KR101049081B1 - Routing method and system in ad-hoc network considering transmission speed - Google Patents

Abstract

PURPOSE: A routing method of ADHOC network and routing system thereof are provided to increase the use efficiency of network resource and to select a route in consideration of transfer rate. CONSTITUTION: A transmission route setting is requested to a routing management module(S910). A first routing module determines the minimum cost routes through the routing table(S920, S930). A second routing module generates minimum cost route per transfer rate corresponding to the transmission route through one or more received route response packets(S940).

Description

Routing method and system in ad-hoc network considering transmission speed}

The present invention relates to a routing method and a routing system, and more particularly to a routing method and a routing system in an ad-hoc network.

Since ad hoc networks do not have a fixed infrastructure, each node must be able to perform router functions for data transfer between nodes with mobility. In addition, network resources are limited, and the topology of the network is dynamically changed. Due to the above features, a number of transmission path determination methods have been proposed to efficiently use limited network resources. The transmission path determination methods generally use a transmission path determination method assuming that link quality between nodes is symmetrical. However, in reality, there are mobile nodes with various transmission powers, and even though they have the same transmission power, the transmission link quality and the reception link quality between nodes are not the same due to the geographical environment. The path is not reliable.

1 is a diagram illustrating an ad hoc network topology.

Referring to FIG. 1, since node C is located near the propagation distance boundary of node A, it is assumed that link quality between node A and node C is below a threshold. If node C broadcasts a routing update packet, the link quality of node A and node C is below the threshold and is not reflected in the network topology. That is, node A does not use the routing information of node C when calculating the routing path. Therefore, when node A intends to send a packet to node F, node A does not consider the path PT2 via node C when calculating the routing path. Therefore, when node A intends to send a data packet to node F, the routing path is determined to be a path PT1 via node B and node E. That is, even if the number of relay hops is relatively small, a path connected to a link having a quality below a threshold value is not set as a routing path.

 As the number of relay hops is increased as a path including a link having a quality below the threshold is excluded from the routing path calculation, a path composed of links having a certain level or more of quality is selected. However, relaying requires competition for channel occupation and time delays due to backoff to avoid collisions. In addition, a collision due to the simultaneous access of a plurality of nodes to a wireless channel cannot be completely excluded. Therefore, if the number of relay hops included in the path increases, the cost of relaying also increases, thereby increasing the transmission cost. Considering this problem, it is desirable to apply a method that minimizes the increase in the number of relay hops in the calculation of the routing path.

The prior art also relies on periodically sharing the sharing of routing information throughout the network so that all nodes in the network share routing information. In particular, in the highly mobile network, the broadcast period should be short in order to share accurate routing information. The larger the number of nodes in the network, the greater the load on the network. Therefore, there is a limitation in applicability in medium and large networks, and it is desirable to apply a method to alleviate this.

The problem to be solved by the present invention is to provide a routing method in an ad hoc network that can improve the use efficiency of limited network resources by selecting a path in consideration of the transmission speed.

Another object of the present invention is to provide a routing system using the routing method.

Routing method in an ad hoc network according to an embodiment of the present invention for achieving the above object is the step of storing the minimum cost path for each node in the N hop (N is a natural number) in the routing table, the routing table If a transmission path exists, determining, by using the routing table, a path having a higher than reference quality and having a minimum path cost among the minimum cost paths corresponding to the transmission path as a final path, the transmission to the routing table. Generating a minimum cost path for each transmission rate corresponding to the transmission path using the received at least one path response packet when the path does not exist or the path that is higher than the reference quality exists and the generated minimum cost path The final path is above the reference quality and the path cost is the least. Furnace may include the step of determining.

Determining the final path using the routing table comprises extracting the least cost paths corresponding to the transmission path using the routing table and above the reference quality, if the transmission packet is a real-time packet Determining a path that satisfies the transmission time limit among the minimum cost paths and has the minimum path cost as the final path, and when the transmission packet is not the real-time packet, the path cost of the extracted paths is Determining a path that is the minimum as the final path.

The generating of the least cost path for each transmission rate may include: broadcasting a path request packet at a first node (for example, a transmitting node) when there is no transmission path or a path above the reference quality in the routing table. Step, when at least one second node that knows the route to the destination has received the route request packet, the at least one second node generates the at least one route response packet comprising the route to the destination. Transmitting to the first node and receiving the at least one path response packet at the first node, and generating a minimum cost path for each transmission rate using the at least one path response packet. Can be.

Determining the final path among the generated minimum cost paths comprises extracting the minimum cost paths that are above the reference quality of the generated minimum cost paths, if the transmission packet is a real-time packet, the extracted minimum Determining a path that satisfies the transmission time limit among the cost paths and has the minimum path cost as the final path, and when the transmission packet is not the real-time packet, the path cost among the extracted paths is the minimum Determining a route as the final route.

The routing system in an ad hoc network according to an embodiment of the present invention for achieving the above another problem is that the transmission path is present in the routing table is stored the least cost path for each node in the N hop (N is a natural number) In this case, the transmission path is present in the first routing module and the routing table, which determine, as the final path, a path having a minimum quality or a minimum path cost among the minimum cost paths corresponding to the transmission path using the routing table. If not, or if there is no path higher than the reference quality, a minimum cost path for each transmission rate corresponding to the transmission path is generated using the received at least one path response packet, and the reference among the generated minimum cost paths. Determining the final path as a path that is above quality and has the least path cost A second routing module may be provided.

The first routing module uses the routing table to extract the least cost paths corresponding to the transmission path and equal to or greater than the reference quality, and if the transmission packet is a real-time packet, the first quality of the extracted least cost paths or more And a path satisfying a transmission time limit and having the minimum path cost as the final path, and if the transmission packet is not the real time packet, the path quality is equal to or greater than the reference quality among the extracted minimum cost paths. The path that is the smallest can be determined as the final path.

The second routing module may be configured to broadcast a route request packet at a first node and to recognize at least one second node that knows a route to a destination when there is no route higher than the transmission path or the reference quality in the routing table. The least cost path for each transmission rate may be generated using at least one path response packet generated and transmitted.

