KR20090108286A - Method for controlling handover signaling in hybrid indoor/outdoor wibro system - Google Patents

Abstract

PURPOSE: A method for controlling handover in a portable internet system configured by indoor/outdoor base stations is provided to prevent a call disconnection phenomenon by increasing accuracy of handover. CONSTITUTION: A method for controlling handover in a portable internet system configured by indoor/outdoor base stations comprises the following steps. Outdoor serving base stations(12,13) periodically broadcast information of an adjacent base station for handover. When the terminal moves from outdoor to indoor, the outdoor serving base station performs handover to an indoor target base station(14) having signal strength with a value larger than the first handover reference value among candidate base stations. The candidate base station is selected based on the measured signal strength through adjacent base station search in a terminal(11).

Description

Handover Control Method in Mobile Internet System Composed of Indoor / Outdoor Base Stations {Method for controlling handover signaling in hybrid indoor / outdoor wibro system}

The present invention relates to a 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 the existing portable Internet system, when the terminal moves from the area of the outdoor base station to the area of the indoor base station, the terminal uses the indoor base station, or the terminal moves from the area of the indoor base station to the area of the outdoor base station, The present invention relates to a handover control method capable of performing a handover process and to prevent service interruption, and a computer-readable recording medium having recorded thereon 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.

Then, the existing handover control process in the outdoor portable Internet network will be described with reference to FIGS. 1 to 7, and the problem in which the existing handover control process cannot be applied in the portable Internet network composed of indoor / outdoor base stations is described. 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.

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 from outdoor base station 12 or 13 to indoor base station 14, handover control procedure from indoor base station 14 to outdoor base station 12 or 13) ] Must be added separately.

In the portable Internet system, since the cells overlap each other, when the portable Internet terminal (MS) 11 moves and performs handover, one or more candidates of the target base station (BS) are present. Therefore, for handover, one base station must be selected from a plurality of target base stations, and at this time, an evaluation is performed with signal strength in selecting a target base station.

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, the serving base station 12 first informs neighbor BS information of a mobile base station 11 for handover of the MOB_NBR-ADV. (Mobile Neighbor Advertisement) message (the IEEE 802.16e neighbor advertisement message, the broadcast base station periodically advertises network attributes for the serving base station and neighbor base stations) (see FIG. 3) periodically broadcasts (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, thereby enabling faster handover. You can use this information to perform

Referring to FIG. 3, it can be seen that the MOB_NBR-ADV message includes 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, the signal strength of the neighboring base stations can be known (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 portable Internet terminal 11 may manage the list of candidate base stations to perform handover by obtaining the ID list of neighbor base stations through the MOB_NBR_ADV message and selecting the appropriate base station based on the real-time link information acquired through scanning.

However, the handover may be initiated 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 receiving a handover request from the portable Internet terminal 11 (203), the serving base station 12 is a candidate base station (target base station 13) recommended by the portable Internet terminal 11 through the backbone network (Backbone) The information of the portable Internet terminal 11 is notified through the message HO_notification to handover (included) (204), and a response message (HO_notification_response) is received from the candidate base station (the target base station 13 is included) (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 BS 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). In step 207, the serving base station 12 includes a list of recommended base stations (candidate base station) in the MOB_BSHO-RSP message. 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.

Specifically, when the serving base station 12 starts handover, the mobile base station 11 transmits a MOB_BSHO-REQ message [BS → MS, the IEEE 802.16e handover request message of the serving base station 12]. 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 searches for the base station and information obtained through the MOB_NBR-ADV. The handover is notified by evaluating the information through the UE 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 and UCD (Uplink Channel Descriptor) are periodically transmitted according to the setting of the target base station 13, and the mobile Internet terminal 11 receives the frame and checks the forwarding 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). In this case, the RN-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 the 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 (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 a 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 from 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 candidate base station (including the target base station 13) recommended by the portable internet terminal 11 informs the handover of 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 11 in the portable internet terminal 11, the mobile base station 11 receives a MOB-HO-IND message 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 according to the signal strength among the recommended neighbor base station (a candidate base station including the target base station 13) The base station 13 finally determines and notifies the serving base station 12 of the handover fact through 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). ), The final decision of the handover target base station 13 according to the signal strength and the final notification 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 indoor / outdoor portable Internet system as it is, the following problems occur.

For example, as the portable Internet terminal 11 moves from the outdoor base station 12 to the indoor base station 14 of FIG. 8, the outdoor serving base station 12 is the handover target base station (candidate base station). 13 and the indoor base station 14. Therefore, in determining the target base station, the portable Internet terminal 11 has a signal strength of the base station among the candidate base station list composed of the indoor base station 14 and the outdoor base stations 12 and 13 recommended by the outdoor serving base station 12. The best base station unilaterally determines handover.

