WO2025053816A1

WO2025053816A1 - A communication method and system

Info

Publication number: WO2025053816A1
Application number: PCT/TR2024/050894
Authority: WO
Inventors: Kaan ÇETINKAYA; Murat Sencer AKYÜZ; Raşit TUTGUN; Ozan KÖROĞLU; Erkan İNCEÖZ; Bahadır Alp ÇAKIR; Can KANBAK
Original assignee: Plan S Uydu Ve Uzay Teknolojileri AS
Current assignee: Plan S Uydu Ve Uzay Teknolojileri AS
Priority date: 2023-09-05
Filing date: 2024-07-30
Publication date: 2025-03-13
Anticipated expiration: 2026-03-05

Abstract

With the present invention, a communication method and system that enables IoT units (N) to transmit data to satellite (S) via satellite access terminals (GW) is developed. The method in question includes a resource planning process performed on the satellite (S) and transmitting a feedback message to the satellite access terminals (GW) regarding the data packets reaching the satellite (S).

Description

A COMMUNICATION METHOD AND SYSTEM

Relevant Technical Field

The present invention relates to an I oT-satellite communication method and system developed to provide reliable data communication between loT units and the satellite.

Prior Art

Internet of Things (loT) provides a communication network that allows physical objects to connect with each other and with larger systems. Nowadays, loT technology enables the embedding of transactional activities into everyday objects, making it possible to perform remote monitoring and activation operations in challenging and critical application areas such as disaster response, smart agriculture, and industrial processes. With the development of loT technology, its usage area is rapidly expanding and becoming widespread. In this direction, while the number of objects requesting data transmission is increasing rapidly, the distribution of these objects on the earth's surface is also spreading over a much wider area. The specified objects can be in residential areas as well as in rural areas; It can be located in desert, ocean and similar regions where terrestrial network access is not possible; It can be stationary or moving.

In the state of the art, there are terrestrial communication solutions, satellite communication solutions or hybrid communication applications where these two solutions are used together for data communication with loT units. In regions where access to terrestrial networks is not possible, satellite communication applications are gaining importance.

In I oT-satellite communication applications, which enable the loT units in question to exchange data with a satellite or a satellite constellation, objects can transmit data directly to the satellite or through a gateway. In applications where data is transmitted directly to the satellite, random access is provided and data may be attempted to be transmitted by more than one object in the same frequency range at the same time. This situation causes significant losses in data transmission as the number of loT units increases. In applications where data is transmitted to the satellite through the gateway, loT units transmit the data they collect to the gateway; the data stored for a while in the gateway is transmitted to the satellite during its passage.

With the increase in the number of loT units, the need for planning for data transmission arises to avoid losses in data transmission. When the number of loT units trying to access the satellite at the same time and in the same frequency band exceeds a certain threshold, losses in data sent to the satellite may increase and cause inefficient use of communication resources on the satellite. In addition, since there is no control as to whether the data sent by the loT units on the ground reaches the satellite, there is no opportunity to resend the data that did not reach to the satellite. This situation also significantly reduces data reliability.

Patent document number CN111711479A describes a resource planning method for low earth orbit (LEO) satellite systems. In this method, an loT gateway collects the data of loT units and transmits it to a determined satellite within a specified time period. With this method, it is aimed to minimize the delay caused by satellite resource constraints in data transmission of loT gateways. Taking into account the data transmission speeds of the gateways and the amount of data they will transmit, it is planned which gateway will transmit data to which satellite in which time period. However, with the expanding of the usage area of loT technology, the diversity of data collected by loT units is also increasing; The time required for the collected data to reach its target in the most appropriate way may vary. For example, the time required to reach the ground station for data regarding disaster response and data regarding soil quality measurement differs. In this direction, with the development of the usage area of loT technology, the need for comprehensive and dynamic planning regarding data transmission emerges. In addition, document numbered CN111711479A does not offer a solution for resending data that does not reach the satellite for any reason.

Object of the invention

The object of the present invention is, to develop a communication method and system that allows reliable data transfer between loT units and the satellite without data loss.

Another object of the present invention is to develop a communication method and system in which data transmission is provided in line with the resource planning carried out on the satellite.

Another object of the present invention is to develop a communication method and system that takes data diversity into account and where resource planning is carried out in line with the urgency of data transmission.

Another object of the present invention is to develop a communication method and system that provides feedback regarding whether the transmitted data reaches the satellite or not.

Another object of the present invention is to develop a communication method and system that enables data to be transmitted to the satellite within the required time by resource planning made in line with a two-stage data prioritization performed on both the gateway device and the satellite. Definition of the Figures

Exemplary applications of the communication method and system developed with the present invention are shown in the attached figures and these figures were configured as below;

Figure 1 ; is an illustration of the communication between loT units and satellite access terminals.

