Managing satellite assistance information during handover procedures

Abstract

There is provided an apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to at least perform: receiving, from a serving cell, a configuration message for handover to a target cell associated with satellite assistance information different from the satellite assistance information associated with the serving cell, wherein the configuration message at least indicates satellite auxiliary information associated with the target cell; and a validity timer for defining validity of at least a portion of the satellite assistance information; wherein the satellite auxiliary information at least comprises reference time and corresponding satellite auxiliary information, and the corresponding satellite auxiliary information is applied after the reference time is reached; it is determined whether to modify a handover timer and / or one or more requirements for handover completion based at least on the reference time.

Description

Technical Field

[0001] Various example embodiments are directed to managing satellite assistance information during a handover process. Background Art

[0002] The handover process is used to provide mobility in a wireless communication system. The handover process can be used, for example, in various cellular communication networks, such as in a cellular communication network operating according to a 5G radio access technology. The 5G radio access technology may also be referred to as a new radio NR access technology. The Third Generation Partnership Project 3GPP develops standards for 5G / NR, and one of the topics under discussion in the 3GPP relates to the handover process. According to the discussion, it is necessary to provide enhanced methods, devices, and computer programs related to joint channel estimation in a cellular communication network. Such enhancements may also be beneficial in other wireless communication networks, such as in non-terrestrial networks (NTNs) and future 6G networks. Summary of the invention

[0003] According to some aspects, the subject matter of independent claims is provided. Some example embodiments are defined in the dependent claims. The scope of protection sought by the various example embodiments is set forth by the independent claims. The example embodiments and features (if any) described in this specification that do not fall within the scope of the independent claims should be interpreted as examples useful for understanding the various example embodiments.

[0004] According to one aspect, a method is provided, comprising: receiving, by a user equipment, from a serving cell, a configuration message for switching to a target cell associated with satellite assistance information different from the satellite assistance information associated with the serving cell, wherein the configuration message at least indicates: the satellite assistance information associated with the target cell; and a validity timer for defining the validity of at least a portion of the satellite assistance information; wherein the satellite assistance information at least includes: a reference time (epoch time) and corresponding satellite assistance information, the corresponding satellite assistance information being applied after reaching the reference time; determining, by the user equipment, whether to modify the switching timer and / or one or more requirements for the completion of the switching based at least on the reference time.

[0005] According to an embodiment, the method includes: determining that the reference time is a time point in the past; and determining whether the satellite assistance information is valid based on determining that the reference time is a time point in the past.

[0006] According to an embodiment, the method includes: detecting that the satellite assistance information is not valid; based on detecting that the satellite assistance information is not valid, receiving updated satellite assistance information with a second reference time; and modifying the switching timer in the following manner: starting the switching timer at the second reference time; or extending the switching timer; and / or modifying one or more requirements for switching completion in the following manner: relaxing the switching delay requirement and / or the interruption time requirement; and / or modifying the start time of the measurement of the switching delay and / or the interruption time.

[0007] According to an embodiment, the method comprises initiating a random access procedure with a target cell using resources allocated in the configuration that are later in time than first resources, the first resources being the earliest resources in time among the allocated resources.

[0008] According to an embodiment, the method includes: detecting that the satellite assistance information is valid; and determining not to modify the handover timer and / or one or more requirements for handover completion based on detecting that the satellite assistance information is valid.

[0009] According to an embodiment, the method includes: determining that the reference time is a time point between the start time of processing the configuration message and the end of the processing delay of the configuration message; based on determining that the reference time is a time point between the start time of processing the configuration message and the end of the processing delay of the configuration message, detecting that the satellite assistance information is valid; and determining not to modify the switching timer and / or one or more requirements for the completion of the switching.

[0010] According to an embodiment, the method includes: determining that the reference time is a time point after the end of the processing delay of the configuration message; based on determining that the reference time is a time point after the end of the processing delay of the configuration message, modifying the switching timer in the following ways: starting the switching timer at the reference time; or extending the switching timer; and / or modifying one or more requirements for switching completion in the following ways: relaxing the switching delay requirement and / or the interruption time requirement; and / or modifying the start time of the measurement of the switching delay and / or the interruption time.

[0011] According to an embodiment, relaxing the handover delay requirement comprises adding a time value to the handover delay requirement; and / or wherein relaxing the interruption time requirement comprises adding a time value to the interruption time requirement.

[0012] According to an embodiment, the method comprises initiating a random access procedure with a target cell using first resources allocated in the configuration, wherein the first resources are resources that are earliest available in time among the allocated resources.

[0013] According to an embodiment, the configuration message indicates a random access channel configuration including a first resource and a second resource, the second resource being later in time than the first resource.

[0014] According to one aspect, an apparatus is provided, comprising a component for executing a method according to the above aspect and its embodiments. The component may include at least one processor; and at least one memory storing instructions, which, when executed by at least one processor, cause the execution of the apparatus. The apparatus may be a user equipment.

[0015] According to one aspect, a computer program comprising instructions is provided, which, when executed by a device, causes the device to at least perform the method of the above aspect and its embodiments.

[0016] According to one aspect, there is provided a (non-transitory) computer-readable medium comprising instructions, which, when executed by an apparatus, cause the apparatus to at least perform the method of the above aspect and embodiments thereof.

[0017] According to one aspect, a method is provided, comprising: receiving, by an apparatus, an acknowledgement for a handover request from a target cell associated with satellite assistance information different from satellite assistance information associated with the apparatus, wherein the acknowledgement indicates at least: a random access channel configuration, including a first resource and an optional second resource, the second resource being later in time than the first resource; satellite assistance information associated with the target cell; and a validity timer for defining the validity of at least a portion of the satellite assistance information; wherein the satellite assistance information includes at least: a reference time and corresponding satellite assistance information, the corresponding satellite assistance information being applied after reaching the reference time; sending a configuration message for handover to a user equipment served by the apparatus, wherein the configuration message indicates at least: the random access channel configuration; the satellite assistance information; and the validity timer. For example, the method may be performed by a network node, such as a source cell or a serving cell, or by a control device configured to control its functions when installed therein.

[0018] According to one aspect, an apparatus is provided, comprising a component for executing a method according to the above aspect. The component may include at least one processor; and at least one memory storing instructions, which, when executed by at least one processor, cause the execution of the apparatus. The apparatus may be a network node, such as a source cell or a serving cell.

[0019] According to one aspect, a computer program comprising instructions is provided, which, when executed by a device, causes the device to at least perform the method of the above aspect.

