KR20040107535A - Method for controlling handover condition adaptively by the number of active set in mobile communication system - Google Patents

Abstract

PURPOSE: A method for adaptively applying handover conditions according to the number of active sets in a mobile communication system is provided to increase the efficiency in using radio resources by efficiently maintaining the number of active sets according to radio environments. CONSTITUTION: In a method that a radio network controller establishes active set addition conditions through the pilot signal information of base stations received from a mobile station, the radio network controller receives a measurement report message, including the pilot strength information of adjacent base stations, from the mobile station. The radio network controller re-establishes an active set addition condition reference offset value(add_reporting_range) and an addition reference time(add_timer) for a base station to be added to the active set according to the number of the base stations belonging to the active set. The radio network controller transmits the re-established active set addition conditions to the mobile station.

Description

{METHOD FOR CONTROLLING HANDOVER CONDITION ADAPTIVELY BY THE NUMBER OF ACTIVE SET IN MOBILE COMMUNICATION SYSTEM}

The present invention relates to a mobile communication system and, more particularly, to a method for controlling soft handover of a mobile station having one or more base station active groups in a mobile communication network.

In general, a code division multiple access (CDMA) mobile communication system uses a cell structure to support a large number of users with limited radio frequency (RF) resources. In other words, the CDMA mobile communication system supports a larger number of users by allocating the entire serviceable area to a small area called a cell and allocating RF resources to each cell. Here, the cell refers to an area where a service is provided by a specific base transceiver station, and each cell is identified through a unique scrambling code used in a corresponding base station.

Therefore, when a mobile station (MS) located in a specific cell moves to another cell in the CDMA mobile communication system, the service must be continuously performed even in a cell moved through hand-over. That is, the handover refers to changing a call path to a moved cell in order to keep a call when the terminal moves out of a serving base station (source base station) area (cell) to another base station (target base station). To this end, the terminal measures the received signal strength from adjacent cells to determine whether the handover is possible. The received signal strength may be expressed in dB.

The handover may be divided into a soft handover and a hard handover. When the handover is required, the soft handover is performed in such a manner that the terminal establishes a new channel with the target base station while the channel with the source base station is set, and disconnects any one channel at a predetermined time. When the handover is required, the hard handover is performed in such a manner that the terminal disconnects the established channel from the source base station and establishes a new channel with the target base station. Here, the channel may be represented as a traffic channel.

Accordingly, the soft handover can improve the quality of service to the terminal, but must simultaneously use channels to the source base station and the target base station. The hard handover needs to use only one channel with either the source base station or the target base station, but has a disadvantage of poor quality of service. Typically, the soft handover is supported in a CDMA mobile communication system using a digital method, and the hard handover is supported in an analog mobile communication system and a part of a mobile communication system using a digital method. The hard handover is used for handover between frequencies or exchange periods corresponding to a part of a mobile communication system using a digital method, and is used in a data service in an asynchronous mobile communication system. In the following description, only the soft handover is assumed.

1 is a diagram conceptually illustrating a soft handover in a CDMA mobile communication system.

Referring to FIG. 1, it can be seen that the terminal 114 located in Cell 1 serviced from the source base station 110 is moving to the handover region. Typically, the terminal 114 simultaneously receives the received signal from the source base station 110 and the received signal from the target base station 112 corresponding to another adjacent base station, and measures and compares the strengths of the two received signals. This determines whether handover is required.

In FIG. 1, when the terminal 114 is located in the handover region, it is shown that the received signal strengths from the source base station 110 and the target base station 112 are measured. However, even when the terminal 114 is located in the cell 1, the received signal strength from the target base station 112 can be measured.

Accordingly, when the terminal 114 moves to the handover region, when the received signal of the desired strength is received from the target base station 112, the terminal 114 receives a pilot strength measurement message for requesting handover processing. Transmit to 110. The source base station receiving the pilot measurement message reports this to a base station controller (not shown), thereby allowing the base station controller to perform a procedure for soft handover processing for the terminal 114 for a predetermined time.

