JP2002094427A - Satellite relay transmission system, and transmitting and receiving device for use in the system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease load of a circuit device for absorbing temporal difference, generated in signals to be respectively transmitted from a satellite and a GF to a receiver. SOLUTION: The timing of a direct signal from a satellite receptor 12 is delayed by τ4max/2 using a ground wave transmission station 11. At the service area end of a GF 13, the timing of an indirect signal from the GF 13 is delayed by τ4max/2, with respect to the direct signal from the satellite repeater 12. In this case, a necessary gate width becomes τ4max. When a receiving device 14 is directly below the GF 13, the timing conversely advances by τ4max/2. In this case also, the necessary gate width becomes τ4max. In this manner, the necessary width is τ4max or less within the service area of the GF 13, and a reception gate width is 1/2 in comparison with the case where nothing is conducted, thereby contributing to a simplification of a structure of the receiving device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a satellite relay transmission system mainly for a mobile object and using a gap filler (GF) together with a satellite repeater, particularly as a measure against obstacles such as building shadows.

[0002]

2. Description of the Related Art A transmission system using a satellite repeater represented by a satellite broadcast is excellent in that information can be simultaneously provided over a wide range. However, when a mobile object such as a car is targeted for service, reception is not possible if an obstacle such as a building or a mountain exists between the satellite and the receiving antenna. For this reason, in a satellite relay transmission system serving mobile objects, a gap filler (G
It is necessary to install a repeater called F) and to expand the service area by transmitting the image to a building shadow or a mountain shadow from here.

In such a system, it is important to simplify the configuration of the receiving apparatus from the viewpoint of reducing the cost of the entire system, and the signal transmitted from the satellite and the signal transmitted from the GF have the same signal format. It is desirable to take. Further, if a transmission method that can withstand a multipath transmission path such as CDM or OFDM is used, a signal transmitted from a satellite and a signal transmitted from a GF can be received simultaneously by one receiver, which simplifies the receiver. Can be achieved.

Here, in the above-mentioned satellite relay transmission system, there is a time difference between signals transmitted from the satellite and the GF. In addition, this time difference varies depending on the GF and the position of the moving object. Switching the demodulated signal on the receiving device side,
Alternatively, even if they are combined, it is necessary to absorb this time difference, and a circuit device such as a memory for performing delay adjustment in the receiving device must be prepared. For this reason, when the time difference between the signals transmitted from the satellite and the GF is large, there is a problem that the load on the circuit device in the receiving device increases.

[0005]

As described above, in the conventional satellite transit transmission system, there is a time difference between the signals transmitted from the satellite and the GF, and the time difference is caused by the time difference between the GF and the position of the mobile unit. Therefore, even if the demodulated signal is switched or combined on the receiving device side, it is necessary to absorb this time difference, and a circuit device such as a memory for delay adjustment must be prepared in the receiving device. For this reason, when the time difference between the signals transmitted from the satellite and the GF is large, there is a problem that the load on the circuit device in the receiving device increases.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problem, and can reduce the load on a circuit device for absorbing a time difference between signals transmitted from a satellite and a GF to a receiving device. Satellite relay transmission system,
An object of the present invention is to provide a transmission device and a reception device suitable for use in this system.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a direct receiving system which directly reaches a receiving device from a terrestrial transmitting station via a satellite transponder; A satellite relay transmission system having an indirect receiving system that indirectly reaches a receiving device via a device and a gap filler, and includes a delay unit that delays at least transmission timing of the direct receiving system from transmission timing of the indirect receiving system. It is characterized by the following.

[0008] The delay means is characterized in that the maximum delay time is at least a propagation delay time from a transmission point of the gap filler to an end of an area covered by the gap filler.

In the above-mentioned satellite relay transmission system, the transmitting device provided in the terrestrial transmitting station is configured to transmit at least the transmission timing of the transmission data sequence transmitted to the direct reception system to the transmission data sequence transmitted to the indirect reception system. It is characterized by including delay means for delaying from the timing.

In this case, the delay means delays at least the transmission data sequence to the direct reception system, and delays the transmission data sequence subjected to the baseband processing or the modulation transmission processing. It is characterized by giving.

