KR20100114345A - Method for controlling signaling and mobile telecommunication system for the same - Google Patents

Abstract

PURPOSE: A method for controlling a handover, and a mobile communication system for the same are provided to effectively control the handover of a terminal having a path loss imbalance of uplink and downlink in a net which outdoor base station and indoor base station having large difference of transmission power are mixed. CONSTITUTION: An outdoor BS(Base Station)(20) broadcasts measurement report conditions about a up/downlink path lass through a common channel. The indoor BS receives an up/downlink path loss value which accords with the measurement report conditions from a terminal(10). Based on a BS transmission power, the up/downlink path loss value is measured. The indoor BS recognizes an environment of a terminal. The indoor BS controls the handover according to the recognition of the environment of the terminal.

Description

Handover control method and mobile communication system for the same {METHOD FOR CONTROLLING SIGNALING AND MOBILE TELECOMMUNICATION SYSTEM FOR THE SAME}

The present invention relates to a mobile communication system, and more particularly, a handover of a terminal having an unbalanced pathloss of uplink (UL) and downlink (DL). It is about how to control effectively.

Recently, due to the rapid development of communication, computer network, and semiconductor technology, various services using wireless communication networks are being provided, and demands of consumers are increasing day by day, and the global market for wireless internet services is exploding. It is a trend. Accordingly, a service provided by a mobile communication system using a wireless communication network is developing not only a voice service but also a multimedia communication service for transmitting various data.

Currently, wireless data services such as Code Division Multiple Access (CDMA) 2000, Evolution Data Only (EV-DO), Wideband CDMA (WCDMA), and Wireless Local Area Network (WLAN) are commercially available. Demand is constantly increasing, and according to this trend, a method of providing a mobile communication service by installing a small mobile communication base station indoors to access a mobile communication core network through an indoor broadband network has been proposed. Such a small mobile communication base station is called an indoor base station or a femto base station, an access point (AP), and a remote node (RN).

At present, the indoor base station is introduced to a communication network composed of an existing outdoor base station (Macro base station), and the development of a communication network technology having a configuration in which the outdoor base station and the indoor base station are mixed is actively progressed. A representative example of such a communication network is a Long Term Evolution (LTE) communication network that is being actively standardized by a 3rd Generation Partnership Project (3GPP). A network according to the LTE standard (hereinafter referred to as an "LTE network") has a data rate of 100 Mbps in the downlink and 50 Mbps in the uplink, operates at a user data bandwidth within 5 ms in terms of delay, and low transmission. Improved transmission efficiency at delay and cell boundaries.

The general LTE network structure includes an outdoor base station (Macro-eNB (Enhanced Node B)), an indoor base station (Home-eNB), a mobility management entity (MME), a self organizing & optimizing network (SON) server, and the like. Since the indoor base station and the outdoor base station each independently have accessibility to the core network, a user equipment (UE) may communicate through either the indoor base station or the outdoor base station for communication. The MME is an entity used to perform handover management and call processing of the terminal. A SON server is any server that performs the installation and optimization of outdoor / indoor base stations and provides the basic parameters or data required for each base station. The functions of the MME and SON server can all be performed from one network management device.

In an LTE network having such a structure, access to an indoor base station cell (femtocell) may be restricted to a specific terminal (subscriber). Specifically, the indoor base station may broadcast system information block type 1 (SIB 1), which is information about a femtocell managed by the indoor base station, and the SSG 1 may indicate whether access to the femtocell is restricted or not. An indicator (Closed Subscriber Group indicator) is included. When the CSG indicator in SIB 1 broadcast by an indoor base station has a value of 'true', communication is performed in a closed manner so that only a particular subscriber can access the femtocell (CSG: Closed Subscriber Group). For example, if the value is 'false', communication is performed in an open manner in which all subscribers have access to the femtocell (OSG: Opened Subscriber Group). If the CSG indicator has a true value, the UE may access the femtocell only when it is confirmed that the femtocell is included in a white list, which is a list of femtocells accessible by the CSG indicator.

However, since the transmission power of the indoor base station is much less than the transmission power of the outdoor base station, the terminal in the handover area is located closer to the indoor base station than the outdoor base station. In this case, the path loss to the indoor base station is much less than the path loss to the indoor base station. Accordingly, it is advantageous in view of the terminal power consumption that the terminal accesses the uplink to the indoor base station and the downlink to the outdoor base station. However, the conventional handover method only performs the downlink (DL) power measurement (DL) power measurement of the base station in the terminal, and does not consider UL (up-link) power measurement. In this case, information necessary for DL power measurement is received through a common channel. When the handover is performed only through the DL power measurement as described above, the UE cannot access the indoor base station cell (femtocell) in proximity to the outdoor base station cell (macrocell) and the outdoor base station (or macro base station). There is a problem that consumes a lot of power for uplink transmission. In addition, the uplink transmission between the terminal and the outdoor base station acts as a significant interference to the uplink of the indoor base station.

