KR101380090B1 - System and method for link quality measurement and link selection in multi-radio wireless ad-hoc networks - Google Patents

Abstract

The present invention relates to a system and method for selecting a link and measuring link quality in a multi-radio wireless ad-hoc network environment. In a data transmission environment through a terminal in the multi-radio wireless ad-hoc network environment, provided is the system for selecting the link and measuring the link quality which includes: a first predicting unit which predicts an available bandwidth of a channel by using an amount of used channels calculated by a transmission node and a reception node in a media access control (MAC) layer; a second predicting unit which predicts the reduction amount of the available bandwidth due to a hidden node; a quality measuring unit which measures the link quality between the transmission node and the reception node by using the available bandwidth and the reduction amount of the available bandwidth; and a link selecting unit which selects the link with high quality among the links whose quality is measured.

Description

TECHNICAL AND METHOD FOR LINK QUALITY MEASUREMENT AND LINK SELECTION IN MULTI-RADIO WIRELESS AD-HOC NETWORKS

The present invention relates to a method and system for measuring link quality and selecting a link in a multi-radio wireless Ad-hoc network environment.

There is a growing demand for high throughput networks such as high definition video and large files in wireless ad hoc networks. In order to support this, a multi-radio environment using multiple network interfaces has attracted attention, and a link quality measurement method in a multi-radio wireless network environment has been studied.

Expected Transmission Time (ETT) is used as a representative link quality measurement method used in a multi-radio wireless ad hoc network. The ETT periodically transmits a Hello packet and a Probe packet to neighbor nodes to measure a packet delivery ratio (PDR) and available bandwidth. In addition, the PDR sends a Hello packet to the neighbor nodes by broadcast every second, and calculates the number of responses by each neighbor node every 10 seconds. The available bandwidth is calculated using the average of the times of transmitting and responding 10 consecutive successive pairs of probe packets of different length in unicast for each neighbor node.

Here, the Hello packet is transmitted to all neighbor nodes in one transmission through broadcast, so the cost is small, but the Probe packet sends a burden to the network because at least 20 packets are continuously sent in proportion to the number of neighbor nodes. do. Therefore, if this task is performed periodically, the problem is that the data cannot be sent as much as the cost of measuring link quality when transmitting the actual data.

The embodiment of the present invention solves the problems of the existing link selection system described above, thereby reducing the cost of the link quality measurement method in a multi-radio wireless ad hoc network environment and improving the accuracy of data transmission throughput between transmitting and receiving nodes. We want to provide a system and a way to increase it.

In detail, to provide a link quality measurement and selection system and method characterized by identifying each node's MAC (Media Access Control) layer information and potential hidden nodes in order to select a high throughput link.

In a data transmission environment through a terminal in a multi-radio wireless ad-hoc network environment, a method for estimating available bandwidth of a channel using channel usage calculated by a transmitting node and a receiving node in a media access control (MAC) layer 1 prediction unit; A second predictor for predicting a decrease in available bandwidth due to the hidden node; A quality measuring unit measuring a link quality between a transmitting node and a receiving node by using an available bandwidth and a reduction amount of the available bandwidth; And a link selector for selecting a link having a high link quality among the links of which the link quality is measured.

In one side, in the first prediction unit, each node calculates channel usage by measuring an occurrence frame of a channel in the MAC layer, and predicts an available bandwidth by multiplying the channel usage by the maximum bandwidth of the channel.

In another aspect, the second prediction unit may estimate the amount of available bandwidth reduction caused by the hidden node at the transmitting node using the difference between the channel usage calculated at the transmitting node and the channel usage calculated at the receiving node. .

In another aspect, the second prediction unit records each channel usage as additional information in the Hello packet, and transmits it to neighboring nodes in a broadcast form every second, and records the channel usage in the Hello packet. The existence of the hidden node can be confirmed by comparing the usage with the channel usage measured by each neighbor node.

In another aspect, the quality measurer may quantify the link quality by using a packet delivery ratio (PDR), an available bandwidth, and an amount of available bandwidth reduction between a transmitting node and a receiving node.

