KR100883113B1 - Method of vertical handover in a wireless communication system and system thereof - Google Patents

Abstract

The present invention relates to a handover method between heterogeneous networks and a system for providing the same. The present invention periodically updates neighboring base station information including neighboring base station information of homogeneous and heterogeneous networks, and when necessary for handover, homogeneous and heterogeneous networks. By providing a handover method and a system for handover to a base station capable of handover using neighboring base station information of a network, there is no need to perform a vertical handover separately when handover is impossible in a homogeneous network. Minimize latency and waste of resources.

Heterogeneous Network, Handover, Public Wireless Network, Mobile Internet, Wireless Communication System

Description

Method and vertical handover in a wireless communication system and system

1 is a view schematically showing the configuration of a wireless communication system according to an embodiment of the present invention.

2 is a view schematically showing an example of the configuration of a portable terminal according to an embodiment of the present invention;

3 is a flowchart illustrating a handover method between heterogeneous networks according to an embodiment of the present invention.

4 is a view for explaining a handover method of a mobile terminal according to an embodiment of the present invention.

TECHNICAL FIELD The present invention relates to a broadband wireless access (BWA) communication system, and more particularly, to a system and a method for providing handover between heterogeneous networks in a wireless communication system.

Commonly used technologies for providing data services to users in the current wireless communication environment include CDMA2000 Code Division Multiple Access 2000 1x Evolution Data Optimized (GPDMA), General Packet Radio Services (GPRS), and Universal Mobile Telecommunication (UMTS). 2.5th or 3rd generation cellular mobile communication technologies such as Service and Global System for Mobile communication (GSM) and Institute of Electrical and Electronics Engineers (IEEE) 802.11 wireless local area networks (LANs) And the like).

In addition, various short-range wireless access technologies, such as IEEE 802.16 based wireless LAN, have appeared in parallel with the evolution of the mobile communication technologies. The short-range wireless access technologies replace wired communication networks such as cable modems or digital subscriber lines (xDSLs) in hot spot areas or home networks, such as public places or schools, As an alternative for providing high speed data service in a wireless environment.

However, when providing a high-speed data service over the wireless LAN described above, there are limitations in providing public network services to users due to extremely limited mobility and narrow service area as well as radio wave interference.

Therefore, efforts to overcome the above limitations are being made at various angles. For example, researches on portable Internet technologies that complement the advantages and disadvantages of cellular mobile communication systems and wireless LANs are being actively conducted. As a representative example of the portable Internet technology, researches on a wireless broadband Internet (WiBro) system are being actively conducted. The WiBro system can provide a high-speed data service in a mobile environment such as a stationary environment, a walking speed, and a medium / low speed (about 60 km / h) by using various types of portable devices.

Currently, various services are being developed and provided based on the portable Internet. As the service area of the portable Internet system overlaps with the service area of the public wireless network (eg, cellular mobile communication system, etc.), the portable Internet providing mobile Internet service is provided. There is a need for an efficient handover scheme between a system and a public wireless communication system.

However, such a portable Internet system (for example, WiBro system) does not specifically present a handover method between heterogeneous networks. In particular, in the portable Internet system, only a handover between portable Internet systems, that is, a handover between homogeneous networks is mentioned, but a handover, that is, heterogeneous manganese, between a portable Internet system and another system (for example, a cellular mobile communication system). There is no specific plan for handover. For this reason, there is a problem in that the mobile terminal cannot provide a continuous service to the mobile terminal when moving to a heterogeneous network.

Therefore, when the portable terminal moves to a heterogeneous network different from the system to which it belongs, an efficient handover scheme between the portable Internet system and the heterogeneous system is required to provide continuous services to the portable terminal.

Accordingly, the present invention has been made to solve the above problems, an object of the present invention to provide a vertical handover method and system in a portable Internet system.

It is still another object of the present invention to provide a vertical handover method and system capable of minimizing resource waste and time delay in handover to a heterogeneous system.

A vertical handover method of a wireless communication system for achieving the above object is a vertical of a wireless communication system including a mobile terminal and a base station which is located adjacent to the current serving base station and the serving base station and having a heterogeneous network. A handover method, comprising: collecting, by a serving base station, neighbor base station information including neighbor base station information of homogeneous networks and heterogeneous networks; and serving base station advertisement message including neighbor base station information including the neighbor base station information. Transmitting to a mobile terminal, and when the handover is required, generating, by the portable terminal, a neighbor base station list including neighboring base stations which can be handed over among base stations of the neighbor base station information based on neighbor base station information of the heterogeneous network; And the mobile terminal leases the neighbor base station. Transmitting a handover request message including a network to the serving base station, generating, by the serving base station, a target base station list including target base station information according to the list, and the serving base station generating the target base station list. And transmitting a handover response message including the handover response message to the portable terminal, and the mobile terminal selects one of the target base station lists and performs a handover.

