Managing satellite aiding information during handover procedures

Abstract

An apparatus is provided that includes at least one processor and at least one memory that stores instructions that, when executed by the at least one processor, cause the apparatus to at least: receive, from a serving cell, a configuration message for a handover to a target cell associated with satellite assistance information that differs from satellite assistance information associated with the serving cell, the configuration message indicating at least satellite assistance information associated with the target cell and a validity timer for defining validity of at least a portion of the satellite assistance information, the satellite assistance information including at least an epoch time and corresponding satellite assistance information to be applied after the epoch time is reached; and determine, based at least on the epoch time, whether to modify the handover timer and / or one or more requirements for handover completion.

Description

[Technical Field]

[0001] Various exemplary embodiments relate to managing satellite assistance information during handover procedures. [Background technology]

[0002] Handover procedures are used to provide mobility in wireless communication systems. Handover procedures may be used in various cellular communication networks, such as cellular communication networks operating according to 5G radio access technology. 5G radio access technology may also be referred to as New Radio (NR) access technology. The Third Generation Partnership Project (3GPP) is developing standards for 5G / NR, and one of the topics in 3GPP discussions relates to handover procedures. According to the discussions, there is a need to provide enhanced methods, apparatus, and computer programs for joint channel estimation in cellular communication networks. Such enhancements may also be beneficial in other wireless communication networks, such as non-terrestrial based networks (NTNs) and future 6G networks. Summary of the Invention

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

[0004] According to an aspect, a method is provided that includes receiving, by a user equipment, from a serving cell, a configuration message for handover to a target cell associated with satellite assistance information that differs from satellite assistance information associated with the serving cell, the configuration message indicating at least satellite assistance information associated with the target cell and a validity timer for defining validity of at least a portion of the satellite assistance information, the satellite assistance information including at least an epoch time and corresponding satellite assistance information to be applied after the epoch time is reached; and determining, by the user equipment, based at least on the epoch time, whether to modify the handover timer and / or one or more requirements for handover completion.

[0005] According to an embodiment, the method includes determining that the epoch time is a time point in the past, and determining whether the satellite assistance information is valid based on determining that the epoch 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; receiving updated satellite assistance information with a second epoch time based on detecting that the satellite assistance information is not valid; modifying the handover timer by starting a handover timer at the second epoch time or extending the handover timer, and / or modifying one or more requirements for handover completion by relaxing the handover delay requirement and / or interruption time requirement and / or modifying a start time for measuring the handover delay and / or interruption time.

[0007] According to an embodiment, a method includes initiating a random access procedure in a target cell using resources allocated in a configuration, where the allocated resources are resources that are later in time than first resources, and the first resources are the earliest of the allocated resources.

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

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

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

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

[0012] According to an embodiment, the method includes initiating a random access procedure in the target cell using first resources allocated in the configuration, the first resources being the earliest available resource in time among the allocated resources.

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

[0014] According to an aspect, there is provided an apparatus including means for carrying out the method according to the above aspect and embodiments thereof. The means may include at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause execution of the apparatus. The apparatus may be a user equipment.

[0015] According to an aspect, there is provided a computer program comprising instructions that, when executed by an apparatus, cause the apparatus to carry out at least the method of the above aspect and embodiments thereof.

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

[0017] According to an aspect, a method is provided that includes receiving, by an apparatus, an acknowledgment of a handover request from a target cell associated with satellite assistance information different from satellite assistance information associated with the apparatus, the acknowledgment indicating at least a random access channel configuration including first resources and optionally second resources that are later in time than the first resources, satellite assistance information associated with the target cell, and a validity timer for defining validity of at least a portion of the satellite assistance information, the satellite assistance information including at least an epoch time and corresponding satellite assistance information to be applied after the epoch time is reached; and transmitting, to user equipment served by the apparatus, a configuration message for handover to the target cell, the configuration message indicating 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 installed therein and configured to control its functionality.

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

[0019] According to an aspect, there is provided a computer program comprising instructions that, when executed by an apparatus, cause the apparatus to perform at least the method of the above aspect.

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

[0021] According to an aspect, a method is provided that includes: transmitting, by an apparatus, an acknowledgment of a handover request to a serving cell associated with satellite assistance information different from satellite assistance information associated with the apparatus, the acknowledgment indicating a random access channel configuration including at least first resources and optionally second resources that are later in time than the first resources, satellite assistance information associated with the target cell, and a validity timer for defining validity of at least a portion of the satellite assistance information, the satellite assistance information including at least an epoch time and corresponding satellite assistance information to be applied after the epoch time is reached; and monitoring random access requests from user equipment previously served by the serving cell. For example, the method may be performed by a network node, such as the target cell, or by a control device configured to control its functionality when installed therein.

[0022] According to an embodiment, a method includes detecting that a random access request is received on a first resource, where the first resource is an earliest resource among the allocated resources, and releasing one or more later resources among the allocated resources.

[0023] According to an embodiment, a method includes detecting that a random access request is not received on a first resource, and monitoring for random access requests on a second resource based on detecting that the random access request is not received on the first resource.

[0024] According to an aspect, there is provided an apparatus including means for carrying out the method according to the above aspect and embodiments thereof. The means may include at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause execution of the apparatus. The apparatus may be a network node, such as a target cell.

[0025] According to an aspect, there is provided a computer program comprising instructions that, when executed by an apparatus, cause the apparatus to carry out at least the method of the above aspect and embodiments thereof.