Specifically, handover by DL power measurement does not have a big problem when the base station transmit power in the network is the same or similar, but in a network where indoor base stations and indoor base stations having a large difference in transmission power, such as 4G network, are mixed It causes the UL and DL path loss imbalance in a plurality of terminals existing in the region, and wastes transmission power of the terminal. However, only DL power measurement cannot recognize the path loss imbalance of DL and UL, and the terminal connects both the UL and the DL to the outdoor base station. At this time, the terminal consumes a lot of power for UL transmission, which acts as a significant amount of interference on the UL of the nearby indoor base station. If the terminal accesses the indoor base station in order to save the UL transmission power, the indoor base station requires a high DL transmission power, so that the indoor base station may run out of power or act as a DL interference to a nearby terminal.

SUMMARY OF THE INVENTION An object of the present invention is a method for effectively controlling a handover of a terminal having an unbalanced path loss of uplink and downlink in a network where outdoor base stations and indoor base stations having a large difference in transmission power are mixed, and a mobile communication system therefor. To provide.

According to an aspect of the present invention, a method for effectively controlling a handover of a terminal having an unbalanced path loss of uplink and downlink in a network in which outdoor base stations and indoor base stations having a large difference in transmission power are mixed and for the same A mobile communication system is disclosed. According to this system and method, an outdoor base station broadcasts a measurement report condition regarding uplink / downlink path loss through a common channel, and uplink / downlink path loss measured based on the base station transmission power and meets the measurement report condition. A value is received from the terminal and the handover is controlled by recognizing the terminal environment based on the uplink / downlink path loss value. As an example of handover control, an outdoor base station allows one of a link connection of an uplink and a downlink connection of a terminal, and allows the other one of the link access to an indoor base station. As another example, an outdoor base station allows uplink and downlink access of a terminal or uplink and downlink access to an indoor base station.

According to the present invention, there is an advantage that the handover of the terminal having an unbalanced path loss of uplink and downlink can be effectively controlled in a network in which outdoor base stations and indoor base stations having a large difference in transmission power are mixed. In particular, there is an advantage that the up / downlink can be handed over to the optimal base station differently from the outdoor base station and the indoor base station.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, well-known functions or constructions will not be described in detail if they obscure the subject matter of the present invention.

1 is a diagram illustrating a configuration of an exemplary mobile communication network in which the present invention may be implemented.

In one embodiment, the mobile communication network includes, for example, Global System for Mobile communication (GSM), 2G mobile communication networks such as CDMA, LTE networks, wireless Internet such as WiFi, Wireless Broadband Internet (WiBro) and World Interoperability for Microwave Access. Mobile communication networks (e.g., 3G mobile networks such as WCDMA or CDMA2000, 3.5G mobile networks such as High Speed Downlink Packet Access (HSDPA) or High Speed Uplink Packet Access (HSUPA)) 4G, etc.) and an outdoor base station (Macro-eNB), an indoor base station (Home-eNB), and any other mobile communication network including a UE as a component, but is not limited thereto.

As shown in FIG. 1, a mobile communication network may be composed of one or more network cells, and different types of network cells may be mixed in the mobile communication network. The mobile communication network includes indoor base stations 21 to 25 for managing a narrow range of network cells (femtocells) indoors, an outdoor base station 20 for managing a wide range of cells (macrocells) outdoors, a terminal 10, and a SON. (Self Organizing & Optimizing Networks) It may include a server 30 and the MME (40). The number of each component shown in FIG. 1 is exemplary, and the number of each component of the mobile communication network to which the present invention may be implemented is not limited to the number shown in the drawings.

The outdoor base station (Macro-eNB) 20 may be used in, for example, an LTE network, a WiFi network, a WiBro network, a WiMax network, a WCDMA network, a CDMA network, a UMTS network, a GSM network, and the like, for example, having a radius of about 1 km. It may include, but is not limited to, features of a macro base station for managing a cell.

The indoor base station (Home-eNB) 21 to 25 may be used in, for example, LTE network, WiFi network, WiBro network, WiMax network, WCDMA network, CDMA network, UMTS network, GSM network, etc. A femto base station for managing a cell having a radius of may include the feature, but is not limited thereto.

