JPH0613956A - Transmission power controller in mobile communication and its system - Google Patents

Abstract

PURPOSE:To increase the capacity of the system by implementing accurate transmission power control at a mobile set side. CONSTITUTION:A control processor 32 detects received power and the reception power is calculated from a strength of a pilot signal fed from a searcher receiver 30 in this case. Thus, the signal strength of a transmission signal from a base station from which a mobile set is communicated is accurately detected. Furthermore, a fading speed is estimated from a change in the received power thereby controlling an averaging time in a transmission power controller 28. Thus, the system copes even with a change in the fading speed and the optimum averaging time is always obtained. Then an electric field median strength is always detected without causing a response delay and accurate transmission power control is attained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to transmission power control in mobile communication using a CDMA (code division multiple access) system.

[0002]

2. Description of the Related Art With the recent advances in electronic communication technology, mobile communication such as car phones and mobile phones has become widespread. Also in the field of mobile communication, digital communication has been studied and various communication systems have been studied.
One of such methods is a CDMA (Code Division Multiple Access) method, which has attracted attention because it has characteristics such as assigning a plurality of mobile units to the same frequency range and easy confidentiality. There is.

In this CDMA system (particularly, direct sequence spread spectrum: CDMA system using DS / SS), in addition to a transmitter, a receiver, and a modulator / demodulator that perform normal radio communication, spread spectrum is performed using a PN code or the like. A spreading means is required, and a despreading means for despreading the PN code is needed.

In the CDMA system, it is necessary to take out a signal that is spectrum-spread with a specific code from a plurality of spread signals in the same frequency band and demodulate it. In a CDMA system, in transmission from a base station to a mobile unit (forward link), a pseudo random code having a different phase shift for each base station is used as a spreading code so that the mobile unit can identify the base station, and each channel Are multiplexed by an orthogonal function (a function having a cross-correlation of 0) and transmitted. A pilot signal is also included therein, and the mobile uses this pilot signal for initial acquisition and synchronization.

Further, in the transmission from the mobile unit to the base station (reverse link), a pseudo random code without offset,
A spread code is a combination of a pseudo random code specified for each user. Since each mobile has a different distance from the base station, it is difficult for the base station to synchronize the transmission signals of all the mobiles, and it is impossible to maintain orthogonality between the mobiles. It is possible. Since the spreading code is determined in consideration of such a point, mutual interference is sufficiently small if the overlapping positions are simply shifted. However, in addition to such interference, if there is a large difference in the received power from the mobile unit at the base station, the mobile unit with a large received power causes a large interference with the mobile unit with a small received power. Will be given. Even in such a situation, it has a transmission power control means for keeping the intensity of the received power from each mobile unit constant.

[0006] Here, the change in the received power in mobile communication includes a loss (path loss) based on the distance of the radio wave propagation path.
There are two types, one is the same on the mobile side and the base station side due to loss (shadowing) caused by radio wave shields such as buildings existing in the propagation path, and the other is on the mobile side and the base station side due to Rayleigh fading. .

For the same intensity change on the mobile unit side and the base station side, the mobile unit measures the received power intensity of the radio wave transmitted from the base station, and this is measured for a time sufficient to eliminate the effects of Rayleigh fading. By averaging and detecting the averaged median value and controlling the transmitted field intensity based on this, the received field intensity at the base station is brought close to a fixed value (this is called open loop control). Specifically, the AGC circuit of the IF signal (intermediate frequency signal obtained by down-converting the received radio frequency signal (RF signal)) at the input stage of the receiver (in order to avoid inputting an excessive signal to the subsequent stage, Received power is detected from the signal about the gain of the circuit that controls the gain of the amplifier according to the strength) and the signal strength of the signal frequency band after passing through the band pass filter (filter that passes only the desired frequency band). The transmission power is controlled according to.

On the other hand, there is a case where the reception power increases rapidly like when a mobile body is out of the shadow of a building. In this case, other transmissions are greatly affected, and therefore the transmission power must be promptly reduced. I have to. Therefore, in order to deal with such a case, the averaging time for obtaining the above-mentioned median value is set to be short with respect to an increase in received power. That is, for a decrease in transmission power (increase in reception power),
Shorter averaging time and higher transmission power (reception power reduction)
For, the averaging time is set to be long and open-loop transmission power control is performed.

On the other hand, open-loop control cannot deal with different electric field strengths on the mobile side and the base station side such as Rayleigh fading. Therefore, in order to deal with this, the base station detects the received electric field strength from each mobile station, and based on this received electric field strength, a command (power control command) for correcting the transmission power is moved to the mobile station side. Send to the station. Then, the mobile body controls the transmission power on the basis of this power control command to make the received electric field strength at the base station desired (this is called closed loop control). The power control command commands whether to increase or decrease the power.
It is transmitted once every 25 msec. Also, with one control ±
The control of about 1 dB is performed around the open loop power control.

By performing such transmission power control, it is possible to reduce the interference by making the strength of the received signal from each mobile unit in the base station equal. Therefore, it becomes possible to communicate with more mobile units,
The capacity of the system can be maximized.

Regarding the transmission / reception equipment and the conventional transmission power control on the mobile side and the base station side (cell site) of the CDMA system, for example, US Pat. No. 5,103,459 and WO 91/07037 are disclosed. Is shown in.

[0012]

However, the conventional transmission power control has the following problems. (A) Received power also includes transmission signals from other base stations, and the transmission signal strength from other base stations is particularly high near the boundary of the jurisdiction range (cell) of the base station. . Therefore, the transmission power control for the target base station becomes inappropriate. Note that, theoretically, this should be solved by closed loop control, but as described above, the amount of power changed by one command by the power control command is limited, so the correction limit is exceeded. there is a possibility.

(B) Since the Rayleigh fading varies depending on the speed of the moving body, the open loop transmission power control may follow Rayleigh fading depending on the fading speed because the average time is too short.
If the averaging time is set too long, it becomes impossible to follow the change in the median fading value.

(C) The power control command is inserted into normal communication data on the forward link and is sent once every 1.25 msec on average, but its insertion position (sending timing) is randomized. Also, in the reverse link, during a silent period, the mobile body does not perform continuous transmission but performs burst transmission, and the transmission timing is also randomized. For example, 20ms
In the ec frame, there are 16 slots of 1.25 msec unit, but in the case of full rate, all 16 slots are transmitted, and in the case of 1/2 rate, 16 slots are transmitted.
Send slots to 8 of the 8 slots. And the phase of that slot is randomized. The transmission rates are full rate, 1/2 rate, 1/4 rate, 1 /
There are 8 rates. Therefore, the time until the base station recognizes the received power from the mobile unit and the mobile unit receives the power control command varies. Therefore, the time for which the transmission power control is performed in accordance with the power control command is not constant, and the control timing may shift, which may prevent accurate transmission power control. Especially, when the fading speed is high, this problem becomes large.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a transmission power control apparatus in mobile communication and a system thereof capable of performing suitable transmission power control in accordance with the situation of the mobile body. To do.

[0016]

A transmission power control apparatus for mobile communication according to the present invention extracts a pilot signal for each base station from a received signal and detects a signal level of the extracted pilot signal. It is characterized by having a receiver and a transmission power control means for controlling the transmission power according to the signal level from the searcher receiver.

Further, there are provided level detecting means for detecting the signal level of the received signal, and averaging means for averaging the detected signal level of the received signal for a predetermined averaging time to obtain an average received signal level. Depending on the average signal level, the transmission power control means for controlling the transmission power, the fading speed detection means for detecting the fading speed from the change in the signal level of the received signal, the averaging time according to the obtained fading speed And averaging time control means for changing.

Further, level detection means for detecting the signal level of the received signal, history storage means for storing the obtained signal level history of the received signal, and signal of the received signal after a predetermined time from the stored history Predicting means for predicting the level, creating means for creating a power control command for transmission power control on the signal transmitting side according to the predicted signal level, and transmitting means for sending the created power control command It is characterized by having.

Further, the prediction means is characterized in that the prediction is performed by linear prediction from the contents of the stored history.

