Table of Contents
What is a Wireless Ad Hoc Network?
In recent years, wireless ad-hoc networks have gradually been applied in industry communications, enabling everyone to have more choices in addition to common carrier public networks, WiFi, and bridge technologies. Although ad hoc networking is an emerging technology, there have been many different subdivisions over the years. Compared with the traditional fixed-deployed wireless network, the author believes that it does not depend on public facilities, and the network that can automatically switch the role of equipment or be configurable can be called an ad hoc network.
What are the types of ad hoc networks?
Common ad hoc networks are Point-to-point, star, relay, MESH, and non-central ad hoc networks Several other networking topologies.
Point-to-point or peer-to-peer network is also known as point-to-point technology, point-to-point protocol, and point-to-point communication; it is used for mutual communication between two points, and the networking method is simple, convenient, and fast. Although the positions of the two nodes are equal, the time slot ratio, transmit power and antenna gain of the two nodes can be different to adapt to different business requirements in both directions.
Star networking is a network structure with one master and multiple slaves. The master node establishes connections with multiple slave nodes, that is, communication through a specific point-to-multipoint connection type. The point-to-multipoint system has been designed as a single or two-way system. The star network mostly uses TDMA to realize multiple address transmission, and the single frequency network can realize more than 64 slave nodes. Common WiFi and LTE base stations are also a star topology network, but the central master or slave node is a dedicated device, and generally cannot be reset as a slave node or master node; an excellent self-organizing star network can be manually configured according to application needs. Or automatically set as master or slave.
The wireless relay network implements signal relay and amplification through relay equipment, thereby extending the coverage of the wireless network. The common ones are chain structure and tree structure. The network topology is relatively fixed. Data can only be transmitted in a fixed direction and cannot be flexibly changed in real-time. This networking method is mostly used in relatively fixed scenarios.
Wireless Mesh network (wireless mesh network), also known as a “multi-hop” network, is a new type of wireless network technology that is completely different from traditional wireless networks; High-speed wireless access to the Internet at any time and anywhere is developed from the AD hoc network. The wireless mesh network is composed of mesh routers (routers) and mesh clients (clients). The mesh routers form the backbone network and are connected to the wired internet network. They are responsible for providing multi-hop wireless internet connections for the mesh clients. Both the backbone part of the wireless Mesh network and the Ad hoc network adopt the idea of distribution and self-organization to form a network. Each node has a routing function and provides routing and relay services for data transmission of other nodes at any time.
Decentralized self-organizing network (Ad hoc)
Ad hoc network is a multi-hop, centerless, self-organizing wireless network, also known as a multi-hop network (Multi-hop Network), infrastructureless network (Infrastructureless Network), or self-organizing network (Self-organizing Network). The entire network has no fixed infrastructure, each node is mobile, and can dynamically maintain contact with other nodes in any way. In such a network, due to the limited range of terminal wireless coverage, two user terminals that cannot communicate directly can use other nodes to forward packets. Each node is also a router, they can complete the function of discovering and maintaining routes to other nodes. The Ad hoc network is mainly applied in the mobile environment to ensure reliable communication between any two nodes in the network. The data flow in the network can include voice, data, and multimedia information.
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Ad Hoc Network Application Scenarios
Ad hoc network is already in drones, robots, emergency communications, and electricity. It is widely used in various fields, and different networking topologies are selected according to the business requirements of each scenario.
According to the transmission direction, the UAV data link can be divided into: uplink and downlink. The uplink mainly completes the sending and receiving of remote control commands from the ground station to the UAV, and the downlink mainly completes the sending and receiving of telemetry data and video images from the UAV to the ground station and uses the uplink and downlink according to the transmission of positioning information. The performance of the data link directly affects the performance of the UAV.
One-stop multi-machine data link
One-station multi-machine data link is a data link between a measurement and control station (ground or air) and multiple UAVs. The measurement and control station generally uses time-division multiple access to send control commands to each drone, and uses time-division multiple access to distinguish telemetry parameters and video image information from different drones. Simplifies the amount of equipment on the ground control station, using one measurement and control station to control multiple UAVs; improves the interconnection and intercommunication capabilities of the system, enables the UAV to achieve multi-machine multi-system compatibility and collaborative work, and improves the UAV measurement and control system. usage efficiency.
Cooperatively controlled UAV formation
The cooperatively controlled UAV formation not only has a wide coverage area and greatly improves work efficiency, but also can solve the problem of limited wireless communication distance of a single UAV through wireless multi-hop, which is conducive to sensing and controlling information. The transmission is an indispensable technical means for unmanned inspection, logistics, and rescue in the future. The data link networking between UAVs requires large capacity, stability, reliability, strong connectivity and interoperability, which requires the network to be a mobile high-bandwidth network; the current decentralized broadband ad hoc network has become an unmanned The research hotspot of aircraft formation data link.
Wireless communication technology enables robots to operate remotely, enhances the flexibility and adaptability of robots, enables robots to cover and control a larger working area, and improves production efficiency and quality. The current wireless communication methods of robots mainly include operator public networks, wireless Wi-Fi, ad hoc networks, etc. In areas where public network capabilities such as fire protection and power inspection are limited, ad hoc network has become an indispensable means of communication .
Now there are many kinds of communication technologies that can be applied in emergency rescue. Each communication method can play a role in some scenarios, but they all have limitations. No communication method can provide a reliable communication guarantee under various disasters. The industry has basically reached a consensus that it is necessary to build an emergency rescue integrated communication network integrating air, space, and ground. In addition, the “last mile” of emergency rescue is usually blocked by buildings, basements, woods, mountains, etc., and line-of-sight transmission cannot be guaranteed, which is the most complicated and difficult for wireless communication; star single-hop non-transmission technology cannot achieve effective communication; With its characteristics of no center, self-organization, and multi-hop, the central ad hoc network is the most ideal communication means for the “last mile” broadband extension transmission of emergency communications.
power transmission line
At present, the inspection of power towers is faced with harsh environments, and it is difficult for inspection personnel to communicate with the background, which cannot guarantee the safety of inspection personnel; there is no public network coverage area, and it is difficult to transmit drone inspection video in real-time. Based on self-organizing network technology, a high-speed communication channel is built on the basis of transmission towers, which facilitates rapid access to the network for drones, machine nests, and inspection personnel, and realizes real-time data return in areas without public networks.