JPH01101037A - System for controlling transmitting power - Google Patents

Abstract

PURPOSE:To utilize the transmitting output of a repeater to the utmost without generating the lowering of a frequency utilizing efficiency by setting the frequency distribution of the transmitting levels of plural transmitting carriers at a transmitting source beforehand, and setting the carrier frequency of a signal to be transmitted according to a status arbitrarily. CONSTITUTION:At each terrestrial station, level differences between respective carriers F2-F5 are semi-fixed, and the output levels of respective carriers are set by means of semi-fixed level adjuster modules 21-24 so as to satisfy a maximum transmitting power compensating quantity necessary in a system and to cause the C/I of a worst C/I carrier to be a fixed value of above. Among respective carriers, an F1 is used for transmitting a line control signal to be used commonly to all stations. At a transmitting source terrestrial station 10, a line setting request signal is transmitted by using the F1. At each terrestrial station, the signal is received, and at the time of its own station destination, each earth station informs the terrestrial station 10 of the F1 carrier line quality information of a its own station receiving. At the transmitting source terrestrial station, a control logic circuit 5 executes a changeover by means of a line switching device 1 so that signals Sa-Sd to respective transmitting destinations are connected to one of the frequencies F2-F5 based on line quality information pieces Ca-Cd from respective transmitting destinations.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a transmission power control system for multiple signals in a communication system using frequency division multiple access.

[Conventional technology]

Conventionally, transmission power control in satellite communications has mainly been carried out at 10GHz.
It is used as a means of compensating for the loss of signal level due to rain when using frequency bands above z, and it is said that the transmission power of the earth station is controlled according to the amount of rain attenuation or the corresponding line quality (bit error rate, etc.). method was used.

For example, Japanese Patent Application No. 54-039742 or Japanese Patent Application No. 5
No. 5-075526, etc., when multiple carriers are amplified by a repeater, the transmission power of the repeater is allocated more to the carrier that is subject to rain attenuation, and the amount of rain attenuation is compensated for to increase the bit error rate or S/ Some transmission power control schemes have been proposed to keep N constant.

What these conventional systems have in common is that a carrier frequency is fixedly assigned in advance to each transmission destination, and the transmission power of each carrier is independently controlled based on the individual line quality.

FIG. 4 is a diagram showing an example of the configuration of a conventional transmission power control circuit.

In FIG. 4, the part surrounded by the minus point MIIA is the basic part of the conventional system, which consists of a frequency converter 3, a transmitter 4, and a level adjuster 6. In this figure, multiple monolayers are parallelized to apply this to multicarrier transmission, and a line control logic circuit 7 generates a line #i setting control signal that is commonly used by each destination earth station. It has been improved so that it can be sent.

It should be noted that for the frequency converter modules 31 to 35 and the transmitter modules 41 to 45, it would be possible to generate all carriers in a common circuit, so the circuit range in that case is each surrounded by a broken line of 3.4. .

In this example, the signal Sa destined for earth station A is fixedly transmitted using F2, and the level is controlled to maintain a preset constant line quality based on line quality information Ca regarding F2 notified from earth station A. A circuit 6 performs feedback control.

Hereinafter, the same control is performed independently for the signal Sb (same as for Sc*Sd) destined for earth station B (same for C and D) based on the line quality information Cb (Cc, Cd).

[The great problem that the invention attempts to solve]

In the conventional system as described above, in the case of multi-carrier transmission where common amplification is performed by the same satellite repeater, when the number of carriers becomes 3 or more, cross-modulation noise due to the non-linear amplification characteristics of the satellite repeater increases in the bandwidth. The specific carrier satellite input level may be increased due to transmit power control due to a drop in the transmit power.

Then, the cross-modulation component related to that carrier is calculated as the carrier power-interference-noise power ratio (C/I) of other carriers.
In order to maintain a certain level of quality, it becomes necessary to further increase the satellite transponder input level even for carrier groups that did not require main-line control, and the control of each carrier diverges, causing problems for the system as a whole. It had the disadvantage of being out of control.