[0026] According to an aspect, a (non-transitory) computer readable medium is provided that includes instructions that, when executed by an apparatus, cause the apparatus to perform at least the method of the above aspect and embodiments thereof.

[0027] Several exemplary embodiments will now be described with reference to the accompanying drawings. [Brief explanation of the drawings]

[0028] [Figure 1] As an example, a network architecture of a communication system is shown. [Figure 2] As an example, a scenario of a handover procedure is given. [Figure 3] As an example, a scenario of a handover procedure is given. [Figure 4] As an example, a scenario of a handover procedure is given. [Figure 5] As an example, a flow chart of the method is shown. [Figure 6] As an example, the signaling between the entities is shown. [Figure 7] As an example, a block diagram of the device is shown. DETAILED DESCRIPTION OF THE INVENTION

[0029] The user equipment may receive a configuration for handover from a source cell to a target cell. The cells may be associated with different satellite assistance information. Before successfully performing a handover to the target cell, the UE may need to verify that it has valid satellite assistance information for the target cell. Obtaining valid satellite assistance information may take time, which may result in, for example, a timer, such as the T304 timer, expiring before the handover is successful 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 time. Methods for modifying the timers and / or modifying the requirements for the handover in certain conditions are provided and described in this description. For example, timers may be delayed or extended and / or requirements may be relaxed so that the UE has valid satellite assistance information for completing the handover.

[0030] For example, the handover timer may be increased or extended until the UE has valid satellite assistance information, or alternatively, the start of the timer may be delayed until the UE has valid satellite assistance information.

[0031] For example, the outage time requirement may be modified by relaxing, e.g., widening or extending, the outage time to encompass the reacquisition of new valid satellite assistance information by the UE. Alternatively, the starting point of the measurement of the outage time may be postponed until the UE has valid satellite assistance information.

[0032] For example, the handover delay requirement may be modified by relaxing the requirement, e.g., by widening or extending the requirement, until the UE has valid satellite assistance information. Alternatively, the starting point for measuring the handover delay may be postponed.

[0033] 1 shows, as an example, a network architecture of a communication system. Below, different exemplary embodiments are described using a radio access architecture based on New Radio (NR), also known as Long Term Evolution Advanced (LTE-Advanced, LTE-A) or fifth generation (5G), as an example of an access architecture to which the embodiments may be applied, without, however, limiting the embodiments to such an architecture. It will be apparent to those skilled in the art that the embodiments may also be applied to other types of communication networks having suitable means by appropriately adjusting parameters and procedures. 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 Interoperable Microwave Access (WiMAX), Bluetooth®, Personal Communications Services (PCS), ZigBee®, Wideband Code Division Multiple Access (WCDMA), systems using Ultra Wideband (UWB) technology, sensor networks, Mobile Ad Hoc Networks (MANET), and Internet Protocol Multimedia Subsystem (IMS), or any combination thereof.

[0034] The example of Figure 1 shows a portion of an illustrative radio access network. Figure 1 shows user devices or user equipment (UE) 100 and 102 configured to wirelessly connect with an access node 104, such as a gNB, i.e., next generation Node B, or eNB, i.e., evolved Node B (eNodeB), serving the cell, over one or more communication channels within the cell. The physical link from the user device to the network node is referred to as the uplink (UL) or reverse link, and the physical link from the network node to the user device is referred to as the downlink (DL) or forward link. It should be understood that network nodes or their functions may be implemented by using any node, host, server, or access point, or other 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 over links, wired or wireless, designed for that 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 interfacing device, including a relay station capable of operating in a wireless environment. The network node includes or is coupled to a transceiver. A connection is provided from the transceiver of the network node to an antenna unit that establishes a bidirectional radio link to a user device. The antenna unit may include multiple antennas or antenna elements. The network node is further connected to a 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, which routes and forwards user data packets), a packet data network gateway (P-GW), or a mobile management entity (MME) for providing a connection of a user device (UE) to an external packet data network.An example of a network node configured to operate as a relay station is an integrated access backhaul (IAB) node. The distributed unit (DU) portion of the IAB node performs the BS functions of the IAB node, and the backhaul connection is performed by the mobile termination (MT) portion of the IAB node. The UE functions may be performed by the IAB MT, and the BS functions 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 with the CN and a wireless connection with the IAB MT.

[0035] A user device, or user equipment (UE), typically refers to a portable computing device, including wireless mobile communication devices that operate with or without a subscriber identity module (SIM), including, but not limited to, the following types of devices: mobile stations (cell phones), smartphones, personal digital assistants (PDAs), handsets, devices using wireless modems (such as alarms or measurement devices), laptop and / or touchscreen computers, tablets, game consoles, notebooks, and multimedia devices. It should be understood that a user device may also be a mostly uplink-only device. An example of this is a camera or video camera that loads images or video clips onto a network. A user device may also be a device capable of operating in an Internet of Things (IoT) network, a scenario in which objects are provided with the ability to transfer data over a network without requiring person-to-person or person-to-computer interaction.

[0036] Additionally, although the devices are shown as single entities, different units, processors, and / or memory units (not all of which are shown in FIG. 1) may be implemented within these devices to enable their functionality.

