JPH08163001A - Spread spectrum communication system - Google Patents

Abstract

PURPOSE: To surely detect a PN code in a short time in the case of communication at a low data rate by spread spectrum communication. CONSTITUTION: A transmitter 23 other than spread spectrum communication equipment sends a signal including a synchronizing signal sufficiently warranting synchronization accuracy of a PN code used for the spread spectrum communication equipment, the spread spectrum transmitter 21 generates a PN code synchronizing signal synchronizing with the synchronizing signal included in the signal sent by the transmitter 23 and a spread spectrum signal as to information data and sends them, a spread spectrum receiver 22 generates a PN code synchronized with the synchronizing signal included in the signal sent by the transmitter 23 to synchronize the spread spectrum transmitter 21 with a PN generator and demodulate the information data with inverse spread spectrum processing.

Description

Detailed Description of the Invention

[0001]

[Table of Contents] The present invention will be described in the following order. Field of Industrial Application Conventional Technology (FIGS. 9 and 10) Problem to be Solved by the Invention Means for Solving the Problem (FIGS. 1, 2 and 5) Operation (FIGS. 1, 2 and 5) Example (FIGS. 1 to 8) Effect of the invention

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spread spectrum communication system, and is particularly suitable for being applied to a communication system using spread spectrum communication and having a low data rate.

[0003]

2. Description of the Related Art Conventionally, in spread spectrum communication, a transmitter multiplies information data or an information-modulated signal by a PN code to spread the band and transmits the signal, and a receiver multiplies a received signal by the PN code to reverse the band. Spread. First, in the spread spectrum transmitter 1 shown in FIG. 9, the information data SI is input to the information modulator 2 and subjected to primary modulation such as frequency modulation and phase modulation. The multiplier 3 multiplies the output of the information modulator 2 and the PN code SP generated by the PN generator 4 to spread the band. The output of the multiplier 3 is converted into a high frequency signal by the frequency conversion unit 4, amplified by the power amplification unit 5 and radiated via the antenna 6.

On the other hand, in the spread spectrum receiver 10 shown in FIG. 10, the signal received by the antenna 11 is amplified by the high frequency amplifier 12 and then converted into a low frequency by the frequency converter 13. The output is input to the PN detection unit 14. The PN detector 14 detects a PN code from the received signal and sends a timing initialization signal to the PN generator 15. In spread spectrum communication, P is used by transmitter 1 and receiver 10.
If the N code is not synchronized, it can be seen only as noise and cannot be demodulated. Synchronizing the PN code is essential for spread spectrum communication. The other output of the frequency conversion unit 13 is input to the multiplier 16. The multiplier 16 multiplies the PN code output from the PN generator 15 and the output from the frequency conversion unit 13 to despread the band. The output of the multiplier 16 is demodulated by the information demodulation unit 17 and output as information data SO.

[0005]

However, in order to increase the communication distance with a constant transmission power, it is necessary to reduce the data rate. However, in the case of a normal communication system, in order to reduce the data rate and extend the communication distance, the bandwidth of the filter of the receiver must be narrowed according to the data rate in order to improve the C / N. However, in order to reduce the bandwidth of the receiving filter, it is required that the receiving frequency of the receiver and the center frequency of the receiving filter be fairly accurate.
For example, in order to set the data rate to 200 [bps], the bandwidth of the receiving filter becomes about 200 [Hz], but 900
About 0.02 [ppm] to realize a communication system in the [MHz] band
] Frequency accuracy is required.

In the spread spectrum communication, it is not necessary to reduce the bandwidth of the reception filter, so that the data rate can be considerably reduced. For example, the data rate is 200
In the case of [bps], if the spreading factor is set to 1000, the bandwidth of the receiving filter becomes 200 [KHz], and the frequency accuracy in the 900 [MHz] band is about 20 [ppm]. However, in spread spectrum communication, data cannot be demodulated unless the timing of the PN code of the receiver is matched with that of the transmitter as described above. A problem in the case of reducing the data rate in spread spectrum communication is to match the timing of the PN code in the transceiver.

When the receiver starts communication, it detects the PN code transmitted by the transmitter and synchronizes the PN code. The lower the data rate, the larger the spreading factor, or the longer the PN code length. The longer it takes to detect the PN code. This is a problem in spread spectrum communication with a low data rate because the data rate is low and the spreading rate is high. When the intermittent operation is performed, the operation time for the intermittent cycle becomes long due to the detection time of the PN code, which becomes an obstacle to reduce the power consumption and prolong the standby time, which hinders realization to the mobile terminal.

