Dvb t2 signal jumps. Determining the reception range of digital DVB-T2 packets
Nevertheless, especially for Moscow residents, we present 3 boundary graphs (Fig. 1) for receiving digital DVB-T2 packets (multiplexes).
All 3 graphs are built for 3 reception conditions:
1 – long-range reception (receiving antennas with a gain of 16-18 dB, “long-range” class);
2 – average reception (receiving antennas with a gain of 10-12 dB, class balcony antennas);
3 – short-range reception (indoor “Delta” antenna).
In all cases it is assumed that used or active antenna with a built-in mast amplifier, or an external low-noise mast amplifier (F=2 dB) is used. Of course, the use of more expensive “long-range” antennas will provide much better (reliable) reception even in all weather conditions and over many years of operation. The higher the price of the antenna, the more attractive it is appearance and greater durability in use.
Reduction cable length at presence of a mast amplifier(of any type) does not make any difference either to the quality of reception or to its “range”. At absence of a mast amplifier The length of the reduction cable (especially when working on 2 or more TVs) is already very important.
When using indoor antennas(Amplification = 6 dB) it is necessary to remember that the walls (and radio waves will certainly pass through the window opening or walls) have shielding (attenuation of radio waves). In the calculations, a radio shielding coefficient of 6 dB was assumed. In practice, it can reach 14...18 dB. In other words, this means that the actual range can be reduced by 2-3 times, depending on the installation location of the indoor antenna and the radio shielding factor of the walls.
Curve with Acceleration=0 dB corresponds to common active indoor foreign antennas (as a rule, they are powered by mains voltage ~220 V/50 Hz). Such antennas have zero gain (without a built-in amplifier), but are quite aesthetic in appearance.
For residents of the regions The figure below shows similar dependences of the reception range R 0 depending on the height of the receiving antenna h for different installation heights of transmitting antennas - N. The curves are plotted for “long-range” antennas with a radiated transmitter power of 4 kW at a frequency of 600 MHz.
If your real transmitter power P differs from 4 kW, then the calculation of the real reception range must be adjusted according to the formula:
It is useful to note that if the height of the receiving antenna is over 15 meters, then you can calculate the reception range R for a height of 15 m, and then recalculate according to the formula:
Thus, for a receiving antenna elevation height of 30 meters, the reception range increases by approximately 1.4 times (for example, from 48.3 km to 68.1 km).
In conclusion, here are a number of useful practical advice for digital DVB-T2 reception:
Tip 1
Currently, it makes no practical sense to install bulky MV antennas. Taking into account the emerging digital DVB-T2 broadcasting is more profitable to spend money on just one quality antenna UHF complete with built-in or externally connected mast amplifier.
Tip 2
Choose a mast amplifier with gain 12-20 dB and minimum noise figure (no more than 3 dB). If you purchase a mast amplifier on the market, then take into account the fact that they are not specialists selling there. Therefore, without listening to their recommendations, try to choose an amplifier with the maximum current consumption (about 40-70 mA). Higher current consumption corresponds to greater dynamic range(minimizing distortion).
Tip 3
Try to ensure that the mast on which the antenna is mounted is grounded. Preferably install a lightning protection device between the antenna and the mast amplifier. If the reception is carried out in a house where a standard lightning protection system is already provided, then there is no additional system you won't need it.
Tip 4
Preferably choose an antenna with the highest possible gain. This criterion for the UHF range when receiving digital DVB-T2 signals is the main one. All other things being equal, choose an antenna with minimal wind load and weight.
Tip 5
Try to minimize the length of the drop cable (between the antenna and the first amplifier). Drop cable length 5-10 meters for most practical applications is considered acceptable.
Tip 6
Comfortable use a mast amplifier with a supply voltage of 5 V instead of traditional 12 V or 24 V. A 5 V remote power supply is present in almost every DVB-T2 receiver, which is very convenient, because no purchase required additional source nutrition.
Tip 7
For normal readability of digital DVB-T2 packets, a signal level at the antenna output of 36 dBµV is sufficient. Mast amplifier serves only to compensate for losses in a reduction cable and a splitter for several TVs.
Tip 8
To increase reception range choose a receiving antenna With maximum possible gain and install it whenever possible, as high as possible relative to the Earth's surface. The mast amplifier should be located as close to the antenna as possible or immediately purchase an active antenna.
