KR102846249B1 - Wireless communication method in high-density IoT wireless sensor network - Google Patents

Abstract

The present invention relates to a wireless communication method in a high-density IoT wireless sensor network, comprising: a step of searching for a pilot signal in a gateway; a step of detecting IoT node identification number information included in the received pilot signal when the gateway receives the pilot signal and registering the corresponding IoT node; a step of transmitting an acknowledgement (ACK) message to the registered IoT node by the gateway; and a step of activating communication with the gateway and transmitting sensor data when the IoT node receives the acknowledgement message from the gateway.
According to the present invention, plug-and-play is performed immediately by minimizing collisions and interference between a gateway and nodes of an IoT (Internet of Things) wireless sensor network based on beam scanning, and the utilization of frequency resources of an IoT (Internet of Things) wireless sensor network operating in a narrow ISM band can be increased.

Description

Wireless communication method in high-density IoT wireless sensor network

The present invention relates to a wireless communication method, and more particularly, to a wireless communication method in a high-density IoT (Internet of Things) wireless sensor communication network.

Internet of Things (IoT) wireless sensor network technology is a technology that transmits sensing data from multiple sensor nodes that can be installed in any random location to a gateway device that includes an antenna adjustment and communication system.

These IoT wireless sensor networks mostly use the ISM (Industrial, Science, and Medical) band, an unlicensed band with no communication fees, and the number of sensor nodes that can be connected to antenna gateways connected to data centers is increasing exponentially, creating an ultra-high-density IoT node environment such as smart cities, smart factories, and smart buildings. As a result, collisions and interference between nodes are becoming serious, making it difficult to freely connect and transmit.

In other words, Internet of Things (IoT) wireless sensor networks must be easy and convenient to connect, without conflict or interference. Since additional sensor nodes are installed regularly after the initial installation of IoT wireless sensor networks, they must be plug-and-play capable, allowing them to operate immediately without conflict or interference, even when installed randomly in any location and time. In other words, once IoT nodes are installed on the network, a gateway, including antenna adjustment and communication systems, must be able to operate in an environment with a large number of IoT nodes without complex additional settings or adjustments, ensuring plug-and-play operation without conflict or interference. However, existing technologies struggle to support a large number of sensor nodes, and as IoT evolves into high-density wireless sensor communication networks, collisions and interference will increase, further exacerbating this problem.

There are various terms used to describe IoT node communication. Machine type communication (MTC) is the term used in 5G mobile communications after 2020, and is also called wireless sensor communication. These mainly use the ISM frequency band, an unlicensed frequency band that does not incur usage fees. The problem is that various systems use this ISM band, such as wireless LAN, WiFi, Zigbee, and LoRa, and the number of IoT nodes is enormous and is expected to increase further in the future. The standardization organization 3GPP, the 5G standardization organization for 5G mobile communications, predicts that by 2030, eMTC (enhanced machine type communication) will be used, with 1 million IoT nodes per square kilometer (Km ² ), or about 1 IoT node per square meter. The 6th generation of mobile communications (6G), expected after 2030, will create an ultra-high-density IoT node environment where the number of IoT nodes will increase exponentially in smart cities, smart factories, and smart buildings. The problem is very serious, as their communication packets collide with each other and cause interference, making communication itself impossible.

The following technologies have been previously proposed or developed to minimize collisions and interference in high-density environments with numerous IoT nodes. However, all of these solutions are only partial solutions, are not suitable for high-density environments, and are even more challenging in high-density unlicensed ISM bands.

The conventional multihop scheme is as follows. For IoT nodes to utilize multihop, they must be able to relay data among themselves and forward information packets to a central gateway. This requires IoT nodes to receive signals and relay them to the gateway or gateway-side nodes as relays. This requires using different frequencies or time zones. However, if the ISM band is used, limited frequency resources preclude this option. If the same frequency resources are used, the system must wait and relay data back to the gateway at a different time. Transmitting data at a different time requires calculating the time and waiting. Fundamentally, for individual IoT nodes to act as relays requires complex system configurations and significant cost increases, making it extremely difficult to implement. Furthermore, IoT nodes lack the ability to navigate to the gateway, making it difficult to relay data to each other. Furthermore, IoT nodes are inherently battery-powered and therefore highly power-sensitive. Therefore, while power consumption must be conserved for their own data transmission, acting as relays to other nodes quickly drains the entire system, necessitating more frequent battery replacement.

The existing Cluster Tree architecture divides the entire system into clusters and structures node operations in a tree-like structure. While it offers some limited advantages, it presents significant challenges for practical use. Furthermore, nodes near the gateway consume significant amounts of power due to their relay function, leading to frequent communication interruptions and frequent battery replacement.

Previous power-hungry node replacement methods involved switching the roles of nodes closer to the gateway, which consumed significant power due to their relaying functions. To prevent this, however, incorporating this functionality into IoT nodes increased the complexity and cost of the node devices. Because nodes are simple, this increased autonomous complexity itself poses a problem. Furthermore, IoT nodes lack the ability to navigate to the gateway, making it difficult for them to relay to each other and reach the gateway.

Conventional frequency hopping multiple access (FHMA) methods require IoT nodes to be equipped with both a frequency synthesizer and communication devices within the node to enable FHMA. They also require a FH receiver. For accurate FHMA information transmission and reception, time and frequency must be synchronized, requiring synchronizers and other devices. This increased device cost, which was not present in existing methods, significantly increases node costs. Furthermore, the cost of building high-density IoT sensor networks, such as smart cities, smart factories, and smart buildings, increases astronomically.

Republic of Korea Publication Patent No. 10-2022-0113301

The present invention has been devised to solve the above problems, and its purpose is to provide a wireless communication method capable of minimizing packet collisions and interference in a high-density IoT wireless sensor network.

That is, the present invention can be used regardless of whether it is a licensed frequency band or an unlicensed frequency band, and the purpose of the present invention is to provide a wireless communication method that can maximize the frequency resource utilization rate of an IoT (Internet of Things) wireless sensor network by minimizing collisions and interference with other wireless IoT sensor communication systems, communication networks, or IoT (Internet of Things) nodes in the ISM (Industrial, Science and Medical) frequency band, which is an unlicensed band where IoT wireless sensor networks are mainly used, and can support plug and play that is easy and immediately operable by minimizing collisions and interference even when installing IoT nodes in a high-density IoT wireless sensor network or installing more IoT nodes.

The purpose of the present invention is not limited to the purposes mentioned above, and other purposes not mentioned will be clearly understood by those skilled in the art from the description below.

