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SYNCHRONIZATION

REPORT OF

COMMITTEE

TERMS OF REFERENCE

To review existing Synchronization plan.

To study current problems in synchronization of network and reasons thereof.

To suggest a new Synchronization plan in accordance with international practices but keeping in view the rollout of BSNL HQ and its interconnection with other operators.

TERMS OF REFERENCE

To suggest actions to be taken in the short term as well as long term.

To identify requirement of additional hardware and instruments needed to implement the full synchronization network.

To formulate a Synchronization Audit and Monitoring strategy.

TERMS OF REFERENCE

To formulate the role of every unit (Regions, Circles, SSAs) in the process as an ongoing activity.

EXISTING SYNCHRONIZATION PLAN

• Separate Synchronization Plans for

I. SWITCHING NETWORK :

II. TRANSMISSION NETWORK:

SYNCHRONIZATION OF SWITCHING NETWORK

This plan envisages to

National Reference Clock.


1. Main National Reference Clock (MNRC)At Mumbai established by VSNL.

2. BackUp National Reference Clock (BNRC) At Delhi .

MNRC(Mumbai)

BNRC(Delhi)


MNRC will normally control the entire network.

BNRC will be with dedicated and duplicated links with MNRC.

MNRC(Mumbai)

BNRC(Delhi)


The Clock Hierarchy follows natural telecom traffic hierarchy.


MNRC & BNRC forms Layer-1.

MNRC(Mumbai)

BNRC(Delhi)

Layer-1

Timing reference is transported over traffic E1-links from MNRC/BNRC.

Except Four Metros where these will be dedicated links.


MNRC & BNRC forms Layer-1.

MNRC(Mumbai)

BNRC(Delhi)

Layer-1


Level-1 TAXs forms Layer-2.

MNRC(Mumbai)

BNRC(Delhi)

Layer-1

Level-1TAXs Layer-2


Level-1 TAXs will have timing I/Ps throw ‘M’ & ‘S’ links.

MNRC(Mumbai)

BNRC(Delhi)

Layer-1

Level-1TAXs Layer-2

M links


Level-1 TAXs will have timing I/Ps thr ‘M’ & ‘S’ links.

MNRC(Mumbai)

BNRC(Delhi)

Layer-1

Level-1TAXs Layer-2

‘M’ links ‘S’ links

In addition, they may also receive Third reference I/P from another Level-1 TAX.


Level-1 TAXs will have timing I/Ps thr ‘M’ & ‘S’ links.

MNRC(Mumbai)

BNRC(Delhi)

Layer-1

Level-1TAXs Layer-2


In addition, they may also receive Third reference I/P from another Level-1 TAX.


Level-2 TAXs forms Layer-3 .

MNRC(Mumbai)

BNRC(Delhi)

Layer-1

Level-1TAXs Layer-2


Level-2TAXs Layer-3


Level-2 TAXs will have three timing I/Ps .

MNRC(Mumbai)

BNRC(Delhi)

Layer-1

Level-1TAXs Layer-2


One from its own parent Level-1 TAX.Second from one of non-parent Level-1 TAX.Third from one of the designated Level-2 TAX.

Level-2TAXs Layer-3


All other Exges will have upto 3 timing I/Ps.

MNRC(Mumbai)

BNRC(Delhi)

Layer-1

Level-1TAXs Layer-2


Level-2TAXs Layer-3

Exchanges



MNRC(Mumbai)

BNRC(Delhi)

Layer-1

Level-1TAXs Layer-2


One from its parent Lev-2 TAX.Second from non-parent Lev-2 TAX. Third from one of the Exchange.

Level-2TAXs Layer-3

Exchanges



MNRC(Mumbai)

BNRC(Delhi)

Layer-1

Level-1TAXs Layer-2


Level-2TAXs Layer-3

Exchanges


In present Scenario,The Clock is extended from Level-1 TAX at Mumbai/Delhi to other TAXs via E1s over TX n/w.

Lev-1 TAX in each T/Circle will be the source for reference clock for the entire Switching Network in that Circle.

Private operators in that Circle should also take the reference clock from designated Lev-1 TAX of that Circle.

