KR20130015800A - Multi-path qos(quality-of-service) routing method for wireless mesh network - Google Patents

Abstract

PURPOSE: A multi-path quality of service routing method in a wireless mesh network is provided to restore and select a path by using an RREQ(Route REQuest) message, an RREP(Route ResPonse) message, and an RERR(Route ERRor) message. CONSTITUTION: The reliability of paths is compared from each other in nodes. Each of the nodes selects a main path and one or more alternative paths(S520). Each of the nodes determines the priority of the paths based on the reliability(S530). Each of the nodes stores the main path, and the alternative path, and the priority in a routing table(S540). When the main path is disconnected, the disconnected node deletes the main path in the routing table(S560). The disconnected node modifies a posterior ranking path to the main path based on the priority. [Reference numerals] (AA) Disconnection of the main path is occurs; (BB) No; (CC) Yes; (S510) Searching paths satisfying QoS which is required by application services; (S520) Selecting a main path and alternative paths; (S530) Determining the priority of the paths; (S540) Storing the main path, alternative paths, and priority in a routing table; (S550) Transmitting packets through the main path; (S560) Deleting the main path from the routing table and modifying a posterior ranking path to the main path

Description

MULTI-PATH QoS (QUALITY-OF-SERVICE) ROUTING METHOD FOR WIRELESS MESH NETWORK}

The present invention relates to a wireless mesh network, and more particularly, to a quality of service (QoS) path selection algorithm in a wireless mesh network.

A mesh network refers to a mesh network in which each node maintains a plurality of connections with neighboring nodes. A wireless mesh network (WMN) refers to a network between mesh nodes. A mesh network using wireless as a transmission medium.

Unicast data transmission between two end nodes of a wireless mesh network is performed along a path discovered and managed by a routing protocol. The routing protocol in the wireless mesh network is largely divided into an on-demand method and a proactive method, and one of two methods may be selected in consideration of mobility of nodes.

Until now, many researches have been conducted on routing protocols that guarantee quality of service (QoS) or provide multiple paths in mesh networks based on "IEEE 802.11" and "IEEE 802.16 Mesh Mode." The research on routing protocols that provide multiple paths in consideration of robustness against transmission failures while guaranteeing QoS in terms of delay time and delay time is still weak.

IEEE 802.16-2009 "Part 16: Air Interface for Broadband Wireless Access Systems"

An object of the present invention is to provide a multi-path quality of service (QoS) routing method in a wireless mesh network.

Another object of the present invention is to provide a routing protocol for searching, selecting, and restoring a route using a Route Request (RREQ) message, a Route Response (RREP) message, and a Route ERRor (RRER) message.

According to an embodiment of the present invention, a multipath routing method is provided. The multi-path routing method includes searching for a plurality of paths satisfying a quality of service (QoS) required by an application service, and comparing a reliability of the plurality of paths to select a primary path and at least one alternative path. Determining a priority of the plurality of routes based on the reliability, storing the primary route, the alternate route, and the priority in a routing table, and when the disconnection occurs in the primary route. Deleting a route from the routing table, and modifying a lower priority route to a primary route based on the priority.

Multi-path routing may be performed to guarantee the quality of service (QoS) of the wireless network.

QoS routing with high robustness can be performed.

The effect can also be expected in terms of load balancing, allowing the efficient use of wireless mesh networks.

1 is an example of path discovery in a wireless mesh network proposed by the present invention.
2 is an example of path selection in a wireless mesh network proposed by the present invention.
3 and 4 are examples of a wireless mesh network for explaining a process of selecting an optimal alternative path when a main path problem occurs.
5 is a flowchart illustrating a path discovery and recovery procedure using a multipath QoS routing method proposed by the present invention.
6 is a block diagram illustrating a node in which an embodiment of the present invention is implemented.

