WO2025071534A1

WO2025071534A1 - Data transfer scheduling in a satellite group

Info

Publication number: WO2025071534A1
Application number: PCT/TR2024/051099
Authority: WO
Inventors: Ahsen TOPBAS TANYERI; Elif Tugce CERAN ARSLAN; Elif UYSAL; Ali ARSAL
Original assignee: Ulak Haberlesme AS
Current assignee: Ulak Haberlesme AS
Priority date: 2023-09-27
Filing date: 2024-09-26
Publication date: 2025-04-03
Anticipated expiration: 2026-03-27
Also published as: TR2023012089A1

Abstract

A scheduling system (10) for scheduling data transfer order of sensor devices (140) that transfer data to related target devices (130), comprising at least a satellite group (100) having plurality of satellites having predetermined trajectories which are configured to receive and transmit data. It is characterized by comprising a source satellite (111) connected to sensor devices (140); said source satellite (111) is configured to realize steps of: determining destination satellites (113) for each sensor device (140) where said destination satellite (113) is responsible for transmitting data to related target device; (130) determining a transmission path between the source satellite (111) and the destination satellite (113) for sensor devices (140) having least number of relaying satellites; (112) calculating estimated peak age of information (PAoI) at destination satellite (113) for each sensor device (140), selecting sensor device (140) that has the highest estimated PAoI at destination satellite (113) using determined transmission paths; scheduling data from selected sensor device (140) to be transmitted in a next time slot.

Description

DESCRIPTION

DATA TRANSFER SCHEDULING IN A SATELLITE GROUP

TECHNICAL FIELD

Invention relates to a scheduling system for scheduling data transfer order of sensor devices that transfer data to related target devices, comprising at least a satellite group having plurality of satellites having predetermined trajectories which are configured to receive and transmit data.

BACKGROUND

Propagation delay is constrained by the laws of physics, specifically the speed of light, as stated in 3GPP TR 22.891 , which is approximately 299,792,458 meters per second in air and 2/3 of that speed in fiber connections. With these limitations, a one-way transmission latency of 1 millisecond corresponds to approximately 300 kilometers in air propagation or 200 kilometers for fiber-based transmission.

When the distance between two locations becomes greater, such as spanning several thousand kilometers, the difference in latency between air and fiber transmission can become significant for certain applications. In such cases, it is worth considering alternative network options instead of relying solely on fiber-based networks.

One potential solution is a constellation of Low-Earth orbiting satellites, where each spacecraft is equipped with a base station (i.e. g-Node B (gNB)) and interconnected with neighboring spacecraft via Inter Satellite Links. This setup enables access to User Equipment (UE) and provides an overlay mesh network. Such a constellation system offers improved latency performance and enhanced end-to-end security, making it suitable for users requiring longdistance connectivity. This satellite constellation contributes to a unified overlay 5G system or as supporting multiple 5G systems across various countries covered by the constellation.

Global organizations with distributed sites worldwide may have a need for long-distance connectivity between these sites, with critical requirements for low latency, reliability, and end- to-end security. This is especially important for supporting critical application domains like High-Frequency Trading (HFT), Banking, or corporate communications (3GPP TR22.822). In such applications where maintaining up-to-date information is crucial, relying solely on delaybased scheduling is insufficient. At this point, the Age of Information (Aol), a novel performance metric proposed in “S. Kaul, M. Gruteser, V. Rai, and J. Kenney, “Minimizing age of information in vehicular networks,” in Proc. 8th Annu. IEEE Conf. Sensor, Mesh Ad Hoc Commun. Netw. (SECON), Jun. 201 1 , pp. 350-358” and “S. Kaul, R. Yates, and M. Gruteser, “Real-time status: How often should one update?” in Proc. IEEE INFOCOM, Mar. 2012, pp. 2731-2735” is more promising than delay in providing up-to-date information. Aol at the destination node, at a given time t, is defined as the duration since the reception of the most recent update packet, naturally a composite function of both sampling frequency and delay. Therefore, the inventors propose an Aol-aware scheduling policy for LEO Mega-Constellations.

