WO2021026913A1

WO2021026913A1 - Handover in communication networks

Info

Publication number: WO2021026913A1
Application number: PCT/CN2019/100863
Authority: WO
Inventors: Kai Zhu; Yu Chen; Wenjian Wang
Original assignee: Nokia Shanghai Bell Co., Ltd.; Nokia Solutions And Networks Oy; Nokia Technologies Oy
Priority date: 2019-08-15
Filing date: 2019-08-15
Publication date: 2021-02-18
Also published as: CN114258719A

Abstract

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

Description

HANDOVER IN COMMUNICATION NETWORKS

FIELD

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

BACKGROUND

Since resources and infrastructure are limited in remote area, it is very difficult for terrestrial network to provide 5G coverage. The main benefits of introducing Non-Terrestrial Network (NTN) is to enable ubiquitous 5G services to terminal devices by extending connectivity in less populated areas with extremely low density of devices and the overall cost of deployment may be much less than providing permanent infra-structure on the ground. Using the space-borne or air-borne platforms may provide reliable coverage in remote areas, which have a distinct advantage. However, it has also brought some problems in other aspects.

SUMMARY

In general, example embodiments of the present disclosure provide a solution for handover in communication networks and corresponding communication devices.

In a first aspect, there is provided a first device. The first device comprises at least one processor; and at least one memory including computer program codes; the at least one memory and the computer program codes are configured to, with the at least one processor, cause the first device to receive, at the first device and from a second device, information concerning a configuration of a feedback-less transmission, the feedback-less transmission using one or more combined transport blocks, TBs, rather than feedback-based retransmission, the combined TBs generated based on original TBs on which the data to be transmitted is carried. The first device is also caused to transmit to the second device a measurement report comprising information reflecting quality of the feedback-less transmission. The first device is further caused to receive, from the second device, an indication of a handover to a third device, the handover triggered based on the information reflecting the quality of the feedback-less transmission.

In a second aspect, there is provided a second device. The second device comprises at least one processor; and at least one memory including computer program codes; the at least one memory and the computer program codes are configured to, with the at least one processor, cause the second device to transmit, to a first device and from the second device, information concerning a configuration of a feedback-less transmission, the feedback-less transmission using one or more combined transport blocks, TBs, rather than feedback-based retransmission, the combined TBs generated based on original TB , on which the data to be transmitted is carried. The second device is further caused to receive, from the first device, a measurement report comprising information reflecting quality of the feedback-less transmission. The second device is also caused to determine whether a handover is trigger based on the information reflecting the quality of the feedback-less transmission. The second device is yet caused to in response to a determination that the handover is triggered, determine a third device for the handover.

In a third aspect, there is provided a third device. The third device comprises at least one processor; and at least one memory including computer program codes; the at least one memory and the computer program codes are configured to, with the at least one processor, cause the third device to receive, at the third device and from a second device, a handover request indicating a first device is to handover to the third device. The third device is also caused to generate an acknowledgment to the handover request, the acknowledgement comprising information concerning a configuration of a feedback-less transmission, the feedback-less transmission using one or more combined transport blocks, TBs, rather than feedback-based retransmission, the combined TBs generated based on original TBs, on which the data to be transmitted is carried. The third device is further caused to transmit the acknowledgment to the second device. The third device is yet caused to transmit a synchronization signal to the first device for the handover.

In a fourth aspect, there is provided a method. The method comprises receiving, at the first device and from a second device, information concerning a configuration of a feedback-less transmission, the feedback-less transmission using one or more combined transport blocks, TBs, rather than feedback-based retransmission, the combined TBs generated based on original TBs on which the data to be transmitted is carried. The method further transmitting to the second device a measurement report comprising information reflecting quality of the feedback-less transmission. The method also comprises receiving, from the second device, an indication of a handover to a third device, the handover triggered based on the information reflecting the quality of the feedback-less transmission.

In a fifth aspect, there is provided a method. The method comprises transmitting, to a first device and from the second device, information concerning a configuration of a feedback-less transmission, the feedback-less transmission using one or more combined transport blocks, TBs, rather than feedback-based retransmission, the combined TBs generated based on original TB , on which the data to be transmitted is carried. The method also comprises receiving, from the first device, a measurement report comprising information reflecting quality of the feedback-less transmission. The method further comprises determining whether a handover is trigger based on the information reflecting the quality of the feedback-less transmission. The method yet comprises in response to a determination that the handover is triggered, determining a third device for the handover.

In a sixth aspect, there is provided a method. The method comprises receiving, at a third device and from a second device, a handover request indicating a first device is to handover to the third device. The method also comprises generating an acknowledgment to the handover request, the acknowledgement comprising information concerning a configuration of a feedback-less transmission, the feedback-less transmission using one or more combined transport blocks, TBs, rather than feedback-based retransmission, the combined TBs generated based on original TBs, on which the data to be transmitted is carried. The method further comprises transmitting the acknowledgment to the second device. The method yet comprises transmitting a synchronization signal to the first device for the handover.

In a seventh aspect, there is provided an apparatus. The apparatus comprises means for receiving, at the first device and from a second device, information concerning a configuration of a feedback-less transmission, the feedback-less transmission using one or more combined transport blocks, TBs, rather than feedback-based retransmission, the combined TBs generated based on original TBs on which the data to be transmitted is carried; means for transmitting to the second device a measurement report comprising information reflecting quality of the feedback-less transmission; and means for receiving, from the second device, an indication of a handover to a third device, the handover triggered based on the information reflecting the quality of the feedback-less transmission.

In an eighth aspect, there is provided an apparatus. The apparatus comprises means for transmitting, to a first device and from the second device, information concerning a configuration of a feedback-less transmission, the feedback-less transmission using one or more combined transport blocks, TBs, rather than feedback-based retransmission, the combined TBs generated based on original TB , on which the data to be transmitted is carried; means for receiving, from the first device, a measurement report comprising information reflecting quality of the feedback-less transmission; means for determining whether a handover is trigger based on the information reflecting the quality of the feedback-less transmission; and means for in response to a determination that the handover is triggered, determining a third device for the handover.

