Preparations for Full Duplex DOCSIS® Technology are Marching Along
Built on the successful completion of CableLabs’ DOCSIS 3.1 specification, Full Duplex (FDX) DOCSIS® technology (now a part of DOCSIS 4.0 technology) is a key component of the 10G platform that will significantly elevate the level of services available to consumers using existing cable broadband networks. With FDX DOCSIS technology (now a part of DOCSIS 4.0 technology), the same frequencies are simultaneously used for both upstream and downstream traffic, virtually greatly increasing the capacity of the coaxial cable. More capacity means lower latency and speeds of up to 10 Gbps for downstream traffic and up to 6 Gbps for upstream traffic. Cable broadband users will be much more satisfied with services, leading to greater customer retention and the ability to attract new customers.
Field Testing Analysis
In the past year, CableLabs has thoroughly scrutinized FDX DOCSIS technology (now a part of DOCSIS 4.0 technology) in the field. Test equipment and engineers have flown around North America performing analysis on real cable broadband networks, including both a newly constructed plant and coaxial cable that was installed back while I was in college (that coax is well past voting age…). Volumes of data were collected, such as technical parameters on various configurations and various weather conditions: data from real networks in the real world.
And it works. The testing results were positive and in line with expectations, and products built to the specifications are expected to deliver the higher symmetrical bit rates associated with full duplex operation. Now, coaxial cable networks won’t be a limiting factor in getting to full duplex and the next generation of broadband services.
Now that CableLabs has developed FDX DOCSIS specifications (now a part of DOCSIS 4.0 technology), members can move forward with this exciting technology. Members can further benefit from the Kyrio testing services that provide all the engineering expertise and lab equipment needed for testing FDX DOCSIS (now a part of DOCSIS 4.0 technology). All the operator has to do is identify network segments where the work is to be performed.
What’s Coming in 2019
Getting back to the lab (which is a lot dryer and warmer than some of the outside plant scenarios where CableLabs has worked), CableLabs is:
- Hosting lab activities to support the development and interoperability of FDX DOCSIS (now a part of DOCSIS 4.0 technology) products
- Bringing back important discoveries from the field testing into the labs to support testing in real-world situations and scenarios.
- Building the lab infrastructure needed to rigorously analyze performance and reliability in a variety of configurations
CableLabs and the cable industry are continuing to advance cutting-edge developments in cable broadband networks to remain ahead of consumer demand. The focus is on developing innovative network technologies, as well as defining optimal network architectures that provide the necessary capacity and performance in each network segment for multi-gigabit services today and in the future.
You can learn more about Full Duplex DOCSIS technology (now a part of DOCSIS 4.0 technology) and the 10G platform by clicking below.
CableLabs Hosting a Free Full Duplex DOCSIS® Technology Seminar
CableLabs is hosting a free Full Duplex (FDX) DOCSIS® technology (now DOCSIS 4.0 technology) seminar , April 17–18, 2018 that will be attended by both cable operators and DOCSIS suppliers. The seminar will take place at a private events center to provide attendees with a comfortable and professional setting to learn all about Full Duplex DOCSIS technology (now DOCSIS 4.0 technology).
Scheduled speakers will be technologists who developed the FDX DOCSIS (now DOCSIS 4.0 technology) specifications, . Most have been involved with DOCSIS technology since the beginning, all are accomplished speakers who possess a wealth of knowledge to share not only about FDX DOCSIS (now DOCSIS 4.0 technology) but also about how the technology integrates into the family of DOCSIS generations.
FDX DOCSIS 3.1 technology (now DOCSIS 4.0 technology) allows cable operators to offer symmetric gigabit-speed data services over their existing Hybrid Fiber/Coax (HFC) networks, building on the core DOCSIS 3.1 orthogonal frequency-division multiplexing (OFDM)/orthogonal frequency-division multiple access (OFDMA) technology. This additional set of features significantly increases upstream capacity and allows for the same spectrum to be simultaneously used for both downstream and upstream.
The technology seminar will cover a wide range of topics, including:
- The physical layer: The physical layer topic includes how both OFDM and OFDMA have been extended to allow full duplex operation. This also includes how FDX DOCSIS (now DOCSIS 4.0 technology) fits into the channel plan, and how the system is expected to operate.
- The Media Access Control (MAC) layer: This topic includes both how the cable modem termination system (CMTS) manages the full duplex spectrum and how today’s FDX (now DOCSIS 4.0 technology) modems initialize and communicate with the CMTS for full duplex operation.
