JP2003018089A - Radio communication device and transmission power control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio communication device that can keep desired reception quality, independently of the magnitude of fluctuations in a propagation environment in outer loop transmission power control. SOLUTION: A frame error detection section 104 detects the presence of an error by each frame, a symbol error rate measurement 105 measures the SER(symbol error rate) by each frame, an update amount decision section 106 determines increase or decrease in a target SIR(signal-to-interference ratio), on the basis of the presence of the frame error detected by the frame error detection section 104 and determines an update amount (increased or decreased amount) of the target SIR, on the basis of the SER measured by the symbol error rate measurement 105 and a target SIR update section 107 updates the target SIR by the update amount determined by the update amount decision section 106.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a wireless communication device and a transmission power control method.

[0002]

2. Description of the Related Art CDMA (Code Division Multiple Acc
In ess) mobile communication, channels of a plurality of mobile station users are mixed in the same frequency band. Therefore, if there is a signal transmitted with more power than necessary, the signal interferes with the signal of another mobile station, which deteriorates the reception quality of the other mobile station. Therefore, transmission power control is important in CDMA mobile communication.

Outer loop transmission power control is one of the transmission power control methods. In the outer loop transmission power control, for example, in order to keep the reception quality such as FER (Frame Error Rate) constant, the target SIR (Signal
al to Interference Ratio; signal power to interference power ratio) is varied, and the variable target SIR and received signal SIR
The transmission power control is performed according to the result of comparison with (hereinafter referred to as "reception SIR"). The target SIR is controlled so as to follow the SIR required to maintain the desired reception quality (hereinafter referred to as "required SIR"). Also, the required SI
It is known that R varies temporally according to the variation of the propagation environment.

As the outer loop transmission power control, for example, the 1999 IEICE General Conference B-5-
145 ', the periodic control method (Period
ic control) and Instantaneous control
There is.

In the periodic control method, F is calculated every predetermined number of frames.
The ER is measured and compared with the target FER. If the measured FER is equal to or higher than the target FER, the target SIR is increased by a predetermined amount, and if the measured FER is less than the target FER,
The target SIR is reduced by a predetermined amount.

In the immediate control method, the presence or absence of an error is checked for each frame, and if there is an error in the frame, the target S
The IR is increased by a predetermined amount, and if there is no error in the frame, the target SIR is decreased by the predetermined amount. Target SIR
The amount of increase and the amount of decrease are determined in advance during system design so that the increase and decrease of the target SIR are balanced in a steady propagation environment.

[0007]

However, in the above-described conventional outer loop transmission power control, the increase amount and the decrease amount of the target SIR are fixed values. Therefore, in a situation where the propagation environment changes greatly, that is, the required SIR changes greatly, the target SIR cannot quickly follow the required SIR, and as a result, the reception quality cannot be maintained at the desired quality.

As a countermeasure against this, it is conceivable to set the increase amount and the decrease amount of the target SIR in advance to be large. However, in this case, when the fluctuation of the propagation environment is small, the increase amount and the decrease amount of the target SIR become larger than the fluctuation of the required SIR, and as a result, the reception quality cannot be maintained at the desired quality as described above.

The present invention has been made in view of the above circumstances, and in outer loop transmission power control, a radio communication apparatus capable of maintaining a desired reception quality regardless of the magnitude of fluctuations in the propagation environment, and An object is to provide a transmission power control method.

[0010]

A wireless communication apparatus of the present invention comprises an error detecting means for detecting the presence / absence of an error for each predetermined transmission unit, a fluctuation detecting means for detecting the magnitude of fluctuation in the propagation environment, and an error. An updating unit that determines whether to increase or decrease the target value of the signal power to interference power ratio depending on the presence or absence of the signal, determines the amount of increase or decrease of the target value according to the magnitude of the fluctuation of the propagation environment, and then updates the target value with the amount of increase or decrease. A generation means for generating transmission power control information according to a result of comparison between the updated target value and the signal power-to-interference power ratio of the received signal; and a transmission means for transmitting the transmission power control information to a communication partner. Adopt a configuration that has.

