CN116095611A

CN116095611A - Data transmission method, communication device and storage medium for multicast service

Info

Publication number: CN116095611A
Application number: CN202111278465.XA
Authority: CN
Inventors: 项弘禹; 李秉肇; 许斌
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2021-10-30
Filing date: 2021-10-30
Publication date: 2023-05-09
Also published as: WO2023071699A1

Abstract

The embodiment of the application provides a data transmission method, a communication device and a storage medium of multicast service. The method comprises the following steps: transmitting a multicast wireless configuration to a terminal, wherein the multicast wireless configuration is used for indicating the terminal to initialize multicast transmission; at least two sub-data packets of a data packet to be transmitted are sent to the terminal in a multicast mode, and each sub-data packet corresponds to a serial number; receiving an acknowledgement message from the terminal, wherein the acknowledgement message is used for determining sub-data packets received by the terminal; determining retransmission sub-data packets in the data packets to be transmitted; sending indication information to the terminal, wherein the indication information is used for modifying the lower boundary value of the reorganization window; and multicasting and sending the retransmission sub-data packet to the terminal. By adopting the embodiment of the application, the occurrence of the event of data packet loss caused by multicast initialization can be avoided, the success rate of data transmission is improved, and the reliability of multicast service can be improved.

Description

Data transmission method, communication device and storage medium for multicast service

Technical Field

The present invention relates to the field of communications technologies, and in particular, to a data transmission method, a communication device, and a storage medium for a multicast service.

Background

Multicast services (e.g., multimedia broadcast multicast service (multimedia broadcast multicast service, MBMS in LTE), multicast broadcast service (multicast broadcast service, MBS in NR), etc.), are mainly applicable to services directed to a plurality of terminals, such as video conferencing, television broadcasting, video on demand, online education, etc. When multicast transmission is performed on multicast traffic, a network device (e.g., a base station) transmits data packets received from a packet data convergence layer protocol (packet data convergence protocol, PDCP) layer to a medium access control (media access control, MAC) entity through a radio link layer control protocol (radio link control, RLC) entity (entity). And then the data packet is sent to a physical layer entity through the MAC entity, and the data packet is sent out through the physical layer entity, so that a plurality of terminals receive the data packet.

Multicast services are multicast transmitted through two transmission modes, namely point-to-multipoint (PTM) and point-to-point (PTP). The PTM RLC entity is configured in unacknowledged mode (unacknowledge Mode, UM). In UM mode, the RLC entity may be referred to as a UM RLC entity and the protocol data units (protocol data unit, PDUs) received by the UM RLC entity may be referred to as UMD PDUs. If the received UMD PDU includes an SN field (field), it indicates that the UMD PDU includes a segment of a service data unit (service data unit, SDU), and that the segment needs to be reassembled with other segments to obtain a complete SDU, and then the complete SDU is transmitted.

Upon receiving the data, the UM RLC entity needs to maintain a reassembly window (reassembly window). The range of the reassembly Window may be set to [ RX_Next_Hight_UM_Window_Size, RX_Next_Hight ]. Where UM_Window_Size is constant. RX_Next_Hight represents the Next Sequence Number (SN) of the largest Sequence Number (SN) in the received UMD PDU, i.e., SN+1. As shown in fig. 1, the Reassembly window is divided into two segments based on rx_next_recossembly. The rx_next_reassembly indicates the minimum SN to be reassembled, that is, the SN value is smaller than the SN value of the first packet including SN received by the terminal when the packet of rx_next_reassembly has been reassembled and the PTM is initialized, the UM RLC entity sets both rx_next_reassembly and rx_next_highest to the SN value of the first packet including SN received by the terminal. If the terminal receives the first SDU containing the SN at the time t1, the SN value of the SDU is larger than the SN value of the SDU received by the terminal. For example, if the SN value of the SDU fragment retransmitted by the MAC layer to the UM RLC entity is smaller than the SN value of the first SDU containing SN, i.e., the SN value is smaller than rx_next_reassembly, the terminal will not buffer the SDU fragment, and the data packet corresponding to the SDU fragment will be discarded. However, the terminal does not receive the data packet before time t1, resulting in that the RLC SDU is not reassembled and is not delivered to an upper layer (i.e., PDCP layer). Therefore, setting rx_next_request and rx_next_high of the PTM to the SN value of the first SN-containing packet received by the terminal affects service performance.

Disclosure of Invention

The embodiment of the application discloses a data transmission method, a communication device and a storage medium of a multicast service, which can avoid the occurrence of a data packet loss event caused by PTM initialization, improve the success rate of data transmission and improve the reliability of the multicast service.

In a first aspect, an embodiment of the present application discloses a data transmission method of a first multicast service, which is applied to a network device, where the method includes: transmitting multicast wireless configuration to a terminal; at least two sub-data packets of the data packet to be transmitted are sent to the terminal in a multicast mode; receiving an acknowledgement message from the terminal; determining retransmission sub-data packets in the data packets to be transmitted; sending indication information to a terminal; and multicasting and sending the retransmission sub-data packet to the terminal.

The multicast wireless configuration is used for indicating the terminal to initialize multicast transmission. Each sub-packet in the data packet to be transmitted corresponds to a sequence number. The acknowledgement message is used to determine the sub-packets that the terminal has received. The indication information is used to modify the lower boundary value of the reassembly window so that the range of discarded packets can be modified. Therefore, the occurrence of the event of data packet loss caused by PTM initialization can be avoided, the success rate of data transmission is improved, and the reliability of multicast service can be improved.

In a second aspect, an embodiment of the present application discloses a data transmission method of a second multicast service, which is applied to a network device, and the method includes: multicast wireless configuration is sent to the terminal multicast; at least two sub-data packets of the data packet to be transmitted are sent to the terminal in a multicast mode; receiving an acknowledgement message from the terminal; determining retransmission sub-data packets in the data packets to be transmitted; and unicast transmitting the retransmission sub-data packet to the terminal.

The multicast wireless configuration is used for indicating the terminal to initialize multicast transmission. Each sub-packet in the data packet to be transmitted corresponds to a sequence number. The acknowledgement message is used to determine the sub-packets that the terminal has received. Therefore, the data packet with the multicast transmission failure is retransmitted by adopting a unicast transmission mode, the occurrence of the event of data packet loss caused by PTM initialization can be avoided, the success rate of data transmission is improved, and the reliability of multicast service can be improved.

In one possible example, the retransmission subpacket is determined by the MAC layer of the network device and unicast sent to the terminal, including: the retransmission subpacket is unicast transmitted from the MAC layer to the terminal based on a cell radio network temporary identity (cell-radio network temporary identifier, C-RNTI) of the terminal. In this way, the MAC layer directly performs unicast transmission on the retransmission sub-packet through the PTP mode, so that the retransmission rate can be improved.

In one possible example, the determining, by the MAC layer of the network device, the retransmission subpacket further includes, after determining the retransmission subpacket in the data packet to be transmitted: hierarchical signaling is sent upward from the MAC layer to cause the PDCP layer of the network device to determine a sequence number of the retransmission subpacket. In this way, the network device can confirm the retransmission sub-data packet to be retransmitted through the hierarchical signaling.

Unicast transmission of the retransmission sub-packet to the terminal includes: the retransmission sub-data is unicast-transmitted from the PDCP layer to the lower side to unicast-transmit the retransmission sub-data packet to the terminal. That is, PTP mode may be adopted to start layer-by-layer downstream from the PDCP layer of the network device, so that the retransmission sub-packet (or the retransmission sub-packet set corresponding to the retransmission sub-packet) is unicast sent to the terminal, so that data loss can be avoided.

In a third aspect, an embodiment of the present application discloses a third data transmission method for a multicast service, where the method is applied to a terminal, and the method includes: receiving multicast wireless configuration from a network device multicast; multicast receiving a sub-packet of a data packet to be transmitted from a network device; sending an acknowledgement message to the network device; receiving indication information from a network device; modifying the lower boundary value based on the indication information; the retransmission subpacket is multicast received from the network device.

In a fourth aspect, an embodiment of the present application discloses a data transmission method for a fourth multicast service, which is applied to a terminal, and the method includes: receiving multicast wireless configuration from a network device multicast; multicast receiving a sub-packet of a data packet to be transmitted from a network device; sending an acknowledgement message to the network device; the retransmission sub-packet of the data packet to be transmitted is received unicast from the network device.

In a fifth aspect, embodiments of the present application disclose a first communication apparatus, the communication apparatus comprising a network device, wherein: the receiving and transmitting unit is used for transmitting multicast wireless configuration to the terminal; at least two sub-data packets of the data packet to be transmitted are sent to the terminal in a multicast mode; receiving an acknowledgement message from the terminal; the processing unit is used for determining retransmission sub-data packets in the data packets to be transmitted; the receiving and transmitting unit is also used for transmitting indication information to the terminal; and multicasting and sending the retransmission sub-data packet to the terminal.

In a sixth aspect, embodiments of the present application disclose a second communication apparatus, the communication apparatus including a network device, wherein: the receiving and transmitting unit is used for transmitting multicast wireless configuration to the terminal; at least two sub-data packets of the data packet to be transmitted are sent to the terminal in a multicast mode; receiving an acknowledgement message from the terminal; the processing unit is used for determining retransmission sub-data packets in the data packets to be transmitted; and the receiving and transmitting unit is also used for unicast transmitting the retransmission sub-data packet to the terminal.

