Satellite based IoT communication method and system

Abstract

The present invention relates to a communication method and a communication system. According to the method of the present invention, the satellite (S) broadcasts a Beacon signal containing a threshold value (Pth) data; the IoT units (N) receive the Beacon signal and following the reception of the Beacon signal they extract the threshold value (Pth) and generate a random transmission time (Tt) and a random probability value (P); if the probability value (P) is greater than the threshold value (Pth), transmit the data packet at the transmission time (Tt); if it is smaller, generate a random waiting time (Tb) and wait for this time period; if the number of data transmission attempts (D) is equal to or greater than the maximum number of attempts (Dmax), complete the process, if it is smaller, return to the step of determining a random probability value (P).

Description

[0001] SATELLITE BASED IOT COMMUNICATION METHOD AND SYSTEM

[0002] Relevant Technical Field

[0003] The present invention relates to a satellite-based loT communication method and system developed for providing direct-to-satellite (D2S) data transmission between loT devices and low earth orbit (LEO) satellites.

[0004] Prior Art

[0005] In today’s increasingly interconnected world, the demand for seamless and ubiquitous connectivity has reached unpredictable levels. This surge in connectivity needs is not limited to densely populated urban areas but extends to various areas such as rural areas, offshore, and aerial platforms. Satellite-based Internet of Things (loT) and non-terrestrial networks have emerged as the backbone of this global digital revolution, offering reliable communication solutions beyond the constraints of terrestrial infrastructure. The use of low earth orbit (LEO) satellites integrated with Low Power Wide Area Networks (LPWAN) stands out as a promising solution for the demand for uninterrupted and all-pervasive loT communication.

[0006] The orbital characteristics of LEO satellites cause them to have limited accessibility I visibility for a fixed point on the Earth, and while this may seem like a disadvantage for some applications, increasing the number of satellites in the constellation can increase the revisit frequency and reduce end-to-end packet transmission delays. Considering the demand for loT communications in various markets such as agriculture, maritime, and energy, it is seen that most applications are delay tolerant in accordance with the nature of LEO satellite communications.

[0007] Long-Range Wide Area Network (LoRaWAN) technology is widely used under the LPWAN umbrella due to its long-range connectivity. To enable satellite-based communication support, the LoRa Alliance introduced the Long-Range Frequency Hopping Spread Spectrum (LR- FHSS) modulation in the LoRaWAN RP2-1.0.2 specification. LR-FHSS is a spread spectrum modulation that uses a pseudo-random sequence to switch between frequencies over a wide band and can be used in direct-to-satellite communication links (D2S links).

[0008] Introducing LEO satellites to the LoRaWAN network through LR-FHSS modulation requires the existing LoRaWAN medium access scheme to be certainly reviewed since a single satellite in the low earth orbit has a beam footprint on the ground which might be as large as a few hundred kilometers per square. Within such a large area, there can be millions of loT devices, each of which wants to transmit its data to a single satellite in the satellite constellation. The limited transmission window of about 10 minutes for each pass of a single satellite makes the access competition among end devices very difficult. Therefore, it is not possible to use random access with the pure Aloha protocol adopted by terrestrial LoRaWAN networks for satellite access. In order to overcome the very high competition in the connection, a more efficient arrangement with better link utilization is needed.

[0009] Brief description of the invention

[0010] With the present invention, a communication method and system that provides data exchange between loT units and low earth orbit (LEO) satellites is developed. With the method and system in question, the efficiency of the communication link is increased and the probability of collision is significantly reduced. In the time-slotted Aloha access in the state of the art, it is expected that the data packets will be of a fixed size to fit within a time slot. However, in the method in question, a data packet can cover more than one time slot. The time slot scheme is used to align the start time of the transmission of data packets that may have variable sizes. In addition, while a fixed wait I backoff period is applied in case the line is full in Aloha access, the backoff period is randomly determined by each loT unit in the method in question. Thus, the probability of collision is reduced during the data transmission process after the backoff period. Since the coverage area of LEO satellites is quite wide, many end devices try to access the satellite directly via the communication link; this causes a very high load on the communication link. All end devices are triggered by the Beacon signal transmitted by the satellite. If all end devices receiving the beacon signal try to transmit data at the same time, this will cause a very high probability of collision. Therefore, in the method of the invention, the transmission times of the end devices are distributed within the transmission window in which they can access the satellite. In the method of the invention, p-persistent data transmission is used to ensure that the communication link load is shared between different satellites.

