Seamless handover of beams and gateways in satellite radio access networks (satellite RANs).

Abstract

This system provides a way to actually transform standard 3GPP UEs, including 2G, 4G, and current 5G UEs, into satellite phones without any modifications. [Solution] The LEO satellite communication system communicates with a first sinking satellite having a first field of view including a first plurality of cells, and a second ascending satellite having a second field of view including a second plurality of cells. The first and second satellites have overlapping fields of view, within which overlapping plurality of cells are located. The first processing unit has a first communication port that communicates with the first cell of the first plurality of cells via a first beam and a first antenna, and a second communication port that communicates with the overlapping cell of the overlapping plurality of cells via a second beam and a second antenna. In response to the first cell of the first plurality of cells moving into the overlapping field of view, the first processing unit switches from the first communication port to the second communication port.

Description

Technical Field

[0001] The present invention relates to seamless handover of beams and gateways in a satellite radio access network (satellite RAN). Cross - reference to related applications This application claims the benefit of priority of U.S. Provisional Application No. 63 / 141,218, filed on January 25, 2021, the content of which is incorporated herein by reference in its entirety.

Background Art

[0002] Achieving 100% coverage for the range that can be covered by mobile phones is globally demanded. Mobile network operators (MNOs) are struggling to justify the high costs of deploying backbone connections and infrastructure for very low - return or no - return requirements, especially in remote areas that have not been covered so far. In current radio access networks (RANs) such as 2G, 3G, 4G, 5G services, there is no direct connection from user equipment (UE, UEs) such as mobile phones to satellites (SAT RAN).

Summary of the Invention

Problems to be Solved by the Invention

[0003] On the other hand, due to the vast number of UEs and weak uplink signals, satellite communications have never directly communicated with UEs compliant with standard 3GPP® specifications. To date, satellite communications have been used at base stations such as eNodeBs and backhaul, but the challenges of directly communicating with multiple standard UEs powered by small batteries are far greater than those for fixed points or customer premises equipment (CPE) with mains power. In 2019, ATIS initiated a Study (SI) and Work Item (WI) for NR Non-Terrestrial Networks (NTN) toward the 3GPP Release 17 specification, which will modify both 5G NR UEs and gNodeBs. This does not cover legacy 4G LTE, 5G NR UEs, and older 2G phones, which are widely used and still in use for a long time, resulting in billions of GSM (2G), LTE (4G), and NR (5G) UEs worldwide that cannot be modified for satellite communications, and to which the new NTN approach cannot be applied. There are no satellite communication solutions that directly support 2G, 4G, or 5G UEs. Furthermore, standard BTS (2G base stations), eNodeB, or gNodeB do not work for satellite-based communications because, for the first 30 years, satellite communications have never been based on 3GPP specifications. NTN's ongoing SI and WI projects are still incomplete. Therefore, under 3GPP specifications, there are currently no commercial satellite RANs, and until NTN completes WI, there are only extremely expensive, specialized satellite phones with high radiation doses to the user's brain—phones most people have never even touched. Moreover, their functionality is inferior to 2G mobile phones and incomparable to even the simplest LTE phones. [Means for solving the problem]

[0004] However, this application will bring about two changes. One is that satellite RAN will be able to cover remote areas without multiple towers of a terrestrial network (TN) or the infrastructure connecting those towers, and the other is that ordinary 3GPP UEs, including 2G, 4G, and current 5G UEs, will be transformed into actual satellite phones without any modifications. This application describes key parts of this innovative approach to satellite RAN, in particular beam handover (BHO) and gateway handover (GHO) for low Earth orbit (LEO) satellite RAN. [Brief explanation of the drawing]

[0005] The attached drawings are incorporated into this specification and constitute part of it, illustrating satellite mobility including both multiple active UEs and their serving gateway sites (GWS). It should be understood that the drawings illustrate only some examples of this disclosure, and other examples or combinations of various examples not specifically illustrated may still be within the scope of this disclosure. Examples will now be described in further detail with reference to the drawings.

[0006] [Figure 1] Figure 1 is an explanatory diagram of multiple cells serviced by two Ge10s (gateways serving satellites defined as having an elevation angle of 10° or more) and three Se20s (satellites with a footprint defined as having an elevation angle of 20° or more). In particular, it shows the footprint (reach) of LEO satellite communications and the overlap situation (overlapping situation) where beam handover occurs between two satellites (a sinking satellite and an ascending satellite). Here, footprint refers to the area within the field of view (FoV) of a satellite or gateway supporting a RAN (Radio Access Network). Footprints can change; for example, a large portion of the ocean is within a satellite's FoV, and even if there is no footprint initially, it can later become part of the satellite RAN footprint. For example, several small islands or oil rigs can become the initial footprint of multiple satellites or gateways.

[0007] [Figure 2] Figure 2 is an explanatory diagram of the 1G2S case (where one GWS links with two adjacent satellites simultaneously), showing that one of the multiple cells in the overlapping area of ​​the two satellite footprints performs a beam handover, and also shows the gateway handover in the 1S2G case (where one satellite RF links with two GWSs simultaneously).

[0008] [Figure 3(a)] Figure 3(a) is a flowchart illustrating the operational concepts of the BHO and GHO in the control plane of this system. [Figure 3(b)] Figure 3(b) is a flowchart illustrating the operational concepts of the BHO and GHO in the control plane of this system, as described above. [Figure 3(c)] Figure 3(c) is a flowchart illustrating the operational concepts of the BHO and GHO in the control plane of this system, as described above.

[0009] Figure 4 shows an example of a handover.

[0010] [Figure 4(a)] Figure 4(a) shows a 1G1S or 1S1G configuration (one gateway linked to only one satellite).

[0011] [Figure 4(b)] Figure 4(b) is a diagram of 1G2S or 2S1G.

[0012] [Figure 4(c)] Figure 4(c) is a diagram of 2G1S or 1S2G.

[0013] [Figure 5] Figures 5(a), (b), and (c) are block diagrams showing gateway interconnection links in a UE mobility case. [Modes for carrying out the invention]

[0014] When describing the exemplary and non-limiting embodiments illustrated in the drawings, certain terms are relied upon for clarity. However, the present disclosure is not intended to be limited to the specific terms so selected, and it should be understood that each specific term includes all technical equivalents that operate in a similar manner to achieve a similar purpose. Although some embodiments are described for illustrative purposes, it is understood that the present specification and claims are not limited to the illustrated embodiments, and other embodiments not specifically shown in the drawings may also be within the scope of the present disclosure.

[0015] A satellite RAN system designed to directly provide services to multiple legacy 2G, 4G, and 5G UEs requires the following four basic mechanisms; otherwise, as can be seen from Starlink and the NTN 3GPP Work Item (WI), an unnecessary amount of satellites, new UEs, and base stations would be required.

[0016] 1. A large phased array that can form hundreds of electronically movable (operable, steerable, stearable) beams to support hundreds of cells.

[0017] 2. Delay and Doppler correction for each beam to normalize the delay consistently and enable operation as a satellite RAN with only simple modifications to a normal base station, regardless of the location of the terrestrial gateway site (GWS), satellite (sat), and multiple cells.

[0018] 3. The process or sequence of beam handover (BHO) and gateway handover (GHO) required for multiple LEO satellites.

[0019] 4. A satellite network control center (NCC) that coordinates RAN equipment such as base stations and space facilities including terrestrial gateway sites and multiple satellites.

[0020] This application focuses on the BHO and GHO, which are the third item.

[0021] As used herein, the term handover or handoff (HO) generally refers to the change of a cell / beam from a descending (lowering) operating (in-service, serving) satellite to an ascending (rising) operating (in-service, serving) satellite. There are several types of handovers. For UE mobility HO in 3GPP specifications, in this disclosure, although outside the scope of 3GPP pre-release 16 (before NTN) specifications, additional HOs (extra HOs) related to satellite beam HO and GWS HO are provided. The innovative part of this disclosure includes rationalizing the necessary BHO and GHO in the satellite RAN by reusing rather than adding new standard protocols for BHO and GHO.

[0022] Referring to FIGS. 1 and 2, low Earth orbit (LEO) satellites 20A and 20B are tracking their respective general cells 51 and 52 served by individual electronically steerable beams 16 and 17. While orbiting the Earth at about 7.5 km / s on satellite orbit 22, satellite 20A takes in a new cell entering its footprint (or FOV) 50A and, for a period, leaves the old cell 51h in the overlapping region 50AB. During that period, the ascending satellite 20B needs to continue to serve multiple UEs within cell 51h by providing a new beam. The same occurs for all satellites within the satellite RAN constellation.

[0023] A Beam Homing (BHO) is changing the service beam of multiple UEs from one satellite 16h to another satellite 17h, while a Gateway Homing (GHO) is changing the feeder links between multiple satellites on the same GWS 31 or different GWSs (31, 32, etc.) on gateway tracking dishes (parabolic antennas) 13, 14, 15. Multiple LEO satellites require BHOs ​​and GHOs to change the multiple GWs they serve and the multiple cells they serve when orbiting multiple cells 51h or GWS 31, 32. BHO is the process by which multiple active UEs change service links for a single cell, while GHO is the process by which multiple beams change feeder links, for example, within a single GWS, changing from one gateway tracking antenna (dish) 14A to another gateway tracking antenna (dish) 14B in the same GWS31, or changing from one gateway tracking dish 14A in one GWS31 to another gateway tracking dish 11B in another GWS32.

[0024] BHO is required when a LEO satellite enters and exits a communication state with a particular cell while orbiting, while GHO is required when a satellite enters and exits a space where it can communicate with a particular GWS while orbiting. BHO generally refers to cell 51h changing the satellite it communicates with, which means changing the beam that the cell uses to communicate with the satellite. This occurs when the cell is in the overlapping region (overlap region) 50AB of the two satellite fields of view (FoV) of a sinking satellite 20A and an ascending satellite 20B in a 1G2S state, and the two HO beams 16h and 17h overlap with the BHO cell 51h. Prior to the BHO, multiple cells (such as 51) communicate via a first tracking beam 16 for the descending or sinking satellite 20A. During the handover, multiple cells (such as 51h) switch from beam 16h for the sinking satellite 20A to beam 17h for the ascending or rising satellite 20B. For example, an eNodeB (e.g., eNodeB12(A)) may be configured to communicate with the UE of cell 51h to control that UE of cell 51h to communicate directly with the second ascending satellite 20B. BHO is performed per UE for multiple active UEs. Thus, after BHO, those cells communicate with the ascending satellite 20B via beam 17 and are served as one of their cells 52. Each eNodeB (e.g., 12(A)) may switch its interface (e.g., gateway antenna) from 14A to 14B, thereby changing the downlink (DL) and uplink (UL) data of the corresponding cell from feeder link 14 to 15. Since GHO is performed via many BHOs, this is an important procedure in forming GHO.

[0025] An eNodeB (eNB) is a 4G base station capable of providing service to one or more 4G cells. In this description, an eNodeB may be a base station for one cell or a base station for multiple cells, as determined as appropriate. It is also compatible with 2GBTS and 5GgNodeB (2G and 5G base stations).