The BS controller determines whether to perform a soft handover after reviewing various conditions through the procedure for the soft handover processing, and if the soft handover is possible, sends a hand-over direction message to the terminal. 114). The terminal 114 transmits a handover completion message to the base station controller in response to a predetermined time elapsed. In this case, the target base station 112 and the newly set channel enters an active state.

As described above, the terminal 114 measures the strength of the received signal from the source base station 110 and the received signal from the target base station 112, respectively, and determines whether to perform handover based on the measured strengths. Done.

Meanwhile, reverse link transmission from the terminal during the soft handover is received by two or more base stations. Since there are at least two base stations trying to detect the transmission of the mobile station during soft handover, the probability of a normal signal connection can be increased and a macro diversity gain can be obtained. An example of macro diversity gain for reverse link coverage is shown in Table 1 below.

Eb / No ITU Pedestrian A ITU Vehicular A Single link 11.3 dB 8.5 dB Macro Diversity Results (Equal Power / 3dB Difference) 7.3dB / 8.6dB 6.3dB / 7.7dB Macro Diversity Gain-Soft Handover Gain (Equal Power / 3dB Difference) 4.0dB / 2.7dB 2.2dB / 0.8dB

Table 1 shows macrodiversity at 3km / h of two base stations and 10ms interleaving. Referring to Table 1, the path loss is the same in both base stations and when the loss between the base stations is 3 dB. In the first case, it gives high macro diversity gain, and when the path loss difference increases, the macro diversity gain decreases and the mobile station is not in soft handover but connected to only one base station. Reducing the available multipath diversity as described above reduces the macrodiversity gain.

Reverse link transmission from the mobile station during soft handover is received by two sectors of one base station. The signals from the two sectors are the maximum ratio combined in the base station baseband rake receiver. Selective combining in soft handover is used in the base station controller. On the other hand, maximum ratio combining of soft handovers provides better performance than selective combining of soft handovers.

By performing the soft handover as described above, the mobile station may have a macro-diversity effect, but when the excessive number of active sets between the mobile station and the radio network control station increases, the efficiency of radio resource usage is reduced. In addition, when the number of fingers of the mobile station is limited and the number of fingers capable of demodulating traffic has three active groups, the increase in macro diversity effect is not significant. In addition, if the maximum allowable number of active groups is limited to 3, handover for frequently replacing cells belonging to the active group occurs frequently in the weak field where the signals of several cells overlap.

On the other hand, the soft handover method of the CDMA mobile communication system is determined based on the pilot signal strength measured by the mobile station, and the handover condition is largely determined by the pilot signal strength measurement value.

The first method is to determine the pilot signal strength measurement value by comparing it to an absolute threshold.

The second method is a method added from IS-95B to determine a handover condition using a relative difference in the strength of pilot signals.

The absolute threshold comparison method determines a handover condition using only an absolute value regardless of the wireless network environment. On the other hand, the method using the relative difference between pilot signal measurements is a more advanced method. The pilot signal strength that generates handover is applied differently according to the wireless network environment, thereby reducing the frequency of handover and reducing the handover area. The efficiency of resource use is increased.

The handover method of the WCDMA method of the 3GPP standard supports both a method of making a handover decision based on an absolute value of the pilot signal strength and a method of determining a handover based on a relative difference between pilot signal strengths.

In the case of using the difference in the strength of the pilot signal, the overall handover frequency and the handover area can be reduced than the absolute threshold comparison method, but in the case of the region where several pilot signals overlap in the medium weak field propagation environment In addition, the terminal receives pilot signals of a weak electric field among similar signals. In such a case, there is a problem in that the frequency of handover is higher than in the case of using an absolute threshold value, and the number of active groups is increased, thereby decreasing radio resource usage efficiency.

Therefore, although the maximum allowable active group may be limited to a small value, when the diversity effect decreases and the number of cells belonging to the active group reaches the maximum allowable active group, cell replacement handover belonging to the active group is frequently performed. There is a problem that occurs.

