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MOBILE COMMUNICATION
STANDARDSBy
Pradip Paudyal
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GSM (GLOBAL SYSTEM FOR MOBILE)
2 G, digital standard
Wide range of services through the use of ISDN
GSM Services and Features
Teleservices: standard mobile telephony Data services: Packet switched traffic; Computer
to computer communication
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GSM SERVICESAND FEATURES
User Services are categorized as:
Telephone Services: emergency calling, facsimile,
videotext and teletext.
Barrier Services/ Data Services: Limited to layer1, 2, 3 of OSI model, support packet switched
protocol, data rates from 300bps to 9.6 Kbps.
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GSM SERVICESAND FEATURES
Supplementary ISDN Services: digital in nature
Call diversion
Caller identification
Closed user group Short massaging services
SMS call broadcast
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GSM SERVICESAND FEATURES
Features
Subscriber Identity Module; Memory devices
stores the information such as subscriber identity
number, network, country, privacy keys .
On the air privacy: Cryptography key known only
for carrier and changes with time for the user;
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GSM SYSTEM ARCHITECTURE
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GSM SYSTEM ARCHITECTURECONT..
BSS (Base Station Subsystem)
Also known as radio subsystem, provides and
manages radio interface for transmission path.
Contains many BS, BSC and MS NSS (Network Switching Subsystem)
Manage switching function of the system
Allow the MSC to communicate with other
network such as PSTN and ISDN.
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GSM SYSTEM ARCHITECTURECONT
NSS handles the switching of GSM call between
external networks and BSCs
NSS is responsible for managing and providing
access to databases.
MSC control the traffic among BSCs
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GSM SYSTEM ARCHITECTURECONT
Contains three databases called;
Home Location Register (HLR):
Contains subscriber information and locationinformation of user.
Each subscriber is assigned a unique IMSI(International Mobile Subscriber Identity) numberto identify the each home user.
Visitor Location Register (VLR):
Temporary store the IMSI and customer
information for each roaming subscriber who isvisiting particular coverage area of MSC.
VLR are linked between several adjoining MSCs inparticular geographical region.
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GSM SYSTEM ARCHITECTURECONT
Authentication Center (AuC):
Strongly protected database which handles the
authentication and encryption keys for every
single subscriber in HLR and VLR.
Contains a register called EIR (Equipment
Identity Register).
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GSM SYSTEM ARCHITECTURECONT
OSS (Operation Support Subsystem)
Support the operation and maintenance of GSM
Allows the system engineer to monitor, diagnose
and troubleshoot of all aspect of GSM system. Support one or more OMC (Operation and
Maintenance Center)
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GSM SYSTEM ARCHITECTURECONT
Three main function of OSS are:
To maintain all telecommunication hardware
and network operation with a particular market.
Manage all charging and billing procedure Manage all mobile equipment in the system
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INTERFACES USEDIN GSM
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INTERFACES USEDIN GSM CONT
Interface which connect BTS and BSC called Abis
interface.
Abis interface carries traffic and maintenance
data.
BSCs are physically connected through
dedicated/leased line or microwave link to the
MSC
A interface uses an SS7 protocol
A interface allows service provider to use base
station and switching equipment made by
different manufacturer.
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GSM RADIO SUBSYSTEM
Use two band of 25 MHz.
890-915 MHz band is used for reverse link.
935-960 MHz band is used for forward link.
It use FDD, TDMA and FHMA.Available band is divided in to 200 KHz sub-
channel called ARFCN (Absolute Radio
Frequency Channel Number)
ARFCN denotes forward and reverse channelpairs which are separated by 45 MHz and shared
by 8 time slots.
0.3 GMSK Modulation
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GSM RADIO SUBSYSTEM
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GSM FRAME STRUCTURE
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GSM RADIO SUBSYSTEM
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SIGNALPROCESSING
Several successive operations have to be
performed to convert a speech signal into a radiosignal and back.
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SIGNALPROCESSING
The following operations take place on the
transmitting side:
Source coding: Converts the analogue speech
signal into a digital equivalent.
Channel coding:Adds extra bits to the data flow.
This way redundancy is introduced into the data
flow, increasing its rate by adding information
calculated from the source data, in order to allowdetection or even correction of bit errors that
might be introduced during transmission.
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SIGNALPROCESSING
Interleaving: Changes sequence of data stream
Reduces loss sequential data (Burst Error
Random Error)
Improves ability to reconstruct original data
1 2 3 4 5 6 7 8 9 10 11 1213 14 15 16 17 18 19 20 21 22 23 24
25 26 27 28 29 30 31 32 33 34 35 36
37 38 39 40 41 42 43 44 45 46 47 48
49 50 51 52 53 54 55 56 57 58 59 60
Data Input
Data
Output
Block Interleaver Input Data : 1, 2, 3, 4, . . . . . . 59, 60
Block Interleaver Output Data : 1, 13, 25, 37, . . . . . . 48, 60
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SIGNALPROCESSING
Ciphering: Modifies the contents of these blocks
through a secret code known only by the mobilestation and the base station.
Burst formatting:Adds synchronization andequalization information to the ciphered data.Part of this is the addition of a training sequence.
