KR20100116531A - Method of releasing an access restriction at high interference cell in a wireless communication system - Google Patents

Abstract

PURPOSE: A method for enabling a terminal to cancel the access limit about a cell which has large interference on a wireless communication system is provided to reduce the interference between a terminal and a base station in case of the terminal is in area of an access-limited base station. CONSTITUTION: Whether access about the cell based on a first parameter included inside the received connection information is limited or not is determined. If the access about the cell is limited, whether the access about the cell is accepted in high interference base on a second parameter included in the receive access information. If the access about the cell is accepted in high interference, interference is estimated. According to the estimated interference, the limited access about the cell is selectively cancelled.

Description

Method of relieving access restriction for cell with high interference in wireless communication system {METHOD OF RELEASING AN ACCESS RESTRICTION AT HIGH INTERFERENCE CELL IN A WIRELESS COMMUNICATION SYSTEM}

The present invention relates to a wireless communication system and a terminal for providing a wireless communication service. The present invention relates to a terminal in an Evolved Universal Mobile Telecommunications System (E-UMTS) or a Long Term Evolution System (LTE), which has been evolved from a Universal Mobile Telecommunications System (UMTS). If there is a large interference to the cell where the current access is limited, as long as the base station allows access to the terminal only in a high interference situation, the access restriction on the cell is removed by itself, and the interference is connected to the cell. It is about how to deliver.

1 is a diagram illustrating a network structure of an E-UTRAN (Evolved Universal Terrestrial Radio Access Network) which is a mobile communication system to which the present invention and the present invention are applied. The E-UTRAN system is an evolution from the existing UTRAN system and is currently undergoing basic standardization work in 3GPP. The E-UTRAN system is also called a Long Term Evolution (LTE) system.

The E-UTRAN is composed of eNBs (e-NodeBs, hereinafter referred to as base stations), and are connected between eNBs through an X2 interface. The eNB is connected to a user equipment (hereinafter abbreviated terminal) through a wireless interface and is connected to an Evolved Packet Core (EPC) through an S1 interface.

The EPC includes a mobility management entity (MME), a serving-gateway (S-GW), and a packet data network-gateway (PDN-GW). The MME has information about the access information of the terminal or the capability of the terminal, and this information is mainly used for mobility management of the terminal. S-GW is a gateway having an E-UTRAN as an endpoint, and PDN-GW is a gateway having a PDN as an endpoint.

Layers of the radio interface protocol between the terminal and the network are based on the lower three layers of the Open System Interconnection (OSI) reference model, which is widely known in communication systems. (Second layer) and L3 (third layer), wherein a physical layer belonging to the first layer provides an information transfer service using a physical channel, and a third layer. The radio resource control layer (hereinafter referred to as RRC) layer located in the layer plays a role of controlling radio resources between the terminal and the network. To this end, the RRC layer exchanges an RRC message between the terminal and the base station.

2 and 3 illustrate a structure of a radio interface protocol between a UE and an E-UTRAN based on the 3GPP radio access network standard. The wireless interface protocol consists of a physical layer, a data link layer, and a network layer horizontally, and vertically, a user plane for transmitting data information (user plane, u-plane). ) And control plane (C-plane) for transmitting signaling. The protocol layers of FIGS. 2 and 3 are based on the lower three layers of the Open System Interconnection (OSI) reference model, which are well known in communication systems, and include L1 (first layer), L2 (second layer), L3 (third layer) can be divided. These radio protocol layers exist in pairs in the UE and the E-UTRAN, and are responsible for data transmission in the radio section.

Hereinafter, each layer of the wireless protocol control plane of FIG. 2 and the wireless protocol user plane of FIG. 3 will be described.

The physical layer, which is the first layer, provides an information transfer service to an upper layer by using a physical channel. The physical layer is connected to the upper medium access control layer through a transport channel, and data between the medium access control layer and the physical layer moves through the transport channel. Then, data moves between physical layers, that is, between physical layers on the transmitting side and the occasional side. The physical channel is modulated by an orthogonal frequency division multiplexing (OFDM) scheme and utilizes time and frequency as radio resources.

