JP3347642B2 - Communication device and communication system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio communication system for performing radio communication between a first communication device and a second communication device, and more particularly to a code division multiple access (hereinafter referred to as CDMA-C).
ode Division Multiple Access. The present invention is suitably applied to a wireless communication system for performing wireless communication by code division multiple access between a base station and a mobile station according to a communication system.

[0002]

2. Description of the Related Art A form in which a number of users communicate with each other while sharing the same frequency band is called a multiple access (Multiple Access).
cess), and in order to prevent interference between the communication of each group, frequency division multiple access (FDMA-Frequency) using a different frequency (radio channel) for each user.
Division Multiple Access-) Multiplexing communication system and time division multiple access (TDMA-Time Division Multiple Access)
s-) It is common to use a multiplex communication system or a combination thereof. That is, each user divides "frequency" or "time" in the space where communication is performed to prevent overlap (interference) with other users.

By the way, in the multiple access as described above, if signal waves of another group of users are regarded as interference waves, the spread spectrum communication system having a remarkably high rejection capability for the interference waves is used. Even if the signal overlaps with the signal on the frequency axis or on the time axis, communication without interference is theoretically possible. In order to pick up only the target signal from the signals that overlap both in frequency and time, the signals are multiplexed by using a kind of key (spreading code sequence) used when modulating each signal. Signal may be separated. The multiple access communication method using this spread spectrum (hereinafter abbreviated as SS-Spread Spectrum-) communication method is the CDM described above.
A, which is said to be the core technology of the next-generation mobile phone system.

In the digital mobile radio communication system, fading in which the electric field intensity of a signal radio wave changes causes a reduction in signal-to-noise ratio (S / N or S / N ratio) and waveform distortion, thereby deteriorating communication quality. There was a problem. Further, in the SS communication method used for the CDMA communication method and the like, fading of frequency selectivity due to multipath and fading caused by a mobile station moving at a high speed with respect to a base station become problems.

[0005] As a method for solving this problem and improving the communication quality, a literature "Andrew J. Viterbi," CD
MA Principles of Spread Spectrum Communication '' p.
As described in p.113-119, AddisonWesley, 1995, issuance, when performing wireless transmission from a mobile station to a base station, perform transmission power control (reverse link power control) on the mobile station side. Thus, a method for keeping the reception level at the base station constant is known.

FIG. 2 shows a schematic configuration of a radio communication system using the reverse link power control method. In FIG. 2, a base station 1 to which a signal affected by fading is supplied includes a digital demodulator 10 that digitally demodulates the received signal, converts the demodulated signal into a received data signal, and outputs the data. Power measurement circuit (POW) for measuring the power (received power level)
And a transmission power information generation circuit 1 for generating transmission power control information based on a difference between the reception power level and the target level
2 and a digital modulator 16 for multiplexing the transmission power control information into transmission data. The transmission power information generation circuit 12 includes a subtractor 13 that calculates a difference between the reception power level and the target power level, a target power level holding unit (M) 14 that holds the target power level, and a subtractor 13.
And a quantizer (Q) 15 that forms 1-bit transmission power control information for instructing an increase or decrease of the transmission power in the mobile station 2 based on the difference output of the above.

[0007] The digital modulator 16 multiplexes the transmission power control information with the transmission data, and then digitally modulates the information to output to the mobile station 2.

On the other hand, the mobile station 2 receiving the digitally modulated transmission data includes a digital demodulator 20 for digitally demodulating the received signal and separating and outputting transmission power control information from the digitally demodulated reception data. ,
A transmission power control circuit 21 that controls transmission power based on the separated transmission power control information, and a linear domain conversion circuit (EXP) that converts the controlled transmission power to a predetermined amplification factor according to a predetermined arithmetic expression and outputs the result. And a transmission power amplifier (A) for variably amplifying transmission power according to the predetermined amplification factor.
26. The transmission power control circuit 21 includes, for example, an inverse quantizer (Q ⁻¹ ) 22 that outputs a power change step of “+0.5 dB” when increasing power and “−0.5 dB” when decreasing power. Adder 23 that adds this power changing step to the power control value one sample before.
And a holding unit (z ^-1 ) 24 for holding the power control value one sample before.

