KR100912419B1 - Handoff method and node device for hanoff in wireless network - Google Patents

Abstract

The present invention provides a gateway router capable of providing optimal performance when a handoff occurs in a multi-hop radio access network according to the quality of service (QoS) characteristics of a communication service as well as the hop number information. To provide a handoff determination method for selecting a path and a path. In addition, the present invention is to provide a performance improvement method that improves the basic forced handoff and the optimal handoff determination method considering the QoS.

Handoff, ad hoc network, quality of service (QoS), Internet access, multi-hop wireless access network

Description

Handoff method and node device for handoff in wireless network {Handoff method and node device for hanoff in wireless network}

1 is a diagram illustrating the structure of a multi-hop radio access network.

2 is a flowchart illustrating a general handoff process.

3 is a schematic diagram of a mobile node according to an embodiment of the invention.

4 is a diagram illustrating a forced handoff process considering QoS and handoff metric information delivered by an advertisement message according to an embodiment of the present invention.

5 is a flowchart for updating a routing table of a mobile node according to an embodiment of the present invention.

6 is a basic flowchart of a forced handoff considering QoS according to an embodiment of the present invention.

6A is an example of a time diagram according to the flowchart of FIG. 6.

FIG. 7 is a flowchart in which the concept of waiting time is applied to a basic flowchart of forced handoff (FIG. 6) considering QoS according to an embodiment of the present invention.

7A is an example of a time diagram according to the flowchart of FIG. 7.

8 is a flowchart in which the concept of valid time is applied to a basic flowchart of forced handoff (FIG. 6) in consideration of QoS according to an embodiment of the present invention.

8A is an example of a time diagram according to the flow chart of FIG. 8.

9 is a flowchart in which the concept of waiting time and valid time is applied to a basic flow chart of forced handoff (FIG. 6) considering QoS according to an embodiment of the present invention.

9A is an example of a time diagram according to the flowchart of FIG. 9.

FIG. 10 is a diagram illustrating an optimal handoff process considering QoS and handoff metric information delivered by an advertisement message according to an embodiment of the present invention.

11 is a flowchart illustrating six optimal handoff schemes considering QoS according to an embodiment of the present invention.

12 is a basic flowchart (case 1) of an optimal handoff considering QoS according to an embodiment of the present invention.

12A is an example of a time diagram according to the flowchart of FIG. 12.

FIG. 13 is a flowchart (case 2) in which a concept of temporary waiting time is applied to a basic flowchart of optimal handoff considering QoS according to an embodiment of the present invention.

13A is an example of a time diagram according to the flow chart of FIG. 13.

14 is a flowchart (case 3) to which the concept of guard time is applied to a basic flowchart of optimal handoff considering QoS according to an embodiment of the present invention.

14A is an example of a time diagram according to the flow chart of FIG. 14.

15 is a flowchart (case 4) in which the concept of guard time and temporary waiting time is applied to a basic flow chart of optimal handoff considering QoS according to an embodiment of the present invention.

15A is an example of a time diagram according to the flow chart of FIG. 15.

16 is a flowchart (case 5) in which the concept of guard time and valid time is applied to a basic flow chart of optimal handoff considering QoS according to an embodiment of the present invention.

16A is an example of a time diagram according to the flowchart of FIG. 16.

17 is a flowchart (case 6) in which the concept of guard time, valid time, and temporary waiting time is applied to a basic flow chart of optimal handoff considering QoS according to an embodiment of the present invention.

17A is an example of a time diagram according to the flow chart of FIG. 17.

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The present invention relates to a handoff decision method considering quality of service in multihop radio access networks. When the mobile node can connect to multiple gateway routers, the quality of service (QoS) is determined. Considering the quality of service, we provide a handoff decision method for selecting a gateway router that provides optimal performance.

A multi-hop radio access network is a network in which ad hoc networks in which multi-hop communication is performed without an infrastructure and the Internet are combined.

1 is a diagram illustrating the structure of a multi-hop radio access network.

As shown in FIG. 1, an ad hoc network is capable of wirelessly communicating mobile nodes collaborating, self-configured to perform ad hoc communication, and access to the Internet through a gateway router, even without a pre-established network infrastructure. Network. Early ad hoc network technologies were researched and developed for the purpose of providing communications in environments where the communications infrastructure has been destroyed by military communications or disasters. However, recently, due to the advantage that the location and time constraints when configuring the network than the existing infrastructure-based network, it is recognized as a wireless access technology suitable for the next generation communication environment. As a result, wireless mobile ad hoc networks are being applied in various areas from temporary network construction for special purpose to access technology of wired / wireless integrated networking technology.

In a multi-hop wireless access network, handoff occurs when you change gateway routers, so that gateway router discovery, gateway router selection, address configuration, registration, and communication tunnel configuration (tunnel setup), maintenance and handoff control.

