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Datacasting (data broadcasting) is the transmission of data over a wide area using radio waves. It typically refers to supplemental information sent by television stations alongside digital terrestrial television (DTT) signals. However, datacasting can also be applied to digital data signals carried on analog TV or radio broadcasts.
Datacasting often provides a variety of information such as news, weather forecasting, traffic reporting, stock market updates, and other data that may or may not relate to the broadcast programs. It can also include interactive elements like gaming, shopping, or educational content. An electronic program guide is typically included, though this feature is sometimes considered inherent to the digital broadcast standard. [1] [2]
The ATSC, DVB, and ISDB standards support broadband datacasting via Digital Terrestrial Television (DTT), although the specifics of implementation are not always defined. For analog TV, moderate and low bandwidths are used via overscan and the Vertical Blanking Interval (VBI), respectively. DirectBand and RDS/RBDS are medium and narrow subcarriers used for analog FM radio. The EUREKA 147 and HD Radio standards both allow for datacasting on digital radio [3] , defining a few basics but also allowing for later expansion.
The term IP Datacasting (IPDC) is used in DVB-H for the technical elements required to send IP packets over DVB-H broadband downstream channel combined with a return channel over a mobile communications network such as GPRS or UMTS. The set of specifications for IP Datacast (phase1) was approved by the DVB project in October 2005.
Ambient Information Network, a datacasting network owned by Ambient Devices presently hosted by U.S.A. Mobility, a U.S. paging service which focuses on information of interest to the local (or larger) area, such as weather and stock indices, and personalized information will be provided with a paid ambient subscription on that particular device.
A slight variation of the European Radio Data System, RBDS is carried on a 57 kHz subcarrier on FM radio stations. While originally intended for program-associated data, it can also be used for datacasting purposes including paging and dGPS.
DirectBand, owned by Microsoft, uses the 67.65 kHz subcarrier leased from FM radio stations. This subcarrier delivers about 12 kbit/s (net after error correction) of data per station, for over 100 MB per day per city. Data includes traffic, sports, weather, stocks, news, movie times, calendar appointments, and local time.
The now-defunct MovieBeam service used dNTSC technology by Dotcast to transmit 720p HDTV movies in the lower vestigial sideband of NTSC analog TV. The set-top box stored the movies to be viewed on demand for a fee. This was distributed through PBS's National Datacast.
TV Guide On Screen is an advertising-supported datacast sent by one local station in each media market. It supplements or replaces the limited electronic program guide sent by each TV station, which is already mandated by the U.S. Federal Communications Commission (FCC).
ATSC-M/H is yet another mobile TV standard, although it is transmitted and controlled by the broadcasters instead of a third party, and is therefore mostly free-to-air (although it can also be subscription-based). From a technical standpoint, it is an IP-encapsulated datacast of MPEG-4 streaming video, alongside the ATSC MPEG transport stream used for terrestrial television broadcasting. Heavy error correction, separate from that native to ATSC, compensates for ATSC's poor mobile (and often fixed) reception.
UpdateTV is a service used by some brands of TV sets and other ATSC tuners to update their firmware via over-the-air programming. This is also transmitted on PBS stations via National Datacast.
Australian broadcast infrastructure company Broadcast Australia undertook a three-year trial in Sydney of a datacasting service using the DVB-T system for use in Australia.
The trial consisted of a number of services on one standard 7 MHz multiplex, collectively known as Digital Forty Four .
The collection included:
More recently a near-Australia wide broadcast of a datacasting channel called MyTalk commenced on April 13, 2007. Broadcasting as part of the multiplex on Southern Cross and Southern Cross Ten stations, it provided news, weather and other information, available free to anyone able to tune in. The stream consisted of text applicable to the viewer's location and a 4:3 video window of terrestrial TV from the relevant Southern Cross/Southern Cross Ten station.
On February 25, 2008, MyTalk ceased broadcasting. Digital Forty Four was shut down at exactly midnight on the night of April 30, 2010.
Malaysian multi-channel pay-TV operator, MiTV Corporation Sdn Bhd launched its IP-over-UHF service in September 2005. The full digital broadcast capacity was used to deliver IP services which such as multicast streaming and datacasting.
Toosheh, or "Knapsack" in Persian is a datacasting technology that uses existing set-top-boxes for reception of files without requiring an Internet connection. No special equipment is required, the transmission is in the form of a standard video stream containing embedded data that is 'recorded' to a USB stick and then viewed using special software on a PC.
