CN113630175B

CN113630175B - Access method of relay network

Info

Publication number: CN113630175B
Application number: CN202111058964.8A
Authority: CN
Inventors: 王伶; 程盼; 粟嘉; 杨欣; 宫延云; 韩闯; 张兆林; 陶明亮; 范一飞
Original assignee: Northwestern Polytechnical University
Current assignee: Northwestern Polytechnical University
Priority date: 2021-09-08
Filing date: 2021-09-08
Publication date: 2022-07-05
Anticipated expiration: 2041-09-08
Also published as: CN113630175A

Abstract

The invention provides an access method for a relay network. The source node listens to the channel until the channel is idle. When the source node needs to send information, it judges the flag bit and forwards the information without entering the MAC layer for processing; and Different unicast and broadcast are carried out according to the information sent by the source node relayed by the drone. When the receiving node receives the information forwarded by the drone, it judges the destination address field of the MAC frame header, so as to receive or discard the forwarded information. The present invention can avoid unnecessary forwarding by checking the flag bit, reduce the forwarding delay, improve the throughput of the system at the same time, and can adopt a corresponding response mechanism more accurately. Compared with all information broadcast and relayed by drones, this broadcast of only important information can reduce the energy consumption of the destination node and make it easier to make judgments and responses.

Description

Access method of relay network

Technical Field

The invention relates to the technical field of communication networking, in particular to a network access method, and particularly relates to a protocol design method in a relay system, wherein the protocol design method is used in an environment for acquiring and forwarding data because environmental conditions are not favorable for people to directly monitor information.

Background

Unmanned Aerial Vehicle (UAV) relay network systems have been widely studied and applied because of their ease of deployment, facilitating expansion of network coverage. Typically, such network systems are referred to as UAV-relay network systems (URNS), which consist of one UAV and a plurality of ground nodes. The UAV hovers or rotates in the air and relays one data frame from the source node to the destination node.

At present, most of the URNS use carrier sense protocol with collision avoidance (CSMA/CA), which requires a data link layer (MAC), thus increasing the forwarding delay undoubtedly and reducing the throughput, first, the UAV does not distinguish whether the node needs to forward or not, defaults to all forwarding, and these meaningless forwarding may interfere with other transmissions and cause performance degradation. Secondly, in the unmanned aerial vehicle relay system, a source node generally relays to a point-to-point transmission of a destination node through an unmanned aerial vehicle, different transmission modes are not adopted for different information in the source node, for some special situations, the information of individual nodes is important, all receiving nodes are required to receive the information, meanwhile, the receiving nodes need the information and the fixed receiving information thereof to carry out joint judgment, otherwise, the receiving nodes cannot make an accurate response mechanism.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides an access method of a relay network. In order to avoid unnecessary relay and simultaneously consider the sending mode adopted by the source node due to different information, the invention provides an improved protocol, which is oriented to a multi-sending and multi-receiving unmanned aerial vehicle relay network system.

The technical scheme adopted by the invention for solving the technical problem comprises the following steps:

step 1: the source node monitors the channel, if the channel is busy, the channel is continuously monitored until the channel is idle, and then the step 2 is carried out;

and 2, step: when the channel is detected to be idle and a source node needs to send information, the node sets a first bit, namely a flag bit f, in a PHY Layer Convergence Protocol (PLCP) header, wherein the bit is a binary bit and is set to be 0 or 1; when the source node does not need the relay information of the unmanned aerial vehicle, setting the flag bit to be 0, and if the unmanned aerial vehicle detects that the flag bit f is 0, not forwarding;

and step 3: information sent by a source node of an unmanned aerial vehicle relay needs different sending modes due to difference, for some special scenes, the information of individual nodes is important, all receiving nodes need to receive the information, the source node data is broadcasted, the 802.11 protocol specifies a setting method of a destination address (32 bits) in an MAC frame header, the setting method is divided into two forms, namely unicast and broadcast, the setting rules of address bits of the unicast and broadcast in the MAC frame header are different, if the 8 th bit of the address bit is set to be 0, the unicast is carried out, and the last 24 bits are specific addresses, namely only one receiving node is arranged; if all the address bits are set to be 1, the broadcast is carried out, namely all the nodes receive the information;

