KR101395020B1 - Vertical handover method of a mobile node in the wireless communication system - Google Patents

Abstract

The present invention relates to a vertical handover method of a mobile node in a heterogeneous mobile communication system. The vertical handover method includes the steps of: (a) collecting information on a candidate network capable of being handed over from an information server; (b) transmitting the QoS class information in use to the base station of the candidate network for the service flow, and checking whether there is a QoS class corresponding to the QoS class information being used for the service flow from the candidate network; (c) mapping a QoS class of the service flow to a QoS class of the corresponding candidate network if a QoS class corresponding to QoS class information in use for the service flow exists in the candidate network, And performing over.

Description

[0001] The present invention relates to a vertical handover method of a mobile station in a wireless communication system,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vertical handover method in a wireless communication system in which heterogeneous networks are superposed, and more particularly, to a method of guaranteeing QoS of a service flow in a vertical handover between heterogeneous networks. In particular, the present invention relates to a method of mapping different QoS classes in order to guarantee QoS of a service flow when performing vertical handover between an LTE-Advanced network and an 802.16m network.

Recently, the mobile communication network is being developed not only with the existing 3G WCDMA network and the WLAN but also with 4G LTE and WiMAX, and the mobile node is also equipped with a dual interface to support various networks. Among them, an efficient vertical handover technique of heterogeneous networks is attracting attention in order to provide high-performance services depending on the network situation or the user's situation. In IEEE, IEEE 802.21 MIHF working group was created to enable handover between IEEE and non-IEEE technologies, and standardization related to IEEE 802.21 MIHF working group was completed. IEEE 802.21 In order to enable smooth handover between networks with different handover policies using Media Independent Event Service (MIES), Media Independent Command Service (MICS), and Media Independent Information Service (MIIS) Technology standards.

FIG. 1 is a diagram exemplarily showing that a QoS for a service flow can not be guaranteed when performing a vertical handover according to a conventional method. As shown in FIG. 1, when a VoIP service flow having a high priority is applied to the conventional IEEE 802.21 MIHF standard, a proper priority can not be guaranteed when a vertical handover is performed.

FIG. 2 is a chart showing 802.16m QoS Class. FIG. Referring to FIG. 2, QoS classes in 802.16m are classified into (1) a BE (Best Effort) supporting low priority services such as E-mail and web browsing, (2) a data service (3) a real-time polling service (rtPS) for streaming services that is sensitive to jitter performance compared to nrtPS, and (4) a real-time polling service (Extended Real-Time Polling Service), (5) Unsolicited Grant Service (UGS), and (6) aGP Service, which is the first QoS class applied in 802.16m.

3 is a chart showing a QCI (QoS Class Indicator) for classifying QoS classes in an LTE (Long-term Evaluation) sequence. Referring to FIG. 3, the LTE series technology is classified into QoS classes by QCI, and is composed of a total of 9 QCIs. Each QCI is largely classified into GBR (Guaranteed Bit Rate) and Non-GBR types, and the service order is determined based on the priority.

4 is a standard framework of IEEE 802.21 MIHF when performing vertical handover. Referring to FIG. 4, the vertical handover according to the IEEE 802.21 MIHF standard consists of four stages. An information request / response step of acquiring information of neighboring networks from an information server (IS), a handover query resource request / response step of checking a resource to a selected target network, Query Resource Request / Response). If the handover is determined to be performed after the resource check, a new network is accessed through a handover commit request / response step, and a handover complete request / response step is performed And releases resources and disconnects from the previous network.

Due to the popularization of multimedia services and the introduction of VoIP technology, proper QoS guarantee at handover is an essential condition for users using these services. However, the IEEE 802.21 MIHF Framework standard does not mention different QoS class mappings. According to the IEEE 802.21 MIHF Framework technical standard, the step of acquiring the QoS information before performing the heterogeneous network vertical handover is mentioned, but there is no specific technical element therefor. Therefore, when performing handover between networks having different QoS classes, proper QoS class mapping may not be performed, which may result in a situation where the user can not guarantee QoS in use of the service flow.

(1) Korean Patent Laid-Open No. 10-2009-0015826 (2) Korean Patent No. 10-0979204 (3) Korean Patent Publication No. 10-2006-0120064

In order to solve the above-described problems, it is an object of the present invention to provide a method for guaranteeing quality of service (QoS) of a service flow in a vertical handover of a mobile station in a wireless communication system in which heterogeneous networks are superimposed.

According to a first aspect of the present invention, there is provided a vertical handover method of a mobile node in a heterogeneous mobile communication system, the method comprising the steps of: (a) Collecting information on an over-potential candidate network; (b) transmitting quality of service (QoS) class information in use to a base station of a candidate network for a service flow, and transmitting a QoS class corresponding to QoS class information in use for the service flow from the candidate network ; (c) mapping a QoS class of the service flow to a QoS class of the corresponding candidate network if a QoS class corresponding to QoS class information in use for the service flow exists in the candidate network, And performing over.

