Synchronization signal indicator

Abstract

An arrangement for non-terrestrial communication networks, where a network node providing a cell transmits an indicator of upcoming change in the transmission of synchronization signals to a user equipment. Based on the received indicator the user equipment may determine whether to change the cell or to camp in the current cell. Similar indicator may be used during cell change procedure when determining whether to access the cell found in the cell search procedure or to re-initiate the cell search procedure for finding another cell.

Description

SYNCHRONIZATION SIGNAL INDICATORTECHNICAL FIELD

[0001] The disclosure relates generally to wireless communications and, more particularly but not exclusively, to a solution for providing a synchronization signal indicator.BACKGROUND

[0002] Non-terrestrial networks (NTN) can provide a large coverage area to user equipment otherwise unreachable by terrestrial cellular networks, or connect loT devices globally. This includes areas, such as sea, desert and other remote areas to where a terrestrial cellular network is not technically or economically feasible. In an NTN system, a satellite may comprise functionality of a standard network protocol (i.e., 5G, 6G or beyond) base station.

[0003] Different types of satellite orbits exist, for example, low earth orbit (LEO) satellites orbiting approximately 600 kilometres above the earth, and a typical beam footprint size for a LEO satellite can be between a 10 - 2500 kilometre radius. Thus, they cover large areas on the Earth and may include multiple countries.

[0004] In existing system with low earth orbit (for example, with 600 km altitude and 50 km beam footprint) satellite downlink coverage ratio can be improved drastically, for example, if synchronization signal block (SSB) periodicity is increased from 20 milliseconds to 80 milliseconds. Further, many times the coverage ratio can be improved even more if the SSB periodicity is increased from 20 ms to 320 ms.

[0005] The SSB periodicity can be configured for each cell, i.e., a serving cell and neighboring cells, and appropriate measurement periodicity can be configured according to channel conditions, and it helps user equipment to avoid unnecessary measurements and reduces power consumption.SUMMARY

[0006] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

[0007] Example embodiments of the present disclosure enable to improve mobility performance and reduce user equipment energy consumption. Furthermore, the embodiments may reduce the traffic load in the network. These and other benefits may be achieved by the features of the independent claims. Further example embodiments are provided in the dependent claims, the description, and the drawings.

[0008] In the following disclosure an arrangement for non-terrestrial communication networks, where a network node providing a cell transmits an indicator of upcoming change in the transmission of synchronization signals to a user equipment. Based on the received indicator the user equipment may determine whether to change the cell or to camp in the current cell. Similar indicator may be used during cell change procedure when determining whether to access the cell found in the cell search procedure or to re-initiate the cell search procedure for finding another cell. The indicator of upcoming change in the transmission of synchronization signals in a cell allows UEs (e.g. UEs that are not connected / camping in the cell associated with the indicator) to assess whether the cell is suitable for registration / re-selection / active connection without acquiring downlink (DL) synchronization. When the UE does not need to acquire DL synchronization (i.e., no acquisition of system information block 1 (SIB1) or other system information (OSI)), reduces UE’s energy consumption, and may improve IDLE and CONNECTED mobility performance. Also, the traffic load in the network may be reduced when the UE does not select / connect to one cell and move to another one right away.

[0009] According to a first aspect, a user equipment is disclosed. The user equipment, comprises at least one processor; and at least one memory storing instructions which, when executed by the at least one processor, cause the user equipment at least to: receive, from a network node of a non-terrestrial network in a broadcast block associated with a synchronization signal, an indicator of an upcoming change in the transmission of synchronization signals in a cell provided by the network node or by another network node of the non-terrestrial network; and determine, based at least partly on the indicator, a cell for camping or for accessing to.

[0010] In an embodiment of the first aspect the instructions, when executed by the at least one processor, further cause the user equipment at least to, while in idle mode: perform a cell search procedure based on the received indicator of the upcoming change in the transmission of synchronization signals.

[0011] In an embodiment of the first aspect the instructions, when executed by the at least one processor, further cause the user equipment at least to detect a cell provided bythe other network node; receive, from the other network node of the non-terrestrial network in a broadcast block an indicator of an upcoming change in transmission of synchronization signals in a cell provided by the other network node; and based on the received indicator, initiate a mobility procedure with the other network node.

[0012] In an embodiment of the first aspect the mobility procedure is one of: a reselection of the cell provided by the other network node for camping; an access procedure with the other network node; a registration procedure with the other network node.

[0013] In an embodiment of the first aspect the cell provided by the network node is the serving cell.

[0014] In an embodiment of the first aspect the instructions, when executed by the at least one processor, further cause the user equipment at least to determine, when in connected mode, based on the indicator of an upcoming change in the transmission of synchronization signals that the serving cell will switch off; and based on the determining that the serving cell will switch off, re-acquire system information from the serving cell before the serving cell switches off and move to idle mode.

[0015] In an embodiment of the first aspect the instructions, when executed by the at least one processor, further cause the user equipment at least to determine based on the received indicator of the upcoming change in the transmission of synchronization signals of the serving cell whether there is a need for a cell change.

[0016] In an embodiment of the first aspect the instructions, when executed by the at least one processor, further cause the user equipment at least to determine that there is no need for a cell change; and based on determining that there is no need for a cell change, determining the serving cell for camping or for accessing to.

[0017] In an embodiment of the first aspect the instructions, when executed by the at least one processor, further cause the user equipment at least to determine that there is the need for a cell change; and initiate, based on determining that there is the need for the cell change, a procedure for the cell change.

[0018] In an embodiment of the first aspect the broadcast block and the associated synchronization signal is a synchronization signal block, SSB.

[0019] In an embodiment of the first aspect the broadcast block is transmitted on a physical broadcast channel.

[0020] In an embodiment of the first aspect the broadcast block is transmitted in a master information block.

[0021] In an embodiment of the first aspect the upcoming change in the transmission of synchronization signals comprises termination of transmission of synchronization signals.

[0022] In an embodiment of the first aspect the upcoming change in the transmission of synchronization signals is a change in the periodicity of the synchronization signals.