However, if the indoor base station 14 is not far from the outdoor base station 12 but is near the outdoor base station 12 (in this case, in the portable Internet terminal 11, the signal strength of the outdoor base station 12 is the outdoor base station). Greater than the signal strength of (13)] In the portable Internet terminal 11, the signal strength of the outdoor base station 12 that is currently being serviced will be better than the signal strength of the indoor base station 14. In general, even when the mobile Internet terminal 11 is located between the outdoor base station 12 and the indoor base station 14, in the mobile Internet terminal 11, the signal strength of the outdoor base station 12 is set to an indoor base station ( This is because the signal strength of 14) is greater. Therefore, since the portable Internet terminal 11 receives a signal from the outdoor serving base station 12 well, the handover to the indoor base station 14 cannot be performed. That is, since signal strength of the outdoor serving base station 12 that is currently being serviced does not become weak, a handover does not occur. This decreases the accuracy of the handover, causing call disconnection, resulting in a large handover delay.

Also, if the indoor base station 14 is not far from the outdoor base station 13 but is near the outdoor base station 13 (in this case, the signal strength of the outdoor base station 13 is greater than the signal strength of the outdoor base station 12). Smaller] In the portable Internet terminal 11, the signal strength of the outdoor base station 13 will be better than the signal strength of the indoor base station 14. Therefore, even if the portable Internet terminal 11 moves from the area of the outdoor base station 12 to the area of the indoor base station 14, the portable Internet terminal 11 does not perform handover to the indoor base station 14. Then, handover is performed to the outdoor base station 13. That is, since the signal strength of the outdoor base station 13 is strong, an unintended handover occurs. This decreases the accuracy of the handover, causing call disconnection, resulting in a large handover delay.

As another example, as the mobile Internet terminal 11 moves from an indoor base station (14 in FIG. 8) to another indoor base station in an enterprise (assuming at least two indoor base stations are installed in an enterprise, etc.), indoor serving The base station 14 is a handover target base station (candidate base station) and includes both the outdoor base stations 12 and 13 and other indoor base stations. Accordingly, in determining the target base station, the portable Internet terminal 11 has the best signal strength among the candidate base station lists composed of the other indoor base stations and the outdoor base stations 12 and 13 recommended by the indoor serving base station 14. A good base station unilaterally determines handover.

However, if the other indoor base station is not far from the outdoor base station 12 or 13 but is near the outdoor base station 12 or 13, in the portable Internet terminal 11, the signal strength of the other indoor base station is set to the outdoor base station 12. or signal strength of 13). Therefore, even if the mobile internet terminal 14 moves from the indoor base station 14 to another indoor base station, the portable internet terminal 11 does not perform a handover to another indoor base station, and the outdoor base station 12 or 13 does not perform handover. Will perform a handover. 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.

Therefore, in the portable Internet system in which indoor / outdoor base stations exist, the present invention allows the terminal to move from the area of the outdoor base station to the area of the indoor base station, or when the terminal uses the indoor base station, to perform a smooth handover process. An object of the present invention is to provide a handover control method for preventing service interruption and a computer-readable recording medium having recorded thereon a program for realizing the method.

That is, a first object of the present invention is a handover control for guaranteeing handover to an indoor base station when a terminal moves from an outdoor base station to an indoor base station in a portable Internet system in which indoor / outdoor base stations exist. A computer-readable recording medium having recorded thereon a method and a program for realizing the method is provided.

In addition, a second object of the present invention is a hand for ensuring handover in an indoor base station when a mobile station moves from an area of an indoor base station to another area of an indoor base station in a portable Internet system in which an indoor / outdoor base station exists. An over-control method and a computer-readable recording medium having recorded thereon a program for realizing the method are provided.

In addition, a third object of the present invention is to provide a handover control method and method for guaranteeing handover in an indoor base station when a mobile station moves in an area of an indoor base station in a mobile Internet system in which indoor / outdoor base stations exist. It is intended to provide a computer readable recording medium that records a program for realization.

In addition, a fourth object of the present invention is a handover control method for ensuring handover to an outdoor base station when a terminal moves from an indoor base station to an outdoor base station in a mobile Internet system in which indoor / outdoor base stations exist. And a computer readable recording medium having recorded thereon a program for realizing the method.

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.

According to an aspect of the present invention, there is provided a method for controlling a handover in a portable Internet system including an indoor / outdoor base station, the outdoor serving base station periodically broadcasting information of a neighbor base station for handover; And an indoor target having a signal strength equal to or greater than a first handover reference value among the candidate serving base stations selected by the outdoor serving base station based on the signal strength measured through the search for the neighboring base station when the terminal moves from indoor to indoor. It characterized in that it comprises a handover step of performing a handover to the base station.

In addition, for the handover control, the indoor / outdoor portable Internet system having a processor, the outdoor serving base station periodically broadcasts the information of the neighboring base station for the handover; And an indoor target having a signal strength equal to or greater than a first handover reference value among the candidate serving base stations selected by the outdoor serving base station based on the signal strength measured through the search for the neighboring base station when the terminal moves from indoor to indoor. A computer readable recording medium having recorded thereon a program for realizing a function of performing a handover to a base station is provided.

On the other hand, the present invention for achieving the second object, in the handover control method in a mobile Internet system consisting of indoor / outdoor base station, the indoor serving base station periodically broadcasts information of the neighbor base station for the handover Making; 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 first handover reference value among 'a candidate base station selected based on signal strength measured by searching for neighbor base stations in the terminal'. It characterized in that it comprises a handover step of performing a handover.

