JP2003046412A - Demodulator, demodulation method and communication device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a demodulator that can surely demodulate a base band signal and to provide a demodulation method and a communication device. SOLUTION: A channel estimate section 223 applies inverse spread processing to a received signal supplied via a reception amplifier 221. The channel estimate section 223 estimates a channel corresponding to a common fixed pattern among channels depending on the inversely spread received signal and estimates respective channels according to the result of estimate. A demodulation section 224 demodulates the spread received signal depending on the common channel estimate result and the respective channel estimate results supplied from the channel estimate section 223.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a demodulation device, a demodulation method and a communication device capable of reliably demodulating a baseband signal.

[0002]

2. Description of the Related Art In code division multiplexing (CDMA) communication used in a communication system such as IMT-2000, it is possible to share the same band by assigning different code sequences to a plurality of mobile terminal devices. Has become.

Direct Spreading (DS)
In the CDMA communication of, for example, four-phase phase modulation (QPSK:
Quadri-Phase Shift Keying) is used to spread the primary modulation component according to the baseband signal by the spreading code sequence that is different for each channel. The information transmission rate per channel is uniquely determined from the number and spreading rate of spreading sequences used for this spreading, the multilevel number of temporary modulation, and the transmission rate of the spread spectrum transmission signal.

The number of spreading code sequences, the spreading factor and the number of modulation levels can be changed as appropriate, and by changing these values within the transmission band, communication services of different transmission rates are provided. You can do it.

In such a CDMA communication, as a technique for simultaneously demodulating a multiplexed signal for a plurality of channels, for example, "" Zero Forcing and Minimum Mean
-square-Error Equalization for Multicast Detection
in Code-Division Multiple-Access Channels ", Anja
Klein, Ghassan Kawas Kaleh, Paul Walter Baier, IEE
E TRANSACSION ON VHEICULAR TECHNOLOGY, VOL.45, No.
2, MAY 1996, pp.276-287 ”is known.

In this JD method, a system matrix A in which a sequence obtained by convolving a spreading code sequence and a channel impulse response of each user is arranged as an element is obtained. Specifically, if the spreading code of the user k is c (k) and the channel impulse response is h (k), h (k) = {h1
(K), h2 (k), ..., hW (k)} ^T [X ^T represents a transposed matrix of the matrix X. ], C (k) = {c1 (k), c
2 (k), ..., cQ (k)} ^T , K = 1, 2, ..., K,
Q is the spreading factor, W is the channel impulse response width, and N is the number of demodulated symbol sets for each user.
(K) is obtained.

B (k) = (b1 (k), b2 (k),
..., bQ + W-1 (k)) ^T = c (k) * h (k), k
= 1, 2, ..., K When this formula is expanded, it becomes a matrix as shown in FIG.

The system matrix A uses the elements of this matrix: A = (A _ij ), i = 1, 2, ..., NQ + W-1, j =
1, 2, ..., KNAQ _{(n-1) +1, n + N (k-1)} = bl (k)
{K = 1, 2, ..., K, n = 1, 2, ..., N, l = 1,
2, ..., Q + W−1}, 0 {k, n, l other than that}.

Here, when the transmitted data symbol is d and the noise is n, the received signal e is represented by e = Ad + n using this system matrix A. For simplicity, e = A
The received signal e is represented by a matrix as shown in FIG.

[0010] With this relationship, the transmitted data symbol d ^may be demodulated by ^{d = (A H A) -1A} H e (ZF). Here, A ^H is a complex conjugate transposed matrix of the system matrix A.

Therefore, in the JD method, the transmission data symbol d is estimated from the operation related to the system matrix A.

Also, by canceling the self-interference due to the delayed wave component from the convolutional component of its own spreading code and the channel estimation value (estimation result of the envelope of the fluctuation of the phase and amplitude of the received signal due to fading), and combining, As a technique for amplifying only the signal addressed to the own station, for example, "" DATA DETECTION ALGORITHMS SPECIALLY DESIGNED
FORTHE DOWNLINK OF CDMA MOBILE RADIO SYSTEMS ", Anj
a Klein, IEEE 47 ^th Vehicular Technology Conferenc
e, pp.203-207, May 1997, "" Low Cost MMSE-BLE_SD
Algorithm for UTRA TDD Mode Downlink ", ETSI STC S
MEG Layer 1 Expert Group, Tdoc SMEG2 UMTS L1, Hels
inki, Finland Sept. 1998 ”and the like, and a single user detection (SUD) method is known.

Particularly, in the downlink, since the channel estimation values between spreading codes are the same, the same channel impulse response is H (hl) and the spreading code matrix is C (c).
(K)), between these and the received signal r, r =
There is a relationship of HCd + n. Here, Cd and H are the matrices shown in FIGS. 28 and 29, respectively.

Further, H is the same in each spreading code,
Since the orthogonality with other spreading codes is high, in the SUD method, only C's own signal is considered, and only its own signal is estimated as d.

