1) mobile int gr b
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MOBILECOMMUNICATION
T15
PREPARED BY
VIVEK CHAKRAVERTY
APT
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EMERGENCY COMMUNICATION -
PRESENT STATUS
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Emergency Communication is provid
portable control phones (PCPs) using
following means:
a) Hooking on the overhead control ali
in non-RE area;
b) Provision of emergency sockets in RE a
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DISADVANTAGES(a) The Driver/Guard have to carry the cumbersome telescopi
masts and the PCP sets;
(b) Hooking up of the telescopic mast on the overhead alignme
procedure;
(c) In some cases, overhead alignment may be far away from th
track.
(d) In RE area, Driver and Guard have to walk about 50
establishing emergency communication.
(e) The emergency sockets and posts are prone to vandalism
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(f) Emergency communication is initiated only from the site of em
driver /guard of the affected train.
(g) The Section Controller/Emergency Controller is not able to
train crew in moving conditions.
(h) The emergency communication is initiated only in static co
the trains come to a halt and not in mobile conditions.
(i) All emergency calls are directed to the Control office and no
Station Master.
(j) SOS facility is not available.
(k) The weight of the Emergency Control phones is fairly heavy.
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PRESENT STATUS
After the GAISAL Accident in 1999, Board have taken a decision to
duplex Mobile Train Radio Communication on A, B & C route
Railways. It has also been decided to provide Universal Communication on D, D (Spl.), E & E (Spl.) routes.
The following factors should be considered so that deficiencies/sh
are taken care of :
a) Technology based on open/standard architecture should be sele
the system can be seamlessly extended and multi vendor sources a
b) Loco equipment should be made an integral part of the loco at
manufacturing itself
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c) The practice of loading and removal of loco equipment should b
d) Adequate number of mobile equipment should be catered fo
the communication requirements are catered for.
e) The backbone communication whether Radio or Optical Fibre b
be reliable and cover the entire run with no dark zones.
f) With the introduction of Radio based Signaling, the system shou
capability of integrating both the Signaling and Telecom
applications.
g) The system should be based on digital technology.
h) Communication to passengers on the trains should also be cat
system.
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Vide RB letter No.95/Tele/MW/5/ Pt. New De
10.09.1999, Board had decided that Mobile T
Communication (MTRC) system may be provided on
Croutes.
Proposal was during Works Programme 2000-2001.
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GSM based MTRC system is being introduced on A,B,C
IR for communication between train crew and
operating staff such as station masters, controllers, m
staff etc.
Work for over 3200 route kilometers have been san
Northern, North Central, Eastern , East Central and
Frontier Railways
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This system has been successfully commissioned o
Pradhankunta (260 RKMs) and Mathura-Jhansi (270 R
Installation of the system on Delhi-Ambala (198 RKM
completed and it is being commissioned.
Guwahati - New Bogaigaon - Katihar/Malda Town (68
Northeast Frontier Railway has been completed and
satisfactorily
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VERY HIGH FREQUENCY
COMMUNICATION
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The frequency band of VHF Communication
300 MHz. The frequency allotted by WPC
Planning and Coordination wing of m
communication) in VHF for Indian Railways band 146 to 174 MHz.
One spot frequency is used for each channe
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Communication during Maintenance andConstructional Blocks
Yard communicationCommunication in the train between Guard
Mobile Communication between moving trai
with fixed location (Station) or another movin
vehicle.Emergency Communication
ART equipped with hand held and base stat
VHF sets.
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Simplex--- One way radio communication
trans or receiveHalf-duplex---Both way radio communicatio
can trans and receive but one
(because the same frequency
for both trans and receive)
Full Duplex--- Both way radio communicatio
simultaneously. (Trans and re
frequencies are different)
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Modes of Propagation:
Line of sight waves,Reflection & scattering of waves
Channel capacity:
Single channel/Four channel/Sixteen chafor Voice or Low speed Data or both.
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. TYPES OF EQUIPMENT
Walkie -Talkie ( Hand Held) Set - 1W/2W/ 5W
Mobile Sets
Output power is 25 Watt,
Operates on 12V battery
Base Station
Installed at desired location,
Operating on AC Mains or by 12V battery
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External antenna with feeder cable connector moun
mast (Roof top) needed
Antennas used are
Whip Antenna for portable sets,
Ground Plane (GP) Antenna for base radio e
Feeder cable: 50 Ohms Unbalanced Coaxial cable
Antennas
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Depends upon terrain.
Average range of a
Walkie -Talkie (Hand Held set) - 1 to 2 km
Mobile Set- Upto 15 kmBase Station - upto 50 Kms. When antenn
are directional & fixed at the height of 15 t
COMMUNICATION RANGE
S.No. Frequency SM at Station to Driver & Shunting Engineering Electrical S&T deptt. Commercial RPF Mechanical
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in MHz all stns. LC gate Guard/Operating
deptt. deptt. deptt. deptt.
