By Dr. Robert L. Howald, ARRIS
The persistence of compound annual growth rates for IP services coupled with the rapid expansion of HD has the industry considering upgrade paths for it most valuable asset – the HFC network. HFC has an unparalleled history of flexibility, consistently adding new services over decades of graceful evolution. Nonetheless, as powerful as the network is, it remains far from optimally using its capacity resources.
Given the dynamics of growth and relentless nature of compounding traffic, the inefficiency of precious HFC resources must be dealt with. New initiatives in DOCSIS and IEEE 802.3bn (EPoC) are determined to do just that.
Fortunately, modern digital communications technology has snuggled up quite closely to theoretical capacity bounds. Capacity starts at the bottom – the bottom of the OSI Stack, that is. Analogous to what Internet Protocol (IP) is for Layer 3 in the OSI stack, Layer 1 in the non-baseband world is “standardizing” around go-to Physical Layers tools such as multi-carrier technology and advanced forward error correction (FEC). These tools push performance against Shannon bounds so tightly that there is little room for further optimization. Cable is poised to take advantage of these breakthroughs to squeeze the most from HFC.In this paper we connect the dots between network performance and network capacity.
We describe application of “standard” Layer 1 tools, and how novel implementations of these tools optimize and breathe new lifespan into the HFC network. A fundamental philosophical break from the past is making use of the fact that network capability varies across users. Optimization approaches not only update the QAM technology itself, but selectively apply modulation “profiles” to make the best use of available capacity. We reveal analysis of QAM potential and profile optimization against key system variables: standard and distributed access architectures, premise architecture, network geography, component performance, and spectrum allocation. We also address the why, how, and implications of kicking the 30year old downstream/upstream spectrum asymmetry habit, and enumerate additional results for evolved band plans in both directions. Lastly, we introduce a recently developed comprehensive, updated HFC channel model. These models go beyond prior lower-limit only references, capturing new limits, but more importantly describing “typical” scenarios and performance. A representation for “typical” channels enables determination of the ability of a network to “scale up” in capacity.
From this discussion, the audience will gain a renewed appreciation of the long runway for HFC, and a thorough understanding of the core elements of the technology upgrade.
They will understand key trade-offs among technology, architecture, and spectrum relative to capacity exploitation. Finally, the paper will convey the innovation the industry is engaged in – innovation that moves technology forward globally, and that reaches beyond cable.