In the vertical handover method according to the first aspect, it is preferable that the vertical handover method determines whether QoS guarantee of the service flow is possible in the currently connected network, and does not perform vertical handover when QoS guarantee is possible Do.

In the vertical handover method according to the first aspect, in the step (b), the MS transmits the QoS class information currently being used for the service flow to the base station of the candidate network, A QoS class mapping table for the service flows is used to confirm whether there is a QoS class of a candidate network corresponding to the QoS class being used for the service flow,

The checking result preferably includes QoS class information of a candidate network corresponding to the QoS class being used for the service flow.

In the vertical handover method according to the first aspect, the mobile communication system may be applied to an IEEE 802.21 MIHF-based LTE-based network and an IEEE 802.16-based network.

In the vertical handover method according to the first aspect, in the step (b), the MS transmits QoS class information to the candidate network using the MIH_N2N_HO_Query_Resources.request standard message during the handover request request / response process based on the IEEE 802.21 MIHF, To the base station,

In step (b), it is determined whether or not the MS can guarantee QoS class of the service flow from the base station of the candidate network using the MIH_N2N_HO_Query_Resources.response standard message during the handover request request / response process based on the IEEE 802.21 MIHF .

A vertical handover method of a base station of each network in a heterogeneous mobile communication system according to a second aspect of the present invention includes the steps of: (a) mapping a QoS class for a service flow of each network to a QoS class mapping table ; (b) receiving QoS class information for a service flow from a mobile terminal; (c) checking whether there is a QoS class corresponding to the QoS class information received from the mobile terminal using the QoS class mapping table; (d) if the QoS class corresponding to the QoS class information received from the mobile terminal exists, transmitting the corresponding QoS class information to the mobile terminal; Respectively.

In the vertical handover method according to the second aspect of the present invention, the network is applied to an IEEE 802.21 MIHF-based LTE-based network or an IEEE 802.16-based network.

In the vertical handover method according to the second aspect of the present invention, in the step (b), during a handover request request / response process based on the IEEE 802.21 MIHF, the MS transmits the QoS class information (MIH_N2N_HO_Query_Resources.request) To the base station of the candidate network. In step (b), the mobile station transmits an MIH_N2N_HO_Query_Resources.Response standard message during the handover request request / response process based on the IEEE 802.21 MIHF to the base station of the candidate network, It is desirable to receive whether or not a QoS class guarantee is possible.

The vertical handover method according to the present invention can prevent an error in mapping a QoS class having a high priority to an unnecessarily high priority service flow by mapping an appropriate QoS class to a service flow at the time of performing a handover, The fairness of the system can be improved. Also, according to the present invention, an appropriate priority can be guaranteed by allocating a QoS class appropriate to a service flow having a high priority.

10 is a simulation scenario for verifying the performance of a wireless communication system to which a vertical handover according to the present invention is applied. Referring to FIG. 10, a mobile node (MN) moves from an LTE network to an 802.16m network and then to an LTE network to confirm whether a service flow can be mapped to an appropriate QoS class. The state of each service network assumes that the 802.16m network is in the current channel congestion state. 1000 VoIP service flows and 1000 FTP and Web service flows perform handover in random order.

11 shows that the present invention has better performance in mapping a VoIP service flow to a QoS class capable of guaranteeing real-time when a handover is performed, rather than a handover based on IEEE 802.21 MIHF standard and a handover performance based on SNR. In the case of the SNR applying algorithm according to the conventional algorithm (2) of FIG. 11, although the 802.16m channel is congested, since the handover is performed because the signal strength is good, the probability of guaranteeing the real time property of the VoIP service is lowered. The handover considering the signal strength and the transmission state of the mobile terminal according to the conventional algorithm (1) of FIG. 11 maps the service flow to the QoS class that can not guarantee the real time because there is no QoS information of the service flow after performing the handover A case occurs.

Accordingly, the vertical handover method according to the present invention proposes a QoS class mapping table and a signaling based on the IEEE 802.21 MIHF for guaranteeing QoS of a service flow when a mobile terminal performs vertical handover between heterogeneous networks, It is possible to prevent an erroneous QoS Class mapping that may occur when a vertical handover is performed through the MIHF standard. In addition, the method according to the present invention can improve QoS class mapping table information, upgrade software in a mobile terminal, and transmit a signaling message before handover without requiring a large change in a network operating on the existing IEEE 802.21 MIHF standard. It can also be implemented as a change.

As a result, the method according to the present invention can guarantee QoS by mapping a service flow to an appropriate QoS class while a mobile terminal performs a vertical handover. That is, in the case of the VoIP service, after the vertical handover, QoS can be guaranteed by mapping the QoS class to which delay and priority are important.

