KR101217135B1 - Method and apparatus for obtaining information for cell re-selection in mobile communication system and system using thereof - Google Patents

Abstract

According to the present invention, when a terminal acquires cell and network information of a neighboring cell before handoff or for cell reselection in a mobile communication system, it is possible to shorten the acquisition time of cell and / or network information while minimizing terminal power consumption. A method and apparatus are disclosed.

In the present invention, the N-bit count information is provided for every PHY frame transmitted from the base station at regular intervals, so that the UE can predict at what time the cell / network information is broadcast. In addition, according to the cell / network information acquisition, the present invention has the advantage of minimizing the power consumption of the terminal and reducing the time required to acquire cell / network information for multiple neighbor cells.

Cell / network information, BCH (Broadcast Channel), BCCH (Broadcast Control Channel)

Description

METHOD AND APPARATUS FOR OBTAINING INFORMATION FOR CELL RE-SELECTION IN MOBILE COMMUNICATION SYSTEM AND SYSTEM USING THEREOF}

1 is a diagram illustrating an example of a frame structure for cell / network information broadcasting in a mobile communication system.

2 is a diagram illustrating a frame structure for broadcasting cell / network information including count information according to an exemplary embodiment of the present invention.

3 is a diagram illustrating a cell / network information acquisition process for a single neighbor cell according to an embodiment of the present invention.

4 is a view for explaining the power consumption savings effect according to the present invention.

5 is a diagram illustrating a process of acquiring cell / network information for multiple neighbor cells according to an exemplary embodiment of the present invention.

6 is a view for explaining the effect of reducing the time required during the cell / network information acquisition process for two adjacent cells in accordance with a preferred embodiment of the present invention.

7 is a block diagram of a terminal device according to an embodiment of the present invention.

The present invention relates to a mobile communication system, and to a method and apparatus for acquiring cell and network information for minimizing power consumption of a terminal.

In general, in a wireless mobile communication system, a terminal may physically connect to a network after obtaining a physical connection with a network through a base station that manages access control in a cell, and then obtain information about the cell and the network. To this end, in general, a base station broadcasts cell / network information at regular intervals so that information can be obtained only by physical connection.

UMTS (Universal Mobile Telecommunication Service) system is based on the European mobile system Global System for Mobile Communications (GSM) and General Packet Radio Services (GPRS), and Wideband Code Division Multiple Access: Third generation asynchronous mobile communication system using " CDMA. &Quot;

The 3rd Generation Partnership Project (3GPP), which is in charge of UMTS standardization, is discussing Long Term Evolution (LTE) as the next-generation mobile communication system of the UMTS system.

LTE is a technology that implements high-speed packet-based communication with a transmission rate of up to 100 Mbps, aiming for commercialization in 2010. To this end, various schemes are discussed. For example, a scheme of reducing the number of nodes located on a communication path by simplifying a network structure, or approaching wireless protocols as close as possible to a wireless channel are under discussion. In the following description of the present invention, the LTE system evolved from the UMTS system is used as an example, but the present invention can be applied to other mobile communication systems.

For cell / network information of the LTE system, in case of a terminal considering handover or a cell attempting cell reselection, corresponding cell / network information on neighbor cells must be acquired in advance.

1 is a diagram illustrating an example of a frame structure for cell / network information broadcasting of an LTE system to which the present invention is applied.

Referring to FIG. 1, the transmission structure is composed of a plurality of physical frames (hereinafter, referred to as 'PHY frames') 100 of the same size. In the LTE system, the PHY frame 100 is transmitted from the base station at an interval of 10 msec. In this case, since the cell / network information 110 has a relatively large amount of information, the cell / network information 110 is broadcast at regular intervals rather than being transmitted every PHY frame. In the present invention, it is assumed that the cell / network information is broadcasted through a broadcast control channel (Broadcast Control Channel: Layer 2 channel, hereinafter referred to as BCCH) for every 8 PHY frames 120 in the LTE system.