Figure 2; is an illustration of the communication between satellite access terminals and the satellite.

Figure 3; is the flow chart showing the communication steps of the satellite.

Figure 4; is a flow chart showing the communication steps of the satellite access terminal.

Figure 5; is a representation of the time-frequency scheme of the resource sharing process.

The elements in the figures are numbered one by one and the equivalents of these numbers are indicated below: loT unit (N)

Satellite access terminal (GW)

Satellite (S)

First communication link (L1)

Second communication link (L2)

Service slot (SS)

First service slot (SS1)

Second service slot (SS2)

Movement direction (Y)

First signal (BC)

Second signal (RTS)

Third signal (CTS)

Fourth signal (SDM)

First coverage area (A1)

Second coverage area (A2)

Satellite transmits a first signal to satellite access terminals within the coverage area (S1)

Satellite receives second signals from satellite access terminals (S2) Satellite performs resource planning based on second signals from satellite access terminals (S3)

Satellite sends a third signal containing resource scheduling information to the satellite access terminals (S4)

Satellite receives data packets from satellite access terminals in accordance with resource planning (S5)

Satellite receives second signals from satellite access terminals for which resource planning has not been made and updates the resource planning in line with new requests (S6).

Satellite checks whether the service slot has expired (S7)

Does the satellite access terminal have a data packet to send? (G1)

Has the satellite access terminal received a first signal from a satellite within coverage area (G2)

Satellite access terminal transmits a second signal to the satellite (G3)

Have resource been allocated to the satellite access terminal (G4)

Satellite access terminal transmits the data packet to the satellite within the allocated time and frequency range (G5)

Satellite access terminal checks if a fourth signal is received from the satellite (G6)

Is there a time-out (G7)

Control channel downlink (CCD)

Control channel uplink (CCU)

Service channel (SC)

First service channel (SC1)

Third service channel (SC3)

Seventh service channel (SC7)

First signal time slot (TS-B)

Uplink time slot (TS-U)

First uplink time slot (TS-U1)

Downlink time slot (TS-D)

Guarding time slot (GT)

First data packet of the first satellite access terminal (GWM)

Second data packet of the seventh satellite access terminal (GW7-2) Description of the Invention

An loT - satellite communication method and system is provided with the present invention, which was developed to solve the above-mentioned technical problems and whose exemplary applications are given in the attached figures.

The communication method of the present invention, which is developed to enable at least one loT unit (N) to transmit data to at least one satellite (S), preferably to a satellite constellation having at least two satellites (S), via at least one satellite access terminal (GW) comprises the steps of: the satellite access terminals (GW) receive data coming from the loT units (N) through a first communication link (L1) and save the received data in a memory (not shown in the figures); wherein the said memory is preferably a temporary memory; the satellite (S) periodically transmits a first signal (BC) indicating that it is within the coverage area, to the satellite access terminals (GW) located on the ground through a second communication link (L2); wherein said period has a service slot (SS) duration; the satellite access terminals (GW) receiving the first signal (BC) transmit a second signal (RTS) to the satellite (S) within the said service slot (SS), containing information regarding the data transmission request in line with the data in their memory; the satellite (S) evaluates the second signals (RTS) coming from the satellite access terminals (GW), makes a resource planning in which only one satellite access terminal (GW) will transmit data in any time and frequency range within the service slot (SS) in question, and repeats this process for new requests during the service slot (SS); the satellite (S) transmits a collective third signal (CTS) containing information about which satellite access terminal (GW) will transmit data in which time and frequency range in line with the resource planning, to said satellite access terminals (GW), for each new resource planning performed during the service slot (SS) in question; each of the satellite access terminals (GW) determines the time and frequency range allocated to it by evaluating the received third signal (CTS) and within the relevant time and frequency range, sends the data packets related to the data stored in the said memory to the satellite (S), through the second communication link (L2); the satellite (S) leaves the coverage area when the service slot (SS) ends and the same process is repeated for the satellite access terminals (GW) in the new coverage area it enters.

