An Efficient Terahertz Wireless Network Directional Access Method with High Time Slot Utilization Rate

Abstract

The present invention relates to a method for directional access of a terahertz wireless network with high efficiency and high time slot utilization rate, belonging to the field of terahertz wireless networks. The present invention proposes an adaptive reduced beamforming mechanism, which operates in the CTAP period of the superframe. On the premise of ensuring the beamforming effect, the beamforming operation is reduced; a node stationary information publishing mechanism based on motion cooperative control and probability is proposed, which operates in the CTAP period of the superframe to ensure or estimate the stationary state of the node, and then publishes the information that the node will remain stationary in the future in a zero or low additional overhead manner; an adaptive low-overhead mechanism for transmitting the sector number is proposed, which operates in the CAP period and the Beacon period of the superframe. In a zero or low additional overhead manner, the sector number where the data frame source node is located on the data frame destination node is transmitted from the data frame source node to the data frame destination node through PNC, so as to facilitate the quick alignment of the antennas of the data frame source and destination nodes.

Description

Technical Field

[0001] The present invention belongs to the technical field of terahertz wireless network directional access, and particularly relates to a terahertz wireless network directional access method with high efficiency and high time slot utilization rate. Background Technique

[0002] A terahertz wireless network (Terahertz Wireless Network, TWN) is a data communication network that uses terahertz band wireless communication technology at the physical layer. Terahertz wireless personal area network (Terahertz Wireless Personal Area Network, THz-WPAN) and terahertz wireless local area network (Terahertz Wireless Local Area Network, THz-WLAN) are two typical types of terahertz wireless networks. Currently, people pay more attention to terahertz wireless personal area networks, and terahertz wireless local area networks have similarities with terahertz wireless personal area networks in terms of network architecture and key technologies.

[0003] A terahertz wireless personal area network consists of one or more PANs (Personal Area Network, personal area network); each PAN consists of one PNC (PicoNet Coordinator, piconet coordinator) and one or more DEVs (Device, device nodes), and the PNC is mainly responsible for the synchronization of the entire network and channel resource management. Any two nodes (DEV or PNC) in the network can communicate directly. Any two nodes in a terahertz wireless personal area network can directly transmit data, and the data transmission rate can be as high as over 10 Gbps.

[0004] A terahertz wireless personal area network adopts the same superframe structure as IEEE802.15.3c. Each superframe is divided into three parts: Beacon (beacon) period, CAP (Contention Access Period, contention access) period, and CTAP (Channel Time Allocation Period, channel time allocation) period.

[0005] During the Beacon period, the PNC mainly sends beacon frames in each sector in turn, and the DEV rotates its antenna to receive the beacon frames; the beacon frames contain the basic information of all nodes in the entire network, as well as the time and duration information of each period. When the DEV receives the beacon frame, it extracts the synchronization information and time slot allocation information from it. The CAP period is mainly used for unconnected DEVs to send access requests to the PNC, and for connected DEVs to apply for time slots from the PNC; during the CAP period, all DEVs access the channel in accordance with the CSMA method. The CTAP period is used for DEVs that have been allocated channel resources to complete data transmission in their allocated CTAs; during this period, the DEVs access the channel in accordance with the TDMA method.

[0006] Nodes in a terahertz wireless local area network can be static or dynamic. The network contains a central control node PNC served by (or specifically designed as) a DEV. This node provides basic networking information through periodic broadcast of beacon frames, and is responsible for the control coordination of the entire micro-network and time slot resource allocation. At the same time, the PNC also serves as an AP, which is the central point of a wireless unit, and all wireless communications within this unit must pass through it for data exchange.

[0007] Due to the serious path loss in terahertz band wireless communication and the significant influence of molecular absorption in the atmosphere, the range of terahertz wireless communication usually does not exceed dozens of meters. Therefore, people increasingly tend to use directional antennas at both the transmitter and receiver ends to expand its communication range.

[0008] In directional communication, since the beams of each DEV randomly point in a certain direction, the two DEVs need to perform beamforming to align their beam directions before data transmission to ensure that they can accurately receive data.

[0009] The purpose of beamforming is to achieve the alignment of the main lobes of the beams between the transmitter and receiver on the premise of directional transmission. According to the existing technology, the directional beams of the transceiver can be divided into three levels: 1. Quasi-omnidirectional level; 2. Sector level; 3. Beam level. The directional gains of these three levels increase in turn, while the coverage ranges decrease in turn. To achieve the same propagation distance, different coding and modulation schemes are used for the three levels. Higher-order modulation schemes are used for the levels with larger directional gains. After the upper level is determined, the lower level is activated according to requirements. The upper level is the premise, and the lower level is the refinement.

[0010] In a terahertz network, the Beacon period is used for the directional access control of network nodes. Different from traditional omnidirectional antennas, the introduction of directional antennas (smart antennas) in a terahertz network can concentrate energy in a certain direction for transmission, enabling the antenna to have the strongest gain in that direction while having a smaller gain in other directions. However, precisely because of the beam directivity of the directional antenna's propagation, while improving the spatial multiplexing degree, the directional antenna also introduces the problem of receiving node positioning for accessing the shared channel: before two nodes communicate, the sending node must first determine the position of the receiving node in order to determine the direction of the transmit beam, so the node must track and locate the positions of neighboring nodes.

[0011] In a terahertz directional network, to ensure that the beacon frames sent by the PNC can be received by all nodes in the network within a superframe time, the PNC will continuously send the number of beacon frames equal to the number of sectors in each sector direction. However, these sent beacon frames can only be accurately received when the beam direction of the receiving node is aligned with the PNC. Therefore, only a few beacon frames can be received by the receiving node during the Beacon period, and the PNC needs to pay a huge cost for this.

[0012] The literature "A Fast and Efficient Directional MAC Protocol for Terahertz Wireless Personal Area Networks" (Qiu Zhongwei, Ren Zhi, Ge Lijia. Application of Electronic Technique, 2019, 45(2): 62 - 66.) proposed the FE-MAC protocol. This protocol proposed the "Fast Beamforming Mechanism" and the "Adaptive Beacon Frame" respectively. Without affecting the beamforming effect and without increasing additional costs, it reduced the time of beamforming and the control cost of the Beacon period, and improved the transmission efficiency of the network.

