WO2018226055A1

WO2018226055A1 - Method and apparatus for deleting system information

Info

Publication number: WO2018226055A1
Application number: PCT/KR2018/006500
Authority: WO
Inventors: Sangwon Kim
Original assignee: Lg Electronics Inc.
Priority date: 2017-06-08
Filing date: 2018-06-08
Publication date: 2018-12-13

Abstract

Provided are a method for a user equipment (UE) to delete system information in a wireless communication. The method include: storing first system information; receiving information on valid area where the first system information is valid, from a network; camping on a cell not belonging to the valid area; upon camping on the cell, starting a timer; and deleting the first system information, if the timer is expired.

Description

METHOD AND APPARATUS FOR DELETING SYSTEM INFORMATION

The present invention relates to a wireless communication system, and more particularly, to a method for a user equipment (UE) to delete system information and an apparatus supporting the same.

In order to meet the demand for wireless data traffic, which has been increasing since the commercialization of a fourth-generation (4G) communication system, efforts are being made to develop an improved fifth-generation (5G) communication system or pre-5G communication system. For this reason, a 5G communication system or pre-5G communication system is referred to as a beyond-4G-network communication system or post-long-term evolution (LTE) system.

System information may include the Minimum SI and the Other SI, in NR, and a random access procedure may be used for requesting the Other SI.

Meanwhile, if the UE is allowed to store some system information block/message for the future use, it also should be specified when to discard the stored system information. This is because that a memory of the UE is limited. Thus, a method for a UE to delete system information and an apparatus supporting the same according to an embodiment of the present invention need to be proposed.

One embodiment provides a method for deleting, by a user equipment (UE), system information in a wireless communication. The method may include: storing first system information; receiving information on valid area where the first system information is valid, from a network; camping on a cell not belonging to the valid area; upon camping on the cell, starting a timer; and deleting the first system information, if the timer is expired.

Another embodiment provides a user equipment (UE) deleting system information in a wireless communication. The UE may include: a memory; a transceiver; and a processor, connected to the memory and the transceiver, that: stores first system information; controls the transceiver to receive information on valid area where the first system information is valid, from a network; camps on a cell not belonging to the valid area; upon camping on the cell, starts a timer; and deletes the first system information, if the timer is expired.

The UE can delete stored system information.

FIG. 1 shows LTE system architecture.

FIG. 2 shows a control plane of a radio interface protocol of an LTE system.

FIG. 3 shows a user plane of a radio interface protocol of an LTE system.

FIG. 4 shows 5G system architecture.

FIG. 5 shows functional split between NG-RAN and 5GC

FIG. 6 shows a system information acquisition procedure.

FIG. 7 shows a system information deletion procedure based on a deletion timer according to an embodiment of the present invention.

FIG. 8 shows a drawing to explain a system information deletion procedure based on a deletion timer according to an embodiment of the present invention.

FIG. 9 shows a system information deletion procedure based on a memory of the UE according to an embodiment of the present invention.

FIG. 10 shows a drawing to explain a system information deletion procedure based on a memory of the UE according to an embodiment of the present invention.

FIG. 11 shows a system information deletion procedure based on a deletion indication according to an embodiment of the present invention.

FIG. 12 shows a system information deletion procedure based on a value tag and an index according to an embodiment of the present invention.

FIG. 13 shows a drawing to explain a system information deletion procedure based on a value tag and an index according to an embodiment of the present invention.

FIG. 14 is a block diagram illustrating a method for a UE to delete system information according to an embodiment of the present invention.

FIG. 15 is a block diagram illustrating a wireless communication system according to the embodiment of the present invention.

The technology described below can be used in various wireless communication systems such as code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier frequency division multiple access (SC-FDMA), etc. The CDMA can be implemented with a radio technology such as universal terrestrial radio access (UTRA) or CDMA-2000. The TDMA can be implemented with a radio technology such as global system for mobile communications (GSM)/general packet ratio service (GPRS)/enhanced data rate for GSM evolution (EDGE). The OFDMA can be implemented with a radio technology such as institute of electrical and electronics engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, evolved UTRA (E-UTRA), etc. IEEE 802.16m is evolved from IEEE 802.16e, and provides backward compatibility with a system based on the IEEE 802.16e. The UTRA is a part of a universal mobile telecommunication system (UMTS). 3rd generation partnership project (3GPP) long term evolution (LTE) is a part of an evolved UMTS (E-UMTS) using the E-UTRA. The 3GPP LTE uses the OFDMA in a downlink and uses the SC-FDMA in an uplink. LTE-advanced (LTE-A) is an evolution of the LTE. 5G communication system is an evolution of the LTE-A.