The loT units (N) in question may be positioned on any object on the ground and arranged to receive any data related to the specified object, or they may also contain a sensor that enables data to be received regarding the environment in which it is located. In exemplary embodiments of the invention, the loT unit (N) in question can receive data about any electronic I electromechanical device, as well as collect data about a living creature (animal, human, plant) or collect data about the soil, ground, air, etc. in its environment. In the example representation in Figure 1 , loT units (N) can transmit their collected data to any satellite access terminal (GW) with which they can communicate with, through the first communication link (L1). The satellite access terminal (GW) records the data it receives and stores it until it transmits it to any satellite (S) it is connected to with the second communication link (L2). The satellite (S) periodically performs the above-mentioned data collection during its movement around its orbit. The period mentioned here has a service slot (SS) duration and the satellite (S) transmits said first signal (BC) at the beginning of each period. In the example representation in Figure 2, the satellite (S) is moving in the direction of movement (Y) indicated by the arrow (from left to right). Due to its movement, the satellite (S) has a first coverage area (A1) during a first service slot (SS1) and a second coverage area (A2) in a second service slot (SS2) following the first service slot (SS1). In the example representation in question, there are K satellite access terminals (GWI ... GWK) in the first coverage area (A1) and there are M satellite access terminals (GWK+I ... GWK+M), which are different from those in the first coverage area (A1), in the second coverage area (A2). There may be different numbers of satellite access terminals (GW) in different coverage areas. The satellite carries out the above-mentioned operations during the first service slot (SS1), which starts with transmitting the first signal (BC); and at the end of the first service slot (SS1), it transmits the first signal (BC) again and repeats the same operations for the next coverage area (A2) and it continues to move in its orbit in this way. The service slots (SS, SS1 , SS2) mentioned here are equal to each other. Accordingly, the service slot (SS) has been determined as a period of time which is sufficient for all processing steps to be completed and at the same time, each satellite access terminal (GW) receiving the first signal (BC) will be within the coverage area of the satellite (S) during the service slot (SS). This ensures that the process continues uninterruptedly. In a preferred embodiment of the invention, the time in question is 30 seconds, but this time may vary depending on system capabilities.

In a preferred embodiment of the invention, the second signal (RTS) transmitted by the satellite access terminals (GW) contains information regarding the amount of data to be transmitted (e.g. the number of data packets to be transmitted and/or the size of the data packets). The satellite (S) evaluates the second signal (RTS) coming from each satellite access terminal (GW) and performs resource planning in line with the amount of data. The resource planning carried out by the satellite (S) can be a planning in which all data packets of all satellite access terminals (GW) requesting data transmission can be transmitted within the service slot (SS), in line with the data transmission constraints. Depending on the amount of data to be transmitted, it may involve planning in which some satellite access terminals (GW) will not transmit data packets within the said service slot (SS) and/or some satellite access terminals (GW) may transmit some of their data packets. In this case, satellite access terminals (GW) which could not transmit data or could not transmit all of their data within said service slot (SS); will transmit a request again at the next first signal (BC) reception for the data packets they could not transmit. The next first signal (BC) can be received in the next pass of the same satellite (S), or preferably from another satellite (S) of the same constellation which enters the same coverage area.

In a preferred embodiment of the invention, the method also comprises the following steps: the satellite (S) creates a fourth signal (SDM) containing feedback regarding the data packets reached it and transmits it to the satellite access terminals (GW) within the service slot (SS); satellite access terminals (GW) evaluate the received fourth signal (SDM) and determine which data packets have reached the satellite (S); satellite access terminals (GW) delete the data packets detected to have reached the satellite (S), from the memory; satellite access terminals (GW) request data transmission again within the same service slot (SS) for data packets detected not to reach the satellite (S).

In this application, the satellite (S) provides feedback to the satellite access terminals (GW) on whether data packets have reached. Satellite access terminals (GW) can request data retransmission for data packets that they detect have not reached the satellite (S). In this case, the satellite access terminal (GW) will request a new data transmission with a new second signal (RTS) regarding the data packets that have not been transmitted to the satellite. If this request is made within the same service slot (SS), it is possible to transmit it to the satellite (S) during the same transition, in line with the resource planning that the satellite will update within the service slot (SS). If the second signal (RTS) newly created by the satellite access terminal (GW) is not within the service slot (SS); the satellite access terminal (GW) will be able to request data transmission again for the relevant data packets at the next first signal (BC) reception.

In a preferred embodiment of the invention, each satellite access terminal (GW) has an identification number, and the satellite (S) obtains information (for example, a prioritization information) regarding the priority of the data transmitted by the relevant satellite access terminal (GW) from the said identification number. In this application, the satellite (S) also takes into account the information regarding the priority of the data during the resource planning process. In the said application, preferably the said identification numbers contain an indicator regarding the prioritization information of the data collected by the relevant satellite access terminal (GW). In another preferred embodiment, the satellite (S) can recognize the satellite access terminals (GW); with which it can communicate with the said second communication link (L2); from said identification number and obtain information about the data content I priority of the data. In the application in question, the relevant identification numbers and prioritization information regarding the data priority matching the identification number are pre-registered in the satellite (S).

In another preferred embodiment of the invention, the second signal (RTS) regarding the data transmission request contains information about the age of the data/data packets to be transmitted. In this application, the satellite (S) evaluates the second signal (RTS) coming from each satellite access terminal (GW) during the resource planning process carries out an assessment to determine deadlines for each data packet to reach the satellite (S), considering the transmission priority of the data and the age of the data together. Thus, it is ensured that all data is transmitted within the required time frame.

