for BSNL internal circulation only

E4E4--E5 (E&WS) E5 (E&WS)

Synchronization Synchronization of of

Telecom NetworkTelecom Network

for BSNL internal circulation only

AGENDA

Network Synchronization

Synchronization Planning

BSNL Synchronization Plan

for BSNL internal circulation only

SYNCRONIZATION

Need of Synchronization

Synchronization of the traffic in the networks

is becoming increasingly important due to:

Telecom Traffic in the network is constantly

increasing .

More and more information is being transported

at higher and higher data speeds

Telecommunications’ reliability is based on the

data signals being synchronized.

for BSNL internal circulation only

SYNCRONIZATION

Clocks for Synchronization:

The basic clock in the SDH networks is

called E1, and it must be exactly 2.048 MHz

In a synchronized SDH network, there is a

very stable and accurate atomic (cesium)

clock of 2.048 MHz, functions as a "master

clock" or primary reference clock (PRC).

for BSNL internal circulation only

SYNCHRONIZATION CLOCKS

Accuracy levels of Sync.clocks

PRC

SSU

SEC

Primaryreferenceclock

Synchronizationsupplyunit

SDHequipmentclock

PDH

10-11

10-9 (TNC)10-8 (LNC)

4.6 x 10-6

A c

c u

r a

c y

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PRIMARY REFERENCE CLOCKPRIMARY REFERENCE CLOCK

Primary Resource Clock (PRC)Primary Resource Clock (PRC)

The PRC is distributed throughout the network

using the transmission backbone ( DWDM and

SDH network. )

Very stable and accurate atomic (cesium) clock

of 2.048 MHz that functions as a "master clock"

or primary reference clock (PRC).

Accuracy better than 10exp-12

for BSNL internal circulation only

SLAVE CLOCKS

SSUs (Synchronization Supply Unit):

The clock is regenerated in the network’s nodes in

“slave clocks” called as synchronization supply units .

The SSUs are clock of the accuracy better than

10exp-11.

SSUs can also temporarily (up to hold over time) be

used as PRCs, if the input connection from the master

clock is interrupted

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SLAVE CLOCKS

SECs (SDH Equip. Clock)

The SECs are the clocks in the network elements.

The SSUs regenerate and distribute the clock thus

received from PRC through a chain of SECs (SDH

Equipment Clocks).

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REGENERATION OF PRC CLOCK

PRC: Primary Resource Clock

SEC: SDH Equipment Clock

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SYNCHRONIZATION PLANNING

SSU

K=1

PRS

SSU

SSU

Rule 1K < 10 SSUsN < 60 SECs

SEC (NE with SONET/SDH Equipment Clock)

Rule 2N < 20 SECs

K=2

K=3

SSUCo-located PRS & TSG

SSUK=1

1

201 20

PRS

1

20

SSU K=1

1

20

1

20

201

201

1

20

SSU K=2

for BSNL internal circulation only

Clock quality keeps on getting deteriorated as

and when it crosses different nodes.

While extending PRC clock from one node to

other node through transmission network of SDH

and DWDM few planning guidelines are required

to be kept in mind.

SYNCHRONIZATION PLANNING

for BSNL internal circulation only

SYNC. PLANNING

Following is the salient planning rules :

From one PRC maximum 10 numbers of SSUs

can be supported

Between two SSUs maximum 20 NE can be

placed.

In total maximum 60 numbers of NEs can be

supported in one PRC chain .

for BSNL internal circulation only

BSNL SYNCHRONIZATION PLAN

It is decided to have 21 numbers of PRCs with two

cesium tubes (mostly at all Level-1 TAX locations) for

geographical diversity and for ensuring the minimum

nodes slippage.

However, in view of the requirement for the orderly

distribution of the PRC clock throughout the transmission

network, the SSUs may be located at the convergent

nodes of the existing DWDM backbone rings.

for BSNL internal circulation only

� DWDM network enables to transport the clock on a

number of SDH rings to the district head quarters, where

SSUs are proposed to be located.

� Most of these nodes are co-located with the Level –I

TAX stations.

� Thus these 21 PRCs are expected to supply clock for all

the Transmission, Switching and Access elements in the

transmission geographic area.

BSNL SYNCHRONIZATION PLAN

for BSNL internal circulation only

The SSU at the PRC Location.

The SSU at the PRC location depends on the

PRC itself for the first master clock input.

In case of failure or deterioration of the PRC, the

SSU fall back on the other three PRC clock

inputs received from the nearest three PRCs

BSNL SYNCHRONIZATION PLAN

for BSNL internal circulation only

The GPS CLOCK FOR SSU.

SSU draws the clock from the GPS, In the event

of complete failure of the PRC inputs or in the

event of the deterioration of clock quality of all the

PRCs below the GPS standard.

GPS Clock shall be in-built in with SSU

BSNL SYNCHRONIZATION PLAN

for BSNL internal circulation only

BSNL SYNC. PLAN

The provision of SSUs:

• It is proposed to place at least one SSU at each of the

SSA Headquarter ( 322 SSUs).

• In the cities, where more than 3 lakh DELs are available,

there will be at least 3 SSUs in the same city for

distributing the clock across the city network

• Similarly in all the cities with more than one Lakh DELs but

less than 3 Lakh DELs, two SSUs are proposed in the

same city for distributing the clock.

for BSNL internal circulation only

QUESTIONS ?QUESTIONS ?

Introspection:

Why Synchronization is needed in Telecom n/w ?

What are the different types of Synchronization clocks ?

Define PRC ?

Give full name: SSU,SEC,GPS .

Give a brief note on BSNL Synchronization Plan.

Thanks

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