Presentation from SIEPON Seminar on 20 April in Czech Republic, sponsored by IEEE-SA & CAG. Opinions presented by the speakers in this presentation are their own, and not necessarily those of their employers or of IEEE.
“EPoC”:The Art of Mixed Media Edwin J. Mallette 04/21/2012
This Talk Will Cover:(A Few) Drivers for the EPON Protocolover a Coax (EPoC) PHYCoaxial Network TypesEPoC Deployment ModelsCoaxial Network VariabilityNeeded Flexibilities in the EPoC PHYClosing Remarks.
(A Few) Drivers for EPoCEPoC is the EPON Protocol over a Coax PHY. Theintent is that the EPON MAC is intended to becommon across EPoC and EPON.Some operators have a strong desire for high line-rateperformance with features included in EPON (e.g. QoSguarantees) where the drop to the subscriber happensto 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 TypesThere 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 anactive plant (as evidenced by the triangle-amplifiericons.)
EPoC Deployment Model1In one case the deployment might involve someEthernet-Optical backhaul of the Coax Line Terminal(CLT)The CLT has EPoC PHYs operating the EPON protocolon 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 theMDU, the deployment might involve an Optical Line Terminal (OLT) in theCentral Office (CO) with an Optical-Coax Unit (OCU).The OCU could operate as a layer-1 repeater / media converter to simplyconvert optical to electrical and electrical to optical.The OCU could operate as a layer-2 bridge which in addition toconverting between media types might provide other functions helpfulfor 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 servicemanagement overhead (single MAC.)
EPoC Deployment Model3This is similar to the previous deployment asthe OLT is centralized in the CO with an OCUoperating to perform the media conversion.In this case, the OCU is deployed into anactive coaxial outside plant.
CxDN Variability1The coaxial plant is widely variable from operator tooperator, within an operator’s networks from market tomarket, even within the same market.The coaxial plant where the EPoC PHY has to live maybe 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 ormay pass a much smaller number like 20.The coaxial plant distance may be small – 200 metersor less, or large – ~2 kilometers.Specific plant conditions, depending on how well thecoaxial plant is maintained, what kind of spuriousnoise is generated into the plant, etc, vary fromdeployment to deployment.
CxDN Variability2In some deployments, the coaxial plant supports a single servicewith all usable frequencies being allocate-able to the EPOC PHY fora single CxDN.In other deployments, the coaxial plant supports a multitude ofother 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 FlexibilityTo 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+ Upstreamand 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 havetwo MACs – one for the EoC and a separate MAC for EPON.This commonly means separate provisioning of both the opticaland coaxial network devices.EPoC provides efficiency in a common MAC, shared with themost widely deployed FTTX technology in EPON.EPoC is expected to simplify forwarding, reduce protocolconversion, and simplify provisioning (over other EoC+EPONsolutions).And coax drops aren’t going away any time soon (largely due totime and money constraints.)The ultimate desire with EPoC is to be able to leverage the vastEPON supplier market to hold down the costs of future EPoCproducts.And provisioning of EPON with specifications like DPoE to alsoprovision EPoC access is KEY.