In addition, the present invention, the indoor / outdoor portable Internet system having a processor for the handover control, the indoor serving base station periodically broadcasts the information of the neighbor base station for the handover; And an indoor target base station having a signal strength equal to or greater than a first handover reference value among the candidate serving base stations selected by the indoor serving base station based on the signal strength measured by the neighbor base station search when the terminal moves indoors. A computer readable recording medium having recorded thereon a program for realizing a function of performing a handover is provided.

On the other hand, the present invention for achieving the third object is a handover control method in a portable Internet system composed of indoor / outdoor base station, the indoor serving base station periodically the information of the neighbor base station for the handover Broadcasting; And when the mobile station moves indoors, even if the indoor base station has a signal strength equal to or greater than a first handover reference value among the candidate base stations selected based on the signal strength measured by the neighbor base station search. And if the signal strength of the indoor serving base station does not become smaller than the second handover reference value, handover to the outdoor base station.

In addition, the present invention, the indoor / outdoor portable Internet system having a processor for the handover control, the indoor serving base station periodically broadcasts the information of the neighbor base station for the handover; And when the mobile station moves indoors, even if the indoor base station has a signal strength equal to or greater than a first handover reference value among the candidate base stations selected based on the signal strength measured by the neighbor base station search. Provided is a computer-readable recording medium having recorded thereon a program for realizing a function of not performing a handover to the outdoor base station if the signal strength of the indoor serving base station is not smaller than the second handover reference value.

On the other hand, the present invention for achieving the fourth object is a handover control method in a portable Internet system consisting of an indoor / outdoor base station, the indoor serving base station periodically the information of the neighbor base station for the handover Broadcasting with; And when the terminal moves from indoor to outdoor, the indoor serving base station is an outdoor target base station having a signal strength equal to or higher than a handover reference value among 'a candidate base station selected based on signal strength measured through neighboring base station search in the terminal'. And performing a handover.

In addition, the present invention, the indoor / outdoor portable Internet system having a processor for the handover control, the indoor serving base station periodically broadcasts the information of the neighbor base station for the handover; And when the terminal moves from indoor to outdoor, the indoor serving base station is an outdoor target base station having a signal strength equal to or higher than a handover reference value among 'a candidate base station selected based on signal strength measured through neighboring base station search in the terminal'. A computer readable recording medium having recorded thereon a program for realizing a function of performing a handover is provided.

The present invention as described above, when moving from the area of the outdoor base station to the area of the indoor base station, or when moving from the area of one indoor base station to the area of the other indoor base station, or when moving in the area of one indoor base station When moving from the area of the indoor base station to the area of the outdoor base station, it is possible to prevent the call disconnection phenomenon by increasing the accuracy of handover, thereby reducing the handover delay.

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 the home (8a), the mobile Internet terminal 11 receives the service through the indoor base station 14.

However, the outdoor base station 12 or 13 is normally connected to the network of the service provider through a control station (ACR), while the indoor base station 14 is directly connected to the public IP network and connects to the public IP network. Information transmission is performed through the authentication server (AAA) and the like.

Indoor base station 14 is a base station installed in homes, businesses, etc., and is designed to be small in size and simple to be easily installed indoors, such as an existing wireless access point (AP).

In particular, the indoor base station 14 includes a home indoor base station which is separately installed in a home and used in a home, and a group of indoor indoor base stations that can be installed in a group or the like and used in a company.

In the present invention, the indoor base station 14 should be interpreted as a concept including a group of indoor indoor base stations and a corporate indoor base station, and the portable Internet terminal 11 is a portable Internet composed of indoor / outdoor base stations 12 to 14. Means the terminal operating in the system.

In the present invention, the handover procedure of the existing portable Internet system is observed, but in the mobile Internet system in which the indoor / outdoor base station exists, the mobile base station 11 is the indoor base station 14 in the area of the outdoor base station 12 or 13. When moving to the area (8a), the handover to the indoor base station 14 (that is, the handover from the outdoor serving base station to the indoor target base station) is guaranteed [first embodiment], and the portable Internet terminal 11 Guarantee handover between indoor base stations (ie, indoor serving base station to indoor target base station) when moving from the area of indoor base station 14 to the area of another indoor base station (not shown in the figure). [Second Embodiment]

That is, in the first embodiment, the handover from the outdoor base station 12 or 13 to the indoor base station 14 is guaranteed. In the second embodiment, the handover to the outdoor base station 12 or 13 is excluded. This ensures a handover of the indoor base station having the largest signal size among the at least two indoor base stations including the indoor serving base station 14 as the indoor target base station.

However, in the second embodiment, even if one indoor base station 14 is installed, even if there is a change in signal strength of the adjacent base station through movement in the area of the indoor base station 14, the outdoor base station 12 or 13) do not perform handover (maintain indoor serving base station 14).

In the first and second embodiments, when the portable Internet terminal 11 moves from the indoor base station 14 to the outdoor base station 12 or 13 (8b), the hand to the outdoor base station 12 or 13 is used. Over (that is, handover from indoor serving base station to outdoor target 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].

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

In FIG. 9, when a mobile Internet terminal 11 that has been serviced through an outdoor base station 12 or 13 outdoors in the indoor / outdoor portable Internet network moves to a home (8a), a handover occurs and the indoor base station 14 ) Shows the process of receiving service.

