WO2009082076A1

WO2009082076A1 - Method of transmitting and receiving system information in the mobile communication system

Info

Publication number: WO2009082076A1
Application number: PCT/KR2008/004166
Authority: WO
Inventors: Kwang-Ryul Jung; Ae-Soon Park
Original assignee: Electronics And Telecommunications Research Institute; Samsung Electronics.Co., Ltd.
Priority date: 2007-12-20
Filing date: 2008-07-16
Publication date: 2009-07-02
Also published as: KR20090066643A; KR100966179B1; WO2009082076A8; EP2235850A1

Abstract

A method of transmitting and receiving changed system information between a User Equipment (UE) and an evolved NodeB (eNB) whose Radio Resource Control (RRC) layers are connected is provided. When a UE connected with an eNB is informed that system information is changed and informed of partial system information by the eNB through a previously set Dedicated Control Channel (DCCH), the UE sets a channel of a lower layer, i.e., Physical (PHY)/Media Access Control (MAC)/Radio Link Control (RLC) layer, as a Dynamic Broadcast Control Channel (DBCCH):Downlink-Shared Channel (DL-SCH) to receive changed system information and receives the entire changed system information. Then, the UE sets an L1 parameter and a channel of L1/L2, which is a lower layer, using the received information and continuously performs data communication and a Discontinuous Reception (DRx) operation. Since it is possible to recognize that system information is changed using a DCCH, the methods can reduce delay time resulting from unnecessary channel setting and also power consumed by periodically demodulating a channel.

Description

METHOD OF TRANSMITTING AND RECEIVING SYSTEM INFORMATION IN THE MOBILE COMMUNICATION SYSTEM

Technical Field

[1] The present invention relates to a next- generation mobile communication system, and more particularly, to a method of transmitting and receiving changed system information between a User Equipment (UE) and an evolved NodeB (eNB) whose Radio Resource Control (RRC) layers are connected.

[2] This work was supported by the IT R&D program of Ministry of Information and

Communication (MIC)/Institute for Information Technology Advancement (IITA) [2005-S-404-33, Research & development on Mobile Terminal Technology based on 3G Evolution]. Background Art

[3] Third Generation Partnership Project (3GPP), which is one of next-generation mobile communication systems, is expected to have high competitiveness for several oncoming years by enhancing radio access technology such as High Speed Packet Access (HSPA) data service (Release 6 (R6)). However, to efficiently provide rapidly developing information and communication service, 3GPP recognizes the necessity of new mobile communication technology that provides various high-quality services while reducing costs of a user and a service provider in comparison with 3GPP R6 technology, and is setting up 3G Long Term Evolution (LTE) standard technology that has low latency and a high data rate and enhances a system capacity and coverage. To be specific, the 3G LTE standard technology has an objective data rate of 100 Mbps in a downlink and 50 Mbps in an uplink, an objective call-setup latency of 100 ms in a control plane, an objective call processing latency of 5 ms in a data plane, and so on. In addition, to support various spectrum allocation, the 3G LTE standard technology is aimed at operation in various bandwidths such as 1.25, 2.5, 5, 10, 15, 20 MHz, etc.

[4] In a conventional R6 system, system information is transmitted by mapping a logical channel Broadcast Control Channel (BCCH) to a transport channel Broadcast Channel (BCH). According to an included content and a transmission period, Master Information Block (MIB) and System Information Block (SIB) are distinguished from each other, but transmitted through the same channel. In addition, connection states of a Radio Resource Control (RRC) layer are classified into a Cell Dedicated Channel (CELL_DCH) (dedicated data) state, a Cell Forward Access Channel (CELL_FACH) (common data) state, a Cell Paging Channel (CELL_PCH) (common radio call signaling) state, a Universal Terrestrial Radio Access Network (UTRAN) Registration Area Paging Channel (URA_PCH) (common radio call signaling) state, and so on. In the CELL_DCH state, a User Equipment (UE) performs communication using only a Dedicated Control Channel (DCCH)/Data Channel (DTCH) allocated to the UE itself, and thus does not receive another channel. In addition, all specific information required for a specific UE is transmitted through a DCCH using a dedicated message.