- Link Budgets and System Performance: This topic will discuss how to manage both signal levels and loss throughout the system in order to maintain peak operating performance.
- FDX DOCSIS support of existing DOCSIS modems: This topic concerns how FDX DOCSIS (now DOCSIS 4.0 technology) modems will be tested for backward compatibility with earlier versions of DOCSIS modems; they will all operate on the same cable plant with no need to upgrade older modems.
- Fiber Node changes: What will change in the Fiber Node, which now supports a Distributed Access Architecture (DAA) solution to distribute part (or all) of the CMTS to the fiber node?
- Node+0 Tips: These tips and considerations will focus on Node+0 (passive coax) plant construction to support FDX DOCSIS (now DOCSIS 4.0 technology).
The technology seminar has been designed to foster interactive discussion with the audience. FDX DOCSIS (now DOCSIS 4.0 technology) is an extension of the DOCSIS 3.1 technology and now involves the HFC network to create a system that offers symmetric capacity. Presentations will offer critical insights into these aspects of the architecture and technology. Attendees will come away with a greater appreciation and understanding of FDX DOCSIS’s (now DOCSIS 4.0 technology) underlying mechanisms.
The FDX DOCSIS technology (now DOCSIS 4.0 technology) seminar is free to attend and is open to all CableLabs members and DOCSIS NDA suppliers. The audience is intended to be composed of technology leaders involved with the early deployments of DOCSIS, including not only the DOCSIS engineers but also experts in outside plant and construction as FDX DOCSIS (now DOCSIS 4.0 technology) uses a Node+0 HFC network.
This technology seminar overlaps with an FDX DOCSIS (now DOCSIS 4.0 technology) interop being held at CableLabs the week of April 16. All CableLabs members and suppliers participating in the interop have the opportunity to tour the interop and witness FDX DOCSIS technology (now DOCSIS 4.0 technology) in operation, viewing—for perhaps the first time—the same spectrum carrying simultaneous upstream and downstream traffic.
With the CableLabs membership spanning five continents, the seminar will provide a unique opportunity for networking, as well as connecting or reconnecting with colleagues involved with the introduction of new DOCSIS technology. The seminar will offer a diverse set of deployment scenarios, and the discussions will include how FDX DOCSIS (now DOCSIS 4.0 technology) can support the needs of cable operators.
Full Duplex DOCSIS® Technology Gets MAC Layer Support
Full Duplex (FDX) DOCSIS® (now a part of DOCSIS 4.0 technology) is an update to DOCSIS 3.1 specifications that builds on the core Orthogonal Frequency Division Multiplexing (OFDM) technology. This additional set of features significantly increases upstream capacity and allows for the same spectrum to be used as downstream or upstream.
The set of MAC Layer technology changes to support FDX DOCSIS has now been incorporated into the next version of the DOCSIS 3.1 MULPI specification. This supports the PHY layer FDX functionality introduced last October. The new FDX DOCSIS capability and functions are introduced as changes across the MULPI (MAC and Upper Layer Protocols Interface) specification and is now an official part of the specification. This important milestone is the result of a great deal of work by CableLabs members, vendors and employees during the past year, and we take this opportunity to acknowledge their valuable contribution to the cable industry.
New MAC Layer Functionality Introduced
The MAC layer functionality introduced supports the new FDX DOCSIS operation on the hybrid-fiber-coax (HFC) link. It is focused on MAC management messaging and operation needed to enable FDX DOCSIS between the CMTS (Cable Modem Termination System) and CM (Cable Modem). This includes FDX DOCSIS channel acquisition/initialization process by a CM, and new processes such as Sounding, Echo Cancellation training, and Resource block assignment.
How it Works – Cable Modem to CMTS Communication
An FDX DOCSIS CMTS will simultaneously receive and transmit in the same FDX DOCSIS spectrum, while FDX DOCSIS (now a part of DOCSIS 4.0 technology) CMs can either receive or transmit in the same FDX DOCSIS spectrum. Thus, communication is full duplex from the perspective of the CMTS but frequency division duplex from the perspective of the CM.
The FDX DOCSIS band is divided into sub-bands and the CMTS assigns which sub-band(s) each CM uses for upstream or downstream operation. This is referred to as a resource block assignment (RBA). Different CMs will have different bandwidth demand for both the upstream and downstream directions which can change over time, and FDX DOCSIS allows for the RBA to be changed dynamically.