FIG. 5 is a diagram for explaining this, and shows the carrier level frequency distribution at a certain point in time when conventional transmission power control is being performed.

In order to increase the satellite power towards the earth station using F2 from the state shown in this figure, increasing the transmission carrier level as shown by the dotted line will cause the third-order cross modulation component to drop. In order to recover, the transmission carrier level is also independently increased by the amount shown by the broken line.

Then, the 14 greenhouse components of F3, Fl, and F2 drop to F5 and F4.

As a result, the cross-modulation components of F4 and F5 further fall to F3, and it becomes necessary to further increase the level of F3, resulting in positive feedback control.

Furthermore, as the overall level increases, the satellite transponder input level also increases, causing it to operate further in the non-linear region, thereby accelerating the operation.

To prevent this, it is necessary to make the effect of cross-modulation noise negligible, that is, to arrange the carrier frequencies so that the cross-modulation noise does not fall within the white band of each other, and to increase the output back-off of the satellite repeater. I need to take it.

However, the Babcock frequency allocation suitable for the former method has the disadvantage that the frequency usage efficiency becomes extremely poor when the number of carriers increases, and the latter method has the disadvantage that the transmission power of the satellite repeater cannot be used effectively to the maximum extent. . Therefore, using conventional transmission power control to maximize the transmit power of a satellite repeater is possible only if the carrier input of the repeater is within the droplet range (in the case of a droplet carrier, due to the Pubcock arrangement, cross-modulation components are out of the band). The disadvantage is that it is limited to cases where it is possible to do so.

In view of these conventional problems, the present invention provides a control method that can control the transmission power of three or more carriers simultaneously without reducing frequency utilization efficiency, thereby improving the transmission power of a repeater. The aim is to make maximum use of the output.

[Means for solving problems]

According to the invention, the above objects are achieved by the means specified in the claims.

That is, in the present invention, for example, a plurality of carriers of a satellite repeater are provided with eight different transmission outputs in a semi-fixed manner in advance, depending on the compensation range of rain depreciation in the downlink, and
Furthermore, in order to minimize the cross-modulation noise C/I due to non-linearity of the repeater, multiple carriers are arranged in frequency from the source earth station with a certain relationship between the level difference and the frequency arrangement, and The carrier output level is controlled by selecting the carrier frequency.

[For production]

The present invention provides, for example, means for setting the frequency distribution of transmission levels of a plurality of transmission carriers and means for setting the carrier frequency of a signal to be transmitted to an arbitrary frequency, especially when a large amount of transmission power is not required. transmits a signal by selecting a carrier frequency with a low level from among multiple carrier frequencies for which an appropriate level has been set for each frequency in advance.On the other hand, if you want to increase the transmission power of the signal to be transmitted, you can change the level. Select a large/high carrier frequency and transmit the signal.

By doing this, the preset frequency distribution of multiple carrier levels input to the satellite transponder is maintained, so the worst value of cross-modulation C/I is compensated for above a certain value, and If a large carrier transmission power is required, it is possible to allocate a large amount of the satellite repeater transmission power. Therefore, when the number of carriers is arbitrary, the total C(N+1) of the cross-modulation C/I and thermal noise C/N is The determined line quality can be comprehensively optimized for all carriers.

〔Example〕

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

In addition, in the following example, to simplify the explanation, we will explain the case where there is one source earth station, four destination earth stations, and one carrier is individually assigned to each destination. There is no limit to the number of carriers or earth stations for each earth station.

FIG. 1 is a diagram showing an example of the configuration of a transmission power control circuit according to an embodiment of the present invention. FIG. 2 is a diagram showing an example of a system configuration to which the present invention is applied.

FIG. 3 is a diagram showing an example of frequency arrangement of set carrier levels.

