CN105812046B - A kind of realization system and method for satellite mobile communication system heartbeat message - Google Patents

Abstract

A system and method for realizing heartbeat messages of a satellite mobile communication system. The system includes a ground control center and a user machine. The ground control center configures the control parameters corresponding to the incoming heartbeat message for the user machine, and calculates the user's geographic location according to the received heartbeat message. , transmit power adjustment, and update the state of the user machine, and then send the configured heartbeat message control parameters and/or user position and/or transmit power adjustment results calculated according to the heartbeat message to the user machine; the user machine receives the configuration of the ground control center heartbeat message control parameters, and send the heartbeat message according to the instruction of the heartbeat message sending unit. By sending the inbound heartbeat message from the user machine, the ground control center can obtain the user's location, transmission power and status information quickly and in real time; and reduce the overhead of heartbeat signaling while ensuring a certain power control accuracy; at the same time, due to the heartbeat message The bit length is very short, which is beneficial to enhance the battery life and battery life of the user machine.

Description

System and method for realizing heartbeat message of satellite mobile communication system

technical field

The invention relates to the technical field of satellite mobile communication, and more specifically, to a method for realizing heartbeat messages of satellite mobile communication.

Background technique

The satellite mobile communication system is mainly composed of the space segment, the ground control center and the user segment. The space segment is composed of a satellite constellation containing several satellites. These satellites (outbound transponder, inbound transponder) forward Outbound signals and inbound signals from user machines. The ground control center completes user signal transmission and reception measurement and information transmission and reception processing, and manages and controls the operation of the entire system. The user segment refers to the user terminal with the function of sending and receiving satellite signals, which receives data services and control messages from the ground control center, and sends inbound messages according to its own business needs and outbound control signaling to realize positioning, timing, short-term Message communication and other functions.

In the field of satellite communication, the transmission power of the user machine is very important, and the accuracy of power control will affect the following two requirements: 1. Sufficient per-bit transmission energy required to achieve Quality of Service; 2. Minimum Minimizing interference with other users of the system and maximizing user equipment battery life/range. To achieve this, UE transmit power control must be adaptive to wireless propagation channel characteristics, including path loss, shadow fading, fast fading, and interference from other UEs.

At present, a communication system often adopts a closed-loop power control method to control the transmission power of the user equipment. Uplink closed-loop power control method: closed-loop power control needs to be completed jointly by the network side and the user. There is a feedback control loop in the closed-loop power control process. The network layer equipment receives the average carrier-to-noise ratio (C/N) _means,ul from the user equipment, and compares it with the required carrier-to-noise ratio (C/N) _threshold,ul , giving a command that the user equipment needs to increase or decrease the transmit power. Specifically, if (C/N) _means,ul <(C/N) _threshold,ul , the network side sends to the user equipment a power control command that increases the transmission power by a step value, and after receiving the command, the user equipment, Increase its own transmit power by a step value; otherwise, the network side device sends a power control command to the user equipment to reduce the transmit power value by a step value, and the user equipment reduces its own transmit power by one step after receiving the command. step value. The network side and the user go back and forth according to this rule.

Closed-loop power control can better adapt to channel changes, but requires the user equipment to send messages more frequently, and the network side equipment receives and measures the signal quality sent by the user equipment, and then feeds back the power adjustment command to the user equipment, so that real-time Changes in the upper channel are tracked, but this increases the signaling overhead of the user equipment to a certain extent.

In addition, the inbound signal of the active Beidou Phase I RDSS satellite communication system consists of three parts: synchronization header, service segment and data segment. Among them, the known pilot sequence is modulated on the synchronization head, which is used by the central station to capture and track the inbound signal; the control signaling of this inbound message is modulated on the service section, which is used to assist the demodulation of the subsequent data section; The data segment carries the specific service content of this inbound information, and the length of the data segment is variable. It can be seen that, regardless of the message type, each inbound message needs to carry a complete service segment. For some inbound messages that need to be sent frequently, the service segment carries too much redundant information, resulting in a decrease in the battery life/endurance of the user equipment and inbound capacity.

Contents of the invention

For satellite communication systems, in order to improve the communication efficiency and inbound capacity of inbound messages, it is necessary to reduce the signaling overhead of non-data services. The invention provides a system and method for realizing the heartbeat message of the satellite mobile communication system for the satellite communication system. The ground control center can realize the closed-loop power control, rough positioning and state monitoring of the user machine in real time and quickly according to the received heartbeat message.

