ISAM clock system and NTR extraction 6-6 6.3 Downstream NTR clock distribution 6-16

6.4 Applicable standards 6-17

6 — Network timing reference support in ISAM

6-2 November 2013 Alcatel-Lucent 7302 ISAM | 7330 ISAM FTTN | 7360 ISAM FX R4.6.02

6.1 Introduction

Scope

This chapter describes the different clock systems and Network Timing Reference (NTR) capabilities of the ISAM. A specific ISAM board will not support all of these capabilities. To know which of these functions are supported on a specific ISAM board, refer to the Product Information document and/or the Unit Data Sheet (UDS) of that board.

This section focuses on both the 24G NT family and the 100G/320G NT + FX NT family. Whether or not an NTR function is supported is board dependent rather than family dependent. This is the rationale to cover both families.

Example: SyncE is supported on some board variants in the 100Gbps/320Gbps NT family, but is not supported on the cheaper ones. And while SyncE is not supported on most boards in the 24Gbps NT family, it is supported on the NRNT-A board (that is, the NT board for Standalone REM).

A summary of NTR capabilities of the most advanced board variants in each family is given in Figure 6-1 and Figure 6-2. In many cases, less advanced board variants with fewer or no NTR capabilities are available. These can be used for deployments where these capabilities are not needed. The next section will clarify this at a high level.

Applications as driver for specific clock or NTR requirements This section discusses high-end NTR capabilities on the ISAM such as BITS, SyncE, NTR on DSL, and so on. However, many applications such as High Speed Internet (HSI), Video, Packet Voice, Data Offload in Mobile Backhaul do not require such high-end clock system (see Table 6-1). For these applications the usual and less complex NTs and LTs are sufficient for network deployments.

Each access technology (ADSL, VDSL2, SHDSL, Ethernet, GPON and EPON) may have its specific clock requirements to guarantee synchronization and proper functioning between both ends (CO and end-user). However, in general, these clock requirements are taken care of in the design of line boards (LTs) for that specific access technology, and do not impose any restrictions on the specific NTs which can be used. Some exceptions exist (for example, voice over POTS line) and they will be covered in the section on that access technology. Clock requirements or restrictions related to a specific access technology, are in general not in the scope of this chapter.

Table 6-1 Specific clock requirements per application

Application

(over DSL, Ethernet or PON)⁽¹⁾

Required on NT Required on LT

High Speed Internet (HSI), Video,

Packet Voice

External NTR source: not required Local Clock Accuracy: low (32 or 50 ppm is sufficient)

All LTs are suited, that is, no specific clock requirements on LT.

(1 of 2)

6 — Network timing reference support in ISAM

Voice via POTS line External NTR source: not required Local Clock Accuracy: 4.6 ppm is required

All voice LTs are suited, that is, no specific clock requirements on LT.

Long fax or modem calls via POTS

line External NTR source: SyncE In or

BITS In All voice LTs are suited,

that is, no specific clock requirements on LT.

NTR distribution from network node to network node (for example, to other DSLAMs)

• External NTR source: SyncE In or BITS In output on an Ethernet LT.

Mobile backhaul data offload External NTR source: not required Local Clock Accuracy: low (32 or 50 ppm is sufficient)

All LTs are suited, that is, no specific clock requirements on LT.

Full mobile backhaul (with

frequency synchronization) External NTR source: SyncE In or

BITS In • DSL LTs: NTR on

VDSL2 or SHDSL (Note: NTR on ADSL is not supported on DSL-LTs)

• Ethernet LTs: SyncE out

Full mobile backhaul with phase synchronization or ToD requirement

Not supported.

Note: Phase synchronization or ToD is only required for some mobile applications, and even then in most cases an alternative option exists which does not require these features.

Alternative solution: Provide Mobile Backhaul data offload only, with phase sync or ToD via a different channel (for example, GPS/ GNSS receiver)

Not supported.

