The cable modem creates interference with Docsis 3.0 television. DOCSIS technology: what it is and how to connect. Do I need to acquire a long warranty
New version of the DocSis - Docsis 3.1 specification, fully changed the principles of DOCSIS, increasing throughput Channel 50%, performance up to 10 GB / s in the direct channel and up to 2 GB / s in reverse - speeds comparable to transmission of data on fiber.
Docsis 3.1 provides more bits per 1 hertz compared to DocSis 3.0 with the same signal / nozzle ratio
The DOCSIS 3.1 specification was released and successfully tested in the laboratory in 2015. At the beginning of 2016, 5 new cable modem supported by DOCSIS 3.1 standards were certified, providers around the world began to implement and test the equipment of this standard.
But what makes unique Docsis 3.1 compared to earlier versions and how will the test methods change in connection with this? This article discusses the two main technologies used in the latest version of the specification: Multiplexing with orthogonal frequency division of channels (Orthogonal Frequency-Division Multiplexing - OFDM) and a small density code for readiness (LOW DENSITY PARITY CHECK - LDPC). The article also describes how to achieve maximum performance levels.
ORTHOGONAL FREQUENCY DOMAIN MULTIPLEXING
The easiest way to understand OFDM is to remember how Docsis 3.0 works. There for one direct Canal It uses one carrier frequency with a strip of 6 MHz (8 MHz in Europe). To modulate this frequency, the QAM with one carrier (SC-QAM) is used and the characters are transmitted at this frequency strictly sequentially. If problems occur with the reception problems, the modulation must be reduced - not only for this frequency, but also for all other channels on the network. This means that the modulation must be optimized for the worst part of the coaxial network.Unlike SC-QAM, OFDM uses a strip width from 24 to 192 MHz. Inside this strip can be placed up to 8 thousand subcarriers with a width of 25 to 50 kHz each. ( More precisely, 7680 subcarriers of 25 kHz or 3840 subcarriers 50 kHz - approx. translator). All subcarriers are synchronized with each other in time and form a single set of characters. These symbols, in turn, are distributed over subcarrier and time-slots and transmit codewords (codewords).
The main advantage of this approach is that the characters are transmitted simultaneously at different frequencies. This creates some unique opportunities. So, if there was no interference on one subcarrier, OFDM simply excludes it, combining neighboring frequencies. This allows you to continue transmitting data with an optimal level of performance. ( In addition, this method of transmission is significantly less sensitive to narrowband and impulse interference, as they affect only some subcarriers, whereas in the case of a conventional signal, it affects its entire spectrum - approx. translator)
Since the type of modulation in OFDM is set to certain period Time, this technology allows you to control the mutual ratio of the phases of the subcarriers. If one subcarrier is on a peak, then the neighboring can be configured in antiphase, i.e. in zero. This reduces the interference between neighboring subcarriers and allows them to use higher modulation levels for them and, accordingly, increase the total bandwidth of the network. Instead of using one modulation level for the entire range, OFDM allows you to use different modulation levels for each subcarrier. In addition, you can create modulation profiles in such a way as to set individual modulation levels for all subcarriers and have several such profiles.
Modulation - SC QAM
Dedicated channels with a strip width of 6 MHz (8 MHz in Europe).
Each frequency channel is independent of the rest.
Symbols in one channel are transmitted sequentially.
Modulation is optimized for the worse part of the cable network.
Take one subcarrier as an example. Each profile has its own modulation level (for example, 64 QAM, 1024 QAM, 2048 QAM or 4096 QAM). OFDM can use a profile with the highest level for this segment HFC network. In one segment it will be 4096 QAM, in the other it can be 1024 QAM. In the third segment at this frequency there may be too large interference and this section of the spectrum will be excluded from the profile, etc.
Now let's see what happens on this subcarrier to understand the work of all 8000. A separate profile describes a separate subcarrier in order to achieve its maximum performance in each period of time.
As mentioned above, all subcarriers are combined with each other to share characters from which code words are formed. Subcarriers are attributed to each code word symbol and their level of modulation is described by the profile. Profiles, in turn, are prescribed alphabetic designations (for example, A, B, C and D). Thus, it turns out that optimization is made not only for each subcarrier separately, but also for all 8000 subcarriers in the complex.
Instead of optimizing modulation under the worst section of the network, it can be optimized for the best plot at any time. It makes docsis 3.1 much more effective technologythan its predecessors. Where the channel on Docsis 3.0 could transmit 6.3 bits per 1 Hz, DOCSIS 3.1 can reach 10.5 bits per 1 Hz when using modulation 4096 QAM. In a more typical case, when several modulation levels are simultaneously used, DOCSIS 3.1 can reach 8.5 bits per 1 Hz, providing an increase in efficiency by 35% unchanged in the HFC network.
