KR20150044213A - Scheme for supporting transceiving mbms service packet in a wireless communication system - Google Patents

Abstract

The present invention relates to a method used to support the transmission of multimedia broadcast and multicast service (MBMS) service packets in a wireless communication system. The method is executed through a cooperative entity which receives the MBMS service packets from a core network and transmits the MBMS service packets to one or more base stations in a single frequency network. The method includes: a step in which the cooperative entity is synchronized with the base stations; a step in which the cooperative entity calculates a reference system frame number (SFN) to point out the time when the base stations begins to transmit the service packets to the terminal; and a step in which the cooperative entity transmits the scheduling information including the calculated reference SFN to the base stations.

Description

Technical Field [0001] The present invention relates to a scheme for supporting transmission and reception of an MBMS service packet in a wireless communication system,

The present invention relates to a technique for supporting continuous reception of MBMS service data in a wireless communication system, and more particularly, to a technique in which one or more base stations simultaneously transmit specific data at a specific time.

The problem of the shortage of radio transmission bandwidth of MBMS (Multimedia Broadcast and Multicast Service) transmission technology using cellular mobile communication network is caused by the LTE (Long Term Evolution) of 3GPP (Third Generation Partnership Project) and the World Interoperability Microwave Access However, the demand for the MBMS service is increasing due to the emergence of a mobile terminal having advanced functions such as a smart phone.

Here, MBMS is a service for simultaneously transmitting a data packet to a plurality of users, and is a service for transmitting multimedia data to each user in the cell based on IP (Internet Protocol) multicast when the user exists in the same cell. As described above, in order to transmit multimedia data, the MBMS allows each cell to share necessary resources so that a plurality of users can receive the same multimedia data. The MBMS system uses a multicast control channel (MCCH), which is a dedicated control channel, for control signaling to a plurality of users to receive the same data in a radio section.

If the neighboring cell uses the same carrier as the carrier used in the serving area for the MBMS service in the asynchronous mode, the cell in the serving area is subject to interference by the neighboring cell signal, so that the MBMS reception quality may be degraded .

Therefore, in order to prevent the problem of the reception quality deterioration, all the base stations in the MBMS system need to share one synchronized carrier wave.

The present invention provides a method of synchronizing a start time at which the base stations transmit specific data to a terminal at one or more base stations existing in a serving area.

In addition, the present invention provides a method for a base station (BS) in a serving area to synchronize a data transmission start time without using a satellite signal such as Global Position System (GPS) in a Broadcast and Multicast Service Center (BM-SC).

In addition, the present invention provides a multicast multicast collaborative entity (MCE) as a physical entity that is a centralized control node that guarantees that the received signals are the same when a terminal receives synchronized signals from different base stations in a single frequency network. : Multi-cell Multicast Coordination Entity (MCE). The MCE may receive the MBMS service packet from the core network and deliver the service packet to at least one base station in a single frequency network.

In addition, the present invention provides a method for synchronizing a transmission start time of packets transmitted to a mobile station by a base station regardless of a network environment and a distance between a base station and an MCE in a single frequency network.

Also, the present invention provides a session initiation procedure in which a physical entity, which is a centralized control node, establishes the same RLC (Radio Link Control) / MAC (Medium Access Control) configuration among base stations in a single frequency domain.

In addition, the present invention provides a method by which base stations within a single frequency domain can transmit a reference time for transmitting the same data at the same time.

Also, the present invention proposes a reference system frame number (Reference SFN) and provides a method of determining a broadcast time of base stations through the reference system frame number.

The present invention also provides an algorithm for calculating a reference system frame number by the centralized control node MCE.

A method of supporting transmission of a Multimedia Broadcast and Multicast Service (MBMS) service packet in a wireless communication system, the method comprising: receiving an MBMS service packet from a core network and transmitting, to at least one base station in a single frequency network, The method of claim 1, further comprising the steps of: performing a synchronization with the at least one base station by a cooperative entity that delivers a service packet to the cooperative entity; And transmitting the service packet to the cooperative entity, wherein the cooperative entity transmits scheduling information including the calculated reference SFN to the base station.

In another aspect of the present invention, there is provided a method for supporting transmission of a Multimedia Broadcast and Multicast Service (MBMS) service packet in a wireless communication system, the method comprising: Performing synchronization with a cooperating entity; receiving, from the cooperating entity, scheduling information including a reference SFN (System Frame Number) indicating a time point at which the base station starts transmission of the service packet from the cooperative entity; And a method for supporting transmission of a service packet.

A cooperative entity supporting transmission of MBMS (Multimedia Broadcast and Multicast Service) packets in a wireless communication system, the cooperative entity comprising: a receiving entity for receiving an MBMS service packet from a core network and transmitting at least one A cooperative entity that transmits the service packet to a base station performs synchronization with the at least one base station and calculates a reference SFN (System Frame Number) indicating a time point at which the base station starts transmission of the service packet, And a transmitting unit for transmitting the calculated scheduling information including the reference SFN to the BS.