In a ninth aspect, there is provided an apparatus. The apparatus comprises means for receiving, at a third device and from a second device, a handover request indicating a first device is to handover to the third device; means for generating an acknowledgment to the handover request, the acknowledgement comprising information concerning a configuration of a feedback-less transmission, the feedback-less transmission using one or more combined transport blocks, TBs, rather than feedback-based retransmission, the combined TBs generated based on original TBs, on which the data to be transmitted is carried; means for transmitting the acknowledgment to the second device; and means for transmitting a synchronization signal to the first device for the handover.

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

It is to be understood that the summary section is not intended to identify key or essential features of embodiments of the present disclosure, nor is it intended to be used to limit the scope of the present disclosure. Other features of the present disclosure will become easily comprehensible through the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

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

Fig. 1 illustrates a principle of a feedback-less 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 among communication devices according to some embodiments of the present disclosure;

Fig. 4 illustrates a schematic diagram of RSRP varying between cells according to some embodiments of the present disclosure;

Fig. 5 illustrates a flowchart of a method implemented at a network device according to some embodiments of the present disclosure;

Fig. 6 illustrates a flowchart of a method implemented at a network device according to some embodiments of the present disclosure;

Fig. 7 illustrates a flowchart of a method implemented at a network device according to some embodiments of the present disclosure;

Fig. 8 illustrates a simplified block diagram of a device that is 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 represent the same or similar element.

DETAILED DESCRIPTION

Principle of the present disclosure will now be described with reference to some example embodiments. It is to be understood that these embodiments are described only for the purpose of illustration and help those skilled in the art to understand and implement the present disclosure, without suggesting any limitation as to the scope of the disclosure. The disclosure described herein can be implemented in various manners other than the ones 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 skills in the art to which this disclosure belongs.

References in the present disclosure to “one embodiment, ” “an embodiment, ” “an example embodiment, ” and the like indicate that the embodiment described may include a particular feature, structure, or characteristic, but it is not necessary that every embodiment includes 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 shall be understood that although the terms “first” and “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 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 “including” , 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 combinations 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) and

(b) combinations of hardware circuits and software, such as (as applicable) :

(i) a combination of analog and/or digital hardware circuit (s) with software/firmware and

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

(c) hardware circuit (s) and or processor (s) , such as a microprocessor (s) or a portion of a microprocessor (s) , that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.

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

As used herein, the term “communication network” refers to a network following any suitable communication standards, such as Long Term Evolution (LTE) , LTE-Advanced (LTE-A) , Wideband Code Division Multiple Access (WCDMA) , High-Speed Packet Access (HSPA) , Narrow Band Internet of Things (NB-IoT) , New Radio (NR) , Non-terrestrial network (NTN) and so on. Furthermore, the communications between a terminal device and a network device in the communication network may be performed according to any suitable generation communication protocols, including, but not limited to, the first generation (1G) , the second generation (2G) , 2.5G, 2.85G, the third generation (3G) , the fourth generation (4G) , 4.5G, the future fifth generation (5G) communication protocols, and/or any other protocols either currently known or to be developed in the future. Embodiments of the present disclosure may be applied in various communication systems. Given the rapid development in communications, there will of course also be future type communication technologies and systems with which the present disclosure may be embodied. It should not be seen as limiting the scope of the present disclosure to only the aforementioned system.

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. The network device may refer to a base station (BS) or an access point (AP) , for example, a node B (NodeB or NB) , an evolved NodeB (eNodeB or eNB) , a NR NB (also referred to as a gNB) , a Remote Radio Unit (RRU) , a radio header (RH) , a remote radio head (RRH) , a relay, a low power node such as a femto, a pico, and so forth, depending on the applied terminology and technology.

The term “terminal device” refers to any end device that may be capable of wireless communication. By way of example rather than limitation, a terminal device may also be referred to as a communication device, user equipment (UE) , a Subscriber Station (SS) , a Portable Subscriber Station, a Mobile Station (MS) , or an Access Terminal (AT) . The terminal device may include, but not limited to, a mobile phone, a cellular phone, a smart phone, voice over IP (VoIP) phones, wireless local loop phones, a tablet, a wearable terminal device, a personal digital assistant (PDA) , portable computers, desktop computer, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback appliances, vehicle-mounted wireless terminal devices, wireless endpoints, mobile stations, laptop-embedded equipment (LEE) , laptop-mounted equipment (LME) , USB dongles, smart devices, wireless customer-premises equipment (CPE) , an Internet of Things (loT) device, a watch or other wearable, a head-mounted display (HMD) , a vehicle, a drone, a medical device and applications (e.g., remote surgery) , an industrial device and applications (e.g., a robot and/or other wireless devices operating in an industrial and/or an automated processing chain contexts) , a consumer electronics device, a device 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, the NTN has also brought some problems in other aspects. For the NTN, the round-trip time (RTT) to the terminal device can be much larger than that in the terrestrial networks. One important deployment feature that may distinguish NTN from terrestrial networks is that NTN base stations are generally satellites located on the Earth orbit with 600 -36000 km orbital altitude relative to terminal devices on Earth surface.

Propagation time for electromagnetic waves to travel through such distance is measured as follows in Table 1 below.

Table 1

It can be seen that propagation delay of NTN is much higher than what can be possibly tolerated by NR Physical Layer, which is limited by maximum propagation distance of 300km. On the other hand, such prolonged propagation delay would also challenge the technological specification of legacy systems and robust NTN mobility is among the most important issues.

Similar to conventional terrestrial networks, mobility also plays a pivotal role in NTN systems, which enables the continuity of radio connectivity and maintains consistent quality of service for nomadic terminal devices. An optimal handover (HO) should, in general, have minimized handover interruption time (HIT) , handover failure (HOF) rate, as well as ping-pong (PP) rate. However, in NTN scenario, good mobility mechanisms achieving the above HO targets become technically difficult resulting from the greatly increased risk of measurement invalidity. Recall that round-trip time (RTT) of radio signals in NTN may be orders of magnitude larger than that of terrestrial networks, such cumulative delay incurred could lead to UE measurements to be either too slow or inaccurate.

The established procedures for most conventional HO schemes follow the guideline of “assisted by UE, controlled by network” rule. When measurements reported by the terminal devices become unreliable, it would be very difficult for the network to make proper HO decisions. The cost of an improper HO in NTN is very expensive as the consequent radio link failure (RLF) recovery process would consume considerable amount of delay and service disruptions due to signalling latency. According to recent analysis, the overall interruption could be as much as several seconds when counting the latency for radio resource control (RRC) message processing and other signalling transfer delays.