Mindset Network has developed an IP satellite datacast platform for the distribution of educational and health content, to sites around South Africa and the rest of Africa as well. The model is a forward and store model, allowing users of the platform to view content in an on-demand fashion. Content distributed in this way includes video content, print-based content (in the form of PDF files), and interactive computer-based multimedia content.
Significantly, the model also includes access to a GPRS network that allows the receiving sites to communicate back to the Mindset central server. Communications include statistics about the physical health of the machine (e.g. power status, disk drive usage), as well as usage statistics indicating what content has been viewed.
The model also includes a distributed deployment of the Moodle LMS, allowing users to take assessments and have the results transmitted via GPRS to the Mindset server for accreditation.
Teletext was used extensively on analogue channels; a type of datacasting using the overscan on analogue transmissions. Teletext Limited and Ceefax were the main providers. Within digital terrestrial television, the Digital Teletext name is used extensively although the technology used to provide this service is unrelated and uses the MHEG-5 UK profile.
Blockstream Satellite broadcasts the Bitcoin blockchain via a global network [4] of broadcast satellites. It also gives everyone the ability to transmit arbitrary files at low cost [5] which can be received in total anonymity worldwide by anyone with a standard DVB-S2 receiver card or USB adapter.
Outernet's goal is to provide free access to content from the web through geostationary and Low Earth orbit satellites, made available effectively to all parts of the world. The project uses datacasting and User Datagram Protocol (UDP) through both small satellites, such as CubeSats, and larger, more conventional geostationary communications satellites in a satellite constellation network. Wi-Fi enabled devices would communicate with the satellite hotspots, which receive data broadcasts from satellites.
Datacasting has certain advantages over using the Internet, specifically concerning privacy and censorship resistance, which can be considered important in an era of mass surveillance.
Both satellite and terrestrial broadcast multiplexes can carry multicast IP data. This can be forwarded onto a LAN with a suitable receiver, such as a low-cost set-top-box running custom firmware. The software to transmit web pages over multicast is fairly easy to implement; some of the technology has been already developed. [6] Content received can be stored automatically on the set-top box's built in hard drive, served to users over Wi-Fi or Ethernet. A fractional broadcast multiplex can transmit up to hundreds of gigabytes of content each day. [7]
In extreme cases a receiver can be physically disconnected from the Internet, thus providing a system much more secure than Internet-based anonymity networks such as Tor. This could ultimately put a complete stop to law enforcement attempts to censor material on the darknet and making many censorship laws virtually impossible to enforce; thus restoring some of the 'anarchic freedom' of the early days of the Internet.
It is much more difficult, on a technical and political level to jam a satellite signal compared to blocking a website. Data streams can be transmitted alongside television channels. An attempt to jam the data stream will end up jamming the TV stations as well.
Despite the very high cost of satellite bandwidth, [8] broadcasting to hundreds of thousands or millions of receivers may well be cheaper than using the Internet. No build-out and maintenance of costly physical infrastructure (e.g. fiber optic cables) is required for the end-user, only a satellite dish or TV antenna is necessary, allowing services such as educational materials to be delivered to underserved communities. [9]
In telecommunications and computer networking, multiplexing is a method by which multiple analog or digital signals are combined into one signal over a shared medium. The aim is to share a scarce resource – a physical transmission medium. For example, in telecommunications, several telephone calls may be carried using one wire. Multiplexing originated in telegraphy in the 1870s, and is now widely applied in communications. In telephony, George Owen Squier is credited with the development of telephone carrier multiplexing in 1910.
Digital Video Broadcasting (DVB) is a set of international open standards for digital television. DVB standards are maintained by the DVB Project, an international industry consortium, and are published by a Joint Technical Committee (JTC) of the European Telecommunications Standards Institute (ETSI), European Committee for Electrotechnical Standardization (CENELEC) and European Broadcasting Union (EBU).
DVB-T, short for Digital Video Broadcasting – Terrestrial, is the DVB European-based consortium standard for the broadcast transmission of digital terrestrial television that was first published in 1997 and first broadcast in Singapore in February 1998. This system transmits compressed digital audio, digital video and other data in an MPEG transport stream, using coded orthogonal frequency-division multiplexing modulation. It is also the format widely used worldwide for Electronic News Gathering for transmission of video and audio from a mobile newsgathering vehicle to a central receive point. It is also used in the US by Amateur television operators.
