KR100965719B1 - Method for renovating random access effectively in a mobile telecommunication system - Google Patents

Abstract

According to an aspect of the present invention, there is provided a method in which a base station controller transmits an access preamble to terminals in a mobile communication system, the method comprising: measuring a number of reverse channels allowed by a base station on a predetermined time basis; And determining the number of attempts to allocate the reverse channel by the terminals on a time basis as the measured number of reverse channels.

Group signaling message, reverse channel, back-off window, radio frame, transmission section update

Description

METHODS FOR RENOVATING RANDOM ACCESS EFFECTIVELY IN A MOBILE TELECOMMUNICATION SYSTEM}             

1 is a diagram schematically illustrating a network structure for providing MBMS in a conventional mobile communication system.

2 is a diagram schematically illustrating operations that must be performed between a user and a network in order for any conventional MBMS to be performed.

3 illustrates specific signaling for some of the procedures taught in FIG.

4 is a diagram illustrating a case where a plurality of users according to the prior art attempts to use a RACH.

5 is a flow chart showing operation of the RACH according to the prior art.

6 is a view illustrating operation of a RACH according to an embodiment of the present invention.

7 is a diagram illustrating a control flow of performing an RACH operation in a UE MAC when P _mbms is continuously updated according to an embodiment of the present invention.

8 is a diagram illustrating a control flow for a UE to update P _mbms according to an embodiment of the present invention.

9 is a diagram illustrating a control flow for a UE to transmit a group response message in response to an MBMS control message from an RNC according to an embodiment of the present invention.

10 illustrates a control flow for the RNC to determine and update P _mbms according to an embodiment of the present invention.

The present invention relates to a mobile communication system, and more particularly, to a method of providing a reverse message transmission interval for preventing a collision caused by a plurality of terminals simultaneously transmit a predetermined reverse message through a random access channel. .

Today, due to the development of the telecommunications industry, the services provided by the code division multiple access (CDMA) mobile communication system are not only voice services but also large capacity such as packet data and circuit data. It is evolving into a multicasting multimedia communication that transmits data. Accordingly, in order to support the multicasting multimedia communication, a broadcast / multicast service which provides a service from a data source to a plurality of mobile terminals (hereinafter referred to as UE) is proposed. It became. The broadcast / multicast service is a cell broadcast service (hereinafter, referred to as a "CBS service"), a message-oriented service, and a multicast multimedia broadcast service supporting multimedia forms such as real-time video, voice, still image, and text ( Multimedia Broadcast / Multicast Service, hereinafter referred to as "MBMS".

Typically, MBMS refers to a service for transmitting the same multimedia data to multiple receivers through a wireless network. The MBMS is serviced through a broadcast channel in that there is a possibility that a large number of services can be simultaneously deployed in one Node B. That is, by allowing a plurality of UEs to share one radio channel, it is possible to save radio resources.

1 is a diagram schematically illustrating a network structure for providing an MBMS in a mobile communication system.

Referring to FIG. 1, a multicast / broadcast-service center (MB-SC) hereinafter referred to as a "MB-SC" 110 is a source for providing an MBMS stream. (source). The MB-SC 110 schedules and transmits the MBMS data stream according to the MBMS to the transport network 120. The transport network 120 selects a network existing between the MB-SC 110 and a service packet radio service support node (SGSN) 130. it means. The transport network 120 transfers the MBMS data stream received from the MB-SC 110 to the SGSN 130. Here, the transport network 120 may be configured with a Gateway Packet Radio Service Support Node (GGSN) (hereinafter referred to as "GGSN") and an external network. A plurality of UEs wishing to receive the MBMS data at any point in time, for example, UE 1 161 and UE 2 162 belonging to a first base station (first Node B), that is, a first cell 1 160. It is assumed that UE 3 163, UE 2 171 and UE 5 172 belonging to the second base station, that is, the second cell 170, are present. The SGSN 130 receiving the MBMS data stream from the transport network 120 controls the MBMS-related services of subscribers, that is, UEs, to receive the MBMS. For example, MBMS-related data such as managing MBMS charging-related data of each UE or selectively transmitting MBMS data to a specific Radio Network Controller (RNC) (hereinafter, referred to as "RNC") 140. Control the service. In order to perform selective transmission for the RNC as described above, the SGSN 130 needs to know a list of RNCs to provide a specific NMBMS. Although not shown in FIG. 1, there may be a plurality of SGSNs for one MBMS and a plurality of RNCs for each SGSN.

The RNC 140 provides a function of selectively transmitting MBMS data transmitted from the SGSN 130 to cells of connected base stations. That is, the RNC 140 controls a plurality of cells and transmits MBMS data to a specific cell in which a UE requesting a specific MBMS exists among cells managed by the RNC 140. To this end, the RNC 140 must know the list of cells that will provide a particular MBMS. In addition, the RNC 140 controls a radio channel configured to provide the MBMS, and manages information on the MBMS with the MBMS data stream received from the SGSN 130. For convenience of explanation, "base station" and "cell" will be used as the same concept. Of course, the base station may manage only one cell or manage multiple cells.

Although not shown in FIG. 1, a Home Location Register (HLR) is connected to the SGSN 130 to perform subscriber authentication for an MBMS service.

Each of the cells 160 and 170 connects to UEs requesting to provide a specific MBMS through one wireless channel and transmits MBMS-related data to the UEs through the wireless channel. When the UEs 161, 162, and 163 are connected to the first cell 160 through one radio channel, the UEs 161, 162, and 163 mean a terminal device or a subscriber that can receive an MBMS through the radio channel. When the UEs 171 and 172 are connected to the second cell 170 via one radio channel, the UEs 171 and 172 mean a terminal device or a subscriber that can receive MBMS through the radio channel.

Considering the process of providing an arbitrary MBMS in the network structure shown in FIG. 1 as follows.

In order to provide an arbitrary MBMS, basic information on the MBMS must first be delivered to UEs, and when the UEs receiving the basic information on the MBMS wish to receive the arbitrary MBMS, the list of UEs is delivered to the network. Should be. When receiving a list of UEs that want to receive the arbitrary MBMS in the network, the network should set up a radio bearer for providing the MBMS by paging the UEs. After the radio bearer is set up with the UEs, the random MBMS is provided through the set radio bearer. On the other hand, when the MBMS is terminated, it must be notified to all UEs, and thus, all UEs must release all resources allocated for the MBMS so that normal MBMS is possible.

2 schematically illustrates operations that must be performed between a user and a network in order for an arbitrary MBMS to be performed. The core network (hereinafter referred to as 'CN') illustrated in FIG. 2 includes the SGSN 130, the Transit N / W 120, and the MB-SC 110.

Referring to FIG. 2, a reservation step (SUBSCRIPTION STEP) 201 is a process of registering a UE to receive a certain MBMS with a service provider. At this time, the service provider and the UE exchange basic information related to charging or service reception. ANNOUNCEMENT STEP 202 is a step in which a service announcement for any MBMS is made. Through the ANNOUNCEMENT STEP 202, UEs wishing to receive any MBMS service may recognize basic information about the corresponding service. For example, the basic information may be an identifier (MBMS ID), service start time and duration of the MBMS. The BM-SC may broadcast a service announcement message or the like using a CBS (Cell Broadcast Service) to deliver the service related basic information to the UEs.                         