[0013] The literature "An Efficient Directional MAC Protocol for Terahertz Wireless Personal Area Networks" (Ren Zhi, Lv Yuhui, Tian Jieli, Zou Mingrui, Xu Zhaokun. Journal of Chinese Computer Systems, 2018, 39(08): 1725 - 1728.) proposed an efficient directional MAC protocol for terahertz wireless personal area networks, ED-MAC (Eficient Directional MAC protocol), to solve the problems of large beamforming training overhead between nodes and insufficient utilization of time slot resources in the directional beacon sub-period existing in the existing terahertz wireless network directional MAC protocols. The ED-MAC protocol can effectively reduce the beamforming training overhead between nodes and improve the success rate of data frame transmission by adopting a whole-network beamforming training mechanism and an opportunistic multiplexing directional Beacon sub-period mechanism.

[0014] To solve the problem of redundant control overhead and bandwidth resource occupation existing in the existing terahertz wireless network directional access method during the CTA beamforming stage, certain efforts and progress have been made in this regard in the prior art, and the transmission of beamforming scan frames has been reduced by pre-acquiring sector information. However, in terms of how to address the problem of inaccurate prior information caused by node movement, there is still a lack of sufficient in-depth and effective solutions in the prior art. Summary of the Invention

[0015] In view of this, the present invention proposes a terahertz wireless network directional access method with high efficiency and high time slot utilization rate. This method is based on adaptive cooperative control of node movement, which can not only streamline the CTA beamforming operation, but also ensure the accuracy of prior information and the reliability of beamforming as much as possible, thereby more securely improving the efficiency and time slot utilization rate of the terahertz wireless network directional access method.

[0016] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0017] A terahertz wireless network directional access method with high efficiency and high time slot utilization rate, which is applied to a terahertz wireless network. The terahertz wireless network includes two types of nodes, namely PNC and DEV. Nodes send and receive data using directional communication methods. The method includes the following steps:

[0018] Step 1: Divide the network operation time into multiple superframes. Each superframe consists of three ordered time periods: Beacon, CAP, and CTAP. The CAP time period includes an associated CAP sub-time period and a regular CAP sub-time period. The CTAP time period includes one or more CTAs with variable lengths.

[0019] Step 2: In the Beacon time period, the PNC broadcasts beacon frames in each sector in sequence using a directional transmission method; the DEV waits to receive beacon frames in each sector in sequence using a directional reception method. If a beacon frame is received, the information therein is extracted and corresponding processing is performed.

[0020] Step 3: In the associated CAP sub-time period of the CAP time period, unconnected DEVs send access request frames to the PNC in their own time slots, and then wait for access request reply frames. If an access request reply frame is received, the information therein is extracted and corresponding processing is performed; the PNC waits to receive access request frames sent by unconnected DEVs in each sector in sequence using a directional reception method. If an access request frame is received, the information therein is extracted to determine whether to grant access, and an access request reply frame is sent to the DEV.

[0021] Step 4, in the regular CAP sub-period of the CAP period, the DEV with data to be sent but without a time slot requests a time slot from the PNC in its own time slot and waits for a time slot request reply frame; the PNC uses the directional reception method to wait in sequence in each sector for the time slot request frame sent by the DEV that wants to obtain a time slot, and makes a judgment and reply after receiving the time slot request frame;

[0022] Step 5, in the CTAP period, if a node is involved in the current CTA and is the source node of the data frame in the current CTA, then execute step 601; if a node is involved in the current CTA and is the destination node of the data frame in the current CTA, then execute step 602; if a node is not involved in the current CTA, that is, it is not the source or destination node of the data frame in the current CTA, then execute step 603;

[0023] Step 601, judge whether the following conditions are satisfied: it knows the sector where the destination node of the data frame is located and the destination node of the data frame also knows the sector where it is located;

[0024] If the condition is satisfied, send 1 beamforming scan frame aiming at the sector where the destination node of the data frame is located, and then wait for the beamforming reply frame. After receiving the beamforming reply frame, send the data frame to the destination node;

[0025] If the condition is not satisfied, then judge: whether it is currently stationary and can also remain stationary in the next two superframes according to the motion cooperative control or the preset probability; if so, carry the information that it will remain stationary in the next two superframes in the beamforming scan frame, and then perform beamforming in the conventional manner; if not, directly perform beamforming in the conventional manner; after beamforming is completed, transmit the data frame;

[0026] Step 602, if it knows the sector where the source node of the data frame is located, aim at the sector where the source node of the data frame is located and wait to receive the beamforming scan frame. After receiving the beamforming scan frame, send 1 beamforming reply frame to the source node of the data frame, and then wait to receive the data frame and perform corresponding processing after receiving the data frame; if it does not know the sector where the source node of the data frame is located, wait in sequence in each sector to receive the beamforming scan frame sent by the source node; if it receives the beamforming scan frame and the frame contains the information that the source node will remain stationary in the next two superframes, then save this information, and save the sector number where the source node is located and the sector number where it is located on the source node; then, send a beamforming reply frame to the source node, and then wait to receive the data frame and perform corresponding processing after receiving the data frame;

[0027] Step 603: In the "extensive listening" mode, wait in each sector in sequence to receive the beamforming scan frames sent by other nodes; if a beamforming scan frame is received and the frame contains information indicating that the source node will remain stationary within the next two superframes, save this information, and save the sector number where the source node of the beamforming scan frame is located, as well as the sector number where it is located on the source node of the beamforming scan frame itself.

[0028] Further, in Step 2, the beacon frame contains the superframe structure, time period delimitation, and time slot allocation result; if there is a sector number where the data frame source node is located on the data frame destination node, carry this sector number in the beacon frame; if the idle frame type value can represent this sector number, use the idle frame type value to carry it; if it cannot be represented, add a "sector number where the source node is located" field after the "destination address" of each time slot allocation unit in the beacon frame to carry this sector number.

[0029] Further, in Step 4, if the DEV knows the sector number where it is located on the data frame destination node, carry this sector number in the time slot application frame; if the idle frame type value can represent this sector number, use the idle frame type value to carry it; if it cannot be represented, add a "sector number where the source node is located" field after the "destination address" of the time slot application frame to carry this sector number; if a time slot application reply frame is received, extract the information therein and perform corresponding processing;

[0030] If the PNC receives a time slot application frame, extract the information therein to determine whether to agree to allocate a time slot to this DEV, and reply to the DEV with a time slot application reply frame; if the received time slot application frame carries the sector number where the data frame source node is located on the destination node, extract and store this sector number.