The flow chart in Figure 3 shows the operations performed by the satellite (S) during the communication process between the satellite (S) and the satellite access terminals (GW) according to a preferred embodiment of the invention. Accordingly, the satellite (S) first transmits the first signal (BC) to the satellite access terminals (GW) within the coverage area (S1) and thus a service slot (SS) begins. After transmitting the first signal (BC), the satellite receives the second signals (RTS) coming from the satellite access terminals (GW) (S2) and then makes resource planning according to received second signals (RTS) (S3). The satellite sends the third signal (CTS), containing resource scheduling information, to the satellite access terminals (GW) (S4). The third signal (CTS) mentioned here is preferably a collective message which is broadcast so that it can be received by all satellite access terminals (GW). The said third signal (CTS) contains information on which satellite access terminal (GW) will transmit which data packets to the satellite (S) on which time and frequency period within the service slot (SS), as a result of resource planning. The satellite (S) receives data packets sent from the satellite access terminals (GW) in accordance with resource planning (S5). At the same time, it receives the second signals (RTS) from satellite access terminals (GW) for which resource planning has not been made and updates the resource planning in line with the new requests (S6). At the end of both processing steps (S5, S6), it checks whether the service slot (SS) has expired (S7). If the service slot (SS) has not yet expired, it returns to step (S4). If the service slot (SS) has expired, it returns to step (S1) and the same operations are carried out for the satellite access terminals (GW) in the new coverage area during a new service slot (SS).

The flow chart in Figure 4 for a preferred embodiment of the invention shows the operations performed by the satellite access terminal (GW) during the communication process between the satellite access terminals (GW) and the satellite (S). Accordingly, the satellite access terminal (GW) checks whether there is a data packet to send in the first step (G1). If there is no data packet to send, it does not take any action; If there is a data packet to be sent, it checks whether it receives a first signal (BC) from a satellite (S) within its coverage area (G2). If the satellite access terminal (GW) has received a first signal (BC) from a satellite (S) within its coverage area, it transmits a second signal (RTS) regarding the data transmission request to the satellite (S) (G3). Said second signal (RTS) is preferably transmitted via random access by the satellite access terminal (GW). The satellite access terminal (GW) then checks whether resource(s) have been allocated to it (G4). In this step (G4), the satellite access terminal (GW) checks whether it receives a third signal (CTS) regarding resource scheduling from the satellite (S) within a predetermined waiting time, and if the third signal (CTS) is received, it evaluates the received third signal (CTS). If the satellite access terminal (GW) has not received a third signal (CTS) during the said waiting period or if the third signal (CTS) it has received does not include a resource allocation for itself, it checks whether there is a timeout (G7). In the timeout check (G7) step, the satellite access terminal (GW) checks whether the service slot (SS) has been exceeded. It performs this control by checking whether the specified service slot (SS) has expired as of the moment the first signal (BC) arrives from the satellite. If there is a timeout, it returns to the step (G2) where it checks whether it has received the first signal (BC) from a satellite (S) within the coverage area. If there is no timeout, it returns to step (G3) where it transmits a second signal (RTS) to the satellite (S), thereby requesting reallocation. If the satellite access terminal (GW) received a third signal (CTS) within the said waiting period in step (G4) and there is a resource allocation for itself in the third signal (CTS) it received; It transmits the data packet to the satellite (S) within the allotted time and frequency range (G5). After the data packet is transmitted (G5) to the satellite (S), the satellite access terminal (GW) checks whether a fourth signal (SDM) is received from the satellite (S) indicating that the transmitted data packet has been received (G6). The fourth signal (SDM) in question is preferably a general signal containing information about all data packets received by the satellite (S), and each satellite access terminal (GW) evaluates this signal and determines whether the data packets they transmit have reached the satellite (S). In the step in question (G6), if the satellite access terminal (GW) received a fourth signal (SDM) and determined that the data packets it transmitted reached the satellite (S) by evaluating the fourth signal (SDM), it deletes the data packets it transmitted and returns to the first step (G1). In the relevant step (G6), if the satellite access terminal (GW) did not receive a fourth signal (SDM) or evaluated the received fourth signal (SDM) and determined that the data packets it transmitted did not reach the satellite (S); First, it goes to the timeout control (G7) step, and if there is a timeout (service slot (SS) is exceeded), it returns to the step (G2) where it checks whether it has received a first signal (BC) from a satellite (S) within the coverage area. If there is no timeout, it returns to step (G3) where it transmits a second signal (RTS) to the satellite (S), thereby requesting reallocation. Thus, satellite access terminals (GW) can request to send data more than once during a service slot (SS). In addition, it can be checked whether the transmitted data has reached the satellite (S), and data transmission can be carried out again during the same transition period (within the service slot (SS)) for data packets that are detected not to reach the satellite (S).

