METHOD AND APPRATUS FOR RECONFIGURING A COMMON CHANNEL

TECHNICAL FIELD

The present invention relates generally to a mobile communication system

and, more particularly, to reconfigure a common channel for a mobile communication.

BACKGROUND ART

FIG. 1 is a diagram illustrating a network structure of a universal mobile

telecommunication system (UMTS). Generally, a UMTS system 10 comprises a user

equipment (UE) 11, a UMTS terrestrial radio access network (UTRAN) 12, and a core

network (CN) 13. ^s Herein, the UE may be a mobile terminal in general. The UTRAN 12

comprises at least one of radio network sub-systems (RNSs) 13, and each RNS

comprises a radio network controller (RNC) 131 and at least one of Node B 132 which

is controlled by the RNC. The Node B includes at least one cell 133.

FIG. 2 is a diagram illustrating a layer structure of radio interface protocol in

mobile communication system. As shown in FIG. 2, the radio interface protocol

comprises horizontally a physical layer, a data link layer and a network layer.

Meanwhile, the radio interface protocol comprises vertically a user plane for

transmitting user data and a control plane for signaling.

The protocol layers of FIG. 2 comprises Ll (the first layer), L2 (the second

layer) and L3 (the third layer). The layers of FIG 2 correspond to 3 layers from the

bottom according to the open system interconnection (OSI) layer structure.

The first layer, i.e., the physical (PHY) layer, provides the higher layer with

information transfer service through physical channels. The PHY layer is connected to

the second layer, i.e., medium access control (MAC) layer, with transport channels and

data is transferred between MAC layer and PHY layer through the transport channels.

Meanwhile, data is transferred between the PHY layers of a transmitting side and the

PHY layer of a receiving side through the PHY channels.

The MAC layer provides a radio link control (RLC) layer with service

through logical channels. The RLC layer of L2 supports reliable data transmission and

may segment and concatenate service data units (SDUs) transferred from a higher layer.

A radio resource control (RRC) layer located at the bottom of L3 in the

protocol layers is defined on the control plane, may control the logical channels, the

transport channels and the physical channels in relation to configuration,

reconfiguration and release of radio bearers (RBs). Herein, the RB means a service

supported by L2 for data transmission between UE and UTRAN. Generally, to set up a

RB means a process for defining a protocol layers and channels for providing a specific

service, as well as a process for configuring parameters and operation, corresponding to

the specific service.

Moreover, the RRC layer may broadcast system information through a broad

control channel (BCCH). The system information regarding a cell is broadcasted to UEs

using at least one of system information block (SIB). If the system information is

modified, the UTRAN transmits BCCH modification information to the UEs through a

paging channel (PCH) or a forward access channel (FACH), for the UEs to have the

latest system information.

As an example of point-to-multipoint service, multimedia

broadcast/multicast service (MBMS) is explained as follows. The MBMS supplies a

streaming or background service using a MBMS bearer which is set up generally for

downlink transmission. A MBMS service comprises at least one session, MBMS data is

transmitted to UEs using the MBMS bearer during ongoing session. If the UE is

activated corresponding to a service to which the UE have been subscribed, the UE may

receive the service.

FIG. 3 is a diagram illustrating channels for MBMS. The UTRAN provides

UEs with MBMS using a RB. The UTRAN may set up two types of RBs, i.e., a point-

to-point RB and a point-to-multipoint RB. Herein, the point-to-point RB corresponds to

a bi-directional RB. The point-to-point RB employs a dedicated traffic channel (DTCH)

as a logical channel, a dedicated channel (DCH) as a transport channel, and a dedicated

physical channel (DPCH) or a secondary common control physical channel (SCCPCH)

as a physical chadnel.

Meanwhile, the point-to-multipoint RB corresponds to a uni-directional RB.

As shown in FIG. 3, the point-to-multipoint RB may employ the MBMS traffic channel

(MTCH) as a logical channel, the FACH as a transport channel, and the SCCPCH as a

physical channel. The MTCH is configured for each MBMS provided in a cell, is used

for transmission of user data corresponding to a MBMS on the user plane. A MBMS

control channel (MCCH) which is a logical channel is mapped to the FACH, and the

transport channel FACH is mapped to the SCCPCH. In general, one MCCH is allocated

to one cell.

According to the related art, if the SCCPCH to which the MCCH is mapped

is reconfigured, the UTRAN transmits control information through both the previously

configured SCCPCH and the reconfigured SCCPCH for a while, because the UE isn't

aware of the timing of SSCPCH reconfiguration. Therefore, the transmission of the

control information through two physical channels causes waste of radio resource.

DISCLOSURE OF INVENTION

Accordingly, the present invention is directed to a channel reconfiguration

method that substantially obviates one or more problems due to limitations and

disadvantages of the related art.

