Demand for bandwidth is an insatiable beast. Subscribers are no longer satisfied by basic broadcast video and data services. They now expect high-definition television (HDTV) programming, video on demand (VoD) and other types of video streaming, 100+ Mbps speeds for data services, and seamless support for multiscreen services, in ever-increasing volumes. Without the right infrastructure in place, this accelerating need for network capacity can be a nightmare for operators. Cable operators need a strategy that incorporates their existing investments to cost-effectively meet tomorrow’s bandwidth challenges.
There are many industry standards to address this issue. One of the most talked about is the CableLabs Converged Cable Access Platform (CCAP) architecture, which was designed from the ground up to enable the narrowcast service densities required for the next generation of growth. The beauty of the CCAP specification is that it is a managed architecture, rather than a technological instant in time. CCAP leverages existing cable technologies and makes provision for new ones that will arise through natural evolution. Because of this foresight, there are many paths to CCAP, and many paths beyond it. This gives operators the ultimate freedom to tailor their migrations to best suit their individual circumstances.
CCAP has been one of the biggest trends in cable since the first product announcements at the SCTE Cable-Tec Expo in 2012. With several of these products currently in field trials and first commercial deployments expected in 2014, the cable industry’s interest in CCAP continues to grow.
The CCAP systems emerging today combine edge QAM and cable modem termination system (CMTS) technology into one device. Some vendors have focused on “densifying” a CMTS, and subsequently adding video QAMs; others have focused on the QAM aspect first and bringing in CMTS functionality later. The existence of two approaches enables operators to choose the migration path and time frame that best suits their criteria, including financial justification, preservation of investments in training and equipment, the merging of video and data operational staff, and long-term strategic direction.
However, both approaches converge in an all-in-one CMTS/QAM platform. The platform will be more space- and power-efficient, easier to manage and configure, and optimized for operational simplifications.
Even as deployments begin, CCAP will continue to evolve. The architecture encompasses both new-to-cable technologies such as EPON and metro Ethernet, and emerging ones designed to preserve the supremacy of the hybrid fiber/coax (HFC) plant as a bandwidth delivery platform, such as distributed PHY, EPON Protocol over Coax (EPoC), and DOCSIS 3.1.
EPON and metro Ethernet support in CCAP will help unify services to end customers, including those connected by direct fiber, regardless of whether they are residential or business customers. Both technologies are already widely used, so the integration burden is more of a back-office operational transition than a technical development.
However, EPoC, DOCSIS 3.1, and distributed PHY are new, cable-focused technologies designed to unlock additional capacity in existing HFC networks. EPoC enables operators to use EPON as a unified high-speed data delivery mechanism, regardless of whether the end-users are connected via fiber or HFC. It would enable the delivery of symmetric 10-Gbps and 1-Gbps (or asymmetric 10G/1G) services, either from headend-to-building or within a coax-wired building fed by fiber. EPoC standardization is currently underway through the Institute of Electrical and Electronic Engineers (IEEE) 802.3 Ethernet Working Group as an addition to the IEEE 802.3 Ethernet in the First Mile (EFM) family of standards.
DOCSIS 3.1 is the upcoming enhancement to DOCSIS 3.0. It will enable approximately 50% better spectral efficiency (bits per hertz) by using a combination of:
- Orthogonal frequency-division multiplexing (OFDM), a more robust signal encoding algorithm than the current ITU-T J.83 QAM modulation technique. OFDM is also expected to be useful in coping with Long Term Evolution (LTE) wireless signals.
- Low density parity check (LDPC), a more efficient error correcting code than the currently used Reed Solomon coding.
- Certain structural accommodations such as smaller guard bands and expanded frequency ranges.
The DOCSIS 3.1 specifications are due to be completed later this year, with product trials starting in 2014.
Distributed PHY, also known as Remote PHY, encompasses a set of products designed to shift the point at which digital signals are transformed into RF signals, and to move that point from the cable headend to the fiber-optic node. The goal is to increase the bandwidth capacity of the HFC plant by eliminating the signal degradation associated with transmitting amplitude-modulated (AM) signals over fiber, thus enabling the use of higher-order modulation or extending the viable frequency range.
Distributed PHY also enables operators to use more wavelengths for any given distance when using baseband optics. An additional operational benefit of Distributed PHY is the power and space savings derived from distributing the heat and power load, rather than concentrating it indoors. For example, estimates predict that a Node QAM implementation can reduce power consumption by up to 70% and rack space by up to 90%, compared to pre-CCAP edge QAMs.
Downstream distributed PHY products, or Node QAM products, are expected to emerge later this year. Upstream distributed PHY, or node-based burst receivers, and different flavors of combined upstream and downstream distributed PHY are currently under investigation among multiple vendors and operators.
No cap on CCAP
Subscribers’ ever-increasing demand for bandwidth is pushing the cable industry to plan for continual growth, rather than discrete leaps forward. The CCAP architecture is poised to be the enabler for this process, providing operational structure and continuity while creating a framework for adopting future technological advances.
Every operator can and will take a unique road to implementing their vision of the future. But CCAP, with edge QAMs and DOCSIS 3.0 today, and Node QAM, DOCSIS 3.1, EPoC, and others in the future, is another helpful tool to position operators ahead of the curve as painlessly, efficiently, and cost-effectively as possible.
Rei Brockett is product manager, video products group, at Aurora Networks.