[0031] The beneficial effects of the present invention are as follows:

[0032] 1. The present invention proposes a new mechanism of "adaptive streamlined beamforming", which runs in the CTAP period of the superframe. It can reduce beamforming operations and shorten the beamforming time while ensuring the beamforming effect.

[0033] 2. The present invention proposes a new mechanism of "node stationary information publishing based on motion collaborative control and probability", which runs in the CTAP period of the superframe. Based on the ideas of motion collaborative control and probability, it guarantees or estimates the stationary state of the node, and then publishes the information that the node will remain stationary within a future period of time in a zero or low additional overhead manner.

[0034] 3. The present invention proposes a new mechanism of "adaptive low-overhead transmission of sector numbers", which operates in the CAP period and Beacon period of a superframe. It transfers the sector number of the data frame source node on the data frame destination node from the data frame source node to the data frame destination node through the PNC in a zero or low additional overhead manner, so as to facilitate the rapid alignment of the antennas of the data frame source and destination nodes and streamline the beamforming operation. Description of the Drawings

[0035] Figure 1 It is a flowchart of the operation of the data frame source node in the new mechanism of "adaptive streamlined beamforming".

[0036] Figure 2 It is a flowchart of the operation of the data frame source node in the new mechanism of "publishing node stationary information based on motion cooperative control and probability".

[0037] Figure 3 It is a flowchart of the operation of other nodes in the new mechanism of "publishing node stationary information based on motion cooperative control and probability".

[0038] Figure 4 It is a flowchart of the operation of the data frame source node in the CAP period in the new mechanism of "adaptive low-overhead transmission of sector numbers".

[0039] Figure 5 It is a flowchart of the operation of the PNC in the CAP period in the new mechanism of "adaptive low-overhead transmission of sector numbers".

[0040] Figure 6 It is a flowchart of the operation of the PNC in the Beacon period in the new mechanism of "adaptive low-overhead transmission of sector numbers". Detailed Implementation Manner

[0041] An efficient and high time slot utilization terahertz wireless network directional access method, the technical problem to be solved by this method is the problem of redundant control overhead and bandwidth resource occupation existing in the existing terahertz wireless network directional access method in the CTA beamforming stage, specifically as follows:

[0042] According to the existing terahertz wireless network directional access method, when the source and destination nodes of a data frame transmit the data frame in the CTA of the CTAP period, the time of the CTA will be divided into two stages: the CTA beamforming stage and the CTA data frame transmission stage. The beamforming stage is used for beamforming to align the directional antennas of the data frame source and destination nodes with each other; the data frame transmission stage is used for the data frame source node to transmit the data frame to the destination node.

[0043] In the CTA beamforming phase, the data frame source node needs to perform CTA beamforming scanning, that is, send N beamforming scanning frames (N is the number of sectors) in each sector in sequence, and send a total of N×N beamforming scanning frames; send a beamforming scanning frame in each basic time slot; each beamforming scanning frame has a "sector number" and "sequence number" field, which respectively indicate the sector in which the beamforming scanning frame is sent. In this process, the data frame destination node changes the sector pointed by the directional antenna in sequence, and stays in each sector for 1 basic time slot (denoted as T slot ), waiting to receive the beamforming scanning frame; if the data frame destination node receives the beamforming scanning frame, it records the sector number of the data frame source node (the sector number indicates the sector number of the data frame source node in the data frame destination node, recorded as F s-d , F s-d ∈[1,N],F s-d = the sector number that the directional antenna points to when the beamforming scanning frame is received); and, extract the value from the "sector number" field in the beamforming scanning frame (the value indicates the sector number of the data frame destination node in the data frame source node, denoted as F d-s ) and save it, extract the value from the "sequence number" field in the beamforming scanning frame (this value indicates the number of frames sent by the received beamforming scanning frame in its sector, denoted as S) and save it. After receiving the beamforming scanning frame, the data frame destination node waits for T w time, and then sends a beamforming reply frame to the data frame source node, aiming at the sector where the data frame source node is located. w Calculated according to the following formula:

[0044] T w =[(NF d-s )×N+(NS)]×T slot +(F d-s -1)×T slot (1)

[0045] After the data frame source node sends the beamforming scanning frame, it waits for a basic time slot in each sector in order to receive the beamforming reply frame sent by the data frame destination node. If the data frame source node receives the beamforming reply frame, it records the sector number FN of the data frame destination node. d-s At this point, the CTA beamforming phase ends. In the following CTA data frame transmission phase, the data frame source node transmits the data frame to the data frame destination node in the sector where the data frame destination node is located.

[0046] As can be seen from the above, during the CTA beamforming stage, the data frame source node in the terahertz wireless network needs to send N×N beamforming scanning frames, which significantly increases control overhead, occupies network bandwidth resources, and consumes running time. If the operation and process can be streamlined while ensuring the beamforming effect, the efficiency of the terahertz wireless network directional access method and the time slot utilization rate can be improved. The existing technology has made certain efforts and progress in this regard, reducing the transmission of beamforming scanning frames by pre-acquiring sector information. However, there is still a lack of sufficient in-depth and effective solutions to address the problem of inaccurate prior information caused by node movement.

[0047] This method adopts the following presets:

[0048] (1) The communication between nodes in the terahertz wireless network is wireless directional communication.

[0049] (2) Both the sending and receiving of frames are directional.

[0050] (3) In the terahertz wireless network, PNC can communicate directly with any DEV.

[0051] (4) It is not guaranteed that DEVs in the terahertz wireless network can communicate directly with each other.

[0052] (5) The total number of nodes in the terahertz wireless network is M.

[0053] (6) When the directional antenna is sending and receiving, it divides the 360-degree horizontal range into N sectors, and the angle of each sector is equal, which is 360 / N degrees.

