CN116567718A - Directional access control method for terahertz wireless network with high efficiency and high bandwidth utilization - Google Patents

Abstract

The present invention requests protection of a high-efficiency and high-bandwidth utilization directional access control method for a terahertz wireless network, including: designing a memory-assisted control interaction mechanism; designing a channel reservation mechanism based on priority: each node in the network maintains a A location information storage table is used to store the location information that the node has broadcast in the network, and the node location information can be quickly obtained by looking up the table. In the process of control interaction, whether to omit the location information field in the control frame is determined by changing the location information, reducing the duration of control interaction and increasing the duration of data transmission in the THz channel. By setting the priority of the nodes, the success rate of the nodes that can transmit data in parallel to compete for the channel is increased, and the channel is reserved in advance to improve the utilization rate of the THz channel.

Description

Directional access control method for terahertz wireless network with high efficiency and high bandwidth utilization

technical field

The invention belongs to the field of terahertz technology, in particular to a directional access control method for a terahertz wireless network.

Background technique

One of the alternatives to the fifth generation (5G) mobile communication system is the millimeter wave (mm Wave) communication scheme, which can provide a large bandwidth ranging from hundreds of MHz to several GHz. With such available bandwidth, mmWave communication systems can provide more bandwidth than traditional microwave communication systems below 5 GHz. Although the data rate of the millimeter wave band can reach several Gbps, it is still not enough to meet the increasing data traffic demand of future wireless communication. For example, future wireless local area network (WLAN) and wireless personal area network (WPAN) systems require data rates of at least 10 Gbps. Additionally, minimum data rates for virtual reality (VR) devices are expected to reach 10Gbps. In addition, data rates for uncompressed UHD video and 3D video will reach 24Gbps and 100Gbps, respectively. Therefore, research on higher frequency resources is imminent.

Terahertz electromagnetic radiation (from 0.1THz to 10THz) between optical frequency and radio frequency has a band width of 0.03mm to 3mm, and is at the junction of microwave and near-infrared light waves. At present, terahertz communication technology is still in the research and development stage, but many research institutions and enterprises have begun to invest a lot of resources and energy in the research and development of terahertz communication technology, and it is expected that in the next few years, terahertz communication technology It will become an important branch in the field of human information and communication.

However, the propagation range of terahertz waves is affected by the high propagation loss in the air and the adsorption loss of water vapor and oxygen on terahertz waves, which greatly restricts its propagation range. Therefore, it is urgent to use high-gain The antenna effectively compensates for it. Therefore, large-scale phased array antennas are suitable for terahertz communication systems. Based on the principle of beam interference, the phase and amplitude of each antenna unit are adjusted through phase control technology to concentrate electromagnetic energy in a predetermined direction. By using array antennas, it can effectively High-gain and high-directivity beams can be effectively obtained to improve the communication range. Due to the particularity of terahertz waves, existing media access control (Media Access Control, MAC) protocols in traditional networks cannot be directly applied because they do not consider the unique characteristics of terahertz bands such as path and molecular loss, multipath, reflection, and scattering. . Therefore, new efficient MAC protocols that consider the characteristics of the terahertz frequency band and antenna requirements are required. Since the characteristics of terahertz waves limit the communication distance of terahertz waves, the use of terahertz directional antennas can enhance the terahertz communication distance, but this requires high synchronization of terahertz transceiver devices. By decoupling the control plane and the data plane, the low frequency band is used to realize the interaction of control information, which provides the information basis for the directional antenna alignment in the high frequency band, and then realizes high-speed data transmission. In this solution, it is necessary to provide each node with a device that can be positioned or install a device that assists ordinary nodes in positioning. Although the cost of this solution is smaller and beamforming is more convenient, the cost of the equipment is relatively higher.

The closest existing technology to the present invention comes from: Zhou Haidong. Research on dual-channel MAC protocol for terahertz wireless personal area network [D]. Chongqing University of Posts and Telecommunications, 2018.

The specific content of the technical solution of prior art one is as follows:

The existing problems in the existing terahertz dual-channel MAC protocol are: (1) control overhead redundancy when the source node and the destination node exchange control information; (2) when the source node and the destination node transmit data in the THz channel , in order to prevent other nodes from affecting the data transmission process between the source node and the destination node, other nodes cannot perform control information interaction, resulting in the WIFI channel being in an idle state, resulting in a low space division multiplexing rate. Aiming at the above problems, this paper designs a parallel transmission terahertz wireless personal area network dual-channel MAC protocol—PTDC-MAC protocol. The PTDC-MAC protocol improves network throughput and reduces data transmission delay by using the transceiver mechanism of adaptive cancellation of RN location information and the parallel transmission mechanism of multiple pairs of nodes.

1. Adaptively cancel the sending and receiving mechanism of RN location information

In the mechanism of "adaptively canceling the sending and receiving of RN location information", when the source node interacts with RTS/CTS frames, each RN stores "whether the other RN knows its own location" and "the other RN knows its own location" in the location In the information acquisition table, if you want to communicate with the other party RN in the future, and the other party RN already knows its own location information and its own position has not changed, then the position can be omitted when performing RTS/CTS interaction with the other party RN information, thereby reducing redundant control overhead in RTS/CTS.