Further, in this SUD method, Cd = (H ^H
H) ⁻¹ H ^H r (ZF), and the modulation data symbol d is d = C ^H Cd = C ^H (H ^H H) ⁻¹ H ^H r
Can be demodulated as

In addition, considering only its own spreading code and combining its own delayed wave due to multipath etc. with the direct wave (maximum ratio combining) to improve the receiving sensitivity, RAKE
The receiver is known.

By the way, in CDMA communication, in order to select a channel to be received, a signal before spreading is added with different pilots for each channel as shown in FIG. 30, or as shown in FIG. , At a certain moment, a common pilot is added to all channels. Such pilots can be extracted from the despread output of the received spread signal.

In particular, in the downlink (radio) line, even if the spreading codes are different, the propagation paths up to a specific mobile terminal device are the same, so the channels of different spreading codes have a common fixed value. The pattern may be used as a pilot to indicate each channel.

As a concrete example, for example, the common pilot allocation (Common Pilot Allocation) using a common pilot for all spreading codes shown in FIG. 6 and the spreading code of its own when there is code multiplexing by one user shown in FIG. Known is a specific pilot allocation (UE Specific Pilot Allocation) for allocating the same common pilot between them.

In such cases, a slot (time slot) having a common fixed pattern between spreading codes
, The channel estimation value using a common fixed pattern is obtained.

After the channel estimation value is obtained in this way, the above-mentioned JD method, SUD method, and
Demodulate with a RAKE receiver. By performing demodulation using the channel estimation result as described above, it is possible to reduce the processing load of demodulation processing as compared with the case where the power of each channel is obtained and demodulation is performed.

[0022]

However, since the power of a fixed pattern common to different spreading codes is not the same as the power of each channel, a channel estimation value according to the power of such a fixed pattern is used. For example, when demodulation by the RAKE receiver described above is performed, as shown in FIG. 17, when the position of the demodulated symbol (black circle in the figure) is the modulation base point (white circle in the figure, QPSK, ± 1 ± j)
/ (2 ^1/2 ))

The RAKE receiver performs maximum ratio combining according to the channel estimation result. In this maximum ratio combination,
Since the received signal is simply multiplied by a real number according to the channel estimation result, the demodulated symbol after combining is out of the modulation base point.

However, even if the demodulated symbol deviates from the modulation base point in this way, the phase of the symbol does not change, but the amplitude of the demodulated symbol simply changes. When QPSK is used as the primary modulation, the demodulated symbols never become symbols of other phases.

However, in order to improve the coding efficiency, QAM (Quadrature Amplitude Modulation) is used for the primary modulation.
(uration) is used, if the distance from the origin of the demodulated symbol changes, as shown in FIG.
Accurate demodulation will not be possible.

The present invention has been made in view of the above-mentioned problems, and it is possible to return the demodulated symbols to the modulation base point and surely demodulate the baseband signal, the demodulating method, and the demodulating method. An object is to provide a communication device.

[0027]

In order to solve the above problems, a demodulator according to the present invention has a channel multiplexed with a plurality of orthogonal spreading code sequences, and is common to at least some channels. The pilot signal of is spread by the spreading code series of each channel, and the receiving means that receives the signal in which the predetermined code (fixed code) common to all channels is spread by the spreading code series and the receiving means Despreading means for despreading the common pilot signal in the received signal, common channel estimation means for performing channel estimation according to the common pilot signal despread by the despreading means, and according to the estimated output of the channel estimation means , Amplitude detection means for obtaining the amplitude of the fixed code for each channel, and the estimated output of the common channel estimation means and for each channel obtained by the amplitude detection means In accordance with the amplitude of the constant code, characterized in that it comprises a restoring means for receiving means to restore the data in the signal received.

The data restoration by the restoration means includes, for example, demodulation of the despread reception signal, decoding of the demodulated data, and the like.

Further, another demodulator according to the present invention has a channel multiplexed by a plurality of orthogonal spreading code sequences, and a pilot signal common to at least some channels is a spreading code sequence of each channel. Is spread by
Receiving means for receiving a signal in which a predetermined code (fixed code) different for each channel is spread by a spreading code sequence, and despreading means for despreading a common pilot signal in the received signal received by the receiving means, The common channel estimation means for performing channel estimation according to the common pilot signal despread by the despreading means, the amplitude detection means for obtaining the amplitude of the fixed code for each channel according to the estimation output of the channel estimation means, and the common channel It is characterized in that it comprises a restoring means for restoring the data in the signal received by the receiving means according to the estimated output of the estimating means and the amplitude of the fixed code for each channel obtained by the amplitude detecting means.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention can be applied to, for example, a mobile communication system for performing communication between a base station and a mobile terminal device.

(First Embodiment) (Structure) A mobile communication system according to the first embodiment of the present invention is, for example, as shown in FIG. 1, a direct sequence code division multiplex communication (CDMA-DS). It comprises a base station 10 and a mobile terminal device 20 which communicate with each other.

The base station 10 is provided for each predetermined area (cell). Further, the base station 10 is connected to a network (hereinafter, simply referred to as a wire telecommunications network) 1 such as a wire telecommunications network. This base station 10 provides a service such as a relay to the wired telecommunication network 1 or a communication between the mobile terminal devices 20 to the mobile terminal devices 20 in the cell.