[0023] In an embodiment of the first aspect the determining, based at least partly on the indicator, a cell for camping or for accessing to comprises comparing the received indicator of an upcoming change in the transmission of synchronization signals with a threshold value.

[0024] In an embodiment of the first aspect the indicator of an upcoming change in the transmission of synchronization signals is an integer.

[0025] In an embodiment of the first aspect A user equipment according to claim 16, wherein the integer indicates the number of broadcast blocks before the upcoming change is activated.

[0026] In an embodiment of the first aspect the integer is a flag indicating a change in periodicity of the synchronization signals.

[0027] In an embodiment of the first aspect the integer is a pointer to a table comprising information with regard an upcoming change in the transmission of synchronization signals.

[0028] In an embodiment of the first aspect the indicator of an upcoming change in the transmission of synchronization signals indicates one of: time left before the upcoming change; or an absolute time point of the upcoming change.

[0029] In an embodiment of the first aspect wherein the indicator of an upcoming change in the transmission of synchronization signals further comprises an offset indicating time between the last synchronization signal and the change in the transmission of synchronization signals.

[0030] According to a second aspect a network node of a non -terrestrial network is disclosed. The network node of a non-terrestrial network comprises at least one processor; and at least one memory storing instructions which, when executed by the at least one processor, cause the network node at least to: generate an indicator of an upcoming change in the transmission of synchronization signals in a cell provided by the network node or by another network node of the non-terrestrial network; and transmit, from the network node of a non-terrestrial network in a broadcast block associated with a synchronization signal, the indicator of an upcoming change in the transmission ofsynchronization signals in a cell provided by the network node or by another network node of the non-terrestrial network.

[0031] In an embodiment of the second aspect the broadcast block and the associated synchronization signal is a synchronization signal block, SSB.

[0032] In an embodiment of the second aspect the broadcast block is transmitted on a physical broadcast channel.

[0033] In an embodiment of the second aspect the broadcast block is transmitted in a master information block.

[0034] In an embodiment of the second aspect the upcoming change in the transmission of synchronization signals comprises termination of transmission of synchronization signals.

[0035] In an embodiment of the second aspect the upcoming change in the transmission of synchronization signals is a change in the periodicity of the synchronization signals.

[0036] In an embodiment of the second aspect the indicator of an upcoming change in the transmission of synchronization signals is an integer.

[0037] In an embodiment of the second aspect the integer indicates the number of broadcast blocks before the upcoming change is activated.

[0038] In an embodiment of the second aspect the integer is a flag indicating a change in periodicity of the synchronization signals.

[0039] In an embodiment of the second aspect the integer is a pointer to a table comprising information with regard an upcoming change in the transmission of synchronization signals.

[0040] In an embodiment of the second aspect the indicator of an upcoming change in the transmission of synchronization signals indicates one of: time left before the upcoming change; or an absolute time point of the upcoming change.

[0041] In a third aspect a user equipment is disclosed. In the third aspect the user equipment comprises at least one processor; and at least one memory storing instructions which, when executed by the at least one processor, cause the user equipment at least to: receive, from a network node of a non-terrestrial network in a broadcast block associated with a synchronization signal, an indicator of an upcoming change in the transmission of synchronization signals in a cell provided by the network node or by another network node of the non-terrestrial network, wherein the indicator of an upcoming change in thetransmission of synchronization signals is an integer; and determine, based at least partly on the indicator, a cell for camping or for accessing to.

[0042] In an embodiment of the third aspect the determining, based at least partly on the indicator, a cell for camping or for accessing to comprises comparing the received indicator of an upcoming change in the transmission of synchronization signals with a threshold value.

[0043] In an embodiment of the third aspect the instructions, when executed by the at least one processor, further cause the user equipment at least to, while in idle mode: perform a cell search procedure when the received indicator of the upcoming change in the transmission of synchronization signals is smaller than the threshold value.

[0044] In an embodiment of the third aspect the instructions, when executed by the at least one processor, further cause the user equipment at least to: detect a cell provided by the other network node; receive, from the other network node of the non-terrestrial network in a broadcast block an indicator of an upcoming change in transmission of synchronization signals in a cell provided by the other network node; and based on the received indicator, initiate a mobility procedure with the other network node when the indicator received from the other network node is at least the threshold value.

[0045] In an embodiment of the third aspect the broadcast block and the associated synchronization signal is a synchronization signal block, SSB.

[0046] In an embodiment of the third aspect the broadcast block is transmitted in a master information block.

[0047] In an embodiment of the third aspect the upcoming change in the transmission of synchronization signals comprises termination of transmission of synchronization signals.

[0048] In an embodiment of the third aspect the upcoming change in the transmission of synchronization signals is a change in the periodicity of the synchronization signals.

[0049] In an embodiment of the third aspect the integer indicates the number of broadcast blocks before the upcoming change is activated.

[0050] In an embodiment of the third aspect the integer is a flag indicating a change in periodicity of the synchronization signals.

[0051] In an embodiment of the third aspect the integer is a pointer to a table comprising information with regard an upcoming change in the transmission of synchronization signals.

[0052] In a fourth aspect a network node of a non-terrestrial network is disclosed. The network node comprises at least one processor; and at least one memory storing instructions which, when executed by the at least one processor, cause the network node at least to: generate an indicator of an upcoming change in the transmission of synchronization signals in a cell provided by the network node or by another network node of the non-terrestrial network, wherein the indicator of an upcoming change in the transmission of synchronization signals is an integer; and transmit, from the network node of a non-terrestrial network in a broadcast block associated with a synchronization signal, the indicator of an upcoming change in the transmission of synchronization signals in a cell provided by the network node or by another network node of the non-terrestrial network.

[0053] In an embodiment of the fourth aspect the integer indicates the number of broadcast blocks before the upcoming change is activated.

[0054] In an embodiment of the fourth aspect is a flag indicating a change in periodicity of the synchronization signals.

[0055] In an embodiment of the fourth aspect the integer is a pointer to a table comprising information with regard an upcoming change in the transmission of synchronization signals.

