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IEEE 802.11 is part of the IEEE 802 set of local area network (LAN) technical standards, and specifies the set of media access control (MAC) and physical layer (PHY) protocols for implementing wireless local area network (WLAN) computer communication. The standard and amendments provide the basis for wireless network products using the Wi-Fi brand and are the world's most widely used wireless computer networking standards. IEEE 802.11 is used in most home and office networks to allow laptops, printers, smartphones, and other devices to communicate with each other and access the Internet without connecting wires.
Wireless communication is the transfer of information between two or more points that do not use an electrical conductor as a medium for the transfer. The most common wireless technologies use radio waves. With radio waves, intended distances can be short, such as a few meters for Bluetooth or as far as millions of kilometers for deep-space radio communications. It encompasses various types of fixed, mobile, and portable applications, including two-way radios, cellular telephones, personal digital assistants (PDAs), and wireless networking. Other examples of applications of radio wireless technology include GPS units, garage door openers, wireless computer mouse, keyboards and headsets, headphones, radio receivers, satellite television, broadcast television and cordless telephones. Somewhat less common methods of achieving wireless communications include the use of other electromagnetic wireless technologies, such as light, magnetic, or electric fields or the use of sound.
Zigbee is an IEEE 802.15.4-based specification for a suite of high-level communication protocols used to create personal area networks with small, low-power digital radios, such as for home automation, medical device data collection, and other low-power low-bandwidth needs, designed for small scale projects which need wireless connection. Hence, Zigbee is a low-power, low data rate, and close proximity wireless ad hoc network.
A wireless mesh network (WMN) is a communications network made up of radio nodes organized in a mesh topology. It can also be a form of wireless ad hoc network.
Clock synchronization is a topic in computer science and engineering that aims to coordinate otherwise independent clocks. Even when initially set accurately, real clocks will differ after some amount of time due to clock drift, caused by clocks counting time at slightly different rates. There are several problems that occur as a result of clock rate differences and several solutions, some being more appropriate than others in certain contexts.
The Precision Time Protocol (PTP) is a protocol used to synchronize clocks throughout a computer network. On a local area network, it achieves clock accuracy in the sub-microsecond range, making it suitable for measurement and control systems. PTP is currently employed to synchronize financial transactions, mobile phone tower transmissions, sub-sea acoustic arrays, and networks that require precise timing but lack access to satellite navigation signals.
Distributed Network Protocol 3 (DNP3) is a set of communications protocols used between components in process automation systems. Its main use is in utilities such as electric and water companies. Usage in other industries is not common. It was developed for communications between various types of data acquisition and control equipment. It plays a crucial role in SCADA systems, where it is used by SCADA Master Stations, Remote Terminal Units (RTUs), and Intelligent Electronic Devices (IEDs). It is primarily used for communications between a master station and RTUs or IEDs. ICCP, the Inter-Control Center Communications Protocol, is used for inter-master station communications. Competing standards include the older Modbus protocol and the newer IEC 61850 protocol.
IEEE 802.11p is an approved amendment to the IEEE 802.11 standard to add wireless access in vehicular environments (WAVE), a vehicular communication system. It defines enhancements to 802.11 required to support Intelligent Transportation Systems (ITS) applications. This includes data exchange between high-speed vehicles and between the vehicles and the roadside infrastructure, so called V2X communication, in the licensed ITS band of 5.9 GHz (5.85–5.925 GHz). IEEE 1609 is a higher layer standard based on the IEEE 802.11p. It is also the basis of a European standard for vehicular communication known as ETSI ITS-G5.
A phasor measurement unit (PMU) is a device used to estimate the magnitude and phase angle of an electrical phasor quantity in the electricity grid using a common time source for synchronization. Time synchronization is usually provided by GPS or IEEE 1588 Precision Time Protocol, which allows synchronized real-time measurements of multiple remote points on the grid. PMUs are capable of capturing samples from a waveform in quick succession and reconstructing the phasor quantity, made up of an angle measurement and a magnitude measurement. The resulting measurement is known as a synchrophasor. These time synchronized measurements are important because if the grid’s supply and demand are not perfectly matched, frequency imbalances can cause stress on the grid, which is a potential cause for power outages.
EtherCAT is an Ethernet-based fieldbus system invented by Beckhoff Automation. The protocol is standardized in IEC 61158 and is suitable for both hard and soft real-time computing requirements in automation technology.
A wireless ad hoc network (WANET) or mobile ad hoc network (MANET) is a decentralized type of wireless network. The network is ad hoc because it does not rely on a pre-existing infrastructure, such as routers in wired networks or access points in wireless networks. Instead, each node participates in routing by forwarding data for other nodes, so the determination of which nodes forward data is made dynamically on the basis of network connectivity and the routing algorithm in use.
Data synchronization is the process of establishing consistency among data from a source to a target data storage and vice versa and the continuous harmonization of the data over time. It is fundamental to a wide variety of applications, including file synchronization and mobile device synchronization e.g., for PDAs.