In another aspect, the link selector may modify a path to a link higher than or equal to a threshold value when there is a link higher than or equal to a threshold value in comparison with the quality of a link being used in real time among the links that may be connected between a transmitting node and a receiving node.

In a multi-radio wireless ad-hoc network environment, a step of estimating available bandwidth of a channel using channel usage calculated by a transmitting node and a receiving node in a media access control (MAC) layer ; Predicting a reduction in the available bandwidth due to the hidden node; Measuring a link quality between a transmitting node and a receiving node using the available bandwidth and the amount of available bandwidth reduction; And selecting a link having a high link quality among the links of which the link quality is measured.

According to an embodiment of the present invention, it is possible to provide a system and a method capable of increasing data transmission throughput between transmission and reception nodes by reducing cost and improving accuracy of a link quality measurement method in a multi-radio wireless ad hoc network environment.

In addition, it is possible to provide a link quality measurement and selection system and method characterized by identifying each node's MAC (Media Access Control) layer information and potential hidden nodes in order to select a high throughput link.

FIG. 1 illustrates a channel that can be connected to a node that is connected between nodes, and a hidden node around the node according to an embodiment of the present invention.
2 is a block diagram for explaining the configuration of a link quality measurement and selection system according to an embodiment of the present invention.
3 is a diagram for describing measurement of channel usage of a MAC layer according to an embodiment of the present invention.
4 is a diagram for explaining prediction of available bandwidth reduction due to a hidden node according to one embodiment of the present invention.
5 is a flowchart illustrating each step of the link quality measurement and selection method according to an embodiment of the present invention.

Hereinafter, a link quality measurement and selection system and a method thereof will be described in detail with reference to the accompanying drawings.

Ad hoc networks Ad-hoc does not require an underlying network device such as a base station or an access point to configure and maintain the network. Therefore, the nodes communicate with each other using a wireless interface, overcome the limitations of the communication distance of the wireless interface by the multi-hop routing function, the nodes are free to move, and the network topology is dynamically changed. .

1 illustrates a transmitting node 110 and a receiving node 120 connected in a link in a typical ad hoc network environment. There are various channels to which the transmitting node 110 and the receiving node 120 can be connected. Here, in a multi-radio wireless ad hoc network utilizing multiple wireless network interfaces, links to next-hop nodes on a path exist in proportion to the number of interfaces.

In addition, since channels are allocated differently for each interface, each link connected to a specific node exhibits different interference and congestion. This can improve throughput by comparing the status of the link currently being used for data transmission with the status of other links and replacing them with a better link.

In addition, when estimating the bandwidth of a channel, if nodes located at two hops over the link are transmitting data, the receiving node conceals that data packets sent by the transmitting node and packets sent by nodes located at two hops collide. Because of the hidden terminal problem, it provides only a lower level than expected bandwidth, and these nodes are called hidden nodes.

Therefore, by connecting the transmitting node 110 and the receiving node 120 infers the available bandwidth using the channel usage information in the MAC layer, it is located in two hops based on the transmitting node 110 of the hidden node using the channel It is possible to predict the presence and channel usage of the hidden node, and to provide a more accurate and efficient link quality measurement system than the existing link quality measurement system.

It also compares the link quality of the current link with the link being used for data transmission among multiple multi-radio links connected to the next hop node in the path, and replaces the data transmission link when a certain level higher link is found than the current link. It may include a selection system.

The transmitting node 110 and the receiving node 120 may describe a transmitting end and a receiving end of a network signal included in a terminal for communication, or may refer to a transmitting terminal and a receiving terminal itself. Various channels exist between the nodes that are connected, and other nodes may exist around the transmitting node 110 and the receiving node 120. All nodes including the transmitting node 110 and the receiving node 120 are movable, and the neighboring nodes have a possibility of being a hidden node causing a collision by being located two hops away from the transmitting node 110.

