KR20080112062A - Handover apparatus and method in mobile communication system - Google Patents

Abstract

A handover apparatus, a method and a system thereof in a mobile communications system are provided to transmit a frame number and perform a handover smoothly. A measurement about a target base station(Target eNB) of a target cell in which a terminal handovers. A measurement report message set up as the system frame number does not existed is transmitted to a source base station(461). A handoff request message which is set up as the system frame number does not existed is transmitted(463). A handover request acknowledgement message is transmitted to the source base station(465). The source base station transmits the handover command message to the terminal(467). The transfer frame of the random access control channel is calculated. The terminal transmits the code of the random access control channel to the target base station.

Description

HANDOVER APPARATUS AND METHOD IN MOBILE COMMUNICATION SYSTEM}

The present invention relates to a handover apparatus and method and system therefor in a wireless communication system.

The present invention relates to a handover apparatus and method and system therefor in a wireless communication system. A general wireless communication system is a system developed for a case in which communication cannot be performed by connecting a fixed wired network to a terminal. Representative systems of such wireless communication systems include wireless LAN, Wibro, and mobile ad hoc networks, as well as general mobile communication systems that provide voice and data services.

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

1 is a diagram illustrating an example of a structure of a long term evolution (LTE) that is an evolved UMTS mobile communication system.

Referring to FIG. 1, as illustrated, an Evolved UMTS Radio Access Network (hereinafter referred to as an 'E-UTRAN') 110 is an evolved Node B (hereinafter referred to as an 'eNB') 120 , 122, 124, 126, and 128 and the upper node (anchor node) 130, 132 is simplified to a two-node structure. The user equipment (hereinafter referred to as 'UE' or 'terminal') 101 is connected to the Internet Protocol (hereinafter referred to as 'IP') network by the E-UTRAN 110. The eNBs 120 to 128 correspond to existing Node Bs present in the UMTS system and are connected to the UE 101 by a radio channel. Unlike the existing Node B, the eNBs 120 to 128 play a more complex role.

In LTE, all user traffic including a real-time service such as Voice over IP (VoIP) over the Internet protocol is serviced through a shared channel, and thus, an apparatus for collecting and scheduling situation information of UEs is needed. 120 to 128 are in charge. One eNB typically controls a number of cells. In addition, the eNB performs Adaptive Modulation & Coding (hereinafter referred to as 'AMC') to determine a modulation scheme and a channel coding rate according to the channel state of the terminal, and performs HSDPA (UMTS) of UMTS. Hybrid ARQ (HARQ) is performed between the eNBs 120 to 128 and the UE 101 in LTE, such as High Speed Downlnk Packet Access (HSUPA) and High Speed Uplink Packet Access (E-DCH: also called Enhanced Dedicated Channel). Since HARQ alone cannot satisfy the requirements of various Quality of Service (QoS), an outer ARQ at a higher layer may be performed between the terminal 101 and the eNBs 120 to 128. have.

The HARQ is a technique of increasing reception success rate by soft combining with retransmitted data without discarding previously received data. It is used to improve transmission efficiency in high speed packet communication such as HSDPA (High Speed Downlink Packet Access) and EDCH (Enhanced Dedicated Channel). LTE is expected to use Orthogonal Frequency Division Multiplexing (OFDM) as its radio access technology in the 20 MHz bandwidth to achieve transmission rates up to 100 Mbps.

2 is a diagram illustrating an example of transmission of a system frame number (SFN: hereinafter referred to as "SFN") in a general 3GPP UMTS system. The SFN represents a system frame number and serves as a reference number for promising when the control information / data is transmitted and received between the terminal and the network node. In the UMTS system, SFN is transmitted through a broadcast channel (BCH) channel. The BCH is a channel for transmitting system information in a cell and has an information transmission period of every two frames (20 ms).

Reference numerals 201, 203, 205, 207, 209, 211, 213, 215, 217 represent P-BCH, and [n] included in reference numbers 201, 203, 205, 207, 209, 211, 213, 215, 217. ] Represents an SFN value included in each BCH. Reference numeral 201 denotes a BCH transmitted over an actual SFN 0,1 frame. In this case, only the even value 0 is included as the SFN value included. When the terminal successfully receives the reference number 201, the terminal recognizes the front frame as SFN 0 and recognizes the rear frame as SFN1. Likewise, reference numerals BCH 203, 205, 207, 209, 211, 213, 215, and 217 also include SFNs in the same manner as reference numeral 201, and the operation of the terminal is identical in principle when receiving them. If the terminal successfully receives the BCH once in the cell, the terminal may know the SFN for every frame thereafter based on the SFN information included in the received BCH.

