JPS63175529A - Tdma satellite communication equipment with variable carrier power - Google Patents

Abstract

PURPOSE:To obtain a system coping flexibly with even a request to different transmission quality by varying the power level of a burst to be transmitted depending on the condition of an opposite earth station and the content to be transmitted so as to attain the TDMA (Time Division Multiple Access) operation. CONSTITUTION:A signal from a satellite is received by an earth station device 32 and subject to processings such as demodulation at a communication terminal station equipment 34 and fed to a ground line 102 via an on-ground line connector 36. An attenuator 210 is provided to the input of a demodulator 608 and the output of an attenuator control circuit 216 controls the attenuation to control the input power level of the received carrier from the earth station equipment 32. Moreover, the attenuator control circuit converts the attenuator control information included in the burst time plan data into a signal controlling the attenuator directly and the control information 111 is added separately to the signal. Thus, the usable power of the satellite is used efficiency and a large effect is given onto the entire cost reduction of the satellite communication.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a TDMA satellite communication system using a plurality of carrier waves within the band of one satellite repeater, and particularly to a TDMA satellite communication device used for business satellite communication. It is.

[Conventional technology]

TDMA (Time Division Multi
The satellite communication system (ple Access: time division multiple access) is a system in which a plurality of earth stations use all or part of the frequency band of a satellite repeater (transponder) in a time division manner. In this case, each earth station needs to transmit the signal in the form of an intermittent signal, that is, a burst, at a specific period, that is, the TDMA frame period, but if a variety of digital signals are handled in an integrated manner, It is known as an efficient communication method because it not only enables the construction of highly flexible networks. In particular, the low-speed TDMA system, which uses a part of the transponder's band and operates at a relatively low transmission speed, is economical in equipment, and can be expanded to a TDMA system using multiple carrier waves using frequency hopping technology, which will be described later. Therefore, it is suitable for so-called business satellite communications where earth stations are installed on the rooftops of buildings in urban areas or near offices.

In a TDMA system, one or two earth stations are usually selected as reference stations from among multiple participating earth stations, and are responsible for transmitting reference timing signals necessary for TDMA synchronization within the system and for other control and monitoring purposes. It is normal to perform a function.

As a way to make TDMA systems more flexible,
TDMA operation is based on the burst time plan (Burs time plan).
There is a method of controlling using software data rather than hardware.

In other words, it controls the transmitting side by giving the position and width of the burst transmitted by each earth station within the TDMA frame, the destinations of various traffic included therein, etc. in the form of data,
On the other hand, the received burst and its content processing method are also provided in the form of data. Since these data can be stored in the storage circuit, the data for the new plan can be stored separately in each station, and the entire system can be switched from the old plan to the new plan all at once without affecting the traffic being transmitted ( It is also possible to change the network configuration on the fly.Normally, a new burst time plan is sent via satellite from the reference station to each earth station using special data lines and downloaded into storage circuitry. Ru.

Next, we will discuss system expansion in the low-speed TDMA system. Since the TDMA system is a system in which a plurality of stations use a common carrier wave in a time-division manner, each station transmits signals only intermittently. This means that the transmission equipment is used only intermittently.

Furthermore, since the signal to be received usually corresponds to the transmitted signal, even if the receiving equipment appears to be receiving signals continuously, it is actually only used intermittently. . Therefore, when transmitting/receiving equipment is not used for a certain carrier within a TDMA frame period, the transmission capacity of the equipment can be expanded if another carrier with a different frequency can be used successfully. When such an operation is performed between a plurality of carrier waves selected within the same carrier, this is called frequency popping.

FIGS. 2(a) and 2(b) illustrate the principle of a multi-carrier TDMA system using frequency hopping. Here, the frequency bands of the satellite transponder include fl, f2.
Assume three carrier waves 4o of f3.

In FIG. 3A, three stations A, B, and C are transmitting using respective specific carrier waves. Here, synchronization and control bursts associated with operation of the TDMA system are omitted, and only the bursts (data bursts) 20 that carry the original traffic are shown. However, for the sake of explanation, the bursts for stations are shown as independent bursts. On the receiving side, on the other hand, the burst destined for the local station is received while switching the reception carrier wave using frequency hopping technology.