A sounding method is used to identify groups of CMs, called Interference Groups (IGs), that would interfere with each other if they were allowed to transmit and receive at the same time in a sub-band. IGs are grouped together into a small number of Transmission Groups (TGs), CMs in the same TG either transmit or receive on any given sub-band and time, as signaled by the CMTS in the RBA. CMs from different TGs have enough isolation to transmit and receive at the same time in the same sub-band.
FDX DOCSIS uses a combination of interference cancellation and intelligent scheduling at the CMTS. On the CM, in order to prevent upstream transmissions from interfering with adjacent downstream channels in the FDX band, echo cancellation techniques are used.
What’s Next for the Full Duplex DOCSIS Technology?
As the FDX DOCSIS specifications mature, we will start to see products with full-duplex capabilities over the next year as silicon designs become available and are incorporated into product designs. In an effort to increase the pace of product development, CableLabs has announced a series of FDX DOCSIS Interoperability events , starting in February. These will start from basic node level echo cancellation and gradually progress into full-blown product interoperability.
The collaborative model at CableLabs for developing common cable industry specifications minimizes interoperability issues and gets the best in class features into the specifications. This accelerates time to market for a product, with the operator getting to deployment faster, and ultimately the consumer gets to reap the benefits of the latest technology.
In the meantime, the big wheels of CableLabs specification work continue to turn:
- We are developing the OSS (Operations Support Systems) changes needed to support FDX DOCSIS.
- We have initiated work for the changes needed to support FDX DOCSIS within the Remote PHY realm. (FDX, now a part of DOCSIS 4.0 technology, assumes a distributed architecture and a plant which supports a node plus zero actives due to the CMTS node echo cancellation functionality)
- As suppliers build the FDX DOCSIS products, the feedback loop into the FDX (now a part of DOCSIS 4.0 technology) specifications remains open and the PHY & MAC specifications continue to be refined.
Full Duplex DOCSIS significantly increases upstream capacity on the HFC network, allows flexible splits of upstream and downstream capacity, and enables cable operators to deploy multi-gigabit symmetrical services. With all the innovations being developed by the industry, it is a great time to be a consumer of high-speed data services over cable.
Karthik Sundaresan is a Principal Architect at CableLabs responsible for the development and architecture of cable access network technologies. He is primarily involved in the DOCSIS family of technologies and their continued evolution.
Subscribe to our blog to stay current on Full Duplex DOCSIS technology (now a part of DOCSIS 4.0 technology).
CableLabs Publishes Full Duplex DOCSIS® Specification
Recently, in a significant step for the cable industry, we announced the successful completion of the Full Duplex DOCSIS® 3.1 specification (now a part of DOCSIS 4.0 technology). Today, we are pleased to announce the release of the DOCSIS® v3.1 Physical Layer Specification, which incorporates the addition of Full Duplex in Annex F per PHYv3.1-N-17.1771-6. The specification is designed to enable cost-effective solutions for cable operators for faster broadband speeds and brings peak upstream of up to 6 Gbps and downstream up to 10 Gbps.
Current DOCSIS networks are well suited to meet today's customer’s demands and needs. Full Duplex DOCSIS networks (now a part of DOCSIS 4.0 technology) enable operators to significantly increase the network’s upstream capacity and be ready for future applications, such as the increasing use of IoT devices, telemedicine, video chats, and virtual reality. Watch the video below to see how Full Duplex DOCSIS technology (now a part of DOCSIS 4.0 technology) solves this problem by enabling simultaneous upstream and downstream transmissions in the same spectrum over existing hybrid fiber/coax (HFC) networks, significantly increasing upstream capacity.
CableLabs Completes Full Duplex DOCSIS Specification
“In the United States, more than 90 percent of households are connected to an HFC (hybrid fiber-coaxial) network, and consumers typically have higher download speeds than upload speeds. By enabling Full Duplex DOCSIS (now a part of DOCSIS 4.0 technology), the upstream can flow up to 6 Gbps and downstream traffic can flow at up to 10 Gigabits concurrently, enabling the efficiency of spectrum use.” -- Phil McKinney, president and chief executive officer of CableLabs
The number of connected devices and bandwidth-hungry online experiences are expected to increase exponentially in the next decade. Also, with the continuous development of new applications that enable new experiences, such as augmented reality and virtual reality, an increase in upstream capacity demand is a matter of “when” and not “if." Operators are continuously challenged to find cost-effective solutions to meet this growing demand for faster broadband speeds. With a focus on solving this challenge of the future, CableLabs recently completed the Full Duplex DOCSIS® (now a part of DOCSIS 4.0 technology) specification.
