KR20090114019A - Method for controlling indoor handover signaling in hybrid indoor/outdoor wibro system - Google Patents

Abstract

PURPOSE: A method for controlling indoor handover in a mobile internet system made of indoor/outdoor base stations is provided to limit a candidate handover object base station as an indoor base station during handover between indoor base stations. CONSTITUTION: When a terminal moves outdoor, an indoor serving base station performs handover to an indoor target base station having signal intensity which is stronger than a handover reference value among indoor candidate base stations based on signal intensity measured by searching an adjacent base station in the terminal. The indoor serving base station sends a MOB HO-IND message to finally notify handover(909). Immediately, the handover is performed(910~916).

Description

Method for controlling indoor handover in portable internet system composed of indoor / outdoor base stations {Method for controlling indoor handover signaling in hybrid indoor / outdoor wibro system}

The present invention relates to an indoor handover control method in a portable Internet system composed of an indoor / outdoor base station and a computer-readable recording medium recording a program for realizing the method. In a mobile Internet system in which a base station exists, at the time of handover of a terminal located in an area of an indoor base station, when handing over neighboring base station information, the handover frequency is limited by inducing and limiting the handover target base station (target base station) to an adjacent indoor base station. The present invention relates to an indoor handover control method which enables a handover to be performed more efficiently by reducing a time delay and a computer-readable recording medium which records a program for realizing the method.

Wireless Broadband (WiBro) systems provide Internet services in a wireless environment, such as Wi-Fi, and provide broadband Internet access, such as high-speed Internet services. In terms of transmission speed, mobility, cell radius, etc., it can supplement the advantages and disadvantages in terms of transmission distance and transmission speed of current mobile communication and wireless LAN. It is a representative mobile communication technology.

The portable Internet system can obtain or utilize various information and contents by accessing the Internet at a high speed transmission speed anytime, anywhere using a portable wireless terminal (portable Internet terminal). Accordingly, like many existing cellular mobile communication systems, the portable Internet system supports handover to ensure mobility of mobile terminals.

However, in the portable Internet system, various kinds of base stations are located at the same time. These various types of base stations can be broadly divided into indoor base stations and outdoor base stations, which are divided into cell coverage perspectives and main installation sites and applications.

In general, handover includes a communication path (base station ↔ terminal communication path) so that a mobile terminal can maintain communication when entering a cell area of another base station out of the cell area of a serving base station currently communicating. This refers to changing to a target base station located in the movement direction of the terminal.

The portable Internet should be able to continuously provide QoS-guaranteed services while moving. To this end, the handover technology used in the mobile Internet uses a hard handover technology that breaks an existing call line and connects to a new base station, but recently, two or more base stations are used for reliability. Soft handover technology that can support high handover is being considered. The handover technique may be divided into a network topology acquisition procedure for periodically measuring parameter values required for handover determination and a procedure for determining and performing a handover.

In general, a portable Internet system in an indoor environment supports a handover as in an outdoor environment in order to provide seamless communication to a portable Internet terminal located in a specific area of an indoor, indoor portable Internet system. When the handover control procedure of the outdoor portable Internet system is applied, the handover target base station (target base station) includes not only the indoor base station but also the adjacent outdoor base station, and the handover target base station is selected according to the signal strength. .

However, if the neighboring outdoor base station is included in the handover target base station according to this method, the handover is performed from the indoor base station to the neighboring outdoor base station or from the neighboring outdoor base station to the indoor base station when the terminal located in the area of the indoor base station moves. Occurs frequently, and when a handover occurs from an indoor base station to a neighboring outdoor base station or from an adjacent outdoor base station to an indoor base station, the core router (ACR) is changed to perform a network reentry procedure. Therefore, there is a problem that a transmission delay and a communication disconnection occur.

Therefore, in a portable Internet system supporting indoor environment, when handover of a terminal located within an area of an indoor base station, the handover frequency is reduced and guided to a neighboring indoor base station when neighboring base station information is broadcast. There is an urgent need for a method to reduce time delay and to perform handover more efficiently.

Next, the existing handover control process in the outdoor portable Internet network will be described with reference to FIGS. 1 to 7, and the existing handover control process in the portable Internet network composed of indoor / outdoor base stations cannot be applied as it is. Let's look at it.

1 is a diagram illustrating a configuration of a general outdoor portable Internet (WiBro) network.

In an outdoor portable Internet system, a handover occurs when the portable Internet terminal (MS) 11 moves to another cell (BS1 → BS2) (1a). That is, in the outdoor portable Internet system, only a handover exists between the outdoor serving base station (BS1) 12 and the outdoor target base station (BS2) 13.

That is, the base station BS serviced by the portable Internet terminal 11 in the process of moving the mobile Internet terminal 11 from cell 1 to cell 2 is an outdoor target in the outdoor serving base station BS1 12. ) Is changed to the base station (BS2) 13 (1a). This process is a handover control process in the existing outdoor portable Internet system. In the existing outdoor portable Internet system, there is only a single handover scenario from the currently serving BS1 12 to the new BS2 13 of the moving cell.

However, if the indoor portable Internet system is coupled to the outdoor portable Internet system [see FIG. 8 below], in addition to the outdoor handover control procedure (handover control procedure from the outdoor base station 12 to the outdoor base station 13), Indoor handover control procedure (i.e., handover control procedure between outdoor base station 12 or 13-indoor base station 14,15, handover control procedure between indoor base station 14-indoor base station 15) Should be added separately.

In a mobile Internet system, cells and cells are not clearly distinguished, and cells overlap each other. That is, the base stations 12 and 13 are not uniformly arranged at a certain distance. Therefore, when the portable Internet terminal (MS) 11 moves and performs handover, one or more candidates of the target base station (BS) exist. Therefore, for handover, one base station must be selected from a plurality of target base stations, and at this time, the target base station is evaluated with a signal strength.

For example, a handover control procedure in an outdoor portable Internet network conforming to the IEEE 802.16e standard is shown in FIG. 2.

In FIG. 2, when a mobile Internet terminal (MS) 11 is moved in an outdoor portable Internet network and a handover occurs, the base station (BS) 12 and 13 and the portable Internet terminal (MS) defined in the IEEE 802.16e standard ( 11) Follow the message format and procedure in between.

Referring to FIG. 2, referring to a handover control procedure in an outdoor portable Internet network, first, the serving base station 12 informs neighbor BS information for handover of the portable Internet terminal 11. Broadcasts a Mobile Neighbor Advertisement (ADV) message (IEEE 802.16e neighbor advertisement message, which the serving base station periodically advertises network attributes for the serving base station and neighboring base stations) (see FIG. 3) (201). ). Therefore, when the mobile Internet terminal 11 receives the MOB_NBR-ADV message periodically advertised from the base station (serving base station) 12 to which it belongs, it acquires IDs, QoS parameters, and channel information of neighboring base stations, so that it is faster. This information can be used to perform handover.

Referring to FIG. 3, it can be seen that the MOB_NBR-ADV message includes information such as a 24-bit Operator ID, PHY Profile ID, FA Index, BS EIRP, BSID, etc. for N neighbors.

Subsequently, the portable Internet terminal 11 performs a task of scanning neighboring base stations as necessary, and thus, it is possible to know the signal strength of the neighboring base stations (202). In this case, the scanning operation is performed by the portable Internet terminal 11 transmitting a MOB_SCN-REQ message requesting Scanning Interval and Iteration to the serving base station 12 and assigned through the MOB_SCN-RSP message. During the Scanning Interval, the portable Internet terminal 11 searches whether several neighboring base stations are suitable for handover.

That is, the mobile Internet terminal 11 may manage the list of candidate base stations to perform handover by obtaining a list of IDs of neighbor base stations through a MOB_NBR-ADV message and selecting an appropriate base station based on real-time link information acquired through scanning. have.

However, the handover may be started by the portable Internet terminal 11 (203) or may be performed by an outdoor base station (BS) 12 (208).

First, referring to the case where the portable Internet terminal 11 starts handover, after the scanning process is finished, the portable Internet terminal 11 sends a MOB_MSHO-REQ message [MS → BS, portable Internet terminal 11 to start the handover]. IEEE 802.16e handover request message) is transmitted to the serving base station 12 (203), and the MOB_MSHO-REQ message includes the carrier to interference and noise ratio (CINR) values of neighboring base stations received through the MOB_NBR-ADV message. Included.