The network cell constituting the mobile communication network may include an outdoor base station cell (macrocell) and an indoor base station cell (femtocell). The macrocell may be managed by the outdoor base station 20, and the femtocell may be managed by the indoor base stations 21 to 25.

The outdoor base station 20 and the indoor base stations 21 to 25 may be connected to be communicated by separate backbone networks, and the indoor base stations 21 to 25 or the outdoor base stations 20 may be independently. This can have connectivity of the core network. In addition, the outdoor base station 20 and indoor base stations 21 to 25 may be replaced with a pico base station or a micro base station in addition to the macro base station and the femto base station.

CSG (Closed Subscriber Group) means a group of indoor base stations 21 to 25 with specific attributes. All indoor base stations 21 to 25 belonging to this group (CSG) allow access only to the terminal 10 allowed to access. The terminal 10 belonging to the femtocell managed by the indoor base stations 21 to 25 has an indoor base station ID called a white list, and can only connect to an indoor base station belonging to the white list. Connection is not allowed. For example, in a femtocell, assuming indoor base stations 22 to 25 as 'CSG base stations' and indoor base station 21 as 'OSG base stations', the indoor base station belonging to the white list is determined by the OSG base station 21. do. Therefore, the indoor base station 21 can be connected to all terminals, but only the terminals permitted to be connected to the indoor base stations 22 to 25 can be connected.

Looking at the procedure of the terminal 10 is connected to the indoor base station (eg, OSG base station 21) belonging to the white list. The terminal 10 may know whether access to the femtocell is restricted based on the CSG indicator of the SIB 1 broadcast by the indoor base stations 21 to 25. In addition, the terminal 10 identifies the indoor base station cell as a physical layer cell identifier (PCI), which is a cell classification factor in the physical layer, and a global cell identifier, which is a unique cell discrimination factor in a mobile communication network. (CGI: Cell Global Identity). The cell identifier is included in SIB 1 broadcast by the indoor base stations 21-25. In one embodiment, if the terminal 10 detects that the OSG base station 21, the outdoor base station 20 is reported, and the outdoor base station 20 received the detection of the detection of the indoor base station 21 from the terminal 10 is The terminal 10 is instructed to read the SIB 1 received from the detected indoor base station 21 to report the cell identifier (PCI or CGI) of the indoor base station 21, and the terminal 10 reads it. It is determined whether the terminal 10 is accessible to the detected indoor base station 21 based on the cell identifier and the white list. If it is determined that the terminal 10 can be connected to the detected indoor base station 21, the outdoor base station 20 allows handover of the terminal 10 to the indoor base station 21. The indoor base station belonging to the white list may be a CSG base station 21 to 25 allowing access to a specific terminal.

In the macro cell, characteristics of the OSG base station 21 and CSG base stations 22 to 25 of the lower femtocell are set in advance, and information on the characteristics of the indoor base stations 21 to 25 (OSG base station, CSG base station) is for outdoor use. It is stored and managed by the base station 20.

UE 10 is used in 2G mobile communication networks such as GSM networks, CDMA networks, wireless Internet networks such as LTE networks, WiFi networks, mobile Internet networks such as WiBro networks and WiMax networks, or mobile communication networks supporting packet transmission. It may include features of the wireless mobile terminal, but is not limited thereto. In one embodiment, the terminal 10 may be a macrocell subscriber station and / or a femtocell subscriber station. In the present invention, the terminal 10 is based on the assumption that the path loss of UL / DL is imbalanced in a network in which a macrocell and a femtocell are mixed. Referring to Figure 2 with respect to the terminal 10 is a UL / DL path loss imbalance as follows. In FIG. 2, the indoor base station 21 is a base station belonging to the white list (it may be a CSG base station allowing access to only a specific terminal 10 or an OSG base station allowing access to all terminals).

In general, handover between outdoor base stations occurs when the UL / DL path loss is about the same (UL / DL balance). The reason is that since the transmission powers (transmission outputs) of the two outdoor base stations are the same, the DL powers measured by the two outdoor base stations are almost the same in the same distance from the terminal to the two outdoor base stations. However, when the transmission powers of the two base stations (eg, the outdoor base station and the indoor base station) are different, even if the measured DL power is the same, the path loss from the two base stations differs by the transmission power. That is, in FIG. 2, the DL measurement power is “-103 + 20 = -83dB” at the indoor base station 21 and “-120 + 43 = -77dB” at the indoor base station 20. Although the side is more advantageous by 6 dB, the UL path loss (= receive power-transmit power) is -103 and -120 dB for the indoor base station 21 and the outdoor base station 20, respectively, and 17 dB for the indoor base station 21 side. It is a more favorable situation. In this case, the UL is advantageous in terms of the link quality in terms of the connection at the indoor base station 21 and the DL is connected in the outdoor base station 20 at the side. This situation often occurs when the transmission powers of the two base stations 20 and 21 are different, and this case is referred to as an "UL / DL imbalance situation".

