Signal processing device, signal processing system, and signal processing method

Abstract

Provided is a signal processing device for processing an Internet telephone signal using a communication satellite. The purpose of the present invention is to, when multiple call requests are made, ensure communication quality by limiting the number of calls without worsening the congestion state in an uplink direction from a terminal station to a base station. A signal processing device 12 is provided with an uplink signal identification unit 38 that identifies a user ID included in a call request from a user terminal 10. A call information management unit 52 causes an uplink signal control unit 40 to permit a call from the user ID if the relation of b < S is established between the number b of users during calls and the upper limit S of the number of simultaneous usage. If b ≥ S, the uplink signal control unit 40 is caused to abolish the call request, and a call management signal generation unit 58 is caused to notify the user terminal 10 corresponding to the user ID of a state of waiting for a call and a waiting order.

Description

[Technical Field]

[0001] The present disclosure relates to a signal processing device, a signal processing system, and a signal processing method suitable for carrying out Internet telephone communications using a communications satellite. [Background technology]

[0002] Fig. 1 shows an example of the configuration of a communication system using a communication satellite. In Fig. 1, a user terminal 10 such as a smartphone is connected to a terminal station 14 via a terminal station signal processing device 12. The terminal station 14 can establish communication with a base station 18 via a communication satellite 16. The base station 18 can establish a connection with a communication partner terminal 24 via a base station signal processing device 20 and the Internet 22.

[0003] 1, communication data can be transmitted and received in both the uplink direction from the terminal station 14 to the base station 18 and the downlink direction from the base station 18 to the terminal station 14. If a voice call application is installed in the user terminal 10 and the communication partner terminal 24, calls via Internet telephone are also possible.

[0004] Internet telephony is a type of VoIP (Voice over Internet Protocol) telephony. It does not use a dedicated IP telephone network, but rather uses the Internet to enable calls using voice calling apps on social networking services (SNS). In this case, calls are not managed using telephone numbers.

[0005] Figure 2 shows an example of Internet telephone communication in a satellite communication system using a communication satellite 16. Multiple user terminals 10 exist under the control of a terminal station 14. Each of the multiple user terminals 10 makes an Internet telephone call at random times. The communication speed of an Internet telephone call using an SNS app such as LINE (registered trademark) phone depends on the app, but the average speed is approximately 50 kbps. On the other hand, communication speeds in the satellite section are generally very slow.

[0006] Therefore, when multiple user terminals 10 simultaneously request upstream communication for Internet telephone, the amount of upstream data may exceed the communication speed of the satellite section. If the amount of data exceeds the satellite section, the excess data is randomly discarded.

[0007] For example, Non-Patent Document 1 discloses a disaster response satellite communications system with an upstream communication capacity of 384 kbps. If more than seven user terminals 10, each with a communication speed of 50 kbps, use the system simultaneously, the satellite section's capacity will be insufficient, resulting in random data discards. Such discarded communication data will degrade the quality of Internet telephone calls for all users. Therefore, to prevent deterioration of telephone quality, it is necessary to prevent data discards.

[0008] To prevent data from being discarded, it is effective to reduce the number of user terminals 10 that are used simultaneously. However, it is difficult to control the actual number of user terminals 10 in use. Therefore, a method can be considered in which the terminal station signal processing device 12 recognizes a user ID, such as an IP address, assigned to each user terminal 10, and sets an upper limit on the number of users who are allowed to access simultaneously.

[0009] An example of this operation is shown in Figure 3. In the example shown in Figure 3, the terminal station signal processing device 12 recognizes the user IDs of the user terminals 10 and sets an upper limit on the number of user terminals 10 that can be used simultaneously. If the number of user terminals 10 requesting simultaneous use exceeds a preset upper limit, the communication data of the user IDs corresponding to the portion exceeding the upper limit is discarded. This operation makes it possible to fit the amount of data in uplink communication from the user terminals 10 within the communication capacity of the satellite section, and ensures the quality of communication data that is permitted for use. [Prior art documents] [Non-patent literature]

[0010] [Non-Patent Document 1] "Quality Evaluation of SNS in Disaster Management Satellite Communication Systems," Mitsuru Nishino, Fumiaki Nagase, Koichi Harada, Daiki Shibayama, Fumihiro Yamashita, Nippon Telegraph and Telephone Corporation, NTT Access Network Service Systems Laboratories, 2021 Institute of Electronics, Information and Communication Engineers General Conference, Proceedings of the IEICE Communications Conference 1, p. 221, March 9, 2021 Summary of the Invention [Problem to be solved by the invention]

[0011] However, if an upper limit is placed on the number of user terminals 10 permitted to be used simultaneously and control is exercised to prevent that number from exceeding the upper limit, a user who requests a call when the number of users exceeds the upper limit will be unable to start the call. In such a case, a user who is subject to a usage restriction will not necessarily give up on the call request and wait. Rather, a user who is subject to a usage restriction is likely to repeatedly request a call until a call is available, which will further increase the call volume and likely worsen congestion on the uplink from the terminal station 14 to the base station 18.

