JP2000332671A - Satellite communication simulation system and its method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a satellite communication simulation system for satisfactorily and efficiently simulating satellite communication, and for reducing the economical load of a system evaluator. SOLUTION: A satellite communication simulation system is provided with two global stations constituted of a master station 4 and a slave station 5. A simulator 6 is connected with the slave station 5. The simulator 6 generates plural calls between set pseudo global stations. The slave station 5 transmits a line connection request signal for requesting the line connection of a generated call through a satellite control line 2 to the master station 4. The master station 4 receives the line connection request signal, and executes line assignment processing, and assigns a free satellite communication line 3 to the call. Thus, the simulation of the line assignment of the plural pseudo calls generated in a traffic simulator 6 can be attained by using the satellite line set between the two global stations. Therefore, a call loss rate can be evaluated by the small number of global stations and in a form close to an real operation system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a satellite communication simulation system and method for simulating satellite communication in order to evaluate a blocking rate of a satellite communication system.

[0002]

2. Description of the Related Art Conventionally, a satellite communication system for realizing satellite communication between communication devices connected to any of a plurality of earth stations has been known. In this type of satellite communication system, when a satellite communication line is established, a random access system such as a slot Aloha system is usually applied. That is, each earth station sends out a control signal for establishing a line via a satellite control line in synchronization with an arbitrary slot timing.

Therefore, control signals may be transmitted from different earth stations at the same slot timing. In this case, the control signals collide with each other. When the control signals collide with each other, the earth station that has received the control signal requests the earth station that has transmitted the collided control signal to retransmit the control signal.

As described above, in a satellite communication system, a line is not always established only by sending a control signal once from an earth station, but rather, a line is established only after sending a control signal a plurality of times. There are many. In this case, the probability that retransmission is requested in response to a line establishment request is called a call blocking rate.

[0005] The call loss rate varies depending on the system environment such as the number of earth stations accommodated in the satellite communication system, the number of satellite communication lines, and a channel allocation algorithm. Therefore, when constructing a satellite communication system, it is necessary to simulate satellite communication under a certain system environment and review the system environment so as to obtain a desired call loss rate.

A simulation technique for satellite communication is disclosed in, for example, Japanese Patent Application Laid-Open Nos. 3-52337 and 2-20
No. 5123. The technology disclosed in these publications is to virtually construct a satellite line in a computer and simulate satellite communication using the virtually constructed satellite line.

[0007]

That is, the technique disclosed in the above publication does not simulate satellite communication using an actual satellite communication line. On the other hand, when a satellite communication is simulated using an actual satellite communication line, the simulation can be performed in a form closer to the actual satellite communication. Therefore, the technology disclosed in the above publication may not be able to sufficiently evaluate satellite communication.

To cope with this, it is conceivable to install a plurality of earth stations and simulate satellite communication using the installed earth stations. However, considering that a satellite communication system is constructed in accordance with the simulation result, simulating using the actual operation system imposes an inefficient and large economic burden on the system evaluator. In particular, since earth stations generally cost millions to tens of millions of yen,
If the number of installed earth stations has to be reduced to obtain the desired call loss rate, the earth stations are wasted. Therefore, the economic burden on the system evaluator becomes extremely large.

Accordingly, an object of the present invention is to solve the above-mentioned technical problems, to simulate satellite communication satisfactorily and efficiently, and to reduce the economic burden on a system evaluator. It is to provide.

[0010]

SUMMARY OF THE INVENTION In order to achieve the above object, according to the present invention, a minimum number of earth stations required for setting up a satellite communication line and a satellite control line via a communication satellite are installed. For any of the installed earth stations, a traffic simulator that generates a plurality of calls each having a predetermined hold time at a predetermined occurrence interval is connected,
When a call is generated from this traffic simulator, an earth station to which the traffic simulator is connected requests another earth station to perform line connection of the call via the satellite control line by a random access method, and When a line connection is requested in another earth station, a line allocation process is executed, a vacant satellite communication line is searched, and if there is a vacancy, the vacant satellite communication line is allocated to the call.

