CN114731542A

CN114731542A - Enhanced handover and timing advance alignment

Info

Publication number: CN114731542A
Application number: CN201980102178.8A
Authority: CN
Inventors: 王文剑; 温萍萍; 朱凯
Original assignee: Nokia Shanghai Bell Co Ltd; Nokia Solutions and Networks Oy
Current assignee: Nokia Shanghai Bell Co Ltd; Nokia Solutions and Networks Oy
Priority date: 2019-11-12
Filing date: 2019-11-12
Publication date: 2022-07-08
Also published as: WO2021092766A1

Abstract

Embodiments of the present disclosure relate to enhanced handover and timing advance alignment. According to an embodiment of the present disclosure, a first device receives a measurement report from a second device, the measurement report comprising information specific to the second device. The first device selects a third device for handover based on the signal strength of the target device and the new criteria. The third device determines whether the current timing advance is valid and performs TA pre-compensation. In this way, the frequency of switching is reduced and fast data transmission is achieved.

Description

Enhanced handover and timing advance alignment

Technical Field

Embodiments of the present disclosure relate generally to the field of communications, and more particularly, in non-terrestrial networks, and more particularly, to a method, apparatus, device, and computer-readable storage medium for enhanced handover and timing advance alignment.

Background

Terrestrial networks have difficulty providing 5G coverage due to limited resources and infrastructure in remote areas. The main benefit of introducing non-terrestrial networks (NTN) is that by extending connectivity in sparsely populated areas where the density of devices is extremely low, ubiquitous 5G services are enabled to end devices, and the overall cost of deployment can be much lower than the overall cost of providing permanent infrastructure on the ground. A new solution for New Radios (NR) supporting NTN has been proposed. However, it also presents some problems in other respects.

Disclosure of Invention

In general, example embodiments of the present disclosure provide solutions for enhanced handover and timing advance alignment and corresponding communication devices.

In a first aspect, a method is provided. The method comprises the following steps: a measurement report is received at a first device from a second device served by the first device, the measurement report including information specific to the second device. The method further comprises the following steps: selecting a third device for handover of the second device based at least in part on a rule associated with signal strengths of one or more candidate devices, the one or more candidate devices including the third device. The method further comprises the following steps: a handover request is sent to a third device, the handover request including a first timing advance value of the second device and information specific to the second device. The method further comprises the following steps: receiving information of a handover from the third device, the information of the handover being related to an applicable timing advance value to the third device. The method further comprises the following steps: an indication of a handover from the first device to the third device is sent to the second device.

In a second aspect, a method is provided. The method comprises the following steps: a measurement report is sent at the second device to the first device serving the second device, the measurement report including information specific to the second device. The method further comprises the following steps: an indication of a handover from the first device to the third device is received from the first device. The method further comprises the following steps: information is obtained about a timing advance value applicable to the third device. The method further comprises the following steps: performing an uplink transmission with a third device based on the timing advance value.

In a third aspect, a method is provided. The method comprises the following steps: a handover request is received at a third device from a first device, the handover request including a first timing advance value of a second device and information specific to the second device served by the first device. The method further comprises the following steps: it is determined whether the first timing advance value applies to the third device based on the information specific to the second device. The method further comprises the following steps: based on the determination, information for a handover from the first device to the third device is generated. The method further comprises the following steps: the information is sent to the first device.

In a fourth aspect, a first device is provided. The first device comprises at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code configured to, with the at least one processor, cause the second apparatus to: a measurement report is received from a second device served by the first device, the measurement report including information specific to the second device. The first device is further caused to: selecting a third device for handover of the second device based at least in part on a rule associated with signal strengths of one or more candidate devices, the one or more candidate devices including the third device. The first device is further caused to: a handover request is sent to a third device, the handover request including a first timing advance value of the second device and information specific to the second device. The first device is further caused to: receiving information of a handover from the third device, the information of the handover being related to an applicable timing advance value to the third device. The first device is further caused to: an indication of a handover from the first device to the third device is sent to the second device.

In a fifth aspect, a second apparatus is provided. The second device comprises at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code configured to, with the at least one processor, cause the second apparatus to: sending a measurement report to a first device serving a second device, the measurement report including information specific to the second device. The second device is further caused to: an indication of a handover from the first device to the third device is received from the first device. The second device is further caused to: information is obtained about a timing advance value applicable to the third device. The second device is further caused to: performing an uplink transmission with a third device based on the timing advance value.

In a sixth aspect, a third apparatus is provided. The third device comprises at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code configured to, with the at least one processor, cause the third apparatus to: a handover request is received from a first device, the handover request including a first timing advance value of a second device and information specific to the second device served by the first device. The third device is further caused to: it is determined whether the first timing advance value applies to the third device based on the information specific to the second device. The third device is further caused to: based on the determination, information for a handover from the first device to the third device is generated. The third device is further caused to: the information is sent to the first device.

In a seventh aspect, an apparatus is provided. The device includes: means for receiving, at a first device, a measurement report from a second device served by the first device, the measurement report comprising information specific to the second device; means for selecting a third device for handover of the second device based at least in part on a rule associated with signal strengths of one or more candidate devices, the one or more candidate devices including the third device; means for sending a handover request to a third device, the handover request comprising a first timing advance value of the second device and information specific to the second device; means for receiving information of a handover from a third device, the information of the handover being related to an applicable timing advance value to the third device; and means for sending an indication of a handover from the first device to the third device to the second device.

In an eighth aspect, an apparatus is provided. The device includes: means for sending, at a second device, a measurement report to a first device serving the second device, the measurement report including information specific to the second device; means for receiving, from a first device, an indication of a handover from the first device to a third device; means for obtaining information on a timing advance value applicable to a third device; and means for performing an uplink transmission with the third device based on the timing advance value.

In a ninth aspect, an apparatus is provided. The apparatus includes means for receiving, at a third device, a handover request from a first device, the handover request including a first timing advance value of a second device and information specific to the second device served by the first device; means for determining whether the first timing advance value applies to the third device based on information specific to the second device; means for generating information for a handover from the first device to the third device based on the determination; and means for transmitting the information to the first device.

In a tenth aspect, there is provided a non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least a method according to any of the first to third aspects described above.

It should be understood that this summary is not intended to identify key or essential features of the embodiments of the disclosure, nor is it intended to be used to limit the scope of the disclosure. Other features of the present disclosure will become readily apparent from the following description.

