“EPoC”:The Art of Mixed Media

Edwin J. Mallette04/21/2012

This Talk Will Cover:

(A Few) Drivers for the EPON Protocol over a Coax (EPoC) PHYCoaxial Network TypesEPoC Deployment ModelsCoaxial Network VariabilityNeeded Flexibilities in the EPoC PHYClosing Remarks.

(A Few) Drivers for EPoC

EPoC is the EPON Protocol over a Coax PHY. The intent is that the EPON MAC is intended to be common across EPoC and EPON.Some operators have a strong desire for high line-rate performance with features included in EPON (e.g. QoSguarantees) where the drop to the subscriber happens to be comprised (in full or in part) of coaxial cable.Specific operator use cases include: Operators that use EPON to backhaul other Ethernet over

Coax solutions which are used to reach subscribers over coaxial cable within a Multiple Dwelling Unit (MDU).

Operators with DOCSIS deployments who are also deploying EPON for higher speed first mile access and are interested in EPON-like performance over a CxDN with DOCSIS Provisioning of EPON (DPoETM).

Coaxial Network Types

There are two general types of coaxial networks The first is the “Passive” coaxial plant; one that does not

use line extenders, amplifiers, or other in-line powered devices.

The second is the “Active” coaxial plant which uses amplifiers to extend reach, distance, supported number of splits on the coaxial plant.

The diagram below depicts two CxDNs with an active plant (as evidenced by the triangle-amplifier icons.)

EPoC Deployment Model1In one case the deployment might involve some Ethernet-Optical backhaul of the Coax Line Terminal (CLT)The CLT has EPoC PHYs operating the EPON protocol on the Coax Distribution Network.Operator would directly manage the in-building CLT.In the example below two CxDNs are shown below, analogous to Optical Distribution Networks (ODNs).

EPoC Deployment Model2In another case, as depicted with a diagram depicting service to the MDU, the deployment might involve an Optical Line Terminal (OLT) in the Central Office (CO) with an Optical-Coax Unit (OCU).The OCU could operate as a layer-1 repeater / media converter to simply convert optical to electrical and electrical to optical.The OCU could operate as a layer-2 bridge which in addition to converting between media types might provide other functions helpful for aggregation, etc.Operator would directly manage the service through the OLT in the CO.The OLT would directly manage the Coaxial Network Units (CNUs) through the OCUs. This model has some benefits in easing some service management overhead (single MAC.)

EPoC Deployment Model3

This is similar to the previous deployment as the OLT is centralized in the CO with an OCU operating to perform the media conversion.In this case, the OCU is deployed into an active coaxial outside plant.

CxDN Variability1

The coaxial plant is widely variable from operator to operator, within an operator’s networks from market to market, even within the same market.The coaxial plant where the EPoC PHY has to live may be active or passive. In active coaxial plants the amplified bands may be as high

as 1000MHz or may be lower like 600MHz. This has implications W.R.T. how far amplifiers are spaced

apart.For EPoC, a single CxDN may pass 1000 subscribers or may pass a much smaller number like 20.The coaxial plant distance may be small – 200 meters or less, or large – ~2 kilometers. Specific plant conditions, depending on how well the coaxial plant is maintained, what kind of spurious noise is generated into the plant, etc, vary from deployment to deployment.

CxDN Variability2

In some deployments, the coaxial plant supports a single service with all usable frequencies being allocate-able to the EPOC PHY for a single CxDN.In other deployments, the coaxial plant supports a multitude of other services including: Video services in 6MHz or 8 MHz channels – either digitally encoded or

legacy analog TV services. Cable-modem (e.g. DOCSIS) services in multiple sets of channels with

channel widths between 800KHz and 8MHz channels. Narrow-band service management and control channels. These same services commonly occupy different frequency ranges

market by market.

Reference : MSO Topology Scenarios, IEEE802.3 EPoC SG 2012‐03‐13 Meeting 

PHY Flexibility

To account for this physical layer variability, the EPoCPHY will need to support: Flexible (and configurable) Upstream and Downstream

frequency placement and frequency band widths. Flexible (and configurable) bit-loading (bits per Hertz)

within a sub-carrier. Flexible upstream and downstream MAC data rates. Traversing in-line amplification, equalization as well as

“unimproved” (e.g. un-amplified) spectrum. Compatibility with other services. Robustness to survive in harsh (e.g. noisy) conditions even

if the MAC data rate must be reduced.With the goal of supporting up to 1Gbps+ Upstream and Downstream in some amount of spectrum.

Closing RemarksThere are many Ethernet over Coax technologies out there.Often in-MDU EoCs that use EPON as the loop to the MDU have two MACs – one for the EoC and a separate MAC for EPON.This commonly means separate provisioning of both the optical and coaxial network devices.EPoC provides efficiency in a common MAC, shared with the most widely deployed FTTX technology in EPON.EPoC is expected to simplify forwarding, reduce protocol conversion, and simplify provisioning (over other EoC+EPONsolutions).And coax drops aren’t going away any time soon (largely due to time and money constraints.)The ultimate desire with EPoC is to be able to leverage the vast EPON supplier market to hold down the costs of future EPoCproducts.And provisioning of EPON with specifications like DPoE to also provision EPoC access is KEY.

Thank You!!->