Handoff schemes proposed in multi-hop radio access networks include forced handoff and optimized handoff. Forced handoff broadcasts a solicitation message when the mobile node is disconnected from the gateway router that is currently registered and used, and an advertisement message broadcasted by the gateway router that received it. Receive an advertisement message, find a gateway router and select the best gateway router. Forced handoff may operate in both a proactive router discovery technique in which a radio access router periodically broadcasts its information, or in a reactive router discovery technique in which information is broadcast at the request of a terminal. Optimal handoff is a technique for performing a handoff when a better radio access router is found, even if the current connection with the wireless access router is not broken.

In a multi-hop wireless access network environment supporting the Internet connection, communication uses various media information such as voice, audio, video, and data having various QoS characteristics as contents. In this environment, the existing handoff considering only the number of hops does not reflect the data transmission characteristics required for various types of information. For example, if path 1 and path 2 exist from the node being served to the gateway router supporting the Internet service, path 1 is 2 hops from gateway router 1, but the minimum bandwidth is 300 Kbps on the path. If path 2 is 3 hops from gateway router 2, but the minimum bandwidth is 800 Kbps, then path 1 with 2 hops is no better than path 2 with 3 hops. Because. Therefore, there is a problem in the existing handoff method based only on the number of hops.

The technical problem to be solved by the present invention is to solve such a problem, various criteria such as bandwidth, delay, etc. to satisfy the QoS characteristics of the communication service as well as the hop number information as the criteria for determining the handoff in a multi-hop radio access network The present invention provides a handoff decision method for selecting a gateway router and a path that exhibit optimal performance using the NN-S. In addition, the present invention is to provide a method and apparatus for performance improvement that improves the basic forced handoff and optimal handoff determination method considering QoS.

A handoff method considering QoS in a multi-hop radio access network according to an aspect of the present invention for achieving the above object,

a) delivering an advertisement message comprising QoS metric information and path; And

b) selecting a gateway router based on the information of the delivered advertisement message.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

In the present invention, handoff means that when a mobile node having mobility in a multi-hop access network environment moves or stops, a handoff is disconnected from a previously communicating gateway router and connected to a new gateway router capable of communicating (forced hand). Off), a series of processes that change the connection from an existing gateway router to a new gateway router (optimal handoff).

2 is a flowchart illustrating a general handoff process.

As shown in FIG. 2, the handoff scheme considering QoS proposed by the present invention selects a gateway router and a path having the minimum cost according to QoS characteristics after the gateway router discovery (S200), and handoffs to the selected gateway router. It is a method of performing a series of processes to execute (S250).

In the handoff scheme considering QoS in the multi-hop radio access network proposed by the present invention, the gateway router discovery (S200) is performed by a gateway node periodically or by a solicitation message of the mobile node. Is performed by receiving an advertising message broadcast by

The gateway router and path selection (S210), in addition to the path information and the hop number of the mobile nodes through which the advertisement message broadcasted by the gateway router passes, bandwidth and latency that may affect communication performance according to QoS characteristics. By performing various parameters such as delay, battery power, etc. as a metric, the communication cost is measured by the cost function proposed by the present invention and the gateway router and the path having the minimum cost are selected.

At this time, the process of address setting (S220), registration (S230), tunnel setting (S240) is in accordance with existing standards. In the address setting (S220), using the prefix address received from the gateway router generates a wide area address to be used when the mobile node communicates with the Internet. In registration (S230), the generated address and various information are notified to the selected gateway router. In the tunnel setup (S240), the route information is set between the gateway router and the mobile node.

The method of performing handoff to the selected gateway router (S250) is described in detail in various ways according to an embodiment of the present invention.

3 is a schematic diagram of a mobile node according to an embodiment of the invention.

As shown in FIG. 3, the mobile node 105-112 according to an embodiment of the present invention includes a transceiver 300 for sending and receiving packets, a packet processor 310 for processing header information of a packet to be transmitted and received, and the like. The weight register 320 used to set weights to the metric which is important according to the QoS characteristics of the service when calculating the cost, the parameter measuring unit 330 to collect information used as the metric, and the parameter register to record and manage the collected information ( 340) a routing table register which manages routing tables by processing information such as routing path information, hop count, minimum bandwidth, delay time, minimum battery amount, and the like, from the received advertisement message to the gateway router ( 350), a handoff processing unit 360 for analyzing a routing table to select a gateway router having a handoff status and a minimum cost and a route; .

4 is a diagram illustrating a forced handoff process considering QoS and handoff metric information delivered by an advertisement message according to an embodiment of the present invention.