When the handover request is received from the portable Internet terminal 11 (203), the serving base station 12 includes candidate base stations (target base station 13) recommended by the portable internet terminal 11 through a backbone network. In step 204, the UE informs the information of the portable Internet terminal 11 through the message HO_notification to handover to 204, and receives a response message HO_notification_response from the candidate base station (including the target base station 13) (205).

After receiving the response (205), the serving base station 12 confirms the recommendable handover target base station 13 (206), and then the MOB_BSHO-RSP message [BS → MS, IEEE 802.16e of the serving base station 12]. The handover response message] is included in the recommended base station list (adjacent base station list) and transmitted to the portable Internet terminal 11 (207).

Thereafter, the portable Internet terminal 11 determines the final handover target base station 13 among the target base stations recommended by the serving base station 12, and sends the MOB_HO-IND message (MS → BS, IEEE 802.16e) to the serving base station 12. A handover execution message) is sent to finally notify the handover (209).

In the above, steps "203" to "207" represent a handover preparation process, and "209" represents an initial process of handover execution.

During the handover preparation process (203 ~ 207), the portable Internet terminal 11 determines the optimal target base station 13 by comparing the signal strength and QoS parameters of the neighboring base stations obtained previously. That is, the portable Internet terminal 11 compares the quality of service provided from the serving base station 12 with the signal strength, etc., and transmits a list of base stations capable of handover to the serving base station 12 in a MOB_MSHO-REQ message (203). The serving base station 12 returns a list of recommended base stations (candidate base station) among them in the MOB_BSHO-RSP message (207). At this time, the serving base station 12 notifies the handovers to the candidate base stations (one of which becomes the target base station 13) through the backbone network and transmits the session and configuration information of the portable Internet terminal 11 in advance (204). ) Handover time can be shortened later.

Subsequently, when the mobile Internet terminal 11 receives the MOB_BSHO-RSP message and determines the target base station 13, the mobile base station 11 sends a MOB_HO-IND message to the serving base station 12 to finally notify the handover (handover execution initial process). ] (209), the handover is immediately executed [handover execution process] (210 to 216). The handover execution process will be described in more detail below.

Meanwhile, in preparation for handover, the serving base station 12 may start the handover process by first transmitting a MOB_BSHO-REQ message to the portable Internet terminal 11.

In detail, when the serving base station 12 starts handover, the mobile base station 11 sends a MOB_BSHO-REQ message [BS → MS, the IEEE 802.16e handover request message of the serving base station 12] to the portable Internet terminal 11. In this case, the MOB_BSHO-REQ message includes a list (recommended base station list) recommended by the serving base station 12, and the mobile Internet terminal 11 transmits the recommended base station through the MOB_NBR-ADV and the base station. The handover is notified by evaluating the information from the search and sending a MOB_HO-IND message to the serving base station 12 (209).

Now, referring to the handover execution process, the serving base station 12 receiving the MOB_HO-IND message disconnects from the portable Internet terminal 11 after the Resource Retain Time and stops the service. At this time, since the MOB_HO-IND message is transmitted, the portable Internet terminal 11 can no longer transmit / receive packets through the serving base station 12, so it moves quickly to a new network and quickly reenters the network (Network Re-entry) procedure. Should be done. At this time, if the target base station 13 receives the information of the portable Internet terminal 11 on the performance capability and authentication, etc. from the serving base station 12, the portable Internet terminal 11 skips the process during the network entry process, handover The process can be shortened. When the network entry process is successfully completed, the target base station 13 starts a service to the portable Internet terminal 11.

Specifically, the new serving node, the target base station 13 transmits Fast_Ranging IE to the mobile Internet terminal 11 (210), the mobile Internet terminal 11 transmits the CDMA ranging code to the target base station 13 (211). [Transmission Parameter Acquisition Process]

Referring to the transmission parameter acquisition process (210, 211), the target base station 13 transmits UL-MAP (Uplink Map), DL-MAP (Downlink Map) message to the portable Internet terminal 11 every frame, DCD (Downlink) Channel Descriptor (UCD) and Uplink Channel Descriptor (UCD) are periodically transmitted according to the setting of the target base station 13, and the portable Internet terminal 11 receives the frame and checks the delivery information. Here, the DCD message includes a transmission / reception time, a center frequency, a mobility support function, a base station identification information, a radio signal calculation method, and a downlink burst profile information for the duplex method. In addition, the UCD message includes uplink burst profile information, contention-based reservation timeout, ranging related information, information for power signal adjustment, and the like.

Thereafter, the portable Internet terminal 11 performs a network re-entry procedure to the target base station 13, which is a new serving node (212 to 215). At this time, the entry procedure to the new network is largely ranging, ranging (212), basic capability negotiation process (213), terminal authentication and key exchange process (214), registration process (215), connection establishment process, IP This can be seen as an address assignment process. In each process, the portable Internet terminal 11 transmits the REQ message to the target base station 13 and receives the RSP message from the target base station 13. When the portable internet terminal 11 enters a new network, the handover procedure is completed, and after completing the handover procedure, the target base station 13, which is a new serving node, transmits data to the portable internet terminal 11 ( 216).

In detail, the ranging process 212, the mobile Internet terminal 11 targets a burst profile, media access control (MAC) information, etc. of the terminal through a ranging request (RNG-REQ) message. Sent to the base station 13, the target base station 13 responds with a ranging response (RNG-RSP: Ranging Response) message (212). At this time, the RNG-RSP message includes information such as ranging status, burst profile, MAC address of the portable Internet terminal 11, and connection identifier (CID).

After performing the ranging (RNG) process 212, the mobile Internet terminal 11 transmits a basic capability negotiation request (SBC-REQ) message to the target base station 13, and the target base station 13. ) Receives a Basic Capability Negotiation Response (SBC-RSP) message and exchanges information for using the radio resource (213). Basic Capability Negotiation Process At this time, the SBC message includes transmission / reception switching time, maximum power, current transmission power, and information related to an orthogonal frequency division multiple (OFDM) according to a time division duplex (TDD) scheme of the portable Internet terminal 11. Included.

After performing the basic capability negotiation (SBC) process 213, the portable Internet terminal 11 requests a PKM (Privacy Key Management) request message to the target base station 13 [EAP transmission request]), and sends a PKM response message. It receives and manages an encryption key necessary for information protection [EAP transmission response] (214). [Terminal authentication and key exchange process]

After the terminal authentication and key exchange process 214 is performed, the portable Internet terminal 11 transmits a registration request message (REG-REQ) message to the target base station 13, and the target base station 13 in response thereto. The registrar transmits a registration response (REG-RSP) message to the portable Internet terminal 11 (215). [Registration Process] At this time, the registration request message includes information such as the number of up / down CIDs, the type of packet (CS: Convergence Sublayer), maximum classification information, service flow, etc. to be used in Internet communication.

After performing the registration process 215, although not shown in the figure, the target base station 13 additionally transmits a dynamic service addition (DSA) request message for establishing a traffic connection to the mobile Internet terminal 11, and When the portable Internet terminal 11 responds with a DSA-RSP (DSA Response) message, it checks with a DSA-ACK (DSA Acknowledge) message. [Connection establishment process] At this time, the DSA message processes the up / down service flow by using the transaction identification number.

In addition, after performing the connection setup process, although not shown in the figure, in the case of IPv4 additionally according to the IP version automatically using the DHCP (Dynamic Host Configuration Protocol) v4 IP address to be used in the mobile Internet terminal 11 Set it. In the case of IPv6, an address to be used by the portable Internet terminal 11 is automatically set using DHCPv6 or an automatic setting function. [IP address assignment process;

In summary, the serving base station 12 first transmits the MOB_NBR-ADV message containing the surrounding base station information to the portable Internet terminal 11. The mobile Internet terminal 11 and the serving base station 12 exchange the MOB_SCN-REQ message and the MOB_SCN-RSP message, and in this process, the mobile Internet terminal 11 receives the target base station 13 according to signal strength and QoS characteristics. Will be chosen. Thereafter, when the portable Internet terminal 11 selects the target base station 13, it enters the handover preparation step. As a preprocessing step for performing the handover, when the MOB_MSHO-REQ message, the MOB_BSHO-RSP message, or the MOB_BSHO-REQ message is exchanged with the current serving base station 12, the handover preparation step ends.

Thereafter, the portable Internet terminal 11 performs the actual handover. To this end, the portable Internet terminal 11 transmits a MOB_HO-IND message to the serving base station 12. Subsequently, the serving base station 12 receiving the MOB_HO-IND message releases the resources allocated to the portable Internet terminal 11 and performs the security function and authentication with the target base station 13.

