KR20100115133A - Routing method and apparatus in communication network containing wireless network - Google Patents

Abstract

PURPOSE: A routing method and a device in a communication network including a wireless network are provided to adaptively perform routing in a state of a changed wireless link that changes dynamically, thereby improving communication performance. CONSTITUTION: A cost calculator sets a cost value of a link infinitely if a corresponding link of an average bit error rate is higher than a T_TH(Triggering Threshold)(240,250). If an average BER of the link is not higher than the T_TH, the cost calculation unit calculates the cost of the link by using a defined cost function according to a link propagation delay(260). A routing unit performs routing according to the cost value.

Description

Routing method and apparatus in communication network containing wireless network

The present invention relates to a routing apparatus and method in a communication network, and more particularly, to an apparatus and method for performing routing in consideration of a change in state of a radio link in a communication network including a wireless network.

In general, the routing technology for the military tactical network is a technology that selects only the shortest path in the military tactical network environment consisting of the wired network only. Representative routing protocols that perform such routing techniques include the Routing Information Protocol (RIP) and the Open Shortest Path First (OSPF) protocol.

RIP is a typical routing protocol using a distance-vector algorithm. The RIP manages a route table using a request message and a response message.

For example, the router sends a request message requesting the whole destination information or the specific part of the destination information. The request message is sent when the router is first booted or when certain specific destination information is no longer valid.

Meanwhile, the response message includes information on the actual destination and is periodically transmitted (once every 30 seconds, the entire destination information is transmitted to the neighbor router) or transmitted in response to the request message of the other party.

The router receiving the response message determines the shortest path to the destination by using the information obtained through the response message. The determined shortest path is then maintained as the path to the destination. In this case, the shortest path is a path having the smallest hop number among several paths to the destination.

On the other hand, if the information about the specific destination is not transmitted from the neighbor router for a certain period (180 seconds), the router considers the specific destination as an invalid destination. Therefore, the router deletes the information corresponding to the specific destination from the route table and informs the neighboring router of this.

However, the RIP has a slow convergence phenomenon due to the use of the distance-vector algorithm. This slow convergence may cause an infinite loop between routers, which may cause a routing loop in which route information is not transmitted. In the communication network applying RIP, the maximum number of hops is limited to 15 hops, and methods such as Split Horizen, Hold down, and Poison Reverse Update are used. Nevertheless, RIP is difficult to apply to large communication networks due to maximum hop count constraints.

Therefore, large communication networks use the OSPF protocol using a link-state algorithm.

In a communication network using the OSPF protocol, a router recognizes a neighbor router using a Hello message. The Hello message is exchanged with neighbor routers when the router first boots up. Thereafter, the router floods information about its route table to neighboring routers periodically through link state updates (LSU) messages or when its link state changes (ie, the link is broken or the router goes down). do.

As such, in a communication network using the OSPF protocol, by exchanging LSU messages between routers, all routers can maintain the same topology information. Therefore, within a communication network using the OSPF protocol, each router considers itself as the center of the network and constructs the shortest path tree. Each router creates and manages its own route table based on the configured shortest route tree. At this time, the shortest path tree is generated by the Dijkstra Horst Path First (SPF) algorithm, and the cost of each link is calculated by Equation 1 below.

Cost of each link = 100 Mbps / original bandwidth of each link

As discussed above, routing protocols considering wired networks have various purposes and characteristics, but all commonly use the cost of the link for the shortest path routing.

Therefore, in order to use the existing routing protocols in a wireless tactical network environment, the following matters should be considered.

First, since the existing routing protocol assumes only a wired network, the data path is changed only when a change in network topology is detected. However, since the military tactical network environment includes a wireless network, it is necessary to be able to adaptively change the data paths not only for network topology changes but also for dynamically changing state of wireless links.

And since military tactical network plays the role of backbone network, it should be able to service as many flows as possible without compromising service quality. However, because the existing routing protocol selects only the shortest path, all flows are biased to the shortest path, which increases the probability of congestion in the path.

In addition, the most important requirements for tactical routing in a military tactical network environment are the stability and viability of the data path. However, because the existing routing protocol only considers the wired network, routing cannot be performed considering the stability and survivability of the path. For example, in a military tactical network environment, even if data is transmitted through the shortest path, if the path is unstable or the link on the path is lost due to an enemy attack, data communication may become impossible.

The present invention provides a routing apparatus and method for adaptively performing routing to a dynamically changing state of a wireless link in a communication network including a wireless network.

In addition, the present invention provides a routing apparatus and method that can improve the communication performance and network resource utilization by performing routing in a high survivability and stability path in a communication network including a wireless network.

