KR20060010018A - A congestion control mechanism for supporting differentiated service in mobile ad hoc networks - Google Patents

Abstract

According to an embodiment of the present invention, in the wireless mobile ad hoc network, when a communication link is disconnected between a source node and a destination node that are communicating in a wireless mobile ad hoc network, and an interference occurs in a third node, 2 Detecting disconnection of communication at any one of the two nodes and forwarding a node discovery message (NSM) to the neighbor node, and checking the channel state table (CST) of the third node to cause interference In the case of using a channel different from the above, resetting the disconnected communication link so that the source node and the destination node can communicate via themselves (third node), and when using the same channel in the fourth step. Checking its own CST and waiting for the NSM if there is an idle channel; if the NSM is received at the third node, By way of a step of resetting the communication link is disconnected.

According to the disclosed invention, not only solves the transmission delay problem occurring in the ad hoc network, but also provides QoS for providing a multimedia service in the future.

Ad Hoc Network, Multichannel, Rerouting, NSM.

Description

Rerouting using multiple channels in mobile ad hoc networks {A congestion control mechanism for supporting differentiated service in mobile ad hoc networks}

1 is a diagram illustrating an example of a channel allocated on a communication link in a wireless mobile ad hoc network topology according to an embodiment of the present invention.

2 is a diagram illustrating channel allocation information of an adjacent node of a node.

3 is a diagram illustrating a method of restoring a communication link again through an adjacent node when the link is disconnected in FIG. 1.

FIG. 4 is a table illustrating a message type and channel allocation information for reestablishing a link in FIG. 3.

FIG. 5 is a diagram illustrating a method for preventing reassignment of a node to a neighbor with respect to a communication link establishment request of a node according to an embodiment of the present invention.

6 is a diagram illustrating a network state that occurs repeatedly upon channel reassignment.

The present invention relates to a rerouting method using multiple channels in a mobile ad hoc network. More particularly, the present invention relates to a method for quickly reestablishing a link disconnection when a node is disconnected out of a radius in a wireless mobile ad hoc network environment. It is about how to.

The Wireless Mobile Ad Hoc Network is a wireless mobile host (node) that forms an ad hoc network without the need for centralized management or standardized support services based on IEEE 802.11 wireless LANs (WLANs). Of people.

The IEEE 802.11 WLAN technology is a set of standards developed by the Working Group of the Institute of Electrical and Electronics Engineers (IEEE).

This ad hoc network forwards packets from the backbone host or other mobile host to other mobile hosts.

In the wireless mobile ad hoc network, if the communicating node is out of radius when moving in any direction, the communicating node is broken due to the use of a single channel. It can cause interference and serious interference to communication.

Node here refers to an independent mobile host on an ad hoc network.

Wireless mobile ad hoc networks can be employed in a variety of areas, where many nodes are distributed over a large area using common channels.

However, due to the nature of the radio, the transmission radius is limited according to the performance of the transceiver and the strength of the transmitted power.

If it is within each other's transmission radius, direct communication is possible, and if it is far apart, communication with the destination node is possible via neighboring neighbor nodes.

In this case, all nodes share one channel, so when other nodes are in use, adjacent nodes cannot communicate. If they communicate, they may interfere with each other or may cause conflicts between channels through simultaneous transmission. This can cause serious communication problems.

In order to solve this problem, a study on the use of a wireless channel in a single channel environment is mainly studied a medium access control (MAC).

The study of the radio channel access access can be divided into the case where the node is operated under the control of the central station node and the case where the node operates individually.

Nodes in a wireless mobile ad hoc network environment generally use the latter method, and in this case are used by a single channel, so as described above, a method for recovering a channel when a node moves and collision due to channel interference with adjacent nodes when moving. Techniques for solving problems have been studied separately.

In addition, two versions conforming to the IEEE 802.11 standard, IEEE 802.11a and IEEE 802.11b, define the multi-channel in the physical layer. According to the standard, the IEEE 802.11b version uses 14 channels in the 2.4Ghz band.

The multi-channel method is a method for efficiently controlling the interference of the node due to the disconnection and movement of the communication link.

Dynamic Channel Assignment (DCA), a dynamic channel allocation technique, is a method of establishing a communication link so as to be allocated by a request of a channel to transmit data to a destination.

The DCA scheme uses a control channel different from a dedicated channel for transmitting a control message.

This method is efficient when the number of data channels is large. However, since a dedicated channel is used when the number of data channels is small, an additional overhead occurs due to message transmission.