[0037] 5G employs multiple-input, multiple-output (MIMO) technology on both the UE and gNB sides, including macro sites operating in conjunction with smaller stations, to enable more base stations or nodes than LTE (the so-called small cell concept) by employing various radio technologies depending on service needs, use cases, and / or available spectrum. 5G mobile communications support a wide range of use cases and related applications, including video streaming, augmented reality, various methods of data sharing, and various forms of machine-type applications (including vehicle safety, various sensors, real-time control, and (massive) machine-type communications (mMTC)). 5G has multiple air interfaces, namely, sub-7 GHz, centimeter wave, and millimeter wave, and is expected to be integrable with existing legacy radio access technologies such as LTE. The frequency range below 7 GHz is referred to as FR1, and the frequency range above 24 GHz (or more precisely, 24-52.6 GHz) is referred to as FR2. Integration with LTE, at least initially, may be implemented as a system in which macro coverage is provided by LTE and 5G air interface access occurs from small cells aggregated to LTE. In other words, 5G is expected to support both inter-RAT operability (e.g., LTE-5G) and inter-RI operability (inter-air interface operability between sub-7 GHz and centimeter wave, sub-7 GHz-centimeter wave and millimeter wave, etc.). One concept expected to be used in 5G networks is network slicing. In network slicing, multiple independent, dedicated virtual subnetworks (network instances) may be created within the same infrastructure to operate services with different requirements regarding latency, reliability, throughput, and mobility.

[0038] The communications system may also be capable of communicating with or utilizing services provided by other networks, such as the public switched telephone network or the Internet 112. The communications network may also be capable of supporting the use of cloud services, e.g., at least a portion of the core network operations may be performed as cloud services (this is illustrated in FIG. 1 by "cloud" 114). The communications system may also include a central control entity, etc., that provides facilities for different operators' networks to cooperate, e.g., in spectrum sharing.

[0039] An edge cloud can be introduced into a radio access network (RAN) by utilizing network function virtualization (NVF) and software-defined networking (SDN). Using an edge cloud can refer to access node operations being performed, at least in part, in a server, host, or node operatively coupled to a base station including a remote radio head or radio portion. Node operations can also be distributed among multiple servers, nodes, or hosts. Application of a cloud RAN architecture allows real-time functions of the RAN to be performed on the RAN side (in the distributed unit DU 104) and non-real-time functions to be performed in a centralized manner (in the centralized unit CU 108).

[0040] 5G may also utilize satellite communications to extend or complement 5G service coverage, for example, by providing backhauling. Possible use cases are providing service continuity to machine-to-machine (M2M) or Internet of Things (IoT) devices, or to passengers aboard vehicles, or ensuring service availability for critical communications and future rail, maritime, and aviation communications. Satellite communications may utilize geostationary Earth orbit (GEO) satellite systems, but may also utilize low Earth orbit (LEO) satellite systems, particularly megaconstellations (systems in which hundreds of (nano)satellites are deployed). Each satellite 106 in the constellation may encompass several satellite-enabled network entities that create ground cells. Ground cells may be created through terrestrial relay nodes 104 or by gNBs located on the ground or on the satellite.

[0041] The term non-terrestrial based network (NTN) may be considered to encompass networks involving non-terrestrial based airborne objects such as satellites. In a non-terrestrial based network (NTN), the delays experienced at the physical layer, e.g., their range and variability, may differ from those observed in terrestrial based applications. Typically, the UEs 100, 102 may be located hundreds or even thousands of kilometers from the network 104, so the range of distances from the UEs to the same serving satellite 106 emitting the network signal is much greater.

[0042] For example, in the case of LEO networks, the variability can be very high since satellites are traveling at high speeds, e.g., up to 7500 m / s. For this reason, more advanced mechanisms are being developed to handle the UL timing alignment of different UEs in order to achieve a more robust timing advance procedure.

[0043] For non-terrestrial networks (NTNs), some agreements have been reached regarding the long delays experienced by UEs due to the large distances to satellites, which may exceed the limits that can be corrected via 5G NR common signaling. There is also agreement to support a corrected frequency Doppler metric due to the high speed of satellites.

[0044] For example, in an NR NTN, a UE may derive at least one of its location or reference time and frequency based on a Global Navigation Satellite System (GNSS) implementation. Based on at least one of these factors, along with additional information, such as serving satellite ephemeris and / or timestamps signaled by the network, the UE may calculate timing and frequency and apply timing advances (TAs) and frequency adjustments for at least UEs in Radio Resource Control (RRC) idle or inactive modes.

[0045] As another example, in an NR NTN, a UE in RRC idle or inactive mode may be required to support at least UE-specific TA calculations based at least on its GNSS-acquired position and serving satellite ephemeris.

[0046] The validity period of the satellite assistance information may be configured per cell or may be indicated to the UE. The range of values ​​may be, for example, {5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 120, 180, 240}, and the validity period may be given in seconds.

[0047] The satellite assistance information may be valid from epoch time T to T+D, where D is the validity period, or duration of the validity timer. For example, the ephemeris may be valid from T to T+D.

[0048] If valid satellite assistance information, eg, ephemeris, is not available at the UE, the UE may be expected to be prevented from performing uplink transmissions.

[0049] In a handover procedure, the network changes or hands over the UE's connection from a source cell to a target cell based on measurement reports from the UE to the network. For example, the link quality of the serving cell may have deteriorated due to UE movement, and the link quality of another cell may have improved. The UE is configured to perform measurements on the link quality of multiple cells and report the measurement results to the network. The network may perform a handover decision based on the measurement reports from the UE.

[0050] For NR over NTN and eMTC over NTN, the handover procedure can be complicated for the UE due to validity timer and interruption time requirements. For example, requirements for maximum interruption time may be specified by the network, and in some cases, the validity timer may expire before the handover is successful.

