CN114258719A

CN114258719A - Handover in a communication network

Info

Publication number: CN114258719A
Application number: CN201980099331.6A
Authority: CN
Inventors: 朱凯; 陈宇; 王文剑
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: 2019-08-15
Filing date: 2019-08-15
Publication date: 2022-03-29
Also published as: WO2021026913A1

Abstract

Embodiments of the present disclosure relate to handover in a communication system. According to an embodiment of the present disclosure, a terminal device transmits a measurement report including information reflecting a state of transport block elimination to the terminal device and a network device determines whether to trigger handover based on the measurement report. In this way, handover is more accurate, so by avoiding unnecessary or inappropriate HO, latency is reduced to a large extent.

Description

Handover in a communication network

Technical Field

Embodiments of the present disclosure relate generally to the field of communications, and in particular, to a method, apparatus, device, and computer-readable storage medium for handover in a communication network.

Background

It is difficult for a land network to provide 5G coverage since resources and infrastructure are limited in remote areas. The main benefit of introducing non-terrestrial networks (NTN) is that ubiquitous 5G services to end devices are achieved by extending connectivity in areas with low population density of very low density devices and the overall cost of deployment can be much less than providing permanent infrastructure provision on land. The use of space borne platforms or airborne platforms can provide reliable coverage in remote areas with significant advantages. However, it has also brought about some problems in other respects.

Disclosure of Invention

In general, example embodiments of the present disclosure provide technical solutions and corresponding communication devices for handover in a communication network.

In a first aspect, a first apparatus is provided. The first device includes: at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code are configured to, with the at least one processor, cause the first device to receive, at the first device, information from a second device regarding a configuration of a feedback-less transmission, the feedback-less transmission using one or more combined transport blocks, TBs, instead of feedback-based retransmissions, the combined TBs being generated based on an original TB on which data to be transmitted is carried. The first device is further caused to send a measurement report to the second device comprising information reflecting the quality of the feedback-free transmission. The first device is also caused to receive an indication from the second device to switch to the third device, the switch being triggered based on the information reflecting the quality of the feedback-free transmission.

In a second aspect, a second apparatus is provided. The second device includes: at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code are configured to, with the at least one processor, cause the second device to transmit information from the second device to the first device regarding a configuration of a feedback-less transmission, the feedback-less transmission using one or more combined transport blocks, TBs, instead of feedback-based retransmissions, the combined TBs being generated based on an original TB on which data to be transmitted is carried. The second device is further caused to receive a measurement report from the first device comprising information reflecting the quality of the feedback-free transmission. The second device is further caused to determine whether the handover is triggered based on information reflecting a quality of the feedback-free transmission. The second device is in turn caused to determine, in response to a determination that the handover is triggered, a third device for handover.

In a third 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 are configured to, with the at least one processor, cause the third device to receive, at the third device, a handover request from the second device indicating that the first device is to handover to the third device. The third device is further caused to generate an acknowledgement of the handover request, the acknowledgement including information on a configuration of a no feedback transmission using one or more combined transport blocks, TBs, instead of a feedback-based retransmission, the combined TBs being generated based on an original TB on which data to be transmitted is carried. The third device is also caused to send an acknowledgement to the second device. The third device is in turn caused to send a synchronization signal to the first device for the handover.

In a fourth aspect, a method is provided. The method comprises the following steps: receiving, at a first device, information from a second device regarding a configuration of a no feedback transmission using one or more combined transport blocks, TBs, instead of feedback-based retransmission, the combined TBs being generated based on an original TB on which data to be transmitted is carried. The method also sends a measurement report to the second device comprising information reflecting the quality of the feedback-free transmission. The method also includes receiving an indication from the second device to switch to a third device, the switch being triggered based on the information reflecting the quality of the no feedback transmission.

In a fifth aspect, a method is provided. The method comprises the following steps: transmitting, from the second device to the first device, information on configuration of a no feedback transmission using one or more combined transport blocks, TBs, instead of feedback-based retransmission, the combined TBs being generated based on an original TB on which data to be transmitted is carried. The method also includes receiving, from the first device, a measurement report including information reflecting a quality of the feedback-free transmission. The method also includes determining whether a handover is triggered based on the information reflecting the quality of the feedback-free transmission. The method also includes determining a third device to use for the handover in response to a determination that the handover is triggered.

In a sixth aspect, a method is provided. The method includes receiving, at a third device, a handover request from a second device indicating that a first device is to handover to the third device. The method also includes generating an acknowledgement of the handover request, the acknowledgement including information regarding configuration of a no feedback transmission using one or more combined transport blocks, TBs, instead of a feedback-based retransmission, the combined TBs generated based on an original TB on which data to be transmitted is carried. The method also includes sending an acknowledgement to the second device. The method also includes transmitting a synchronization signal to the first device for handover.

In a seventh aspect, an apparatus is provided. The device includes: means for receiving, at a first device, information from a second device regarding a configuration of a no feedback transmission, the no feedback transmission using one or more combined transport blocks, TBs, instead of feedback-based retransmission, the combined TBs being generated based on an original TB on which data to be transmitted is carried; means for transmitting a measurement report including information reflecting the quality of the feedback-less transmission to the second device; and means for receiving an indication from the second device to switch to a third device, the switch being triggered based on the information reflecting the quality of the non-feedback transmission.

In an eighth aspect, an apparatus is provided. The device includes: means for transmitting information about configuration of a no feedback transmission from a second device to a first device, the no feedback transmission using one or more combined transport blocks, TBs, instead of feedback-based retransmission, the combined TBs being generated based on an original TB on which data to be transmitted is carried; for receiving a measurement report from the first device comprising information reflecting the quality of the feedback-less transmission; means for determining whether a handover is triggered based on information reflecting quality of feedback-free transmission; and means for determining a third device to use for the handover in response to a determination that the handover is triggered.

In a ninth aspect, an apparatus is provided. The device includes: means for receiving, at a third device, a handover request from a second device indicating that a first device is to be handed over to the third device; means for generating an acknowledgement of the handover request, the acknowledgement comprising information on a configuration of a no feedback transmission using one or more combined transport blocks, TBs, instead of a feedback-based retransmission, the combined TBs being generated based on an original TB on which data to be transmitted is carried; means for sending an acknowledgement to the second device; and means for transmitting a synchronization signal to the first device for switching.