Referring to FIG. 9, referring to a handover control procedure in an indoor / outdoor portable Internet network, first, an outdoor serving base station 12 or 13 is used for indoor and outdoor base stations for handover of the portable Internet terminal 11. MOB_NBR-ADV (Mobile Neighbor Advertisement) message (IEEE 802.16e Neighbor Advertisement Message), which informs neighbor BS information about an NB-NBR-ADV. Advertisements periodically] (see FIG. 3) (901). Therefore, when the mobile internet terminal 11 receives the MOB_NBR_ADV message periodically advertised from the outdoor serving base station 12 or 13 to which it belongs, IDs, QoS parameters, and QoS parameters of neighboring base stations (indoor indoor and outdoor base stations) and the like. This information can be used to obtain channel information and to perform handover later.

Thereafter, the portable Internet terminal 11 performs a task of scanning neighboring base stations as necessary, and measures the signal strength of the neighboring base stations through this (902). 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 outdoor serving base station 12 or 13 and being allocated 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 portable Internet terminal 11 may manage the list of candidate base stations to perform handover by obtaining the ID list of neighbor base stations through the MOB_NBR_ADV message and selecting the appropriate base station based on the real-time link information acquired through scanning.

Here, after measuring the signal strength of neighboring base stations, if the indoor base station 14 is included in the neighboring base station, the signal strength of the indoor base station 14 is the indoor handover reference value (Target BS received signal strength threshold Greater than the received signal strength from the indoor target base station, the signal strength of the currently serving outdoor serving base station 12 or 13 is the target BS received signal strength threshold. Even if it is not smaller than [that is, the handover reference value of the received signal strength received from the outdoor serving base station 12 or 13 currently being serviced], the portable Internet terminal 11 performs the handover to the indoor base station 14. .

That is, if the signal strength of the indoor target base station 14 is greater than the indoor handover reference value, the handover is performed even if the signal strength of the outdoor serving base station 12 or 13 is not less than or equal to the outdoor handover reference value (usually, less than or equal to the reference value). , The priority is given to the indoor base station 14 to perform a handover to the indoor base station 14.

In this case, the handover may be started by the portable Internet terminal 11 (903), or may be performed by the outdoor serving base station 12 or 13 (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 outdoor serving base station (12 or 13) (903), wherein the MOB_MSHO-REQ message includes the carrier to interference and noise ratio of the neighbor base stations received through the MOB_NBR-ADV message. ) Value is included. That is, the CINR value of the candidate base station (indoor base station 14) is transmitted through the MOB_MSHO-REQ message.

When receiving a handover request from the portable internet terminal 11 (903), the outdoor serving base station 12 or 13 is a candidate base station recommended by the portable internet terminal 11 (i.e., indoor target) through a backbone network. The information on the portable Internet terminal 11 is notified through the message HO_notification to handover to the base station 14 (904), and the response message HO_notification_response is received from the candidate base station (the indoor target base station 14) ( 905).

After receiving the response (905), the outdoor serving base station (12 or 13) is confirmed by the recommendable handover target base station (indoor base station) 14 (906), the MOB_BSHO-RSP message [BS → MS, outdoor use The IEEE 802.16e handover response message of the serving base station 12 or 13 is included in the recommended BS list and transmitted to the portable Internet terminal 11 (907).

Thereafter, the portable Internet terminal 11 determines the final handover target base station (indoor base station) 14 among the target base stations recommended by the outdoor serving base station 12 or 13, and sends the MOB_HO to the outdoor serving base station 12 or 13. An IND message (MS → BS, IEEE 802.16e handover execution message) is sent 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 14 by comparing the signal strength and QoS parameters of the neighboring base stations previously obtained. That is, the portable Internet terminal 11 compares the quality of service and signal strength provided from the outdoor serving base station 12 or 13 and puts a list of base stations capable of handover in the MOB_MSHO-REQ message to serve the outdoor serving base station 12 or 13. In step 903, the outdoor serving base station 12 or 13 includes a list of recommended base stations (candidate base station) in the MOB_BSHO-RSP message and returns (907). At this time, the outdoor serving base station 12 or 13 notifies the handovers to the candidate base stations (one of which becomes the indoor target base station 14) through the backbone network to inform the session and configuration information of the portable Internet terminal 11. By transmitting in advance (904), it is possible to shorten the time for performing handover later.

After the mobile Internet terminal 11 receives the MOB_BSHO-RSP message and determines the indoor target base station 14, the mobile Internet terminal 11 sends a MOB_HO-IND message to the outdoor serving base station 12 or 13 to finally notify the handover [ Initial handover execution process] (909), the handover is executed immediately [handover execution process] (910 ~ 916). The handover execution process will be described in more detail below.

Meanwhile, in the handover preparation process, the outdoor serving base station 12 or 13 may start the handover process by first transmitting the MOB_BSHO-REQ message to the portable Internet terminal 11.