[0020] According to one aspect, there is provided a (non-transitory) computer-readable medium comprising instructions, which when executed by an apparatus causes the apparatus to at least perform the method of the above aspect.

[0021] According to one aspect, a method is provided, comprising: sending, by a device, an acknowledgement for a handover request to a serving cell associated with satellite assistance information different from satellite assistance information associated with the device, wherein the acknowledgement indicates at least: a random access channel configuration, including a first resource and an optional second resource, the second resource being later in time than the first resource; satellite assistance information associated with a target cell; and a validity timer for defining the validity of at least a portion of the satellite assistance information; wherein the satellite assistance information comprises at least: a reference time and corresponding satellite assistance information, the corresponding satellite assistance information being applied after reaching the reference time; monitoring a random access request from a user equipment previously served by the serving cell. For example, the method may be performed by a network node, such as a target cell, or by a control device configured to control its functions when installed therein.

[0022] According to an embodiment, the method comprises: detecting that a random access request has been received on a first resource, wherein the first resource is an earliest resource among the allocated resources; releasing one or more subsequent resources among the allocated resources.

[0023] According to an embodiment, the method comprises: detecting that a random access request has not been received on a first resource; and monitoring a random access request on a second resource based on detecting that a random access request has not been received on the first resource.

[0024] According to one aspect, an apparatus is provided, comprising a component for executing a method according to the above aspects and its embodiments. The component may include at least one processor; and at least one memory storing instructions, which, when executed by at least one processor, cause the execution of the apparatus. The apparatus may be a network node, such as a target cell.

[0025] According to one aspect, a computer program comprising instructions is provided, which, when executed by a device, causes the device to at least perform the method of the above aspect and its embodiments.

[0026] According to one aspect, there is provided a (non-transitory) computer-readable medium comprising instructions, which, when executed by an apparatus, cause the apparatus to at least perform the method of the above aspect and embodiments thereof. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Some example embodiments will now be described with reference to the accompanying drawings.

[0028] Figure 1 The network architecture of the communication system is shown by way of example;

[0029] Figure 2 The switching process is illustrated by way of example.

[0030] Figure 3The switching process is illustrated by way of example.

[0031] Figure 4 The switching process is illustrated by way of example.

[0032] Figure 5 A flow chart of the method is shown by way of example;

[0033] Figure 6 The signaling between entities is shown by way of example;

[0034] Figure 7 A block diagram of an apparatus is shown by way of example. DETAILED DESCRIPTION

[0035] A user equipment may receive a configuration for a handover from a source cell to a target cell. Cells may be associated with different satellite assistance information. Before successfully performing a handover to a target cell, the UE may need to ensure that it has valid satellite assistance information for the target cell. It takes time to obtain valid satellite assistance information, which may result in, for example, a timer (e.g., a T304 timer) expiring before a successful handover, or one or more requirements for the handover not being met. For example, an interruption time requirement or a handover delay requirement may not be met in a timely manner. A method for modifying a timer and / or modifying requirements for handovers for certain conditions is provided, which will be explained in the specification. For example, a timer may be delayed or extended, and / or requirements may be relaxed so that the UE will have valid satellite assistance information for completing the handover.

[0036] For example, the handover timer may be increased or extended until the UE has valid satellite assistance information. Alternatively, the start time of the timer may be postponed until the UE has valid satellite assistance information.

[0037] For example, the outage time requirement may be modified by relaxing (eg, by enlarging or extending) the outage time to cover the UE's reacquisition of new valid satellite assistance information. Alternatively, the start point of the measurement of the outage time may be postponed until the UE has valid satellite assistance information.

[0038] For example, the handover delay requirement may be modified by relaxing the requirement, for example by enlarging or extending the requirement until the UE has valid satellite assistance information. Alternatively, the starting point of the measurement of the handover delay may be postponed.

[0039] Figure 1The network architecture of a communication system is illustrated by way of example. In the following, different exemplary embodiments will be described using a radio access architecture based on Long Term Evolution-Advanced (LTE-A) or New Radio (NR), also known as fifth generation (5G), as an example of an access architecture to which the embodiments may be applied, however, the embodiments are not limited to such architectures. It will be apparent to those skilled in the art that the embodiments may also be applied to other kinds of communication networks with suitable components by appropriately adjusting the parameters and processes. Some examples of other options for suitable systems are Universal Mobile Telecommunications System (UMTS) Radio Access Network (UTRAN or E-UTRAN), Long Term Evolution (LTE, same as E-UTRA), Wireless Local Area Network (WLAN or WiFi), Worldwide Interoperability for Microwave Access (WiMAX), Personal Communications Service (PCS), Wideband Code Division Multiple Access (WCDMA), systems using Ultra-Wideband (UWB) technology, sensor networks, mobile ad hoc networks (MANETs), and Internet Protocol Multimedia Subsystem (IMS), or any combination thereof.

[0040] Figure 1 The example of FIG. 1 shows a portion of an exemplary radio access network. Figure 1User equipment or user equipment (UE) 100 and 102 are shown, which are configured to wirelessly connect to an access node (such as a gNB, i.e., next generation Node B, or an eNB, i.e., evolved Node B (eNodeB)) 104 providing the cell on one or more communication channels in the cell. The physical link from the user equipment to the network node is called the uplink (UL) or reverse link, and the physical link from the network node to the user equipment is called the downlink (DL) or forward link. It should be understood that the network node or its functions can be implemented by using any node, host, server or access point entity suitable for such use. A communication system typically includes more than one network node, in which case the network nodes may also be configured to communicate with each other via wired or wireless links designed for this purpose. These links may be used for signaling purposes. A network node is a computing device configured to control the radio resources of the communication system to which it is coupled. A network node may also be referred to as a base station (BS), an access point, or any other type of interface device including a relay station capable of operating in a wireless environment. A network node includes or is coupled to a transceiver. From the transceiver of the network node, a connection is provided to an antenna unit that establishes a bidirectional radio link to the user equipment. The antenna unit may include multiple antennas or antenna elements. The network node is also connected to the core network 110 (CN or next generation core NGC). Depending on the system, the counterpart on the CN side may be: a serving gateway (S-GW, routing and forwarding user data packets); a packet data network gateway (P-GW), used to provide a connection for the user equipment (UE) to an external packet data network; or a mobile management entity (MME), etc. An example of a network node configured to operate as a relay station is an integrated access and backhaul node (IAB). The distributed unit (DU) portion of the IAB node performs the BS function of the IAB node, while the backhaul connection is performed by the mobile terminal (MT) portion of the IAB node. The UE function may be performed by the IAB MT, and the BS function may be performed by the IAB DU. The network architecture may include a parent node, i.e., an IAB donor, which may have a wired connection to the CN and a wireless connection to the IAB MT.