Quality of Service Routing in the path discovery process aims to find a path that satisfies the user's data throughput or bandwidth requirements. To this end, it is possible to determine the amount of available radio resources on each path, and to exclude paths for which a sufficient amount of radio resources cannot be allocated. The amount of available radio resources on each path is dependent on the amount of each radio link resource, and may vary depending on the medium access control scheme. Media access control methods commonly used in wireless mesh networks (WMNs) include collision-free time division multiple access (TDMA) and competition based carrier sense multiple access (CSMA). . In general, a non-conflicting media access control (MAC) -based wireless mesh network can relatively secure estimation and allocation of radio resources, thereby guaranteeing similar hard QoS. Wireless mesh network supports soft QoS because resource management is done probabilistically.

QoS routing protocols for most wireless mesh networks that have been studied so far can selectively manage and use only paths that satisfy the user's QoS during path discovery, so that specified QoS performance can be obtained in data transmission. In addition, some protocols use multi-path algorism to ensure a path that meets the user's QoS requirements. However, this is not a way to improve reliability.

Multi-path routing is a commonly used technique to improve the transmission reliability of routing protocols in wireless mesh networks. It mainly searches and manages multiple paths that can be transmitted to the same destination node, and transmits the same data packets simultaneously or salvage packets. (packet salvaging) is applied based on a method of attempting retransmission using an alternate path when a path is disconnected from an arbitrary node.

However, multipath routing generally has disadvantages such as path discovery overhead, waste of resources, increased processing complexity, and increased storage space requirements, and there are few examples that satisfy both QoS guarantees and robustness considerations. none.

Hereinafter, a multi-path quality of service (QoS) routing method in a wireless mesh network proposed by the present invention will be described in detail with reference to the accompanying drawings.

Each node of the mesh network periodically transmits a network configuration message to inform neighboring nodes of its network. Each node may receive a network configuration message from its neighbors to construct a neighbor table for neighboring nodes two hops away and use it for routing. In this case, the exchanged messages may include QoS related information. Thus, multi-path routing is possible for a packet transmitted to adjacent nodes within a 2-hop distance without guaranteeing a separate path search. However, a route search process is required for routing to nodes more than two hops away.

On the other hand, the mesh network composed of mobile nodes has a high probability of breaking the path due to the movement of the nodes. In this situation, if each node uses a table-driven or proactive routing protocol that shares the information of all nodes except itself, the entire network is generated by sharing routing information. High overhead can cause performance degradation.

In addition, if the QoS information of the node is changed or if the information of the target node stored in the routing table becomes invalid, it is difficult to perform routing to guarantee the QoS.

1 is an example of path discovery in a wireless mesh network proposed by the present invention.

Referring to FIG. 1, the path search procedure method according to the present invention is described below. In this case, it is assumed that the QoS requirement of the wireless mesh network is that the available bandwidth is 4 slots or more and the delay bound is 10 ms or less. The source node is a node S 100, and the destination node is a node D 150.

The node S 100 broadcasts a Route Request (RREQ) to the node A 110 and the node C 130.

In this case, the RREQ includes the bandwidth required by the application service, the delay limit that must be satisfied at the end-to-end, and the accumulated delay time from the source node to the node. An accumulate sum and the like are recorded. After receiving the RREQ, the node checks the bandwidth information recorded in the RREQ and checks whether it can allocate slots corresponding to the bandwidth. In addition, it is checked whether the result value obtained by adding the average delay time with the corresponding node and the accumulated delay time up to the present time does not exceed the delay limit recorded in the RREQ. Nodes satisfying the above two conditions may rebroadcast the RREQ.

Therefore, since Node A 110 and Node C 130 of FIG. 1 satisfy bandwidth and delay limit conditions, the Node A 110 and Node C 130 may accumulate their information in RREQ and rebroadcast.

On the other hand, since the RREQ delivered to Node B 120 through Node A 110 satisfies the QoS requirements, it can be rebroadcasted again, but the RREQ delivered to Node B 120 through Node C 130 is As the cumulative delay exceeds the 10ms requirement, it is no longer rebroadcast and is discarded.

