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64-1096: Data Over Cable Service Interface Specification ( DOCSIS ) is an international telecommunications standard that permits the addition of high-bandwidth data transfer to an existing cable television (CATV) system. It is used by many cable television operators to provide cable Internet access over their existing hybrid fiber-coaxial (HFC) infrastructure. DOCSIS was originally developed by CableLabs and contributing companies, including Arris , BigBand Networks , Broadcom , Cisco , Comcast , Conexant , Correlant, Cox , General Instrument , Harmonic , Intel , Motorola , Netgear , Terayon , Time Warner Cable , and Texas Instruments . Several DOCSIS versions can co exist by using frequency division multiplexing and separating new DOCSIS versions from old ones according to their operation frequencies. As frequency allocation bandwidth plans differ between United States and European CATV systems, DOCSIS standards earlier than 3.1 have been modified for use in Europe. These modifications were published under

128-439: A public key infrastructure (PKI), based on digital certificate authorities (CAs) of the certification testers, currently Excentis (formerly known as tComLabs) for EuroDOCSIS and CableLabs for DOCSIS. Typically, the cable service operator manually adds the cable modem's MAC address to a customer's account with the cable service operator; and the network allows access only to a cable modem that can attest to that MAC address using

192-403: A "mid-split" or "high-split". A mid-split increases the upstream frequency range to 5–85 MHz, supporting a total shared upstream capacity of ~450 Mbit/s (assuming 4 SC-QAM + OFDMA channels) for the service group. A high-split increases the upstream frequency range to 5–204 MHz, supporting a total shared upstream capacity of ~1.5 Gbit/s (assuming 4 SC-QAM + OFDMA channels) for

256-547: A combination of frequency-domain and time-domain multiple access, where the resources are partitioned in the time–frequency space, and slots are assigned along the OFDM symbol index, as well as OFDM sub-carrier index. OFDMA is considered as highly suitable for broadband wireless networks, due to advantages including scalability and use of multiple antennas ( MIMO -friendliness), and ability to take advantage of channel frequency selectivity. In spectrum sensing cognitive radio , OFDMA

320-405: A dedicated analog circuit-switched service. Other advantages include better voice quality and integration to a Voice over Internet Protocol (VoIP) network providing cheap or unlimited nationwide and international calling. In many cases, digital cable telephone service is separate from cable modem service being offered by many cable companies and does not rely on Internet Protocol (IP) traffic or

384-436: A given location, cable distribution lines must be available on the local utility poles or underground utility lines. Coaxial cable brings the signal to the customer's building through a service drop , an overhead or underground cable. If the subscriber's building does not have a cable service drop, the cable company will install one. The standard cable used in the U.S. is RG-6 , which has a 75 ohm impedance , and connects with

448-543: A high elevation. At the outset, cable systems only served smaller communities without television stations of their own, and which could not easily receive signals from stations in cities because of distance or hilly terrain. In Canada, however, communities with their own signals were fertile cable markets, as viewers wanted to receive American signals. Rarely, as in the college town of Alfred, New York , U.S. cable systems retransmitted Canadian channels. Although early ( VHF ) television receivers could receive 12 channels (2–13),

512-466: A higher rate. At the local headend, the feed signals from the individual television channels are received by dish antennas from communication satellites . Additional local channels, such as local broadcast television stations, educational channels from local colleges, and community access channels devoted to local governments ( PEG channels) are usually included on the cable service. Commercial advertisements for local business are also inserted in

576-405: A local VHF television station broadcast. Local broadcast channels were not usable for signals deemed to be a priority, but technology allowed low-priority signals to be placed on such channels by synchronizing their blanking intervals . TVs were unable to reconcile these blanking intervals and the slight changes due to travel through a medium, causing ghosting . The bandwidth of the amplifiers also

640-463: A microwave-based system, may be used instead. Coaxial cables are capable of bi-directional carriage of signals as well as the transmission of large amounts of data . Cable television signals use only a portion of the bandwidth available over coaxial lines. This leaves plenty of space available for other digital services such as cable internet , cable telephony and wireless services, using both unlicensed and licensed spectra. Broadband internet access

