JP4908496B2 - Mobile communication system, base station, and transmission method - Google Patents

Description

  The present invention relates to the technical field of mobile communication, and more particularly to a mobile communication system, a communication node, a base station and a method for transmitting multicast broadcast multimedia service (MBMS) data.

  With the development of mobile communication systems, it is considered to transmit not only a unicast channel addressed to a specific user apparatus but also a channel addressed to one or more specific or unspecified user apparatuses. A typical example of the latter is MBMS. The same MBMS data is transmitted from a plurality of cells, and the user apparatus synthesizes MBMS data received from the plurality of cells. This can improve the quality of service related to MBMS data. In order to perform the synthesis properly, the user apparatus must appropriately determine what the received MBMS data is (such as what number of data).

  FIG. 1 is a conceptual diagram of a conventional mobile communication system. A radio access network device (RAN: Radio Access Network) provided between a user equipment (UE: User Equipment) and a core network (CN: Core Network) is a plurality of base stations (NodeB) and a radio network controller that controls them. Alternatively, it is composed of a central node (RNC: Radio Network Controller). The base station performs wireless communication with the user apparatus. Thus, in the conventional IMT-2000 mobile communication system, the radio link control (RLC) layer is terminated at the RNC. Therefore, the RNC assigns a common sequence number (SN) in the RNS to the MBMS data from the host device and transmits it to each base station at an appropriate timing, and the user device appropriately selects and synthesizes the MBMS data from each cell. You can

Non-patent document 1 describes, for example, the assignment of a common sequence number within a RAN. Further, for example, non-patent document 2 describes that the MBMS data received from a plurality of cells is selectively combined by the user apparatus.
3GPP TS.25.346.5.2.2 3GPP TS.25.346.7.1

  By the way, from the viewpoint of shortening the line connection time to the user equipment, in the LTE (Long Term Evolution) system which is a future mobile communication system, the function of the radio network equipment (RNC) is set to many base stations (NodeB). And a new base station (eNodeB) that integrates the RNC function and the base station (NodeB) function is proposed (excluding the central node). Each base station is connected to a certain communication node (for example, may be called an access gateway, a router, a switch, etc.) in the core network. It has been proposed that the access gateway (aGW) integrates the GGSN function, the SGSN function, and the RNC function. Such a scheme is particularly advantageous for unicast channel communication. On the other hand, when transmitting MBMS data as described above, the user apparatus (UE) must appropriately determine what the received MBMS data is. However, in the LTE system, a function equivalent to RLC (which may be called Outer ARQ) is terminated at the base station, so that a common sequence number among multiple base stations is attached to the MBMS data and appropriate from each base station. It is not easy to transmit at a proper timing. In this case, for example, if all base stations are equipped with a timing adjustment function using GPS or the like, and each base station transmits MBMS data in synchronization with each other, the timing problem may be solved. Such a method is not appropriate because of a request for constructing a system easily. In particular, it is difficult for an indoor base station to receive GPS radio waves directly, and it may be preferable to operate asynchronously.

  An object of the present invention is to distinguish between MBMS data transmitted from a plurality of asynchronous base stations to a user apparatus in a mobile communication system having a plurality of base stations connected to a core network through an access gateway and managing line connections. It is to make sure.

A mobile communication system according to an embodiment is:
Communicate node in the core network, connected to the communication node, a mobile communication system of the LTE scheme and a plurality of base stations which manages the line connection of the user equipment,
The communication node is
Means for receiving packet data representing multicast broadcast multimedia service (MBMS) data in the core network;
Means for giving a first sequence number for each predetermined data unit to the packet data;
Have a means for transmitting packet data to one or more base stations with said first sequence number,
Each of the plurality of base stations is
When the predetermined data unit is compared with the data unit of the wireless packet, and the predetermined data unit is not larger than the data unit of the wireless packet, one second sequence with one first sequence number Means for associating a plurality of second sequence numbers with one first sequence number when the predetermined data unit is larger in size than the data unit of the wireless packet;
First sequence number and the same or it has been received with a means to transmit a wireless packet to user devices with different second sequence number
This is a mobile communication system .

  In a mobile communication system having a plurality of base stations that are connected to a core network through an access gateway and manage line connections, it is possible to ensure the discrimination of MBMS data transmitted from a plurality of asynchronous base stations to a user apparatus .

