JP2003051763A - Receiver used for spread frequency multiplex transmission system and its channel estimation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an excellent reception characteristic independently of a fluctuating speed of received power even when the received power of a pilot channel is small. SOLUTION: Fluctuations in average power of a received signal depend on an averaging period and a fluctuation speed of the received signal. First when the averaging period is decreased, the fluctuation in the average power has the same tendency as instantaneous fluctuation and as the fluctuation speed of the received signal is slower, fluctuations in the average power is more reduced. Further, when the averaging period is extended, the fluctuation in the average power has the same tendency as long term fluctuation, and as the fluctuation speed of the received signal is slower, the fluctuation in the averaged power gets larger. The above natures are utilized, the fluctuation speed of the received signal is estimated from the fluctuation of the average power of a pilot channel and when the fluctuation speed of the received signal is slow, the averaging period of the channel estimation value is controlled longer. Thus, the SNR of the channel estimation value is improved, even when the received power of the pilot channel is small, an excellent characteristic can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiver used in a spread spectrum multiplex transmission system using a code division multiple access (CDMA) or code division multiplex (CDM) transmission technique. The present invention relates to a transmission path response estimation method.

[0002]

2. Description of the Related Art The CDMA communication system has become one of the US digital mobile telephone standards (IS-95) and is being studied as a next-generation digital mobile communication system in Japan.
-CDMA (Wide-band CDMA) system and digital mobile communication system (IMT-20) that is being standardized by ITU.
00) is being considered. Furthermore, the CDM transmission system is under study as a wireless transmission system for satellite digital broadcasting using the 2.6 GHz band.

In a downlink channel or CDM broadcasting system of a CDMA communication system as described above (collectively referred to as a communication system hereinafter), a broadcast or dedicated channel and a common pilot channel are spread in frequency and then multiplexed in the same frequency band. Send. The common pilot channel is a signal based on a known data string, and when demodulating, estimates the timing, phase, and strength of the received signal (channel response estimation: Ch
annel estimation). in this case,
For the broadcast or dedicated channel, the transmission power is controlled so that the reception power becomes optimum in the corresponding receiving device, but since the common channel is used by all receiving devices,
The transmission power varies depending on the reception environment.

[0004]

In the receiver used in the above-described conventional spread spectrum multiplex transmission system, a method of controlling the averaging time for estimating the transmission path response with a fixed or average received power is proposed. I am taking it. Therefore, when the received power of the pilot channel is small, if the fluctuation speed of the received power due to fading is slow, a period in which the SNR of the transmission path response estimation value is small occurs, and the power of the individual channel is increased by the transmission power control. However, there is a problem that the characteristics above a certain level cannot be obtained, and conversely, if the fluctuation speed of the received power is fast, the characteristics deteriorate due to fluctuations within the transmission averaging time.

Further, in the above-mentioned conventional transmission system, a method of invariably denormalizing or normalizing the channel response estimated value by weight calculation is adopted. Therefore, when performing soft-decision error correction decoding after despreading demodulation, there is a problem that the soft-decision data is not properly weighted due to the magnitude of the received power of the pilot channel, and the characteristics after decoding deteriorate.

Therefore, the present invention solves the above problems, and a receiver used in a spread spectrum multiplex transmission system capable of preventing characteristic deterioration after reception regardless of the received power of a pilot channel and its transmission. It is an object to provide a road response estimation method.

In particular, the present invention provides a receiver used in a spread spectrum multiplex transmission system and a channel response estimation method therefor which can obtain good reception characteristics regardless of the fluctuation speed of the received power even when the received power of the pilot channel is small. A first object of the present invention is to provide a receiver and a channel response estimation method for a spread spectrum multiplex transmission system capable of improving characteristics after soft-decision error correction decoding regardless of the received power of a pilot channel. The second purpose is to provide.

[0008]

(1) The receiver of the spread spectrum multiplex transmission system according to the present invention achieves the first object by the following configuration.

A spread spectrum multiplex transmission system for transmitting a spread spectrum multiplexed signal in which the pilot channel and a plurality of information channels are multiplied by spread sequences each having a speed higher than the data transmission rate of the channel to spread the spectrum and are multiplexed in the same frequency band. Is used to despread demodulate a pilot channel and a data string of an arbitrary information channel from the received output of the frequency spread multiplexed signal, and despread demodulated data string of the pilot channel is a known data string in a predetermined averaging period. In the receiving device that RAKE-combines the despread demodulation data sequence of any information channel based on the estimated value, the transmission channel response estimation value is calculated from the comparison result, and the reception power or the reception phase of the pilot channel is calculated. Power / phase measurement means to measure and received power measured by this means or Fluctuating speed estimation means for estimating the speed at which the received signal fluctuates using the signal phase, and an averaging period for adaptively controlling the averaging period of the transmission path response estimated value according to the fluctuating speed estimated by this means. And a control means.