[0056] In a fifth aspect a user equipment is disclosed. The user equipment comprises at least one processor; and at least one memory storing instructions which, when executed by the at least one processor, cause the user equipment at least to: receive, from a network node of a non-terrestrial network in a broadcast block associated with a synchronization signal, an indicator of an upcoming change in the transmission of synchronization signals in a cell provided by the network node or by another network node of the non-terrestrial network, wherein the indicator of an upcoming change in the transmission of synchronization signals indicates one of: time left before the upcoming change; or an absolute time point of the upcoming change; and determine, based at least partly on the indicator, a cell for camping or for accessing to.

[0057] In an embodiment of the fifth aspect the determining, based at least partly on the indicator, a cell for camping or for accessing to comprises comparing the received indicator of an upcoming change in the transmission of synchronization signals with a threshold value.

[0058] In an embodiment of the fifth aspect the instructions, when executed by the at least one processor, further cause the user equipment at least to, while in idle or inactivemode: perform a cell search procedure when the received indicator of the upcoming change in the transmission of synchronization signals is smaller than the threshold value.

[0059] In an embodiment of the fifth aspect the instructions, when executed by the at least one processor, further cause the user equipment at least to: detect a cell provided by the other network node; receive, from the other network node of the non-terrestrial network in a broadcast block an indicator of an upcoming change in transmission of synchronization signals in a cell provided by the other network node; and based on the received indicator, initiate a mobility procedure with the other network node when the indicator received from the other network node is at least the threshold value.

[0060] In an embodiment of the fifth aspect the mobility procedure is one of: a reselection of the cell provided by the other network node for camping; an access procedure with the other network node; a registration procedure with the other network node.

[0061] In an embodiment of the fifth aspect the cell provided by the network node is the serving cell.

[0062] In an embodiment of the fifth aspect the instructions, when executed by the at least one processor, further cause the user equipment at least to: determine, when in connected mode, based on the indicator of an upcoming change in the transmission of synchronization signals that the serving cell will switch off; and determine that the serving cell will switch off when the received indicator of the upcoming change in the transmission of synchronization signals is smaller than the threshold, re-acquire system information from the serving cell before the serving cell switches off and move to idle mode.

[0063] In an embodiment of the fifth aspect the instructions, when executed by the at least one processor, further cause the user equipment at least to: determine when the received indicator of the upcoming change in the transmission of synchronization signals is smaller than the threshold that there is a need for a cell change.

[0064] In an embodiment of the fifth aspect the broadcast block and the associated synchronization signal is a synchronization signal block, SSB.

[0065] In an embodiment of the fifth aspect the indicator of an upcoming change in the transmission of synchronization signals or a mapping of the indicator of an upcoming change in the transmission of synchronization signals is transmitted on a physical broadcast channel.

[0066] In an embodiment of the fifth aspect the indicator of an upcoming change in the transmission of synchronization signals or a mapping of the indicator of an upcoming change in the transmission of synchronization signals is transmitted in a master information block.

[0067] In an embodiment of the fifth aspect the upcoming change in the transmission of synchronization signals comprises termination of transmission of synchronization signals.

[0068] In an embodiment of the fifth aspect the upcoming change in the transmission of synchronization signals is a change in the periodicity of the synchronization signals.

[0069] In an embodiment of the fifth aspect the indicator of an upcoming change in the transmission of synchronization signals further comprises an offset indicating time between the last synchronization signal and the change in the transmission of synchronization signals.

[0070] In a sixth aspect a network node of a non-terrestrial network is disclosed. The network node comprises at least one processor; and at least one memory storing instructions which, when executed by the at least one processor, cause the network node at least to: generate an indicator of an upcoming change in the transmission of synchronization signals in a cell provided by the network node or by another network node of the non-terrestrial network, wherein the indicator of an upcoming change in the transmission of synchronization signals indicates one of: time left before the upcoming change; or an absolute time point of the upcoming change; and transmit, from the network node of a non-terrestrial network in a broadcast block associated with a synchronization signal, the indicator of an upcoming change in the transmission of synchronization signals in a cell provided by the network node or by another network node of the non-terrestrial network.

[0071] Example embodiments of the present disclosure can thus provide apparatuses, methods, computer programs, computer program products, or computer readable media for improving various aspects of wireless tethering. Any example embodiment may be combined with one or more other example embodiments. These and other aspects of the present disclosure will be apparent from the example embodiment s) described below. According to some aspects, there is provided the subject matter of the independent claims. Some further aspects are defined in the dependent claims.DESCRIPTION OF THE DRAWINGS

[0072] The accompanying drawings, which are included to provide a further understanding of the example embodiments and constitute a part of this specification, illustrate example embodiments and, together with the description, help to explain the example embodiments. In the drawings:

[0073] FIG. 1 illustrates a non-terrestrial network system, wherein example embodiments may be applied in;

[0074] FIG. 2 illustrates a state machine according to an example embodiment;

[0075] FIGS. 3A and 3B illustrates a method according to an example embodiment;

[0076] FIG. 4 illustrates a method according to an example embodiment;

[0077] FIG. 5 illustrates a signalling diagram according to an example embodiment;

[0078] FIG. 6 illustrates a signalling diagram according to an example;

[0079] FIG. 7 illustrates a signalling diagram according to an example;

[0080] FIG. 8 illustrates a user equipment according to an example embodiment; and

[0081] FIG. 9 illustrates illustrates a network node according to an example embodiment.

[0082] Like references are used to designate like parts in the accompanying drawings.DETAILED DESCRIPTION

[0083] Reference will now be made in detail to example embodiments, examples of which are illustrated in the accompanying drawings. The detailed description provided below in connection with the appended drawings is intended as a description of the present examples and is not intended to represent the only forms in which the present example may be constructed or utilized. The description sets forth the functions of the example and the sequence of steps for constructing and operating the example. However, the same or equivalent functions and sequences may be accomplished by different examples.

