KR20090019461A - Mac method and apparatus for fast packet forwarding in wireless network - Google Patents

Abstract

A MAC(Media Access Control) method for fast packet forwarding in a wireless network and an apparatus thereof are provided to transmit an existing acknowledge response frame through an acknowledge control frame for packet forwarding and reserve a transmission channel simultaneously at the next hop node to forward a packet, thereby supporting fast forwarding at a middle node. A final destination of a packet which the first node(20) receives is checked(S504). If the final destination is not the first node, the first node detects address information of the next hop node to be forwarded to generate ACK(Acknowledgement) and ACR(Acknowledge and Request to send) frames(S505,S506). A checking response and the ACR frame simultaneously perform the ACK and channel reservation to the next hop node. The first node broadcasts the ACK and ACR frames(S507). The first node transmits a packet to the next hop node after SIFE(Short Interframe Space) waiting(S508,S509).

Description

Method and apparatus for controlling medium access for fast packet forwarding in wireless network {MAC method and apparatus for fast packet forwarding in wireless network}

The present invention relates to a method and apparatus for controlling medium access for packet forwarding in a wireless network.

In particular, the present invention relates to medium access control (MAC) for supporting label switching for efficient packet forwarding of intermediate nodes in a multi-hop wireless network.

The present invention relates to a method and apparatus for controlling medium access for packet forwarding in a wireless network.

When two hosts send and receive packets in a wireless network, the route of the packet sent from the source may be delivered to the destination through multi-hop. That is, packets originating at the source are received at the final destination via one or more intermediate nodes in the wireless network. At this point, intermediate nodes (eg, routers) that pass through the packet until it arrives at the last node forward the packet to the next adjacent node according to the routing information if the final destination of the received packet is not itself.

1 is a block diagram illustrating multi-hop packet forwarding on a conventional network.

Referring to FIG. 1, the packet transmitted by the originating node 10 is shown to be delivered to the destination node 40 through a path composed of several intermediate nodes 20 and 30 in the network. At this time, the intermediate nodes 20 and 30 in the path refer to the destination of the received packet and their routing table, and find the interface of the next hop (neighbor node) existing in the path and transmit the packet.

In this case, the transmission delay that occurs when the intermediate nodes 20 and 30 perform packet forwarding includes the time and network interface card (NIC) for processing the route finding with the address information (IP destination address) in the packet. There is a time taken to secure a channel in order to use the medium.

In more detail, this transmission delay occurs because a prefix matching operation to find an output port of a network interface card (NIC) to forward a packet must be performed through a routing table search. In order to solve this problem, Multi-Protocol Label Switching (MPLS) has been developed.However, unlike the wired, the media access method has to compete with neighboring nodes to secure the channel. There is a problem that a delay time occurs.

Meanwhile, the conventional media access control (MAC) scheme will be described with reference to FIG. 2.

2 illustrates a medium access control (MAC) scheme used in a conventional WLAN-based network.

The conventional media approach checks whether the originating node with the data to be transmitted is idle using the air interface. That is, the originating node transmits a frame immediately if the medium is not used by another node for one period of time (Distributed inter-frame space, DIFS) defined in the standard, otherwise waits for another period (DIFS) After that, a random backoff process is performed. In this case, the backoff counter decreases by one slot only when the medium is not used by another node, and the originating node may immediately transmit a frame when the backoff counter value reaches zero.

The intermediate node receiving the packet from the originating node transmits an acknowledgment frame (ACK MAC PDU) to the originating node after a short inter-frame space (SIFS) time of one cycle when the received packet is normal. If the originating node does not receive an acknowledgment frame within a certain period of time (SIFS + transmission time), it determines that the transmission has failed and performs retransmission.In this case, except that the retransmission increases the backoff window and proceeds, same.

On the other hand, in the case of a wired network, since each physical interface (port) of devices corresponding to intermediate nodes such as a router or a switch is connected by a dedicated wire, the medium can be directly accessed during packet forwarding. However, in the case of a wireless network, since the medium is not in the form of a line like a wire, but in the form of a virtual link with all neighboring nodes in a transmission distance of radio waves, it may cause mutual interference. The medium must be accessed to secure the transmission channel. Therefore, in the wireless network, intermediate nodes may not be forwarded immediately because they compete with the neighboring nodes for packet forwarding, which results in a large delay in the overall transmission time of the packet.