The receiver used in the above-mentioned satellite relay transmission system is characterized in that a maximum level signal or a signal having a maximum signal power to interference power ratio is tracked so as to be located at the center of the reception gate. And

In this case, the reception gate width is a propagation delay time from a transmission point of the gap filler to an end of an area covered by the gap filler.

That is, in the system according to the present invention, the propagation delay difference between the system that receives directly via the satellite repeater and the system that receives via the satellite repeater and the gap filler is controlled, and the receiving apparatus Is achieved by limiting the range in which the received signal is demodulated and combined.

Regarding the delay control, at any point from the transmission point of the gap filler to the end of the area covered by the gap filler, a signal passing only through the satellite repeater and a signal passing through the satellite relay and the gap filler are provided. Is adjusted so that the timing difference between the two becomes zero.

In a preferred embodiment, the transmission timing of the signal passing only through the satellite repeater is delayed.

In the case where the demodulation and synthesis range of the receiving apparatus is limited, only a signal which falls within a certain timing difference before and after, centering on the timing of the optimum signal for demodulation in the received signal, is determined as an object to be demodulated and synthesized. I do.

In a preferred embodiment, the optimum signal has the highest signal level, and the timing difference is set to の of the propagation delay time corresponding to the area covered by the gap filler.

[0018]

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

FIG. 1 shows a general system diagram of a mobile satellite broadcasting system including a GF as an example of a satellite relay transmission system to which the present invention is applied.

In FIG. 1, two uplink signals having different frequencies for direct reception and indirect reception via GF 13 are transmitted from a terrestrial transmission station 11 to a satellite repeater 12. The propagation delay time up to this point is common, and is assumed to be τ1. In the case of direct reception, the satellite transponder 1
The delay time .tau.2 from 2 to the receiving device 14 is added, and the total delay time is .tau.d = .tau.1 + .tau.2. On the other hand, GF1
3, the delay time .tau.3 from the satellite repeater 12 to the GF13 and the delay time .tau.4 from the GF13 to the receiver 14 are added, and the total delay time is .tau.g = .tau.1 + .tau.
3 + τ4.

Normally, since τ2 and τ3 are almost equal, τd
The difference between τg and τg is dominated by τ4. Therefore, if the receiving device 14 is directly below the GF13, the propagation delay time difference is minimal, and gradually increases as the distance from the GF13 increases.
It is maximum at the end of the service area of GF13. The value of τ4 at this time is τ4max.

On the other hand, the receiving device 14 simultaneously receives and demodulates and combines both the direct signal from the satellite repeater 12 and the indirect signal from the GF 13 to improve the signal power to noise power ratio (S / N). can do. Ideally, the receiving device 14 should always be able to respond to any signal at any timing, but usually, the most desirable received signal is determined to avoid the complexity of the device, and this timing is determined. Chase. It is also employed for the purpose of simplifying the apparatus that only signals before and after this timing are to be demodulated. The range to be demodulated is called a reception gate width.

Here, consider the input of the receiving apparatus at the edge of the service area of the GF13. Assuming that the uplink signal for direct reception and the uplink signal for indirect reception are transmitted simultaneously from the terrestrial transmission station 11, the direct signal from the satellite repeater 12 and G
The indirect signal from F13 has a time difference of τ4max as described above.

Selecting the signal with the maximum level as the most desirable signal is effective in facilitating the configuration of the receiving device 14. In this case, the above-mentioned receiving gate width is τ4m.
twice as much as ax. This is because at the edge of the service area of the GF13, the level difference between the direct signal from the satellite transponder 12 and the indirect signal from the GF13 is small, and there is a possibility that both signals may be tracked. The other signal has a timing difference of ± τ4max. As described above, in the conventional method, it is necessary to control the signal timing to be tracked so as to be located at the center of the reception gate, and to have a gate width of τ4max before and after that.

The smaller the reception gate width is, the less the load of signal analysis is, and the smaller the scale of a device such as a memory for combining is. Therefore, it is proposed that the present invention is applied, and here, the terrestrial transmitting station 11 delays the timing of the direct signal from the satellite repeater 12. In a preferred embodiment,
The delay amount is τ4max / 2 described above.