(2) The transmission path response estimation method of the receiver of the spread spectrum multiplex transmission system according to the present invention achieves the first object by including the following processing steps.

A spread spectrum multiplex transmission system for transmitting a spread spectrum multiplexed signal in which the pilot channel and a plurality of information channels are multiplied by spreading sequences each having a speed higher than the data transmission rate of the channel to spread the spectrum and are multiplexed in the same frequency band. Is used to despread demodulate a pilot channel and a data string of an arbitrary information channel from the received output of the frequency-spreading multiplexed signal, and optionally based on a channel response estimation value based on the despread demodulated data string of the pilot channel. In the transmission path response estimation method of the receiving device for RAKE combining the despread demodulated data sequence of the information channel, the despread demodulated data sequence of the pilot channel is compared with a known data sequence in a predetermined averaging period, and the comparison result A comparison step for obtaining an estimated value of a transmission path response from the pilot channel; The power / phase measurement step for measuring the received power or the received phase of the signal, the fluctuation speed estimation step for estimating the speed at which the received signal fluctuates using the received power or the received phase measured in this step, and the estimation in this step Averaging period control step for adaptively controlling the averaging period of the transmission path response estimated value according to the varying speed.

In the above configuration, the averaging period of the channel response estimated value is lengthened when the speed of fluctuation of the received signal is slow, and the averaging period is shortened when the speed of the received signal is fast, so that the received power of the pilot channel is reduced. Even if it is small, good reception characteristics can be obtained regardless of the fluctuation speed of the received signal.

(3) The receiver of the spread spectrum multiplex transmission system according to the present invention achieves the second object by the following configuration.

A spread spectrum multiplex transmission system for transmitting a spread spectrum multiplexed signal in which a pilot channel and a plurality of information channels are multiplied by spreading sequences each having a speed higher than the data transmission rate of the channel to spread the spectrum and are multiplexed in the same frequency band. Is used for despreading and demodulating a data sequence of a pilot channel and an arbitrary information channel from the received output of the frequency-spreading multiplexed signal, and comparing the despread demodulation data sequence of the pilot channel with a known data sequence, and comparing them. A transmission line response estimation value is obtained from the result, and soft-decision error correction decoding is performed on the despread demodulation data sequence of the arbitrary information channel based on the size of the despreading output and the transmission line response estimation value. In the device,
Reception power measuring means for measuring the reception power of the pilot channel for each propagation path of the reception signal, and comparing the reception power measured by this means with a separately determined threshold value,
Based on the comparison result, a standardization deciding means for adaptively deciding whether or not to standardize the power sum of the transmission path response estimated value for each propagation path to be a constant value is configured. When the standardization determining means determines to normalize the transmission path response estimation value, soft decision data is weighted only by the size of the despreading output of the information channel, and not standardized. Then, the soft decision data is weighted by both the despread output of the information channel and the transmission path response estimation value.

(4) The transmission path response estimation method of the receiver of the spread spectrum multiplex transmission system according to the present invention achieves the second object by including the following processing steps.

A spread spectrum multiplex transmission system for transmitting a spread spectrum multiplexed signal in which the pilot channel and a plurality of information channels are multiplied by spread sequences each having a speed higher than the data transmission rate of the channel to spread the spectrum and are multiplexed in the same frequency band. Is used for despreading and demodulating a data sequence of a pilot channel and an arbitrary information channel from the received output of the frequency-spreading multiplexed signal, and comparing the despread demodulation data sequence of the pilot channel with a known data sequence, and comparing them. A transmission line response estimation value is obtained from the result, and soft-decision error correction decoding is performed on the despread demodulation data sequence of the arbitrary information channel based on the size of the despreading output and the transmission line response estimation value. In the transmission path response estimation method of the device, the despread demodulation data string of the pilot channel is known. A comparison step of comparing with a data string and obtaining a transmission line response estimation value from the comparison result, a reception power measuring step of measuring the reception power of the pilot channel for each propagation path of the reception signal, and a reception measured in this step The power is compared with a separately determined threshold value, and based on the comparison result, it is adapted whether or not to normalize the power sum of the transmission path response estimation values for each of the propagation paths to a constant value. And a softening decision based on only the magnitude of the despreading output of the information channel when the normalization deciding means decides to normalize the transmission path response estimation value. When data weighting is performed and it is determined that normalization is not to be performed, soft decision data weighting is performed on both the despread output of the information channel and the channel response estimation value. .

