METHOD FOR TRANSMITTING A SIGNAL TO A BASE STATION AND USER EQUIPMENT - Patent application

Abstract

A method performed by a user equipment connected to a base station of a satellite communication network transmitting a signal using an updated value of a timing advance, the user equipment determining a value of the timing advance based on at least aiding information, measurements and a timing advance command, the method comprising: selecting a transmission time of the signal from among a target transmission time of the signal and a deferred transmission time of the signal later than the target transmission time based on a combination of at least two elements from among a time-related parameter, a final timing advance command received at a final command time, a final measurement taken at a final measurement time, a final aiding information received at a final aiding time, a final measurement time, a final command time and a final aiding time; and transmitting the signal to the base station at the transmission time using the updated value of the timing advance.

Description

[Technical field]

[0001] The present disclosure relates to the field of telecommunications in non-terrestrial based networks (NTNs), and more particularly to transmissions using satellite communication networks. [Background technology]

[0002] The deployment of satellite constellations in non-geostationary satellite orbits (NGSO), such as low-Earth orbit (LEO) and medium-Earth orbit (MEO), forms a satellite communication network with time- and space-varying coverage (through satellite cells) on the Earth's surface. Thus, user equipment (UE) communicating through the satellite communication network performs various procedures in wireless communication standards, such as LTE, LTE-Advanced, or New Radio (NR), to obtain and / or maintain a connection to the satellite communication network. For example, to gain initial access to a satellite cell deployed by a satellite, the user equipment performs a random access procedure (RACH procedure) to connect to the satellite communication network and receive allocation of resources for further transmission. For example, when a change in coverage occurs (e.g., due to a movement of the satellite constellation), in order to maintain an existing connection with the satellite communication network, the user equipment may perform a handover procedure to switch the connection from a serving cell to another target cell. When a user equipment establishes a connection with a satellite communication network via a satellite cell, the user equipment can transmit and receive signals to and from the satellite communication network via the satellite cell by communicating with a base station serving such satellite cell.

[0003] Interaction with such a satellite communications network therefore includes data and control signals transmitted from the user equipment to the satellite communications network, and further, when transmitting signals through a satellite cell, the user equipment takes into account the timing advance value used in the satellite cell to compensate for the propagation delay between the user equipment and the reference point in the satellite communications network that receives such signals.

[0004] For example, such a timing advance value determination is made during an initial access procedure based on the first message of the RACH procedure received by the base station from the user equipment (Msg1 of the RACH procedure). Later in the same RACH procedure, the value of the timing advance of the user equipment in the base station is estimated by the base station and transmitted to the UE (Msg2 of the RACH procedure). The UE uses this value to introduce a time delay when sending signals through the target cell.

[0005] When a user equipment is connected to a serving cell (i.e., a serving base station), the user equipment periodically updates the timing advance used when transmitting signals on that serving cell in order to maintain uplink timing synchronization with the network. In particular, the timing advance update when the user equipment is connected to a serving cell relies on a double-loop mechanism. Such a double-loop mechanism comprises: - A closed loop mechanism, where the user equipment receives an explicit timing advance command (TAC) from the network. Such a timing advance command provides an update to the timing advance used by the user equipment in the serving cell. The timing advance command is received by the user equipment as a network reaction to previous signals sent by the user equipment to the network, and the network can derive a timing advance update based on such previous signals. - An open loop mechanism, which consists in self-updating the timing advance by the user equipment based on the values ​​of various measurements performed by the user equipment and on assistance information received by the user equipment (notably from the network).

[0006] In particular, the closed-loop mechanism and the open-loop mechanism operate in parallel, and thus the user equipment is provided with different sources of timing advance updates at different times. Depending on the time such information is received by the user equipment and the timing advance corrections that such information implies, the user equipment may perform incorrect timing advance updates. Indeed, depending on their timing, the open-loop information and the closed-loop commands may contain redundant or contradictory information, and the user equipment may perform timing advance overcompensation or timing advance update jumps. An incorrect timing advance update leads to a loss of uplink timing synchronization. Such a loss of uplink timing synchronization may further cause radio link failure (RLF), which results in time waste, reliability loss and / or radio resource waste for both the user equipment and the satellite communication network.

[0007] As a result, to maintain synchronization with the satellite communications network, connected user equipment is required to provide consistent and reliable timing advance updates based on various sources of timing advance corrections received according to different time patterns. Summary of the Invention

[0008] The present disclosure improves this situation.

[0009] 1. A method performed by a user equipment (UE) for transmitting a signal using a timing advance update to a base station, the user equipment (UE) being connected to a base station, the base station corresponding to a cell supported by a non-geostationary orbit satellite of a satellite communications network, the user equipment (UE) comprising at least Data relating to assistance information received by the user equipment associated with an assistance time; data relating to measurements taken by the user equipment relating to a measurement time; data associated with a timing advance command received from the network associated with a command time; Determine the value of the timing advance based on The method is: The time of transmission of the signal is at least A target transmission time for the signal; and a postponement time for sending the signal, the postponement time being later than the target time; Choose from among transmitting a signal to a base station at a transmission time using the updated timing advance; Including, The selected transmission time is at least: Time-related parameters; data relating to a final timing advance command associated with a final command time; data relating to the last measurement associated with the last measurement time; data relating to last assistance information associated with a last assistance time; Data relating to the last measurement time; Data relating to the last command time; Data related to the time of last aid; is selected based on a combination of at least two factors from among:

[0010] The proposed method therefore enables a user equipment connected to a satellite communication network in a cell to use as accurately as possible the value of the timing advance in the cell to transmit signals, more particularly uplink transmissions, to the base station serving said user equipment. In particular, the method proposes to compare different but parallel sources of information enabling the updating of the value of the timing advance. Such different sources of information may be redundant or complementary to each other, depending on the time at which they provide the information to the user equipment.

[0011] Thus, by actively selecting the transmission timing of a signal, the proposed method allows the user equipment to avoid jumps in timing advance or, conversely, over-compensation of the timing advance applied when transmitting a signal, both of which may result in a loss of timing synchronization between the user equipment and the network side, and may even lead to Radio Link Failure (RLF) situations.

[0012] Indeed, the present disclosure proposes selecting the transmission time of a signal based on both: Data making it possible to quantify the last value used as the timing advance (i.e. data relating to the last timing advance command, the last measurement and / or the last aiding information), and - Data making it possible to identify the time of obsolescence of the data used to quantify such last value used as timing advance (i.e. data related to the last command time, last measurement time and / or last assistance time).

[0013] Thus, unlike existing methods, a user equipment does not, by default, transmit a signal to a base station at the very next time opportunity (or time occasion) in which the user equipment has to transmit a signal to the base station (e.g., the very next time window allocated or provided to the user equipment by the network). The present disclosure allows the user equipment to play an active part in determining when to transmit a signal to a base station. Moreover, such a decision is made by the user equipment in a manner that optimizes the accuracy of the update value used as the timing advance for transmitting the signal.

[0014] As a result of such a selection, the method offers the possibility for the user equipment to spontaneously (i.e., intentionally) postpone the transmission of the signal to a postponed transmission time, instead of transmitting the signal at the very next scheduled time opportunity provided by the network. Such a postponement of the transmission time of the signal can be decided by the user equipment, for example, if the user equipment determines that the data at its disposal to determine the value to be used as the timing advance is stale and / or reflects a substantial timing advance adjustment. In such a case, the user equipment can decide to transmit the signal at a postponed transmission time beyond the target transmission time, so that a more suitable timing advance value can be determined, subject to the timing requirements of the user equipment transmitting the signal. For example, by postponing the transmission of the signal, the user equipment can retrieve additional updated information in the meantime and determine an updated value of the timing advance to be used to transmit the signal based on such additional updated information. Thus, the method allows the user equipment to evaluate the information it currently knows (i.e., has at its disposal when it intends to transmit the signal) used to determine the value of the timing advance and to query the suitability of such information. It should be noted that such an evaluation potentially affects the planning of the timing of the user equipment to transmit the signal to the base station.

[0015] Transmitting a signal to a base station can be interpreted as performing an uplink communication to a base station of a satellite communication network. The signal transmitted from the user equipment to the base station can be a data signal (or data traffic). The signal transmitted from the user equipment to the base station can be a control signal such as a Scheduling Request (SR) or a Buffer Status Report (BSR). Such a signal can be transmitted to the base station, for example, in the context of a configured grant, a semi-configured grant or a dynamic grant. For example, in the case of a configured grant, the signal can be a periodic traffic data signal transmitted to the base station using radio resources (e.g. Physical Uplink Shared Channel resources, i.e. PUSCH resources) allocated by the network to the user equipment UE. In the case of a dynamic grant, the signal can be an SR signal transmitted to the base station using radio resources (e.g. Physical Uplink Control Channel resources, i.e. PUCCH resources) allocated by the network to the user equipment UE to request a PUSCH resource allocation. More generally, such a signal can be transmitted to the base station within a scheduled time window (or time opportunity) allocated by the network.

[0016] Being connected to a base station corresponding to a cell supported by a non-geostationary orbit satellite of a satellite communication network is interpreted as a user equipment being in RRC_CONNECTED state via a cell projected by one or more satellite beams of the satellites of this network. Such a cell is allocated radio resources managed by the corresponding base station. In particular, the user equipment is connected to a base station after performing an initial access procedure (e.g. a RACH procedure) or a handover procedure from a previous cell managed by another base station to which the user equipment was connected.

[0017] A last element (e.g. a last timing advance command, a last aiding information or a last measured value) is interpreted as an element stored in the memory of the user equipment that is used by the user equipment for a current event (such as determining the current value of the timing advance). Such a last element may for example be the only element at the user equipment's disposal (e.g. a pre-configured element stored by the user equipment) or an element for which the user equipment receives an update (e.g. a timing advance command, aiding information or a measured value). The user equipment thus has the last element available in its memory, for example in the case of a last-in-first-out (LIFO) memory. Such a last element is therefore the latest element at the user equipment's disposal, taking into account a given state of the user equipment's memory. Such a last element may then be updated accordingly. As a result, such a last element is no longer the latest element at the user equipment's disposal in such an updated state of the user equipment's memory. For example, a last measured value refers to the measurement last taken by the user equipment, which is stored at the top of the memory, for example in the case of a LIFO memory structure. Further measurements may then be performed.

[0018] Data related to assistance information is interpreted as open loop (OL) information acquired or received by the user equipment from a network entity. Such a network entity may refer to a base station, a satellite, or any other entity on the network side. Data related to assistance information may be content included in a System Information Block (SIB) originating from the network that the user equipment can acquire. Data related to assistance information may also refer to content of network signaling related to location, ephemeris, satellite characteristics, satellite beams, cells of a satellite communication network. Data related to assistance information may also refer to epoch time, radio resource configuration information, cell related information. More generally, data related to assistance information may refer to any content that is pre-configured, pre-set, set, predictable, and / or known on the network side. Based on such data related to assistance information, the user equipment may for example acquire, receive, and / or calculate the position of a satellite serving such user equipment. Such data related to assistance information may be acquired by the user equipment via broadcast downlink signals, groupcast downlink signals, and / or dedicated downlink signals in cells provided by the network.

[0019] Data related to the last aiding information is interpreted as data related to the aiding information last received by the user equipment at the current time under consideration. In other words, the last aiding information can be interpreted as the most recently updated aiding information at the disposal of the user equipment at the current time. In particular, the user equipment may have already determined the last value used in the timing advance (also referred to as the current value used as timing advance) based on such last aiding information.

[0020] An assistance time is interpreted as a time associated with the assistance information obtained by the user equipment. Such a time may be expressed in time units, time steps, time samples, time slots, etc., or according to a timestamp of a timer of the user equipment. Such an assistance time may for example refer to the time at which data related to the assistance information is received by the user equipment. Such an assistance time may for example be the time at which the user equipment can request the assistance information. Such an assistance time may also refer to the time at which data related to such assistance information is actually used or calculated by the user equipment, for example to determine a value to be used as a timing advance. In fact, there may be a time delay between the time of reception of the assistance information and the time of calculation of such assistance information. An assistance time may then be interpreted as the respective time at which data related to the assistance information is successively received by the user equipment. Such an assistance time may in particular be set by the network according to a configured periodicity. Such an assistance time may in particular correspond to a particular time window or time gap during which data related to the assistance information can be provided to the user equipment or during which the user equipment can request this data.

[0021] A last assistance time is interpreted as a time associated with the last assistance information. Such a last assistance time may also be referred to as a "last assistance time". Such a last assistance time may therefore refer to, for example, the time at which data related to the last assistance information is received by the user equipment. Such a last assistance time may also refer to the time at which data related to such last assistance information is actually used or calculated by the user equipment, for example to determine a current value to be used as a timing advance. In other words, the last assistance time is the most recent time at which the user equipment received data related to the assistance information.

[0022] Measurement-related data is understood to be open-loop (OL) information obtained, calculated and / or measured by the user equipment. Such measurement-related data may be radio signal measurements performed by the user equipment using positioning techniques. Such measurement-related data may be data collected by the user equipment from sensors integrated in the user equipment. Such measurement-related data may in particular enable the user equipment to estimate its position. Data related to a last measurement value is to be interpreted as data related to the measurement value last performed or obtained by the user equipment at the current time under consideration. In other words, a last measurement value can be interpreted as the most recent updated measurement value at the disposal of the user equipment at the current time. In particular, the user equipment may have already determined the last value to be used in the timing advance based on such a last measurement value.

[0023] A measurement time is interpreted as a time associated with a measurement performed or obtained by the user equipment. Such a time may be expressed in time units, time steps, time samples, time slots, etc. or according to a timestamp of a timer of the user equipment. Such a measurement time may for example be a time at which the user equipment can obtain data related to the measurement. Such an aiding time may also refer to a time at which the user equipment can actually use or calculate data related to such a measurement, for example to determine a value to be used as a timing advance. In fact, there may be a time delay between the time of performing a measurement or obtaining a measurement and the time of calculation or processing of such measurement to determine a value to be used as a timing advance. The measurement time corresponds in particular to a measurement time gap configured by the network, during which the user equipment can perform the measurement. The measurement time may be a time set by the user equipment to perform the measurement.

[0024] A last measurement time is interpreted as a time associated with the last measurement performed or obtained by the user equipment. Such a last measurement time may also be referred to as a "last measurement time". Such a last measurement time may therefore refer to, for example, the time at which data associated with the last measurement is received by the user equipment. Such a last measurement time may also refer to the time at which data associated with such a last measurement is actually used or calculated by the user equipment, for example to determine a current value to be used as a timing advance. In other words, the last measurement time is the time at which the user equipment most recently obtained or processed data associated with a measurement.

[0025] The timing advance command related data is understood to be data included in a timing advance command (TAC) signal sent by the network. Such a TAC signal is specifically transmitted as a dedicated downlink signal via the MAC-CE to the user equipment. Such timing advance command related data corresponds to a 6-bit value of a timing advance command included in the MAC-CE TAC signal. Such timing advance command related data may therefore relate to closed loop (CL) information providing a timing advance adjustment source from the network to the user equipment. Such timing advance command related data may be a timing advance adjustment value comprised between 0 units and 63 units.