For clarity, the following description will focus on LTE-A. However, technical features of the present invention are not limited thereto.

FIG. 1 shows LTE system architecture. The communication network is widely deployed to provide a variety of communication services such as voice over internet protocol (VoIP) through IMS and packet data.

Referring to FIG. 1, the LTE system architecture includes one or more user equipment (UE; 10), an evolved-UMTS terrestrial radio access network (E-UTRAN) and an evolved packet core (EPC). The UE 10 refers to a communication equipment carried by a user. The UE 10 may be fixed or mobile, and may be referred to as another terminology, such as a mobile station (MS), a user terminal (UT), a subscriber station (SS), a wireless device, etc.

The E-UTRAN includes one or more evolved node-B (eNB) 20, and a plurality of UEs may be located in one cell. The eNB 20 provides an end point of a control plane and a user plane to the UE 10. The eNB 20 is generally a fixed station that communicates with the UE 10 and may be referred to as another terminology, such as a base station (BS), a base transceiver system (BTS), an access point, etc. One eNB 20 may be deployed per cell. There are one or more cells within the coverage of the eNB 20. A single cell is configured to have one of bandwidths selected from 1.25, 2.5, 5, 10, and 20 MHz, etc., and provides downlink or uplink transmission services to several UEs. In this case, different cells can be configured to provide different bandwidths.

Hereinafter, a downlink (DL) denotes communication from the eNB 20 to the UE 10, and an uplink (UL) denotes communication from the UE 10 to the eNB 20. In the DL, a transmitter may be a part of the eNB 20, and a receiver may be a part of the UE 10. In the UL, the transmitter may be a part of the UE 10, and the receiver may be a part of the eNB 20.

The EPC includes a mobility management entity (MME) which is in charge of control plane functions, and a system architecture evolution (SAE) gateway (S-GW) which is in charge of user plane functions. The MME/S-GW 30 may be positioned at the end of the network and connected to an external network. The MME has UE access information or UE capability information, and such information may be primarily used in UE mobility management. The S-GW is a gateway of which an endpoint is an E-UTRAN. The MME/S-GW 30 provides an end point of a session and mobility management function for the UE 10. The EPC may further include a packet data network (PDN) gateway (PDN-GW). The PDN-GW is a gateway of which an endpoint is a PDN.

The MME provides various functions including non-access stratum (NAS) signaling to eNBs 20, NAS signaling security, access stratum (AS) security control, Inter core network (CN) node signaling for mobility between 3GPP access networks, idle mode UE reachability (including control and execution of paging retransmission), tracking area list management (for UE in idle and active mode), P-GW and S-GW selection, MME selection for handovers with MME change, serving GPRS support node (SGSN) selection for handovers to 2G or 3G 3GPP access networks, roaming, authentication, bearer management functions including dedicated bearer establishment, support for public warning system (PWS) (which includes earthquake and tsunami warning system (ETWS) and commercial mobile alert system (CMAS)) message transmission. The S-GW host provides assorted functions including per-user based packet filtering (by e.g., deep packet inspection), lawful interception, UE Internet protocol (IP) address allocation, transport level packet marking in the DL, UL and DL service level charging, gating and rate enforcement, DL rate enforcement based on APN-AMBR. For clarity MME/S-GW 30 will be referred to herein simply as a "gateway," but it is understood that this entity includes both the MME and S-GW.

Interfaces for transmitting user traffic or control traffic may be used. The UE 10 and the eNB 20 are connected by means of a Uu interface. The eNBs 20 are interconnected by means of an X2 interface. Neighboring eNBs may have a meshed network structure that has the X2 interface. The eNBs 20 are connected to the EPC by means of an S1 interface. The eNBs 20 are connected to the MME by means of an S1-MME interface, and are connected to the S-GW by means of S1-U interface. The S1 interface supports a many-to-many relation between the eNB 20 and the MME/S-GW.

The eNB 20 may perform functions of selection for gateway 30, routing toward the gateway 30 during a radio resource control (RRC) activation, scheduling and transmitting of paging messages, scheduling and transmitting of broadcast channel (BCH) information, dynamic allocation of resources to the UEs 10 in both UL and DL, configuration and provisioning of eNB measurements, radio bearer control, radio admission control (RAC), and connection mobility control in LTE_ACTIVE state. In the EPC, and as noted above, gateway 30 may perform functions of paging origination, LTE_IDLE state management, ciphering of the user plane, SAE bearer control, and ciphering and integrity protection of NAS signaling.