DVB-T2 is the second generation of the European standard for terrestrial digital television broadcasting DVB-T.
TV broadcasting DVB-T standard 2 is produced using MPEG-4 encoding, the bit rate is up to 50 Mbit/s. Digital format ensures picture stability even in conditions of high noise and interference. This makes it fundamentally different from the analog format, which is characterized by systemic distortions.
Note. The DVB-T2 standard is the last in the family of DVB terrestrial digital television broadcasting standards, because it is impossible to physically implement a higher data rate per unit of spectrum.
DVB-T2 has fundamental differences from DVB-T both in relation to the system level architecture and at the physical level. This causes the incompatibility of DVB-T receivers with DVB-T2.
The DVB-T2 standard has undeniable advantages before its predecessor: it is designed to increase throughput radio channel by at least 30%, while the infrastructure existing networks and there is no need to change frequency resources. This will expand the number of transmitted television programs on one RF assignment, as well as improve the quality of radio frequency networks.
Despite the fact that the DVB-T2 standard is a successor to DVB-T, it has improved and expanded functionality. While maintaining such basic signal processing ideas as scrambling, as well as data interleaving and encoding, each stage is improved and expanded. The changes did not affect only OFDM modulation (orthogonal frequency division multiplexing).
To encapsulate data in the DVB-T2 system, it is possible to use a transport stream not only MPEG, but also general purpose(GSE). This ensures a reduction in the amount of transmitted overhead data and makes adaptation of the flow to the network more flexible. Compared to its predecessor (DVB-T), the DVB-T2 standard is not tied to any data structure at the transport level.
There are also differences in the use of stripes. If in the DVB-T standard the entire band is used for transmitting one stream, then in DVB-T2 the so-called PLP concept. This abbreviation stands for Physical Layer Pipes, or channels physical level, and means the transmission of several logical channels in one physical channel. 2 modes are possible:
mode A – transmission of one PLP;
mode B – transmission of several PLPs (or multiPLP). At this mode There is simultaneous transmission of several transport streams, with each of these streams placed in its own PLP. Thanks to this, in one radio frequency channel it is possible to coexist services that are transmitted with varying degrees of noise immunity. It is possible to select the modulation mode and the noise-resistant coding mode individually for each PLP. In other words, the operator for each program in the package can choose higher speed transmission or better noise immunity. The receiver decodes only the selected PLP, and turns off during the transmission of PLPs that are not of interest to the user. This ensures energy savings.
The DVB-T2 standard has a more complex interleaving system. Bit and frequency interleaving are used, as well as, additionally, time interleaving. It is carried out both within one modulation symbol and within a superframe, which makes it possible to increase the stability of the signal to impulse noise, as well as to change the characteristics of the transmitting path.
For the DVB-T2 standard, there are 8 ways to place pilot signals. That is, if for DVB-T the number of pilot signals from the total number of carriers was 8%, then for the DVB-T2 system it is possible to vary given value: 1, 2, 4 and 8%. The placement pattern is affected by the value of the guard interval.
Another innovation of the DVB-T2 standard is the rotation of the signal constellation, which increases the noise immunity of the system.
Thus, key features DVB-T2 are:
compared to DVB-T: no less than 30% increase in throughput and improvement in SFN characteristics;
transmission stability determined by the service;
transmission of programs to both mobile and stationary receivers;
use of existing DVB-T infrastructure;
Reduced operating costs on the transmission side due to a reduction in the peak power/average power ratio.
New standard digital television DVB-T2 in simple answers to questions that concern residents of the region.
What is DVB-T2?
This is the second generation of the European standard for terrestrial digital television. It differs significantly from the first generation DVB-T in physical characteristics. It is for this reason that set-top boxes and televisions with a DVB-T receiver are incompatible with DVB-T2. The second generation standard is used in a number of countries of the European Union, Ukraine, Belarus, Kyrgyzstan, Tajikistan and Armenia.
In Russia, DVB-T2 has been chosen as the digital standard terrestrial television within the framework of the Federal target program"Development of television and radio broadcasting in Russian Federation for 2009–2015." FSUE "Russian Television and Radio Broadcasting Network", the program executor, has formed two free packages(multiplex) of two dozen channels.