Technical scheme of the present invention is:

A system for realizing a heartbeat message of a satellite mobile communication system is characterized in that it includes a ground control center and a user machine, and the ground control center is used to configure the control parameters corresponding to the incoming heartbeat message for the user machine, and calculate according to the received heartbeat message The user's geographic location, the amount of transmission power adjustment, and updating the state of the user machine, and then send the configured heartbeat message control parameters and/or the user position and/or transmission power adjustment results calculated according to the heartbeat message to the user machine; the user machine It is used for receiving the heartbeat message control parameters configured by the ground control center, and sending the heartbeat message according to the instructions of the heartbeat message sending unit.

Wherein, the ground control center includes an inbound heartbeat message receiving unit, a heartbeat message control signaling configuration unit, a heartbeat message processing unit and a control parameter sending unit; the inbound heartbeat message receiving unit is used to receive the heartbeat signal sent by the user machine; The message control signaling configuration unit is used to configure the control parameters corresponding to the heartbeat signal for the user machine; the heartbeat message processing unit is used to process the heartbeat message to obtain the position of the user machine, the amount of transmission power adjustment and the status information of the satellite link; the control parameters The sending unit is used to notify the user machine of the results of the heartbeat message control signaling configuration unit and the heartbeat message processing unit;

The user machine includes an outbound signal measurement unit, an outbound heartbeat message control signaling receiving unit, a heartbeat message timer unit and an inbound message sending unit; the outbound signal measurement unit is used to measure the received downlink signal power level and/or or signal quality; the outbound heartbeat message control signaling receiving unit is used to analyze the control signaling of the inbound heartbeat message issued by the ground center station; the heartbeat message timer unit is used to set the heartbeat message sending cycle and sending time; the inbound The message sending unit is used to send the heartbeat message, and at the same time feed back the sending time to the heartbeat message timer unit.

Based on the system for realizing the heartbeat message of the satellite mobile communication system, the present invention also provides a method for realizing the heartbeat message of the satellite mobile communication system, specifically: the user machine sends the heartbeat message periodically and/or triggered by an event, and the heartbeat message The message contains the synchronization header and the duty segment, and the effective information of the duty segment includes the user address and/or locked outbound beam number; after receiving the heartbeat message sent by the user machine, the ground control center performs active positioning on the heartbeat message to obtain the user's or the ground control center obtains the adjustment amount of the transmission power of the user machine by calculating the quality of the heartbeat signal, and decides whether to feed back the power adjustment amount to the corresponding user machine, so as to realize the closed-loop power control of the user machine transmission power; or the ground The control center quickly obtains the satellite link status of the current user computer through the heartbeat message.

In the present invention, the heartbeat message includes a synchronization header and a service section, the synchronization header is used for the ground center station to capture and track the inbound heartbeat signal, the service section message contains a user address and a service beam, and the user address is used to instruct the user The identity of the service beam is used for active positioning of the user machine.

In the present invention, the user machine sends a heartbeat message triggered by an event means that when the heartbeat message timer unit of the user machine times out or the service beam is switched, the user machine sends a heartbeat message, so that the ground control center can update the user machine location, transmission power and satellite link status information; when the heartbeat message timer unit of the user machine does not expire and the service beam does not switch, the user machine does not send a heartbeat message.

In the present invention, the restarting method of the heartbeat message timer unit of the user machine is: the user machine just restarts the heartbeat message timer unit every time an inbound message is sent, and the inbound message includes a heartbeat message and a non-heartbeat message; when the heartbeat message timer When the unit times out, the user machine sends a heartbeat message and restarts the heartbeat message timer unit; or every time the user machine sends a heartbeat message, it restarts the heartbeat message timer unit.

In the present invention, the configuration method of the duration of the heartbeat message timer unit of the user machine is: the ground control center configures the duration of the heartbeat message timer unit according to the number of real-time online users and the inbound flow, and periodically passes the outbound link to The updated heartbeat message timer unit duration is broadcast to all user machines; or the ground control center periodically broadcasts the current system inbound flow or inbound load to all users, and the user machines are based on the preset system inbound flow or load and heartbeat The corresponding relationship between the duration of the message timer determines the duration of the current heartbeat message timer.

