JPH08256088A - Frequency hopping receiving device - Google Patents

Abstract

PURPOSE: To prevent out-of-synchronism at the time of recovering the interruption of communication by following up the timing signal of a received signal in a synchronism follow-up mode and synchronizing it but maintaining a clock signal phase set in the follow-up mode in a synchronism maintenance mode even when the quality of the received signal is changed. CONSTITUTION: A clock signal generation circuit 1 is provided with the synchronism follow-up mode and the synchronism maintenance mode in the first mode, the timing signal of the received signal is followed up and synchronized but in the latter mode, the clock signal phase set in the follow-up mode is maintained even when the quality of the received signal is changed. In the synchronism follow-up mode, a level is detected and transferred to a comparator circuit 5 and a threshold value in a threshold value memory 4 is compared with this detected result. When the level of the received signal is higher than the threshold value, the synchronism follow-up mode is continued. When the level of the received signal is lower than the threshold value, a switcher 6 is set into the synchronism maintenance mode.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention finds use in wireless communications, particularly spread spectrum communications. The present invention is suitable for use in a mobile communication system. The present invention is suitable for use in a wireless communication system that requires confidentiality. In particular, it relates to a technique for improving a signal error rate of wireless communication using a frequency hopping communication system.
The present invention was developed for a mobile communication system used in one large business site such as an airport, but can be widely used for spread spectrum communication.

[0002]

2. Description of the Related Art A frequency hopping communication system is known in which communication is performed while changing a carrier frequency used for communication according to a predetermined rule. Frequency hopping requires that transmission and reception be performed in synchronism, and the carrier frequency is changed every 20 mS with respect to a carrier frequency of, for example, over 1000, which is assigned in advance. Therefore, the transmitter / receiver must hold the same hopping pattern as to which carrier frequency is used next. This frequency hopping communication system is suitable for communication requiring confidentiality because it is impossible for a third party who does not know a predetermined hopping pattern to intercept the communication contents.

Frequency hopping communication was developed for military use, but in recent years its general use has been approved and 2G
When the transmission power is below a certain level in the Hz band, wideband frequency allocation was performed without requiring a license to open an individual radio station.

Further, regarding the communication carried out within the same frequency band, by setting different hopping patterns for each user, it is possible to carry out the communication effectively utilizing the idle channel, so that the radio wave is effective. Can contribute to utilization. For example, in the case of a communication method in which N channels are assigned to N users, there are various restrictions on the use of that channel by other users, even if one of the users becomes dormant. . In such a case, the frequency hopping communication system allows the operating communication terminal to effectively utilize all of the N channels. Therefore, it is possible to allocate N channels to N or more users while considering the operating status.

[0005]

When this system is used for mobile communication, the communication quality changes as the device moves.
In some cases, communication may be interrupted in underground passages or inside buildings where radio waves do not reach. In that case, frequency hopping may not follow. When the frequency hopping stops following, the synchronization with the transmission side or the base station is lost for a long time until the synchronization marker is received.

Further, when used at an airport where there are many buildings and airplanes take off and land, complex reflection occurs in the radio wave propagation path, and multiple paths for radio wave propagation occur and this also fluctuates.
Therefore, the sampling circuit clock signal timing of the received signal may become out of synchronization. Even if they are synchronized with each other, if the phase of the clock signal is disturbed, it has no great influence on the voice communication, but when multimedia communication is performed, the received image in the image communication portion is distorted.

Further, when another user operates the system in the same frequency band in the vicinity, each user uses his or her own frequency hopping pattern, which may cause channel collision. When channel collision occurs, the quality of the received signal deteriorates, and the synchronization of the receiving device does not follow. As the number of users increases, the number of channel collisions increases, and there is a possibility that even those who have built a system in that frequency band from the beginning cannot use it. Therefore, the number of users is limited.

The present invention has been made against such a background, and provides a frequency hopping receiver which does not lose synchronization when communication is restored even if the communication is temporarily interrupted. With the goal. It is an object of the present invention to provide a frequency hopping receiver that can reduce the signal error rate. An object of the present invention is to provide a frequency hopping receiver capable of coping with a change in transmission quality of a radio signal transmission line. An object of the present invention is to provide a frequency hopping receiver that can effectively use radio waves. It is an object of the present invention to provide a frequency hopping receiver capable of simplifying transmission / reception and processing of error correction codes. It is an object of the present invention to provide a frequency hopping receiving device that can be downsized. It is an object of the present invention to provide a frequency hopping receiver that can avoid information retransmission. It is an object of the present invention to provide a frequency hopping receiver that can shorten communication time. An object of the present invention is to provide a frequency hopping receiver capable of widening the system. An object of the present invention is to provide a frequency hopping receiver capable of increasing the number of stations that can join one system.