In another aspect of the present invention, there is provided a base station supporting transmission of MBMS (Multimedia Broadcast and Multicast Service) packets in a wireless communication system, And a receiver for receiving scheduling information including a reference SFN (System Frame Number) indicating a time point at which the base station starts transmission of the service packet from the cooperative entity, the control unit performing synchronization with the cooperative entity .

The present invention is effective in enabling one or more base stations existing in a serving area to efficiently transmit specific data to terminals simultaneously.

In addition, the present invention has an effect of allowing each entity constituting the MBMS system to perform synchronization without a separate procedure for understanding a specific protocol in order to determine a synchronous transmission start time.

Further, the present invention has the effect of reducing costs due to the fact that each entity of the MBMS system does not use a satellite satellite signal such as GPS.

1 is a diagram illustrating an MBMS system configuration,
2 is a diagram illustrating an MBMS system according to an embodiment of the present invention,
3 is a diagram illustrating an MBMS flow diagram according to an embodiment of the present invention,
4 is a diagram illustrating a transmission time point of broadcast data by a base station applying a reference SFN according to an embodiment of the present invention;
5 is a diagram illustrating an operation flow diagram of an MCE according to an embodiment of the present invention,
6 is a diagram illustrating an operation flowchart of a base station according to an embodiment of the present invention,
7 is a diagram illustrating a configuration of an MCE according to an embodiment of the present invention.
8 is a diagram illustrating a configuration of a base station according to an embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

According to an embodiment of the present invention to be described later, the MBMS system proposed in the present invention includes a Broadcast and Multicast Service Center (BM-SC) located in the core network, a centralized cooperative entity MCE Multi-cell Multicast Coordination Entity) base station and a UE, and a process of starting an MBMS session between the MCE and base stations in a single frequency network managed by the MCE itself (MCE) is provided.

In addition, the present invention proposes a reference system frame number (SFN) for transmitting the same packet to the mobile station at the same time in the process of starting the session.

The present invention also proposes a synchronization algorithm for determining the reference system frame number.

In the present invention, a service area of one or more base stations or cells sharing one synchronized radio resource is referred to as a single frequency network (SFN) area. For example, the radio resource may be a carrier. Hereinafter, the system frame number is referred to as 'SFN', and the single frequency network is referred to as 'SFN' in order to distinguish between a system frame number (SFN) and a single frequency network (SFN) We will use the original name without abbreviating it as 'SFN'.

The single frequency network region may include one or more cells for transmitting data to the UE, and may include cells having a continuous geographical region. The area synchronously transmitting MBMS data including a plurality of cells is referred to as a multi-cell MBMS synchronization area. That is, the multi-cell MBMS synchronization region is a group of cells that allocate the same frequency band to the MBMS service. The group of cells is capable of transmitting MBMS data through a single frequency network model.

On the other hand, one multi-cell MBMS synchronization region can support one or more single frequency network regions, while one designated frequency band can be used for only one multi-cell MBMS synchronization region. When a plurality of multicell MBMS synchronization areas are defined in the same geographical area, different multi-cell MBMS synchronization areas are allocated different frequency bands. That is, although the multi-cell MBMS synchronization region can support a plurality of single frequency network regions, in order to reduce interference, it is preferable that adjacent single frequency networks among the plurality of single frequency networks do not use the same frequency. Hereinafter, the 'multi-cell MBMS synchronization area' may simply be referred to as an 'MBMS service area'.

A terminal receiving MBMS service data from the base stations in the MBMS service area must simultaneously receive specific data from the base stations. Accordingly, it is required that one or more BSs constituting the same MBMS service area not only synchronize with each other but also transmit the same specific data to the MS at the same time.

Various methods are being developed according to the requirement that the base station transmits the same data to the terminal at the same time, and one of the methods under consideration is to use a clock (Clock) using the Institute of Electrical and Electronics Engineers There may be a method of synchronizing base stations. In the synchronization method using the above protocol, it is possible to adjust a series of clocks at the base station and synchronize with a precision of several microseconds (for example, 3 microseconds).

In addition, there may be a method in which the BM-SC transmits a synchronization signal to a base station through a satellite satellite signal such as GPS.

1 illustrates an MBMS system using time stamps based on GPS or UTC time.

Referring to FIG. 1, the BM-SC uses a timestamp based on a GPS (global positioning system GPS) or Universal Time Coordinated UTC (UTC) (Hereinafter referred to as " SYNC ") protocol.

Referring to FIG. 1, an MBMS system may include a BM-SC 101, one or more base stations 103, and a terminal (not separately shown).

The BM-SC 101 generates a time stamp based on GPS or UTC time, and transmits MBMS synchronized PDU (Protocol data unit) using the SYNC protocol to the base station 103 in the single frequency domain 105 and time stamp . The SYNC protocol is a time synchronization transmission protocol used between a BM-SC and a base station.