In the present invention, the outbound signal measurement unit of the user machine receives and measures the signal average power level <P _i > and signal quality of each outbound beam in real time, and the signal quality is defined by the carrier-to-noise ratio <CNR _i > or the signal-to-noise ratio <SNR _i > to represent; if the outbound beam with the best signal quality received by the user machine is higher than the specified threshold compared with the signal quality of the current service beam, the following formula is satisfied:

〈SNR _{non-serving beam, i} 〉-〈SNR _{serving beam} 〉＞Threshold

Then the current serving beam will be switched to the new outbound beam with the best signal quality.

In the present invention, the ground control center adopts the RDSS positioning method to obtain the geographic location of the user machine after receiving the heartbeat message sent by the user machine, and the specific steps are:

Step 101: The ground control center receives multiple copies of the same heartbeat message forwarded inbound by the user machine via different satellite i, and measures the arrival time T _Rx,i of each inbound heartbeat message, thereby calculating the time between sending the outbound signal and receiving the user The space propagation delay ΔT _i required for the machine to respond to its outbound signal:

Receive-send time difference ΔT _i = the time when the ground control center receives the inbound signal from the user machine T _{Rx, i} - the time when the ground control center transmits the outbound message T _Tx

Step 102: The ground control center calculates the user position according to the following formula:

Where (X _{control center} , Y _{control center} , Z _{control center} ) is the position coordinates of the ground control center; (X _i , Y _i , Z _i ) is the position coordinates of satellite i, X ₀ , Y ₀ , Z ₀ ) is the user (X _{user machine} , Y _{user machine} , Z _{user machine} ) are the position coordinates of the user machine to be requested.

In the present invention, the ground control center obtains the adjustment amount of the transmission power of the user machine by calculating the quality of the heartbeat signal, and decides whether to feed back the power adjustment amount to the corresponding user machine. The specific method is:

Step 201: The ground control center calculates the carrier-to-noise ratio CNR _true or signal-to-noise ratio SNR _true corresponding to the inbound heartbeat message, and compares it with the target carrier-to-noise ratio CNR _target or target signal-to-noise ratio SNR _target , and the difference between the two is the user machine Transmit power adjustment ΔP:

ΔP = CNR _target – CNR _true

Alternatively, ΔP = SNR _Target – SNR _True

ΔP is a positive number, which means that the user machine needs to increase the transmission power, and ΔP is a negative number, which means that the user machine needs to reduce the transmission power;

Step 202: The ground control center decides whether to feed back the transmission power adjustment amount to the corresponding user machine according to the current outbound channel resource and the size of ΔP;

If the absolute value of ΔP is lower than the threshold M, that is, |ΔP|≤M, the ground control center does not feed back the adjustment amount of the transmit power of the corresponding user machine; if |ΔP|>M, the ground control center sends the adjustment amount according to the specified quantization accuracy.

The beneficial effects of the present invention are:

By sending the inbound heartbeat message from the user machine, the ground control center can quickly and real-time obtain user location, transmission power and status information; and while ensuring a certain power control accuracy, it can reduce the overhead of heartbeat signaling; at the same time, due to The bit length of the heartbeat message is very short, which is beneficial to enhance the battery life and battery life of the user machine.

Description of drawings

Fig. 1 is a schematic diagram of the message structure of the heartbeat message sent by the user machine provided by the embodiment of the present invention

2 is a schematic diagram of the workflow of the heartbeat signal sending unit of the user machine provided by the embodiment of the present invention;

Fig. 3 is the flow chart of calculating the geographical position of the user machine by using the RDSS positioning method after the ground control center receives the heartbeat message of the user machine provided by the embodiment of the present invention;

Fig. 4 is a flow chart of calculating the user machine power adjustment amount after the ground control center receives the user machine heartbeat message provided by the embodiment of the present invention;

Fig. 5 is a schematic structural diagram of a user machine provided by an embodiment of the present invention;

Fig. 6 is a schematic structural diagram of a ground control center provided by an embodiment of the present invention;

Fig. 7 is a schematic structural diagram of a heartbeat message sending and receiving system provided by an embodiment of the present invention.