The present invention also provides a satellite access terminal (GW) suitable for performing the communication method described above. The satellite access terminal (GW) in question comprises a first communication link (L1) that enables it to exchange data with at least one loT unit (N), at least one memory (preferably a temporary memory) where it records the data it receives from the loT units (N) with the first communication link (L1); at least one second communication link (L2) that enables the data in the memory to be transmitted to at least one satellite (S); and at least one processing unit (not shown in the figures), wherein said processing unit being arranged to perform the following operations; evaluating the data stored in memory and checking whether there is a data packet to be sent; if there is a data packet to be sent, checking whether a first signal (BC) is received through the second communication link (L2) from a satellite (S) within the coverage area; if a first signal (BC) from a satellite (S) within the coverage area is received, generating a second signal (RTS) regarding the data transmission request and transmitting it to the satellite (S) through said second communication link (L2); checking whether a third signal (CTS) regarding resource planning is received from the satellite (S) within a predetermined waiting period; if the third signal (CTS) is received, evaluating the received third signal (CTS) and checking whether resources are allocated to the satellite access terminal (GW); if a third signal (CTS) is not received within said waiting period or if the received third signal does not include a resource allocation for said satellite access terminal (GW), checking whether a timeout has occurred; if there is a timeout, returning to the step of checking whether a first signal (BC) is received from a satellite (S) within the coverage area; if there is no timeout, returning to the step where a second signal (RTS) is transmitted to the satellite (S) and requesting resource reallocation; if a third signal (CTS) is received within the said waiting period and there is a resource allocation for the satellite access terminal (GW) in the received third signal (CTS), the relevant data packet will be sent to the satellite (S) via the second communication link (L2) in the time and frequency range allocated to it.

In the timeout control step, the control unit checks whether the service slot (SS) has been exceeded; and preferably it performs this by checking whether the specified service slot (SS) has expired as of the moment the first signal (BC) arrives from the satellite.

In a preferred embodiment of the invention, the processing unit is also arranged to carry out the following operations; after transmitting the data packet to the satellite (S), checking whether a fourth signal (SDM) indicating that the transmitted data packet has been received is received from the satellite (S); evaluating the received fourth signal (SDM) and determining whether the transmitted data packets reach the satellite (S); if it is detected that the data packets have reached the satellite (S), deleting the transmitted data packets from the memory and returning to the first step of checking whether there is a data packet to be sent; if the fourth signal (SDM) is not received or it is determined that the data packets have not reached the satellite (S), returning to the step of checking whether there is a timeout and, if there is a timeout (service slot (SS) has been exceeded), returning to the step where it is checked that whether a first signal (BC) from a satellite within the coverage area is received or not; if there is no timeout (service slot (SS) has not been exceeded), returning to the step where a second signal (RTS) is transmitted to the satellite (S) and requesting data transmission again

With the present invention, a satellite (S) suitable for performing said communication method is also provided; The satellite (S) in question comprises a second communication link (L2) that enables communication with the satellite access terminal (GW) and at least one processing unit arranged to perform the relevant processing steps.

The processing unit of the satellite is preferably arranged to perform the following operations: transmitting the first signal (BC) via the said second communication link (L2) to the satellite access terminals (GW) within the coverage area of the satellite (S); receiving second signals (RTS) from satellite access terminals (GW); evaluating received second signals (RTS) and resource planning; transmitting the third signal (CTS) containing resource scheduling information to the satellite access terminals (GW); receiving data packets from satellite access terminals (GW) in line with resource planning; at the same time, receiving second signals (RTS) from satellite access terminals (GW) for which resource planning has not been made and updating the resource planning in line with new incoming demands; checking whether the service slot (SS) has expired; transmitting the third signal (CTS) of the updated resource scheduling to the satellite access terminals (GW), if the service slot (SS) has not yet expired; if the service slot (SS) has expired, terminating the process and executing the same operations for a new service slot (SS).

The present invention also provides a communication system comprising at least one satellite access terminal (GW) and at least one satellite (S) (preferably a satellite constellation comprising at least two satellites (S) as mentioned above.

Figure 5 shows an example representation of the time-frequency diagram of the resource planning process carried out within a service slot (SS) regarding the method and system of the invention. In the diagram, the vertical axis shows frequency and the horizontal axis shows time values.