In a tenth aspect, there is provided a non-transitory computer-readable medium comprising instructions for causing an apparatus to perform at least the method of any of the fourth to sixth aspects 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 the principle of feedback-free transmission;

FIG. 2 illustrates an example communication network in which embodiments of the present disclosure may be implemented;

FIG. 3 illustrates a schematic diagram of interactions between communication devices, in accordance with some embodiments of the present disclosure;

figure 4 illustrates a schematic diagram of RSRP varying between cells, in accordance with some embodiments of the present disclosure;

fig. 5 illustrates a flow diagram of a method implemented at a network device in accordance with some embodiments of the present disclosure;

fig. 6 illustrates a flow diagram of a method implemented at a network device in accordance with some embodiments of the present disclosure;

fig. 7 illustrates a flow diagram of a method implemented at a network device in accordance with some embodiments 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 numerals denote the same or similar elements.

Detailed Description

The principles of the present disclosure will now be described with reference to some example embodiments. It should be understood that these principles of the present disclosure will now be described with reference to some exemplary embodiments. It is understood that these examples are described for illustrative purposes only and to aid those skilled in the art in understanding and enabling the present disclosure, and do not imply any limitation as to the scope of the present disclosure. The present 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 could be termed a second element, and, similarly, a second element could 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 items.

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 "including," when used herein, specify the presence of stated features, elements, and/or components, 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 more or all of the following:

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

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

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

(ii) hardware processor(s) with software (including digital signal processor (s)), software and any portion of memory(s) working 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), that require software (e.g., firmware) for operation, but which may not be present when it is not required for operation.

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

As used herein, the term "communication device" 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 on. Additionally, communication between the terminal device and the network device in the communication network may be performed according to any suitable communication protocol 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 protocol currently known or to be developed in the future. Embodiments of the present disclosure may be applied in various communication systems. Due to the rapid development of communications, there will of course also be future types of communication technologies and systems with which the present disclosure may be embodied. It should not be considered 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. A network device may refer to a Base Station (BS) or an Access Point (AP), e.g., a NodeB (NodeB or NB), evolved NodeB (eNodeB or eNB), NR NB (also referred to as gNB), Remote Radio Unit (RRU), Radio Head (RH), Remote Radio Head (RRH), relay, low power node (such as femto, pico, etc.), depending on the terminology and technology of the application.

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). The 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 appliances, in-vehicle wireless end devices, wireless endpoints, mobile stations, laptop embedded devices (LEEs), laptop installed devices (LMEs), USB dongles, smart devices, wireless client devices (CPEs), internet of things (loT) devices, watches or other wearable apparatuses, 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 an industrial and/or automated processing chain context), 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 mentioned above, NTN has also brought about some problems in other respects. For NTN, the Round Trip Time (RTT) to the terminal device may be much larger than in a terrestrial network. One important deployment feature that can distinguish NTN from land networks is that the NTN base stations are typically satellites located in earth orbit with an orbital height of 600-.

The propagation time for the electromagnetic wave to travel through such a distance is measured in table 1 below.

TABLE 1

It can be seen that the propagation delay of NTN is much higher than can be tolerated by the NR physical layer (which is limited by a maximum propagation distance of 300 km). On the other hand, such extended propagation delay will also challenge the technical specifications of conventional systems and robust NTN mobility is among the most important issues.

Similar to traditional terrestrial networks, mobility also plays a crucial role in NTN systems, which enables continuity of radio connectivity and maintains a consistent quality of service for nomadic terminal devices. An optimal Handover (HO) should generally have a minimized Handover Interruption Time (HIT), handover failure (HOF) rate, and ping-pong (pp) rate. However, in NTN scenarios, a good mobility mechanism to achieve the above HO targets becomes technically difficult due to the greatly increased risk of measurement ineffectiveness. Recall that the Round Trip Time (RTT) of radio signals in the NTN may be several orders of magnitude greater than that of the terrestrial network, and such cumulative delays incurred may cause the UE measurements to be too slow or inaccurate.

The procedures established for most conventional HO schemes follow the guidelines of the "UE-assisted, network-controlled" rule. When the measurement results reported by the terminal device become unreliable, it will be difficult for the network to make an appropriate HO decision. The cost of an improper HO in NTN is high because the ensuing Radio Link Failure (RLF) recovery procedure will consume a significant amount of delay and service interruption due to signaling delays. According to a recent analysis, the overall interruption can be up to several seconds when counting delays for Radio Resource Control (RRC) message processing and other signaling transmission delays.

There may be two areas of interest for RAN 2: propagation delay identifying timing requirements and solutions on layer 2 aspects including Media Access Control (MAC), Radio Link Control (RLC), RRC, and radio link management; handover, which studies and identifies mobility requirements and measurements that may be needed for handover between non-GEO satellites moving at high speed but on predictable paths.

Additionally, other discussions encompassing these aspects are in the context of mobility. Although it was determined that it was too early to focus RAN2 on mobility solutions, several observations related to possible challenges of Rel-15 mobility procedures in extended NTNs were captured in 38.821: for GEO NTN: the mobility management procedure requires adaptation to accommodate large propagation delays. In particular, radio link management may require a specification configuration; for LEO NTN: the mobility management procedure should be enhanced to account for satellite movements related to aspects such as measurement validity, UE speed, direction of movement, large and varying propagation delays and dynamic neighbor cell sets.

In RAN2#105, the following observations were agreed to be captured: the company is not ready to identify and agree on solution options for RRM or HO for NTN; for GEO NTN, large propagation delays are identified as critical issues and the impact on performing measurements and for measurement configuration should be considered; specific to LEO NTN, aspects related to satellite movement such as measurement validity, UE velocity, direction of movement, large varying propagation delays, and dynamic neighbor cell sets are identified.

To summarize the protocols listed above, a satellite in non-GEO orbit moves at high speed (7.5 km/s for LEO) relative to the earth's surface, and the current consensus in 3GPP is that frequent handovers are unavoidable because it is handling a moving New Radio (NR) cell. Due to the measurement validity issues mentioned earlier and the ping-pong effect, inappropriate mobility actions are expected to occur more often than NR terrestrial networks, and such results are not tolerable given the very stringent NTN performance requirements.

To overcome the limited functionality provided by the NR HO mechanism, the incorporation of a make-before-break (MBB) HO appears to be a suitable choice for NTN mobility. MBB HO is discussed in Rel 14 as an evolved improved HO feature for long term evolution, LTE. The MBB HO method generally assumes that data exchange with the serving cell is not "broken" until a new connection with the target cell is established (i.e., "connected").