Drawings

Some example embodiments will now be described with reference to the accompanying drawings, in which:

FIG. 1 illustrates an example communication network in which embodiments of the present disclosure may be implemented;

fig. 2 illustrates a schematic diagram of interactions between communication devices according to an embodiment of the present disclosure;

fig. 3 illustrates a schematic diagram of handover criteria according to an embodiment of the present disclosure;

FIG. 4 illustrates a schematic diagram of beam footprints and differential propagation in accordance with an embodiment of the present disclosure;

fig. 5 illustrates a flow diagram of a method implemented at a first device in accordance with an embodiment of the disclosure;

fig. 6 illustrates a flow chart of a method implemented at a second device in accordance with an embodiment of the present disclosure;

fig. 7 illustrates a flow chart of a method implemented at a third device in accordance with an embodiment of the present disclosure;

FIG. 8 illustrates a simplified block diagram of a device suitable for implementing embodiments of the present disclosure; and

fig. 9 illustrates a block diagram of an example computer-readable medium in accordance with some embodiments of the present disclosure.

Throughout the drawings, the same or similar reference numbers refer to the same or similar elements.

Detailed Description

The principles of the present disclosure will now be described with reference to a few exemplary embodiments. It is understood that these examples are described solely to illustrate and assist those skilled in the art in understanding and practicing the disclosure, and are not meant to imply any limitations on the scope of the invention. The disclosure described herein may be implemented in various ways other than those described below.

In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

References in the present disclosure to "one embodiment," "an example embodiment," etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element may be termed a second element, and, similarly, a second element may be termed a first element, without departing from the scope of example embodiments. As used herein, the term "and/or" includes any and all combinations of one or more of the listed terms.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises," "comprising," "has," "having," "includes" and/or "containing," when used herein, specify the presence of stated features, elements, and/or components, etc., but do not preclude the presence or addition of one or more other features, elements, components, and/or groups thereof.

As used in this application, the term "circuitry" may refer to one or to all of the following:

(a) hardware-only circuit implementations (such as implementations in analog and/or digital circuitry only) and

(b) a combination of hardware circuitry and software, such as (as applicable):

(i) combinations of analog and/or digital hardware circuit(s) and software/firmware, and

(ii) any portion of hardware processor(s) with software (including digital signal processor (s)), software, and memory(s) that work together to cause a device, such as a mobile phone or server, to perform various functions, and

(c) hardware circuit(s) and/or processor(s), such as microprocessor(s) or a portion of microprocessor(s), require software (e.g., firmware) for operation, but software may not be present when software is not required for operation.

This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also encompasses implementations of only a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and/or firmware. For example, the term circuitry, if applicable to a particular claim element, also encompasses a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in a server, a cellular network device, or other computing or network device.

As used herein, the term "communication network" refers to a network that conforms to any suitable communication standard, such as Long Term Evolution (LTE), LTE advanced (LTE-a), Wideband Code Division Multiple Access (WCDMA), High Speed Packet Access (HSPA), narrowband internet of things (NB-IoT), New Radio (NR), non-terrestrial network (NTN), and so forth. Further, communication between the terminal devices and the network devices in the communication network may be performed according to any appropriate generation of communication protocols, including but not limited to first generation (1G), second generation (2G), 2.5G, 2.85G, third generation (3G), fourth generation (4G), 4.5G, future fifth generation (5G) communication protocols, and/or any other protocols currently known or developed in the future. Embodiments of the present disclosure may be applied in various communication systems. In view of the rapid development of communications, there will, of course, also be future types of communication techniques and systems in which the present disclosure may be implemented. And should not be taken as limiting the scope of the disclosure to only the above-described systems.

As used herein, the term "network device" refers to a node in a communication network via which a terminal device accesses the network and receives services therefrom. Depending on the terminology and technology applied, a network device may refer to a Base Station (BS) or an Access Point (AP), e.g., a node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), an NR NB (also known as a gNB), a Remote Radio Unit (RRU), a Radio Head (RH), a Remote Radio Head (RRH), a relay, a low power node (such as femto, pico), etc.

The term "terminal device" refers to any terminal device capable of wireless communication. By way of example, and not limitation, a terminal device may also be referred to as a communication device, User Equipment (UE), Subscriber Station (SS), portable subscriber station, Mobile Station (MS), or Access Terminal (AT). End devices may include, but are not limited to, mobile phones, cellular phones, smart phones, voice over IP (VoIP) phones, wireless local loop phones, tablet computers, wearable end devices, Personal Digital Assistants (PDAs), portable computers, desktop computers, image capture end devices (such as digital cameras), gaming end devices, music storage and playback devices, in-vehicle wireless end devices, wireless endpoints, mobile stations, laptop embedded devices (LEEs), laptop installed devices (LMEs), USB dongle, smart devices, wireless client devices (CPE), internet of things (loT) devices, watches or other wearable devices, Head Mounted Displays (HMDs), vehicles, drones, medical devices and applications (e.g., tele-surgery), industrial devices and applications (e.g., robots and/or other wireless devices operating in industrial and/or automated processing chain environments), Consumer electronics devices, devices operating on commercial and/or industrial wireless networks, and the like. In the following description, the terms "terminal device", "communication device", "terminal", "user equipment" and "UE" may be used interchangeably.

As previously mentioned, NTN also presents problems in other respects. For NTN, the Round Trip Time (RTT) to the terminal device may be much larger than in a terrestrial network. Therefore, it is necessary to consider its impact on different aspects of New Radio (NR) design, including cell search, handover, Timing Advance (TA) adjustment.

For systems of Medium Earth Orbit (MEO), Low Earth Orbit (LEO) and High Altitude Pseudolite (HAPS) in NTN networks, there is a strong varying delay because the satellites and terminal devices are moving rapidly and not relatively stationary.

It has approved solution evaluation for NR to support non-terrestrial networks. The targets for the physical layer and the higher layer are reported below, respectively.

Physical layer:

physical layer control procedures (e.g., Channel State Information (CSI) feedback, power control);

uplink timing advance/Random Access Channel (RACH) procedure, including PRACH sequence/format/message;

appropriately make the retransmission mechanism of the physical layer more delay tolerant. This may also include the ability to deactivate the hybrid automatic repeat request (HARQ) mechanism.

Layer 2 and higher layers, and RAN architecture:

study several aspects and identify relevant solutions when needed: propagation delay: timing requirements and solutions for layer 2 aspects, Medium Access Channel (MAC), Radio Link Control (RLC), Radio Resource Control (RRC) are identified to support NTN propagation delay considering Frequency Division Duplex (FDD) and Time Division Duplex (TDD) duplex modes. This includes radio link management;

handover: research and identify mobility requirements and necessary measurements that may be required for handoff between some non-terrestrial space vehicles (such as non-geostationary satellites) moving at higher speeds but on predictable paths;

architecture: identify the radio access network architecture of 5G to support the requirements of non-terrestrial networks (e.g., handling of network identification);

paging: procedure adaptation in case of a mobile satellite footprint or cell.