[0026] A command time is interpreted as a time associated with data related to a timing advance command. Such a time may be expressed in time units, time steps, time samples, time slots, etc., or according to a timestamp of a timer of the user equipment. Such a command time may refer, for example, to the time when data related to a TAC signal is received by the user equipment. Such a command time may also refer to the time when the user equipment can actually use, calculate or apply data related to such timing advance command, for example, to determine a value to be used as a timing advance. In fact, there may be a time delay between the time of reception of a timing advance command signal and the application of the content of such timing advance command signal to determine a value to be used as a timing advance. Such a time delay may be, for example, six time slots in case of closed loop adjustment. The command time is determined by the network. The command time may also depend on the transmission of an uplink signal by the user equipment to the base station. The network may send a timing advance correction via a TAC signal, for example based on timing information of such uplink signal. In other words, as long as an uplink signal is transmitted by the user equipment, the base station may send a timing advance command at the command time.

[0027] A final command time is interpreted as a time associated with a final timing advance command signal received by a user equipment. Such a final command time may also be referred to as a "last command time". Thus, such a final command time may refer to, for example, a time when data associated with a final timing advance command is received by a user equipment. Such a final command time may also refer to a time when data associated with such a final timing advance command (e.g., a timing advance adjustment value included in a TAC) is actually used or applied by a user equipment, for example, to determine a current value used as a timing advance or to transmit a signal using the current value used as a timing advance. In other words, the final command time is the most recent time when the user equipment received or applied data associated with a timing advance command.

[0028] The target transmission time of a signal is interpreted as the very next time opportunity (or time window) given to the user equipment to transmit a signal S. Such a target transmission time may be the very next scheduled time opportunity allocated by the network for example with respect to a configuration grant or semi-configuration grant. Such a target transmission time may also refer to the very next scheduled time opportunity provided by the network to transmit a control signal (such as a BSR signal or an SR signal). More generally, the target transmission time of a signal refers to the closest future time opportunity with respect to the current time for the user equipment to transmit a signal to the base station.

[0029] A deferred transmission time of a signal is interpreted as the next time opportunity (or time window) given to the user equipment to transmit a signal S. Such a deferred transmission time may be the next scheduled time window configured by the network, for example for a configured or semi-configured grant. Such a deferred transmission time may also refer to a time opportunity allocated by the network to transmit a control signal (e.g., a BSR signal or an SR signal) to the base station. In particular, such a deferred transmission time is interpreted as a later time opportunity with respect to the target transmission time. In other words, such a deferred transmission time is a postponed time opportunity for the user equipment to transmit a signal to the base station. Such a deferred transmission time may be one or several time slots later than the target transmission time.

[0030] Selecting a transmission time of a signal is interpreted as choosing a particular time window (also called a particular time window or time opportunity) configured by the network for transmitting a signal to a base station. In other words, it is a deliberate choice (or decision) of the user equipment to select the timing of transmitting the signal. In particular, by selecting a transmission time at a postponed time beyond the target transmission time, the user equipment deliberately decides to postpone the transmission of the signal, even though an earlier time opportunity (i.e., the target transmission time) is available for transmitting the signal.

[0031] The selected transmission time is chosen based on a combination of at least two factors, which is to be interpreted as meaning that such a selection can be made taking into account one or more constraints (or criteria). In other words, the user equipment considers several factors to determine the transmission time to be selected. Such constraints can include time-related parameters. The time-related parameters are to be interpreted as time-related constraints taken into account by the user equipment to transmit a signal. The time-related parameters can refer, for example, to bounded specific time opportunities allocated by the network within which the transmission time can be selected. For example, for configured or semi-configured grants, the user equipment can be allocated several configured time windows within which the user equipment can transmit a signal to the base station. Such configured time windows can include, in particular, at least a target transmission time and a deferred transmission time. For dynamic grants, the user equipment can be allocated several configured time windows within which the user equipment can transmit a control signal (e.g., transmit an SR) to the base station, for example to obtain further resources for transmitting a data signal. The time-related parameters can also refer to timing requirements to be met by the user equipment, for example with respect to delay requirements defined in a service level agreement (SLA) for the service provided by the user equipment. In other words, the transmission time of the signal can be selected to respect the latency requirement. The time related parameters can also refer to time thresholds that are set, pre-configured, configured or pre-determined, for example, by the user equipment or the network. Such time thresholds may depend in particular on the current time at which the user equipment selects the transmission time. Such time thresholds allow for an obsolescence check to be performed on current information possessed by the user equipment for transmitting the signal to the base station, for example timing advance commands, assistance information and / or measurements already acquired by the user equipment.In other words, the time threshold may enable the user equipment to distinguish information received recently enough to be considered relevant, particularly for determining a timing advance update, from information that may be outdated and therefore not relevant. In particular, the time threshold may be used by the user equipment to identify whether the user equipment needs to obtain updated information for determining a timing advance update.

[0032] The transmission time may also be selected based on data related to the last measurement time, the last command time and / or the last assistance time. In other words, the last measurement time, the last command time and / or the last assistance time may be taken into account by the user equipment to select a transmission, in particular to possibly postpone the transmission of a signal. In other words, the user equipment may select a transmission time based on the time when the latest information was obtained or used by the user equipment. For example, if the last measurement time, the last command time and / or the last assistance time is considered to be stale, the user equipment may select the transmission time to be a deferred transmission time.

[0033] The transmission time may also be selected based on data associated with the last timing advance command, the last measurement, and / or the last aiding information. In other words, the user equipment may select the transmission time based on the content of the most recent update obtained or used by the user equipment. For example, if the last timing advance command, the last measurement, and / or the last aiding information reflects a timing advance adjustment that is so large that the user equipment may postpone the transmission of a further information signal, the user equipment may select the transmission time to be a postponed transmission time.

[0034] An updated timing advance value is understood to be a value determined by the user equipment and used to transmit a signal to a base station in order to compensate for the propagation delay between the user equipment UE and a predefined network reference point. This network reference point may be located, for example, in a base station BS that manages the cell, or in a satellite SAT that supports the cell, or it may be any reference point between these two points. In particular, such an updated timing advance value may be determined before the transmission time of a signal, so that the user equipment can use such an updated timing advance value to transmit a signal to a base station. Such an updated timing advance value may be determined by the user equipment to be equal to a current value used as a timing advance, i.e. a value already determined or used by the user equipment at the current time. The current value used as a timing advance may for example have been determined at a previous time (before the current time) and used to transmit a previous signal. For example, the current value used as a timing advance may have been used to transmit the last signal transmitted by the user equipment to the base station. Such a current value used as a timing advance may be determined based on, in particular, a last timing advance command, a last measurement value and a last assistance information. The updated value used as timing advance may be different from the current value used as timing advance, especially if, for example, information possessed by the user equipment is considered stale at the current time and updated information can be obtained.

[0035] According to one embodiment of the present disclosure, the method further comprises sending a support signal to the base station that is different from the signal, the support signal being transmitted at a support time that is dependent on a target transmission time of the signal.

[0036] As a result, the user equipment can transmit another signal different from the signal transmitted at the transmission time to prepare for the transmission of a later signal. In particular, such a support signal can be transmitted to the network as a request for updated support information or measurement update values ​​for the final support information or final measurement values, respectively. Such a support signal can also be transmitted to the network as a request for an updated timing advance command for a final timing advance command. Furthermore, the support signal can also be transmitted for a configured grant, a semi-configured grant or a dynamic grant. In particular, the user equipment can transmit a support signal to the base station in which the user equipment has pre-allocated Physical Uplink Shared Channel (PUSCH) resources even in the case of a configured grant. The user equipment can decide to postpone the transmission of the signal to a deferred transmission time and transmit the support signal in advance, for example, to request updated information for determining an update value to be used as a timing advance.

[0037] A support signal is understood to be an uplink transmission from the user equipment to the base station. Such a support signal is in particular transmitted before a transmission signal. Such a support signal may in particular be a control signal such as a BSR signal or a SR signal.

[0038] Such a support signal being dependent on a target transmission time is to be interpreted as the user equipment being able to determine the timing of the support time depending on the next scheduled time opportunity for transmitting a signal to the base station, which may be either earlier than the target transmission time or later than the target transmission time.

[0039] According to one embodiment of the present disclosure, the data related to the aiding information providing the self-correction parameters and the data related to the measurements are used by the user equipment to determine a value of the timing advance, The sending of the support signal shall comply with the following criteria: A first time gap between the last command time and the current time exceeds a first pre-defined gap threshold; or The Last Command Time precedes the Last Assist Time, and a second time gap between the last assistance time and / or the measurement time and the current time exceeds a second pre-defined gap threshold; or a self-calibration parameter determined based on data related to the final assistance information and / or the final measurement value exceeds a pre-defined self-calibration threshold; is further based on at least one of

[0040] As a result, the proposed method allows the transmission of a support signal to the base station to request updated information for determining an updated value to be used as the timing advance.

[0041] A first time gap between the last command time and the current time exceeding a first preset gap threshold is interpreted as a support signal being able to be transmitted if the last timing advance command at the user equipment's disposal is outdated at the current time, and the user equipment may therefore require an updated timing advance command and transmit the support signal for that purpose.

[0042] The first preset gap threshold is interpreted as a time gap set by the user equipment or the network. Such a first preset gap threshold specifically quantifies the staleness of the closed-loop information. For example, if the time gap between a command time and a current time exceeds the first preset gap threshold, the timing advance command associated with such command time is considered as a stale content for determining an update value to be used as the timing advance.

[0043] The last command time preceding the last assistance time and the second time gap between the last assistance time and / or the last measurement time and the current time exceeding the second preset gap threshold is interpreted as a support signal can be sent if the most recent information acquired by the user equipment is open-loop information and this open-loop information is outdated at the current time. Thus, the user equipment may require updated closed-loop information and / or updated open-loop information and can send a support signal for this purpose.

[0044] The second preset gap threshold is interpreted as a time gap set by the user equipment or the network. Such a second preset gap threshold quantifies in particular the staleness of the open-loop information. For example, if a time gap between an aiding time and / or a measurement time and a current time exceeds the second preset gap threshold, the aiding information associated with such aiding time and / or the measurement associated with such measurement time is considered as stale content for determining an update value to be used as timing advance. The second preset gap threshold may be different from or equal to the first preset gap threshold.

[0045] The last command time preceding the last aiding time and the second time gap between the last aiding time and / or the last measurement time and the self-correction parameter determined based on the data related to the last aiding information and / or the last measurement value exceeding the preset self-correction threshold is interpreted as a support signal being transmitted if the most recent information acquired by the user equipment is open-loop information and if the open-loop information reflects a large (or significant) timing advance adjustment (or correction) required, where large is interpreted as exceeding the self-correction parameter. Thus, the user equipment may require updated closed-loop and / or updated open-loop information to further quantify such required timing advance adjustment and may transmit a support signal for that purpose.

[0046] A self-correction parameter is interpreted as a timing advance correction (or adjustment) value provided by assistance information obtained from the network and / or measurements performed by the user equipment. Both pieces of information result in a self-adjustment of the timing advance by the user equipment. Such a self-correction parameter therefore allows the user equipment to make larger adjustments to the value of the timing advance compared to a correction parameter provided by the network, e.g. via a timing advance command (since the correction parameter provided by the network is limited in size). Such a self-correction parameter quantifies open-loop information (i.e. open-loop correction of the timing advance).

[0047] A preset self-correction threshold is understood to be a threshold set by the network or the user equipment. Such a threshold may be expressed in terms of a number of timing advance correction units. Such a preset self-correction threshold may in particular reflect how large (or significant) the open-loop correction is. For example, if the self-correction parameter is below the preset self-correction threshold, the open-loop correction may be considered to be negligible, whereas if the self-correction parameter is above the preset self-correction threshold, the open-loop correction may be considered to be significant.

[0048] According to one embodiment of the present disclosure, the time related parameter is related to the validity time of the data used to determine the value of the timing advance, and the sending of the support signal is further based on the following criteria: Any one of the last command time, the last measurement time, and the last assistance time is earlier than the validity time.

[0049] As a consequence, the user equipment can take the initiative to transmit a supporting signal to the base station if any part of the up-to-date information at its disposal is considered to be stale, where stale is understood to be prior to the validity time.

[0050] A valid time may be interpreted as a time slot prior to the current time. Such a valid time may be set or configured by the user equipment or the network. Such a valid time may vary depending on, among other things, the current time. For example, the valid time may be a time slot having a two-slot gap with the current time. In particular, comparing the last command time with the valid time is equivalent to comparing a first time gap between the last command time and the current time with a first preset gap threshold. In particular, comparing the last assistance time and / or the last measurement time with the valid time is equivalent to comparing a second time gap between the last assistance time and / or the last measurement time and the current time with a second preset gap threshold. In particular, in case the first and second preset gap thresholds are equal, such gap threshold corresponds to the time gap between the current time and the valid time.

[0051] According to one embodiment of the present disclosure, the support signal is sent using a timing advance support value, the timing advance support value being at least: Time-related parameters; data associated with the last timing advance command received; and Data relating to the final measurement performed; Data relating to the received final assistance information; and Data relating to the last measurement time; Data relating to the last command time; Data related to the time of last aid; It is based on a combination of at least two of the following:

[0052] As a result, the support signal can be sent using a timing advance support value in order to at least partially predict the timing advance adjustment to be applied to the transmission of the signal to the base station. Indeed, by applying the timing advance support value when transmitting the support signal based on the most recent information at the user equipment's disposal, the user equipment reduces the time difference compensated by the timing advance when transmitting an uplink transmission to the base station. The subsequently received updated open-loop or closed-loop information (if any) therefore takes such timing advance support value into account when indicating the timing advance correction to be applied to the user equipment. In particular, such timing advance support value can be determined based on the most recent information at the user equipment's disposal at the current time. In other words, the timing advance support value corresponds to the current value of the timing advance last determined by the user equipment.

[0053] According to one embodiment of the present disclosure, the support signal comprises at least: an uplink reference signal, such as a sounding reference signal; A control signal; Buffer status report, A scheduling request; It is one element of.

[0054] As a result, the support signals transmitted to the base station can be transmitted for configured, semi-configured or dynamic grants. Such signals can therefore be transmitted using Physical Uplink Shared Channel (PUSCH) or Physical Uplink Control Channel (PUCCH) resources. In particular, unlike existing methods, the user equipment can decide to transmit the support signals even in case of configured grants, where the user equipment already has dedicated PUSCH resources for transmitting the signals.

[0055] According to one embodiment of the present disclosure, the transmission time is: Data relating to the updated assistance information is predicted to be associated with an updated assistance time that falls between the target transmission time and the deferred transmission time; and / or The data associated with the updated measurement is determined to be associated with an updated measurement time that falls between the target transmission time and the deferred transmission time. In this case, the deferred transmission time is selected to be the

[0056] As a result, if the user equipment determines that postponing the transmission of the signal will allow it to obtain updated information to determine an update value to be used as a timing advance, the user equipment can intentionally decide to postpone the transmission of the signal by selecting the transmission time to be a postponed transmission time that is past the target transmission time. In particular, the user equipment postpones the transmission of the signal if it predicts or determines that updated open loop information will be received, obtained or applied between the target transmission time and the postponed transmission time. Thus, the user equipment intentionally decides to give up the time opportunity to transmit a signal at the target transmission time in order to wait for updated information to be used to determine a relevant update value to be used as a timing advance, compared to using only the information currently at the user equipment's disposal (in particular the last timing advance command, the last aiding information and the last measurement value).

