KR20230018705A - Wireless adhoc network system and accessing distributed channel method thereof - Google Patents

Abstract

Disclosed are a wireless ad hoc network system and a distributed channel access method thereof. According to a specific implementation of this technology, after pre-scheduling a plurality of neighboring nodes that want to transmit data packets and broadcasting a prepared pre-scheduler message to a plurality of neighboring nodes, data packets from neighboring nodes corresponding to designated time slots according to the pre-scheduler are sequentially received. Accordingly, the waiting time for channel access performed by each adjacent node can be reduced, and the number of control packets between each neighboring node and a receiving node can be reduced. Thus, data loss is prevented, and fairness in accessing shared media and channels on networks with high node density can be improved.

Description

Wireless ad hoc network system and distributed channel access method thereof

The present invention relates to a wireless ad hoc network system and a distributed channel access method thereof, and more particularly, data packets can be sequentially delivered to a source node according to a prior schedule through prior scheduling of a plurality of adjacent nodes to transmit data. It's about the technology that made it possible.

Recently, there is a tendency for network devices to be deployed in an ad-hoc or distributed manner and to communicate through wireless media using various applications including low-latency Internet of Things applications, mobile ad-hoc networks, and advertisements. For example, There are hoc networks and flying ad hoc networks.

Here, in the wireless ad hoc network system, when a plurality of nodes exist outside each other's transmission range and simultaneously try to send data packets to the same intermediate node, there is a possibility of signal collision at the receiving node.

In recent years, research on increasing the number of control frames (messages) or transmitting data packets only in designated time slots has been conducted, but the waiting time and data packet loss increase have reached the limits of network splitting.

In addition, each channel occupancy allows access to data on the occupied channel for data transmission to the same node, but may result in unfair results for shared medium/channel access on networks with high node density.

Accordingly, the present invention pre-schedules a plurality of adjacent nodes to transmit data, broadcasts the created pre-scheduler message to the plurality of adjacent nodes, and then sequentially transmits data packets of adjacent nodes corresponding to time slots designated according to the pre-scheduler. It is intended to provide a wireless ad-hoc network system and a method for accessing a distributed channel thereof, which can reduce the waiting time for channel access performed by each neighbor node upon reception.

Accordingly, the present invention can reduce the number of control packets between each neighboring node and a receiving node, thereby preventing data loss, and improving fairness in accessing shared media and channels on a network with high node density. It is intended to provide an ad hoc network system and a distributed channel access method thereof.

The object of the present invention is not limited to the above-mentioned object, and other objects and advantages of the present invention not mentioned above can be understood by the following description and will be more clearly understood by the examples of the present invention. It will also be readily apparent that the objects and advantages of the present invention may be realized by means of the instrumentalities and combinations indicated in the claims.

Distributed channel access device of wireless ad hoc network according to an embodiment of the present invention

a plurality of adjacent nodes to transmit data; and

A receiving node sequentially receiving data packets transmitted from the plurality of adjacent nodes through distributed channel access;

The receiving node,

Pre-scheduling based on the channel gain included in the RTS (Request To Send) message received from the plurality of neighboring nodes, and then broadcasting a pre-schedule SFT (Schedule For Transmission) message to the plurality of neighboring nodes;

Each of the plurality of adjacent nodes is

Receive the pre-scheduler SFT message;

An adjacent node corresponding to a time slot designated according to the received advance scheduler is

It is characterized in that it is provided to transmit the data packet to the receiving node.

Preferably, the remaining adjacent nodes of the plurality of adjacent nodes except for the adjacent node corresponding to the time slot designated according to the advance scheduler

It may be provided to perform counting based on NAV (Network Allocation Vector) and wait for a predetermined media use reservation time.

Preferably the receiving node is

It may be provided to broadcast an Acknowledgement (ACK) message to the plurality of adjacent nodes after waiting time SIFS (Short Inter Frame Space) has elapsed after data packet reception of the adjacent node corresponding to the time slot designated by the advance scheduler is completed.