This mobile communication system also includes a communication management device 2 connected to each base station 10 via a wired telecommunication network 1. The base station 10 that communicates with a specific mobile terminal device 20 is selected by the communication control by the communication management device 2.

In this mobile communication system, the base station 10
The communication between the mobile terminal device 20 and the mobile terminal device 20 is a so-called W-CDM.
A (Wideband-Code Division Multiple Access). In this W-CDMA, different spreading codes having high orthogonality to each other are assigned to each of a plurality of channels using the same band, and a transmission signal is spread by the spreading code assigned to each channel. The receiving side despreads the received signal using the same spreading code as the transmitting side to reproduce the received signal.

The base station 10 is, for example, as shown in FIG.
A communication interface (I / F) 100 that performs communication with the wired telecommunication network 1, a downlink system 110 that transmits a signal to the mobile terminal device 20, and a mobile terminal device 20.
And an uplink system 120 for receiving a signal from.

The downlink system 110 is a communication I / F 10
A separation unit 111 that separates data received via 0 for each predetermined logical channel, and a process of dividing the data supplied from the separation unit 111 for each predetermined length, adding a parity, interleaving, etc. A data configuration unit 112 that configures data to be transmitted to the mobile terminal device 20 and, for example, quadrature phase modulation (QPSK: Quad) according to the configured data.
ri-Phase Shift Keying), quadrature phase modulation (QAM: Qua)
a modulation unit 113 that performs modulation (primary modulation) by drature amplitude modulation, etc., and a spreading unit 114 that spreads the modulation output with a different spreading code for each predetermined channel,
A combining unit 115 that combines the outputs of the spreading units 114 of the respective logical channels and a transmitting amplifier 116 that drives the transmitting antenna 117 according to the signals of all the channels that are spread according to the combined signals are provided.

The modulation section 113 is adapted to, for example, adapt to the QoS of the wireless communication line with the mobile terminal apparatus 20 which is detected separately, and to perform the primary modulation method and the like (the number of QAM symbols and the like). There is. The modulator 113 can be configured by a DSP, for example, and can adaptively change the modulation method according to a parameter such as QoS.

The number of QAM symbols can be 16 values as shown in FIG. 3, for example. In this case, for example, Q
When the QoS drops to a predetermined level, the number of QAM symbols is set to 8 values, and when the QoS is increased to a predetermined level or more, the number of QAM symbols is set to 64 values as shown in FIG. 4, for example. You may. Note that the number of QAM symbols is not limited to these examples, and can be changed as appropriate.

The uplink system 120 also includes a reception amplifier 122 that amplifies a signal received through the reception antenna 121, and a separation unit 12 that separates the reception signal for each channel.
3 and the despreading unit 124 that performs despreading for each spreading code.
A channel estimation unit 125 that executes channel estimation according to the despread output, a demodulation unit 126 that demodulates the despread output according to the channel estimation value of the channel estimation unit 125, and receive data is extracted from the demodulated data. Data extraction unit 1
27 and a synthesizing unit 128 for synthesizing the data extracted by each data extracting unit 127.

In this embodiment, as shown in FIG. 2, the receiving antenna 121 is provided separately from the transmitting antenna 117.
Although the case where the above is provided has been described, the transmitting antenna and the receiving antenna can be shared by using a device such as a duplexer or a circulator.

Further, the mobile terminal device 20 is, for example, as shown in FIG. 5, an input / output I / F 200 for inputting / outputting voice signals or inputting / outputting data to be transmitted / received, and an uplink for transmitting signals to the base station 10. The system 210, a downlink system 220 that receives a signal from the base station 10, a transmission / reception antenna 230, and a duplexer 240 that switches a signal to be transmitted / received.

The uplink system 210 has an input / output I / F 2
The data configuration unit 211 is configured to configure data to be transmitted to the base station 10 by subjecting data to be transmitted from data supplied from 00 to processing such as division into predetermined lengths, addition of parity, and interleaving. Modulator 212 that performs modulation by QPSK, QAM, etc. according to transmission data
A spreading unit 213 that spreads the modulated output, and a transmission amplifier 21 that drives the transmitting / receiving antenna 230 according to the spreading output.
4 and.

The downlink system 220 comprises the duplexer 2
A reception amplifier 221 for amplifying a reception output supplied via 40, a despreading unit 222 for despreading the reception signal,
A channel estimation unit 223 that performs channel estimation according to the despread output, a demodulation unit 224 that demodulates the despread output according to the channel demodulation output of the channel demodulation unit 223, and a data extraction that extracts received data from the demodulation output. Section 225.

In this mobile communication system, for example, FIG.
As shown in, a pilot signal including a predetermined code (fixed pattern: m (x)) common to all channels from the base station 10 is transmitted at predetermined intervals. The pilot signals of the respective channels are spread codes (Code 1, Code 2, ..., Co) assigned to the respective channels.
de n) and then transmitted.

