Digital TV Europe
Advances in DOCSIS technology can help cable squeeze more life out of HFC networks, but how do the costs and benefits stack up for operators?
With global IP traffic expected to grow at a rate of 22% to 2020, to effectively accommodate ever-growing bandwidth demands cable operators are investing heavily in their existing hybrid fibre coaxial (HFC) networks and in new fibre networks.
The Data Over Cable Service Interface specification is the industry’s long-term initiative aimed at incrementally increasing data carriage capabilities over coax. Version 3.1’s core promise is to provide 10Gbps downstream (10 times faster than the previous version) and 1Gbps upstream.
Although multi-service operators can develop networks based on optical fibre to the premises (FTTP), the majority are currently focused on deploying DOCSIS 3.1.
“This requires minimal investment and works with proven technology such as CMTS, already available,” says Nik Dimitrakopoulos, market segment manager audio and video, Rohde & Schwarz. “Furthermore, DOCSIS 3.1 utilises the frequency spectrum much more efficiently than its predecessors thus reducing the cost per-bit transmitted in the households.”
Several MSOs are beginning to deploy DOCSIS 3.1 in earnest. These include Cox Communications, Rogers Communications, Liberty Global, Charter Communications and Shaw at various stages of planning, testing or in commercial deployment.
For Swedish operator Com Hem it is a “high priority”. Following its CCAP (Converged Cable Access Platform) rollout, the Swedish MSO is testing DOCSIS 3.1 to a few thousand customers and will begin a “massive scale” rollout by end of the year for completion in
Helbo intimates that the operator doesn’t see much consumer demand for even higher speeds, but fibre providers have been ramping up their advertising to boast of greater speeds, and that has forced their cable competitor’s hand.
“The bandwidth that customers are actually using and that which the market is asking for are two very different requirements,” he says. “We currently have 1Gbps downstream on DOCSIS 3.1. It’s not very high profile and not something we’ve promoted to customers but it is available for when we need it.”
Liberty Global meanwhile plans to have DOCSIS 3.1 up and running by the end of the year. Virgin Media in the UK, for example, has already begun its DOCSIS 3.1 rollout. It’s worth noting that Virgin Media’s £3 billion (e3.5 billion) Project Lightning network expansion, which aims to cover around 60- 65% of UK homes and businesses by the end of 2019, includes about two million premises that will be covered via FTTP technology. Virgin Media will maintain compatibility with DOCSIS by using the Radio Frequency over Glass/RFoG technology developed to enable operators to roll out fibre while providing broadband from a unified headend infrastructure.
“We’ll do most of the networks in 2018 and that will come with the first 1Gbps services in the majority of our markets,” Colin Buechner, managing director at Liberty’s Access Network division told Cable Congress in March.
One of those markets is Germany, where Liberty Global subsidiary Unitymedia has begun a DOCSIS 3.1 rollout starting in the city of Bochum. However, Liberty Global SVP and CTO Balan Nair has said that the firm will initially target higher-end customers with the service, due to the current high costs of DOCSIS 3.1-based consumer premises equipment (CPE).
Stefan Vanhastel, head of marketing for fixed networks at Nokia also says that upgrades involve hidden costs. “DOCSIS 3.1 requires many components to get to 10Gbps, including spectrum availability or frequency extensions up to 204MHz upstream and 1.2GHz for the downstream channel – with further possible expansion to 1.8 GHz in some cases – as well as potentially substantial infrastructure upgrades to realise the highest coding efficiencies. As a result, we see many cases of gradual introduction and maybe the full benefits will require a move to a different architecture.”
At the RF layer there is a major shift to OFDM (Orthogonal Frequency Division Multiplexing) signal technology on both the upstream and downstream frequencies and multiple profile support within a single downstream channel.
“These changes bring new testing requirements across the whole eco-chain of DOCSIS 3.1 from network operators, to CATV amplifier makers as well as cable modem and chipset manufacturers,” says Dimitrakopoulos, all of which is adding cost.
Arris disagrees with this analysis, however. “The economics of migration are not driven by the economics of the kit itself but the cost of construction and replacement of cable if required to dig it up and replace with fibre. That cost can be astronomical in Europe where most cables are buried,” says Cornel Ciocirlan, CTO EMEA at Arris.
“It’s not a forklift upgrade,” says Belal Hamzeh, VP of wireless technologies at cable industry technology standards organisation CableLabs. “We developed the technology to be backwards-compatible so that MSOs can pre-seed a network, with DOCSIS 3.1 modems which will operate with 3.0. Right now, operators are focused on 3.1.”