[0057] Updated assistance information is interpreted as assistance information received after the last assistance information. Such updated assistance information is more accurate open-loop information for determining an updated value used as a timing advance for transmitting a signal compared to the last assistance information. Such updated assistance information is not at the user equipment's disposal (i.e., is unknown to the user equipment) at the current time. The user equipment may predict or determine that such updated assistance information is available to the user equipment at an updated assistance time in particular. An updated assistance time is interpreted as a time later than the current time associated with the updated assistance information. Such an updated assistance time may be the time at which the user equipment receives, acquires, applies or utilizes the updated assistance information.

[0058] The data related to the updated assistance information is predicted to be associated with an updated assistance time, which is interpreted as the user equipment being able to estimate the very next scheduled assistance time when the updated assistance information will be at the user equipment's disposal. In particular, such prediction is possible in situations where system information blocks (SIBs) and other network information are broadcast by the network at configured times or according to a configured periodicity known by the user equipment. Such an updated assistance time can be predicted based on previous assistance information previously received at the previous assistance time.

[0059] Data related to an updated measurement is interpreted as data related to measurements performed after the last measurement. Such measurements are more accurate open-loop information for determining an updated value used as a timing advance to transmit a signal compared to the last measurement. Such updated measurements are not owned by the user equipment at the current time. The user equipment can determine that such updated measurements can be obtained, performed or applied by the user equipment at the updated measurement time. An updated measurement time is interpreted as a time later than the current time associated with the updated measurement by the user equipment. Such updated measurement times can be expected when chosen by the user equipment, especially if the user equipment has the hardware capability to determine the measurement time. Such updated measurement times can also be configured by the network as a network-provided measurement gap in which the user equipment can perform the updated measurements.

[0060] According to one embodiment of the present disclosure, data associated with the timing advance command providing the correction parameter is used by the user equipment to determine a value of the timing advance; The sending time is The gap between the last command time and the current time is less than a first preset threshold, and A correction parameter determined based on data associated with the final timing advance command exceeds a preset correction threshold, and The data associated with the updated assistance information is predicted to be associated with an updated assistance time that is later than the final assistance time and later than the current time, the updated assistance time being between the target transmission time and the deferred transmission time; and / or determining that the data associated with the updated measurement is associated with an updated measurement time that is later than the last measurement time and later than the current time, the updated measurement time being between the target time and the deferral time; In this case, the deferred transmission time is selected to be the

[0061] As a result, even if the last timing advance command is not considered to be stale information, the user equipment may intentionally decide to forgo the nearest time opportunity provided by the network to transmit the signal and postpone the transmission of the signal. In fact, the user equipment may decide to postpone the transmission of the signal if the last timing advance command reflects a large timing advance adjustment (large is interpreted here as the timing advance correction transmitted by the network exceeding a pre-set correction threshold) and if it can potentially receive impending open-loop information to further confirm, invalidate or quantify such closed-loop correction. In fact, in such a situation, if the user equipment determines or predicts that updated assistance information and / or updated measurements are associated (i.e. received, acquired or applied) after the target transmission time, the user equipment may decide to wait for such next scheduled information by postponing the transmission of the signal. In this way, the proposed method allows the prevention of potential over-compensation of the timing advance due to overlapping and simultaneous timing advance correction sources (i.e. open-loop and closed-loop).

[0062] According to one embodiment of the present disclosure, determining an updated value of the timing advance used to transmit the signal is based on at least updated aiding information associated with an updated aiding time and / or updated measurement values ​​associated with updated measurement times.

[0063] As a result, the timing advance update determined by the user equipment and used for transmitting a signal to the base station depends on updated open-loop information when the user equipment is able to obtain such information prior to the transmission time. Thus, the proposed method enables the user equipment to determine a more relevant update to be used as timing advance compared to a timing advance update determined solely on the basis of the information at the user equipment's disposal at the current time.

[0064] According to one embodiment of the present disclosure, the user equipment updates a timing error parameter related to an error estimate when determining the value of the timing advance, and the method includes: updating a timing error parameter if the transmission time is selected to be the target time; Further includes.

[0065] As a result, the user equipment can evaluate the accuracy of the timing advance implementation value used when determining the value used as the timing advance to transmit the signal to the base station. In particular, when the user equipment decides to transmit the signal at the very next scheduled time opportunity provided by the network, the user equipment can quantify the timing error parameter so that the user has knowledge of the accuracy of the calculation process of the timing error parameter. In fact, since the user equipment determines that it does not need updated information and determines that the last timing advance command, the last assistance information and the last measurement value are still relevant for determining the updated value used as the timing advance, the user equipment can decide to transmit the signal at the target transmission time. In such a case, the user equipment has no reason to intentionally postpone the transmission of the signal and decides to transmit the signal as early as possible, i.e. at the target transmission time. In such a case, the timing error parameter can be updated to increase the accuracy of the timing advance implementation value. On the other hand, the user equipment may decide to transmit a signal at the target transmission time despite needing updated closed-loop and / or open-loop information, e.g., due to delay requirements for transmitting the signal (e.g., the user equipment cannot postpone its transmission to a postponed transmission time due to delay requirements). In such a case, the timing error parameter may be updated to reduce the accuracy of the timing advance implementation value, since the user equipment knows that the updated value used as the timing advance is inaccurate by relying only on the last information.

[0066] A timing error parameter is understood to be a counter value, e.g. a cumulative counter value or a percentage, quantifying the error (equivalently, the accuracy) of the user equipment's implementation of the timing advance. Such a timing error parameter may be increased if the value used as the user equipment's determined timing advance is known by the user equipment to be inaccurate. Such a timing error parameter may be decreased if the value used as the user equipment's determined timing advance is known by the user equipment to be accurate.

[0067] According to one embodiment of the present disclosure, data associated with the timing advance command providing the correction parameter is used by the user equipment to determine a timing advance value; The timing error parameters are updated as follows: - the gap between the last command time and the current time is less than a first preset threshold, and a correction parameter determined based on data associated with the final timing advance command exceeds a preset correction threshold; and if the data associated with the updated assistance information is predicted to be associated with an updated assistance time that is later than the last assistance time, the updated assistance time being later than the deferral time, and / or the data associated with the updated measurement is predicted to be associated with an updated measurement time that is later than the last measurement time, the updated measurement time being later than the deferral time; It consists of increasing the timing error parameter.

[0068] As a result, the user equipment may increase the timing error parameter if the final closed-loop information reflects a large timing advance correction (i.e., a closed-loop correction that exceeds a preset correction threshold), but the user equipment does not have a next scheduled opportunity to obtain updated open-loop information to further quantify, nullify or verify such closed-loop correction before transmitting the signal. This is especially true when updated open-loop information is expected to be obtained, received or applied after the deferred transmission time. In such a case, the user equipment knows that, despite needing updated information, such updated information will not be obtained in time to determine an updated value to be used as a timing advance to transmit the signal. Thus, the updated value to be used as a timing advance is not as accurate as it would be by relying on updated open-loop information, which causes the timing error parameter to increase.

[0069] A correction parameter is interpreted as a timing advance correction (or adjustment) value provided by the network, in particular via a timing advance command. Such a threshold may be expressed in terms of a number of timing advance correction units. Such a correction parameter may be bounded by the timing advance value included in the MAC-CE timing advance command in particular and may therefore have a bounded correction size. The user equipment depends in particular on such a correction parameter to determine the value of the timing advance. Such a correction parameter quantifies the closed-loop information (i.e. the closed-loop correction of the timing advance).

[0070] A preset correction gap threshold is understood to be a threshold set by the network or by the user equipment. Such a threshold may reflect, inter alia, how large (or significant) the closed-loop correction is. For example, if the correction parameter is below the preset correction threshold, the closed-loop correction may be considered negligible, whereas if the correction parameter is above the preset correction threshold, the closed-loop correction may be considered significant.

[0071] According to an embodiment of the present disclosure, data related to the assistance information providing a self-correction parameter and data related to the measurement are used by the user equipment to determine a timing advance value, and data related to the timing advance command providing a correction parameter are used by the user equipment to determine a timing advance value; The timing error parameters are updated as follows: - the gap between the last command time and the current time is less than a preset alternative first threshold, and if the correction parameter determined based on the data associated with the final timing advance command is less than a preset alternative correction threshold; Or, The last command time precedes one of the last assistance time and the last measurement time, and the self-calibration parameter determined based on the data associated with the final assistance information and / or the data associated with the final measurement value is less than a pre-defined alternative self-calibration threshold value; and If the gap between the last assistance time and / or the last measurement time and the current time is less than a second predetermined alternative threshold value, It consists in reducing the timing error parameter.

[0072] As a result, if the final closed-loop or final open-loop information reflects negligible timing advance corrections (i.e., corrections below the preset alternative correction threshold or self-correction threshold) and further such final information is not considered stale (i.e., the last aided time, the last commanded time and / or the last measured time are below the preset alternative first and / or second thresholds), the user equipment may decrease the timing error parameter. In such a case, the user equipment determines that the updated value used as the timing advance corresponds to the current value used as the timing advance determined based on the final information at the user equipment's disposal. Thus, the user equipment determines that the updated value of the timing advance determined in dependence on such final information is accurate and the timing error parameter is decreased.

[0073] In particular, the alternative preset first or second threshold and the alternative preset correction or self-correction threshold may be equal or different from the alternative preset first or second threshold and the alternative preset correction or self-correction threshold, respectively. Such thresholds may be different in particular when the update of the timing error parameter is normalized or adjusted so that the timing error parameter does not take negative values. Such thresholds may also be different depending on the accuracy level of the timing advance calculation process performed by the user equipment. That is, for example, decreasing the timing advance error requires higher reliability than increasing the timing advance error. In the remainder of this disclosure, for simplicity, the alternative preset first (or second) threshold and the alternative preset first (or second) threshold are considered equal and the term "preset first (or second) threshold" is used. Similarly, the alternative preset correction (or self-correction) threshold and the alternative preset correction (or self-correction) threshold are considered equal and the term "preset correction (or self-correction) threshold" is used.

[0074] According to one embodiment of the present disclosure, the time-related parameter is associated with a transmission deadline time, and the transmission time of the signal is selected to precede the transmission deadline time.

[0075] As a result, the user equipment can select a transmission time subject to the delay requirements to be met by the user equipment, for example with respect to the SLA of the service offered by the user equipment.

[0076] The transmission deadline time can be interpreted as the latest time slot in which a signal must be transmitted to the base station. In such a case, the time-related parameter can be a time slot or a time interval reflecting a delay level of the signal transmitted to the base station.

[0077] According to one embodiment of the present disclosure, the method further includes performing an updated measurement at an updated measurement time if a third time gap between the last measurement time and the last assistance time exceeds a pre-set third gap threshold.

[0078] As a result, the proposed method also ensures that the open loop information used by the user equipment to determine the update value used as timing advance is coherent, in particular between the timing of the assistance information obtained by the user equipment from the network and the timing of the measurements performed by the user equipment. For example, when determining the propagation delay between a satellite and a user equipment, the user equipment needs data related to the position of the user equipment on the one hand and the position of the satellite on the other hand. The data related to the position of the user equipment can be obtained via measurements, while the data related to the position of the satellite can be obtained via assistance information. Such information must still be time coherent (more precisely, those time gaps, called third time gaps, cannot exceed a pre-set third gap threshold) so that a comparison of such user equipment position data with the position data of the satellite is meaningful. Such a pre-set third gap threshold can be set by the user equipment or by the network. Such a pre-set third gap threshold can correspond for example to a one-slot gap. Such a pre-set third gap threshold can be for example smaller than both the pre-set first and second gap thresholds.

[0079] In another aspect of the disclosure, a user equipment is configured to transmit a signal to a base station using a timing advance update, the user equipment being connected to the base station, the base station corresponding to a cell supported by a non-geostationary orbit satellite of a satellite communications network; The user equipment comprises at least Data relating to assistance information received by the user equipment associated with the assistance time; data relating to measurements taken by the user equipment associated with a measurement time; data relating to a timing advance command received from the network associated with the command time; Based on this, the value of the timing advance can be calculated. The user equipment includes a processor and a non-transitory computer-readable medium containing instructions stored thereon that, when executed by the processor, The time of signal transmission, A target transmission time for the signal; and A postponement time that is later than the target time; and Choose from among transmitting a signal to a base station at a transmit time using the updated timing advance; configuring the user equipment to The selected transmission time is at least: Time-related parameters; data relating to a final timing advance command associated with a final command time; data relating to the last measurement associated with the last measurement time; data relating to last assistance information associated with a last assistance time; Data relating to the last measurement time; Data relating to the last command time; Data related to the time of last aid; It is also proposed that the user equipment is selected based on a combination of at least two factors from among:

[0080] In another aspect of the disclosure, a computer program product is also proposed, comprising program instruction code stored on a computer readable medium for carrying out the method as previously described.

[0081] In another aspect of the disclosure, a non-transitory computer readable medium is also proposed storing instructions of a computer program which, when said program is executed by a processor, implements the method as described above.

[0082] Other features, details and advantages are set forth in the following detailed description and figures. [Brief description of the drawings]

[0083] [Figure 1] FIG. 1 illustrates an overall architecture of a satellite communications network in one embodiment of the present disclosure. [Diagram 2] FIG. 1 illustrates an overall architecture of a satellite communications network in one embodiment of the present disclosure. [Diagram 3] 4 is a flow chart illustrating the steps for transmitting a signal to a satellite communications network. [Figure 4] 4 is a flow chart illustrating the steps for transmitting a signal to a satellite communications network. [Diagram 5] 1 is a timeline of signals received and sent by a user equipment in one embodiment of the present disclosure. [Figure 6] 1 is a timeline of signals received and sent by a user equipment in one embodiment of the present disclosure. [Figure 7] 1 is a timeline of signals received and sent by a user equipment in one embodiment of the present disclosure. [Figure 8] FIG. 2 is a diagram illustrating the overall architecture of a user equipment in one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0084] Please refer to Figures 1 and 2. Figures 1 and 2 show the overall architecture of the same portion of a satellite communication network NW according to a possible embodiment of the present disclosure at two different times t1 and t2, where t2 is a later time than t1. Although the present disclosure is not limited to any particular standard, for simplicity, the present disclosure will be described in terms of the New Radio (NR) standard.

[0085] The satellite communication network NW includes at least one artificial satellite SAT. Such an artificial satellite SAT is deployed in a non-geostationary satellite orbit (NGSO) such as a low Earth orbit (LEO) or a medium Earth orbit (MEO). Therefore, the artificial satellite SAT has an altitude of 300 km to 30,000 km relative to the earth's surface.

[0086] Just as the satellite SAT is linked to the core network via a ground station, the satellite SAT is linked to at least one ground station or gateway node (not shown in Figures 1 and 2) via a feeder link.