However, if the handover is performed only through the DL power measurement as in the related art, the terminal 10 cannot access an indoor indoor base station cell (femtocell) and has no choice but to access the outdoor base station cell (macrocell) unconditionally. Even when the path loss is disadvantageous, a lot of power is consumed for uplink transmission with the outdoor base station (or macro base station) 20, and the uplink transmission between the terminal 10 and the outdoor base station 20 is performed with the indoor base station 21. ) Also acts as a significant interference (Interference).

In contrast, the present invention considers UL and DL power measurements simultaneously during handover. In one embodiment, the terminal 10 has information about the transmission power of the neighboring base station (including both indoor base station and outdoor base station) in order to calculate the path loss. In this case, the information about the transmission power of the neighboring base stations may be included in the SIB or the base stations 20, 21 to 25 may inform the terminal 10 through signaling. Here, the outdoor base station 20 informs a condition corresponding to a path loss to the terminal measurement report condition through a common channel. The terminal 10 reports UL and DL path loss values as measurement report information to the outdoor base station 20 when the outdoor base station 20 satisfies the condition determined by the outdoor base station 20. A handover control procedure according to an embodiment will be described later with reference to FIG. 3.

In another embodiment, the path loss value may be measured by the indoor base stations 21 to 25 and reported to the outdoor base station 20. In this case, a random access (RA) channel may be used. In general, the RA channel is a common channel that can be used by all the terminals 10, and since the parameters, resources, and the like necessary for using the RA channel are already set by the base stations 20, 21 to 25, the dedicated channel ( Unlike the dedicated channel, there is a feature that can be used without a separate negotiation procedure between the base station (20, 21 ~ 25) and the terminal 10. The purpose of the communication using the RA channel is as follows. Communication through the RA channel is used as the first uplink signal for the terminal 10 to initiate access to the base stations 20, 21 to 25, and is also used as an uplink reporting means for maintaining physical layer synchronization. . In addition, the terminal 10 is also used as a signal indicating that there is a specific request to the base station (20, 21 ~ 25), the terminal 10 is also used for the purpose of adjusting the physical layer synchronization with the destination base station during the handover.

In the present invention, the terminal 10 provides a multiple destination random access (MDRA) type of communication for transmitting an RA code to a plurality of indoor base stations 21 to 25. According to the MDRA scheme of the present invention, the terminal 10 may transmit the RA code to one indoor base station 21 to 25. In one embodiment, since the indoor base stations 21 to 25 are located near the terminal 10 compared to the outdoor base station 20, the terminal 10 may transmit the RA code at low power or at a predetermined value of power. Can be. The indoor base stations 21 to 25 receiving the RA code may report the information about the terminal 10 such as the received RA code and the strength of the received signal to the outdoor base station 20 through the backbone network, for example. A part of the RA communication process with (10) may be relayed or acted on. In an embodiment, the indoor base stations 21 to 25 may select and report only the signals received at a strength equal to or greater than a predetermined threshold to the outdoor base station 20. In this case, the threshold may be dynamically changed as necessary. In another embodiment, the terminal 10 transmits an RA code at a transmission power of a predetermined value, and indoor base stations 21 to 25 receiving the same compare the predetermined transmission power with the actual received reception power. Based on the difference, the path loss can be calculated. Such path loss information may be included in information (eg, RA code index, received power, etc.) of the terminal 10 reported to the outdoor base station 20. The outdoor base station 20 determines whether the current terminal 10 exists in the service area of which indoor base stations 21 to 25 based on the location of the indoor base stations 21 to 25 which reported the information on the terminal 10. can do. For example, in FIG. 1, when only the indoor base station 21 reports the information of the terminal 10 to the outdoor base station 20, the outdoor base station 20 is located at the indoor base station 21. It can be inferred that the service area of. As another example, when the indoor base station 21 and the indoor base station 22 reports the information of the terminal 10 to the outdoor base station 20, the outdoor base station 20 may be located in the indoor base station 20. It can be inferred that the area 21 and the indoor base station 22 are within the overlapping area. Also, based on the path loss information, it may be estimated how far the terminal 10 is located from the indoor base station 21 or 22. A handover control procedure according to another embodiment will be described later with reference to FIGS. 4 to 6.