As discussed above, handover may be initiated by the portable Internet terminal 11 (203) or by the serving base station 12 (208).

4 and 5, when the portable Internet terminal 11 starts handover, the process of handover control in the portable Internet terminal 11 and the base stations 12 and 13 will be described. do.

Referring to FIG. 4, the portable Internet terminal 11 receives a MOB_NBR-ADV message (see FIG. 3) periodically broadcasted from the serving base station 12 to inform neighbor BS information (401). If scanning of neighboring base stations is necessary (402), the serving base station 12 sends a MOB_SCN-REQ message to request Scanning Interval and Iteration (403). Subsequently, the mobile Internet terminal 11 receives the MOB_SCN-RSP message from the serving base station 12 (404), and scans adjacent base stations in earnest. Accordingly, the portable Internet terminal 11 searches for whether it is suitable for handover (scanning whether neighboring base stations are suitable for handover during the scanning interval), and thus, the signal strength of neighboring base stations can be known (405).

If the portable Internet terminal 11 feels that the handover should be performed (406), the portable Internet terminal 11 determines the CINR value of the neighbor base stations (the candidate base stations including the target base station 13) to start the handover. In step 407, the MOB_MSHO-REQ message is transmitted to the serving base station 12.

Subsequently, when the mobile base station 11 receives the MOB_BSHO-RSP message including the candidate base station list recommended by the serving base station 12 from the serving base station 12 (408), the portable Internet terminal 11 according to the signal strength of the handover target base station 13 ) And inform the serving base station 12 of the final handover target base station 13 via the MOB_HO-IND message (409). At this time, since the MOB_HO-IND message is transmitted, the portable Internet terminal 11 can no longer transmit or receive a packet through the serving base station 12, so after moving to a new network, a procedure for acquiring transmission parameters and reentering the network (Network Re-entry procedure (Ranging process, basic capability negotiation process, terminal authentication and key exchange process, registration process, connection establishment process, IP address allocation process, etc.) must be performed (410 ~ 412). However, if the target base station 13 receives the information of the portable Internet terminal 11 on the performance capability and authentication, etc. from the serving base station 12, the portable Internet terminal 11 skips the process during the network entry process to handover The process can be shortened.

Therefore, when the portable internet terminal 11 receives the Fast_Ranging_IE from the target base station 13 (410), the portable internet terminal 11 transmits the RNG-REQ to the target base station 13 (411), the RNG-RSP response In step 412, the fast ranging operation is completed.

If the network entry process is successfully completed, the portable Internet terminal 11 may receive a service from the target base station 13.

Meanwhile, referring to FIG. 5, the serving base station 12 transmits a MOB-NBR-ADV message including neighbor BS information to the portable Internet terminal 11 (501) and the portable Internet terminal 11. When a MOB_SCN-REQ message requesting Scanning Interval and Iteration is received (502), the MOB_SCN-RSP message is transmitted to the portable Internet terminal 11 by assigning Scanning Interval and Iteration (503).

Subsequently, when the serving base station 12 receives the MOB_MSHO-REQ message including the CINR value of the neighbor base stations (the candidate base stations including the target base station 13 included) recommended by the portable Internet terminal 11 (504), The handover of the portable Internet terminal 11 is notified to the candidate base station (including the target base station 13) recommended by the portable internet terminal 11 through the backbone network (505). If a response is received from the recommended target base stations (the candidate base station including the target base station 13) (506), based on the response, the serving base station 12 selects the target base station 13 that can be recommended again ( In operation 507, the handover is confirmed to the selected recommended target base station 13 through message exchange using a backbone network (508).

Next, the serving base station 12 includes the recommended target base station list in the MOB_BSHO-RSP message in response to the MOB_MSHO-REQ message transmitted by the portable internet terminal 11 and transmits the list to the portable internet terminal 11 (509). .

Subsequently, as the serving base station 12 determines the target base station 13 in the portable internet terminal 11, a MOB-HO-IND message is received from the portable internet terminal 11 to receive a final notification of handover (510). After the Resource Retain Time, it disconnects from the portable Internet terminal 11 (511).

Referring to FIGS. 6 and 7, when the serving base station 12 starts handover, the handover control process in the portable Internet terminal 11 and the base stations 12 and 13 will be described separately. .

Referring to FIG. 6, the portable Internet terminal 11 receives a MOB_NBR-ADV message (see FIG. 3) periodically broadcasted from the serving base station 12 to inform neighbor BS information (601). After receiving the MOB_BSHO-REQ message including the recommended target base station list from the serving base station 12 (602), the handover target base station according to signal strength among the recommended neighbor base stations (the candidate base station including the target base station 13) Final determination (13) and final notification of handover fact to the serving base station 12 via the MOB-HO-IND message (603).

At this time, since the MOB_HO-IND message is transmitted, the portable Internet terminal 11 can no longer transmit or receive a packet through the serving base station 12, so after moving to a new network, a procedure for acquiring transmission parameters and reentering the network (Network Re-entry procedure (Ranging process, basic capability negotiation process, terminal authentication and key exchange process, registration process, connection establishment process, IP address allocation process, etc.) must be performed (604-606). However, if the target base station 13 receives the information of the portable Internet terminal 11 on the performance capability and authentication, etc. from the serving base station 12, the portable Internet terminal 11 skips the process during the network entry process to handover The process can be shortened.

Therefore, when the portable Internet terminal 11 receives the Fast_Ranging_IE from the target base station 13 (604), the portable Internet terminal 11 transmits the RNG-REQ to the target base station 13 (605), the RNG-RSP response In step 606, the Fast Ranging operation is completed.

If the network entry process is successfully completed, the portable Internet terminal 11 may receive a service from the target base station 13.

Meanwhile, referring to FIG. 7, the serving base station 12 transmits a MOB-NBR-ADV message including neighbor BS information to the portable Internet terminal 11 (701), if it feels that handover is necessary ( In operation 702, a message informing a candidate of handover is transmitted to the candidate base stations (including the target base station 13) through a backbone network (703).

Subsequently, the serving base station 12 transmits the MOB_BSHO-REQ message including the recommended target base station list to the portable Internet terminal 11 (704), and the candidate base station (target base station 13 to which the portable Internet terminal 11 is recommended). If the final decision of the handover target base station 13 in accordance with the signal strength of the handover fact through the MOB-HO-IND message (705), the serving base station 12 after the Resource Retain Time In operation 706, the connection with the portable Internet terminal 11 is terminated and the service is stopped.

When the handover control method according to the prior art as described above is applied to the outdoor / indoor portable internet system as it is (when the handover control procedure of the outdoor portable internet system is used in the indoor portable internet system), the following problems This will occur.

For example, when the mobile Internet terminal 11 moves from an indoor base station (14 of FIG. 8) to another indoor base station 15 in an enterprise or the like (at least two indoor base stations 14 and 15 are installed in an enterprise or the like). Assumes that the indoor serving base station 14 includes both the outdoor base stations 12 and 13 and the other indoor base stations 15 as handover target base stations (candidate base stations). Therefore, in determining the target base station, the mobile Internet terminal 11 is a signal of the base station from the list of candidate base stations consisting of the other indoor base station 15 and the outdoor base station 12,13 recommended by the indoor serving base station 14 The handover is determined unilaterally with the best base station.

However, if the other indoor base station 15 is not located far from the outdoor base station 12 or 13 but near the outdoor base station 12 or 13, the mobile Internet terminal 11 signals the other indoor base station 15. The strength will be lower than the signal strength of the outdoor base station 12 or 13. Therefore, even if the mobile internet terminal 14 moves from the indoor base station 14 to another indoor base station 15, the portable internet terminal 11 does not perform a handover to the other indoor base station 15, The handover to the outdoor base station 12 or 13 will be performed. That is, since the signal strength of the outdoor base station 12 or 13 is strong, an unintended handover occurs. This decreases the accuracy of the handover, causing call disconnection, resulting in a large handover delay.

Looking at this in more detail as follows.

In a handover that occurs as the portable Internet terminal 11 moves in an indoor portable internet network environment, an indoor serving base station (eg, FIG. 8 of FIG. 8) is an indoor base station 15 adjacent to a base station to be handed over. And an outdoor base station 12 or 13. Therefore, in the process of determining the target base station, the mobile Internet terminal 11 is selected from the list of base stations consisting of the indoor base station 15 and the outdoor base station 12 or 13 recommended by the indoor serving base station 14. or 13), the highest signal strength is determined to handover to the outdoor base station 12 or 13, if the signal strength of the indoor base station 15 is the highest, the handover is determined to the indoor base station 15.