2. Multi-pair node parallel transmission mechanism

The basic idea of this new mechanism is: node A sends RTS frame to node B on the WiFi channel, and nodes other than node B will be silent for a period of time after receiving the RTS frame (the silent time is RTT/2), and according to the RTS frame The location information of node A shields the beam direction aligned with the directional antenna of node A in the terahertz channel, and the shielding time is the sum of the time required for node A to send data in the terahertz channel and the test delay (according to the "duration" in the RTS frame value obtained). Then node A transmits data to node B on the THz channel. During this data transmission period, if node C has a data transmission requirement to send to node D at this time, then node C sends an RTS frame to node D, and node D receives the RTS After the frame, according to the position information in the RTS frame, obtain the beam direction aligned with the directional antenna of the C node, and then judge whether the beam direction is shielded. ) frame, node C is silent for a period of time according to the value of the Duration field in the NCTS frame (the silent time is the beam direction shielding time), if not, node D will reply a CTS frame to node C, so that node C and node D can interact with each other according to The message adjusts the directional antennas and aligns them with each other, and finally transmits data on the THz channel.

The closest prior art to the present invention 2

The second prior art closest to the present invention comes from: Zhao Zijun. Research on dual-channel MAC protocol in terahertz wireless network [D]. Chongqing University of Posts and Telecommunications, 2020.

The specific content of the technical solution of prior art 2 is as follows:

1. Low space division multiplexing rate

In the TAB-MAC protocol, considering the problem of message collisions between nodes, the TAB-MAC protocol adopts the CSMA/CA protocol to access the channel. Through the interaction of RTS/CTS frames, on the one hand, it prevents messages by reserving the channel time. The occurrence of the collision problem, on the other hand, exchanged the position information of the two nodes. However, it is precisely because of the existence of the reserved channel time mechanism that the TAB-MAC protocol cannot achieve parallel transmission and does not make better use of the high data transmission rate of THz.

2. Low channel resource utilization

Due to the reserved channel time mechanism, only one pair of nodes is allowed to communicate during the reserved channel time, while other nodes must remain silent. The TAB-MAC protocol reserved channel time includes the time of occupying the WIFI channel and the time of occupying the THz channel. Therefore, when the node transmits data on the THz channel, the WIFI channel is in an idle state, which leads to a waste of channel resources.

Contents of the invention

The present invention aims to solve the above problems of the prior art. A directional access control method for terahertz wireless networks with high efficiency and high bandwidth utilization is proposed. Technical scheme of the present invention is as follows:

A method for directional access control of a terahertz wireless network with high efficiency and high bandwidth utilization, comprising the following steps:

Design a memory-assisted control interaction method: For the first time in the network for the control information interaction process or the node that retransmits the control frame after the first failure to send the control frame, operate according to the control information interaction process in the TAB-MAC protocol; for the nodes that have successfully communicated For a node that has communicated successfully, if the node has data to transmit or receive at a certain moment and its own node location information has not changed, then remove the location information field in the control frame; for nodes that have successfully communicated, if the source node and the destination node If the location information of the node has changed, the updated location information will be broadcast omnidirectionally to all nodes in the network through the Sub-6G frequency band. After receiving the new location information of the node, other nodes will update the location information storage table maintained by their own nodes. The location information entry, and control the interaction process according to the original protocol;

Design a priority-based channel reservation method: After the nodes in the network successfully reserve the channel, the remaining nodes can start the next round of channel reservation, that is, all nodes except the communicating nodes can reserve the channel; if the reserved channel If the node does not affect the data transmission of the node in communication, the node is set as a high priority node, and the other nodes that affect the node in communication are set as low priority nodes, and the channel is reserved normally.

Further, the specific operation steps of the design memory-assisted control interaction method are as follows:

Step A1: All nodes in the network maintain a location information storage table, which records the location information and MAC address information of other nodes in the network except this node. The location information storage tables of all nodes are all Table entries are all set to NULL;

Step A2: When the source RN needs to send data, the source RN judges whether the node is sending the RTS frame for the first time or retransmitting the RTS frame for the first time, if so, execute step A3; if not, execute step A4;

Step A3: the source RN sends an RTS frame with location information, and executes step A5;

Step A4: The source RN judges whether the location information of the node has changed, and if changed, sends an RTS frame with new location information; if not changed, sends an RTS frame omitting the location information;

Step A5: After receiving the RTS frame, the destination RN extracts the information carried in the RTS frame. If there is no location information in the RTS frame, it means that the location information of the source RN has not changed, and the destination RN directly uses the node location information storage table to store source RN location information; otherwise, use the location information carried in the RTS frame;

Step A6: The destination RN judges whether this node is replying a CTS frame for the first time or retransmitting a CTS frame for the first time, if so, then reply a CTS frame with the location information of the destination RN; if not, reply a CTS frame without location information;

Step A7: After the source RN and the destination RN successfully exchange control information, the source and destination RN have obtained the location information and antenna information of the other node, and the source and destination RN switch to the THz channel and perform beamforming to align the THz directional antennas with each other , the source RN sends a TTS frame directionally on the THz channel, and the destination RN returns an ACK frame directionally after receiving it. Then the source RN uses a directional antenna to send data to the target RN on the THz channel. After receiving the data frame and confirming that the data frame is correct, the target RN replies to the source RN with an ACK frame.