2 illustrates a configuration of a system 200 for measuring a link quality in a data communication environment through a terminal in a multi-radio wireless ad hoc network environment and selecting a link to be connected based on the measured link quality according to an embodiment of the present invention. It is a figure for following. In an embodiment, the system 200 may include a first predictor 210, a second predictor 220, a quality measurer 230, and a link selector 240.

The first prediction unit 210 may estimate the available bandwidth by calculating the channel usage of the current use channel, that is, the channel usage of the channel connecting the transmitting node and the receiving node in the media access control (MAC) layer. In an embodiment of the present invention, in the MAC layer, packets are made in units of frames and transmitted. In this case, the transmitted frames can be recognized by all nodes within a transmission range regardless of a transmitting / receiving node. Therefore, each node can identify how many frames are occurring in the channel in the MAC layer, and calculates the channel usage using this.

Therefore, the channel usage measurement of the MAC layer will be described with reference to the drawing of FIG. 3. Figure 3 shows the channel state over time. T _d is the data transmission time, T _i is the interval not used, and T _e is the interval between two identified packets. Therefore, the channel idle ratio R _idle can be obtained as shown in Equation 1.

The available bandwidth can be estimated by multiplying the maximum bandwidth of the channel by this value.

The second predictor 220 may estimate the amount of available bandwidth reduction due to the presence of the hidden node. In the present invention, for link quality measurement, additional information is recorded in a Hello packet. As an additional information, each node records the channel usage calculated in the MAC layer in a Hello packet and transmits it to neighbor nodes in a broadcast form every second.

Here, when a transmitting node transmits data to a receiving node, the transmitting node may compare the channel usage recorded in the Hello packet received from the receiving node with the channel usage currently measured by the node itself. If the channel usage of the receiving node is less than the channel usage measured by the transmitting node, the hidden node is located 2 hops away from the transmitting node beyond the receiving node, and the hidden node is performing data communication using the corresponding channel. Can be guessed.

In the embodiment, Figure 4 is a view for explaining how to predict the amount of available bandwidth reduction due to the hidden node. The small circles labeled 1 through 4 represent the nodes, respectively, and the arrows indicate the direction in which the data is sent. Thus, in the embodiment, node 1 and node 3 are transmitting nodes, node 2 and node 4 are receiving nodes.

PPL _HT (i, j) refers to the amount of available bandwidth reduction due to the hidden node when transmitting data from node i to node j, from transmitting node to receiving node, and as shown in Equation 2, channel usage of the transmitting node. This can be obtained as the difference in channel usage of the receiving node.

In FIG. 4, the channel usage R _idle (1) value of node 1 is 0.7, the channel usage R _idle (2) value of node 2 is 0.4, and the R _idle (3) value is 0.7, which is measured at each node. . Since node 1 cannot detect the data transmission of node 3, it can be determined that no node is using the same channel, but node 2 can detect that node 1 and node 3 are using the same channel. . Referring to the embodiment based on node 1, node 3 can be thought of as a hidden node that causes a collision using node 1's channel.

In addition, since node 3 is not in a range capable of detecting whether node 1 transmits data using the same channel as that used by node itself, node 3 may determine that only node 3 uses a data transmission channel.

Therefore, when the above embodiment appears, the amount of available bandwidth reduction is predicted to prevent the occurrence of an error. If Equation 2 is used to predict the amount of available bandwidth reduction due to the hidden node at Node 1, R _idle (1)-R _idle (2) = 0.7-0.4 = 0.3. As such, the amount of available bandwidth reduction due to the hidden node can be obtained by subtracting the channel usage of the receiving node from the channel usage of the transmitting node.

The quality measuring unit 230 may finally measure the link quality between the transmitting node and the receiving node. The transmitting node and the receiving node calculate a packet delivery ratio (PDR) for each neighboring node using Hello packets exchanged with each other. Here, the link quality between the final transmitting node and the receiving node is measured by using the available bandwidth obtained by each node and the amount of available bandwidth reduction due to the hidden node.