In order to solve the above technical problem, a routing method in a communication network including a wireless network according to the present invention uses a cost function defined according to an available bandwidth and an average bit error rate of a corresponding link for each connected link. Calculating a corresponding cost; And performing routing according to the cost corresponding to each of the calculated links.

Here, the cost function may be defined according to the deviation of the average bit error rate of the corresponding link together with the available bandwidth and the average bit error rate.

Further, the cost function may be defined according to the link propagation delay of the corresponding link along with the available bandwidth, the average bit error rate and the deviation of the average bit error rate.

In addition, the available bandwidth or the deviation of the average bit error rate or the average bit error rate may be normalized through a logarithmic function and reflected in the cost function.

In this case, the cost function may be defined according to the following equation.

Further, the average bit error rate may be calculated as an exponentially weighted moving average of the currently measured bit error rate and the previously calculated average bit error rate.

In addition, the deviation of the average bit error rate may be calculated as an exponentially weighted moving average of the deviation of the currently measured bit error rate and the previously calculated deviation of the average bit error rate.

The routing method further includes determining whether a change occurs in which the average bit error rate of at least one of the connected links is higher or lower than a predetermined threshold, and wherein calculating the cost comprises: May be performed when is generated.

In the determining of whether the change occurs, checking whether a change occurs in which the average bit error rate is higher than the predetermined threshold among the links being used as a data path among the connected links, and checking the average bit among the connected links. It can be checked whether a change occurs in which the error rate is lower than the predetermined threshold.

In order to solve the above technical problem, a routing device in a communication network including a wireless network according to the present invention includes: a routing unit configured to perform routing according to a cost corresponding to each link; And a cost calculator configured to calculate a cost corresponding to each link by using a cost function defined according to the available bandwidth and the average bit error rate of the corresponding link for each link connected to the routing device.

According to the present invention described above, in a communication network including a wireless network, routing can be adaptively performed in response to a dynamically changing state of a wireless link, and routing can be performed through a path having high survivability and stability, thereby improving communication performance and network resource utilization rate. Can improve.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description and the accompanying drawings, substantially the same components are denoted by the same reference numerals, and redundant description will be omitted. In addition, in the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

1 illustrates a configuration of a routing device in a communication network including a wireless network according to an embodiment of the present invention. The routing device according to the present embodiment includes a cost calculator 120 for calculating a cost corresponding to each link connected to the routing device, and routing according to the cost value for each link calculated by the cost calculator 120. It comprises a routing unit 110 for performing a, and a data transmission unit 130 for transmitting data by wireless or wired to the data path according to the routing of the routing unit 110.

The data transmitter 130 periodically transmits the available bandwidth for each link connected to the routing device and the bit error rate (hereinafter, referred to as BER) to the cost calculator 120.

The cost calculator 120 has available bandwidth and BER values for each link transmitted from the data transmitter 130, and the available bandwidth, average BER, average BER deviation of each link, and link for each link. The cost corresponding to each link is calculated using the cost function defined by the propagation delay.

The cost calculator 120 manages a bandwidth value and a BER value for each link received from the data transmitter 130. The average BER may be calculated with a previously calculated average BER and a current BER value received from the data transmitter 130. The deviation of the average BER may be calculated by using the previously calculated average BER deviation and the current BER value received from the data transmitter 130.

In addition, the cost calculator 120 determines a time point at which the cost is calculated. Preferably, the timing is determined by whether normal communication is possible on each link, that is, whether the link is viable. To this end, the present embodiment defines an average BER value in which communication is no longer possible. This value will be referred to as triggering threshold (hereinafter, T_TH) for convenience. If the average BER of any link is higher than T_TH, the link may be considered incapable of communication. Therefore, the cost calculator 120 calculates the cost corresponding to each link connected to the routing device when the average BER of a link becomes higher or lower than T_TH and transfers the calculated values to the routing unit 110. do.

The routing unit 110 performs routing using a predetermined routing protocol according to the cost value of each link received from the cost calculating unit 120.

2 illustrates a control flow for performing routing in a communication network including a wireless network according to an embodiment of the present invention. In the following description of the operation according to Figure 2 will be referred to the configuration shown in Figure 1 for better understanding.

The cost calculator 120 obtains bandwidth and BER available for each link from the data transmitter 130 (step 210). The cost calculator 120 calculates an average BER for each link (step 220). The cost calculator 120 determines whether there is a link having a change in which the calculated average BER is higher or lower than T_TH among the links connected to the routing device (step 230).

