A method for accurate paging in a satellite communication system

Abstract

The application relates to a method for accurate paging in a satellite communication system: a user terminal UE sends its current beam information to an on-board base station at initial registration, the on-board base station maintains a beam tracking list of the user terminal UE, and a core network maintains an on-board base station tracking list of the user terminal UE; the on-board base station configures an SRS-Config-IE and sends the same to the user terminal UE, wherein the SRS-Config-IE is used to define time-frequency resources and specific SRS sequence parameters for the user terminal UE to transmit an SRS signal; the user terminal UE transmits an SRS message in the time-frequency resources defined by the SRS-Config-IE and according to the specific SRS sequence parameters under a new beam of a new on-board base station, wherein the SRS message carries a new on-board base station number and a beam number; the new on-board base station sends the on-board base station number of the user terminal UE to the core network as a current on-board base station, and the core network updates a satellite tracking list. The application reports UE satellite and beam information by multiplexing time-frequency resources of an SRS probe reference signal, thereby greatly reducing service link signaling overhead.

Description

Technical Field

[0001] This invention belongs to the field of satellite communication technology, and more specifically, relates to a method for precise paging in a satellite communication system. Background Technology

[0002] Compared to terrestrial cellular networks, low-Earth orbit (LEO) satellite communication systems offer advantages such as high mobility, wide beam coverage, and longer transmission times. This can lead to frequent location update signaling overhead and make existing paging capacity insufficient to meet paging demands. Therefore, designing location area division and paging mechanisms suitable for satellite communication systems to reduce location update signaling overhead and enhance paging capacity is crucial.

[0003] Since location update and paging are relatively contradictory designs, in order to reduce the signaling overhead of location update, it is necessary to design a larger location area containing multiple cells. However, the current coverage paging method sends paging messages to all cells within the location area, meaning that the paging message must be transmitted in all beams, resulting in a significant reduction in the actual number of paging user terminals (UEs).

[0004] To address this issue, technical standards and literature have proposed various adaptive paging methods, such as sequential paging, concurrent paging, hierarchical paging, and time-based, mobility-based, distance-based, and configuration file- or historical data-based paging, to further narrow the paging area and reduce paging load. However, these methods still transmit paging messages across multiple beams and do not achieve precise paging. Summary of the Invention

[0005] The technical problem solved by this invention is to overcome the shortcomings of the prior art and provide a method for accurate paging in a satellite communication system, thereby reducing the signaling overhead of the service link.

[0006] The solution of this invention is: a method for precise paging in a satellite communication system, the method comprising the following steps:

[0007] S1. During initial registration, the user terminal (UE) sends its current beam information to the satellite base station. The satellite base station maintains the beam tracking list of the user terminal (UE), and the core network maintains the satellite base station tracking list of the user terminal (UE). The beam tracking list contains the UE identifier and the beam number used by the UE. The satellite tracking list contains the UE identifier and the satellite base station number to which the UE belongs.

[0008] S2. The satellite base station configures SRS-Config-IE and sends it to the user terminal UE. The SRS-Config-IE is used to specify the time and frequency resources and specific SRS sequence parameters for the user terminal UE to transmit SRS signals.

[0009] S3. When the user terminal UE does not leave the coverage area of ​​the current satellite base station and enters the two beam overlap area of ​​the current satellite base station, and meets the beam switching conditions, the RRC inactive state user terminal UE sends the new beam number to the current satellite base station through SRS message in the time and frequency resources specified in SRS-Config-IE, and the current satellite base station updates the beam tracking list of the user terminal UE.

[0010] S4. When the user terminal UE enters the overlapping range of two satellites and meets the conditions for handover of the satellite base station, the RRC inactive user terminal UE sends the new satellite base station number to the current satellite base station through SRS message in the time and frequency resources specified in SRS-Config-IE. The current satellite base station sends the UE information to the new satellite base station through the inter-satellite link. The UE information includes the satellite base station to which the UE belongs and the beam.

[0011] S5. The new satellite base station configures SRS-Config-IE to allocate time and frequency resources and specific SRS sequence parameters to the user terminal UE, and feeds them back to the current satellite base station. The current satellite base station then sends SRS-Config-IE to the user terminal UE.