In the forced handoff process considering QoS according to the embodiment of the present invention shown in FIG. 4, the mobile node 405 connected to the Internet 401 through a gateway router in the multi-hop wireless access network 400 is connected. If it is disconnected, the mobile node 405 broadcasts a solicitation message 409. The broadcasted solitation message is delivered through neighboring nodes 406 and 407, and the delivery process is repeated so that the solicitation message 409 is delivered to the gateway routers 402 and 403 connected to the Internet 401. . The solicitation message 409 includes address information and a sequence number of the mobile node 405 that broadcasted the message. The gateway router 402, 403 receiving the solicitation message broadcasts the advertisement message 410, 412. The advertisement message GR1_ADV 410 broadcast at the gateway router 402 is forwarded to the neighboring mobile node 406 one distance away. The advertisement message GR1_ADV 410 includes metric information such as hop count, minimum bandwidth, delay time, minimum battery amount, and path information of the mobile node in which the advertisement message has been delivered from the gateway router 402. For example, the advertisement message GR1_ADV 411 broadcast from the gateway router 402 may include hop count (1), minimum bandwidth (2 Mbps), latency (30 ms), minimum battery amount (70%), route information (gateway). Router GR1-mobile node 406) or the like.

The reason for broadcasting the advertisement messages 410 and 412 in the present invention is that the mobile node 405 requesting the advertisement message acquires the multipath information with the gateway router and the metric information of the path to determine the QoS characteristics required by the service. The best acceptable gateway router is to provide optimal handoff. In addition, the relay nodes relaying the broadcasted advertisement message can obtain the latest routing information and metric information along the path without overhearing, so that performance can be improved.

5 is a flowchart for updating a routing table of a mobile node according to an embodiment of the present invention.

The flow chart shown in FIG. 5 shows an advertisement message at all mobile nodes when the advertisement messages 410, 412 broadcasted at the gateway routers 402, 403 are received at the mobile nodes 405-408 as described above. A flow chart for updating the routing table by processing the route information and the metric information delivered by the. The same applies to both forced handoff and optimal handoff.

The routing table proposed by the present invention is different from the routing table generated by the routing protocol used in the existing ad hoc network, and is based on the metric information and the route information through which the advertisement message passes to provide a handoff considering QoS. It is composed. That is, it is a routing table that processes multipath information, manages various metric information, and processes cost information according to required services. The routing table can be applied differently depending on the routing method used in the ad hoc network. For example, when using a reactive routing protocol, the ad hoc on-demand distance-vector (AODV) protocol, the mobile node does not request a connection to the Internet or sends a route request (RREQ) message when the connection is lost during communication. Sending a messaging message and receiving an advertising message in response can be applied to real applications. When using the DSDV (Destination Sequenced Distance-Vector) protocol, which is a proactive routing protocol, routing can be performed considering the entire path with reference to the routing table proposed in the present invention.

Referring to the flowchart of FIG. 5 according to an embodiment of the present invention, when the mobile node 405 receives the advertisement messages 411 and 414, the mobile node broadcasts the received advertisement message 411. It is determined whether the router 402 is registered in the routing table (S500). If the router 402 is not registered in the routing table, a gateway router field is generated in the routing table (S501), and the advertisement message 411 is used. The received route information is stored, a route index indicating the information is added (S502), and the routing table is updated (S507).

If the router is already registered in the routing table, it is determined whether or not the sequence number of the received advertisement message 411 is greater than or equal to the sequence number most recently updated with the routing table (S503). In the case of discarding the advertisement message (S504), the process for the received advertisement message is terminated (411). Here, the sequence number is incremented by one each time the gateway routers 402 and 403 broadcast the advertisement messages 410 and 412, indicating whether the gateway routers 402 and 403 are up-to-date. You can decide.

If the sequence number of the received advertisement message is the same as or greater than the sequence number recently updated from the same gateway router, the route information registered in the advertisement message is checked to determine whether the routing route is looped. It is determined whether the same information exists compared with the address information (S505). If the same address information exists, it is determined as loop information and the advertisement message is discarded (S504).

If it is determined that the loop information is not determined, it is determined whether the route information from the gateway router registered in the received advertisement message exists in the routing table (S506). If it does not exist, new route information is registered in the routing table. The path index is added (S502).

When the processing for the route information is finished, the routing table update for processing the metric information is performed (S507). The routing table update (S507) includes a function of processing a received message and a routing table management function for deleting unnecessary information of the routing table.

The received message processing function is used for routing table management such as updating metric information such as hop count, minimum bandwidth, delay time, minimum battery amount, and recording registration time information according to an embodiment of the present invention. Looking at the minimum bandwidth information and the minimum battery information among the metric information, both information is used to convey the metric information of the path that has the greatest impact on the performance on the path from the gateway router to the current mobile node.