In addition, the vertical handover method according to the present invention does not perform the unconditional handover that the performance of the new network is good before the handover is performed, but does not perform the handover when the current network satisfies the QoS, The battery consumption of the mobile terminal due to the handover can be reduced.

FIG. 1 is a diagram exemplarily showing that a QoS for a service flow can not be guaranteed when performing a vertical handover according to a conventional method.
FIG. 2 is a chart showing 802.16m QoS Class. FIG.
3 is a chart showing a QCI (QoS Class Indicator) for classifying QoS classes in an LTE (Long-term Evaluation) sequence.
4 is a standard framework of IEEE 802.21 MIHF when performing vertical handover.
5 is a flowchart sequentially illustrating a vertical handover method of a mobile station according to a preferred embodiment of the present invention.
6 and 7 are diagrams illustrating exemplary QoS class mapping tables provided in base stations of respective networks according to a preferred embodiment of the present invention. FIG. 6 is a flowchart illustrating a handover from an LTE network to an 802.16m network FIG. 7 illustrates a QoS class mapping table used in a handover from an 802.16m network to an LTE network.
FIG. 8 illustrates a message MIH_N2N_HO_Query_Resources.request in a handover query resource request / response step to which a vertical handover method according to a preferred embodiment of the present invention is applied.
FIG. 9 illustrates a message MIH_N2N_HO_Query_Resources.response in a handover query resource request / response step to which a vertical handover method according to a preferred embodiment of the present invention is applied.
10 is a simulation scenario for verifying the performance of the present invention.
11 shows that the present invention has better performance in mapping a VoIP service flow to a QoS class capable of guaranteeing real-time when a handover is performed, rather than a handover based on IEEE 802.21 MIHF standard and a handover performance based on SNR.

Hereinafter, a vertical handover method capable of guaranteeing QoS of a service flow according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

5 is a flowchart sequentially illustrating a vertical handover method of a mobile station according to a preferred embodiment of the present invention.

A mobile terminal in a heterogeneous mobile communication system according to a preferred embodiment of the present invention is applied to performing a handover based on IEEE 802.21 MIHF in performing a vertical handover. Also, in the embodiment of the present invention, the overlapped heterogeneous networks are described based on the LTE-Advanced network and the 802.16m network, but this is only for convenience of explanation and understanding, and other wireless networks may be applied.

First, the mobile terminal accesses an information server to request information about neighboring networks and acquires the information (step 500). At this time, when handover is performed based on IEEE 802.21 MIHF, information about neighboring networks is obtained through information request / response to the information server. The mobile terminal acquires the information of the available networks periodically or through event triggering.

Next, it is determined whether QoS guarantee of the service flow is possible in the currently connected network (step 510). If it is possible to guarantee the QoS of the service flow in the currently connected network, the handover is terminated without performing handover (step 515) .

If QoS guarantee of the service flow is not possible in the currently connected network, the vertical handover is performed according to the IEEE 801.21 MIHF. In order to perform the vertical handover, a candidate network among the connectable neighbor networks is selected, and a handover query request / response process to the base station of the candidate network is performed The available bandwidth is checked (step 520).

Next, the QoS class information used by the current service flow is transmitted to the base station of the candidate network, and it is confirmed whether or not the QoS class mapped to the currently used QoS class exists in the candidate network. Lt; RTI ID = 0.0 > 530). ≪ / RTI > In this case, the base station of each network is provided with a QoS class mapping table for each of the heterogeneous networks in advance. The base station of the candidate network checks whether there is a QoS class mapped to the candidate network using the QoS class mapping table according to the request of the mobile station and transmits information about the mapped QoS class of the candidate network to the mobile station.

FIG. 6 and FIG. 7 are exemplary diagrams illustrating QoS class mapping tables provided in base stations of respective networks according to a preferred embodiment of the present invention. FIG. 6 is a diagram illustrating a QoS class mapping table that can be used when a mobile station handover from an LTE network to an 802.16m network according to a preferred embodiment of the present invention. Referring to FIG. 6, the QCI 1, 2, and 3 services in the LTE series network are services that are sensitive to jitter and delay, such as VoIP, and services that require continuous resource allocation in order to guarantee real-time performance. Therefore, UGS, aGP, ertPS maps the service flow. In addition, the QCI 4 service in the LTE network is mapped to the IEEE 802.16m rtPS rather than the QoS class having too high priority because it can guarantee service QoS by guaranteeing latency, jitter and minimum transmission rate as a unidirectional service. In addition, since QCI 6 in LTE network is used for video services such as buffered streaming, unidirectional latency and guarantee of minimum guaranteed rate are very important quality factors, so service flow is mapped to rtPS or nrtPS of IEEE 802.16m.

