Telecom manual

 PPTC - Power and Telecommunication Co-ordination Committe.

Central standing committee for co-ordination of Power and Telecommunication system.

Local Telephone Equipment ( LTE)

LTE is used to provide 20 local telephones at HQ.

Types of cables 

A)  Quad Cable 0.9 mm or 1.4 mm dia.

1.4 dia Quad used for Block Section more than  12 kms.

Suitable for underground laying.

Used for control Circuits and block interfaces.

IRS Specifications IRS: TC 30/05

B)  PIJF cable-

 Multi pair ( from 10 pairs to 200) Multi dia ( 0.5 mm/0.63 mm/0.9 mm)

Suitable for underground laying.

Used for exchange subscriber lines or branch cables branching off from main quad cable.

C) Twisted Pair Switch Board Cable ( 0.5 mm/0.6 mm)

Not designed for underground laying.

Used for indoor applications such as distribution to various telephone subscribers in a building.

Jointing Kit-

For quad cable jointing- RTSF ( Reinforced Thermo Shrink Jelly Filled kit) type jointing kit to be used.

Laying -

Quad cable should be laid 1 meter inside railway boundary.

Cable Markers should be provided at 50 m intervals.

Quad cable should be laid 1 meter below surface of ground.

When the depth of cable trench exceeds 0.5 mm near the OHE Mast. It shall be ensured that nearest edge of cable trench is at least 3m away from OHE mast.

When independent earth is provided for an OHE structure, the cables shall be laid 01 m away from the earth.

In the vicinity of Traction sub station, the cable shall be laid at least one meter away from any metallic body of sub station, which is fixed in ground.

Further, this cable should be laid in concrete pipes for a length of 300 m,on either side of sub station.

As far as possible, cable shall be laid on the side of track opposite to the sub station.

In the vicinity of OHE switching Station , the cable shall be laid at least one meter away from any metallic body of sub station, which is fixed in ground and 5 m away from station Earthing. This distance can be reduced 1 m, provided cables are laid in concrete pipes. 

Outside station limit,cable shall be laid 10 m distance from centre of nearest track.

When signal and telecom both cables laid in the same trench,  a distance of 100 mm to be maintained between them.

While laying cables shall not be subjected to sharp bends.The bending radius of cable shall not be less than 40 times the dia of cable.

IP MPLS ( Multi Protocol Label Switching)-

It is networking technique used to improve speed and management of IP network.

MPLS assigns a short fixed length label to packets.

Labels are used by Routers to forward packets through network without looking IP header.

MPLS is widely used for creating secure VPN.

Facilitates the transport of voice,video and data over a single network.

MPLS works in between Data link layer and network layer and often summarized as layer 2.5.

Cost of MPLS is more than Eathernet.

MPLS header is 32 bit.

 VHF Communication-

Frequency band is 30 Mhz to 300 Mhz.

Frequency alloted by WPC to Railway is 146.2 Mhz to 167.95 Mhz

Type of operation- Simplex,Duplex 

Type of Equipment-

5W set - Guard,driver

25W set - ASM room ( operating on 12 V battery)

Range - max 25 kms.

Feeder cable - 50 ohms unbalanced.

ART- 147.975 Mhz

Cable Length-

a) Route length as per actual measurement plus contour Allowance of 2.5%.

b) Extra length for track crossing- 2.5 m loop on each side.

c) Bridge/culvert crossing- 10 m extra on each side.

d) Major steel bridges - 5 m on either side.

e) Short bridges - 2.5 m on either side.

f) At every joint - 10 m on either side

g) Cable huts- 10 m in the cable pit.

Bending of OFC-

Bending in the fibre optic cable can damage the cable if the radius of bend is too small. Bending radius should be greater than 30 times the diameter of the OFC cable.For anarmoured it is 20 times.

For Quad it is 30 TIMES.

Blowing of OFC Cable-

Cable will be blown into pre lubricated HDPE duct with help of compressor and blowing equipment.Blowing method involves feeding of optical fibre cable into duct with help of consistent high pressure airflow,equally distributed along the entire cable throughout the duct.

Loss in OFC -

End to end loss should not exceed 0.25 db/km at 1550 nm.

End to end loss should not exceed 0.40 db/km at 1310 nm.

RCC marker color-

Red path of ofc quad

Yellow quad joint

Green Ofc joint

Duct integrity test of OFC-

Synchronus Transport Module ( STM) -

Fundamental unit in SDH framework,which is used for high speed Telecommunication transmission over Optical fiber.

STM defines the basic transmission rate for SDH.

The base level is STM 1,which operates at transmission rate of 155.52 Mbps.