[0026] In some examples, a satellite RAN gateway may have a single tracking dish (parabolic) antenna serving one satellite. Multiple satellites require LEO (low Earth orbit) satellites rather than MEO (medium Earth orbit) or GEO (geostationary orbit) satellites to communicate directly with multiple typical UEs on the ground, and multiple satellites use their beams to track multiple geographical cells on the ground that they serve. GHO can be referred to as changing satellite feeder links from 14 to 15, which is "cell-level" because it is at the granularity of cells, whereas BHO is at the UE level. Therefore, GHO is performed between the GW tracking dishes (antennas) of one or more GWSs.

[0027] A GHO within one GWS may indicate that the cell signal is moving from one tracking antenna 14A to another tracking antenna 14B within the same GWS 31, while a GHO between two GWSs 31 and 32 may indicate that the satellite 20A changes the feeder link between the GWS and the satellite (GW-SAT) from feeder link 14 to feeder link 13 while the satellite 20A is orbiting on the orbit or path 22. Prior to the GHO, the satellite 20A communicates with the first GWS 31 via the first GWS-SAT link (GWS-satellite link) 14. During the GHO, the satellite 20A also communicates with the second GWS 32 via the second GWS-SAT link 13, as shown in the 1S2G state in Figure 2.

[0028] The GHO is performed on a cell-by-cell basis over the period that the satellite covers multiple cells serviced by multiple eNB farms belonging to the GWS. After the GHO, satellite 20A communicates with the second GWS 32 via the second GW-SAT link 13.

[0029] GHO can be implemented in 1S2G (one satellite communicating with two GWSs) and 1G2S (one satellite communicating with two GWSs). Se20 refers to a satellite whose footprint is defined by a minimum elevation angle of 20° (20 degrees). GWe10 refers to a gateway dish antenna with a minimum elevation angle of 10° (10 degrees). Elevation angle is the angle between the horizontal plane of a point of interest on Earth and the intended direction of interest. GW elevation angle refers to the angle of the tracking dish (antenna) relative to the horizontal plane of the point where the GW is installed, while satellite elevation angle refers to the angle of the beam descending from the satellite relative to the horizontal plane of the observation point (e.g., the center of the cell).

[0030] HO failure (HOF) indicates a handover failure (R12 enhancement is used). 1G1S (one gateway communicating with one satellite) indicates the relative position of the satellite and GWS, where the GWS has only one satellite and one link, the serving area (area in service) is smaller than the satellite's footprint, and the satellite beam only needs to track multiple cells within the serving area, with multiple eNBs for those cells hosted (accepted, controlled) at a single GW site.

[0031] Both of these GHO (Global Human Resources) processes are carried out over a set period of time at the cell level, which is composed of many BHOs ​​(Business Human Resources).

[0032] This disclosure addresses satellite mobility (satellite fluidity, fluid operation) as an extension (additional functionality) of BTS / e / gNodeB, relaying GSM (2G), LTE (Long Term Evolution such as 4G), and 5G New Radio (NR) signals to and from multiple UEs of unmodified GSM / LTE / NR. Satellite mobility management (mobile or fluid management of satellites) is outside the scope of 3GPP specifications and will be a new base station background activity, including standard UE handover procedures. There will be coordination (coordination, harmony) between satellites and gateways, but no complexity in managing which satellites need to be linked with the GW. RF paths are handled by satellite ground stations. Neither feeder links nor service link details are handled by the eNB and UEs (3GPP equipment for 2G / 4G / 5G). The satellite RAN design disclosed herein makes the complexity of these satellites completely transparent to base stations and UEs while maintaining their RF connectivity.

[0033] This disclosure aims to lower the HOF, achieve synchronized HO, efficient eNodeB and GWS distribution, and quality of experience (QoE), thereby reducing or minimizing interruptions to voice and data calls and providing a good user experience.

[0034] The diagram shows a single satellite orbital plane, such as directly below the equator, but it can handle any suitable orbit. This approach can also be applied to inter-plane orbital planes (HO). Beam handover

[0035] Referring to the figure, Figure 2 shows a gateway site or ground station 31 according to one embodiment of the present disclosure. The gateway site (gateway base) 31 includes a gateway channel routing block 10 that provides the correct channel signals for two antennas 14A and 14B, which are directional antennas that track satellites, and a plurality of eNodeBs such as 12(A) and 12(B) for each geographic cell. The gateway site 31 communicates with a plurality of user equipment (UEs) via a sinking satellite 20A and an ascending satellite 20B. Satellites 20A and 20B communicate with the plurality of UEs via their respective sinking TRx (transceiver) beam 16 and ascending TRx beam 17. The plurality of UEs may be idle, and they only monitor a plurality of cells and perform cell reselection and tracking area updates when necessary (e.g., for paging), and the plurality of eNodeBs do not need to take care of them in the BHO. The BHO targets only active UEs. Multiple active UEs are either UEs in a call, or include UEs in a call, requiring dedicated control for the eNodeB to move from the beam of a sinking satellite to the beam of an ascending satellite. The gateway channel routing block 10 manages multiple channels required by satellites 20A and 20B so that they dynamically provide scheduled services to the intended cells. All channel / cell signals provided by one satellite are packed together and passed between the GW and the satellite via feeder link (different from the MNO's LTE spectrum) beams 14 and 15, and each cell provided by the satellite uses the MNO's (Mobile Network Operator) spectrum via an electronically steerable beam. The gateway site 32 includes gateway antennas 11A and 11B and multiple eNodeBs (such as multiple BBUs (Baseband Units) for cell 53) that service each of them. The feeder link beams 14 and 15 may have a wide bandwidth, for example, with a frequency of 40-50 GHz. The service link beam is controlled by the Network Mobile Operator (NMO).

[0036] Figure 1 shows the footprint or field of view (FoV) 50A, 50B of the RAN (Radio Access Network, e.g., GSM, LTE, and 5GNR) signals of satellites 20A and 20B on the Earth's surface. The sinking satellite 20A has a sinking satellite FoV 50A, and the rising satellite 20B has a rising satellite FoV 50B. In these sinking satellite FoV 50A and rising satellite FoV 50B, multiple satellites communicate directly with multiple UEs within their cells using downlink (DL) and uplink (UL) serving beams. The sinking FoV 50A and rising FoV 50B overlap (or at least partially overlap) in an overlapping area 50AB. According to one embodiment, a BHO occurs for multiple cells 51h located inside the overlapping FoV area 50AB.

[0037] Figure 2 shows multiple ground cells provided by two satellites 20A and 20B linked to a gateway channel routing block 10, which in turn are linked to the gateway channel routing block 10 via gateway antennas 14A and 14B that interface with their respective processing devices (i.e., eNodeBs) 12 that serve these ground cells. These processing devices 12 control communication with multiple UEs via the multiple satellites 20, 20A, and 20B (see also Figure 1). In particular, Figure 2 shows one embodiment of a system including a 1G2S (one gateway linked with two satellites) mobile communication system 5, but other configurations can also be covered. As illustrated, the satellite communication system 5 includes a base station or ground station 31 containing a farm (such as an eNodeB farm) 3 and a GW channel routing block 10 that communicates via two satellites 20A and 20B, and multiple UEs 30 in beam HO cells 51h within the satellite overlapping region 50AB (here, overlapping ground cells are denoted as 51h and non-overlapping cells as 51, 52. Multiple cells 51 change into multiple cells 52 as the satellite orbits the Earth along path 22). In a particular example, the gateway may include gateway antennas 14A and 14B and a gateway channel routing block 10.

[0038] In some embodiments, the ground station 31 has several base station BBUs, e.g., eNB farms, and at least two directional antennas 14A, 14B, which carry BTS / LTE / 5G downlink (DL) and uplink (UL) signals for their footprints 50A, 50B via gateway-satellite feeder links 14, 15, respectively. In the figure, one of the HO cells 51h within the overlapping area 50AB is highlighted to illustrate where the BHO occurs. One or more UEs are located within the BHO cell 51h. The processing device 12 may be a server or computer, such as a RAN base station configuration such as a BTS for GSM, an eNodeB for LTE, and a gNodeB for 5G, which can transmit (Tx) and receive (Rx) LTE signals and communicate with the GWS device located at the ground station. Satellites 20A, 20B are communicating with the ground station antennas 14A, 14B. The first satellite 20A is descending and beginning to move away from its current footprint 50A for ground station antenna 14A, while the second satellite 20B is ascending and serving footprint 50B for ground station antenna 14B.

[0039] GWS31 can use, for example, Q / V band feeder link tracking antennas 14A and 14B for gateway satellite feeder links 14 and 15. Satellites 20A and 20B can use the operator's LTE spectrum as a service link for multiple UEs, such as RF beams for each cell within their footprint, e.g., 16 and 17.

[0040] In Figures 1 and 2, for multiple cells within the overlapping area 50AB, the serving BBU is informed by the satellite RAN control center of the duration for BHO for multiple active UEs, for example, the polarity of one or more HO cells 51h. That is, when multiple cells 51 enter the overlapping area 50AB, a satellite beam handover process is initiated to switch the communication of those overlapping cells 51h from the sinking satellite beam 16h to the rising satellite beam 17h. Note that beams 16h and 17h are slightly different from the other beams 16 and 17, as in BHO, beams 16h and 17h are beams from the same eNodeB and associated with the sinking satellite 20A, but in beam HO, that eNodeB is associated with both the sinking satellite 20A and the rising satellite 20B. Beam 16h is the same as beam 16, which holds the initial PCI (physical cell ID) 13A(1), but during BHO, the priority is not data traffic but the HO of multiple active UEs into beam 17h, which may be one of the MIMO RF ports of multiple cells, or a newly initiated BBU / cell by the same serving eNodeB, and 16h and 17h may form a coherent Rx signal like a MIMO signal. Other RF ports or BBUs may have different PCI 13A(2) entering via the rising satellite 20B, and the selection of PCI pairs is possible so that they do not interfere with each other, allowing them to work like MIMO and expand with each other. Thus, beam 17h is added to the beam of the newly rising satellite, and 16h and 17h coexist during the BHO period. Thus, BHO only occurs in cells where the satellites of the sinking satellite 20A and the rising satellite 20B overlap. HO beam 17h maintains the same configuration for user traffic and becomes one of multiple beams 17. The 3GPP specification only covers the mobility management of multiple UEs moving between cells. Satellite relay and its mobility are not part of the 3GPP specification. Most active UEs in the HO beam or cell will experience a radio link failure (RLF) if instant hard switching from a sinking satellite 20A to an ascending satellite 20B is used and the HO is unsuccessful.