[0011]

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

Embodiment 1 FIG. 1 is a conceptual diagram showing a configuration of a satellite communication simulation system according to Embodiment 1 of the present invention. This satellite communication simulation system simulates satellite communication in order to construct a satellite communication system having a desired call loss rate. In this case, the satellite communication system to be simulated applies a random access method such as a slot aloha method when establishing a line.

More specifically, the satellite communication simulation system includes two earth stations 4 which are the minimum numbers required for setting up a satellite communication line 2 and a satellite control line 3 via a communication satellite 1. , 5 are installed, and a satellite communication is simulated between the two earth stations 4 and 5 using the satellite control line 2 and the satellite communication line 3. The system evaluator refers to this simulation result and refers to the number of earth stations accommodated in the satellite communication system,
Design the number of satellite communication lines and the channel allocation algorithm. In this way, a satellite communication system having a desired call loss rate is constructed.

More specifically, the satellite communication simulation system includes two earth stations 4 and 5, a communication satellite 1, and a traffic simulator 6. 2
The earth stations 4 and 5 are respectively installed at different positions on the earth. Each of the earth stations 4 and 5 sets up a satellite control line 2 and a satellite communication line 3 via a communication satellite 1, and transmits a control signal and a communication signal via the set satellite control line 2 and the satellite communication line 3, respectively. Send and receive.

The earth stations 4 and 5 respectively include aperture antennas 4a and 5a for satellite communication and TDMA (Time Division Multiple
tiple Access) devices 4b, 5b and DAMA (Demand A)
ssign Multiple Access) devices 4c and 5c.
The TDMA devices 4b and 5b modulate and demodulate control signals and communication signals transmitted and received by the earth stations 4 and 5, respectively. For example, when transmitting a control signal, TDMA
After modulating the control signal, the devices 4b and 5b transmit the modulated signal at a timing synchronized with a predetermined time slot. The TDMA devices 4b and 5b can be connected to a terrestrial communication network (not shown) via terrestrial interfaces 4d and 5d, respectively.

The DAMA devices 4c and 5c allocate the satellite communication line 3 when there is a line connection request. One of the two DAMA devices 4c functions as a parent device, and the other 5c functions as a child device. Therefore, hereinafter, for convenience, the earth station 4 having the DAMA device 4c as a parent device is referred to as a “master station 4”, and the DAMA device 4
c is referred to as “master station DAMA device 4c”. Also, the earth station 5 having the DAMA device 5c as a child device is referred to as a "child station 5".
And the DAMA device 5c is referred to as “slave station DAMA device 5”.
c ".

The master station DAMA device 4c manages the assignment status of a plurality of set satellite communication lines 3. On the other hand, the slave station DAMA device 5c requests the master station DAMA device 4c to connect a call line via the satellite control line 3. The master station DAMA device 4c executes a line assignment process in response to a request from the slave station DAMA device 5c, searches for a free satellite communication line, and if it is free, assigns that line to the call.

The traffic simulator 6 is provided in the slave station 5 among the two earth stations 4 and 5. More specifically, the traffic simulator 6 is connected to the slave station DAMA device 5b by wire. The traffic simulator 6 virtually constructs a plurality of pseudo earth stations inside,
A plurality of calls are generated in a simulated manner. Specifically, the traffic simulator 6 arbitrarily selects two stations from the number of pseudo earth stations set by the system evaluator, and transmits the selected one pseudo earth station to the other pseudo earth station. Then, a call is generated in a pseudo manner in response to the start timing of the occurrence interval set by the system evaluator. In response to the elapse of the hold time set by the system evaluator, the traffic simulator 6 terminates the call for which the hold time has elapsed.

The call generated by the traffic simulator 6 is given to the slave station DAMA device 5b. Slave station D
The AMA device 5b creates a line connection request signal for the call, and sends the created line connection request signal to the satellite control line 2.
To the master station 4 via TDMA device 4b of master station 4
Demodulates the received line connection request signal to restore the line connection request data, and provides the restored line connection request data to the master station DAMA device 4c. Master station DAMA device 4
In step c, an available line is checked based on the given line connection request data as described above.