According to this configuration, since the update amount of the target value is adaptively changed according to the change in the propagation environment, the reception quality can be maintained at a desired quality regardless of the magnitude of the change in the propagation environment. it can.

In the radio communication apparatus of the present invention, the fluctuation detecting means detects the magnitude of fluctuation of the propagation environment by measuring the error rate for each predetermined transmission unit, and the updating means detects an error when there is an error. The increase amount is increased as the error rate is higher, and when there is no error, the decrease amount is increased as the error rate is lower and the target value is updated.

According to this configuration, the magnitude of the fluctuation of the propagation environment is detected by the error rate, and the increase / decrease amount of the target value is adaptively changed according to the error rate. The amount of increase or decrease of the target value can be increased.

In the wireless communication device of the present invention, the fluctuation detecting means detects the magnitude of fluctuation in the propagation environment by obtaining the amount of change in the moving speed of the communication terminal device for each predetermined transmission unit, and the updating means, When there is an error, the increase amount is increased as the change amount is larger, and when there is no error, the decrease amount is increased as the change amount is increased and the target value is updated.

According to this structure, the magnitude of the fluctuation of the propagation environment is detected by the change amount of the moving speed of the communication terminal device,
Since the increase / decrease amount of the target value is adaptively changed according to the change amount of the moving speed, the increase / decrease amount of the target value can be increased in a section where the fluctuation of the propagation environment is large.

The base station apparatus of the present invention has a configuration in which any one of the above radio communication apparatuses is mounted. A communication terminal device of the present invention has a configuration in which any one of the above wireless communication devices is mounted.

According to these configurations, since any one of the above-mentioned wireless communication devices is mounted, the same effect as described above is exhibited in the base station device and the communication terminal device.

The transmission power control method of the present invention comprises an error detection step of detecting the presence / absence of an error for each predetermined transmission unit, a fluctuation detection step of detecting the magnitude of fluctuation in the propagation environment, and a signal power depending on the presence / absence of an error. After updating the target value of the interference power ratio and updating the target value with the amount of increase and decrease of the target value according to the magnitude of the fluctuation of the propagation environment A generation step of generating transmission power control information according to a result of comparison between the target value and the signal power to interference power ratio of the received signal, and a transmission step of transmitting the transmission power control information to a communication partner are provided. .

According to this method, since the update amount of the target value is adaptively changed according to the variation of the propagation environment, the reception quality can be maintained at the desired quality regardless of the magnitude of the variation of the propagation environment. it can.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The essence of the present invention is to adaptively change the update amount of the target SIR according to the fluctuation of the propagation environment. That is, in the present invention, the increase or decrease amount of the target SIR is increased in the section where the fluctuation of the propagation environment is large, and the target SIR is increased.
The IR can quickly follow the required SIR. By this means, it is possible to maintain the reception quality at the desired quality.

(Embodiment 1) In the present embodiment, a case will be described in which the magnitude of fluctuation in the propagation environment is detected by an error rate and the target SIR increase / decrease amount is adaptively changed according to the error rate. . In the following description, SER (Symbol Error Rate) is used as an example of the error rate, but the usable error rate is not limited to this. For example, instead of SER, BER (Bit Erro
r Rate) can be used in the same manner.

When there is no fluctuation in the propagation environment, that is, when the level fluctuation, the phase fluctuation, and the Doppler frequency fluctuation that the signal transmitted from the transmitter receives in the propagation path are constant, the outer loop transmission power control controls the signal The transmission power converges to a transmission power that keeps the FER on the receiver side at a desired FER. Further, at this time, since there is no change in the propagation environment, the reception quality of each symbol in the frame also becomes constant, so that the SER is also kept constant.

