HK1077422B - Mbms (multimedia broadcast/multicast service) service providing method in mobile communication system - Google Patents

Description

Method for providing multimedia broadcast/multicast service in mobile communication system

Technical Field

The present invention relates to a method for providing a multimedia broadcast/multicast service (MBMS) in a Universal Mobile Telecommunications System (UMTS), and more particularly, to a method for transmitting multicast data through a downlink shared channel.

Background

The development of wireless mobile communications has led to user preferences for using mobile phones rather than wired phones. However, for a service providing a large amount of data via a radio access network, for example, when the amount of data provided to a mobile phone through the radio access network is larger than that generally provided by voice communication, the performance of the mobile communication system cannot match the existing wired communication system. Therefore, technology development of IMT-2000 (a communication system allowing high-capacity data communication) is performed by a plurality of companies and organizations, and standardization of the technology is actively being performed.

The Universal Mobile Telecommunications System (UMTS) is a third generation mobile communication system that has evolved from a standard known as the global system for mobile communications (GSM). This standard is a european standard intended to provide improved mobile communication services based on the GSM core network and wideband code division multiple access (W-CDMA) technology.

12 months 1998, ETSI in Europe, ARIB/TTC in Japan, T1 in the United states, and TTA in Korea form the third Generation partnership project (3 GPP). The 3GPP created detailed specifications for UMTS technology. In order to achieve fast and efficient technology development of UMTS, five Technical Specification Groups (TSGs) have been created in 3GPP to perform standardization of UMTS, considering independent characteristics of network components and their operation.

Each TSG develops, approves, and manages standard specifications in the related art. Among these groups, the Radio Access Network (RAN) group (TSG-RAN) develops functions, requirements and interfaces for the UTMS Terrestrial Radio Access Network (UTRAN), which is a new radio access network for supporting the W-CDMA access technology in UMTS.

Fig. 1 shows a network structure of a general UMTS.

As shown in fig. 1, UMTS is largely divided into a terminal (UE: user equipment), UMTS Terrestrial Radio Access Network (UTRAN), and a core network.

The UTRAN includes one or more Radio Network Subsystems (RNSs). Each RNS includes a Radio Network Controller (RNC) and one or more node bs (nodebs) managed by the RNC.

The node B is managed by the RNC to receive information transmitted from a physical layer of a terminal (such as a mobile station, user equipment, and/or subscriber unit) through an uplink and transmit data to the terminal through a downlink. Thus, the node B functions as an access point of the UTRAN for the terminal.

The RNC performs functions including allocation and management of radio resources and functions as an access point to the core network.

One of the main functions of UTRAN is to establish and maintain a Radio Access Bearer (RAB) for a call connection between a terminal and a core network. The core network applies end-to-end quality of service (QoS) requirements to the RAB, and accordingly, the UTRAN can satisfy the end-to-end QoS requirements by establishing and maintaining the RAB.

The RAB service is divided into an Iu bearer service and a radio bearer service with a lower conceptual level. The Iu bearer service handles reliable user data transmission between the UTRAN and the border nodes of the core network, while the radio bearer service handles reliable user data transmission between the terminal and the UTRAN.

The core network includes a Mobile Switching Center (MSC) and a Gateway Mobile Switching Center (GMSC) coupled together to support circuit-switched (CS) services. The core network also includes a Serving GPRS Support Node (SGSN) and a gateway GPRS support node coupled together for supporting Packet Switched (PS) services.

Services provided to a specific terminal are roughly divided into a Circuit Switched (CS) service and a Packet Switched (PS) service. For example, a general voice session service is a circuit switched service, and a web browsing service via an internet connection is classified as a Packet Switched (PS) service.

To support circuit switched services, the RNC is connected to the MSC of the core network and the MSC is connected to the GMSC that manages the connection with other networks. To support packet switched services, the RNC is connected to the SGSN and GGSN of the core network. The SGSN supports packet communications with the RNC and the GGSN manages connections with other packet switched networks, such as the internet.

There are many types of interfaces between network components that allow the network components to send and receive information to each other. The interface between the RNC and the core network is defined as the Iu interface. Specifically, an Iu interface for a packet-switched system between the RNC and the core network is defined as "Iu-PS", and an Iu interface for a circuit-switched system between the RNC and the core network is defined as "Iu-CS".

A Radio Network Temporary Identifier (RNTI) is used to identify a terminal when maintaining a connection between the terminal and the UTRAN. Four RNTIs are defined: S-RNTI, D-RNTI, C-RNTI and U-RNTI. The S-RNTI (serving RNC RNTI) is allocated by the SRNC (serving RNC) when setting up a connection between the terminal and the UTRAN. The S-RNTI is information by which the SRNC identifies a corresponding terminal.

D-RNTI (drift RNC RNTI) is allocated by DRNC (drift RNC) when handover occurs between RNCs according to movement of a terminal. The D-RNTI is information by which the DRNC identifies a corresponding terminal.

The C-RNTI (cell RNTI) is information by which a terminal is identified in a CRNC (controlling RNC). When a terminal enters a new cell, it is assigned a new C-RNTI value by the CRNC.

U-RNTI (UTRAN RNTI) includes SRNC identity and S-RNTI. Because the SRNC and the terminals in the SRNC can be identified, the U-RNTI can be considered to provide absolute identification information.

