KR20150086919A - Power control and channel allocation method of nodes and media access method of nodes for multi-channel wireless networks - Google Patents

Abstract

A power control and channel allocation method of nodes in a multi-channel wireless network includes the steps of: a first step of allocating initial transmission power(P_t); a second step of determining whether information is received from neighboring nodes in the case the P_t is lower than a maximum transmission power (P_max); a third step of producing a interference graph in the case the information is received from the neighboring nodes; a fourth step of estimating the number of minimum channels (C_est) (i) for avoiding interference; a fifth step of controlling the Pt based on the estimated C_est (i); a sixth step of updating the interference graph by the Pt control; a seventh step of transmitting the C_est (i) information and the interference information between neighboring nodes to the neighboring nodes; and an eighth step of performing a channel allocation based on a vertex coloring.

Description

TECHNICAL FIELD [0001] The present invention relates to a method of controlling transmission power of a node in a multi-channel network, a method of performing channel allocation, and a method of controlling a medium access control of a node. [0002]

The present invention relates to a method for controlling transmission power and channel allocation of a node in a multi-channel network, and a method for controlling a medium access control of a node. More specifically, (non-overlapping) channel is allocated, and the transmission power of the node is adjusted and the channel allocation is performed in the multi-channel network in which the transmission power is adjusted based on the calculated information and the channel is allocated. And more particularly to a medium access control method of a node in a multi-channel network to which a distributed multi-channel medium access control protocol (DMCP) is applied in order to efficiently communicate between nodes.

In a wireless network environment, a sender transmits a packet with a specific transmission power.

As the transmission distance increases due to the attenuation of the transmitted packet, the signal strength gradually decreases and the receiver receives the packet with a power lower than the transmission power value.

Basically, a receiver can successfully receive a packet when a signal-to-noise plus interference ratio (SINR) value that is a ratio of interference and noise to a received power value of a packet is greater than a threshold value.

That is, if the received power of the packet is high and the network interference and noise are low, the SINR value becomes high, and the probability of successfully receiving the packet increases.

However, if the sender uses a higher power value, the receiving power of the receiver may be increased to increase the reception probability, but the interference to the surrounding node may be considerably interfered, thereby lowering the overall network throughput performance.

Accordingly, various researches have been conducted to improve the network throughput performance by adjusting the transmission power. For example, a graph theory based scheduling algorithm is proposed to reduce the interference between nodes, or a method of increasing the space recycling and controlling the simultaneous transmission of nodes by adjusting the transmission power has been proposed. Algorithms for reducing network interference using multiple channels have also been studied.

However, the prior art focuses on the technologies of each of the above three methods without comprehensive consideration of the method of controlling the transmission power of the node and the channel assignment and the method of controlling the access control of the node in the multi-channel network. The prior art fails to provide a technique for calculating the minimum channel number using the interference graph and the maximum clique in the transmission power and channel allocation.

Korean Patent Publication No. 10-2011-0139749

SUMMARY OF THE INVENTION It is an object of the present invention to calculate how many non-overlapping channels should be allocated to a neighbor node in order to avoid interference from the interference based on the interference graph, In order to efficiently communicate between the node and the nodes assigned to different channels and to adjust the transmission power of the node and perform the channel allocation in a multi-channel network for controlling power and allocating channels, a distributed multi- And a method for controlling access to a medium in a multi-channel network.

According to an aspect of the present invention, there is provided a method for adjusting transmission power and channel allocation of a node in a multi-channel network, the method comprising: a first step of allocating an initial transmission power P _t ; A second step of determining whether information is received from a neighboring node when the initial transmission power P _t is less than a maximum transmission power P _max ; A third step of generating an interference graph when information is received from the neighboring node; A fourth step of estimating a minimum number of channels C _est (i) for interference avoidance; A fifth step of adjusting the initial transmission power P _t based on the estimated minimum number of channels C _est (i); A sixth step of updating an interference graph according to the initial transmission power (P _t ) adjustment; A seventh step of transmitting interference information between the minimum number of channels C _est (i) and neighboring nodes to the neighboring node; And performing channel allocation based on vertex coloring.