What is the difference new standard digital terrestrial television from the old one?
Due to opportunities modern equipment and more complex mathematical signal processing in the new standard, the capacity of broadcasting networks increases significantly, allowing the transmission more information V digital package. The standard provides prospects for organizing “local” broadcasting. The DVB-T2 stream is better protected from interference. If the frequency resource is freed up, it becomes possible to receive more channels in high and ultra-high definition modes and even watch 3D television.
In addition, already now, when broadcasting the first and second multiplexes, TV viewers have access to new service: "TV Guide". In general, DVB-T2 TV is more suitable for implementing SMART functions.
Why are these changes needed at all if I was happy with everything before?
Firstly, to be confident in the future. Digital television has already replaced analog television almost all over the world. The DVB-T2 standard was chosen as the main one for use in Russia at the highest federal level, this means that in the future all television broadcasting will be carried out precisely on its basis.
In addition, modern life directly depends on information flows, and do not ignore the data transmission capabilities provided by the DVB-T2 standard. If previously a TV was just a means for watching several TV channels, today it already combines a lot of functions, from recording missed programs to working with the Internet.
In the end, despite the fact that analogue broadcasting of channels is still fully available, the final transition to digital television is only a matter of time. Contain outdated technologies analogue television broadcasting too expensive, and new technologies provide a lot of opportunities to improve the quality of life of Russians.
Who is affected by the transition to the new broadcasting standard DVB-T2?
The changes affected exclusively those residents of the region who were already digital television subscribers and used equipment of the previous DVB-T standard. Set-top boxes, televisions with built-in decoders and DVB-T computer TV tuners are incompatible with the new standard, and broadcasting of multiplexes in the old standard in the Kaliningrad region has been stopped since mid-January.
However, according to statistics, the majority of residents of the region today use cable or satellite television, as well as IP-TV. These subscribers were not affected by the transition to the new standard. Only subscribers cable networks Over the course of several days, rare interruptions in the broadcast of individual programs could be observed.
What equipment is required to watch channels in the new standard?
First, you will need an antenna - either a common one on the roof, or your own indoor one.
It is very likely that your TV already supports digital television standards adopted in Russia (DVB-T2 standard, MPEG-4 compression, Multiple PLP mode). Most of the world's leading manufacturers supply such TVs to our country. If you are just going to buy new TV, be sure to make sure it supports these standards.
If for some reason your TV is not compatible with digital television standards, then you will need to purchase a set-top box to receive reception digital signal. It may also be called a digital terrestrial receiver or SetTopBox (STB). The standard of the set-top box is usually written on its front, make sure that the set-top box supports the DVB-T2 standard.
If you want to receive a digital television signal and cable TV channels at the same time, then you will need a so-called TV signal combiner.
It's important to know that your satellite antenna does not allow you to use digital television broadcasting, since it works in a completely different standard. In addition, it should be noted that one set-top box does not allow you to watch different digital television channels on different TVs.
Is the new broadcast standard expensive?
No, now DVB-T2 TVs and set-top boxes are no more expensive than the old standard equipment. In addition, remember - federal multiplexes are guaranteed free for the Russian population, unlike cable, satellite or Internet television. Price required console starts from 1300 rubles.
How to set up a TV to receive a signal in the DVB-T2 standard?
First of all, you should read the instructions for your TV and/or digital set-top box to connect the equipment. You may also need to enable digital tuner your TV (by selecting the country in the corresponding section of the settings menu - Poland, Lithuania or Germany). Then you should run automatic search channels - in most cases, a built-in signal level and quality indicator will allow you to optimally configure your antenna for receiving digital television.
If you need manual setting digital TV channels, then use following settings: the first multiplex is broadcast on 47 TVK, frequency 682 MHz, the second multiplex - on 30 TVK, frequency 546 MHz (RTPS Kaliningrad).
What channels can you watch in the DVB-T2 standard?
Currently, two multiplexes (packages) are broadcast in the Kaliningrad region: RTRS-1 and RTRS-2.