There may be two areas of focus for RAN2: propagation delay which identifies timing requirements and solutions on layer 2 aspects including medium 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 handovers between Non GEO satellites that move at high speeds but over predictable paths.

Furthermore, other discussions covered these aspects are in the context of mobility. While it is determined too early for RAN2 to converge on mobility solutions, several observations related to possible challenges to extending Rel-15 mobility procedures in NTN were captured in 38.821: for GEO NTN: Mobility management procedures require adaptations to accommodate large propagation delay. In particular radio link management may require specification configuration; for LEO NTN: Mobility management procedures should be enhanced to take into account satellite movement related to aspects such as measurement validity, UE velocity, movement direction, large and varying propagation delay and dynamic neighbour cell set.

In RAN2#105, it was agreed to capture following observations: companies were not ready to identify and agree on solution options for RRM or HO for NTN; for GEO NTN, the large propagation delay was identified to be the key issue and the effect on performing measurements and for measurement configuration should be considered; specific for LEO NTN, satellite movement related aspects such as measurement validity, UE velocity, movement direction, large and varying propagation delay and dynamic neighbour cell set were identified.

To summarize the agreements listed above, satellites in non-GEO orbits move at high speed (～7.5 km/sfor LEO) relative to Earth surface, it is current consensus in 3GPP that frequent handover is unavoidable as it is dealing with moving new radio (NR) cells. Because of the measurement invalidity issue and ping-pong effect mentioned earlier, improper mobility action is expected to happen more often than NR terrestrial network and such consequences are unaffordable given the very stringent NTN performance requirements.

To overcome the limited functionalities provided by NR HO mechanisms, the incorporation of make-before-break (MBB) HO seems a suitable choice for NTN mobility. MBB HO was discussed in Rel 14, as an improved HO feature for the evolution of long term evolution LTE. MBB HO approach generally assumes the data exchange with the serving cell does not “break” until a new connection with a target cell is established (i.e., “make” ) .

Furthermore, it appears to be a justified supposition that downlink transmission from the serving cell occurring upon the reception of HO command may end up a lot of incorrect data reception resulting from the deteriorating channel condition. Handling those incorrect data in the means of retransmissions while HO is being executed could require additional complexity over the terminal device and network device sides. This motivates the incorporation of another important ingredient into NTN paradigm to avoid explicit retransmissions and HARQ feedback signalling, that is a NTN-specific enhancement termed feedback-less transmission scheme.

Fig 1 shows the TB combination and TB elimination process summarized for one example where two original TBs are transmitted using 3 combined TBs. In the first phase, the inputs (for example, TB301 and TB 302) are “combined” , i.e., XOR operations are performed with these TBs. In this example, there are two combined TBs of degree-1 (TB301 and TB 3021) and one of degree-2 (TB301+302, where + represents the XOR operation) . In this example, assuming TB301 is missed, whereas other two TB302 and, TB301+302 are received with success. In the TB elimination phase, the TB of degree-1 effectively received are assumed to have been eliminated and become the “ripple” . In the next phase the “ripple” is used to perform further TB elimination with other successfully received TB combinations. The process continues until all original TBs have been recovered or all TBs in the ripple have been eliminated from the others.

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

Principle and embodiments of the present disclosure will be described in detail below with reference to the accompanying 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 can be implemented. The communication system 200 comprises the first devices 210, the second device 220-1 and the third device 220-2. For the purpose of illustrations, the first devices 210 may be referred to as the terminal device 210 and the second device 220-1 and the third device 220-2 may be referred to as the network device 220 hereinafter. It should be noted that the first devices the second devices, the third devices are interchangeable. For example, the procedures which are described to be implemented at the terminal device may also be able to be implemented at the network device and the procedures which are described to be implemented at the network device may also be able to be implemented at the terminal device.

The link from the second device 220-1 and the third device 220-2 to the first devices 210 may be referred to as the “downlink” and the link from the first devices 210 to the second device 220-1 and the third device 220-2 may be referred to as the “uplink” .

The communication system 200, which is a part of a communication network, comprises terminal devices 210-1, 210-2, ..., 210-N (collectively referred to as “terminal device (s) 210” where N is an integer number) . The communication system 200 comprises one or more network devices, for example, network devices 220-1 and 220-2.

It should be understood that the communication system 200 may also comprise other elements which are omitted for the purpose of clarity. It is to be understood that the numbers of terminal devices and network devices shown in Fig. 2 are given for the purpose of illustration without suggesting any limitations. The terminal devices 210, the network device 220-1 and the network devices 220-2 may communicate with each other.

It is to be understood that the number of network devices and terminal devices is only for the purpose of illustration without suggesting any limitations. The system 100 may include any suitable number of network devices and terminal devices adapted for implementing embodiments of the present disclosure.

Communications in the communication system 200 may be implemented according to any proper communication protocol (s) , comprising, but not limited to, cellular communication protocols of the first generation (1G) , the second generation (2G) , the third generation (3G) , the fourth generation (4G) and the fifth generation (5G) and on the like, wireless local network communication protocols such as Institute for Electrical and Electronics Engineers (IEEE) 802.11 and the like, and/or any other protocols currently known or to be developed in the future. Moreover, the communication may utilize any proper wireless communication technology, comprising 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 (OFDM) , Discrete Fourier Transform spread OFDM (DFT-s-OFDM) and/or any other technologies currently known or to be developed in the future.

Fig. 3 illustrates a schematic diagram of interactions 300 in contention-based system in accordance with embodiments of the present disclosure. The interactions 300 may be implemented at any suitable devices. Only for the purpose of illustrations, the interactions 300 are described to be implemented at the terminal device 210-1, the network device 220-1 and the network device 220-2. By way of example, the network device 220-1 may be the source network device and the network device 220-2 may be the target network device. It should be noted that the phrase “combined TBs” and “TB combinations” have the same meaning and they can be used interchangeably throughout this document and the phrase “eliminated TBs” and “TB elimination” have the same meaning and they can be used interchangeably throughout this disclosure.

The network device 220-1 transmits 3005 the information about configuration of a feedback-less transmission. The term “feedback-less transmission” used herein refers to the transmission uses combined transport blocks (TB) rather than feedback-based retransmission. The configuration may comprise one or more of: a feedback-less transmission redundancy rate, a TB degree or a TB combination pattern.