The present invention has been made in consideration of the above points, and a spread spectrum communication system capable of surely detecting a PN code in a short time when performing communication at a low data rate using spread spectrum communication. Is to propose.

[0009]

In order to solve the above problems, the present invention provides a spread spectrum transmitter (21) which modulates information data (SI) and spreads a band to generate a spread spectrum signal, and a spread spectrum signal. A spread spectrum communication system (20) comprising a spread spectrum communication device including a spread spectrum receiver (22) for despreading and demodulating a signal, and a transmitting device (23) for transmitting a signal including a synchronization signal. The device (23)
The spread spectrum transmitter (21) transmits a signal including a synchronization signal that sufficiently guarantees the synchronization accuracy of the PN code used in the spread spectrum communication device, and the spread spectrum transmitter (21) transmits the spread spectrum transmitter (2, 3, 30, 5, 6, 7) and a receiving unit (25, 26, 27, 28, 29) for synchronous extraction, and the receiving unit (25, 26, 27, 28, 28, 29) receives the synchronization signal included in the signal transmitted by the transmitting device (23). 29), a PN code is generated in synchronization with the extracted synchronization signal, a spread spectrum signal is generated for information data (SI), and the transmission unit (2, 3, 30, 5, 6, 7) And the spread spectrum receiver (22) transmits the spread spectrum receiver (11,
12, 13, 35, 36, 16, 17) and a receiver (31, 32, 33, 34) for synchronization extraction, and a receiver (31, 32, 33, 34) for receiving the synchronization signal included in the signal transmitted by the transmitter (23). 31, 32, 33, 34), a PN code is generated in synchronization with the extracted synchronization signal, and a spread spectrum transmitter (21) and a PN generator (36) are synchronized to perform spectrum despreading. Information data (SO) is demodulated.

[0010]

Operation: A transmitting device other than the spread spectrum communication device (2
In 3), a signal including a synchronization signal that sufficiently guarantees the synchronization accuracy of the PN code used in the spread spectrum communication device is transmitted, and in the spread spectrum transmitter (21), the transmission device (2
3) P synchronized with the synchronization signal included in the signal transmitted by
An N code is generated, a spread spectrum signal for information data (SI) is generated and transmitted, and the spread spectrum receiver (22) synchronizes with a synchronization signal included in the signal transmitted by the transmission device (23). Spread spectrum communication is used by generating a PN code, synchronizing a spread spectrum transmitter (21) and a PN generator (36), and performing despreading of the spectrum to demodulate information data (SO). Thus, when performing communication at a low data rate, the PN code can be detected reliably and in a short time.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

In practice, when the data rate is reduced by spread spectrum communication, the PN code may be synchronized with the accuracy of the chip clock which is the operation clock. When the data rate is 200 [bps] and the spreading factor is 1000, the frequency of the chip clock is 200 [KHz]. Therefore, the synchronization accuracy may be about 1 [μs].

In this embodiment, as a signal transmitted from an existing system other than the spread spectrum communication system, for example, a television broadcasting signal or a short wave standard wave (JJ) is used.
Y) A synchronization signal is extracted from the transmission signal, and the PN code of the transmitter and the receiver is synchronized with the synchronization signal. As a result, in spread spectrum communication with a very low data rate,
It is possible to realize synchronization of PN codes of a transmitter / receiver in a short time and to realize a communication system with low power consumption and long communication distance.

In FIG. 1, reference numeral 20 indicates a spread spectrum communication system according to the present invention as a whole, a spread spectrum transmitter 21 for transmitting a spread spectrum signal, a spread spectrum receiver 22 for receiving a spread spectrum signal,
It is configured with another transmitter 23 that is not involved in spread spectrum communication. If the other transmitter 23 includes a synchronization signal that sufficiently guarantees the synchronization accuracy of the PN code required for the spread spectrum transmitter 21 and the spread spectrum receiver 22,
Various systems are available. For example, both vertical and horizontal synchronizing signals in a television broadcast signal can be used.