Since the terminal attempts a physical connection to the neighbor cell at any point in time, it is not possible to guess exactly at what point the BCCH message is broadcast. Therefore, every PHY frame must be read to detect the presence of the BCCH message. The detailed process is as follows.

The UE reads the corresponding region, which is assumed to be the BCCH message region of the broadcast channel (Broadcast Channel: Layer 1 channel, hereinafter referred to as 'BCH') of each PHY frame 100, performs CRC check and checks whether the information is corresponding. If the CRC has been successfully checked, it is determined to be a BCH carrying a BCCH message and decodes cell / network information. On the other hand, if the CRC check fails, the PHY frame 100 determines that the BCH does not carry the BCCH message and receives the next PHY frame.

As described in this series of processes, the terminal must proceed with the reading process every PHY frame until the CRC check is successful.

As described above, in the conventional method, since the terminal does not know the broadcast time of the cell / network information message at all, the reception mode should be maintained until the message is received. This, in turn, has the problem of causing unnecessary power consumption. In addition, when acquiring cell / network information for multiple neighbor cells, power consumption continues to increase as the time required increases in proportion to the number of neighbor cells.

Therefore, when a terminal acquires cell / network information in a mobile communication system, there is a need for a specific method for minimizing power consumption.

Accordingly, an aspect of the present invention is to provide a method and apparatus for acquiring cell / network information while minimizing power consumption in a mobile communication system.

The present invention also provides a method and apparatus for reducing a time for acquiring cell / network information of a neighbor cell when a terminal is handed off in a mobile communication system.

In addition, the present invention provides a method and apparatus for minimizing power consumed when a terminal reselects a cell in a mobile communication system regardless of the number of neighboring cells.

According to an embodiment of the present invention, a method for acquiring information for cell reselection from neighbor cells by a mobile station in a mobile communication system includes: a physical frame including frame count information determined according to a transmission period of the information for cell reselection; Receiving a signal; and checking a transmission time of information for cell reselection based on the frame count information and a transmission period of the physical frame, transitioning to a sleep mode, and wake-up at the transmission time -up) transitioning to a mode to obtain information for the cell reselection.

According to an embodiment of the present invention, a method in which a terminal acquires information for cell reselection from a plurality of cells in a mobile communication system is determined according to a transmission period of information for cell reselection from each of the plurality of cells. Receiving a physical frame including frame count information of a size, checking a transmission time of a broadcast control message based on frame count information received from each of the plurality of cells, and constructing a list in which the transmission time is arranged And obtaining information for cell reselection at the time point of transmitting the broadcast control message from each of the plurality of cells with reference to the list.

In a mobile communication system for transmitting and receiving information for cell reselection according to an embodiment of the present invention, a base station for transmitting a physical frame including frame count information having a variable size according to a transmission period of information for cell reselection And after receiving the physical frame and checking a transmission time of a broadcast control message including the cell count information of the physical frame and information for cell reselection based on a transmission period of the physical frame, transition to a sleep mode. And a terminal transitioning to a wake-up mode at the time of transmission to obtain information for cell reselection.

According to an embodiment of the present invention, a terminal apparatus for acquiring information for cell reselection from neighbor cells in a mobile communication system includes: a transceiver for receiving a physical frame, a frame count information, and a transmission period of the physical frame; Obtains a transmission time of a frame including information for cell reselection, a frame count decoding unit controlling reception of the transmission / reception unit, a cell and network for processing information for cell reselection received at the transmission time It includes an information decryption unit.

Hereinafter, with reference to the accompanying drawings will be described in detail the operating principle of the preferred embodiment of the present invention. In the following description of the present invention, if it is determined that a detailed description of a known function or configuration may unnecessarily flow the gist of the present invention, the detailed description thereof will be omitted. The following terms are defined in consideration of the functions of the present invention, and may be changed according to the intentions or customs of the user, the operator, and the like. Therefore, the definition should be based on the contents throughout this specification. In addition, although the LTE system is used as an example in describing the present invention, it can be applied to all mobile communication systems to which cell reselection is applied without any addition or subtraction.

