KR20090029620A - Method for updating system information in wireless communication system - Google Patents

Abstract

A method for updating system information in a wireless communication system is provided to effectively update the system information without performing unnecessary processing processes. A terminal monitors a downlink control channel to detect system information change notification(S210). The terminal receives a scheduling system information message(S220). The terminal receives the updated dynamic system information message(S230). If the system information change notification is detected, the scheduling system information message including at least one dynamic system information message and an update indicator indicating the dynamic system information message is received.

Description

Method for updating system information in wireless communication system

The present invention relates to wireless communication, and more particularly, to a method for updating system information in a wireless communication system.

3rd generation partnership project (3GPP) mobile communication systems based on wideband code division multiple access (WCDMA) wireless access technology are widely deployed around the world. High Speed Downlink Packet Access (HSDPA), which can be defined as the first evolution of WCDMA, provides 3GPP with a highly competitive wireless access technology in the mid-term future. However, as the demands and expectations of users and operators continue to increase, and the development of competing wireless access technologies continues to progress, new technological evolution in 3GPP is required to be competitive in the future.

In general, at least one cell is disposed in one base station (BS). A plurality of user equipments (UEs) may be located in one cell. When the terminal attempts to access a new cell for the first time, the terminal synchronizes downlink and receives system information (SI) from a network to be accessed. The system information includes essential information that the terminal needs to know in order to communicate with the base station. Therefore, the terminal must receive all system information before accessing the base station, and must always maintain the latest system information. The base station informs the terminal of basic information for accessing the network using the system information.

1 illustrates a method for receiving system information according to the prior art.

Referring to FIG. 1, since system information is information that every terminal in a cell should know, the base station periodically transmits system information. The terminal continuously receives the system information transmitted periodically and performs decoding. The terminal communicates with the base station using the received system information until the system information is changed.

System information may be changed / updated periodically or as needed. However, since the terminal cannot know the change of the system information, it receives and decodes all system information transmitted periodically. In the case of the DRX (Discontinuous Reception) mode, the UE turns on the power at regular intervals and receives only system information transmitted through a paging message in order to reduce battery consumption. However, the terminal of the RRC connected mode (RRC Connected Mode) receives and decodes all system information transmitted periodically. If the system information has been previously received and the system information has not been changed, the terminal communicates with the base station using the previously received system information without having to periodically receive the system information, and if the system information is changed. Receiving and using changed system information only is a method of reducing battery consumption of the terminal. Periodically receiving and decoding the entire system information by the UE in the RRC connected mode causes unnecessary battery consumption.

What is needed is a way to efficiently change / update system information.

The present invention is to provide an efficient system information update method.

A system information updating method in a wireless communication system according to an aspect of the present invention, the method comprising: monitoring a downlink control channel to detect a system information change notification, and if the system information change notification is detected, at least one dynamic system information message. And receiving a scheduling system information message including an update indicator indicating update of the dynamic system information message.

In a wireless communication system according to another aspect of the present invention, a system information update method includes transmitting a system information change identifier through a downlink control channel to notify a terminal of a change in system information, and scheduling information of at least one dynamic system information message. And transmitting a scheduling system information message including an update indicator indicating update of the dynamic system information message through the DL-SCH.

A terminal according to another aspect of the present invention is connected to the RF unit for transmitting and receiving a radio signal and the RF unit, to monitor the downlink control channel to detect a system information change notification, the system information change notification is detected And a processor configured to receive a scheduling system information message that includes an update indicator indicating an update of the dynamic system information message.

The terminal does not continuously receive the system information, and monitors the PDCCH and receives updated dynamic system information transmitted through the PDSCH when the system information changes, thereby reducing battery consumption. The base station notifies the change of the system information through the PDCCH, and transmits the scheduling information and the update indicator of the dynamic system information through the PDSCH so that the terminal can efficiently update the system information without performing unnecessary processing.