Assuming that one earth station has only one communication device, it cannot transmit on more than one carrier at the same time, nor can it receive on more than one carrier at the same time. Therefore, when creating a burst time plan, the positions of the bursts transmitted by each station and the destinations of the bursts must be determined with consideration given to ensuring that there are no contradictions.

In FIG. 4B, the frequency of the received carrier wave is assigned to each station, and the transmitting side transmits using the corresponding carrier wave depending on the destination of the traffic to be sent. That is, this is the case when carrier hopping technology is used on the transmitting side. These diagrams are either simplifications, or the actual system would be more complex because there would be a large number of earth stations and each station would have a different transmission capacity. Furthermore, frequency hopping is often required to be performed not only on either the transmitting side or the receiving side, but on both sides.

[Problem that the invention seeks to solve]

However, when constructing such a TDMA system, the circuit is designed with the idea of passing one carrier wave through the entire transponder band or a part of the allocated band. The maximum power level above is specified.

On the other hand, each earth station using that carrier transmits bursts at a power corresponding to its maximum power level to make effective use of its power, so the power level of each burst passing through the transponder depends on its content and destination. The relationship is constant. As a result, each earth station participating in a TDMA system requires approximately the same scale of equipment, regardless of the transmission capacity required by each, resulting in large initial investments and limited application areas from an economical point of view. This resulted in a narrowing.

The present invention solves this problem and enables TDMA operation even between earth stations of different sizes, thereby making it possible to construct a system more economically. Also,
The present invention provides a system that can flexibly respond to different transmission quality requirements, and also provides a system that can flexibly respond to requirements for different transmission quality.
Solving the problem of rainfall attenuation specific to the GH2 band6 is also helpful.

[Means for solving problems]

In order to solve the above-mentioned problems, one of the characteristics of the system to which the present invention is applied is that although it is a TDMA system, the power level of the burst to be transmitted is changed depending on the conditions of the destination earth station and the content to be transmitted. Originally, the transmission power level of each burst or carrier wave is constant and should be determined at the line design stage, but in the present invention, the bandwidth allowed within the satellite transponder as a whole of multiple carrier waves used in the system, Assuming that the available power allocation conditions are not met, the number of carrier waves, the burst power level transmitted on each carrier wave, etc. can be changed flexibly according to the network situation, and this can be changed based on the burst time plan. It is something that we try to thoroughly internalize.

That is, in a TDMA satellite communication system in which carrier waves up to a maximum of (N22) waves can be used within the same transponder of a satellite, mutually compatible burst time
There are multiple earth stations operating according to a system, at least some of which can transmit and/or receive multiple carriers in a time-sharing manner by frequency hopping, while within a system For a particular value indicating the total power level of the carrier waves available in N waves, the carrier power level of M waves (N ≧M≧
1) and separately setting the power level of each burst transmitted using each carrier.

The value of N is the number of carriers possible if the width of the frequency band allowed in the transponder and the available power are used to transmit traffic with normal quality between the large earth stations in the network during clear weather. Consider it the maximum value.

If there are small earth stations mixed in the system,
Each earth station can operate within the same network by appropriately increasing the transmission power level of bursts that smaller earth stations should receive.

In this case, the power distribution naturally changes and the number of carrier waves in the system inevitably decreases.

If higher quality traffic transmission is required, the higher quality transmission can also be achieved by increasing the transmission power level of the bursts carrying that traffic. In this case as well, this is a factor that reduces the number of carrier waves in the entire system.

Further, as will be described later, if a margin is provided in power distribution in consideration of rain attenuation, the number of carrier waves may be reduced.

One way to set the power level of each burst is to set it permanently or on an ad hoc basis depending on the reception conditions of the earth station receiving the carrier.

A permanent power level setting condition is the size of the receiving earth station, that is, the signal receiving ability. The rainfall characteristics of the region may also be taken into consideration. These conditions are taken into account when creating burst time plan data, so once the data burst containing the traffic that a certain earth station should receive is determined, the transmission power level of the corresponding burst for each earth station is determined. . When a burst time plan specifies transmission quality requirements for traffic to be transmitted, this also becomes a condition for power level setting.