The DCA & R (Reassignment) scheme, which uses a channel reassignment scheme similar to the DCA scheme, uses a channel similar to the DCA scheme, but has very low performance when all nodes are asynchronous in a mobile environment.

In order to complement the DCA and DCA & R schemes, the CDMA coding scheme in which CDMA codes the channels used by each node so that multiple nodes can use the same channel at the same time has a problem of increasing the price of the host because a multi-transceiver must be installed.

[1] (CY Chang, PC Huang, CT Chang, and YS Chen, "Dynamic Channel Assignment and Reassignment for Exploiting Channel Reuse Opportunities in Ad Hoc Wireless Networks," in IEICE TRANS. COMMUN., Vol. E86-B, No.4, April 2003.) discloses an algorithm that does not limit the number of data channels and assumes a situation in which a destination and a source host move simultaneously, but the channels are variably allocated when the communicating nodes move. There is no description of a technique for enabling this.

See also [2] (CR Lin and JS Lin, "QoS Routing in Ad Hoc Wireless Networks," in IEEE Journal on Selected Areas in Comm., Vol. 17, Aug. 1999.). Algorithms have been disclosed to allow channels that are allocated and not used by neighboring hops to be used by other hops. However, since the allocation method for cases where neighbors cannot be allocated while in use is not disclosed, channel utilization can be increased. There was no.

Disclosure of Invention An object of the present invention, which is devised to solve the above-mentioned problem, is a method for solving a communication link disconnection and interference with a neighboring node when a node using the same channel moves in a wireless mobile ad hoc network. The present invention provides a stable communication environment by quickly recovering damaged links.

In order to achieve the above object, the present invention uses a node search message to find a node disconnected during communication without additional overhead when a node in communication in the wireless mobile ad hoc network moves and the link is disconnected.

In addition, the present invention allocates unused channels in a channel reassignment scheme in order to prevent interference between channels when a moving node uses a channel such as a neighbor node.

Hereinafter, the configuration and operation of the present invention will be described with reference to the accompanying drawings.

In FIG. 1, a channel reassignment method performed by each node (terminal) is as follows.

Here, each node has channel allocation information (source node, destination node, busy channel, idle channel) of an adjacent node, as shown in FIG.

① A moving node A is communicating with node D, and node A is out of the communication radius of node D, and the communication link is disconnected.

② If node A accesses other communicating nodes F and C and node F and A share the same channel, interference occurs between node F and node A.

③ At ①, node D detects the disconnection of communication and delivers node search message (NSM) to neighbor nodes (G, B, F).

As illustrated in FIG. 4, the NSM includes source node, destination node, and idle channel information.

④ At the same time, Node F in communication in ② detects the interference of communication and checks its channel status table so that it can communicate with the source node via itself when using another channel.

⑤ If the same channel is used, it checks whether there is an idle channel, and if there is an idle channel, it waits for receiving an NSM message.

⑥ When the NSM message arrives, reset the disconnected communication link via itself along the reverse path.

Next, the four processes performed by each node to perform channel reassignment in the inter-node connection reconfiguration are as follows.

The OneHop (X) process finds a pair of nodes that are within the communication radius of node X (within one hop).

The FreeChannel (X) process calculates an unallocated channel among the channels of node X.

The Neighbor (OneHop (X)) process finds a node that can communicate with a neighbor that is within the communication radius of node X (within one hop).

The Connect (X) process finds the number of nodes that can communicate with Note X.

Referring to the above four operations and the repetitive channel reallocation problem with reference to Figures 5 and 6 as follows.

5 illustrates a method for reallocating a channel, and FIG. 6 illustrates a network state that occurs repeatedly during channel reallocation.

Assuming that the source node X and the destination node Y are Y, and node X wants to deliver data to node Y, first node X checks whether there is an unassigned channel (S502).

The node X transmits a channel reassignment message (CRM) to the node Y (S504), and the node Y receiving the CRM checks its channel status table (CST) (S506).

The CRM includes source node, destination node, and idle channel information.

Node Y has an unassigned channel to itself (S508), and if the number of channels allocated to it is greater than the number of connectable channels (S510), it sends a CRM-ACK (Acknowledgement) message to the source node X ( In step S512, the node in its communication radius is checked (S514).

The CRM-ACK message includes source node, destination node, and idle channel information.

When the CRM-ACK message is received, the node X checks a node within its communication radius (S520).

Nodes X and Y are both present in node X and Y that are capable of communicating with neighbors that are within their communication radius (S522), and nodes X and Y are checking whether their unallocated channels are available to each other. If both are available, it is determined whether the channel information of the node X and the channel information of the node Y are the same (S524). Since the exchange of channels continues to occur due to repeated collisions with each other, the CRM request is ignored (S526). .