The second routing module determines, as the final path, a path having the minimum quality path that is equal to or greater than the reference quality and satisfies a transmission time limit and has the minimum path cost when the transmission packet is a real-time packet. When the packet is not the real-time packet, the final path may be determined as a path having the above standard quality and the path cost being the least among the generated least cost paths.

The routing method and routing system in an ad hoc network according to an embodiment of the present invention can increase the efficiency of use of limited network resources by selecting a path in consideration of a transmission speed, and apply routing information by applying a hybrid routing scheme. Network overhead for sharing can be alleviated, and network scalability problem can be solved and can be applied in medium-sized networks.

More specifically, according to an embodiment of the inventive concept, link quality (eg, Bit Erroe Rate (BER)) according to a change in transmission speed for a mobile node supporting a plurality of transmission speeds and By actively setting the routing path in consideration of the change in communication distance, it is possible to reduce the hop relay which is relatively expensive. Therefore, it is possible to increase the efficiency of using radio resources more than the method of determining the transmission path simply by considering only the link quality.

In addition, according to an embodiment of the present invention, network scalability and control packet overhead may be alleviated. That is, the inside of the routing area divided by the set hop number may apply a proactive routing method in consideration of link quality, and the outside of the routing area may apply a reactive routing method in which link quality is applied. Therefore, by limiting the proactive routing control packet broadcasting region for periodic routing information sharing to the set routing region hop number, the control packet overhead problem can be alleviated and network scalability can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS In order to better understand the drawings cited in the detailed description of the invention, a brief description of each drawing is provided.
1 is a diagram illustrating an ad hoc network topology.
2 is a block diagram of a routing system according to an embodiment of the inventive concept.
3 is a block diagram illustrating in detail the routing management module of FIG. 2.
4 is a configuration example of a routing area according to an embodiment of the inventive concept.
5 is a flowchart illustrating a hello packet transmission procedure according to an embodiment of the present invention.
6 is a flowchart illustrating a hello packet reception procedure according to an embodiment of the present invention.
7 is a flowchart illustrating a routing update packet transmission method according to an embodiment of the present invention.
8 is a flowchart illustrating a routing update packet receiving method according to an embodiment of the present invention.
9 is a flowchart illustrating a routing method according to an embodiment of the inventive concept.
FIG. 10 is a flowchart illustrating an embodiment of step S930 of FIG. 9 in more detail.
FIG. 11 is a flowchart illustrating another embodiment of step S930 of FIG. 9 in more detail.
FIG. 12 is a flowchart illustrating an embodiment of steps S940 and S950 of FIG. 9 in more detail.
FIG. 13 is a flowchart illustrating another embodiment of steps S940 and S950 of FIG. 9 in more detail.
14 is a diagram illustrating an ad hoc network topology according to an embodiment of the present invention.
15 is a diagram illustrating a network topology for explaining a process of forwarding a route request packet.
16 is a diagram illustrating a network topology for explaining a path response packet forwarding process.
17 is a diagram for explaining a transmission time limit.

DETAILED DESCRIPTION In order to fully understand the present invention, the operational advantages of the present invention, and the objects achieved by the practice of the present invention, reference should be made to the accompanying drawings which illustrate preferred embodiments of the present invention and the contents described in the drawings.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Like reference numerals in the drawings denote like elements.

In general, mobile nodes include a plurality of transmission modes according to transmission rates, and link quality (eg, Bit Error Rate;) per transmission rate for the same signal quality (eg, Signal-to-Noise Ratio; SNR). BER) is not the same. Even at the same signal quality, the link quality does not satisfy the transmission reference link quality at any transmission rate, but at other lower transmission speeds, the link quality may satisfy the transmission reference link quality. In other words, the communication distance increases at a relatively low speed, thereby reducing or minimizing the number of hops of a relatively expensive transmission. According to an embodiment of the inventive concept, a path is actively selected by changing a transmission rate by reflecting this characteristic in a routing path determination process.

2 is a block diagram of a routing system 200 according to an embodiment of the inventive concept.

2, the routing system 200 includes a network stack 210, a signal quality calculation module 220, a neighbor node management module 230, a first routing module 240, a second routing module 250, The routing management module 260 and the routing packet transmission / reception module 270 may be included.

The network stack 210 may transmit and receive data by using layered packetization, a path determination function, and a transmission collision avoidance function. When requesting data transmission in the routing packet transmission / reception module 270 or application layer, the network stack 210 packetizes, and when the routing management module 260 makes a request for transmission path setting, the network stack 210 establishes a routing path. Pass to neighbor node. When receiving a packet, the network stack 210 receives or relays a packet according to a destination. If the IP address of the network stack 210 is a destination, if the packet is a routing update packet, the network stack 210 transmits a routing update packet to the routing packet transmission / reception module 270, and if the packet is a general packet, the network stack 210. 210 forwards the normal packet to the application layer.

The signal quality calculation module 220 may measure signal quality of the neighbor node by using a hello packet that is periodically received. For example, the signal quality may mean a signal-to-noise ratio (SNR) as the signal quality for the received hello packet. In general, the higher the signal quality, the lower the bit error rate (BER), which is the link quality, and the higher the transmission success probability. The lower the signal quality, the higher the bit error rate and the lower the transmission success probability. The signal quality measured in the signal quality calculation module 220 is transmitted to the neighbor node management module 230 and finally updated in the phase table in the routing module 240, and this information is updated in the routing management module 250. Used to calculate the least cost path stored in the routing table for each transmission rate.

The neighbor node management module 230 updates the transmission / reception signal quality information with the neighbor node in the neighbor node table through periodic transmission of the hello packet and reception of the hello packet sent by the neighbor node. In detail, when the hello packet is received, the signal quality calculation module 220 updates the received signal quality information from the neighboring node and its own transmission signal quality information measured by the neighboring node included in the hello packet in the neighbor node table. When the hello packet is received, the neighbor node table is updated and then broadcasts one hop to the neighbor node periodically by including the hello packet transmission / reception signal quality information with the neighbor node in the neighbor node table. The neighbor node management module shares the signal quality change between neighbor nodes by transmitting and receiving the hello packet.