[0012] Figure 4 shows an example of a case where congestion worsens in the uplink direction from terminal station 14 to base station 18. Let a be the number of call requests from user terminal 10, b be the number of users currently in conversation, and S be the upper limit for the number of users allowed to simultaneously use the Internet telephone. Call request a from user terminal 10, a-(Sb), is dropped. The dropped user cannot make the call. If the dropped user of a-(Sb) tries to re-call rather than giving up, the number of call requests will increase, further worsening the congestion.

[0013] The present invention has been made in view of the above-mentioned problems, and its primary object is to provide a signal processing device that, when a large number of call requests are made in an Internet telephone system using a communications satellite, limits the number of calls and ensures call quality without worsening the congestion in the uplink direction from the terminal station to the base station.

[0014] Moreover, a second object of the present invention is to provide a signal processing system that restricts the number of calls without deteriorating the upward convergence state from the terminal station to the base station when a large number of call requests occur in an Internet phone using a communication satellite, thereby ensuring call quality.

[0015] Furthermore, a third object of the present invention is to provide a signal processing method for restricting the number of calls without deteriorating the upward convergence state from the terminal station to the base station when a large number of call requests occur in an Internet phone using a communication satellite, thereby ensuring call quality.

Means for Solving the Problems

[0016] A first aspect is a signal processing apparatus for processing signals of an Internet phone using a communication satellite, which identifies a user ID included in a call request received from a subordinate user terminal, when a relationship of b < S holds between the number of users b in a call and the upper limit S of simultaneous use, permits a call for the user ID, when a relationship of b ≥ S holds between b and S, discards the call request and notifies the user terminal corresponding to the user ID that it is in a call waiting state and the waiting order, when the relationship of b < S holds, notifies the user terminal corresponding to the user ID at the head of the call waiting queue that it can accept a call request, and is preferably configured to execute the above.

[0017] Also, a second aspect is a signal processing system for providing an Internet phone using a communication satellite, which includes a signal processing apparatus, and a user terminal belonging to the subordinate of the signal processing apparatus, where the signal processing apparatus identifies a user ID included in a call request received from the user terminal, When the relationship b < S holds between the number of users b in a call and the upper limit S of concurrent usage, a process of permitting a call to the user ID, and When the relationship b ≥ S holds between b and S, discarding the call request and notifying the user terminal corresponding to the user ID of being in a call waiting state and the waiting order; When the relationship b < S holds, a process of notifying the user terminal corresponding to the user ID located at the head of the call waiting list that it can receive a call request; It is desirable to be configured to execute.

[0018] Further, a third aspect is a signal processing method for providing an Internet phone using a communication satellite, a step in which a signal processing device identifies a user ID included in a call request received from a user terminal belonging to the signal processing device; a step in which the signal processing device permits a call to the user ID when the relationship b < S holds between the number of users b in a call and the upper limit S of concurrent usage; a step in which the signal processing device discards the call request when the relationship b ≥ S holds between b and S, and notifies the user terminal corresponding to the user ID of being in a call waiting state and the waiting order; a step in which the signal processing device notifies the user terminal corresponding to the user ID located at the head of the call waiting list that it can receive a call request when the relationship b < S holds; It is desirable to include.

Advantages of the Invention

[0019] According to the first to third aspects, when a large number of call requests occur in an Internet phone using a communication satellite, the number of calls can be limited without deteriorating the upward convergence state from the terminal station to the base station. For this reason, according to these aspects, the call quality of the Internet phone using a communication satellite can always be kept good.

