JPH0856216A - Synchronous communication system - Google Patents

Abstract

PURPOSE:To provide a synchronous communication system in which the increase in a delay time is suppressed when one frequency simultaneous transmission reception system is configured via a relay station. CONSTITUTION:A relay control section 1-3 is provided in a signal path between radio equipments 1-1 and 1-2 of a relay station 1 and a timing for changeover of transmission and reception between radio equipments 2, 3 at a terminal station is set in synchronism with a predetermined time slot by the relay station 1 by controlling a signal transmission time between the radio equipments A and B. Since the burst signal subjected time compression in the one-frequency simultaneous transmission reception system is directly relayed in the relay station 1 without any modification, the increase in the delay time due to repeated time compression and expansion is avoided and the communication without a sense of incongruity is attained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a relay system in a communication system, and more particularly to a synchronous communication system in a one-frequency simultaneous transmission / reception system communication system including a relay station.

[0002]

2. Description of the Related Art In recent years, a communication system called a single-frequency simultaneous transmission / reception system has been put into practical use, which enables two-way simultaneous communication similar to an ordinary telephone while using a carrier of one kind of frequency. . Note that, hereinafter, this single-frequency simultaneous transmission / reception method will be referred to as the SFD method.
Abbreviation for requency Duplex.

Therefore, the conventional technique of this SFD system will be described. As shown in FIG. 8, the radio stations 2 and 3 facing each other have time-base compression circuits 2a and 3a, transmission circuits 2b and 3b, and a changeover switch. 2c, 3c, receiving circuit 2
d, 3d, and time axis expansion circuits 2e, 3e, and signals such as audio signals that are temporally continuous in the time axis shown in FIG. 9 (a), as shown in FIG. 9 (b). Are sequentially divided by the time axis compression circuits 2a and 3a for each period t ₁ and time-compressed to a period t ₂ ≈t _1/2 to create a burst signal as shown in FIG. Signal transmission circuit 2b,
3b and the changeover switches 2c and 3c, every period t ₁ ,
The transmission is from one to the other, which results in a period t ₁
By the time t ₂ ≒ t _1/2, it produced within the reception period of the signals from the other, allowing two-way simultaneous transmission and reception under the carrier signal of a single frequency f _1.

In the conventional example of the FCD system, the burst signal actually transmitted is, as shown in FIG. 10, an MSK system modem or the like, which is used for bit synchronization at the beginning of the audio signal time-compressed in the period t _2. A frame is formed by adding a synchronization signal composed of the frame synchronization and then transmitted.

Then, in the radio device on the receiving side, the synchronizing signal is identified from the burst signals received by the receiving circuits 2d and 3d, the time-compressed audio signal following the synchronizing signal is taken out, and the time axis expanding circuit 2e, Fig. 9 (d) by 3e
, The signal compressed in the period t ₂ is changed to the period t ₁
By extending the audio signal, the original audio signal that is temporally continuous is reproduced.

Here, the role of the synchronizing signal will be roughly described as follows. Identify the start position of the time-compressed audio signal and smooth the joint of the audio signal during playback. To establish the synchronization required for switching operation between transmission and reception between opposing radios.

Next, the actual time distribution of the time compression / expansion will be described. In _one example, the period t ₁ is 400 m.
s, the time compression rate t ₂ / t _{1 is set} to 1 / 2.2, and 1
A period t _{1 is obtained} by embedding the above-mentioned synchronization signal, the time required for the transmission circuit to rise in transmission, the switching time from transmission to reception by the changeover switch, etc., in the gap time generated by setting the compression ratio to more than / 2. 1/2, that is 200 ms
, Respectively, so that the transmission period and the reception period are almost the same. As a result, in this case, the absolute delay time associated with the compression / expansion of the audio signal is 200 ms.

Here, in the configuration of FIG. 8, in the opposite communication, that is, in the case of direct communication between two terminal stations, the mutual synchronization relationship is that one wireless device, for example, the wireless device 2 is the calling station and the other is the other. If the wireless device 3 of is a called station, the calling station is used as a reference point for synchronization,
The called station employs a so-called slave synchronization system in which a burst signal is transmitted following the received synchronization signal of the calling station.

In this case, the radio transmission path has a propagation delay due to band limitation, etc., and the burst signal received from one station to the other station under the subordinate synchronization is affected by the propagation delays of the forward path and the backward path. Although delay and jitter occur, as described above, the compression rate is set to ½ or more to allow a margin for the gap time so that communication can be performed without any trouble.

