KR20010046296A - forward link power control method, and apparatus for the same in CDMA communication system - Google Patents

Abstract

PURPOSE: A forward power controller and a controlling method thereof are provided to offer an exact power control by using a signal applying real forward power control rather than a transmitted PCB(Power Control Bit). CONSTITUTION: The energy ratio of the traffic signal energy received previously from a base station to pilot signal energy is compared with the ratio of the currently received traffic signal energy to pilot signal energy. A power control command for a PCB(Power Control Bit) that was previously transmitted to the base station is estimated from the comparison result. A ratio off the full rate traffic energy to pilot energy is calculated from the PCB value corresponding to the estimated power control command and the previously estimated PCB value.

Description

Forward link power control method, and apparatus for the same in CDMA communication system

TECHNICAL FIELD The present invention relates to a communication system, and more particularly, to a forward power control apparatus and method for more efficiently controlling the power of a CDMA signal in a CDMA communication system.

In general, in a CDMA communication system, a forward link from a base station to a mobile terminal includes a pilot channel, and several traffic channels including a fundamental channel and a dedicated channel.

Of these forward link channels, pilot channels are decoded by all mobile terminals, but each traffic channel is decoded only by a specific mobile terminal. Thus, the pilot channel is encoded using a code known to the base station and all mobile terminals, while each traffic channel is encoded using a code known only to the base station and one specific mobile terminal.

The forward link also includes reverse power control indicators for pilot channels, multiple traffic channels, as well as reverse traffic channels. This power control identifier is periodically sent from the base station to the mobile terminal in order to control the transmit power of the mobile terminal. The power control identifier consists of several unencoded binary values.

The mobile terminal must adjust the transmission power according to the channel state change. For this purpose, the mobile terminal receives the power control identifier to increase or decrease the transmission power.

In the conventional CDMA communication system, only the reverse power control outlined above was possible.

However, recent Cdma2000 systems in accordance with the IS-2000.2 standard include forward power control as well as reverse power control. Thus, the reverse link includes a pilot channel and a forward power control indicator.

Forward power control herein refers to controlling transmission power of a base station, and the mobile terminal periodically transmits a power control identifier to the base station.

Forward power control includes inner loop power control and outer loop power control.

The outer loop power control determines the power control reference value based on the signal power to noise power ratio (Eb / Nt) for obtaining the frame error rate (FER) of the allocated forward link traffic channel.

In addition, the inner loop power control is to control the transmit power of the base station by transmitting the PCB to the base station through the reverse power control sub-channel, the mobile terminal is received to determine the PCB to transmit to the base station The signal power-to-noise power ratio (Eb / Nt) of the forward traffic channel is measured and compared with the power control reference value determined by the outer loop power control.

However, in the inner loop power control procedure, the signal power value per unit time of the forward traffic channel measured by the mobile terminal varies depending on the channel environment, but also varies because the forward link uses a variable rate rather than a fixed rate.

Therefore, the mobile terminal cannot distinguish whether the change in the signal power value is due to the change in the channel environment or the variable rate transmission.

As a result, in the conventional method, the signal-to-noise power ratio (Eb / Nt) was measured and used during the transmission period of the PCB transmitted at a constant level regardless of the rate change of the forward link in the mobile terminal.

Then, the mobile terminal compares the signal power to noise power ratio (Eb / Nt) measured during the transmission period of the PCB with the power control reference value determined by the outer loop power control, and when the measured value exceeds the power control reference value. Transmits a PCB for reducing the base station transmit power, and transmits a PCB for increasing the base station transmit power if the measured value is less than the power control reference value.

In the conventional forward power control described above, since the energy measurement interval of the power control subchannel used to measure the signal power to noise power ratio (Eb / Nt) is short, the accurate signal power to noise power ratio (Eb / Nt) This is difficult to measure. Therefore, as an alternative to this, there is a conventional method using not only a power control subchannel but also a pilot channel.

This method uses pilot energy, noise power, and the ratio of full-rate traffic energy to pilot energy in the transmission interval of the PCB. From these three values, the required signal power to noise power ratio (Eb / Nt) Obtain This is shown in Equation 1.