[0087] The satellite SAT deploys at least one satellite beam, which is configured in a particular frequency band, through which the satellite can transmit and receive data according to radio resources allocated in the frequency band configured for the satellite beam. These radio resources can be shared according to a frequency division scheme (e.g., Frequency Division Multiplexing (FDM) or Orthogonal Frequency-Division Multiplexing (OFDM)), or by a time division scheme (e.g., Time-Division Multiplexing (TDM)) or a code division scheme (code division multiplexing (CDM)), polarization multiplexing, or a combination thereof.

[0088] The allocation of radio resources of the satellite beams is realized by at least one base station BS, also called gNodeB or gNB. Each base station BS manages the radio resources of one or more satellite beams. The base station BS can also be located on board the satellite SAT, such that the distance between the base station BS and the satellite SAT is considered to be zero. The base station BS can also be located on the Earth's surface, as represented in Figures 1 and 2, for example by a ground station linked to the satellite SAT. In such a case, the distance between the base station BS and the satellite SAT is not zero, but changes as the satellite SAT moves according to a non-geostationary satellite orbit. Such a change in the distance between the base station BS and the satellite SAT due to the movement of the satellite SAT is illustrated in Figures 1 and 2 by different distances d1 and d2, respectively.

[0089] Through one or more satellite beams deployed by the satellite SAT, the satellite SAT projects a footprint, also called the service area of ​​the coverage zone of the satellite SAT, on the Earth's surface. Such a footprint deploys one or more cells, each cell being formed by the deployment of one or more satellite beams. The radio resources allocated in each cell are managed by a base station BS. In other words, being covered by a cell is equivalent to being allocated radio resources by the corresponding base station BS.

[0090] With reference to Figures 1 and 2, the illustrated satellite communication network NW includes one satellite SAT displaying one satellite beam. The satellite SAT projects a unique cell (schematically represented by a greyed zone in Figures 1 and 2) corresponding to a base station BS. In other possible embodiments, the satellite communication network NW may include several satellites SAT and / or the satellite SAT may include several satellite beams and / or project one or several cells.

[0091] For the purposes of this disclosure, the satellite SAT of the satellite communication network NW is considered to have a non-geostationary orbit. In other words, the satellite SAT moves relative to the surface of the Earth according to a predefined ephemeris and according to a predefined satellite constellation dynamic and network topology. Such an ephemeris is known, for example, in the core network. As a result, the movement and successive positions of the satellite SAT over time are known by the core network and, by extension, are accessible to any network entity. The network entity is, for example, the satellite SAT, the base station BS or the ground station. The network entity does not usually refer to the user equipment UE or the device that provides the service by the network NW. Data regarding the movement and successive positions of the satellite SAT over time can be exchanged between different network entities of the satellite communication network NW, for example, using intersatellite link (ISL) communication and / or feeder link communication. The movement of the satellite SAT is diagrammed as an arrow SAT MOV, which shows the satellite SAT moving from the left to the right in a portion of the satellite communication network NW.

[0092] In particular, the movement of the satellite SAT according to a predictable satellite constellation dynamic results in the movement of the footprint projected by the satellite SAT on the Earth's surface in a predictable manner. As a result, each zone (e.g., the Earth's surface) covered by cells deployed by the satellite communication network NW changes in coverage due to the non-geostationary nature of the satellite orbit. For a considered zone covered by the satellite communication network NW, this change in coverage occurs in predictable coverage states according to a predictable timeline, in particular depending on the architecture of the satellite communication network NW. For example, referring to Figures 1 and 2, the grey area representing the cells deployed by the satellite SAT moves between time t1 and time t2.

[0093] The architecture of the satellite communication network NW may include fixity or steerability of the satellite beam of the satellite SAT. Indeed, if the satellite SAT is equipped with a fixed satellite beam, the satellite beam does not move relative to the satellite SAT. In particular, such a fixed satellite beam has a fixed orientation relative to the satellite SAT during the deployment of the satellite beam. Thus, the cell deployed by the satellite SAT moves progressively according to the movement of the satellite SAT. If the satellite SAT is equipped with a steerable (or moving) satellite beam, the satellite beam is steered as the satellite SAT moves according to its predefined orbital trajectory. Such beam steering is adjusted to the movement of the satellite SAT such that the cell deployed by such satellite beam is approximately maintained in the same coverage zone during a given time. As a result, the cell (or at least the center of the cell) can be considered as stationary in the coverage zone during a given time. Such time depends on the extent to which the steerable characteristics of the satellite beam allow the satellite beam to compensate for the movement of the satellite SAT, for example, until it reaches a given elevation angle between the satellite beam and the surface of the Earth, beyond which it is switched off and replaced by another satellite beam (not shown in Figs. 1 and 2). The duration and state of coverage under the considered cell deployed by the satellite SAT is therefore a function of such an architecture of the satellite communication network NW. For the purposes of this disclosure, either fixed or steerable satellite beams can be considered for the satellite SAT. Figs. 1 and 2 show an example of a satellite SAT with fixed satellite beams.

[0094] At least one user equipment UE is considered to be connected to the satellite communication network NW. This user equipment UE may generally refer to an Internet of Things (IoT) device that can receive connectivity services by the satellite communication network NW. The user equipment UE may be located on the surface of the Earth. The user equipment UE may also be located remotely from the surface of the Earth, for example in the case of an aircraft in flight.

[0095] In accordance with the present disclosure, the user equipment UE is covered by at least one cell of the satellite communication network NW and can be allocated radio resources by a corresponding base station BS. In another embodiment, the user equipment UE can be covered by several different cells corresponding to several respective base stations.

[0096] The user equipment UE is considered to be in RRC_CONNECTED state via a cell corresponding to a base station BS of the network NW, in other words, the user equipment UE is connected to the considered cell by performing an initial access procedure (e.g. a random access procedure or RACH) or a handover procedure.

[0097] Thus, the user equipment UE can transmit and receive signals using radio resources allocated by the base station BS. Such signals can be exchanged with the base station BS. Such signals can also be exchanged with other devices via direct (or sidelink) communication without relaying such signals through the base station BS.

[0098] In the connected state, the user equipment UE can transmit control signaling and / or traffic data to the base station BS. For example, the user equipment UE can perform data transmission to the base station BS, can transmit a scheduling request (SR) to the base station BS, and / or can transmit a buffer status report (BSR) to the base station BS. The user equipment UE can perform uplink transmission.

[0099] The traffic data and signaling transmitted by the user equipment UE may be aimed at providing different services, in particular for Enhanced Mobile Broadband (eMBB), Massive Machine Type Communication (mMTC) or Ultra Reliable and Low Latency Communication (URLLC) use cases. Such services provided by the user equipment UE have Quality of Service (QoS) requirements, in particular regarding reliability and delay. The user equipment UE may thus transmit buffered traffic data to the base station BS and / or may transmit different signals (such as SR and BSR signals) before transmitting the traffic data.

[0100] Scheduling Requests (SR) and / or Buffer Status Reports (BSR) may be sent by the user equipment UE in situations where data to be transmitted is available in the buffer of the user equipment UE. SRs and / or BSRs may also be sent for periodic reports made by the user equipment UE. More generally, SRs and / or BSRs may be sent for a number of events that require the user equipment UE to transmit information to the network NW or to request resource allocation from the network NW.

[0101] The user equipment UE can transmit such signals according to a specific time window (also called transmission opportunity) configured by the network NW. For example, the network NW can configure a specific delimited timing opportunity for transmitting SR or BSR signals to the base station BS as well as for data transmission. Such time windows can be defined by a configuration grant, a semi-configuration grant or a dynamic grant for transmission to the base station BS. Thus, in case of a configuration grant, for example for traffic data transmitted periodically, the network NW allocates radio resources (e.g. physical uplink shared channel resources, i.e. PUSCH resources) to the user equipment UE for transmitting BSR messages to the base station BS and / or for uplink data transmission based on the scheduled time window. The network NW can also allocate radio resources (e.g. physical uplink control channel resources, i.e. PUCCH resources) to the user equipment UE for transmitting SR messages to the base station BS within a specially allocated time window to request PUSCH resource allocation. In the case of a dynamic grant, the network NW may allocate radio resources (e.g., PUCCH resources) representing one or more time opportunities during which the user equipment UE may transmit a BSR signal, for example to request one dedicated time opportunity to transmit a data signal.

[0102] In a connected state, the user equipment UE can also receive signals from at least the base station BS. For example, the user equipment UE can receive system information (SI), control information, network commands and / or data signals. The user equipment UE can receive downlink transmissions.

[0103] For example, the user equipment UE may receive system information blocks (SIBs) from various network entities (such as base stations of the network NW) via one or more cells covering the location of the user equipment UE. The user equipment UE may receive network information related to satellite ephemeris, epoch time, radio resource configuration information, cell-related information, etc. Such information received from the network NW via cells covering the location of the user equipment UE is called assistance information. Such assistance information may be received by the user equipment UE, for example, as a unicast signal sent from the base station BS to the user equipment UE via dedicated downlink signaling. Such assistance information may also be common information transmitted to several devices including the user equipment UE, for example, as a groupcast signal via a groupcast channel or as a broadcast signal via a broadcast channel. For example, intra-cell assistance information may be received by all devices covered by the same cell.

[0104] Such assistance information can be transmitted by the network NW according to a preset periodicity. The content of such assistance information and the preset periodicity of its transmission can be realized by a network entity (e.g., a base station BS) via reconfiguration. The user equipment UE then has a preset periodic opportunity to retrieve such assistance information. Such periodic opportunity may occur at an assistance time A N The user equipment UE may also request assistance information within a preset opportunity for requesting assistance information.

[0105] The user equipment UE can also receive commands (or orders) and adjustment information from the base station BS. In particular, the user equipment UE can receive Timing Advance Commands (TAC), also called MAC-CE TAC (MAC Control Element Timing Advance Command), via the Medium Access Control (MAC) layer.

[0106] Such a TAC signal can be received by the user equipment UE from the base station BS. The time at which such a TAC order is provided is entirely up to the network NW to decide, but in order for the base station BS to be able to estimate the actual timing error of the uplink synchronization, it is convenient for the BS to transmit such a command signal after one or more uplink transmissions made by the user equipment UE to the base station BS. The time at which such a TAC signal can be received by the user equipment UE is the command time C N It is called.

[0107] Such a TAC signal contains in particular a command value related to the timing advance used by the user equipment UE for transmitting signals to the base station BS. Such a command value takes 6 bits in the MAC-CE and therefore varies between 0 and 63 characters. The timing advance used by the user equipment UE for transmitting signals to the base station BS is described in further detail in this specification.

[0108] The user equipment UE may also perform measurements such as measuring the location of the user equipment UE. To this end, the user equipment UE may be equipped with a Global Navigation Satellite System (GNSS). The user equipment UE may also use positioning techniques based on radio signal measurements (through the network NW) or hybrid techniques (combining radio measurements with information from integrated sensors) or any other technique for obtaining data related to the location of the user equipment itself.

[0109] Such measurements can be performed simultaneously with New Radio (NR) signaling. In such a case, the user equipment UE may have specific hardware that allows simultaneous use of measurement and signaling functions. Such measurements can also be performed in pre-configured time windows (i.e. time opportunities) set by the network NW. In such a case, the network NW may provide specific measurement time windows where the user equipment UE does not receive signals from the network NW and has the opportunity to perform measurements. The network pre-configured measurement times at which measurements are performed can be set if the hardware of the user equipment UE does not allow simultaneous use of measurement and signaling functions. Measurements can also be performed according to the implementation of the user equipment UE depending on its requirements and its hardware capabilities. The times at which the user equipment UE can perform such measurements are either depending on the user equipment UE or pre-configured by the network NW, but may be different from the measurement times M. N It is called.

[0110] As a result, when the user equipment UE is connected to the satellite communication network NW via a cell corresponding to a base station BS, the user equipment UE can exchange control and traffic data signals with the base station BS and can perform various measurements. However, such exchanges and measurements can be performed subject to certain timing requirements. For example, the timing of transmitting signals depends, among others, on: -Pre-configured transmission opportunities set by the network NW, - A service level specification (SLS), or more generally a delay requirement set by a service level agreement (SLA), guaranteed by the transmitting user equipment UE (e.g. data transmission).

[0111] For example, the timing of receiving a signal depends on, among other things: -pre-configured and / or reconfigured periodicity set by the network NW for transmitting assistance information; - Command time C when the base station BS sends a TAC signal to the user equipment UE N , A pre-configured request time opportunity of the user equipment UE for requesting assistance information and, more generally, for transmitting a signal to the base station BS.

[0112] For example, the measurement time M N depends on the following: - User equipment UE hardware capabilities; - A pre-defined measurement time window set by the network NW.

[0113] Furthermore, in order to transmit a signal to the base station BS through a cell, the user equipment UE needs an adjustment of the timing of the transmitted signal. Such a time adjustment is called the timing advance TA used in the cell. The timing advance TA in the cell, from the user equipment UE's point of view, refers to the time difference between the time of transmission of an uplink communication from the user equipment UE through the cell and the reception of a downlink communication through that same cell. The timing advance TA is variable and depends on the propagation delay between the user equipment UE and a predefined network reference point, e.g. the base station BS managing the cell or the satellite SAT supporting the cell, or any reference point between those two points. The timing advance TA is further specific for each user equipment UE depending on its location relative to the network reference point considered. The timing advance TA is intended to compensate for such a propagation delay. That is, after acquiring such a time advance, the user equipment UE advances the time of its uplink transmission through the cell by an amount of time corresponding to the timing advance TA. Each user equipment UE under the coverage of a given cell advances the time of its own uplink transmissions through this cell by an amount of time corresponding to its own timing advance TA, thereby ensuring that all uplink transmissions reach the network side (i.e., a defined network reference point) respectively at the time corresponding to the radio resources to which they are assigned. Moreover, at such reference point, both uplink and downlink transmissions are synchronized.

[0114] The reference point is set as a parameter of the network NW. For example, the network reference point is set in the base station BS in the case of a terrestrial communication network. In that case, by implementing a user equipment UE-specific timing advance TA in each user equipment UE, it is ensured that all uplink transmissions from such UE arrive at the base station BS synchronously with respect to the base station BS, and that the uplink and downlink transmissions are time-aligned at the base station BS. In another example, the network reference point can be placed in the satellite SAT. In that case, by implementing a user equipment UE-specific timing advance TA in each user equipment UE, it is ensured that all uplink transmissions from such UE arrive at the satellite SAT synchronously with respect to the base station BS, and that the uplink and downlink transmissions are time-aligned at the satellite SAT. In another example, the network reference point can be placed anywhere on the feeder link linking the satellite SAT and its gateway. Such a network reference point is predefined for a given cell and fixed for its distance (partially, possibly zero) to the corresponding base station BS, the cell and the gateway.

[0115] In the present disclosure (particularly in FIG. 1 and FIG. 2), a user equipment UE is connected to a satellite communication network NW via a cell corresponding to a base station BS, which serves the user equipment UE. The user equipment UE has performed at least one timing advance synchronization, for example, via a random access procedure (RACH procedure) during an initial access procedure. The user equipment UE has received at least one timing advance command (TAC), for example, via a TAC Random Access Response (TAC-RAR) from the base station BS during the initial access procedure, which provides an initial value related to a timing advance TA that the user equipment UE uses to connect to the network NW via the base station BS. Such an initial access procedure using an initial value related to a timing advance TA that the user equipment uses to connect to the base station BS may have been performed, for example, at a time prior to time t1.

