A method for performing energy efficient GNSS fix between NB-IOT devices and satellite

Abstract

A method for energy-efficient communication in a non-terrestrial network (NTN) (100) comprising a plurality of user equipment (120) (UEs) and a satellite (110). The method includes coordinating wake-up and sleep times of UEs (120) located in close proximity, establishing a connection between a first UE (121) and the satellite (110), and performing an uplink transmission. It is characterized by establishing a device-to-device connection between the first UE (121) and a next intermediate UE (122) during a buffer time, transferring scheduling information, and allowing the intermediate UE (122) to skip certain procedures based on the received information. Skipping procedure is realized for the rest of the UEs (120) that are in close proximity. The method optimizes power consumption for various IoT applications.

Description

[0001] DESCRIPTION

[0002] A METHOD FOR PERFORMING ENERGY EFFICIENT GNSS FIX BETWEEN NB-IOT DEVICES AND SATELLITE

[0003] TECHNICAL FIELD

[0004] Invention relates to a method for communication in a non-terrestrial network (NTN) comprising a plurality of user equipment (UEs) and a satellite.

[0005] PRIOR ART

[0006] Narrow Band-Internet of Things (NB-loT), a cellular technology standardized by 3GPP, aims to improve coverage for a large number of low throughput, low power devices at low cost. However, NB-loT devices often operate in remote areas where terrestrial networks are not available. Integrating NB-loT into an non terrestrial network (NTN) aims to provide a standardized solution for global loT connectivity. However, the introduction of NB-loT into satellite systems requires adjustments to the protocol.

[0007] A significant hurdle in this regard is the Global Navigation Satellite System (GNSS) fix, which determines the location of the receiver to a specified accuracy. However, the energy requirements of this process, coupled with frequent satellite handovers, exceed the long-term capabilities of NB-loT devices. This creates an imperative for energy-efficient design to overcome this challenge. [1], [2],

[0008] In addition to the GNSS fix, another significant hurdle in NB-loT satellite systems is the random access (RA), which is responsible for handling uplink synchronization and data transmission scheduling requests. Currently, the current NB-loT RA preamble, specifically the narrowband physical RA channel (NPRACH), struggles to accommodate satellite channel impairments such as strong Doppler effects and longer delays, which are more severe than those encountered by terrestrial networks (TNs) [3].

[0009] Despite some initial studies in the literature addressing the adaptation of GNSS fix and RA in NB-loT, none of these studies specifically focus on energy efficiency issues. For example, in [4], the proposed method aims to mitigate the effects of frequency offset and Doppler rate while extending the coverage range beyond the usual limits of NB-loT systems in terrestrial networks (TNs). In [5], a method is proposed to reduce intercarrier interference (ICI) to ensure that false alarm and miss probabilities remain low. In [6], the design and implementation of a novel sensor node is outlined that integrates low-power, long-range communication with GNSS to achieve both high accuracy and energy efficiency.

[0010] Based on the current state of the art, it is evident that there is a gap in the literature regarding the energy efficiency requirements of NB-loT devices within satellite networks.

[0011] Traditional Global Navigation Satellite System (GNSS) positioning techniques often suffer from a significant drawback, which is the excessive power consumption. For NB-loT devices powered by batteries or energy harvesting mechanisms, this is a major challenge that hinders their operational efficiency and longevity. In addition, the RA procedure for each handover of satellites causes the energy resources of NB-loT devices to be drained as well. The proposed technique optimises power consumption without compromising the accuracy and reliability of location data, which is a key requirement for various loT applications, including smart agriculture, asset tracking and environmental monitoring.

[0012] References:

[0013]

[0001] “3rd generation partnership project; technical specification group radio access network; study on new radio (NR) to support non terrestrial networks (release 15), v15.1.0,” 3GPP, Sophia Antipolis, France, Rep. TR 38.811 , Jun. 2019.

[0014] [2] “3rd generation partnership project; technical specification group radio access network; solutions for NR to support non-terrestrial networks (NTN) (release 16), v16.0.0,” 3GPP, Sophia Antipolis, France, Rep. TR 38.821 , Dec. 2019.

