Small data transmitting method in a non-terrestrial network

Abstract

A method realized by a wireless device (100) of a non-terrestrial network (NTN) for small data transmission to a satellite (200). It comprises steps of: receiving, satellite (200) ephemeris data comprising calculated position and velocity of satellites (200) at specific times; calculating a t0 time when a satellite (200) will start serving a location where the wireless device (100) is located and a t1 time when the satellite (200) will stop serving said location based on ephemeris data; determining a size of data to be transmitted; estimating a transmission time to transmit data to be transmitted to satellite (200) of each bandwidth part (BWP) from a list of available BWPs; calculating a t1' time when current serving satellite (200) will stop serving said location, continuously estimating an available time window before current serving satellite (200) stops serving the location, if available time window is higher than a first predetermined threshold determining the smallest BWP from a list of BWPs that has the transmission time less than the remaining transmission time, attempting to a transmission for data to be transmitted using selected BWP.

Description

[0001] SMALL DATA TRANSMITTING METHOD IN A NON-TERRESTRIAL NETWORK

[0002] TECHNICAL FIELD

[0003] The invention relates to a method realized by a wireless device of a non-terrestrial network (NTN) for data transmission to a satellite and a wireless device thereof.

[0004] PRIOR ART

[0005] Small data transmission is a critical concept in satellite communications, characterized by the transmission of relatively small-sized data packets. Unlike traditional large-scale data payloads, these packets typically comprise only a few bytes to a few kilobytes. Such a scale is particularly suitable for applications that necessitate minimal data exchange, such as transmitting sensor readings or sending brief status updates.

[0006] The significance of small data transmission in the satellite communication realm cannot be overstated. It offers a highly efficient way to manage the limited resources available in satellite operations. The small size of the data packets ensures minimal bandwidth usage, which is a crucial factor in environments where bandwidth is a scarce and valuable resource. Additionally, this efficiency extends to power consumption — a paramount consideration in loT technology.

[0007] This method of data transmission is particularly well-suited to the unique challenges presented by satellite-loT networks. loT devices, by their nature, operate under stringent constraints regarding power and bandwidth. Therefore, the ability to transmit data efficiently in small quantities is not just beneficial but often a fundamental requirement for the successful operation of satellite-loT networks.

[0008] In the current state of the art as defined by the 3GPP standards, particularly for Non-Terrestrial Networks (NTNs), the procedure for Small Data Transmission (SDT) is outlined in TS 38.300. This procedure allows for data transmission while the device remains in the RRCJNACTIVE state, without needing to transition to the RRC_CONNECTED state. SDT is enabled on a radio bearer basis and is initiated by the wireless device. The conditions for the SDT procedure as specified by 3GPP include situations where less than a configured amount of uplink data awaits across all radio bearers, and the downlink Received Signal Reference Power (RSRP) is above a configured threshold. A valid SDT resource, as specified in TS 38.321 , must be available for the SDT procedure to commence. The maximum duration of the SDT procedure is determined by an SDT failure detection timer, which is configured by the network.

[0009] The SDT procedure can start in one of two ways: RA-SDT or CG-SDT. RA-SDT uses a 'raise hand to speak' method (Random Access Channel or RACH) that is set up based on general system information. CG-SDT, on the other hand, uses a 'pre-allocated time to speak' method (Type 1 Configured Grant or CG) set up by dedicated signals.

[0010] In the existing mechanism of Release 17, the power-saving strategy for SDT-capable UEs is limited to operating on the initial Bandwidth Part (BWP), which is specified either through Type 0 Physical Downlink Control Channel (PDCCH) Common Search Space (CORESETO) or the bandwidth disclosed in System Information Block 1 (SIB1 ). BWPs are defined as subsets of contiguous Resource Blocks (RBs) on a carrier, supporting wireless devices that cannot receive the full carrier bandwidth and facilitating bandwidth adaptation, allowing wireless devices to dynamically adjust their reception bandwidth based on the data traffic they are scheduled to receive.

[0011] Additionally, in 5G NR, the maximum channel bandwidth can be up to 100 MHz for FR1 frequency bands and 400 MHz for FR2 (e.g., millimeter-wave frequency band). However, not all devices need to monitor the entire frequency band in all scenarios. Some lower-cost devices may not support such large channel bandwidths due to limited radio capability. A component in charge of BWP management oversees this switching based on set criteria, taking into account the device's capabilities and the network's configuration, as well as operational aspects like data session communication rates, quality of service (QoS), and the device's power levels. This helps in making informed decisions about managing BWPs efficiently. loT devices are anticipated to be deployed in exceedingly large quantities, presenting a challenge of substantial signaling overhead that could potentially burden the network infrastructure and lead to rapid depletion of the devices' battery life. Moreover, the existing methodologies for initiating SDT predominantly rely on fixed intervals or predefined triggers. All the problems mentioned above have made it necessary to make an innovation in the relevant technical field as a result.