SYNCHRONIZATION OF TRANSMISSION NETWORK

Till PDH Systems were in use,Synchronization of Transmission N/W was not an issue.After deployment of SDH Systems, Synchronization of Transmission N/W has become essential.“A separate guideline has been issued from TEC/DOT for synchronizing all the SDH Rings with PRC(MNRC) at Mumbai.

SYNCHRONIZATION OF REAL TIME CLOCK

Elements in standalone mode – OMCNMSLCT

These are not synchronized to show the same time everywhere.

Need forReview of ‘Synchronization plan’.

RECOMMENDATIONS of COMMITTEE

SHORT TERM MEASURES

LONG TERM MEASURES

SHORT TERM MEASURES

BSNL HQRS should issue guidelines for synchronizing all the switches with the 2MHz clocks from the SSU’s/ADM’s.

SHORT TERM MEASURES 1. The SDH equipment procured from SIEMENS

(HTL) has the capability to resynchronize the E1’s at its output by configuring the E1’s to the retimed mode with the software. It has been tried by the committee and found to improve the clock quality of the traffic PCM. The results of the experiment on a traffic PCM after retiming in the Siemens system can be seen at Annexure-3.

Instructions may be issued that wherever the SIEMENS system is deployed, all the E1’s should be configured to the Resync mode. This will improve the data services delivered from the RLU’s, RSU’s. It will also benefit the BTS and improve the mobile services.

SHORT TERM MEASURES

Instructions for synchronizing the MSC’s, BTS can be issued to reduce the call drop rates.

Guidelines for synchronizing the DLC, MLLN, NIB with clock from SDH system/SSU also must be issued.

SHORT TERM MEASURES

o In case of DLC, the parent exchange should be synchronized with the SDH clock and the DLC (COT) should be synchronized with the exchange.

The experiment done at Bangalore in BGTD has shown encouraging result by bringing down the slips in data circuits to zero

SDH

EXGE

DLC

CLOCK SIG

SHORT TERM MEASURES

o The DXC & V-MUX of MLLN should be synchronized using the external clock input taken from the SSU/ADM in that building.

Clear instructions need to be issued from BSNL HQRs to the vendor, QA, A/T, and field units since there seems to be some confusion amongst the engineers working on behalf of ITI.

SSU/ADM

MLLN

CLOCK SIG

SHORT TERM MEASURES

o NIB nodes should be synchronized with the clock derived from the STM signal, or SSU, or SDH system whichever is applicable.

o Similarly, equipment of VPN and other broadband services should be synchronized with the clock from SSU, ADM as per availability.

SHORT TERM MEASURES

Synchronization of real time clocks:

Immediate action is required for synchronizing the clocks of the NMS, OMCs etc so that the time exhibited by them is matching with others.

This is required for coherence of performance data and billing information.

SHORT TERM MEASURES

In order to gauge the effectiveness of synchronization,

Sync Audit need to be carried out at strategically important stations immediately

(This may require the purchase of 2 Nos of GPS clock urgently).

Measuring the true clock quality will provide the true picture of the synchronization of the network.

SHORT TERM MEASURES

The SSUs deployed in the network should be used properly.

Measurement and recording of the MTIE graph of all the input clocks at specified time intervals regularly.

This will give data regarding the deterioration in the clock as it flows through the network and also the section which may be adding errors on the clock.

SHORT TERM MEASURES

The A/T of the SSU’s needs to be carried out. In the long run, these must also be tested once every year for the accuracy of the clock output. This can be carried out by the Sync Audit team.

The A/T schedule of all telecom equipments should include the compliance of synchronization requirements and this should be tested thoroughly before deployment in the network.

SHORT TERM MEASURES

Expert guidance may be sought for initial planning. ALTTC may be asked to conduct seminars with foreign experts for the select officers and sync audit team for effective synchronization of the network.