In the conventional radio communication system having the above functions, the difference between the received power level and the target power level is quantized by one bit at the base station 1 and transmitted, and the mobile station 2 integrates the difference. By restoring the fading signal and controlling the variable amplifier 26 with the inverse characteristic of the characteristic of the fading signal, it can be interpreted that the fading signal is canceled.

The processing in such a conventional radio communication system utilizes the property that the fading signal hardly changes in a short time.

[0011]

However, in the conventional radio communication system, control is performed on the assumption that the fading signal hardly fluctuates in a short time. There has been a problem that the base station 1 cannot make the transmission power control follow a sudden fading fluctuation that occurs when moving at high speed.

The transmission power control on the mobile station 2 side requires transmission power control information from the base station 1 side.
When transmission power control information is transmitted from the base station 1 to the mobile station 2, a processing delay occurs. Therefore, as the processing delay increases, fading greatly varies during the processing delay. In this case, the conventional wireless communication system also has a problem that the followability to fading is deteriorated and the communication quality is degraded as the error in the transmission power control increases.

[0013] In view of the above problems, the present invention can cope with a sudden fading fluctuation when one of the communication devices moves at high speed, and furthermore, a processing delay in transmitting control information. It is an object of the present invention to provide a communication device and a communication system capable of following the above.

[0014]

According to a first aspect of the present invention, a first communication apparatus measures reception power from a second communication apparatus, and measures the measured reception power and a target power. And generates transmission power control information corresponding to the difference between
The communication device, which is the second communication device in the communication system in which the communication device controls the transmission power according to the transmission power control information transmitted from the first communication device,
(1) A difference signal obtained by inversely quantizing the transmission power control information supplied from the first communication device is converted into a fading signal, and a Doppler frequency is estimated from the fading signal sequence. Transmission power control means for estimating an estimated value of a fading signal when a processing time in the power control system has elapsed from the current time based on the estimated value of the Doppler frequency; and (2) a target power level held in advance; Adding means for adding the estimated value of the fading signal generated by the transmission power control means to generate a power control value.

According to a second aspect of the present invention, the first communication device measures the received power from the second communication device and transmits transmission power control information according to a difference between the measured received power and the target power. In the communication device that is the first communication device in the communication system in which the second communication device generates and controls the transmission power according to the transmission power control information transmitted from the first communication device, (1) Power measuring means for measuring the received power level; (2) target level subtracting means for calculating the difference between the received power level and the target power level; and (3) the difference signal output from the target level subtracting means is converted into a predetermined number of bits. And (4) inversely quantize the transmission power control information output from the quantization means, and convert the inversely quantized difference signal into a fading signal. conversion The Doppler frequency is estimated from the fading signal sequence, and based on the fading signal sequence and the Doppler frequency estimation value, the estimated value of the fading signal when the processing time in the power control system has elapsed from the current time is calculated. Local transmission power control means for estimating the estimated value of the fading signal when one unit time has elapsed from the time; and (5) output from the local transmission power control means to the reception power level output from the power measurement means. Adding means for adding the estimated value of the fading signal when the processing time has elapsed from the current time, and (6) from the output of the adding means, 1 from the current time output from the local transmission power control means. The estimated value of the fading signal when the unit time has elapsed is subtracted, and the signal after the subtraction is set as the reception power level, and the target level subtraction is performed. Characterized in that it comprises a subtraction means for providing a stage.

Further, according to a third aspect of the present invention, the first communication device measures the reception power from the second communication device, and transmits transmission power control information according to a difference between the measured reception power and the target power. In the communication system in which the second communication device generates and controls the transmission power according to the transmission power control information transmitted from the first communication device, as the first communication device,
The communication device according to the second aspect of the present invention is applied, and the communication device according to the first aspect of the present invention is applied as the second communication device.

Still further, according to a fourth aspect of the present invention, the first communication device measures the reception power from the second communication device, and transmits the transmission power control information according to the difference between the measured reception power and the target power. In the communication system in which the second communication device controls the transmission power according to the transmission power control information transmitted from the first communication device, (1) the first communication device transmits the reception power Power measuring means for measuring the level, target level subtracting means for calculating a difference between the target power level from the measured received power level, and a difference signal output from the target level subtracting means, quantized to a code of a predetermined number of bits, (2) The communication device according to the first aspect of the present invention is applied to the second communication device as the second communication device.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of a wireless communication system according to the present invention will be described in detail with reference to the accompanying drawings.