Accordingly, an object of the present invention is to provide a method and apparatus for rapidly forwarding a packet received by an intermediate node in a multi-hop wireless network to a next hop node without contention with neighboring nodes.

In order to solve the above technical problem, a medium access control method for packet forwarding in a wireless network according to an embodiment of the present invention,

a) checking the final destination of the packet received by the first node; b) Acknowledgment and Request to Send (ACR) frame by detecting address information of the next hop node to be forwarded if the final destination is not its own as a result of the check in step a), where acknowledgment and reservation (ACR) a frame is a frame that simultaneously performs an acknowledgment (ACK) and channel reservation to the next hop node; c) broadcasting the acknowledgment and reservation (ACR) frame; And d) transmitting a packet to a next hop node after waiting for Short Interframe Space (SIFE).

Here, the method may further include responding with an acknowledgment (ACK) frame after waiting for SIFE if the final destination is itself.

On the other hand, the medium access control apparatus for packet forwarding in a wireless network according to an embodiment of the present invention,

A label switching table having an entry consisting of an input label and a MAC address pair and an output label and MAC address pair corresponding thereto; Acknowledgment and Request to Send (ACR) frames with reference to the label switching table, where the Acknowledgment and Request (ACR) frames perform simultaneous acknowledgment (ACK) and channel reservation to the next hop node. A label switching table lookup module for generating frame; And a label switching table updating module for updating the node's input or output label and MAC address based on the packet's routing path.

The label switching table lookup module extracts an output label corresponding to an input label of a received packet and a MAC address of a next hop node from the label switching table.

The acknowledgment and reservation frame further includes a next hop address, a channel duration and an output label field in an acknowledgment (ACK) frame for the received packet.

On the other hand, in the multi-hop wireless network according to an embodiment of the present invention, the recording medium in which the structure of the medium access control frame for packet forwarding of the intermediate node is recorded,

A subtype field having a value distinguishing an acknowledgment (ACK) frame or an acknowledgment (ACR) frame; A duration field for storing a time required for transmitting a packet to a node corresponding to the next hop during forwarding; A first address field for storing an address of a node that has sent a packet to itself; A second address field for storing an own address of a channel to be reserved in a forwarding operation; A third address field for storing an address of a next hop node in the forwarding operation; And a label field that stores its output label value as a label switching table output interface index for the packet.

By the above-described configuration, the apparatus for accessing a medium of a multi-hop wireless network according to an embodiment of the present invention has to forward packets while simultaneously transmitting an existing acknowledgment (ACK) frame through an acknowledgment control frame for packet forwarding. By reserving a transport channel in a hop node, blocking channel contention of neighboring nodes in the channel contention scheme supports fast packet forwarding at an intermediate node.

The present invention relates to a method and apparatus for controlling medium access for packet forwarding in a wireless network, and more particularly, to a method and apparatus for reducing end-to-end transmission delay by minimizing channel contention of an intermediate node in a multi-hop path composed of multiple nodes. will be.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is said to "include" a certain component, it means that it can further include other components, without excluding other components unless specifically stated otherwise. In addition, the terms “… unit”, “… unit”, “module”, etc. described in the specification mean a unit that processes at least one function or operation, which may be implemented by hardware or software or a combination of hardware and software. have.

Now, a method and apparatus for controlling a medium access for fast packet forwarding in a wireless network according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

3 is a structural diagram showing a media access control apparatus according to an embodiment of the present invention.

Referring to FIG. 3, the media access control apparatus 100 according to an embodiment of the present invention may be a network interface card installed in each node of a wireless network, and includes a packet buffer queue 110, The label switching table 120, the label switching table lookup module 130, the label switching table updating module 140, and the communication unit 150 are included.

The wireless network may be, for example, any one of an IEEE 802.11 WLAN, an ad hoc network, a mesh network, and a sensor network. In addition, the node may be a WLAN access point, a wired / wireless gateway, a mobile gateway, a router, or a switch, which has a lot of forwarding packets received from other nodes in the middle of sending the packet.

Next, components of the media access control apparatus 100 according to the embodiment of the present invention will be described with reference to FIG. 3.

First, the packet buffer queue 110 is a storage device for temporarily storing a packet received by the network interface card 100 before processing it.