Referring back to FIG. 1, the SON server 30 may include any server that functions to perform installation and optimization of outdoor / indoor base stations and to provide basic parameters or data required for each base station.

The MME 40 may include any entity used to manage handover management, call processing, and the like of the terminal 10.

In one embodiment, one network management device may perform all of the functions of the SON server 30 and the MME 40, the SON server 30 and the MME 40 is one or more of the outdoor base station 20 and One or more indoor base stations 21-25 may be managed. Since the SON server 30 and the MME 40 are not directly related to the present invention, a detailed description thereof will be omitted.

In one embodiment, the outdoor base station 20 and indoor base stations 21 to 25 store and manage a neighbor cell list, which is a list of cells physically adjacent to the base station 20. In one embodiment, the neighbor cell list includes a femtocell list which is a list of femtocells managed by the outdoor base station 20. The femtocell list includes ID information of the OSG base station and the CSG base station. Accordingly, the femtocell list includes a list of indoor base station cells accessible by the terminal 10 (ID of the OSG base station), for example, a white list (ie, an OSG femtocell list).

3 is a flowchart illustrating a handover control process according to an embodiment of the present invention.

In order to calculate the path loss in the terminal 10, the base stations (including both indoor base stations and outdoor base stations) 20, 21 to 25 include information on the transmission power in the SIB or transmit the information to the terminal 10 through signaling. (301, 302).

The outdoor base station 20 stores and manages not only the femtocell list (IDs of the CSG base station and the OSG base station) but also the path loss reporting condition of the terminal 10, information necessary for measurement, and information that the terminal 10 needs to report. . The outdoor base station 20 includes the path loss reporting condition of the terminal 10, information necessary for measurement, and information (measurement report information) that the terminal 10 needs to report in the SIB information to include all terminals 10 in the macrocell. Broadcast to the server (303).

Here, the path loss reporting condition of the terminal 10 is transmitted by including the path loss minimum value Pathloss_min and the path loss maximum value Pathloss_max of the SIB information broadcasted by the outdoor base station 20. In addition, the information necessary for the measurement includes the base station transmission power required for the UL / DL path loss measurement. In addition, the information (measurement report information) to be reported by the terminal 10 includes the measured path loss value and the identifier (ID) of the indoor base station (for example, 21).

The terminal 10 measures the UL / DL path loss values of the indoor base station 21 and the outdoor base station 20 (304) so that the measured path loss values of the UL / DL are the maximum values (for example, in case of UL). Between -90 dB, -70 dB for DL) and the minimum value (e.g., -130 dB for UL, -90 dB for DL) or satisfying either of the measured UL / DL path losses and the corresponding indoor An identifier (ID) of the base station (eg, 21) is transmitted to the outdoor base station 20 (305).

Looking at the method 304 for the terminal 10 to measure the path loss value in detail, SIB information broadcast by the outdoor base station 20 and the indoor base station 21 includes the corresponding outdoor base station 20 and the indoor base station ( There is a field indicating the transmission power of 21), and the terminal 10 calculates a power difference between the field value and the measured reference signal (eg, preamble) to measure the path loss value of the UL / DL. In one embodiment, the DL measurement power on the indoor base station 21 side is -83 dB (= -103 dB + 20 dB) and the UL path loss value (receive power-transmit power) is -103 dB. In addition, the DL measurement power at the outdoor base station 20 side is -77 dB (= -120 dB + 43 dB) and the UL path loss value (receive power-transmit power) is -120 dB. The terminal 10 transmits the UL / DL path loss value of the indoor base station 21 and the outdoor base station 20 and the ID of the indoor base station 21 to 'information (measurement report information)' which the terminal 10 should report. As an outdoor transmission to the base station 20 for outdoor use.

In the above, when the terminal 10 detects an identifier (ID) of an indoor base station (eg, 21), the terminal 10 reads the SIB 1 received from the indoor base station 21 by reading the corresponding indoor. The cell identifier (PCI or CGI) of the base station 21 is detected.

