KR20140010551A - Method and apparatus transmitting control information in heterogeneous network - Google Patents

Abstract

Provided are a control information transmitting method and apparatus in a heterogeneous network. In the method, a terminal receives a PCI (physical cell ID) of a target cell and an RRC (radio resource control) connection reset including cell-related control information of the target cell and determines if the target cell indicated by the PCI is a pico-cell based on the PCI or the cell-related control information. According to the present invention, the power consumption of a terminal can be reduced since continuous measurement for an inter-frequency pico-cell or intra-frequency pico-cell is not necessary. Also, in case of proximity indication operation for a pico-cell, the power consumption of the terminal is reduced since, even if system information is not decoded and only main synchronization sequence and sub-synchronization sequence are decoded in case of proximity indication operation for a pico-cell, it is possible to know if the target cell is a pico-cell. [Reference numerals] (400) Macro base station; (420) Pico base station; (450) Terminal; (S480) X2 interface (PCI, cell-related control information); (S500) RRC connectino resetting (PCI, cell-related control information, recorded proximity setting information); (S505) Proximity indication; (S510) RRC connection resetting (measurement setting); (S515) Measurement report; (S520) Handover request (terminal context); (S525) Approval control; (S530) Handover request check; (S535) Handover determination; (S540) Handover process

Description

METHOD AND APPARATUS TRANSMITTING CONTROL INFORMATION IN HETEROGENEOUS NETWORK}

The present invention relates to a wireless communication system, and more particularly, to a method and apparatus for transmitting control information in a heterogeneous network system.

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.

In particular, the hot spot picocell using the inter-frequency is not installed because the signal strength of the macro cell is weak and is installed for the traffic offloading of the macro cell serving cell. In order to detect and handover a cell, measurement must be continuously performed, which causes a problem of high battery consumption. There is a need for a handover method and apparatus that can avoid such continuous measurements.

An object of the present invention is to provide a method and apparatus for transmitting pico cell related information.

Another technical problem of the present invention is to provide a method and apparatus for determining whether a cell to be handed over is a pico cell based on a physical cell ID.

Another technical problem of the present invention is to provide a method and apparatus for minimizing performance of unnecessary measurement or decoding of system information.

According to an aspect of the present invention, a method of receiving control information by a terminal in a heterogeneous network system includes a physical cell ID (PCI) of a target cell to which the terminal accesses and cell-related control of the target cell. Receiving a Radio Resource Control (RRC) connection reconfiguration including information from a base station of a serving cell providing a service; And determining whether the target cell indicated by the PCI is a pico cell based on the PCI or the cell related control information.

According to another aspect of the present invention, a terminal receiving control information in a heterogeneous network system includes a radio including a physical cell ID (PCI) of a target cell to which the terminal accesses and cell related control information of the target cell. A receiving unit for receiving RRC connection reconfiguration from a base station of a serving cell providing a service; And a controller configured to determine whether the target cell indicated by the PCI is a pico cell based on the PCI or the cell related control information.

According to another aspect of the present invention, a method for transmitting control information by a base station in a heterogeneous network system includes a physical cell ID (PCI) of a neighbor cell and cell related control information of the neighbor cell through an X2 configuration message. Receiving from the neighbor cell; And transmitting a radio resource control (RRC) connection reconfiguration (RRC) connection reconfiguration including the PCI and the cell related control information to the terminal.

According to another aspect of the present invention, a base station transmitting control information in a heterogeneous network system transmits a physical cell ID (PCI) of a neighbor cell and cell related control information of the neighbor cell through an X2 configuration message to the neighbor. Receiving unit for receiving from the cell; And a transmitter for transmitting a radio resource control (RRC) connection reconfiguration (RRC Connection Reconfiguration) including the PCI and the cell related control information to the terminal.

According to the present invention, in the handover to the pico cell, it is not necessary to perform continuous measurement on the intra-frequency pico cell or the inter-frequency pico cell, thereby reducing power consumption of the terminal.

In addition, in the proximity indication operation for the picocell, even if only the main synchronization sequence and the sub-synchronization sequence are decoded without decoding the system information, it is possible to know whether the target cell is a pico cell, thereby reducing power consumption of the terminal.

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 flowchart illustrating an example of a process of a UE handing over from a macro base station to a CSG cell using a proximity indication to which the present invention is applied.
4 shows an example of a picocell proximity scenario to which the present invention is applied.
5 is a flowchart illustrating an example of a method for transmitting control information according to the present invention.
6 shows another example of a proximity scenario to which the present invention is applied.
7 is a flowchart illustrating another example of a method for transmitting control information according to the present invention.
8 is a block diagram illustrating a base station and a terminal for transmitting control information 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 thereof will be omitted.

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".

Simple cell segmentation of macro cells and micro cells makes it 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 (HetNet), not only the shadow areas 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. The femtocell can be connected to the mobile communication core network using a home or office DSL or cable broadband.

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. For example, for each cell size, the diameter of one site may be about 600m, the diameter of the macro cell may be about 300m, and the diameter of the small cell may be about 20-30m.