FIG. 2 shows a control plane of a radio interface protocol of an LTE system. FIG. 3 shows a user plane of a radio interface protocol of an LTE system.

Layers of a radio interface protocol between the UE and the E-UTRAN may be classified into a first layer (L1), a second layer (L2), and a third layer (L3) based on the lower three layers of the open system interconnection (OSI) model that is well-known in the communication system. The radio interface protocol between the UE and the E-UTRAN may be horizontally divided into a physical layer, a data link layer, and a network layer, and may be vertically divided into a control plane (C-plane) which is a protocol stack for control signal transmission and a user plane (U-plane) which is a protocol stack for data information transmission. The layers of the radio interface protocol exist in pairs at the UE and the E-UTRAN, and are in charge of data transmission of the Uu interface.

A physical (PHY) layer belongs to the L1. The PHY layer provides a higher layer with an information transfer service through a physical channel. The PHY layer is connected to a medium access control (MAC) layer, which is a higher layer of the PHY layer, through a transport channel. A physical channel is mapped to the transport channel. Data is transferred between the MAC layer and the PHY layer through the transport channel. Between different PHY layers, i.e., a PHY layer of a transmitter and a PHY layer of a receiver, data is transferred through the physical channel using radio resources. The physical channel is modulated using an orthogonal frequency division multiplexing (OFDM) scheme, and utilizes time and frequency as a radio resource.

The PHY layer uses several physical control channels. A physical downlink control channel (PDCCH) reports to a UE about resource allocation of a paging channel (PCH) and a downlink shared channel (DL-SCH), and hybrid automatic repeat request (HARQ) information related to the DL-SCH. The PDCCH may carry a UL grant for reporting to the UE about resource allocation of UL transmission. A physical control format indicator channel (PCFICH) reports the number of OFDM symbols used for PDCCHs to the UE, and is transmitted in every subframe. A physical hybrid ARQ indicator channel (PHICH) carries an HARQ acknowledgement (ACK)/non-acknowledgement (NACK) signal in response to UL transmission. A physical uplink control channel (PUCCH) carries UL control information such as HARQ ACK/NACK for DL transmission, scheduling request, and CQI. A physical uplink shared channel (PUSCH) carries a UL-uplink shared channel (SCH).

A physical channel consists of a plurality of subframes in time domain and a plurality of subcarriers in frequency domain. One subframe consists of a plurality of symbols in the time domain. One subframe consists of a plurality of resource blocks (RBs). One RB consists of a plurality of symbols and a plurality of subcarriers. In addition, each subframe may use specific subcarriers of specific symbols of a corresponding subframe for a PDCCH. For example, a first symbol of the subframe may be used for the PDCCH. The PDCCH carries dynamic allocated resources, such as a physical resource block (PRB) and modulation and coding scheme (MCS). A transmission time interval (TTI) which is a unit time for data transmission may be equal to a length of one subframe. The length of one subframe may be 1 ms.

The transport channel is classified into a common transport channel and a dedicated transport channel according to whether the channel is shared or not. A DL transport channel for transmitting data from the network to the UE includes a broadcast channel (BCH) for transmitting system information, a paging channel (PCH) for transmitting a paging message, a DL-SCH for transmitting user traffic or control signals, etc. The DL-SCH supports HARQ, dynamic link adaptation by varying the modulation, coding and transmit power, and both dynamic and semi-static resource allocation. The DL-SCH also may enable broadcast in the entire cell and the use of beamforming. The system information carries one or more system information blocks. All system information blocks may be transmitted with the same periodicity. Traffic or control signals of a multimedia broadcast/multicast service (MBMS) may be transmitted through the DL-SCH or a multicast channel (MCH).

A UL transport channel for transmitting data from the UE to the network includes a random access channel (RACH) for transmitting an initial control message, a UL-SCH for transmitting user traffic or control signals, etc. The UL-SCH supports HARQ and dynamic link adaptation by varying the transmit power and potentially modulation and coding. The UL-SCH also may enable the use of beamforming. The RACH is normally used for initial access to a cell.

A MAC layer belongs to the L2. The MAC layer provides services to a radio link control (RLC) layer, which is a higher layer of the MAC layer, via a logical channel. The MAC layer provides a function of mapping multiple logical channels to multiple transport channels. The MAC layer also provides a function of logical channel multiplexing by mapping multiple logical channels to a single transport channel. A MAC sublayer provides data transfer services on logical channels.