Alternatively, for example, as shown in FIG. 7, fixed patterns (m (x), ..., M) common to some channels are used.
(Y)) is transmitted, or as shown in FIG. 8, the same fixed pattern (m
(C)) is the spreading code (Code) of each channel.
, Code 2, ..., Code n) may be spread and transmitted.

Downlink system 220 of mobile terminal apparatus 20
Then, a part of the received transmission signal from the base station 10 is despread with a spreading code for each channel, and the despread output is subjected to correlation calculation with the above-mentioned fixed pattern by, for example, a correlator calculation. And channel estimation is performed, for example, in FIG.
The despread reception signal is demodulated according to the result of channel estimation as shown in.

In the demodulation in the downlink system 220, for example, the received signal is despread for some symbols of the channel in which the received signal exists at the timing corresponding to the maximum peak in FIG. The amplitude of the symbol corresponding to the power value of 1 is obtained, and the amplitude is determined according to the obtained amplitude of the predetermined symbol (individual channel estimation value described later).

By the way, in this mobile communication system,
The individual channel signals code-division-multiplexed as described above are divided into time slots at predetermined time intervals, as shown in FIG. 10 (A), for example.

In a frame of a time slot (for example, DPCH: Dedicated Physical Channel) having a downlink signal transmitted from the base station 10 to the mobile terminal device 20, for example, as shown in FIG. Formatting bits, TPC (power control) bits, and other control information are included.

Further, the frame of the other time slot includes TFCI (channel format) bits which are divided and arranged in the frame as shown in FIG. 11, for example.

Since these TFCI bit and TPC bit are set to predetermined values (symbols) in advance, it is appropriate to use them to obtain the amplitude of the symbol corresponding to the power value per unit symbol.

(Operation) In the mobile communication system configured as described above, reception processing (channel estimation, demodulation) is executed by the procedure shown in FIG. 12, for example.

First, before the communication between the base station 10 and the mobile terminal device 20 is started, a spreading code determined in a predetermined procedure is transmitted from the base station 10 to the downlink line to the mobile terminal device 20. Assigned. Diffusion part 1
14 spreads the modulated output from the modulator 113 according to the spreading code assigned to each mobile terminal device 20. The spread downlink transmission signal is transmitted to the transmission amplifier 116.
Is amplified and transmitted to the mobile terminal device 20 via the transmitting antenna 117.

The transmitting / receiving antenna 23 of each mobile terminal device 20
The downlink transmission signal received at 0 and amplified by the reception amplifier 221 is supplied to the despreading unit 222. The despreading unit 222 despreads the supplied downlink transmission signal. The spreading code at this time is the spreading code assigned to each channel as described above.

The channel estimation unit 223 performs channel estimation as described above according to the despread received signal and supplies the channel estimation value to the demodulation unit 224 (S1). Further, the channel estimation unit 223 despreads the common fixed pattern (for example, the above-mentioned TFCI bit, TPC bit, etc.) (S2), and obtains the amplitude of the symbol corresponding to the power value per unit symbol as described above ( S3), demodulation unit 22
Supply to 4.

Further, the channel estimation section 223 obtains an individual channel estimation result for each channel, and the demodulation section 224.
(S4 to S7).

The demodulation section 224 demodulates the despread reception signal according to the supplied channel estimation value and the like (S
8). The data extraction unit 225 extracts the received data from the demodulated output and outputs it via, for example, the input / output I / F 200.

Further, the channel estimation unit 223 obtains the reception characteristic and the like based on the demodulation result and the like (S9), and the base station 10
Used for controlling communication with the

(Channel estimation) As described above, the channel estimation unit 223 estimates the channel by the correlation between the despread received signal and the fixed pattern (see FIG. 1 described above).
S1 in 2). The estimation result of this channel has peaks at some timings, for example, as shown in FIG. 9 described above. From this, the channel estimation unit 223 despreads the received signal for some symbols of the channel in which the received signal exists at the timing corresponding to the maximum peak (S2), and corresponds to the power value per unit symbol. The amplitude of the symbol is obtained (S3).

Specifically, the received signals of all the channels in which the received signals exist at the timing corresponding to the maximum peak of the channel estimation value are despread, for example, in the periods corresponding to the above-mentioned TFCI bit and TPC bit, The amplitude of the symbol corresponding to the power value per unit symbol corresponding to these bits is obtained.

The despreading at this time may be performed by multiplying the scrambling code and the spreading code by one or a plurality of symbols. Alternatively, the despreading may be performed after the scrambling code is solved. Good.

Further, although there is some deterioration due to the influence of multipath, in the downlink channel, since the orthogonality of the spreading code of each channel is high, the accuracy of the amplitude per unit symbol obtained as described above is high. Has become.

The number of symbols to obtain the amplitude by despreading may be one or plural. When obtaining the amplitudes of a plurality of symbols, the average of the amplitudes of the plurality of symbols may be obtained.

The period of the received signal for which the symbol amplitude is despread to obtain the symbol amplitude is the TFCI bit, T
The symbol is such that the amplitude corresponding to the power value of the channel during the period corresponding to the PC bit is known.