[0041] User equipment or user equipment UE generally refers to a portable computing device including a wireless mobile communication device operating with or without a subscriber identity module (SIM), including but not limited to the following types of devices: mobile stations (mobile phones), smart phones, personal digital assistants (PDAs), cell phones, devices using wireless modems (alarm or measurement devices, etc.), laptop and / or touch screen computers, tablet computers, game consoles, notebooks and multimedia devices. It should be understood that a user device may also be an almost exclusively uplink-only device, an example of which is a camera or video camera that loads images or video clips to a network. A user device may also be a device with the ability to operate in an Internet of Things (IoT) network, which is a scenario in which objects are provided with the ability to transmit data over a network without the need for human-to-human or human-to-computer interaction.

[0042] Additionally, although the apparatus has been depicted as a single entity, different units, processors and / or memory units (not all of which are shown in FIG. Figure 1 ) can be implemented inside these devices to achieve their functions.

[0043] 5G is capable of using multiple input multiple output (MIMO) technology on both the UE and gNB side, more base stations or nodes than LTE (the so-called small cell concept), including macro stations that operate in collaboration with smaller stations and employ various radio technologies depending on service requirements, use cases and / or available spectrum. 5G mobile communications support a wide range of use cases and related applications, including video streaming. Augmented reality, different ways of sharing data and various forms of machine type applications (such as (massive) machine type communications (mMTC), including vehicle safety, different sensors and real-time control). 5G is expected to have multiple radio interfaces, namely below 7 GHz, cmWave and mmWave, and can also be integrated with existing legacy radio access technologies (such as LTE). The frequency range below 7 GHz can be referred to as FR1, while above 24 GHz (or more precisely, 24-52.6 GHz) can be referred to as FR2. Integration with LTE can be implemented, at least in the early stages, as a system in which macro coverage is provided by LTE and 5G radio interface access comes from small cells through aggregation to LTE. In other words, 5G is planned to support inter-RAT operability (such as LTE-5G) and inter-RI operability (inter-radio interface operability, such as sub-7GHz-cmWave, sub-7GHz-cmWave-mmWave). One of the concepts considered to be used in 5G networks is network slicing, in which multiple independent and dedicated virtual sub-networks (network instances) can be created within the same infrastructure to run services with different requirements for latency, reliability, throughput, and mobility.

[0044] The communication system can also communicate with other networks, such as the public switched telephone network or the Internet 112, or utilize services provided by them. The communication network can also support the use of cloud services, for example, at least a portion of the core network operations can be performed as a cloud service (this is in the Figure 1 114). The communication system may also include a central control entity or the like which provides facilities for networks of different operators to collaborate, for example in spectrum sharing.

[0045] The edge cloud can be brought to the radio access network (RAN) by leveraging network function virtualization (NVF) and software defined networking (SDN). Using edge cloud can mean that access node operations are to be performed at least partially in a server, host or node operably coupled to a remote radio head or base station including radio components. Node operations may also be distributed among multiple servers, nodes or hosts. The application of cloud RAN architecture enables RAN real-time functions to be performed on the RAN side (in distributed units DU 104), while non-real-time functions are performed in a centralized manner (in centralized units CU 108).

[0046] 5G can also make use of satellite communications to enhance or supplement the coverage of 5G services. For example, by providing backhaul. Possible use cases are to provide service continuity for machine-to-machine (M2M) or Internet of Things (IoT) devices or for passengers on vehicles, or to ensure service availability for critical communications and future rail / maritime / aeronautical communications. Satellite communications can make use of geostationary earth orbit (GEO) satellite systems, but also low earth orbit (LEO) satellite systems, in particular mega constellations (systems in which hundreds of (nano) satellites are deployed). Each satellite 106 in the constellation can cover several satellite-supporting network entities that create ground cells. Ground cells can be created by ground relay nodes 104 or by gNBs located on the ground or in satellites.

[0047] Non-terrestrial network (NTN) as a term may be considered to cover networks involving non-terrestrial flying objects such as satellites. In a non-terrestrial network (NTN), the delays experienced in the physical layer (e.g., their range and rate of change) may differ from the delays observed for terrestrial applications. Typically, because the UE 100, 102 may be located hundreds or even thousands of kilometers away from the network 104, the range of distances from the UE to the same serving satellite 106 radiating the network signal is much greater.

[0048] For example, for LEO networks the rate of change can be very high since the satellites are travelling at high speeds, e.g. up to 7500 m / s. Therefore, more advanced mechanisms have been developed to handle the UL timing alignment of different UEs in order to achieve a more robust timing advance procedure.

[0049] For non-terrestrial networks (NTN), several agreements have been reached for UEs experiencing long delays due to the large distance to the satellite. For example, the delay may be higher than the limit that can be corrected via 5G NR common signaling. Agreements have also been reached to support corrective frequency Doppler measures due to the high satellite speeds.

[0050] For example, in NR NTN, the UE is able to derive at least one of the following based on its Global Navigation Satellite System (GNSS) implementation: its position; or a reference time and frequency. Based on at least one of these elements, and together with additional information about the serving satellite ephemeris and / or timestamps signaled by the network, for example, the UE can calculate timing and frequency, and apply timing advance (TA) and frequency adjustment at least for UEs in Radio Resource Control (RRC) idle or inactive mode.

[0051] As another example, in NR NTN, a UE in RRC idle or inactive mode may be required to support at least UE-specific TA calculation based at least on its GNSS acquired position and serving satellite ephemeris.

[0052] The validity period of the satellite assistance information can be configured per cell and indicated to the UE. The value range can be, for example, {5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 120, 180, 240}, and the validity period can be given in seconds.

[0053] Satellite assistance information may be valid from a reference time T to T+D, where D is the validity duration or the duration of a validity timer. For example, ephemeris may be valid from T to T+D.

[0054] If no valid satellite assistance information (eg, ephemeris) is available on the UE side, it can be expected that the UE will be precluded from performing uplink transmission.

[0055] During the handover process, the network changes or switches the UE's connection from the source cell to the target cell based on the measurement report from the UE to the network. For example, the link quality of the serving cell may decrease due to the movement of the UE, while the link quality of another cell may improve. The UE is configured to perform measurements on the link quality of multiple cells and report the measurements to the network. The network can perform handover decisions based on the measurement reports from the UE.

