Reduce the size according to the number of previous consecutive error occurrences (up steps).

-To prevent the SIR _TARGET from stalling as the up step size approaches zero, set a threshold to prevent the up step size from shrinking below a certain value.

(Down step size update)

1. First down step size: increases the down step size for the first non-error that occurs newly, depending on the number of previous consecutive error occurrences (up steps).

2. Down step size after second:

   Reduce the size according to the previous number of consecutive non-errors (down steps).

- the down step size closer to 0 SIR _TARGET is appointed to prevent the threshold value to prevent the decline in the identity-down step size below a certain value.

Hereinafter, the updating of the up step size and the down step size will be described in more detail with reference to FIGS. 5 to 7. For the sake of convenience, the figures continuously show changes in SIR _TARGET , up step size and down step size. However, actual values will be displayed discretely on the graph of the figure.

5 (a) shows the change of SIR _TARGET according to the number of consecutive errors (step up times). Referring to FIG. 5A, the SIR _TARGET is divided into two stages and increases as an error continues to occur. In the first stage, the SIR _TARGET increases in a convex upward fashion as the up step size continues to decrease (510). The second stage begins with the up step size decreasing below the threshold. In the second stage, the up step size remains constant and the SIR _TARGET increases in a straight line (520).

5 (b) to 5d show changes in the up step size according to the number of consecutive errors (step up times). Referring to Figures 5 (b)-(d), the first up step size is always the same as the _default up step size (UP _default ) regardless of the previous non-error number.

Thereafter, the up step size may decrease linearly with respect to successive error times (Fig. 5 (b)). For example, the current up step size (STEP _up ) may be smaller than the _default up step size (UP _default ) by a predetermined size, and the predetermined size may increase constantly according to the number of consecutive errors. Also, the current up step size STEP _up may be smaller than the previous up step size STEP _up-1 by a predetermined size, and the predetermined size may be constant at every power control step.

In addition, the up step size can be reduced non-linearly with respect to the number of consecutive errors (Fig. 5 (c) (d)). In Fig. 5C, the up step size has a large decrease in the initial stage of the error, and decreases as the error continues. For example, this may correspond to a case where the current up step size decreases exponentially from the base up step size according to the number of consecutive errors. Since the SIR _TARGET can already be set high enough at the first up step, reducing the subsequent up step size quickly can help to maintain an appropriate SIR _TARGET . On the other hand, in Fig. 5 (d), the up step size has a small decrease in the initial stage of the error, and the decrease increases as the error continues. For example, the difference between the current up step size STEP _up and the previous up step size STEP _up-1 may increase in proportion to the number of consecutive errors. Maintaining a large up-step size initially increases SIR _TARGET rapidly, which can prevent early occurrence of errors. Therefore, overhead and power waste due to unnecessary up steps can be prevented.

5 (b) to (d), the up step size does not continuously decrease, and is maintained at a constant value when the value falls below the threshold value UP _min . The constant value may be a threshold value or may be a previous up step size.

6 (a) to 6 (c) show the change of the first down step size according to the previous consecutive number of errors (step up count). Referring to Figures 6 (a)-(c), the first down step size DOWN _first may increase linearly with respect to the previous consecutive error count (Figure 6 (a)). For example, the first down step size may be determined as the product of the default down step size (DOWN _default ) and the previous consecutive error count. In addition, the down step size may increase non-linearly with respect to successive non-errors (Fig. 6 (b) (c)). In Fig. 6B, the down step size increases as the number of previous consecutive errors increases. For example, it may be the case that the first down step size increases exponentially from the default down step size according to the number of consecutive errors. It may also be the case that the first down step size is a higher order (> first order) function relationship with the previous successive error count. Basically the up step size is quite large compared to the down step size. Therefore, if the up step has been performed several times due to previous successive errors, increasing the increase in down step size to match the number of previous successive errors may help keep the SIR _TARGET at an appropriate level.

On the other hand, in FIG. 6C, the first down step size increases as the number of previous consecutive errors increases. For example, it may be the case that the increase width of the first down step size decreases exponentially with the number of consecutive errors. It may also be the case that the first down step size is a low order (<first order) function relationship with a previous successive error count. If, in the previous up step process, the up step size decreases as the error continues, the increase of the first down step size according to the previous successive error number is made smaller as the previous successive error number increases. This may help to keep the SIR _TARGET at an appropriate level.

Fig. 7 (a) shows the change of SIR _TARGET with the number of consecutive non-errors (step down times). Referring to FIG. 7A, the SIR _TARGET is divided into two stages and decreases as non-errors continue to occur. In the first stage, the SIR _TARGET increases 710 concave down as the down step size continues to decrease. The second stage begins with the down step size decreasing below the threshold. In the second stage, the down step size remains constant and the SIR _TARGET is reduced to a straight line 720.

