KR20160007959A - Methods and apparatus for load balancing in IDLE mode - Google Patents

Abstract

The present invention relates to a load distribution method for effectively redistributing a terminal of an idle state through a plurality of carriers, and to an apparatus thereof. Specifically, according to an embodiment of the present invention, a method for performing, by a terminal, a cell reselection operation comprises the following steps: receiving information on priority from a base station; and performing the cell reselection operation to make the cell reselection for a load cell reduced based on the priority information in an idle state.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a load balancing method,

 The present invention relates to a load balancing method and apparatus for effectively redistributing an IDLE state terminal over a plurality of carriers.

A method for a terminal to perform a cell reselection operation, the method comprising: receiving information about a priority from a base station; And performing a cell re-selection operation such that cell re-selection for a load cell is reduced based on the priority information in an IDLE state.

1 is a diagram illustrating a cell-ranking criterion.
2 is a diagram showing an example of a scenario for the present invention.
3 is a diagram illustrating a configuration of a base station according to another embodiment of the present invention.
4 is a diagram illustrating a configuration of a user terminal according to another embodiment of the present invention.

Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. 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 numerals whenever possible, even if they are shown in different drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

The wireless communication system in the present invention is widely deployed to provide various communication services such as voice, packet data and the like. A wireless communication system includes a user equipment (UE) and a base station (BS, or eNB). The user terminal in this specification is a comprehensive concept of a terminal in wireless communication. It is a comprehensive concept which means a mobile station (MS), a user terminal (UT), an SS (User Equipment) (Subscriber Station), a wireless device, and the like.

A base station or a cell generally refers to a station that communicates with a user terminal and includes a Node-B, an evolved Node-B (eNB), a sector, a Site, a BTS A base transceiver system, an access point, a relay node, a remote radio head (RRH), a radio unit (RU), and a small cell.

That is, in the present specification, a base station or a cell has a comprehensive meaning indicating a part or function covered by BSC (Base Station Controller) in CDMA, Node-B in WCDMA, eNB in LTE or sector (site) And covers various coverage areas such as megacell, macrocell, microcell, picocell, femtocell and relay node, RRH, RU, and small cell communication range.

Since the various cells listed above exist in the base station controlling each cell, the base station can be interpreted into two meanings. i) a device itself providing a megacell, a macrocell, a microcell, a picocell, a femtocell, or a small cell in relation to a wireless region, or ii) the wireless region itself. i indicate to the base station all devices that are controlled by the same entity or that interact to configure the wireless region as a collaboration. An eNB, an RRH, an antenna, an RU, an LPN, a point, a transmission / reception point, a transmission point, a reception point, and the like are exemplary embodiments of a base station according to a configuration method of a radio area. ii) may indicate to the base station the wireless region itself that is to receive or transmit signals from the perspective of the user terminal or from a neighboring base station.

Therefore, a base station is collectively referred to as a megacell, a macrocell, a microcell, a picocell, a femtocell, a small cell, an RRH, an antenna, an RU, a low power node (LPN), a point, an eNB, Quot;

Herein, the user terminal and the base station are used in a broad sense as the two transmitting and receiving subjects used to implement the technical or technical idea described in this specification, and are not limited by a specific term or word. The user terminal and the base station are used in a broad sense as two (uplink or downlink) transmitting and receiving subjects used to implement the technology or technical idea described in the present invention, and are not limited by a specific term or word. Here, an uplink (UL, or uplink) means a method of transmitting / receiving data to / from a base station by a user terminal, and a downlink (DL or downlink) .

There are no restrictions on multiple access schemes applied to wireless communication systems. Various multiple access schemes such as Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), OFDM-FDMA, Can be used. An embodiment of the present invention can be applied to asynchronous wireless communication that evolves into LTE and LTE-Advanced via GSM, WCDMA, and HSPA, and synchronous wireless communication that evolves into CDMA, CDMA-2000, and UMB. The present invention should not be construed as limited to or limited to a specific wireless communication field and should be construed as including all technical fields to which the idea of the present invention can be applied.

A TDD (Time Division Duplex) scheme in which uplink and downlink transmissions are transmitted using different time periods, or an FDD (Frequency Division Duplex) scheme in which they are transmitted using different frequencies can be used.

In systems such as LTE and LTE-Advanced, the uplink and downlink are configured on the basis of one carrier or carrier pair to form a standard. The uplink and the downlink are divided into a Physical Downlink Control Channel (PDCCH), a Physical Control Format Indicator CHannel (PCFICH), a Physical Hybrid ARQ Indicator CHannel, a Physical Uplink Control CHannel (PUCCH), an Enhanced Physical Downlink Control Channel (EPDCCH) Transmits control information through the same control channel, and is configured with data channels such as PDSCH (Physical Downlink Shared CHannel) and PUSCH (Physical Uplink Shared CHannel), and transmits data.

