JP2001285133A - Multi-carrier and spread spectrum transmitter, its receiver, system and method for communication using them - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multi-carrier/spread spectrum transmitter, its receiver, a system and method for communications using these which show excellent path diversity and frequency diversity effects by a constitution simpler than that of conventional technique and has resistance against even an interference wave in a narrow band. SOLUTION: The transmitter 1 is provided with a DPSK/DQPSK modulation part 11, a spread spectrum modulation part 12, a mapping part 13, an inverse Fourier transform part 14 and a guard interval part 15. The receiver 2 is provided with a guard interval removing part 23, a Fourier transform part 24, a peak removing part 25, a DPSK/DQPSK demodulation part 26, a demapping part 27 and an integration part 28.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multicarrier spread spectrum transmitter which combines a multicarrier communication system and a spread spectrum communication system, a receiver thereof, a communication system using the same, and a communication method.

[0002]

2. Description of the Related Art Conventionally, SR-chirp (Subban)
A spread spectrum communication method using a d Reception of Chirp method has been proposed, and is applied to mobile moving image transmission.

In the SR-Chirp (chirp) method, as shown in FIG. 5, a transmitting side 100 spreads an information signal with a chirp signal 100a, and a receiving side 101 does not have a normal despreading process, This is a system in which reception detection is performed by dividing into a plurality of partial bands 101a and 101b called bands, and these are combined 102 to obtain final demodulated data 102a, and has the following features.

A path diversity effect equivalent to a rake generated by a combination of a spreading code and a reception band limitation can be obtained.

A frequency diversity effect is obtained by combining and receiving a plurality of subbands (subband diversity).

[0006] A high avoidance capability of interference waves having a local spectrum due to sub-band diversity can be obtained.

[0007]

However, in the conventional configuration, it is necessary to prepare a plurality of subbands in order to obtain effective path diversity, frequency diversity, or high interference wave avoidance capability. In that case, it is necessary to prepare receiving circuits in the number of subbands, and there is a problem that the circuit scale is significantly increased.

When two receivers having the minimum configuration are used, only a part of the sub-bands is used, so that the signal power cannot be used effectively and there is a problem that the communication performance is greatly deteriorated.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, to provide a simpler configuration than the prior art, to have excellent path diversity and frequency diversity effects, and to reduce narrow-band interference waves. It is an object of the present invention to provide a multi-carrier spread spectrum transmitter which is resistant to the above, a receiver thereof, a communication system and a communication method using the same.

[0010]

According to the first aspect of the present invention,
DPSK / DQPSK modulator, spread spectrum modulator,
It is characterized by comprising a mapping unit, an inverse Fourier transform unit and a guard interval unit.

According to a second aspect of the present invention, a guard interval removing section, a Fourier transform section, a peak removing section, a DPSK /
A DQPSK demodulation unit, a demapping unit, and an integration unit are provided.

According to a third aspect of the present invention, there is provided a multicarrier spread spectrum transmitter according to the first aspect and a multicarrier spread spectrum receiver according to the second aspect.

According to a fourth aspect of the present invention, there is provided a multi-carrier
A spread spectrum receiver has a Fourier transform unit for transforming a time domain into a frequency domain, and performs phase correction by delay detection, demapping and integration on the output of the Fourier transform unit, and performs the inverse of the spread spectrum communication method. Data demodulation is performed without a spreading process.

According to a fifth aspect of the present invention, a transmission signal in a time domain is randomized by changing a phase in one data by a spread code using a spread spectrum method mainly with a multicarrier method.

The invention according to claim 6 is to provide data redundancy by a spread spectrum system mainly with a multicarrier system.

[0016]

An embodiment of the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, 1 indicates a multi-carrier spread spectrum transmitter, and 2 indicates a multi-carrier spread spectrum receiver. The transmitter 1 has a DPSK / D
The transmission data is converted to a DP by the QPSK modulation (mod) unit 11.
After differential encoding such as SK or DQPSK, spread spectrum modulation (SS mod) section 12 performs spread modulation in units of one symbol (symbol). Here, a finite length code such as a Barker code or an M-sequence code is used as the spread code.

