KR20130078188A - Method and apparatus for selective handover in wireless communication system - Google Patents

Abstract

PURPOSE: A selective handover method and an apparatus thereof in a wireless communication system are provided to selectively perform handover based on a movement state of a terminal. CONSTITUTION: A receiving unit (1260) receives a measurement value of a mobility state estimation (MSE) of a terminal from the terminal. A determining unit (1270) determines handover execution based on the MSE measurement value. A transmitting unit (1280) transmits a handover command message based on a result determined in the determining unit. The MSE measurement value includes estimation speed information of the terminal. [Reference numerals] (1210,1260) Receiving unit; (1220,1280) Transmitting unit; (1270) Determining unit; (AA) Message for re-setting RRC connection; (BB) Handover command; (CC) MES measurement value

Description

METHOD AND APPARATUS FOR SELECTIVE HANDOVER IN WIRELESS COMMUNICATION SYSTEM}

The present invention relates to a wireless communication system, and more particularly, to a method and apparatus for selectively performing a handover.

3rd generation partnership project (3GPP) long term evolution (LTE), an improvement of the Universal Mobile Telecommunications System (UMTS), uses orthogonal frequency division multiple access (OFDMA) multiplexing in downlink, and single carrier SC-FDMA in uplink -frequency division multiple access) Use multiplexing. MIMO (multiple input multiple output) with up to four antennas is adopted. Recently, 3GPP LTE-A (LTE-Advanced), an evolution of 3GPP LTE, is under discussion.

In particular areas, such as hot spots inside a cell, there is a particularly high demand for communication, and in certain areas such as cell edges or coverage holes, the reception sensitivity of radio waves may be reduced. . Background of the Invention As wireless communication technology has developed, small cells in a macro cell, for example, a pico cell, have been used for the purpose of enabling communication in an area such as a hot spot, a cell boundary, A pico cell, a femtocell, a remote radio head (RRH), a relay, and a repeater are installed together. Such a network is called a heterogeneous network (HetNet). In a heterogeneous network environment, when compared with a femto cell and a pico cell, a macro cell is a large coverage cell, and a femto cell and a pico cell are small coverage cells.

A terminal connected to a heterogeneous network can perform communication with an arbitrary cell or perform a cell change according to a channel environment or a moving state. For example, a terminal may disconnect from a macro cell and connect to another macro cell or picocell due to deterioration of a channel state in a state of being connected to a macro cell. Or, as the terminal moves while connected to the macro cell, it can disconnect from the macro cell and connect to another macro cell or picocell.

When a terminal receiving a wireless service from a macro cell moves at a high speed to a pico cell region, which is a hot spot, the terminal is likely to leave the pico cell region again within a short time after handover from the macro cell to the pico cell. In the spot, since the service is available not only by the pico cell but also by the macro cell, it may be more effective that the UE does not handover to the pico cell. On the other hand, when the terminal receiving the wireless service from the macro cell moves to the pico cell area, which is a coverage hole, at high speed, the wireless service may not be possible unless the terminal is handed over to the pico cell. It is effective to make a handover.

As such, there is a need for a method and apparatus for selectively performing handover based on a movement state of a terminal in a heterogeneous network system.

An object of the present invention is to provide a method and apparatus for selectively performing a handover based on a mobile state of a terminal.

Another technical problem of the present invention is to provide a method and apparatus for selectively performing a handover based on the type of a base station.

Another object of the present invention is to provide a method and apparatus for transmitting a mobile station mobile state measurement value using a proximity indication message.

According to an aspect of the present invention, a method for performing a selective handover by a base station in a wireless communication system, the method comprising: receiving a measurement value of a mobility state estimation (MSE) of a terminal from the terminal, the MSE measurement value And determining whether to perform handover based on type information of the base station and transmitting a handover command message to the terminal according to the determined result, wherein the MSE measurement value includes estimated speed information of the terminal. The estimated speed of the terminal is one of high speed, medium speed, or low speed.

According to another aspect of the present invention, a method for performing a selective handover by a terminal in a wireless communication system is configured to set a proximity indication operation indicating that the terminal enters or exits a cell having a CSG ID in the CSG whitelist of the terminal. Receiving proximity indication configuration information through an RRC connection reestablishment message; transmitting a proximity indication message including a measurement value of a mobility state estimation (MSE) of the terminal based on the proximity indication configuration information to the base station; And receiving a handover command message including information on whether to perform handover, wherein the proximity indication setting information includes information indicating whether to include the MSE measurement value in the proximity indication message. The MSE measurement value includes estimated speed information of the terminal. Estimated velocity is one of the high speed, medium speed or low speed.

According to another aspect of the present invention, a base station performing a selective handover in a wireless communication system is a receiving unit for receiving a measurement value of a mobility state estimation (MoSE) of the terminal from the terminal, based on the MSE measurement value And a transmitter configured to determine whether to perform a handover, and a transmitter configured to transmit a handover command message to the terminal based on the determination result, wherein the MSE measurement value includes estimated speed information of the terminal. The estimated speed of the terminal is one of high speed, medium speed or low speed.

According to another aspect of the present invention, a UE performing selective handover in a wireless communication system is configured to set a proximity indication operation for indicating that the UE enters or exits a cell having a CSG ID in the CSG whitelist of the UE. A receiver for receiving an RRC connection reconfiguration message including information and a transmitter for transmitting a proximity indication message including a measurement value of a mobility state estimation (MSE) of the terminal based on the proximity indication configuration information to the base station; Includes, wherein the receiving unit receives a handover command message including information on whether to perform a handover, the proximity indication setting information includes information indicating whether to include the MSE measurement value in the proximity indication message. The MSE measurement value includes estimated speed information of the terminal. The horse's estimated speed is one of high speed, medium speed or low speed.

According to the present invention, when performing the handover from the source base station to the target base station, the handover may be selectively performed based on the cell type and the installation purpose type information of the target base station.

According to the present invention, the UE can minimize the unnecessary handover.

According to the present invention, a more efficient service can be received by using the terminal and the system efficiently.

1 schematically illustrates a concept of a heterogeneous network composed of a macro cell, a femtocell, and a picocell.
2 shows a distribution diagram of cells of various coverages in a heterogeneous network.
3 is a diagram illustrating estimation of a mobile state of a terminal in a heterogeneous network according to the present invention.
4 is a flowchart illustrating a process of handing over a terminal from a macro base station to a CSG cell by using a proximity indication to which the present invention is applied.
5 is an example of a flowchart illustrating a method for selectively handing over an MSE measurement value of a terminal according to the present invention.
6 is a flowchart illustrating another example of a selective handover according to the present invention.
7 is a flowchart illustrating still another example of a selective handover according to the present invention.
8 is a flowchart illustrating still another example of a selective handover according to the present invention.
9 is a flowchart illustrating still another example of a selective handover according to the present invention.
10 is a flowchart illustrating an operation of a terminal for selectively performing handover according to the present invention.
11 is a flowchart illustrating an operation of a source base station selectively performing handover according to the present invention.
12 is a block diagram illustrating a base station and a terminal performing a handover according to an embodiment of the present invention.

Hereinafter, the contents related to the present invention will be described in detail with reference to exemplary drawings and embodiments, together with the contents of the present invention. It should be noted that, in adding reference numerals to the constituent elements of the drawings, the same constituent elements are denoted by the same reference symbols as possible even if they are shown in different drawings. In addition, in describing the embodiments of the present specification, when it is determined that the detailed description of the related well-known configuration or function may obscure the subject matter of the present specification, the detailed description will be made.

In describing the components of the present specification, terms such as first, second, A, B, (a), and (b) may be used. These terms are intended to distinguish the constituent elements from other constituent elements, and the terms do not limit the nature, order or order of the constituent elements. If a component is described as being "connected", "coupled", or "connected" to another component, that component may be directly connected or connected to that other component, but there is another component between each component. It will be understood that may be "connected", "coupled" or "connected".

In addition, the present invention will be described with respect to a wireless communication network. The work performed in the wireless communication network may be performed in a process of controlling a network and transmitting data by a system (e.g., a base station) Work can be done at a terminal connected to the network.

Simple cell division of macro and micro cells is difficult to meet the growing demand for data services. Accordingly, a data service for small indoor and outdoor areas can be provided by using a pico cell, a femto cell, a relay, or the like. Although the use of small cells is not particularly limited, in general, picocells can be used in a communication shadow area, which is not covered only by macro cells, or in an area where data service demand is high, that is, hotspots. Femtocells are generally available in indoor offices or homes. In addition, the wireless relay can compensate for the coverage of the macrocell. By configuring a heterogeneous network, not only the shadow area of the data service can be eliminated, but also the data transmission speed can be increased.