On the other hand, control information can also be transmitted using EPDCCH (enhanced PDCCH or extended PDCCH).

In this specification, a cell refers to a component carrier having a coverage of a signal transmitted from a transmission point or a transmission point or a transmission / reception point of a signal transmitted from a transmission / reception point, and the transmission / reception point itself .

The wireless communication system to which the embodiments are applied may be a coordinated multi-point transmission / reception system (CoMP system) or a coordinated multi-point transmission / reception system in which two or more transmission / reception points cooperatively transmit signals. antenna transmission system, or a cooperative multi-cell communication system. A CoMP system may include at least two multipoint transmit and receive points and terminals.

The multi-point transmission / reception point includes a base station or a macro cell (hereinafter referred to as 'eNB'), and at least one mobile station having a high transmission power or a low transmission power in a macro cell area, Lt; / RTI >

Hereinafter, a downlink refers to a communication or communication path from a multipoint transmission / reception point to a terminal, and an uplink refers to a communication or communication path from a terminal to a multiple transmission / reception point. In the downlink, a transmitter may be a part of a multipoint transmission / reception point, and a receiver may be a part of a terminal. In the uplink, the transmitter may be a part of the terminal, and the receiver may be a part of multiple transmission / reception points.

Hereinafter, a situation in which a signal is transmitted / received through a channel such as PUCCH, PUSCH, PDCCH, EPDCCH, and PDSCH is expressed as 'PUCCH, PUSCH, PDCCH, EPDCCH and PDSCH are transmitted and received'.

In the following description, an indication that a PDCCH is transmitted or received or a signal is transmitted or received via a PDCCH may be used to mean transmitting or receiving an EPDCCH or transmitting or receiving a signal through an EPDCCH.

That is, the physical downlink control channel described below may mean a PDCCH, an EPDCCH, or a PDCCH and an EPDCCH.

Also, for convenience of description, EPDCCH, which is an embodiment of the present invention, may be applied to the portion described with PDCCH, and EPDCCH may be applied to the portion described with EPDCCH according to an embodiment of the present invention.

Meanwhile, the High Layer Signaling described below includes RRC signaling for transmitting RRC information including RRC parameters.

The eNB performs downlink transmission to the UEs. The eNB includes a physical downlink shared channel (PDSCH) as a main physical channel for unicast transmission, downlink control information such as scheduling required for reception of a PDSCH, A physical downlink control channel (PDCCH) for transmitting scheduling grant information for transmission in a Physical Uplink Shared Channel (PUSCH). Hereinafter, the transmission / reception of a signal through each channel will be described in a form in which the corresponding channel is transmitted / received.

E- UTRAN  Cell Reselection

In the conventional cell reselection method standardized in TS 36.304 which is a standard related to the E-UTRAN IDLE mode terminal procedure, the carrier priority value in the cell re-selection has a great influence.

If the priority of the target carrier is higher than the priority of the current serving carrier, most IDLE terminals on the serving carrier will reselect the target carrier if the link condition of the target carrier is good (greater than the specified threshold value). On the other hand, for low priority carriers, when the link condition of the serving carrier is poor (less than the specific threshold value), the cell reselection is performed for the case where the target carrier is sufficiently good (greater than the specific threshold value) do.

For an E-UTRAN inter-frequency or inter-RAT frequency with a reselection priority higher than the reselection priority of the current E-UTRA frequency, the terminal must perform E-UTRAN inter-frequency or inter-RAT frequency cell measurements . (E-UTRAN inter-frequency or inter-RAT frequencies with a reselection priority higher than the current E-UTRAN frequency)

For an E-UTRAN inter-frequency having a reselection priority that is equal to or lower than the reselection priority of the current E-UTRA frequency and a reselection priority lower than the reselection priority of the current E-UTRA frequency, For frequency, the terminal may not perform the same or lower priority E-UTRAN inter-frequency or inter-RAT frequency cell measurements if the serving cell is of good quality. Otherwise the terminal shall perform equal or lower priority E-UTRAN inter-frequency or inter-RAT frequency cell measurements. UTRAN frequency and a reselection priority of the current E-UTRAN frequency and a reselection priority of the current E-UTRAN frequency and a reselection priority of the current E-UTRAN frequency and an inter-

- If the serving cell fulfills Srxlev> SnonIntraSearchP and Squal> SnonIntraSearchQ, the UE may choose not to perform measurements of E-UTRAN inter-frequencies or inter-RAT frequency cells of equal or lower priority.