Accordingly, an object of the present invention is to provide a method for controlling soft handover of a mobile station having one or more base station active groups in a mobile communication network, wherein the conditions for adding and deleting active groups are adaptively changed according to the number of active groups. In providing a method.

In addition, an object of the present invention is to apply a method for adaptively varying the handover condition according to the number of active groups in a handover condition determination method using a relative difference in the strength of pilot signals, in a region where several pilot signals overlap, It is to increase the efficiency of radio resource use without reducing the diversity effect and to prevent frequent ping-pong phenomenon.

The present invention for achieving the above object is, in a mobile communication system using a code division multiple access scheme in which a mobile communication terminal communicates with a predetermined base station and one or more neighboring base stations, the base station received by the wireless network controller from the terminal A method for setting a condition of adding an active group through pilot signal information of the mobile station, the method comprising: receiving, by the wireless network controller, a measurement report message including pilot strength information of neighboring base stations of the terminal from the terminal; Resetting an active group addition condition reference offset value (add_reporting_range) and an additional reference time (add_timer) of the base station added to the active group according to the number of base stations included in the active group among the base stations communicating; Send active group additional conditions to the terminal It is characterized in that it comprises the process.

In addition, the present invention for achieving the above object, in a mobile communication system using a code division multiple access scheme in which a mobile communication terminal communicates with a predetermined base station and one or more neighboring base stations, the wireless network controller is received from the terminal A method for setting a condition for deleting an active group based on pilot signal information of received base stations, the method comprising: receiving, by the wireless network controller, a measurement report message including pilot strength information of neighboring base stations of the terminal from the terminal; Resetting an active group deleting condition reference offset value (add_reporting_range) and a deleting reference time (add_timer) of the base station deleted from the active group according to the number of base stations included in the active group among the base stations communicated by the terminal; Reset active group deletion conditions It is characterized in that it comprises a process of transmitting to the base.

In addition, the present invention for achieving the above object, in a mobile communication system using a code division multiple access scheme in which a mobile communication terminal communicates with a predetermined base station and one or more adjacent base stations, the terminal is received from the base stations A method of adding an active group through pilot signal information, the method comprising: transmitting, by a terminal, a measurement report message including pilot strength information of neighboring base stations of the terminal to a wireless network controller; Receiving an active group addition condition reference offset value (add_reporting_range) and an additional reference time (add_timer) of the base station added to the active group reset according to the number of base stations included in the active group among the base stations communicating; Pre-stored information according to received active group additional conditions A it characterized in that it comprises the step of updating.

In addition, the present invention for achieving the above object, in a mobile communication system using a code division multiple access scheme in which a mobile communication terminal communicates with a predetermined base station and one or more adjacent base stations, the terminal is received from the base stations A method of deleting an active group through pilot signal information, the method comprising: transmitting, by the terminal, a measurement report message including pilot strength information of neighboring base stations of the terminal to a wireless network controller; Receiving an active group deletion condition reference offset value (add_reporting_range) and a deletion reference time (add_timer) of the base station deleted from the active group reset according to the number of base stations included in the active group among the base stations communicating; Prestored according to received active group deletion conditions It characterized in that it comprises the step of updating the beams.

1 is a diagram illustrating a handover process in a code division multiple access mobile communication system.

2 is a graph showing a characteristic curve of a displacement value applied to a handover condition according to the present invention.

Figure 3 is a graph showing a radio link addition condition measurement report when there is one active group according to the present invention.

Figure 4 is a graph showing a radio link addition condition measurement report when there are three active groups according to the present invention.

5 is a graph showing a radio link deletion condition measurement report when there are two active groups according to the present invention.

6 is a graph showing a radio link deletion condition measurement report when there are four active groups according to the present invention.

7 is a flowchart illustrating a handover procedure in a wireless network controller applying an adaptation condition according to the number of active groups according to the present invention.