1 schematically illustrates a concept of a heterogeneous network composed of a macro cell, a femtocell, and a picocell. For convenience of description, a heterogeneous network composed of macro cells, femtocells, and picocells is described, but the heterogeneous network may also include other types of cells. A femto cell is a low power wireless access point, which is a small base station for mobile communication used indoors such as a home or an office. A femto cell can access a mobile communication core network using DSL or cable broadband in a home or office.

Referring to FIG. 1, a macro base station 110, a femto base station 120, and a pico base station 130 are operated together in a heterogeneous network. The macro base station 110, the femto base station 120, and the pico base station 130 have unique cell coverage. The cell provided by the macro base station 110 is referred to as a macro cell 111 and the cell provided by the femto base station 120 is referred to as a femto cell 121 and the cell provided by the pico base station 130 is referred to as a pico cell 131. [

The femto base station 120 is a low power wireless access point, for example, a base station for a small mobile communication used in a room such as a home or an office. The femto base station 120 can access the mobile communication core network using a home or office DSL or cable broadband. The femto base station 120 is connected to a mobile communication network through a wired network such as the Internet. A terminal in a femtocell can access a mobile communication network or an Internet network through a femto base station. Although FIG. 1 illustrates a heterogeneous network composed of macro cells, femtocells, and picocells for convenience of description, the heterogeneous network may be configured to include relays or other types of cells.

2 shows a distribution diagram of cells of various coverages in a heterogeneous network.

Referring to FIG. 2, macro cells and small cells are distributed in horizontal and vertical planes in meters, and the degree of distribution may be expressed by the number of macro cells and small cells. One hexagon represents a macro cell, and three hexagons (ie, macro cells) are collectively called a site. Many small cells are densified in each macro cell. The small cell may be located at the boundary of multiple macro cells. Looking at the size of each cell, the diameter of one site is about 600m, the diameter of the macro cell is about 300m, and the diameter of the small cell is about 20-30m.

3 is a diagram illustrating a mobility state estimation (MSE) of a mobile station in a heterogeneous network according to the present invention. The movement state of the terminal may include at least one of a movement path of the terminal, an estimated speed of the terminal, and an estimated speed of the terminal. That is, the scale indicating the movement state of the terminal may be the movement path or speed of the terminal.

Referring to FIG. 3, the macro cell 1 and the macro cell 2 are adjacent to each other, and the small cell 1 and the small cell 2 are located in the macro cell 1. UE A and UE B move from macro cell 1 to macro cell 2 at the same (or similar) speed. However, the terminal A moves through the small cell 1 and the small cell 2, and the terminal B does not go through any small cell.

As the terminal A moves to the small cell 1, the terminal A may disconnect from the macro cell 1 and perform a cell change to the small cell 1. Here, the terminal A may be in an idle mode or may be in a radio resource control (RRC) connected mode. The idle mode is a state in which the terminal does not exchange data with the base station, and the RRC connection mode is a state in which the terminal exchanges data with the base station. As an example of cell change, when UE A is in the idle mode, UE A may perform cell reselection with small cell 1. As another example of cell change, if UE A is in the RRC connected mode, UE A may perform a handover to small cell 1. Hereinafter, "cell change" means that the UE in the idle mode performs reselection or the UE performs the handover in the RRC connected mode.

In either mode, the terminal A attempts to change the cell to the small cell 1. As the terminal performs cell change, the cell change count N _A of the terminal A increases by one. For example, in order to effectively increase the number of cell changes, it may be assumed that the terminal stays in the cell for more than k seconds. Where k = 1.

On the other hand, when the terminal A moves and changes the cell from the small cell 1 to the macro cell 1 again, N _A increases to 2. Similarly, when terminal A moves and changes the cell from macro cell 1 to small cell 2, N _A increases to 3, while terminal A changes cell from small cell 2 to macro cell 1 again, N _A increases to 4. . When UE A moves from macro cell 1 to macro cell 2, cell change is performed and N _A increases to five. Meanwhile, the terminal B does not pass any small cells and performs cell change as it moves from the macro cell 1 to the macro cell 2. The increase in the cell change number (N _B) of terminal B 1.

The estimated speed of the terminal is calculated based on the number of cell changes performed by the terminal per unit time (the number of cell changes). In this case, the estimated speed of the terminal may be classified into two or more levels based on whether the terminal is high or low relative to a specific reference value. As an example, the estimated speed of the terminal may be classified into two levels, high and low. As another example, the estimated speed of the terminal may be classified into three levels of high speed, medium speed, and low speed. As another example, the estimated speed of the terminal may be classified into three levels of high speed, medium speed, and normal.

For example, the medium speed is an estimated speed when the number of cell changes (N) exceeds the medium speed reference value (Th _M ) and does not exceed the high speed reference value (Th _H ) during a specific reference time (that is, Th _M <N ≤ Th _H ). The high speed is an estimated speed when the cell change count N exceeds the high speed reference value Th _H during a specific reference time (that is, N> Th _H ). The low speed is an estimated speed when the number of cell changes (N) does not exceed the medium speed reference value (Th _M ) during a specific reference time (i.e., N≤Th _M ), or when it is not judged to be medium speed or high speed during a specific reference time. to be. When the estimated speed of the terminal calculated based on the number of cell changes of the terminal is matched to the actual speed, the low speed is approximately 0 to 30 km / h (0 to 8.3 m / s), and the medium speed is approximately 30 to 60 km / h. (8.3 to 16.6 m / s), high speed can be defined as approximately 60 to 120 km / h (16.6 to 33.2 m / s).

The reason for the error between the actual speed of the terminal and the estimated speed of the terminal occurs because the case of a cell change that is not related to the movement state of the terminal is not considered in calculating the estimated speed. Therefore, in order to increase the reliability of the estimated speed of the terminal calculated based on the number of cell changes, a cell change that is not related to the mobile state of the terminal should be considered. Hereinafter, the present invention is disclosed on the assumption that the estimated speed of the terminal is three levels. Even if the number of levels of estimated speeds is different, it may be appropriately changed and applied.

The UE more successfully performs the cell change by scaling the cell change parameters Q _hyst , T _reselection , and trigger time (TTT) based on the mobile state estimation value of the UE. A new cell change parameter can be derived that enables this.

The cell change parameter is a parameter based on estimating the mobile state of the terminal. The terminal determines whether the estimated speed of the terminal is high speed, medium speed, or low speed based on the cell change parameter. The cell change parameter received from the base station is a value defined in the corresponding system and may be transmitted by the base station of the macro cell or the base station of the picocell. In addition, the cell change parameter is control information used to reduce cell change failure when the UE performs cell change from the current cell to another cell.

The cell change parameter may be defined differently according to a mode (eg, idle mode or RRC connection mode) of the terminal.

First, when the terminal is in the idle mode, the cell change parameters include Q _hyst , T _reselection , scaling index, medium speed reference value (Th _M ) and high speed reference value (Th _H ), estimation time for estimating the speed of the terminal, and low speed determination time. It includes.

Q _hyst is a value that adds or subtracts a value indicating the good or bad state of the radio state of the current cell, and controls the good or bad of the radio state relative to the new cell. T _reselection is a time during which a new cell must maintain a radio state superior to a current cell in order for the idle mode terminal to _{reselect a} new cell.

A scaling factor is a value that is multiplied to scale T _reselection or added to scale Q _hyst according to the estimated speed of the terminal. It may have a different value depending on the speed level of the terminal. If the estimated speed of the UE in the idle mode is high speed, the UE scales the T _reselection and Q _hyst values so that the cell _reselection can be performed quickly, and if the estimated speed is low, the UE increases the T _reselection and Q _hyst values. To scale.

For example, Q _hyst scaling Q _hyst The scaling index may be -6 dB, -4 dB, -2 dB or 0 dB. The scaling index of each Q _hyst may be set to correspond to any one of a high speed, a medium speed, and a low speed estimated speed. The following table is an example of the scaling index of Q _hyst corresponding to the estimated speed.

Estimated speed Scaling index of Q _hyst high speed -6 dB Medium speed -4 dB or -2 dB sleaze 0dB

In this case, the scaling of Q _hyst is carried out by following the further scaling factor for Q _hyst as the mathematical expression.

Referring to Equation 1, when a scaling factor is added to the previous Q _hyst (old Q _hyst ), a new Q _hyst (new Q _hyst ) reflecting an estimated speed is obtained.