In addition, the following seems to be a reasonable assumption: downlink transmissions from the serving cell that occur after the reception of the HO command may end up a large amount of incorrect data reception caused by degraded channel conditions. Handling those incorrect data in retransmission while the HO is running may require additional complexity on the terminal equipment and network equipment side. This forces another important component to be combined into the NTN paradigm to avoid explicit retransmissions and HARQ feedback signaling, which is an NTN-specific enhancement named feedback-less transmission scheme.

Fig. 1 shows an example outlined TB combining and TB elimination procedure for one example in which two original TBs are transmitted using 3 combined TBs. In the first phase, the inputs (e.g., TB301 and TB 302) are "combined," i.e., an XOR operation is performed with respect to these TBs. In this example, there are two combinations of degree-1, TB301 and TB 3021, and one degree-2 of degree-2 (TB301+302, where + represents an XOR operation). In this example, it is assumed that TB301 is missing, while the other two TBs 302 and TB301+302 are successfully received. In the TB elimination phase, the TBs of degree-1 that are effectively received are assumed to have been eliminated and become "rippled". In the next stage, the "ripple" is used to perform additional TB cancellation on other successfully received TB combinations. This process continues until all original TBs have been restored or all TBs in the ripple have been eliminated from other TBs.

According to an embodiment of the present disclosure, a terminal device transmits an additional measurement report including information reflecting a state of transport block elimination to a network device, and the network device determines whether to trigger handover based on the measurement report. In this way, the handover is more accurate and the delay is reduced.

The principles and embodiments of the present disclosure will be described in detail below with reference to the drawings. Reference is first made to fig. 2, which illustrates an example communication system 200 in which embodiments of the present disclosure may be implemented.

Fig. 2 illustrates a schematic diagram of a communication system 200 in which embodiments of the present disclosure may be implemented. The communication system 200 includes a first device 210, a second device 220-1, and a third device 220-2. For purposes of illustration, the first device 210 may be referred to as a terminal device 210, and the second device 220-1 and the third device 220-2 may be referred to as a network device 220, hereinafter. It should be noted that the first device, the second device, the third device are interchangeable. For example, processes described as being implemented at a terminal device may also be capable of being implemented at a network device, and processes described as being implemented at a network device may also be capable of being implemented at a terminal device.

The link from the second device 220-1 and the third device 220-2 to the first device 210 may be referred to as a "downlink", and the link from the first device 210 to the second device 220-1 and the third device 220-2 may be referred to as an "uplink".

The communication system 200, which is part of a communication network, includes terminal devices 210-1,210-2., 210-N (collectively referred to as terminal device(s) 210 ", where N is an integer). Communication system 200 includes one or more network devices, such as network devices 220-1 and 220-2.

It should be understood that communication system 200 may also include other elements that have been omitted for clarity purposes. It should be understood that the number of terminal devices and network devices shown in fig. 2 is given for illustrative purposes and does not imply any limitation. Terminal device 210, network device 220-1, and network device 220-2 may communicate with each other.

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 200 may be implemented according to any appropriate communication protocol(s) including, but not limited to: cellular communication protocols of first generation (1G), second generation (2G), third generation (3G), fourth generation (4G), and fifth generation (5G), and so forth, wireless local network communication protocols such as Institute of Electrical and Electronics Engineers (IEEE)802.11, and so forth, and/or any other protocol currently known or to be developed in the future. Further, the communication may utilize any appropriate 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 multiple access (OFDM), discrete Fourier transform spread OFDM (DFT-s-OFDM), and/or any other technique now known or later developed.

Fig. 3 illustrates a schematic diagram of interactions 300 in a contention-based system according to an embodiment of the present disclosure. The interaction 300 may be implemented at any suitable device. For purposes of illustration only, interaction 300 is described as being implemented at terminal device 210-1, network device 220-1, and network device 220-2. By way of example, network device 220-1 may be a source network device and network device 220-2 may be a target network device. It should be noted that the phrases "combined TB" and "TB combined" have the same meaning and they may be used interchangeably in this document, and the phrases "eliminated TB" and "TB eliminated" have the same meaning and they may be used interchangeably in this disclosure.

Network device 220-1 sends 3005 information regarding the configuration of the transmission without feedback. The term "feedback-free transmission" as used herein refers to a transmission that uses a combined Transport Block (TB) rather than feedback-based retransmission. The configuration may include one or more of: no feedback transmission redundancy rate, TB degree or TB combination pattern.

The combined TB may be generated based on an original TB on which data to be transmitted is carried. The feedback-free transmission redundancy rate may indicate the ratio of the number of original TBs to be communicated to the number of actual transmitted TB combinations. The TB degree may indicate the number of original TBs from which a particular TB combination was generated. The TB combination pattern may indicate which original TBs were selected to generate a particular TB combination. It should be noted that the acknowledgement may include any suitable parameters related to the combining and elimination of TBs.

By way of example only, table 2 below shows a combined pattern for feedback-free transmission. It should be noted that the numbers and values shown in table 2 are merely examples and are not limiting.

TABLE 2

Transport example #	TB combination to be transmitted	Buffer ID #
			1	TB0	1
2	TB1	2
			3	TB2+TB0	3
4	TB3+TB1+TB0	4
			5	TB3+TB2	5
6	TB2	6
			7	TB3	7
8	TB1+TB2	8

The number of original TBs to be transmitted from the transmitter side to the receiver side is 4, TB0, TB1, TB2, TB 3. The number of combined TBs actually transmitted over the air interface is 8. Therefore, the non-feedback transmission redundancy rate is 4/8. TB degree (or, simply, just "degree") is 1 because TB0 is the original TB, which may be denoted as "degree-1". The TB degree of "TB 3+ TB1+ TB 0" is 3 because it is generated based on three original TBs, which may be represented as "degree-3", where + represents an XOR operation.

In some embodiments, the information may be part of the broadcasted system information. In other embodiments, the information may be downlink control information. Alternatively, the information may be part of dedicated RRC signaling.

In some embodiments, if terminal device 210-1 is in the RRC _ CONNECTED state, terminal device 210-1 and network device 220-1 may communicate with each other using feedback-free transmission due to high latency of the air interface. For example, network device 220-1 may send 3010 data to terminal device 210-1 using a feedback-less transmission.