3 is a flowchart illustrating an example of a process of handing over a UE from a macro base station to a CSG cell using a proximity indication to which the present invention is applied. In this case, the source base station means a macro base station, the target base station means a base station of the CSG cell.

Here, the CSG (Closed Subscriber Group) cell refers to a cell providing a service only to specific subscribers. A specific subscriber is a subscriber that can access one or more cells of a specific Public Land Mobile Network (PLMN). The CSG ID is an ID broadcasted by the CSG / Hybrid cell so that authorized members of the CSG cell can access it. The CSG whitelist is a list containing the IDs of subscribers authorized to access.

On the other hand, the terminal technology (implementation) of the terminal with respect to when and when to search (single frequency band (intra frequency) or other frequency band (inter frequency) in the same frequency band (intra frequency) or other frequency band (inter frequency)) This technique is called 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. 3, the source base station sets up a terminal for control related to proximity indication (S300). For example, the base station may set the terminal by transmitting an RRC connection reconfiguration message, the RRC connection reconfiguration message may include information on 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 (S305).

If there is no measurement setting for the associated frequency / RAT, the source base station performs the measurement setting (S310). 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. In order to minimize the request for handover preparation information of a CSG cell or a hybrid cell, the network also does not request information for a cell that has a CSG ID in the UE's CSG white list but is not in the geographical area of the UE. 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 measurement 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.

Following step S310, the terminal performs the measurement according to the measurement method set by the source base station and transmits the measurement result including the physical cell ID (PCI) to the source base station using the measurement report message (S315). 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.

For example, the measurement may be an S-measurement. The S-measurement is a measurement in which it is determined based on a predetermined threshold whether or not the terminal is required to perform the measurement. For example, if the RSRP of the serving cell is smaller than a predetermined threshold, the measurement is performed. That is, the terminal performing intra-frequency, inter-frequency, or inter-RAT measurement is controlled based on a predetermined threshold. In this case, the predetermined threshold may be an RSRP-range, an integer between 0 and 97, and a unit may be dBm. If the predetermined threshold is zero, the S-measurement is performed in the same manner as the general measurement.

The source base station configures the terminal to acquire system information (SI) and to report a specific PCI (S320).

The terminal acquires system information (CGI, Tracking Area ID, TSG, etc.) from the target base station (target HeNB) using an autonomous gap (S325). 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 (S330)

The source base station includes the target E-CGI and CSG ID in the handover request message and transmits it to the MME (S335). 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 (S340). 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) (S345). 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 succeeds (S350). 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 (S355). 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 (S360).

The source base station transmits a handover command message (an RRC connection reconfiguration message including mobility control information) to the terminal (S365).

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 has not previously visited the target base station, the terminal does not need to give a proximity indication.

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 (S370).

On the other hand, unlike handover to a CSG cell, in the handover to an inter-frequency hot spot pico cell, even if S-measurement is enabled, the signal strength of the macro cell is not weak in the region where the hot spot pico cell is installed. Inter-frequency measurements that are S-measurement criteria may not be triggered. Accordingly, the UE has to repeatedly perform inter-frequency measurement on a corresponding frequency in order to handover to an inter-frequency hot spot pico cell.

Now, a method apparatus for transmitting cell-related control information to a terminal in advance using a proximity indication operation according to the present invention will be described.

First, the kind of pico cell is demonstrated. The types of picocell are "picocell for coverage hole" (hereinafter referred to as "coverage hole picocell") and "picocell for hot spot" (hereinafter referred to as hotspot picocell).

The Coverage Hole Pico cell is used when a terminal can not transmit / receive data through a macro cell and a terminal transmits / receives data via a pico cell instead of a macro cell. A hotspot picocell is a device in which a terminal transmits and receives data through a picocell in place of a macrocell in order to reduce the load of the macrocell, although the terminal can transmit and receive data through the macrocell.

Hot spots may also refer to areas where the population is flooded or residential, or where demand traffic is high. Generally, a hot spot region may occur irrespective of an electro-magnetic field. In this case, the pico-cell may be divided into two types, i.e., an intra-frequency pico cell and an inter-frequency pico cell. .

An intra-frequency picocell refers to a picocell that uses the same frequency band as a macrocell. By reusing the same frequency resources in spatially separated areas, the same radio resources as the macro cells can be secured within the pico cell coverage. A picocell for most coverage holes corresponds to an intra-frequency picocell.

An inter-frequency picocell is a picocell that uses a different frequency band from a macrocell. When the signal of the macro cell received in the hot spot region is strong, the performance degradation due to the interference problem between the pico cell and the macro cell may occur. And can be used when a hot spot exists at a position close to the center of the macro cell.

In general, the UE performs measurements to determine whether neighbor cells exist or not. At this time, the neighboring cells existing in the intra-frequency transmit signals through the same frequency band as the current serving cell. Therefore, it is possible to measure neighbor cells at the same time while transmitting and receiving with the serving cell.