An object of the present invention is to provide method for reconfiguration

of a channel through which control information for point-to-multipoint service is

transmitted.

Additional advantages, objects, and features of the invention will be set forth

in part in the description which follows and in part will become apparent to those

having ordinary skill in the art upon examination of the following or may be learned

from practice of the invention. The objectives and other advantages of the invention

may be realized and attained by the structure particularly pointed out in the written

description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with the

purpose of the invention, as embodied and broadly described herein, in one embodiment,

a method of reconfiguring a common channel in a communication system comprises

receiving modified channel configuration information of a first common channel

(MCCH) through a second common channel (BCCH). The method also comprises

determining a starting time of reconfiguring the first common channel, according to a

type of an information element including the modified channel configuration

information. The method also comprises reconfiguring the first common channel from

the determined starting time.

Preferably, the starting time is determined as a starting point of a next

modification period, if the information element corresponds to a first type information

element.

Preferably, the first control channel is reconfigured on receiving the

modified channel configuration information, if the information element corresponds to a

second type information element.

Preferably, the starting time is determined as a starting point of a next

modification period, if the information element corresponds to a second type

information element and the modified channel configuration information include an

indicator indicating the starting time of reconfiguring.

In another aspect of the present invention, a mobile terminal of the present

invention comprises

The foregoing and other objects, features, aspects and advantages of the

present invention will become more apparent from the following detailed description of

the present invention when taken in conjunction with the accompanying drawings. It is

to be understood that both the foregoing general description and the following detailed

description of the present invention are exemplary and explanatory and are intended to

provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a further

understanding of the invention and are incorporated in and constitute a part of this

application, illustrate embodiments of the invention and together with the description

serve to explain the principles of the invention.

FIG. 1 is a diagram illustrating a network structure of a universal mobile

telecommunication system (UMTS).

FIG. 2 ₍ is a diagram illustrating a layer structure of radio interface protocol in

mobile communication system.

FIG. 3 is a diagram illustrating channels for MBMS.

FIG. 4 is a diagram illustrating a method for transmitting MCCH

information through the MCCH.

FIG. 5 is a flow chart illustrating a process for reconfiguring the MCCH

according to the first embodiment.

FIG. 6' is a flow chart illustrating a process for reconfiguring the MCCH

according to the second embodiment.

FIG. 7 is a flow chart illustrating the MCCH reconfiguration method in a UE

according to the first embodiment.

FIG. 8 is a flow chart illustrating the MCCH reconfiguration method in a UE

according to the second embodiment.

FIG. 9 is a structural diagram illustrating a UE according to the present

invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Reference will now be made in detail to the preferred embodiments of the

present invention, examples of which are illustrated in the accompanying drawings.

Wherever possible, the same reference numbers will be used throughout the drawings to

refer to the same or like pails.

FIG. 4 is a diagram illustrating a method for transmitting MCCH

information through the MCCH. As illustrated in FIG. 4, the MCCH information is

transmitted through MCCH with two types of periods, i.e., modification period and

repetition period. The MCCH information comprises critical information and non-

critical information. The non-critical information may be modified in the modification

period or in the repetition period. But, the critical information may be modified in the

modification period. That is, the critical information is transmitted (repeatedly) during

- ^■ the modification period, and modified critical information is transmitted at the start time

of the modification period. The MCCH information means a control message regarding

MBMS, and the control message may be a RRC message. The MCCH information

includes modified service information (MSI), unmodified service information (USI),

point-to-multipoint RB information and access information. Herein, the access

information message corresponds to the non-critical information, and the other

information message corresponds to the critical information. The access information is

transmitted per aij access period which is equal to or less than the repetition period.

Further, the repetition period may comprise multiple of the access period.

If the UTRAN transmits a control message corresponding to a MBMS, the

control message includes a MBMS transmission identity. Herein, the MBMS

transmission identity comprises a MBMS session identity and a MBMS service identity.

For example, when the UTRAN transmits the MBMS MSI message, the MBMS MSI

message includes the MBMS transmission identity and service information

corresponding to, fshe MBMS transmission identity.

The UTRAN periodically transmits information regarding whether the

MCCH information is modified, thorough a MBMS notification Indicator channel

(MICH). Therefore, if a UE wants to receive a specific MBMS data but a session of the

specific MBMS doesn't start yet, the UE receives information through a MICH instead

of a MCCH or a MTCH.