The combined TBs may be generated based on the original TBs on which the data to be transmitted is carried. The feedback-less transmission redundancy rate may indicate a ratio between the number of the original TBs to be conveyed and the number of TB combinations actually transmitted. The TB degree may indicate the number of the original TBs from which a specific TB combination is generated. The TB combination pattern may indicate which original TBs are selected to generate a specific TB combination. It should be noted that the confirmation may comprise any suitable parameters related to combination and elimination of the TBs.

Only as an example, Table 2 below shows the combination pattern of the feedback-less transmission. It should be noted that the numbers and values shown in Table 2 are only examples, not limitations.

Table 2

Transmission instance#	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 TB to be conveyed from the transmitter side to the receiver side is 4, TB0, TB1, TB2, TB3. The number of combined TBs, which are actually transmitted over the air interface, is 8. Thus, feedback-less transmission redundancy rate is 4/8. The TB degree (or, just “degree” for short) of “TB0” is 1 since TB0 is the original TB, which can be represented as “degree-1. ” The TB degree of “TB3+TB1+TB0” is 3 since it is generated based on three original TBs, which can be represented as “degree-3” , where + represents the XOR operation.

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

In some embodiments, if the terminal device 210-1 is in RRC_CONNECTED state, the terminal device 210-1 and the network device 220-1 may communicate with each other using the feedback-less transmission due to the high latency on the air interface. For example, the network device 220-1 may transmit 3010 the data using the feedback-less transmission to the terminal device 210-1.

In some embodiments, the network device 220-1 may transmit 3015 signaling to active the feedback-less transmission. In some embodiments, the signaling may be RRC message dedicated to the terminal device 210-1. Alternatively or in addition, the signaling may be broadcasted to multiple terminal devices.

The terminal device 210-2 transmits 3020 the measurement report to the network device 220-1. The measurement report comprises information reflecting the quality of the feedback-less transmission. In some embodiments, the measurement report comprises one or more of: the number of degree-1 TBs obtained from TB combinations sent from the second device, a ratio of successful recovery of original TBs from TB combinations, a ratio of failed recovery of original TBs from TB combinations, indices of original TBs which recovered successfully from TB combinations, or indices of original TBs which failed to recover from TB combinations. . In some embodiments, the procedure of recovery of original TBs may also refer to “TB elimination. ”

In some embodiments, the recovery of original TBs may depend on successive cancellation of degree-1 TBs from the received TB combinations. During each cancellation, new degree-1 TB must be generated to keep further cancellation going. When radio link condition deteriorating or experience outage causing too many missing or erroneously received TB combinations, the TB elimination is likely to suspend in the middle of the process as the number of degree-1 TBs generated becomes inadequate to sustain the rest of elimination, a large portion of received TB combinations are therefore unrecoverable.

The 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 conditions are satisfied. It is noticed that making NTN HO decisions only rely on received power strength would be less reliable because the additional erasure property of NTN channel. On the contrary, the measurement report related to information reflecting state of transport blocks elimination is able to describe the condition of erasure channel from the erasure likelihood dimension. In this way, the handover decision is more accurate.

In some embodiments, the network device 220-1 may compare the quality of the feedback-less transmission with the threshold quality. If the quality exceeds the threshold quality, the network device 220-1 may trigger into handover state. If the quality is below the threshold quality, the network device 220-1 may not trigger into handover state. The network device 220-1 may ignore the measurement report and keep monitoring. The network device 220-1 may reconfigure the feedback-less transmission, for example, the TB redundancy rate, the TB degree or the TB combination pattern. The network device 220-1 may also reconfigure other transmitting parameters for future transmission, for example modulation and coding scheme (MCS) and transmitting power.

In some embodiments, there may be several different thresholds to avoid “false-alarm” where radio link between the terminal device 210-1 and the network device 220-1 is only temporarily degraded and will be recovered soon. Event-X1: quality of the feedback-less transmission at serving cell is above a threshold-1, but below a threshold-2. The proposed HO condition can be described below as shown in Table 3.

Table 3

In some embodiments, the number of degree-1 TBs generated during TB elimination is the key to sustain continuous TB elimination and is more sensitive to the varying of channel compared with signal-power.

In some embodiments, if the channel condition is relatively good, TB combinations have no significant benefit, which means each of the TB elimination is successful. In some embodiments, when the channel condition starts degrading, the TB elimination experiences some small degree of failures. By waiting for more TB combinations to be received for assisting the elimination, eventually TB elimination can be successful. When the channel condition keeps degrading below certain threshold, the TB elimination experiences so many failures that degree-1 TBs generated during elimination becomes inadequate to sustain the rest of elimination, eventually TB elimination is collapsed.

Only for the purpose of illustrations, the configuration of the feedback-less transmission is shown in aforementioned Table 2. If the channel condition starts degrading, the first and second transmissions (for example, TB0 and TB1) may not be received. Since there is no knowledge of neither TB0 nor TB1 to perform the TB elimination, TB2+TB0 and TB3+TB1+TB0 can only be stored waiting for further combined TBs to arrive. In this example, TB elimination can be successful, with the following steps: (1) buffer#6 + buffer#3→ TB0 (a new degree-1 TB) ; (2) buffer #6 + buffer#5→ TB3 (a new degree-1 TB) ; (3) buffer#4 + TB0 (new) + TB3 (new) ->TB1 (a new degree-1 TB) . Thus, all the data on the TB0 to TB3 can be recovered successfully and three new degree-1 TBs are generated during the process.

In some embodiments, if the channel condition has been degraded below a threshold. For example, the first, second, fifth and sixth TB combinations being missing, there is one degree-1 TB at the beginning of elimination. And more importantly, no matter how to perform the elimination, there would be no way to generate new degree-1 TB, hence in this example, the degree-1 TB generated is inadequate to sustain elimination, the elimination is failed. It is not hard to see TB elimination operate in a successive way. The degree-1 TBs are the key to sustain continuous TB elimination and are more sensitive to the status of channel.

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

The network device 220-2 generates 3032 the acknowledgement (ACK) to the handover request. In some embodiments, the ACK may also comprise configuration information of another feedback-less transmission that the network device 220-2 supports. For example, the ACK may comprise one or more of a feedback-less transmission redundancy rate, a TB degree, or a TB combination pattern. The TB redundancy rate may indicate a ratio between the number of the original TBs to be conveyed and the number of TB combinations actually transmitted. The network device 220-2 may transmit 3035 the ACK to the handover request to the network device 220-1. In some embodiments, the ACK may also comprise configuration information of another feedback-less transmission that the network device 220-2 supports. In some embodiments, the network device 220-1 may transmit 3040 the information of another feedback-less transmission to the terminal device 210-1. The network device 220-2 may transmit 3045 the indication of the handover to the network device 220-2 to the terminal device 210-1.

