JPH08172419A - Cdma transmitter-receiver - Google Patents

Abstract

PURPOSE: To eliminate inter-code interference and to correct frequency deviation by turning the real number part and imaginary number part of complex numbers to the product of the complex numbers by non-correlated random complex spreading codes and spreading and modulating transmission data. CONSTITUTION: At the ti.me of transmission, the transmission data D are distributed for each data cycle in a serial/parallel converter 10 and real number part modulation input waves R1 and imaginary number part modulation input waves C1 are outputted to a spread modulation part 13. Simultaneously, PN signal generation parts 11 and 12 output real number complex spreading codes R2 and imaginary number complex spreading codes C2 to the modulation part 13. Then, the input waves R1 and the codes R2 and the input waves C1 and the codes C2 are subtracted after multiplication and turned to real number signals R3, the codes R2 and the input waves C1 and the codes C2 and the input waves R1 are added after the multiplication and turned to imaginary number signals C3 and a receiver 20 receives modulation signals S synthesized in a vector synthesizer 14. Then, sampling is performed by the double of a spread rate in the sampling part 40 of a fractional interval type equalizer 22 and further, the signals S are demodulated in a waveform equalizer 23.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CDMA transceiver capable of eliminating intersymbol interference.

[0002]

2. Description of the Related Art In order to improve the frequency utilization efficiency of cellular digital mobile communications, it is necessary to remove co-channel interference waves. In order to use an interference canceller in a cellular system, it is necessary to be able to receive a random access signal such as an access channel and a user packet. Further, in order to prevent the user capacity from decreasing in a multipath environment, it is necessary to follow the multipath.

In the signal transmission of a cellular system,
As a technique for removing intersymbol interference distortion generated in a multipath propagation path, there is an adaptive equalization method, and linear equalization and decision feedback equalization (D
FE), maximum likelihood sequence estimation (MLSE), and the like. Demodulation for the purpose of removing intersymbol interference is performed by combining these techniques. In addition, the causes of transmission failure in data transmission under multipath environment include carrier phase shift,
There are timing phase shift, carrier frequency shift, timing frequency shift and the like. Therefore, such frequency deviation must be corrected.

As a conventional technique for removing the intersymbol interference and correcting the frequency shift as described above, Japanese Patent Laid-Open No. 4-352 is known.
No. 523 discloses a data transmission demodulator. FIG. 2 is a block diagram showing the configuration. According to this technique, a phase rotation is given to an addition output from an adder 101 to be given to a determiner 100 so as to compensate for the amount of phase fluctuation according to the amount of phase fluctuation.

[0005] In addition, a decision output from the decision unit 100 to be provided to a rear filter constituted by a shift register 102 and a multiplier 103, which is located after the decision unit 100, and an error to be given to the tap coefficient control unit 104 are as follows. , Phase control unit 1
05, the complex conjugate unit 106, and the multiplier 107 provide a phase rotation so as to add a phase fluctuation amount corresponding to the phase fluctuation amount.

With this configuration, when a phase variation such as a frequency offset occurs, it is possible to remove intersymbol interference and correct a frequency shift without lowering convergence and speed. .

[0007]

However, according to the above-described conventional technique, it is possible to remove intersymbol interference and correct a frequency shift without lowering the speed. Unit 108 and shift register 1
02 and the multiplier 103, the phase control unit 105, the complex conjugate unit 106, the multiplier 107, and a number of other components, which requires a circuit configuration, which complicates the circuit configuration and increases the size of the entire device. There's a problem.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a CDMA transceiver capable of removing intersymbol interference and correcting frequency shift with a simple structure.

[0009]

In order to achieve the above object, a CDMA transceiver according to the present invention transmits as a product of complex numbers by using a complex spreading code in which real and imaginary parts of a complex number are uncorrelated and random. The transmission means for spreading and modulating the data, and the reception means for demodulating the transmission data by a fractional interval type equalizer and a waveform equalizer using a complex number type RLS adaptive algorithm are provided.