By giving such a delay, GF
At the end of the service area 13, the timing of the indirect signal from the GF 13 is delayed by τ4max / 2 with respect to the direct signal from the satellite repeater 12. In this case, the required gate width is τ4max. On the other hand, when the receiving device is located immediately below the GF 13, the signal is advanced by τ4max / 2. Also in this case, the required gate width is τ4max. Thus, GF13
In this service area, the required gate width is τ4max or less. By applying the present invention, the reception gate width is halved compared to the case where nothing is performed, which contributes to simplification of the configuration of the reception device.

On the other hand, the delay amount may be set to τ4max.
In this case, at the edge of the service area of the GF 13, the timing of the direct signal from the satellite repeater 12 and the timing of the indirect signal from the GF 13 match, so that the request for the reception gate width is most relaxed. Within the service area of the GF13, the reception gate width needs to be set wide, but since the signal from the GF13 is dominant, it can be considered that it is sufficient to capture only the signal from the GF13. According to this method, the direct signal from the satellite repeater 12 and the indirect signal from the GF 13 can be stored in the reception gate even outside the service area of the GF 13, so that this method is suitable when importance is placed on interference resistance.

FIG. 2 shows the relationship between the reception signal timing and the reception gate in the conventional method. Immediately below the GF 13, a direct signal (SAT) from the satellite transponder 12 and the GF
13, the timing of the indirect signal (GF) is the same. At the edge of the service area of the GF13, the delay time difference between the two signals is τ4max, and the reception gate width is twice that of 2 · τ.
4max is required.

FIG. 3 shows the relationship between the reception signal timing and the reception gate in the method of the present invention.
The case of 4max / 2 is shown. It can be seen that the width of the reception gate is １ ／ compared to the case of FIG.

FIG. 4 shows an example of a configuration in which a delay unit for directly delaying a receiving system is provided in the transmitting device of the terrestrial transmitting station 11.
After performing processing such as error correction processing and interleaving at 11, the signal is distributed to two systems of a direct reception system and an indirect reception system. The baseband transmission data sequence distributed to the direct reception system is delayed by τ4max by the delay unit 112, put on the carrier signal of the frequency f1 by the modulator 113, amplified by the power amplifier 114, and transmitted from an antenna (not shown) to the satellite. It is sent out to the repeater 12. On the other hand, the baseband transmission data sequence distributed to the indirect reception system is
After being input to the carrier signal of frequency f2,
The signal is amplified by the power amplifier 116 and transmitted from the antenna (not shown) to the satellite repeater 12. Thereby, a time difference τ4max can be given between the direct receiving system and the indirect receiving system.

In addition to the above configuration example, the same effect can be obtained by giving a delay to the signal after modulation. Also, GF
If 13 is a so-called regenerative relay system in which data is once demodulated and then re-modulated, it is of course possible to include a delay in the baseband processing process.

FIG. 5 shows an example of the configuration of a receiving apparatus 14 for receiving a transmission signal transmitted from the terrestrial transmitting station 11. The reception signal received by the antenna 141 has a gate width τ.
The signal is supplied to the demodulator 143 via the reception gate processor 142 having a time window of 4max, and is demodulated and output. The output of the reception gate processor 142 is also supplied to a reception level detector 144. The reception level detector 144 detects the maximum level of the reception signal, and the detection result is supplied to the reception gate controller 145. This reception gate controller 1
45 sweeps the reception gate of the reception gate processor 142 and controls so that the maximum reception level is located at the center of the reception gate.

In the receiving apparatus having the above configuration, the timing of the direct signal from the satellite repeater 12 is delayed by the delay amount τ4max / 2 at the terrestrial transmitting station 11. Timing of the indirect signal from GF13 is τ4max
/ 2, and if it is directly below GF13, τ4m
By ax / 2, it is possible to smoothly switch between direct reception from a satellite and indirect reception from a GF even with a reception gate of τ4max. As described above, by applying the present invention, the reception gate width is halved compared to the case where nothing is performed, which can contribute to the simplification of the configuration of the receiving device.