- Otherwise, the UE will perform measurements of E-UTRAN inter-frequencies or inter-RAT frequency cells of equal or lower priority.

If the quality of the higher priority E-UTRAN or UTRAN FDD RAT / frequency cell is greater than a certain threshold since the terminal camps in the current serving cell, selly selection is performed with a higher priority E-UTRAN frequency or inter-RAT frequency cell . (If threshServServiceLowQ is provided in SystemInformationBlockType3 and more than 1 second has been elapsed since the UE camped on the current serving cell, cell reselection to a cell on a higher priority E-UTRAN frequency or inter- :

- A cell of a higher priority EUTRAN or UTRAN FDD RAT / frequency fulfilled Squal> Thresh _{X, HighQ} during a time interval TreselectionRAT; or

- A cell of a higher priority UTRAN TDD, GERAN or CDMA2000 RAT / frequency fulfill Srxlev> Thresh _{X, HighP} during a time interval _{TreselectionRAT} .

Otherwise, cell reselection to a cell on a higher priority E-UTRAN frequency or inter-

- A cell of a higher priority RAT / frequency fulfill Srxlev> Thresh _{X, HighP} during a time interval _{TreselectionRAT} ; and

- The UE has camped on the current cell for more than 1 second.

1 is a diagram illustrating a cell-ranking criterion.

Cellular selection on the same priority E-UTRAN frequency is based on the rankings for the intra-frequency and the same priority inter-frequency cell re-selection as defined in TS 36.304 5.2.4.6. TS 36.304 According to the intra-frequency and the same priority inter-frequency selly selection criterion defined in 5.2.4.6, the cells must be ranked according to the criteria of FIG.

 If one cell is ranked with the best cell, the terminal has to perform a selly selection on that cell. (If a cell is ranked as the best cell, the UE shall perform cell reselection to that cell)

In all cases, the terminal shall re-select a new cell only when the following conditions are satisfied.

- The new cell ranks better than the serving cell

- More than one second elapsed since the terminal camped in the serving cell

(In all cases, the UE shall reselect the new cell, only if the following conditions are met:

- the new cell is better than the serving cell during a time interval TreselectionRAT;

- more than 1 second has elapsed since the UE camped on the current serving cell.

Cellular selection with lower priority E-UTRAN or inter-RAT frequency cells since the UE camps in the current serving cell is performed if the quality of the serving cell is less than a certain threshold and the quality of the lower priority cell is greater than a certain threshold (If threshServServiceLowQ is provided in SystemInformationBlockType3 and more than one second has been elapsed since the UE camped on the current serving cell, cell reselection to a cell on a lower priority shall be E-UTRAN frequency or inter-RAT frequency shall exceed the serving frequency shall if performed if:

- The serving cell fulfills Squal <Thresh _{Serving, LowQ} and a cell of a lower priority EUTRAN or UTRAN FDD RAT / frequency fulfill Squal> Thresh _{X, LowQ} during a time interval _{TreselectionRAT} ; or

- The serving cell fulfills Squal <Thresh _{Serving, LowQ} and a cell of a lower priority UTRAN TDD, GERAN or CDMA2000 RAT / frequency fulfill Srxlev> Thresh _{X, LowP} during a time interval _{TreselectionRAT} .

Otherwise, cell reselection to a cell on a lower priority E-UTRAN frequency or inter-

- The serving cell fulfills Srxlev <Thresh _{Serving, LowP} and a cell of a lower priority RAT / frequency fulfill Srxlev> Thresh _{X, LowP} during a time interval _{TreselectionRAT} ; and

- More than 1 second has elapsed since the UE camped on the current serving cell.

E- UTRAN  Cell Reselection  Priority processing

The priorities of different E-UTRAN frequencies or inter-RAT frequencies may be determined via system information (cellReselectionPriority), via an RRC Connection Release message, or from another RAT in an inter-RAT cell selection Can be provided. (RAT cell interleaving (RAT) selection), which is different from the E-UTRAN frequencies or inter-RAT frequencies.

If priority is provided via dedicated signaling, the terminal shall ignore all priorities provided via system information. (If priorities are provided in dedicated signaling, the UE shall ignore all the priorities provided in system information.)

While the terminal camps in the appropriate CSG cell, the terminal always has to consider the current frequency as the highest priority frequency. (While the UE is camped on a CSG cell, the UE shall always consider the current frequency to be the highest priority frequency (i.e., higher than the eight network configured values), irrespective of any other priority value allocated to this frequency.