According to a second aspect of the present invention, the transmitting means generates the modulated input wave of the real number part and the modulated input wave of the imaginary number part of the transmission data, and the serial-parallel converter has no correlation between the real number part and the imaginary number part. PN signal generator for generating a real complex random spread code and an imaginary complex spread code, and a real part modulated input wave and an imaginary part modulated input wave from the serial-parallel converter and the PN signal generator. A spread modulation unit that performs spread spectrum modulation by a complex product of a real complex spread code and an imaginary complex spread code, a vector synthesis unit that performs vector synthesis of a real signal and an imaginary signal from this spread modulation unit, and a vector synthesis unit A receiving filter for limiting the band of the output signal is provided, and the receiving means performs a sampling filter for limiting the band of the receiving signal and a sampling filter for the received signal at twice the spreading rate by performing fractional interval equalization. A fractionally spaced equalizer that graying is configured to include a waveform equalizer is transversal digital filter using the RLS adaptive algorithm coefficient update algorithm of the filter.

[0011]

According to the CDMA transceiver of the first aspect, in the transmitting means, transmission data is spread-modulated as a product of complex numbers using a complex spreading code in which a real part and an imaginary part of a complex number are respectively uncorrelated and random, In the receiving means, the transmission data is demodulated by a fractionally spaced equalizer and a waveform equalizer using a complex RLS adaptive algorithm.

According to the CDMA transceiver of the present invention, the serial-parallel converter of the transmitting means generates the modulated input wave of the real part and the modulated input wave of the imaginary part of the transmission data, and the PN signal generator generates the modulated input wave of the real part. And a imaginary part are uncorrelated and random, respectively, and a real complex spreading code and an imaginary complex spreading code are generated.
Then, in the spread modulator, spread spectrum modulation is performed by a complex product of the real part modulated input wave and the imaginary part modulated input wave from the serial-parallel converter and the real complex spread code and the imaginary complex spread code from the PN signal generator. Will be

Thereafter, the vector synthesis section performs vector synthesis of the real number signal and the imaginary number signal from the spread modulation section, and the transmission filter limits the band of the output signal of the vector synthesis section. Then, at the time of reception, after the band of the received signal is limited by the reception filter of the receiving means, the fractionally-spaced equalizer performs fractional-spaced equalization, and is sampled at twice the spreading rate of the received signal. It The received signal is demodulated by the waveform equalizer using the RLS adaptive algorithm.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a CDMA according to an embodiment of the present invention.
It is a block diagram which shows a transceiver. In FIG. 1, reference numeral 1 denotes a transmitting unit as a transmitting unit, and 2 denotes a receiving unit as a receiving unit.

The transmitting unit 1 uses a complex spreading code in which the real part and the imaginary part of a complex number are uncorrelated and random, respectively.
A part for spreading and modulating the transmission data D as a product of complex numbers. The serial / parallel converter 10, PN signal (pseudo noise signal) generators 11 and 12, a spreading modulator 13, a vector synthesizer 14, A transmission filter 15 and a transmitter 16 are provided.

The serial-parallel converter 10 distributes the transmission data D, which is digital data, for each data cycle, and the modulated input wave R1 of the real part (I phase, In-phase) and the imaginary part (Q phase, Quadrature-phase). ) Is a device for generating a modulated input wave C1. PN signal generator 1
Reference numerals 1 and 12 denote devices for generating a real complex spreading code R2 and a imaginary complex spreading code C2 in which the real part and the imaginary part are uncorrelated and random, respectively.

The spread modulation unit 13 includes a real part modulated input wave R 1 and an imaginary part modulated input wave C 1 from the serial-parallel converter 10,
The real number complex spread code R2 and the imaginary complex spread code C2 from the N signal generators 11 and 12 are input, and spread spectrum modulation is performed by a complex product of these. Specifically, multipliers 31 and 32 and a subtractor 33 are provided on the output side of the serial-parallel converter 10. The multiplier 31 multiplies the real part modulated input wave R1 and the real complex spread code R2, and the multiplier 32 calculates the imaginary part modulated input wave C1 and the imaginary complex spread code C2.
, And the subtractor 33 subtracts the output signals from the multipliers 31 and 32.

On the output side of the PN signal generators 11, 12, multipliers 34, 35 and an adder 36 are provided. The multiplier 34 multiplies the real complex spreading code R2 by the imaginary part modulated input wave C1, and the multiplier 35 multiplies the imaginary complex spreading code C2 by the real part modulated input wave R1.
Reference numeral 6 adds the output signals from the multipliers 34 and 35.

The vector synthesizing section 14 is a section for performing vector synthesizing of the real number signal R3 from the subtractor 33 of the spread modulation section 13 and the imaginary number signal C3 from the adder 36. The transmission filter 15 is a so-called root cosine filter,
The bandwidth of the combined modulation signal S from the vector combining unit 14 is limited. The transmitter 16 is a device that transmits the modulated signal S band-limited by the transmission filter 15.

On the other hand, the receiver 2 includes a receiver 20, a reception filter 21, a fractionally-spaced equalizer 22, and a waveform equalizer 2.
3, a fractionally-spaced equalizer 22 and a complex type RLS
(Recursive Least Square) This is a part for demodulating the transmission data D with the waveform equalizer 23 using an adaptive algorithm.

The receiver 20 receives the modulated signal S from the transmitter 1.
Is received and output to the reception filter 21.
The reception filter 21 is a so-called root cosine filter, and limits the band of the reception signal S.

The fractionally-spaced equalizer 22 is a sampling circuit that performs fractionally-spaced equalization, and can sample the received signal S at twice the spreading rate. Specifically, a plurality of delay elements 41-1 to 41-n-1 connected in series via a sampling section 40 and a plurality of switch sections 42-1 to 42-n are provided. Further, a clock 43 for outputting a clock signal S1 for operating the sampling unit 40 at twice the spreading rate of the received signal S is provided. The clock signal S1 is supplied to the switch unit 4
It is also input to 2-1 to 42-n, and the switch section 42-1 to
42-n operate in synchronization with the sampling section 40.

The waveform equalizer 23 is a transversal type digital filter using an RLS adaptive algorithm as a filter coefficient updating algorithm. Specifically, it has a plurality of tap coefficient sections F1 to Fn to which the switch sections 42-1 to 42-n are connected on the input side. The tap coefficient units F1 to Fn have a function of controlling the output signal so that the fed back difference signal e (n) described later becomes zero. Then, such tap coefficient parts F1 to Fn
The adder 51 for adding the output signals from the tap coefficient units F1 to Fn is provided on the output side of the. On the output side of the adder 51, output signals Y (n) of the tap coefficient units F1 to Fn are provided.
And the desired signal d (n) are subtracted, and the difference signal e (n) is obtained.
Is provided to each of the tap coefficient units F1 to Fn.

Next, the operation of this embodiment will be described.
At the time of transmission by the transmitter 1, the serial-parallel converter 10 distributes the transmission data D for each data cycle, and outputs the real number modulated input wave R1 and the imaginary number modulated input wave C1 to the spread modulator 13. It In parallel with this operation, the PN signal generators 11 and 12 generate a real complex spreading code R2 and an imaginary complex spreading code C2 and output them to the spreading modulator 13.

Then, the multiplier 31 of the spread modulator 13 multiplies the real part modulated input wave R 1 by the real complex spread code R 2, and the multiplier 32 multiplies the imaginary part modulated input wave C 1
And the imaginary complex spreading code C2,
In, the output signals from the multipliers 31 and 32 are subtracted. In parallel with this operation, the multiplier 34
The real complex spreading code R2 is multiplied by the imaginary part modulation input wave C1, and the imaginary complex spreading code C2 is multiplied by the real part modulation input wave R1 in the multiplier 35. The output signals from 35 are added.

Then, the real number signal R3
And the imaginary number signal C3 are output,
, These signals are vector-synthesized, and the synthesized modulated signal S is band-limited by the transmission filter 15, and then transmitted from the transmitter 16 to the receiver 2.

Then, the modulated signal S is received by the receiver 20 of the receiving unit 2, band-limited by the reception filter 21, and then input to the fractionally spaced equalizer 22. When the received signal S is input to the fractionally-spaced equalizer 22, the sampling unit 40 of the fractionally-spaced equalizer 22 samples the signal at twice the spreading rate, and each signal is sequentially delayed by the delay element 41-1.
To 41-n-1 and a switch unit 42-n-1.
1 to 42-n, the tap coefficient section F of the waveform equalizer 23
1 to Fn.

The signals input to the tap coefficient portions F1 to Fn are controlled and output so that the difference signal e (n) fed back from the subtractor 52 becomes zero. Then, the signals output from the tap coefficient units F1 to Fn are added by the adder 51 and then output as the output signal Y (n). In parallel with this, the output signal Y (n) and the desired signal d (n) are subtracted by the subtractor 52, and the difference signal e (n) is fed back to the tap coefficient units F1 to Fn. That is, in the waveform equalizer 23, the received signal S is demodulated by using the RLS adaptive algorithm for updating the filter coefficients.

[0029]

As described above, according to the CDMA transceiver of the present invention, in the transmitting means, the real part and the imaginary part of the complex number are each transmitted using the uncorrelated and random complex spreading code as a product of the complex numbers. Is spread-modulated, so that the symbol period is doubled as compared with the case where the modulation is performed by the BPSK modulation method, so that the spreading code length can be doubled. As a result, the number of types of spreading codes can be increased, which leads to an increase in the number of multiplex users,
There is an effect that intersymbol interference in multipath over a wider range can be removed.

In the receiving means, the complex number type RLS is used.
Since the waveform equalizer using the adaptive algorithm is applied, the I-phase (In-phase) and the Q-phase (Quadra) are used.
Thus, there is no need to provide a demodulation unit independent of the true-phase, so that the configuration of the receiving means can be simplified, and as a result, the size of the entire CDMA transceiver can be reduced. Furthermore, since the fractionally-spaced equalizer is also used, timing jitter can be absorbed, and the intersymbol interference removal capability can be further improved.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a CDMA transceiver according to an exemplary embodiment of the present invention.

FIG. 2 is a block diagram showing a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transmitting part 2 Receiving part 10 Serial-parallel converter 11, 12 PN signal generator 13 Spreading modulation part 14 Vector synthesis part 15 Transmission filter 21 Reception filter 22 Fractionally-spaced equalizer 23 Waveform equalizer

Claims (2)

[Claims] 1. A transmission means for spreading-modulating transmission data as a product of complex numbers using a complex spreading code in which real and imaginary parts of a complex number are uncorrelated and random, a fractionally-spaced equalizer and a complex-type RLS. A CDMA transceiver comprising: a waveform equalizer that uses an adaptive algorithm; and a receiving unit that demodulates the transmission data. 2. A serial-parallel converter for generating the modulated input wave of the real part and the modulated input wave of the imaginary part by the transmission means, and a real number in which the real part and the imaginary part are uncorrelated and random. , A PN signal generator for generating a complex spread code and an imaginary complex spread code, a real part modulated input wave and an imaginary part modulated input wave from the serial-parallel converter, and a real complex spread code from the PN signal generator, Spread spectrum modulator that performs spread spectrum modulation by complex product with imaginary complex spread code, vector synthesizer that synthesizes vector of real signal and imaginary signal from this spread modulator, and band limitation of output signal of vector synthesizer A receiving filter for limiting the band of the received signal, and a receiving filter for performing a fractional interval equalization to spread the received signal at a spreading rate of 2 or more.
The CDMA transceiver according to claim 1, further comprising: a fractionally-spaced equalizer that doubles the sampling frequency; and a waveform equalizer that is a transversal digital filter that uses an RLS adaptive algorithm as a filter coefficient updating algorithm.