(A) First Embodiment In the wireless communication system according to the first embodiment of the present invention shown in FIG. 1, the first communication device of the present invention is applied to a base station of a mobile communication system. And an example in which the second communication device is applied to a mobile station of a mobile communication system.

FIG. 1 is a block diagram showing a schematic configuration of power control in a reverse link power control method for a mobile communication system according to the first embodiment.
In this figure, the same or corresponding components as those of the conventional wireless communication system shown in FIG.

In FIG. 1, the radio communication system according to the first embodiment includes a base station 1A as a first communication device.
And a mobile station 2A as a second communication device.

The base station 1A includes a digital demodulator 10 for digitally demodulating a received signal input from the mobile station 2A under the influence of fading, and a digital demodulator 1
Power measurement circuit (POW) 11 for measuring a reception level of demodulated data signal RBS demodulated by 0, transmission power information generation circuit 30 for generating transmission power information according to the measured reception level, and transmission power information generation A digital modulator 16 for digitally modulating the transmission power information generated by the circuit and outputting the result to the mobile station 2A.

First, a power control operation according to the reverse link power control method of the base station 1A having the above configuration will be described.

The digital demodulator 10 receives a received signal from the mobile station 2A affected by fading, digitally demodulates the received signal, and demodulates the demodulated data signal RBS (i) (i represents a sample number. Integer greater than 0 representing; sample number corresponding to information symbol period)
To the power measurement circuit 11 as well as to a demodulation data signal processing circuit (not shown).

The power measuring circuit 11 outputs the demodulated data signal RB
From S (i), the power P (n) [dB] is measured as reception level information (transmission power information of the mobile station 2A).
The power measurement circuit 11 is, specifically, a digital demodulator 1
0, the demodulated data signal RBS (i) output every 32 KHz of the information symbol is input, and as shown in equation (1), the square mean of every 20 samples converted to a decibel is converted into a power P (n ). _{P (n) = 10log 10 (} ΣR BS (i-k) 2/20) ... (1) where the sample number 20 to be subjected to the average has been determined by the transmission power control period and information symbol period the In the case of the embodiment, the transmission power control is set to 1.6 kHz (32 kHz).
(Hz / 20). Also, n
Represents the sampling time of the power control. The sum Σ in Equation 1 is calculated from “(n−1) × 20 + 1” to “n × 2”.
0 ". As an averaging method for calculating the reception power P (n), a method based on weighted averaging, exponential smoothing, or the like can be used.

The power control information generation circuit 30 includes a subtractor 3
1. Target level holding unit (M) 32, quantization circuit (Q) 3
3 and a scale adaptation circuit (S) 34.

The subtractor 31 and the target level holding unit 32
From the measured mobile station transmission power P (n), the target level M
A target level subtraction circuit for subtracting [dB] is formed, and the signal E (n) after the subtraction is supplied to the quantization circuit 33. That is, as shown in equation (2), the received power P
(N) and the target power M (n), the difference signal E
(N) [dB] is calculated. The target power M (n) is arbitrarily set so that the communication quality falls within a certain allowable range, and is always a fixed value. Base station 1A
There is also a communication system in which the target power is transmitted and received in advance by the mobile station 2A, but when performing power control, it is treated as a fixed value.

E (n) = P (n) −M (n) (2) The quantization circuit 33 converts the difference signal E (n) from the scale adaptation circuit 34 into a scale (quantization step) S ( n) (substantially equal to the standard deviation of the difference signal E (n), as will be described later)
, And then obtains a quantized value PC (n) according to the table shown in FIG. 4 and outputs the quantized value PC (n) to the scale adaptation circuit 34 and the digital modulator 16 as transmission power control information. I do.

When the quantized value PC (n) is "01", it means that the transmission power at the mobile station 2A is considerably large, and when the quantized value PC (n) is "00", the mobile station 2A has the transmission power. 2A
Means that the transmission power is large, and the quantization value PC
If (n) is "10", it means that the transmission power at the mobile station 2A is small, and if the quantization value PC (n) is "11", it is that the transmission power at the mobile station 2A is quite small. Means.