Full Duplex DOCSIS (now a part of DOCSIS 4.0 technology) technology builds on the successful completion of CableLabs’ DOCSIS 3.1 specification, which made deployments of 10 Gbps downstream and 1 Gbps upstream broadband possible. Full Duplex DOCSIS technology (now a part of DOCSIS 4.0 technology) improves upon the DOCSIS 3.1 standard by:
- Significantly increasing upstream capacity
- Enabling symmetric multi-gigabit services over existing hybrid fiber-coaxial (HFC) technology
- Ensuring that cable operators are ready to meet future usage needs for technologies, such as virtual and augmented reality - although widespread consumer demand for high speed upstream is not yet here, operators need to be prepared when the time comes
Current DOCSIS networks have to juggle available upstream and downstream traffic. Full Duplex DOCSIS technology (now a part of DOCSIS 4.0 technology) supports multi-gigabit symmetric services by enabling concurrent transmissions in the same spectrum, providing the ability to increase the upstream capacity without sacrificing downstream capacity. This has the potential to greatly improve network efficiency and, in turn, customer experience.
Starting from Full Duplex DOCSIS (now a part of DOCSIS 4.0 technology) as an internal innovation, CableLabs developed this solution in collaboration with our members and industry partners, enabling cable operators to deliver multi-gigabit symmetric services. Full Duplex DOCSIS technology (now a part of DOCSIS 4.0 technology) offers high speeds over the existing infrastructure and is less expensive to deploy than fiber, while still maintaining backwards compatibility with previous generations of DOCSIS technology.
You can read more about our Full Duplex DOCSIS (now a part of DOCSIS 4.0 technology) specification effort in my article “Full Duplex DOCSIS Technology: Raising the Ante with Symmetric Gigabit Service.” Make sure to check our website later this month for the complete Full Duplex DOCSIS (now a part of DOCSIS 4.0 technology) specification.
Future Proofing Cable’s Optical Access Network: “A Coherent Story”
The demand for data network capacity has been growing exponentially year after year with no sign of stopping. If the past is a guide to the future, the cable industry must come up with radically more efficient use of the existing cable infrastructure in order to meet demand.
Today, the most constrained part of the network, and the most costly to upgrade, is the fiber infrastructure between the headend and the fiber node, to the wireless cell radio or to large business customers. Avoiding costly fiber re-trenching requires a fundamentally new approach to this part of the network. This is where coherent technology provides an opportunity.
If you are familiar with coherent optics, then you are aware that the technology has been used in long-haul fiber optic networks for decades. CableLabs has adapted that technology for use in short-haul access networks, and simplified it to reduce the cost. And it has much higher capacity for future growth than the analog optics that are used in many of today’s HFC networks – possibly more than 1,000 times more capacity! We have already demonstrated 50 times more capacity than analog optics can achieve today by using coherent optics on 80 kilometers of fiber, and more improvements are on the way.
Using traditional analog optics, to achieve that high transport medium quality requires increasing the optical transmit power level, which unfortunately reduces the number of optical analog carriers the fiber can support due to fiber non-linearity effects. Figure 1 shows a representation of fiber’s wavelength spectrum with 4 analog optical carriers.
Figure 1 – Fiber spectrum with 4 analog carriers
This limitation on analog optical transport has prompted the cable industry to look into other architectural evolution approaches. One approach that solves the analog limitation problem, while also tackling space limitations that may exist in certain hubs, is the distributed architecture approach. In a distributed architecture no radio frequency (RF) is transported through the optical link. The optical link does not contribute to distortion of the DOCSIS® RF signal, only the coaxial portion of the network is responsible for the degradation of the RF signal.
Today, this digital optical link uses intensity modulated direct detection systems such as the ones found in 10 Gigabit Ethernet links and in passive optical networks (PON). In these non-coherent systems, the signal modulation used is On-Off Keying (OOK). OOK is achieved by simply switching the laser source off and on. Non-coherent systems operate at lower power than analog optics and can therefore make better use of the wavelength spectrum in fiber. Figure 2 depicts the wavelength spectrum of fiber with several non-coherent OOK optical carriers.
Figure 2 – Fiber spectrum with intensity modulated non-coherent carriers
A high-capacity non-coherent (but digital) optical link can carry 100 Gbps using 10 wavelengths (optical carriers) carrying 10 Gbps each. Non-coherent systems are a suitable near term approach, but there are additional fiber resource challenges that have to be considered when evaluating a long-term strategy.