UEs 161 to 172 that have acquired basic information about a specific service through the ANNOUNCEMENT STEP 202 perform a JOINING STEP 203 if they want to receive the service. . In the connection step 203, the UE delivers a service identifier (MBMS ID) to be received in an arbitrary message to the network. The devices located between the BM-SC 110 and the UEs, that is, the SGSN 130, the Transit NW 120, and the like, are UEs that want to receive MBMS data according to an arbitrary MBMS and devices in which the UEs are located. It can be recognized. For example, the SGSN 130 may grasp the list of UEs and the list of RNCs 140 where the UEs are located, and will later transmit MBMS data only to the RNC 140 where the UEs are located.

In the broadcast mode bearer setup step 204, a transport bearer for providing the MBMS on the SGSN 130 and the Transit NW 120 may be preset. For example, a GTP-U / UDP / IP / L2 / L1 bearer (see 3GPP TS 23.060) for the MBMS may be preset between the SGSN 130 and the GGSN (not shown).

NOTIFICATION STEP 205 is a step in which UEs wishing to receive a service are called, since the MBMS will be started soon. In the notification step 205, an existing calling method may be used or an calling method optimized for MBMS may be used. The NOTIFICATION STEP 205 will be described in detail with reference to FIG. 3.

RADIO RESOURCE ALLOCATION STEP 206 is a step of actually allocating a radio resource for providing the MBMS, and notifying the relevant devices of the information.

In the current standard meeting, when providing MBMS, an efficient method between point to point (PTP) and point to multi-point (PTM) method is provided. How to choose is discussed. The PTM scheme is a scheme in which a plurality of UEs share a stream transmitted through one common channel. The PTP scheme uses a dedicated channel to transmit a stream for each UE. In general, the PTM method is more efficient than the PTP method. However, since the power control is not performed in the PTM scheme, when the number of UEs is smaller than a certain number, the PTP scheme may be more efficient. In an extreme example, if only one UE wants to receive a particular MBMS in a cell, it would be more efficient to use the PTP scheme. Therefore, the number of UEs should be considered as the selection criteria of the PTP scheme and the PTM scheme. The number of UEs (hereinafter, referred to as “MBMS thresholds”) that are the selection criteria of the PTP scheme and the PTM scheme in the specific cell is a variable determined for each cell and may vary depending on a situation. Referring to the current discussion of the standards meeting, the MBMS threshold is expected to be less than 10.

Referring to the foregoing, in order to allocate radio resources in the RADIO RESOURCE ALLOCATION STEP 206, the RNC needs to know whether the number of UEs to be provided with the corresponding MBMS for each cell is larger or smaller than the MBMS threshold. That is, if it is larger than the MBMS threshold, the PTM scheme is set. If it is less than the MBMS threshold, the PTM scheme is set. In allocating radio resources for providing a specific MBMS to a specific cell, a process of determining whether the number of UEs is greater than the MBMS threshold is called counting. If necessary, the process of re-determining whether the number of UEs in a specific cell is larger than the MBMS threshold is called recounting. The counting and recounting will be described in more detail with reference to FIG. 3. In the RADIO RESOURCE ALLOCATION STEP 206, a radio resource is allocated in correspondence with the PTP scheme or the PTM scheme.

After the RADIO RESOURCE ALLOCATION STEP 206, the actual MBMS data is transmitted to the UEs in the DATA TRANSFER STEP 207. At this time, updating of a ciphering key may be performed. For example, if there is a need to change the ciphering key for any MBMS, the RNC 140 sends a new ciphering key to all UEs receiving the MBMS.

Thereafter, when the MBMS is terminated, the radio resource set in the radio resource release step RADIO RESOURCE RELEASE STEP 208 is released, and a message such as MBMS RB RELEASE is transmitted to all UEs receiving the MBMS. do.

3 illustrates specific signaling according to some operations in operations that must be performed between a user and a network in order for an arbitrary MBMS to be performed. The core network illustrated in FIG. 2 includes the SGSN 130, the Transit N / W 120, and the MB-SC 110, but FIG. Only SGSN was considered. Steps specifically shown in FIG. 3 include the JOINING STEP 203, the NOTIFICATION STEP 205, the RADIO RESOURCE ALLOCATION STEP 206, and the radio in FIG. 2. A RADIO RESOURCE RELEASE STEP 208.

Referring to FIG. 3, the UE, upon recognizing basic information about an arbitrary MBMS, that is, an MBMS ID, through an ANNOUNCEMENT STEP 202, transmits an ACTIVATE MBMS PDP CONTEXT REQUEST message to the SGSN (step 301). . Upon receiving the message, the SGSN configures an MBMS PDP CONTEXT to store the UE in the CONTEXT and performs a necessary operation with the GGSN, if the UE is the first UE to request a corresponding service. The necessary operation may be a GTP tunnel setup process, and may include a process in which SGSN notifies the GGSN of the service related information and exchanges logical identifiers to be used with each other. More details are described in 3GPP TS 23.060. The MBMS PDP CONTEXT is a set of variables in which relevant information about an arbitrary MBMS service is stored, and stores a list and a location of UEs that have transmitted the ACTIVATE MBMS PDP CONTEXT REQUEST message and information related to a transmission bearer for transmitting the corresponding MBMS data. You may be doing The SGSN sends an ACTIVATE MBMS PDP CONTEXT ACCEPT message to the UE, notifying the completion of the connection step (step 302). Steps 301 and 302 described above correspond to the JOINING STEP 203 of FIG. 2.

The NOTIFICATION STEP 205 for calling UEs in which the JOINING STEP 203 has been performed at the beginning of the MBMS is performed in steps 303 and 304. That is, the SGSN wakes up UEs who wish to receive the service through the NOTIFICATION STEP 205 near the start of the MBMS or after receiving the first MBMS data. The UEs to receive the service will be UEs that transmit the ACTIVATE MBMS PDP CONTEXT REQUEST message in step 301. First, the SGSN transmits a NOTIFICATION message to RNCs in which UEs that have performed the JOINING STEP are located in step 303. The RNCs receiving the NOTIFICATION message from the SGSN transmit a NOTIFICATION message to the corresponding UEs through the cells where the UEs having performed the JOINING STEP are located in step 304. Therefore, the NOTIFICATION message is received by all UEs that have performed the connection step for the MBMS. That is, UEs in all states including an idle mode should be able to receive the NOTIFICATION message. For this purpose, the NOTIFICATION message may be transmitted through a PAGING MESSAGE. This is described in detail in the previously filed P2002-0068597.

In steps 305, 306, and 307, it is determined whether to provide MBMS for a specific cell by PTP or PTM.

The UE may be in an idle mode, URA_PCH, CELL_PCH, CELL_FACH, CELL_DCH, or the like. The other states except for the idle mode are collectively referred to as an RRC connected mode. If any UE is in the RRC connected mode, the RNC is burdened to keep storing information about the UEs. Therefore, when a plurality of UEs are provided with a particular MBMS, steps 305 to 307 are proposed in order to ensure that only a minimum number of UEs (UEs per MBMS threshold per cell) are in the RRC connected mode. It became. In other words, when UEs having an MBMS threshold or higher in a specific cell want to provide a specific MBMS, only UEs corresponding to the MBMS threshold maintain RRC connection. In this case, the PTM method will be set for the cell. However, if UEs below the MBMS threshold in a specific cell want to provide a particular MBMS, all the UEs maintain the RRC connection. In this case, a PTP scheme may be set for the corresponding cell.

As described above, UEs which have transitioned to the RRC connected mode are tracked in cell units, and the tracked location information is managed by the RNC.