In FIG. 2, Fl is a line control signal transmission carrier commonly used by all earth stations 8I-84. Also, in this figure, earth stations 8I to 8. Signals directed toward the earth station 10 (hereinafter described as earth stations A-D) are not shown.

Furthermore, in FIG. 2, destination earth station 8. ~8, (A,
B, C, D) are geographically dispersed, but each satellite
The link parameters between the satellite and the satellite are uniform (if the satellite output power is constant, the downlink C/N is constant), and the link quality of each carrier is determined by uplink thermal noise C/N, downlink thermal noise C/N, and satellite repeater interference. Although it is determined by the noise addition of each modulation C/I, here, in order to simplify the explanation, it is assumed that the upstream thermal noise C/N is ignored.

Furthermore, to explain the control operation, at the time of transmitting the signal, earth stations B and C have a downlink C/N decrease (11) due to rain.
Lb * Lc (dB) -2R>Lb>R>
Assume that there is Lc).

In FIG. 1, a line switching device 1 can connect any transmission signal of Sa to Sd to any carrier frequency. The level difference between each carrier is semi-fixed, and the output level of each carrier is semi-fixed so that the maximum transmission power compensation required by the system is satisfied and the C/I of the worst C/I carrier is above a certain value. It is set by the level adjuster modules 21 to 24 of.

However, this can be achieved with a single circuit using a bandpass filter, and in that case, the part surrounded by the broken line in 2 is one level. 11 circuit.

The frequency converter 3 and transmitter 4 are the same as in the conventional example.

The control logic circuit 5 receives line quality information Ca- from each destination.
Logic for generating a control signal for controlling the switch 1 so that signals 5a-3d for each destination follow # on one of the frequencies F2 to F5 as described below based on Cd, and each earth station. This is a logic circuit that generates a line setting control signal that is commonly used.

Figure 3 shows an example of the earth station transmission spectrum, and the level is F1.
= F5 , F2 = F4 , Fl > F2 > F3 are semi-fixed by the level adjuster 2 in Fig. 1, and the level difference is assumed to be R (dB) (the maximum transmission power control range is 2R).

In this transmission spectrum distribution, the third-order greenhouse f between large signals is
To prevent the I4 product from falling into the small signal carrier band
1K, it is possible to improve the C/I of the worst channel compared to the case where large signals and small signals are randomly arranged as in the conventional example.

In addition, mixed 'I! 4C/I is determined at the time of output from the satellite repeater, so it does not change due to rain, F2 and F4
It is assumed that the line parameters are set so that the noise sum of the downlink C/N and the worst-case C/I (when all carriers are transmitted) satisfies the required line quality in the absence of rain.

The stabbing operation will be explained below.

First, an example will be described in which a call setup request is made from the earth station 10 and a new line is set up to each earth station.

Of the carriers in Figure 3, Fl is used for line control signal transmission common to all stations, and each earth station always uses F1 when on standby.
shall be received. The source earth station 10 transmits a line setting request signal using Fl, and each earth station receives the line setting request signal and determines whether the request is addressed to its own station. F1 carrier line product? 7 information (code error rate, S/N, etc.) is notified to the global station 10.

Regarding the notification means, some kind of line will be provided from each earth station to the earth station 10, but since it is not particularly relevant to the essence of the invention, a description thereof will be omitted here.

First, when the earth station 10 makes a transmission request to the earth station A, since the earth station A has not received rain attenuation, the line quality information Ca of the F1 signal notified from A is determined by the line setting by F2 or F4. This shows that it is possible. Based on this, in the earth station 10, the control logic circuit 5 of FIG.
uses the line switch 1 to connect the signal Sa destined for earth station A to the F2 carrier (or F4).