When transmitting data via a common transport channel, the MAC-C/sh entity adds C-RNTI or U-RNTI to a header of the transmitted MAC PDU. A UE ID type indicator indicating the type of RNTI added in the header of the MAC PDU is also added to the header.

Fig. 2 illustrates a radio protocol between a terminal and a UTRAN based on the 3GPP radio access network standard.

Referring to fig. 2, the radio access interface protocol includes a horizontal layer consisting of a physical layer, a data link layer, and a network layer, and a vertical plane consisting of a user plane for transmitting data information and a control plane for transmitting control signals.

User traffic information such as voice or IP packets is sent to the user plane area. Control information such as network interfaces or maintenance and management of calls is sent to this area of the control plane.

In fig. 2, protocol layers may be divided into a first layer (L1), a second layer (L2), and a third layer (L3) based on the lower three layers of the Open System Interconnection (OSI) well known in the art of communication systems.

The first layer (physical layer (PHY)) provides an information transfer service to a higher layer by using a different radio transmission technology.

The first layer is connected to the medium access control layer through a transport channel, and data is transferred between the medium access control layer and the physical layer through the transport channel.

Data is transmitted through a transport channel according to a Transmission Time Interval (TTI). The physical channel transmits data by segmenting data based on a time unit of a certain length, which is called a frame. In order to synchronize the transport channel between the UE and the UTRAN, a Connection Frame Number (CFN) is used. In addition to the Paging Channel (PCH), the CFN value ranges from 0 to 255 in the case of transport channels. In other words, the CFN is repeatedly recycled at a period of 256 frames.

In addition to the connection frame number, a System Frame Number (SFN) is also used for synchronizing the physical channels. The SFN has a value range of 0 to 4095 and is repeatedly used with a period of 4096 frames.

The second layer (L2) includes a MAC layer, a Radio Link Control (RLC) layer, a broadcast/multicast control (BMC) layer, and a Packet Data Convergence Protocol (PDCP) layer.

A Medium Access Control (MAC) layer provides a reallocation service of MAC parameters for allocating and reallocating radio resources.

The MAC layer is connected to a Radio Link Control (RLC) layer (the RLC layer is an upper layer) through a logical channel, and provides different logical channels according to the kind of transmitted information. In general, a control channel is used when transmitting information of a control plane. The traffic channel is used when transmitting information of the user plane.

The MAC is divided into a MAC-b sublayer, a MAC-d sublayer, and a MAC-c/sh sublayer according to the kind of transport channel to be managed. The MAC-b sublayer manages a Broadcast Channel (BCH) for processing system information broadcasting, and the MAC-c/sh manages a shared transport channel such as a Forward Access Channel (FACH), a Downlink Shared Channel (DSCH), and the like, which are shared with other terminals.

In UTRAN, the MAC-c/sh sublayer is located at the Controlling Radio Network Controller (CRNC) for managing channels shared by each terminal in a cell, and thus each cell has one MAC-c/sh sublayer.

The MAC-d sublayer manages a Dedicated Channel (DCH), which is a dedicated transport channel for a specific terminal. Accordingly, the MAC-d sublayer is disposed at a Serving Radio Network Controller (SRNC) for managing the corresponding terminals, and each terminal also has one MAC-d sublayer.

The RLC layer supports reliable data transmission and may perform segmentation and concatenation functions on RLC Service Data Units (SDUs) from a higher layer. The RLC SDU transferred from the higher layer is sized according to the throughput capacity of the RLC layer, to which header information is added at the RLC layer, and then transferred to the MAC layer in the form of a Protocol Data Unit (PDU). The RLC layer includes an RLC buffer for storing RLC SDUs or RLC from a higher layer.

A broadcast/multicast control (BMC) layer performs a function of scheduling cell broadcast information (CB) transmitted from a core network and broadcasting the CB to user equipments located in a specific cell. At UTRAN, CB information transmitted from a higher layer is combined with information such as an information identifier, a sequence number, or a coding scheme, and transmitted to the RLC layer and the MAC layer through a Common Traffic Channel (CTCH), which is a logical channel, in the form of BMC information. In this case, the logical channel CTCH is mapped to a forward access channel (EACH), which is a transport channel, and a secondary common control physical channel (S-CCPCH), which is a physical channel.

The Packet Data Convergence Protocol (PDCP) layer, which is a higher layer of the RLC layer, allows data to be efficiently transmitted over a radio interface having a relatively small bandwidth through network protocols such as IPv4 and IPv 6. For this reason, the PDCP layer performs a function of reducing unnecessary control information, which is called header compression. In this regard, RFC2507 and RFC3095 (robust header compression: ROHC) may be used. ROHC is a header compression technique defined by an international standard organization called the internet engineering special working group (IETF). In these methods, since only information necessary for a header portion of data is transmitted, control information is transmitted, thereby reducing the number of data transmissions.

A Radio Resource Control (RRC) layer located at the bottom of the third layer (L3) is defined only in the control plane and controls logical channels, transport channels, and physical channels related to the setting, reconfiguration, and release of RBs. The RB refers to a service provided by the second layer for data transmission between the terminal and the UTRAN, and the setting of the RB refers to a process of stipulating characteristics of protocol layers and channels, which are necessary to provide a specific service, and setting respective detailed parameters and operation methods.