Further, the function of the location information storage table is to record all nodes in the network that have omnidirectionally broadcast location information and MAC address information in the low frequency band. The location information storage table has three entries in total, which are serial number , node location information and node MAC address information, among which, the sequence number records the order in which all nodes in the network broadcast control information through the control frame for the first time; when a node sends an RTS control frame omnidirectionally in the Sub-6G frequency band, the destination node also The CTS control frame will be replied, therefore, each node can add the location information and MAC address information of the source node and the destination node in the location information storage table maintained by the node.

Further, the specific operation steps of the priority-based channel reservation method are as follows:

Step B1: The node judges whether it has data to send, if not, it does not do anything; if it does, execute step B2;

Step B2: The source RN judges whether the destination RN is a communicating node in the network. If so, set the node as a high-priority node and set the initial value of retry_count; if not, set the node as a low-priority node , and set the initial value of retry_count;

Step B3: The node monitors whether the channel is idle, and if the channel is busy, continues to monitor; if the channel is idle, execute step B4;

Step B4: After the source RN waits for the DIFS duration, send an RTS frame omnidirectionally on the 5G channel, and judge whether the source RN has received the CTS frame sent by the destination RN; if the CTS frame is not received, perform step B5; if the CTS frame is received, Execute step B6;

Step B5: Set the retry_count value of high-priority nodes and low-priority nodes. If the retry_count value of low-priority nodes is greater than the maximum number of backoffs or the retry_count value of high-priority nodes is equal to the maximum number of backoffs, end the current round of channel reservation process; otherwise , recalculate the backoff time, re-monitor the channel and wait for the channel to be free;

Step B6: The source RN judges the priority setting type of the node. If it is a high priority node, perform step B7; if the node is a low priority node, wait for the destination RN to complete transmitting or receiving data before performing step B7;

Step B7: The source RN and the target RN align the antennas through beamforming, and then send a TTS test frame on the THz channel. If the source RN does not receive the ACK frame replied by the target RN, end the current round of channel reservation process; if the target RN receives The ACK frame replied by the RN, the source RN sends a data frame to the destination RN, and the destination RN replies with an ACK frame after receiving the data frame;

Step B8: After the communication between the source RN and the destination RN is completed, the high-priority node resets the retry_count value to 0 according to the original BEB algorithm; the low-priority node randomly selects a random value in the range [0, retry_count] as the next In one round, the node initializes the initial value of retry_count.

Further, in the design priority-based channel reservation method: in order to make the nodes that can transmit in parallel have a greater probability of successfully competing for the channel, the nodes that transmit in parallel are set as high-priority nodes, and parallel transmission is not allowed and A node that can only wait for the communicating node to transmit data or receive data before it can communicate is set as a low priority node; the core of setting the priority node is the value of the b4 bit in the frame control field, when the b4 bit When the value is 0, it indicates that the node sending the frame is a low-priority node, otherwise, when it is 1, it is a high-priority node.

Advantage of the present invention and beneficial effect are as follows:

(1) Each node in the network of the present invention maintains a location information storage table for storing the location information that the node has broadcast in the network, and the node location information can be quickly obtained by looking up the table.

(2) In the process of control interaction, whether to omit the location information field in the control frame is determined by changing the location information, reducing the duration of control interaction and increasing the duration of data transmission in the THz channel.

(3) By setting the priority of the nodes, the success rate of the nodes that can transmit data in parallel to compete for the channel is increased, and the channel is reserved in advance to improve the utilization rate of the THz channel.

Description of drawings

FIG. 1 is a schematic structural diagram of a Terahertz Wireless Personal Area Networks (THz-WPAN) according to a preferred embodiment of the present invention;

Figure 2 is a schematic diagram of the composition of THz-WLAN;

Fig. 3 is a TAB-MAC protocol network model;

Fig. 4 is a TAB-MAC protocol RTS/CTS frame structure diagram;

Fig. 5 is an RTS/CTS frame structure diagram omitting location information;

Fig. 6 is the operation flowchart of source RN;

FIG. 7 is a flowchart of the operation of the target RN;

Fig. 8 is a flowchart of the operation of the memory-assisted control interaction mechanism;

FIG. 9 is a flowchart of the operation of the priority-based channel reservation mechanism.

Detailed ways

The technical solutions in the embodiments of the present invention will be described clearly and in detail below with reference to the drawings in the embodiments of the present invention. The described embodiments are only some of the embodiments of the invention.

The technical scheme that the present invention solves the problems of the technologies described above is:

Abbreviations and key terms involved in the present invention are:

Abbreviations and Key Terms

Terahertz wireless personal area network basic architecture

The structure diagram of Terahertz Wireless Personal Area Networks (THz-WPAN) is shown in Figure 1. The network consists of multiple DEVs (Device) and a piconet coordinator PNC (PicoNetCoordinator).

THz-WPAN is a wireless communication network that uses the terahertz frequency band as the communication carrier and has a communication range within 10 meters. The terahertz wireless personal area network provides a larger bandwidth and a higher transmission rate on the basis of the existing wireless personal area network providing rich business types and opening up the final link connection between the wireless network and the mobile smart terminal, which can effectively alleviate the current situation. There is a problem of shortage of wireless spectrum resources. Terahertz wireless personal area network is divided into the category of high-speed wireless personal area network, which provides peripheral smart mobile terminals with the ability to access wireless networks for high-speed data communication.