8 is a flowchart illustrating a handover procedure in a terminal to which an adaptation condition is applied according to the number of active groups according to the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that in the following description, only parts necessary for understanding the operation according to the present invention will be described, and descriptions of other parts will be omitted without departing from the scope of the present invention.

The present invention is to adaptively vary the handover condition according to the number of active groups in the method of determining the handover condition by the relative difference of the measured value of the pilot signal strength.

Parameters for determining a condition for determining the handover include parameters such as add_reporting_range, drop_reporting_range, add_timer and drop_timer.

According to the present invention, four kinds of values of the handover decision condition, add_reporting_range, drop_reporting_range, add_timer, and drop_timer, are varied according to the number of active groups.

First, the above four parameters used as handover decision conditions will be described.

The add_reporting_range is a condition for adding an inactive cell to the wireless link as an active set. When the difference between the pilot signal strength of the active cell and the pilot signal strength measurement value of the inactive cell becomes less than the add_reporting_range, the wireless link Additional conditions are met.

The drop_reporting_range is a condition for deleting a radio link from an active cell to an inactive state. When the difference between pilot signal measurement values between the active group cells is greater than or equal to drop_reporting_range, the radio link deleting condition is satisfied.

The add_timer is a time for which the radio link addition condition should be continued, and the drop_timer is a time for which the radio link deletion condition should be continued.

The terminal reports a radio link addition event to the base station when the add_reporting_range and add_timer conditions are met. In addition, if the drop_reporting_range and drop_timer conditions are met, the radio link drop event is reported.

Meanwhile, the wireless network controller has add_reporting_range_ref and add_timer_ref as initial values of the radio link addition condition, and has drop_reporting_ref and drop_timer_ref as initial values of the radio link deletion condition, and R_add and R_drop which are variation values for adaptively changing according to the number of active groups. Additionally manages T_add and T_drop.

First, the radio network controller transmits add_reporting_range, T_add, drop_reporting_range, and T_drop values to a mobile station through a system broadcast channel. In the initial broadcast channel, add_reporting_range_ref, T_add_ref, drop_reporting_range_ref and T_drop_ref values are transmitted to the mobile station, respectively.

That is, the wireless network controller initially transmits the parameters required for adding or deleting an active group for handover as add_reporting_range_ref, T_add_ref, drop_reporting_range_ref and T_drop_ref, and then add_reporting_range, which is a determined new value considering the number of active groups for transmission. Sends the values of, T_add, drop_reporting_range, and T_drop.

Meanwhile, the wireless network controller determines the handover based on the measurement report message received from the terminal, and when the handover procedure is performed, the add_reporting_range, add_timer, drop_reporting_range, and drop_timer values according to the changed number of active groups. Change to <Equation 4>. In the following n means the number of active groups.

add_reporting_range (n) = add_reporting_range_ref-R_add (n)

drop_reporting_range (n) = drop_reporting_range_ref-R_drop (n)

add_timer (n) = add_timer_ref + T_add (n)

drop_timer (n) = drop_timer_ref-T_drop (n)

Referring to Equations 1 and 2, whenever the number of active groups is added, add_reporting_range (n) and drop_reporting_range (n) related to reference pilot signal strengths for adding and deleting active groups are R_add ( n) and R_drop (n). In addition, referring to Equations 3 and 4, add_timer (n) and drop_timer (n) related to a duration in a condition for adding and deleting active groups are added whenever the number of active groups is added. It can be seen that it is changed by T_add (n) and T_drop (n).

Here, the R_add, R_drop, T_add and T_drop is a displacement value for adaptively changing the handover condition according to the number of active groups, 0 when the number of active groups is 1, a function of the number of active groups n, and the following conditions Must be satisfied.

