JP2991862B2 - Transmission power control device and system in mobile communication - Google Patents

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 by the CDMA (Code Division Multiple Access) system.

[0002]

2. Description of the Related Art Along with recent advances in electronic communication technology, mobile communications such as automobile telephones and mobile telephones have become widespread. In the field of mobile communication, digital communication is being studied, and various communication methods are being studied.
One of such systems is a CDMA (Code Division Multiple Access) system, which has attracted attention because it has features such as being able to assign a plurality of mobile stations to the same frequency range and easy secrecy. I have.

In this CDMA system (particularly, a CDMA system using DS / SS), spread spectrum is performed by a PN code or the like in addition to a transmitter, a receiver, and a modulation / demodulation device for performing ordinary radio communication. Spreading means is required, and despreading means for despreading the PN code is required.

[0004] In the CDMA system, it is necessary to extract a signal that is spread with a specific code from a plurality of spread signals in the same frequency band and demodulate the signal. In a CDMA system, in a 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. Are multiplexed by an orthogonal function (a function with zero cross-correlation) and transmitted. The mobile station uses the pilot signal for initial acquisition and synchronization.

In transmission (reverse link) from a mobile station to a base station, a pseudo-random code without offset and
A concatenated pseudo-random code specified for each user is a spreading code. Since each mobile station has a different distance from the base station, it is difficult for the base station to synchronize the transmission signals of all mobile stations, and it is not possible to maintain orthogonality between the mobile stations. It is possible. Since the spreading code is determined taking such points into consideration, mutual interference is sufficiently small if the overlapping position is simply shifted. However, in addition to such interference, if there is a large difference in the reception power from the mobile station at the base station, the power of the mobile station having a high reception power will cause a large interference for the mobile station having a low reception power. Will give. In such a situation, the number of mobile devices that can talk at the same time decreases. For this reason, the conventional apparatus also has a transmission power control means for keeping the intensity of the reception power from each mobile device constant.

Here, a change in received power in mobile communication includes a loss (path loss) based on the distance of a radio wave propagation path.
Mobile station side and base station side due to loss (shadowing) caused by radio wave shielding such as buildings and buildings on the propagation path, and different between mobile station side and base station side due to Rayleigh fading etc. There is.

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

[0008] On the other hand, there are cases where the received power suddenly increases, such as when the mobile station comes out of the shadow of a building. In this case, the transmission power must be reduced promptly because other communications are greatly affected. Must. Therefore, in order to cope with such a case, the averaging time for obtaining the above-mentioned median is set short for an increase in the received power. That is, for a decrease in transmission power (an increase in reception power),
Shorter averaging time and higher transmission power (reception power reduction)
, The averaging time is set long, and open loop transmission power control is performed.

[0009] On the other hand, open-loop control cannot cope with a difference in electric field strength between the mobile station side and the base station side, such as Rayleigh fading. To cope with this, the base station detects the received electric field strength from each mobile station, and moves a command (power control command) for correcting the transmission power to the mobile station based on the received electric field strength. Send to machine. Then, the mobile station controls the transmission power based on the power control command, so that the received electric field strength at the base station is made desired (this is called closed-loop control). The power control command instructs whether to increase or decrease the power.
It is transmitted once every 25 msec. In addition, ±
Control of about 1 dB is performed around open loop power control.

[0010] By performing such transmission power control, it is possible to reduce the interference by making the strengths of the signals received from the mobile stations in the base station equal. Therefore, communication with more mobile devices becomes possible,
System capacity can be maximized.

The transmission / reception facilities on the mobile station side and the base station side (cell site) side and the conventional transmission power control of the CDMA system are described in, for example, US Pat. No. 5,103,459 and International Publication WO 91/07037. Etc. are shown.

[0012]

However, the conventional transmission power control has the following problems. (A) The received power includes a transmission signal from another base station. In particular, near the boundary of the area (cell) under the jurisdiction of the base station, the transmission signal strength from the other base station is large. . Therefore, the transmission power control for the target base station becomes inappropriate. In theory, this can be solved by closed-loop control, but as described above, the amount of power changed by one power control command is limited, and therefore exceeds the correction limit. there is a possibility.