In the vertical handover method of a mobile terminal according to an embodiment of the present invention for achieving the above object, a process of updating neighbor base station information including information of homogeneous and heterogeneous networks by periodically receiving a neighbor base station advertisement message; And, when a handover is required, scanning neighboring base stations according to the neighbor base station information to generate a neighboring base station list capable of handover, and transmitting a handover request message including the neighboring base station list to the serving base station. And receiving a handover response message including a target base station list from the serving base station, and performing a vertical handover to any one base station of the target base station list.

In the vertical handover method of the serving base station according to the preferred embodiment of the present invention for achieving the above object, the neighbor base station information having the homogeneous network and heterogeneous network information is transmitted to the mobile terminal through the neighbor base station advertisement message. Receiving a handover request message including a neighbor base station list according to the neighbor base station information from the mobile terminal, generating a target base station list including target base station information according to the neighbor base station list; And transmitting a handover response message including the target base station list to the portable terminal, and disconnecting the portable terminal upon receiving a handover instruction message from the portable terminal.

The vertical handover system of the wireless communication system according to an embodiment of the present invention for achieving the above object, by periodically updating the neighbor base station information of the homogeneous network and heterogeneous networks of the heterogeneous network, if the handover needs A mobile station that creates a neighbor base station list with reference to the station information, transmits the created neighbor base station list to the serving base station through a handover request message, and performs vertical handover according to receiving a handover response message including target base station information. And a serving base station for transmitting a terminal and the neighbor base station information to the portable terminal, and transmitting the target base station information to the portable terminal.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In the following description, only parts necessary for understanding the operation according to the embodiment of the present invention will be described, and descriptions of other parts will be omitted so as not to obscure or clarify the gist of the present invention.

The terms or words used in the specification and claims described below should not be construed as being limited to the ordinary or dictionary meanings, and the inventors are appropriate to the concept of terms in order to explain their invention in the best way. It should be interpreted as meanings and concepts in accordance with the technical spirit of the present invention based on the principle that it can be defined. Therefore, the embodiments described in the specification and the drawings shown in the drawings are only one of the most preferred embodiments of the present invention, and do not represent all of the technical idea of the present invention, various modifications that can be replaced at the time of the present application It should be understood that there may be equivalents and variations.

For example, the handover method between heterogeneous networks described below uses a portable Internet (eg, wibro) network and a public wireless network (eg, cellular mobile communication network, etc.). However, the handover method between heterogeneous networks of the present invention is not limited to such a network or systems supporting such a network.

That is, the handover method between heterogeneous networks according to an embodiment of the present invention is not only the portable Internet and public wireless networks and the system supporting the same, but also IEEE (Institute of Electrical and Electronics Engineers) 802.1x, IEEE similar to the portable Internet system. It includes a network that can provide IP (Internet Protocol) based packet service to subscribers, such as 802.2x based wireless LAN, and the public wireless network includes GSM (Global System for Mobile communication) and General packet radio service (GPRS). Communication networks such as Enhanced Data GSM Environment (EDGE), Universal Mobile Telecommunications System (UMTS), Code Division Multiple Access (CDMA), Wideband Code Division Multiple Access (WCDMA), Wi-Fi, and 3rd Generation Partnership Project (3GPP) In addition, the present invention may be variously applied to the expanded form and modified forms of the above-described communication networks.

In addition, in the following description, in order to clarify the gist of the invention and to facilitate the explanation and understanding thereof, the portable terminal supports at least dual mode that can be connected to a general mobile communication network as well as a communication network such as a wireless LAN or a portable Internet. A terminal can be used.

In addition, the term "serving base station (BS)" or "serving radio access station" (hereinafter referred to as "RAS"), which will be described below, refers to a base station to which the mobile terminal currently belongs or As RAS, this indicates a base station or RAS that currently provides services to the mobile terminal. That is, the serving base station means a base station that currently provides a service to a mobile terminal in a public wireless network, and the serving RAS means a base station that currently provides a service to a mobile terminal in a portable internet network. Hereinafter, for convenience of description, the base station and the RAS will be collectively referred to as a 'base station'.

In addition, the term "target base station" described below means a base station to which the portable terminal is to move from the serving base station, i.e., handover and continuously receive a service.

The handover between heterogeneous networks described below indicates that the mobile terminal handovers from a current network to a network of different types in an overlay network in which two or more types of networks having different characteristics are mixed.

