Intra-satellite switching method of low-orbit satellite system

Abstract

The invention discloses an in-satellite switching method for a low-earth-orbit satellite system, and relates to the technical field of low-earth-orbit satellite communication. According to the method, the on-satellite load receives the notification of the ground access gateway to enter the in-satellite switching state, the target beam is quickly established after the terminal reconfiguration message is sent through the source beam, and after the reconfiguration message ACK sent by the terminal on the target beam is received, the on-satellite load starts to execute the process of switching the source beam to the target beam, so that the switching time of the target beam is shortened. And meanwhile, data in the switching process is cached to an uplink and downlink data register, so that data transmission in the on-satellite load control switching process can be ensured. The method can be used for an in-satellite switching scene of a low-orbit satellite system, switching time delay of in-satellite switching can be effectively reduced, the process complexity of in-satellite switching is reduced, and meanwhile it is guaranteed that a terminal and an on-satellite load do not lose packets in transmission of a source beam and a target beam.

Description

Technical Field

[0001] The present invention relates to the technical field of low-orbit satellite communications, and in particular to an intra-satellite switching method for a low-orbit satellite system. Background Art

[0002] Satellites can be divided into low-orbit (LEO), medium-orbit (MEO) and high-orbit (GEO) satellites according to their orbital altitude. Low-orbit satellites are usually located at an altitude of 500-2000 kilometers above the earth's surface. Due to their low orbital position, low-orbit satellites have the advantages of smaller transmission delay, low link loss, greater flexibility, suitability for a variety of application scenarios, and low cost. However, since LEO is not in a geostationary orbit, satellite terminals may frequently switch beams within a single satellite or between different satellites when real-time connection is required.

[0003] At present, in the process of intra-satellite switching, the satellite terminal sends a reconfiguration message confirmation message (ie, ACK) on the source beam channel, and the onboard payload starts to configure the target beam channel only after the source beam channel receives the message. This process is highly complex, resulting in a long intra-satellite switching delay. In addition, the onboard payload does not have an uplink and downlink data register, resulting in uplink and downlink data packet loss during the process of switching from the source beam to the target beam. Summary of the invention

[0004] In view of this, the present invention proposes an intra-satellite switching method for a low-orbit satellite system. The present invention solves the problem of long switching time caused by the on-board payload waiting for the terminal to send a reconfiguration message ACK in the source beam channel, effectively reduces the switching delay of the intra-satellite switching, reduces the complexity of the intra-satellite switching process, and ensures that the terminal and the on-board payload do not lose packets on the channels of the source beam and the target beam.

[0005] The object of the present invention is achieved in that:

[0006] A low-orbit satellite system intra-satellite switching method is implemented based on a low-orbit satellite system consisting of a satellite terminal, an on-board payload, a ground access gateway and a ground core network; the method comprises the following steps:

[0007] (1) The satellite terminal reports the measurement result and sends an uplink RRC direct transmission message to the ground access gateway through the on-board payload. The ground access gateway triggers the intra-satellite handover process and sends a terminal context modification request message to the on-board payload. The terminal context modification request message includes the channel configuration of the target beam and the RRC reconfiguration message of the satellite terminal.

[0008] (2) After receiving the terminal context modification request message, the onboard payload verifies whether the source beam channel and the target beam channel exist. If not, a terminal context modification failure message is sent to the ground access gateway to end the process. If so, the intra-satellite switching timer is started.

[0009] (3) The onboard payload sends an RRC reconfiguration message to the satellite terminal through the source beam channel. At the same time, the onboard payload caches the terminal uplink data received through the source beam channel into the uplink data register.

[0010] (4) The onboard payload immediately establishes the target beam channel and receives the RRC reconfiguration message confirmation message replied by the satellite terminal on the target beam channel;

[0011] (5) After receiving the RRC reconfiguration message, the satellite terminal switches from the source beam to the target beam according to the configuration of the ground access gateway, and replies with an RRC reconfiguration message confirmation message in the target beam channel;

[0012] (6) After the onboard payload receives the RRC reconfiguration message confirmation message replied by the satellite terminal, go to step (7); if the onboard payload does not receive the RRC reconfiguration message confirmation message replied by the satellite terminal in the target beam channel within the intra-satellite switching timer, then after the intra-satellite switching timer times out, go to step (7);

[0013] (7) The onboard payload caches the terminal uplink data received on the target beam channel into the uplink data register, and caches the downlink data sent by the ground access gateway through the source beam into the downlink data register; then, the channel and configuration of the source beam are deleted;

[0014] (8) After the onboard payload deletes the channel and configuration of the source beam, it establishes the target beam configuration. After the configuration is completed, the onboard payload sends a terminal context modification response message to the ground access gateway; if the onboard payload receives an RRC reconfiguration completion message from the satellite terminal before sending the terminal context modification response message, the onboard payload caches the RRC reconfiguration completion message from the satellite terminal;