[0056] For NR over NTN and eMTC over NTN, the handover process may be complex for the UE due to validity timer requirements and interruption time requirements. For example, the requirement for maximum interruption time may be specified by the network, and in some cases, the validity timer may expire before a successful handover.

[0057] The source cell and the target cell may be broadcast by the same satellite or by different satellites. When broadcast by the same satellite, the satellite assistance information may be used for both cells. The serving cell satellite assistance information may be given in the NTN configuration. The satellite assistance information may include, for example, validity timer, ephemeris information, timing advance parameter, Koffset, Kmac, polarization information and / or common delay.

[0058] The satellite assistance information sent to the source cell may still be different from the satellite assistance information sent to the target cell when broadcast by the same satellite because a single satellite may have different feeder links which may be associated with different satellite assistance information.

[0059] When broadcast by different satellites, or when the target cell and the source cell are associated with different satellite assistance information, the UE may need to acquire synchronization in terms of time-frequency aligned uplink transmissions towards the target satellite (i.e., the satellite broadcasting the target cell) before initiating a random access channel (RACH) procedure. Therefore, the UE may be required to acquire satellite assistance information for the target satellite before the handover is completed. This may increase the outage time, which is the time when the UE is not transmitting during the handover execution.

[0060] The satellite assistance information includes at least a reference time and an ephemeris. The ephemeris describes the position and movement of the satellite in space. The reference time defines the point in time when the UE considers the ephemeris valid. The reference time defines the first point in time, for example T, when the satellite assistance information is valid for the UE. The satellite assistance information remains valid for the duration D of the validity timer. Therefore, the satellite assistance information is valid from T to T+D. For example, the ephemeris is valid from T to T+D. At least a part of the satellite assistance information will be applied after reaching the reference time.

[0061] The UE may not be allowed to transmit to the network without valid ephemeris because the UE uses ephemeris to determine time and frequency adjustments for uplink transmissions.

[0062] Figure 2 The scenario of the handover process is shown by way of example. The target cell 230 and the source cell 220 are associated with different satellites and may be connected to different gateways on the ground. Time advances from left to right. The target cell 230 sends a confirmation 235 of the handover (HO) request to the source cell 220. The confirmation message may include a system information block including satellite assistance information of the target cell 230. Thus, the confirmation message may include information about the satellite assistance information associated with the target cell 230. For example, the satellite assistance information may include a reference time 250.

[0063] Source cell 220 sends a radio resource control (RRC) reconfiguration 225 to UE 210. The configuration message includes at least satellite assistance information with reference time 250. When UE 210 receives the configuration, the content (e.g., SIB sent by the target cell along with the HO request confirmation) may have aged by tens or hundreds of milliseconds.

[0064] exist Figure 2 In the example of , the reference time 250 is advanced in the future, which may cause a long waiting time before the UE can complete the handover command, because the UE should not apply the ephemeris information before the reference time is reached. A large time interval 240 may be required for synchronization, during which the UE cannot connect to the target cell 230.

[0065] After receiving the configuration 225, the UE 210 may start a timer, such as a T304 timer. If the handover is successful, the T304 timer stops. If the T304 timer expires before the random access to the target cell 230 is successfully completed, the UE may initiate an RRC re-establishment procedure. If the T304 timer expires before the reference time, the handover will fail because the UE may not be able to start the RACH procedure before the reference time. After the expiration, the UE may start the re-establishment procedure and start a timer, such as a T311 timer. If the connection to the source cell 220 is still good, the UE may successfully perform the re-establishment procedure. Otherwise, when T311 expires, the UE enters an idle mode, i.e., a mode without connection to the network, and may perform cell selection. In an NTN, a re-establishment failure to the source cell may occur because the source cell moves away due to satellite movement.

[0066] Upon receiving the handover configuration message, the UE is expected to meet the requirements for handover completion, such as interruption time requirements and handover delay requirements.

[0067] The handover delay requirement indicates the maximum time interval that the UE should be ready to start transmission on the new uplink PRACH (Physical Random Access Channel) after receiving a handover command.

[0068] The interruption time indicates the maximum interruption interval of uplink transmission between the time when the UE starts to perform handover and the time when the UE starts to transmit a new PRACH.

[0069] Figure 3The scenario of the handover process is shown by way of example. The target cell 330 and the source cell 320 are associated with different satellites and may be connected to different gateways on the ground. Time advances from left to right. The target cell 330 sends a confirmation 335 of the handover (HO) request to the source cell 320. The confirmation message may include a system information block including satellite assistance information of the target cell 330. Thus, the confirmation message may include information about the satellite assistance information associated with the target cell 330. For example, the satellite assistance information may include a reference time 350.

[0070] The source cell 320 sends a radio resource control (RRC) reconfiguration 325 to the UE 310. The configuration message includes at least satellite assistance information with a reference time 350. When the UE receives the configuration, the content (e.g., SIB sent by the target cell along with the HO request confirmation) may have aged by tens or hundreds of milliseconds.

[0071] exist Figure 3 In the example of , due to the large delay in signaling the HO request confirmation 335 message and the configuration message 325, when the UE 310 receives the configuration message 325, the reference time 350 has been reached. The UE 310 has no chance to start the validity timer and update the synchronization process. Therefore, the UE may no longer be able to use the ephemeris information, and the UE cannot initiate a random access procedure to the target cell. The UE 310 may have been assigned a contention-free reserved random access opportunity 340, but the UE cannot use it because it does not have a running validity timer.

[0072] If the reference has passed, then when initiated from the original reference time, the satellite assistance information may be considered valid from a point in time later than the reference time until the validity timer expires. In this case, the duration of validity will be shorter than the duration given by the validity timer. Using a reference time in the past to start the validity timer may be referred to as using a non-causal reference time. Even in Figure 3 In the example of the example above, a validity timer may be started, which may also expire before the UE has a chance to access the target cell using random access resources (e.g., contention-free reserved random access (CFRA) resources 340). This is particularly true for conditional handover (CHO), in which the UE is allowed to decide to perform a handover when a given condition is met. There may be a delay in meeting the condition, and the network may not be able to predict when the CHO condition or trigger will be met on the UE side.