However, there are the following problems when performing handover in this manner.

First, the indoor portable Internet system supports seamless communication through the indoor base stations 14 and 15 to the portable Internet terminal 11 within the area of the indoor environment. The handover between 15) is handed over within one core router (ACR), thereby reducing the network re-entry procedure. However, when the handover is performed in the indoor portable Internet system according to the existing outdoor handover procedure, not only the handover between the indoor base stations 14 and 15, but also the indoor base station 12 or 15 in the indoor base station 14 or 15. 13), handover from the outdoor base station 12 or 13 to the indoor base station 14 or 15, and in this case, move to another core router (ACR), so the network re-entry procedure is performed. Should be carried out according to the prior art. Therefore, when a handover occurs between the indoor base station 14 or 15 and the outdoor base station 12 or 13, the handover overhead due to the network reentry procedure is increased, and the handover latency is also a serious problem. Will cause. That is, when the outdoor base station 12 or 13 is selected as the handover target base station, the handover overhead is increased.

Second, when the mobile Internet terminal 11 receiving the service indoors performs the handover according to the existing outdoor handover procedure, the indoor base stations 14 and 15 are included in the neighbor base station information which is a candidate of the handover target base station. In addition, outdoor base stations 12 and 13 will be included. Therefore, the indoor portable Internet system is designed so that the portable Internet terminal 11 receives seamless services by the indoor base stations 14 and 15, but according to the change in the indoor channel environment and the mobile environment of the portable Internet terminal 11. Since the interference by the outdoor base stations 12 and 13 is intermittently present, handover is performed from the indoor base station 14 or 15 to the outdoor base station 12 or 13, and then again by the outdoor base station 12 or 13. Handover to the indoor base station 14 or 15 is performed.

As a result, when the handover control procedure of the outdoor portable internet system is used in the indoor portable internet system, the handover occurs more frequently. That is, the handover frequency is increased due to the interference of the outdoor base station 12 or 13.

Accordingly, an object of the present invention is to provide an indoor handover control procedure that observes an outdoor handover control procedure and minimizes interference of an outdoor base station to ensure handover between indoor base stations.

Therefore, the present invention provides a handover target base station (target base station) adjacent to an indoor base station at the time of handover of a terminal located in the area of the indoor base station in a mobile Internet system in which indoor / outdoor base stations exist. An indoor handover control method for reducing handover frequency and time delay by reducing and inducing a handover, and a computer-readable recording medium recording a program for realizing the method. The purpose is to provide.

In particular, since there are various handover scenarios in the indoor portable Internet system [see FIG. 8], the handover overhead is increased accordingly, and according to the present invention, the handover overhead is reduced in the indoor portable internet system, and the frequent hand is performed. This reduces the number of overs.

The objects of the present invention are not limited to the above-mentioned objects, and other objects and advantages of the present invention which are not mentioned above can be understood by the following description, and will be more clearly understood by the embodiments of the present invention. Also, it will be readily appreciated that the objects and advantages of the present invention may be realized by the means and combinations thereof indicated in the claims.

In order to achieve the above object, the present invention provides a handover control method in a portable Internet system including an indoor / outdoor base station, wherein an indoor serving base station that manages an area without an external door is provided with information of neighboring base stations for handover. Including only indoor base stations in the broadcast; And when the terminal moves indoors, the indoor serving base station is an indoor target base station having a signal strength equal to or greater than a handover reference value among 'indoor candidate base stations selected based on the signal strength measured by the neighbor base station search. And performing a handover.

In addition, the present invention relates to a handover control method in a portable Internet system composed of indoor / outdoor base stations. Including all of the outdoor base stations for broadcasting; And the indoor serving base station having a signal strength equal to or greater than a first handover reference value among the indoor / external candidate base stations selected based on the signal strength measured by searching for neighboring base stations at the terminal when the terminal moves indoors. And performing a handover to the target base station.

In addition, the present invention relates to a handover control method in a portable Internet system composed of indoor / outdoor base stations. Including all of the outdoor base stations and broadcasting them; And when the terminal moves indoors, the indoor serving base station selects a signal strength of the indoor serving base station from among the indoor / external candidate base stations selected based on the signal strength measured by the neighbor base station search. And performing a handover when the signal is equal to or greater than the over reference value and the signal strength of the outdoor base station is equal to or greater than the second handover reference value.

In addition, the present invention is a handover control method in a portable Internet system consisting of an indoor base station, the indoor serving base station that manages the area with an external door, the indoor and outdoor base station to the information of the adjacent base station for the handover Broadcasting all inclusive; And when the terminal moves from indoors to outdoors, the indoor serving base station has a signal strength equal to or greater than a second handover reference value among 'indoor / outdoor candidate base stations selected based on signal strength measured through neighbor base station search'. And performing a handover to an outdoor target base station.

On the other hand, the present invention, in the indoor / outdoor portable Internet system with a processor for handover control, the indoor serving base station that manages the area without the external entrance door is indoors to the information of the adjacent base station for the handover A broadcast function including only a base station; And when the terminal moves indoors, the indoor serving base station is an indoor target base station having a signal strength equal to or greater than a handover reference value among 'indoor candidate base stations selected based on the signal strength measured by the neighbor base station search. A computer readable recording medium having recorded thereon a program for realizing a function of performing a handover is provided.

The present invention also provides an indoor / outdoor portable Internet system equipped with a processor for handover control, wherein an indoor serving base station that manages an area where an external door is located is provided with indoor and outdoor information for handover. A broadcast function including all of the outdoor base stations; And the indoor serving base station having a signal strength equal to or greater than a first handover reference value among the indoor / external candidate base stations selected based on the signal strength measured by searching for neighboring base stations at the terminal when the terminal moves indoors. A computer readable recording medium having recorded thereon a program for realizing a function of performing a handover to a target base station is provided.

The present invention also provides an indoor / outdoor portable Internet system equipped with a processor for handover control, wherein an indoor serving base station that manages an area where an external door is located is provided with indoor and outdoor information for handover. A broadcast function including all of the outdoor base stations; And when the terminal moves indoors, the indoor serving base station selects a signal strength of the indoor serving base station from among the indoor / external candidate base stations selected based on the signal strength measured by the neighbor base station search. The present invention provides a computer-readable recording medium having recorded thereon a program for realizing a function that does not perform handover when the reference value is greater than the reference value and the signal strength of the outdoor base station is equal to or greater than the second handover reference value.

The present invention also provides an indoor / outdoor portable Internet system equipped with a processor for handover control, wherein an indoor serving base station that manages an area where an external door is located is provided with indoor and outdoor information for handover. Broadcasting to include all outdoor base stations; And when the terminal moves from indoors to outdoors, the indoor serving base station has a signal strength equal to or greater than a second handover reference value among 'indoor / outdoor candidate base stations selected based on signal strength measured through neighbor base station search'. A computer readable recording medium having recorded thereon a program for realizing a function of performing a handover to an outdoor target base station is provided.

The present invention as described above has the effect of reducing the additional signaling overhead and handover delay by limiting the handover target base station which is a candidate for handover between indoor base stations to the indoor base station.

In addition, the present invention has the advantage that can reduce the network re-entry procedure during handover between indoor base stations.

In addition, the present invention has the advantage that it is possible to reduce the number of handover by preliminary interception of the intermittent interference by the outdoor base station according to the indoor channel environment changes and the mobile environment of the mobile Internet terminal.

The above objects, features, and advantages will become more apparent from the detailed description given hereinafter with reference to the accompanying drawings, and accordingly, those skilled in the art to which the present invention pertains may share the technical idea of the present invention. It will be easy to implement. In addition, in describing the present invention, when it is determined that the detailed description of the known technology related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

8 is an exemplary configuration diagram of an indoor / outdoor portable Internet (WiBro) network to which the present invention is applied.

When the mobile Internet terminal 11, which has been serviced outdoors through the outdoor base station 12 or 13, moves to a home, a company, or the like, the mobile internet terminal 11 receives the service through indoor base stations 14 and 15.

However, while the outdoor base stations 12 and 13 are normally connected to a network of a service provider through a control station (ACR), the indoor base stations 14 and 15 are directly connected to a public IP network and are connected to a public IP network. Information transmission is performed through an authentication server (AAA) and the like through a network. However, it is not limited to this, and it should be noted that the indoor base stations 14 and 15 may also be managed through the control station (ACR).