Medium access control (hereinafter referred to as MAC) of the second layer provides a service to a radio link control layer, which is a higher layer, through a logical channel. The radio link control layer (hereinafter referred to as RLC) layer of the second layer supports reliable data transmission. The functionality of the RLC layer may be implemented as a functional block inside the MAC. In this case, the RLC layer may not exist. The PDCP layer of the second layer is a header compression that reduces the IP packet header size, which is relatively large and contains unnecessary control information, for efficient transmission in a low bandwidth wireless section when transmitting an IP packet such as IPv4 or IPv6. Compression) function.

The radio resource control layer (hereinafter abbreviated as RRC) layer located at the top of the third layer is defined only in the control plane, and the configuration and reset of the radio bearer (abbreviated as RB) are performed. It is responsible for the control of logical channels, transport channels and physical channels in relation to configuration and release. In this case, RB means a service provided by the second layer for data transmission between the terminal and the UTRAN. When there is an RRC connection (RRC Connection) between the RRC of the terminal and the RRC layer of the radio network, the terminal is in the RRC_CONNECTED state, otherwise it is in the RRC idle state (RRC_IDLE).

A downlink transmission channel for transmitting data from a network to a UE includes a broadcast channel (BCH) for transmitting system information and a downlink shared channel (SCH) for transmitting user traffic or control messages. Traffic or control messages of a downlink multicast or broadcast service may be transmitted through a downlink SCH or may be transmitted through a separate downlink multicast channel (MCH). Meanwhile, the uplink transmission channel for transmitting data from the terminal to the network includes a random access channel (RAC) for transmitting an initial control message and an uplink shared channel (SCH) for transmitting user traffic or control messages.

It is located above the transport channel, and the logical channel mapped to the transport channel is a broadcast control channel (BCCH), a paging control channel (PCCH), a common control channel (CCCH), a multicast control channel (MCCH), and a multicast traffic (MTCH). Channel).

The physical channel is composed of several subframes on the time axis and several subcarriers on the frequency axis. Here, one sub-frame consists of a plurality of symbols on the time axis. One subframe consists of a plurality of resource blocks, and one resource block consists of a plurality of symbols and a plurality of sub-carriers. In addition, each subframe may use specific subcarriers of specific symbols (eg, the first symbol) of the corresponding subframe for a physical downlink control channel (PDCCH), that is, an L1 / L2 control channel. One subframe is 0.5 ms, and a transmission time interval (TTI), which is a unit time for transmitting data, is 1 ms corresponding to two subframes.

Hereinafter, the RRC state and the RRC connection method of the UE will be described in detail. The RRC state refers to whether or not the RRC of the UE is in a logical connection with the RRC of the E-UTRAN. If connected, the RRC connected state (RRC_CONNECTED state), and if not connected, the RRC idle state (RRC_IDLE). state). Since the UE of the RRC_CONNECTED state has an RRC connection, the E-UTRAN can grasp the existence of the UE in units of cells, and thus can effectively control the UE. On the other hand, the UE of the RRC_IDLE state cannot be understood by the E-UTRAN, and the core network manages the tracking area unit, which is a larger area unit than the cell. That is, the RRC_IDLE state terminal is identified only in a large area unit, and must move to the RRC_CONNECTED state in order to receive a normal mobile communication service such as voice or data.

When the user first powers on the terminal, the terminal first searches for an appropriate cell and then stays in the RRC Idle state in the cell. When the UE staying in the RRC_IDLE state needs to establish an RRC connection, the UE establishes an RRC connection with the RRC of the E-UTRAN through an RRC connection procedure and transitions to the RRC_CONNECTED state. There are several cases in which the UE in the idle state needs to establish an RRC connection. For example, an uplink data transmission is necessary due to a user's call attempt, or a paging message is received from the E-UTRAN. In one case, the response message may be transmitted.

The NAS (Non-Access Stratum) layer located above the RRC layer performs functions such as session management and mobility management.

In order to manage mobility of the UE in the NAS layer, two states of EMM-REGISTERED (EPS Mobility Management-REGISTERED) and EMM-DEREGISTERED are defined, and these two states are applied to the UE and the MME. The initial terminal is in the EMM-DEREGISTERED state, and the terminal performs a process of registering in the network through an initial attach procedure to access the network. If the attach procedure is successfully performed, the UE and the MME are in an EMM REGISTERED state.