[0073] Figure 4The scenario of the handover process is shown by way of example. The target cell 430 and the source cell 420 are associated with different satellites and may be connected to different gateways on the ground. Time advances from left to right. The target cell 430 sends a confirmation 435 of the handover (HO) request to the source cell 420. The confirmation message may include a system information block including satellite assistance information of the target cell 430. Thus, the confirmation message may include information about the satellite assistance information associated with the target cell 430. For example, the satellite assistance information may include a reference time 450.

[0074] The source cell 420 sends a radio resource control (RRC) reconfiguration 425 to the UE 410. The configuration message includes at least satellite assistance information with a reference time 450. When the UE 410 receives the configuration, the content (e.g., SIB sent by the target cell along with the HO request confirmation) may have aged by tens or hundreds of milliseconds.

[0075] In this example, the reference time 450 has not elapsed before processing of the configuration message is complete, but the validity timer duration 460 is not long enough. The conditions for CHO are met 440 after the validity timer expires, so when the conditions are met, the UE 410 no longer has valid ephemeris.

[0076] A method is provided for reducing the interruption time of transmission of a UE during handover from a source cell to a target cell (the cells are associated with different satellite assistance information).

[0077] Figure 5 A flow chart of the method is shown by way of example. The stages of the method shown may be performed by a UE, or by a control device configured to control its functions when installed therein. The UE may be, for example, Figure 6 The device 610 is configured to perform at least the method 500. The method 500 includes receiving 510, by the user equipment, from the serving cell, a configuration message for handover to a target cell, the target cell being associated with satellite assistance information different from the satellite assistance information associated with the serving cell. The configuration message indicates at least: the satellite assistance information associated with the target cell; and a validity timer for defining the validity of at least a portion of the satellite assistance information. The satellite assistance information includes at least: a reference time and corresponding satellite assistance information, the corresponding satellite assistance information being applied after reaching the reference time. The method 500 includes determining 520, by the user equipment, whether to modify the handover timer and / or one or more requirements for handover completion based at least on the reference time.

[0078] The handover timer specifies or relates to the interruption time of transmission during the handover execution. For example, the handover timer can be a T304 timer. The T304 timer gives the maximum time before the UE successfully completes the RACH with the target cell. The interruption time defines the latest point in time before the UE should send a RACH to the target cell.

[0079] The UE may determine to modify the handover timer based on the reference time. In other words, the requirement for handover completion may be modified based on the reference time. Modifying the handover timer may include, for example, starting a timer, pausing a timer, extending a timer, or postponing a timer. In at least some embodiments, modifying the handover timer includes starting a handover timer.

[0080] Figure 6 The signaling between entities is shown by way of example. The source cell 620 may determine 640 that the UE is to be handed over to another cell, such as the target cell 630, based on the measurement report received from the UE 610. The source cell 620 sends a handover request 642 to the target cell 630. The target cell 630 receives the handover request 642 and performs admission control and determines satellite assistance information for the UE. The target cell 630 and the source cell 620 (which is the current serving cell) are associated with different satellite assistance information.

[0081] Optionally, the target cell 630 may determine additional random access resources for the UE 610 .

[0082] The target cell 630 sends an acknowledgement 646 for the handover request to the source cell 620. Together with the acknowledgement message, the target cell may send satellite assistance information. Optionally, the target cell 630 may send information about additional RA resources to the source cell 620.

[0083] The source cell 620 sends a configuration message 648 for handover to the target cell to the UE 610. The configuration message indicates at least satellite assistance information associated with the target cell and a validity timer for defining the validity of at least a portion of the satellite assistance information. The satellite assistance information includes at least a reference time and corresponding satellite assistance information. The corresponding satellite assistance information will be applied after reaching the reference time. The corresponding satellite assistance information may include, for example, ephemeris. The corresponding satellite assistance information (e.g., ephemeris) may be valid from the reference time until the duration of the validity timer ends, wherein the validity timer starts at the reference time.

[0084] The configuration message optionally includes information about additional RA resources.

[0085] UE 610 receives configuration message 648. UE determines whether to modify the handover timer and / or one or more requirements for handover completion based at least on the reference time. The handover timer specifies or relates to the interruption time of the transmission of the UE during the handover execution. For example, the handover timer can be a T304 timer or a timer for detecting handover failure.

[0086] The UE may determine 650 a relationship between a reference time, a current time, and a processing delay for a configuration message. Based on the determination, the UE may modify 652 a handover timer and / or one or more requirements for handover completion. Modifying the handover timer may include, for example, starting a timer, pausing a timer, or extending a timer. Modifying the requirements may include, for example, relaxing requirements such as an interruption time requirement and / or a handover delay requirement. As another example, modifying the requirements may include modifying a starting point for a measurement of the requirement, for example, postponing a start time for a measurement of an interruption time and / or a handover delay.

[0087] Relaxing one or more requirements for handover completion may include adding a time value to one or more requirements. For example, a time value may be added to a handover delay requirement and / or an interruption time requirement. For example, the time value may be given in milliseconds. For example, the time value may be configured by the network.

[0088] There may be four different exemplary scenarios for modifying the switching timer depending on the reference time and the relationship between the reference time, the current time and the processing delay of the configuration message.

[0089] In scenario 1 654, the UE determines that the reference time has not passed and occurs after the RRC processing delay or the processing delay of the configuration message. In other words, the UE determines that the reference time is a time point after the end of the processing delay of the configuration message.

[0090] Based on determining that the reference time is a point in time after the end of the processing delay of the configuration message, the UE 610 may start 656 a handover timer at the reference time. For example, the UE 610 may postpone or extend the T304 timer. Alternatively or additionally, the UE may decide to modify one or more requirements for handover completion, such as by relaxing a handover delay requirement and / or an interruption time requirement. As another example, modifying the requirements may include modifying a starting point for a measurement of the requirements, such as postponing a start time for a measurement of an interruption time and / or a handover delay.

[0091] The UE 610 may use the first resource allocated in the configuration to initiate 658 a random access procedure with the target cell 630. The first resource is the earliest available resource in time among the allocated resources.

[0092] In scenario 2 660, the UE 610 determines that the reference time has not passed and occurs before the processing delay of the configuration message. In other words, the UE determines that the reference time is a time point between the start time of the processing of the configuration message and the end of the processing delay of the configuration message.

[0093] Based on determining that the reference time is a point in time between the start time of processing the configuration message and the end of the processing delay of the configuration message, the UE may start 662 a handover timer at the end of processing the configuration message or at the end of the processing delay of the configuration message. In other words, the UE may decide not to modify the handover timer and / or not to modify one or more requirements for handover completion.

