KR20040050173A - The method of handovering for synchronization timing failure - Google Patents

Abstract

PURPOSE: A method of performing a handover process for a synchronous timing error is provided to stop a handover process when a synchronous error is generated while a mobile station moves between cells, or to cancel a pre-generated wireless link, thereby preventing a waste of wireless resources. CONSTITUTION: A mobile station transmits a signal to a wireless base station, and measures a synchronous value(310). The mobile station transmits a measurement report that includes the measured synchronous value therein to a wireless network control station(320). The wireless network control station calculates a synchronous reference value to perceive whether the wireless base station is synchronized with the mobile station(330). The control station decides whether the synchronous value included in the measurement report is within the range of the synchronous reference value(340). If so, the control station performs a soft handover process(350). If the synchronous value is not included, the control station transmits a measurement control message to the mobile station(360).

Description

How to perform a handover for a synchronous timing error {THE METHOD OF HANDOVERING FOR SYNCHRONIZATION TIMING FAILURE}

The present invention relates to an asynchronous IMT-2000 system. In particular, when an error of synchronization time occurs as a mobile radio station moves between a cell or a radio base station, the handover is stopped or the radio link is released to optimize radio resources. The present invention relates to a method for performing handover.

In general, the IMT-2000 system is divided into a synchronous method centering on Europe and Japan and an asynchronous method centering on the United States, which does not require synchronization between base stations using a Global Positioning System (GPS). It is distinguished from synchronous in that it does not. Asynchronous is continuously being standardized through the 3rd Generation Partnership Project (3GPP).

The asynchronous IMT-2000 system uses the DS_MAP (Direct Sequence Mobile Application Protocol), which has the advantage of high frequency efficiency and global roaming.

In general, in a communication system, when a handover or handoff mobile station moves out of an area where a call is set up to move to another radio station (or cell), after moving to a call path to maintain a call It refers to converting into a wireless base station (or cell). The handover is divided into a hard handover that disconnects an existing call and then connects to a new wireless base station, and a soft handover that maintains a call path with two wireless base stations (or cells) at the same time. In particular, soft handover between cells of the same radio base station is referred to as softer handover.

1 is a block diagram illustrating an asynchronous IMT-2000 system.

Asynchronous IMT-2000 system is composed of a core network 100, a radio network control station 120, a plurality of radio base station 140 and a mobile radio station (160). The core network (100) is connected to the radio network control station 120 via the Iu interface. The core network 100 includes a circuit switched network (not shown), which is an area for processing voice call-based bearer connection and signal, and a packet switched network (not shown), which is an area for processing packet call-based bearer connection and signal.

The radio network control station (120) supports soft handover and radio resource management algorithms, and uses the same interface for the circuit switched and packet switched domain connections of the core network and circuit switched and packet switched to the air interface protocol stack. Perform data processing functions. The radio network control station 120 is connected to the plurality of radio base stations 140 via an Iub interface.

The radio base station 140 is composed of a plurality of cells, and performs an L1 processing function that is an air interface such as channel coding, interleaving, speed matching, spreading, and the like. The radio base station is coupled to the mobile radio station 160 via a 140 Uu interface. The mobile station 160 has subscriber identification, authentication algorithm implementation, authentication and password storage, and subscriber information.

The following describes a softer handover process in the asynchronous IMT-2000 system according to the related art having the above configuration.

First, when the mobile radio station 160 moves to another radio base station 140 or a cell area, a handover occurs, and the mobile radio station 160 performs a measurement quantity for the cell after the movement to perform a radio link. A measurement report for addition is sent to the radio network control station 120.

Upon receiving the measurement report, the radio network control station 120 transmits a radio link add request message to the radio base station 140a to add a radio link. Upon receiving the ad message, the radio base station (140a) transmits a response message to the radio network control station (120).

Upon receiving the response message, the radio network control station 120 transmits an active set update message to the mobile radio station 160 to modify the active set of the mobile radio station 160. If the active set is normally modified, the mobile station 160 sends an active set update complete message to the wireless network control station 120.

