Mobile Communication Standards

7/31/2019 Mobile Communication Standards

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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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Supplementary ISDN Services: digital in nature

Call diversion

Caller identification

Closed user group Short massaging services

SMS call broadcast


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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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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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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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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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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



Half rate TCH

Half Rate Speech Channel: 6.5 Kbps from the speech coderand after channel coding 11.4 Kbps




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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



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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



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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



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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



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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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