The terminal does not need to continuously receive the SFN value in the cell in which the SFN has been acquired once by increasing the initial SFN value by 1 as each frame increases. If a handover occurs by moving the terminal, the terminal should know the timing of when to use a random access channel (RACH) or an uplink / downlink control channel allocated to the target cell. In a UMTS system using SFN, FIG. 2 illustrates the use of a paging indicator (hereinafter, referred to as PI) for a terminal. PI 221 is an indicator indicating whether or not to receive a paging message transmitted on the physical channel. The terminal is promised to receive the PI transmitted in frame SFN 68 by reference rule 221. If the terminal acquires SFN information of this cell in SFN 12, 13, it does not need to receive the PI every frame. Only when a frame becomes SFN 68, it wakes up and receives PI.

The present invention provides a handover apparatus and method and system therefor in a mobile communication system.

The present invention provides an apparatus and method for performing handover using a system frame number in a mobile communication system, and a system thereof.

In a mobile communication system according to the present invention, a handover method includes a process of a UE performing a target base station (Target_eNB) of a target cell to be handed over, and a case where a system frame number for the target cell is not maintained. Transmitting a measurement report message configured to have no system frame number to a source base station; and when the source base station receives the measurement report message, a handover request message configured to have no system frame number at the target base station; And a frame offset value for local frame numbering within a boundary of a P-BCH information transmission period to the terminal when the terminal does not maintain the system frame number. A handover request acknowledgment message to the source base station Transmitting, the source base station receiving the handover request acknowledgment message, transmitting a handover command message to the terminal, and when the terminal receives a handover command message from the source base station, Calculating a transmission frame of a random access control channel using a local frame number of a primary broadcast channel included in a handover command message; transmitting, by the terminal, a code of the random access control channel to the target base station; And transmitting, by the destination base station, a frame number in which a response message for the received random access control channel code is transmitted in a random access control channel code response message.

In a mobile communication system according to the present invention, a handover method includes a process of checking whether a terminal has a system frame number (SFN) of a target cell when a terminal receives a handover command message; If the SFN is not known, at least one frame position of the random access channel and the control channel in the target cell using the least significant 2 bits of the SFN that can be obtained from the target cell through a prime broadcast control channel (P-BCH). It includes the process of calculating.

In the mobile communication system according to the present invention, it is possible to efficiently transmit the system frame number, thereby smoothly performing handover.

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 the detailed description of the related configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. The terms to be described below are terms defined in consideration of functions in the present invention, which may vary according to a user's or operator's intention or custom, and the definitions should be made based on the contents throughout the specification.

In particular, the following description will be described with reference to the 3GPP Long Term Evolution (LTE) system, which is a next generation mobile communication system currently being discussed in the 3rd Generation Partnership Project (3GPP) for convenience of description.

In addition, the present invention described below will describe an apparatus and method for performing a handover by knowing a system frame number in a mobile communication system and a system thereof.

3 is a diagram illustrating an embodiment of transmitting system information in a 3GPP LTE system to which the present invention is applied.

The system information is information for broadcasting configuration information, channel configuration information, and information about neighbor cells in a cell. In LTE, a primary broadcast channel (P-BCH), a scheduling unit-1 (SU-1), and a D-BCH ( Dynamic Broadcast Channel). The P-BCH may include the most basic hardware information, configuration information, or measurement related information of the cell. The SU-1 includes scheduling information about the D-BCH, and the D-BCH includes most general channel information and configuration information. System information is included. In the LTE system, a resource is composed of a sub-frame and a frame. The subframe is composed of 1ms, the basic unit of data / control information transmission and reception, and the frame is a unit composed of 10 subframes. That is, one frame consists of 10 subframes.

Currently, in 3GPP LTE, SFN is considered to be transmitted through P-BCH. However, since P-BCH is transmitted with a short period such as every frame or every two frames, there is a lot of overhead due to SFN transmission.

In FIG. 3, the information transmission period of the P-BCH is 4 frames (40 ms), and is represented by reference numerals 301, 303, 305, 307, and 309. [N] included in reference numerals 301, 303, 305, 307, and 309 represents SFN values included in each P-BCH. Similar to the UMTS method described with reference to FIG. 2, this includes the SFN value of the first frame of the transmission period of four frames.

P-BCHs transmitted with an information transmission period of 4 frames are distributed and transmitted in 4 frames, respectively, to obtain time diversity gain. For example, the P-BCH of the reference number 301 is transmitted as the same information in each frame of SFN 0, 1, 2, 3, as shown by reference numbers 311, 313, 315, and 317, or the reference number 301 is segmented to provide different information in each frame. Can be sent as. If the P-BCH [0] 301 is transmitted with the same information without segmentation in reference numbers 311, 313, 315, and 317, the eNB transmits at a small power while the terminal combines the same information transmitted in every frame. You can also achieve combining gain.

PBCH transmission with reference numeral 303 may be distributed and transmitted in SFN 4, 5, 6, and 7 frames in the same manner as in reference numerals 321, 323, 325, and 327. Reference numerals 341 and 343 denote SU-1 transmission. As shown by reference numbers 341 and 343, SU-1 is transmitted with a relatively long period compared to P-BCH, and FIG. 3 shows that 8 frames (80ms) are shown as an example of the SU-1 information transmission period.