The following describes a soft handover procedure when moving between different radio base stations according to the prior art.

First, when a handover between different base stations occurs, the radio network controller 120 transmits a radio link setup request message to the radio base station 140b after moving to add a new radio link.

Upon receiving the setup message, the radio base station 140b transmits a response message to the radio network control station 120. When the wireless network control station 120 receives the response message, it performs ALCAP Iub data transport bearer setup to break through the ATM network. The physical layer of the radio base station 140b is then set up.

After setting up the physical layer, the radio network control station 120 sends an active set update message to the mobile radio station 160 to modify the active set. If the active set is normally modified, the mobile station 160 transmits an active set update complete message to the wireless network control station 120.

2 is a state transition diagram of a radio link set through a window finder (not shown) of a radio base station modem. The radio base station modem starts window searching using the frame offset and the chip offset included in the radio setup request message received from the radio network control station 120 (not shown).

Referring to FIG. 2, first, in the initial state, when the window finder (160) captures a signal of a predetermined level or more from the mobile radio station (160), the radio link establishment message is transmitted to the radio network control station (120) and the radio link is in a synchronous state. Transition. Then, if the signal degrades below a certain level, a radio link failure message is sent and the radio link transitions to an asynchronous state. Therefore, a transition between the synchronous state and the asynchronous state occurs due to the quality of the signal. The radio link failure message occurs while transitioning to the asynchronous state only when the transition to the synchronous state occurs.

However, the handover method in the prior art IMT-2000 system having the configuration and operation process as described above poses the following problems.

If there is an error in the mobile station's 160 synchronization measurement, the wireless network control station 120 may receive an incorrect OFF and Tm, and thus the window finder of the radio base station modem (not shown) that is operated from the mobile station (160). ) The signal will not be captured, and the wireless link will not be able to transition to a synchronous state, and will eventually be unable to transmit a wireless link failure (see FIG. 2).

Accordingly, unnecessary UTRAN resources are used from the radio network control station 120 to the radio base station 140, thereby reducing the efficiency of the system and increasing the load due to unnecessary messages.

The purpose of the handover method for the synchronization timing error in accordance with the present invention for solving the problems of the prior art as described above is to stop the handover when the synchronization time error occurs as the mobile station moves between the cell or radio base station or This is to optimize the radio resources by releasing the radio link.

1 is a block diagram of an asynchronous IMT-2000 system configuration of a spread spectrum method (DS_MAP; Direct Spread_Mobile Application Part).

2 is a state transition diagram of a set of radio links through a window searcher of a radio base station modem.

3 is a flow chart for performing softer handover when moving between cells of a mobile radio station in accordance with the present invention.

4 is a flow chart for performing soft handover release when moving between radio base stations of a mobile radio station according to the present invention.

5 is a graph illustrating a radio link releasing procedure due to synchronization failure when moving between radio base stations.

<Description of the symbols for the main parts of the drawings>

100: core network 120: wireless network control station

140a, 140b: Radio base station 160: Mobile radio station

A method for performing handover for a synchronization timing error according to the present invention for achieving the above object, when the mobile station moves between cells of the same radio base station, the mobile station measures the synchronization value for the cell after the movement Transmitting the measured synchronization value to a wireless network control station by the mobile radio station, calculating a synchronization reference value required for synchronization timing of a radio link, and measuring the measured synchronization value. And performing a handover only when included in the range of the calculated synchronization reference value.

The synchronization reference initial value for calculating the synchronization reference value may be stored in advance in the radio network control station. The synchronization reference initial value is stored in a database of the wireless network control station including a frame offset and a chip offset.

In another aspect, the present invention, when the mobile station moves between other wireless base stations, measuring the delayed arrival time of the data transmitted from the wireless network control station to the wireless base station after the handover is carried out, and the timing adjustment message including the delayed arrival time Transmitting to the physical layer of the wireless network control station; transmitting, by the physical layer of the wireless network control station, a synchronization_failure message to its network layer when the delayed arrival time is out of a tolerance range; The network layer is characterized in that it is executed sequentially, including the step of releasing the already created radio link.