(B) Since the Rayleigh fading differs depending on the speed of the mobile station, the average time may be too short and the open-loop transmission power control may follow the Rayleigh fading depending on the fading speed.
If the averaging time is too long, it becomes impossible to follow the change of the median fading value.

(C) The power control command is inserted into normal communication data on the forward link, and sent once every 1.25 msec on average. The insertion position (sending timing) is randomized. In the reverse link, during a silent period, the mobile unit does not continuously transmit 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. In the case of full rate, all 16 slots are transmitted, and in the case of 1/2 rate, 16 slots are transmitted.
The slots are transmitted to eight of the eight locations. The phase of the slot is randomized. Note that the transmission rates include full rate, 1/2 rate, 1/4 rate, 1 /
There are eight rates. For this reason, the time until the base station recognizes the received power from the mobile device and the power control command is received by the mobile device varies. Therefore, the time during which the transmission power control according to the power control command is performed is not constant, and the control timing is shifted, so that accurate transmission power control may not be performed. In particular, when the fading speed is high, this problem becomes serious.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to provide a transmission power control apparatus and a system for mobile communication capable of performing suitable transmission power control in accordance with the situation of a mobile station. I 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 has a receiver and transmission power control means for controlling transmission power according to a signal level from the searcher receiver.

Further, 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 are obtained. Transmission power control means for controlling the transmission power according to the average signal level, fading speed detection means for detecting the fading speed from a change in the signal level of the received signal, and the averaging time according to the obtained fading speed. Averaging time control means for changing.

Further, level detecting means for detecting the signal level of the received signal, history storing means for storing the history of the obtained signal level of the received signal, and signal of the received signal after a predetermined time from the stored history. A prediction unit for predicting the level, a generation unit for generating a power control command for transmission power control on the signal transmitting side according to the predicted signal level, and a transmission unit for transmitting the generated power control command. It is characterized by having.

Further, the prediction means performs a prediction by linear prediction from the contents of the stored history.

Further, the fading speed detecting means includes:
It is characterized in that the change state of the received signal level is checked, and detection is performed based on the number of times the received signal level crosses a predetermined value within a predetermined time.

Further, a searcher receiver for extracting a pilot signal from a received signal and detecting a signal level of the extracted pilot signal, averaging a signal level from the searcher receiver for a predetermined averaging time, and Averaging means for obtaining a signal level, transmission power control means for controlling transmission power according to the obtained average signal level, and fading speed detection means for detecting a fading speed from a change in signal level from a 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 on the mobile device side in mobile communication between the base station and the mobile device, wherein the base station side is transmitted from the mobile device. Signal level detecting means for detecting a received signal level of an incoming radio wave, history storing means for storing a history of signal levels of the obtained received signal, and predicting a signal level of the received signal after a predetermined time from the stored history Prediction means to perform, according to the predicted signal level, creating means for creating a power control command for transmission power control on the signal transmitting side, and transmitting means for transmitting the created power control command, The mobile station extracts a pilot signal from the received signal, detects a signal level of the extracted pilot signal, and a signal from the searcher receiver. Averaging means for averaging the bells for a predetermined averaging time to obtain an average signal level, and determining transmission power according to the average signal level, and changing the determined transmission power according to the power transmission command. And transmission power control means.

[0023]

As described above, according to the present invention, since the reception power is detected using the pilot signal, the transmission power is controlled with respect to the reception signal power of only the base station with which the mobile station is currently communicating. And appropriate power control can be performed. In addition, 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 be always performed at an appropriate time, and the median value of the fading electric field can be estimated. For this reason, open loop control can be performed appropriately,
The transmission power can be increased without increasing the interference of the system. Further, it is possible to prevent the transmission characteristics of the own station from deteriorating without increasing the interference of the system.

Further, the base station predicts the future state of the radio wave from the mobile station received by the base station,
Since the power control command is transmitted, by controlling the transmission power in accordance with 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 and the line capacity are improved.