Packet-based Business

applications External NTR source: not required Local Clock Accuracy: low (32 or 50 ppm is sufficient)

All LTs are suited, that is, no specific requirements on LT.

Business applications with NTR requirements (for example, TDM leased lines)

External NTR source: SyncE In or

BITS In • DSL LTs: NTR over

SHDSL or VDSL2

• Ethernet LTs: SyncE out

Application

(over DSL, Ethernet or PON)⁽¹⁾

Required on NT Required on LT

6 — Network timing reference support in ISAM

6-4 November 2013 Alcatel-Lucent 7302 ISAM | 7330 ISAM FTTN | 7360 ISAM FX R4.6.02 Only some applications such as Full Mobile Backhaul (with frequency

synchronization) and some Business Applications (for example, TDM leased lines) will require NTR support (see Table 6-1). This then means that NT boards are required which either support BITS inputs or SyncE inputs, and LT boards

supporting NTR over DSL in case of SHDSL or VDSL2, and SyncE out on Ethernet lines. For PON LTs, there are no specific requirements, since the framing of PON has inherent sufficient high clock quality (assuming the appropriate NT is used). But, an ONT needs to be selected with an NTR output (for example, SyncE on an Ethernet output port, or a BITS out).

NTR in mobile applications, and especially in mobile backhaul, frequency

synchronization has always been sufficient in the past, and phase synchronization or ToD was not required. With new mobile generations (for example, LTE) also the latter requirements may appear. However, in general, different options exist in the new mobile standards, and only some of these options (for example, TDD

technology) require ToD, while mostly alternative options (for example, FDD) exist which do not require this. It depends very much on the selected technology which will be used in a mobile network, if phase synchronization or ToD will be possibly required there. Even if the latter is the case, the ISAM is then still capable to transport the mobile data, if the phase synchronization or ToD timing signal is transported in parallel via an alternative way (for example, via GPS/ GNSS).

To know which NT boards and LT boards in the ISAM portfolio support the specific NTR requirements for a certain application (according to for example, Table 6-1), please consult the Product Information document and/or the UDS of that board.

The ISAM NTR features support a very wide range of applications. On the market other clock solutions are available, which in most cases are just alternatives, that is, they just support the same applications in a different way. In some cases, they may be transparent to the ISAM, and could therefore also be used. An example is Adaptive Clock Recovery (ACR). ACR requires larger buffers and a better local oscillator in the end-receiver, and will therefore be more expensive. An investment in a somewhat more expensive ISAM NT board with SyncE or BITS support will then probably be better than having to deploy a more expensive receiver with ACR at every end-user. Secondly, the larger buffers needed for ACR increase the end-to-end delay and may therefore require echo-cancellation for interactive services (for example, voice or video calls).

Overview of NTR support on ISAM

Table 6-1 made clear that NTR is not required for all applications. However, in some cases it is required. Figure 6-1 and Figure 6-2 give a high-level view on the supported options on NT boards and LT boards for the FD 24Gbps family and the FD

100/320Gbps NT and FX NT family, respectively.

6 — Network timing reference support in ISAM

Figure 6-1 Overview of possible NTR support on some LTs and some NTs in the FD 24Gbps NT ISAM family

Figure 6-2 Overview of possible NTR support on some LTs and some NTs in the FD 100/320Gbps NT ISAM family

GPONVoice NT EthNTIO DSL LT

8 kHz

BITS G.703Sync Eth GE PHYor

6 — Network timing reference support in ISAM

6-6 November 2013 Alcatel-Lucent 7302 ISAM | 7330 ISAM FTTN | 7360 ISAM FX R4.6.02 Figure 6-3 NTR options for FX NT ISAM family

Although not shown in these figures, also deployments with a mix of nodes are possible from both figures. For example, a standalone REM connected via SyncE to an Ethernet output on an Hub ISAM with NT from the FD 100/320Gbps NT and FX NT family.