On the other hand, when the propagation environment fluctuates in the direction of deteriorating the reception quality, the FER temporarily becomes high on the receiver side and the SER in the frame also temporarily becomes high. On the contrary, when the propagation environment fluctuates in the direction of improving the reception quality, the FER temporarily becomes low on the receiver side, and the SER in the frame also temporarily becomes low. Also, the greater the deterioration of the reception quality, the higher the SER, and the greater the improvement of the reception quality, the lower the SER.

Here, the term "temporary" means that the outer loop transmission power control causes the transmission power to be increased and the reception quality to be improved when the propagation environment changes in the direction of degrading the reception quality, and conversely, When the propagation environment changes to improve the reception quality, the transmission power decreases and the reception quality deteriorates. After a while, the SER becomes the original SER.
It will be constant after returning to.

Therefore, under the outer loop transmission power control, the magnitude of the fluctuation of the propagation environment can be grasped by the SER. Therefore, in the present embodiment, the increase / decrease amount of the target SIR is adaptively changed according to SER as follows. FIG. 1 is a block diagram showing a configuration of a wireless communication device according to the first exemplary embodiment of the present invention.

In the radio communication apparatus shown in FIG. 1, reception section 102 performs radio processing, despreading processing and demodulation processing on a signal received via antenna 101. The demodulated signal is input to error correction decoding section 103, symbol error rate measurement section 105 and SIR measurement section 108.

The error correction decoding unit 103 performs error correction decoding on the received signal based on, for example, the Viterbi algorithm. The data after error correction decoding is input to the frame error detection unit 104 and the symbol error rate measurement unit 105. In the frame error detection unit 104, CRC (Cy
Clic Redundancy Check) and the like detect the presence or absence of an error for each predetermined transmission unit, that is, for each frame.
The signal indicating the presence / absence of a frame error is the update amount determination unit 106.
Entered in.

The symbol error rate measuring section 105 measures the SER for each predetermined transmission unit, that is, for each frame. In other words, the variation amount of the propagation environment in one frame section is measured. Symbol error rate measuring section 105 compares the symbol obtained by re-encoding the bit after error correction decoding with the received symbol input from receiving section 102, and if they are different, an error occurs in that symbol. It is judged that it was done. Then, the ratio of the number of symbols in which an error has occurred to the number of symbols included in one frame is measured as SER. The signal indicating the measured SER is input to the update amount determination unit 106.

The update amount determination unit 106 determines whether the target SIR is increased or decreased depending on the presence or absence of the frame error detected by the frame error detection unit 104, and the target SIR is updated from the SER measured by the symbol error rate measurement unit 105. The amount (increase or decrease) is determined. That is, the target S
The IR is updated for each frame. A signal indicating the determined update amount is input to the target SIR update unit 107. A detailed description of determining the target SIR update amount will be given later.

In the target SIR updating unit 107, the target SIR used at the time of the previous generation of power control information is updated by the update amount determined by the update amount determining unit 106, and the target SIR used at the time of generating the power control information this time. Is required. The signal indicating the updated target SIR is the power control information generation unit 1
09 is input.

SIR measuring section 108 measures the received SIR for each transmission power control slot. The signal indicating the received SIR is input to power control information generating section 109. In the power control information generation unit 109, power control information for instructing the communication partner to increase or decrease the transmission power according to the comparison result of the reception SIR and the target SIR (for example, 1-bit information increases “1”, increases “0”). 'Indicates a decrease) is generated.
That is, the power control information is generated for each transmission power control slot, and when the received SIR is equal to or higher than the target SIR,
Power control information instructing a decrease in transmission power is generated, and conversely, when the reception SIR is less than the target SIR, power control information instructing an increase in transmission power is generated. The generated power control information is input to the transmission unit 110. In addition,
Usually, the length of the transmission power control slot is set to be shorter than the frame length (for example, a 20 ms frame includes 16 slots).

In transmission section 110, after the power control information is mapped to the transmission signal, the signal is subjected to radio processing. The signal to which the power control information is mapped is transmitted to the communication partner via the antenna 101. In the communication partner,
The transmission power is controlled according to the received power control information. As described above, the outer loop transmission power control according to the present embodiment is performed between the wireless communication devices.

