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Unformatted text preview: Terrestrial telecommunication infrastructures
Terrestrial, means of relating to earth or its
inhabitants. Examples of terrestrial
telecommunication infrastructures include but are not
paging systems (POCSAG, FLEX, etc.)
trunked radio systems (analogue trunked radio
system, iDEN, TETRA)
cellular radio systems (AMPS, TACS, IS-95, GSM,
EDGE, WCDMA, CDMA2000, etc.);
wireless broadband systems (LMDS, MMDS)
satellite-based mobile communication systems
(Iridium, Globalstar, Teledesic). Paging system A system consisting of personal paging
receivers, radio transmitters, and an encoding
device, designed to alert an individual, or group
of individuals, and deliver a short message Cordless Telephones PSTN
Phone Base unit A cordless phone is a model of telephone which replaces the coiled wire
between the handset and base unit with wireless radio technology. The
land line connection from the phone company is still fed into the base unit,
but the powered handset transmits and receives radio signals in place of
traditional electronic pulses. As long as the base antenna can receive
transmissions from the handset, the user is free to roam a few hundred
feet without being Tethered to a coiled wire. Cellular radio systems
Functional network elements User Equipment (UE)
interfaces with user and radio interface Radio Access Network: handles all radio-related
functionality. Core Network
switches and routes calls and data connections to
external networks Core Network GSM Architecture
Access Network PSTN GMSC BSC Internet cloud
MSC BTS/RBS BSC databases BSC BTS
MS BTS MTN NETWORK ACHITECTURE
Accra IA Site
BSC7 BSC8 BSC10 Kumasi-Kwadaso Site
MSC5 MSC8 MSC6 Accra Graphic Rd. Site
BSC2 BSC12 PSTN & Other PLMN MSC2 Kumasi Site GMSC2 Accra IA
BSC4 MSC7 GMSC1 Accra
Graphic Rd. BSC9 TDM
(Transit) MSC-S11 GMSC3
Kumasi BSC13 MSC3 BSC6 MGW1 MSC4 Tema MSC9 MGW3 BSC16 BSC14 MSC12 BSC5 BSC11 BSC15 MSC-S14 Cape Coast
Site Tamale Site
MGW5 MSC-S13 MGW2 BSC3 MGW4 BSC17 MSC1
BSC1 BSC18 Position of RNC in WCDMA
Uu CN MSC Server Iu
Iu-PS PS Iub NodeB RNC
Iu-BC CBC GSM SYSTEM INTERFACES
Um interface or Air interface is the interface between the
GSM mobile station and the GSM Base station.
The Air interface (RF Interface) uses the TDMA
technique to transmit and receive traffic and
signaling information between the BTS and MS.
The A-bis interface is responsible for transmitting traffic
and signaling information between the BSC and the BTS.
A-interface provides two distinct types of information,
signaling and traffic, between the MSC and the BSC. GSM Network Architecture GSM NETWORK COMPONENTS
The GSM network is divided into three systems. Each
of these systems are comprised of a number of
functional units which are individual components of
the mobile network. The GSM network can be
divided into following broad parts.
The Base Station Subsystem (BSS)
The Network Switching Subsystem (NSS)
The Operation Support Subsystem (OSS) Abbreviations
The SS is responsible for performing call processing and subscriber
related functions. It includes the following functional units:
• Mobile services Switching Center (MSC)
• Home Location Register (HLR)
• Visitor Location Register (VLR)
• AUthentication Center (AUC)
• Equipment Identity Register (EIR)
The BSS performs all the radio-related functions. The BSS is
comprised of the following functional units:
• Base Station Controller (BSC)
• Base Transceiver Station (BTS)
The OMC performs all the operation and maintenance tasks for the
network such as monitoring network traffic and network alarms. The
OMC has access to both the SS and the BSS.
MSs do not belong to any of these systems SWITCHING SYSTEM (SS) COMPONENTS
The MSC performs the telephony switching functions for the
mobile network. It controls calls to and from other telephony
and data systems, such as the Public Switched Telephone
Network (PSTN), Integrated Services Digital Network
data networks, private networks and other
Gateway functionality enables an MSC to interrogate a
network's HLR in order to route a call to a Mobile Station.