The spread spectrum transmitter 21 receives a signal transmitted by another transmitter 23, extracts a synchronization signal contained therein, synchronizes the PN code with the extracted synchronization signal, and then spread spectrum receiver 22. To, the data is transmitted. The spread spectrum receiver 22 receives the signal transmitted by the second transmitter 23, extracts the synchronization signal contained therein, synchronizes the PN code with the extracted synchronization signal, and then receives the data. The other transmitter 23 is used for TV broadcasting or JJY.
The present invention is not limited to an existing system such as a transmission signal, but may be installed together when the spread spectrum communication system 20 is constructed.

Here, the spread spectrum transmitter 21 is shown in FIG.
2, the signal including the synchronization signal of the other transmitter 23, which is received by the antenna 25, is amplified by the high frequency amplification unit 26, and the frequency conversion unit 2
The frequency is converted at 7 and input to the synchronization extraction unit 28. The sync extraction unit 28 extracts a sync signal such as a vertical sync signal for television broadcasting. The synchronization signal thus extracted is input to the timing control circuit 29. The timing control circuit 29 initializes the PN generator 30 and adjusts the timing thereafter.

The information data SI is first-modulated by the information modulator 2. The multiplier 3 multiplies the output of the PN generator 30 and the output of the information modulator 2 to perform spread modulation. The output of the multiplier 3 is converted into a high frequency by the frequency converter 5, and is transmitted via the power amplifier 6 and the antenna 7. As a result, the information data SI is spectrum-spread with the PN code synchronized with the synchronization signal in the signal transmitted from the other transmitter 23 and transmitted.

As shown in FIG. 3, the period of the PN code is set to be the same as that of the sync signal to be extracted or divided by an integer so that the spread spectrum receiver 22 can quickly acquire the PN code. be able to. That is, since the head of the synchronization signal always matches the head of the PN code, extracting the synchronization signal used by the spread spectrum transmitter 21 in the spread spectrum receiver 22 means extracting the beginning of the PN code.

The temporal accuracy of the synchronization signal extracted from the other transmitter 23 needs to be sufficiently smaller than the chip length of the PN code used in spread spectrum communication. That is, as shown in FIG. 4, if the speed of the PN code is sufficiently slow, even if the synchronization signal fluctuates with time, the chip of the PN code is not confused. The circuit for making it unnecessary is also unnecessary.

On the other hand, the spread spectrum receiver 22 is shown in FIG.
5, the signal including the synchronization signal of the other transmitter 23 received by the antenna 31 is amplified by the high frequency amplification section 32, and the frequency conversion section 3
The frequency is converted in 3 and input to the synchronization extraction unit 34. The sync extraction unit 34 extracts a sync signal such as a vertical sync signal for television broadcasting. The extracted synchronization signal is input to the initialization circuit 35. The initialization circuit 35 is a circuit that initializes the PN generator 36, and sends an initialization signal to the PN generator 36 based on the synchronization signal extracted by the synchronization extraction unit 34.

The sync signal extracted by the sync extractor 34 is
It is also input to the timing control circuit 37. The timing control circuit 37 sends a timing adjustment signal to the PN generator 36 based on the synchronization signal. Timing control circuit 37
Supplies the signal for maintaining the synchronization to the PN generator 36 by using the synchronization signal extracted by the synchronization extraction unit 34 from the signal of the other transmitter 23 used for the initialization of the PN code. Another transmitter 2 used to initialize the PN generator 36
This method can be used when the synchronization signal of 3 is sufficiently accurate.

The PN generator 36 generates a PN code according to the initialization signal input from the initialization circuit 35 and the timing adjustment signal input from the timing control circuit 37, and sends it to the multiplier 16. The spread spectrum signal received by the antenna 11 is amplified by the high frequency amplifier 12 and frequency converted by the frequency converter 13. The frequency-converted signal is multiplied by the output of the PN generator 36 in the multiplier 16, spectrum despreading is performed, and the information demodulator 17 demodulates the information data SO.

In the spread spectrum receiver 22, the PN
The timing adjustment of the generator 36 is controlled based on the synchronization signal extracted by the synchronization extraction unit 34. However, as shown in FIG. 6 in which the same parts as those in FIG. The timing information of the unit 17 may be received and the control may be performed based on the timing information. The timing control circuit 38 controls the timing of the PN generator 36 using the information on the advance or delay of the demodulation timing obtained by the information demodulation unit 17. This method is indispensable when the synchronization signal of the other transmitter 23 used for initialization of the PN generator 36 does not have sufficient accuracy.