In order to manage a signaling connection between the UE and the EPC, two states are defined, ECM-IDLE (EPS Connection Management) and ECM_CONNECTED, and these two states are applied to the UE and the MME. When the UE in the ECM-IDLE state establishes the RRC connection with the E-UTRAN, the UE enters the ECM-CONNECTED state. The MME in the ECM-IDLE state becomes the ECM-CONNECTED state when it establishes an S1 connection with the E-UTRAN. When the terminal is in the ECM-IDLE state, the E-UTRAN does not have context information of the terminal. Accordingly, the UE in the ECM-IDLE state performs a UE-based mobility related procedure such as cell selection or reselection without receiving a command from the network. On the other hand, when the terminal is in ECM-CONNECTED, the mobility of the terminal is managed by the command of the network. In the ECM-IDLE state, if the position of the terminal is different from the position known by the network, the terminal informs the network of the corresponding position of the terminal through a tracking area update procedure.

The following is a description of system information. The system information includes essential information that the terminal needs to know in order to access the base station. Therefore, the terminal must receive all system information before accessing the base station, and must always have the latest system information. In addition, since the system information is information that all terminals in a cell should know, the base station periodically transmits the system information.

The system information is divided into MIB, SB, and SIB. The master information block (MIB) allows the terminal to know the physical configuration of the cell, for example, bandwidth. SB (Scheduling Block) informs the transmission information of the SIBs, for example, the transmission period. SIB (System Information Block) is a collection of system information related to each other. For example, some SIBs contain only information of neighboring cells, and some SIBs contain only information of uplink radio channels used by the terminal.

In the related art, if a terminal is limited in access to a cell selected by a terminal, or if the terminal is in an area of a base station with limited access, the terminal receives a large interference from the base station. The base station also suffers greatly from this terminal. Such interference lowers the communication signal quality between the terminal and the base station, and causes a large problem in communication.

Therefore, the present invention is to reduce the interference between the terminal and the base station in a wireless communication system more effectively than the prior art. In particular, the present invention is to provide a method for reducing interference between the terminal and the base station when the terminal is in the region of the restricted access base station.

In order to solve the above problems of the present invention, a method of accessing a cell in a wireless communication system, comprising: receiving access information from a network; Determining whether access to the cell is restricted based on a first parameter included in the received access information; If it is determined that access to the cell is restricted, determining whether access to the cell is allowed in high interference based on a second parameter included in the received access information; If it is determined that access to the cell is allowed in the high interference, estimating interference; And selectively terminating the restricted connection to the cell in accordance with the estimated interference.

Preferably, the access information is characterized in that the access control information (access control information) related to the interference.

Preferably, the first parameter of the access information is an interference access indicator and the second parameter of the access information is characterized in that an interference threshold.

Preferably, the network is characterized in that the Home NodeB (HNB) or Macro NodeB.

Preferably, the first and second parameters of the access information is received through cell specific signaling or UE specific signaling.

Preferably, the interference is estimated using a reference signal in the downlink direction.

Preferably, the amount of interference is related to the quality of the reference signal.

Preferably, the interference is estimated using the power of a random access channel (RACH) preamble transmitted last in the uplink direction.

Advantageously, the amount of interference has an inverse relationship with a power of the last transmitted RACH preamble.

Advantageously, if the estimated interference is greater than or equal to the interference threshold included in the connection information, the restricted connection to the cell is terminated.

Preferably, if the estimated interference is less than the interference threshold included in the connection information, the restricted connection to the cell is not terminated.

If the access of the terminal is limited to the cell selected by the terminal, or when the terminal is in the region of the access-limited base station, if the present invention is applied, both the base station and the terminal can be alleviated from interference effects. That is, the base station may move the terminal to another frequency through a mobility procedure at any time after accepting the access of the terminal that greatly affects the interference, so that temporarily accepting the access-limited terminal is effective for avoiding interference. It is a way.