[0084] In the following disclosure network nodes transmitting signals to a plurality of user / client devices is discussed. User devices can be ordinary mobile telephones, other personal computing devices or any user equipment. In addition to conventional mobile devices user devices can be internet of things devices that can be connected wirelessly to a network node providing an indicator for an upcoming change in synchronization signals. The network node may be any wireless base station or transmitting station that is locatedin a satellite of a non-terrestrial network configured to provide a network access for the connected devices. On example of a network node is a base station of 5G network, also known as Next-Generation Node B, also known as gNodeB. However, the present embodiments are not limited to gNodeB and can be applied to many other arrangements that are or could be using an indicator for an upcoming change in synchronization signals. Thus, any reference to expressions specific to 5G networks should be understood as examples given in view of the existing technology.

[0085] Fig 1 illustrates an example of a non -terrestrial network (NTN) system 100, in which the various example embodiments discussed below may be applied in. A satellite 110 provides a coverage area 112 comprising a plurality of beam footprints 114. A service link 122 is established with a user equipment 150 (UE 150) residing in the coverage area 112 for communications. A feeder link 124 is established between the satellite 110 and a gateway 130, and the gateway 130 may have access to a general data network 140, for example, the internet. For example, the gateway 130 may be connected to the core network, through which the connection to the internet 140 is arranged. Alternatively, in a so called transparent architecture, the base station, such as gNodeB of a 5G network, can be on the ground. In another example architecture, the base station is onboard of the satellite (the regenerative architecture).

[0086] A beam footprint 114, i.e. a cell, may be, for example, inactive or active, or as in other example cases, the cell 114 may be in a low-activity state, an inactive state or a high-activity state.

[0087] A coverage ratio of the satellite 110, or any other network node, for example, can be expressed as a number of beams in an active state against the total number of beam footprints within the coverage area 112.

[0088] In the NTN system 100, the satellite 110 may comprise functionality of a standard mobile communication network (for example, 5G, 6G or beyond) base station.

[0089] Different types of satellite orbits exist, for example, low earth orbit (LEO) satellites orbiting approximately 600 kilometres above the earth, and a typical beam footprint size for a LEO satellite may be, for example, between a 10 to 2500 kilometre radius. Due to low altitude of satellites in LEO, a satellite may move with a speed of approximately 7.5 km / s relative to the earth, and earth-fixed cells (EFC) and earthmoving cells (EMC) can be considered. The EFC entails that the satellite continuously adjusts satellite beam pointing direction to fix the cell and beam to a specific point on theearth, while the EMC entails that the satellite beam pointing di-rection is fixed and thus the beam footprint (i.e., a radio cell) is moving on the earth.

[0090] One objective in, for example, new radio (NR) applications is to ensure that all UEs can be served across the satellite beam footprints while maximizing the efficient use of satellite’s available resources. These enhancements may be needed to accommodate satellite payload constraints (i.e., limited power / energy on board) while maximizing the number of beams that can be active simultaneously.

[0091] FIG. 2 illustrates an example state machine 200, which can be used to denote a level of activity or inactivity in a cell provided by a network node (or satellite etc.). The number of states may be higher or lower than three, and the three states is given only as one possible example to express level of cell activity. The state machine 200 may comprise N1 state 210, in which the cell is considered “off’ (i.e., inactive) and no channel is active and initial access is not possible. The state machine 200 may comprise N2 state 220, in which common control can be active (for example, reference signals, SSB, random access channel (RACH), system information block (SIB), paging, master information block (MIB), other broadcast block or similar) and the common control can comprise extended periodicity for the control signals. N2 state 220 can be considered as “partially- active” or the like and may in one example allow the cell to receive signalling such as Random Access preamble, but not transmit user plane data / traffic. The state machine 200 may further comprise N3 state 230, denoting the “active” state (or “fully -active” state). In the N3 state 230, control signalling and user traffic are both active. The arrows illustrated in FIG. 2 illustrate how the cell can move between the states in the state machine 200.

[0092] At user equipment (UE) side, UEs should meet certain requirements for an initial transmission provided that at least one broadcast block comprising synchronization signals is available at the UE during a certain time period, such as 160 ms.

[0093] A broadcast block carrying synchronization signals, such as an SSB, is transmitted periodically by the base station in the downlink direction. Transmission periodicity of the broadcast blocks can be configured for each cell, for example, as 5, 10, 20, 40, 80 or 160 ms. The UE does not, however, need to measure the cell signal with the periodicity of the broadcast block. The SSB and appropriate measurement periodicity can be configured according to channel conditions. This helps the UE to avoid unnecessary requirements and to reduce the power consumption of the UE. An S SB-based radio resource management measurement timing configuration (SMTC) window can be usedto notify the UE regarding measurement periodicity and timings of SSBs that the UE can use for measurements.

[0094] SMTC window periodicity can be set in the same range as the SSB periodicity (i.e., 5, 10, 20, 40, 80, or 160 ms) and a window duration can be 1, 2, 3, 4, or 5 ms, according to the number of SSBs transmitted on the cell being measured. Different cells can be measured with a different window periodicity and a different window duration. When a UE has been notified of an SMTC window by a base station, it attempts to detect and measure the SSBs within that window and reports the measurements back to the base station. The UE does not measure any SSB index outside of the STMC window.

[0095] Cell measurement activity (for example, SMTC window) can be configured to use a first periodicity (for example, 20 ms) in certain time periods and a second periodicity (e.g., 80 - 320 ms) in other time periods, and in some other time periods the cell can be completely off. As described above, two adjacent cells may be configured with different measurement activity “patterns” or “sequences” (for example, a sequence of the states in the state machine 200), which may lead to some undesired issues for neighboring cell measurements.

[0096] With the introduction of different activity levels of the cell, as illustrated with the N1 , N2 and N3 states, it is commonly assumed that the broadcast block and associated synchronization signal frequency will change depending on the cell activity state. As mentioned in the above, the number of states may be higher. The higher number of states may be used, for example, if the states are differentiated according to the broadcast block periodicity. For instance, an NTN cell, depending on traffic demand, may be configured to use a broadcast block periodicity of 20 ms in certain periods, while in other periods it may use longer broadcast block periodicity (e.g., 80-640ms). In other periods, where there is no UE activity, the cell may completely switch off (i.e., no broadcast block transmission). As explained in the above, two adjacent cells may be configured with different state patterns. In addition to the above explained state changes, it is possible that the frequency of broadcast blocks or the periodicity of synchronization signal transmissions change also without a state change.