Modulation: Transforms the binary signal into ananalogue signal at the right frequency. Therebythe signal can be transmitted as radio waves.
The receiver side performs the reverse operations
as follows:Demodulation: Transforms the radio signal
received at the antenna into a binary signal.
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SIGNALPROCESSING
Deciphering: Modifies the bits by reversing the
ciphering code.De-interleaving: Puts the bits of the different
bursts back in order to rebuild the original codewords.
Channel decoding: Tries to reconstruct the sourceinformation from the output of the demodulator,using the added coding bits to detect or correctpossible errors, caused between the coding andthe decoding.
Source decoding: Converts the digitally decodedsource information into an analogue signal toproduce the speech.
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GSM CHANNELS
Channels
Traffic Channels (TCH): may be full rate or half rateWhen transmitted at full rate user data is contained withinone time slot per frame; but for half rate same time slot butin alternative frame
Full rate TCH
Full Rate Speech Channel (TCH/FS): 13 Kbps from the sourceand after channel coding 22.8 Kbps.
Full Rate Data Channel for 9600 Bps
Full Rate Data Channel for 4800 Bps
Full Rate Data Channel for 2400 Bps
Half rate TCH
Half Rate Speech Channel: 6.5 Kbps from the speech coderand after channel coding 11.4 Kbps
Full Rate Data Channel for 4800 Bps
Full Rate Data Channel for 2400 Bps
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GSM CONTROL CHANNEL
Control Channels:
For signaling and synchronization commands
Broadcast Channel (BCH)
Forward link and in TS0 of certain frame
Broadcast Control Channel (BCCH): Used tobroadcast certain information such as cell and
network identity, operating characteristics of cell, list
of channel that are currently being used
Frequency Correction Channel (FCCH): TS0 on
every 10 frames, frequency synchronization of user tosystem
Synchronization Channel (SCH): to identify
serving base station
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GSM CONTROL CHANNEL
Common Control Channel (CCCH): Ifchannel is not used by BCH or if idle
Paging Channel (PCH): Provides paging signal
from BS to MS, transmits IMSI number of user along
with request for acknowledgement from the mobile
unit on RACH, to broadcast text message e.g. SMS Random Access Channel (RACH): Reverse link
channel, to ACK page from PCH and to originate
mobile call. (slotted ALOHA )
Access Grant Channel (AGCH): used by BS to
provide forward link communication to mobile and
carries data which instruct mobile to operate on
particular channel.
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GSM CONTROL CHANNEL
Dedicated Control Channel (DCCH)
Stand Alone Dedicated Control Channel (SDCCH):carries the signaling data just before TCH assignment by
BS, to remain in connection when BS and MSC verify the
subscriber unit and allocate resource for mobile. E.g.
temporary channel
Slow Associated Control Channel (SACCH):Associated with TCH/SDCCH, on forward link used to send
slow (13th frame)but regularly changing control
information e.g. transmit power level and timing, on
reverse link received signal strength and quality of TCH
and BCH strength from neighboring cell.
Fast Associated Control Channel (FACCH): Carries
urgent message e.g. hand-off request, by stealing time slot
from TCH.
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EXAMPLEOF GSM CALL
First MS must be synchronize with near by BS as itmonitors BCH.
By receiving FCCH (frequency Correction Channel),BCCH (Broadcast Control Channel) and SCH(Synchronization Channel) message the subscriberwould be locked on system and appropriate BCH.
First user dial the number and press send button
MS will transmit a burst of RACH (Random AccessChannel) data using same ARFCN as locked with BS.
BS responds with AGCH; which assign a new channelfor SDCCH (Stand-alone Dedicated Control Channel )connection.
Once tuned to SDCCH, MS waits for SACCH (SlowAssociated Control Channel) which gives power leveland timing command.
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EXAMPLEOF GSM CALL
Then MS is able to transmit normal burst
message.
SDCCH send message between MS and BS;
making care of validation and authentication.
After few second MS is commanded by BS via
SDCCH to retune to a new ARFCN and new TSfor TCH assignment.
Then speech data is transferred on forward and
reverse link.