In a preferred embodiment of the invention, the second communication link (L2) comprises:

- at least one control channel downlink (CCD) used for transmission of said first signal (BC), third signal (CTS) and fourth signal (SDM) from the satellite (S) to the satellite access terminals (GW);

- at least one control channel uplink (CCU) used for transmission of said second signal (RTS) from the satellite access terminals (GW) to the satellite (S), and; - at least two, preferably seven, service channels (SC, SC1... SC7) used for the transmission of said data packets from the satellite access terminals (GW) to the satellite (S) each with a different frequency range.

In this embodiment, preferably, a service slot (SS) is divided into certain time intervals including a first signal time slot (TS-B) located at the beginning of said service slot (SS); at least one uplink time slot (TS-ll) and at least one downlink time slot (TS-D) following the said first signal time slot (TS-B). In said first signal time slot (TS-B), the satellite (S) transmits said first signal (BC) from the control channel downlink (CCD) to the satellite access terminals (GW). In the said uplink time slot (TS-ll), the satellite access terminals (GW) transmit the second signal (RTS) from the said control channel uplink (CCU) and/or data packets from the said service channels (SC1-SC7) to the satellite (S). In the mentioned downlink time slot (TS-D), the satellite (S) transmits the said third signal (CST) and fourth signal (SDM) to the satellite access terminals (GW). In a preferred embodiment of the invention, each of the said first signal time slot (TS-B), uplink time slot (TS-ll) and downlink time slot (TS-D) contains a guarding time slot (GT) in which no data transmission is made. In this application, the processing unit of the satellite is arranged to ensure that the specified operations are carried out.

In the embodiment of the invention shown in Figure 5, the satellite (S) transmits the said first signal (BC) at the beginning of the service slot (SS) and in the said first signal time slot (TS- B). Each of the satellite access terminals (GW), which are within the coverage area of the satellite (S) in the said service slot (SS) and therefore receive the first signal (BC), sends the second signal (RTS) containing the data transmission request for the data packets they contain, to the satellite in the first uplink time slot (TS-LI1) following the first signal time slot (TS-B). Unlike other uplink time slots (TS-U), here, since no resource planning has been done yet, only second signals (RTS) will be transmitted. The satellite (S) makes resource planning by evaluating the received second signals (RTS) and transmits the third signal (CTS) regarding the resource planning to all satellite access terminals (GW) in the downlink time slot (TS-D). According to the resource planning, the satellite (S) allocates service channels (SC) to satellite access terminals (GW) in upstream time slots (TSU). For example, the first service channel (SC1) can be reserved for the first data packet of the first satellite access terminal (GW1-1) in the first uplink time slot (TS-U), while the third service channel (SC3) is reserved for the second data packet of the seventh satellite access terminal (GW7-2) in the same time slot. Satellite access terminals (GW) evaluate the third signal (CTS) related to resource planning and transmit the relevant data packets to the satellite (S) through the service channel (SC) and time slot allocated to them. At the same time, the second signal (RTS) transmission from the control channel uplink (CCU) continues during the said uplink time slots (TS-ll). During the service slot (SS) in question, the resource planning is updated and the process is repeated until the end of the service slot (SS) with data exchange in successive uplink time slots (TS-ll) and downlink time slots (TS-D). When the service slot (SS) is completed, the same process is carried out for the next service slot (SS).

With the present invention the following are provided: a communication method as explained above; a satellite access terminal (GW) and a satellite (S) arranged in accordance with the above-mentioned method; and a communication system comprising the satellite (S) and the satellite access terminal (GW).

Claims

1. A communication method developed to enable at least one loT unit (N) to transmit data via at least one satellite access terminal (GW) to at least one satellite (S), preferably to a satellite constellation with at least two satellites (S), comprising the following processing steps: the satellite access terminals (GW) receive data coming from the loT units (N) through a first communication link (L1) and save the received data in a memory; the satellite (S) periodically transmits a first signal (BC) indicating that it is within the coverage area, to the satellite access terminals (GW) located on the ground through a second communication link (L2); wherein said period has a service slot (SS) duration; the satellite access terminals (GW) receiving the first signal (BC) transmit a second signal (RTS) to the satellite (S) within the said service slot (SS), containing information regarding the data transmission request in line with the data in their memory; the satellite (S) evaluates the second signals (RTS) coming from the satellite access terminals (GW), makes a resource planning in which only one satellite access terminal (GW) will transmit data in any time and frequency range within the service slot (SS) in question, and repeats this process for new requests during the service slot (SS); the satellite (S) transmits a collective third signal (CTS) containing information about which satellite access terminal (GW) will transmit data in which time and frequency range in line with the resource planning, to said satellite access terminals (GW), for each new resource planning performed during the service slot (SS) in question; each of the satellite access terminals (GW) determines the time and frequency range allocated to it by evaluating the received third signal (CTS) and within the relevant time and frequency range, sends the data packets related to the data stored in the said memory to the satellite (S), through the second communication link (L2); the satellite (S) leaves the coverage area when the service slot (SS) ends and the same process is repeated for the satellite access terminals (GW) in the new coverage area it enters.