Looking at this in more detail, UEs in the idle mode having received the NOTIFICATION message perform an RRC CONNECTION SETUP procedure in step 305. The procedure is completed by the UE sending an RRC CONNECTION REQUEST message to the RNC, the RNC sending an RRC CONNECTION SETUP message to the UE, and then the UE sending an RRC CONNECTION SETUP COMPLETE message to the RNC. The UE inserts and transmits an MBMS ID in the RRC CONNECTION REQUEST message, and the RNC counts reception for each MBMS included in the RRC CONNECTION REQUEST message in step 306. When the number of RRC CONNECTION REQUEST messages including a specific MBMS ID reaches the MBMS threshold, the RNC no longer needs to receive a response message. If such a situation occurs, the RNC transmits a STOP message requesting not to transmit a response message including the specific MBMS ID in step 307. Upon receiving the STOP message, the UEs stop attempting to transmit a response message to the NOTIFICATION message received in step 304. Since the RRC CONNECTION REQUEST message is transmitted through a random access channel (hereinafter referred to as "RACH"), stopping the transmission attempt of the response message is equivalent to stopping the RACH usage attempt.

The SGSN transmits an MBMS RAB ASSIGNMENT REQUEST message to the RNC in step 308. The MBMS RAB ASSIGNMENT REQUEST message may include Quality of Service (QoS) information required to provide an MBMS service. The RNC determines MBMS RB information for each cell based on the received QoS information and the counting value in step 306. The MBMS RB information includes Layer 2 (hereinafter referred to as "L2") information and Layer 1 (hereinafter referred to as "L1") information. The L2 information may include RLC / PDCP related information. The L1 information may include TFS information, TFCS information, channelization code information, transmission output related information, and the like. The RNC determines the information for each cell in a cell where a radio channel according to the PTM scheme is to be configured, and determines the information for each UE for a cell in which a radio channel according to the PTP scheme is to be established.

The RNC delivers the MBMS RB information to UEs in step 309. If the setting of the radio channel according to the PTM scheme is determined, the radio channel information according to the PTM scheme will be inserted into the MBMS RB SETUP message. If the setting of the radio channel according to the PTP scheme is determined, the radio according to the PTP scheme is determined. Channel information will be inserted.                         

A data transmission step of transmitting MBMS data through the wireless channel established in step 207 is performed between the SGSN and the UEs receiving the MBMS RB SETUP message.

UEs may move to another cell while receiving MBMS data according to MBMS in step 207. Due to the mobility of these UEs, the number of UEs receiving a particular MBMS in one cell may vary. In order to provide a more efficient MBMS, it is necessary to periodically update the number of UEs thus varied. For example, at the time of initial provision for a particular MBMS, any cell would have had as many UEs as the MBMS threshold for receiving that particular MBMS. However, assuming some UEs have moved to another cell after some time has elapsed, the RNC should be able to additionally provide the particular MBMS for UEs in the moved number of idle modes. However, when a large number of UEs move to another cell but there are no UEs in idle mode waiting for the specific MBMS, the type of radio channel for the cell may be changed to a radio channel according to the PTP scheme.

To this end, the RNC transmits a RECOUNTING message to the UEs in the idle mode in step 310. The RECOUNTING message may include the corresponding MBMS ID. Upon receiving the RECOUNTING message, UEs in idle mode perform an RRC CONNECTION SETUP procedure in step 310. The RNC counts a response message from UEs in the idle mode. When the sum of the count value and the number of UEs continuously receiving a specific MBMS reaches an MBMS threshold, the RNC blocks a further response message by transmitting a STOP message in step 311.                         

As described above, a group signaling message (eg, a notification message or a RECOUNTING message) that provides the same information to multiple UEs using one message may result in a situation in which multiple response messages are transmitted at the same time from the UEs. Can be. For this reason, since the response messages are transmitted through a RACH that can be shared by all UEs, when many UEs intend to use them at the same time, the performance of the RACH having a limited capacity may be degraded.

Typically, the RACH is a channel used by UEs not having a dedicated channel to transmit data in the reverse direction. UEs that do not have the dedicated channel are represented by UEs in Cell_FACH, Cell_PCH, URA_PCH, or idle mode. The PRACH may be defined as a set of radio resources used for RACH transmission, and the radio resources are configured as follows.

1. Preamble scrambling code: Preamble scrambling code: One scrambling code corresponding to one specific PRACH. Preamble and RACH data transmitted in the reverse direction for use of the PRACH is scrambled by the preamble scrambling code and transmitted.

2. Signature set: OVSF codes with a spread factor (SF) of 16, which can be assigned up to 16 per PRACH, are used to code preamble and RACH data.

3. Access slot set: Composed of two time slots, preamble transmission is started at the start of each access slot.                         

5 is a diagram illustrating a typical control flow of a UE for transmitting data on the RACH. The control flow shown in FIG. 5 is for a UE in idle mode or a UE in Cell_PCH / URA_PCH / Cell_FACH state.

Referring to FIG. 5, if data to be transmitted in the reverse direction occurs in step 501, the UE proceeds to step 502. When data to be transmitted in the reverse direction occurs, the corresponding UE needs to receive a call message or transmit a location information update message.

In FIG. 5, steps 502 to 507 correspond to an RACH signal transmission operation. The UE performs what is called a persistence value test in step 502. To do this, you must determine the persistence value.

To this end, each UE is assigned an Access Service Class (ASC) according to the type of data to be transmitted through the RACH at a specific time. There are a total of eight ASCs from ASC # 0 to ASC # 7. For each of the ASCs, a persistence value, an available signature set and available access slots are determined. The information is conveyed to the UEs as system information. Each UE may have several types of data streams, which are called radio bearers. The radio bearer may include a radio bearer for transmitting a control message and a radio bearer for voice call. The radio bearers are set through a RADIO BEARER SETUP process. At this time, each radio bearer is assigned an ASC. Therefore, the generation of data to be transmitted in the reverse direction in step 501 means that the UE already knows the ASC corresponding to the radio bearer to transmit the data.

In step 502, the UE performs a persistence value test by using a persistence value corresponding to the corresponding ASC. The persistence value is a real value between 0 and 1, which essentially means the probability of success of the persistence value test. For example, assuming that the persistence value is 0.5, it means that the probability of success by the persistence value test is 50%. If the persistence value test is successful, the UE proceeds to step 503. If the UE fails, the UE waits for 10 ms and attempts the persistence value test again.

In step 503, the UE transmits a preamble. At this time, the UE randomly selects one of the available signatures corresponding to the ASC, codes the preamble by using the selected signature, and sets an initial power and transmits the preamble. . Since the initial power setting is described in detail in 3GPP TS 25.331, a detailed description thereof will be omitted.

In step 504, the UE monitors whether an Acquisition Indication Channel (AICH) signal is received from the Node B in response to the transmitted preamble. The AICH signal informs the UE that has transmitted a specific signature that the preamble signal has been successfully received and allows the message transmission through the RACH.

If the UE determines in step 504 that the AICH signal does not include the signature transmitted by the UE, step 506 is performed. The fact that the AICH signal does not include the signature transmitted by the AICH signal means that an ACK signal or a NACK signal for a signature transmitted by the AICH signal is not detected (no response situation).

In step 506, the UE selects one of the available signatures again, increases the transmission power by a step size, and proceeds to step 503 to select the preamble including the reselected signature. Transmitted by increased power. Increasing the transmission power is for increasing the probability that the Node B recognizes the preamble transmitted by the UE.