[0041] To enable satellite mobility (satellite mobility, fluidity), this disclosure provides BHO conditions or methods that apply existing 3GPP HO procedures to achieve BHO. According to the 3GPP specification, each eNodeB has, by default, at least two RF ports, and their signals pass through two separate TRxGWS-satellite feeder links 14, 15, and then the satellites use the MNO spectrum for multiple beams, and there are service links 16h, 17h (both DL and UL) from two satellites 20A, 20B, and furthermore, 16h and 17h are overlaid on BHO cell 51h in overlapping region 50AB during the BHO period. Figure 2 shows how the eNodeB12(A) of one cell has two RF ports 12A(1) and 12A(2) and distributes DL and UL LTE signals via two GW antennas 14A and 14B that serve two satellites 20A and 20B, and how each baseband unit (BBU) of the cell provides beam signals for HO service links 16h / 17h via feeder links 14 / 15 for two TRx paths to the two RF ports 12A(1) and 12A(2) on eNodeB3BBU12(A). The newly added beam 17h initiates communication with the target GW antenna 14B of interface 1214B, indicated by a thin line, and it should be noted that this is a new BHO signal newly applied to BHO cell 51h by the new beam 17h from target satellite 20B for BHO from 20A to 20B. In contrast to the source cell's PCI13A(1), the 1214B uses a different PCI13A(2), so to the UE it appears as a new cell.During the BHO period, the two beams 16h and 17h function as a serving cell and a neighbor cell, respectively. 16h, as the source cell, sets its system information to an inaccessible state (no access occurs) and notifies UEs to leave the cell as soon as possible (idle UEs reselect cells, UEs that have just completed a BHO do not return to that cell, and newly powered-on UEs do not RACH to that cell). As a result, 16h abandons service to 51h and is finally HO'd to 17h. On the 20B side, once all active UEs have moved to 17h, the BHO procedure for that cell is complete, and cell 51h becomes the general cell 17 within 20B's FoV. A new target cell is born, and because the core network maintains the same Tracking Area Code / Location Area Code (TAC / LAC), multiple UEs that have moved to the new cell are paged (called) via beam 17h instead of 16h, as 16h can no longer serve UEs after the BHO.

[0042] Each cell is assigned two PCIs (or 2G cell color codes, BTS color codes, and training sequence codes), which are used alternately in each BHO instance. PCI deployment requires careful consideration of the reference signal RE location; for source and target cells, the reference signals must not be on the same RE to avoid interference on the UE side. The two cells should function like two layers in a MIMO setup, assisting each other rather than causing problems.

[0043] It's worth mentioning that BHO is seamless because it's primarily a procedure for PRACH (Physical Random Access Channel) channels, and can continue with all traffic channels, PDSCH (Physical Downlink Shared Channel) and PUSCH (Physical Uplink Shared Channel), just as standard HOs do.

[0044] Furthermore, after the BHO, when beam 17h becomes one of beam 17, it is packed together with the current multiple cells of 50B, incorporated into part of eNodeB12(B), and fed to the gateway antenna 14B interface of the IQ stream. Such signals are then passed from eNodeB12(A) to eNodeB12(B), from GW antenna 14A to GW antenna 14B, and from feeder link 14 to feeder link 15, achieving a BHO from satellite 20A to satellite 20B. The data for the BHO cell is no longer needed from 20A and is supplied from 20B. This can also be treated similarly as a two-cell HO. It should be noted that by default, each cell has two RF ports, and the BHO only borrows one of them for a short period, so no extra hardware is needed, saving feeder link bandwidth if the first satellite RAN providing global-scale coverage uses 1T1R. In MIMO operation, one port can be temporarily used for the BHO.

[0045] The power levels from two RF ports (e.g., two communication ports) 12A(1) and 12A(2) via a sinking and ascending satellite are similar, and there are no HO cell edge conditions like those in a terrestrial network. In BHO, this beam superposition occurs, so the entire cell receives equally good signal from the symmetrical beams of the two satellites. The shape of the overlapping area is such that most RF paths (or beams) 16h and 17h are symmetrical with respect to the cell, although there may be some differences due to locality if the terrain is uneven. However, statistically, they are almost the same in terms of covering a remote area. Therefore, most of the BHO is smooth unless one side, for example, the side of beam 17h, is blocking the path (e.g., a mountain). Cell planning should address such situations to avoid them, but there are always exceptional cases, such as tunnels and buildings, as with all wireless communications.

[0046] In operation, cells 51 and 52 within the FoV of each satellite 20A and 20B communicate with the respective eNodeB's BBU 12(A) and 12(B) via designated RF ports. Specifically, cell 51 within the FoV of the sinking satellite 20A communicates via the sinking satellite 20A and the first beam 16. Then, the sinking satellite 20A communicates via the first (primary) RF transmit / receive (TRx) port 12A(1) through the first GW antenna 14A and the first BBU 12(A) of the eNodeB farm of cluster 12(CA) at gateway site 31. Then, cell 52 within the FoV of the rising satellite 20B communicates via the rising satellite 20B and the second beam 17. The ascending satellite 20B then communicates with one or more second BBUs 12(B) of the cluster 12(CB) eNodeB farm via the second antenna 14B and the first RFTRx port 12B(1). Each eNodeB communicates with a single cell 51, 52.

[0047] When multiple cells enter the overlapping region 50AB, a smooth and seamless beam HO is triggered. At the moment of beam HO, two RF ports (e.g., 12A(1) and 12B(1)) are used separately, but for simplicity, only the SIMO (Single Input Multiple Output) configuration is illustrated for both satellites. All cells 51 and 52 in the non-overlapping region use only one of the two RFTRx ports 12A(1) or 12B(1), and each footprint has its own beams 16 and 17 for normal user data traffic operation.

[0048] However, within the overlapping region 50AB, multiple cells 51h are engaged in beam handover and gateway handover. In the exemplary embodiments of Figures 2 and 3, beam handover refers to the process of moving from a first set of eNodeB12(A) to a second set of eNodeB12(B) and switching from satellite 20A to satellite 20B. Gateway handover (GHO) may refer to the process of moving from a first antenna 14A to a second antenna 14B.

[0049] Initially, cell 51 communicates with BBU 12(A) of the first eNodeB farm 3 of cluster 12(CA) for satellite 20A via primary port 12A(1) using PCI 13A(1) through the first GW antenna 14A. When these cells 51 enter overlapping region 50AB, these cells 51 also communicate with secondary port 12A(2) of the same eNodeB farm 3's BBU 12(A) via the rising satellite 20B and GW antenna 14B, but using a different PCI 13A(2). At this point, eNodeB 12(A) enables secondary TRx port 12A(2) and communicates with the rising satellite 20B via beam 15 through the second GW antenna 14B, and also communicates with the cell via the new beam 17h. In this way, the beam from satellite 20A can initiate HO from serving beam 16h to serving beam 17h.

[0050] Thus, as the sinking satellite 20A continues its descent and the rising satellite 20B continues its ascent, multiple cells 51 move from the sinking FoV 50A to the overlapping region 50AB, and then to the rising FoV 50B. When they enter the overlapping region 50AB, BHO processing is performed, and multiple ground cells 51 are changed to 51h. The essential part of BHO is that the rising satellite 20B provides a different "fake cell" with a different PCI for the rising satellite 20B, which is a new target cell for the rising satellite 20B, but is geographically the same cell 51h. The new cell requires another process device called a baseband unit (BBU) within the eNB farm 3, and generally, by default, each cell has two BBUs with RF ports for a primary TRx and a secondary TRx. In the following description, two TRx are used for one cell, but other BBU resources in the eNB farm may be used to provide the new BHO cell 17h.

[0051] For example, BBU-p12(A) in eNodeB farm 3 is serving cell 51, and the Satellite Network Control Center (NCC) notifies the eNB and BBU-p that 51 will become 51h, so the eNB switches on or turns (directs) the secondary BBU-s and RF port 12A(2) of eNodeB 12(A) to the target cell, in addition to the primary RF port 12A(1). The first antenna 14A still carries the setting beam 16 for BHO purposes and is labeled 16h in the BHO process, while the secondary RF port 12A(2) of the same eNodeB 12(A) acquires the route of the target beam, i.e., the second antenna 14B (which tracks its ascending satellite 20B). When communication is initiated with multiple active UEs within cell 51h via the secondary port 12A(2) through the second antenna 14B and the ascending satellite 20B, communication via the primary port 12A(1) and the first antenna 14A ceases. These cells continue communication with eNodeB12(A) via the secondary RF port 12A(2) and the second antenna 14B (where each BBU12(A) may become BBU12(B), and each secondary RF port 12A(2) of BBU12(A) may become or be considered to be the primary RF port 12B(1) of BBU12(B)), and this state continues until a new ascending satellite arrives, at which point they switch to communicating with the new ascending satellite via the first antenna 14A and port 12A(1) of the first BBU12(A). BBUs 12(A) and 12(B) are one of the signal processing units for their clusters 12(CA) and 12(CB), respectively, illustrating processing devices that dynamically service the GW tracking antennas 14A and 14B and most of the cells within their FoV, respectively, except for the BHO cells, each HO cell has two RF ports, and therefore the source cell uses both 14A and 14B simultaneously via the two RF ports p and s, as shown for multiple BBUs. After the BHO, the cell's BBU conceptually transitions from 12(CA) to 12(CB).Because the satellite serves different ground cells under its orbit, the pool (community) of BBUs serving the tracking dish (tracking antenna) is not static, and the GW channel routing block 10 performs channel routing functions under the supervision of the NCC. The gateway channel routing block 10 at gateway site 31 routes or connects ports 12A(1) and 12A(2) to beams 16h and 17h, respectively, with the appropriate antennas 14A and 14B, where the beam 17h signal on GW antenna 14B is represented (or corresponds) as a separate thin wire 1214B (e.g., a separate thin wire interface) in the IQ interface streaming of the GW or GW antenna 14B, meaning the corresponding eNB begins processing the BHO for its cell 51h.

[0052] By default, one eNB (i.e., eNodeB) 12 has two RF ports and transmits signals for one cell (same PCI) in the terrestrial network (TN). Beam HO uses both ports, each labeled (1) and (2), and transmits signals from the same eNB but uses PCIs (13A(1), 13A(2)) with two different physical cell IDs. However, even though they are the same cell from one eNB, they are operationally associated with different cells, and one PCI needs to correspond to satellite 20B and gateway antenna 14B. Thus, its beam can be directed from the rising satellite 20B, and the different PCIs will trick the UE into thinking another adjacent cell is available, and the HO procedure and protocol can be used to get the current beam of 12A(1) to HO into 12A(2), which may be the same cell from the same eNB, however, by using its two RF ports via two GWs, the two satellites become "Ncell" for the purpose of beam HO.

[0053] Multiple RF ports on each eNB can be switched to any GW antenna (14A or 14B), and the items related to the two GW antennas 14A and 14B in Figure 2 are distinguished as A and B respectively, with 12(A) being one of the eNBs that transmits a signal to GW antenna 14A, and 12(B) being another eNB that typically transmits a signal to GW antenna 14B. However, during beam HO, 12A(2) can initiate streaming to GW antenna 14B as a step in HO, and ports (1) and (2) can initiate mapping to A and B, respectively, which are satellite / GW antenna labelings, reflecting an innovative part of the BHO mechanism for the UE to have a smooth HO.

[0054] In other words, 12(B) refers to those eNBs that serve multiple cells 52 within footprint 50B, and RF port 12A(2) corresponds to BHO cell 51h during the transition from cell 51 in footprint 50A to cell 52 in footprint 50B via a second RF port 12A(2), assuming that BHO cell 51h is cell 52. RF port 12A(1) corresponds to cell 51 in footprint 50A and communicates via GW antenna 14A. RF ports 12A(2) are added one by one to the BHO GW antenna 14B when each cell 51h is in overlapping area 50AB. RF port 12A(2) is used during BHO to handle unmodified UEs.