The first routing module 240 generates a routing update packet including signal quality information of the transmission and reception with the neighbor node by referring to the neighbor node table managed by the neighbor node management module 230 and then sends the routing packet to the routing packet transmission / reception module 270. Forwarding and routing packet transmission and reception module 270 periodically broadcasts to nodes within an N hop (N is a natural number) radius set as a proactive routing area by making a request to the network stack 210 for transmission. Upon receipt of the routing update packet, the first routing module 240 updates the phase table in the routing table. By periodically broadcasting all nodes within the N hop radius, each node's first routing module 240 shares the changes in transmit and receive signal quality for all nodes within the N hop radius. Each time the topology table managed by the first routing module 240 is updated, the routing management module 260 updates the routing table by calculating the minimum path for each transmission speed for all nodes in the proactive routing area.

If the destination node of the packet does not exist in the routing table at the time of packet transmission, that is, if the number of hops to the destination node is determined to exceed N hops from the transmitting node and requires the path search, the second routing module 250 manages routing. In response to the request of the module 260, a routing request (RREQ) packet is generated and requested to be broadcasted to the routing packet transmission / reception module 270. The routing packet transceiving module 270 broadcasts the route request packet through the network stack 210. Nodes passing while the route request packet is broadcast to a node that knows route information to the destination node add link information with the previous hop node to the route request packet and broadcast again when receiving the route request packet. . When a node that knows route information to the destination node (e.g., a node in the same proactive routing area as the destination node) receives the broadcasted route request packet, it no longer broadcasts the route request packet. A Routing Reply (RREP) packet is generated to inform the node that sent the route request packet to the destination node without casting the route information. The node that knows the route information to the destination node, in the process of transmitting routing information of the links and the route request packet from the forwarding node (the route request packet transmitting node to the destination node) from itself to the destination node. The routing information of the forward links of the nodes passing through is included in the path response packet. Therefore, the routing path of the forward links from the node that sent the route request packet to the destination node is completed, and the routing information included in the route response packet is forward from the node that sent the route request packet to the destination node. Signal quality values of the links.

The destination node or a node that knows the path information of the destination node should forward the path response packet to the node that sent the path request packet, but in an asymmetric link, a unicast path in the reverse direction of the path where the path request packet is transmitted. Cannot be assumed to exist, the route response packet should be broadcasted if the node that sent the route request packet is outside the proactive routing area. If the node that sent the route request packet is in the proactive routing area and the node that knows routing information to the node that sent the route request packet first receives the broadcasted route response packet, the routing table. The unicast transmission is performed with reference to the path response packet as a destination node of the path request packet.

Detailed operations of the first routing module 240 and the second routing module 250 will be described in more detail with reference to FIGS. 4 to 17.

When the routing management module 260 receives the routing request packet for the transmission packet from the network stack 210 at the time of packet transmission, the routing management module 260 receives a path to the destination of the transmission request packet in the routing table managed by the proactive routing method. Search for the existence If the search result is present, the route with the lowest transmission cost is transmitted to the network stack 210 in the routing table. If the route to the destination does not exist in the routing table, the route request is made to the second routing module 250. The second routing module 250 transmits the route request packet, and then receives the route response packet and transmits route information to a destination node in the packet to the routing management module 260. The routing management module 260 transmits a path having the smallest transmission cost among the routing information received from the second routing module 250 to the network stack 210.

The routing packet transmit / receive module 270 is responsible for requesting transmission of routing control packets to the network stack 210 and receiving routing control packets from the network stack 210. The hello packet from the neighbor node management module 230, the routing update packet from the first routing module 240, and the route request packet and the route response packet are received from the second routing module 250 and transmitted to the network stack 210. Perform the send request. On the contrary, the routing control packet is received from the network stack 210 and transferred to the neighbor node management module 230, the first routing module 240, or the second routing module 250 according to the routing control packet type.

3 is a block diagram illustrating in detail the routing management module 260 of FIG. 2.

2 and 3, the routing management module 260 includes a path request processing submodule 310, a transmission speed determining submodule 320, a MAC interworking submodule 330, and a first interworking submodule 340. And a second interworking submodule 350.

The route request processing submodule 310 checks whether route information of the destination node exists in the routing table when requesting route establishment from the network stack 210. If there is routing information as a result of the check, the path is determined by using the proactive routing information. If the routing information does not exist, the path is determined by the reactive routing information. When receiving the proactive routing information, which is the information included in the routing table, or the reactive routing information included in the path response packet, the optimum path is calculated and determined by considering the transmission speed to the transmission speed determining submodule 320. To ask. Upon receiving the determined optimal path from the transmission rate determining submodule 320, the determined routing information is transmitted to the network stack 210, and the transmission rate set at the time of determining the optimum path is transmitted to the MAC interworking submodule 330 to provide the physical layer ( For example, request to control the transmission speed of the modem).

 The transmission speed determination submodule 320 determines the optimal path considering the transmission speed to the destination using the reactive routing information or the proactive routing information, and transmits the result to the path request processing submodule 310. The proactive routing interworking submodule 340 transmits routing table information for each transmission rate, which is generated by referring to the phase information in the first routing module 240, as the proactive routing information to the route request processing submodule 310. In addition, the second interworking submodule 260 may transmit the path information for each transmission rate generated by using the signal quality based path information from the second routing module 250 to the destination generated by the path request packet transmission and the path response packet reception. The reactive routing information is transmitted to the route request processing submodule 310.

The MAC interworking submodule 330 transfers the set transmission rate to the physical layer in order to reflect the set transmission rate to the physical layer in determining the optimal path.

4 is a configuration example of a routing area according to an embodiment of the inventive concept.