The routing table management function ensures that only valid information is managed by removing the routing table information that exceeds the valid registration time by leaving a valid registration time.

When the routing table update is completed (S507), the metric information updated in the routing table is included in the advertisement message and broadcasted to the neighboring mobile node.

6 is a basic flowchart of forced handoff in consideration of QoS according to an embodiment of the present invention. 6A is an example of a time diagram according to the flowchart of FIG. 6.

6 and 6A, the forced handoff begins with determining whether the mobile node has lost connection with the gateway router (S600). When the mobile node observes whether the connection with the gateway router is lost (610), and detects that the connection with the gateway router is lost (610), the mobile node detects that the connection with the gateway router is lost (610). Determines that it is not valid, broadcasts the solicitation message (S601, 612), and withholds the handoff decision and waits (S602) to receive the advertisement message of the gateway router during the waiting time (613).

When the waiting time 613 ends, it is determined whether there has been an update of the routing table during the waiting time 613 after the solicitation message has been broadcast (S603), and no update has occurred. If it is determined that the number of broadcasts of the solicitation message has exceeded the limit (S606), if it does not exceed, the solicitation message 409 is broadcasted (614) (S601), and the waiting time (616) again. In order to receive the advertisement message of the gateway router, the handoff decision is suspended and waited (S602). If the number of broadcasts of the solicitation message is more than the solicitation limit, the solicitation message is no longer broadcast and the connection attempt to the gateway router is terminated and the reason for termination is reported to the user.

If the routing table is updated according to the flow chart of FIG. 5 by the advertisement messages 617, 618, 619 received during the waiting time 616, the waiting time thereafter after the waiting time 616 has expired (620). It is determined whether there is an update of the routing table (S503). When there is an update of the routing table, a gateway router and a route having the smallest cost are selected from the updated routing table information (S604), and a handoff is performed (S605). do. If the number of broadcasts of the solicitation message exceeds a certain number of times (S606), the mobile node 405 determines that there is no gateway router that can communicate, and connects to the Internet through the gateway router. Terminate the attempt.

The cost function according to an embodiment of the present invention is calculated by the following equation (1).

Cost function

= Weight of hops x hops (hop_count)

+ Minimum bandwidth weight x 1 / minimum bandwidth (min_bandwidth)

+ Delay weight x delay

+ Minimum battery weight x 1 / minimum battery capacity (min_battery_power)

In Equation 1, if the advertisement message 411 received by the mobile node 405 is valid information, the routing table is updated (S603) and stored in the routing table 417 of the mobile node 405 to be used for the cost function calculation. The required communication cost can be calculated by applying weights to information on the number of hops, the minimum bandwidth, the delay time, and the minimum battery amount.

In addition to the metric considered in Equation 1, the cost function may further consider various metrics. Equation 1 is generalized in view of this characteristic is the same as equation (2).

In Equation 2, an index is composed of a pair of gateway routers and a path, so that even when receiving an advertisement message from the same gateway router, different paths may be used to distinguish each other.

Equation 3 is a generalized equation 2 in consideration of various services required for communication.

In Equation 3, a service indicates a type of a service required by a user of a mobile node, and according to the type of service, a weight applied to the same hop number may be different. For example, the weight according to the type of service is given differently depending on whether it is moving picture information, voice information or data transmission.

는 게이트웨이 라우터와 경로로 해당 서비스를 제공할 때의 비용을 의미한다. 측정 단위(metric)는 비용 계산에 사용되는 라우팅 정보의 종류를 의미한다.

는 해당 서비스에서 측정 단위의 가중치를 의미하고,

은 게이트웨이 라우터와 경로에서 라우팅 테이블에 등록된 측정 단위의 값을 의미한다. 예를 들어, 홉 수, 최소 대역폭, 지연 시간, 최소 배터리량 이외에도 사용하기 원하는 임의의 측정 단위를 추가하여 적용할 수 있다.In equation (3)

Means the cost of providing the service through the gateway router and the route. A metric refers to a kind of routing information used for cost calculation.

Means the weight of the unit of measurement in the service,

Means the value of the unit of measurement registered in the routing table in the gateway router and the route. For example, in addition to hop count, minimum bandwidth, delay time, and minimum battery amount, any additional unit of measurement may be added.

만을 1로 두고 나머지는 0으로 선택하여 계산을 하면 홉 수만이 고려된 비용이 계산되고, 홉 수와 최소 대역폭을 고려하여 비용을 계산한다면

:

=

로 하여 비용을 계산할 수 있다. 일반적으로, 비용 함수에서 홉 수가 커지면 비용은 증가하고, 지연 시간이 증가하면 비용은 증가한다. 그리고, 최소 대역폭이 커지면 비용은 감소하고, 최소 배터리량이 커지 면 비용은 감소한다. 이런 특성에 따라서, 최소 대역폭과 최소 배터리량의 정보는

의 값으로 1/대역폭으로 연산하거나, 특성을 감안한 가중치가 주어져야 한다.The result depends on how the weighting information is set in the cost function. For example, if you only consider hop count with the existing developed handoff decision method,

If you calculate only the number of hops and the minimum bandwidth, you can calculate the cost considering only the number of hops.