According to another aspect of the present invention, there is provided a method of controlling a medium access control method for a node in a multi-channel network, the method comprising: a first step of a sender moving to a channel of a receiver; a backoff for transmitting a REQ packet; A second step of performing the second step; A third step of determining success of handshake through transmission of a transmission request (REQ) packet and reception of a transmission response (RES); A fourth step in which the sender and the receiver move to a sender channel when it is determined that the handshake is successful in the third step; A fifth step of performing back-off for data transmission; A sixth step of exchanging data (DATA) and acknowledgment (ACK) packets; And the seventh step of the receiver returning to the receiver channel in the transmitter channel.

INDUSTRIAL APPLICABILITY The present invention has the technical effect of being able to avoid the inter-node interference effect in the wireless multi-channel as much as possible and to improve the network throughput.

FIG. 1 is a flowchart illustrating a method of performing transmission power and channel allocation in a multi-channel network according to the present invention.
FIG. 2A is a diagram for explaining the estimation of the minimum number of channels required for interference avoidance using the interference graph in the process of FIG.
FIG. 2B is a diagram for explaining a channel allocation method based on vertex coloring in the process of FIG.
FIG. 3 is a flowchart of a method of controlling access to a medium according to the present invention.
4 shows a basic operation of the medium access control method according to the present invention.
FIG. 5A is a graph illustrating a throughput performance relationship according to an increase in the number of nodes in a single hop when a transmission power control (PC) algorithm and a distributed multi-channel medium access control protocol (DMCP) according to the present invention are used.
FIG. 5B is a graph illustrating a throughput performance relationship according to an increase in the number of nodes in a multi-hop when a transmission power control (PC) algorithm and a distributed multi-channel medium access control protocol (DMCP) according to the present invention are used.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a flowchart illustrating a method of performing transmission power and channel allocation in a multi-channel network according to the present invention.

First, the reason for using a multi-channel network instead of a single channel in the present invention will be briefly described below.

As a standard of wireless communication, IEEE 802.11 defines a plurality of channels, and among them there exists a non-overlapping channel in which frequency bands do not overlap each other. For example, there are 12 non-overlapping channels in the 5 GHz band in the IEEE 802.11a standard, and three non-overlapping frequencies in the 2.4 GHz band in the IEEE 802.11b / g standard.

Since the channels of the respective frequencies do not overlap with each other, the transmission signals do not interfere with each other. Thereby, the links using different channels, that is, the connections of the nodes, can be simultaneously transmitted.

Further, since multi-channel is used based on the IEEE 802.11 standard, the interference phenomenon between nodes is reduced, so that the throughput is significantly improved as compared with the case of a single channel.

Hereinafter, a method of performing transmission power and channel allocation in a multi-channel network according to the present invention will be described in detail with reference to FIGS. 1 to 2B.

(S10) of allocating initial transmission power (P _t ).

In this case, the initial transmission power (P _t ) value is obtained from the transmission power adjustment algorithm LMST.

In the LMST, each node uses the minimum transmission power that can be transmitted to its neighbor node, while ensuring the connectivity of all nodes in the network. By using the value of LMST initially, This is because the connectivity of all nodes in the network can be guaranteed.

Next, a second step S20 is performed to determine whether the initial transmission power P _t is less than or equal to the maximum transmission power P _max .

If it is determined in step S20 that the initial transmission power P _t is not less than the maximum transmission power P _max , the process proceeds to step S90 based on Vertex coloring based on the final process do.

If it is determined in step S20 that the initial transmission power P _t is less than or equal to the maximum transmission power P _{max in step} S20, S30).

In this case, the minimum number of channels (C _est ) for interference avoidance transmitted by the neighbor node , It means that the transmission power of the neighboring node is updated, and the transmission power of the neighboring node is changed according to the value of the transmission power of the neighboring node.