Low Denety Parity Check
Improvements achieved by the use of OFDM would not be possible without using error correction algorithms. DOCSIS 3.0 uses an algorithm for proactive error correction with the Reda Solomon code (FEC) and measures the level of bit errors (BER). Ber refers to one carrier, and OFDM uses a lot. Due to the fact that OFDM distributes transmitted data on a plurality of subcarriers, the use of BER no longer makes sense.DOCSIS 3.1 Instead of FEC uses LPDC. This algorithm works throughout the range and evaluates errors not separate bits, but the codeword is entirely. If such an error can be corrected, LPDC automatically makes it that allows you to use higher modulation levels and significantly reduces the need to re-transmit code words. LPDC brings the channel bandwidth to the theoretical limits described by the Channon Theorem.
But LDPC has one drawback. Since this algorithm changes in real time settings, the system can achieve maximum power values \u200b\u200band modulating levels by adjusting errors. This means that the network will degrade imperceptibly for the operator and at some point the error will become incorrect, and users will notice a reduction in the quality of the service. In order to avoid such a situation, it is necessary to test the system more thoroughly.
Achieve maximum network bandwidth
So that testing has passed successfully it is very important to understand what OFDM consists of. The basis is based on the PLC level - Phy Link Channel, which contains information on how to decode an OFDM signal. Without this level, the modem will not be able to "see" the carrier ofDM and understand how to decode it. The level above is the pointer to the following codeword (NEXT CodeWord Pointer - NCP), which tells the modem about which code word you need to read the following and which profile is used to decode each code word. Next is the profile A. This is a boot profile that every modem Docsis 3.1 should be able to use to "understand" higher QAM modulation levels in other profiles.
Profiles are a simplified situation. To simplify, we assume that profiles use the same modulation on all subcarriers.
Power level parameters, Mer and noise in profile A are selected for the reliable operation of OFDM. If this profile is working, then standard B, C and D profiles can be used. Profiles are different from them can be created by CMTS manufacturers and cable modems at their discretion and their number is not limited.
When transmitting the PLC level information, it is important to achieve the lack of uncorrectable codeword errors (Uncorrectable Codeword Errors - CWE). At the PLC level, the transfer of information must be as reliable as possible, so the power and MER level must be strictly in the specified range. To do this, the parameters of this level must be strictly fixed - the DOCSIS 3.1 specification limits the use for PLC only BPSK or 16 QAM.
If at the PLC level everything works without errors, the NCP parameters are also fixed and should not allow incorrect errors (CWE). If there are loss of messages at this level, the modem will reward information or that even worse, the connection will not be completely. In Docsis 3.1, only QPSK, 16 QAM or 64 QAM can be used to transmit NCP.
Since the profile A is booting, then it is assigned lower modulation levels compared to others: QAM 16 and QAM 64. This is done so that all modems can work even in the worst part of the cable network. The signal with a lower level of modulation can operate at lower power and MER levels. Just as the two previous levels, Profile A must have fixed parameters and not allow incorrect errors. If incorrect errors appear, the modem will switch to DCOSIS 3.0 mode and there will be no increase in efficiency. Profile A can work at higher modulation levels, while you are allowed CWE corrected errors, this is normal, the main thing is not to be uncorrectable.
Profiles are a real situation. OFDM allows you to exclude certain subcarriers and allows everyone to have different modulation levels for different subcarriers. This optimizes the total bandwidth of the channel - each profile has its own exceptions.
When all 3 levels work within the specified limits, you can look at the total bandwidth of the channel. One of the errors at this stage may be measured by the signal level in the entire 32 MHz band. It should be remembered that the total power in this spectrum band is equal to the power of 6 MHz signal taking into account the bandwidth. Thus, the total output signal of the signal is very different from the power of a single carrier with a width 6 (8) MHz. In order to more accurately configure the OFDM signal power, all levels must be measured relative to the signal power with a 6 MHz bandwidth.
OFDM has a few more unique characteristics. The levels of the first and last 6 MHz in the specified OFDM signal band will be about 0.8 dB less than the levels of the remaining subcarriers due to the decline in the protective range (Guard Band). This becomes important when standard devices are used for measurement or if the power is measured in the frequency range of 6 MHz, isolated from the total range. In addition, carrier with PLC approximately 0.8 dB is higher than other subcarriers due to additional pilot signals and data transmitted. Thus, the total range (Flatness) of the OFDM signal compared to a standard signal of 6 MHz will range from 1.6 dB due to the initial and final recession and PLC influences.
In order for the OFDM to work with peak performance, the average power level should not leave the specified limits, Mer must be good and noise levels must be minimal. Noise affects the OFDM signal very much and can lead to the fact that the profiles with high modulation levels will not be used at all.
If all of these requirements are followed, it becomes possible to use profiles with high modulation levels. It is important that the parameters are fixed within the profile (Locked). High modulation profiles may have a number of corrected errors (CWE), as it is not as critical, as for lower levels, but incorrect errors will result in maximum performance will be achieved. For example, if the C profile has uncorrectable errors, the profiles D and higher will not be able to use higher modulation than the profile C. To achieve high modulation levels, the HFC network must be clean and not allowed incorrect errors (which is true for earlier versions. Docsis).