Detailed ways

Below in conjunction with accompanying drawing, the present invention will be further described:

Fig. 1 is a schematic diagram of the message structure of the heartbeat message sent by the user machine provided by the technology of the present invention. The heartbeat message includes two parts, a synchronization header and a service segment. The synchronization head is used by the ground central station to capture and track the inbound heartbeat signal, and the service segment message contains the user address (used to indicate the identity of the user), and the service beam (used for active positioning of the user machine).

Fig. 2 is a schematic diagram of the work flow of sending a heartbeat message from a user machine provided by the technology of the present invention, including the following functions:

Whether the user machine sends a heartbeat message is jointly determined by whether the heartbeat message timer unit of the user machine times out and whether the service beam is switched.

When the heartbeat message timer unit of the user machine times out or the service beam is switched, the user machine sends a heartbeat message, so that the ground control center can update the user machine position, transmission power and satellite link status information. When the heartbeat message timer unit of the user machine does not time out and the service beam does not switch, the user machine does not send a heartbeat message.

On the one hand, the method for restarting the heartbeat message timer unit of the user machine is:

Every time the user machine sends an inbound message, the inbound message includes a heartbeat message and a non-heartbeat message, and the heartbeat message timer is restarted; when the heartbeat message timer expires, the user machine sends a heartbeat message and restarts the heartbeat message timer.

or,

Every time the user computer sends a heartbeat message, the heartbeat message timer is restarted.

Further, the configuration method of the user machine heartbeat message timer duration can be:

The ground control center configures the duration of the heartbeat message timer according to the number of real-time online users and inbound traffic, and periodically broadcasts the updated duration of the heartbeat message timer to all user machines through the outbound link. For example, if the current inbound traffic is large and the number of online users is large, you can configure a longer heartbeat message timer to avoid inbound congestion; otherwise, you can configure a shorter heartbeat message timer.

or,

The ground control center regularly broadcasts the current system inbound traffic or inbound load to all users, and the user machine determines the current heartbeat message timer according to the corresponding relationship between the preset system inbound traffic or load and the heartbeat message timer duration. duration.

or,

The user machine determines the length of its own heartbeat message timer according to the current heartbeat message timer broadcast by the ground control center, or the inbound traffic or inbound load of the system, and combines the state of the user machine itself to determine the length of its own heartbeat message timer. The timer duration is lower than recommended by the ground control center. Wherein, the state of the user machine itself may be the current remaining battery capacity, the set power usage mode, the geographical environment, etc. For example, when the current remaining power of the user machine is lower than a certain threshold, in order to save power, the user machine can choose a longer duration than the timer recommended by the ground control center; or when the user machine is set to power saving mode, the user machine You can also choose a longer duration than the timer recommended by the ground control center; or when the user machine detects that the outbound channel quality status is relatively stable for a long time, this situation is common in fixed user machines, or the moving speed is slow And for the user machine in an open area, the user machine can also choose a longer duration than the timer recommended by the ground control center. Since the state of each user machine may be different, the duration of the heartbeat message timer of each user machine may also be different.

On the other hand, the switching method of the outbound service beam of the user machine is:

The outbound signal quality measurement unit of the user machine receives and measures the signal average power level 〈P _i 〉 and signal quality of each outbound beam in real _{time .} express. If the outbound beam with the best signal quality received by the user machine is higher than the specified threshold compared with the signal quality of the current service beam, the following formula is met:

〈SNR _{non-serving beam, i} 〉-〈SNR _{serving beam} 〉＞Threshold

Then the current serving beam will be switched to the new outbound beam with the best signal quality.

Fig. 3 is a flow chart of calculating the geographical location of the user computer by using the RDSS positioning method after the ground control center receives the heartbeat message of the user computer.

Step 101: The ground control center receives multiple copies of the same heartbeat message forwarded inbound by the user machine via different satellite i, and measures the arrival time T _Rx,i of each inbound heartbeat message, thereby calculating the time between sending the outbound signal and receiving the user The space propagation delay ΔT _i required for the machine to respond to its outbound signal:

Receive-send time difference ΔT _i = the time when the ground control center receives the inbound signal from the user machine T _{Rx, i} - the time when the ground control center transmits the outbound message T _Tx

Step 102: The ground control center calculates the user position according to the following formula:

Where (X _{control center} , Y _{control center} , Z _{control center} ) is the position of the ground control center, which is a known value; (X _i , Y _i , Z _i ) is the position of satellite i, and (X ₀ , Y ₀ , Z ₀ ) is the satellite position to which the outbound service beam of the user machine belongs, and is also a known value; (X _{user machine} , Y _{user machine} , Z _{user machine} ) is the desired user machine position.