When the received signal is modulated by QAM, even if the received signal is despread, the obtained symbol points are
It is not known which symbol point corresponds to it. However, even when a normal data frame is modulated by QAM, the frame including the control information such as the above-mentioned TFCI bit and TPC bit has a conventional structure such as QPSK from the viewpoint of maintaining compatibility. It may be modulated by the modulation method of.

In such a case, the amplitude of the symbol corresponding to the power value per unit symbol can be obtained by despreading the control signal modulated by QPSK and spread by the same procedure as described above. .

Further, for the other peaks of the channel estimation value shown in FIG. 9 described above, the amplitude of the symbol corresponding to the power value per unit symbol of the received signal may be obtained in the same manner as described above. However, since the downlink line is orthogonally multiplexed for each spreading code,
The timing of the delayed wave on the time axis of channel estimation (received by the mobile terminal device 20) is the same for all channels. Therefore, the amplitude of the symbol corresponding to the power value per unit symbol of each channel is multiplied by a real number according to the offset between the symbol amplitude of the common fixed pattern and the symbol amplitude of each channel.

Therefore, for example, as shown in FIG. 13, the amplitude of the maximum peak of the channel estimation value by the common fixed pattern in FIG. 9 is normalized as 1 (S5), and further, as shown in FIG. Is multiplied by the symbol amplitude value for each channel (S6) to obtain the same result as when the amplitude is obtained by performing despreading for each peak (S7).

Using the individual channel estimation values for each channel thus obtained, for example, the JD method, SUD
The demodulated symbol can be restored to the base point of modulation by performing demodulation by the method, RAKE receiver, or the like (S8). As a result, the symbols can be reliably restored even when the above-described QAM is used as the modulation method of the primary modulation in the modulator 113. In addition,
Since the demodulated symbol can be returned to the base point of the modulation, another modulation method (for example, the QPS described above) can be used as the primary modulation.
Even when (K, etc.) is used, it is possible to contribute to the improvement of the certainty of demodulation.

(Demodulation) When demodulation according to the individual channel estimation result for each channel obtained as described above is performed by combining multipath received signals by a RAKE receiver or the like, for example, the method shown in FIG. (Multi-pass composite modulation base point demodulation) can be used.

In this method, the channel obtained as described above is used.
Channel estimation results (c _n) Complex conjugate (c
_n ^*) And compute this complex conjugate of the individual channel estimates
Square (| c_n｜^Two) Divided by (complex number) as a coefficient
Spread output of received signals of each multipath (c1, c2, ...)
To obtain the components (d1, d2, ...) Of each multipath
It The multipath components obtained in this way are combined and reconstructed.
Adjust output d.

Each multipath component returns to the modulation base point because the value obtained by dividing the complex conjugate by the square of the individual channel estimation value is multiplied as a coefficient as described above. Therefore, the demodulation output d obtained by combining these components also returns to the modulation base point.

In demodulation using the conventional RAKE receiver,
For example, as shown in FIG. 16, the values obtained by multiplying the individual multipath components by the complex numbers of the channel estimation values as coefficients are combined (maximum ratio combination), so the phase rotation due to fading or the like is corrected. The amplitude of the thing was not retained. Thus, in the demodulation using the conventional RAKE receiver, the amplitude changes as shown in FIGS. When phase modulation such as QPSK is used as the primary modulation as in the prior art, there is a problem because the phase component can be used for demodulation even if the amplitude shifts from the modulation base point as shown in FIG. There wasn't. However, when a modulation method that requires an amplitude component such as QAM as the primary modulation is used as in this mobile communication system, the demodulated symbol points are displaced from the modulation base points as shown in FIG. If this happens, accurate demodulation will not be possible.

Therefore, in the case of QAM, for example, as shown in FIG.
It is necessary to return to the modulation base point as shown in 9 (A). In order to satisfy such a need, for example, as described above, for example, when a fixed code shared between channels as described above is transmitted as a pilot signal, a common channel estimation value as in the conventional case is used. Instead of using, the symbol width corresponding to the received signal power for each channel (the power obtained by adding the change in amplitude due to fading in the transmission path to the transmitted signal power) is detected and the channel (spreading code) is detected.
It is necessary to obtain the channel estimation value for each.

Therefore, as in this mobile communication system, demodulation is performed in accordance with the above-described individual channel estimation values, so that the demodulation output is returned to the modulation base point as shown in FIG. 19 (B). be able to. Therefore, even a modulation method that requires an amplitude component such as QAM can be surely demodulated.

Further, in this mobile communication system, as described above, the received signal is multiplied by the value obtained by dividing the complex conjugate of the channel estimation value by the square of the individual channel estimation value to synthesize the components of each multipath. Therefore, the amplitude of the received signal is small, as shown in FIG. However, since the noise component included in the received signal is also small, the demodulated symbol can be returned to the modulation base point without changing the SN ratio.

By the way, the demodulation according to the channel estimation value obtained as described above is not limited to the demodulation using the RAKE receiver described above by the process shown in FIG. 20, for example, and the process shown in FIG. The JD method according to the above, the SUD method according to the processing shown in FIG.