[0012] S6. Under the new beam of the new satellite base station, the user terminal (UE) sends an SRS message according to the specific SRS sequence parameters on the time and frequency resources specified in SRS-Config-IE. The SRS message carries the new satellite base station number and beam number. The new satellite base station, as the current satellite base station, sends the satellite base station number of the user terminal (UE) to the core network, and the core network updates the satellite tracking list.

[0013] S7. The core network sends a paging message to the satellite base station to which the user terminal UE belongs based on the satellite base station number in the user terminal UE's satellite tracking list. The satellite base station sends a paging message on the corresponding beam based on the beam number in the user terminal's beam tracking list.

[0014] Preferably, in step S3, the user terminal UE in the RRC active state updates the beam information during the handover process.

[0015] Preferably, in step S4, the user terminal UE in the RRC active state updates the satellite information to which the user terminal UE belongs through the handover process.

[0016] Preferably, the SRS reuses existing SRS time-frequency resources.

[0017] Preferably, the UE identifier is one of the identifiers of the 5G standard such as 5G-S-TMSI or GUTI, or a custom UE address.

[0018] Preferably, the SRS sequence is a ZC sequence, and the SRS-Config-IE configuration ensures that the same time-frequency resource sequences under the same satellite are orthogonal and can uniquely distinguish the user terminal (UE).

[0019] Preferably, the user terminal carries the satellite base station number and beam number in the SRS information in the following manner:

[0020] The satellite base station number and beam number are XORed with the ZC sequence in the SRS information to obtain the SRS information carrying the satellite base station number and beam number. This SRS information is then transmitted in the corresponding time and frequency resources. After receiving the SRS signal and obtaining the SRS information carrying the satellite base station number and beam number, the satellite base station queries the correspondence between the time and frequency resources, the UE, and the ZC sequence, and XORs it with the ZC sequence of the corresponding UE to obtain the satellite base station number and beam number carried in the SRS.

[0021] Preferably, the beam switching condition is:

[0022] The average received signal strength of the broadcast signal in the current beam coverage area measured by the user terminal (UE) is less than the cell reselection threshold, while the average received signal strength in the other beam coverage area is greater than the cell reselection threshold.

[0023] Preferably, the base station handover conditions are as follows:

[0024] The average received signal strength of the current beam broadcast signal in the coverage area of ​​the current satellite base station measured by the user terminal (UE) is less than the cell reselection threshold, while the average received signal strength of a certain beam coverage area of ​​another satellite base station is greater than the cell reselection threshold.

[0025] The advantages of this invention compared to the prior art are:

[0026] (1) This invention uses the time and frequency resources of SRS (Sounding Reference Signal) to report the UE’s satellite base station and beam information, which greatly reduces the service link signaling overhead. Furthermore, it reduces the power supply link signaling overhead by storing distributed satellite base station and beam information, thereby alleviating the signaling overhead of the satellite base station tracking list location update and the paging load of the beam tracking list.

[0027] (2) This invention is applicable not only to satellite communication systems under different network architectures defined by 3GPP, but also to terrestrial cellular networks, and has universality.

[0028] (3) The UE information reporting based on the detection reference signal of the present invention can not only be used in the paging process, but also in auxiliary handover and other scenarios that require terminal location, and has broad application prospects. Attached Figure Description

[0029] Figure 1 This is a flowchart illustrating the registration process of the UE as described in this embodiment of the invention.

[0030] Figure 2 This describes the beam update process of a UE in an inter-beam cell reselection scenario according to an embodiment of the present invention.

[0031] Figure 3 This describes the UE's location update process in an inter-satellite cell reselection scenario according to an embodiment of the present invention.

[0032] Figure 4 This describes the UE's location update process in inter-beam and inter-satellite handover scenarios according to an embodiment of the present invention.

[0033] Figure 5(a) shows the paging process initiated by CN in an embodiment of the present invention.

[0034] Figure 5(b) shows the paging process initiated by the RAN in an embodiment of the present invention.

[0035] Figure 6 This is a flowchart of a precise paging method according to an embodiment of the present invention. Detailed Implementation

[0036] The present invention will be further described below with reference to the embodiments.