CN107070534A discloses a method and system for dynamic pre-emptive task scheduling in a relay satellite, specifically designed to achieve load balance.

CN113783598A discloses a method for transmitting data in a multi-user multi-relay satelliteground fusion network. The method involves employing an opportunity scheduling approach and applies to satellites, ground relay nodes, and ground user nodes. Each satellite calculates the instantaneous signal-to-noise ratios of the channels between itself and all relay nodes. The relay node with the highest signal-to-noise ratio (SNR) is selected, and the satellite sends a signal to that relay node. The chosen relay node receives and boosts the satellite signal, then determines the instantaneous signal-to-noise ratios of the channels between itself and all user nodes. The relay node selects the user node with the highest signal-to-noise ratio and sends a signal to that user node. This method improves communication capacity and the coverage area, however it may greatly increase peak age of information of nodes having poor SNR.

All the problems mentioned above have made it necessary to make an innovation in the relevant technical field as a result.

BRIEF DESCRIPTION OF THE INVENTION

The present invention relates to a system and a method to eliminate the above-mentioned disadvantages and bring new advantages to the relevant technical field.

An object of the invention is to reduce the peak age of information at client devices that receive data from sensor devices via a satellite group. To achieve all the objects mentioned above and that will emerge from the following detailed description, the present invention relates to a scheduling system for scheduling data transfer order of sensor devices that transfer data to related target devices, comprising at least a satellite group having plurality of satellites having predetermined trajectories which are configured to receive and transmit data. Accordingly, it is characterized in that comprising a source satellite connected to sensor devices; said source satellite is configured to realize steps of:

- determining destination satellites for each sensor device where said destination satellite is responsible for transmitting data to related target device;

- determining a transmission path between the source satellite and the destination satellite for sensor devices having least number of relaying satellites;

- calculating an estimated peak age of information (PAol) at destination satellite for each sensor device; selecting a sensor device that has the highest estimated PAol at destination satellite;

- scheduling data from selected sensor device to be transmitted in a next time slot. Thus, PAol is reduced at destination nodes. This allows system to meet certain PAol requirements of devices.

A possible embodiment of the invention is characterized in that comprising the strep of scheduling rest data from rest of the sensor devices depending on calculated estimated PAol where data belonging to sensor devices having higher estimated PAol at destination satellite are scheduled to be transmitted sooner than the data belonging to sensor devices having lower estimated PAol at destination satellite.

Another possible embodiment of the invention is characterized in that commanding a relay device that is connected to sensor devices to pull data from scheduled sensor device.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a drawing illustrating the top schematic view of the system.

REFERENCE NUMBERS GIVEN IN THE FIGURE

10 System

100 Satellite group

110 Satellite 11 1 Source satellite

112 Relaying satellite

113 Destination satellite

120 Relaying device

130 Target device 140 Sensor device

DETAILED DESCRIPTION OF THE INVENTION

In this detailed description, the subject matter is explained with references to examples without forming any restrictive effect only in order to make the subject more understandable.

Referring to figure 1 , the system (10) comprises a satellite group (100) having plurality of satellites that are configured in a manner that allow data transfer from sensor devices (140) to target device (130). Subject matter system (10) and method provides reduced peak age of information (PAol) at target device (130).

The first satellite that receive data from sensor device (140) is defined as a source satellite (11 1 ) and the last satellite that transmits data to target device (130) is defined as destination device.

Satellite group (100) may be a satellite constellation having a known constellation scheme. Satellites may be for instance low earth orbit (LEO) satellites. Satellite constellation may be Walker-Delta constellation.

Sensor devices (140) may be internet of things (loT) devices that generated data via measurements. Sensor devices (140) may comprise data transmission means. Relaying devices (120) may be provided between satellites and sensor device (140). Sensor devices (140) may be configured to transmit data to relay devices via cables or in a wireless manner. Related communication interfaces may be provided associated with sensor device (140). Relay devices may be devices that are equipped with antennas that are capable of transmitting data to satellites. Satellites may also be configured to request data (pull) from relaying devices (120). Relaying devices (120) may store sensor device (140) data before they are transmitted. Relay devices may comprise means for storing data and interfaces for transmitting and receiving data. Relaying devices (120) may be provided between destination satellite (113) and target device (130) which may be similar to relaying devices (120) described above.