7 (b)-(d) show the change of the down step size according to the number of consecutive non-errors (step down times). Referring to Figures 7 (b)-(d), SIR _TARGET starts from the first down step size DOWN _first as a non-error occurs.

Thereafter, the down step size may decrease linearly with respect to successive non-error times (Figure 7 (b)). For example, the current down step size STEP _down may be smaller than the default down step size DOWN _default by a predetermined size, and the predetermined size may increase constantly according to the number of consecutive non-errors. In addition, the current down step size (STEP _down ) may be smaller than the previous down step size (STEP _down-1 ) by a predetermined size, and the predetermined size may be constant in every power control step.

In addition, the down step size may decrease non-linearly with respect to successive non-errors (Fig. 7 (c) (d)). In Fig. 7 (c), the down step size has a large decrease in the initial non-error, and decreases as the non-error continues. For example, it may be the case that the current down step size decreases exponentially from the default down step size according to the number of consecutive non-errors. Since the SIR _TARGET may already be sufficiently low at the first down step, reducing the subsequent down step size quickly may help to maintain an appropriate SIR _TARGET .

On the other hand, in Fig. 7 (d), the down step size has a small decrease in the initial non-error, and the decrease increases as the non-error continues. For example, it may be the case that the difference between the current down step size and the previous up step size increases in proportion to the number of consecutive non-errors. If the error occurs excessively before the start of the down step, or if there is a windup, keeping the down step size large at the beginning may help to quickly reduce the SIR _TARGET to an appropriate level. Thereafter, the decrease of the down step size according to the number of consecutive non-errors can be increased, so that the SIR _TARGET can be maintained at an appropriate level.

7 (b) to (d), the down step size does not continuously decrease, and remains constant when the value falls below the threshold value DOWN _min . The constant value may be a threshold or a previous up step size.

8 is a flowchart illustrating an operation of updating an up step size and a down step size according to an embodiment of the present invention. The illustrated step size update process is a process of determining the down step size or the up step size according to the CRC result and the previous outer loop power control result. Table 1 describes the code for the above flow chart.

if CRC == OK
CNT _down = CNT _down-1 + 1
if CNT _down == 1
STEP _down (DOWN = _first) = CNT _{up default} · DOWN
else
_{if DOWN first - (BLER TARGET)} 2 · (CNT down) ≥ DOWN threshold · DOWN default
_{STEP down = DOWN first - (BLER} TARGET) 2 · (CNT down -1)
else
STEP _down = DOWN _threshold · DOWN _default
end
end
CNT _up = 0
else
CNT _up = CNT _up-1 + 1
if UP _default- (BLER _{TARGETCNT up} ) ≥ UP _{thresholdUP default}
STEP _up = UP _default -BLER _TARGET (CNT _up -1)
else
STEP _up = UP _threshold · UP _default
CNT _down = 0
end

Here, CNT _down is the number of down steps including the current operation, CNT _down-1 is the number of down steps previously performed consecutively, STEP _down is the down step size to be applied in the current step, STEP _down-1 is the down step size applied in the previous step, DOWN _default is the default down step size, DOWN _threshold is a real number greater than 0 and less than 1 for the threshold, and BLER _TARGET is the target block error rate. In addition, CNT _up is the number of upsteps including the current operation, CNT _up-1 is the number of upsteps previously performed continuously, STEP _up is the upstep size to be applied in the current step, UP _default is the default up step size The UP _threshold is a real number greater than 0 and less than 1 for the threshold. For example, BLER _TARGET may be 1%, UP _default is 0.5dB, DOWN _default is 0.005dB, UP _threshold is 0.5, and DOWN _threshold is 0.2.

Referring to the code of FIG. 8 and Table 1, the down step size is updated when CRC OK, that is, when no block error occurs (S480). If CRC not OK, that is, if a block error occurs, the upstep size is updated (S440).

The procedure for updating the down step size is as follows. If the CRC is OK, before the adjustment of the down step size, the down step counter CNT _down is used to store in the memory how many down steps are applied successively (S881). In the subsequent process, the down step counter serves as a weight when determining the down step size. Thereafter, it is determined whether the value of the down step counter is 1 (S882). In step S882, CNT _down is an integer greater than or equal to 1 and means the number of down steps continuously performed including the current step. Thus, a value of 1 for the down step counter means that the result of the previous outer loop power control is the up step. In addition, the value of the down step counter not being 1 means that the result of the previous outer loop power control is the down step.