Fig. 4 is a flow chart of obtaining and processing the power adjustment amount of the user machine after the ground control center receives the heartbeat message of the user machine.

Step 201: The ground control center calculates the carrier-to-noise ratio CNR _true or signal-to-noise ratio SNR _true corresponding to the inbound heartbeat message, and compares it with the target carrier-to-noise ratio CNR _target or target signal-to-noise ratio SNR _target , and the difference between the two is the user machine Transmit power adjustment ΔP:

ΔP = CNR _target – CNR _true

Alternatively, ΔP = SNR _Target – SNR _True

ΔP is a positive number, which means that the user machine needs to increase the transmission power, otherwise, it means that the user machine needs to reduce the transmission power.

Step 202: The ground control center decides whether to feed back the transmission power adjustment amount to the corresponding user machine according to the current outbound channel resource and the size of ΔP. If the outbound channel resource is relatively tight or the absolute value of ΔP is lower than the threshold M, ie |ΔP|≤M, the ground control center may not feed back the transmit power adjustment amount of the corresponding user machine. If the outbound channel resource is sufficient and |ΔP|>M, the ground control center sends the adjustment amount at a certain quantization granularity, for example, assuming M=3dB, the quantization granularity is 0.5dB, |ΔP|=3.61, then the power adjustment amount is 3.5dB.

In addition, the ground control center can obtain the latest service beam number from the inbound heartbeat message, which can be used to update the service beam number information in the user machine status, preferably as the outbound beam of the user machine.

In the embodiment of the present invention, by sending an inbound heartbeat message from the user machine, the ground control center can obtain user location, transmission power and status information quickly and in real time. Moreover, compared with non-heartbeat messages, the bit length of heartbeat messages is very short, which is beneficial to enhance the battery life and battery life of the user machine.

Those of ordinary skill in the art can understand that all or part of the steps in the above-mentioned embodiments can be implemented by hardware related to program instructions, and the above-mentioned program can be stored in a computer-readable storage medium, and the above-mentioned storage medium can be a ROM/ RAM, Disk, CD, etc.

FIG. 5 shows a user machine provided by an embodiment of the present invention, capable of implementing the method for realizing heartbeat messages of a satellite mobile communication system provided by the above-mentioned method embodiments of the present invention. The user machine includes: an outbound signal quality measurement unit, an outbound heartbeat message control signaling receiving unit, a heartbeat message timer unit, and an inbound signal sending unit. Among them: the outbound signal quality measurement unit is used to measure the signal power level and/or signal quality of each outbound beam received, if the outbound beam with the best signal quality received by the user machine and the signal quality of the current service beam If it is higher than the specified threshold, the current service beam is switched to the outbound beam with the best signal quality, and the inbound signal sending unit is triggered at the same time to send a heartbeat message; the outbound heartbeat message controls the signaling receiving unit for Analyze the control signaling of the inbound heartbeat message issued by the ground center station to configure the duration of the heartbeat message timer; the heartbeat message timer unit is used to set the heartbeat message sending cycle and sending time, when the heartbeat message timer expires , trigger the inbound signal sending unit to send a heartbeat message, and restart the heartbeat message timer; the inbound signal sending unit, when beam switching occurs or the heartbeat message timer times out, trigger the inbound signal sending unit to send a heartbeat message, and at the same time The sending time is fed back to the heartbeat message timer unit, and the heartbeat message timer is restarted immediately.

FIG. 6 shows a ground control center provided by an embodiment of the present invention, capable of realizing the implementation method of the heartbeat message of the satellite mobile communication system provided by the above-mentioned method embodiments of the present invention. The ground control center includes an inbound heartbeat message receiving unit, a heartbeat message control signaling configuration unit, a heartbeat message processing unit and a control parameter sending unit. Among them, the inbound heartbeat message receiving unit is used to receive the heartbeat signal sent by the user machine; the heartbeat message control signaling configuration unit is used to configure the control parameters corresponding to the heartbeat signal for the user machine; The message is processed to obtain information such as the position of the user machine, the amount of transmission power adjustment, and the status of the satellite link. The control parameter sending unit is configured to notify the user equipment of the results of the heartbeat message control signaling configuration unit and the heartbeat message processing unit.