FIG. 7 is a diagram illustrating a QoS class mapping table that can be used in a handover from an 802.16m network to an LTE network according to a preferred embodiment of the present invention. Referring to FIG. 7, a UGS service of IEEE 802.16m maps a service having a highest priority (GBR) while guaranteeing a transmission speed, and aGP and ertPS are mapped to services having a high priority (GBR) So that it can guarantee real-time property. In the case of rtPS in IEEE 802.16m, it can be mapped to the appropriate QCI to support streaming service, and the nrtPS and BE service flows of IEEE 802.16m are mapped to non-GBR service with relatively low priority.

At this time, if there is no Qos class corresponding to the candidate network, another candidate network among the accessible neighbor networks is selected and the vertical handover is retried (step 545).

Next, the mobile station receiving the information on the QoS class mapped in the candidate network maps the service flow to the QoS class of the received candidate network (step 550). Next, the MS performs handover by performing a HO Commit Request / Response process to the BS of the candidate network, and performs HO Complete Request / Response with the currently connected network. The connection with the currently connected network is terminated, and the vertical handover to the candidate network is completed (step 560).

An exemplary case in which the vertical handover according to the preferred embodiment of the present invention is attempted as an IEEE 802.16m network in an LTE-Advanced network will be exemplified. The mobile station adds the QoS class information currently used by the service flow using MIH_N2N_Query_Resources.request, which is one of the messages of the handover query request / response process, and transmits the QoS class information to the base station of the IEEE 802.16m network. The base station of the IEEE 802.16m network that received this information from the mobile terminal confirms whether mapping to the QoS class appropriate to the QCI received from the mobile terminal is possible using the pre-configured QoS class mapping table as shown in FIG. For example, if the service flow is VoIP, if the received QCI is one of 1, 2, and 3, it is checked whether QoS mapping is possible with UGS, aGP, and ertPS. If the network status is QoS class mapping enabled, the QoS status is additionally set to 'success' through the MIH_N2N_Resources.response message as shown in FIG. If the QoS status is 'success' in the received MIH_N2N_Query_Resources.response, the mobile terminal completes the remaining handover process based on the IEEE 802.21 MIHF standard, and if it is 'fail', it attempts handover to another network.

Meanwhile, when the MS attempts a handover from the IEEE 802.16m network to the LTE-Advanced network, the same procedure as the handover from the LTE-Advanced network to the IEEE 802.16m network is performed. And the QoS table is used to confirm whether QoS is guaranteed or not.

In the conventional IEEE 802.21 MIHF, when the information of the neighboring network is acquired, the handover is performed to the better performance network unconditionally. However, the handover method according to the preferred embodiment of the present invention ensures QoS of the service flow even in the currently connected network And determines whether or not to perform the handover according to the determination.

The vertical handover method according to the present invention can be widely used in a mobile communication system in which heterogeneous networks are overlapped and can be widely used in a system for performing vertical handover while ensuring QoS of a service flow.

Claims (11)

In a vertical handover method of a mobile node in a mobile communication system in which heterogeneous networks are superimposed,
(a) collecting information on a candidate network capable of being handed over from an information server;
(b) transmitting quality of service (QoS) class information in use to a base station of a candidate network for a service flow, and transmitting a QoS class corresponding to QoS class information in use for the service flow from the candidate network ;
(c) mapping a QoS class of the service flow to a QoS class of the corresponding candidate network if a QoS class corresponding to QoS class information in use for the service flow exists in the candidate network, And performing an over-
After step (a), it is determined whether QoS guarantee of the service flow is possible in the currently connected network, and when the QoS guarantee is possible, the process is terminated without performing vertical handover. A vertical handover method of a mobile terminal.
delete The method of claim 1, wherein the step (b) comprises: transmitting QoS class information currently being used by the MS to the service flow to a base station of the candidate network; performing QoS class mapping for heterogeneous networks managed by the base station of the candidate network And determining whether there is a QoS class of a candidate network corresponding to the QoS class being used for the service flow using the table and receiving the confirmation result. 4. The method as claimed in claim 3, wherein the confirmation result includes QoS class information of a candidate network corresponding to a QoS class being used for the service flow. 2. The method of claim 1, wherein the mobile communication system is an IEEE 802.21 MIHF-based LTE-based network and an IEEE 802.16-based network superimposed on each other. The method of claim 5, wherein, in step (b), the MS transmits QoS class information to the base station of the candidate network using the MIH_N2N_HO_Query_Resources.request standard message during a handover request request / response procedure based on the IEEE 802.21 MIHF A vertical handover method of a mobile terminal capable of ensuring QoS of a service flow. 6. The method of claim 5, wherein, in step (b), the MS uses an MIH_N2N_HO_Query_Resoures.response standard message during a handover request request / response process based on the IEEE 802.21 MIHF, The method of claim 1, further comprising the step of: delete delete delete delete

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