[0009]

The first aspect of the present invention is to:
A control circuit for changing a carrier frequency of a received signal according to a designated hopping pattern, a means for extracting a timing signal from the received signal, and a clock signal generation for generating a clock signal synchronized with the timing signal extracted by the means. And a frequency hopping receiver including a circuit.

Here, a feature of the present invention is that the clock signal generating circuit has a synchronous tracking mode and a synchronous maintaining mode, and in the synchronous tracking mode, the clock signal generating circuit tracks and synchronizes with the timing signal of the received signal and maintains the synchronous state. The mode is provided with a control means for maintaining the clock signal phase set in the tracking mode even if the quality of the received signal changes. It is preferable that the sampling timing of the signal received within one frequency hopping period is synchronized with the clock signal.

Preferably, the timing of frequency hopping is synchronized with the clock signal, and the control circuit includes means for maintaining the hopping pattern for a long time (T ₁ ) even when the received signal is interrupted.

As a result, even if there is time when the quality of the received signal deteriorates and synchronization tracking becomes impossible, reception can be continued according to a predetermined hopping pattern. Alternatively, the sampling timing of the received signal does not become out of synchronization. Therefore, the signal error rate is reduced and the communication quality can be improved.

The control means includes means for detecting the quality of the received signal, and the control means includes means for automatically setting the synchronization maintaining mode when the quality of the received signal detected by the detecting means falls below a threshold value. Is desirable. The quality of the received signal may be the received signal level.

It is also possible to adopt a configuration provided with an operating means for forcibly setting the synchronization follow-up mode. Thereby, for example, the timing signal can be forcibly received at the time of start-up and the synchronization of the clock signal can be established.

The control means includes means for detecting the identification code of the transmission source included in the received signal, and the control means sets means for setting the synchronization follow-up mode when the identification code is a preset specific identification code. It can also be configured to include. Thereby, for example, when the identification code from the transmission device which is the transmission source of the timing signal can be received, the synchronization follow-up mode can be set.

The control means comprises means for detecting the quality of the received signal, and the control means automatically sets the synchronization follow-up mode when the quality of the received signal detected by the detecting means is equal to or more than a threshold value. It can also be configured to include. As a result, even if the specific identification code is detected and the synchronization follow-up mode is about to be set, the synchronization maintaining mode can be continued if the quality of the received signal is less than the threshold value.

It is also possible to provide a means for controlling so as to receive the signal including the specific identification code at a constant cycle (T ₂ , where T ₂ <T ₁ ) in the standby state. As a result, the clock signal synchronized with the timing signal can be secured even during standby, so that the reception operation can be performed promptly in synchronization with the hopping pattern when the operation is resumed.

A second aspect of the present invention is a frequency hopping communication system in which at least one frequency hopping receiver is present.

Here, a feature of the present invention is that a transmission device (for example, as a base station device) for transmitting the specific identification code as an identification code of a transmission source is provided.

The transmitting device for transmitting the specific identification code as the transmission source identification code preferably includes means for transmitting the specific identification code on the control channel.

The frequency hopping receiver may be configured such that all or some of the receivers are mounted in one housing together with the frequency hopping transmitter. Thus, transmission or reception can be performed by one device including the frequency hopping receiver of the present invention.

[0022]

The carrier frequency of the received signal is sequentially changed according to the specified hopping pattern, and the timing signal which is the information for generating the clock signal for controlling the change of the hopping pattern in the receiving device is inserted into the received signal. And transmitted to the receiving device.

At this time, according to the present invention, the clock signal generating circuit of the receiving device newly generates a synchronous tracking mode in which the clock signal is generated by following a timing signal that arrives every moment, and a clock signal set by this synchronous tracking mode. A synchronization maintaining mode for maintaining the timing signal arriving at the same without following it.

For example, communication may be temporarily interrupted, for example, when the receiving device moves through a place where the electric field strength is small. At this time, in the receiving apparatus of the present invention, the clock signal generating circuit is automatically switched from the synchronization tracking mode to the synchronization maintaining mode, and the clock signal set in the synchronization tracking mode is maintained. During this time, the frequency hopping is continuously maintained at the same time without contacting the transmitter.
Therefore, when the reception state is recovered after passing through a place where the electric field strength is small, frequency hopping is executed at the same timing as the transmitter, and it is not necessary to reset the synchronization, and immediately after the reception electric field strength is recovered. Normal reception can be performed.