Referring to FIG. 4, based on the N hops as the set number of hops, the inner region 410 may be a proactive routing method using an active path selection method considering a transmission rate, and the outer region 450 may be an active path selection method considering a transmission speed. Apply the reactive routing method applied. The inner area 410 shares routing information for nodes in the N hops by setting and broadcasting the TTL field of the routing update packet to N hops for sharing the proactive routing based routing table. On the other hand, nodes exceeding N hops set the path by the reactive routing method by transmitting the path request packet and receiving the path response packet. By applying the hybrid routing method as described above, it is possible to reduce the routing control packet load and increase the scalability. In addition, the transmission cost is considered by considering the transmission rate in the final path determination for both path determination within N hops (e.g., proactive routing) and path determination of N hop over nodes (e.g., reactive routing). By minimizing the number of relay hops that occur frequently, the transmission efficiency can be improved more than in the conventional scheme that considers only link quality.

The distinction between inner zone routing and outer zone routing can be determined by the number of hops set by the user. The user decides the number of hops separating the internal and external routing areas by considering the density of nodes based on the network operation concept or the network configuration scenario.

5 is a flowchart illustrating a hello packet transmission procedure according to an embodiment of the present invention.

2 to 5, it is determined whether the hello packet transmission period is performed (S510). In the hello packet transmission period, the neighbor node management module 230 of each node refers to the neighbor node table with the node. And a hello packet may be generated by extracting routing information including a transmission signal quality and a reception signal quality with a node which is one hop (S520). In addition, the neighbor node management module 230 may transfer the generated hello packet to the routing packet transmission / reception module 270 (S530). The routing packet transceiving module 270 may request a network stack to transmit the received hello packet one-hop broadcast.

6 is a flowchart illustrating a hello packet reception procedure according to an embodiment of the present invention.

2 to 6, when the hello packet is received at the physical layer of the network stack 210 (S610), the signal quality calculation module 220 receives a signal for the received hello packet received from the network stack 210. Measure the quality. In step S610, the hello packet is received by the network stack 210, and finally receives the hello packet from the routing packet transmission / reception module 270 and delivers the hello packet to the neighbor node management module 230. The neighbor node management module 230 parses and interprets the received hello packet, and extracts the transmit / receive signal quality for the source 1 hop neighbor nodes included in the hello packet. That is, the neighbor node management module 230 receives the received signal quality measurement value for the hello packet from the signal quality calculation module 220 and extracts the transmit / receive signal quality value for the neighbor node from the hello packet to all neighbor nodes. Transmission and reception signal quality information can be known (S620). The neighbor node management module 230 may update the received signal quality value of the extracted hello packet and the transmitted / received signal quality value of the extracted neighbor node to the neighbor node table (S630). Transmitting / receiving signal quality values of neighbor nodes extracted from the hello packet may be transmitted to the first routing module 260 to update a phase table (S640). Each node recognizes a signal quality change of a neighbor node through periodic transmission and reception of the hello packet, and may update the neighbor node table.

7 is a flowchart illustrating a routing update packet transmission method according to an embodiment of the present invention.

2 to 7, a hop number for determining the internal routing area is set, and the setting information is transmitted to the first routing module 240 so that the first routing module 240 transmits the routing update packet. The number of hops may be determined (S710). Proactive routing can be performed only within the set hop number (N hops). The first routing module 240 determines whether the routing update packet transmission period is performed (S720), and the first routing module 240 may generate the routing update packet when the routing update packet transmission period is performed. That is, in the routing update packet transmission period, the first routing module 240 may generate the routing update packet by extracting the transmission and reception signal quality of each neighbor node from the neighbor node table (S730). In addition, the first routing module 240 may transfer the generated routing update message to the routing packet transmission / reception module 270. The routing packet transmission / reception module 270 may set a time to live (TTL) of the routing update packet to N (N is a natural number) and broadcast the routing update packet up to N hops (S740).

8 is a flowchart illustrating a routing update packet receiving method according to an embodiment of the present invention.

2 to 8, the routing packet transceiving module 270 delivers the routing update packet received from the network stack 210 to the first routing module 240, and the first routing module 240 performs routing. The update packet is received and parsed (S810). The first routing module 240 extracts the transmission / reception signal quality of neighboring nodes of the transmitting node included in the routing update packet based on the parsed result (S820). The first routing module 240 updates the transmission / reception signal quality of neighboring nodes of the extracted transmission node in the phase table (S830). The first routing module 240 converts the transmission / reception signal quality of neighboring nodes of the extracted transmission node into link quality for each transmission rate through a signal quality-link quality conversion (SNR-to-BER) table (S840). The signal quality-link quality conversion table is generated by using a mathematical calculation of the relationship between signal quality and link quality for each transmission rate, or through real-time results or implementation through iterative simulation on the relationship between signal quality and link quality. Can be generated using the results of the test. The first routing module 240 converts the transmission / reception link quality calculated for each transmission rate into transmission / reception path costs (S850). The first routing module 240 selects paths having the smallest average transmission cost per hop (hereinafter, referred to as "path cost") among the transmittable paths for all nodes included in the phase table for each transmission speed (S860). However, the first routing module 240 may preferentially select a path that does not include a link below the transmission threshold value among the paths. The first routing module 240 may update the minimum cost paths according to transmission speeds for all nodes in the routing table in the routing table (S870).

Thereafter, through the periodic routing update packet transmission and reception process, each node may calculate a minimum cost path for all nodes within N hops around the node, update the routing table based on the proactive routing, and use the packet during transmission.

9 is a flowchart illustrating a routing method according to an embodiment of the inventive concept.

2 to 9, when a packet is generated in the application layer and requests transmission to the network stack, the IP layer in the network stack 210 may request the routing management module 260 to set up a transmission path (S910). . As described above, the first routing module 240 determines whether the transmission path exists in the routing table in which the minimum cost path for each transmission rate is stored (S920). When the transmission path exists in the routing table as a result of the determination in step S920, the first routing module 240 uses the routing table to determine a path quality higher than a reference quality among the minimum cost paths corresponding to the transmission path. The smallest path may be determined as the final path (S930). When the transmission path does not exist in the routing table as a result of the determination in step S920, the second routing module 250 transmits the transmission path corresponding to the transmission path using the received at least one path response packet as described above. The minimum cost path for each rate may be generated (S940), and the second routing module 250 may determine a path having the minimum or higher path quality among the generated minimum cost paths as the final path. It may be (S950).