The outdoor base station 20 is based on the UL / DL path loss values of the indoor base station 21 and the outdoor base station 20 transmitted from the terminal 10, the corresponding terminal 10 is' unbalanced UL / DL path loss; The terminal 'recognized that (306). According to the first embodiment, the outdoor base station 20 recognizes that UL is advantageous in connection with the indoor base station 21 side and DL is advantageous in terms of link quality in connection with the outdoor base station 20 side. Done. According to the second embodiment, the outdoor base station 20 recognizes that the connection of the indoor base station 21 on both the UL and the DL is advantageous in terms of link quality. According to the third embodiment, the outdoor base station 20 recognizes that the UL and DL connections on the outdoor base station 20 side are advantageous in terms of link quality. Here, the outdoor base station 20 determines the difference between the path loss between the two base stations 20 and 21 and how long the difference is maintained, and instructs the user to handover when the predetermined difference is maintained for a predetermined time.

According to the first embodiment, the outdoor base station 20 allows the terminal 10 to allow UL connection to the indoor base station 21 and DL connection to the outdoor base station 20 (307 and 308). The DL allows the DL RS power to be greater and the UL to the path loss to the least. To this end, the outdoor base station 20 transmits a message for allowing the UL connection of the terminal 10 to the indoor base station 21 (307), and also provides the terminal 10 with the UL connection of the indoor base station 21. Send a message to allow (308). In this case, the access permission message transmitted to the terminal 10 further includes information indicating that the DL access is allowed to the outdoor base station 20. Accordingly, the terminal 10 transmits a random access channel (RACH) to the indoor base station 21 (309) and receives a response thereto from the indoor base station 21 (310) to receive a UL access request. Will run. In addition, the terminal 10 transmits a random access channel (RACH) to the outdoor base station 20 (311) and receives the response from the outdoor base station 20 (312) to execute the DL connection request.

Thereafter, the terminal 10 performs a network entry procedure for UL to the indoor base station 21 and a network entry procedure for DL to the outdoor base station 20. In one embodiment, network entry includes a handover procedure, where indoor base station 21 becomes a handover target base station for UL and outdoor base station 20 becomes a handover target base station for DL. . The network entry procedure includes a transmission parameter acquisition process, a ranging process, a basic capability negotiation process, a terminal authentication and key exchange process, a registration process, a connection setup process, and the like.

According to the second embodiment, the outdoor base station 20 permits the terminal 10 to the UL, DL connection to the indoor base station 21 (307, 308). To this end, the outdoor base station 20 transmits a message to the indoor base station 21 to allow UL and DL access of the terminal 10 (307), and also to the terminal 10 the UL of the indoor base station 21. In step 308, a message is sent that allows the DL connection. Accordingly, the terminal 10 transmits a random access channel (RACH) to the indoor base station 21 (309) and receives a response from the indoor base station 21 (310) to execute the UL, DL access request. do. Thereafter, the terminal 10 performs a network entry procedure for UL and DL to the indoor base station 21. In one embodiment, network entry includes a handover procedure, and indoor base station 21 becomes a handover target base station for UL and DL.

According to the third embodiment, the outdoor base station 20 allows the terminal 10 to UL (DL) connection to itself (outdoor base station 20) (308). To this end, the outdoor base station 20 transmits a message to the terminal 10 to allow the UL, DL connection to itself (outdoor base station 20) (308). Accordingly, the terminal 10 transmits a random access channel (RACH) to the outdoor base station 20 (311) and receives the response from the outdoor base station 20 (312) to execute the UL, DL access request. Thereafter, the terminal 10 performs a network entry procedure for UL and DL to the outdoor base station 20. In one embodiment, network entry includes a handover procedure, and the outdoor base station 20 becomes a handover target base station for UL and DL.

4 to 6 illustrate first to third embodiments of the RA channel communication procedure between the terminal 10 and the base stations 20, 21 to 25 according to another embodiment of the present invention.

Referring to FIG. 4, the outdoor base station 20 and the indoor base stations 21 to 25 may use configuration information (eg, RA code, channel resource) for MDRA communication through a backbone network or provisioning. Etc.) (401). The outdoor base station 20 broadcasts configuration information on the MDRA channel to the terminal 10 (402). In this case, the configuration information includes an RA code, an uplink RA channel, and the like that can be used by the terminal 10. The terminal 10 selects an RA code and an uplink RA channel according to the configuration information for the MDRA channel defined by the base stations 20, 21 to 25 (403). The terminal 10 transmits the RA code to the plurality of indoor base stations 21 to 25 at a predetermined power through the selected channel resource (404). The RA code is transmitted to one or more nearby indoor base stations 21 to 25 instead of the outdoor base station 20.

