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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.
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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.
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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
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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
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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
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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.
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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
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for an example of field measured benefits of SFN in mobile cellular urban environments and cell topologies, see
Christian Le Floc’h, Regis Duval "SFN over DVB-SH manifestations at full network level (S-UMTS band radio propagation performances evaluation)", March 20, 2009, at open access website
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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.
98:(MFN) transmission. An SFN may also increase the coverage area and decrease the outage probability in comparison to an MFN, since the total received signal strength may increase to positions midway between the transmitters.
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communication and high-data rate digital communications, since the fading in that case is frequency-selective (as opposed to flat fading), and since the time spreading of the echoes may result in
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instead of one fast wide-band modulator. Each modulator has its own frequency sub-channel and sub-carrier frequency. Since each modulator is very slow, one can afford to insert a
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between the symbols, and thus eliminate the ISI. Although the fading is frequency-selective over the whole frequency channel, it can be considered as
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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.
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radio broadcast networks as well as digital broadcast networks can operate in this manner. SFNs are not generally compatible with
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code (FEC) can counteract some of the sub-carriers being exposed to too much fading to be correctly demodulated.
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Digital Video
Broadcasting (DVB); Implementation guidelines for DVB terrestrial services; Transmission aspects
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were not very good at handling multipath propagation, but later systems have seen significant improvements.
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510:"Tests of ATSC 8-VSB Reception Performance of Consumer Digital Television Receivers Available in 2005"
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as the direction of signal minima or signal maxima can differ from the direction to the transmitter.
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within the narrowband sub-channel. Thus, advanced equalization filters can be avoided. A
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numbering, a multi-frequency network (MFN) can appear as an SFN to the viewer in ATSC.
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Alternatives to using OFDM modulation in SFN self-interference cancellation would be:
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Transmitters, which are part of a SFN, should not be used for navigation via
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and at the same frequency. The versatility of time-transfer systems such as
377:(SC-FDE), i.e. single-carrier modulation combined with guard intervals and
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for SFNs, A/110. ATSC SFNs have seen widest use in mountainous areas like
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A simplified form of SFN can be achieved by a low power co-channel
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modulation method. OFDM uses a large number of slow low-bandwidth
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381:-based frequency domain equalization, or its multi-user version
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SFN transmission can be considered as creating a severe form of
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While not designed with on-channel repeaters in mind, the
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and wireless computer networks, is called transmitter
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101:SFN schemes are somewhat analogous to what in non-
39:simultaneously send the same signal over the same
151:(ISI). Fading and ISI can be avoided by means of
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90:The aim of SFNs is efficient utilization of the
542:Technical overview of Single Frequency Network
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416:Multicast-Broadcast Single Frequency Network
375:Single-carrier frequency-domain-equalization
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72:transmission, since the SFN results in
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309:for digital TV is relatively good at
209:OFDM is utilized in the terrestrial
143:. This is problematic especially in
105:wireless communication, for example
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135:among these echoes (also known as
76:due to echoes of the same signal.
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122:Dynamic Single Frequency Networks
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396:Distributed transmission system
297:Distributed transmission system
56:Bottom:Single Frequency Network
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443:Quasi-synchronous transmission
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51:Single Frequency Network model
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54:Top:Multi Frequency Network
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421:Digital Video Broadcasting
305:modulation method used in
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574:Radio resource management
313:. Early experiments at
204:forward error correction
149:intersymbol interference
25:single-frequency network
347:Alternative modulations
96:multi-frequency network
182:is facilitated by the
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569:Broadcast engineering
549:Google Sites: Sign-in
406:Cooperative diversity
213:broadcasting system
129:multipath propagation
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401:Broadcast translator
221:and other regions),
176:digital broadcasting
157:equalization filters
85:broadcast translator
18:SFN (disambiguation)
16:For other uses, see
383:Single-carrier FDMA
339:Through the use of
327:Southern California
245:systems, including
564:Digital television
311:ghost cancellation
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519:. 2 November 2005
496:"RabbitEars.Info"
480:ETSI TS 101 191:
466:ETSI TR 101 190:
164:direction finding
153:diversity schemes
137:self-interference
107:cellular networks
70:analog television
33:broadcast network
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323:Puerto Rico
235:Philippines
558:Categories
449:References
385:(SC-FDMA).
317:led to an
233:, and the
211:digital TV
192:modulators
261:DVB-T SFN
237:) and in
225:(used in
217:(used in
103:broadcast
43:channel.
41:frequency
390:See also
371:antenna)
251:HD Radio
239:ATSC 3.0
145:wideband
124:(DSFN).
81:repeater
74:ghosting
523:17 July
315:WPSU-TV
60:Analog
425:ISDB-T
332:Early
253:, and
231:Brazil
223:ISDB-T
219:Europe
141:fading
513:(PDF)
255:T-DMB
227:Japan
215:DVB-T
188:COFDM
31:is a
525:2023
434:OFDM
429:ATSC
365:MIMO
356:CDMA
325:and
303:8VSB
200:flat
184:OFDM
155:and
120:and
115:CDMA
64:and
517:FCC
379:FFT
272:GPS
247:DAB
186:or
29:SFN
27:or
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457:^
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66:FM
62:AM
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