Are You Ready for the DOCSIS Impact on Fiber?
Data Over Cable Service Interface specification (DOCSIS) is the international standard developed by CableLabs used to provide internet access over the cable system. Introduced way back in 1998, the standard has evolved over time, with ever-increasing data rates.
The latest version, DOCSIS 3.1, allows up to 10Gbps downstream and 1Gbps upstream, which to-date had only been possible with a fiber optic connection, and can, with few infrastructural changes, be easily deployed over existing infrastructure. It should be mentioned that to meet these speeds, DOCSIS 3.1 must be supported on both ends of the connection. This game changer gives cable operators the ability to prolong the lifespans of their existing Hybrid Fiber Coax (HFC) investments, keep up with rival fiber optic Internet Service Providers (ISPs), and not have to change out the ‘last mile’ of their existing deployments.
DOCSIS 3.1 enables things like Ultra-High Definition (UHD) or 4K broadcast, faster WiFi access speeds, and with Active Queue Management (AQM), delay can be reduced for time-sensitive applications, such as online gaming. Given the insatiable appetite subscribers are showing for bandwidth consumption for things like Over-the-Top (OTT) and other applications, DOCSIS 3.1 will only further exacerbate the packet-bandwidth conundrum. We live in interesting times.
With such an improvement over DOCSIS 3.0, DOCSIS 3.1 will become commonplace in homes and businesses alike, as vendors expect to ship millions of DOCSIS 3.1 cable modems in the next few years - even Walmart is getting into the game!
There are over 40 million DOCSIS cable modems already deployed worldwide, and up to 80% of those units are expected to migrate to DOCSIS 3.1, not to mention additional growth in the next few years. Doing the rough math, this translates to a theoretical load of 32 terabits per second on the network! Only one medium can economically deliver those kind of capacity numbers – fiber.
As a shared medium, coaxial cable is about to get very crowded.
As a limited shared medium, coaxial cable has delivered DOCSIS 3.0 services for almost a decade. However, over those years, average customer broadband bandwidth rates were in the 10s and 100s of megabits, not gigabits. This meant cable operators really didn’t have to change much of their fiber distribution networks.
However, with bandwidth rates soaring, without change, pretty much every broadband customer, and remember there are millions, will experience severe negative impact to their quality of experience. For cable operators to secure their packet-bandwidth futures, significant changes to the cable access and distribution network are required to re-sod cable MSO brownfields.
It follows then that the knock-on effect of all this extra bandwidth on the cable infrastructure cannot be ignored. For the cable operator, fiber technology enabling unprecedented density, capacity, and scalability will be needed to drive down energy and transport costs.
Ciena’s modular packet-optical architecture approach, along with coherent optical technology, allows cable operators to maximize capacity at any distance, seamlessly upgrading to higher speeds, up to and including 400Gbps. By driving optical fiber deeper, cable operators can improve performance and reliability, increase capacity, reduce the high cost of coaxial cable, and provide faster download and upload speeds – not bad at all!
Just wait until Virtual Reality (VR) and Augmented Reality (AR) take hold and significant packet-centric bandwidth is needed in the upstream. If you’re thinking DOCSIS is the answer, you’re right, as a full-duplex version allowing 10Gbps down and 10Gbps upstream is already being planned - effectively doing the same to the upstream.
With Ciena. your need-for-speed can be satiated.
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by Wayne Hickey
Barry, thanks for the comment. Typically, Point-to-Point PON supports an Ethernet protocol, using a dedicated fiber to/from the customer terminating on an Ethernet Switch in the Central Office (CO). The two most common Passive Optical Network (PON) technologies of the day are EPON/GPON, both using symmetrical Gigabit Ethernet upstream and downstream speeds. GPON (ITU-T G.984) was developed for higher speeds and used in Point-to-Multipoint Fiber-To-The-Home (FTTH).
Both Point-To-Point and Point-To-Multipoint suit fiber rich and green field deployments very well. However, most cable operators are not fiber rich, using fiber assets for their business class (enterprise customers) endeavors. Also, there are significant challenges, if not impossible, to gain access in the last mile. You must have customer, civic and legal right of way approvals fixed line infrastructures. While it can be done, it’s not cheap, not everyone will allow access or wait for the disruption.
Tightening up active coaxial systems has been the ‘bane’ of cable operators for decades, and one of the major reasons to push fiber deeper, not to forget capacity too. Eliminating actives, using passive coax, and reducing the service group size to 64, provides cleaner plant to enable D3.1 and alleviate that ‘bane’.
D3.1 uses new technologies, like OFDM (Orthogonal Frequency Division Multiplexing), variable modulation profiles, and LDPC (Low Density Parity Check), to allow increased spectrum utilization.
You bring up another really good point, in trouble isolation and maintenance. Automated or embedded tools can allow finding the location of fiber cuts and other impairments, avoiding unnecessary truck rolls and expensive test equipment.
by Barry Miller
D3.1 is very smart technology for sweating the asset but the total cost of ownership is still considerably higher than a GPON or P2P fibre network and getting your HFC environment clean enough to realise 2k QAM or 4k QAM to see beyond 1Gb after deploying D-CMTS and segmenting your nodes and housing your amps beyond 750MHz, ultimately means you've invested about the same amount you would have to over build your coax plant with micro ducting and voiding fibre, while still maximising the use of as much of your layer zero infrastructure as possible.
Both solutions require subscriber visits for upgrades, product development with OSS/BSS uplifts for provisioning of new products on new technologies and updates of network records systems.
PNM has the potential to be a very useful tool to drive impressive efficiency in trouble isolation and resolution but the fact that we had to build a tool help maintain the HFC environment is a great indicator of the level of maintenance, and therfore operating cost and effort, associated with the solution.
Were I faced, again, with the decision to upgrade my HFC plant or overbuild it with fibre I would fight tooth and nail for fibre, as that is beyond any doubt the most robust foundation for any operator to build their next generation network foundation on and it will never be cheaper to do that than it is today.