[0094] The UE 610 may use the first resource allocated in the configuration to initiate 664 a random access procedure with the target cell 630. The first resource is the earliest available resource in time among the allocated resources.

[0095] In scenario 3 666, the UE determines that the reference time has passed. In other words, the UE determines that the reference time is a time point in the past or a time point before the start time of the processing of the configuration message. Then, the UE can determine whether the validity timer has expired or whether the satellite assistance information is valid.

[0096] The UE may detect 666 that the validity timer has expired. In other words, the UE may detect that the satellite assistance information is not valid. Based on detecting that the validity timer has expired, the UE may receive 668 updated satellite assistance information having a new reference time or a second reference time. The second reference time is later than the reference time previously received together with the configuration. The target cell 630 may be configured to broadcast its satellite assistance information, e.g., updated satellite assistance information or the latest satellite assistance information.

[0097] The UE 610 may start 670 a handover timer at the second reference time. Postponing the start of the handover timer reduces the interruption time experienced by the UE. For example, the UE 610 may postpone or extend the T304 timer. Alternatively or additionally, the UE may modify one or more requirements for handover completion, for example by relaxing a handover delay requirement and / or an interruption time requirement. As another example, modifying the requirements may include modifying a starting point for a measurement of the requirements, for example, postponing a start time for a measurement of an interruption time and / or a handover delay.

[0098] The UE 610 may use the next available resource to initiate 672 a random access procedure with the target cell 630. The next available resource may be a resource allocated in the configuration that is later in time than the first resource, which is the earliest in time of the allocated resources.

[0099] In scenario 4 674, the UE determines that the reference time has passed. In other words, the UE determines that the reference time is a time point in the past or before the start time of the processing of the configuration message. Then, the UE can determine whether the validity timer has expired or whether the satellite assistance information is valid.

[0100] The UE may detect 674 that the validity timer has not expired. In other words, the UE may detect that the satellite assistance information is valid. Based on detecting that the validity timer has not expired, the UE may start 676 a handover timer at the end of processing of the configuration message. In other words, the UE may decide not to modify the handover timer and / or not to modify one or more requirements for handover completion. The UE 610 may initiate 678 a random access procedure with the target cell 630 using the first resource allocated in the configuration. The first resource is the earliest available resource in time among the allocated resources.

[0101] The method disclosed herein can reduce the interruption time of the UE, or at least prevent the interruption time from increasing, while maintaining consistency with satellite assistance information (e.g., ephemeris information and validity timer). In the scenario where the UE obtains new satellite assistance information from the target cell, the additional time required can be minimized.

[0102] The handover delay (e.g., Dhandover) may be equal to the RRC command delay plus the interruption time. The interruption time may be the time between the end of the last transmission time interval (TTI) including the RRC configuration on the old physical downlink shared channel (PDSCH) and the time when the UE starts transmitting the new physical random access channel (PRACH) excluding the RRC configured processing delay. The RRC command delay may be defined as the maximum of: the RRC configured processing delay; the delay between the end of the last transmission time interval (TTI) including the RRC configuration and the reference time provided in the RRC configuration.

[0103] Figure 7 A block diagram of an apparatus capable of performing at least one or more of the methods disclosed herein is shown by way of example. A device 700 is shown, which may include, for example, a mobile communication device such as Figure 1 Mobile or UE 100 or Figure 6UE 610. The device 700 includes a processor 710, which may include, for example, a single-core or multi-core processor, wherein the single-core processor includes one processing core and the multi-core processor includes more than one processing core. The processor 710 may generally include a control device. The processor 710 may include more than one processor. The processor 710 may be a control device. The processing core may include, for example, a Cortex-A8 processing core manufactured by ARM Holdings or a Steamroller processing core designed by Advanced Micro Devices Corporation. The processor 710 may include at least one Qualcomm Snapdragon and / or Intel Atom processor. The processor 710 may include at least one application-specific integrated circuit ASIC. The processor 710 may include at least one field programmable gate array FPGA. The processor 710 may be a component for executing the method steps in the device 700. The processor 710 may be configured at least in part by computer instructions to perform actions.

[0104] The processor may include circuitry or be configured as one or more circuits configured to perform the stages of the method according to the example embodiments described herein. As used in this application, the term "circuitry" may refer to one or more or all of the following: (a) a hardware-only circuit implementation, such as an implementation in analog and / or digital circuitry only, and (b) a combination of hardware circuitry and software, such as, where applicable: (i) a combination of analog and / or digital hardware circuitry with software / firmware, and (ii) any portion of a hardware processor with software (including a digital signal processor, software, and memory that work together to enable an apparatus (such as a user equipment or network node) to perform various functions), and (c) a hardware circuit and / or processor, such as a microprocessor or a portion of a microprocessor, that requires software (e.g., firmware) to operate, but the software may not be present when the software is not required to operate.

[0105] This definition of circuitry applies to all uses of the term in this application, including any claims. As another example, as used in this application, the term circuitry also covers an implementation of a hardware circuit only, or a processor (or multiple processors), or a 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 a particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in a server, cellular network device, or other computing or network device.

[0106] The device 700 may include a memory 720. The memory 720 may include a random access memory and / or a permanent memory. The memory 720 may include at least one RAM chip. The memory 720 may include, for example, solid-state, magnetic, optical and / or holographic memory. The memory 720 may be at least partially accessible by the processor 710. The memory 720 may be at least partially included in the processor 710. The memory 720 may be a component for storing information. The memory 720 may include instructions, such as computer instructions or computer program codes, that the processor 710 is configured to execute. When instructions configured to cause the processor 710 to perform certain actions are stored in the memory 720, and the device 700 is generally configured to run under the guidance of the processor 710 using instructions from the memory 720, the processor 710 and / or at least one of its processing cores may be considered to be configured to perform the certain actions. The memory 720 may be at least partially external to the device 700, but accessible by the device 700.

[0107] The device 700 may include a transmitter 730. The device 700 may include a receiver 740. The transmitter 730 and the receiver 740 may be configured to transmit and receive information, respectively, according to at least one cellular or non-cellular standard. The transmitter 730 may include more than one transmitter. The receiver 740 may include more than one receiver. The transmitter 730 and / or the receiver 740 may be configured to operate according to, for example, the Global System for Mobile Communications GSM, Wideband Code Division Multiple Access WCDMA, 5G, Long Term Evolution LTE, IS-95, Wireless Local Area Network WLAN, Ethernet, and / or Worldwide Interoperability for Microwave Access WiMAX standards.