A distributed channel access method of a wireless ad hoc network according to another embodiment of the present invention,

(a) In the receiving node, if the channel state is free, receive the RTS (Request To Send) message transmitted from one of the plurality of adjacent nodes to transmit data, and then perform CTS (Clear To Send) broadcasting a message to the plurality of neighboring nodes;

(b) At the receiving node, a pre-scheduler SFT (Schedule For Transmission) message is generated by performing pre-scheduling with a channel gain included in an RTS message transmitted from each of a plurality of neighboring nodes, and the generated SFT message is transmitted to the plurality of neighboring nodes. broadcasting to the node; and

(c) receiving, at the receiving node, a data packet of an adjacent node corresponding to a designated time slot based on the received pre-scheduler SFT.

Preferably in step (c),

Waiting for a medium use reservation time by counting the remaining adjacent nodes with a predetermined Network Allocation Vector (NAV), excluding the adjacent node corresponding to the time slot designated according to the pre-scheduler, among the plurality of adjacent nodes. there is.

Preferably after step (c)

The method may further include broadcasting an ACK message to a plurality of neighboring nodes when the receiving node completes receiving the data packet.

Preferably after step (c)

When the receiving node completes reception of the data packets of the plurality of adjacent nodes determined according to the pre-scheduler, it may delay for a predetermined back-off time and then check channel conditions between the plurality of adjacent nodes and the receiving node.

According to the present invention, pre-scheduling is performed for a plurality of neighboring nodes to transmit data packets, and a pre-scheduler message created is broadcasted to the plurality of neighboring nodes, and then data packets of neighboring nodes corresponding to time slots designated by the pre-scheduler It is possible to reduce the waiting time for channel access performed for each adjacent node by sequentially receiving the .

In addition, according to the present invention, it is possible to reduce the number of control packets between each neighboring node and a receiving node, thereby preventing data loss, and improving fairness in accessing shared media and channels on a network with high node density. there is.

The following drawings attached to this specification illustrate preferred embodiments of the present invention, and together with the detailed description of the present invention serve to further understand the technical idea of the present invention, the present invention is the details described in such drawings should not be construed as limited to
1 is an overall configuration diagram of an ad hoc network system to which an embodiment is applied.
Figure 2 is a diagram showing the signal flow of the system of one embodiment.
Figure 3 is an overall flow chart showing the operating process of the system of one embodiment.

Hereinafter, a sensor network according to the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description will be omitted. In addition, the terminology used in this specification is a term used to appropriately express a preferred embodiment of the present invention, which may vary according to the intention of a user or operator or customs in the field to which the present invention belongs. Therefore, definitions of these terms will have to be made based on the content throughout this specification.

FIG. 1 is a diagram showing an ad hoc network system to which an embodiment is applied, and FIG. 2 is a diagram showing a signal flow between a plurality of adjacent nodes 1 to n and a receiving node 20 in the ad hoc network system of FIG. 1 . 1 and 2, the ad hoc network system to which an embodiment is applied exists outside the transmission range of the receiving node 20, and a plurality of adjacent nodes (1 to n) to transmit data are randomly distributed, and simultaneously transmits the data packet to the receiving node 20, but the receiving node 20 generates a preliminary scheduler for a plurality of adjacent nodes (1 to n) to which data is to be transmitted, and the time specified in the generated preliminary scheduler Receives data packets from adjacent nodes corresponding to slots.

Each of the plurality of adjacent nodes 1 to n and the receiving node 20 uses a non-directional antenna.

Hereinafter, with reference to FIG. 2, a distributed channel access process between a plurality of adjacent nodes 1 to n and the receiving node 20 will be described in more detail.

As shown in FIG. 2, suppose that a plurality of neighboring nodes A and C, which want to transmit data, request data transmission through distributed channel access between receiving nodes B, for example.

