KR20080047947A - Method and system for cell selection in mobile communication system - Google Patents

Abstract

The present invention relates to a method and system for performing cell selection in a mobile communication system. When the UE receives a multimedia broadcasting multicast service (MBMS service) or a unicast service, the UE performs cell search by dividing each frequency band in an overlapping region of a broadcast service dedicated frequency band and a unicast service capable frequency band. To perform. In the first embodiment, in order to perform a cell search, the user terminal allocates a combination of PSC and SSC differently for each frequency band for each cell. In the second embodiment, system information broadcast through a P-BCH from a network is used to indicate whether each cell belongs to a broadcast service dedicated frequency band.

Description

METHOD FOR PERFORMING CELL SELECTION IN MOBILE TELECOMMUNICATION SYSTEM AND THEREFOR SYSTEM}

1 is a block diagram showing the structure of a mobile communication system.

2 is a block diagram showing a simplified structure of a mobile communication system for providing a broadcast service.

3 is a view showing a broadcast service dedicated frequency band and a unicast service available frequency band in a mobile communication system.

4 is a diagram illustrating a terminal operation in a broadcast service dedicated frequency band in a mobile communication system.

5 is a message flow diagram illustrating an attach procedure in a mobile communication system.

6 is a message flow diagram illustrating a routing area update (RAU) procedure in a mobile communication system.

7 is a message flow diagram illustrating a service request procedure in a mobile communication system.

8 is a flowchart illustrating a cell selection operation between a broadcast service dedicated frequency band and a unicast service capable frequency band according to the first embodiment of the present invention.

9 is a flowchart illustrating a cell selection operation between a broadcast service dedicated frequency band and a unicast service capable frequency band according to a second embodiment of the present invention.

The present invention relates to a mobile communication system, and more particularly, to a method and system for performing cell selection for receiving a broadcast service and a unicast service in a mobile communication system.

The UMTS system is based on the Global System for Mobile Communications (GSM) and General Packet Radio Services (GPRS), a European mobile communication system, and uses a wideband Code Division Multiple Access (CDMA). The third generation asynchronous mobile communication system used. The 3rd Generation Partnership Project (3GPP), which is in charge of UMTS standardization, is discussing the Long Term Evolution (LTE) system as the next generation mobile communication system of the UMTS system. LTE is a technology that implements high-speed packet-based communication with a transmission rate of up to 100 Mbps, aiming for commercialization in 2010. To this end, various schemes are discussed. For example, a scheme of reducing the number of nodes located on a communication path by simplifying a network structure, or approaching wireless protocols as close as possible to a wireless channel are under discussion.

Today, due to the development of communication technology, the services provided by the mobile communication system are developing not only a conventional voice service but also a packet service communication and a multimedia broadcasting / communication capable of transmitting a multimedia service. In order to support multimedia broadcasting / communication, a Multimedia Broadcast and Multicast Service (hereinafter, referred to as 'UE') from one or more multimedia data sources to a plurality of user equipments (hereinafter referred to as 'UE') MBMS service) is discussed.

MBMS service refers to a service for transmitting the same multimedia data to multiple receivers through a wireless network. In this case, by allowing multiple receivers to share one radio channel, it is possible to save radio transmission resources. The MBMS service supports multimedia transmission forms such as real-time video, audio, still images, text, etc., and can simultaneously provide audio data and video data according to the multimedia transmission format, and requires a large amount of transmission resources. In the case of the MBMS service, since the same data must be transmitted to a plurality of cells in which users are located, one-to-one (Point to Point: 'PtP') or one-to-many depending on the number of users located in each cell. : Hereinafter called 'PtM') Connection is made.

In a broadcast service such as an MBMS service, in order to provide better broadcast quality, a broadcast service dedicated frequency band may be used. Unlike the unicast serviceable frequency bands that can be used to provide not only broadcast services but also general unicast services, the broadcast service dedicated frequency bands are used only to provide specific broadcast services and are used for uplink (UL). ) Transport is not supported. When there is a broadcast service to be received, the user terminal may move to a broadcast service dedicated frequency band corresponding to the broadcast service through cell selection or reselection.