1 146.400 X Security D
2 147.975 ART Frequency Accident S
3 148.100 X Mechanica
4 149.750 X Engineeri
5 150.100 XC F1 for PL
6 150.150 XC F2 for PL
7 159.600 XC F3 for PL
8 159.650 X S&T Depar
9 159.700 XC XC Communic
10 160.400 X X X X X X X X Common F
11 160.550 XE XE Train Esco
12 161.150 X X Driver & G
13 161.425 X Electrical D
14 162.100 X X Shunting &
15 146.200 XC F4 for PL
16 148.050 XC F5 for PL
17 149.500 XC F6 for PL
18 149.550 XC F7 for PL
19 151.400 XC F8 for PL
20 151.450 XC F9 for PL
Note:
X - Channel programmed
XC - Channel programmed with CTCSS/MF coding.
XE - For Train duties only.
LIMITATIONS OF VHF COMMUNICATION
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LIMITATIONS OF VHF COMMUNICATION
-Short distance coverage
-Blank Zones occur due to terrain, high rise buildings & other
-Simplex/Half Duplex mode of working
-Maintenance of rechargeable batteries
-The set requires more than one battery set for continuous op
-Interference due to other user having adjacent frequencies.
-Effect of prevailing noise in the surrounding
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GSMHistory
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Compatibility
Noise Robust
Increased Capacity & Flexibility
Use of Standard Open Interfaces
Improved Security & Confidentiality
Cleaner Handovers
Subscriber Identification
ISDN Compatibility
Enhanced Range of Services
Development of the GSM Standar
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Development of the GSM Standar
1982: Groupe Spcial Mobile (GSM)
created
1984: Description of GSM features
1985: List of recommendations settled
1987: Initial MoU (Memorandum of
Understanding) aside the drafting of
technical specifications was signed by
network operators of 13 countries:
1988: Validation and trials, of the radiointerface.
1991: First system trials are demonstrated at
the Telecom 91 exhibition.
1992: Official commerc
service in Europ
Finland
1993: The GSM-MoU hin 39 countries w
1800
network launched
1995: Specifications of G
are frozen. First G
network launched
1999: GSM MoU joins 3GPRS Trials beg
2000: 480M GSM subsc
First GPRS Netw
End 2002: 792M GSM subWorldwide
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GSM-900 (Channels 125 operating band
carrier spacing 200khz spacing 45Mhz)
GSM -1800 (Channels 374 spacing 95Mhz)
GSM -1900(Used in USA)
What are the types in GSM Network?
Different Standards Worldwide
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GSM - 900
The term GSM-900 is used for any GSM system which operates in any 900 MHz band.
P-GSM - 900
P-GSM-900 band is the primary band for GSM-900 Frequency band for primary GSM-900 (P-GSM-900)
890 915 MHz for MS to BTS (uplink)
935 960 MHz for BTS to MS (downlink)
E-GSM - 900
In some countries, GSM-900 is allowed to operate in part or in all of the following extension band. E-G
900) band includes the primary band (P-GSM-900)andthe extension band :
880 890 MHz for MS to BTS (uplink)
925 935 MHz for BTS to MS (downlink)
R-GSM-900
R-GSM-900 (Railway GSM-900) band includes the primary band (P-GSM-900) and the following extens
876 880 MHz for MS to BTS (uplink)
921 925 MHz for BTS to MS (downlink)
Carrier frequency = ARFCN=Absolute Radio Frequency Channel Nu
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Ful(n) = 890.0 + (0.2) *n MHz
Fdl(n) = Ful + 45 MHz
where n =ARFCN ; 1 n 124
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RF CONCEPTS
F S
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Frequency Spectrum
Designation Abbreviation FrequenciesFree-spWavelen
Very Low Frequency VLF 9 kHz - 30 kHz 33 km -
Low Frequency LF 30 kHz - 300 kHz 10 km -
Medium Frequency MF 300 kHz - 3 MHz 1 km - 1
High Frequency HF 3 MHz - 30 MHz 100 m -
Very High Frequency VHF 30 MHz - 300 MHz 10 m - 1
Ultra High Frequency UHF 300 MHz - 3 GHz 1 m - 10
Super High Frequency SHF 3 GHz - 30 GHz 100 mm
Extremely High Frequency EHF 30 GHz - 300 GHz 10 mm -
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RADIO WAVES
Ground wavesSky wavesSpace waves
F t ff ti RF ti
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Factors affecting RF propagation
Free space loss
Multi path propagation
Building & vehicle penetration
Interference
Fading of signal
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A directional antenna
An Omni-directional antenna
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2
4
3
1
7
5
1
6 3
CELLULAR CON
WHY DO WE NEED CELLS?
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WHY DO WE NEED CELLS?
FREQUENCY (RESOURCE)SCARCITY
DEMAND FOR HIGHER
CAPACITY
COST EFFECTIVENESS
Base Sta
Base Station
Base Station
Base Stati
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Cellular Radio involves dividing a large servic
regions calledcells
.