1 is a network structure of E-UTRAN, which is a mobile communication system to which the present invention and the present invention are applied.
Figure 2 is an exemplary view showing a control plane structure of a radio interface protocol between the terminal and the E-UTRAN in the prior art.
3 is an exemplary diagram illustrating a user plane structure of a radio interface protocol between a terminal and an E-UTRAN in the prior art.
4 is an exemplary diagram illustrating a network structure of an E-UTRAN operating an H (e) NB using an H (e) NB gateway (GW).
5 is an exemplary view illustrating a method of confirming an access mode of a base station by a terminal according to the present invention.
6 is an exemplary diagram showing an influence of an interference signal between a terminal and a base station.
7 is an exemplary diagram illustrating downlink interference experienced by a terminal from a cell of limited access.
FIG. 8 is an exemplary diagram illustrating uplink interference interlinked by a cell restricting access from a signal transmitted by a terminal in a service area of a cell where access is restricted.
FIG. 9 illustrates an example of interference between a UE and a CSG cell in a CSG cell to which the UE is restricted. FIG.
10 is an exemplary diagram illustrating a connection operation procedure of a terminal according to the present invention.
11 is a first exemplary diagram showing how a terminal estimates interference according to the present invention.
12 is a second exemplary diagram illustrating how the terminal estimates interference according to the present invention.

The present invention is applied to 3GPP communication technology, in particular, a Universal Mobile Telecommunications System (UMTS) system or a Long Term Evolution (LTE) system, a communication device, and a communication method. However, the present invention is not limited thereto and may be applied to all wired and wireless communication to which the technical spirit of the present invention can be applied.

A basic concept of the present invention is a method of accessing a cell in a wireless communication system, comprising: receiving access information from a network; Determining whether access to the cell is restricted based on a first parameter included in the received access information; If it is determined that access to the cell is restricted, determining whether access to the cell is allowed in high interference based on a second parameter included in the received access information; If it is determined that access to the cell is allowed in the high interference, estimating interference; And selectively terminating the restricted connection to the cell according to the estimated interference, and propose a method of accessing a cell in a wireless communication system, and perform the method. Propose a communication terminal or network.

Hereinafter, the configuration and operation of the embodiments according to the present invention will be described with reference to the accompanying drawings.

In general, services provided by a network to a terminal can be classified into three types as follows. In addition, the terminal also recognizes the cell type differently according to which service can be provided. The following describes the service type first, followed by the cell type.

1) Limited service This service provides Emergency Call and Tsunami Warning System (ETWS), which can be provided by an acceptable cell.

2) Normal service This service is a general purpose public service, and can be provided in a normal cell.

3) Operator service This service means service for network operator. This cell can be used only by network operator and not by general users.

In relation to the service type provided by the cell, the cell type may be classified as follows.

1) Acceptable cell A cell in which the terminal can receive limited service. This cell is a cell that is not barred from the viewpoint of the terminal and satisfies the cell selection criteria of the terminal.

2) Suitable cell A cell where the terminal can receive normal service. This cell satisfies the conditions of an acceptable cell and at the same time satisfies additional conditions. As an additional condition, this cell must belong to a PLMN to which the terminal can access and must be a cell which is not prohibited from performing a tracking area update procedure of the terminal. If the cell is a CSG cell, the terminal should be a cell that can be connected to the cell as a CSG member.

3) Barred cell A cell that broadcasts information indicating that the cell is a barred cell through system information.

4) Reserved cell A cell that broadcasts information indicating that a cell is a reserved cell through system information.

4 is an exemplary diagram illustrating a network structure of an E-UTRAN operating an H (e) NB using an H (e) NB gateway (GW).

As shown in FIG. 4, the HeNBs are connected to the EPC or directly to the EPC via the HeNB GW. Here, the HeNB GW looks like a normal eNB to the MME. The HeNB GW also looks like the MME to the HeNB. Therefore, the HeNB GW and the EPC are connected through the S1 interface between the HeNB and the HeNB GW. In addition, when the HeNB and the EPC are directly connected, they are connected to the S1 interface. The function of HeNB is mostly the same as that of general eNB.

In general, the H (e) NB has a lower radio transmission power than the (e) NB owned by the mobile network operator. Therefore, the coverage provided by the H (e) NB is generally smaller than the coverage provided by the (e) NB. Due to this characteristic, a cell provided by an H (e) NB is often classified as a femto cell in comparison with a macro cell provided by (e) NB from a service area perspective. On the other hand, in terms of the service provided, when the H (e) NB provides a service only to the CSG group, the cell provided by the H (e) NB is called a CSG cell.

Each CSG has its own unique identification number, which is called a CSG identity (CSG identity). The terminal may have a list of CSGs belonging to the member, and the CSG list may be changed by a request of the terminal or a command of the network. In general, one H (e) NB may support one CSG.