HFC Networks have been typically designed with 6 to 8 fibers connecting the hub to the fiber node. Two of these fibers are used for primary downstream and upstream connection and in some cases two additional fibers are used for redundancy purposes. The rest of the fibers were left for future use. Unfortunately, a large amount of these ‘future use’ fibers, because of an ever-increasing demand for bandwidth, have since been repurposed for business services, cell backhaul, node splits and fiber deep architectures. In some cases, only the two primary fibers that are feeding the fiber node remain available for access transport.
In fact, the architecture migration toward Full Duplex DOCSIS, which strives towards a more symmetric transport, relies on a node plus zero amplifiers (N+0) architecture. A typical node in today’s HFC networks will supply services to 500 households. When converted into an N+0 architecture, the result is the creation of 12 to 18 deeper N+0 nodes. The challenge for the optical portion of the access network becomes supplying enough bit rate capacity to 12-18 N+0 nodes, each capable of supplying 10 Gbps to residential subscribers.
This fiber shortage problem will only intensify as fiber demand for business services and wireless backhaul increases. Assuming that costly fiber re-trenching from hub to original fiber node is to be avoided, a different solution must be found to provide the required capacity. This is where coherent technology provides an opportunity!
Coherent technology has been used to achieve higher speeds than any other optical technology. In coherent optics, both amplitude and phase modulation are used to put information onto an optical carrier. This enables the generation of Quadrature Phase Shift Keying (QPSK) and Quadrature Amplitude Modulation (QAM) constellations carrying information. The nature of the coherent signal also allows the separation of the optical signal in two orthogonal polarizations. Each polarization can independently carry the two-dimensional constellations mentioned above. The signal processing used in coherent systems facilitates shaping of the spectrum of the signal to avoid interference with adjacent optical carriers. Along with the much lower power requirements, coherent technology allows for efficient multiplexing of the optical carriers within the wavelength spectrum of fiber. Figure 3 shows the wavelength spectrum of fiber with coherent optical carriers over 2 polarizations.
Figure 3 – Efficiently packed coherent optical carriers over orthogonal polarizations
Coherent optics has been used in the long-haul environment for over 30 years. The long-haul environment is a harsh environment that consists of very long distances, sometimes up to 3000 km. In a long-haul environment, significant channel compensation is employed to correct the long distance related impairments, making long haul solutions expensive.
The access network environment is very different from long haul networks in one key respect, optical links in access networks are typically no longer than 30 km. That is two orders of magnitude shorter than long haul. The complex and expensive system implementation that long haul is known for no longer applies to access implementation. The shorter fiber lengths result in minimal dispersion of the optical signal. Furthermore, since no in-line amplification is needed, non-linear distortion and noise are significantly reduced. This increases the link margin and enables much lower implementation costs. It is NOT your father’s coherent implementation!
Here at CableLabs® we have re-engineered the coherent link to meet the special conditions of the access network. We have developed technology that is higher performance and much lower cost when compared to long-haul or metro environments.
In the laboratory, we have achieved 256 Gbps over 80 km on a single wavelength with minimal dispersion compensation. That is ~26 times the capacity of what can be achieved over an analog optical carrier fully loaded with 1.2 GHz worth of DOCSIS 3.1 signals. We have achieved that using a symbol rate of 32 GBaud (32 GHz), using 16QAM modulation (4 bits per symbol) over 2 polarizations (32*4*2=256 Gbps). In addition, we have multiplexed eight of these wavelengths to achieve 2048 Gbps. That is 50 times more than what can be achieved over 4 analog optical carriers each with 10 Gbps of DOCSIS 3.1 payload!
The optical access environment could lend itself to further improvement in capacity per wavelength by further increasing symbol rate and/or modulation order. A future achievement of 64 QAM modulation could represent the pinnacle in efficiency and capacity per wavelength of our optical access environment. One can only dream of such transport efficiencies in the long-haul environment.
Coherent optics is extremely flexible. Capacities per wavelength greater than 256 Gbps may not be needed at each target end-point in the near future. Maybe 100 or 200 Gbps will do. The fact that modulation order, polarization and symbol rate can be varied enables significant flexibility in the type of supported services. Lower symbol rates allow for multiplexing 100 or 200 Gbps wavelengths to end points. In the access network, it makes sense to dedicate a single wavelength to a target end point (subscriber). In the access, since wavelength spectrum is a precious commodity, higher speed should not be wasted on multiple wavelengths but used to reach a greater diversity of target end-points. This avoids retrenching from the hub to original fiber node in order to lay additional fiber strands. Ideally, operators would only have to deploy more fiber from the original fiber node to deeper end-points in their networks.