However, since neighboring cells existing in the inter-frequency transmit signals through a frequency band different from that of the serving cell, the UE temporarily suspends transmission / reception with the serving cell, retunes the RF chain, A signal for a frequency band identified as having a possibility of being present. Here, an RF chain refers to a portion of an antenna in which a filter and a power amplifier are combined. Therefore, measurements on neighboring cells in inter-frequency are limited in terms of time.

4 shows an example of a picocell proximity scenario to which the present invention is applied. This is referred to as a first scenario below.

Referring to FIG. 4, the macro base station 400 serves in the macro cell 401 area.

Pico base station 420 serves within the area of pico cell 421.

The macro base station 400 and the pico base station 420 are connected to an X2 interface 425.

When the terminal 450 approaches the proximity area 430 of the pico cell 421, an operation such as handover or cell reselection may be performed from the macro cell 401 to the pico cell 421.

If the cell-related control information of the picocell is transmitted to the terminal in advance, when the terminal is in proximity to the picocell, the terminal does not need to decode system information or unnecessary measurement while performing the handover while performing the proximity indication operation. The power consumption can be reduced.

5 is a flowchart illustrating an example of a method for transmitting control information according to the present invention. In the first scenario, the terminal 450 performs handover as the macro base station 400 approaches the pico base station 420. The macro base station 400 serves in the macro cell area, and the pico base station 420 serves in the pico cell area.

Referring to FIG. 5, the terminal is receiving a service using a macro cell as a serving cell. The macro base station performs RRC connection reconfiguration and transmits control information including a PCI (Physical Cell ID) value to the UE (S500). The PCI may be a physical cell ID of a pico cell, which is a neighboring cell of a macro base station, and the control information may include pico cell related information corresponding to the PCI. Hereinafter, the control information is referred to as cell related control information. The PCI value may be included in the cell related control information, and the PCI value and the cell related control information may be transmitted respectively.

Here, the macro base station 400 is in a state of transmitting and receiving various control information including PCI information in advance using an X2 interface with a neighbor cell (for example, another macro cell or pico cell) (S480). For example, when the macro base station 400 transmits an X2 setup request message to the pico base station 420, the pico base station 420 sends an X2 setup response message to the second macro base station 400 (X2 setup). send a response message). The X2 configuration request message may include information for requesting the PCI value and the cell related control information, and the X2 configuration response message may include the PCI value and the cell related control information.

Table 1 below shows an example of cell-related control information included in the X2 configuration request message or the X2 configuration response message. Or an example of an information element including cell-related control information.

IE / Group Name Presence IE type and reference PCI M INTEGER (0..503,…) Cell type M ENUMERATED (CSG cell, pico, micro, macro,…) or (verysmall, small, medium, large,…)

Referring to Table 1, the cell related control information includes configuration information of a cell that the neighboring base station needs for the X2 interface.

Here, the IE / Group Name is the name of an information element or a group of repeated information elements, and includes a PCI value or cell type information.

Presence is the existence of the information element / group, and M (Mandatory) means that it must exist.

IE type and reference is the type of the information element and reference means that the type of the information element is defined elsewhere. PCI has an integer value from 0 to 503, and the cell type information has one of "verysmall", "small", "medium", or "large", or "CSG", "pico", "micro". It can have a value of either "or" macro ".

Accordingly, the macro base station 400 transmits an RRC connection reconfiguration including the state of the pico base station 420 identified through the X2 interface, that is, a physical cell ID (PCI) value and cell-related control information, to the terminal. (S500). For example, the RRC connection reset may be performed through an RRC connection reset message.

In addition, the RRC connection reset message may include report proximity configuration information. The report proximity setting information is information for setting a proximity indication to report as the UE approaches (or approaches) a CSG cell or pico cell.

For example, the cell related control information includes a PCI value and information indicating a size of a cell. The size information of the cell may be one of "large", "medium", "small", or "very small". Whether the corresponding cell is a pico cell may be transmitted through the cell size information. In addition, the small (or berry small) indicates the pico cell may be preset in the terminal and the base station.

In another example, the cell related control information includes a PCI value and type information of a cell. The cell type information may be one of femto, pico, micro, and macro. It is indicated whether the pico cell is based on the cell type information.

As another example, the cell related control information includes a PCI range of the pico cell. At this time, the PCI range corresponding to the pico cell may be one or a plurality of values from 50 to 100.

As another example, when the pico cell is an inter-frequency pico cell, the cell related control information includes an inter-frequency value used by the pico cell.

In another example, the cell-related control information includes a PCI value and an indicator indicating whether a cell using the PCI is a pico cell (this is called a pico cell indicator). Picocell indicators can have either TRUE or FALSE values. Alternatively, the picocell indicator may have a value of "1" or "0". For example, TRUE or 1 may indicate a picocell.

As described above, the cell related control information may further include information indicating what kind of pico cell, as well as information indicating whether the pico cell is a pico cell. For example, the information indicating the type of pico cell may be “for hot spot” or “for coverage hole”.