In a possible example, the communication device further includes a MAC layer, the retransmission subpacket is determined by the MAC layer, and the transceiving unit is specifically configured to unicast transmit the retransmission subpacket from the MAC layer to the terminal based on the C-RNTI of the terminal, so as to unicast transmit the retransmission subpacket to the terminal. In this way, the MAC layer directly performs unicast transmission on the retransmission sub-packet through the PTP mode, so that the retransmission rate can be improved.

In one possible example, the communication device further includes a MAC layer and a PDCP layer, the retransmission subpacket is determined by the MAC layer, and the transceiving unit is further configured to send level signaling upward from the MAC layer to cause the PDCP layer to determine a sequence number of the retransmission subpacket; the transceiving unit is specifically configured to unicast-send the retransmission sub-data from the PDCP layer to the terminal to unicast-send the retransmission sub-data packet. It will be appreciated that the network device may acknowledge the retransmission sub-packets to be retransmitted internally by means of hierarchical signaling. And then, the retransmission sub-data packet (or the retransmission sub-data packet set corresponding to the retransmission sub-data packet) can be sent downwards layer by layer from the PDCP layer of the network equipment by adopting the PTP mode so as to be unicast sent to the terminal, and the data loss can be avoided.

In a seventh aspect, embodiments of the present application disclose a third communication apparatus, the communication apparatus including a terminal, wherein: the receiving and transmitting unit is used for receiving multicast wireless configuration from the network equipment in a multicast mode; multicast receiving a sub-packet of a data packet to be transmitted from a network device; sending an acknowledgement message to the network device; receiving indication information from a network device; the processing unit is used for modifying the lower boundary value based on the indication information; and the receiving and transmitting unit is also used for multicasting and receiving the retransmission sub-data packet from the network equipment.

In an eighth aspect, embodiments of the present application disclose a fourth communication apparatus, the communication apparatus including a terminal, wherein: a transceiver unit for receiving multicast wireless configuration from a network device in multicast mode; multicast receiving a sub-packet of a data packet to be transmitted from a network device; sending an acknowledgement message to the network device; the retransmission subpacket is multicast received from the network device.

With reference to the first aspect, or the third aspect, or the fifth aspect, in one possible example, the indication information includes an absolute value of the retransmission subpacket. The absolute value includes the minimum value of the sequence number in the retransmission sub-packet, and the indication information is specifically used for indicating that the lower boundary value of the reassembly window is modified into the absolute value. Thus, the lower boundary value of the reorganization window can be directly set to the absolute value, so that the setting efficiency is improved. Under the condition that the absolute value is the minimum value of the sequence number in the retransmission sub-data packet, the retransmission sub-data packet can be prevented from being lost, and the service reliability can be improved.

With reference to the first aspect, or the third aspect, or the fifth aspect, in one possible example, the indication information includes an offset value of the retransmission subpacket. Wherein the offset value is related to at least two of the following information: the minimum value of the sequence number in the retransmission sub-data packet, the sequence number of the first sub-data packet received by the terminal, and a preset constant, wherein the preset constant is a positive integer. The indication information is specifically used for indicating that the lower boundary value of the reorganization window is adjusted based on the offset value, so that the range of the reorganization window can be adjusted to avoid the loss of the data packet.

With reference to the first aspect, or the third aspect, or the fifth aspect, in one possible example, the multicast radio configuration includes an initial value of the lower boundary value and is a minimum value of sequence numbers in the sub-packets. Thus, the boundary value of the reorganization window can be set when the multicast transmission is initialized. And the lower boundary value of the reorganization window is the value of the sub-data packet with the minimum sequence number in the data packet to be transmitted, the sequence number of the lost data packet is not larger than the value, and the effectiveness of setting the boundary value of the reorganization window can be improved.

In a ninth aspect, embodiments of the present application disclose providing a fifth communications device comprising a processor coupled to a memory, wherein the memory is configured to store one or more programs for execution by the processor to implement the method of any of the above aspects or possible examples.

In a tenth aspect, embodiments of the present application disclose a computer-readable storage medium having instructions stored therein that, when run on a computer, cause the computer to perform the method of any of the above aspects or possible examples.

In an eleventh aspect, embodiments of the present application disclose a computer program product for storing a computer program for causing a computer to perform the method of any of the above aspects when the computer program is run on the computer.

In a twelfth aspect, embodiments of the present application disclose a first chip, including a processor, configured to invoke from a memory and execute instructions stored in the memory, so that a terminal device on which the chip is installed performs the method of any of the above aspects or possible examples.

In a thirteenth aspect, embodiments of the present application disclose a second chip, which may be a chip in a communication device, the chip comprising: the input interface, the output interface and the processing circuit are connected through internal connection paths, and the processing circuit is used for executing the method of any one of the aspects or possible examples.

In a fourteenth aspect, embodiments of the present application disclose a third chip, including: the input interface, the output interface, and the processor, optionally, further comprise a memory, where the input interface, the output interface, the processor, and the memory are connected by an internal connection path, the processor is configured to execute code in the memory, and when the code is executed, the processor is configured to execute the method in any one of the aspects or possible examples.

In a fifteenth aspect, embodiments of the present application provide a communication system including a communication device as in any one of the above aspects or possible examples.

Drawings

The drawings used in the embodiments of the present application are described below.

FIG. 1 is a schematic diagram of an effective range of SNs according to an embodiment of the present application;

fig. 2 is a schematic structural diagram of a communication system according to an embodiment of the present application;

fig. 3 is a schematic structural diagram of a data transmission device for multicast service according to an embodiment of the present application;

fig. 4 is a flow chart of a data transmission method of a multicast service according to an embodiment of the present application;

fig. 5 is a schematic view of a scenario in which a multicast service performs data transmission according to an embodiment of the present application;

fig. 6 is a flow chart of another data transmission method of multicast service according to an embodiment of the present application;

fig. 7 is a flow chart of another data transmission method of multicast service according to an embodiment of the present application;

fig. 8 is a schematic structural diagram of a communication device according to an embodiment of the present application;

fig. 9 is a schematic structural diagram of another communication device according to an embodiment of the present application.

Detailed Description

The technical solution of the embodiment of the application can be applied to various communication systems, for example: the present communication systems such as global system for mobile communications (Global System for Mobile Communications, GSM) corresponding to The second generation mobile communication technology, general packet Radio service (General Packet Radio Service, GPRS) interposed between The second generation mobile communication technology and The third generation mobile communication technology, code division multiple access (Code Division Multiple Access, CDMA) system corresponding to The third generation mobile communication technology (The 3rd Generation Telecommunication,3G), wideband code division multiple access (Wideband Code Division Multiple Access, WCDMA) system and universal mobile communication system (Universal Mobile Telecommunication System, UMTS), long term evolution (Long Term Evolution, LTE) system corresponding to The fourth generation mobile communication technology, new Radio, NR) system corresponding to The fifth generation mobile communication technology, and future communication systems such as 6G system are applied.

The present application will present various aspects, embodiments, or features about a system that may include multiple devices, components, modules, etc. It is to be understood and appreciated that the various systems may include additional devices, components, modules, etc. and/or may not include all of the devices, components, modules etc. discussed in connection with the figures. Furthermore, combinations of these schemes may also be used.

In addition, in the embodiments of the present application, the term "exemplary" is used to mean serving as an example, instance, or illustration. Any embodiment or design described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments or designs. Rather, the term use of an example is intended to present concepts in a concrete fashion.

In the embodiment of the present application, information, signals, messages, channels may be mixed in some cases, and it should be noted that, when the distinction is not emphasized, the meaning to be expressed is consistent. "of", "corresponding" and "corresponding" are sometimes used in combination, and it should be noted that the meaning of the expression is consistent when the distinction is not emphasized.

The network architecture and the service scenario described in the embodiments of the present application are for more clearly describing the technical solution of the embodiments of the present application, and do not constitute a limitation on the technical solution provided in the embodiments of the present application, and those skilled in the art can know that, with the evolution of the network architecture and the appearance of the new service scenario, the technical solution provided in the embodiments of the present application is also applicable to similar technical problems.

For the purposes, technical solutions and advantages of the present application, the embodiments of the present application will be described below with reference to the drawings in the embodiments of the present application.

A communication system suitable for use in the embodiments of the present application will be described in detail first taking the communication system shown in fig. 2 as an example. Fig. 2 shows a schematic diagram of a communication system suitable for the data transmission method of the multicast service according to the embodiment of the present application. As shown in fig. 2, the communication system includes an access network device, a terminal, and a core network device.

A terminal in an embodiment of the present application may be a device that provides voice or data connectivity to a user, and the terminal may be referred to as a User Equipment (UE), a mobile station (mobile station), a subscriber unit (subscriber unit), a station, a terminal equipment (terminal equipment, TE), or the like. The terminal may be a cellular phone (cellular phone), a personal digital assistant (personal digital assistant, PDA), a wireless modem (modem), a hand-held device (hand hold), a laptop computer (laptop computer), a cordless phone (cord phone), a wireless local loop (Wireless Local Loop, WLL) station, a mobile phone (mobile phone), a tablet computer (pad), etc. With the development of wireless communication technology, devices that can access to a wireless communication network, communicate with a wireless network side, or communicate with other objects through the wireless network may be terminals in the embodiments of the present application. Such as terminals and automobiles in intelligent transportation, home appliances in intelligent homes, meter reading instruments for electric power in smart grids, voltage monitoring instruments, environment monitoring instruments, video monitoring instruments in intelligent security networks, cash registers, etc. The terminals may be stationary or mobile.