Instead of the dependent synchronization method, when the calling station starts transmission, this calling station is used as a reference point for synchronization, and the called station follows the received synchronizing signal of the calling station. Then, the burst signal is transmitted, but thereafter, a so-called half-duplex synchronization system may be used in which, after alternately receiving a signal from the other party, the transmission is started at a predetermined timing accordingly.

[0011]

The above-mentioned prior art has not been considered for application to a system in which communication is performed via a relay station, and has the following problems. That is, as described above, in the wireless system which is terminated by the opposite communication, there is no particular problem in practical use even in the conventional technique, but in the wireless system, the service area is expanded and the like.
As shown in FIG. 1, it is often the case that the two radios 2 and 3 communicate with each other via a relay station installed at a high altitude.

In this case, however, the conventional technique has the following problems.

Problem 1 As shown in FIG. 11, in a network including a relay station, SF
In the case of performing communication by the D method, in the conventional technique shown in FIG. 8, there are two transmission sections with two radios A and B in the relay station being back-to-back. At this time, if the wireless devices A and B of the relay station extend the burst signal received from each terminal station, reproduce it into a continuous audio signal, and exchange it with each other, that is, one terminal station ( The transmission section by the SFD system between the calling station) and one of the radio stations of the relay station (for example, A), and the other radio station of the relay station (for example, B)
Therefore, two sections of the transmission section by the SFD system between the other terminal station (called station) and the other terminal station operate independently. Therefore, in this case, there is no particular problem in signal transmission / reception itself.

However, this means that compression / expansion is repeated twice between the speakers of the terminal station, and as a result, the delay time of the voice signal is twice as long as that in the case of the above-mentioned opposite communication. , 400 ms, for example.

The delay time of 400 ms is considerably long,
It will be close to two hops (two jumps) on the satellite line, and it will be a problem for the terrestrial communication system because it will be in a region where the talkers feel uncomfortable due to the delay in the response of the other party. It ends up.

Problem 2 In order to prevent the delay of the voice signal from increasing, it is necessary to directly send and receive between the radios A and B of the relay station in the form of a burst signal which has been time-compressed. In order to enable direct exchange, it is essential to establish synchronization between at least two sections.

That is, in FIG. 11, assuming that one of the terminal stations is a calling station and the other is a called station, and is operated in a slave synchronization system using the calling station as a reference point as in the prior art.
The burst signal transmitted by the calling station at the frequency f ₁ is received by the wireless device A of the relay station, retransmitted by the wireless device B at the frequency f ₂ , and received by the called station.

The called station detects the synchronizing signal in the received burst signal and follows the signal to transmit the burst signal of its own station at the frequency f ₂ . Then, in the relay station, the data is relayed from the wireless device B to the wireless device A in the opposite direction, retransmitted at the frequency f ₁ , and received by the calling station.

Therefore, at this time, since the burst signal of the called station received by the calling station passes through two sections of frequencies f ₁ and f ₂ , the delay and the jitter are equivalent to twice those of the conventional opposite communication. It will increase.

Focusing on the relay operation between the radios A and B in the relay station, in FIG. 11, the radio A receives the signal of the frequency f ₁ and the radio B transmits the signal of the frequency f _2. As a means for starting up, the transmission of the wireless device B is generally activated by the squelch signal of the wireless device A, but the relay operation of the wireless device by this squelch is accompanied by a delay, which is The delay time is considerably larger than the propagation delay of, and further, it is affected twice as much as the forward and return paths.

However, in order to cope with the delay and the jitter thus increased, the compression ratio is increased as described above to 1 /
It is necessary to allocate time with a large gap time by setting the compression rate to a value greater than 2, but this causes a problem that the transmission bandwidth is narrowed and the factors that cause deterioration of the call quality increase. is there.

Problem 3 In a large-scale wireless communication system, the frequency f _{1 in} FIG.
A so-called MCA method in which f ₂ is paired and a plurality of channels are used for each group of frequency f ₁ and frequency f ₂ is widely used. Then, M having a relay station
When the SFD method is applied to the wireless communication system of the CA method, as described above, when a plurality of mobile stations simultaneously talk by the dependent synchronization method with the terminal station (calling station) as a reference point,
In the relay station, the mutual operation of the channels becomes a completely asynchronous operation.