In step 230, the cost calculator 120 determines whether the average BER is higher than T_TH in step 230. The cost calculator 120 changes the average BER higher than T_TH for links used in the data path among the links connected to the routing device. Check if it is done. On the other hand, in determining whether a change in which the average BER is lower than T_TH occurs, it is checked whether a change in which the average BER is lower than T_TH occurs for all links connected to the routing apparatus.

The cost calculator 120 determines that a cost corresponding to each link needs to be calculated when an event corresponding to the above-described change occurs, and calculates the cost corresponding to each link by performing steps 240 to 260 described later. . Steps 240 to 260 are performed for each link.

When it is determined that there is a change in the average BER in the previous operation, the cost calculator 120 determines whether the average BER of the corresponding link is higher than T_TH (step 240). If the average BER of the link is higher than T_TH, the cost calculator 120 sets the cost value of the link to infinity (250). However, if the average BER of the link is not higher than T_TH, the cost calculator 120 uses the cost function defined by the available bandwidth of the link, the average BER, the deviation of the average BER, and the link propagation delay. Calculate the cost of the program (step 260).

Hereinafter, the cost function used in step 260 will be described in more detail.

In one embodiment according to the present invention, the cost function may be defined according to the following equation (2).

Here, the available bandwidth means available bandwidth for each link in the routing device.

In the present invention, the greater the available bandwidth of a link, the greater the amount of data flows available to serve over that link. Therefore, the cost function according to the present embodiment uses the available bandwidth as a parameter of the cost function in order to be able to service as much data flows as possible. In this case, since the cost value should be lower as the available bandwidth increases, the cost function is reflected in the form of '44 Mbps / available bandwidth '. 44Mbps assumes the bandwidth of the inter-router link based on the TICN (Tactical Information Communication Network), which is a next-generation tactical network, and may be replaced with any other value. Furthermore, the use of available bandwidth values can achieve the effect of distributing the load on the network. In other words, the routing device transmits data over the link with the largest available bandwidth among the available links, which gradually decreases the available bandwidth and becomes smaller than the available bandwidth of another link after a certain time. Will be. Therefore, the routing unit 110 may select a new link to distribute the load.

In general, the wireless tactical network has a high transmission error rate of the wireless link due to jamming, etc., and thus it is difficult to continuously perform stable data communication. Therefore, in the cost function according to the present embodiment, the deviation of the average BER and the average BER is used as a parameter of the cost function for more stable data communication. By selecting a path with a low deviation between the mean BER and the mean BER, a stable and high survival path can be selected.

In the present embodiment, the deviation between the average BER and the average BER can be calculated through Equation 3 below. The calculation of the average BER described herein is applied in step 220, and the value calculated in step 220 may be used for the cost function.

Mean BER [t] = 10 ⁶ {(1-β) × average BER [t-1] + β × current BER [t]}

Mean BER Deviation [t] = 10 ⁶ {(1-γ) × Average BER Deviation [t-1] + γ × Current BER [t] -Average BER [t]}

(0 <β, γ <1)

First, the equation for calculating the average BER will be described. Due to the nature of the radio link, the BER value has a very irregular value that changes from time to time. Therefore, in the present embodiment, the average value is used to properly estimate the BER value, but since the latest BER value reflects the state of the current radio link better, as shown in Equation 3, the average measured at the previous time and the BER measured before. BER's Exponential Weighted Moving Average (EWMA) is used. On the other hand, the deviation of the average BER is a prediction of how far the currently measured BER value deviates from the average BER value, the deviation of the average BER will be small if there is no change in the currently measured BER value. Otherwise the deviation of the mean BER will be large. As shown in Equation 3, the average BER deviation uses the EWMA of the current BER deviation and the average BER deviation calculated at a previous time.

In addition, the military tactical network environment consists of wired and wireless networks including satellite networks. However, in the case of real-time application services such as VoIP service, where end-to-end latency is the most important measure of quality of service, providing services over wired networks is more efficient than satellite or wireless networks with long link propagation delays. . Therefore, in this embodiment, the link propagation delay time is used as a parameter of the cost function. The link propagation delay time can use an integer value that is a constant that is different for each network type. The magnitude of the link propagation delay is wired network, wireless network, and satellite network.

The available bandwidth, average BER, and deviation of the average BER are highly dynamic values, and whenever the values change slightly, if the values are reflected differently in the cost function, the data path flapping occurs. May cause a problem in that data communication performance is degraded. Therefore, in the cost function according to the present embodiment, the available bandwidth, the average BER, and the deviation value of the average BER are normalized through a logarithmic function so that the changed value is reflected in the cost function only when the change amount of each parameter value is changed by a certain amount or more. To avoid data path flapping. Furthermore, the amount of change in each parameter value can be determined by adjusting the base value of the logarithm function. In particular, in the case of a parameter having a significant influence on the cost function, the weight can be reflected so that the cost function is more affected by the parameter value by setting the base value relatively smaller than other parameters.