Such an MSC is called a Gateway MSC (GMSC). For example, if a
person connected to the PSTN wants to make a call to a GSM mobile
subscriber, then the PSTN exchange will access the GSM network by first
connecting the call to a GMSC. The same is true of a call from an MS to
Any MSC in the mobile network can function as a gateway by integration of
the appropriate software. The Network Switching Subsystem
The main role is to manage the
communications between MS users and
other users, such as ISDN users, Fixed
telephony users etc.
It includes databases needed in other to
store information about the subscribers
and to manage their mobility. MOBILE SWITCHING CENTER (MSC)
It is the central components of the NSS.
The MSC preforms the switching functions
of the network.
It also provides connection to other
Perform the routing path search, signal
routing and service feature processing.
Associated with MSC is a functional unit
enabling the networking of GSM network
and the fixed network (PSTN, ISDN) Gateway MSC
GMSC is a node interconnecting two networks.
It is the interface between the mobile cellular
networks and the PSTN.
GMSC is in charge of routing calls from fixed
network towards a GSM user.
GMSC is often implemented in the same machines
GMSC pass the voice traffic between the fixed
network and the mobile network.
International switching center (ISC) is used to
connect the mobile networks to the international
networks Home Location Register
The HLR is a centralized network database that stores and
manages all mobile subscriptions belonging to a specific
operator. It acts as a permanent store for a person's
subscription information until that subscription is canceled.
The information stored includes:
• Subscriber identity
• Subscriber supplementary services
• Subscriber location information
• Subscriber authentication information
The HLR can be implemented in the same network node as the
MSC or as a stand-alone database. If the capacity of a HLR is
exceeded by the number of subscribers, additional HLRs may
be added. Visitor Location Register (VLR)
The VLR database contains information about all the mobile
subscribers currently located in an MSC service area. Thus,
there is one VLR for each MSC in a network.
The VLR temporarily stores subscription information so that
the MSC can service all the subscribers currently visiting that
MSC service area.
The VLR can be regarded as a distributed HLR as it holds a
copy of the HLR information stored about the subscriber.
When a subscriber roams into a new MSC service area, the
VLR connected to that MSC requests information about the
subscriber from the subscriber's HLR.
The HLR sends a copy of the information to the VLR and
updates its own location information. When the subscriber
makes a call, the VLR will already have the information
required for call set-up. AUthentication Center (AUC)
The main function of the AUC is to
authenticate the subscribers attempting to
use a network. In this way, it is used to
protect network operators against fraud.
The AUC is a database connected to the
HLR which provides it with the
authentication parameters and ciphering
keys used to ensure network security. Equipment Identity Register
The EIR is a database containing mobile
equipment identity information which helps
to block calls from stolen, unauthorized, or
It should be noted that due to subscriberequipment separation in GSM, the barring
of MS equipment does not result in
automatic barring of a subscriber. Base Station Subsystem
The BSS connect the MS and the NSS. It
is in charge of the transmission and
The BSS can be divided into two The Base Transceiver station (BTS) The Base station controller (BSC) The Base Transceiver station
A BTS is usually placed in the center of
It’s transmitting power define the size of
Each BTS has between one and sixteen
transceivers depending on the density of
the users in the cell. Base Transceiver Station (BTS)
Terminating the radio links with the mobile station.
A group of BTSs are controlled by a BSC.
RF resources such as frequency assignments,
sector separation, transmit power control.
Typically equated to the physical site of the
3-cell BTS configuration is most common (max. up
to 6 cell BTS).
BTS connects to BSC through un-channelized
T1/E1 facilities or direct cables in co-located
equipment (Abis) RBS/BTS Base Station Controller (BSC)
Radio resource management
Transmission facilities management
SDU (Selection/distribution unit) : when soft handoff,
this selects the best incoming air interface data frame
from the receivers.
BSC-BTS : Abis a set of trunks : backhaul
BSC-MSC : A1/A2/A5 a set of trunks : fronthaul Base Station Controller (BSC) A number of BSCs may be controlled by each
MSC. BSC principally in charge of frequency hopping,
control of the radio frequency power levels of the
BTSs. Operation and Maintenance
An OMC is a computerized monitoring center which
is connected to other network components such as
MSCs and BSCs via X.25 data network links.