Further, the fading speed detecting means is
It is characterized in that the change state of the received signal level is examined and detected based on the number of times the received signal level crosses a fixed value within a predetermined time.

Further, a pilot signal is extracted from the received signal, the searcher receiver for detecting the signal level of the extracted pilot signal, and the signal level from this searcher receiver are averaged for a predetermined averaging time, and then averaged. Averaging means for obtaining a signal level, according to the obtained average signal level, a transmission power control means for controlling the transmission power, a fading speed detection means for detecting a fading speed from a change in the signal level from the searcher receiver,
Averaging time control means for changing the averaging time according to the obtained fading speed.

Further, the present invention is a transmission power control system for controlling the transmission power on the mobile side in mobile communication between the base station and the mobile, and the base station side is sent from the mobile. Signal level detecting means for detecting the received signal level of the radio wave, history storage means for storing the history of the signal level of the obtained received signal, and predicting the signal level of the received signal after a predetermined time from the stored history The mobile unit has a prediction unit, a creation unit that creates a power control command for transmission power control on the signal transmission side according to the predicted signal level, and a transmission unit that sends the created power control command. The body side extracts the pilot signal from the received signal and detects the signal level of the extracted pilot signal, and the signal from this searcher receiver. Bells are averaged for a predetermined averaging time to obtain an average signal level, and the transmission power is determined according to the average signal level, and the determined transmission power is changed according to the power transmission command. And a transmission power control means for controlling the transmission power.

[0023]

As described above, according to the present invention, since the received power is detected by using the pilot signal, the transmitted power can be controlled with respect to the received signal power of only the base station of the own station. Power control can be performed. Further, since the fading speed is estimated and the time for averaging the received signal power is determined according to the fading speed, the averaging can always be performed at an appropriate time, and the median value of the fading electric field can be estimated. Therefore, the open loop control can be appropriately performed, and the transmission power can be increased without increasing the system interference. Further, it is possible to prevent deterioration of the transmission characteristics of the own station without increasing system interference.

Further, on the side of the base station, the future situation of the radio wave from the mobile body received at the base station is predicted,
Since the power control command is transmitted, by controlling the transmission power according to the power control command, it is possible to accurately control the reception power on the base station side. As a result, the transmission power control becomes accurate, and the transmission characteristics are improved and the line capacity is increased.

[0025]

Embodiments of the present invention will be described below with reference to the drawings.

Configuration on Mobile Side FIG. 1 is a block diagram showing the overall configuration of a mobile unit to which the transmission control device according to the present invention is applied. In the figure,
The antenna 10 receives a radio wave including at least a frequency used for communication. This antenna 10
The analog receiver 12 is connected to the analog receiver 12, and the analog receiver 12 converts (down-converts) the received radio wave into an intermediate frequency, obtains an IF signal, and selects a signal of a predetermined frequency only in a band. Further, the AGC means controls so that the signal level of the output IF signal becomes constant. A digital data receiver 14 is connected to the analog receiver 12, and the digital data receiver 14
Converts analog signals to digital data, synchronous detection,
Processing such as spectrum despreading is performed. The user digital baseband circuit 20 is connected to the digital data receiver 14, and the user digital baseband circuit 20 is connected.
Performs data demodulation and the like to obtain an audio signal through an interface such as a voice signal. Then, this audio signal is supplied to the handset 22, and the audio signal is reproduced. Ie handset 2
The voice received from the second speaker is output.

On the other hand, the handset 22 is also provided with a microphone, and the voice signal is supplied to the user digital baseband circuit 20 as an audio signal. The user digital baseband circuit 20 is connected to a transmission modulator 24 through an interface such as voice coding, where A / D conversion, modulation (for example, QPSK modulation), spread spectrum (for example, direct spread by PN code). Etc. are processed. And the transmission modulator 2
4, transmission power controllers 26 and 28 are connected in series, where amplification processing with a predetermined gain is performed, and the signal is transmitted from the antenna 10 (usually, it is transmitted after being up-converted).

Utilization of Pilot Signal The analog receiver 12 also includes a searcher receiver 3
0 is connected, and the pilot signal included in the received signal is extracted here to detect the signal strength. This pilot signal is a signal used for initial acquisition of the base station in the mobile station, and the same code is used in each base station, but since the codes of different shift amounts are given, it is based on this. Can be identified. Further, this pilot signal is multiplexed on communication data etc. by the Walsh function, and is usually W0 (Walsh function of No. 0).
Is assigned. Therefore, the Hadamard filter can be used to extract the pilot signal, and the signal level can be known. The measurement of the pilot level here is performed using path diversity. this is,
In mobile communication, frequency selective fading often caused by multiplex transmission delay is separated by the resolution of the spread code, and the separated large ones are given greater weighting and combined with time. is there.
By using this pass-distance, it is possible to measure the pilot level with high accuracy. Then, the searcher receiver 30 compares the signal levels of pilot signals from a plurality of base stations, and generates a signal for changing the base station.

In the present embodiment, the searcher receiver 3
A control processor 32 is connected to 0, to which a signal regarding the level of the pilot signal is supplied. The control processor 32 is also supplied with a signal regarding the AGC gain from the analog receiver 12 and a signal regarding the power control command from the digital data receiver 14.

Then, the control processor 32
Know the level of the pilot signal received from both the AGC gain from the analog receiver 12 and the level of the pilot signal from the searcher receiver 30. Then, the control processor 32 generates an analog level control signal from the obtained reception intensity, thereby controlling the power of the output signal in the transmission power controller 28. Further, the control processor 32 knows the content of the transmission power control sent from the base station side from the power control command supplied from the digital data receiver 14, and controls the transmission power controller 26 accordingly. In this way, the control processor 32 can perform open-loop and closed-loop transmission power control.

Configuration for Transmission Power Control FIG. 2 shows members for transmission power control. As described above, the analog receiver 12 includes the down converter 12a, the bandpass filter 12b, the IF amplifier 12c, and the AGC detector 12d. Therefore, the antenna 10
The RF signal supplied from the converter is converted into an IF signal by the down converter, and the band pass filter 12b selects a signal in the frequency band used for communication. The output of the bandpass filter 12b is converted into an IF signal of a substantially constant level by the IF amplifier 12c and supplied to the A / D converter of the digital data receiver 14. In addition, in order to control the output level of the IF amplifier, the AGC detector 12
d is provided, and this AGC detector 12d is I
The output level of the F amplifier 12c is detected and I
The gain of the F amplifier 12c is feedback-controlled.

The AGC detector 12d is
A signal regarding the gain to be fed back is supplied to the control processor 32. Therefore, the control processor 32 can recognize the level of the pilot signal received from both the level of the pilot signal supplied from the searcher receiver 30 and the signal regarding the AGC gain. In particular, the level of this pilot signal is separately recognized for each base station in the searcher receiver 30 as described above. Therefore, the received power obtained here excludes the signals from other base stations, and the received power of the signal from the base station with which communication is performed can be accurately known. Therefore, it is possible to accurately detect the signal level received from a target base station even near the boundary of a cell (area under the control of one base station) where the signal levels from a plurality of base stations become large. By supplying a signal of the difference between this detection result and the desired mobile station level to the transmission power controller, it is possible to perform suitable transmission power control.

The control processor 32 controls the transmission power controller 28 according to the obtained reception power. The transmission power controller 28 is the IF amplifier 28a.
And gain controller 2 that controls this gain
It consists of 8b. Then, based on the gain control signal supplied from the control processor 32, the gain controller 28b controls the gain of the IF amplifier 28a.

Here, in this embodiment, the control processor 32 supplies not only the gain control signal but also the time constant control signal to the gain controller 28b. And
As shown in FIG. 3, the gain controller 28b has variable resistors R1 and R2, diodes D1 and D2, and a capacitor C. Also, the variable resistor R1 and the diode D
1 and the series connection of the variable resistor R2 and the diode D2 are connected in parallel, the gain control signal is input to the variable resistor R1R2, and the diodes D1 and D2 are connected.
2 is connected to the capacitor C and the gain control terminal of the IF amplifier 28. Therefore, when the potential of the gain control signal increases, the time constant determined by the values of R1 and C becomes IF.
When the potential of the signal that controls the gain of the amplifier 28 rises and the potential of the gain control signal decreases, the potential of the signal that controls the gain of the IF amplifier 28 falls with a time constant determined by the values of R2 and C. Therefore, the response of the transmission power to the gain control signal can be made different by making the values of R1 and R2 different. The time constant R1C in the power increasing direction is set to be larger than the time constant R2C in the power decreasing direction. For example, R1 = 10R2 is set.