In detail, when the outdoor serving base station 12 or 13 starts handover, the mobile internet access message includes a MOB_BSHO-REQ message [BS → MS, an IEEE 802.16e handover request message of the outdoor serving base station 12 or 13]. In step 908, the MOB_BSHO-REQ message includes a list (recommended base station list) recommended by the outdoor serving base station 12 or 13, and the mobile Internet terminal 11 transmits the recommended base station to the MOB_NBR. The handover is notified by evaluating the information obtained through the ADV and the information obtained by the base station search by transmitting a MOB_HO-IND message to the outdoor serving base station 12 or 13 (909).

Now, referring to the handover execution process, the outdoor serving base station 12 or 13 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 or receive a packet through the outdoor serving base station 12 or 13, so that the network re-entry quickly after moving to a new network. entry) procedures should be performed. At this time, if the indoor target base station 14 receives the information of the portable Internet terminal 11 on the performance capability and authentication, etc. from the outdoor serving base station 12 or 13, the portable Internet terminal 11 during the network entry process By omitting the handover process can be shortened. When the network entry process is successfully completed, the indoor target base station 14 starts the service to the portable Internet terminal 11.

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

In this case, the DCD message includes a transmission / reception time, a center frequency, mobility support function, 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 indoor target base station 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 14 and receives the RSP message from the indoor target base station 14. When the portable Internet terminal 11 enters a new network, the handover procedure is completed, and after completing the handover procedure, the indoor target base station 14, which is a new serving node, transmits data to the portable Internet terminal 11. (916).

In detail, the ranging process 912, the portable Internet terminal 11 reads a burst profile, media access control (MAC) information, etc. of the terminal through a ranging request (RNG-REQ) message. It sends to the content target base station 14, and the indoor target base station 14 responds (912) with a ranging response (RNG-RSP: Ranging Response) message. In this case, the RN-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 912, the portable Internet terminal 11 transmits a basic capability negotiation request (SBC-REQ) message to the indoor target base station 14, The content target base station 14 receives a basic capability negotiation response (SBC-RSP) message and exchanges information for using radio resources (913). 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 913, the portable Internet terminal 11 requests a privacy key management (PKM) request message to the indoor target base station 14 [EAP transmission request]), and a PKM response. A message is received to manage an 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 14, and the indoor target The base station 14 transmits a registration response (REG-RSP) message to the portable Internet terminal 11 (915). [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 915, although not shown in the drawing, the indoor target base station 14 additionally transmits a dynamic service addition (DSA) request message for establishing a traffic connection to the portable Internet terminal 11, In response to this, 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 outdoor serving base station 12 or 13 transmits the MOB_NBR-ADV message containing the base station information to the portable Internet terminal 11. The mobile Internet terminal 11 and the outdoor serving base station 12 or 13 exchange the MOB_SCN-REQ message and the MOB_SCN-RSP message. In this process, the mobile Internet terminal 11 changes the indoor target according to signal strength and QoS characteristics. Base station 14 is selected. Thereafter, when the portable Internet terminal 11 selects the indoor target base station 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 outdoor serving base station 12 or 13, the handover preparation step ends.

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 outdoor serving base station 12 or 13. Subsequently, the outdoor serving base station 12 or 13 receiving the MOB_HO-IND message releases the resources allocated to the portable Internet terminal 11 and performs security functions and authentication with the indoor target base station 14.

FIG. 10 is a flowchart illustrating a handover control process from indoor to outdoor in the indoor / outdoor portable Internet (WiBro) network of FIG. 8 according to the second embodiment.

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

In FIG. 10, when an indoor / outdoor portable Internet network moves to another place (indoor) when a mobile Internet terminal 11 that has been serviced indoors through an indoor base station 14 is moved to another indoor, a handover occurs. Shows the process of receiving service through the base station.

Referring to FIG. 10, a handover control procedure in an indoor / outdoor portable Internet network is described. First, an indoor serving base station (BS1) 14 is configured to perform indoor and outdoor indoor handovers for handover of the portable Internet terminal 11. MOB_NBR-ADV (Mobile Neighbor Advertisement) message (IEEE 802.16e Neighbor Advertisement Message) that informs neighbor BS information about an outdoor base station. 14 broadcasts periodically (see FIG. 3) (1001). Therefore, when the mobile Internet terminal 11 receives the MOB_NBR_ADV message periodically advertised from the indoor serving base station (BS1) 14 to which it belongs, ID, QoS of neighbor base stations (indoor and outdoor base stations). This information can be used to obtain parameter and channel information and perform faster handover later.

Thereafter, the portable Internet terminal 11 performs a task of scanning neighboring base stations as necessary, and measures the signal strength of the neighboring base stations through this (1002). 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 indoor serving base station (BS1) 14 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 portable Internet terminal 11 may manage the list of candidate base stations to perform handover by obtaining the ID list of neighbor base stations through the MOB_NBR_ADV message and selecting the appropriate base station based on the real-time link information acquired through scanning.

Here, after measuring the signal strength of neighboring base stations, if another indoor base station BS2 is included in the neighboring base station, even if the signal strength of the outdoor base station 12 or 13 is larger than the outdoor handover reference value, If the signal strength of the indoor base station BS2 is greater than the target BS received signal strength threshold (that is, the handover reference value of the received signal strength received from the indoor target base station BS2) (in this case, The signal strength of the indoor serving base station (BS1) 14 is smaller than the indoor handover reference value), and the portable Internet terminal 11 performs the handover to another indoor base station BS2.