In addition, since the node E 140 does not satisfy the required available bandwidth, the node E 140 may not rebroadcast the RREQ received from the node C 130.

As a result, the RREQ passes from node S 100 to node D 150 through node A 110 and node B 120 (hereafter SABD path) and from node S 100 to node C 130. It may be propagated through a path (hereinafter referred to as an SCD path) through which the node D 150 is transmitted.

2 is an example of path selection in a wireless mesh network proposed by the present invention. Here, the same reference numerals as in the above-described drawings indicate the same node.

Referring to FIG. 2, the path selection procedure method according to the present invention is described as follows. In this case, path reliability may be obtained by multiplying link reliability of each link. Reliability is recorded in both RREQ and Route Response (RREP).

When a plurality of paths satisfying bandwidth and delay limits exist in a node's routing table, the paths having higher reliability are given a higher priority by comparing the reliability of the paths.

Referring to FIG. 2, as described above, the node S 100 receives a route response (RREP) through two paths (S-A-B-D path and S-C-D path). Therefore, since the S-C-D path has the highest path reliability, the highest priority is given to this path and used as the main path, and the other path (S-A-B-D path) is given a lower priority and used as an alternative path. It also records this in its routing table.

3 and 4 are examples of a wireless mesh network for explaining a process of selecting an optimal alternative path when a main path problem occurs. Like reference numerals in the two drawings indicate the same nodes.

3 and 4, a process of selecting an optimal alternative path is as follows.

When a packet is sent from node S 300 to node D 350, along the solid arrows (a, b, c, d), which is the fastest and most reliable path, unless the link break occurs, that is, the main path, the SAGKD path. Will be sent along. However, if a disconnection occurs on any of the links in this path, the transmission should be made using the alternate path immediately.

If the disconnection occurs in the link d as shown in FIG. 3, the node K 330 first checks whether it has an alternate path by referring to its routing table. Since node K 330 has an alternate route m, it does not send a route ERRor (RERR) to node G 320, deletes the primary route d from the routing table, and attempts to transmit a packet using alternate route m. . Node L 340 receives the packet from node K 330 and terminates the routing by sending the packet to node D 350.

If disconnection occurs in the links d and o as shown in FIG. 4, the node K 330 first checks whether it has an alternate path by referring to its routing table. Since node K 330 has an alternate path m, it deletes the primary path d from the routing table and attempts to transmit a packet using the alternate path m. However, link o is also disconnected, so transmission from node L 340 to node D 350 cannot be performed. Thus, node L 340, which does not have another alternate path, sends a RERR to node K 330. Since node K 330, which has received the RERR from node L 340, no longer has a path to transmit a packet, node K 330 sends a RERR to node G 320, which itself sends the packet to the node. Notify that it cannot forward to D 350, and delete the routing table destined for node D 350.

In this way, the nodes receiving the RERR attempt a transmission using an alternate path to replace the primary path, and if the alternative path does not exist, the node performs a path recovery process of transmitting the RERR to its previous node. This process is repeated until the packet transmission to the destination node is successful. Also, if it turns out that none of the current paths reach the destination node, the source node again enters the path search process to find a new path.

Therefore, the multipath QoS routing protocol operating in the manner proposed by the present invention can perform QoS guarantee routing if there is no transmission failure on the link, and use an alternate path even if transmission failure occurs. It is possible to perform routing with high robustness to send packets to the destination node.

Referring back to FIG. 3, when link d is disconnected, node L 340 may recognize that transmission of node K 330 has failed, and thus from node K 330 to node D 350. Rather than waiting for a packet transmission, a packet that has been received and stored by the node K 330 may be transmitted to the node D 350. If the transfer from node L 340 to node D 350 succeeds, node L 340 acknowledges to node K 330 to terminate the transfer from node K 330 to node D 350. ) To complete the routing process.

