Patent Description:
Multicast is a manner in which a plurality of receive ends form a multicast group and a data source transfers data to the plurality of receive ends in the multicast group. With rapid development of mobile communications services, a large quantity of multimedia services emerge. For some application services such as video live broadcast, television broadcast, a video conference, online education, and an interactive game, a plurality of receive ends can simultaneously receive same data. Compared with common data, these mobile multimedia services are characterized by a large data volume, long duration, and latency sensitivity.

To make the most effective use of mobile network resources, a multimedia broadcast/multicast service (multimedia broadcast/multicast service, MBMS) is introduced into the 3rd generation partnership project (Third Generation Partnership Project, 3GPP) Rel-<NUM>, to provide a multicast service for a universal mobile telecommunications system (universal mobile telecommunications system, UMTS) by using a cellular network. Standardization of the MBMS is always in an evolution process.

To ensure that the MBMS can cover a sufficient area and that all user equipments (User Equipment, UE) in a multicast group can successfully receive multicast service data, an MBMS system sets a corresponding modulation and coding scheme and a multimedia resource by using user equipment with the worst signal quality in the multicast group as a reference. Because attenuation of wireless signal strength and a distance have an exponential relationship, spectral efficiency of user equipment with relatively poor signal quality in the multicast group is usually five to dozens of times less than average spectral efficiency, resulting in very low transmission efficiency.

<CIT> refers to a method of data transmission in multicast or broadcast service, for a network in a wireless communication system. The method comprises providing a multicast stream of the multicast or broadcast service to a mobile device of the wireless communication system, and transmitting an indication to the mobile device, wherein the indication is used for resource allocation of a data stream of the multicast or broadcast service.

<CIT> refers to a data transmission method, apparatus, and system, where the method includes: receiving, by a base station, a Multimedia Broadcast Multicast Service MBMS service transmission request and MBMS service data that are sent by a core network device; after receiving the MBMS service transmission request or the MBMS service data, sending, by the base station, an MBMS service paging message in a cell served by the base station; and sending, by the base station, the MBMS service data to user equipment UE according to the MBMS service transmission request.

<CIT> refers to a radio communication system, when switching of a multicast communication and a unicast communication is performed, a radio communication base station determines whether to switch a communication mode based on reception information received from a mobile terminal, newly establishes a logical channel between the mobile terminal and the radio communication base station by the same logical channel as before switching based on the determination result, converts to a transport channel of a communication mode different from before switching in the newly established logical channel, and switches communication with each mobile terminal to a communication mode represented by the converted transport channel. Thus, switching of the communication mode is performed limitedly only in between the radio communication base station and each mobile terminal.

<CIT> refers to a UE maintaining continuity of reception of a service of interest that is available over eMBMS broadcast service and unicast. The UE receives the service of interest over eMBMS from a network within a first MBSFN area supporting the eMBMS broadcast service. The UE receives at least one MBSFN threshold from the network and at least one MBSFN measurement from the network. The UE switches from reception of the eMBMS broadcast from the first MBSFN area to one of reception through unicast or reception through a second MBSFN area supporting the eMBMS broadcast service, based on the at least one MBSFN threshold and the at least one MBSFN measurement.

A technical problem to be resolved in embodiments of the present invention is low transmission efficiency of multicast communication. A communication method and a related product are provided, to improve the transmission efficiency of the multicast communication. The above mentioned problem is solved by the subject matter of the independent claims. Further implementation forms are provided in the dependent claims.

To describe the technical solutions in the embodiments of the present invention or in the background more clearly, the following briefly describes the accompanying drawings required for describing the embodiments of the present invention or the background.

<FIG> each are a schematic structural diagram of a communications system according to an embodiment of the present invention.

The communications system in <FIG> includes user equipment, an access network device, a gateway device, a management device, a router, a server, and the like. The management device and the gateway device may be classified as core network devices, and the router and the server may belong to a data network (data network, DN).

In <FIG>, the user equipment may be connected, by using a wireless air interface, to the access network device deployed by an operator, and then connected to the data network. The access network device is mainly configured to implement functions such as a radio physical layer function, resource scheduling and radio resource management, radio access control, and mobility management. The management device included in the core network devices is mainly used for device registration, security authentication, mobility management, location management, and the like of the user equipment. The gateway device in the core network devices is mainly configured to: establish a channel to the user equipment, and forward a data packet between the user equipment and an external data network on the channel. The data network is mainly configured to provide a plurality of data services for the user equipment. The server included in the data network may be a fast channel change (Fast Channel Change, FCC) server. <FIG> is merely an example architectural diagram. In addition to the functional units shown in <FIG>, the network architecture may further include another functional unit. This is not limited in this embodiment of the present invention.

In the communications system shown in <FIG>, when a communications network shown in <FIG> is a <NUM> network, the user equipment may be a mobile phone or a computer, or may be a cellular phone, a cordless phone, a session initiation protocol (session initiation protocol, SIP) phone, a smartphone, a wireless local loop (wireless local loop, WLL) station, a personal digital assistant (personal digital assistant, PDA), a computer, a laptop computer, a handheld communications device, a handheld computing device, a satellite wireless device, a wireless modem card, a set top box (set top box, STB), a customer-premises equipment (customer premise equipment, CPE), and/or another device used for communication in a wireless system. The access network device may be an access network (access network, AN)/radio access network (radio access network, RAN) device, and the access network or the radio access network is a network including a plurality of <NUM>-AN/<NUM>-RAN nodes. The <NUM>-AN/<NUM>-RAN node may be an access point (access point, AP), a next-generation NodeB (NR nodeB, gNB), a transmission reception point (transmission receive point, TRP), a transmission point (transmission point, TP), or another access node. The core network device may include functional units such as an access and mobility management function (access & mobility function, AMF), a session management function (session management function, SMF), a policy control function (policy control function, PCF), and a user plane function (user plane function, UPF). These functional units may work independently, or may be combined together to implement some control functions. For example, the AMF, the SMF, and the PCF may be combined together as a management device to implement access control and mobility management functions such as access authentication, security encryption, and location registration of the user equipment, and session management functions such as establishment, release, and change of a user plane transmission path, and functions of analyzing some data (such as congestion) related to a slice (slice) and user equipment-related data. The UPF mainly completes functions such as routing and forwarding of user plane data, for example, is responsible for data packet filtering, data transmission/forwarding, rate control, charging information generation, and the like for the user equipment.

<FIG> is a schematic diagram of a network architecture of a <NUM> communications system. In a <NUM> network shown in <FIG>, functional units may communicate with each other by establishing a connection between the functional units by using a next generation (next generation, NG) interface. For example, the user equipment may establish a control plane signaling connection to the AMF by using an NG interface <NUM> (N1 for short). The AN/RAN device, for example, a next-generation radio access NodeB (NR NodeB, gNB), may establish a user plane data connection to the UPF by using an NG interface <NUM> (N3 for short), and the AN/RAN device may establish a control plane signaling connection to the AMF by using an NG interface <NUM> (N2 for short). The UPF may establish a control plane signaling connection to the SMF by using an NG interface <NUM> (N4 for short), and the UPF may exchange user plane data with the data network by using an NG interface <NUM> (N6 for short). The AMF may establish a control plane signaling connection to the SMF by using an NG interface <NUM> (N11 for short). The SMF may establish a control plane signaling connection to the PCF by using an NG interface <NUM> (N7 for short). It should be noted that <FIG> is merely an example architectural diagram. In addition to the functional units shown in <FIG>, the network architecture may further include another functional unit. For example, the core network device may further include a unified data management (unified data management, UDM) function. This is not limited in this embodiment of the present invention.