The receiving apparatus according to the present invention may be configured to track the signal of the maximum level so as to be located at the center of the receiving gate as described above. However, the signal power to interference power ratio (C / I It goes without saying that a similar effect can be obtained even if the signal is tracked so that the signal having the largest value is located at the center of the reception gate.

[0035]

As described above, according to the present invention, there is provided a satellite relay transmission system capable of reducing the load on a circuit device for absorbing a time difference between signals transmitted from a satellite and a GF to a receiving device. Therefore, it is possible to provide a transmission device and a reception device suitable for use in this system.

[Brief description of the drawings]

FIG. 1 is a diagram showing a general system diagram of a mobile satellite broadcasting system including a GF as a configuration example of a satellite relay transmission system to which the present invention is applied.

FIG. 2 is a diagram showing a relationship between a reception signal timing and a reception gate in a conventional method.

FIG. 3 is a diagram showing a relationship between a reception signal timing and a reception gate in the satellite broadcasting system according to the present invention.

FIG. 4 is a block diagram showing a configuration in a case where a delay unit for directly delaying a receiving system is provided in a transmitting device of a terrestrial transmitting station as one embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of a receiving apparatus according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Terrestrial transmission station 111 ... Base band processing part 112 ... Delay device 113 ... Modulator 114 ... Power amplifier 115 ... Modulator 116 ... Power amplifier 12 ... Satellite repeater 13 ... Gap filler (GF) 14 ... Receiving device 141 ... Antenna 142: reception gate processor 143: demodulator 144: reception level detector 145: reception gate controller

Claims (9)

[Claims] 1. A direct receiving system that directly reaches a receiving device from a ground transmitting station via a satellite repeater, and indirectly reaches a receiving device from the ground transmitting station via a satellite repeater and a gap filler. A satellite relay transmission system having an indirect receiving system, comprising: a delay unit that delays at least a transmission timing of the direct receiving system from a transmission timing of the indirect receiving system. 2. The satellite relay transmission according to claim 1, wherein said delay means sets a maximum delay time as a propagation delay time from at least a transmission point of said gap filler to an end of an area covered by said gap filler. system. 3. A direct receiving system that directly reaches a receiving device from a ground transmitting station via a satellite repeater, and indirectly reaches a receiving device from the ground transmitting station via a satellite repeater and a gap filler. Delay means provided at a terrestrial transmitting station of a satellite relay transmission system having an indirect receiving system, wherein at least a transmission timing of a transmission data sequence transmitted to the direct receiving system is delayed from a transmission timing of a transmission data sequence transmitted to the indirect receiving system A transmission device for a satellite relay transmission system, comprising: 4. The transmitting apparatus of a satellite broadcasting system according to claim 3, wherein said delay means delays at least a transmission data sequence to said direct receiving system. 5. The transmitting apparatus of a satellite relay transmission system according to claim 4, wherein said delay means gives a delay to a transmission data sequence subjected to baseband processing. 6. The transmitting apparatus of a satellite relay transmission system according to claim 4, wherein said delay means gives a delay to a transmission data sequence subjected to modulation processing. 7. A direct receiving system that directly reaches a receiving device from a terrestrial transmitting station via a satellite repeater, and indirectly reaches a receiving device from the terrestrial transmitting station via a satellite repeater and a gap filler. Used in a satellite relay transmission system having an indirect receiving system, such that the signal of the maximum level is located at the center of the receiving gate when at least the transmission timing of the direct receiving system is delayed from the transmitting timing of the indirect receiving system. A receiving device for a satellite relay transmission system, characterized by tracking. 8. A direct receiving system that directly reaches a receiving device from a terrestrial transmitting station via a satellite repeater, and indirectly reaches a receiving device from the terrestrial transmitting station via a satellite relay and a gap filler. For use in a satellite relay transmission system having an indirect receiving system, when at least the transmission timing of the direct receiving system is delayed from the transmitting timing of the indirect receiving system, a signal having a maximum signal power-to-interference power ratio is output to a receiving gate. A receiver for a satellite relay transmission system, characterized in that tracking is performed so as to be located at the center. 9. The reception gate width is a propagation delay time from a transmission point of the gap filler to an end of an area covered by the gap filler.
Or the receiving device of the satellite relay transmission system according to 8.