The first multiplex, broadcast simultaneously from five transmitting stations at a frequency of 682 MHz, includes the following channels: “Channel One”, “Russia” (Russia-1), “Russia-2” (Russia-2, sports channel), “NTV”, “Petersburg - Channel 5”, “Russia - Culture” (Rossiya-K), “Russia-24” (Russia-24), “Carousel”, “Public Television of Russia”, “TV Center”.
The second multiplex, broadcast from a transmitting station in Kaliningrad at a frequency of 546 MHz, includes the channels: “Ren-TV”, “Spas”, “STS”, “Domashny”, “TV3”, “NTV Plus Sport”, “Zvezda”, “ Mir", "TNT", "Muz TV".
Reception of digital TV signal (DVB-T2) in extremely harsh conditions.Due to the greyhound nature of Tricolor, I decided to “finish off” digital terrestrial TV at my dacha.
The first (winter) attempt ended in failure: it worked in cold weather, but at zero and above there was not enough signal. Reasons: in summer the absolute humidity is much higher than in winter, lowland near the river and nearby forest. Let me remind you that my directional relief to the repeater gives a completely “closed interval”, i.e. the signal should not pass through... A relief with a refractive ellipse is attached. A
I bought a highly sensitive receiver (-82dBm) and moved the antenna from the house away from the forest (to the summer kitchen). Now it’s 100 meters to the forest, but it was probably 20 meters (an acute angle towards the repeater).
I bought and connected/stretched 23-25 meters of RG-6U cable.
I installed an antenna lightning arrester at the receiver input. We should probably install it at the output of the amplifier, but we won’t get around to it yet. And at the entrance antenna amplifier It has short circuit By DC, so I think it’s protected well.
Result, in general, positive (compared to what it was before): at 650 MHz the signal strength is 80%, and at 722 MHz - 48%. On both, “quality” is 100%, which I don’t believe. Of course, 48% is not enough, but it works. On the verge. When the receiver warms up and as the play progresses, there are signal interruptions... Moreover, the antenna had to be very precisely aligned in the direction.
I didn’t like it and decided to “finish off” further.
I installed a second amplifier in the house in front of the receiver (an ancient one, from an old antenna).
At the same time, I had to overcome the excitation of the amplifier and the too strong signal.
A strong signal won out over splitters, which is right for me, because I want to distribute DVB-T2 around the house.
Now both multiplexes have a signal level above 90%. And the quality... - see Note-3.
Liked.
Lightning protection:
I attached a meter-long thick aluminum lightning rod to the top of the antenna mast, and organized it through an aluminum-to-copper adapter With his lower part(and not from the bottom of the mast!) a copper descent to the grounding, for which I bought and hammered a galvanized pipe 1.6 meters under the antenna. A steel cable was welded to the same grounding, to which it was tied antenna cable, going from the summer kitchen to the house. Copper to steel pipe - through stainless washers.
Note-1:
It is assumed that the TV (at least) and the rest are grounded, otherwise interference may form at the receiver input (up to 100-150 Volts), which, with the antenna grounded and temporarily open antenna input may (when connected) break through the mast antenna amplifier at the output. And this is not a theory, but a cruel truth of life.
Note-2:
It’s strange that my signal quality indicator is almost always 100%. I do not believe!
Update dated July 11, 2015:
Note to those who insist that reception does not deteriorate when it rains.
The other day we had a wild downpour. So during it, the signal at 722 MHz completely disintegrated, and was added to 650...
It’s clear, because My signal-to-noise ratio is borderline. And the antenna is not the longest-range...
I scratched my turnips and tore up the ones that were lying around old antenna, made 6 directors about 14.5 cm long (this is the length of the directors of the purchased part of the antenna), screwed them to the main antenna. After this, the signal level, deliberately roughened to 50%, rose to 65% (compared to a purchased antenna). How many in decibels, of course, is unknown...
We're waiting, out of the rain!
Update dated July 21, 2015:
Result of antenna modification:
Today we had a very heavy downpour again, both of my Tricolors (I temporarily have two antennas pointing at 36E) went off for 5-10 minutes, and my CETV didn’t turn off for a second...
Here, by amplifying the antenna itself, I raised the signal-to-noise ratio and therefore the signal was no longer “on the edge” and the effect was no longer noticeable. However, the signal level during rainfall decreased from 91% to 72% (at the minimum point).