Next, the determination of the update amount of the target SIR will be described in detail. As described above, the update amount determination unit 10
6, the increase or decrease of the target SIR is determined depending on the presence or absence of the frame error detected by the frame error detection unit 104, and the SER measured by the symbol error rate measurement unit 105.
From this, the update amount (increase amount or decrease amount) of the target SIR is determined. That is, the increase amount D _inc is obtained when there is a frame error, and the decrease amount D _dec is obtained when there is no frame error.

As described above, the greater the deterioration of the reception quality, the higher the SER, and the greater the improvement of the reception quality, the lower the SER. Therefore, the update amount determination unit 106, if there is a frame error, S
The higher the ER, the larger the increase amount D _inc of the target SIR,
If there is no frame error, the lower the SER, the target S
Increase the IR reduction amount D _dec .

As a specific example, the update amount determination unit 106 has a table as shown in FIG. 2, which shows the correspondence relationship between the SER and the increase amount D _inc and the decrease amount D _dec of the target SIR,
The increase amount D _inc and the decrease amount D _dec are determined with reference to these tables. That is, the update amount determination unit 106
When there is a frame error, the increase amount D _inc is determined based on SER by referring to the table shown in FIG. In FIG. 2A, A>B> C, and k> l.
>M> n. For example, when there is a frame error and C ≦ SER <B, the update amount determination unit 106 determines the increase amount D _{in c} of the target SIR as m.

Further, when there is no frame error, the update amount determining unit 106 refers to the table shown in FIG. 2B to determine the decrease amount D _dec based on SER. Figure 2
In (b), A '>B'> C ', and k'> l '>
m '>n'. For example, when there is no frame error and C ′ ≦ SER <B ′, the update amount determination unit 106 determines the target SIR reduction amount D _dec as 1 ′.

Here, although the increase amount D _inc and the decrease amount D _dec are determined using a table, the increase amount D _inc and the decrease amount D _dec are defined as a function of SER, and a predetermined calculation formula is used. You may ask.

As described above, by determining the target SIR update amount by the SER, the target SIR update amount can be adaptively changed according to the magnitude of the fluctuation of the propagation environment. This makes it possible to cause the target SIR to quickly follow the required SIR even when the propagation environment greatly changes.

The tracking state of the target SIR with respect to the change of the required SIR is shown in FIG. In FIG. 3, 201 shows a change in the required SIR, 202 shows a change in the target SIR in the present invention, and 203 shows a change in the target SIR in the conventional example.

In the conventional example, the increase amount and the decrease amount of the target SIR are fixed values. Therefore, as shown in FIG. 3, the propagation environment changes greatly, that is, the required SIR (201)
In a situation in which fluctuates greatly, the target SIR (203) cannot quickly follow the required SIR (201). In FIG. 3, in particular, in t ₀ ~t _5, target SIR (20
3) cannot follow the required SIR (201).

On the other hand, in the present invention, the increase amount and the decrease amount of the target SIR are adaptively changed according to the magnitude of the fluctuation of the propagation environment. Therefore, as shown in FIG. 3, even if the propagation environment fluctuates greatly, that is, the required SIR (201) fluctuates greatly, the target SI can be adjusted according to the magnitude of the fluctuation.
To change the increase and decrease of R, the target SIR
(202) can quickly follow the required SIR (201).

Here, error correction decoding is usually performed in a wireless communication apparatus used in mobile communication. Therefore, even if there is an error in the symbol before decoding, the error may be corrected and the frame error may not be detected. For example, S
Even if the ER is relatively high, it may be possible to sufficiently correct the error if the error occurs randomly in the frame. In other words, the presence or absence of frame error is determined by SER.
It cannot be judged directly from. Also, what is desired to be kept constant in the wireless communication device is usually the reception quality (that is, FER) in frame units. Therefore, in the present embodiment, first, the target SIR is determined according to the presence / absence of a frame error.
To either increase or decrease, then SER
The update amount is decided by. By this means, it is possible to maintain the desired reception quality on a frame-by-frame basis in consideration of error correction.

