CableLabs develops DOCSIS 4.0 annex targeting 25 Gbps via 3GHz spectrum
CableLabs is actively developing an optional annex to DOCSIS 4.0 to support 3GHz spectrum and 25 Gbit/s speeds, while also exploring future possibilities at 6GHz for 50 Gbit/s. This alongside ongoing DOCSIS 4.0 certification and interoperability events ensures vendors can develop compatible devices for the cable industry's next-generation broadband infrastructure. The organization emphasizes the importance of reliability over pure speed in HFC networks.
Key Takeaways
- DOCSIS 4.0 optional annex aims for 25 Gbps speeds by expanding usable spectrum to 3GHz, significantly beyond the current 1.8GHz limit.
- Six modem manufacturers, including Gemtek, Sagemcom, and Sercomm, recently achieved 'verified for interoperability' status for D4.0-based hardware on existing 3.1 networks.
- Certification submission fees for D4.0 modems range from $195,000 to $245,000, with the higher tier supporting Broadcom's unified FDX/ESD chipsets.
- Future feasibility studies are underway for 6GHz spectrum, which theoretically offers 50 Gbps capacity but requires extensive power and amplifier respacing analysis.
Why It Matters
The push toward 3GHz is a strategic defensive play to keep hybrid fiber-coaxial (HFC) competitive with 10G and 25G PON fiber technologies. By aiming for 25 Gbps, cable operators hope to extend the lifespan of existing copper infrastructure without the capital expense of full fiber overbuilds. However, the requirement for new amplifiers and high power consumption at multi-GHz frequencies adds operational complexity. The industry is currently in a transition phase where 'interoperability' milestones for DOCSIS 3.1 networks are serving as a bridge while full DOCSIS 4.0 certification remains pending. Watch for the August CableLabs interop event to signal whether vendor hardware is stabilizing around the 1.8GHz standard before the 3GHz pivot begins.
Additional Context
The cable industry faces intensifying pressure from fiber and fixed wireless access (FWA) competitors, forcing a pivot toward symmetrical multi-gigabit capabilities. Per reports from The Business Research Company in May 2026, the global DOCSIS market is projected to reach $7 billion by 2030, driven by the need for ultra-low latency and network modernization. Major US operators are already in varying stages of this transition; while Comcast has deployed DOCSIS 4.0 to millions of homes as of early 2026, other providers are taking more measured paths. Mediacom commercially launched D4.0 in limited markets in late 2025, and Charter Communications expects its full deployment to ramp through 2026 and 2027 following earlier equipment certification delays. Technological choice remains a key differentiator among top-tier operators. Comcast leads with Full Duplex (FDX) technology, while Charter and Cox have leaned toward the Extended Spectrum DOCSIS (ESD) variant. Per Dell'Oro Group analysis in January 2026, the industry is approaching a turning point where large-scale distributed access architecture (DAA) upgrades will finally take form. Despite the focus on speed, industry analysts at Actiontec noted in June 2025 that maintaining market share now requires more than just high downstream numbers; cable must match fiber’s transport characteristics, such as stable latency and high upload capacity, to stem subscriber losses to telcos like AT&T and Frontier. On the hardware front, the market remains a duopoly between Broadcom and MaxLinear. In May 2026, CableLabs confirmed that modems powered by MaxLinear’s Puma 8 and Broadcom’s unified chipsets achieved interoperability milestones, according to Light Reading. This ensures that as operators move toward DOCSIS 3.1+ or 4.0, they have a choice of silicon providers. The high certification fees and the move toward 'unified' chips—supporting both FDX and ESD—suggest a move toward industry-wide standardization to gain economies of scale against the falling costs of global fiber equipment.
Read full article at lightreading.com