SFN may refer to:
In DVB-T a SFN functionality is described as a system in the implementation guide. It allows for re-transmitters, gap-filler transmitters (essentially a low-power synchronous transmitter) and use of SFN between main transmitter towers.
In order to achieve the same transmission time on all transmitters, the transmission delay in the network providing the transport to the transmitters needs to be considered. Since the delay from the originating site to the transmitter varies, a system is needed to add delay on the output side such that the signal reaches the transmitters at the same time. This is achieved by the use of special information inserted into the data stream called the Mega-frame Initialization Packet (MIP) which is inserted using a special marker in the MPEG-2 Transport Stream forming a mega-frame. The MIP is time-stamped in the SFN adapter, as measured relative the PPS signal and counted in 100 ns steps (period time of 10 MHz) with the maximum delay (programmed into the SFN adapter) alongside. The SYNC adapter measures the MIP packet against its local variant of PPS using the 10 MHz to measure the actual network delay and then withholding the packets until the maximum delay is achieved. The details is to be found in ETSI TR 101 190 and mega-frame details in ETSI TS 101 191.
It should be understood that the resolution of the mega-frame format is being in steps of 100 ns, whereas the accuracy needs can be in the range of 1-5 µs. The resolution is sufficient for the needed accuracy. There is no strict need for an accuracy limit as this is a network planning aspect, in which the guard-interval is being separated into system time error and path time-error. A 100 ns step represents a 30 m difference, while 1 µs represents a 300 m difference. These distances needs to be compared with the worst-case distance between transmitter towers and reflections. Also, the time accuracy relates to nearby towers in a SFN domain, since a receiver is not expected to see the signal from transmission towers being geographically far apart, so there is no accuracy requirements between these towers.
The DVB-T SFN uses the fact that the guard interval of the COFDM signal allows for various length of path echoes to occur is not different from that of multiple transmitters transmitting the same signal onto the same frequency. The critical parameters is that it needs to occur about in the same time and at the same frequency. The versatility of time-transfer systems such as GPS receivers (here assumed to provide PPS and 10 MHz signals) as well as other similar systems allows for phase and frequency coordination among the transmitters. The guard interval allows for a timing budget, of which several microseconds may be allocated to time errors of the time-transfer system used. A GPS receiver worst-case scenario is able to provide +/- 1 µs time, well within the system needs of DVB-T SFN in typical configuration.
So called GPS-free solutions exist, which essentially replace GPS as the timing distribution system. Such system may provide benefit in integration with transmission system for the MPEG-2 Transport Stream. It does not change any other aspect of the SFN system as the basic requirements can be met.
In an SFN, two or more transmitters with an overlapping coverage send the same program content simultaneously on the same frequency. The 8VSB modulation used by ATSC allows SFN transmissions. To allow regular channel approximation, ATSC-M/H provides additional training sequences. ATSC A/110 defines a method to synchronize the ATSC modulator as part of the transmitter. The A/110 standard sets up the Trellis coder in a pre-calculated way to all transmitters of the SFN. In such an SFN, the ATSC-M/H multiplexer and the ATSC-M/H transmitter are synchronized by a GPS reference. The ATSC-M/H multiplexer operates as a network adapter and inserts time stamps in the MPEG transport stream. The transmitter analyzes the time stamp, delays the transport stream before it is modulated and transmitted. Eventually, all SFN transmitters generate a synchronized signal.
The first sanctioning body in the Netherlands was called the Stichting Fietscross Nederland (SFN) (in English the Dutch Bicycle Motocross Foundation (DBMXF)) and was co-founded on October 19, 1978 by Gerrit Does and Louis Vrijdag. It held its first race on April 21, 1979. In December 1980 it was folded into the KNWU (see below) but a second incarnation was created in 1987 called the Stichting Fietscross Promotie Nederland (the Dutch BMX Promotion Foundation) to promote Dutch racing in the Netherlands. This second "SFN" was dessoved in 1997.
Mindscape was a French (previously American) video game developer and publisher based in Boulogne-Billancourt. The company was founded by Roger Buoy in October 1983 in the Northbrook, Illinois, originally as part of SFN Companies until a management buyout was completed in 1987. Mindscape went public in 1988 and was subsequently acquired in 1990 by The Software Toolworks, eyeing Mindscape's Nintendo license. When Toolworks was acquired by Pearson plc in 1994, Mindscape became the primary identity for the development group. Mindscape was then sold to The Learning Company in 1998, and bought out by Jean-Pierre Nordman in 2001. Following the poor performance of its products, Mindscape exited the video game industry in August 2011. Notable titles released by Mindscape include Déjà Vu, Balance of Power, Sub Mission: A Matter of Life and Death, and Lego Island.
After leaving city government, Price entered the private sector. He was the founder and president of Price Communications Corp., creating the company in 1979 but activating it two years later, when the company obtained capital. By 1985, Price Communications Corp. owned and operated three television stations and eleven radio stations. In the same year, Price Communications made its first print acquisition when it purchased the New York Law Journal and its companion publication, the National Law Journal, from SFN Companies, for $20.5 million.