As the industry evolves toward Node+0 architectures, the volume of optical connections to intelligent nodes will increase substantially compared to traditional architectures. Interoperability and a robust vendor ecosystem are therefore key to providing a low-cost solution using coherent optics.
With key goals being interoperability and vendor diversity, CableLabs intends to develop specifications which leverage the aforementioned benefits of coherent optics in the access network. Similar to previous specification development efforts, the coherent optics specifications will focus on interface requirements, signal integrity requirements, configuration, and management. As usual, CableLabs welcomes involvement from the vendor community to develop these specifications. In the near future, look for announcements related to the establishment of a coherent optics working group to develop the specifications.
At CableLabs, we are developing and specifying technology that allows the cable industry to support the growing requirements of broadband access. Come and join us in developing tomorrow’s high capacity network solutions!
Dr. Curtis Knittle, VP of Wired Technologies, also contributed to this article.
Full Duplex DOCSIS® Specification Effort Launches
During the CableLabs 2016 Winter Conference, CableLabs announced the Full Duplex DOCSIS (now a part of DOCSIS 4.0 technology) specification project that will significantly increase upstream speeds on the DOCSIS network. The announcement of the Full Duplex DOCSIS (now a part of DOCSIS 4.0 technology) extension of the DOCSIS 3.1 specification, and its potential of offering multi-Gbps symmetric services over the HFC network, created a lot of excitement in the industry. Since then a lot has been going on behind the scenes.
CableLabs has been actively collaborating with the vendor community to further refine the concept and system architecture of a Full Duplex DOCSIS (now a part of DOCSIS 4.0 technology) system. The ecosystem support for the Full Duplex DOCSIS technology (now a part of DOCSIS 4.0 technology) has been staggering, with many vendors collaborating and contributing to the development of the technology. A recent example is Cisco’s contribution of a new silicon reference design of a digital echo canceler that maximizes the use of HFC capacity to provide a scalable multi-gigabit return path.
In June, CableLabs officially launched the Full Duplex DOCSIS (now a part of DOCSIS 4.0 technology) project, transitioning it from the innovation phase to the R&D phase focused on specification development. Our first face-to-face meeting held in Louisville last month featured strong participation from CableLabs members and the vendor community including several new participants. Working group meetings will be held on a regular basis until the specification development is complete.
Full Duplex DOCSIS technology (now a part of DOCSIS 4.0 technology) will radically change the art-of-the-possible on the HFC network by delivering an unparalleled experience to cable customers.
Keeping Pace with Nielsen’s Law
The telecommunications industry typically uses Nielsen’s Law of Internet Bandwidth to represent historical broadband Internet speeds and to forecast future broadband Internet speeds. Mr. Nielsen predicted many years ago the high-end user’s downstream connection speed grows by approximately 50% compound annual growth rate (CAGR). In reality, actual peak service tiers offered by service providers over the years may be following something closer to 60% compound annual growth rate, as shown in the figure below.
The point of this blog is not to debate whether the growth rate is 50% or 60%, but rather if the growth rate continues, how do we evolve our networks to keep pace?
For point-to-multipoint networks there is a general rule of thumb for determining the peak service tier given a particular peak network capacity. This capacity-to-peak-tier ratio of 2:1 isn’t necessarily based in scientific fact, but comes from years of experience that a 2:1 ratio allows service providers to have a reasonable level of confidence that speed test measurements will accurately reflect a user’s subscription level. For example, for a particular access network technology, if the network supports 2 Gbps transmission rates to/from the access termination device (i.e., a cable modem) then the peak service tier typically won’t exceed 1 Gbps.
The present state of the art access network technology peaks at 10 Gbps. The IEEE 802.3 10 Gbps Ethernet Passive Optical Network (10G-EPON) has been deployed in China and the United States. ITU-T has recently consented XGS-PON, another 10 Gbps symmetric PON standard that uses the physical layer of XG-PON (ITU-T G.987.2) and 10G-EPON. Even the ITU-T’s NG-PON2 standard, which uses multiple wavelengths to increase network capacity, only defines a single wavelength per optical network unit (ONU), which puts NG-PON2 on par with 10G-EPON and XGS-PON in terms of meeting peak service tier rates. Finally, CableLabs is now certifying DOCSIS 3.1 devices which are capable of 10 Gbps downstream, and soon will certify 10 Gbps symmetric devices based on Full Duplex DOCSIS technology. What does this mean for accommodating Nielsen’s Law? Assuming the peak service tier trends continue, and given the 10 Gbps peak network capacity of current solutions, the maximum peak service tier will level off at approximately 5 Gbps (see red dashed line in chart above) until technology advances to allow higher rates. The telecommunications industry needs a technology roadmap beyond the current state of the art which allows for peak service tiers to exceed 5 Gbps.