As shown in Equation 3, a modified Expected Transmission Count (mETX) can be obtained by dividing the available bandwidth reduction due to the hidden node in the PDR for the receiving node, and using the obtained mETX, the Expected Throughput of the link. ) Can be obtained. The unit of ETH, which is a standard for comparing link quality, is bps. Where B is the maximum bandwidth of the channel.

The link selector 240 may modify a data transmission path by selecting a link having a high link quality among the links whose quality is measured by the quality measurer 230. In an embodiment, if there is another link among the plurality of links from the transmitting node to the receiving node that is higher than a quality of the link currently used for data transmission, the path may be modified by replacing the link. have.

Here, the threshold for changing the link may take into account the energy that may be consumed while changing the link, for example, setting the link as a reference 20% higher than the ETH of the link that is currently connected, If there is more than one ETH, the link with the highest ETH value can be selected.

5 is a flowchart illustrating each step of the link quality measurement and selection method according to an embodiment of the present invention. The flowchart of FIG. 5 may be implemented in the link quality measurement and selection system 200 shown in FIG. 2, whereby the steps may be combined or divided by the system 200.

In operation S510, the link quality measurement and selection system 200 may estimate an available bandwidth of a channel using channel usage calculated by a transmitting node and a receiving node in a media access control (MAC) layer. In detail, the channel usage is calculated by measuring an occurrence frame of a channel in the MAC layer, and since each node can identify how many frames are occurring in the channel in the MAC layer, the channel usage can be used to calculate the channel usage. .

In operation S520, the system 200 may predict the amount of available bandwidth reduction due to the hidden node. Here, as additional information, each node records a channel usage calculated by the MAC layer in a Hello packet and transmits the data to neighboring nodes in a broadcast form every second.

Therefore, when a transmitting node transmits data to the receiving node, the transmitting node may compare the channel usage recorded in the Hello packet received from the receiving node with the channel usage currently measured by the node itself.

For example, if the channel usage of the receiving node is less than the channel usage measured by the transmitting node, the hidden node is located 2 hops away from the transmitting node beyond the receiving node, and the hidden node is transmitting data using the corresponding channel. Can be guessed.

In operation S530, the system 200 may measure a link quality between a transmitting node and a receiving node. The link quality can be calculated by combining the respective PDRs, the available bandwidth, the amount of available bandwidth reduction due to the hidden node, and the maximum bandwidth obtained from the transmitting node and the receiving node.

In operation S540, the system 200 may select a link having a high link quality among the links whose quality is measured in operation S530, and may modify a data transmission path. Here, if there is another link among the plurality of links from the transmitting node to the receiving node that is higher than the quality of the link currently used for data transmission, that is, higher than the threshold, the link is replaced by replacing the path. Can be modified.

Link quality measurement and selection method in a multi-radio ad hoc network environment according to the embodiment is implemented in the form of program instructions that can be executed by various computer means may be recorded on a computer readable medium. The computer-readable medium may include program instructions, data files, data structures, and the like, alone or in combination. The program instructions to be recorded on the medium may be those specially designed and configured for the embodiments or may be available to those skilled in the art of computer software. Examples of the computer-readable recording medium include magnetic media such as a hard disk, a floppy disk and a magnetic tape, optical media such as CD-ROM and DVD, magnetic disks such as a floppy disk, - Magneto-optical media, and hardware devices specifically configured to store and execute program instructions such as ROM, RAM, flash memory, and the like. Examples of program instructions include machine language code such as those produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter or the like. The hardware devices described above may be configured to operate as one or more software modules to perform the operations of the embodiments, and vice versa.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. For example, it is to be understood that the techniques described may be performed in a different order than the described methods, and / or that components of the described systems, structures, devices, circuits, Lt; / RTI > or equivalents thereof, the appropriate results may be achieved.

Therefore, other implementations, other embodiments, and equivalents to the claims are also within the scope of the following claims.