Basic architecture of terahertz wireless local area network

THz-WLAN uses the terahertz frequency band as the carrier, which can support data transmission rates up to 10Gbps and various types of network applications and services. THz-WLAN is mainly used for high-speed data transmission and communication between low-power devices, such as robots, sensors, medical equipment and smart home devices. In addition, THz-WLAN can also be applied to indoor positioning, Internet of Things and other fields. As shown in Figure 2, the THz-WLAN network architecture model is a network composed of multiple regular nodes (RegularNodes, RN) and a central control node (Control Node, CN), where the central control node acts as the access point The role is the control center of the entire network. In THz-WLAN, the communication methods between nodes include point-to-point communication and multicast communication. In point-to-point communication, two nodes can directly establish a connection to communicate, one node acts as a sender, and the other node acts as a receiver, each node has its own address, so that other nodes can directly broadcast their addresses to the rest of the nodes, And according to the broadcast address information, beamforming is used to align the terahertz antenna; multicast communication means that a node sends data packets to multiple nodes at the same time. In THz-WLAN, multicast communication can be realized through CN. The sender sends the packet to the CN, and the CN copies and forwards the packet to multiple receivers. Multicast communication can effectively improve network transmission efficiency, especially in scenarios where the same data needs to be broadcast to multiple nodes.

TAB-MAC protocol

Figure 3 shows the network model of the TAB-MAC protocol. The network consists of regular nodes and anchor nodes (AnchorNodes, AN). Both anchor nodes and regular nodes can exchange control information in the Sub-6G frequency band through omnidirectional antennas. , the anchor node can identify its location by being equipped with a GPS module or manually configured and periodically broadcast beacon signals, and regular nodes determine their own location by receiving beacon signals. Additionally, conventional nodes are configured with beamforming antenna arrays for terahertz communications.

In a terahertz communication network, in order to deal with the "facing" problem, a node can solve the problem by estimating its own position and using the Sub-6G frequency band to communicate with a specific transmitter or receiver. The agreement selects the Sub-6G frequency band for the exchange of control information because this frequency band has the advantages of transmission distance and omnidirectionality. The position of regular nodes in two-dimensional space requires three non-collinear anchor nodes to assist localization, while in three-dimensional space, at least four non-coplanar anchor nodes are required to assist localization. When establishing a terahertz link, the terahertz beamforming antenna arrays of the transmitter and receiver need to be properly aligned, which can be achieved by nodes estimating their own positions. Due to the severe path loss and limited transmission power of terahertz systems, very high directional gain or very narrow beamwidth is required. These parameters depend on the transmission frequency and the distance between the transmitter and receiver and can be calculated from the node position. The communication process of the protocol is divided into two stages, and the specific operation steps are as follows:

1. Node discovery and coupling phase

The protocol is designed to discover and couple transmitters and receivers by taking advantage of the omnidirectional 5G channel communication, and then align their terahertz beamforming antennas with each other. First, the sender sends an extended RTS (Request-To-Send, RTS-NI) frame containing node location information. When the receiver is available, the receiver will reply with an extended CTS (Clear-To-Send , CTS-NI) frame. Once the two nodes have obtained each other's location information and antenna information, they can calculate the straight-line distance between each other, the beam width, and align each other with the beamforming antenna.

In the TAB-MAC protocol, all RNs use CSMA/CA to access the channel. If the RN finds that the information sent by itself collides with the information sent by other RNs, it will perform a binary backoff operation according to formula (1), and resend the information after waiting for T _BF time. Where T _BF is calculated as:

T _BF ＝[rand(n)×(2 ^CW -1)]×2τ (1)

In the formula, T _BF is the binary exponential backoff time; rand(n) is a random number; CW is the backoff window; τ is the backoff basic time slot.

The value method of CW is CW=min{retry_count,3}, and retry_count is the number of backoffs. When the number of back-offs is greater than 3 and less than the maximum number of back-offs, the value of CW is 3. When the number of back-offs is greater than the maximum number of back-offs, retransmission of the message is abandoned and the channel is reserved again.

2. THz channel data transmission stage

After the above-mentioned stages, the beamforming antennas of the transmitter and receiver are pointing towards each other, i.e. the transmitter is ready to transmit data in the terahertz band. First, to check the channel conditions between the transmitter and receiver, the transmitters will send a TTS frame to ensure that their directional antennas are pointing at each other and line-of-sight propagation between them is available. Once the sending end receives an acknowledgment (Acknowledgment, ACK) frame from the receiving end, it starts to transmit data.

In order to solve the above problems, the HEPT-MAC protocol is proposed to solve it. The HEPT-MAC protocol is divided into a multi-pair node parallel transmission mechanism.

The main idea of the multi-pair node parallel transmission mechanism is: when the source and destination nodes are exchanging control frames, the time for channel reservation should be redistributed. It is no longer the time of occupying the WIFI channel and the total time of occupying the THz channel. It is redistributed as Controls the timing of frame interactions. When the channel reservation time is over, other nodes immediately start a new round of channel competition process, that is, re-reserve the channel.