If the UE receives the ACK signal by the AICH signal in step 504, the UE proceeds to step 505 and transmits RACH data. At this time, the UE waits for 3 or 4 time slots after receiving the ACK signal and then transmits the RACH data. The RACH data is transmitted using an OVSF code located on the same OVSF code tree as a signature included in a preamble that caused the reception of the ACK signal.

If the UE receives the NACK signal by the AICH signal in step 504, the UE proceeds to step 507. The UE waits for NBO ₁ × 10 ms in step 507 and proceeds to step 502. The NBO ₁ is a value given as system information.

As described above, a problem that may occur when UEs attempt to use the RACH at the same time will be described in detail with reference to FIG. 4. In FIG. 4, it is assumed that UE 1 410 and UE 2 420 use the same PRACH and share the same signature set and access slots. In addition, it is assumed that the signatures corresponding to the ASCs to which the UE 1 410 and the UE 2 420 belong to 9 of [S1, .., S9] for the purpose of effective description of the present invention. The consideration of slots will be omitted.

Referring to FIG. 4, the UE 1 410 transmits a preamble 411 after selecting S1, but no ACK or NACK corresponding to the S1 is transmitted through the corresponding AICH. In this case, the UE 1 410 selects S2 as a new signature, increases the transmission output by a step size, and transmits a second preamble 412. In response to the second preamble 412, the UE 1 410, which has not received ACK or NAC, selects S4 as a new signature and transmits a third preamble 413 by the transmission power increased by the step size. . Correspondingly, the UE 1 410 which has not received an ACK or NACK again selects S9 as a new signature and transmits a fourth preamble 414 by the transmission power increased by the step size. The Node B receives the fourth preamble transmitted from the UE 1 410 and then transmits an ACK 441 including the signature S9 through the AICH in response thereto. Accordingly, the UE 1 410 receives the ACK 441 in response to the fourth preamble 414. The UE 1 410 that receives the ACK 441 transmits the RACH data 415 through the allocated PRACH after a predetermined time elapses.

Meanwhile, the UE 2 420 transmits the first preamble 421 by the signature S3 when the second preamble 412 is transmitted by the UE 1 410. Since the UE 2 420 does not receive an ACK or NACK in response to the first preamble 421, the UE 2 420 selects S1 as a new signature and increases the transmission power by a step size to transmit the second preamble 422. do. Correspondingly, the UE 2 420 which has not received an ACK or NACK again selects S9 as a new signature and transmits a third preamble 423 by the transmission power increased by the step size. In this case, the third preamble 423 was transmitted by the same signature at the same time point as the preamble 414 transmitted by the UE 1 410. Accordingly, the UE 2 420 also receives the ACK 441 from the Node B in response to the third preamble 423. The UE 2 420 receiving the ACK 441 transmits the RACH data 424 on the allocated PRACH after a predetermined time elapses.

As described above, when two or more UEs select the same signature and transmit the preamble at the same time, the two or more UEs understand the received ACK signal as an ACK signal for the preamble transmitted by the UE. Start. In this case, since the RACH data transmitted from the plurality of UEs use the same OVSF code on the same OVSF code tree as the signature corresponding to the ACK, there is no orthogonality between the RACH data. That is, the Node B cannot properly receive any RACH data transmitted from the plurality of UEs.

As such, when a plurality of UEs select the same signature at the same time point, the possibility of failing to transmit the RACH data increases, and in addition, backward interference may increase by transmitting two or more UEs. That is, when a general reverse message is simultaneously transmitted by a plurality of UEs as in the transmission of the RACH data, there is always a possibility that such a problem may occur.

On the other hand, such a situation may cause a more serious problem in the performance of the MBMS that a large number of UEs can attempt to transmit RACH data simultaneously by one group signaling message.

An object of the present invention for solving the above problems is to provide a method for increasing the transmission probability of a response message corresponding to a group signaling message in a mobile communication system.

Another object of the present invention is to provide a method for adjusting in real time the probability that a response message is transmitted in response to a group signaling message in a mobile communication system.

Another object of the present invention is to provide a method for efficiently transmitting a response message corresponding to a group signaling message in a mobile communication system based on a transmission probability adjusted in real time.

It is still another object of the present invention to provide a method for allowing response messages that can be simultaneously transmitted from a plurality of terminals in a mobile communication system to be transmitted by scheduling.

Another object of the present invention is to provide a method for optimizing the performance of random access channels for transmitting response messages from a plurality of terminals in a mobile communication system.

Another object of the present invention is to provide a method for periodically updating a transmission probability for terminals to which an MBMS response message is to be transmitted.

The method proposed in the present invention; A method for providing a section in which a base station controller transmits an access preamble to terminals in a mobile communication system, the method comprising: measuring a number of reverse channels allowed to be used by a base station in a predetermined time unit; And determining the number of attempts to allocate the reverse channel by the terminals, wherein the number of attempts to allocate the reverse channel is the number of the measured reverse channels.
Another method proposed by the present invention; Claims [1] A method of transmitting an access preamble by a terminal in which a terminal continuously updates by a base station controller in a mobile communication system, the method comprising: receiving the duration value and changing a previous duration value to the duration value; And arbitrarily determine a real value between and transmitting the access preamble to a base station if the real value is less than the changed duration value.

Another method proposed by the present invention is; A method for providing a section in which a base station controller transmits an access preamble to terminals in a mobile communication system, the method comprising: measuring a number of reverse channels permitted by a base station in a predetermined time unit, and measuring Updating the number of reverse channels to a duration value and transmitting the updated duration value to the terminals, and the terminals receive the updated duration value, change the updated duration value to a previous duration value, and range from 0 to 1 And transmitting the access preamble to the base station when the randomly determined real value is smaller than the changed previous sustain value.

Another method proposed by the present invention is; A method for providing a section in which a base station controller transmits an access preamble to a mobile station in a mobile communication system, the terminal to notify that a multimedia broadcast multicast service (MBMS) requested from the terminals will be provided. Calling the terminal to transmit an initial persistence value to the terminals, thereby causing the terminals to transmit the access preamble using the initial persistence value, and corresponding to the access preambles in predetermined time units. Measuring a number of grants for which the base station permits the use of reverse channels, updating the measured number of grants to the initial duration value, and accessing an access control message including the updated duration value through the MBMS control channel; The process of transmitting to them.

Another method proposed by the present invention is; A method for transmitting terminals an access preamble by a persistence value provided by a base station controller in a mobile communication system, wherein the multimedia broadcast multicast service (MBMS) requested from the base station controller is provided. And transmitting the access preamble requesting allocation of a random access channel using an initial sustain value provided from the base station controller, and transmitting the access preamble using the initial sustain value. Receiving an updated persistence value, changing the initial persistence value or the previous persistence value to the updated persistence value, randomly determining a real value between 0 and 1, wherein the real value is greater than the changed persistence value If small, transmitting the access preamble to a base station It includes forward.

Another method proposed by the present invention is; In a method for providing a section in which a base station controller transmits an access preamble to a mobile communication system, the base station controller provides a multimedia broadcast multicast service (MBMS) requested by the terminals. Sending an initial persistence value to the terminals when calling the terminals, and a response message corresponding to the call using the initial persistence value received by the terminals from the base station controller indicating that the MBMS will be provided; Transmitting the access preamble to the base station controller for requesting allocation of a random access channel to transmit a message; and using the reverse channels in response to the access preambles in predetermined time units. The number of permits allowed Determining, and updating, by the base station controller, the measured number of permits to the initial duration value, and transmitting an MBMS control channel including the updated duration value to the terminals through a second common control physical channel. When the terminals receive the updated duration value while transmitting the access preamble using the initial duration value, changing the initial duration value or the previous duration value to the received duration value; And transmitting the access preamble requesting allocation of a random access channel to transmit a response message corresponding to the call to the base station controller using the changed duration value.