The label switching table 120 has an entry consisting of a pair of input labels and a MAC address and a corresponding pair of output labels and MAC addresses. In this case, multiprotocol label switching (MPLS) refers to a data packet having a separate label instead of an IP address and routing to a label instead of an IP address. Because label switching (MPLS) accommodates a variety of protocols, it applies to IP networks, ATMs, and frame relays. That is, in a network that supports label switching, nodes can view and switch labels without forwarding IP addresses, thereby enabling fast switching.

The label switching table lookup module 130 takes the input label of the packet to be forwarded, searches the label switching table 120 to find the MAC address of the output label and the next hop node, and based on the acknowledgment and request to send, ACR) frame.

Here, the acknowledgment and reservation (ACR) frame generated by the label switching table lookup module 130 has three functions. The first function is a function of an acknowledgment (ACK) frame, which informs a node that has sent a packet to a node that has received the packet. The second function is to reserve a channel to the next node to transmit a packet. The first function is to limit channel contention between adjacent nodes. In addition, a detailed description of the acknowledgment and reservation (ACR) frame will be described later.

The label switching table update module 140 maintains an entry of the label switching table 120 based on the result of performing the higher routing module or the label distribution protocol. That is, the I / O label and MAC address of the node are updated based on the routing path of the packet determined by the higher routing module or the label distribution protocol.

The communication unit 150 has a function of receiving and transmitting a packet forwarded through the network interface card 100.

Meanwhile, an acknowledgment and reservation (ACR) frame generated by the apparatus for accessing media according to an embodiment of the present invention will be described in detail with reference to FIG. 4.

4 is a structural diagram illustrating an acknowledgment and reservation (ACR) frame generated by the apparatus for accessing media according to an embodiment of the present invention.

After receiving the packet, the medium access control apparatus 100 of the intermediate node checks the final destination of the received packet. If the packet forwarding is necessary because the final destination of the packet is not itself, the acknowledgment and reservation (ACR) is performed. ) To generate and broadcast the frame 200. On the contrary, if the final destination of the packet is itself and no packet forwarding is necessary, the existing acknowledgment (ACK) frame indicating that the packet has been received without error is transmitted.

Referring to FIG. 4, the acknowledgment and reservation (ACR) frame 200 is configured to extend an existing acknowledgment (ACK) frame, and includes a subtype 210 and a duration field of the frame control field. 220, a first address field 230, a second address field (Transmitter Address (TA)) 240, a third address field (Forwarding Address (FA)) 250, and a label field 260.

The subtype 210 of the frame control field has an arbitrary assignment value that distinguishes an existing acknowledgment (ACK) frame from an acknowledgment and reservation (ACR) frame 200 according to an embodiment of the present invention. For example, if the subtype 210 of the frame control field is an existing acknowledgment (ACK) frame, it may be set to ACK, and in the case of the acknowledgment control frame 200 according to an embodiment of the present invention, it may be set to ACR. . However, the method of notifying the allocation value is not limited thereto, and may be set to different notations such as 0 or 1.

The duration field 220 indicates information on how much the channel is used, and stores the time required to transmit a packet to a node corresponding to the next hop when forwarding the acknowledgment and reservation (ACR) frame 200.

The first address field 230 stores the address of the node that sent the packet to itself.

The second address field 240 stores its own address, which is a node to reserve a channel in a forwarding operation, via an acknowledgment and reservation (ACR) frame 200.

The third address field 250 stores the address of the next hop node that should receive the packet transmitted in the forwarding operation.

The label field 260 stores its output label value as the label switching table output interface index for the packet.

As such, the apparatus 100 according to an embodiment of the present invention generates and broadcasts an acknowledgment and reservation (ACR) frame 200 to transmit a packet while simultaneously transmitting an existing acknowledgment (ACK) frame. By reserving the transmission channel to the next hop node to be forwarded, it blocks the channel contention of neighboring nodes in the channel competition diagram, thereby supporting fast packet forwarding at the intermediate node.

Meanwhile, a media access control method for fast packet forwarding in a wireless network according to an embodiment of the present invention will be described with reference to FIG. 5.

5 is a flowchart illustrating a method of controlling medium access for fast packet forwarding in a wireless network according to an embodiment of the present invention.