Condition 1: add_reporting_range (n) ≥ add_reporting_range (n + 1)

Condition 2: drop_reporting_range (n) ≥ drop_reporting_range (n + 1)

Condition 3: add_timer (n) ≤ add_timer (n + 1)

Condition 4: drop_timer (n) ≥ drop_timer (n + 1)

Condition 5: add_reporting_range (n) <drop_reporting_range (n)

Condition 6: add_reporting_range (n) <drop_reporting_range (n + 1)

Condition 7: drop_reporting_range (n)-add_reporting_range (n) ≥ drop_reporting_range (n + 1)-add_reporting_range (n + 1)

Looking at the conditions, it can be seen that the first condition 1 to condition 4, as the number of active groups increases, the criteria that can be newly included in the active group becomes more stringent.

That is, each time the number of active groups increases one by one, the reference of the pilot strength to be newly added to the active group becomes larger, and the time to be maintained is set longer. On the other hand, each time the number of active groups increases, the criterion of pilot strength falling into the inactive group becomes larger, and the time to be maintained becomes shorter. By doing so, it is possible to cope with the handover situation more effectively than when the condition is kept constant regardless of the number of active groups.

Meanwhile, the condition 5 and the condition 6 of the above conditions are to prevent the ping-pong phenomenon due to the change of the handover condition. That is, the ping-pong phenomenon can be prevented by keeping add_reporting_range (n), which is an additional condition of the active group, smaller than drop_reporting_range (n), which is an active group deletion criterion. It is condition 7 above to more strictly limit the number of active groups.

In addition, the R_add, R_drop, T_add, and T_drop values are set to satisfy all the conditions 1 to 6 above. In addition, if the number of active groups is to be strictly limited, the condition 7 must be satisfied as described above.

On the other hand, as the number of active groups increases, the reference displacement value for further deletion of the active group may increase to the maximum limit value and its characteristic curve is shown in FIG. 2.

2 is a graph showing a characteristic curve of a displacement value applied to a handover condition according to the present invention.

Referring to FIG. 2, it can be seen that as the number of active groups increases, the displacement value 201 that is applied to the handover condition rapidly increases and converges to the maximum limit value 200 when the predetermined number exceeds the predetermined number. That is, since the displacement value 201 applied to the handover condition is set based on the largest value among the strengths of the pilot signals of the respective active groups at a certain point in time, the predetermined maximum limit value 200 increases as the number of active groups increases. Close to.

As described above, when the handover condition is adaptively applied according to the present invention, the influence according to the number of active groups is as follows.

1) As the number of active groups increases, add_reporting_range decreases and add_timer value increases.

2) As the number of active groups increases, the drop_reporting_range becomes smaller and the drop_timer value becomes smaller.

3) The smaller the number of active groups, the larger the add_reporting_range and the smaller the add_timer value.

4) As the number of active groups decreases, the drop_reporting_range increases and the drop_timer value increases.

By adaptively changing the handover condition as described above, the larger the number of active groups, the more stringent the radio link addition condition becomes, and the radio link deletion condition becomes more flexible. In addition, as the number of active groups decreases, the radio link addition condition becomes more flexible and the radio link deletion condition becomes more stringent.

3 and 4, the change of the radio link addition condition in the case of one active group and three groups will be described.

3 is a graph showing a radio link addition condition measurement report when there is one active group according to the present invention.

In FIG. 3, A 300 is a cell belonging to an active group and M 301 is an inactive cell.

Therefore, since there is only one cell A 300 that currently belongs to the active group, a value as small as a predetermined offset value (add_reporting_range_ref) 305 based on the value A 300 is set as an additional condition of the active group.

If the mobile station measures the pilot signal strength of the inactive cell in the add_reporting_range_ref 305 in FIG. 3 (1) (303) and the condition persists for an additional reference time (add_timer) 306, the wireless signal is transmitted from (2) to (304). Report the measurement to the access network. Accordingly, the M 301 belongs to the active group in the inactive state.

On the other hand, Figure 4 is a graph showing a radio link additional condition measurement report when there are three active groups according to the present invention.