CableLabs and its members, along with other service providers and the IEEE, are determined to stay ahead of the trends displayed in the graph above by contributing to the world’s first 100 Gbps EPON solution as part of the IEEE 802.3ca Task Force. The prevailing sentiment of the 802.3ca Task Force is to create a generational standard that allows for growth of peak network capacity (and corresponding peak service tiers) if and when such growth becomes necessary, without creating a new standard. This growth is expected to be achieved through defining four wavelengths, with each wavelength supporting 25 Gbps. Initial product developments will revolve around a single wavelength to provide a 25 Gbps EPON solution. When market conditions demand it, using two wavelengths along with a channel bonding solution will allow an ONU to transmit and receive at up to 50 Gbps. Similarly, with four wavelengths and channel bonding the ONU will transmit and receive at up to 100 Gbps. Examining the chart above, and assuming historical trends continue, the reader can see the 100G-EPON standard will support peak service tiers out to approximately 2030, give or take a couple years, assuming the 50% CAGR predicted by Nielsen continues.
One of the interesting facets of the 802.3ca Task Force activities relates to the improvement in efficiencies in the media access control (MAC). Previously, the IEEE 802.3 standard did not allow frame fragmentation, but recently with the completion of the IEEE 802.3br Interspersing Express Traffic Task Force, frame fragmentation is now allowed in networks based on the 802.3 standard. The 802.3ca Task Force plans to leverage fragmentation to make transmission more efficient in a multi-wavelength, channel-bonded environment. Additionally, contributions to the 802.3ca Task Force will improve the efficiency of the upstream bandwidth allocation process by allowing multiple service flow queue depth reporting and upstream granting in a single message pair. Considering the ITU-T SG15/Q2 is also investigating 25 Gbps per wavelength, the more promising and exciting aspect of these 802.3ca Task Force decisions is that the next generation of IEEE EPON and ITU-T GPON standards could be more closely aligned than ever before in the very near future! This makes a converged optical access solution closer to reality. (see a previous blog regarding a converged optical access initiative)
In his role as Vice President Wired Technologies at CableLabs, Curtis Knittle leads the activities which focus on cable operator integration of optical technologies in access networks. Curtis is also Chair of the IEEE 802.3ca Task Force.
A Sneak Peek of SCTE Cable-Tec Expo
CableLabs and Kyrio will be hosting a booth at the SCTE Cable-Tec Expo 2016. To provide you with a sneak peek of what we plan to show at the event, below are highlights of six demonstrations:
Full Duplex DOCSIS® 3.1 Technology
With Full Duplex DOCSIS 3.1 technology, the HFC network can support 10 Gbps Downstream x 6 Gbps Upstream symmetrical capacities in 1.2 GHz of spectrum. Multi-Gbps symmetric services will meet user demands and support future applications. Learn more about the next evolution of DOCSIS technology.
3.5GHz Shared Spectrum and Wi-Fi Traffic Aggregation
3.5 GHz (3.55 – 3.7GHz) shared spectrum offers the potential democratization of LTE. Cable operators can deploy LTE-based solutions within homes, offices and even in public environments to create low cost mobile networks. See how CableLabs multi-path TCP technology can help cable operators aggregate IP traffic from both 3.5 GHz spectrum and existing Wi-Fi access points to provide their customers with great wireless speeds.
Energy Efficiency of CPE (Consumer Premises Equipment)
CableLabs provides technical leadership to the industry through influencing energy efficiency voluntary agreements for set-top boxes and small network equipment as well as other energy efficiency initiatives. CableLabs also works closely with SCTE Energy 2020 to address end-to-end energy efficiency in the cable infrastructure. Learn more about the voluntary agreement initiatives and see CPE energy efficiency in action!
Automated Leakage Detection and Time Domain Reflectometer (TDR)
Cable operators can automatically gather their own leakage data for use as a diagnostic tool. This new detection method employs GPS and a continuous wave test signal and can pinpoint leakage sources. The leakage data can be used to make Proactive Network Maintenance (PNM) map overlays to speed problem resolution and to prevent LTE interference. The TDR uses standing waves on digital signals to accurately calculate the distance to reflections without interrupting service. Learn more about how these methods can improve network performance.