The network device 220-2 transmits 3050 the synchronization signal to the terminal device 210-1. In some embodiments, the terminal device 210-1 can perform simultaneous reception of synchronization signals from the network device 220-2 for initial access purpose while continuing data transmissions with the network device 220-1. For example, the terminal device 210-1 may continue transmitting 3055 the data to the network device 220-1. In some embodiments, the terminal device 210-1 may also transmit new measurement report to the network device 220-1.

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

With the knowledge of TB elimination status reported from the terminal device 210-1, the network device 220-1 is able to keep track of TB elimination progress. The indices of TBs that have been successfully eliminated or have not been successfully eliminated would give the network device 220-1 clear guidance on which portion of data shall be forwarded so that the received TB combinations (partly from the network device 220-1, and partly from the network device 220-2) provide the largest TB combination redundancy gain at the expense of forwarding only reasonably small amount of data.

In one example, the TB combination redundancy rate of 4/8 is chosen, which means every 8 transmissions over the physical interface may transmit a total of 4 original TBs, denoted as TB0, TB1, TB2 and TB3. The combination pattern is shown in Table 4 below. It should be noted that the numbers and values shown in Table 4 are only examples not limitations.

Table 4

In the first example, assuming that TB0 and TB1 (corresponding to the 1st and 2nd transmission from the network device 220-1) are not received due to the deteriorating channel condition of serving cell. It assumes that 3rd and 4th transmission from network device 220-1b are successful. Since there is no knowledge of neither TB0 nor TB1 to perform the TB elimination, TB2+TB0 and TB3+TB1+TB0 can only be stored in the buffer#2 and #3 waiting for further combined TBs to arrive after switching to the target network device 220-2 with the expectation of improved radio quality. In the present example, only two out of four TB combinations need to be forwarded to the network device 220-2 and sent to the terminal device 210-1 after the handover, that is TB3+TB2 and TB2 located in buffer#4 and #5 or TB3+TB2 and TB3 located in buffer#4 and #6. The respective TB elimination at terminal deice 210-1 side can 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, it assumes that the transmission of TB2+TB0 at the 3rd transmitting instance is missing. In this case, TB0 and TB1 are both degree-1 TBs, hence they are received ‘as-is’ . Then, TB3 can be obtained via: buffer#3 + TB0 + TB1 → TB3. Thus, the network device 220-1 may only have to forward one copy of TB combination to the network device 220-2 for the purpose of recovering TB2. This copy could be any one of: TB3 +TB2; TB2; or TB1+TB2.

The terminal device may transmit 3070 the ACK to the network device 220-1. The terminal device 210-1 may further detach 3080 from the network device 220-1. In some embodiments, the terminal device 210-1 may set a timer for the handover. This timer is started upon the transmission of RRC reconfiguration complete signaling. The duration of such timer can be configured by pre-defined by upper layer, system information, or RRC signaling.

When the timer expires, if the number of degree-1TBs received by the terminal device 210-1 is not increased over a given margin, it is considered as an unsuccessful handover. Corresponding actions to handle failed HO can be triggered. It could be either fall back to original serving cell (ping-pong) or initiate RLF process. For example, at the moment of t1 in Fig. 4, the terminal device 210-1 is detached from the network device 220-1, the new connection established with target network device 220-2 is expected to be more reliable and should be keeping improving along with time as illustrated by Fig 4. Under such assumption, it is intuitive to predict that more TB combinations should be correctly received by the terminal device 210-1, which further implies an increasing number of degree-1 TBs should be generated after HO. The handover can be decided more accurately, therefore embodiments of the present disclosure can reduce latency by, to a large extent, avoiding unnecessary or improper HO..

Fig. 5 shows a flowchart of an example method 500 implemented at a terminal device in accordance with some embodiments of the present disclosure. The method 500 may be implemented at any suitable devices. For the purpose 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 the information about configuration of a feedback-less transmission. The combined TBs may be generated based on the original TB on which data to be transmitted is carried.

The configuration may comprise one or more of: a feedback-less transmission redundancy rate, a TB degree or a TB combination pattern. The combined TBs may be generated based on the original TB on which the data to be transmitted is carried. The feedback-less transmission redundancy rate may indicate a ratio between the number of the original TBs to be conveyed and the number of TB combinations actually transmitted. The TB degree may indicate the number of the original TBs from which a specific TB combination is generated. The TB combination pattern may indicate which original TBs are selected to generate a specific TB combination.

At block 520, the terminal device 210-1 transmits the measurement report to the network device 220-1. The measurement report comprises information reflecting state of transport blocks elimination. In some embodiments, the measurement report comprises one or more of: the number of degree-1 TBs obtained from TB combinations sent from the second device, a ratio of successful recovery of original TBs from TB combinations, a ratio of failed recovery of original TBs from TB combinations, indices of original TBs which recovered successfully from TB combinations, or indices of original TBs which failed to recover from TB combinations. In some embodiments, the procedure of the recovery of original TBs may also refer to “TB elimination. ”

At block 530, the terminal device 210-1 receives an indication of the handover from the network device 220-1. In some embodiments, the terminal device 210-1 may receive the information of another feedback-less transmission supported by the network device 220-2. The information may comprise 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 the original TBs and the combined TBs to the number of the original TBs.

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

In some embodiments, the terminal device 210-1 may set a timer for the handover. This timer is started upon the transmission of RRC reconfiguration complete signaling. The duration of such timer can be configured by pre-defined by upper layer, system information, or RRC signaling. The terminal device 210-1 may detect the failure of the handover by comparing the number of original TBs obtained from the third device and the threshold number. When the timer expires, if the number of obtained original TBs is not increased over a given margin, it is considered as an unsuccessful handover.

Fig. 6 shows a flowchart of an example method 600 implemented at a terminal device in accordance with some embodiments of the present disclosure. The method 600 may be implemented at any suitable devices. For the purpose of discussion, the method 600 will be described from the perspective of the network device 220-1 with reference to Fig. 2.