The terminal may determine whether a cell corresponding to the PCI is a pico cell based on the PCI value and / or cell related control information. In this case, information obtained from the primary synchronization sequence (PSS) and the secondary synchronization sequence (SSS) may be used together in the determination.

Upon receiving the cell-related control information, the terminal detects PCI of each neighboring cell by reading various control information including PSS / SSS from neighboring cells as well as the macro base station. In this case, the terminal may determine whether the neighbor cell is a pico cell based on the detected PCI value and the information received through the RRC connection reconfiguration.

Unlike when the UE accesses the CSG cell, when the UE accesses the pico cell, the UE does not need to decode system information such as SIB1. The system information is information necessary for determining whether the corresponding cell is a CSG cell, but is not necessary for determining whether the cell is a pico cell. This can reduce the power consumption of the terminal.

As the terminal approaches the pico cell, the terminal performs a proximity indication operation to the macro base station serving as the serving base station (S505). In this case, the terminal may perform a proximity indication by transmitting a proximity indication message. The proximity indication message may include information (or a separate indicator) indicating that the cell accessed by the terminal is a pico cell. The indicator may be 0 or 1 bitmap information.

Following step S505, the macro base station performs an RRC connection reset to the terminal. The UE sets the measurement for the pico cell approaching (S510). In this case, the macro base station may perform an RRC connection reset by transmitting an RRC connection reset message, and the RRC connection reset message may include measurement setting information.

Based on the measurement setting information, the terminal reports the measurement result to the macro base station after performing the measurement (S515). For example, the terminal transmits the measurement report to the macro base station after the TTT time after the A3 event occurs.

The terminal may perform measurement based on the PCI and / or cell related control information received through the RRC connection reconfiguration.

When the neighbor cell to be measured by the terminal is an intra-frequency pico cell, the terminal may perform measurement on the same frequency as the macro base station.

When the neighbor cell to be measured by the UE is an inter-frequency pico cell, the UE may perform measurement on a corresponding frequency band, and the inter-frequency may be information previously received through RRC connection reconfiguration.

Based on the measurement report, the macro base station may determine the necessity of handover and whether or not to perform handover.

Based on the received measurement report, the macro base station requests a handover to the pico base station. At this time, UE context information is transmitted together (or through a separate message) to the pico base station (S520). For example, the macro base station may transmit a handover request message to the pico base station, and the handover request message may include terminal context information.

The terminal context information includes user subscription information, bearer list, and UE capability information.

Based on the terminal context information, the pico base station may more easily perform a handover or provide a service to the terminal after the handover.

Following step S520, the pico base station that has received the handover request determines whether to approve the handover (S525). This is also called admission control. At this time, the pico base station may allow or disallow handover of the terminal in consideration of the state of the resources available to it.

The pico base station transmits a handover request acknowledgment including information on whether to allow handover to the macro base station (S530). At this time, the pico base station may transmit a handover request confirmation message to the macro base station.

The macro base station finally determines whether to allow the terminal to handover based on the handover request confirmation (S535).

If the macro base station determines to perform the handover, the macro base station transmits a handover command to the terminal (S540). At this time, the handover command message may be transmitted from the macro base station to the terminal.

Upon receiving the handover command, the UE performs a handover procedure from the macro base station to the pico base station (S545). Specifically, the terminal terminates the connection with the cell of the macro base station being accessed, and starts the process for accessing the cell of the pico base station which is the target base station. The macro base station transmits uplink and downlink PDCP sequence numbers (SN) and hyper frame number (HFN) status information to the pico base station.

Subsequently, the terminal performs an operation for layer 1 and 2 related connection to access the pico cell. The layer 1 and 2 connection operations may include operations such as random access. After completing the handover, the terminal completes the connection with the pico cell and becomes a transmittable state capable of transmitting and receiving packet data.

6 shows another example of a proximity scenario to which the present invention is applied. This is hereinafter referred to as a second scenario.

Referring to FIG. 6, the first macro base station 600 serves in the area of the first macro cell 601. The second macro base station 610 serves in the area of the second macro cell 611.

Pico base station 620 serves within the area of pico cell 621.

The first macro base station 600 and the second macro base station 610 are connected to the X2 interface 615, and the second macro base station 610 and the pico base station 620 are connected to the X2 interface 625.

When the terminal 650 approaches the proximity area 630 of the pico cell 621 after performing a handover to the area of the second macro cell 611 within the area of the first macro cell 601, the second macro cell ( At 611, an operation such as handover or cell reselection to the pico cell 621 may be performed.

7 is a flowchart illustrating another example of a method for transmitting control information according to the present invention. In the second scenario, the terminal performing the handover from the first macro base station to the second macro base station 610 performs handover to the pico base station 620 again. The first and second macro base stations serve in the first and second macro cell regions, respectively, and the pico base station serves in the pico cell region.

Referring to FIG. 7, the second macro base station transmits and receives various control information including PCI information using a neighbor cell (for example, a pico cell) and an X2 interface (S700).