In a mapping (Mapping) section 13, a Fourier transform (FFT) section 2 of the receiver 2 described later is used.
In step 4, in order to satisfy the Nyquist interval at the time of sampling the received signal, the rearrangement of the spreading code pattern (the data-modulated spreading code) is performed. FIG. 2 shows an example in which the spreading code is an 11-chirp barker code. Here, after the Barker code, a null ("
0 ") is added for 5 chips to make one symbol 16 chips.

Next, an inverse Fourier transform (IFFT) unit 1
Numeral 4 performs an inverse Fourier transform of the mapped code pattern in units of one symbol, and transforms a frequency domain into a time domain. Here, the code pattern in the frequency domain is called a subcarrier.

The guard interval (GI) unit 15 adds a guard interval to obtain multipath fading resistance. This guard interval is the same as that of a generally known multicarrier communication system.

Finally, the signal to which the guard interval has been added is converted into a high frequency by the high frequency converter 16 and then transmitted through the antenna 17.

In the receiver 2, first, the high-frequency signal received from the antenna 21 is converted into baseband by the converter 22, and then the guard interval is removed (Remove G).
I) The unit 23 removes the guard interval and sets an appropriate sampling position. The Fourier transform (FFT) unit 24 performs a Fourier transform on a symbol-by-symbol basis, and transforms a time domain into a frequency domain.

Peak rejection
n) In the case where the specific subcarrier (code pattern) is larger than the other subcarriers in one symbol and there is a level difference of a predetermined level or more within one symbol, the narrowband interference occurs. , The removal or amplitude limitation is performed in real time. As a result, it is possible to obtain resistance to interference in a narrow band having a frequency shift. In the Fourier transform processing, the side lobe level is increased in the Fourier transform processing to periodically process the interference signal (because the interference signal is cut off in the middle).
ing) and Blackman (Blackman) processing to reduce the side lobe of the interference signal.

As long as there is no interference wave in all subcarriers, interference can be removed and good communication quality can be ensured.

Next, DPSK / DQPSK demodulation (de
mod) unit 26 outputs DPSK or DSK in units of one symbol.
Performs differential detection (differential decoding) such as QPSK. In this configuration, since differential encoding / decoding is adopted as the modulation / demodulation method, resistance to a carrier error in transmission / reception and a phase variation due to fading can be obtained.

Next, a demapping (De-mappi)
The ng) unit 27 removes nulls (“0”) added by the mapping unit 13 on the transmitter 1 side, and integrates (Integ)
The ratio unit 28 performs integration for one symbol and performs data demodulation.

Here, by integrating all the subcarriers, that is, the signal power for one symbol, excellent frequency diversity and path diversity effects can be obtained with a simple configuration.

FIG. 3 shows an example of the frequency diversity and path diversity effects in a multipath environment, and FIG. 4 shows an example of the narrow-band interference removal.

These are examples of the waveforms of the computer simulation, and the waveforms here show the in-phase components when the modulation / demodulation is DQPSK.

The received signal shown in FIG. 3A has a variation in frequency due to multipath, which is subjected to Fourier transform by the Fourier transform unit 24 and DPSK / DQPS
By performing the delay detection by the K demodulation unit 26, FIG.
As shown in FIG. 3B and FIG. 3C, the variation in the time domain is converted into the variation in the frequency domain.
By performing the integration for one symbol at 8, the data is restored as shown in FIG. 3D.

The received signal shown in FIG. 4A contains a strong narrow-band interference signal.
4b, the variation of the interference signal in the time domain is converted into the variation of the interference signal in the frequency domain as shown in FIG. 4b, and after the interference is removed by the peak removing unit 25 as shown in FIG. 4c. , As shown in FIG.
By performing delay detection by the / DQPSK demodulation unit 26 and performing integration for one symbol by the integration unit 28 via the demapping unit 27, data is restored as shown in FIG. 4E.

The present multi-carrier spread spectrum communication system described above is particularly characterized by the configuration of the demodulation unit.

In the conventional system combining the multicarrier system and the spread spectrum system, the demodulation unit generally uses a Fourier transform (FFT) for the time and frequency conversion process of the multicarrier signal, and performs the despreading process of the spread spectrum signal. Uses a correlator for each carrier. According to this, processing of a spread spectrum signal requires correlators as many as the number of carriers, resulting in a very large circuit scale.

