Fast RACH-free Handover Method, Access Network, and Handover System Based on Resource Reservation

Abstract

The present invention belongs to the technical field of mobility management for low-orbit satellite mobile communications, and specifically discloses a fast RACH-free handover method, access network and handover system based on resource reservation. The handover system includes a satellite, a terminal and an access network. The access network receives measurement information of the terminal. After determining the target beam, the access network queries the source beam burst type and time-frequency resources of the terminal according to the terminal ID. The radio resource control (RRC) layer of the access network controller applies for the same burst type to the radio resource management module. After the RRC layer receives a request success instruction, the RRC layer determines whether it is an inter-satellite handover. The access network determines whether to complete the switch-on of the intra-satellite or inter-satellite RACH-free handover algorithm switch, and controls whether to perform RACH handover. By adopting the technical solution of the present invention, burst configuration resources are reserved in advance to achieve fast RACH-free handover without the terminal being aware of it.

Description

Technical Field

[0001] The present invention belongs to the technical field of low-earth orbit satellite mobile communication mobility management, and relates to a fast RACH (Random Access Channel)-free handover method, access network and handover system based on resource reservation Background Art

[0002] The overall purpose of handover scheme design is to ensure that the communication link from the user to the satellite in communication is not interrupted with the movement of the satellite or the user, and that user data can be smoothly accessed to the satellite and can be smoothly converted between the spaceborne bearer network and the access network

[0003] In the ground operator network, mobility management requests the target beam resources after the network completes the "handover judgment" by the terminal reporting measurement reports, and informs the terminal whether it can perform handover through a Handover Command. Since the traditional method requires multiple steps of signaling to complete handover, in the satellite Internet scenario, there is a large delay in signaling interaction, which is very likely to cause handover failure Summary of the Invention

[0004] The purpose of the present invention is to provide a fast RACH-free handover method, access network and handover system based on resource reservation, realizing fast RACH-free handover without the terminal's awareness and reducing signaling overhead

[0005] To achieve the above purpose, the basic solution of the present invention is: A fast RACH-free handover method based on resource reservation, including the following steps

[0006] The access network receives the measurement information of the terminal. After the access network determines the target beam, it queries the source beam burst type and time-frequency resources of the terminal according to the terminal ID

[0007] The RRC layer of the access network controller applies to the radio resource management module for the same burst type. If the target beam does not have this burst type, the radio resource management module sends a rejection instruction to the RRC layer, and the access network tries other target beams; if this burst type exists, the radio resource management module sends a request success instruction to the RRC layer

[0008] When the RRC layer receives the request success instruction, the RRC layer judges whether it is an inter-satellite handover. If it is an intra-satellite handover, the RRC layer judges whether to turn on the intra-satellite RACH-free handover algorithm switch. If it is turned on, the rachIndicator is not carried in the mobility control information; if it is an inter-satellite handover, it judges whether to turn on the inter-satellite RACH-free handover algorithm switch. If it is turned on, the rachIndicator is not carried in the mobility control information, and at the same time, burst resources are reserved in advance for the terminal and new time-frequency resources are allocated, and are sent to the terminal through RRC reconfiguration

[0009] If the access network determines that the process of enabling the intra-satellite or inter-satellite RACH-free handover algorithm switch cannot be completed, then perform RACH handover. The rachIndicator is carried in the mobile control information, and the RRC layer sends an RRC reconfiguration to the terminal through the serving satellite. The reconfiguration carries the mobile control information for channel control. The serving satellite receives the RRC reconfiguration command and forwards it to the terminal. After sending the reconfiguration command, the access network immediately stops sending downlink data and caches the data in the network;

[0010] Otherwise, do not perform RACH handover, and the data remains on the original channel.

[0011] The working principle and beneficial effects of this basic solution are as follows: Reserve resources on the network side in advance to ensure that handover failures will not occur due to lack of network resources. At the same time, according to the resource situation and synchronization situation of the network during handover, flexibly select the handover method, increasing the success rate of handover. By reserving burst configuration resources in advance, fast RACH-free handover is achieved, without going through the traditional random access process, reducing signaling overhead, also reducing transmission delay, and reducing the possibility of handover failure caused by excessive signaling transmission delay. Place the processes such as resource preparation for handover and handover scheme decision on the ground, reducing the computing pressure on satellite nodes and lowering the commercial cost.