That is, if the signal strength of the other indoor target base station BS2 is greater than the indoor handover reference value, the other indoor base station BS2 is given priority and handover is performed to the other indoor base station BS2.

At this time, the handover may be initiated by the portable Internet terminal 11 (1003), or may be performed by the indoor serving base station (BS1) 14 (1008).

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) 14 (1003), where the MOB_MSHO-REQ message includes the carrier to interference and CINR of neighboring 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) is transmitted through the MOB_MSHO-REQ message.

When the handover request is received from the portable Internet terminal 11 (1003), the indoor serving base station (BS1) 14 is a candidate base station recommended by the portable internet terminal 11 through the backbone network (that is, jade). Informs the information of the mobile Internet terminal 11 through the message HO_notification that the user hands over to the content target base station BS2 (1004), and receives a response message HO_notification_response from the candidate base station (indoor target base station BS2). 1005.

After receiving the response (1005), the indoor serving base station (BS1) 14 checks the recommendable handover target base station (indoor base station) BS2 (1006), and then the MOB_BSHO-RSP message [BS → MS, including the recommended BS list in the indoor serving base station (BS1) 14 IEEE 802.16e handover response message] and transmits to the portable Internet terminal 11 (1007).

Thereafter, the portable Internet terminal 11 determines the final handover target base station (indoor base station) BS2 from among the target base stations recommended by the indoor serving base station BS1 14, and performs the indoor serving base station BS1 ( In step 1409, a MOB_HO-IND message (MS → BS, IEEE 802.16e handover execution message) is sent to notify the user of the handover.

In the above, steps "1003" to "1007" represent a handover preparation process, and "1009" represents an initial process of handover execution.

During the handover preparation process (1003 to 1007), the portable Internet terminal 11 determines the optimal indoor target base station (BS2) by comparing the signal strength and QoS parameters of the neighboring base stations previously obtained. That is, the portable Internet terminal 11 compares the quality of service and signal strength provided from the indoor serving base station (BS1) 14 with a list of base stations capable of handover in the MOB_MSHO-REQ message to display the indoor serving base station ( It transmits to BS1) 14 (1003), and the indoor serving base station (BS1) 14 responds with the list of recommended base stations (candidate base station) among them in the MOB_BSHO-RSP message (1007). At this time, the indoor serving base station (BS1) 14 notifies the handover to the candidate base stations (one of which becomes the indoor target base station BS2) through the backbone network to establish a session and setup of the portable Internet terminal 11. By transmitting the information in advance (1004), it is possible to shorten the time for performing handover later.

After the mobile Internet terminal 11 receives the MOB_BSHO-RSP message and determines the indoor target base station BS2, the mobile Internet terminal 11 sends a MOB_HO-IND message to the indoor serving base station BS1 14 to finally notify the handover. And [handover execution initial process] (1009), and immediately execute the handover [handover execution process] (1010 to 1016). The handover execution process will be described in more detail below.

Meanwhile, in the preparation for handover, the indoor serving base station (BS1) 14 may start the handover process by first transmitting a MOB_BSHO-REQ message to the portable Internet terminal 11.

In detail, when the indoor serving base station (BS1) 14 starts handover, the IEEE 802.16e handover request message of the MOB_BSHO-REQ message [BS → MS, the indoor serving base station (BS1) 14). ] To the portable Internet terminal 11 (1008), in which the MOB_BSHO-REQ message includes a list recommended by the indoor serving base station (BS1) 14 (candidate base station list), and the portable Internet terminal 11 In step 1009, the recommended base station evaluates the information obtained through the MOB_NBR-ADV and the information through the base station discovery, and sends a MOB_HO-IND message to the indoor serving base station (BS1) 14 to notify the handover (1009).

Now, referring to the handover execution process, the indoor serving base station BS1 14 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 mobile Internet terminal 11 can no longer transmit or receive packets through the indoor serving base station (BS1) 14, so it moves quickly to a new network and quickly reenters the network. Re-entry procedures should be performed. At this time, if the indoor target base station BS2 receives the information of the portable Internet terminal 11 regarding the performance capability and authentication from the indoor serving base station BS1 14, the portable Internet terminal 11 is performed during the network entry process. The handover process can be shortened by omitting this procedure. When the network entry process is successfully completed, the indoor target base station BS2 starts the service to the portable Internet terminal 11.

Specifically, the indoor serving base station BS2, which is a new serving node, transmits the Fast_Ranging IE to the portable Internet terminal 11 (1010), and the portable Internet terminal 11 transmits the CDMA ranging code to the indoor target base station BS2. (1011). [Transmission Parameter Acquisition Process] That is, the indoor target base station BS2 transmits UL-MAP and DL-MAP messages to the portable Internet terminal 11 every frame, and transmits the DCD and UCD to the indoor target base station BS2. It transmits periodically according to the setting, the mobile Internet terminal 11 receives the frame and confirms the delivery information.