The logical channels are classified into control channels for transferring control plane information and traffic channels for transferring user plane information, according to a type of transmitted information. That is, a set of logical channel types is defined for different data transfer services offered by the MAC layer. The logical channels are located above the transport channel, and are mapped to the transport channels.

The control channels are used for transfer of control plane information only. The control channels provided by the MAC layer include a broadcast control channel (BCCH), a paging control channel (PCCH), a common control channel (CCCH), a multicast control channel (MCCH) and a dedicated control channel (DCCH). The BCCH is a downlink channel for broadcasting system control information. The PCCH is a downlink channel that transfers paging information and is used when the network does not know the location cell of a UE. The CCCH is used by UEs having no RRC connection with the network. The MCCH is a point-to-multipoint downlink channel used for transmitting MBMS control information from the network to a UE. The DCCH is a point-to-point bi-directional channel used by UEs having an RRC connection that transmits dedicated control information between a UE and the network.

Traffic channels are used for the transfer of user plane information only. The traffic channels provided by the MAC layer include a dedicated traffic channel (DTCH) and a multicast traffic channel (MTCH). The DTCH is a point-to-point channel, dedicated to one UE for the transfer of user information and can exist in both uplink and downlink. The MTCH is a point-to-multipoint downlink channel for transmitting traffic data from the network to the UE.

Uplink connections between logical channels and transport channels include the DCCH that can be mapped to the UL-SCH, the DTCH that can be mapped to the UL-SCH and the CCCH that can be mapped to the UL-SCH. Downlink connections between logical channels and transport channels include the BCCH that can be mapped to the BCH or DL-SCH, the PCCH that can be mapped to the PCH, the DCCH that can be mapped to the DL-SCH, and the DTCH that can be mapped to the DL-SCH, the MCCH that can be mapped to the MCH, and the MTCH that can be mapped to the MCH.

An RLC layer belongs to the L2. The RLC layer provides a function of adjusting a size of data, so as to be suitable for a lower layer to transmit the data, by concatenating and segmenting the data received from an upper layer in a radio section. In addition, to ensure a variety of quality of service (QoS) required by a radio bearer (RB), the RLC layer provides three operation modes, i.e., a transparent mode (TM), an unacknowledged mode (UM), and an acknowledged mode (AM). The AM RLC provides a retransmission function through an automatic repeat request (ARQ) for reliable data transmission. Meanwhile, a function of the RLC layer may be implemented with a functional block inside the MAC layer. In this case, the RLC layer may not exist.

A packet data convergence protocol (PDCP) layer belongs to the L2. The PDCP layer provides a function of header compression function that reduces unnecessary control information such that data being transmitted by employing IP packets, such as IPv4 or IPv6, can be efficiently transmitted over a radio interface that has a relatively small bandwidth. The header compression increases transmission efficiency in the radio section by transmitting only necessary information in a header of the data. In addition, the PDCP layer provides a function of security. The function of security includes ciphering which prevents inspection of third parties, and integrity protection which prevents data manipulation of third parties.

A radio resource control (RRC) layer belongs to the L3. The RLC layer is located at the lowest portion of the L3, and is only defined in the control plane. The RRC layer takes a role of controlling a radio resource between the UE and the network. For this, the UE and the network exchange an RRC message through the RRC layer. The RRC layer controls logical channels, transport channels, and physical channels in relation to the configuration, reconfiguration, and release of RBs. An RB is a logical path provided by the L1 and L2 for data delivery between the UE and the network. That is, the RB signifies a service provided the L2 for data transmission between the UE and E-UTRAN. The configuration of the RB implies a process for specifying a radio protocol layer and channel properties to provide a particular service and for determining respective detailed parameters and operations. The RB is classified into two types, i.e., a signaling RB (SRB) and a data RB (DRB). The SRB is used as a path for transmitting an RRC message in the control plane. The DRB is used as a path for transmitting user data in the user plane.

Referring to FIG. 2, the RLC and MAC layers (terminated in the eNB on the network side) may perform functions such as scheduling, automatic repeat request (ARQ), and hybrid automatic repeat request (HARQ). The RRC layer (terminated in the eNB on the network side) may perform functions such as broadcasting, paging, RRC connection management, RB control, mobility functions, and UE measurement reporting and controlling. The NAS control protocol (terminated in the MME of gateway on the network side) may perform functions such as a SAE bearer management, authentication, LTE_IDLE mobility handling, paging origination in LTE_IDLE, and security control for the signaling between the gateway and UE.