[0011] Object of the invention

[0012] The object of the present invention is to develop a communication method and system to enable loT devices within the coverage area to transmit data directly to the satellite.

[0013] Another object of the present invention is to develop a communication method and system that enables increasing connection usage efficiency and reducing the data collision rate.

[0014] Another object of the present invention is to develop a satellite-based loT communication method and system integrated with LPWAN. Definition of the figures

[0015] Application examples of the communication system and method developed with the present invention are shown in the attached figures and from these figures;

[0016] Figure 1 is an exemplary representation of the system architecture of the communication system and method according to the present invention.

[0017] Figure 2 is a flow chart of an exemplary application of the communication method according to the present invention.

[0018] Figure 3 is a flow chart of another exemplary application of the communication method according to the present invention.

[0019] Figure 4 is a flow chart of another exemplary application of the communication method according to the present invention.

[0020] The reference numbers for the elements in Figure 1 are as follows:

[0021] Satellite (S) loT unit (N)

[0022] Coverage area (A)

[0023] The abbreviations in the flow charts in Figure 2-4 are as follows:

[0024] Threshold value (Ptn)

[0025] The moment the beacon signal is received (To)

[0026] Maximum transmission time (Ttmax)

[0027] Transmission time (Tt)

[0028] Probability value (P)

[0029] Number of attempts (D)

[0030] Maximum waiting time (Tbmax)

[0031] Waiting time (Tb)

[0032] Maximum number of attempts (Dmax)

[0033] Number of transmissions (I)

[0034] Maximum number of transmissions (lmax)

[0035] Slot duration (Tsiot)

[0036] Data duration (Tv)

[0037] Maximum data duration (Tvmax) Detailed description of the invention

[0038] In order to solve the technical problems mentioned above, a communication method and system that enables data exchange between loT units and low earth orbit (LEO) satellites is being developed with the present invention.

[0039] The communication method which is the subject of the invention that provides data exchange between at least one loT unit (N) and at least one low earth orbit satellite (S) via a two-way communication link comprises the following process steps:

[0040] - the satellite (S) periodically broadcasts a Beacon signal containing a threshold value (Pth) data;

[0041] - the loT units (N) located within the coverage area (A) of the satellite (S) detect the broadcasted Beacon signal; each of the loT units (N) which detected the Beacon signal: o determines the threshold value (Ptn) in the Beacon signal; o generates a random transmission time (Tt) value between the moment the beacon signal is received (To) and a predefined maximum transmission time (Ttmax) ; o generates a random probability value (P) to compare with the said threshold value (Pth) and increases a number of attempts (D) by 1 ; o compares the probability value (P) with the threshold value (Pth) ; o if the comparison meets a predetermined criterion, transmits the data packet at the said transmission time (Tt) and ends the process; o if the comparison does not meet the specified criterion, generates a random waiting time (Tb) between 0 and a predetermined maximum waiting time (Tbmax) and waits for this time; o at the end of the waiting time (Tb), compares the number of attempts (D) with a predetermined maximum number of attempts (Dmax); o if the number of attempts (D) is equal to or greater than the maximum number of attempts (Dmax), completes the process; o if the number of attempts (D) is less than the maximum number of attempts (Dmax), determines a random probability value (P) and returns to the step of increasing the number of attempts (D) by 1