The content of the traffic is sent to Haas 1. When not managed by a time plan, each earth station monitors the transmission quality requirements of the traffic that each earth station accepts, and the results are used to create a burst time plan for each earth station. It is possible to allocate the necessary power by having the station submit it as a request.

Setting the power level at any time is mainly a rain attenuation countermeasure. Transmission power control technology that compensates for rain attenuation in the link from the earth station to the satellite has already been put into practical use. The problem is compensation for rain attenuation in the downlink. Here 2
There are two possible methods.

One method is to have each earth station monitor the quality of its received signal, i.e., the hint error rate, and broadcast an alarm signal into the network when an earth station detects that the quality of its received signal has deteriorated beyond a standard; Each earth station receiving the burst autonomously changes the power level of the burst it is receiving according to a prescribed procedure. Another method is to have a reference station interposed, which receives the alarm signal and commands to change the transmit power of each station.

In this case, by utilizing the monitoring function of the reference station, the above-mentioned transmission power control function can also be executed in the form of a command from that station, and the related equipment of each station is simplified.

The premise that this method is possible is that the burst time
When creating a plan, it is necessary to take into account the power margin for rainfall. However, this power margin can be applied to any of the multiple bursts simultaneously present on the transponder. Therefore, if you adopt this method,
It is possible to eliminate wasteful efforts such as securing extra power for all lines during clear weather, and it is possible to achieve a remarkable effect in terms of effective use of satellite power.

FIG. 3 shows the principle of one method to which the present invention is applied. In the figure, the available frequency bands of the satellite transponder include fl, f2. Assuming carrier wave 40 of f3, 3
It is assigned as a transmission carrier wave for three stations, A station, B station, and 0 station. That is, f3 is for transmission from station A, f2 is for transmission from station B, and fl is for transmission from station 0, which is smaller in scale than stations A and B, or is under poorer reception conditions such as rain. The power level of each carrier wave is appropriately set depending on its purpose, that is, whether it is for voice transmission, data transmission requiring high transmission quality, or for an earth station with poor reception conditions. Of course, the total power of the entire carrier must be within the power level assigned to this system in the satellite transponder.

Among the bursts transmitted by station A, the bursts labeled "broadcast" distribute data in broadcast mode, which is a characteristic of satellite communications. In this case, if all stations other than A, such as B and 0, receive this burst, this time
The slot cannot be used for transmission by stations other than station A. However, it is possible to set the power level of broadcasting bursts higher by that amount, making it possible to distribute data with sufficiently high transmission quality even to stations under the worst reception conditions due to rain, etc. . In this case, this time
It can be considered that the number of carrier waves in the slot is reduced from three waves to one wave.

The present invention provides a specific TD to enable the above method.
This realizes an MA satellite communication device.

In order to make the effects of the above system a reality, the receiving side of the communication device also needs a function to deal with fluctuations in the general transmission power for each burst and to efficiently demodulate it.

The present invention realizes this function on the receiving side.

Most of the reception performance of a communication device depends on the performance of the demodulator. In TDMA communication systems, a receiving demodulator must receive and demodulate multiple bursts transmitted from different earth stations within a TDMA frame. However, because they contain carrier and clock signal components that are asynchronous to each other, the demodulator must extract the carrier network and clock signal for each burst before demodulating the traffic data contained in the burst. This type of operation is called a "burst," and requires more advanced technology than a demodulator that receives and demodulates continuous signals, and in order to effectively utilize its function, the power of each input burst is required. It is necessary to keep the level extremely constant. That is, an object of the present invention is to maintain a constant power level input to a demodulator in a TDMA system in which the carrier wave power level of each burst is intentionally changed. Of course, a simple method would be to use a circuit such as a beam soter, but in recent digital signal transmission, spectrum shaping is strictly performed using Nyquist filters etc. to improve transmission characteristics, so it is difficult to Intentionally inserting a circuit with linear characteristics is undesirable as it leads to deterioration of the characteristics. For this reason,
The present invention attempts to achieve the objective by applying transmission power control technology to the receiving side.