The RLC layer may belong to a user plane or a control plane according to the type of a layer connected to an upper layer of the RLC layer. If the RLC layer receives data from the RRC layer, the RLC layer belongs to the control plane. Otherwise, the RLC layer belongs to the user plane.

As shown in fig. 2, there may be several entities in one RLC layer or one PDCP layer. Since one terminal generally has a plurality of RBs and only one RLC entity and only one PDCP entity are used for one RB, there may be more than one layer.

The MAC-sublayer will now be described.

One of the main functions of the MAC layer existing between the RLC layer and the physical layer is to map logical channels and transport channels. The reason is that the channel processing methods of the upper and lower layers of the MAC layer are different. That is, at a higher layer of the MAC layer, data is separately processed by using a control channel of the control plane and a traffic channel of the user plane according to the content of data transmitted by the channel. Meanwhile, at a lower layer, data is separately processed by using a common channel and a dedicated channel according to whether channels are shared, and thus mapping between channels is important.

Fig. 3 illustrates a mapping relationship between logical channels and transport channels of a user equipment. In UTRAN, the arrows are pointing in opposite directions.

Another important function of the MAC layer is logical channel multiplexing. The MAC maps several logical channels to one transport channel, obtaining a multiplexing gain that improves the efficiency of use of the transport channel. Such multiplexing provides a much higher gain for intermittently transmitted data and packet data. Thus, the multiplexing function is used for Signaling Radio Bearers (SRBs) or Packet Service (PS) Radio Access Bearers (RABs). Since data is continuously transmitted in the Circuit Services (CS) RAB, the multiplexing function is not used. The SRB is an RB used particularly for exchanging RRC messages or NAS messages between the terminal and the UTRAN.

Accordingly, the MAC provides flexibility of channel selection and improves use efficiency of channel resources through channel mapping and logical channel multiplexing. In this case, additional functions are required to support channel mapping and logical channel multiplexing. Rather, the MAC performs four additional functions.

1. Processing of priorities

To support different channel mapping structures, the MAC performs a priority handling function. The priority processing includes two types: one is priority handling among several UEs, and the other is priority handling for one UE.

Priority handling among several UEs refers to the following case: data for several UEs is sent on the downlink over a common transport channel (FACH or DSCH). In this case, the MAC transmits data of the higher priority UE first. That is, the MAC allocates a common channel to each UE at every Transmission Time Interval (TTI) in time, thereby improving the use efficiency of channel resources. This is related to the dynamic scheduling function.

The priority handling for one UE refers to the following case: several logical channels belonging to the same UE are mapped onto one transport channel. The medium access control layer determines the priority according to the logical channel priority. This is related to the selection of the transport format combination, and the MAC selects a transport format combination that can transmit data of a higher priority logical channel first.

2. Selection of transport format combinations

The MAC transmits a Transport Block (TB) to the physical layer through a transport channel. The Transport Format (TF) means a rule of the size of data transmitted by one transport channel and the number of TBs. The MAC should even consider transport channel multiplexing of the physical layer when determining the transport format of a particular transport channel.

Transport channel multiplexing refers to mapping a plurality of channels to one code division multiplexed transport channel (CCTrCH). Although this function is performed in the physical layer, the MAC should consider each transport channel mapped to the same CCTrCH in determining the TF. In fact, the amount of data processed in the physical layer is the amount of data transmitted by the CCTrCH, and thus the MAC should determine the TF of each transport channel in consideration of the CCTrCH. In this case, the combination of transport formats is referred to as a Transport Format Combination (TFC). The TFC is not determined by the MAC itself but is selected from an available Transport Format Combination Set (TFCs) specified by the RRC layer. That is, the RRC specifies available TFCS for one CCTrCH for the MAC in an initial setting, and then the MAC selects one appropriate TFC from the TFCS every TTI.

The selection of a suitable TFC from a given TFCS per TTI is a function performed by the MAC which includes two steps.

First, the MAC forms an effective TFC set from TFCS allocated to the CCTrCH and selects an appropriate TFC in the effective TFC set. This valid TFC set is a set of TFCs actually available for the corresponding TTI among the allocated TFCs. The selection of the appropriate TFC takes into account the channel environment that is changing from time to time. When one TFC is selected for a corresponding TTI in the valid TFCS, the MAC selects a transport format combination based on the priority of the logical channel. That is, the MAC selects a TFC that can preferentially transmit data of a logical channel of higher priority, and such TFC selection is associated with the priority handling function.

As for the common transport channel RACH or CPCH of the uplink, since one transport channel constitutes one CCTrCH, this term is selected using TF for these channels.

3. Identification

The MAC needs to have an identification function. The reason is that: first, a common transport channel is shared by several UEs and therefore needs to be identified for each UE, and second, each logical channel needs to be identified due to logical channel multiplexing. Accordingly, the MAC inserts four types of fields for identification in the header of the MAC PDU, as shown in fig. 4. The fields of the MAC header do not necessarily exist, and their existence is determined by the mapping relationship between the logical channel and the transport channel.