Now the antenna looks like this:
Addition to the antenna modification results:
There were heavy rains and thunderstorms. I noticed that at the moment of a distant lightning discharge the image is disrupted for 2-3 seconds...
Note-3:
I bought a slightly different receiver from the same company for a friend and was additionally convinced that the almost constant 100% signal quality on my receiver was a fiction. This new receiver"measures" more or less normally. The quality on it (from the same antenna-feeder system) is 60-70%. By the way, its software menu and controls are different.
Apparently, I will shake the manufacturer/representative to provide a software update, which is much better in terms of convenience.
Note-4:
Forum member about static electricity during snowfall from an antenna on the 27 MHz band ( copper wire vertical):
Note-5:
The DVB Consortium (located in Europe) has developed DVB-T2 technology as an extension of the existing DVB-T standard to provide more effective use frequency resource due to integration advanced technologies signal processing. With the new standard, up to a 50% increase in data transfer rates is expected when operating in the same frequency band.
Main features of DVB-T2
The specification is designed primarily for reception on fixed outdoor antennas and has the same frequency spectrum characteristics as DVB-T, which implies the possibility backward compatibility with the existing broadcast infrastructure...
Like DVB-T, DVB-T2 uses OFDM (orthogonal frequency division multiplexing) modulation and provides a range of modes with different numbers of carriers (1k, 2k, 4k, 8k, 16k, 32k, 16k extended, 32k extended) and modulation constellations (QPSK, 16QAM, 64QAM, 256QAM). For error protection, DVB-T2 uses LDPC (Low Density Parity Check) and BCH (Bose-Chowdhury-Hocquengham) coding. New technology, known as rotated constellations, were introduced to provide additional stability in certain conditions.
The DVB-T2 standard also requires careful maintenance of transmission equipment. Particularly in 32k mode, high power peaks are generated and thus the amplifier's efficiency is minimized (or it may even fail). To limit these peaks without losing information, a special characteristic called PAPR (Peak to Average Power Ratio) reduction was introduced into the standard specification.
Comparison of DVB-T2 and DVB-T
| DVB-T2 | DVB-T | |
|---|---|---|
| FEC | LDPC + BCH | CC+RS |
| Encoding speed | 1/2, 3/5 , 2/3, 3/4, 4/5 , 5/6 | 1/2, 2/3, 3/4, 5/6, 7/8 |
| Constellation | QPSK, 16QAM, 64QAM, 256QAM | QPSK, 16QAM, 64QAM |
| Guard interval | 1/4, 19/256 , 1/8, 19/128 , 1/16, 1/32, 1/128 | 1/4, 1/8, 1/16, 1/32 |
| FFT size | 1K, 2K, 4K, 8K, 8K ext., 16K, 16K ext., 32K, 32K ext. | 2K, 8K |
| Distributed pilots | 1% , 2% , 4% , 8% of total carriers | 8% of total carriers |
| Continuous pilots | 0,35% of the total number of carriers | 2.6% of total carriers |
| Occupied frequency band | 1,7 ; 5; 6; 7; 8; 10 MHz | 5; 6; 7; 8 MHz |
| Maximum speed | 50.34 Mbps | 31.66 Mbps |
DVB-T2 system architecture
The main difference between DVB-T2 and DVB-T systems is that the multiplexer must be connected to a T2 gateway. This T2 gateway receives one or more multiplexes, that is, one per PLP, from the multiplexer and encapsulates them into unmodulated frames. The T2 gateway then sends this content to the DVB-T2 modulator using the T2-MI modulator interface protocol.
DVB-T2 frame structure
DVB-T2 borrows the PLP (or Physical Layer Link) concept introduced in the DVB-S2 specification. A PLP is a physical channel that can carry one or more services. Each PLP may have different speeds data transfer and error protection parameters. For example, you can separate SD and HD services into different PLPs. Another example is the DVB-NGH (New Generation Handheld) standard, which will be based on the ability to use multiple PLPs to enable broadcasting mobile television over DVB-T2.
The DVB-T2 standard defines several profiles:
If necessary, you can define a type (1 or 2) for each PLP, and then combine PLPs of different types in a T2 frame.
The T2 frame begins with preambles P1 and P2. The structure of a T2 frame is shown below.