[0054] On this basis, the specific steps of this method are as follows:

[0055] The network running time is divided into multiple superframes, and each superframe consists of three ordered time periods: Beacon, CAP, and CTAP. The CAP time period includes an associated CAP sub-time period and a regular CAP sub-time period. The CTAP time period includes one or more CTAs with variable lengths;

[0056] During the Beacon time period, the PNC broadcasts beacon frames in each sector in sequence using the directional transmission method; the beacon frame includes information such as the superframe structure, time period delimitation, and time slot allocation results; if there is the sector number where the data frame source node is located on the data frame destination node, the beacon frame carries this sector number; if the idle frame type value can represent this sector number, the idle frame type value is used to carry it. If it cannot be represented, a "source node sector number" field is added after the "destination address" in each time slot allocation unit of the beacon frame to carry this sector number;

[0057] During the Beacon period, the DEV uses the directional reception method to wait for receiving beacon frames in each sector in sequence; if received, it extracts the information therein and performs corresponding processing;

[0058] During the association CAP sub-period of the CAP period, the unassociated DEV sends an association request frame to the PNC in its own time slot, and then waits for an association request response frame; if the association request response frame is received, it extracts the information therein and performs corresponding processing;

[0059] During the association CAP sub-period of the CAP period, the PNC uses the directional reception method to wait for receiving association request frames sent by unassociated DEVs in each sector in sequence; if received, it extracts the information therein to judge whether to approve the association, and sends an association request response frame to the DEV;

[0060] During the regular CAP sub-period of the CAP period, the DEV with data to send but without getting a time slot sends a time slot request frame to the PNC in its own time slot, and waits for a time slot request response frame; if the DEV knows the sector number where it is located in the destination node of the data frame, it carries this sector number in the time slot request frame; if the idle frame type value can represent this sector number, it uses the idle frame type value to carry it, if not, it adds a "sector number where the source node is located" field after the "destination address" of the time slot request frame to carry this sector number; if the time slot request response frame is received, it extracts the information therein and performs corresponding processing;

[0061] During the regular CAP sub-period of the CAP period, the PNC uses the directional reception method to wait for receiving time slot request frames sent by DEVs wanting to get a time slot in each sector in sequence; if received, it extracts the information therein to judge whether to approve allocating a time slot to this DEV, and replies a time slot request response frame to the DEV; if the received time slot request frame carries the sector number where the source node of the data frame is located in the destination node, it extracts and stores this sector number;

[0062] During the CTAP period, if a node is involved in the current CTA and is the source node of the data frame in the current CTA, it judges whether the following conditions are met: does it know the sector where the destination node of the data frame is located and does the destination node of the data frame also know its location? If the conditions are met, it sends a beamforming scan frame aiming at the sector where the destination node of the data frame is located, and then waits for a beamforming response frame, and sends the data frame to the destination node after receiving the beamforming response frame; if the conditions are not met, it judges: whether it is currently stationary and can also remain stationary in the next two superframe times according to motion cooperative control or preset probability? If so, it carries the information that it will remain stationary in the next two superframe times in the beamforming scan frame, and then performs beamforming in the conventional way; if not, it directly performs beamforming in the conventional way; after beamforming is completed, it transmits the data frame;

[0063] During the CTAP period, if a node is involved in the current CTA and is the destination node of the data frame in the current CTA, and if it knows the sector where the data frame source node is located, it aligns with the sector where the data frame source node is located and waits to receive the beamforming scan frame. After receiving the beamforming scan frame, it sends 1 beamforming reply frame to the data frame source node; then it waits to receive the data frame and performs corresponding processing after receiving the data frame; if it does not know the sector where the data frame source node is located, it waits in each sector in sequence to receive the beamforming scan frame sent by the source node; if it receives the beamforming scan frame and the frame contains information that the source node will remain stationary within the next two superframes, it saves this information, and saves the sector number where the source node is located, as well as the sector number where it is located on the source node; then, it sends a beamforming reply frame to the source node, and next waits to receive the data frame and performs corresponding processing after receiving the data frame;

[0064] During the CTAP period, if a node is not involved in the current CTA, that is, it is neither the source nor the destination node of the data frame in the current CTA, it adopts the "passive listening" method and waits in each sector in sequence to receive the beamforming scan frame sent by other nodes; if it receives the beamforming scan frame and the frame contains information that the source node will remain stationary within the next two superframes, it saves this information, and saves the sector number where the beamforming scan frame source node is located, as well as the sector number where it is located on the beamforming scan frame source node.

[0065] This method proposes three new mechanisms:

[0066] 1. The new mechanism of "adaptive reduced beamforming":

[0067] During the CTA beamforming stage, the data frame source node determines whether it can perform the "reduced beamforming" operation according to certain conditions (whether it and the data frame destination node know each other's sectors); if the conditions are met, it takes the operation, otherwise it takes the conventional beamforming operation (when the node is in motion) or the "extended beamforming operation" (when the node is stationary).

[0068] The "reduced beamforming" operation mainly includes: after the start of the CTA beamforming stage, the data frame destination node aligns with the sector where the data frame source node is located and waits to receive the frame; the data frame source node aligns with the sector where the data frame destination node is located and sends 1 beamforming scan frame; after the data frame destination node receives the beamforming scan frame, it sends 1 beamforming reply frame to the data frame source node. Conventional beamforming requires the data frame source node to send N×N beamforming scan frames, while reduced beamforming only requires the data frame source node to send 1 beamforming scan frame.

[0069] "Extended beamforming operation" is a beamforming operation that adds a new mechanism of "publishing node stationary information based on motion collaborative control and probability" to the conventional beamforming operation. The main idea is to publish the information of whether the node remains stationary during the beamforming process by using the frame type value or adding a field. Both extended beamforming and conventional beamforming require the data frame source node to send N×N beamforming scan frames.

[0070] The new mechanism of "adaptive reduced beamforming" runs on the data frame source and destination nodes, as Figure 1 shown, and the main operation steps are as follows:

[0071] (1) Data frame source node

[0072] N1-S-1: Judgment: Has it entered its own CTA? If yes, execute the next step; if no, continue to execute this step.

[0073] N1-S-2: Judgment: Does the data frame destination node know the sector it is in? If yes, perform "reduced beamforming" operation and then end; if no, execute the next step.

[0074] N1-S-3: Judgment: Is the current node in a moving state? If yes, perform conventional beamforming operation and then end; if no, perform "extended beamforming" operation and then end.

[0075] (2) Data frame destination node

[0076] N1-D-1: Judgment: Has it entered its own CTA? If yes, execute the next step; if no, continue to execute this step.

[0077] N1-D-2: Judgment: Does it know the sector where the data frame source node is located? If yes, perform "reduced beamforming" operation and then end; if no, perform conventional beamforming operation and then end.