When a dedicated logical channel such as DTCH or DCCH is mapped onto a common transport channel such as RACH, FACH, CPCH (control physical channel), DSCH, or Uplink Shared Channel (USCH), the terminal needs to be identified. To identify each UE, the MAC adds a Radio Network Temporary Identifier (RNTI) to a user equipment-ID field of the header and transmits it, wherein the RNTI is identification information for the terminal. The RNTI includes UTRAN radio network temporary identifier (U-RNTI), cell radio network temporary identifier (C-RNTI), and downlink shared channel radio network temporary identifier (DSCH-RNTI), so the MAC also adds a UE-ID type field to indicate which RNTI is used and transmitted.

The identification of the dedicated logical channel is achieved by means of the C/T field. The reason is that: first, several dedicated channels can be mapped to one transport channel, unlike other logical channels; second, dedicated logical channels are handled in the MAC-d sublayer of the Serving Radio Network Controller (SRNC), while other logical channels are provided in the MAC-c/sh sublayer of the Controlling Radio Network Controller (CRNC). Dedicated logical channels mapped to the same transport channel each have a logical channel identification, which is used as a C/R field value. The C/T field is not used if there is only one dedicated logical channel in the transport channel.

Fig. 5 illustrates MAC header information according to a mapping relationship between a dedicated logical channel and a transport channel in accordance with the conventional art.

As shown in fig. 5, the C/T field exists only when several dedicated logical channels (DCCHs or DTCHs) are mapped, 'N' means that there is no header, 'one' means that there is no mapping region. In addition, since the UE-ID field and the UE-ID type field coexist, they can be simply represented by UE-ID.

4. Traffic measurement and transport channel type switching

To support RRC when dynamically controlling radio bearers, MAC performs functions of measuring traffic and changing transport channel types.

The measurement of the traffic is performed on the transmission channel. The MAC measures the size of the RLC buffer of each logical channel mapped to the transport channel every TTI and adds the sizes to calculate the traffic volume of the transport channel. The traffic volume of the transport channel indicates the amount of data to be transmitted by the transport channel. The MAC reports the measurement result to the RRC, and the measurement result is used as a basis for the RRC to determine whether the corresponding transport channel is sufficient to transmit the measured amount of data.

The MAC reports the measurement results to the RRC. Unlike the measurement of traffic volume performed at every TTI, the measurement result reporting is performed only when a specific condition is satisfied. The report type includes an event-triggered method of reporting the measurement result when the measurement result exceeds a critical value, and a periodic method of reporting the measurement result at every predetermined time.

The RRC, upon receiving the measurement results, determines whether the current transport channel is suitable for each radio bearer. The RRC commands the MAC to change the transport channel of the radio bearer if the current transport channel is not suitable. That is, the change of the transport channel type is a function of efficiently managing the transport channel resources by selectively using an appropriate transport channel based on a given amount of data.

When using DCH, the efficiency of code division channels is problematic and there may not be enough codes for data transmission with bursty characteristics resulting from data congestion at a particular time during a communication session. To solve this problem, several encryption codes may be used. However, the complexity of the receiver may increase without increasing the efficiency of the code division channel.

The DSCH is a channel shared by several users transmitting dedicated control or traffic data. By performing code multiplexing, several users can share one channel. Accordingly, the DSCH may be defined as a series of code sets.

Unlike the uplink, code shortage occurs in the downlink because code data that one sector can have in one base station is limited because of the spreading factor. For high transmission rates, a low spreading factor must be used, thereby reducing the number of physical channels.

In addition, such data services typically have a bursty nature. Therefore, if one channel is continuously allocated to one service, the code cannot be effectively used.

To solve these problems, a method is adopted in which one channel is shared by a plurality of users. In order to share one channel, code multiplexing is used. Code allocation, e.g. time multiplexing, is performed for each radio frame.

We will now describe a multimedia broadcast/multicast service (MBMS).

CBS has limitations. First, the maximum size of a CBS message is limited to 1230 octets. Therefore, CBS messages are not suitable for broadcasting or multicasting multimedia data. Second, because CBS messages are broadcast to each terminal in a particular cell, multicasting to provide services only to a particular group of terminals may not be wireless. For these reasons, a new service called MBMS has been proposed.

The MBMS is a service for transmitting multimedia data such as audio, video or image data to a plurality of terminals using a unidirectional point-to-multipoint bearer service. MBMS is classified into a broadcast mode and a multicast mode. In other words, the MBMS is divided into an MBMS broadcast service and an MBMS multicast service.

1. The user receives a service announcement provided by the network. The service announcement indicates a list of services to be provided and provides related information to the terminal.

2. The network sets a bearer (bearer) for the corresponding broadcast service.

3. The user receives a service notification provided by the network. The service notification provides information on broadcast data transmitted to the terminal.

4. The user receives broadcast data from the network.

5. The network releases the bearer for the corresponding broadcast service.

The MBMS broadcast mode is a service for transmitting multimedia data to each user within a broadcast area. The broadcast area refers to an area where a broadcast service is available. There may be one or more broadcast areas in a Public Land Mobile Network (PLMN), one or more broadcast services may be provided in one broadcast area, and one broadcast service may be provided to several broadcast areas.

The MBMS multicast mode is a service for transmitting multimedia data only to a specific user group within a multicast area. The multicast area refers to an area where multicast services are available. One or more multicast areas may exist in one PLMN, one or more multicast services may be provided in one multicast area, and one multicast service may be provided to several multicast areas.

In the multicast mode, to receive a specific multicast service, a user needs to join a certain multicast group. Here, the multicast group means a user group receiving a specific multicast service, and the joining means a behavior of being allowed to join the multicast group for receiving the specific multicast service.