The present invention, which aims to achieve the above object, relates to a wireless communication method in a high-density IoT wireless sensor network, comprising: a step of searching for a pilot signal in a gateway; a step of detecting IoT node identification number information included in the received pilot signal when the gateway receives the pilot signal and registering the corresponding IoT node; a step of transmitting an acknowledgement (ACK) message to the registered IoT node by the gateway; and a step of activating communication with the gateway and transmitting sensor data when the IoT node receives the acknowledgement message from the gateway.

In the step of searching for a pilot signal in the gateway, the step may include a step of periodically transmitting a pilot signal by an IoT node and a step of searching for a pilot signal by alternately switching a beam forming mode in which beam scanning is performed in the gateway and an omnidirectional omnidirectional mode in which omnidirectional reception is performed.

Alternatively, the step of searching for a pilot signal in the gateway may include a step of periodically transmitting a pilot signal by an IoT node and a step of searching for a pilot signal simultaneously using a beam forming mode in which beam scanning is performed in the gateway and an omnidirectional mode in which omnidirectional reception is performed.

When the above gateway detects a pilot signal while performing beam scanning, it detects node identification number information of an IoT node included in the detected pilot signal, and creates or updates a table based on the detected node identification number information to assign IoT nodes to each beam zone.

In the step of transmitting the above sensor data, the step of searching for an RTS (Request To Send) frame by alternately switching between a beam forming mode in which beam scanning is performed at the gateway and an omnidirectional omnidirectional mode in which omnidirectional reception is performed may be further included.

Alternatively, in the step of transmitting the sensor data, the step may further include searching for an RTS (Request To Send) frame by simultaneously using a beam forming mode for performing beam scanning at the gateway and an omnidirectional mode for performing omnidirectional reception.

The above gateway may further include a step of beamforming and transmitting a CTS (Clear To Send) frame to an IoT node corresponding to the IoT node identification number of the received RTS frame when receiving an RTS frame.

An IoT node that receives a CTS frame can activate communication with the gateway and transmit sensor data.

The above gateway may further include a step of replying a confirmation message and terminating communication when receiving a termination packet from an IoT node with communication enabled.

In the step of transmitting the above sensor data, the IoT node may further include a step of checking whether there is sensor data to be transmitted, a step of the IoT node entering a sleeping mode if there is no data to be transmitted, a step of performing channel sensing to detect a channel if there is data to be transmitted, and a step of the IoT node transmitting an RTS (Request To Send) frame through the channel if the channel is available as a result of performing channel sensing, and waiting until a CTS (Clear To Send) frame is received from the gateway.

The IoT node may wait until it receives a CTS (Clear To Send) frame from the gateway, and may wait until it receives a CTS frame including its own node identification number information from the gateway.

The IoT node may further include a step of entering a sleeping mode when the communication with the gateway is terminated by sending a termination packet.

The above gateway can return to the process of searching for RTS frames again by replying a confirmation message to the IoT node that sent the termination packet and terminating the communication.

The above gateway performs beam scanning by performing beam forming according to a preset beam forming code book, and can perform beam scanning of surrounding IoT nodes by sequentially performing beam forming in a specific direction.

The above gateway stores the reception signal strength information included in the pilot signal, and stores node identification number information from each of two or more pilot signals, and when two or more pieces of node identification number information are stored, gives priority to the node identification number information in order of highest reception signal strength, and can assign IoT nodes to each beam zone accordingly.

In the step of transmitting the above sensor data, the gateway can adjust the size of the transmission signal according to the size of the received signal strength of the IoT node.

According to the present invention, there is an effect that plug-and-play is performed immediately by minimizing collisions and interference between a gateway and nodes of an IoT (Internet of Things) wireless sensor network based on beam scanning, and the utilization of frequency resources of an IoT (Internet of Things) wireless sensor network operating in a narrow ISM band can be increased. In the present invention, since effective identification and management of IoT (Internet of Things) nodes located by beam area is possible through beam scanning using a codebook-based beamforming technology preset in a gateway including an antenna adjustment and communication system, there is an advantage that the scarce frequency resources of the ISM band can be managed by dividing them according to time and space.

FIG. 1 illustrates a high-density IoT wireless sensor network system and a wireless communication method in a high-density IoT wireless sensor network according to one embodiment of the present invention.
FIG. 2 illustrates the frame structure of signals exchanged between a gateway and an IoT node in a wireless communication system in a high-density IoT wireless sensor network of the present invention.
FIG. 3 is a flowchart illustrating a back-off time readjustment algorithm implemented by an IoT node in a wireless communication system in a high-density IoT wireless sensor network according to one embodiment of the present invention.
FIG. 4 illustrates beam scanning performed by a gateway in a network based on beam division by beam cluster through beam scanning of the present invention.
FIG. 5 illustrates signal transmission between an IoT node and a gateway in a wireless communication system in a high-density IoT wireless sensor network of the present invention.
Figure 6 is an exemplary diagram for explaining the process of assigning nodes and storing them in a table format by a gateway in the present invention.
Figure 7 illustrates Embodiment 1 in which information is transmitted in a network between a gateway and node A, node B, and node C after the registration procedure of surrounding IoT nodes in the gateway is completed.
Figure 8 illustrates Embodiment 2 in which information is transmitted in a network between a gateway and node A, node B, and node C after the registration procedure of surrounding IoT nodes in the gateway is completed.
Figure 9 illustrates Example 3 in which information is transmitted in a network between a gateway and node A, node B, and node C after the registration procedure of surrounding IoT nodes in the gateway is completed.
Figure 10 illustrates Example 4 in which information is transmitted in a network between a gateway and node A, node B, and node C after the registration procedure of surrounding IoT nodes in the gateway is completed.
Figure 11 illustrates Example 5 in which information is transmitted in a network between a gateway and node A, node B, and node C after the registration procedure of surrounding IoT nodes in the gateway is completed.
Figure 12 illustrates Example 6 in which information is transmitted in a network between a gateway and node A, node B, and node C after the registration procedure of surrounding IoT nodes in the gateway is completed.
Figure 13 illustrates Example 7 in which information is transmitted in a network between a gateway and node A, node B, and node C after the registration procedure of surrounding IoT nodes in the gateway is completed.

The present invention is susceptible to various modifications and embodiments. Specific embodiments are illustrated and described in detail in the drawings. However, this is not intended to limit the present invention to specific embodiments, but rather to encompass all modifications, equivalents, and alternatives falling within the spirit and technical scope of the present invention.

The terminology used in this application is only used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, it should be understood that the terms "comprise" or "have" indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and will not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

In addition, when describing with reference to the attached drawings, identical components will be assigned the same reference numerals regardless of the drawing numbers, and redundant descriptions thereof will be omitted. When describing the present invention, if a detailed description of a related known technology is judged to unnecessarily obscure the gist of the present invention, the detailed description will be omitted.