One or more base stations 103 in the single frequency domain 105 receiving the MBMS synchronization PDU and the time stamp simultaneously transmit specific data to the terminals at a specific time indicated by the time stamp. Here, the time stamp is information for notifying a specific time, for example, may include a time stamp of a SYNC PDU transmitted by the BM-SC.

However, the method of using the SYNC protocol based on the absolute time or UTC time, such as GPS, between the BM-SC and the base stations in this way requires installation of the GPS receiver in the BM-SC by the communication carrier. However, according to the service provider's policy, it may be impossible to install a GPS receiver on BM-SC, and even if it is possible, the cost of installation of GPS receiver causes financial burden to carrier.

Further, in order for the base stations in a single frequency domain to understand the specific time (for example, the time to transmit through the SYNC protocol) that the BM-SC provides, additional clock synchronization schemes should be provided to the base station, heterogeneous base station equipment may be difficult to match.

2 is a diagram illustrating an MBMS system according to an embodiment of the present invention.

Referring to FIG. 2, the MBMS system may include a BM-SC 201, an MCE 203, one or more base stations 205, and a terminal (not shown).

The MBMS system according to the embodiment of the present invention proposes a new component, the MCE 203. The MCE 203 configures a single frequency network area and can schedule the MBMS. Also, the MCE 203 may set the same RLC (Radio Link Control) / MAC (Medium Access Control) configuration for the base stations within a single frequency domain. Although the MCE is shown as an entity separate from the BM-SC and the BS in FIG. 2, the operation of the MCE to be described below may be implemented in the BM-SC and may be implemented in any one of the one or more base stations . That is, the MCE may be included in the BM-SC or the base station.

For example, the BM-SC 201 can receive a packet from the LTE network, and can transmit the acquired packet to the base station in cooperation with an external content server. Here, the packet may be broadcast content, for example.

Accordingly, the BM-SC 201 proceeds with the MBMS session start procedure with the MCE 203 to deliver the broadcast content to the BS.

During the session initiation procedure, the BM-SC 201 may transmit a MinTimeToDataTransfer, a broadcast channel number, and service area information to the MCE 203. The minimum data transmission time (hereinafter, referred to as MinTimeToDataTransfer) refers to a broadcast preparation time that the base station should wait before transmitting broadcast contents to the terminal.

For example, the MinTimeToDataTransfer may have a value ranging from 1 to 256, and the unit of the MinTimeToDataTransfer may be a radio frame (RF, 1 RF = 10 ms). The RF may be a unit radio frame (RF) indicated by the SFN. For example, a MinTimeToDataTransfer having a value of 10 means that the base station transmits the broadcast content to the terminal after 10 RF (i.e., 100 ms).

Accordingly, the MCE can calculate the reference SFN using the MinTimeToDataTransfer value, and can transmit the calculated reference SFN to the BS.

Herein, the reference SFN is information indicating a specific time point at which the base station transmits the broadcast content to the UE. The reference SFN is not limited to the minimum data transmission time described above by the MCE, but also includes a delay offset, (MCCH modification period) and a current SFN (Current System Frame Number).

Hereinafter, a method for determining the reference SFN through the minimum data transmission time, the delay offset, the MCCH change period, and the current SFN will be described with reference to specific embodiments.

The first embodiment is a method of determining a reference frame number using a delay offset.

The delay offset is a value obtained by measuring the time required for data transmission between the base station 205 and the MCE 203. For example, the MCE 203 can send and receive messages to and receive base stations in its own area, and directly calculate and store the delay offset value between each base station and itself (the MCE) using the time information transmitted and received . As another example, the MCE 203 may receive and store the delay offset from base stations in the area of the MCE 203 without calculating a direct delay offset.

The time at which the MCE 203 confirms the delay offset may be, for example, the time when the session initiation procedure between the MCE 203 and the BM-SC 201 is performed, It is possible.

The MCE 203 may determine the reference SFN of the MCE 203 using the maximum delay offset among the delay offsets determined through signal transmission / reception with one or more base stations. For example, the maximum delay offset may be a value reflecting a round trip time between the base station 205 physically located the farthest from the MCE 203 and the MCE 203, It may be a result of reflecting the round trip time of the base station 205 having the worst environment.

The MCE 203 may calculate the reference SFN using the determined maximum delay offset.

The second embodiment is a method of determining the SFN using an MCCH modification period.

The MCCH change period is a period during which the BS transmits a specific broadcast packet to the UE. That is, the MCCH change period means a period in which the MCCH is changed, and may indicate a period in which the base station transmits information on a specific broadcast to the terminal. For example, when the MCCH change period is 512 RF, the MCCH change period includes 512 radio frames (RF) and 1024 RFs, and the BS transmits channel information necessary for receiving a specific broadcast to the terminal every 5 seconds (5120 ms) Transmission.

Also, all base stations in the single frequency network region can confirm the same MCCH change period through synchronization process.

The MCCH change period can be received from the BM-SC 201 as an example, and the MCE 203 can directly determine and store its MCCH change period. And may receive the MCCH change period from the base stations in the MCE 203 area.