Furthermore, the resistance values of the variable resistors R1 and R2 can be changed by the time constant control signal while maintaining the above relationship. Therefore, the speed of response to the received power can be changed by a command from the control processor 32. Then, in the present embodiment, the control processor 32 detects the fading speed from the change in the received power, changes the resistance values of R1 and R2 accordingly, changes the time constant in this circuit, and performs gain control. It controls the response of the transmit power controller 28 to the signal.

Detection of Fading Speed The fading detection operation in the control processor 32 will be described with reference to FIG.

First, the level crossing counter is initialized (reset) and the operation of the timer for defining the count cycle is started (S1). Then, input the value x _n of the received power that is input, and input the previous value x x
_It is determined whether _n-1 <preset level and _xn ≥ preset level (S3). That is, it is determined whether or not there is a level crossing by determining whether or not the value has changed from a value less than the preset preset level to the above value. Then, if YES, the value of the level crossing counter is incremented (added by 1) (S4). On the other hand, if there is no intersection at S3, this S
Bypass 4. Next, it is determined whether or not the timer has expired (whether the timer value is checked and one count cycle has elapsed) (S5). If not, S
Return to 2 and repeat the counting of level crossings. The reception level x _n is an average of pilot levels of about 1 msec, and the timer period may be set to 1 second, for example.

Since the number of level crossings within the predetermined time is counted in this way, the maximum Doppler frequency f _d is then obtained (S6). This maximum Doppler frequency is obtained by the level crossing count value x π ^1/2 e ^-1/2 . This is because, in fading in a moving body that travels at a considerable speed such as an automobile, the fading speed often corresponds to the maximum Doppler frequency, and it is known that the number of level crossings and the maximum Doppler frequency have the above-mentioned relationship. Is. Note that this is shown, for example, in "Basics of Mobile Communications" issued by the Institute of Electronics, Information and Communication Engineers of Japan, 140.01.

Then, the obtained maximum Doppler frequency f
An averaging time T suitable for obtaining the median of fading from _d is determined. For example, it may be determined by the equation T = N / f _d . Here, N is a constant, and 36
It is said that the position is suitable. In this way, when the averaging time T is obtained, the time constant control signal is obtained from the table according to this and is output (S8).

That is, the variable resistors R1 and R in FIG.
The value of 2 is modified according to R1 = T / C, R2 = T / 10C so that the time constant of this circuit is such that the gain control signal is averaged over time T. If the moving speed of the moving body is slow, the average time becomes too long, so an upper limit is set (for example, 10 seconds). Then, the gain of the IF amplifier 28a is controlled by the gain control signal averaged by the circuit whose time constant is set in this way.

As described above, in this embodiment, the fading frequency (maximum Doppler frequency) is obtained, and the averaging time T is changed according to the fading frequency. Therefore, the averaging time T can always be optimized. Therefore, it is possible to prevent the averaging time from being too short and the open-loop transmission power control to follow the fading.Also, when the fading speed is fast, shorten the averaging time to reduce the open-loop transmission power control. It can be responsive. Although the maximum Doppler frequency is used as the fading speed in the above example, if the fading speed can be detected even with other fading, the averaging time can be controlled accordingly. Further, although the control processor 32 detects the received power from the level of the pilot signal, the present invention is not limited to this, and the received power can be detected by the level of the IF signal output from the analog receiver.

Configuration on Base Station Side Next, the configuration of the communication device on the base station side will be described with reference to FIG. The antenna 40 has an analog receiver 4
2 is connected, the received radio wave is supplied to the analog receiver 42, and the IF signal is output. The IF signal from the analog receiver 42 is a mobile unit "N".
(Mobile units are provided corresponding to the number of mobile units that perform communication, N is a code that identifies one of them), and is supplied to the digital data receiver 44. The signal output from the digital data receiver 44 and subjected to the processing such as despreading is supplied to the exchange through the user digital baseband circuit 46.

The signal from the exchange is also supplied from the user digital baseband circuit 46 to the transmission modulator 48, where it undergoes processing such as modulation and spread spectrum. The transmission signal output from the transmission modulator 48 is
The adder 50 multiplexes it with signals from other transmission modulators, and the adder 52 multiplexes pilot signals from the pilot signal generator 54, and then the antenna 4
It is supplied to 0 and transmitted from here. The closed loop power control processor 56 is provided on the base station side, and based on the received signal level of the mobile station supplied from the digital data receiver 44, the transmission to be used when the mobile station performs transmission. Calculate power and create power control commands. Then, the closed loop power control processor 56 supplies this power control command to the transmission modulator 48, and the transmission modulator 48 inserts the power control command into the transmission signal.

The structure of the digital data receiver 44 is shown in FIG. In this way, the A / D converter 62 to which the IF signal from the analog receiver 42 is input, the PN generator 64 that generates a predetermined PN code, and the PN code supplied from the PN generator 64 are correlated. It is composed of a PN correlator 66, a Hadamard transform filter 68 that Hadamard transforms the correlation signal output from the PN correlator 66, and removes Walsh coding, and a user decoder 70 that demodulates data. And the analog receiver 4
The IF signal supplied from 2 is converted into digital data by the A / D converter 62 and supplied to the PN correlator 66. The PN correlator 66 calculates the correlation between the PN signal assigned to the mobile station with which the mobile unit "N" supplied from the PN generator 64 is communicating and the received signal. That is, the correlation signal of a specific PN code is extracted from the signal that has been spectrum-spread by the PN code, and spectrum despreading is performed. As a result, the user channel is extracted from the multi-accessed data. Next, the signal obtained by despreading is subjected to Walsh coding by the Hadamard transform filter 68, and original data is obtained from the maximum value. This data is supplied to the user decoder 70. The user decoder 70 performs maximum likelihood decoding on the convolutionally encoded data on the transmission side to obtain user data. Also, the user decoder 70
Outputs the decoded data level in symbol units.

This decoded data level is then provided to the closed loop power control processor 56 where it is used to create power control commands.

Next, FIG. 7 shows the configuration of the closed loop power control processor 56. In this way, the decoded data level is supplied to the power average calculator 80, where the power average is calculated. The power averaging is performed in slot units (1.25 msec) by well-known digital processing. Then, the output from the power average calculator 80 is compared with the reference power level in the comparator 82. The decoded data level is also supplied to the threshold detector 84, where power values below a predetermined threshold are replaced with zero. This is 1.25 for transmissions from mobile stations.
This may be done in bursts in units of msec slots, so that data is not taken in when transmission is not being performed. The output of the threshold detector 84 is supplied to the buffer memory 86, and a plurality of decoded data power levels for a predetermined period are stored in the buffer memory 86 in units of symbols. Then, the power history of the buffer memory 86 is supplied to the predictor 88, and the predictor 88 predicts the received power at a predetermined time ahead from the power history. Then, the value of the received power predicted by the predictor 88 is the comparator 9
0, where it is compared to a reference power level.

The signal of the comparison result of the comparator 82 and the comparator 90 is supplied to the power control command generator 94 via the AND gate 92. Therefore, the power control command generator 94 generates the power control command according to the comparison result of both the comparators 82 and 90. That is, the power value for each slot of the power average calculator 80,
When the prediction value of the symbol unit of the predictor 88 is less than the reference level, the outputs of both the comparators 82 and 90 become signals for increasing the mobile station transmission power, the outputs of both become H, and the AND gate 92 The H signal is output, which causes the power control command generator 94 to generate a command to increase power. Based on this command, the mobile station increases the transmission power by a predetermined level, and the reception level in the base music from the mobile station is increased.