[5] However, a UE in the CELL_DCH state performs communication using only a dedicated channel, and thus is not informed of a change in system information. In the CELL_FACH, CELL_PCH and URA_PCH states, a UE must perform communication through a common channel, i.e., an FACH/Random Access Channel (RACH) and CELL_FACH, or be on standby for a PCH, i.e., a CELL_PCH/URA_PCH. System information includes information on a common channel or a PCH. Therefore, when system information is changed, an eNB informs a UE that system information is changed using a paging type 1 message, a system information change indication (system info.) message, and so on. The UE receiving the paging type 1 message or the system information change indication (system info.) message compares a tag included in information on the system information change (BCCH modification indication information) included in the message with a tag of system information that the UE stores.

[6] When the system information is changed, the UE creates a setup for receiving a BCH in L1/L2 of the UE, and receives system information. When reception of changed system information is completed, the UE returns to a previous state, and continues communication through a common channel, i.e., an FACH/RACH and a CELL_FACH, or is on standby for a PCH, i.e., a CELL_PCH/URA_PCH.

[7] In a 3GPP LTE system that is currently being standardized, system information is classified by mapping a Primary Broadcast Control Channel (PBCCH) transmitting an MIB: a Dynamic Broadcast Control Channel (DBCCH) performing BCH mapping and transmitting an SIB/Scheduling Block (SB): a Downlink Shared Channel (DL-SCH). An RRC-connected state is the same as the CELL_DCH state of an R6 system, and denotes a state in which a DCCH is set, and communication is performed or can be performed using a DTCH. In the LTE system, a UE in a connected state requires system information to normally operate, but a process of receiving system information has not yet been proposed. To be informed that system information of a base station is changed, a UE in the RRC-connected state must periodically or continuously receive an MIB transmitted through a BCH and check whether or not system information is changed. A UE in a connected state sets up and uses a DL-SCH for data transmission/ reception.

[8] Therefore, to periodically receive a BCH, the UE must stop data communication for a little while, set up the BCH to receive system information, and set up again a DL-SCH to perform data communication. In order to continuously receive a BCH and check whether or not system information is changed, two or more demodulators must operate in a UE, thereby performing data communication and simultaneously receiving BCH information. To perform these operations, the BCH must be continuously demodulated, and thus power consumption of the UE may increase. In particular, when a UE includes two or more demodulators, complexity and price of the UE may increase. Disclosure of Invention Technical Problem

[9] The present invention provides a method whereby a User Equipment (UE) whose

Radio Resource Control (RRC) layer is connected can receive changed system information from a base station in a short time, and a system information transmission method of the base station to support the reception method.

[10] The present invention also provides a system information reception method of a UE that can reduce power consumption caused by periodically demodulating a Broadcast Channel (BCH), and a system information transmission method of the base station to support the reception method.

[11] Additional features of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. Technical Solution

[12] The present invention discloses a method of receiving system information in a mobile communication terminal, including: receiving a dedicated paging message for informing that system information is changed from a base station; setting up a lower layer channel required for receiving changed system information; receiving one or more pieces of system change information transmitted from the base station through the set channel; and resetting a parameter and a channel of a lower layer using the received system change information and performing data communication or a discontinuous reception process.

[13] The present invention also discloses a method of transmitting system information in a base station of a mobile communication system, including: when system information is changed, selecting a UE to be informed that system information is changed; generating a dedicated paging message for informing that system information is changed; and transmitting the generated dedicated paging message to the selected UE through a Dedicated Control Channel (DCCH).

[14] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. Advantageous Effects

[15] According to the present invention, a User Equipment (UE) can be informed by a

Radio Resource Control (RRC) -connected base station that system information is changed through a Dedicated Control Channel (DCCH) already set up and ready for reception, and thus does not need to set up an additional channel for informing that system information is changed. Since a process of setting up an additional channel is not required, it is possible to rapidly receive information on a system information change and reduce power consumption caused by periodically demodulating a channel. Brief Description of the Drawings

[16] The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention, and together with the description serve to explain the principles of the invention.

[17] FIGS. 1 and 2 are a flowchart of a process in which a User Equipment (UE) in a

Radio Resource Control (RRC) -connected state receives changed system information, i.e., a Master Information Block (MIB)/System Information Block (SIB) in a Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) system according to an exemplary embodiment of the present invention.

[18] FIGS. 3 and 4 are a flowchart of determining a UE to be informed that system information is changed in the process of FIGS. 1 and 2.