In addition, the time when the MCE 203 can confirm the MCCH change period can be confirmed through a session initiation procedure between the MCE 203 and the BM-SC 201 as described above. For example, MCCH change period can be confirmed.

The MCE 203 can calculate the reference SFN using the determined MCCH change period.

The third embodiment is a method of determining a reference SFN using a current SFN (Current System Frame Number).

The current SFN is a Radio Frame (RF) number that increases in units of 10 ms, and refers to an RF being transmitted at the present time by one or more BSs synchronized in the MBMS service area. The base station and the MCE are synchronized with each other and have the same current SFN.

In the process of synchronization, for example, the MCE may receive the current SFN from the BM-SC 201. [ As another example, the MCE 203 may directly determine its current SFN, store it, and transmit the current SFN to the base stations in the single frequency domain. The MCE 203 may also receive the current SFN from the base stations in a single frequency domain.

In addition, the time when the MCE 203 can confirm the current SFN can be confirmed through the session initiation procedure between the MCE 203 and the BM-SC 201 as described above. For example, SFN can be confirmed.

The MCE 203 can determine the reference SFN using the confirmed current SFN.

The fourth embodiment is a method of determining a reference SFN using the minimum data transmission time, the delay offset, the MCCH change period, and the current SFN

To determine the reference SFN, the MCE 203 uses the algorithm of Table 1 presented below.

Table 1 shows an algorithm in which the MCE outputs a reference SFN.

Reference SFN Algorithm Input MinTimeToDataTransfer: τ
delay offset: θ
Current SFN: SFN
MCCH modification period: μ Output Reference SFN: R_SFN

The input variables for the MCE 203 to output the reference SFN are τ, θ, SFN _, and μ, respectively, and each means a data transmission minimum time (MinTimeToDataTransfer), a delay offset, a current SFN, and an MCCH change period.

The output parameter is the information that the MCE 203 transmits to the base station 205 and indicates the time when all the base stations in the MBMS service area start transmitting broadcast content to the mobile station. The output variable is expressed as R_SFN with reference SFN.

Specifically, for each of the parameters,? Representing MinTimeToDataTransfer is information transmitted by the BM-SC 201 to the MCE, which means, for example, a broadcast preparation time for the base station 205 to transmit data to the UE

Examples θ _n is one, which means the delay offsets, n represents a measure of the time required for data transfer between the second base station 205 and the MCE (203). The MCE (203) is the received θ ₁ ... The maximum of θ _n values θ _max , where &thetas; and &thetas; _The method of determining _max is calculated as shown in Equation (1) below.

Herein, t ₀ is a time when the MCE 203 sends a request message to the base station 205, and t ₁ is a time when the MCE 203 receives a request message from the base station 205. t ₂ denotes a time when the MCE 203 has transmitted a response message to the base station 205 and t ₃ denotes a time when the MCE 203 has received a response message from the base station 205. That is, the MCE 203 measures a time required for two message transmissions between itself and the base station 205, and determines an average thereof as a delay offset for the base station 205.

and? ₁ to? _n denote the delay offset of the first to nth base stations. That is, _max may mean a delay offset between the base station 205 where the greatest delay occurs in the message transmission, for example, the farthest from the MCE 203 or the worst in the radio environment.

The SFN indicating the current SFN is an example, and the base station 205 and the MCE 203 are synchronized with each other and have the same value.

As an example of the MCCH change period, it means a period in which a base station transmits information on a specific broadcast to a mobile station, and all base stations in the SFN region may have the same MCCH change period.

Hereinafter, a process of obtaining a reference SFN, which is an output value using one or more input variables, through Equation (2) and the detailed description will be given.

The reference frame number is given by the following equation (2).

The R_SFN is calculated by summing the SFNs,? And?, And then taking a ceiling at the value divided by?.

That is, the R_SFN is a sum of the current SFN indicating the system time information of the current base station, the delay offset according to the physical distance between the base station and the MCE, and the minimum data transmission time representing the time information remaining before the broadcast data transmission starts in the core network And then the ceiling function is taken at the value obtained by dividing the summed result by the MCCH changing period. Dividing the summed result value by the MCCH changing period is for changing the unit into the MCCH changing period.

In the fourth embodiment, the current SFN, the delay offset, the minimum data transmission time, and the MCCH change period are all used to determine the reference SFN. However, using at least one of the above variables, It is also possible to determine the reference SFN. That is, each of the input variables described in the first to third embodiments is substituted into the algorithm shown in Table 1, and the remaining input variables not described in the first to third embodiments are set to a predetermined value The reference SFN can be calculated.

The algorithm shown in Table 1 can be repeatedly performed. For example, when the MCCH change period value changes frequently, the changed value is applied to the reference SFN. Similarly, the MCE can be updated iteratively to the most recently calculated reference SFN by repeatedly performing the algorithm shown in Table 1 to flexibly reflect the current SFN and maximum delay offset.