[0025] Also. For example, when the receiving device of the present invention is being used in an airport premises, the clock signal follows the temporary change when the received signal temporarily changes due to a change in multiple propagation paths due to takeoff and landing of an airplane. If so, the sampling timing of the received signal changes and the signal error rate increases. In such a case, in the present invention, by switching the synchronization follow-up mode to the synchronization maintaining mode, sampling is continued at the timing of the reference clock signal without being affected by this temporary change.
Therefore, the signal error rate can be reduced.

The sampling timing of the signal received within one frequency hopping period may be synchronized with the clock signal. In addition, the clock signal is synchronized with the frequency hopping timing, and even when the received signal is interrupted, the hopping pattern is maintained for a long time (T ₁ , for example, several tens of seconds) to immediately receive the signal when the received signal is restored. It can be restarted.

By detecting the quality of the received signal and automatically setting the synchronization maintaining mode when the detection result falls below the threshold value, it is possible to automatically avoid a decrease in the signal error rate. The quality of the received signal may be determined by the level of the received signal.

If the follow-up mode can be forcibly set by an operation, the timing signal from the transmitter, which is the source of the timing signal, is forcibly forced at the time of start-up or when synchronization is lost. It can be operated so that the synchronization of the receiving device is forcibly followed by the source.

In order to identify the received signal from the transmission device which is the transmission source of the timing signal, the identification code of the transmission source is inserted in advance in the reception signal, and the identification code indicates the transmission source of the timing signal. It is preferable that the code of is automatically set to the synchronous tracking mode.

Even in this case, the quality of the received signal is detected, and when the detection result is less than the threshold value, the synchronization maintaining mode may be continued.

Even in the standby state, it is preferable to control so as to receive the signal including the specific identification code at a constant cycle (T ₂ , where T ₂ <T ₁ ). As a result, reception can be performed immediately in synchronization with the hopping pattern when the operation is resumed.

In the frequency hopping communication system including one or more frequency hopping receivers of the present invention, it is preferable that a transmitter for transmitting a specific identification code indicating the transmission source of the timing signal is provided. At this time, this specific identification code may be transmitted by the control channel. Further, the transmitter and the receiver may be mounted in one housing.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The construction of a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram of the first embodiment of the present invention. FIG. 2 is a block diagram of the control unit of the first embodiment of the present invention.

According to the present invention, the control circuit 12 for changing the carrier frequency of the received signal according to the designated hopping pattern, the receiving section 30 including means for extracting the timing signal from the received signal, and the receiving section 30 extract the timing signal. And a clock signal generating circuit 1 for generating a clock signal synchronized with the timing signal.

Here, the feature of the present invention is that the clock signal generating circuit 1 has a synchronization follow-up mode and a synchronization maintaining mode. In the synchronization following mode, the clock signal generating circuit 1 synchronizes with the timing signal of the received signal and maintains the synchronization. In the mode, even if the quality of the received signal changes, the threshold value memory 4 as a control means for maintaining the clock signal phase set in the tracking mode, the comparison circuit 5, the switch 6, the synchronization tracking clock generating circuit 7, the synchronization maintaining clock. It is provided with the generation circuit 8. The sampling timing of the signal received within one frequency hopping period is synchronized with the clock signal. Further, the frequency hopping timing is synchronized with the clock signal, and the control circuit 12 maintains the hopping pattern for a long time (T ₁ ) even when the received signal is interrupted, the address read circuit 2, the ROM 3, the variable frequency oscillation circuit. The circuit 9 is provided.

The comparison circuit 5 is provided with a reception level detection unit 40 as a means for detecting the quality of the reception signal, and the comparison circuit 5 compares the quality of the reception signal detected by the reception level detection unit 40 with the threshold value stored in the threshold value memory 4. It includes means for automatically setting the sync hold mode when below. The quality of the received signal is the level of the received signal.

The control circuit 12 includes the clock signal generation circuit 1
A local oscillation frequency used in the frequency hopping communication system is oscillated in accordance with the clock signal from. First, the clock signal generated from the clock signal generation circuit 1 is input to the address read circuit 2. The ROM 3 stores N codes corresponding to hopping frequencies as random numbers. By giving the read address signal of a certain rule to the ROM 3 by the address read circuit 2, the ROM 3 outputs N codes corresponding to the hopping frequency as random numbers. The code is input to the variable frequency oscillation circuit 9 via the input / output circuit 17. The variable frequency oscillation circuit 9 sends the local oscillation frequency corresponding to this code to the reception unit 30 or the transmission unit 20.