If the SFN is included in the P-BCH and transmitted as shown in FIG. 3, since the SFN value is transmitted every frame, radio resource overhead due to SFN transmission is large. Unlike in FIG. 3, even though P-BCH information is not repeated every frame, P-BCH generally has a short information transmission period, thereby causing an overhead problem.

Accordingly, in the embodiment of the present invention described below, in order to reduce the overhead of transmitting the SFN to the P-BCH, while transmitting the SFN through SU-1 (Scheduling Unit-1) having scheduling information on the system information of the cell In this case, an efficient apparatus and method for detecting timing of an RACH channel or an uplink / downlink control channel of a target cell at handover are proposed.

To this end, if the terminal does not have SFN information on the cell of the measurement report in the measurement report (Measurement Report), it notifies the network node through the measurement report message. Measurement reporting is performed periodically or by promised rules. For example, it may be performed when a cell having a better radio channel state than the current serving cell is detected. Also, if the P-BCH information transmission period boundary obtained through the measurement is obtained, the RACH channel frame timing is found by using the local frame numbering in the P-BCH information transmission period boundary of the target cell. .

On the other hand, the network node transmits a frame offset value for the local frame numbering within the boundary of the RACH channel and the P-BCH information transmission period through a handover command message to the terminal. By including the terminal so that the terminal can know the frame timing of the RACH channel, and the network node receives the RACH code transmitted by the terminal on the RACH channel after the handover (in the destination cell that has already received through the measurement report of the terminal) If there is no SFN acquisition information of the UE) the SFN information in the target cell is informed by including the full or partial SFN information of the frame in which the response message for the RACH code is transmitted in the response message for the RACH code.

In the present invention, regardless of the SFN acquisition information in the destination cell received through the measurement report of the terminal may be informed by including the SFN information in the response message for the corresponding RACH code. The terminal knows the timing of the uplink / downlink control channel in the target cell based on the full / part SFN information included in the response message to the RACH code.

As an example of determining the frame timing of the RACH channel, if the P-BCH is received and the information transmission period of the P-BCH is 4 frames (40 ms), the terminal receives a boundary for the P-BCH information transmission period through the reception of the P-BCH. As a result, local frame numbering can be obtained within a P-BCH information transmission period. That is, local frame numbering 0, 1, 2, or 3 may be performed for 4 frames within a 40 ms P-BCH information transmission period.

If the UE fails to acquire the entire SFN value of the destination cell when performing the measurement report, the UE reports this in the measurement report and the network node transmits the RACH as the RACH frame timing information of the destination cell through the handover command when a handover occurs. Period P-BCH information transmission period When the terminal receives this by sending a frame offset value for local frame numbering in the boundary, the terminal divides the local frame numbering 0, 1, 2, and 3 into the RACH transmission period. Calculates a frame having a frame offset value for local frame numbering in the P-BCH information transmission period boundary as a RACH frame. That is, a frame satisfying Equation 1 below represents a RACH transmission frame. The RACH timing information is information for finding a frame in which the RACH should be performed. In the present invention, a transmission period and an RACH frame offset are proposed, but the above information is interworked with a local frame number in a boundary of a P-BCH information transmission period.

(Local frame numbering in boundary of P-BCH information transmission cycle) MOD (RACH transmission cycle) = Frame offset value for local frame numbering in boundary of P-BCH information transmission cycle (= RACH frame offset) )

That is, according to the first embodiment of the present invention as shown in Equation 1, the UE knows the RACH transmission timing by using local frame numbering in the P-BCH information transmission period obtained through P-BCH reception even though the entire SFN is not known. Serve

If the terminal transmits a measurement report message that may cause a handover or receives a handover command message, the terminal does not acquire the entire SFN information for the measurement reported cell or the target cell of the handover. Receive SU-1 to obtain SFN. If the entire SFN information is received through the RACH code response message before receiving the SU-1, the SU-1 does not need to be received.

In the second embodiment of the present invention to be described with reference to FIGS. 11 to 12, a terminal receives a prime broadcast control channel (P-BCH) of a target cell to be handed over, and sends a handover command message indicating a handover to the target cell. SFN that can be obtained through prime broadcast control channel reception instead of the actual SFN value to find out where the random access channel frame and the control channel frame are when the system frame number of the target cell is not obtained or maintained when received. Least Significant Bit (LSB) 2 bits (or local frame numbering in boundary of prime broadcast control channel information transmission period. In the second embodiment of the present invention, the "SFN LSB 2 bits (= 2LSB)" and "prime broadcast control" are shown. Local frame numbering in the boundary of channel information transmission period shall be used as the same meaning.) Use information or a value.