It is a figure which shows the conventional mobile communication system. It is a figure which shows the mobile communication system by one Example of this invention. 1 is a diagram illustrating an access gateway according to an embodiment of the present invention. FIG. FIG. 2 is a diagram illustrating a base station according to an embodiment of the present invention. It is a figure which shows the example which applies a 1st sequence number as it is to a 2nd sequence number. FIG. 6 is a diagram illustrating an example in which a plurality of second sequence numbers correspond to one first sequence number. It is a figure which shows the operation example by one Example of this invention. 1 is a diagram illustrating an access gateway according to an embodiment of the present invention. FIG. FIG. 2 is a diagram illustrating a base station according to an embodiment of the present invention. FIG. 3 is a diagram illustrating a user apparatus according to an embodiment of the present invention.

Explanation of symbols

31 Wired transmission section
32 FP section
32'MBMS UPE
33 Scheduler
34 Control unit
41 Wired transmission section
42 FP section
42 'scheduler
43 Data size analyzer
44 Transmission data generator
45 Wireless transmission section
46 Control unit
101 Control unit
102 Wireless transmission unit
103 MBMS UPE Department
CN core network
RAN radio access network equipment
RNC wireless network controller
RLC radio link control
Conventional base station under NodeB RNC
LTE base station without eNodeB RNC
UE user equipment
FP frame protocol
PDU packet data unit

  According to an embodiment of the present invention, a U-Plane (UP) protocol for transferring user data is defined between an access gateway and a base station, and a sequence number (for each data) is defined as a data unit of the protocol. Sequence number). The term access gateway in the present application is a concept that is widely used in relation to an upper node of a base station and is used for any node that performs the functions described below, and may be called, for example, an SAE gateway.

  The base station sets the sequence number assigned to the UP protocol PDU transferred from the central node as the sequence number for the automatic retransmission request processing function (for example, Outer ARQ).

  The data frame includes a data transmission schedule, and the PDU is preferably stored in the base station until the transmission schedule (until the timing scheduled in the scheduling arrives).

  When the data size of the data frame is larger than the wireless packet, the data is divided, and the sequence number given to the PDU is incremented every time the data frame is divided.

  As described above, according to an embodiment of the present invention, the sequence number of the UP protocol assigned by the central node is used as the sequence number of the Outer ARQ PDU, and the sequence numbers can be synchronized between base stations. In other words, when MBMS data is transmitted in a mobile communication system in which a terminal node of ARQ is a base station, sequence numbers can be appropriately synchronized between base stations. In addition, it is ensured that the same data is transmitted between the base stations, and the data received from each cell by the user apparatus can be easily combined.

  Furthermore, from the viewpoint of transmitting MBMS data to an appropriate base station according to service contents, an MBMS scheduler that determines one or more base stations as destinations of packet data representing MBMS data according to MBMS data is a central node. May be provided. From the viewpoint of transmitting MBMS data from each base station at an appropriate period, the MBMS scheduler may determine the timing for transmitting packet data to one or more base stations.

  From the viewpoint of easily determining a sequence number to be assigned to a wireless packet, packet data to each of one or more base stations may be divided and transmitted according to the data unit of the wireless packet.

  Also, according to an aspect of the present invention, a protocol / functional entity for transmitting MBMS data is newly defined between ACGW and UE, and in the present embodiment, this is referred to as MBMS UPE. The ACGW MBMS UPE assigns a sequence number to each predetermined data unit and transmits a data frame to one or more base stations.

  The base station recognizes that the corresponding data is MBMS data, turns off the automatic retransmission control processing function (for example, Outer ARQ, HARQ function), and turns on only the scheduler. Therefore, unlike the unicast channel, the MBMS data is not subjected to the automatic retransmission control processing function (ARQ) for each user (instead, the same MBMS data may be repeatedly transmitted to all users a predetermined number of times. .) The data frame includes a data transmission schedule, and the PDU is preferably stored in the base station until the transmission schedule (until the timing scheduled in the scheduling arrives).

  The mobile station can appropriately synchronize the sequence numbers between the base stations when transmitting MBMS data in the mobile communication system by receiving the wireless packet with the corresponding protocol / functional entity. In addition, it is ensured that the same data is transmitted between the base stations, and the data received from each cell by the user apparatus can be easily combined.

  Furthermore, from the viewpoint of transmitting MBMS data to an appropriate base station according to service contents, an MBMS scheduler that determines one or more base stations as destinations of packet data representing MBMS data according to MBMS data is a central node. May be provided. From the viewpoint of transmitting MBMS data from each base station at an appropriate period, the MBMS scheduler may determine the timing for transmitting packet data to one or more base stations.