1. For subscribing to a multicast subscription group. Subscription involves establishing a relationship between a service provider and a user. The multicast subscription group is a group of users who have completed the subscription process.

2. Users who have subscribed to the multicast subscription group receive an announcement of a service provided by the network. The service announcement indicates a list of services provided and provides related information to the terminal.

3. In order for a user who has subscribed to the multicast subscription group to receive a particular multicast service, the user must join the multicast group. A multicast group is a group of users that receive a particular multicast service joining the multicast group, including joining a multicast group intended to receive the particular multicast service. Joining a multicast group is also known as MBMS multicast activation. With MBMS multicast activation, a user can receive specific broadcast data.

4. The network sets up a bearer for the corresponding multicast service.

5. A user joining a multicast group receives a service notification provided by the network. The service notification provides information about multicast data transmitted to the terminal.

6. The user receives multicast data from the network.

7. The network releases the bearer for the corresponding broadcast service.

MBMS data is transmitted from the RNC to the base station and the terminal by using services of the PDCP layer, the RLC layer, the MAC layer, and the physical layer located on the user plane of the UTRAN protocol. That is, MBMS data transmitted from a Core Network (CN) is header-compressed at a PDCP layer and transferred as an RLC Unacknowledged Mode (UM) entity through an RLC UM access point (SAP), and then the RLC UM entity is transferred to a MAC layer through a common traffic channel, a logical channel.

The MAC layer adds a MAC header to the received MBMS data and transfers it to a physical layer of the base station through a common transport channel. Then, the MBMS data is encoded and modulated at a physical layer and transmitted to the terminal through a common physical channel.

An MBMS Radio Bearer (RB) is an RB for MBMS, which transmits user data of one specific MBMS service, which is transferred from a core network to a UTRAN, to a specific terminal group. MBMS RBs can be roughly divided into point-to-multipoint RBs and point-to-point RBs. In order to provide the MBMS service, the UTRAN selects one of two types of MBMS RBs. In order to select the MBMS rb, the UTRAN needs to know the number of users of a specific MBMS service in one cell. A threshold is set in the UTRAN, and if the number of users existing in the cell is less than the threshold, the UTRAN sets a point-to-multipoint MBMS RB, whereas if the number of users existing in the cell is greater than the threshold, the UTRAN sets a point-to-multipoint MBMS RB.

The third generation partnership project (3GPP) wireless system proposes a Downlink Shared Channel (DSCH), including a high speed downlink shared channel (HS-DSCH), particularly for supporting packet data services.

In order for the DSCH to provide a multicast service, it should support a point-to-multipoint radio bearer, and at this time, a common logical channel such as CTCH or multimedia broadcast/Multicast Traffic Channel (MTCH) should be mapped on the DSCH. In this regard, however, since the DSCH transmits only data of a dedicated logical channel in the conventional art, a field for identifying a logical channel mapped on the DSCH is not added to the MAC header. Therefore, when the common logical channel data is transmitted through the DSCH, in the DSCH transmission, in the case that a field indicating a logical channel type is not included in a MAC header, a terminal cannot know to which type of logical channel a data unit received through the DSCH belongs, and thus, a communication error is likely to occur.

The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.

Disclosure of Invention

Therefore, one object of the present invention is: when multicast service data is transmitted through a shared channel, a data transmission method capable of distinguishing the type of the multicast service data is provided.

Another object of the present invention is to provide a data transmission method capable of providing a multicast service through a shared channel.

To achieve at least the above objects in whole or in parts, there is provided a multicast service method in a wireless system, in which service data of a logical channel is mapped to a common transport channel and transmitted to a terminal, including: adding a logical channel identifier to service data to be transmitted; and maps the corresponding traffic data to the common transport channel.

The logical channel is preferably a common logical channel, which may be a Common Traffic Channel (CTCH), a common control channel, an MBMS Traffic Channel (MTCH), or an MBMS Control Channel (MCCH), or a dedicated logical channel.

The common transport channel is preferably a Downlink Shared Channel (DSCH).

The common transport channel is preferably a high speed downlink shared channel (HS-DSCH).

The service data is preferably multimedia broadcast/multicast service (MBMS) data.

The service data is preferably MBMS protocol data units, the latter being MAC protocol data units.

The logical channel identifier is preferably a Target Channel Type Field (TCTF) indicating whether a logical channel mapped to the common transport channel is a common logical channel or a dedicated logical channel. The logical channel identifier is added when service data is transmitted from a Medium Access Control (MAC) layer to a lower layer.

The logical channel identifier is preferably added by a general type of MAC entity such as MAC-c/sh, which manages common radio resources for each terminal in the cell.

The logical channel identifier is preferably included in a header of the traffic data, and the header is a MAC header.

The multicast service method further includes adding a terminal identifier and an indicator for indicating a type of the terminal identifier to service data to be transmitted. The terminal identifier is an MBMS Radio Network Temporary Identifier (RNTI), a terminal group identifier, or an MBMS service identifier.

In order to achieve at least the above advantages in whole or in parts, there is further provided a multicast service method in a wireless communication system, in which service data of a common logical channel or a dedicated logical channel is mapped to a Downlink Shared Channel (DSCH) or a high speed downlink shared channel (HD-DSCH) and transmitted to a terminal, where when a Medium Access Control (MAC) transmits the service data through the DSCH or HD-DSCH, it also transmits an indicator for indicating a type of mapping of the logical channel to the service data.