For example, when k is given from the base station as a value for finding a random access channel or control channel frame, the terminal performs SFN 2LSB obtained through the reception of the prime broadcast control channel instead of the actual SFN value. ≫ and the frame position of the random access channel and the uplink or downlink control channel in the target cell through Equation 2 below. That is, the frame position is a position of a frame having an SFN satisfying Equation 2 below, and transmits a random access channel preamble or a frame of a control channel through a frame of a random access channel at the position of the frame. .

SFN LSB 2-bit value (2LSB) (or local frame numbering in boundary of prime broadcast control channel information transmission period) mod k = 0

Here, k is a value for calculating a random access channel or a control channel frame, and is a value given from the base station, and mod represents a modulo operation.

4 is a diagram illustrating a SFN transmission method and a handover procedure according to a first embodiment of the present invention.

Reference numerals 401, 403, 405, 407, and 409 denote P-BCHs having a 40 ms information transmission period, and reference numerals 411, 413, 415, and 417 denote P-BCHs in which reference numeral 401 is distributed and transmitted in each frame. , 421, 423, 425, and 427 denote P-BCHs in which reference numeral 403 is distributed and transmitted in each frame. Reference numerals 441 and 443 denote SU-1. In the first embodiment of the present invention, it is proposed to transmit the SFN through SU-1. Accordingly, SFN 0 is transmitted at 441 and SFN 8 is transmitted at 443.

When the SFN is transmitted through SU-1 as shown in FIG. 4, the handover procedure according to the first embodiment of the present invention operates as follows. The UE 470 transmits a measurement report message 461 to the source eNB 472 if it needs to transmit a measurement report message for the target cell. At this time, the terminal 470 informs whether the terminal acquires SFN information of the target cell through the SFN_Knowledge_Indication flag included in the measurement report message. At reference numeral 451, the terminal 470 knows the boundary of the P-BCH information transmission period when receiving the P-BCH of the target cell, and accordingly, may perform local frame numbering for each frame within the P-BCH information transmission period boundary. . That is, the P-BCH of the target cell is received through the reference numeral 451 to find the local frame number in the boundary of the P-BCH information transmission period.

For example, if the terminal 470 knows the boundary of the P-BCH information transmission period through the reception of the P-BCH indicated by reference numeral 401, local frame numbering of 0, 1, 2, and 3 may be performed for each frame. SFNs 4, 5, 6, and 7 to which reference numeral 403 is transmitted are also numbered local frames as 0, 1, 2, and 3. When the source eNB 472 receives the measurement report message 461, the source eNB 472 requests a handover of the terminal 470 to the target eNB 474 for controlling the target cell. A Handover Request message 463 is transmitted.

The handover request message 463 includes SFN_Knowledge_Indication information included in the measurement report message 461 transmitted by the terminal 470. Upon receiving the handover request message 463, the target eNB 474 stores SFN_Knowledge_Indication information for the terminal 470, and if a handover to the target cell is possible, a handover request acknowledgment message (Handover Request ACK) message. 465 is sent to the source eNB 472. The handover request acknowledgment message (Handover Request ACK) 465 includes RACH channel configuration information and uplink / downlink control channel configuration information for use in the destination cell. An example of an uplink / downlink channel includes channel quality information (CQI), ACK / NACK, and scheduling request (SR). The RACH channel configuration information of the target cell includes RACH timing information of the target cell. The information includes frame offset values for local frame numbering within the RACH cycle and P-BCH information transmission cycle boundary (hereinafter referred to as RACH frame offset). (Referred to as Offset), and a RACH subframe offset.

The configuration information for the uplink / downlink control channel also includes timing information for each channel, which indicates the SFN value itself or the K value that can use the SFN value. When the K value is reported, the terminal may calculate a frame having SFN mod K = 0 as frame timing of a corresponding uplink / downlink control channel. The source eNB 472 receiving the handover request acknowledgment message 465 instructs the terminal 470 to handover to the destination cell while forwarding the information through a handover command message 467. do.

Upon receiving the handover command message 467, the terminal 470 first calculates an RACH timing to be performed in the destination cell. In order to calculate the RACH timing, a frame is first calculated as in Equation 1 above.

For example, the actual SFNs 0, 1, 2, 3, 4, 5, 6, and 7 are mapped to local frame numbering 0, 1, 2, 3, 0, 1, 2, 3 in the P-BCH information transmission boundary. If the RACH transmission period is 4 frames (40ms) and the RACH frame offset is 1, Equation 1 is satisfied when the local frame numbering is 1, and the local frame numbering 1 substantially represents SFN 1 and 5. That is, frames of SFNs 1 and 5 are RACH transmission frames.

As described above, when the RACH transmission frame is calculated through Equation 1, the subframe in the frame is calculated with the subframe offset. Reference numeral 473 denotes a RACH transmission frame calculated according to the first embodiment of the present invention. If the subframe offset is 3, the RACH channel is included in subframe 3 of the frames of SFN 1 and 5.