When the communications network shown in <FIG> is a <NUM> network, for the user equipment, refer to related descriptions of the user equipment in <FIG>, and details are not described herein again. The access network device may be a NodeB (nodeB, NB), an evolved NodeB (evolution nodeB, eNB), a TRP, a TP, an AP, or another access unit. The core network device may include a management device such as a mobility management entity (mobility management entity, MME) or a policy and charging rules function (policy and charging rules function, PCRF), and a gateway device such as a serving gateway (serving gateway, SGW) or a PGW, and may further include a local gateway (local gateway, LGW).

For example, <FIG> is a schematic diagram of an architecture of a <NUM> network according to an embodiment of the present invention. In the <NUM> network shown in <FIG>, the user equipment may establish an air interface connection to an eNB by using a Uu interface; the eNB establishes a control plane signaling connection to the MME by using an S1-C interface, and the eNB establishes a user plane data connection to the SGW by using an S <NUM>-U interface; and the SGW establishes a control plane signaling connection to the MME by using an S <NUM> interface, and the SGW establishes a user plane data connection to the PGW by using an S5/S8 interface. It should be noted that <FIG> is merely an example architectural diagram. In addition to the functional units shown in <FIG>, the network architecture may further include another functional unit. This is not limited in this embodiment of the present invention.

To avoid loss of generality, <FIG> is a schematic diagram of a communications system having a multicast architecture according to an embodiment of the present invention. A core network device includes a control plane network element and a user plane network element, which are separately connected to an access network device. User equipment may be connected to the access network device by using a wireless air interface. The access network device is mainly configured to implement functions such as a radio physical layer function, resource scheduling and radio resource management, radio access control, and mobility management. The multicast core network device may include a multicast core network control plane (control plane, CP), including multicast bearer management. The multicast core network device further includes a multicast core network user plane (user plane, UP), configured to manage sending of multicast data from a multicast data network to the access network device. The multicast core network user plane may correspond to an MBMS-GW in a <NUM> architecture, and the multicast core network control plane may correspond to an MME in the <NUM> architecture. It should be noted that <FIG> is merely an example architectural diagram, and includes only a minimum quantity of network elements required by the multicast network architecture. Therefore, in addition to the functional units shown in <FIG>, the network architecture may further include another functional unit. <FIG> shows a process of establishing a multicast service bearer. User equipment participating in multicast may be referred to as a multicast terminal. The user equipment, an access network device, a multicast core network, and a multicast service platform first undergo a multicast service discovery process. The multicast core network exchanges multicast service information with the multicast service platform, and the access network device exchanges multicast service information with the multicast core network, so that a multicast service is established. The user equipment and the access network device determine a network resource used for multicast, and then establish the radio bearer. A specific example is as follows:
The user equipment may find the multicast service platform in the multicast service discovery process. For example, the user equipment may browse an over the top (Over The Top, OTT) website and interact with a server corresponding to the multicast service platform, to obtain multicast data. Alternatively, the user equipment may find the multicast service platform from a preconfigured address of the multicast service platform. For example, a multicast service platform is usually pre-configured in a set top box device. The user equipment interacts with the multicast service platform to obtain a multicast program list configuration. The multicast program list configuration includes multicast address information, identifier information, or the like, and specifically includes an internet protocol (internet protocol, IP) multicast address, an air interface multicast identifier, or the like. A user selects a program in the user equipment, so that the user equipment interacts with the multicast service platform, the user equipment is added as a receiver of the multicast service, and the user equipment becomes a participant of the multicast service. Compared with the foregoing process in which the user triggers the establishment of the multicast service, when the multicast service is in broadcast mode, the multicast service platform may also initiate a multicast service establishment process with the multicast core network without triggering of interaction between the multicast service platform and the user equipment. The multicast service may include a service such as group communication of trunking communication or group forwarding of internet of vehicles. A manner of establishing the multicast service in these application scenarios is similar to the foregoing OTT video or broadcast manner.

Multicast session establishment: The multicast service platform exchanges information with the multicast core network, to trigger establishment of a multicast session between the multicast core network and the multicast access network device (for example, a base station). Alternatively, the core network may receive a message indicating that the user equipment joins the multicast service, to trigger establishment of the multicast session. The multicast session may be carried by a multicast tunnel or may be identified by a multicast flow. In the former manner, the multicast tunnel is established, the multicast data is placed in the multicast tunnel and sent to the access network device, and multicast data of different multicast services (with different multicast addresses or different multicast QoS) are placed in different multicast tunnels. In the latter manner, a multicast flow identifier is carried by a multicast packet, to distinguish between different multicast services. If the multicast session has been established before the user equipment joins the multicast service (for example, another user equipment in a same access network has applied for joining the multicast service previously), the user equipment may directly join a multicast group to receive the multicast data.

In this embodiment of the present invention, to enable the access network device to flexibly adjust a manner of performing the multicast service based on statuses of different user equipments, the access network device needs to learn of multicast service information of the user equipment, and the multicast service information may include user identifier information and a multicast service identifier. As shown in <FIG>, the multicast service information may be carried by a multicast session establishment message during multicast session establishment. Alternatively, as shown in <FIG>, the multicast service information may be carried by a multicast join request or multicast member change information. Alternatively, as shown in <FIG>, the multicast service information may be carried by multicast service receiving information.

<FIG>, <FIG> show three different application scenarios, which are separately described below in detail.

<FIG> may show a scenario in which a multicast service is established for the first time. A specific procedure may include the following steps.

401A: User equipment sends a multicast service join request to an access network device.

402A: The access network device forwards the received multicast service join request to a multicast core network. 403A: The multicast core network sends a multicast session establishment request to the access network device, where the multicast session establishment request may carry multicast service information and multicast configuration information.

The multicast service information may include user identifier information and a multicast service identifier. The multicast configuration information may include information about a resource that needs to be used by the multicast service.

404A: The access network device establishes a radio bearer based on the multicast configuration information. If a radio bearer has been established between the access network device and the user equipment, and the radio bearer that has been established satisfies a requirement of a multicast configuration, this step may not be performed.

405A: The access network device sends a multicast session establishment complete message to the multicast core network.

<FIG> may show a procedure of changing a multicast member after a multicast service is established. A specific procedure may include the following steps.

401B: User equipment sends a multicast service join request to an access network device.

402B: The access network device forwards the received multicast service join request to a multicast core network. 403B: The multicast core network finds that the multicast service to be joined by the user equipment has been established, and sends multicast member change information to the access network device, where the multicast member change information may carry user identifier information and a multicast service identifier.

403B may alternatively be: The multicast core network finds that the multicast service to be joined by the user equipment has been established, and sends a multicast service join response to the access network device, where the multicast service join response may carry user identifier information and a multicast service identifier.

404B: The access network device establishes a radio bearer based on multicast configuration information corresponding to the multicast service to be joined by the user equipment. If a radio bearer has been established between the access network device and the user equipment, and the radio bearer that has been established satisfies a requirement of the multicast service, this step may not be performed.