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DETAILED DESCRIPTION A detailed description of preferred embodiments of the present invention will now be described with reference to the accompanying drawings. In the following description of the reference numerals to the components of the drawings it should be noted that the same reference numerals as possible even if displayed on different drawings. In addition, in describing the present invention, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. In addition, terms to be described below are terms defined in consideration of functions in the present invention, which may vary according to the intention or custom of a user or a chip designer, and the definitions should be made based on the contents throughout the present specification.

In the present invention to be described later, the duration value (hereinafter referred to as "P _mbms ") is adjusted according to the situation in which the MBMS response messages from the plurality of UEs requesting the provision of a specific MBMS arrives, and the plurality of UEs adjust the adjustment. We will propose a method of controlling the allocation request of the RACH by the P _mbms . That is, in a situation where one MBMS control message triggers a plurality of response messages, the UE presents P _mbms to be used when transmitting a response message to the MBMS control message, and then considers the success rate of response messages of the UEs. _{This is} to continuously update the P _mbms . It is continually updated as the P _mbms is performed by changing the P _mbms in consideration of the response message transmission success rate of the UE, and the process is repeated indicating the changed P _mbms to the UE.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

6 is a diagram illustrating a signaling procedure in a mobile communication system according to an embodiment of the present invention. The signaling in FIG. 6 targets UEs that are located in a specific cell and are provided or want to receive a specific MBMS.

Referring to FIG. 6, a common measurement initialization procedure is performed between the RNC and the Node B in step 605. The COMMON MEASUREMENT INITIATION procedure is initiated by the RNC sending a COMMON MEASUREMENT INITIATION REQUEST message to the Node B and completed by the Node B sending a COMMON MEASUREMENT INITIATION RESPONSE message to the RNC. Since the messages transmitted for the common measurement initialization procedure are described in detail in 3GPP TS 25.433, description thereof is omitted. Through the COMMON MEASUREMENT INITIATION procedure, the RNC configures a measurement called "acknowledged PRACH preambles" for the cell where the MBMS is to be provided. This is a request to measure and report the number of acknowledged PRACH preambles in units of 20 msec in a specific cell. The reporting process is performed through a message of COMMON MEASUREMENT REPORT in step 625. The acknowledged PRACH preamble can be used as reference data when the RNC changes P _mbms in the future. The common measurement is described again in step 625.

In step 610, the RNC transmits an MBMS CONTROL message that triggers response messages from a plurality of UEs wishing to provide a specific MBMS. The MBMS CONTROL message includes the initial value of P _mbms . The initial value of P _mbms may be determined in consideration of the number of UEs _scheduled to transmit a response message in the cell and the PRACH resource situation of the cell. As an example, the initial value of P _mbms may be determined as the inverse of BOW_X_Y. In detail, the BOW_X_Y means the most suitable size of the back-off window in consideration of the number of UEs to transmit a response message to the MBMS control message in a specific cell and the PRACH resource situation of the corresponding cell. The BOW_X_Y is an integer having a unit of 10 msec. The UE selects one of the values between 0 and BOW_X_Y with equal probability, waits for the selected value, and starts the RACH operation. In other words, when the inverse of the BOW_X_Y is assumed that any UE operates most efficiently, it may mean a probability that the UE starts an RACH operation at a specific time point. Of course, the initial value of P _mbms may be uniformly set to a specific value. For that reason, the initial value of P _mbms is set to a value that is too large, so that even if a RACH congestion occurs, the RNC will later resolve the congestion by adjusting P _mbms . On the other hand, _{even if} the initial value of the P _mbms is set to a value that is too small to slow the transmission of the response message, the RNC will improve the situation by adjusting the P _mbms later. However, _when the initial value of P _mbms is set to an appropriate value, since the degree of adjustment is small, there is an advantage that the degree of RACH performance improvement can be further increased.

UEs receiving the MBMS CONTROL message perform PVT using the initial value of the received P _mbms prior to transmitting the response message (step 615). The UEs transmit a response message in step 620 when passing the PVT performed using the P _mbms . As the PVT is performed for each UE, transmission of the response message is also performed for each UE. The response message may be a message such as an RRC CONNECTION REQUEST, and the message includes an MBMS ID.

The RNC performs a counting operation using the MBMS ID included in the response message received for each UE in step 623. The counting operation refers to an operation of counting the number of response messages transmitted for each UE for a specific MBMS control message and stopping transmission of response messages from UEs when a predetermined condition is met. The predetermined condition may be a case where the number of UEs having an RRC connection among UEs to be provided with the MBMS becomes equal to an MBMS threshold.

The Node B reports the number of acknowledgments (hereinafter referred to as "# of ACK") sent to UEs that transmit a preamble for a specific MBMS for the last 20 msec through a COMMON MEASUREMENT REPORT message in step 625. The reporting of # of ACK through the COMMON MEASUREMENT REPORT message corresponds to the measurement of "acknowledged PRACH preambles" configured in step 605. The acknowledgment is a forward signal transmitted on the AICH. In general, n acknowledgments sent at time t means that n UEs send messages using the RACH just after t. However, if multiple UEs used the same signature, the UEs will fail to send the message and the # of ACK is related to the number of response messages that the RNC will receive. In addition, the # of ACK indicates the degree to which the RACH is used in the corresponding cell. That is, the larger the size of the # of ACK, the more UEs in the cell attempt to use the RACH. In this case, the probability of occurrence of a RACH congestion situation increases. The smaller the # of ACK, the smaller the number of UEs in the cell attempting to use the RACH. In this case, the efficient use of a given RACH resource is not achieved.

The RNC adjusts the P _mbms when adjustments are required and whether the adjustment of the P _mbms at step 626 to execute the Pmbms deciding algorithm for determining a new P _mbms. In the figure, the execution of the P _{mbms deciding} algorithm is indicated after step 625 for convenience, but actually starts with transmitting a control message for a specific MBMS in step 610.

[P _{mbms deciding} algorithm]

First, when the RNC starts updating period _mbms P, the P _mbms update period for COMMON MEASUREMENT REPORT combined and all of the # ACK of the message received on, and updates the value obtained by the sum total # of the ACK. The P _mbms update period is a unit of time for determining P _mbms update. The RNC determines whether to adjust P _mbms and the size of adjustment at the end of every P _mbms update period. The start time of the P _mbms update period is a time when the transmission of the MBMS control message that triggered the start of the P _{mbms deciding} algorithm is completed. The RNC determines whether to adjust the P _mbms every time the P _mbms update period ends. That is, when the total # of ACK is smaller than the congestion threshold_up, the RNC increases the existing P _mbms by PV STEP SIZE to determine a new P _mbms and _delivers the newly determined P _mbms to the UEs. As described above, the total # of ACK means the number of ACKs transmitted through the AICH for a certain period of time. The parameter is related to the frequency of RACH usage attempts of UEs during an update period of P _mbms . That is, if the total # of ACK is large, this means that many UEs have attempted to use the RACH. If the total # of ACK is small, it means that a small number of UEs have attempted to use the RACH. Therefore, when the total # of ACK is too small, it is desirable to increase the P _mbms, to increase the attempt to use the RACH of the UEs. However, if the total # of ACK is greater than the congestion threshold_down, it may be desirable to reduce the frequency of UE attempts to use RACH by lowering the P _mbms by PB STEP SIZE. Finally, the RNC maintains the existing P _mbms when the total # of ACK is a value between the congestion threshold_down and the congestion threshold_up. The P _mbms update period, the congestion threshold_up, the congestion threshold_down, and the STEP SIZE are internal parameters determined by the RNC according to the situation. The values may be determined appropriately through field tests.