Indoor base stations 14 and 15 are base stations installed in homes or businesses, and are designed to be small in size and simply designed to be easily installed indoors, such as an existing wireless access point (AP).

In particular, indoor base stations 14 and 15 include home indoor base stations installed separately in homes and used in homes, and indoor indoor base station groups used by companies in groups and the like.

In the present invention, indoor base station (14, 15) refers to a group of indoor indoor base station, in particular, the mobile Internet terminal 11 refers to a terminal that operates in a mobile Internet system consisting of indoor / outdoor base station (12 ~ 15). do.

However, on the floor where there is no access to the inside of the building (for example, two or more floors or one basement level without external doors), and the floor that has access to the outside within the building (for example, the first floor above the ground with an external door). It should be noted that, if it is possible to distinguish between, indoor indoor base stations are also possible. In addition, in the present invention, even when the first floor is above ground, when a plurality of indoor base stations are installed in a large area (eg, home, factory, company, etc.), the indoor base station and the external door that cover the area of the external door side are provided. It should be noted that when the indoor base station which manages the area which is not at all possible can be distinguished, it is also made into the object.

Therefore, indoor base stations 14 and 15 in the present invention should be interpreted as a concept including a group of indoor indoor base stations and a corporate indoor base station.

In the present invention, while complying with the handover procedure of the existing portable Internet system, in the portable Internet system in which the indoor / outdoor base stations 12 to 15 exist, the portable Internet terminal 11 is located in the area of the indoor base station 14 or 15. When moving to another indoor base station 15 or 14, handover between indoor base stations 14 and 15 (ie, indoor serving base station to indoor target base station) is guaranteed.

That is, among the at least two indoor base stations 14 and 15 including the indoor serving base station 14 or 15 without the handover to the outdoor base station 12 or 13 in a home, a company, a factory, etc. A handover is ensured, where the indoor base station with the largest signal is the indoor target base station.

However, even if there is a change in the signal strength of the adjacent base station 14 through the movement in the area of the indoor base station 14 that manages the area of the external door side, if the signal strength of the indoor base station 14 is equal to or larger than the handover threshold value, Even if the signal strength of the outdoor base station 12 or 13 is greater than the signal strength of the indoor base station 14, no handover is performed to the outdoor base station 12 or 13 (maintain the indoor serving base station 14).

However, when the mobile Internet terminal 11 moves from the indoor base station 14 to the outdoor base station 12 or 13, handover to the outdoor base station 12 or 13 (that is, indoor serving base station → outdoor target). Handover to a base station). In this case, as in the known handover control procedure, the base station having the largest signal size is determined as the outdoor target base station. (In general, since the signal strength of the outdoor base station is larger than the signal strength of the indoor base station, the outdoor base station is the target base station. Selected].

The present invention proposes an indoor handover control procedure to effectively solve the problem of the existing outdoor handover control procedure using the neighbor base station information message of the serving base station in the indoor portable Internet system. The indoor handover control procedure proposed by the present invention is a method for minimizing handover interference by outdoor base stations 12 and 13 to ensure handover between indoor base stations 14 and 15 in an indoor portable Internet system. To present.

The portable Internet system of FIG. 8 is comprised of existing outdoor base stations 12 and 13 and indoor base stations 14 and 15 for supporting services in a building.

In scenario 1, a mobile Internet terminal 11 of a user who continues to reside in a building having no access to the outside (for example, two or more floors or one underground floor without an external door) is located in an indoor base station 15 area. The case in which the signals of the outdoor base stations 12 and 13 are received in a situation in which a service is supported in the home is shown.

However, in scenario 1, when handover occurs as the portable Internet terminal 11 moves, when the existing outdoor handover control procedure is used, the signal strength of the outdoor base station 12 or 13 among the handover candidate base stations is used. Is the largest, the handover to the outdoor base station 12 or 13, but in the present invention, considering that the floor in which the indoor serving base station 15 is installed does not have access to the outside of the building, the outdoor base station 12, 13 To avoid handover to the indoor base station 14 or to maintain the indoor serving base station 15.

On the other hand, in scenario 2, the mobile Internet terminal 11 of a user who resides on a floor having access to the outside in the building (for example, the ground floor with an external door) supports a service in the indoor base station 14 area. The case of receiving the signals of the outdoor base stations 12 and 13 in the receiving situation is shown.

However, in scenario 2, since the portable internet terminal 11 may go out of the building, the interference of the outdoor base stations 12 and 13 may not be excluded as in scenario 1. Therefore, if the signal strength of the outdoor base station 12 or 13 is the largest among the handover candidate base stations, it should be possible to handover to the outdoor base station 12 or 13. However, in order to minimize the handover of the portable Internet terminal 11 to the outdoor base station 12 or 13 for the purpose of continuing to stay indoors, that is, the outdoor base station 12 or 13 only to the terminal 11 that is sure to move outdoors. If the signal strength of the indoor base stations 14 and 15 as well as the signal strengths of the indoor base stations 14 and 15 are higher than the handover threshold value to allow handover to the indoor base stations 12 and 13, Ensure handover.

The present invention proposes a handover control procedure in an indoor portable Internet system, a handover control procedure in an area in which a building can be accessed from the outside according to scenario 2, and a communication with the outside according to scenario 1 above. It is divided into handover control procedure in the area where there is no access.

As in scenario 1, handover between indoor base stations 14 and 15 is guaranteed in an area where there is no access to the outside [first embodiment], and indoors in an area where access to the outside is possible as in scenario 2 above. In the indoor base station 14 to be handed over to the outdoor base station (12 or 13) to enable seamless communication when moving from the outdoor to the outdoor [second embodiment].

First, according to the first embodiment, a handover control procedure in an area without access to the outside will be described with reference to FIG. 9.

Since there is no possibility to move outdoors in areas where there is no access outside (for example, more than two floors or one basement level without external doors, and indoor base stations that do not manage doors on floors with external doors). The interference of the outdoor base stations 12 and 13 is eliminated and the handover between the indoor base stations 14 and 15 is guaranteed.

Since indoor base stations 14 and 15 are fixed, they have a constant neighbor base station, and neighbor base station information can be known in advance. Therefore, the indoor serving base station 15 located in the area where there is no access to the outside, except for the outdoor base stations 12 and 13 from the neighbor base station list, only the indoor base station 14 is written in the MOB_NBR-ADV message of FIG. In step 901, the MOB_NBR-ADV message is broadcasted for handover of the portable Internet terminal 11.

That is, in an area where there is no access to the outside, the indoor serving base station 15 transmits a MOB_NBR-ADV message (notice of neighboring base station information about the surrounding indoor base station 14 for handover of the mobile Internet terminal 11). As an IEEE 802.16e neighbor advertisement message, the indoor serving base station 15 periodically advertises network attributes for the serving base station and neighbor base stations) (see FIG. 3) periodically. Therefore, when the mobile Internet terminal 11 receives the MOB_NBR-ADV message periodically advertised from the indoor serving base station 15 to which it belongs, IDs, QoS parameters and channel information of neighboring base stations (indoor indoor base stations). This information can be used to obtain a and to perform a faster handover later.

Subsequently, the portable Internet terminal 11 performs a task of scanning neighboring base stations as necessary, and thus, it is possible to know the signal strength of the neighboring base stations (902), where the outdoor base stations 12 and 13 are used. Since scanning is excluded from the neighboring base station, the scanning operation is performed only for the indoor base stations 15 and 14, and the indoor serving base station 15 is the indoor base station as the target base station. Only base station 14 is recommended so that indoor base station 14 becomes the final handover target base station. That is, if the signal strength of the indoor base station 14 is greater than the indoor handover reference value (that is, the handover reference value of the received signal strength received from the indoor target base station 14) (in this case, the indoor serving base station 15). Is less than the indoor handover reference value), the mobile Internet terminal 11 performs the handover to the indoor base station (14). Therefore, if the signal strength of the indoor target base station 14 is greater than the indoor handover reference value, the indoor base station 14 is given priority to perform the handover to the indoor base station 14.

Of course, when the signal strength of the indoor serving base station 15 is greater than the signal strength of the indoor target base station 14, the indoor serving base station 15 is maintained.

The scanning operation is performed by the portable Internet terminal 11 transmitting a MOB_SCN-REQ message requesting Scanning Interval and Iteration to the indoor serving base station 15 and assigned through the MOB_SCN-RSP message. During the Scanning Interval, the portable Internet terminal 11 searches whether several neighboring base stations are suitable for handover. That is, the mobile Internet terminal 11 may manage the list of candidate base stations to perform handover by obtaining a list of IDs of neighbor base stations through a MOB_NBR-ADV message and selecting an appropriate base station based on real-time link information acquired through scanning. have.