2. A communication method according to Claim 1 ; wherein the said service slot (SS) is determined as a period during which each satellite access terminal (GW) receiving the said first signal (BC) will be in the coverage area of the satellite (S).

3. A communication method according to any of the preceding claims wherein, the second signal (RTS) sent by the satellite access terminals (GW) comprises information about the amount of data which will be sent and the satellite (S) makes the resource allocation in accordance with the results of the evaluation of the second signal (RTS) received from each of the satellite access terminals (GW).

4. A communication method according to any of the preceding claims comprising the following processing steps; the satellite (S) creates a fourth signal (SDM) containing feedback regarding the data packets reached it and transmits it to the satellite access terminals (GW) within the service slot (SS); satellite access terminals (GW) evaluate the received fourth signal (SDM) and determine which data packets have reached the satellite (S); satellite access terminals (GW) delete the data packets detected to have reached the satellite (S), from the memory; satellite access terminals (GW) request data transmission again within the same service slot (SS) for data packets detected not to reach the satellite (S).

5. A communication method according to any of the preceding claims wherein each satellite access terminal (GW) has an identification number, and the satellite (S) obtains information regarding the priority of the data transmitted by the relevant satellite access terminal (GW) from the said identification number and makes the resource planning in accordance with the information regarding the priority of the data.

6. A communication method according to Claim 4 wherein; the second signal (RTS) regarding the data transmission request contains information about the age of the data/data packets to be transmitted and the satellite (S) carries out an assessment to determine deadlines for each data packet to reach the satellite (S), considering the transmission priority of the data and the age of the data together.

7. A communication method according to any of the preceding claims comprising the following processing steps performed by the satellite (S): transmitting the first signal (BC) to the satellite access terminals (GW) within the coverage area (S1), thereby initiating a service slot (SS); receiving second signals (RTS) from satellite access terminals (GW) (S2) and making resource planning according to said second signals (RTS) (S3); sending the third signal (CTS) containing resource scheduling information to the satellite access terminals (GW) (S4); receiving data packets from satellite access terminals (GW) in line with resource planning (S5) and at the same time receiving second signals (RTS) from satellite access terminals (GW) for which resource planning has not been made and updating the resource planning in line with new incoming requests (S6); receiving second signals (RTS) from satellite access terminals (GW) and updating the resource planning in line with new requests (S6); if the service slot (SS) has not yet ended, returning to step (S4); If the service slot (SS) has ended, returning to step (S1) and carrying out the same operations for the satellite access terminals (GW) in the new coverage area during a new service slot (SS).

8. A communication method according to any of the preceding claims comprising the following processing steps performed by the satellite access terminal (GW): checking whether there is a data packet to be sent (G1); if there is a data packet to be sent, checking whether a first signal (BC) is received from a satellite (S) within the coverage area (G2); if a first signal (BC) is received from a satellite (S) within the coverage area, transmitting a second signal (RTS) regarding the data transmission request to the satellite (S) (G3); checking whether resources are allocated to it (G4); if there is no resource allocated for it, checking whether the service slot (SS) has been exceeded (G7); if the service slot (SS) has been exceeded, returning to step (G2) in which it is checked whether the first signal (BC) is received from a satellite (S) within the coverage area; if the service slot (SS) has not been exceeded, returning to step (G3) in which a second signal (RTS) is transmitted to the satellite (S), thus requesting reallocation; if there is resource allocated, transmitting the data packet to the satellite (S) within the allocated time and frequency range (G5); checking (G6) whether a fourth signal (SDM) indicating the receipt of the transmitted data packet is received from the satellite (S); evaluating the received fourth signal (SDM) and if it is determined that the transmitted data packets have reached the satellite (S), deleting the transmitted data packets from the memory and returning to the first step (G1); if a fourth signal (SDM) was not received or, when the received fourth signal (SDM) was evaluated, it was determined that the transmitted data packets did not reach the satellite (S); returning to step (G7) and if timeout occurred, returning back to step (G2); if there is no timeout, going back to step (G3) and thus requesting reallocation.

9. A communication method according to Claim 8 wherein; the step of checking whether the resource is allocated (G4) comprises the steps of checking whether a third signal (CTS) regarding resource planning is received from the satellite (S) within a predetermined waiting time, and if the third signal (CTS) is received, evaluating the received third signal (CTS).