The present invention provides a method and apparatus for shortening acquisition time while minimizing power consumption in acquiring cell / network information of neighbor cells before handoff or cell reselection. The cell / network information collectively refers to some or all of the system information that can be used for cell reselection of the terminal.

2 illustrates an example of a PHY frame structure using N bits of count information according to a preferred embodiment of the present invention. In the present invention, it is assumed that an LTE system broadcasts the cell / network information through a broadcast control channel (Broadcast Control Channel: Layer 2 channel, hereinafter referred to as 'BCCH') for every eight PHY frames 230.

Referring to FIG. 2, the base station transmits the PHY frame 200 at 10 msec intervals, and broadcasts the cell / network information through a BCCH message at 80 msec intervals. Accordingly, the base station sets a 3-bit PHY_frame_count value 220 for a specific Layer 1 (L1) channel in each PHY frame and informs the terminal.

If the cell and network information is not transmitted every frame, the specific Layer 1 (L1) channel may be a separate channel from the cell and network information. If there is a transmission for each frame, it may be the same channel as the channel for transmitting the cell and network information transmitted every frame. Hereinafter, the present invention does not exclude a case in which some of cell and network information transmitted every frame may exist.

In the example of FIG. 2, since cell / network information is repeatedly transmitted for every eight PHY frames, the size of the PHY_frame_count is set to 3 bits. In this case, the size of the PHY_frame_count 220 may be adjusted according to the period of the cell / network information 210.

Setting of the PHY_frame_count value by the base station is as follows.

The PHY_frame_count value in the PHY frame including the cell / network information message is set to '0'. The PHY_frame_count value of the next PHY frame has 7. That is, PHY_frame_count in other PHY frames is decremented by one based on the PHY frame including the cell / network information message.

Accordingly, in the present invention, the UE reads the PHY_frame_count value in one PHY frame at any point in time, so that the UE can know at what point the BCCH message is broadcast.

In addition, when the terminal reads the PHY_frame_count value in one PHY frame at the time, confirms that the current time is not the time when the broadcast control information message is broadcasted, (PHY_frame_count-1) x switches to the sleep mode during the PHY frame interval. After that, the device wakes up at the correct time using the PHY_frame_count. Thereafter, the terminal in the wake up mode acquires cell / network information from the received frame.

3 illustrates a cell / network information acquisition process for a single neighbor cell of a terminal according to the present invention.

Referring to FIG. 3, at step 300, a terminal attempting to acquire neighbor cell information first receives one PHY frame through a physical connection. In step 310, the UE extracts PHY_frame_count from the L1 channel of the received PHY frame and reads the value. At this time, in step 320, the UE checks whether the value of the PHY_frame_count is set to '0', which is a value indicating that it is an L1 channel including cell / network information. If the PHY_frame_count value is '0' in step 320, the flow proceeds to step 340 to extract and read cell / network information in the PHY frame and complete the cell / network information acquisition process.

On the other hand, if the PHY_frame_count value has a specific m (> 0) value other than '0', the flow proceeds to step 330 and enters a sleep mode by (m-1) x 'interval of the PHY frame'. In one embodiment of the present invention, the interval of the PHY frame is 10msec.

If the sleep mode time determined in step 350 has passed, the terminal wakes up again and transitions to step 300 again. At this time, the terminal proceeds to step 300, the step is necessarily branched from step 320 to step 340 in the transition process to confirm the cell / network information and complete the process.

In other words, when the UE detects that the sleep mode has expired in step 350, the UE detects a time point of PHY_frame_count = 0, that is, a time point of a PHY frame in which cell / network information is transmitted, based on one PHY frame received in step 300. It has transitioned to the wake up mode. Accordingly, the terminal proceeds to step 300 again to obtain cell / network information through steps 320 and 340.

4 is a view for comparing the present invention with the conventional method in terms of power consumption reduction.

Referring to FIG. 4, it is assumed that a terminal attempts to acquire cell / network information by receiving a PHY frame transmitted from a base station at an arbitrary time point 420.