In some embodiments, network device 220-1 may send 3015 signaling to activate the no feedback transmission. In some embodiments, the signaling may be an RRC message dedicated to terminal device 210-1. Alternatively or additionally, the signaling may be broadcast to a plurality of terminal devices.

The terminal device 210-2 sends 3020 a measurement report to the network device 220-1. The measurement report includes information reflecting the quality of the feedback-less transmission. In some embodiments, the measurement report comprises at least one of: a number of degree-1 TBs obtained from the TB combinations transmitted from the second device, a rate at which the original TBs are successfully restored from the TB combinations, a rate at which the original TBs are not successfully restored from the TB combinations, an index of the original TBs which are successfully restored from the TB combinations, or an index of the original TBs which are not successfully restored from the TB combinations. In some embodiments, the process of recovery of the original TB may also be referred to as "TB elimination.

In some embodiments, the recovery of the original TB may rely on the successful cancellation of the degree-1 TB from the received TB combination. During each cancellation, a freshness-1 TB must be generated to keep another cancellation going. When the radio link conditions deteriorate or experience an interruption causing too many missing or erroneously received TB combinations, TB cancellation is likely to pause in the middle of the process, as the number of degree-1 TBs generated becomes insufficient to maintain the remainder of the cancellation, and the majority of the received TB combinations are therefore unrecoverable.

Network device 220-1 determines 3025 whether the handover is triggered based on the measurement report. The network device 220-1 may evaluate the measurement report and trigger the HO decision if the condition is met. It should be noted that making NTN HO decisions simply relying on received power strength would be less reliable due to the additional erasure properties of the NTN channel. Instead, measurement reports related to information reflecting the status of transport block erasure can describe the condition of the erasure channel from the erasure possibility dimension. In this way, the handover decision is more accurate.

In some embodiments, network device 220-1 may compare the quality of the no feedback transmission to a threshold quality. Network device 220-1 may trigger into a handoff state if the quality exceeds a threshold quality. If the quality is below the threshold quality, network device 220-1 may not be triggered into the handoff state. Network device 220-1 may ignore the measurement report and keep monitoring. Network device 220-1 may reconfigure no feedback transmission, such as TB redundancy rate, TB degree, or TB combination pattern. Network device 220-1 may also reconfigure other transmission parameters for future transmissions, such as Modulation and Coding Scheme (MCS) and transmit power.

In some embodiments, there may be several different thresholds to avoid "false alarms" if the radio link between the terminal device 210-1 and the network device 220-1 is only temporarily down and will recover quickly. event-X1: the quality of the feedback-less transmission at the serving cell is above threshold-1, but below threshold-2. The proposed HO conditions may be described as shown in table 3 below.

TABLE 3

In some embodiments, the number of degree-1 TBs generated during TB cancellation is critical to maintaining continuous TB cancellation and is more sensitive to changes in the channel than the signal power.

In some embodiments, if the channel conditions are relatively good, TB combining has no significant benefit, which means that each of the TB cancellations is successful. In some embodiments, TB cancellation experiences some small degree of failure when channel conditions begin to drop. The final TB cancellation may succeed by waiting for more TB combinations to be received for auxiliary cancellation. When the channel conditions remain falling below a certain threshold, TB cancellation experiences so many failures that the degree-1 TBs generated during cancellation become insufficient to maintain the remaining cancellation, eventually the TB cancellation collapses.

For illustration purposes only, the configuration of no feedback transmission is shown in table 2 above. If the channel conditions begin to drop, the first and second transmissions (e.g., TB0 and TB1) may not be received. Since there is no knowledge that neither TB0 nor TB1 performs TB elimination, TB2+ TB0 and TB3+ TB1+ TB0 may simply be stored to wait for additional combined TBs to arrive. In this example, TB elimination may succeed with the following steps: (1) buffer #6+ buffer #3 → TB0 (New degree-1 TB); (2) buffer #6+ buffer #5 → TB3 (New degree-1 TB); (3) buffer #4+ TB0 (new) + TB3 (new) - > TB1 (new degree-1 TB). Thus, all data on TB0 through TB3 could be successfully recovered and three new degree-1 TBs were generated during the process.

In some embodiments, if the channel condition has dropped below a threshold. For example, the first, second, fifth and sixth TB combinations are missing, with one degree-1 TB at the beginning of the elimination. And more importantly, no new degree-1 TB will be generated regardless of how the cancellation is performed, so in this example, the generated degree-1 TB is not sufficient to maintain the cancellation, which is faulty. It is readily seen that TB elimination operates in a continuous manner. The degree-1 TB is to maintain continuous TB cancellation and is more sensitive to the state of the channel.

If network device 220-1 determines to trigger a handover, network device 220-1 determines 3026 a target network device. Network device 220-1 may search for neighboring network devices whose trajectories may be aligned with the coverage area of terminal device 210-1 for a given window. For example, network device 220-1 may determine the target network device based on the velocity of terminal device 210-1, the direction of movement of terminal device 210-1 and the dynamic neighbor cell set. After network device 220-1 determines 3030 the handover request to network device 220-2 after network device 220-1 determines network device 220-2 as the target network device.

Network device 220-2 generates 3032 receives an Acknowledgement (ACK) to the handover request. In some embodiments, the ACK may also include configuration information for another feedback-free transmission supported by network device 220-2. For example, the ACK may include one or more of a no feedback transmission redundancy rate, a TB degree, or a TB combination pattern. The TB redundancy rate may indicate the ratio of the number of original TBs to be communicated to the number of TB combinations actually transmitted. Network device 220-2 may send 3035 an ACK to the handover request to network device 220-1. In some embodiments, the ACK may also include configuration information for another feedback-free transmission supported by network device 220-2. In some embodiments, network device 220-1 may send 3040 information for another no feedback transmission to terminal device 210-1. Network device 220-2 may send 3045 an indication to terminal device 210-1 to switch to network device 220-2.

The network device 220-2 sends 3050 a synchronization signal to the terminal device 210-1. In some embodiments, terminal device 210-1 may perform simultaneous reception of a synchronization signal from network device 220-2 for initial access purposes while continuing data transmission with network device 220-1. For example, terminal device 210-1 may continue to send 3055 data to network device 220-1. In some embodiments, terminal device 210-1 may also send a new measurement report to network device 220-1.