[0108] The device 700 may include a near field communication NFC transceiver 750. The NFC transceiver 750 may support at least one NFC technology, such as NFC, Bluetooth, Wibree, or similar technology.

[0109] The device 700 may include a user interface UI 760. The UI 760 may include at least one of a display, a keyboard, a touch screen, a vibrator arranged to signal a user by vibrating the device 700, a speaker, and a microphone. The user is able to operate the device 700 via the UI 760, for example to accept an incoming phone call, place a phone call or video call, browse the Internet, manage digital files stored in the memory 720 or on a cloud accessible via the transmitter 730 and receiver 740 or via the NFC transceiver 750, and / or play games.

[0110] The device 700 may include or be arranged to accept a user identification module 770. The user identification module 770 may include, for example, a user identification module SIM card installable in the device 700. The user identification module 770 may include information identifying a subscription of a user of the device 700. The user identification module 770 may include cryptographic information that may be used to verify the identity of the user of the device 700 and / or to facilitate encryption of transmitted information and billing of the user of the device 700 for communications enabled via the device 700.

[0111] The processor 710 may be equipped with a transmitter that is arranged to output information from the processor 710 to other devices included in the device 700 via electrical leads inside the device 700. Such a transmitter may include a serial bus transmitter that is arranged to output information to the memory 720 for storage therein, for example, via at least one electrical lead. As an alternative to the serial bus, the transmitter may include a parallel bus transmitter. Similarly, the processor 710 may include a receiver that is arranged to receive information in the processor 710 from other devices included in the device 700 via electrical leads inside the device 700. Such a receiver may include a serial bus receiver that is arranged to receive information from the receiver 740, for example, via at least one electrical lead, for processing in the processor 710. As an alternative to the serial bus, the receiver may include a parallel bus receiver.

[0112] The device 700 may include Figure 7 Other devices not shown in the figure. For example, where the device 700 comprises a smart phone, it may include at least one digital camera. Some devices 700 may include a rear camera and a front camera, wherein the rear camera is intended for digital photography and the front camera is used for video telephony. The device 700 may include a fingerprint sensor arranged to at least partially authenticate a user of the device 700. In some example embodiments, the device 700 lacks at least one of the above-mentioned devices. For example, some devices 700 may lack an NFC transceiver 750 and / or a user identification module 770.

[0113] The processor 710, the memory 720, the transmitter 730, the receiver 740, the NFC transceiver 750, the UI 760 and / or the user identification module 770 may be interconnected in a variety of different ways via electrical leads inside the device 700. For example, each of the above devices may be connected to a main bus inside the device 700, respectively, to allow the devices to exchange information. However, as will be appreciated by those skilled in the art, this is only an example, and various ways of interconnecting at least two of the aforementioned devices may be selected depending on the embodiment.

[0114] As used herein, the term "non-transitory" is a limitation of the medium itself (ie, tangible, not a signal), not a limitation on data storage persistence (eg, RAM versus ROM).

[0115] As used herein, “at least one of: ” and “at least one of ” and similar expressions, where a list of two or more elements is combined by “and” or “or”, mean at least any one of the elements, or at least any two or more of the elements, or at least all of the elements.

Claims

1. A device comprising: at least one processor; as well as at least one memory storing instructions, which, when executed by the at least one processor, cause the apparatus to at least perform: Receiving, from a serving cell, a configuration message for handover to a target cell associated with satellite assistance information different from satellite assistance information associated with the serving cell, wherein the configuration message at least indicates: the satellite assistance information associated with the target cell; as well as a validity timer for defining the validity of at least a portion of the satellite assistance information; The satellite assistance information at least includes: a reference time and corresponding satellite assistance information, and the corresponding satellite assistance information is applied after reaching the reference time; A determination is made based at least on the reference time whether to modify a handover timer and / or one or more requirements for handover completion.

2. The apparatus according to claim 1, being configured to perform: determining that the reference time is a point in time in the past; and Based on determining that the reference time is the past time point, it is determined whether the satellite assistance information is valid.

3. The apparatus according to claim 2, being configured to perform: Detecting that the satellite assistance information is not valid; receiving updated satellite assistance information having a second reference time based on detecting that the satellite assistance information is not valid; as well as The switching timer is modified by: Start the switching timer at the second reference time; or The switching timer is extended.

4. The apparatus according to claim 2 or 3, being configured to perform: Detecting that the satellite assistance information is not valid; receiving updated satellite assistance information having a second reference time based on detecting that the satellite assistance information is not valid; as well as Modifying the one or more requirements for handover completion by: Relaxation of switching delay requirements and / or interruption time requirements; and / or Modify the start time of the measurement of switching delay and / or interruption time.

5. The apparatus according to claim 3 or 4, being configured to perform: A random access procedure with the target cell is initiated using resources allocated in the configuration that are later in time than first resources, the first resources being earliest in time among the allocated resources.

6. The apparatus according to claim 2, being configured to perform: Detecting that the satellite assistance information is valid; Based on detecting that the satellite assistance information is valid, determining not to modify the handover timer and / or the one or more requirements for handover completion.

7. The apparatus according to claim 1, being configured to perform: Determining that the reference time is a time point between a start time of processing the configuration message and an end time of a delay in processing the configuration message; detecting that the satellite assistance information is valid based on determining that the reference time is the time point between the start time of the processing of the configuration message and the end of the processing delay of the configuration message; and A determination is made not to modify the handover timer and / or the one or more requirements for handover completion.

8. The apparatus according to claim 1, being configured to perform: determining that the reference time is a time point after the end of the processing delay of the configuration message; Based on determining that the reference time is the time point after the end of the processing delay of the configuration message, modifying the switching timer in the following manner: Start the switching timer at the reference time; or The switching timer is extended.

9. The apparatus according to claim 1 or 8, being configured to perform: determining that the reference time is a time point after the end of the processing delay of the configuration message; Based on determining that the reference time is the point in time after the end of the processing delay of the configuration message, modifying the one or more requirements for handover completion by: Relaxation of switching delay requirements and / or interruption time requirements; and / or Modify the start time of the measurement of switching delay and / or interruption time.

10. The apparatus of claim 4 or 9, wherein said relaxing said switching delay requirement comprises adding a time value to said switching delay requirement; and / or wherein said relaxing said interruption time requirement comprises adding a time value to said interruption time requirement.