704-564: A rarity, found in an ever-dwindling number of markets. Analog television sets are accommodated, their tuners mostly obsolete and dependent entirely on the set-top box. Cable television is mostly available in North America , Europe , Australia , Asia and South America . Cable television has had little success in Africa , as it is not cost-effective to lay cables in sparsely populated areas. Multichannel multipoint distribution service ,

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768-455: A receiver box. The cable company will provide set-top boxes based on the level of service a customer purchases, from basic set-top boxes with a standard-definition picture connected through the standard coaxial connection on the TV, to high-definition wireless digital video recorder (DVR) receivers connected via HDMI or component . Older analog television sets are cable ready and can receive

832-766: A series of signal amplifiers and line extenders. These devices carry the signal to customers via passive RF devices called taps. The very first cable networks were operated locally, notably in 1936 by Rediffusion in London in the United Kingdom and the same year in Berlin in Germany, notably for the Olympic Games , and from 1948 onwards in the United States and Switzerland. This type of local cable network

896-417: A special telephone interface at the customer's premises that converts the analog signals from the customer's in-home wiring into a digital signal, which is then sent on the local loop (replacing the analog last mile , or plain old telephone service (POTS) to the company's switching center, where it is connected to the public switched telephone network ( PSTN ). The biggest obstacle to cable telephone service

960-605: A type F connector . The cable company's portion of the wiring usually ends at a distribution box on the building exterior, and built-in cable wiring in the walls usually distributes the signal to jacks in different rooms to which televisions are connected. Multiple cables to different rooms are split off the incoming cable with a small device called a splitter . There are two standards for cable television; older analog cable, and newer digital cable which can carry data signals used by digital television receivers such as high-definition television (HDTV) equipment. All cable companies in

1024-529: A valid certificate issued via the PKI. The earlier BPI specification (ANSI/SCTE 22-2) had limited service protection because the underlying key management protocol did not authenticate the user's cable modem. Security in the DOCSIS network is vastly improved when only business critical communications are permitted, and end user communication to the network infrastructure is denied. Successful attacks often occur when

1088-498: A variant of DOCSIS 1.1 that is designed to operate in Japanese cable systems. The ITU-T Recommendation J.122 main body corresponds to DOCSIS 2.0, J.122 Annex F corresponds to EuroDOCSIS 2.0, and J.122 Annex J describes the Japanese variant of DOCSIS 2.0 (analogous to Annex C of J.112). DOCSIS provides a variety of options available at Open Systems Interconnection (OSI) layers 1 and 2—the physical and data link layers . Bandwidth

1152-835: Is 30.72 Mbit/s per 6.4 MHz channel (approximately 27 Mbit/s after overhead), or 10.24 Mbit/s per 3.2 MHz channel (approximately 9 Mbit/s after overhead). DOCSIS 3.1 supports a downstream throughput with 4096-QAM and 25 kHz subcarrier spacing of up to 1.89 Gbit/s per 192 MHz OFDM channel. The upstream throughput possible is 0.94 Gbit/s per 96 MHz OFDMA channel. Tables assume 256-QAM modulation for downstream and 64-QAM for upstream on DOCSIS 3.0, and 4096-QAM modulation for OFDM/OFDMA (first downstream/upstream methods) on DOCSIS 3.1, although real-world data rates may be lower due to variable modulation depending on SNR. Higher data rates are possible but require higher order QAM schemes which require higher downstream modulation error ratio (MER). DOCSIS 3.1

1216-516: Is a multi-user version of the popular orthogonal frequency-division multiplexing (OFDM) digital modulation scheme. Multiple access is achieved in OFDMA by assigning subsets of subcarriers to individual users. This allows simultaneous low-data-rate transmission from several users. OFDMA is often compared to the combination of OFDM with statistical time-division multiplexing . The advantages and disadvantages summarized below are further discussed in

1280-584: Is a possible approach to filling free radio frequency bands adaptively. Timo A. Weiss and Friedrich K. Jondral of the University of Karlsruhe proposed a spectrum pooling system in which free bands sensed by nodes were immediately filled by OFDMA subbands. OFDMA is used in: OFDMA is also a candidate access method for the IEEE 802.22 Wireless Regional Area Networks (WRAN), a cognitive radio technology which uses white spaces in television spectrum, and

1344-422: Is achieved over coaxial cable by using cable modems to convert the network data into a type of digital signal that can be transferred over coaxial cable. One problem with some cable systems is the older amplifiers placed along the cable routes are unidirectional thus in order to allow for uploading of data the customer would need to use an analog telephone modem to provide for the upstream connection. This limited

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1408-454: Is executed by Belgian company Excentis (formerly known as tComLabs), while DOCSIS certification testing is executed by CableLabs. Typically, customer premises equipment receives "certification", while CMTS equipment receives "qualification". The ITU Telecommunication Standardization Sector (ITU-T) has approved the various versions of DOCSIS as international standards. DOCSIS 1.0 was ratified as ITU-T Recommendation J.112 Annex B (1998), but it

1472-651: Is intended to prevent cable users from listening to each other. It does this by encrypting data flows between the CMTS and the cable modem. BPI and BPI+ use 56-bit Data Encryption Standard (DES) encryption, while SEC adds support for 128-bit Advanced Encryption Standard (AES). The AES key, however, is protected only by a 1024-bit RSA key. BPI/SEC is intended to allow cable service operators to refuse service to uncertified cable modems and unauthorized users. BPI+ strengthened service protection by adding digital certificate based authentication to its key exchange protocol, using

1536-441: Is shared among users of an HFC, within service groups which are groups of customers that share RF channels . The first three versions of the DOCSIS standard support a downstream throughput with 256-QAM of up to 42.88 Mbit/s per 6 MHz channel (approximately 38 Mbit/s after overhead), or 55.62 Mbit/s per 8 MHz channel for EuroDOCSIS (approximately 50 Mbit/s after overhead). The upstream throughput possible

1600-482: Is the need for nearly 100% reliable service for emergency calls. One of the standards available for digital cable telephony, PacketCable , seems to be the most promising and able to work with the quality of service (QOS) demands of traditional analog plain old telephone service (POTS) service. The biggest advantage to digital cable telephone service is similar to the advantage of digital cable, namely that data can be compressed, resulting in much less bandwidth used than

1664-652: The Characteristics and principles of operation section. See also the list of OFDM key features . Based on feedback information about the channel conditions, adaptive user-to-subcarrier assignment can be achieved. If the assignment is done sufficiently fast, this further improves the OFDM robustness to fast fading and narrow-band cochannel interference, and makes it possible to achieve even better system spectral efficiency . Different numbers of sub-carriers can be assigned to different users, in view to support differentiated quality of service (QoS), i.e. to control

1728-492: The DVB-C , DVB-C2 stream to IP for distribution of TV over IP network in the home. Many cable companies offer internet access through DOCSIS . In the most common system, multiple television channels (as many as 500, although this varies depending on the provider's available channel capacity) are distributed to subscriber residences through a coaxial cable , which comes from a trunkline supported on utility poles originating at

1792-616: The high band 7–13 of North American television frequencies . Some operators as in Cornwall, Ontario , used a dual distribution network with Channels 2–13 on each of the two cables. During the 1980s, United States regulations not unlike public, educational, and government access (PEG) created the beginning of cable-originated live television programming. As cable penetration increased, numerous cable-only TV stations were launched, many with their own news bureaus that could provide more immediate and more localized content than that provided by

1856-415: The 5–42 MHz frequency range. The 5–65 MHz range is used by EuroDOCSIS. This is known as a "low-split" or "sub-split" design, capable of a total shared capacity of ~108 Mbit/s upstream (assuming 4 SC-QAM upstream channels) for the service group. In recent years, cable operators have begun to increase the amount of bandwidth dedicated to the upstream. The two most popular options for this include

1920-507: The CMTS is configured for backward compatibility with early pre-standard DOCSIS 1.1 modems. These modems were "software upgradeable in the field", but did not include valid DOCSIS or EuroDOCSIS root certificates. Cable television A cable channel (sometimes known as a cable network ) is a television network available via cable television. Many of the same channels are distributed through satellite television . Alternative terms include non-broadcast channel or programming service ,

1984-551: The Internet. Traditional cable television providers and traditional telecommunication companies increasingly compete in providing voice, video and data services to residences. The combination of television, telephone and Internet access is commonly called triple play , regardless of whether CATV or telcos offer it. More than 400,000 television service subscribers. Orthogonal frequency-division multiple access Orthogonal frequency-division multiple access ( OFDMA )

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2048-485: The United States have switched to or are in the course of switching to digital cable television since it was first introduced in the late 1990s. Most cable companies require a set-top box ( cable converter box ) or a slot on one's TV set for conditional access module cards to view their cable channels, even on newer televisions with digital cable QAM tuners, because most digital cable channels are now encrypted, or scrambled , to reduce cable service theft . A cable from

2112-404: The basic selection. By subscribing to additional tiers, customers could get specialty channels, movie channels, and foreign channels. Large cable companies used addressable descramblers to limit access to premium channels for customers not subscribing to higher tiers, however the above magazines often published workarounds for that technology as well. During the 1990s, the pressure to accommodate

2176-563: The cable box itself, these midband channels were used for early incarnations of pay TV , e.g. The Z Channel (Los Angeles) and HBO but transmitted in the clear i.e. not scrambled as standard TV sets of the period could not pick up the signal nor could the average consumer de-tune the normal stations to be able to receive it. Once tuners that could receive select mid-band and super-band channels began to be incorporated into standard television sets, broadcasters were forced to either install scrambling circuitry or move these signals further out of

2240-429: The cable company's local distribution facility, called the headend . Many channels can be transmitted through one coaxial cable by a technique called frequency division multiplexing . At the headend, each television channel is translated to a different frequency . By giving each channel a different frequency slot on the cable, the separate television signals do not interfere with each other. At an outdoor cable box on

2304-548: The cable modem, which is in turn connected through the HFC network to the CMTS. The CMTS then routes traffic between the HFC and the Internet. Using provisioning systems and through the CMTS, the cable operator exercises control over the cable modem's configuration. DOCSIS 2.0 was also used over microwave frequencies (10 GHz) in Ireland by Digiweb , using dedicated wireless links rather than HFC network. At each subscriber premises

2368-515: The cable to send data from the customer box to the cable headend, for advanced features such as requesting pay-per-view shows or movies, cable internet access , and cable telephone service . The downstream channels occupy a band of frequencies from approximately 50 MHz to 1 GHz, while the upstream channels occupy frequencies of 5 to 42 MHz. Subscribers pay with a monthly fee. Subscribers can choose from several levels of service, with premium packages including more channels but costing

2432-675: The case of no local CBS or ABC station being available – rebroadcast the programming from a nearby affiliate but fill in with its own news and other community programming to suit its own locale. Many live local programs with local interests were subsequently created all over the United States in most major television markets in the early 1980s. This evolved into today's many cable-only broadcasts of diverse programming, including cable-only produced television movies and miniseries . Cable specialty channels , starting with channels oriented to show movies and large sporting or performance events, diversified further, and narrowcasting became common. By

2496-508: The chosen channel into the TV set on Channel 2, 3 or 4. Initially, UHF broadcast stations were at a disadvantage because the standard TV sets in use at the time were unable to receive their channels. With the passage of the All-Channel Receiver Act in 1964, all new television sets were required to include a UHF tuner, nonetheless, it would still take a few years for UHF stations to become competitive. Before being added to

2560-423: The data rate and error probability individually for each user. OFDMA can be seen as an alternative to combining OFDM with time-division multiple access (TDMA) or time-domain statistical multiplexing communication. Low-data-rate users can send continuously with low transmission power instead of using a "pulsed" high-power carrier. Constant delay, and shorter delay, can be achieved. OFDMA can also be described as

2624-415: The fact that the descrambling circuitry was for a time present in these tuners, depriving the cable operator of much of their revenue, such cable-ready tuners are rarely used now – requiring a return to the set-top boxes used from the 1970s onward. The digital television transition in the United States has put all signals, broadcast and cable, into digital form, rendering analog cable television service

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2688-457: The growing array of offerings resulted in digital transmission that made more efficient use of the VHF signal capacity; fibre optics was common to carry signals into areas near the home, where coax could carry higher frequencies over the short remaining distance. Although for a time in the 1980s and 1990s, television receivers and VCRs were equipped to receive the mid-band and super-band channels. Due to

2752-450: The headend, the electrical signal is translated into an optical signal and sent through the fiber. The fiber trunkline goes to several distribution hubs , from which multiple fibers fan out to carry the signal to boxes called optical nodes in local communities. At the optical node, the optical signal is translated back into an electrical signal and carried by coaxial cable distribution lines on utility poles, from which cables branch out to

2816-460: The jack in the wall is attached to the input of the box, and an output cable from the box is attached to the television, usually the RF-IN or composite input on older TVs. Since the set-top box only decodes the single channel that is being watched, each television in the house requires a separate box. Some unencrypted channels, usually traditional over-the-air broadcast networks, can be displayed without

2880-490: The late 1980s, cable-only signals outnumbered broadcast signals on cable systems, some of which by this time had expanded beyond 35 channels. By the mid-1980s in Canada, cable operators were allowed by the regulators to enter into distribution contracts with cable networks on their own. By the 1990s, tiers became common, with customers able to subscribe to different tiers to obtain different selections of additional channels above

2944-678: The latter being mainly used in legal contexts. The abbreviation CATV is used in the US for cable television and originally stood for community antenna television , from cable television's origins in 1948; in areas where over-the-air TV reception was limited by distance from transmitters or mountainous terrain, large community antennas were constructed, and cable was run from them to individual homes. In 1968, 6.4% of Americans had cable television. The number increased to 7.5% in 1978. By 1988, 52.8% of all households were using cable. The number further increased to 62.4% in 1994. To receive cable television at

3008-423: The maximum number of channels that could be broadcast in one city was 7: channels 2, 4, either 5 or 6, 7, 9, 11 and 13, as receivers at the time were unable to receive strong (local) signals on adjacent channels without distortion. (There were frequency gaps between 4 and 5, and between 6 and 7, which allowed both to be used in the same city). As equipment improved, all twelve channels could be utilized, except where

3072-500: The name EuroDOCSIS . The differences between the bandwidths exist because European cable TV conforms to PAL / DVB-C standards of 8 MHz RF channel bandwidth and North American cable TV conforms to NTSC / ATSC standards which specify 6 MHz per channel. The wider channel bandwidth in EuroDOCSIS architectures permits more bandwidth to be allocated to the downstream data path (toward the user). EuroDOCSIS certification testing

3136-451: The nearest network newscast. Such stations may use similar on-air branding as that used by the nearby broadcast network affiliate, but the fact that these stations do not broadcast over the air and are not regulated by the FCC, their call signs are meaningless. These stations evolved partially into today's over-the-air digital subchannels, where a main broadcast TV station e.g. NBC 37* would – in

3200-408: The old analog cable without a set-top box. To receive digital cable channels on an analog television set, even unencrypted ones, requires a different type of box, a digital television adapter supplied by the cable company or purchased by the subscriber. Another new distribution method that takes advantage of the low cost high quality DVB distribution to residential areas, uses TV gateways to convert

3264-442: The ordinary CM is connected to an antenna box which converts to/from microwave frequencies and transmits/receives on 10 GHz. Each customer has a dedicated link but the transmitter mast must be in line of sight (most sites are hilltop). DOCSIS includes media access control (MAC) layer security services in its Baseline Privacy Interface specifications. DOCSIS 1.0 used the initial Baseline Privacy Interface (BPI) specification. BPI

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3328-504: The programming at the headend (the individual channels, which are distributed nationally, also have their own nationally oriented commercials). Modern cable systems are large, with a single network and headend often serving an entire metropolitan area . Most systems use hybrid fiber-coaxial (HFC) distribution; this means the trunklines that carry the signal from the headend to local neighborhoods are optical fiber to provide greater bandwidth and also extra capacity for future expansion. At

3392-454: The programming without cost. Later, the cable operators began to carry FM radio stations, and encouraged subscribers to connect their FM stereo sets to cable. Before stereo and bilingual TV sound became common, Pay-TV channel sound was added to the FM stereo cable line-ups. About this time, operators expanded beyond the 12-channel dial to use the midband and superband VHF channels adjacent to

3456-476: The range of reception for early cable-ready TVs and VCRs. However, once consumer sets had the ability to receive all 181 FCC allocated channels, premium broadcasters were left with no choice but to scramble. The descrambling circuitry was often published in electronics hobby magazines such as Popular Science and Popular Electronics allowing anybody with anything more than a rudimentary knowledge of broadcast electronics to be able to build their own and receive

3520-516: The service group. DOCSIS 4.0 in both full-duplex (FDX) and extended spectrum DOCSIS (ESD) configurations will support upstream speeds surpassing 5 Gbit/s. A DOCSIS architecture includes two primary components: a cable modem located at the customer premises, and a cable modem termination system (CMTS) located at the CATV headend. The customer PC and associated peripherals are termed customer-premises equipment (CPE). The CPE are connected to

3584-418: The signals are typically encrypted on modern digital cable systems, and the set-top box must be activated by an activation code sent by the cable company before it will function, which is only sent after the subscriber signs up. If the subscriber fails to pay their bill, the cable company can send a signal to deactivate the subscriber's box, preventing reception. There are also usually upstream channels on

3648-403: The subscriber's residence, the company's service drop cable is connected to cables distributing the signal to different rooms in the building. At each television, the subscriber's television or a set-top box provided by the cable company translates the desired channel back to its original frequency ( baseband ), and it is displayed onscreen. Due to widespread cable theft in earlier analog systems,

3712-532: The upstream speed to 31.2 Kbp/s and prevented the always-on convenience broadband internet typically provides. Many large cable systems have upgraded or are upgrading their equipment to allow for bi-directional signals, thus allowing for greater upload speed and always-on convenience, though these upgrades are expensive. In North America , Australia and Europe , many cable operators have already introduced cable telephone service, which operates just like existing fixed line operators. This service involves installing

3776-519: The width of the channels selected in the upstream direction, and hardware constraints limit the maximum amount of channels in each direction. Note that the maximum downstream bandwidth on all versions of DOCSIS depends on the version of DOCSIS used and the number of upstream channels used if DOCSIS 3.0 is used, but the upstream channel widths are independent of whether DOCSIS or EuroDOCSIS is used. Traditional DOCSIS upstream in North America uses

3840-439: Was designed to support up to 8192-QAM/16,384-QAM, but only support of up through 4096-QAM is mandatory to meet the minimum DOCSIS 3.1 standards. For DOCSIS 3.0, the theoretical maximum throughput for the number of bonded channels are listed in the table below. Note that the number of channels a cable system can support is dependent on how the cable system is set up. For example, the amount of available bandwidth in each direction,

3904-684: Was later improved with the release of the Baseline Privacy Interface Plus (BPI+) specification used by DOCSIS 1.1 and 2.0. Most recently, a number of enhancements to the Baseline Privacy Interface were added as part of DOCSIS 3.0, and the specification was renamed "Security" (SEC). The intent of the BPI/SEC specifications is to describe MAC layer security services for DOCSIS CMTS to cable modem communications. BPI/SEC security goals are twofold: BPI/SEC

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3968-427: Was limited, meaning frequencies over 250 MHz were difficult to transmit to distant portions of the coaxial network, and UHF channels could not be used at all. To expand beyond 12 channels, non-standard midband channels had to be used, located between the FM band and Channel 7, or superband beyond Channel 13 up to about 300 MHz; these channels initially were only accessible using separate tuner boxes that sent

4032-559: Was mainly used to relay terrestrial channels in geographical areas poorly served by terrestrial television signals. Cable television began in the United States as a commercial business in 1950s. The early systems simply received weak ( broadcast ) channels, amplified them, and sent them over unshielded wires to the subscribers, limited to a community or to adjacent communities. The receiving antenna would be taller than any individual subscriber could afford, thus bringing in stronger signals; in hilly or mountainous terrain it would be placed at

4096-500: Was superseded by DOCSIS 1.1 which was ratified as ITU-T Recommendation J.112 Annex B (2001). Subsequently, DOCSIS 2.0 was ratified as ITU-T Recommendation J.122 . Most recently, DOCSIS 3.0 was ratified as ITU-T Recommendation J.222 ( J.222.0 , J.222.1 , J.222.2 , J.222.3 ). Note: While ITU-T Recommendation J.112 Annex B corresponds to DOCSIS/EuroDOCSIS 1.1, Annex A describes an earlier European cable modem system (" DVB EuroModem") based on ATM transmission standards. Annex C describes

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