If the terminal is capable of providing MBMS service continuity or is interested in receiving an MBMS service and is able to receive an MBMS service while camping on a provided frequency, the terminal will broadcast the SIB 13 in the cell reselected during the MBMS session And the frequency can be considered as the highest priority during the following conditions. (If the UE is capable of MBMS service continuity and receiving or interested in receiving an MBMS service and can only receive this MBMS service while camping on a frequency on which is provided, the UE may consider the frequency of the highest priority during the MBMS session as long as the reselected cell is broadcasting SIB13 and as long as:

- SIB 15 of the serving cell indicates that the frequency is one or more MBMS SAIs included in the MBMS User Service Description (USD) of this service; or

- SIB15 is not broadcast in the serving cell and that frequency is included in the USD of this service.)

After changing the priority, the terminal should search for a higher priority for cell selection as soon as possible. (UE should search for a higher priority layer for cell reselection as soon as possible after the change of priority.)

The terminal shall delete the priority given by dedicated signaling under the following conditions.

- When the terminal enters the RRC CONNECTED state, or when the T320 valid time expires, or when the PLMN selection is performed by a request by the NAS

(The UE shall delete priorities provided by dedicated signaling when:

- the UE enters RRC_CONNECTED state; or

- the optional validity time of dedicated priorities (T320) expires; or

- a PLMN selection.

As described above, in the prior art, the reselection with the priority broadcasted can be reselected to the cell of the carrier having the highest priority of most IDLE terminals of all the carriers having the low priority. Although the priority can be adjusted when an overload occurs, this can cause a swing of the inter-carrier load surge, which can not solve the problem. There is a problem that load distribution of the IDLE terminal in the overload cell is difficult because the priority re-selection allocated by the dedicated signaling when the terminal goes to the IDLE state is deleted when the terminal enters the RRC_CONNECTED state or expires when the valid time expires.

It is an object of the present invention to provide a load balancing method capable of effectively redistributing IDLE terminals under overlapping coverage of a plurality of cells to a plurality of cells.

As mobile data increases, the use of multiple carriers is also increasing. A plurality of macrocells can be constructed with overlapping coverage through a plurality of carriers. A plurality of small cells can be constructed with overlapping coverage through a plurality of carriers. One or more macrocells and one or more small cells may be constructed with overlapping coverage through multiple carriers. Each macrocell and small cell may have the same carrier frequency or different carrier frequencies.

2 shows an example of a scenario for an embodiment of the present invention.

In FIG. 2, each base station has one cell. The cells of each base station have different frequencies. The present invention is also applicable to scenarios other than that of FIG. For example, it can be applied to various scenarios such as a scenario in which cell 1 and cell 2 are provided through one base station in FIG. 2, and a scenario in which each base station adds another cell in FIG. 2. 2 is an exemplary scenario for explaining the present invention, and the following description can be applied to various multi-carrier scenarios other than FIG.

In an environment where multiple carriers are stacked, the terminal and the network can use the following methods for load distribution of the ILDE terminal or for redistribution.

Perform selly selection randomly for the same priority frequencies

In the prior art, selly selection was performed only on cells with better ranking according to the criteria defined in TS 36.304 5.2.4.6 for the same priority inter-frequency cell. If the serving cell is of a better ranking, it does not perform cell selection. TS 36.304 Since the criterion defined in 5.2.4.6 has a significant effect on the RSRP measurement value of the corresponding cell, it is highly likely that the cell selection is not performed in the adjacent cell region overlapped with the serving cell. Or TS 36.304 5.2.4.6 is influenced by the Qoffset and Qhys settings, most terminals in overlapping coverage are likely to have a high ranking in a particular cell. If a setting value having a high possibility of ranking a serving cell / carrier / frequency is set, there is a high possibility that cell selection will not be performed. If a setting value having a high possibility of being ranked high in a neighboring cell is set, There is a high possibility that cell selection is performed on the adjacent cell.

In the present invention, the UE may select the highest priority cell / carrier / frequency among the cells / carriers / frequencies designated with the same priority as the serving cell / carrier / frequency randomly or at the same rate or with a specific probability value. Alternatively, in the present invention, the UE may select a cell / carrier / frequency to perform selly selection randomly or at the same rate or with a certain probability value among the same set cell / carrier / frequency with the highest priority.

For example, consider a case where the CellReselectionPriority of the cell 1 frequency is 6, the CellReselectionPriority of the cell 2 frequency is 4, and the CellReselectionPriority of the cell 3 frequency is 2 in FIG. According to the prior art, since the CellReselectionPriority of the cell 1 is the highest, most IDLE terminals camping / reselecting / selecting the cell 1 when Squal or Srxlev of the cell 1 is not smaller than Thresh _{Serving, LowQ} or Thresh _{Serving, LowP} . If an overload occurs in cell 1 or if the load of cell 1 goes up to a certain level or more, the performance for the connected terminals deteriorates. This may result in connection delays when the UEs in the IDLE state transition to the CONNECTED state and transmit data, which may further exacerbate the overloaded network conditions. In this case, the base station can provide information necessary for selly selection of the IDLE mode terminals to other cells through the cell 1 through the system information or the RRC Connection Release message.