[0015] [3] Lin, J. C. (2023). NB-loT Physical Random-Access Channels (NPRACHs) With Intercarrier Interference (ICI) Reduction. IEEE Internet of Things Journal.

[0016] [4] Chougrani, H., Kisseleff, S., Martins, W. A., & Chatzinotas, S. (2021 ). NB-loT random access for nonterrestrial networks: Preamble detection and uplink synchronization. IEEE Internet of Things Journal, 9(16), 14913-14927.

[0017] [5] Lin, J. C. (2023). NB-loT Physical Random-Access Channels (NPRACHs) With Intercarrier Interference (ICI) Reduction. IEEE Internet of Things Journal.

[0018] [6] Mayer, P., Magno, M., Berger, A., & Benini, L. (2020). RTK-LoRa: High-precision, long- range, and energy-efficient localization for mobile loT devices. IEEE transactions on instrumentation and measurement, 70, 1 -11.

[0019] 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

[0020] The present invention relates to a method to eliminate the above-mentioned disadvantages and bring new advantages to the relevant technical field.

[0021] An object of the invention is to significantly reduce the energy consumption of user equipment (NB-loT devices) during frequent GNSS fix.

[0022] To achieve all the objects mentioned above and that will emerge from the following detailed description, the present invention relates to a method for communication in a non-terrestrial network (NTN) comprising a plurality of user equipment (UEs) and a satellite. Accordingly, it is characterized in that comprising the steps of: coordinating wake-up and sleep times of the plurality of UEs located in close proximity to each other by arranging their wake-up and sleep times, wake-up mode durations, and sleep mode durations;

[0023] - performing an initial connection step comprising the steps of:

[0024] • establishing a connection between a first UE and the satellite, wherein the first UE performs a Global Navigation Satellite System (GNSS) fix and a random access (RA) procedure;

[0025] • performing, by the first UE, an uplink transmission to the satellite;

[0026] • establishing a device-to-device connection between the first UE and a next intermediate UE during a buffer time in which the first UE remains awake and the next intermediate UE wakes up;

[0027] • transferring, by the first UE, scheduling information comprising a frequency offset between the fist UE and the satellite via the device-to-device connection during the buffer time;

[0028] - performing an intermediate sharing step comprising steps of;

[0029] • by the next intermediate UE, calculating a frequency offset value between the satellite and itself based on received frequency offset and a predetermined time offset between a previous intermediate UE or the first UE and itself;

[0030] • performing, by the next intermediate UE, an uplink transmission to the satellite based on calculated frequency offset;

[0031] • establishing a device-to-device connection between the next intermediate UE and a another next intermediate UE or a last UE during a buffer time in which the next intermediate UE remains awake and the another next intermediate UE or the last UE wakes up;

[0032] • transferring, by the next intermediate UE, scheduling information comprising the calculated frequency offset via the device-to-device connection during the buffer time; • performing the intermediate sharing step until all the intermediate UEs performs uplink transmission; further comprising the steps of;

[0033] • by the last UE, calculating a frequency offset value between the satellite and itself based on received frequency offset and a predetermined time offset between the previous intermediate UE and itself;

[0034] • performing, by the last UE, an uplink transmission to the satellite based on calculated frequency offset. Thus, only the first UE realizes GNSS fix and RA procedure, rest of the user equipment which are in close proximity with the first UE (intermediate UEs and the last UE) receives information from first UE which allows them to transmit uplink data without GNSS fix and RA procedures. This significantly reduces energy consumption of the intermediate UEs and the last UE. This method also significantly reduces the time spent by the UEs to realize GNSS fix and Ra procedure.

[0035] A possible embodiment of the invention comprises the step of performing, by the intermediate UEs and the last UE, the uplink transmission using the same channel the first UE used. Thus the spectrum is secured for the same group of UEs for reliable transmission.

[0036] A possible embodiment of the invention is characterized in that the GNSS fix determines a location of the first UE and synchronizes the first UE with the satellite.

[0037] Another possible embodiment of the invention is characterized in that satellite moves with a constant speed to maintain its orbit.