The terminal 470 transmits a RACH code 471 for handover using the RACH channel configuration information received in the subframe of the RACH frame calculated at 473. The destination eNB 474 receiving the RACH code 471 transmits a RACH code response 481 in response to the received RACH code 471. The RACH code response message 481 includes full or partial SFN information of a frame in which the RACH code response message is transmitted. Upon receiving the RACH code response message 481, the terminal 470 may calculate timing information of an uplink / downlink control channel in the target cell.

In FIG. 4, the RACH period, the RACH frame offset, and the RACH subframe offsets are explicitly signaled, but fixed and hardcoded to one of the parameters is fixed without needing to be explicitly signaled. You can use The first embodiment of the present invention also includes a method of hardcoding a fixed value with respect to the parameters. In addition, although FIG. 4 is shown to include all or partial SFN information in the response message for the RACH code of the terminal after the handover, the operation may be partially performed only for the terminal dedicated RACH code. The terminal dedicated RACH code is a RACH code assigned to the terminal by the destination eNB 474 via the handover request acknowledgment message 465 and the handover command message 467.

In addition, the full / part SFN information is included in the RACH code response message 481 so that the RACH code response message 481 does not include all of the RACH codes when the target eNB 474 transmits the above. SFN_Knowledge_Indication received through the handover request message 463 is included in the response message for the RACH code only when a terminal-specific RACH code assigned to the terminal indicating that the terminal 470 has not obtained the SFN of the destination cell is received. It may also include.

Hereinafter, an operation flowchart and an apparatus configuration diagram of an eNB and a terminal according to a first embodiment of the present invention will be described with reference to the accompanying drawings.

5 is an operation flowchart when a target eNB of the LTE system receives a handover request message according to the first embodiment of the present invention.

In step 501, the target eNB 474 receives a Handover Request message requesting a handover of the terminal 470 from the source eNB 472. In step 511, the destination eNB 474 stores SFN_Knowledge_Indication information corresponding to the terminal 470 included in the handover request message received from the source eNB 472. In step 513, the destination eNB 474 sets the RACH channel frame timing information and sets the RACH cycle, the RACH frame offset, etc. based on the local frame number within the P-BCH information transmission period. In step 515, the target eNB 474 sets radio channel information of other target cells such as a UL / DL control channel. In this case, the timing information for the UL / DL control channel may be set based on the local frame number within the P-BCH information transmission period or may be set based on the actual SFN instead. In step 521, the destination eNB 474 transmits a handover request acknowledgment (ACK) message to accept the handover request of the terminal to the source eNB 472 in response to step 501.

6 is an operation flowchart when a target eNB of an LTE system receives a handover RACH code from a terminal according to the first embodiment of the present invention.

In step 531, the destination eNB 474 receives a handover RACH code from the terminal 470 through the RACH channel. In this case, the handover RACH code is a RACH-related parameter set in step 515 and refers to a RACH code allocated exclusively to the terminal 470 by the target eNB 474. The information set in steps 513 and 515 is transferred from the target eNB 474 to the source eNB 472 through the handover request acknowledgment message in step 521, and the source eNB 472 sends a handover command (Handover). command) forwards to the terminal 470 through the message.

In step 541, the target eNB 474 extracts context information of the terminal 470 that has allocated the RACH code through the RACH code received in step 531. In step 543, the target eNB 474 checks whether SFN_Knowledge_Indication of the terminal information indicates that the target cell has SFN information of the target cell. In this case, if the SFN_Knowledge_indication flag in the handover request message received in step 463 is set to true, the target eNB 474 may know that the terminal has already obtained / maintained SFN information of the target cell. If the SFN-Knowledge_Indication indicates that the UE does not have SFN information of the target cell in step 543, the target eNB 474 proceeds to step 545, and the response message for the RACH code received in step 531 appears. Sets up all / part SFN information corresponding to the transmitted DL frame.

In step 547, other information is set in a RACH code response 481 for the RACH code received in step 531. In step 551, the frame received by the SFN set in step 545 is received in step 531. The RACH code response message, which is a response message for the RACH code, is transmitted.

7 is an operation flowchart of a terminal in an LTE system according to a first embodiment of the present invention. In step 601, the terminal 470 transmits a measurement result measurement report message 461 to the source eNB 472. In step 611, the terminal 470 checks whether the SFN information is acquired or maintained for the report target cell (the cell to perform the measurement report). If the terminal 470 acquires or maintains SFN information on the cell to be reported, in step 611, the terminal 470 proceeds to step 621 and indicates that the SFN_Knowledge_Indication flag is obtained / maintained by the SFN information of the report cell. The alert is set to a value of "true". In operation 623, the terminal 470 sets other information for the measurement report message. In operation 625, the terminal report 470 includes information including the SFN_Knowledge_Indication flag and other information for the measurement report message. 461).