  FIG. 2 shows a mobile communication system according to an embodiment of the present invention. The mobile communication system includes an access gateway (ACGW), one or more base stations (eNodeB), and a user apparatus (UE) that performs radio communication with the base station. The user equipment is typically a mobile station, but may be a fixed station. In this embodiment, the radio access network device (RAN) is composed of a plurality of base stations (eNodeB), and there is no host device (RNC in 3G) of the plurality of base stations (eNodeB) in the RAN. The access gateway (ACGW) is a functional element or entity belonging to the core network. In addition to having the function of transferring MBMS data to the lower level, the function of assigning a sequence number (SN) by the frame protocol (FP) and one or more Has a function to perform scheduling for transmitting MBMS data to the base station. MBMS data is supplied from a server such as a broadcast multicast service center (BM-SC) connected to the core network. In this embodiment, the elements having these functions and those described later are access gateways (ACGW). However, similar functions may be provided in a communication node that transmits packets to routers, routing controllers, switches, and other base stations. Good. Each base station has a function of performing wireless communication with a user apparatus and wired communication with an access gateway (ACGW), management related to line connection, wireless scheduler, automatic retransmission control (ARQ), handover control, etc. It also has the function.

  FIG. 3 shows a functional block diagram of the access gateway (ACGW). FIG. 3 shows a wired transmission unit 31, an FP unit 32, a scheduler 33, and a control unit 34. Although other functional elements actually exist, it should be noted that only functional elements particularly relevant to the present invention are shown for the sake of simplicity of explanation (the same applies to other figures).

  The wired transmission unit 31 has a function of receiving a packet from the host device and a function of transmitting the packet to one or more base stations in accordance with an instruction from the scheduler 33.

  The FP unit 32 continuously assigns a sequence number (first sequence number) to each received data unit (focusing on a packet representing MBMS data in this embodiment) for each predetermined data unit. The packet with the sequence number is transmitted to the wired transmission unit 31. Packet transmission is performed between the access gateway (ACGW) and the base station using a certain data frame. In this embodiment, the protocol that defines the data frame is a frame protocol (FP). However, the present invention is not limited to that protocol, and any appropriate protocol such as GTP (General Packet Radio Service (GPRS) tunneling protocol) may be used. In any case, the size of the “predetermined data unit” is defined according to the protocol used.

  The scheduler 33 determines to which base station a packet representing MBMS data is transmitted at what timing, and notifies the wired transmission unit 31 of the determined content. The wired transmission unit 31 transmits a packet with a sequence number to one or more base stations according to the determined content (scheduling content). One or more cells to which the same MBMS data is transmitted may be different depending on the service content. Therefore, the scheduler 33 determines which one or more base stations deliver MBMS data according to the service content. Also, the frequency or cycle at which the same MBMS data is transmitted from each base station may be different depending on the service content. For this reason, the scheduler 33 also has a function of appropriately adjusting the transmission timing to each base station according to the service content so that MBMS data is transmitted from each base station at an appropriate cycle.

  The control unit 34 controls various functional elements in the access gateway (ACGW).

  FIG. 4 shows a base station (eNodeB) according to an embodiment of the present invention. FIG. 4 illustrates a wired transmission unit 41, an FP unit 42, a data size analysis unit 43, a transmission data creation unit 44, a wireless transmission unit 45, and a control unit 46.

  The wired transmission unit 41 receives a packet from the access gateway (ACGW) (in this embodiment, focusing on a packet representing MBMS data). In this embodiment, this packet is transmitted in a data frame defined by the FP protocol, and is referred to as an FP data frame for convenience. The FP data frame is transmitted to the FP unit 42.

  The FP unit 42 confirms the sequence number (first sequence number) of the FP data frame and notifies the transmission data creation unit 44 of the sequence number.

  The data size analysis unit 43 analyzes the data size of the received FP data frame, and notifies the transmission data creation unit 44 of the analysis result. As described above, the first sequence number is assigned to the FP data frame for each predetermined data unit. The data size analysis unit 43 analyzes how large the “predetermined data unit” is.

  The transmission data creation unit 44 compares the predetermined data unit of the FP data frame with the data unit of the wireless packet, and assigns the sequence number (second sequence) to the wireless packet according to the comparison result (the magnitude relationship between the data units) Number). For example, if the data unit of the FP data frame and the wireless packet is small, the first sequence number may be used as it is for the second sequence number. However, in general, the predetermined data unit is larger than the data unit of the wireless packet. In this case, a plurality of second sequence numbers may correspond to one first sequence number. The transmission data creation unit 44 adjusts the size of the received FP data frame for a wireless packet, and continuously assigns a second sequence number to each.