The initialization circuit 35 is a circuit for initializing the PN generator 36. For example, as shown in FIG.
The timing of the synchronization signal extracted in 4 is delayed by the delay circuit 40, and the initialization signal generation circuit 41 generates the initialization signal of the PN generator 36. The delay circuit 40 adjusts the timing of the extracted synchronization signal and the PN code of the PN generator 36. In addition to absorbing the delay of the receiving circuit, the delay circuit 40 intentionally shifts the PN code for each terminal. This prevents the signals from colliding and becoming unable to be demodulated.

The initialization circuit 35 may be constructed as shown in FIG. In the initialization circuit 35, the timing of the synchronization signal extracted by the synchronization extraction unit 34 is delayed by the delay circuit 40. The delay circuit 40 is provided to match the timing of the extracted synchronization signal with the PN code of the PN generator 43. In addition to absorbing the delay of the receiving circuit, the delay circuit 40 intentionally shifts the PN code for each terminal. This prevents the signals from colliding and being unable to be demodulated. The PN detector 43, based on the timing of the output of the delay circuit 40,
The PN code is detected from the received signal. The reason why the PN detector 43 uses the output of the delay circuit 40 is to limit the time range in which the PN code is detected, whereby the detection time can be dramatically shortened. The initialization signal generating circuit 41 generates an initialization signal for the PN generator 36 from the output of the PN detector 43.

Which configuration of FIGS. 7 and 8 is used as the initialization circuit 35 is determined by the accuracy of the synchronization signal extracted from the other transmitter 23. When the precision of the extracted synchronization signal is high, it is not necessary to detect the PN code from the received spread spectrum signal, and the initialization circuit 35 of FIG. 7 can be used to simplify the circuit configuration accordingly. it can.

According to the above configuration, a signal transmitted from another transmitter 23 unrelated to spread spectrum communication and including a sync signal sufficiently guaranteeing the synchronization accuracy of the PN code required for spread spectrum communication. Since the PN code is generated in the spread spectrum transmitter 21 and the spread spectrum receiver 22 based on the above, it takes a long time to detect the PN code, which occurs when the data rate is lowered in the spread spectrum communication. The problem can be solved, the ratio of the reception time to the intermittent reception cycle in the intermittent reception mode can be reduced, and a transmission / reception terminal with low power consumption can be realized.

[0028]

As described above, according to the present invention, a transmitting device other than the spread spectrum communication device transmits a signal including a synchronization signal that can sufficiently guarantee the synchronization accuracy of the PN code used in the spread spectrum communication device. , A spread spectrum transmitter generates a PN code synchronized with a synchronization signal included in a signal transmitted by the transmission device, generates a spread spectrum signal for information data and transmits the PN code, and a spread spectrum receiver transmits the spread device. The PN code is generated in synchronization with the synchronization signal included in the signal transmitted by, the spectrum spread transmitter and the PN generator are synchronized, and the spectrum despreading is performed to demodulate the information data. When performing low data rate communication using spread communication, P
It is possible to realize a spread spectrum communication system capable of surely detecting the N code in a short time.

[Brief description of drawings]

FIG. 1 is a block diagram showing a spread spectrum communication system according to the present invention.

2 is a block diagram illustrating the spread spectrum transmitter of FIG. 1. FIG.

FIG. 3 is a timing chart showing a relationship between a synchronization signal included in a transmission signal of another transmitter and a period of a PN code.

FIG. 4 is a timing chart showing a relationship between a jitter of a synchronization signal included in a transmission signal of another transmitter and a speed of a PN code.

5 is a block diagram showing the spread spectrum receiver of FIG. 1. FIG.

6 is a block diagram showing the spread spectrum receiver of FIG. 1. FIG.

FIG. 7 is a block diagram showing a configuration of an initialization circuit in a spread spectrum receiver.

FIG. 8 is a block diagram showing an initialization circuit in a spread spectrum receiver.

FIG. 9 is a block diagram showing a conventional spread spectrum transmitter.

FIG. 10 is a block diagram showing a conventional spread spectrum receiver.