It is well known that handover and RACH procedures are important issues for non-terrestrial networks. The problem is that there is a large varying delay because the satellites and terminal devices are moving rapidly and not relatively stationary. As a result, the duration of stay in a given spot beam for a given terminal device is very short, which can cause frequent handoff problems from the serving spot beam or satellite to a new target spot beam or new target satellite. The respective timing advance of the terminal device must also be dynamically updated quickly and a suitable TA index value is required. In addition, agreement is reached in link level and system level evaluation, as shown in table 1 below:

TABLE 1

In addition to terrestrial terminal devices, some scenarios do not exclude airborne terminal devices. Therefore, seamless mobility services and efficient handover are particularly important for those aviation terminal devices that are suitable for military, industrial use, such as delivery services or disaster warning, which could be fully controlled, even a small disconnection, could be a serious operational problem. Indeed, handover failures and radio link failures may also cause delays on the RTT already long in the NTN network. When the aviation terminal device generates a message just before receiving the handover command, it may not be able to send the message at the source cell. The terminal device then needs to delay transmission of the message until the RRC connection re-establishment is successfully completed in the cell.

Because the transmission channel is line of sight unobstructed at flight altitude, typically the drone terminal device may move at a very fast speed and the strongest signal may come from a different spot beam or from a different satellite for a short period of time.

However, in the conventional art, when the NTN terminal device satisfies the handover condition, the random access and RRC reestablishment procedure is still required, which may cause much delay. Furthermore, the frequent handover problem remains unsolved.

According to an embodiment of the present disclosure, a first device receives a measurement report from a second device, the measurement report comprising information specific to the second device. The first device selects a third device for handover based on the signal strength of the target device and the new criteria. The third device determines whether the current timing advance is valid and performs TA pre-compensation. In this way, the frequency of switching is reduced and fast data transmission is achieved.

The principles and embodiments of the present disclosure will be described in detail below with reference to the drawings. Referring initially to fig. 1, fig. 1 illustrates an example communication system 100 in which embodiments of the present disclosure may be implemented.

Fig. 1 illustrates a schematic diagram of a communication system 100 in which embodiments of the present disclosure may be implemented. For purposes of illustration, device 110 may be referred to hereinafter as network device 110 and device 120 may be referred to as terminal device 120. It should be noted that the first device and the second device are interchangeable. For example, processes described as being implemented on a terminal device can also be implemented on a network device, while processes described as being implemented on a network device can also be implemented on a terminal device.

The link from device 120 to device 110 may be referred to as an "uplink" and the link from device 110 to device 120 may be referred to as a "downlink".

Communication system 100, which is part of a communication network, includes devices 110-1, 110-2. The device 110 may be an over-the-air skeletal network device, such as a satellite.

Communication system 100 includes devices 120-1, 120-2, a. The device 120 may be a ground terminal device or an aviation terminal device.

It should be understood that communication system 100 may also include other elements that have been omitted for clarity. It should be understood that the number of devices shown in FIG. 1 is given for illustrative purposes and does not imply any limitations.

It should be understood that the number of network devices and terminal devices is for illustration purposes only and does not imply any limitation. System 100 may include any suitable number of network devices and terminal devices suitable for implementing embodiments of the present disclosure.

Communications in communication system 100 may be implemented in accordance with any suitable communication protocol(s), including, but not limited to, first-generation (1G), second-generation (2G), third-generation (3G), fourth-generation (4G), and fifth-generation (5G), etc. cellular communication protocols, wireless local area network communication protocols, such as Institute of Electrical and Electronics Engineers (IEEE)802.11, etc., and/or any other protocol currently known or developed in the future. Further, the communication may utilize any suitable wireless communication technology, including but not limited to: code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Frequency Division Duplex (FDD), Time Division Duplex (TDD), Multiple Input Multiple Output (MIMO), Orthogonal Frequency Division Multiplexing (OFDM), discrete Fourier transform spread OFDM (DFT-s-OFDM), and/or any other technique now known or later developed.

As shown in fig. 1, spot beams 140-1, 140-2, and 140-3 come from device 110-1. Spot beams 150-1, 150-2, and 150-3 come from device 110-2. It should be noted that a device may have any suitable number of beams. The device 120-1 may be an airborne terminal device flying in a circle or "8" shape across different devices. For purposes of illustration only, device 110-1 hereinafter refers to a first device, device 120 hereinafter refers to a second device, and device 110-2 hereinafter refers to a third device. The first device and the third device may be interchangeable.

Fig. 2 illustrates a schematic diagram of interactions 200 in a contention free system according to an embodiment of the present disclosure. The interaction 200 may be implemented on any suitable device. For purposes of illustration only, the interaction 200 is described as being implemented at the first device 110-1, the second device 120, and the third device 110-2.

The second device 120-1 may perform 2005 measurements for handover. For example, the second device 120-1 may measure the signal strength of the first device 110-1. The first device 110-1 is currently serving the second device 120-1. The second device 120-1 may receive the measurement configuration from the first device 110-1. The measurement configuration may include a measurement object and/or a reporting configuration. The measurement object may refer to an object on which the UE will perform measurement, i.e., what is measured. A reporting configuration may refer to a list of reporting configurations including reporting criteria and reporting formats.

The second device 120-1 sends 2010 a measurement report to the first device 110-1. The measurement report includes information specific to the second device 120-1. For example, the information specific to the second device 120-1 may include identification information of the second device 120-1. The information specific to the second device 120-1 may also include the velocity of the second device 120-1. Alternatively or additionally, the information specific to the second device 120-1 may include a direction of movement of the second device 120-1. In some embodiments, if the second device 120-1 is a GNSS terminal device. The information specific to the second device 120-1 may also include the location of the second device 120-1. In other embodiments, the information specific to the second device 120-1 may include an altitude of the second device 120-1. The information specific to the second device 120-1 may also include an altitude range for the second device 120-1.

The first device 110-1 may obtain 2015 signal strengths of other devices (e.g., the third device 110-2). For example, the first device 110-1 may obtain a Reference Signal Received Power (RSRP) of the candidate device indicating the signal strength. In some embodiments, the second device 120-1 may measure RSRP of one or more candidate devices and send RSRP to the first device 110-1. It should be noted that the signal strength may be any suitable measurement.

The first device 110-1 selects 2020 the third device 110-2 based at least in part on a rule associated with a signal strength of at least one candidate device. The first device 110-1 may receive the signal strengths of one or more candidate devices from the second device 120-1. In some embodiments, the first device 110-1 determines weighting factors for other candidate devices. The first device 110-10 may determine the threshold signal strength based on the signal strength and the weighting factor. The first device 110-1 may select the third device if the signal strength of the third device 110-2 exceeds the threshold signal strength. The first device 110-1 may collect RSRP and weighting factors (τ) based on the decreasing RSRP of devices other than the serving cell₁＞τ₂＞τ₃＞τ_n). The first device 110-1 may then determine a combination of devices from the collected RSRP.