On the other hand, if the terminal 470 does not acquire the full SFN information on the report target cell in step 611, the terminal does not acquire / maintain the SFN information of the report cell using the SFN_Knowledge_Indication flag in step 631. Set to "FALSE" value. After transmitting the measurement report message in step 625, if the terminal 470 has not acquired / maintained SFN information of the report cell, the terminal 470 transmits a SU to the SU-1 reception timing of the report cell in step 627. Receive -1 to obtain SFN information.

8 is an operation flowchart of a terminal receiving a handover command in the LTE system according to the first embodiment of the present invention.

When the terminal 470 receives a handover command message from the source eNB 472 in step 641, the RACH frame timing information of the target cell included in the received handover command message in step 643 (RACH cycle). , RACH frame offset, RACH sub-frame offset) is extracted. In step 645, the terminal 470 calculates a transmission frame of the RACH channel. The RACH channel transmission frame may be calculated as shown in Equation 1 above. That is, as shown in Equation 1, the frame satisfies the MOD (RACH transmission cycle = RACH frame offset) (local frame numbering in the P-BCH information transmission period boundary).

In step 647, the terminal 470 calculates the subframe timing in the RACH transmission frame calculated in step 645. The subframe may be mapped to a value indicated by the RACH subframe offset. For example, if the RACH subframe offset is 3, it becomes subframe 3. In step 649, the terminal 470 transmits the RACH code through the RACH channel in the frames and subframes calculated in step 645, and step 647. After receiving the handover command message from the source eNB 472, if the terminal 470 has not acquired / maintained SFN information of the target cell, the terminal 470 at the SU-1 reception timing of the target cell in step 651. Receive -1 to obtain SFN information.

9 is a device block diagram of the target eNB 474 according to the first embodiment of the present invention.

The transceiver 701 performs communication with the source eNB 472 or the terminal 470. In FIG. 7, the transceiver for the source eNB 472 and the terminal 470 is shown as one, but the transceiver for communicating with the source eNB 472 and the transmitter / receiver for communicating with the terminal 470 are physically different entities ( Entity). The Handover Request message received from the source eNB 472 via the transceiver 701 is analyzed through the L2 / L3 message analyzer / generator 711 and then the L2 / L3 message analyzer / generator ( 711 transmits SFN_Knowledge_Indication information included in the handover request message to the UE information (Context info) storage unit 721, the UE information storage unit 721 stores the SFN_Knowledge_Indication. The L2 / L3 message analysis / generation unit 711 receives the RACH channel information and uplink / downlink channel configuration information in the target cell from the scheduler / radio resource allocator 731, and then the RACH channel information and uplink. After generating a handover request acknowledgment message (465) including the link / downlink channel configuration information, and transmits it to the source eNB (470) through the transceiver 701.

In addition, when the L2 / L3 message analysis / generation unit 711 receives the RACH code from the terminal through the transceiver 701, the L2 / L3 message analyzer / generator 711 searches for the terminal to which the RACH code has been allocated through the UE information storage unit 721. After analyzing the information, if necessary, the SFN value of the DL frame in which the RACH code response message, which is a response to the RACH code, is set, and the RACH code response message is transmitted to the terminal 470 through the transceiver 701.

10 is a block diagram of a terminal 470 according to an embodiment of the present invention.

The transceiver 801 communicates with the eNBs 472 and 474, and the measurer 811 performs a radio channel state through the transceiver 801. The measurement unit 811 measures radio intensity of a sync channel (SCH) / pilot channel, receives a P-BCH, and applies a measurement related parameter included in the P-BCH to the measured radio intensity. Should be. The management unit 811 may calculate a local frame number within a P-BCH information transmission period when receiving the P-BCH to perform the measurement through the transceiver 801, and the SFN maintenance unit 831 ) Maintains / manages a local frame number within the P-BCH information transmission period calculated by the measurement unit 811. As a result of the measurement performed by the management unit 801 of the terminal 470 according to whether the SFN maintenance unit 831 obtains or maintains the full SFN information, the L2 / L3 message analysis / generation unit 821 is performed. It determines which value (true or false) to set the SFN_Knowledge_Indication flag when sending a measurement report message.

The L2 / L3 message analyzer / generator 821, which receives the handover command message through the transceiver 801, analyzes the RACH, uplink / downlink channel configuration information, and then, in the RACH timing parameter and SFN maintenance unit 831, The RACH transmission timing is calculated using the local frame number in the P-BCH information transmission period that has been maintained, and the RACH is performed. When the L2 / L3 message analysis / generation unit 821 receives the RACH code response message, which is a response message to the RACH code transmitted by the L2 / L3 message analyzer 801, if the RACH response message includes SFN information, The analysis is performed to maintain the SFN maintenance unit 831.

11 is a diagram illustrating a SFN transmission method and a handover procedure according to a second embodiment of the present invention.