  The wireless transmission unit 45 transmits each wireless packet together with the second sequence number to the user apparatus.

  The control unit 46 controls various functional elements in the base station.

FIG. 5 is an explanatory diagram of an operation example according to this embodiment. In the illustrated example, the first sequence number is applied to the second sequence number as it is. The access gateway (ACGW) transmits a packet representing MBMS data to each base station according to the FP protocol. A packet to be transmitted is transmitted in a predetermined data unit (PDU: packet data unit) defined by the FP protocol as indicated by FPPDU ₁ , FPPDU ₂ , FPPDU ₃ ,. FPPDU ₁ , FPPDU ₂ , FPPDU ₃ ,... Are successively assigned sequence numbers SN _A1 , SN _A2 , SN _A3 ,. In the illustrated example, the data unit is equal to or smaller than the data unit of the wireless packet. Therefore, the second sequence numbers SN _B1 , SN _B2 , SN _B3 ,... Can be used as they are for the first sequence numbers SN _A1 , SN _A2 , SN _{A3 ,.} Each base station assigns second sequence numbers SN _B1 , SN _B2 , SN _B3 ,... To the radio packets PDU ₁ , PDU ₂ , PDU _{3 ,.}

FIG. 6 is also an explanatory diagram of an operation example according to this embodiment. In the illustrated example, the data unit of the FPPDU transmitted from the access gateway (ACGW) to the base station (eNodeB) is larger than the data unit of the radio packet. Therefore, the second sequence number is derived so that a plurality of second sequence numbers correspond to one first sequence number. FIG. 6 shows a state in which three second sequence numbers (SN _B1 , SN _B2 , SN _B3 ) correspond to one first sequence number (SN _A1 ). The number of second sequence numbers corresponding to the first sequence number can be changed as appropriate.

  In the first embodiment, the frame protocol (FP) terminated between the access gateway (ACGW) and the base station (eNodeB) is used. However, in the second embodiment of the present invention, the access gateway (ACGW) and the user equipment ( A protocol terminated between UEs is newly defined and referred to or illustrated as “MBMS UPE (MBMS U-Plane Entity)” for convenience.

  As shown in FIG. 7, MBMS UPE is a U-plane functional entity for MBMS. By executing this function, packets received from the core network (CN) are divided into predetermined data units, for example, the size of radio packets, which are transmitted to one or more base stations. A sequence number is assigned according to the size of the wireless packet. Regarding transmission of MBMS data, the base station operates with an automatic retransmission control function (for example, Outer ARQ, HARQ) turned off (that is, operates in a transparent mode). Data generated by the MBMS UPE of the access gateway (ACGW) is transmitted to the base station together with the sequence number. As the sequence number assigned to the wireless packet, the sequence number created by the access gateway can be used as it is. Therefore, the base station does not need to reassign the sequence number, and MBMS data can be appropriately wirelessly transmitted to the user apparatus by simply performing scheduling related to the radio resource.

  In the above description, the sequence number (SN) of OuterARQ (RLC) is used, but the present invention is naturally applicable to the sequence number of PDCP.

  FIG. 8 shows a functional block diagram of an access gateway (ACGW) used in this embodiment. FIG. 8 shows a wired transmission unit 31, an MBMS UPE unit 32 ′, a scheduler 33, and a control unit 34.

  The wired transmission unit 31 has a function of receiving a packet from the host device and a function of transmitting the packet to one or more base stations in accordance with an instruction from the scheduler 33.

  The MBMS UPE unit 32 ′ assigns a sequence number (first sequence number) to each received data unit (focusing on a packet representing MBMS data in this embodiment) continuously for each predetermined data unit. The packet with the sequence number is transmitted to the wired transmission unit 31. The MBMS UPE unit 32 ′ adjusts the packet size so that data transmission is performed using a protocol terminated between the access gateway (ACGW) and the user apparatus. The packet size is divided according to the size of the wireless packet, and a sequence number is assigned to each divided packet data.

  The scheduler 33 determines to which base station a packet representing MBMS data is transmitted at what timing, and notifies the wired transmission unit 31 of the determined content. The wired transmission unit 31 transmits a packet with a sequence number to one or more base stations according to the determined content (scheduling content). Similar to the first embodiment, the scheduler 33 determines which one or more base stations deliver MBMS data according to the service contents. The scheduler 33 also has a function of appropriately adjusting the timing of transmission to each base station according to the service contents so that MBMS data is transmitted from each base station at an appropriate cycle.