[0012] Further, the measurement information of the terminal includes: The terminal obtains the frequency points and time slots for neighbor cell measurement and the signal strength according to the measurement gap configuration information configured by the network side; when the terminal measures, it saves the time offset of the neighbor beam and the time offset relative to its own beam.

[0013] Obtain the corresponding information for subsequent use. Further, the resource configuration of the beam is configured through the LSC interface of the access network to the satellite, and the corresponding burst type and time-frequency resources are queried in the access network according to the IDs of the source beam and the target beam.

[0014] Ensure that the corresponding burst type and time-frequency resources can be successfully queried for subsequent operations.

[0015] Further, the method for determining whether it is an inter-satellite handover is as follows:

[0016] Query the source beam ID according to the identifier of the terminal, and combine it with the target beam ID. By presetting the corresponding relationship between the beam ID and the satellite ID in the access network, it can be determined whether the target beam is on the same satellite.

[0017] The operation is simple and convenient for use.

[0018] Further, the method for enabling the intra-satellite RACH-free handover algorithm switch:

[0019] The time-frequency synchronization process can be continuous. When the terminal switches to the target satellite without re-synchronization, it does not send the RACH process and directly sends data on the allocated dedicated channel. The pre-compensation process before the transmission of the uplink signal of the target beam continues with the source beam.

[0020] Through the engineering application of the RACH-free algorithm, the signaling overhead is reduced and the delay is decreased.

[0021] Furthermore, the method for enabling the inter-satellite RACH-free handover algorithm switch:

[0022] When the terminal switches to the target satellite, it does not send the RACH process and directly sends data on the allocated dedicated channel, and performs pre-compensation processing on the uplink signal of the target beam in advance.

[0023] It does not need to go through the traditional random access process, reducing the signaling overhead and decreasing the transmission delay.

[0024] Furthermore, performing a RACH handover means that the terminal switches to the target satellite, synchronizes through the RACH or SYCH process, and then enters the dedicated channel.

[0025] The method is simple to operate and convenient to use.

[0026] The present invention also provides an access network, and the access network executes the method of the present invention.

[0027] The access network can operate according to the set method to achieve RACH-free handover, which is beneficial to use.

[0028] The present invention also provides a fast RACH-free handover system based on resource reservation, including a satellite, a terminal, and an access network. The access network receives the measurement information of the terminal, and the access network executes the method of the present invention to perform RACH-free handover and realize the connection between the terminal and the satellite.

[0029] Using this system, based on the burst type time-frequency resources of the terminal in the original beam, by reserving resources in advance on the network side, fast RACH-free handover without the terminal's awareness is realized. It not only reduces the signaling overhead and achieves fast handover, but also concentrates the computing power on the ground network, reduces the on-satellite overhead, and effectively reduces the commercial cost. Description of the Drawings

[0030] Figure 1 is a flowchart of the fast RACH-free handover method based on resource reservation of the present invention;

[0031] Figure 2 is a flowchart of the fast RACH-free handover system based on resource reservation of the present invention. Detailed Embodiments

[0032] Embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are only used to explain the present invention and should not be construed as a limitation of the present invention.

[0033] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation of the present invention.

[0034] In the description of the present invention, unless otherwise specified and defined, it should be noted that the terms "mounted", "connected", and "connected" should be understood in a broad sense. For example, it can be a mechanical connection or an electrical connection, or it can be the communication inside two elements. It can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific situations.

[0035] As Figure 1 shown, the present invention discloses a fast RACH-free handover method based on resource reservation. This solution designs a handover resource preparation and handover scheme selection mechanism. After the access network determines the target beam, it reserves burst configuration resources in advance, including information such as frequency band, carrier, and time slot configuration. According to the synchronization situation between the terminal and the target beam, it indicates whether the terminal triggers RACH. The method includes the following steps:

[0036] The access network receives the measurement information of the terminal. The measurement information of the terminal includes: the frequency points and time slots (which can be used to calculate time-frequency characteristics) measured by the terminal for neighboring cells (adjacent serving cells) according to the measurement gap configuration information (MeasGapConfig) configured by the network side, and the signal strength (which can be used to judge the target beam). When the terminal measures, it saves the time offset of the neighboring beam and the time offset relative to its own beam;