In the case of providing a broadcast service through a dedicated broadcast service band in a mobile communication system as described above, when the cell (re) selection, the terminal selects a suitable cell having the strongest signal strength for each subcarrier. When camped on a cell belonging to a broadcast service dedicated frequency band, uplink signaling transmission for a routing area update (hereinafter referred to as RAU) or a system access may not be performed. Accordingly, a problem arises in that the terminal needs to reselect a cell belonging to a unicast serviceable frequency band for the uplink signaling.

Therefore, in the conventional mobile communication system supporting a broadcast service using a broadcast service dedicated frequency band, an efficient cell (re) selection of the terminal to prevent the terminal from unnecessarily camping on in an unsuitable frequency band There is a need to define behavior.

Therefore, the present invention devised to solve the problems of the prior art operating as described above, when the terminal does not receive a broadcast service having a broadcast service dedicated frequency band, the broadcast service dedicated frequency at the time of cell selection or cell reselection Provided are a method and system for controlling to select a cell in a frequency band other than the band.

The present invention provides a method and system for controlling to preferentially select a unicast service capable frequency band at the time of cell (re) selection of a terminal in a mobile communication system operating a broadcast service dedicated frequency band.

According to a preferred embodiment of the present invention, in a cell selection method in a mobile communication system,

Determining whether a cell search for a dedicated broadcast service band for providing a broadcast service is necessary;

If the cell search for the broadcast service dedicated frequency band is not necessary as a result of the determination, except for the combination of the primary synchronization code (PSC) and the secondary synchronization code (SSC) commonly assigned to the cells belonging to the broadcast service dedicated frequency band Performing a cell search using combinations of PSCs / SSCs of cells belonging to a unicast service capable frequency band;

And performing camping on the selected cell as a result of performing the cell search.

According to a preferred embodiment of the present invention, in a mobile communication system,

A network node including a plurality of cells, allocating different PSC / SSC combinations to cells belonging to a broadcast service dedicated frequency band and cells belonging to the unicast service enabled frequency band;

A terminal connecting to the network node through at least one of the cells,

The terminal,

If it is determined that cell search for the broadcast service dedicated frequency band is not necessary, the PSC / s of the cells belonging to the unicast serviceable frequency band are excluded, except for the PSC / SSC combination commonly assigned to the cells belonging to the broadcast service dedicated frequency band. It is characterized by performing cell search using combinations of SSCs.

According to a preferred embodiment of the present invention, in a cell selection method in a mobile communication system,

Receiving system information broadcasted through a primary broadcast channel (P-BCH) from a cell selected for cell selection or cell reselection;

Determining whether the cell belongs to a broadcast service dedicated frequency band from the system information;

If the cell does not belong to the broadcast service dedicated frequency band, characterized in that it comprises a step of camping in the selected cell.

According to a preferred embodiment of the present invention, in a mobile communication system,

A network node including a plurality of cells, the system node broadcasting system information on the P-BCH from the cells indicating whether each cell belongs to a broadcast service dedicated frequency band;

And a terminal accessing the network node through at least one of the plurality of cells,

The terminal,

Receiving system information broadcast from a cell selected for cell selection or cell reselection, and determining whether the selected cell belongs to a broadcast service dedicated frequency band from the system information;

If the selected cell does not belong to the broadcast service dedicated frequency band, it is characterized in that the camping in the selected cell.

Hereinafter, with reference to the accompanying drawings will be described in detail the operating principle of the preferred embodiment of the present invention. In the following description of the present invention, detailed descriptions of well-known functions or configurations will be omitted if it is determined that the detailed description of the present invention may unnecessarily obscure the subject matter of the present invention. Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout the specification.

The main subject of the present invention to be described later is to support efficient cell selection or cell reselection operation of a terminal in a mobile communication system supporting a broadcast service dedicated frequency band.