In the above, the handover may be initiated by the portable Internet terminal 11 (903) or by the indoor serving base station 15 (908).

First, referring to the case where the portable Internet terminal 11 starts handover, after the scanning process is finished, the portable Internet terminal 11 sends a MOB_MSHO-REQ message [MS → BS, portable Internet terminal 11 to start the handover]. IEEE 802.16e handover request message] is transmitted to the indoor serving base station (BS1) 15 (903), where the MOB_MSHO-REQ message includes the carrier to interference and the neighbor base stations received through the MOB_NBR-ADV message. Noise Ratio) value is included. That is, the CINR value of the candidate base station (another indoor base station (BS2) 14) is transmitted through the MOB_MSHO-REQ message.

When receiving a handover request from the portable Internet terminal 11 (903), the indoor serving base station (BS1) 15 is a candidate base station recommended by the portable Internet terminal 11 via the backbone network (i.e., jade). Inform the information of the mobile Internet terminal 11 through the message HO_notification that the user handovers to the content target base station (BS2) 14] (904), and responds from the candidate base station (indoor target base station (BS2) 14). A message HO_notification_response is received (905).

After receiving the response (905), the indoor serving base station (BS1) 15 checks (906) the recommended handover target base station (indoor base station) (BS2) 14, and then the MOB_BSHO-RSP message [ BS → MS, IEEE 802.16e handover response message of indoor serving base station (BS1) 15] is included in the recommended BS list and transmitted to portable Internet terminal 11 (907).

Thereafter, the portable Internet terminal 11 determines the final handover target base station (indoor base station) (BS2) 14 among the target base stations recommended by the indoor serving base station (BS1) 15, and performs the indoor serving base station ( A MOB_HO-IND message (MS → BS, IEEE 802.16e handover execution message) is sent to BS1) 15 to finally notify the handover (909).

In the above, steps "903" to "907" represent a handover preparation process, and "909" represents an initial process of handover execution.

During the handover preparation process (903 ~ 907), the portable Internet terminal 11 determines the optimal indoor target base station (BS2) 14 by comparing the signal strength and QoS parameters of the neighboring base stations previously obtained. That is, the mobile Internet terminal 11 compares the quality of service and signal strength provided from the indoor serving base station (BS1) 15 and puts a list of base stations capable of handover in the MOB_MSHO-REQ message. In step 903, the indoor serving base station (BS1) 15 transmits a list of recommended base stations (candidate base station) to the BS1) 15 in the MOB_BSHO-RSP message and returns (907). At this time, the indoor serving base station (BS1) 15 notifies the handovers to the candidate base stations (one of which becomes the indoor target base station (BS2) 14) through the backbone network to notify the handover of the portable Internet terminal 11. By transmitting the session and configuration information in advance (904), it is possible to shorten the time for performing handover later.

After that, when the mobile Internet terminal 11 receives the MOB_BSHO-RSP message and determines the indoor target base station (BS2) 14, the mobile Internet terminal 11 sends the MOB_HO-IND message to the indoor serving base station (BS1) 15 to perform a handover. Finally, it notifies [handover execution initial process] 909 and immediately executes handover [handover execution process] (910 to 916). The handover execution process will be described in more detail below.

Meanwhile, in the preparation for handover, the indoor serving base station (BS1) 15 may start the handover process by first transmitting the MOB_BSHO-REQ message to the portable Internet terminal 11.

In detail, when the indoor serving base station (BS1) 15 starts handover, the IEEE 802.16e handover request message of the MOB_BSHO-REQ message [BS → MS, the indoor serving base station (BS1) 15) ] To the mobile Internet terminal 11 (908), where the MOB_BSHO-REQ message includes a list (recommended base station list) recommended by the indoor serving base station (BS1) 15, and the mobile Internet terminal 11 ) Evaluates the information obtained through the MOB_NBR-ADV and the information through the base station discovery, and notifies the handover by transmitting a MOB_HO-IND message to the indoor serving base station (BS1) 15 (909).

Now, referring to the handover execution process, the indoor serving base station (BS1) 15 receiving the MOB_HO-IND message disconnects from the portable Internet terminal 11 and stops the service after the Resource Retain Time. At this time, since the MOB_HO-IND message is transmitted, the portable Internet terminal 11 can no longer transmit or receive a packet through the indoor serving base station (BS1) 15, and thus re-enter the network quickly after moving to a new network. Re-entry procedures should be performed. At this time, if the indoor target base station (BS2) 14 receives the information of the portable Internet terminal 11 on the performance capability and authentication, etc. from the indoor serving base station (BS1) 15, the portable Internet terminal 11 is a network The handover process can be shortened by omitting this process during the entry process. If the network entry process is successfully completed, the indoor target base station (BS2) 14 starts the service to the portable Internet terminal (11).

Specifically, the indoor serving base station (BS2) 14, which is a new serving node, transmits Fast_Ranging IE to the portable Internet terminal 11 (910), and the portable Internet terminal 11 transmits the CDMA ranging code indoors. The target base station (BS2) 14 is transmitted to (911). [Transmission Parameter Acquisition Process] That is, the indoor target base station (BS2) 14 transmits a UL-MAP and DL-MAP message to the portable Internet terminal 11 every frame, and transmits the DCD and UCD to the indoor target base station ( It transmits periodically according to the setting of BS2) 14, and the portable Internet terminal 11 receives the frame and checks the delivery information.

Thereafter, the portable Internet terminal 11 performs a network re-entry procedure to the indoor target base station (BS2) 14, which is a new serving node (912 to 915). At this time, the procedure for entering into a new network includes a ranging process 912, a basic capability negotiation process 913, a terminal authentication and key exchange process 914, a registration process 915, a connection establishment process, and an IP. This can be seen as an address assignment process. In each process, the portable Internet terminal 11 transmits the REQ message to the indoor target base station (BS2) 14 and receives the RSP message from the indoor target base station (BS2) 14. When the portable Internet terminal 11 enters a new network, the handover procedure is completed, and after completing the handover procedure, the indoor serving base station BS2 14, which is a new serving node, is transferred to the portable Internet terminal 11. The data is transmitted (916).

In detail, the ranging process 912 is described in detail. The portable Internet terminal 11 uses a ranging request (RNG-REQ) message to display a burst profile, MAC information, etc. of an indoor target base station (BS2) 14. Indoor target base station (BS2) 14 responds with a ranging response (RNG-RSP) message (912). At this time, the RNG-RSP message includes the ranging status, the burst profile, the MAC address of the portable Internet terminal 11, CID, and the like.

After performing the ranging (RNG) process 912, the portable Internet terminal 11 transmits a basic capability negotiation request (SBC-REQ) message to the indoor target base station (BS2) 14, and the indoor target base station. (BS2) 14 receives a basic capability negotiation response (SBC-RSP) message and exchanges information for using the radio resource (913). Basic Skills Negotiation Process

After performing the basic capability negotiation (SBC) process 913, the portable Internet terminal 11 requests the PKM request message to the indoor target base station (BS2) 14 [EAP transmission request], and sends the PKM response message. Receives and manages the encryption key necessary for information protection [EAP transmission response] (914). [Terminal authentication and key exchange process]

After performing the terminal authentication and key exchange process 914, the portable Internet terminal 11 transmits a registration request message (REG-REQ) message to the indoor target base station (BS2) 14, and to the indoor target. The base station (BS2) 14 transmits a registration response (REG-RSP) message to the portable Internet terminal 11 (915). [Registration Process]

After performing the registration process 915, the indoor target base station (BS2) 14 transmits a DSA request message for establishing a traffic connection to the portable Internet terminal 11, and the portable Internet terminal 11 transmits the DSA request message to the DSA. If the response to the message -RSP can be confirmed by DSA-ACK message, the connection setup process.

In addition, after performing the connection setup process, in the case of IPv4 according to the IP version automatically set the IP address to be used in the mobile Internet terminal 11 using DHCPv4, in the case of IPv6 using DHCPv6 or automatic configuration function The portable Internet terminal 11 may automatically set an address to use [ IP address assignment process].