That is, a feature of the present invention is that the device operates based on burst time plan information stored within the device. The device includes a demodulator, an attenuator that controls the input level of the demodulator, and an attenuator control circuit that controls the attenuator, and the amount of attenuation provided by the attenuator is determined based on burst time plan information. It is configured to convert to i at the TDMA frame period according to a specific pattern determined directly or indirectly.

Furthermore, specifically, the attenuator control circuit includes a memory circuit, and this memory circuit stores the correspondence between the communication partner station and the control information of the attenuator, and changes the amount of attenuation of the attenuator within the TDMA frame. pattern is controlled by the information read out by this storage circuit, corresponding to the information regarding the communication partner station in the burst time plan.

In this case, the control information for the attenuator stored corresponding to the communication partner station may be data given from the outside as a system parameter, or may be the result of measurement by the own station at any time.

Alternatively, a storage circuit in the attenuator control circuit stores the correspondence between the identification code or number of the transmission burst and the attenuator control information, and the pattern of change in the attenuation amount of the attenuator within the TDMA frame is determined by the burst time. - It is controlled by this storage circuit based on information regarding the identification code or number of the transmission burst in the plan.

Alternatively, the attenuator control circuit (y circuit) stores the correspondence between the carrier wave selection information in frequency hopping and the attenuator control information, and the pattern of change in the attenuation amount of the attenuator within the TDMA frame is determined by the burst/y circuit. It is to be controlled by information read out by this storage circuit in response to selection information of the receiving carrier wave in the time plan.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 shows an example of a control circuit configuration used in the present invention.

Here, the signal from the satellite is received by the earth station device 32, applied to the communication terminal device 34, subjected to demodulation and other processing, and then supplied to the terrestrial line 102 via the terrestrial line connection device 36.

The circuit of the present invention is included in the communication terminal device 34, but of course equivalent functions may be distributed and included in several devices. Think of it as a communication device. In the figure, a frame period counter 204 is a counter that determines the reference timing on the receiving side, generates various timing signals at the period of the TDMA frame, and controls the operations of various circuits inside the communication terminal device. The burst time plan downloaded from the reference station via the satellite is sent to the monitoring and control device 3, for example.
8 and then loaded into the storage circuit 202. The contents of the memory circuit 202 are the frame period counter 20
It is read out sequentially according to the count number of 4, and is used for received data/burst separation processing in burst separation circuit 606, as well as added to attenuator control circuit 216. The oscillator 212 includes up to N frequency synthesizers;
One output, selected by any suitable method, is applied to demodulator 608 to define the carrier frequency of the demodulator input. After the received carrier wave is appropriately frequency-converted by the earth station device 32, it is usually sent to a demodulator 608 in the communication terminal device 34.
The data is supplied to the earth station and demodulated, and only the traffic data portion required by the earth station is extracted from each data burst in the burst separation circuit 606, and then added to the terrestrial line connection device 36. In the present invention, an attenuator 210 is provided at the input of the demodulator 608, and the amount of attenuation is controlled by the output of the attenuator control circuit 216.
Controls the power level of the received carrier from.

Note that the attenuator control circuit converts the attenuator control information included in the burst time plan data into a signal that directly controls the attenuator, but the generation of this signal requires a separate control. Information 110 can also be taken into account.

FIG. 4 shows an example of a circuit that utilizes the burst time plan, and although this circuit itself is well known, it will be explained as it is one of the important components of the present invention. The figure shows the storage circuit 202 and frame period counter 204 of FIG. The frame period counter includes a one-digit binary counter 302 that is clocked by a symbol clock 350 and a frame period decoder 304, and a two-digit binary counter 302 that is clocked by a symbol clock 350 and a frame period decoder 304.
A frame period counter is realized by resetting 2 to the initial state.

The main components of storage circuit 202 are RAM circuit 308, address counter 310, and comparator 312. R.A.
The M circuit 308 stores the supplied burst time plan in a readily available form. In this example, the stored burst time plan has been converted into a code word, Sera I, consisting of timing information, control information ■, and control information n. Each code word corresponds to one event and is arranged in order of occurrence within the TDMA frame.

The timing information, which is the content of the code word, is the number of binary counts at which the event should occur, the control information ■ is the meaning of the event, information on the circuit to be controlled, etc., and the control information ■ is the number of binary counts that should occur. Each indicates the operating state between the event and the next event.