In the present invention, wireless communication methods in a high-density IoT wireless sensor network are largely divided into two types. First, a beam is allocated to each cluster of a wireless sensor network based on beam division by beam cluster through beam scanning, and media access control (MAC: Media Access Control) is performed through carrier sensing for sensor nodes within the zone to perform communication that minimizes collisions and interference in a high-density IoT (Internet of Things) sensor network.

Secondly, the IoT node can determine the optimal backoff time in terms of the length and number of backoff times according to the number of IoT nodes, node distribution, and node type through a backoff time determination algorithm that adjusts the backoff time depending on the situation when there is already a user through carrier sensing, i.e. channel sensing.

Specifically, beams can be allocated according to surrounding areas through beam allocation information per cluster preset in the gateway including antenna adjustment and communication system, and information on IoT (Internet of Things) nodes for each area is stored in the gateway in the form of a table, and then beam scanning and omnidirectional omnidirectional reception are alternately switched, or the two modes are performed simultaneously to receive RTS (Request To Send) frames, which are communication request signals sent by each IoT (Internet of Things) node, as evenly as possible. In addition, the IoT (Internet of Things) node counts the number of RTS (Request To Send) frame transmission failures through its own backoff time determination algorithm, and adaptively occupies a random backoff time slot with a number of backoff time slots, thereby solving the problem that each IoT (Internet of Things) node may continuously fall into a backoff state.

In the present invention, the gateway can transmit and receive throughout the entire space like a conventional omnidirectional antenna, and can perform beamforming by cluster, so that it can scan the divided zones and recognize and assign IoT nodes to each beamforming zone. The number of beamforming zones is proportional to the total number of nodes, and as the number of nodes increases, the zones (clusters) are divided into many more so that the number of nodes per zone is less than a certain number. In other words, the gateway has two modes of function: a beamforming mode that performs beam scanning with a single antenna, and an omnidirectional mode, and these modes can be operated alternately periodically at a certain time interval, or antennas that operate in the omnidirectional mode and the beamforming mode can be installed in the gateway. In other words, by adding an antenna with the beamforming function of the present invention to a system that operates only with a conventional omnidirectional antenna, and additionally installing a processing and control device for integrated operation, the performance and function of the present invention can be improved. In addition, the beamforming mode operation is divided into zones in two-dimensional and three-dimensional space, and a multi-beam zone simultaneous support system is configured to form and process a multi-node simultaneous communication system, thereby providing a system configuration and operation characteristic that supports more nodes simultaneously and increases communication capacity.

In the present invention, unlike the backoff time determination used in existing nodes, the IoT node performs channel sensing, i.e., carrier sensing, for transmission. This is the time interval during which the node stops and tries again when another user is using the channel. The node empirically determines the length of time when adjusting this backoff time. That is, if the frequency of use by other users continues to increase, the backoff time is lengthened, and if the frequency of use by other users decreases during a transmission attempt, the backoff time is shortened so that it varies depending on the network environment and the board density of the surrounding beam cluster area. This function can be simply implemented using the processor and memory in the sensor node.

The present invention relates to a wireless communication method in a high-density IoT wireless sensor network, comprising: a step of searching for a pilot signal in a gateway; a step of detecting IoT node identification number information included in the received pilot signal when the gateway receives the pilot signal and registering the corresponding IoT node; a step of transmitting an acknowledgement (ACK) message to the registered IoT node by the gateway; and a step of activating communication with the gateway and transmitting sensor data when the IoT node receives the acknowledgement message from the gateway.

In the step of searching for a pilot signal in the gateway, the step may include a step of periodically transmitting a pilot signal by an IoT node and a step of searching for a pilot signal by alternately switching a beam forming mode in which beam scanning is performed in the gateway and an omnidirectional omnidirectional mode in which omnidirectional reception is performed.

Alternatively, the step of searching for a pilot signal in the gateway may include a step of periodically transmitting a pilot signal by an IoT node and a step of searching for a pilot signal simultaneously using a beam forming mode in which beam scanning is performed in the gateway and an omnidirectional mode in which omnidirectional reception is performed.

When the above gateway detects a pilot signal while performing beam scanning, it detects node identification number information of an IoT node included in the detected pilot signal, and creates or updates a table based on the detected node identification number information to assign IoT nodes to each beam zone.

In the step of transmitting the above sensor data, the step of searching for an RTS (Request To Send) frame by alternately switching between a beam forming mode in which beam scanning is performed at the gateway and an omnidirectional omnidirectional mode in which omnidirectional reception is performed may be further included.

Alternatively, in the step of transmitting the sensor data, the step may further include searching for an RTS (Request To Send) frame by simultaneously using a beam forming mode for performing beam scanning at the gateway and an omnidirectional mode for performing omnidirectional reception.

The above gateway may further include a step of beamforming and transmitting a CTS (Clear To Send) frame to an IoT node corresponding to the IoT node identification number of the received RTS frame when receiving an RTS frame.

An IoT node that receives a CTS frame can activate communication with the gateway and transmit sensor data.

The above gateway may further include a step of replying a confirmation message and terminating communication when receiving a termination packet from an IoT node with communication enabled.

In the step of transmitting the above sensor data, the IoT node may further include a step of checking whether there is sensor data to be transmitted, a step of the IoT node entering a sleeping mode if there is no data to be transmitted, a step of performing channel sensing to detect a channel if there is data to be transmitted, and a step of the IoT node transmitting an RTS (Request To Send) frame through the channel if the channel is available as a result of performing channel sensing, and waiting until a CTS (Clear To Send) frame is received from the gateway.

The IoT node may wait until it receives a CTS (Clear To Send) frame from the gateway, and may wait until it receives a CTS frame including its own node identification number information from the gateway.

The IoT node may further include a step of entering a sleeping mode when the communication with the gateway is terminated by sending a termination packet.

The above gateway can return to the process of searching for RTS frames again by replying a confirmation message to the IoT node that sent the termination packet and terminating the communication.

The above gateway performs beam scanning by performing beam forming according to a preset beam forming code book, and can perform beam scanning of surrounding IoT nodes by sequentially performing beam forming in a specific direction.

The above gateway stores the reception signal strength information included in the pilot signal, and stores node identification number information from each of two or more pilot signals, and when two or more pieces of node identification number information are stored, gives priority to the node identification number information in order of highest reception signal strength, and can assign IoT nodes to each beam zone accordingly.

In the step of transmitting the above sensor data, the gateway can adjust the size of the transmission signal according to the size of the received signal strength of the IoT node.

FIG. 1 illustrates a high-density IoT wireless sensor network system and a wireless communication method in a high-density IoT wireless sensor network according to one embodiment of the present invention.

Figure 1 illustrates the operation flow between a gateway and a node in a network based on beam division by beam cluster through beam scanning of the present invention.