Each cell has the equipment to switch, transmit a
calls.
Cells - Reduce the need of High powered transmiss
Cells - Conventionally regarded as being hexagoreality they are irregularly shaped.
Cell shape is determined by the nature of the surro
e.g. Hills , tall building etc.
Hexagonal shaped cells are
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Hexagonal shaped cells are
artificial and cannot be generated
in the real world.
This shape is chosen to simplify planning and design of a ce
hexagons fit together without any overlap or gap in between them.
Another advantage of using hexagons is that it approaches a circula
the ideal power coverage area.
The real cell shape will keep changing due to prevailing conditions.
If the Point of Transmission is at the centre of a Cell, the maximum C
available from a Hexagonal Cell i.e., this layout needs minimum nu
cover a given Area, hence lesser number of Transmitting Sites are n
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Large Cells Small Cells
About 35 Km Nearly 1 KM
Remote Areas Urban Areas
High Transmission Power Low Transmission Po
Few subscribers Many Subscribers
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There are 124 carries in GSM Band. With each carriertimeslots, only 124 x 8 = 992 calls can be made !
Frequency Reuse is the solution
Using same frequency channel to serve more than
in the same given area
Interference problems caused by mobile units usingchannel in adjacent areas (cells) proved that all channot be reused in every cell.
Areas (cells) have to be skipped before the same freqreused
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The actual center to center distance of the
adjacent hexagon is
3R = (2R cos 300
),where R is the center to vertex distance.
The concept of number of cells per cluster is
important for locating co channel cell with in
the cellular structure.
It can be shown that co channel reuse ratio
D/R = 3Nwhere N is Cluster size
CELLULAR CONCEPTS
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N Q=D/R
1 1.733 3.004 3.467 4.589 5.2012 6.00
Q = D/R =
3N = 6 ( S/ I)
-
where is propagation constant
Much higher level of interference is tolerated if digital transmused.S / I 18 dB For Digital Cellular Mobile Systems.
Higher Q Less Interference.
Higher N
Larger Cluster Size.
Less Freq./ cell.
Lower Traffic Handling
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The same group of channels can be used in different cells that are f
away from each other so that their frequencies do not interf
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No similarly colored cells are adjacent, and therefore there are
adjacent cells using the same channel.
Performance/Capacity Trade Off
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Performance/Capacity Trade Off
Higher values of N Lower values of N
Reduce co channel interference Increase co channel inte
Leads to more cells/clusterLeads to few cells/cluste
Less no. of chls/cells More no. of chls/cell
Less traffic handling capacity More traffic handling cap
Principle Of Sectorizati
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A Directional Antenna is a
better solution for reducing the
Co-channel Interference
Each Cell is divided into 3 or 6
Sectors and uses 3 or 6
Directional Antennas at the
Base Stations.
In practice, Sectored Cells with
120Beam Antennas are used
Principle Of Sectorizati
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Omni Directional Cells
120 degree Sectors
60 Degree sectors
Each Sector in a Site has its own allocation of Radio Carr
Advantage By frequent reuse of frequency more capacity can be
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a1
a2
a3a3
a4a6
a5
OMNI CELL
1 ANTENNA
b1
b
120OC
3 ANTEN
60OCELLS
6 ANTENNAS
CELL TYPES
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Macro cells: Very Large Radius (more than 35 kms)
Micro cells: Medium Radius (upto 3 kms)
Pico cells: Extremely Small Radius cells (for Indoor coverage
Umbrella cells: for fast moving vehicles (to avoid frequent loading of the network)
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HANDOVER
HANDOVER
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A problem encountered in Cellular Communication is to provide con
Communication for a subscriber, who moves from one Cell to another
No two adjacent Cells in a Cluster have the same Radio Channels
So, Re-allocation of Radio channels must be fast and smooth.
This process is called Handover.
Processing Load per Subscriber on the system increases when Subsc
crosses Boundaries and cause frequent handoff of Calls between the
Practically, reduction of Cell Radius by 4 times increases Proc
approximately by a factor of 10.
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BS1
A B
RSL
Lev
Level w
HandoverMechanism
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Handovers
Hard Handoff
Analog, TDMA and GSM
Soft Hando
CDMA
Break before Make Make before Brea
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The mobile measures up to 32 adjacent cells for
Signal Strength (RxLevel)
Signal Quality (RxQual)
updated every 480 mS and sends to BTS
Handover is based on the following conditions:
RxLevel
Interference RxQual
Timing Advance
Power Budget
Interference- If signal level is high and still there is RXQUAL ph bl i b f i f
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the problem is because of interference.
RXQUAL - It is the receive quality. It ranges from 0 to 7 , 0 being7 the worst
RXLEV- It is the receive level. It varies from -47dBm to -110dBm
Timing Advance- Ranges from 0 to 63.
Power budget- It is used to save the power of the MS.