[0025]

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

[0026] The mobile station-side configuration diagram 1 is a block diagram showing the overall configuration of a mobile station 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.
This is the antenna 10 are analog receiver 12 is connected, analog receiver 12 converts the received radio wave to an intermediate frequency (down-conversion), with obtaining an IF signal, for selecting only signal - band of a predetermined frequency. Also, AGC
Control is performed by means to keep the signal level of the output IF signal 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, the audio signal is supplied to the handset 22, and 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 an audio 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 it is subjected to A / D conversion, modulation (for example, QPSK modulation), and spread spectrum (for example, direct spread by PN code). Are performed. And the transmission modulator 2
4, transmission power controllers 26 and 28 are connected in series. Here, amplification processing of a predetermined gain is performed, and transmission is performed from the antenna 10 (normally, after up-conversion, transmission is performed).

Use of pilot signal In addition, the analog receiver 12 includes the searcher receiver 3
0 is connected, where a pilot signal included in the received signal is extracted and its signal strength is detected. This pilot signal is a signal to be used for initial acquisition of a base station in a mobile device, and the same PN code is used in each base station. Based on the identification. Further, this pilot signal is multiplexed with communication data or the like by a Walsh function, and W0 (No. 0 Walsh function) is usually assigned. The WO is composed of all 0 's, and the result of multiplying by 2's complement (0 corresponds to + and 1 corresponds to-) 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 pilot level measurement here is
This is done using path diversity. This is because, in mobile communications, frequency selective fading often caused by multiplex transmission delay is separated by the resolution of the spreading code, and larger separated levels are weighted more heavily and combined in time. Technology. By using this path diversity, highly accurate pilot level measurement can be performed. Then, the searcher receiver 30 compares the signal levels of the pilot signals from the plurality of base stations and generates a signal for changing the base station and the like.

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

Then, the control processor 32
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 is known. Then, the control processor 32 generates an analog level control signal from the obtained reception intensity, and thereby controls the power of the output signal in the transmission power controller 28. The control processor 32 takes the contents of the transmission power control transmitted from the base station 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.

[0031] Configuration Figure 2 for transmission power control, showing the members for transmission power control. As described above, the analog receiver 12 includes the down converter 12a, the band pass filter 12b, the IF amplifier 12c, and the AGC detector 12d. Therefore, the antenna 10
Is converted to an IF signal by a down-converter, and a signal in a frequency band used for communication is selected by the band-pass filter 12b. The output of the band-pass 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, an AGC detector 1 controls the output level of the IF amplifier.
The AGC detector 12d detects the output level of the IF amplifier 12c, and feedback-controls the gain of the IF amplifier 12c accordingly.

The AGC detector 12d is
A signal about the gain to be fed back is supplied to the control processor 32. Thus, the control processor 32 can recognize the level of the received pilot signal 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 the pilot signal is recognized separately for each base station in the searcher receiver 30 as described above. Therefore, the received power obtained here excludes signals from other base stations, and the received power of signals from base stations that are performing communication can be accurately known. Therefore, even near the boundary of a cell (an area under the control of one base station) where the signal levels from a plurality of base stations increase, the level of the received signal from the target base station can be accurately detected. By supplying a signal indicating the difference between the 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 in accordance with the obtained reception power.
And a gain controller 2 for controlling this gain
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 a time constant control signal to the gain controller 28b in addition to the gain control signal. And
The gain controller 28b has variable resistors R1 and R2, diodes D1 and D2, and a capacitor C, as shown in FIG. The variable resistor R1 and the diode D
1 and a series connection of a variable resistor R2 and a diode D2 are connected in parallel, a gain control signal is input to the variable resistor R1R2, and the diodes D1, D2
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, IF is determined by a time constant determined by the values of R1 and C.
When the potential of the signal for controlling the gain of the amplifier 28 increases and the potential of the gain control signal decreases, the potential of the signal for controlling the gain of the IF amplifier 28 decreases with a time constant determined by the values of R2 and C. Therefore, by making the values of R1 and R2 different, the response of the transmission power to the gain control signal can be made 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.