and 4, step 4: when receiving the information forwarded by the unmanned aerial vehicle, the receiving node judges whether the destination address fields of the MAC frame header are all 1, if so, the data frame is broadcast data, and then the data frame is received; if not all 1, receiving according to the destination address; if no receiving destination node exists, discarding the forwarded information; then, jumping to the step 1 and repeating continuously.

In step 1, after the DCF interframe space DIFS, the source node backs off for two time slots, and sends request frame information (RTS) to the drone, and the drone checks whether a flag bit f in a PLCP header in the RTS frame is 1, and if the flag bit f is 1, the method proceeds to step 2, and if the flag bit f is not 1, no processing is performed.

The beneficial effects of the invention are embodied in two aspects, the first aspect is that a flag bit f is set in a convergence protocol (PLCP) header in a physical layer, an unmanned aerial vehicle can avoid unnecessary forwarding by checking the flag bit, and meanwhile, when the unmanned aerial vehicle detects that a current data frame needs to be sent, the current data frame is directly forwarded without entering an MAC layer protocol. This reduces the forwarding delay while improving the throughput of the system. In the second aspect, the invention considers that some node information in the source node information is important, so the node information is relayed and broadcasted through the unmanned aerial vehicle, that is, all destination address fields of the MAC frame header in the source node information are set to be 1, so that all destination nodes can receive the information, the destination nodes carry out comprehensive comparison and judgment through the information and self fixed receiving information, and a corresponding response mechanism can be more accurately adopted. All information is compared and is relayed through unmanned aerial vehicle broadcast, and this kind just broadcasts important information, then can make the purpose node power consumption reduce, makes judgement and response more easily simultaneously.

Drawings

Fig. 1 is a schematic diagram of a related application scenario.

Fig. 2 is a schematic diagram of a relay protocol of the drone.

Fig. 3 is a schematic diagram of a flag bit design in a PHY Layer Convergence Protocol (PLCP) header.

Fig. 4 is an access flow chart of the relay network of the present invention.

Detailed Description

The invention is further illustrated with reference to the following figures and examples.

According to the protocol design method, improvement is carried out on the basis of CSMA/CA protocol, the design of the physical layer zone bit in the source node is increased, and corresponding setting is carried out according to whether the source node information needs to be broadcasted or not, so that the whole relay system is simplified, the unmanned aerial vehicle only needs to adopt the physical layer protocol for forwarding, and does not need to enter an MAC layer, the forwarding time delay is reduced, and the throughput of the system is increased.

In the figure 1, the area a is a forest area, various types of sensor nodes are arranged in the forest area, the unmanned aerial vehicle collects node information of the area and forwards the information to the node corresponding to the area b in the figure, and the nodes in the area b are not communicated with each other. Fig. 2 is a design method of a mirror protocol based on a drone. Fig. 3 is a schematic diagram of a flag bit design in a PHY Layer Convergence Protocol (PLCP) header.

In the present invention, in order to avoid unnecessary relay, the source node sets the first bit to a flag bit f in 8 bits reserved in the SERVICE field in the physical layer (PHY) convergence protocol (PLCP) header, as shown in fig. 3, a schematic diagram of a PLCP frame structure is shown in fig. 3, which includes three parts, namely a preamble, a header and a MAC frame structure, where the flag bit is set in the first bit in the SERVICE field in the header and the other 7 bits are reserved. And if the source node information needs to be relayed by the unmanned aerial vehicle, setting the flag bit to be 1, otherwise, setting the flag bit to be 0, and judging whether to forward by the unmanned aerial vehicle according to the value of the flag bit. In addition, according to the characteristics of the source node information, the invention defines some special node information to be broadcast when the unmanned aerial vehicle relays, so that all receiving nodes can receive the information, and a receiver can conveniently and comprehensively consider the relevant information to make accurate judgment.