In the above configuration, when the received power of the pilot channel is large, the influence of the fluctuation of the channel response estimated value is removed, and when the received power of the pilot channel is small, the channel response estimated value is used for weighting. ,
It is possible to improve the characteristics after soft-decision error correction decoding regardless of the received power of the pilot channel.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram showing a configuration example of a transmitter of a CDMA communication system to which the present invention is applied.
This transmission device has one pilot channel, m broadcast channels i (i = 1, 2, ..., M), and n individual channels j (j = 1, 2, ..., N), respectively. Diffuser 11
In p, 11bi and 11dj, frequency spreading is performed by multiplying by a spreading sequence having a speed higher than the data transmission speed of the channel, and multipliers 12p, 12bi and 12dj multiply the coefficients Gp, Gbi and Gdj indicating the output gain. And
The multiplication result of each channel is linearly added by the multiplexer 13 to be multiplexed in the same frequency band, and the wireless device 14 performs quadrature modulation, waveform shaping, frequency conversion, power amplification, and outputs from the antenna 15. The spreader and the multiplier have the same number as the number of channels to be multiplexed.

The pilot channel is a pre-defined data string which is known in the receiving device and is used to extract the reference timing and reference phase for receiving another channel. The broadcast channel i is a data string transmitted to a plurality of receiving devices. Individual channel j
Is a data string transmitted to a specific receiving device. Each channel has an in-phase component and a quadrature-phase component, respectively.

FIG. 2 shows the diffuser 11p (11
FIG. 11 is a block diagram showing a configuration example of (bi, 11dj are also the same). The spreader 11p includes the CC generator 111 and the SC generator 1
12, and multipliers 113 and 114.

The CC generator 111 generates a channelization code (hereinafter, CC). An orthogonal code such as a Hadamard sequence or a Walsh sequence is used as a CC, and a different CC is used for each channel.

The SC generator 112 generates a scrambling code (hereinafter, SC). As SC, a pseudo-random sequence such as M sequence or Gold sequence is used, and a common SC is used for all channels. Also, different sequences are used for the in-phase component and the quadrature-phase component.

In this CDMA communication system, the CC and SC rates are the same. The repetition cycle of CC is the same as the symbol length of the input data string and is inversely proportional to the transmission rate of the input data string. Furthermore, CC
It is desirable that the period of is a power of 2, for example, from 4 to 256. On the other hand, the repetition cycle of SC is 38,
Like 400, it is longer than the cycle of CC.

The multipliers 113 and 114 complexly multiply the input data string by CC and SC.

FIG. 3 shows the multipliers 113 and 11 in FIG.
4 is a block diagram showing a configuration example of No. 4 of FIG. In FIG. 3, A
1 to A4 are complex multipliers, A5 and A6 are adders, and A7 is a sign inverter. In this circuit configuration, the in-phase component of one input value is DI, the quadrature-phase component is DQ, the in-phase component of the other input value is AI, the quadrature-phase component is AQ, the in-phase component of the output value is TI, and the quadrature-phase component is TQ. Then, the relationship of TI = DI * AI-DQ * AQ TQ = DI * AQ + DQ * AI is established.

FIG. 4 is a block diagram showing an example of the configuration of the receiving device of the CDMA communication system. This receiving device uses a CDMA signal received by an antenna 21 as a radio 22
After inputting to, power amplification, frequency conversion, waveform shaping, and quadrature demodulation, the desired number of channels (here, 1 pilot channel, 3 broadcast channels, and 3 individual channels in total, are used for RAKE combining). Systematic 6
Input to the despreaders 231-236 of the channel),
Despread demodulation is performed using the spreading sequence corresponding to the desired channel. At this time, the demodulation signal of the wireless device 22 is input to the timing estimator 24, the path delay time of each channel is estimated, the timing of the demodulation output is obtained, and each despreader 231-2
The outputs of 36 are controlled to have the same timing.

The despreaders 231 and 232 despread demodulate the pilot channels. With respect to this demodulated data sequence, after averaging the comparison results with the known data sequence by the averaging units 251, 252, the weight calculator 26 obtains the transmission line response estimation value by the method described later, and based on this estimation value The combining ratio of the combiners 271, 272 is determined.

The despreaders 233 and 234 select one desired channel from the m broadcast channels and perform despread demodulation. These demodulated data sequences are weighted by the combiner 271 based on the estimated value of the channel response, and RAKE-combined to produce a broadcast channel output. Also, the despreader 235,
At 236, a desired one channel is selected from n individual channels and is subjected to despread demodulation. These demodulated data strings are weighted by the combiner 272 on the basis of the channel response estimated value, and RAKE-combined to produce individual channel outputs.