The service data is preferably multimedia broadcast/multicast service (MBMS) data.

The service data is preferably MBMS protocol data units, the latter being MAC protocol data units.

The indicator is preferably a Target Channel Type Field (TCTF).

The MAC layer is preferably a MAC-c/sh layer that manages common resources for each terminal in the cell.

The indicator is preferably included in a header of the traffic data, and the header is a MAC header. The MAC header includes a terminal identifier and an indicator for indicating a type of the terminal identifier.

The terminal identifier is preferably an MBMS Radio Network Temporary Identifier (RNTI), a terminal group identifier, or an MBMS service identifier.

In order to achieve at least the above advantages in whole or in parts, there is further provided a multicast service method in a wireless communication system, in which a service received through a downlink shared channel is transmitted to a higher layer of a terminal, comprising: reading a logical channel identifier from traffic data and recognizing a logical channel through which the corresponding data is transmitted; and transmitting the received data to a higher layer of the terminal through the recognized logical channel.

The received data is preferably multimedia broadcast/multicast service (MBMS) data.

The logical channel identifier is preferably a Target Channel Type Field (TCTF).

If the logical channel for transmitting the service data is a common logical channel, the received data is preferably transmitted to a Resource Link Control (RLC) layer through the common logical channel. If the logical channel for transmitting the traffic data is a dedicated logical channel, the received data is transmitted to the MAC-d layer, which manages dedicated resources through the dedicated logical channel.

The recognizing step is preferably performed at a Medium Access Control (MAC) layer of a general type of the terminal, such as a MAC-c/sh layer.

In order to achieve at least the above advantages in whole or in parts, there is further provided a multicast service method in a wireless communication system, in which data received through a downlink shared channel is transmitted to a higher layer of a terminal, comprising: reading a logical channel identifier and a terminal identifier from the received data; and transmitting the received data to a higher layer through a predetermined logical channel based on the read logical channel identifier and the terminal identifier.

The logical channel identifier is preferably a target channel type identifier (TCTF).

The terminal identifier is preferably an MBMS Radio Network Temporary Identifier (RNTI), a terminal group identifier, or an MBMS service identifier.

The transmitting step preferably includes: checking whether the logical channel identifier indicates a common logical channel; checking whether the terminal identifier indicates a terminal group to which the corresponding terminal belongs; and transmitting the received data to a higher layer according to the checking result.

Preferably, if the logical channel identifier indicates a common logical channel and the terminal identifier indicates a terminal group to which the corresponding terminal belongs, the received data is transmitted to a Resource Link Control (RLC) layer through the common logical channel. If the logical channel identifier indicates a common logical channel but the terminal identifier does not indicate a terminal group to which the corresponding terminal belongs, the received data is discarded.

The received data is preferably transmitted to the MAC-d layer if the logical channel identifier indicates a dedicated logical channel and the terminal identifier indicates a terminal group to which the corresponding terminal belongs. If the logical channel identifier indicates a dedicated logical channel but the terminal identifier does not indicate a terminal group to which the corresponding terminal belongs, the received data is discarded.

In order to achieve at least all or some of the above advantages, there is provided a method of transmitting a multicast service in a mobile communication system, the method comprising: mapping at least one logical channel to a common transport channel; and transmitting data of the at least one logical channel having a header to the terminal through the common transport channel, wherein the header has a first identifier identifying the at least one logical channel and a second identifier identifying the MBMS service.

In order to achieve at least all or some of the above advantages, there is provided a method for receiving a multicast service in a mobile communication system, the method comprising: receiving data of at least one logical channel having a header through a common transport channel, wherein the header has a first identifier identifying the at least one logical channel and a second identifier identifying the MBMS service; identifying at least one logical channel and the MBMS service according to the first identifier and the second identifier included in the header; and transmitting the data to a radio link control, RLC, layer through a logical channel mapped to the common transport channel according to the first identifier.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims.

Drawings

The present invention will now be described in detail with reference to the following drawings, wherein like reference numerals represent like elements:

fig. 1 illustrates a network structure of a general UMTS system.

Fig. 2 illustrates a radio access interface protocol between a terminal and a UTRAN based on the 3GPP radio access network standard.

Fig. 3 illustrates a mapping relationship between logical channels and transport channels in a user equipment.

Fig. 4 illustrates a structure of a Medium Access Control (MAC) Protocol Data Unit (PDU) of a point-to-point DSCH according to a conventional art.

Fig. 5 illustrates MAC header information according to a mapping relationship between a dedicated logical channel and a transport channel in accordance with the conventional art.

Fig. 6 illustrates a structure of a MAC PDU of the point-to-multipoint DSCH according to the present invention.

Fig. 7 illustrates a structure of a general type MAC of CRNC for a point-to-multipoint DSCH and a multicast data processing method; and

fig. 8 illustrates a structure of a general type MAC for a terminal of a point-to-multipoint DSCH and a multicast data processing method.

Detailed Description

The invention is implemented in a mobile communication system developed according to the 3GPP standard, such as UMTS (universal mobile telecommunications system). The invention is also applicable to communication systems open to different standards.