Thereafter, the portable Internet terminal 11 performs a network re-entry procedure to the indoor target base station BS2 which is a new serving node (1012 to 1015). At this time, the entry procedure to the new network is largely ranging (Ranging) process (1012), basic capability negotiation process (1013), terminal authentication and key exchange process (1014), registration process (1015), 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 indoor target base station BS2 and receives the RSP message from the indoor target base station BS2. When the portable Internet terminal 11 enters a new network, the handover procedure is completed, and after completing the handover procedure, the indoor target base station BS2, which is a new serving node, transmits data to the portable Internet terminal 11. (1016).

In detail, the ranging process 1012, the portable Internet terminal 11 sends a burst profile, MAC information, etc. of the terminal to the indoor target base station BS2 through a ranging request (RNG-REQ) message. The indoor target base station BS2 responds with a ranging response (RNG-RSP) message (1012). In this case, the RN-RSP message includes information such as ranging status, burst profile, MAC address, CID, etc. of the portable Internet terminal 11.

After performing the ranging (RNG) process 1012, the portable Internet terminal 11 transmits a basic capability negotiation request (SBC-REQ) message to the indoor target base station BS2, and the indoor target base station BS2. Receives a basic capability negotiation response (SBC-RSP) message and exchanges information for using the radio resource (1013). Basic Skills Negotiation Process

After performing the basic capability negotiation (SBC) process 1013, the mobile Internet terminal 11 requests the PKM request message to the indoor target base station BS2 [EAP transmission request], and receives the PKM response message for information. Manage the encryption key required for protection [EAP transmission response] (1014). [Terminal authentication and key exchange process]

After performing the terminal authentication and key exchange process 1014, the portable Internet terminal 11 transmits a registration request message (REG-REQ) message to the indoor target base station BS2, and the indoor target base station BS2 ) Transmits a registration response (REG-RSP) message to the portable Internet terminal 11 (1015). [Registration Process]

After performing the registration process 1015, the indoor target base station BS2 transmits a DSA request message for establishing a traffic connection to the portable Internet terminal 11, and the portable Internet terminal 11 transmits a DSA-RSP message. If it responds with DSA-ACK message, it can be confirmed by [Connection establishment 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 address to be used in the portable Internet terminal 11 can be set automatically [IP address assignment process].

In summary, the indoor serving base station (BS1) 14 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 indoor serving base station (BS1) 14 exchange the MOB_SCN-REQ message and the MOB_SCN-RSP message, and in this process, the mobile Internet terminal 11 changes the number according to signal strength and QoS characteristics. The content target base station BS2 is selected. Thereafter, when the portable Internet terminal 11 selects the indoor target base station BS2, the mobile internet terminal 11 enters a 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) 14, 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) 14. Afterwards, the indoor serving base station (BS1) 14 receiving the MOB_HO-IND message releases the resources allocated to the portable Internet terminal 11 and performs security functions and authentication with the indoor target base station BS2. do.

Meanwhile, in the second embodiment of FIG. 10, when only one indoor base station 14 is installed, the mobile Internet terminal 11 receives the service from the indoor base station 14. Even if the signal strength of 12 or 13 is greater than the target BS received strength threshold (that is, the handover reference value of the received signal strength received from the outdoor target base station 12 or 13), If the signal strength of the content base station 14 is not smaller than the Serving BS received strength threshold (that is, the handover reference value of the received signal strength received from the indoor serving base station 14 currently being served). The portable Internet terminal 11 does not perform handover to the outdoor base station 12 or 13 (maintain the indoor serving base station 14).

That is, if the signal strength of the indoor base station 14 that is currently being serviced is greater than the indoor handover reference value, the indoor base station 14 is given priority and no handover is performed to the outdoor base station 12 or 13.

On the other hand, in the first and second embodiments, when the portable Internet terminal 11 moves from the indoor base station 14 to the outdoor base station 12 or 13 (8b), to the outdoor base station 12 or 13 Handover (that is, handover from indoor serving base station to outdoor target base station) is performed. 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 12 or 13 (since the signal strength of the outdoor base station is larger than the signal strength of the indoor base station). Outdoor base station is selected as a target base station].

Further, in the first and second embodiments, the indoor handover reference value is smaller than the outdoor handover reference value.

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.

6 is a flowchart illustrating a handover control process in a mobile Internet (MS) when the base station BS performs handover in FIG. 2;

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 outdoor to indoor in the indoor / outdoor portable Internet (WiBro) network of FIG. 8;

FIG. 10 is a flowchart illustrating a handover control process from indoor to indoor in the indoor / outdoor portable Internet (WiBro) network of FIG. 8.

* Explanation of symbols for the main parts of the drawings

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

14: indoor base station (BS)

Claims (26)