[0078] 2. The new mechanism of "publishing node stationary information based on motion collaborative control and probability":

[0079] Before the data frame source node starts beamforming scanning during the CTA beamforming phase, if it is stationary, it determines whether it can collaboratively control its own movement (to collaboratively control node movement, the node needs to have a digital motion control device with an external communication interface); if it can, it makes itself remain stationary for a calculated short period of time and publishes the information that it is stationary in a zero or low-overhead manner; if it cannot collaboratively control node movement, it informs other nodes with a certain probability and in a zero or low-overhead manner that it will remain stationary for a short period of time. If the data frame source node is moving before starting beamforming scanning, it performs conventional operations according to the definition of existing relevant directional access methods. The MAC sublayer of other nodes rotates the receiving beamforming scanning frame in a "sniffing" manner (the destination of the received frame is not itself and it is not directly discarded); if it receives a beamforming scanning frame and the frame contains the information that the source node will remain stationary in the next two superframes, it saves the information.

[0080] The operation of the new mechanism of "node stationary information publishing based on motion collaborative control and probability" is completed by the data frame source node and other nodes during the beamforming phase of each CTA in the CTAP period; this new mechanism will only run when the data frame source node takes the "extended beamforming" operation. As Figure 2 shown, the main operation steps are as follows:

[0081] (1) Data frame source node

[0082] N2-S-1: Initialization, set a "node stationary probability threshold" Th s , which is used to estimate from the perspective of probability whether the current node can remain stationary in the next two superframes (the recommended value is Th s = α k ; where α is the motion state change probability factor, and the recommended α = 0.5; k is the number of superframes required to remain stationary; because the first superframe application time slot is followed by the second superframe for data transmission, so k = 2; there is a recommended value Th s = 0.5×0.5 = 0.25); taking a value less than this as meeting the condition.

[0083] N2-S-2: Judgment: Can it collaboratively control its own movement? If it can, go to the next step; if not, go to N2-S-4.

[0084] N2-S-3: Calculate the time T ks that the node needs to remain stationary next, and calculate it with the following formula:

[0085] T ks = T sf -(T B+T CAP +N a ×T slot ) + 2×T sf (2)

[0086] Among them, T sf represents the time length of a superframe, T B and T CAP respectively represent the lengths of the Beacon and CAP periods of a superframe, N a represents the number of basic time slots included in all CTAs before the CTA of the data frame source node in the current superframe, and T slot represents the time length of a basic time slot; then, the value of T ks is transmitted to the motion control device of this node, notifying it to keep the node stationary within the next T ks time, so as to facilitate the smooth implementation of the "compact beamforming" operation. Then, go to N2-S-6.

[0087] N2-S-4: Generate a random number r, r ∈ (0, 1); then judge: r < Th s ? If it holds (indicating that the condition of keeping stationary is met in terms of probability), go to N2-S-6; if it does not hold (indicating that the condition of keeping stationary is not met in terms of probability), execute the next step.

[0088] N2-S-5: Create a traditional beamforming scan frame and fill in the content as the beamforming scan frame to be sent; then go to N2-S-7.

[0089] N2-S-6: Judge: Is there an unused frame type value that can be accommodated in the "type" field of the frame? If there is, create a new type of beamforming scan frame. Except for filling in a new value in the "type" field, all other fields and field values are the same as those of the traditional beamforming scan frame, and then use it as the beamforming scan frame to be sent; if not, expand the traditional beamforming scan frame by adding a "source node stationary" field (recommended length is 1 byte, field value = 1 indicates that the source node remains stationary in the next two superframes, and field value = other values indicates that stationary is not guaranteed) behind the "destination address" field, thereby forming an "extended beamforming scan frame", and then use it as the beamforming scan frame to be sent.

[0090] N2-S-7: Sequentially send the previously created beamforming scan frames in N sectors, N for each sector. Then end the operation.

[0091] (2) Other nodes. As Figure 3 shown, the steps are as follows:

[0092] N2-O-1: The MAC sublayer adopts the "eavesdropping" method (frames received with a destination other than itself are not directly discarded), and the rotating antenna waits for received frames in each sector in sequence.

[0093] N2-O-2: Judgment: Is a frame received? If yes, proceed to the next step; if no, loop through this step.

[0094] N2-O-3: Judgment: Is the received frame a beamforming scan frame? If yes, proceed to the next step; if no, end the operation.

[0095] N2-O-4: Judgment: Is the received beamforming scan frame of a new type? If yes, go to N2-O-7; if no, proceed to the next step.

[0096] N2-O-5: Extract the value of the "source node stationary" field.

[0097] N2-O-6: Judgment: Is the value of the "source node stationary" field = 1? If true, proceed to the next step; if no, end the operation.

[0098] N2-O-7: Extract the value of the "source address" of the frame, store the information that it will remain stationary in the next two superframes (recommended to be represented by the "stationary" variable K s ; if it remains stationary, let K s = 1), and obtain and store the sector number where it is located on this node (obtained from the "sector number" field value of the beamforming scan frame; as the sector number where the source node of the data frame is located on the destination node, i.e., F s-d ). Then, end the operation.

[0099] 3. The new mechanism of "adaptive low-overhead transmission of sector numbers":

[0100] During the CAP period of the superframe, the time slot application node (which is the source node of the data frame) zero or low-additional-overhead transmits the sector number where it is located on the destination node of the data frame to the PNC by means of the idle frame type value or adding 1 field. During the Beacon period of the superframe, the PNC zero or low-additional-overhead transmits the sector number where the source node of the data frame is located on the destination node of the data frame to the destination node of the data frame by means of the idle frame type value or adding a field.

[0101] The new mechanism of "adaptive low-overhead transmission of sector numbers" runs on the PNC and the source and destination nodes of the data frame. The main operation steps are as follows:

[0102] (1) The process of the source node of the data frame (i.e., the node applying for the time slot) during the CAP period is as Figure 4 shown, including:

[0103] N3-CS-1: Judgment: Do you know the sector number where you are located at the destination node of the data frame? If yes, proceed to the next step; if no, go to N3-CS-5.

[0104] N3-CS-2: Judgment: Does the "Type" field of the frame have an idle value (i.e., an unused value)? If yes, proceed to the next step; if no, go to N3-CS-6.

[0105] N3-CS-3: Judgment: Are the idle values in the "Type" field of the frame continuous and the number not less than the number of sectors? If yes, proceed to the next step; if no, go to N3-CS-7.

[0106] N3-CS-4: Create a new type of time slot application frame. Compared with the traditional time slot application frame, it only differs in the value of the "Type" field of the frame: the value of the "Type" field of the new time slot application frame = the minimum value of the continuous idle values in the "Type" field of the frame + (the sector number where the source node of the data frame is located at the destination node of the data frame - 1), that is, use the frame type value to carry the sector number where the source node of the data frame is located; and use this new type of time slot application frame as the time slot application frame to be sent to the PNC; then, go to N3-CS-8.