Figure 1 illustrates the overall system in which a wireless IoT node based on beam division by beam cluster through beam scanning of the present invention operates and is operated. Figure 1 shows the system configuration and operation process, which are divided into two stages: IoT node registration and beam assignment, and sensor data transmission.

Referring to FIG. 1, a high-density IoT wireless sensor network system according to one embodiment of the present invention includes a gateway (100) and an IoT node (200). Here, the gateway (100) is a concept that includes an antenna adjustment and communication system for adjusting an antenna.

A wireless communication method in a high-density IoT wireless sensor network according to one embodiment of the present invention can be broadly divided into IoT node registration and beam assignment steps (S101 to S105) and sensor data transmission steps (S107 to S129). In one embodiment of the present invention, even if a new IoT node is added, the IoT node registration and beam assignment steps (S101 to S105) and the sensor data transmission steps (S107 to S129) can be performed in the same manner.

In the IoT node registration and beam assignment steps (S101 to S105), the gateway (100) performs a beamforming mode that performs beam scanning and an omnidirectional mode that performs omnidirectional reception to detect a pilot signal (S101). Here, the gateway (100) may periodically switch between the beamforming mode and the omnidirectional mode, or may use the beamforming mode and the omnidirectional mode simultaneously. At this time, the gateway (100) may be equipped with one antenna to periodically switch between the beamforming mode and the omnidirectional mode. Alternatively, the gateway (100) may be equipped with two antennas, a first antenna for performing the beamforming mode and a second antenna for performing the omnidirectional mode, to use the beamforming mode and the omnidirectional mode simultaneously.

The IoT node (200) periodically transmits a pilot signal and receives an acknowledgement (ACK) message from the gateway (100) (S103).

When the gateway (100) receives a pilot signal, it detects node identification number information of IoT nodes for each beam zone (cluster), and accordingly creates a table containing IoT node identification number information for each beam zone or updates an existing table, and transmits a confirmation message to the IoT node (200) (S105).

In the sensor data transmission step (S107 to S129), the gateway (100) performs a beamforming mode that performs beam scanning and an omnidirectional mode that performs omnidirectional reception to detect an RTS frame (S107). Here, the gateway (100) may periodically switch between the beamforming mode and the omnidirectional mode, or may use the beamforming mode and the omnidirectional mode simultaneously. At this time, the gateway (100) may be equipped with one antenna to periodically switch between the beamforming mode and the omnidirectional mode. Alternatively, the gateway (100) may be equipped with two antennas, a first antenna for performing the beamforming mode and a second antenna for performing the omnidirectional mode, to use the beamforming mode and the omnidirectional mode simultaneously.

The IoT node (200) enters sleeping mode when there is no sensor data to transmit (S109, S131), and performs channel sensing when there is sensor data to transmit (S109, S111).

If the IoT node (200) determines that the channel is being used by another device as a result of channel sensing, it enters a back off state, waits for the back off time, and then performs the channel sensing process again (S113, S115).

If the IoT node (200) determines that the channel is available based on the channel sensing result, it transmits an RTS frame and waits until it receives a CTS frame from the gateway (100) (S113, S117).

When the gateway (100) receives an RTS frame from the IoT node (200), it transmits a CTS frame to the IoT node (200) using beamforming (S119, S121).

And, when the IoT node (200) receives a CTS frame that matches its own node identification number, communication with the gateway (100) is activated (S123, S125). When communication between the IoT node (200) and the gateway (100) is activated, the IoT node (200) transmits sensor data to the gateway (100), and the gateway (100) that receives the sensor data transmits an acknowledgment (ACK) message to the IoT node (200).

And, when the gateway (100) receives an end of packet from the IoT node (200), it responds with a confirmation message and terminates communication with the IoT node (200) (S127, S129).

When communication is terminated, the gateway (100) returns to the process of performing beamforming mode for performing beam scanning to receive RTS frames again and omnidirectional mode for performing omnidirectional reception (S107).

And, when communication is terminated, the IoT node (200) enters sleeping mode (S131).

In Fig. 1, a high-density separate additional node operates like a conventional IoT node, and a system configuration and operation flow diagram showing the system operation and operation to minimize collisions and interference and achieve plug-and-play (P&P) operation that operates immediately. A detailed description of the operation and operation is as follows.

Step 1: The gateway (100) including the antenna adjustment and communication system periodically performs beam scanning. This beam scanning is for registering the IoT node (200) and is performed through a code book for beam forming installed and stored in the gateway (100). In the case of the IoT node (200), a pilot signal is periodically transmitted. However, unlike the gateway (100), it does not support beam forming and instead emits the pilot signal in all directions like a beacon signal. In performing the periodic beam scanning of the gateway (100) and the periodic pilot signal transmission of the IoT node (200), the pilot signal is continuously transmitted until an acknowledgment message (ACK: acknowledgment) is received for node registration and beam area allocation determination.

Step 2: When a gateway (100) including an antenna adjustment and communication system performs beam scanning and detects pilot signals of IoT nodes (200) by zone (cluster), it detects node identification number information of the IoT node (200) contained in the pilot signal and creates or updates a table containing identification number information of the IoT node (200) according to the zone. In the present invention, steps 1 to 2 correspond to IoT node (200) registration and beam assignment steps that operate while minimizing collision and interference.

Step 3: When the procedure for registering IoT nodes (200) in the gateway (100) including antenna adjustment and communication system is completed, the gateway (100) switches beam scanning or omnidirectional reception for receiving RTS (Request To Send) frames. Then, the IoT node (200) enters a sleeping mode until sensor data to be sent is generated. When sensor data to be sent is generated, the IoT node (200) performs channel sensing. If the result of performing channel sensing determines that the current channel is being used by another device, the IoT node (200) enters a back off state, waits for the back off time, and then returns to channel sensing. If the channel is available, the gateway (100) transmits an RTS (Request To Send) frame and then waits for a CTS (Clear To Send) frame from the gateway (100).

Step 4: The gateway (100) including the antenna adjustment and communication system performs beam scanning or omnidirectional reception for receiving an RTS (Request To Send) frame, and if the RTS (Request To Send) frame is not received, the gateway continues to perform beam scanning or omnidirectional reception for receiving an RTS (Request To Send) frame. If the RTS (Request To Send) frame is received, the gateway transmits the CTS (Clear To Send) frame by beamforming to a node matching the IoT node (200) identification number of the RTS (Request To Send) frame. The beamforming performed at this time finds a zone (cluster) where an IoT node (200) registered in the table is located, installs a beam corresponding to the zone in the gateway (100), and beamforms the beam using the set beamforming codebook (Code Book).