In telecommunications, a diversity scheme refers to a method for improving the reliability of a message signal by using two or more communication channels with different characteristics. Diversity is mainly used in radio communication and is a common technique for combatting fading and co-channel interference and avoiding error bursts. It is based on the fact that individual channels experience different levels of fading and interference. Multiple versions of the same signal may be transmitted and/or received and combined in the receiver. Alternatively, a redundant forward error correction code may be added and different parts of the message transmitted over different channels. Diversity techniques may exploit the multipath propagation, resulting in a diversity gain, often measured in decibels.
TSMP, an acronym for Time Synchronized Mesh Protocol, was developed by Dust Networks as a communications protocol for self-organizing networks of wireless devices called motes. TSMP devices stay synchronized to each other and communicate in time-slots, similar to other TDM systems. Such deterministic communication allows the devices to stay extremely low power, as the radios only turn on for the periods of scheduled communication. The protocol is designed to operate very reliably in a noisy environment. It uses channel hopping to avoid interference -- the packets between TSMP devices get sent on different radio channels depending on time of transmission. TSMP distinguishes itself from other time-slotted mesh-based protocols, in that time-slot timing is maintained continuously and enables a network to duty-cycle on a transmitter-receiver pair-wise basis, as opposed to putting the entire network to sleep for extended periods of time.
Parallel Redundancy Protocol (PRP) is a network protocol standard for Ethernet that provides seamless failover against failure of any network component. This redundancy is invisible to the application.
A communication protocol is a system of rules that allows two or more entities of a communications system to transmit information via any kind of variation of a physical quantity. The protocol defines the rules, syntax, semantics and synchronization of communication and possible error recovery methods. Protocols may be implemented by hardware, software, or a combination of both.
xAP is an open protocol used for home automation and supports integration of telemetry and control devices primarily within the home. Common communications networks include RS232, RS485, Ethernet and wireless. xAP protocol always uses broadcast for sending the messages. All the receivers listens to the message and introspects the message header to verify whether the message is of its interest. xAP protocol has the following key advantages.
Two independent clocks, once synchronized, will walk away from one another without limit. To have them display the same time it would be necessary to re-synchronize them at regular intervals. The period between synchronizations is referred to as holdover and performance under holdover relies on the quality of the reference oscillator, the PLL design, and the correction mechanisms employed.
White Rabbit is the name of a collaborative project including CERN, GSI Helmholtz Centre for Heavy Ion Research and other partners from universities and industry to develop a fully deterministic Ethernet-based network for general purpose data transfer and sub-nanosecond accuracy time transfer. Its initial use was as a timing distribution network for control and data acquisition timing of the accelerator sites at CERN as well as in GSI's Facility for Antiproton and Ion Research (FAIR) project. The hardware designs as well as the source code are publicly available. The name of the project is a reference to the White Rabbit appearing in Lewis Carroll's novel Alice's Adventures in Wonderland.
Avnu Alliance is a consortium of member companies working together to create an interoperable ecosystem of low-latency, time-synchronized, highly reliable networking devices using the IEEE open standard, Time-Sensitive Networking (TSN) and its Pro AV networking protocol, Milan. Avnu Alliance creates comprehensive certification programs to ensure interoperability of network devices. In the Professional Audio Video (AV) industry, Alliance member companies worked together to develop Milan: a standards-based, user-driven deterministic network protocol for professional media, that through certification, assures devices will work together at new levels of convenience, reliability, and functionality. Milan™ is a standards-based deterministic network protocol for real time media. Avnu Members may use the Avnu-certified or Milan-certified logo on devices that pass the conformance tests from Avnu. Not every device based on AVB or TSN is submitted for certification to the Avnu Alliance. The lack of the Avnu logo does not necessarily imply a device is incompatible with other Avnu-certified devices. Not every device based on AVB or TSN is submitted for certification to the Avnu Alliance.The lack of the Avnu logo does not necessarily imply a device is incompatible with other Avnu-certified devices. The Alliance, in conjunction with other complimentary standards bodies and alliances, provides a united network foundation for use in professional AV, automotive, industrial control and consumer segments.
References
- ↑ Cena, G.; Scanzio, S.; Valenzano, A.; Zunino, C. (September 2012), "The reference-broadcast infrastructure synchronization protocol", 2012 IEEE 17th Conference on Emerging Technologies & Factory Automation (ETFA), IEEE Press: 1–4, doi:10.1109/ETFA.2012.6489696, ISBN 978-1-4673-4737-2, S2CID 15595842
- ↑ Cena, G.; Scanzio, S.; Valenzano, A.; Zunino, C. (June 2015), "Implementation and Evaluation of the Reference Broadcast Infrastructure Synchronization Protocol", IEEE Transactions on Industrial Informatics, IEEE Press, 11 (3): 801–811, doi:10.1109/TII.2015.2396003, S2CID 17867070