The scale adaptation circuit 34 generates quantized values PC (n),..., Of six samples from the present to the past.
The scale S (n + 1) is output using PC (n-5) as follows. First, according to the chart of FIG. 5, the 2-bit quantized value PC (n) is converted into a value F (PC (n)) representing a positive or negative magnitude, and then, according to equation (3), Find the average m (n). Finally,
According to equation (4), scale S (n + 1) at the next time
Ask for. The sum 総 in the equation (3) is for k = 0 to 5.

M (n) = Σ | F (PC (nk) | / 6 (3) S (n +) = S (n) × 2 ^{((m (n) -1.5) / 4)} (4) When the scale S (n) is appropriate, the sequence of the quantized values PC (n) can take four codes at random, and therefore take a value near the average absolute value m (n) F1.52. In this case, the scale S (n) becomes substantially equal to the standard deviation of the difference signal E (n), and the scale S (n + 1) at the next time is obtained.
Is updated to be equal to the scale S (n) at the current time.

When the scale S (n) is smaller than the standard deviation of the difference signal E (n), the sequence of the quantized values PC (n) takes many values of "01" and "11", and Average value m
Since (n) is larger than 1.5, the scale S (n + 1) at the next time is updated so as to be larger than the scale S (n) at the current time.

When the scale S (n) is larger than the standard deviation of the difference signal E (n), the opposite operation is performed, so that the scale S (n + 1) at the next time is the scale S at the current time. It is updated so as to be smaller than (n).

As described above, the scale S (n + 1) is adaptively updated so that it always becomes equal to the standard deviation of the difference signal E (n).

Note that the number of samples used for updating the scale (ie, 6 samples) and parameters such as “4” in equation (4) that affect the amount of update to the scale at the next time depend on the fading of power control. This influences the following speed, and the wireless communication system according to the first embodiment uses an empirically obtained value. The digital modulator 16 multiplexes the 2-bit quantized value PC (n) output from the quantizing circuit 33 as transmission power control information into transmission data, and then digitally modulates it and transmits it to the mobile station 2A. I do.

Next, the mobile station 2A as the second communication device
The configuration and operation of power control according to the reverse link power control method will be described.

In the mobile station 2A, the components for controlling the transmission power include the digital demodulator 20, the transmission power control circuit 40, the target level holding unit (M) 28, and the adder 2.
7, a linear domain conversion circuit (EXP) 25 and a transmission power amplifier 26 are provided.

The transmission power control circuit 40 includes an inverse quantization circuit (Q ^-1 ) 41, a scale adaptation circuit (S) 42, and an adder 4.
3. Filter circuit (P) 44 and prediction coefficient calculation circuit (A
P) 45, a coefficient calculation circuit 4 to be placed aside
5 includes a Doppler frequency estimation circuit (FD) 46 and a coefficient conversion circuit (CF) 47.

The digital demodulator 20 digitally demodulates a signal received from the base station 1A, and in the demodulated data signal, generates a transmission power control cycle (0.625 msec = 1 /
A series of 2-bit quantized values PC (n) as transmission power control information inserted at every 1.6 kHz) is separated and provided to the scale adaptation circuit 42 and the inverse quantization circuit 41.

The scale adaptation circuit 42 performs the same processing as that of the scale adaptation circuit 34 of the base station 1A, and the quantized values PC (n-1),.
Using 6), a scale S (n) is formed and input to the inverse quantization circuit 41.

The inverse quantization circuit 41 is a digital demodulator 20
From the quantized value PC (n) of the base station 1A and the scale S (n) from the scale adaptation circuit 42, as shown in the table of FIG. 6, a difference signal E between the reception level at the base station 1A and the target level E The inversely quantized difference signal Eq (n) corresponding to (n)
And input it to the adder 43.

The filter circuit 44 includes an adder 43 described later.
From a time n to a time n-p + 1, which is internally managed, and is a restored signal Xq of the fading signal.
(N), Xq (n-1), ..., Xq (n-p + 1)
And p times n given from the prediction coefficient calculation circuit 45
A1 (n), A2 (n),..., Ap
From (n), the time n
At the predicted time Xe of the fading signal at the next time n + 1
(N + 1 | n) is generated and given to the adder 43. In addition,
The sum Σ in equation (5) is for k from 1 to p.