In a general frequency arrangement in this MCA type wireless communication system, the frequencies f ₁ and f ₂ can be sufficiently separated, but the frequency intervals in the f ₁ group and the f ₂ group are occupied. Because the frequency band is limited,
For example, an equally-spaced array with a narrow frequency interval of about 12.5 KHz or 25 KHz is applied.

However, when each channel operates asynchronously under such a narrow frequency arrangement, the relay station is in a state in which one channel is transmitting and the other channel is receiving between adjacent channels, and the bandwidth of the channel being transmitted is generated. Outer spurs interfere with the receiving channel. Further, since they are arranged at equal intervals, so-called inter-channel interference occurs, such as the intermodulation components of the two transmitting channels interfering with the receiving channel, resulting in a state where normal communication cannot be performed. There is a fear.

In the conventional half-duplex transmission system, the frequency f ₁ is used from the relay station to the mobile station and the frequency f ₂ is used from the mobile station to the relay station. Since the transmitted wave and the received wave were sufficiently separated from each other, there was no problem. Therefore, it can be said that these are new problems caused by applying the SFD method.

A first object of the present invention is to address the first problem, and in order to avoid an increase in delay time of a voice signal or the like, a relay station can directly relay in the form of a time-compressed burst signal. It is to provide such a synchronization method. A second object of the present invention is to address the second problem, and to provide a synchronization method in which the time compression rate does not need to be increased in order to avoid deterioration of the call quality. A third object of the present invention is to address the third problem and to provide a relay system in which inter-channel interference does not occur even in a relay station having a plurality of wireless channels.

[0027]

In order to achieve the above first and second objects, in the first aspect of the present invention, a reference point for synchronization of the entire system is set in a relay station, and two radio devices of the relay station are provided. The transmission / reception timing of and the timing of the synchronization signal (first synchronization signal) included in the burst signal transmitted by the relay station to the terminal station are controlled in the relay station according to a predetermined timing sequence, and the terminal station relays The burst signal of the local station is transmitted following the synchronization signal in the burst signals transmitted by the station, and then the relay station receives the burst signal of the terminal station and the timing of the first synchronization signal. In order to match the phase, the burst signal is reconstructed and transmitted to enable direct relay in the form of the burst signal.

Similarly, in order to achieve the above first and second objects, in the second aspect of the present invention, the reference point for synchronization of the entire system is set in the relay station, and the transmission / reception timings of two radios of the relay station are set. , The timing of the synchronization signal for time axis expansion (first synchronization signal) included in the burst signal transmitted by the relay station to the terminal station is controlled in the relay station according to a predetermined timing sequence, and the relay station controls the terminal. Separately from the burst signal transmitted to the station, before or after this burst signal, transmit a synchronization signal for time slot synchronization (second synchronization signal),
The terminal station transmits the burst signal of its own station following the second synchronization signal, and the relay station receives the burst signal of the terminal station and the second synchronization signal transmitted by the relay station. By transmitting a burst signal received after or before the signal, it is possible to directly relay in the form of a burst signal.

Further, in order to achieve the third object, in the third aspect of the present invention, a reference point for synchronization of the entire system is set in a relay station, and transmission and reception timings are synchronized among a plurality of channels. Achieved by

[0030]

First, by synchronizing the entire system with the relay station as a reference, it is possible to control the transmission and reception of the two radios of the relay station in a predetermined timing sequence. This eliminates the need for squelch relay and improves the delay, as well as shortens the delay time by predictive control of rising and falling.

Further, when the relay station receives the burst signal of the terminal station and retransmits it by following the synchronization signal (first synchronization signal) in the burst signal transmitted by the relay station, it synchronizes with the reference clock of the relay station. The burst signal is reconstructed and transmitted in accordance with the timing phase of the first synchronization signal to be transmitted, so that not only relaying in the form of the burst signal but also delay and jitter due to the propagation delay of the path However, the time compression rate can be suppressed to the same level as that of the conventional technique, and the call quality is not impaired, since it is equivalent to the range of one section in the case of opposite communication.

Next, by adding the second synchronization signal, the synchronization signal (first synchronization signal) in the burst signal transmitted from the calling station (or relay station) to the called station (or terminal station). ) Is reduced, and as a result, the burst signal having the first synchronization signal becomes equivalent to a packet in the field of digital communication, and even if it has delay or jitter, it can be predicted. As long as it fits within the defined time allocation, it will be expanded in time and a continuous audio signal will be reproduced.
There can be no problems.