In some embodiments, the first device 110-1 may determine a duration for which the signal strength of the third device 110-2 exceeds a threshold signal strength. The first device 110-1 may select the third device if the duration exceeds a threshold duration.

In some embodiments, the first device 110-1 may select the third device 110-2 according to rules associated with signal strengths of one or more candidate devices (as shown below):

wherein RSRP_{targ et candidatesm}Representing the RSRP received from the candidate device-m and N representing the number of candidate target devices. Tau.₁＞τ₂＞τ₃＞τ_nIs the weighting factor to be used as a weighted average of all candidate target devices. The definition of τ depends on the RSRP ratio, H, from the candidate target devices_marginIs to cutA trade-off amount, which is used as an index for connection to a device having higher power. T is_TTTFor stopping the excessive handover in a short time.

Figure 3 shows a schematic diagram of a handover procedure with movement of the second device and fluctuation of the weighted average of RSRP from the candidate device. As shown in FIG. 3, line 350 represents the signal strength of the first device 110-1 as a function of time, and line 360 represents the signal strength of the third device 110-2 as a function of time. Line 370 represents the threshold signal strength determined based on the signal strength and the weighting factor. T310 shown in fig. 3 is a start time of time-to-trigger (TTT) measurement of the conventional scheme, and T320 shown in fig. 3 indicates that RSRP of the target device is greater than the first device 110-1 by H for the time duration of the TTT_margin. According to conventional techniques, the first device 110-1 may determine to switch to the third device 110-2 if the duration 390 between T210 and T320 exceeds a threshold duration. As shown in FIG. 3, T330 is the start time of the TTT measurement, and T340 denotes that the RSRP of the third device 110-2 is greater than the threshold signal strength by H for the time duration of the TTT_margin. The first device 110-1 may determine to switch to the third device 110-2 if the duration 380 between T330 and T340 exceeds the threshold duration. Thus, the excessive switching time is reduced.

In some embodiments, the threshold duration may be adjusted to accommodate the NTN. For example, an adjustment factor δ may be set_thresholdIf RSRP_serving-H_margin≥δ_thresholdThen the serving device may be deemed to still have sufficient RSRP to maintain the network connection, then the TTT is increased to T_TTT+T_δ. If T'_duration≥T_TTT+T_δThen handover may be performed and the handover trigger timing is delayed. In this way, the system will delay the occurrence of a handover, thereby reducing the frequency of handovers by adjusting the TTT.

The first device 110-1 sends 2025 a handover request to the third device 110-2. The handover request includes information specific to the second device 120. The handover request also includes a first timing advance value for the second device 120-1. The information specific to the second device 120 may indicate that the second device 120 is an NTN terminal device that should avoid frequent handovers and has fast data transmission.

The third device 110-2 determines 2030 whether the first timing advance applies to the third device 110-2 based on the information specific to the second device 120. The third device 110-2 generates 2035 handover information based on the determination. The third device 110-2 may generate an indication that the first timing advance may be reused if the first timing advance value applies. The information of the handover may comprise an indication.

If the first timing advance value is not applicable, the third device 110-2 may generate an indication that the first timing advance is not applicable. The indication may be included in the information of the handover.

In some embodiments, the third device 110-2 may determine an applicable second advance timing if the first timing advance value does not apply. In some embodiments, if the second device 120 is a non-GNSS end device, the third device 110-2 may indicate a common propagation delay d1/c and have d_compensationThe differential delay of/c is compensated such that the residual differential delay can be controlled to within 200km/c, where c is the speed of light. In this way, uplink reception from different terminal devices is synchronized at the network device to within the accuracy of the CP length, so that the current NR preamble does not have to be changed during handover to reduce handover overhead and improve efficiency.

Fig. 4 illustrates a schematic diagram of satellite beam footprints and differential propagation. As shown in fig. 4, within the satellite footprint, the beam of device 110-2 may broadcast a common timing advance, shown as d410, corresponding to the shortest distance in the footprint. If the differential delay d 430-d 410 is controlled to be within 200km, it can be supported at the current NR and the legacy NR PRACH format can be reused. Table 2 below shows the relationship between differential delay and device elevation.

TABLE 2

Alpha 440[ degree ]]	Cell radius (S460/2) [ km]	d430[km]
			10	200	390
20	200	372
			30	200	343
40	200	303
			50	200	254
60	200	197
			70	200	134
80	200	67

As can be seen from Table 2 above, for device elevation angles less than 60 degrees, the differential delay d₃＝d₂-d₁The maximum cell coverage supported by the NR preamble format may be exceeded. In this case, the target device may be selected according to the data in the target device

Is pre-compensated in advance so that the residual differential delay is within the maximum cell coverage supported by the NR preamble. Considering different elevation angles, it can be known that 190 ≦ d_compensation267 below. In one example embodiment, assume d_compensationAt 200, the compensated differential delay d3' is shown in table 3 below. It can be seen that the absolute value of d3 after compensation (denoted as d3') falls within the range of 0-200 km.

TABLE 3

Alpha 440[ degree ]]	Cell radius (S460/2) [ km]	d3’[km]
			10	200	190
20	200	172
			30	200	143
40	200	103
			50	200	54
60	200	-3
			70	200	-66
80	200	-133

In some embodiments, after compensation, a terminal device for which the CP length is insufficient to account for uncertainty in the differential delay corresponds to a negative value in table 3. In this case, severe inter-carrier interference (ICI) and inter-symbol interference (ISI) may be caused, and the NR preamble format needs to be redesigned or extended in consideration of different footprints. To keep the timing advance error within the cyclic prefix of Orthogonal Frequency Division Multiplexing (OFDM), the effect of residual differential delay can be mitigated by: case 1: the NTN differential delay is ≦ the currently specified maximum NR PRACH CP duration. In this case, there is no need to change the designated NR RACH procedure; case 2: NTN differential delay > currently specified maximum NR PRACH CP duration. In this case, different solutions are possible, to be studied further.

In case 2 above, there are currently two types of PRACH formats in NR, i.e. with L_RA839 long and short preamble L_RA139 as shown in tables 4-1 and 4-2.

TABLE 4-1 for L_RA839 and Δ f^RAPRACH preamble format of e {1.25, 5} kHz

Tables 4-2 for L_RA139 and Δ f^RA＝15·２^μPRACH preamble format of kHz, wherein

μ∈{0，1，2，3}

The PRACH sequence and CP time length are detailed in tables 4-3. It can be seen that the CP length is no greater than 684.37us, while the maximum differential delay within a beam is 1.6ms at GEO and 0.65ms at LEO, much greater than 684.37us or close to this value. Thus, the current NR preamble format may not be sufficient to satisfy all NTN scenarios.