[0107] N3-CS-5: Create 1 traditional time slot application frame and use it as the time slot application frame to be sent to the PNC; then, go to N3-CS-8.

[0108] N3-CS-6: Change the time slot application frame to an extended time slot application frame: Add 1 "sector number where the source node is located" field after the "destination address" of the time slot application frame, and use this field to load the sector number where the source node of the data frame is located at the destination node of the data frame (if there is no sector number to load, an invalid value can be set, such as -1); create 1 extended time slot application frame and use it as the time slot application frame to be sent to the PNC; then, go to N3-CS-8.

[0109] N3-CS-7: Create a new type of extended time slot application frame. Compared with the traditional time slot application frame, the "Type" field of the frame uses idle values, and 1 "sector number where the source node is located" field is added after the "destination address", and use this field to load the sector number where the source node of the data frame is located at the destination node of the data frame (if there is no sector number to load, an invalid value can be set, such as -1); use this new extended time slot application frame as the time slot application frame to be sent to the PNC; then, go to N3-CS-8.

[0110] N3-CS-8: In its own transmission time slot in the regular CAP, send the time slot application frame to the PNC.

[0111] (2) The process of the PNC during the CAP period is as Figure 5 shown, including:

[0112] N3-CP-1: Judgment: Is a time slot application frame received? If yes, proceed to the next step; if no, loop and execute this step.

[0113] N3-CP-2: Judge the type of the received time slot application frame: If it is a new time slot application frame, proceed to the next step; if it is a new extended time slot application frame or an extended time slot application frame, go to N3-CP-4; if it is a traditional time slot application frame, go to N3-CP-5. N3-CP-3: Extract the frame type value, calculate and store the sector number where the data frame source node is located according to the following formula:

[0114] Sector number where the data frame source node is located = Frame type value - Minimum value of consecutive idle values in the frame type field + 1

[0115] Then, go to N3-CP-5.

[0116] N3-CP-4: Extract and store the value from the "sector number where the source node is located" field; then go to N3-CP-5.

[0117] N3-CP-5: Process the time slot application frame in the traditional way; then end the operation.

[0118] (3) The process of the PNC during the Beacon period is as Figure 6 shown, including:

[0119] N3-BP-1: Before broadcasting the beacon frame, judge: Is it necessary to transmit the sector number where the data frame source node is located? If yes, proceed to the next step; if no, go to N3-BP-5.

[0120] N3-BP-2: Judge: Is there an idle value (i.e., an unused value) in the "type" field of the frame? If yes, proceed to the next step; if no, go to N3-BP-6.

[0121] N3-BP-3: Judge: Are the idle values in the "type" field of the frame consecutive and the number is not less than the number of sectors, and only one sector number where the data frame source node is located needs to be transmitted? If yes, proceed to the next step; if no, go to N3-BP-7.

[0122] N3-BP-4: Create a new type of beacon frame. Compared with the traditional beacon frame, it only differs in the value of the "Type" field of the frame: the value of the "Type" field of the new beacon frame = the minimum value of the consecutive idle values of the "Type" field of the frame + (the sector number where the source node of the data frame is located on the destination node of the data frame - 1), that is, use the frame type value to carry the sector number where the source node of the data frame is located; and place the time slot allocation unit that needs to transmit the sector number where the source node of the data frame is located at the top. Next, use this new beacon frame as the beacon frame to be broadcast. Then, go to N3-BP-8.

[0123] N3-BP-5: Create 1 traditional beacon frame and use it as the beacon frame to be broadcast; then, go to N3-BP-8.

[0124] N3-BP-6: Change the beacon frame to an extended beacon frame: Add 1 "Sector number where the source node is located" field after the "Destination address" of each time slot allocation unit of the beacon frame, and use this field to load the sector number where the source node of the data frame is located on the destination node of the data frame (if there is no sector number to load, an invalid value can be set, such as -1); create 1 extended beacon frame and use it as the beacon frame to be broadcast; then, go to N3-BP-8.

[0125] N3-BP-7: Create a new type of extended beacon frame. Compared with the traditional beacon frame, the "Type" field of the frame uses idle values, and 1 "Sector number where the source node is located" field is added after the "Destination address" of each time slot allocation unit, and use this field to load the sector number where the source node of the data frame is located on the destination node of the data frame (if there is no sector number to load, an invalid value can be set, such as -1); use this new extended beacon frame as the beacon frame to be sent to the PNC.

[0126] N3-BP-8: Broadcast the beacon frame in the traditional way; then end the operation.

[0127] (4) Source node of the data frame in the Beacon period

[0128] N3-SP-1: Judge: Is a beacon frame received? If yes, execute the next step; if no, loop and execute this step.

[0129] N3-SP-2: Judge the type of the received beacon: If it is a new beacon frame, execute the next step; if it is a new extended beacon or extended beacon frame, go to N3-SP-4; if it is a traditional time slot application frame, go to N3-SP-5.

[0130] N3-SP-3: Is the time slot allocation unit corresponding to itself at the first position? If yes, store the information of "the destination node of the data frame knows the sector where the source node is located" (recommended method: set a variable, and let the variable value = 1), and then go to N3-SP-5; if no, directly go to N3-SP-5.

[0131] N3-SP-4: Extract the value of the "sector number where the source node is located" field from the time slot allocation unit corresponding to itself, and judge: Is it valid? If yes, store the information of "the destination node of the data frame knows the sector where the source node is located" (recommended method: set a variable, and let the variable value = 1), and then go to N3-SP-5; if no, directly go to N3-SP-5.

[0132] N3-SP-5: Process the beacon in the traditional way; then end the operation.

[0133] (5) Destination node of the data frame in the beacon period

[0134] N3-DP-1: Judge: Is a beacon frame received? If yes, execute the next step; if no, loop and execute this step.

[0135] N3-DP-2: Judge the type of the received beacon: If it is a new type of beacon frame, execute the next step; if it is a new type of extended beacon or extended beacon frame, go to N3-SP-4; if it is a traditional time slot application frame, go to N3-DP-5.

[0136] N3-DP-3: Is the time slot allocation unit corresponding to itself at the first position? If yes, calculate and store the sector number where the source node of the data frame is located according to the following formula:

[0137] Sector number where the source node of the data frame is located = frame type value - minimum value of consecutive idle values of the frame type field + 1

[0138] Then, go to N3-DP-5.