Step 5: The IoT node (200) checks whether it has received a CTS (Clear To Send) frame response that matches its node identification number. If it does not receive a CTS (Clear To Send) frame, it enters a back-off state. When the CTS (Clear To Send) frame is received, communication is activated between the gateway (100) and the IoT node (200) that received the CTS (Clear To Send) frame, and sensor data is transmitted. Other IoT nodes (200) waiting for the CTS (Clear To Send) frame automatically enter a back-off state because they have not received the CTS (Clear To Send) frame. When the back-off time passes, the IoT node (200) returns to the channel sensing procedure.

Step 6: When sensor data is transmitted between the gateway (100) including the antenna adjustment and communication system and the IoT node (200) that has received the CTS (Clear To Send) frame, the IoT node (200) terminates the communication and transmits the last end packet (End Of Packet) signal to the gateway (100). The gateway (100) that has received the last end packet (End Of Packet) signal also terminates the communication and returns to the procedure of switching beam scanning or omnidirectional reception for receiving the RTS (Request To Send) frame again. In addition, the IoT node (200) enters a sleeping mode when the communication is terminated. In the present invention, steps 3 to 6 correspond to the IoT sensor data transmission steps that minimize collisions and interference and enable a plug-and-play function that operates immediately.

FIG. 2 illustrates the frame structure of a signal exchanged between a gateway (100) and an IoT node (200) in a wireless communication system in a high-density IoT wireless sensor network of the present invention.

FIG. 2 illustrates the structure of a pilot signal, an RTS (Request To Send) frame transmitted by an IoT node (200) to a gateway (100) and a CTS (Clear To Send) frame transmitted by the gateway (100) to the IoT node (200) while operating in a network based on beam division by beam cluster through beam scanning of the present invention to minimize collisions and interference.

FIG. 2 shows the structure of a pilot signal, a node recognition confirmation message signal, an RTS (Request To Send) frame, and a CTS (Clear To Send) frame transmitted by the gateway (100) to the IoT node (200) to minimize collisions and interference and to enable plug and play immediately when additional nodes are installed in a network based on beam division by beam cluster through beam scanning of the present invention.

Referring to Fig. 2, the pilot signal basically contains IoT node (200) ID information and is transmitted from the IoT node (200) to the gateway (100). The pilot signal is transmitted continuously to determine node registration and beam zone assignment until a simple confirmation message (ACK: acknowledgment) is received.

The RTS (Request To Send) frame has IoT node (200) ID information as a header and RTS (Request To Send) request information as a payload, and is transmitted from the IoT node (200) to the gateway (100).

The CTS (Clear To Send) frame has IoT node (200) ID information as a header and CTS (Clear To Send) response information as a payload, and is transmitted from a gateway (100) including an antenna adjustment and communication system to the IoT node (200).

FIG. 3 is a flowchart illustrating a backoff time readjustment algorithm implemented by an IoT node (200) in a wireless communication system in a high-density IoT wireless sensor network according to one embodiment of the present invention. FIG. 3 shows a flowchart of a backoff time readjustment algorithm implemented by an IoT node (200).

Referring to FIG. 3, first, the IoT node (200) performs channel sensing to determine whether the channel is in use (S301). Basically, there are two backoff time adjustment parameters: time length adjustment and random number adjustment. In other words, two backoff time adjustment parameters, namely the default time slot and the number of default random numbers, can be set as initial values.

An IoT node (200) can perform channel sensing to determine whether the channel is being used by another IoT node (200) (S303), and if the channel is not being used by another IoT node (200), it decreases the time slot and reduces the number of random numbers (S307). Then, if the channel is being used by another node, it increases the time slot and increases the number of random numbers (S305).

By multiplying the changed time slot by the number of random numbers, a new backoff time can be obtained, and backoff can be performed by the backoff time depending on the channel conditions (S309). Specifically, depending on the channel conditions, if the channel is frequently busy as a result of channel sensing, the backoff time can be increased, and if the channel is idle and communication is easy, the backoff time can be shortened. In other words, a changed backoff time can be obtained by multiplying the increased or decreased time slot as a result of channel sensing by the number of random numbers. The backoff time readjusted in this way is used when the IoT node (200) backs off.

For example, assuming that the initial value of the time slot is 1ms and the initial value of the number of random numbers is 9, the time slot can be decreased or increased to 0.5ms, 5ms, 10ms, etc., and the number of random numbers can be decreased or increased to 5, 20, 100, etc. If the time slot is increased to 10ms and the number of random numbers is also increased to 100, the IoT node has a backoff time of 1s = 1 second, which is the product of the time slot 10ms and the number of random numbers 100.

In one embodiment of the present invention, in a method for an IoT node to readjust a backoff time, the backoff time can be adjusted by adjusting the time length and adjusting an arbitrary random number. That is, two backoff time adjustment parameters, namely, a default time slot and a number of default random numbers, can be set as initial values, and the IoT node can perform channel sensing and determine whether the channel is being used by another IoT node. If the channel is not being used by another IoT node, the time slot and the number of random numbers can be decreased, and if the channel is being used by an IoT node, the time slot and the number of random numbers can be increased. In addition, a new backoff time can be obtained by multiplying the time slot and the number of random numbers. That is, depending on the channel situation, if the channel is frequently busy as a result of channel sensing, the backoff time can be increased, and if the channel is idle and communication is easy, the backoff time can be shortened.

In one embodiment of the present invention, the gateway performs periodic node registration and beam scanning for beam assignment, and the IoT node periodically transmits a pilot signal, and the timing or cycle can be adjusted synchronously or asynchronously.

FIG. 4 illustrates beam scanning performed by a gateway in a network based on beam division by beam cluster through beam scanning of the present invention.

FIG. 4 illustrates an embodiment of beam scanning performed by a gateway including an antenna adjustment and a communication system in a network based on beam division by beam cluster through beam scanning of the present invention. In the present invention, beam scanning is performed through a preset beamforming code. Specifically, beam scanning is implemented by forming a beam that rotates by a certain angle over time using beamforming parameters or beamforming codes set in a beamforming codebook stored in the gateway.

Figure 4 (a) shows an embodiment in which a gateway performs beamforming using a beamforming codebook. Figure 4 (b) shows an embodiment in which a gateway performs beamforming by rotating a certain angle over time using a beamforming codebook. Figure 4 (c) shows an embodiment in which beam scanning is implemented using beamforming that rotates a certain angle over time.

As shown in Fig. 4, in a conventional IoT wireless sensor network, the gateway receives signals from IoT nodes in all directions, but in the gateway of the present invention, beam scanning enables beam division by beam cluster, thereby improving the connectivity of the network.

In one embodiment of the present invention, for beam scanning performed by a gateway, angles that can be divided according to the arrangement of a plurality of beamforming antenna arrays can be used, and a beam scanning area can be provided for each divided angle of each beamforming antenna.