FIG. 2 is a block diagram showing the internal configuration of the traffic simulator 6. The traffic simulator 6 includes a keyboard 10, a condition setting unit 11, a call generation unit 12, a communication station number setting unit 13, a call termination unit 14, and a signaling processing unit 15. The keyboard 10
This is for the system evaluator to input simulation conditions. The simulation conditions include the assumed number of pseudo earth stations, call occurrence intervals, and hold time. The system evaluator sets the call generation interval according to the number of stations. That is, the system evaluator sets a large occurrence interval if the number of stations is small, and sets a small occurrence interval if the number of stations is large. In addition, the system evaluator refers to the average time during which the line is actually used in telephone and data communication, and sets the average time as the hold time. The simulation condition input from the keyboard 10 is given to the condition setting unit 11.

The condition setting unit 11 gives the input simulation conditions to the call generation unit 12, the communication station number setting unit 13 and the call termination unit 14 according to the type. In particular,
The condition setting unit 11 sets the input occurrence interval to the call generation unit 12
Give to. Also, the condition setting unit 11 gives the input number of stations to the communication station number setting unit 13. Further, the condition setting unit 1
1 gives the input hold interval to the call termination unit 14.

The call generating unit 12 generates a call according to the given occurrence interval. Specifically, the call generation unit 12 generates a random number based on the given occurrence interval so that the occurrence interval becomes an average value. The call generation unit 12 generates a call using the generated random number as the generation timing of the call. The call generating unit 12 gives the generated call to the communication station number setting unit 13.

The communication station number setting section 13 associates the call given by the call generation section 12 with the communication station number of the earth station to be transmitted / received. Specifically, the communication station number setting unit 13
Extracts two communication station numbers at random from the number of communication station numbers corresponding to the given number of stations, and uses the extracted two communication station numbers as a calling station and a called station, respectively, for the call. Associate with The communication station number setting unit 13 gives the call associated with the communication station number to the signaling processing unit 14. The signaling processing unit 14 instructs the slave station DAMA device 5b to create a line connection request signal corresponding to the call associated with the given communication station number.

The call termination unit 14 sets the hold time of each call based on the hold time given from the condition setting unit 11. Specifically, the call termination unit 11 generates a random number based on the given hold time so that the hold time becomes an average value. The call termination unit 14 sets the generated random number as a hold time of the call. The call termination unit 14 instructs the signaling processing unit 15 to terminate the call in response to the timing when the hold time has elapsed. When the call termination is instructed, the signaling processing unit 15 instructs the slave station DAMA device 5b to create a call termination request signal.

FIG. 3 is a flowchart for explaining the operation of the satellite communication simulation system. First, the system evaluator inputs simulation conditions via the keyboard 10 (step S1). The call generating unit 12 generates a random number based on the occurrence interval among the input simulation conditions, and generates a call (Step S).
2). The communication station number setting unit 13 selects any two stations as a calling station and a called station from the input simulation conditions based on the number of stations, and generates the communication station numbers of the two stations in the call generation unit 12. (Step S)
3). The signaling processing unit 15 includes the communication station number setting unit 1
In step 3, the slave station DAMA device 5b is instructed to create a line connection request signal for the call associated with the communication station number.

The slave station DAMA device 5b creates a line connection request signal in response to this instruction. Slave station DAMA device 5
b transmits the created line connection request signal to the master station 4 via the satellite control line 2 (step S4). The master station 4 that has received the line connection request signal executes the line allocation process and checks for an empty line as described above. At this time, the master station DA
The MA device 4c executes a line assignment process according to the set line assignment algorithm (step S5).

More specifically, the master station DAMA device 4c checks whether or not the satellite communication line 3 is free in a time slot in TDMA when the line connection request signal is received. Line 3 is assigned to the call. At this time, the master station DAMA device 4c transmits a line assignment signal permitting use of the satellite communication line 3 to the slave station 4 via the satellite control line 2. On the other hand, if there is no vacant line in the time slot, the master station DAMA device 4c
Transmits a busy signal to the slave station 5 via the satellite control line 2 without permitting the assignment of the satellite communication line 3.