DOCSIS® 3.1 Profile Management Application (PMA)
The Profile Management Application implements a software application that can configure and manage DOCSIS 3.1 OFDM subcarrier modulation profiles on a DOCSIS 3.1 CMTS. This demonstration shows how PMA interacts with CMTSs, CMs, and other network elements to monitor, create, modify and then assign specific profiles to specific DOCSIS 3.1 CMs to optimize and maximize the capacity on a DOCSIS 3.1 OFDM Channel.
Real World Testing
In a world of constant change and innovation, the need for agility and assurance is crucial. Learn how Kyrio Testing Services provides their customers with the ability to adapt to new requirements, accelerate change, and assure quality of product performance and usability from the end user perspective.
We look forward to meeting you at the SCTE Cable-Tec Expo, Booth # 1424, September 26 – 29 in Philadelphia.
Full Duplex DOCSIS® Technology: Raising the Ante with Symmetric Gigabit Service
Building on state of the art technology, ongoing DOCSIS 3.1 technology deployments have squarely set the cable industry on the path to deliver Gigabit services over HFC networks.
But there’s more to come! A newly unveiled project at CableLabs illustrates how DOCSIS 3.1 technology provides the basis for continued evolution of system capacities by supporting symmetric multi-Gigabit service over the cable network. During its recent 2016 Winter Conference, CableLabs unveiled a Full Duplex DOCSIS technology (now a part of DOCSIS 4.0 technology) which applies emerging techniques from wireless networks to achieve a breakthrough increase in the upstream speeds for DOCSIS delivered broadband service. A Full Duplex DOCSIS (now a part of DOCSIS 4.0 technology) network is a prime example of the CableLabs 2.0 vision using its rich innovation funnel of technologies to transform the industry.
How is full duplex different from existing technologies?
Existing technologies mostly use either Frequency Division Duplexing (FDD) or Time Division Duplexing (TDD). In FDD, upstream and downstream (or uplink and downlink in the terms of the wireless world) traffic operate separately in dedicated parts of the spectrum. In current DOCSIS network deployments, the lower part of the spectrum is dedicated for upstream traffic and the upper part of the spectrum is dedicated for downstream traffic. In TDD, the upstream and downstream traffic share the same spectrum, but take turns in using the spectrum, similar to how Wi-Fi, or DSL, operate. In Full Duplex communication, the upstream and downstream traffic use the same spectrum at the same time, doubling the efficiency of spectrum use. A DOCSIS 3.1 Full Duplex network (now a part of DOCSIS 4.0 technology) provides the peak speeds and flexibility of TDD solutions, but one-ups both TDD and FDD with double the capacity.
Using a combination of Passive HFC and the self-interference cancellation and intelligent scheduling of DOCSIS 3.1 technology, CableLabs has built a solution that proves the viability of full duplex communication. Its approach significantly increases upstream data capacity in order to enable symmetric multi-Gigabit broadband data services for consumers and the enterprise. These developments are expected to yield DOCSIS 3.1 network performance of up to 10 Gbps symmetrical on 1 GHz HFC networks, with the potential for even higher performance by utilizing spectrum that is currently available for future expansion above 1 GHz.
One of the compelling attributes of a Full Duplex DOCSIS 3.1 network (now DOCSIS 4.0 technology) for the next evolution in HFC delivery is the strong foundation DOCSIS 3.1 technology provides. Our design and analysis shows that the existing Physical and MAC layer protocols in DOCSIS 3.1 technology can largely support this new symmetric service. The evolution to a DOCSIS 3.1 Full Duplex network (now a part of DOCSIS 4.0 technology) is an incremental evolution of DOCSIS 3.1 technology and will support both backward compatibility and coexistence with previous generations of DOCSIS network deployments.
So what’s next for the Full Duplex DOCSIS 3.1 technology (now a part of DOCSIS 4.0 technology)?
Over the next few months, we will engage with a team composed of our members and vendors who can help us further validate and mature the technology. Following which, if all signs remain positive, the project will transition from an innovation effort into an R&D project, open to all interested participants.
We are excited about this development effort, and look forward to its further evolution. Stay tuned to this blog for more exciting news from CableLabs.
Dan Rice also contributed to this article.
Belal Hamzeh is Vice President of Research & Development in Wireless Technologies group at CableLabs.