In <FIG>, the user equipment sends the multicast service join request, and the multicast service join request may also carry the user identifier information and the multicast service identifier, so that the access network device may also learn that the user equipment is to join the multicast service corresponding to the multicast service identifier.

In the foregoing procedure, for a process in which the user equipment sends the multicast service join request to the access network device, and the access network device forwards the multicast service join request, the multicast service join request may be sent by using non-access stratum signaling, and is transparently transmitted by the access network device. In <FIG>, the multicast member change information may be dedicated indication information, and the dedicated indication information may include identifier information of one or more multicast member users.

401C: User equipment sends multicast service receiving information to an access network device.

The multicast service receiving information may indicate a specific multicast service that needs to be received by the user equipment. A specific manner may be that the multicast service receiving information carries a multicast service identifier. For example, the multicast service identifier is a multicast IP address of the multicast service, or similar to a temporary mobile group identity (temporary mobile group identity, TMGI) of an MBMS.

402C: After receiving the multicast service receiving information, the access network device determines, based on the multicast service identifier carried in the multicast service receiving information, a specific multicast service group to which the user equipment joins. The access network device may forward the multicast service receiving information to a multicast core network.

403C: The multicast core network may return a multicast service join response, to notify the access network device that the user equipment has joined the multicast service.

In addition, in this embodiment of the present invention, for multicast information to be obtained by the access network device, the access network device may monitor a multicast join message of the user equipment, such as an internet group management protocol (internet group management protocol, IGMP) join (join) message sent by the user equipment, to obtain a correspondence between the user equipment and the multicast service.

The access network device may select or adjust a multicast data sending manner based on statuses of different user equipments. The access network device may use an air interface wireless multicast manner, or may use an air interface wireless unicast manner, or may use an air interface wireless multicast and unicast cooperation manner. The following provides several common multicast service application scenarios.

As shown in <FIG>, the unicast manner is used when there are a small quantity of user equipments, and the multicast manner is used when there are a large quantity of user equipments. A hexagonal area is an example of a cell. The hexagonal area may be one cell or a cell set including a plurality of cells. One black dot on the left side indicates one user equipment. Because there are a relatively small quantity of user equipments in a multicast group, to be specific, there are a relatively small quantity of user equipments participating in a multicast service, the unicast manner may be selected to be used. There are four user equipments in a multicast group on the right side, and the multicast manner may be used. An example of a specific application scenario is as follows:.

The multicast area may be one cell or more cells, or may similar to a plurality of single frequency network cells in an MBSFN.

The access network device may be a base station, or a centralized unit (centralize unit, CU) of a base station.

As shown in the left hexagonal area in <FIG>, if there are a relatively small quantity of user equipments that receive the multicast service data, the access network device may configure the user equipment to receive the multicast service data in the unicast manner. In this case, the user equipment may receive scheduling information of the base station for a specific identity (identity, ID) of the user equipment, and perform corresponding data receiving and feedback. The specific ID may be a cell radio network temporary identity (cell radio network temporary identity, C-RNTI), a medium access control (medium access control, MAC) address, or another ID that can uniquely identify the user equipment. As shown in the right hexagonal area in <FIG>, if a quantity of user equipments that receive the multicast service data in the multicast area is greater than a specified threshold, the base station may select to send the multicast service data to the user equipment in the multicast group in the multicast manner, to save air interface resources. The base station may configure the user equipment that receives the multicast service data, so that all the user equipments can receive same scheduling information by using a same multicast ID, and receive same multicast service data on a same radio resource. The multicast ID may be, for example, a Group-RNIT, a group MAC address, a TMGI, or another similar multicast service air interface ID. The specified threshold may be preconfigured by an access network management system, or may be carried by a core network to an access network when a multicast session is established.

A specific procedure is shown in <FIG> and may include the following steps.

<NUM>: After a multicast session is established, the access network device finds that there are a small quantity of user equipments, so that the access network device establishes a radio bearer with user equipment <NUM>, and sends multicast data in the unicast manner, and the user equipment receives the multicast data in the unicast manner.

In step <NUM>, the user equipment <NUM> is configured to receive multicast service data in the unicast manner. A configuration message may carry configuration information sent by the access network device to the user equipment. The configuration information may usually include one of the following content: a configuration of a multicast bearer, multicast session information corresponding to the multicast bearer, logical channel information of the multicast bearer, and indication information transmitted in the unicast manner. The multicast session information may include evolved packet system (evolved packet system, EPS) bearer (bearer) information or EPS flow (flow) information.

More specifically, in step <NUM>, after the multicast session is established, because the quantity of user equipments is too small, the access network device determines, based on the small quantity of user terminals that currently receive the multicast service data, that sending efficiency is relatively high when the unicast manner is used, so that the user equipment <NUM> may be configured to receive the multicast service data in the unicast manner. The configuration message may carry the configuration information sent by the access network device to the user equipment, and the configuration information may include at least one of the following configuration information: bearer configuration information and resource layer configuration information.

The bearer configuration information may include at least one of the following information: a radio bearer configuration and a security configuration. The radio bearer configuration may carry one of the following information: a radio bearer ID, an evolved packet system bearer ID (bearer ID) corresponding to a multicast service, a quality of service (quality of service, QoS) flow (flow), configuration information of multicast service session information, PDCP configuration information, or RLC configuration information.

The multicast service session information may include a session identifier (session ID), a TMGI identifier, and the like. The RLC configuration information may be a corresponding acknowledged mode (acknowledged mode, AM) RLC configuration or an unacknowledged mode (Unacknowledged Mode, UM) RLC configuration, and a mapping relationship between the RLC configuration and a logical channel, to be specific, the RLC configuration may be mapped to a unicast logical channel or a multicast logical channel, or may be mapped to both a unicast logical channel and a multicast logical channel. The RLC configuration may further include an AM or UM sending manner, and information about a logical channel to which the RLC configuration is mapped, for example, information indicating that the logical channel is a multicast logical channel or a unicast logical channel, or a logical channel ID. The PDCP configuration information may include a mapping relationship between a PDCP layer and the RLC configuration (including whether the RLC configuration is mapped to only the unicast manner or the multicast manner, or in a manner combining the unicast manner and the multicast manner), and indication information indicating that the PDCP layer supports a retransmission function. The multicast logical channel includes a multicast control channel (multicast control channel, MCCH)/multicast traffic channel (multicast traffic channel, MTCH). The unicast logical channel includes a dedicated control channel (dedicate control channel, DCCH)/dedicated traffic channel (dedicated traffic channel, DTCH).

The resource layer configuration information may include a MAC layer configuration and a physical layer configuration. The physical layer configuration may include a spectrum resource configuration, and may be in a form of one or more pieces of physical cell configuration information, carrier configuration information, or carrier fragment configuration information, including a corresponding ID, a bandwidth, a subframe format, and the like. Further, the physical layer configuration may further include physical video resource configuration information of a corresponding physical channel/signal and corresponding identifier information, for example, configuration information of a unicast physical control and shared channel and a unicast scheduling identifier, or configuration information of a multicast physical control and shared channel and a multicast scheduling identifier. The unicast physical control and shared channel and the multicast physical control and shared channel may be the same or share a same physical resource. The MAC layer configuration may include a mapping relationship between a unicast or multicast logical channel and a corresponding physical channel, logical channel priority information, and HARQ configuration information.