And what about Upstream?
DOCSIS 3.1 For the reverse channel uses OFDMA - Orthogonal Frequency-Division Multiple Access.Separate subcarriers in OFDMA may turn off to ensure reverse compatibility with DocSis 2 / 3.0
Comparative Table Docsis 3.0 and Docsis 3.1
Conclusion
Docsis 3.1 solves the main dilemma that stood before operators for long years: "spend money on the full modernization of the entire cable network or gradually make changes to the existing network?" Using OFDM and LDPC technologies, operators can significantly increase network bandwidth when minimal upgrade it.It is enough to modernize the physical network structure in order to increase its efficiency (speed and bandwidth) by 35% using Docsis 3.1. It will also give operators an extra time for further gradual upgrades, which, in turn, will give an opportunity to further increase bandwidth.
However, operators need to be quite gently approaching the implementation and testing of DOCSIS 3.1. If it is wrong to do this, then there will be no improvement in comparison with DocSis 3.0. Add Tags
So! Subtleties of buying a router:
If you are looking for best speeds The Internet for your home, cable Internet service - is still a good choice for most users. But what does not know most users, this is what they sometimes pay much more than they should for cable broadband - especially if they use the equipment proposed by the cable company.
Indeed, many users can save up to $ 5 per month - more than $ 60 per year - on their current cable Internet connection. To this end, I collected the five most popular questions from readers that I usually receive on the subject of the cable Internet. I included both the short and deployed answers to each question, including proposals on how to save on your monthly account (spoiler: Buy, do not take your cable modem for rent).
What cable modem do you really need?
Short answer:
Choose one that is able to maintain the speed of the tariff plan to which you have subscribed. If you doubt, select the one that supports Docsis 3.0. Of these, it is worth choosing not the most expensive, and for sure - from the list of supported equipment of your provider.
Note: Your actual Internet connection speed depends on the speed of the modem, router, Wi-Fi connections, switches, and the user's most user device, and by the way on the tariff plan that you have chosen. Most of the time what you pay is the smallest common denominator, and does not determine real speed Your Internet connection.
Long answer:
The cable modem is a device that receives an Internet signal from the cable provider and turns it into a data signal that can understand computing devices, such as personal computers, tablets or smartphones. The modem comes with a coaxial connector of the "socket" type - just like that behind your HDTV - and LAN port. This means that with the modem, you can connect only one computer with the Internet. To connect more devices, you will need to get a Wi-Fi router. (More on this below.)
Modems are usually very simple devices, and because of this, most of them practically do not differ from each other. The biggest difference between them is the standard that they support, which determines the velocities of the Internet, which it is capable of maintaining how to download it and for returns. This standard is called D aTA OVER Cable Service Interface Specification, or docsis.
Currently, the market has DocSis 1.x, Docsis 2.0 and Docsis 3.0 modems. Both DOCSIS 1.x (mostly the outdated standard) and DOCSIS 2.0 support only one channel, which supports the loading speed of 43 Mbps and the rate of return 10 Mbps and 31 Mbps, respectively.
DOCSIS 3.0 (which is inversely compatible with older standards) The speed of one channel remains 43 Mbps to load and 31 Mbps for returns, but modems are now capable of processing multiple channels (channel binding) at a time. A typical Docsis 3.0 modem usually offers four or eight channels for loading, which gives a speed of 172 Mbps or 344 Mbps, respectively. For recoil, they usually support four channels, offering speed up to 124 Mbps. Relatively soon will appear DocSis 3.0, which can handle even more channels.
Your actual Internet speed also depends on what you pay for; The faster you want, the more monthly payment. If you pay for the Internet tariff with a load speed of 30 Mbps or less, there is a chance that you will be enough DocSis 2.0 modem, which costs almost half of the price of DocSis 3.0. Moreover, if your tariff is called: lightweight, main, starter or standard, then you will certainly have a modem DocSis 2.0, but if you choose more high level, such as: Turbo, Premier, Super or Extreme, then Docsis 3.0 modem with four or even eight download channels is simple.
Please note that all broadband services offer a much slower rate of return rather than download speed. Most of the time, the majority of tariff plans offer the rate of return of only 10 Mbps. In addition, it is necessary to check whether the modem supports the DocSis standard and is in the list of approved Internet provider modem, or otherwise it may not earn at all. In addition, sometimes one ISP comes across, which does not allow the use of consumer modems in its network.
In a typical home network, you must connect the modem with the WAN port of the Wi-Fi router using (preferably) a short network cable.
Rent or buy?
Short answer:
When it is possible, it is better to purchase your own modem. It is a good savings for a long time.