In FIG. 4, A_1 400, A_2 401 and A_3 402 are cells belonging to an active group and M 404 is an inactive cell.

Referring to FIG. 4, since there are three cells belonging to the current active group, a predetermined offset value (add_reporting_range = add_reporting_range_ref-R_add based on the pilot signal strength of the cell having the highest pilot signal strength among the three cells at a certain point in time. 407) is set as an additional condition of the active group.

Here, it can be seen that the offset value (add_reporting_range) is smaller than R_add than the value of add_reporting_range_ref when there is only one active cell described with reference to FIG. 3. That is, as the number of cells belonging to the active group increases, the offset value is made smaller, and as a result, the reference intensity of the pilot signal to be newly added to the active group becomes larger, so that the condition in which the cell is added to the active group is strict. Let's do it.

In addition, the R_add value increases as the number of cells belonging to the active group increases, and as the number of active cells increases, the offset value decreases as a result, thereby increasing the reference strength of the pilot signal to be added to the active group. Make.

If the mobile station measures the pilot signal strength of the inactive cell maintained within the offset value (add_reporting_range) in (1) to (405) of FIG. 4 and the condition persists for an additional reference time (add_timer = add_timer_ref + T_add) 408, (2) to 406 report the measurement to the wireless access network. Accordingly, the M 404 belongs to the active group in the inactive state.

Here, it can be seen that the additional reference time add_timer is greater than T_add than the add_timer_ref value when there is only one active cell described above with reference to FIG. 3. That is, as the number of cells belonging to the active group increases, the additional reference time is made longer, thereby making the conditions for adding the cells to the active group more stringent.

5 and 6, the change of the radio link deletion condition in the case of two and four active groups will be described.

5 is a graph showing a radio link deletion condition measurement report when there are two active groups according to the present invention.

A_1 500 and A_2 501 of FIG. 5 are cells belonging to the current active group, and the pilot signal strength of the cell A_2 (501) is measured to be less than or equal to drop_reporting_range_ref (1) to (503) and a drop reference time (drop_timer_ref; If the condition persists up to 506, the mobile station reports a measurement from (2) to (504).

Referring to FIG. 5, since two cells belonging to the current active group are A_1 500 and A_2 501, predetermined cells are determined based on the pilot signal strength of a cell having a higher pilot signal strength among the two cells at a certain point in time. A value as small as the offset value (drop_reporting_range_ref) 505 of the active group is set.

If the mobile station measures the pilot signal strength of the inactive cell in the drop_reporting_range_ref 505 in (1) (503) of FIG. 5 and the condition continues for the drop reference time (drop_timer_ref; 506), the wireless signal is transmitted from (2) to (504). Report the measurement to the access network. Accordingly, the A_2 501 transitions from the active group to the inactive state.

6 is a graph showing a radio link deletion condition measurement report when there are four active groups according to the present invention.

In FIG. 6, A_1 601, A_2 602, A_3 603 and A_4 604 are cells belonging to an active group.

Referring to FIG. 6, since four cells belong to the current active group, a predetermined offset value (drop_reporting_range = drop_reporting_range_ref-R_drop based on a pilot signal strength of a cell having the highest pilot signal strength among the four cells at a given time point 508) is set as a deletion condition of the active group.

Here, it can be seen that the offset value drop_reporting_range is smaller than R_drop than the drop_reporting_range_ref value when there are two active cells described above with reference to FIG. 5. That is, as the number of cells belonging to the active group increases, the offset value is made smaller, and as a result, the reference intensity of the pilot signal to be newly deleted from the active group becomes larger, so that the cell is deleted from the active group. Make it flexible Therefore, due to the high pilot reference strength, the cells corresponding to the conditions for deletion from the active group increase.

In addition, the R_drop value increases as the number of cells belonging to the active group increases, and as the number of active cells increases, the offset value decreases as a result, thereby increasing the reference strength of the pilot signal to be deleted from the active group. Make.