If the value of the down step counter is 1, the first down step size DOWN _first is determined by multiplying the CNT _down by the default down step size DOWN _default (S883). The up step counter refers to the number of up steps previously performed continuously. That is, the first down step size dynamically increases with the number of previously performed up steps. Therefore, the larger the number of upsteps, the larger the first downstep size is, leading to a rapid reduction in excessively large transmission power.

On the other hand, if the value of the down step counter is not 1, it is determined whether the down step size to be currently applied is greater than or equal to the threshold before updating the down step size (S884). The threshold is to prevent the down step size from continuously decreasing and converging to zero. For example, the threshold value is the normal down step size and a predetermined ratio: may be determined using (DOWN _threshold such as 0.5 (50%) to 0.1 (10%)).

If the down step size to be currently applied is greater than or equal to a threshold value, the down step size is reduced by using CNT _down in order to maintain the SIR _target (S885). In general, since the down step has a smaller operating range than the up step, the current down step size can be reduced by BLER _TARGET ² compared to the previous down step size.

On the other hand, if the down step size to be applied currently is less than the threshold value, the down step size is set to the threshold value (S886). In addition, the down step size to be currently applied may be maintained at the previous down step size. The last step in the down step size update process is to initialize CNT _up to zero. Therefore, when an error occurs, CNT _up is increased from the initial value in the up-step size update process which is newly started (S887).

The process of updating the up step size is performed when an error is detected through the CRC. The basic process is similar to the down step size update process. However, unlike the down step, the up step size update process does not increase the size of the first up step considering the previous external power control result unlike the down step. Therefore, the first up step size is fixed to the _default up step size UP _default regardless of the previous external power control result. That is, the up step size update process only performs an operation of decreasing the _default up step size UP according to a previous outer loop control result. In detail, when a CRC error is detected, the memory stores a number of consecutive up steps to be applied using the up step counter CNT _up before adjusting the up step size (S841). In the subsequent process, the up step counter serves as a weight when determining the down step size. Thereafter, before updating the up step size, it is determined whether the currently applied up step size is equal to or greater than a predetermined threshold value (S842). The threshold is for preventing the up step size from continuously decreasing and converging to zero. For example, the threshold may be determined using the default up step size and a predetermined ratio (UP _threshold : 0.5 (50%) to 0.1 (10%)).

If the currently applied up step size is greater than or equal to the threshold value, the up step size is reduced by using the CNT _up to maintain the SIR _target (S843). In general, since the up step has a large operating range, the current up step size can be reduced from the base up step size by the product of the previous consecutive error times and the BLER _TARGET .

On the other hand, if the up step size to be applied currently is less than the threshold value, the up step size is set to the threshold value (S844). In addition, the up step size to be currently applied may be maintained at the previous up step size. In the last step of the up step size update process, CNT _down is initialized to 0 (S845). Therefore, in case of non-error, CNT _down increases from the initial value in the process of newly starting down step size update.

FIG. 9 illustrates a change of the SIR _target over time when outer loop power control is performed according to the flowchart illustrated in FIG. 8. Related parameters are assumed to be UP _default = 0.5dB, UP _threshold = 0.5, DOWN _threshold = 0.2, BLER _target = 1%, and DOWN _defalut = 0.005dB.

9 (a) shows a case where a block error occurs continuously in the received block. Although not clearly shown in the figure, the first up step size is fixed at UP _default = 0.5 dB, regardless of the number of previous non-error occurrences. If a block error occurs, the SIR _target is incremented by an up step. SIR _target to continue despite the increase by increasing the SIR _target by an up step each time an error occurs when the block error. In this case, the step size applied at every step up decreases as the number of previous successive step ups increases. In addition, the step size may decrease linearly or nonlinearly with respect to the block error rate. For example, the current step size is determined by the following equation.

STEP _up = UP _default -BLER _TARGET (CNT _up -1)

According to the above equation, the current up step size is made smaller by the target block error rate (BLER _TARGET = 1%, 0.01 dB) than the previous up step size whenever an error occurs. In FIG. 9A, it can be seen that the upstep size decreases to 0.5 dB => 0.49 dB => 0.48 dB (910). As the error occurs continuously, the up step size continues to decrease. However, if the up step size to be applied currently is smaller than the threshold value (UP _default x UP _threshold = 0.25 dB), the current up step size is fixed to the threshold value. Therefore, after a certain number of errors occur continuously, even if the error continues to occur, the upstep size is fixed at 0.25 dB, so that the SIR _target is small but increases constantly (920).