In summary, the indoor serving base station (BS1) 15 transmits only the indoor base station 14 information in the MOB_NBR-ADV message to the portable Internet terminal 11 except for the outdoor base stations 12 and 13. The mobile Internet terminal 11 and the indoor serving base station (BS1) 15 exchange the MOB_SCN-REQ message and the MOB_SCN-RSP message. The content target base station (BS2) 14 is selected. Then, when the portable Internet terminal 11 selects the indoor target base station (BS2) 14, it enters the handover preparation step. As a preprocessing step for performing the handover, when the MOB_MSHO-REQ message, the MOB_BSHO-RSP message, or the MOB_BSHO-REQ message is exchanged with the current indoor serving base station (BS1) 15, the handover preparation step is terminated. .

Thereafter, the portable Internet terminal 11 performs the actual handover. To this end, the portable Internet terminal 11 transmits the MOB_HO-IND message to the indoor serving base station (BS1) 15. Subsequently, the indoor serving base station (BS1) 15 receiving the MOB_HO-IND message releases the resources allocated to the portable Internet terminal 11, and secures and authenticates the indoor target base station (BS2) 14. Will be performed.

As described above, only the handover between the indoor base stations 14 and 15 occurs in an area where there is no access to the outside, thereby reducing network re-entry procedures, changing the indoor channel environment and the portable Internet terminal 11. The interference by the outdoor base stations 12 and 13 in accordance with the mobile environment is reduced in advance, thereby reducing handover overhead and the number of handovers.

Meanwhile, according to the second embodiment, a handover control procedure in an area where there is no access to the outside is as follows. For better understanding, the following description will be made with reference to FIG. 9.

In areas where access to the outside is possible (for example, the ground floor with an external door, or an area where an indoor base station is installed on the floor with an external door), the user may move outdoors. 14, 15) can not be limited to handover.

Therefore, handover should be performed similarly to the existing outdoor handover control procedure. That is, the indoor serving base station 14 includes the outdoor base stations 12 and 13, which will be serviced when moving outdoors with the adjacent base station 15 indoors, in the neighbor base station list and carries them in the MOB_NBR-ADV message of FIG. The MOB_NBR-ADV message is broadcasted periodically for handover of the Internet terminal 11 (901).

At this time, since the outdoor base stations 12 and 13 which are handed over when moving from indoors to outdoors are fixed, the indoor serving base station 14 has constant neighbor base station information. Subsequently, the portable Internet terminal 11 performs a task of scanning neighboring base stations as necessary, and thus, it is possible to know the signal strength of the neighboring base stations (902). In this case, the indoor / outdoor neighboring base stations 12 to 15 may be scanned (scanning), and thus, the indoor / outdoor base stations 12, 13, and 15 may all become final handover target base stations.

Subsequently, the same procedure is performed for the handover preparation process 903 to 907, the initial handover execution process 909, and the handover execution process 910 to 916. However, when moving from indoors to indoors, the handover target base station becomes the indoor base station 15, whereas when moving from indoors to outdoor, the handover target base station becomes the outdoor base station 12 or 13.

The direction of movement of the mobile Internet terminal 11 in an area where access to the outside is possible is uncertain. Therefore, the portable Internet terminal 11 that continues to exist indoors should minimize handover to the outdoor base station 12 or 13. That is, only the portable Internet terminal 11 that is sure to move indoors to outdoors can be handed over to the outdoor base station 12 or 13.

To this end, the indoor portable Internet system is designed to support a service without shadow areas in the entire indoor area as much as possible, so that the handover signal is required and the signals of the adjacent outdoor base stations 12 and 13, which are candidate base stations The strength is equal to or greater than the handover reference value (that is, the handover reference value of the received signal strength received from the outdoor target base station), and the signal strength of all the indoor base stations 14 and 15 is the handover reference value [the indoor serving base station currently being served. (14) or the handover reference value of the received signal strength received from the adjacent indoor base station 15, the outdoor movement is considered. When the portable Internet terminal 11 is regarded as outdoor movement in this manner, the portable Internet terminal 11 should be able to determine the outdoor base station 12 or 13 as the base station to be handed over.

However, if there is an indoor base station 15 having a signal strength equal to or greater than the handover reference value among the candidate base stations to be candidates, the indoor base station 15 is considered to exist indoors, even if the signal strength of the outdoor base stations 12 and 13 is the largest. Handover to indoor base station 15 should be made to reduce the overhead of handing over to base station 12 or 13.

That is, if the signal strength of the indoor serving base station 15 currently being serviced is less than or equal to the handover reference value, even if the signal strength of the outdoor base station 12 or 13 is the largest among the neighboring base stations, the indoor base station 15 among the neighboring base stations If the signal strength of the signal is equal to or greater than the handover reference value, the indoor base station 15 is determined as the base station to be handed over.

Of course, even if the signal strength of the outdoor base station 12 or 13 among the neighboring base stations is the largest, the indoor serving base station 15 is maintained when the signal strength of the currently serving indoor serving base station 15 is higher than the handover reference value. do.

In an area where access to the outside is possible, the following handover control procedure is required to operate in this manner.

As a prerequisite, in the portable Internet system, the base station (BS) is divided into indoor and outdoor use, and indoor base station (14, 15) is the recommended target base station indoor base station (14, 15) whether the outdoor base station (12, 13) It is assumed that the information can be identified through the base station information.

As described above, handover may begin 903 and the indoor serving base station 14 may begin 908.

First, referring to FIG. 10, the handover control process in the indoor serving base station 14 when the portable Internet terminal 11 starts handover will be described.

Referring to FIG. 10, the indoor serving base station 14 transmits a MOB-NBR-ADV message including neighbor BS information to the portable Internet terminal 11 (1001), and then from the portable Internet terminal 11. When the MOB_SCN-REQ message requesting the Scanning Interval and Iteration is received (1002), the MOB_SCN-RSP message is transmitted to the portable Internet terminal 11 by assigning the Scanning Interval and Iteration (1003).

Thereafter, the indoor serving base station 14 includes the MOB_MSHO- that includes the CINR values of the neighbor base stations (the candidate base stations including the indoor / outdoor target base stations 12, 13, and 15) recommended by the portable Internet terminal 11. When the REQ message is received (1004), the candidate base stations (indoor / outdoor target base stations 12, 13, 15) recommended by the portable Internet terminal 11 of the portable Internet terminal 11 through the backbone network. The handover is notified (1005). In response to the response from the recommended target base stations (indoor / outdoor target base stations 12, 13, and 15) (1006), the indoor serving base station 14 selects a target base station that can be recommended again based on the response. In operation 1009, the mobile station verifies the handover to the selected recommended target base station through message exchange using a backbone network (1009).

In the indoor serving base station 14 determines the handover target base station, the indoor base station 15 and the outdoor base stations 12 and 13 are distinguished from the indoor base station 15 and the outdoor base station through the base station information. 12, 13) If both the handover reference value is exceeded, if indoor base station 15 is selected as a recommendable handover target base station irrespective of the magnitude of the signal strength, and only the outdoor base station 12 or 13 exceeds the handover reference value The outdoor base station 12 or 13 is selected as a recommended handover target base station (1007, 1008), and handovers to the selected recommended target base station 12 or 13 or 15 through message exchange using a backbone network. Confirm the fact (1009).

Next, the indoor serving base station 14 may consist of a list of recommended target base stations (indoor base station 15 only) in the MOB_BSHO-RSP message in response to the MOB_MSHO-REQ message transmitted by the portable Internet terminal 11, It may be composed of indoor / outdoor base station 12, 13, 15] and transmits to the portable Internet terminal 11 (1010).

Subsequently, as the indoor serving base station 14 determines the target base station 12 or 13 or 15 in the portable Internet terminal 11, a MOB-HO-IND message is received from the portable Internet terminal 11 to indicate a handover fact. Final notification is received (1011), and disconnects from the portable Internet terminal 11 after the Resource Retain Time (1012).

Referring to FIG. 11, the handover control process in the indoor base station 14 when the indoor serving base station 14 starts handover will be described.

Referring to FIG. 11, the indoor serving base station 14 transmits a MOB-NBR-ADV message including neighbor BS information to the portable Internet terminal 11 (1101), if it feels that a handover is necessary ( In operation 1102, a message informing a candidate of handover is transmitted to candidate base stations (handover target base stations 12, 13, and 15) through a backbone network (1103).