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POWER CONTROL
POWER CONTROL
RF power control is employed to minimise the tra
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RF power control is employed to minimise the trarequired by MS or BS while maintaining the quality of th
By minimising the transmit power levels, interference tusers is reduced.
Power control is implemented in the MS as well as the B
Power control on the Uplink also helps to increase the b
Power received by the MS is continuously sent in the mreport.
Similarly uplink power received from the MS by the BTSby the BTS.
Complex algorithm evaluate this measurements and tasubsequently reducing or increasing the power in the downlink.
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DTX is a mechanism which allows the radio transmitter to be switch
DISCONTINUOUS TRANSMISSION (DTX)
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DTX is a mechanism which allows the radio transmitter to be switch
rate transmission (~ 500 bit/s) during silences )most of the time
pauses for the following purposes:
To save power in the MS
To reduce the overall interference level on the air
The DTX mechanism requires the following functions
A Voice Activity Detector on the transmit side
Evaluation of the background acoustic noise on the transmit side,
transmit characteristic parameters to the receive side
Generation on the receive side of a similar noise, called comfort n
periods where the radio transmission is cut
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Frequency Hopping
Multipath Fading results in variations in signal strength which is known
Frequency Hopping
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Multipath Fading results in variations in signal strength which is known
Fading.
Rayleigh Fading phenomenon is dependent on path difference and hen
of reception.
A fast moving mobile may not experience severe effect of this fading sin
difference is continuously changing.
A slow moving mobile ( or a halted mobile ) may experience severe dete
quality.
But, if the frequency of reception is changed when this problem occurs,
The fadingphenomenon is fast and almost continuous, this means the
changeshould also be continuous.
This process of continuously changing frequency is known as Frequenc
Frequency hopping is the technique of improving the S/N in a link by ad
frequency diversity.
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q y y
The base station commands the mobile station to activate frequency hop
mobile station moves towards the edge of a cell or into an area of high in
When frequency hopping is activated in the mobile station, the base stat
mobile station a set of RF channels, rather than a single RF channel.
A frequency hopping algorithm is also assigned to the mobile and is used
mobile of the pattern of the available frequencies it is to use.
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MULTIPLE ACCESS TECHNIQUES
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In order to several links to be in progress simultaneousame geographical area without mutual interference access techniques are deployed.
The commonly used multiple access techniques are
Frequency Divis ion Mult iple Access (FDM
Time Divis ion Mult iple Access (TDMA ) Code Divis ion Mult iple Access (CDMA )
FDMA F Di i i M l i l A FDMA
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FDMA - Frequency Division Multiple Access
( eg: GSM each Frequency channel is
200KHz)
TDMA - Time Division Multiple Access
( eg: GSM each frequency channel is divided
into 8 timeslots)
CDMA - Code Division Multiple Access
(eg: IS95- Each User data is coded with a
unique code)
Power
TDMA
Power
FDMA
Power
CDMA
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Mobile Station
Base Station
SubsystemNetwork Subsystem
ARCHITECTURE OF A GSM NETWO
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SD
Mobile Station
BTS
MSC/
VLR
SIM ME
BSC
Subsystem
GMSC
y
AUCEIR HLR
Note: Interfaces have been omitted
+
Network Structure
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GSM Service AreaPLMN Service AreaMSC Service AreaLocation Area
Cells
Network Structure
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GSM SERVICE AREA
PLMN SERVICE AREA
MSC SERVICE AREA
LOCATIONAREA
CELLS
SYSTEM ENTITY FUNCTIONS
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Mobile station:
The mobile station represents the t
equipment used by cellular sub
supported by GSM system
Functions of Mobile Station
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Voice and data transmission
Frequency and time synchronization
Monitoring of power and signal quality of the surroucells
Provision of location updates even during inactive st
Equalization of multi path distortions
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The MS consists of two entities
Mobile Equipment (ME)
Subscriber Identity Module (SI
Mobile equipment (ME)It is the mobile handset.
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The major components of the Handset are Transmitter,
Receiver,Number Alignment Module,
Logic Unit,
Frequency Synthesizer,
Antenna and
the required software.
Identified by a unique International Mobile Equipmen(IMEI) (different from the phone number)
Class Power O/p
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p
1 20 W
2 8 W
3 5 W
4 2 W
5 0.8 W
Subscriber Identity Module (SIM)Contains subscriber-related information
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Contains subscriber related information
A smart card that holds information required to id
particular subscription to a mobile service
Can be used with any approved GSM handset
Identified by a unique International Mobile SubsIdentity (IMSI)
(different from the phone number)
COMPONENTS OF THE SIM CARD
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Central processing unit (CPU)
intelligence of the chip
performs all the mathematical functions
takes all the decisions required by the SIM.
Read Only Memory (ROM):
sufficient memory to store the operating system (s
commands that SIM understands)
contents of the ROM are permanent and it is not poto change them.
can be created as part of the manufacturing process
R d A M (RAM)
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Random Access Memory (RAM):
area of volatile memory
contents are lost each time the power is turned off
The memory can be at least 256 KB.