Long answer:
When you register an application for connecting in the cable Internet service system, the provider often includes a modem in the service package. This device is usually not free; It costs you a monthly rent. Often, the provider clearly does not tell you about it at the conclusion of the contract, and the same thing you can avoid this using your own equipment. This modem rental fee may first be not so big, but then it usually increases and sometimes up to $ 10 per month, which may not be quite interesting for you.
It does not seem to be a big amount, but for a long time, it is generally not so little. And if you plan to use the Internet for one year, much better to purchase your own modem, which costs between $ 50 and $ 100, and new. You can buy one before signing the contract or any time after that. In the latter case, make sure that you return the modem service providers, or otherwise you will pay for it. From my personal experience, It is better to bring this device and return it personally at the nearest subscriber service center to avoid his loss.
Even if you are planning to use the Internet from this operator for a short time, it's still a good idea to purchase your own modem. You can always use it again for a new connection, only if the connection type will be the same, or sell it and return most of what you paid for it, back.
In the continuation of the conversation about the sale of an old modem, you can also purchase a used one.
New, used, or after return?
Short answer:
It never hurts to buy a completely new modem, but you can also save much, and do not lose anything if you get used or after return.
Long answer:
Cable modems are simple devices and after the initial installation, they usually do not touch them, they simply remain in the same place. You will never change the settings anymore or establish anything. Also in modems no moving parts (most of them do not even have fans). Therefore, they can work for a long time and simply outdated before they actually stop working. This means that the acquisition of a completely new modem will not bring you more benefit than getting the returned modem of the same type.
In truth, the most frequent reasons for the return of modems are either the lack of further need for them, or the inconsistency of the appearance of the interior design devices. And from the inside they practically do not differ from new devices. In many cases, the modem that the Internet provider offers you, can be just after return, and previous customers used this device. In the modehem market, after returning up to two thirds of the price of the new price.
Acquisition of used modems is associated with a higher risk that is associated with previous owners. If the modem did not drop and there are no noticeable external damage, it should work well. However, if you buy a used, make sure you can return it after a few days, because if it can work for several days without problems, that is, a chance that it will work for a long time. In turn, a used modem tends to cost about a third of the price of the new one.
From my personal experience, the most frequent thing breaks in the modem is a power adapter, which is quite simple to replace.
Create a modem with a built-in router or two separate devices?
Short answer:
If you are not provided with a free provider of a modem with a built-in router (which is unlikely to), always ask for a modem and take a separate router separately. After receiving the modem, simply take one of the routers, not the most expensive, according to your need. If you really want a combined device for practical reasons, such as a decrease in the number of wires, Motorola SBG6782-AC SURFBOARD EXTREME is yours the best choice at the moment. Make sure you first read its full review.
Long answer:
As mentioned above, you need a router to share an Internet connection from a cable modem more than on one computer; total amount - Up to 254 devices for most routers. You simply have to connect the LAN modem port with the router WAN port using a power cable. This is the preferred installation and also the most popular, as it gives you the flexibility and the ability to customize your network based on your needs and your budget.
| Equipment | Behind | Against | The best choice |
|---|---|---|---|
| Separately modem I. Wi-Fi Router | Flexibility in price, functions, performance functions, flexibility in updating, replacing the new one. | More wires and need two outlets | The modem approved by the provider and one of the top routers |
| Modem / Wi-Fi router two in one | One device, you need one outlet, fewer wires | Lack of flexibility, the built-in router is not always the best, difficulty in updating the device is more expensive and will have to be changed entirely. | Motorola SBG6782-AC SURFBOARD EXTREME. |
There are also combined devices that consist of a modem and router in one box. I usually do not recommend them for two main reasons. First, it is dangerous. If any part of the device, modem or router module, is damaged or out of fashion and outdated, you must replace the device entirely. The second reason is, a hundred in most existing combined devices, a portion of the router is usually very limited by making your home network less flexible and functional than it could be.
If you are doing business, try to avoid the acquisition of a combined device, because its part of the router probably will not be all the configuration parameters required for your business. The capable system administrator can still make everything work normally by adding another router to the network, but it is much more work than just to purchase a modem immediately and the correct router.
Do I need to acquire extended warranty?
No, it is not worth it. Cable modems (or combined devices), even returned, usually come with a factory warranty ranging from 90 days to two years. Since these are simple devices, if anything unusual must occur, for example, a defective device will fall, or you will come across problems when it is installed, this will happen immediately after purchase. After that, it is little likely that something like this will happen.
Buying an extended warranty is just a waste of money. Instead, it is better to use this money to buy a means of protection against voltage jumps for your home network devices, as the races of voltage of the power grid and lightning are the two most common causes that damage the equipment. It is also better to install the device in the open space and where it is dry to avoid damage caused by water or overheating.
Do I need to try to bring down the price?
Definitely!!