Further, the resistance values of the variable resistors R1 and R2 can be changed by a time constant control signal while maintaining the above relationship. Therefore, the speed of response to the received power can be changed based on a command from the control processor 32. 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 in accordance with the detected fading speed, changes the time constant in this circuit, and controls the gain control. It controls the response of the transmission power controller 28 to the signal.

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

First, the level crossing counter is initialized (reset), and the operation of a timer for defining a counting cycle is started (S1). Then, a value x _n for the received power input is input, and the previous value x
_It is determined whether _n-1 <preset level and _xn ≧ preset level (S3). That is, it is determined whether or not a level crossing has occurred by determining whether or not the value has changed from a value less than a predetermined preset level to a value higher than the preset level. If YES, the value of the level crossing counter is incremented (added by 1) (S4). On the other hand, if it does not intersect in S3, this S
Bypass 4 Next, it is determined whether the timer has expired (check the value of the timer and whether one count cycle has elapsed) (S5).
Return to 2 and repeat the level crossing count. The reception level _xn is obtained by averaging the pilot level by about 1 msec, and the period of the timer may be set to, for example, 1 second.

[0038] In this manner, since the number of level crossings in a predetermined time is counted, then obtaining the maximum Doppler frequency f _d (S6). The maximum Doppler frequency is obtained by the level cross count value × π ^1/2 e ^−1/2 . This is because, in fading in a mobile device running at an equivalent speed such as an automobile, the fading speed often corresponds to the maximum Doppler frequency, and it is known that the above-described relationship exists between the number of level crossings and the maximum Doppler frequency. It is. This is described in, for example, “Basics of Mobile Communication” published by the Institute of Electronics, Information and Communication Engineers, October 1, 1986.

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

That is, the variable resistors R1, R in FIG.
The value of 2 is changed according to R1 = T / C, R2 = T / 10C, and the time constant of this circuit is set so that the gain control signal is averaged with time T. If the moving speed of the mobile device is slow, the average time is 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 in which the time constant is set as described above.

As described above, in this embodiment, since the fading speed (maximum Doppler frequency) is obtained and the averaging time T is changed in accordance with the phasing speed, 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, it is possible to shorten the averaging time and make the response of the open loop transmission power control fast. . In the above example, the maximum Doppler frequency is used as the fading speed. However, if the fading speed can be detected even for other fading, the averaging time can be controlled accordingly. Further, the control processor 32 detects the received power from the level of the pilot signal. However, the present invention is not limited to this. The received power can also be detected based on the level of the IF signal output from the analog receiver.

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 an IF signal is output. The IF signal from the analog receiver 42 is a mobile unit "N"
(The mobile units are provided corresponding to the number of mobile units that perform communication, and N is a code specifying one of the mobile units.) The digital data receiver 44 is supplied to the digital data receiver 44. The signal output from the digital data receiver 44 and subjected to processing such as despreading is supplied to the exchange via the user digital baseband circuit 46.

A signal from the exchange is supplied from a user digital baseband circuit 46 to a transmission modulator 48, where processing such as modulation and spread spectrum is performed.
You . The transmission signal output from the transmission modulator 48 is
After being multiplexed with a signal from another transmission modulator in an adder 50 and multiplexed with a pilot signal from a pilot signal generator 54 in an adder 52, the antenna 4
0 and transmitted from here. On the base station side, a closed loop power control processor 56 is provided, and based on the reception 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 the power control command to the transmission modulator 48, and the transmission modulator 48 inserts the power control command into the transmission signal.

Here, the configuration of the digital data receiver 44 is shown in FIG. Thus, 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 correlation between the PN code supplied from the PN generator 64 are performed. It comprises a PN correlator 66, a Hadamard transform filter 68 for performing a Hadamard transform on a correlation signal output from the PN correlator 66 and solving Walsh coding, and a user decoder 70 for demodulating data. And the analog receiver 4
The IF signal supplied from 2 is converted into digital data by an A / D converter 62 and supplied to a PN correlator 66. The PN correlator 66 calculates the correlation between the PN signal assigned to the mobile unit with which the moval unit “N” supplied from the PN generator 64 is communicating and the received signal. That is, a correlation signal of a specific PN code is extracted from the signals that have been spread by the PN code, and spectrum despreading is performed. As a result, a user channel is extracted from the data that has been multiple-accessed. 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. User decoder 70
Outputs the decoded data level in symbol units.