In addition, in the embodiment of the present invention, the mobile terminal is described as an example of a mobile communication terminal supporting dual mode or more, but the present invention is not limited thereto. Therefore, the portable terminal according to an embodiment of the present invention is a terminal supporting the above-described dual mode, preferably, a digital broadcasting terminal, a personal digital assistant (PDA), a smart phone, an IMT- 2000 (International Mobile Telecommunication 2000) terminal, Code Division Multiple Access (CDMA) terminal, Wideband Code Division Multiple Access (WCDMA) terminal, Global System for Mobile communication (GSM) terminal, Universal Mobile Telecommunication Service (UMTS) terminal, Cellular phone, It will be apparent to all telecommunications and multimedia devices such as Palmtop computers and laptops, and applications thereof.

In the proposed embodiment of the present invention, representative wireless broadband Internet (WiBro, Wireless Broadband Internet, hereinafter referred to as 'mobile Internet') network and public wireless network (for example, GPRS, WCDMA, HSDPA, Wi) We propose a handover method between hand-to-fi networks, that is, heterogeneous networks, and use it in combination with a vertical handover.

First, an example of a system and a portable terminal to which a function according to an embodiment of the present invention is applied will be described with reference to FIGS. 1 to 2.

1 is a diagram illustrating an example of a structure of a wireless communication system to which a function according to an embodiment of the present invention is applied. In particular, FIG. 1 shows an example of a structure in which the portable Internet system and the public wireless network communication system overlap.

Referring to FIG. 1, the portable Internet system 300 is an access control router (Access Control Router) that largely controls the functions of the RAS (310, 330) and the RAS to communicate wirelessly with the portable terminal 100 (Access Control) Router, hereinafter referred to as 'ACR'), and a core network (CN) 400 for relaying service interworking with the portable Internet system 300 and other external systems.

Each of the ACRs 310 and 330 is a system located between a core network (CN) 400 and the RASs 310, and includes a convergence sublayer (CS) function and an automatic retransmission (ARQ). Automatically Request) function and handover control function. ACRs 3110 and 330 also provide an interface with the core network 400.

The core network 400 identifies the location information of the ACRs 310 and 330, and also identifies the location information of the surrounding heterogeneous network (eg, the public wireless network 500), and the portable terminal 100. It is responsible for relaying connection-related information required for handover from the portable Internet system 300 to the public wireless network 500 or the handover from the public wireless network 500 to the portable internet system 300.

Each of the RASs 310 and 330 is a system located between the ACR 350 and the mobile terminal 100, and provides a wireless access interface that conforms to a wireless connection standard, for example, the Institute of Electrical and Electronics Engineers (IEEE) 802.16 standard. Therefore, the mobile terminal 100 connects to the RASs 310 and 330 according to the wireless access standard as described above to perform communication.

In addition, although not shown in FIG. 1, the mobile terminal 100 may connect to the public wireless network 500 to perform communication. That is, it is assumed that the portable terminal 100 according to an embodiment of the present invention supports at least dual mode for communicating with different communication systems.

An example of the configuration of the portable terminal 100 will be described with reference to FIG. 2 to be described later. The public wireless network 500 is representative of a network different from the portable Internet system formed by the public wireless network communication system. In the following description, terms of a public wireless network or a public wireless network communication system are mixed and described for convenience of description, but they refer to the same system. In particular, the network of all types of communication systems different from the portable Internet system 300 will be referred to collectively. It should be noted that it is shown.

The public wireless network 500 includes a base station supporting wireless section communication with the portable terminal 100, a base station controller (BSC) for controlling the base station and at least one base station controller when the data network service includes the data network service. And a switch (MSC, Mobile Switching Center) for performing a call exchange.

2 is a diagram schematically illustrating an example of a configuration of a portable terminal according to an exemplary embodiment of the present invention. Referring to FIG. 2, the portable terminal 100 to which a function according to an exemplary embodiment of the present invention is applied includes an antenna 110 and a portable Internet as shown in FIG. 2 to support a dual mode or more. A first module 120 for a service, a second module 130 for a public wireless network communication service, and a common module 140 are included.

The antenna 110 may simultaneously process a frequency band for a public wireless network communication service and a frequency band for a portable Internet service. In FIG. 2, the antenna 110 is illustrated in one configuration. However, the antenna 110 may be configured as a dual antenna or more corresponding to each system.

The first module 120 for providing a portable Internet service includes a duplexer 122 that operates as a band pass filter for processing each frequency and a first wireless transceiver 124 for separating transmission and reception radio waves into a predetermined frequency band. And a first modem unit 126 for processing a wireless section protocol with the portable Internet system 300.