[0055] Figure 3 illustrates the interaction between multiple active UE30s, eNodeB12(A), and gateway channel routing block 10, and how they cooperate or operate for BHO. BHO uses CFRA (Contention Free Random Access) under the control of multiple eNodeBs to achieve a smooth and seamless BHO. Multiple idle UEs do not require such eNodeB support. After BHO, the idle UEs reselect their cells as described above and receive services from the eNodeBs using CBRA (Contention Based Random Access) when needed.

[0056] Similar to how the 3GPP specification intends for CFRA to be used for HO of UEs across multiple cells, the arrow diagram illustrates the conditions that are met so that CFRA is pre-scheduled, MSG1 to MSG2 are sufficiently prepared to have the appropriate TA for each UE in the BHO, and the HO runs as a fully synchronous HO.

[0057] In a specific example, when two HO beams 16h and 17h are overlaid on BHO cell 51h, the PCI values ​​of the two RF ports are selected to avoid CRSRE overlay and minimize or reduce interference with each other, and the two beamframe structures are given a time offset such as 1.5ms to avoid overlap of MIB, SSS, PSSSSB (for 5G), and SIB, thereby allowing multiple active UEs to easily distinguish them and differentiate the details of the two cells.

[0058] In another example, gateway site 31 identifies (or determines whether an active user equipment (UE) exists in cell 51h within overlapping area 50AB) via eNodeB12(A), and if no active UE is identified, applies a hard beam handover from sinking satellite 20A to rising satellite 20B (for example, turning off the source beam, e.g., 16h, while simultaneously turning on the target beam, e.g., 17h). One gateway site links to two satellites simultaneously (1G2S).

[0059] Figures 1 and 2 show one gateway site 31 and two satellites 20A and 20B. The two satellites 20A and 20B are serviced by the same GWS (1G2S), and gateway site 31 may have multiple gateway antennas (tracking dish antennas) 14A and 14B serving multiple satellites. A BHO from satellite 20A to satellite 20B can use the two dish antennas 14A and 14B respectively to track its serving satellites 20A and 20B. Beam 16 serves multiple cells within satellite 20A's FoV (or footprint) 50A, and beam 17 serves multiple cells within satellite 20B's FoV (or footprint) 50B. In the illustrated embodiment, each satellite (e.g., 20A, 20B) communicates with the eNodeB farm 3, and each satellite is in constant or required to communicate with one or more clusters of eNodeB 12(A) or one or more clusters of eNodeB 12(B) within the eNodeB farm 3 (e.g., installed in the same location as the GW antennas 14A, 14B and forming the GWS 31), thereby providing LTE services, with each cell being serviced by the eNodeB within its respective cluster of eNodeBs. Multiple cells 51 within the sinking satellite FoV 50A are serviced by the clusters of eNodeB 12(A) via satellite 20A while satellite 20A is passing. Near the end of service for satellite 20A (before those cells leave its FoV), those cells 51 are on the satellite overlapping region 50AB and can pass through the BHO by an exemplary process as described below.

[0060] 1. Two overlapping beams, 16h and 17h, can be applied to the BHO cell, and the label of the BHO cell will be 51h.

[0061] 2. Serving beam 16 is changed to HO sourcing beam 16h. HO sourcing beam 16h is almost identical to beam 16 and continues to use PCI13A(1), but beam 16h is prioritized for BHO. Figure 3 shows the main functions of beam 16h, which can work in conjunction with the corresponding beam 17h to smoothly achieve BHO.

[0062] 3. Target HO beam 17h is similar to beam 16, but has an alternative (different) PCI13A(2) and is supplied from a different RF port on the same eNodeB12(A).

[0063] As shown in Figure 2, beam 16h is supplied as usual from the primary TRx port 12A(1) of eNodeB12(A) using PCI13A(1), and target beam 17h is a new HO beam from the same eNodeB12(A), but is supplied from the secondary TRx port 12A(2) via the target satellite 20B using a new PCI13A(2). After HO, beam 17h from the second RF port of the same BBU (if the cell BW is the same, HO of the eNodeB is not performed here, but beam HO is performed. This is satellite mobility, not UE mobility processing, so the same eNodeB is maintained) becomes the new target beam 17. Furthermore, the BBU of the same serving eNodeB can leave cluster 12(CA) for BBU12(A) and join cluster 12(CB) for BBU12(B), becoming one of the BBUs serving the ascending satellite 20B. BHO is achieved by superimposing the target HO beam 17h onto the same cell currently covered by the source HO beam 16h. If the cell BW needs to be changed, BHO is a good opportunity to use a different BBU configured for the newly requested cell BW (CBW), and the examples of primary and secondary RF ports for the same CBW above will need to be adapted to the new CBW. However, the deployment and mechanism of the ping-pong PCI remain the same.

[0064] Beams 16h and 17h are used for both downlink (UE Rx) and uplink (UE Tx). In a HO cell with 50AB, a pair of ping-pong PCIs 13A(1) and 13A(2) are assigned to two TxRF paths and delivered to the same cell 51h by the same eNodeB. Since UEs do not HO to cells with the same PCI, different PCIs are used when a BHO occurs. Thus, each cell has two PCIs, for example, 1 and 4, and there are different PCIs for each BHO. If the PCI of one cell was 1, the HO beam may have a PCI of 4, and the HO of the next beam may have a PCI back to 1. In this way, the PCIs of a single cell may alternate, such as 1-4-1-4-1-4, and the ping-pong PCI design allows multiple eNodeBs and multiple UEs to solve satellite mobility problems using HO procedures defined by 3GPP for BHOs.

[0065] The overlapping beam 17h from the ascending satellite is almost identical to 16h, but has a different PCI. Initially, the PCI difference for overlapping beam 17h is due to the UE performing a CFRA (Critical Frequency Response) on the target beam from satellite 20B, instructed by source beam 16h, which serves the UE. BHO beams 16h and 17h originate from the same eNodeB. Once the UE synchronizes with the new beam 17h, the active UE reads the broadcast information and selects the appropriate cell. These UEs use System Information Blocks (SIBs) to understand when and where PRACH (Predictive Radio Frequency) should occur. Furthermore, source beam 16h transmits a Radio Resource Control (RRC) connection reconfiguration, instructing multiple active UEs to measure the target beam on the PCI of the ascending satellite 50B. The RSRP (Reference Signal Receiving Power) and RSRQ (Reference Signal Receiving Quality) of the target beam are measured and reported to eNodeB, allowing eNodeB to know that the BHO conditions are correct.

[0066] In cell 51h's eNodeB12(A), while target satellite 20B transmits a new target HO beam 17h with a different PCI, the Tx signal on source HO beam 16h provides the PCI of target beam 17h to the UE, which then measures and synchronizes with target beam 17h accordingly. Rx on the target beam provides eNodeB with the timing advance (TA) value required for the CFRA's Random Access Response (RAR). The source satellite's Tx transmits target PCI 13A(2) for multiple UEs for the CFRA. Multiple cell eNodeB12(A) share the HO tasks in overlapping region 50AB, allowing these processes to be performed in parallel for each of the HO cells 51h. BHO is at the top of the normal eNodeB scheduling and tasks, including UE mobility, and modifies multiple beams and cells as needed when multiple UEs move between them. One satellite links to two gateway sites (1S2G).

[0067] As shown on the left side of Figure 2, if satellite 20A's FoV has two or more GW footprints (GFPs) and service is required from both GFPs, then 1S2G is the condition for GHO. GHO is initiated when the first cell 53 of 50A requests service from satellite 20A and a second GW-SAT (GW satellite) link 13 is needed for eNodeB to service multiple cells 53 (dashed cells) on another gateway site 32. Therefore, satellite 20A requires the 1S2G condition.

[0068] Figure 5 further shows the core network associated with the GHO, including interconnected GWs and two GWSs, and includes a UE mobility case between cell 51 and cell 53 served by different GWSs shown in Figure 2. operation

[0069] Multiple eNodeB farms host thousands of cells, with hundreds of eNodeBs serving corresponding cells anchored to the Earth's surface. Because satellites move at high speeds, some cells dynamically enter the satellite footprint while others dynamically leave it. This means that the GWS serving the satellite changes its eNodeB cluster as the satellite moves, and multiple eNodeBs also change the GW-satellite links. To address the challenges of such dynamic cell changes, in some cases, the eNodeB software running on the eNodeB farm hardware needs to float to other hardware (HW), which may be hundreds of kilometers away (in the case of a GWS diversity design), and the GWS and its eNodeB farm hardware can quickly capture a mirrored image of the eNodeB when they are optimally (or appropriately) configured for the software serving the cells. For example, in a GWS diversity design, two GWSs may be hundreds of kilometers apart, and redundant sites can quickly perform GWS mirroring to improve the user experience. Any fixed cell can be served by any eNodeB hardware at any GWS location while maintaining the software context for the fixed cell running on a different host; this is referred to here as eNodeB mirroring. In some examples, the eNodeB hardware serving the fixed cell can be changed from the first eNodeB hardware to the second eNodeB hardware, and the software context can be moved from the first eNodeB hardware to the second eNodeB hardware. The core network must make corresponding changes to deliver paging and system information in response to the change in serving eNB. This is particularly useful in certain exceptional cases.

[0070] Another way to leverage GWS diversity without duplicating the eNB hardware is to use long-distance fronthaul fiber links between GWSs. This is a less expensive option, but it requires calculating the delay of the fiber TRx, which is usually fixed and stable once the fiber links are set up and functioning as expected.

[0071] Referring to Figure 3, the system operation (process) 200 is shown, specifically the operation (process) in multiple UEs 30, their serving eNodeB 12(A), and the associated serving gateway, including the gateway channel routing block 10. The BHO starts with an active cell served by one eNodeB 12(A), and the multiple active UEs 30 acquire service with IQ streaming from GW antenna 14A for DL ​​and UL, and satellite 20A tracks all cells such as 51 within its FoV. That is, in step 260, gateway 10 establishes connections to their eNodeB and satellite on one or more or all GWSs. One GWS (e.g., 31, 32) knows or recognizes that incoming satellites and associated GWs are ready at any time for the necessary links with any satellite, thus meeting the needs of the GHO. This is pre-scheduled and related to the location of the paths of multiple GWSs and multiple satellites. In step 262, the GW (e.g., GW channel routing block 10) performs delay compensation (or delay normalization) and Doppler compensation for cells 51, 52, and 53 so that delay variations and Doppler effects caused by satellites 20A and 20B are no longer factors to be handled by eNodeB, i.e., delay and Doppler are compensated for relative to the center of each cell to provide, for example, dynamically near-zero differential delay and Doppler. This correction (compensation) is performed relative to the cell center, and at the edges of the cell, residual delay and Doppler effects are within the UE's pull-in range (tuning range) and LTE service is available. In some examples, the GW (e.g., GW10) may be configured to perform delay normalization so that at the cell center, the UE's timing advance (TA) is equal to the timing advance (TA) value at the midpoint. In other words, for example, at the cell center (e.g., the beam center), the UE can make its timing advance equal to the intermediate timing advance (TA) value, which is the midpoint of the range of TA values.

[0072] When the active cell enters overlapping region 50AB in step 220, the satellite communications system tells (or instructs) the eNodeB to start the BHO. For example, the eNodeB may start the BHO in response to receiving a start instruction signal transmitted from the satcom system (satellite communications system) when the active cell enters overlapping region 50AB. Steps 222 and 264 are the eNodeB and GW handshake signals and operations for subframe-by-subframe adjustments to switch the IQ stream to the correct satellite and the correct GW.