In the OMC, staff are presented with information
about the status of the network and can monitor and
control a variety of system parameters.
There may be one or several OMCs within a network
depending on the network size. Network Management Center
Centralized control of a network is done at a Network
NMC. Only one NMC is required for a network and
this controls the subordinate OMCs.
The advantage of this hierarchical approach is that staff
at the NMC can concentrate on long term system-wide
issues, whereas local personnel at each OMC can
concentrate on short term, regional issues.
OMC and NMC functionality can be combined in the
same physical network node or implemented at
different locations. Cables Distribution Figure
(X.25 data network links) NMC VIEW MOBILE STATION (MS)
An MS is used by a mobile subscriber to communicate with
the mobile network. Several types of MSs exist, each
allowing the subscriber to make and receive calls.
Manufacturers of MSs offer a variety of designs and features
to meet the needs of different markets.
The range or coverage area of an MS depends on the output
power of the MS. Different types of MSs have different
output power capabilities and consequently different ranges.
For example, hand-held MSs have a lower output power and
shorter range than car-installed MSs with a roof mounted
GSM MSs consist of:
• A mobile terminal
• A Subscriber Identity Module (SIM) The Terminal
There are different types of terminals
distinguished principally by their power and
application The fixed terminals are the ones install in cars.
The max allowed out power is 20w.
GSM portable terminals can also installed in
vehicles. The max allowed out power is 8w.
The handheld terminals have experienced the
biggest success, thanks to their weight and
volume, which are continually decreasing. This
terminals can emit up to 2W.
The evolution of technologies allow decreases
the max allowed power to 0.8W The SIM The SIM is a smart card that identify the terminal. By inserting the
sim card into the terminal the user can have access to all
Without the sim card the Terminal is not operational.
The SIM card is protected by four digits, Personal identification
In other to identify the subscriber to the system, the SIM card
contains some parameters of the user such international mobile
subscriber identity (IMSI).
Another advantage of the SIM card is the mobility of the users, in
fact the only element that personalizes a terminal is the SIM card.
SIM achieved separation of user mobility from equipment
mobility. This enabled international roaming independent to the
mobile equipment and the network technology.
SIM card store short messages, charging information and list of
numbers for fast dialing and all cryptographic algorithms. Example: mobile phone
• Typical phone has a
microcontroller (SIM card) with
a small program
– Drive GUI
– Control devices (keypad,
microphone, a/d, dsp,
decoder) Channels in GSM
The logical channels are divided into two
Traffic channel (TCH): used in transmitting
user payload (speech, data). TCH do not
carry any control information.
Communication can be circuit switched of
Signaling Channel (BCCH): Broadcast control channel
This is a unidirectional point to multipoint
channel between MS and BS. The
following kind of information is sent: Radio channel config.(current and nearby cell)
Synchronization (Frequency and frame
Registration identifiers Synchronization channel (SCH):
Broadcast info to identify BS and for frame
synchronization of the MS. Forward link Channels
The forward link channel uses four types of
channels to transmit voice and control data
to the mobile. Pilot
Traffic Pilot Channels
BTS constantly transmit Pilot channels
The MS uses the pilot signal to acquire the
It then uses the pilot signal to monitor and
adjust the power needed in other to
transmit back to the BTS. Sync
BTS constantly transmit over the sync
channels so that the MS can synchronize
with the BTS.
It provides the mobile with the system time
and identification number of the cell site.
The mobile ignore the sync channel after it
has synchronized. Paging channels
Paging channel transmit overhead
information such as commands, pages to
the mobile and traffic channel assignment
during call set up.
The mobile ignore the paging channel
after a traffic channel has been
Paging, sync and pilot channels are
referred to as FORWARD CONTROL
CHANNEL (FCC) Traffic Channels
About sixty-one forward traffic channels
are used to send both voice and overhead
control data during a call.
Once the call is completed, the mobile
tunes back into the paging channel for
commands and pages.
Traffic channels is known as FORWARD
VOICE CHANNEL (FVC) Reverse link channel
The channels provide from the mobile to
the Base station.
Uses two types of channels to transmit
voice and control data to the BTS. Access
Traffic Access Channel (RCC)
The mobile uses the access channel when
not assigned to a traffic.