The TDMA device 5b of the slave station 5 demodulates the received signal to restore the data, and the DAMA device 5c
Give to. The slave station DAMA device 5c refers to the received data and determines whether or not the line assignment has been permitted (step S6). If there is no free line and the line assignment is not permitted (NO in step S6), the slave station DAMA device 5
c forcibly terminates the call. On the other hand, if the line assignment is permitted (YES in step S6), the slave station DA
The MA device 5c executes pseudo communication via the permitted satellite communication line 3. Also, the slave station DAMA device 5
c indicates that the line assignment permission signal is
Give to.

The signaling processing unit 15 in the traffic simulator 6 transmits the line assignment permission signal to the call termination unit 1.
Give to 4. The call termination unit 14 generates a random number based on the hold time given from the condition setting unit 11 in response to the reception of the line assignment permission signal, and determines the hold time of the call (step S7). The call termination unit 14 starts measuring the determined hold time. When the hold time elapses, the call termination is notified via the signaling processing unit 15 to the slave station DAMA device 5.
Instruct c. When the termination of the call is instructed, the slave station DAMA device 5c creates a call termination request signal. Call center DAM
The A device 5c transmits the created call termination request signal to the master station 4 via the satellite control line 2 (step S8).

The TDMA device 4b of the master station 4 restores the call termination request data from the received call termination request signal, and supplies the restored call termination request data to the master station DAMA device 4c. The master station DAMA device 4c terminates the call when the call termination request data is given.

As described above, the traffic simulator 6 generates a plurality of calls based on the input occurrence intervals. Therefore, the above-described processing is performed for all of the plurality of calls generated by the traffic simulator 6. Therefore, the master station DAMA device 4c, which is required to connect the lines of a plurality of calls generated by the traffic simulator 6, can manage the line allocation status of all the calls. In this case, lines cannot be allocated for all calls, and lines may not be allocated depending on the call generation timing. That is, the master station DAMA device 4c can obtain call blocking rates for a plurality of calls generated by the traffic simulator 6.

However, the call loss rate obtained in this way may not always be the call loss rate desired by the system evaluator. This is because the line allocation algorithm and the number of satellite communication lines set in the master station DAMA device 4c and the traffic conditions (particularly the number of stations) set by the traffic simulator 6 may not be appropriate.

Therefore, the system evaluator changes the line allocation algorithm or changes the satellite communication algorithm if the call loss rate under the set line allocation algorithm and the number of satellite communication lines and traffic conditions (particularly the number of stations) is not the desired loss probability. After changing the number of lines or changing the traffic condition (particularly the number of stations), the above-described simulation processing is executed again. Then, the system evaluator compares the call loss rate in the simulation processing performed previously with the call loss rate in the simulation processing performed this time. By doing so, it is possible to finally obtain a satellite communication system having a desired call loss rate.

As described above, according to the first embodiment, since the actual satellite communication line 3 is used to evaluate the call loss rate of the satellite communication system, the call loss rate can be evaluated in a manner closer to the actual operation system. Therefore, highly reliable evaluation can be realized. In addition, it is only necessary to install the minimum number of earth stations necessary for setting the actual satellite control line 2 and satellite communication line 3. Therefore, the call loss rate can be evaluated efficiently and economically.

Embodiment 2 In the first embodiment, each call blocking rate under a plurality of set line allocation algorithms and / or simulation conditions is relatively evaluated. On the other hand, in the second embodiment, the call loss rate under an arbitrary simulation condition with respect to the call loss rate under the reference condition is absolutely evaluated.

The reference condition is a condition that there is no pseudo collision. Here, no pseudo collision means that the master station DAMA device 4c
In the line allocation processing in the above, when there is actually a free line, it is determined that there is a free line.

FIG. 4 is a conceptual diagram for explaining a channel assignment process in TDMA which is a communication system in the satellite communication simulation system. In FIG.
The horizontal direction indicates a time slot, and the vertical direction indicates a satellite communication line. In TDMA, a plurality of satellite communication lines can be assigned to one time slot. Therefore, the master station DAMA device 4c
Executes a line allocation process in units of time slots, and attempts to allocate any line in one time slot to a call for which line connection is requested.