:

=

The cost can be calculated with In general, as the number of hops in the cost function increases, the cost increases, and as the delay increases, the cost increases. And as the minimum bandwidth increases, the cost decreases. As the minimum battery capacity increases, the cost decreases. Based on these characteristics, the minimum bandwidth and minimum battery information

The value of must be calculated as 1 / bandwidth or weighted to account for characteristics.

In this way, the cost function is used to calculate costs for all gateway routers and routes in the routing table, and select the gateway router and routes having the smallest cost among the costs (S604). The mobile node 405 performs handoffs S605 and 621 in the path with the selected gateway router.

Table 1, Table 2, Table 3, Table 4, and Table 5 are examples shown using tables for easy understanding of the above contents. Each table is in accordance with an embodiment of the present invention, and Table 1 is a table of bandwidth and delay times for other adjacent mobile nodes (one-hop mobile node) measured by mobile node 105.
Adjacent node (1 hop) Bandwidth Delay time MN (106) 400 Kbps 14 ms MN (107) 800 Kbps 6 ms MN (110) 500 Kbps 7 ms
Table 2 is its battery level table measured by the mobile node 105.
Measuring time Battery level 15:25:30 50%
Table 3 is a table that records the weight value of the unit of measurement that the mobile node 105 requests according to the service.
Type of service Hop_count Minimum bandwidth (min_bandwidth) Delay Battery capacity (min_battery_power) Video 10 40 10 20 Voice 10 5 40 10 File Transfer (FTP) 10 20 5 20
Table 4 is a routing table generated through table information that the mobile node 105 measures and manages itself, and advertisement messages received from neighboring nodes.
index Gateway router Path index Hops Bandwidth Delay time Battery level Registration time Sequence number One GR1 One 2 400 Kbps 30 ms 75% 15:19:30 X 2 GR1 2 3 500 Kbps 21 ms 25% 15:19:45 X 3 GR2 One 3 700 Kbps 21 ms 54% 15:19:34 X 4 GR2 2 2 500 Kbps 25 ms 25% 15:19:42 X 5 GR2 3 3 300 Kbps 40 ms 37.5% 15:19:50 X
Table 5 is a cost table in which weights according to services of Table 3 and information in the routing table of Table 4 are calculated as a cost function.
index Video service Voice service 1 (GR1,1) 176.6 168.83 2 (GR1,2) 211 161 3 (GR1,1) 145.2 139.65 4 (GR1,2) 205 170 5 (GR1,3) 256.7 233.3
Based on the flowchart shown in FIG. 6, performance improvements such as a method of applying a timeout extension, a method of applying a valid_time, and a method of simultaneously applying a waiting time extension and a valid time are possible.

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FIG. 7 is a flowchart in which the concept of waiting time is applied to a basic flowchart of forced handoff (FIG. 6) considering QoS according to an embodiment of the present invention. 7A is an example of a time diagram according to the flowchart of FIG. 7.

The flow diagram is then wait time (timeout _{n +1),} if not received the advertisement message for any current waiting time (timeout _n) in the flow chart of Figure 6 shown in Figure 7 is the same wait time by using the time increased than the previous wait time of The following flowchart shows how to reduce network load caused by expected solicitation message when using (timeout ₀ ). In this case, the increased waiting time may be determined by various algorithms. For example, it may be assumed that the waiting time is increased by twice the previous waiting time.

The time diagram shown in FIG. 7A is similar to FIG. 6A, but if a valid advertisement message has not been received during the default waiting time 713, the next waiting time 716 is a waiting time longer than the existing waiting time 713. It is used.

8 is a flowchart in which the concept of valid time is applied to a basic flowchart of forced handoff (FIG. 6) in consideration of QoS according to an embodiment of the present invention. 8A is an example of a time diagram according to the flow chart of FIG. 8.

The flowchart shown in FIG. 8 confirms whether the routing table has been updated during a valid time transfer from the time (815) of the connection failure with the gateway router (S800) (S801). In step S802, a gateway router having a network path is selected and a gateway router is selected through a procedure of broadcasting a solicitation message (S804) in the same manner as in the flowchart of FIG. 6. With this effective time-off, it is possible to solve the problem of delay, which is the disadvantage of forced handoff, when communication is lost during connection, and reduce the load on the network by reducing the resolution broadcasting. Do. At this time, the advertisement message broadcast during the effective time is possible by overhearing.

