KR20030055413A - A method for controlling power in cdma mobile communication system and thereof system - Google Patents

Abstract

PURPOSE: A method for controlling power in a CDMA mobile communication system is provided to vary a power control amount of a mobile terminal according to time and tendentious trends, thereby reducing errors of power control and quickly applicable to wireless channel characteristics. CONSTITUTION: A system presets all parameters related to power control(S201). If a signal is received from a mobile terminal, the system measures receiving power of the signal(S202). The system calculates receiving power changes, and stores the power changes in a memory(S203). The system determines weight for each receiving power change(S204). The system decides whether a set power control amount exceeds a preset minimal power control amount and a maximum power control amount(S206). If not, the system decides whether the power control amount is smaller than the minimal power control amount(S208). If not, the system measures a BER(Bit Error Rate)(S210). The system decides whether a measured frame error exceeds a preset threshold value(S211). If not, the system determines low control of a power control indicator(S213). The system transmits the signal by including the determined power control amount and the power control indicator to the mobile terminal(S214).

Description

Power control method and system in a CDM type mobile communication system {A METHOD FOR CONTROLLING POWER IN CDMA MOBILE COMMUNICATION SYSTEM AND THEREOF SYSTEM}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of controlling power in a code division multiple access (CDMA) mobile communication system, and more particularly, to a method for controlling a reverse closed loop power.

Since the CDMA type mobile communication system has the characteristic of using the same frequency band by multiple users at the same time, it is very important to maximize the capacity of multiple users to talk simultaneously in the frequency band provided by the system. One way to maximize the capacity of such a system is to control the power of the mobile communication system.

In the CDMA mobile communication system, the distance and radio wave transmission path between the base station and each mobile terminal are different. The strength of the signal transmitted from the mobile terminal located near the base station to the base station is stronger than that of the signal transmitted from the mobile terminal located relatively far from the base station to the base station. This is called the near / far problem. If proper power control is not achieved, mobile terminal signals located close to the base station are transmitted to the base station with more strength than necessary. In a CDMA mobile communication system, such extra power may cause interference to signals transmitted from other mobile terminals. do.

Therefore, by allocating less power to a mobile terminal requiring relatively less power and allocating the extra power generated therein to a mobile terminal requiring more power, the signal originating from the mobile terminal is a signal of the minimum call quality requirement level. If received at the base station at the interference ratio can maximize the system capacity.

There are two methods for controlling power of the mobile communication system, a forward power control method for controlling power transmitted from a base station to a mobile terminal and a reverse power control method for controlling power transmitted from a mobile terminal to a base station.

Forward power control is performed at the base station, which reduces transmission power for a mobile terminal that is not on a call or is relatively close to the base station, or a mobile terminal that is less affected by multipath fading and propagation shading or has less interference from other base stations, Instead, they provide additional power to mobile terminals with a high error rate by being located far from poor reception space areas or base stations.

Reverse power control has become a more important element in the system because the connected mobile terminal has the characteristic of moving randomly. When a mobile terminal moves in a mobile communication system, a propagation path varies according to a distance, an obstacle, or the like between the base station and the mobile terminal. In this way, the radio channel changes due to a different propagation path. In terms of time, the channel environment of mobile communication changes dynamically. The reverse power control is a technique for compensating for the channel change by changing the output power of the mobile terminal in order to overcome the dynamic change of the channel in a CDMA mobile communication system.

Such reverse power control includes reverse open-loop power control and reverse closed-loop power control, among which closed loop power control is based on information obtained by the base station about the mobile terminal. By transmitting a power control command to the mobile terminal, the mobile terminal adjusts the output power according to the command received from the base station.

The conventional closed loop power control method of the prior art determines the power control by checking the information on the amount of power received from the mobile terminal at a specific time or the content of the frame error rate (FER) in the base station receiver, and determines the power control. When changing the output power of the mobile terminal by a predetermined power control amount. That is, if the receiver of the base station calculates the FER of the corresponding mobile terminal and is received with a predetermined quality or more, the power down adjustment command is determined to minimize the influence on other mobile terminals. In order to ensure the power up command is determined. When the power up or down adjustment command is determined as described above, the base station commands the mobile station to adjust the amount of power by a predetermined amount. As such, when power control is performed in a constant amount, it is difficult to accurately compensate for both a fast change and a slow change.

4 is a graph illustrating a result of power control according to a closed loop power control method according to the related art.