In the present specification, as an example of a mobile communication system, reference will be made to a 3GPP Long Term Evolution (LTE) system, which is a next generation (Evolved) mobile communication system discussed in the 3rd Generation Partnership Project (3GPP). Reference will be made to the Multimedia Broadcast Multicast Service (MBMS) discussed. However, this particular standard and system configuration does not limit the scope of the present invention, and the efficient cell selection or cell reselection operation of the terminal, which is a basic object of the present invention, may be performed in other mobile communication systems having a similar technical background and system structure. It is possible to apply a slight modification in the range without departing greatly from the scope of the present invention, which will be possible in the judgment of those skilled in the art.

1 is a block diagram showing the structure of a mobile communication system according to a preferred embodiment of the present invention.

Referring to FIG. 1, an Evolved UMTS Radio Access Network (hereinafter referred to as 'E-RAN' or 'E-UTRAN') 110 and 112 may be referred to as an Evolved Node B (ENB). (120, 122, 124, 126, 128) and the upper node (anchor node) 130, 132 is simplified to a two-node structure. The user equipment (hereinafter referred to as 'UE' or 'terminal') 101 connects to the Internet Protocol 114 via the E-UTRAN 110. The ENBs 120 to 128 correspond to Node Bs of a typical UMTS system and are connected in a radio channel with the UE 101.

Unlike the existing Node B, the ENBs 120 to 128 play a more complex role. Specifically, in LTE, all user traffic including a real-time service such as Voice over IP (VoIP) through the Internet protocol is serviced through a shared channel, so it is necessary to collect and schedule UE information. The same scheduling operation is handled by the ENB (120 to 128). Each ENB typically controls a number of cells.

In addition, the ENB performs Adaptive Modulation & Coding (hereinafter referred to as 'AMC') to determine a modulation scheme and a channel coding rate according to a channel state of a terminal. Hybrid ARQ (HARPA), such as High Speed Downlink Packet Access (HSDPA) and High Speed Uplink Packet Access (HSUPA), also known as Enhanced Dedicated Channel (E-DCH). Since HARQ alone cannot satisfy the requirements of various Quality of Service (QoS), an outer ARQ at a higher layer may be performed between the terminal 101 and the ENBs 120 to 128. have. The HARQ is a technique of increasing reception success rate by soft combining with retransmitted data without discarding previously received data.

It is used to improve transmission efficiency in high speed packet communication such as HSDPA (High Speed Downlink Packet Access) and EDCH (Enhanced Dedicated Channel). LTE is expected to use Orthogonal Frequency Division Multiplexing (OFDM) as its radio access technology in the 20 MHz bandwidth to achieve transmission rates up to 100 Mbps.

2 shows a simplified structure of a mobile communication system for a broadcast service. Here, an example of a configuration of UTRAN applying MBMS service to 3GPP system is shown.

Referring to FIG. 2, user terminals (UEs) 261, 262, 263, 271, and 272 refer to terminal devices or subscribers capable of receiving MBMS services, and include cell 1 260 and cell 2 270. Is a geographical or logical area for wirelessly transmitting MBMS-related data to subscribers, which is controlled by the base station apparatus, Node B. A radio network controller (hereinafter, referred to as 'RNC') 240 controls the cells 260 and 270 to selectively transmit multimedia data to a specific cell and to provide MBMS service. Control wireless channels. The connection between the RNC 240 and the UEs 261-272 is called a Radio Resource Control (RRC) interface.

The RNC 240 is connected to a Packet Switched or Packet Service (PS) network such as the Internet by a Serving GPRS Support Node (hereinafter referred to as 'SGSN') 230. Communication between the RNC 240 and the PS network is made by packet switched signaling (PS signaling). In particular, the connection between the RNC 240 and the SGSN 230 is called an Iu-PS interface.

SGSN 230 controls the MBMS-related services of each subscriber. Typical examples of the role played by the SGSN 230 include a role of managing data charging related to each subscriber and a role of selectively transmitting multimedia data to a specific RNC 240.