As another example, a T _reselection that scales a T _reselection The scaling index can be 0.25, 0.5, 0.75 or 1. The scaling index of each T _reselection may be set to correspond to any one of high speed, medium speed, or low speed final estimated speed. The following table is an example of the scaling index of T _reselection corresponding to the final estimated speed.

Estimated speed Scaling index for T _reselection high speed 0.25 Medium speed 0.5 or 0.75 sleaze One

In this case, the scaling of the T _reselection is performed by multiplying the scaling factor then the T _reselection as mathematical expression of.

Referring to Equation 2, multiplying the previous T _reselection (old T _reselection ) by the scaling index to obtain a new T _reselection (new T _reselection ) reflecting the final estimated speed.

Meanwhile, both the medium speed reference value and the high speed reference value included in the cell change parameter may be integer values between 1 and M. Here, M = 16. For example, when the medium speed reference value is 5 and the high speed reference value is 10, when the number of cell changes is 1 to 5, the estimated speed is low, and when the number of cell changes is 6 to 10, the estimated speed is medium speed and the number of cell changes is 11 ~. If it is 16, the estimated speed is high.

Estimating time for estimating the speed of the terminal may have a value of 30 seconds, 60 seconds, 180 seconds, 240 seconds. The terminal cumulatively increases the number of cell changes before the estimation time expires. The terminal may use a timer that operates until the estimated time expires (hereinafter, referred to as an "estimation timer").

The low speed determination time is a specific time value for determining the speed of the terminal as a low speed when the estimated speed of the terminal is not determined to be medium speed or high speed for a predetermined time, and may have values such as 30 seconds, 60 seconds, 180 seconds, 240 seconds, and the like. Can be.

Second, when the terminal is in RRC connected mode, the cell change parameter includes a trigger time, a scaling index, a medium speed reference value (Th _M ) and a high speed reference value (Th _H ), an estimated time for estimating the speed of the terminal, and a low speed determination time. do.

The trigger time is a handover preparation such as the UE starting a measurement report when the radio state is maintained for the trigger time after the radio state of the new cell is greater than a certain reference value than the current cell. The parameter used to initiate the step.

The scaling index is a value multiplied to scale the trigger time according to the estimated speed of the terminal. It may have a different value depending on the speed level of the terminal. If the estimated speed of the UE in the RRC connection mode is a high speed, the UE scales so that the trigger time is short so that handover is made quickly. If the estimated speed is low, the UE scales the trigger time to be large.

For example, a scaling index that scales the trigger time may be 0.25, 0.5, 0.75, or 1. Each scaling index may be set to correspond to any one of a high speed, a medium speed, and a low speed estimated speed. The following table is an example of the scaling index of the trigger time corresponding to the estimated speed.

Estimated speed Scaling Index of Trigger Time high speed 0.25 Medium speed 0.5 or 0.75 sleaze One

Table 3 assumes that the scaling index of the trigger time is 0.25 when the estimated speed is high, but this is only an example and the scaling index corresponding to each speed may be variously modified.

In this case, scaling of the trigger time is performed by multiplying the triggering time by a scaling index as in the following equation.

Referring to Equation 3, multiplying a previous trigger time by a scaling factor to obtain a new trigger time reflecting an estimated speed.

Upon receipt of the cell change parameter, the UE performs a cell change based on the cell change parameter (S805). Here, the UE in the idle mode performs cell selection (or cell reselection) and the UE in the RRC connected mode is a hand. Detect Over

When the terminal performs cell change, the scaling index value may be applied to the cell change parameter according to the movement state of the terminal estimated during the previous estimation time. That is, the terminal in the idle mode scales as shown in Equations 1 and 2 by using the scaling index values of Table 1 and Table 2 in the Q _hyst value and the T _reselection value. The UE of the RRC connected mode scales the trigger time value as shown in Equation 3 by using the scaling index values of Table 3.

Meanwhile, the terminal may select a scaling index corresponding to the updated moving speed estimation result. For example, the terminal in the idle mode may select a scaling index of Q _hyst and T _reselection based on Tables 1 and 2 above. As another example, the UE in the RRC connected mode may select the scaling index of the trigger time based on Table 3 above.

Meanwhile, the terminal may scale a cell change parameter using the selected scaling index. By scaling the cell change parameter, a new cell change parameter is derived. As an example, the terminal in the idle mode obtains new Q _hyst and T _reselection by scaling Q _hyst and T _reselection based on Equation 1 and Equation 2. As another example, the UE in the RRC connected mode obtains a new trigger time by scaling the trigger time based on Equation 3 above.

4 is a flowchart illustrating a process of handing over a terminal from a macro base station to a CSG cell using a proximity indication to which the present invention is applied. The source base station means a macro base station, and the target base station means a base station of a CSG cell.

The UE itself according to the implementation technology of the UE regarding when and in which frequency band (intra frequency or other frequency) to search for the licensed CSG cells This technique is called terminal autonomous search function (ASF).

The terminal may search for the CSG cell based on the ASF technology, and when the terminal enters or leaves the CSG cell (CSG cells having the CSG ID in the terminal's CSG whitelist), The relevant information may be transmitted to the base station through a proximity indication message.

Referring to FIG. 4, the source base station sets up a terminal for control related to proximity indication (S400). For example, the base station may set the terminal by transmitting the RRC connection reconfiguration message, the RRC connection reconfiguration message may include information about the recognition of the CSG cell.

The base station includes the proximity indication configuration information in the RRC connection reconfiguration message and transmits to the terminal. The proximity indication configuration information sets whether the UE reports the proximity indication to the base station in cells including the CSG ID in the CSG white list of the UE. That is, the proximity indication configuration information instructs the terminal to transmit (or not) a proximity indication message.

If it is determined that the terminal is close to the cell having the CSG ID in the CSG white list of the terminal, the terminal transmits a proximity indication message indicating "entering (or leaving)" to the base station (S405).

If there is no measurement setting for the associated frequency / RAT, the source base station performs the measurement setting (S410). The source base station transmits an RRC connection reconfiguration message including the measurement configuration information to the terminal.

Due to the measurement setting information, the terminal may perform the measurement at the reported RAT and frequency. The network also does not request information for a cell that has a CSG ID in the terminal's CSG white list but is not in the geographical area of the terminal, so as to minimize the request for handover preparation information of the CSG cell or hybrid cell. Proximity indications can be used.

The measurement configuration information includes at least one of a measurement object, a reporting configuration, a measurement identities, a quantity configuration, or measurement gaps.

The measurement object refers to a carrier frequency to be measured, a list frequency and frequency offset of cells, and cell-specific offset values.

The report setting refers to whether a periodic report or an event-triggered report, a report measurement result (Reference Signal Received Power (RSRP) or Reference Signal Received Quality (RSRQ)). In case of event-triggered reporting, i.e., triggering of the event to be reported is the A1 event (when the measurement result of the serving cell is greater than the predetermined threshold), the A2 event (when the measurement result of the serving cell is smaller than the predetermined threshold) ), A3 event (when the measurement result of the neighbor cell is larger than the measurement result of the serving cell) by a predetermined offset, A4 event (when the measurement result of the neighbor cell is larger than the predetermined threshold value), A5 event (measurement of the serving cell) If the result is smaller than the measurement result of the neighbor cell by a predetermined offset), in case of inter-RAT mobility, the B1 event (when the measurement result of the neighbor cell is larger than the predetermined threshold value) or B2 There is an event (when the measurement result of the serving cell is smaller by a predetermined threshold value than the measurement result of the neighboring cell).

The measurement ID is an ID of a measurement object and a report setting.

The quantity setting is filtering to apply to the measurement.

The measurement gap is a value between them for stopping transmission of uplink and downlink when the phase is an inter frequency measurement.

Subsequently to step S410, the terminal performs the measurement by the measurement method set by the source base station and transmits a measurement report message to the source base station a measurement result including a physical cell ID (PCI) (S415). As an example, the terminal may transmit the measurement report due to the triggering of the A3 event.

The measurement report message includes an RSRP or RSRQ value, PCI, and Cell Global ID (CGI). In addition, a lot of information can be reported through the measurement report message.

The source base station configures the terminal to perform system information (SI) acquisition and reporting of a specific PCI (S420).

The terminal acquires system information (CGI, Tracking Area ID (TAI), CSG ID, etc.) from the target base station (target HeNB) using an autonomous gap (S425). For example, the terminal suspends reception and transmission with the source base station within the limits specified in the standard in order to request relevant system information from the target base station.

The terminal transmits the measurement report including the received system information (CGI (or E-CGI), TAI, CSG ID and member / non-member indication) to the source base station (S430).