Table 4-3 preamble parameters in different formats

To compensate for the large differential delay in NTN, the conventional CP length may be considered. The subcarrier spacing (SCS) of preamble formats 0, 1, 2, and 3 currently supported may not be sufficient in systems with high residual frequency uncertainty. In some embodiments, the third device 110-2 may generate information indicating a handover of at least one of the physical random access channel formats if the first timing advance value is not applicable. To mitigate RA detection impairments caused by large delays, path loss and frequency uncertainty, new formats 4 and 5 can be introduced here based on the legacy long preamble format with a suitable scaling factor μ. Format 4 may be used for LEO scenarios and format 5 may be used for GEO systems. Table 5 shows the proposed preamble format for NTN.

TABLE 5

Format 4 has a CP length of about 2ms and format 6 has a CP length of about 0.79ms, which is sufficient to satisfy the maximum differential delay in the NTN scenario described above. Further, these new PRACH formats may be signaling from the third device to the first device for preparation of a handover of the terminal device. For example, if the second device 120-1 and the delay of the second device 120-1 having the compensation range of the cyclic prefix length cannot perform uplink transmission with the third device 110-2, the second device 120-1 may perform retransmission using the physical random access channel format. In this way, it resolves the uncertainty of the differential delay.

In some embodiments, the third device 110-2 may determine a resource allocation for the second device 120 and generate information including a handover of the resource allocation.

The third device 110-2 sends 2040 handover information to the first device 110-1. The information of the handover may include a second timing advance value. Alternatively or additionally, the information of the handover may comprise an indication that the first timing advance value is not applicable to the third device. In other embodiments, the information for the handover may include an indication that the first timing advance value is reused. In further embodiments, the information of the handover may indicate at least one of physical random access channel formats. In some embodiments, the information for handover may include resource allocation.

The first device 110-1 sends 2045 an indication of the handover to the second device 120-1. In some embodiments, the indication of the handover may comprise a resource allocation. Alternatively or additionally, the indication of the handover may comprise an uplink procedure avoidance indication assigned by the third device 110-1. In other embodiments, the indication to switch may comprise an indication to reuse the first timing advance value. In further embodiments, the indication of the handover may comprise an indication of a second timing advance value.

The second device 120-1 obtains 2050 information about the timing advance. In some embodiments, the second device 120-1 may obtain an indication from the indication of the handover to reuse the first timing advance value. In other embodiments, the second device 120-1 may obtain an indication of the second timing advance value from the indication of the handover. In other embodiments, the second device 120-1 may obtain an indication that the first timing advance is not applicable and receive ephemeris for the third device 110-2 from the first device 110-1. The second device 120-1 may estimate a timing advance value required by the third device 110-2.

The second device 120-1 performs 2055 an uplink transmission with the third device 110-2. For example, the second device 120-1 may perform uplink transmission based on the resource allocation with a desired timing advance. If the second device 120-1 fails to perform uplink transmission with the third device 110-1, the second device 120-1 may compare the delay of the second device 120-1 with a compensation range of the cyclic prefix length. The second device 120-1 may perform retransmission using the physical random access channel format if the delay exceeds the backoff range.

Fig. 5 illustrates a flow chart of an example method 500 implemented at a terminal device, in accordance with some embodiments of the present disclosure. Method 500 may be implemented on any suitable device. For discussion purposes, the method 500 will be described with reference to fig. 1 from the perspective of the first device 110-1.

At block 510, the first device 110-1 receives a measurement report for the first device 110-1. The measurement report includes information specific to the second device 120-1. For example, the information specific to the second device 120-1 may include identification information of the second device 120-1. The information specific to the second device 120-1 may also include the velocity of the second device 120-1. Alternatively or additionally, the information specific to the second device 120-1 may include a direction of movement of the second device 120-1. In some embodiments, if the second device 120-1 is a GNSS terminal device. The information specific to the second device 120-1 may also include the location of the second device 120-1. In other embodiments, the information specific to the second device 120-1 may include an altitude of the second device 120-1. The information specific to the second device 120-1 may also include an altitude range for the second device 120-1.

The first device 110-1 may obtain the signal strength of other devices, such as the third device 110-2. For example, the first device 110-1 may obtain a Reference Signal Received Power (RSRP) of a candidate device indicating signal strength from the second device 120-1. It should be noted that the signal strength may be any suitable measurement.

At block 520, the first device 110-1 selects the third device 110-2 based at least in part on rules associated with signal strengths of one or more candidate devices. In some embodiments, the first device 110-1 determines weighting factors for other candidate devices. The first device 110-10 may determine the threshold signal strength based on the signal strengths of the one or more candidate devices and the weighting factor. The first device 110-1 may select the third device if the signal strength of the third device 110-2 exceeds the threshold signal strength.

In some embodiments, the first device 110-1 may determine a duration for which the signal strength of the third device 110-2 exceeds a threshold signal strength. The first device 110-1 may select the third device if the duration exceeds the threshold duration. In some embodiments, the first device 110-1 may select the third device 110-2 according to predetermined criteria.

At block 530, the first device 110-1 sends a handover request to the third device 110-2. The handover request includes information specific to the second device 120. The handover request also includes a first timing advance value for the second device 120-1. The information specific to the second device 120 may indicate that the second device 120 is an NTN terminal device that should avoid frequent handovers and has fast data transmission.

At block 540, the first device 110-1 receives information for the handover from the third device. The information for the handover may be about a timing advance value applicable to the third device 110-2. The information of the handover may include one of: a second timing advance, an indication that the first timing advance applies, or an indication that the first timing advance does not apply.

At block 550, the first device 110-1 sends an indication of the handover to the second device 120-1. In some embodiments, the indication of the handover may comprise a resource allocation. Alternatively or additionally, the indication of the handover may comprise an uplink procedure avoidance indication assigned by the third device 110-1. In other embodiments, the indication to switch may comprise an indication to reuse the first timing advance value. In further embodiments, the indication of the handover may comprise an indication of a second timing advance value.

Fig. 6 illustrates a flowchart of an example method 600 implemented at a terminal device, in accordance with some embodiments of the present disclosure. Method 600 may be implemented on any suitable device. For discussion purposes, the method 600 will be described with reference to fig. 1 from the perspective of the second device 120-1.