[0051] The source cell and the target cell may be broadcast by the same satellite or by different satellites. In the case of broadcast by the same satellite, satellite assistance information may be used for both cells. The satellite assistance information of the serving cell may be provided in the NTN configuration. The satellite assistance information may include, for example, a validity timer, ephemeris information, timing advance parameters, Koffset, Kmac, polarization information, and / or a common delay.

[0052] In the case of broadcasting by the same satellite, the satellite assistance information transmitted to the source cell may still be different from the satellite assistance information transmitted to the target cell, since a single satellite may have different feeder links that may be associated with different satellite assistance information.

[0053] In the case of broadcasts by different satellites, or if the target cell and source cell are associated with different satellite assistance information, the UE may need to acquire synchronization in terms of time-frequency aligned uplink transmissions to the target satellite, i.e., the satellite broadcasting to the target cell, before initiating the random access channel (RACH) procedure. Thus, the UE may need to acquire satellite assistance information for the target satellite before the handover can be completed. This may increase the interruption time, which is the time without transmission by the UE while performing the handover.

[0054] The satellite assistance information includes at least an epoch time and an ephemeris. The ephemeris describes the position and movement of the satellite in space. The epoch time defines the point in time at which the UE may consider the ephemeris valid. The epoch time defines the first point in time, e.g., T, at which the satellite assistance information is valid for the UE. The satellite assistance information remains valid for the duration of a validity timer, D. Thus, the satellite assistance information is valid from T to T+D. For example, the ephemeris may be valid from T to T+D. At least a portion of the satellite assistance information will be applied after the epoch time is reached.

[0055] Because the UE uses the ephemeris to determine time and frequency adjustments for uplink transmissions, the UE may not be allowed to transmit to the network without valid ephemeris.

[0056] 2 illustrates, by way of example, a handover procedure scenario. The target cell 230 and the source cell 220 may be associated with different satellites and connected to different terrestrial gateways. Time progresses from left to right. The target cell 230 sends an acknowledgement 235 to the source cell 220 for the handover (HO) request. The acknowledgement message may include a system information block containing satellite assistance information for the target cell 230. Thus, the acknowledgement message may include information regarding the satellite assistance information associated with the target cell 230. For example, the satellite assistance information may include an epoch time 250.

[0057] The source cell 220 sends a radio resource control (RRC) reconfiguration 225 to the UE 210. The configuration message includes at least satellite assistance information with an epoch time 250. When the UE 210 receives the configuration, the content, e.g., the SIB sent by the target cell along with the HO request acknowledgment, may be tens or hundreds of milliseconds old.

[0058] 2, which is far into the future, the UE should not apply the ephemeris information before the epoch time is reached, which may result in a long wait before the UE can complete the handover command. A large time interval 240 may be required for synchronization, during which the UE cannot connect to the target cell 230.

[0059] After receiving the configuration 225, the UE 210 may start a timer, such as the T304 timer. If the handover is successful, the T304 timer is stopped. 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 epoch time, the handover fails because the UE may not be able to initiate the RACH procedure before the epoch time. After expiration, the UE may initiate the re-establishment procedure and start a timer, such as the T311 timer. If the connection to the source cell 220 is still good, the UE may successfully perform the re-establishment procedure. Otherwise, upon expiration of T311, the UE may enter idle mode, i.e., a mode without a network connection, and perform cell selection. In NTNs, re-establishment to the source cell is likely to fail because the source cell moves away due to satellite movement.

[0060] Upon receiving the handover configuration message, the UE is expected to meet requirements for handover completion, such as interruption time requirements and handover delay requirements.

[0061] The handover delay requirement represents the maximum time interval after which the UE is ready to start transmission on a new uplink PRACH (Physical Random Access Channel) after receiving a handover command.

[0062] The interruption time represents the maximum interruption interval for uplink transmission between the time when the UE starts to perform handover and the time when the UE starts to transmit a new PRACH.

[0063] 3 illustrates, by way of example, a handover procedure scenario. The target cell 330 and the source cell 320 may be associated with different satellites and connected to different terrestrial gateways. Time progresses from left to right. The target cell 330 sends an acknowledgement 335 to the source cell 320 for the handover (HO) request. The acknowledgement message may include a system information block containing satellite assistance information for the target cell 330. Thus, the acknowledgement message may include information regarding the satellite assistance information associated with the target cell 330. For example, the satellite assistance information may include an epoch time 350.

[0064] 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 an epoch time 350. When the UE receives the configuration, the content, e.g., the SIB sent by the target cell with the HO request acknowledgment, may be tens or hundreds of milliseconds old.

[0065] Due to the long delay in signaling the HO request acknowledgement 335 message and the configuration message 325, when the UE 310 receives the configuration message 325, the epoch time 350 has already been reached in the example of Figure 3. The UE 310 has not had a chance to start the validity timer and update the synchronization procedure. 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. A contention-free reserved random access opportunity 340 may have been assigned to the UE 310, but the UE cannot use the opportunity 340 because it does not have a validity timer running.

[0066] If the epoch has already passed, the satellite assistance information may be considered valid from a point after the epoch time until the end of the validity timer if started from the original epoch time. In that case, the validity period will be shorter than the period given by the validity timer. Starting the validity timer using a past epoch time may be referred to as using a non-causal epoch time. Even if the validity timer may be started in the example of FIG. 3, the validity timer may expire before the UE has an opportunity to access the target cell using a random access resource, e.g., contention-free reserved random access (CFRA) resource 340. This may be particularly true in the case of conditional handover (CHO), where the UE may decide to perform a handover once 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.