Referring to FIG. 5, a packet sent by the originating node 10 is a destination node that is the final destination through packet forwarding of the first intermediate node 20 and the second intermediate node 30 according to an embodiment of the present invention. Assume that 40 is transmitted. That is, the intermediate nodes 20 and 30 include the media access control apparatus 100 according to the embodiment of the present invention. Further, although omitted in the drawing, there are a plurality of neighboring nodes in the wireless network that perform channel contention in addition to the nodes of the forwarding path.

First, the first intermediate node 20 receives a MAC frame from the originating node 10 (S501). The first intermediate node 20 receiving the MAC frame has the label information of the packet and searches the label switching table 120 to check the final destination of the packet (S502). As a result of the search in step S502, the first intermediate node 20 transmits a conventional acknowledgment (ACK) frame to the originating node 10 when the final destination of the packet is itself (S503).

On the other hand, when the search result of step S502, the final destination of the packet is not the packet that should be forwarded to the next hop information including the output label and the MAC address corresponding to the input label of the label switching table 120 Extract (S504) and generate an acknowledgment and reservation (ACR) frame 200 based on the extracted next hop information (S504). The first intermediate node 20 transmits the generated acknowledgment and reservation (ACR) frame 200 to the originating node 10 and the second intermediate node 30 of the next hop (S507). In this case, the acknowledgment and reservation (ACR) frame 200 transmitted from the first intermediate node 20 is transmitted to the broadcasting, and the packet transmission to the first intermediate node 20 is normally performed at the originating node 10. ACK, and the second intermediate node 30 has a channel reservation function. In addition, the acknowledgment and reservation (ACR) frame 200 transmitted by the first intermediate node 20 may be transmitted to itself and adjacent nodes in the channel contention scheme to limit channel contention.

The first intermediate node 20 transmits an acknowledgment and reservation (ACR) frame 200 in step S507, waits for one period of SIFS (S508), and then transmits the data frame to the second intermediate node, which is the next hop. Transmit (S509).

After receiving the data frame from the first intermediate node 20, the second intermediate node 30 repeats the operations of steps S502 to S508 (S510), and transmits the data frame to the destination node 40, which is the final destination. (S511).

Meanwhile, the packet forwarding time according to the prior art and the exemplary embodiment of the present invention will be described with reference to FIGS. 6A and 6B. In FIG. 6, it is assumed that a network path through which a packet is delivered is an originating node 10, a first intermediate node 20, a second intermediate node 30, and a destination node 40 as shown in FIG. 5.

6A illustrates forwarding a packet using a conventional packet forwarding method.

Referring to the attached first intermediate node 20 in FIG. 6A, the forwarding transmission to the second intermediate node 30 of the next hop and the transmission 611 before the first intermediate node 20 receives the data packet is performed. Disconnection of 612 results in a channel delay. This delay increases with the increase in the number of intermediate nodes present in the packet's transmission path, and the time delays due to contention of intermediate nodes to obtain a channel may result in a decrease in the transmission efficiency of the entire network. For example, when there are N hop paths between the originating node 10 and the destination node 40, N channel competition is required in the related art. In this case, the forwarding operation suffers a delay and increases the end-to-end delay.

On the other hand, Figure 6b shows the delivery of the packet using a packet forwarding method according to an embodiment of the present invention.

With reference to the first intermediate node 20 in FIG. 6A attached, the first intermediate node 20 may compete for obtaining a channel only at the original originating node 10, which is the transmission 621 before receiving the data packet. After that, the first intermediate node 20 and the second intermediate node 30 forward the packet immediately without channel contention. Therefore, the channel is secured by one channel access competition, and the forwarding process does not undergo a separate channel access competition.

As such, when intermediate nodes on a path of a multi-hop wireless network according to an embodiment of the present invention receive a packet to be forwarded to a node of a next hop, that is, the received packet is not the best destination, so the packet is forwarded. In this case, the channel can be directly accessed by avoiding unnecessary channel competition. This enables fast packet forwarding of intermediate nodes, and reduces the channel usage time that is wasted due to channel contention, thereby reducing jitter, which is a variation in the propagation delay and the interval between packet arrivals, and increasing the utilization of bandwidth provided by the channel. It has the effect of improving the performance.

Although the embodiments of the present invention have been described above, the present invention is not limited only to the above embodiments, and various other changes are possible.

For example, in the embodiment of the present invention shown in FIG. 3, the network interface card in the label switching (MPLS) is configured to identify the address of each node as a label, but may be formed as an IP address instead of the label.