110: sending node
120: receiving node
200: link quality measurement and selection system
210: first prediction unit
220: second prediction unit
230: quality measurement unit
240: link selection unit

Claims (12)

In the link quality measurement and selection system in a multi-radio wireless ad-hoc network environment,
A first predictor configured to calculate a first channel usage of a channel connected in a media access control (MAC) layer, and to predict an available bandwidth of the channel using the calculated first channel usage;
A second predictor for predicting a reduction in the available bandwidth due to a hidden node;
A quality measuring unit calculating a link quality between a transmitting node and a receiving node by using the available bandwidth and the decrease amount of the available bandwidth; And
A link selecting unit that selects one link among the links of which the link quality is measured according to the link quality
Lt; / RTI >
The second prediction unit,
Reading the second channel usage of the receiving node recorded in the Hello packet received from the receiving node,
By using the difference between the second channel usage calculated by the second prediction unit and the second channel usage of the receiving node, predicting the reduction amount of the available bandwidth caused by the hidden node at the transmitting node side
Link quality measurement and selection system. The method of claim 1,
The first prediction unit,
Calculate the first channel usage by measuring an occurrence frame of the channel in the MAC layer,
Predicting the available bandwidth by multiplying the first channel usage by the maximum bandwidth of the channel
Link quality measurement and selection system. delete The method of claim 1,
The second prediction unit,
The first channel usage is recorded as additional information in a Hello packet and transmitted to neighbor nodes in a broadcast form at regular intervals.
Link quality measurement and selection system. The method of claim 1,
The quality measuring unit
The link quality is calculated using a packet delivery ratio (PDR), the available bandwidth, and the amount of decrease in the available bandwidth between the transmitting node and the receiving node.
Link quality measurement and selection system. The method of claim 1,
The link selector,
Calculate a first link quality of a link currently connected between the transmitting node and the receiving node,
Calculate a second link quality of a second link capable of connecting between the transmitting node and the receiving node,
Selecting the second link when the second link quality is higher than or equal to the first link quality.
Link quality measurement and selection system. In the method of measuring and selecting link quality in a multi-radio wireless ad-hoc network environment,
Calculating a first channel usage of a connected channel in a media access control (MAC) layer and predicting an available bandwidth of the channel using the calculated first channel usage;
Predicting an amount of reduction in the available bandwidth due to a hidden node;
Calculating a link quality between a transmitting node and a receiving node using the available bandwidth and the decrease amount of the available bandwidth; And
Selecting one of the links of which the link quality is measured according to the link quality
Lt; / RTI >
Predicting the amount of reduction in the available bandwidth due to the hidden node,
Reading a second channel usage amount of the receiving node recorded in a Hello packet received from the receiving node; And
Estimating the reduction amount of the available bandwidth generated by the hidden node at the transmitting node side by using a difference between the first channel usage calculated by the first prediction unit and the second channel usage of the receiving node.
Link quality measurement and selection method comprising a. 8. The method of claim 7,
Predicting the available bandwidth of the channel,
Calculating the first channel usage amount by measuring an occurrence frame of the channel in the MAC layer; And
Predicting the available bandwidth by multiplying the first channel usage by the maximum bandwidth of the channel
Link quality measurement and selection method comprising a. delete 8. The method of claim 7,
Predicting the amount of reduction in the available bandwidth due to the hidden node,
Recording the first channel usage amount as additional information in a hello packet, and transmitting the first channel usage amount to the neighboring nodes in a broadcast form at regular intervals;
Link quality measurement and selection method comprising a. 8. The method of claim 7,
Computing the link quality between the transmitting node and the receiving node
Quantifying a link quality using a packet delivery ratio (PDR), the available bandwidth, and the decrease amount of the available bandwidth between the transmitting node and the receiving node;
Link quality measurement and selection method comprising a. 8. The method of claim 7,
The step of selecting one of the links measured the link quality according to the link quality,
Calculate a first link quality of a link currently connected between the transmitting node and the receiving node,
Calculate a second link quality of a second link capable of connecting between the transmitting node and the receiving node,
Selecting the second link when the second link quality is higher than a reference value by the first link quality.
Link quality measurement and selection method comprising a.

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