Buffers incoming data as a scratch pad for calculat
Electrically Erasable programmable Read Only Memory (EE
Stores all the application data such as the operatorparameters and the subscribers data.
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SIM
Most of the data contained within the SIM is protected against ror alterationsafter the SIM is issued.
Some of the parameters ( eg. LAI ) will be continuously updatecurrent location of the subscriber.
The SIM card can be protected by use of Personal Identity N
password.
The SIM is capable of storing additional information such as ac
charges.
MOBILE IDENTIFICATION NUMBERS
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i) MSISDN (Mobile subscribers ISDN number)
ii) IMSI (International mobile subscribers identity)
iii) TMSI (Temporary mobile subscribers identity)
iv) MSRN (Mobile subscribers roaming number)
v) IMEI ( International Mobile subscribers equipment
Human identity used to call a MS
MOBILE SUBSCRIBERS ISDN (MSISDN) NU
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The Mobile Subscriber ISDN (MSISDN) number is the telephthe MS.
This is the number a calling party dials to reach the subscri It is used by the land network to route calls toward the MSC
Mobile Subscriber No.
NDCNetwork destination code
SN--subscriber number
CC--country code(allotted internationally)
International mobile subscribers Identity
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The IMSI is an unique identity which
internationally and used within the network t
the mobile subscribers.
The IMSI is stored on the SIM, the HLR, VLR
database
IMSI finds its use in call routing.
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MCC--Mobile country code
MNC--Mobile network code
MSIN--Mobile subscriber identification number
-- identifies the country of domicile of the subsc
-- identifies the home GSM PLMN of the mobile s
-- identifies the MS within a G
TEMPORARY MOBILE SUBSCRIBERS IDENTITY
The GSM system can also assign a Temporary Mobil
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The GSM system can also assign a Temporary MobilIdentity (TMSI).
After the subscriber's IMSI has been initialized on theTMSI can be used for sending messages backwards aacross the network to identify the subscriber.
The system automatically changes the TMSI at reguthus protecting the subscriber from being identifiedattempting to monitor the radio channels.
The TMSI is a local number and is always allocated by
The TMSI is maximum of 4 octets.
MOBILE STATION ROAMING NUMBER (M
Suitable for the purpose of call processing when the custom
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Suitable for the purpose of call processing when the custom
in any other VLR area having connectivity with his home ne
The HLR of the roaming subscribers request the visited VLallotment of the temporary number.
Accordingly the visited VLR generates MSRN.
GMSC (gateway MSC) uses it for routing of calls to this cust
MSRN is stored in visited VLR, HLR.
INTERNATIONAL MOBILE EQUIPMENT IDENTIT
Provided to the mobile equipment through a unique
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Provided to the mobile equipment through a unique
its authentication and identification
The code is entered in SIM card of the user MS
Also recorded in the data base of the EIR of mobile s
sub system.
During the course of call processing, the IMEI entere
compared with the corresponding IMEI recorded in E
6 digits 2 digits 6 digits unit length
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TAC is 6 digits and approved by a national body.
FAC is 2 digits and is provided by the manufacturer.
SNR is 6 digits provided by manufacturer in serial sequence.
SP is spare digit of unit length.
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Base Transceiver Station (B
BTS is the equipment which facilitates the wireless
BTS
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BTS is the equipment which facilitates the wirelesscommunication between user equipments (UE) andnetwork.
BTS is a radio-end which determine a cell coverageprovide link with MS.
BTS include Transmitters and Receivers, antenna aprocessing unit as well as interface.
BTS communicate with MS via Um (air) interface
FUNCTION OF BTS
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Encodes, encrypts, multiplexes, modulates and feedRF signals to the antenna
Transcoding and rate adaption Functionality
Time and frequency synchronisation signals transmi
11 power classes from .01 watts (Micro cell) to 320 w(Umbrella cell)
A BTS has the following units
TRX : Transceiver--- Quite widely referred to as DRX (Drive
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TRX : Transceiver Quite widely referred to as DRX (Drive
Receiver). Basically does transmission and reception of signals
Power Amplifier : Amplifies the signal from DRX for transmthrough antenna. May be integrated with DRX
Combiner :- Combines feeds from several DRXs so that they
sent out through a single antenna. Used for reduction of numb
antenna
Duplexer : For separating sending and receiving signals to/
antenna. Does sending and receiving signals through the same
ports (cables to antenna)
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Antenna : Antenna is considered as part of BTS
Alarm Extension System : Collects working statu
alarms of various units in BTS and extends them to
Operations and Maintenance (O&M) monitoring sta
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A group of BTSs are connected to a particular BS
which manages the radio resources for them.
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The primary function of the BSC is call maintena
The mobile stations normally send a report of th
received signal strength to the BSC every 480 ms.
With this information the BSC decides to initiatehandovers to other cells, change the BTS transmitte
power, etc.