Embodiments of the present invention also provide a system for realizing a heartbeat message of a satellite mobile communication system, as shown in FIG. 7 , including a ground control center and a user machine;

The ground control center is used to configure the control parameters corresponding to the inbound heartbeat message for the user machine, and calculate the user's geographic location, transmit power adjustment, and update the state of the user machine according to the received heartbeat message, and then set the configured heartbeat message control parameters And/or send the user position and/or transmit power adjustment results calculated according to the heartbeat message to the user machine;

The user machine is configured to receive the heartbeat message control parameters configured by the ground control center, and send the heartbeat message according to the instructions of the heartbeat message sending unit.

It should be noted that the drawings and related descriptions are only for illustrating the principles of the present invention, and are not intended to limit the protection scope of the present invention. For example, message names and entities in the embodiments of the present invention may vary according to different networks, and some messages may also be omitted. Therefore, any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present invention are included in the protection scope of the present invention. Although the present invention has been illustrated and described with reference to the embodiments of the present invention, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit of the present invention. and range.

Claims (8)

1. A system for realizing a heartbeat message of a mobile satellite communication system, characterized in that it includes a ground control center and a user machine, and the ground control center is used to configure the control parameters corresponding to the incoming heartbeat message for the user machine, and according to the received heartbeat The message calculates the user's geographic location, the transmission power adjustment amount, and updates the state of the user machine, and then sends the configured heartbeat message control parameters and/or the user position and/or transmission power adjustment results calculated according to the heartbeat message to the user machine; the user The machine is used to receive the heartbeat message control parameters configured by the ground control center, and send a heartbeat message according to the heartbeat message control parameters; the ground control center includes an inbound heartbeat message receiving unit, a heartbeat message control signaling configuration unit, a heartbeat message The processing unit and the control parameter sending unit; the inbound heartbeat message receiving unit is used to receive the heartbeat signal sent by the user machine; the heartbeat message control signaling configuration unit is used to configure the control parameters corresponding to the heartbeat signal for the user machine; the heartbeat message processing unit is used for By processing the heartbeat message, the location of the user machine, the amount of transmission power adjustment and the status information of the satellite link are obtained; the control parameter sending unit is used to notify the user machine of the results of the heartbeat message control signaling configuration unit and the heartbeat message processing unit; The user machine includes an outbound signal quality measurement unit, an outbound heartbeat message control signaling receiving unit, a heartbeat message timer unit and an inbound signal sending unit; the outbound signal quality measurement unit is used to measure the received downlink signal power level Peace and/or signal quality; the outbound heartbeat message control signaling receiving unit is used to analyze the control signaling of the inbound heartbeat message issued by the ground central station; the heartbeat message timer unit is used to set the heartbeat message sending cycle and sending time; The inbound signal sending unit is used to send a heartbeat message, and at the same time feed back the sending time to the heartbeat message timer unit. 2. A method for realizing the heartbeat message of a mobile satellite communication system, characterized in that: the user machine periodically and/or is triggered by an event to send a heartbeat message, the heartbeat message includes a synchronization header and a duty segment, and the effective duty segment Messages containing user addresses and/or locked outbound beam numbers; After receiving the heartbeat message sent by the user machine, the ground control center performs active positioning on the heartbeat message to obtain the geographic location of the user machine. The method is as follows: Step 101: The ground control center receives multiple copies of the same heartbeat message forwarded inbound by the user machine via different satellite i, and measures the arrival time T _Rx,i of each inbound heartbeat message, thereby calculating the time between sending the outbound signal and receiving the user The space propagation delay ΔT _i required for the machine to respond to its outbound signal: Receive-send time difference ΔT _i = the time when the ground control center receives the inbound signal from the user machine T _{Rx, i} - the time when the ground control center transmits the outbound message T _Tx Step 102: The ground control center calculates the user position according to the following formula: Where (X _{control center} , Y _{control center} , Z _{control center} ) is the position coordinates of the ground control center; (X _i , Y _i , Z _i ) is the position coordinates of satellite i, X ₀ , Y ₀ , Z ₀ ) is the user The satellite position coordinates to which the machine's outbound service beam belongs; (X _{user machine} , Y _{user machine} , Z _{user machine} ) are the position coordinates of the user machine to be requested; Or the ground control center obtains the adjustment amount of the transmit power of the user machine by calculating the quality of the heartbeat signal, and decides whether to feed back the power adjustment amount to the corresponding user machine, so as to realize the closed-loop power control of the transmit power of the user machine; Or the ground control center quickly obtains the satellite link status of the current user machine through the heartbeat message. 