The number of despreaders and combiners is not limited to the number shown in FIG. 4, but is prepared for each desired channel. Further, in a CDMA communication system, so-called "RAK" is performed in which despread demodulation is performed for each multipath in radio propagation and linear demodulation is performed by aligning the timing of demodulation results.
E ”reception is possible. In RAKE reception, the reception characteristics improve as the number of despreaders per channel increases.
In addition, as many averaging devices are needed as there are despreaders per channel.

A specific configuration of each block in the receiving apparatus having the above configuration will be described.

FIG. 5 is a timing estimator 2 in FIG.
4 is a block diagram showing a configuration example of No. 4 of FIG. The timing estimator 24 includes a correlator 241 and a peak detector 242. The correlator 241 finds the correlation between the output signal of the wireless device 22 and the waveform obtained by multiplying the pilot channel by CC and SC. Although a sharp peak appears in the output of the correlator 241, a plurality of peaks appear in a multipath environment. The peak detector 242 obtains the timing at which the peak is detected and notifies the despreaders 231 to 236 of the timing.
Since the output of the correlator 241 is affected by noise and interference waves, the timing of peaks that appear large and periodically is obtained.

FIG. 6 shows the despreader 231 (2) shown in FIG.
32 to 236 are the same). The despreader 231 includes an SC generator 23a,
CC generator 23b, multipliers 23c and 23d, integrator 23
e, a sampling device 23f, and a delay device 23g.

The SC generator 23a generates the same SC as the SC generated by the transmitter. The timing of generating the SC is controlled by the timing estimator 24. SC
If the in-phase component and the quadrature-phase component of are different, the quadrature-phase component is inverted. The CC generator 23b generates a CC corresponding to the channel to be received among the CCs generated by the transmission device. The timing of generating the CC is controlled by the timing estimator 24.

The multipliers 23c and 23d are for multiplying the output signal of the wireless device by SC and CC, and their configurations are the same as those shown in FIG. The integrator 23e integrates the output signal of the multiplier 23d over the period of one cycle of CC. The initialization timing of the integration is the timing estimator 2
Controlled by 4. The sampler 23f samples at the end of integration of the integrator 23e. The timing of sampling is controlled by the timing estimator 24. The delay device 23g includes other despreaders 232 to 236.
Timing adjustment is performed to match the timing with the output signal of. The delay time is controlled by the timing estimator 24.

FIG. 7 shows the averager 251 (2
FIG. 52 is a block diagram showing a configuration example of the same). The averaging unit 251 is a pilot channel generator 25.
a, multiplier 25b, integrator 25c, sampler 25
d, averaging time calculator 25e.

The pilot channel generator 25a generates a data stream of a defined pilot channel. The multiplier 25b is a despreader 2 that receives the pilot channel.
31 output signal and pilot channel data string,
The in-phase component and the quadrature-phase component are multiplied. Integrator 25
c integrates the output signal of the multiplier 25b. The integration initialization timing is controlled by the averaging time calculator 25e. The sampler 25d samples at the end of the integration of the integrator 25c. The sampling timing is controlled by the averaging time calculator 25e.

The averaging time calculator 25e is an integrator 25c.
And the sampling timing of the sampling device 25d are controlled. The initialization and sampling intervals are fixed values or are changed according to the average power of the output of the despreader 231. Specifically, the signal power to noise ratio (SNR) can be increased by making the interval longer as the average power is smaller.

FIG. 8 is a block diagram showing a configuration example of the weight calculator 26 in FIG. This weight calculator 26
The weight controller 261, the multipliers 262 and 263, the phase correctors 264 and 265, and the complex conjugators 266 and 267 are included.

The weight controller 261 calculates the power sum of the output signals of the despreaders 231 and 232 which receive the pilot channel, and outputs a fixed value or a value inversely proportional to the power sum as a weight coefficient. The multipliers 262 and 263 multiply the in-phase component and the quadrature-phase component of the output signals of the despreaders 231 and 232 by the weight coefficient from the weight controller 261. The phase correctors 264 and 265 complex-multiply the output signals of the multipliers 262 and 263 by a signal obtained by inverting the quadrature phase component of the pilot channel data sequence. Complex conjugators 266,2
67 inverts and outputs the quadrature phase component of the output signals of the phase correctors 264 and 265. The output signal of the weight calculator 26 is called a transmission line response estimation value.

FIG. 9 shows a combiner 271 (27) in FIG.
FIG. 2 is a block diagram showing a configuration example of (2) as well.
The combiner 271 includes multipliers 27a and 27b and an adder 2
7c. The multipliers 27a and 27b are the same as those in FIG.
Has the same configuration as the complex multiplier shown in FIG.
The output signal of H.234 is complex-multiplied by the channel response estimation value output from the weight calculator 26. The adder 27c linearly combines the output signals of the multipliers 27a and 27b.