[0012] BRIEF DESCRIPTION OF THE INVENTION

[0013] The present invention relates to a method to eliminate the above-mentioned disadvantages and bring new advantages to the relevant technical field.

[0014] An object of the invention is to increase the effective data rate and reduce the energy consumption amount of wireless devices in non-terrestrial networks that realize small data transmission.

[0015] Another object of the invention is to reduce transmission attempts per wireless device and increase successful transmission attempts per wireless device which realizes small data transmission.

[0016] To achieve all the objectives mentioned above and that will emerge from the following detailed description, the present invention relates to a method realized by a wireless device of a nonterrestrial network (NTN) for small data transmission to a satellite. Accordingly, it is characterized by comprising steps;

[0017] - receiving, satellite ephemeris data comprising calculated position and velocity of satellites at specific times;

[0018] - calculating a to time when a satellite will start serving a location where the wireless device is located and a t1 time when the satellite will stop serving said location based on ephemeris data;

[0019] - determining a size of data to be transmitted;

[0020] - estimating a transmission time to transmit data to be transmitted to satellite of each bandwidth part (BWP) from a list of available BWPs;

[0021] - calculating a t1 ’ time when current serving satellite will stop serving said location,

[0022] - continuously estimating an available time window before current serving satellite stops serving the location, if available time window is higher than a first predetermined threshold

[0023] - determining the smallest BWP from a list of BWPs that has the transmission time less than the remaining transmission time, - attempting to a transmission for data to be transmitted using selected BWP. Thus, narrowest BWP that can transmit data within the satellite's coverage period is utilized in order to balancing resource efficiency and successful transmission.

[0024] A possible embodiment of the invention is characterized in that comprising the step of;

[0025] - if the transmission time of smallest BWP in the list is smaller than last estimated available time window attempting a rapid transmission using highest BWP from the list. This achieves transmitting as much data as possible until losing the connection when efficient BWPs cannot be used.

[0026] Another possible embodiment of the invention is characterized in that comprising the step of;

[0027] - if it is determined that attempting to the transmission using selected BWP is failed, selecting the next higher BWP from selected BWP and attempting the transmission using selected BWP.

[0028] Another possible embodiment of the invention is characterized in that comprising the step of;

[0029] - if it is determined that attempting to the transmission using selected BWP is successful, storing selected BWP to be primarily used in next attempt to the transmission.

[0030] Another possible embodiment of the invention is characterized in that comprising the steps of;

[0031] - counting failed transmission attempts to the transmission of data to be transmitted;

[0032] - if it is determined that a failed transmission attempts exceeds a predetermined threshold, switching wireless device to an idle operation mode. If repeated attempts fail, the network device enters IDLE mode to save energy and reduce unnecessary network traffic for a specific duration.

[0033] Another possible embodiment of the invention is characterized in comprising the steps of;

[0034] - receiving correction margin of the satellite ephemeris data to.

[0035] Another possible embodiment of the invention is characterized in that comprising the step of;

[0036] - if it is determined that time before to for next satellite exceeds a predetermined threshold, switching wireless device to an idle operation mode until tO.

[0037] Invention is also a wireless device of a non-terrestrial network (NTN) for small data transmission to a satellite which is configured to realize steps of any one of the methods above. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is a drawing illustrating schematic view of the non-terrestrial network.

[0039] Figure 2 is a drawing illustrating a more detailed schematic view of the wireless device.

[0040] Figure 3 is a drawing illustrating wireless devices state machine and state transitions in new radio (NR).

[0041] Figure 4 is a drawing illustrating Transition from RRCJNACTIVE state in current art.

[0042] REFERENCE NUMBERS GIVEN IN THE FIGURE

[0043] 100 Wireless device

[0044] 110 Processing means

[0045] 120 Communication means

[0046] 130 Data source

[0047] 200 Satellite

[0048] DETAILED DESCRIPTION OF THE INVENTION

[0049] 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.