When cost values corresponding to each of the links connected to the routing device are calculated in steps 250 and 260, the values are transferred to the routing unit 110, and the routing unit 110 according to the cost value of each link. Perform routing (step 270).

An embodiment of a routing protocol in step 270 is described below. The routing device floods information about its route table to neighboring routers periodically or through its Link State Updates (LSU) message when its link state changes (that is, when the link is down or the router goes down). flooding). By exchanging LSU messages between routers, all routers maintain the same topology information, so each router can construct the shortest path tree by considering itself as the center of the network. Based on this, each router creates and manages its own route table. At this time, the shortest path tree is generated through the Dijkstra Horst Path First (SPF) algorithm, and the cost corresponding to each link is calculated according to the cost function according to the above-described embodiment. Thus, if any router detects a change in the link state that it is connected to, or one of its neighbors is down, it uses the cost function described above for every link to which it is attached. To get the cost. The router informs the network of the updated cost values for the links connected to it by flooding the neighbor routers with an LSU message including the updated cost value for each link, and updates its route table.

In the present invention, step 270 of performing routing according to the cost value corresponding to each link is not limited to the above-described routing protocol, but may be applied to all routing protocols using the cost value corresponding to the link.

According to the present invention described above, it is possible to adaptively route to a state change of a dynamically changing wireless link in a communication network including a wireless network, and to perform routing with a path having high survivability and stability. Therefore, it is possible to realize efficient routing in military tactical network environment including wireless link, improve service quality and throughput for application services, and increase the number of flows that satisfy minimum quality of VoIP service especially for VoIP service. You can. As described above, according to the present invention, communication performance and network resource utilization rate can be improved.

Meanwhile, the above-described embodiments of the present invention can be written as a program that can be executed in a computer, and can be implemented in a general-purpose digital computer that operates the program using a computer-readable recording medium. The computer-readable recording medium may be a magnetic storage medium (for example, a ROM, a floppy disk, a hard disk, etc.), an optical reading medium (for example, a CD-ROM, DVD, etc.) and a carrier wave (for example, the Internet). Storage medium).

So far I looked at the center of the preferred embodiment for the present invention. Those skilled in the art will appreciate that the present invention can be implemented in a modified form without departing from the essential features of the present invention. Therefore, the disclosed embodiments should be considered in descriptive sense only and not for purposes of limitation. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the scope will be construed as being included in the present invention.

1 is a block diagram of a routing device in a communication network including a wireless network according to an embodiment of the present invention.

2 is a flowchart illustrating a routing method in a communication network including a wireless network according to an embodiment of the present invention.

Claims (9)

In a routing method in a communication network including a wireless network, Calculating a cost corresponding to each link by using a cost function defined according to the available bandwidth of the link and the average bit error rate for each connected link; And And performing routing according to the calculated cost corresponding to each link. The method of claim 1, The cost function is defined according to the deviation of the average bit error rate of the corresponding link together with the available bandwidth and the average bit error rate, and may be defined by further considering the link propagation delay of the corresponding link. Routing method. The method according to claim 1 or 2, Said available bandwidth or said average bit error rate or deviation of said average bit error rate is normalized through a logarithmic function and reflected in said cost function. The method of claim 2, The average bit error rate is calculated as an exponential weighted moving average of the currently measured bit error rate and the previously calculated average bit error rate, wherein the deviation of the average bit error rate is equal to the deviation of the currently measured bit error rate. And an exponentially weighted moving average of the deviation of the average bit error rate already computed in. The method of claim 1, Determining whether a change occurs in which an average bit error rate of at least one of the connected links is higher or lower than a predetermined threshold value; Wherein the at least one link is a link in use as a data path, and the step of calculating the cost is performed when the change occurs. A routing device in a communication network including a wireless network, A routing unit which performs routing according to a cost corresponding to each link; And And a cost calculator configured to calculate a cost corresponding to each link by using a cost function defined according to the available bandwidth and the average bit error rate of the link for each link connected to the routing device. The method of claim 6, The cost function is defined according to the deviation of the average bit error rate of the corresponding link together with the available bandwidth and the average bit error rate, and may be defined by further considering the link propagation delay of the corresponding link. Routing device. The method of claim 6, The available bandwidth or the deviation of the average bit error rate or the average bit error rate is normalized through a logarithmic function and reflected in the cost function. The method of claim 6, Further comprising a data transmission unit for transmitting data by wireless or wired, And the cost calculator calculates the cost based on the available bandwidth and bit error rate for each link obtained from the data transmitter.

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