Prediction of Received Power Next, prediction by the predictor 88 will be described. For example, as shown in FIG. 8, it is assumed that the received power T changes with time t as shown in the figure. In this case, the electric powers at the times t _{0 to} t _n are P _{0 to} P _n .

On the other hand, since the power control command is randomly inserted in the transmission signal as described above, the time for transmission to the moving body is not constant. Therefore, the predictor 88 receives a signal about the timing of power control command insertion from the transmission modulator 48, and a control delay in the mobile unit (from the time when the mobile unit receives the power control command until the actual power control is performed). The delay time) is used to determine the time actually controlled by the power control command. That is, the current time is t _n, if the time until the actual control is performed were delta, predicts the received power P _tp at time t _n + Δ = t _p.

Next, this prediction will be described with reference to the flowchart of FIG. First, the command transmission timing is input from the data in the command transmission modulator 48 (S11). Then, from this command transmission timing, the time (predicted time t _p ) in which the mobile unit controls the transmission power by this command is determined (S12).

Next, the correlation coefficient is obtained in order to predict the power by linear prediction. (S13). In this example, we assume that fading is Rayleigh facings, calculating the correlation coefficient γ (t _p -t _j) by calculating the Bessel function for _{2πf d (t p -t j)} .

Γ (t _p −t _j ) = J ₀ [2πf ₀ (t _p −t _j )] where f _d is the maximum Doppler frequency and t _j is j =
Each time when the received power of 0 to n is obtained is shown. Then, to determine the prediction coefficients α ₁ ~α _n (S14), the prediction coefficient alpha ₁ to? _N of mean square prediction error is minimized determined by solving the following equation (S15).

[0053]

[Equation 1] Here, γ ₀ is at time t _p −t ₀ , and γ ₁ is at time t _p
-T ₁ , ..., γ _n-1 represents the _one at time t _p -t _n-1 , and γ _n represents the one at time t _p -t _n .

Next, based on the calculated α _{1 to} α _n , P _tp = α ₁ P ₀ + α ₂ P ₁ α ₃ P ₂ + ... + α _n P
P _tp is calculated from _n-1 (S16). In this way, the received power P _tp at the predetermined time t _p can be predicted.

Therefore, the predictor 88 in FIG. 7 sends this predicted power value to the comparator 90.

As described above, transmitting the power control command requesting the power increase only when both of the power value at that time and the predicted power value increases the power is adversely affected when the power is erroneously increased. This is because when is accidentally decreased, it is larger than when accidentally decreased. It should be noted that the power control command may be created from the determination result of only the predicted value.

Other Embodiments Next, FIG. 10 shows a modification of the present invention. In this example,
Compared to the one shown in FIG. 1, a digital data receiver 16 and a diversity combiner 18 are added. In this way, two digital data receivers are provided in order to achieve path diversity reception, and by performing spectrum despreading for the same PN code at different timings, both arrive at different paths. The same signal can be retrieved. The two digital data receivers 14 and 16 are connected to the diversity combiner 18, and the diversity combiner 18 adds the two supplied signals in synchronization. That is, the difference in arrival time corresponding to the route difference is compensated and the addition is performed in the same phase. As a result, the signals that have reached the moving body in the two paths can be added, and the energy of the received signal can be increased. Here, this addition is not a simple addition, but may be a weighted addition for increasing the weight for a more reliable signal. As a result, a suitable increase in signal energy can be achieved.

In this embodiment, the output signal from the diversity combiner 18 is sent to the control processor 32.
Are typing in. Therefore, the control processor 32 changes the received power after weighted addition from
The fading rate can be estimated. However, in this case, the formula for obtaining the maximum Doppler in FIG. 4 needs to be modified into a formula considering diversity reception. Therefore, the fading speed can be estimated with higher accuracy, and the averaging time in the transmission power controller 28 can be controlled accordingly. Note that in this example, the gain setting in the transmission power controller 28 by the control processor 32 is also calculated from the energy of the signal supplied from the path diversity combiner 18 and the AGC gain supplied from the analog receiver 12. .

FIG. 11 shows an example in which path diversity reception is also performed on the base station side. Therefore, the digital data receiver 93 and the diversity combiner 94 are added. Then, the data is demodulated by the path diversity reception, and in the closed loop power control processor 56, the future received power in consideration of fading is predicted from the correlation signal after the weighted addition.

In the above embodiment, the maximum Doppler frequency is used as the fading speed, but it can be applied to other fading as long as the fading speed can be estimated. Furthermore, in power estimation, the correlation coefficient was determined by the Ressel function on the premise of Rayleigh fading. However, if other fading is used, a function corresponding to it may be used. Other functions may be given as a table or the like. That is, the formula for obtaining the correlation coefficient can be determined by obtaining the power spectrum and subjecting it to Fourier transform. Furthermore, the prediction need not be linear prediction but may be another prediction method.

[0061]

As described above, according to the present invention,
Since the reception power is detected using the pilot signal, the transmission power can be controlled with respect to the reception signal power of only the base station of the own station, and appropriate power control can be performed. Further, since the fading speed is estimated and the time for averaging the received signal power is determined according to the fading speed, the averaging can always be performed at an appropriate time, and the median value of the fading electric field can be estimated. Therefore, there are few errors in the open loop control, and the transmission power can be increased without increasing the system interference. Further, it is possible to prevent deterioration of the transmission characteristics of the own station without increasing system interference.

Further, on the side of the base station, the future situation of the radio wave from the mobile body received by the base station is predicted,
Since the power control command is transmitted, by controlling the transmission power according to the power control command, it is possible to accurately control the reception power on the base station side. As a result, the transmission power control becomes accurate, and the transmission characteristics are improved and the line capacity is increased.

[Brief description of drawings]

FIG. 1 is a block diagram showing the overall configuration of a mobile unit.

FIG. 2 is a block diagram of members related to power control of the embodiment.

FIG. 3 is a circuit diagram showing a gain control mechanism in a transmission power controller 28.

FIG. 4 is a flowchart illustrating an operation of fading speed estimation.

FIG. 5 is a block diagram showing an overall configuration of a base station side.

FIG. 6 is a block diagram showing details of a digital data receiver 44 of the embodiment.

FIG. 7 is a block diagram showing details of a closed power control processor 56.

FIG. 8 is an explanatory diagram showing prediction of received power.

FIG. 9 is a flowchart showing an operation of predicting received power.

FIG. 10 is a block diagram showing the configuration of another embodiment on the mobile unit side.

FIG. 11 is a block diagram showing the configuration of another embodiment on the base station side.

[Explanation of symbols]

 12, 42 Analog receiver 14, 44 Digital data receiver 20, 46 User digital baseband circuit 24, 48 Transmission modulator 26, 28 Transmission power controller 30 Searcher receiver 32 Control processor 56 Closed power control processor

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[Procedure amendment]

[Submission date] March 19, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction content]

[Document name] Statement

Title: Transmission power control apparatus and system in mobile communication

[Claims]

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to transmission power control in mobile communication using a CDMA (code division multiple access) system.

[0002]

2. Description of the Related Art With the recent advances in electronic communication technology, mobile communication such as car phones and mobile phones has become widespread. Also in the field of mobile communication, digital communication has been studied and various communication systems have been studied.
As one of such methods, there is a CDMA (Code Division Multiple Access) method, which has attracted attention because it has characteristics such as assigning a plurality of mobile devices to the same frequency range and easy confidentiality. There is.

In this CDMA system (particularly, direct sequence spread spectrum: CDMA system using DS / SS), in addition to a transmitter, a receiver, and a modulator / demodulator that perform normal radio communication, spread spectrum is performed using a PN code or the like. A spreading means is required, and a despreading means for despreading the PN code is needed.

In the CDMA system, it is necessary to take out a signal that is spectrum-spread with a specific code from a plurality of spread signals in the same frequency band and demodulate it. In a CDMA system, in transmission from a base station to a mobile station (forward link), a pseudo random code having a different phase shift for each base station is used as a spreading code so that the mobile station can identify the base station, and each channel Are multiplexed by an orthogonal function (a function having a cross-correlation of 0) and transmitted. A pilot signal is also included therein, and the mobile station uses this pilot signal for initial acquisition and synchronization.