By the way, as the demodulated symbol returned to the modulation base point using the individual channel estimation value by the above-described processing, or the signal amplitude value corresponding to the power individually obtained for each spreading code is modulated. The reception characteristic can be obtained with high accuracy by obtaining the Euclidean distance using the value obtained by multiplying the base point as the reference symbol point.

The reception characteristic that can be obtained is, for example, RSSI (Received Signal Strength Indicato).
r), RSCP (Received Signal Code Power), IS
CP (Interference Signal Code Power), SIR (Si
gnal to Interference Ratio), Eb / Io, etc.

These reception characteristics can be obtained with high accuracy by using the individual channel estimation values obtained for each channel as described above, as compared with the case where a common channel estimation value with a fixed pattern is used.

By the way, in the demodulation stage as described above, it is not necessary to return the received signal to the modulation base point using the individual channel estimation value obtained for each channel. Specifically, for example, as shown in FIG. 23, at the time of decoding by error correction or hard decision (a process of reproducing received data from a modulation output), an individual channel estimation value (or power of each channel corresponding thereto) Error correction or decoding according to

In the case of performing such processing, first, as in S1 to S3 in FIG. 12 described above, a common channel estimation value by a common fixed pattern and an individual channel estimation value for each channel are obtained. After that, demodulation is performed using the common channel estimation value (S14).

In this demodulation, for example, Ap is the amplitude of a common fixed pattern between spreading codes, Ad is the transmission amplitude of the channel, α is the complex fading channel, and γ is the estimated value of the common fixed pattern. The demodulation symbol Z is obtained according to the equation shown in A).

After that, when a metric (for example, Euclidean distance) at the time of performing error correction or hard-decision decoding is obtained, a value including the amplitude corresponding to the power of the channel is used as a metric reference point (Euclidean distance) according to an individual channel estimation value. In the case of distance, error correction or hard decision decoding is performed as a Euclidean reference point (S15).

In this decoding, for example, the amplitude of each individual channel corresponding to the channel estimation value obtained by the common fixed pattern is not used, but the individual channel is actually used by the device according to the equation shown in FIG. Decoding is performed by obtaining an amplitude Ad ′ according to the estimated value and using this amplitude Ad ′ as a metric at the time of decoding to obtain a decoded value (d _j ).

Further, according to the individual channel estimation value, the reception characteristic is measured using the value including the amplitude corresponding to the power of the channel as the Euclidean reference point (S16).

The coefficient by which the modulation base point is multiplied when obtaining the metric at the time of decoding (S15) is determined in consideration of the processing at the time of demodulation, as shown in FIG.

In order to accurately obtain the Euclidean distance as a metric at the time of decoding even when the signal amplitude has information such as QAM, at the time of demodulation or decoding, as described above, each Euclidean distance is individually calculated for each channel. The obtained channel estimation value (or power for each channel) is required.
For this reason, in this mobile communication system, as described above, the processing is performed using the individual channel estimation value or the like obtained for each channel.

As described above, by performing error correction or hard decision using individual channel estimation values or the like for each channel to perform decoding, it is possible to contribute to improving the reliability of decoding received data. .

(Second Embodiment) (Structure) A mobile communication system according to a second embodiment of the present invention has the same structure as the mobile communication system shown in FIG.

In the above-described first embodiment, the pilot signal used in each channel transmitted from the base station 10 to the mobile terminal device 20 is transmitted in each channel as shown in FIGS. 6 to 8 described above. It had been.

In addition to this, in the mobile communication system of the second embodiment, from the base station 10 to the mobile terminal device 20.
On the other hand, for example, as shown in FIG. 25, a specific fixed pattern is transmitted for each channel (for each spreading code).

Further, in this mobile communication system, the channel estimation unit 223 obtains a common channel estimation value by a pattern common to all or some of the channels, as described above.

In the first embodiment, the received signal is despread for a predetermined number of symbols according to the common channel estimation result, and the amplitude of the symbol corresponding to the power value per unit symbol, Therefore, the channel estimation value for each channel is calculated. In the first embodiment,
For example, TFCI bits and TPC bits of all channels are used as the predetermined symbols for this purpose.

On the other hand, in the second embodiment, the individual channel estimation value is obtained by using the fixed pattern peculiar to each channel. The fixed pattern unique to each channel is the above-mentioned TFCI bit,
The symbol is longer than the TPC bit or the like.

(Operation) When performing the above-mentioned channel estimation,
The channel estimation unit 223 estimates the channel by the correlation between the despread received signal and the fixed pattern, as in the first embodiment described above.

After obtaining the common channel estimation value in this way, the channel estimation unit 223 despreads the received signal with respect to the above-mentioned fixed pattern unique to each channel,
The amplitude of the symbol corresponding to the power value per unit symbol is calculated. Further, the amplitude of such a symbol is obtained for each channel, and a channel estimation value unique to each channel is obtained.

In this way, when the channel estimation value peculiar to each channel is obtained, the channel estimation unit 223 supplies this peculiar channel estimation value and the common channel estimation value obtained as described above to the demodulation unit 224. To do.