Here, in the prior art, in the averaging devices 251, 252 having the configuration of FIG. 7, the averaging time is fixed or is controlled by the average received power. Therefore, if the received power of the pilot channel is small,
When the fluctuation speed of the received power due to fading is slow, a period in which the SNR of the transmission path response estimation value is small occurs, and even if the power of the individual channel is increased by the transmission power control, a certain characteristic or more cannot be obtained. If the fluctuation speed of the received power is fast, there is a problem that the characteristics deteriorate due to fluctuations within the transmission averaging time.

Further, in the prior art, the weight calculator 26 having the configuration shown in FIG. 8 is configured to invariably denormalize or normalize the transmission path response estimation value. Therefore, when performing soft-decision error correction decoding after despreading demodulation, there is a problem that the soft-decision data is not properly weighted due to the magnitude of the received power of the pilot channel and the characteristics after decoding deteriorate. .

Therefore, in the present embodiment, even if the received power of the pilot channel is small, the averaging time calculator 25e in FIG. , A function of estimating the varying speed of the output signal of the despreader that receives the pilot channel, and a function of adaptively controlling the averaging time based on the estimated varying speed.

Further, in the present embodiment, the weight controller 26 in FIG. 8 is provided in order to improve the characteristics after the soft decision error correction decoding regardless of the received power of the pilot channel.
1 has a function of calculating the power sum of the output signals of the respective averaging devices 251, 252 and a function of adaptively controlling whether or not the transmission path response estimation value is standardized according to the power sum. I shall.

FIG. 10 is a block diagram showing a configuration example when the present invention is applied to the averaging time calculator 25e in FIG. The averaging time calculator 25e includes a power calculator B11, an integrator B12, a sampling device B13, a delay device B14, a difference device B15, a speed estimator B16, and a timing controller B17.

The power calculator B11 calculates the power of the output signal of the despreader 231 which receives the pilot channel. The integrator B12 integrates the output signal of the power calculator B11. The initialization timing of integration is controlled by the timing controller B17. The sampling device B13 is
Sampling is performed when the integration of the integrator B12 is completed. The timing of sampling is controlled by the timing controller B17. By dividing the output signal of the sampler B13 by the integration period, the average power during the integration period can be obtained.

The delay device B14 delays the output signal of the sampling device B13 by one sample time. The differencer B15 is
The difference between the output signals of the sampling device B13 and the delay device B14 is obtained. The speed estimator B16 estimates the fluctuation speed of the received signal based on the output signal of the differencer B15 and the control interval of the timing controller B17, and determines the averaging time. The slower the fluctuation speed of the received signal, the longer the averaging time.

The fluctuation of the average power of the received signal depends on the averaging period and the fluctuation speed of the received signal. First, when the averaging period is shortened, fluctuations in average power have the same tendency as instantaneous fluctuations. In this case, the slower the fluctuation speed of the received signal, the smaller the fluctuation of the average power. Further, when the averaging period is lengthened, the fluctuation of the average power has the same tendency as the long-term fluctuation.
In this case, the slower the fluctuation speed of the received signal, the larger the fluctuation of the average power. Using the above property, the fluctuation speed of the received signal is estimated from the fluctuation of the average power of the received signal.

FIG. 11 is a block diagram showing another configuration example when the present invention is applied to the averaging time calculator 25e in FIG. This configuration is similar to that of FIG. 10 except that the power calculator B11 shown in FIG. 10 is replaced with the phase calculator B18.
The configuration is the same as that of. Therefore, in FIG.
The same parts as 0 are designated by the same reference numerals, and redundant description will be omitted here. Phase calculator B, which is a feature of this configuration
18 is a despreader 231 for receiving the pilot channel
The phase of the output signal of is calculated.

The fluctuation of the average phase of the received signal depends on the averaging period and the fluctuation speed of the received signal. First, when the averaging period is shortened, the fluctuation of the average phase has the same tendency as the instantaneous fluctuation. In this case, the slower the fluctuation speed of the received signal, the smaller the fluctuation of the average phase. Further, when the averaging period is lengthened, the fluctuation of the average phase has the same tendency as the long-term fluctuation.
In this case, the slower the fluctuation speed of the received signal, the larger the fluctuation of the average phase. Using the above properties, the fluctuation speed of the received signal is estimated from the fluctuation of the average phase of the received signal.

The transmission path response estimation method in the above configuration is summarized as shown in FIG.