The second module 130 for providing a public wireless network communication service includes a duplexer 132 that operates as a band pass filter for separating and processing respective frequencies, and a second wireless transmission / reception for separating transmission and reception radio waves into predetermined frequency bands. And a second modem unit 136 for processing a radio section protocol with the unit 134 and the public wireless network communication system 400.

The common module 140 operates as a central processing unit for controlling the first modem unit 126 and the second modem unit 136 and performs a multimedia function. An application processor, a memory, an input / output unit, other application processing units, and the It may include a control unit for performing the signal flow and control between each component. As described above, the portable terminal 100 supports two or more communication connection modes.

Next, a vertical handover method according to an embodiment of the present invention will be described. 3 is a flowchart illustrating a handover method between heterogeneous networks according to an embodiment of the present invention.

Before describing FIG. 3, it is assumed that the first base station 310 is a portable Internet base station and is a serving base station of the current mobile terminal. In addition, it is assumed that the second base station 330 is a base station of the same network as the first base station 310, and the third base station 500 is a base station of a heterogeneous network. In addition, it is assumed that the third base station 500 is a base station of a network supported by the second modem unit 136 of the mobile terminal 100. In addition, it is assumed that the second and third base stations 330 and 500 are neighbor base stations (BSs) of the first base station 310. In addition, it is assumed that the mobile terminal 100 requires a handover due to poor network conditions with the first base station 310 which is the current serving base station.

Referring to FIG. 3, the core network 400 collects neighbor base station information in step S301. The core network 400 may periodically collect information on neighboring base stations of the homogeneous and heterogeneous networks capable of handover, maintain the information for a predetermined period, and then update the information. In addition, the core network 400 may receive neighbor base station information through a backbone network.

Subsequently, the core network 400 transmits the neighbor base station information to the first base station 330 through the VHO_info_indication message in step S303. This transmission of neighbor base station information occurs periodically.

Then, the first base station 310 generates a Neighbor Advertisement (MOB_NBR-ADV) message using the received neighbor BS information. Then, the first base station 310 transmits the MOB_NBR-ADV message to the mobile terminal 100 in step S305. The MOB_NBR-ADV message is periodically transmitted to the mobile terminal and informs the potential mobile station of the initial base station and handover of the neighbor base station information. The MOB_NBR-ADV message will be described in more detail. Tables 1a to 1c below are for explaining MOB_NBR-ADV messages according to an embodiment of the present invention.

syntax size notes MOB_NBR-ADV_Message_format () { - Management Message Type = 53 8bit Skip-optional-fields bitmap 8bit Bit [0]: if set to 1, omit Operator ID field. Bit [1]: if set to 1, omit NBR BS ID field. Bit [2]: if set to 1, omit HO process optimization field. Bit [3]: if set to 1, omit QoS related fields. Bit [4] [7]: Reserved. (Deleted in the present invention) Bit [4]: if set to 1, omit N_VERTICAL_NBRS field. Bit [5]-[7]: Reserved. . . . . . . . . .

syntax size notes Configuration Change Count 8bit Incremented each time the information for the associated neighbor BS has changed.

syntax size notes ...     For (j = 0; j <N_NEIGHBORS; j ++) { - - ... } ... TLV Encoded Neighbor information variable TLV specific. N_VERTICAL_NBRS 8bit The count of the unique combination of Vertical Network Neighbor BSID, except the Neighbor BS of Mobile WiMax. For (j = 0; j <N_NEIGHBORS; j ++) { - -     Vertical Network Type 8bit Bit [0]: if set to 1, means 2.5G (ie GPRS) Bit [1]: if set to 1, means 3G (ie WCDMA) Bit [2]: if set to 1, means 3.5G (ie HSDPA) Bit [3]: if set to 1, means 2.5G (ie Wi-Fi) Bit [4] ■ [7]: Reserved.     Frequency info 8bit Frequency information about Vertical NBRs BS     Vertical NBRs BSID 24bit BS ID of Vertical Network NBRs     TLV Encoded Vertical Network NBR Info variable Vertical Network TLV specific    } }

Tables 1a to 1c add contents necessary for an embodiment of the present invention to a MOB_NBR-ADV message according to the IEEE 802.16 standard document, and a part not necessary for the description is omitted. Therefore, it should be noted that the MOB_NBR-ADV message includes neighboring base station information of the same type.

The MOB_NBR-ADV message has a field called Configuration Change Count (hereinafter referred to as Configuration Change Count) to distinguish the contents of a periodically sent message. That is, if the value of Configuration Change Count is the same, it indicates that MOB_NBR-ADV message is the same as MOB_NBR-ADV message received previously. If the value of Configuration Change Count is changed, MOB_NBR-ADV message is received previously Indicates that the content is different from.