Brief Description of the Drawings

[0020] [Figure 1] 1 shows an example of the configuration of a communication system using a communication satellite. [Figure 2] 1 shows an example of Internet telephone communication in a satellite communication system using a communication satellite. [Figure 3] An example of operation in a satellite communication system when an upper limit is set on the number of users who are allowed to simultaneously access a terminal station signal processing device will be described. [Figure 4] An example of a case where congestion worsens in the uplink direction from a terminal station to a base station in a satellite communication system will be described. [Figure 5] FIG. 1 is a diagram illustrating a configuration of a signal processing system according to a first embodiment of the present disclosure. [Figure 6A] 1 shows an example of an active call list used in the first embodiment of the present disclosure. [Figure 6B] 1 shows an example of a call waiting list used in the first embodiment of the present disclosure. [Figure 7] 1 is a flowchart illustrating a processing flow in the first embodiment of the present disclosure. [Figure 8] 10 is a flowchart illustrating a processing flow according to a second embodiment of the present disclosure. [Figure 9] FIG. 10 is a diagram illustrating the configuration of a signal processing system according to a third embodiment of the present disclosure. [Figure 10] 10 is a timing chart for explaining a modified example in which SIP messages are used for call management of Internet telephone calls. DETAILED DESCRIPTION OF THE INVENTION

[0021] Embodiment 1 [Configuration of the First Embodiment] The first embodiment of the present disclosure can be used in the satellite communication system described with reference to Fig. 1. Fig. 5 is a block diagram for explaining a configuration unique to the system of the first embodiment of the present disclosure. In Fig. 5, elements common to elements shown in Fig. 1 are assigned the same reference numerals.

[0022] 5, the system of this embodiment includes a user terminal 10, a terminal station signal processing device 12, and a terminal station 14. The terminal station 14 can establish wireless communication in both uplink and downlink directions with a satellite network 30 including the communication satellite 16 shown in FIG.

[0023] The user terminal 10 includes a transmitter 32 and a receiver 34. The terminal station signal processing device 12 includes an uplink receiver 36 that receives signals input from the transmitter 32 of the user terminal 10, an uplink signal identifier 38 that identifies the uplink signal, an uplink signal controller 40 that controls the uplink signal, and an uplink transmitter 42 that sends the controlled uplink signal to the terminal station 14. The terminal station signal processing device 12 also includes a downlink receiver 44 that receives downlink signals from the terminal station 14, a downlink signal identifier 46 that identifies the downlink signal, a downlink signal controller 48 that controls the downlink signal, and a downlink transmitter 50 that transmits the controlled downlink signal to the receiver 34 of the user terminal 10.

[0024] The terminal station signal processing device 12 further includes a call information management unit 52 that manages call information. The call information management unit 52 includes an active call list 54 and a call waiting list 56. More specifically, the call information management unit 52 includes storage that stores the active call list 54 and the call waiting list 56. The terminal station signal processing device 12 includes a call management signal generation unit 58 that can access the storage.

[0025] The call management signal generation unit 58 generates a call management signal by referring to the active call list 54 and the call waiting list 56 stored in the storage. The call management signal generation unit 58 can provide the generated call management signal to the user terminal 10 via the downlink transmission unit 50.

[0026] An example of the traffic control operation in this embodiment will be described below with reference to the same figure. In FIG. 5, when a call request signal is input from the user terminal 10 to the terminal station signal processing apparatus 12, the upstream signal identification unit 38 identifies the user ID of the user terminal 10. Then, the upstream signal identification unit 38 notifies the call information management unit 52 of the occurrence of the call request and the user ID.

[0027] Upon receiving the above notification, the call information management unit 52 checks the in-call list 54 and the call waiting list 56.

[0028] FIG. 6A shows an example of the in-call list 54 stored in the call information management unit 52. As shown in the figure, here, the user ID of the calling user terminal 10, the user ID of the called terminal, and the confirmation time of the call start signal are recorded in serial numbers.

[0029] FIG. 6B shows an example of the call waiting list 56 stored in the call information management unit 52. As shown in the figure, here, the user ID of the call request source user terminal 10 and the confirmation time of the call request signal are recorded in serial numbers.

[0030] The call information management unit 52 compares the number b of users in the call with the upper limit number S that allows simultaneous use. When b < S, it instructs the upstream signal control unit 40 to pass a signal requesting a call. As a result, the user terminal 10 becomes in a state where a call can be started.

[0031] Thereafter, when the upstream signal identification unit 38 detects a call start signal of the corresponding user ID, it notifies the call information management unit 52 of the user ID in the call. The call information management unit 52 registers the user ID in the call in the in-call list 54 and adds 1 to the number b of users in the call.