If there are no paths that are equal to or greater than the reference quality among the least cost paths in step S930, steps S940 and S950 may be performed, and it is determined that the path setting has failed, and a condensation setting failure message is sent to the IP layer in the network stack 210. You can also pass it. In addition, when there is no path to be determined as the final path in step S950, if there is another path response packet, steps S940 and S950 may be performed again with respect to another path response packet. The packet may be determined to have failed, and a condensation setting failure packet may be delivered to the IP layer in the network stack 210.

FIG. 10 is a flowchart illustrating an embodiment of step S930 of FIG. 9 in more detail.

2 to 10, when the transmission path exists in the routing table as a result of the determination in step S920, the first routing module 240 corresponds to the transmission path using the routing table and is equal to or greater than the reference quality. The minimum cost paths may be extracted (S1010). The first routing module 240 determines whether the transmission packet is a real time packet (for example, a VoIP voice packet) (S1020), and when the transmission packet is the real time packet, the first routing module 240 extracts the packet. Among the minimum cost paths, a path satisfying a transmission time limit and having the minimum path cost may be determined as the final path (S1030). For real time communication such as voice communication, real time data must satisfy the delay limit time. If the delay time is not satisfied, the received data is no longer needed because of poor service quality or far exceeding the delay time. Therefore, in case of a real time packet, the delay limit time must be satisfied. If the transmission packet is not the real-time packet, the first routing module 240 may determine a path having the minimum path cost among the extracted paths as the final path (S1040).

If there is no path to be determined as the final path when the step S1030 is to be performed or if there is no path to be determined as the final path when the step S1040 is performed, the first routing module 240 according to the routing policy is performed by S940 of FIG. 9. Step S950 may be performed or it may be determined that path establishment has failed, and a condensation establishment failure packet may be delivered to the IP layer in the network stack 210.

FIG. 11 is a flowchart illustrating another embodiment of step S930 of FIG. 9 in more detail.

2 through 11, the first routing module 240 may determine whether a minimum cost path corresponding to a transmission path based on a current transmission speed and having a reference quality or more exists in the routing table (S1110). If a minimum cost path corresponding to the transmission path and equal to or greater than a reference quality exists in the routing table, the first routing module 240 determines whether the transmission packet is a real-time packet (S1120). If the transmission packet is determined to be the real-time packet, the first routing module 240 determines whether the transmission time of the minimum cost path satisfies the transmission time limit (S1130). When the transmission time of the minimum cost path satisfies the transmission time limit in step S1130 or when the transmission packet is not a real-time packet in step S1120, the first routing module 240 determines the minimum cost corresponding to the current transmission rate. The path is stored (S1140), and it is determined whether there is a transmission rate lower than the current transmission rate (S1150). If there is a transmission rate lower than the current transmission rate, the first routing module 240 performs steps S1110 to S1150 again for the transmission rate lower than the current transmission rate. In addition, when the minimum cost path corresponding to the transmission path in step S1110 and above the reference quality does not exist in the routing table or when the transmission time of the minimum cost path does not satisfy the transmission time limit in step S1130, S1160. The steps can be performed.

If a transmission rate lower than the current transmission rate no longer exists, the first routing module 240 determines a path having a minimum path cost among the minimum cost paths stored in step S1140 as the final path (S1170). The transmission rate corresponding to the determined final path may be determined as the final transmission rate (S1180).

If there is no stored minimum cost path, the first routing module 240 may perform steps S940 and S950 of FIG. 9, and determines that the path setting has failed. The condensation setting failure packet may be delivered to the IP layer.

FIG. 12 is a flowchart illustrating an embodiment of steps S940 and S950 of FIG. 9 in more detail.

2 to 12, when it is determined in step S920 that the transmission path does not exist in the routing table, the second routing module 250 determines that no destination exists within N hops as the proactive routing area. In operation S1210, a route request packet for finding a route to a destination node as a whole may be broadcast. When the node that knows the route to the destination node or the destination node receives the route request packet, the route response packet including the route to the destination node may be unicast to the node that sent the route request packet. . The node that has transmitted the path request packet may receive the path response packet from the node that knows the path to the destination node or the destination node (S1220). The second routing module 250 may generate a minimum cost path for each transmission rate corresponding to the transmission path using the path response packet in operation S1230. That is, the second routing module 250 uses the path response packet to link the inter-node signal quality (eg, signal-to-noise ratio) value included in the transmission path through the signal quality-link quality conversion table. Converting to a quality (for example, bit error rate) value, the link quality value for each transmission rate may generate a minimum cost path for each transmission rate. Steps S1210 to S1230 described above may correspond to step S940 of FIG. 9.

The second routing module 250 may extract minimum cost paths having a reference quality or higher among the generated minimum cost paths (S1240). The second routing module 250 determines whether the transmission packet is a real time packet (for example, a VoIP voice packet) (S1250), and when the transmission packet is the real time packet, the second routing module 250 extracts the packet. Among the minimum cost paths, a path that satisfies the transmission time limit and has the minimum path cost may be determined as the final path (S1260). If the transmission packet is not the real-time packet, the second routing module 250 may determine a path having the minimum path cost among the extracted paths as the final path (S1270). Steps S1240 to S1270 may correspond to step S950 of FIG. 9.

If there is no path to be determined as the final path when the step S1260 is to be performed or if there is no path to be determined as the final path, the second routing module 250 receives another path response packet. Check it. If the other path response packet exists, the second routing module 250 may perform the other path response packet again from step S1230. If the other route response packet does not exist, the second routing module 250 determines that the route establishment has failed and may transmit a packet indicating the route establishment failure to the IP layer of the network stack 210 that has made the route request. have.

FIG. 13 is a flowchart illustrating another embodiment of steps S940 and S950 of FIG. 9 in more detail.

2 to 13, since steps S1310 to S1330 of FIG. 13 correspond to steps S1210 to S1230 of FIG. 12, detailed descriptions of steps S1310 to S1330 are omitted.