Base Station Controller (BSC)
responsible for radio interface manageme
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responsible for radio interface manageme
BTS and MS, i.e.channel management and
handovers
responsible for communication with the N
a single BSC typically manages 100-200 B
The functions of the base station are
1. Radio source control (Channels)
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a. Configuration of Radio channels
b. Selection, allocation and de-allocation of radio channels.
c. Monitoring of radio channel busy / idle.
d. Encryption of radio interface.
2. Frequency hopping and power control
a. Assignment of frequency hops sequence and start time.
b. Assignment of effective radiated power (ERP) values to mobile stat
3. Hand off management
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a.Collect signal quality data from adjacent BSSs.
b. Analyze signal quality and determine hand off need.
c. Keep MSC informed regarding hand off activity.
4. Digital signal processing
a. Trans coding and rate adoption.
b. Channel coding and decoding.
BSS functions are partitioned into a BSC and BTS( a single BSC generally controlling multiple BTS)
N k d
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Network and
Switching Subsystem
(NSS)
NSS performs the switching functions of GS
as well as databases for Subscriber and
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mobility management
Its main feature is to manage the communic
between the Mobile Station and other users
the Cellular Network.
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Mobile Service Switching Centre (MSC)The Switching part, is controlled by the MSC.
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Acts like a standard exchange in a fixed network and additionally prov
functionality needed to handle a mobile subscriber.
The main functions are
registration,
authentication,
location updating,
handovers and
call routing to a roaming subscriber.
Connections to external Networks like PSTN, PLMN and Intelligent Net
are also controlled by MSC.
An MSC, which provides connection to Networks
outside the area under the MSC is generally kno
GATEWAY MSC (GMSC)
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outside the area under the MSC, is generally kno
as Gateway MSC.
Gateway MSC (GMSC)
gateway to external networkincoming call is routed to GMSC, which the
determines MS locationGMSC function is often in the same machin
as the MSC
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IMSI, MSISDN and current VLR Address are also kepHLR.
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As soon as the Mobile Station crosses a Cell bounda
this information is updated in the HLR.
The HLR also maintains the services associated with
MS
One HLR can serve several MSCs
One PLMN may contain one or several HLR
Visitor Location Register (VLR) dynamically stores Subscriber
Information, when a Mobile Station is in the Location Area cove
VISITOR LOCATION REGISTER (VLR)
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,
the VLR
One VLR may be incharge of one or more LA.
A VLR is connected to one MSC and is normally integrated into
MSC's hardware
VLR is updated by HLR on entry of MS in its area.
VLR assigns TMSI which keeps on changing
Whenever a Roaming Subscriber enters in an area c
by an MSC, the information is passed to the VLR, whic
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by an MSC, the information is passed to the VLR, whic
recognizes the Subscriber as an outsider for the MSC.
If the Subscriber is allowed to Roam, VLR finds the
HLR of the Subscriber and downloads all relevant info
for the Subscriber from it.
VLR reduces the number of queries to HLR
IMSI & TMSI
MSISDN
DATA IN VLR
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MSISDN
MSRN.
Location Area
Supplementary service parameters
MS category
Authentication Key
The EIR is a database that stores IMEIfor all mobile equipments regis
particular MSC and is unique to every ME.
EQUIPMENT IDENTITY REGISTER (EIR
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Only one EIR per PLMN.
Any Cell Phone can be used fraudulently by inserting an authentic SIM
soon as a report is registered that a handset is stolen or misplaced, EIR D
updated to render the handset useless.
The EIR has three databases
White list: IMEI, assigned to valid ME. Black list: IMEI reported stolen
Gray list : IMEI having problems like faulty software, wro
of equipment etc.
AUC is a separate entity and physically included in HAUTHENTICATION CENTRE (AUC)
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It protects User Identity and allows a Secured Trans
i.e., Protect against intruders in air interface
Authentication (Ki) and ciphering(Kc) key are stored
data base.
Keys change randomly with each call
Keys are never transmitted to MS on air Only calcula
response are sent.
It monitors and controls all other components of GSM.
Operation and Maintenance Centre (O
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The OMC assists the network operator in Dynamic monitoring and main
satisfactory operation of the GSM network
The OMC is responsible for controlling and maintaining the MSC, BSC an
BTS.
It can be in charge of an entire PLMN or just some parts of the PLMN.
Its main functions are Traffic Monitoring,
Subscriber as well as Security Management and
Status report Generation.
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Mobile Train Radio Communication (MTRC) won GSM-R (Global System for Mobile
Communications for Railways) Technology.