The second synchronizing signal is a signal transmitted under the reference clock of the relay station. Therefore, the delay or jitter of the burst signal at the responding terminal station is predicted in advance, and the delay signal or jitter is predicted. The time allocation can be allowed so that the relay station can directly relay the signal without adjusting the timing phase.

Furthermore, since the synchronization can be performed on the basis of the relay station, the synchronization between a plurality of channels in the relay station can be achieved at the same time, and as a result, the transmission and reception operations between the plurality of channels can be synchronized. Therefore, it is possible to prevent the occurrence of communication interference due to inter-channel interference.

[0035]

Embodiments of the synchronous communication system according to the present invention will be described below.
This will be described in detail with reference to the illustrated embodiment. FIG. 1 shows a basic configuration of a wireless communication system having a relay station to which an embodiment of the present invention is applied. In the figure, 1 is a relay station and 2 is a terminal station (calling station). Wireless device, 3 is a terminal station
(Called station) wireless device 1-1, wireless device A facing terminal station (calling station), 1-2 relay control unit, 1-3 terminal station
It is a radio device B facing the (called station).

FIG. 3 shows an embodiment of the relay control section 1-2 in the relay station 1. 101a is an input signal line from the receiving section of the wireless device A, and 101b is an input signal from the receiving section of the wireless device B. line,
102a and 102b are MSK modems, 103a and 103
b is a synchronization detector, 104a and 104b are timing control units, 105a and 105b are A / D converters, 106a and 1
06b is a memory, 107a and 107b are D / A converters,
108a is an output signal line to the transmitter of the wireless device B, and 108b
Is an output signal line to the transmitter of the wireless device A, 109a is a control signal line from the wireless device B, and 109b is a control signal line from the wireless device A.

Next, the operation of this embodiment will be described with reference to FIG. In the timing chart of FIG. 2, first, (a) is the reference clock of the relay station 1, and the period t ₀
The unit is a time slot such as ,. In this embodiment, the period t ₀ is 200 ms. Further, in the following description, the period t
Is sometimes referred to as time t, but in any case, it has no meaning and is the same. For this reason, although not shown, the relay station 1 is provided with a predetermined time slot management means, whereby the transmission timing of the wireless device A of the relay station 1 is as shown in FIG. 2 (b). The transmission timing of the wireless device B is controlled as shown in FIG.

As a result, the burst signal from the wireless device A is, as shown in FIG.
Then, in this figure, the signal is transmitted in every odd time slot, while the burst signal from the wireless device B is, as shown in FIG. It will be transmitted for each slot.
In this burst signal, the part (a) is shown in FIG.
The part (b) is a time-compressed audio signal, which is the synchronization signal for time-axis expansion described above, and therefore the time compression rate is set to CR.
Then, CR = t ₂ / t ₁ .

Next, FIG. 2 (e) shows the transmission timing of the wireless device 2 of the terminal station (calling station), (f) is the burst signal transmitted from the same station, and (g) is the wireless device of the relay station. These are burst signals transmitted from B, and these have the same time allocation as the burst signal of (d).

First, in this embodiment, until a radio wave is emitted from any of the terminal stations, the radio equipment in the relay station 1
Both A and B are configured to be in a standby reception state. Then, when any terminal station starts transmission, this calling station is used as a reference point for synchronization, and the relay station transmits the burst signal following the received synchronization signal of the calling station. Is an operation method in which a relay station alternately receives a signal from a partner and then transmits at a predetermined timing in response to the signal.

Therefore, now, when the transmission from the wireless device 3 of one terminal station starts, the wireless device A of the relay station 1 bursts as shown in FIG. 2 (d) in the time slot of FIG. 2 (a). Suppose you have sent a signal. Then, the wireless device 2 of the terminal station receives the burst signal transmitted by the wireless device A of the relay station 1 and, as shown in FIG. 2 (e), after the period t ₄ from the time point of detecting the first synchronization signal. The transmitter circuit in the wireless device 2 is started up, and after a further period t ₃ , the burst signal of its own station is transmitted as shown in FIG. In the relay station 1, the wireless controller A receives the burst signal, and in order to match the timing phase of the burst signal transmitted by the wireless device B, the relay controller 1-
At 2, the time is adjusted.

The time axis adjustment operation by the relay controller 1-2 will be described. As shown in FIG. 3, the burst signal input through the input signal line 101a of the wireless device A is
First, the sync signal detector 1 via the MSK modem 102a
It is input to 03a. When the sync signal detector 103a detects the first sync signal of the burst signal, it instructs the timing control unit 104a to activate the A / D converter 105a to convert the time-compressed audio signal in the burst signal into a digital signal. It is converted and stored in the memory 106a.