As can be seen from Equation 1, the value of the pilot energy And noise power The ratio of the full rate traffic energy to the pilot energy in the PCB transmission interval Multiply by to find the required signal power-to-noise power ratio (Eb / Nt).

In the case of obtaining the ratio of full rate traffic energy to pilot energy in the PCB transmission interval, not only the current traffic energy to pilot energy ratio but also the previously obtained ratio values are used together. In contrast, PCBs transmitted through traffic channels and pilot channels are observed in units of a power control group (PCG) section, and in particular, in order to use PCBs of four consecutive power control group (PCG) sections, Stores the value of the forward PCB in successive power control group (PCG) sections.

At this time, if the forward PCB of the previous three consecutive power control group (PCG) interval is the transmission power increase command, the value obtained by reducing the ratio of the previous traffic energy to pilot energy by the corresponding power increase and decrease step size. On the other hand, for the transmit power reduction command, a value obtained by increasing the ratio of previous traffic energy to pilot energy by the corresponding power increase / decrease step size is obtained. These values are summed with the ratio of the ratio of full rate traffic energy to pilot energy measured by observing the current power control group (PCG) intervals, thereby providing accurate signal-to-noise power ratio (Eb / Nt) of the forward traffic channel. ) Is obtained.

In this conventional power control, it is realized only under the assumption that the forward power control by the forward PCB transmitted in the previous power control group (PCG) section is applied directly in the subsequent next power control group (PCG) section.

In addition, the conventional power control has a disadvantage that it is normally realized under the assumption that the transmitted forward PCB is received at the base station without error and applied to power control for the forward traffic channel.

An object of the present invention has been made in view of the above, by using an estimated previous forward PCB that has been transmitted through the calculation, unlike the previous transfer PCB is stored and fed back and used for forward power control In addition, the present invention provides a high performance forward power control method applicable to a case in which forward power control by a forward PCB transmitted in a previous power control group (PCG) section does not immediately affect a subsequent next power control group (PCG) section. It also provides an apparatus for realizing this high performance forward power control method.

A characteristic of the forward power control method according to the present invention for achieving the above object is the ratio value of the traffic signal energy to the pilot signal energy ratio previously received from the base station and the ratio value of the currently received traffic signal energy to pilot signal energy. Comparing, estimating a power control command by a power control bit (PCB) previously transmitted to the base station according to the comparison result, and a power control bit (PCB) value corresponding to the estimated power control command And calculating a ratio of full rate traffic energy to pilot energy from other previously estimated and stored power control bit (PCB) values.

Preferably, after calculating the ratio of the full rate traffic energy to the pilot energy, the pilot power to noise power previously calculated in the calculated ratio of full rate traffic energy to pilot energy. The signal power to noise power ratio (Eb / Nt) used to multiply the ratio and determine the forward power control bit (PCB) transmitted to the next base station from the multiplication result.

Further, in the comparison result after the comparing step, if the currently received ratio value is increased by one power control group (1 PCG) interval compared to the previously received ratio value, the transmit power during the previous power control bit (PCB) transmission interval It is assumed that an increase command has been sent, whereas if it is decreased, it is assumed that a transmit power decrease command has been sent.

In addition, a feature of the forward power control apparatus according to the present invention for achieving the above object is the ratio of the ratio of traffic signal energy to pilot signal energy received from the base station and delayed by a predetermined period of time and the currently received traffic signal energy to pilot signal energy. Estimate a power control command by a power control bit (PCB) that would have been previously transmitted to the base station using a ratio value, and a power control bit (PCB) value corresponding to the estimated power control command and previously estimated and stored A first calculation block for calculating a ratio of full rate traffic energy to pilot energy from another power control bit (PCB) value, and a ratio for calculating the ratio of pilot power and noise power of the CDMA signal received from the base station; 2 calculation blocks, a calculation result of the first calculation block and a calculation result of the second calculation block A multiplying multiplier and a power control decision block for determining a forward power control bit (PCB) to be transmitted to the base station by comparing a signal power to noise power ratio (Eb / Nt) that is an output of the multiplier with a preset threshold; It is composed.