The contents of the RAM circuit 308, ie code words, appear one by one at the output terminals one by one by feeding the contents of the address counter 310 to its address terminals, and the timing information therein is output to the comparator as a parallel signal of bits. 31
2. On the other hand, since the contents of the K-digit binary counter are also supplied to the comparator 312 as a bit parallel signal,
When the two match, a match pulse 356 is generated. This match pulse 356 is applied as a clock signal to the address counter and advances the contents of the address counter by one. As a result, new content or code words also appear at the output of RAM circuit 308. One frame period ends and the frame period decoder 304 resets.
When pulse 352 is generated, it is also supplied to the address counter as a reset pulse, returning the address counter to its initial state. Therefore, during one period of the frame period counter 204, code words corresponding to each event are read out one after another.

On the other hand, the control information ■ of the code word is added to the control content decoder 314, the content is translated, and the AND gate 31
One of the numbers 6 is set as "open". When a match pulse occurs,
This pulse passes through AND gate 316, which is open, and is provided as an event pulse 358 to related circuitry. Registration again? The 111f signal I[ is latched by the latch circuit 330 by the coincidence pulse 356 and held until the next coincidence pulse occurs. The output of this launch circuit is also supplied to each part of the device as is or via a decoder 239 or the like.

FIG. 5 shows another example of a burst time plan utilization circuit. In this case, each transition within a TDMA frame is designed to occur every 2L counts of symbol clock 350 or an integer multiple thereof. Therefore, the contents of the last 11 digits of the K-digit binary count 302 are applied to the timing decoder 305 to generate timing pulses 357 every 21 counts, and the AND gate 31
6 is open, an event pulse 358 is generated.

On the other hand, the contents of counter 302 (K-L) digits are stored in RAM.
It is used as an address signal for circuit 308.

Therefore, this circuit does not require the address counter 310 or code word timing information as shown in FIG.

FIG. 6 is an example of an attenuator circuit 210 used in the present invention. Attenuators are 1dB, 2dB, 4d respectively
Fixed attenuator 4 with attenuation of B, 8 dB,...
02°404, 406, 408 are connected in series, and each attenuator is equipped with a switch So, S1 . ．． S2゜S
A bypass circuit that is opened and closed by 3... is attached. Each switch is a high speed diode switch and is individually controlled by bypass switch control circuit 410. Control circuit 410 is controlled by an attenuator control signal 116 provided by an attenuator control circuit. If the control signal 116 is a binary number representing the amount of attenuation in dB, then
The control circuit 410 becomes a mere decoder, and by opening and closing the bypass switch appropriately, the terminal equipment 115 can be operated manually.
and the demodulator power 113, any attenuation can be created from 0 clB to 15 dB in 1 dB steps.

FIG. 7 shows another example of the attenuator circuit. Here the PIN
A diode attenuator 412 is used. Normally, one stage of PIN diode can provide attenuation of about 20 dB, so if more attenuation is required, another PIN dimate attenuator 414 is used in series. As a method of obtaining a bias voltage to be applied to the PIN diode, in the figure, the output of the ROM circuit 432, which is read out using the attenuator control signal 116 as an address signal, is transferred to the D/A converter 4.
22 (and 424).

FIG. 8 shows an example of the configuration of an attenuator control circuit which is the core of the configuration of the present invention. Here, the control information is the output of the launch circuit 330 in FIG. 4 or 5, that is, the burst time.
Control information in the plan data is used. When the attenuation amount of the attenuator 210 is uniquely controlled by the burst time plan, the code corresponding to the attenuation amount is directly included in the burst time plan,
It is supplied as attenuator direct control information 126. However, in such applications, since the amount of attenuation is usually conveyed in large steps such as 3 dB or 5 dB, 12G of control information is displayed in 2 to 3 bits, and the converter 508 converts it into an attenuator control signal 116 representing the actual amount of attenuation. will be converted.