[0073] At some point, cell 51 is in overlapping area 50AB, i.e., the overlapping area of ​​FoV (or footprint) of the two satellites 50A and 50B. BHO is on, and the cell becomes BHO cell 51h. BHO must occur in area 50AB. The process of moving all active UEs from beam 16 of the sinking satellite to beam 17 of the rising satellite is initiated. At this point, gateway 10 and eNodeB 12 are notified in step 264 to begin beam handover by changing beam 16 to 16h and 17h, and eNodeB will perform the BHO function. In steps 222 and 266, eNodeB 12(A) and gateway 10 switch on the second RF port 12A(2) of eNodeB 12(A) for beam 17h, 16h remains the same as 16, and processing of the newly added beam 17h begins. The BHO from 20A to 20B has ended, and both satellites (20A and 20B) are orbiting above them. Cell 51h is no longer included in the FoV 50A of the sinking satellite 20A, but is included in the FoV 50B of the rising satellite 20B. Therefore, cell 51h is a newly added cell under the rising satellite 20B, and becomes the same as cell 52 under satellite 20B, and beam 17h is changed to beam 17.

[0074] The BHO procedure is as follows: The target TRx beam 17h is sent to beamHO cell 51h. GWS31 uses the intermediate frequency (IF) signal of the extra RF port 12A(2) to map to the GW-satellite link 15 for satellite 20B, supplying the new beam 17h and causing it to overlay (overlap) on cell 51h. Cell 51h (within the overlapping region 50AB of both satellites 20A and 20B) has two beams, 16h from source satellite 20A and 17h from target satellite 20B, and an active UE (RRC_connected state) is aware that the BHO procedure (command or step 226) is initiated from eNodeB with target beam 17h. The RRC has three states: idle, disconnected, and connected. When connected, it essentially means that a connection between eNodeB and UE has been established and is ready to serve the UE. If a UE does not require service for a certain period, the UE becomes idle after a period of inactivity, and the eNodeB reserves service for that UE's multiple radio resources (multiple RRs) (i.e., those radio resources are allocated to other active UEs).

[0075] The source beam 16h and target beam 17h are superimposed (overlaid) on the same physical cell 51h fixed to the ground, using two different PCIs 13A(1) and 13A(2), respectively. Therefore, multiple UE30s within cell 51h can recognize beams 16h and 17h as corresponding to two different cells, and satellite BHO can be realized by using PCIs alternately. The two RF ports 12A(1) and 12A(2) of the eNodeB deliver ping-pong PCIs from the two satellites 20A and 20B to cell 51h via the two RF paths 16h and 17h.

[0076] Gateway 10 works with eNodeB to route or switch these RF paths at appropriate times between steps 260 and 266. The TRx action in step 224 ensures a smooth start to the satellite BHO and maintains a good user experience under the control of eNodeB through the steps in Figure 3. In some examples, the TRx action in step 224 may also include sending a new PCI and receiving the UE's response to the BHO scheduling. Once multiple UEs are fully HO'd to beam 17h and the BHO has ended, and those UEs are in service with satellite 20B or are located in one of the cells in service with satellite 20B, the beam in service becomes one of beams 17h. The BBU remains the same for the same CBW, but may be different (e.g., hardware-wise) for different CBWs of GWS31, and conceptually change from cluster 12(CA) to cluster 12(CB), and accordingly, the eNodeB (or its labeling) may change from eNodeB12(A) to eNodeB12(B). The satellite changes from satellite 20A to satellite 20B before the overlapping region leaves cell 51h and that cell becomes one of cell 52. All cells in 50AB perform this BHO procedure in parallel with the eNodeB in service, but there is ample time (many seconds) to do so (there should be ample time depending on the satellite constellation design).

[0077] Furthermore, in Figure 3, eNodeB12(A) starts as a source eNodeB along with the PCI preparation, and the handover starts in step 222. In addition, in step 224, eNodeB12(A) uses source cell PCI13A(1) (for example, with a value of 1) on one RF port 12A(1), prepares another RF port 12A(2), and transmits another PCI13A(2).

[0078] On the side of multiple active UE30s, those UE30s start service as well as multiple UEs on multiple TN cells. Step 205 shows the general starting point for UEs with respect to BHO and GHO. In step 226, eNodeB starts scheduling multiple UEs in the RRC_connected state, as shown in step 210, and communicates or instructs the UEs to find the target beam PCI13A(2) and report the BHO measurements.

[0079] Multiple (M) UEs further transmit measurement reports 212 (multiple UEs can be scheduled for efficiency). The eNodeB12(A) of the BHO in cluster 12(CA) receives the measurement reports and knows that beam 17h meets the HO conditions and is in a suitable state to take over. Simultaneously, the UL signal 212 (e.g., measurement report) allows the eNodeB12(A) to obtain, in step 230, each new RF path TA for the (WRT) beam 17h of the M UEs in the batch. Next, the eNodeB12(A) pauses the ongoing user plane traffic on beam 16h and assigns a preamble for contention-free random access (CFRA) of the BHO. Next, in step 232, the eNodeB of the BHO transmits the preambles for the M CFRAs to the M UEs 30, so that multiple CFRAs occur on beam 17h and the eNodeB can know or recognize each UE by the assigned preamble. In step 234, multiple eNodeB12(A) on the BHO also prepare RARs with the correct TAs for all UEs in the batch and transmit them before acquiring MSG1, as scheduled in 236. The method for acquiring multiple TAs for multiple UEs on the BHO of handover beam 17h is based on multiple TAs of the beam in service of the sinking satellite. Both of these beams are processed by the baseband signal processing unit of the same eNB, and by UL Grant Command, it is possible to know which RB is for which UE, and by correlating the two received signals of those RBs, new TAs for the rising satellite beam can be calculated in advance without waiting for RACH in CFRA, and RAR(MSG2) can be transmitted in advance to align with the UE's planned (expected) MSG2. If a new error occurs in the TA, the change in TA can be tracked from MSG1, which is received after MSG2. This is a significant innovative addition to solve the BHO speed problem, which is a challenge when many active UEs pass through the BHO every few minutes.

[0080] In step 214, the multiple UE30s, in response to signal 232, send MSG1 containing CFRA to beam 17h for PRACH (e.g., in the procedure defined in the specification) to inform eNodeB12(A) that the UE30s are attempting to move from source HO beam 16h to target HO beam 17h. A preamble is used or included to help beam 17h identify and distinguish the multiple UE30s. Thus, in step 216, the multiple UE30s send CFRA of M MSG1s to eNodeB12(A) of cluster 12(CA). Furthermore, in step 236, eNodeB12(A) of cluster 12(CA) sends RAR of M MSG2s to the multiple UE30s.

[0081] In response to MSG2, in step 218, M UEs 30 know or identify a new TA to use on beam 17, and the user plane (i.e., data traffic) is restarted. Then, in response to MSG1, in step 240, the user planes of the M UEs (along with the eNode B12(A) of the BHO) are restarted with PCI13A(2) (value 4), and the next BHO uses PCI13A(1) (value 1), and this cell PCI is changed periodically, for example every few minutes, as [1,4,1,4...] when the next ascending satellite is serviced.

[0082] Furthermore, in step 238, eNodeB12(A) sends a cell HO status update to gateway 10 when the HO of all RRC-connected (RRC_connected) UEs is completed. Gateway 10 then turns off RF port 12A(1) of eNodeB, which has PCI13A(1) for BHO, and uses RF port 12A(2) and PCI13A(2) for the user plane in progress under the service of satellite 20B. The coexisting beams 16h and 17h from the two RF ports 12A(1) and 12A(2) via the two GW antennas 14A and 14B and the two satellites 20A and 20B improve the reliability of the BHO, and if CFRA fails for some UEs, the above procedure can be repeated until all scheduled CFRAs have been successfully processed. From step 238, via the control channels of the eNodeB and GWS interfaces, multiple BBUs behind the two overlapping beams know that all active UEs are HO'd to the new beam 17h / 17 and no longer need the old beam 16 / 16h, and terminate them in step 268. The eNodeB also stops transmitting signals from the old port. This terminates the BHO, and the eNodeB of the BHO is registered with the eNodeB farm and GWS as eNodeB12(B) in cluster 12(CB) in steps 242 and 270, and returns to normal user plane traffic data processing via satellite 20B in step 272. In some examples, the eNodeB can terminate the BHO in response to receiving a termination instruction signal transmitted from the satellite communications system.

[0083] It is worth mentioning that each LEO satellite can service cells within its FoV, depending on whether it starts from initialization with the GW and eNodeB in service. One LEO satellite is always in constant relative motion with multiple cells it serves, so it not only constantly steers its beam to track multiple existing cells, but also constantly performs BHO with neighboring satellites as multiple cells enter or leave its FoV. Step 244 in Figure 3 shows the overall ongoing procedure in handling satellite-cell dynamics. Each satellite, from the point of view (PoV) of the BHO, is simultaneously the source and target, and in coordination with the switching of the eNodeB and GWS, it abandons the old beam and starts a new one. GWe10 for SE20 at LEO 18, 700km above the equator

[0084] Referring to Figures 4(a), (b), and (c), it is desirable that the density between GWS and satellites be sufficient. Therefore, for BHO and GHO, we consider three cases here as non-limiting examples of this disclosure. Figure 4(a) shows the 1G1S (one gateway, one satellite) scenario. In this case, one satellite can only connect to one gateway. Figure 4(b) shows the 1G2S case where two satellites can connect to one gateway station simultaneously.

[0085] Figure 4(c) illustrates 2G1S, where, for example, if a satellite traverses a wide country, two gateways are connected to one satellite to realize Gateway HO (GHO). eNodeB farms are located at each gateway or in the data center between gateways, enabling GWS diversity to accommodate conditions such as rain. To achieve this, both GWSs of both GWs (or both GWs) are connected via high-bandwidth CPRI or eCPRI fiber links (fronthaul) to pass DL and UL IQ data for hundreds of cells from both gateways required for the two GWSs. Otherwise, multiple cells between the two GWSs would require duplicate eNodeBs at both GW sites to serve those cells.

[0086] In areas where satellites overlap, in addition to arranging rerouting for CUs and DUs, action alignment is required using inter-GWS eNodeB gateway interconnect links (such as X2) that pass through TAs of multiple UEs relative to the target cell, along with scheduling of multiple active UEs, multiple beams of BHOs, satellites, GWSs, eNodeBs, and BHOs, as well as multiple different eNodeBs of ascending satellites and GWSs. The 10-15ms delay of the inter-GWS gateway interconnect link (GIL) is taken into account as part of delay normalization, pre-scheduling is performed so that UEs can recognize new DL frames. The system compensates for the main time delay, and the TAs handle the remainder related to the UE's position within the cell. X2 is commonly used in LTE and is used here as an example of a GIL. The GIL enables communication between gateways and supports handover cases.

[0087] Figure 4(b) shows the case of 1G2S, where the satellite performs beam HO while maintaining the same GWS, for example, as shown in Figure 2. In the HO scheme, two simple information elements (IEs) are introduced to the gateway interconnect link eNodeB link of the UE's HO procedure in order to meet the UE's mobility HO needs using standard 3GPP procedures. These two key changes are ping-pong PCI to the two RF ports of the cell eNodeB.