[0015] (9) After the onboard payload sends the terminal context modification response message, the downlink data cached in the downlink data register is sent to the satellite terminal through the target beam channel, and the uplink data cached in the uplink data register in step (3) and step (7) is sent to the ground access gateway through the target beam channel;

[0016] (10) After receiving the RRC reconfiguration completion message sent by the satellite terminal or cached by the satellite payload, the onboard payload fills the message into the RRC message container and sends it to the ground access gateway through the uplink RRC direct transmission message of the onboard payload;

[0017] (11) After receiving the terminal context modification response message from the satellite payload, the ground access gateway switches the source beam to the target beam. After receiving the uplink RRC direct transfer message containing the RRC reconfiguration completion message container, the intra-satellite handover is completed.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] 1. The present invention designs an improved intra-satellite switching method, which quickly establishes a target beam channel after the on-board payload sends a terminal switching message, effectively reducing the switching delay of the intra-satellite switching and reducing the process complexity of the intra-satellite switching.

[0020] 2. The intra-satellite switching process designed by the present invention caches the data in the switching process into the uplink and downlink data registers, which can ensure that the data transmission task in the switching process is controlled by the on-board payload. Therefore, no matter before, during or after the switching, the data transmission is completed in the on-board payload to ensure that the data transmission is not lost. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of an application scenario of a low-orbit satellite system intra-satellite switching method according to an embodiment of the present invention;

[0022] Figure 2 It is a timing diagram of the intra-satellite switching method of the low-orbit satellite system in an embodiment of the present invention. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0024] A low-orbit satellite system intra-satellite switching method is implemented based on a low-orbit satellite system consisting of a satellite terminal, an on-board payload, a ground access gateway and a ground core network. The satellite terminal accesses the ground access gateway through the on-board payload to communicate with the ground core network. Figure 1 This is a schematic diagram of the application scenario of the present method, which shows a low-orbit satellite system, including a satellite terminal LS-UE, an onboard payload LS-DU, a ground access gateway LS-CU and a ground core network LS-EPC. LS-UE accesses the LS-EPC through the LS-DU and LS-CU, and the intra-satellite switching is switched from the source beam LS-Src-Beam to the target beam LS-Tgt-Beam. The black solid line in the figure indicates that the satellite terminal communicates with the ground access gateway through the source beam of the onboard payload before the intra-satellite switching; the black dotted line indicates that the satellite terminal communicates with the ground access gateway through the target beam of the onboard payload after the intra-satellite switching.

[0025] like Figure 2 As shown, the method comprises the following steps:

[0026] (1) The satellite terminal LS-UE reports the measurement result and sends an uplink RRC direct transfer message to the ground access gateway LS-CU through the onboard payload LS-DU. The ground access gateway LS-CU triggers the intra-satellite handover process and sends a terminal context modification request message to the onboard payload LS-DU. The terminal context modification request message includes the channel configuration of the target beam LS-Tgt-Beam and the RRC reconfiguration message of the satellite terminal LS-UE.

[0027] (2) After receiving the terminal context modification request message, the onboard payload LS-DU verifies whether the source beam LS-Src-Beam channel and the target beam LS-Tgt-Beam channel exist. If not, a terminal context modification failure message is sent to the ground access gateway LS-CU to end the process. If they exist, the intra-satellite handover timer is started.

[0028] (3) The onboard payload LS-DU sends an RRC reconfiguration message to the satellite terminal LS-UE through the source beam LS-Src-Beam channel; at the same time, the onboard payload LS-DU caches the terminal uplink data received through the source beam LS-Src-Beam channel into the uplink data register;

[0029] (4) The onboard payload LS-DU immediately establishes the target beam LS-Tgt-Beam channel and receives the RRC reconfiguration message confirmation ACK message replied by the satellite terminal LS-UE on the target beam LS-Tgt-Beam channel;

[0030] (5) After receiving the RRC reconfiguration message, the satellite terminal LS-UE switches from the source beam LS-Src-Beam to the target beam LS-Tgt-Beam according to the configuration of the ground access gateway LS-CU, and replies with an RRC reconfiguration message confirmation ACK message in the target beam LS-Tgt-Beam channel;

[0031] (6) After the on-board payload LS-DU receives the RRC reconfiguration message confirmation ACK message replied by the satellite terminal LS-UE, it goes to step (7); if the on-board payload LS-DU does not receive the RRC reconfiguration message confirmation ACK message replied by the satellite terminal LS-UE in the target beam LS-Tgt-Beam channel within the intra-satellite switching timer, then after the intra-satellite switching timer times out, it goes to step (7);

[0032] (7) The onboard payload LS-DU caches the terminal uplink data received on the target beam LS-Tgt-Beam channel into the uplink data register, and caches the downlink data sent by the ground access gateway through the source beam into the downlink data register; then, the channel and configuration of the source beam LS-Src-Beam are deleted;