FIG. 9 is a flowchart in which the concept of waiting time extension and valid time is applied to a basic flowchart of forced handoff (FIG. 6) considering QoS according to an embodiment of the present invention. 9A is an example of a time diagram according to the flowchart of FIG. 9.

In the flowchart shown in FIG. 9, both the waiting time extension method of FIG. 7 and the effective time application method of FIG. 8 are applied to reduce a network load caused by a solitation message, and a reconnection time after a communication connection failure, which is a disadvantage of forced handoff. Is a flow chart that shows how to reduce this problem.

The flowchart shown in FIG. 9 checks whether the routing table has been updated during the valid time before the connection time with the gateway router (S900) (S900) (S901), and when the update is made, processes the same as the flowchart of FIG. If the update is not made, the process is performed in the same manner as in the flowchart of FIG. 7.

FIG. 10 is a diagram illustrating an optimal handoff process considering QoS and handoff metric information delivered by an advertisement message according to an embodiment of the present invention.

According to the embodiment of the present invention shown in FIG. 10, the delivery of an advertisement message of an optimal handoff considering QoS is performed as follows. The gateway router 1002 relaying communication with the Internet 1001 in the multi-hop wireless access network 1000 periodically broadcasts the advertisement message GR_ADV1 1009 and receives the broadcasted advertisement message GR_ADV1 1009. The mobile node 1006 adds its own route information and updates metric information such as hop count, minimum bandwidth, delay time, and minimum battery amount included in the received advertisement message through the routing table update (S507) of FIG. 5. The advertisement message GR_ADV1 1010 is broadcast to the neighboring mobile node 1005 by substituting the generated information. The mobile node receiving the advertisement message repeats a similar process and the advertisement message is delivered to the mobile node several hops through this process. The advertisement message having the looped path information is discarded as shown in S505 of FIG. 5. Processing of the received advertising message and updating the routing table are performed as in the flowchart of FIG. The delivery method after the advertisement message is broadcast in the above-described gateway router is the same as the procedure after the gateway router broadcasts the advertisement message after receiving the solicitation message in FIG. 4.

11 is a flowchart illustrating six optimal handoff performance improvement techniques considering QoS according to an embodiment of the present invention.

As shown in FIG. 11, each technique is classified according to whether a guard time (guard_time) is considered, a valid time is considered, or a temporary waiting time is considered. In the present invention, the guard time is used to prevent the handoff for a predetermined time after the handoff, to prevent performance degradation due to frequent handoff. The valid time is used only when the guard time is applied. The information considered in the handoff is limited to routing information updated by the advertisement message during the valid time before the guard time expires. When the valid time is used, the advertisement message received during the guard time can be utilized to select the optimal gateway router to reduce the handoff time. Temporary latency is used to prevent performance degradation due to frequent handoffs that can occur when advertisement messages broadcast by multiple gateway routers arrive with a small time difference.

As shown in FIG. 11, case 1 is a basic type of optimal handoff technique in which guard time, valid time, and temporary waiting time are not all considered.

12 is a basic flowchart (case 1) of an optimal handoff considering QoS according to an embodiment of the present invention. 12A is an example of a time diagram according to the flowchart of FIG. 12.

12A is a flowchart of FIG. 12A, as shown in FIG. 12A, a gateway router and an updated gateway currently selected and used each time an advertisement message periodically broadcasted by a gateway router is received to update a routing table (S1200). By comparing the cost of the router, the flow chart is a flowchart illustrating a method of performing a handoff by selecting a gateway router having a minimum cost and a path (S1201), determining whether a handoff is necessary (S1202). When the new gateway router is selected, the handoff is performed using the optimal path to the selected gateway router (S1203). When the existing gateway router is selected, the routing path is modified to the optimal path based on the updated information (S1204). Through the technique shown in FIG. 12, the mobile node performs handoff as soon as it finds an optimal gateway router.

12A shows that handoff is performed to the gateway router broadcasting the received advertisement message, and connection maintenance indicates that the existing gateway router is used as it is. Even when using an existing gateway router, if better route information is obtained by the advertisement message, a route change may be requested.

FIG. 13 is a flowchart (case 2) in which a concept of temporary waiting time is applied to a basic flowchart of optimal handoff considering QoS according to an embodiment of the present invention. 13A is an example of a time diagram according to the flow chart of FIG. 13.

13 is a flowchart of FIG. 13A, when the routing table is updated (S1300) after the last temporary waiting time (handoff determination time point S1307), the temporary waiting time starts (S1301). It is a flowchart showing a technique of selecting a gateway router having the minimum cost by comparing the updated routing information until the end (S1305) and the cost of the currently used gateway router (S1305). The process after the selection of the gateway router is the same as the flowchart of FIG.