Higher levels are STM-4,STM-16,STM-64 and STM -256.

In railway STM-1 and STM-4 are used.STM1 can accommodate max 63 E1s

Used for high speed internet and Telecommunication services.

Supports various types of traffic such as voice,data and video.

STM 1 - 155.52 Mbps bit rate

STM 4- 622 Mbps bit rate

STM 16- 2488 Mbps bit rate.

Data Network -

Indian Railways has three major data networks.

1. Railnet

2. UTN ( unified ticketing network)

3. FOIS network ( freight operations information System)

The various applications are as under:

* PRS( Passenger information system)

* UTS ( Unreserved ticketing system)

* COIS ( Coaching operation information system)

* COA ( Control Office Automation)

* CMS ( Crew Management System)

* MMIS ( Material Management information system)

* PMS ( Parcel Management System)

* E Drishti ( A dashboard for Indian Railway)

* SMMS ( Signalling maintenance management system)

* RTIS ( Real time train information system)

The general purpose wide area intranet of IR is known as Railnet.Railnet is also widely used for accessing Internet.

Railnet is built by Railway own transport network, utilizing bandwidth from RCIL ( Railtel cooperation of India) or leasing bandwidth from BSNL.

Communication Media-

The communication links making up the data network are combination of media like OFC,GSM- R/LTE,VSAT and twisted pair copper cable.

Network Security -

a) Firewall -

First level of defense at Network perimeter.

b) UTM ( Unified Threat Management)-

It consists firewall as well as key security features.

ART:-

Complete testing by JE/SSE - Once in 15 days

ADSTE/ DSTE- Once in 3 months 

Sr DSTE - Once in year.

Mobile Train Radio Communications - GSM - R

MTRC is digital wireless network based on GSM-R ( Global System for Mobile Communication).

LTE( long term evolution)

It is a standard for wireless broadband communication for mobile devices and data terminals.

LTE is often marked as 4G LTE.

LTE is fully IP based ,enhancing IP based,enhancing the efficiency and integration of voice,video and data services.

EPC ( Evolved Packet Core) is core Network in LTE.

Spectrum alloted to Railway for LTE is 5 Mhz paired in 700 Mhz band.

OFDMA

Uses of LTE -R

1) TCAS 

2) Video surveillance system in Locomotives 

3) Internet of things ( IoT) based asset reliability monitoring.

4) On board video surveillance for passenger security.

5) Broadband internet on running train ( on Board wi fi facility through LTE)

Indian Railways is migrating from GSM -R to LTE for railway automation system and Broadband services.

Passenger Information system -

Following types of Passenger information system are provided by telecom department of Railway 

1) Interactive Voice Response System (IVRS)

2) Prerecorded Announcement and Auto Announcement system

3) Train indicator 

4) Coach Guidance system 

5) GPS Clock/ Master slave Clock. 

Satellite communication System -

VSAT( Very small Aperture Terminal) Network 

It provides point to point or point to  multipoint data connectivity using Geostationary Satellite as repeater location.

VSAT network is used for UTS/PRS & FOIS connectivity and as accident site communication for voice,data and video transmission.

IR VSAT Network Components-

It works in star architecture and consists of  

i) Hub Earth Station 

ii) Remote Earth Station 

iii) Satellite transponder & Space link

iv) Network control centre

v) Interface Equipment 

IR Satelite network operates on Ku Band and operates on up link frequency of 13.75 to 14.5 Ghz and down link frequency of 10.70 to 12.75 Ghz.

Up link frequency- Carrier frequency on which Hub or remote earth station transmits the signal to satellite.

Dn link frequency- Carrier frequency on which Satellite transmits the signal to Hub or remote earth station.

IR 's present Earth Station is situated at New Delhi.

It is heart of entire network.

THE NDLS Satellite Hub has now been upgraded to latest HX Satellite technology.

Calculation of Earth Resistence- 

Approximate Earth Resistence of the rod/pipe

R= 0.75 × o/L    if 25< L/d < 100

R = o/L                if 100 < L/d < 600

R = 1.2 o/L          if  600 < L/d < 3000

where o = Resistivity of earth in Ohm meter.

              L =     Length of electrode in meter

              d =      Diameter of electrode in meter

If Resistence of single pipe is R and desirable earth Resistence is R(d). Then

R(d) = (1.5/ N) × R

N is no of electrodes in parallel at a distance of 3 to 4 m intervals.

Types of Fire -

A Class:-

Wood,charcoal,jute etc - water is sufficient to extinguish the fire.

B Class-

Oil, petrol,  paint etc- Foam is sufficient to extinguish the fire.

C class - 

Electric fire- Water not used,only CO2 used.