[0088] Embodiments (or examples) of the BHO in this disclosure involve spoofing the PCI so that the BHO becomes a standard UE HO event for each UE, so that a normal UE does not need to care which satellite and gateway is serving it, and the same applies to eNodeB. This procedure greatly simplifies the requirements for satellite RAN for multiple UEs and base stations, making the satellite complexity transparent (e.g., completely transparent) to both parties to the RAN, so that all normal phones become satellite phones (e.g., satellite phones that can communicate with satellites), so that transparent satellites are enabled and can communicate directly with the low PHY (i.e., the lower physical layer) of the modified base station and multiple 3GPP-compliant UEs that are not modified. In some examples, the base station is configured to implement the functionality to work with the satellite RAN. Since no cell is actually modified, the core network does not need to divert data flow, no real cell HO occurs, and no extra load is placed on the system.

[0089] It's worth noting that, from an initial look at the system architecture, such changes can be treated as a handover between two cells and can be done using the two RF ports of a single cell without adding any extra hardware. By default, each cell has two RF ports, so the MIMO operation of multiple UEs performing a BHO will be interrupted for a few frames for the BHO and then resumed after the BHO.

[0090] The above functions are software (SW) changes required at base stations (BTS for 2G, eNB for 4G, and gNB for 5G). In addition to SW changes related to BHO procedures, there are also general satellite RAN SW changes. A brief summary of the main baseline changes related to BHO is as follows: 1. Because the RF paths of the feeder link and service link are over 1000 km long, extra delays occur in the DL and UL signals. However, these can be normalized to appropriate values, and the delay function is as described above. This affects the Rx of the base station, but since this is known in the system configuration, the Rx scheduling of the satellite RAN base station is modified to take such delays into account. 2. For time-sensitive procedures such as LTE PRACH, CFRA should be used as much as possible (see description in this disclosure), CBRA should be used for the initial random access, and a set of preemptive MSG2 with a high probability of matching the UE's requirements should be required, and by including the use of a limited preamble of CBRA, it is possible to anticipate the TA before sending multiple PRACHs, and for 2G, this is necessary to adjust the Rx time. 3. Any system configuration with timers that are sensitive to long round-trip times (RTT) must be modified to withstand longer RTTs. 4. The CN is modified to accommodate two cells for one geographic cell, allowing two identical parameter sets to be assigned to two PCIs, and ensuring that the destination of user data does not change unless the BBU is actually changed. The CN is aware of the fact that an additional fake cell exists for each real cell.

[0091] Figures 4a, 4b, and 4c illustrate system cases implemented with 1G1S, 1G2S, and 2G1S, respectively. Each is suitable for a different case. However, information between gateways flows via the GIL, not through satellites. This is to eliminate inter-satellite relay and avoid violating local data security regulations. In the 1G1S period and case shown in Figure 4(a), a beam HO is not required. For example, if the satellite's FoV is much larger than the area that needs service, 1S can completely cover the area. As a more specific example, island nations like the UK and Japan can be covered by the FoV of a single satellite for a certain period. However, if the area is near the edge of the FoV, a BHO is required to continue service, and therefore 1G2S as shown in Figure 4(b) may be necessary. As the area approaches the FoV edge, another satellite needs to take over the cells on this edge, so 1S1G ends and transitions to 1G2S. Figure 4(c) shows the next moment or another case. Furthermore, as a satellite flies within its FoV, it needs to cover new cells. The GWS hosting the new cell requires 1S2G to provide additional services. Therefore, 1G1S is temporary, and will be followed by, for example, 1G2S or 1S2G. Backhauling (return shipping)

[0092] Referring to Figures 5(a), 5(b), and 5(c), backhauling of gateway interconnect links is shown, and gateway interconnect links (e.g., inter-gateway links) are one type of interface introduced by LTE radio access networks. Here, backhauling refers to connectivity to the core network, essentially where traffic goes from the UE and where traffic comes from to the UE. GILs connect multiple adjacent eNodeBs peer-to-peer, supporting UE mobility handover (traditional TN cell HO where UEs move across cells) and providing a means to quickly coordinate radio resources. Gateway interconnect links do not require dedicated physical connections between eNodeBs. Gateway interconnect links are logical interfaces that can pass through existing IP transport networks. Gateway interconnect links do not require L3 routing. Switching can be used where possible, and switching is preferable for higher performance.

[0093] Gateway interconnect link interfaces are not required between all eNodeBs in the TN (Terrestrial Network). NTN Beam HO requires gateway interconnect links for eNodeB gateway interconnect links of multiple neighboring GWSs to pass information about multiple target UEs. Clarification of gateway interconnect links between eNodeB farms is necessary and will be initiated.

[0094] Gateway interconnection link interfaces are only required between multiple adjacent eNodeBs (i.e., controlling multiple cells whose coverage areas overlap in a 1G2S+1G1S+1G2S configuration). Handovers and interference adjustments only occur between adjacent devices.

[0095] Figures 5(a), 5(b), and 5(c) illustrate a case of UE mobility handover between two cells serviced by a single satellite, where the source and target cells are each serviced by two gateways. In such an active UE cell handover, the core network 35 needs to handle the user data flow from the source eNB of GWS31 to the target eNB of GWS32.

[0096] In some examples, gateway site handovers occur or are performed at the cell granularity, with one cell associated with one GWS, and satellites moving from one gateway coverage area (or one gateway site coverage area) to another gateway coverage area while orbiting. Multiple satellites can transfer (or switch) communications from source satellite 20A to target satellite 20B in a 1G2S state (see Figure 2), and / or, in a 1S2G state where gateway antennas 11B and 14A belong to two GWSs 32 and 31 respectively, communications can be transferred to satellite 20A from gateway antenna 14A at gateway site 31 to gateway antenna 11B at gateway site 32. Thus, GHOs are embedded in BHOs, soft HOs are applied to BHOs, and GHOs are executed one by one in each cell under the control of the eNB, at the UE granularity, over a much longer period of time (several seconds), including seamless HOs for each active UE. GHO is a function of a satellite; when a satellite (for example, 20A in Figure 2) passes over one GWS, another GWS provides service to that satellite, and this process occurs sequentially and naturally, along with many BHOs.

[0097] In other words, GHO is performed at the BHO granularity. When all beams from one GWS are moved from satellite (e.g., 20A in Figure 2) to another satellite (e.g., 20B in Figure 2), satellite (e.g., 20A) has resources available to take in the new cell to another GWS (e.g., 32). Both BHO and GHO are "performed before breaking" in each active UE. The eNodeB only turns off 16h when 17h takes over, and more importantly, BHO does not change the cell's eNB, so the context of all active UEs is preserved and can be enabled seamlessly as needed, and the transition from 17h to 17 is very smooth because the eNB is the same before and after the BHO (e.g., BHO shown in Figure 2).

[0098] A satellite footprint has a leading edge and a trailing edge. BHO (Block-Holding Offset) occurs at two semicircular edges. The leading edge of a satellite can acquire a new cell when another satellite in front of it HOs its cell to it. The trailing edge of a satellite can relinquish a cell when it HOs its cell to another satellite behind it. These edges are generally defined at elevation angles of 20 degrees or more, but may be extended to cover multiple cells at lower elevation angles if necessary.

[0099] In some cases, a GWS also has a footprint, which may be smaller than or much smaller than its FoV. The FoV of a GWS refers to the area that the GWS can cover or reach. However, operators can (but are able to) choose or configure the GWS to cover only a portion of the FoV, rather than the entire FoV, usually to save costs. The area that an operator assigns to cover or reach the FoV of a GWS is called its footprint, and it is not only the area that the GWS can reach, but also the area where its "foot" (infantry) lies.

[0100] One of the GHO processes, as mentioned earlier, is for the movement (mobility) of a UE from cell 51 to cell 53, as shown in Figure 2. This has three phases: preparation (Figure 5(a)), execution (Figure 5(b)), and completion (Figure 5(c)). During the preparation phase (Figure 5(a)), the UE 30 is connected to the source eNodeB in GWS 31, from which it is connected to the core network 35 (for example, the core is made up of multiple nodes, and these nodes provide multiple functions such as mobility management, authentication, session management, bearer (carry) configuration, and application of different QoS). At some point, when the UE moves to cell 53, which is in GWS 32, the eNodeB receives a beam HO handover notification. In the execution phase (Figure 5(b)), the UE 30 is connected to the target eNodeB in GWS 32, but traffic is routed to the source GWS 31 via the gateway interconnection link (forward link) 34, and then routed to the core 35. Finally, in the completion phase (Figure 5(c)), UE30 is connected to the target GWSeNodeB32, from which it is connected to the core 35. Thus, communication between satellite 20 and core 35 initially takes place via the eNodeB of GWS31 at the source gateway site and is then forwarded to the eNodeB of GWS32 at the target gateway site.

[0101] In the illustrated embodiments, the gateway (or gateway site) may include a processing device, such as eNodeB12, that performs various functions and operations in accordance with the present invention. The processing device may be a computing device such as a computer, processor, application-specific integrated circuit (ASIC), or controller. The processing device may comprise one or more of a wide variety of components or subsystems, including, for example, wired or wireless link and / or storage devices such as analog or digital memory or database. All or part of the systems, processes, and / or data used in the present invention may be stored on or read from a storage device. The processing device may execute software that may be stored on the storage device. Unless otherwise stated, the processes are preferably performed automatically by the processor in substantially real time and without delay. The systems and methods of this disclosure can be implemented using standard UEs by computer software that accesses data from electronic sources. This includes one or more non-transient physical media that store, or are intended to store, the content described above.

[0102] In one embodiment, the satellite communication system of the Disclosure maintains a one-to-one mapping between a base station and the cells it serves via fixed cell tracking while the satellite dynamically passes at high speed (7-8 km / s). In one embodiment, the satellite communication system of the Disclosure is arranged such that the satellite serving the gateway cells has a line of sight (LOS) to the gateway for smooth GW HO.

[0103] In one example, the satellite communication system is configured to mirror, and the base station software is transparent to the UE, embedded GWHO, GW / base station (BTS, eNodeB, gNodeB) core network, providing adequate support for tracking area codes, paging, and system information X2 links, including phase and timing changes due to GWS changes to meet 3GPP specifications, where phase and timing may refer to (or correspond to) large delays caused by feeder and service links. These adjustments or settings must be made to make the system work and to operate with an unmodified UE. In a particular example, adequate support for the core network may refer to, or include, modifications to the eNB and changes to PCI assignments, and phase and timing may refer to long delays caused by feeder and service links. These adjustments can be made to allow the system to operate with an unmodified UE.

[0104] In some examples, the base station may support a configurable fixed round-trip delay and appropriately configure various timers related to long RF path delays.

[0105] In certain cases, beam handovers of multiple active UEs achieve synchronized, seamless handovers one by one using standard UE HO procedures, without multiple UEs or base stations having to handle which satellite and which gateway is providing service; this functionality is handled by the satellite network control center. Gateway handovers at the cell level may be achieved via numerous beam handovers in orbit.