[0032] The upstream signal identification unit 38 then, when it detects an end call signal of the corresponding user ID, notifies the call information management unit 52 of the user ID that ended the call. Upon receiving this notification, the call information management unit 52 deletes the user ID that ended the call from the in-call list 54 and subtracts 1 from the number b of users in the call.

[0033] When the call information management unit 52 receives a notification of the occurrence of a call request from the uplink signal identification unit 38 and the condition b≧S is satisfied, it instructs the uplink signal control unit 40 to discard the request signal for starting communication and registers the corresponding user ID at the end of the call waiting list 56. Further, the call information management unit 52 instructs the call management signal generation unit 58 to notify the corresponding user terminal 10 of the state of being in the call waiting state and the information indicating the waiting order. The call management signal generation unit 58 notifies the user terminal 10 of the corresponding user ID via the downlink transmission unit 50 with the signal generated in response to the instruction.

[0034] The in-call list 54 and the call waiting list 56 synchronize information as appropriate. For example, if the user ID located at the head of the call waiting list is added to the in-call list 54, the user ID is deleted from the call waiting list 56. The call information management unit 52 periodically acquires the latest information from those lists and checks whether the corresponding user ID can make a call request. That is, it checks whether the relationship b<S holds and whether the corresponding user ID is located at the head of the call waiting list 56. When it is confirmed that a call request is possible, the call management signal generation unit 58 is instructed to notify the corresponding user terminal 10 that the reception of a call request is possible, and the corresponding user ID is deleted from the call waiting list. The call management signal generation unit 58 notifies the user terminal 10 of the corresponding user ID via the downlink transmission unit 50 with the signal generated in response to the instruction.

[0035] Note that even when the corresponding user ID cannot make a call request, the user terminal 10 may be periodically notified of the call waiting state and the information representing the waiting order.

[0036] In this embodiment, the user determines the timing to transmit a call request signal based on his or her own judgment based on the information such as the call waiting state and the waiting order transmitted from the call management signal generation unit 58. Therefore, if the user does not make a call request even after the user terminal 10 of the corresponding user ID receives the notification, the call is not started. When the user issues a call request again, the user will go to the end of the waiting queue.

[0037] [Operation of Embodiment 1] FIG. 7 is a flowchart showing the flow of the above-described processing executed in the terminal station signal processing apparatus 12 of the present embodiment. As shown in the figure, when the terminal station signal processing apparatus 12 confirms a call request signal from the user terminal 10 (step 100), it acquires the latest information from the in-call list 54 (step 102), and compares the number of users b in the call with the upper limit S of the simultaneous use number (step 104).

[0038] If the latest b acquired from the in-call list 54 satisfies the relationship b < S, the call request signal is passed through (step 106). Thereafter, when a call start signal is confirmed (step 108), the user ID in the call is registered in the in-call list 54, and the value of b is incremented by 1 (step 110).

[0039] Thereafter, the in-call state is continued until an end call signal is confirmed. When the end call signal is confirmed (step 112), the user ID of the ended call is deleted from the in-call list 54, and the value of b is decremented by 1 (step 114).

[0040] On the other hand, in step 104 above, when it is determined that the relationship b ≧ S holds for the latest b, the call request signal is discarded, and the corresponding user ID is registered at the end of the call waiting list 56. Further, it is notified to the user terminal 10 of the corresponding user ID that it is in the call waiting state and the information of its order (step 116).

[0041] Thereafter, the latest information is periodically acquired from the list (step 118), and it is confirmed that the corresponding user ID is call-requestable, that is, b < S holds, and the corresponding user ID is at the head of the call waiting list 56 (step 120). When that state can be confirmed, it is notified to the user terminal 10 of the corresponding user ID that the call request can be received, and the corresponding user ID is deleted from the call waiting list 56 (step 122).

[0042] As described above, even if the user ID is not available to make a call request, the user terminal 10 may be periodically notified that it is in a call waiting state and information regarding the order of waiting.

[0043] As described above, in this embodiment, by recognizing the user ID of the user terminal 10, it is possible to create a busy list 54 that manages the number of active users b and their user IDs, and a waiting list 56 that manages the number of waiting users and their user IDs. Using the information in these lists, users can be notified of their waiting status and their waiting order. Receiving such notification allows the user to appropriately control upstream traffic to avoid unnecessary repeated call re-attempts and maintain good call quality. Therefore, according to the system of this embodiment, when the number of call requests from the user terminal 10 increases in an Internet telephone system using a communication satellite 16, it is possible to appropriately limit the number of calls and ensure good call quality without worsening upstream congestion.