[0042] An exemplary system architecture in which the method according to the invention is applied is shown in Figure 1 ; the process steps performed by loT units (N) are shown in Figure 2. The satellite (S) in Figure 1 periodically broadcasts a Beacon signal while moving in its orbit. The period in question has a predetermined duration and in an exemplary embodiment of the invention, this duration is 30 seconds. The Beacon signal broadcast by the satellite (S) contains the mentioned threshold value (Ptn) data. loT units (N) located within the satellite's coverage area (A) initiate the data transmission process when they detect the incoming Beacon signal. Each loT unit (N) randomly generates a transmission time (Tt) having a value between the moment it receives the Beacon signal (To) and the maximum transmission time (Ttmax), which is predetermined as the time that can be waited for data transmission as of the moment the Beacon signal is received (TO). Thus, since each loT unit (N) will try to transmit data at the transmission time (Tt) that is generated by itself, it prevents all loT units (N) receiving the Beacon signal from trying to transmit data at the same time. loT units (N) also detect the threshold value (Ptn) embedded in the Beacon signal, and each loT unit (N) generates a random probability value (P) to be compared with the threshold value (Ptn). In an exemplary implementation of the invention, the threshold value (Ptu) and the probability value (P) are values between 0 and 1 , and when these two values are compared, if the probability value (P) is equal to orgreaterthan the threshold value (Ptn), the data packet is transmitted to the satellite (S) at the determined transmission time (Tt). If the probability value (P) is less than the threshold value (Ptu), the loT unit generates a random waiting time (Tb) having a value between 0 and the maximum waiting time (Tbmax) and tries to transmit the data packet again after waiting for this period. Thus, the probability of loT units that have generated the same transmission time (Tt) trying to transmit data at the same time is reduced; and it is provided that the communication link load can be divided into different satellites (S). loT units (N) also monitor the number of times data transmission is attempted within the same Beacon period with the number of attempts (D) value. Starting from the moment that the Beacon signal is received, the number of attempts (D) is increased by one each time a probability value (P) is created. Accordingly, the number of attempts (D), which is initialized as 0 when the Beacon arrives, is updated to 1 when the first probability value (P) is created and is increased by one for each trial. loT units (N) compare the number of attempts (D) with the predetermined maximum number of attempts (Dmax). This comparison is made after waiting for the mentioned waiting time (Tb) and if the number of attempts (D) is equal to or greater than the maximum number of attempts (Dmax), the process is terminated. In this case, no action will be taken until the next Beacon arrives, and when the Beacon arrives, the process in question will start over again. If the number of attempts (D) is less than the maximum number of attempts (Dmax), we return to the step of generating a probability value (P) and increasing the number of attempts (D) by one. Thus, the number of attempts (D) made by each loT unit (N) within a Beacon period is limited to a maximum value, which provides balancing the communication link load. With this method, direct to satellite (D2S) communication is provided between loT units (N) and satellite (S) via random access via the mentioned communication link. The method is preferably implemented in a system architecture where a plurality of loT units (N) and a satellite constellation comprising multiple satellites (S) are present; each loT unit (N) and each satellite (S) in the constellation performs the specified processing steps.

[0043] In a preferred embodiment of the invention, the threshold value (Ptn) is generated dynamically by the satellite (S). The threshold value (Ptn) is preferably generated depending on the communication link density. In a preferred embodiment of the invention, location-based threshold values (Ptn) are pre-recorded in the satellite (S) and the satellite (S) performs location detection during its movement and generates and broadcasts the Beacon signal containing the threshold value (Ptn) associated with the location.

[0044] In a preferred embodiment of the invention, loT units (N) also monitor a number of transmissions (I) value, and following the transmission of the data packet, number of transmissions (I) is increased by 1 and the number of transmissions (I) is compared with a predetermined maximum number of transmissions (lmax) value. If the number of transmissions (I) is equal to or greater than the maximum number of transmissions (lmax), the process is terminated, thus the loT unit will wait for the next Beacon signal. If the number of transmissions (I) is less than the maximum number of transmissions (lmax), it is returned to the step of generating a random probability value (P) and increasing the number of attempts (D) value by 1 . Figure 3 shows the process steps performed by loT units (N) in an exemplary implementation.