For example, the base station may designate a plurality of cells / carriers / frequencies with the same priority through system information (for example, SIB5 or SIB3) or an RRC Connection Release message. For example, in the scenario of FIG. 2, the cellReselectionPriority of the cell 1 frequency is set to 6 through the cellReselectionServingFreqInfo of the SIB 3, and the cellReselectionPriority of the cell 2 frequency or the cell 3 frequency is set through the InterFreqCarrierFreqInfo of the SIB 5, Can be set to the same value (6) as the cell 1 frequency.

The UE may select the highest priority cell / carrier / frequency out of the cell / carrier / frequency assigned with the same priority at random or with the same ratio / probability or with a certain probability value. For example, if the cell 1 frequency and the cell 2 frequency are set to the same value (6), the terminal may randomly select (with random probability) the cell 2 frequency as the highest priority cell / carrier / frequency. The terminal considers the selected cell / carrier / frequency as the highest priority frequency. And perform an existing priority-based reselection procedure. For example, the UE may determine a probability proportional to the highest priority cell / carrier / frequency among the priorities received through the system information (for example, if two frequencies have the highest priority, 50%) to select the highest priority cell / carrier / frequency for cell selection. If the cell 1 frequency and the cell 2 frequency are set to the same value (6), the cell 2 frequency may be selected with the highest priority cell / carrier / frequency with a 50% probability. (E.g., the UE may generate a random number in an evenly distributed range between 0 and 1, and may select the highest priority cell / carrier / frequency if the generated random number is less than or greater than 50). ) The terminal considers the selected cell / carrier / frequency as the highest priority frequency. And perform an existing priority-based reselection procedure. In another example, the base station may provide a probability of being reselected to the cell for the highest priority frequency among the priority values provided through the system information. The terminal may cause the cell 2 frequency to be selected as the highest priority cell / carrier / frequency according to the probability of being received. (E.g., the UE may generate a random number in an evenly distributed range between 0 and 1, and may select the highest priority cell / carrier / frequency if the generated random number is less than the received probability. ) The terminal considers the selected cell / carrier / frequency as the highest priority frequency. And perform an existing priority-based reselection procedure.

In another example, the base station may provide the terminal access class information to perform the selly select in a bitmap form by selecting a specific frequency through the system information. The UE may select the cell 2 frequency as the highest priority cell / carrier / frequency when it corresponds to the access class according to the received access class information. The terminal considers the selected cell / carrier / frequency as the highest priority frequency. And perform an existing priority-based reselection procedure.

The base station randomly selects the highest priority cell / carrier / frequency among the cells / carriers / frequencies designated with the same priority as the serving cell / carrier / frequency through the system information (for example, SIB5 or SIB3) ) Or with the same probability / probability or with a specific probability value, or with random or at the same rate or with a certain probability value among the cells / carriers / frequencies for which the terminal is set to be the same with the highest priority, To select the cell / carrier / frequency to perform. The terminal can perform selly selection by checking the instruction information. If there is no indication information or if the indication information is set to OFF, seli selection can be performed according to the prior art (criteria defined in TS 36.304 5.2.4.6). It is possible to configure the terminal to process it without sending the above-mentioned instruction information in another way.

Perform selly selection with the next highest / second highest priority

In an environment in which multiple carriers are stacked together, the UE and the network use the next higher (second highest) priority cell / carrier / frequency than the serving cell / carrier / frequency for load balancing or for redistribution of the IDLE terminals with the highest priority Cell / carrier / frequency randomly or with a certain probability value. Or a higher priority cell / carrier / frequency next to the highest priority may be selected randomly or a cell / carrier / frequency to perform cell selection with a certain probability value.

For example, consider a case where the CellReselectionPriority of the cell 1 frequency is 6, the CellReselectionPriority of the cell 2 frequency is 4, and the CellReselectionPriority of the cell 3 frequency is 2 in FIG.

The base station randomly sets the next highest (second highest) cell / carrier / frequency to the highest priority cell / carrier / frequency higher than the serving cell / carrier / frequency through the system information (for example SIB5 or SIB3) Or to select with a particular probability value, or to select the next highest priority cell / carrier / frequency immediately below the highest priority, randomly or with cell / carrier / frequency for cell selection, with a particular probability value The instruction information can be sent together.

The UEs camping / reselecting / selecting in cell 1 may randomly select the cell 2 frequency that is the next highest (second highest) priority with a certain probability value (if the probability value is broadcast through the system information) Select as priority. The terminal considers the selected cell / carrier / frequency as the highest priority frequency. And perform an existing priority-based reselection procedure.

