Editing DOCSIS (section)

==Features==
DOCSIS provides a variety of options available at [[OSI model|Open Systems Interconnection]] (OSI) layers 1 and 2—the [[Physical layer|physical]] and [[data link layer]]s.

===Physical layer===
* Channel width:
** Downstream: All versions of DOCSIS earlier than 3.1 use either 6&nbsp;MHz channels (e.g. North America) or 8&nbsp;MHz channels ("EuroDOCSIS"). DOCSIS 3.1 uses channel bandwidths of up to 192&nbsp;MHz in the downstream.<ref>{{cite web |title=DOCSIS Technology |url=https://www.rohde-schwarz.com/pl/technologies/cable_tv/docsis/docsis-technology/docsis_technology_55513.html |website=Rohde & Schwarz}}</ref>
** Upstream: DOCSIS 1.0/1.1 specifies channel widths between 200&nbsp;kHz and 3.2&nbsp;MHz. DOCSIS 2.0 & 3.0 specify 6.4&nbsp;MHz, but can use the earlier, narrower channel widths for backward compatibility. DOCSIS 3.1 uses channel bandwidths of up to 96&nbsp;MHz in the upstream.
* Modulation:
** Downstream: All versions of DOCSIS prior to 3.1 specify that 64-level or 256-level [[Quadrature amplitude modulation|QAM]] (64-QAM or 256-QAM) be used for modulation of downstream data, using the [[ITU-T]] J.83-Annex B standard<ref>{{cite web |url=http://www.itu.int/rec/T-REC-J.83-200611-S!Amd1/en |title=Recommendation J.83 (1997) Amendment 1 (11/06) |date=November 2006 |access-date=June 20, 2013 }}</ref> for 6&nbsp;MHz channel operation, and the DVB-C modulation standard for 8&nbsp;MHz (EuroDOCSIS) operation. DOCSIS 3.1 adds 16-QAM, 128-QAM, 512-QAM, 1024-QAM, 2048-QAM and 4096-QAM, with optional support of 8192-QAM/16384-QAM.
** Upstream: Upstream data uses [[Phase-shift keying#Quadrature phase-shift keying (QPSK)|QPSK]] or 16-level QAM (16-QAM) for DOCSIS 1.x, while QPSK, 8-QAM, 16-QAM, 32-QAM, and 64-QAM are used for DOCSIS 2.0 and 3.0. DOCSIS 2.0 and 3.0 also support 128-QAM with [[Trellis modulation|trellis coded modulation]] in [[SCDMA|S-CDMA]] mode (with an effective [[spectral efficiency]] equivalent to that of 64-QAM). DOCSIS 3.1 supports data modulations from QPSK up to 1024-QAM, with optional support for 2048-QAM and 4096-QAM.

=== Data link layer ===
* DOCSIS employs a mixture of deterministic access methods for upstream transmissions, specifically [[time-division multiple access]] (TDMA) for DOCSIS 1.0/1.1 and both TDMA and S-CDMA for DOCSIS 2.0 and 3.0, with a limited use of contention for bandwidth reservation requests. In TDMA, a cable modem requests a time to transmit and the CMTS grants it an available time slot.<ref>{{Cite web |title=Understanding Data Throughput in a DOCSIS World |url=https://www.cisco.com/c/en/us/support/docs/broadband-cable/data-over-cable-service-interface-specifications-docsis/19220-data-thruput-docsis-world-19220.html |website=Cisco |access-date=February 21, 2024 }}</ref>
* For DOCSIS 1.1 and above, the data layer also includes extensive [[Quality of service|quality-of-service]] (QoS) features that help to efficiently support applications that have specific traffic requirements such as low latency, e.g. [[voice over IP]].
* DOCSIS 3.0 features [[channel bonding]], which enables multiple downstream and upstream channels to be used together at the same time by a single subscriber.<ref name="cablelabs.com">{{cite web |url=http://www.cablelabs.com/news/pr/2006/06_pr_docsis30_080706.html |title=CableLabs Issues DOCSIS 3.0 Specifications Enabling 160 Mbps |publisher=CableLabs |access-date=December 2, 2017 |archive-url=https://web.archive.org/web/20101120234649/http://cablelabs.com/news/pr/2006/06_pr_docsis30_080706.html |archive-date=November 20, 2010 }}</ref>

=== Throughput ===
Bandwidth is shared among users of an HFC, within service groups which are groups of customers that share [[Television channel frequencies|RF channels]].<ref>{{cite book | url=https://books.google.com/books?id=4mUkzG0P6fQC&dq=pon+shared+bandwidth&pg=PA184 | isbn=978-1-931695-37-4 | title=Achieving the Triple Play: Technologies and Business Models for Success: Comprehensive Report | date=March 15, 2024 | publisher=Intl. Engineering Consortium}}</ref>

The first three versions of the DOCSIS standard support a downstream throughput with 256-QAM of up to 42.88&nbsp;Mbit/s per 6&nbsp;MHz channel (approximately 38&nbsp;Mbit/s after overhead), or 55.62&nbsp;Mbit/s per 8&nbsp;MHz channel for EuroDOCSIS (approximately 50&nbsp;Mbit/s after overhead). The upstream throughput possible is 30.72&nbsp;Mbit/s per 6.4&nbsp;MHz channel (approximately 27&nbsp;Mbit/s after overhead), or 10.24&nbsp;Mbit/s per 3.2&nbsp;MHz channel (approximately 9&nbsp;Mbit/s after overhead).

DOCSIS 3.1 supports a downstream throughput with 4096-QAM and 25&nbsp;kHz [[subcarrier spacing]] of up to 1.89&nbsp;Gbit/s per 192&nbsp;MHz OFDM channel. The upstream throughput possible is 0.94&nbsp;Gbit/s per 96&nbsp;MHz [[Orthogonal frequency-division multiple access|OFDMA]] channel.<ref>{{Cite web |last=Sinclair |first=Dave |title=DOCSIS What's Next - An Overview |url=http://scte-sandiego.org/uploads/3/4/5/9/3459873/docsis_3_1_sandiego_rev6_bw.pdf |website=SCTE-SanDiego.org |url-status=live |archive-url=https://archive.today/20170815033612/http://scte-sandiego.org/uploads/3/4/5/9/3459873/docsis_3_1_sandiego_rev6_bw.pdf |archive-date=August 15, 2017 |access-date=March 6, 2023 }}</ref>

=== Network layer ===
* DOCSIS modems are managed via an [[Internet Protocol]] (IP) address.
* The 'DOCSIS 2.0 + IPv6' specification allowed support for IPv6 on DOCSIS 2.0  modems via a firmware upgrade.<ref>{{Cite web|url=http://www.cablemodem.com/specifications/specifications20.html|title=DOCSIS 2.0 Interface|website=CableModem.com |archive-url=https://web.archive.org/web/20090904062229/http://www.cablemodem.com/specifications/specifications20.html|archive-date=September 4, 2009 }}</ref><ref>{{cite web |first=Dan |last=Torbet |title=IPv6 and Cable: How Cable is managing the transition from IPv4 to IPv6 |url=http://www.rmv6tf.org/wp-content/uploads/2012/10/Dan-Torbet-IPv6andCablev211.pdf |work=Rocky Mountain IPV6 Task Force |date=April 9, 2008 |access-date=February 12, 2015 }}</ref>
* DOCSIS 3.0 added management over [[IPv6]].<ref name="cablelabs.com" />