As an embodiment, as shown in fig. 2, the terminal is a mobile phone. In the embodiment of the present application, the terminal refers to a terminal that may be in a wireless connection relationship with the access network device and supports a multicast service. The terminal may be, without limitation, a terminal within the coverage area of the access network device that is receiving multicast traffic, and/or is transmitting and/or is about to start transmitting and/or is interested in multicast traffic, etc.

The access network device in the embodiment of the present application is a device deployed in a radio access network to provide a wireless communication function for a terminal, and has the main functions of: management of radio resources, compression of internet protocol (internet protocol, IP) headers and encryption of user data flows, selection of a mobility management entity (mobile management entity, MME) at the time of user equipment attachment, routing of user plane data to a Serving Gateway (SGW), organization and transmission of paging messages, organization and transmission of broadcast messages, measurement and measurement report configuration for mobility or scheduling purposes, etc.

Access network devices may include, but are not limited to: an evolved Node B (eNB), a radio network controller (radio network controller, RNC), a Node B (NB), a base station controller (base station controller, BSC), a base transceiver station (base transceiver station, BTS), a home base station (home evolved NodeB, for example, or home Node B, HNB), a Base Band Unit (BBU), an Access Point (AP) in a wireless fidelity (wireless fidelity, WIFI) system, a wireless relay Node, a wireless backhaul Node, a transmission point (transmission and reception point, TRP or transmission point, TP), etc., may also be 5G, such as NR, a gbb in a system, or a transmission point (TRP or TP), one or a group (including a plurality of antenna panels) of base stations in a 5G system, an antenna panel, or may also be a network Node constituting a gbb or a transmission point, such as a baseband unit (BBU), or a Distributed Unit (DU), etc.

In some deployments, the gNB may include a Centralized Unit (CU) and DUs. The gNB may also include a Radio Unit (RU). The CU implements part of the functions of the gNB, the DU implements part of the functions of the gNB, for example, the CU implements the functions of a radio resource control (radio resource control, RRC), a packet data convergence layer protocol (packet data convergence protocol, PDCP) layer, and the DU implements the functions of a radio link control (radio link control, RLC), a medium access control (media access control, MAC), and a Physical (PHY) layer. Under this architecture, higher layer signaling, such as RRC layer signaling or PDCP layer signaling, may also be considered as being sent by DUs, or by dus+cus, since the information of the RRC layer is eventually transformed into or from the information of the PHY layer. It is understood that the access network device may be a CU node, or a DU node, or a device comprising a CU node and a DU node. In addition, the CU may be divided into access network devices in the access network RAN, or may be divided into access network devices in the core network CN, which is not limited herein.

In a specific implementation, as an embodiment, as shown in fig. 2, the access network device is a base station. In the embodiment of the present application, different base stations may be base stations with different identifiers, or may be base stations with the same identifier and deployed in different geographic locations. Because the base station does not know whether it will relate to the scenario in which the embodiments of the present application are applied before the base station is deployed, the base station, or the baseband chip, should support the methods provided by the embodiments of the present application before deployment. It will be appreciated that the aforementioned base stations with different identities may be base station identities, cell identities or other identities.

The access network devices and terminals may be deployed on land, e.g., indoors or outdoors, hand-held or vehicle-mounted, etc. The access network equipment and the terminal can be deployed on the water surface, and can also be deployed on aircrafts, balloons and satellites in the air. The embodiment of the application is not limited to the application scene of the access network equipment and the terminal.

Communication between the access network device and the terminal, between the access network device and the access network device, and between the terminal and the terminal can be performed through a licensed spectrum (licensed spectrum), communication can be performed through an unlicensed spectrum (unlicensed spectrum), and communication can also be performed through the licensed spectrum and the unlicensed spectrum simultaneously. The embodiment of the application does not limit the spectrum resources used between the access network equipment and the terminal.

It will be appreciated that one access network device may communicate with a plurality of terminals. A terminal may communicate with multiple access network devices simultaneously. Fig. 2 is a simplified schematic diagram, which is only illustrated for ease of understanding, and other network devices or other terminal devices may be included in the communication system, which are not shown in fig. 2.

In the embodiment of the present application, the core network device may also be referred to as a core network element. The core network device may be connected to one or more access network devices and may provide one or more of session management, access authentication, internet protocol (internet protocol, IP) address assignment, and data transmission for terminals in the system. For example, the core network device may be a mobility management entity (mobile management entity, MME) or a Serving Gateway (SGW) in a 4G access technology communication system, an access and mobility management function (access and mobility management function, AMF) network element or a user plane capability (user plane function, UPF) network element in a 5G access technology communication system, and so on. In the embodiment of the present application, the network device may be the access network device or the core network device, which is not limited herein.

In describing embodiments of the present application, some concepts used in the following description are explained below.

(1) Protocol data units (protocol data unit, PDU) and service data units (service data unit, SDU).

The PDU refers to unit information exchanged between peer entities of each layer. SDU, also called service data unit, is the data set of user service of a designated layer, and the data is not changed when the SDU is transmitted to the receiver in the same protocol layer, namely the service part. And then sent to the lower layer, which encapsulates it in a PDU and sends it out. SDUs are information units that are transferred from higher layer protocols to lower layer protocols. The layer N service data units SDU are in one-to-one correspondence with the PDUs of the upper layer. And sending the data to a designated layer of a receiving end according to the difference of the data of the protocol data units. That is, the PDU of the present layer is the SDU of the lower layer, and the SDU of the present layer is the PDU of the upper layer.

(2) Multicast traffic.

In systems employing different radio access technologies, the names of multicast services may be different, e.g. in LTE systems, called multimedia broadcast multicast services (multimedia broadcast multicast service, MBMS); in the NR system, it is called multicast broadcast service (multicast broadcast service, MBS), etc. The multicast service is mainly applicable to services directed to a plurality of terminals, such as video conference, television broadcast, video on demand, online education, etc.

When multicast traffic is multicast transmitted, network devices (e.g., base stations) transmit data packets to a medium access control (media access control, MAC) entity via a radio link layer control protocol (radio link control, RLC) entity (entity). And then the data packet is sent to a physical layer entity through the MAC entity, and the data packet is sent out through the physical layer entity, so that a plurality of terminals receive the data packet.

The following is an illustration of the base station transmitting MBS traffic to the UE.

Multicast services are multicast transmitted through two transmission technologies, point-to-multipoint (PTM) and point-to-point (PTP). The PTM transmission technology, i.e. the technology of establishing a dedicated bearer for MBS service, simultaneously transmits MBS service to a plurality of UEs through a common transmission channel or through a group scheduling manner in the form of multicast (multicast), supports RLC unacknowledged mode (unacknowledge Mode, UM). In the embodiment of the present application, the PTM transmission technology may also be referred to as PTP transmission mode, PTM mode, or multicast mode, etc. Multicast transmission is performed by using a PTM transmission method, which may also be referred to as multicast transmission for a multicast service (e.g., MBS).

PTP transmission technology, i.e. setting up a UE-specific bearer, is sent by a network device to a UE in unicast (unicasting) form, supporting RLC Acknowledged Mode (AM) or UM Mode. In the embodiment of the present application, the PTP transmission technology may also be referred to as a PTP transmission mode, a PTP mode, or a unicast form, or the like. The PTP transmission method is used for multicast transmission, and may also be referred to as unicast transmission for a multicast service (e.g., MBS).

When MBS service is transmitted from a base station to UE, two transmission modes of PTP and PTM can be adopted, and the two transmission modes can be dynamically switched. When a large number of UEs need to receive a certain MBS service, sending the service in unicast mode needs to establish a dedicated bearer for a large number of UEs, which consumes resources. When the multicast is sent to the UE, all the UE interested in the service can receive the MBS through the special bearer of the MBS, thereby saving air interface resources, improving the frequency spectrum utilization rate and improving the transmission efficiency.

For a UE, if the quality of service (quality of service, qoS) requirement for MBS service sent via PTM cannot be met, switching to RLC-AM mode may be supported and related services are transmitted for the UE using PTP transmission. For a split multicast radio bearer (multicast radio bearer, MRB), switching between the RLC entity corresponding to PTM and the RLC entity corresponding to PTP is possible. In the context of CU-DUs, it may be decided by the gNB-DUs to switch to work under a certain RLC entity. In some scenarios, such as retransmitting data or forwarding data from other access network devices, indication information may be sent by the CU to the DU to indicate to which mode the DU is switched. The indication information may be explicitly carried in at least one of the following signaling: f1 interface signaling, RRC messages, control Elements (CEs) of MAC, control protocol data units (protocol data unit, PDUs) of PDCP or control PDUs or downlink control information (downlink control information, DCI) of RLC.

Optionally, the PDCP layer may notify in an implicit manner, for example, PDCP only delivers the data packet to a unicast logical channel, and then performs multicast transmission by using PTP transmission; PDCP only submits the data packet to a multicast logic channel, and then multicast transmission is carried out by adopting a PTM transmission mode; if the PDCP delivers the data packet to both the unicast logical channel and the multicast logical channel, the PDCP may perform multicast transmission in a PTP transmission mode, or may perform multicast transmission in a PTM transmission mode.