At block 610, the network device 220-1 transmits the information about configuration of a feedback-less transmission. The combined TBs may be generated based on the original TB on which data to be transmitted is carried. The configuration may comprise one or more of: a feedback-less transmission redundancy rate, a TB degree or a TB combination pattern. The combined TBs may be generated based on the original TB on which the data to be transmitted is carried. The feedback-less transmission redundancy rate may indicate a ratio between the number of the original TBs to be conveyed and the number of TB combinations actually transmitted. The TB degree may indicate the number of the original TBs from which a specific TB combination is generated. The TB combination pattern may indicate which original TBs are selected to generate a specific TB combination.

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

In some embodiments, the network device 220-1 may transmit signaling to active the feedback-less transmission. In some embodiments, the signaling may be RRC message dedicated to the terminal device 210-1. Alternatively or in addition, the signaling may be broadcasted to multiple terminal devices.

At block 620, the network device 220-1 receives the measurement report from the terminal device 210-1. The measurement report comprises information reflecting the quality of the feedback-less transmission. In some embodiments, the measurement report comprises one or more of: the number of degree-1 TBs obtained from TB combinations sent from the second device, a ratio of successful recovery of original TBs from TB combinations, a ratio of failed recovery of original TBs from TB combinations, indices of original TBs which recovered successfully from TB combinations, or indices of original TBs which failed to recover from TB combinations. In some embodiments, the procedure of recovery of original TBs may also refer to “TB elimination. ”

At block 630, the network device 220-1 determines 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 conditions are satisfied.

In some embodiments, the network device 220-1 may compare the quality of the feedback-less transmission with the threshold quality. If the quality exceeds the threshold quality, the network device 220-1 may trigger into handover state. If the quality is below the threshold quality, the network device 220-1 may not trigger into handover state. The network device 220-1 may ignore the measurement report and keep monitoring. The network device 220-1 may reconfigure the feedback-less transmission, for example, the TB redundancy rate, the TB degree or the TB combination pattern. The network device 220-1 may also reconfigure other transmitting parameters for future transmission, for example MCS and transmitting power.

At block 640, the network device 220-1 determines the network device 220-2 to be the target network device. The network device 220-1 may search for neighboring network devices of which trajectory may be aligned with the coverage area of the terminal device 210-1 for a given window. For example, the network device 220-1 may determine the target network device based on the velocity of the terminal device 210-1, movement direction of the terminal device 210-1 and the dynamic neighbor cell sets. After the network device 220-1 determines the network device 220-2 to be the target network device, the network device 220-1 may transmits the handover request to the network device 220-2.

In some embodiments, the network device 220-1 may receive the acknowledgement (ACK) to the handover request from the network device 220-2. In some embodiments, the ACK may also comprise configuration information of another feedback-less transmission that the network device 220-2 supports. For example, the ACK may comprise 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 the original TBs and the combined TBs to the number of the original TBs. In some embodiments, the network device 220-1 may forward the information of another feedback-less transmission to the terminal device 210-1. The network device 220-2 may transmit the indication of the handover to the network device 220-2 to the terminal device 210-1.

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

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

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

At block 720, the network device 220-2 generates the ACK to the handover request. In some embodiments, the ACK may also comprise configuration information of another feedback-less transmission that the network device 220-2 supports. For example, the ACK may comprise one or more of a feedback-less transmission redundancy rate, a TB degree, or a TB combination pattern. The TB redundancy rate may indicate a ratio between the number of the original TBs to be conveyed and the number of TB combinations actually transmitted.

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

In some embodiments, an apparatus for performing the method 500 (for example, the terminal device 210-1) may comprise respective means for performing the corresponding steps in the method 500. These means may be implemented in any suitable manners. For example, it can be implemented by circuitry or software modules.

In some embodiments, the apparatus comprises means for receiving, at the first device and from a second device, information concerning a configuration of a feedback-less transmission, the feedback-less transmission using one or more combined transport blocks, TBs, rather than feedback-based retransmission, the combined TBs generated based on original TBs on which data to be transmitted is carried; means for transmitting to the second device a measurement report comprising information reflecting quality of the feedback-less transmission; and means for receiving, from the second device, an indication of a handover to a third device, the handover triggered based on the information reflecting the quality of the feedback-less transmission.

In some embodiments, the configuration of the feedback-less transmission comprises at least one of: a feedback-less transmission redundancy rate indicating a ratio between the number of the original TBs to be conveyed and the number of TB combinations actually transmitted, a TB degree indicating the number of the original TBs from which a specific TB combination is generated, or a TB combination pattern indicating which original TBs are selected to generate a specific TB combination.

In some embodiments, the measurement report comprises at least one of: the number of degree-1 TBs obtained from TB combinations sent from the second device, a ratio of successful recovery of original TBs from TB combinations, a ratio of failed recovery of original TBs from TB combinations, indices of original TBs which recovered successfully from TB combinations, or i indices of original TBs which failed to recover from TB combinations.

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

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

In some embodiments, the apparatus further comprises means for setting a timer for handover to the third device; means for upon expiration of the timer, determining the number of degree-1 TBs obtained from TB combinations sent from the third device; and means for detect a failure of the handover by comparing the number of degree-1 TBs obtained from TB combinations sent from the third device with the 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 for performing the method 600 (for example, the network device 220-1) may comprise respective means for performing the corresponding steps in the method 600. These means may be implemented in any suitable manners. For example, it can be implemented by circuitry or software modules.

In some embodiments, the apparatus comprises means for transmitting, to a first device and from the second device, information concerning a configuration of a feedback-less transmission, the feedback-less transmission using one or more combined transport blocks, TBs, rather than feedback-based retransmission, the combined TBs generated based on original TB , on which the data to be transmitted is carried; means for receiving, from the first device, a measurement report comprising information reflecting quality of the feedback-less transmission; means for determining whether a handover is trigger based on the information reflecting the quality of the feedback-less transmission; and means for in response to a determination that the handover is triggered, determining a third device for the handover.

In some embodiments, the measurement report comprises at least one of: the number of degree-1 TBs obtained from TB combinations sent from the second device, a ratio of successful recovery of original TBs from TB combinations, a ratio of failed recovery of original TBs from TB combinations, indices of original TBs which recovered successfully from TB combinations, or indices of original TBs which failed to recover from TB combinations.