Further, in the transmission from the mobile station to the base station (reverse link), a pseudo random code without offset,
A spread code is a concatenation of a pseudo random code specified for each user. Since the distance between each mobile unit and the base station is different, it is difficult to synchronize the transmission signals of all mobile units at the base station, and it is not possible to maintain the orthogonality between the mobile units. It is possible. Since the spreading code is determined in consideration of such a point, mutual interference is sufficiently small if the overlapping positions are simply shifted. However, in addition to such interference, if there is a large difference in the received power from the mobile station at the base station, the mobile station with a large received power causes a large interference with the mobile station with a small received power. Will be given. In such a situation, the number of mobile devices that can simultaneously talk becomes small. For this reason, the conventional device also has a transmission power control means for keeping the intensity of the received power from each mobile unit constant.

[0006] Here, the change in the received power in mobile communication includes a loss (path loss) based on the distance of the radio wave propagation path.
The same on the mobile side and the base station side due to loss (shadowing) etc. due to radio wave shields such as buildings existing in the propagation path, and on the mobile side and the base station side due to Rayleigh fading etc. There is.

For the mobile station and the base station that have the same intensity change, the mobile station measures the received power intensity of the radio wave transmitted from the base station, and this is the time for removing the influence of Rayleigh fading. By detecting the averaged median value by averaging and controlling the transmitted field intensity based on this, the received field intensity at the base station is brought close to a constant value (this is called open loop control). Specifically, the AGC circuit of the IF signal (intermediate frequency signal obtained by down-converting the received radio frequency signal (RF signal)) at the input stage of the receiver (in order to avoid inputting an excessive signal to the subsequent stage, Received power is detected from the signal about the gain of the circuit that controls the gain of the amplifier according to the strength) and the signal strength of the signal frequency band after passing through the band pass filter (filter that passes only the desired frequency band). The transmission power is controlled according to.

On the other hand, there is a case where the received power increases sharply as when the mobile unit is out of the shadow of the building. In this case, other communication will be greatly affected, and therefore the transmitted power must be rapidly reduced. I have to. Therefore, in order to deal with such a case, the averaging time for obtaining the above-mentioned median value is set to be short with respect to an increase in received power. That is, for a decrease in transmission power (increase in reception power),
Shorter averaging time and higher transmission power (reception power reduction)
For, the averaging time is set to be long and open-loop transmission power control is performed.

On the other hand, open-loop control cannot deal with different electric field strengths such as Rayleigh fading on the mobile unit side and the base station side. Therefore, to deal with this, the base station detects the received electric field strength from each mobile station, and based on this received electric field strength, a command (power control command) for correcting the transmission power is moved to the mobile device side. Send to the machine. Then, the mobile device controls the transmission power based on this power control command, thereby making the received electric field strength at the base station desired (this is called closed loop control). The power control command commands whether to increase or decrease the power.
It is transmitted once every 25 msec. Also, with one control ±
The control of about 1 dB is performed around the open loop power control.

By performing such transmission power control, it is possible to reduce the interference by making the strength of the received signal from each mobile unit in the base station equal. Therefore, it becomes possible to communicate with more mobile devices,
The capacity of the system can be maximized.

Regarding the transmission / reception equipment and the conventional transmission power control on the mobile station side and the base station side (cell site) of the CDMA system, for example, US Pat. No. 5,103,459 and WO 91/07037 are disclosed. Etc.

[0012]

However, the conventional transmission power control has the following problems. (A) Received power also includes transmission signals from other base stations, and the transmission signal strength from other base stations is particularly high near the boundary of the jurisdiction range (cell) of the base station. . Therefore, the transmission power control for the target base station becomes inappropriate. Note that, theoretically, this should be solved by closed loop control, but as described above, the amount of power changed by one command by the power control command is limited, so the correction limit is exceeded. there is a possibility.

(B) Since the Rayleigh fading varies depending on the speed of the mobile device, the open loop transmission power control may follow the Rayleigh fading depending on the fading speed because the average time is too short.
If the averaging time is set too long, it becomes impossible to follow the change in the median fading value.

(C) The power control command is inserted into normal communication data on the forward link and is sent once every 1.25 msec on average, but its insertion position (sending timing) is randomized. Also, in the reverse link, during a silent period, the mobile body does not perform continuous transmission but performs burst transmission, and the transmission timing is also randomized. For example, 20ms
In the ec frame, there are 16 slots of 1.25 msec unit, but in the case of full rate, all 16 slots are transmitted, and in the case of 1/2 rate, 16 slots are transmitted.
Send slots to 8 of the 8 slots. And the phase of that slot is randomized. The transmission rates are full rate, 1/2 rate, 1/4 rate, 1 /
There are 8 rates. Therefore, the time until the base station recognizes the received power from the mobile device and the mobile device receives the power control command varies. Therefore, the time for which the transmission power control is performed in accordance with the power control command is not constant, and the control timing may shift, which may prevent accurate transmission power control. Especially, when the fading speed is high, this problem becomes large.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a transmission power control apparatus in mobile communication and a system thereof capable of performing suitable transmission power control in accordance with the situation of a mobile device. To do.

[0016]

A transmission power control apparatus for mobile communication according to the present invention extracts a pilot signal for each base station from a received signal and detects a signal level of the extracted pilot signal. It is characterized by having a receiver and a transmission power control means for controlling the transmission power according to the signal level from the searcher receiver.

Further, there are provided level detecting means for detecting the signal level of the received signal, and averaging means for averaging the detected signal level of the received signal for a predetermined averaging time to obtain an average received signal level. Depending on the average signal level, the transmission power control means for controlling the transmission power, the fading speed detection means for detecting the fading speed from the change in the signal level of the received signal, the averaging time according to the obtained fading speed And averaging time control means for changing.

Further, level detection means for detecting the signal level of the received signal, history storage means for storing the obtained signal level history of the received signal, and signal of the received signal after a predetermined time from the stored history Predicting means for predicting the level, creating means for creating a power control command for transmission power control on the signal transmitting side according to the predicted signal level, and transmitting means for sending the created power control command It is characterized by having.

Further, the prediction means is characterized in that the prediction is performed by linear prediction from the contents of the stored history.

Further, the fading speed detecting means is
It is characterized in that the change state of the received signal level is examined and detected based on the number of times the received signal level crosses a fixed value within a predetermined time.

Further, a pilot signal is extracted from the received signal, the searcher receiver for detecting the signal level of the extracted pilot signal, and the signal level from this searcher receiver are averaged for a predetermined averaging time, and then averaged. Averaging means for obtaining a signal level, according to the obtained average signal level, a transmission power control means for controlling the transmission power, a fading speed detection means for detecting a fading speed from a change in the signal level from the searcher receiver,
Averaging time control means for changing the averaging time according to the obtained fading speed.

Further, the present invention is a transmission power control system for controlling transmission power of a mobile unit in mobile communication between a base station and a mobile unit, wherein the base station side is sent from the mobile unit. Signal level detection means for detecting the received signal level of the incoming radio wave, history storage means for storing the history of the signal level of the obtained received signal, and predicting the signal level of the received signal after a predetermined time from the stored history Prediction means, and, according to the signal level to be predicted, a creation means for creating a power control command for transmission power control on the signal transmission side, and a transmission means for sending the created power control command, The mobile device side extracts the pilot signal from the received signal and also detects the signal level of the extracted pilot signal and the signal from this searcher receiver. Bells are averaged for a predetermined averaging time to obtain an average signal level, and the transmission power is determined according to the average signal level, and the determined transmission power is changed according to the power transmission command. And a transmission power control means for controlling the transmission power.

[0023]

As described above, according to the present invention, since the received power is detected by using the pilot signal, the transmitted power is controlled with respect to the received signal power of only the base station with which the mobile station is currently communicating. Therefore, appropriate power control can be performed. Further, since the fading speed is estimated and the time for averaging the received signal power is determined according to the fading speed, the averaging can always be performed at an appropriate time, and the median value of the fading electric field can be estimated. Therefore, the open loop control can be properly performed,
The transmission power can be increased without increasing the system interference. Further, it is possible to prevent deterioration of the transmission characteristics of the own station without increasing system interference.