If the channel information of the node X and the channel information of the node Y are different in step S524 (step S528), channel reallocation is performed (S528). Then, the reallocated information is transferred to two hop neighbor nodes and the CST is updated (S530). ).

If the number of channels allocated to the self is smaller than the number of connectable channels in step S510, channel reallocation is performed (S516), and information between the nodes X and Y is exchanged (S518).

1 and 3 illustrate the practical application of the present invention described above in a wireless mobile ad hoc network.

1 illustrates a node in communication using a channel and a channel allocated on a communication link in a wireless mobile ad hoc network topology.

Node A and Node D are communicating and use channel 1 (ch # 1).

When node A communicating with node D approaches node F, node A breaks the link communicating with node D and causes channel interference with node F.

Node D sends an NSM, one of the messages shown in FIG. 4, to the neighbor node to detect the disconnection of the communicating link, inform the neighboring node of the communicating node, and quickly reestablish the link, and the node that has received the NSM. Searches for node A, which has moved around it.

If node A is found, node A forwards an NSM-ACK message to the node that forwarded the NSM.

Receiving the NSM-ACK message, the forwarding node determines whether it can relay data by referring to its node state table, and forwards the message in the reverse direction if possible.

If the forwarding node uses the same channel as node A, the algorithm of FIG. 5 is used to compare whether the repetitive channel exchange takes place and if the exchange of repetitive channels occurs, the message itself is discarded, otherwise the unallocated channel is used. Reallocate and forward the NSM-ACK message to the source node D via itself.

When the reset is completed, the node A and the node D simultaneously transmit the reset information to the two-hop neighbors and the channel reassignment process ends.

As described above, the present invention using the multi-channel technology not only solves the transmission delay problem occurring in the ad hoc network, but also provides QoS for providing a multimedia service in the future.

In addition, it will not only increase the use of idle channels in the future, but also solve hot spot problems in disaster areas.

Claims (8)

A first step in which a communication link is disconnected between a source node and a destination node in communication in a wireless mobile ad hoc network, and an interference occurs at a third node by one of the two nodes; A second step of detecting disconnection of communication at one of the two nodes in communication and delivering a node discovery message (NSM) to a neighboring node; When the third node uses its own channel state table (CST) to check the channel state table and uses a different channel from the interfering node, the source node and the destination node can communicate via themselves (third node). Resetting the disconnected communication link so that A fourth step of waiting for the NSM reception if there is an idle channel when the same channel is used in the third step; And a fifth step of resetting a disconnected communication link via itself along a reverse path when the NSM is received at the third node. The method of claim 1, A method for rerouting using multiple channels in a mobile ad hoc network characterized in that disconnection of a communication link occurs out of a communication radius by moving one of the node of the source node and the destination node. The method of claim 1, wherein the NSM includes source side node, destination side node, and idle channel information. The method of claim 1, wherein the third node in the third or fifth communication link resetting step, OneHop (X), which finds a pair of nodes that are within the communication radius of any node X (within one hop), FreeChannel (X), which computes an unallocated channel from channels on node X, Neighbor (OneHop (X)), which finds nodes that can communicate with neighbors within the communication radius of node X, In Connect (X), which finds the number of nodes that can communicate with Note X, A multi-channel rerouting method in a mobile ad hoc network characterized by preventing re-allocation of channels by four processes. The method of claim 4, wherein Reassigning a channel from a third node to a fourth node using the four processes, Step A, which checks whether a third node has an unassigned channel to itself, A B that sends a channel reassignment message (CRM) at a third node to a fourth node, and checks its channel status table (CST) at the fourth node receiving the CRM. Steps, If the fourth node has a channel unallocated to itself, and determines whether the number of channels allocated to itself is greater than the number of connectable channels, it sends a CRM-ACK message to the third node and sends its own communication. Step C for inspecting nodes within radius; Receiving a CRM-ACK message from the third node, examining the node within its communication radius; If both the third node and the fourth node are capable of communicating with neighbors within their communication radius, and all of their unallocated channels are available, the channel information of the third node and the fourth node. Determining whether the channel information is the same, and if it is different, re-allocating the channel. The method of claim 5, And relocating channels and exchanging information with each other when the number of channels allocated in step C is smaller than the number of connectable channels. The method of claim 5, And in step E, if the channel information of the third node and the channel information of the fourth node are the same, the CRM transmitted from the third node is ignored. The method of claim 5, And reassigning information between the third node and the fourth node to two-hop neighbor nodes after the channel is reassigned in the step E. 2.

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