If it is determined in step S30 that the information is not received from the neighboring node (NO), the process proceeds to step S90 based on the vertex coloring based on the last process.

If it is determined in step S30 that information is received from the neighboring node (Yes), a fourth step (S40) is performed to generate an interference graph in the next step.

In this case, for example, the node i located at the i-th position generates a local interference graph composed of itself and neighbor nodes, and determines whether there is interference between the nodes.

Here, the interference graph consists of nodes and trunks, and when there is interference between two nodes, they interfere with each other by connecting them in a straight line.

Each node generates an interference graph composed of itself and neighbor nodes based on the neighbor node information received through the wireless channel.

Based on the interference graph, it calculates how many non-overlapping channels should be allocated to the neighboring node in order to avoid interference from itself, and adjusts its own transmission power and allocates channels based on the calculated information. (See S50 to S90)

In the next step, there is a fifth step (S50) of estimating the minimum number of channels C _est (i) for interference avoidance.

In this case, the value of C _est (i) represents the size of maximum clique including node i. Here, a clique means a complete graph in which one node is connected to all the remaining nodes, and a maximum clique means a clique having the largest size.

Hereinafter, a process of estimating the minimum number of channels C _est (i) for interference avoidance will be described with reference to FIG. 2A, for example.

In the interference graph, N _1, as shown bars in Figure _{2a, (N 1, N 2} , N 3), (N 1, N 5), (N 1, N 5, N 6), (N 1, N ₆ , N ₇ ). In this case, the size of the maximum clique is 3, so C _est (i) = 3.

Ie for the three channels in the interference graph of N _1, by a neighbor node in N ₁ and interference relationship are allocated to use the different channels, and N ₁ (for example, N ₁ and that the interference between the neighboring nodes is less than 3 channel, N ₂ (2), N ₃ (1), N ₅ (2), N ₆ (1), N ₇ (1)) so that neighboring nodes are not affected by interference when N ₁ is transmitted .

As a next step, there is a sixth step (S60) of adjusting transmission power based on C _est (i) estimated in the fifth step (S50).

The detailed processes (S61 to S64) of the sixth process (S60) will be described below.

First, there is a 61st step S61 of determining whether the minimum channel number C _est (i) for interference avoidance is smaller than the number C _{non-overlap of} non-overlapping channels usable in the network.

If it is determined in step S61 that the minimum channel number C _est (i) for interference avoidance is smaller than the number C _{non-overlap of} non-overlapping channels usable in the network (for example), the initial transmission power The process proceeds to step S62 (step S62) in which the value P _t is increased by a certain amount.

That is, if C _est (i) is smaller than C _non-overlap , different channels can be allocated to node i and surrounding nodes so that neighboring nodes are not interfered, thereby increasing transmission power of node i.

If it is determined in step S61 that the minimum channel number C _est (i) for interference avoidance is not smaller than the number C _{non-overlap of} non-overlapping channels usable in the network (No), C _est (i) is greater than C _non-overlap (S63).

If it is determined in step S63 that C _est (i) is greater than C _non-overlap (Yes), the flow proceeds to step S64 in which the initial transmission power P _t is decreased by a certain amount.

In other words, if C _est (i) is larger than C _non-overlap , it can not allocate another channel to neighboring neighboring nodes. Therefore, since neighboring node receives interference when node i transmits, its own transmission power is reduced Thereby allowing the surrounding nodes to receive less interference.

If it is determined in step S63 that C _est (i) is not larger than C _non-overlap (NO), the process returns to step S20.

Next, there is a seventh step (S70) of updating the interference graph according to the initial transmission power adjustment.

In this case, the interference graph is updated according to the transmission power adjusted by the 62nd step (S62) or the 64th step (S64).

In other words, if the transmission power is increased in step 62 (S62), a node affected by the interference may be newly generated. If the transmission power is decreased in step 64 (S64), the interference node It is possible that you will not.