[0037] After the access network determines the target beam, it queries the source beam burst type and time-frequency resources of the terminal according to the terminal ID; since the resource configuration of the beam is configured through the LSC interface (LEO-satellite control interface, low-earth orbit satellite control interface) of the access network to the satellite, the corresponding burst type and time-frequency resources can be queried in the access network according to the IDs of the source beam and the target beam;

[0038] The RRC (Radio Resource Control) layer of the access network requests the same burst type from the radio resource management module. If the target beam does not have this burst type, the radio resource management module sends a rejection instruction to the RRC layer, and the access network tries other target beams. If this burst type exists, the radio resource management module sends a request success instruction to the RRC layer;

[0039] Upon receiving the request success instruction, the RRC layer determines whether it is an inter-satellite handover. If it is an intra-satellite handover, the RRC layer determines whether to enable the intra-satellite RACH-free handover algorithm switch. If the overlapping area of the beams of the same satellite used before and after the handover is small, less than the threshold, the intra-satellite RACH-free handover algorithm is enabled. If enabled, the rachIndicator (channel indication information) is not carried in the MobilityControlInfo (mobility control information). If it is an inter-satellite handover, it is determined whether to enable the inter-satellite RACH-free handover algorithm switch. If the overlapping area of the beams of different satellites used before and after the handover is small, less than the threshold, the inter-satellite RACH-free handover algorithm is enabled. If enabled, the rachIndicator is not carried in the mobility control information, and burst resources are reserved in advance for the terminal and new time-frequency resources are allocated, which are sent to the terminal through RRC reconfiguration (RRC Connection Reconfiguration); By reserving burst configuration resources in advance, fast RACH-free handover is achieved, without going through the traditional random access process, reducing signaling overhead, reducing transmission delay, and reducing the possibility of handover failure caused by too long signaling transmission delay;

[0040] If the access network determines that the process of enabling the intra-satellite or inter-satellite RACH-free handover algorithm switch cannot be completed, RACH handover is performed. Performing RACH handover means that the terminal switches to the target satellite, synchronizes through the RACH or SYCH (Synchronization Channel) process, and then enters the dedicated channel. The rachIndicator is carried in the mobility control information, and the RRC layer sends RRC reconfiguration to the terminal through the serving satellite. The reconfiguration carries the mobility control information for channel control. The serving satellite receives this RRC reconfiguration command and forwards it to the terminal. After sending the reconfiguration command, the access network immediately stops sending downlink data and caches the data in the network;

[0041] Otherwise, no RACH handover is performed, and the data remains on the original channel.

[0042] In a preferred embodiment of the present invention, the method for determining whether it is an inter-satellite handover is as follows:

[0043] Query the source beam ID (Serving Beam ID) according to the identifier of the terminal, combine it with the target beam ID (targetBeamId), and based on the preconfigured correspondence between the beam ID and the satellite ID in the access network, it can be determined whether the target beam is on the same satellite.

[0044] In a preferred embodiment of the present invention, the method for enabling the in-satellite RACH-free handover algorithm switch:

[0045] The time-frequency synchronization process can be continued (i.e., without random access). When the terminal does not need to resynchronize and switches to the target satellite, the RACH process is not sent, and data is directly sent on the allocated dedicated channel. The pre-compensation process before the uplink signal of the target beam is sent is continued with the source beam.

[0046] In a preferred embodiment of the present invention, the method for enabling the inter-satellite RACH-free handover algorithm switch:

[0047] When the terminal switches to the target satellite, the RACH process is not sent, and data is directly sent on the allocated dedicated channel, and pre-compensation processing is performed on the uplink signal of the target beam in advance.

[0048] The present invention also provides an access network that executes the method of the present invention. Placing processes such as handover resource preparation and handover scheme decision on the ground reduces the computing pressure on satellite nodes and lowers the commercial cost.

[0049] The access network can operate according to a set method to achieve RACH-free handover, which is beneficial for use.

[0050] Such as Figure 2 As shown, the present invention also provides a fast RACH-free handover system based on resource reservation, including a satellite, a terminal, and an access network. The access network receives the measurement information of the terminal, executes the method of the present invention to perform RACH-free handover, and realizes the connection between the terminal and the satellite.