The size of the P _mbms update period may be determined in multiples of 20 msec. The larger the size of the P _mbms update period is, the slower the P _mbms update operation is, but the determination of the P _mbms is made more carefully. On the other hand, the smaller the size of the P _mbms update period is, the faster the P _mbms update operation proceeds, but there is a greater possibility of error in P _mbms determination.

If in step 627, the RNC _mbms P is changed, the platter P newly determined _mbms by the change in step 630 to ACCESS CONTROL message and transmits to the UE. The ACCESS CONTROL message is a broadcast channel that can be received by all UEs in a cell. The ACCESS CONTROL message is provided to the physical layer through an MBMS control channel (hereinafter referred to as "MCCH") as a logical channel. The MCCH including the ACCESS CONTROL message is transmitted to UEs in a cell through a physical channel. In this case, the physical channel may be a second common control physical channel (S-CCPCH). An example of the ACCESS CONTROL message format is shown in Table 1 below.

Information Element / Group name Need Multi Type and reference Message Type MBMS ID MP P _mbms MP real (0.00..1.00

The ACCESS CONTROL message shown in Table 1 is composed of Message Type, MBMS ID, and P _mbms . The Message Type is an information element (hereinafter referred to as "IE") indicating that the message is an ACCESS CONTROL message. The MBMS ID is an identifier of the MBMS to which the ACCESS CONTROL message affects. UEs receiving the ACCESS CONTROL message use the IE to determine whether to update their P _mbms . That is, when an arbitrary UE is connected to a specific MBMS, if the ACCESS CONTROL message is received, and the MBMS ID of the ACCESS CONTROL message is the specific MBMS, it is determined that the information included in the message is valid. However, if the MBMS ID of the ACCESS CONTROL message is a value other than the specific MBMS, the information included in the ACCESS CONTROL message is ignored. The P _mbms is a Persistence value that UEs will use when transmitting a response message related to MBMS through the RACH. The Persistence Value is not used for reverse data transmission that is not related to the MBMS.

UEs that do not succeed in using RACH among UEs that want to be provided with the specific MBMS update to a new P _mbms in step 635 and attempt PVT using the value. UEs with successful PVT performed using the new P _mbms transmit a response message such as an RRC CONNECTION REQUEST message through the RACH in step 640.

The RNC continues the counting operation for the response message received for each UE. If the RNC receives response messages for UEs corresponding to MBMS thresholds, the RNC proceeds to step 645 and transmits a COUNTING STOP message. The COUNTING STOP message may be replaced with an ACCESS CONTROL message in which P _mbms is set to zero.

As described above, in the embodiment of the present invention, when the RNC transmits a control message for a specific MBMS, the MBMS control message triggers a plurality of response messages, and the plurality of response messages are transmitted through the RACH, the response The UE transmitting the messages adjusts the Persistence Value, which is a probability of success in using the RACH, according to the RACH situation, thereby avoiding congestion that may occur in the RACH. At this time, the RNC may use the acknowledged PRACH preamble value of the COMMON MEASUREMENT REPORT reported by the Node B to determine the state of the RACH at any time.

7 is a diagram illustrating a control flow of performing a RACH operation in a UE MAC when P _mbms is continuously updated according to an embodiment of the present invention. The MAC, RRC, RLC, physical layer, etc. below indicate protocol entities described in 3GPP TS 25.301.

Referring to FIG. 7, the RRC of the UE transmits RACH transmission control information to the MAC of the UE in step 705. The RACH transmission control information includes the following ones, and P _mbms is a parameter proposed for the present invention.

RACH transmission control information = M_max, N_BO1min, N_BO1max, ASC parameters, Pmbms

Among the parameters, M_max, N_BO1min, N_BO1max, and ASC parameters are information obtained through system information. When the RRC of the UE acquires the information for the first time or obtains the updated information, the RRC of the UE transmits the information to the MAC of the UE through a primitive called CMAC-CONFIG-Req. The use of these parameters will be described later in the relevant section.

Among the parameters, P _mbms is a parameter proposed for the present invention, and can be received through an MBMS control message requesting a group response or acquired through system information. For example, the RNC can deliver to the UE through the P _mbms field of the MBMS CONTROL message shown in FIG. As another example, the P _mbms field may be added to the existing system information and transmitted to the UE. Of the UE RRC transmits the first case to obtain the acquired or updated P _mbms the P _mbms through the primitive called CMAC-CONFIG-Req to the MAC of the UE.

In the above description, a primitive refers to a bundle of information transmitted between layers. The 3GPP specification currently defines various kinds of primitives between RRC and MAC. The CMAC-CONFIG-Req is a primitive mainly used when the RRC transfers control information to the MAC. The P _mbms is stored in a P_mbms variable managed by the UE.

The UE waits until it is determined that a group response is necessary in step 710, and proceeds to step 715 when it is determined that the group response is needed. The group response refers to a response message having a high likelihood that other UEs will also transmit a response message for the same purpose when sending any response message. The UE determines whether a group response to a specific reverse message is based on the following criteria.

[Group Response Criteria]

1. Reverse message is MBMS related message.

2. P _mbms should be stored in the P_mbms variable.

The MBMS related message also includes an RRC CONNECTION REQUEST message including an MBMS ID.                     

When the UE proceeds to step 715 due to the necessity of the group response, the UE selects the ASC, checks the PRACH partition of the selected ASC, and checks P _mbms in the P_mbms variable. The ASC selection scheme is well described in 3GPP TS 25.321. In brief, the ASC selection means selecting an ASC to be used for the RACH operation according to the priority of data to be transmitted to the RACH. The priority of the data is determined by the priority (MLP: MAC Logical Channel Priority) of the logical channel through which the data is transmitted, and the priority is notified to the UE for each logical channel through an RRC connection setup process. do. The ASC is composed of eight classes, and the PRACH resources to be used for each class are determined. This is called a PRACH partition. In step 715, the PRACH partition i refers to a PRACH resource allocated to the ASC i when the UE selects the ASC i through the ASC selection process. The PRACH partition i includes signatures and access slots.

In step 720, the UE sets M, which is a variable controlling the number of attempts of the RACH operation (steps 725 to 775), to zero. Whenever the RACH operation is repeated, M increases by 1 in step 725. If M is greater than or equal to M_ max in step 730, the process proceeds to step 735. When the UE proceeds to step 75, the UE notifies that data transmission on the RACH has failed, and terminates the RACH process. In the figure, the preamble cycle refers to an operation between steps 745 and 775. The preamble cycle starts with updating the RACH transmission control information and is completed by receiving L1 access information from the physical layer. The variable M_max is informed to the UE through system information, and the network can adjust the M_max appropriately to prevent the UE from repeating the RACH transmission attempt more than necessary.

The UE updates RACH transmission control information in step 745. The RACH transmission control information is updated by transmitting the CMAC-CONFIG-Req primitive to the MAC after the RRC receives the updated system information. Alternatively, in the case of P _mbms , the RRC receives the ACCESS CONTROL message and _sends a CMAC-CONFIG-Req primitive containing the new P _mbms to the MAC.