The synchronization failure message may be stored in advance in the radio network control station.

According to the present invention, when the mobile radio station moves between cells of the same radio base station, the mobile radio station measures the synchronization value for the cell after the movement, and the mobile radio station transmits the measured synchronization value to the radio network control station. A function of calculating a synchronization reference value required for synchronization timing of a radio link by the wireless network control station, and a function of performing a handover only when the measured synchronization value is within a range of the calculated synchronization reference value. A computer readable recording medium having recorded thereon a program is provided.

In addition, according to the present invention, when the mobile station moves between other radio base stations, a function of measuring the delayed arrival time of data transmitted from the radio network controller to the radio base station after the handover is performed, and a timing adjustment message including the delayed arrival time. Is transmitted to the physical layer of the radio network controller, and the physical layer of the radio network controller is configured to transmit a sync_failure message to its network layer when the delayed arrival time is out of tolerance. The network layer provides a computer readable recording medium having recorded thereon a program for sequential execution, including the function of releasing an already created radio link.

The following describes in detail with reference to the accompanying drawings a preferred embodiment of the present invention handover method for the synchronization timing error.

First, the present invention has the same configuration as the apparatus of the asynchronous IMT-2000 system according to the prior art, even if the present invention performs the handover method for the synchronous timing error. Accordingly, the apparatus according to the present invention consists of the core network 100, the radio network control station 120, the radio base stations 140a and 140b and the mobile radio station 160.

The following describes an operation process by the handover method for the synchronization timing error of the present invention having the configuration as described above.

First, the frame offset and chip offset (i.e., synchronization reference base value) for each cell of the radio base station 140a, which have been set up in advance, are stored in the database of the radio network control station 120. In addition, a Tcell indicating a difference in arrival time of a signal transmitted and received between the radio base station 140a and the mobile radio station 160 in each cell is also stored in the database of the radio network control station 120.

3 is a flow chart for softer handover performance during inter-cell movement of mobile radio station 160 according to the present invention.

First, the mobile radio station 160 transmits a signal to the radio base station 140a through the Uu interface to measure synchronization values (OFF and Tm) (step 310).

After performing step 310, the mobile station 160 transmits the measurement report including the measured synchronization value to the wireless network control station 120 (step 320).

The radio network controller 120 calculates a synchronization reference value (that is, OFF and Tm) as a reference for determining whether the radio base station 140 and the mobile radio station 160 are synchronized (step 330). Hereinafter, when the mobile station 160 is located in the optical repeater range, the OFF and Tm margins are calculated.

First, find the photo_margin for the optical repeater.

{Equation 1}

Optical_Margin [chip] = optical_range [m] / 78 + cable_length [Km] * cable propagation delay [chip / Km] ---- --------(One)

Here, wide_range means the radius of the optical repeater. This corresponds to 78m light propagation length per chip. Cable_Length represents the length of the cable connecting the radio network control station 120 and the radio base station 140a. Cable_propagation delay indicates the time delay in transmitting a signal through the cable in units of chips.

For example, the cable length is set to 2 km, the cable propagation delay is set to 15 chips, and the light radius is set to 780 m. Thus, the photo_margin is 780/78 + 2 * 15 = 40 chips.

Next, calculate the T-cell margin for the cell before and after the movement.

{Equation 2}

Tcell_Margin_ [chip] = Tcell (Pre-Move Cell)-Texel (Post-Move Cell) ------------ (2)

For example, the tissel of the cell before the movement is set to 0 and the ticell of the cell after the movement is set to 512 chips. Thus, the T-cell margin is -512 chips. In general, the tissel ranges from 0 to 2304 chips.

Next, the gross margin is calculated by the photo margin and the other margin factors obtained above.