[0044] In the first embodiment described above, the user ID is managed for each user terminal 10, but the present disclosure is not limited to this. For example, the user ID may be managed for each internet telephone call, that is, for each call. This also applies to the other embodiments described below.

[0045] Furthermore, in the above-described first embodiment, when b≧S, the call information management unit 52 registers the corresponding user ID in the call waiting list 56 without checking the status of the call waiting list 56, but the present disclosure is not limited to this. For example, when b≧S, it may be possible to check whether the corresponding user ID is already registered in the call waiting list 56 before registering the corresponding user ID in the call waiting list 56. If the corresponding user ID is not already registered, the corresponding user ID may be registered at the end of the call waiting list. On the other hand, if the corresponding user ID is already registered, the registration may be deleted first, and then the corresponding user ID may be registered at the end of the call waiting list 56.

[0046] Embodiment 2 Next, a second embodiment of the present disclosure will be described with reference to Fig. 8 in addition to Fig. 1 and Fig. 5. Similar to the first embodiment, the second embodiment of the present disclosure can be used in the satellite communication system described with reference to Fig. 1. The system of this embodiment can be realized by causing the terminal station signal processing device 12 shown in Fig. 5 to execute processing in accordance with the flowchart shown in Fig. 8 instead of the flowchart shown in Fig. 7 above.

[0047] In the first embodiment described above, when the call information management unit 52 determines that b≧S, it registers the corresponding user ID in the call waiting list 56 without checking the status of the call waiting list 56. In contrast, in the present embodiment, when it determines that b≧S, it checks whether the corresponding user ID is already registered in the call waiting list 56 before registering the corresponding user ID in the call waiting list 56. If the corresponding user ID is not already registered, it registers the ID at the end of the call waiting list, whereas if the corresponding user ID is already registered, it temporarily deletes the registration and then registers the corresponding user ID at the end of the call waiting list 56.

[0048] Fig. 8 is a flowchart for explaining the flow of processing executed by the terminal station signal processing device 12 in this embodiment to realize the above-mentioned functions. In Fig. 8, the same steps as those shown in Fig. 7 are denoted by the same reference numerals, and their explanations are omitted or simplified.

[0049] 8, when it is determined in step 104 that b≧S, the call request signal is discarded as in the first embodiment, and the corresponding user ID is checked against the call waiting list 56 (step 130). If the corresponding user ID has already been registered in the call waiting list 56 (step 132), the registration is deleted (step 134), and the corresponding user ID is registered again at the end of the call waiting list 56 (step 136).

[0050] A user who is waiting for a call will avoid making unnecessary call requests if each time he or she requests a call, his or her waiting position drops to the bottom of the queue. In other words, according to this embodiment, the user can be encouraged to refrain from making further call requests until he or she receives notification that the call request can be accepted. Therefore, according to this embodiment, it is possible to more efficiently avoid worsening of the congestion state compared to the first embodiment, and to provide the user with even better call quality.

[0051] Embodiment 3 Next, a third embodiment of the present disclosure will be described with reference to Fig. 9 together with Fig. 1. Similar to the first embodiment, the third embodiment of the present disclosure can be used in the satellite communication system described with reference to Fig. 1.

[0052] Fig. 9 is a block diagram for explaining a configuration unique to the system according to the second embodiment of the present disclosure. In Fig. 9, elements corresponding to those explained with reference to Fig. 5 are given the same reference numerals, and their explanation will be simplified or omitted.

[0053] As shown in FIG. 9 , in the system of this embodiment, the user terminal 10 includes a terminal call management application 60. The terminal call management application 60 has a function of recognizing information on the call waiting state and waiting order transmitted from the call management signal generation unit 58 of the terminal station signal processing device 12, and autonomously issuing a call request signal at an appropriate timing. More specifically, upon receiving a signal indicating that the call request can be accepted from the call management signal generation unit 58, the terminal call management application 60 promptly retransmits the communication request. Therefore, in this embodiment, it is possible to initiate a call with the user terminal 10 of the corresponding user ID at an appropriate timing, thereby freeing the user from the hassle of having to voluntarily issue a re-request at an appropriate time.