T-VIPS was founded in 2004 and is headquartered in Oslo, Norway, with a US office in Millburn, New Jersey. T-VIPS was founded by 11 engineers and managers from Tandberg Television with knowledge and experience of the broadcast and telecommunications industry. The T-VIPS team has experience in transport stream multiplexing, processing, monitoring, switching and broadcast video over IP transport, having for a number of years been involved in MPEG over IP contribution solutions and broadband IPTV to the home. It manufactures professional video transport solutions for contribution, distribution and Digital Terrestrial Television (DTT). T-VIPS is involved in the transport of SD, HD and 3D video over IP networks, JPEG 2000 compression, MPEG transport stream processing, transport stream monitoring and switching, remultiplexing, IP-based terrestrial transmission systems and SFN adaption. T-VIPS solutions are utilized in video broadcast applications such as contribution to terrestrial head-ends, regional and local multiplexing, service filtering, PSIP insertion and SI adaptation, disaster recovery and live events back-haul.
OFDM allows the use of single-frequency networks (SFN), which means that a network of transmitters can provide coverage to a large area – up to the size of a country – where all transmitters use the same transmission frequency. Transmitters that are part of an SFN need to be very accurately synchronised with other transmitters in the network, which requires the transmitters to use very accurate clocks.
The length of the Guard Interval can be chosen. It is a trade-off between data rate and SFN capability. The longer the guard interval the larger is the potential SFN area without creating intersymbol interference (ISI). It is possible to operate SFNs which do not fulfill the guard interval condition if the self-interference is properly planned and monitored.
OFDM is utilized in the terrestrial digital TV broadcasting systems DVB-T (used in Europe and many other areas), ISDB-T (used in Japan and Brazil) and in ATSC 3.0. OFDM is also widely used in digital radio systems, including DAB, HD Radio, and T-DMB. Therefore, these systems are well-suited to SFN operation.
In November 2012 SFN workers began job shadowing City of Nanaimo CUPE Local 401 water crews members to learn foundational skills in maintaining quality water systems through an innovative mentoring program. CUPE's long-term goal is to expand this pilot project to First Nations communities across Vancouver Island. According to Blaine Gurrie, CUPE Local 401 President and member of the Vancouver Island Water Watch Coalition, CUPE working to assist SFN employees to,
WBFF had announced in September 2015 that test broadcasts would begin in Baltimore and Washington, D.C. for ATSC 3.0 (dubbed "Futurecast") via a two-transmitter SFN with one transmitter in each city on UHF 43 delivering 4K UHDTV and mobile feeds to viewers. This station, named WI9XXT, began experimental broadcasts on August 24, 2015, and the Special temporary authority ends on February 25, 2016. WI9XXT's broadcasts are from WRC-TV's tower in the northwest section of Washington, and from WBFF's tower in Woodberry, Baltimore.
Nucleases are components of DNA and RNA metabolism that carry out functions in DNA repair, replication, and recombination and in RNA processing and degradation. SFN is a homolog of Orn, a 3-prime-to-5-prime exoribonuclease of E. coli that attacks the free 3-prime hydroxyl group on single-stranded RNA, releasing 5-prime mono-nucleotides in a sequential manner.
Numerical example: Analog FM requires 0.2 MHz per programme. The frequency reuse factor in most countries is approximately 15 for stereo transmissions (with lesser factors for mono FM networks), meaning (in the case of stereo FM) that only one out of 15 transmitter sites can use the same channel frequency without problems with co-channel interference, i.e. cross-talk. Assuming a total availability of 102 FM channels at a bandwidth of 0.2MHz over the Band II spectrum of 87.5 to 108.0 MHz, an average of 102/15 = 6.8 radio channels are possible on each transmitter site (plus lower-power local transmitters causing less interference). This results in a system spectral efficiency of 1 / 15 / (0.2 MHz) = 0.30 programmes/transmitter/MHz. DAB with 192 kbit/s codec requires 1.536 MHz * 192 kbit/s / 1,136 kbit/s = 0.26 MHz per audio programme. The frequency reuse factor for local programmes and multi-frequency broadcasting networks (MFN) is typically 4 or 5, resulting in 1 / 4 / (0.26 MHz) = 0.96 programmes/transmitter/MHz. This is 3.2 times as efficient as analog FM for local stations. For single frequency network (SFN) transmission, for example of national programmes, the channel re-use factor is 1, resulting in 1/1/0.25 MHz = 3.85 programmes/transmitter/MHz, which is 12.7 times as efficient as FM for national and regional networks.
Mindscape was founded in October 1983 as a wholly owned subsidiary of holding company SFN Companies. Mindscape's founder, Australian entrepreneur Roger Buoy, had previously been a computer analyst for Rolls-Royce Limited and later worked for the software division of Scholastic Inc., before being hired by SFN in October 1983 to set up Mindscape. For Mindscape, Buoy acted as president and chief executive officer (CEO). Mindscape released its first product in April 1984. Early games published by the company include Déjà Vu, Balance of Power, and Sub Mission: A Matter of Life and Death. In its early years, Mindscape lost about US$6 million annually.
On the foundation of all of these activities, Huda Akil, the 2003 President of the Society for Neuroscience (SfN) established the Brain Information Group (BIG) to evaluate the importance of neuroinformatics to neuroscience and specifically to the SfN. Following the report from BIG, SfN also established a neuroinformatics committee.