When the second routing module 250 generates the minimum cost path for each transmission rate in step S1330, the second routing module 250 corresponds to the transmission path based on the current transmission speed among the generated minimum cost paths, and It may be determined whether there is a minimum cost path that is greater than or equal to the quality (S1340). If there is a minimum cost path corresponding to the transmission path and above the reference quality, the second routing module 250 determines whether the transmission packet is a real-time packet (S1350). If the transmission packet is determined to be the real-time packet, the second routing module 250 determines whether the transmission time of the minimum cost path satisfies the transmission time limit (S1360). When the transmission time of the minimum cost path satisfies the transmission time limit in step S1360 or when the transmission packet is not a real-time packet in step S1350, the second routing module 250 determines the minimum cost corresponding to the current transmission speed. The path is stored (S1370) and it is determined whether there is a transmission rate lower than the current transmission rate (S1380). If there is a transmission rate lower than the current transmission rate, the second routing module 250 performs steps S1340 to S1370 again for the transmission rate lower than the current transmission rate. In addition, when there is no minimum cost path corresponding to the transmission path among the generated minimum cost paths in step S1340 and above the reference quality or in step S1360, the transmission time of the minimum cost path does not satisfy the transmission time limit. If not, step S1390 may be performed.

If a transmission rate lower than the current transmission rate no longer exists, the second routing module 250 determines a path having the lowest path cost among the minimum cost paths stored in operation S1370 as the final path (S1393). The transmission rate corresponding to the determined final path may be determined as the final transmission rate, and the physical layer may be controlled at the determined final transmission rate through the MAC interworking submodule 330 (S1395). Steps S1340 to S1395 may correspond to step S950 of FIG. 9.

If there is no stored minimum cost path, the second routing module 250 checks whether another received path response packet exists. If the other path response packet exists, the second routing module 250 may perform the other path response packet again from step S1330. If the other route response packet does not exist, the second routing module 250 determines that the route establishment has failed and may transmit a packet indicating the route establishment failure to the IP layer of the network stack 210 that has made the route request. have.

14 is a diagram illustrating an ad hoc network topology according to an embodiment of the present invention.

It is assumed that the nodes shown in FIG. 14 represent the same positional relationship as the nodes shown in FIG. 1. As described with reference to FIG. 1, in the prior art, since node C is located near the propagation distance boundary of node A, the link quality between node A and node C has a threshold below a certain level, and the link quality is constant. A path PT1 consisting of more than one level of links is selected as the routing path. Accordingly, in the path PT1 selected as the routing path, the number of data packet relays increases from one to two times compared to the path PT2. When data packets are relayed, contention for channel occupancy is required, and time delay occurs due to MAC backoff to avoid collisions. In addition, multiple nodes do not completely exclude collision due to simultaneous access to a wireless channel. As a result, when the number of relay hops increases, the cost of relaying also increases. In consideration of such a problem, it is necessary to minimize the increase in the number of relay hops when calculating the routing path.

All nodes support a plurality of transmission speeds, and assuming that transmission speed 1 is faster than transmission speed 2, it is assumed that transmission speed 1 is 1410 and transmission speed 2 is 1450. Also, with respect to the signal quality (for example, signal-to-noise ratio) of node A and node C, at the current transmission rate 1, node C is located near the boundary of propagation distance of node A, so that link quality below a certain threshold ( For example, bit error rate. In addition, based on the transmission rate 2, which is lower than the transmission rate 1, with respect to the signal quality of the node A and the node C, the radio communication distance is extended, and the node C is located at the stable part of the node A, so that the node A and the node C Assume that the link quality has a link quality above a certain threshold.

Based on these assumptions, an embodiment of the present invention will be described. In the present invention, a link having a link quality of less than a predetermined level for each transmission speed is not included in the network topology. That is, if the link quality of transmission rate 1 with respect to the signal quality of a specific link has a value below a certain threshold, it is excluded from the topology based on transmission rate 1, but the link quality of transmission rate 2 is higher than the threshold. If yes, it is included in the topology. All nodes in the proactive routing area set by the user setting share the transmission and reception signal quality with neighboring nodes included in the routing update packet through periodic broadcast, and transmit and receive with the neighbor node in the received routing update packet. The link quality for each transmission rate is calculated from the received signal quality and included in the topology table for each transmission rate for links having a link quality above a predetermined threshold. When the topology table for each transmission rate is updated by the routing update packet, the routing table for each transmission rate is updated by recalculating the routing paths to each node for each transmission rate.

 When we want to pass data from node A to node F, we first look up the routing table for all transmission rates. Since the signal quality from node A to node C has a link quality of less than a certain threshold value based on the transmission rate 1, the routing table corresponding to the transmission rate 1 is excluded from the topology information and excluded from the routing path calculation. The path PT1 is set from node A to node F. The routing table corresponding to transmission rate 2 is included in the topology information because the signal quality from node A to node C has a link quality higher than a predetermined threshold value based on transmission rate 2. Therefore, the path from node A to node F is included in the routing path calculation and the path PT2 is set. Since the path from node A to node F stored in the routing table at the current rate 1 is 3 hops, it is checked whether there is a path smaller than 3 hops at the other transmission rate. Since there is a two-hop routing path from node A to node F in the routing table at transmission rate 2, make sure that transmission is possible on this path.

If the packet to be transmitted is a real-time packet with a transmission time limit, the total transmission time is determined by applying the packet transmission time and the average backoff time in the MAC for the path (PT2), which is the routing path at transmission rate 2. Calculate As a result of the calculation, if the time limit satisfies the real-time transmission time limit, the routing path from node A to node F at transmission rate 2 is set as the final path and transferred to the IP layer in the network stack. If the calculation does not satisfy the real-time transmission timeout, the routing path from node A to node F at transmission rate 1 is set as the final path, and the routing path set to the IP layer in the network stack is delivered.

15 is a diagram illustrating a network topology for explaining a path request packet forwarding process.

Referring to FIG. 15, FIG. 15 illustrates a case where the proactive routing area is set to two hops. However, the present invention is not limited to this case, and the proactive routing area may be set to N hops (N is a natural number). The first area 1510 is a proactive routing area based on node I, and can share routing information for node I, and the second area 1550 is a proactive routing area based on node E, for node E. This is an area where routing information can be shared.