DVB-T2 modulator interface
The T2 gateway encapsulates the data in an unmodulated (BaseBand) frame. These BB frames are sent to the DVB-T2 modulator using a special DVB-T2 modulator interface protocol MI, the structure of which is shown below.
DVB-T2 testing
Testing of the specification began in the UK in June 2008. The BBC, together with the broadcast network of operators Arqiva and National Grid Wireless, carried out the first test transmission in the DVB-T2 standard. In September 2008, at the IBC (Amsterdam), the DVB stand featured a series of presentations on the latest technologies, celebrating the latest achievements made by the DVB consortium in the field of digital terrestrial TV (DTT). For the first time, visitors to the stand saw HD content encoded using H.264 and delivered through the current end-to-end terrestrial TV broadcasting system using DVB-T2 technologies.
In the first DVB demonstrations, three HD channels were broadcast in one multiplex, each encoded at 11 Mbit/s latest version H.264 encoder. The signal was decoded by the BBC's latest H.264 demodulator and decoder and then displayed on an HD monitor.
At the second presentation, ENENSYS Technologies, NXP Semiconductors and Pace were recognized for the most reliable performance of DVB-T2 equipment. The purpose of this end-to-end demonstration was to show how the standard can handle injected noise and interference and, under such conditions, successfully process a DVB-T2 signal to provide excellent reception.
The first live multi-PLP broadcast was performed during Mediabroadcast's PlugFest in June 2010.
DVB-T2 technical testing in the UK
The BBC and Ofcom have been working on implementation various changes needed to modernize the first multiplex in the Granada region. This included DVB-T2 technical testing, which aimed to validate the DVB-T2 standard and determine the preferred transmission mode for approval in the UK. The tests, which included both laboratory tests and broadcasts, also served to provide a DVB-T2 signal to the receiving equipment being developed, which also needed to be tested.
For this purpose, a transmitter was recently installed for test broadcasting in the DVB-T2 standard from the Crystal Palace television tower. This was followed by the successful completion of end-to-end laboratory tests from the signal source to the receiver screen, made possible through the close collaboration between Arqiva and ENENSYS. ENENSYS provided a real-time DVB-T2 hardware modulator that was connected to Arqiva's transmission equipment.
This ambitious program will also support the DVB-T2 manufacturing community by providing test broadcasts for testing and developing new products. Prototypes of DVB-T2 receivers will soon become available and will be ready for use in a technical pilot project within the coming weeks or months.
Approval of the new DVB-T2 standard
UK telecoms regulator Ofcom has decided to upgrade one terrestrial digital television multiplex (Multiplex B) to operate the Freeview HD service using DVB-T2 and MPEG-4 standards. The upgraded multiplex will be capable of delivering HD services from BBC, ITV and Channel4. It is expected that delivery of six HD services will be possible over time. The first services were launched during the Digital Switchover (DSO) on December 2, 2009.
In Finland, DNA Oy received a license to operate two DVB-T2 multiplexes. The trial began in December 2009 in the city of Lahti. The launch in Finland took place in November 2010.
In Italy, Europa7 launched seven HD channels in the spring of 2010.
In some countries, for example, Austria, Turkey, Serbia, Czech Republic, India, South Africa, Kenya, Sri Lanka, Singapore, Slovakia, Russia, Thailand, Vietnam, Malaysia, Australia have already approved or are seriously considering DVB-T2.
DVB-T2 Glossary
| Abbreviation | Transcript (English) | Transcript (Russian) |
|---|---|---|
| BB | BaseBand | Unmodulated, direct (transmission) |
| FEC | Forward Error Correction | Forward error correction |
| FEF | Future Extension Frame | Frame of future expansion |
| MISO | Multiple Input Single Output | Multiple inputs - one output |
| PAPR | Peak to Average Power Ratio | Peak power to average power ratio |
| PLP | Physical Layer Pipe | Physical Layer Channel |
| T2-MI | T2 Modulator Interface | T2 modulator interface |
| TI Block | Time Interleaving Block | Time interleaving block |
| TFS | Time Frequency Slicing | Time-frequency diversity |
| LDPC | Low Density Parity Check | Low Density Parity Checking |
| BCH | Bose Chaudhuri Hocquengham | Bose-Chowdhury-Hocquingham coding |