Next, there is an eighth step (S80) of broadcasting _Cest (i) and interference information between neighboring nodes to a neighboring node.

In order to provide information and channel allocation information for generating an interference graph, a neighbor node transmits C _est (i) calculated by itself and interference information between its own neighbor node to a neighbor node .

As a final step, there is a ninth step (S90) of performing channel allocation based on vertex coloring.

In this case, when the transmission power adjustment of its own is completed and it is determined that there is no change in the transmission power of the neighboring node, channel allocation is performed based on vertex coloring.

Here, vertex coloring refers to a method of assigning different colors, that is, different channels, to two nodes having an edge, as shown in FIG. 2B.

In the present invention, two nodes having interference with each other are displayed using different colors (for example, red, blue, and green) by a vertex coloring scheme, thereby displaying different channels in a manner of assigning different channels .

FIG. 3 is a flowchart illustrating a method of controlling access to a medium according to the present invention, and FIG. 4 is a flowchart illustrating a basic operation of a method of controlling access to a medium according to an embodiment of the present invention.

3 and 4, a medium access control method of a node according to the present invention will be described.

First, the sender has a first step (S310) of moving to the channel of the receiver.

Since the sender and the receiver are in a range in which they can communicate with each other, they are in interference with each other. Therefore, since the sender and the receiver are allocated different channels, they must be located on the same channel in order to communicate with each other, so that the sender moves to the receiver's channel to make a transmission request to the receiver.

Next, there is a second step S320 of performing a back-off for transmission request (REQ) packet transmission.

In this case, backoff is performed before transmission of a REQ (Request) packet in preparation for the possibility that communication is proceeding on the receiver's channel.

Next, a third step (S330a) of determining whether or not the handshake is successful based on the REQ / RES is determined.

In this case, when a sender transmits a REQ packet and a receiver receives a REQ packet and then transmits a RES response packet to the sender, the sender receives a RES response packet Determine the success of the handshake.

On the other hand, the case where the receiver can not transmit the transmission response (RES) packet can be divided into the following two cases and will be described with reference to FIG.

4, a primary channel means a channel assigned to a node, and a secondary channel means a channel of a receiver to which the secondary channel is to be transmitted.

First, if the recipient is communicating with another node on the recipient's channel, it can not send a RES reply packet. In this case, the sender tries to transmit after back off while waiting for the receiver's communication to be completed.

Second, the receiver communicates with other nodes on different channels.

In this case, the sender returns to its own channel, waits for the total transmission time DATA + SIFS + ACK + CHSW, waits for the receiver to complete the communication on the other channel, Move.

If it is determined in step S330a that the handshake via the REQ / RES has failed (NO), a third step S330b is performed in the case of a handshake failure.

Hereinafter, each step S331 to S333 of the third step S330b will be described in detail.

First, in the third step S330a, if it is determined that the handshake via the REQ / RES has failed (No), step 331 (S331) of determining whether the receiver is communicating with another node.

Next, if it is determined in step 331 that the receiver is communicating with another node (YES), the flow returns to the second step (S320) of performing a backoff for transmission of a REQ packet do.

If it is determined in step S331 that the recipient is not communicating with another node (No), the sender has step 332 (S332) of returning to the sender channel on the receiver channel.

Next, the sender waits for the total time of the transmission time (DATA + SIFS + ACK + CHSW) in step 333 (S333) in which the receiver waits for the communication to be completed on the other channel, The process returns to the first step S310.

On the other hand, if it is determined in step S330a that the handshake through the REQ / RES is successful (YES), the sender and the receiver have a fourth step S340 of moving to the sender channel.

That is, if the data transmission between the sender and the receiver has been agreed upon, the two nodes move to the sender's channel and prepare for data transmission.

In the present invention, an algorithm employing a Distributed Multi-Channel MAC Protocol (DMCP) is used in order to efficiently communicate between nodes allocated with different channels.