In another example, the base station may provide the terminal access class information to perform the selly select in bitmap form by selecting the next higher priority frequency through the system information. The UE may select the cell 2 frequency as the highest priority cell / carrier / frequency when it corresponds to the access class according to the received access class information. The terminal considers the selected cell / carrier / frequency as the highest priority frequency. And perform an existing priority-based reselection procedure.

Inter-cell / inter-cell coordination

According to the prior art, the priority assigned by dedicated signaling is deleted when the UE enters the RRC_CONNECTED state or the expiration time expires. Therefore, when the UE continues state transition between the IDLE mode and the CONNECTED mode in a short period, or when the valid time elapses, the reselection is performed to the highest priority frequency cell again.

For example, consider a case where the CellReselectionPriority of the cell 1 frequency is 6, the CellReselectionPriority of the cell 2 frequency is 4, and the CellReselectionPriority of the cell 3 frequency is 2 in FIG.

If an overload occurs in the cell 1 or the load of the cell 1 rises to a certain level or more, the UE enters the IDLE mode in the CONNECTED mode by setting the CellReselectionPriority of the cell 2 frequency to 7 through the RRC Connection Release message, So that the rosary selection can be performed. When the UE enters the RRC CONNECTED mode, the priority for the cell 2 frequency is canceled. Therefore, when the UE moves to the RRC IDLE mode again, the UE performs a reselection to Cell 1 (where an overload occurs).

In order to prevent this, when an overload occurs in a specific cell or when the load increases to a certain level or more, it is necessary to rebalance the cell-selection related information between cells / base stations equally or appropriately through collaboration between cells / base stations.

To do so, the base station may be able to provide CellReselectionPriority information to neighboring base stations (by cell / carrier / frequency) via the X2AP procedure. For example, the CellReselectionPriority information may be included in a Load Indication procedure (Load Information message) for conveying load and interference coordination information. As another example, the CellReselectionPriority information may be included in the X2 Setup procedure (X2 Setup Request message) for exchanging application level configuration data. As another example, the CellReselectionPriority information may be included in the eNB Configuration Update message (eNB Configuration Update message) for updating the application level configuration data. As another example, the CellReselectionPriority information may be sent to another base station by including it in a Resource Status Request message or a Resource Status Response message for load measurement reporting or a Resource Status Update message. As another example, CellReselectionPriority information can be sent to a new X2AP message or to an existing X2AP message.

The base station that has received the selly selection related information through the X2AP message can update the received selly selection related information and broadcast it through the system information.

For example, if the CellReselectionPriority of the cell 1 frequency is 6, the CellReselectionPriority of the cell 2 frequency is 4, and the CellReselectionPriority of the cell 3 frequency is 2 in FIG. 2, if an overload occurs in the cell 1 or a load of the cell 1 exceeds a certain level The base station 1 providing cell 1 may expect / request that cell 1 frequency has a low CellReselectionPriority value to avoid base station 2 selecting cell 1 frequency as the highest priority frequency and reselecting. For example, base station 1 may request CellReselectionPriority of the expected / requested Cell 1 frequency to be 2, and CellReselectionPriority of the expected / requesting Cell 2 frequency to be 6. The base station 2 can update the selly selection related information received from the base station 1 and broadcast it through the system information of the cell 2. IDLE terminals camping / reselecting / selecting in cell 2 may have camped on cell 2 as long as the link quality is not lower than the threshold value of the serving cell because the frequency priority of cell 2 is the highest.

In another example, if the CellReselectionPriority of the cell 1 frequency is 6, the CellReselectionPriority of the cell 2 frequency is 4, and the CellReselectionPriority of the cell 3 frequency is 2 in FIG. 2, if an overload occurs in the cell 1, , The base station 1 providing the cell 1 transmits the current cell / carrier / frequency specific CellReselectionPriority information (CellReselectionPriority 6 of the cell 1 frequency 6, (2) CellReselectionPriority of Cell 2 frequency 4), indication information (and / or cell 1 load information) requesting cell reselection priority adjustment due to overload, and so on. The base station 2 can adjust the celluler priority based on the celluli selection related information received from the base station 1 (adjust the priority of the cell 2 upward), and broadcast it through the system information. IDLE terminals camping / reselecting / selecting in cell 2 may have camped in cell 2 as long as the link quality is not lower than the threshold value of the serving cell because the frequency priority of cell 2 is the highest.

For another example, consider a case where a base station provides a cell-to-carrier / frequency-dependent reselection probability through system information.