[0097] In some example embodiments, network cells (network nodes providing the cells) may coordinate, with or without network operation & management (O&M) system, transmission of synchronization signals in terms of a pattern or sequence. For example, the pattern or sequence may define that a first periodicity for the transmission of synchronization signals occurs for a certain time duration Y-X, where Y may be aperiodicity of an activity period X. For the remainder of the period, the network may transmit broadcast blocks with a second broadcast block periodicity or a third broadcast block periodicity or it may stop transmitting the broadcast blocks.

[0098] In the following disclosure an indicator indicating an upcoming change in the transmission of synchronization signals or broadcast blocks carrying synchronization signals is used to facilitate more dynamic behaviour of the network. The indicator is transmitted in a broadcast block, which may be SSB or similar. The indicator can indicate how much there is time or how many transmissions there are left before the current periodicity of transmitting broadcast blocks carrying one or more synchronization signals changes. The time may be indicated in several different ways, for example, as a time interval before the change, as a moment of time when the change occurs, as a number of transmitted broadcast blocks before the change, as a pointer to a table indicating the moment of change or similar.

[0099] The indicator is transmitted in a broadcast block carrying one or more synchronization signals. In one example, the indicator may be included in the Master Information Block or in the Physical Broadcast Channel of the broadcast block. The indicator may be carried for the serving cell and / or one or more neighbouring cells. In the following disclosure the broadcast block should be understood as a (one) broadcast block or a burst of broadcast blocks. In a burst of broadcast blocks some of the broadcast blocks may carry information with regard to different cells. Thus, it is possible for the UE to acquire, via the broadcast blocks, information of the upcoming change in the transmission of synchronization signals for the serving cell and one or more neighbouring cells or other cells.

[0100] In the following, figures 3 - 7 illustrate methods and signalling charts of example embodiments how the indicator of an upcoming change in synchronization signals may be used in improving non-terrestrial networks. In the examples the indicator of an upcoming change in synchronization signals facilitates the user equipment to maintain connectivity even when the network is optimizing the coverage and power consumption by activating and deactivating cells. The following examples should be understood as examples and the indicator may be used also in other embodiments similar to the disclosed ones.

[0101] FIG. 3A illustrates a method according to an example embodiment. In the method a user equipment is configured to communicate with a network node of a nonterrestrial network. The network node transmits broadcast blocks to the user equipment.Among the broadcast blocks the user equipment receives, step 300, a broadcast block associated with a synchronization signal. The received broadcast block comprises an indicator of an upcoming change in the transmission of synchronization signals. The indicator may be related to the cell provided by the network node from which the indicator is received. Instead of the network node, the indicator of the upcoming change in the transmission of synchronization signals may be related to another cell, such as a neighbouring cell. It is possible, that the indicator is received for one or more neighbouring cell or other cells that are located in the vicinity of the serving cell. The broadcast block carrying the synchronization signals may be a single broadcast block or a group of broadcast blocks. In a group of broadcast blocks each of the broadcast blocks in the group may comprise one or more indicators. The indicators may be for different cells depending on the configuration of the network.

[0102] After receiving an indicator of an upcoming change in the transmission of synchronization signals for a cell, the user equipment determines a cell for camping or for accessing to, step 302. The user equipment may receive an indicator for the serving cell. Based on the value of the received indicator, the user equipment determines what to do next. If the value indicates that there is no need for a change of the serving cell, the user equipment may decide to do nothing. If the value indicates that there is an upcoming change in the transmission of synchronization signals, the user equipment may react to the upcoming change. The user equipment may decide to camp in the cell or to search for a new cell that can be accessed. The indicating value may be, for example, a number of remaining transmissions or remaining transmission time, which is then compared to a threshold value. When deciding whether there is a need for a change, the user equipment compares the value with a threshold value. If the value exceeds a threshold value, or alternatively is at least the threshold value, then the user equipment may decide to do nothing.

[0103] FIG. 3B illustrates a method according to an example embodiment. In the method a user equipment is configured to receive an indicator of an upcoming change of transmission of synchronization signals, step 310. The indicator is typically received in a broadcast block, such as an SSB in a 5G network or similar. The indicator can be received for a serving cell and / or one or more other cells. Based on the received indicator the user equipment may decide to maintain the connection to the current serving cell as it is, change the connection characteristics or search a new cell, step 312.

[0104] In the example of FIG. 3B the user equipment performs a cell search procedure, step 314. In the cell search procedure the user equipment starts scanning radio frequency channels looking for a cell to connect to. It is possible that the user equipment detects a plurality of different cells during the cell search procedure. After detecting a cell to connect, the user equipment receives an indicator of an upcoming change in the transmission of synchronization signals in the detected cell, step 318.

[0105] Based on the received indicator the user equipment determines whether the found / detected cell is suitable for accessing, step 320. If the indicator indicates that there is an upcoming change soon, the user equipment may decide to search for another cell. This may be done by returning to the cell search procedure, step 314, or by using the results of the earlier cell search and to detect a cell provided by another network node from the earlier cell search results. If the cell is suitable for accessing, then, based on the received indicator, the user equipment initiates a mobility procedure with another network node for accessing the detected cell, step 322.

[0106] FIG. 4 illustrates a method according to another embodiment. In the embodiment the user equipment receives an indicator of upcoming change in the transmission of synchronization signals from the serving cell, step 400. The indicator is received in a broadcast block, such as an SSB and indicates when a change in the transmission of synchronization signals of the serving cell occurs. The received indicator may indicate the upcoming change as a number of broadcast cells before the change, as a time interval before the change, as an absolute moment of time or similar. The indicator may include complete information of the upcoming change in the broadcast block or the indicator may be a pointer or a mapping to a table indicating the change. The indicator may include additional information about the change, such as how the synchronization signals are sent after the change. Furthermore, it is possible that the indicator is left empty or indicates that currently there is no planned change.