The source base station includes the target E-CGI and CSG ID in the handover request message and transmits it to the MME (S435). In this case, if the target cell is a hybrid cell, a cell access mode of the target cell is included.

The MME performs UE access control on the CSG based on the CSG ID received in the handover request message, and stores CSG subscription data regarding the UE (S440). If the access control procedure fails, the MME sends a handover preparation failure message to terminate the handover procedure. If there is a cell access mode, the MME determines that the UE handles the CSG membership status of the UE as a hybrid cell, and includes the determined CSG membership status in the handover request message.

The MME transmits a handover request message including the target CSG ID received from the terminal to the target base station via the HeNB GW (gateway) (S445). If the target is a hybrid cell, the CSG membership status is included in the handover request message.

The target base station checks whether the CSG ID received through the handover request message matches the CSG ID broadcasted to the target cell, and allocates an appropriate resource if the check is successful (S450). If the terminal indicates that the terminal is a member in the CSG membership state, the priority task of the terminal is applied.

The target base station may allow or disallow handover of the terminal in consideration of the status of resources available to the target base station.

The target base station transmits a handover request acknowledgment message to the MME via the HeNB GW (S455). The handover request confirmation message includes information on whether the target base station allows handover.

The MME transmits a handover command message to the source base station (S460).

The source base station transmits a handover command message (an RRC connection reconfiguration message including mobility control information) to the terminal (S465).

After the terminal transmits an entrance proximity indication, if the cell whose CSG ID is included in the CSG whitelist of the terminal is no longer nearby, the terminal transmits the entrance proximity indication to the source base station. Upon receiving this indication, the source base station sets the terminal to stop measuring for the reported RAT and frequency.

If the terminal visited the target base station in advance, the terminal does not need to give a proximity instruction.

Upon receiving the handover command, the UE terminates the access with the cell of the currently connected base station and starts a handover procedure for accessing the cell of the new base station (S470).

Now, another selective handover method and apparatus will be described.

5 is an example of a flowchart illustrating a method for selectively handing over an MSE measurement value of a terminal according to the present invention.

Referring to FIG. 5, the terminal for transmitting and receiving data with the source base station transmits the MSE measurement value to the source base station (S500). The MSE measurement value may be transmitted through a proximity indication message or a measurement report message. In addition, the MSE measurement value may be transmitted through another new message such as RRC signaling.

The source base station determines whether to perform handover based on the MSE measurement value of the terminal (S505).

In this case, in determining whether to perform the handover, not only the MSE measurement value of the terminal but also the type information of the target base station (or the type information of the cell of the target base station) may be used together.

There are two types of type information of the target base station: "Pico cell for coverage hole" type and "Pico cell for hot spot" type.

The pico cell for the coverage hole is a pico cell that transmits and receives data with the terminal instead of the macro cell, and is used when the terminal cannot transmit or receive data through the macro cell. Here, the coverage hole refers to a region within the coverage of the macro cell but a region in which the wireless signal is weak so that sufficient wireless service cannot be received.

A pico cell for hot spots is a pico cell that transmits and receives data with a macro cell together with a macro cell. Although the terminal may transmit and receive data through the macro cell, the macro cell may be accommodated because there are many terminals requiring wireless service in a corresponding area. It is a picocell installed in an area that exceeds its available load. By installing pico cells in such a region, it is used when data transmission and reception beyond the capacity that a macro cell can provide. In this case, the terminal may transmit and receive data through the pico cell instead of the macro cell. Here, the hot spot refers to an area where a large number of floating or resident populations are gathered, or an area where required traffic is very high. Hot spot regions can occur independent of the electro-magnetic field of the macro cell. A pico cell for hot spots may be divided into a frequency band picocell and a frequency band picocell.

An intra-frequency pico cell is a pico cell using the same frequency band as the macro cell. By reusing the same frequency resources in spatially separated areas, it is possible to secure the same radio resources as the macro cells within pico cell coverage. This is the pico cell for most hot spots.

And, an inter-frequency pico cell is a pico cell using a frequency band different from that of the macro cell. When the signal of the macro cell is strong in the hot spot region, frequency resources separated from each other are used between the pico cell and the macro cell to prevent performance degradation due to interference between the pico cell and the macro cell and to secure coverage of the pico cell. Therefore, different frequency band pico cells can be usefully used when supporting hot spots located close to the center of the macro cell.

The UE performs measurement to determine the existence of the neighbor cell. Since the neighbor cells existing in the same frequency band transmit signals through the same frequency band as the current serving cell, the UE performs transmission and reception with the serving cell and simultaneously Measurements can be made on the cells. On the other hand, since neighboring cells in different frequency bands transmit and receive signals through different frequency bands, the UE stops transmitting and receiving signals with the serving cell and retunes the RF chain to allow neighboring cells to retune. You must receive a signal for a frequency band that is known to exist. Here, the RF chain refers to the sum of the antenna, the filter, and the power amplifier. Thus, the measurements for neighboring cells that are in different frequency bands are relatively time limited.

If the estimated speed of the terminal is high, the signal strength of each cell changes significantly with time, and therefore, it is relatively difficult for the terminal to handover to a different frequency band than to handover to the same frequency band. Therefore, when determining whether to perform the handover based on the estimated speed of the terminal, it may be considered whether the frequency band of the pico cell for the hot spot is the same frequency band or different frequency band.

The type information of the target base station may be information directly provided by the pico cell or information determined by the pico cell based on information (eg, a measurement report) received from the terminal.

For example, the pico cell may directly provide type information of the target base station. That is, the pico cell may have its own type information. The type information of the target base station may be provided to a neighbor cell or a base station. Through this, the neighbor cell or base station may check the type information of the target base station, and thus may know the purpose of the neighbor pico cell.

The type information of the target base station may be transmitted to the neighbor cell or the base station through the X2 interface. For example, when the target base station transmits a handover request confirmation message to the source base station in response to the handover request, the handover request confirmation message may include the type information of the target base station.

Meanwhile, based on the measurement report of the terminal, it may be determined whether the target base station is in the pico cell area for the coverage hole or the pico cell area for the hot spot. For example, when an A3 event, which is a criterion for determining handover, occurs, if the measurement result of the serving cell (eg, RSRP, RSRQ) is less than or equal to a predetermined threshold, the pico cell is configured for the coverage hole. If it is determined that the measurement result of the serving cell is greater than or equal to a predetermined threshold value, the pico cell may be determined to be for hot spot.

Examples 1 to 4 of the method for determining whether to perform the handover procedure using the aforementioned MSE measurement value or the type information of the target base station are as follows.

As an example of determining whether to perform the handover procedure (Embodiment 1), the source base station may determine whether to perform the handover based only on the MSE measurement value of the UE.

That is, if the estimated speed of the terminal is a high speed, the source base station may decide not to perform a handover. If the estimated speed of the terminal is not high speed (medium speed or slow), the source base station may decide to perform a handover.

As another example of determining whether to perform the handover procedure (Embodiment 2), the source base station may determine whether to perform the handover based only on the type information of the target base station.

That is, if the target base station is in the pico cell for the coverage hole, it may be decided to perform a handover, and if it is in the pico cell for the hot spot, it may be determined not to perform the handover.

As another example of determining whether to perform the handover procedure (Example 3), the source base station may determine whether to perform the handover by considering both the MSE measurement value of the terminal and the type information of the target base station.

That is, when the estimated speed of the terminal is a high speed, the target base station determines to perform the handover if it is in the pico cell for the coverage hole, and if it is in the pico cell for the hot spot, it is determined not to perform the handover. On the other hand, when the estimated speed of the terminal is not high speed (medium speed or low speed), regardless of the type information of the target base station (both for the coverage hall and for the hot spot) it is determined to perform the handover.

As another example of determining whether to perform the handover procedure (Example 4), the source base station may determine whether to perform the handover in consideration of the frequency band information among the type information of the target base station as well as the MSE measurement value of the terminal.

That is, if the estimated speed of the terminal is high and the target base station is in the pico cell for the coverage hall, the source base station determines to perform handover regardless of the frequency band of the pico cell (both the same frequency and different frequency). On the other hand, if the estimated speed of the terminal is high and the target base station is in the pico cell for hot spot, the source base station decides to perform the handover procedure when the pico cell uses the same frequency as the macro cell that is the serving cell and pico If the cell uses a different frequency from the macro cell, it is decided not to perform the handover procedure. On the other hand, if the estimated speed of the terminal is not high speed (both medium speed or low speed), it is decided to perform the handover regardless of the type information of the target base station (both for the coverage hall and for the hot spot). .