The method provided by the invention comprises the following steps: when the UTRAN transmits radio bearer data through a Downlink Shared Channel (DSCH), the terminal determines which logical channel is used to transmit the data received through the DSCH. In the present invention, the DSCH provides a point-to-multipoint radio bearer service and a point-to-point radio bearer service, and particularly transmits data of a common traffic channel such as CTCH and MTCH to a specific terminal group.

In order to distinguish the DSCH in the present invention from the conventional art, if the DSCH is used to provide a point-to-multipoint radio bearer service, it is referred to as a point-to-multipoint DSCH. On the other hand, if the DSCH is used to provide a point-to-point radio bearer service, it is referred to as a point-to-point DSCH. In the present invention, the DSCH also includes a high speed downlink shared channel (HS-DSCH), and thus the DSCH may be replaced with the HS-DSCH.

In the present invention, an indicator of whether corresponding data is multicast data or dedicated data is added to multicast service data and transmitted through a Downlink Shared Channel (DSCH). This indicator is contained as a Target Channel Type Field (TCTF) in the header of the MAC PDU.

Preferred embodiments of the present invention will now be described.

Referring to a conventional downlink shared transport channel (DSCH), since only data of a dedicated logical channel is transmitted, the MAC header does not contain a field for identifying a logical channel type mapped to the DSCH. However, in order for the DSCH to provide not only a dedicated service but also a multicast service, the DSCH should support a point-to-multipoint Radio Bearer (RB), and in this method, a common logical channel such as CTCH or MTCH should be mapped to the DSCH.

Fig. 6 illustrates a structure of a MAC PDU of the point-to-multipoint DSCH according to the present invention.

As shown in fig. 6, the MAC PDU transmitted through the DSCH is composed of a MAC header and a MAC sdu. The MAC header contains TCTF, UE ID type, MBMS identifier (m-RNTI), etc.

The MAC header contains a TCTF field for identifying the type of logical channel. The TCTF field indicates whether a channel mapped to the DSCH is a dedicated logical channel (DTCH/DCCH) or a common logical channel (CTCH, BCCH, CCCH, MTCH, MCCH). That is, the TCTF field indicates whether multicast service data transmitted through a Downlink Shared Channel (DSCH) is multicast data or dedicated data.

The UE ID type field indicates whether the UE ID contained in the MAC header is U-RNTI, C-RNTI, DSCH-RNTI or MBMS identifier (m-RNTI).

The MBMS (m-RNTI) field indicates terminal identifier information. Typically, for point-to-point DSCH, DSCH-RNTI is used as the UE-ID in the MAC header, while for point-to-multipoint DSCH, MBMS identifier (m-RNTI) is used as the UE-ID. Alternatively, instead of using the MBMS identifier, the MBMS service identifier or the terminal group identifier may be used as the UE-ID.

Accordingly, the UTRAN MAC attaches MAC header information to the RLC transmitted through the DSCH to compose a MAC PDU, i.e., a transport block, and transmits it to the physical layer through the DSCH.

Fig. 7 illustrates a structure of a common type MAC of CRNC for a point-to-multipoint DSCH. The common type MAC of CRNC supports MBMS in UTRAN. MAC-c/sh can be used as a generic type of MAC in CRNC.

As shown in fig. 7, an RLC Unacknowledged Mode (UM) of the RLC 10 exists for each MBMS and UE ID, and TCTF multiplexing is performed (steps S21, S23, and S24). At this time, step S22 refers to the flow control between c/sh and MAC-d.

Thereafter, the MAC-c/sh performs a downlink scheduling function for appropriately allocating a downlink shared channel to the terminal every Transmission Time Interval (TTI) and a priority processing function for transmitting data having a higher priority first (step S25). At this time, the MAC-c/sh 20 can perform the following three types of priority processing:

1. priority handling among multiple MBMS multicast groups (or MBMS services).

2. Priority handling on one MBMS multicast group (or one MBMS service).

Priority handling among data of an MBMS multicast group (or MBMS service).

For example, when data of several MBMS multicast groups is transmitted on the downlink through a common transport channel such as FACH, DSCH, or HS-DSCH, the MAC-c/sh 20 transmits MBMS data having a higher priority first. This is related to a dynamic scheduling function, and such a method can improve the utilization rate of channel resources by appropriately allocating a common channel to a terminal every TTI.

If several logical channels belonging to one MBMS service or one MBMS multicast group are mapped to one transport channel, the MAC-c/sh 20 determines the priority according to the priority of the logical channels. This is related to the transport format combination selection, and the MAC-c/sh selects a Transport Format Combination (TFC) that can transmit data of a logical channel having a higher priority first (step S26).

The MAC-c/sh selects a TFC of data to be transmitted through the point-to-multipoint DSCH and selects a code of a downlink for transmitting the corresponding MAC PDU, i.e., a channel code of a Physical Downlink Shared Channel (PDSCH) (physical channel) (step S27). In a specific PDSCH radio frame, PDSCH channel coding is used to transmit a corresponding MBMS service or MBMS multicast group data.

Fig. 8 illustrates a structure of a general type MAC of a terminal for a point-to-multipoint DSCH. The general type MAC of the terminal supports MBMS in the user equipment. The MAC-c/sh may be used as a general type of MAC in the user equipment.