This is the truth that most of us live in the area that is served by just one cable company, but there are other alternatives, such as FDDI, satellite or DSL (which is almost everywhere and usually cheaper). You must use them as your levers in negotiations with a cable company for the best deal. You can also get the best conditions, signing packets with a variety of services, such as TV, Internet and telephone, although not subscribe to what you do not plan to use.
Some cable companies can give you good conditions for some time, for example, for six months, and then start taking a complete tariff with you, which up to 50 percent higher. You can always type the operator or look at the site when this period ends, and ask about existing or new promotions, or you can simply break the contract and then subscribe. It's worth nothing, and you already have a modem.
Most importantly, check from time to time when there are new promotions or discounts, or simply call them to ask the lower rate. It works. In the end, you can't get what you have not asked.
That's all for now. If you still have questions, you can safely write me in,
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Another 3-4 years ago, the cable operator firmly knew that the best solution for providing TRIPLE PLAY (television, Internet access and telephony) is a television cable network with a reverse channel for data transmission using DocSis technology. Such a concept of cable networks was supported by everything without exception manufacturers of CATV equipment, providing the possibility of equipping the entire active distribution equipment with passive or active reverse channel modules. In accuracy, following such a concept, a huge number of large and small cable networks were built in Russia. Not in all built networks, the reverse channel was actually used, but the potential ability to activate the reverse channel is available from almost any cable operator using equipment such as Teleste, Wisi, Hirschmann, Arcadan, Fuba, C-Cor, GL, Vector and many others .
In Russia, there are examples of quite successful commercial projects Triple Play, performed precisely on such technology, for example, in Kostroma, many thousands of subscribers of the Verkhnevolzhsky branch of the Centhelecom cable network receive not only multi-program cable television and the Internet, but also a telephone service using cable modems, with telephone Adapters. It would seem that by introducing the Triple Play service pack (or, more often, Double Play, i.e. without telephony) on the basis of at one time the advanced technology DocSis 2.0, the cable operator could not feel quite confident in the market. However, in the last 3-4 years, the market situation is rapidly changing, and in the new conditions the cable operator, which has a classic HFC network with a reverse channel, is already clearly inferior to operators with a higher technological level.
Recently, not only in Moscow and other major cities of Russia, but also in small regional and district centers Competition in the service market broadband access The extremely aggravated. If several years ago, operators were enough to "capture" the most attractive territories and geographically divided the zones of influence, now the situation is already quite common practice when several multiservice operators operate at once. Moreover, large companies We start expansion or buy regional players, counting faster to cover the market.
We will list briefly essential trends in the Russian market of broadband services, which already take place or are expected in the very near future:
- tightening competition even in small settlements;
- access to regional markets of large all-Russian players;
- mass consolidation (combination, absorption) of operators;
- a significant increase in the speed of access and quality of service provision;
- the emergence of new services (HDTV, VOD, content on request, etc.);
- the emergence of new business models, penetration into the television advertising market of products and services of non-mask (target) demand, etc.
Naturally, in conditions of such acute competition, the best perspectives have operators providing subscribers and corporate customers the most advanced level of broadband access. In connection with the increased modern requirements of the market, the widespread construction of metroethernet networks, providing the subscriber who was unprecedented earlier access speed of 100 Mbps, and large corporate customers can connect directly to the IP highway, in which speeds range from 1 to 10 Gb / s. Such high access speeds make it possible to provide a variety of previously inaccessible services, for example, IPTV in high-resolution format immediately for several TVs in the apartment, network ultradynamic games and much more.
It is clear that the multiservice operator, building its network "from a clean sheet," has good reasons to build a network using the "Optics to House" technology with a parallel gigabitethernet network, physically combined in a common building infrastructure with a television network, simply speaking, for each logical The network is highlighted in its fiber in the main optical cable. But in what situation there is a cable operator today, which has long built his broadband network on the basis of far from obsolete technologies with developed infrastructure and a reverse channel and inserted considerable funds to its construction? Could it provide subscribers the speed of access commensurate with the proposals of METROETHERNET operators? Can he provide the latest ultra-free services on the basis of extremely high access speeds?
Honestly responding to these questions, we must state that today in the conditions of such acute competition and the emergence of the latest advanced access services cable operator, which has a technological basis for transmitting data on the basis of a recently recent version of DocSis, i.e. Docsis 2.0, can no longer answer modern requirements Market. Using the DOCSIS version of the version is not higher than 2.0, deployed from most operators, it is impossible to achieve data transfer rates of more than 55 Mbps on a fairly large group of subscribers, and in fact for one user - no more than 25 Mbps.
Cable operator starts to acute today that DOCSIS 2.0 technology puts development limitations additional services, namely high-speed and ultra-high-speed Internet access, IP telephony, etc. Under the conditions of rigid competition with MetroETherNet operators, the cable operator is experiencing increasing difficulties, having no speed of access to the subscriber as the main argument, but more accessible tariffs, i.e. In any case, reduces its income. In addition, the HFC network requires significant staff efforts to bring it to normal condition and maintaining in humiliated state in most cases. Thus, the cable operator on one side continues to carry significant operating costs, and on the other hand, can not make an adequate competitive offer.