On the other hand, the wireless device B starts transmitting the synchronization signal at the timing shown in FIG.
09a to instruct the timing control unit 104a to output D /
The A converter 107a is started up, a digital signal is taken out from the memory 106a, decompressed into a time-compressed audio signal, and output to the wireless device B through the output signal line 108a.

Since the sampling cycle of the A / D converter 105a and the de-sampling cycle of the D / A converter 107a are the same so that the time compression rate does not change, the time axis adjustment is A / D conversion. This can be done by the time difference from the starting time of the device 105a to the starting time of the D / A converter 107a, whereby the predetermined adjustment time Δt shown in FIG. 2 (g) can be obtained.

However, in order to enable this time axis adjustment, it is necessary to advance the transmission timing at which the wireless device 2 of the terminal station responds, as shown in FIG. 2 (e). For this reason, the radio 2 of the terminal station is set to the transmission timing when the period t ₄ has elapsed from the synchronization signal (a) included in the transmission signal of the radio A shown in FIG. There is.

In this embodiment, the period t ₄ is set as follows. First, (d) and (e) of FIG.
As is clear from the above, since the wireless device 2 of the terminal station only has to start the transmission when the transmission signal from the wireless device A of the relay station 1 has ended, the period t ₄ is the synchronization signal. It should be equal to the period t ₂ from the trailing edge of (a) to the end of reception of the time compression signal (b).

However, in reality, it is considered that the period t ₂ fluctuates due to the influence of jitter or the like. Therefore, if the period t ₄ = the period t ₂ , the time compression signal
Since there is a possibility that the transmission timing of the wireless device 2 of the terminal station shown in FIG. 2 (e) may be entered before the reception of (b) is completed, it is assumed that the period t ₄ does not change. It is set as a time obtained by adding a slight margin time α to the considered period t ₂ , that is, t ₄ = t ₂ + α. As the margin time α, the value of the time slot time t ₀ is 2
Since it is 00 ms, an error of several percent may be set for a time of several ms.

As a result, as is clear from FIGS. 2B and 2E, the rise time t ₃ of the wireless device 2 and the fall time t ₅ of the wireless device A overlap each other. However, actually, even in this case, no particular trouble occurs in communication. Therefore, since the margin time α can be minimized, the time required for the relay operation can also be minimized.

On the other hand, with regard to the delay due to squelch relay, which is one of the problems in the conventional technique, in this embodiment, as is clear from FIGS. ,
Since B operates according to a predetermined time slot and is not a dependent operation, the delay due to squelch relay is essentially nonexistent.

In the above description, the relay operation from the wireless device A to the wireless device B of the relay station has been described, but conversely, in the relay operation from the wireless device B to the wireless device A, the wireless devices are simply replaced. Since it is exactly the same, the description is omitted. Further, the input signal line 101b, the MSK modem 102b, and the synchronization detector 103 in the trunk line control unit 1-2 of FIG.
b, timing control unit 104b, A / D converter 105
Regarding b, the memory 106b, the D / A converter 107b, the output signal line 108b, and the control signal line 109b, the corresponding radios are simply replaced with A and B, and the description thereof will be omitted.

Next, another embodiment of the present invention will be described. FIG. 4 shows a second embodiment of the present invention.
Reference numeral -4 is a synchronization signal addition unit, and other configurations are the same as those of the embodiment of FIG. The synchronization signal adding unit 1-4 converts the burst signal transmitted between the wireless device A and the wireless device B in the relay station 1 into
Each radio A, B functions to add a synchronization signal (second synchronization signal) for time slot synchronization at each timing when the operation is started at the transmission timing. As a result, FIG. As shown in the figure, in addition to the synchronization signal (a) for time axis expansion, the second synchronization signal (c) is added to the burst signal (b) at a predetermined timing and transmitted from the relay station. It has become. Then, in response to this, the radios 2 and 3 of each terminal station respectively identify the second synchronization signal (c) from the synchronization signal (a) and perform the operation described later. It is configured.