Further, on the side of the base station, the future situation of the radio wave from the mobile station received at the base station is predicted,
Since the power control command is transmitted, by controlling the transmission power according to the power control command, it is possible to accurately control the reception power on the base station side. As a result, the transmission power control becomes accurate, and the transmission characteristics are improved and the line capacity is increased.

[0025]

Embodiments of the present invention will be described below with reference to the drawings.

Configuration of Mobile Station FIG. 1 is a block diagram showing the overall configuration of a mobile station to which the transmission control apparatus according to the present invention is applied. In the figure,
The antenna 10 receives or radiates a radio wave including at least a frequency used for communication.
An analog receiver 12 is connected to the antenna 10, and the analog receiver 12 converts (down-converts) a received radio wave into an intermediate frequency, obtains an IF signal, and selects a signal of a predetermined frequency only in a band. Also, AG
The C means controls so that the signal level of the IF signal to be output becomes constant. A digital data receiver 14 is connected to the analog receiver 12, and the digital data receiver 14 performs processes such as conversion of an analog signal into digital data, synchronous detection, and spectrum despreading.
A user digital baseband circuit 20 is connected to the digital data receiver 14, and the user digital baseband circuit 20 performs data demodulation and the like and obtains an audio signal through an interface such as a vocoder. Then, this audio signal is transmitted to the handset 22.
The audio signal is reproduced. That is, the sound received from the speaker of the handset 22 is output.

On the other hand, the handset 22 is also provided with a microphone, and the voice signal is supplied to the user digital baseband circuit 20 as an audio signal. The user digital baseband circuit 20 is connected to a transmission modulator 24 through an interface such as voice coding, where A / D conversion, modulation (for example, QPSK modulation), spread spectrum (for example, direct spread by PN code). Etc. are processed. And the transmission modulator 2
4, transmission power controllers 26 and 28 are connected in series, where amplification processing with a predetermined gain is performed, and the signal is transmitted from the antenna 10 (usually, it is transmitted after being up-converted).

Utilization of Pilot Signal The analog receiver 12 also includes a searcher receiver 3
0 is connected, and the pilot signal included in the received signal is extracted here to detect the signal strength. This pilot signal is a signal used for initial acquisition of a base station in a mobile device, and the same PN code is used in each base station. It becomes possible to identify based on this. Further, this pilot signal is multiplexed with communication data or the like by the Walsh function, and W0 (Walsh function of No. 0) is usually assigned. The WO is composed of all 1's, and the product of these is the same as the original signal. Therefore, the pilot signal level can be known only by the correlation operation of the PN code. The measurement of the pilot level here is performed using path diversity. This is because, in mobile communications, frequency selective fading often caused by multiple transmission delay is separated by the resolution of the spread code, and the separated one having a large level is given a greater weighting and combined in time. It is a technology to do. By using this path diversity, the pilot level can be measured with high accuracy. Then, the searcher receiver 30 compares the signal levels of pilot signals from a plurality of base stations, and generates a signal for changing the base station.

In the present embodiment, the searcher receiver 3
A control processor 32 is connected to 0, to which a signal regarding the level of the pilot signal is supplied. The control processor 32 is also supplied with a signal regarding the AGC gain from the analog receiver 12 and a signal regarding the power control command from the digital data receiver 14.

Then, the control processor 32
Know the level of the pilot signal received from both the AGC gain from the analog receiver 12 and the level of the pilot signal from the searcher receiver 30. Then, the control processor 32 generates an analog level control signal from the obtained reception intensity, thereby controlling the power of the output signal in the transmission power controller 28. Further, the control processor 32 knows the content of the transmission power control sent from the base station side from the power control command supplied from the digital data receiver 14, and controls the transmission power controller 26 accordingly. In this way, the control processor 32 can perform open-loop and closed-loop transmission power control.

Configuration for Transmission Power Control FIG. 2 shows members for transmission power control. As described above, the analog receiver 12 includes the down converter 12a, the bandpass filter 12b, the IF amplifier 12c, and the AGC detector 12d. Therefore, the antenna 10
The RF signal supplied from the converter is converted into an IF signal by the down converter, and the signal in the frequency band used for communication is selected by the band pass filter 12b. The output of the bandpass filter 12b is converted into an IF signal of a substantially constant level by the IF amplifier 12c and supplied to the A / D converter of the digital data receiver 14. Also, in order to control the output level of the IF amplifier, the AGC detector 1
2d is provided, and this AGC detector 12d detects the output level of the IF amplifier 12c, and feedback-controls the gain of the IF amplifier 12c according to this.

The AGC detector 12d is
A signal regarding the gain to be fed back is supplied to the control processor 32. Therefore, the control processor 32 can recognize the level of the pilot signal received from both the level of the pilot signal supplied from the searcher receiver 30 and the signal regarding the AGC gain. In particular, the level of this pilot signal is separately recognized for each base station in the searcher receiver 30 as described above. Therefore, the received power obtained here excludes the signals from other base stations, and the received power of the signal from the base station with which communication is performed can be accurately known. Therefore, it is possible to accurately detect the signal level received from a target base station even near the boundary of a cell (area under the control of one base station) where the signal levels from a plurality of base stations become large. By supplying a signal of the difference between the detection result and the desired mobile unit level to the transmission power controller, suitable transmission power control can be performed.

The control processor 32 controls the transmission power controller 28 according to the obtained reception power. The transmission power controller 28 is the IF amplifier 28a.
And gain controller 2 that controls this gain
It consists of 8b. Then, based on the gain control signal supplied from the control processor 32, the gain controller 28b controls the gain of the IF amplifier 28a.

Here, in this embodiment, the control processor 32 supplies not only the gain control signal but also the time constant control signal to the gain controller 28b. And
As shown in FIG. 3, the gain controller 28b has variable resistors R1 and R2, diodes D1 and D2, and a capacitor C. Also, the variable resistor R1 and the diode D
1 and the series connection of the variable resistor R2 and the diode D2 are connected in parallel, the gain control signal is input to the variable resistor R1R2, and the diodes D1 and D2 are connected.
2 is connected to the capacitor C and the gain control terminal of the IF amplifier 28. Therefore, when the potential of the gain control signal increases, the time constant determined by the values of R1 and C becomes IF.
When the potential of the signal that controls the gain of the amplifier 28 rises and the potential of the gain control signal decreases, the potential of the signal that controls the gain of the IF amplifier 28 falls with a time constant determined by the values of R2 and C. Therefore, the response of the transmission power to the gain control signal can be made different by making the values of R1 and R2 different. The time constant R1C in the power increasing direction is set to be larger than the time constant R2C in the power decreasing direction. For example, R1 = 10R2 is set.

Furthermore, the resistance values of the variable resistors R1 and R2 can be changed by the time constant control signal while maintaining the above relationship. Therefore, the speed of response to the received power can be changed by a command from the control processor 32. Then, in the present embodiment, the control processor 32 detects the fading speed from the change in the received power, changes the resistance values of R1 and R2 accordingly, changes the time constant in this circuit, and performs gain control. It controls the response of the transmit power controller 28 to the signal.

Detection of Fading Speed The fading detection operation in the control processor 32 will be described with reference to FIG.

First, the level crossing counter is initialized (reset) and the operation of the timer for defining the count cycle is started (S1). Then, input the value x _n of the received power that is input, and input the previous value x x
_It is determined whether _n-1 <preset level and _xn ≥ preset level (S3). That is, it is determined whether or not there is a level crossing by determining whether or not the value has changed from a value less than the preset preset level to the above value. Then, if YES, the value of the level crossing counter is incremented (added by 1) (S4). On the other hand, if there is no intersection at S3, this S
Bypass 4. Next, it is determined whether or not the timer has expired (whether the timer value is checked and one count cycle has elapsed) (S5). If not, S
Return to 2 and repeat the counting of level crossings. The reception level x _n is an average of pilot levels of about 1 msec, and the timer period may be set to 1 second, for example.