A subcarrier is a sideband of a radio frequency carrier wave, which is modulated to send additional information. Examples include the provision of colour in a black and white television system or the provision of stereo in a monophonic radio broadcast. There is no physical difference between a carrier and a subcarrier; the "sub" implies that it has been derived from a carrier, which has been amplitude modulated by a steady signal and has a constant frequency relation to it.
Integrated Services Digital Broadcasting is a Japanese broadcasting standard for digital television (DTV) and digital radio.
Advanced Television Systems Committee (ATSC) standards are an International set of standards for broadcast and digital television transmission over terrestrial, cable and satellite networks. It is largely a replacement for the analog NTSC standard and, like that standard, is used mostly in the United States, Mexico, Canada, South Korea and Trinidad & Tobago. Several former NTSC users, such as Japan, have not used ATSC during their digital television transition, because they adopted other systems such as ISDB developed by Japan, and DVB developed in Europe, for example.
Digital radio is the use of digital technology to transmit or receive across the radio spectrum. Digital transmission by radio waves includes digital broadcasting, and especially digital audio radio services.
A cable television headend is a master facility for receiving television signals for processing and distribution over a cable television system. A headend facility may be staffed or unstaffed and is typically surrounded by some type of security fencing. The building is typically sturdy and purpose-built to provide security, cooling, and easy access for the electronic equipment used to receive and re-transmit video over the local cable infrastructure. One can also find head ends in power-line communication (PLC) substations and Internet communications networks.
Broadcasttelevision systems are the encoding or formatting systems for the transmission and reception of terrestrial television signals.
In most telecommunications organizations, a virtual channel is a method of remapping the program number as used in H.222 Program Association Tables and Program Mapping Tables to a channel number that can be entered as digits on a receiver's remote control.
The Program and System Information Protocol (PSIP) is the MPEG and privately defined program-specific information originally defined by General Instrument for the DigiCipher 2 system and later extended for the ATSC digital television system for carrying metadata about each channel in the broadcast MPEG transport stream of a television station and for publishing information about television programs so that viewers can select what to watch by title and description. Its FM radio equivalent is Radio Data System (RDS).
DVB-H is one of three prevalent mobile TV formats. It is a technical specification for bringing broadcast services to mobile handsets. DVB-H was formally adopted as ETSI standard EN 302 304 in November 2004. The DVB-H specification can be downloaded from the official DVB-H website. From March 2008, DVB-H was officially endorsed by the European Union as the "preferred technology for terrestrial mobile broadcasting".
In broadcasting, digital subchannels are a method of transmitting more than one independent program stream simultaneously from the same digital radio or television station on the same radio frequency channel. This is done by using data compression techniques to reduce the size of each individual program stream, and multiplexing to combine them into a single signal. The practice is sometimes called "multicasting".
IP over DVB implies that Internet Protocol datagrams are distributed using some digital television system, for example DVB-H, DVB-SH, DVB-T, DVB-S, DVB-C or their successors like DVB-T2, DVB-S2, and DVB-C2. This may take the form of IP over MPEG, where the datagrams are transferred over the MPEG transport stream, or the datagrams may be carried in the DVB baseband frames directly, as in GSE.
ATSC-M/H is a U.S. standard for mobile digital TV that allows TV broadcasts to be received by mobile devices.
A free-to-air or FTA Receiver is a satellite television receiver designed to receive unencrypted broadcasts. Modern decoders are typically compliant with the MPEG-2/DVB-S and more recently the MPEG-4/DVB-S2 standard for digital television, while older FTA receivers relied on analog satellite transmissions which have declined rapidly in recent years.
Digital multimedia broadcasting (DMB) is a digital radio transmission technology developed in South Korea as part of the national IT project for sending multimedia such as TV, radio and datacasting to mobile devices such as mobile phones, laptops and GPS navigation systems. This technology, sometimes known as mobile TV, should not be confused with Digital Audio Broadcasting (DAB) which was developed as a research project for the European Union.
Satellite subcarrier audio is audio transmitted by way of satellite that uses a separate analog or digital signal carried on a main radio transmission on a specific satellite transponder. More technically, it is an already-modulated signal, which is then modulated into another signal of higher frequency and bandwidth. In a more general sense, satellite subcarrier audio is an early form of satellite radio not intended for the consumer market but was initially unencrypted, thus receivable to satellite hobbyists.
Astra is a professional software to organize digital broadcasting service for TV operators and broadcasters, internet service providers, hotels, etc. Astra is an acronym for "advanced streaming application".