As shown in FIG. 4, when the base station determines that the value required for the output power of the mobile terminal is the same as the graph A, when the base station commands the mobile terminal a predetermined amount of power control at a predetermined time interval, the graph B ), It is impossible to keep up with the required amount of power. This difference between the required amount of power and the amount of power being transmitted can degrade the call quality or increase the overall noise of the system, resulting in a drop in capacity.

As mentioned above, the power control method in the existing mobile communication system that adjusts the power to a constant power control amount regardless of the environment changes has a disadvantage in that it is unable to efficiently adapt to a fast or slow change in the wireless channel environment.

Therefore, in order to solve such a problem, the technical problem to be achieved by the present invention is to reduce the error of the power control and to control the power to adapt quickly to the changing radio channel characteristics.

Another object of the present invention is to reduce the power control error by variably determining the power control amount.

1 is a block diagram illustrating a closed loop power control system in a CDMA mobile communication system according to an embodiment of the present invention.

2 is a flowchart illustrating a closed loop power control method in a CDMA mobile communication system according to an embodiment of the present invention.

3 is a graph illustrating a result of controlling power according to a closed loop power control method according to an embodiment of the present invention.

4 is a graph illustrating a result of controlling power according to a closed loop power control method according to the related art.

According to an aspect of the present invention for achieving the above object, first, the received power received from the mobile terminal is measured to obtain a change amount of the received power, and the power control amount is variably determined by weighting the change amount of the received power. Next, by measuring the quality received from the mobile terminal to determine whether to power up or down, and transmits the power control amount and the power control instruction obtained above to the mobile terminal to control the power of the mobile terminal.

When determining the power control amount, it is preferable to use the current received power change amount and the past received power change amount together. At this time, the weight given to the change amount of the current received power is preferably greater than the weight given to the amount of change in the past received power. In addition, the weight given to the change amount of the received power may be determined in consideration of the change tendency of the received power.

Here, when the power control amount is greater than or equal to the predetermined maximum power control amount, the power control amount is set to be equal to the maximum power control amount, and when the power control amount is less than or equal to the predetermined minimum power control amount, the power control amount is preferably set to be equal to the minimum power control amount. .

The reception quality of the mobile terminal may be determined by measuring a frame error rate (FER) or a bit error rate (BER). At this time, if the frame error rate is greater than or equal to the predetermined threshold, the power control instruction is determined to increase the output power of the mobile terminal. If the frame error rate is less than the predetermined threshold, the power control instruction is determined to be lower to lower the output power of the mobile terminal. desirable.

According to another feature of the invention, there is provided a power control system including a transceiver and a modulation and demodulation. The transceiver receives a signal from the mobile terminal and transmits a signal including a power control indicator and a power control amount indicating whether the output power of the mobile terminal is to be raised or lowered to the mobile terminal. The demodulation unit determines the power control amount and the power control indicator from the signal received from the mobile terminal, and variably determines the power control amount according to the change amount of the received power.

When determining the power control amount, it is preferable to use the current received power change amount and the past received power change amount together. In this case, it is preferable to give a weight greater than the amount of change in the past received power to the amount of change in the current received power. In addition, the power control amount may be determined by weighting the change amount of the received power in consideration of the change tendency of the received power.

Here, it is preferable that the modulation / demodulation unit determines the power control amount equal to the maximum power control amount if the power control amount is greater than the predetermined maximum power control amount, and sets the power control amount equal to the minimum power control amount if the power control amount is smaller than the predetermined minimum power control amount.

The modulation / demodulation unit preferably determines the power control indicator upward when the frame error rate (FER) in the transceiver unit is greater than or equal to a predetermined threshold, and determines the power control indicator downward by less than the predetermined threshold.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram of a power control system in a mobile communication system according to an embodiment of the present invention.

As shown in FIG. 1, a power control system 1 according to an embodiment of the present invention includes a base station 10 and a mobile terminal 20, and the base station 10 transmits and receives an RF demodulator 11 and an RF transceiver. The mobile terminal 20 includes a modulator 12 and an RF transceiver 22.

Modulation and demodulation unit 11 of the base station 10 measures the quality of the mobile terminal signal transmitted through the RF transceiver 12 determines the parameters for closed-loop power control and delivers it to the RF transceiver 12 . The RF transceiver 12 of the base station 10 receives a signal transmitted from the mobile terminal 20 and transmits the signal to the demodulation demodulator 11, and loads the parameter determined by the demodulation demodulator 11 on the signal to the mobile terminal 20. To send).