The base station can know the time (i.e., SFN) at which the broadcast data is to be transmitted to the UE by multiplying the received reference SFN by a previously known MCCH change period. That is, the BS may calculate a time point at which broadcast data transmission should start in the future by using the received reference SFN, although the time of receiving the reference frame number may differ from the MCE, That is, it is possible to transmit a packet to the UEs at the same time as other base stations using the reference SFN.

In summary, the MCE 203 receives the minimum data transmission time from the BM-SC 201, which is a core network, to transmit the reference SFN to all the base stations 205 in the single frequency domain 207, The maximum delay offset, the current SFN, and the MCCH change period between the base station 205 and the MCE 203 in the synchronization process with the base stations 205 in the area 207. Then, the MCE 203 repeatedly performs the algorithm shown in Table 1 using the information received from the BM-SC 201 and the confirmed information. Thereafter, the reference SFN, which is the result of the algorithm, is transmitted to all the base stations 205 in the single frequency domain. The base station 205 receiving the reference SFN multiplies the reference SFN by the MCCH change period to calculate a time at which future broadcasting starts, and transmits the broadcast content to the UE according to the calculated time.

3 is a diagram illustrating an MBMS flow diagram according to an embodiment of the present invention.

Referring to FIG. 3, the MBMS system includes a core network 340, an MCE 330, a base station 320, and a terminal 310. The core network 340 may be, for example, a BM-SC, and the BS 320 refers to a BS 320 within a single frequency range managed by the MCE 330.

In FIG. 3, the BM-SC 340, the MCE 330, and the base station 320 may operate based on an evolved MBMS (eMBMS) call processing flow.

The core network 340 transmits a first session initiation request message to the MCE 330 (step 301). The first session initiation request message may include MinTimeToDataTransfer information indicating a broadcast preparation time. The first session initiation request message may further include at least one of a Temporary MBMS Group Identifier (TMGI) and service area information. The MinTimeToDataTransfer may be set to a value between 1 and 256 RF. Upon receiving the first session initiation request message, the MCE 330 adds a session to the core network 340 with respect to the broadcast channel number.

Thereafter, the MCE 330 transmits a first session initiation response message to the core network 340 (step 303).

The MCE 330 determines (or calculates) the reference SFN using at least one of the delay offset, the current SFN, the MCCH change period, and the minimum data transmission time included in the first session initiation request message.

The delay offset is a value obtained by measuring a time required for data transmission between the MCE and the base station. The delay offset may be directly calculated using the signals transmitted / received by the MCE, or may be received from the base stations in the MCE's own area . For example, the above-described equation (1) may be used.

Accordingly, the time at which the MCE confirms the delay offset can be any time before the MCE transmits the second session initiation request message to the base station, and determines the maximum delay offset having the largest value of the delay offsets. For example, the maximum delay offset may be determined as a delay offset of the base station having the largest physical distance between the MCE and the base station, or may be determined as a delay offset of the base station having the worst network environment between the base station and the MCE.

The current SFN is an RF (Radio Frequency) frame number that increases in units of 10 ms, for example, and refers to an RF being transmitted at the present time by one or more synchronized BSs in the MBMS service area, It is possible to confirm the current SFN.

That is, the MCE can receive the current SFN from the BM-SC 201 in the process of synchronizing with the base station in its own area. As another example, the MCE 203 may directly determine its current SFN, store it, and transmit the current SFN to the base stations in the single frequency domain. The MCE 203 may also receive the current SFN from the base stations in a single frequency domain.

In addition, the time when the MCE 203 can confirm the current SFN can be confirmed through the first session initiation request and response procedure between the MCE 203 and the BM-SC 201 described above as an example, You can check the current SFN before the procedure.

The MCCH change period can be received from the core network as an example. In another example, the MCE can directly determine and store the MCCH change period. And may also receive the MCCH change period from the base stations in the MCE region.

As an example, the time when the MCE can confirm the MCCH change period can be confirmed through the first session initiation request and response procedure between the MCE and the core network as described above. Alternatively, the MCCH change period can be confirmed before the session procedure.

The MCE 330 may determine a reference SFN using at least one of a delay offset, a current SFN and an MCCH change period, and a minimum data transmission time included in the first session start request message, and the MCE may determine the reference SFN And transmits a second session initiation request message including all of the first session initiation request messages to all base stations within a single frequency domain (step 305).

The second session initiation request message may include, for example, M2 scheduling information, and the M2 scheduling information may inform the MBMS change period. 2 base station SFN in the MCCH update field of the Session Initiation Request message and transmit the same to the base station.

Accordingly, the BS 320 transmits a second session initiation response message to the MCE 330 in response to the second session initiation request message (step 307).

Then , the base station 320 starts broadcasting data transmission to the terminal 310 (Step 309). That is, all the base stations within the single frequency domain receive and store the same reference SFN, and wait for transmission until time corresponding to the reference SFN. Thereafter, the BS 320 transmits the broadcast data to the MS 310 at a time corresponding to the received reference SFN (Step 309).