In some embodiments, network device 220-1 may forward 3060 data buffered in network device 220-1 for future transmission from network device 220-1 to network device 220-2. For example, if the number of degree-1 TBs received by terminal device 210-1 decreases, network device 220-1 may forward data that has not yet been transmitted. Alternatively or additionally, network device 220-1 may forward data that has not been transmitted if the number of degree-1 TBs received by terminal device 210-1 is below a threshold number. The threshold number may be predefined. Alternatively or additionally, the threshold number may be set via RRC or system messages or other control signaling. The threshold number may also be dynamically determined by network device 220-1.

With knowledge of the TB elimination status reported from terminal device 210-1, network device 220-1 can keep track of the TB elimination procedure. The index of TBs that have been successfully eliminated or have not been successfully eliminated will give network device 220-1 a clear guidance as to which data portion should be forwarded so that the received TB combination (partly from network device 220-1 and partly from network device 220-2) provides the greatest TB combination redundancy gain at the expense of forwarding only a relatively small amount of data.

In one example, a TB combination redundancy ratio of 4/8 is selected, which means that a total of 4 original TBs, denoted TB0, TB1, TB2, and TB3, may be transmitted per 8 transmissions over the physical interface. The combination pattern is shown in table 4 below. It should be noted that the numbers and values shown in table 4 are merely examples and are not limiting.

TABLE 4

Transport example #	TB combination to be transmitted	Buffer ID #
			Network device 220-1#1	TB0	0
Network device 220-1#2	TB1	1
			Network device 220-1#3	TB2+TB0	2
Network device 220-1#4	TB3+TB1+TB0	3
			Network device 220-2#1	TB3+TB2	4
Network device 220-2#2	TB2	5
			Network device 220-2#3	TB3	6
Network device 220-2#4	TB1+TB2	7

In a first example, assume TB0 and TB1 (corresponding to the first transmission and the second transmission from network device 220-1) were not received due to degraded channel conditions of the serving cell. Assume that the third transmission and the fourth transmission from network device 220-1b were successful. Since there is no knowledge that neither TB0 nor TB1 performs TB elimination, TB2+ TB0 and TB3+ TB1+ TB0 may simply be stored in buffers #2 and #3 to wait for an additional combined TB to arrive after the handover to target network device 220-2 with the desire for improved wireless quality. In this example, only two of the four TB combinations need to be forwarded to network device 220-2 and sent to terminal device 210-1 after the switch, namely TB3+ TB2 and TB2 located in buffers #4 and #5 or TB3+ TB2 and TB3 located in buffers #4 and # 6. The respective TB elimination at the terminal device 210-1 side may be performed in the following order shown in table 5:

TABLE 5

Forwarding TB3+ TB2 and TB2	Forwarding TB3+ TB2 and TB3
		Buffer #5+ buffer #2 → TB0	Buffer #6+ buffer #4 → TB2
Buffer #5+ buffer #4 → TB3	Buffer #2+ TB2 → TB0
		Buffer #3+ TB0+ TB3 → TB1	Buffer #3+ TB0+ TB3 → TB1

In another example, assume that transmission of TB2+ TB0 at the third transmission instance is missing. In this case, both TB0 and TB1 are degree-1 TBs, so they are received 'as-is'. TB3 can then be obtained via the following formula: buffer #3+ TB0+ TB1 → TB 3. Thus, network device 220-1 may only have to forward one copy of the TB combination to network device 220-2 for the purpose of recovering TB 2. The copy may be any of: TB3+ TB 2; TB 2; or TB1+ TB 2.

The terminal device may send 3070 an ACK to network device 220-1. Terminal device 210-1 may also be separate 3080 from network device 220-1. In some embodiments, terminal device 210-1 may set a timer for the handover. The timer starts during transmission of RRC reconfiguration complete signaling. The duration of such a timer may be configured to be predefined by upper layers, system information, or RRC signaling.

When the timer expires, if the number of degree-1 TBs received by the terminal device 210-1 does not increase above a given boundary, it is considered an unsuccessful handover. The corresponding action of handling the failed HO may be triggered. It may be a return to the original serving cell (ping-pong) or an initiation of an RLF procedure. For example, at time t1 in FIG. 4, terminal device 210-1 detaches from network device 220-1, and the new connection established with target network device 220-2 is expected to be more reliable and should remain improved over time, as illustrated by FIG. 4. Under such an assumption, it is intuitive to predict that more TB combinations should be correctly received by the terminal device 210-1, which further implies that an increased number of-1 TBs should be generated after HO. Handover may be more accurately decided, and thus embodiments of the present disclosure may reduce latency to a large extent, thereby avoiding unnecessary or inappropriate HO.

Fig. 5 illustrates a flow diagram of an example method 500 implemented at a terminal device, in accordance with some embodiments of the present disclosure. Method 500 may be implemented at any suitable device. For purposes of discussion, the method 500 will be described from the perspective of the terminal device 210-1 with reference to FIG. 2.

At block 510, the terminal device 210-1 receives information regarding the configuration of the no feedback transmission. The combined TB may be generated based on an original TB on which data to be transmitted is carried.

The configuration may include one or more of: no feedback transmission redundancy rate, TB degree or TB combination pattern. The combined TB may be generated based on an original TB on which data to be transmitted is carried. The feedback-free transmission redundancy rate may indicate the ratio of the number of original TBs to be communicated to the number of actual transmitted TB combinations. The TB degree may indicate the number of original TBs from which a particular TB combination was generated. The TB combination pattern may indicate which original TBs were selected to generate a particular TB combination.

In some embodiments, the information may be part of broadcast system information. In other embodiments, the information may be downlink control information. Alternatively, the information may be part of dedicated RRC signaling.

At block 520, terminal device 210-1 sends a measurement report to network device 220-1. The measurement report includes information reflecting the status of transport block erasure. In some embodiments, the measurement report includes one or more of: a number of degree-1 TBs obtained from the TB combinations transmitted from the second device, a rate at which the original TBs are successfully restored from the TB combinations, a rate at which the original TBs are not successfully restored from the TB combinations, an index of the original TBs which are successfully restored from the TB combinations, or an index of the original TBs which are not successfully restored from the TB combinations. In some embodiments, the process of recovery of the original TB may also be referred to as "TB elimination.

At block 530, terminal device 210-1 receives an indication of a handover from network device 220-1. In some embodiments, terminal device 210-1 may receive information for another feedback-free transmission supported by network device 220-2. The information may include a TB redundancy rate, a TB degree, or a TB combination pattern. The TB redundancy rate may indicate a ratio of the number of combinations of original TBs and combined TBs to the number of original TBs.