Next, the operation of the first embodiment of the present invention will be described with reference to FIG. FIG. 3 is a flow chart showing the operation of the clock signal generation circuit 1 of the first embodiment of the present invention. Here, the steps set in the synchronization follow-up mode will be described. When set to synchronous tracking mode (S
1), the reception level detector 40 detects the level of the reception signal (S2). The detection result of the received signal level is transferred to the comparison circuit 5 of the clock signal generation circuit 1. Here, the threshold value previously stored in the threshold value memory 4 is compared with the detection result (S3). If the received signal level is higher than the threshold value, the synchronous tracking mode is continued.

However, if the received signal level is smaller than the threshold value, the switch 6 is set to the synchronization maintaining mode (S
4).

Next, a second embodiment of the present invention will be described with reference to FIGS.
Will be described with reference to. FIG. 4 is a block diagram of the apparatus of the second embodiment of the present invention. FIG. 5 is a block diagram of the control unit 10 according to the second embodiment of the present invention. FIG. 6 is a flowchart showing the operation of the clock signal generation circuit 1 of the control unit 10 according to the second embodiment of the present invention. FIG. 7 is an overall configuration diagram of a frequency hopping communication system to which the second embodiment of the present invention is applied. FIG. 8 is a block diagram showing the base station device. FIG. 9 is a block diagram of the control unit 10 'of the base station device. In the second embodiment of the present invention, the receiving section 30 is provided with an identification code detecting section 14 for detecting the identification code of the transmission source included in the received signal, and when the identification code is a specific identification code, the synchronization tracking mode is used. The clock signal generation circuit 1 is provided with a specific code detection circuit 11 for setting

The second embodiment of the present invention is assumed to be applied to the frequency hopping communication system as shown in FIG. The transmission device and the reception device of the present invention are configured as a transmission / reception device in one housing. The base station B includes a transmitter / receiver having the configuration shown in FIG. 8, and its control unit 10 'has the configuration shown in FIG. The base station B performs frequency hopping based on the clock signal generated by the base station clock signal generation circuit 16, and the synchronization information of the clock signal is generated by the timing signal generation circuit 15, and the transmitter 2
At 0, it is inserted in the transmission signal and transmitted to the mobile station C or the fixed station F.

In the second embodiment of the present invention, a specific identification code is inserted in the control signal transmitted from the base station B, and the received signal received by the fixed station F or the mobile station C is from the base station B. It is possible to identify whether or not there is.
If the received signal is from the base station B, it is desirable to set the synchronous tracking mode because the timing signal is inserted therein. However, also in this case, like the first embodiment of the present invention, if the received signal level is less than the threshold value, the synchronous follow-up mode is stopped.

Further, the switch 13 has a function of forcibly setting the synchronization follow-up mode. This is because the switch 13 is operated in a situation where the timing signal must be received at the time of startup, so that the startup can be performed quickly.

Next, the operation of the second embodiment of the present invention will be described with reference to the flowchart of FIG. Here, the steps set in the synchronization follow-up mode will be described. When the synchronous follow-up mode is set (S11), the switch 13 which is the synchronous follow-up mode switch is released (S11).
12), the identification code detection result of the identification code detection unit 14 is (S
13) If the specific code is not detected (S14), the synchronization maintaining mode is set (S15). However, if the specific code is detected (S14), the received signal level is detected (S16), and if the level is equal to or higher than the threshold (S1).
7) The sync following mode is continued. If the level is less than the threshold value (S17), the synchronization maintaining mode is set (S15).

In the second embodiment of the present invention, when in the standby state, control is performed so as to receive a signal including a specific identification code from the base station B at a constant cycle (T ₂ , where T ₂ <T ₁ ). As a result, the reception operation can be started immediately when the operation is resumed.

The overall configuration diagram of the second embodiment of the present invention shown in FIG. 7 assumes that the device of the present invention is used in an airport premises. At an airport, when an airplane takes off and takes off, the conditions of multiple propagation paths change and the received signal changes. If the receiving device follows this temporary change in the received signal as it is, the clock signal may change temporarily and the synchronization with the hopping pattern of the base station B may be lost. In such a situation, it is useful to detect a change in the received signal and maintain the clock signal as it was before the change.