The configuration message may further carry measurement information, for example, measurement event configuration information used for switching between the multicast manner and the unicast manner. The configuration message may further carry secure encryption/decryption information, for example, an encryption/decryption algorithm for the multicast service.

<NUM>: New user equipment joins a multicast group.

<NUM>: A core network side may send a multicast session update message to the access network device, to notify the access network device that the new user equipment joins the multicast service.

<NUM>: The access network device finds that there are n user equipments in the multicast group, and n reaches a threshold for specifying that the service data is sent in the multicast manner. If the radio bearer established in the unicast manner is not applicable to the multicast manner, the radio bearer between the access network device and the user equipment <NUM> may be updated.

<NUM>: The access network device establishes a radio bearer with the user equipment n, where the radio bearer is used to transmitting the data in the multicast manner.

In the foregoing procedure, after receiving the information about the increase in the quantity of user equipments of the same multicast service, the access network device determines, according to a selection algorithm of the access network device, to select the multicast manner for sending the multicast service data, and the access network device configures the corresponding configuration information for the corresponding user equipment, where the configuration information carries the corresponding multicast configuration.

In the foregoing procedure, the access network device in step <NUM> and step <NUM> may learn of the quantity of user equipments in the multicast group. The foregoing selection algorithm may be: determining, if a threshold of a specified quantity of user equipments is reached, or based on a channel status of the user equipment, that fewer radio resources are used to send the multicast service data in the multicast manner than to send the multicast service data in the unicast manner separately, so that the access network device may determine to select the multicast manner for sending the multicast service data, and correspondingly, the user equipment receives the multicast service data in the multicast manner.

In the foregoing procedure, when the multicast radio bearer is established in step <NUM>, the access network device may send the multicast configuration to the terminal, and the multicast configuration may usually carry one of the following content: a configuration of a multicast bearer, multicast session information corresponding to the multicast bearer, logical channel information of the multicast bearer, a multicast scheduling identifier, a configuration of a multicast transmission channel, a configuration of a multicast logical channel, measurement configuration of a multicast channel, multicast-associated unicast configuration. A multicast session may include an EPS bearer or an EPS flow, the multicast scheduling identifier may include a group radio network temporary identifier (group RNTI, G-RNTI, multicast identifier for short), the configuration of the multicast transmission channel may include a subframe or a carrier, and the configuration of the multicast logical channel may include a logical channel identifier.

A difference between the manner of receiving the multicast service data by the user equipment in the unicast manner and the manner of receiving the multicast service data by the user equipment in the multicast manner lies in a difference in monitoring of physical layer scheduling identifiers. If the user equipment receives the multicast service data in the unicast manner, the user equipment monitors and receives, based on an identifier (such as a C-RNTI) of the user equipment, scheduling signaling sent by a physical layer. If the user equipment receives the multicast service data in the multicast manner, the user equipment monitors and receives, based on a multicast identifier (such as a G-RNTI), scheduling signaling sent by a physical layer. Others such as formats or sizes of control signaling for the unicast manner and the multicast manner may also be different. The control signaling may be downlink control information (downlink control information, DCI). The user equipment may be in one of a unicast manner receiving status or a multicast manner receiving status, so that an amount of signaling that needs to be monitored and detected can be reduced. In addition, the user equipment may alternatively be in both a unicast manner receiving status and a multicast manner receiving status. In this case, the user equipment simultaneously detects unicast scheduling signaling and multicast scheduling signaling that are sent by the access network device, and receives the multicast service data on corresponding time-frequency resources as indicated by the scheduling signaling.

(B) <FIG> shows another application scenario of selecting a multicast manner or a unicast manner. In user equipments that receive same multicast service data, signal quality of some user equipments is relatively poor due to reasons such as being located at an edge of a cell. If all these user equipments are included in a multicast group, when sending the multicast service data in the multicast manner, an access network device needs to send the multicast data with relatively low efficiency in consideration of user equipment with the worst signal quality. This causes a decrease in overall efficiency. In this case, the access network device may group the user equipments based on channel quality of the user equipments, and designate the user equipment with good channel quality to receive the multicast service data in the multicast manner, and designate the user equipment with the poor channel quality to receive the multicast service data in the unicast manner.

A manner of obtaining the channel quality of the user equipment by the access network device may be that the access network device receives a channel measurement feedback sent by the user equipment, for example, a measurement report or a channel state information (channel state information, CSI) feedback reported by the user equipment. The user equipment designated to receive the multicast service data in the multicast manner may be user equipment whose channel quality is greater than a specified threshold. For the user equipment whose channel quality is lower than the specified threshold, the multicast manner for receiving the multicast service data may be deleted or deactivated, to avoid the decrease in the overall transmission efficiency of the multicast service data because the user equipments with the poor channel quality are enabled to successfully receive the data. For the user equipment with the relatively poor channel quality, the access network device may send the multicast service data in the unicast manner.

As shown in <FIG>, a specific procedure may be as follows:.

In the foregoing procedure, for a radio bearer establishment process, refer to the foregoing embodiment, and details are not described herein again. In the foregoing procedure shown in <FIG>, in the radio bearer establishment process, only configuration information required by the radio bearer to be established may be sent. Specifically, in step <NUM>, the access network device may send only multicast configuration information to the user equipment, and does not need to send unicast configuration information. In step <NUM>, the access network device may send only unicast configuration information, and does not need to send multicast configuration information. In addition, if the multicast service is established for the first time, the user equipment may first perform step <NUM>, and then determine a type of a radio bearer to be established by the user equipment. In addition, for newly added user equipment, step <NUM> may not be performed. In the foregoing procedure, the multicast configuration information and the unicast configuration information may alternatively be sent in step <NUM>, and subsequently, in step <NUM>, the user equipment is instructed to only switch to the unicast manner, or the user equipment determines that the channel quality is poor and switches to the unicast manner.

As shown in <FIG> is an example of an implementation of another application scenario, including the following steps.

<NUM>: After a multicast session is established or a new multicast session is established, an access network device sends information such as multicast configuration information, unicast configuration information, and a switching threshold to user equipment; and the user equipment determines, based on the switching threshold, to establish a radio bearer with the access network device.

<NUM>: The user equipment may send a channel measurement report to the access network device, to notify the access network device of channel quality of the user equipment.

Because the user equipment already knows the switching threshold, the user equipment may make a switching decision by itself. Another purpose of sending the measurement report may be to notify the access network device that the user equipment has completed the switching.

In this embodiment, the access network device sends both the multicast configuration information and the unicast configuration information to the user equipment, and may further send, to the user equipment, a measurement threshold or a measurement event condition for receiving multicast service data in a multicast manner or a unicast manner. When the user equipment determines, through measurement and based on the switching threshold, a condition for switching the receiving manner, the access network device is notified by using signaling, so that a multicast configuration or a unicast configuration is activated, a corresponding radio bearer is established, and then a corresponding receiving manner is switched to. The signaling used to notify the access network device may be the channel measurement report.