[0107] In the example of FIG. 4 the user equipment determines that the change is such that serving cell will switch off, step 402. Based on determining that the serving cell will switch off, the user equipment autonomously re-acquires the system information from the serving cell, step 404, right before the switch off. This way the UE has up-to-date cell reselection information. In the example of FIG. 4, as well as in the other examples, the determination may include a threshold value. The threshold valued may be defined in a specification, configured by the network or be a user equipment internal value. The indicator is compared with the threshold value and if the threshold value indicates thatthe upcoming change is coming soon, then the determination of the following actions is initiated. The indicator may be compared as such, or the indicator may be used in determining a value that is compared with the threshold. For example, if the indicator indicates an absolute moment of time, then, the value compared with the threshold may be the time difference between the current time and the indicated absolute moment of time. When comparing the indicator with the threshold value, the operator determines if the exact threshold value is included or excluded as being sufficient to initiate the actions. The UE may move 406 to idle mode before the last transmission of the synchronization signal (SSB), at the last transmission of the synchronization signal (SSB), or a time offset after the last transmission of the synchronization signal (SSB). For example, the cell does not immediately switch off after the last SSB transmission to allow the network and / or the UE to finish pending transmissions.

[0108] FIG. 5 illustrates a signalling chart of an example embodiment. In the example embodiment the UE 500 is in connected mode, e.g. in ordinary communication 504 with a serving cell 502. The ordinary communication comprises downlink and uplink data transmissions. During the communication also broadcast blocks are received. The broadcast block comprises an indicator of an upcoming change in the transmission of synchronization signals. The signal 506 comprises counter value 3 and signal 508 counter value 2. The values of the counter are evaluated, step 510, and when the counter value reaches a threshold value, an action for responding to the situation is performed. In the example of FIG. 5 the action is to move into idle mode. The threshold has been set to be two so that the action can be taken before the last broadcast block, or a synchronization signal, before the change. Instead of an RRC idle mode the user equipment may move to RRC inactive mode or any other similar mode. The indicator may also comprise an offset between time between the last synchronization signal and the change in the transmission of synchronization signals.

[0109] FIG. 6 illustrates a signalling chart of an example embodiment. In the example embodiment the UE 600 is in connected mode, e.g. in ordinary communication 606 with a serving cell 602. The ordinary communication comprises transmitting and receiving data, for example, for facilitating calls, internet browsing, applications and similar. During the communication also broadcast blocks associated with a synchronization signal are received. The broadcast block comprises an indicator of an upcoming change in the transmission of synchronization signals for the serving cell. Counter values 3 and 2 are shown as example signals 608 and 610. The values of the counter are evaluated, step 612,and when the counter value reaches a threshold value, a cell search is started as an action for responding to the situation.

[0110] The cell search finds a second cell 604, from which the broadcast blocks are received with signals 614 and 616. These signals indicate that there is an upcoming change of synchronization signals. The user equipment 600 determines by evaluating the counter values to access the second cell, step 618.[01 1 1 ] The example of FIG. 6 includes only one cell search, however, if the evaluation at step 618 reveals that the second cell 604 has an upcoming change in the transmission of synchronization signals, it may perform a new cell search or other action instead of accessing the second cell.

[0112] FIG. 7 illustrates another signalling chart according to an example embodiment. In the signalling chart the UE 700 initiates a cell search procedure, step 706. The UE is in RRC idle / inactive mode. During the cell search procedure the UE 700 first receives broadcast blocks 708, 710 from a first cell 702. The first cell 702 is having an upcoming change in the transmission of synchronization signals soon. This is indicated by the low counter value. The user equipment evaluates the counter, decides to skip access to first cell, and determines that there is a need for another cell search, step 712.

[0113] During the re-initiated cell search the UE 700 receives broadcast blocks 714, 716 from a second cell 704. The counter associated with the indicator of an upcoming change in the transmission of synchronization signals indicates higher number of broadcast blocks or groups of broadcast blocks. The counter number indicated by the indicator may be indicating number of blocks or number of block groups. The evaluating UE is configured accordingly so that it can estimate the time left before the upcoming change. Finally, the UE determines to access the second cell at least partially based on the indicator of an upcoming change in the transmission of synchronization signals.

[0114] As explained in the above, the indicator may be an integer indicating the number of broadcast blocks or groups of broadcast blocks. An integer -based indicator may be used in any of the embodiments discussed in the above. The integer may be indicating the number of blocks or groups before the upcoming change. Alternatively, the integer may be a pointer or a mapping pointing to another location, such as a table or data base, from where the information may be retrieved. Additionally, the indicator may also include information about what kind of a change is coming. Alternatively, the integer may also be a flag indicating that there is an upcoming change. In such case the user equipmentcan prepare for the change by detecting the change by measuring the frequency of broadcast blocks.[01 1 5] Instead of an integer number, the indicator may indicate a time interval when the upcoming change in the transmission of synchronization signals occur. Instead of a time interval, it is possible that the indicator comprises an absolute moment of time when the change takes place. Instead of an integer or time interval, a hybrid approach maybe used, wherein the indicator comprises an integer used as a pointer or a mapping to an external data source for retrieving the moment of time.

[0116] The indicator for an upcoming change in transmission of synchronization signals is carried by a broadcast block associated with at least one synchronization signal. Thus, one block may contain, for example, a primary synchronization signal and / or a secondary synchronization signal. The primary synchronization signal and the secondary synchronization signal may be transmitted in the same broadcast block. In addition to primary and secondary synchronization signals additional synchronization related signals may be included in a broadcast block with or without primary and secondary synchronization signals.

[0117] In all of the embodiments the determination based on the indicator of an upcoming change in synchronization signals may be done in several ways. It is possible to use a comparison with a predetermined threshold value. Instead of a predetermined threshold value it is possible to use a dynamically adapted threshold value. For example, it is possible to have a set of possible threshold values, and the current threshold value is chosen from the set of possible threshold values. Also other suitable mechanisms may be used.