14 is a flowchart (case 3) to which the concept of guard time is applied to a basic flowchart of optimal handoff considering QoS according to an embodiment of the present invention. 14A is an example of a time diagram according to the flow chart of FIG. 14.

In the flowchart shown in FIG. 14, as shown in FIG. 14A, routing information updated during the guard time S1405 started after performing the handoff operation (S1404) is not considered when selecting the gateway router (S1400), and the guard time ends. After that, when the routing table is updated (S1401), a flow chart of a method of selecting a gateway router by comparing costs with a current gateway router is shown. Same as the basic flow chart of FIG. 12 except that updated routing information during guard time is not taken into account.

15 is a flowchart (case 4) in which the concept of guard time and temporary waiting time is applied to a basic flow chart of optimal handoff considering QoS according to an embodiment of the present invention. 15A is an example of a time diagram according to the flow chart of FIG. 15.

15 is a flowchart to which the temporary waiting time applied to FIG. 13 and the guard time applied to FIG. 14 are applied, as shown in FIG. 15A. The temporary waiting time is started (S1502) when the routing table is updated (S1501) after the guard time ends (S1500). The process from the temporary wait start until the handoff execution (s1509) is the same as the flowchart of FIG. 13. The guard time is started (S1510) when the handoff is performed (S1509) as in the flowchart of FIG. 14, and the routing information updated during the guard time is not considered in selecting the gateway router. Therefore, it is possible to prevent performance degradation due to frequent handoff through the use of temporary waiting time and guard time.

16 is a flowchart (case 5) in which the concept of guard time and valid time is applied to a basic flow chart of optimal handoff considering QoS according to an embodiment of the present invention. 16A is an example of a time diagram according to the flowchart of FIG. 16.

16 is a flowchart to which a guard time applied to FIG. 14 and a valid time that can be applied when there is a guard time are applied, as shown in FIG. 16A. The guard time is started (S1605) when the handoff is performed (S1604) as in the flowchart of FIG. 14, and the routing information updated during the guard time is not taken into consideration when selecting the gateway router. However, when the guard time ends (S1600) because the valid time is applied, if the routing information updated by the advertisement message exists during the valid time before the guard time ends (S1601), the routing information updated during the valid time is considered. . In this case, the mobile node selects the gateway router by comparing the updated information during the valid time with the cost of the currently used gateway router (S1602). When a new gateway router is selected (S1603), handoff is performed (S1604) and guard time is started (S1605). If the existing gateway router is selected or there is no updated routing information during the valid time, the same as after the guard time termination of the flowchart of FIG. 14.

17 is a flowchart (case 6) in which the concept of guard time, valid time, and temporary waiting time is applied to a basic flow chart of optimal handoff considering QoS according to an embodiment of the present invention. 17A is an example of a time diagram according to the flow chart of FIG. 17.

17 is a flowchart of FIG. 13 to which a temporary waiting time is applied to the flowchart of FIG. 16 to which a guard time and an effective time are applied, as shown in FIG. 17A. 17 is a flow diagram after the guard time is terminated when the selected gateway router is an existing gateway router even if the guard time is terminated (S1700) and there is no update of the routing table during the valid time, or there is an update of the routing table during the valid time. When the table is updated (S1706), the process after the routing table update is the same as the flowchart of FIG. The portion to which the flowchart of FIG. 13 is not applied is the same as the flowchart of FIG. 16. Thus, the flow diagram of FIG. 17 shows that if the existing connection is better, even if the guard time 1720 ends and the advertisement message 1722 is received during the valid time 1721 as shown in the time diagram of FIG. 17A. If the new gateway router of the advertisement message (1736, 1737) received during the validity time (1735) is selected (1723), handoff is performed (1738). When the mobile node is not in the guard time interval, receiving the advertisement message 1724 always starts a temporary wait time 1725, and when the temporary wait time ends, compare the existing gateway router with the newly updated information for optimal Select the gateway router to perform a handoff.

As described above, according to the present invention, by selecting a gateway router in consideration of multiple QoS metrics simultaneously in a multi-hop wireless access network, forced and optimal handoff may be performed while satisfying various QoS requirements according to services.