[0106] In certain examples, the satellite communication systems of this disclosure link multiple gateways by long-distance fronthaul optical fibers, which are far longer than those used in terrestrial networks, ranging from several hundred kilometers to over 1,000 kilometers, enabling gateway site handover along with GWS diversity and coverage efficiency.

[0107] This disclosure describes a LEO satellite communication system that solves satellite mobility by reusing UE handover procedures to solve one of the most challenging problems in satellite RAN, and can turn a conventional UE into a satellite phone, communicating with a first sinking satellite having a first field of view including a first plurality of cells and a second ascending satellite having a second field of view including a second plurality of cells. The first and second satellites have an overlapping field of view (overlapping field of view) in which the overlapping plurality of cells are located. The first processing unit has a first communication port that communicates with the first cell of the first plurality of cells via a first beam and the first antenna, and a second communication port that communicates with the overlapping cell of the overlapping plurality of cells via a second beam and the second antenna. The first processing unit switches from the first communication port to the second communication port in response to the first cell of the first plurality of cells moving into the overlapping field of view (overlapping field of view).

[0108] Accordingly, as disclosed above, the satellite communications handover system communicates with a first sinking satellite having a first field of view including a first plurality of cells where active user equipment (UEs) that are communicating directly with the first sinking satellite are located, and with a second ascending satellite having a second field of view, the first and second satellites having a field of view where the first field of view overlaps with the second field of view, and a plurality of overlapping cells located within the overlapping field of view. The satellite communications handover system includes a first feeder link and a first tracking antenna configured to communicate with a plurality of active UEs via the first sinking satellite that directly serves the first plurality of cells, and a second feeder link and a second tracking antenna configured to communicate with a second ascending satellite that directly serves a plurality of active UEs in the second plurality of cells. The system also includes processing devices configured to communicate with a plurality of active UEs and to control a plurality of active UEs that communicate directly with a second ascending satellite.

[0109] The processing device may also be configured to initiate or terminate beam handover in response to instruction signals from a first sinking satellite and a second ascending satellite. An active UE communicates directly with the first sinking satellite via the first service link beam, and that active UE communicates directly with the second ascending satellite via the second service link beam. A first antenna communicates with the first sinking satellite via the first feeder link beam, and a second antenna communicates with the second ascending satellite via the second feeder link beam. The processing device may further be configured to control the active UE to cease communication with the first sinking satellite. The first antenna ceases communication with the first sinking satellite. The processing device may be configured to communicate with the active UE via the first physical cell ID (PCI) and with the second ascending satellite via the second PCI when the active UE enters an overlapping field of view.

[0110] The satellite communication handover system efficiently performs BHO for multiple active UEs by determining the TA of each active UE required for the BHO destination beam of an ascending satellite by correlating the RB reception times of each UE's uplink when signals are received via two feeder links and overlapping service links before multiple UEs acquire CFRA on the destination beam. This system can be applied to 2G, 4G, and 5G without modifying legacy UEs, and CFRA (MSG1) is used for further TA tracking when needed on the target beam. The first descending satellite and the second ascending satellite are transparent and can communicate directly with the modified base station's low PHY (lower physical layer) and the unmodified standard 3GPP-compliant UE.

[0111] Layer 0 of the smart satellite relays a large phase array that forms an electronically steerable beam for tracking numerous cells on the ground. Tracking the fixed cells maintains a one-to-one mapping between the base station and the cells it serves, while the satellite dynamically passes through them at high speed (7-8 km / s). The gateway arrangement allows for smooth GWHO, with satellites serving multiple cells across multiple gateways having a Line of Sight (LOS) to those gateways. Gateways are configured to dynamically perform delay normalization and Doppler correction for the center of each cell. Gateways can be configured to perform delay normalization so that the cell center UE's timing advance (TA) is equal to the midpoint TA value. The system is adapted to support modifiable fixed round-trip delays and appropriately sets various timers related to long RF path delays. This system seamlessly performs beam handover using two physical cell identifiers (PCIs) assigned to two radio frequency (RF) ports, each functioning as a first and second communication port or multiple cells, generating two radio frequency (RF) downlink signals that each carry one of the two assigned PCIs, forming two beams, and overlaying the two beams onto an overlapping cell for beam or cell handover via the first sinking satellite and the second ascending satellite.

[0112] The two PCIs are selected in a similar manner to the placement (deployment) of adjacent cell PCIs, orthogonal to each other to avoid interference, and the MIMO principle is applied so that the two overlapping handover beams operate without interfering with each other. For beam handovers of multiple active UEs, standard UE HO procedures are used, achieving a one-to-one synchronized and seamless handover, without requiring multiple UEs or base stations to handle which satellite and which gateway is the serving entity; this function is handled by the satellite network control center. Furthermore, hard BHO is performed for idle cells without active UEs, shifting the same beam / PCI / RF port from one feeder link to another to service the same idle cell without changing the PCI. Gateway handovers are achieved on a cell-by-cell basis through multiple beam handovers along the orbit.

[0113] The satellite communications handover system mirrors the base station software and is transparent to the active UE, embedded GWHO, and GW / base station core network, providing appropriate support for tracking area codes, paging, and system information X2 links, including phase and timing changes due to GWS changes. Inter-gateway links support the mobility of active UEs for both voice and data calls. Multiple gateways are linked by long-haul fronthaul optical fiber, far longer than that used in terrestrial networks (several hundred to over 1,000 km), enabling handovers across multiple gateway sites and improving GWS diversity and coverage efficiency. This system relays 3GPP downlink and uplink signals between base stations and user equipment, turning regular phones into satellite phones without modification, reaching multiple regular UEs worldwide. It also provides 3GPP RAN coverage to remote areas not covered by the LEO satellite constellation without the enormous cost of building ground-based infrastructure.

[0114] The base station modifications are due to new functional requirements for satellite RAN, which enable satellite RAN by reusing 3GPP specifications without requiring UEs or base stations to manage connections with satellites or gateways. The satellite RAN system makes satellite and gateway management completely transparent, and performs RAN functionality by modifying the base station. The satellite communications handover system enables BHO to service normal active UEs using a standard 3GPP HO process without making any changes (modifications) to the multiple active UEs. The base station is modified to have multiple alternate cell IDs to support beam handover (BHO). Two cell IDs are used alternately, and the core network supports the corresponding changes. The base station is modified so that BHO is initiated from the network side by changing the RF levels of the two beams or by the network initiating the UE's HO. Furthermore, LEO satellite RAN beam handover can be replaced with standard UE mobility handover by faking (using, pretending to use) a phantom cell (a non-existent cell, a dummy cell) for each geographical satellite RAN cell. In this process, two PCIs that do not interfere with each other are assigned to each satellite RAN cell for BHO, and multiple active UEs are made to believe that there is another cell, so that BHO can be performed seamlessly and multiple active UEs can naturally change the beam they are serving.

[0115] The satellite communications handover system has long-distance fronthauls using fiber links, enabling diversity at gateway sites and expanding the gateway's FoV and footprint. Fiber latency is encapsulated in latency compensation, allowing for fronthauls much longer than those of terrestrial networks, e.g., several hundred kilometers to over 1,000 kilometers. The satellite communications handover system can achieve satellite beam handovers using standard HO mechanisms. This system handles satellite mobility in a manner compatible with standard UE handover mobility procedures and uses standard UE mobility handover procedures for satellite RAN beam handovers (BHOs) via satellite mobility. The base station includes at least one of a BTS, eNodeB, or gNodeB.

[0116] Furthermore, it should be noted that the systems and methods of this disclosure can be used in large phased arrays, such as those disclosed in U.S. Patent No. 1,0979,133 and No. 1,112,1764, the full contents of which are incorporated herein by reference.

[0117] The system of the present disclosure includes a satellite communications handover system for communicating with a first sinking satellite having a first field of view and a second ascending satellite having a second field of view. The first field of view includes a first plurality of cells, in which active user equipment (UEs) are located that communicate directly with the first sinking satellite. The first and second satellites further have overlapping fields of view where the first field of view overlaps with the second field of view, and overlapping plurality of cells located in the overlapping field of view. The satellite communications handover system includes a first feeder link and a first tracking antenna configured to communicate with a plurality of active UEs via the first sinking satellite that directly provides service to the first plurality of cells; a second feeder link and a second tracking antenna configured to communicate with a second ascending satellite that directly provides service to the plurality of active UEs in the second plurality of cells; and a processing unit configured to communicate with the plurality of active UEs and to control the plurality of active UEs to communicate directly with the second ascending satellite.

[0118] The processing unit may be configured to initiate or terminate beam handover in response to instruction signals from the first sinking satellite and the second ascending satellite. The active UE may communicate directly with the first sinking satellite via the first service link beam, and further, the active UE may communicate directly with the second ascending satellite via the second service link beam. The first antenna may communicate with the first sinking satellite via the first feeder link beam, and the second antenna may communicate with the second ascending satellite via the second feeder link beam. The processing unit may be further configured to control the active UE to cease communication with the first sinking satellite. The first antenna may cease communication with the first sinking satellite.

[0119] The processing unit may communicate with the active UE and the first physical cell ID (PCI) via the first sinking satellite, and further, when the active UE enters the overlapping field of view, it may communicate with the active UE and the second PCI via the second rising satellite. The system determines the TA of each active UE required for the destination beam, before acquiring the CFRA of the multiple UEs on the destination beam, by correlation of the reception times of the uplink RB signals of each UE received by the two feeder links and overlapping service links, thereby achieving efficiency in BHO of many active UEs. Furthermore, the system can be applied to 2G, 4G, and 5G without modifying the existing multiple UEs, and the CFRA (MSG1) may be used for further TA tracking when needed on the target beam. The first sinking satellite and the second rising satellite are transparent and may communicate directly with the modified base station's low PHY and the unmodified standard 3GPP-compliant multiple UEs. Layer 0 of multiple smart satellites may relay to a large phase array that forms an electronically stairable beam for tracking a large number of cells on the ground. The first feeder link and the first tracking antenna are located at a base station, and a one-to-one mapping between the base station and the cells in service may be maintained by tracking the fixed multiple cells as the satellite dynamically passes through the fixed multiple cells at high speed (7-8 km / s). The gateway arrangement may have multiple satellites serving multiple cells of multiple gateways having LOS to those gateways for smooth GWHO. Furthermore, the system may have gateways configured to dynamically perform delay normalization and Doppler correction with respect to the center of each cell. Furthermore, the system may have gateways configured to perform delay normalization so that the timing advance (TA) of the UE at the center of the cell is equal to the TA value at the midpoint.

[0120] The system supports a reconfigurable fixed round-trip delay and may appropriately set various timers related to long RF path delays. The first feeder link and the first tracking antenna are located at a base station, and the system performs seamless beam handover using two physical cell identifiers (PCIs) assigned to two radio frequency (RF) ports, each functioning as a first and second communication port or multiple cells, and generates two radio frequency (RF) downlink signals, each transmitting one of the two assigned PCIs, and further, forms two beams via the first sinking satellite and the second ascending satellite, and is configured to superimpose the two beams onto overlapping cells for beam or cell handover, the two PCIs are selected in a similar manner to the PCI arrangement of neighboring cells so as to be orthogonal to each other to avoid interference, and further, the MIMO principle is applied so that the two overlapping handover beams cooperate without interfering with each other, and the two The PCI is PCI with the same cell bandwidth or different cell bandwidths, supporting both beam handovers with the same cell bandwidth and different cell bandwidths, and in the beam handover of the multiple active UEs, the standard UE HO procedure is used, achieving synchronized and seamless handovers one by one, without multiple UEs or base stations having to deal with which satellite and which gateway is the entity in their service, this function is handled by the satellite network control center, hard BHO is performed for idle cells without active UEs, the same beam / PCI / RF port is shifted from one feeder link to another feeder link to serve the same idle cell without changing the PCI, and furthermore, gateway handovers on a cell-by-cell basis may be achieved by multiple beam handovers along the orbit.