[0038] Another possible embodiment of the invention is characterized in that the satellite receives the uplink transmissions from the first UE, intermediate UEs and the last UE.

[0039] Another possible embodiment of the invention is characterized in that wherein the first UE and intermediate UE or UEs go into a deep sleep mode after transferring the scheduling information and last UE goes into deep sleep mode after uplink transmission.

[0040] BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is a drawing illustrating top schematic view of NTN. Figure 2 is a drawing depicting coordinated sleep mode and wake up mode schedule of the UEs.

[0042] Figure 3 is a drawing depicting time line of uplink transmission and device to device communication of UEs on the wake up mode and sleep mode schedule.

[0043] REFERENCE NUMBERS GIVEN IN THE FIGURE

[0044] 100 Non-Terrestrial Network (NTN)

[0045] 110 Satellite

[0046] 120 User equipment

[0047] 121 First UE

[0048] 122 Intermediate UE

[0049] 123 Last UE

[0050] DETAILED DESCRIPTION OF THE INVENTION

[0051] 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.

[0052] Referring to figure 1 , a Non-Terrestrial Network (NTN) (100) is provided. NTN network comprises a satellite (1 10). Satellite (1 10) may be GEO, MEO, or LEO type. The satellite (1 10) moves in its orbit with a constant velocity for each time iteration.

[0053] NTN comprises plurality of user equipment (120) (UE). UEs (120) are configured to realize short transmission over NTN. Short transmission may be realized as defined in 3GPP. UEs (120) are loT devices located with close proximity to each other. For example UEs may be a group of UEs (120) located at a home or a factory or a site. They may be for example in close proximity such as 50 cm to 10 meter. This distance is given as example to clarify what is meant by close proximity. Any other distance that allows subject matter invention method would also work.

[0054] UEs have sleep modes and wake up modes. In sleep mode UEs (120) are in state of low power consumption as well known in the art. In wake up mode, they are programmed to perform their routine uplink transmission. Each UE (120) stores the distance information between UEs (120) and time offset / frequency between UEs (120). The information may be stored in the codebooks.

[0055] UEs are capable of performing Global Navigation Satellite System (GNSS) fix and perform random access procedure with the satellite (1 10). UEs (120) are defined as a first UE (121 ), intermediate UEs (122) and a last UE (123). In subject matter method first UE (121 ) realizes GNSS fix and RA than shares related information with the next intermediate UE (122) and performs uplink transmission. Each intermediate UE (122) performs uplink transmission based on received information from the first UE (121 ) or the previous intermediate UE (122) without the need of GNSS fix and RA procedure and shares the information with the next UE. And the last UE (123) performs uplink transmission based on information received form the previous intermediate UE (122).

[0056] Wake-up and sleep times of the plurality of UEs (120) located in close proximity to each other are coordinated by arranging their wake-up and sleep times, wake-up mode durations, and sleep mode durations. UEs’ Wake up and sleep times are configured in such way that there is a shared buffer time when two consecutive UE (120) where one of the UE (120) end its wake up mode and the other UE (120) starts its wake up mode. Thus, data transmission between the two is possible. This arrangement is depicted in figure 2.

[0057] Below table 1 gives an exemplary wake up duration, wake up time and sleep mode duration of 5 exemplary user equipment (120).

[0058] Table 1

[0059] After the coordination between the UEs (120) are ensured, an initial connection step is performed by the the first UE (121 ). starts to establish the connection between the satellite (1 10) and itself. During its wake up duration the first UE (121 ) establishes a connection between with the satellite (1 10), wherein the first UE (121 ) performs a Global Navigation Satellite System (GNSS) fix and a random access (RA) procedure. The first UE (121 ), performs an uplink transmission to the satellite (110). The first UE (121 ) establishes a device-to-device connection with a next intermediate UE (122) during the buffer time in which the first UE (121 ) remains awake and the next intermediate UE (122) wakes up. The first UE (121 ) transfers scheduling information comprising a frequency offset between the fist UE and the satellite (110) via the device-to-device connection during the buffer time. The first UE (121 ) may also transfer user ID to the next intermediate UE (122).