As described above, according to the present embodiment, the magnitude of the fluctuation of the propagation environment is detected by the error rate, and the increase / decrease amount of the target SIR is adaptively changed according to the error rate. The increase / decrease amount of the target SIR can be increased as the section in which the environment changes greatly. As a result, the target S
The IR can be made to quickly follow the required SIR, and as a result, the reception quality can be maintained at the desired quality regardless of the magnitude of fluctuations in the propagation environment.

(Embodiment 2) In the present embodiment, the magnitude of fluctuation in the propagation environment is detected by the amount of change in the moving speed of the communication terminal device, and the target SIR is detected in accordance with the amount of change in the moving speed.
A case of adaptively changing the increase / decrease amount of will be described.

When the communication partner is moving, the larger the change in moving speed, the greater the change in the propagation environment, resulting in a large change in the required SIR. In addition, when the communication partner stops or moves at a constant speed, the propagation environment becomes steady.

Therefore, in this embodiment, the increase / decrease amount of the target SIR is adaptively changed according to the change amount of the moving speed as follows. FIG. 4 is a block diagram showing the configuration of the wireless communication device according to the second exemplary embodiment of the present invention. In addition, in FIG. 4, the same components as those in the first embodiment (FIG. 1) are denoted by the same reference numerals as those in FIG. 1, and detailed description thereof will be omitted.

In the wireless communication device shown in FIG. 4, the moving speed detecting section 301 detects the moving speed of the communication terminal device at every predetermined time, and calculates the amount of change in the moving speed in the predetermined time from the difference in moving speed. . Since the update amount determination unit 302 updates the target SIR for each frame, the predetermined time is also set to the frame length accordingly. Therefore, the moving speed detection unit 301 calculates the variation amount of the propagation environment in one frame section. A signal indicating the change amount of the moving speed is input to the update amount determination unit 302.

As a method of detecting the moving speed, a method of estimating the fading cycle from the envelope shape of the received signal to detect the moving speed, or a GPS (Global Positioning S
ystem) A method of detecting the moving speed by obtaining the moving amount per unit time from the position information obtained by the receiver, and the like, are not limited to these methods.

The update amount determining unit 302 determines the update amount (increase amount or decrease amount) of the target SIR. A signal indicating the determined update amount is input to the target SIR update unit 107. The update amount of the target SIR is specifically determined as follows.

That is, the update amount determination unit 302 determines whether the target SIR is increased or decreased depending on the presence or absence of the frame error detected by the frame error detection unit 104, and the change amount of the moving speed calculated by the moving speed detection unit 301. From this, the target SIR update amount is determined. That is, the increase amount D _inc is obtained when there is a frame error, and the decrease amount D _dec is obtained when there is no frame error.

Further, as described above, the greater the change in moving speed, the more the propagation environment fluctuates. As a result, the required S
IR fluctuates greatly. Therefore, the update amount determination unit 302
Increases the increase amount D _inc and the decrease amount D _dec of the target SIR as the moving speed change amount increases.

As a specific example, the update amount determination unit 302 uses the change amount (ΔV) of the moving speed and the target SI as shown in FIG.
It has a table showing the correspondence relationship between the increase amount D _inc and the decrease amount D _{dec of} R, and referring to this table, the increase amount D _inc
And the reduction amount D _dec is determined. That is, the update amount determination unit 302 determines the increase amount D _inc based on the change amount of the moving speed when there is a frame error, and decreases the increase amount D _inc based on the change amount of the moving speed when there is no frame error. Amount D
Decide on _dec . In FIG. 5, A>B> C, and
k>l>m> n. For example, the update amount determination unit 302
Determines that the increase amount D _inc of the target SIR is m when there is a frame error and C ≦ SER <B.