[0037] To accurately locate the UE's beam within a large location area, reduce paging overhead, and enhance paging capacity, this invention discloses a precise paging method based on the satellite beam coverage area as the tracking zone. For example... Figure 6 As shown, the steps include:

[0038] S1. During initial registration, the user terminal (UE) sends its current beam information to the satellite base station. The satellite base station maintains the beam tracking list of the user terminal (UE), and the core network maintains the satellite base station tracking list of the user terminal (UE). The beam tracking list contains the UE identifier and the beam number used by the UE. The satellite base station tracking list contains the UE identifier and the satellite base station number to which the UE belongs.

[0039] The UE identifier is one of the 5G standard identifiers such as 5G-S-TMSI or GUTI, or a custom UE address.

[0040] S2. The satellite base station configures SRS-Config-IE and sends it to the user terminal UE. The SRS-Config-IE is used to specify the time and frequency resources and specific SRS sequence parameters for the user terminal UE to transmit SRS signals.

[0041] The SRS can reuse existing SRS time and frequency resources. After receiving the SRS, the satellite base station not only retains the original functions such as channel estimation, but also obtains the satellite base station and beam information of the UE based on this signal, thereby reducing the signaling overhead of the serving link while accurately locating the beam where the UE is located.

[0042] The SRS sequence is a ZC sequence. The SRS-Config-IE configuration ensures that the same time-frequency resource sequences under the same satellite base station are orthogonal and can uniquely distinguish the user terminal (UE). That is, the ZC sequence sets between different beams under the same satellite base station have no intersection.

[0043] S3. When the user terminal UE does not leave the coverage area of ​​the current satellite base station and enters the two beam overlap area of ​​the current satellite base station, and meets the beam switching conditions, the RRC inactive state user terminal UE sends the new beam number to the current satellite base station through SRS message in the time and frequency resources specified in SRS-Config-IE, and the current satellite base station updates the beam tracking list of the user terminal UE.

[0044] The beam switching condition is:

[0045] The average received signal strength of the broadcast signal in the current beam coverage area measured by the user terminal (UE) is less than the beam reselection threshold, while the average received signal strength in the other beam coverage area is greater than the beam reselection threshold.

[0046] S4. When the user terminal UE enters the overlapping range of two satellite base stations and meets the base station handover conditions, the RRC inactive state user terminal UE sends the new satellite base station number to the current satellite base station through SRS message in the time and frequency resources specified in SRS-Config-IE. The current satellite base station sends the new satellite base station number to the new satellite base station through the inter-satellite link.

[0047] The user terminal (UE) in the RRC active state updates beam information during the handover process.

[0048] The base station handover conditions are as follows:

[0049] The average received signal strength of the broadcast signal in the coverage area of ​​the current satellite base station measured by the user terminal (UE) is less than the base station reselection threshold, while the average received signal strength in the coverage area of ​​another satellite base station is greater than the base station reselection threshold.

[0050] This invention changes the previous situation where location information was only stored in the core network. The satellite base station and the core network distribute the storage of the UE's satellite base station number and beam number. Changes in location information between beams are only notified to the satellite base station, thereby reducing the signaling overhead of the power supply link.

[0051] S5. The new satellite base station configures SRS-Config-IE to allocate time and frequency resources and specific SRS sequence parameters to the user terminal UE, and feeds them back to the current satellite base station. The current satellite base station then sends SRS-Config-IE to the user terminal UE.

[0052] The user terminal UE in the RRC active state updates the satellite base station information to which the user terminal UE belongs through the handover process.

[0053] S6. Under the new beam of the new satellite base station, the user terminal UE sends an SRS message according to the specific SRS sequence parameters on the time and frequency resources specified in SRS-Config-IE. The SRS message carries the new satellite base station number and beam number. The new satellite base station, as the current satellite base station, sends the satellite base station number of the user terminal UE to the core network, and the core network updates the satellite base station tracking list.

[0054] The user terminal (UE) can carry the satellite base station number and beam number in the SRS information using methods such as XOR:

[0055] The satellite base station number and beam number are XORed with the ZC sequence in the SRS information to obtain the SRS information carrying the satellite base station number and beam number. This SRS information is then transmitted in the corresponding time and frequency resources. After receiving the SRS signal and obtaining the SRS information carrying the satellite base station number and beam number, the satellite base station queries the correspondence between the time and frequency resources, the UE, and the ZC sequence, and XORs it with the ZC sequence of the corresponding UE to obtain the satellite base station number and beam number carried in the SRS.