The Transit NW 220 provides a communication path between the Broadcast Multicast Service Center (BM-SC) 210 and the SGSN 230 and to an external network through a Gateway GPRS Support Node (GGSN). Can be connected. The BM-SC 210 is responsible for scheduling MBMS data as a source of MBMS data. The MBMS data stream generated by the BM-SC 210 is sent to the UEs 261, 262, 263, 271 via the transport network 220, SGSN 230, RNC 240, and cells 260, 270. And 272). Each cell 260, 270 serves at least one frequency band to provide MBMS service and other services.

3 illustrates a broadcast service dedicated frequency band and a unicast service available frequency band in a mobile communication system. Here, the unicast serviceable frequency band generally refers to a frequency band where unicast service and broadcast service are multiplexed. In order to multiplex unicast service and broadcast service, TDM (Time Division Multiplexing) or FDM (Frequency Division Multiplexing) may be used.

Referring to FIG. 3, FA (Frequency Assignment) # 1 310 is an MBMS dedicated frequency band, that is, a broadcast service dedicated frequency band, and provides an MBMS service exclusively to terminals connected to the FA # 1 310. As a band allocated for the purpose, only a downlink (DL) signal can be transmitted, and an uplink (UL) signal cannot be transmitted. FA # 2 311 is a general frequency band, not a broadcast service dedicated frequency band. In the FA # 2 311, not only a downlink signal but also an uplink signal can be transmitted. That is, since most of general services are available in FA # 2 311, it is called a unicast service capable frequency band.

4 is a view illustrating a terminal operation in a broadcast service dedicated frequency band in a mobile communication system. Here, FA # 1 410 is an MBMS dedicated frequency band in which unicast service is not possible, and FA # 2 411 is a unicast service capable frequency band. The terminal performs cell search by dividing each frequency band in an overlapping region of FA # 1 410 and FA # 2 411.

Referring to FIG. 4, in step 420, the terminal performs initial access to FA # 1 410, which is a dedicated broadcast service band in a power-on state, and attaches to FA # 1 in step 430. Transmit an uplink signal to attempt. However, since FA # 1 does not support uplink transmission, the access attempt fails in step 440. In step 441, the UE attempts a RAU operation as it enters a new routing area RA while accessing the FA # 1, but for the same reason, the RAU operation fails. If the UE attempts a service request to the network to start a new service in FA # 1 in step 442, the service request attempt fails for the same reason.

5 to 7, a detailed procedure of uplink signaling transmission will be described.

5 is a flowchart illustrating an access procedure in a mobile communication system. Here, the access procedure is performed when the terminal first connects to the network.

Referring to FIG. 5, in step 510, the terminal transmits an ATTACH REQUEST message to the SGSN, indicating that the terminal attempts to access the data service. In step 520 and 521, in response to the access request, the SGSN exchanges an IDENTITY REQUEST message and an IDENTITY RESPONSE message with a terminal to obtain identification information (eg, an international mobile station identity (IMSI), etc.) of the terminal.

In step 530, the SGSN performs an authentication process for the terminal with a Home Location Register (HLR) to determine whether the terminal can access a network and receive a service. After completing the authentication process, in step 540, the SGSN transmits an ATTACH ACCEPT message to the terminal to inform that the access operation for the network of the terminal is completed. Then, in step 550, the terminal reports to the SGSN that the access procedure is finally completed through the ATTACH ACCEPT COMPLETE message.

6 is a diagram illustrating a routing area update (RAU) procedure in a mobile communication system.

Referring to FIG. 6, in step 610, the terminal receives RA information indicating which RA the current cell belongs to from the network, and updates the changed RA when the RA changes, that is, when entering a cell belonging to another RA. RRC ROUTING AREA UPDATE REQUEST message to request is sent to SGSN through RNC. With respect to the ROUTING AREA UPDATE REQUEST message, in step 620, the SGSN grants the RAU through the ROUTING AREA UPDATE ACCEPT message. Thereafter, in step 630, the terminal finally transmits a ROUTING AREA UPDATE COMPLETE message to complete the RAU.