(C) As shown in <FIG>, a multicast group may be divided into different sub-multicast groups. In this embodiment, multicast service data may further be grouped in a predetermined manner to improve overall transmission efficiency. Because user equipments have different directions, an access network device may cover different user equipments through different beamforming. In addition, user equipments having different moving speeds may also be grouped into different sub-multicast groups, and user equipments with different receiving capabilities may also be grouped into different groups. Different receiving capabilities may be determined by, for example, a quantity of supported antennas, such as two antennas or four antennas.

In this embodiment, the access network device may obtain information such as the receiving capability and a motion status of the user equipment by using a feedback channel of the user equipment, and reduce a difference between users in a group as much as possible through flexible grouping, thereby avoiding a decrease in multicast efficiency. To be specific, the multicast service data may be divided and sent by a plurality of sub-multicast groups, and may be sent by using an air interface based on different multicast configurations. Multicast users of different sub-multicast groups may be distinguished by configuring different multicast scheduling identifiers or multicast transmission channel configurations, to avoid resource conflicts or interference between the groups. The multicast scheduling identifier is, for example, a group RNTI; and the multicast transmission channel configuration is, for example, a subframe or a carrier.

In addition, the difference between the users in the group may also be referred to as an intra-group difference, and is a difference between the user equipments in the sub-multicast group. Because grouping is to improve transmission efficiency of the multicast service data, a reference value is usually a basis for grouping. The reference value may be, for example, the motion status in the foregoing example. User equipments with slow motions may be grouped into one group, and user equipments with fast motions may be grouped into one group. Alternatively, the reference value may be, for example, the direction of the user equipment. The user equipments may be grouped based on whether antenna beamforming of the access network device can cover the user equipment and possible channel quality division after the coverage. This difference is finally reflected by whether transmission efficiency of the sub-multicast group is reduced because impact exists between the user equipments. Usually, the smaller a difference between reference values, the smaller the impact between the user equipments.

In the following example, user equipment participating in receiving multicast service data may receive the multicast service data in both the multicast manner and the unicast manner. The following example focuses on dynamic adjustment of the multicast manner and the unicast manner.

(A) As shown in <FIG>, three curves A, B, and C respectively represent change statuses of channel quality in a period of time when three user equipments receive same multicast service data. In a time period t0 to t1, A, B, and C are in a phase in which the channel quality is relatively good, and an access network device sends the data to A, B, and C in a multicast manner. In a time period t1 to t2, relatively strong deterioration occurs in the channel quality of the user equipment C. The channel quality deterioration may be caused by movement, temporary signal blocking, interference, or the like, and consequently, it cannot be ensured that the multicast service data is correctly received. Receiving of the multicast service data in the unicast manner may be adjusted through hybrid automatic retransmission (hybrid automatic repeat request, HARQ), dynamic scheduling, or adaptive modulation and coding (adaptive modulation and coding, AMC), to compensate for the deterioration of the channel condition of the user equipment. Therefore, in the time period t1 to t2, the user equipment A and the user equipment B may continue to receive the multicast service data in the multicast manner, and the user equipment C may receive the multicast service data in the unicast manner. After a moment t2, the channel quality of the user equipment C is restored to a relatively good state, and the user equipment C may receive the multicast service data in the multicast manner again. A specific procedure may be shown in <FIG>, and includes the following steps.

<NUM>: Establish a radio bearer with user equipment after a multicast session is established.

In this step, multicast configuration information and unicast configuration information may be sent at a time, and a multicast radio bearer or a unicast radio bearer may be selected for the radio bearer. Refer to the foregoing embodiment, and details are not described herein again.

<NUM>: The user equipment sends a channel measurement feedback to an access network device.

Herein, the channel quality feedback carries information about channel quality of the user equipment, and may be specifically a measurement report, a channel status report, or an uplink reference signal. In addition, in step <NUM>, a switching threshold may be specified in the configuration information. Therefore, if the user equipment determines whether to switch a manner of receiving multicast service data, the user equipment may also send receiving manner switching indication information in this step.

<NUM>: The access network device may determine, based on the channel measurement feedback sent by the user equipment or the receiving manner switching indication information sent by the user equipment, that the user equipment switches from receiving the multicast service data in a multicast manner to receiving the multicast service data in a unicast manner, or switches from receiving the multicast service data in a multicast manner to receiving the multicast service data in a unicast manner. The access network device sends a switching instruction to the user equipment, and the user equipment switches the manner of receiving the service data.

In <FIG>, at a moment t1, the access network device determines that the user equipment C switches from receiving the multicast service data in the multicast manner to receiving the multicast service data in the unicast manner; and at the moment t2, the access network device determines that the user equipment C switches from receiving the multicast service data in the unicast manner to receiving the multicast service data in the multicast manner.

In this embodiment, the access network device may instruct, by using signaling, the user equipment C to switch from receiving the multicast service data in the multicast manner to receiving the multicast service data in the unicast manner. In step <NUM>, the manner of receiving the multicast service data by the user equipment may be switched through radio bearer reconfiguration. To perform switching more quickly, and match a fast channel status change, when the multicast service is established in step <NUM>, the access network device sends both the multicast configuration information and the unicast configuration information to the user equipment. When the manner needs to be switched, the access network device instructs, by using the switching instruction, the user equipment to switch the manner of receiving the multicast service data, or activates a specified manner of receiving the multicast service data. The switching instruction may be, for example, sent by using a physical layer downlink control indicator (downlink control indicator, DCI) or a MAC layer control element (control element, CE).

In the following example, a manner of receiving multicast service data by user equipment may switch between a multicast manner and a unicast manner. In the following example, the multicast service data needs to be sent to the user equipment in the unicast manner, and subsequently, the user equipment may receive the multicast service data in the multicast manner.

<FIG> shows a scenario in which a service triggers switching of a receiving manner. Because in a multicast manner, sending and receiving are usually performed at a fixed rate, if user equipment has a specific requirement, for example, needs to receive multicast service data at a higher rate, the user equipment may interact with an access network device by using signaling, and the access network device sends the multicast service data to the user equipment in a unicast manner. As shown in the scenario marked in <FIG>, the user equipment is receiving a video service. In a current common video encoding/decoding manner H. <NUM>, image frames are organized by using a sequence as a unit, and there are an I-frame, a B-frame, and a P-frame, where the I-frame is a full-frame compressed coded frame, and a complete image can be reconstructed during decoding by using only data of the I-frame. The B-frame and the P-frame are based on the I-frame and only a part that is different from the I-frame is transmitted. In video information, there is much same information between consecutive frames. Therefore, transmission of the same information can be reduced by using the B-frame/P-frame, thereby saving a transmission bandwidth. However, when the user equipment receives a new video, for example, clicks a new video, drags a progress bar, or switches a channel, an I-frame needs to be decoded first to successfully play the new video. In a unicast service, a server always sends data starting from an I-frame. However, in a multicast service, data is sent to a plurality of users at a same time, a newly joined user cannot ensure that when the user joins the multicast service, the user can receive a new I-frame. As shown in <FIG>, the user equipment starts to receive the multicast service data at a moment T1, and at this moment, a previous I-frame has been sent, a next I-frame is not sent, and the user equipment cannot correctly construct a complete video frame based on a P-frame and a B-frame that are currently received. Therefore, the user equipment can be only in a black screen state, and cannot immediately start to play a video. In this case, the user equipment may instruct the access network device to send the multicast service data in the unicast manner, to send, at a relatively high rate, an I-frame and the B-frame that are not received before, so that the user equipment can immediately start to play the video. When a data frame received by the user equipment in the unicast manner is greater than or equal to a sequence number of a current multicast data frame, the user equipment may release a unicast resource, and switch back to the multicast manner to receive the multicast service data.