[0139] N3-DP-4: Extract the value of the "sector number where the source node is located" field from the time slot allocation unit corresponding to itself, and judge: Is it valid? If yes, store the value, and then execute the next step; if no, directly execute the next step.

[0140] N3-DP-5: Process the beacon in the traditional way; then end the operation.

[0141] The following describes specific embodiments by presenting the main operations of nodes during three periods: Beacon, CAP, and CTAP. Since the new extended time slot application frame, the new extended beacon frame, and the new beamforming scan frame occupy fewer frame type idle values (each occupying 1), they are relatively easier to meet the usage conditions. Therefore, it is preset to use them when needed. And it is preset that the number of DEVs in the network is 8, the number of sectors N = 8, the sector angles are equal, and the basic time slot length is 1 ms.

[0142] 1.1.1 Beacon Period

[0143] 1.1.1.1 PNC Main Operations

[0144] B-P-1: Before creating a beacon frame, check whether it is necessary to send the sector number where the source node of the data frame is located; if so, create 1 new extended beacon frame, load the sector number where the source node of the data frame to be sent is located into the "sector number where the source node is located" field of the corresponding time slot allocation unit, and fill in other fields; if not, create 1 traditional beacon frame and fill in the fields.

[0145] B-P-2: Broadcast the beacon frame 8 times in each sector in sequence, each time taking 1 ms.

[0146] 1.1.1.2 DEV Main Operations

[0147] B-P-1: Set a parameter BF s-d to store the value of the "sector number where the source node is located" field in the new extended beacon frame; set BF s-d = -1 at the start of the Beacon period.

[0148] B-P-2: If a beacon frame is received, whether it is a traditional beacon frame or a new extended beacon frame, extract the information in the frame and use or store it.

[0149] B-P-3: If the received frame is a new extended beacon frame, then make: BF s-d = the value of the "sector number where the source node is located" field in the time slot allocation unit corresponding to the current DEV.

[0150] 1.1.2 CAP Period

[0151] 1.1.2.1 PNC Main Operations

[0152] CA-P-1: During the associated CAP phase, stay in each sector for 2 ms (2 basic time slots) in sequence, waiting to receive the association request frame sent by the DEV.

[0153] CA-P-2: If an association request frame is received, immediately extract the information in the frame for processing, and based on the processing result, generate an association request response frame and send it to the DEV.

[0154] CA-P-3: In the regular CAP phase, stay in each sector for 2 ms (2 basic time slots) in sequence, waiting to receive a time slot application frame sent by the DEV.

[0155] CA-P-4: If a time slot application frame is received, immediately extract the information in the frame for processing, and based on the processing result, generate a time slot application response frame and send it to the DEV.

[0156] CA-P-5: If a new type of extended time slot application frame is received, extract the value of the "sector number where the source node is located" field in it for storage.

[0157] 1.1.2.2 DEV Main Operations

[0158] CA-D-1: In the association CAP phase, if not networked, send an association request frame to the PNC in its own time slot.

[0159] CA-D-2: Wait for 2 ms to receive an association request response frame; if an association request response frame is received, record that it has been networked and execute the subsequent operations in the current superframe; if not received, do not perform subsequent operations.

[0160] CA-D-3: If applying for a time slot and not sure whether the destination node of the data frame knows the sector number where it is located (i.e., ), then generate a traditional time slot application frame, fill in the content, and then send it to the PNC. Then wait for 2 ms to receive a time slot request response frame. If a time slot request response frame is received, extract the content in it for backup storage.

[0161] CA-D-4: If applying for a time slot and sure that the destination node of the data frame knows the sector number where it is located (i.e., F s-d ∈[1,N]), then generate a new type of extended time slot application frame, fill in the content, fill in the value of F s-d into the "sector number where the source node is located" field in the frame, and then send the frame to the PNC. Then wait for 2 ms to receive a time slot request response frame. If a time slot request response frame is received, extract the content in it for backup storage.

[0162] 1.1.3 CTAP Period

[0163] 1.1.3.1 Data Frame Source Node Main Operations

[0164] CT-S-1: During the beamforming phase of a CTA that does not belong to itself, the rotating antenna sequentially receives beamforming scan frames in each sector. If a frame is received, the "general listening" method is used to extract the values of the "source address" field and the "sector number" field, and they are stored in the "sector number where the source node is located" list (this list has two columns: destination node address, sector number where the source node is located).

[0165] CT-S-2: During the beamforming phase of a CTA that belongs to itself, it is judged whether the destination node of the data frame knows the sector number where it is located (i.e., whether BF s-d ∈[1,8] holds)? If so, let the transmission sector number = F d-s (the value of F d-s has been obtained and stored previously), generate a traditional beamforming scan frame and fill in the content, and then send it to the destination node of the data frame. If not, determine the type of beamforming scan frame to be used by running the new mechanism of "node stationary information publishing based on motion cooperative control and probability"; next, generate a beamforming scan frame and fill in the content; then, in accordance with the traditional beamforming scan method, sequentially send the beamforming scan frame 8 times in each sector.

[0166] CT-S-3: Stay in each sector for 1 ms (1 basic time slot) in sequence, waiting to receive the beamforming reply frame sent by the destination node of the data frame. If the beamforming reply frame is received, record the sector number where the frame is received; then, use this sector number to send the data frame to the destination node of the data frame.

[0167] 1.1.3.2 Main operations of the source and destination nodes of the data frame

[0168] CT-D-1: During the beamforming phase of a CTA that does not belong to itself, the rotating antenna sequentially receives beamforming scan frames in each sector (each time lasting 8×8 = 64 ms). If a frame is received, the "general listening" method is used to extract the values of the "source address" field and the "sector number" field, and they are stored in the "sector number where the source node is located" list.

[0169] CT-D-2: During the beamforming phase of a CTA that belongs to itself, it is judged whether it knows the sector number where the source node of the data frame is located (i.e., whether BF s-d ∈[1,8] holds)? If so, wait to receive the beamforming scan frame sent by the source node of the data frame in the sector indicated by BF s-d (lasting 1 ms); if not, the rotating antenna sequentially receives beamforming scan frames in each sector (lasting 8×8 = 64 ms), waiting to receive the beamforming scan frame sent by the source node of the data frame.

[0170] CT-D-3: If a beamforming scan frame sent by the data frame source node is received, a beamforming reply frame is sent back to it in the same sector; then, wait in that sector for the data frame sent by the data frame source node to be received.

