The last several years have been marked by significant advancements in the core network, as operators have evolved their backbones to maximize connectivity to the cloud, represented by hyperscale data centers.
As many core networks have been upgraded to manage terabit levels of traffic and reduce latencies for interconnections between operator networks and internet peering and cloud operators, increased attention is now focused on the access network.
Access bandwidth needs have grown considerably year-over-year, both for downstream and upstream traffic. The COVID pandemic has exacerbated this trend, as increased telecommuting/work-from-home and virtual/e-learning has driven an explosion in bandwidth demand, particularly for consumer households. Applications like video conferencing (Zoom, Microsoft Teams, etc.) are pushing the upstream capabilities of many operators who offer asymmetrical broadband service.
Spurred on by the ongoing pandemic, many operators are reassessing their access network plans to ensure they are well positioned for the future. In many cases, operators are actively deploying and/or seriously considering fiber-to-the-home (FTTH) builds. In many markets, the adage “He Who Builds Fiber First, Wins” applies.
Significant infusions of capital are spurring FTTH network builds. A portion of this capital formation is driven by private investment, and in some countries like the United States there are numerous government funding initiatives to deploy fiber-based broadband with significant scale.
Cable operators, phone companies, municipalities, power utilities, global internet giants, and competitive broadband providers including ISPs and WISPs are all bringing increased competition to local markets. 2020 saw many network operators launching gigabit and multi-gigabit services over fiber. With increased competition, operators have been forced into more aggressive access network planning and are deploying FTTH to provide high-bandwidth symmetrical services to position their companies for future success.
FTTH deployment strategies vary by operator and are primarily dictated by two factors. First, whether the network to be built is a new, or “greenfield,” network versus an existing “brownfield” network that needs to be upgraded. And second, for brownfield networks, the legacy technology the operator has relied on to provide broadband service.
In all instances where FTTH is being deployed, 10G PON is increasingly the deployment choice for new builds. Passive optical network (PON) technology is a widely adopted cost-efficient method for utilizing a single fiber to deploy FTTH.
Why 10G PON?
Today’s consumer broadband network needs high-speed symmetrical bandwidth and low latency to deliver superior customer experience for applications like 5G, augmented reality/virtual reality (AR/VR), over-the-top streaming video, cloud gaming, videoconferencing, and other peer-to-peer networking services. While in many cases not every household today represents the “high usage” profile indicative of cloud gamers, operators are deploying 10G for reasons that include:
- Access networks are a 10-year investment: Network operators want to make the platform and technology choice that will meet the needs of the network for the length of the investment and beyond.
- Back-office systems simplification: Deploying a single technology simplifies the OSP records, integration, spares inventory, service installation, and turn-up. In a brownfield network, this is a cap-and-grow strategy.
- Enable growth of the subscriber base: Returning to the existing customer premises to upgrade to a new technology increases cost, typically through additional labor, truck roll expense, and premises equipment outlay. Investing in future proofing the access network now ensures the operator does not have to initiate a complex, expensive upgrade program at a later point and frees up the operator to focus on service innovation and profitable growth initiatives.
To accommodate exploding bandwidth needs that are forecasted to grow unabated for years to come, operators are increasingly focused on fiber preservation. Network operators have found efficiencies in moving a variety of applications onto a single-fiber PON optical data network (ODN), in addition to network traffic tied to consumer subscribers.
Examples of high bandwidth, low latency applications being served by 10G PON include:
- MDU/MTU: A multi-dwelling unit (MDU) is a classification of housing where multiple separate housing units for residential inhabitants are contained within one building or several buildings within one complex. Units can be next to each other or stacked on top of each other. A common form is an apartment building. A commonly used term for the business version would be an MTU, or multi-tenant unit. MDU/MTU’s require much higher fiber-to-the-building speeds than what has traditionally been utilized in terms of 2.5-Gbps GPON, point-to-point Gigabit Ethernet, or asymmetrical DOCSIS.
- Business Services: Businesses including SMBs and enterprises often require multi-gigabit speeds and committed information rates. In particular, symmetrical services are required to handle the upstream traffic driven by two-way business applications. Businesses often have more stringent requirements than consumers in terms of network availability and latency, and PONs can be engineered to enable the operator to support service-level agreements.
- Mobile: As mobile network operators build out 5G small cell networks, they require fiber transport within each market. Fiber network operators are leveraging industry advances in PON technology to utilize 10G PON to support mobile xhaul requirements including fronthaul and midhaul.