[0056] S7. The core network sends a paging message to the satellite base station to which the user terminal UE belongs, based on the satellite base station number in the user terminal UE's satellite base station tracking list. The satellite base station then sends the paging message on the corresponding beam based on the beam number in the user terminal's beam tracking list. Paging information is generally used when downlink messages arrive, system messages change, or earthquake / tsunami warnings are issued.

[0057] Example:

[0058] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to specific embodiments and accompanying drawings.

[0059] After powering on, the UE undergoes a cell search and random access process to connect to a specific beam cell of a satellite-based base station. The beam cell allocation is based on the coverage area of ​​the beam where the UE is located as the tracking area, and refers to... Figure 1 Complete the following registration process.

[0060] 1. The UE sends a registration request message to the satellite base station, which carries the UE identifier, beam, etc.

[0061] 2. The beam tracking list for the UE is initialized by the satellite-based base station, in the following format:

[0062] 1 UE1 identifier 2 UE2 identifier …… ……

[0063] 3. The satellite base station sends a registration request to the AMF of the core network. The registration request includes the UE identifier and the satellite base station number.

[0064] 4. Based on the received registration request message, the AMF initializes the UE's onboard base station tracking information list, in the following format:

[0065] 1 UE1 identifier 2 UE2 identifier …… ……

[0066] 7. The AMF sends a registration and reception message to the UE. During this process, the satellite base station configures parameters to determine the UE's specific SRS time-frequency resources and sequences. The configured parameters should ensure that the UE can be uniquely identified under the same satellite base station.

[0067] 8. The UE sends a registration completion message to the AMF.

[0068] After the UE camps on the beam cell, it will continuously measure the beam cell. Depending on the UE's state, mobility management is divided into the following processes.

[0069] 1. For UEs in the RRC inactive state that determine whether they are still within the coverage area of ​​that beam of the satellite base station by receiving broadcast messages, refer to... Figure 2 Perform the following inter-beam cell reselection procedure.

[0070] 1) When the UE measures that the average received signal strength of the broadcast signal in the current beam coverage area is less than the cell reselection threshold, and the average received signal strength of the other beam coverage area is greater than the cell reselection threshold, it performs inter-beam reselection and sends the new beam information along with the SRS message.

[0071] 2) After receiving the SRS, the satellite base station updates the beam information of the UE.

[0072] 2. For UEs that are in the RRC inactive state and have entered the coverage area of ​​a new satellite base station as determined by receiving broadcast messages, refer to... Figure 3 Perform the satellite base station reselection process.

[0073] 3. For UEs in RRC connected state, refer to Figure 4 Perform inter-beam and inter-satellite switching.

[0074] 1) When the UE measures its average received signal strength as less than the handover threshold of the satellite base station;

[0075] 2a) If the UE is performing intra-satellite beam switching, the beam information of the UE in the satellite base station is updated directly.

[0076] 2b) If the UE is performing an inter-satellite handover, the handover process is performed between the UE and satellite base station 1 and satellite base station 2.

[0077] 3) The satellite base station 2 updates the UE information, which includes the UE's corresponding beam and satellite base station information.

[0078] 4) Satellite base station 2 sends updated UE information to the AMF of the core network.

[0079] 5) Satellite base station 2 sends UE deletion information to satellite base station 1

[0080] 6) After receiving 4), the core network AMF updates the UE's onboard base station tracking list.

[0081] 7) After receiving 5), the satellite base station 1 deletes the UE's beam tracking list.

[0082] During this process, for paging triggered by downlink data arrival, system message changes, or earthquake / tsunami warnings, the paging process is performed according to the RRC status of the UE, as shown in Figures 5(a) and 5(b).

[0083] For UEs in RRC inactive state (RRC_IDLE), the AMF sends a paging message to the corresponding satellite based on the UE's satellite number in the UE's onboard base station tracking list. After receiving the paging message, the satellite pages the UE within the corresponding beam according to the UE's beam tracking list.

[0084] For a UE in the RRC active state, the satellite will page the UE in the corresponding beam according to the beam number of the UE in the beam tracking list.