[0118] In the above example embodiments have been given. It should be noted that these are only examples and the mechanisms described above may be used also in other embodiments. For example, if the use of indicator indicates that the cell is switching of and no other suitable cells are available, it is possible that the user equipment changes the requirements for a cell change. For example, the user equipment may reduce the power threshold for a cell and consider other cells with less good radio conditions for maintaining a connection. Instead of changing the requirements it is also possible to apply other known power saving techniques after the user equipment has, based on the received indicators, determined that there is no suitable cell.

[0119] FIG. 8 illustrates a block diagram of user equipment 800 configured to practice example embodiments discussed above. The UE 800 may comprise at least one processor802 and at least one memory 804 comprising program code, in other words, program instructions.

[0120] The UE 800 may also include other nodes, such as at least one transceiver 806. The transceiver 806 may be configured to enable the UE 800 to transmit and / or receive information to / from other devices, as well as other nodes not shown in FIG. 8. In one example, the UE 800 may use the transceiver to transmit or receive signalling information and data in accordance with at least one cellular communication protocol. The transceiver 806 may be configured to provide at least one wireless radio connection, such as for example a 3GPP mobile broadband connection (for example, 5G, 6G or beyond). The transceiver 806 may comprise or be configured to be coupled to at least one antenna to transmit and / or receive radio frequency signals.

[0121] Furthermore, the at least one processor 802 is capable of executing the stored instructions. In an embodiment, the at least one processor 802 may be embodied as a multi-core processor, a single core processor, or a combination of one or more multi -core processors and one or more single core processors. For example, the at least one processor 802 may be embodied as one or more of various processing devices, such as a coprocessor, a microprocessor, a controller, a digital signal processor (DSP), a processing circuitry with or without an accompanying DSP, or various other processing devices including integrated circuits such as, for example, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a microcontroller unit (MCU), a hardware accelerator, a special-purpose computer chip, a neural network (NN) chip, an artificial intelligence (Al) accelerator, a tensor processing unit (TPU), a neural processing unit (NPU), or the like. In an embodiment, the at least one processor 802 may be configured to execute hard-coded functionality. In an embodiment, the at least one processor 802 may be embodied as an executor of software instructions, wherein the instructions may specifically configure the at least one processor 802 to perform the algorithms and / or operations described herein when the instructions are executed.

[0122] The at least one memory 804 may be embodied as one or more volatile memory devices, one or more non-volatile memory devices, and / or a combination of one or more volatile memory devices and non-volatile memory devices. For example, the at least one memory 804 may be embodied as semiconductor memories (such as mask ROM, PROM (programmable ROM), EPROM (erasable PROM), flash ROM, RAM (random access memory), etc.).

[0123] In an example embodiment of the UE 800, when executed by at least one processor 802, instructions stored in at least one memory 804 may cause the UE 800 at least to receive, from a network node of a non-terrestrial network in a broadcast block associated with a synchronization signal, an indicator of an upcoming change in the transmission of synchronization signals in a cell provided by the network node or by another network node of the non-terrestrial network; and determine, based at least partly on the indicator, a cell for camping or for accessing to.

[0124] FIG. 9 illustrates a block diagram of network node 900 configured to practice example embodiments. The network node 900 may comprise at least one processor 902 and at least one memory 904 that comprise computer program code (i.e., instructions). The network node 900 may also include other nodes, such as a transceiver 906 configured to enable the network node 900 to transmit and / or receive information to / from other devices, as well as other nodes not shown in Fig. 9 In one example, the network node 900 may use the transceiver 906 to transmit or receive signalling information and data in accordance with at least one cellular communication protocol. The transceiver 906 may be configured to provide at least one wireless radio connection, such as for example a 3GPP mobile broadband connection (for example, 5G or beyond). The transceiver 906 may comprise, or be configured to be coupled to, at least one antenna to transmit and / or receive radio frequency signals.

[0125] Although the network node 900 is depicted to include only one processor 902, the network node 900 may include more than one processor. In an embodiment, the memory 904 is capable of storing instructions, such as an operating system and / or various applications. Furthermore, the memory 904 may include a storage that may be used to store, for example, at least some of the information and data used in the disclosed embodiments.

[0126] Furthermore, the at least one processor 902 is capable of executing the stored instructions. In an embodiment, the at least one processor 902 may be em-bodied as a multi-core processor, a single core processor, or a combination of one or more multi -core processors and one or more single core processors. For example, the at least one processor 902 may be embodied as one or more of various processing devices, such as a coprocessor, a microprocessor, a controller, a digital signal processor (DSP), a processing circuitry with or without an accompanying DSP, or various other processing devices including integrated circuits such as, for example, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a microcontroller unit (MCU),a hardware accelerator, a special-purpose computer chip, a neural network (NN) chip, an artificial intelligence (Al) accelerator, a tensor processing unit (TPU), a neural processing unit (NPU), or the like. In an embodiment, the at least one processor 902 may be configured to execute hard-coded functionality. In an embodiment, the at least one processor 902 is embodied as an executor of software instructions, wherein the instructions may specifically configure the at least one processor 902 to perform the algorithms and / or operations described herein when the instructions are executed.

[0127] The at least one memory 904 may be embodied as one or more volatile memory devices, one or more non-volatile memory devices, and / or a combination of one or more volatile memory devices and non-volatile memory devices. For example, the at least one memory 904 may be embodied as semiconductor memories (such as mask ROM, PROM (programmable ROM), EPROM (erasable PROM), flash ROM, RAM (random access memory), etc.).

[0128] It is to be noted that when referring to, for example, “providing”, “transmitting”, “receiving” or “obtaining” etc., it may comprise the network node 900 and the UE 800 communicating information via, for example, the at least one transceiver 806 and the at least one transceiver 906.

[0129] In an example embodiment of the network node 900, the instructions, when executed by the at least one processor 902, may cause the network node 900 at least to: generate an indicator of an upcoming change in the transmission of synchronization signals in a cell provided by the network node or by another network node of the nonterrestrial network; and transmit, from the network node of a non-terrestrial network in a broadcast block associated with a synchronization signal, the indicator of an upcoming change in the transmission of synchronization signals in a cell provided by the network node or by another network node of the non-terrestrial network.

[0130] Any range or device value given herein may be extended or altered without losing the effect sought. Also, any embodiment may be combined with another embodiment unless explicitly disallowed.