When the nodes on both sides of the communication switch to the THz channel to prepare for data transmission, it is assumed that the source node is S and the destination node is D. It is assumed that the source and destination nodes are communicating, and C, E, and F are other nodes. When other nodes C receive the omnidirectional RTS frame from the source node S, they extract the site address information of the source and destination nodes in the RTS frame. If at the next moment, other nodes C have a data request to send, according to the half-duplex communication mode of the existing terahertz dual-channel MAC protocol node, node C should also judge whether the destination address is the site address of the communicating node. If the destination address of node C to send data at the next moment is source node S or destination node D, it must wait for the data transmission of the communicating node to be completed; if the destination address of node C to send data is not the site address of the communicating node , the normal contention channel and reservation channel. When other nodes E receive the RTS frame and C-ACK frame sent omnidirectionally from the source node S, they extract the position coordinates of the source node in the RTS frame and the position coordinates of the destination node in the C-ACK frame. If at the next moment, node E has a data request to send, and the destination address of the transmission is not source node S or destination node D, if the destination address of node E is node F, then when node F receives the RTS sent by node E After the frame, extract the position coordinates of node E, and judge whether nodes E and F are collinear with nodes S and D. If they are collinear, beam overlap will occur and interference will occur. Node F should remain silent until the data transmission is completed. If not collinear, reply D-TTS frame to node E immediately.

Basic Presuppositions of the Invention

The technical solution contained in the present invention involves the following assumptions:

(1) Data transmission between nodes in a terahertz wireless local area network uses directional antennas.

(2) The sending and receiving of control frames are omnidirectional;

(3) Some RNs in the terahertz wireless local area network can communicate directly with each other.

The technical problem to be solved in the present invention

Under the environment of terahertz wireless personal area network, the main problem that the present invention needs to solve is:

In the existing protocol, before an idle node wants to transmit data with other nodes, it needs to exchange control information with the destination node to obtain the location information and antenna information of the destination node, which provides basic information for subsequent high-speed data transmission in THz. Since the control information interaction process of nodes needs to send control frames omnidirectionally in the low frequency band, all nodes in the network can obtain the node’s location information and antenna information. However, the control frame with location information is still sent according to the original protocol control interaction process, which brings additional control overhead. If a network table is maintained for each node to record the location information broadcast by other nodes in the network except this node in the process of channel reservation in the past, the control overhead can be reduced.

When all nodes can reserve channels in advance, it is assumed that there are several communicating node pairs in the network. When an idle node wants to shake hands with other nodes in the network, all nodes use CSMA/CA to compete for the channel. Although this method is relatively fair in the TAB-MAC protocol, there are two situations in this network; the first situation is that after the idle node successfully competes for the channel, it will not affect the transmission of the node in communication, and can immediately communicate with other nodes in communication. Communicating pairs of nodes transfer data in parallel. The second situation is that the idle node cannot transmit data immediately after successfully competing for the channel, but waits for the node in communication to transmit data or receive data before transmitting data. Obviously, CSMA/CA is no longer applicable to this network. Therefore, it can be considered to increase the channel competition success rate of nodes capable of parallel transmission to improve network throughput.

The new mechanism proposed by the present invention

The present invention proposes a high-utilization and low-overhead terahertz wireless network dual-channel media access control method, which includes the following two innovative mechanisms:

(1) Memory-assisted control interaction mechanism.

(2) Priority-based channel reservation mechanism.

The following two new mechanisms are introduced in detail.

Memory Assisted Control Interaction Mechanism

The main thinking direction of the memory-assisted control interaction mechanism is mainly divided into three aspects.

1. For the node that performs the control information exchange process in the network for the first time or retransmits the control frame after failing to send the control frame for the first time, operate according to the control information exchange process in the TAB-MAC protocol.

2. For a node that has passed (the node can be the source node that sends data, or the destination node that receives data), if the node has data to transmit or receive at a certain moment and its own node location information has not changed, Then it may be considered to remove the location information field in the control frame to reduce the control overhead.

3. For a node that has successfully communicated, if the location information of the source node and the destination node have changed, the updated location information will be omnidirectionally broadcast to all nodes in the network through the Sub-6G frequency band, and other nodes will receive the node After receiving the new location information, update the location information entry in the location information storage table maintained by its own node, and perform the control interaction process according to the original protocol.

The main idea of the new mechanism is to reduce the control overhead of the entire network by reducing unnecessary location information overhead, and save more time for each node to transmit data on the THz channel. In order to save the location information of each node, each node needs to maintain a location information storage table, which is used to record all nodes in the network that have broadcast location information and MAC address information in the low frequency band omnidirectionally. Table 1 shows the location information storage table maintained by each node. There are three entries in the table, which are serial number, node location information and node MAC address information. Among them, the sequence number records the order of all nodes in the network broadcasting control information through the control frame for the first time. When a node sends an RTS control frame omnidirectionally in the Sub-6G frequency band, the destination node will also reply a CTS control frame. Therefore, each node can add the location information and MAC address information.

Table 1 Location information storage table

When there are too many nodes in the network and most of the nodes have sent the control frames of their own nodes in the Sub-6G low frequency band, according to the idea of the control interaction mechanism of the memory-assisted omitting position, if the position of the node has not changed, use The control frame structure in the TAB-MAC protocol as shown in Figure 4; if the position of the node changes, the position information field in the control frame needs to be removed, as shown in Figure 5, the control frame structure with the position information omitted.