3. the realization method of satellite mobile communication system heartbeat message according to claim 2, it is characterized in that: described heartbeat message comprises synchronous header and service section, and synchronous header is used for ground central station to capture and track inbound heartbeat signal , the service segment message includes a user address and a service beam, the user address is used to indicate the identity of the user, and the service beam is used for active positioning of the user machine. 4. The method for realizing the heartbeat message of the satellite mobile communication system according to claim 3 is characterized in that: the user machine sends the heartbeat message triggered by an event and refers to when the heartbeat message timer unit of the user machine is overtime or the service beam is switched , the user machine sends a heartbeat message, so that the ground control center can update the user machine location, transmission power and satellite link status information; when the heartbeat message timer unit of the user machine does not time out and the service beam does not switch, the user machine does not send a heartbeat information. 5. the method for realizing the heartbeat message of the satellite mobile communication system according to claim 4 is characterized in that: the method that the heartbeat message timer unit of the user machine restarts is: the user machine sends an inbound message every time, just restarts the heartbeat message timing The inbound messages include heartbeat messages and non-heartbeat messages; when the heartbeat message timer unit times out, the user machine sends a heartbeat message and restarts the heartbeat message timer; or the user machine restarts the heartbeat message every time it sends a heartbeat message timer unit. 6. the method for realizing the heartbeat message of the satellite mobile communication system according to claim 4 is characterized in that: the configuration method of the heartbeat message timer unit duration of the user machine is: the ground control center according to the number of real-time online users and the inbound flow To configure the duration of the heartbeat message timer unit, and periodically broadcast the updated heartbeat message timer unit duration to all user machines through the outbound link; or the ground control center periodically broadcasts the current system inbound traffic or inbound flow to all users Load condition, the user machine determines the duration of the current heartbeat message timer according to the preset corresponding relationship between the system inbound flow or load condition and the duration of the heartbeat message timer. 7. the method for realizing the heartbeat message of the satellite mobile communication system according to claim 4 is characterized in that: the outbound signal quality measurement unit of the user machine receives and measures the signal average power level <P _i > and the signal average power level of each outbound beam in real time Signal quality, signal quality is represented by carrier-to-noise ratio <CNR _i > or signal-to-noise ratio <SNR _i >; if the outbound beam with the best signal quality received by the user machine is higher than the signal quality of the current service beam The specified threshold Threshold satisfies the following formula: <SNR _{non-serving beam,i} >-<SNR _{serving beam} >>Threshold Then the current serving beam will be switched to the new outbound beam with the best signal quality. 8. the method for realizing the heartbeat message of the satellite mobile communication system according to claim 2, is characterized in that: the ground control center obtains the adjustment amount of user machine transmission power by calculating the heartbeat signal quality, and decides whether to feed back the power adjustment amount to The corresponding user machine, the specific method is: Step 201: The ground control center calculates the carrier-to-noise ratio CNR _true or signal-to-noise ratio SNR _true corresponding to the inbound heartbeat message, and compares it with the target carrier-to-noise ratio CNR _target or target signal-to-noise ratio SNR _target , and the difference between the two is the user machine Transmit power adjustment ΔP: ΔP = CNR _target – CNR _true Alternatively, ΔP = SNR _Target – SNR _True ΔP is a positive number, which means that the user machine needs to increase the transmission power, and ΔP is a negative number, which means that the user machine needs to reduce the transmission power; Step 202: The ground control center decides whether to feed back the transmission power adjustment amount to the corresponding user machine according to the current outbound channel resource and the size of ΔP; If the absolute value of ΔP is lower than the threshold M, that is, |ΔP|≤M, the ground control center will not feed back the adjustment amount of the transmission power of the corresponding user machine; if |ΔP|>M, the ground control center will send the adjustment amount according to the set quantization accuracy .