Next, when the earth station 10 makes a transmission request to the earth station B, the line quality information cb notified from the earth station B includes the quality deterioration Lb due to rain loss (deterioration due to downlink C/N). Therefore, at the earth station 10, the control logic circuit 5 estimates from the mixed 31iC/I and C/N that it knows in advance whether or not the line can be set up with the F3 carrier, and if possible, the control logic circuit 5 uses the signal sb for the earth station B. Connect to F3 carrier.

In F3, if it is estimated that the downlink C/N improvement is insufficient, it is further estimated whether it is possible to set up a line with an F5 carrier, and if possible, connect to the F5 carrier to compensate for rain attenuation even at the F5 level. If this is not possible, it is assumed that the line cannot be set up and the connection will not be made.

In this example, since 2R>Lb>R, F5 is selected as the sb transmission carrier frequency if the cross-modulation noise is below a certain value. Hereinafter, by making similar measurements for the earth stations C-D, F2, F5, F3, and F4 are set for the earth stations A-D, respectively.

Furthermore, once the carrier frequency has been set, each earth station transmits line quality information (C) for the set carrier.
a-Cd) to the earth station 10, and the earth station 10 uses the control logic circuit 5 to comprehensively check the line quality for all earth stations, and determines whether the level margin of each carrier is uneven due to geographical changes in rainfall, etc. If you become suspicious, turn on line switch 1.
control to change the carrier frequency allocation for each earth station and redistribute the transmission level for each station.

Since this change does not involve a change in the frequency level distribution of the transmission carrier as a whole, it is possible to optimize the amount of transmission power for each station as a system without considering the deterioration of 111c/I. Can be done.

〔Effect of the invention〕

As explained above, the present invention provides stable transmission of each carrier even when carriers are arranged at equal intervals on the frequency axis through a multi-carrier transmission system in which common amplification is performed by repeaters with non-linear amplification characteristics. Not only is it possible to control the transmit power for each carrier, but it also improves the C/(N+I) of the carrier under the worst condition compared to the conventional method that controls the transmit power for each carrier. It becomes possible to turn it off small.

Reducing the output backoff of the repeater in this way creates a power margin in the system, which can be used to increase channel capacity or increase the C/N margin of each carrier.

Further, by applying the present invention, it is possible to eliminate restrictions on frequency allocation such as the Pubcock arrangement, so it is also possible to utilize frequencies effectively.

Note that in this document, to simplify the explanation, a satellite-mounted repeater is mainly explained as an example of a repeater, but the present invention generally controls the transmission power of multiple carriers and The present invention can be applied to a transmission system in which carriers are commonly amplified to obtain an effect.

[Brief explanation of the drawing]

FIG. 11 is a diagram showing an example of the configuration of a transmission power control circuit according to an embodiment of the present invention, FIG. 2 is a diagram showing an example of a system configuration to which the present invention is applied, and rjSa is an example of frequency allocation of set carrier levels. FIG. 4 is a diagram showing an example of the configuration of a conventional transmission power control circuit, and FIG. tIS5 is a diagram showing an example of a conventional carrier level frequency distribution. 1...Line switching device, 2...
... Level adjuster, 3 ... Frequency converter, 4 ... Transmitter, 5 ...
... Control logic circuit, 6 ... Level control circuit, 7 ... Line control logic circuit, 8
．． ~s,,io...Earth station, 9...
...satellite, 21, 22. 23.24 Level adjuster module, 3
1, 32, 33, 34, 35...
...Frequency converter module, 41
, 42. 44. 45... Transmitter monoyl agent Patent attorney Takashi Honma Ca Cb Cc Cd Fig. 2 Fig. F, F2 F, F4 Fs No. 3
Figure 5

Claims (1)

[Claims] In a signal transmission system that uses multiple carriers lined up on a frequency, a level difference is established in advance between the transmission levels of each carrier at the transmission source, and a certain relationship is created in the frequency arrangement in correspondence with the transmission level of each carrier. , a transmission power control method characterized by controlling the transmission level by selecting a carrier frequency when transmitting a signal to each destination.