The decoded data level is supplied to a closed loop power control processor 56, where it is used to generate a power control command.

Next, FIG. 7 shows the configuration of the closed loop power control processor 56. As described above, the decoded data level is supplied to the power average calculator 80, where the power average is calculated. Power averaging is performed in slot units (1.25 msec) by well-known digital processing. The output from the power average calculator 80 is compared in the comparator 82 with the reference power level. The decoded data level is also supplied to a threshold detector 84, where power values below a predetermined threshold are replaced by zero. This means that the transmission from the mobile device is 1.25.
In some cases, the data is transmitted in bursts in units of msec slots, so that data that has not been transmitted is not taken in. The output of the threshold detector 84 is supplied to a buffer memory 86, where a plurality of decoded data power levels for a predetermined period are stored in symbol units. 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. The value of the received power predicted by the predictor 88 is calculated by the comparator 9.
0, where it is compared to a reference power level.

The signal of the comparison result between 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 a power control command according to the comparison result between the comparators 82 and 90. That is, the power value of the power average calculator 80 per slot,
When both the predicted values of the symbol unit of the predictor 88 are equal to or lower than the reference level, the outputs of both of the comparators 82 and 90 become signals for increasing the transmission power of the mobile station. An H signal is output, which causes the power control command generator 94 to create a command to increase power. The mobile station increases the transmission power by a predetermined level based on this command, and the reception level at the base station from the mobile station is increased.

Prediction of Received Power Next, prediction in the predictor 88 will be described. For example, as shown in FIG. 8, it is assumed that the received power T has changed as shown in FIG. In this case, each power of time t ₀ ~t _n becomes P ₀ to P _n.

On the other hand, since the power control command is randomly inserted into the transmission signal as described above, the time of transmission to the mobile station is not constant. Therefore, the predictor 88 receives the timing information of the insertion of the power control command from the transmission modulator 48 and the control delay in the mobile device (from the reception of the power control command by the mobile device to the actual power control). Delay time), the time actually controlled by the power control command created is determined. That is, if the current time is t _n and the time until the actual control is performed is Δ, the time t _n +
It predicts the received power _{P tp} at delta = t _p.

Next, the 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, based on the command transmission timing, a time (predicted time t _p ) at which the mobile station controls the transmission power by this command is determined (S12).

Next, in order to predict the power by linear prediction, a correlation coefficient is obtained. (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, each time being 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 those of time t _p -t _{0, γ 1} at time t _p
Those of _{-t 1, ..., γ n-} 1 is that of the time t _p -t _n-1, γn represents the things of time t _p -t _n.

Next, based on the alpha ₁ to? _N calculated, to calculate the _{P tp = α 1 P 0 +} α 2 P 1 + α 3 P 2 + ... + α n P n-1 from the P _tp (S16). In this manner, it is possible to predict the received power P _tp at a predetermined time t _p.

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

As described above, the transmission of the power control command requesting the power increase only when the power increases at both the power value at that time and the predicted power value is a bad effect when the power is erroneously increased. Is larger than the case of accidentally decreasing. Note that the power control command may be created from the determination result of only the predicted value.

Another Embodiment Next, FIG. 10 shows a modification of the present invention. In this example,
A digital data receiver 16 and a diversity combiner 18 are added to those of FIG. The reason why two digital data receivers are provided in this way is to achieve path diversity reception, and both perform spectrum despreading on the same PN code at different timings, thereby arriving on different paths (paths). The same signal can be extracted. The two digital data receivers 14 and 16 are provided with a diversity combiner 18.
And the diversity combiner 18 synchronizes and adds the two supplied signals. That is, the difference in the arrival time corresponding to the path difference is compensated and the addition is performed at the same phase. As a result, signals arriving at the mobile device through two paths can be added, and the energy of the received signal can be increased. Here, this addition is not a simple addition, but a weighted addition that increases the weight toward a more certain signal. Thereby, a suitable increase in signal energy can be achieved.