The specific operation steps of this mechanism are as follows:

Step 1: All nodes in the network each maintain a location information storage table, which records the location information and MAC address information of other nodes in the network except this node. The location information storage tables of all nodes are all Table entries are all set to NULL.

Step 2: When the source RN needs to send data, the source RN judges whether this node is sending an RTS frame for the first time or retransmitting an RTS frame for the first time, if so, go to step 3; if not, go to step 4.

Step 3: The source RN sends an RTS frame with location information, and executes Step 5.

Step 4: The source RN judges whether the location information of the node has changed, and if changed, sends an RTS frame with new location information; if not, sends an RTS frame omitting the location information.

Step 5: After receiving the RTS frame, the destination RN extracts the information carried in the RTS frame. If there is no location information in the RTS frame, it indicates that the location information of the source RN has not changed, and the destination RN directly uses the node location information storage table to store The location information of the source RN; otherwise, the location information carried in the RTS frame is used.

Step 6: The destination RN judges whether this node is replying a CTS frame for the first time or retransmitting a CTS frame for the first time, if so, then reply a CTS frame with the location information of the destination RN; if not, reply a CTS frame without location information.

Step 7: After the source RN and the destination RN successfully exchange control information, the source and destination RN have obtained the location information and antenna information of the other node, and the source and destination RN switch to the THz channel and beamforming to align the THz directional antennas with each other , the source RN sends a TTS frame directionally on the THz channel, and the destination RN returns an ACK frame directionally after receiving it. Then the source RN uses a directional antenna to send data to the target RN on the THz channel. After receiving the data frame and confirming that the data frame is correct, the target RN replies to the source RN with an ACK frame.

Priority-based channel reservation mechanism

The main idea of this mechanism is: after the nodes in the network successfully reserve the channel, the remaining nodes can start the next round of channel reservation, that is, all nodes except the communicating nodes can reserve the channel. If the node that reserved the channel does not affect the data transmission of the node in communication, set the node as a high-priority node, and the other nodes that affect the node in communication are set as low-priority nodes, and reserve the channel normally. Compared with the existing protocol, the new mechanism guarantees as much as possible the probability that the data nodes that can transmit in parallel successfully compete for the channel without affecting the channel reservation of other common nodes. Successfully reserving the channel will eventually lead to a long time waiting for the node that is transmitting data or receiving data to complete. The nodes that can transmit data in parallel have been in a waiting state due to the failure of competing for the channel. If the node successfully shakes hands with another node, this will cause some nodes to be unable to transmit data to the destination node for a long time, affecting network throughput.

In the new mechanism proposed by the present invention, in order to make the nodes that can transmit in parallel have a greater probability of successfully competing for the channel, this mechanism intends to set it as a high-priority node, which cannot perform parallel transmission and can only wait for the communicating node Nodes that can communicate only after transmitting data or receiving data are set as low-priority nodes. The core of setting the priority node is the value of the b4 bit in the frame control field. When the value of the b4 bit is 0, it indicates that the node sending the frame is a low priority node, otherwise it is a high priority node when it is 1. The types of each control frame are shown in Table 2.

Table 2 Control frame type

Compared with the traditional binary exponential back-off (Binary Exponential Back off, BEB) algorithm, this mechanism changes the initialization method of the competition window value on the basis of the BEB algorithm, that is, the back-off window value of the high-priority node in the network and the low-priority node The back-off window values of level nodes are different, this is because parallel transmission can be performed without affecting other nodes that are communicating. When the amount of network data is large, the throughput and channel utilization of parallel transmission are better than queuing for data transmission. . Therefore, when the BEB algorithm is used for backoff for the first time, the backoff window of the high-priority node will not be changed, in order to increase the probability of the node successfully competing for the channel in the next competition window. In the original BEB algorithm, when a node completes successful communication, it will initialize the retry_count value to 0 when reserving a channel next time. In this mechanism, the retry_count value of the high-priority node is the same as the initialization method of the original BEB algorithm, while the low-priority node randomly selects a value between [0, retry_count] as the retry_count value of the node in the next round of channel competition. Initial value, if the destination node of the next round of competition for the low-priority node is not the node that is communicating, then set the node as a high-priority node. This mechanism increases the success rate of high-priority nodes competing for the channel, Improve channel utilization.

The specific operation steps of the priority-based channel reservation mechanism proposed by the present invention are as follows:

Step 1: The node judges whether it has data to send, if not, it does not do any operation; if it does, execute step 2.

Step 2: The source RN judges whether the destination RN is a communicating node in the network. If so, set the node as a high-priority node and set the initial value of retry_count; if not, set the node as a low-priority node , and set the initial value of retry_count.

Step 3: The node monitors whether the channel is idle, and if the channel is busy, continues to monitor; if the channel is idle, execute step 4.

Step 4: After the source RN waits for the DIFS period, send an RTS frame omnidirectionally on the 5G channel to determine whether the source RN has received the CTS frame sent by the destination RN; if the CTS frame is not received, perform step 5; if the CTS frame is received, Go to step 6.