In some embodiments, the means for determining whether the handover is triggered comprises: means for in response to the information indicating quality of the feedback-less transmission being below a threshold quality, determining the handover is triggered.

In some embodiments, the apparatus further comprises means for forwarding, to the third device, data buffered in the second device for future transmission, in response to at least one of the following being satisfied the number of degree-1TBs received by the first device is decreasing, or the number of degree-1TBs 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 concerning further configuration of a further feedback-less transmission supported by the third device; and means for forwarding the further information to the first device.

In some embodiments, an apparatus for performing the method 700 (for example, the network device 220-2) may comprise respective means for performing the corresponding steps in the method 700. These means may be implemented in any suitable manners. For example, it can be implemented by circuitry or software modules.

In some embodiments, the apparatus comprises means for receiving, at a third device and from a second device, a handover request indicating a first device is to handover to the third device; means for generating an acknowledgment to the handover request, the acknowledgement comprising information concerning a configuration of a feedback-less transmission, the feedback-less transmission using one or more combined transport blocks, TBs, rather than feedback-based retransmission, the combined TBs generated based on original TBs, on which data to be transmitted is carried; means for transmitting the acknowledgment to the second device; and means for transmitting a synchronization signal to the first device for the handover.

FIG. 8 is a simplified block diagram of a device 800 that is suitable for implementing embodiments of the present disclosure. The device 800 may be provided to implement the communication device, for example the network device 120 or the 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 processor 810, and one or more communication module (for example, transmitters and/or receivers (TX/RX) ) 840 coupled to the processor 810.

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

The processor 810 may be of any type suitable to the local technical network and may include one or more of the following: general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multicore processor architecture, as non-limiting examples. The device 800 may have multiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock which synchronizes the main processor.

The memory 820 may include one or more non-volatile memories and one or more volatile memories. Examples of the non-volatile memories include, but are not limited to, a Read Only Memory (ROM) 824, an electrically programmable read only memory (EPROM) , a flash memory, a hard disk, a compact disc (CD) , a digital video disk (DVD) , and other magnetic storage and/or optical storage. Examples of the volatile memories include, but are not limited to, a random access memory (RAM) 822 and other volatile memories that will not last in the power-down duration.

A computer program 830 includes computer executable instructions that are executed by the associated processor 810. The program 830 may be stored in the ROM 824. The processor 810 may perform any suitable actions and processing by loading the program 830 into the RAM 822.

The embodiments of the present disclosure may be implemented by means of the program 830 so that the device 800 may perform any process of the disclosure as discussed with reference to Figs. 3 to 6. The 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 contained in a computer readable medium which may be included in the device 800 (such as in the memory 820) or other storage devices that are accessible by the device 800. The device 800 may load the program 830 from the computer readable medium to the RAM 822 for execution. The computer readable medium may include any types of tangible non-volatile storage, such as ROM, EPROM, a flash memory, a hard disk, CD, DVD, and the like. Fig. 9 shows an example of the computer readable medium 900 in form of CD or DVD. The computer readable medium has the program 830 stored thereon.

Generally, various embodiments of the present 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 embodiments of the present disclosure are illustrated and described as block diagrams, flowcharts, or using some other pictorial representations, it is to be understood that the block, apparatus, system, technique or method 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 includes computer-executable instructions, such as those included in program modules, being executed in a device on a target real or virtual processor, to carry out the methods 500-700 as described above with reference to Figs. 5-7. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, or the like 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 a local or distributed device. In a distributed device, program modules may be located in both local and remote storage media.

Program code for carrying out 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 flowcharts and/or block diagrams to be implemented. The program code may execute entirely on a 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, the computer program codes or related data may be carried by any suitable carrier to enable the device, apparatus or processor to perform various processes and operations as described above. Examples of the 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 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 the 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 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 certain circumstances, multitasking and parallel processing may be advantageous. Likewise, while several specific implementation details are contained in the above discussions, these should not be construed as limitations on the scope of the present 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 may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable sub-combination.

Although the present disclosure has been described in languages specific to structural features and/or methodological acts, it is to be understood that the present 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

A first device comprising:

at least one processor; and

at least one memory including computer program codes;

the at least one memory and the computer program codes are configured to, with the at least one processor, cause the first device to:

receive, at the first device and from a second device, information concerning a configuration of a feedback-less transmission, the feedback-less transmission using one or more combined transport blocks, TBs, rather than feedback-based retransmission, the combined TBs generated based on original TBs on which data to be transmitted is carried;

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

receive, from the second device, an indication of a handover to a third device, the handover triggered based on the information reflecting the quality of the feedback-less transmission.
The first device of claim 1, wherein the configuration of the feedback-less transmission comprises at least one of:

a feedback-less transmission redundancy rate indicating a ratio between the number of the original TBs to be conveyed and the number of TB combinations actually transmitted,

a TB degree indicating the number of the original TBs from which a specific TB combination is generated, or

a TB combination pattern indicating which original TBs are selected to generate a specific TB combination.
The first device of claim 1, wherein the measurement report comprises at least one of:

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

a ratio of successful recovery of original TBs from TB combinations,

a ratio of failed recovery of original TBs from TB combinations,

indices of original TBs which recovered successfully from TB combinations, or

indices of original TBs which failed to recover from TB combinations.
The first device of claim 1, wherein the first device is caused to receive, from the second device, the indication of the handover to the third device by:

receiving, from the second device, further information concerning further configuration of a further feedback-less transmission supported by the third device.
The first device of claim 1, wherein the first device is further caused to:

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

in response to receiving a further indication of performing the handover, transmit further data to the third device.
The first device of claim 1, wherein the first device is further caused to:

set a timer for handover to the third device;

upon expiration of the timer, determine the number of degree-1 TBs obtained from TB combinations sent from the third device; and

detect a failure of the handover by comparing the number of degree-1 TBs obtained from TB combinations sent from the third device with the threshold number.
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.
A second device comprising:

at least one processor; and

at least one memory including computer program codes;

the at least one memory and the computer program codes are configured to, with the at least one processor, cause the second device to:

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

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

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

in response to a determination that the handover is triggered, determine a third device for the handover.
The second device of claim 8, wherein the configuration of the feedback-less transmission comprises at least one of:

a feedback-less transmission redundancy rate indicating a ratio between the number of the original TBs to be conveyed and the number of TB combinations actually transmitted,

a TB degree indicating the number of the original TBs from which a specific TB combination is generated, or

a TB combination pattern indicating which original TBs are selected to generate a specific TB combination.
The second device of claim 8, wherein the measurement report comprises at least one of:

