ITU-T G.9804.2 PDF

This Recommendation specifies the common transmission convergence (ComTC) layer of Higher Speed passive optical network (HSP) systems, providing optical access for residential, business, mobile backhaul, and other applications. HSP systems operate at rates specified in related PMD recommendations. This Recommendation supports both time division multiplexing (TDM) and time and wavelength division multiplexing (TWDM) modes of operation. As a general rule, TDM operation is considered a single wavelength channel pair case of TWDM operation. This Recommendation uses line rate parameterization to generalize the TC functions to enable a line rate agnostic TC specification for all HSP systems.

This Recommendation specifies:

– a layered structure containing three sublayers;

– functionality of the ComTC service adaptation sublayer, including the use of 10-Gigabit passive optical network (XG-PON) encapsulation method (XGEM), XGEM frame delineation, and service data unit (SDU) fragmentation;

– functionality of the ComTC framing sublayer with the specification of the downstream frame and upstream burst formats;

– functionality of the ComTC physical interface (PHY) adaptation sublayer, including synchronization, forward error correction, scrambling, and downstream interleaving;

– PON embedded management functionality, including control of the upstream time-division multiple access and dynamic bandwidth assignment mechanisms;

– the physical layer operation, administration, and management (PLOAM) messaging channel;

– the optical network unit (ONU) activation cycle state machine, covering activation, and wavelength channel handover;

– timing aspects of PON point-to-multipoint operation and time-of-day communication;

– performance monitoring, supervision, and defects;

– security including cryptographic mechanisms for authentication, integrity verification, channel isolation, and data protection along with the associated key exchange protocols;

– signalling mechanisms and protocols to support ONU power management;

– wavelength channel management;

– system protection;

– alien device and rogue ONU behaviour mitigation.

Line rate parameterization and PMD specification applicability

The present Recommendation is compatible with a wide class of PMD layer specifications describing single channel (TDM) and multiple channel (TWDM) PON systems that operate at the nominal downstream line rate in excess of 9.95328 Gbit/s and maintain the physical layer frame size of 125 µs. Any linkage to the actual line rates specified in such PMD specifications is confined to this subclause. With the line rate parameterization introduced below, the present specification is fully applicable to the HSP PON systems compliant with any PMD layer specification listed in Table 1-1.It is expected that minimal or no modifications should be necessary when expanded to support future systems.

Notation ρ₀ denotes the fundamental rate of the system, from which any actual line rate in either downstream or upstream direction is obtained as an integer multiple.

Notation Ø0 denotes a multiplicative integer line rate factor that is used to obtain the full nominal line rate in the system, which is necessarily the nominal downstream line rate. The line rate factors used to obtain the other nominal line rates in the system are denoted Ø1, Ø2, etc. Whenever used without a subscript, line rate factor Ø applies to the operational nominal line rate of a device. Thus, the nominal line rate is ρ₀Ø.

Table 1-1 lists the HSP PMD layer Recommendations with which the present Common TC Layer Recommendation is compatible, along with the respective parameter values. The future PMD Recommendations may provide additional rows to this table.

Compliance

The present Recommendation specifies general principles, methods, formats, and procedures applicable across multiple nominal line rates and to PON systems with variable number of wavelength channels. A PON system compliant with the present Recommendation may be restricted to a specific set of line rates and to a TDM system as a single wavelength channel pair case ofmultiple wavelength channel pair system, e.g., TWDM. Therefore, a compliant system has a restricted rate or set of rates and a chosen operating mode. It can be envisioned that a system could support a range of specified operating rates, operating in TDM or TWDM mode, depending on the deployed configuration. In either mode, a compliant system must conform to all the normative behaviours consistent with a selected rate or mode as described herein.