[0050] Referring to figure 1 , present invention is a wireless device (100) in a non-terrestrial network (NTN) node which realizes small data transmission (SDT) to satellite (200) and a method thereof. Network device utilizes satellite (200) ephemeris data to predict when it will be in the optimal position relative to a satellite (200) in order to attempt transmission. Satellites (200) move in predetermined trajectories. Thus, a satellite’s (200) coverage area moves accordingly creating time window for wireless devices (100) to realize STD. (100)

[0051] Referring to figure 2, wireless device (100) comprises a communication means (120) which provides radio frequency signal transmission and radio frequency signal reception. Such communication means (120) are well known in the art. Wireless device (100) may comprise a processing unit that executes steps of subject matter method. Wireless device (100) may further comprise a data source (130) which provides data to be transmitted. Processor unit, transmits data to be transmitted using communication means (120). Wireless device (100) may be an internet of things device of a NTN node. Such device may be programmed to periodically transmit sensor measurements.

[0052] Wireless device (100) may operate in idle mode, and at least an operating mode. In idle mode wireless device (100) is not connected to satellite (200) and saves energy. For instance, wireless device (100) may be switched to operating mode periodically, on a timer or when received a wake-up signal (WUS). Operating modes may include an RRCJNACTIVE mode and RRC_CONNECTED mode.

[0053] Referring to figure 3 and 4, wireless device may comprise the RRCJDLE mode, RRC_CONNECTED mode and RRCJNACTIVE mode. Data transmission is started the wireless device (100) which is either in the RRCJDLE or RRCJNACTIVE mode, aiming to establish a connection with the satellite. Additionally, a wireless device (100) already in the RRC_CONNECTED mode has the capability to initiate this procedure.

[0054] A wireless device (100) is configured to receive satellite (200) travel information (satellite ephemeris data). For instance, satellite (200) travel information may be received through downlink messages from a base station, which can be used to calculate the propagation delay of the service link. The information received may include satellite (200) ephemeris data, which provides specific details about the satellite's (200) location and movement, such as state vectors, orbital velocity, or Kepler orbit elements. The wireless device (100) can then use this information to accurately determine the satellite's (200) location at any given time.

[0055] Periodically, the satellite (200) ephemeris may be broadcasted as part of the system information, and this broadcast may include details on how frequently the wireless device (100) should update its round-trip time (RTT) calculations based on the new satellite (200) ephemeris data received.

[0056] Satellite ephemeris broadcast can be adjusted based on factors like the satellite’s (200) altitude and velocity, ensuring that the data is updated more frequently for satellites (200) that move more quickly or are closer to Earth. This approach helps to minimize the signaling overhead and communication latency in a Non-Terrestrial Network (NTN). However, there may still be situations where the satellite (200) ephemeris data is not completely accurate, such as if the satellite’s (200) movement gradually drifts from its predicted path. In these cases, the ephemeris data may include a correction margin, which the wireless device (100) can use to compensate for any inaccuracies and ensure more reliable communication.

[0057] Wireless device realizes STD using bandwidth parts (BWPs). Wireless (100) device stores a list of BWPs having different bandwidths in a storage unit (not shown). BWPs may be sorted based on their bandwidth size. Predetermined thresholds are stored in a storage unit.

[0058] Wireless device (100) may store, calculate or receive its geographical location. So it can calculate relative location of the satellite (200). Wireless device (100) signals from neighboring wireless devices (100) which indicate signal angles from satellites (200) and their locations. Wireless device (100) may use this information in order to estimate its location.

[0059] A first embodiment of subject matter method comprises following steps realized by wireless device: (100)

[0060] - Receiving satellite (200) ephemeris data;

[0061] - Calculating a tO time when a satellite (200) will start serving a location where the wireless device (100) is located and a t1 time when the satellite (200) will stop serving said location based on ephemeris data.

[0062] - Determining a size of data to be transmitted.

[0063] - Estimating a transmission time to transmit data to be transmitted to satellite (200) of each bandwidth part (BWP) from a list of available BWPs.

[0064] - Calculating a t1 ’ time when current serving satellite (200) will stop serving said location.

[0065] - Continuously estimating an available time window before current serving satellite (200) stops serving the location. if available time window is higher than a first predetermined threshold

[0066] - determining the smallest BWP from a list of BWPs that has the transmission time less than the remaining transmission time. For instance in this step, smallest BWP is selected, its transmission time is compared to remaining transmission time. If it is not lower than remaining transmission time selecting next higher BWP. Iteratively selecting and comparing remaining time with calculated transmission times of related BWPs.