Xe (n + 1 | n) = − (ΣAk (n) × Xq (n−k + 1)) (5) Further, the filter circuit 44 recursively calculates the estimated value of the fading signal represented by the equation (5). Using equation (6), an estimated value Xe (n + D | n) of the fading signal at time n + D, which is later than time n by time D, is calculated, and the adder 2 is used.
7 is output. The first sum Σ in equation (6) is k
Is from 1 to j, and the second sum Σ is k is j
For +1 to p. J is 2 to D.

Xe (n + j | n) = − (ΣAk (n) × Xe (n + jk | n) + ΣAk (n) × Xq (nk−j + 1)) (6) Here, time D is the base station 1A. The time may be selected as a time corresponding to a processing delay from when the power measuring circuit 11 measures the power to when the gain of the transmission power amplifier 26 of the mobile station 2A changes. The propagation delay in the propagation path is much smaller than the processing delay in the base station 1A or the mobile station 2A, so that the time D can be determined almost correctly in the design stage. Most of the processing delay time D is a waiting time for the digital modulator 16 to add transmission power control information to transmission data.

The prediction coefficient calculation circuit 45 includes the filter circuit 4
4 use linear prediction coefficients A1 (n), A2 (n),.
.., Ap (n) are formed as follows. Doppler frequency estimation circuit 4 in prediction coefficient calculation circuit 45
6 is output from an adder 43, which will be described later, at each time, and a fading restoration signal Xq (n), internally managed.
The normalized Doppler frequency fd is estimated based on Xq (n−1),. At this time, the fading signal uses a feature in the frequency domain that is a band-limited signal from -fd to + fd in the frequency domain. That is, the fading restoration signals Xq (n), Xq (n−q),... Are converted into the frequency domain using a method such as FFT (Fast Fourier Transform), and the The highest frequency is fd.

Fd = f _max (7) Here, f _max represents the highest frequency among the frequency components included after converting Xq (n) into the frequency domain. From the normalized Doppler frequency fd obtained by the Doppler frequency estimation circuit 46, prediction coefficients A1 (n) to Ap (n) are obtained by the following equation (8) and supplied to the filter circuit 44.

[0047] _{A1 (n) = F FD 1} (fd) A2 (n) = F FD 2 (fd) · · · · Ap (n) = F FD Dp (fd) ... (8) where, for conversion Function F _FD 1 (fd) to F _FD p (f
d) is empirically determined in advance and is stored in the memory inside the conversion circuit.

As shown in Expression 9, the adder 43 calculates the predicted value Xe (n + 1 | n) of the fading signal at the next time n + 1 from the filter circuit 44 and the inverse quantum at the time n + 1 from the inverse quantization circuit 41. Is added to the difference signal eq (n + 1) to obtain a decoded signal Xq (n + 1) of the fading signal at time n + 1, and outputs it to the filter circuit 44 and the prediction coefficient calculation circuit 45.

Xq (n + 1) = Eq (n + 1) + Xe (n + 1 | n) (9) Estimated value Xe (n of fading signal at time n + D output from filter circuit 44 at time n + D after time n
+ D | n) is provided to the adder 27. Adder 27
Is the target power level M (n +) held in the target level holding unit (M) 28 for the estimated values Xe (n + D | n).
D) is added to calculate the power level after the transmission signal from the mobile station 2A at time n + D has been affected by fading.

Then, the linear area conversion circuit 25 outputs the output of the amplification factor A (n +
D) and apply it to the control terminal of the transmission power amplifier 26. Since the processing up to the linear area conversion circuit 25 processes the value in the decibel notation, the linear area conversion circuit 25 is required.

A (n + D) = 10 ^{((−Xe (n + D | n) + M (n + D)) / 10)} (10) As described above, the wireless communication system according to the first embodiment And according to the communication device, from the power measurement in the base station,
Considering the processing delay time D until the power control of the mobile station according to the measured power is executed, the mobile station sets the time n
In the case of −D, an estimated value Xe (n | n−D) of the fading signal X (n) at the time n is formed, and transmitted to cancel the fading at the time n (approximately equal to X (n)). Since power control is performed, better tracking characteristics can be provided for fading signals than when such prediction is not performed, and high-quality communication can be provided.

Here, since the number of stages is increased by using 2-bit information as the power control information, the prediction accuracy can be improved and the above effect can be effectively exerted. . Also, when quantizing to 2-bit power control information, the scale is adaptively changed. Therefore, also in this regard, the prediction accuracy of the fading signal after the time D can be improved, and the above-described effect is effectively achieved. Can be demonstrated. Further, there is an advantage that the amount of calculation for estimating the Doppler frequency and converting the estimated Doppler frequency to a prediction coefficient is small.