For example, when the second macro base station transmits an X2 setup request message to the pico base station, the pico base station transmits an X2 setup response message to the second macro base station. The X2 configuration request message may include information for requesting the PCI value and the cell related control information, and the X2 configuration response message may include the PCI value and the cell related control information.

The cell related control information may include PCI of a neighbor cell (for example, a pico cell) or picocell related information corresponding to the PCI. For example, the cell related control information includes a PCI value and information indicating a size of a cell. The size information of the cell may be one of "large", "medium", "small", or "very small". Whether the corresponding cell is a pico cell may be transmitted through the cell size information. In addition, the small (or berry small) indicates the pico cell may be preset in the terminal and the base station.

In another example, the cell related control information includes a PCI value and type information of a cell. The cell type information may be one of femto, pico, micro, and macro. It is indicated whether the pico cell is based on the cell type information.

As another example, the cell related control information includes a PCI range of the pico cell. At this time, the PCI range corresponding to the pico cell may be one or a plurality of values from 50 to 100.

As another example, when the pico cell is an inter-frequency pico cell, the cell related control information includes an inter-frequency value used by the pico cell.

In another example, the cell-related control information includes a PCI value and an indicator indicating whether a cell using the PCI is a pico cell (this is called a pico cell indicator). Picocell indicators can have either TRUE or FALSE values. Alternatively, the picocell indicator may have a value of "1" or "0". For example, TRUE or 1 may indicate a picocell.

As described above, the cell related control information may further include information indicating what kind of pico cell, as well as information indicating whether the pico cell is a pico cell. For example, the information indicating the type of pico cell may be “for hot spot” or “for coverage hole”.

The terminal may determine whether a cell corresponding to the PCI is a pico cell based on the PCI value and / or cell related control information. In this case, information obtained from the PSS and the SSS by the terminal may be used together in the determination.

The terminal receiving the cell-related control information detects PCI of each neighboring cell by reading various control information including PSS / SSS from neighboring cells as well as the macro base station. In this case, the terminal may determine whether the neighbor cell is a pico cell based on the detected PCI value and the information received through the RRC connection reconfiguration.

Unlike when the UE accesses the CSG cell, when the UE accesses the pico cell, the UE does not need to decode system information such as SIB1. The system information is information necessary for determining whether the corresponding cell is a CSG cell, but is not necessary for determining whether the cell is a pico cell. This can reduce the power consumption of the terminal.

In step S700, another example, when the pico base station first transmits an X2 setup request message to the second macro base station, the second macro base station transmits an X2 setup response message to the pico base station. Can be.

The PCI (Physical Cell ID) value and cell related control information included in the X2 interface, that is, the X2 configuration request message or the X2 configuration response message are the same as described in step 480 of FIG. 5. In order to perform a handover to the second macro base station, the terminal moving to the second macro cell area within the first macro cell area performs measurement and transmits a measurement report to the first macro base station (S705). For example, the terminal transmits a measurement report message to the first macro base station after the TTT time after the A3 event occurs.

When the neighbor cell to be measured by the terminal is an intra-frequency pico cell, the terminal may perform measurement on the same frequency as the first macro base station. Alternatively, when the neighbor cell to be measured by the terminal is an inter-frequency pico cell, the measurement may be performed for the corresponding frequency band, and the inter-frequency may be information previously received through RRC connection reconfiguration.

On the basis of the measurement report, the first macro base station performs a handover request to the second macro base station (S710). For example, the first macro base station transmits a handover request message including the terminal context information to the second macro base station.

Upon receiving the handover request, the second macro base station determines whether to approve the handover (S715). That is, the second macro base station performs admission control. In this case, the second macro base station may allow or disallow handover of the terminal in consideration of the state of resources available to the second macro base station.

The second macro base station transmits a handover request acknowledgment including information on whether to allow handover to the first macro base station (S720). In this case, the second macro base station may transmit a handover request confirmation message to the first macro base station.

The first macro base station finally determines whether to allow the terminal to handover based on the handover request confirmation (S725).

According to the present invention, the handover request confirmation message may include cell related control information including PCI information of pico cells located in the second macro cell region or at a cell boundary. Specifically, it includes PCI information and / or cell related control information of pico cells connected to the X2 interface with the second macro base station.

The following table shows an example of cell-related control information included in the handover request confirmation message. Or one example of an information element including cell related control information.

IE / Group Name Range IE type and reference Pico PCI list 1 .. <maxnoofPico cells> Pico PCI INTEGER (0..503,…)

Referring to Table 2, the Pico PCI list is a group name of pico PCI information elements. maxroofPicoCells is the maximum number of pico PCI information elements

Pico PCI is the PCI value of the pico cell, an integer of 0 to 503 or more.

The second macro base station may transmit a resource (eg, pico cell related information) prepared to the second macro base station to the first macro base station through the handover request confirmation message.