[0067] 4 illustrates, by way of example, a handover procedure scenario. The target cell 430 and the source cell 420 may be associated with different satellites and connected to different terrestrial gateways. Time progresses from left to right. The target cell 430 sends an acknowledgement 435 to the source cell 420 for the handover (HO) request. The acknowledgement message may include a system information block containing satellite assistance information for the target cell 430. Thus, the acknowledgement message may include information regarding the satellite assistance information associated with the target cell 430. For example, the satellite assistance information may include an epoch time 450.

[0068] 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 an epoch time 450. When the UE 410 receives the configuration, the content, e.g., the SIB sent by the target cell with the HO request acknowledgment, may be tens or hundreds of milliseconds old.

[0069] In this example, the epoch time 450 does not elapse before the processing of the configuration message is complete, but the validity timer period 460 is not long enough: the condition for CHO is met 440 after the validity timer expires, and therefore the UE 410 no longer has a valid ephemeris when the condition is met.

[0070] A method is provided for reducing interruption of transmission by a UE in a handover procedure from a source cell to a target cell, the source cell and the target cell being associated with different satellite assistance information.

[0071] FIG. 5 shows a flowchart of a method, by way of example. The steps of the illustrated method may be performed by a UE or by a control device installed therein and configured to control its functions. The UE may be, for example, device 610 of FIG. 6 configured to perform at least method 500. Method 500 includes receiving 510, by the user equipment, a configuration message for handover from a serving cell to a target cell associated with satellite assistance information different from the satellite assistance information associated with the serving cell. The configuration message indicates at least satellite assistance information associated with the target cell and a validity timer for defining validity of at least a portion of the satellite assistance information. The satellite assistance information includes at least an epoch time and corresponding satellite assistance information to be applied after the epoch time is reached. 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 epoch time.

[0072] The handover timer specifies or relates to a transmission interruption time during handover. For example, the handover timer may be a T304 timer. The T304 timer gives the UE a maximum time to successfully complete a RACH with the target cell. The interruption time defines the latest point in time at which the UE should transmit a RACH to the target cell.

[0073] The UE may determine to modify the handover timer based on the epoch time. In other words, the requirements for handover completion may be modified based on the epoch time. Modifying the handover timer may include, for example, starting the timer, pausing the timer, extending the timer, or postponing the timer. In at least some embodiments, modifying the handover timer includes starting the handover timer.

[0074] 6 shows, by way of example, signaling between entities. Based on a measurement report received from a UE 610, a source cell 620 may determine 640 that the UE should be handed over to another cell, e.g., a target cell 630. The source cell 620 sends a handover request 642 to the target cell 630. The target cell 630 receives the handover request 642, performs admission control, and determines satellite assistance information for the UE. The target cell 630 and the current serving cell, the source cell 620, are associated with different satellite assistance information.

[0075] Optionally, the target cell 630 may determine additional random access resources for the UE 610.

[0076] The target cell 630 sends an acknowledgement 646 to the handover request to the source cell 620. Along 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.

[0077] The source cell 620 sends a configuration message 648 to the UE 610 for handover to the target cell. The configuration message indicates at least satellite assistance information associated with the target cell and a validity timer for defining validity of at least a portion of the satellite assistance information. The satellite assistance information includes at least an epoch time and corresponding satellite assistance information. The corresponding satellite assistance information is to be applied after the epoch time is reached. The corresponding satellite assistance information may include, for example, ephemeris. The corresponding satellite assistance information, for example, ephemeris, may be valid from the epoch time until the end of the validity timer period, and the validity timer starts at the epoch time.

[0078] Optionally, the configuration message may include information about additional RA resources.

[0079] The UE 610 receives the configuration message 648. The UE determines whether to modify the handover timer and / or one or more requirements for handover completion based at least on the epoch time. The handover timer specifies or relates to a period of interruption in transmission by the UE during handover. For example, the handover timer may be a T304 timer or a timer for detecting handover failure.

[0080] The UE may determine 650 a relationship between the epoch time, the current time, and the processing delay of the configuration message. Based on this determination, the UE may modify 652 a handover timer and / or one or more requirements regarding handover completion. Modifying a handover timer may include, for example, starting a timer, pausing a timer, or extending a timer. Modifying a requirement may include, for example, relaxing a requirement, such as an interruption time requirement and / or a handover delay requirement. As another example, modifying a requirement may include modifying the starting point of measurements for the requirement, for example, postponing the start time of measurements of the interruption time and / or handover delay.

[0081] 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.

[0082] There may be four exemplary different scenarios of modifying the handover timer depending on the epoch time and the relationship between the epoch time, the current time, and the processing delay of the configuration message.

[0083] In scenario 1 654, the UE determines that the epoch time has not yet elapsed and occurs after the RRC processing delay or the configuration message processing delay. In other words, the UE determines that the epoch time is the time point after the end of the configuration message processing delay.

[0084] Based on determining that the epoch time is a time point after the end of the configuration message processing delay, the UE 610 may start 656 a handover timer at the epoch time. For example, the UE 610 may postpone or extend the T304 timer. Alternatively, or additionally, the UE may determine to modify one or more requirements regarding handover completion, for example, by relaxing a handover delay requirement and / or an interruption time requirement. As another example, modifying a requirement may include modifying a starting point of measurement for the requirement, for example, postponing the start time of measurement of the interruption time and / or handover delay.

[0085] The UE 610 may initiate 658 a random access procedure with the target cell 630 using the first resource assigned in the configuration, which is the earliest available resource in time among the assigned resources.