As shown in fig. 8, a physical layer of a terminal belonging to an MBMS multicast group first receives control information through a DPCH, and then determines whether to receive a DSCH during a specific radio frame according to the content of the received DSCH control information.

If the DSCH control information indicates that DSCH should be received for service during a specific radio frame, the physical layer of the terminal receives MAC-c/sh during the specific radio frame according to the DSCH control information.

Next, the MAC-c/sh40 of the terminal separates the TCTF field from the received MAC PDU (step S43), and checks whether the information of the TCTF field inserted into the MAC PDU indicates a dedicated logical channel (DTCH or DCCH) mapping or a common logical channel (such as CTCH, MTCH, or) mapping.

If the TCTF field information indicates a dedicated logical channel (DTCH or DCCH) mapping, the MAC-c/sh40 processes data using the same method as the point-to-multipoint DSCH in the conventional art. That is, if the information of the TCTF field indicates dedicated logical channel mapping, the MAC-c/sh of the terminal reads out the UE ID from the MAC header and distinguishes whether the corresponding UE ID is its own ID. If the corresponding UE ID is its own ID, the MAC-c/sh of the terminal transmits the corresponding MAC PDU to the MAC-d layer.

If the TCTF field information inserted into the MAC PDU indicates a common logical channel (such as, or MTCH) mapping, the MAC-c/sh of the terminal checks whether the UE ID type field indicates the inclusion of MBMS RNTI (m-RNTI). If the UE ID type field does not indicate the inclusion of the m-RNTI, the MAC-c/sh discards the corresponding MAC PDU.

If the UE ID type field indicates that m-RNTI is included, the MAC-c/sh40 reads the m-RNTI from the MBMS identifier field (step S43) and checks whether the read m-RNTI indicates a multicast service that the terminal desires to receive. If the read m-RNTI does not indicate multicast service expected to be received by the terminal, the MAC-c/sh40 discards the corresponding MAC PDU.

If the corresponding m-RNTI indicates a multicast service that the terminal desires to receive, the MAC-c/sh40 transmits the RLC PDU to the RLC entity 31 of the terminal RLC layer 30 through a corresponding common logical channel (CTCH) using a logical channel type such as CTCH and identifier information inserted in the corresponding MAC PDU. That is, the MAC-c/sh.40 of the terminal can recognize through which logical channel data (MAC PDU) is transferred and through which logical channel data is to be transferred to the RLC layer of the terminal, according to the TCTF and MBMS identifier field information inserted in the MAC PDU.

As described so far, the method of transmitting multicast data through a downlink shared channel in the present invention has the following advantages. That is, by including the TCTF field in the header of the mac pdu transmitted by the DSCH, the type of logical channel mapped can be known when the DSCH supports a point-to-multipoint radio bearer. Accordingly, the MAC-c/sh of the terminal receiving the DSCH data can recognize through which logical channel the data (MAC PDU) is transmitted and through which logical channel to be transmitted to the RLC layer of the terminal.

The foregoing embodiments and advantages are merely exemplary of the invention, which is not to be construed as limiting. The principles of the present invention may be readily applied to other types of apparatuses. The description of the present invention is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures.

Claims (18)

1. A method of transmitting a multimedia broadcast/multicast service MBMS in a mobile communication system, the method comprising:

mapping at least one logical channel to a common transport channel; and

transmitting data of at least one logical channel having a header with a first identifier identifying the at least one logical channel and a second identifier identifying the MBMS service to the terminal through the common transport channel.

2. The method of claim 1, wherein the first identifier is a Target Channel Type Field (TCTF).

3. The method of claim 1, wherein the second identifier is a multimedia broadcast/multicast service (MBMS) identifier.

4. The method of claim 3, wherein the MBMS identifier is a radio network temporary identifier m-RNTI.

5. The method of claim 1, wherein the header includes a third identifier for identifying a type of the second identifier.

6. The method of claim 5, wherein the third identifier is a UE ID type.

7. The method of claim 1, wherein the at least one logical channel is a dedicated logical channel or a common logical channel.

8. The method of claim 1, wherein the common transport channel is a shared transport channel.

9. The method of claim 8, wherein the shared transport channel is a downlink shared channel, DSCH.

10. A method of receiving a multimedia broadcast/multicast service MBMS in a mobile communication system, the method comprising:

receiving data of at least one logical channel having a header through a common transport channel, wherein the header has a first identifier identifying the at least one logical channel and a second identifier identifying the MBMS service;

identifying at least one logical channel and the MBMS service according to the first identifier and the second identifier included in the header; and

transmitting the data to a radio link control, RLC, layer through a logical channel mapped to the common transport channel according to the first identifier.

11. The method of claim 10, wherein the first identifier is a Target Channel Type Field (TCTF).

12. The method of claim 10, wherein the second identifier is a multimedia broadcast/multicast service (MBMS) identifier.

13. The method of claim 12, wherein the MBMS identifier is a radio network temporary identifier m-RNTI.

14. The method of claim 10, wherein the header includes a third identifier for identifying a type of the second identifier.

15. The method of claim 14, wherein the third identifier is a UE ID type.

16. The method of claim 10, wherein the at least one logical channel is a dedicated logical channel or a common logical channel.

17. The method of claim 10, wherein the common transport channel is a shared transport channel.

18. The method of claim 17, wherein the shared transport channel is a downlink shared channel, DSCH.