9 (b) shows a case where block error exists in the received block. As in FIG. 9 (a), the size of the up-step first applied when a block error occurs is fixed at 0.5 dB. As the error occurs continuously, the up step size decreases by 0.01 dB. After that, if the SIR _target becomes large enough, no block error occurs, so the down step process starts. The first down step size increases in proportion to the number of previous successive up steps. As an example, the first down step size is determined by the following equation.

STEP _down (DOWN = _first) = CNT _{up default} · DOWN

Therefore, if the number of upsteps performed consecutively before the start of the downstep is three, the first downstep size is 0.015 dB (930a). In addition, if the number of previously performed up steps is one time, the first down step size is 0.005 dB (930b). Thereafter, the step size applied at every down step decreases as the number of previous consecutive step downs increases. In addition, the step size may decrease linearly or nonlinearly with respect to the block error rate. For example, the current down step size is determined by the following equation.

_{STEP down = DOWN first - (BLER} TARGET) 2 · (CNT down -1)

In accordance with the above equation, the current down step size is the square of the number of consecutive non-errors and the target block error rate from the first down step size as non-errors (ie, CRC OK) occur continuously (BLER _TARGET ² = 0.01%, 0.0001dB) is reduced by the size corresponding to the product. In FIG. 9B, it can be seen that the down step size decreases to 0.015 dB => 0.0149 dB => 0.0148 dB or 0.005 dB => 0.0049 dB (940).

9 (c) illustrates a case in which non-error (CRC OK) continuously occurs in the received block. Referring to FIG. 9C, the first down step size may be increased in proportion to the number of previously occurring errors. In FIG. 9C, since the number of previously generated errors is 1, the first down step size starts from 0.005 dB, which is the default down step size (DOWN _default ). As non-errors occur continuously, the down step size continues to decrease (0.005 dB => 0.0049 dB => 0.0048 dB; 940). However, if the down step size to be currently applied is smaller than the _threshold (DOWN _default x DOWN _threshold = 0.001 dB), the current down step size is fixed to the threshold. Thus, after a certain number of non-errors occur continuously, the SIR _target is small but constant decreases since the down step size is fixed at 0.001 dB even if the non-errors continue to occur.

In summary, according to an embodiment of the present invention, each step size may be dynamically adjusted by using the number of previous successive up steps and / or down steps in the outer loop power control. In the case of the up step, if the up step operation occurs continuously, it is possible to reduce the step size to facilitate the return of the SIR _target to an appropriate level during channel improvement. In the case of the down step, the first down step size can be set high to be proportional to the increase of the SIR _target due to the continuous up step operation, thereby rapidly reducing the unnecessarily high SIR _target . In addition, as the down step operation continues, the SIR _target can be maintained at a stable level by decreasing the step size.

The embodiments illustrated herein have been described based on block and target block error rates. However, power control using an outer loop in a WCDMA system may be performed based on the frame. In this regard, blocks and frames may be used interchangeably. Therefore, in the above-described embodiment, "block" may be replaced with "frame" and "target block error rate BLER _TARGET " may be replaced with "target frame error rate FER _TARGET ."

The embodiments described above are the components and features of the present invention are combined in a predetermined form. Each component or feature is to be considered optional unless stated otherwise. Each component or feature may be implemented in a form that is not combined with other components or features. It is also possible to combine some of the components and / or features to form an embodiment of the invention. The order of the operations described in the embodiments of the present invention may be changed. Some configurations or features of certain embodiments may be included in other embodiments, or may be replaced with corresponding configurations or features of other embodiments. It is obvious that the claims may be combined to form an embodiment by combining claims that do not have an explicit citation relationship in the claims or as new claims by post-application correction.

In this document, the embodiments of the present invention have been mainly described with reference to the data transmission / reception relationship between the terminal and the base station. The specific operation described herein as being performed by the base station may be performed by its upper node, in some cases. That is, it is apparent that various operations performed for communication with a terminal in a network including a plurality of network nodes including a base station can be performed by a network node other than the base station or the base station. A 'base station' may be replaced by terms such as a fixed station, a Node B, an eNode B (eNB), an access point, and the like. In addition, the term "terminal" may be replaced with terms such as a user equipment (UE), a mobile station (MS), a mobile subscriber station (MSS), and the like.

Embodiments according to the present invention may be implemented by various means, for example, hardware, firmware, software, or a combination thereof. In the case of a hardware implementation, an embodiment of the present invention may include one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), FPGAs ( field programmable gate arrays), processors, controllers, microcontrollers, microprocessors, and the like.