The base station provides the cell selection / carrier / frequency dependent reselection probability information, which is a probability / ratio value that the terminal selects the cell / carrier / frequency with the highest priority frequency through the system information (for example, SIB5 or SIB3) . For example, in the scenario of FIG. 2, the probability value for selecting the cell 1 frequency continuously to the highest priority is 30% through the cellReselectionServingFreqInfo of the SIB 3, and the probability value for selecting the cell 2 frequency as the highest priority through the InterFreqCarrierFreqInfo of the SIB 5 is 60 %, Or the probability that the cell 3 frequency is selected as the highest priority can be set to 10%. Alternatively, in the scenario of FIG. 2, the probability value for selecting the cell 2 frequency as the highest priority may be set to 60%, or the probability value for selecting the cell 3 frequency as the highest priority may be set to 10% through InterFreqCarrierFreqInfo of the SIB 5.

The UE receives the information indicating to select a frequency having the highest priority for cell selection through the cell / carrier / frequency dependent re-selection probability information in the system information (for example, SIB5 or SIB3) And selects the highest priority frequency for reselection according to received cell / carrier / frequency-dependent reselection probability information. Alternatively, when the UE receives the cell-to-carrier / frequency-dependent reselection probability information through the system information (for example, SIB5 or SIB3), the UE calculates the reselection probability for each cell / carrier / Select a higher priority frequency. (For example, when the probability value of selecting the cell 2 frequency as the highest priority is 60%, the UE generates a random number in an evenly distributed range between 0 and 1, and the generated random number is 0 to 60 , The cell 2 frequency may be selected as the highest priority cell / carrier / frequency for cell selection.) The terminal considers the selected cell / carrier / frequency as the highest priority frequency. And perform an existing priority-based reselection procedure.

For example, when an overload occurs in cell 1 in FIG. 2 or a load rises to a certain level or more, cell-selection related information (cell / carrier / frequency-dependent reselection probability information) It is necessary to readjust them equally or suitably.

To this end, the base station can provide the reselection probability information for each cell / carrier / frequency to the neighbor base station through the X2AP procedure. For example, the reselection probability information for each cell / carrier / frequency may be included in a Load Indication procedure (Load Information message) for transmitting load and interference coordination information. As another example, the cell-to-carrier / frequency-dependent reselection probability information may be included in an X2 Setup procedure (X2 Setup Request message) for exchanging application level configuration data. As another example, reselection probability information for each cell / per carrier / frequency may be included in an eNB Configuration Update message (eNB Configuration Update message) for updating application level configuration data. As another example, the reselection probability information for each cell / carrier / frequency may be transmitted to another base station by including in a Resource Status Request message, a Resource Status Response message or a Resource Status Update message for load measurement reporting. As another example, the cell-to-carrier / frequency-dependent reselection probability information can be transmitted to a new X2AP message or an existing X2AP message.

The base station which has received the cell selection related information (cell / carrier / frequency dependent cell selection probability information) through the X2AP message updates the received cellulization related information and broadcasts it through the system information.

For example, if the CellReselectionPriority of the cell 1 frequency is 6, the CellReselectionPriority of the cell 2 frequency is 4, and the CellReselectionPriority of the cell 3 frequency is 2 in FIG. 2, if an overload occurs in the cell 1 or a load of the cell 1 exceeds a certain level The base station 1 providing the cell 1 can determine whether the base station 2 (cell 2 provided by the base station 2) is expecting / requesting per cell / carrier / carrier to avoid selecting cell 1 frequency as the highest priority frequency and reselecting, Frequency-based reselection probability information. The base station 2 can update the cell selection probability information by cell / carrier / frequency received from the base station 1 and broadcast it through the system information. For example, cell 1 may update the reselection probability to 0 or lower to broadcast. In another example, if the CellReselectionPriority of the cell 1 frequency is 6, the CellReselectionPriority of the cell 2 frequency is 4, and the CellReselectionPriority of the cell 3 frequency is 2 in FIG. 2, if an overload occurs in the cell 1 or a load The base station 1 providing the cell 1 can transmit the cell selection information (and / or the cell 1 load information) requesting the cell priority adjustment due to the overload, To base station 2, which provides cell 2, The base station 2 can adjust the cell selection related information (cell / carrier / frequency dependent re-selection probability information) based on the cell selection information received from the base station 1 and broadcast it through the system information. For example, cell 1 (frequency) reselection probability can be updated to 0 or lower to broadcast.

The above-described cell selection-related information is not limited to CellReselectionPriority, cell-to-carrier / frequency-dependent reselection probability information. Similar information that induces selly selection for load balancing of IDLE terminals may also be included in the scope of the present invention.