[0051] Using this system, based on the burst type time-frequency resources of the terminal in the original beam, by pre-reserving resources on the network side, fast RACH-free handover without terminal awareness is achieved. This not only reduces signaling overhead and realizes fast handover, but also concentrates the computing power on the ground network, reduces the on-board overhead, and effectively reduces the commercial cost. Based on the characteristics of the satellite communication network, that is, the access network has the correspondence between the beam and the satellite and all beam resource configuration information, it has engineering feasibility.

[0052] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "examples", "specific examples", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples.

[0053] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A fast RACH-free handover method based on resource reservation, characterized in that It includes the following steps: The access network device receives the measurement information of the terminal. After the access network device determines the target beam, it queries the source beam burst type and time-frequency resources of the terminal according to the terminal ID; The RRC layer of the controller of the access network device requests the same burst type from the radio resource management module. If the target beam does not have this burst type, the radio resource management module sends a rejection instruction to the RRC layer, and the access network device tries other target beams; if the target beam has this burst type, the radio resource management module sends a request success instruction to the RRC layer; When the RRC layer receives the request success instruction, the RRC layer determines whether it is an inter-satellite handover. If it is an intra-satellite handover, the RRC layer determines whether to enable the intra-satellite RACH-free handover algorithm switch. If it is enabled, the rachIndicator is not carried in the mobility control information; if it is an inter-satellite handover, it determines whether to enable the inter-satellite RACH-free handover algorithm switch. If it is enabled, the rachIndicator is not carried in the mobility control information, and at the same time, burst resources are reserved in advance for the terminal and new time-frequency resources are allocated, and are sent to the terminal through RRC reconfiguration; If the access network device determines that it cannot complete the process of enabling the intra-satellite or inter-satellite RACH-free handover algorithm switch, then RACH handover is performed, the rachIndicator is carried in the mobility control information, the RRC layer sends an RRC reconfiguration command to the terminal through the serving satellite, the RRC reconfiguration command carries the mobility control information for channel control, the serving satellite receives the RRC reconfiguration command and forwards it to the terminal, and the access network device immediately stops sending downlink data after sending the RRC reconfiguration command and caches the data to the network; If the access network device determines that the intra-satellite or inter-satellite RACH-free handover algorithm switch is enabled, RACH handover is not performed, and the data remains on the original channel.

2. The fast RACH-free handover method based on resource reservation according to claim 1, wherein, The measurement information of the terminal includes: the terminal obtains the frequency points, time slots, and signal strength of neighbor cell measurements according to the measurement gap configuration information configured by the network side; when the terminal measures, it saves the time offset of the neighbor beam and the time offset relative to its own beam.

3. The method for fast RACH-free handover based on resource reservation according to claim 1 or 2, characterized in that, The beam is configured through the LSC interface of the access network device to the satellite, and the corresponding burst type and time-frequency resources are queried in the access network device according to the IDs of the source beam and the target beam.

4. The fast RACH-free handover method based on resource reservation according to claim 1, wherein The method for determining whether it is an inter-satellite handover is as follows: Query the source beam ID according to the terminal ID, combine the target beam ID, and judge whether the target beam is on the same satellite by presetting the corresponding relationship between the beam ID and the satellite ID in the access network device.

5. The fast RACH-free handover method based on resource reservation according to claim 1, characterized in that If the intra-satellite RACH-free handover algorithm switch is enabled, then: The time-frequency synchronization process can continue. Without re-synchronization and without the terminal switching to the target satellite, the RACH process is not sent, and data is directly sent on the allocated dedicated channel. The pre-compensation process before the uplink signal of the target beam is continued with the source beam.

6. The fast RACH-free handover method based on resource reservation according to claim 1, wherein, If the inter-satellite RACH-free handover algorithm switch is enabled, then: When the terminal switches to the target satellite, the RACH process is not sent, and data is directly sent on the allocated dedicated channel. The uplink signal of the target beam is pre-compensated in advance.

7. The fast RACH-free handover method based on resource reservation according to claim 1, wherein, Performing RACH handover means that the terminal hands over to the target satellite, synchronizes through the RACH or SYCH process, and then enters the dedicated channel.

8. An access network device, characterized in that The access network device executes the method according to any one of claims 1-7.

9. A fast RACH-free handover system based on resource reservation, characterized in that, It includes a satellite, a terminal, and an access network device. The access network device executes the method according to any one of claims 1-7 to realize the connection between the terminal and the satellite.

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