[0060] The satellite (1 10) moves with a constant speed and the distance between the UEs (120) are stored in each UE (120), each UE (120) can calculate the frequency offset between itself and the satellite (110) based on the frequency offset received from the previous UE and the stored time offset information.

[0061] After the first UE (121 ) transfers frequency offset to the next intermediate UE (122), an intermediate sharing step is realized. In the intermediate sharing step each intermediate UE (122) calculates a frequency offset value between the satellite (1 10) and itself based on received frequency offset and a predetermined time offset between a previous intermediate UE (122) or the first UE (121 ) and itself. Each intermediate UE (122), performs an uplink transmission to the satellite (1 10) based on calculated frequency offset during its wake up duration. Each intermediate UE (122) establishes a device-to-device connection between the itself and the next intermediate UE (122) or a last UE (123) during its buffer time in which the next intermediate UE (122) remains awake and the another next intermediate UE (122) or the last UE (123) wakes up. Each intermediate UE (122), transfers scheduling information comprising the calculated frequency offset via the device-to-device connection during the buffer time.

[0062] And the last UE (123), calculates a frequency offset value between the satellite (110) and itself based on received frequency offset and a predetermined time offset between the previous intermediate UE (122) and itself. Then performs an uplink transmission to the satellite (1 10) based on calculated frequency offset.

[0063] This procedure is depicted in time line in figure 3. In each device to device transmission, an ID of the transmitter may be transmitted. Thus, receiver identify the frequency offset between itself and the transmitter UE based on the received ID and the codebook.

[0064] In a possible embodiment, the intermediate UEs (122) and the last UE (123) uses the same channel as the first UE (121 ) for performing uplink transmission. Simulations relating to subject matter method and the prior art.

[0065] A simulation given in Fig.1 was conducted to evaluate the energy efficiency of a proposed method for GNSS fix and PRACH procedures in Narrowband loT (NB-loT) devices. These devices, which often operate in remote areas and rely on satellite networks, face significant energy consumption challenges under traditional methods. The simulation aimed to compare the energy consumption of the traditional and proposed methods across various numbers of devices and signal-to-noise ratios (SNRs).

[0066] The traditional method requires each device to independently perform energy-intensive GNSS fixes and PRACH procedures. This redundancy leads to a linear increase in total energy consumption as the number of devices grows. In contrast, the proposed method introduces a coordination mechanism where nearby devices synchronize their wake-up times and share critical GNSS fix and PRACH scheduling information. Only the first device in a sequence performs the complete energy-intensive steps, while subsequent devices utilize the shared information, thus conserving energy.

[0067] In the simulation, specific energy consumption values were assigned for GNSS fixes, PRACH procedures, and the energy consumed during deep sleep modes.

[0068] Results showed that the total energy consumption for the traditional method increased proportionally with the number of devices. Each device independently incurred the full energy cost of GNSS and PRACH procedures, leading to significant overall energy use. On the other hand, the proposed method demonstrated a substantial reduction in total energy consumption. This reduction was attributed to the coordinated wake-up and shared information mechanism, which effectively minimized redundant energy expenditure.

[0069] For the proposed method, the first device in the sequence performed the complete GNSS fix and PRACH steps. Subsequent devices used the information shared by the first device, thereby avoiding the need to repeat these energy-intensive steps. This sharing mechanism significantly reduced the energy required for each subsequent device. The efficiency gain from this approach became more pronounced as the number of devices increased, showcasing the scalability of the proposed method.

[0070] Time Efficiency

[0071] A simulation was conducted to evaluate the time efficiency of a proposed method for GNSS fix and PRACH procedures in Narrowband loT (NB-loT) devices in Figure 1. These devices often operate in remote areas where time efficiency is critical to maintain reliable and continuous connectivity. The simulation aimed to compare the time consumption of the traditional and proposed methods across various numbers of devices and signal-to-noise ratios (SNRs).