In step S505, when the source base station determines to perform the handover procedure, the source base station transmits a handover command to the target base station instructing the handover to be performed (S510). The handover command may be transmitted through a handover command message.

If the source base station determines not to perform the handover in step S505, the source base station sends a handover No handover command message to the terminal to inform the terminal that it has decided not to perform the handover procedure. (Not shown). Alternatively, handover non-execution command information may be included in the handover command message.

Upon receiving the handover command, the terminal terminates the connection with the cell of the source base station and initiates a handover procedure for accessing the cell of the target base station (S515). Specifically, the terminal performs an operation for layer 1 and layer 2 related access for accessing a target base station, and the layer 1 and layer 2 related access operations include an operation such as random access. It may include. When the terminal completes the connection with the target base station, the terminal is in a state capable of transmitting and receiving packet data.

Meanwhile, in step S510, when the source base station determines not to perform the handover procedure, the source base station transmits a predetermined message to the terminal to indicate that the handover procedure is not performed (not shown). The predetermined message may be a handover command message.

6 is a flowchart illustrating another example of a selective handover according to the present invention. This is the case where the MSE measurement value of the UE is included in the proximity indication message and transmitted.

Referring to FIG. 6, the source base station performs an RRC connection reconfiguration to set a proximity indication operation of the terminal (S600). RRC connection reset may be performed through an RRC connection reset message.

The RRC connection reset message includes proximity indication configuration information for setting the proximity indication operation. The proximity indication configuration information may include information on whether the MSE measurement value should be included in the proximity indication message transmitted from the terminal to the source base station. The MSE measurement value may be a value measured by the terminal.

For example, the proximity indication configuration information includes cell type information, wherein the cell type is at least one of a CSG cell, a pico cell, a pico cell for a coverage hole, a pico cell for a hot spot, or all cells. Can be. For example, when the cell type is a pico cell for a coverage hole, the MSE measurement value is included in the proximity indication message when the UE enters or exits the pico cell area for the coverage hole. It is set to. As another example, when the cell type is all cells, the UE is configured to include the MSE measurement value in the proximity indication message when the UE enters into or exits from the areas of all kinds of cells.

In addition, the proximity indication configuration information may further include MSE configuration event information along with cell type information, and the MSE configuration event information may have one of entering or leaving. have. For example, when the cell type is a pico cell for a coverage hole and the MSE configuration event information is an entry, the UE is set to include an MSE measurement value in a proximity indication message when the terminal enters into an area of the pico cell for the coverage hole. do. As another example, when the cell type is a pico cell for a hot spot and the MSE configuration event information is advancing, when the terminal exits from the region of the pico cell for the hot spot, the UE is configured to include the MSE measurement value in the proximity indication message.

After step S600, the terminal transmits a proximity indication message to a source base station based on the proximity indication setting information to perform a proximity indication operation (S605). The proximity indication message may indicate that the terminal enters the pico cell or may indicate that the terminal exits the pico cell. In addition, the proximity indication message includes the MSE measurement value of the terminal. The MSE measurement may be one of high speed, medium speed or low speed. As another example, regardless of the proximity indication configuration information, the terminal may determine and transmit an MSE measurement value to the proximity indication message by itself.

Following step S605, the source base station determines whether to perform handover based on the received MSE measurement value (S610). If it is appropriate not to perform the handover, no further procedure (step S615 or below) is performed.

In this case, in determining whether to perform the handover, not only the MSE measurement value but also type information of a target base station (or cell type information of a target base station) may be used together. However, it is possible when the source base station has the type information of the target base station in advance or when it can be determined based on the proximity indication message received from the terminal.

Embodiments 1 to 4 described with reference to FIG. 5 may be applied.

That is, as an example, the source base station determines whether to perform a handover based only on the MSE measurement value of the terminal, and determines not to perform the handover if the estimated speed of the terminal is high, and if the estimated speed of the terminal is not high speed (medium speed) Or low speed) handover.

As another example, the source base station determines whether to perform handover based only on the type information of the target base station, and if the target base station is in the pico cell for the coverage hall, determines to perform the handover, and if it is in the pico cell for the hot spot You may decide not to perform a handover.

As another example, the source base station considers both the MSE measurement value of the terminal and the type information of the target base station, and determines to perform a handover if the target base station is in a pico cell for the coverage hole when the estimated speed of the terminal is high. If it is in the pico cell for the hot spot, it is decided not to perform the handover. On the other hand, if the estimated speed of the terminal is not high speed (medium speed or low speed), regardless of the type information of the target base station (both for coverage hall and for hot spot) it is determined to perform the handover.

As another example, the source base station considers not only the MSE measurement value of the terminal but also the frequency band information among the type information of the target base station, and if the estimated speed of the terminal is high and the target base station is within the pico cell for the coverage hole, Determining to perform a handover regardless of the frequency band of (both the same frequency and different frequencies). On the other hand, if the estimated speed of the terminal is high and the target base station is in the pico cell for hot spot, the source base station decides to perform the handover procedure when the pico cell uses the same frequency as the macro cell that is the serving cell and pico If the cell uses a different frequency from the macro cell, it is decided not to perform the handover procedure. On the other hand, if the estimated speed of the terminal is not high speed (both medium speed or low speed), it is decided to perform the handover regardless of the type information of the target base station (both for the coverage hall and for the hot spot). .

Following step S610, the source base station transmits an RRC connection reconfiguration message to the terminal to set the measurement to be performed by the terminal (S615). Subsequently, the terminal reports the measurement result using the measurement report message (S620).

The source base station determines whether to perform handover based on the measurement report message (S625). Although it is determined that it is appropriate to perform the handover in step S610, if it is determined that it is appropriate not to perform the handover based on the measurement report message, the subsequent procedure (step S625) is not performed.

For example, Embodiments 1 to 4 described with reference to FIG. 5 may be applied. If it is not determined whether to perform the handover in step S610, it may be determined in consideration of the measurement result of the measurement report message. Alternatively, the decision made in step S610 may be changed based on the measurement result. That is, when an A3 event, which is a criterion for determining handover, occurs, if the measurement result of the serving cell (for example, RSRP, RSRQ) is less than or equal to a predetermined threshold, the pico cell is determined to be for a coverage hole. If the measurement result of the serving cell is greater than or equal to a predetermined threshold value, the pico cell may be determined to be for a hot spot. The type information of the pico cell thus obtained may be applied to determining whether to perform handover of Embodiments 1 to 4 described above with reference to FIG. 5.

If it is determined to perform the handover, the source base station requests the handover to the target base station through the handover request message (S630).

If the source base station or the terminal does not know the type information of the target base station, the source base station via the handover request message and the cell type information (macro cell, pico cell, CSG cell, etc.) of the target base station and the installation purpose (coverage hole or Hot spots, etc.).

The target base station determines whether to approve the handover based on the handover request message (S635). Even if the source base station decides to perform the handover, the handover may be performed only after approval of the target base station.

The target base station transmits a handover request confirmation message (or handover response message) to the source base station, and transmits handover approval information on whether the target base station has approved the handover (S640). The handover request confirmation message may include type information of the target base station. In particular, if the source base station or the terminal does not know the type information of the target base station and requests the information on the cell type information and the installation purpose of the target base station through the handover request message, the target base station targets through the handover request confirmation message Cell type information of the base station and information on the installation purpose can be transmitted.

Based on the handover request confirmation message, the source base station may determine whether to perform the handover (S645). Although it is determined that it is appropriate to perform the handover in steps S610 and S625, if it is determined that it is appropriate not to perform the handover based on the handover approval information, the subsequent procedure (step S650 or less) is not performed.

Finally, when it is determined to perform the handover, the source base station sends a handover command message to the terminal to command the handover (S650).

Subsequently, the terminal initiates a procedure for performing handover from the source base station to the target base station (S655).

If it is determined in step S610, S625, or S645 that no handover is to be performed, the handover command message may indicate that the handover procedure is determined not to be performed without performing a subsequent procedure (not shown).

7 is a flowchart illustrating still another example of a selective handover according to the present invention. This is the case where the measurement report message includes the MSE measurement value of the terminal.

Referring to FIG. 7, the source base station transmits an RRC connection reconfiguration message to the terminal to set measurement to be performed by the terminal (S700). The RRC connection reset message includes measurement setting information for setting a measurement to be performed by the terminal. In this case, whether or not the terminal should include the MSE measurement value in the measurement report message transmitted to the source base station may be included in the measurement configuration information. The MSE measurement value may be a value measured by the terminal.