First, in FIG. 5, (a) is a reference clock of the relay station, and (b) and (c) are transmission timings of the wireless device A and the wireless device B, which are the same as those in the embodiment of FIG. Is. Next, FIG. 5 (d) shows a signal transmitted from the wireless device A, and (a) and (b) are the same burst signals as in FIG. 2, but (c)
Is the second synchronizing signal which is one of the features of the second embodiment. 5 (e) is the transmission timing of the radio of the terminal station (calling station), (f) is the transmission timing of the burst signal transmitted by the same station, and (g) is the transmission timing of the signal transmitted by radio B. Same as (d).

First, in the first time slot when the relay operation is started, the synchronization signal adding section 1-4 of the relay station, when the operation is started at the transmission timing of the wireless device A, as shown in FIG. To the second synchronization signal (C). Therefore, from the wireless device A, the synchronization signal for time-axis extension sent from the wireless device 3 is sent following the second synchronization signal (C).
(A) and the burst signal (b) will be transmitted.

The terminal station (calling station) receives the signal transmitted by the wireless device A of the relay station 1 as shown in FIG.
As shown in (e), the radio 2 is set to the transmitting state after a time t ₄ ′ from the time when the second synchronization signal (c) is detected, and then the time is set as shown in FIG. 5 (f). The burst signal of its own station is transmitted after t ₃ .

At this time, the length of this period t ₄ 'is set as follows. That is, in a certain time slot of FIG. 5 (the same applies to other time slots ...)
And the time width of the synchronization signal (C) is t ₆ , and the period t ₇ is t ₇ = t
₀ -t ₃ when the -t _6, including delay and jitter due to the propagation path, in a window that is determined in this period t _7, bursts transmitted from the radio unit 2 of the terminal station shown in FIG. 5 (g) The time t ₄ 'is set so that the signal arrives.

Therefore, the wireless device A of the relay station is set to the position shown in FIG.
The burst signal shown in (f) is received and directly input to the wireless device B. On the other hand, the wireless device B starts the transmission operation at the timing shown in (c) of FIG. 5, and at the same time, the synchronization signal adding unit 1-4 adds the second synchronization signal (c). From the wireless device B, as shown in Fig. 5 (g).
As shown in, the burst signal input from the wireless device A is transmitted following the second synchronization signal (C).

Here, the burst signal input from the wireless device 2 is a signal responded by the terminal station (calling station) following the second synchronization signal transmitted by the wireless device A, and therefore the round-trip propagation path. the delaying or jitter determined by, but time t ₄ '
As the time for which this fluctuation is expected is set in advance, under the control of the relay station 1,
The operation according to the timing chart of will be accurately executed.

That is, the variation due to the delay and the jitter described above appears between the second synchronizing signal (c) and the first synchronizing signal (a) in FIG. In the process of restoring the audio signal, the conversion is performed based on the first synchronization signal, so there is no risk of being affected by this variation.

Therefore, according to this embodiment, the relay station simply adds the second synchronization signal at a predetermined timing and does not need to adjust the transmission time of the signal and directly inputs it to the radio device B. It will be possible.

In the above, the relay operation of the relay station in the direction from the wireless device A to the wireless device B has been described, but the operation in the direction from the wireless device B to the wireless device A is exactly the same except that the devices are simply replaced. Therefore, the description is omitted.

Here, with respect to the radio equipment of the terminal station corresponding to the operation centered on the relay station in the embodiments described in FIGS. 4 and 5, the points different from the embodiments described in FIGS. In summary, the first point is the identification of the first and second sync signals. As described with reference to FIG. 10, the structure of this kind of sync signal is composed of a bit sync part and a frame sync part. Therefore, the difference between the first and first sync signals in the above embodiment is that the sync signal of the frame sync part is different from that of the frame sync part. Only the bit patterns are different. Therefore, by performing frame synchronization detection corresponding to two types of bit patterns, the embodiments of FIGS. 4 and 5 can be easily realized.

The second difference is the difference in operation after synchronization detection. In the embodiment of FIGS. 1 to 3, the detection of the first synchronization signal causes the burst signal response of the local station and the expansion of the time-compressed burst signal to start at the same timing. In this embodiment, the former is started by the second synchronizing signal and the latter is started by the first synchronizing signal, but this is not a particularly difficult factor in implementation.

The third difference is the time compression rate. The time compression rate CR in the embodiment of FIG.
t ₂ ′ / t ₁ , where the period t ₂ ′ needs to be shortened by the addition of the second synchronization signal compared to t ₂ in FIG. 2, but this is on the order of several percent. , Therefore, it does not affect the call quality. Rather, in the relay station,
It can be said that the embodiments of FIGS. 4 and 5 are superior in that no means for adjusting the time as described in FIG. 3 is required.