That is, a plurality of adjacent nodes A wait for a Distributed Inter Frame Space (DIFS) and forward a Request To Send (RTS) message to the receiving node B, and receiving the received node B, the channel gain can be estimated through the received RTS message. there is.

Then, the receiving node B waits for Short Inter Frame Space (SIFS) and then broadcasts a clear to send (CTS) message to a plurality of neighboring nodes A and C.

Subsequently, the receiving node B performs pre-scheduling using the estimated channel gains of a plurality of adjacent nodes A and C to generate a scheduler message having an advance scheduler, and the generated schedule for multicasting (SFT) message is After waiting for SIFS, it multicasts to multiple adjacent nodes A and C.

A plurality of adjacent nodes A and C receiving such a Schedule For Multcasting (SFT) message wait for SIFS (Short Inter Frame Space), and among a plurality of adjacent nodes A and C, the adjacent node A reaches the designated time of the advance scheduler. It forwards the data packets to the receiving Node B according to the slot.

At this time, the adjacent node C among the plurality of adjacent nodes starts counting for a predetermined Network Allocation Vector (NAV) value after receiving a schedule for multicasting (SFT) message.

On the other hand, when the reception of the data packet from the neighboring node A is completed, the receiving node B broadcasts an ACK (Acknowledgment) message to a plurality of neighboring nodes A and C, and the neighboring node A that received it broadcasts a predetermined Network Allocation Vector (NAV) message. ) value, and the neighboring node C ends the counting, then transfers the data packet to the receiving node B according to the pre-scheduler's designated time slot.

And when the receiving node B completes receiving the data packet from the neighboring node C, the receiving node B broadcasts an ACK (Acknowledgment) message to a plurality of neighboring nodes A and C, and the neighboring node A receiving it broadcasts a predetermined NAV ( Network Allocation Vector) ends counting.

This series of processes is sequentially performed in predetermined time slots of a pre-scheduler for a plurality of neighboring nodes to transmit. In one embodiment, since a channel access process for each of a plurality of neighboring nodes (1 to n) to which data is to be transmitted is omitted, waiting time can be reduced and data collision between a plurality of neighboring nodes can be prevented. Accordingly, the system can improve performance. In addition, it is possible to reduce the number of control packets between each neighboring node and a receiving node, thereby preventing data loss, and improving fairness in accessing a shared medium and a channel on a network with a high node density.

Meanwhile, FIG. 3 is an overall flow chart showing a distributed channel access process between a plurality of adjacent nodes and a receiving node in the wireless ad hoc network system of FIG. explain

Referring to FIG. 3, in the process of accessing a distributed channel in a wireless ad hoc network system according to an embodiment, a reception node 20 generates a pre-scheduler for a plurality of adjacent nodes 1 to n to transmit data, and the pre-scheduler It has a configuration to sequentially receive data packets from adjacent nodes corresponding to a designated time slot.

In steps S11 and S12, the plurality of adjacent nodes 1 to n of the wireless ad hoc network system perform continuous carrier sense multiple access (CSMA) if the number of adjacent nodes to which data is to be transmitted is 0. Through this, it is determined whether the channel is free by checking the channel state between the receiving nodes 20.

Here, the channel state through carrier sensing is determined by the Persistence Strategy, which is an algorithm that checks whether a channel is used to reduce the possibility of collision between nodes and improve performance when multiple channels are shared and used, and is used to supplement network efficiency and collision probability. For this purpose, there are various 1-Persistence Strategy, non-Persistence Strategy, or p-Persistence Strategy algorithms. For example, the p-Persistence Strategy algorithm increases data transmission by increasing p when the probability of collision is low, and increases the transmission of data when the probability of collision is high. By reducing p, we can improve performance by reducing collisions.