[0086] In scenario 2 660, the UE 610 determines that the epoch time has not yet elapsed and occurs before the configuration message processing delay. In other words, the UE determines that the epoch time is the time point between the start time of the configuration message processing and the end of the configuration message processing delay.

[0087] Based on determining that the epoch 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, the UE may start 662 the 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 determine not to modify the handover timer and / or not to modify one or more requirements for handover completion.

[0088] The UE 610 may initiate 664 a random access procedure with the target cell 630 using a first resource assigned in the configuration, which is the earliest available resource in time among the assigned resources.

[0089] In scenario 3 666, the UE determines that the epoch time has already passed. In other words, the UE determines that the epoch time is a time point in the past or before the start time of the configuration message processing. The UE may then determine whether the validity timer has already expired or whether the satellite assistance information is valid.

[0090] 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 with a new epoch time or a second epoch time. The second epoch time is later than the epoch time previously received 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.

[0091] The UE 610 may start 670 the handover timer at the second epoch time. Postponing the start of the handover timer reduces the disruption 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 regarding handover completion, for example, by relaxing a handover delay requirement and / or a disruption time requirement. As another example, modifying a requirement may include modifying the starting point of measurements for the requirement, for example, postponing the start time of measurements of the disruption time and / or handover delay.

[0092] The UE 610 may initiate 672 a random access procedure with the target cell 630 using the next available resource. The next available resource may be a resource assigned in the configuration that is later in time than the first resource, which is the earliest resource in time among the assigned resources.

[0093] In scenario 4 674, the UE determines that the epoch time has already passed. In other words, the UE determines that the epoch time is a time point in the past or before the start time of the configuration message processing. The UE may then determine whether the validity timer has already expired or whether the satellite assistance information is valid.

[0094] 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 the handover timer at the end of processing 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 a first resource assigned in the configuration. The first resource is the earliest available resource in time among the assigned resources.

[0095] The methods disclosed herein may reduce, or at least prevent an increase in, UE disruption time while maintaining consistency with satellite assistance information, e.g., ephemeris information and validity timers. In scenarios where the UE acquires new satellite assistance information from a target cell, the additional time required may be minimized.

[0096] 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) containing the RRC configuration on the old physical downlink shared channel (PDSCH) and the time the UE starts transmitting on the new physical random access channel (PRACH), excluding the processing delay of the RRC configuration. The RRC command delay may be defined as the maximum of the processing delay of the RRC configuration, the delay between the end of the last transmission time interval (TTI) containing the RRC configuration and the epoch time provided in the RRC configuration.

[0097] FIG. 7 illustrates, by way of example, a block diagram of an apparatus capable of performing at least one or more methods disclosed herein. Device 700 is shown, which may include, for example, a mobile or mobile communications device, such as UE 100 of FIG. 1 or UE 610 of FIG. 6. Included in device 700 is a processor 710, which may include, for example, a single-core processor or a multi-core processor, where a single-core processor includes one processing core and a multi-core processor includes more than one processing core. Processor 710 may generally include a control device. Processor 710 may include more than one processor. Processor 710 may be the 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. Processor 710 may include at least one Qualcomm Snapdragon and / or Intel Atom processor. 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 means for performing method steps in the device 700. The processor 710 may be configured to perform actions at least in part by computer instructions.

[0098] A processor may include circuitry or may be configured as one or more circuits, the one or more circuits configured to perform steps of a 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: (a) a hardware-only circuit implementation, such as an implementation with only analog and / or digital circuitry, and (b) a combination of hardware circuitry and software, for example, if applicable, (i) a combination of analog and / or digital hardware circuitry and software / firmware, and (ii) any portion of a hardware processor (including a digital signal processor) with software, software, and memory that work together to cause a device, such as a user equipment or network node, to perform various functions, and (c) a processor, such as a microprocessor or portion of a microprocessor, that requires hardware circuitry and / or software (e.g., firmware) to operate, but the software may not be present when not necessary for operation.

[0099] This definition of circuit applies to all uses of the term in this application, including in any claims. As a further example, the term circuit as used herein also encompasses a simple hardware circuit or processor(s), or portion of a hardware circuit or processor, as well as its(their) accompanying software and / or firmware implementations. The term circuit also encompasses, for example, and where applicable to particular claim elements, a baseband or processor integrated circuit for a mobile device, or similar integrated circuit in a server, cellular network device, or other computing or network device.

[0100] Device 700 may include memory 720. Memory 720 may include random access memory and / or permanent memory. Memory 720 may include at least one RAM chip. Memory 720 may include, for example, solid-state memory, magnetic memory, optical memory, and / or holographic memory. Memory 720 may be at least partially accessible to processor 710. Memory 720 may be at least partially included in processor 710. Memory 720 may be a means for storing information. Memory 720 may include instructions, such as computer instructions or computer program code, configured to be executed by processor 710. When instructions configured to cause processor 710 to perform an action are stored in memory 720 and device 700 as a whole is configured to operate under the direction of processor 710 using instructions from memory 720, processor 710 and / or at least one processing core thereof may be considered to be configured to perform the action. The memory 720 may be at least partially external to the device 700 but accessible to the device 700 .

[0101] 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 standards, for example, 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.

[0102] 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 a similar technology.

[0103] Device 700 may include a user interface, UI 760. UI 760 may include at least one of a display, a keyboard, a touchscreen, a vibrator configured to send signals to a user by vibrating device 700, a speaker, and a microphone. A user may be able to operate device 700 via UI 760, for example, to receive incoming calls, make phone or video calls, browse the Internet, manage digital files stored in memory 720 or stored on the cloud accessible via transmitter 730 and receiver 740 or via NFC transceiver 750, and / or play games.