[0054] [Modifications of the First to Third Embodiments] FIG. 10 is a timing chart for explaining a technique for using SIP (Session Initiation Protocol) messages to manage calls over the Internet. SIP is generally used to manage calls over the Internet. In this case, SIP messages can be used as the user IDs and the like used in the first to third embodiments. Specifically, for example, the IP address information included in (0) REGISTER can be used as the user ID. (1) INVITE can be used as a call request signal. Also, (4) ACK can be used as a call start signal. Furthermore, (7) 200 OK following (6) BYE can be used as a call termination signal.

[0055] Furthermore, in the above-described first to third embodiments, a specific user is permitted to continue a call for a long period of time, but the present disclosure is not limited to this. For example, by using the call start signal confirmation time recorded in the call in progress list 54, if a certain period of time has elapsed, frames may be forcibly discarded and the call for the corresponding ID may be terminated. [Explanation of symbols]

[0056] 10 User terminal 12 Terminal station signal processing device 14 Terminal Station 16. Communications satellites 18 base station 52 Call information management department 54 Call List 56 Call waiting list 58 Call management signal generation section 60 Device call management app

Claims

1. A signal processing device for processing signals for Internet telephone using a communication satellite, A process of identifying a user ID included in a call request received from a subordinate user terminal; A process of permitting a call to be made to the user ID when a relationship b<S is established between the number of users currently on a call b and the maximum number of simultaneous users S; a process of discarding the call request when a relationship of b≧S is established between the b and the S, and notifying the user terminal corresponding to the user ID of a call waiting state and the waiting order; a process of notifying a user terminal corresponding to a user ID at the head of a call queue that a call request can be accepted when the state where the relationship b≧S is satisfied changes to a state where the relationship b<S is satisfied; a process of waiting for a call request from the user terminal that provided the notification in the same manner as for call requests from other user terminals after notifying that the call request can be accepted; a signal processor configured to perform

2. The signal processing device includes: Equipped with storage for a list of active calls, a process of adding 1 to the sequence number of the busy list when a call start signal from the user terminal is confirmed; a process of subtracting 1 from the serial number of the busy list when a call-end signal from the user terminal is confirmed; A process of reading the call number b from the serial number of the busy call list; The signal processing apparatus of claim 1 further configured to perform:

3. The signal processing device includes: It has storage for a call waiting list, a tail registration process for registering the user ID included in the discarded call request at the tail of the call waiting list if b≧S; a process of deleting the user ID that has been notified that the call request can be accepted from the call waiting list; A process of reading the waiting order of the user ID from the information of the call waiting list; 3. A signal processing apparatus according to claim 1 or 2, further configured to perform the following:

4. The last registration process is a process of determining whether the user ID included in the discarded call request has been registered in the call waiting list; If the user ID is already registered in the call waiting list, the registration is deleted and the user ID is registered at the end of the call waiting list; The signal processing device according to claim 3 , comprising:

5. A signal processing system for providing internet telephone using a communications satellite, comprising: a signal processing device; a user terminal that belongs to the control of the signal processing device, The signal processing device includes: A process of identifying a user ID included in a call request received from the user terminal; A process of permitting a call to be made to the user ID when a relationship b<S is established between the number of users currently on a call b and the maximum number of simultaneous users S; a process of discarding the call request when a relationship of b≧S is established between the b and the S, and notifying the user terminal corresponding to the user ID of a call waiting state and the waiting order; a process of notifying a user terminal corresponding to a user ID at the head of a call queue that a call request can be accepted when the state where the relationship b≧S is satisfied changes to a state where the relationship b<S is satisfied; a process of waiting for a call request from the user terminal that provided the notification in the same manner as for call requests from other user terminals after notifying that the call request can be accepted; a signal processing system configured to perform

6. 1. A signal processing method for providing Internet telephony using a communications satellite, comprising: a step of identifying a user ID included in a call request received by a signal processing device from a user terminal under the control of the signal processing device; a step of allowing the user ID to make a call when a relationship of b<S is established between the number of users currently in communication b and the maximum number of simultaneous users S; a step in which the signal processing device discards the call request when a relationship b≧S is established between the b and the S, and notifies the user terminal corresponding to the user ID of a call waiting state and the waiting order; when the state where the relationship b≧S is satisfied changes to a state where the relationship b<S is satisfied, notifying a user terminal corresponding to a user ID located at the head of a call queue that a call request can be accepted; a step of waiting for a call request from the user terminal that provided the notification in the same manner as for call requests from other user terminals, after notifying that the call request can be accepted; A signal processing method comprising:

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