FIG. 5 illustrates signal transmission between an IoT node and a gateway in a wireless communication system in a high-density IoT wireless sensor network of the present invention.

In Fig. 5, (a) an embodiment in which an IoT node transmits a pilot signal, and (b) an embodiment in which a gateway including an antenna adjustment and communication system and three IoT nodes are located and the three IoT nodes are transmitting a pilot signal are illustrated.

Figure 5 (a) illustrates an embodiment in which an IoT node transmits a pilot signal. The IoT node can emit the pilot signal in all directions, like a beacon, without beamforming the signal. The IoT node continuously transmits the pilot signal for node registration and beam zone assignment determination, and transmits the pilot signal until it receives a simple acknowledgment message (ACK) from the gateway.

Figure 5 (b) illustrates an embodiment in which a gateway and three IoT nodes are positioned, and the three IoT nodes are transmitting pilot signals. Here, the gateway performs beam scanning to accurately receive the pilot signals emitted in all directions by surrounding IoT nodes along a beam.

Figure 6 is an exemplary diagram for explaining the process of assigning nodes and storing them in a table format by a gateway in the present invention.

Figure 6 illustrates an embodiment in which a gateway receives pilot signals of IoT nodes along a beam using beam scanning, assigns nodes according to the strength of received signals from nodes that have received duplicate signals, and stores the signals in a table format.

Figure 6 shows an embodiment in which a gateway receives pilot signals of IoT nodes located in the vicinity along a beam through beam scanning, assigns nodes according to the identified node information and the reception signal strength of nodes that have received duplicate signals, and stores the information in a table format.

In the embodiment of FIG. 6, node 1045 is stored in beam O and beam P, node 1897 is stored in beam S, beam T, and beam U, and node 0723 is stored in beam A and beam X in the table. Through this table, the gateway can perform beam allocation by beam cluster. However, here, node 1045, node 1897, and node 0723 are stored in two or more beams. This duplication problem causes a problem in that the gateway does not know which beam to transmit when transmitting a CTS frame, etc. to an IoT node.

To address the issue of node overlap along these beams, prioritization is necessary. Prioritization is determined by the strength of the received signal. The stronger the signal strength of the IoT node receiving the beam, the higher the beam priority for that IoT node.

In the embodiment of Fig. 6, among beams O and P, beam O has the highest signal strength received by node 1045, so beam O has the first priority with respect to node 1045.

Among beams S, T, and U, beam T has the highest signal strength received by node 1897, so beam T has priority 1 for node 1897, beam U, which has the next highest signal strength, has priority 2 for node 1897, and beam S has priority 3.

Among beams A and X, beam A has the highest signal strength received by node 0723, so beam A has the highest priority for node 0723.

Therefore, beam A is finally assigned to node 0723, beam O is finally assigned to node 1045, and beam T is assigned to node 1897, so that when communication occurs between the gateway and the nodes, communication occurs through the assigned beams.

Figure 7 illustrates Embodiment 1 in which information is transmitted in a network between a gateway and node A, node B, and node C after the registration procedure of surrounding IoT nodes in the gateway is completed.

In Example 1 of Fig. 7, sensor data is transmitted between the gateway and the active node B, and nodes A and C have sensor data to transmit, so they are each in a channel sensing state.

Figure 8 illustrates Embodiment 2 in which information is transmitted in a network between a gateway and node A, node B, and node C after the registration procedure of surrounding IoT nodes in the gateway is completed.

In Example 2 of FIG. 8, after the sensor data transmission between the gateway and Node B is completed, Node B may enter a sleeping mode. Accordingly, since the channel is not in use, Node A and Node C, which were performing channel sensing, transmit an RTS (Request To Send) frame and enter a waiting state for a CTS (Clear To Send) frame response.

Figure 9 illustrates Example 3 in which information is transmitted in a network between a gateway and node A, node B, and node C after the registration procedure of surrounding IoT nodes in the gateway is completed.

In Example 3 of FIG. 9, among the RTS (Request To Send) frames transmitted by Node A and Node C, the gateway can respond with a CTS (Clear To Send) frame to the RTS (Request To Send) frame of Node C by means of counterclockwise beam scanning. At this time, Node C is in a state of receiving a CTS (Clear To Send) frame response (CTS (Clear To Send) received), but Node A may still be in a state of waiting for a CTS (Clear To Send) frame response. In a conventional IoT sensor network, additional device configuration or procedure was required to resolve a hidden node such as Node A, but in the present invention, a gateway located in a data center performs beam division by zone, and IoT nodes belonging to a zone adjust carrier sensing, i.e. channel sensing, and an appropriate backoff time within the zone to use it, thereby resolving the signal collision problem caused by a hidden node.

Figure 10 illustrates Example 4 in which information is transmitted in a network between a gateway and node A, node B, and node C after the registration procedure of surrounding IoT nodes in the gateway is completed.

In Example 4 of Fig. 10, node C receives a CTS (Clear To Send) frame and communication is performed between the gateway and node C. Since node A does not receive a CTS (Clear To Send) frame response, it enters a back-off state after a certain period of time. If the beam scanning is staggered with that of node A of Fig. 8, node A may continue to enter a back-off state and sensor data transmission may not be performed smoothly. To solve this, in the present invention, the gateway switches between beam scanning and omnidirectional reception to receive an RTS (Request To Send) frame.

Figure 11 illustrates Example 5 in which information is transmitted in a network between a gateway and node A, node B, and node C after the registration procedure of surrounding IoT nodes in the gateway is completed.

In Example 5 of Fig. 11, after the sensor data transmission between the gateway and Node C is completed, Node C may enter a sleeping mode. Node A, which has been in a backoff state for the duration of the backoff time, may return to the channel sensing procedure. At this time, since the channel is not in use, Node A may transmit an RTS (Request To Send) frame and wait for a CTS (Clear To Send) frame response.

Figure 12 illustrates Example 6 in which information is transmitted in a network between a gateway and node A, node B, and node C after the registration procedure of surrounding IoT nodes in the gateway is completed.

In Example 6 of Fig. 12, the gateway performs beam scanning in a counterclockwise direction, receives an RTS (Request To Send) frame from node A, and transmits a CTS (Clear To Send) frame to node A by beamforming. Then, node A is in a state of receiving a CTS (Clear To Send) frame from the gateway.

Figure 13 illustrates Example 7 in which information is transmitted in a network between a gateway and node A, node B, and node C after the registration procedure of surrounding IoT nodes in the gateway is completed.

In Example 7 of Fig. 13, since Node A has received a CTS (Clear To Send) frame response from the gateway, communication between the gateway and Node A can be activated. Accordingly, Node A becomes active, and sensor data transmission between the gateway and Node A takes place.