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

a ratio of successful recovery of original TBs from TB combinations ,

a ratio of failed recovery of original TBs from TB combinations,

indices of original TBs which recovered successfully from TB combinations, or

indices of original TBs which failed to recover from TB combinations.
The second device of claim 8, wherein the second device is caused to determine whether the handover is triggered by:

in response to the information indicating quality of the feedback-less transmission being below a threshold quality, determining the handover is triggered.
The second device of claim 8, wherein the second device is further caused to:

forward, to the third device, data buffered in the second device for future transmission, in response to at least one of the following being satisfied:

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

the number of degree-1TBs received by the first device is below a threshold number.
The second device of claim 8, wherein the second device is further caused to:

receive, from the third device, further information concerning further configuration of a further feedback-less transmission supported by the third device; and

forward the further information to the first device.
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.
A third device comprising:

at least one processor; and

at least one memory including computer program codes;

the at least one memory and the computer program codes are configured to, with the at least one processor, cause the third device to:

receive, at the third device and from a second device, a handover request indicating a first device is to handover to the third device;

generate an acknowledgment to the handover request, the acknowledgement comprising information concerning a configuration of a feedback-less transmission, the feedback-less transmission using one or more combined transport blocks, TBs, rather than feedback-based retransmission, the combined TBs generated based on original TBs, on which the data to be transmitted is carried;

transmit the acknowledgment to the second device; and

transmit a synchronization signal to the first device for the handover.
The third device of claim 15, wherein the configuration of the feedback-less transmission comprises at least one of:

a feedback-less transmission redundancy rate indicating a ratio between the number of the original TBs to be conveyed and the number of TB combinations actually transmitted,

a TB degree indicating the number of the original TBs from which a specific TB combination is generated, or

a TB combination pattern indicating which original TBs are selected to generate a specific TB combination.
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.
A method comprising:

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

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

receiving, from the second device, an indication of a handover to a third device, the handover triggered based on the information reflecting the quality of the feedback-less transmission.
The method of claim 18, wherein the configuration of the feedback-less transmission comprises at least one of:

a feedback-less transmission redundancy rate indicating a ratio between the number of the original TBs to be conveyed and the number of TB combinations actually transmitted,

a TB degree indicating the number of the original TBs from which a specific TB combination is generated, or

a TB combination pattern indicating which original TBs are selected to generate a specific TB combination.
The method of claim 18, wherein the measurement report comprises at least one of:

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

a ratio of successful recovery of original TBs from TB combinations,

a ratio of failed recovery of original TBs from TB combinations,

indices of original TBs which recovered successfully from TB combinations, or

indices of original TBs which failed to recover from TB combinations.
The method of claim 18, wherein receiving, from the second device, the indication of the handover from the second device to the third device comprises:

receiving, from the second device, further information concerning further configuration of a further feedback-less transmission supported by the third device.
The method of claim 18, further comprising:

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

in response to receiving a further indication of performing the handover, transmitting further data to the third device.
The method of claim 18, further comprising:

setting a timer for handover to the third device;

upon expiration of the timer, determining the number of degree-1 TBs obtained from TB combinations sent from the third device; and

detect a failure of the handover by comparing the number of degree-1 TBs obtained from TB combinations sent from the third device with the threshold number.
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.
A method comprising:

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

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

determining whether a handover is trigger 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 for the handover.
The method of claim 25, wherein the configuration of the feedback-less transmission comprises at least one of:

a feedback-less transmission redundancy rate indicating a ratio between the number of the original TBs to be conveyed and the number of TB combinations actually transmitted,

a TB degree indicating the number of the original TBs from which a specific TB combination is generated, or

a TB combination pattern indicating which original TBs are selected to generate a specific TB combination.
The method of claim 25, wherein the measurement report comprises at least one of:

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

a ratio of successful recovery of original TBs from TB combinations,

a ratio of failed recovery of original TBs from TB combinations,

indices of original TBs which recovered successfully from TB combinations, or

indices of original TBs which failed to recover from TB combinations.
The method of claim 25, wherein determining whether the handover is triggered comprises:

in response to the information indicating quality of the feedback-less transmission being below a threshold quality, determining the handover is triggered.
The method of claim 25, further comprising:

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

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

the number of degree-1TBs received by the first device is below a threshold number.
The method of claim 25, further comprising:

receiving, from the third device, further information concerning further configuration of a further feedback-less transmission supported by the third device; and

forwarding the further information to the first device.
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.
A method comprising:

receiving, at a third device and from a second device, a handover request indicating a first device is to handover to the third device;

generating an acknowledgment to the handover request, the acknowledgement comprising information concerning a configuration of a feedback-less transmission, the feedback-less transmission using one or more combined transport blocks, TBs, rather than feedback-based retransmission, the combined TBs generated based on original TBs, on which data to be transmitted is carried;

transmitting the acknowledgment to the second device; and

transmitting a synchronization signal to the first device for the handover.
The method of claim 32, wherein the configuration of the feedback-less transmission comprises at least one of:

a feedback-less transmission redundancy rate indicating a ratio between the number of the original TBs to be conveyed and the number of TB combinations actually transmitted,

a TB degree indicating the number of the original TBs from which a specific TB combination is generated, or

a TB combination pattern indicating which original TBs are selected to generate a specific TB combination.
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.
An apparatus, comprising:

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

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

means for receiving, from the second device, an indication of a handover to a third device, the handover triggered based on the information reflecting the quality of the feedback-less transmission.
An apparatus, comprising:

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

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

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

means for in response to a determination that the handover is triggered, determining a third device for the handover.
An apparatus comprising:

means for receiving, at a third device and from a second device, a handover request indicating a first device is to handover to the third device;

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

means for transmitting the acknowledgment to the second device; and

means for transmitting a synchronization signal to the first device for the handover.
A computer readable medium storing instructions thereon, the instructions, when executed by at least one processing unit of a machine, causing the machine to perform the method according to any one of claims 18-24.
A computer readable medium storing instructions thereon, the instructions, when executed by at least one processing unit of a machine, causing the machine to perform the method according to any one of claims 25-31.
A computer readable medium storing instructions thereon, the instructions, when executed by at least one processing unit of a machine, causing the machine to perform the method according to any one of claims 32-34.