The UE sets a T2 timer in step 750. The usage of the T2 timer is described in step 767.

In step 760, the UE randomly selects R1, which is a real number between 0 and 1. In step 765, the size of the R1 and P _mbms is compared, and if the P _mbms is greater than or equal to step 770. Otherwise, if R1 is large, the flow proceeds to step 767. Steps 760 and 765 are referred to as a persistence value test.

Before the UE performs the new PVT in step 767, the UE waits for the set T2 and then proceeds to step 745. The reason for the step 767 is to allow the UE to wait for a certain time before attempting a new PVT. If the step 767 does not exist, the UE will repeat the operation of attempting a new PVT as soon as the PVT fails until the PVT succeeds, so the meaning of the PVT is lost. The T2 value may be set, for example, about 10 msec.

The UE, which has passed the PVT of steps 760 and 765, transmits the PHY-ACCESS-REQ primitive to the physical layer in step 770. The PHY-ACCESS-REQ primitive includes an identifier of a PRACH partition of the ASC selected at 715.

The physical layer receiving the PHY-ACCESS-REQ primitive executes a preamble transmission process using a PRACH partition corresponding to a PRACH partition identifier included in the PHY-ACCESS-REQ primitive. This process is described in detail in 3GPP TS 25.214. In brief, the physical layer randomly selects a signature of one of the signatures and an access slot of one of the access slots assigned to the corresponding PRACH partition, and transmits a preamble through the selected signature and the access slot. , Monitor the AICH. If the ACK signal is received through the AICH, it is reported to the MAC through the L1 access info of the PHY-ACCESS-CNF primitive. When the NACK signal is received instead of the ACK signal, it is reported to the MAC through the L1 access info of the PHY-ACCESS-CNF. However, if no signal is detected through the AICH, the preamble is retransmitted by increasing the transmit power by the step size. This process is repeated until the ACK or NACK signal is received or the transmit power of the preamble is greater than or equal to a predetermined value. When the transmission power of the preamble is greater than or equal to a predetermined value, the preamble is recognized as a no ack situation and reported to the MAC through the L1 access info of the PHY-ACCESS-CNF.

In step 775, the MAC interprets the value of the L1 access info of the PHY-ACCESS-CNF transmitted by the physical layer, and determines the next action. If L1 access info is no Ack, the process proceeds to step 755. In case of ACK, the process proceeds to step 780. In the case of NACK, the process proceeds to step 777.

If the L1 access info is 'No Ack', data cannot be transmitted. Therefore, the RACH process is performed again from step 725. At this time, the process waits for T2 in step 755 before restarting the RACH process and proceeds to step 725.

When the L1 access info is 'Nack', data cannot be transmitted in the same manner, so the RACH process is performed again from step 725. In this case, the process waits for T2 in step 777 before restarting the RACH process, waits for T _BO1 again in step 779, and then proceeds to step 725. The T _BO1 is N _BP1 × 10 msec, and the N _BO1 is an arbitrary value randomly extracted between N _BO1max and N _BO1min . The above process has the effect of randomly selecting a waiting time before UEs receiving the NACK signal retry the RACH operation.

If the L1 access info is 'ACK', the MAC transmits the data to be transmitted to the physical layer in a primitive called PHY-DATA-REQ in step 780. The physical layer transmits data contained in the primitive through a PRACH.

The RACH operation of the UE according to the embodiment of the present invention shown in FIG. 7 described above may be differentiated from the conventional RACH operation by the following proposal.

First, in step 705, the UE's MAC additionally acquires P _mbms as RACH transmission control information.

Secondly, in step 710, the MAC of the UE proceeds with the process when it is necessary to transmit a group response through the RACH. A typical RACH operation performs the RACH operation when it is necessary to send reverse data on the RACH.

Thirdly, in step 715, the UE's MAC uses P _mbms instead of the persistence value of the selected ASC.

Fourth, in step 745, the UE's MAC also performs P _mbms update during the RACH transmission control information update process.

Fifth, in step 765, the UE's MAC uses P _mbms instead of the persistence value of the ASC selected in step 715.

8 is a diagram illustrating a control flow for updating a UE P _mbms according to an embodiment of the present invention.

Referring to FIG. 8, the UE proceeds to step 810 when receiving an arbitrary message including P _mbms from the RNC in step 805. For example, the P _mbms may be received through the MBMS CONTROL message and the ACCESS CONTROL message in FIG. 6. When the UE proceeds to step 810, the UE compares the MBMS ID included in the received random message with the MBMS ID of the MBMS on which the UE performs a joining step. If the two MBMS IDs match, the UE proceeds to step 815, and if it does not match, the UE proceeds to step 805 and waits for another P _mbms to arrive.

In step 815, the RRC of the UE includes the received P _mbms in the CMAC-CONFIG-Req primitive and _delivers the received _information to the MAC. In step 820, the MAC of the UE stores the received P _mbms in a P_mbms variable and terminates the procedure for updating P _mbms . The MAC of the UE updates the stored value with a new value if another value is already stored in the P_mbms variable. The P_mbms variable is a variable in which a specific UE stores a P _mbms value and is updated through the above-described procedure. Meanwhile, when the RACH process for transmitting the group response message ends, the MAC of the UE clears the P_mbms variable.

9 is a diagram illustrating a control flow for a UE to transmit a group response message in response to an MBMS control message from an RNC according to an embodiment of the present invention.

Referring to FIG. 9, the UE monitors whether a group response message to be transmitted to the RNC is generated in step 900, and proceeds to step 905 when the group response message is generated. The generation of the group response message is caused by receiving an MBMS control message requiring a group response from the RNC.

Whether or not a group responds to any RRC message is determined as follows.

[Group Response Criteria]

1. Reverse message must be MBMS related message

2. P _mbms should be stored in the P_mbms variable.

In step 905, the RRC of the UE makes a group response message to be transmitted as an RLC-DATA-Req primitive and transmits the group response message to the RLC. At this time, the primitive includes a group response indicator. The RLC-DATA-Req includes all of the RLC-AM-DATA-Req, RLC-UM-DATA-Req, and RLC-TM-DATA-Req. The group response indicator is a 1-bit flag indicating whether or not data transmitted through the primitive is a group response. For convenience, it can be assumed that 0 represents a group response and 1 represents a non-group response.

The RLC of the UE stores the data of the RLC-DATA-Req received from the RRC in an RLC buffer in step 910, and transmits a MAC-STATUS-Response primitive to the MAC to indicate that there is data to be transmitted. At this time, the primitive includes a group response indicator, and the value uses the value received from the RRC as it is. Through the primitive, parameters such as a buffer occupancy ratio (BO) indicating the situation of the RLC buffer are also delivered.

The MAC of the UE receives the MAC-STATUS-Response from the RLC in step 915, and checks a group response indicator of the primitive in step 920. If it is determined that the group response is required by the check, the operation described with reference to FIG. 7 is performed. However, if it is determined that the test result is not a group response, the process proceeds to step 930 to perform a normal RACH operation. The typical RACH operation is described in chapter 11.2.2 of 3GPP TS 25.321.

The group response message stored in the RLC buffer is transmitted through PHY-DATA_REQ when the physical layer receives an Ack signal due to the success of the RACH operation shown in FIG.

10 is a diagram illustrating a control flow for the RNC to determine and update P _mbms according to an embodiment of the present invention.