A core network device may distinguish between data packets of different types by using tags in headers of the data packets, and the access network device may send the multicast service data based on indication information of the core network device, and buffer the multicast service data for a time. When new user equipment joins a multicast group or original user equipment starts to receive the multicast service data, the access network device may first send a segment of the multicast service data in the unicast manner. The multicast service data may be buffered by the access network device previously, and a sent start data packet may be within a period of time or start from a latest special type of data packet. If the access network device does not buffer the multicast service data that needs to be sent in the unicast manner, the multicast service data sent in the unicast manner may be sent by the core network device to the access network device. In a process of establishing or updating a multicast session, a unicast sending channel is established between the core network device and the access network device, to send the multicast service data. After the multicast service data that needs to be sent in the unicast manner is sent, the access network device or the user equipment switches back to the multicast manner to receive the multicast service data. In the foregoing scenario in which the core network device sends the multicast service data to the access network device, a core network may notify an access network of when to end sending of the multicast service data in the unicast manner, and separate signaling or a special identifier (for example, an end marker of a GTP-U) in a data packet may be used to indicate that sending of the multicast service data in the unicast manner ends. Similarly, the access network device may also instruct, by using dedicated signaling or an end data packet identifier, the user equipment to switch back to the multicast manner to receive the multicast service data. A video playing scenario is used as an example. For a specific process, refer to <FIG>. The process includes the following steps.

<NUM>: After a multicast session is established, user equipment joins a multicast group, or user equipment switches to receive multicast service data in a multicast manner, and establishes a radio bearer applicable to receiving the multicast service data in the multicast manner.

In this step, the user equipment may be user equipment that newly joins the multicast group, or may be existing user equipment in the multicast group.

<NUM>: An access network device determines that a part of the multicast service data needs to be sent to the user equipment in a unicast manner, and establishes a radio bearer with the user equipment, to send the multicast service data in the unicast manner.

A manner in which the access network device determines that the multicast service data needs to be sent to the user equipment in the unicast manner may include: specifying, by a core network device in protocol headers of data packets, that some data packets, such as a B-frame and a P-frame, need to be sent in the unicast manner; or the access network device parses a received data packet, and if finding that the data packet is a B-frame or a P-frame, the access network device determines that the data packet needs to be sent in the unicast manner.

<NUM>: The access network device sends, to the user equipment, the multicast service data that needs to be sent in the unicast manner.

The multicast service data sent by the access network device in the unicast manner may be buffered by the access network device. For example, during a process of performing a multicast service, the access network device buffers a recently sent I-frame and data between the I-frame and a next I-frame that is not received, and uses the buffered data as the multicast service data that needs to be sent in the unicast manner. Alternatively, the multicast service data may be data obtained from a source end of the multicast service. How to specifically obtain the multicast service data that needs to be sent in the unicast manner is not uniquely described in this embodiment of the present invention.

<NUM>: After sending the multicast service data that needs to be sent in the unicast manner, the access network device switches the radio bearer between the access network device and the user equipment back to the radio bearer used to receive the multicast service data in the multicast manner.

A switching manner may be sending, by the access network device, a switching instruction to the user equipment, or may be reconfiguring the radio access bearer, to enable a newly established radio bearer to be adapted to send the service data in the multicast manner.

<NUM>: The access network device sends the multicast service data to the user equipment in the multicast manner.

When the multicast manner is switched to the unicast manner, to ensure continuity of a multicast service, after switching to the unicast manner, user equipment may notify, by using a data packet number, an access network device of a data packet that starts to be sent in the unicast manner. For example, the access network device may be notified of a sequence number of a last successfully received data packet, or a sequence number of a next data packet that needs to be received; or the access network device may be notified by using a PDCP status report, where the PDCP status report is used to indicate that in data packets from a sequence number N to a sequence number M, an identifier of a data packet that is successfully received by the user equipment is <NUM>, and an identifier of a data packet that is not successfully received is <NUM>. Based on information sent by the user equipment, the access network device sends, in the unicast manner, a data packet that is not received by the user equipment, to ensure service continuity of the user equipment.

The unicast manner and the multicast manner can be switched to each other and can cooperate with each other. Currently, multicast service data is transmitted in the multicast manner without feedback information, and cannot be retransmitted. Therefore, a multicast service can be transmitted only in a relatively conservative robust transmission manner, to ensure that a terminal can successfully receive the multicast service data once in most scenarios. Because the conservative transmission manner needs to sacrifice resource efficiency, in the multicast enhancement solution of this application, a feedback mechanism of user equipment participating in a multicast service may be introduced. After the user equipment in a multicast group fails to receive multicast service data, an access network device retransmits the multicast service data. In this embodiment of the present invention, the multicast service data may be retransmitted in the unicast manner.

As shown in <FIG> and <FIG>, each of A, B, and C represents user equipment in a multicast group. Channel quality of the user equipment C deteriorates from T1 to T2, for example, the user equipment C enters a cell edge or a channel is blocked, so that the user equipment C fails to receive multicast service data. The user equipment C may notify, by using feedback information, an access network device of a data packet that needs to be retransmitted. In a process of retransmitting a data packet, the user equipment may receive the multicast service data in both a multicast manner and a unicast manner. With assistance of the unicast manner, reliability of the multicast manner can be higher, and the multicast service data can be sent in a more efficient multicast manner.

A manner in which the user equipment notifies the access network of the data packet that needs to be retransmitted may be specifically as follows:
The user equipment specifies, by using a fixed relationship between feedback information and a retransmitted data packet, for example, a manner of sending a NACK by using a physical layer feedback channel, that the access network device retransmits, in the unicast manner, a data packet sent in an (n-k)th subframe, where n is a subframe for sending the NACK. Alternatively, the user equipment may explicitly indicate, by using an explicit data packet number, for example, an RLC or PDCP status report, that one or more data packets whose sequence numbers are (sequence number x, SNx) needs to be retransmitted.

In the foregoing embodiments, several typical scenarios and procedures in which the multicast service is related to the air interface transmission are described by using examples. The following embodiments focus on describing user plane protocol stack structures of the access network device and the user equipment in a centralized manner.

<FIG> and <FIG> and <FIG> show protocol stack structures for implementing multicast and unicast cooperation at a PDCP layer, including a protocol stack structure on a transmit side of a multicast user plane of an access network device and a protocol stack structure in which user equipment <NUM> to user equipment n are used as a receive side. For a service interface of an RLC layer, refer to multicast- and unicast-related protocol specifications, and details are not described herein again.