Developed requirement
common communicatio
for the railway
UIC
GSM-R Spcification
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Railway communicationbody selected GSM as th
standardEIRENE
Development & testing
system based on EIRENspecifications
MORANE
ETSI
INDUSTRIALPARTNERS
UIC = Union Internationale des Chemins de fer
EIRENE = European Integrated Railway radio Enhanced NEtwo
MORANE = Mobile radio for RAilway Network in Europe
ETSI = European
Telecommunications
Standards Institute
GSM-R : In operatio
GSM-R Requir ements :
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Sl
No
GSM GSM-R
1 Honey-comb network Linear network
2 th th
GSM and GSM-RA Comparison
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2 Repetition of frequency at the 4thCell Repetition of frequency at the 5thC
3 360D coverage 33D coverage (Directive antennas a
4 Only one type of Handset is used Different types of Mobile sets are u
the type of use)
5 No priority, group call or broadcast call Priority, group call or broadcast cal
6 No functional addressing or locationdependent addressing
Both functional & location dependeused
7 Power output of Handset
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Frequency bands for use by GSM-railway may differ i
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Frequency bands for use by GSM railway may differ i
individual countries (especially in non UIC countries)
national regulations and have to be agreed.
If the frequencies are outside GSM-R band, GSM-R
applications are still possible but border crossing tra
be not functional due to different frequency ranges.
CHANNEL-WISE ALLOCATION OF FREQUE(ON THE BASIS OF 4-CELL REUSE/ 5TH CELL REPETITION PATTERN
SL NO SL NOFrequencies(MHz)
CHL CHLFrequen
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UP LINK DN LINK UP LINK
1 1 907.8 952.8 7 8 909.2
2 2 908 953 8 9 909.4
3 3 908.2 953.2 9 *10 f10
4 4 908.4 953.4 10 *11 f11
5 6 908.8 953.8 11 *13 f13
6 7 909 954
Frequencies(MHz)NO. NO.
Frequen
* To be allotted by WPC in addition to 8-pair already allotted for the R
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ARCHITECTURE OF GSM-R NETWORK
The MTRC system consist of following sub-system:-
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Mobile Station(MS)
Base Station Sub-System(BSS) Switch sub- System(SSS)
Operation & Maintenance Subsystem
MS consist of two parts :-i) Subscriber identity module(SIM)
ii) Mobile equipment(ME)/Handset
The functionality of the above systems are same adescribed in GSM networks except some ratings li
powers of MS and BTS.
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There are different types of mobile equipments, distinprincipally by their power and application.
The fixed terminals (8W)are the ones installed in driv
Hand held sets are of 2W power.
RF power of BTS will be 20-25 W.
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enhanced MULTILEVEL PRECEDENCE AND PREEMPTION
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If a handover to neighbouring Cells is unsuccessful due to conge
radio channel, a preemption service is necessary to allow imme
to a traffic channel occupied by a low priority application
enhanced MULTILEVEL PRECEDENCE ANDPREEMPTION (eMLPP)
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to a traffic channel occupied by a low priority application.
A preemption service will release ongoing low priority calls t
channels for emergency call setup.
These calls shall be set up in 2 second or less.
Up to 7 different eMLPP levels (2 network and 5 subscriber leintroduced.
One or more priority levels can be assigned to a mobile subscrib
Network Level 1 is reserved for Railway Emergency C
Network Level 2 for ETCS.
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Maximum allowed and default priority will be stored
HLR with the related subscriber data.
When an eMLPP priority call is build up, the MSC / VL
insert the priority into the call set-up message to the B
The BSC will evaluate the Priority and give access to t
appropriation channel for either call set-up or hand-o
Two subscribers are involved in a point to point call
Train controller initiates a REC in the Group Area
The subscribers are notified
GSM-R Indian Railways
eMLPP
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The subscribers are notified
The ongoing ptp is terminated and the REC is connected
Point to point callOKOK
Emergency...Emergency...
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FUNCTIONAL ADDRESSIN
To call Driver of train :
Driver of particular train keeps changing.
Functional Addressing
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Without Functional Addressing: Controller must always know the changing
number (MSISDN) of the specific Train Driver of
train 2423
With Functional Addressing : Controller dials the Unique Number and is
connected to the driver currently on duty. No
Need to remember the mobile no of each Driver.Train Driver o
USSD string for MSC IN
Functionalnumber
(Train nr. +f ti d )
Basicsregistration/deregistration
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USSD string for
RegistrationDeregistrationInterrogation
MSC INfunction code)
Registration com
Association betw
Number and MSI
Train Driver now
OK
REGISTRATIONA Train Driver or employees on the Train, registers to the respective func
by establishing an USSD dialogue via MSC / VLR to the HLR, where their M
stored (HLRmobile).
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This HLR is establishing a dialogue to the HLRfunctional regarding the callin
The HLRfunctional, in turn, establishes a Call Forwarding from the required
Number to the MSISDN.
After completion, the registering Subscriber will get an acknowledgemen
Only one MSISDN can register under one functional number. Users tryingfunctional number already in use will be rejected.
Same way, a Functional Number is unique inside the HLR functional and cann
duplicated
DEREGISTRATIONMSISDN registered to a Functional Number will be de-registered b
establishing an USSD dialogue via MSC / VLR to the HLR, where th
stored (HLR bil ).