In the present system, as described above, the Fourier transform (FFT) output obtained by converting the time domain into the frequency domain has a simple configuration such as phase correction by delay detection, demapping, and integration. Data can be demodulated without having the despreading process of
This has an effect that excellent frequency diversity and path diversity can be obtained.

Since the configuration after the Fourier transform (FFT) output is simple, the processing time does not increase much.

Furthermore, a microwave oven (2.4 GHz band) or a coexisting FH (Bluetooth) is used with a simple algorithm.
h) can be removed and suppressed in real time with respect to narrow-band interference having a frequency shift such as h). In addition, this method satisfies the 2.4 GHz ISM band radio law.

The present multi-carrier spread spectrum communication system mainly employs the multi-carrier system, and does not simply continue the two signal processes of the multi-carrier system and the spread spectrum system.

In the multi-carrier system, if there is no change in data, the transmission signal waveform becomes impulse-like, which places a burden on the transmission power amplifier.

In the present embodiment, the transmission signal in the time domain is randomized by varying the phase in one data (1 symbol) by a spread code by the spread spectrum method, thereby reducing the peak power. is there.

Further, in the multi-carrier system, if a strong narrow band exists in a band and is removed or suppressed, a data error occurs.

In the present embodiment, data errors are reduced by providing data with redundancy by a spread spectrum method.

Although the present invention has been described with reference to one embodiment, it is apparent that the present invention is not limited to this.

[0043]

According to the present invention, by combining the multi-carrier communication system and the spread spectrum communication system,
It is possible to effectively use the frequency diversity and path diversity effects that are both features. In addition, since all carriers (subbands) can be used with a simple configuration, a frequency diversity effect superior to that of the related art (SR-chirp system) can be obtained.

Furthermore, by converting the received signal from the time domain to the frequency domain by the FFT processing, it is possible to easily realize interference removal in a narrow band.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a multi-carrier spread spectrum communication system.

FIG. 2 is a diagram illustrating an example of an operation (11-chip Barker code) of a mapping unit.

FIG. 3 shows examples of frequency diversity and a path diversity effect in a multipath environment, and FIGS. 3A to 3D show output waveforms.

FIG. 4 is a diagram illustrating an example of narrowband interference elimination, in which a to e show output waveforms.

FIG. 5 is a diagram showing a conventional SR-chirp system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Multi-carrier spread-spectrum transmitter 2 Multi-carrier spread-spectrum receiver 11 DPSK / DQPSK modulation part 12 Spread-spectrum modulation part 13 Mapping part 14 Inverse Fourier transformation part 15 Guard interval part 16 High-frequency converter 17 Antenna 21 Antenna 22 Converter 23 Guard interval removing unit 24 Fourier transforming unit 25 Peak removing unit 26 DPSK / DQPSK demodulating unit 27 Demapping unit 28 Integrating unit

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Katsuo Onozaki, Inventor 5-35-2 Hakusan, Bunkyo-ku, Tokyo Clarion Co., Ltd. (72) Shinichi Kuromoto 5-35-2, Hakusan, Bunkyo-ku, Tokyo Clarion On-term Inc. F-term (reference) 5K004 AA05 FA05 FA23 FE10 FG02 5K022 EE01 EE08 EE23 EE32

Claims (6)

[Claims] 1. A multicarrier spread spectrum transmitter comprising a DPSK / DQPSK modulation section, a spread spectrum modulation section, a mapping section, an inverse Fourier transform section, and a guard interval section. 2. A multi-carrier spread spectrum receiver comprising a guard interval removing section, a Fourier transform section, a peak removing section, a DPSK / DQPSK demodulating section, a demapping section and an integrating section. 3. A multicarrier spread spectrum communication system, comprising: the multicarrier spread spectrum transmitter according to claim 1; and the multicarrier spread spectrum receiver according to claim 2. 4. A multi-carrier spread spectrum receiver has a Fourier transform unit for transforming a time domain into a frequency domain, and performs phase correction by differential detection, demapping and integration on an output of the Fourier transform unit. And performing data demodulation without despreading the spread spectrum communication method. 5. A multi-carrier spread-spectrum communication method characterized in that a transmission signal in a time domain is randomized by changing a phase in one data by a spread code in a spread spectrum method mainly using a multi-carrier method. 6. A multi-carrier spread-spectrum communication method characterized in that data is made redundant by a spread-spectrum method mainly using a multi-carrier method.