[19] FIG. 5 is a table showing a structure of a dedicated paging message according to an exemplary embodiment of the present invention. Mode for the Invention

[20] The invention is described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure is thorough, and will fully convey the scope of the invention to those skilled in the art. Like reference numerals in the drawings denote like elements. Exemplary embodiments of the present invention will be described below on the assumption that a Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) system is an example of a next-generation mobile communication system.

[21] First, terms required for understanding the present invention will be described. A message of a Radio Resource Control (RRC) layer transmitting system information in a 3GPP LTE system is referred to as a System Information Block (SIB). SIBs include a general system parameter, but SIBs including the following specific information are defined as Master Information Blocks (MIBs), Scheduling Blocks (SBs) and so on. [22] MIBs include a restrictive parameter that is very frequently transmitted, and SBs include scheduling information on times when other pieces of system information are transmitted. MIBs are transmitted through a Broadcast Channel (BCH) at fixed periods, and SBs and SIBs are transmitted through a Downlink Shared Channel (DL-SCH) at fixed or dynamic periods. Sizes of an MIB, an SB and an SIB are changed according to set information, and sizes of a BCH and a DL-SCH for transmitting system information are fixed. Therefore, a base station (for example, eNB) appropriately divides and transmits MIBs, SBs and SIBs according to the size of a transmission channel, and a User Equipment (UE) receives all divided MIB parts, SB parts and SIB parts and combines them. To receive a specific SIB based on a dynamic period, a DL-SCH must be continuously received until all divided SIB parts are received, or the divided SIB parts must be received using division and transmission scheduling information of the specific SIB included in an SB.

[23] The constitution and operation of an exemplary embodiment of the present invention will be described with reference to the above described terms. FIGS. 1 and 2 are a flowchart of a process in which a UE whose Radio Resource Control (RRC) layer is connected with an evolved Node Base station (eNB) receives changed system information, i.e., an MIB/SIB, in a 3GPP LTE system according to an exemplary embodiment of the present invention. FIGS. 3 and 4 are a flowchart of determining a UE to be informed that system information is changed in the process of FIGS. 1 and 2. FIG. 5 is a table showing a structure of a dedicated paging message according to an exemplary embodiment of the present invention.

[24] Referring to FIGS. 1 and 2, a UE 100 in an RRC-connected state performs communication with an eNB, 110 through a Data Channel (DTCH) or a dedicated channel, or a Discontinuous Reception (DRx) process of waking up and checking whether or not data is received for only a specific time to reduce power consumption when there is no data to be transmitted (operation 120)

[25] If system information of the eNB 110 is changed (operation 121) while the UE 100 performs data communication or the DRx process (operation 120), the eNB 110 selects a UE to be informed that system information is changed (operation 122). A method of selecting a UE, which will be informed by the eNB 110 that system information is changed, will be described with reference to FIGS. 3 and 4.

[26] If system information is changed due to a change of a wireless parameter, cell management, etc. (operation 201), the eNB 110 checks which UE the changed information affects (operation 202). Then, it is determined how soon the changed information must be applied to the corresponding UE (operations 205 and 213). Finally, current operation state of the corresponding UE is checked (operations 208 and 216).

[27] If the changed information affects a specific UE alone (203) and must be im- mediately applied (206), and the corresponding UE is performing high-speed communication (209), an RRC 111 of the eNB 110 generates a dedicated paging message including all of an MIB and an SIB (operation 211) and transfers the generated dedicated paging message to a lower layer 112 (operation 221).

[28] On the other hand, if the changed information affects a specific UE alone (203) and does not need to be immediately applied (207), a dedicated paging message including an MIB, an SB, etc., is generated regardless of whether or not the corresponding UE is currently operating (operation 212), and transferred to the lower layer 112 (operation 221).

[29] If it is checked in operation 202 that the changed information affects a plurality of

UEs, it is checked whether or not the changed information must be immediately applied (operation 213) and what current operating states of the UEs are (operation 216), like the case in which the changed information affects a specific UE alone. Subsequently, a dedicated paging message including an MIB and an SB for the UEs is generated according to the checked result (operations 219 and 220). Then, the generated message is transferred to a lower layer (operation 221) to be transmitted to the corresponding UEs.