Referring to FIG. 3, the RLC and MAC layers (terminated in the eNB on the network side) may perform the same functions for the control plane. The PDCP layer (terminated in the eNB on the network side) may perform the user plane functions such as header compression, integrity protection, and ciphering.

FIG. 4 shows 5G system architecture.

Referring to FIG. 4, a Next Generation Radio Access Network (NG-RAN) node may be either a gNB providing NR Radio Access (NR) user plane and control plane protocol terminations towards the UE or an ng-eNB providing Evolved Universal Terrestrial Radio Access (E-UTRA) user plane and control plane protocol terminations towards the UE. The gNBs and ng-eNBs may be interconnected with each other by means of the Xn interface. The gNBs and ng-eNBs may be also connected by means of the NG interfaces to the 5G Core Network (5GC), more specifically to the AMF (Access and Mobility Management Function) by means of the NG-C interface and to the UPF (User Plane Function) by means of the NG-U interface. The NG-C may be control plane interface between NG-RAN and 5GC, and the NG-U may be user plane interface between NG-RAN and 5GC.

FIG. 5 shows functional split between NG-RAN and 5GC

Referring to FIG. 5, the gNB and ng-eNB may host the following functions:

- Functions for Radio Resource Management: Radio Bearer Control, Radio Admission Control, Connection Mobility Control, Dynamic allocation of resources to UEs in both uplink and downlink (scheduling);

- IP header compression, encryption and integrity protection of data;

- Selection of an AMF at UE attachment when no routing to an AMF can be determined from the information provided by the UE;

- Routing of User Plane data towards UPF(s);

- Routing of Control Plane information towards AMF;

- Connection setup and release;

- Scheduling and transmission of paging messages;

- Scheduling and transmission of system broadcast information (originated from the AMF or O&M);

- Measurement and measurement reporting configuration for mobility and scheduling;

- Transport level packet marking in the uplink;

- Session Management;

- Support of Network Slicing;

- QoS Flow management and mapping to data radio bearers;

- Support of UEs in RRC_INACTIVE state;

- Distribution function for NAS messages;

- Radio access network sharing;

- Dual Connectivity;

- Tight interworking between NR and E-UTRA.

The Access and Mobility Management Function (AMF) may host the following main functions:

- NAS signalling termination;

- NAS signalling security;

- AS Security control;

- Inter CN node signalling for mobility between 3GPP access networks;

- Idle mode UE Reachability (including control and execution of paging retransmission);

- Registration Area management;

- Support of intra-system and inter-system mobility;

- Access Authentication;

- Access Authorization including check of roaming rights;

- Mobility management control (subscription and policies);

- Support of Network Slicing;

- SMF selection.

The User Plane Function (UPF) may host the following main functions:

- Anchor point for Intra-/Inter-RAT mobility (when applicable);

- External PDU session point of interconnect to Data Network;

- Packet routing & forwarding;

- Packet inspection and User plane part of Policy rule enforcement;

- Traffic usage reporting;

- Uplink classifier to support routing traffic flows to a data network;

- Branching point to support multi-homed PDU session;

- QoS handling for user plane, e.g. packet filtering, gating, UL/DL rate enforcement;

- Uplink Traffic verification (SDF to QoS flow mapping);

- Downlink packet buffering and downlink data notification triggering.

The Session Management function (SMF) may host the following main functions:

- Session Management;

- UE IP address allocation and management;

- Selection and control of UP function;

- Configures traffic steering at UPF to route traffic to proper destination;

- Control part of policy enforcement and QoS;

- Downlink Data Notification.

Hereinafter, System information (SI) is described.

FIG. 6 shows a system information acquisition procedure.

The system information (SI) may be divided into Minimum SI and Other SI. Minimum SI may be periodically broadcast and comprise basic information required for initial access and information for acquiring any other SI broadcast periodically or provisioned on-demand, i.e. scheduling information. The Other SI may encompass everything not broadcast in the Minimum SI and may either be broadcast, or provisioned in a dedicated manner, either triggered by the network or upon request from the UE. The Minimum SI may be transmitted over two different downlink channels using different messages (MasterInformationBlock and SystemInformationBlockType1). The term Remaining Minimum SI (RMSI) may be also used to refer to SystemInformationBlockType1. Other SI may be transmitted in SystemInformationBlockType2 and above.