In this case, assuming that there is a pseudo collision as in the first embodiment, the master station DAMA device 4c
May determine that there is no free line due to TDMA restrictions even when there is a free line. In particular,
If the satellite communication line 3 has already been assigned to the time slot for a call in which either the calling station or the earth station serving as the called station is the calling station or the called station, the parent The station DAMA device 4c determines that there is no line to be allocated to the call, even if there is an empty line in the time slot.

More specifically, in slot 1, a call from the earth station having the communication station number "3" to the earth station having the number "1" and the earth station having the communication station number "1" to the earth station having the number "4" are made. Are already assigned to the satellite communication lines 1 and 2, respectively. At this time, the communication station number "4"
When a call is made from the earth station to the earth station of "3", these earth stations are already the calling station and the called station on the lines 1 and 2, respectively. Therefore, the master station DAM
The A device 4c determines that there is no vacant line in the slot 1 even though the line 3 is vacant.

On the other hand, in the case where there is no pseudo collision, the master station DAMA device 4c determines that there is a line to be allocated to the call and allocates the empty line to the call even in the above case. That is, in the case of the above example, the master station DA
Since the line 3 in the slot 1 is vacant, the MA device 4c allocates the line 3 to the call from the earth station having the communication station number "4" to the earth station having the number "3".

As described above, when there is no pseudo collision, the master station DAMA device 4c determines that there is a free line when there is a free line, and manages the line allocation status. Therefore, the call blocking rate in this case is a very low value. Therefore,
In the second embodiment, an optimal line allocation algorithm and / or simulation conditions are obtained by comparing the reference loss ratio with various line allocation algorithms and / or loss ratios under simulation conditions based on the loss probability at this time. I have to do that.

More specifically, referring to FIG. 2, the system evaluator can input the presence or absence of a pseudo collision from the keyboard 10. Condition setting unit 11
Provides the input pseudo presence / absence information directly to the signaling processing unit 15 via the line 20. The signaling processing unit 15 sends the pseudo collision presence / absence information to the slave station DAMA.
It is given to the device 5c. The slave station DAMA device 5c creates a control signal containing information on the presence or absence of a pseudo collision, and transmits the created control signal to the master station 4 via the satellite control line 2. Upon receiving this control signal, the master station DAMA device 4c executes a line allocation process according to the presence or absence of the above-described pseudo collision.

As described above, according to the second embodiment, the presence / absence of a pseudo collision can be set in the traffic simulator 6, so that an absolute evaluation of the call blocking rate under various line allocation algorithms and / or simulation conditions can be performed. Therefore, the system evaluator:
The loss rate of the system can be evaluated well. Therefore, a satellite communication system having a desired call loss rate can be constructed.

Other Embodiments Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. For example, in the above embodiment, two earth stations 4 and 5 are installed.
More than one earth station may be installed.

[0045]

As described above, according to the present invention, the minimum number required to set up the actual satellite communication line and the satellite control line, that is, at least two earth stations are installed. Using a satellite control line set between the earth stations, to perform a line assignment process for a plurality of calls generated by the traffic simulator, and to establish a satellite communication set between the two earth stations installed for the call. Assign a line.

Therefore, the satellite communication can be simulated in a manner closer to the actual operation system than when the satellite communication is simulated only inside the computer. In addition, the satellite communication can be efficiently and economically simulated as compared with the case where all the earth stations are installed and the satellite communication is simulated.
Therefore, the call blocking rate of the satellite communication system can be efficiently and economically evaluated. Therefore, a satellite communication system can be constructed with high quality and at low cost.

If the traffic simulator can set the number of earth stations, the occurrence interval, and the hold time, the system evaluator can simulate satellite communication by combining various conditions. Therefore, the call blocking rate of the satellite communication can be compared between various conditions.
Therefore, the call loss rate of the satellite communication system can be evaluated well. Therefore, a satellite communication system can be constructed with high quality and at low cost.