Claims (24)

Receiving an advertisement message including route information broadcast from a plurality of gateway routers located on a wireless network, metric information about a route from the gateway router, and a sequence number indicating the number of broadcasts of the gateway router; Updating data included in a routing table of an index structure based on the sequence number and route information included in the advertisement message; Calculating a communication cost for the route based on the data constituting the metric information included in the updated routing table and the weights assigned to the data; And Connecting to a gateway router that broadcasts an advertisement message including metric information for minimizing the communication cost. The method of claim 1, Updating data included in the routing table, If the identification number of the gateway router that broadcasted the advertisement message is larger than the sequence number registered in the routing table corresponding to the identification number, and the route information included in the advertisement message is not registered in the routing table, Changing route information registered corresponding to an identification number into route information included in the advertisement message; Registering each data constituting metric information included in the advertisement message in the routing table to correspond to the identification number; And And removing data having a predetermined valid registration time elapsed from the data included in the routing table. The method of claim 2, If the identification number is not included in the routing table, a gateway router field including the identification number is generated, and route information included in the advertisement message is registered in the routing table so as to correspond to the identification number. Handoff method. The method of claim 1, Receiving a broadcast message from a gateway router that has accepted a request message among the plurality of gateway routers. The method according to any one of claims 1, 2 or 4, And updating the data included in the routing table when the advertisement message is received within a preset waiting time from a connection termination point with a previously connected gateway router. The method of claim 5, If the advertisement message is not received during the waiting time, the advertisement is included in the routing table based on the information included in the received advertisement message until the extended waiting time longer than the waiting time elapses after the end of the waiting time. And the updated data is updated. The method according to any one of claims 1, 2 or 4, And updating the data included in the routing table based on the information included in the advertisement message received during the preset valid time before the connection termination with the gateway router. The method of claim 1, And receiving broadcast messages periodically broadcasted from the plurality of gateway routers, respectively. The method according to claim 1 or 8, Handoff, characterized in that for updating the data contained in the routing table on the basis of the information contained in the received advertising message from the time when the data contained in the routing table is updated until a predetermined temporary waiting time elapses. Way. The method according to claim 1 or 8, A handoff method comprising updating data included in the routing table based on information included in an advertisement message received after a preset boundary time elapses from a connection point to a gateway router. . The method of claim 10, And updating the data included in the routing table based on the information included in the advertisement message received during the preset valid time before the end of the boundary time. The method according to claim 1 or 2, The communication cost is calculated by the following equation A Handoff method: Equation A

Here, C is a communication cost for the path from each gateway router, W is each data constituting the metric information for each path, and R is a weight assigned to the data. A transceiver for receiving an advertisement message including route information broadcast from a plurality of gateway routers located on a wireless network, metric information about a route from the gateway router, and a sequence number indicating the number of broadcasts of the gateway router; A routing table register for updating data included in a routing table of an index structure based on a sequence number and route information included in the advertisement message; And An advertisement including metric information for calculating a communication cost for the route based on the respective data constituting the metric information included in the updated routing table and a weight assigned to the data, and minimizing the communication cost And a handoff processing unit for connecting to the gateway router that has broadcast the message. The method of claim 13, The routing table register, If the identification number of the gateway router that broadcasted the advertisement message is larger than the sequence number registered in the routing table corresponding to the identification number, and the route information included in the advertisement message is not registered in the routing table, Changing route information registered corresponding to an identification number into route information included in the advertisement message; Registering each data constituting metric information included in the advertisement message in the routing table to correspond to the identification number; And And removing data having a valid valid registration time elapsed from the data included in the routing table, by updating the data included in the routing table. The method of claim 14, If the identification number is not included in the routing table, a gateway router field including the identification number is generated, and route information included in the advertisement message is registered in the routing table so as to correspond to the identification number. Node device. The method of claim 13, And the transceiver receives a broadcast message from the gateway router that has accepted the request message among the plurality of gateway routers. The method according to any one of claims 13, 14 or 16, And the routing table register updates data included in the routing table when the advertisement message is received within a preset waiting time from a connection termination point with a previously connected gateway router. The method of claim 17, If the advertisement message is not received during the waiting time, the advertisement is included in the routing table based on the information included in the received advertisement message until the extended waiting time longer than the waiting time elapses after the end of the waiting time. And a node device for updating the data. The method according to any one of claims 13, 14 or 16, And the routing table register updates data included in the routing table based on information included in an advertisement message received for a predetermined valid time before connection termination with the gateway router. The method of claim 13, And the transceiver receives a broadcast message periodically broadcasted from the plurality of gateway routers, respectively. The method of claim 13 or 20, The routing table register updates the data included in the routing table based on the information included in the received advertisement message from the time when the data included in the routing table is updated until a preset temporary waiting time elapses. Node device characterized in that. The method of claim 13 or 20, The routing table register updates the data included in the routing table based on the information included in the advertisement message received after a preset boundary time elapses from the time when the connection to the gateway router was previously performed. Node device. The method of claim 22, And updating the data included in the routing table based on the information included in the advertisement message received during a preset valid time before the end of the boundary time. The method according to claim 13 or 14, The communication cost is calculated by the following equation A node device: Equation A

Here, C is a communication cost for the path from each gateway router, W is each data constituting the metric information for each path, and R is a weight assigned to the data.

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