If the mobile station measures the pilot signal strength of the active cell maintained within the offset value (add_reporting_range) from (1) to (606) of FIG. 6 and the condition persists for the drop reference time (drop_timer = drop_timer_ref-T_add) 609, (2) to 607 report the measurement to the radio access network. Accordingly, the A_4 604 transitions from the active group to the inactive state.

Here, it can be seen that the drop reference time drop_timer is a value smaller than T_drop than the drop_timer_ref value when the two active cells described above in FIG. 5 are used. In other words, by shortening the additional reference time as the number of cells belonging to the active group increases, the conditions under which the cells are deleted from the active group become more flexible. Therefore, the larger the number of cells in the active group is, the shorter the time maintained below the erase condition reference pilot strength is, so that the cells are easily transitioned from the active group to the inactive state.

Hereinafter, a handover procedure performed by a wireless network controller and a terminal according to the present invention will be described with reference to FIGS. 7 and 8.

7 is a flowchart illustrating a handover procedure in a wireless network controller applying an adaptation condition according to the number of active groups according to the present invention.

According to the present invention, if the wireless network controller performs a handover based on the measurement report message received from the terminal and there is a change in the number of active groups, the wireless network controller satisfies the seven conditions in the condition 1 described above and has the characteristics of FIG. The displacement value is calculated to calculate add_reporting_range, add_timer, drop_reporting_range, and drop_timer according to the above Equations 1 to 4, and the changed information is transmitted to the mobile station as a measurement control message.

Referring to FIG. 7, the wireless network controller first receives 700 a measurement report message from a terminal. The measurement report message includes strength information of a pilot signal received from neighboring base stations communicating with the terminal.

The wireless network controller receiving the measurement report message performs a handover according to the predetermined handover condition described above. At this time, the addition and deletion conditions of the active cells are reset in consideration of the number of the active cells according to the present invention. If the number of active cells has not changed, it is not necessary to reset the addition and deletion condition parameters of the active cells.

Meanwhile, if the addition and deletion conditions of the active cell are initially transmitted to the terminal, as described above, add_reporting_range_ref, add_timer_ref, drop_reporting_range_ref and drop_timer_ref are transmitted, and then adaptively according to the number of active groups from the first transmitted condition. The newly calculated add_reporting_range, add_timer, drop_reporting_range, and drop_timer values are applied in consideration of the variation values R_add, R_drop, T_add, and T_drop, which are changed to 706.

The newly calculated and changed parameters are transmitted 708 to the terminal via a measurement control message.

Hereinafter, a handover procedure in a terminal to which an adaptation condition according to the number of active groups according to the present invention is applied will be described with reference to FIG. 8.

In FIG. 8, if the measurement report condition is satisfied by the condition received in the previous system information broadcast channel or the measurement control message, the terminal transmits the measurement report message to the wireless access network and performs handover as directed by the wireless access network. When the measurement control message is received from the wireless access network, the changed condition is updated and the measurement is performed accordingly. Even if there is a pilot signal that satisfies the add_reporting_range or drop_reporting_range condition before the condition update, the mobile station measures based on the newly changed condition.

Referring to FIG. 8, when a predetermined measurement report condition 800 is reached, pilot strengths of neighbor base stations are measured, and a measurement report message is transmitted to the wireless network controller 802. The terminal that transmits the measurement report message performs a handover when a predetermined handover condition is satisfied (804).

Meanwhile, the terminal receives the measurement control message from the wireless network controller which has received the measurement report message as described above with reference to FIG. 7 (806). As described above, the measurement control message includes parameters in which the condition of adding and deleting active cells is reset according to the number of active cells of the terminal. The terminal receiving the measurement control message updates a changed condition according to the received information, and measures pilot strength of neighbor base stations according to the changed condition.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications may be made without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the scope of the following claims, but also by the equivalents of the claims.

As described above, the present invention can efficiently maintain the number of active groups according to a wireless environment by controlling a handover condition according to the number of active groups without fixing the maximum allowable number of active groups to a small value. It can increase the efficiency of use. In addition, according to the present invention, it is possible to prevent a frequent ping-pong phenomenon in an environment where signals of several cells overlap.

