Cable operators are ever pressed in keeping up with their customers’ increasing demand for faster bandwidth over their coaxial cable. For most subscribers around the world, many of whom live in apartment buildings, fiber cable stops at the street, basement, or curb, with coax spanning the remaining distance. Replacing that coax with faster optical fiber or pulling fiber from the street to the buildings takes time and is expensive. But the IEEE 802.3 Ethernet Working Group believes it has a solution: use the Ethernet passive optical fiber network, known as EPON, and have it feed those end-of-the-line coax cables. After all, notes the working group, by supporting more than 60 million subscribers, the IEEE 802.3 EPON standard is already the market leader in fiber access technology. That number is expected to grow to 100 million by the end of this year.
Key to the effort by the IEEE P802.3bn EPON Protocol Over Coax (EPoC) Task Force is a new PHY (Physical Layer) standard for operating the EPON protocol transparently over coaxial distribution networks. The idea is to increase throughput while maintaining a single protocol from end to end.
“We are working to extend Ethernet over cable operators’ coax networks in a seamless fashion so it looks like EPON and delivers the same class of service,” says Senior Member Mark Laubach, chair of the task force and technical director at Broadcom, in Irvine, Calif.
One of the ways some operators are delivering more gigabits is through a Data Over Cable Service Interface Specification, known as DOCSIS. The standard allows for high-speed data transfer and Internet access over the existing hybrid fiber-coaxial (HFC) infrastructure. The North American cable industry is currently developing the next version of the DOCSIS specification, DOCSIS 3.1, with the initial work due out this year. In addition, this and the new IEEE P802.3bn EPoC will allow cable operators to delay costly fiber-to-the-home deployments or avoid them altogether by extending the life of HFC.
“Many operators offering high-speed Ethernet services to businesses have been using the EPON standard in parallel to the DOCSIS system,” says Laubach. “Likewise, EPoC will be in addition to DOCSIS, not in competition with it. One important aspect of adding EPoC to the mix of access network services is that it gives a cable operator more options for the future. Using EPoC, operators will be able to deliver from the same cable TV head ends but use EPON to extend business-class service to their customers. One of the nice things about the EPON protocol is that it very much adheres to metropolitan-area Ethernet.” (Such Ethernet covers subscribers in larger service networks.)
The idea for EPoC started in China, according to Laubach. Cable operators there were looking for a way to supply EPON services from optical fiber cables in the streets to coax customers not a kilometer or even 100 meters away, who were mostly in multiple-dwelling units. But they couldn’t do it on their own. Rather, an international standard had to be developed. Accordingly, individuals from various vendors and cable operators developed a Call for Interest and approached the IEEE 802.3 Working Group about extending the EPON network over coax to supply gigabit services that would meet metro Ethernet standards.
“The working group thought about it and decided, ‘Yes, we can do that,’” Laubach says. A study group was formed and first met in January 2012, and drafted the IEEE Standards Association Project Authorization Request and other documents that were submitted into the approval process. As a result, the IEEE P802.3bn EPoC PHY Task Force was created in August 2012. Cable operators in North America as well as in Europe and Japan liked the idea as well, and their representatives are also on the task force.
The IEEE P802.3bn effort seeks to enable cable operators to offer an end-to-end Ethernet network capable of efficiently supporting next-generation services such as video over IP and Internet Protocol Television. It will be designed for adapting to a cable operator’s network with an architecture-scaling requirement for up to 10 Gb/s using OFDM (Orthoginal Frequency Division Multiplexing).
“It also will maintain compatibility with existing IEEE 1G-EPON and 10G-EPON standards,” Laubach says.
IEEE P802.3bn objectives include a PHY specification capable of a baseline data rate of 1 Gb/s at the interface between the MAC layer and the physical layer data rate when transmitting in 120 MHz or less of assigned spectrum under defined baseline plant conditions; or a data rate lower than the baseline rate when transmitting in less than 120 MHz of assigned spectrum or under poorer-than-defined conditions. The standard also will handle a higher than 1 Gb/s baseline data rate and up to 10 Gb/s when transmitting in its assigned spectrum if channel conditions permit it.
The project is also defining an optional Energy-Efficient Ethernet setting for operation on EPoC PHYs that will allow power consumption to be reduced by half or more during periods of low activity.
“Everyone views the EPoC solution as a very straightforward extension of Ethernet,” says Laubach. “It’s not complicated; it’s straightforward and it’s tailored to make sure Ethernet runs over that medium.”
The standard is on track to be approved in early 2015.