JPS63175528A - Tdma satellite communication equipment with variable output power - Google Patents

Abstract

PURPOSE:To obtain a system coping flexibly even to a request to different transmission quality by varying the power level of the 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 even between earth stations different in scale. CONSTITUTION:A traffic data supplied from a ground line 102 is formed to be a data burst by a burst forming circuit 206 via a ground line connector 36 to modulate the carrier by a modulator 208. an attenuator 210 is provided to the output of the modulator 208 to control the attenuation by the output of an attenuator control circuit 216 thereby controlling the output power of the carrier from an earth station device 32. Moreover, the attenuator control circuit converts the attenuator control information included in the data of burst time plan into a signal controlling the attenuator directly and the signal is also added with control information 110. Thus, the usable power of the satellite is used efficiently and the large effect to reduce the cost of the entire satellite communication is displayed.

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 Mu
The satellite communication system (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 transponder in a time division manner. In this case, each earth station needs to transmit signals in the form of intermittent signals, that is, bursts, at a specific period, that is, the TDMA frame period, but it is not possible to handle a variety of digital signals in an integrated manner. It is known as an efficient communication method because it not only allows you to build a highly flexible network. 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, the transmitting side is controlled by giving the position and width within the TDMA frame of the parse 1~ transmitted by each earth station, and the destination of the various 1 included therein in the form of data, and on the other hand, the receiving burst and The method for processing the contents is also provided in the form of data. Since these data can be stored in the memory 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, allowing the network to be updated without affecting the traffic being transmitted. It is also possible to change the configuration instantly. Usually a new burst
The time plan is sent from the reference station via satellite to each earth station using a special data line and downloaded into the memory circuit.

Next, we will discuss the expansion of the system in the low-speed TDMA method. 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 transbonder, this is called frequency hopping.

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 a three-wave carrier wave 40 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 the operation of the TDMA system are omitted, and only the bursts (data bursts) 20 that carry the original traffic are shown. However, the bursts for stations that are beyond the scope of explanation 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 popping 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 to be transmitted by each station and the destinations of the bursts must be determined with consideration to avoid inconsistencies.

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. Although these diagrams are simplified, an actual system would be more complex because there would be many 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. It remains constant regardless. 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 different transmission quality requirements, and also provides a system that can be used for business satellite communications (14/11 GHz, 30/20 GHz).
It is also useful for solving the problem of rain attenuation especially in the GH□ zone).

[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 where up to (N≧2) carrier waves can be used within the same transponder of a satellite, mutually compatible burst time
There are a plurality of earth stations operating according to a system, at least some of which can use frequency hopping to transmit and/or receive multiple carrier waves in a time-sharing manner; N for a particular value indicating the total power level of the carriers available within
M wave carriers (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 at any time 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 transmit power level of the corresponding burst for each earth station is determined. Become. When a request for the transmission quality of the l-rahisok to be transmitted is specified in the burst time plan, this also becomes a condition for setting the power level.

When the content of the traffic is not managed by the burst time plan, each earth station monitors the transmission quality requirements of the traffic that each earth station accepts, and the results are used by each earth station to create the burst time plan. It is possible to allocate the necessary power by having it submitted 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 uplinks from earth stations to satellites is already in practical use.

The problem is compensation for rain attenuation in the downlink. Two methods are possible here.

One method is that each earth station monitors the quality of its received signal, i.e., the bit error rate, and when a certain earth station detects that the quality of its received signal has degraded beyond a standard, it sends an alarm signal within the work. Each earth station that broadcasts and receives a burst autonomously changes the power level of the burst it is receiving according to a prescribed procedure. Another method involves a reference station intervening, the reference station receives the alarm signal,
This is to change the transmission power of each station as a command.

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 this figure, carrier waves 40 of fl, [2, f3 are assumed to be in the usable frequency band of the satellite transponder, and there are three stations, A station and B station.

It is assigned as the transmission carrier for station 0. That is, f
3 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 than the others, such as due to 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 communication. 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 is to realize the MA satellite station.

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 modulator, an attenuator that controls the output level of the modulator, and an attenuation control circuit that controls the attenuator, and the amount of attenuation provided by the attenuator is directly controlled by the burst time plan information. It is configured to change at the TDMA frame period according to a specific pattern that is determined indirectly 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 this storage circuit based on information about the correspondent station in the burst time plan.

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 based on 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, a storage circuit in the attenuator control circuit stores the correspondence between carrier wave selection information in frequency hopping and 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. This is controlled by the circuit described in Section 4.1 based on the transmission carrier selection information in the 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 traffic to be transmitted at the earth station is supplied by the terrestrial line 102, is added to the communication terminal equipment 34 via the terrestrial line connection device 36, and is transmitted through the earth station equipment 32 toward the satellite.

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 transmitting 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 supervisory control device 38, for example.
After processing, the data is loaded into the storage circuit 202.