Arris’ SB8200 modem, (which Comcast and Cox have approved), for example, will support both DOCSIS 3.0 and 3.1, enabling MSOs to build momentum by deploying them in existing networks.
“For many operators, the shift from 3.0 to 3.1 represents a change not only in the protocol don’t put any amplifiers between the node and the home), Remote PHY or Remote MAC PHY, Remote PHY shelf, RFoG, Node PON, EPON and GPON, and so on.
According to Ciocirlan, MSOs will pace their rollout based on how subscriber usage evolves and the availability of capital investment. Some operators plan to spend as much as US$1 billion (e900 million) in each of the next few years to address the demand they are experiencing, Arris suggests.
Arris highlights a number of pressing factors impacting MSO decision-making. These include headend capacity – where space, power and other facility considerations constrain the ability to add more equipment, operators have two choices: seek denser more itself, but in the approach to architecting their entire DOCSIS delivery chain – from the headend to the outside plant and home gateway components,” says Ciocirlan.
Operators are choosing from a number of new approaches based on the nature of their deepening fibre deployments and their desire to make more efficient use of headend facilities. Arris claims to have a unique perspective on the aggregate decisions that these operators face, due to its work in DOCSIS 3.1 deployments and the success of its E6000 CCAP platform.
“Our operator customers look to us for evolutionary pathways that enable them to make full use of their HFC plant and fibre deployments, while building on their installed base of E6000s and their outside plant,” says Ciocirlan. “One of the biggest challenges we see is that there is no one decision path to choose from that is expected to reach the market in the next few years.”
In other words, operators will choose different approaches, including HFC with Node+0 splits (fibre deep HFC networks that power efficient solutions or move capabilities and functionality into the outside plant. This is one of the cases for Remote PHY.
Economics is also a factor. Capex and opex costs come into play as operators replace old equipment (nodes, amplifiers, and headend equipment) and move to support 1.2GHz and 85MHz return expansion. Where this requires new equipment and truck rolls, it creates an imperative to minimise the number of times outside plant has to be accessed while making service groups smaller to cope with the increased bandwidth demands.
In the case of greenfield rollouts, it makes economic sense to put in FTTH from day one, especially as replacing coax to a home with fibre can cost as much as €900 per home passed. PON becomes the logical choice here, especially when the system can still support DPOE (the DOCSIS spec for cable modem provisioning at the headend). Similarly, for urban multi-dwelling units where fibre can be pulled past a high density of subscriber dwelling units, PON may be more efficient from a capacity and cost perspective.
Depending on the socio-economics of neighbourhoods, pulling the intelligent, expensive components back into the secured environments and using lower-cost outside plant systems can allow operators to manage failures and loss while offering similar traffic and service level performance. Operators’ range of approaches will also be impacted by silicon availability, finalisation of specifications, and levels of testing required to verify deployment capabilities.
“In many cases, the transition from one stage to the next can be accomplished with simple software upgrades, permitting the operator to activate the change in a convenient, cost-effective fashion,” says Ciocirlan. “This enables operators to select their ideal architecture as they look to support multi-gigabit data services and migrate from QAM to IP video services without having to make massive changes to their provisioning and headend systems.”
The fundamentals of technology deployments may not have changed. FTTP still means high investment costs, but is economically competitive for new networks. Cable upgrades offer lower deployment costs in areas with completed infrastructure, and arguably their capacity potential make them competitive for years to come.
In certain countries, a pending analogue TV shutdown may also increase the capacity of existing DOCSIS networks and this has already made some operators postpone their network upgrades, according to network solutions provider Teleste.
“On the other hand, many consumers may still be willing to pay for services like FM radio,” says SVP of network products, Hanno Narjus. “Fibre is the future of networks in the long run, and fibre networks can also carry DVB-C based TV delivery. However, operators need to consider how to provide their customers with reliable, high-performing broadband services today. The investments will be determined by which services customers are willing to pay and how much they are willing to pay. Eventually, consumers will decide which services they want, and those decisions will affect which technologies will bring reasonable returns on investment to operators.”
Part of that equation will be based on value for money, not just the number of Gigabits, which has recently dominated network investments.
“Service quality is becoming a competitive advantage for operators in addition to sufficient transmission speeds,” says Narjus. “To achieve better service quality, operators need to deploy solutions that will improve network operation overall. Such solutions include proactive network maintenance and devices using intelligent HFC technology.”
“In practice, the only real options for fixed broadband networks today are fibre [FTTP] and cable [including DOCSIS 3.1 and Remote PHY], and it is difficult to see how supporting multiple technologies simultaneously would be a rational path to take for the majority of operators,” says Narjus. “However, the situation changes when we are talking about the last mile of the network. In future, we will see networks with a fibre backbone and, for example, the last mile in coax. We will also see versatile options and technologies for last mile network implementations.”