7 is a message flow diagram illustrating a service request procedure in a mobile communication system.

Referring to FIG. 7, in step 710 and 720, an RRC connection is established by exchanging an RRC CONNECTION REQUEST message and an RRC CONNECTION SETUP message between a terminal and an RNC. Afterwards, in order to start a new service, a SERVICE REQUEST message is transmitted from the terminal to the SGSN in step 730. That is, in step 730, the terminal transmits a SERVICE REQUEST message to SGSN to request a new service to be started. In this case, the service type and the identification number (IMSI) of the terminal are included in the SERVICE REQUEST message so that the terminal provides the service. Indicates to request. In response to this, in step 740, the SGSN accepts the terminal to start the service through a SERVICE ACCEPT message.

In the above procedures, when the terminal is in a broadcast service dedicated frequency band, the uplink signal transmitted by the terminal cannot be transmitted to the network, so uplink signaling becomes unnecessary. Therefore, embodiments are disclosed to prevent unnecessary uplink signaling transmission in a broadcast service dedicated frequency band. In a first preferred embodiment of the present invention, one of cell identification codes used in an LTE system, for example, possible combinations of primary synchronization codes (PSCs) and secondary synchronization codes (SSCs), is a cell of a dedicated frequency band of a broadcast service. By using to refer to, the broadcast service dedicated frequency band and the unicast service available frequency band is distinguished. In the second embodiment, system information broadcast through a Primary Broadcast Channel (P-BCH) from a network is used to indicate whether each cell belongs to a broadcast service dedicated frequency band.

<< first embodiment >>

The PSC and the SSC used in the first embodiment are as follows. The PSC is a code constituting a Primary Synchronization Channel (P-SCH), which is generated based on a Zadoff-Chu (ZC) code, and is composed of repetitive codes. PSCs consist of three PSCs that separate three cell groups, with each PSC representing one cell group. Each PSC is mapped to 72 subcarriers and is symmetrically mapped to upper and lower subcarriers about a center frequency direct current (DC) subcarrier.

SSC is generated based on binary code, and has a structure in which two short codes are combined. The SSCs represent code information corresponding to each cell, two frame timing information, and antenna number information so as to distinguish 170 cells. Thus, the maximum number of possible hypothesis of SSCs is as follows.

170 (Cell_ID) * 2 (Frame_Timing) * N (Number_of_Antenna)

Each SSC is mapped to 72 subcarriers and is symmetrically mapped to upper and lower subcarriers about the DC subcarrier. The PSC and SSC are located in different subframes within one frame.

According to the first embodiment, in the network, in order to distinguish a cell belonging to a broadcast service dedicated frequency band and a cell belonging to a unicast service enabled frequency band, a cell belonging to a broadcast service dedicated frequency band and a cell belonging to a unicast service available frequency band The cell is assigned different cell identification codes, for example combinations of PSC and SSC. In this specification, all cells including a broadcast service dedicated frequency band will be described as an example in which a combination of one PSC and SSC (hereinafter, referred to as PSC / SSC combination) is commonly used. That is, cells belonging to a broadcast service transmission frequency band may use one PSC / SSC combination or a plurality of predetermined PSC / SSC combinations.

If the terminal does not wish to receive a broadcast service having a dedicated frequency band, the terminal may assign a PSC / SSC allocated to cells belonging to a unicast serviceable frequency band during cell search during initial cell selection and cell reselection. The cell search is performed using only combinations. Accordingly, the terminal can select a cell that does not belong to the broadcast service dedicated frequency band.

8 is a flowchart illustrating an operation of selecting one cell among a broadcast service dedicated frequency band and a unicast service capable frequency band according to the first embodiment of the present invention.