[0171] CT-D-4: If a data frame is received, an ACK frame is sent back to the data frame source node, and the data part is extracted from the data frame and transferred to the upper layer of the current node.

[0172] 1.1.3.3 Other Node Main Operations

[0173] CT-O-1: In the beamforming phase of each CTA, the rotating antenna sequentially receives beamforming scan frames in each sector (each time lasting 8×8 = 64 ms).

[0174] If received, the "general listening" method is adopted to extract the values of the "source address" field and the "sector number" field, and store them in the "sector number where the source node is located" list.

[0175] In summary, the present invention proposes three new mechanisms: "adaptive reduced beamforming", "node stationary information publishing based on motion cooperative control and probability", and "adaptive low-overhead transfer of sector numbers". Generally speaking, in the beamforming phase of the CTA sub-period of the superframe, the number of beamforming scan frames sent by the node is reduced, thereby reducing the control overhead of the access method and improving the efficiency. For the CTA of the superframe, the time ratio of the beamforming phase is reduced, while the time ratio of the data frame transmission phase for transmitting data frames increases accordingly. Therefore, the network time slot utilization rate is improved. In addition, since the time used in the beamforming phase of some CTAs is significantly reduced (from the original N×N + 0.5N basic time slots to 2 basic time slots), the data frame can be transmitted relatively faster, which is conducive to reducing the average end-to-end delay of data packets.

[0176] The present invention can be used for the access of terahertz wireless networks, and can also be used for the access of 60 GHz ultra-high-speed wireless networks and other wireless networks that adopt the superframe form and beamforming mechanism.

Claims

1. A method for directional access in a terahertz wireless network with high efficiency and high time slot utilization rate, characterized in that, applied to a terahertz wireless network, the terahertz wireless network includes two types of nodes, PNC and DEV, and both nodes use directional communication methods for sending and receiving data; the method includes the following steps: Step 1, divide the network operation time into multiple superframes, each superframe consists of three ordered time periods: Beacon, CAP, and CTAP. The CAP time period includes an associated CAP sub-time period and a regular CAP sub-time period, and the CTAP time period includes one or more CTAs with variable lengths; Step 2, in the Beacon time period, the PNC broadcasts beacon frames in each sector in sequence by using the directional transmission method; the DEV waits to receive beacon frames in each sector in sequence by using the directional reception method. If a beacon frame is received, extract the information therein and perform corresponding processing; Step 3, in the associated CAP sub-time period of the CAP time period, the unconnected DEV sends an access request frame to the PNC in its own time slot, and then waits for an access request reply frame. If an access request reply frame is received, extract the information therein and perform corresponding processing; the PNC waits to receive access request frames sent by unconnected DEVs in each sector in sequence by using the directional reception method. If an access request frame is received, extract the information therein to determine whether to allow access, and send an access request reply frame to the DEV; Step 4, in the regular CAP sub-time period of the CAP time period, the DEV with data to send but without obtaining a time slot sends a time slot request frame to the PNC in its own time slot, and waits for a time slot request reply frame; the PNC waits to receive time slot request frames sent by DEVs that want to obtain time slots in each sector in sequence by using the directional reception method, and makes a judgment and reply after receiving a time slot request frame; Step 5, in the CTAP time period, if a node is involved in the current CTA and is the source node of the data frame in the current CTA, execute step 601; if a node is involved in the current CTA and is the destination node of the data frame in the current CTA, execute step 602; if a node is not involved in the current CTA, that is, it is not the source or destination node of the data frame in the current CTA, execute step 603; Step 601, judge whether the following conditions are satisfied: it knows the sector where the destination node of the data frame is located and the destination node of the data frame also knows the sector where it is located; If the condition is satisfied, send one beamforming scan frame towards the sector where the destination node of the data frame is located, and then wait for a beamforming reply frame. After receiving the beamforming reply frame, send the data frame to the destination node; If the condition is not satisfied, judge: whether it is currently stationary and can also remain stationary in the next two superframes according to motion cooperative control or preset probability; if so, carry the information that it will remain stationary in the next two superframes in the beamforming scan frame, and then perform beamforming in the conventional manner; if not, directly perform beamforming in the conventional manner; after beamforming is completed, transmit the data frame; Step 602: If the sector where the data frame source node is located is known, align with the sector where the data frame source node is located and wait to receive the beamforming scan frame. After receiving the beamforming scan frame, send 1 beamforming reply frame to the data frame source node, then wait to receive the data frame, and perform corresponding processing after receiving the data frame; if the sector where the data frame source node is located is unknown, sequentially wait to receive the beamforming scan frame sent by the source node in each sector; if the beamforming scan frame is received and the frame contains the information that the source node remains stationary within the next two superframes, save this information, and save the sector number where the source node is located, as well as the sector number where it is located on the source node; then, send a beamforming reply frame to the source node, next wait to receive the data frame, and perform corresponding processing after receiving the data frame. Step 603: Adopt the "general listening" method, and sequentially wait to receive the beamforming scan frames sent by other nodes in each sector; if the beamforming scan frame is received and the frame contains the information that the source node remains stationary within the next two superframes, save this information, and save the sector number where the beamforming scan frame source node is located, as well as the sector number where it is located on the beamforming scan frame source node.

2. An efficient high time-slot utilization terahertz wireless network directional access method according to claim 1, characterized in that in step 2, the beacon frame includes a superframe structure, time period delimitation, and time-slot allocation result; if there is a sector number where the data frame source node is located on the data frame destination node, carry this sector number with the beacon frame; if the idle frame type value can represent this sector number, use the idle frame type value to carry it, if it cannot be represented, add 1 "sector number where the source node is located" field after the "destination address" of each time-slot allocation unit in the beacon frame to carry this sector number.

3. An efficient high time-slot utilization terahertz wireless network directional access method according to claim 1, characterized in that in step 4, if the DEV knows the sector number where it is located on the data frame destination node, carry this sector number with the time-slot application frame; if the idle frame type value can represent this sector number, use the idle frame type value to carry it, if it cannot be represented, add 1 "sector number where the source node is located" field after the "destination address" of the time-slot application frame to carry this sector number; if the time-slot application reply frame is received, extract the information therein and perform corresponding processing; If the PNC receives the time-slot application frame, extract the information therein to determine whether to agree to allocate a time slot to this DEV, and reply a time-slot application reply frame to the DEV; If the received time-slot application frame carries the sector number where the data frame source node is located on the destination node, extract and store this sector number.

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