Preferably, the ratio of the traffic signal energy to the pilot signal energy and the ratio of the currently received traffic signal energy to the pilot signal energy received by the first calculation block by one power control group (1 PCG) interval is received. And a hard decision block for estimating a power control command by a power control bit (PCB) that has been previously transmitted to the base station according to the comparison result, and a power control corresponding to the power control command estimated at the hard decision block. A lookup table for storing a bit value (PCB) value and another previously estimated power control bit (PCB) value, and each coefficient corresponding to each power increase / decrease step size corresponding to the value stored in the register. LUT) and the currently received traffic signal energy versus pilot using the coefficients stored in the lookup table as tap coefficients. By combining the scale value of the arc energy it is linearly configured to include a FIR filter that.

1 is a block diagram showing some components of a mobile terminal for explaining a high performance forward power control procedure according to the present invention.

2 is a block diagram illustrating a general device configuration for obtaining a ratio of full rate traffic energy to pilot energy.

3 is a block diagram illustrating an apparatus configuration of the present invention for obtaining a ratio of full rate traffic energy to pilot energy.

* Description of the symbols for the main parts of the drawings *

10 receiver 21 complex despreader

22 Walsh despreader 23 dot multiplier

24: pilot filter 25: pilot power estimation unit

26: noise power estimation unit 30: symbol combining unit

40: PCB power coupling portion 50: pilot power coupling portion

60: noise power coupling unit 70: decoder

80: first calculation block 90: second calculation block

100: power control decision block 110: encoder

120: modulator 130: transmitter

Hereinafter, a preferred embodiment of a forward power control apparatus and method according to the present invention will be described with reference to the accompanying drawings.

In general, since the energy measurement interval of the power control subchannel used to measure the signal power to noise power ratio (Eb / Nt) is short, it is difficult to accurately measure the signal power to noise power ratio (Eb / Nt).

For this reason, a conventional method using not only a power control subchannel but also a pilot channel has been used. The present invention uses not only a power control subchannel but also a pilot channel.

1 is a block diagram illustrating some components of a mobile terminal for explaining a high performance forward power control procedure according to the present invention.

Referring to FIG. 1, a CDMA signal received by a mobile terminal is input to a complex despreader 21 through a receiver 10.

The complex despreader 21 despreads the received CDMA signal using a pseudo noise (hereinafter, abbreviated as PN) code.

This despread signal is processed in the symbol processing path, the pilot filter processing path, and the noise power calculation path, respectively.

First, in the symbol processing path, the Walsh despreader 22 despreads the signal despread by the short PN code back into the Walsh code. Thereafter, the dot multiplication unit 23 dot-dots a signal obtained by despreading the input signal and the weight obtained by the pilot filter 24 and outputs a symbol.

In the next pilot filter processing path, the signal despread with the short PN code is input to the pilot power estimator 25 after passing through the pilot filter 24, and the pilot power estimator 25 receives the pilot power from the input signal. Calculate

In the next noise power calculation path, the noise power estimator 26 calculates the noise power from the despread signal with the short PN code together with the signal passed through the pilot filter 24.

The processing of each of these paths is performed by several fingers, and if the symbols output from the symbol processing path of each finger are symbols of each PCB transmission interval, each PCB power corresponding to these symbols is transferred to the PCB power combiner 40. Are combined, on the other hand, if it is not a symbol of each PCB transmission interval is input to the symbol combining unit 30 and then combined.

The combined symbol at the symbol combiner 30 is transferred to the decoder 70, and the PCB power coupled at the PCB power combiner 40 is used to determine the forward PCB, which will be described later.

In addition, the pilot power and noise power calculated in the pilot filter processing path and the noise power calculation path of each finger are also combined by the pilot power combiner 50 and the noise power combiner 60, and then used to determine the forward PCB. .

The first calculation block 80 calculates a ratio of full rate traffic energy to pilot energy, the ratio value being the PCB power coupled at the PCB power combiner 40 and at the pilot power combiner 50. Obtained using the combined pilot power.

The second calculation block 90 calculates a ratio of pilot power to noise power, and the ratio value uses the pilot power coupled in the pilot power combiner 50 and the noise power coupled in the noise power combiner 60. Obtain it by

The ratio values obtained in these first calculation block 80 and the second calculation block 90 are multiplied and then passed to the power control decision block 100, which is the same principle as Equation 1 described above.