[0067] - Attempting to a transmission for data to be transmitted using selected BWP. In a possible embodiment, if it is determined that the transmission time of the smallest Bandwidth Part (BWP) in the list is less than the last estimated available time window, an attempt is made for a rapid transmission using the highest BWP from the list. Despite its resource-intensive nature, this method prioritizes transmitting the maximum amount of data possible before a connection loss occurs.

[0068] In a possible embodiment, if it is determined that attempting to the transmission using selected BWP is possibly failed(device checks before transmission) or failed after transmission, selecting the next higher BWP from selected BWP and attempting the transmission using selected BWP.

[0069] In another possible embodiment, if it is determined that attempting to the transmission using selected BWP is successful, storing selected BWP to be primarily used in next attempt to the transmission. In another embodiment t, failed BWPs may be stored too. An artificial intelligent model may be trained using size of data to be transmitted, failed BWPs, successful BWPs and related time windows in order to output suggested BWPs for attempting a transmission.

[0070] In a possible embodiment the method comprises following steps: Counting failed transmission attempts to the transmission of data to be transmitted. If it is determined that a failed transmission attempts exceeds a predetermined threshold, switching wireless device (100) to an idle operation mode. It may also comprise step of switching to an operation mode on a predetermined timer or when received a wake up signal.

[0071] In a possible embodiment the method comprises following step: receiving correction margin of the satellite (200) ephemeris data to. Wireless device (100) corrects satellite (200) ephemeris data in order to more accurately calculate tO time, t1 time and remaining time window.

[0072] In another embodiment method comprises step of: If it is determined that time before tO for next satellite (200) exceeds a predetermined threshold, switching wireless device (100) to an idle operation mode until tO. Thus, further energy saving is provided. Method may comprise a wake up step where network device switches to operating mode on a timer, periodically or when received a wake up signal.

[0073] Another embodiment which comprises following step in addition to first embodiment: If it is determined that transmission attempt has failed next higher BWP is selected and attempt for transmission is realized. This failure for instance may be due to interference or signal degradation.

[0074] Attempt success and attempt failure is determined based on response signal received from the satellite (200).

[0075] The main goal of this solution is to minimize the power consumption of wireless device (100) during the SDT procedure utilizing satellite (200) ephemeris data. This is achieved by configuring BWPs. The method ensures that the data transmission requirements and uplink coverage are still met despite the reduced configuration.

[0076] 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 realized by a wireless device (100) of a non-terrestrial network (NTN) for small data transmission to a satellite (200) characterized in that comprising steps of;- receiving, satellite (200) ephemeris data;- calculating a tO time when a satellite (200) will start serving a location where the wireless device (100) is located and a t1 time when the satellite (200) will stop serving said location based on ephemeris data;- determining a size of data to be transmitted;- estimating a transmission time to transmit data to be transmitted to satellite (200) of each bandwidth part (BWP) from a list of available BWPs;- calculating a t1 ’ time when current serving satellite (200) will stop serving said location,- continuously estimating an available time window before current serving satellite (200) stops serving the location, if available time window is higher than a first predetermined threshold- determining the smallest BWP from a list of BWPs that has the transmission time less than the remaining transmission time,- attempting to a transmission for data to be transmitted using selected BWP.

2. The method according to claim 1 , characterized in that comprising the step of;- if the transmission time of smallest BWP in the list is smaller than last estimated available time window attempting a rapid transmission using highest BWP from the list.

3. The method according to claim 1 , characterized in that comprising the step of;- if it is determined that attempting to the transmission using selected BWP is failed, selecting the next higher BWP from selected BWP and attempting the transmission using selected BWP.

4. The method according to claim 1 or claim 3, characterized in that comprising the step of;- if it is determined that attempting to the transmission using selected BWP is successful, storing selected BWP to be primarily used in next attempt to the transmission.

5. The method according to claim 3, characterized in that comprising the steps of;- counting failed transmission attempts to the transmission of data to be transmitted;- if it is determined that a failed transmission attempts exceeds a predetermined threshold, switching wireless device (100) to an idle operation mode.

6. The method according to claim 1 , characterized in that comprising the step of;- receiving correction margin of the satellite (200) ephemeris data to.

7. The method according to claim 1 , characterized in that comprising the step of; - if it is determined that time before to for next satellite (200) exceeds a predetermined threshold, switching wireless device (100) to an idle operation mode until tO.

8. The method according to claim 1 , characterized in that comprising the step of;- if it is determined that transmission attempt has failed or possibly failed next higher BWP is selected and attempt for transmission is realized.

9. A wireless device (100) of a non-terrestrial network (NTN) for small data transmission to a satellite (200) which is configured to realize steps of a method according to claim 1 to 8.

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