When node E wants to transfer data to node I (the path from node E to node I is called the forward path, and from node I to node E, the path is called the reverse path), node I is the node E's pro. It is outside the active routing area and does not exist in the routing table. Thus, node E broadcasts a route request (RREQ) packet to discover the path of node I. Intermediate nodes that are being routed while being broadcast to a node I, which is a route search target or to a node that knows the route information of the node I, add routing information with the previous node to the route request packet upon receiving the route request packet. That is, when node B receives a route request packet broadcast packet sent by node E, node B adds a signal quality value for the link from node E to node B, which it knows, to the route request packet. Rebroadcast the route request packet. The broadcasted route request packet is no longer a route request because node D in the proactive routing area of node I criteria (assuming that it received the route request packet (RREQ 1) first) knows the routing path of node I. Do not broadcast the packet.

16 is a diagram illustrating a network topology for explaining a path response packet forwarding process.

Referring to FIG. 16, after the path request packet is received, the node I generates a path response (RREP) packet to which routing information of the forward links DH and HI to the node I and the path request packet are delivered. Routing information of the forward links (EC, EA, AD) of the nodes passing through the process is included in the packet. This completes the routing path of the forward links from node E to node I, and the routing information included is the signal quality values of the forward links from node E to node I. Node D should forward the Path Response Packet to Node E, but broadcast it for the following reasons: In general, a symmetric link is assumed. Therefore, the path response packet unicasts the path response packet in the reverse direction of the path request packet transmission path by using forward path information on the passthru nodes included in the path request packet. Because the path request packet cannot be assumed to exist in the reverse direction of the forward path, it must be broadcast in order to deliver the path response packet to node E outside the proactive routing area of node D. When a node that is in a proactive routing area based on node E and knows routing information to node E first receives a broadcasted route response packet, the route response packet is referred to as its destination by referring to its own routing table. Unicast transmission.

In general, in a network including an asymmetric link, when a route request packet and a route response packet are transmitted, the broadcast is transmitted to the entire area of the network. However, while the route request packet and the route response packet are broadcast, the routing information of the destination node is known. When a node in a region receives a unicast transmission to the destination, the overhead of frequent broadcasts can be reduced.

Distinguish between the proactive routing area and the reactive routing area to limit the broadcast propagation range of periodic proactive routing control packets to the proactive routing area (N hops) set by the user, and to broadcast the reactive routing control packets When delivered into the proactive routing area of the destination, since the unicast transmission is performed using the proactive routing information as described above, the overhead caused by the routing control packet can be alleviated.

17 is a diagram for explaining a transmission time limit.

Referring to FIG. 17, BufferingTime (u) is a time for buffering u real-time unit data and depends on the applied codec. In addition, PlayingTime (u) is a time for reproducing u real-time unit data and is the same time as BufferingTime (u). MacDelayAvgTime is the average backoff delay in the MAC, TxProcessingDelay is the transmission processing delay in the modem after the backoff delay in the MAC, and RxProcessingDelay is the reception processing delay in the modem. PacketTxTime (PacketSize (h, u), s) is a packet transmission time determined by PacketSize (h, u) which is a packet size determined by the header size h and the number of real-time data u and a transmission rate s in the modem. That is, the packet transmission time required means the time from the completion of the modem transmission processing of the sending node to the start of the modem reception processing of the receiving node for the given packet size and modem transmission speed.

In Figure 17, the method to determine the transmission timeout range for two-hop communication of real-time packets is as follows. The assumption in Figure 17 is that there are only three nodes needed for two-hop communication, the MAC backoff delay occurs only once, and only real-time packets are sent. After buffering is completed at the transmitting node, the time taken for real-time data packets to communicate two hops is two times of MAC backoff delay, transmission processing delay, and two packet transmission times. Assuming that the previously sent real-time packet is received by the destination node (2 hops) and then transmits the next packet, the transmitting node should transmit after the MAC backoff delay after transmission is completed after receiving the real-time packet. Therefore, after real time data buffering time, transmission after MAC backoff delay does not conflict with transmission at the relay node. Considering this, the destination node can continuously play the real-time data only when the time taken for the two-hop communication of the real-time data packet is less than the real-time data buffering time plus the MAC backoff delay time at the transmitting node. In FIG. 17, T_REF shows a transmission timeout range for real-time two hop communication. Under the assumptions described above, a transmission time limit for enabling two-hop communication of real-time data is shown in Equation 1 below.

[Equation 1]

If the previous assumption is changed to a realistic assumption, in addition to the three nodes involved in the two-hop communication, there are other nodes that require channel occupancy competition, which causes the average number of MAC backoff delays to occur b times. In order to be able to send and receive other general data packets at the same time, it is changed to a realistic assumption that a time that is a times of the real time packet transmission time is needed to reflect the time that the general packet occupies the channel and not the other real time packet.

Under this assumption, a condition for satisfying a transmission time limit for enabling two-hop communication of real-time data is shown in Equation 2 below.

[Equation 2]

In the same manner, a condition for satisfying a transmission time limit for enabling real-time data communication for at least three hops under the same assumption is expressed by Equation 3 below.

&Quot; (3) "

Accordingly, a and u, which determine the number of real-time unit data, the header overhead size s in the packet, the average delay time of the MAC, and the number of normal packets that can be accommodated during the real-time packet transmission according to the network operating conditions, When b, a factor that considers node density in a network, is determined, it is determined whether the path at the changed transmission rate is available according to whether the above inequality is satisfied by substituting the changed transmission rate into the transmission rate s factor.