At this time, if the channel is in a free state as a result of the determination in step S12, in step S13, one adjacent node K among a plurality of adjacent nodes 1 to n is determined to be an available channel, and after inter frame space (IFS) standby, random The RTS message is transmitted to the receiving node 20 by selecting a time slot accordingly. That is, the neighboring node K transmits the RTS message to the receiving node 20 through a time slot R _TH selected from random time slots between 0 and 2 ^k -1. And the timer counting the waiting time SIFS of the plurality of adjacent nodes (1 to n) is reset.

And in step S14, the receiving node 20 receives the RTS message transmitted from one of the plurality of neighboring nodes 1 to n and transmits the CTS message to the plurality of neighboring nodes before the SIFS waiting time elapses. Broadcast to (1~n).

In steps S15 and S16, each of the plurality of adjacent nodes 1 to n receiving the CTS message forwards the RTS message to the receiving node 20 after the SIFS waiting time has elapsed, and the receiving node 20 receiving the RTS message performs pre-scheduling for a plurality of adjacent nodes (1 to n) based on the RTS message received after the SIFS waiting time has elapsed. Here, the pre-scheduling may be set in order of the channel gain included in the RTS message.

In step S16, the receiving node 20 generates a Schedule For Transmission (SFT) message as a result of pre-scheduling and broadcasts the generated pre-scheduler message to a plurality of neighboring nodes 1 to n. .

In step S17, among the plurality of adjacent nodes 1 to n that have received the advance scheduler message, the adjacent node K corresponding to the time slot designated by the advance scheduler forwards the data packet to the receiving node 20 after the SIFS waiting time has elapsed do. At this time, the plurality of adjacent nodes (1 to K-1, K+1 to n) excluding the adjacent node K set Network Allocation Vector (NAV) values and then perform counting. The NAV value is a timer counting waiting time for transmission of data packets.

In step S18, the receiving node 20 that has received the data packet from the neighboring node K broadcasts an ACK (Acknowledge) message to a plurality of neighboring nodes 1 to n after the SIFS waiting time has elapsed when the data packet is received. cast

In step S19, the receiving node 20 of the wireless ad hoc network system according to an embodiment of the present invention performs a backoff time when the neighboring node K is the last neighboring node n (limit) among a plurality of neighboring nodes (1 to n) to which data is to be transmitted. After waiting for T _B , the process proceeds to step S11.

Meanwhile, in step S19, the receiving node 20 transmits data to the next neighboring node K+1 when the neighboring node K is not the last neighboring node n (limit) among a plurality of neighboring nodes (1 to n) to which data is to be transmitted. Step S17 is performed for

Here, each of SIFS, DIFS, L _CM , L _RTS , P _t , T _xt , and DP _Rt can be expressed by Equations 1 to 7 below.

[Equation 1]

[Equation 2]

[Equation 3]

[Equation 4]

[Equation 5]

[Equation 6]

[Equation 7]

Where, St is time slot, D is distance, T is time, Pt is propagation time, Tx is reception time, Qt is queuing time, Prot is execution time, Ps is packet size, DR is distance ratio, and LCM is control message Latency, LRTS is the latency for the RTS message, DPRt is the data packet reception time, Pres is the preamble size, and PLCPHL is the PLCP header length. Here, the waiting time of IFS, SIFS, NAV, etc. is determined based on wireless local area network standard 802.11.

When each of the above parameters is in Table 1 below, the Distributed Channel Access Pre Schedule (DCAP) method through pre-scheduling according to an embodiment consumes about 45% of energy and controls 27% compared to the existing method. messages, and latency of 14% can be reduced, respectively.

[Table 1]

Accordingly, an embodiment pre-schedules data packets for a plurality of neighboring nodes to be transmitted, broadcasts the prepared pre-scheduling to the plurality of neighboring nodes, and then sequentially receives data packets from neighboring nodes in a designated time slot. It is possible to reduce the waiting time for channel access performed for each adjacent node of

In addition, it is possible to reduce the number of control packets between each neighboring node and a receiving node, thereby preventing data loss, and improving fairness in accessing shared media and channels on a network with high node density.