First, the despread demodulation data string of the pilot channel is compared with a known data string in a predetermined averaging period,
A transmission line response estimation value is obtained from the comparison result (S1).
Here, the reception power or reception phase of the pilot channel is measured (S2), and the speed at which the reception signal fluctuates is estimated using the measured reception power or reception phase (S3).
It is judged whether or not the fluctuation speed of the estimated received signal becomes slow (S4), and if it becomes slow, the averaging period of the transmission path response estimated value is lengthened (S5). The estimated value averaging period is shortened (S6).

When the SNR of the transmission path response estimation value is small and the fluctuation speed of the received signal is slow, the desired characteristic may not be obtained no matter how large the power of the individual channel is increased by the transmission power control. According to the above configuration, when the fluctuation speed of the received signal is slow, by controlling the averaging period of the transmission channel estimated value to be long, the transmission channel response estimated value S
Since the NR is improved, good characteristics can be obtained even when the received power of the pilot channel is small.

Further, in the case where the fluctuation speed of the received signal is fast, if the averaging period of the transmission path response estimation value is lengthened, the phase fluctuation during the averaging period becomes large, so that the performance deteriorates as compared with the case where the averaging period is short. There is. The present invention prevents the averaging period of the channel response estimated value from being unnecessarily lengthened when the fluctuation speed of the received signal is high.

FIG. 13A shows a computer simulation result of the reception characteristic when the transmission power control of the downlink dedicated channel is performed. DPCH Ec is the power of the individual channel, Ior
Is the power of all channels, Ioc is the noise power, and fd is the Doppler frequency. Here, the averaging time for channel response estimation is 4 symbols. When the signal power-to-noise ratio of the common pilot channel is small (Ior / Ioc = -3dB) and the Doppler frequency is small (fd = 5Hz), increasing the transmission power of the individual channels does not improve the performance (floor is It occurs) was observed.

FIG. 13 (b) shows that fd = 5 Hz in FIG. 13 (a).
In the case of, the computer simulation result is obtained when the number of averaged symbols for channel response estimation is changed. The reception characteristic can be improved by increasing the number of averaged symbols for channel response estimation (4 symbols → 8 symbols → 16 symbols).

From the above simulation results, it is apparent that the reception characteristic can be improved by measuring the fluctuation speed of the received signal and lengthening the averaging period of the channel response estimation when the fluctuation is slow.

FIG. 14 shows the weight controller 261 in FIG.
It is a block diagram which shows the structural example at the time of applying this invention to. The weight controller 261 includes a power sum calculator C1, a divider C2, a comparator C3, and a selector C4. The power sum calculator C1 calculates the power sum of the output signals of the respective averagers 251 and 252. If the number of averaging devices is N and the output of each averaging device is Wi (i = 1, 2, ..., N), the output of the power sum calculator C1 is

[Equation 1] Becomes The divider C2 outputs a value obtained by dividing the constant A by the value P. The comparator C3 compares the value P with the threshold value B. Based on the result of the comparator C3, the selector C4 outputs the value A / P when the value P is larger than the threshold value B, and outputs the constant A when the value P is smaller than the threshold value B.

The transmission line response estimation method in the above configuration is summarized as shown in FIG.

First, the despread demodulation data sequence of the pilot channel is compared with a known data sequence, and a transmission line response estimation value is obtained from the comparison result (S7). Here, the reception power of the pilot channel is measured for each propagation path of the reception signal (S8), and the measured reception power is compared with a separately determined threshold value (S9). At this time, if the received power value is equal to or higher than the threshold value, the power sum of the transmission path response estimated values for each propagation path is standardized to be a constant value (S10), and if the threshold value is not reached, it is left as it is. And

That is, in a CDMA communication system, when performing soft-decision error correction decoding after despreading demodulation, the magnitude of the output signal of the despreader that receives the desired channel and the magnitude of the channel response estimation value are soft-decision. It becomes the weight of data.

In the region where the SNR of the channel response estimated value is sufficiently large, the reliability of the channel response estimated value can be regarded as substantially constant regardless of the magnitude of the value. From this,
By standardizing the channel response estimation value, better characteristics can be obtained by weighting the soft decision data only with the despread output of the desired channel.

On the other hand, in a region where the SNR of the transmission channel response estimation value is small, the reliability of the transmission channel response estimation value increases as the value increases. Therefore, it is possible to obtain better characteristics by using both the despread output of the desired channel and the channel response estimated value as the weight of the soft decision data by using the channel response estimated value as it is without normalization.

Therefore, according to the above configuration, based on the result of comparing the power sum of the transmission path response estimated value and the threshold value, it is adaptively determined whether or not the transmission path response estimated value is standardized. , Depending on the magnitude of the channel response estimation value,
It is possible to improve the characteristics when performing soft-decision error correction decoding after the frequency despreading.