As described above, optimal embodiments have been disclosed in the drawings and the specification. Although specific terms have been used herein, they are used only for the purpose of describing the present invention and are not intended to limit the scope of the invention as defined in the claims or the claims. Therefore, those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Claims (20)

Storing the least cost paths per transmission rate for all nodes in N hops (N is a natural number) in a routing table;
If there is a transmission path in the routing table, the minimum cost paths corresponding to the transmission path and higher than a reference quality are extracted using the routing table, and if the transmission packet is a real-time packet, among the extracted minimum cost paths. The final path satisfies a transmission time limit and has the minimum path cost, and determines the final path as the final path. When the transmission packet is not the real-time packet, the final path is one of the extracted paths. Determining to;
Generating a minimum cost path for each transmission rate corresponding to the transmission path using the received at least one path response packet when the transmission path does not exist or the path above the reference quality does not exist in the routing table; And
Determining the final path among the generated least cost paths that is equal to or greater than the reference quality and the path cost is minimum;
The transmission time limit is a time determined by considering a time that a normal packet is transmitted through a channel, a MAC backoff delay time, and a MAC backoff delay number, and the transmission time limit does not exceed a real time data buffering time. Routing method in an ad hoc network. delete delete delete delete The method of claim 1, wherein the generating of the least cost path for each transmission rate comprises:
Broadcasting a route request packet at a first node when there is no route above the reference route or the reference quality in the routing table;
When at least one second node that knows a route to a destination has received the route request packet, the at least one second node sends at least one of the at least one route response packet including a route to the destination. Generating and transmitting to the first node; And
Receiving the at least one path response packet at the first node and generating the least cost path for each transmission rate using the at least one path response packet. . The method of claim 1, wherein determining the final one of the generated least cost paths comprises:
Extracting the least cost paths that are above the reference quality of the generated least cost paths;
If the transmission packet is a real-time packet, determining a final path that satisfies a transmission time limit among the extracted minimum cost paths and has the minimum path cost; And
And if the transmission packet is not the real time packet, determining the final path among the extracted paths with the lowest path cost as the final path. delete The method of claim 1, wherein determining the final one of the generated least cost paths comprises:
(a) determining whether there is the least cost path that is above the reference quality among the generated least cost paths;
(b) if there is a minimum cost path that is equal to or greater than the reference quality and the path cost of the minimum cost path is less than the path cost of the final path, determining the minimum cost path corresponding to the current transmission rate as the final path;
(c) changing the current transmission rate if there is no minimum cost path above the reference quality or if the path cost of the minimum cost path is greater than the path cost of the final path; And
and (d) performing steps (a) to (c) based on the changed transmission rate. The method of claim 1, wherein determining the final one of the generated least cost paths comprises:
(a) determining whether there is the least cost path that is above the reference quality among the generated least cost paths;
(b) determining whether the transmission packet is a real-time packet when there is a minimum cost path that is greater than or equal to the reference quality;
(c) if the transmission packet is a real-time packet and the transmission time of the minimum cost path satisfies a transmission time limit and the path cost of the minimum cost path is less than the path cost of the final path, corresponding to the current transmission rate. Determining a minimum cost path as the final path;
(d) if the transmission packet is not a real-time packet and the path cost of the minimum cost path is less than the path cost of the final path, determining the minimum cost path corresponding to the current transmission rate as the final path;
(e) the current transmission rate if there is no minimum cost path above the reference quality, or if the transmission time of the minimum cost path does not meet a transmission time limit or if the path cost of the minimum cost path is greater than or equal to the path cost of the final path; Changing the; And
(f) performing the steps (a) to (e) on the basis of the changed transmission rate. When a transmission path exists in a routing table in which a minimum cost path for each node in every N hops (N is a natural number) is stored, the minimum cost path corresponding to the transmission path using the routing table and above the reference quality. If the transmission packet is a real-time packet, and determines that the final path of the extracted minimum cost paths are greater than the reference quality and satisfies the transmission time limit and the path cost is the minimum path, and the transmission packet is A first routing module for determining, as not the real-time packet, the final path that has a path quality equal to or greater than the reference quality among the extracted minimum cost paths and has a minimum path cost; And
When the transmission path does not exist in the routing table or there is no path higher than the reference quality, a minimum cost path for each transmission rate corresponding to the transmission path is generated using the received at least one path response packet, and A second routing module that determines, as the final path, a path having a minimum or higher path quality among the generated minimum cost paths;
The transmission time limit is a time determined by considering a time that a normal packet is transmitted through a channel, a MAC backoff delay time, and a MAC backoff delay number, and the transmission time limit does not exceed a real time data buffering time. Routing system in an ad hoc network. delete delete delete delete The method of claim 11, wherein the second routing module,
At least one generated and transmitted by at least one second node that broadcasts a route request packet at a first node and knows a route to a destination when there is no route in the routing table that is greater than the transmission path or the reference quality. The routing system in the ad hoc network, characterized in that for generating the minimum cost path for each transmission rate using the path response packet of the. The method of claim 11, wherein the second routing module,
When the transmission packet is a real-time packet, a path having the minimum quality path that is greater than or equal to the reference quality and satisfies a transmission time limit and whose path cost is minimum is determined as the final path, and the transmission packet is the real-time packet. If not, the routing system in the ad hoc network, characterized in that the final path of the minimum cost paths generated above the reference quality and the path cost is the minimum. delete The method of claim 11, wherein the second routing module,
If there is the least cost path that is greater than or equal to the reference quality among the generated least cost paths and the path cost of the minimum cost path is less than the path cost of the final path, the final least cost path corresponding to the current transmission rate is determined. Determined by the path,
Determining the final path by changing the current transmission rate when the minimum cost path that is greater than or equal to the reference quality among the generated minimum cost paths does not exist or the path cost of the minimum cost path is greater than or equal to the path cost of the final path. Routing method in an ad hoc network, characterized in that for performing the operation again. The method of claim 11, wherein the second routing module,
Determining whether the transmission packet is a real-time packet when there is the minimum cost path that is equal to or greater than the reference quality among the generated minimum cost paths based on a current transmission rate,
If the transmission packet is a real-time packet and the transmission time of the minimum cost path satisfies a transmission time limit and the path cost of the minimum cost path is less than the path cost of the final path, the minimum cost path corresponding to the current transmission rate Is determined as the final path,
If the transmission packet is not a real-time packet and the path cost of the minimum cost path is less than the path cost of the final path, the minimum cost path corresponding to the current transmission rate is determined as the final path,
Based on the current transmission rate, the minimum cost path that is greater than or equal to the reference quality among the generated minimum cost paths does not exist, or the transmission time of the minimum cost path does not satisfy a transmission time limit or the path cost of the minimum cost path is If the path cost of the final path is greater than or equal to, changing the current transmission rate.

Images