Referring to FIG. 8, in step 810, an initial cell selection procedure, a cell reselection procedure due to a failure of the initial cell selection, or a general cell reselection procedure is started. In step 811, one frequency is determined through the cell (re) selection procedure. The band is selected. In step 812, the terminal determines whether cell search for a unicast service capable frequency band and a broadcast service dedicated frequency band is necessary. In detail, when the initial cell selection procedure or the cell reselection procedure due to the failure of the initial cell selection is performed, the process proceeds directly to step 821 without any judgment. On the other hand, if a general cell reselection procedure is performed, not due to a failure of initial cell selection, in step 812, the terminal selects a selected cell (referred to as a previous cell) prior to performing the cell reselection procedure to the dedicated broadcast band. It is determined whether it belongs and was receiving a broadcast service through the previous cell.

If the cell reselection procedure is being performed and the previous cell belongs to the broadcast service dedicated frequency band and receives the broadcast service through the previous cell, the cell search must also be performed for the broadcast service dedicated frequency band. The cell proceeds to step 841 after performing cell search and measurement for all cell identification codes, that is, all combinations of the PSC and the SSC. If not, go to step 821.

In the case of initial cell selection, cell reselection due to a failure of initial cell selection, or cell reselection in a state in which no broadcast service is received anymore, in step 821, the terminal is pre-determined that is mapped to a dedicated broadcast service frequency band. The PSC / SSC combinations are removed from the PSC / SSC combination cell search target list, and the PSC / SSC combination codes included in the cell search target list, that is, the PSC / SSC combination codes of cells belonging to a predefined unicast serviceable frequency band (831). After performing the cell search and measurement by using the process, the process proceeds to step 841. Specifically, the cell search means correlating a received signal from the network with PSC / SSC combinations included in the cell search target list to determine whether the strength of the correlated signal exceeds a predetermined threshold.

In step 841, the terminal selects a strongest cell having the largest received signal strength as a result of the cell search and measurement, and in step 852, a suitable cell in which the maximum strength cell can receive a normal service Check if it is (suitable cell). Whether or not it is the suitable cell can be known from system information broadcast from the maximum strength cell as an example. If it is a suitable cell, in step 861 the terminal camps into the maximum strength cell. If the maximum strength cell is not a suitable cell, the terminal proceeds to step 871 to select another frequency band, and returns to step 812 to repeat the above steps.

On the other hand, the above has been described a case of using a combination of PSC / SSC to distinguish the cells belonging to the broadcast service dedicated frequency band, another type of code that can distinguish the cells, for example, a specific scrambling code is a broadcast service dedicated frequency band May be assigned to.

<< 2nd Example >>

According to the second embodiment, in the network, in order to distinguish a cell belonging to a broadcast service dedicated frequency band and a cell belonging to a unicast service enabled frequency band, system information broadcast from each cell through P-BCH, that is, P-BCH information By using it tells whether each cell is a cell belonging to the broadcast service dedicated frequency band. When not receiving a broadcast service from a broadcast service dedicated frequency band, the terminal receives system information broadcast from a cell selected in an initial cell selection or cell reselection procedure to determine whether the selected cell belongs to a broadcast service dedicated frequency band. If the selected cell belongs to a broadcast service dedicated frequency band, the selected cell is not camped. The structure of the P-BCH information is shown in Table 1 as an example.

Down frequency band Transmission power of the reference signal MBSFN related values Transmit Antenna Number CRC 4 bits 0-6 bits 0-9 bits 1-2 bits 16 bits

The P-BCH information has four fields and a Cyclic Redundancy Check (CRC) code as shown in Table 1, and the meaning of each field is as follows. The first field indicates the frequency band of the downstream system and consists of 4 bits. The second field indicates 0 to 6 bits of the transmission power of the reference signal (RS), and indicates the ratio of the transmission power of the reference signal to the total power of the base station. The third field is a MBSFN (Multicast / Broadcast over Single Frequency Network) related value and indicates the location information of MBSFN frames and subframes with 0 to 9 bits. Herein, the MBSFN frame and the subframe mean a specific frame in which a broadcast service is performed and a specific subframe within the specific frame, and the position of the specific frame / subframe is indicated by the MBSFN related value. The fourth field indicates the number of transmit antennas by 1-2 bits, and the fifth field is CRC 16 bits for error correction of the preceding fields.