[0072] In the traditional method, each NB-loT device independently performs GNSS fixes and PRACH procedures, leading to repetitive time consumption for each device. This redundancy results in a linear increase in total time consumption as the number of devices grows. The proposed method, however, introduces a coordination mechanism where nearby devices synchronize their wake-up times and share critical GNSS fix and PRACH scheduling information. This technique ensures that only the first device in a sequence performs the full GNSS fix and PRACH steps, while subsequent devices utilize the shared information, thereby reducing the overall time required for connectivity.

[0073] Results showed that the total time consumption for the traditional method increased proportionally with the number of devices. Each device independently performed the GNSS fix and PRACH procedures, resulting in significant overall time use. In contrast, the proposed method demonstrated a substantial reduction in total time consumption. This reduction was due to the coordinated wake-up and shared information mechanism, which effectively minimized redundant time expenditure.

[0074] For the proposed method, the first device in the sequence performed the complete GNSS fix and PRACH steps. Subsequent devices used the information shared by the first device, thereby avoiding the need to repeat these time-intensive steps. This sharing mechanism significantly reduced the time required for each subsequent device. The efficiency gain from this approach became more pronounced as the number of devices increased, showcasing the scalability of the proposed method. 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

CLAIMS1 . A method for communication in a non-terrestrial network (NTN) (100) comprising a plurality of user equipment (120) (UEs) and a satellite (110), characterized in that comprising the steps of:- coordinating wake-up and sleep times of the plurality of UEs (120) located in close proximity to each other by arranging their wake-up and sleep times, wake-up mode durations, and sleep mode durations;- performing an initial connection step comprising the steps of:• establishing a connection between a first UE (121 ) and the satellite (110), wherein the first UE (121 ) performs a Global Navigation Satellite System (GNSS) fix and a random access (RA) procedure;• performing, by the first UE (121 ), an uplink transmission to the satellite (110);• establishing a device-to-device connection between the first UE (121 ) and a next intermediate UE (122) during a buffer time in which the first UE (121 ) remains awake and the next intermediate UE (122) wakes up;• transferring, by the first UE (121 ), scheduling information comprising a frequency offset between the first UE (121 ) and the satellite (110) via the device-to-device connection during the buffer time;- performing an intermediate sharing step comprising steps of;• by the next intermediate UE (122), calculating a frequency offset value between the satellite (1 10) and itself based on received frequency offset and a predetermined time offset between a previous intermediate UE (122) or the first UE (121 ) and itself;• performing, by the next intermediate UE (122), an uplink transmission to the satellite (110) based on calculated frequency offset;• establishing a device-to-device connection between the next intermediate UE (122) and a another next intermediate UE (122) or a last UE (123) during a buffer time in which the next intermediate UE (122) remains awake and the another next intermediate UE (122) or the last UE (123) wakes up;• transferring, by the next intermediate UE (122), scheduling information comprising the calculated frequency offset via the device-to-device connection during the buffer time;• performing the intermediate sharing step until all the intermediate UEs (122) performs uplink transmission; further comprising the steps of;• by the last UE (123), calculating a frequency offset value between the satellite (1 10) and itself based on received frequency offset and a predetermined time offset between the previous intermediate UE (122) and itself;• performing, by the last UE (123), an uplink transmission to the satellite (1 10) based on calculated frequency offset.

2. The method according to claim 1 , wherein performing, by the intermediate UEs (122) and the last UE (123), the uplink transmission using the same channel the first UE (121 ) used.

3. The method according to claim 1 , wherein the GNSS fix determines a location of the first UE (121 ) and synchronizes the first UE (121 ) with the satellite (110).

4. The method according to claim 1 , wherein the satellite (110) moves with a constant speed to maintain its orbit.

5. The method according to claim 1 , wherein the satellite (1 10) receives the uplink transmissions from the first UE (121 ), intermediate UEs (122) and the last UE (123).

6. The method according to claim 1 , wherein the first UE (121 ) and intermediate UE (122) or UEs go into a deep sleep mode after transferring the scheduling information and last UE (123) goes into deep sleep mode after uplink transmission.

7. A non-terrestrial network (NTN) (100) comprising a plurality of user equipment (120) (UEs) and a satellite (1 10) characterized in that the NTN is configured to perform one of the method of claim 1 -6.

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