(B) Second Embodiment Next, a communication device and a communication system according to a second embodiment of the present invention will be described in detail with reference to FIG.

Also in the radio communication system according to the second embodiment, the first communication device is applied to a base station of a mobile communication system, and the second communication device is applied to a mobile station. FIG. 3 is a block diagram showing a power control configuration according to the reverse link power control method of the mobile communication system according to the second embodiment, which is the same as or equivalent to FIG. 2 and FIG. 1 showing the first embodiment. The same reference numerals are given to the same parts, and the duplicate description will be omitted.

Since the configuration and functions of the mobile station 2B in the second embodiment are the same as those of the mobile station 2A in the first embodiment, a description thereof will be omitted and the second embodiment will be described below. Only the form of base station 1B will be described.

The base station 1B of the second embodiment differs from the base station 1A of the first embodiment mainly in the internal configuration of the power control information generation circuit 50.

The power control information generation circuit 50 includes a subtractor 31, a target level holding unit (M) 32, a quantization circuit (Q) 33, which are constituent elements of the power control information generation circuit 30 of the first embodiment. In addition to the scale adaptation circuit (S) 34,
It has a local transmission power control circuit 60, a time D delay circuit 51, an adder 52 and a subtractor 53, and introduces the concept of so-called predictive encoding into encoding of a difference signal from a target level.

The local transmission power control circuit 60 controls the mobile station 2B
Has the same configuration as the transmission power control circuit 40 of FIG. That is, the local transmission power control circuit 60 includes an inverse quantization circuit (Q ^-1 ) 61, a scale adaptation circuit (S) 34, and an adder 6.
3. Filter circuit (P) 64 and prediction coefficient calculation circuit (A
P) 65, and performs the same operation as the transmission power control circuit 40 of the mobile station 2B by using the sequence of the output code PC (n) of the quantization circuit 33 as an input. The scale adaptation circuit 34 includes a quantization circuit 33.
The circuit used in (1) is also a component of the local transmission power control circuit 60 as it is.

The local transmission power control circuit 60 calculates the (n + D) fading signal estimated value Xe (n
+ D | n) is supplied to the time D delay circuit 51, and the formed fading signal estimated value Xe (n | n-1) at the time n at the time n-1I6 is supplied to the subtractor 53 as a subtraction input. The time D delay circuit 51 delays an input signal by a time D and outputs it. Therefore,
The fading signal estimated value Xe (n
+ D | n) is input at the time D delay circuit 5
1 outputs a fading signal estimated value Xe (n | n-D), and the fading signal estimated value Xe (n |
n−D) is supplied to the adder 52.

In the second embodiment, the output P (n) of the power measuring circuit 11 is supplied to the adder 52. The adder 52 adds the estimated fading signal Xe (n | n-D) from the time D delay circuit 51 and the output P (n) of the power measurement circuit 11 and supplies the addition result to the subtractor 53. I do. By this addition processing, the power control signal -Xe (n | n-D) in the mobile station 2B is canceled and given to the subtractor 53.

The subtractor 53 outputs 1 from the output of the adder 52.
The fading signal estimated value Xe (n | n-1) at the time n predicted from the information before the time is subtracted, and the subtraction result is provided to the subtractor 31. The processing after the subtractor 31 is the first
This is the same as the wireless communication system of the embodiment.

The effects of the wireless communication system according to the second embodiment are as follows. Since the subtraction by the subtractor 53 is a subtraction between the actual fading signal and its estimated value (predicted value), the result of the subtraction has a small dynamic range in which the influence of fading is almost eliminated. Therefore, even if encoding is performed after the subtractor 31, the quantization error is small. This second
According to the second embodiment, the basic technical concept is the same as that of the first embodiment, and therefore, the same effect as that of the first embodiment is obtained. However, as described below, the effect is further enhanced. It is.

That is, after removing the influence of the power control based on the prediction processing at the mobile station 2B from the measured power, the effect of fading is removed by the prediction processing at the base station 1B, and then the difference from the target level is calculated. Since the quantization is performed, the quantization error is further reduced, and the restoration and prediction accuracy of the fading signal in the mobile station 2B is improved.
It is possible to realize better tracking performance than the wireless communication system according to the embodiment, and to provide high communication quality.