2 is a block diagram illustrating a wireless communication system. This may be a network structure of an Evolved-Universal Mobile Telecommunications System (E-UMTS). The E-UMTS system may be referred to as a Long Term Evolution (LTE) system. Wireless communication systems are widely deployed to provide various communication services such as voice, packet data, and the like.

Referring to FIG. 2, an Evolved-UMTS Terrestrial Radio Access Network (E-UTRAN) includes a base station (BS) 20 that provides a control plane and a user plane.

The UE 10 may be fixed or mobile and may be called by other terms such as a mobile station (MS), a user terminal (UT), a subscriber station (SS), a wireless device, and the like. The base station 20 generally refers to a fixed station communicating with the terminal 10, and may be referred to as other terms such as an evolved-NodeB (eNB), a base transceiver system (BTS), and an access point. have. One or more cells may exist in one base station 20. An interface for transmitting user traffic or control traffic may be used between the base stations 20. Hereinafter, downlink (DL) means communication from the base station 20 to the terminal 10, and uplink (UL) means communication from the terminal 10 to the base station 20.

The base stations 20 may be connected to each other through an X2 interface. The base station 20 is connected to an Evolved Packet Core (EPC), more specifically, a Mobility Management Entity (MME) / Serving Gateway (S-GW) 30 through an S1 interface. The S1 interface supports a many-to-many-relation between base station 20 and MME / S-GW 30.

3 is a block diagram illustrating a functional split between an E-UTRAN and an EPC.

Referring to FIG. 3, hatched blocks represent radio protocol layers and empty blocks represent functional entities in the control plane.

The base station performs the following functions. (1) Radio resource management such as radio bearer control, radio admission control, connection mobility control, and dynamic resource allocation to a terminal RRM), (2) Internet Protocol (IP) header compression and encryption of user data streams, (3) routing of user plane data to S-GW, and (4) paging messages. Scheduling and transmission, (5) scheduling and transmission of broadcast information, and (6) measurement and measurement report setup for mobility and scheduling.

The MME performs the following functions. (1) distribution of paging messages to base stations, (2) Security Control, (3) Idle State Mobility Control, (4) S-GW Bearer Control, (5) NAS (Non) -Ciphering and Integrity Protection of Access Stratum signaling.

S-GW performs the following functions. (1) termination of user plane packets for paging, and (2) user plane switching to support terminal mobility.

Layers of the radio interface protocol between the terminal and the network are based on the lower three layers of the Open System Interconnection (OSI) model, which is well known in communication systems. (Second layer) and L3 (third layer). Among them, the physical layer belonging to the first layer provides an information transfer service using a physical channel, and is a radio resource control (RRC) layer located in the third layer. The role of controlling the radio resources between the terminal and the network. To this end, the RRC layer exchanges RRC messages between the UE and the network.

4 is a block diagram illustrating a radio protocol architecture for a user plane. 5 is a block diagram illustrating a radio protocol structure for a control plane. This shows the structure of the air interface protocol between the terminal and the E-UTRAN. The data plane is a protocol stack for user data transmission, and the control plane is a protocol stack for control signal transmission.

4 and 5, a physical layer (PHY), which is a first layer, provides an information transfer service to a higher layer using a physical channel. The physical layer is connected to the upper Media Access Control (MAC) layer through a transport channel, and data between the MAC layer and the physical layer moves through this transport channel. Data moves between physical layers between physical layers, that is, between physical layers of a transmitting side and a receiving side. The physical channel is modulated by an orthogonal frequency division multiplexing (OFDM) scheme, and may use time and frequency as radio resources.