H (e) The NB transmits the CSG ID of the CSG supported by itself to the member terminal of the corresponding CSG through the system information. When the UE finds a CSG cell, it can check which CSG the CSG cell supports by reading the CSG ID included in the system information. The terminal reading the CSG ID is regarded as a cell to which the cell can be accessed only when the UE is a member of the CSG cell.

H (e) NB does not always need to allow access to the CSG terminal. Depending on the configuration of the H (e) NB, it is also possible to allow connection of a terminal other than the CSG member. Which terminal is allowed to access is changed according to the configuration of H (e) NB, where the configuration setting means the setting of the operation mode of H (e) NB. The operation mode of the H (e) NB is divided into three types according to which UE provides a service.

1) Closed access mode A mode that provides services only to specific CSG members. H (e) NB provides the CSG cell.

2) Open access mode General (e) Mode that provides service without restriction of specific CSG member like NB. H (e) NB provides a general cell that is not a CSG cell.

3) Hybrid access mode It is possible to provide CSG service to specific CSG members and to provide services like non-CSG members to non-CSG members. CSG member UEs are recognized as CSG cells, and non-CSG member UEs are recognized as normal cells. These cells are called hybrid cells.

The H (e) NB informs the UE whether the cell it serves is a general cell, which is a CSG cell, so as to know whether the UE can access the cell. The H (e) NB operating in the closed access mode broadcasts that it is a CSG cell through system information. The H (e) NB operating in the open access mode broadcasts that it is not a CSG cell through the system information. As such, the H (e) NB includes a 1-bit CSG indicator in the system information indicating whether or not the cell it serves is a CSG cell. For example, the CSG cell broadcasts by setting the CSG indicator to TRUE. If the serving cell is not a CSG cell, the CSG indicator may be set to FALSE or a method of omitting CSG indicator transmission may be used. Since the UE should be able to distinguish the general cell provided by the (e) NB from the CSG cell, the general (e) NB also sends a CSG indicator (eg, FALSE) so that the UE knows that the cell type provided by the UE is the general cell. can do. In addition, the general (e) NB may not let the UE know that the cell type provided by the UE is a general cell by not transmitting the CSG indicator. Table 1 shows CSG related parameters transmitted by a corresponding cell for each cell type. Table 2 shows the types of terminals that allow connection by cell type.

5 is an exemplary view illustrating a method of confirming an access mode of a base station by a terminal according to the present invention.

In a first step, the terminal first checks the CSG indicator in the system information of the target cell to determine what type of cell the target cell is. After confirming the CSG indicator, in a second step, if the CSG indicator indicates that the target cell is a CSG cell, the UE recognizes the cell as a CSG cell. Thereafter, the terminal checks the CSG identity (CSG identity or CSG identifier) in the system information to determine whether the UE is a CSG member of the target cell. When the terminal determines that the UE is a CSG member of the target cell from the CSG identifier, the terminal recognizes the cell as an accessible CSG cell.

If the terminal confirms that it is not a CSG member of the target cell from the CSG identifier, the terminal regards the cell as a cell that is not accessible. In the first step, if the CSG indicator indicates that the target cell is not a CSG cell, the terminal recognizes the target cell as a general cell. In addition, if the CSG indicator is not transmitted in the first step, the terminal recognizes the target cell as a general cell.

In general, a CSG cell and a macro cell may be operated simultaneously at a specific frequency. This frequency is called the mixed carrier frequency. The network may reserve specific physical layer cell identifiers for the CSG cell separately at the mixed carrier frequency. The physical layer cell identifier is called PCI (Physical Cell Identity) in the E-UTRAN system, and PSC (Physical Scrambling Code) in the UTRAN. For convenience of description, the physical layer identifier is expressed in PCI. At the mixed carrier frequency, the CSG cell informs the system information about the PCIs reserved for CSG at the current frequency. Upon receiving this information, the UE can determine whether a cell is a CSG cell or not a CSG cell from PCI of this cell when it discovers a cell at a corresponding frequency. The following describes how two terminals use this information.

First, in case of a UE that does not support CSG-related functions or does not have a CSG list as a member thereof, the UE does not need to consider the CSG cell as a selectable cell during cell selection / reselection. In this case, the terminal checks only the PCI of the cell, and if the PCI is a PCI reserved by the CSG, the cell can be immediately excluded from the cell selection / reselection process. In general, the PCI of a cell can be known immediately at the terminal when the physical layer confirms the existence of the cell.