[0116] When the user equipment UE is connected to the network NW, the user equipment UE needs to periodically update the timing advance to maintain uplink timing synchronization with the base station BS when transmitting signals to such base station BS. In fact, due to the movement of the satellite SAT, the movement of the satellite beam, and the possible movement of the user equipment UE, the propagation delay between the user equipment UE and the considered network reference point (for example, set to the base station BS in Figures 1 and 2) may change over time. Therefore, the value that the user equipment UE uses as the timing advance TA when transmitting signals to the base station BS also changes, and an updated value of the timing advance TA used in the cell corresponding to the base station BS is required.

[0117] To update the timing advance TA value used when transmitting signals to the base station BS in RRC_CONNECTED state, the user equipment UE can rely on two different sources of timing advance adjustment information: - Closed loop information. This information consists of Timing Advance Command (TAC) signals received from the base station BS via the MAC-CE. Such TAC signals are sent at time C i The timing advance command is received by the user equipment UE at command time C, where i corresponds to an integer. Typically, after receiving the TAC signal, the user equipment UE applies the received TAC value at a predefined time (e.g., a TAC signal received in slot n is applied starting from slot n+6). In this respect, with respect to the present disclosure, the timing advance command is applied at command time C i associated with command time C i can be the time when the TAC command is received by the user equipment UE, or the time when the TAC command is applied by the user equipment UE. More generally, the command time C i may refer to a time related to or associated with the reception of a timing advance command TAC. In the remainder of this disclosure, "command time C i However, such a time C i may refer to the time (or time slot) when the TAC order is actually used or applied by the user equipment UE. As mentioned above, the TAC signal is received based on an uplink signal previously transmitted from the user equipment UE to the base station BS. In NR, each TAC signal received via MAC-CE has a fixed size of 8 bits, with 6 bits corresponding to a timing advance command. Thus, as long as the user equipment UE sends an uplink signal to the base station BS, the user equipment UE can receive an updated TAC signal. The correction of the timing advance TA value is limited to a length of 6 bits in each TAC signal, which limits the amount of timing advance adjustment the user equipment UE can make to the timing advance TA. In particular, the possible timing advance adjustment provided by the TAC signal is between 0 units and 63 units. - Open loop information, which consists of information of the self-adjustment of the value of the timing advance calculated by the user equipment UE on the basis of the assistance information received from the network NW and the measurements performed by the user equipment UE. The assistance information is the assistance time A i The measurement is received by the user equipment UE at measurement time M i The user equipment UE executes the above-mentioned process at the time A i and measurement time M i and can also refer to the time at which the aiding information and measurements are applied by the user equipment UE, respectively. More generally, aiding time A i and measurement time M i may refer to a time related to or associated with the acquisition of the aiding information and the measurement, respectively. In the remainder of this disclosure, "aiding time A i "Acquisition of support information at measurement time M i The measurement is taken at time A i and M i can refer to the time (or time slot) when the aiding information and measurements are actually used or applied by the user equipment UE. As mentioned above, a part of the open-loop information can be retrieved by the user equipment UE within a certain pre-set aiding time window according to a pre-set periodicity and / or depending on the hardware capabilities of the user equipment UE. In particular, the user equipment UE can make a larger adjustment of the timing advance TA value using the open-loop information with respect to the adjustment using the closed-loop information. Indeed, as mentioned above, the closed-loop information has a limited information size defined by the 6-bit size of each TAC signal, whereas the open-loop information allows the user equipment UE to make a self-adjustment of the timing advance TA value, and thus a more flexible adjustment with respect to the TAC-related adjustment.

[0118] More generally, the timing advance TA value applied by a user equipment UE in a cell corresponding to a base station BS can be expressed as: TA=(N TA +N TA,UE-specific +N TA,common +N TA,offset )×T c Where: -TA is the updated timing advance value (eg, in ms or ns). -N TA is the command value of the timing advance TA provided by the closed loop. -N TA,UE-specific is a self-adjustment value determined by the user equipment UE on an open loop basis. -N TA,common is a predefined value set by the network NW depending on the propagation delay between the satellite SAT and the network reference point under consideration. -N TA,offset is an offset value assigned to the user equipment UE. -T c is the chip period. Such chip period may be fixed or configurable. For example, in the 3GPP NR standard, this value is fixed at 0.509 ns.

[0119] Thus, while in RRC_CONNECTED mode, the user equipment UE has, at each considered time instant, a current value of the timing advance TA. Such a current value of the timing advance TA may for example correspond to the last timing advance TA value calculated by the user equipment UE at the considered time instant or before that time instant. Such a current value of the timing advance TA may for example correspond to the last timing advance TA value used by the user equipment UE when transmitting a signal to the base station BS. Such a current value of the timing advance TA at the considered time instant depends in particular on: - The last (or latest) command time C received by the user equipment UE from the base station BS N A final (or last) command value N determined based on at least one last TAC signal associated with TA,N . The final (or final) self-adjustment value N, which is determined based on the following two things: TA,UE-specific,N . --The last (or latest) assistance time A received by the user equipment UE from one or more network entities (e.g., base stations BS) N The last (or final) supporting information associated with. --The last measurement time M performed by the user equipment UE N The value of the last (or latest) measurement associated with.

[0120] Command Value N TA,i is sometimes called a correction parameter or closed loop correction. TA,UE-specific,i is sometimes called a self-correction parameter or an open-loop correction.

[0121] Last self-adjustment value N TA,UE-specific,N is the position of the user equipment UE and the distance d of the user equipment UE to the artificial satellite SAT UE,1 , d UE,2 The last self-adjustment value N TA,UE-specific,N can be periodically updated by the user equipment UE based on the assistance information according to a configured periodicity, for example when the network NW transmits a system information block (SIB) in the cell. Such a periodicity can typically be on the order of a few seconds. Such a last self-adjusted value N TA,UE-specific,N can also be updated by the user equipment UE based on GNSS measurements performed by the user equipment UE. The frequency and time of these measurements M i depends on the capabilities and implementation of the user equipment UE.

[0122] A pre-defined value N that the user equipment UE uses to determine the value of the timing advance TA at the time under consideration. TA,commondepends in particular on the distance between the satellite SAT and the network reference point. In particular, if the network reference point is set in the satellite, such a preset value N TA,common is a constant value of zero. Such a preset value N TA,common can be updated by the user equipment UE when the network NW transmits a system information block (SIB) in the cell according to a configured periodicity or when the user equipment UE receives, for example, radio resource control parameters.

[0123] For example, referring to FIG. 1, it is considered that at time t1, the user equipment UE has already determined a current value to be used as the timing advance TA in the cell. Such a current value to be used as the timing advance TA is the distance d between the position of the user equipment UE at time t1, which corresponds to the position of the cell in the network NW, and the position of the satellite SAT at time t1. UE,1 and the distance d1 between the satellite SAT and the network reference point (corresponding to the base station BS in FIG. 1) at time t1. In such a situation of the satellite communication network NW, the current value used as the timing advance TA in the cell at time t1 is the time C of the last command received before time t1. N , support time A N , and measurement time M N The determination may have been made by the user equipment UE based on the open-loop and closed-loop information acquired by the user equipment UE in

[0124] The real-time position of the satellite SAT at a given time, such as time t1, may not be known by the user equipment UE with high accuracy. The user equipment UE may calculate an approximate position of the satellite SAT at a given time, for example, by aiding information and / or a predefined equation representing the trajectory of the satellite SAT. For example, the user equipment UE may estimate the position of the satellite SAT at a given time using the position of the satellite SAT (e.g., transmitted by the network NW via the SIB) at a previous time (e.g., ephemeris at an associated epoch time) and a predefined formula. In this disclosure, the position of the satellite SAT may refer to an approximate position of the satellite SAT calculated by the user equipment UE, or may refer to the exact position of the satellite SAT if the exact position is known by other means, or may refer to a position related to the actual position of the satellite SAT at the current time or a previous time, the actual position itself, or a position derived from the actual position.

[0125] Referring to FIG. 2, the situation of a part of the satellite communication network NW at time t2 has changed with respect to time t1. In fact, the artificial satellite SAT is moving according to a preset satellite ephemeris SAT MOV. Therefore, the distance d of the user equipment UE to the artificial satellite SAT at time t1 is UE,1 is the new distance d UE,2 and the distance d1 between the satellite SAT and the network reference point at time t1 is changed to a new distance d2. In another embodiment, some conditions of such a satellite communication network NW may have changed at time t2 due to the movement of the user equipment UE within the fixed location of the cell between time t1 and time t2. In such a case, the distance d between the user equipment UE and the satellite SAT may be changed to a new distance d2. UE,1is changed. The distance d1 between the satellite SAT and the network reference point may or may not change between time t1 and time t2 depending on how the reference point is defined. Considering the change in the situation of the satellite communication network NW between time t1 and time t2, the current value used as the timing advance TA in the cell at time t1 may become inaccurate for transmitting a signal to the base station BS by time t2. In fact, such a current value of the timing advance TA may no longer allow compensation of the propagation delay between the user equipment UE and the network reference point at time t2, so that if the user equipment UE transmits a signal S by time t2 using the current value of the timing advance TA, there is a risk that the signal S will not be able to reach the network side (e.g. the base station BS) at the time corresponding to the resource to which the signal S is assigned.

[0126] If the inaccurate value of the timing advance TA cannot compensate for the propagation delay between the user equipment UE and the network reference point (e.g., if the current value of the timing advance determined for time t1 is reused at a later time t2), timing desynchronization between the uplink signal expected from the user equipment UE and the uplink signal expected from other UE equipment will occur on the network side, causing inter-user interference. In addition, the uplink signal actually received by the network side from the user equipment UE and the downlink signal sent by the network side will also occur. As a result, the quality of the link between the user equipment UE and the network NW will deteriorate, some uplink and / or downlink messages cannot be decoded, and the user equipment UE may consider that there is a loss of connection to the network NW, which is called a radio link failure (RLF). When an RLF occurs, an outage occurs, and the user equipment UE may further initiate another random access procedure (RACH procedure) to try to reconnect to the network NW. Thus, such a repetition of the random access procedure wastes a lot of time and resources on both the user equipment UE and the network side.

[0127] In such a situation, the present disclosure proposes a method executed by the user equipment UE to transmit a signal S to the base station BS using an updated value of the timing advance TA.

[0128] A diagram of the overall structure of a user equipment UE capable of executing such a method in accordance with the present disclosure is shown diagrammatically in FIG.

[0129] The user equipment UE comprises at least an input communication means INP, a storage memory unit MEM-UE, a processing unit PROC-UE and an output communication means OUT. In an embodiment the input communication means INP and the output communication means OUT can be merged in a single communication unit.

[0130] The input communication means INP enables the user equipment UE to receive signals from other entities including network entities such as base stations of the satellite communication network NW. The input communication means INP optionally also enables the user equipment UE to receive signals from other devices and user equipments, for example via sidelink communication. To this end, the input communication means INP may comprise a receiver such as a radio frequency antenna, a demultiplexer, etc. In particular, the input communication means INP may comprise New Radio (NR) hardware.

[0131] The storage memory unit MEM-UE allows the user equipment UE to store information received via the input communication means INP and / or processed by the processing unit PROC-UE. In particular, the storage memory unit MEM-UE may comprise a non-volatile memory unit MEM1, a volatile memory unit MEM2 (e.g. a random access memory) and a buffer unit BUF. The buffer unit BUF may for example store traffic data transmitted by the user equipment UE.

[0132] The processing unit PROC-UE enables the user equipment UE to process information received via the input communication means INP and information stored by the storage memory unit MEM-UE, so as to send signals, calculate values, decide actions, etc. In particular, the processing unit PROC-UE of the user equipment UE is capable of executing the methods proposed in the present disclosure and further detailed in the description of figures 3 and 4. To that end, the processing unit PROC-UE may for example comprise a general purpose processing unit PU1, a determination unit PU2, a timing advance calculation unit PU3 and a sending unit PU4. The general purpose processing unit PU1 may pre-process and / or process data received via the input communication means INP and data stored in the storage memory unit MEM-UE. For example, the general purpose processing unit PU1 may timestamp the received and / or stored information. The general purpose processing unit PU1 may manage the overall functionality and applications of the user equipment UE. The decision unit PU2 can trigger any decision made by the user equipment UE, such as sending a signal, calculating a value of timing advance, performing a random access procedure, postponing any of them. The timing advance calculation unit PU3 can determine an updated value to be used as timing advance TA in the cell. The transmission unit PU4 can send signals S, S', such signals S, S' being for example data signals or control signals. Such a transmission unit PU4 can in particular send signals S, S' via an output communication means OUT, which can transmit the signals S, S' sent by the transmission unit PU4. Such a transmission unit PU4 can perform transmissions such as uplink transmissions or optionally sidelink unicast, groupcast and / or broadcast transmissions. The output communication means OUT can comprise a transmitter, a multiplexer, etc.

[0133] Reference is now made to Figure 3, which illustrates the steps of transmitting a signal S to a base station BS using an updated value of the timing advance TA according to the present disclosure.

[0134] In step S1, the user equipment UE plans to transmit a signal S to a base station BS to which the user equipment UE is connected via a cell corresponding to the base station BS. The planning of transmitting the signal S can be triggered by various events on the user equipment UE side. For example, the planning of transmitting the signal S can be triggered by the availability of data buffered in a buffer unit BUF of the user equipment UE, a timer of the user equipment UE, a periodic report sent to the network NW, a requirement to retrieve information or to be allocated resources by the network NW, etc. Step S1 can be performed at a time T, also called the current time T.

[0135] In step S2, the user equipment UE can collect information to be used for transmitting the signal S in anticipation of the signal S being transmitted. In particular, the user equipment UE can obtain data related to the current value of the timing advance in the cell in step S2. Such data related to the current value of the timing advance in the cell can include, in particular: -Last received (or last applied) closed-loop information for the current time T: the user equipment UE receives in step S2 the respective last command time C N The last (or latest) TAC signal received from the base station BS associated with may be considered. Last obtained open-loop information for the current time T: In step S2, the user equipment UE N The user equipment UE may take into account the last (or latest) assistance information signal retrieved from one or more base stations associated with the last measurement time M N It is also possible to process the last (or latest) measurement associated with -Predefined parameters required to determine the value of timing advance.

[0136] In particular, in step S2, the user equipment UE is able to determine, taking into account the current time T, whether such data related to the current value of the timing advance in the cell are sufficient and relevant in order to obtain a value to be used as the timing advance TA in the cell when transmitting the signal S. To this end, the user equipment UE determines whether such data related to the current value of the timing advance in the cell are sufficient and relevant in order to obtain a value to be used as the timing advance TA in the cell when transmitting the signal S. N , support time A N and measurement time M N For example, the user equipment UE may compare the last aiding time A N The last measurement time M N The last support time A N and the last measurement time M N The user equipment UE may in particular compare the time gap between the last command time C N , support time A N and measurement time M N can also be compared against the current time T. The user equipment UE compares the last command time C N , support time A N and measurement time M N is a predefined threshold time T ths (or a predefined threshold ths). ths The time of the last command C may also be called the validity time or the threshold time. Such a comparison of times may be aimed at determining whether data related to the current value of the timing advance TA in the cell should be considered as stale, particularly with respect to the current time T. N , support time A N and measurement time M N Any of the valid times T ths (i.e., the last command time C N , support time A N and measurement time M Nt ... ths is such a valid time T ths can be predefined in a dynamic way so that it can change with the current time T. For example, if the current time T is defined as a given time slot, then the valid time T ths may be defined as the time slot that is 10 slots prior to the given time slot.