If the first macro base station determines to perform a handover, the first macro base station transmits a handover command to the terminal, and the terminal receiving the handover command performs a handover procedure from the first macro base station to the second macro base station. Perform (S730). In this case, a handover command message may be transmitted from the first macro base station to the terminal, and the handover command message may include cell related control information such as a pico PCI list included in the handover request confirmation. The terminal may know the pico cell in the second macro cell region through the pico PCI list. In addition, the terminal stores cell-related control information such as the pico PCI list information until the handover to another macro base station after the handover to the second macro base station is successful.

Table 3 below is another example of cell-related control information delivered to the terminal in the handover command message. For example, the handover command message may be an RRC connection reset message. The RRC connection reestablishment message may include reporting proximity setting information, and the reporting proximity setting information may include information about presence or absence of proximity indication or a pico cell PCI list.

Here, maxPicoCellPCIList is the maximum number of pico cells that can be located inside or in a macro cell and is an integer within 520. In addition, reportProximityConfig is report proximity configuration information. Information for setting a report on proximity indication. PhysCellId is PCI, indicates an ID of a cell's physical layer, and is an integer of 0 to 503.

When the UE approaches the pico cell, the UE performs a proximity indication operation to the second macro base station serving as a serving base station (S735). In this case, the terminal may transmit the proximity indication message to perform the proximity indication. The proximity indication message may include information (or a separate indicator) indicating that the cell accessed by the terminal is a pico cell. The indicator may be 0 or 1 bitmap information.

For example, the terminal detects PCI by reading PSS / SSS information of neighboring cells and compares and determines whether the corresponding PCI value matches the pico cell PCI value received through the report proximity configuration information included in the handover command message. If there is a match, it determines that the terminal approaches the pico cell and transmits a proximity indication message to the second macro base station.

Unlike when the UE accesses the CSG cell, when the UE accesses the pico cell, the UE does not need to decode system information such as SIB1. The system information is information necessary for determining whether the corresponding cell is a CSG cell, but is not necessary for determining whether the cell is a pico cell. This can reduce the power consumption of the terminal.

Subsequently to step S735, the second macro base station performs RRC connection reestablishment to the terminal and sets measurement for the pico cell to which the terminal approaches (S740). In this case, the second macro base station may perform an RRC connection reset by transmitting an RRC connection reset message, and the RRC connection reset message may include measurement setting information.

Based on the measurement setting information, the terminal reports the measurement result to the second macro base station after performing the measurement (S745). For example, the terminal transmits the measurement report to the macro base station after the TTT time after the A3 event occurs.

The terminal may perform measurement based on the PCI and / or cell related control information received through the handover command message.

When the neighbor cell to be measured by the terminal is an intra-frequency pico cell, the terminal may perform measurement on the same frequency as the second macro base station.

When the neighbor cell to be measured by the UE is an inter-frequency pico cell, measurement may be performed for a corresponding frequency band, and the inter-frequency may be information previously received through the RRC connection reconfiguration message (S740). .

Based on the measurement report, the second macro base station may determine whether to perform handover or whether to perform handover.

Based on the received measurement report, the second macro base station requests a handover to the pico base station. At this time, the terminal context information is transmitted together (or through a separate message) to the pico base station (S750). For example, the second macro base station may transmit a handover request message to the pico base station, and the handover request message may include terminal context information.

Following step S750, the pico base station that has received the handover request determines whether to approve the handover (S755). The pico base station may allow or disallow handover of the terminal in consideration of the state of resources available to it.

The pico base station transmits a handover request acknowledgment including information on whether to allow handover to the second macro base station (S760). At this time, the pico base station may transmit a handover request confirmation message to the second macro base station.

The second macro base station finally determines whether to allow the terminal to handover based on the handover request confirmation (S765).

If the second macro base station determines to perform a handover, the second macro base station transmits a handover command to the terminal, and the terminal receiving the handover command performs a handover procedure from the second macro base station to the pico base station. .

8 is a block diagram illustrating a base station and a terminal for transmitting control information according to an embodiment of the present invention.

Referring to FIG. 8, the terminal 800 includes a receiver 810, a transmitter 820, and a controller 830.

The receiver 810 receives an RRC connection reconfiguration from the base station 850 and receives control information including a physical cell ID (PCI) value. The PCI may be a physical cell ID of a pico cell, which is a neighboring cell of the base station 850, and the control information may include picocell related information corresponding to the PCI. For example, the RRC connection reset may be performed through an RRC connection reset message. The RRC connection reset message may include Report Proximity Configuration information. The report proximity setting information is information for setting a proximity indication that the terminal 800 reports as it approaches (or approaches) a CSG cell or a pico cell. For example, the cell related control information includes a PCI value and information indicating the size of the cell. The size information of the cell may be one of "large", "medium", "small", or "very small". Whether the corresponding cell is a pico cell may be transmitted through the cell size information. In addition, the small (or berry small) indicating the pico cell may be preset in the terminal 800 and the base station 850. In another example, the cell related control information includes a PCI value and type information of a cell. The cell type information may be one of femto, pico, micro, and macro. It is indicated whether the pico cell is based on the cell type information. As another example, the cell related control information includes a PCI range of the pico cell. At this time, the PCI range corresponding to the pico cell may be one or a plurality of values from 50 to 100. As another example, when the pico cell is an inter-frequency pico cell, the cell related control information includes an inter-frequency value used by the pico cell. In another example, the cell-related control information includes a PCI value and an indicator indicating whether a cell using the PCI is a pico cell (this is called a pico cell indicator). Picocell indicators can have either TRUE or FALSE values. Alternatively, the picocell indicator may have a value of "1" or "0". For example, TRUE or 1 may indicate a picocell. As described above, the cell related control information may further include information indicating what kind of pico cell, as well as information indicating whether the pico cell is a pico cell. For example, the information indicating the type of pico cell may be “for hot spot” or “for coverage hole”.