FIG. 16 is a computer simulation result for comparing a method in which the amplitude of the channel response estimated value is temporally constant and a method in which it is not. When the signal power to noise ratio of the common pilot channel is large (Ior / Ioc = 9dB)
The better the characteristics, the better. Moreover, when the signal power to noise ratio of the common pilot channel is small (Ior / Ioc = -3dB), it is better not to make it constant.

From the above simulation results as well, it is possible to improve the reception characteristics by measuring the signal power-to-noise ratio of the common pilot channel and selecting whether or not the amplitude of the transmission path response estimation value is constant. it is obvious.

In the above embodiment, the downlink channel of the CDMA communication system has been described, but the same can be applied to the CDM broadcasting system. Other CDs
It goes without saying that it can also be used in a system using the MA or CDM transmission method.

[0069]

As described above, according to the present invention, a receiving apparatus for a spread spectrum multiplex transmission system and a receiving apparatus which can obtain good reception characteristics regardless of the fluctuation speed of the reception power even when the reception power of the pilot channel is small, A transmission path response estimation method can be provided. Further, it is possible to provide a receiver of a spread spectrum multiplex transmission system and a transmission path response estimation method thereof that can improve the characteristics after soft-decision error correction decoding regardless of the received power of a pilot channel. From the above, it is possible to provide a receiving apparatus of a spread spectrum multiplex transmission system and its channel response estimation method capable of preventing characteristic deterioration after reception regardless of the received power of a pilot channel.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration example of a transmitter of a CDMA communication system to which the present invention is applied, as an embodiment according to the present invention.

FIG. 2 is a block diagram showing a configuration example of a spreader in FIG.

FIG. 3 is a block diagram showing a configuration example of a multiplier in FIG.

FIG. 4 is a block diagram showing a configuration example of a receiving device of the CDMA communication system.

5 is a block diagram showing a configuration example of a timing estimator in FIG.

6 is a block diagram showing a configuration example of a despreader in FIG.

7 is a block diagram showing a configuration example of an averager in FIG.

8 is a block diagram showing a configuration example of a weight calculator in FIG.

9 is a block diagram showing a configuration example of a combiner in FIG.

10 is a block diagram showing a configuration example when the present invention is applied to the averaging time calculator in FIG. 7.

FIG. 11 is a block diagram showing another configuration example when the present invention is applied to the averaging time calculator in FIG. 7.

FIG. 12 is a flowchart showing a transmission path response estimation method in the case of the configuration of FIG. 10 or FIG.

13 is a computer simulation result of reception characteristics when transmission power control of a downlink dedicated channel is performed in the case of using the configuration of FIG. 10 or 11, and the average number of symbols for channel response estimation at the specific frequency. FIG. 6 is a characteristic diagram showing the results of computer simulation when the value is changed.

14 is a block diagram showing a configuration example when the present invention is applied to the weight controller in FIG.

FIG. 15 is a flowchart showing a transmission path response estimation method when the configuration of FIG. 14 is used.

16 is a characteristic diagram showing computer simulation results for comparing a method in which the amplitude of the transmission path response estimated value is temporally constant and a method in which the configuration of FIG. 13 is not used, with and without a method.

[Explanation of symbols]

11p, 11bi, 11dj ... Diffuser 12p, 12bi, 12dj ... Multiplier 13 ... Multiplexer 14 ... Radio 15 ... Antenna 111 ... CC generator 112 ... SC generator 113, 114 ... Multiplier A1 to A4 ... Complex multiplier A5, A6 ... Adder A7 ... Sign inverter 21 ... Antenna 22 ... Radio 231-236 ... Despreader 24 ... Timing estimator 251,252 ... Averager 26 ... Weight calculator 271,272 ... Synthesizer 241 ... Correlator 242 ... Peak detector 23a ... SC generator 23b ... CC generator 23c, 23d ... Multiplier 23e ... integrator 23f ... Sampling device 23g ... delay device 25a ... Pilot channel generator 25b ... Multiplier 25c ... integrator 25d ... Sampling device 25e ... Averaging time calculator 261 ... Weight controller 262, 263 ... Multiplier 264, 265 ... Phase corrector 266, 267 ... Complex conjugator 27a, 27b ... Multiplier 27c ... Adder B11 ... Power calculator B12 ... integrator B13 ... Sampling device B14 ... Delay device B15 ... Differentiator B16 ... Speed estimator B17 ... Timing controller B18 ... Phase calculator C1 ... Power sum calculator C2 ... Divider C3 ... Comparator C4 ... Selector

Claims (4)