[0137] In one embodiment, the final command time C N can be compared with a first preset threshold value. N The final timing advance command associated with is the final command time C N If the last assistance time A is earlier than a first preset threshold, the closed-loop information is deemed to be out of date. N and / or the last measurement time M N The last assistance time A can be compared with a second preset threshold value. N and / or the last measurement time M N The final support information and / or final measurement value associated with each of the final support times A N and / or the last measurement time M N If the valid time T is earlier than the second preset threshold, the open-loop information is deemed to be stale. In the remainder of this disclosure, the first and second preset thresholds are assumed to be equal, and the valid time T ths However, in other embodiments, such thresholds may be different, especially if the time tolerance between closed-loop and open-loop information is different.

[0138] In step S2, the user equipment UE may also process the final closed-loop information and the final open-loop information to estimate a required size, value or scale of a timing advance adjustment relative to a current value of the timing advance TA. To that end, the user equipment UE estimates a value of the timing advance adjustment relative to a current value of the timing advance TA used in the cell and compares such value of the timing advance adjustment with a threshold adjustment value N ths In particular, the estimated required value of the timing advance adjustment can be compared to the threshold adjustment value N ths If so, the user equipment UE determines that a large timing advance correction is required relative to the current value of the timing advance in anticipation of the transmission of the signal S.

[0139] In particular, such timing advance adjustments include timing advance adjustments indicated by final closed loop information, also referred to as final closed loop corrections or correction parameters. Such timing advance adjustments also include timing advance adjustments indicated by final open loop information, also referred to as final open loop corrections or self-correction parameters. Timing advance adjustments and threshold adjustment values ​​N thsThe comparison with may consist of comparing the correction parameter with a preset correction threshold and comparing the self-correction parameter with a preset self-correction threshold, respectively. Such preset correction threshold and self-correction threshold are intended to quantify how large the open-loop correction and closed-loop correction, respectively, are. Thus, if the correction parameter included in the final timing advance command exceeds the preset correction threshold, this means that the final timing advance command indicates a large (or significant) timing advance adjustment. Similarly, if the self-correction parameter obtained from the final measurement and / or the final aiding information exceeds the preset self-correction threshold, this means that the final aiding information and / or the final measurement indicates a large (or significant) timing advance adjustment. In the remainder of this disclosure, for simplicity, the timing advance adjustment is referred to as a threshold adjustment value N. ths , it being understood that such a comparison can be made on the scale of the open-loop and closed-loop information.

[0140] As a result, during step S2, the user equipment UE determines whether it needs updated information in order to determine an updated value of the timing advance TA in the cell for transmitting the signal S. In other words, the user equipment UE determines in step S2 based on the information stored in the storage memory unit MEM-UE enabling the determination of a current value of the timing advance whether it is possible to send the signal S without causing timing desynchronisation on the network side.

[0141] If the user equipment UE determines that there is no need to obtain updated closed-loop and / or open-loop information to calculate an updated value of the timing advance TA in the cell for transmitting the signal S, the user equipment UE determines in step S2 a transmission time T corresponding to a time opportunity configured by the network NW for transmitting the signal S. snd In particular, the user equipment UE determines the transmission time Tsnd can be selected as the next time opportunity to transmit a signal S with respect to a current time T. The next time opportunity to transmit a signal S with respect to a current time T is the target transmission time T t It is also called.

[0142] In such a case, the transmission time T snd After determining T, the user equipment UE determines in step S5 an updated value to be used as the timing advance TA in the cell when transmitting the signal S. In particular, such a value may be determined as corresponding to a current value of the timing advance TA in the cell (e.g. previously calculated by the user equipment UE and / or used for the transmission of a signal preceding the signal S). Then, in step S7, the user equipment UE finally determines the target time T using the current value used as the timing advance in the cell as an updated value to be used as the timing advance TA in the cell. t A signal S is transmitted to a base station BS at.

[0143] On the other hand, in the context of the present disclosure, the user equipment UE may determine in step S2 that the current value of the timing advance in the cell is out of date with respect to the current time T. The user equipment UE may determine in step S2 that a large timing advance correction (or adjustment) is required for the current value of the timing advance in anticipation of the transmission of the signal S. In other words, the user equipment UE determines in step S2 that the determination of an update value to be used as the timing advance TA in the cell requires updated closed-loop and / or open-loop information with respect to the last received closed-loop and / or open-loop information (i.e. with respect to the last timing advance command, and / or the last assistance information, and / or the last measurement). Based on such a determination that the calculation of an update value to be used as the timing advance TA for transmitting the signal S in the cell requires updated closed-loop and / or open-loop information, the user equipment UE determines whether and / or when the user equipment UE can obtain such required information update. The user equipment UE also determines a possible delay requirement associated with the transmission of the signal S. For example, the transmission of the signal S may be determined in accordance with a particular service level agreement (SLA) guaranteed by the user equipment UE and / or more generally in accordance with a predefined transmission deadline time T r may have to be done before.

[0144] Taking into account the requirements of the updated closed-loop and / or open-loop information and possible delay requirements and / or other time constraints associated with the transmission of the signal S as described above, the user equipment UE selects in step S2 at least two different time opportunities T configured by the network NW for transmitting the signal S. t , T p The transmission time T of the signal S is snd In particular, the user equipment UE selects the transmission time T snd can be selected. The next (or next scheduled) time opportunity to transmit a signal S relative to the current time T, which is the target transmission time T tAlso called time opportunity, and -Current time T and target transmission time T t the next time opportunity to transmit a signal S after both of the postponed transmission time T p Also called time opportunity.

[0145] Such a transmission time T snd is expressed as a slot index or symbol index relative to a predefined reference time. snd The criteria for selecting is explained in further detail in the description of FIG.

[0146] In step S3, the user equipment UE can, in some embodiments, which are further detailed in the description of FIG. 4, emit an auxiliary signal S', also called a support signal S', which is different from the signal S. Such a support signal S' can in particular be a control signal transmitted to the base station BS. Such a support signal S' can be aimed at obtaining updated closed-loop and / or open-loop information used to determine an updated value used as a timing advance TA for transmitting the signal S in the cell. The time of emitting such a support signal S' is also called a support time and is referred to as a target transmission time T t In one embodiment, the time to send such a support signal S' depends on the target transmission time T t In particular, the time of sending such a support signal S′ can be earlier than the postponed transmission time T p In one embodiment, the time for sending such a support signal S′ can be earlier than the target transmission time T t and the postponed transmission time T p For example, in step S2, the user equipment UE may set the transmission time T snd Postpone the transmission time T p and the target transmission time T t After but deferred transmission time T pA support signal S' may be transmitted before the TAC value. The support signal S' may be sent during a pre-configured time window (i.e. time opportunity) configured by the network NW that allows the user equipment UE to transmit such a support signal S' to the base station BS. The pre-configured time window for transmitting the support signal S' may be similar to or different from the time window for transmitting the signal S. Such a support signal S' may be sent using a current value used as the timing advance TA in the cell. Such a value of the timing advance used for transmitting the support signal S' is called a support value of the timing advance. Such a support signal S' may request assistance information, such as, for example, a specific content, from the base station BS. Such a support signal S' may request, for example, an update of the TAC value. Such a support signal S' may be sent so that the base station BS may transmit an updated TAC signal to the user equipment UE, for example based on a decision related to the reception timing of the support signal S' on the network side, or any other measurement, or any implementation on the network side. Such a signal S' may also correspond to updated measurements performed by the user equipment UE. Such a signal S' may also be a request to ascertain the value of the timing advance used in the transmission of S' (eg, the current value of the timing advance).

[0147] In step S4, in some embodiments, which are further detailed in the description of FIG. 4, the user equipment UE may receive updated closed-loop and / or open-loop information. The reception of the closed-loop and / or open-loop information in step S4 may in particular be subsequent to the sending of the supporting signal S′ in step S3. In particular, the updated closed-loop and / or open-loop information may for example be determined on the network side based on the supporting signal S′ sent by the user equipment UE in step S3. The updated open-loop information may also be derived by the user equipment UE without the need to send the supporting signal S′ in step S3. Such updated closed-loop and / or open-loop information may be updated in accordance with the target transmission time T t The received signal may be received and / or retrieved by the user equipment UE before

[0148] In another embodiment, steps S3 and S4 are performed when the user equipment UE transmits at a transmission time T snd , i.e., before step S2. snd can indeed be selected once the user equipment UE has obtained updated closed-loop and / or open-loop information used to determine an updated value to be used as the timing advance TA for transmitting the signal S in the cell, provided that the delay requirement for transmitting the signal S allows the user equipment UE to transmit the signal S. snd The selection of the transmission time T may be made after the expiry of a time limit after the transmission of the supporting signal S′ in step S3. For example, the user equipment UE may select the transmission time T depending on the reception or non-reception of updated open-loop and / or closed-loop information in step S4 following the transmission of the supporting signal S′ in step S3. snd can be selected.

[0149] In step S5, the user equipment UE determines the selected transmission time T snd, the timing advance TA is updated to be used for transmitting a signal S in the cell at the selected transmission time T snd The updated value used as the timing advance TA for transmitting the signal S in can correspond to the current value of the timing advance, i.e. the value of the timing advance used by the user equipment UE to transmit its last signal to the base station BS. In particular, the current value of the timing advance depends on the last timing advance command, the last assistance information and the last measurement (more generally, the latest information at the user equipment's disposal at the current time T). Such a case occurs, for example, if the user equipment UE did not receive updated open-loop and / or closed-loop information in step S4. The user equipment UE can determine an updated value of the timing advance TA without relying on updated closed-loop and / or open-loop information. The reason is either that such updated closed-loop and / or open-loop information is not considered to be required by the user equipment UE to determine an accurate updated value of the timing advance TA, or that the delay requirements for transmitting the signal S do not allow the user equipment UE to wait for such updated closed-loop and / or open-loop information. Such recognition of updated open-loop and / or closed-loop information is further detailed in the description of FIG. 4.

[0150] In another embodiment, the updated value to be used as the timing advance TA can be determined in step S5 based on the updated closed-loop and / or open-loop information received in step S4. An embodiment enabling the user equipment UE to take into account obtaining updated closed-loop and / or open-loop information for determining the updated value to be used as the timing advance TA for transmitting the signal S is further detailed in the description of figure 4.

[0151] In an optional step S6, the user equipment UE can also estimate a value related to the timing advance error, also called timing error parameter, of the updated value of the timing advance TA determined in step S5. In fact, the user equipment UE can self-implement an incremental or differential algorithm, for example to determine the accuracy and / or fitness of the timing advance calculation. Thus, after each value of the timing advance TA determined by the user equipment UE in step S5, the user equipment UE can increase or decrease a stored value, for example representing an accumulated error when calculating the value of the timing advance during the RRC_CONNECTED mode of the user equipment UE. The criteria for increasing or decreasing such a timing error parameter are further detailed in the description of FIG. 4.

[0152] Finally, in step S7, the user equipment UE uses the updated timing advance TA for the cell determined in step S5 to determine the selected transmission time T snd A signal S is transmitted to a base station BS at.

[0153] Reference is now made to Figure 4, which is a flow chart illustrating the steps performed by the user equipment UE to transmit a signal S to the base station BS using an updated value of the timing advance TA. In particular, the steps of Figure 4 further elaborate the method proposed in Figure 3 with regard to: -Sent time T snd In particular, in some embodiments, the selection of the target transmission time T t Delayed transmission time beyond T p Selection of a user equipment UE to select; obtaining updated closed-loop and / or open-loop information possibly triggered by the user equipment UE by transmitting a support signal S′ to the base station BS, - Implementation of timing error parameters by the user equipment UE.

[0154] In the above mentioned step S1, the user equipment UE plans to transmit a signal S to the base station BS. Such signal S is planned to be transmitted using an updated value of the timing advance TA in the cell in order to compensate as accurately as possible for the propagation delay between the user equipment UE transmitting the signal S and the network reference point (considered to be the location of the base station BS for the purposes of this disclosure) receiving the signal S. In the proposed method, the user equipment UE further proceeds to: - Time T of transmission of signal S snd Selecting transmitting a support signal S' possibly different from the signal S, and - Determining an updated value of the timing advance TA in the cell used to transmit the signal S.

[0155] In step S20, the user equipment UE determines the final command time C associated with the final timing advance command received from the base station BS (via the final closed loop information). N and the current time T. Such first time gap is then compared with a pre-configured first gap threshold known by the user equipment UE. Similarly, N is effective at time T ths In step S20, the final command time C N is the effective time T ths (i.e., the last command time C Nand the current time T exceeds a preset first gap threshold), the user equipment UE determines that the last TAC signal (and thus the correction parameter associated with the value of the timing advance command included in such last TAC signal, also called final closed-loop correction) is outdated at the current time T. In such a case, the user equipment UE determines that updated information is needed to associated determine an updated value to be used as the timing advance TA for transmitting the signal S. In particular, in such a case, the user equipment UE determines that the updated value to be used as the timing advance TA for transmitting the signal S should be different from the current timing advance value.

[0156] If the user equipment UE determines in step S20 that updated information is required due to the last TAC signal being out of date, the user equipment UE determines in step S22 the transmission time T snd In step S22, the user equipment UE determines whether the transmission of the signal S is predictable, for example, whether the signal S can be transmitted based on the configuration grant. If the user equipment UE determines in step S22 that the transmission of the signal S is predictable, the user equipment UE can transmit a support signal S' to the base station BS in step S42. In particular, the support signal S' is a signal that is transmitted at a time T snd , and / or a request to receive an updated TAC signal in advance. Conversely, if in step S22 the user equipment UE determines that the transmission of the signal S cannot be predictable (e.g., there is no configuration grant to transmit the signal S), the user equipment UE continues with step S30, which will be described in more detail later. On the other hand, in step S20, N is the effective time T ths (i.e., after the last command time C N and the current time T at which step S20 is executed is less than a preset first gap threshold), the user equipment UE determines the final command time C N, the user equipment UE determines that the final TAC signal associated with the timing advance command (and therefore the correction parameter associated with the value of the timing advance command included in the TAC signal, i.e. the final closed-loop correction) is still relevant at the current time T. In particular, the user equipment UE can use the value of the timing advance command included in the final TAC signal as a guideline to adjust the update value used for the timing advance TA with respect to the current value of the timing advance. To that end, in step S21, the user equipment UE determines that the value of the final timing advance command included in the final TAC signal (i.e. the correction parameter corresponding to the final closed-loop correction) is still relevant at the current time T, i.e. the final closed-loop correction, which is set by the user equipment UE or which is predefined or transmitted to the user equipment UE by the base station BS. ths,OL The preset correction threshold T ths,OL can be set, for example, between 30 and 50, and can be expressed in steps, samples, or time units.