[30] In brief, if changed system information affects a specific UE, the eNB 110 according to an exemplary embodiment of the present invention generates a dedicated paging message (operations 211 and 212) and then instructs a lower layer to transmit the message using a Dedicated Control Channel (DCCH) of the specific UE (operation 221). On the other hand, when the changed system information affects all or a plurality of UEs having a DCCH rather than a specific UE, the eNB 110 generates a dedicated paging message (operations 219 and 220) and then instructs a lower layer to transmit the message through DCCHs of all the corresponding UEs (operation 221). When the message is transmitted to a plurality of UEs as described above, a Physical (PHY) layer 114 may use a group Identification (ID), and so on.

[31] The structure of a dedicated paging message generated from the eNB 110 will be described below with reference to FIG. 5.

[32] The dedicated paging message includes Message Type Information Element (IE) for distinguishing the message from another message transmitted through a DCCH; Paging Cause IE describing a paging reason; MIB Info IE including a frequency, which is the minimum information, whether or not Multiple Input Multiple Output (MIMO) is used, a value tag used as a system information index, etc.; SB Info IE including the number of divided SIB parts, a repetition period, an initial location, an offset, etc.; SIB #1, SIB #n IE including various types of information such as cell information, a timer/counter and a wireless parameter; and so on.

[33] Among them, Message Type Paging Cause and MIB Info, which are Mandatory Present parameters (MPs), must be included in a dedicated paging message. When a UE receives all SIBs, SB Info IE, which is an Optional Parameter (OP), may not be included in a dedicated paging message. When a UE receives only a specific SIB, scheduling information of the specific SIB is included in a dedicated paging message. SIB #1, , SIB #n IE may be included in a dedicated paging message when changed system information to be received is little, or a parameter must be rapidly transmitted during data communication. When an SIB to be received is included in a dedicated paging message, a UE receives all information required in operation 131 of FIGS. 1 and 2, and thus it is possible to omit operations 136, 139, 140, 141 and 142.

[34] As described above, when the RRC layer 111 of the eNB 110 selects a UE to be informed that system information is changed, the eNB 110 generates a dedicated paging message to be transmitted to the selected UE (operation 123). The generated message may include a paging reason, changed MIB information, scheduling information, i.e., an SB, on the location of a changed specific SIB that the specific UE 100 must receive, etc., or changed system information itself, i.e., an SIB, that the UE must receive. Content of the dedicated paging message may vary according to the type of included system information, the length of the message, and a receiver, i.e., one or more UEs, of the message.

[35] The RRC 111 layer requests a Radio Link Control (RLC) layer 112 to transmit the generated message data (operation 124), and the message data is transmitted to the UE through a Media Access Control (MAC) layer 113 and the PHY layer 114 (operations 125 and 126). Here, the message is transmitted using a DCCH as a logical channel and a DL-SCH as a transmission channel (operation 127).

[36] Meanwhile, a PHY layer 104 of the UE is continuously awaken or periodically wakes up to receive the message through the DCCH on standby for reception, and transfer the message to the MAC layer 103 (operation 128). The message transferred to the MAC layer 103 is passed through an RLC layer 102 (operation 129) and transferred to an RRC layer 101 (operation 130).

[37] The RRC layer 101 of the UE 100 receiving the dedicated paging message through the DCCH checks that system information is changed from the paging reason, and calculates the type and location of system information to be received using included information (operation 131). Subsequently, to receive changed system information, channels of the PHY/MAC/RLC layers 101, 103 and 102 are set as a Downlink Shared Channel (DL-seH: DBCCH) (operation 136). When an SIB is included in the dedicated paging message, the process proceeds to operation 143 without setting up a BCH.

[38] Meanwhile, after system information is changed, the eNB 110 periodically transmits an MIB divided through an internal process into one or more parts using a Primary Broadcast Control Channel (PBCCH):BCH (operations 132, 134 and 137) and several SIBs divided through an internal process into one or more parts using a DBCCH:DL-SCH (operations 133, 135 and 138). In the UE 100, when setting of a lower layer for receiving an SIB is completed (operation 136), the PHY layer 104 receives an SIB through the set DBCCH:DL-SCH (operation 138). The received data is passed through the MAC layer 103 and the RLC layer 102 (operations 139 and 140) and transferred to the RRC layer 101 (operation 141). When the RRC layer 101 repeatedly performs the above described operations 138, 139, 140 and 141 and thereby receives the entire SIB (operation 142), a parameter and a channel of L1/L2 are set using the received information (operation 143). Subsequently, the UE 100 continuously performs the process of operation 120, that is, a data communication/DRx process performed before system information is changed (operation 144).