If the link o is also disconnected as in the case of FIG. 4, node K 330 may not receive an ACK from node L 340. Thus, in this case, node K 330 sends a RERR toward node G 320 to inform the surrounding node that it no longer has a path towards node D 350.

In this way, the nodes that failed to transmit transmit the RERR to their previous node, and the node receiving the RERR transmits the packet through the alternate path according to the path recovery procedure. This process is repeated until the transmission to the destination node is successful, and if it is found that no known path can reach the destination node, the source node performs a new path search process.

The method using the cooperative communication limits the participating nodes to the nodes included in the routing table, thereby preventing the nodes not directed to the destination node from wasting bandwidth by participating in the cooperative communication. Thus, faster and more efficient routing is possible while having the same QoS guarantee and reliability.

5 is a flowchart illustrating a path discovery and recovery procedure using a multipath QoS routing method proposed by the present invention.

Each node searches for a plurality of paths satisfying the QoS required by the application service of the wireless mesh network using the RREQ (S510). As described above, the RREQ is a cumulative sum of the bandwidth required by the application service, the delay limit that must be satisfied at the end-to-end, and the accumulated delay time from the source node to the node. (accumulate sum). When each node transmits an RREQ to the neighboring node, the node receiving the RREQ checks the bandwidth information and / or delay time recorded in the RREQ, and re-broadcasts the RREQ to the neighboring node when the QoS required by the application service is satisfied. If not, discard the received RREQ.

Each node selects a primary path and at least one alternative path by comparing reliability of a plurality of paths satisfying the found QoS (S520). The reliability is recorded in the RREQ and / or RREP. Each node chooses the most reliable route as its primary route and uses the remaining routes as alternate routes.

Each node determines the priority of the paths based on the reliability (S530), and stores the primary path and the alternate path together in its routing table (S540). Routes with high reliability are given high priority. Paths with lower reliability are given lower priority.

Each node transmits a packet through a main path (S550). In other words, the packet is transmitted through the primary paths of the nodes from the source node to the destination node of the wireless mesh network.

If the disconnection occurs in the main path, the node having the disconnection deletes the main path from the routing table, and modifies the lower priority path to the main path based on the priority stored in the routing table (S560).

The above-described steps are not limited to the order, but may occur in different order or at the same time. In addition, the steps shown in the flowchart may be included in other steps, and may be deleted without departing from the scope of the present invention.

6 is a block diagram illustrating a node in which an embodiment of the present invention is implemented.

The node 50 includes a processor 51, a memory 52, and an RF unit 53. The memory 52 is connected to the processor 51 and stores various information for driving the processor 51. [ The RF unit 53 is connected to the processor 51 to transmit and / or receive a radio signal.

The processor 51 implements the proposed functions, procedures and / or methods. In the embodiments of FIGS. 1-5, the operation of the node may be implemented by the processor 51.

The processor may comprise an application-specific integrated circuit (ASIC), other chipset, logic circuitry and / or a data processing device. The memory may include read-only memory (ROM), random access memory (RAM), flash memory, memory cards, storage media, and / or other storage devices. The RF unit may include a baseband circuit for processing the radio signal. When the embodiment is implemented in software, the above-described techniques may be implemented with modules (processes, functions, and so on) that perform the functions described above. The module is stored in memory and can be executed by the processor. The memory may be internal or external to the processor and may be coupled to the processor by any of a variety of well known means.

Claims (1)

In the multi-path routing method by a node in a wireless mesh network,
Searching for a plurality of paths satisfying a Quality of Service (QoS) required by an application service;
Comparing the reliability of the plurality of paths to select a primary path and at least one alternative path;
Determining a priority of the plurality of paths based on the reliability;
Storing the primary path, the alternate path and the priority in a routing table; And
And deleting the main route from the routing table when the disconnection occurs in the main route, and modifying the subsequent route to the main route based on the priority.

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