The MOB_NBR-ADV message according to an embodiment of the present invention further defines an N_VERTICAL_NBR field indicating the number of neighbor base stations of a heterogeneous network capable of vertical handover, in addition to neighbor base station information of the same network. In addition, the MOB_NBR-ADV message further defines a Vertical Network Type field, a Frequency Info field, a Vertical NBRs BSID field, and a TLV Encoded Vertical Network NBR Info field as information corresponding to neighboring base stations of each heterogeneous network. For this reason, the mobile terminal 100 does not need to perform a procedure for obtaining neighbor base station information of a heterogeneous network in a situation where handover is not possible to the homogeneous network.

The Vertical Network Type field indicates the type of the network such as GPRS, WCDMA, HSDPA, and Wi-Fi network, and the type of network of the base station is in the order of 2.5G, 3G, 3.5G and Bit [0] to Bit [3]. It corresponds to 2.5G network. The Frequency Info field indicates physical channel frequency information of the corresponding heterogeneous base station. The Vertical NBRs BSID field is identification information of a corresponding heterogeneous base station, and has this base station identification (BSID) of the base station. In the TLV Encoded Vertical Network NBR Info field, unique information about a physical channel of a corresponding heterogeneous base station is recorded.

After transmitting the MOB_NBR-ADV message including the information to the mobile terminal 100, the first base station 310 receives a handover request (mobile station handover request) message from the mobile terminal 100 (hereinafter referred to as MOB_MSHO-REQ). It retains the handoverable base station and identification information of the base station until receiving.

Receiving the MOB_NBR-ADV message, the mobile terminal 100 interprets this to update the neighbor base station information of the same type and the different types. According to the neighbor base station information, the mobile terminal 100 scans the neighbor base station in step S307. Here, the scan means measuring the state of the base station for handover by the mobile terminal. That is, it refers to measuring a signal received from the neighbor base station with reference to neighbor base station information included in the MOB_NBR-ADV message.

The scans are called Received Signal Strength Indicator (RSSI), Carrier to Interference and Noise Ratio (CINR), and Quality of Service (QoS). It is made for any one or more of the elements), and may be made in addition to the above-described elements.

Through such a scan, the mobile terminal 100 may prepare a list of base stations capable of handover according to a desired RSSI, CINR, or QoS. For example, a neighbor base station whose RSSI value is equal to or larger than a predetermined request value is selected to create a list. This list will be referred to as 'neighbor base station list'. Here, it is assumed that the second and third base stations 330 and 500 are base stations capable of handover by their RSSI values. However, the present invention is not limited thereto. For example, the CINR or the QoS may be considered when preparing the handover capable base station list, and other than the above factors may be considered.

The mobile terminal 100 transmits a MOB_MSHO-REQ message including a list of neighbor base stations capable of handover to the first base station 310 in step S309. Transmit to network 400.

Then, the core network 400 transmits a handover notification (hereinafter, referred to as HO_notification) message to the second base station 330 which is the same base station in step S313 with reference to the list, and in step S315 A vertical handover notification (hereinafter referred to as VHO_notification) message is transmitted to the third base station 500, which is a base station of FIG.

The HO_notification message and the VHO_notification message may include requirements for the base station of the mobile terminal 100 (eg, bandwidth, RSSI, CINR, QoS, etc.), handover start estimated time, and the like. The base stations 330 and 500 that have received the HO_notification message and the VHO_notification message determine whether the service can be provided in consideration of requirements (RSSI, CINR, QoS, etc.), handover expected time, and the like.

Here, it is assumed that the second base station 330 is not serviceable, and the third base station 500 is in a serviceable state. Then, the second base station 330 transmits a handover notification response (HO_notification_response) message in step S317 in response to the HO_notification message, and the message indicates that the handover cannot be performed. (NACK, non acknowledge, hereinafter referred to as NACK) signal. In response to the VHO_notification message, the third base station 500 transmits a vertical handover notification response (hereinafter, referred to as VHO_notification_response) in step S319. ACK, acknowledge, ACK).

The core network 400 receiving the VHO_notification_response message including the ACK signal from the third base station 500 transmits the target base station information to the first base station 310 in step S321. Then, the first base station 310 creates a list based on the target base station information. This list will be referred to as a 'target base station list'. In this case, the first base station 310 recognizes the target base station capable of handover as the third base station 500 and includes the third base station 500 in the target base station list.

Next, the first base station 310 transmits a mobile handover response (MOB_BSHO-RSP) message including the target base station list and the corresponding target base station information to the mobile terminal 100 in step S323. .

