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Packet radio is a form of digital data transmission used in amateur radio to construct wireless computer networks. Its name is a reference to the use of packet switching between network nodes, which allows multiple virtual circuits to coexist on a single radio channel. Packet radio networks use the AX.25 data link layer protocol, derived from the X.25 protocol suite and designed for amateur radio use. Jump to: navigation, search A digital system is one that uses numbers, especially binary numbers, for input, processing, transmission, storage, or display, rather than a continuous spectrum of values (an analog system) or non-numeric symbols such as letters or icons. ...
Jump to: navigation, search DATA (Debt, AIDS, Trade, Africa) was established in 2002 by Bono (Paul Hewson) of the Rock band U2, and Bobby Shiver, along with activists from the Jubilee 2000 Drop the Debt Campaign, as an organisaton focused on Justice, not charity. ...
In communications, transmission is the act of transmitting electrical messages (and the associated phenonomena of radiant energy that pass through media). ...
Jump to: navigation, search Mrs. ...
A computer network is a system for communication among two or more computers. ...
In computer networking and telecommunications, packet switching is a communications paradigm in which packets (messages or fragments of messages) are individually routed between nodes, with no previously established communication path. ...
A node is a device connected to a computer network. ...
A virtual circuit (VC) is a communications arrangement in which data from a source user may be passed to a destination user over more than one real circuit configuration during a single period of communication, but the switching is hidden from the users. ...
AX.25 is a data link layer protocol derived from the X.25 protocol suite and designed for use by amateur radio operators. ...
The data link layer is layer two of the seven-layer OSI model. ...
X.25 is an ITU-T standard protocol suite for WAN networks using the phone or ISDN system as the networking hardware. ...
(The term "packet radio" also was used for early version of mobile ad hoc networks, but this technology has little in common with the description below.) A mobile ad-hoc network (MANET) is a self-configuring network of mobile routers (and associated hosts) connected by wireless links—the union of which form an arbitrary topology. ...
Station configuration
A basic packet radio station consists of a computer, a modem, and a transceiver with an antenna. Traditionally, the computer and modem are combined in one unit, the terminal node controller (TNC), with a dumb terminal (or terminal emulator) used to input and display data. Increasingly, however, personal computers are taking over the functions of the TNC, with the modem either a standalone unit or implemented entirely in software. Jump to: navigation, search A computer is a device or machine for processing information from data according to a program — a compiled list of instructions. ...
Jump to: navigation, search A modem (a portmanteau word constructed from modulator and demodulator) is a device that modulates a carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. ...
Jump to: navigation, search A transceiver is a device that has a transmitter and receiver which is combined into a one unit. ...
A yagi antenna Most simply, an antenna is an electronic component designed to send or receive radio waves. ...
A terminal node controller (TNC) is a device used by amateur radio operators to participate in AX.25 packet radio networks. ...
A dumb terminal in computing consists of a computer screen and keyboard, but practically no processing ability. ...
A terminal emulator, terminal application, term, or tty for short, is a program that emulates a dumb video terminal within some other display architecture. ...
Computer software (or simply software) refers to one or more computer programs and data held in the storage of a computer for some purpose. ...
The computer is responsible for managing network connections, formatting data as AX.25 packets, and controlling the radio channel. Frequently it provides other functionality as well, such as a simple bulletin board system to accept messages while the operator is away. Jump to: navigation, search A bulletin board system or BBS is a computer system running software that allows users to dial into the system over a phone line and, using a terminal program, perform functions such as downloading software and data, uploading data, playing games, reading news, and exchanging messages...
Layers Following the OSI model, packet radio networks can be described in terms of the physical, data link, and network layer protocols on which they rely. Jump to: navigation, search The Open Systems Interconnection Reference Model (OSI Model or OSI Reference Model for short) is a layered abstract description for communications and computer network protocol design, developed as part of the Open Systems Interconnect initiative. ...
Physical layer: modem and radio channel Modems used for packet radio vary in throughput and modulation technique, and are normally selected to match the capabilities of the radio equipment in use. The first amateur packet radio stations were constructed using surplus Bell 202 1,200 bit/s modems, and despite its low data rate, Bell 202 modulation has remained the standard for VHF operation in most areas. More recently, 9,600 bit/s has become a popular alternative. At HF frequencies, Bell 103 modulation is used, at a rate of 300 bit/s. The Bell 202 modem was an early telephone-line modem for computers developed by AT&T. It used audio frequency-shift keying to encode and transfer data at a rate of 1,200 bits per second. ...
In telecommunications and computing, bit rate (sometimes written bitrate) is the frequency at which bits are passing a given (physical or metaphorical) point. It is quantified using the bit per second (bit/s) unit. ...
Very high frequency (VHF) is the radio frequency range from 30 MHz (wavelength 10 m) to 300 MHz (wavelength 1 m). ...
HF or Hf might be an acronym or abbreviation for: High frequency Radio hafnium, a chemical element the chemical formula for Hydrofluoric acid Historisk-filosofisk fakultet, abbr. ...
The Bell 103 modem was the first commercial modem for computers, released by AT&T in 1962. ...
Custom modems have been developed which allow throughput rates of 19.2 kbit/s, 56 kbit/s, and even 1.2 Mbit/s over amateur radio links. However, special radio equipment is needed to carry data at these speeds, and their adoption has been limited.
Data link layer: AX.25 Packet radio networks rely on the AX.25 data link layer protocol, derived from the X.25 protocol suite and intended specifically for amateur radio use. Despite its name, AX.25 defines both the physical and data link layers of the OSI model. (It also defines a network layer protocol, though this is seldom used.) AX.25 is a data link layer protocol derived from the X.25 protocol suite and designed for use by amateur radio operators. ...
The data link layer is layer two of the seven-layer OSI model. ...
X.25 is an ITU-T standard protocol suite for WAN networks using the phone or ISDN system as the networking hardware. ...
Network layer Packet radio has most often been used for direct, keyboard-to-keyboard connections between stations, either between two live operators or between an operator and a bulletin board system. No network services above the data link layer are required for these applications. Jump to: navigation, search A bulletin board system or BBS is a computer system running software that allows users to dial into the system over a phone line and, using a terminal program, perform functions such as downloading software and data, uploading data, playing games, reading news, and exchanging messages...
To provide automated routing of data between stations (important for the delivery of electronic mail), several network layer protocols have been developed for use with AX.25. Most prominent among these are NET/ROM, ROSE, and TexNet. Electronic mail, abbreviated e-mail or email, is a method of composing, sending, and receiving messages over electronic communication systems. ...
In principle, any network layer protocol may be used, including the ubiquitous Internet protocol. Internet protocol may refer to: The Internet_Protocol, a data-oriented protocol used for communicating data across a packet-switched internetwork. ...
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