The MAC layer of the second layer provides a service to a radio link control (RLC) layer, which is a higher layer, through a logical channel. The RLC layer of the second layer supports reliable data transmission. In the RLC layer, there are three operation modes according to a data transmission method: transparent mode (TM), unacknowledged mode (UM), and acknowledged mode (AM). TM RLC is a mode in which no overhead is attached to the RLC Service Data Unit (SDU) received from the upper layer in configuring an RLC Protocol Data Unit (PDU). PDU refers to a block data unit delivered from another layer to another layer, and SDU refers to a block data unit transferred from another layer to the corresponding layer. This is called TM RLC because the RLC passes the SDU transparently. The UM RLC attaches a PDU header including a sequence number (SN) to each PDU so that the receiver can know which PDU is lost during transmission. The AM RLC provides a bidirectional data transmission service, and supports retransmission when an RLC Protocol Data Unit (PDU) fails to transmit.

The Packet Data Convergence Protocol (PDCP) layer of the second layer contains relatively large and unnecessary control information in order to efficiently transmit packets in a wireless bandwidth having a low bandwidth when transmitting an Internet Protocol (IP) packet such as IPv4 or IPv6. Perform header compression to reduce the IP packet header size.

The radio resource control (RRC) layer of the third layer is defined only in the control plane. The RRC layer is responsible for controlling logical channels, transport channels, and physical channels in connection with configuration, re-configuration, and release of radio bearers (RBs). RB means a service provided by the second layer for data transmission between the UE and the E-UTRAN. If there is an RRC connection (RRC Connection) between the RRC of the terminal and the RRC of the network, the terminal is in the RRC Connected Mode, otherwise it is in the RRC Idle Mode.

The RRC connected mode refers to a state in which the UE is connected to the RRC of the E-UTRAN. In the RRC connected mode, (1) the UE has a context, which is information for radio bearer setup, so that user plane data can be transmitted between the BS and the UE, and (2) the E-UTRAN knows the cell to which the UE belongs. (3) the network can transmit and receive data to and from the terminal and control the mobility of the terminal, (4) neighbor cell measurement can be performed, and (5) PDCP / RLC / MAC Data transmission and reception between the terminal and the network in the layer, control signaling channel monitoring for the allocation of data channels to the terminal, reporting of channel quality information and feedback information, power saving of the terminal and effective resource utilization The configuration of a Discontinuous Reception (DRX) cycle may be performed.

The non-access stratum (NAS) layer located above the RRC layer performs functions such as session management and mobility management.

A logical channel mapped to a transport channel is divided into a control channel and a traffic channel according to the type of data to be transmitted. The control channel is a channel for transmitting data on the control plane, and according to the type of control information, BCCH (Broadcast Control Channel), PCCH (Paging Control Channel), CCCH (Common Control Channel), DCCH (Dedicated Control Channel), MCCH (Multicast) Control Channel) is used. As a traffic channel, a dedicated traffic channel (DTCH), a multimedia broadcast multicast service (MBMS) traffic channel (MTCH), or the like is used as a channel for transmitting user traffic data. The transport channel is responsible for the transmission of data transmitted from the logical channel, and several logical channels may be mapped to one transport channel.

As a downlink transport channel for transmitting data from a network to a terminal, a BCH (Broadcast Channel) for transmitting system information, a PCH (paging channel) for transmitting a call message, and a user traffic or control message are transmitted. DL-SCH (Downlink-Shared Channel). Traffic or control messages of the downlink multicast or broadcast service may be transmitted through the DL-SCH, or may be transmitted through the downlink multicast channel (MCH). An uplink transport channel for transmitting data from a terminal to a network includes a random access channel (RAC) for transmitting an initial control message and an uplink-shared channel (UL-SCH) for transmitting user traffic or a control message.

The downlink channel in the physical layer includes a physical downlink control channel (PDCCH) for transmitting control information, and a physical downlink shared channel (PDSCH) for transmitting user data and / or control information. The uplink channel in the physical layer includes a PUCCH (Physical Unlink Control Channel), PUSCH (Physical Unlink Shared Channel).

6 is a block diagram illustrating elements of a terminal.

Referring to FIG. 6, the terminal 50 includes a processor 51, a memory 52, an RF unit 53, a display unit 54, and a user interface unit. , 55).