Here, although only one base station is included in the target base station list, a plurality of base stations may be included in the target base station list, and neighbor base stations of homogeneous and heterogeneous networks may be included in the target base station list.

Next, the mobile terminal 100 transmits a mobile handover indication message (hereinafter referred to as MOB_HO-IND) to the first base station 310 in response to the MOB_BSHO-RSP message. The mobile terminal 100 may finally determine handover with a MOB_HO-IND message.

Herein, the mobile terminal 100 transmits the value of the HO_IND type field of the MOB_HO-IND message as '0b00' (serving BS release) to release the connection information and the connection with the first base station 310. Can be. The mobile terminal 100 transmits the identifier (Target_BS_ID) of the base station to be handed over, that is, the third base station 500 which is the target base station to the MOB_HO-IND message.

In the embodiment of the present invention, a description has been made on the assumption of the third base station 500 in the target base station list. However, the first base station 310 transmits a MOB_BSHO-RSP message including a plurality of base station information in the target base station list in step S323. 100, and in this case, the mobile terminal 100 may select one of the base stations of the target base station list as the target base station through the MOB_HO-IND message.

When the first base station 310 receives the MOB_HO-IND message, the first base station 310 recognizes that the mobile terminal 100 will hand over to the third base station 500, and the current connection information and connection established with the mobile terminal 100 in step S327. Release The connection information and the release of the connection may be executed immediately upon reception of the MOB_HO-IND message or the connection information may be maintained for a preset set time until a notification from the third base station 500 that the handover procedure is completed.

Next, the portable terminal 100 performs a vertical handover process of connecting to the third base station 500 in step S331. In this case, the vertical handover may be performed in various ways depending on the type of heterogeneous network, and thus the detailed description thereof will be omitted.

Hereinafter, a method for performing handover of a mobile terminal in the above-described vertical handover system will be described with reference to FIG. 4 and Table 1. 4 is a view for explaining a handover method of a mobile terminal according to an embodiment of the present invention. Herein, the mobile terminal 100 measures the RSSI of the current serving base station, that is, the first base station 310 and the serving base station 300, and the measured RSSI is less than a preset reference value. Assume Here, it should be noted that the criteria for handover occurrence is not limited to the RSSI. For example, depending on the situation, handover may occur to a high quality base station such as CINR and QoS.

Referring to FIG. 4, the mobile terminal 100 is performing the standby mode in step S401. During the standby mode of the mobile terminal 100, the first base station 310 transmits a MOB_NBR-ADV message to the mobile terminal. Then, the mobile terminal 100 receives it in step S403 and determines whether the message received in step S405 is an updated message.

In step S405, the mobile terminal 100 searches the Configuration Change Count field of the MOB_NBR-ADV message to determine whether the received message has updated information. The first base station 310 increases the value of the Configuration Change Count field each time information about the neighboring base station is updated. That is, each time the MOB_NBR-ADV message is updated, the value of the field is changed. Therefore, the mobile terminal 100 can know whether the message has been updated with reference to the value.

If the determination result in step S405 has updated information, the mobile terminal 100 proceeds to step S407 to decode the received MOB_NBR-ADV message to update the neighbor base station information.

On the other hand, if the determination result in step S405 does not have updated information, the mobile terminal 100 proceeds to step S409 to read the neighbor base station information of the previously received MOB_NBR-ADV message.

Then, in step S411, the mobile terminal 100 scans the neighbor base station based on the neighbor base station information obtained in the previous step. Here, the scan means that the mobile terminal 100 measures conditions for handover in order to select a neighboring base station that can be handed over according to neighboring base station information of the MOB_NBR-ADV message. In an embodiment of the present invention, RSSI is measured.

As a result of the scan, the portable terminal 100 prepares a list of neighboring base stations that can be handed over in step S413. For example, if the remaining amount of battery of the mobile terminal is to be handed over to a neighboring base station with a high RSSI value, the neighboring base stations whose RSSI value is greater than or equal to a preset request value are selected to create a list. As another example, if a user wants to hand over to a neighbor base station having a good quality of service such as a video call, a neighbor base station having a quality of service higher than or equal to a preset reference value is selected to create a list. In an embodiment of the present invention, a list is created by selecting neighboring base stations whose RSSI value is greater than or equal to a preset request value.

Next, in step S415, the mobile terminal 100 transmits a MOB_MSHO-REQ message including the neighbor base station list to the first base station 310.

Then, the first base station 310 delivers it to the core network 500, and the core network 400 performs a process of selecting a serviceable base station from the list of base stations capable of handover. This is done by the core network 400 through VHO_notification message transmission and VHO_notification_response message transmission using the backbone network, which will be omitted since the detailed description has been made with reference to FIG. 3.