Taking the base station as the gNB, the terminals as the UE1 and the UE2 as an example, the route transmitted in the PTM mode may be referred to as PTM leg, and the route transmitted in the PTP mode may be referred to as PTP leg. In the schematic structural diagram of a data transmission apparatus for multicast service shown in fig. 3, the gNB may send multicast data to UE1 and UE2 through PTP leg, and may also send multicast data to UE1 and UE2 through PTM leg. Specifically, the gNB sends data packets to UE1 and/or UE2 through its PDCP layer, RLC layer and MAC layer, respectively, and UE1 or UE2 receives data packets through its MAC layer, RLC layer and PDCP layer, respectively. In PTM mode the UE needs to monitor both cell-radio network temporary identity (cell-radio network temporary identifier, C-RNTI) and group network temporary identity (group radio network temporary identifier, G-RNTI), while in PTP mode the UE may monitor only the C-RNTI or both the C-RNTI and the G-RNTI. If the UE configures PTP leg and PTM leg with separate MRBs, the UE needs to monitor the C-RNTI all the time. Alternatively, a deactivation procedure (the UE does not listen to the G-RNTI) and an activation procedure may be configured for the PTM leg.

In this embodiment of the present application, multicast transmission refers to transmitting data by a network device in a PTM transmission mode, and multicast reception refers to receiving data by a terminal from the network device based on the PTM transmission mode. Unicast transmission means that the network device adopts a PTP transmission mode to transmit data, and unicast reception means that the terminal receives data from the network device based on the PTP transmission mode. That is, the multicast transmission and the multicast reception perform data transmission based on a dedicated bearer of the MBS service established by the network device. Unicast transmission and unicast reception perform data transmission based on a dedicated bearer established by the network device for each terminal. The network device may transmit data by using a PTM transmission method, or may transmit data by using a PTP transmission method, without limiting whether the multicast transmission or the unicast transmission is performed. The terminal may receive data from the network device based on the PTM transmission scheme or receive data from the network device based on the PTP transmission scheme, which is not limited herein.

(3) UM mode.

In UM mode, the RLC entity may be referred to as a UM RLC entity. The PDU that the UM RLC entity interacts with the lower layer (or lower layer) may be referred to as a UMD PDU, and the SDU that the UM RLC entity interacts with the upper layer (upper layer) may be referred to as an RLC SDU. The UMD PDU contains a data field (data field) and a UMD PDU header block (header). Whether a complete RLC SDU is received may be determined based on whether the UMD PDU header contains a Sequence Number (SN) field. That is, if the received UMD PDU includes an SN value, it means that the UMD PDU includes a segment (segment) of the RLC SDU, which may be understood as a sub-packet of the RLC SDU. Otherwise, it means that the UMD PDU contains a complete RLC SDU. If the received UMD PDU contains a complete RLC SDU, the RLC header is directly removed, and then data transmission is carried out. If the segmentation (or sub-data packet) of the RLC SDU in the UMD PDU is received, the segmentation of other RLC SDUs in the UMD PDU is also required to be reassembled to obtain a complete SDU, and then the complete SDU is subjected to data transmission.

Upon receiving the data, the UM RLC entity needs to maintain a reassembly window (reassembly window). The range of the reassembly Window may be set to [ RX_Next_Hight_UM_Window_Size, RX_Next_Hight ]. Where UM_Window_Size is constant. If the SN length is configured to be 6 bits, um_window_size may be 32. If the SN length is configured to be 12 bits, um_window_size may be 2048.

RX_Next_Hight represents the Next Sequence Number (SN) of the largest Sequence Number (SN) in the received UMD PDU, i.e., SN+1. In a schematic diagram of an SN validity range shown in fig. 1, the Reassembly window is divided into two segments based on rx_next_reassembly. The RX_Next_Recassambly is used to represent the minimum SN waiting for Reassembly.

If the SN value of the RLC SDU in the UMD PDU belongs to the interval corresponding to [ rx_next_high-um_window_size, rx_next_request_size ], it indicates that the segment corresponding to the SN value has been received, and the UMD PDU needs to be discarded. Otherwise, the UMD PDU is placed into a receive buffer. The UMD PDU with sn=x is in the receive buffer, indicating that x is to the right of rx_next_request in the figure. The right side is divided into a section corresponding to [ RX_Next_Recessed, RX_Next_Highest) and a section corresponding to RX_Next_Highest or more.

If x belongs to the interval corresponding to [ RX_Next_Recasssembly, RX_Next_Highest), and all byte segments of SN=x are received, then the RLC SDU is reassembled, the RLC header is removed, and the reassembled SDU is delivered to the upper layer. If x=rx_next_request, then rx_next_request is updated to the minimum SN in the retransmission packet set consisting of packets that are not currently reassembled and delivered to the upper layer. Note that sn+1 is not simple here, because SN within the interval corresponding to [ rx_next_reassembly, rx_next_highest) may not be continuous.

If x is greater than RX_Next_Hight, it means that x falls outside the reorganization window. And updating RX_Next_Hight=x+1 according to the definition requirement, discarding PDU with SN outside the window, and shifting the reorganization window to the right by a plurality of lengths. If RX_Next_Recessed is extruded out of the Reassembly Window, then the RX_Next_Recessed value needs to be updated, which may be determined from the minimum value of SN > = (RX_Next_Hight-UM_Window_Size) in the set of packets that are not currently reassembled and delivered to the upper layer. If the current x is too large, the reassembly window will move far to the right, which easily results in the SN that has not been reassembled being discarded.

At the time of PTM initialization, the PTM RLC entity is configured in UM mode. The UM RLC entity sets rx_next_high and rx_next_request to the SN value of the first SN-containing packet received by the terminal. If the terminal receives the first SDU containing the SN at the time t1, the SN value of the SDU is larger than the SN value of the SDU received by the terminal. For example, if the SN value of the SDU fragment retransmitted by the MAC layer to the UM RLC entity is smaller than the SN value of the first SDU containing SN, i.e., the SN value is smaller than rx_next_reassembly, the terminal will not buffer the SDU fragment, and the data packet corresponding to the SDU fragment will be discarded. However, the terminal does not receive the data packet before time t1, resulting in that the RLC SDU is not reassembled and is not delivered to an upper layer (i.e., PDCP layer). Therefore, setting rx_next_request and rx_next_high of the PTM to the SN value of the first SN-containing packet received by the terminal affects service performance. Particularly, multicast services with high reliability requirements, such as the Vehicle-to-evaluation (V2X) and the like, are affected.

Based on the above, the application provides a data transmission method of the multicast service, which can avoid the occurrence of the event of data packet loss caused by PTM initialization, improve the success rate of data transmission and improve the reliability of the multicast service.

Referring to fig. 4, fig. 4 is a flow chart of a data transmission method of a multicast service provided in the present application, where the method is applied to a communication network as shown in fig. 2. Hereinafter, the embodiments of the present application will be described in detail by taking an interaction procedure between one terminal and one network device as an example without losing generality. It is understood that the network device may transmit the data packet based on the same technical scheme with a plurality of terminals having a wireless connection relationship in the wireless communication system. The present application is not limited in this regard. Specifically, as shown in fig. 4, the method may include the following steps S400 to S406.

S400: the network device sends the multicast wireless configuration to the terminal.

Accordingly, the terminal receives the multicast wireless configuration from the network device.

In the embodiment of the application, the multicast wireless configuration is used for indicating the terminal to perform multicast transmission initialization. That is, the terminal may perform PTM initialization based on the multicast radio configuration, so that the terminal can receive data sent by the network device based on the dedicated bearer of the multicast service. The terminals may also perform PTP initialization based on the multicast radio configuration, so that the terminals may receive data sent by the network device based on the dedicated bearer of each terminal. The multicast radio configuration may include MRB as described previously. The multicast radio configuration may include a PDCP configuration and an RLC configuration. Wherein, the PDCP configuration can include PDCP SN bit number, header compression configuration, integrity protection, status report enabling, and the like; RLC configuration may include logical channel ID, RLC SN bit number, etc., without limitation.

In one possible example, the multicast wireless configuration includes an initial value of a lower boundary value of the reassembly window, the initial value of the lower boundary value being a minimum value of sequence numbers in sub-packets to be transmitted by the network device.

In the embodiment of the present application, the Reassembly window may be Reassembly window, and the lower boundary value may be rx_next_reassembly. The initial value of the lower boundary value is the minimum value of the sequence numbers in the sub-data packets to be transmitted by the network device, so that the sequence numbers of the retransmission sub-data packets can be ensured to be larger than or equal to the lower boundary value, and the data packet loss can be avoided. The upper boundary value of the reassembly window may be rx_next_highest. The setting of the upper boundary value may refer to an existing rule, and the initial value of the upper boundary may be set as the sequence number of the first sub-packet received by the terminal.

For example, assuming that the minimum SN value of the RLC layer packet to be transmitted in the MAC layer of the network device is 4 and the SN value of the first subpacket received by the terminal is 9, the lower boundary value (e.g., rx_next_reassembly) of the Reassembly window may be set to 4 and the upper boundary value (e.g., rx_next_highest) of the Reassembly window may be set to 9.