Also, the system information (SI) may be divided into the MasterInformationBlock (MIB) and a number of SystemInformationBlocks (SIBs). The MIB may be always transmitted on the BCH with a periodicity of 80 ms and repetitions made within 80 ms. The MIB may include parameters that are needed to acquire SystemInformationBlockType1 (SIB1) from the cell. The SIB1 may be transmitted on the DL-SCH with a certain periodicity and repetitions made within certain period. The SIB1 may include information regarding the availability and scheduling (e.g. periodicity, SI-window size) of other SIBs. Also, the SIB1 may indicate whether they (i.e. other SIBs) are provided via periodic broadcast basis or only on-demand basis. If other SIBs are provided on-demand then SIB1 may include information for the UE to perform SI request. SIBs other than SystemInformationBlockType1 may be carried in SystemInformation (SI) messages, which are transmitted on the DL-SCH. Each SI message is transmitted within periodically occurring time domain windows (referred to as SI-windows).

The UE may apply the SI acquisition procedure to acquire the AS and NAS information. The procedure may apply to UEs in RRC_IDLE, in RRC_INACTIVE and in RRC_CONNECTED. The UE in RRC_IDLE and RRC_INACTIVE shall ensure having a valid version of (at least) the MasterInformationBlock, SystemInformationBlockType1 as well as SystemInformationBlockTypeX through SystemInformationBlockTypeY (depending on support of the concerned RATs for UE controlled mobility). The UE in RRC_CONNECTED shall ensure having a valid version of (at least) the MasterInformationBlock, SystemInformationBlockType1 as well as SystemInformationBlockTypeX (depending on support of mobility towards the concerned RATs). The UE shall store relevant SI acquired from the currently camped/serving cell. A version of the SI that the UE acquires and stores remains valid only for a certain time. The UE may use such a stored version of the SI e.g. after cell re-selection, upon return from out of coverage or after SI change indication.

Meanwhile, if the UE is allowed to store some system information block/message for the future use, it also should be specified when to discard the stored system information. This is because that a memory of the UE is limited. Hereinafter, a method for a UE to delete system information and an apparatus supporting the same according to an embodiment of the present invention are described in detail.

Referring to FIG. 7, in step S710, a UE may store certain system information. The certain system information may be system information for using in the future. The certain system information may include multiple versions of system information block (SIB). For example, the UE may store three versions of SIB5, i.e., SIB5 #1, SIB5 #2 and SIB5 #3.

In step S720, the UE may receive information on valid area where the certain system information is valid, from a network. Based on the information on valid area, the UE may know which system information is valid in a certain cell, and which system information is not valid in a certain cell. Also, based on the information on valid area, the UE may know which version of SIB is valid in a certain cell, and which version of SIB is not valid in a certain cell.

In step S730, the UE may move to a neighboring cell. It is assumed that the certain system information is not valid in the neighboring cell. If the UE moves to the neighboring cell, the UE may start a timer (e.g. deletion timer). For example, if the UE camps on the neighboring cell, the UE may start a timer. For example, if the UE reselects the neighboring cell, the UE may start a timer.

In step S740, the UE may delete/discard all corresponding system information, if timer is expired. The certain system information not valid in the neighboring cell may be deleted upon expiring timer. That is, while the timer is running, the UE may keep the certain system information even if the certain system information is not valid in the neighboring cell. If a certain version of the SIB is not valid in the neighboring cell, the certain version of the SIB may be deleted, but other version of the SIB may not be deleted.

Alternatively, the UE may delete/discard all corresponding system information. In this case, the timer is not defined.

According to an embodiment of the present invention, the UE may delete invalid system information in a certain cell so that the UE can secure memory for storing necessary system information in the cell.

Referring to FIG. 8, the UE may move from a cell A to a cell B. It is assumed that the UE may be storing 3 versions for a SIB5, i.e., SIB5 #1, SIB5 #2 and SIB5 #3. Also, it is assumed that the valid area of SIB5 #1 and SIB5 #2 is the cell A, the cell B and the cell C, while the valid area of SIB5 #3 is the cell A and the cell B.

Upon moving from the cell B to the cell C, the UE may start a timer (e.g. deletion timer). That is, the timer is initiated at T1. It is assumed that the timer expires at T2. Upon the timer expiry, the UE may delete/discard stored SIB5 #3 because the SIB5 #3 is not valid in the cell C.

Referring to FIG. 9, in step S910, a UE may store at least one system information. The at least one system information may be system information for using in the future. The at least one system information may include multiple versions of system information block (SIB).

In step S920, the UE may receive system information. For example, the UE may receive a system information block and/or a system information message.

In step S930, the UE may determine whether or not to delete certain system information among stored at least one system information. If at least one of following conditions are met, the UE may determine to delete certain system information among stored at least one system information.