When the core network 400 delivers the selected serviceable target base station information to the first base station 310, the first base station 310 uses this to prepare a target base station list. Subsequently, the mobile terminal 100 transmits a MOB_BSHO-RSP message including the target base station list.

Then, in step S417, the mobile terminal 100 receives the MOB_BSHO-RSP message including the target base station list, and selects one of the base stations in the target base station list as the target base station. Then, the mobile terminal 100 transmits a MOB_HO-IND message including the target base station information in step S419 in response to the MOB_BSHO-RSP message. The mobile terminal 100 may finally determine handover with a MOB_HO-IND message. That is, the handover may be performed, canceled and rejected, and the target base station may be finally determined.

In operation S417, the target base station list may include one or more base station information. In addition, it may include base station information of heterogeneous and homogeneous networks. In this case, the mobile terminal 100 may select a base station that is most advantageous to itself in step S419. For example, when base stations of homogeneous and heterogeneous networks are included in the target base station list, a base station having a higher RSSI value may be selected as the target base station.

The portable terminal 100 may cancel or reject the handover by setting the values of the HO_IND type field to '0b00' (HO cancel) and '0b10' (HO reject). In case of handover, the mobile terminal 100 releases the connection information with the serving base station by transmitting the value of the HO_IND type field as '0b00' (serving BS release). The mobile terminal 100 transmits the identifier (Target_BS_ID) of the target base station in the MOB_HO-IND message.

When the first base station 310 receiving the MOB_HO-IND message releases the connection with the mobile terminal 100, the mobile terminal 100 performs a vertical handover to connect with the target base station in step S421. In this case, the vertical handover may be performed in various ways depending on the type of heterogeneous network, and thus the detailed description thereof will be omitted.

As described above, when using the MOB_NBR-ADV message including the heterogeneous network information presented in the present invention, the mobile terminal periodically receives the neighbor base station information of the heterogeneous network as well as the neighbor base station information of the homogeneous network. It is possible to perform a handover to the most advantageous base station in.

In addition, since the handover to the heterogeneous network can be performed without performing the scan for the homogeneous network handover and the heterogeneous network handover, that is, without performing the vertical handover procedure separately, the delay time caused by the vertical handover. Can be minimized. In particular, the portable terminal supporting dual mode or more periodically supplies power to turn on the modem for the heterogeneous network to check the state of the heterogeneous network. Since the present invention does not need to supply such unnecessary power, there is an advantage of reducing waste of current consumption. In addition, since only the state of the handoverable base station provided by the MOB_NBR-ADV message is scanned, waste of current consumption can be reduced.

As described above, the present invention periodically updates the base station information of the heterogeneous network, so that handover to the heterogeneous network can be performed when handover is required.

In addition, unnecessary procedures, current consumption, and time for handover to heterogeneous networks can be minimized.

Claims (26)