[0104] The device 700 may include or be configured to accept a user identity module 770. The user identity module 770 may include, for example, a subscriber identity module, a SIM card, or the like that is installable in the device 700. The user identity module 770 may include information that identifies the subscription of the user of the device 700. The user identity module 770 may include cryptographic information useful for verifying the identity of the user of the device 700 and / or for facilitating encryption of communicated information and billing of the user of the device 700 for communications originating from the device 700.

[0105] The processor 710 may include a transmitter configured to output information from the processor 710 to other devices included in the device 700 via electrical leads within the device 700. Such a transmitter may include, for example, a serial bus transmitter configured to output information via at least one electrical lead to the memory 720 for storage therein. Instead of a serial bus, the transmitter may include a parallel bus transmitter. Similarly, the processor 710 may include a receiver configured to receive information at the processor 710 from other devices included in the device 700 via electrical leads within the device 700. Such a receiver may include, for example, a serial bus receiver configured to receive information for processing in the processor 710 from the receiver 740 via at least one electrical lead. Instead of a serial bus, the receiver may include a parallel bus receiver.

[0106] Device 700 may include additional devices not shown in FIG. 7 . For example, if device 700 includes a smartphone, it may include at least one digital camera. Some devices 700 may include a rear camera and a front camera, where the rear camera may be intended for digital photography and the front camera may be intended for video calling. Device 700 may include a fingerprint sensor configured to at least partially authenticate a user of device 700. In some exemplary embodiments, device 700 lacks at least one of the above-mentioned devices. For example, some devices 700 may lack NFC transceiver 750 and / or user identity module 770.

[0107] The processor 710, memory 720, transmitter 730, receiver 740, NFC transceiver 750, UI 760, and / or user identity module 770 may be interconnected by electrical leads within device 700 in a number of different ways. For example, each of the above-mentioned devices may be separately connected to a master bus within device 700 to allow the devices to exchange information. However, as one skilled in the art will appreciate, this is merely one example, and various methods of interconnecting at least two of the above-mentioned devices may be selected depending on the embodiment.

[0108] The term "non-transitory" as used herein is not a limitation on data storage permanence (eg, RAM vs. ROM), but rather a limitation on the medium itself (ie, tangible, not a signal).

[0109] As used herein, "at least one of " and "at least one of " and similar phrases, when a list of two or more elements is connected 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. 1. An apparatus comprising: at least one processor; at least one memory that, when executed by the at least one processor, causes the device to 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, the configuration message comprising 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; indicates, receiving the satellite assistance information, the satellite assistance information including at least an epoch time and corresponding satellite assistance information to be applied after the epoch time is reached; determining whether to modify a handover timer and / or one or more requirements for handover completion based on at least the epoch time; at least one memory storing instructions for causing the An apparatus comprising:

2. determining that the epoch time is a time point in the past; determining whether the satellite assistance information is valid based on determining that the epoch time is the time point in the past; and The apparatus of claim 1 , wherein the apparatus causes the execution of the following:

3. detecting that the satellite assistance information is not valid; and receiving updated satellite assistance information with a second epoch time based on detecting that the satellite assistance information is not valid; and modifying the handover timer, starting the handover timer at the second epoch time; or extending the handover timer; modifying the handover timer by The apparatus of claim 2 , wherein the apparatus causes the following to be executed:

4. detecting that the satellite assistance information is not valid; and receiving updated satellite assistance information with a second epoch time based on detecting that the satellite assistance information is not valid; and modifying one or more requirements for completion of the handover; Relaxing handover delay and / or interruption time requirements; and / or Modifying the start time of the handover delay and / or interruption time measurement; modifying one or more requirements for completion of the handover by The apparatus according to claim 2 or 3, which causes the following to be executed.

5. 5. The apparatus of claim 3, wherein the apparatus is configured to initiate a random access procedure in the target cell using resources allocated in the configuration, the allocated resources being later in time than first resources, and the first resources being the earliest of the allocated resources.

6. detecting that the satellite assistance information is valid; and determining, based on detecting that the satellite assistance information is valid, not to modify the handover timer and / or one or more requirements for completing the handover; The apparatus of claim 2 , wherein the apparatus causes the following to be executed:

7. determining the epoch time to be a time point between a start time of processing the configuration message and an end of a processing delay of the configuration message; detecting that the satellite assistance information is valid based on determining that the epoch time is the time point between the start time of processing the configuration message and the end of the processing delay of the configuration message; determining not to modify the handover timer and / or one or more requirements for the handover completion; The apparatus of claim 1 , wherein the apparatus causes the execution of the following:

8. determining the epoch time to be a time point after the end of a processing delay of the configuration message; based on determining that the epoch time is the time point after the end of the processing delay of the configuration message; starting the handover timer at the epoch time; or extending the handover timer; modifying the handover timer by The apparatus of claim 1 , wherein the apparatus causes the execution of the following:

9. determining the epoch time to be a time point after the end of a processing delay of the configuration message; based on determining that the epoch time is the time point after the end of the processing delay of the configuration message; Relaxing handover delay and / or interruption time requirements; and / or Modifying the start time of the handover delay and / or interruption time measurement; modifying one or more requirements for completion of the handover by The apparatus according to claim 1 or 8,

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

11. 11. The apparatus according to claim 7, further comprising: an apparatus configured to initiate a random access procedure in the target cell using first resources allocated in the configuration, the first resources being the earliest available resources among the allocated resources.