- Condition 1: the UE receives a system information; and/or

- Condition 2: the UE determine that it needs to store the received system information; and/or

- Condition 3: a volume of the received system information exceeds the UE's memory reserved for the system information storing; and/or

- Condition 4: the UE's memory reserved for the system information storing becomes full.

In step S940, the UE may delete/discard certain system information. The certain system information may be the earliest stored system information. Alternatively, the certain system information may include the earliest stored system information. The UE may delete/discard system information until the UE's memory reserved for the system information storing has enough available memory to store the received system information.

Desirably, the UE may delete/discard all system information which belongs to the same group with the earliest stored system information. If the same valid area is configured for two different system information, then the UE considers that two different system information belongs to the same group. For example, if SIB2 is the earliest stored system information, and if valid area of SIB2 and SIB3 is the same, the UE consider that SIB2 and SIB3 belongs to the same group. Then, the UE may delete/discard SIB3 as well as the earliest stored SIB2.

Referring to (a) of FIG. 10, the UE may be storing some system information. 6 octets memory may be reserved for the system information storing. The UE may receive SIB15 #1 from network, and the UE may determine the SIB15 #1 needs to be stored, but the memory of the UE may be full.

Referring to (b) of FIG. 10, thus the UE may discard the earliest stored system information, i.e., SIB7 #1. However, the memory of the UE still does not have enough available memory to store the received system information because the received system information is 2 octets.

Referring to (c) of FIG. 10, thus the UE may discard the earliest stored system information once more. Then, referring to (d) of FIG. 10, the UE may store received system information, i.e., SIB15 #1.

Referring to FIG. 11, in step S1110, a UE may store at least one system information. The at least one system information may be system information for using in the future. The at least one system information may include multiple versions of system information block (SIB).

In step S1120, the UE may receive the deletion indication from a network. The deletion indication may include a list of index of system information, identifier of system information, and/or value tag of system information. The deletion indication may be broadcast via system information, and/or paging message.

In step S1130, the UE may delete certain system information among stored at least one system information, based on deletion indication. That is, when the UE receives the deletion indication from the network, the UE may discard all system information which correspond to the index of system information, identifier of system information, and/or value tag of system information listed in the deletion indication.

Referring to FIG. 12, in step S1210, a UE may store at least one system information. The at least one system information may be system information for using in the future. The at least one system information may include multiple versions of system information block (SIB).

In step S1220, the UE may receive the value tag as well as the index. The value tag and the index are signaled, separately. For system information, there are multiple versions and each version may be identified by the index. Further, the value tag may indicate whether or not a system information version is valid.

In step S1230, the UE may delete certain system information among stored at least one system information, based on value tag. That is, if the value tag changes for a stored certain system information, the UE may discard the stored certain system information.

Referring to FIG. 13, the UE may be storing some system information. The UE may receive system information change notification from a network. Then, the UE may read minimum system information, i.e., MIB, SIB1 and/or SIB2, to update it. The minimum SI may indicate that the value tag for SIB3 and SIB5 changes from 101 to 102. If the UE detects changing of the value tag, the UE may discard SIB3 #3, SIB3 #5, SIB5 #1 and SIB5 #2.

According to an embodiment of the present invention, not only the index but also the value tag can be used for notification of change of the system information. Therefore, compared with the case where only the index is used, the number of bits used for notification of change of the system information can be reduced, so that the network can efficiently notify the UE of the change of the system information.

Referring to FIG. 14, in step S1410, the UE may store first system information. The first system information may include multiple versions of system information block (SIB). A certain version of the SIB, which is not valid in the cell, may be deleted among the multiple versions of the SIB. The first system information may be system information which is scheduled to be used.

In step S1420, the UE may receive information on valid area where the first system information is valid, from a network.

In addition, the UE may determine that the stored first system information is not valid in the cell, based on the information on valid area.

In step S1430, the UE may camp on a cell not belonging to the valid area.

In step S1440, the UE may start a timer upon camping on the cell.

In step S1450, the UE may delete the first system information, if the timer is expired.

In addition, the UE may delete second system information, if a memory of the UE reserved for storing system information is full. The second system information may be the earliest stored system information. In addition, upon deleting the second system information, the UE may delete third system information belonging to the same group as the second system information. The valid area of the second system information and the third system information may be the same.

In addition, the UE may receive third system information, and delete second system information, if size of the third system information exceeds a memory of the UE reserved for storing system information.

In addition, the UE may receive deletion indication including a list of the system information, from the network, and delete the system information included in the list of the system information. The list of the system information may include at least one of an index of the system information, an identifier of the system information or a value tag of the system information.