In some embodiments, terminal device 210-1 may receive the synchronization signal of terminal device 210-1. In some embodiments, terminal device 210-1 may perform simultaneous reception of a synchronization signal from network device 220-2 for initial access purposes while continuing data transmission with network device 220-1. For example, terminal device 210-1 may continue to transmit data to network device 220-1. In some embodiments, terminal device 210-1 may also send a new measurement report to network device 220-1.

In some embodiments, terminal device 210-1 may set a timer for the handover. The timer starts during transmission of RRC reconfiguration complete signaling. The duration of such a timer may be configured to be predefined by upper layers, system information, or RRC signaling. The terminal device 210-1 may detect a failure of the handover by comparing the number of original TBs obtained from the third device with a threshold number. When the timer expires, the number of acquired original TBs is considered an unsuccessful handover if it does not increase above a given boundary.

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 at any suitable device. For purposes of discussion, the method 600 will be described from the perspective of the net-end device 220-1 with reference to fig. 2.

At block 610, network device 220-1 sends information regarding the configuration of the no feedback transmission. The combined TB may be generated based on an original TB on which data to be transmitted is carried. The configuration may include one or more of: no feedback transmission redundancy rate, TB degree or TB combination pattern. The combined TB may be generated based on an original TB on which data to be transmitted is carried. The feedback-free transmission redundancy rate may indicate the ratio of the number of original TBs to be communicated to the number of actual transmitted TB combinations. The TB degree may indicate the number of original TBs from which a particular TB combination was generated. The TB combination pattern may indicate which original TBs were selected to generate a particular TB combination.

In some embodiments, the information may be part of the broadcast system information. In other embodiments, the information may be downlink control information. Alternatively, the information may be part of dedicated RRC signaling.

In some embodiments, if terminal device 210-1 is in the RRC _ CONNECTED state, terminal device 210-1 and network device 220-1 may communicate with each other using feedback-free transmission due to high latency of the air interface. For example, network device 220-1 may send data to terminal device 210-1 using feedback-less transmission.

In some embodiments, network device 220-1 may send signaling to activate the no feedback transmission. In some embodiments, the signaling may be an RRC message dedicated to terminal device 210-1. Alternatively or additionally, the signaling may be broadcast to a plurality of terminal devices.

At block 620, network device 220-1 receives a measurement report from terminal device 210-1. The measurement report includes information reflecting the quality of the feedback-less transmission. In some embodiments, the measurement report includes one or more of: a number of degree-1 TBs obtained from the TB combinations transmitted from the second device, a rate at which the original TBs are successfully restored from the TB combinations, a rate at which the original TBs are not successfully restored from the TB combinations, an index of the original TBs which are successfully restored from the TB combinations, or an index of the original TBs which are not successfully restored from the TB combinations. In some embodiments, the process of recovery of the original TB may also be referred to as "TB elimination.

At block 630, network device 220-1 determines whether a handover is triggered based on the measurement report. The network device 220-1 may evaluate the measurement report and trigger the HO decision if the condition is met.

In some embodiments, network device 220-1 may compare the quality of the no feedback transmission to a threshold quality. Network device 220-1 may trigger into a handoff state if the quality exceeds a threshold quality. If the quality is below the threshold quality, network device 220-1 may not be triggered into the handoff state. Network device 220-1 may ignore the measurement report and keep monitoring. Network device 220-1 may reconfigure no feedback transmission, such as TB redundancy rate, TB degree, or TB combination pattern. Network device 220-1 may also reconfigure other transmit parameters for future transmissions, such as MCS and transmit power.

At block 640, network device 220-1 determines network device 220-2 as the target network device. Network device 220-1 may search for neighboring network devices whose trajectories may be aligned with the coverage area of terminal device 210-1 for a given window. For example, network device 220-1 may determine the target network device based on the velocity of terminal device 210-1, the moving direction of terminal device 210-1 and the dynamic set of neighboring cells. After network device 220-1 determines network device 220-2 as the target network device, network device 220-1 may send a handover request to network device 220-2.

In some embodiments, network device 220-1 may receive an Acknowledgement (ACK) of the handover request from network device 220-2. In some embodiments, the ACK may also include configuration information for another feedback-free transmission supported by network device 220-2. For example, the ACK may include one or more of a TB redundancy rate, a TB degree, or a TB combination pattern. The TB redundancy rate may indicate a ratio of the number of combinations of original TBs and combined TBs to the number of original TBs. In some embodiments, network device 220-1 may forward information of another feedback-free transmission to terminal device 210-1. Network device 220-2 may send an indication to terminal device 210-1 to switch to network device 220-2.

In some embodiments, network device 220-1 may forward data buffered in network device 220-1 for future transmission from network device 220-1 to network device 220-2. For example, if the number of degree-1 TBs received by terminal device 210-1 decreases, network device 220-1 may forward data that has not yet been transmitted. Alternatively or additionally, network device 220-1 may forward data that has not been transmitted if the number of degree-1 TBs received by terminal device 210-1 is below a threshold number. The threshold number may be predefined. Alternatively or additionally, the threshold number may be set via RRC or system messages or other control signaling. The threshold number may also be dynamically determined by network device 220-1.

Fig. 7 illustrates a flowchart of an example method 700 implemented at a terminal device, in accordance with some embodiments of the present disclosure. Method 700 may be implemented at any suitable device. For discussion purposes, the method 700 will be described from the perspective of the terminal device 220-2 with reference to fig. 2.

At block 710, network device 220-2 receives a handover request from network device 220-1.

At block 720, network device 220-2 generates an ACK for the handover request. In some embodiments, the ACK may also include configuration information for another feedback-free transmission supported by network device 220-2. For example, the ACK may include one or more of: no feedback transmission redundancy rate, TB degree or TB combination pattern. The TB redundancy rate may indicate the ratio of the number of original TBs to be communicated to the number of TB combinations actually transmitted.

At block 730, network device 220-2 sends an ACK to network device 220-1. At block 740, the network device 220-2 transmits a synchronization signal to the terminal device 210-1.

In some embodiments, an apparatus (e.g., network device 210-1) for performing method 500 may include corresponding means for performing the corresponding steps in method 500. 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 first device, information from a second device regarding a configuration of a no feedback transmission, the no feedback transmission using one or more combined transport blocks, TBs, instead of feedback-based retransmission, the combined TBs being generated based on an original TB on which data to be transmitted is carried; means for transmitting a measurement report including information reflecting a quality of the feedback-free transmission to the second device; and means for receiving an indication from the second device to switch to a third device, the switch being triggered based on the information reflecting the quality of the non-feedback transmission.