The indoor base stations 21 to 25 detect the RA code according to a predetermined setting with the outdoor base station 20 in step 401 (405). The indoor base stations 21 to 25 report information (eg, RA codes) on the terminal 10 to the outdoor base station 20 according to the message received from the terminal 10 (406). In one embodiment, the information about the terminal 10 includes the reception power from the terminal 10 received by the indoor base stations 21 to 25. In an embodiment, the indoor base stations 21 to 25 may provide information on the terminal 10 (eg, RA code index and receive power) only when the reception power from the terminal 10 is greater than or equal to a predetermined threshold. And the like) are reported to the outdoor base station 20.

The outdoor base station 20 broadcasts an RA response to the terminal 10 according to the information on the terminal 10 reported by the indoor base stations 21 to 25 (407). In one embodiment, the RA response includes the RA code and RA channel information received from the indoor base stations 21-25. Upon receiving the RA response, the terminal 10 determines whether the RA code and RA channel information included in the RA response match the RA code and RA channel information transmitted by the UE 10 (408). As a result of the determination, if the information matches, the terminal 10 transmits an RA message to the outdoor base station 20 and requests a necessary service (409). Upon receiving the RA message, the outdoor base station 20 recognizes which terminal is the terminal 10 requesting the RA service, and performs the requested service (410). In operation 410, the mobile station 10 may determine whether the mobile station 10 is within a service area of the indoor base station based on the received RA message and information from the indoor base stations 21 to 25.

The second embodiment will be described with reference to FIG. 5. The second embodiment is useful when the outdoor base station 20 and the indoor base stations 21 to 25 have insufficient time to exchange messages with each other at each stage.

In the second embodiment of FIG. 5, steps "501" to "505" are the same as steps "401" to "405" in the first embodiment of FIG. Unlike the first embodiment, in the second embodiment, an RA response is broadcast from the indoor base stations 21 to 25 to the terminal 10 (506). The RA response includes the RA code and RA channel information received by the indoor base stations 21 to 25.

Upon receiving the RA response from the indoor base stations 21 to 25, the terminal 10 determines whether the RA code and the RA channel information included in the RA response correspond to the RA code and the RA channel information transmitted by the terminal 10 (507). As a result of the determination, if the information matches, the terminal 10 transmits an RA message to the indoor base stations 21 to 25 to request necessary services (508). Thereafter, the indoor base stations 21 to 25 report the RA message received from the terminal 10 and information on the terminal 10 (eg, an RA code, a received power, etc.) to the outdoor base station 20 (509). . Upon receiving the RA message, the outdoor base station 20 recognizes which terminal is the terminal 10 requesting the RA service, and performs the requested service (510).

A third embodiment will be described with reference to FIG. 6. In the third embodiment, the indoor base stations 21 to 25 report the information about the terminal 10 to the outdoor base station 20 (for example, the step "406" or "509" in FIG. 4) is a backbone. This is useful when time is consuming due to the nature of the network.

Steps “601” to “603” in the third embodiment of FIG. 6 include steps “401” to “403” in the first embodiment of FIG. 4 and steps “501” to the second embodiment of FIG. 5. Same as step "503". Unlike the first and second embodiments, in the third embodiment, the terminal 10 transmits the RA code to both the outdoor base station 20 and the indoor base stations 21 to 25 through the selected channel resource (604,605). .

The outdoor base station 20 and the indoor base stations 21 to 25 respectively detect the RA codes according to the predetermined settings (606 and 607). In the third embodiment, the outdoor base station 20 broadcasts the RA response to the terminal 10 (609). The RA response includes the RA code and the RA channel information received from the terminal 10. Upon receiving the RA response from the outdoor base station 20, the terminal 10 determines whether the RA code and the RA channel information included in the RA response match the RA code and the RA channel information transmitted by the UE 10 (610). As a result of the determination, if the information matches, the terminal 10 transmits an RA message to the outdoor base station 20 to request necessary services (611).

On the other hand, indoor base stations 21 to 25 that detect the RA code transmitted from the terminal 10 in step "607", the information about the terminal 10 (for example, RA code, received power, etc.) the outdoor base station 20 (608). Since this reporting procedure is performed in parallel with the RA response and RA message transmission / reception steps 609 and 611, it may take some time. Upon receiving the RA message, the outdoor base station 20 recognizes which terminal is the terminal 10 requesting the RA service, and performs the requested service (612).