Target devices (130) may be user equipment or other computing devices that receive data from sensor device (140). Each sensor device (140) may be associated with at least one target device (130).

The source satellite (1 11 ) is responsible for scheduling data transmission order of the data received from sensor data. The source satellite (1 11 ) may have a memory unit for storing known trajectories of other satellites.

Source satellite (11 1 ) is configured to execute below steps in order to realize subject matter invention:

- Source satellite (11 1 ) determines destination satellites (1 13) for each sensor device (140) where said destination satellite (1 13) is responsible for transmitting data to related target device (130). This step may be realized by considering predetermined trajectories and current locations of satellites.

- Source satellite (11 1 ) determines a transmission path between the source satellite (1 11 ) and the destination satellite (1 13) that has minimum number of relaying satellites (1 12). Transmission paths are determined for each sensor node. This step may be realized by considering predetermined trajectories and current locations of satellites. This step will be elaborated further in this description.

- Source satellite (1 11 ) calculates estimated peak age of information (PAol) at destination satellite (113) for each sensor device (140) using determined transmission paths. Source satellite (11 1 ) selects sensor device (140) that has the highest estimated PAol.

- Source satellite (11 1 ) schedules data from selected sensor device (140) to be transmitted in the next time slot.

In a possible embodiment source satellite (11 1 ) for each sensor device ((-140) considers realtime Aol at destination node (113) when calculating estimated PAol at destination node.

Age of Information (Aol) represents the time elapsed since the last data received at the destination node was generated. For instance, if data is generated at t1 and it arrived to destination node in t2 and it is the most recent data that has arrived to destination node; and current time is t3; age of information in destination node is t3-t1 . When a fresh update packet is received at the destination node, the Aol decreases to the time that has passed since the generation of that received packet. On the other hand, if no fresh packet is received, the Aol increases linearly with time.

Peak age of information is defined as the maximum value reached by the Aol just before the reception of an update data. According to above example; For instance another data (update data) is generated by sensor device on t4 and it is calculated to arrive to destination node at t5. PAol is Aol + (t5-t2). This means that the maximum age reached before receiving an update becomes important in situations where there are specific age limitations or constraints. Present invention aims to reduce PAol and make network more balanced (fair scheduling) in terms of PAol.

Satellites (1 10) in the system (10) for instance may be equipped with four wireless terminals, enabling the establishment of two connections within its orbital plane and two connections with neighboring satellites (110) in different planes. The notations used to represent the satellites (110) that come before and after a given satellite (100) (i, j) are (i, (j— 1) modQ) and (i, (j+1 ) modQ), respectively. If there is a neighbour to the left, it is denoted as (i-1 , j) unless i equals zero, in which case it is denoted as (P-1 , (j- F) modQ). Similarly, the neighbour to the right is represented as (i+1 , j) unless i is equal to P-1 , in which case it is denoted as (0, (j+F) modQ).

Satellites (1 10) comprises processing means for executing scheduling steps that are realized by the invention. Satellites (1 10) may comprise, other components that are well-known to be utilized by satellites (1 10). Such components are well known in the art and are not explicitly disclosed herein.

In a possible embodiment, other satellite (110) types may be utilized. In another possible embodiment, senor devices may be connected to satellites (1 10) directly. In another possible embodiment non terrestrial network nodes may be utilized in order to connect to source satellite (11 1 ) and destination satellites (1 13) from sensor device (140).

Satellites (110) in satellite group (100) forms a mesh-grid network.

Flows in transmission paths are unicast and consist of a single known path to forward updates from the source satellite (11 1 ) to target satellites. There is no queuing at any relaying nodes and each relaying node has a single packet buffer with Last Come First Serve with preemption. In an embodiment where satellite group (100) is Walker-Delta constellation, transmission path having minimum number of satellites (may also called having minimum number of hops) may be calculated as follows: Determining the minimum number of inter-plane hops, denoted as H_h- It is determined by the horizontal distance that needs to be covered to move from the starting orbital plane to the target plane. Consequently, H_h relies on the disparity between the longitudes of the ascending nodes associated with each respective plane.