In some embodiments, the configuration of the no feedback transmission comprises at least one of: a feedback-free transmission redundancy rate indicating a ratio of a number of original TBs to be communicated to a number of actual transmitted TB combinations; a TB degree indicating the number of original TBs from which a particular TB combination was generated; or a TB combination pattern that indicates which original TBs were selected to generate a particular TB combination.

In some embodiments, the measurement report comprises at least one of: a number of degree-1 TBs obtained from the TB combinations transmitted from the second device, a rate at which the original TBs are successfully restored from the TB combinations, a rate at which the original TBs are not successfully restored from the TB combinations, an index of the original TBs which are successfully restored from the TB combinations, or an index of the original TBs which are not successfully restored from the TB combinations.

In some embodiments, the means for receiving, from the second device, an indication of a handover from the second device to the third device comprises: means for receiving, from the second device, further information on a further configuration of a further feedback-free transmission supported by the third device.

In some embodiments, the apparatus further comprises: means for transmitting data to the second device while receiving a synchronization signal from the third device; and means for transmitting further data to the third device in response to receiving a further indication to perform the handover.

In some embodiments, the apparatus further comprises: means for setting a timer for switching to the third device; means for determining the number of degree-1 TBs obtained from the TB combination transmitted from the third device after the timer expires; and means for detecting a failure of the switching by comparing the number of degree-1 TBs obtained from the TB combinations transmitted from the third device with a threshold number.

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

In some embodiments, an apparatus (e.g., network device 220-1) for performing method 600 may include respective means for performing corresponding steps in 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 transmitting information about configuration of a no feedback transmission from a second device to a first device, the no feedback transmission using one or more combined transport blocks, TBs, instead of feedback-based retransmission, the combined TBs being generated based on an original TB on which data to be transmitted is carried; for receiving a measurement report from the first device comprising information reflecting the quality of the feedback-less transmission; means for determining whether a handover is triggered based on information reflecting quality of feedback-free transmission; and means for determining a third device to use for the handover in response to a determination that the handover is triggered.

In some embodiments, the means for determining whether the handover is triggered comprises: means for determining that a handover is triggered in response to the information indicating that the quality of the no feedback transmission is below a threshold quality.

In some embodiments, the apparatus further comprises means for forwarding data buffered in the second device for future transmission to the third device in response to at least one of: the number of degree-1 TBs received by the first device is reduced or the number of degree-1 TBs received by the first device is below a threshold number.

In some embodiments, the apparatus further comprises means for receiving, from the third device, further information regarding a further configuration of a further feedback-free transmission supported by the third device; and means for forwarding the further information to the first device.

In some embodiments, an apparatus (e.g., network device 220-2) 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 second device indicating that a first device is to be handed over to the third device; means for generating an acknowledgement of the handover request, the acknowledgement comprising information on a configuration of a no feedback transmission using one or more combined transport blocks, TBs, instead of a feedback-based retransmission, the combined TBs being generated based on an original TB on which data to be transmitted is carried; means for sending an acknowledgement to the second device; and means for transmitting the synchronization signal to the first device for switching.

In some embodiments, the configuration of the no feedback transmission comprises at least one of: a feedback-free transmission redundancy rate indicating a ratio of a number of original TBs to be communicated to a number of TB combinations actually transmitted; a TB degree indicating the number of original TBs from which a particular TB combination was generated; or a TB combination pattern that indicates which original TBs were selected to generate a particular TB combination.

Fig. 8 is a simplified block diagram of a device 800 suitable for implementing embodiments of the present disclosure. Device 800 may be provided to implement a communication device, such as network device 120 or terminal device 110-1 as shown in fig. 1. As shown, the device 800 includes one or more processors 810, one or more memories 820 coupled to the processors 810, and one or more communication modules (e.g., transmitters and/or receivers (TX/RX))840 coupled to the processors 810.

The communication module 840 is used for bidirectional communication. The communication module 840 has at least one antenna to facilitate communication. A 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 one or more of the following, as non-limiting examples: 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 subordinate in time to a clock that synchronizes the host 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 Disk (CD), a Digital Video Disk (DVD), and other magnetic and/or optical storage devices. Examples of volatile memory include, but are not limited to, Random Access Memory (RAM)822 and other volatile memory that does not persist during shutdown.

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 as discussed with reference to fig. 3-6. 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 that may be included in the device 800 (such as in the memory 820) or other storage device 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 storage device, such as a ROM, EPROM, flash memory, hard disk, CD, DVD, or the like. 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 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 devices, 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 500 to 700 as described above with reference to fig. 5 to 7. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, etc. that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or split between program modules as desired in various embodiments. 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 or partially on the machine, as a stand-alone software package, partly on the machine, 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.

Additionally, while operations are depicted 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. Similarly, 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 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 apparatus to:

receiving, at the first device, information from a second device regarding a configuration of a feedback-less transmission using one or more combined transport blocks, TBs, instead of feedback-based retransmission, the combined TBs generated based on an original TB on which data to be transmitted is carried;

sending a measurement report to the second device including information reflecting a quality of the feedback-less transmission; and

receiving an indication from the second device to switch to a third device, the switch being triggered based on the information reflecting the quality of the no feedback transmission.

2. The first device of claim 1, wherein the configuration of the no feedback transmission comprises at least one of:

a feedback-free transmission redundancy rate indicating a ratio of the number of original TBs to be communicated to a number of actual transmitted TB combinations,

a TB degree indicating the number of the original TBs from which a particular TB combination was generated, or

A TB combination pattern that indicates which original TBs were selected to generate a particular TB combination.

3. The first device of claim 1, wherein the measurement report comprises at least one of:

a number of degree-1 TBs obtained from TB combinations transmitted from the second device,

the rate at which the original TB was successfully recovered from the TB combination,

the rate at which the original TB is not recovered from the TB combination,

the index of the original TB successfully recovered from the TB composition, or

The index of the original TB that cannot be recovered from the TB combination.

4. The first device of claim 1, wherein the first device is caused to receive the indication to switch to the third device from the second device by:

receiving, from the second device, further information on a further configuration of a further feedback-free transmission supported by the third device.