(C) Other Embodiments In the above embodiment, the code after quantization is 2 bits. However, the code may be quantized to a code of 3 bits or more. Also, quantization step (scale)
Also, differently from the above-mentioned embodiment, it may be fixed.

In the above embodiment, the estimated value of the fading signal after the time D at the time n is
Although what is obtained by linear prediction is shown, other prediction methods may be applied. However, it is necessary that the coefficient used in this case can be changed according to the Doppler frequency.

Further, although the above-described embodiment has been made with consideration for a mobile communication system conforming to the CDMA communication system, the present invention is applied to a mobile communication system conforming to another communication system such as the TDMA communication system and the FDMA communication system. Can be applied. Also, the present invention can be applied to a communication system in which two communicating stations are both mobile stations.

[0067]

As described above, in the communication device and the communication system according to the present invention, the second communication device which actually controls the transmission power uses the first communication device as the communication partner to control the reception power. In consideration of the processing delay time D from the measurement to the time when the power control is performed by the own device, an estimated value of the fading signal at a future time later than the current time by the delay time D is formed, and the estimated value of the fading signal at the future time is calculated. Since the transmission power is controlled so as to cancel the fading, the signal has a better tracking characteristic with respect to the fading signal as compared with the case where such prediction is not performed. , It is possible to provide high-quality communication with a small amount of calculation.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a communication system according to a first embodiment.

FIG. 2 is a block diagram illustrating a configuration of a conventional wireless communication system.

FIG. 3 is a block diagram illustrating a configuration of a communication system according to a second embodiment.

FIG. 4 is a table illustrating processing of a quantization circuit in the communication system according to the first embodiment.

FIG. 5 is a chart for explaining processing of a scale adaptation circuit in the communication system according to the first embodiment;

FIG. 6 is a table illustrating processing of an inverse quantization circuit in the communication system according to the first embodiment.

[Explanation of symbols]

 1A, 1B First communication device (base station) 2A, 2B Second communication device (mobile station) 11 Power measurement circuit 30, 50 Transmission power information generation circuit 31, 53 Subtractor 32 Target level holding unit 33 Quantization circuit 34 Scale adaptation circuit 40 Transmission power control circuit 41,61 Inverse quantization circuit 42 Scale adaptation circuit 43,52,63 Adder 44,64 Filter circuit 45,65 Prediction coefficient calculation circuit 46,66 Doppler frequency estimation circuit 47,67 Coefficient Conversion circuit 51 Time D delay circuit 60 Local transmission power control circuit 64 Filter circuit

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-10-79701 (JP, A) JP-A-10-126336 (JP, A) JP-A-10-84313 (JP, A) JP-A-10-108 107766 (JP, A) JP-A-8-32513 (JP, A) JP-A-7-283783 (JP, A) Chiharu Yamano, Yuichi Shiraki, Kiyohito Tokuda, "Adaptive Predictive Transmission Power Control in CDMA Systems" Examination, "Proceedings of the 1997 IEICE General Conference, Communications 1, Japan, March 6, 1997, p. 463, (B-5-76) Yuichi Shiraki, Kiyoo Sekine, Chiharu Yamano, Kiyohito Tokuda, "Evaluation of Variable Step-Size Transmission Power Control", Proc. Of the 1996 IEICE Communications Society Conference. 1, Japan, August 30, 1996, p. 329, (B-328) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04B 7/00 H04Q 7/00 H04B 3/00 H04J 13/00 INSPEC (DIALOG) JICST file (JOIS)

Claims (10)