[Explanation of symbols]

1, 21 ... Spread spectrum transmitter, 2 ... Information modulator, 3, 16 ... Multiplier, 4, 15, 30, 36 ... P
N generator, 5, 13, 27, 33 ... Frequency converter, 6
...... Power amplifier, 7, 11, 25, 31 …… Antenna,
10, 22 ... Spread spectrum receivers, 12, 26, 3
2 ... High frequency amplifier, 14, 43 ... PN detector, 17
...... Information demodulation unit, 20 ...... Spread spectrum communication system, 23 ...... Other transmitter, 28, 34 ...... Synchronous extraction unit,
29, 37, 38 ... Timing control circuit, 35 ... Initialization circuit, 40 ... Delay circuit, 41 ... Initialization signal generator.

Claims (9)

[Claims] 1. A spread spectrum communication device including a spread spectrum transmitter for modulating information data and band spreading to generate a spread spectrum signal, and a spread spectrum receiver for despreading and demodulating the spread spectrum signal. In a spread spectrum communication system having a transmitter for transmitting a signal including a synchronization signal, the transmitter transmits a signal including the synchronization signal for sufficiently ensuring synchronization accuracy of a PN code used in the spread spectrum communication device. Transmitting, the spread spectrum transmitter includes a spread spectrum transmitting section and a receiving section for synchronization extraction, the synchronizing signal included in the signal transmitted by the transmitting device is extracted by the receiving section, and the extracted Generate a PN code in synchronization with the synchronization signal,
A spread spectrum signal is generated from the information data and transmitted from a transmission unit, and the spread spectrum receiver includes a spread spectrum reception unit and a reception unit for synchronization extraction, and the transmission device includes a signal included in a signal transmitted by the transmission device. A synchronizing signal is extracted by the receiving unit, a PN code is generated in synchronization with the extracted synchronizing signal,
A spread spectrum communication system characterized in that the spread spectrum transmitter and the PN generator are synchronized to perform reverse spread spectrum and demodulate information data. 2. The spread spectrum transmitter comprises: an information modulator, a spread modulator, a PN generator, a frequency converter,
A spread spectrum transmission unit including a power amplification unit and an antenna, and a synchronization extraction reception unit including an antenna, a high frequency amplification unit, a frequency conversion unit, and a synchronization signal extraction unit, and the synchronization included in the signal transmitted by the transmission device. The spread spectrum communication system according to claim 1, wherein a signal is extracted by the synchronization extraction receiving unit, and the timing of the PN code generated by the PN generator is matched with the synchronization signal. 3. The PN generator generates a PN code in which the cycle of the synchronization signal extracted by the synchronization extraction receiving section is equal to the cycle of the PN code or an integer multiple thereof. The spread spectrum communication system according to claim 2. 4. The PN generator generates a PN code at a speed low enough to ignore the temporal accuracy of the sync signal extracted by the sync extraction receiver. A spread spectrum communication system as described. 5. The spread spectrum receiver comprises an information demodulation section, a spread demodulation section, a PN generator, a PN initialization circuit, a timing adjustment section, a frequency conversion section, a high frequency amplification section,
The PN initialization circuit includes a spread spectrum reception unit including an antenna and a synchronization extraction reception unit including an antenna, a high frequency amplification unit, a frequency conversion unit, and a synchronization signal extraction unit. The spread spectrum communication system according to claim 1, wherein the PN generator is initialized in response to the synchronization signal so that the timing of the PN code matches the PN code of the spread spectrum transmitter. 6. The PN initialization circuit has a delay circuit and an initialization signal generator, and the initialization signal generator is operated at a timing at which the synchronization signal extracted by the synchronization extraction receiver is delayed. The spread spectrum communication system according to claim 5, wherein a PN generator is initialized. 7. The PN initialization circuit includes a delay circuit, a PN detector, and an initialization signal generator, and the PN initialization circuit delays the synchronization signal extracted by the synchronization extraction receiving section.
6. The time range for detecting a code is limited to operate the PN detector, and the initialization signal generator initializes the PN generator according to the PN detection result. A spread spectrum communication system as described. 8. The timing adjustment unit extracts a synchronization signal from a signal transmitted from the transmission device during despreading and demodulation, and applies the timing of the PN generator of the spread spectrum reception unit to the synchronization signal. The spread spectrum communication system according to claim 5, wherein the spread spectrum communication is continued. 9. The timing adjustment unit detects the advance or delay of demodulation timing from a signal obtained by despreading and demodulating a spread spectrum signal including the information data during despreading and demodulation, and performing the spread spectrum reception. Part P
The spread spectrum communication system according to claim 5, wherein the timing of the N code is adjusted.