In the case of implementation by firmware or software, an embodiment of the present invention may be implemented in the form of a module, procedure, function, etc. that performs the functions or operations described above. The software code may be stored in a memory unit and driven by a processor. The memory unit may be located inside or outside the processor, and may exchange data with the processor by various known means.

It will be apparent to those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit of the invention. Accordingly, the above detailed description should not be construed as limiting in all aspects and should be considered as illustrative. The scope of the invention should be determined by reasonable interpretation of the appended claims, and all changes within the equivalent scope of the invention are included in the scope of the invention.

The present invention can be applied to power control of a wireless communication system. More specifically, the present invention can be applied to outer loop power control of a wireless communication system.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included as part of the detailed description in order to provide a thorough understanding of the present invention, provide an embodiment of the present invention and together with the description, illustrate the technical idea of the present invention.

1 shows a flow diagram for state transition of outer loop power control in a code division multiple access scheme.

2 shows a schematic flowchart of a tracking state in outer loop power control.

3 illustrates a change in target reception quality over time when power control is performed according to the flowchart shown in FIG. 2.

4 is an operation flowchart of performing outer loop power control according to an embodiment of the present invention.

5 (a)-(d) illustrate changes in target reception quality and upstep size according to successive error times in an embodiment of the present invention.

6 (a)-(c) show the change of the first down step size according to the number of consecutive errors in one embodiment of the present invention.

7 (a)-(d) illustrate a change in target reception quality and a change in down step size according to the number of consecutive non-errors in one embodiment of the present invention.

8 is a flowchart illustrating an operation of updating an up step size and a down step size according to an embodiment of the present invention.

9 (a)-(c) show a change in target reception quality over time when outer loop power control is performed according to the flowchart illustrated in FIG.

Claims (18)

In the outer loop power control method of a wireless communication system, Determining whether an error has occurred in the received block; And Up or down step of the target reception quality value according to the error occurrence of the block, And wherein the up step size changes dynamically according to a previous consecutive number of errors. The method of claim 1, And wherein said previous number of consecutive errors is determined according to a previous number of consecutive up steps. The method of claim 1, The first up step size is fixed to the default up step size, the outer loop power control method. The method of claim 1, And if an error occurs in the block, reducing the up step size by a predetermined size proportional to the previous number of consecutive errors compared to a basic up step size. The method of claim 4, wherein And wherein said predetermined magnitude is linearly or nonlinearly proportional to said previous consecutive number of errors. The method of claim 5, And wherein the predetermined size is proportional to a target block error rate (BLER _TARGET ). The method of claim 6, Wherein the up step size is determined according to the following equation: STEP _up = UP _default -BLER _TARGET × (CNT _up -1) Here, STEP _up is the up step size, UP _default is the default up step size, BLER _TARGET is the target block error rate, and CNT _up is an integer equal to or greater than 1 as the previous consecutive up step number. The method of claim 1, And if the up step size is smaller than a threshold value, maintaining the up step size at a previous up step size or setting the threshold value to the threshold value. In the outer loop power control method of a wireless communication system, Determining whether an error has occurred in the received block; And Up or down step of the target reception quality value according to the error occurrence of the block, And wherein the down step size changes dynamically according to a previous consecutive error or non-error number of times. 10. The method of claim 9, Wherein the number of previous consecutive errors or non-errors is determined according to the number of previous consecutive up or down steps. 10. The method of claim 9, Wherein the first down step size is linearly or non-linearly proportional to the previous consecutive number of errors. The method of claim 11, And wherein the first down step size is proportional to the basic down step size. The method of claim 12, Wherein the first down step size is determined by the following equation: DOWN _first = CNT _up × DOWN _default Here, DOWN _first is the first down step size, CNT _up is the number of previous successive up steps, and DOWN _default is the default down step size. 10. The method of claim 9, If no error occurs in the block, the down step size is compared with a first down step size to reduce the size by a predetermined amount proportional to the previous consecutive non-error number. The method of claim 14, And wherein said predetermined magnitude is linearly or nonlinearly proportional to said previous consecutive non-error number. The method of claim 15, And wherein the predetermined size is proportional to a target block error rate (BLER _TARGET ). The method of claim 15, The down step size is determined according to the following formula, the outer loop power control method: STEP _down = DOWN _first- (BLER _TARGET ) ² × (CNT _down -1) Here, STEP _down is the down step size, DOWN _first is the first down step size, BLER _TARGET is the target block error rate, and CNT _down is an integer equal to or greater than 1 as the previous consecutive down step count. 10. The method of claim 9, And if the down step size is smaller than a threshold value, maintain the down step size at a previous down step size or set the threshold value.

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