Referring to FIG. 10, the RNC monitors whether an MBMS control message is generated to cause a group response in step 1000, and proceeds to step 1005 when such an MBMS control message occurs. Examples of the MBMS control message that may cause the group response include a notification message and a RECOUNTING message. The RNC determines an initial value of P _mbms in step 1005. The method of setting the initial value of P _mbms has already been described with reference to FIG. 6. The RNC transmits the generated MBMS control message in step 1010. The MBMS control message includes the initial value of P _mbms determined above. The MBMS control message will be transmitted through a broadcast channel such as S-CCPCH so that all UEs in a cell can receive it.

The RNC _executes the "P _{mbms deciding} algorithm" as an algorithm for updating the P _mbms in step 1015 after transmitting the MBMS control message. The P _mbms deciding algorithm means an algorithm for determining whether or not the P _mbms needs to be changed and a new P _mbms when a change is required. An example of this has already been described with reference to FIG. 6. According to the example proposed with reference to FIG. 6, the P _{mbms deciding} algorithm requests the appropriate Node B to set an appropriate COMMON MEASUREMENT, and determines whether to _reset the P _mbms by the COMMON MEASUREMENT reported by the Node B. It then covers the steps to set up a new P _mbms .

If the RNC determines that the new P _mbms is set by the P _{mbms deciding} algorithm in step 1020, the RNC proceeds to step 1025. If the new P _mbms is not set, the _RNC returns to step 1015 to continue executing the P _{mbms deciding} algorithm.

When the RNC proceeds to step 1025, the RNC transmits an ACCESS CONTROL message containing the new P _mbms to UEs through a broadcast channel of the corresponding cell, and returns to step 1015.

The operation of the above-described RNC ends when the group response is completed. For example, if the operation of the RNC according to FIG. 10 was started while sending a notification message, the operation of the RNC would be terminated by sending a STOP message that stops sending a response message.

As described above, in the present invention, by continuously updating the probability that the response message is transmitted in consideration of the cell situation, the transmission success rate of the response message can be improved and the performance of the RACH can be optimized. That is, in the case of a multicast multimedia broadcasting service in which data transmission from multiple terminals is frequently performed at the same time, congestion and collision on a random access channel caused by multiple reverse messages are simultaneously transmitted can be alleviated.

Claims (21)

A method for providing a section in which a base station controller transmits an access preamble to terminals in a mobile communication system, Measuring the number of reverse channels allowed by the base station in a predetermined time unit; Determining the number of attempts to allocate a reverse channel by the terminals on a time basis; And wherein the number of attempts to allocate the request is to transmit the access preamble, characterized in that the measured number of reverse channels. The method of claim 1, The number of reverse channels is measured by the initially set number of attempts to request reverse channel allocation, and the initially set number of attempts to allocate reverse channel is updated by the number of attempts to allocate reverse channels by the terminals. A method for providing an interval for transmitting an access preamble. delete The method of claim 1, The determining process, And determining a number of attempts for allocation request of a reverse channel by the terminals by using resources of a random access channel that can be allocated by the base station. The method of claim 1, And a forward control message transmitted by the base station is a message for multicast multimedia broadcasting. The method of claim 1, The determining process, If the number of reverse channels allowed to use is less than a first threshold, increase the number of attempts to allocate the reverse channel by the terminals by a predetermined number, and if the number of reverse channels allowed to use is greater than or equal to a second threshold, A method for transmitting an access preamble, the method comprising: reducing the number of attempts to allocate a reverse channel by a terminal by a predetermined number. What is claimed is: 1. A method of transmitting an access preamble by a terminal in a mobile communication system with a sustain value continuously updated by a base station controller, Receiving the duration value and changing a previous duration value to the duration value; And randomly determining a real value between 0 and 1, and transmitting the access preamble to a base station if the real value is less than the changed duration value. The method of claim 7, wherein And after the duration value is changed, after waiting for a predetermined time, comparing the duration value with the real number value. The method of claim 7, wherein And if the real value is greater than or equal to the changed duration value, waiting for a predetermined time and then receiving the duration value. A method for providing a section in which a base station controller transmits an access preamble to terminals in a mobile communication system, Measuring, by the base station controller, the number of reverse channels allowed to be used by the base station in a predetermined time unit, updating the measured number of reverse channels to a continuous value, and transmitting the same to the terminals; The terminals receive the updated duration value, change the updated duration value to a previous duration value, and if the real value randomly determined from 0 to 1 is smaller than the changed previous duration value, the access preamble is sent to the base station. A method for providing an interval for transmitting an access preamble including a step of transmitting. The method of claim 10, The number of reverse channels is measured using a duration value initially set, and the duration value initially set is updated using the number of attempts to allocate the reverse channels. delete The method of claim 10, The process of transmitting to the terminals, And providing an interval for transmitting an access preamble including updating the sustain value using resources of a random access channel that can be allocated by the base station. The method of claim 10, And a forward control message transmitted by the base station is a message for multicast multimedia broadcasting. The method of claim 10, If the number of reverse channels is less than a first threshold, increasing the sustain value by a predetermined level; And if the number of reverse channels is greater than or equal to a second threshold, reducing the duration value by a predetermined level. The method of claim 10, The process of transmitting to the base station, Changing the updated duration value to a previous duration value, waiting for a predetermined time, and then comparing the changed duration value with the real value. The method of claim 10, And if the real value is greater than or equal to the changed duration value, waiting for a predetermined time and receiving the duration value. A method for providing a section in which a base station controller transmits an access preamble to terminals in a mobile communication system, When invoking the terminals to notify that the requested Multimedia Broadcast Multicast Service (MBMS) will be provided from the terminals, sending the initial duration value to the terminals, thereby allowing the terminals to carry out the initial duration. Transmitting the access preamble using a value; Measuring a number of allowances for which a base station allows use of reverse channels in correspondence to the access preambles in a predetermined time unit; Providing an interval for transmitting an access preamble including updating the measured permission number to the initial duration value and transmitting an access control message including the updated duration value to the terminals through an MBMS control channel; Way. The method of claim 18, And the MBMS control channel transmits an access preamble through a second common control physical channel. A method for transmitting terminals in a mobile communication system by using a sustain value provided by a base station controller, the method comprising: The access preamble requesting the allocation of a random access channel using an initial duration value provided from the base station controller along with notifying that a multimedia broadcast multicast service (MBMS) requested from the base station controller will be provided; The process of transmitting, Changing the initial duration value or the previous duration value to the updated duration value when receiving the updated duration value by the base station controller while transmitting the access preamble using the initial duration value; And randomly determining a real value between 0 and 1, and transmitting the access preamble to a base station if the real value is less than the changed duration value. A method for providing a section in which a base station controller transmits an access preamble to terminals in a mobile communication system, Transmitting an initial duration value to the terminals when calling the terminals to notify that the Multimedia Broadcast Multicast Service (MBMS) requested by the terminals will be provided; The access preamble requesting the allocation of a random access channel to transmit a response message corresponding to the call using the initial persistence value received by the terminals from the base station controller with the call informing that the MBMS will be provided. Transmitting to a base station controller; Measuring, by the base station controller, a number of allowances for which the base station allows use of reverse channels in correspondence to the access preambles in predetermined time units; Updating, by the base station controller, the measured number of permits to the initial duration value, and transmitting an MBMS control channel including the updated duration value to the terminals through a second common control physical channel; If the terminals receive the updated duration value while transmitting the access preamble using the initial duration value, changing the initial duration value or the previous duration value to the received duration value; And providing, by the terminals, an access preamble including transmitting the access preamble requesting allocation of a random access channel to transmit a response message corresponding to the call to the base station controller using the changed persistence value. How to.

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