The UTRAN may modify the MCCH information by generating, adding,

changing or deleting parameters from the MCCH information. The UTRAN transmits a

MICH message and a MSI message to notify the UE of whether the MCCH information

is going to be modified during the modification period. The MSI message includes at

least one service identity corresponding to each service modified in the modification

period, and information for operating the UE subscribed to the service. Herein, the

service identity may be a MBMS transmission identity. The MBMS transmission

identity may comprise a MBMS service identity identifying a service. Also, the MBMS

transmission identity may comprise combination of a MBMS session identity and a

MBMS service identity, the MBMS session identity identifies a service session. A

service identity corresponding to a service not being modified during the modification

period, among the services currently provided in a cell, is transmitted using a USI

message. Herein, the service identity may be a MBMS transmission identity

corresponding to the service.

When a service session of a MBMS starts, the UTRAN transmits, through

the MICH, a notification indicator (NI) notifying UEs of receiving information through

the MCCH. If a UE receives the NI from the UTRAN, the UE is trying to receive the

MBMS data. If a UE receives a NI notifying the service modification through the MICH,

the UE receives the MCCH information during the modification period indicated by the

NI. During receiving the MCCH information, the UE receives the MSI message, and

checks whether the MBMS is modified. If the UE detects modification of the MBMS,

the UE receives modified MCCH information. Meanwhile, the UE receives the MSI and.,

the USI messages which are transmitted during the modification period, and may

acquire a service list listing all services currently provided in the cell in the modification

period'.

A UE trying to receive a MBMS service using a point-to-multipoint RB

receives MCCH information including RB information through a MCCH, and sets up

the point-to-multipoint RB in itself using the MCCH information. After setting up the

point-to-multipoint RB, the UE receives MBMS data through the physical channel

SCCPCH to which the ^' logical channel MTCH is mapped.

The UTRAN may transmit the MBMS data through the MTCH. Herein, as

illustrated FIG. 3, the UTRAN transmits a scheduling message to the UE through a

MBMS scheduling channel (MSCH) corresponding to the SCCPCH to which the

MTCH is mapped. The scheduling message includes information regarding a start point

and an ending point of MBMS data transmission in a scheduling period. Therefore, the

UTRAN informs the UE of a transmission period of scheduling information (scheduling

period) in advance.

FIG. 5 is a flow chart illustrating a process for reconfiguring the MCCH

according to the first embodiment. As shown in FIG. 5, the UTRAN broadcasts SIB

including secondary CCPCH system information MBMS, through the BCCH. Herein,

the secondary CCPCH system information MBMS includes MCCH reconfiguration

information. Then, a UE is able to be aware the modification of the BCCH channel

information, and receives the secondary CCPCH system information MBMS through

the BCCH. The UE is able to acquire the MCCH reconfiguration information from the

secondary CCPCH system information MBMS S51.

The UE doesn't reconfigure the MCCH until the modification period in

which the~UE receives the secondary CCPCH system information MBMS is finished. If

it is necessary to receive the MCCH information, the UE is able to receive the MCCH

information according to the previous configuration S52.

When the, modification period in which the secondary CCPCH system

information MBMS is finished, the UE starts to reconfigure the MCCH using the

MCCH reconfiguration information S53. Then, the UTRAN starts to transmit signals

through the reconfigured MCCH, and the UE starts to receive signals through the

reconfigured MCCH also S54.

FIG. 6 is a flow chart illustrating a process for reconfiguring the MCCH

according to the second embodiment. The embodiment illustrated in FIG. 6 corresponds

to a case that the reconfiguration of the MCCH starts at the starting time of next

modification period.

In FIG. 6, a UTRAN broadcasts SIB including secondary CCPCH system

information, through the BCCH. Herein, the secondary CCPCH system information

includes MCCH reconfiguration information. Then, a UE is able to be aware the

modification of the BCCH channel information, and receives the secondary CCPCH

system information through the BCCH. The UE is able to acquire the MCCH

reconfiguration information from the secondary CCPCH system information S61.

Then, the UE decides starting time of the MCCH reconfiguration according

to the secondary CCPCH system information S62. Herein, the UE may decide the

starting time of the MCCH reconfiguration according to an indication which is included

in the secondary CCPCH system information. Also, the UE may decide the starting time

of the MCCH reconfiguration according to the secondary CCPCH system information

without indication.

According to the MCCH reconfiguration method using the indication, the

UE receives the secondary CCPCH system information and checks whether the

secondary CCPCH system information includes the indication. If the secondary CCPCH

system information doesn't include the indication, the UE may start to reconfigure the

MCCH at the starting time of the next modification period. But, if the secondary

CCPCH system information includes the indication, the UE may start to reconfigure the

MCCH on receiving the secondary CCPCH system information. Meanwhile, if the

secondary CCPCH system information includes the indication, the UE may start to

reconfigure the MCCH at the starting time of the next modification period. Also, if the

secondary CCPCH system information doesn't include the indication, the UE may start

to reconfigure the MCCH on receiving the secondary CCPCH system information.