The contents of the memory circuit 202 are the frame period counter 204
The data is sequentially read out according to the count number of , and is used to create data bursts in the burst forming circuit 206 as well as being added to the attenuator control circuit 216 . Oscillator 212
includes up to N frequency synthesizers, one output selected by a suitable method is applied to the modulator 208,
Define the frequency of the modulator output.

Traffic data supplied from the terrestrial line 102 passes through the terrestrial line connection device 36, is converted into a data burst by the burst forming circuit 206, and is modulated onto a carrier wave by the modulator 208. Normally, the modulator output is applied to the earth station device 32 and is transmitted to the satellite after frequency conversion and high power amplification, but in the present invention, an attenuator 210 is provided at the output of the modulator 208, By controlling the amount of attenuation using the output of the attenuator control circuit 216, the output power of the carrier wave from the earth station device 32 is controlled.

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 consideration.

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 driven by a symbol clock 350 and a frame period decoder 304; a reset pulse 352, which is the output of the decoder 304,
A frame period counter is realized by resetting 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 set of code words consisting of timing information, control information I, and control information ■. 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 count number of the binary counter 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 from the event. Each indicates the operating state until 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 I of the code word is applied to the control content decoder 314, the content is translated, and the AND gate 31
Let one of the numbers 6 be "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? allill is latched into latch circuit 330 by match pulse 356 and held until the next match pulse occurs. The output of this latch 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 event 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 lower digits of the K-digit binary counter 302 are based on timing and
It is applied to the decoder 305 to generate a timing pulse 357 every 2L counts, resulting in an event pulse 358 when any of the AND gates 316 are open.

On the other hand, the contents of the counter 302 (K-L) digits are used as an address signal for the RAM 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 40 with attenuation of B, 8dB,...
2゜404, 406, 408 are connected in series, and each attenuator is equipped with switches So, Sl, S2゜S3,
It is accompanied by a bypass circuit that is opened and closed by... 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, the control circuit 410 is simply a decoder, which allows the modulator output 112 and the end station output 114 to be connected by opening and closing the bypass switch appropriately. 1d from OdB to 15dB between
Any attenuation can be created with the B step.

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 diode attenuator 414 is used in series. As a method of obtaining a bias voltage to be applied to the PIN diode, this figure shows an example in which the output of the ROM circuit 432, which is read out using the attenuator control signal 116 as an address signal, is converted by the D/A converter 422.

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 output of the launch circuit 330 in FIG. 4 or 5, ie, the control information (2) in the burst time plan data, is used as the control information. 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, and the attenuator direct control information 126 Supplied as. however,
In such applications, the attenuation is typically delivered in large steps, such as 3 dB or 5 dB, so the control information 126 is
, and will be converted by converter 508 into an attenuator control signal 116 representing the actual amount of attenuation.

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 the identification code of the destination station, the identification code of the transmission burst, or some of them included in the control information (2) and used as an address signal. The attenuation amount is stored in the RAM circuit in correspondence with the address signal, and the information about the read out attenuation amount becomes the attenuator control signal 116 via the converter 508. 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. R.A.
The M circuit 506 is normally used for reading only, but for example, if there is heavy rain around a certain earth station and it is necessary to amplify the transmission power only for bursts directed to that earth station,
When there is a change in the operating conditions, the information supplied as data line information 122 is decoded by the attenuation setting processor 502 having a micro-brossasse, and is stored in the TDMA frame with the help of the RAM control circuit 504. By rewriting the corresponding data during a period when the RAM circuit is not being read, it is possible to adapt it to 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]

FIG. 1 is a control circuit configuration diagram of the present invention, and FIGS. 2(a) and (
b) is a block diagram showing the principle of the multi-carrier TDMA communication system, FIG. 3 is a diagram of the principle of the system to which the present invention is applied, and FIG. 4 is a block diagram of an example of the burst time plan utilization circuit used in the present invention. Figure 5 shows the burst time
A block diagram of another example of the plan utilization circuit, FIG. 6 is a block diagram of an example of an attenuator circuit used in the present invention, FIG. 7 is a block diagram of another example of the attenuator circuit, and FIG. 8 is a block diagram of another example of the attenuator circuit used in the present invention. FIG. 2 is a block diagram of the configuration of an attenuator control circuit which is the main part of the attenuator control circuit. 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 ... Memory arm, 204 ... Frame period counter, 206 High speed forming circuit, 208
... Modulator, 210 ... Attenuator, 212 ... Oscillator, 216 ... Attenuator control circuit. 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 modulator and its It has an attenuator that controls the output level of the modulator and an attenuator control circuit that controls the attenuator.
A variable TDMA satellite communication device characterized in that the output power changes 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 output power TDMA satellite communication device according to claim 1, wherein the variable output power TDMA satellite communication device is controlled by information read 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 transmission burst in the burst time plan. Variable output 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 output power TDMA satellite communication according to claim 1, characterized in that the variable output power TDMA satellite communication is controlled by information read out from this storage circuit in accordance with transmission carrier selection information in the burst time plan. Device.