Hereinafter, a process of transmitting broadcast data to a mobile station by applying the reference SFN will be described in detail.

4 is a diagram illustrating a method in which a base station applies a reference system frame number.

Referring to FIG. 4, it is assumed that at least one base station is in the same single frequency domain and the MCCH scheduling period (i.e., MCCH changing period) of the base station is 64 seconds.

The base stations receive the same reference SFN 403 from the MCE and store it. The base station stores the broadcast data received from the MCE in the packet buffer 407. For example, the time when the BS receives the broadcast data from the MCE is SFN 1536 (401). However, at least one of the base stations in the single frequency domain transmits the broadcast data received in the SFN 1536 (401) to the terminal only after the time indicated by the reference SFN, i.e. SFN 1600 (403).

5 is a diagram illustrating a flow diagram of an MCE according to an embodiment of the present invention.

5, optionally, the MCE may perform synchronization with its base station in a single frequency domain (step 501).

In step 501, the MCE calculates a delay offset of each base station from each base station and determines a maximum delay offset having the largest value among the delay offsets. In addition, the BS can further confirm the current SFN and the MCCH change period of the BSs (step 503).

Thereafter, the MCE receives a first session initiation request message from the BM-SC (step 505). The first session initiation request message includes a data transmission minimum time (MinTimeToDataTransfer), and the MinTimeToDataTransfer indicates a broadcast preparation time.

The MCE determines a reference SFN using at least one of the minimum data transmission time, the current SFN, the MCCH change period, and the maximum delay offset (step 507)

The reference SFN refers to a time at which the BS starts transmission of broadcast data to the UE. The reference SFN is used by the MCE to use at least one of the delay offset, the MCCH change period, and the current SFN, Lt; / RTI > Since the process of determining (or calculating) the reference SFN has been described with reference to Table 1 and Equations 1 and 2 described above, detailed description thereof will be omitted here.

Optionally, the MCE may send a first session initiation response message to the BM-SC, which is a response to the first session initiation request message (step 509). However, the transmission of the first session initiation response message is not necessarily performed in step 507, but may be performed immediately after step 505. [

The MCE transmits a second session initiation request message including the reference SFN determined in step 507 to all base stations within its single frequency domain (step 511). Alternatively, the second session initiation request message may include M2 scheduling information.

Alternatively, the MCE may receive a second session initiation response message, which is a response message to the message, from the base stations that have received the second session initiation request message (step 513).

6 is a diagram illustrating a flowchart of a base station according to an embodiment of the present invention.

Referring to FIG. 6, the base station MCE and the base station MCE are synchronized with each other (Step 601). At this time, the base station may perform reception or transmission of a message (an arbitrary request message and a response message) necessary for the MCE to calculate a delay offset, and may provide corresponding reception or transmission time information to the MCE. Alternatively, in step 601, the base station may transmit at least one of the delay offset, the current SFN, and the MCCH change period to the MCE.

Thereafter, the BS receives a second session initiation request message from the MCE (step 603). The second session initiation request message includes information on a reference SFN. The reference SFN is information that the MCE instructs to the base station to start transmission of broadcast data to the terminal.

Optionally, the base station may send a second session initiation response message to the MCE in response to the second session initiation request message (step 605). The transmission of the second session initiation response message is not necessarily performed immediately after step 603 and may be performed at any time after step 603. [

In step 607, the BS starts transmission of the broadcast data to the UEs at a time corresponding to the reference SFN included in the second session initiation request message.

That is, in step 607, the BS transmits the broadcast content to the UEs at a time corresponding to the reference SFN. In step 607, the base station transmits the broadcast content to the UE in accordance with the reference SFN included in the second session start request message And waiting for the broadcast contents to be transmitted to the terminals until the SFN is reached.

7 is a diagram illustrating a configuration of an MCE according to an embodiment of the present invention.

Referring to FIG. 7, the MCE includes a transmitter 720, a receiver 730, and a controller 710.

The MCE receives an MBMS service packet from the core network and delivers the service packet to at least one base station in a single frequency domain. Accordingly, the controller 710 in the MCE may perform synchronization with the at least one base station and calculate a reference SFN indicating a time point at which the base station starts transmission of the service packet. Also, the controller 710 measures at least one period required for exchanging messages with the at least one base station before calculating the reference SFN, and calculates a delay offset, which is a maximum value among the measured at least one period You can decide. In addition, the controller 710 may calculate the reference SFN based on the current SFN indicating the system time information of the current base station, the delay offset according to the physical distance between the base station and the MCE, Calculating a ceiling function at a value obtained by adding the minimum data transmission time representing the time information and the summed result value divided by the MCCH changing period. In addition, although all of the current SFN, the delay offset, the minimum data transmission time, and the MCCH change period are used to determine the reference SFN, the reference SFN is determined by substituting the at least one of the above variables into the algorithm shown in Table 1 It is also possible to do.

The transmitter 720 may transmit the calculated scheduling information including the reference SFN to the BS and may transmit the first session initiation response message to the core network. The first session initiation response message has been described in detail with reference to FIG. 3, and will not be described below.