[0121] The system may mirror the base station software to be transparent to the active UE, embedded GWHO, and GW / base station core network, and may provide appropriate support for tracking area codes, paging, and system information X2 links, including changes in phase and timing due to GWS modifications to conform to 3GPP specifications. Links between gateways may support the mobility of the active UE for both voice and data calls. Multiple gateways may be linked by fronthaul optical fibers of much longer distances than those used in terrestrial networks, ranging from several hundred kilometers to over 1,000 kilometers, enabling handovers at multiple gateway sites and improving the efficiency of GWS diversity and coverage. The satellite communications handover system may relay 3GPP downlink and uplink signals between the first feeder link and the first tracking antenna and user equipment, converting regular telephones into satellite phones without modification, reaching multiple regular UEs worldwide, and providing 3GPP RAN coverage to remote areas not covered by the LEO satellite constellation without the enormous cost of building ground-based infrastructure. The base station change may be due to the requirements of a new satellite RAN function that enables satellite RAN by reusing the 3GPP specification without the UE and base station managing the connection between the satellite and the gateway, and the satellite RAN system may make the management of the satellite and the gateway completely transparent to them, and the RAN function may be performed by changing the base station.

[0122] The satellite communications handover system may implement a beam handover (BHO) to serve the active multiple UEs by a standard 3GPP HO process without making any changes to the active multiple UEs. The first feeder link and the first tracking antenna are provided at a base station, and the base station is modified to have multiple cell IDs that can be used alternately to support beam handover (BHO), two of the cell IDs are used alternately, the core network supports the corresponding changes, and the base station is modified so that the BHO is initiated from the network side by changing the RF levels of the two beams or by the NW initiating the HO of the UEs, and the beam handover of the LEO satellite RAN is streamlined by faking a phantom cell for each geographic satellite RAN cell, assigning two PCIs that do not interfere with each other for each satellite RAN cell of the BHO, and making the active multiple UEs believe there is another cell, thereby replacing the BHO with a standard UE mobility handover by the active multiple UEs naturally changing the serving beam.

[0123] In the system, to enable diversity at gateway sites and expand the gateway's FoV and footprint, long-distance fronthauls may use fiber links, the delay of the fiber may be encapsulated in delay compensation, and it may be possible to support fronthauls of several hundred kilometers to over 1,000 kilometers, which are much longer than fronthauls of typical terrestrial networks. In the system, a standard HO mechanism may be used to implement satellite beam handover. The satellite communication system may handle satellite mobility in a manner compatible with standard UE handover mobility procedures, and a standard UE mobility handover procedure may be used for satellite RAN beam handover (BHO) via satellite mobility. In the system, the first feeder link and the first tracking antenna are located at a base station, which may include at least one of a BTS, eNodeB, and gNodeB. Each of the first sinking satellite and the second ascending satellite may have a large phase array that forms hundreds of electronically steerable beams to serve hundreds of cells. The satellite communications handover system may be configured to perform delay and Doppler compensation for each beam in order to normalize the delay to a constant amount, regardless of the location of the ground gateway site (GWS), the first and second satellites, and the multiple cells. The satellite communications handover system may have a base station, a ground gateway site, and a satellite network control center (NCC) that directs the first and second satellites. In the system, the Rx scheduling of the satellite RAN base station may be changed with delay.

[0124] Furthermore, the above discloses a satellite communications handover system for communicating with a first sinking satellite having a first field of view and a second ascending satellite having a second field of view. The first field of view includes a first plurality of cells, in which active user equipment (UEs) communicating directly with the first sinking satellite are located. The first and second satellites have overlapping fields of view where the first field of view overlaps with the second field of view, and overlapping plurality of cells located in the overlapping field of view. The satellite communications handover system includes a first feeder link and a first tracking antenna configured to communicate with a plurality of active UEs via the first sinking satellite that directly provides service to the first plurality of cells, and a second plurality of cells that directly provide service to the plurality of active UEs. The satellite communication handover system has a second feeder link and a second tracking antenna configured to communicate with the second ascending satellite providing the service, wherein the active plurality of UEs communicate directly with the first sinking satellite via the first service link beam, and further, the active plurality of UEs communicate directly with the second ascending satellite via the second service link beam, and further, the satellite communication handover system has a processing unit configured to communicate with the active plurality of UEs and control the active plurality of UEs to communicate directly with the second ascending satellite and to cease communication with the first sinking satellite.The first feeder link and the first tracking antenna are part of the base station, and the processing unit performs seamless beam handover using two physical cell identifiers (PCIs) assigned to two radio frequency (RF) ports that function as first and second communication ports, respectively, generating two radio frequency (RF) downlink signals, each transmitting one of the two assigned PCIs, and further forming two beams via the first sinking satellite and the second ascending satellite, and is configured to superimpose the two beams onto overlapping cells for beam or cell handover, the two PCIs are selected to be orthogonal to each other to avoid interference, and further the MIMO principle is applied so that the two overlapping handover beams cooperate without interfering with each other, and the two PCIs are PCIs of the same cell bandwidth or different cell bandwidths, and may be further configured to support both beam handovers of the same cell bandwidth and different cell bandwidths.

[0125] The foregoing description and drawings should be considered solely as illustrative of the principles of the disclosure, and the disclosure may be constructed in various ways and is not intended to be limited by the embodiments described herein. A number of applications of the disclosure will readily be conceivable to those skilled in the art. Therefore, the disclosure is not intended to be limited to the specific examples disclosed or the exact structures and operations illustrated and described. Rather, all suitable modifications and possible equivalents fall within the scope of the disclosure. [Explanation of Symbols]

[0126] 10 Gateways, 20A, 20B Satellites 30 UE (User Equipment)

Claims

1. A satellite communication handover system for communicating with a first sinking satellite having a first field of view and a second ascending satellite having a second field of view, wherein the first field of view includes a first plurality of cells, in which active user equipment (UE) communicating directly with the first sinking satellite is located, and further, the first and second satellites have overlapping fields of view where the first field of view overlaps with the second field of view, and overlapping plurality of cells located in the overlapping field of view, and the satellite communication handover system is The system comprises a first feeder link and a first tracking antenna configured to communicate with a plurality of active UEs via a first sinking satellite that directly provides service to the first plurality of cells, and a second feeder link and a second tracking antenna configured to communicate with a second ascending satellite that directly provides service to the plurality of active UEs in the second plurality of cells, wherein the plurality of active UEs communicate directly with the first sinking satellite via a first service link beam including a first physical cell identifier (PCI), and further, the plurality of active UEs also communicate directly with the second ascending satellite via a second service link beam including a second PCI different from the first PCI, and further, The satellite communications handover system is A satellite communications handover system comprising a processing unit configured to communicate with the plurality of active UEs, to communicate directly with the second ascending satellite via the second service link beam including the second PCI, and to control the cessation of communication with the first sinking satellite via the first service link beam including the first PCI.

2. In claim 1, A satellite communications handover system in which the processing device is configured to start or end beam handover in response to instruction signals from the first sinking satellite and the second ascending satellite.

3. In claim 1 or 2, A satellite communications handover system in which the first tracking antenna ceases communication with the first sinking satellite via the first feeder link.

4. In claim 1 or 2, The processing device communicates between the active UE and the first physical cell ID (PCI) via the first sinking satellite, and further, A satellite communication handover system in which, when the active UE enters the overlapping field of view, the active UE and the second PCI communicate via the second ascending satellite.

5. In claim 1 or 2, A satellite communications handover system in which the first sinking satellite and the second ascending satellite are transparent and communicate directly with multiple UEs that are low PHY and unmodified standard 3GPP compliant with modified base stations.

6. In claim 1 or 2, A satellite communications handover system in which the first feeder link and the first tracking antenna are part of a base station, and a one-to-one mapping between the base station and the cells in service is maintained by tracking the fixed cells while either the first satellite or the second satellite dynamically passes through the fixed cells at a speed of 7-8 km / s.

7. In claim 1 or 2, further, A satellite communications handover system having a gateway configured to dynamically perform delay normalization and Doppler correction relative to the center of each cell.

8. In claim 1 or 2, further, A satellite communications handover system having a gateway configured to perform delay normalization such that the timing advance (TA) of the UE at the center of the cell is equal to the TA value at the midpoint.

9. In claim 1 or 2, The processing device is further configured to support a reconfigurable fixed round-trip delay and to set at least one timer related to a long RF path delay, in a satellite communications handover system.

10. In claim 1 or 2, The first feeder link and the first tracking antenna are part of the base station, and the processing unit is Two physical cell identifiers (PCIs) assigned to two radio frequency (RF) ports, each functioning as a first and second communication port, are used as the first PCI and the second PCI to perform seamless beam handover. It generates two radio frequency (RF) downlink signals, each transmitting through one of the two assigned PCIs, and further, The system is configured to form two beams through the first sinking satellite and the second ascending satellite, and to superimpose the two beams onto overlapping cells for beam or cell handover. The two PCIs are selected to be orthogonal to each other to avoid interference, and furthermore, the MIMO principle is applied so that the two overlapping handover beams cooperate without interfering with each other. The two PCIs are PCIs of the same cell bandwidth or different cell bandwidths, and are further configured to support both beam handovers of the same cell bandwidth and different cell bandwidths in a satellite communications handover system.

11. In claim 1 or 2, The aforementioned processing device The 3GPP downlink and uplink signals are relayed between the first feeder link and the first tracking antenna. A satellite communications handover system that provides 3GPPRAN coverage to remote areas not covered by the LEO satellite constellation.

12. In claim 1 or 2, The satellite communications handover system is a satellite communications handover system that achieves a beam handover to provide service to the active UE by a 3GPP beam handover process without making any changes to the active UE.

13. In claim 1 or 2, It has a long-range fronthaul configured to use fiber links to enable diversity at the gateway site and expand the gateway's field of view and footprint. The aforementioned fiber link delay is encapsulated in delay compensation in a satellite communications handover system.

14. In claim 1 or 2, The first feeder link and the first tracking antenna are part of a base station, and the base station is a satellite communications handover system comprising at least one of BTS, eNodeB, and gNodeB.

15. In claim 1 or 2, A satellite communications handover system comprising a first sinking satellite and a second ascending satellite, each of which has a large phase array configured to form at least 100 electronically steerable beams to serve at least 100 cells.

16. In claim 1 or 2, The satellite communications handover system is configured to perform delay and Doppler compensation for each beam in order to normalize the delay to a constant amount.

17. In claim 1 or 2, The satellite communications handover system comprises a base station, a ground gateway site, and a satellite network control center (NCC) that directs the communication processing of the first and second satellites, wherein the receiving (Rx) scheduling of satellite radio access network (RAN) base stations is modified by delay.

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