[0033] (8) After the on-board payload releases the channel and configuration of the source beam LS-Src-Beam, it establishes the configuration of the target beam LS-Tgt-Beam. After the configuration is completed, the on-board payload LS-DU sends a terminal context modification response message to the ground access gateway LS-CU; if the on-board payload LS-DU receives an RRC reconfiguration completion message of the satellite terminal LS-UE before sending the terminal context modification response message, the RRC reconfiguration completion message of the satellite terminal LS-UE is cached;

[0034] (9) After sending the terminal context modification response message, the onboard payload LS-DU sends the downlink data cached in the downlink data register to the satellite terminal LS-UE through the target beam LS-Tgt-Beam channel, and sends the uplink data cached in the uplink data register in step (3) and step (7) to the ground access gateway LS-CU through the target beam LS-Tgt-Beam channel;

[0035] (10) After receiving the RRC reconfiguration completion message sent by the satellite terminal LS-UE or cached by the onboard payload LS-DU, the onboard payload LS-DU fills the message into the RRC message container and sends it to the ground access gateway LS-CU through the uplink RRC direct transfer message of the onboard payload LS-DU;

[0036] (11) After receiving the terminal context modification response message from the onboard payload LS-DU, the ground access gateway LS-CU switches the source beam LS-Src-Beam to the target beam LS-Tgt-Beam. After receiving the uplink RRC direct transfer message containing the RRC reconfiguration completion message container, the intra-satellite switching is completed.

[0037] In summary, the present invention enters the intra-satellite switching state through the on-board payload receiving the notification from the ground access gateway, and after sending the terminal reconfiguration message through the source beam, quickly establishes the target beam channel, and after receiving the reconfiguration message ACK sent by the terminal in the target beam, the on-board payload starts to execute the configuration process of switching from the source beam to the target beam, and at the same time caches the data in the switching process to the uplink and downlink data registers, which can ensure the data transmission during the on-board payload control switching process. The present invention can be applied to the intra-satellite switching scenario of the low-orbit satellite system, can effectively reduce the switching delay of the intra-satellite switching, reduce the process complexity of the intra-satellite switching, and at the same time ensure that the terminal and the on-board payload do not lose packets in the source beam and target beam transmission.

Claims

1. A low-orbit satellite system intra-satellite switching method, based on a low-orbit satellite system consisting of a satellite terminal, an on-board payload, a ground access gateway and a ground core network; characterized in that: The following steps are involved: (1) The satellite terminal reports the measurement result and sends an uplink RRC direct transmission message to the ground access gateway through the on-board payload. The ground access gateway triggers the intra-satellite handover process and sends a terminal context modification request message to the on-board payload. The terminal context modification request message includes the channel configuration of the target beam and the RRC reconfiguration message of the satellite terminal. (2) After receiving the terminal context modification request message, the onboard payload verifies whether the source beam channel and the target beam channel exist. If not, a terminal context modification failure message is sent to the ground access gateway to end the process. If so, the intra-satellite switching timer is started. (3) The onboard payload sends an RRC reconfiguration message to the satellite terminal through the source beam channel. At the same time, the onboard payload caches the terminal uplink data received through the source beam channel into the uplink data register. (4) The onboard payload immediately establishes the target beam channel and receives the RRC reconfiguration message confirmation message replied by the satellite terminal on the target beam channel; (5) After receiving the RRC reconfiguration message, the satellite terminal switches from the source beam to the target beam according to the configuration of the ground access gateway, and replies with an RRC reconfiguration message confirmation message in the target beam channel; (6) After the onboard payload receives the RRC reconfiguration message confirmation message replied by the satellite terminal, go to step (7); if the onboard payload does not receive the RRC reconfiguration message confirmation message replied by the satellite terminal in the target beam channel within the intra-satellite switching timer, then after the intra-satellite switching timer times out, go to step (7); (7) The onboard payload caches the terminal uplink data received on the target beam channel into the uplink data register, and caches the downlink data sent by the ground access gateway through the source beam into the downlink data register; then, the channel and configuration of the source beam are deleted; (8) After the onboard payload deletes the channel and configuration of the source beam, it establishes the target beam configuration. After the configuration is completed, the onboard payload sends a terminal context modification response message to the ground access gateway; if the onboard payload receives an RRC reconfiguration completion message from the satellite terminal before sending the terminal context modification response message, the onboard payload caches the RRC reconfiguration completion message from the satellite terminal; (9) After the onboard payload sends the terminal context modification response message, the downlink data cached in the downlink data register is sent to the satellite terminal through the target beam channel, and the uplink data cached in the uplink data register in step (3) and step (7) is sent to the ground access gateway through the target beam channel; (10) After receiving the RRC reconfiguration completion message sent by the satellite terminal or cached by the satellite payload, the onboard payload fills the message into the RRC message container and sends it to the ground access gateway through the uplink RRC direct transmission message of the onboard payload; (11) After receiving the terminal context modification response message from the satellite payload, the ground access gateway switches the source beam to the target beam. After receiving the uplink RRC direct transfer message containing the RRC reconfiguration completion message container, the intra-satellite handover is completed.

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