For example, the measurement configuration information includes cell type information, and the cell type may be at least one of a CSG cell, a pico cell, a pico cell for a coverage hole, a pico cell for a hot spot, or all cells. For example, when the cell type is a pico cell for a coverage hole, the MSE measurement value is included in the measurement report message when the terminal enters or exits the pico cell region for the coverage hole. It is set to. As another example, when the cell type is all cells, the UE is configured to include the MSE measurement value in the measurement report message when the UE enters into or exits from all types of cells.

In addition, the measurement configuration information may further include MSE configuration event information together with cell type information, and the MSE configuration event information may have one value of entry or exit. For example, when the cell type is a pico cell for a coverage hole and an MSE configuration event is an entry, the terminal is configured to include an MSE measurement value in a measurement report message when the terminal enters into an area of the pico cell for a coverage hole. . As another example, when the cell type is a pico cell for a hot spot and an MSE configuration event is advancing, the terminal is configured to include the MSE measurement value in the measurement report message when the terminal exits from the region of the pico cell for the hot spot.

After step S700, the terminal reports the result of the measurement based on the measurement setting information to the source base station using the measurement report message (S705).

The measurement report message includes the MSE measurement value of the terminal. The MSE measurement may be one of high speed, medium speed or low speed. As another example, regardless of the measurement configuration information, the terminal may determine and transmit the MSE measurement value to the measurement report message by itself.

Subsequently to step S705, the source base station determines whether to perform handover based on the received MSE measurement value (S710). If it is appropriate not to perform the handover, the subsequent procedure (step S710 or less) is not followed. In this case, in determining whether to perform the handover, not only the MSE measurement value but also type information of a target base station (or cell type information of a target base station) may be used together. However, when the source base station has the type information of the target base station in advance or can be determined based on the measurement report indication message received from the terminal.

Embodiments 1 to 4 described with reference to FIG. 5 may be applied.

For example, the source base station determines whether to perform the handover based only on the MSE measurement value of the terminal, and determines not to perform the handover if the estimated speed of the terminal is high, and if the estimated speed of the terminal is not high speed (medium speed or low speed). ) May decide to perform a handover.

As another example, the source base station determines whether to perform handover based only on the type information of the target base station, and if the target base station is in the pico cell for the coverage hall, determines to perform the handover, and if it is in the pico cell for the hot spot You may decide not to perform a handover.

As another example, the source base station considers both the MSE measurement value of the terminal and the type information of the target base station, and determines to perform a handover if the target base station is in a pico cell for the coverage hole when the estimated speed of the terminal is high. If it is in the pico cell for the hot spot, it is decided not to perform the handover. On the other hand, if the estimated speed of the terminal is not high speed (medium speed or low speed), regardless of the type information of the target base station (both for coverage hall and for hot spot) it is determined to perform the handover.

As another example, the source base station considers not only the MSE measurement value of the terminal but also the type information of the target base station and the frequency band information of the target base station, so that if the estimated speed of the terminal is high and the target base station is in the pico cell for the coverage hole, the source base station Determines to perform the handover regardless of the frequency band of the pico cell (both the same frequency and different frequencies). On the other hand, if the estimated speed of the terminal is high and the target base station is in the pico cell for hot spot, the source base station decides to perform the handover procedure when the pico cell uses the same frequency as the macro cell that is the serving cell and pico If the cell uses a different frequency from the macro cell, it is decided not to perform the handover procedure. On the other hand, if the estimated speed of the terminal is not high speed (both medium speed or low speed), it is decided to perform the handover regardless of the type information of the target base station (both for the coverage hall and for the hot spot). .

If it is determined to perform the handover, the source base station requests the handover to the target base station through the handover request message (S715).

If the source base station or the terminal does not know the type information of the target base station, the source base station via the handover request message and the cell type information (macro cell, pico cell, CSG cell, etc.) of the target base station and the installation purpose (coverage hole or Hot spots, etc.).

The target base station determines whether to approve the handover based on the handover request message (S720). Even if the source base station decides to perform the handover, the handover is performed only after approval of the target base station.

The target base station transmits a handover request confirmation message (or a handover response message) to the source base station, and transmits handover grant information on whether the target base station has approved the handover (S725). The handover request confirmation message may include type information of the target base station. Particularly, if the source base station or the terminal does not know the type information of the target base station and requests the information on the cell type information of the target base station and the installation purpose through the handover request message, the target base station sends the handover request confirmation message. Through the cell type information and the installation purpose of the target base station can be transmitted through.

Based on the handover approval information (or handover request confirmation message), the source base station may determine whether to perform the handover (S730). Although it is determined that it is appropriate to perform the handover in step S710, if it is determined that it is appropriate not to perform the handover based on the handover approval information, the subsequent procedure (step S735 or less) is not performed.

When finally determined to perform the handover, the source base station sends a handover command message to the terminal to command the handover (S735). Subsequently, the terminal initiates a handover procedure from the source base station to the target base station (S740).

If it is determined not to perform the handover in steps S710 and S730, it may be informed that the handover procedure is determined not to be performed through the handover command message without performing the subsequent procedure (not shown).

Meanwhile, since the MSE measurement value is transmitted through the measurement report message, the proximity indication operation is not essential. However, there is an advantage in that information about whether a terminal accesses a pico cell is obtained through the proximity indication operation. Therefore, prior to the transmission of the measurement report message, the source base station may perform RRC connection reconfiguration to set the proximity indication operation of the terminal, and the proximity indication message may be transmitted to the source base station based on the RRC connection reconfiguration message (not shown). ).

8 is a flowchart illustrating still another example of a selective handover according to the present invention. The MSE measurement value of the terminal is transmitted through a separate MSE report message.

Referring to FIG. 8, the terminal reports the entry into the cell area of the target base station to the source base station through an MSE report message (S800). At this time, the MSE measurement value is also reported through an MSE report message, which is a separate message. The MSE measurement value may be a value measured by the terminal and may be one of high speed, medium speed, or low speed. The terminal may determine and transmit the MSE report message by itself, or may be transmitted by an indication of a source base station.

Following step S800, the source base station determines whether to perform handover based on the received MSE measurement value (S805). If it is appropriate not to perform the handover, no subsequent procedure (step S810 or less) is followed.

In this case, in determining whether to perform the handover, not only the MSE measurement value but also type information of a target base station (or cell type information of a target base station) may be used together. However, it is possible when the source base station has the type information of the target base station in advance.

Embodiments 1 to 4 described with reference to FIG. 5 may be applied.

For example, the source base station determines whether to perform the handover based only on the MSE measurement value of the terminal, and determines not to perform the handover if the estimated speed of the terminal is high, and if the estimated speed of the terminal is not high speed (medium speed or low speed). ) May decide to perform a handover.

As another example, the source base station determines whether to perform handover based only on the type information of the target base station, and if the target base station is in the pico cell area for the coverage hall, determines to perform the handover, and the pico cell area for the hot spot. If you are in, you can decide not to perform a handover.

As another example, the source base station considers both the MSE measurement value of the terminal and the type information of the target base station, and determines to perform a handover if the target base station is in a pico cell for the coverage hole when the estimated speed of the terminal is high. If it is in the pico cell for the hot spot, it is decided not to perform the handover. On the other hand, if the estimated speed of the terminal is not high speed (medium speed or low speed), the source base station is to perform the handover regardless of the type information of the target base station (both for the coverage hall and for the hot spot) Decide

As another example, the source base station considers not only the MSE measurement value of the terminal but also the type information and frequency band information of the target base station, so that if the estimated speed of the terminal is high and the target base station is in the pico cell region for the coverage hole, Regardless of the cell's frequency band (both the same frequency and different frequencies) it is decided to perform a handover. On the other hand, if the estimated speed of the terminal is high and the target base station is in the pico cell region for hot spot, the source base station decides to perform the handover procedure when the pico cell uses the same frequency as the macro cell that is the serving cell. If the pico cell uses a different frequency from that of the macro cell, it is decided not to perform the handover procedure. On the other hand, when the estimated speed of the terminal is not high speed (both medium speed or low speed), the source base station performs handover regardless of the type information of the target base station (both for the coverage hall and for the hot spot). Decide on

In step S805, the source base station transmits an RRC connection reconfiguration message to the terminal to set measurement to be performed by the terminal (S810). The RRC connection reset message includes measurement setting information for setting a measurement to be performed by the terminal.

The terminal reports the result of the measurement based on the measurement setting information to the source base station using the measurement report message (S815).

The source base station determines whether to perform handover based on the received measurement report message and the MSE measurement value (S820). Although it is determined that it is appropriate to perform the handover in step S805, if it is determined that it is appropriate not to perform the handover based on the measurement report message, subsequent steps (below step S825) are not performed.