[0157] In step S21, the timing advance command value included in such a final TAC signal is adjusted to a value smaller than a preset correction threshold T ths,OLIf it is determined that the timing advance command value T is less than the current time T, the user equipment UE determines that the amount of closed loop correction applied to the current timing advance value is not large: in other words, the propagation delay compensated between the user equipment UE and the network reference point has not changed significantly compared to the current value of the timing advance last calculated by the user equipment UE at a time before the current time T. Therefore, the user equipment UE determines that, in step S41 following step S21, an updated value of the timing advance TA can be determined as corresponding to the current value of the timing advance TA. In a particular embodiment, since the user equipment UE determines that the updated timing advance value determined in step S41 is fairly accurate considering the current time T, in step S41, the user equipment UE can also update the timing error parameter by decreasing the timing error parameter value. On the other hand, if the value of the timing advance command included in the final TAC signal in step S21 is less than the predetermined correction threshold T, the user equipment UE determines that the timing advance command value T is less than the predetermined correction threshold T. ths,OL If so, the user equipment UE determines in step S21 that a large timing advance correction is required for the current value of the timing advance TA in anticipation of the transmission of the signal S. In particular, if the final closed loop correction is deemed large in the final TAC signal, the user equipment UE determines that updated information is required to determine an updated value to be used as the timing advance TA. Since the timing advance command value has a limited size (and therefore can only indicate a limited correction), the updated value will be larger than the timing advance command value contained in the final TAC signal.

[0158] To this end, following step S21, the user equipment UE, in step S30 following either step S21 or step S22, updates the updated assistance information to an updated assistance time A after the current time T. N+1In other words, the user equipment UE predicts when the next scheduled transmission of updated open-loop information from the network NW will occur and determines whether the corresponding updated assistance time A can be retrieved, possibly according to time-related parameters. N+1 is acceptable (or early enough) for the user equipment UE, for example with respect to time-related parameters. Such time-related parameters may be, for example, the transmission deadline time T r The terms “acceptably” and “sufficiently early” are used herein to refer to a transmission deadline T r In some cases, "acceptable" and "early enough" can be understood to be before the postponed transmission time T p "Acceptably" and "sufficiently early" can also be understood to be before the expiration of a given timer related to a time-related parameter. N-1 , A N-2 etc. and / or final support time A N Based on a preset periodicity of the assistance information transmission, which is determined or estimated by the user equipment UE by using the above, it is possible to predict when the next transmission of updated open-loop information from the network NW will occur.

[0159] In step S30, the user equipment UE transmits the updated open-loop information to the network NW sufficiently early, for example at a target transmission time T t After but deferred transmission time T p If the user equipment UE determines that it can transmit before the next scheduled time opportunity to transmit the signal S (i.e., the target transmission time T t In order to voluntarily abandon the transmission time T snd Postpone the transmission time T pIn the case of step S43, the user equipment UE may not need to transmit any support signal S'. That is, the user equipment UE determines that the updated open-loop transmission is within the predictable time of the updated support time A'. N+1 On the other hand, in step S30, the user equipment UE determines that the open-loop information transmission from the network NW is not performed early enough (for example, the updated assistance time A predicted by the user equipment UE is not updated early enough), and the user equipment UE determines an updated value to be used as the timing advance TA based on the updated open-loop transmission. N+1 is the deadline for sending signal S. r , the user equipment UE decides to determine an updated value of the timing advance TA without using updated open-loop and / or closed-loop information in a step S40 following step S30. In particular, the user equipment UE can determine an updated value of the timing advance TA as the current value of the timing advance (and thus based on the last TAC signal). In a particular embodiment, since the user equipment UE determines that the determined updated value of the timing advance TA is inaccurate taking into account the large correction indicated in the last TAC signal, the user equipment UE can also update the timing error parameter in step S40 by increasing the timing error parameter value. In such a case, since the user equipment UE determines that it is not interested in postponing the transmission of the signal S (no updated information can be expected in the meantime), the user equipment UE decides to determine an updated value of the transmission time T snd The target transmission time T t On the other hand, updating the timing error parameter allows the user equipment UE to evaluate the accuracy of its timing advance implementation and, in case of step S40, can evaluate that due to lack of updated information, the determined update of timing advance TA is inaccurate.

[0160] Similarly, the user equipment UE may, in step S30, obtain updated measurement times M associated with updated measurements obtained by the user equipment UE. N+1 It is also possible to obtain or predict the updated assistance time A N+1 The reasoning applied to the updated measurement time M N+1 can also be applied to

[0161] In step S20, the user equipment UE determines the last command time C when the last TAC signal was received by the user equipment UE. N The final support time A associated with the final support information that the user equipment UE has at its disposal is also N and / or the last measurement time M associated with the last measurement N In step S20, the final command time C N However, the final support time A N and / or the last measurement time M N If the TAC signal is received before either (or both) of the TAC signal received before the TAC signal received, the user equipment UE proceeds to step S23. In particular, the user equipment UE proceeds to step S23 regardless of whether the last TAC signal is stale (or not) as described above.

[0162] In step S23, the user equipment UE determines whether the final open-loop information reflects a large timing advance correction relative to the current value of the timing advance. To that end, in step S23, the user equipment UE may compare the open-loop correction provided by the final assistance information and / or the final measurement. The open-loop correction is also called a self-correction parameter. The self-correction parameter is then compared in step S23 with a pre-defined self-correction threshold N ths,OL is compared with the preset self-correction threshold N ths,OL is intended to quantify the magnitude of the open loop correction. In one embodiment, a preset self-correction threshold N ths,OL is the preset correction threshold T ths,OLThe user equipment UE may use the self-correction parameter obtained based on the final open-loop information as a preset self-correction threshold N ths,OL If it is determined that the last measurement time M exceeds the current value of the timing advance, the user equipment UE may determine that the last open-loop information reflects a large timing advance adjustment (i.e., a large open-loop correction) of the current value of the timing advance. N The last measurement performed by the user equipment UE at N-1 In the case where the last open loop information results in a drastic change in the position of the user equipment UE (e.g., more than one or several kilometers) compared to the value of the previous position measurement performed at the last assistance time A, the last open loop information can be considered by the user equipment UE to reflect a large timing advance adjustment. N For example, the final support information obtained at the previous support time A N-1 If the final open loop information results in a significant movement of the satellite SAT according to the satellite ephemeris relative to the previous satellite position obtained in, the final open loop information can be taken by the user equipment UE to reflect a large timing advance adjustment.

[0163] If in step S23 the user equipment UE determines that the last open loop information reflects a large timing advance adjustment applied to the current value of the timing advance, the user equipment UE determines that updated information is required to accurately determine an updated value of the timing advance TA to be used when transmitting the signal S, since the updated value TA may potentially be significantly different from the current value of the timing advance. To that end, in a step S44 following step S23, the user equipment UE may send a support signal S' to the base station BS. In particular, such a support signal S' may be a signal requesting updated assistance information and / or an updated timing advance command. In a particular embodiment, the user equipment UE may send such a support signal S' using a support value used as the timing advance corresponding to the current value of the timing advance TA (and thus taking into account the last open loop information when transmitting the support signal S'). Thus, the user equipment UE at least partially compensates for the actual propagation delay at the current time T between the user equipment UE and the network reference point. Such a support signal S' can be sent at the very next opportunity to request assistance information provided by the network NW. r If the transmission is accompanied by a transmission deadline T r The support signal S' may also include an indication requesting a possible reconfiguration of the support information transmission and / or the updated TAC signal, so that the user equipment UE may retrieve the updated support information and / or the updated timing advance command before the measurement time M. In one embodiment, the user equipment UE may, in step S44, determine the updated measurement time M, subject to its hardware capability and / or a pre-configured time opportunity to perform the updated measurement. N+1The user equipment UE may then continue to perform updated measurements in step S44, which may optionally also relate to the configuration of the measurement gaps (and therefore the measurement occasions) if measurements on the user equipment UE side can only be performed during measurement gaps configured by the network. The reception (or non-reception) of the updated assistance information following the sending of the support signal S' in step S44 is not controlled by the user equipment UE. Thus, in step S44 the user equipment UE may, for example, perform the measurement in step S44, until the transmission deadline time T r , subject to a delay requirement for transmitting the signal S reflected by snd Postpone the transmission time T p Depending on the delay requirement, the user equipment UE may then wait until expiration of a predefined timer after transmitting the supporting signal S' (even if no updated information has been obtained) to transmit the signal S. Depending on the delay requirement, the user equipment UE may also wait until expiration of a predefined timer after transmitting the supporting signal S' to transmit another supporting signal S'. The user equipment UE may select the transmission time T of the signal S if the supporting signal S' is sent in advance. s The target transmission time T t It is also possible to select it so that

[0164] If, in step S23, the user equipment UE determines that the final open loop information does not reflect a significant timing advance adjustment compared to the current value of the timing advance (e.g., the user equipment UE has determined that neither its position nor the position of the satellite SAT, e.g., the aiding time A N-1 and measurement time M N-1 In step S31 following step S23, if the user equipment UE determines that the last open-loop information has not changed or has not changed significantly with respect to the open-loop information previously obtained in step S23, the user equipment UE subsequently determines whether the last open-loop information is outdated with respect to the current time T. To this end, in step S31, the user equipment UE determines whether the last open-loop information is outdated with respect to the current time T and the last assistance time A N and / or the last measurement time M NThe user equipment UE can then compare the second time gap with a preset second gap threshold. Similarly, the user equipment UE can compare the second time gap with the last assistance time A N and / or the last measurement time M N Effective time T ths In particular, in step S31, the user equipment UE determines whether the last support time A N and / or the last measurement time M N is the effective time T ths If it is determined that the assistance time is after the last assistance time A N and / or the last measurement time M N and the current time T is less than a second preset gap threshold), the user equipment UE considers the last open-loop information to be recent (i.e. not stale) with respect to the current time T. In such a case, the user equipment UE determines in step S46 following step S31 that the last open-loop information does not require a large timing advance correction to be applied to the current value of the timing advance for transmitting the signal S taking into account the current time T. Thus, in step S46, the user equipment determines an updated value of the timing advance TA without needing updated information. In particular, in step S46, the user equipment UE can determine that the updated value of the timing advance TA used for transmitting the signal S corresponds to the current value of the timing advance TA. In a particular embodiment, since the user equipment UE determines that the updated value of the timing advance TA cannot be significantly different from the current value of the timing advance, the user equipment UE can also update the timing error parameter in step S46 by decreasing the timing error parameter value. In such a case, the user equipment UE does not need to postpone the transmission of the signal S to wait for any updated information, so in step S46 the user equipment UE determines the transmission time T snd The target transmission time T t It can be selected so that

[0165] On the other hand, in step S31, the user equipment UE N and / or the last measurement time M N is the effective time T ths If it is determined that the time is earlier than the last assistance time A N and / or the last measurement time M N In one embodiment, the user equipment UE determines in step S31 that the last open-loop information is stale if a second time gap between any one of the last assistance time A and the current time T exceeds a second gap threshold. N and the final measurement time M N A third time gap between the last assistance time A and the last open-loop information A may also be determined. Such a third time gap may then be compared to a preset third gap threshold to determine the consistency of the final open-loop information. N and / or the last measurement time M N If either the second time gap between any of the last aiding time A and the current time T exceeds a preset second gap threshold, or the third time gap between any of the last aiding time A and the current time T exceeds a preset third gap threshold, the last open-loop information may be considered stale in step S31. If the last open-loop information is stale, the user equipment UE determines in step S31 that the last aiding information and / or the last measurement (and thus the indication of the small open-loop correction as determined in step S23) is unreliable at the current time T and thus requires updated information. For example, if the last aiding time A is stale, the user equipment UE determines in step S31 that the last aiding information and / or the last measurement (and thus the indication of the small open-loop correction as determined in step S23) is unreliable at the current time T and thus requires updated information. N and / or the last measurement time M NBetween the current time T and the current time T, the user equipment UE and / or the satellite SAT may have moved significantly. In such a case, in step S45, the user equipment UE continues to send out supporting signals S' requesting updated open loop information in a similar manner as in step S44. In one embodiment, the user equipment UE may also continue to perform updated measurements in step S45, subject to hardware capabilities and / or pre-set time opportunities to perform updated measurements. The user equipment UE then determines, in particular, the potential delay requirements for transmitting the signal S, the potential updated supporting times A and B, and the time required for the updated measurements to be performed. N+1 and / or the updated measurement time M N+1 Transmit a signal S according to a transmission time T snd In particular, the user equipment UE may determine a transmission time T snd Postpone the transmission time T p For example, the support signal S′ can be selected to have a target transmission time T t If the updated information is sent before the target transmission time T t If the signal is received before the transmission time T snd The target transmission time T t In such a case, the signal S may be transmitted using an updated value of the timing advance TA determined based on the updated information. The timing error parameter may then be updated by decreasing the timing error parameter value. On the other hand, if the updated information is selected to determine the target transmission time T t For example, a support signal S′ may be received before the target transmission time T t , and delay requirements do not allow the user equipment UE to forgo the very next scheduled time opportunity for the transmission of the signal S. snd The target transmission time T tIn such a case, the signal S may be transmitted using an updated value of the timing advance TA determined based on the final open-loop and closed-loop information. The timing error parameter may then be updated by increasing the timing error parameter value.

[0166] Figures 5, 6 and 7 further provide examples of transmitting a signal S to a base station BS using an updated value of the timing advance TA according to different embodiments of the present disclosure. Figures 5, 6 and 7 represent timelines of signals transmitted and received by the user equipment UE and signals from measurements performed by the user equipment UE. Signals and information received by the user equipment UE from other entities such as the base station BS and more generally from the network NW are represented by downward arrows pointing towards the timelines. Signals and information transmitted by the user equipment UE and measurements performed by the user equipment UE are represented by upward arrows pointing outwards from the timelines. The several represented transmission, reception and measurement steps are associated with respective times. In each of Figures 5, 6 and 7, the time T represents the current time T at which the proposed method is considered.

[0167] 5, 6 and 7, the user equipment UE plans to transmit a signal S to the base station BS at a current time T. As mentioned above, the signal S can be, for example, a data signal, an SR signal, and / or a BSR signal. t , T p is proposed to transmit a signal S. There are two time opportunities T t , T p 5, 6 and 7, in other possible embodiments, more or less time opportunities exist for transmitting a signal to the base station BS. The time opportunity for transmitting a signal S to the base station BS is at least as long as the target transmission time T t and the target transmission time T t A postponed transmission time T that is later than pIncludes:

[0168] Referring to FIG. 5, at the current time T, - The user equipment UE has received final assistance information associated with the last (or final) assistance time A0 from the network NW. After the user equipment UE has sent three uplink signals to the base station BS as represented by the three upward arrows, it has also received three Timing Advance Command (TAC) signals from the base station BS at respective command times C0, C1 and C2. In particular, such command times C0, C1 and C2 are calculated on the base station BS side and do not directly depend on the transmission times of the sent uplink signals. Such TAC signals are received by the user equipment UE as long as the user equipment UE sends uplink signals to the base station BS. The latest closed loop information is therefore associated with the final command time C2.