In the current situation, he actually has 2 ways:
1) or look for all existing opportunities for a significant increase in access speed, without changing the architecture and infrastructure of the network, that is, to use much as much as possible, as we will see on, DOCSIS technology reserves;
2) or become an Ethernet operator, i.e. Build a parallel Ethernet network and operate at once 2 networks, producing significant capital investments and increasing the operating expenses, which dramatically reduces today's profit and moves back to the future payback period.
Generally speaking, for the CATV operator, it is quite logical to use exactly the technology that the community of large cable operators and manufacturers of telecommunications equipment, namely the DOCSIS standard. The authors, honestly, have never heard that, for example, Comcast would quite seriously consider the issue of moving to MetroetherNet, as, however, no one heard that any major Ethernet provider felt even the middle cable or telephone operator in North America. Those. In the US or, say, in Germany, using the cable operator of another technology, except DocSis, namely Metroethernet, PON, etc., is considered anti-abnormal. A natural approach is considered when the cable lies and is used until a broadband signal can be completely successfully transmitted.
Also, recently, the operators are increasingly moving to digital television broadcasts, while using complexes to provide services, in no way interacting with each other, except that are within one rack and using the same network. The generalized solution scheme used by operators in this case is presented in Fig. one.
Fig.1
So, how is a far cable operator can move the technological limitations of the Docsis 2.0 standard? The answer lies on the surface - not so long ago, blinder the efforts of the CABLELABS consortium, the newest standard appeared - Docsis 3.0 With its European version of Eurodocsis 3.0, which, apparently, solves all the urgent questions and, as usual, does not require construction new network. Moreover, all subscriber devices already installed in subscribers can continue to be used with new DOCSIS 3.0 stations, although they will work with them according to its previous version.
The main advantage of DOCSIS 3.0 is the ability to combine several frequency channels, providing much higher access speeds. Explaining the principle of operation of a new standard, usually lead a graphic illustration showing that when combining several frequency channels, a kind of "pipe" is formed a much larger diameter than the "pipe" of a separate channel. So, the combination of 4 frequency channels in Downstream allows you to reach speeds over 200 Mbps.
So, the most important differences between the 3rd version of DocSis from the 2nd are to unite channels (Channel Bonding) downstream and in the union of the Upstream channels. DOWNSTREAM Channel Combination is the most an important feature Docsis 3.0 and today is supported by a number of cable modems manufacturers. Already today you can purchase custom modems that support combining, for example, 3 DOWNSTREAM channels, i.e. Today you can give a subscriber to 150 Mbps, see Fig. 2. And this is something. This is exactly what knocks out the trumps from the hands of competitors of the skirting operator! In addition, Docsis 3.0 provides:
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Fig. 2. |
- extended Multicast functions;
- iPv6 support;
- support improved AES encryption method;
- additional control functions.
Features each version of DocSis for access speed, see Table. one.
Also cablelabs made innovative changes to the CMTS architecture. Now in the new QAM standard, modulation is physically separated from Docsis Mac. The CMTS station is still between the Master IP and telematic services on the one hand, and user modems on the other; The difference is that physically the DOWNSTREAM modulation unit is separately. This concept is called M-CMTS (Modular Cable Modem Termination System), see fig. 3, and this gives a lot of advantages.
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First, it effectively reduces the cost of downstream-modulation. Secondly, finally, you can combine digital broadcasting from IP through one QAM. Moreover, manufacturers are unleashed by hand to implement DVB processing options on one platform.
At the moment, many manufacturers stated that they support a new standard, but so far no one has implemented all the features of DocSis 3.0, so all implementations are called "PreDocsis 3.0". However, the main task is to provide compared to DocSis 2.0 many times higher speed of incoming subscriber traffic (from 100 Mbps) - CMTS stations in the PREDOCSIS 3.0 version are successfully solved. Further Upgrade until the full version 3.0 will be programmatically. In the view of the authors, the most impressive results in the practical implementation of DOCSIS 3.0 systems have two vendors from the USA: Bigband Networks and Casa Systems.
The first vendor is Bigband Networks, unlike all other vendors, provides support for a new standard based on its DOCSIS 2.0 CUDA 12000. Thanks to the innovative Meshflow architecture, which ensures the processing of all traffic not in the nucleus, but distributed by station modules, which ensures Unclear and enhanced reliability and availability of the entire system, new features of DocSis 3.0 are conceptually easily combined with CUDA 12000 and thereby make it possible to make just upgrade software to DocSis 3.0, all available interface modules can be used in M-CMTS and on. Especially lucky those who have already acquired CUDA 12000 and installed them. For these operators, migration in Docsis 3.0 will be the easiest and most cost effective. It is very difficult on the equipment of other vendors.