The modulator 22 of the mobile terminal 20 extracts a power control parameter from the signal transmitted through the RF transceiver 21 and transmits the power control parameter to the RF transceiver 11. The RF transceiver 21 of the mobile terminal 20 receives a signal carrying a parameter for power control from the base station 10 and transmits the signal to the demodulation demodulator 22, and receives and extracts the parameter extracted from the demodulation demodulator 22. The output power of the terminal is adjusted and transmitted to the base station 10.

Hereinafter, a power control method in a mobile communication system according to an embodiment of the present invention will be described in detail with reference to FIG. 2.

2 is a flowchart illustrating a power control method in a mobile communication system according to an embodiment of the present invention.

When a call channel is allocated between the mobile terminal 20 and the base station 10, the system enters power control. First, all parameters related to power control are set in advance (S201). These parameters include the maximum power control amount, the minimum power control amount, the frame error rate (FER) threshold, and the like. The frame error rate threshold represents the frame error rate of the level required by the system, and the maximum and minimum power control amounts are the upper and lower limits of the power control amount to prevent the temporary error of the received power directly affecting the transmission power of the mobile terminal. to be.

When a signal is received from the mobile terminal 20 through a communication channel allocated by the RF transceiver 11 of the base station 10, the received power pwr (i) of the received signal is measured (S202). The measured received power value is then stored in memory for use in determining the power control value. Next, the received power change amount [slope_pwr (i)] which is a difference between the received power value [pwr (i)] and the received power value [pwr (i-1)] measured just before the step S202 and stored in the memory. Is calculated and stored in the memory (S203). That is, the received power variation slope_pwr (i) becomes [pwr (i)-pwr (i-1)].

In general, information on past changes in received power is used to determine the power control amount. Information measured in the past will be less relevant than information measured in the past. In addition, if the historical information has a certain trend, there is a high possibility that the channel is changed to a trend similar to that trend. Therefore, by using these two trends, the weight [w (i)] for each received power variation amount slope_pwr (i) is determined (S204).

The method for determining the weight will be described in detail. First, since the currently measured information has a high relationship, a high value is given to the most recently measured received power change amount. In order to measure the tendency of the channel to change, the weight is determined using the change amount of the received power stored in the memory. For example, the weight may be determined in proportion to the measured value using Equation 1 below.

,

Here, slope_pwr (i) is the difference between the i-th measured received power amount pwr (i) and the (i-1) th measured received power amount pwr (i-1).

The power control amount "det_step" is determined using the weight determined as described above and the change amount of the received power (S205). The power control amount det_step is equal to the sum of the product of the received power variation slope_pwr multiplied by the weight w, that is, Equation (2).

Here, det_step is the power control amount, slope_pwr (i) is the difference between the i-th measured received power amount [pwr (i)] and the (i-1) th measured received power amount [pwr (i-1)], and w ( i) is the weight imposed on slope_pwr (i).

Next, it is determined whether the power control amount det_step set in step S205 falls outside the ranges of the minimum power control amount and the maximum power control amount preset in step S201. That is, it is determined whether the power control amount det_step determined in step S205 is greater than the maximum power control amount (S206). If the determination result is greater than the maximum power control amount, the power control amount det_step is set equal to the maximum power control amount (S207). Next, if the maximum power control amount is not exceeded, it is determined whether it is smaller than the minimum power control amount (S208). If the determination result is smaller than the minimum power control amount, the power control amount det_step is set equal to the minimum power control amount (S209). In this way, it is possible to prevent the temporary error of the reception power from directly affecting the transmission power of the mobile terminal.

Next, in order to determine whether the base station 10 is to adjust the power up or down, the frame error rate or bit error rate, which is a reception characteristic of the mobile terminal reported by the mobile terminal 20, is determined. rate, BER) (S210). It is determined whether the measured frame error rate (bit error rate) is greater than or equal to the preset threshold in step S201 (S211). If the threshold value is greater than or equal to the threshold value, the data quality received from the mobile terminal 20 is in a bad state. The output power must be increased. Therefore, the power control indicator is determined to be adjusted upward (S212). If the frame error rate (bit error rate) is less than the threshold, since the data quality received from the mobile terminal 20 is in a good state, the output power of the mobile terminal 20 needs to be lowered, so that the power control indicator is adjusted downward (S213). .

The power control amount and the power control indicator determined above are loaded on the signal and transmitted to the mobile terminal 20 (S214). The transceiver 22 of the mobile terminal 20 transmits this signal and transfers this signal to the modulation / demodulation unit 21. The modulating demodulator 21 extracts the power control amount and the power control indicator from this signal and adjusts its output power.

3 is a graph illustrating a result of controlling power according to a closed loop power control method according to an embodiment of the present invention.