Accordingly, in one possible example, the terminal sets an initial value of a lower boundary value of the reorganization window based on the multicast wireless configuration; and setting the initial value of the upper boundary value of the reorganization window as the sequence number of the sub-data packet received by the terminal first. That is, the network device determines the minimum value of the sequence number in the sub-packet to be transmitted, and then transmits the minimum value to the terminal as a parameter in the multicast radio configuration, so that the terminal sets the minimum value to an initial value of the lower boundary value of the retransmission window based on the multicast radio configuration. After the sequence number of the first sub-packet of data to be transmitted received by the terminal, setting an upper boundary value of the reorganization window based on the sequence number. Thus, the boundary value of the reorganization window can be set when the multicast transmission is initialized. And the lower boundary value of the reorganization window is the value of the sub-data packet with the minimum sequence number in the data packet to be transmitted, the sequence number of the lost data packet is not larger than the value, and the effectiveness of setting the boundary value of the reorganization window can be improved.

If the multicast radio configuration does not include a lower boundary value used at the initialization of the multicast transmission, in one possible example, the initial value of the lower boundary value and the initial value of the upper boundary value of the reassembly window are equal and equal to the sequence number of the first sub-packet received by the terminal.

Accordingly, in one possible example, the terminal sets an initial value of the lower boundary value and an initial value of the upper boundary value of the reassembly window as a sequence number of the sub-packet received by the terminal first. That is, the network device does not consider the size of the sequence number in the sub-packet to be transmitted. The terminal may set the lower boundary value and the upper boundary value of the reassembly window based on the sequence number of the received sub-packet of the first data to be transmitted according to existing rules.

Illustratively, assuming that the SN value of the first subpacket received by the terminal is 9, initial values of a lower boundary value (e.g., rx_next_reassembly) and an upper boundary value (e.g., rx_next_high) of the Reassembly window are both set to 9.

S401: the network device multicasts at least two sub-packets of the data packet to be transmitted to the terminal.

Accordingly, the terminal multicasts sub-packets of the data packet to be transmitted from the network device.

The present application does not limit a data packet to be transmitted, and the data packet to be transmitted includes at least two sub-data packets. That is, the sub-packets are segments of the data packet to be transmitted. Each sub-packet corresponds to a sequence number SN. The sub-packets may be packets to be newly transmitted or may include retransmitted packets.

In the embodiment of the application, the sub-data packet in the PDCP layer may be transmitted to the MAC entity of the network device through the RLC entity of the network device. And then the sub-data packet is sent to a physical layer entity of the network equipment through a MAC entity of the network equipment, and the sub-data packet is sent out through the physical layer entity of the network equipment so that the terminal receives the sub-data packet.

Accordingly, the terminal transmits the sub-packet to the MAC entity of the terminal through the physical layer of the terminal. And the MAC entity transmits the sub-data packet to the RLC entity of the terminal. Because the sub-data packet is a segment of the data packet to be transmitted, the RLC entity of the terminal will reorganize the sub-data packet in the data packet to be transmitted to obtain a complete data packet to be transmitted. And transmitting the complete data packet to be transmitted to the PDCP layer of the terminal so that the terminal receives the data packet to be transmitted. If the terminal has a sub-packet which is not received, the sub-packet needs to be retransmitted. In this embodiment of the present application, a sub-packet that is not received by a terminal in a data packet to be transmitted may be referred to as a retransmission sub-packet.

It is to be appreciated that a MAC PDU of a network device can include one or more MAC subpdus, each of which can include one MAC SDU. One MAC PDU corresponds to a plurality of MAC SDUs, and one MAC SDU corresponds to RLC PDU one by one. Taking the MAC layer transmission of the network device as an example, the MAC layer of the network device may send the MAC subPDU in the MAC layer to the MAC layer of the terminal in the form of a MAC PDU through the physical layer of the network device and the physical layer of the terminal. The MAC layer of the terminal may receive the MAC PDU and retransmit it to the RLC layer of the terminal. The RLC layer of the terminal needs to reassemble the MAC subPDU in the MAC PDU to obtain a complete MAC SDU. The RLC layer of the terminal then transmits the MAC SDU as RLC PDU to the PDCP layer.

S402: the terminal sends an acknowledgement message to the network device.

Accordingly, the network device receives an acknowledgement message from the terminal.

In the embodiment of the application, the confirmation message is used for determining the sub-data packet received by the terminal. The acknowledgement message may be an acknowledgement message (ACK) or may be a non-acknowledgement message (negative acknowledgement, NACK). The sequence number in the ACK is used to determine that the terminal has received the sub-packet corresponding to the sequence number. The sequence number in the NACK is used for determining that the terminal does not receive the sub-data packet corresponding to the sequence number. It will be appreciated that after receiving the sub-packet, the terminal feeds back an acknowledgement message to the network device to inform that the sub-packet has been received. In this manner, the sub-packets that are not received may be determined based on the acknowledgement message.

For example, after the base station receives ACK for#9 after its MAC layer transmits a MAC packet corresponding to RLC sn=9, it may be determined that the terminal has received a sub-packet with sequence number 9. The MAC layer may also receive NACKs corresponding to RLC sn=4, 5,6, respectively, and may determine that the terminal does not receive sub-packets with

sequence numbers

4,5,6, so as to determine that the sequence numbers of the retransmitted sub-packets are 4,5, 6.

S403: the network device determines a retransmission subpacket of the data packets to be transmitted.

In this embodiment of the present application, the retransmission sub-packet includes a sub-packet retransmitted by the network device before the terminal receives the acknowledgement message sent after the first sub-packet, or may include a sub-packet retransmitted by the network device after the terminal receives the acknowledgement message sent after the first sub-packet. It will be appreciated that the network device, upon receiving the acknowledgement message, may determine retransmission subpackets to be retransmitted in the data packets to be transmitted based on the acknowledgement message.

Exemplary, refer to a schematic view of a scenario in which a multicast service performs data transmission, which is provided in fig. 5. As shown in fig. 5, the network device transmits #9 (MAC) to the terminal at time t1 (indicating that the MAC PDU transmitted by the network device to the terminal includes a subpacket with sequence number 9). After time t1 the network device sends #4 (MAC) to the terminal (meaning that the MAC PDU sent by the network device to the terminal includes a subpacket with sequence number 4). The terminal then sends an ACK for #9 (MAC) to the network device (indicating that the MAC PDU received by the terminal includes a sub-packet with sequence number 9), and the sub-packet is the first sub-data received by the terminal. Therefore, #4 (MAC) sent before ACK for #9 (MAC), and #5, 6 (MAC) sent after ACK for #9 (MAC), which means that the MAC PDU sent by the network device to the terminal includes sub-packets with

sequence numbers

5 and 6, are both retransmission sub-packets. That is, all the sub-packets for which no ACK is received are retransmitted sub-packets from the time t1 to the time t2 (before step S404).

S404: the network device sends indication information to the terminal.

Accordingly, the terminal receives the indication information from the network device.

In the embodiment of the application, the indication information is used for modifying the lower boundary value of the reorganization window. As described above, if the initial value of the lower boundary value exists in the multicast radio configuration for instructing the terminal to perform the multicast transmission initialization, the initial value of the lower boundary value is the minimum value of the sequence number in the sub-packet. If the initial value of the lower boundary value does not exist in the multicast wireless configuration, the initial possible value of the lower boundary value is equal to the initial value of the upper boundary value and is equal to the sequence number of the first received sub-data packet of the terminal. It will be appreciated that modifying the lower boundary value of the reassembly window may modify the range of the reassembly window, and thus avoid packet loss.

In one possible example, the indication information includes an absolute value of the retransmitted sub-packet, e.g., a minimum value of sequence numbers in the retransmitted sub-packet. The indication information is specifically used for indicating that the lower boundary value of the reorganization window is modified to the absolute value. Illustratively, if the sequence numbers of the retransmission sub-packets are 4, 5, and 6, the absolute value of the retransmission sub-packets may be 4. Thus, the lower boundary value of the reorganization window can be directly set to the absolute value, so that the setting efficiency is improved. Under the condition that the absolute value is the minimum value of the sequence number in the retransmission sub-data packet, the retransmission sub-data packet can be prevented from being lost, and the service reliability can be improved.

In another possible example, the indication information includes an offset value (offset) of the retransmission subpacket. The indication information is specifically configured to indicate that the lower boundary value of the reorganization window is adjusted based on the offset value. Thus, the initial value of the lower boundary value can be adjusted based on the offset value, and the range of the reorganization window can be adjusted to avoid data packet loss.

The offset value may be related to at least two of the following information: and retransmitting the minimum value of the sequence number in the sub-data packet, the sequence number of the first sub-data packet received by the terminal and a preset constant. The preset constant may be a positive integer. The method for calculating the offset value is not limited in this application, for example, the offset value is a first difference between the sequence number of the first sub-packet received by the terminal and the minimum value of the sequence numbers in the retransmission sub-packet. Illustratively, the sequence numbers of the retransmitted sub-packets are 4, 5, and 6, and the sequence number of the sub-packet received by the terminal first is 9, the offset value may be the difference between 9 and 4, i.e., 5. For another example, the offset value is a second difference value obtained based on the first difference value and a preset constant described above. For example, if the sequence number of the retransmitted sub-packet is 4, 5, or 6, the sequence number of the sub-packet received by the terminal first is 9, and the preset constant is 3, the offset value may be 2 (9-4-3), so that the initial value of the lower boundary value may be adjusted based on the offset value. That is, the lower boundary value is set as the difference between the initial value of the lower boundary value and the offset value, and the range between the lower boundary value and the upper boundary value is enlarged, thereby enlarging the range of the reassembly window and avoiding packet loss.

The signaling carrying the indication information is not limited, and if the indication information is sent by the MAC layer of the network device, the indication information may be CE of the MAC layer, DCI of the PHY layer, or a new status PDU of the RLC layer. The indication information may also include an identification of the terminal such that the terminal modifies a lower boundary value of the reassembly window based on the offset value of the retransmitted sub-packet after the receipt of the indication information.