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Fig. 3. |
The second vendor is Casa Systems, which provides an extremely high DOWNStream and Upstream density in one-time device. In particular, such a configuration is supported as 32 DS × 16 US. Such high density is achieved thanks to the applied innovative solutions and high engineering art engineers. In fact, at the moment, this is the only Pizza Box manufacturer for Docsis 3.0. It is advantageously distinguished by this platform that it is used and under DOCSIS, and under DVB, and under IPTV. It is so universal solution that it is difficult to choose an equivalent to him. Most likely, it will be a whole rack with different telecommunications equipment, as well as with many software solutions. This solution is really unique also by the fact that the operators choosing the MetroETherNet network construction path can use such a device and subsequently, after a complete transition to Ethernet, as a scrambler and a QAM modulator for broadcasting in DVB. It should be noted that, in contrast to many others, the two producers mentioned are not limited to declarations of readiness for the release of CMTS Docsis 3.0 in some happy future, and already really place orders for the production of such CMTS.
For example, Bigband Networks currently supplying and installing the M-CMTS modular head station to a large cable operator Multikabel (Holland), which is the first company in the world, a practically deploying data network based on DocSis 3.0. At the same time, CASA Systems offers a flexible and effective solution to the supply of DOCSIS, as well as QAM-modulation in conjunction with PSI / SI-processing, CAS Symulcrypt support, and the like. On one compact 1U compact platform !!! Thanks to this solution, the operator may acquire one platform under both tasks, as well as flexibly adjust the strip under the service as needed.
Now and implement IPTV through this platform, incl. And through DocSis, absolutely real. This, for example, refers to such a service as "video on request", a strip of which can be highlighted in QAM. Deploying the M-CMTS platform makes it possible to use the UEQ (Universal Edge QAM) more efficiently. To obtain new advantages of DOCSIS 3.0, you must purchase a new modem. Not every user wants to pay for it. It is easier for this to make a small business, for which the price of the question is small compared to new features, while the majority of subscribers will weigh and reflect. Nevertheless, this technology allows cable operators to keep up with the times and more effectively disappear from the pressure of competitors. For example, M-CMTS manufactured by Bigband Networks and CMTS C2200. Casa Systems makes it possible to offer cable operators on one chassis of access speed over 100 Mbps with subscribers with DOCSIS 3.0 modem and speed of about 25 Mbps, who has the current generation modem.
Deploying the same M-CMTS architecture as the initial stage of movement strategy to DOCSIS 3.0, allows cable operators to grow as the market needs - add capacity and functionality for the availability of demand.
Thus, the new standard gives cable operators the ability to develop a DOCSIS standard, to offer high-speed access over 100 Mbps on its basis now, successfully competing in the market for access services, offering a range of services requiring a wide band, incl. DVB and IPTV on the same platform using a flexible M-CMTS architecture. By purchasing now solutions based on a preliminary version of PREDOCSIS 3.0, subsequently without replacing the hardware operator can go to the completed DOCSIS 3.0 standard, only changing software. This allows you to effectively protect the investments invested in the construction of the HFC network.
In our opinion, only with the advent of the third version of Docsis, this technology has done a truly strong jerk forward, ensuring the introduction of new high-speed services, previous versions only tried to adapt the RTV networks for Internet access, using its percentage resources on 5 just as a person Uses the meager part of the capabilities of its brain. Docsis 3.0 allows you to use the RTT network at full power.
We get acquainted with the features of the modem, as well as data rates on DOCSIS 3.0 technology, in the network of the company "Will". How practical speed corresponds to the stated provider? How "leads" himself a modem in work, as well as what are the conditions for the provision of a device for home and business users?
Appearance and connection
I will make a reservation immediately - modems that support DOCSIS 3.0 technology from the "Will" of several species, and all of them are provided to users on certain conditions. But let's not to delve into the conditions of providing devices to the end consumer, and consider the features of a particular model - a device that stayed with me on testing - Thomson TCM 470.
So, the device body is implemented from two colors of matte plastic - black and white. Of course, this combination cannot be called such that "clings", but the device itself is pretty and not to take it away.
To say that in the build of the housing, black or white color of plastic is dominated - and the other is equal: the lower part of the housing, as well as the front and rear walls are made of black plastic, while the upper part, as well as the right and left side walls white.
Although the top of the modem and white, however, dust remains on the surface. Personally, I wiped the outer part of the modem case, almost every third day, together with the room cleaning, in which the device is located.
The device assembly is wonderful. Despite the fact that the white part of the hull seems to be "dressed" on black, besides, it is already quite easy to feel that we are dealing with durable and in some extent massive materials, the gaps in the end turned out to be minimal, not to mention the backlash. Nothing is staggering, does not crunch and other examples of the galant assembly is no different.