AL₀ = (L_{0 2} - L_{0 1}) mod 2n represents the longitudinal angle that needs to be traveled while moving from the orbital plane of the source satellite to the plane of the destination satellite (1 13) in an eastward direction. Consequently, the difference in the Right Ascension of Ascending Node (RAAN) in the westward direction can be expressed as 2n - L_o- Considering that each transition from one plane to the next covers an angle of A , the overall count of inter-plane hops, either in the eastward or westward direction, can be calculated as follows:

Subsequently, the differences in phase angles between the two satellites need to be taken into account. When hopping within the same plane towards the next satellite, the phase angle experiences an increment of < . Conversely, when hopping between different planes in the eastward direction, the phase angle increases by To simplify, if hops are considered towards the succeeding satellite and its right neighbor, the following relationship holds.

In order to determine the number of intra-plane hops H_V, the fraction u of the phase angle difference that will be covered by these hops should be calculated. Again, it is necessary to distinguish between two directions:

Lastly, similar calculations can be carried out, as previously done for H to find the intra-plane hop count in both directions.

Finally, the minimum hop count can be determined by the minimum of the four possible combinations:

In another possible embodiment scheduling may be realized considering predetermined maximum PAol.

The scope of protection of the invention is specified in the attached claims and cannot be limited to those explained for sampling purposes in this detailed description. It is evident that a person skilled in the art may exhibit similar embodiments in light of the above-mentioned facts without drifting apart from the main theme of the invention.

Claims

1. A scheduling system (10) for scheduling data transfer order of sensor devices (140) that transfer data to related target devices (130), comprising at least a satellite group (100) having plurality of satellites having predetermined trajectories which are configured to receive and transmit data characterized in that comprising a source satellite (11 1 ) connected to sensor devices; (140) said source satellite (11 1 ) is configured to realize steps of:

- determining destination satellites (1 13) for each sensor device (140) where said destination satellite (113) is responsible for transmitting data to related target device (130);

- determining a transmission path between the source satellite (1 11 ) and the destination satellite (113) for each sensor device (140) having least number of relaying satellites (1 12);

- calculating an estimated peak age of information (PAol) at destination satellite (113) for each sensor device (140); selecting a sensor device (140) that has the highest estimated PAol at destination satellite (1 13) using determined transmission paths;

- scheduling (113) data from selected sensor device (140) to be transmitted in a next time slot.

2. The scheduling system (10) according to claim 1 , characterized in that comprising the step of scheduling rest data from rest of the sensor devices (140) depending on calculated estimated PAol where data belonging to sensor devices (140) having higher estimated PAol at destination satellite (113) are scheduled to be transmitted sooner than the data belonging to sensor devices (140) having lower estimated PAol at destination satellite (113).

3. The scheduling system (10) according to claim 1 , characterized in that commanding a relay device that is connected to sensor devices (140) to pull data from scheduled sensor device (140).

4. A scheduling method for scheduling data transfer order of sensor devices (140) that transfer data to related target devices (130), wherein said data transfer is realized via at least a satellite group (100) having plurality of satellites having predetermined trajectories which are configured to receive and transmit data characterized in that comprising below steps that are realized by a source satellite (11 1 ) connected to sensor devices; (140)

- determining destination satellites (1 13) for each sensor device (140) where said destination satellite (113) is responsible for transmitting data to related target device; (130)

- determining a transmission path between the source satellite (1 11 ) and the destination satellite (113) for each sensor device (140) having least number of relaying satellites (1 12); - calculating an estimated peak age of information (PAol) at destination satellite (113) for each sensor device (140) that has the highest estimated PAol at destination satellite (1 13) using determined transmission paths;

5. The a scheduling method according to claim 4, characterized in that scheduling rest data from rest of the sensor devices (140) depending on calculated estimated PAol where data belonging to sensor devices (140) having higher estimated PAol at destination satellite (1 13) are scheduled to be transmitted sooner than the data belonging to sensor devices (140) having lower estimated PAol at destination satellites (113).