The access network device establishes multicast bearers for different multicast sessions, and each multicast bearer corresponds to one multicast PDCP layer. Mapping function entities from various services to the bearer may be further added before the PDCP layer. For example, in <NUM>, there is an SDAP (service data adaptation protocol, service data adaptation protocol) layer above the PDCP layer, and the SDAP layer is used for mapping from a flow (flow) to the PDCP layer, and is irrelevant to a function of core content in this embodiment of the present invention, so that descriptions are omitted subsequently. The multicast PDCP adds a sequence number (sequence number, SN) to the multicast service SDU, and the SN is used by a receive side for data packet sorting and retransmission requests. The multicast PDCP layer can further encrypt a multicast data packet. The multicast PDCP layer uses a service encryption key instead of a terminal encryption key, to ensure that different users can decrypt the multicast PDCP layer. The PDCP layer may also perform header compression on a header of the data packet. Then, a PDCP header is added to the data packet, and the data packet with the PDCP header is sent to a replication and routing module. A data packets sent in the unicast manner at a bottom layer can be replicated and then buffered to a queue for processing a subsequent retransmission request. A data packet sent in the multicast manner may not need to be replicated and buffered.

After processing the data packet, the PDCP layer sends obtained packet data unit (packet data unit, PDU) data to an RLC module. Because feedback cannot be performed in the multicast manner, a multicast RLC entity may further map the data to a multicast MAC entity at the bottom layer by using a UM mode, and send, by using an independent HARQ entity and an independent scheduling identifier (such as a G-RNTI), the data on a multicast physical channel provided by a corresponding multicast physical layer. For user equipment in a unicast state, the multicast PDCP layer may send, based on member information of a multicast group, the data to a unicast RLC entity that is associated with a multicast service and that is of the corresponding user equipment. Herein, the RLC entity may select an AM mode or the UM mode, and then the RLC entity of the user equipment sends the data to a unicast MAC entity. The unicast HARQ entity of the user equipment is responsible for unicast scheduling, and sending HARQ data at a unicast physical layer.

It can be learned from the foregoing scenario descriptions that the user equipment may use the unicast manner or the multicast manner, or may use a hybrid mode in which both the unicast manner and the multicast manner work. When only one receiving or sending manner is used, the user equipment may receive the data packet by using the multicast RLC entity or the unicast RLC entity based on a configuration of the access network device, and then deliver the data packet to the multicast PDCP layer. In the hybrid mode, the multicast RLC entity and the unicast RLC entity may simultaneously submit the PDU data to the multicast PDCP layer, and the PDCP layer sorts or repeatedly determines, based on the SN, the PDU data submitted by the RLC entity. When the PDCP layer determines that a data packet is lost, for example, when SNs are inconsecutive, the PDCP layer may initiate a retransmission request, for example, notify the access network device of a missing data packet SN number by using a PDCP status report. The retransmission request is fed back to a unicast RLC entity corresponding to the access network device in the unicast manner, and is submitted by the unicast RLC entity of the access network device to the multicast PDCP layer. The multicast PDCP layer retransmits the PDU data with the corresponding SN by using the unicast RLC entity. In this way, data retransmission is complete.

<FIG> shows a protocol stack structure in which a multicast manner and a unicast manner are switched at an RLC layer. A multicast RLC entity is responsible for segmenting a data packet, and then sends the data packet to a multicast MAC entity for sending. For user equipment that uses the unicast manner, the multicast RLC entity replicates PDU data and sends the PDU data to a unicast MAC HARQ entity corresponding to the user equipment for unicast sending. When the user equipment is in a hybrid mode and receiving in the multicast manner fails, an ARQ entity of the user equipment initiates an RLC status report, to request a multicast RLC entity of an access network device to retransmit PDU data corresponding to a missing RLC SN identifier. Compared with the method in which the switching is controlled by the PDCP layer, retransmission initiated by the multicast RLC entity may be performed at an RLC PDU granularity, thereby avoiding retransmission of entire PDCP PDU data. The entire PDCP PDU data is usually retransmitted at an IP packet granularity, and the multicast RLC entity may segment the multicast PDCP PDU data into several segments based on a resource status of an air interface, so that a problem of a waste of retransmission resources caused by a large retransmission granularity is avoided. When the user equipment requests to retransmit data, the multicast RLC entity may further segment, based on a current radio resource status of the user equipment, the RLC PDU data again that needs to be retransmitted.

The embodiments of the present invention may be applied to various radio access standards, and cooperation between the multicast manner and the unicast manner is implemented based on the PDCP layer, so that, for example, LTE multicast, NR unicast, LTE multicast, or WLAN unicast is implemented.

An embodiment of the present invention further provides an access network device. As shown in <FIG>, the access network device includes:.

In an optional implementation, the access network device further includes:
a configuration sending unit <NUM>, configured to send configuration information to the user equipment, where the configuration information is used to receive the multicast service data.

In an optional implementation, the configuration information includes:
at least one of configuration information of a multicast bearer, multicast session information corresponding to the multicast bearer, logical channel information of the multicast bearer, multicast scheduling identifier information, information about a transmission channel for sending the multicast service data in the multicast manner, information about a transmission channel for sending the multicast service data in the unicast manner, multicast logical channel information, measurement configuration information of the transmission channel of the multicast service data, and multicast-associated unicast configuration information.

In an optional implementation, the access network device further includes:
an information receiving unit <NUM>, configured to receive multicast service information sent by the user equipment or a core network device, where the multicast service information is used to instruct the user equipment to receive the multicast service data, and the multicast service information includes identifier information of the user equipment and identifier information of a multicast service.

In an optional implementation, that the information receiving unit <NUM> is configured to receive multicast service information sent by the user equipment or a core network device includes:.

In an optional implementation, the access network device further includes:.

In an optional implementation, the configuration information includes first multicast configuration information and second multicast configuration information; and
the indication information indicates that the manner of receiving the multicast service data includes the multicast manner, and the indication information indicates that the first multicast configuration information or the second multicast configuration information is used to receive the multicast service data.

In an optional implementation, the at least one data packet is multicast service data that has been sent in the multicast manner and that is buffered in the access network device, or multicast service data that has been sent in the multicast manner and that is received from a multicast service data source.

In an optional implementation, the data sending unit <NUM> is configured to: send to-be-sent multicast service data to a unicast radio link control RLC entity by using a packet data convergence protocol PDCP layer, and send the to-be-sent multicast service data in the unicast manner.

In an optional implementation, the data sending unit <NUM> is further configured to: replicate the to-be-sent multicast service data at the packet data convergence protocol PDCP layer, and store the to-be-sent multicast service data.

In an optional implementation, the data sending unit <NUM> is configured to: send to-be-sent multicast service data to a multicast radio link control RLC entity by using a multicast packet data convergence protocol PDCP layer, where the multicast radio link control RLC entity sends the to-be-sent multicast service data to a unicast medium access control MAC entity, and the unicast medium access control MAC entity sends the to-be-sent multicast service data in the unicast manner.

An embodiment of the present invention further provides user equipment. As shown in <FIG>, the user equipment includes:.

In an optional implementation, the user equipment further includes:
a configuration receiving unit <NUM>, configured to receive configuration information sent by the access network device, where the configuration information is used to receive the multicast service data.

In an optional implementation, the user equipment further includes:
an information sending unit <NUM>, configured to send multicast service information to the access network device, where the multicast service information is used to instruct the user equipment to receive the multicast service data, and the multicast service information includes identifier information of the user equipment and identifier information of a multicast service.

In an optional implementation, that the information sending unit <NUM> is configured to send multicast service information to the access network device includes: sending multicast member change information to the access network device.