[Claims] 1. A spread spectrum multiplexing method for spreading a pilot channel and a plurality of information channels by spreading sequences each having a speed higher than the data transmission rate of the channel to spread the spectrum and transmitting a spread spectrum multiplexed signal multiplexed in the same frequency band. Used in a transmission system, despread demodulates a data sequence of a pilot channel and an arbitrary information channel from the received output of the frequency spread multiplexed signal, and despreads demodulated data sequence of the pilot channel is known in a predetermined averaging period. The transmission line response estimation value is obtained from the comparison result with the data sequence, and the despread demodulation data sequence of any information channel is RA based on this estimation value.
In a receiving device for KE combining, a power / phase measuring means for measuring the received power or the received phase of the pilot channel, and a fluctuation for estimating the speed at which the received signal fluctuates using the received power or the received phase measured by this means. Spread spectrum multiplex transmission comprising: speed estimation means; and averaging period control means for adaptively controlling the averaging period of the transmission path response estimation value according to the fluctuation speed estimated by this means. Receiver used in the system. 2. A spread spectrum multiplexing method for spreading a pilot channel and a plurality of information channels by spreading sequences each having a speed higher than the data transmission rate of the channel to spread the frequency and transmitting a spread spectrum multiplexed signal multiplexed in the same frequency band. Used in a transmission system, despread demodulating a data string of a pilot channel and an arbitrary information channel from the reception output of the frequency spreading multiplexed signal, and comparing the despread demodulated data string of the pilot channel with a known data string, A channel response estimated value is obtained from the comparison result, and for the despread demodulation data sequence of the arbitrary information channel, soft decision error correction decoding is performed based on the magnitude of the despread output and the channel response estimated value. In the receiving device to perform, measure the received power of the pilot channel for each propagation path of the received signal The signal power measuring means compares the received power measured by this means with a separately determined threshold value, and based on the comparison result, the power sum of the transmission path response estimated values of the propagation paths is constant. A standardization determining means for adaptively determining whether or not to standardize the transmission path response estimated value, and the standardization determining means determines when the transmission path response estimated value is standardized. The soft decision data is weighted only by the size of the despreading output of the information channel, and when it is determined not to standardize, the soft decision data of both the despreading output of the information channel and the channel response estimated value are A receiver used in a spread spectrum multiplex transmission system characterized by weighting. 3. A spread spectrum multiplexer for transmitting a spread spectrum multiplexed signal, which is obtained by multiplying a pilot channel and a plurality of information channels by spreading sequences each having a speed higher than the data transmission rate of the channel to spread the spectrum, and which is multiplexed in the same frequency band. Used in a transmission system, despread demodulates a data sequence of a pilot channel and an arbitrary information channel from the received output of the frequency spread multiplexed signal, and based on a channel response estimation value based on the despread demodulation data sequence of the pilot channel. In a transmission path response estimation method of a receiving device for RAKE combining a despread demodulation data sequence of an arbitrary information channel, the despread demodulation data sequence of the pilot channel is compared with a known data sequence in a predetermined averaging period, and A comparison step of obtaining a channel response estimation value from the comparison result; Power / phase measurement step for measuring the received power or received phase of the received signal, and a variable speed estimation step for estimating the speed at which the received signal changes using the received power or received phase measured in this step, and the estimation in this step Averaging period control step for adaptively controlling the averaging period of the transmission channel response estimation value in accordance with the generated fluctuating speed, the transmission line of the receiving apparatus used in the spread spectrum multiplex transmission system. Response estimation method. 4. A spread spectrum multiplexing system for spreading a pilot channel and a plurality of information channels by spreading sequences each having a speed higher than the data transmission rate of the channel to spread the spectrum and transmitting a spread spectrum multiplexed signal multiplexed in the same frequency band. Used in a transmission system, despread demodulating a data string of a pilot channel and an arbitrary information channel from the reception output of the frequency spreading multiplexed signal, and comparing the despread demodulated data string of the pilot channel with a known data string, A channel response estimated value is obtained from the comparison result, and for the despread demodulation data sequence of the arbitrary information channel, soft decision error correction decoding is performed based on the magnitude of the despread output and the channel response estimated value. In the method of estimating a channel response of a receiving device, the despread demodulation data sequence of the pilot channel is Comparison step for obtaining a channel response estimated value from the comparison result, and a reception power measurement step for measuring the reception power of the pilot channel for each propagation path of the reception signal, and the measurement step The received power is compared with a separately determined threshold value, and based on the comparison result, whether or not to standardize the power sum of the transmission path response estimated values for each of the propagation paths to be a constant value is determined. And a standardization determining step of adaptively determining, when the standardization determining unit determines to normalize the transmission path response estimation value, the softening is performed only by the size of the despreading output of the information channel. When the decision data is weighted and is determined not to be standardized, the soft decision data is weighted by both the despread output of the information channel and the channel response estimation value. A method of estimating a channel response of a receiver used in a spread spectrum multiplex transmission system characterized by the above.