[0131] Although the subject matter has been described in language specific to structural features and / or acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as examples of implementing the claims and other equivalent features and acts are intended to be within the scope of the claims.

[0132] It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments. The embodiments are not limited to those that solve any or all of the stated problems or those that have any or all of the stated benefits and advantages. It will further be understood that reference to 'an' item may refer to one or more of those items.

[0133] The steps or operations of the methods described herein may be carried out in any suitable order, or simultaneously where appropriate.

[0134] Additionally, individual blocks may be deleted from any of the methods without departing from the scope of the subject matter described herein. Aspects of any of the example embodiments described above may be combined with aspects of any of the other example embodiments described to form further example embodiments without losing the effect sought.

[0135] The term 'comprising' is used herein to mean including the method, blocks, or nodes identified, but that such blocks or nodes do not comprise an exclusive list and a method or apparatus may contain additional blocks or nodes.

[0136] As used herein, “at least one of the following: ” and “at least one of ” and similar wording, where the list of two or more nodes are joined by “and” or “or”, mean at least any one of the nodes, or at least any two or more of the nodes, or at least all the nodes. Expression “or” may be understood as a non-exclusive “or” and therefore a list or two or more nodes indicated to be mutually optional by the expression “or” means at least any one of the nodes, or at least any two or more of the nodes, or at least all the nodes.

[0137] Although subjects may be referred to as ‘first’ or ‘second’ subjects, this does not necessarily indicate any order or importance of the subjects. Instead, such attributes may be used solely for the purpose of making a difference between subjects.

[0138] As used in this application, the term ‘circuitry’ may refer to one or more or all of the following: (a) hardware-only circuit implementations (such as implementations in only analog and / or digital circuitry) and (b) combinations of hardware circuits and software, such as (as applicable):(i) a combination of analog and / or digital hardware circuit(s) with software / firmware and (ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and (c) hardware circuit(s) and or processor(s), such as a microprocessor s) or a portion of a microprocessor s), that requires software (e.g., firmware) for operation, butthe software may not be present when it is not needed for operation. This definition of circuitry applies to all uses of this term in this application, including in any claims.

[0139] As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

[0140] It will be understood that the above description is given by way of example only and that various modifications may be made by those skilled in the art. The above specification, examples and data provide a complete description of the structure and use of exemplary embodiments. Although various embodiments have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from scope of this specification.

Claims

25CLAIMS1. A user equipment (800), comprising: at least one processor (802); and at least one memory (804) storing instructions which, when executed by the at least one processor, cause the user equipment (800) at least to: receive, from a network node of a non-terrestrial network in a broadcast block associated with a synchronization signal, an indicator of an upcoming change in the transmission of synchronization signals in a cell provided by the network node or by another network node of the non-terrestrial network; and determine, based at least partly on the indicator, a cell for camping or for accessing to.

2. The user equipment (800) according to claim 1, wherein the instructions, when executed by the at least one processor (802), further cause the user equipment (800) at least to, while in idle mode: perform a cell search procedure based on the received indicator of the upcoming change in the transmission of synchronization signals.

3. The user equipment according to claim 2, wherein the instructions, when executed by the at least one processor (802), further cause the user equipment (800) at least to: detect a cell provided by the other network node; receive, from the other network node of the non-terrestrial network in a broadcast block an indicator of an upcoming change in transmission of synchronization signals in a cell provided by the other network node; and based on the received indicator, initiate a mobility procedure with the other network node.

4. The user equipment according to claim 3, wherein the mobility procedure is one of: a reselection of the cell provided by the other network node for camping; an access procedure with the other network node; a registration procedure with the other network node.

5. The user equipment (800) according to claim 1, wherein the cell provided by the network node is the serving cell.

6. The user equipment (800) according to claim 5, wherein the instructions, when executed by the at least one processor (802), further cause the user equipment (800) at least to: determine, when in connected mode, based on the indicator of an upcoming change in the transmission of synchronization signals that the serving cell will switch off; and based on the determining that the serving cell will switch off, re-acquire system information from the serving cell before the serving cell switches off; and move to idle mode.

7. The user equipment according to claim 5, wherein the instructions, when executed by the at least one processor (802), further cause the user equipment (800) at least to: determine based on the received indicator of the upcoming change in the transmission of synchronization signals of the serving cell whether there is a need for a cell change.

8. The user equipment according to claim 7, wherein the instructions, when executed by the at least one processor (802), further cause the user equipment (800) at least to: determine that there is no need for a cell change; and based on determining that there is no need for a cell change, determining the serving cell for camping or for accessing to.

9. The user equipment according to claim 7, wherein the instructions, when executed by the at least one processor (802), further cause the user equipment (800) at least to: determine that there is the need for a cell change; and initiate, based on determining that there is the need for the cell change, a procedure for the cell change.

10. The user equipment according to any of claims 1 to 9, wherein the broadcast block and the associated synchronization signal is a synchronization signal block, SSB.

11. The user equipment according to any of claims 1 to 10, wherein the broadcast block is transmitted on a physical broadcast channel.

12. The user equipment according to any of claims 1 to 11, wherein the upcoming change in the transmission of synchronization signals comprises termination of transmission of synchronization signals.

13. The user equipment according to any of claims 1 to 12, wherein the upcoming change in the transmission of synchronization signals is a change in the periodicity of the synchronization signals.

14. The user equipment according to any of claims 1 to 13, wherein the determining, based at least partly on the indicator, a cell for camping or for accessing to comprises comparing the received indicator of an upcoming change in the transmission of synchronization signals with a threshold value.

15. A network node of a non-terrestrial network (900), comprising: at least one processor (902); and at least one memory (904) storing instructions which, when executed by the at least one processor, cause the network node (900) at least to: generate an indicator of an upcoming change in the transmission of synchronization signals in a cell provided by the network node or by another network node of the non-terrestrial network; and transmit, from the network node of a non-terrestrial network in a broadcast block associated with a synchronization signal, the indicator of an upcoming change in the transmission of synchronization signals in a cell provided by the network node or by another network node of the non-terrestrial network.

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