Reference numerals 1101, 1103, 1105, 1107, and 1109 indicate P-BCHs having a 40 ms information transmission period, and reference numerals 1111, 1113, 1115, and 1117 indicate that reference numerals 1101 are distributed and transmitted in each frame. 1121, 1123, 1125, and 1127 indicate that reference numeral 1103 is transmitted distributed in each frame.

Reference numerals 1141 and 1143 denote SU-1. In the second embodiment of the present invention, it is proposed to transmit the SFN through SU-1. Accordingly, SFN1 is transmitted at 1141 and SFN9 is transmitted at 1143. As shown in FIG. 11, in the second embodiment of the present invention, unlike FIG. 4, which is the first embodiment of the present invention, the SFN starts from 1, but it can be applied in the same manner in principle.

As shown in FIG. 11, when the SFN is transmitted through SU-1, the handover procedure according to the second embodiment of the present invention operates as follows.

First, at 1151, a UE 1130 receives a P-BCH for a target cell. The terminal 1130 detects a scrambling code used for the received P-BCH through P-BCH reception, and obtains a value of SFN 2LSB mapped to the detected scrambling code. For example, if the scrambling code used for the P-BCH received at reference numeral 1151 is the scrambling code used for the P-BCH 1113 of the second frame within 40 ms of the P-BCH information transmission period, SFN 2LSB (Least significant bit) value This is mapped to 2. The terminal updates and maintains the SFN 2LSB value calculated at reference numeral 1151 whenever the frame increases.

For example, every time the frame increases, the SFN 2LSB value is 2-> 3-> 4-> 1-> 2-> 3-> 4. Circulate An operation of acquiring the SFN 2LSB value or information through P-BCH reception may be referred to after reference numeral 1151 in FIG. 11. For example, the reference number 1171 or later may be used.

Thereafter, the terminal 1130 transmits a measurement report message to the source base station 1132 at reference numeral 1161, and the source base station 1132 transmits the target base station 1134 as shown by reference numeral 1163. Handover Request message is sent to the user. The target base station 1134 receiving the handover request message transmits a handover request acknowledgment message to the source base station 1132 at reference numeral 1165 and the RACH frame and uplink or downlink to be used in the target cell. Control channel frame information is indicated by k value.

The k value is a parameter that allows the terminal 1130 to find out which frame is a RACH frame or an uplink or downlink control channel frame. When the source base station 1132 that has received the handover request acknowledgment message at 1165 determines the handover, it transmits a handover command message to the terminal 1130 at the reference 1167 to handover to the target cell. To instruct.

However, if the terminal 1130 does not obtain or maintain the actual SFN information of the target cell when the terminal 1130 receives the handover command message at 1167, the terminal 1130 may transmit a RACH frame, uplink or downlink control channel. Performing the RACH procedure by using the SFN 2LSB value obtained through P-BCH reception at 1151 instead of the actual SFN value and updated every frame as a value for finding a frame as shown in Equation 2 above. To calculate the position of the RACH frame for transmitting the RACH preamble or the position of the frame to transmit and receive control information for the uplink or downlink control channel. That is, the position of the frame having the SFN satisfying Equation 2 is the position of the RACH frame calculated according to the second embodiment of the present invention or the position of the frame for transmitting control information.

That is, the frame satisfying Equation 2 is an RACH frame or an uplink / downlink control channel frame. For example, when k = 2 for calculating the position of the RACH frame, the SFN 2LSB value at the time of receiving the handover command message 1171 is 3 as shown by reference numeral 1172, so that the next frame is the RACH frame. It can be seen that. This is because the next frame 1117 has an SFN 2LSB value of 4 as shown by reference numeral 1174, and satisfies 4 mod 2 = 0 of Equation 2 above. The terminal 1130 transmits a PACH preamble to the target base station 1134 as shown by reference numeral 1183 through the radio resource of the indicated subframe of the next frame at 1181. After receiving the handover command message (1167), the terminal 1130 generally transmits a random access preamble in the nearest RACH frame, but is received in the RACH frame that satisfies Equation 2 even after 1181. A random access preamble can be transmitted through a radio resource of a subframe.

As another example of the second embodiment of the present invention, if the position of the CQI channel frame in the target cell is k = 4, the terminal 1130 receives the handover and then the SFN 2LSB value of Equation 2 above. Compute the CQI frame that satisfies mod 4 = 0. That is, a frame having a SFN 2LSB value of 4 becomes a CQI channel frame. The terminal 1130 transmits CQIs as shown by reference numerals 1195 and 1197 through radio resources of subframes indicated by reference numerals 1191 and 1193.

12 is a flowchart illustrating an operation when the terminal 1130 receives a handover command message according to the second embodiment of the present invention.