{Equation 3}

Total Margin = Propagation Delay Margin PD_Margin + RTX Margin + Photo Margin ------------ (3)

Since the propagation delay is 768 chips according to the TS specification of 3GPP, the propagation delay_margin is set to 768 chips. RTX margin refers to a time difference between Rx and Tx of the mobile station 160 when the handover occurs more than two times.

In this regard, when two or more handovers occur, the Tx moves because the reference finger of the mobile station 160 changes. The spec recommends moving 1/2 chip per 10 frames, moving to 5 chips per second. If the time delay between Rx of the mobile radio station 160 is within 256 chips, the normal call proceeds, and if it is more than 256 chips, the radio link that is already established is released or remeasured through internal measurement of the mobile radio station 160. (Reconfigure). Therefore, set the RTX margin to 256 chips.

According to the above, the total margin is 768 + 256 + 40 = 1064 chips.

Subsequently, the evaluation value A and the evaluation value B are obtained using the gross margin and the T-cell margin calculated above, and the evaluation value minimum and evaluation value maximum are obtained.

{Equation 4}

Estimate_A (chip) = frame offset * 38400 + Tm + total_margin + tissel_margin ------------ (4)

Here, the frame offset is stored in advance in the radio network control station 120. According to equations (3) and (4), the evaluation value A is -1064 + (-512) = -1576 chips. In the following, the evaluation_minimum (Estimate_Min) is obtained according to whether evaluation_A is positive or negative.

First, if evaluation_A is positive,

{Equation 5}

Val_min = val_a -------------- (5)

Next, if evaluation_A is negative,

{Equation 6}

Val_min = 256 * 38400-val_A ------------- (6)

According to the above, since evaluation value_A is -1576 chips, evaluation value_minimum becomes 9828824 chips by Equation (6).

{Equation 7}

Estimated_B (Estimate_B) = Frame Offset * 38400 = Tm + Total_Margin + Tissel_Margin ------------- (7)

According to equations (3) and (4), the evaluation value B is 1064 + (-512) = 552 chips. In the following, Estimate_Max is calculated according to whether evaluation_B is positive or negative.

If evaluation_B is positive,

{Equation 8}

Val_max = val_B mod 9830400 --------- (8)

The mod symbol "mod" means the remainder after division.

If evaluation_B is negative,

{Equation 9}

Val_max = 256 * 38400-val_B ---------- (9)

According to the above, since the evaluation value B is 552 chips, the evaluation value maximum is 552 chips according to Equation (8).

Finally, OFF and Tm are calculated using the above-mentioned evaluation value_max and evaluation value_minimum.

{Equation 10}

OFF * 38400 + Tm = (0 ~ val_max) or {val_min ~ val_min ~ (38400 * 256-1)} ------------- (10)

OFF is frame unit, so multiply by 38400 to switch to chip unit. According to equations (6) and (8), OFF + Tm becomes (9828824 to 9830399) or (0 to 552). Therefore, if OFF is 0, Tm is from 0 to 552, and if OFF is 255, Tm is from 36824 to 38399.

If the mobile station 160 is not in the optical repeater region, there is no propagation delay, and only one handover has occurred, then OFF is 255 and Tm is 37888.

After performing step 330, the wireless network control station 120 determines whether OFF and Tm included in the measurement report fall within the range of OFF and Tm obtained in step 330 (step 340).

As a result of performing step 340, if the synchronization value belongs to the synchronization reference value, softer handover is performed (operation 350). Accordingly, the radio network control station 120 transmits a radio link add request message to the radio base station 140a.

As a result of performing step 340, if the synchronization value does not belong to the synchronization reference value, the mobile station 160 transmits a measurement control message (operation 360). Upon receiving the message, the mobile station initializes its physical layer to prevent an error in re-measurement 160.

Hereinafter, a method of performing handover when the mobile station 160 moves to another radio base station 140b area will be described.

4 is a flow chart for performing soft handover release when the mobile radio station 160 moves between radio base stations according to the present invention.