The processor 51 is implemented with layers of the air interface protocol to provide a control plane and a user plane. The functions of each layer may be implemented through the processor 51. The processor 51 processes the system information to be described later and applies valid system information.

The memory 52 is connected to the processor 51 to store a terminal driving system, an application, and a general file. The display unit 54 displays various information of the terminal, and may use well-known elements such as liquid crystal display (LCD) and organic light emitting diodes (OLED). The user interface unit 55 may be a combination of a well-known user interface such as a keypad or a touch screen. The RF unit 53 is connected to a processor and transmits and / or receives a radio signal.

Now, transmission and change / update of system information will be described. A base station manages radio resources of one or more cells, and one cell is set to one of bandwidths such as 1.25, 2.5, 5, 10, and 20 MHz to provide downlink or uplink transmission services to multiple terminals. In this case, different cells may be configured to provide different bandwidths. In addition, a cell may be configured such that a plurality of cells are geographically overlapped using multiple frequencies. The base station informs the terminal of basic information for accessing the network using system information (SI). The system information includes essential information that the terminal needs to know in order to communicate with the base station. Therefore, the terminal must receive all system information before accessing the base station, and must always maintain the latest system information. In addition, since the system information is information that should be known to all terminals in one cell, the base station periodically transmits system information.

The system information is an RRC message for transmitting a plurality of system information blocks (SIBs). In this case, the system information block transmitted as one system information has the same scheduling condition, which is called periodicity. More than one system information message may be sent at the same periodicity. Each system information block contains system information parameters.

7 is a flowchart illustrating a process of transmitting system information.

Referring to FIG. 7, the base station transmits broadcast system information to the terminal (S110). The broadcast system information includes physical layer parameters, a system frame number (SFN), scheduling information about scheduling system information, and the like.

Parameters of the physical layer may include a downlink system bandwidth, a number of transmit antennas, a reference signal transmit power, and the like. The system frame number is included in the broadcast system information when the system frame number is not transmitted by other means. Scheduling system information is system information that is repeatedly transmitted most frequently among system information.

Broadcast system information is transmitted through a broadcast channel (BCH). The system information transmitted through the BCH includes one system information block. This system information block is called a master information block.

The base station transmits scheduling system information to the terminal (S120). The scheduling system information is a system information that is repeatedly transmitted most frequently among system information and is transmitted through a downlink-shared channel (DL-SCH). The terminal may obtain scheduling information about the scheduling system information from the broadcast system information. The scheduling system information includes scheduling information about dynamic system information.

The base station transmits the dynamic system information to the terminal (S130). Dynamic system information is transmitted via the DL-SCH. The dynamic system information transmitted through the DL-SCH includes various system information not included in the broadcast system information. Scheduling system information is transmitted more often than dynamic system information. The terminal may obtain scheduling information for the dynamic system information from the scheduling system information.

8 is a flowchart illustrating a method of receiving system information by a terminal according to an embodiment of the present invention.

Referring to FIG. 8, the terminal monitors a downlink control channel in order to detect a system information change notification (S210). The base station transmits a message for notifying the change of system information through the downlink control channel. The system information change notification may be referred to as an identifier for notifying the system information change, and this may be referred to as a system information change RNTI (System information change Radio Network Temporary Identity). The downlink control channel may be a physical downlink control channel (PDCCH). The base station may repeatedly transmit an identifier for notifying the system information change over the PDCCH.

The UE monitors the downlink control channel at a periodic occasion specifically defined for system information change notification. While monitoring the downlink control channel, the terminal may know that system information will change when a system information change notification is received. At this time, the UE monitors the downlink control channel in the RRC connected mode.

If the terminal has previously received system information, the terminal regards the previously received system information as valid system information until the system information change notification message is received. If the UE monitors the downlink control channel and does not receive the system information change notification message, the terminal does not decode the scheduling system information and the dynamic system information transmitted through the physical downlink shared channel (PDSCH).