Deployment Strategies
For pure greenfield networks, the decision to deploy FTTH via 10G PON is straightforward and many if not most operators currently building FTTH have made that decision. There are also examples where primarily business-focused competitive providers have incorporated 10G PON as part of their overall fiber architecture, even though their business model does not include serving residential subscribers.
Brownfield networks introduce additional complexity, and to a large degree the deployment strategies depend on the technology used to provide the existing broadband services. For cable operators, DOCSIS-based hybrid fiber/coax (HFC) networks have served these companies well for several decades, allowing them to complement their traditional RF video offering with an asymmetrical data service.
Cable operators have a variety of options to evolve their network, but those can be boiled down to two basic approaches: upgrade the HFC and DOCSIS, or deploy 10G PON via FTTH.
Operators with HFC networks generally have two options for addressing bandwidth demand and competitive pressures. First, they can segment nodes to boost per-subscriber bandwidth. By splitting a node designed for 500 households among 250 subscribers, an operator can provide more bandwidth without fundamental technology changes. Second, they can add blocks of additional DOCSIS channels through channel bonding. More DOCSIS channels means more bandwidth on a per-node basis but consumes precious spectrum.
There are challenges to the more traditional approaches. Cable operators have limited RF spectrum for services. They use most of this spectrum for video and a smaller portion for broadband data services. This usage trend will reverse over the next decade, as subscribers consume more data and watch more over-the-top video through streaming services.
Some cable operators have embraced a Node+0 architecture. This approach removes the cascade of amplifiers (e.g., six amplifiers equates to a Node+6 architecture) typically deployed along the coaxial run between the node and subscribers’ home. It allows operators to push the fiber portion of the HFC network closer to subscribers and make the coax run shorter. By removing amplifiers and moving the optical-to-electrical conversion deeper in the network, operators can achieve a cleaner, lower-noise plant that supports new higher-bandwidth DOCSIS technologies.
To better understand the difficult choices facing cable operators, Calix, with assistance from CCI Systems, analyzed the cost of evolving brownfield cable networks using different technologies and deployment options. This analysis focused on comparing the cost of constructing and operating gigabit-capable HFC and PON networks. Specifically, the study compared the cost to upgrade a traditional HFC network – in low-, medium-, and high-density serving areas – to either a fiber-deep Node+0 or an FTTH network architecture. The study revealed that FTTH is the best upgrade choice for low- and medium-density serving areas, with lower capital expense (capex) and operational expense (opex) to that of a fiber-deep approach. The best choice was less clear in high-density serving areas. Readers may access the study here: https://go.pardot.com/l/2172/2018-06-18/3t9c4g?utm_source=none&utm_campaign=none&utm_content=none&utm_medium=none&utm_term=none.
For low-density serving areas, the FTTH option (including all engineering, material, and construction costs) required just under 20% less investment than a fiber-deep Node+0 architecture. For the medium-density neighborhoods, deployment costs for FTTH and Node+0 are comparable; however, an FTTH rollout offers the benefits of lower opex and greater flexibility to address future bandwidth demands.
In contrast, for high-density serving areas, the best choice of upgrade paths was less clear. Node+0 requires 36% less cost than FTTH. FTTH offsets this disadvantage with several advantages including overall lower opex and scalability—future proofing the access network so that the platform is already in place and fully amortized when an upgrade to 25G or 50G is required.
For markets served by smaller regional cable operators (those outside of the top handful of MSOs), 10G PON may be the most cost-effective and logical network evolutionary path. Offloading select high-bandwidth businesses and residential subscribers to a co-located PON eliminates the need for incremental HFC upgrades and a reliance on technologies such as Full Duplex or Expanded Spectrum DOCSIS. In addition, by deploying FTTH via 10G PON the cable operator can mobilize their network now to position them for future success.
Conversely, operators moving down the DOCSIS 4.0 path will have to wait until integral components are commercially available. A move to DOCSIS 4.0 requires nodes/Remote PHY devices (RPDs), amps, taps, drops, and modems that must be changed to enable spectrum usage beyond DOCSIS 3.1. Commercially available modems are not anticipated to be available for another 18 to 24 months. Operators will exert significant cycles implementing these network upgrades, all of which will have material impacts to customer service availability. For operators who have yet to move to DOCSIS 3.1, a strategy to eventually deploy DOCSIS 4.0 means planning for waves of operational and customer-impacting initiatives.
As network demands continue throughout the coming years, and an influx of capital is driving broadband deployments, operators are moving more quickly to deploy their access network of tomorrow, today. For many operators, FTTH and 10G PON is the chosen deployment and will position their companies to offer high-speed symmetrical service to multiple customer segments including consumer, business, and wholesale.
Jeff Brown is director, product and field marketing, at Calix.