S405: the terminal modifies the lower boundary value based on the indication information.

The method for modifying the lower boundary value is not limited in this application, and reference may be made to the foregoing, and in the case where the indication information includes the absolute value of the retransmission sub-packet, the lower boundary value may be modified to the absolute value of the retransmission sub-packet. In case the indication information comprises an offset value for retransmitting the sub-packet, the lower boundary value may be adjusted based on the offset value.

S406: the network device multicasts the retransmission sub-packet to the terminal.

Accordingly, the terminal receives the retransmission subpacket from the network device in a multicast manner.

In the embodiment of the present application, step S406 may be performed after step S404, so as to retransmit the retransmission sub-packet of the network device before receiving the first acknowledgement message, and retransmit the retransmission sub-packet after receiving the first acknowledgement message. After the terminal modifies the lower boundary value of the reorganization window, the number corresponding to the modified lower boundary value is smaller than or equal to the sequence number of the retransmission sub-data packet, so that the data packet loss can be avoided.

Illustratively, as shown in fig. 5, the acknowledgement message received by the network device for the first time is ACK for#9 (MAC), the initial value of the lower boundary value and the initial value of the upper boundary value are 9. The retransmission subpacket includes #4 (MAC) transmitted before ACK for #9 (MAC) and #5, 6 (MAC) transmitted after ACK for #9 (MAC). If the network device sends the absolute value of the retransmission subpacket to the terminal at time t2, for example, the absolute value is 4, the terminal modifies the lower boundary value to 4. If the network device sends an offset value for the retransmission of the sub-packet to the terminal at time t2, for example, the offset value is 5, the lower boundary value may be modified to 4 (9-5). And then multicast and send the retransmission sub-data packet sets corresponding to #4 (MAC), #5 (MAC) and #6 (MAC) to the terminal, wherein the retransmission sub-data packets corresponding to #4 (MAC), #5 (MAC) and #6 (MAC) are not discarded, but are recombined. And transmitted after the reorganization is completed.

In the method shown in fig. 4, before multicasting sub-packets of a data packet to be transmitted to a terminal, the network device sends a multicast radio configuration to the terminal, so that the terminal performs multicast transmission initialization. And after the terminal receives the sub-data packet sent by the terminal, sending an acknowledgement message of the sub-data packet to the terminal. After receiving the first acknowledgement message, the network device determines a retransmission subpacket of the data packets to be transmitted. And then sending indication information to the terminal so that the terminal modifies the lower boundary value of the reorganization window, thereby modifying the range of the discarded data packet. And then the network equipment multicasts and sends the retransmission sub-data packet to the terminal, so that the occurrence of the event of data packet loss caused by PTM initialization can be avoided, the success rate of data transmission is improved, and the reliability of multicast service can be improved.

Referring to fig. 6, fig. 6 is a flow chart of another data transmission method of multicast service provided in the present application. The method is applied in a communication network as shown in fig. 2. As shown in fig. 6, the method may include the following steps S600 to S604, in which:

s600: the network device sends the multicast wireless configuration to the terminal.

S601: the network device multicasts at least two sub-packets of the data packet to be transmitted to the terminal.

S602: the terminal sends an acknowledgement message to the network device.

S603: the network device determines a retransmission subpacket of the data packets to be transmitted.

The steps S600 to S603 may refer to the descriptions of the steps S400 to S403, and are not described herein.

S604: the network device unicast transmits the retransmission sub-packet to the terminal.

Accordingly, the terminal unicast receives the retransmission subpacket from the network device.

In one possible example, step S603 is specifically determining, for the MAC layer in the network device, a retransmission subpacket among the data packets to be transmitted. Step S604 may specifically include unicast transmitting the retransmission subpacket from a MAC layer in the network device downward based on the C-RNTI of the terminal to unicast transmit the retransmission subpacket to the terminal.

Illustratively, the network device is the gNB in FIG. 3, and the terminal is UE1 in FIG. 3. Referring to fig. 3, a retransmission sub-packet set corresponding to a retransmission sub-packet may be transmitted to UE1 through a C-RNTI by the MAC layer of the gNB. In this way, the MAC layer directly performs unicast transmission on the retransmission sub-packet through the PTP mode, so that the retransmission rate can be improved.

In another possible example, step S603 is specifically determining, for the MAC layer in the network device, a retransmission subpacket among the data packets to be transmitted. After step S603, before step S604, the method further includes the steps of: hierarchical signaling is sent upward from the MAC layer of the network device to cause the PDCP layer of the network device to determine the sequence number of the retransmission subpacket. Step S604 specifically includes unicast transmitting the retransmission sub-data from the PDCP layer to the downlink to unicast transmitting the retransmission sub-data packet to the terminal.

It will be appreciated that the network device may acknowledge the retransmission sub-packets to be retransmitted internally by means of hierarchical signaling. For example, the MAC layer of the network device sends the RLC layer of the network device through level signaling, and then the RLC layer sends the RLC layer to the PDCP layer of the network device. In this way, the PDCP layer may determine a retransmission subpacket. And then adopting a PTP mode to start layer-by-layer downward transmission from the PDCP layer of the network equipment so as to make the retransmission sub-data packet (or the retransmission sub-data packet set corresponding to the retransmission sub-data packet) unicast and send to the terminal, thereby avoiding data loss.

Fig. 7 is a schematic flow chart of another data transmission method of multicast service provided in the present application. As shown in fig. 7, the sequence numbers of sub-packets in the data packets to be transmitted, which are sent from the PDCP layer of the network device to the RLC layer of the network device, are 3, 4,5,6, 7, 8, 9. And the RLC layer of the network device sends the above data packets to be transmitted to the MAC layer of the network device. However, after the MAC layer of the network device sends the data packet to be transmitted to the MAC of the terminal through the physical layer, the MAC layer of the network device may determine that the sequence number of the sub-packet to be retransmitted is 4,5,6 if the sequence number of the sub-packet corresponding to the ACK received by the first MAC layer of the network device is 9 and the sequence number of the sub-packet corresponding to the NACK received is 4,5, 6. The MAC layer of the network device may also inform the RLC layer of the network device through level signaling. The RLC layer of the network device informs the PDCP layer of the network device through level signaling such that the PDCP layer determines the sequence numbers of the retransmission sub-packets as 4,5,6, and can retransmit the retransmission sub-packets. The PDCP layer may record a retransmission packet set corresponding to a retransmission sub-packet as { PDCP SN = {4,5,6}. The PDCP layer, RLC layer, MAC layer and PHY layer of the network device perform unicast transmission downwards, so that the terminal can record the received data packet set as { SN = {4,5,6}, that is, the sequence number of the retransmission sub-data packet of the RLC layer to be received by the terminal is 4,5, 6. The PTP leg shown in fig. 3 may be used to unicast the retransmission sub-packet to implement sub-packet retransmission, so as to avoid packet loss.

In a CU-DU scenario, in one possible example, signaling is transmitted to the DU through the F1 interface, which may include an identification of the terminal and a sequence number of the retransmission subpacket, for indicating that the retransmission subpacket of the terminal is retransmitted. Therefore, unicast transmission can be carried out on the retransmission sub-data packet through the PTP mode, so that the retransmission of the sub-data packet can be realized, and the data packet loss can be avoided.

In the method shown in fig. 6, before multicasting sub-packets of a data packet to be transmitted to a terminal, a network device sends a multicast radio configuration to the terminal, so that the terminal performs multicast transmission initialization. And after the terminal receives the sub-data packet multicast-transmitted by the network equipment, transmitting an acknowledgement message of the sub-data packet to the terminal. After receiving the first acknowledgement message, the network device determines a retransmission subpacket of the data packets to be transmitted. And then unicast transmitting the retransmission sub-data packet to the terminal. Therefore, the data packet with the multicast transmission failure is retransmitted by adopting a unicast transmission mode, the occurrence of the event of data packet loss caused by PTM initialization can be avoided, the success rate of data transmission is improved, and the reliability of multicast service can be improved.

The foregoing details the method of embodiments of the present application, and the apparatus of embodiments of the present application is provided below.

Referring to fig. 8, fig. 8 is a schematic structural diagram of a communication device according to an embodiment of the present application. The communication device may comprise a transceiving unit 801 and a processing unit 802 as shown in fig. 8. In one possible example, the communication apparatus may be a network device, wherein:

the transceiver 801 is configured to send a multicast wireless configuration to a terminal, where the multicast wireless configuration is used to instruct the terminal to perform multicast transmission initialization; at least two sub-data packets of a data packet to be transmitted are sent to the terminal in a multicast mode, and each sub-data packet corresponds to a serial number; receiving an acknowledgement message from the terminal, wherein the acknowledgement message is used for determining sub-data packets received by the terminal;

the processing unit 802 is configured to determine a retransmission sub-packet in the data packet to be transmitted;

the transceiver unit 801 is further configured to send indication information to the terminal, where the indication information is used to modify a lower boundary value of the reorganization window; and multicasting and sending the retransmission sub-data packet to the terminal.

Optionally, the indication information includes an absolute value of the retransmission sub-packet, and the indication information is specifically configured to indicate that a lower boundary value of the reassembly window is modified to the absolute value, where the absolute value includes a minimum value of sequence numbers in the retransmission sub-packet.