In this case, since the interference graph of each node considers whether the neighboring node is affected by the interference from the viewpoint of its own transmission, the DMCP protocol is characterized in that data transmission is performed in the channel allocated to the sender.

Next, a fifth step S350 of performing a back off for data transmission is performed.

 In this case, if back off is performed before data transmission, a collision of a packet is prevented, thereby improving the throughput, which is the amount of data transmission per hour.

Next, there is a sixth step (S360) of exchanging DATA and ACK.

In this case, the sender transmits data (DATA) to the receiver, and the receiver transmits an acknowledgment (ACK) packet for data reception to complete mutual communication.

As a final step, the receiver has a seventh step (S370) of returning to its receiver channel in the sender channel.

FIG. 5A is a graph illustrating a throughput performance relationship as the number of nodes increases in a single hop when a transmission power control (PC) algorithm and a distributed multi-channel medium access control protocol (DMCP) according to the present invention are used.

Referring to FIG. 5A, when the PC power control algorithm and the distributed multi-channel media access control protocol (DMCP) according to the present invention are used, as the number of nodes increases in a single hop, As compared with other algorithms.

FIG. 5B is a graph illustrating a throughput performance relationship as the number of nodes increases in a multi-hop when using a transmission power control (PC) algorithm and a distributed multi-channel medium access control protocol (DMCP) according to the present invention.

Referring to FIG. 5B, when the transmission power control (PC) algorithm and the distributed multi-channel media access control protocol (DMCP) according to the present invention are used, as the number of nodes increases in multi-hop, Which is higher than that of other algorithms.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit of the invention.

P _t : Initial transmission power
P _max : Maximum transmit power
C _est : Minimum number of channels for interference avoidance
C _{non - overlap} : Number of non-overlapping channels

Claims (6)

A first step of allocating an initial transmission power (P _t );
A second step of determining whether information is received from a neighboring node when the initial transmission power P _t is less than a maximum transmission power P _max ;
A third step of generating an interference graph when information is received from the neighboring node;
A fourth step of estimating a minimum number of channels C _est (i) for interference avoidance;
A fifth step of adjusting the initial transmission power P _t based on the estimated minimum number of channels C _est (i);
A sixth step of updating an interference graph according to the initial transmission power (P _t ) adjustment;
A seventh step of transmitting interference information between the minimum number of channels C _est (i) and neighboring nodes to the neighboring node; And
And performing channel allocation based on vertex coloring in the multi-channel network. The method according to claim 1,
In the fifth step, the minimum channel number C _est (i)
Wherein a clique is obtained from the interference graph and a size of a maximum clique of the clique is determined as a size of a maximum clique in the clique. The method according to claim 1, wherein, in the sixth step,
If the minimum number of channels C _est (i) the determined non-overlapping (non-overlapping) channel is less than the number of C _non-overlap, the process 6a to increase the initial transmit power (P _t) value; And
When the minimum number of channels C _est (i) the non-overlapping (non-overlapping) is determined larger than the channel number of C _non-overlap, characterized in that it comprises a first 6b process for reducing the initial transmission power (P _t) value A method for controlling transmission power and channel assignment in a multi - channel network. A first step in which a sender moves to a receiver's channel;
A second step of performing a back-off for transmission of a REQ packet;
A third step of determining whether a handshake through the transmission of the REQ packet and the reception of the RES packet is successful;
A fourth step in which the sender and the receiver move to a sender channel when it is determined that the handshake is successful in the third step;
A fifth step of performing back-off for data transmission;
A sixth step of exchanging data (DATA) and acknowledgment (ACK) packets; And
And returning the receiver to its receiver channel in the sender channel. ≪ Desc / Clms Page number 19 > 5. The method of claim 4,
If the handshake is not successful in the third step,
And determining whether the receiver is communicating with another node in the multi-channel network. 6. The method of claim 5,
If it is determined in step 3a that the receiver is communicating with another node, returning to the second step,
If it is determined in step 3a that the recipient is not communicating with another node,
And the sender returns from the receiver channel to the sender channel.

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