In addition, the UE may receive a value tag indicating whether or not the stored first system information is valid. In addition, the UE may delete the first system information, if the value tag of the stored first system information is changed.

According to an embodiment of the present invention, the UE may delete invalid system information in a certain cell, and/or the earliest stored system information in the UE, and/or certain system information indicated by the network. Thus, the UE can secure memory for storing necessary system information.

A BS 1500 includes a processor 1501, a memory 1502 and a transceiver 1503. The memory 1502 is connected to the processor 1501, and stores various information for driving the processor 1501. The transceiver 1503 is connected to the processor 1501, and transmits and/or receives radio signals. The processor 1501 implements proposed functions, processes and/or methods. In the above embodiment, an operation of the base station may be implemented by the processor 1501.

A UE 1510 includes a processor 1511, a memory 1512 and a transceiver 1513. The memory 1512 is connected to the processor 1511, and stores various information for driving the processor 1511. The transceiver 1513 is connected to the processor 1511, and transmits and/or receives radio signals. The processor 1511 implements proposed functions, processes and/or methods. In the above embodiment, an operation of the user equipment may be implemented by the processor 1511.

The processor may include an application-specific integrated circuit (ASIC), a separate chipset, a logic circuit, and/or a data processing unit. The memory may include a read-only memory (ROM), a random access memory (RAM), a flash memory, a memory card, a storage medium, and/or other equivalent storage devices. The transceiver may include a base-band circuit for processing a wireless signal. When the embodiment is implemented in software, the aforementioned methods can be implemented with a module (i.e., process, function, etc.) for performing the aforementioned functions. The module may be stored in the memory and may be performed by the processor. The memory may be located inside or outside the processor, and may be coupled to the processor by using various well-known means.

Various methods based on the present specification have been described by referring to drawings and reference numerals given in the drawings on the basis of the aforementioned examples. Although each method describes multiple steps or blocks in a specific order for convenience of explanation, the invention disclosed in the claims is not limited to the order of the steps or blocks, and each step or block can be implemented in a different order, or can be performed simultaneously with other steps or blocks. In addition, those ordinarily skilled in the art can know that the invention is not limited to each of the steps or blocks, and at least one different step can be added or deleted without departing from the scope and spirit of the invention.

The aforementioned embodiment includes various examples. It should be noted that those ordinarily skilled in the art know that all possible combinations of examples cannot be explained, and also know that various combinations can be derived from the technique of the present specification. Therefore, the protection scope of the invention should be determined by combining various examples described in the detailed explanation, without departing from the scope of the following claims.

Claims

A method for deleting, by a user equipment (UE), system information in a wireless communication, the method comprising:

storing first system information;

receiving information on valid area where the first system information is valid, from a network;

camping on a cell not belonging to the valid area;

upon camping on the cell, starting a timer; and

deleting the first system information, if the timer is expired.
The method of claim 1, wherein the first system information includes multiple versions of system information block (SIB).
The method of claim 2, wherein a certain version of the SIB, which is not valid in the cell, is deleted among the multiple versions of the SIB.
The method of claim 1, further comprising:

determining that the stored first system information is not valid in the cell, based on the information on valid area.
The method of claim 1, further comprising:

deleting second system information, if a memory of the UE reserved for storing system information is full.
The method of claim 5, wherein the second system information is the earliest stored system information.
The method of claim 5, further comprising:

upon deleting the second system information, deleting third system information belonging to the same group as the second system information.
The method of claim 7, wherein the valid area of the second system information and the third system information is the same.
The method of claim 1, further comprising:

receiving third system information; and

deleting second system information, if size of the third system information exceeds a memory of the UE reserved for storing system information.
The method of claim 1, further comprising:

receiving deletion indication including a list of the system information, from the network; and

deleting the system information included in the list of the system information.
The method of claim 10, wherein the list of the system information includes at least one of an index of the system information, an identifier of the system information or a value tag of the system information.
The method of claim 1, further comprising:

receiving a value tag indicating whether or not the stored first system information is valid.
The method of claim 12, further comprising:

deleting the first system information, if the value tag of the stored first system information is changed.
The method of claim 1, wherein the first system information is system information which is scheduled to be used.
A user equipment (UE) deleting system information in a wireless communication, the UE comprising:

a memory; a transceiver; and

a processor, connected to the memory and the transceiver, that:

stores first system information;

controls the transceiver to receive information on valid area where the first system information is valid, from a network;

camps on a cell not belonging to the valid area;

upon camping on the cell, starts a timer; and

deletes the first system information, if the timer is expired.