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ABOUT IS-95 CDMA
IS-95 is specified as:
Reverse Link: 824-849 MHz
Forward Link: 869-894 MHz
Forward and reverse is separated by 45 MHz
Maximum user data rate is 9.6 Kbps
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Forward IS-95B Channel Structure
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Pilot Channel (Walsh Code 0)
- The Pilot is structural beacon which does not contain a
character stream
- Allows Mobile to Acquire the System
- Reference Signal for System Acquiring, Timing, Coherent
Modulation
- Provides Mobile with Signal Strength Comparison during
handoffs
- Transmitted Constantly- Non-Modulated Spread Spectrum Signal (Transmit Short PN
Code)
- Has Unique PN Offset(512) for each Cell or Sector
- Approximately 20% of radiated BTS power is in the pilot
Forward IS-95B Channel Structure
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Sync Channel (Walsh Code 32)
- Used by Mobile to Synchronize with System
- Carries a data stream of system identification and
Parameter information used by MS during system
acquisition
- Pilot PN Offset
- System Time
- Long PN Code
- System ID
-Network ID
- Paging Channel Data Rate
- Tx at 1200 bps
Forward IS-95B Channel Structure
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Paging Channel (Walsh Code 1 up to 7)
- Used by Base Station to :
-Page Mobile Information
-Transmit Overhead
-MS Control
-Assign Mobile to Traffic Channel
- Provides Mobile with:
-System parameter Message
- Neighbor List Message
-Access Parameter Message
-CDMA Channel List Message
- Tx at 9600 or 4800 bps
Forward IS-95B Channel Structure
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Reverse IS-95B Channel Structure
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Access Channel
- Used by Mobiles not yet in a call to transmit :
-Registration Requests
-Call Setup Requests
-Page Responses
-Order Responses
- other Signaling information
- Be really just a public Long Code Offset unique to the BTS Sector
- Be Paired to Paging Channel (Each Paging Channel can have up
32 access channels)
- Tx at 4800 bps, 20ms frame length
Reverse IS-95B Channel Structure
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Reverse IS-95B Channel Structure
Traffic Channel- Be used by individual users during their actual calls to transmit traffic to the BTS
- Be really just a user-specific public or private Long Code Mask
- there are many reverse Traffic channels as there are CDMA phones in the world
- 64-ary Orthogonal Modulator : For Non-coherent detection
- Data Burst Randomizer : For Power Control and Variable Rate Transmission
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SUMMARYOF POWER CONTROL
All types of power control work together to minimizes power
consumption at the mobile stations and BS, and increases the overall
capacity of the system
FERFER
Mobile BTS BSC
Signal StrengthMeasurement
Setpoint
or
Adjust Fwd.power
Reverse Outer
Loop Power
Control
Reverse Closed Loop
Power Control
Forward Link Power Control
Reverse Open Loop
Power Control
F Q P C
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FORWARD QUICK POWER CONTROL
Received the Frame
Quality Informationfrom the Forward Link
Eb/Nt>Eb/No?
Outer-loop
Algorithm
Up PowerControl Bit
Down PowerControl Bit
Puncture toPower ControlSubchannel
Power ControlCommand
Measurement
Power ControlCommand
Measurement
Demodulate andmeasure Eb/Nt
Outer Loop Correction
Closed-loop Control
Mobile Station
Base Station
Eb/No
No
Yes
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DECT DECT (Digital European Cordless Telephone)
standardized by ETSI (ETS 300.175-x) for cordlesstelephones
standard describes air interface between base-stationand mobile phone
DECT has been renamed for international marketingreasons into Digital Enhanced CordlessTelecommunication
Characteristics frequency: 1880-1990 MHz
channels: 120 full duplex
duplex mechanism: TDD (Time Division Duplex) with 10 msframe length
multiplexing scheme: FDMA with 10 carrier frequencies,TDMA with 2x 12 slots
modulation: digital, Gaussian Minimum Shift Key (GMSK)
power: 10 mW average (max. 250 mW)
range: ca 50 m in buildings, 300 m open space
DECT SYSTEM ARCHITECTURE REFERENCE
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DECT SYSTEMARCHITECTUREREFERENCE
MODEL
globalnetwork
local
network
local
network
FT
FT
PTPA
PTPA
VDB
HDB
D1
D2
D3D4
PA - Portable Application
PT - Portable radioTransmission
FT - Fixed radio
Transmission
HDB - Home Data Base
VDB - Visitor Data Base
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physical layer
medium access control
data link
control
data link
control
network
layer
OSI layer 1
OSI layer 2
OSI layer 3
U-PlaneC-Planesignaling,
interworking
application
processes
DECT REFERENCEMODEL
close to the OSI
reference model management plane
over all layers
several services in
C(ontrol)- and U(ser)-plane
management
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DECT LAYERS I Physical layer
modulation/demodulation
generation of the physical channel structure with aguaranteed throughput
controlling of radio transmission
channel assignment on request of the MAC layer
detection of incoming signals
sender/receiver synchronization
collecting status information for the management plane
MAC layer
maintaining basic services, activating/deactivating physicalchannels
multiplexing of logical channels
e.g., C: signaling, I: user data, P: paging, Q: broadcast
segmentation/reassembly
error control/error correction
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DECT LAYERS II
Data link control layer
creation and keeping up reliable connections between
the mobile terminal and basestation
two DLC protocols for the control plane (C-Plane)
several services specified for the user plane (U-Plane) null-service: offers unmodified MAC services
frame relay: simple packet transmission
frame switching: time-bounded packet transmission
error correcting transmission: uses FEC, for delay critical,
time-bounded services
bandwidth adaptive transmission
Escape service: for further enhancements of the standard
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DECT LAYERS III
Network layer similar to ISDN (Q.931) and GSM (04.08)
offers services to request, check, reserve, control, andrelease resources at the basestation and mobileterminal
resources necessary for a wireless connection
necessary for the connection of the DECT system to thefixed network
main tasks call control: setup, release, negotiation, control
call independent services: call forwarding, accounting,call redirecting
mobility management: identity management,authentication, management of the location register
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DECT: For detailed Ref: T.S.R
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Thank You..????????????????
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