In the case of the conventional method 430, the UE should continue to consume the received power by maintaining the wake-up mode starting with the time point 420 until the PHY frame including the cell / network information is received.

On the other hand, in the case of the present invention 440, after 420, after receiving the PHY frame having the PHY_frame_count value of 5, the terminal confirms that the PHY_frame_count value of the PHY frame is 5, that is, the cell in the received PHY frame / Confirms that the network information does not exist, and transitions to the sleep mode during '(5-1) x interval of the predetermined PHY_frame' as shown in 440.

In other words, in the present invention, after the UE operates in the sleep mode for (5-1) x10msec = 40msec, that is, after receiving the PHY frame having the PHY_frame_count value of 5, after 40msec, the PHY_frame_count value is 0. Cell-network information is acquired by waking up from a frame.

As described above, the present invention achieves a power saving effect for 40 msec, such as 450.

5 is a diagram illustrating a cell / network information acquisition process for multiple neighbor cells of a terminal in the present invention.

Referring to FIG. 5, in step 500, the UE initializes a broadcast control message list (hereinafter referred to as 'BCCH_list') for multiple neighbor cells for which cell / network information is to be obtained. In step 510, one of the cells in the BCCH_list is selected, and in step 520, one PHY frame is received in the cell, and the cell / network information message broadcast time of the cell is registered in the BCCH_list. According to the present invention, when the UE receives the PHY frame including the PHY_frame_count, the UE determines the broadcast time of the correct cell / network information message.

In step 530, it is determined whether registration of all the cells in the BCCH_list is completed, and if all is completed, branching to step 550 to sequentially sort the cell / network information message broadcast timings per cell registered in the BCCH_list and sorting the cells / cells according to the order. Acquire network information and complete the process.

On the other hand, if the registration for all the cells in the BCCH_list has not been completed in step 530, the process branches to step 540 to determine whether there is a cell whose cell / network information broadcast time is imminent in the BCCH_list. If it is determined in step 540 that there is an impending cell, the process proceeds to step 560 where a physical connection is attempted to the cell to obtain cell / network information and then removed from the BCCH_list and the step 520 is shifted.

On the other hand, if it is determined in step 540 that there is no impending cell, the process immediately proceeds to step 520.

6 is a view for explaining the effect of reducing the time required during the cell / network information acquisition process for two adjacent cells in accordance with the present invention.

Referring to FIG. 6, in general, cell 1 600 and cell 2 610 may have a system in which a PHY frame transmission time is synchronized, and there may be a system that does not. The present invention is applicable to both cases.

FIG. 6 illustrates that a terminal attempts to acquire cell / network information of cell 1 600 at an arbitrary time 620.

In case of the conventional method 640, the terminal must maintain a physical connection to cell 1 from time 620 until acquiring cell / network information of cell 1. Only after that can the cell / network information acquisition of cell 2 be attempted. In this case, physical connection to cell 2 must be maintained until cell / network information of cell 2 is obtained.

On the other hand, in the case of the present invention 650, since the UE can predict when the cell / network information of cell 1 is to be broadcasted by receiving only one PHY frame in cell 1, the information is registered in BCCH_list. The cell / network information is immediately acquired. Similarly, since the cell / network information of cell 2 can be predicted by receiving one PHY frame of cell 2, the information is registered in BCCH_list.

Since the accurate cell / network information acquisition time per cell can be predicted by the prepared BCCH_list, the time required for obtaining cell / network information can be significantly reduced compared to the conventional method.

7 is a block diagram of an apparatus of a terminal according to an embodiment of the present invention.

Referring to FIG. 7, the transceiver 711 controls and performs message transmission and reception with an E-NBRAN B. The transceiver 711 receives an arbitrary PHY frame and, upon receiving the PHY_frame_count through the received PHY frame, transmits it to the PHY_frame_count decoder 721.