(57) [Claims] A first communication device that measures received power from a second communication device, generates transmission power control information corresponding to a difference between the measured received power and a target power, and In the communication device that is the second communication device in the communication system in which the communication device controls transmission power in accordance with the transmission power control information transmitted from the first communication device, the communication device is supplied from the first communication device. The difference signal obtained by dequantizing the transmission power control information is converted into a fading signal, the Doppler frequency is estimated from the fading signal sequence, and the power is calculated from the current time based on the fading signal sequence and the Doppler frequency estimation value. Transmission power control means for estimating an estimated value of the fading signal when a processing time in the control system has elapsed, and the transmission power control means Ri communication device by adding the estimated value of the generated the fading signal, characterized in that an adding means for generating a power control value. 2. The transmission power control means, comprising: an inverse quantization means for inversely quantizing the transmission power control information supplied from the first communication device to restore a difference signal; Doppler frequency estimating means for obtaining an estimated value of Doppler frequency based on a series of past fading signals obtained by processing the difference signal, and a prediction coefficient based on the Doppler frequency estimated by the Doppler frequency estimating means. Based on the prediction coefficient from the coefficient conversion means and the difference signal restored by the dequantization means, when the processing time in the power control system has elapsed from the current time. 2. The apparatus according to claim 1, further comprising a filter for forming an estimated value of the fading signal and a fading signal to be supplied to the Doppler frequency estimating means. The communication apparatus according. 3. The transmission power control means according to claim 1, wherein the prediction processing is performed according to a linear prediction method.
Or the communication device according to 2. 4. The apparatus according to claim 1, wherein said transmission power control means further comprises scale adaptation means for adaptively changing a scale of said inverse quantization means according to a sequence of said received transmission power control information. 4. The communication device according to 2 or 3. 5. The first communication device measures reception power from the second communication device, generates transmission power control information according to a difference between the measured reception power and a target power, and generates the second power control information. A communication device that is a first communication device in a communication system in which the communication device controls transmission power according to transmission power control information transmitted from the first communication device; Target level subtraction means for calculating the difference between the received power level and the target power level; and quantization means for quantizing the difference signal output from the target level subtraction means into a code having a predetermined number of bits and outputting the code as transmission power control information. And dequantizes the transmission power control information output from the quantizing means, converts the dequantized difference signal into a fading signal, and performs Doppler The wave number is estimated, and based on the fading signal sequence and the Doppler frequency estimation value, the fading signal estimated value when the processing time in the power control system has elapsed from the current time and the unit time elapsed from the current time by one unit time Local transmission power control means for estimating the estimated value of the fading signal at the time, and the reception power level output from the power measurement means, output from the local transmission power control means, the processing time has elapsed from the current time Adding means for adding the estimated value of the fading signal at the time of subtraction; and subtracting the estimated value of the fading signal when one unit time has elapsed from the current time, output from the local transmission power control means, from the output of the adding means. And a subtraction means for providing the signal after subtraction as a reception power level to the target level subtraction means. 6. The local transmission power control means includes: inverse quantization means for inversely quantizing the transmission power control information output from the quantization means to restore a difference signal; and the local transmission power control means restored by the inverse quantization means. Doppler frequency estimating means for obtaining an estimated value of Doppler frequency based on a sequence of past fading signals obtained by processing the difference signal, based on the Doppler frequency estimated by the Doppler frequency estimating means, A fading when a processing time in a power control system has elapsed from a current time based on a coefficient transforming means to be formed, and a prediction coefficient from the coefficient transforming means and the difference signal restored by the dequantizing means. The estimated value of the signal, the estimated value of the fading signal when one unit time has elapsed from the current time, and the fading signal given to the Doppler frequency estimation means The communication apparatus according to claim 5, characterized in that it comprises a filter means for forming a grayed signal. 7. The communication apparatus according to claim 5, wherein the prediction processing of the local transmission power control means is based on a linear prediction method. 8. The local transmission power control means adaptively changes the scales of the quantization means and the inverse quantization means according to the sequence of the transmission power control information output from the quantization means. 8. The communication device according to claim 6, further comprising scale adaptation means. 9. The first communication device measures reception power from the second communication device, generates transmission power control information according to a difference between the measured reception power and a target power, and generates the second power control information. 9. A communication system in which a communication device controls transmission power in accordance with transmission power control information transmitted from the first communication device, wherein the first communication device is the communication device according to claim 5. Is applied, and as the second communication device,
A communication system to which the communication device according to claim 1 is applied. 10. The first communication device measures received power from a second communication device, generates transmission power control information according to a difference between the measured received power and a target power, and In a communication system in which a communication device controls transmission power in accordance with transmission power control information transmitted from the first communication device, the first communication device includes: a power measurement unit configured to measure a reception power level; Target level subtraction means for obtaining a difference between the target power level from the received power level, and quantization means for quantizing the difference signal output from the target level subtraction means into a code having a predetermined number of bits and outputting the code as transmission power control information. A communication system comprising: the communication device according to claim 1 as the second communication device.