Since the wireless network control station 120 cannot infer OFF and Tm using the frame offset and the chip offset, the mobile network control station establishes a call based on the measurement report requested by the mobile station 160 (step 410). In addition, the synchronization_failure message between the physical layer and the network layer 120 of the wireless network control station is defined.

After performing step 410, if downlink data is not received in the receiving window of the channel terminal of the radio base station 140b, the delay time for the arrival of the actual data is measured (step 420). Referring to FIG. 5, since downlink data is for frame 150 of the radio base station 140 and did not enter the reception window of the radio base station 140b, the delayed arrival time should be measured.

After performing step 420, a timing adjustment message including the measured delayed arrival time is transmitted to the physical layer of the wireless network control station 120 (step 430).

The physical layer 120 of the radio network control station determines whether the radio base station 140b is synchronized with the mobile radio station 160 through the received delayed arrival time (step 440). Here, if the delayed arrival time is more than -10 ms or +10 ms, the synchronization has failed.

After performing step 440, if the delayed arrival time is more than -10 ms or +10 ms, the physical layer 120 of the wireless network control station transmits a sync_failure message to its network layer (step 450).

In step 450, the network layer that receives the sync_failure message performs a handover release procedure to the radio base station 140b (step 455). Thus, to release the established radio link and transmit a measurement control message to the mobile radio station 160 to prevent re-errors of the measurement. In this case, the mobile station 160 initializes its physical layer for remeasurement.

As a result of performing step 440, if the delayed arrival time is within -10 ms or +10 ms, the previously set call is maintained (step 460).

The above embodiments of the present invention are merely one embodiment of the technical idea of the present invention, and of course, other modifications can be made within the technical idea of the present invention by those skilled in the art.

According to the method of performing the handover for the synchronization timing error of the present invention having the above configuration and operation process, the following effects are obtained.

In case of an error in synchronization time when moving between a cell or a base station of a mobile station, stopping the handover or releasing the radio link prevents the radio network control station from generating unnecessary messages, thereby preventing waste of UTRAN resources and optimizing radio resources. Will be able to.

Claims (7)

When the mobile station moves between cells of the same radio base station, the mobile station measuring a synchronization value for the cell after the movement; Transmitting, by the mobile radio station, the measured synchronization value to a radio network control station; Calculating, by the radio network control station, a synchronization reference value necessary for synchronization timing of a radio link; And performing a handover only when the measured synchronization value is within the range of the calculated synchronization reference value. The method as claimed in claim 1, wherein the initial value of the synchronization reference for calculating the synchronization reference value is pre-stored in the radio network control station. 3. The method according to claim 2, wherein the synchronization reference initial value is stored in a database of the radio network control station including a frame offset and a chip offset. When the mobile station moves between other wireless base stations, measuring a delayed arrival time of data transmitted from the wireless network control station to the wireless base station after handover is performed; Transmitting a timing adjustment message including the delayed arrival time to a physical layer of the radio network control station; Transmitting, by the physical layer of the radio network control station, a synchronization_failure message to its network layer when the delayed arrival time is out of a tolerance range; And wherein said network layer is executed sequentially, including releasing a radio link that has already been created. 5. The method as claimed in claim 4, wherein the synchronization_failure message is stored in advance in the radio network control station. When the mobile station moves between cells of the same radio base station, the mobile station measures a synchronization value for the cell after the move; Transmitting, by the mobile radio station, the measured synchronization value to a radio network control station; A function of the radio network controller calculating a synchronization reference value necessary for synchronization timing of a radio link; And a program for executing a function for executing a handover only when the measured synchronization value falls within a range of the calculated synchronization reference value. A function of measuring a delayed arrival time of data transmitted from a radio network controller to the radio base station after the handover is performed when the mobile station moves between other radio base stations; Transmitting a timing adjustment message including the delayed arrival time to a physical layer of the radio network control station; A physical layer of the wireless network control station, transmitting a sync_failure message to its network layer when the delayed arrival time is out of a tolerance range; And said network layer recorded a program for sequentially executing, including the function of releasing a radio link which has already been generated.