A handover control method in a portable internet system composed of indoor / outdoor base stations, Periodically broadcasting, by an outdoor serving base station, information of an adjacent base station for handover; And When the terminal moves from outdoors to indoors, the indoor serving base station has an indoor target base station having a signal strength equal to or greater than a first handover reference value among 'a candidate base station selected based on signal strength measured by searching for neighbor base stations in the terminal'. Handover phase to perform handover Handover control method comprising a. The method of claim 1, The first handover reference value is, And a handover reference value of the received signal strength received from the indoor target base station adjacent to the outdoor serving base station. The method of claim 1, In the handover step, Even if the signal strength of the outdoor serving base station adjacent to the indoor target base station does not become smaller than a second handover reference value, handover is performed to the indoor target base station having a signal strength equal to or greater than the first handover reference value. Handover control method. The method of claim 3, The second handover reference value is, And a handover reference value of the received signal strength received from the outdoor serving base station currently being serviced by the terminal. The method of claim 4, wherein 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 to 5, Performing, by the terminal, a network reentry procedure to the indoor target base station Handover control method further comprising. The method of claim 6, The terminal, When the signal strength of neighboring base stations is measured by searching for neighboring base stations, and the signal strength of indoor base stations among neighboring base stations is greater than the first handover reference value, the signal strength of the outdoor serving base station is not smaller than the second handover reference value. And if not, selecting the indoor base station 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, The indoor serving base station periodically broadcasting information of an adjacent base station for handover; And When the terminal moves indoors, the indoor serving base station hands the indoor target base station having a signal strength equal to or greater than a first handover reference value among 'a candidate base station 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 8, The first handover reference value is, And a handover reference value of the received signal strength received from the indoor target base station. The method of claim 8, In the handover step, Handover to the indoor target base station having a signal strength equal to or greater than the first handover reference value, even if the signal strength of the outdoor base station adjacent to the indoor target base station is greater than the second handover reference value. Control method. The method of claim 10, The second handover reference value is, And a handover reference value of the received signal strength received from the outdoor base station adjacent to the indoor target base station. The method of claim 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 8 to 12, Performing, by the terminal, a network reentry procedure to the indoor target base station Handover control method further comprising. The method of claim 13, The terminal, When the indoor serving base station is being serviced, the signal strength of neighboring base stations is measured by searching for neighboring base stations, and if the signal strength of another indoor base station among neighboring base stations is greater than the first handover reference value, the indoor target base station A handover target base station is selected as the handover target base station, even if the signal strength of the outdoor base station adjacent to the second handover reference value is greater than the second handover reference value; Over control method. A handover control method in a portable internet system composed of indoor / outdoor base stations, The indoor serving base station periodically broadcasting information of an adjacent base station for handover; And When the terminal moves indoors, the indoor serving base station may be selected even if the outdoor base station has a signal strength equal to or greater than a first handover reference value among the candidate base stations selected based on the signal strength measured by the neighbor base station search. If the signal strength of the content serving base station is not smaller than the second handover reference value, not performing the handover to the outdoor base station Handover control method comprising a. The method of claim 15, The first handover reference value is, And a handover reference value of the received signal strength received from the outdoor base station adjacent to the indoor serving base station. The method of claim 15, The second handover reference value is, And a handover reference value of the received signal strength received from the indoor serving base station currently being served by the terminal. The method according to any one of claims 15 to 17, The first handover reference value is, Handover control method, characterized in that greater than the second handover reference value. The method of claim 18, The terminal, When the indoor serving base station is being serviced, the signal strength of neighboring base stations is measured by searching for neighboring base stations, and even if the signal strength of the outdoor base station among neighboring base stations is greater than the first handover reference value, the indoor serving base station. The handover control method according to claim 1, wherein the handover is not performed to the outdoor base station if the signal strength of the signal is not smaller than the second handover reference value. A handover control method in a portable internet system composed of indoor / outdoor base stations, The indoor serving base station periodically broadcasting information of an adjacent base station for handover; And When the terminal moves from indoors to outdoors, the indoor serving base station is handed to an outdoor target base station having a signal strength equal to or greater than a handover reference value among 'a candidate base station selected based on the signal strength measured by searching for adjacent base stations in the terminal'. Steps to Over Handover control method comprising a. The method of claim 20, The handover reference value is, And a handover reference value of the received signal strength received from the outdoor target base station adjacent to the indoor serving base station. The method of claim 20 or 21, Performing, by the terminal, a network reentry procedure to the outdoor target base station Handover control method further comprising. In the indoor / outdoor portable Internet system with a processor for handover control, A function of periodically broadcasting information of an adjacent base station for handover by an outdoor serving base station; And When the terminal moves from outdoors to indoors, the indoor serving base station has an indoor target base station having a signal strength equal to or greater than a first handover reference value among 'a candidate base station selected based on signal strength measured by searching for neighbor base stations in the terminal'. The ability to perform a handover 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, The indoor serving base station periodically broadcasts information of an adjacent base station for handover; And When the terminal moves indoors, the indoor serving base station hands the indoor target base station having a signal strength equal to or greater than a first handover reference value among 'a candidate base station 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, The indoor serving base station periodically broadcasts information of an adjacent base station for handover; And When the terminal moves indoors, the indoor serving base station may be selected even if the outdoor base station has a signal strength equal to or greater than a first handover reference value. A function that does not perform handover to the outdoor base station unless the signal strength of the content serving base station is smaller than the second handover reference value A computer-readable recording medium having recorded thereon a program for realizing this. For handover control, indoor / outdoor portable Internet systems with processors, The indoor serving base station periodically broadcasts information of an adjacent base station for handover; And When the terminal moves from indoors to outdoors, the indoor serving base station is handed to an outdoor target base station having a signal strength equal to or greater than a handover reference value among 'a candidate base station selected based on the signal strength measured by searching for adjacent base stations in the terminal'. Function to do over A computer-readable recording medium having recorded thereon a program for realizing this.

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