In step 1211, the terminal 1130 analyzes the P-BCH scrambling code through P-BCH reception of the target cell and obtains an SFN 2LSB value mapped to the P-BCH scrambling code in the received frame. In step 1212, the terminal 1130 updates and maintains the SFN 2LSB value obtained in step 1211 for each frame. For example, if the SFN LSB 2-bit value obtained through P-BCH reception in step 1211 is 1, the next frame is 2, the next frame is 3, the next frame is 4, the next frame is 1,. Is maintained as 2, 3, 4, 1, 2, 3, 4.

In step 1215, the terminal 1130 receives a RACH frame or an uplink / downlink control channel frame k value through a handover command message. In FIG. 12, steps 1211 and 1213 are shown as operations before receiving the handover command message in step 1215, but steps 1211 and 1213 may be performed after receiving the handover command message in step 1215. In step 1221, the terminal 1130 checks whether the actual SFN value of the target cell is obtained / maintained. If the result of the check in step 1221 is obtained or maintained, the UE 1130 proceeds to step 1231 to use the actual SFN value. The RACH frame or uplink and downlink control channel frames of the target cell are found. For example, the frame satisfies the actual SFN value mod k = 0.

On the other hand, if the result of the check in step 1221 does not acquire or maintain the actual SFN value of the target cell, the terminal 1130 proceeds to step 1233 by using the SFN LSB 2-bit value as in the second embodiment of the present invention. Identify the cell's RACH frame or uplink and downlink control channel frames. For example, as shown in Equation 2, a frame satisfying the SFN 2LSB value mod k = 0 becomes an RACH frame or an uplink and downlink control channel frame of a target cell. In operation 1231 or 1233, the terminal 1130 having calculated the RACH or uplink / downlink control channel frame position transmits and receives the RACH preamble or corresponding control information through the radio resource of the subframe indicated in step 1241.

1 is a diagram illustrating an example of a Long Term Evolution (LTE) structure of a next generation (Evolved) UMTS mobile communication system;

2 is a diagram illustrating an example of system frame number transmission in a general 3GPP UMTS system;

3 is a diagram illustrating an embodiment of transmitting system information in a 3GPP LTE system to which the present invention is applied;

4 is a diagram illustrating a SFN transmission method and a handover procedure according to the first embodiment of the present invention;

5 is an operation flowchart when a target eNB of a LTE system receives a handover request message according to the first embodiment of the present invention;

6 is an operation flowchart when a target eNB of an LTE system receives a handover RACH code from a terminal according to the first embodiment of the present invention;

7 is an operation flowchart of a terminal in an LTE system according to a first embodiment of the present invention;

8 is an operation flowchart of a terminal receiving a handover command in the LTE system according to the first embodiment of the present invention;

9 is a device block diagram of a target eNB according to a first embodiment of the present invention;

10 is a block diagram of a terminal according to an embodiment of the present invention;

FIG. 11 is a diagram illustrating a SFN transmission method and a handover procedure procedure according to a second embodiment of the present invention; FIG.

12 is a flowchart illustrating an operation when a terminal receives a handover command message according to a second embodiment of the present invention.

Claims (5)

In the handover method in a mobile communication system, Performing a measurement by the terminal on the target base station (Target_eNB) of the target cell to be handed over; When the terminal does not maintain a system frame number for the target cell, transmitting a measurement report message that is set to have no system frame number to a source base station; When the source base station receives the measurement report message, transmitting a handover request message set to have no system frame number to the target base station; When the terminal does not maintain the system frame number, the target base station acknowledges a handover request acknowledgment including a frame offset value for local frame numbering in a boundary of a P-BCH information transmission period to the terminal. Transmitting a message to the source base station; The source base station receiving the handover request acknowledgment message, transmitting a handover command message to the terminal; When the terminal receives a handover command message from the source base station, calculating a transmission frame of a random access control channel using a local frame number of a primary broadcast channel included in the handover command message; Transmitting, by the terminal, a code of the random access control channel to the target base station; And transmitting, by the target base station, a frame number in which a response message for the received random access control channel code is transmitted, to be included in a random access control channel code response message and transmitted. In the handover method in a mobile communication system, Checking whether the terminal has a system frame number (SFN) of the target cell when the terminal receives the handover command message; If the SFN for the target cell is not known, among the random access channel and the control channel in the target cell by using the least significant 2 bits of the SFN that can be obtained from the target cell through a prime broadcast control channel (P-BCH). Handover method in a mobile communication system comprising the step of calculating at least one frame position. The method of claim 2, If the calculated frame is the random access channel frame, transmitting a random access channel preamble for performing the random access channel procedure at the calculated position. The method of claim 2, And if the calculated frame is the control frame, transmitting and receiving control information for the control channel at the calculated position. The method of claim 2, The position of the frame is a handover method in a mobile communication system, characterized in that the frame having a SFN satisfying the following equation, 2 LSB (Least Significant Bit) mod k = 0 Here, k is a value for calculating a frame position of a random access channel or a control channel, a value given from a base station, and mod represents a modular operation, and a position of a frame satisfying the equation.

Images