In this embodiment, the output signal from the diversity combiner 18 is transmitted to the control processor 3.
2 has been entered. Thus, the control processor 32 can estimate the fading speed from the change in the received power after the weighted addition. However, in this case, it is necessary to transform the equation for obtaining the maximum Doppler in FIG. 4 into an equation that takes into account diversity reception. Therefore, it is possible to estimate the fading speed with higher accuracy, and to control the averaging time in the transmission power controller 28 accordingly. In this example, the gain setting of the transmission power controller 28 by the control processor 32 also depends on the energy of the signal supplied from the path diversity combiner 18 and the analog receiver 12.
From the two AGC gains supplied from.

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

In the above-described embodiment, the maximum Doppler frequency is used as the fading speed. However, if the fading speed can be estimated, the present invention can be applied to other fading. Further, in estimating the power, the correlation coefficient is determined by the Bessel function on the premise of Rayleigh fading, but if the fading is other, a function corresponding to the fading may be used. Other functions may be given in a table or the like. That is, an expression for obtaining a correlation coefficient can be determined by obtaining a power spectrum and performing Fourier transform on the power spectrum. Further, the prediction is not limited to the 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 transmission power can be controlled with respect to the received signal power of only the base station with which the mobile station is currently communicating, and appropriate power control can be performed. it can. In addition, 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 be always performed at an appropriate time, and the median value of the fading electric field can be estimated. For this reason, there are few errors in the control of the open loop, and it is possible to increase the transmission power without increasing the interference of the system. Further, it is possible to prevent the transmission characteristics of the own station from deteriorating without increasing the interference of the system.

Further, the base station predicts the future state of the radio wave from the mobile station received by the base station,
Since the power control command is transmitted, by controlling the transmission power in accordance with 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 and the line capacity are improved.

[Brief description of the drawings]

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

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

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

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

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

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 of the mobile device side.

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

[Explanation of symbols]

 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 transform filter 70 user decoder 80 power average 82, 90 comparator 84 threshold detector 86 buffer memory 88 Predictor 92 AND gate 94 Power control command generator

Continuation of the front page (56) References JP-A-59-226525 (JP, A) JP-A-62-285533 (JP, A) JP-A 64-32727 (JP, A) JP-A-3-35625 (JP) JP-A-4-502841 (JP, A) JP-T-7-500460 (JP, A) JP-T-7-502631 (JP, A) European Patent Application Publication 462952 (EP, A1) (58) Field surveyed (Int. Cl. ⁶ , DB name) H04B 7/00-7/38

Claims (16)