The invention provides a method for broadcasting information of certain source nodes by an unmanned aerial vehicle according to whether a flag bit f in a PHY Layer Convergence Protocol (PLCP) header in the source node is 1 or not, wherein the whole processing process comprises the following steps:

step 1: after the source node passes through the DCF interframe space DIFS, the source node retreats for two time slot times, request frame information (RTS) is sent to the unmanned aerial vehicle, the unmanned aerial vehicle checks whether a flag bit f in a PLCP header in the RTS frame is 1, if the flag bit f is 1, the step two is carried out, and if the flag bit f is not 1, no processing is carried out;

step 2: if the flag bit f is 1, after a short interframe space SIFS, forwarding an RTS frame, wherein the RTS frame is called a relay RTS, so that all source nodes receive the relay RTS frame and calculate time required to be occupied by current communication, also called backoff time (NAV) of other nodes, and in the backoff time, the other nodes do not send information to the unmanned aerial vehicle; the relay RTS is equivalent to the response frame CTS in CSMA/CA, and the node will share the channel alone at this time;

and step 3: when the source node receives the relay RTS, the DATA frame DATA is sent to the unmanned aerial vehicle, after the unmanned aerial vehicle receives the DATA frame, the DATA frame DATA is forwarded immediately after a short interframe space (SIFS) and is called a relay DATA frame, at the moment, the source node can also receive the relay DATA frame, the DATA is considered to be sent successfully, and the relay DATA frame is equivalent to an acknowledgement frame ACK in a CSMA/CA protocol. If the source node does not receive the relay data frame, the source node considers that the transmission fails, detects a channel and retransmits the message;

and 4, step 4: after receiving the relay data frame, the receiving node judges whether the destination address field of the MAC frame header is all 1, if so, the data frame is broadcast data, and if not, the data frame is received or discarded according to the destination address.

The invention omits CTS frame and ACK in the traditional CSMA/CA protocol, thus saving part of overhead, namely saving forwarding time delay and increasing the throughput of the system.

Claims

1. an access method for a relay network, characterized in that it comprises the following steps:

Step 1: The source node listens to the channel. If the channel is found to be busy, it continues to listen to the channel until the channel is idle, and then enters step 2;

Step 2: When it is detected that the channel is idle and the source node needs to send information, the node will set the first bit in the PHY layer convergence protocol header, that is, the flag bit f, which is a binary bit and is set to 0 or 1 , when the source node needs the drone to relay information, set the flag bit to 1, and then send the data. As long as the drone detects that the flag bit is 1, it indicates that the information needs to be forwarded, and then forwarded immediately without entering MAC layer processing; when the source node does not need the UAV relay information, the flag bit is set to 0, and if the UAV detects that the flag bit f is 0, it will not forward;

Step 3: The information sent by the source node of the UAV relay needs different sending modes because of the difference. If the 8th bit of the address bit is set to 0, it is unicast, and the last 24 bits are the specific address, that is, there is only one receiving node. ; If the address bits are all set to 1, it is broadcast, that is, all nodes have received the information;

Step 4: When the receiving node receives the information forwarded by the drone, it determines whether the destination address field of the MAC frame header is all 1. If it is all 1, then the data frame is broadcast data, and it is received; if it is not all 1, Then receive according to the destination address; if there is no destination node for receiving, discard the forwarded information; then jump to step 1 and repeat continuously.

2. The access method of the relay network according to claim 1, wherein:

In the step 1, the source node backs off two time slots after the inter-frame interval DIFS, and sends the request frame information to the drone, and the drone checks whether the flag bit f in the convergence protocol header in the request frame is 1, If it is 1, go to step 2, if it is not 1, do not perform any processing.