11. An apparatus according to any one of claims 7 to 10, configured to perform: A random access procedure is initiated with the target cell using first resources allocated in the configuration, wherein the first resources are the earliest available resources in time among the allocated resources.

12. The apparatus according to any one of the preceding claims, wherein the configuration message indicates a random access channel configuration comprising a first resource and a second resource, the second resource being later in time than the first resource.

13. An apparatus according to any preceding claim, wherein the apparatus is user equipment.

14. An apparatus comprising: at least one processor; as well as at least one memory storing instructions, which, when executed by the at least one processor, cause the apparatus to at least perform: Receiving an acknowledgement for the handover request from a target cell that is associated with satellite assistance information that is different from satellite assistance information associated with the apparatus, wherein the acknowledgement indicates at least: A random access channel configuration, comprising a first resource and an optional second resource, wherein the second resource is later in time than the first resource; Satellite assistance information associated with the target cell; as well as a validity timer for defining the validity of at least a portion of the satellite assistance information; The satellite assistance information at least includes: a reference time and corresponding satellite assistance information, and the corresponding satellite assistance information is applied after reaching the reference time; A configuration message for handover to the target cell is sent to a user equipment served by the apparatus, wherein the configuration message indicates at least: the random access channel configuration; the satellite assistance information; and the validity timer.

15. The apparatus according to claim 14, wherein the apparatus is an access node of a serving cell for the user equipment.

16. An apparatus comprising: at least one processor; as well as at least one memory storing instructions, which, when executed by the at least one processor, cause the apparatus to at least perform: sending an acknowledgement for the handover request to a serving cell associated with satellite assistance information different from satellite assistance information associated with the apparatus, wherein the acknowledgement indicates at least: A random access channel configuration, comprising a first resource and an optional second resource, wherein the second resource is later in time than the first resource; Satellite assistance information associated with the target cell; as well as a validity timer for defining the validity of at least a portion of the satellite assistance information; The satellite assistance information at least includes: a reference time and corresponding satellite assistance information, and the corresponding satellite assistance information is applied after reaching the reference time; Monitoring random access requests from user equipment previously served by the serving cell.

17. The apparatus according to claim 16, being configured to perform: detecting that a random access request has been received on a first resource, wherein the first resource is an earliest resource among the allocated resources; One or more subsequent resources in the allocated resources are released.

18. The apparatus according to claim 16, being configured to perform: detecting that a random access request has not been received on the first resource; Based on detecting that a random access request has not been received on the first resource, monitoring the second resource for a random access request.

19. The apparatus according to any one of claims 16 to 18, wherein the apparatus is an access node of the target cell for the user equipment.

20. A method comprising: A configuration message for handover to a target cell associated with satellite assistance information different from satellite assistance information associated with the serving cell is received by a user equipment from a serving cell, wherein the configuration message at least indicates: the satellite assistance information associated with the target cell; as well as a validity timer for defining the validity of at least a portion of the satellite assistance information; The satellite assistance information at least includes: a reference time and corresponding satellite assistance information, and the corresponding satellite assistance information is applied after reaching the reference time; A determination is made by the user equipment whether to modify a handover timer and / or one or more requirements for handover completion based at least on the reference time.

21. The method according to claim 20, comprising: Determining that the reference time is a point in time in the past; as well as Based on determining that the reference time is the past time point, it is determined whether the satellite assistance information is valid.

22. The method according to claim 21, comprising: Detecting that the satellite assistance information is not valid; receiving updated satellite assistance information having a second reference time based on detecting that the satellite assistance information is not valid; as well as The switching timer is modified by: Start the switching timer at the second reference time; or The switching timer is extended.

23. The method according to claim 21 or 22, comprising: Detecting that the satellite assistance information is not valid; receiving updated satellite assistance information having a second reference time based on detecting that the satellite assistance information is not valid; as well as Modifying the one or more requirements for handover completion by: Relaxation of switching delay requirements and / or interruption time requirements; and / or Modify the start time of the measurement of switching delay and / or interruption time.

24. The method according to claim 22 or 23, comprising: A random access procedure with the target cell is initiated using resources allocated in the configuration that are later in time than first resources, the first resources being earliest in time among the allocated resources.

25. The method according to claim 21, comprising: Detecting that the satellite assistance information is valid; Based on detecting that the satellite assistance information is valid, determining not to modify the handover timer and / or the one or more requirements for handover completion.

26. The method according to claim 20, comprising: Determining that the reference time is a time point between a start time of processing the configuration message and an end time of a delay in processing the configuration message; detecting that the satellite assistance information is valid based on determining that the reference time is the time point between the start time of the processing of the configuration message and the end of the processing delay of the configuration message; and A determination is made not to modify the handover timer and / or the one or more requirements for handover completion.

27. The method according to claim 20, comprising: determining that the reference time is a time point after the end of the processing delay of the configuration message; Based on determining that the reference time is the time point after the end of the processing delay of the configuration message, modifying the switching timer in the following manner: Start the switching timer at the reference time; or The switching timer is extended.

28. The method according to claim 20 or 27, comprising: determining that the reference time is a time point after the end of the processing delay of the configuration message; Based on determining that the reference time is the point in time after the end of the processing delay of the configuration message, modifying the one or more requirements for handover completion by: Relaxation of switching delay requirements and / or interruption time requirements; and / or Modify the start time of the measurement of switching delay and / or interruption time.

29. The method of claim 23 or 28, wherein said relaxing said switching delay requirement comprises adding a time value to said switching delay requirement; and / or wherein said relaxing said interruption time requirement comprises adding a time value to said interruption time requirement.

30. A method according to any one of claims 26 to 29, comprising: A random access procedure is initiated with the target cell using first resources allocated in the configuration, wherein the first resources are the earliest available resources in time among the allocated resources.

31. The method according to any one of the preceding claims 20 to 30, wherein the configuration message indicates a random access channel configuration comprising a first resource and a second resource, the second resource being later in time than the first resource.

32. A computer program comprising instructions which, when executed by an apparatus, cause the apparatus to at least: Receiving, from a serving cell, a configuration message for handover to a target cell associated with satellite assistance information different from satellite assistance information associated with the serving cell, wherein the configuration message at least indicates: the satellite assistance information associated with the target cell; as well as a validity timer for defining the validity of at least a portion of the satellite assistance information; The satellite assistance information at least includes: a reference time and corresponding satellite assistance information, and the corresponding satellite assistance information is applied after reaching the reference time; A determination is made based at least on the reference time whether to modify a handover timer and / or one or more requirements for handover completion.

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