Step 5: Set the retry_count value of high-priority nodes and low-priority nodes according to the method described above. If the retry_count value of low-priority nodes is greater than the maximum number of backoffs or the retry_count value of high-priority nodes is equal to the maximum number of backoffs, end this Round channel reservation process; otherwise, recalculate the backoff time, re-monitor the channel and wait for the channel to be free.

Step 6: The source RN judges the priority setting type of the node. If it is a high priority node, perform step 7; if the node is a low priority node, wait for the destination RN to transmit or receive data before performing step 7.

Step 7: The source RN and the target RN align the antennas through beamforming, and then send a TTS test frame on the THz channel. If the source RN does not receive the ACK frame replied by the target RN, end the current round of channel reservation process; if the target RN receives For the ACK frame replied by the RN, the source RN sends a data frame to the destination RN, and the destination RN replies with an ACK frame after receiving the data frame.

Step 8: After the communication between the source RN and the destination RN is completed, the high-priority node resets the retry_count value to 0 according to the original BEB algorithm; the low-priority node randomly selects a random value in the range of [0, retry_count] as the next In one round, the node initializes the initial value of retry_count.

The concrete embodiment that the technology of the present invention realizes

Node operations are divided into two types: source RN and destination RN. This section illustrates specific embodiments by giving the main operation modes of nodes in each time period.

Source RN main operations

The main operations of the source RN during the control interaction are as follows:

(1) Before sending the control frame, the source RN determines whether the sent control frame carries the location information according to whether the location information of the node changes. If the position of the node changes, a control frame with position information is sent, otherwise, a control frame without a position information field is sent.

(2) At the same time, the node judges whether it can send data to the destination RN immediately after successfully competing for the channel, if it can, set the node as a high-priority node, if not, set the node as a low-priority node.

(3) The node sends an RTS control frame.

(4) Switch to the THz channel. After beamforming, it is decided to send data immediately or wait for a period of time before sending data according to the priority of the node.

The operation flow of the source RN is shown in FIG. 6 .

The main operation of the target RN

The main operations of nodes other than PNC during the Beacon period are as follows:

(1) Receive RTS frame.

(2) Determine whether the RTS frame carries location information and the priority of the control frame.

(3) If the RTS frame does not carry location information, it means that the location of the source RN has not changed, and the location information of the source RN stored in the location information storage table maintained by the destination RN is directly used.

(4) If the RTS frame carries location information, the location information is directly used for beamforming.

(5) Switch to the THz channel. After beamforming, it is decided to receive data immediately or wait for a period of time according to the priority of the RTS frame.

The flow chart of the operation of the target RN is shown in Fig. 7 .

Beneficial effects brought by the technical solution of the present invention

The beneficial effects brought by the technical solution of the present invention are mainly reflected in the following two aspects:

In the process of control information interaction, for nodes that have broadcast location information and have no change in location when reserving channels again, the control overhead in the control interaction process is reduced by reducing the location information in the control frame. By setting the priority, the nodes that can transmit in parallel have a greater chance of successfully competing for the channel. At the same time, more data is transmitted on the THz channel, improving channel utilization and throughput.

Key technical points and protection points of the present invention

The technical key point of the present invention and desire protection point have:

Each node in the network maintains a location information storage table, which is used to store the location information that the node has broadcast in the network, and the node location information can be quickly obtained by looking up the table.

In the process of control interaction, whether to omit the location information field in the control frame is determined by changing the location information, reducing the duration of control interaction and increasing the duration of data transmission in the THz channel.

By setting the priority of the nodes, the success rate of the nodes that can transmit data in parallel to compete for the channel is increased, and the channel is reserved in advance to improve the utilization rate of the THz channel.

Thinking of the present invention can also be used for:

(1) Parallel data transmission between nodes in a terahertz wireless ad hoc network;

(2) Reduce control overhead in terahertz wireless ad hoc networks.

The systems, devices, modules, or units described in the above embodiments can be specifically implemented by computer chips or entities, or by products with certain functions.

It should also be noted that the term "comprises", "comprises" or any other variation thereof is intended to cover a non-exclusive inclusion such that a process, method, article, or apparatus comprising a set of elements includes not only those elements, but also includes Other elements not expressly listed, or elements inherent in the process, method, commodity, or apparatus are also included. Without further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article or apparatus comprising said element.

The above embodiments should be understood as only for illustrating the present invention but not for limiting the protection scope of the present invention. After reading the contents of the present invention, skilled persons can make various changes or modifications to the present invention, and these equivalent changes and modifications also fall within the scope defined by the claims of the present invention.

Claims (5)