10. A communication method according to any of Claims 4 to 9 wherein; the service slot (SS) comprises a first signal time slot (TS-B) located at the beginning of said service slot (SS), at least one uplink time slot (TS-ll) and at least one downlink time slot (TS- D) following the first signal time slot (TS-B) wherein; in said first signal time slot (TS-B) the satellite (S) transmits the first signal (BC) to the satellite communication terminals (GW); in said uplink time slot (TS-ll) satellite communication terminals (GW) transmit said second signal (RTS) and/or their data packets to the satellite (S) and in said downlink time slot (TS-D) the satellite (S) transmits the third signal (CST) and the fourth signal (SDM) to the satellite access terminals (GW).

11. A satellite Access terminal (GW) comprising a first communication link (L1 ) that enables data exchange with at least one loT unit (N), at least one memory in which the data received from the loT units (N) through the first communication link (L1) is recorded; at least one second communication link (L2) that enables the data in the memory to be transmitted to at least one satellite (S) and at least one processing unit wherein the said processing unit is arranged to perform the following operations: evaluating the data stored in the memory and checking whether there is a data packet to be sent; if there is a data packet to be sent, checking whether a first signal (BC) is received through the said second communication link (L2) from a satellite (S) within the coverage area; if a first signal (BC) is received from a satellite (S) within the coverage area, generating a second signal (RTS) regarding the data transmission request and transmitting it to the satellite (S) trough said second communication link (L2); checking whether a third signal (CTS) regarding resource planning is received from the satellite (S) within a predetermined waiting period; if the third signal (CTS) is received, evaluating the received third signal (CTS) and checking whether any resource allocated to the satellite access terminal (GW) exists; checking whether a timeout has occurred if a third signal (CTS) is not received within said waiting period or if the received third signal (CTS) does not include a resource allocation for said satellite access terminal (GW); if there is a timeout, returning to the step of checking whether a first signal (BC) is received from a satellite (S) within the coverage area; if there is no timeout, requesting resource reallocation by returning to the step where a second signal (RTS) is transmitted to the satellite (S); if a third signal (CTS) is received within the said waiting period and there is a resource allocation for the satellite access terminal (GW) in the received third signal (CTS), transmitting the relevant data packet to the satellite (S) via the second communication link (L2) in the time and frequency range allocated to it.

12. A satellite Access terminal (GW) according to Claim 11 wherein said processing unit is arranged to additionally perform the following operations: after transmitting the data packet to the satellite (S), checking whether a fourth signal (SDM) indicating that the transmitted data packet has been received is received from the satellite (S); evaluating the received fourth signal (SDM) and determining whether the transmitted data packets have reached the satellite (S); if it is detected that the data packets have reached the satellite (S), deleting the transmitted data packets from the memory and returning to the first step of checking whether there is a data packet to be sent; if the fourth signal (SDM) is not received or it is determined that the data packets have not reached the satellite (S), returning to the step of checking whether the service slot (SS) has been exceeded and, if timeout has occurred, returning to the step of checking whether a first signal (BC) is received from a satellite within the coverage area; if there is no timeout, returning to the step where a second signal (RTS) is transmitted to the satellite (S) and requesting data transmission again.

13. A satellite (S) comprising a second communication link (L2) that enables it to communicate with a satellite access terminal (GW) in accordance with any of claims 11 or 12 and at least one processing unit which is arranged to perform the following operations: transmitting the first signal (BC) via the said second communication link (L2) to the satellite access terminals (GW) within the coverage area of the satellite (S); receiving second signals (RTS) from satellite access terminals (GW); evaluating received second signals (RTS) and making resource planning; transmitting the third signal (CTS) containing resource planning information to the satellite access terminals (GW); receiving data packets from satellite access terminals (GW) in line with resource planning; at the same time, receiving second signals (RTS) from satellite access terminals (GW) for which resource planning has not been made and updating the resource planning in line with new incoming demands; checking whether the service slot (SS) has expired; if the service slot (SS) has not yet expired, transmitting the third signal (CTS) of the updated resource scheduling to the satellite access terminals (GW); if the service slot (SS) has expired, terminate the process and execute the same operations for a new service slot (SS).

14. A communication system comprising at least one satellite access terminal (GW) according to any of Claims 11 or 12 and a satellite (S) according to Claim 13.

15. A communication system according to Claim 14 comprising a satellite constellation having at least two satellites (S).

16. A communication system according to Claim 15, comprising the said second communication link (L2) having at least one control channel downlink (CCD) arranged for transmitting the first signal (BC), the third signal (CTS) and the fourth signal (SDM) from the satellite (S) to the satellite access terminals (GW); at least one control channel uplink (CCU) arranged for transmitting the second signal (RTS) from the satellite access terminals (GW) to the satellite (S) and at least two service channels (SC, SC1...SC7) arranged for transmitting the data packets from the satellite access terminals (GW) to the satellite (S); each of which having a frequency range different from the others.