[0045] In a preferred embodiment of the invention, the communication window formed as of the moment the Beacon signal is received (To) is divided into time slots with a predetermined slot duration (Tsiot) and the loT units (N) form the transmission time (Tt) as multiples of the said slot duration (Tsiot) . Data packets can preferably have different sizes that can be transmitted in more than one time slot and the said time slots ensure the alignment of the beginning of the data packet transmission. The transmission time created in the said embodiment can be shown with the formula (Tt) = (To) + n. (Tsiot) provided that "n" is 1 or an integer greater than 1 .

[0046] In a preferred embodiment of the invention, the loT unit (N) transmits the generated data packets to the satellite in LR-FHSS format.

[0047] In a preferred embodiment of the invention, loT units (N) compare the data duration (Tv), which is the time elapsed from the moment the data packet to be transmitted is created, with a predetermined maximum data duration (Tvmax) after generating a random waiting time (Tb) and waiting forthis time period; and thus they determine whetherthe data is useful data. As a result of the comparison, if the data duration (Tv) is equal to or greater than the mentioned maximum data duration (Tvmax), it is determined that the data is not useful data and the loT unit (N) checks whether there is a more up-to-date data packet; if there is a more up-to-date data packet, it deletes the data packet that is determined not to be useful data and terminates the process. In this case, the loT unit will try to transmit the up-to-date data packet with the next Beacon signal. If the data duration (Tv) of the relevant data packet is smaller than the mentioned maximum data duration (Tvmax), it is determined that the relevant data packet contains useful data and the step of determining the probability value (P) and increasing the number of attempts (D) by one is returned. Figure 4 shows the processing steps performed by loT units (N) in an exemplary application.

[0048] With the present invention, an loT unit (N) comprising at least one sensor collecting time series data related to the environment it is located in, at least one memory unit where the data collected by the sensor is stored in the form of data packets until transmitted, at least one communication unit that enables the reception of the Beacon signal broadcast by at least one LEO satellite (S) within the coverage area (A) and the transmission of the collected data to the said LEO satellite, and at least one processing unit arranged to perform the above-mentioned processing steps performed by the loT unit is also provided. The said communication unit preferably comprises a transceiver with LR-FHSS application capability. In the specified implementation, data packets are transmitted to the satellite in LR-FHSS format.

[0049] With the present invention, a low earth orbit satellite (S) comprising at least one processing unit arranged to embed said threshold value (Ptn) in the Beacon signal and broadcast it periodically and at least one satellite communication unit arranged to broadcast said Beacon signal and receive data packets transmitted by loT units (N) located within the coverage area (A) in line with the broadcasted Beacon signal is also provided. Said processing unit preferably determines said first threshold (Ptn) value depending on the density of the communication link between the satellite (S) and loT units (N). In another preferred embodiment, said processing unit is arranged to access a location-based threshold value (Ptn) data set, that is predetermined and recorded; and to embed the relevant threshold value (Ptn) in the Beacon signal to be broadcasted in line with the location of the satellite (S).

[0050] The present invention also provides a satellite-based loT communication system comprising at least one loT unit (N), at least one satellite (S) and a communication link providing bidirectional communication between the two. The communication link is preferably a halfduplex communication link. Over the said communication link, the Beacon signal is broadcasted from the satellite (S) towards the ground; and the data packets of the loT units (N) are transmitted from the ground to the satellite (S). The said communication link comprises at least one upward communication channel and the said communication channel is preferably divided into time slots.

Claims

CLAIMS1. A communication method for providing data exchange between at least one loT unit (N) and at least one low earth orbit satellite (S) via a two-way communication link comprising the following process steps:- the satellite (S) periodically broadcasts a Beacon signal containing a threshold value (Pth) data;- the loT units (N) located within the coverage area (A) of the satellite (S) detect the broadcasted Beacon signal; each of the loT units (N) which detected the Beacon signal: o determines the threshold value (Ptn) in the beacon signal; o generates a random transmission time (Tt) between the moment the beacon signal is received (To) and a predefined maximum transmission time (Ttmax); o generates a random probability value (P) to compare with the said threshold value (Pth) and increases a number of attempts (D) by 1 ; o compares the probability value (P) with the threshold value (Ptn); o if the comparison meets a predetermined criterion, transmits the data packet at the said transmission time (Tt) and ends the process; o if the comparison does not meet the said predetermined criterion, generates a random waiting time (Tb) between 0 and a predetermined maximum waiting time (Tbmax) and waits for this time; o at the end of the waiting time (Tb), compares the number of attempts (D) with a predetermined maximum number of attempts (Dmax); o if the number of attempts (D) is equal to or greater than the maximum number of attempts (Dmax), completes the process; o if the number of attempts (D) is less than the maximum number of attempts (Dmax) , determines a random probability value (P) and returns to the step of increasing the number of attempts (D) by 1 .