In an optional implementation, the user equipment further includes:
an indication sending unit <NUM>, configured to instruct the access network device to send at least one data packet in the multicast service data in the unicast manner.

In an optional implementation, the user equipment further includes:.

In an optional implementation, the status sending unit <NUM> is further configured to perform packet loss detection at a packet data convergence protocol PDCP layer to obtain the receiving status information.

In an optional implementation,
the data receiving unit <NUM> is further configured to send, at a unicast radio link control RLC entity, the received multicast service data to the multicast packet data convergence protocol PDCP layer.

<FIG> shows a device <NUM> according to an embodiment of the present invention. The device <NUM> includes a processor <NUM>, a memory <NUM>, and a transceiver <NUM>. The processor <NUM>, the memory <NUM>, and the transceiver <NUM> are connected to each other by using a bus.

The memory <NUM> includes but is not limited to a random access memory (random access memory, RAM), a read-only memory (read-only memory, ROM), an erasable programmable read-only memory (erasable programmable read only memory, EPROM), or a compact disc read-only memory (compact disc read-only memory, CD-ROM). The memory <NUM> is configured to store a related instruction and related data. The transceiver <NUM> is configured to receive and send data.

The processor <NUM> may be one or more central processing units (central processing unit, CPU). When the processor <NUM> is one CPU, the CPU may be a single-core CPU or a multi-core CPU.

The processor <NUM> in the device <NUM> is configured to read program code stored in the memory <NUM>,
The memory <NUM> stores program code.

The processor <NUM> is configured to read the program code, and cooperate with the transceiver <NUM> to implement any method performed by the access network device or the user equipment according to any one of the embodiments of the present invention. The transceiver <NUM> may implement functions of various units that implement reception and transmission functions in the foregoing user equipment or the access network device, and another function is implemented by the processor <NUM>.

<FIG> shows user equipment <NUM> according to some embodiments of this application. As shown in <FIG>, the user equipment <NUM> may include input/output modules (including an audio input/output module <NUM>, a key input module <NUM>, a display <NUM>, and the like), a user interface <NUM>, one or more processors <NUM>, a transmitter <NUM>, a receiver <NUM>, a coupler <NUM>, an antenna <NUM>, and a memory <NUM>. These components may be connected by using a bus or in another manner. In <FIG>, an example in which the components are connected by using a bus is used.

The antenna <NUM> may be configured to convert electromagnetic energy into an electromagnetic wave in free space, or convert an electromagnetic wave in free space into electromagnetic energy in a transmission line. The coupler <NUM> is configured to divide a mobile communications signal received by the antenna <NUM> into a plurality of signals, and allocate the plurality of signals to a plurality of receivers <NUM>.

The transmitter <NUM> may be configured to transmit a signal output by the processor <NUM>.

The receiver <NUM> may be configured to receive a mobile communications signal received by the antenna <NUM>.

In some embodiments of this application, the transmitter <NUM> and the receiver <NUM> may be considered as a wireless modem. In the user equipment <NUM>, there may be one or more transmitters <NUM> and one or more receivers <NUM>.

In addition to the transmitter <NUM> and the receiver <NUM> shown in <FIG>, the user equipment <NUM> may further include other communications components, for example, a GPS module, a Bluetooth (Bluetooth) module, and a wireless fidelity (wireless fidelity, Wi-Fi) module. In addition to the foregoing described wireless communications signal, the user equipment <NUM> may support another wireless communications signal, for example, a satellite signal or a short wave signal.

The input/output modules may be configured to implement interaction between the user equipment <NUM> and a user/an external environment, and may mainly include the audio input and output module <NUM>, the key input module <NUM>, the display <NUM>, and the like. Specifically, the input/output modules may further include a camera, a touchscreen, a sensor, and the like. All the input/output modules communicate with the processor <NUM> by using the user interface <NUM>.

The memory <NUM> is coupled to the processor <NUM>, and is configured to store various software programs and/or a plurality of sets of instructions. Specifically, the memory <NUM> may include a high-speed random access memory, and may include a non-volatile memory, for example, one or more magnetic disk storage devices, a flash memory device, or another non-volatile solid-state storage device. The memory <NUM> may store an operating system (briefly referred to as a system below), for example, an embedded operating system such as Android, iOS, Windows, or Linux. The memory <NUM> may further store a network communications program. The network communications program may be configured to communicate with one or more additional devices, one or more user equipments, or one or more network devices. The memory <NUM> may further store a user interface program. The user interface program may vividly display content of an application program by using a graphical operation interface, and receive control operations of a user for the application program by using input controls such as a menu, a dialog box, and a key.

In some embodiments of this application, the memory <NUM> may be configured to store a program for implementing, on a side of the user equipment <NUM>, the system message receiving method according to one or more embodiments of this application. For implementation of the system message receiving method according to one or more embodiments of this application, refer to subsequent embodiments.

The processor <NUM> may be configured to read and execute a computer-readable instruction. Specifically, the processor <NUM> may be configured to: invoke a program stored in the memory <NUM>, and execute an instruction included in the program, to implement the method in subsequent embodiments.

It may be understood that the user equipment <NUM> may be user equipment in the communications system described above in the embodiments of the present invention, and may be implemented as a mobile device, a mobile station (mobile station), a mobile unit (mobile unit), a radio unit, a remote unit, a user agent, a mobile client, or the like.

It should be noted that the user equipment <NUM> shown in <FIG> is merely an implementation of the embodiments of this application. In an actual application, the user equipment <NUM> may include more or fewer components, and this is not limited herein. In this embodiment, the processor <NUM> may correspond to the processor shown in <FIG>. The transmitter <NUM> and the receiver <NUM> may respectively correspond to units for implementing a transmission function and a reception function.

An embodiment of the present invention further provides a storage medium. The storage medium stores program code, and the program code includes a program instruction. When the program instruction is executed by a processor, the processor cooperates with a transceiver to perform the foregoing method according to any one of the embodiments of the present invention.

An embodiment of the present invention further provides a computer program product. The computer program product includes a program instruction. When the program code is executed by a processor, the processor cooperates with a transceiver to perform the foregoing method according to any one of the embodiments of the present invention.

Claim 1:
A communication method performed by an access network device, the method comprising the steps:
• sending indication information to a user equipment, wherein the indication information is used to indicate a receiving manner of multicast service data of a multicast service, and the receiving manner comprises a unicast manner, a multicast manner or a hybrid manner, wherein the hybrid manner comprises the unicast manner and the multicast manner;
• if the indication information indicates that the receiving manner of the multicast service data is the unicast manner, sending the multicast service data to a unicast radio link control, RLC, entity in the access network device through a multicast packet data convergence protocol, PDCP, layer, and sending the multicast service data in the unicast manner to the user equipment;
• if the indication information indicates that the receiving manner of the multicast service data is the multicast manner, sending the multicast service data to a multicast RLC entity in the access network device through the multicast PDCP layer, and sending the multicast service data in the multicast manner to the user equipment; and
• if the indication information indicates that the receiving manner of the multicast service data is the hybrid manner:
o sending the multicast service data to the multicast RLC entity and the unicast RLC entity in the access network device through the multicast PDCP layer, and sending the multicast service data in the multicast manner and the unicast manner to the user equipment.