The power control decision block 100 determines the forward PCB to be transmitted to the base station by multiplying the input value after the multiplication with a preset signal power to noise power ratio (Eb / Nt) threshold (= power control reference value).

The forward PCB thus determined is transmitted to a modulator 120, and the forward PCB is punctured to a symbol of modulated user data and transmitted to the base station through the transmitter 130. In addition, the PCB obtained in the power control determination block 100 is input to the first calculation block 80 in the conventional case and used for the next PCB determination.

2 is a block diagram illustrating a general device configuration for obtaining a ratio of full rate traffic energy to pilot energy.

The device configuration of FIG. 2 is present inside the first calculation block 80 shown in FIG.

The two inputs A and B of the I channel block 200 are traffic signals and pilot signals. That is, input A is a full rate traffic signal and input B is a pilot signal.

In the I-channel block 200, the divider 210 divides the input full rate traffic signal into a pilot signal, and the divided ratio value is an infinite impulse response consisting of four taps; Hereinafter, the FIR is input to a square 230 through a filter 220. The square unit 230 squares an input ratio value.

The output of the I channel block 200 is summed with the output of the Q channel block 300.

In addition, the first calculation block 80 includes a register 400 for storing, by feedback, a previous forward PCB determined in the power control decision block 100, and a look up table (LUT) 410 is provided. A coefficient corresponding to each power increase / decrease step size corresponding to previous forward PCBs stored in this register 400 is stored. These coefficients are used as tap coefficients to linearly combine and output ratio values input by the FIR filter 220.

In order to use the apparatus configuration of FIG. 2 described above in forward power control, a feedback path in dotted lines is required in the configuration of FIG. 1.

However, the present invention does not require this feedback route. For a more clear description of this, see FIG. 3.

FIG. 3 is a block diagram illustrating an apparatus configuration of the present invention for obtaining a ratio of full rate traffic energy to pilot energy.

The device arrangement of FIG. 3 is also present inside the first calculation block 80 shown in FIG. 1, but without a feedback path provided with the previous forward PCB.

The two inputs A and B of the I channel block 500 are traffic signals and pilot signals. That is, input A is a full rate traffic signal and input B is a pilot signal.

In the I-channel block 500, the divider 510 divides the input full-rate traffic signal into pilot signals, and the divided ratio is squared through the FIR filter 520 composed of four taps. Input to a square 530. The square unit 530 squares an input ratio value.

The output of the I channel block 500 is summed with the output of the Q channel block 600.

In addition, in the first calculation block 80 according to the present invention, a delay unit Z for delaying the ratio of the input full rate traffic signal energy and pilot signal energy by one power control group (1 PCG) section (Z) ^-1 ) 710, and the hard decision block 700 determines the ratio of the traffic signal energy and the pilot signal energy at the full rate currently input by the delay unit 710. Compare with the previous ratio value delayed by 1 PCG section. The comparison result is stored in the register 720, and the lookup table (LUT) 730 stores the coefficient corresponding to each power increase / decrease step size corresponding to the value stored in the register 720. These coefficients are used as tap coefficients to linearly combine and output ratio values inputted by the FIR filter 520.

The forward power control procedure executed by the device configuration and operation described so far is described.

In the present invention, the ratio of the full rate traffic energy to the pilot energy calculated by the device configuration shown in FIG. 3 is multiplied by the ratio of the pilot power to noise power calculated in the second calculation block 90 of FIG. The required signal power to noise power ratio (Eb / Nt) is obtained.

Here, the ratio of full rate traffic energy to pilot energy is calculated as follows.

The hard decision block 700 of FIG. 3 compares the ratio of the ratio of the previous traffic signal energy to the pilot signal energy with the ratio of the ratio of the current traffic signal energy to the pilot signal energy. If increased, the transmit power increase command is assumed to be transmitted during the previous PCB transmission interval, while if decreased, the transmit power decrease command is assumed to be transmitted.