Second, in case of a UE having a CSG list of which the UE is a member, when the UE wants to know a list of neighboring CSG cells at the mixed carrier frequency, the CSG identifier of the system information of all cells found in the entire PCI range. Instead of verifying, we only find a cell with a PCI reserved for CSG and we know that the cell is a CSG cell.

In general, the terminal selects a cell of the highest quality in an environment in which the radio quality changes, and tries to receive the most stable quality service. However, if the terminal has limited access to a cell selected by the terminal, or if the terminal is located in a region of a base station to which access is restricted, the terminal receives large interference from the base station. The base station also suffers from large interference from the terminal. 6 is an exemplary view showing the influence of the interference signal between the terminal and the base station. In FIG. 6, while a normal signal is communicated between the terminal and the base station on cell A, an unwanted interference signal is generated between the terminal and the base station on cell B. Here, the base station on the cell B may be a base station of a cell in which the access of the terminal is limited.

The interference situation will be described in more detail. FIG. 7 is a diagram illustrating downlink interference experienced by a terminal from a cell with limited access, and FIG. 8 is a diagram illustrating uplink interference bound by a cell restricting access from a signal transmitted by a terminal in a service area of a cell with limited access. to be.

As shown in FIG. 7 and FIG. 8, since the distance between the base station restricting access to the terminal is much closer than the distance between the base stations of the two cells, the cell restricting access to the terminal is more than the interference between the two cells. The interference received is more severe.

This interference situation can be a big problem when the UE is in the region of a non-member CSG cell. FIG. 9 is a diagram illustrating an example of interference between a UE and a CSG cell in a closed subscriber group (CSG) cell in which a UE is restricted from access.

As shown in FIG. 9, since the UE cannot access a non-member CSG cell, the UE accesses a cell A far away. In this case, since the cell A is far from the terminal, the terminal transmits a signal with high power, and the signal acts as interference to the non-member CSG cell. In addition, the terminal also suffers from persistent interference from this cell within the region of the non-member CSG cell.

Therefore, in the present invention, when the terminal is giving a large interference to the cell where the current access is limited, as long as the base station permits the access to the terminal only in a high interference situation, the access restriction for the cell is removed by itself and the corresponding cell is removed. And transmits the interference condition to the corresponding cell.

10 is an exemplary view illustrating a connection operation process of a terminal according to the present invention. As shown in FIG. 10, first, when a terminal obtains access pipe related information from a base station and confirms that access is restricted through information provided by the base station, the terminal accesses a terminal having high interference with the base station. Make sure you allow it. Thereafter, if the base station confirms that the access restriction is removed and the access is allowed for the terminal with high interference, the terminal estimates the interference. Here, if it is determined that the estimated interference is large, the terminal attempts to cancel the access restriction, and if it is determined that the estimated interference is not large, the terminal does not attempt to connect. Then, the process may be repeated again, or the frequency priority is arbitrarily changed to move to another frequency (the priority of another frequency is set equal to or higher than the current frequency priority, or the priority of the current frequency is changed. It may be set lower than the priority of other frequencies so that the interference is limited (temporary) to other frequencies to reduce interference. In the above process, if the terminal removes the access restriction and attempts to access, the terminal may inform the base station that the interference is high in the access procedure. In addition, if the base station recognizes from the terminal that the interference is high, it may allow the connection of the terminal once to avoid the interference.

Hereinafter, two embodiments of the present invention that vary depending on how the terminal estimates interference will be described.

As a first embodiment, the present invention proposes a method of estimating the amount of uplink interference based on the downlink quality of the terminal and notifying that the interference is large by accessing a restricted cell when the uplink interference is large. 11 is a first exemplary diagram showing how a terminal estimates interference according to the proposal of the present invention.