(57) [Claims] 1. A transmission power control apparatus for use in a mobile station performing mobile communication by code division multiple access by transmitting and receiving a code-spread signal, comprising: a correlation operation using a spread code for a code-spread received signal. Mobile communication, comprising: a searcher receiver that separately detects pilot signal levels from a plurality of base stations, and transmission power control means that controls transmission power according to the signal levels from the searcher receiver. The transmission power control device in. 2. A transmission power control device for use in a mobile station that performs mobile communication by code division multiple access by transmitting and receiving a code-spread signal, comprising: converting a signal received by an antenna into an intermediate frequency signal; An analog receiver for selecting a signal of a predetermined band from the intermediate frequency; an AGC means for controlling the output of the analog receiver to be at a predetermined level; and a correlation operation using a spread code for the output of the analog receiver. A searcher receiver that separately detects a pilot signal level, a searcher receiver that detects a pilot signal level for each base station by a correlation operation using a spreading code, and an analog receiver AGC signal and a pilot signal level from the searcher receiver. Control transmission power based on both A control processor, the transmission power control apparatus in a mobile communication, characterized in that and a transmission power control means for controlling the transmission power according to the signal level from the control processor. 3. The apparatus according to claim 1, wherein the searcher receiver separates frequency-selective fading caused by a multiplex transmission delay with a resolution of a spreading code, and further separates the frequency-selective fading with a large separated level. A transmission power control apparatus in mobile communication, wherein a pilot level from each base station is measured using path diversity that performs weighting and combines at the same time. 4. A transmission power control apparatus for use in a mobile station which performs mobile communication by code division multiple access by transmitting and receiving a code-spread signal, comprising: a correlation operation using a spread code for a code-spread received signal. Level detecting means for detecting the signal level of the received signal, and averaging means for averaging the signal level of the detected received signal for a predetermined averaging time to obtain an average received signal level. Transmission power control means for controlling the transmission power, fading speed detection means for detecting a fading speed from a change in the signal level of the received signal, and averaging for changing the averaging time according to the obtained fading speed. A transmission power control device in mobile communication, comprising: time control means. 5. The mobile communication system according to claim 4, wherein said level detecting means includes a searcher receiver for separately detecting pilot signal levels from a plurality of base stations by a correlation operation. Transmission power control device. 6. The apparatus according to claim 4, wherein said fading speed detecting means checks a change state of a received signal level, and detects based on a number of times the received signal level crosses a predetermined value within a predetermined time. Transmission power control apparatus in mobile communication. 7. The apparatus according to claim 6, wherein said fading speed detecting means detects a maximum Doppler frequency based on the detected number of crossings, and said averaging time control means is inversely proportional to the detected maximum Doppler frequency. A transmission power control device in mobile communication, wherein an averaging time is obtained as a value, and an upper limit is set for the obtained averaging time. 8. A transmission power control device used for mobile communication by code division multiple access by transmitting and receiving a code-spread signal, wherein a radio wave from a specific mobile device is despread by using a predetermined code. Level detecting means for detecting the signal level of the received signal, history storing means for storing the history of the obtained signal level of the received signal, and predicting the signal level of the received signal after a predetermined time from the stored history. Prediction means; creation means for creating a power control command for transmission power control on the signal transmitting side according to the predicted signal level; and transmission means for sending the created power control command. Transmission power control device in mobile communication. 9. The apparatus according to claim 8, wherein the prediction unit considers a delay time until the mobile station controls the transmission power by the power control command, and determines a signal level of the reception signal after a predetermined time. A transmission power control device in mobile communication characterized by predicting. 10. The transmission power control device in mobile communication according to claim 9, wherein the prediction unit performs prediction in consideration of a transmission timing of the generated power control command. 11. The apparatus according to claim 9, wherein the prediction unit performs prediction in consideration of a control delay from when the mobile station receives the power control command to when the mobile station performs transmission power control. Characteristic transmission power control device in mobile communication. 12. The apparatus according to claim 8, wherein the transmission power is set only when both the signal level detected by the level detection means and the signal level predicted by the prediction means are equal to or less than a predetermined value. A transmission power control device for mobile communication, wherein the transmission power control device generates a power control command requesting an increase in transmission power. 13. The transmission in mobile communication according to claim 8, wherein said prediction means performs a prediction by linear prediction from the contents of a stored history. Power control device. 14. A transmission power control system for controlling transmission power on a mobile device side in mobile communication in which communication between a base station and a mobile device is performed by code division multiple access by transmitting and receiving a code-spread signal. The base station side despreads the radio wave transmitted from the mobile station, and detects the signal level of the received signal from the predetermined mobile station obtained by despreading. History storing means for storing the history of the signal level of the signal; predicting means for predicting the signal level of the received signal after a predetermined time from the stored history; and transmission on the signal transmitting side according to the predicted signal level. A generating unit for generating a power control command for power control; and a transmitting unit for transmitting the generated power control command. A searcher receiver for separately detecting pilot signal levels from a plurality of base stations by a correlation operation using a spread code for the searcher, and averaging signal levels from the searcher receiver for a predetermined averaging time to obtain an average signal level And the transmission power is determined according to the average signal level.
A transmission power control system for mobile communication, comprising: transmission power control means for changing the determined transmission power according to a power transmission command. 15. The system according to claim 14, further comprising: a fading speed detecting means for detecting a fading speed from a change in the signal level of a received signal; and changing the averaging time according to the obtained fading speed. A transmission power control system in mobile communication, comprising: averaging time control means. 16. The system according to claim 14, wherein the prediction unit performs prediction in consideration of a control delay until the mobile station performs transmission power control based on the generated power control command. Power control system in mobile communication.