Given these channel estimates,
The demodulation unit 224 demodulates the received signal as in the first embodiment described above.

As a result, similarly to the first embodiment, the demodulated symbol can be returned to the modulation base point for demodulation. As a result, the baseband signal can be demodulated reliably.

Further, as described above, since the fixed pattern unique to each channel has a longer symbol than the above-mentioned TFCI bit, TPC bit, etc., this is used to obtain an individual channel estimation value for each channel. By asking
It is possible to improve the accuracy of the channel estimation value individually for each channel.

Therefore, the demodulation accuracy can be improved by demodulating the received signal using the individual channel estimation value for each channel. Therefore,
The certainty of demodulation can be improved.

Further, by using the individual channel estimation value for each channel as described above, the reception characteristic is obtained as in the first embodiment, which contributes to the improvement of the accuracy of the reception characteristic. it can.

Alternatively, similarly to the above-described first embodiment, by performing error correction or hard decision using each channel estimation value or the like for each channel to perform decoding,
This can contribute to improving the certainty of decoding the received data.

In the description of the second embodiment, the case where only the fixed pattern unique to each channel is used to obtain the channel estimation value unique to each channel has been described. The channel estimation value unique to each channel may be obtained by the same procedure as in the first embodiment described above.

For the channel estimation values peculiar to the respective channels obtained, their average may be used for demodulation or the like, or Qo
Only one of them may be used for demodulation or the like depending on the reception status such as S.

[0107]

In the demodulation according to the present invention, a common pilot signal in a received signal received is despread, channel estimation is performed according to the despread common pilot signal, and each channel is estimated according to the estimated output. Find the amplitude of the fixed code,
By restoring the data in the received signal according to the estimated output and the amplitude of the fixed code for each channel, it is possible to improve the certainty of the restoration as compared with the case where the data is simply restored by the estimated output. You can

In this demodulation, the demodulated symbol can be returned to the modulation base point by executing a predetermined process in the data restoration.

Thus, for example, QAM is used as the primary modulation.
Even when the method is used, the baseband signal can be surely demodulated.

In another demodulation according to the present invention, the common pilot signal in the received signal received is despread, channel estimation is performed according to the despread common pilot signal, and the channel is estimated according to the estimated output. By obtaining the fixed code amplitude for each, and by restoring the data in the received signal according to the estimated output and the fixed code amplitude for each channel,
The certainty of the restoration can be improved as compared with the case where the data is simply restored by the estimated output.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of a mobile communication system according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a base station configuring the mobile communication system.

FIG. 3 is a diagram showing an example of QAM symbol points by a modulator that constitutes the base station.

FIG. 4 is a diagram showing an example of QAM symbol points by a modulator that constitutes the base station.

FIG. 5 is a block diagram showing a configuration of a mobile terminal device which constitutes the mobile communication system.

FIG. 6 is a diagram showing an example of pilot signals of each channel transmitted by the base station.

FIG. 7 is a diagram showing an example of pilot signals of each channel transmitted by the base station.

FIG. 8 is a diagram showing an example of pilot signals of each channel transmitted by the base station.

FIG. 9 is a diagram showing a channel estimation result in a downlink system of a mobile terminal device which constitutes the mobile communication system.

FIG. 10 is a diagram showing a structure of a frame in a time slot in a signal of each channel.

FIG. 11 is a diagram showing a structure of a frame in a time slot in a signal of each channel.

FIG. 12 is a flowchart showing an example of reception processing in the mobile terminal device.

FIG. 13 is a diagram showing an example of normalized channel estimation values.

FIG. 14 is a diagram showing an example of an individual channel estimation value obtained by multiplying a normalized channel estimation value by a symbol amplitude value of each channel.

FIG. 15 is a diagram illustrating an example of demodulation by a RAKE receiver.

FIG. 16 is a diagram showing an example of demodulation by a conventional RAKE receiver.

FIG. 17 is a diagram showing an example of symbols after demodulation of a QPSK modulated wave by a conventional RAKE receiver.

FIG. 18 is a diagram showing an example of symbols after demodulation of a QAM modulated wave by a conventional RAKE receiver.

FIG. 19 is a diagram showing an example of demodulation in which a symbol after demodulation is returned to a modulation base point.

FIG. 20 is a diagram illustrating an example of demodulation by a RAKE receiver.

FIG. 21 is a diagram illustrating an example of demodulation by the JD method.

FIG. 22 is a diagram showing an example of demodulation by the SUD method.

FIG. 23 is a flowchart showing an example of reception processing in the mobile terminal device.

FIG. 24 is a diagram showing an example of Euclidean distance obtained in the reception process.

FIG. 25 is a diagram showing an example of pilot signals transmitted from a base station to a mobile terminal device in the mobile communication system according to the second embodiment of the present invention.

FIG. 26 is a diagram for explaining a reception procedure according to the conventional JD method.

FIG. 27 is a diagram for explaining a reception procedure according to the conventional JD method.

FIG. 28 is a diagram for explaining a reception procedure according to the conventional SUD method.