In addition, in the embodiment of the present invention illustrated in FIG. 5, the first intermediate node 20 and the second intermediate node 30 have been described as including the media access control apparatus 100 according to the embodiment of the present invention. Not all intermediate nodes need to include the media access control device 100. That is, the apparatus 100 for controlling access to media according to an embodiment of the present invention may be used in conjunction with a conventional network interface card. In this case, the intermediate node including the conventional network interface card may be an existing IEEE 802.11 Distributed Coordination Function (DCF). Perform the transfer.

An embodiment of the present invention is not implemented only through the above-described apparatus and / or method, but through a program for realizing a function corresponding to the configuration of the embodiment of the present invention, a recording medium on which the program is recorded, and the like. The implementation may be easily implemented by those skilled in the art from the description of the above-described embodiments.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

1 is a block diagram illustrating multi-hop packet forwarding on a conventional network.

2 illustrates a medium access control (MAC) scheme used in a conventional WLAN-based network.

3 is a structural diagram showing a media access control apparatus according to an embodiment of the present invention.

4 is a structural diagram illustrating an acknowledgment and reservation (ACR) frame generated by the apparatus for accessing media according to an embodiment of the present invention.

5 is a flowchart illustrating a method of controlling medium access for fast packet forwarding in a wireless network according to an embodiment of the present invention.

6A illustrates forwarding a packet using a conventional packet forwarding method.

6B illustrates delivery of a packet using a packet forwarding method according to an embodiment of the present invention.

Claims (10)

In the medium access control method for packet forwarding in a wireless network, a) checking the final destination of the packet received by the first node; b) Acknowledgment and Request to Send (ACR) frame by detecting address information of the next hop node to be forwarded if the final destination is not its own as a result of the check in step a), where acknowledgment and reservation (ACR) a frame is a frame that simultaneously performs an acknowledgment (ACK) and channel reservation to the next hop node; c) broadcasting the acknowledgment and reservation (ACR) frame; And d) sending a packet to the next hop node after waiting for Short Interframe Space (SIFE); Medium access control method comprising a. The method of claim 1, and e) responding with an acknowledgment (ACK) frame after waiting for SIFE if the final destination is itself as a result of the check in step a). The method of claim 1, B), b-1) retrieving an input label of the packet; And b-2) retrieving the MAC address of the output label next hop node corresponding to the input label Medium access control method comprising a. The method of claim 1, C), c-1) acknowledging that the packet has been successfully received; And c-2) reserving a transport channel to the next hop node to forward the packet to Medium access control method characterized in that to perform at the same time. In the medium access control apparatus for packet forwarding in a wireless network, A label switching table having an entry consisting of an input label and a MAC address pair and an output label and MAC address pair corresponding thereto; Acknowledgment and Request to Send (ACR) frame with reference to the label switching table, where the Acknowledge and Request (ACR) frame is a frame that simultaneously performs acknowledgment (ACK) and channel reservation to the next hop node. A label switching table lookup module for generating an im; And Label switching table update module to update the node's input or output label and MAC address based on the packet's routing path Medium access control device comprising a. The method of claim 5, wherein The label switching table lookup module, And an output label corresponding to an input label of a received packet and a MAC address of a next hop node from the label switching table. The method according to claim 5 or 6, The confirmation response and the reservation frame, And a next hop address, channel duration, and output label field in an acknowledgment (ACK) frame for the received packet. The method of claim 7, wherein The confirmation response and the reservation frame, And the first address field, the second address field, the third address field and the label field in each node are changed. A recording medium on which a structure of a medium access control frame for packet forwarding of an intermediate node in a multi-hop wireless network is recorded. A subtype field having a value distinguishing an acknowledgment (ACK) frame or an acknowledgment (ACR) frame; A duration field for storing a time required for transmitting a packet to a node corresponding to the next hop during forwarding; A first address field for storing an address of a node that has sent a packet to itself; A second address field for storing an own address of a channel to be reserved in a forwarding operation; A third address field for storing an address of a next hop node in the forwarding operation; And A label field for storing its output label value as a label switching table output interface index for the packet Recording medium in which the structure of the medium access control frame comprising a. The method of claim 9, The duration field is A recording medium on which a structure of a medium access control frame is recorded, which limits channel competition for a time required to transmit a packet to a next hop node.

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