At block 610, the second device 120-1 sends a measurement report to the first device 110-1. The measurement report includes information specific to the second device 120-1. For example, the information specific to the second device 120-1 may include identification information of the second device 120-1. The information specific to the second device 120-1 may also include the velocity of the second device 120-1. Alternatively or additionally, the information specific to the second device 120-1 may include a direction of movement of the second device 120-1. In some embodiments, if the second device 120-1 is a GNSS terminal device. The information specific to the second device 120-1 may also include the location of the second device 120-1. In other embodiments, the information specific to the second device 120-1 may include an altitude of the second device 120-1. The information specific to the second device 120-1 may also include an altitude range for the second device 120-1.

In some embodiments, the second device 120-1 may perform measurements for handover. For example, the second device 120-1 may measure the signal strength of the first device 110-1. The first device 110-1 is currently serving the second device 120-1. The second device 120-1 may receive the measurement configuration from the first device 110-1. The measurement configuration may include a measurement object and/or a reporting configuration. The measurement object may refer to an object on which the UE will perform measurement, i.e., what is measured. A reporting configuration may refer to a list of reporting configurations including reporting criteria and reporting formats. In some embodiments, the second device 120-1 may measure RSRP of one or more candidate devices and send RSRP to the first device 110-1.

At block 620, the second device 120-1 receives an indication of a handover from the first device 110-1. In some embodiments, the indication of the handover may comprise a resource allocation. Alternatively or additionally, the indication of the handover may comprise an uplink procedure avoidance indication assigned by the third device 110-1. In other embodiments, the indication to switch may comprise an indication to reuse the first timing advance value. In further embodiments, the indication of the handover may comprise an indication of a second timing advance value.

At block 630, the second device 120-1 obtains information regarding the timing advance. In some embodiments, the second device 120-1 may obtain an indication from the indication of the handover to reuse the first timing advance value. In other embodiments, the second device 120-1 may obtain an indication of the second timing advance value from the indication of the handover. In other embodiments, the second device 120-1 may obtain an indication that the first timing advance is not applicable and receive ephemeris for the third device 110-2 from the first device 110-1. The second device 120-1 may estimate a timing advance value required by the third device 110-2.

At block 640, the second device 120-1 performs an uplink transmission with the third device 110-2. For example, the second device 120-1 may perform uplink transmission based on the resource allocation with a desired timing advance. If the second device 120-1 fails to perform uplink transmission with the third device 110-1, the second device 120-1 may compare the delay of the second device 120-1 with a compensation range of the cyclic prefix length. The second device 120-1 may perform retransmission using the physical random access channel format if the delay exceeds the backoff range.

Fig. 7 illustrates a flowchart of an example method 800 implemented at a terminal device, in accordance with some embodiments of the present disclosure. Method 800 may be implemented on any suitable device. For discussion purposes, the method 800 will be described with reference to fig. 1 from the perspective of the third device 110-2.

At block 710, the third device 110-2 receives a handover request from the first device 110-1. The handover request includes information specific to the second device 120. The handover request also includes a first timing advance value for the second device 120-1. The information specific to the second device 120 may indicate that the second device 120 is an NTN terminal device that should avoid frequent handovers and has fast data transmission.

At block 720, the third device 110-2 determines whether the first timing advance applies to the third device 110-2 based on the information specific to the second device 120.

At block 730, the third device 110-2 generates information for the handover based on the determination. The third device 110-2 may generate an indication that the first timing advance may be reused if the first timing advance value applies. The information of the handover may comprise an indication.

In some embodiments, the third device 110-2 may determine an applicable second advance timing if the first timing advance value is not applicable. In some embodiments, if the second device 120 is a non-GNSS end device, the third device 110-2 may indicate the common propagation delay d1/c and have

Such that the residual differential delay can be controlled to within 200km/c, where c is the speed of light. In this way, uplink receptions from different terminal devices are synchronized at the network device to within the accuracy of the CP length, so that the current NR preamble does not have to be changed during handover, to reduce handover overhead and improve efficiency

In some embodiments, the third device 110-2 may determine a resource allocation for the second device 120 and generate handover information including the resource allocation. In further embodiments, the third device 110-2 may generate information indicating a handover of at least one of the physical random access channel formats.

The third device 110-2 sends information of the handover to the first device 110-1 at block 740. The information of the handover may include a second timing advance value. Alternatively or additionally, the information of the handover may comprise an indication that the first timing advance value is not applicable to the third device. In other embodiments, the information for the handover may include an indication that the first timing advance value is reused. In further embodiments, the information of the handover may indicate at least one of the physical random access channel formats. In some embodiments, the information for handover may include resource allocation.

In some embodiments, an apparatus (e.g., first device 110-1) for performing method 500 may include respective means for performing corresponding steps in method 500. These components may be implemented in any suitable manner. It may be implemented, for example, by circuitry or software modules.

In some embodiments, the apparatus includes means for receiving, at a first device, a measurement report from a second device served by the first device, the measurement report including information specific to the second device; means for selecting a third device for handover of the second device based at least in part on a rule associated with signal strengths of one or more candidate devices, the one or more candidate devices including the third device; means for sending a handover request to a third device, the handover request comprising a first timing advance value of the second device and information specific to the second device; means for receiving information of a handover from a third device, the handover information regarding an applicable timing advance value to the third device; and means for sending an indication to the second device to switch from the first device to the third device.

In some embodiments, the means for selecting the third device comprises: means for obtaining signal strengths of one or more candidate devices from a second device; means for determining one or more weighting factors for one or more candidate devices; means for determining a threshold signal strength based at least in part on the signal strength and one or more weighting factors; and means for selecting the third device in accordance with a determination that the signal strength of the third device exceeds the threshold signal strength.

In some embodiments, the means for selecting the third device comprises: means for determining a duration for which the signal strength exceeds a threshold signal strength; means for comparing the duration to a threshold duration; and means for selecting the third device in dependence on the determination that the duration exceeds the threshold duration.

In some embodiments, the means for sending an indication of the handover comprises: receiving, from a third device, a resource allocation for a second device; and means for transmitting an indication comprising the resource allocation to the second device.

In some embodiments, the means for sending an indication of the handover comprises: for sending an indication comprising a second timing advance value to the second device in dependence on the information comprising a handover of the second timing advance value of the first device.

In some embodiments, the means for sending an indication of the handover comprises: means for transmitting an indication to the second device to reuse the first timing advance value in accordance with information comprising a handover of a further indication that the first timing advance value applies to the third device.

In some embodiments, the apparatus includes means for transmitting, to the second device, ephemeris information and a physical random access channel format of the third device in accordance with the information including the further indication that the first timing advance value is not applicable for the third device and the switching of the physical random access channel format.

In some embodiments, wherein the information specific to the second device comprises at least one of: identification information of the second device, a speed of the second device, a direction of movement of the second device, a location of the second device, an altitude of the second device, or an altitude range of the second device.