Since the number of level crossings within the predetermined time is counted in this way, the maximum Doppler frequency f _d is then obtained (S6). This maximum Doppler frequency is obtained by the level crossing count value x π ^1/2 e ^-1/2 . This is because in fading in mobile devices that travel at a considerable speed such as an automobile, the fading speed often corresponds to the maximum Doppler frequency, and it is known that the number of level crossings and the maximum Doppler frequency have the above-mentioned relationship. Is. Note that this is shown, for example, in "Institute of Electronics, Information and Communication Engineers,""Basics of Mobile Communications," issued October 1, 1986.

Then, the obtained maximum Doppler frequency f
An averaging time T suitable for obtaining the median of fading from _d is determined. For example, it may be determined by the equation T = N / f _d . Here, N is a constant, and 36
It is said that the position is suitable. In this way, when the averaging time T is obtained, the time constant control signal is obtained from the table according to this and is output (S8).

That is, the variable resistors R1 and R in FIG.
The value of 2 is modified according to R1 = T / C, R2 = T / 10C so that the time constant of this circuit is such that the gain control signal is averaged over time T. If the moving speed of the mobile device is slow, the average time becomes too long, so an upper limit is set (for example, 10 seconds). Then, the gain of the IF amplifier 28a is controlled by the gain control signal averaged by the circuit whose time constant is set in this way.

As described above, in the present embodiment, the fading speed (maximum Doppler frequency) is obtained, and the averaging time T is changed according to this, so that the averaging time T can always be optimized. So the averaging time is too short,
It is possible to prevent the open loop transmission power control from following the fading, and when the fading speed is fast, the averaging time can be shortened to make the response of the open loop transmission power control fast. . In the above example, the maximum Doppler frequency was used as the fading speed, but if the fading speed can be detected even with other fading, the averaging time can be controlled accordingly. Further, although the control processor 32 detects the received power from the level of the pilot signal, the present invention is not limited to this, and the received power can be detected by the level of the IF signal output from the analog receiver.

Configuration on Base Station Side Next, the configuration of the communication device on the base station side will be described with reference to FIG. The antenna 40 has an analog receiver 4
2 is connected, the received radio wave is supplied to the analog receiver 42, and the IF signal is output. The IF signal from the analog receiver 42 is a mobile unit "N".
(Mobile units are provided corresponding to the number of mobile units that perform communication, N is a code that identifies one of them) and is supplied to the digital data receiver 44. The signal output from the digital data receiver 44 and subjected to the processing such as despreading is supplied to the exchange through the user digital baseband circuit 46.

Further, the signal from the exchange is supplied from the user digital baseband circuit 46 to the transmission modulator 48, where it is subjected to processing such as modulation and spread spectrum. The transmission signal output from the transmission modulator 48 is
The adder 50 multiplexes it with signals from other transmission modulators, and the adder 52 multiplexes pilot signals from the pilot signal generator 54, and then the antenna 4
It is supplied to 0 and transmitted from here. A closed loop power control processor 56 is provided on the base station side, and based on the received signal level of the mobile device supplied from the digital data receiver 44, the transmission to be used when the mobile station performs transmission. Calculate power and create power control commands. Then, the closed loop power control processor 56 supplies this power control command to the transmission modulator 48, and the transmission modulator 48 inserts the power control command into the transmission signal.

The structure of the digital data receiver 44 is shown in FIG. In this way, the A / D converter 62 to which the IF signal from the analog receiver 42 is input, the PN generator 64 that generates a predetermined PN code, and the PN code supplied from the PN generator 64 are correlated. It is composed of a PN correlator 66, a Hadamard transform filter 68 that Hadamard transforms the correlation signal output from the PN correlator 66, and removes Walsh coding, and a user decoder 70 that demodulates data. And the analog receiver 4
The IF signal supplied from 2 is converted into digital data by the A / D converter 62 and supplied to the PN correlator 66. The PN correlator 66 obtains the correlation between the received signal and the PN signal assigned to the mobile station with which the mobile unit "N" supplied from the PN generator 64 is communicating. That is, the correlation signal of a specific PN code is extracted from the signal that has been spectrum-spread by the PN code, and spectrum despreading is performed. As a result, the user channel is extracted from the multi-accessed data. Next, the signal obtained by despreading is subjected to Walsh coding by the Hadamard transform filter 68, and original data is obtained from the maximum value. This data is supplied to the user decoder 70. The user decoder 70 performs maximum likelihood decoding on the convolutionally encoded data on the transmission side to obtain user data. Also, the user decoder 70
Outputs the decoded data level in symbol units.

This decoded data level is then provided to the closed loop power control processor 56 where it is used to create power control commands.

Next, FIG. 7 shows the configuration of the closed loop power control processor 56. In this way, the decoded data level is supplied to the power average calculator 80, where the power average is calculated. The power averaging is performed in slot units (1.25 msec) by well-known digital processing. Then, the output from the power average calculator 80 is compared with the reference power level in the comparator 82. The decoded data level is also supplied to the threshold detector 84, where power values below a predetermined threshold are replaced with zero. This is 1.25 from the mobile device
This may be done in bursts in units of msec slots, so that data is not taken in when transmission is not being performed. The output of the threshold detector 84 is supplied to the buffer memory 86, and a plurality of decoded data power levels for a predetermined period are stored in the buffer memory 86 in units of symbols. Then, the power history of the buffer memory 86 is supplied to the predictor 88, and the predictor 88 predicts the received power at a predetermined time ahead from the power history. Then, the value of the received power predicted by the predictor 88 is the comparator 9
0, where it is compared to a reference power level.

The signal of the comparison result of the comparator 82 and the comparator 90 is supplied to the power control command generator 94 via the AND gate 92. Therefore, the power control command generator 94 generates the power control command according to the comparison result of both the comparators 82 and 90. That is, the power value for each slot of the power average calculator 80,
When the predicted value of the symbol unit of the predictor 88 is less than the reference level, both outputs of the comparators 82 and 90 become signals for increasing the transmission power of the mobile unit, both outputs become H, and the AND gate 92 outputs The H signal is output, which causes the power control command generator 94 to generate a command to increase power. Based on this command, the mobile device increases the transmission power by a predetermined level, and the reception level from the mobile device at the base station is increased.

Prediction of Received Power Next, prediction by the predictor 88 will be described. For example, as shown in FIG. 8, it is assumed that the received power T changes with time t as shown in the figure. In this case, the electric powers at the times t _{0 to} t _n are P _{0 to} P _n .

On the other hand, since the power control command is randomly inserted in the transmission signal as described above, the time for transmission to the mobile device is not constant. Therefore, the predictor 88 receives a signal about the timing of power control command insertion from the transmission modulator 48, and this and the control delay in the mobile station (from when the mobile station receives the power control command until the actual power control is performed). The delay time) is used to determine the time actually controlled by the power control command. That is, the current time is t _n, if the time until the actual control is performed were delta, predicts the received power P _tp at time t _n + Δ = t _p.

Next, this prediction will be described with reference to the flowchart of FIG. First, the command transmission timing is input from the data in the command transmission modulator 48 (S11). Then, from this command transmission timing, the time (predicted time t _p ) in which the mobile device controls the transmission power by this command is determined (S12).

Next, the correlation coefficient is obtained in order to predict the power by linear prediction. (S13). In this example, we assume that fading is Rayleigh facings, calculating the correlation coefficient γ (t _p -t _j) by calculating the Bessel function for _{2πf d (t p -t j)} .

Γ (t _p −t _j ) = J ₀ [2πf ₀ (t _p −t _j )] where f _d is the maximum Doppler frequency and t _j is j.
= 0 to n represent the times when the received power is obtained. Then, to determine the prediction coefficients α ₁ ~α _n (S14), the prediction coefficient alpha ₁ to? _N of mean square prediction error is minimized determined by solving the following equation (S15).

[0053]

[Equation 1] Here, γ ₀ is at time t _p −t ₀ , and γ ₁ is at time t _p
-T ₁ , ..., γ _n-1 represents the _one at time t _p -t _n-1 , and γ _n represents the one at time t _p -t _n .