[0085] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A method for precise paging in a satellite communication system, characterized in that... Includes the following steps: S1. During initial registration, the user terminal (UE) sends its current beam information to the satellite base station. The satellite base station maintains the beam tracking list of the user terminal (UE), and the core network maintains the satellite tracking list of the user terminal (UE). The beam tracking list contains the UE identifier and the beam number used by the UE. The satellite tracking list contains the UE identifier and the satellite base station number to which the UE belongs. S2. The satellite base station configures SRS-Config-IE and sends it to the user terminal UE. The SRS-Config-IE is used to specify the time and frequency resources and specific SRS sequence parameters for the user terminal UE to transmit SRS signals. S3. When the user terminal UE does not leave the coverage area of ​​the current satellite base station and enters the two beam overlap area of ​​the current satellite base station, and meets the beam switching conditions, the RRC inactive state user terminal UE sends the new beam number to the current satellite base station through SRS message in the time and frequency resources specified in SRS-Config-IE, and the current satellite base station updates the beam tracking list of the user terminal UE. S4. When the user terminal UE enters the overlapping range of two satellites and meets the conditions for handover of the satellite base station, the RRC inactive user terminal UE sends the new satellite base station number to the current satellite base station through SRS message in the time and frequency resources specified in SRS-Config-IE. The current satellite base station sends the UE information to the new satellite base station through the inter-satellite link. The UE information includes the satellite base station to which the UE belongs and the beam. S5. The new satellite base station configures SRS-Config-IE to allocate time and frequency resources and specific SRS sequence parameters to the user terminal UE, and feeds them back to the current satellite base station. The current satellite base station then sends SRS-Config-IE to the user terminal UE. S6. Under the new beam of the new satellite base station, the user terminal (UE) sends an SRS message according to the specific SRS sequence parameters on the time and frequency resources specified in SRS-Config-IE. The SRS message carries the new satellite base station number and beam number. The new satellite base station, as the current satellite base station, sends the satellite base station number of the user terminal (UE) to the core network, and the core network updates the satellite tracking list. S7. The core network sends a paging message to the satellite base station to which the user terminal UE belongs based on the satellite base station number in the user terminal UE's satellite tracking list. The satellite base station sends a paging message on the corresponding beam based on the beam number in the user terminal's beam tracking list.

2. The method for precise paging in a satellite communication system according to claim 1, characterized in that... In step S3, the user terminal UE in the RRC active state updates the beam information during the handover process.

3. The method for precise paging in a satellite communication system according to claim 1, characterized in that... In step S4, the user terminal UE in the RRC active state updates the satellite information to which the user terminal UE belongs through the handover process.

4. The method for precise paging in a satellite communication system according to claim 1, characterized in that, The SRS reuses existing SRS time-frequency resources.

5. A method for precise paging in a satellite communication system according to claim 1, characterized in that... The UE identifier is one of the identifiers of the 5G-S-TMSI or 5G-GUTI standard, or a custom UE address.

6. A method for precise paging in a satellite communication system according to claim 1, characterized in that... The SRS sequence is a ZC sequence. The SRS-Config-IE configuration ensures that the time-frequency resource sequences under the same satellite are orthogonal and can uniquely distinguish the user terminal (UE).

7. A method for precise paging in a satellite communication system according to claim 6, characterized in that... The user terminal carries the satellite base station number and beam number in the SRS information in the following manner: The satellite base station number and beam number are XORed with the ZC sequence in the SRS information to obtain the SRS information carrying the satellite base station number and beam number. This SRS information is then transmitted in the corresponding time and frequency resources. After receiving the SRS signal and obtaining the SRS information carrying the satellite base station number and beam number, the satellite base station queries the correspondence between the time and frequency resources, the UE, and the ZC sequence, and XORs it with the ZC sequence of the corresponding UE to obtain the satellite base station number and beam number carried in the SRS.

8. A method for precise paging in a satellite communication system according to claim 1, characterized in that... The beam switching condition is: The average received signal strength of the broadcast signal in the current beam coverage area measured by the user terminal (UE) is less than the cell reselection threshold, while the average received signal strength in the other beam coverage area is greater than the cell reselection threshold.

9. A method for precise paging in a satellite communication system according to claim 1, characterized in that... The handover conditions for the satellite-borne base station are as follows: The average received signal strength of the current beam broadcast signal in the coverage area of ​​the current satellite base station measured by the user terminal (UE) is less than the cell reselection threshold, while the average received signal strength of a certain beam coverage area of ​​another satellite base station is greater than the cell reselection threshold.

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