  The control unit 34 controls various functional elements in the access gateway (ACGW).

  FIG. 9 shows a base station (eNodeB) according to this embodiment. FIG. 9 shows a wired transmission unit 41, a scheduler 42 ′, a wireless transmission unit 45, and a control unit 46.

  The wired transmission unit 41 receives a packet from the access gateway (ACGW) (in this embodiment, focusing on a packet representing MBMS data). In this embodiment, this packet is a packet adjusted to the wireless packet size processed by the MBMS UPE unit 32 '(referred to as a UPE data frame for convenience). The UPE data frame is transmitted to the scheduler 42 '.

  The scheduler 42 ′ performs scheduling for the radio packet to be transmitted to the user apparatus, and outputs it to the radio transmission unit 45 together with the sequence number of the UPE data frame.

  The wireless transmission unit 45 transmits each wireless packet together with the notified sequence number to the user apparatus.

  The control unit 46 controls various functional elements in the base station.

  FIG. 10 shows a user apparatus used in this embodiment. FIG. 10 shows a control unit 101, a wireless transmission unit 102, and an MBMS UPE unit 103. The control unit 101 controls various functional elements in the user device. The wireless transmission unit 102 receives a wireless packet (focusing on transmission of a packet representing MBMS data in this embodiment) from the base station. The MBMS UPE unit 103 detects a sequence number given to the MBMS data received by the wireless transmission unit 102. This processing unit corresponds to the MBMS UPE unit 32 ′ of FIG. The detected sequence number is transmitted to an element (not shown) and used for synthesis of MBMS content.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to this, and various modifications and changes can be made within the scope of the gist of the present invention. For convenience of explanation, the present invention has been described in several embodiments. However, the division of each embodiment is not essential to the present invention, and one or more embodiments may be used as necessary.

  This international application claims priority based on Japanese Patent Application No. 2006-089426 filed on Mar. 28, 2006, the entire contents of which are incorporated herein by reference.

Claims (3)

Communicate node in the core network, connected to the communication node, a mobile communication system of the LTE scheme and a plurality of base stations which manages the line connection of the user equipment,
The communication node is
Means for receiving packet data representing multicast broadcast multimedia service (MBMS) data in the core network;
Means for giving a first sequence number for each predetermined data unit to the packet data;
Means for transmitting packet data together with the first sequence number to one or more base stations;
Each of the plurality of base stations is
When the predetermined data unit is compared with the data unit of the wireless packet, and the predetermined data unit is not larger than the data unit of the wireless packet, one second sequence with one first sequence number Means for associating a plurality of second sequence numbers with one first sequence number when the predetermined data unit is larger in size than the data unit of the wireless packet;
Mobile communication system characterized by having a means to transmit the first sequence number and same received or with different second sequence number a wireless packet to the user equipment. Is connected to a communication node of core network, manages the line connection of the user equipment, a base station in a mobile communication system of the LTE scheme,
Means for receiving packet data representing multicast broadcast multimedia service (MBMS) data from the communication node together with a first sequence number assigned to each predetermined data unit;
When the predetermined data unit is compared with the data unit of the wireless packet, and the predetermined data unit is not larger than the data unit of the wireless packet, one second sequence with one first sequence number Means for associating a plurality of second sequence numbers with one first sequence number when the predetermined data unit is larger in size than the data unit of the wireless packet;
Means for transmitting a radio packet to a user equipment with a second sequence number that is the same as or different from the first sequence number;
A base station characterized by comprising: Communicate node in the core network, connected to the communication node, a transmission method for use in a mobile communication system of the LTE scheme and a plurality of base stations which manages the line connection of the user equipment,
Said communication node, said in the core network receives the packet data representing a multicast broadcast multimedia service (MBMS) data, the first sequence number is assigned to each predetermined data unit in the packet data, the first sequence Transmitting packet data together with a number to one or more base stations ;
Each of the plurality of base stations compares the predetermined data unit with a data unit of a radio packet, and if the predetermined data unit has a size equal to or smaller than the data unit of the radio packet, one first If one second sequence number is associated with a sequence number, and the predetermined data unit is larger than the data unit of the radio packet, a plurality of second sequence numbers are assigned to one first sequence number. to correspond, and sending a radio packet to the user apparatus together with the first sequence number and same or different from the second received sequence number
Transmission method characterized in that it comprises a.

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