The receiving unit 730 may receive MintimeToDataTransfer, which is a broadcast preparation time to wait before the service packet is transmitted to the MS, from the core network and may receive the second session initiation response message shown in FIG. 3 from the BS . Since the second session initiation response message has been described in detail with reference to FIG. 3, it will not be described below.

Although the MCE is shown as a separate component separate from the BM-SC or the BS in FIG. 7, all the components of the MCE described above may be implemented in the BM-SC or implemented in any one of the one or more base stations . That is, the MCE may be included in the BM-SC or the base station.

8 is a diagram illustrating a configuration of a base station according to an embodiment of the present invention.

Referring to FIG. 8, the base station includes a transmitter 820, a receiver 830, and a controller 810.

The base station receives the service packet from a cooperating entity that receives an MBMS service packet from the core network, and simultaneously delivers the service packet to the terminals in its own area.

Accordingly, the control unit 810 in the base station synchronizes with the cooperating entity, and controls the operations of the transmitting unit 820 and the receiving unit 830. That is, the control unit 810 controls the transmission unit 820 and the reception unit 830 to perform transmission or reception of a message (an arbitrary request message and a response message) necessary for the MCE to calculate the delay offset during the synchronization process Can be controlled. Also, the controller 810 may control to wait for the broadcast contents to be transmitted to the UEs until the reference SFN is reached according to the reference SFN information included in the second session start request message received from the MCE have.

The receiving unit 830 may receive scheduling information including a reference SFN (System Frame Number) indicating a time point at which the BS starts transmission of the service packet from the cooperative entity.

The transmitter 820 may transmit at least one of the delay offset, the current SFN, and the MCCH change period to the MCE. Also, a second session initiation response message may be sent to the MCE in response to the second session initiation request message.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but is capable of various modifications within the scope of the invention. Therefore, the scope of the present invention should not be limited by the illustrated embodiments, but should be determined by the scope of the appended claims and equivalents thereof.

Claims (30)

A method of supporting transmission of a Multimedia Broadcast and Multicast Service (MBMS) service packet in a wireless communication system,
The method comprising the steps of: receiving a MBMS service packet from a core network and performing synchronization with a cooperative entity for delivering the service packet to at least one base station in a single frequency network,
The cooperative entity calculating a reference SFN (System Frame Number) indicating a time point at which the BS starts transmission of the service packet,
And transmitting, by the cooperative entity, scheduling information including the calculated reference SFN to the BS. The method according to claim 1,
Prior to calculating the reference SFN,
Wherein the cooperative entity measures at least one period required for exchanging messages with the at least one base station and determining a delay offset which is a maximum value of the measured at least one period,
Wherein the reference SFN is calculated in consideration of the delay offset. 3. The method of claim 2,
Further comprising the step of receiving, from the core network, a minimum data transmission time (MintimeToDataTransfer), which is a broadcast preparation time that the cooperative entity should wait before the service packet is transmitted to the terminal. How to Apply. The method of claim 3,
The reference SFN,
The current data frame transmission time, the data maximum transmission time, the current SFN (Current System Frame Number) obtained as a result of the synchronization, and the MCCH (Multicast Control Channel) change period. The method according to claim 1,
Wherein the scheduling information is included in an MCCH update field of a session initiation request message transmitted by the cooperative entity to the base station. The method according to claim 1,
Wherein the cooperative entity is a multi-cell multicast coordinated entity (MCE), which is a centralized control node. The method according to claim 6,
Wherein the cooperating entity is implemented on a BM-SC located in the core network or is implemented in one of the one or more base stations. 3. The method of claim 2,
The process of calculating the delay offset is determined by the following equation,
θ =

Theta represents the delay offset between the base station and the MCE,

Is a time when the MCE sends a request message to the BS,

Is the time at which the MCE received a request message from the base station,

Is a time at which the MCE transmits a response message to the BS,

Is a time at which the MCE receives a response message from the base station. 5. The method of claim 4,
The process of calculating the delay offset is determined by the following equation,

Wherein R_SFN denotes the reference R_SFN, SFN denotes the current SFN, θ _n denotes the delay offset between the nth base station and the MCE, τ denotes the MinTimeToDataTransfer, μ denotes the MCCH change period Wherein the R_SFN adds the SFN, the _n and the τ, and then takes a ceiling at a value divided by the μ. A method of supporting transmission of a Multimedia Broadcast and Multicast Service (MBMS) service packet in a wireless communication system,
The base station receiving the service packet from the cooperating entity receiving the MBMS service packet from the core network performs synchronization with the cooperating entity,
Wherein the base station receives, from the cooperative entity, scheduling information including a reference SFN (System Frame Number) indicating a time point at which the base station starts transmission of the service packet. 11. The method of claim 10,
Wherein the reference SFN is calculated in consideration of the delay offset. 12. The method of claim 11,
The reference SFN,
The current data frame transmission time, the data maximum transmission time, the current SFN (Current System Frame Number) obtained as a result of the synchronization, and the MCCH (Multicast Control Channel) change period. 11. The method of claim 10,
Wherein the scheduling information is included in an MCCH update field of a session initiation request message received from the cooperating entity by the base station. . 12. The method of claim 11,
The process of calculating the delay offset is determined by the following equation,
θ =