For example, Embodiments 1 to 4 described with reference to FIG. 5 may be applied. If it is not determined whether to perform the handover in step S805, the source base station may determine whether to perform the handover in consideration of the measurement report message.

If it is determined to perform the handover, the source base station requests the handover to the target base station through the handover request message (S825).

If the source base station or the terminal does not know the type information of the target base station, the source base station via the handover request message and the cell type information (macro cell, pico cell, CSG cell, etc.) of the target base station and the installation purpose (coverage hole or Hot spots, etc.).

The target base station determines whether to approve the handover based on the handover request message (S830). Even if the source base station decides to perform the handover, the handover is performed only after approval of the target base station.

The target base station transmits a handover request confirmation message (or handover response message) to the source base station, and transmits handover approval information on whether the target base station has approved the handover (S835). The handover request confirmation message may include type information of the target base station. In particular, if the source base station or the terminal does not know the type information of the target base station and requests the information on the cell type information and the installation purpose of the target base station through the handover request message, the target base station targets through the handover request confirmation message Cell type information of the base station and information on the installation purpose can be transmitted.

On the basis of the handover grant information and the type information of the target base station, the source base station may determine whether to perform the handover (S840). Although it is determined that it is appropriate to perform the handover in step S805 or S820, if it is determined that it is appropriate not to perform the handover based on the handover approval information, the subsequent procedure (step S845 or less) is not performed.

For example, Embodiments 1 to 4 described with reference to FIG. 5 may be applied.

Finally, when it is determined to perform the handover, the source base station sends a handover command message to the terminal to command the handover (S845). Subsequently, the terminal initiates a procedure for performing handover from the source base station to the target base station (S850).

If it is determined in step S805, S820, or S840 that the handover is not to be performed, the handover command message may indicate that the handover procedure is determined not to be performed without performing a subsequent procedure (not shown).

Meanwhile, since the MSE measurement value is transmitted through the MSE report message, the proximity indication operation is not essential. However, there is an advantage in that information about whether a terminal accesses a pico cell is obtained through the proximity indication operation. Therefore, prior to transmitting the MSE report message or before transmitting the RRC connection reestablishment message for the measurement report setup after the transmission of the MSE report message, the terminal performs the proximity indication operation set by the source base station, so as to source the proximity indication message. It can transmit to the base station.

9 is a flowchart illustrating still another example of a selective handover according to the present invention.

Referring to FIG. 9, when the source base station requests the MSE measurement value to the terminal (S900), the terminal transmits a message (proximity indication message, measurement report message, or MSE report message) including the MSE measurement value to the source base station ( S905).

Following step S605, the source base station determines whether to perform handover based on the received MSE measurement value (S610). In this case, in determining whether to perform the handover, not only the MSE measurement value but also type information of a target base station (or cell type information of a target base station) may be used together. However, this is possible when the source base station has the type information of the target base station in advance or when it can be determined based on the message received from the terminal. Embodiments 1 to 4 described with reference to FIG. 5 may be applied.

If the source base station decides not to perform the handover in step S910, the source base station transmits a handover No handover command message to the terminal to inform the terminal that it has decided not to perform the handover procedure. Alternatively, the handover non-execution command information may be included in a handover command message (or an RRC connection reestablishment message).

10 is a flowchart illustrating an operation of a terminal for selectively performing handover according to the present invention.

Referring to FIG. 10, a terminal for transmitting and receiving data with a source base station transmits an MSE measurement value to a source base station (S1000). The MSE measurement value may be transmitted through a proximity indication message or a measurement report message. In addition, the MSE measurement value may be transmitted through another new message such as RRC signaling.

The terminal receives a handover command from the source base station instructing to perform handover from the source base station to the target base station (S1005). The handover command may be transmitted through a handover command message.

The terminal receiving the handover command terminates the connection with the cell of the source base station, and initiates a handover procedure for accessing the cell of the target base station (S1010). In detail, the terminal performs an operation for accessing the layer 1 and the layer 2 related accesses to the target base station. The access operation for the layer 1 and the layer 2 may include an operation such as random access. When the terminal completes the connection with the target base station, the terminal is in a state capable of transmitting and receiving packet data.

11 is a flowchart illustrating an operation of a source base station selectively performing handover according to the present invention.

Referring to FIG. 11, the source base station receives an MSE measurement value from the terminal (S1100). The MSE measurement value may be transmitted through a proximity indication message or a measurement report message. In addition, the MSE measurement value may be transmitted through another new message such as RRC signaling.

The source base station determines whether to perform handover based on the MSE measurement value of the terminal (S1105). In this case, in determining whether to perform the handover, not only the MSE measurement value of the terminal but also the type information of the target base station (or the type information of the cell of the target base station) may be used together. The type information of the target base station may be information directly provided by the pico cell or information determined by the pico cell based on information (eg, a measurement report) received from the terminal. Examples 1 to 4 of FIG. 5 may be applied as an example of a method for determining whether to perform a handover procedure using the aforementioned MSE measurement value or type information of a target base station.

The source base station transmits a handover command to the terminal instructing to perform handover to the target base station (S1110). The handover command may be transmitted through a handover command message.

Upon receiving the handover command, the terminal terminates the connection with the cell of the source base station and initiates a handover procedure for accessing the cell of the target base station (S1115).

12 is a block diagram illustrating a base station and a terminal performing a handover according to an embodiment of the present invention. The base station may be a source base station.

Referring to FIG. 12, the terminal 1200 includes a receiver 1210 and a transmitter 1220.

The receiver 1210 receives an RRC connection reconfiguration message from the base station. The RRC connection reset message may include proximity indication configuration information for setting the proximity indication operation. The proximity indication configuration information may include information on whether the MSE measurement value should be included in the proximity indication message transmitted from the terminal to the source base station. In addition, the RRC connection reset message includes measurement setting information for setting the measurement to be performed by the terminal. In this case, whether or not the terminal should include the MSE measurement value in the measurement report message transmitted to the source base station may be included in the measurement configuration information. The proximity indication setting information or the measurement setting information includes cell type information, and the cell type may be at least one of a CSG cell, a pico cell, a pico cell for a coverage hole, a pico cell for a hot spot, or all cells. In addition, the proximity indication configuration information or the measurement configuration information may further include MSE configuration event information together with the cell type information, and the MSE configuration event information may have one value of entry or exit.

The receiver 1210 receives a handover command from the base station 1250. The handover command may be sent through a handover command message. If it is determined not to perform the handover, the receiver 1210 receives a no handover command message, and the handover non-execution command message indicates that the handover procedure is determined not to be performed. The handover non-execution command message may be included in the handover command message.

The transmitter 1220 transmits the MSE measurement value to the source base station 1250. The MSE measurement value may be transmitted through a near indication message or a measurement report message. In addition, the MSE measurement value may be transmitted through an MSE report message, which is another new message such as RRC signaling.

The base station 1250 includes a receiver 1260, a determiner 1270, and a transmitter 1280.

Base station 1250 may be a source base station in handover.

The receiver 1260 receives an MSE measurement value from the terminal. The MSE measurement value may be received through a proximity indication message or a measurement report message. In addition, the MSE measurement value may be received through another new message such as RRC signaling.

The determiner 1270 determines whether to perform handover based on the MSE measurement value. In determining whether to perform the handover, not only the MSE measurement value of the terminal but also the type information of the target base station (or the type information of the cell of the target base station) may be used together. There are two types of target base stations: a pico cell type for coverage holes and a pico cell type for hot spots. The type information of the target base station may be information directly provided by the pico cell or information determined by the pico cell based on information (eg, a measurement report) received from the terminal.

The determiner 1270 determines whether to perform handover based on only the MSE measurement value of the terminal. If the estimated speed of the terminal is a high speed, it is determined not to perform a handover, and if the estimated speed of the terminal is not high speed (medium speed or low speed), it may be determined to perform a handover. In addition, the determiner 1270 may determine whether to perform the handover based on only the type information of the target base station. If the target base station is in a pico cell for the coverage hall, it may be determined to perform a handover, and if it is in a pico cell for a hot spot, it may be determined not to perform a handover. In addition, the determiner 1270 may determine whether to perform handover in consideration of both the MSE measurement value of the terminal and the type information of the target base station. If the estimated speed of the terminal is high, it is determined to perform a handover if the target base station is in the pico cell for the coverage hole, and not to perform the handover if it is in the pico cell for the hot spot. On the other hand, if the estimated speed of the terminal is not high speed (medium speed or low speed), it is determined to perform the handover regardless of the type information of the target base station (both for the coverage hall and for the hot spot). In addition, the determiner 1270 may determine whether to perform the handover in consideration of the frequency band information among the type information of the target base station as well as the MSE measurement value of the terminal. If the estimated speed of the terminal is high and the target base station is within the pico cell for the coverage hole, the source base station is determined to perform handover regardless of the frequency band of the pico cell (both the same frequency and different frequency). On the other hand, if the estimated speed of the terminal is high and the target base station is in a pico cell for hot spots, the source base station is determined to perform a handover procedure when the pico cell uses the same frequency as the macro cell that is the serving cell and pico If the cell uses a different frequency than the macro cell, it is determined not to perform the handover procedure. On the other hand, if the estimated speed of the terminal is not high speed (both medium speed or low speed), it is determined to perform the handover regardless of the type information of the target base station (both for the coverage hall and for the hot spot). .