5. The first device of claim 1, wherein the first device is further caused to:

transmitting data to the second device while receiving the synchronization signal from the third device; and

in response to receiving a further indication to perform the handover, sending further data to the third device.

6. The first device of claim 1, wherein the first device is further caused to:

setting a timer for switching to the third device;

determining the number of degree-1 TBs obtained from TB combinations transmitted from the third device after the timer expires; and

detecting a failure of the switching by comparing a number of degree-1 TBs obtained from a TB combination transmitted from the third device with a threshold number.

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

8. 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:

transmitting, from the second device to the first device, information on configuration of a feedback-less transmission using one or more combined transport blocks, TBs, instead of feedback-based retransmission, the combined TBs being generated based on an original TB on which data to be transmitted is carried;

receiving, from the first device, a measurement report including information reflecting a quality of the feedback-less transmission;

determining whether a handover is triggered based on the information reflecting the quality of the feedback-less transmission; and

in response to a determination that the handover is triggered, determining a third device to use for the handover.

9. The second device of claim 8, wherein the configuration of the no feedback transmission comprises at least one of:

10. The second device of claim 8, wherein the measurement report comprises at least one of:

the rate at which the original TB is not recovered from the TB combination,

the index of the original TB successfully recovered from the TB composition, or

The index of the original TB that cannot be recovered from the TB combination.

11. The second device of claim 8, wherein the second device is caused to determine whether the handover is triggered by:

determining that the handover is triggered in response to the information indicating that the quality of the feedback-free transmission is below a threshold quality.

12. The second device of claim 8, wherein the second device is further caused to:

forwarding data buffered in the second device for future transmission to the third device in response to at least one of:

the number of degree-1 TBs received by the first device is reduced, or

The number of degree-1 TBs received by the first device is below a threshold number.

13. The second device of claim 8, wherein the second device is further caused to:

receiving, from the third device, further information on a further configuration of further feedback-free transmissions supported by the third device; and

forwarding the further information to the first device.

14. The second device of claim 8, wherein the first device comprises a terminal device, the second device comprises a network device, and the second device comprises a further network device.

15. 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 apparatus to:

receiving, at the third device, a handover request from a second device indicating that a first device is to be handed over to the third device;

generating an acknowledgement to the handover request, the acknowledgement comprising information on a configuration of a no feedback transmission using one or more combined transport block, TB, instead of a feedback-based retransmission, the combined TB being generated based on an original TB on which data to be transmitted is carried;

sending the acknowledgement to the second device; and

transmitting a synchronization signal to the first device for the handover.

16. The third device of claim 15, wherein the configuration of the no feedback transmission comprises at least one of:

17. The third device of claim 15, wherein the first device comprises a terminal device, the second device comprises a network device, and the second device comprises a further network device.

18. A method, comprising:

receiving, at a first device, information from a second device regarding a configuration of a feedback-less transmission using one or more combined transport blocks, TBs, instead of feedback-based retransmission, the combined TBs generated based on an original TB on which data to be transmitted is carried;

19. The method of claim 18, wherein the configuration of the no feedback transmission comprises at least one of:

20. The method of claim 18, wherein the measurement report comprises at least one of:

the rate at which the original TB is not recovered from the TB combination,

the index of the original TB successfully recovered from the TB composition, or

The index of the original TB that cannot be recovered from the TB combination.

21. The method of claim 18, wherein receiving, from the second device, the indication to switch from the second device to the third device comprises:

22. The method of claim 18, further comprising:

23. The method of claim 18, further comprising:

setting a timer for switching to the third device;

detecting a failure of the switching by comparing a number of degree-1 TBs obtained from a TB combination transmitted from the third device with the threshold number.

24. The method of claim 18, wherein the first device comprises a terminal device, the second device comprises a network device, and the second device comprises a further network device.

25. A method, comprising:

26. The method of claim 25, wherein the configuration of the no feedback transmission comprises at least one of:

27. The method of claim 25, wherein the measurement report comprises at least one of:

the rate at which the original TB is not recovered from the TB combination,

the index of the original TB successfully recovered from the TB composition, or

The index of the original TB that cannot be recovered from the TB combination.

28. The method of claim 25, wherein determining whether the handover is triggered comprises:

29. The method of claim 25, further comprising:

the number of degree-1 TBs received by the first device is reduced, or

30. The method of claim 25, further comprising:

forwarding the further information to the first device.

31. The method of claim 25, wherein the first device comprises a terminal device, the second device comprises a network device, and the second device comprises a further network device.

32. A method, comprising:

receiving, at a third device, a handover request from a second device indicating that a first device is to be handed over to the third device;

sending the acknowledgement to the second device; and

transmitting a synchronization signal to the first device for the handover.

33. The method of claim 32, wherein the configuration of the no feedback transmission comprises at least one of:

34. The method of claim 32, wherein the first device comprises a terminal device, the second device comprises a network device, and the second device comprises a further network device.

35. An apparatus, comprising:

means for receiving, at a first device, information from a second device regarding a configuration of a feedback-less transmission, the feedback-less transmission using one or more combined transport blocks, TBs, instead of feedback-based retransmission, the combined TBs generated based on an original TB on which data to be transmitted is carried;

means for transmitting a measurement report including information reflecting a quality of the feedback-less transmission to the second device; and

means for receiving an indication from the second device to switch to a third device, the switch being triggered based on the information reflecting the quality of the no feedback transmission.

36. An apparatus, comprising:

means for transmitting, from the second device to the first device, information on configuration of a feedback-less transmission using one or more combined transport blocks, TBs, instead of feedback-based retransmissions, the combined TBs being generated based on an original TB on which data to be transmitted is carried;

means for receiving a measurement report from the first device comprising information reflecting a quality of the feedback-less transmission;

means for determining whether a handover is triggered based on the information reflecting the quality of the no feedback transmission; and

means for determining a third device to use for the handover in response to a determination that the handover is triggered.

37. An apparatus, comprising:

means for receiving, at a third device, a handover request from a second device indicating that a first device is to be handed over to the third device;

means for generating an acknowledgement to the handover request, the acknowledgement comprising information on a configuration of a feedback-less transmission using one or more combined transport blocks, TBs, instead of feedback-based retransmissions, the combined TBs generated based on an original TB on which data to be transmitted is carried;

means for transmitting the acknowledgement to the second device; and

means for transmitting a synchronization signal to the first device for the handover.

38. 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 18 to 24.

39. 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 25 to 31.

40. 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 32 to 34.