First, the base station broadcasts access related information. Here, the base station may transmit an interference access indicator to the terminal to release the access restriction according to the interference level of the terminal to the base station. In addition, the base station may transmit a reference threshold (interference threshold) of the amount of interference to be used as a reference for the terminal to release the access restriction. The Interference Access Indicator and the Interference Threshold may generally be delivered to the UE through cell specific signaling, and may perform UE specific signaling (eg, cell re-selection parameter). It does not exclude the way of passing through. The terminal receives the access related information from the base station, and checks whether or not the base station is an access restricted base station. If it is determined that the access point is a restricted access point, the access point confirms whether the access point is a cell (or a base station) that can release access restriction only when the interference is large. In this case, when the terminal receives the Interference Access Indicator from the base station or the Interference Threshold, the base station may be regarded as a base station (or cell) that can solve the access restriction in a situation where the interference is large. If the base station is identified as a base station that can solve the access restriction only when the interference is large, the terminal estimates the amount of interference based on the measurement result of the signal transmitted by the base station. The terminal may measure downlink quality of the base station by measuring a reference signal transmitted by the base station. The terminal estimates the downlink interference that the base station exerts on the terminal based on the quality of the downlink. Here, the downlink interference and downlink quality have a positive relationship. That is, if the downlink quality measured for the base station is high (if good), the interference of the base station to the terminal is also large. In addition, the terminal may properly estimate the uplink quality based on the measured downlink quality. If the base station notifies the channel quality difference between the uplink and the downlink through the broadcast information, the terminal may estimate the uplink quality by using the difference value as a correction factor in the measured downlink quality. If the base station does not inform the terminal of the difference in channel quality between uplink and downlink, the terminal may assume that the quality of the uplink is equal to the quality of the downlink. Here, the uplink interference is positively related to the uplink quality. That is, if the downlink quality measured for the base station is high (if good), the interference of the base station to the terminal is also large. When evaluating the amount of interference between the base station and the terminal, the terminal may consider only the amount of interference in the downlink, only the amount of interference in the uplink, or both. In general, it is preferable to consider only the uplink because the influence of the directional link interference from the terminal is large.

If the estimated amount of interference is greater than the interference threshold transmitted by the base station, the terminal removes the access restriction and attempts to access the base station. If the estimated amount of interference of the uplink is smaller than the interference threshold transmitted by the base station, the terminal does not attempt the access request while maintaining the access restriction.

When the terminal makes an access request, in the access request process, the terminal informs the base station that it is accessing because the uplink interference to the base station is large. To this end, the terminal includes a 1-bit (Interference Indicator) when transmitting to the access request message (RRC Connection Setup request) or access completion message (RRC Connection Setup Complete) to the base station or the connection connection request message The cause field may be set to high interference. Here, the high interference is a cause field newly introduced compared to the prior art.

When the base station recognizes that the terminal is a terminal causing a lot of interference when the connection is rejected through the interference indicator during the access process, the base station accepts the access of the terminal. After accommodating the access of the corresponding terminal, the base station may additionally avoid the interference from the corresponding terminal by moving the corresponding terminal to a different frequency through a mobility procedure (Mobility procedure).

In a second embodiment, the present invention estimates uplink interference based on the random access preamble transmission power used by the UE in the access procedure, and when the uplink interference is large, the interference is large by accessing a restricted cell. Suggest ways to communicate the facts. 12 is a second exemplary diagram illustrating how the terminal estimates interference according to the present invention.

First, the base station broadcasts access related information. Here, the base station may transmit an interference access indicator to the terminal to release the access restriction according to the interference level of the terminal to the base station. In addition, the base station may transmit an uplink interference threshold value to be used as a reference for the terminal to release the access restriction. The Interference Access Indicator and the Uplink Interference Threshold may be generally transmitted to the UE through cell specific signaling, and a method of transmitting the UE through the UE specific signaling is not excluded. The terminal receives the access related information from the base station, and confirms whether or not the base station is a restricted access base station. If the base station is identified as a base station with limited access, the terminal checks whether the base station is a cell (or base station) that can solve the access restriction only when the interference is large. In this case, when the terminal receives the Interference Access Indicator from the base station or the Uplink Interference Threshold, the base station may be regarded as a base station (or cell) capable of solving the access restriction in a situation where the interference is large. If the base station is identified as a base station capable of solving the access restriction in a situation where the interference is large, the terminal starts a random access procedure to start the access connection procedure. In this case, the UE may estimate the quality of the uplink based on the RACH preamble power finally transmitted until the RACH response is received. Here, the uplink interference may be regarded as being in a reverse relationship with the uplink quality.