Remote PHY is one option in the spectrum of functionality an operator can put into remote nodes. It pushes more intelligence deeper into the network while a central CCAP platform performs the higher layer processing. CCAP and R-PHY both have the benefits of lowering capex and opex for operators and making the network more efficient.
“While DOCSIS 3.1 allows cable operators to better compete [with rival operators] on speed, it lives up to its true potential when complemented by a remote PHY deployment,” says Asaf Matatyaou, VP of solutions and product management for the cable edge business at Harmonic. “Cable operators can continue to invest in technology that extends the life of their existing network and simultaneously prioritize the deployment of technologies like DOCSIS 3.1 and R-PHY based on where they’re feeling the most pressure from customers or other providers.”
Harmonic’s software-based CableOS solution addresses these challenges “by enabling the migration to gigabit capacity while also providing the benefits associated with distributed access architecture, in addition to immediate virtualisation advantages for centralised deployments”, says Matatyaou.
Arris, Cisco and other vendors will want to continue selling CCAP equipment but there is an alternative to R-PHY. This is to use a virtual CCAP device that is also designed to push many of the functions of a DOCSIS-powered cable network closer to the network edge. The goal is to miniaturise and virtualise the functions of a CCAP chassis so that more of the cable network can be software-controlled, and operators can save both space and power in the headend.
Nokia is pursuing this approach via Gainspeed, a US start-up it acquired last year. “We have a strong believe that the economics are not sustainable based on a centralised architecture and that cable operators will require a move to distributed architectures,” says Vanhastel. “We are working hard with the standards committee at CableLabs toward standards which we think will be ready end of year with potential to trial early 2018.”
Nokia’s unified cable access solution leverages Software Defined Networking (SDN) techniques to virtualise the CCAP, completely eliminating what it terms ‘Big Iron’ hardware from the headend and delivering a sevenfold reduction in rack space and an eightfold reduction in power comsumption.
The solution also replaces legacy analogue optical transmission with 10Gbps Ethernet and supports both last mile access for both cable and fibre.
Nokia says Gainspeed’s cable access products are designed from the ground up to support DOCSIS 3.0 and DOCSIS 3.1 and the approach is “particularly well suited” to implementing Full-Duplex DOCSIS.
Moreover, Nokia Bell Labs has already demonstrated, via a proof of concept in 2016, that providing 10Gbps symmetrical services over HFC networks is a real possibility for operators.
DOCSIS 3.1 is considered a necessary first step toward bringing data-hungry technologies such as augmented reality, UHD 4K television, ‘tele-existence’, medical imaging and advanced gaming systems to cable customers.
The evolution of this, Full Duplex DOCSIS (FDX) is a bit further away and will require a total rework of network topology. Development of Full Duplex is also slowed down by the fact that symmetrical transmission speeds don’t yet seem to be important to consumers today. “We see growth downstream of 40-50% a year and below 10% in upstream traffic,” notes Com Hem’s Helbo. “While services don’t yet require it there is a need in the market to claim you have symmetrical speed so you can be ready when demand does come.”
Com Hem will begin the first phase of installing FDX in 2018. Virgin Media reportedly has this timeframe in mind too. Rather than requiring a cable system to separate spectrum dedicated to the downstream and the upstream with a traditional ‘split,’ FDX will enable dual-use bands for traffic that runs in both directions. FDX will also require an N+0, passive network, which fits in with the plans of some operators to pull fibre deeper and remove the active amplifiers present between the node and the home.
“Today, there is no critical need for a symmetric tier since traffic is much heavier on the downstream than upstream but MSOs looking to the future for a symmetric service tier will be able to offer it,” says Hamzeh.
DOCSIS 3.1 and Full Duplex DOCSIS hold out the promise of keeping cable competitive, but there are alternative broadband technologies – not least 5G, which could serve as a fixed-line substitute.
“MSOs will have to make a judgement about the merits of fibre, cable and 5G when it comes to bandwidth and quality of service in different cases. 5G can give you faster time to market, since you don’t have to dig up the street, but fixed may well give you an order of magnitude in terms of speed,” says Hans Slabbinck, product line manager, MSO access, Nokia.
While 5G will probably emerge as a substiture for fixed line access in rural areas, it will also require backhaul over fibre, and as CableLabs’ Hamzeh points out, wireless can still be subject to bad weather and obstructions.
“You have to keep in mind it’s not like fibre or wireline is standing still,” says Hamzeh. “We are still developing and pushing higher capacity to the end user.”