Next, based on the calculated α _{1 to} α _n , P _tp = α ₁ P ₀ + α ₂ P ₁ + α ₃ P ₂ + ... + α _n P
P _tp is calculated from _n-1 (S16). In this way, the received power P _tp at the predetermined time t _p can be predicted.

Therefore, the predictor 88 in FIG. 7 sends this predicted power value to the comparator 90.

As described above, transmitting the power control command requesting the power increase only when both of the power value at that time and the predicted power value increases the power is adversely affected when the power is erroneously increased. This is because when is accidentally decreased, it is larger than when accidentally decreased. It should be noted that the power control command may be created from the determination result of only the predicted value.

Other Embodiments Next, FIG. 10 shows a modification of the present invention. In this example,
Compared to that of FIG. 1, a digital data receiver 16 and a diversity combiner 18 are added. As described above, the two digital data receivers are provided to achieve the path diversity reception, and both perform the spectrum despreading for the same PN code at different timings, so that they arrive on different paths. The same signal can be retrieved. The two digital data receivers 14 and 16 are connected to the diversity combiner 18
And the diversity combiner 18 synchronously adds the two supplied signals. That is, the difference in arrival time corresponding to the route difference is compensated and the addition is performed in the same phase. As a result, the signals arriving at the mobile device in the two paths can be added, and the energy of the received signal can be increased. Here, this addition is not a simple addition, but may be a weighted addition for increasing the weight for a more reliable signal. As a result, a suitable increase in signal energy can be achieved.

In this embodiment, the output signal from the diversity combiner 18 is sent to the control processor 3
You are typing in 2. Therefore, the control processor 32 can estimate the fading speed from the change in the received power after weighted addition. However, in this case, it is necessary to transform the formula for obtaining the maximum Doppler in FIG. 4 into a formula in consideration of diversity reception. Therefore, the fading speed can be estimated with higher accuracy, and the averaging time in the transmission power controller 28 can be controlled accordingly. In this example, the gain setting in the transmission power controller 28 by the control processor 32 is also performed by the energy of the signal supplied from the path diversity combiner 18 and the analog receiver 12.
It is calculated from two AGC gains supplied from

FIG. 11 shows an example in which path diversity reception is also performed on the base station side. Therefore, the digital data receiver 93 and the diversity combiner 94 are added. Then, while demodulating the data by the path diversity reception, the closed loop power control processor 56 predicts the future received power in consideration of fading from the correlation signal after the weighted addition.

In the above embodiment, the maximum Doppler frequency is used as the fading speed, but it can be applied to other fading as long as the fading speed can be estimated. Furthermore, in power estimation, the correlation coefficient was determined by the Bessel function on the premise of Rayleigh fading, but if other fading is used, a function corresponding to it may be used. Other functions may be given as a table or the like. That is, the formula for obtaining the correlation coefficient can be determined by obtaining the power spectrum and subjecting it to Fourier transform. Furthermore, the prediction need not be linear prediction but may be another prediction method.

[0061]

As described above, according to the present invention,
Since the received power is detected using the pilot signal, the transmitted power can be controlled with respect to the received signal power of only the base station with which the mobile device is currently communicating, and appropriate power control can be performed. it can. Further, since the fading speed is estimated and the time for averaging the received signal power is determined according to the fading speed, the averaging can always be performed at an appropriate time, and the median value of the fading electric field can be estimated. Therefore, there are few errors in the open loop control, and the transmission power can be increased without increasing the system interference. Further, it is possible to prevent deterioration of the transmission characteristics of the own station without increasing system interference.

Further, on the side of the base station, the future situation of the radio wave from the mobile station received at the base station is predicted,
Since the power control command is transmitted, by controlling the transmission power according to the power control command, it is possible to accurately control the reception power on the base station side. As a result, the transmission power control becomes accurate, and the transmission characteristics are improved and the line capacity is increased.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of a mobile device side.

FIG. 2 is a block diagram of members related to power control of the embodiment.

FIG. 3 is a circuit diagram showing a gain control mechanism in a transmission power controller 28.

FIG. 4 is a flowchart illustrating an operation of fading speed estimation.

FIG. 5 is a block diagram showing an overall configuration of a base station side.

FIG. 6 is a block diagram showing details of a digital data receiver 44 of the embodiment.

FIG. 7 is a block diagram showing details of a closed power control processor 56.

FIG. 8 is an explanatory diagram showing prediction of received power.

FIG. 9 is a flowchart showing an operation of predicting received power.

FIG. 10 is a block diagram showing the configuration of another embodiment on the mobile unit side.

FIG. 11 is a block diagram showing the configuration of another embodiment on the base station side.

[Explanation of Codes] 10, 40 Antenna 12, 42 Analog Receiver 14, 16, 44, 93 Digital Receiver 18, 96 Diversity Combiner 20, 46 User Digital Baseband 22 Handset 24, 48 Transmit Modulator 26, 28 Transmit Power Controller 30 Searcher Receiver 32 Control processor 50, 52 Adder 54 Pilot signal generator 56 Closed loop power control processor 62 A / D converter 64 PN generator 66 PN correlator 68 Hadamard conversion filter 70 User decoder 80 Power average 82, 90 Comparator 84 Threshold detection 86 Buffer memory 88 Predictor 92 AND gate 94 Power control command generator

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Fig. 10

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[Figure 10]

[Procedure 3]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 11

[Correction method] Change

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FIG. 11

Claims (7)

[Claims] 1. A searcher receiver for extracting a pilot signal for each base station from a received signal and detecting the signal level of the extracted pilot signal, and transmission power is controlled according to the signal level from this searcher receiver. A transmission power control device in mobile communication, comprising: transmission power control means; 2. A level detecting means for detecting a signal level of a received signal, and an averaging means for averaging the detected signal level of the received signal for a predetermined averaging time to obtain an average received signal level. Depending on the average signal level, the transmission power control means for controlling the transmission power, the fading speed detection means for detecting the fading speed from the change in the signal level of the received signal, and the averaging time according to the obtained fading speed. A transmission power control device in mobile communication, comprising: averaging time control means for changing. 3. A level detecting means for detecting a signal level of a received signal, a history storing means for storing a history of the obtained signal level of the received signal, and a signal of the received signal after a predetermined time from the stored history. Predicting means for predicting the level, creating means for creating a power control command for transmission power control on the signal transmitting side according to the predicted signal level, and transmitting means for sending the created power control command A transmission power control device in mobile communication, comprising: 4. The transmission power control device in mobile communication according to claim 3, wherein the prediction means performs prediction from the stored history contents by linear prediction. 5. The apparatus according to claim 2, wherein the fading speed detection means examines a change state of the received signal level and detects the received signal level based on the number of times the received signal level crosses a constant value within a predetermined time. A transmission power control device for mobile communication. 6. A searcher receiver for extracting a pilot signal from a received signal and detecting the signal level of the extracted pilot signal, and averaging the signal levels from the searcher receiver for a predetermined averaging time, and averaging Averaging means for obtaining the signal level, transmission power control means for controlling the transmission power according to the obtained average signal level, fading speed detecting means for detecting the fading speed from the change in the signal level from the searcher receiver, An averaging time control means for changing the averaging time according to the obtained fading speed, and a transmission power control device in mobile communication, comprising: 7. A transmission power control system for controlling transmission power on a mobile body side in mobile communication between a base station and a mobile body, wherein the base station side is a reception signal of a radio wave transmitted from the mobile body. Signal level detection means for detecting the level, history storage means for storing the history of the signal level of the obtained reception signal, prediction means for predicting the signal level of the reception signal after a predetermined time from the stored history, According to the predicted signal level, it has a creating means for creating a power control command for transmission power control on the signal transmitting side, and a sending means for sending the created power control command. The pilot signal is extracted from the signal, and the searcher receiver that detects the signal level of the extracted pilot signal and the signal level from this searcher receiver are Averaging processing at a constant averaging time, and averaging means for obtaining an average signal level, in response to the average signal level, and determines the transmission power,
A transmission power control system in mobile communication, comprising: a transmission power control unit that changes the determined transmission power according to a power transmission command.