Further, when a burst signal is continuously transmitted by time division multiplexing using a duplexer radio using two frequencies as described in Japanese Patent Laid-Open No. 3-181236, It is not necessary to switch the transmission / reception of the radio at each burst cycle, and if the time allocated to the rise and fall of the radio is allotted to the addition of this second synchronization signal, it will be almost the same time as the conventional opposite communication. A compression rate can be realized.

Next, FIG. 6 shows an embodiment in which the second synchronizing signal (c) is inserted after the first synchronizing signal (a) and the burst signal (b). This embodiment is shown in FIG.
As is clear from (c) and (d), after the period t ₇ has elapsed and the period t ₄ ″ has further elapsed since the wireless devices A and B of the relay station reached the transmission timing, respectively, Sync signal (C)
The synchronization signal adding unit 1-4 is configured to generate the. As a result, in the embodiment of FIG. 6, the period obtained by subtracting the period t ₇ from the period t ₄ ′ (FIG. 5) is defined as t ₄ ″. Therefore, this embodiment will also be described with reference to FIGS. 4 and 5 above. It is possible to obtain the same operation and effect as in the embodiment described above.

Next, FIG. 7 is a further embodiment of the present invention, this figure is shown only relay station, in this figure, 1-1a, 1-1b ......, respectively f ₁ a , F ₂ b
In the group of radios A operating at the carrier frequency of ...
-3a, 1-3b ... Are groups of radio devices B operating at carrier frequencies of f ₂ a, f ₂ b, respectively, 1-2 are relay control units, 102 are MSK modems, and 104 is a timing control unit. , 110 are switching units, 110a, 110b ..., 1
30a, 130b ... are switching devices. The embodiment of FIG. 7 is a combination of the embodiments already described,
The system consisting of the radios 1-1a, 1-1b of the A group and the radios 1-3a, 1-3b of the B group ...
This is equivalent to each terminal station in the embodiment of FIG.

Next, the operation of this embodiment will be described. In this embodiment, first, switching between transmission and reception of the wireless devices A and B shown in (b) and (c) of FIG. 5 is performed under the control of the timing control unit 104 for each group of A and B. It is designed to be controlled alternately and simultaneously. Next, as shown in FIG.
The insertion of the second synchronization signal and the relay of the burst signal shown in (g) are performed by the MSK modem 102 and the switching unit 110 under the control of the timing control unit 104.

That is, at the transmission timing of the second synchronization signal shown in (d) of FIG.
.., 110b ... are pushed to the MSK modem 102 side to be transmitted all at once, and are controlled to be returned to the wireless device B side upon completion of the transmission. Next, at the transmission timing of the second synchronization signal shown in FIG. 5 (g) in the B group, the switching devices 130a, 130b
.. is sent to the MSK modem 102 side and transmitted all at once, and is controlled to return to the wireless device A side upon completion of transmission.

In order to obtain the same operation as that of the embodiment of FIG. 2 in the embodiment of FIG. 7, the switching timing of transmission and reception of the radio units A and B is slightly different from the switching timing of FIG. Although different, it can be similarly performed under the configuration of this figure. Here, the time adjustment according to FIGS. 2D and 2G can be realized by inserting the conversion unit described in FIG. 3 into each of the wireless devices A and B instead of the switching unit 110. It is possible.

In the above embodiments, the wireless line has been described as an example, but the present invention is not necessarily limited to the wireless line. For example, in the field related to CATV, "Advanced Integrated Information Communication System" of the Ministry of Posts and Telecommunications. MCA / C (Multi
It is also applicable to wired communication systems such as Cannel Access on Cable). Further, the burst signal is not limited to the analog signal obtained by time-compressing the audio signal, but can be applied to various signals including a digital signal.

Further, in the embodiment of FIG. 7, the case where the second synchronizing signal is inserted before the burst signal has been described, but the present invention is not limited to this position, and for example, even after the burst signal. I don't care.

By the way, in the above embodiment, when there is no transmission from any terminal station, the radio stations A and B of the relay station are configured to stand by in the standby reception state. Then, while there is no transmission from any terminal station, in the case of the embodiment of FIG. 2, the wireless devices A and B receive only the first synchronization signal (a), and as shown in FIGS. In the embodiment, only the second synchronization signal (C) is repeatedly transmitted for each time slot, and accordingly,
Each terminal station may make a call transmission.