On the other hand, the base station may transmit a system information change notification using a paging message (paging message) for the terminal in the RRC idle mode (RRC Idle Mode). The paging message is transmitted through a paging channel (PCH). The UE in the RRC idle mode may receive a paging message and recognize that system information is to be changed.

The terminal receives a scheduling system information message (S220). When the system information change notification is detected in the downlink control channel, the terminal receives the scheduling system information message. The terminal may obtain scheduling information about the scheduling system information message from the broadcast system information message transmitted through a broadcast channel (BCH). The scheduling system information message is transmitted through the DL-SCH / PDSCH. The scheduling system information message may be transmitted with a fixed periodicity. That is, the scheduling system information message may be transmitted through a fixed subframe in a radio frame including a plurality of subframes. For example, a radio frame may have a length of 10 ms, including 10 subframes having a length of 1 ms, and scheduling system information may be transmitted through a fifth subframe.

The scheduling system information message includes scheduling information and update indicators for at least one dynamic system information message. The scheduling information for the dynamic system information message is scheduling information indicating the periodicity of other system information except for the scheduling system information message. For example, the scheduling information for the dynamic system information message may indicate a start time of the dynamic system information message. The terminal may know when the updated system information is transmitted through scheduling information on the dynamic system information. Scheduling system information messages are received more frequently than dynamic system information messages. The update indicator indicates whether a change of dynamic system information occurs. The UE may confirm by using an update indicator that previously acquired system information is valid until it leaves the cell coverage and returns to the cell range again.

The scheduling system information message includes one or more Public Land Mobile Network (PLMN) identifiers that are identifiers for the cells providing the wireless connection, a tracking area code that is an identifier for the tracking area to which the cell belongs, and a cell that is a unique identifier of the cell. The cell may further include an identifier (Cell identity), system information block mapping information, and the like.

The terminal receives an updated dynamic system information message (S230). The terminal may receive the updated dynamic system information message by using the scheduling information on the dynamic system information obtained from the scheduling system information message. The dynamic system information message is transmitted on the DL-SCH / PDSCH. The dynamic system information message may be repeatedly transmitted during a system information repetition period. There may be various types of dynamic system information messages, and different types of dynamic system information messages may have the same periodicity or different periodicities. That is, the system information repetition period may have various periods according to the type of the dynamic system information message.

When changing the system information, the base station transmits the updated dynamic system information in the system information repetition period after the current system information repetition period. The terminal receives the updated dynamic system information message after a system information repetition period in which the update indicator is received.

9 illustrates a system information transmission method according to an embodiment of the present invention.

Referring to FIG. 9, the base station periodically transmits system information. The base station transmits broadcast system information on the BCH, scheduling system information on the PDSCH, and dynamic system information according to each period. The broadcast system information includes scheduling information about the scheduling system information. The scheduling system information includes scheduling information for the dynamic system information and an update indicator indicating the update of the dynamic system information.

The UE having previously received system information monitors only the PDCCH without decoding the scheduling system information and the dynamic system information through the PDSCH.

When the network determines the change of the system information, the base station transmits a system information change notification through the PDCCH to inform the terminal of the change of the system information. The base station indicates that the dynamic system information is updated by an update indicator included in the scheduling system information. When the UE monitors the PDCCH and receives a system information change notification, the terminal receives scheduling system information transmitted through the PDSCH. The terminal may confirm that the dynamic system information is updated from the update indicator included in the scheduling system information, and may know when the updated dynamic system information is transmitted from the scheduling information of the dynamic system information.

The base station transmits the updated dynamic system information through the PDSCH when the current system information repetition period for the dynamic system information ends and the next system information repetition period starts. The terminal receives the updated dynamic system information according to the scheduling information of the dynamic system information.

10 illustrates a system information update method according to an embodiment of the present invention.