[39] According to the exemplary embodiment of the present invention, when a UE connected with an eNB is informed by the eNB that system information is changed through a previously set DCCH, the UE sets a channel of a lower layer, i.e., a PHY/ MAC/RLC layer, as a DBCCH:DL-SCH to receive changed system information and receives the entire changed system information. Then, the UE sets an Ll parameter and a channel of L1/L2, which is a lower layer, using the received information and continuously performs data communication and a DRx operation.

[40] Therefore, the present invention can recognize that system information is changed using a DCCH and thus can reduce delay time resulting from unnecessary channel setting and also power consumed by periodically demodulating a channel.

[41] It will be apparent to those skilled in the art that various modifications and variation can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents. Industrial Applicability

[42] The present invention can be efficiently applied to a next-generation mobile communication system in which changed system information needs to be received in short time, and power consumption needs to be reduced.

Claims

[1] A method of receiving system information in a mobile communication terminal, comprising: receiving a dedicated paging message for informing that system information is changed from a base station; setting up a lower layer channel required for receiving the changed system information; receiving one or more pieces of system change information transmitted from the base station through the set channel; and resetting a parameter and a channel of a lower layer using the received system change information and performing data communication or a discontinuous reception process.

[2] The method of claim 1, wherein the dedicated paging message is received through a Dedicated Control Channel (DCCH).

[3] The method of claim 2, wherein the lower layer channel is a channel of a lower layer of a Radio Resource Control (RRC) layer.

[4] The method of claim 2, wherein the dedicated paging message includes at least: message type information for distinguishing the dedicated paging message from other messages transmitted through the DCCH; information for describing a paging reason; and

Master Information Block (MIB) information including value tag information used as a system information index.

[5] The method of claim 1, wherein the lower layer channel is a channel of a lower layer of a Radio Resource Control (RRC) layer.

[6] The method of claim 1, wherein the dedicated paging message includes at least: message type information for distinguishing the dedicated paging message from other messages transmitted through a Dedicated Control Channel (DCCH); information for describing a paging reason; and

[7] A method of transmitting system information in a base station of a mobile communication system, comprising: when system information is changed, selecting a User Equipment (UE) to be informed that system information is changed; generating a dedicated paging message for informing that system information is changed; and transmitting the generated dedicated paging message to the selected UE through a Dedicated Control Channel (DCCH).

[8] The method of claim 7, wherein the dedicated paging message includes at least: message type information for distinguishing the dedicated paging message from other messages transmitted through the DCCH; information for describing a paging reason; and

[9] The method of claim 7, wherein a paging message for a specific UE is generated according to the number of the selected UE and a time when changed system information is applied, and the paging message includes a Master Information Block (MIB) and a System Information Block (SIB).

[10] The method of claim 9, wherein the dedicated paging message includes at least: message type information for distinguishing the dedicated paging message from other messages transmitted through the DCCH; information for describing a paging reason; and

MIB information including value tag information used as a system information index.

[11] The method of claim 7, wherein a paging message for a specific UE is generated according to the number of the selected UE and a time when changed system information is applied, and the paging message includes a scheduling Information block on transmission of the changed system information and a Master Information Block (MIB).

[12] The method of claim 11, wherein the dedicated paging message includes at least: message type information for distinguishing the dedicated paging message from other messages transmitted through the DCCH; information for describing a paging reason; and

[13] The method of claim 7, wherein a paging message for a plurality of UEs is generated according to the number of the selected UE and a time when changed system information is applied, and the paging message includes a Master Information Block (MIB) and a System Information Block (SIB).

[14] The method of claim 13, wherein the dedicated paging message includes at least: message type information for distinguishing the dedicated paging message from other messages transmitted through the DCCH; information for describing a paging reason; and

[15] The method of claim 7, wherein a paging message for a plurality of UEs is generated according to the number of the selected UE and a time when changed system information is applied, and the paging message includes a scheduling Information block on transmission of the changed system information and a Master Information Block (MIB).

[16] The method of claim 15, wherein the dedicated paging message includes at least: message type information for distinguishing the dedicated paging message from other messages transmitted through the DCCH; information for describing a paging reason; and