The RAM circuit 506 is used when the setting of the attenuation amount is not fixed but is determined based on operational conditions. RAM
The circuit 506 is supplied with one or more of the transmission destination station identification code, transmission burst identification code, or carrier selection information in burst number 1 frequency hopping included in the control information (2), and is used as an address signal. . The attenuation amount is stored in the RAM circuit in accordance with the address signal, and the information on the read out attenuation amount is sent to the converter 508.
It becomes the attenuator control signal 116 through the process. When the attenuator direct control information 126 is simultaneously supplied to the transducer, addition is performed in the transducer and the result is output as the control signal 116. The RAM circuit 506 is normally used for reading only, but if there is a change in operating conditions, for example, there is heavy rain near a certain earth station and it is necessary to amplify the transmission power only for bursts directed to that earth station. teeth,
For example, it is supplied as data line information 122 -
The obtained information is decoded and calculated by an attenuation amount setting processor 502 having a microprocessor, and then transferred to the RAM control circuit 50.
With the help of 4, the corresponding data can be rewritten aiming at the period in which no reading of the RAM circuit is performed within the TDMA frame, thereby making it possible to correspond to the new conditions. The control information 110 in FIG. 1 corresponds to information related to such changes in operating conditions.

〔Effect of the invention〕

As explained above, the present invention makes it possible to individually set the power level of the burst to be transmitted depending on the size of the receiving station, the receiving condition, the content of the traffic to be transmitted, etc. in the TDMA satellite communication system that uses multiple carrier waves. This solves many problems in business communications, makes it possible to use the available power of the satellite efficiently, and has a great effect on reducing the overall cost of satellite communications.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the control circuit configuration of the present invention, Figure 2 is a block diagram showing the control circuit configuration of the present invention.
Figures (a) and (b) are the principle diagrams of the multi-carrier TDMA communication system, Figure 3 is the principle diagram of the system to which the present invention is applied, and Figure 4 is the Huff-first time plan utilization used in the present invention. A block diagram of an example of a circuit,
FIG. 5 is a block diagram of another example of the burst time plan utilization circuit, FIG. 6 is a block diagram of another example of the attenuator circuit used in the present invention, and FIG. 7 is a block diagram of another example of the attenuator circuit. 8 are block diagrams of the configuration of an attenuator control circuit which is the core of the present invention. 20...Data burst, 40...Carrier wave, 32
...Earth station equipment, 34...Communication terminal equipment, 36...
・Terrestrial line connection device, 102...Terrestrial line, 110・
...Control information, 202...Storage circuit, 204...Frame period counter, 210...Attenuator, 212...
...Oscillator, 216...Attenuator control circuit, 606...
- Burst separation circuit, 608... demodulator. Procedural master's letter (spontaneous) April 5, 1986

Claims (4)

[Claims] (1) In a TDMA satellite communication device that is used for the TDMA method using multiple carrier waves within the band of one satellite repeater and operates based on burst time plan information stored inside the device, a demodulator and its It has an attenuator that controls the input level of the demodulator and an attenuator control circuit that controls the attenuator.
A variable TDMA satellite communication device characterized in that carrier wave power is changed at a TDMA frame period according to a specific pattern determined directly or indirectly by time plan information. (2) The attenuator control circuit has a memory circuit that stores the correspondence between the communication partner station and the attenuator control information, and the pattern of change in the attenuation amount of the attenuator within the TDMA frame is determined by the burst time 2. The variable carrier power TDMA satellite communication device according to claim 1, wherein the carrier wave power variable TDMA satellite communication device is controlled by information read out from the storage circuit in accordance with information regarding the communication partner station in the plan. (3) The attenuator control circuit includes a memory circuit that stores the identification code of the transmission burst or the correspondence between the number and the attenuator control information, and the pattern of change in the attenuation amount of the attenuator within the TDMA frame is , and is controlled by information read out from this storage circuit in correspondence with information regarding the identification code or number of the received burst in the burst time plan. Variable carrier power TDMA satellite communication device. (4) The attenuator control circuit includes a memory circuit that stores the correspondence between carrier wave selection information in frequency hopping and attenuator control information, and the pattern of change in attenuation amount of the attenuator within a TDMA frame is The variable carrier power TDMA satellite communication according to claim 1 is controlled by information read out from this storage circuit in response to selection information of a receiving carrier in a burst time plan. Device.