Theta represents the delay offset between the base station and the MCE,

Is a time when the MCE sends a request message to the BS,

Is the time at which the MCE received a request message from the base station,

Is a time at which the MCE transmits a response message to the BS,

Is a time at which the MCE receives a response message from the base station. 13. The method of claim 12,
The process of calculating the reference SFN is determined through the following equation,

Wherein R_SFN denotes the reference SFN, SFN denotes the current SFN, θ _n denotes the delay offset between the nth base station and the MCE, τ denotes the MinTimeToDataTransfer, μ denotes the MCCH change period Wherein the R_SFN adds the SFN, the _n and the τ, and then takes a ceiling at a value divided by the μ.
In a cooperative entity supporting transmission of a Multimedia Broadcast and Multicast Service (MBMS) service packet in a wireless communication system,
A cooperative entity that receives an MBMS service packet from a core network and delivers the service packet to at least one base station in a single frequency network performs synchronization with the at least one base station, A control unit for calculating a reference SFN (System Frame Number) indicating a start time of transmission of a service packet; and a transmitter for transmitting the calculated scheduling information including the reference SFN to the base station. 17. The method of claim 16,
The control unit measures at least one period required for exchanging messages with the at least one base station before calculating the reference SFN, determines a delay offset which is a maximum value among the measured at least one period, SFN is calculated considering the delay offset. 18. The method of claim 17,
Further comprising a receiver for receiving, from the core network, a minimum data transmission time (MintimeToDataTransfer), which is a broadcast preparation time which must be waited before the service packet is transmitted to the terminal. 19. The method of claim 18,
Wherein the reference SFN is calculated using at least one of a data maximum transmission time, a current system frame number (SFN) obtained as a result of the synchronization, and a MCCH (Multicast Control channel) change period. 17. The method of claim 16,
Wherein the scheduling information is included in an MCCH update field of a session initiation request message transmitted by the cooperative entity to the base station. 17. The method of claim 16,
Wherein the cooperative entity is a multi-cell multicast coordinated entity (MCE), which is a centralized control node. 22. The method of claim 21,
Wherein the cooperating entity is implemented on a BM-SC located in the core network, or is implemented in one of the one or more base stations. 18. The method of claim 17,
The process of calculating the delay offset is determined by the following equation,
θ =

Theta represents the delay offset between the base station and the MCE,

Is a time when the MCE sends a request message to the BS,

Is the time at which the MCE received a request message from the base station,

Is a time at which the MCE transmits a response message to the BS,

Is the time at which the MCE received a response message from the base station. 20. The method of claim 19,
The process of calculating the delay offset is determined by the following equation,

Wherein R_SFN denotes the reference R_SFN, SFN denotes the current SFN, θ _n denotes the delay offset between the nth base station and the MCE, τ denotes the MinTimeToDataTransfer, μ denotes the MCCH change period Wherein the R_SFN takes a ceiling at a value divided by the μ after summing the SFN, the θ _n, and the τ. A base station supporting transmission of a Multimedia Broadcast and Multicast Service (MBMS) service packet in a wireless communication system,
A base station that receives the service packet from a cooperative entity that receives an MBMS service packet from the core network includes a control unit for performing synchronization with the cooperative entity and a control unit for notifying the cooperative entity of a time point at which the base station starts transmitting the service packet And a receiving unit for receiving scheduling information including a reference SFN (System Frame Number) indicating the scheduling information. 26. The method of claim 25,
Wherein the reference SFN is calculated in consideration of the delay offset. 27. The method of claim 26,
The reference SFN,
Wherein the base station is further calculated using at least one of a data maximum transmission time, a current system frame number (SFN) obtained as a result of the synchronization, and a multicast control channel (MCCH) change period. 26. The method of claim 25,
Wherein the scheduling information is included in an MCCH update field of a session initiation request message received from the cooperating entity by the base station. . 27. The method of claim 26,
The process of calculating the delay offset is determined by the following equation,
θ =

Theta represents the delay offset between the base station and the MCE,

Is a time when the MCE sends a request message to the BS,

Is the time at which the MCE received a request message from the base station,

Is a time at which the MCE transmits a response message to the BS,

Is a time at which the MCE receives a response message from the base station. 28. The method of claim 27,
The process of calculating the reference SFN is determined through the following equation,

Wherein R_SFN denotes the reference SFN, SFN denotes the current SFN, θ _n denotes the delay offset between the nth base station and the MCE, τ denotes the MinTimeToDataTransfer, μ denotes the MCCH change period Wherein the R_SFN adds the SFN, the θ _n, and the τ, and then takes a ceiling at a value divided by μ.

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