As described above, when initiating a handover from the outdoor base station to the indoor base station, information of the terminal (for example, received signal strength from the terminal) obtained by the indoor base station can be used. In general, when a handover is necessary, when a base station broadcasts a neighbor list to a neighbor base station, and the terminal searches for base stations belonging to the list, the handover is initiated. However, when the number of indoor base stations is large, waste of data for the base station broadcasting a list for neighboring base stations is severe, and the terminal requires a large amount of computation to find a base station with a strong received signal. According to the MDRA method of the present invention, since the outdoor base station can determine the indoor base station to which the terminal belongs and the received signal strength of the terminal for each indoor base station, broadcasting a list of neighboring base stations separately or the terminal receives the best reception. There is no need to search the base station to find the signal strength.

When connected to an indoor base station, the terminal can save in particular UL power. The reason for this is as follows. Since the link quality is determined by the base station transmission power (the transmission power is increased when the path loss is large), the power consumed by the terminal is determined by the power received by the DL. However, since UL determines the link quality according to the UE transmission power, when the path loss is large, the UE consumes as much power as the path loss difference in order to obtain the same link quality. 2 consumes as much power as 17 dB when connected to an outdoor base station to obtain the same link quality. Therefore, the terminal can save UL power by connecting to an indoor base station instead of an outdoor base station. In particular, the UL connection may be differently connected to the indoor base station and the DL connection to the outdoor base station, thereby enabling optimal handover.

Although the present invention has been described in connection with some embodiments thereof, it should be understood that various changes and modifications may be made therein without departing from the spirit and scope of the invention as understood by those skilled in the art. something to do. It is also contemplated that such variations and modifications are within the scope of the claims appended hereto.

1 is a diagram illustrating a configuration of a mobile communication network in which the present invention can be implemented.

2 is an explanatory diagram illustrating a terminal in which a path loss of an UL / DL is unbalanced according to an embodiment of the present invention.

3 is a flowchart illustrating a handover control process according to an embodiment of the present invention.

4 to 6 are flowcharts illustrating a RA channel communication procedure between a terminal and a base station according to another embodiment of the present invention.

* Explanation of symbols for the main parts of the drawings

10: UE 20: Outdoor base station

21-25: Indoor base station 30: SON server

40: MME

Claims (12)

A handover control method in a network in which an outdoor base station and an indoor base station are mixed, a) the outdoor base station broadcasting a measurement report condition regarding an uplink / downlink path loss through a common channel; b) receiving, by the outdoor base station, an uplink / downlink path loss value measured based on a base station transmission power and satisfying the measurement report condition; c) the outdoor base station recognizing a terminal environment based on the uplink / downlink path loss value; And d) controlling the handover as the outdoor base station recognizes the terminal environment. The method of claim 1, In step d), the outdoor base station allows one of the link connection of the uplink, downlink access of the terminal, and allows the other link connection to the indoor base station, handover control method. The method of claim 1, In step d), the outdoor base station allows the uplink and downlink access of the terminal, or uplink and downlink access to the indoor base station, handover control method. The method according to any one of claims 1 to 3, The terminal environment, the uplink and downlink path loss is unbalanced, handover control method. The method of claim 4, wherein Transmitting, by the indoor base station, the configuration information to the terminal such that the terminal transmits an uplink signal at a preset transmission power; Calculating, by the indoor base station, a path loss by comparing the received power of the received uplink signal with the preset transmission power; And And the indoor base station reports the calculated path loss value to the outdoor base station. The method of claim 5, The uplink signal is a signal including a random access (RA) code. The method of claim 4, wherein The base station transmission power is transmitted through the SIB message, or transmitted to the terminal through the base station signaling, handover control method. As a mobile communication system in an environment where an outdoor base station and an indoor base station are mixed, Broadcasting a measurement report condition regarding uplink / downlink path loss through a common channel, receiving uplink / downlink path loss value measured based on the base station transmission power and meeting the measurement report condition from the terminal, A mobile communication system that recognizes and controls handover. The method of claim 8, In the handover control, the outdoor base station allows the link connection of one of the uplink, downlink connection of the terminal, and allows the other link connection to the indoor base station. The method of claim 8, And, during the handover control, the outdoor base station allows uplink and downlink access of the terminal or uplink and downlink access to the indoor base station. The method according to any one of claims 8 to 10, The terminal environment, the uplink and downlink path loss is imbalanced. The method of claim 11, The indoor base station transmits configuration information to the terminal so that the indoor base station transmits an uplink signal at a preset transmission power, and compares the reception power of the received uplink signal with the preset transmission power. Calculates the path loss, and reports the calculated path loss value to the outdoor base station, The uplink signal is a signal including a random access (RA) code.

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