The transmitter 1280 transmits a handover command to the terminal. When it is determined to perform the handover procedure, the transmitter 1280 transmits a handover command to the target base station instructing the handover to be performed. The handover command may be transmitted through a handover command message. If it is determined not to perform the handover, it informs that the decision is made not to perform the handover procedure. This may also be sent via a handover command message.

The transmitter 1280 transmits an RRC connection reset message to the terminal. The RRC connection reset message may include proximity indication configuration information for setting the proximity indication operation. The proximity indication configuration information may include information on whether the MSE measurement value should be included in the proximity indication message. In addition, the RRC connection reset message includes measurement setting information for setting the measurement to be performed by the terminal. In this case, whether the MSE measurement value should be included in the measurement report message may be included in the measurement setting information. The proximity indication setting information or the measurement setting information includes cell type information, and the cell type may be at least one of a CSG cell, a pico cell, a pico cell for a coverage hole, a pico cell for a hot spot, or all cells. In addition, the proximity indication configuration information or the measurement configuration information may further include MSE configuration event information together with the cell type information, and the MSE configuration event information may have one value of entry or exit.

In the above-described exemplary system, the methods are described on the basis of a flowchart as a series of steps or blocks, but the present invention is not limited to the order of the steps, and some steps may occur in different orders or simultaneously . It will also be understood by those skilled in the art that the steps shown in the flowchart are not exclusive and that other steps may be included or that one or more steps in the flowchart may be deleted without affecting the scope of the invention.

The above-described embodiments include examples of various aspects. While it is not possible to describe every possible combination for expressing various aspects, one of ordinary skill in the art will recognize that other combinations are possible. Accordingly, it is intended that the invention include all alternatives, modifications and variations that fall within the scope of the following claims.

Claims (18)

In the method of performing a handover by the base station in a wireless communication system,
Receiving a measurement value of a mobility state estimation (MSE) of the terminal from the terminal;
Determining whether to perform handover based on the MSE measurement value and cell type information of a target base station; And
According to the determination result comprising the step of transmitting a handover command message to the terminal,
The MSE measurement value includes estimated speed information of the terminal, and the estimated speed of the terminal is one of high speed, medium speed or low speed. The method of claim 1,
And a cell type of the target base station is one of a cell for a coverage hole or a cell for a hot spot. 3. The method of claim 2,
Before determining whether to perform the handover,
And receiving the cell type information of the target base station from the target base station. 3. The method of claim 2,
Before determining whether to perform the handover, determining the cell type of the target base station based on a result of the measurement performed by the terminal;
If the result of the measurement is less than or equal to a predetermined threshold, the cell type of the target base station is determined to be a cell for a coverage hole. If the result of the measurement is greater than or equal to a predetermined threshold, the cell type of the target base station is determined to be a cell for hot spots. Handover, characterized in that for performing. The method of claim 1,
In the step of determining whether to perform the handover based on the MSE measurement value,
If the estimated speed of the terminal is a high speed, it is determined not to perform a handover, and if the estimated speed of the terminal is a medium speed or low speed handover performing method characterized in that it is determined to perform a handover. 3. The method of claim 2,
In the determining of whether to perform the handover based on the MSE measurement value, in consideration of the cell type information of the target base station to determine whether to perform the handover,
If the estimated speed of the terminal is a high speed, it is determined to perform a handover if the cell type of the target base station is a cell for a coverage hall, and if the cell type of the target base station is a cell for a hot spot, the handover is not performed. Decide not to,
And performing handover when the estimated speed of the terminal is medium speed or low speed. 3. The method of claim 2,
In the determining of whether to perform the handover based on the MSE measurement value, in consideration of the cell type information of the target base station to determine whether to perform the handover,
When the estimated speed of the terminal is a high speed, if the cell type of the target base station is a cell for a coverage hall, it is determined to perform a handover, and the cell type of the target base station is a cell for hot spot and the cell of the target base station If using the same frequency as the cell of the base station is determined to perform a handover procedure, if the cell type of the target base station is a cell for the hot spot and the cell of the target base station uses a different frequency than the cell of the base station Decide not to perform the handover procedure,
And performing handover when the estimated speed of the terminal is medium speed or low speed. The method of claim 1,
RRC (Radio Indication Configuration Information) for setting a proximity indication operation for instructing the terminal to enter or leave a cell having a CSG ID in a CSG whitelist of the UE. Resource Control) further comprises the step of sending through a connection reset message,
The proximity indication setting information includes information indicating whether or not to include the MSE measurement value measured by the terminal in the proximity indication message transmitted by the terminal to the base station,
And the MSE measurement value is received from the terminal through the proximity indication message. The method of claim 1,
The method may further include transmitting measurement setting information for setting measurement performed by the terminal through an RRC connection reset message.
The measurement setting information includes information indicating whether the terminal includes the MSE measurement value measured by the terminal in a measurement report indication message transmitted to the base station,
The MSE measurement value is received from the terminal via the measurement report message. The method of claim 1,
And performing the MSE measurement value through an MSE report message. The method of claim 1,
Transmitting a handover request message to the target base station requesting to perform a handover; And
Receiving a handover request confirmation message including information on whether the target base station permits handover;
The handover method is determined based on the handover request confirmation message. The method of claim 11,
The handover request message further includes information for requesting cell type information of the target base station;
The handover request confirmation message further comprises cell type information of the target base station. The method of claim 1,
If the base station decides not to perform a handover,
The handover command message includes information indicating that the handover is not performed. In the method of performing a handover by the terminal in a wireless communication system,
Receiving proximity indication configuration information for setting a proximity indication operation indicating that the UE enters or exits a cell having a CSG ID in a CSG whitelist of a UE through an RRC connection reconfiguration message;
Transmitting a proximity indication message including a measurement value of a mobility state estimation (MSE) of the terminal to the base station based on the proximity indication configuration information; And
Receiving a handover command message including information on whether to perform handover;
The proximity indication setting information includes information indicating whether to include the MSE measurement value in the proximity indication message,
The MSE measurement value includes estimated speed information of the terminal, and the estimated speed of the terminal is one of high speed, medium speed or low speed. 15. The method of claim 14,
The proximity indication setting information further includes a cell type parameter, wherein the cell type is a CSG cell, a pico cell, a pico cell for a coverage hole, a pico cell for a hot spot, or all cells.
When the terminal enters or exits a cell indicated by the cell type parameter, the MSE measurement value is included in the proximity indication message. The method of claim 15,
The proximity indication setting information further includes an MSE setting event parameter, wherein the MSE setting event is an entry or exit,
And when the event indicated by the MSE configuration event occurs for a cell indicated by the cell type parameter, including the MSE measurement value in the proximity indication message. A base station performing selective handover in a wireless communication system,
A receiver configured to receive a measurement value of a mobility state estimation (MSE) of the terminal from the terminal;
A decision unit to determine whether to perform a handover based on the MSE measurement value; And
A transmitter for transmitting a handover command message to the terminal based on a result determined by the determination unit,
The MSE measurement value includes the estimated speed information of the terminal, and the estimated speed of the terminal is characterized in that one of the high speed, medium speed or low speed. In the terminal performing a selective handover in a wireless communication system,
A receiving unit receiving an RRC connection reconfiguration message including proximity indication setting information for setting a proximity indication operation indicating that the UE enters or exits a cell having a CSG ID in a CSG whitelist of a UE; And
A transmitter for transmitting a proximity indication message including a measurement value of a mobility state estimation (MSE) of the terminal to the base station based on the proximity indication setting information,
The receiver receives a handover command message including information on whether to perform handover.
The proximity indication setting information includes information indicating whether to include the MSE measurement value in the proximity indication message,
The MSE measurement value includes estimated speed information of the terminal, and the estimated speed of the terminal is characterized in that one of the high speed, medium speed or low speed.

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