In some embodiments, wherein the first device comprises a network device, the second device comprises a terminal device, and the third device comprises a further network device.

In some embodiments, an apparatus (e.g., the second device 120-1) for performing the method 600 may include respective means for performing the corresponding steps in the method 600. These components may be implemented in any suitable manner. For example, it may be implemented by circuitry or software modules.

In some embodiments, the apparatus comprises: means for sending, at a second device, a measurement report to a first device serving the second device, the measurement report including information specific to the second device; means for receiving, from a first device, an indication of a handover from the first device to a third device; means for obtaining information on a timing advance value applicable to a third device; and means for performing an uplink transmission with the third device based on the timing advance value.

In some embodiments, the means for receiving an indication of a handover comprises: means for receiving an indication comprising a resource allocation used for uplink transmission with a third device.

In some embodiments, the means for obtaining information about the timing advance value comprises: means for obtaining a timing advance value applicable to a third device based on the indication received from the first device.

In some embodiments, the means for obtaining information about the timing advance comprises: means for receiving ephemeris information of a third device from the first device; and means for determining a timing advance based on the ephemeris information.

In some embodiments, the apparatus further comprises means for receiving information of a physical random access channel format from the first device; means for comparing a delay of the second device with a compensation range for a cyclic prefix length based on performing uplink transmission failure; and means for performing retransmission using the physical random access channel format in accordance with the delay exceeding the backoff range.

In some embodiments, the information specific to the second device comprises at least one of: identification information of the second device, a speed of the second device, a direction of movement of the second device, a location of the second device, an altitude of the second device, or an altitude range of the second device.

In some embodiments, the first device comprises a network device, the second device comprises a terminal device, and the third device comprises a further network device.

In some embodiments, an apparatus (e.g., third device 110-2) for performing method 700 may include respective means for performing corresponding steps in method 700. These components may be implemented in any suitable manner. For example, it may be implemented by circuitry or software modules.

In some embodiments, the apparatus comprises: means for receiving, at a third device, a handover request from a first device, the handover request comprising a first timing advance value of a second device and information specific to the second device served by the first device; means for determining whether the first timing advance value applies to the third device based on information specific to the second device; means for generating information for a handover from the first device to the third device based on the determination; and means for transmitting the information to the first device.

In some embodiments, the means for generating information for handover comprises: means for determining, in accordance with the determination that the first timing advance value is not applicable to the third device, a second timing advance value applicable to the third device based on the information specific to the second device; and means for generating information comprising a switch of the second timing advance value.

In some embodiments, the means for generating information for handover comprises: means for generating an indication that the first timing advance value is not applicable to the third device in dependence on determining that the first timing advance value is not applicable to the third device; and means for generating information comprising the indicated handover.

In some embodiments, the means for generating information for handover comprises: means for generating a further indication that the first timing advance value is reused in dependence on determining that the first timing advance value applies to the third device; and means for generating information comprising the further indicated handover.

In some embodiments, the means for generating information for handover comprises: means for generating a resource allocation for a second device; and means for generating information comprising the resource allocation.

In some embodiments, the means for generating information for handover comprises: means for generating information indicative of a handover of at least one of the physical random access channel formats in dependence on determining that the first timing advance value is not applicable to the third device.

Fig. 8 is a simplified block diagram of a device 800 suitable for implementing embodiments of the present disclosure. The device 800 may be provided to implement a communication device, such as the first device 110-1, the second device 120-1, or the third device 110-2 shown in fig. 1. As shown, device 800 includes one or more processors 810, one or more memories 820 coupled to processors 810, and one or more communication modules (e.g., transmitters and/or receivers (TX/RX)) coupled to processors 810.

The communication module 840 is used for bidirectional communication. The communication module 840 has at least one antenna to facilitate communication. The communication interface may represent any interface necessary to communicate with other network elements.

The processor 810 may be of any type suitable for a local technology network and may include, as non-limiting examples, one or more of the following: general purpose computers, special purpose computers, microprocessors, Digital Signal Processors (DSPs) and processors based on a multi-core processor architecture. Device 800 may have multiple processors, such as application specific integrated circuit chips that are time-dependent from a clock synchronized to the main processor.

The memory 820 may include one or more non-volatile memories and one or more volatile memories. Examples of non-volatile memory include, but are not limited to, Read Only Memory (ROM)824, Electrically Programmable Read Only Memory (EPROM), flash memory, a hard disk, a Compact Disc (CD), a Digital Video Disk (DVD), and other magnetic and/or optical storage. Examples of volatile memory include, but are not limited to, Random Access Memory (RAM)822 and other volatile memory that does not persist during a power failure.

The computer programs 830 include computer-executable instructions that are executed by the associated processor 810. The program 830 may be stored in the ROM 824. Processor 810 may perform any suitable acts and processes by loading programs 830 into RAM 822.

Embodiments of the present disclosure may be implemented by way of program 830 such that device 800 may perform any of the processes of the present disclosure discussed with reference to fig. 2-7. Embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.

In some embodiments, the program 830 may be tangibly embodied in a computer-readable medium, which may be included in the device 800 (such as in the memory 820) or other storage accessible by the device 800. Device 800 can load program 830 from the computer-readable medium into RAM 822 for execution. The computer readable medium may include any type of tangible, non-volatile memory, such as ROM, EPROM, flash memory, a hard disk, a CD, a DVD, etc. Fig. 9 shows an example of a computer readable medium 900 in the form of a CD or DVD. The computer readable medium has program 830 stored thereon.

In general, the various embodiments of the disclosure may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. While various aspects of the embodiments of the present disclosure are illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that the blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples: hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing device, or some combination thereof.

The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer-readable storage medium. The computer program product comprises computer-executable instructions, such as those included in program modules, that are executed in a device on a target real or virtual processor to perform the methods 200 to 400 as described above with reference to fig. 2 to 6. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, etc. that perform particular tasks or implement particular abstract data types. In various embodiments, the functionality of the program modules may be combined or split between program modules as desired. Machine-executable instructions for program modules may be executed within local or distributed devices. In a distributed facility, program modules may be located in both local and remote memory storage media.

Program code for performing the methods of the present disclosure may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the program codes, when executed by the processor or controller, cause the functions/operations specified in the flowchart and/or block diagram to be implemented. The program code may execute entirely on the machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.

In the context of the present disclosure, computer program code or related data may be carried by any suitable carrier to enable a device, apparatus or processor to perform various processes and operations as described above. Examples of a carrier include a signal, computer readable medium, and the like.

The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable medium may include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of a computer-readable storage medium would include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

Further, while operations are described in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In some cases, multitasking and parallel processing may be advantageous. Also, while several specific implementation details are included in the above discussion, these should not be construed as limitations on the scope of the disclosure, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination.