The PHY_frame_count decoder 721 obtains information on how many frames and cell information can be received after the received PHY_frame_count. The reception of the transceiver 711 is controlled using the obtained information. That is, the PHY_frame_count decoder 721 controls the transceiver 711 in the sleep mode or the wake up mode using the obtained PHY_frame_count. This includes that the PHY_frame_count decoder 721 controls the power consumption applied to the transceiver 711 according to the sleep mode or the wake up mode.

For example, if it is confirmed that the cell and network information can be received after 6 frames through the obtained PHY_frame_count. The transceiver 711 may not perform the reception of the transceiver 711 until a frame capable of receiving cell and network information.

According to the frame information obtained by the PHY_frame_count decoder 721, the transceiver 711 receives the cell and network information at a predetermined frame transmission time point and transmits the cell and network information to the cell and network information decoder 731. The cell and network information decryption unit 731 processes the received cell and network information.

As described above, the present invention does not exclude the case where there may be cell and network information transmitted every frame. In this case, since the PHY_frame_count information may be transmitted in the same channel as the channel through which the cell and network information is transmitted every frame, in this case, the PHY_frame_count decoder 721 and the cell and network information decoder 731 are the same. It may be configured as a device.

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

The present invention has the advantage that the terminal can receive the PHY frame including the count information to predict when the cell / network information is broadcast (broadcast). Therefore, the power consumption of the terminal is minimized, and the cell / network information acquisition time for the multiple neighbor cells can be shortened.

Claims (9)

In a method for obtaining information for cell reselection from neighbor cells in a mobile communication system, Receiving a physical frame including frame count information determined according to a transmission period of information for cell reselection; Checking a transmission time of the information for cell reselection based on the frame count information and the transmission period of the physical frame, and then transitioning to a sleep mode; Transitioning to a wake-up mode at the time of transmission to obtain information for cell reselection. The method of claim 1, wherein the frame count information, Information for cell reselection of a terminal having a specific value in a physical frame including information for cell reselection, and a value sequentially decreasing in every physical frame after the physical frame having the specific value Acquisition method. The method of claim 1, wherein the frame count information, And a length determined according to a transmission period of information for cell reselection, and included in a broadcast channel in the physical frame. The method of claim 1, wherein the transition to the sleep mode comprises: Subtracting 1 from the frame count information, and then slipping for the amount of time obtained by multiplying the subtracted value by the transmission period of the physical frame. The method of claim 1, wherein the transmission time point, And a point in time at which a physical frame including information for cell reselection and frame count information which is a specific value is received. A method for acquiring information for cell reselection from a plurality of cells by a terminal in a mobile communication system, Receiving, from each of the plurality of cells, a physical frame including frame count information having a predetermined size according to a transmission period of information for cell reselection; Checking a transmission time point of a broadcast control message based on frame count information received from each of the plurality of cells, and constructing a list in which the transmission time points are arranged;  And obtaining information for cell reselection at the time point at which the broadcast control message is transmitted from each of the plurality of cells with reference to the list. The method according to claim 6, After transitioning to the wake-up mode at the time of transmission of the broadcast control message of the arbitrary cell based on the frame count information of the arbitrary cell of the plurality of cells, obtaining information for the cell reselection from the arbitrary cell Process, The method of claim 1, further comprising removing the random cell from the list. In the mobile communication system for transmitting and receiving information for cell reselection, A base station transmitting a physical frame including frame count information having a variable size according to a transmission period of information for cell reselection; Receiving the physical frame, checking a transmission time of a broadcast control message including the cell count information of the physical frame and information for cell reselection based on a transmission period of the physical frame, and then transitioning to a sleep mode, And a terminal for transitioning to a wake-up mode at the time of transmission to obtain information for cell reselection. A terminal device for acquiring information for cell reselection from neighbor cells in a mobile communication system, A transceiver for receiving a physical frame, A frame count decoding unit for obtaining a transmission time of a frame including information for reselecting the cell based on the frame count information and the transmission period of the physical frame, and controlling reception of the transceiver unit; And a cell and a network information decoding unit for processing information for cell reselection received at the transmission time point.

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