Optionally, the indication information includes an offset value of the retransmission subpacket, and the indication information is specifically configured to indicate that a lower boundary value of the reassembly window is adjusted based on the offset value, where the offset value is related to at least two of the following information: and retransmitting the minimum value of the sequence number in the sub-data packet, the sequence number of the first sub-data packet received by the terminal and a preset constant, wherein the preset constant is a positive integer.

Optionally, the multicast wireless configuration includes an initial value of the lower boundary value and is a minimum value of sequence numbers in the sub-data packet.

In one possible example, the communication apparatus may be a network device, wherein:

The transceiver unit 801 is further configured to unicast transmit the retransmission sub-packet to the terminal.

Optionally, the communication device further includes a MAC layer, the retransmission sub-packet is determined by the MAC layer, and the transceiver unit is specifically configured to unicast send the retransmission sub-packet from the MAC layer to the downlink based on the C-RNTI of the terminal, so as to unicast send the retransmission sub-packet to the terminal.

Optionally, the communication device further includes a MAC layer and a PDCP layer, the retransmission subpacket is determined by the MAC layer, and the transceiver unit is further configured to send level signaling upward from the MAC layer, so that the PDCP layer determines a sequence number of the retransmission subpacket; the transceiving unit is specifically configured to unicast-send the retransmission sub-data from the PDCP layer to the terminal, so as to unicast-send the retransmission sub-data packet to the terminal.

In one possible example, the communication device may be a terminal, wherein:

the transceiver unit 801 is configured to receive, from a network device, a multicast radio configuration in a multicast manner, where the multicast radio configuration is used to instruct the communication device to perform multicast transmission initialization; receiving a sub-data packet of a data packet to be transmitted from the network equipment in a multicast mode, wherein the sub-data packet corresponds to a serial number; transmitting an acknowledgement message to the network device, the acknowledgement message being used to determine that the sub-packet has been received by the communication device; receiving indication information from the network equipment, wherein the indication information is used for modifying the lower boundary value of the reorganization window;

The processing unit 802 is configured to modify the lower boundary value based on the indication information;

the transceiver unit 801 is further configured to multicast-receive the retransmission subpacket from the network device.

Optionally, the indication information includes an offset value of the retransmission subpacket, and the indication information is specifically configured to indicate that a lower boundary value of the reassembly window is adjusted based on the offset value, where the offset value is related to at least two of the following information: and retransmitting the minimum value of the sequence number in the sub-data packet, the sequence number of the first sub-data packet received by the communication device, and a preset constant, wherein the preset constant is a positive integer.

In one possible example, the communication device may be a terminal, wherein:

a transceiver unit 801, configured to receive a multicast radio configuration from a network device in a multicast manner, where the multicast radio configuration is used to instruct the communication device to perform multicast transmission initialization; receiving a sub-data packet of a data packet to be transmitted from the network equipment in a multicast mode, wherein the sub-data packet corresponds to a serial number; transmitting an acknowledgement message to the network device, the acknowledgement message being used to determine that the sub-packet has been received by the communication device; the retransmission subpacket is received from the network device in a multicast manner.

It should be noted that the implementation of each unit may also correspond to the corresponding description of the method embodiment shown in fig. 4 or fig. 6.

Referring to fig. 9, fig. 9 is a schematic structural diagram of another communication device according to an embodiment of the present application. The communication device comprises a processor 901, a memory 902 and a communication interface 903. The processor 901, the memory 902 and the communication interface 903 are interconnected by a bus 904.

The processor 901 may be a device with a processing function, and may include one or more processors. The processor may be a general purpose processor or a special purpose processor, etc. The processor may be a baseband processor, or a central processor. The baseband processor may be used to process communication protocols and communication data, and the central processor may be used to control the communication device, execute software programs, and process data of the software programs.

The communication interface 903 is used to communicate with an external device, for example, the network device sends a sub-packet of a data packet to be transmitted to the terminal. For another example, the network device receives an acknowledgement message sent by the terminal. The communication interface 903 is also used for information exchange inside the network device, for example, the MAC layer sends messages to the RLC layer. For another example, the PDCP layer transmits a message to the RLC layer.

The memory 902 may be a device having a memory function including, but not limited to, a random access memory (random access memory, RAM), a read-only memory (ROM), an erasable programmable read-only memory (erasable programmable read only memory, EPROM), or a portable read-only memory (compact disc read-only memory, CD-ROM). The memory 902 is configured to store one or more programs and sub-packets of a data packet to be transmitted, where the sub-packets of the data packet to be transmitted include retransmission sub-packets of the data packet to be transmitted. The one or more programs are executed by the processor 901 to perform the method of any preceding claim.

Specifically, in one possible example, the communication apparatus may be a network device, where the processor 901 is configured to perform the following operations:

transmitting a multicast wireless configuration to a terminal, wherein the multicast wireless configuration is used for indicating the terminal to initialize multicast transmission;

at least two sub-data packets of a data packet to be transmitted are sent to the terminal in a multicast mode, and each sub-data packet corresponds to a serial number;

receiving an acknowledgement message from the terminal, wherein the acknowledgement message is used for determining sub-data packets received by the terminal;

Determining retransmission sub-data packets in the data packets to be transmitted;

sending indication information to the terminal, wherein the indication information is used for modifying the lower boundary value of the reorganization window;

and multicasting and sending the retransmission sub-data packet to the terminal.

In one possible example, the communication apparatus may be a network device, and the processor 901 in the network device is configured to perform the following operations:

Multicast wireless configuration is sent to a terminal in a multicast mode, and the multicast wireless configuration is used for indicating the terminal to initialize multicast transmission;

and unicast transmitting the retransmission sub-data packet to the terminal.

Optionally, the retransmission subpacket is determined by the MAC layer of the network device, and the processor 901 is specifically configured to perform the following operations in unicast sending the retransmission subpacket to the terminal:

and unicast transmitting the retransmission sub-data packet from the MAC layer to the terminal based on the C-RNTI of the terminal so as to unicast transmit the retransmission sub-data packet to the terminal.

Optionally, the retransmission sub-packet is determined by the MAC layer of the network device, and after the determining the retransmission sub-packet in the to-be-transmitted packet, the processor 901 is further configured to:

transmitting level signaling upward from the MAC layer to cause a PDCP layer of the network device to determine a sequence number of the retransmission subpacket;

In terms of unicast transmission of the retransmission subpacket to the terminal, the processor 901 is specifically configured to:

and unicast transmitting the retransmission sub-data from the PDCP layer to the terminal to unicast transmit the retransmission sub-data packet to the terminal.

In one possible example, the communication device may be a terminal, and the processor 901 in the terminal is configured to perform the following operations:

multicast receiving a multicast wireless configuration from a network device, wherein the multicast wireless configuration is used for indicating a terminal to initialize multicast transmission;

receiving a sub-data packet of a data packet to be transmitted from the network equipment in a multicast mode, wherein the sub-data packet corresponds to a serial number;

transmitting an acknowledgement message to the network device, the acknowledgement message being used to determine that the terminal has received the sub-packet;

receiving indication information from the network equipment, wherein the indication information is used for modifying the lower boundary value of the reorganization window;

modifying the lower boundary value based on the indication information;

the retransmission subpacket is received from the network device in a multicast manner.

and unicast receiving a retransmission sub-data packet in the data packet to be transmitted from the network equipment.

It should be noted that the implementation of the respective operations may also correspond to the respective description of the method embodiment shown with reference to fig. 4 or fig. 6.

The embodiment of the application also provides a communication device, which is used for executing any method and function related to the network equipment or the terminal in any embodiment.

The communication device may be a network device or a terminal, or may be a chip applied to the network device or the terminal, or other combined devices, components, etc. capable of implementing the functions of the device. When the communication device is a network apparatus or a terminal, the receiving unit may be a receiver, the transmitting unit may be a transmitter, the receiving unit and the transmitting unit may also be an integrated transceiver, an antenna or a radio frequency circuit, etc., and the processing unit may be a processor, such as a baseband chip, etc. When the communication device is a component having the above-described device functions, the receiving unit and the transmitting unit may be an integrated radio frequency unit, and the processing unit may be a processor. When the communication device is a chip system, the receiving unit may be an input interface of the chip system, the transmitting unit may be an output interface of the chip system, and the processing unit may be a processor of the chip system, for example: a central processing unit (central processing unit, CPU).

The embodiment of the application also provides a communication system, which comprises at least one network device and at least one terminal, wherein the at least one network device and the at least one terminal are involved in any embodiment.

Embodiments of the present application also provide a computer-readable storage medium having instructions stored therein that, when executed on a computer, implement the method flow shown in fig. 4 or fig. 6.

Embodiments of the present application also provide a computer program product for storing a computer program which, when run on a computer, implements the method flow shown in fig. 4 or fig. 6.

The embodiment of the application also provides a first chip, which comprises a processor and a memory, wherein the processor is used for calling and running instructions stored in the memory from the memory, so that a device provided with the chip executes the method shown in fig. 4 or 6.

The embodiment of the application also provides a second chip, which comprises: the device comprises an input interface, an output interface and a processing circuit, wherein the input interface, the output interface and the processing circuit are connected through an internal connection path, and the processing circuit is used for executing the method shown in fig. 4 or 6.

The embodiment of the application also provides a third chip, which comprises: the device comprises an input interface, an output interface and a processor, and optionally further comprises a memory, wherein the input interface, the output interface, the processor and the memory are connected through an internal connection path, the processor is used for executing codes in the memory, and when the codes are executed, the processor is used for executing the method shown in fig. 4 or 6.