EXPERIENCE AFTER SYNCHRONIZATION

TAX Level II (e.g. JND) :

Station July 11, 2003 Jan 23, 2003 Remark

AM (B) 36.47 40.17

AM (BT) 46.83 48.89

ANAND 43.32 45.55

AMRELI 44.75 52.89

BARODA 45.32 41.65

BHARUCH 44.44 48.85

BHAVNAGAR 44.03 51.65

BHUJ 39.63 42.45

MBI-FTN 4.052 45.34

MBI-G’GAON 44.75 38.12

MBI-PDI 35.87 50.38


TAX Level I & II :

Station July 11, 2003 Jan 23, 2003 Remark

JMN 46.96 49.85

MEHSANA 38.27 45.15

RJ BKT 46.25 50.86

SURAT 40.96 43.35


LOCAL EXCHANGES :

Vadodara SSA, Savil SDCC --

Repeated Failure of dependent Exchanges

-- Required to be reset

After Synchronization with SDH Clock

-- No such prolem

-- CCR improves by 4 to 5%.


MSC :

Rajkot, Surat and Ahmedabad –

Earlier CCR was of the order 50%.

After few months dropped to less than 40%

After synchronization again improved to above 50%.


InterNet :

Earlier

Frequent Problems of Disconnection.

(Since Launch of Internet services)

Very slow.

After Synchronization

Both the problems are Solved

Examples:

Umargaon SDCC of Valsad SSA.


ISDN : Waghodia SDCC –

Apollo Tyre using ISDN for Video Conferencing.

** Before Synchronization --Freezing of images

Low speed

**After Synchronization --

No freezing

Full Speed


ISDN : Dholka SDCC (AM SSA)-ZS-Cadilla –

** Before Synchronization --Not able to commission ISDN connection

High error rate

**After Synchronization --

Error free ISDN got commissioned.


Data Circuit (G3/G4) : For some of the MUX at Rajkot and

Ahmedabad –** Before Synchronization --

Complaint of Slip/ErrorEvery time it was required to JO/JI the control Card

**After Synchronization –No slips observed.Speed improvement for circuits of Stock Exchange Rajkot .

LONG TERM MEASURES

The PRC of VSNL (TATA’s) is being used as the reference for whole of BSNL Network.

N D

C A

B Y

C N I

IT is suggested that BSNL should have its own PRC’s at all the four Metros – Delhi, Mumbai, Chennai, Kolkata.

LONG TERM MEASURES

N D

C A

B Y

C N I

Each PRC should be connected to Three SSU’s located at three different places in each metro.

LONG TERM MEASURES

N D

C A

B Y

C N I

Every station in the network should have access to all the three SSU’s to build redundancy in the clock distribution network.

LONG TERM MEASURES

In all future procurements, the TM’s should have provision delivering Retimed E1’s. This can be used as clock source in addition to carrying traffic.

LONG TERM MEASURES

At location of RLU, BTS where Retimed E1’s cannot be provided, a separate Retiming unit can do the job of retiming the E1’s.

The process of framing the GR can be initiated and at the same time alternate ways of procuring the same can be examined.

LONG TERM MEASURES

The detailed plan for carrying out the Sync Audit for BSNL network in long run may be chalked out .

In all future procurement of any telecom equipment, the synchronization aspect should be taken care of – provision of external clock input port, compatibility, etc.

Action To Be Taken

1. Issue of orders/guidelines for synchronization of all TAXs and Switches with 2 MHz clock

NM cell, BSNL New Delhi

Implementation by all circles and Maintenance Regions.

2. Configuration of 2 Mb tributary (TEX 1) cards in the Re-synch mode

All territorial circles Orders to be issued by HQRS

Sl.No. Action To Be Taken Unit Concerned Remarks

3. Redeployment of already supplied Siemens TM’s in areas where RLUs/RSUs/BTS are to be connected.


4. Guidelines for Synchronization of DLC, MLLN with clock from SDH source


Action To Be Taken

5. Synchronization of NIB with clock taken from SDH.

Data Networks

6. Synch Audit of Synchronization network of BSNL.

All Maintenance Regions

Initially NTR and WTR may do it on top priority after procuring GPS clock ALTTC can be involved in the exercise

Sl.No. Action To Be Taken Unit Concerned Remarks

7. Performance monitoring in the SSUs at regular intervals-MRTIE, TDEV, FFOFF, SPREAD.

All Maintenance Regions

To be done at mutually agreed times and schedule in consultation with ALTTC.