In addition, even in a region where signals of several cells overlap, if multiple pilot signals are received at the mobile station with almost the same intensity, the radio link can be added to the active groups as much as the maximum allowable active group, so that the macro diversity effect can be maximized.

In addition, the present invention has the advantage that it is possible to improve the call quality and increase the capacity of the network by bringing the effect of the efficient use of radio resources, preventing frequent handover, and maximizing the macro diversity effect.

Claims (16)

In a mobile communication system using a code division multiple access scheme in which a mobile communication terminal communicates with a predetermined base station and one or more neighboring base stations, a wireless network controller adds an active group through pilot signal information of base stations received from the terminal. In the method of setting the condition, Receiving, by the wireless network controller, a measurement report message including pilot strength information of neighboring base stations of the terminal from the terminal; Resetting an active group addition condition reference offset value (add_reporting_range) and an additional reference time (add_timer) of the base station added to the active group according to the number of base stations included in the active group among the base stations communicated by the terminal; And transmitting the reset active group addition conditions to the terminal. The method of claim 1, The active group additional condition reference offset value is reduced as the number of active groups increases. The method of claim 1, The method of adding an active group is increased as the number of active groups increases. The method of claim 1, And if the number of the active groups does not change, resetting the active group addition conditions. In a mobile communication system using a code division multiple access scheme in which a mobile communication terminal communicates with a predetermined base station and one or more neighboring base stations, a wireless network controller deletes an active group through pilot signal information of base stations received from the terminal. In the method of setting the condition, Receiving, by the wireless network controller, a measurement report message including pilot strength information of neighboring base stations of the terminal from the terminal; Resetting an active group deleting condition reference offset value (add_reporting_range) and a deleting reference time (add_timer) of a base station deleted from the active group according to the number of base stations included in an active group among the base stations communicated by the terminal; Transmitting the reset active group deletion conditions to the terminal. The method of claim 5, The active group deletion condition reference offset value is reduced as the number of active groups increases. The method of claim 5, The method of deleting the active group is characterized in that as the number of active groups decreases. The method of claim 5, And if the number of the active groups does not change, the active group deletion conditions are not reset. In a mobile communication system using a code division multiple access scheme in which a mobile communication terminal communicates with a predetermined base station and one or more neighboring base stations, the terminal adds an active group through pilot signal information received from the base stations. In Transmitting, by the terminal, a measurement report message including pilot strength information of neighboring base stations of the terminal to a wireless network controller; The active group addition condition reference offset value (add_reporting_range) and the additional reference time (add_timer) of the base station added to the active group reset according to the number of base stations included in the active group among the base stations with which the terminal communicates from the wireless network controller. ), And updating previously stored information according to the received active group addition conditions. The method of claim 9, The active group additional condition reference offset value is reduced as the number of active groups increases. The method of claim 9, The method of adding an active group is increased as the number of active groups increases. The method of claim 9, And if the number of the active groups does not change, resetting the active group addition conditions. In a mobile communication system using a code division multiple access scheme in which a mobile communication terminal communicates with a predetermined base station and one or more neighboring base stations, the terminal deletes an active group through pilot signal information received from the base stations. In Transmitting, by the terminal, a measurement report message including pilot strength information of neighboring base stations of the terminal to a wireless network controller; Active group deletion condition reference offset value (add_reporting_range) and deletion reference time (add_timer) of a base station deleted from the active group reset according to the number of base stations included in an active group among the base stations with which the terminal communicates from the wireless network controller. ), And updating previously stored information according to the received active group deletion conditions. The method of claim 13, The active group deletion condition reference offset value is reduced as the number of active groups increases. The method of claim 13, The method of deleting the active group is characterized in that as the number of active groups decreases. The method of claim 13, And if the number of the active groups does not change, the active group deletion conditions are not reset.