As shown in Fig. 3, when the required transmission power of the mobile terminal is the same as the graph A, according to the power control method according to the embodiment of the present invention, the output power of the mobile terminal is the same as the graph B, You can accurately follow the amount of power that is being added.

The embodiments of the present invention described above are not limited to the one embodiment only, and are not limited by the above-described contents and the accompanying drawings, and various substitutions, modifications, and changes without departing from the spirit and scope of the present invention. Of course, change is possible.

As described above, the power control method and system in the CDMA mobile communication system of the present invention vary the power control amount of the mobile terminal according to the temporal and trending trends, thereby reducing errors in power control and changing the radio channel characteristics. Power can be controlled to adapt quickly.

Claims (16)

In the method for controlling the output power of the mobile terminal in the base station of the mobile communication system, A first step of measuring received power received from the mobile terminal; Obtaining a change amount of the measured received power; A third step of variably determining a power control amount by weighting the change amount of the received power; A fourth step of determining whether to increase or decrease a power control instruction by measuring a quality received from the mobile terminal; And A fifth step of transmitting the power control amount and the power control instruction to a mobile terminal; Power control method in a mobile communication system comprising a. The method of claim 1, wherein the third step And using the current received power change amount and the past received power change amount together to give the current received power change amount a weight greater than the past received power change amount to determine the power control amount. The method of claim 2, wherein the third step expression [Where, det_step is the power control amount, slope_pwr (i) is the i-th received power change amount, which is the difference between the i-th received power and (i-1) -th received power, and w (i) is a weight given to slope_pwr (i) Determining the power control amount using the power control method. The method of claim 2, wherein the third step And determining the weight given to the change amount of the received power in consideration of the change tendency of the received power. The method of claim 4, wherein the third step expression Wherein the slope_pwr (i) is the i-th received power change amount, which is the difference between the i-th received power and the (i-1) th received power, and w (i) is a weight given to the slope_pwr (i). The output power control method of a mobile terminal comprising the step of. The method of claim 1, wherein the third step And setting the power control amount equal to the maximum power control amount when the determined power control amount is equal to or greater than a predetermined maximum power control amount. The method of claim 1, wherein the third step And setting the power control amount equal to the minimum power control amount when the determined power control amount is less than or equal to a predetermined minimum power control amount. The method of claim 1, wherein the fourth step Determining a reception quality of the mobile terminal by measuring a frame error rate (FER) or a bit error rate (BER). The method of claim 8, wherein the fourth step Power in a mobile communication system, when the frame error rate is greater than or equal to a predetermined threshold, determining the power control instruction upward to increase the output power of the mobile terminal; and determining the power control instruction downward when the frame error rate is less than the threshold. Control method. In a system for controlling the output power of a mobile terminal in a mobile communication system, A transceiver for receiving a signal from the mobile terminal and transmitting a signal including a power control indicator and a power control amount indicating whether to output the output power of the mobile terminal upward or downward; and The modulation and demodulation unit which receives the signal from the transceiver and determines the power control amount and the power control indicator and transmits the power control amount to the transceiver, and variably determines the power control amount according to the change amount of the received power. Power control system in a mobile communication system comprising a. The method of claim 10, wherein the modulation demodulation unit A power control system in a mobile communication system that determines the power control amount by giving a weight greater than a current received power change amount to a current received power change amount. The method of claim 11, wherein the modulation and demodulation unit expression [Where, det_step is the power control amount, slope_pwr (i) is the i-th received power change amount, which is the difference between the i-th received power and (i-1) -th received power, and w (i) is a weight given to slope_pwr (i) Power control system in the mobile communication system to determine the power control amount. The method of claim 11, wherein the modulation and demodulation unit The power control system in the mobile communication system to determine the weight in consideration of the change tendency of the received power. The method of claim 13, wherein the modulation demodulation unit expression Wherein the slope_pwr (i) is the i-th received power change amount, which is the difference between the i-th received power and the (i-1) th received power, and w (i) is a weight given to the slope_pwr (i). Power control system in a mobile communication system. The method of claim 10, wherein the modulation demodulation unit Setting the power control amount to be equal to the maximum power control amount if the power control amount is greater than a predetermined maximum power control amount; and setting the power control amount to be equal to the minimum power control amount if the power control amount is less than a predetermined minimum power control amount. Power control system in mobile communication system. The method of claim 10, wherein the modulation demodulation unit The power control indicator in the mobile communication system to determine the power control indicator upward when the frame error rate (FER) in the transceiver unit is greater than or equal to a predetermined threshold, and the power control indicator downward when the frame error rate is less than the threshold. system.