[0169] In other words, at the current time T, the user equipment UE has received a more recent (and therefore up-to-date) timing advance adjustment from the closed loop information relative to the timing advance adjustment from the open loop information.

[0170] In the context of this disclosure, at a current time T, the user equipment UE then receives a time opportunity T t , T p In particular, the time window for transmitting the signal S to the base station BS can be selected from among sndSuch selection may include, in the embodiment of Fig. 5, determining an updated assistance time A1 from which the user equipment UE can retrieve updated assistance information. The updated assistance time A1 may be specifically predicted by the user equipment UE based on the last assistance time A0 and a configured periodicity of the assistance information transmission. The configured periodicity of the assistance information transmission may be determined and / or calculated by the user equipment UE based on data related to the last assistance time A0. The data related to the last assistance time A0 may include several assistance times (not shown in Fig. 5) prior to the last assistance time A0. In the situation shown in Fig. 5, the user equipment UE determines whether the updated assistance time A1 is within the target transmission time T t After the postponed transmission time T p The user equipment UE predicts that the deferred transmission time T p It may also be determined that the measurement can be performed at a measurement time M0 earlier than 0. Such measurement time M0 may be specifically predicted or expected by the user equipment UE based on its hardware capabilities (e.g., the user equipment UE has the capability to perform such measurements whenever such measurements are required) and / or a time opportunity provided by the network NW (e.g., a measurement opportunity is provided to the user equipment UE at the measurement time M0).

[0171] In such a situation, the user equipment UE transmits a transmission time T snd Postpone the transmission time T p In other words, the next scheduled time opportunity to transmit the signal S (i.e., the target transmission time T t ), the user equipment UE may choose to transmit such a transmission at a later time opportunity (i.e., at a postponed transmission time T p ) to deliberately postpone the deadline.

[0172] Based on the updated assistance information associated with the updated assistance time A1 and the updated measurement performed at the updated measurement time M0, the user equipment UE determines a deferral time T p , the value used as the timing advance TA in the cell when transmitting a signal S in the cell.

[0173] In a particular embodiment, the TAC signals received at the respective command times C0, C1 and C2 may all indicate a large correction of the updated value used as the timing advance TA in the cell compared to the last value used by the user equipment UE as the timing advance in the cell. Such a large correction may indicate, for example, a timing advance value switch between 50 and 63 in each TAC signal. In such a case, the user equipment UE may update the transmission time T based on the requirement to make a significant timing advance correction. snd Postpone the transmission time T p Such a substantial timing advance correction can be quantified via open loop tuning.

[0174] In a particular embodiment, potential delay requirements and / or timing constraints to be observed by the user equipment UE when transmitting the signal S are determined to determine such a deferred transmission time T p If the condition is satisfied by transmitting a signal S at the transmission time T snd is the postponed transmission time T p For example, referring to FIG. 5, the timing constraints are selected such that the potential transmission deadlines T r The user equipment UE may be requested to transmit a signal S before

[0175] Referring to FIG. 6, before the current time T, The user equipment UE has received the last assistance information from the network NW at the last assistance time A0. The user equipment UE has performed the last measurement at the last measurement time M0. The user equipment UE has also received a last Timing Advance Command (TAC) signal from the base station BS at a last command time C0 after sending an uplink signal to the base station BS, as represented by an upward arrow. Such a last aiding time A0, a last measurement time M0 and a last command time C0 may be, for example, a valid time T0 that may be preset by the user equipment UE or transmitted to the user equipment UE. ths , and is therefore considered stale at the current time T. In other words, at the current time T, the user equipment UE determines that the last information from both the open-loop and closed-loop sources that allows updating of the value used as timing advance for transmitting the signal S is stale. Similarly, the time gap between the last command time C0 and the current time T can be compared with a pre-defined first gap threshold, and the time gap between each of the last aided time A0 and the last measured time M0 and the current time T can be compared with a pre-defined second gap threshold. For simplicity, such gap thresholds are assumed to be the time gaps between the current time T and the valid time T. ths In one embodiment, the time gap between the last assistance time A0 and the last measurement time M0 (also referred to as the third time gap) may also be compared to a preset third gap threshold.

[0176] The user equipment UE receives the configured time opportunity T t , T p , for transmitting the signal S to the base station BS. However, with reference to Fig. 6, since the last assistance information, measurements and TAC are considered to be stale, the user equipment UE determines that updated information is required to determine an accurate updated value to be used as timing advance in the cell when transmitting the signal S. In one embodiment, the user equipment UE may determine that updated information is required since a third time gap between the last assistance time A0 and the last measurement time M0 exceeds a pre-configured third gap threshold.

[0177] Thus, the user equipment UE transmits a signal S to the base station BS at any configured time opportunity T t , T p It can be determined at a current time T whether an uplink transmission can be sent to the base station BS at a time opportunity T' earlier than 0. Such an uplink transmission is predictable to the user equipment UE, for example if periodic reporting is performed by the user equipment UE.

[0178] In the situation of Fig. 6 (and provided that the user equipment UE has a time opportunity T' to do so), the user equipment UE can decide to send an auxiliary signal S' to the base station BS, as represented at time T' in Fig. 6. Such an auxiliary signal S' is different from the signal S.

[0179] After sending such an auxiliary signal S', the user equipment UE can potentially receive an updated TAC signal at an updated command time C1.

[0180] Based on such an updated TAC signal, the user equipment UE updates the value used as timing advance in the cell as described above and adjusts the target transmission time T according to the updated command time C1. t or postponed transmission time T p The transmission time T is selected to be either snd A signal S is transmitted at

[0181] In a particular embodiment, potential delay requirements and / or timing constraints to be respected by the user equipment UE when transmitting the signal S may be determined based on such a deferred transmission time T p If the condition is satisfied by transmitting a signal S at the transmission time T snd is the postponed transmission time T p For example, referring to FIG. 6, the timing constraints are selected such that the potential transmission deadlines T r The user equipment UE may be requested to transmit the signal S before (which may further allow for some internal processing time).

[0182] Referring to FIG. 7, prior to the current time T: - The user equipment UE has received the last assistance information from the network NW at the last assistance times A0 and A1. The user equipment UE has performed the last measurements at the last measurement times M0 and M1. After the user equipment UE sends an uplink signal to the base station BS, as represented by the upward arrow, the user equipment UE has also received a last Timing Advance Command (TAC) signal from the base station BS at a last command time C0. In particular, as represented in FIG. 7, the last command time C0 is earlier than the last aiding time A1.

[0183] With reference to FIG. 7, the last aiding information received at the last aiding time A1 is considered to indicate a large timing advance adjustment relative to the last timing advance value used by the user equipment UE in the cell (e.g., performing the last uplink signal). In other words, the self-correction parameter provided by the last aiding information is larger than the pre-configured self-correction threshold N ths,OL Furthermore, the last support time A1 is the effective time T ths Since the last such aiding information is prior to , the aiding information is considered to be out of date.

[0184] Thus, at the current time T, the user equipment UE determines that, based on such received last assistance information, a potentially significant timing correction is made to update the value used as the timing advance TA in the cell when transmitting the signal S. However, since such last assistance information is considered as stale by the user equipment UE at the current time T, such last assistance information cannot be suitable for determining an updated value to be used as the timing advance TA for transmitting the signal S.

[0185] Thus, in such a situation depicted in Fig. 7, the user equipment UE may determine a value of the support timing advance based on the last assistance information received at the last assistance time A1. The user equipment UE may then transmit a support signal S' to the base station BS using the value of the support timing advance (provided that the user equipment UE has the time opportunity to do so). Such a support timing advance value may in particular correspond to a current value of the timing advance determined by the user equipment at a time prior to the current time T based on the last information. Such a support signal S' may request the transmission of updated assistance information and / or an updated timing advance command and / or the configuration of a measurement gap (or time) for measurements, provided that such measurement gap is under the control of the network NW.

[0186] Upon receiving the updated assistance information at the updated assistance time A2, the user equipment UE can then determine an updated value of the timing advance TA used to transmit the signal S. The user equipment UE then determines the target transmission time T t or postponed transmission time T p The transmission time T is selected to be either snd A signal S is transmitted at

[0187] In a particular embodiment, the potential delay requirements and / or timing constraints to be observed by the user equipment UE when transmitting the signal S are determined as a deferred transmission time T p If the condition is satisfied by transmitting a signal S at the transmission time T snd is such a postponed transmission time T p For example, referring to FIG. 7, the timing constraints are selected such that the potential transmission deadlines T r The user equipment UE may be requested to transmit a signal S before

Claims

1. 1. A method performed by a user equipment (UE) for transmitting a signal using a timing advance update to a base station, the user equipment (UE) being connected to the base station, the base station corresponding to a cell supported by a non-geostationary orbit satellite of a satellite communications network, the method comprising: Data relating to assistance information received by the user equipment associated with an assistance time; data relating to measurements taken by the user equipment associated with a measurement time; data relating to a timing advance command received from the satellite communications network associated with a command time; Determine the value of the timing advance based on The method comprises: The transmission time of the signal is at least a target transmission time of said signal; a deferred transmission time of the signal, the deferred transmission time being later than the target transmission time; Choose from among transmitting the signal to the base station at the transmit time using the updated timing advance; Including, The selected transmission time is at least: Time-related parameters; data relating to a final timing advance command associated with a final command time; data relating to the last measurement associated with the last measurement time; data relating to last assistance information associated with a last assistance time; Data relating to the last measurement time; and data relating to the last command time; data relating to the time of last assistance; The method is selected based on a combination of at least two factors from the following:

2. sending a support signal to the base station that is different from the signal; The method of claim 1 , wherein the supporting signals are transmitted at supporting times that depend on the target transmission times of the signals.

3. data associated with the aiding information providing self-correction parameters and data associated with the measurements are used by the user equipment to determine a value for the timing advance; The sending of the support signal shall comply with the following criteria: A first time gap between the last command time and the current time exceeds a first preset gap threshold; or the final command time precedes the final assistance time; and a second time gap between the last assistance time and / or the last measurement time and the current time exceeds a second pre-defined gap threshold; or the self-correction parameter determined based on the data related to the final assistance information and / or the data related to the final measurement value exceeds a preset self-correction threshold value; The method of claim 2 further based on at least one of

4. The time related parameters relate to the validity time of the data used to determine the value of the timing advance, and the sending of the support signal is based on the following criteria: any one of the last command time, the last measurement time, and the last assistance time is earlier than the validity time; The method according to claim 2 or 3, further based on

5. The support signal is sent using a timing advance support value, the timing advance support value comprising at least The time-related parameters; and data associated with said final timing advance command; Data relating to the final measurements; and Data related to the final support information; Data relating to the last measurement time; and data relating to the last command time; data relating to the time of last assistance; The method according to claim 2 or 3, wherein the determination is based on a combination of at least two factors from among:

6. The support signal includes at least an uplink reference signal, such as a sounding reference signal; A control signal; Buffer status report, A scheduling request; The method according to claim 2 or 3, wherein the method is one of the following:

7. The transmission time is Data relating to the updated assistance information is predicted to be associated with an updated assistance time that falls between the target transmission time and the deferred transmission time; and / or data associated with the updated measurement is determined to be associated with an updated measurement time that falls between the target transmission time and the deferred transmission time; The method according to any one of claims 1 to 3, wherein the deferred transmission time is selected if

8. data associated with a timing advance command providing a correction parameter is used by the user equipment to determine a value for the timing advance; The transmission time is a gap between the last command time and the current time is less than a first preset gap threshold; and the correction parameter determined based on data associated with the final timing advance command exceeds a preset correction threshold; and data associated with updated assistance information is predicted to be associated with an updated assistance time that is later than the final assistance time and later than the current time, the updated assistance time being between the target transmission time and the deferred transmission time; and / or data associated with updated measurement values ​​is determined to be associated with an updated measurement time that is later than the final measurement time and later than the current time, the updated measurement time being between the target transmission time and the deferred transmission time. The method according to any one of claims 1 to 3, wherein the deferred transmission time is selected if

9. 8. The method of claim 7, wherein determining an updated value of the timing advance used to transmit the signal is based on at least the updated aiding information associated with the updated aiding time and / or the updated measurement value associated with the updated measurement time.

10. The user equipment updates a timing error parameter related to an estimate of an error when determining the value of the timing advance, the method comprising: updating the timing error parameter if the transmit time is selected to be the target transmit time; The method of any one of claims 1 to 3, further comprising:

11. Data associated with a timing advance command providing a correction parameter is used by the user equipment to determine a value of the timing advance, and data associated with the assistance information providing a self-correction parameter and data associated with measurements are used by the user equipment to determine a value of the timing advance; The updating of the timing error parameter includes: a gap between the last command time and the current time is less than a first preset gap threshold; and the correction parameter determined based on data associated with the final timing advance command exceeds a preset correction threshold; and data associated with the updated assistance information is predicted to be associated with an updated assistance time that is later than the last assistance time, the updated assistance time being later than the deferred transmission time; and / or data associated with the updated measurement values ​​is determined to be associated with an updated measurement time that is later than the last measurement time, the updated measurement time being later than the deferred transmission time. increasing the timing error parameter if and / or the gap between the last command time and the current time is less than a preset alternative first gap threshold; and the correction parameter determined based on data associated with the final timing advance command is less than a preset alternative correction threshold; or the last command time precedes one of the last assistance time and the last measurement time; and the self-calibration parameter determined based on the data associated with the final assistance information and / or the data associated with the final measurement value is less than a preset alternative self-calibration threshold value; and If the gap between the last assistance time and / or the last measurement time and the current time is less than a preset alternative second gap threshold, Reducing the timing error parameter; The method of claim 10, comprising:

12. The method according to any one of claims 1 to 3, wherein the time-related parameter is associated with a transmission deadline time, and the transmission time of the signal is selected to precede the transmission deadline time.

13. 4. The method of claim 1, further comprising performing an updated measurement at an updated measurement time if a third time gap between the last measurement time and the last assistance time exceeds a preset third gap threshold.

14. A user equipment configured to transmit a signal using a timing advance update to a base station, the user equipment being connected to the base station, the base station corresponding to a cell supported by a non-geostationary orbit satellite of a satellite communications network; The user equipment comprises at least Data relating to assistance information received by the user equipment associated with an assistance time; data relating to measurements taken by the user equipment associated with a measurement time; data relating to a timing advance command received from the satellite communications network associated with a command time; Based on this, the value of the timing advance can be calculated. The user equipment includes a processor and a non-transitory computer-readable medium containing instructions stored thereon that, when executed by the processor, The transmission time of the signal is a target transmission time of said signal; a postponed transmission time that is later than the target transmission time; Choose from among transmitting the signal to the base station at the transmit time using the updated timing advance; and configuring the user equipment to: The selected transmission time includes at least Time-related parameters; data relating to a final timing advance command associated with a final command time; data relating to the last measurement associated with the last measurement time; data relating to last assistance information associated with a last assistance time; Data relating to the last measurement time; and data relating to the last command time; data relating to the time of last assistance; The user equipment is selected based on a combination of at least two factors from among:

15. A computer program product comprising program instruction code stored on a computer readable medium for carrying out the method of any one of claims 1 to 3.

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