Uses to Register with the network
Response to pages and commands from the
Transmit overhead messages to the Base
station. Reverse link Traffic Channels
The reverse traffic channel is only used
when there is call
Transmit voice data to the BTS
Transmit overhead control information to
the BTS. Forward and Reverse Channels
To establish a call between the BS and the MS
we need channels.
Forward Voice Channel (FVC): Used for voice
transmission from BS to MS.
Reverse Voice Channel (RVC): Used for voice
transmission from MS to BS.
Forward Control Channel (FCC): Used for
initiating a call from the BS to MS
Reverse Control Channel (RCC): Used for
initiating a call from the MS to BS.
FCC and RCC are called setup channels and
are used as overheads Call processing stages
Traffic mode Initialization and idle mode
During initialization mode, the mobile
acquire the system via the pilot channel.
Synchronizes with the system via the sync
Idle mode: MS not involve in a call but
must stay in communication with the BTS,
this is done over the access and paging
The mobile obtain overhead info via the
paging channels. Access mode
The MS Accesses the network via the
access channel during call originating
The Access channel and Paging channel
carry the require call set up
communication between the MS and the
BTS until the traffic channel is established. Call from PSTN to Mobile Phone
When a PSTN subscriber calls a mobile user, the MSC dispatch the
request to all base stations(BS). The mobile identification
number(MIN) is broadcast as a paging message over the forward
control channels (FCC).
The MS receives the paging message sent by the BS and respond by
identify itself over the reverse control channel(RCC). The BS relays
the ACK sent by the MS and informs the MSC of the handshake.
MSC instruct the BS to move the call to an unused voice channel
within the cell.
The BS signals the MS to change frequencies to an unused forward
and reverse voice channel pair. An alert is transmitted over the FVC
to instruct the MS to ring.
MSC adjusts the Tx pwr of the MS and change the channel in order
to maintain call quality during movement in and out of range of each
BS. This is called HANDOFF. Call from Mobile Phone to PSTN
When a MS originates a call, initiation request is sent
on the RCC with MIN, electronic serial number
(ESN) and the telephone number of the called party.
Also transmit station class mark (SCM) to indicate
max power level to be used.
The BS received this data and send it to the MSC for
MSC instruct FCC of originating BS to move MS to a
pair of voice channels via a page msg.
BS receives page data and matches MIN and move to
MSC connect to the called party on PSTN and begin
voice Tx/Rx Roaming Mobile Phone
This allows subscriber’s to operate in service areas other than the one from
which service is subscribed. When a mobile enters a city or geographic
area that is different from it home service area, it is registered as a roamer
in the new service area. This is accomplished by:
MSC issues a global command over each FCC in the system at all time,
asking for the all mobile which are previously unregistered to report their
MIN and ESN over the RCC.
New unregistered MS in the system periodically report back their
subscriber info upon receiving the registration request, MSC then uses the
MIN/ESN data to request billing status from the home location register
MSC register the subscriber if the MS has authorization for billing
purposes. Once registered, roaming MS are allowed to Tx/Rx and the
billing is routed automatically to the subscriber’s home service provider. HANDOFF
When a mobile moves into a different cell
while a call is in progress the MSC
automatically transfers the call to a new
channel belonging to the new BS.
The handoff operation involves identifying
a new BS and the allocation of voice and
control channels associated with the new
BS. VERIFY YOR MOBILE PHONES QUALITY USING IMEI MOBILE TRICK
Find IMEI ID of your mobile.
Dial *#06#. A 15-digit number will be displayed on the screen. This is your
mobile IMEI ID.
Here is a sample IMEI number : 2 4 5 6 6 1 0 2 3 0 7 2 4 0 9
How to Check Cell Phones Quality Using IMEI
Look on the 7th and 8th digit. These two digits ensure your cell phone quality.
7th and 8th Value Made in Quality 02 or 20 Emirates poor 08 or 80 Germany fair 01 or 10 Finland high 00 Original Mobile Factory best 03/30 or 04/40 China average 05 or 50 Finland USA or Brazil good 06 or 60 China, Mexico or Hong Kong good 13 Azerbaijan poor, cause heath hazards Any QUESTIONS? ...
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- Fall '16