Even when entering the RRC CONNECTED state,

As described above, according to the prior art, the priority assigned by the dedicated signaling is deleted when the UE enters the RRC_CONNECTED state or the expiration time expires. Therefore, when the UE continues state transition between the IDLE mode and the CONNECTED mode in a short period, or when the valid time elapses, the reselection is performed to the highest priority frequency cell again.

For example, consider a case where the CellReselectionPriority of the cell 1 frequency is 6, the CellReselectionPriority of the cell 2 frequency is 4, and the CellReselectionPriority of the cell 3 frequency is 2 in FIG.

If an overload occurs in the cell 1 or a load of the cell 1 rises to a certain level or more, the UE enters the IDLE mode in the CONNECTED mode by setting the CellReselectionPriority of the cell 2 frequency to 7 through the RRC Connection Release message, So that the rosary selection can be performed. When the UE enters the RRC CONNECTED mode, the priority for the cell 2 frequency is canceled. Therefore, when the UE moves to the RRC IDLE mode again, the UE performs a reselection to Cell 1 (where an overload occurs).

The same problem may also occur when the base station provides the cell selection / carrier / frequency dependent reselection probability information through the system information (for example, SIB5 or SIB3). The UE selects the highest priority frequency for reselection according to received cell / carrier / frequency-based reselection probability information. The terminal considers the selected cell / carrier / frequency as the highest priority frequency. The terminal may consider the previous / last cell / carrier / frequency as the lowest priority frequency. And perform an existing priority-based reselection procedure. In this case, however, the priority is deleted when the terminal enters the RRC CONNECTED mode. Therefore, when the UE moves to the RRC IDLE mode again, the UE performs a reselection to Cell 1 (where an overload occurs).

To prevent this, the base station may include information for instructing not to delete the priority even when entering the RRC CONNECTED state through the system information (for example, SIB5 or SIB3) or the RRC Connection Release message. When the UE receives the information for instructing not to delete the priority even when entering the RRC CONNECTED state, the UE may not delete the priority even when entering the RRC CONNECTED state. The timer t320, which represents the validity period for which the dedicated priority is configured, can have a value from 5 minutes to 180 minutes and can be set for a sufficient amount of time until the overload is released. Therefore, when entering the RRC CONNECTED state, information including the instruction to not delete the priority can be included together with the t320 information. As another example, the information for instructing not to delete the priority even when entering the RRC CONNECTED state may be new timer information. In another example, the information to indicate not to delete the priority even when entering the RRC CONNECTED state can be set to ENUMERATED {true}.

Fast moving UE operation

A fast moving terminal may not be desirable to camp / reselect / select in a small cell. Since a fast moving terminal is highly mobile, it can ignore the information for load balancing or redistribution of the IDLE terminal. For example, if the terminal detects a high-mobility state, the base station may ignore the (additional) information for load distribution of the IDLE terminal through the system information (for example, SIB5 or SIB3).

As described above, according to the present invention, when an overload occurs in a specific cell in an environment configured through a plurality of carriers, an IDLE terminal is redistributed to other cells, thereby preventing an increase in the load of a cell that can be caused by switching the CONNECTED state of the IDLE state terminal There is an effect.

3 is a diagram illustrating a configuration of a base station according to another embodiment of the present invention.

3, the base station 1000 according to another embodiment includes a control unit 1010, a transmission unit 1020, and a reception unit 1030.

The controller 1010 controls the overall operation of the base station according to the load balancing method capable of effectively redistributing IDLE terminals under overlapping coverage of a plurality of cells required to perform the above-described present invention to a plurality of cells.

The transmitting unit 1020 and the receiving unit 1030 are used to transmit and receive signals, messages, and data necessary for carrying out the present invention to and from the terminal.

4 is a diagram illustrating a configuration of a user terminal according to another embodiment of the present invention.

4, a user terminal 1100 according to another embodiment includes a receiving unit 1110, a control unit 1120, and a transmitting unit 1130.

The receiving unit 1110 receives downlink control information, data, and messages from the base station through the corresponding channel.

The controller 1120 controls the overall operation of the terminal according to the load balancing method capable of effectively redistributing IDLE terminals under overlapping coverage of a plurality of cells required to perform the present invention to a plurality of cells.

The transmitter 1130 transmits uplink control information, data, and a message to the base station through the corresponding channel.

The standard content or standard documents referred to in the above-mentioned embodiments constitute a part of this specification, for the sake of simplicity of description of the specification. Therefore, it is to be understood that the content of the above standard content and portions of the standard documents are added to or contained in the scope of the present invention.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

Claims (1)

A method for a terminal to perform a cell reselection operation,
Receiving information on a priority from a base station; And
And performing a cell re-selection operation such that cell re-selection for the load cell is reduced based on the priority information in the IDLE state.

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