If the power of the last transmitted RACH preamble before receiving the RACH response is greater than the Interference Threshold value received from the base station, the terminal considers the interference to the corresponding uplink is large and restricts access to the base station. And the terminal continuously tries to request a connection to the base station. If the power of the last transmitted RACH preamble before receiving the RACH response is less than the Interference Threshold value received from the base station, the terminal considers that the interference to the corresponding uplink is small, and to the base station Maintain access restriction and the terminal does not request access to the base station.

When the terminal makes an access request, in the access request process, the terminal informs the base station that it is accessing because the uplink interference to the base station is large. To this end, the terminal includes a 1-bit (Interference Indicator) when transmitting to the access request message (RRC Connection Setup request) or access completion message (RRC Connection Setup Complete) to the base station or the connection connection request message The cause field may be set to high interference. Here, the high interference is a cause field newly introduced compared to the prior art.

When the base station recognizes that the terminal is a terminal causing a lot of interference when the connection is rejected through the interference indicator during the access process, the base station accepts the access of the terminal. After accommodating the access of the corresponding terminal, the base station may additionally avoid the interference from the corresponding terminal by moving the corresponding terminal to a different frequency through a mobility procedure (Mobility procedure).

The present invention can be used not only for the above-described RRC connection establishment procedure, but also for RRC connection reestablishment, and the present invention provides that the terminal is connected to the base station except when the base station is HNB It may be used in other cases where it is limited for some reason. For example, the present invention can be applied to a case where a terminal tries to access a relay or a relay attempts to access a base station. In addition, the present invention can be applied to the non-member CSG terminal to terminate the access restriction in the cell restricted access in an emergency.

Hereinafter, a terminal according to the present invention will be described.

The terminal according to the present invention includes all types of terminals that can use a service that can exchange data with each other over the air. That is, the terminal according to the present invention is a mobile communication terminal capable of using a wireless communication service (for example, user equipment (UE), mobile phone, cellular phone, DMB phone, DVB-H phone, PDA phone, and PTT phone, etc.) It is a comprehensive meaning including laptops, laptops, laptops, digital TVs, GPS navigation, handheld game consoles, MP3s, and other consumer electronics.

The terminal according to the present invention may include a basic hardware configuration (transmitter / receiver, processor or controller, storage, etc.) required to perform functions and operations for efficient system information reception illustrated in the present invention.

The method according to the invention described thus far can be implemented in software, hardware, or a combination thereof. For example, the method according to the present invention may be stored in a storage medium (eg, internal memory of a mobile terminal or base station, flash memory, hard disk, etc.), and may be stored in a processor (eg, mobile terminal or base station). Code or instructions within a software program that can be executed by an internal microprocessor).

In the above, the present invention has been described with reference to the embodiments shown in the drawings, which are merely exemplary and will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. . Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Claims (11)

CLAIMS What is claimed is: 1. A method of accessing a cell on a wireless communication system,
Receiving connection information from a network;
Determining whether access to the cell is restricted based on a first parameter included in the received access information;
If it is determined that access to the cell is restricted, determining whether access to the cell is allowed in high interference based on a second parameter included in the received access information;
If it is determined that access to the cell is allowed in the high interference, estimating interference; And
Selectively terminating the restricted connection to the cell in accordance with the estimated interference. 2. The method of claim 1 wherein the access information is access control information related to interference. The cell of claim 1, wherein the first parameter of the access information is an interference access indicator and the second parameter of the access information is an interference threshold. How to access). 10. The method of claim 1, wherein the network is a Home NodeB (HNB) or a Macro NodeB. 4. The cell of claim 3, wherein the first and second parameters of the access information are received through cell specific signaling or UE specific signaling. How to access). 2. The method of claim 1, wherein the interference is estimated using a reference signal in the downlink direction. 7. The method of claim 6, wherein the amount of interference is related to the quality of the reference signal. 2. The method of claim 1, wherein the interference is estimated using the power of a random access channel (RACH) preamble transmitted last in the uplink direction. . 9. The method of claim 8, wherein the amount of interference has an inverse relationship with the power of the last transmitted RACH preamble. 4. The method of claim 3, wherein if the estimated interference is greater than or equal to the interference threshold contained in the connection information, then a restricted connection to the cell is terminated. . 4. The method of claim 3, wherein if the estimated interference is less than the interference threshold contained in the connection information, then no restricted connection to the cell is terminated. .

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