DOCSIS 3.0 vs 3.1 vs 4.0: A Detailed Comparison

This article compares DOCSIS 3.0, DOCSIS 3.1, and DOCSIS 4.0, highlighting the key differences between these Data Over Cable Service Interface Specifications.

Introduction

DOCSIS stands for Data Over Cable Service Interface Specification. It’s an international telecom standard that enables high-bandwidth data transmission over existing cable television systems. Telecom operators leverage existing HFC (Hybrid Fiber Coaxial) networks to deliver internet services to consumers.

The DOCSIS standard specifications are developed by CableLabs, in collaboration with companies like Cisco, Broadcom, Intel, Netgear, Texas Instruments, ARRIS, and Comcast.

The initial version, DOCSIS 1.0, was released in March 1997, followed by DOCSIS 1.1, 2.0, 3.0, 3.1, and 4.0.

DOCSIS 3.0 Features

• Baseband focused, single channel QAM.
• Uses QAM, where the entire channel is consumed during single Cable Modem (CM) use.
• Supports channel bonding, dynamic frequency assignment, modular CMTS, and enhanced security.
• Offers lower latency, reduced packet loss, IPv6 support, better diagnostics, and multicast support.
• PMD (Physical Media Dependency Layer) specification: Employs 64 QAM to 256 QAM, using 6 to 8 bits to represent binary data.
• Channel width: Downstream frequencies range from 54 to 1002 MHz, utilizing a fixed 6 MHz wide channel.

DOCSIS 3.1 Features

• Broadband focused, multi-channel QAM.
• Utilizes OFDM, making unique frequencies available for concurrent use.
• Spectrum Management is available.
• PMD specification:
  • Downstream: Defines 64QAM to 16384 QAM, using 6 to 14 bits to represent binary data.
  • Upstream: Defines 16QAM to 4096 QAM, using 4 to 12 bits to represent binary data. Also employs BPSK or QPSK to represent 2 or 3 bits for data mapping. It also utilizes OFDM technique which assigns different subcarrier frequencies for concurrent upstream transmission.
• MAC specification:
  • Provides security extensions at the DL (Data Link) layer.
  • Allows CMTS (Cable Modem Termination System) to control bandwidth allocation.
  • Negotiates access to the US (Upstream) channel when CM data transmission is pending.
  • Supports performance options like variable length packets and traffic prioritization (QoS).
• Channel width: Downstream frequencies range from 108 to 1794 MHz, utilizing subcarrier frequencies to define a channel.

DOCSIS 4.0 Features

• An enhancement to DOCSIS 3.1, also known as “Full Duplex DOCSIS 3.1.”
• Delivers download speeds up to 10 Gbps and upload speeds up to 6 Gbps.
• Offers lower latency and faster speeds.
• Increases upstream spectrum to 684 MHz and downstream spectrum to 1.8 GHz, providing a larger spectrum for data.
• Allows the use of multi-gigabit symmetric services over HFC networks.
• Ideal for applications requiring higher upstream speeds, including video conferencing, healthcare, remote learning, IoT, and virtual reality.

DOCSIS 3.0 vs DOCSIS 3.1 vs DOCSIS 4.0: Tabular Comparison

The following table highlights the key differences between DOCSIS 3.0, DOCSIS 3.1, and DOCSIS 4.0. DOCSIS 4.0 was initially known as “DOCSIS 3.1 Full Duplex”.