The PCB value corresponding to this estimated power control command is stored in register 720, and the corresponding coefficient of each power increase / decrease step size corresponding to the PCB value stored in this register 720 is the lookup table (LUT) 730. The FIR filter 520 uses the stored coefficients as tap coefficients to linearly combine and output the ratio values.

Finally, the FIR filter 520 averages the input ratio values according to each tap coefficient. As a result, the square of the mean in the I-channel block 500 and the square of the mean in the Q-channel block 600 are added to calculate the ratio of full rate traffic energy to pilot energy.

Then, the signal power to noise power ratio (Eb / Nt) obtained by multiplying the ratio of the full rate traffic energy to the pilot energy calculated above by the pilot power to noise power ratio calculated in the second calculation block 90. Is provided to the power control decision block 100 to determine the forward PCB to be sent to the base station next.

Using the forward power control device and the control method according to the present invention described above, the assumption that the forward PCB transmitted in the previous power control group (PCG) interval should be applied directly to the next power control group (PCG) consecutively You do not need this.

The existing method also applies under the assumption that the transmitted forward PCB is received at the base station without error. However, since the forward PCB transmission is transmitted without being encoded, the wrong PCB may be received at the base station due to a transmission error, which may result in incorrect power control. The present invention does not use the transmitted PCB, but actually measures the signal to which the forward power control is applied, thereby enabling more accurate power control.

As a result, the forward power control apparatus and the control method according to the present invention can be widely applied in a communication system of various and complex capabilities.

Claims (5)

Comparing the ratio of the ratio of the traffic signal energy to the pilot signal energy previously received from the base station and the ratio of the ratio of the currently received traffic signal energy to the pilot signal energy; Estimating a power control command by a power control bit (PCB) that was previously transmitted to the base station according to the comparison result; Calculating a ratio of full rate traffic energy to pilot energy from a power control bit (PCB) value corresponding to the estimated power control command and another power control bit (PCB) value previously estimated and stored; Forward forward power control method characterized in that it comprises a. The method of claim 1, wherein after calculating the ratio of full rate traffic energy to pilot energy: The calculated ratio of full rate traffic energy to pilot energy is multiplied by the previously calculated pilot power to noise power ratio and used to determine the forward power control bit (PCB) transmitted to the next base station from the multiplication result. And a signal power to noise power ratio (Eb / Nt) is calculated. The method of claim 1, wherein in the comparison result after the comparing step, If the currently received rate value is increased by one power control group (1 PCG) interval compared to the previously received rate value, then it is assumed that the transmit power increase command was transmitted during the previous power control bit (PCB) transmission interval, while And if it is decreased, estimates that a transmit power reduction command has been sent. By a power control bit (PCB) that has previously been transmitted to the base station by using the ratio of the traffic signal energy to the pilot signal energy received from the base station and delayed by a period of time and the ratio of the currently received traffic signal energy to pilot signal energy. Estimate a power control command, and calculate full rate traffic energy versus pilot energy from a power control bit (PCB) value corresponding to the estimated power control command and another power control bit (PCB) value previously estimated and stored. A first calculation block for calculating a ratio of A second calculation block for calculating a ratio of pilot power and noise power of the CDMA signal received from the base station; A multiplier for multiplying the calculation result of the first calculation block and the calculation result of the second calculation block; And a power control decision block for determining a forward power control bit (PCB) to be transmitted to the base station by comparing the signal power to noise power ratio (Eb / Nt), which is the output of the multiplier, with a preset threshold. Forward power control device. The method of claim 4, wherein the first calculation block, The ratio of the ratio of the traffic signal energy to the pilot signal energy received from the base station and delayed by one power control group (1 PCG) interval is compared with the ratio of the ratio of the currently received traffic signal energy to the pilot signal energy. A hard decision block for estimating a power control command by a power control bit (PCB) that has been transmitted to the base station at A register for storing a power control bit (PCB) value corresponding to the power control command estimated in the hard decision block and another power control bit (PCB) value previously estimated; A look-up table (LUT) for storing each coefficient corresponding to each power increase / decrease step size corresponding to the value stored in the register; And a FIR filter that linearly combines and outputs the ratio of the currently received traffic signal energy to pilot signal energy using the coefficients stored in the lookup table as tap coefficients. .