On all walls of the case, except facial, a lot of fine holes are implemented. These are the so-called ventilation grids. Air ventilation system silent. It is impossible not to note the fact that the possibilities of the ventilation system implemented in this modem are very modest - when working at least 9-10 hours, the device body is noticeably heated. It is good and the fact that even a tangible heating on the functionality of the device will not affect an even account.
On the front panel there are various indicators of displaying the status of processes in the system. It is not necessary to know a clear destination, it is enough to understand a simple thing - in order for the device to work correctly, it is necessary that the POWER, DS, US indicators, and online burned without winking, and blinked only an exceptionally indicator with the signature of LINK. If this task is performed, then the device works correctly.
If the user connects to the Wi-Fi modem router or another "distributor" of the signal, it must "reset" the basic modem settings that the system automatically assigns the modem during the previous connection. To do this, it is enough just to click and release the RESET button, which is on the back side panel. After that, only a reboot of the computer is needed, during which the router is best and to connect is a matter of several minutes.
In addition to the RESET button on the same panel there is an output to connect a cable that comes from the distribution panel in the house or business center. Here is the port for connecting the cable connecting directly to the modem itself with a computer or laptop plus the device's power button.
On the bottom of the working panel, in addition to the set of ventilation holes, there is a sticker with various technical data on the device, as well as two gaps for fastening the modem on the walls on the wall or vertically located platform.
Practical speed
The NetMeter utility, with which all calculations were performed, is interesting not only solely as speed tester. We have a fairly simple and overnight in the development of traffic "Registrar" of traffic, with which any user can conduct detailed statistics of the spent traffic for the period - one day, month or just a session.
Another, no less interesting feature, this tester is the simplest way to test the Internet speed in mode. various features Traffic consumption. For example, personally I really liked the ability to track speed when playing streaming video in various formats. To do this, I used the player Videolan VLC Media Player 0.8.5, which, as you know, works with almost all formats, besides it is easy to launch a media file. All videos were reproduced by resolving 720x576 points.
Average traffic consumption when playing video in VOB format was 1.15 Mbps. During the playback of the DivX file, the maximum speed was 415 kbps, and during playing video in MPEG4 format, the peak velocity for the "flow" was 1.85 Mbps. The volume of each of the files did not exceed 1.5 GB.
Regarding speeds, the situation in this case is as follows. On the Upload was easily managed to achieve the "up to 3 Mbps" provider. During the measurement, the speed was in the "floating" state - from 2.2 Mbps to 2.9 Mbps.
As for download, in this case the scatter in the indicators turned out to be the following. During the so-called peak loads on the network, the speed did not exceed 17-19 Mbps, and in the period from 7-8 am and to 17-18 hours, the indicators were fluided from 30-35 Mbps to 55 Mbps.
Terms of provision
For private users, the company "Volya" provides modems exclusively on rental rights - to buy them no longer. At least for now.
The cost of renting the provider is included in the cost of one or another tariff plan. Depending on what speed, the subscriber wants to order, a multiple device is provided to choose from, among which the Thomson TCM 470, and some others described above, in particular Thomson TCW 690/710, Arris WBM750B / NU DOCSIS 3.0, etc.
For business customers, the conditions are different. It is allowed both rental of devices and their purchase. At the moment, the list of devices offered by the provider is limited to two ARRIS WBM750B / NU and SCIENTFIC ATLANTA EPC 3000. The price of the first 389 hryvnia. The second will cost 699 hryvnia. The cost of renting a modem business user is similar to the cost of renting the device by the domestic user.
Some results
Despite the fact that in practice, the speed in the download mode does not reach the declared 150 Mbps provider, however, the speed in DocSis 3.0 is an order of magnitude higher than the previous standard. Watch the video on the same YouTube in high resolution or on-line HD-film, as well as perform a lot of other tasks associated with the need to have a high-speed Internet user can with a clearly large comfort than in the preceding standard mode.
A little annoying that for legal entities Today, this service is still quite expensive. Although its popularity is gaining momentum, and therefore it is possible that at least in the direction of increasing the popularization of the service, the company will reduce prices in the foreseeable future.
pros
- Almost 100% coating in Kiev;
- The only provider providing the Internet in the DOCSIS 3.0 standard;
- The interesting proposal of "Absolute will" is at a speed of up to 150 Mbps for 200 hryvnia per month for home users. This package is particularly interesting when buying new services "TV + Internet" (http://volia.com/bundle/price). In this case, the subscription decreases almost twice. For example, for the same 200 hryvnia, you can buy the so-called "Bandle" - a basic TV package (more than 80 channels) and an Internet package at a speed of up to 150 Mbps.
- A wide selection of tariff plans in general;
- Good speed to view video in streaming mode;
- Stable connection
Minuses
- For business customers, quite high cost;
- Restrictions in speeds are possible when the Fair Use Policy is violated for home users. Although there is a plus - less than 1% of users fall into this restriction.