[0047]

As described above, according to the present invention,
The signal error rate can be reduced by coping with the change in the transmission quality of the wireless signal transmission path. For this reason, since it is possible to avoid information retransmission, it is possible to shorten the communication time. This is useful from the viewpoint of effective use of radio waves.

Furthermore, since the transmission and reception and processing of the error correction code can be simplified, the device can be downsized. This is useful for mobile terminals.

As for the system configuration, since the signal error rate can be reduced, the system can be broadened. Alternatively, the number of stations that can join one system can be increased.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of an apparatus according to a first embodiment of the present invention.

FIG. 2 is a block configuration diagram of a control unit according to the first embodiment of the present invention.

FIG. 3 is a flowchart showing the operation of the clock signal generation circuit of the first embodiment of the present invention.

FIG. 4 is a block configuration diagram of a second embodiment device of the present invention.

FIG. 5 is a block configuration diagram of a control unit according to a second embodiment of the present invention.

FIG. 6 is a flowchart showing the operation of the clock signal generation circuit of the control unit according to the second embodiment of the present invention.

FIG. 7 is an overall configuration diagram of a frequency hopping communication system to which a second embodiment of the present invention is applied.

FIG. 8 is a block diagram showing a base station device.

FIG. 9 is a block configuration diagram of a control unit of the base station device.

[Explanation of symbols]

 B base station C mobile station F fixed station 1 clock signal generation circuit 2 address read circuit 3 ROM 4 threshold memory 5 comparison circuit 6 switcher 7 synchronization tracking clock generation circuit 8 synchronization maintenance clock generation circuit 9 variable frequency oscillation circuit 10, 10 ' Control unit 11 Specific code detection circuit 12 Control circuit 13 Switch 14 Identification code detection unit 15 Timing signal generation circuit 16 Base station clock signal generation circuit 17 Input / output circuit 19 Antenna 20 Transmission unit 30 Reception unit 40 Reception level detection unit 50 Antenna switch

Claims (12)

[Claims] 1. A control circuit for changing a carrier frequency of a received signal according to a designated hopping pattern, a means for extracting a timing signal from the received signal, and a clock signal synchronized with the timing signal extracted by this means. In a frequency hopping receiver including a clock signal generating circuit for generating, the clock signal generating circuit has a synchronous tracking mode and a synchronous maintaining mode, and in the synchronous tracking mode, tracks and synchronizes with the timing signal of the received signal, A frequency hopping receiver characterized by comprising control means for maintaining the clock signal phase set in the tracking mode even when the quality of the received signal changes in the maintenance mode. 2. The frequency hopping receiver according to claim 1, wherein the sampling timing of a signal received within one frequency hopping period is synchronized with the clock signal. 3. The frequency hopping timing is synchronized with the clock signal, and the control circuit includes means for maintaining the hopping pattern for a long time (T ₁ ) even when the received signal is interrupted. Frequency hopping receiver. 4. A means for detecting the quality of the received signal, wherein the control means automatically sets the synchronization maintaining mode when the quality of the received signal detected by the detecting means falls below a threshold value. 4. The frequency hopping receiver according to claim 1, further comprising: 5. The frequency hopping receiver according to claim 4, wherein the quality of the received signal is the level of the received signal. 6. The frequency hopping receiver according to claim 1, further comprising operation means for forcibly setting the synchronization tracking mode. 7. A means for detecting an identification code of a transmission source included in the received signal is provided, and the control means sets the synchronization follow-up mode when the identification code is a preset specific identification code. Claims 1 to 3 including means
The frequency hopping receiver according to any one of 1. 8. A means for detecting the quality of the received signal is provided, and the control means automatically sets the synchronization follow-up mode when the quality of the received signal detected by the detecting means is equal to or higher than a threshold value. The frequency hopping receiver according to claim 7, further comprising means. 9. A fixed cycle (T
9. The frequency hopping receiver according to claim 7, further comprising: a control unit that controls the reception of the signal including the specific identification code when T ₂ , T ₂ <T ₁ . 10. A frequency hopping communication system having one or more frequency hopping receivers according to claim 7, further comprising a transmitter for transmitting the specific identification code as an identification code of a transmission source. A frequency hopping communication method characterized by the above. 11. The frequency hopping communication system according to claim 10, wherein the transmission device that transmits the specific identification code as the identification code of the transmission source includes means for transmitting the specific identification code through a control channel. 12. The frequency hopping receiver is mounted in a single housing together with the frequency hopping transmitter for all or some of the receivers.
The frequency hopping communication method described.