The controller 830 may determine whether a cell corresponding to the PCI is a pico cell based on the PCI value and / or cell related control information. In this case, the information obtained from the primary synchronization sequence (PSS) and the secondary synchronization sequence (SSS) by the terminal 800 may be used together in the determination.

The controller 830 reads various control information including PSS / SSS from neighbor cells as well as the base station 850 and detects PCI of each neighbor cell. In this case, the controller 830 may determine whether the neighbor cell is a pico cell based on the detected PCI value and the information received through the RRC connection reconfiguration.

As the transmitter 820 approaches the pico cell, the transmitter 820 performs a proximity indication operation to the base station 850 serving as the serving base station 850. The transmitter 820 may perform a proximity indication by transmitting a proximity indication message. The proximity indication message may include information (or separate indicator) indicating that the cell accessed by the terminal 800 is a pico cell. The indicator may be 0 or 1 bitmap information.

The receiver 810 receives the RRC connection reconfiguration, and receives measurement setting information on the pico cell to which the terminal 800 approaches. An RRC connection reset message may be transmitted, and the RRC connection reset message may include measurement setting information.

The transmitter 820 reports the measurement result to the base station 850 after the terminal 800 performs the measurement based on the measurement setting information. For example, the terminal 800 transmits a measurement report to the base station 850 after the TTT time after the A3 event occurs. For example, the measurement may be an S-measurement. As another example, the terminal 800 may perform measurement based on PCI and / or cell related control information received through RRC connection reconfiguration.

When the neighbor cell to be measured by the terminal 800 is an intra-frequency pico cell, the terminal 800 may measure the same frequency as the base station 850.

When the neighbor cell to be measured by the terminal 800 is an inter-frequency pico cell, measurement may be performed for a corresponding frequency band, and the inter-frequency may be information previously received by resetting an RRC connection.

When the base station 850 determines to perform a handover, the receiver 810 receives a handover command from the base station 850.

The terminal 800 receiving the handover command performs a handover procedure from the base station 850 to another base station.

The base station 850 includes a receiver 860, a controller 870, and a transmitter 880. The base station may be a source base station in handover.

The transmitter 880 performs RRC connection reconfiguration and transmits control information including a PCI (Physical Cell ID) value to the terminal 800. The PCI is a pico cell which is a neighbor cell of the base station 850. It may be a physical cell ID of the control information may include picocell related information corresponding to the PCI. Hereinafter, the control information is referred to as cell related control information. The PCI value may be included in the cell related control information, and the PCI value and the cell related control information may be transmitted respectively. For example, the RRC connection reset may be performed through an RRC connection reset message. The RRC connection reset message may include Report Proximity Configuration information. The report proximity setting information is information for setting a proximity indication that the terminal 800 reports as it approaches (or approaches) a CSG cell or a pico cell.

The receiver 860 receives a proximity indication as the terminal 800 approaches the pico cell. At this time, a proximity indication message may be transmitted. The proximity indication message may include information (or separate indicator) indicating that the cell accessed by the terminal 800 is a pico cell. The indicator may be 0 or 1 bitmap information.

The transmitter 880 performs the RRC connection reset to the terminal 800. The terminal 800 sets a measurement for the pico cell approaching. The transmitter 880 may perform an RRC connection reset by transmitting an RRC connection reset message, and the RRC connection reset message may include measurement setting information.

The receiver 860 receives the measurement result of performing the measurement from the terminal 800. For example, the measurement may be an S-measurement.

Based on the received measurement report, the transmitter 880 requests a handover to the target base station. In this case, the terminal 800 transmits context information (UE context) together (or through a separate message) to the target base station. For example, a handover request message may be transmitted, and the handover request message may include the terminal 800 context information.

The controller 870 determines whether to approve the handover after receiving the handover request. The controller 870 may allow or disallow the handover of the terminal 800 in consideration of the state of available resources.

The receiving unit 860 receives a handover request acknowledgment including information on whether to allow handover.

The controller 870 finally determines whether to allow the terminal 800 to perform a handover based on the handover request confirmation.

The transmitter 880 transmits a handover command to the terminal 800. The terminal 800 receiving the handover command performs a handover procedure from the base station 850 to the target base station.