In the MCA system consisting of a dedicated control channel and a call channel, the call connection control is performed by the control channel, and at the stage of shifting to a predetermined call channel, the above-mentioned call channel is used. The synchronization signal of 1 may be transmitted by the relay station.

[0074]

As described above, according to the present invention, it is possible to perform relay in the form of a time-compressed burst signal, and there is no increase in delay time equivalent to the above-mentioned two-hop satellite line. As a result, it is possible to make a call without a sense of discomfort similar to general terrestrial communication.

The time compression rate that influences the call quality is equivalent to that of the conventional opposite communication in the first invention of the present application, and the same radio itself of the terminal station can be used. In the second aspect of the invention, it is necessary to slightly increase the time compression rate, but almost no deterioration in call quality is observed. Therefore, the great advantage of the second invention is that the relay control unit of the relay station is simplified, so that an economical relay station apparatus can be provided.

With respect to inter-channel interference due to a plurality of radio channels of the relay station, according to the present invention, a slave synchronization system with the relay station as a reference point can be realized, so that complete synchronization control of the radio equipment of the relay station is possible. Therefore, not only is it unnecessary to remove a large-scale interference wave by a filter or the like, but also a system can be configured which is not affected by legal regulations such as radio frequency allocation.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of a synchronous communication system according to the present invention.

FIG. 2 is a time chart showing the operation of the first exemplary embodiment of the present invention.

FIG. 3 is a block diagram of a relay control unit in the first embodiment of the present invention.

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

FIG. 5 is a time chart showing the operation of the second exemplary embodiment of the present invention.

FIG. 6 is a time chart showing the operation of the third exemplary embodiment of the present invention.

FIG. 7 is a block diagram showing a fourth embodiment of the present invention.

FIG. 8 is a block diagram showing a conventional technique of a synchronous communication system using a single-frequency simultaneous transmission / reception method.

FIG. 9 is a time chart for explaining the operation of the conventional technique.

FIG. 10 is an explanatory diagram of a burst signal and a synchronization signal.

FIG. 11 is a block diagram showing a conventional technique of a synchronous communication system using a single frequency simultaneous transmission / reception method when passing through a relay station.

[Explanation of symbols]

 1 Relay Station 2 Terminal Station (Calling Station) Radio 3 Terminal Station (Called Station) Radio 1-1 Relay Station Radio A 1-2 Relay Control Unit 1-3 Relay Station Radio B 1 -4 Sync signal adder

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Otoshi, Tohoku Electric Power Co., Inc. Applied Technology Research Laboratory, 7-1, Nakayama, Aoba-ku, Sendai City, Miyagi Prefecture

Claims (3)

[Claims] 1. A burst signal composed of a plurality of terminal stations and a relay station, wherein a signal to be transmitted is time-axis compressed at predetermined time intervals, and transmission / reception switching at the plurality of terminal stations is added to the burst signal. In the communication system in which the single-frequency simultaneous transmission / reception method is performed between the relay station and the terminal station by performing the synchronization with the synchronizing signal for time axis expansion, the signal transmission path in the relay station By providing a time axis adjusting means for adjusting the transmission time of the burst signal on the signal transmission path, transmission / reception switching at the plurality of terminal stations is synchronized with the time slot set at the relay station. A synchronous communication system characterized by being configured to be performed. 2. A burst signal composed of a plurality of terminal stations and a relay station, wherein a signal to be transmitted is time-axis compressed at predetermined time intervals, and transmission / reception switching at the plurality of terminal stations is added to the burst signal. A burst signal transmitted through the signal transmission path in a communication system in which the one-frequency simultaneous transmission / reception method is performed between the relay station and the terminal station by performing the synchronization signal in synchronization with the synchronized signal. Further, a synchronization signal adding means for adding a synchronization signal for time slot synchronization, which is different from the synchronization signal for time axis expansion added thereto, is provided, and transmission / reception switching at the plurality of terminal stations is performed by the time slot synchronization. By synchronizing with a synchronization signal for transmission, switching between transmission and reception at the plurality of terminal stations is performed in synchronization with the time slot set at the relay station. A synchronous communication system characterized by. 3. Applying the synchronous communication system according to claim 1 or 2 to a communication system using a plurality of channels and having a relay station, and dividing the plurality of channels into a predetermined group unit for transmission. A synchronous communication system characterized in that it is configured to prevent inter-channel interference by synchronizing the switching operation of reception with each other in units of groups.