One of all bit combinations of the remaining four fields except the CRC among the system information transmitted through the P-BCH is used as information indicating a cell using a broadcast service dedicated frequency band. For example, P-BCH information in which all bits of all fields are "0" indicates that the current cell is a cell using a broadcast service dedicated frequency band. In this case, it is possible to provide additional cell information by using the above fields without allocating additional bits to P-BCH information to indicate a cell using a broadcast service dedicated frequency band.

9 is a flowchart illustrating an operation of selecting one cell of a broadcast service dedicated frequency band and a unicast service capable frequency band according to a second embodiment of the present invention.

Referring to FIG. 9, an initial cell selection procedure or a cell reselection procedure is started in step 910, and one frequency band is selected in step 911 through the cell (re) selection procedure. In step 921, the terminal performs cell search and measurement on the cells of the selected frequency band, selects the maximum strength cell having the largest received signal strength, and in step 931, the system information broadcast from the maximum strength cell, The fields of the P-BCH information are analyzed to determine whether the maximum strength cell belongs to a broadcast service dedicated frequency band.

If the initial cell selection procedure is performed and the maximum strength cell belongs to a broadcast service dedicated frequency band, the process proceeds directly to step 941. On the other hand, if the cell reselection procedure is performed, in step 931, the terminal determines whether the maximum-strength cell belongs to a broadcast service dedicated frequency band and the cell selected before performing the cell reselection procedure (called a previous cell) is broadcasted. It is determined whether it belongs to a service-dedicated frequency band and has received a broadcast service through the previous cell. If the maximum strength cell belongs to a broadcast service dedicated frequency band and the previous cell has not received a broadcast service, the process proceeds to step 941 as well.

If the maximum strength cell does not belong to the broadcast service dedicated frequency band, but the previous cell belongs to the broadcast service dedicated frequency band and receives the broadcast service through the previous cell, the terminal proceeds to step 951. Check whether or not a suitable cell is capable of receiving a service. If it is a suitable cell in step 961 the terminal camps to the maximum strength cell. On the other hand, if the maximum strength cell is not a suitable cell, the terminal proceeds to step 951 to select another frequency band, and returns to step 921 to perform the cell search again.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the scope of the following claims, but also by those equivalent to the scope of the claims.

In the present invention operating as described in detail above, the effects obtained by the representative ones of the disclosed inventions will be briefly described as follows.

The present invention provides an efficient cell selection and cell reselection operation of a mobile station in a mobile communication system operating a broadcast service dedicated frequency band for a broadcast service, thereby allowing the terminal to camp on unnecessary frequency bands for system access, routing area update, and service request. There is an effect of preventing the uplink signaling transmission, such as failure.

Claims (17)