Meanwhile, the transmitter 880 or the receiver 860 may transmit or receive various control information including PCI information by using an X2 interface with a neighbor cell (for example, a pico cell).

For example, when the base station 850 transmits an X2 setup request message to the target base station, the target base station transmits an X2 setup response message to the base station 850. The X2 configuration request message may include information for requesting the PCI value and the cell related control information, and the X2 configuration response message may include the PCI value and the cell related control information.

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 (20)

In the heterogeneous network system, the terminal receives the control information,
RRC connection reconfiguration including a physical cell ID (PCI) of a target cell accessed by the terminal and cell-related control information of the target cell Receiving from the base station of the serving cell providing the service; And
And determining whether the target cell indicated by the PCI is a pico cell on the basis of the PCI or the cell-related control information. The method of claim 1,
And determining whether the target cell is a pico cell based on a Primary Synchronization Sequence (PSS) and a Secondary Synchronization Sequence (SSS). The method of claim 1,
The RRC connection reset message further includes Report Proximity Configuration information.
The report proximity setting information is control information receiving method, characterized in that for setting the proximity indication to report as the terminal approaches the pico cell. The method of claim 1,
The cell related control information includes a PCI value or information indicating the size of a cell indicated by the PCI,
And information indicating the size of the cell is one of large, medium, small, or very small. The method of claim 1,
The cell related control information includes a PCI value or type information of a cell indicated by the PCI,
The type information of the cell is femto (femto), pico (pico), micro (micro), micro (macro) of the control information receiving method, characterized in that one of. The method of claim 1,
The cell related control information includes a PCI range corresponding to the pico cell,
The PCI range corresponding to the pico cell is a control information receiving method, characterized in that an integer of one of 50 to 100. The method of claim 1,
If the target cell is an inter-frequency picocell providing a service in a frequency band different from that of the serving cell, the cell-related control information includes an inter-frequency value used by the target cell. . The method of claim 1,
The cell related control information includes a PCI value and a picocell indicator indicating whether the pico cell is indicated by the PCI,
And the picocell indicator has one of TRUE and FALSE, and if the picocell indicator has a TRUE value, the picocell indicator indicates that the target cell is a pico cell. The method of claim 1,
The cell related control information further includes pico cell type information indicating what kind of pico cell the target cell is,
The picocell type information includes one of a hot spot picocell and a coverage hole picocell. In a terminal receiving control information in a heterogeneous network system,
The RRC connection reconfiguration service includes a physical cell ID (PCI) of a target cell accessed by the terminal and cell-related control information of the target cell. Receiving unit for receiving from the base station of the serving cell to provide; And
And a controller configured to determine whether the target cell indicated by the PCI is a pico cell based on the PCI or the cell-related control information. In a heterogeneous network system, a base station transmits control information,
Receiving a physical cell ID (PCI) of a neighbor cell and cell-related control information of the neighbor cell from the neighbor cell through an X2 configuration message; And
And transmitting a radio resource control (RRC) connection reconfiguration including the PCI and the cell related control information to a terminal. The method of claim 11,
The RRC connection reset message further includes Report Proximity Configuration information.
The report proximity setting information is information for setting a proximity indication to report as the terminal approaches the pico cell. The method of claim 11,
The cell related control information includes a PCI value or information indicating the size of a cell indicated by the PCI,
And information indicating the size of the cell is one of a large, medium, small, or very small. The method of claim 11,
The cell related control information includes a PCI value or type information of a cell indicated by the PCI,
The type information of the cell is femto (femto), pico (pico), micro (micro), micro (macro), characterized in that one of the control information transmission method. The method of claim 11,
The cell related control information includes a PCI range corresponding to the pico cell,
The PCI range corresponding to the pico cell is a control information transmission method, characterized in that one of 50 to 100. The method of claim 11,
If the neighbor cell is an inter-frequency picocell providing a service in a different frequency band from the serving cell, the cell-related control information includes an inter-frequency value used by the neighbor cell. . The method of claim 11,
The cell related control information includes a PCI value and a picocell indicator indicating whether the pico cell is indicated by the PCI,
And the picocell indicator has one of TRUE and FALSE, and if the picocell indicator has a TRUE value, the picocell indicator indicates that the neighboring cell is a pico cell. The method of claim 11,
The cell related control information further includes pico cell type information indicating what kind of pico cell the neighboring cell is.
The picocell type information includes one of a hot spot picocell and a coverage hole picocell. 12. The method of claim 11,
Transmitting an X2 setup request message requesting a physical cell ID and cell related control information to a base station of the neighboring cell;
The X2 setup message is a response to the X2 setup request message. In the base station for transmitting control information in a heterogeneous network system,
A receiver configured to receive a physical cell ID (PCI) of a neighbor cell and cell-related control information of the neighbor cell through an X2 configuration message from the neighbor cell; And
And a transmitter for transmitting a radio resource control (RRC) connection reconfiguration (RRC) connection reconfiguration including the PCI and the cell-related control information to a terminal.

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