At this time, the indoor serving base station 14 determines the handover target base station based on the response. The indoor base station 15 is distinguished from the indoor base station 15 and the outdoor base stations 12 and 13 by the base station information. If both the base station and the outdoor base stations 12 and 13 exceed the handover reference value, the indoor base station 15 is unconditionally selected as the recommended handover target base station regardless of the signal strength, and only the outdoor base station 12 or 13 is handovered. If the reference value is exceeded, the outdoor base station 12 or 13 is selected as a recommendable handover target base station (1104), and the MOB_BSHO-REQ message including the recommended target base station list is transmitted to the portable Internet terminal 11 (1105). ), The handover target base station among the recommended candidate base stations (which may be composed of only indoor base stations 15 or indoor / outdoor base stations 12, 13, 15). 12 or 13 or 15), the final notification of the handover fact through the MOB-HO-IND message (1106), the indoor serving base station 14 after the Resource Retain Time, the mobile Internet terminal 11 and Disconnect and stop service (1107).

In the above, the indoor handover reference value (the handover reference value of the received signal strength received from the outdoor base station) is smaller than the outdoor handover reference value (the handover reference value of the received signal strength received from the outdoor base station).

On the other hand, the method of the present invention as described above can be written in a computer program. And the code and code segments constituting the program can be easily inferred by a computer programmer in the art. In addition, the written program is stored in a computer-readable recording medium (information storage medium), and read and executed by a computer to implement the method of the present invention. The recording medium may include any type of computer readable recording medium.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the technical spirit of the present invention for those skilled in the art to which the present invention pertains. It is not limited by the drawings.

The present invention can be used for an integrated portable Internet system composed of indoor / outdoor base stations.

1 is a configuration example of a typical outdoor portable Internet (WiBro) network,

2 is a flowchart illustrating a handover control process in the outdoor WiBro network of FIG. 1;

3 is an explanatory diagram showing the format of a MOB_NBR-ADV message in FIG. 2;

4 is a flowchart illustrating a handover control process in the portable Internet terminal MS when the portable Internet terminal MS starts handover in FIG.

FIG. 5 is a flowchart illustrating a handover control process at a base station BS when the portable Internet terminal MS starts handover in FIG.

FIG. 6 is a flowchart illustrating a handover control process in a portable Internet terminal MS when the base station BS starts handover in FIG.

FIG. 7 is a flowchart illustrating a handover control process in a base station BS when the base station BS starts handover in FIG.

8 is an exemplary configuration diagram of an indoor / outdoor portable Internet (WiBro) network to which the present invention is applied;

FIG. 9 is a flowchart illustrating a handover control process from indoor to indoor in the indoor / outdoor portable Internet (WiBro) network of FIG. 8;

10 is a flowchart illustrating a handover control process in a base station (BS) when the mobile Internet terminal (MS) starts handover according to the present invention;

11 is a flowchart illustrating a handover control process at a base station BS when a base station BS starts handover according to the present invention.

* Explanation of symbols for the main parts of the drawings

11: mobile Internet terminal (MS) 12,13: outdoor base station (BS)

14,15: indoor base station (BS)

Claims (17)

A handover control method in a portable internet system composed of indoor / outdoor base stations, An indoor serving base station that manages an area without an external door and broadcasts only the indoor base station to information of a neighbor base station for handover; And When the terminal moves indoors, the indoor serving base station is handed to an indoor target base station having a signal strength equal to or greater than a handover reference value among 'indoor candidate base stations selected based on the signal strength measured by the neighbor base station search. Handover Phase to Perform Over Handover control method comprising a. The method of claim 1, Performing, by the terminal, a network reentry procedure to the indoor target base station Handover control method further comprising. The method according to claim 1 or 2, The terminal, When the indoor serving base station is being served, the signal strength of neighboring indoor base stations is measured by searching for neighboring indoor base stations, and an indoor base station having a larger handover reference value among neighboring indoor base stations is selected as a handover target base station. And performing handover to the indoor target base station. A handover control method in a portable internet system composed of indoor / outdoor base stations, An indoor serving base station that manages an area having an external door and broadcasts the indoor and outdoor base stations in the information of the adjacent base station for handover; And When the terminal moves indoors, the indoor serving base station has an indoor target having a signal strength equal to or greater than a first handover reference value among 'indoor / outdoor candidate base stations selected based on signal strength measured by searching for neighbor base stations in the terminal'. Handover phase to perform handover to base station Handover control method comprising a. The method of claim 4, wherein In the handover step, If the signal strength of the indoor target base station is greater than or equal to the first handover reference value and the signal strength of the 'outdoor base station adjacent to the indoor target base station' is also greater than or equal to a second handover reference value, perform the handover to the indoor target base station. Handover control method, characterized in that. The method of claim 5, Performing, by the terminal, a network reentry procedure to the indoor target base station Handover control method further comprising. A handover control method in a portable internet system composed of indoor / outdoor base stations, An indoor serving base station that manages an area having an external door and broadcasts the indoor and outdoor base stations in the information of the adjacent base station for handover; And When the terminal moves indoors, the indoor serving base station is the first handover signal strength of the indoor serving base station of the "indoor / outdoor candidate base station selected based on the signal strength measured by the neighbor base station search in the terminal" If the signal is greater than the reference value and the signal strength of the outdoor base station is also equal to or greater than the second handover reference value, performing no handover Handover control method comprising a. The method of claim 7, wherein In the handover step, If the signal strength of the indoor serving base station is greater than or equal to the first handover reference value and the signal strength of the outdoor base station is also greater than or equal to the second handover reference value, handover control characterized in that no handover is performed to the outdoor base station. Way. A handover control method in a portable internet system composed of an indoor base station, An indoor serving base station that manages an area having an external door and broadcasts the indoor and outdoor base stations in the information of the adjacent base station for handover; And When the terminal moves from indoor to outdoor, the indoor serving base station has a signal strength equal to or greater than a second handover reference value among indoor / external candidate base stations selected based on signal strength measured by searching for neighboring base stations in the terminal. Handover step of performing handover to outdoor target base station Handover control method comprising a. The method of claim 9, In the handover step, When the signal strength of the indoor base station adjacent to the outdoor target base station is less than the first handover reference value, and only the outdoor target base station is more than the second handover reference value, handover to the outdoor target base station is performed. Handover control method. The method of claim 10, Performing, by the terminal, a network reentry procedure to the outdoor target base station Handover control method further comprising. The method according to any one of claims 5 to 8, 10 or 11, The first handover reference value is, Handover control method, characterized in that less than the second handover reference value. The method according to any one of claims 1 or 2, 4 to 11, The indoor serving base station, Handover control method characterized in that it is possible to distinguish whether the recommended indoor / outdoor base stations are indoor base station or outdoor base station through base station information. In the indoor / outdoor portable Internet system with a processor for handover control, An indoor serving base station that manages an area without an external door and broadcasts only the indoor base station to information of a neighbor base station for handover; And When the terminal moves indoors, the indoor serving base station is handed to an indoor target base station having a signal strength equal to or greater than a handover reference value among 'indoor candidate base stations selected based on the signal strength measured by the neighbor base station search. Function to do over A computer-readable recording medium having recorded thereon a program for realizing this. In the indoor / outdoor portable Internet system with a processor for handover control, An indoor serving base station that manages an area having an external entrance door and broadcasts both indoor and outdoor base stations to information of neighbor base stations for handover; And When the terminal moves indoors, the indoor serving base station has an indoor target having a signal strength equal to or greater than a first handover reference value among 'indoor / outdoor candidate base stations selected based on signal strength measured by searching for neighbor base stations in the terminal'. Ability to perform handover to base station A computer-readable recording medium having recorded thereon a program for realizing this. In the indoor / outdoor portable Internet system with a processor for handover control, An indoor serving base station that manages an area having an external entrance door and broadcasts both indoor and outdoor base stations to information of neighboring base stations for handover; And When the terminal moves indoors, the indoor serving base station is the first handover signal strength of the indoor serving base station of the "indoor / outdoor candidate base station selected based on the signal strength measured by the neighbor base station search in the terminal" A function that does not perform handover when the reference value is greater than the signal strength of the outdoor base station and the second handover reference value or more. A computer-readable recording medium having recorded thereon a program for realizing this. In the indoor / outdoor portable Internet system with a processor for handover control, An indoor serving base station that manages an area having an external entrance door and broadcasts both indoor and outdoor base stations to information of neighbor base stations for handover; And When the terminal moves from indoors to outdoors, the indoor serving base station has outdoor signal strength having a signal strength equal to or greater than a second handover reference value among 'indoor / outdoor candidate base stations selected based on the signal strength measured by the neighbor base station search.' Ability to perform handover to the target base station A computer-readable recording medium having recorded thereon a program for realizing this.

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