In the cell selection method in a mobile communication system, Determining whether a cell search for a dedicated broadcast service band for providing a broadcast service is necessary; If the cell search for the broadcast service dedicated frequency band is not necessary as a result of the determination, except for the combination of the primary synchronization code (PSC) and the secondary synchronization code (SSC) commonly assigned to the cells belonging to the broadcast service dedicated frequency band Performing a cell search using combinations of PSCs / SSCs of cells belonging to a unicast service capable frequency band; And camping in a selected cell as a result of performing the cell search. The method of claim 1, wherein the determining is performed. When initial cell selection is performed, when cell reselection is performed due to a failure of initial cell selection, or when cell reselection is performed when a broadcast service is no longer received, a cell for the broadcast service dedicated frequency band And determining that no search is necessary. The method of claim 1, wherein if the cell search for the broadcast service dedicated frequency band and the unicast capable frequency band is necessary, the cell is allocated to cells belonging to the broadcast service dedicated frequency band and the unicast service capable frequency band. And performing cell search using combinations of PSC / SSC. The method of claim 3, wherein the determining is performed. If cell reselection is performed and a previous cell located before the cell reselection is performed belongs to the broadcast service dedicated frequency band and receives a broadcast service from the previous cell, the broadcast service dedicated frequency band and the uni And determining that a cell search for a cast service capable frequency band is necessary. The method of claim 1, wherein performing the cell search comprises: Selecting a maximum strength cell having a virtual large received signal strength; Determining to camp on the maximum intensity cell if the maximum intensity cell is a suitable cell for cell selection or cell reselection; And if the maximum strength cell is not a suitable cell, selecting another frequency band and performing cell selection or cell reselection again in the other frequency band. The method of claim 1, wherein a combination of different PSC / SSCs is assigned to cells belonging to the broadcast service dedicated frequency band and cells belonging to the unicast service available frequency band. In the mobile communication system, A network node including a plurality of cells, allocating different PSC / SSC combinations to cells belonging to a broadcast service dedicated frequency band and cells belonging to the unicast service enabled frequency band; A terminal connecting to the network node through at least one of the cells, The terminal, If it is determined that cell search for the broadcast service dedicated frequency band is not necessary, the PSC / s of the cells belonging to the unicast serviceable frequency band are excluded, except for the PSC / SSC combination commonly assigned to the cells belonging to the broadcast service dedicated frequency band. And a cell search using combinations of SSCs. The method of claim 7, wherein the terminal, When initial cell selection is performed, when cell reselection is performed due to a failure of initial cell selection, or when cell reselection is performed when a broadcast service is no longer received, a cell for the broadcast service dedicated frequency band A mobile communication system, characterized in that it is determined that the search is not necessary. The method of claim 7, wherein the terminal, When the cell search for the broadcast service dedicated frequency band and the unicast capable frequency band is necessary as a result of the determination, combinations of PSC / SSCs allocated to cells belonging to the broadcast service dedicated frequency band and the unicast service capable frequency band are determined. A mobile communication system, characterized in that for performing a cell search. The method of claim 9, wherein the terminal, If the cell reselection is performed, and the previous cell located before the cell reselection is performed belongs to the broadcast service dedicated frequency band and receives the broadcast service from the previous cell, the broadcast service dedicated frequency band and the And a cell search for a unicast service capable frequency band. The method of claim 7, wherein the terminal, As a result of the cell search, a maximum strength cell having a virtual large received signal strength is selected, and if the maximum strength cell is a suitable cell for cell selection or cell reselection, it is decided to camp on the maximum strength cell, and the maximum strength cell And if the cell is not a suitable cell for cell selection or cell reselection, another frequency band is selected to perform cell selection or cell reselection in the other frequency band. In the cell selection method in a mobile communication system, Receiving system information broadcasted through a primary broadcast channel (P-BCH) from a cell selected for cell selection or cell reselection; Determining whether the cell belongs to a broadcast service dedicated frequency band from the system information; And if the cell does not belong to a broadcast service dedicated frequency band, camping in the selected cell. The method of claim 12, wherein if the selected cell belongs to a broadcast service dedicated frequency band and initial cell selection has been made or if a broadcast service has not been received from a previous cell, another frequency band is selected. And performing a cell selection or cell reselection in the cell selection method. The method of claim 12, wherein the determining comprises: And determining whether the selected cell belongs to a broadcast service dedicated frequency band by using all bits of the system information. In the mobile communication system, A network node including a plurality of cells, the system node broadcasting system information on the P-BCH from the cells indicating whether each cell belongs to a broadcast service dedicated frequency band; And a terminal accessing the network node through at least one of the plurality of cells, The terminal, Receiving system information broadcast from a cell selected for cell selection or cell reselection, and determining whether the selected cell belongs to a broadcast service dedicated frequency band from the system information; And if the selected cell does not belong to a broadcast service dedicated frequency band, camping in the selected cell. The method of claim 15, wherein the terminal, If the selected cell belongs to a broadcast service dedicated frequency band and initial cell selection has been made or if a previous cell has not been receiving a broadcast service, a different frequency band is selected to select a cell or reselect a cell. A mobile communication system, characterized in that for performing the selection. The method of claim 15, wherein the terminal, And determining whether the selected cell belongs to a broadcast service dedicated frequency band by using all bits of the system information.

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