2. A communication method in accordance with Claim 1 , wherein the threshold value (Pt) is determined by the satellite (S) depending on the communication link density.

3. A communication method in accordance with Claim 1 , wherein location-based threshold values (Pt) are pre-recorded in the satellite (S) and the satellite (S) determines the location during its movement and creates and broadcasts the Beacon signal containing the threshold value (Pt) associated with the location.

4. A communication method in accordance with any of the preceding Claims comprising the following steps performed by the loT units (N) monitoring a number of transmissions (I) value, increasing the number of transmissions (I) value by 1 following the transmission of the data packet, comparing the number of transmissions (I) value with a predetermined maximum number of transmission (lmax) value,- terminating the process if the number of transmissions (I) value is equal to or greater than the maximum number of transmissions (lmax) value, returning to the step of generating a random probability value (P) and increasing the number of attempts (D) value by 1 if the number of transmissions (I) value is less than the maximum number of transmissions (lmax) value.

5. A communication method in accordance with any of the preceding Claims wherein, the communication window that occurs as of the moment the beacon signal is received (To) is divided into time slots with a predetermined slot duration (Tsiot) , and loT units (N) form the transmission time (Tt) as multiples of the slot duration (Tsiot).

6. A communication method in accordance with any of the preceding Claims comprising the following steps performed after the process of generating a random waiting time (Tb) and waiting for this period is carried out by the loT units (N): comparing the data duration (Tv) of the data packet to be transmitted, which is the time elapsed since it was created, with a predetermined maximum data duration (Tvmax); if the data duration (Tv) is equal to or greater than the said maximum data duration (T vmax) , checking whether there is a more recent data packet; if there is a more recent data packet, deleting the current data packet and terminating the process; if there is no more recent data packet, terminating the process; if the data duration (Tv) is less than the said maximum data duration (Tvmax), determining the probability value (P) and returning to the step of increasing the number of attempts (D) value by one.

7. A low earth orbit satellite (S) comprising at least one satellite processing unit configured to ensure that said threshold value (Ptn) is embedded in the Beacon signal and broadcasted periodically, and at least one satellite communication unit configured tobroadcast said Beacon signal and to receive data packets transmitted by loT units (N) located within the coverage area (A) in line with the broadcasted Beacon signal.

8. A satellite (S) in accordance with Claim 7, comprising said satellite processing unit arranged to determine said first threshold value (Ptu) depending on the density of the communication link between the satellite (S) and the loT units (N).

9. A satellite (S) in accordance with any of Claims 7 or 8, comprising said satellite processing unit arranged to access a predetermined and recorded location-based threshold value (Ptu) data set and to embed the relevant threshold value (Ptu) in the Beacon signal to be broadcasted in line with the location of the satellite (S).

10. An loT unit (N) comprising at least one sensor collecting time series data regarding the environment in which it is located, at least one memory unit in which the data collected by the sensor is stored in the form of data packets until transmitted, at least one communication unit that enables the reception of the Beacon signal broadcast by at least one LEO satellite (S) within the coverage area (A) and the transmission of the collected data to the said LEO satellite, and at least one processing unit arranged to perform the process steps related to a method according to any one of Claims 1-6.

11. A satellite-based loT communication system comprising at least one satellite (S) according to any one of Claims 7-9; at least one loT unit (N) according to Claim 10; and a communication link providing two-way communication between said satellite (S) and the loT unit (N).

12. A communication system in accordance with Claim 11 , comprising a satellite constellation having at least two satellites (S).