Wi Fi-

Railnet is general purpose Enterprise Wide Area Network of Indian Railways. Wi fi network is allowed to be established as a part of network.

Wi fi network operates using Radio frequency ( RF) technology in the free band mostly at 2.4 GHz and 5GHz in public band.

An access point (AP) is used for providing a wireless network. The access point is connected to the wired network( Railnet)  to provide internet services to its clients.

An access point works as combination of Router,switch and wireless radio in one device.

The closer to an access point,the stronger is the Signal and faster is connection speed.

Following security measures are used for improved security of networks using Wi-Fi

a. SSID hiding 

b. Mac filtering 

c. Static IP Addressing 

d. Use of strong passwords for admin as well as wi fi access

e. Use of strong end to end encryption standard like WPA.

f. Changing default IP address and password of the access point.

IP Addressing ( Internet protocol)-

IANA- Internet Assigned Number Authority 

IP address is essential to each device connected to a network that uses IP for communication.It serves both network interface identification and location addressing.

Two versions of IP addressing are common today.Original version is IPv4 and next version is IPv6.

IPv4 address has a size of 32 bits.

IPv4 addresses are represented in dot decimal notation, consisting four decimals. each ranging from 0 to 255.

E.g.     172.16.244.1

Each decimal digit can be denoted by 8 bits binary number. Thus total no bits = 32.

Sub Networks-( Subnet)

Sub Network is also called Subnet 

IP network may be divided into sub networks.

A subnet is smaller,segmented portion of larger network. 

Subnetting involves Dividing a network into multiple smaller,more manageable sections,which improves network performance and enhances security.

For this purpose, an IP Address consists of two parts :

The Network prefix in the high order bits 

and remaining bits called Rest field or host identifier used for hosting numbering within network.

The subnet mask notation determines how the IP address is divided into networks and host parts.

Subnet Mask-

It is also 32 bit number used in IPv4 network to divide IP address into Network and Host Portion.

It defines which part of IP address defines network and which parts defines Host.

It's binary form consists a series of 1s followed by 0s

1s represent network Portion 

0s represent Host Portion.

E. g.

For an IP Address 192.168.1.1 with a subnet mask 255.255.255.0 (11111111.11111111.11111111.00000000)

Network Portion is 192.168.1

Private IP Address-

A private IP  address is an IP Address used within private network ( home , office, enterprise network) to identify devices.These addresses are not accessible directly from public internet.

An Internet service provider (ISP) is a company that provides internet access to organizations and home users.

At present RCIL is ISP of Indian Railways.

IPv6 Addressing Scheme -

Address size increases to 128 bits. Thus providing 2 to the power 128 addresses.

Important features of IPV6

1. Sufficient address space for the near future.

2. Enhanced security.

3. No need for NAT.Since every device has a globally unique IPv6 Address, there is no need for NAT.

4. IPv6 hosts can automatically configure themselves with an IPv6 Address even without a DHCP server.

5. The 128 bits of IPv6 are arranged in 8 quartets of 4 hexadecimal digit separated by a colon (:).

Not case sensitive for A,B,C,D,E and F

Leading zeros in any quartet can be omitted.

Methods from Migration from IPv4 to IPv6

Dual Stack method-

This will allow both IPv4 and IPv6 to co exist and gradual transition of IPv4 to IPv6 can happen.

Tunneling-

It allows IPv6 hosts to communicate over IPV4 infrastructure.

Transmission loss Per KM on 4/6  Quad Cable for BPAC/ SSDAC/ MSDAC application - 1.2 dB.

Sound power and Ambient Noise Level-

In waiting room - Sound level should be higher than 5 dB.

Railway platform- Sound level should be higher than 10 dB

Closed Auditorium- 5 to 10 dB

Loco sheds,outdoor stadium- 12 to 15 dB.

Telecom Radio towers

Painted at 5 years intervals 

Orange and white,orange at top

Inspection of Control Office and test room-

Monthly by DSTE/ADSTE.

FRMC - LTE technology .

Exchange-

IP Exchange shall be worked on 230 V AC/48 V DC.

For provision of 230 V AC, 2 sets of UPS along with 2 sets of batteries of Adequate capacity shall be provided at each location.

For provision of 48V DC,2 sets of Telecom chargers along with 2 sets of batteries shall be provided to ensure 12 hours of back up at each location. 

Inspection by DSTE/ADSTE

Exchange- yearly 

Control Office- monthly 

Outdoor OFC/ quad/ EC sockets- Inspection of 100% in a year.

Indoor OFC/Quad - All station in a year.

No of 5W VHF Walkie Talkie sets in ART =30

Ec socket -once in year painting.