In the table shown in FIG. 5, the increase amount D
_Inc and decrease amount D _dec are set to the same amount, but increase amount D
_{The inc} and the decrease amount D _dec may be different. In addition, here, the increase amount D _inc and the decrease amount D _dec are determined using the table, but the increase amount D _inc and the decrease amount D _dec are defined as a function of the change amount of the moving speed, and the predetermined calculation formula is used. You may ask by.

As described above, according to the present embodiment, the magnitude of the fluctuation of the propagation environment is detected by the change amount of the moving speed of the communication terminal device, and the target SI is changed according to the change amount of the moving speed.
Since the increase / decrease amount of R is adaptively changed, the increase / decrease amount of the target SIR can be increased in a section where the fluctuation of the propagation environment is large. By this means, the target SIR can be made to quickly follow the required SIR, and as a result, the reception quality can be maintained at the desired quality regardless of the magnitude of fluctuations in the propagation environment.

The radio communication apparatus of the present invention can be applied to a communication terminal apparatus such as a base station apparatus or a mobile station apparatus used in a digital radio communication system such as a mobile communication system.

[0056]

As described above, according to the present invention,
In outer loop transmission power control, the reception quality can be maintained at a desired quality regardless of the magnitude of fluctuations in the propagation environment.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a wireless communication device according to a first exemplary embodiment of the present invention.

FIG. 2 is a table included in an update amount determination unit of the wireless communication device according to the first exemplary embodiment of the present invention.

FIG. 3 is a diagram showing a tracking state of a target SIR with respect to a change in required SIR.

FIG. 4 is a block diagram showing a configuration of a wireless communication device according to a second exemplary embodiment of the present invention.

FIG. 5 is a table included in an update amount determination unit of the wireless communication device according to the second exemplary embodiment of the present invention.

[Explanation of symbols]

101 antenna 102 receiver 103 error correction decoding unit 104 frame error detector 105 Symbol error rate measurement unit 106, 302 update amount determination unit 107 Target SIR update unit 108 SIR measurement unit 109 power control information generator 110 transmitter 301 Moving speed detector

Claims (6)

[Claims] 1. An error detecting means for detecting the presence / absence of an error for each predetermined transmission unit, a fluctuation detecting means for detecting the magnitude of fluctuation of a propagation environment, and a target value of a signal power to interference power ratio depending on the presence / absence of an error. And an increase / decrease of the target value according to the magnitude of the fluctuation of the propagation environment, and an updating means for updating the target value with the increase / decrease amount, and the updated target value and the signal of the received signal. A wireless communication apparatus comprising: a generation unit that generates transmission power control information according to a result of comparison with a power-to-interference power ratio, and a transmission unit that transmits the transmission power control information to a communication partner. 2. The fluctuation detecting means detects the magnitude of fluctuation of the propagation environment by measuring the error rate for each predetermined transmission unit, and the updating means, if there is an error, the higher the error rate is. The wireless communication device according to claim 1, wherein the increase amount is increased, and when there is no error, the decrease amount is increased as the error rate is lower, and the target value is updated. 3. The fluctuation detecting means detects the magnitude of fluctuation in the propagation environment by obtaining the amount of change in the moving speed of the communication terminal device for each predetermined transmission unit, and the updating means detects the magnitude of the fluctuation in the propagation environment. , The larger the change amount, the larger the increase amount,
If there is no error, the decrease amount is increased as the change amount is increased, and the target value is updated.
The wireless communication device described. 4. A base station device comprising the wireless communication device according to claim 1. 5. A communication terminal device, comprising the wireless communication device according to claim 1. 6. An error detection step of detecting the presence / absence of an error for each predetermined transmission unit, a fluctuation detection step of detecting the magnitude of fluctuation in the propagation environment, and a target value of a signal power to interference power ratio depending on the presence / absence of an error. And an increase / decrease of the target value according to the magnitude of the fluctuation of the propagation environment, and an updating step of updating the target value with the increase / decrease amount, and the updated target value and the signal of the received signal. A transmission power control method comprising: a generation step of generating transmission power control information according to a result of comparison with a power to interference power ratio; and a transmission step of transmitting the transmission power control information to a communication partner.