Referring to FIG. 10, the base station transmits scheduling system information and dynamic system information through the PDSCH. The scheduling system information is repeatedly transmitted most frequently among the system information. That is, scheduling system information is transmitted more frequently than dynamic system information. One or more dynamic system information may be transmitted within its own system information repetition period, and dynamic system information including the same system information parameter is transmitted in the same system information repetition period. In the current system information repetition period, an update indicator indicating update of system information may be transmitted through the scheduling system information, and in the system information repetition period in which the update indicator is transmitted, the old system information before the update is transmitted. The updated system information is updated in the next system information repetition period.

The terminal may update the system information by receiving the updated dynamic system information after a system repetition period for receiving the update indicator.

All of the above functions may be performed by a processor such as a microprocessor, a controller, a microcontroller, an application specific integrated circuit (ASIC), or the like according to software or program code coded to perform the function. The design, development and implementation of the code will be apparent to those skilled in the art based on the description of the present invention.

Although the present invention has been described above with reference to the embodiments, it will be apparent to those skilled in the art that the present invention may be modified and changed in various ways without departing from the spirit and scope of the present invention. I can understand. Therefore, the present invention is not limited to the above-described embodiment, and the present invention will include all embodiments within the scope of the following claims.

1 illustrates a method for receiving system information according to the prior art.

2 is a block diagram illustrating a wireless communication system.

3 is a block diagram illustrating a functional split between an E-UTRAN and an EPC.

4 is a block diagram illustrating a radio protocol architecture for a user plane.

5 is a block diagram illustrating a radio protocol structure for a control plane.

6 is a block diagram illustrating elements of a terminal.

7 is a flowchart illustrating a process of transmitting system information.

8 is a flowchart illustrating a method of receiving system information by a terminal according to an embodiment of the present invention.

9 illustrates a system information transmission method according to an embodiment of the present invention.

10 illustrates a system information update method according to an embodiment of the present invention.

Claims (15)

In the method of updating system information in a wireless communication system, Monitoring a downlink control channel to detect a system information change notification; And Receiving a scheduling system information message including at least one dynamic system information message and an update indicator indicating update of the dynamic system information message when the system information change notification is detected. . The method of claim 1, wherein the scheduling system information message and the at least one dynamic system information message are transmitted through a downlink shared channel (DL-SCH). The method of claim 1, wherein the downlink control channel is a physical downlink control channel (PDCCH). The method of claim 1, wherein the system information change notification is detected when a system information change identifier is transmitted through the downlink control channel. The method of claim 1, wherein the downlink control channel is monitored in a radio resource control (RRC) connection mode. The method of claim 1, wherein the downlink control channel is monitored at a periodic opportunity. 2. The method of claim 1, further comprising the step of receiving the updated dynamic system information message after the update indicator has received a received system information repetition period. The method of claim 1, wherein the scheduling system information message is received more frequently than the dynamic system information message. The method of claim 1, wherein the scheduling system information message is transmitted through a fixed subframe in a radio frame including a plurality of subframes. The method of claim 1, further comprising receiving a broadcast system information message including scheduling information about the scheduling system information message through a broadcast channel. In the method of updating system information in a wireless communication system, Transmitting a system information change identifier through a downlink control channel to notify the terminal of the change of system information; And And transmitting a scheduling system information message including a scheduling information of at least one dynamic system information message and an update indicator indicating update of the dynamic system information message through a DL-SCH. . 12. The method of claim 11, wherein the scheduling system information message is transmitted with a fixed periodicity. 12. The method of claim 11, further comprising transmitting an updated dynamic system information message. 12. The method of claim 11, further comprising transmitting a broadcast system information message including scheduling information about the scheduling system information through a broadcast channel. RF unit for transmitting and receiving a wireless signal; And A scheduling system information message connected to the RF unit, the downlink control channel being monitored to detect a system information change notification, and an update indicator indicating an update of a dynamic system information message when the system information change notification is detected; And a processor configured to receive.

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