Although the disclosure has been described in language specific to structural features and/or methodological acts, it is to be understood that the disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

1. A method, comprising:

receiving, at a first device, a measurement report from a second device served by the first device, the measurement report including information specific to the second device;

selecting a third device for handover of the second device based at least in part on a rule associated with signal strengths of one or more candidate devices, the one or more candidate devices including the third device;

sending a handover request to a third device, the handover request including a first timing advance value of the second device and the information specific to the second device;

receiving information of the handover from the third device, the information of the handover relating to an applicable timing advance value to the third device; and

sending an indication of the handover from the first device to the third device to the second device.

2. The method of claim 1, wherein selecting the third device based on the rule comprises:

obtaining the signal strengths of the one or more candidate devices from the second device;

determining one or more weighting factors for the one or more candidate devices;

determining a threshold signal strength based at least in part on the signal strength and the one or more weighting factors; and

in accordance with a determination that the signal strength of the third device exceeds the threshold signal strength, selecting the third device.

3. The method of claim 2, wherein selecting the third device comprises:

determining a duration for which the signal strength exceeds the threshold signal strength;

comparing the duration to a threshold duration; and

in accordance with a determination that the duration exceeds the threshold duration, selecting the third device.

4. The method of claim 1, wherein sending the indication of the handover comprises:

receiving, from the third device, a resource allocation for the second device; and

transmitting the indication comprising the resource allocation to the second device.

5. The method of claim 1, wherein sending the indication of the handover comprises:

sending the indication comprising a second timing advance value of the first device to the second device in accordance with the information comprising the handover of the second timing advance value.

6. The method of claim 1, wherein sending the indication of the handover comprises:

in accordance with the information of the handover comprising a further indication that the first timing advance value applies to the third device, sending the indication to the second device to reuse the first timing advance value.

7. The method of claim 1, further comprising:

sending ephemeris information for the third device and a physical random access channel format to the second device in accordance with the information for the handover comprising an additional indication that the first timing advance value is not applicable for the third device and the physical random access channel format.

8. The method of claim 1, wherein the information specific to the second device comprises at least one of: identification information of the second device, a speed of the second device, a direction of movement of the second device, a location of the second device, an altitude of the second device, or an altitude range of the second device.

9. The method of claim 1, wherein the first device comprises a network device, the second device comprises a terminal device, and the third device comprises a further network device.

10. A method, comprising:

sending, at a second device, a measurement report to a first device serving the second device, the measurement report including information specific to the second device;

receiving, from the first device, an indication of a handover from the first device to a third device;

obtaining information about a timing advance value applicable to the third device; and

performing an uplink transmission with the third device based on the timing advance value.

11. The method of claim 10, wherein receiving the indication of the handover comprises:

receiving the indication comprising a resource allocation used for the uplink transmission with the third device.

12. The method of claim 10, wherein obtaining the information regarding the timing advance value comprises:

obtaining the timing advance value applicable to the third device in accordance with the indication received from the first device.

13. The method of claim 10, wherein obtaining the information regarding the timing advance comprises:

receiving ephemeris information for the third device from the first device; and

determining the timing advance based on the ephemeris information.

14. The method of claim 10, further comprising:

receiving information of a physical random access channel format from the first device;

comparing a delay of the second device with a compensation range of a cyclic prefix length according to a failure to perform the uplink transmission; and

performing retransmission using the physical random access channel format in accordance with the delay exceeding the backoff range.

15. The method of claim 10, wherein the information specific to the second device comprises at least one of: identification information of the second device, a speed of the second device, a direction of movement of the second device, a location of the second device, an altitude of the second device, or an altitude range of the second device.

16. The method of claim 10, wherein the first device comprises a network device, the second device comprises a terminal device, and the third device comprises a further network device.

17. A method, comprising:

receiving, at a third device, a handover request from a first device, the handover request comprising a first timing advance value of a second device and information specific to the second device served by the first device;

determining whether the first timing advance value applies to the third device based on the information specific to the second device;

generating information of the handover from the first device to the third device based on the determination; and

sending the information to the first device.

18. The method of claim 17, wherein generating the information for the handover comprises:

in accordance with a determination that the first timing advance value is not applicable to the third device, determining a second timing advance value applicable to the third device based on the information specific to the second device; and

generating the information for the handover comprising the second timing advance value.

19. The method of claim 17, wherein generating the information for the handover comprises:

in accordance with a determination that the first timing advance value is not applicable to the third device, generating an indication that the first timing advance value is not applicable to the third device; and

generating the information of the handover including the indication.

20. The method of claim 17, wherein generating the information for the handover comprises:

in accordance with a determination that the first timing advance value is applicable to the third device, generating a further indication that the first timing advance value is reused; and

generating the information of the handover comprising the further indication.

21. The method of claim 17, wherein generating the information for the handover comprises:

generating a resource allocation for the second device; and

generating the information comprising the resource allocation.

22. The method of claim 17, wherein generating the information for the handover comprises:

in accordance with a determination that the first timing advance value is not applicable to the three devices, generating the information indicative of the handover of at least one of physical random access channel formats.

23. The method of claim 17, wherein the information specific to the second device comprises at least one of: identification information of the second device, a speed of the second device, a direction of movement of the second device, a location of the second device, an altitude of the second device, or an altitude range of the second device.

24. The method of claim 17, wherein the first device comprises a network device, the second device comprises a terminal device, and the third device comprises a further network device.

25. A first device, comprising:

at least one processor; and

at least one memory including computer program code;

the at least one memory and the computer program code configured to, with the at least one processor, cause the first device to perform the method of any of claims 1-9.

26. A second device, comprising:

at least one processor; and

at least one memory including computer program code;

the at least one memory and the computer program code configured to, with the at least one processor, cause the second apparatus to perform the method of any of claims 10 to 16.

27. A third device, comprising:

at least one processor; and

at least one memory including computer program code;

the at least one memory and the computer program code configured to, with the at least one processor, cause the third device to perform the method of any of claims 17-24.

28. A computer-readable medium having stored thereon instructions that, when executed by at least one processing unit of a machine, cause the machine to perform the method of any of claims 1-9.

29. A computer-readable medium having instructions stored thereon, which, when executed by at least one processing unit of a machine, cause the machine to perform the method of any one of claims 10 to 16.

30. A computer-readable medium having stored thereon instructions that, when executed by at least one processing unit of a machine, cause the machine to perform the method of any one of claims 17 to 24.

31. An apparatus comprising means for performing the method of any of claims 1-9.

32. An apparatus comprising means for performing the method of any of claims 10-16.

33. An apparatus comprising means for performing the method of any of claims 17-24.