Furthermore, if the presence or absence of a pseudo collision can be set in the traffic simulator, the call loss rate when there is no pseudo collision and the call loss rate when there is a pseudo collision can be compared. Therefore, the call blocking rate of the satellite communication system can be absolutely evaluated. Therefore, the call loss rate of the satellite communication system can be evaluated well. Therefore, a satellite communication system can be constructed with high quality and at low cost.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a configuration of a satellite communication simulation system according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing an internal configuration of a traffic simulator.

FIG. 3 is a flowchart for explaining the operation of the satellite communication simulation system.

FIG. 4 is a conceptual diagram for explaining a channel assignment process in TDMA according to Embodiment 2 of the present invention.

[Explanation of symbols]

1 communication satellite, 2 satellite control line, 3 satellite communication line,
4 earth station (master station), 4c DAMA device (master station DAMA
Device), 5 earth station (slave station), 5c DAMA device (slave station DAMA device), 6 traffic simulator, 1
0 keyboard, 11 condition setting unit, 12 call generation unit,
13 communication station number setting unit, 14 call termination unit.

Claims (5)

[Claims] 1. A minimum number of earth stations required to set up a satellite communication line and a satellite control line via a communication satellite are installed, and a predetermined number of earth stations are set to one of the installed earth stations. Connect a traffic simulator that generates a plurality of calls each having a hold time at predetermined occurrence intervals,
When a call is generated from this traffic simulator, an earth station to which the traffic simulator is connected requests another earth station to perform line connection of the call via the satellite control line by a random access method, and When a line connection is requested at another earth station, a line allocation process is executed, a vacant satellite communication line is searched, and if there is a vacancy, the vacant satellite communication line is allocated to the call. Satellite communication simulation system. 2. A system for simulating satellite communication in a satellite communication system to which a random access method is applied for channel assignment, comprising: a communication satellite, a satellite communication line and a satellite control line passing through the communication satellite. An earth station having at least one child earth station and one parent earth station installed as required for setting; and a plurality of calls connected to the child earth station and each having a predetermined hold time. And a traffic simulator that generates the traffic at a predetermined occurrence interval. The child earth station communicates with the parent earth station via the satellite control line by a random access method when a call is generated by the traffic simulator. Means for requesting a line connection for the call, and wherein the parent earth station receives a line connection from the child earth station. And a means for executing a line allocation process when a request is made, searching for a vacant satellite communication line and, if there is a vacancy, allocating the vacant satellite communication line to the call. Simulation system. 3. The traffic simulator according to claim 2, wherein the traffic simulator comprises: input means for inputting the number of pseudo earth stations defining the number of call occurrences, the occurrence interval of each call, and the hold time of each call; Call generation means for generating a call in accordance with the call generation interval of the call input by the user; and a call selected from the pseudo earth station input by the input means for the call generated by the call generation means. Number setting means for associating station numbers unique to the two pseudo earth stations serving as a calling station and a called station; and a hold time inputted by the input means elapses for a call associated with a station number by the number setting means. A satellite communication simulation system including a call output means provided to the slave earth station. 4. The method according to claim 3, wherein the input means inputs the presence or absence of a pseudo collision for instructing whether or not to determine that there is no free line due to the restriction of the communication system even if there is a free line in the line allocation processing. When the presence or absence of a pseudo collision is input by the input means, the child earth station notifies the parent earth station of the presence or absence of the pseudo collision via the satellite control line. Wherein the parent earth station, when notified of the presence or absence of a pseudo collision from the child earth station, executes a line allocation process according to the presence or absence of the pseudo collision. Simulation system. 5. A child earth station of a child earth station and a parent earth station installed at least one each as necessary for setting a satellite communication line and a satellite control line via a communication satellite. A satellite communication simulation method in a satellite communication simulation system to which a traffic simulator for generating a plurality of calls each having a predetermined hold time at a predetermined occurrence interval is connected, wherein a call is generated from the traffic simulator. In this case, the child earth station requests a line connection of the call via the satellite control line by a random access method from the child earth station to the parent earth station. Executes the allocation process, searches for a vacant satellite communication line, and if there is a vacancy, calls the vacant satellite communication line for the call. Satellite simulation method and allocating.