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stored (HLRmobile).
This HLR is establishing a dialogue to the HLRfunctional regarding t
MSISDN.
The HLRfunctionalin turn cancels the call forwarding from the requir
number to the MSISDN.
After completion, the registering subscriber gets an acknowledge
registered).
EXPIRATION DATEAll functional numbers contain a programmablevalidity p
hours).
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During the registration process, the Expiration Date of the s
member inside this functional number will be computed anAfter exceeding the expiration date, the service ignores the
owner.
In case the value of the validity period is set to 0, the featur
switched off for this functional number. That means a regis
any member for this functional number has no time limit.
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LOCATION DEPENDENT ADDRES
To call Controller :
Without LDA
GSM-R Indian Railways
Location Dependent Addressing
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Driver wishes to communicate emergency to controller.
Driver is not aware of who is Controller of that area.
Driver must know the no of each controller on route.
With LDA
Driver dials the short code i.e 1200 and is connected to c
charge of that area.
Short Code is common throughout journey.
LOCATION DEPENDENT ADDRESSIt provides the Automatic Routing of Mobile Originated Cal
pre-defined destinations relative to the geographic area wh
subscriber is roaming.
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Train driver dials a short number as defined in the EIRENE
plan. This short number will be automatically converted int
corresponding long number(s) of the train controller(s) res
the area the train is actually moving through.
If a train is passing between two controller areas the conne
made to both controllers.
IN MSC
GSM-R Indian Railways
Location Dependent Addressing ( LDA)
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Controller B
Cont
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VOICE BROADCAST SERVICE (VBS)
A VBS is characterized by following key points
One Broadcast Call Number combines all members of a certai
VOICE BROADCAST SERVICE (VBS)
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For each Broadcast Call, a Service Area composed out of a ncells is assigned
Dialing the broadcast call number initialises the parallel set-upconnections into all Cells of the assigned service area. All memb
group being in the service area will be paged to receive a notifi
ongoing voice broadcast call
Dependent on the call ID a priority members of the group call join the call
The MSC retrieves all necessary information from the co-located Group
(GCR), which stores Tables having
The Group ID (1 to 7 digit depending on the length of the group call ar
The Group Call Area ID (MCC + MNC + LAC + CI)
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The Group Call Reference (27 bit binary encoded field with Group IDArea ID)
The Cell List corresponding to the Group Call Area ID (max. 50 cells)
The Dispatcher List corresponding to the group call references (up to
per group call reference )
An information whether the call is active or not
Security Information
MSC connects the so called Dispatcherwith a duplex connectio
Each cell of the required group call area is setup with half-dupl
connections.
M b ll i hi ill b d d
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Membersactually present in this area will be paged and connec
common channel down-link (can only listen)
If a member of the group enters the Cell after beginning of the vo
he will just join the ongoing voice broadcast at his time of entry.
If a member of the group leaves the voice broadcast area, he willdisconnected.
The setup of a VBS is possible with eMLPP or as a normal cal
priority and preemption.
The Group Area is predefined
Train controller initiates a VBS call in a Group Area
The speech is broadcasted to all users in the area
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TraTrain is
Train is
Train is
(One way communication)
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VOICE GROUP CALL SERVICE(VGCS)
VGCS is characterised by the key point that the actual spea
change during a call.
G b ill ll li t t th i V i G
(VGCS)
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Group members will normally listen to the ongoing Voice G
As soon as the initiator of the VGCS stops speaking, he indic
he releases the up-link.
All group members will be notified that they can now requ
linkto become the next talker by using their Push-To-Tal
A dedicated duplex channel will be allocated in the respecti
Initial talker releases the up-link (and changes to the common
this cell, if he is a mobile subscriber)
Possible new talker sends an up-link request
The BSC serving this area selects the first Uplink Request and p
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The BSC serving this area selects the first Uplink Request and p
the MSC
The MSC serves the first UPLINK_REQUEST of all BSC in the Gr
The new talker confirms his up-link request
The other group member get an up-link seized or up-link rejec
The duplex channel for the new talker is switched through
The Group Area is predefined
Train controller initiates a VGCS call in a Group Area
The speech is broadcasted to all users
The user can confirm by using Push To Talk, PTT
The Call can be initiated by any group Member
Group group call - group Id
- priority (n
- call setup
GSM-R Indian Railways
Voice Group Call - VGCS
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Train
acknoh
The Call can be initiated by any group Member.Train is
Train is
Train is
OK
OK
OK
HANDSETs USEd IN MTRC, NFR
OPH HAND SET
PROVIDED
To Loco Pilots
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GPH HAND SET
PROVIDED
To Station Master
To Guards
To Lobby & Officers
To S&T Maintenance staff, P WAY staff
Operational Handheld
(OPH 940)
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Emergency Button Robust Design IP 54 resistant housing Push to talk button
GSM-R Cab Radio Front Pan
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GSM-R Controllers Termin
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Thank You
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