In one embodiment of the present invention, a gateway of a wireless IoT sensor network that operates a gateway using an existing omnidirectional antenna is additionally installed with a beam forming antenna for beam cluster assignment and a beam scanning function for node registration and assignment of the present invention, thereby including a configuration for coordinating the operation and management of these two antennas, and a configuration can be proposed in which a system of these two antenna methods is configured to operate alternately by switching them alternately or operating them simultaneously to eliminate collision and interference.

In one embodiment of the present invention, in configuring a beam forming antenna for beam scanning function and beam cluster assignment for IoT node registration and assignment, the number of beam scanning zones is divided according to the beam forming mode resolution, and the number of beam cluster zones is initially not divided from omnidirectional 1 zone, and is gradually divided into 2 zones, 4 zones, 8 zones, 16 zones, 32 zones, etc. in two-dimensional and three-dimensional space according to the number of IoT sensor nodes, and the overall system optimization is evaluated in a data center (10) by considering transmission quality (QoS: quality of service), packet success rate, collision resolution rate, information transmission rate (Data Throughput), etc. through readjustment of the number of zone nodes and backoff time, and the operation mode of the gateway can be determined.

In one embodiment of the present invention, in assigning a beam scanning function and a beam cluster for registering and assigning IoT nodes, if one IoT sensor node is a node that receives multiple neighboring beam zones, the received signal strength (RSS: received signal strength) of the node signal received by the gateway can be compared and the IoT node can be assigned to the beam zone where a large RSS is received. Since such assignment may cause reinstallation of nodes, mobility of nodes, node battery problems, etc., the data that must be transmitted to the data center (10) through real-time sensing can be re-examined and re-assigned at regular intervals so that there is no problem in transmitting the data.

In one embodiment of the present invention, in the sensor data transmission step, the transmission distance can be estimated based on the size of the received signal strength (RSS) of the sensor data of the IoT node received by the gateway. That is, if the received signal strength (RSS) is large, it is determined that the node is close, and if it is small, it is determined that the node is far away. By adjusting the transmission signal size of the gateway in proportion to this and transmitting it, interference and collisions with other nodes and other surrounding systems can be minimized. In addition, the IoT node can check the received signal strength (RSS) of the signal transmitted by the gateway, and lower the transmission power when it is close to the gateway, and adjust the transmission power to be large when it is far away, thereby saving battery power while maintaining communication quality.

In one embodiment of the present invention, a multi-node simultaneous communication system can be configured and processed by dividing the beamforming mode operation of a gateway into zones in two-dimensional and three-dimensional space and configuring a multi-beam zone simultaneous support system, and in relation to this, the beam zones divided in two-dimensional and three-dimensional space can be simultaneously applied in parallel to two zones, four zones, eight zones, etc., and a multi-node simultaneous communication system can be configured with this configuration to support more node communications simultaneously and implement a multi-node simultaneous communication system configuration and method having the characteristic of increasing communication capacity.

In one embodiment of the present invention, a multi-node simultaneous communication system is configured and operated to support more node communications simultaneously and increase communication capacity, thereby enabling the system to be implemented as a system that has no problem transmitting data that must be sensed in real time and transmitted to a data center (10) in an ultra-high density IoT sensor node network situation.

The present invention can be implemented as a system configuration and operating method that configures a system of these two antenna methods by alternately switching them to operate them alternately or simultaneously to eliminate collisions and interference by additionally installing a beam forming antenna for beam scanning function for node registration and assignment and a beam cluster assignment antenna for beam cluster assignment in a gateway of a wireless IoT sensor network that operates a gateway using an existing omnidirectional antenna, and including a device configuration and steps for coordinating the operation and operation of these two antennas.

In configuring a beam forming antenna for beam scanning function and beam cluster assignment for node registration and assignment of the present invention, the number of beam scanning zones is divided according to the beam forming mode resolution, and the number of beam cluster zones is initially not divided from omnidirectional 1 zone, and is gradually divided into 2 zones, 4 zones, 8 zones, 16 zones, 32 zones, etc. in two-dimensional and three-dimensional space according to the number of IoT nodes, and the entire system is optimized through readjustment of the number of zone nodes and backoff time, etc., and the process of determining an operation mode in the gateway and the reconfiguration process are used as a system configuration and operation method for resolving collisions and interference in the final operating system.

In addition, in the beam scanning function for node registration and assignment of the present invention and the beam cluster assignment, if one sensor node is a node that receives multiple neighboring beam zones, the received signal strength (RSS: received signal strength) of the node signal received by the gateway is compared and the node is assigned to the beam zone where a large RSS is received. Since such assignment may cause reinstallation of nodes, mobility of nodes, node battery problems, etc., the present invention can be used for a system configuration and an operating method that maintains the optimal and best state of the entire operating system, including an operation and process for re-examining and re-assigning at regular intervals so that there is no problem in transmitting data that must be transmitted to the data center (10) by always sensing in real time.

In the present invention, in the step of transmitting sensor data of an IoT node, the transmission distance is estimated based on the size of the signal strength (RSS: received signal strength) of the sensor data of the IoT node received by the gateway, that is, if the signal strength RSS is large, it is determined that the node is close, and if it is small, it is determined that the node is far away, and the size of the transmission signal of the gateway is adjusted in proportion to the size of the signal strength RSS for transmission. By doing so, interference and collisions with other nodes and other surrounding systems can be minimized, and when the IoT node is close by and the strength (RSS) of the signal transmitted by the gateway is checked, the transmission power is lowered and when the IoT node is far away, the transmission power is increased, thereby maintaining communication quality while saving battery power, and the system configuration and operation method can be used for overall system optimization and collision and interference resolution.

An important aspect of the present invention is that the present invention can be used as a system and method for configuring and processing a multi-node simultaneous communication system. Although the complexity of the system may increase somewhat, the technology proposed in the present invention is a key technology for a dramatic increase in communication capacity and for simultaneous real-time transmission of many IoT sensor communications in an ultra-high-density IoT node environment, and can be used in important fields. That is, the system and method for configuring and processing a multi-node simultaneous communication system by dividing the beamforming mode operation of the gateway into zones in two-dimensional and three-dimensional space and configuring a system that simultaneously supports multiple beam zones, and the system having the configuration and function proposed in the present invention can be used in parallel and simultaneously in two, four, and eight beam zones divided in two-dimensional and three-dimensional space, and the processing and device configuration of the system can be used to configure a multi-node simultaneous communication system, thereby configuring and operating a system that supports more node communications simultaneously and increases communication capacity.

In addition, the present invention provides a multi-node simultaneous communication system that supports more node communications simultaneously and increases communication capacity, and a system configuration and operation that is capable of transmitting data to a data center (10) by sensing in real time in an ultra-high density IoT node network situation without any problems, and a system configuration and operation method that maintains an optimal and best state by resolving conflicts and interferences in the entire operating system and network configuration and operation.