As described above, the present invention has been described by the limited embodiments and drawings, but the present invention is not limited to the above embodiments, and those skilled in the art in the field to which the present invention belongs can make various modifications and transformation is possible Therefore, the spirit of the present invention should be grasped only by the claims described below, and all equivalent or equivalent modifications thereof will be said to belong to the scope of the spirit of the present invention.

Pre-scheduling for a plurality of neighboring nodes to which data packets are to be transmitted, broadcasting the pre-scheduling to the plurality of neighboring nodes, and then sequentially receiving the data packets of the neighboring nodes in the designated time slot for each separate neighboring node. It is possible to reduce the waiting time for performing channel access, and to reduce the number of control packets between each neighboring node and the receiving node, thereby preventing data loss, and accessing a shared medium and channel on a network with high node density. A wireless ad hoc network system that can improve fairness and its distributed channel access method can bring about great progress in terms of operational accuracy and reliability, and furthermore, in terms of performance efficiency. It is an invention with industrial applicability because it is not only possible to market or sell wireless ad hoc communication systems such as work and flight ad hoc networks, but also to a level that can be clearly implemented in reality.

Claims (7)

a plurality of adjacent nodes to transmit data; and
A receiving node sequentially receiving data packets transmitted from the plurality of adjacent nodes through distributed channel access;
The receiving node,
Pre-scheduling based on the channel gain included in the RTS (Request To Send) message received from the plurality of neighboring nodes, and then broadcasting a pre-schedule SFT (Schedule For Transmission) message to the plurality of neighboring nodes;
Each of the plurality of adjacent nodes is
Receive the pre-scheduler SFT message;
An adjacent node corresponding to a time slot designated according to the received advance scheduler is
A wireless ad hoc network system configured to transmit the data packet to the receiving node. The method of claim 1, wherein the remaining adjacent nodes of the plurality of adjacent nodes except for the adjacent node corresponding to the time slot designated according to the advance scheduler
A wireless ad-hoc network system characterized in that it is provided to wait for a predetermined media use reservation time by performing counting based on a network allocation vector (NAV). The method of claim 2, wherein the receiving node
and broadcasting an ACK (Acknowledgment) message to the plurality of neighboring nodes after data packets received by the neighboring node corresponding to the time slot designated by the advance scheduler are completed. A method for accessing a distributed channel executed based on the wireless ad hoc network system of claim 1,
(a) In the receiving node, if the channel state is free, receive the RTS (Request To Send) message transmitted from one of the plurality of adjacent nodes to transmit data, and then perform CTS (Clear To Send) broadcasting a message to the plurality of neighboring nodes;
(b) At the receiving node, a pre-scheduler SFT (Schedule For Transmission) message is generated by performing pre-scheduling with a channel gain included in an RTS message transmitted from each of a plurality of neighboring nodes, and the generated SFT message is transmitted to the plurality of neighboring nodes. broadcasting to the node; and
(c) receiving, at the reception node, data packets from adjacent nodes corresponding to time slots designated based on the received pre-scheduler SFT. The method of claim 4, wherein in step (c),
Waiting for a medium use reservation time by counting the remaining adjacent nodes with a predetermined Network Allocation Vector (NAV), excluding the adjacent node corresponding to the time slot designated according to the pre-scheduler, among the plurality of adjacent nodes. Distributed channel access method of a wireless ad-hoc network system. The method of claim 4, after the step (c)
and broadcasting an ACK message to a plurality of neighboring nodes when the receiving node completes receiving the data packet. The method of claim 6, after the step (c)
When the receiving node completes reception of data packets from a plurality of adjacent nodes determined according to a pre-scheduler, delaying for a predetermined back-off time and then checking a channel state between the plurality of adjacent nodes and the receiving node. Characterized in that Distributed channel access method of a wireless ad hoc network system.

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