Furthermore, if the indication indicates that the starting time of the MCCH

reconfiguration corresponds to the starting time of the next modification period, the UE

may start to reconfigure the MCCH at the starting time of the next modification period,

according to the indication. But, if the indication indicates immediate reconfiguration of

MCCH, the UE may start to reconfigure the MCCH on receiving the secondary CCPCH

system information.

According to the MCCH reconfiguration method without the indication, the

UE receives the secondary CCPCH system information without indication, and may

start to reconfigure the MCCH at the starting time of the next modification period.

Herein, the secondary CCPCH system information includes other channel

reconfiguration information than the MCCH, the UE may decide to employ the channel

reconfiguration information on receiving the secondary CCPCH system information.

In case that the UE starts to reconfigure the MCCH at the starting time of the

next modification period, the UE may receive signals through the MCCH which is not

reconfigured yet, until the end time of the present modification period (i.e. the starting

time of the next modification period) S63. When the next modification period starts, the

UE starts to reconfigure the MCCH S64. After the reconfiguring of the MCCH, the

UTRAN transmits control information through the reconfigured MCCH and the UE

receives the control information through the reconfigured MCCH S65.

FIG. 7 is a flow chart illustrating the MCCH reconfiguration method in a UE

according to the first embodiment. As shown in FIG. 7, a UE receives a SIB including

the MCCH reconfiguration information through the BCCH, in a modification period

S71. And, the UE examines which information element of the SIB includes the MCCH

reconfiguration information S72.

If the MCCH reconfiguration information is included in Secondary CCPCH

system information MBMS which is included in the SIB, the UE may start to

reconfigure the MCCH at the starting time of the next modification period S73.

But, if the MCCH reconfiguration information is included in Secondary

CCPCH system information which is included in the SIB, the UE may start to

reconfigure the MCCH on receiving the Secondary CCPCH system information S74.

FIG. 8Js a flow chart illustrating the MCCH reconfiguration method in a UE

according to the second "embodiment. As shown in FIG. 8, a UE receives a SIB

including the MCCH reconfiguration information through the BCCH, in a modification

period S81. And, the UE examines which information element of the SIB includes the

MCCH reconfiguration information S82.

If the MCCH reconfiguration information is included in Secondary CCPCH

system information MBMS which is included in the SIB, the UE may start to

reconfigure the MCCH at the starting time of the next modification period S 83.

But, if the MCCH reconfiguration information is included in Secondary

CCPCH system information which is included in the SIB, the UE may determine the

starting time of the MCCH reconfiguration using an indication which is included in the

Secondary CCPCH system information. That is, the UE may start to reconfigure the

MCCH at the starting time of the next modification period S84 or on receiving the

Secondary CCPCH system information S85, according to the indication.

FIG. 9 is a structural diagram illustrating a UE according to the present

invention. As shown in FIG. 9, the UE comprises an antenna unit 91, a radio frequency

(RF) unit 92, a signal processing unit 93 and memory unit 94. The signal processing

unit 93 includes a procession unit such as a micro process or a digital signal processor.

Further, the UE may also comprise a display unit 95, a key pad unit 96 and speaker unit

97.

The UE receives signals through the MCCH and the BCCH using the

antenna unit 91 and the RF unit 92. The signal processing unit 93 reconfigures the

MCCH using the signals received through the MCCH and the BCCH according to

' above-explained process."

INDUSTRIAL APPLICABILITY

The present invention is applicable to a personal digital assistant and a

notebook computer capable of mobile communication as well as a mobile phone. Also,

the preferred embodiments may be implemented as a method, apparatus or article of

manufacture using standard programming and/or engineering techniques to produce

software, firmware, hardware, or any combination thereof. The term "article of

manufacture" as used herein refers to code or logic implemented in hardware logic (e.g.,

an integrated circuit chip, Field Programmable Gate Array (FPGA), Application

Specific Integrated Qircuit (ASIC) ₅ etc.) or a computer readable medium (e.g., magnetic

storage medium (e.g., hard disk drives, floppy disks, tape, etc.), optical storage (CD-

ROMs, optical disks, etc.), volatile and non- volatile memory devices (e.g., EEPROMs,

ROMs, PROMs, RAMs, DRAMs, SRAMs, firmware, programmable logic, etc.).

Although various embodiments of the present invention have been described

with reference to a node-B, the present invention may be applied to a base station or any

other type of fixed communication station.

It will be apparent to those skilled in the art that various modifications and

variations may be made in the present invention without departing from the spirit or

scope of the inventions. Thus, it is intended that the present invention covers the

modifications and variations of this invention provided they come within the scope of

the appended claims and their equivalents.