The present invention minimizes collisions and interference between a gateway and nodes of an Internet of Things (IoT) wireless sensor network based on beam scanning, thereby enabling plug-and-play operation that operates immediately, and can increase the utilization of frequency resources of an Internet of Things (IoT) wireless sensor network operating in a narrow ISM band. In addition, since beam scanning using a codebook-based beamforming technology preset in a gateway including an antenna adjustment and communication system enables effective identification and management of IoT (Internet of Things) nodes located by beam area, it is possible to manage the scarce frequency resources of the ISM band by dividing them according to time and space.

In addition, in the present invention, the IoT node uses a method in which the node readjusts the backoff time by itself by increasing or decreasing the number of time slots and random numbers based on the result of channel sensing, with the number of basic time slots and basic random numbers for readjusting the backoff time as initial values, thereby enhancing the connectivity of the IoT (Internet of Things) wireless sensor network, and effectively minimizing collisions and interference, thereby enabling plug-and-play (P&P) support that operates immediately.

Since it is possible to manage IoT nodes according to beam division through the aforementioned beam scanning, the back-off time of each node can be reduced, and in an IoT wireless sensor network where any IoT node can transmit sensor data at any time, there is an advantage in that the connectivity between the gateway and IoT nodes, including the antenna adjustment and communication system, can be greatly improved. At the same time, by switching between beam scanning and omnidirectional reception, the number of hidden nodes that may be excluded by beam scanning can be reduced.

In addition, in configuring the beam forming antenna for beam scanning function for node registration and assignment of the present invention and beam cluster assignment, the number of zones of beam scanning is divided according to the resolution of the beam forming mode, and the number of beam cluster zones is initially not divided from omnidirectional 1 zone, and is gradually divided into 2 zones, 4 zones, 8 zones, 16 zones, 32 zones, etc. according to the number of IoT nodes, and the optimization of the entire system is evaluated in the data center by considering the transmission quality (QoS: quality of service), packet success rate, collision resolution rate, information transmission rate (Data Throughput), etc., and a process and reconfiguration process are used to determine the operation mode of the gateway, thereby resolving collisions and interference in the final operating system, and an operating method is achieved.

While the present invention has been described using several preferred embodiments, these embodiments are illustrative and not limiting. Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit and scope of the invention as set forth in the appended claims.

100 gateways 200 IoT nodes

Claims (16)

In a wireless communication method in a high-density IoT wireless sensor network,
Step of searching for pilot signals at the gateway;
The above gateway detects IoT node identification number information included in the received pilot signal and registers the corresponding IoT node when receiving a pilot signal;
The gateway transmits an acknowledgement (ACK) message to the registered IoT node; and
When the IoT node receives a confirmation message from the gateway, communication with the gateway is activated to transmit sensor data,
In the step of searching for a pilot signal from the above gateway,
A step in which an IoT node periodically transmits a pilot signal; and
It comprises a step of searching for a pilot signal by alternately switching between a beam forming mode performing beam scanning in the above gateway and an omnidirectional mode performing omnidirectional reception, or
Or, in the step of searching for a pilot signal from the gateway,
A step in which an IoT node periodically transmits a pilot signal; and
It comprises a step of searching for a pilot signal by simultaneously using a beam forming mode for performing beam scanning in the above gateway and an omnidirectional mode for performing omnidirectional reception,
When the above gateway detects a pilot signal while performing beam scanning, it detects the node identification number information of the IoT node included in the detected pilot signal, and creates or updates a table based on the detected node identification number information to assign IoT nodes to each beam zone.
In the step of transmitting the above sensor data,
It further includes a step of searching for an RTS (Request To Send) frame by alternately switching between a beam forming mode that performs beam scanning in the above gateway and an omnidirectional omnidirectional mode that performs omnidirectional reception, or
Or, in the step of transmitting the above sensor data,
It further comprises a step of searching for an RTS (Request To Send) frame by simultaneously using a beam forming mode that performs beam scanning in the above gateway and an omnidirectional omnidirectional mode that performs omnidirectional reception.
The above gateway further includes a step of beamforming and transmitting a CTS (Clear To Send) frame to an IoT node corresponding to the IoT node identification number of the received RTS frame when receiving the RTS frame.
An IoT node that receives a CTS frame can activate communication with the gateway and transmit sensor data.
The above gateway further comprises a step of replying a confirmation message and terminating communication when receiving a termination packet from an IoT node with communication enabled.
In the step of transmitting the above sensor data,
The IoT node checks whether there is sensor data to transmit;
The IoT node enters a sleeping mode when there is no data to transmit, and performs channel sensing to detect the channel when there is data to transmit; and
The IoT node further comprises a step of transmitting an RTS (Request To Send) frame through the channel if the channel is available as a result of performing channel sensing, and waiting until a CTS (Clear To Send) frame is received from the gateway.
The IoT node waits until it receives a CTS (Clear To Send) frame from the gateway, and waits until it receives a CTS frame including its own node identification number information from the gateway.
The IoT node further includes a step of transmitting a termination packet and entering a sleeping mode when communication with the gateway is terminated.
The above gateway replies with a confirmation message to the IoT node that sent the termination packet and terminates the communication, then returns to the process of searching for the RTS frame again.
The above gateway performs beam scanning by performing beam forming according to a preset beam forming code book, and can perform beam scanning of surrounding IoT nodes by sequentially performing beam forming in a specific direction.
The above gateway stores the reception signal strength information included in the pilot signal, stores node identification number information from each of two or more pilot signals, and when two or more node identification number information are stored, gives priority to the node identification number information in order of the highest reception signal strength, and assigns IoT nodes to each beam zone accordingly.
In the step of transmitting the above sensor data, the gateway adjusts the size of the transmission signal according to the size of the received signal strength of the IoT node.
In the step of transmitting the above sensor data,
The IoT node further includes a step of entering a back-off state and waiting for a back-off time if the channel is being used by another IoT node as a result of performing channel sensing, and then performing the channel sensing process again. At this time, an optimal back-off time is determined in terms of the length and number of back-off times according to the number of IoT nodes, the distribution of nodes, and the type of nodes through a back-off time readjustment algorithm that adjusts the back-off time according to the situation.
A wireless communication method in a high-density IoT wireless sensor network, characterized in that when the IoT node determines an optimal backoff time through a backoff time readjustment algorithm, the IoT node performs channel sensing, and if the channel is not being used by another IoT node, the IoT node decreases a time slot and decreases a number of random numbers, and if the channel is being used by another IoT node, the IoT node increases a time slot and increases a number of random numbers, and calculates a new backoff time by multiplying the changed time slot and the number of random numbers, and backs off by the new backoff time according to the channel situation. delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete