Coaxial cable based access technology series: CMTS+CM technologies

 Coaxial cable based access technology

CMTS: cable modem termination system; CM: cable modem

  After the two-way transformation of the cable television network, an uplink return channel was added. In addition to the use of the uplink channel to carry out interactive digital television and digital television value-added services, it can also perform bidirectional data transmission and become a broadband access technology. Therefore, the access technology based on coaxial cable can also be divided into two major categories of CMTS+CM and EoC technologies. From a broad perspective,CMTS+CM technology can also be regarded as anEoC technology, but because it differs from the commonly usedEoC technology in network structure and frequency band usage, CMTS and EoC technologies are still separately presented, in this blog post.

Cable operators CATV FTTH triple play solution (updated by friendship partner)

  The CMTS+CM technology is designed specifically for cable television networks. There are three main standards, namely the DOCSIS (Data-Over-Cable Service Interface Specifications) standard developed by the CableLabs in the United States, and the European DVB/DAVIC alliance. The DVB-RCC standard and the IEEE802.14 standard developed by IEEE were developed. The main DOCSIS standard is currently used.
  EoC technology is a general term for a wide range of technologies, and various access technologies originally used in other media (such as Category 5 lines, power lines, and wireless, etc.) can be applied to coaxial cables. The main technologies include baseband EoC technology, MoCA, HomePlug (AV) over Coax, WiFi over Cable, and HomePNA over Cable.

CMTS+CM access technology

  In November 1995, CableLabs, the main cable TV operator and research institute of the United States, launched the multimedia cable network system (MCNS) cooperative organization. The purpose was to establish a set of protocols to tell bidirectional data transmission on the hfc network. Users provide services such as internet, and at the same time make full compatibility of various manufacturers and other cm products. The organization issued a DOCSIS standard in March 1997 that defines how to provide two-way data services over cable modems. The DOCSIS1.0 standard of MCNS was adopted by ITU in March 1998 and became the international standard ITU-T J.112b. In the DOCSIS 1.0 standard, a 6MHz channel is separated from the 87-860MHz television channel for downlink data transmission, and the downlink data is 64QAM modulation or 256am modulation. Uplink data is transmitted through a frequency spectrum between 5 and 65 MHz, and in order to effectively suppress uplink noise accumulation, QPSK modulation is generally used. The DOCSIS standard is a series of interface specifications, including the physical layer specification, the mac layer and the upper layer specification, the security specification, and the operational support system interface specification. DOCSIS protocol level as shown in the table

DOCSIS protocol layers specification (from wiki)

  Subsequent versions of DOCSIS 1.0 are DOCSIS 1.1, which provides standards for IP telephony and other time-critical services, and extends the QoS functionality in version 1.0 to provide strong forward error correction capabilities. And make the cable modem system have a stronger channel transmission anti-HFC network backhaul noise performance. In November 2002, DOCSIS version 2.0 was introduced, and A-TDMA (advanced time division multiplexing) was adopted to increase the uplink data rate, but the downlink rate remained unchanged.

  In August 2006, CableLabs officially launched the DOCSIS 3.0 standard. Through channel bonding, it can increase the user bandwidth to 160 mbps in the downlink and 120 mbps in the uplink.
   DOCSIS’s four versions of DOCSIS 1.0, 1.1, 2.0, and 3.0 are fully backward-compatible, and each version is introduced relative to the previous major version. Refer to wikipedia for details.

CMTS+CM network structure and workflow


CMTS+CM network system topology

  A cable modem is needed to support high-speed data access over HFC by using the cable TV infrastructure. Cable modems function like special-purpose routers, linking the cable network’s Layer 3 to another network or device. Generally this requires an external box with cable and Ethernet connections. Figure below illustrates cable modem connectivity. On the left side of the figure is a single neighborhood with users attaching to the shared coax system via their cable modems. These various coax trunks, then, come into the headend facility, where they terminate on a cable modem termination system (CMTS). The CMTSs are linked together by accessing a common Ethernet hub, which, in turn, feeds into the IP router, which then develops the optimum path to take over an optical backbone onto the ISP.

Technical Features of CMTS+CM Access Mode

  • With a relatively complete international agreement system support, a complete business system and operation support system have been formed; the technology is relatively mature and has been widely used worldwide. The compatibility between the front-end, terminal, and management system of the system is good, and it is operational and available. Manageability features.
  • It has several service flow classifications, QoS policies, and strict bandwidth guarantees. It has strict access terminal signing rights and data security transmission capabilities. It has open service control interface specifications and can construct manageable IP networks.
  • The user does not need to re-wiring when there is service access, and the cable TV terminal box in the user’s home has digital media and broadband access capabilities, which is suitable for the development of interactive media services.
  • The two-way network coverage can gradually install data front-end equipment according to the scale of users and business development. The networking method is flexible and suitable for the gradual development of broadband services. By using multiple data channel or channel bundle technologies, the system can be smoothly expanded to meet the needs of business development bandwidth requirements.

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