12. 12. The apparatus of claim 1, wherein the configuration message indicates a random access channel configuration including a first resource and a second resource, the second resource being a resource that is later in time than the first resource.

13. The device according to any one of claims 1 to 12, wherein the device is a user equipment.

14. 1. An apparatus comprising: at least one processor; at least one memory that, when executed by the at least one processor, causes the device to receiving an acknowledgement of the handover request from a target cell associated with satellite assistance information that differs from satellite assistance information associated with the device, the acknowledgement comprising at least: a random access channel configuration including a first resource and optionally a second resource that is a resource that is 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; indicates, receiving the satellite assistance information, the satellite assistance information including at least an epoch time and corresponding satellite assistance information to be applied after the epoch time is reached; transmitting a configuration message for handover to the target cell to user equipment served by the apparatus, the configuration message indicating at least the random access channel configuration, the satellite assistance information, and the validity timer; at least one memory storing instructions for causing the An apparatus comprising:

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

16. 1. An apparatus comprising: at least one processor; at least one memory that, when executed by the at least one processor, causes the device to sending an acknowledgement of the handover request to a serving cell associated with satellite assistance information different from satellite assistance information associated with the device, the acknowledgement comprising at least: a random access channel configuration including a first resource and optionally a second resource that is a resource that is 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; indicates, transmitting the satellite assistance information, the satellite assistance information including at least an epoch time and corresponding satellite assistance information to be applied after the epoch time is reached; monitoring random access requests from user equipment previously served by the serving cell; at least one memory storing instructions for causing the An apparatus comprising:

17. detecting that a random access request is received on a first resource, the first resource being an earliest resource among the assigned resources; Releasing one or more subsequent ones of the allocated resources; and The apparatus of claim 16,

18. Detecting that a random access request is not received on the first resource; monitoring for random access requests on the second resource based on the detecting that a random access request has not been received on the first resource; The apparatus of claim 16,

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

20. 1. A method comprising: receiving, by a user equipment, 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, the configuration message comprising 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; indicates, receiving the satellite assistance information, the satellite assistance information including at least an epoch time and corresponding satellite assistance information to be applied after the epoch time is reached; determining, by the user equipment, whether to modify a handover timer and / or one or more requirements regarding handover completion based on at least the epoch time; A method comprising:

21. determining that the epoch time is a time point in the past; determining whether the satellite assistance information is valid based on determining that the epoch time is the time point in the past; and 21. The method of claim 20, comprising:

22. detecting that the satellite assistance information is not valid; and receiving updated satellite assistance information with a second epoch time based on detecting that the satellite assistance information is not valid; and modifying the handover timer, starting the handover timer at the second epoch time; or extending the handover timer; modifying the handover timer by 22. The method of claim 21, comprising:

23. detecting that the satellite assistance information is not valid; and receiving updated satellite assistance information with a second epoch time based on detecting that the satellite assistance information is not valid; and modifying one or more requirements for completion of the handover; Relaxing handover delay and / or interruption time requirements; and / or Modifying the start time of the handover delay and / or interruption time measurement; modifying one or more requirements for completion of the handover by 23. The method of claim 21 or 22, comprising:

24. 24. The method of claim 22 or 23, comprising initiating a random access procedure in the target cell using resources allocated in the configuration, the allocated resources being resources that are later in time than first resources, and the first resources being the earliest of the allocated resources.

25. detecting that the satellite assistance information is valid; and determining, based on detecting that the satellite assistance information is valid, not to modify the handover timer and / or one or more requirements for completing the handover; 22. The method of claim 21, comprising:

26. determining the epoch time to be a time point between a start time of processing the configuration message and an end of a processing delay of the configuration message; detecting that the satellite assistance information is valid based on determining that the epoch time is the time point between the start time of processing the configuration message and the end of the processing delay of the configuration message; determining not to modify the handover timer and / or one or more requirements for the handover completion; 21. The method of claim 20, comprising:

27. determining the epoch time to be a time point after the end of a processing delay of the configuration message; based on determining that the epoch time is the time point after the end of the processing delay of the configuration message; starting the handover timer at the epoch time; or extending the handover timer; modifying the handover timer by 21. The method of claim 20, comprising:

28. determining the epoch time to be a time point after the end of a processing delay of the configuration message; based on determining that the epoch time is the time point after the end of the processing delay of the configuration message; Relaxing handover delay and / or interruption time requirements; and / or Modifying the start time of the handover delay and / or interruption time measurement; modifying one or more requirements for completion of the handover by 28. The method of claim 20 or 27, comprising:

29. 30. The method of claim 23 or 28, wherein relaxing the handover delay requirement comprises adding a time value to the handover delay requirement, and / or relaxing the interruption time requirement comprises adding a time value to the interruption time requirement.

30. 30. The method of claim 26, comprising initiating a random access procedure in the target cell using first resources allocated in the configuration, the first resources being the earliest available resources in time from among the allocated resources.

31. 31. The method of claim 20, wherein the configuration message indicates a random access channel configuration including a first resource and a second resource, the second resource being a resource that is later in time than the first resource.

32. A computer program that, when executed by an apparatus, causes 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, the configuration message comprising 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; indicates, receiving the satellite assistance information, the satellite assistance information including at least an epoch time and corresponding satellite assistance information to be applied after the epoch time is reached; determining whether to modify a handover timer and / or one or more requirements for handover completion based on at least the epoch time; A computer program containing instructions to cause a program to be executed.

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