1. A terahertz wireless network directional access control method with high efficiency and high bandwidth utilization rate, is characterized in that, comprising the following steps: Design a memory-assisted control interaction method: For the first time in the network for the control information interaction process or the node that retransmits the control frame after the first failure to send the control frame, operate according to the control information interaction process in the TAB-MAC protocol; for the nodes that have successfully communicated For a node that has communicated successfully, if the node has data to transmit or receive at a certain moment and its own node location information has not changed, then remove the location information field in the control frame; for nodes that have successfully communicated, if the source node and the destination node If the location information of the node has changed, the updated location information will be broadcast omnidirectionally to all nodes in the network through the Sub-6G frequency band. After receiving the new location information of the node, other nodes will update the location information storage table maintained by their own nodes. The location information entry, and control the interaction process according to the original protocol; Design a priority-based channel reservation method: After the nodes in the network successfully reserve the channel, the remaining nodes can start the next round of channel reservation, that is, all nodes except the communicating nodes can reserve the channel; if the reserved channel If the node does not affect the data transmission of the node in communication, the node is set as a high priority node, and the other nodes that affect the node in communication are set as low priority nodes, and the channel is reserved normally. 2. The directional access control method for terahertz wireless networks with high efficiency and high bandwidth utilization according to claim 1, wherein the specific operation steps of the design memory-assisted control interaction method are as follows: Step A1: All nodes in the network maintain a location information storage table, which records the location information and MAC address information of other nodes in the network except this node. The location information storage tables of all nodes are all Table entries are all set to NULL; Step A2: When the source RN needs to send data, the source RN judges whether the node is sending the RTS frame for the first time or retransmitting the RTS frame for the first time, if so, execute step A3; if not, execute step A4; Step A3: the source RN sends an RTS frame with location information, and executes step A5; Step A4: The source RN judges whether the location information of the node has changed, and if changed, sends an RTS frame with new location information; if not changed, sends an RTS frame omitting the location information; Step A5: After receiving the RTS frame, the destination RN extracts the information carried in the RTS frame. If there is no location information in the RTS frame, it means that the location information of the source RN has not changed, and the destination RN directly uses the node location information storage table to store source RN location information; otherwise, use the location information carried in the RTS frame; Step A6: The destination RN judges whether this node is replying a CTS frame for the first time or retransmitting a CTS frame for the first time, if so, then reply a CTS frame with the location information of the destination RN; if not, reply a CTS frame without location information; Step A7: After the source RN and the destination RN successfully exchange control information, the source and destination RN have obtained the location information and antenna information of the other node, and the source and destination RN switch to the THz channel and perform beamforming to align the THz directional antennas with each other , the source RN sends a TTS frame directionally on the THz channel, and the destination RN returns an ACK frame directionally after receiving it. Then the source RN uses a directional antenna to send data to the target RN on the THz channel. After receiving the data frame and confirming that the data frame is correct, the target RN replies to the source RN with an ACK frame. 3. The high-efficiency and high-bandwidth utilization terahertz wireless network directional access control method according to claim 2, characterized in that, the function of the location information storage table is to record all the low-frequency omnidirectional access control methods in the network. For nodes that have broadcast location information and MAC address information, the location information storage table has three entries in total, which are serial number, node location information and node MAC address information, wherein the serial number records the first time all nodes in the network pass the control The sequence of frame broadcast control information; when a node sends an RTS control frame omnidirectionally in the Sub-6G frequency band, the destination node will also reply a CTS control frame, so each node can add the source node to the location information storage table maintained by the node and the location information and MAC address information of the destination node. 4. The directional access control method for terahertz wireless networks with high efficiency and high bandwidth utilization according to claim 1, wherein the specific operation steps of the priority-based channel reservation method are as follows: Step B1: The node judges whether it has data to send, if not, it does not do anything; if it does, execute step B2; Step B2: The source RN judges whether the destination RN is a communicating node in the network. If so, set the node as a high-priority node and set the initial value of retry_count; if not, set the node as a low-priority node , and set the initial value of retry_count; Step B3: The node monitors whether the channel is idle, and if the channel is busy, continues to monitor; if the channel is idle, execute step B4; Step B4: After the source RN waits for the DIFS duration, send an RTS frame omnidirectionally on the 5G channel, and judge whether the source RN has received the CTS frame sent by the destination RN; if the CTS frame is not received, perform step B5; if the CTS frame is received, Execute step B6; Step B5: Set the retry_count value of high-priority nodes and low-priority nodes. If the retry_count value of low-priority nodes is greater than the maximum number of backoffs or the retry_count value of high-priority nodes is equal to the maximum number of backoffs, end the current round of channel reservation process; otherwise , recalculate the backoff time, re-monitor the channel and wait for the channel to be free; Step B6: The source RN judges the priority setting type of the node. If it is a high priority node, perform step B7; if the node is a low priority node, wait for the destination RN to complete transmitting or receiving data before performing step B7; Step B7: The source RN and the target RN align the antennas through beamforming, and then send a TTS test frame on the THz channel. If the source RN does not receive the ACK frame replied by the target RN, end the current round of channel reservation process; if the target RN receives The ACK frame replied by the RN, the source RN sends a data frame to the destination RN, and the destination RN replies with an ACK frame after receiving the data frame; Step B8: After the communication between the source RN and the destination RN is completed, the high-priority node resets the retry_count value to 0 according to the original BEB algorithm; the low-priority node randomly selects a random value in the range [0, retry_count] as the next In one round, the node initializes the initial value of retry_count. 5. The directional access control method for terahertz wireless networks with high efficiency and high bandwidth utilization according to claim 4, characterized in that, in the design of the priority-based channel reservation method: in order to enable the nodes that can transmit in parallel to have more If there is a high probability of successfully competing for the channel, set the node that transmits in parallel as a high-priority node, and set it as Low priority node; set the core of the priority node to the value of the b4 bit in the frame control field. When the value of the b4 bit is 0, it indicates that the node sending the frame is a low priority node, otherwise it is a high priority node when it is 1 .