JPH09232994A - Communication equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To extend the utilizing efficiency of frequencies by spreading input data with a long period and a short period code, modulating the code, sending the modulated signal, providing a reception function having a demodulation function and a correlation detecting function so as to make re-use of cells close to the unity thereby increasing number of subscribers in a cell. SOLUTION: A long period M series code is used for a spread code being an M series code EXORed with input data 31 and the code is changed for each user to assign different codes to lots of subscribers. Let a pulse width of the input data 31 be T1 and let a pulse width of a spread code be Ts, then a spread gain by the M series code is T1 /Ts, the spread signal is spread by a short period spread code. The spread is conducted by exclusively EXOR. The signal is S/P-converted at an S/P converter 34 corresponding to given K-channels. To which channel the signal is to be assigned is decided in advance between a transmitter and a receiver. The signals are synthesized by a synthesizer 37 via a filter 35 and the result is outputted and the signal is P/S-converted and received.

Description

Detailed Description of the Invention

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a mobile communication system, and more particularly to a structure of a communication device.

[0002]

2. Description of the Related Art Conventionally, this type of communication method has been called "V. Vandendr
ope, “Multitone Spectrum MultipleAccess Communica
tions System in a Multipath Rician Fading Channel "
1EEETransactions on Vehicular Technology Vol.44, N
O.2, May 1995 ”, page 328, FIG. 1, applying error correction to input data and converting encoded data into multiple frequency channels via serial and parallel conversion. Then, modulation is performed for each channel. The configuration was such that each modulated channel is combined, spectrum-modulated using a spreading code, and transmitted.

In addition, "T. Muller et al.," Comparison of di
fferent Detection Algorithms for OFDM-CDMA in Broad
There is one disclosed in FIG. 1 on page 835 of "IEEE VTC95 of band Rayleigh fading". This was a configuration in which the input data was converted with the walsh matrix, converted with IFFT, and output. The structure is shown in FIG.

[0004]

However, in the first conventional configuration, the same spreading code is used for each frequency channel, and therefore the number of subscribers that can be accommodated in the system is limited only by the code to which it applies. It is determined by the correlation property and autocorrelation property, and it is not possible to obtain sufficient subscribers. Further, it is difficult to digitize the circuit configuration because the spread spectrum modulation is performed after the frequency modulation of each channel.

In the second conventional configuration, the input data is wals.
Since only h conversion is applied, subscribers with more than walsh codes cannot be accommodated, and particularly when applied to a cellular system, there is a problem that the same walsh codes interfere with each other between adjacent cells. The structure is shown in FIG.

An object of the present invention is to provide a communication device that solves such problems.

[0007]

The gist of the present invention will be described with reference to the accompanying drawings.

In the structure of a receiver having a transmitter having a plurality of frequency channels and a detector for detecting the frequency channels, a function of spreading input data by a long-period code and a function of spreading a short-period code are used. A transmission function that has a spreading function, modulates the signals spread by each of them using a plurality of frequency channels, and transmits, a function that demodulates each frequency channel signal, and a short period spread signal and correlation detection The present invention relates to a communication device characterized by comprising a receiving function having a function of performing the above and a function of performing correlation detection with a long-period spread signal.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION A preferred embodiment of the present invention (how to implement the invention), which is considered to be the best, will be briefly described with reference to the drawings, showing its operational effects.

In the structure of the transmitter of the present invention, the input data is spread using the code unique to each correspondent. This code generally uses a long-period M-sequence code so that it can be assigned to many correspondents. The spread signal is converted into a spread signal using a converter.

For this conversion, spreading with an orthogonal code, conversion with an M array, or a Gold short cycle code with excellent cross-correlation characteristics is used. The spread signal is spread by this converter. The spread signal is divided into a plurality of channels by a serial / parallel converter.

Therefore, the data rate of one channel is
Lower by a few minutes of the channel. The signals of the respective channels are modulated with orthogonal carrier frequencies and output.

In the structure of the receiver, the received data for simultaneously receiving the signals sent by a plurality of correspondents is divided into the same number of channels as the transmission, and each signal is correlated with the same short period code as the transmitter. As a result, the data of each correspondent is demodulated for each short period code corresponding to each correspondent in all channels.

Data is decoded for each communicator by performing parallel-serial conversion for each demodulated communicator and performing correlation with the long-period code assigned to each communicator.

[0015]

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

First Embodiment 1. Description of Configuration FIG. 3 is a block diagram of a transmitter on the mobile station side showing a first embodiment of the present invention, in which input data 31 is spread by a spreading code 32.

The spread data is converted into a spread signal by the converter 33. As the conversion code, for example, Hadamard code, M-array coding, or short period Gold code is used. Data of the converted signal is converted into a plurality of channels N by the serial / parallel converter 34. The speed of the converted data is almost 1 / N with respect to the input data speed 1 of the serial / parallel converter. Each channel is modulated by a respective carrier frequency 36 through a filter 35 and sent as an output signal 38 through a combiner 37.

FIG. 4 is a block diagram of a receiver on the base station side showing a first embodiment of the present invention. A signal 41 received through a line such as a wireless line passes through a distributor 42 and is the same as that on the transmission side. It is distributed over several channels.

The signals of the respective channels are multiplied by the same reception carrier frequency 43 as that of the transmission and passed through a filter 44 to be demodulated into a baseband signal. The baseband signals are converted by the converter 45, passed through the distributor 46, collected for each signal of the same mobile station, returned to serial data via the parallel-serial converter 47 for each mobile station, and converted into a spread code. Correlation is performed using the same code 48 and demodulated as demodulated data 49.

FIG. 5 is a block diagram of a transmitter on the base station side showing the first embodiment of the present invention. Input data 51 different for each user is sent to each user by a multiplier (EXOR) 52. It is spread by the corresponding spreading code 52.

The spreading code 52 is spread by the converter 34 in accordance with the signal for each user. As the conversion code, the same Hadamard code, M array coding, or short period Gold code as in FIG. 3 is used.

The converted signal is a serial-parallel converter
It is converted into a parallel signal by 53.

The parallel signal is distributed to each channel by the distributor 55. The output is modulated by a transmission carrier frequency 57 orthogonal to each channel through a filter 56 and output as an output signal 59 through a combiner 58.

FIG. 6 shows the configuration of the receiver on the base station side, showing the first embodiment of the present invention.

The signal transmitted from the transmitter is received as a reception signal 61 via the wireless line. Received signal 61 is a distributor
The signals are distributed by 62, and each signal is multiplied by the received carrier signal 63 and is demodulated into a baseband signal through a filter 64. The user signals separated by the converter 65 are combined into a signal for each user by the distributor 66, converted into a serial signal by the parallel-serial converter 67, and a product correlation is obtained by the spreading code 68 for each user. It is performed and output as demodulated data 69.

2. Description of Operation FIG. 7 shows an example of a time chart in the configuration of the transmitter of FIG. M that multiplies (EXOR) the input data (a)
As the spreading code (b), which is a sequence code, an M sequence code with a long cycle is used, and different codes can be assigned to many subscribers by changing the code for each user. The pulse width of the input data is T _{I. Let} the pulse width of the spreading code be T _S. Here, assuming that the pulse width T _I of the input data and the pulse width T _{S of the} spreading code are, the spreading gain by the M-sequence code is T _I / T _S. The spread signal (c) is spread by the short cycle spreading code (d).

The spread data is shown in (e). The diffusion is performed by the product (EXOR). This signal is serial / parallel converted corresponding to the given K channels. Here, as an example, four channels are converted. The channel to which the signal obtained by serial / parallel conversion of data is assigned is determined in advance between transmission and reception.

In FIG. 6, the data of section 1 on the spread data (e) by the short cycle spread code is assigned to the first channel.

FIG. 7 (f) shows the result of a part allocated to the first channel. Similarly, the second section is also allocated to the second channel by the same method for the third and fourth sections. Second
The allocation results of 3 and 4 are not shown.

If the length of the short period spreading code is K, the spreading gain obtained by this spreading is K. In the example of FIG. 7, k = 4. Which short-cycle spreading code is used for which channel is determined in advance between transmission and reception. Each channel signal that has been orthogonally converted by the short-period spreading code and serial-parallel converted is modulated with a carrier frequency for each channel. The carrier frequency can be made orthogonal by setting the input data rate of FIG. 7 (f) as a frequency interval, thereby reducing inter-channel interference. Each channel signal is transmitted via an amplifier or the like. The receiver time chart is obtained by reversing the procedure of the transmitter time chart of FIG.

A guard interval may be used to remove interference. This is not an essential requirement of the present invention.

In the demodulator of the receiver of the base station of FIG. 4, the received signal is distributed to the same number of channels as the transmitting side, and the demodulated data of the base band is obtained by multiplying by the same carrier frequency as the transmission. Next, the demodulated data of each baseband signal is obtained by the correlation of the short-period spreading code. In this case, a short cycle code can be easily demodulated even by a matched filter.
Further, by using a plurality of correlators and combining the signals received at different times due to the influence of multipath in a rake receiver configuration, it is possible to obtain a path diversity effect and increase received power. The distributor determines and distributes which correlation output corresponds to the signal of the same channel. Parallel-serial conversion is performed on the data of the same channel to output serial data for each channel. User correlation is performed by correlating this data with M-sequence signals for each user.

The configuration of the transmitting side of the base station shown in FIG. 5 is basically the same as that of the mobile station except that signals of multiple users are simultaneously transmitted. Input data for each user is spread by the long-period M-sequence code assigned to each user. The spread user signal is spread by a short cycle spreading code. The spread signal is converted into parallel data by a serial / parallel converter. Of the converted data for each user, for example, the first parallel signal is the first
Input to the channel of. Which parallel signal is assigned to which channel is determined in advance.

Explaining according to the above example, it is determined in advance which channel signal will be used with which data converted by the short period spreading code. The converted output is modulated by the orthogonal frequency in each channel and output. The respective channel signals are combined and output. In this channel signal,
It is also possible to send out a pilot signal for determining the amplitude and phase of the propagation path characteristic. It is also possible to send out a pilot signal for establishing data synchronization.

The receiver of the mobile device shown in FIG. 6 receives the transmission signal from the base station and multiplies it for each channel at the same frequency as the carrier frequency of each channel of the base station. The multiplied signal is converted by using a predetermined code and a short cycle spread code. The converted signal is distributed to a signal for each user by a distributor. The distributed signal is subjected to parallel-to-serial conversion, a correlation operation is performed with a long-period M-sequence code assigned to each user, and data is received.

Although error correction and interleaving have not been described in the above description, if error correction and interleaving are applied to data, it is possible to transmit user data with few errors. In this case, error correction and interleaving can be inserted after the data input, or after the serial-parallel converter. When transmitting voice as data, by distinguishing between the voiced section and the silent section so that the voiced section is not adjacent between adjacent channels, the amount of inter-channel interference can be reduced and transmission can be performed with less error. . Further, by applying the method of transmitting only the voiced section to the present invention, it is possible to reduce the total interference and to perform transmission with few data errors.

As the short period spreading code in the present invention, the same result can be obtained by using an error correction code such as Hadamard transform, Sword Solomon code or the like, or a Gold code having a large cross-correlation characteristic, an orthogonal transform method by M array or the like. Obtainable.

A similar result can be obtained by using a scrambler as the product of the long-period spreading code of the present invention and the input data.

3. Description of Effects When configured as in the first embodiment, since the data of one user, which is a characteristic peculiar to multicarrier, is divided into a plurality of multicarrier signals and transmitted, the data rate for one channel frequency is reduced. Therefore, deterioration can be suppressed to a low level with respect to high-speed fading. When used in a cellular system, the same carrier frequency can be used between adjacent cells by using different combinations of the Hadamard code and carrier frequency between adjacent cells.

Further, when signals obtained by modulating the same short period spreading code with the same carrier frequency between adjacent cells are used, interference occurs between adjacent channels. In this case, a device for spreading the code between adjacent channels with a small code is provided between the distributor 45 and the filter 46 in FIG. Therefore, the reuse of the cell is close to 1, and the number of subscribers in the cell can be increased. This indicates that the frequency utilization efficiency can be increased.

Second Embodiment 1. Description of Configuration FIG. 8 shows a second embodiment including a channel equalizer. The configuration is the same as that of FIG. 4, but an equalizer that performs channel equalization on the characteristics of the wireless channel is inserted after the converter.

2. Description of operation In a wireless line, transmission signals transmitted at the same time are received at different times at the time of reception due to the influence of multipath. This causes fluctuations in the phase and amplitude, becomes intersymbol interference noise, deteriorates the signal-to-noise ratio, and reduces the subscriber capacity of the entire system. When the data transmission rate is low, the amount of interference noise can be reduced by using a transmission line equalizer.

3. Description of Effect When configured as in the second embodiment, the influence of the propagation path is removed by performing waveform equalization on the received signal due to waveform distortion due to the influence of the multipath propagation path, and detection on the receiving side is performed. With this, detection with few errors can be performed.

Third Embodiment 1. Description of Configuration A configuration having a Rake detector including a plurality of correlators will be referred to as a third embodiment. The configuration is the same as in FIG. A rake is inserted instead of the channel equalizer in FIG.
The rake receiver is composed of multiple correlators.

2. Description of Operation Each correlator performs detection for each path of the multipath wireless propagation path and performs diversity combining.

3. Description of Effects With the configuration as in the third embodiment, it is possible to perform detection for each path at a place where the diffusion speed is sufficiently faster than each delay time of the multipath signal, and the propagation path The detection characteristics are improved by equalizing the.

Description of Utilization Mode This embodiment has been described as an example of an apparatus used in a wireless line, but is also applied to an optical communication apparatus using an optical fiber in which a baseband signal is modulated with light instead of a wireless modulation signal. It is possible. Further, the present invention is also applicable to a wired communication device using modem analog modulation used for a wired line instead of a wireless modulation signal.

Although the modulation is performed at the carrier frequency, it can be applied to an underwater communication device by using a vibrator.

[0049]

Since the present invention is configured as described above, the data transmission rate per channel of the transmitter is low, and the signal from each transmitter can be transmitted by the orthogonal code of a short period without correlation, and the noise resistance is high. A communication device with excellent characteristics can be realized.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of a conventional multicarrier modulator.

FIG. 2 is an explanatory diagram showing a configuration of a conventional multicarrier modulator.

FIG. 3 is an explanatory diagram showing a configuration of a transmitter of a mobile station according to the first embodiment.

FIG. 4 is an explanatory diagram showing a configuration of a receiver of the mobile station of the first embodiment.

FIG. 5 is an explanatory diagram showing a configuration of a transmitter of the base station of the first embodiment.

FIG. 6 is an explanatory diagram showing a configuration of a receiver of the base station of the first embodiment.

FIG. 7 is a transmitter time chart of the first embodiment.

FIG. 8 is an explanatory diagram showing a configuration of a receiver of a mobile device including an equalizer according to the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Soichi Watanabe 1799-2, Yasuda, Kashiwazaki-shi, Niigata Corp. No. 203 Yasuda Corp. (72) Takeo Abe 7-23, Terao Asahi, Niigata, Niigata Prefecture

Claims (1)

[Claims] 1. In a structure of a receiver having a transmitter having a plurality of frequency channels and a detector for detecting the frequency channels, the function of spreading input data by a long-period code and Having a function of spreading by a code, a transmission function of modulating and transmitting the signal spread by each of them by using a plurality of frequency channels,
A communication device comprising: a receiving function having a function of demodulating each frequency channel signal, a function of performing correlation detection with a short period spread signal, and a function of performing correlation detection with a long period spread signal.