FIG. 29 is a diagram for explaining a reception procedure according to the conventional SUD method.

FIG. 30 is a diagram showing an example of a pilot signal transmitted from a base station to a mobile terminal device in a conventional mobile communication system.

[Explanation of symbols]

1 ... Wired telecommunication network 2 ... Communication management device 10 ... Base station 110 ... Downlink system 120 ... Uplink system 20 ... Mobile terminal device 210 ... Uplink system 220 ... Downlink system

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 5K004 AA05 AA08 FA05 FG02 FH00                       JG01 JH06                 5K022 EE01 EE31

Claims (7)

[Claims] 1. A pilot signal having a channel multiplexed by a plurality of orthogonal spreading code sequences, wherein a pilot signal common to at least some channels is spread by the spreading code sequence of each channel, and common to all channels. Receiving means for receiving a signal in which the predetermined code (fixed code) is spread by the spreading code sequence, and despreading means for despreading the common pilot signal in the received signal received by the receiving means, Common channel estimation means for performing channel estimation according to the common pilot signal despread by the despreading means, and amplitude detection for obtaining the amplitude of the fixed code for each channel according to the estimated output of the channel estimation means Means for estimating the output of the common channel estimating means and the amplitude of the fixed code for each channel obtained by the amplitude detecting means. Demodulation device characterized by comprising a restoring means for restoring the data in the signal received by the receiving means. 2. A pilot signal having a channel multiplexed with a plurality of orthogonal spreading code sequences, wherein a pilot signal common to at least some channels is spread by the spreading code sequence of each channel, and a predetermined value different for each channel. Receiving means for receiving a signal whose code (fixed code) is spread by the spreading code sequence, despreading means for despreading the common pilot signal in the received signal received by the receiving means, and the despreading means. Common channel estimation means for performing channel estimation according to the common pilot signal despread by the spreading means, and amplitude detection means for obtaining the amplitude of the fixed code for each channel according to the estimated output of the channel estimation means. In accordance with the estimated output of the common channel estimating means and the amplitude of the fixed code for each channel obtained by the amplitude detecting means, Serial receiving means demodulator, wherein a and a restoring means for restoring the data in the signal received. 3. A reception state detection means for obtaining a reception state by the reception means according to the amplitude of the fixed code for each channel detected by the amplitude detection means. 2. The demodulator according to 2. 4. A pilot signal having a channel multiplexed by a plurality of orthogonal spreading code sequences, wherein a pilot signal common to at least some channels is spread by the spreading code sequence of each channel and common to all channels. Receiving a signal in which a predetermined code (fixed code) is spread by the spreading code sequence, a despreading step for despreading the common pilot signal in the received received signal, and the despreading Common channel estimation step for performing channel estimation according to the common pilot signal, amplitude detection step for obtaining the amplitude of the fixed code for each channel according to the estimated output, and the estimated output and for each channel A restoration step of restoring the data in the received signal according to the amplitude of the fixed code. Demodulation method. 5. A predetermined multiplexed signal having a channel multiplexed with a plurality of orthogonal spreading code sequences, wherein a pilot signal common to at least some channels is spread by the spreading code sequence of each channel, and different for each channel. Receiving a signal whose code (fixed code) is spread by the spreading code sequence, despreading the common pilot signal in the received received signal, and despreading the common pilot signal. A common channel estimation step for performing channel estimation according to a common pilot signal, an amplitude detection step for obtaining the amplitude of the fixed code for each channel according to the estimated output, the estimated output and a fixed code for each channel A restoration step of restoring the data in the received signal according to the amplitude of Method. 6. A pilot signal having channels multiplexed by a plurality of orthogonal spreading code sequences, wherein a pilot signal common to at least some channels is spread by the spreading code sequences of each channel, and common to all channels. Receiving means for receiving a signal in which the predetermined code (fixed code) is spread by the spreading code sequence, and despreading means for despreading the common pilot signal in the received signal received by the receiving means, Common channel estimation means for performing channel estimation according to the common pilot signal despread by the despreading means, and amplitude detection for obtaining the amplitude of the fixed code for each channel according to the estimated output of the channel estimation means Means for estimating the output of the common channel estimating means and the amplitude of the fixed code for each channel obtained by the amplitude detecting means. , The communication device characterized by comprising a restoring means for restoring the data in the signal received by the receiving means. 7. A pilot signal having a channel multiplexed with a plurality of orthogonal spreading code sequences, wherein a pilot signal common to at least some of the channels is spread by the spreading code sequence of each channel, and each channel has a different predetermined value. Receiving means for receiving a signal whose code (fixed code) is spread by the spreading code sequence, despreading means for despreading the common pilot signal in the received signal received by the receiving means, and the despreading means. Common channel estimation means for performing channel estimation according to the common pilot signal despread by the spreading means, and amplitude detection means for obtaining the amplitude of the fixed code for each channel according to the estimated output of the channel estimation means. In accordance with the estimated output of the common channel estimating means and the amplitude of the fixed code for each channel obtained by the amplitude detecting means, Communication device, characterized in that it comprises a restoring means for serial reception means to restore the data in the signal received.