In the vertical handover method of a wireless communication system comprising a mobile terminal and a base station of the mobile terminal and the current serving base station and the serving base station and having a heterogeneous network, Transmitting, by the serving base station, neighbor base station information having information of base stations of a homogeneous network and heterogeneous networks to a mobile terminal; Generating, by the portable terminal, a neighbor base station list including neighbor base stations capable of handover among neighbor base stations of the same and heterogeneous networks included in the neighbor base station information when handover is required; Transmitting, by the portable terminal, a handover request message including the neighbor base station list to the serving base station; Generating, by the serving base station, a target base station list including target base station information according to the list; Transmitting, by the serving base station, a handover response message including the target base station list to the mobile terminal; And performing the handover by the mobile terminal selecting one of the target base station lists and performing a handover. The method according to claim 1, The neighbor base station information of the heterogeneous network is A wireless communication system comprising the number of neighbor base stations of a heterogeneous network, the type of network, physical channel frequency information of the heterogeneous base station, identification information of the heterogeneous base station, and unique information of the physical channel of the heterogeneous network base station. Vertical Handover Method. The method according to claim 2, Generating the neighbor base station list, In accordance with the information, the base station having a predetermined value or more required by the mobile terminal in consideration of the channel state of each of the neighboring base stations and the service level that each of the neighboring base stations can service is included in the list. Vertical Handover Method of Wireless Communication System. The method according to claim 2, The process of generating the target base station list, Transmitting, by the serving base station, a notification message to neighbor base stations of the neighbor base station list through a backbone network; Receiving a response message corresponding to the notification message from the neighbor base stations; And including, in the target base station list, a neighbor base station transmitting the response message including a positive signal among the neighbor base stations. In the vertical handover method of a mobile terminal, Periodically receiving neighbor base station advertisement messages and updating neighbor base station information including information of base stations of the same kind and heterogeneous networks; Generating a neighbor base station list which is a list of base stations capable of handover by simultaneously scanning neighbor base stations of homogeneous networks and heterogeneous networks included in the neighbor base station information when handover is required; Transmitting a handover request message including the neighbor base station list to the serving base station; Receiving a handover response message including a target base station list from the serving base station; And performing a vertical handover to any one base station in the target base station list. The method according to claim 5, The process of updating the neighbor base station information, Periodically receiving the neighbor BS advertisement message; Determining whether the neighbor BS advertisement message is up to date; And updating the neighboring base station information stored in advance if the result of the determination is up-to-date. The method according to claim 6, The neighbor base station information of the heterogeneous network is And a serving base station receives neighbor base station information collected by a network core and periodically provides the same to the portable terminal. The method according to claim 6, The neighbor base station information of the heterogeneous network is The vertical number of the mobile terminal comprising the number of neighbor base stations of the heterogeneous network, the type of network, physical channel frequency information of the heterogeneous base station, identification information of the heterogeneous base station, and unique information of the physical channel of the heterogeneous network base station. Handover method. delete The method according to claim 6, Generating the handoverable neighbor base station list, And a base station having a received electric field strength measured by the scan equal to or greater than a reference value of the received electric field strength required by the mobile terminal in a list. The method according to claim 6, Generating the handoverable neighbor base station list, And a base station having a signal-to-noise noise ratio measured through the scan in a list including a base station having a value equal to or larger than a reference value required by the portable terminal. The method according to claim 6, Generating the handoverable neighbor base station list, And a base station whose quality of service measured by the scan is equal to or larger than a reference value required by the portable terminal in a list. delete The method according to claim 6, The target base station information is And wherein the serving base station confirms whether the serving base station is available through backbone network communication with the base stations in the list, and generates the service. In the vertical handover method of the serving base station, Transmitting neighbor base station information including information of base stations of the same type and multiple kinds of heterogeneous networks to the mobile terminal through a neighbor base station advertisement message; Receiving, from the portable terminal, a handover request message including a neighbor base station list, which is a list of base stations to which the portable terminal is capable of handover, among base stations of the same kind and multiple kinds of heterogeneous networks included in the neighbor base station information; Generating a target base station list including target base station information according to the neighbor base station list; Transmitting a handover response message including the target base station list to the mobile terminal; And disconnecting from the portable terminal when receiving a handover instruction message from the portable terminal. The method according to claim 15, The neighbor base station information of the heterogeneous network is The vertical number of the serving base station including the number of neighbor base stations of the heterogeneous network, the type of network, physical channel frequency information of the heterogeneous base station, identification information of the heterogeneous base station, and unique information about the physical channel of the heterogeneous network base station. Handover method. The method according to claim 16, The neighbor base station list is And a base station whose channel state and service level of the base station corresponding to the neighbor base station information are greater than or equal to a preset value. The method according to claim 16, The target base station list is A method for vertical handover of a serving base station, comprising: neighboring base stations that have sent an acknowledgment that service is possible through backbone network communication. The method according to claim 16, The target base station information is And wherein the serving base station confirms whether the serving base station is available through backbone network communication with the base stations in the list, and generates the serving base station. In the vertical handover system of a wireless communication system, Periodically updating neighboring base station information including base station information of homogeneous network and heterogeneous network, If a handover is required, a base station list, which is a list of base stations capable of handover, is simultaneously scanned by scanning base stations of the same type and multiple types of heterogeneous networks included in the neighbor base station information. Transmit the created neighbor base station list to the serving base station through a handover request message, A portable terminal performing vertical handover upon receiving a handover response message including target base station information; And Transmit the neighbor base station information to the mobile terminal, And the serving base station for transmitting the target base station information to the portable terminal. The method of claim 20, The neighbor base station information is A vertical handover system of a wireless communication system comprising the number of neighboring base stations, the type of network, physical channel frequency information of the heterogeneous base station, identification information of the base station, and unique information about the physical channel of the base station. The method according to claim 21, The serving base station And periodically updating the neighbor base station information and transmitting the information to the portable terminal. The method according to claim 21, The serving base station And vertical base station information including neighbor base station information of the heterogeneous network included in a neighbor base station advertisement message and transmitted to the portable terminal. delete The method according to claim 21, The serving base station And determining target base station information by determining whether service is possible through backbone network communication with the base station of the neighbor base station list. The method according to claim 21, The mobile terminal According to the neighbor base station information A vertical handover system of a wireless communication system comprising measuring a transmission signal of a neighboring base station and including a base station having a predetermined reference value or more in a list of neighboring base stations capable of handover.

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