The embodiment of the application also provides a chip system, which comprises at least one processor, a memory and an interface circuit, wherein the memory, the transceiver and the at least one processor are interconnected through lines, and instructions are stored in the at least one memory; the instructions, when executed by the processor, implement the method flow shown in fig. 4 or fig. 6.

In summary, by implementing the embodiment of the present application, before multicasting a sub-packet of a data packet to be transmitted to a terminal, a network device sends a multicast radio configuration to the terminal, so that the terminal performs multicast transmission initialization. And after the terminal receives the sub-data packet sent by the terminal, sending an acknowledgement message of the sub-data packet to the terminal. After receiving the first acknowledgement message, the network device determines a retransmission subpacket of the data packets to be transmitted. And then sending indication information to the terminal so that the terminal modifies the lower boundary value of the reorganization window, thereby modifying the range of the discarded data packet. And then the network equipment multicasts and sends the retransmission sub-data packet to the terminal, so that the occurrence of the event of data packet loss caused by PTM initialization can be avoided, the success rate of data transmission is improved, and the reliability of multicast service can be improved.

On the other hand, after the network device determines the retransmission sub-packet in the data packet to be transmitted, the retransmission sub-packet is unicast transmitted to the terminal. Therefore, the data packet with the multicast transmission failure is retransmitted by adopting a unicast transmission mode, the occurrence of the event of data packet loss caused by PTM initialization can be avoided, the success rate of data transmission is improved, and the reliability of multicast service can be improved.

Those of ordinary skill in the art will appreciate that implementing all or part of the above-described embodiment methods may be accomplished by a computer program in hardware associated with the computer program, which may be stored on a computer readable storage medium, which when executed may comprise the above-described embodiment methods. And the aforementioned storage medium includes: various media capable of storing computer program code, such as ROM or random access memory RAM, magnetic or optical disk.

Claims

1. A data transmission method for multicast service, comprising:

2. The method according to claim 1, wherein the indication information comprises an absolute value of the retransmission subpacket, the indication information being specifically used to indicate that a lower boundary value of the reassembly window is modified to the absolute value, the absolute value comprising a minimum value of sequence numbers in the retransmission subpacket.

3. The method according to claim 1, wherein the indication information comprises an offset value of the retransmission subpacket, the indication information being specifically configured to indicate that a lower boundary value of the reassembly window is adjusted based on the offset value, the offset value being related to at least two of the following information: and retransmitting the minimum value of the sequence number in the sub-data packet, the sequence number of the first sub-data packet received by the terminal and a preset constant, wherein the preset constant is a positive integer.

4. The method of claim 1, wherein the multicast radio configuration includes an initial value of the lower boundary value and is a minimum value of sequence numbers in the subpackets.

5. A data transmission method for multicast service, comprising:

and unicast transmitting the retransmission sub-data packet to the terminal.

6. The method of claim 5, wherein the retransmitting subpacket is determined by a medium access control MAC layer of a network device, and wherein unicast transmitting the retransmitting subpacket to the terminal comprises:

and unicast-transmitting the retransmission sub-data packet from the MAC layer based on the cell radio network temporary identifier C-RNTI of the terminal so as to unicast-transmit the retransmission sub-data packet to the terminal.

7. The method of claim 5, wherein the retransmission subpacket is determined by a medium access control MAC layer of a network device, and wherein after determining the retransmission subpacket in the data packet to be transmitted, further comprising:

transmitting layer signaling upward from the MAC layer to cause a packet data convergence layer protocol PDCP layer of the network device to determine a sequence number of the retransmission subpacket;

The unicast transmission of the retransmission sub-packet to the terminal includes:

8. A data transmission method for multicast service, comprising:

modifying the lower boundary value based on the indication information;

9. The method according to claim 8, wherein the indication information comprises an absolute value of the retransmission subpacket, the indication information being specifically used to indicate that a lower boundary value of the reassembly window is modified to the absolute value, the absolute value comprising a minimum value of sequence numbers in the retransmission subpacket.

10. The method according to claim 8, wherein the indication information comprises an offset value of the retransmission subpacket, the indication information being specifically configured to indicate that a lower boundary value of the reassembly window is adjusted based on the offset value, the offset value being related to at least two of the following information: and retransmitting the minimum value of the sequence number in the sub-data packet, the sequence number of the first sub-data packet received by the terminal and a preset constant, wherein the preset constant is a positive integer.

11. The method of claim 8, wherein the multicast radio configuration includes an initial value of the lower boundary value and is a minimum value of sequence numbers in the subpackets.

12. A data transmission method for multicast service, comprising:

13. A communication device, comprising:

the receiving and transmitting unit is used for sending multicast wireless configuration to the terminal, wherein the multicast wireless configuration is used for indicating the terminal to initialize multicast transmission; at least two sub-data packets of a data packet to be transmitted are sent to the terminal in a multicast mode, and each sub-data packet corresponds to a serial number; receiving an acknowledgement message from the terminal, wherein the acknowledgement message is used for determining sub-data packets received by the terminal;

the processing unit is used for determining retransmission sub-data packets in the data packets to be transmitted;

the receiving and transmitting unit is further configured to send indication information to the terminal, where the indication information is used to modify a lower boundary value of the reorganization window; and multicasting and sending the retransmission sub-data packet to the terminal.

14. The communication apparatus according to claim 13, wherein the indication information comprises an absolute value of the retransmission subpacket, the indication information being specifically configured to indicate that a lower boundary value of the reassembly window is modified to the absolute value, and the absolute value comprises a minimum value of sequence numbers in the retransmission subpacket.

15. The communication apparatus according to claim 13, wherein the indication information comprises an offset value of the retransmission subpacket, the indication information being specifically configured to indicate that a lower boundary value of the reassembly window is adjusted based on the offset value, the offset value being related to at least two of the following information: and retransmitting the minimum value of the sequence number in the sub-data packet, the sequence number of the first sub-data packet received by the terminal and a preset constant, wherein the preset constant is a positive integer.

16. The communication apparatus according to claim 13, wherein the multicast radio configuration includes an initial value of the lower boundary value and is a minimum value of sequence numbers in the sub-packets.

17. A communication device, comprising:

the receiving and transmitting unit is further configured to unicast send the retransmission sub-packet to the terminal.

18. The communication apparatus according to claim 17, further comprising a MAC layer, wherein the retransmission subpacket is determined by the MAC layer, and wherein the transceiving unit is specifically configured to unicast transmit the retransmission subpacket from the MAC layer to the terminal based on a C-RNTI of the terminal.

19. The communication apparatus according to claim 17, further comprising a MAC layer and a PDCP layer, wherein the retransmission subpacket is determined by the MAC layer, and wherein the transceiving unit is further configured to transmit hierarchy signaling upward from the MAC layer to cause the PDCP layer to determine a sequence number of the retransmission subpacket; the transceiving unit is specifically configured to unicast-send the retransmission sub-data from the PDCP layer to the terminal, so as to unicast-send the retransmission sub-data packet to the terminal.

20. A communication device, comprising:

a transceiver unit, configured to receive a multicast wireless configuration from a network device in a multicast manner, where the multicast wireless configuration is configured to instruct the communication device to perform multicast transmission initialization; receiving a sub-data packet of a data packet to be transmitted from the network equipment in a multicast mode, wherein the sub-data packet corresponds to a serial number; transmitting an acknowledgement message to the network device, the acknowledgement message being used to determine that the sub-packet has been received by the communication device; receiving indication information from the network equipment, wherein the indication information is used for modifying the lower boundary value of the reorganization window;

A processing unit for modifying the lower boundary value based on the indication information;

the receiving and transmitting unit is further configured to multicast and receive the retransmission sub-packet from the network device.

21. The communication apparatus according to claim 20, wherein the indication information comprises an absolute value of the retransmission subpacket, the indication information being specifically configured to indicate that a lower boundary value of the reassembly window is modified to the absolute value, and the absolute value comprises a minimum value of sequence numbers in the retransmission subpacket.

22. The communication apparatus according to claim 20, wherein the indication information comprises an offset value of the retransmission subpacket, the indication information being specifically configured to indicate that a lower boundary value of the reassembly window is adjusted based on the offset value, the offset value being related to at least two of the following information: and retransmitting the minimum value of the sequence number in the sub-data packet, the sequence number of the first sub-data packet received by the communication device, and a preset constant, wherein the preset constant is a positive integer.

23. The communication apparatus of claim 20, wherein the multicast wireless configuration includes an initial value of the lower boundary value and is a minimum value of sequence numbers in the subpackets.

24. A communication device, comprising:

a transceiver unit, configured to receive a multicast wireless configuration from a network device in a multicast manner, where the multicast wireless configuration is configured to instruct the communication device to perform multicast transmission initialization; receiving a sub-data packet of a data packet to be transmitted from the network equipment in a multicast mode, wherein the sub-data packet corresponds to a serial number; transmitting an acknowledgement message to the network device, the acknowledgement message being used to determine that the sub-packet has been received by the communication device; the retransmission subpacket is received from the network device in a multicast manner.

25. A communication device comprising a processor and a memory, wherein the processor is coupled to the memory, the memory for storing one or more programs that are executed by the processor to perform the method of any of claims 1-12.

26. A computer readable storage medium for storing a computer program, wherein the computer program causes a computer to perform the method of any one of claims 1-12.