Intro to CDMA & GSM.

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Introduction to CDMA GSMMobile
Communication

• By Abhishek sinha
• (Electronics communication Engg.)
• Email- aksinha246_at_gmail.com

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It all started like this
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Contents-

• History
• Generations
• CDMA
• TDMA
• FDMA
• GSM- TDMAFDMA
• What is cellular ?
• Cellular principles
• GSM conclusion.

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CDMA History-

• CDMA is based around a form of transmission known
  as Direct Sequence Spread Spectrum.
• The CDMA history can be directly linked back to
  the 1940s when this form of transmission was
  first envisaged.
•  it is difficult to decipher without the
  knowledge of the right codes
• The first CDMA system was launched in September
  1995 by Hutchison Telephone Co. Ltd. in Hong Kong
• And SK Telecom in Korea soon followed along with
  networks in the USA.
• This was only one cellular telecommunications
  system, although it was the first. Its
  development lead on to the CDMA2000 series of
  standards.
• Multiple access -  The use of the spreading
  codes which are independent for each user along
  with synchronous reception allow multiple users
  to access the same channel simultaneously.

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GSM History-

• 1982- Group Special Mobile (GSM) is formed by
  the (CEPT) to design a pan-European mobile
  technology.
• CEPT -Confederation of European Posts and
  Telecommunications
• 1984-France Germany sign a joint development
  agreement for GSM.
• 1986-EU Heads of State endorse the GSM project.
• The European Commission initiatitive proposes to
  reserve 900MHz spectrum band for GSM.
• agreed in the EC Telecommunications Council.
• 1987-Basic parameters of the GSM standard agreed
  in February.

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GSM History-

• 1988-Completion of first set of detailed GSM
  specifications for infrastructure tendering
  purposes.
• 1990-GSM adaptation work started for the DCS1800
  band.
• 1991-First GSM call made by Radiolinja in
  Finland.

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GSM History-

• 1992-First international roaming agreement signed
  between Telecom Finland and Vodafone (UK).
• 1992-First SMS sent.
• 1996-First GSM networks in Russia and China go
  live.
• 1996-Pre-paid GSM SIM cards launched.
• And now a days

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Generations of mobile-

• 1st generation (1-G) -
• 1979-80 (America)
• AMPS- Advance mobile phone service
• TCS- Total communnication system
• NMI- Nordic mobile telephony
• Nature of the system was Analog

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2nd generation (2-G) -

• In 1990s
• DAMPS- Digital advance mobile phone service
• GSM- Global system for mobile communication
• CDMA- Code division multiple access
• Digital in nature
• Technology used TDMAFDMA
• TDMA- Time division multiple access
• FDMA- Frequency division multiple access

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3rd generation (3-G) -

• WLL- Wireless in local loop
• Technology used is,
• CDMA
• Information
• gt0
  Seperation code
• 
  (DIGITAL)
• Data speed will increase and go for 144 kbps to
  384 kbps

gt0gt0gt0gt0gt0gt0gt0gt0gt0gt0gt0gt0.. .gt0gt0gt0gt0gt0gt0
gt0gt0.
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CDMA-

• CDMA- Code division multiple access
• CDMA is green mobile
• Used in 3-G WLL
• All information of the customers are on the same
  frequency/seperation.
• Each information is seperated by a digital code
• Digital codes separate one information to another
  to avoid interference of call/talk.

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CDMA-

• The technology employed shall depend upon various
  radio access techniques, like FDMA, TDMA and CDMA
• Frequency of operation 824-849Mhz and 869-894
  Mhz
• Duplexing Mehtod Frequency Division Duplexing
  (FDD)
• Access Channel per carrier Maximum 61 Channels
• RF Spacing 1.25 Mhz
• Coverage 5 Km with hand held telephones and
  approx.
• 20 Km with fixed units
• The various technological options available are
  as follows -
• 1. Multi Access Radio Relay
• 2. Wireless In Local Loop
• 3. Fibre In the Local Loop

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CDMA-

• WLL - wireless in local loop-
• Fixed Wireless telephony in the subscriber access
  network also known
  
  
  as (WLL)
• WLL is generally used as the last mile solution
  to deliver basic phone service
• It is also used in remote areas
• The technology employed shall depend upon various
  radio access techniques, like FDMA, TDMA and CDMA

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CDMA-

• WLL-
• BTS BSC
  MSC
• BTS, BSC MSC are the Units of mobile

WLL
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Units of mobile-

• BTS- Base transceiver station
• BTS

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Base transceiver station

• A base transceiver station (BTS) is a piece of
  equipment that facilitates wireless communication
  between user equipment (UE) and a network.

Trans Receiver
Transceiver
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BTS-

• BTS is also known as CELL
• Its size and shape are hexagonal
• BTS range upto 35 km Max.
• QUES- WHAT IS CELL ?
• ANS- Cell is unit
• In Battery, cell is made up of carbon which
  generate radiation in mobile phone/cell phone.
• CELL PHONE- Area covered by a BTS is called cell
  And the device which is used in communication
  between a cell is known as Cell phone.

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2. BSC-

• BSC- Base station controller
• BSC
• A base station controller (BSC) is a critical
  mobile network component that controls one or
  more base transceiver stations (BTS),
• also known as base stations or cell sites
• Key BSC functions include radio network
  management (such as radio frequency control), BTS
  handover management and call setup.

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3. MSC-

• MSC- Mobile switching center
• MSC
• Mobile-services Switching Center (MSC) performs
  the switching functions for all mobile stations
  located in the geographic area

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MSC-

• Functions of the MSC include- 
• Call handling that copes with mobile nature of
  subscribers (e.g., paging)
• Management of required logical radio-link channel
  during calls
• Management of MSC-BSS signalling protocol
• Handling location registration and ensuring
  interworking between Mobile Station and VLR
• Control of inter-BSS and inter-MSC handovers
• Acting as a gateway MSC to interrogate the HLR
• Exchange of signalling information with other
  system entities
• Standard functions of a local exchange switch in
  the fixed network (example charging)

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Connections -
BTS
OFC
BSC
BTS
BTS
OFC
OFC
OFC
BTS
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Connections -

• BTS are connected with BSC
• BSC is the controller of BTS
• Each BSC will be connected with the MSC
• MSC- Mobile switching center
• It is a responsible center for setting of a cell
• When this all connected with optical fibre cable
  (OFC) it will be becomes GSM Exchange.
  

MSC
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Connections -
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TDMA-

• Time Division Multiple Access
• Each channel is divided into timeslots, each
  conversation uses one timeslot.
• Many conversations are multiplexed into a single
  channel.
• In a TDMA system each channel is split up into
  time segments
• And a transmitter is given exclusive use of one
  or more channels only during a particular time
  period.
• Shares single carrier frequency with multiple
  users
• Higher synchronization overhead than CDMA
• Used in GSM

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FDMA-

• FDMA- Frequency Division Multiple Access
• FDMA is a familiar method of allocating bandwidth
• FDMA can be used with both analog and digital
  signal
• FDMA requires high-performing filters in the
  radio hardware, in contrast to TDMA and CDMA.
• Used in GSM
• where a base station is allowed to transmit on
  one or more number of preassigned carrier
  frequencies
• and a mobile unit transmits on corresponding
  reverse channels.

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GSM-

• GSM- Global system for mobile communication
• The GSM network is called Public Land Mobile
  Network (PLMN)
• It is organised in three subsystems - 
• Base Station Subsystem (BSS)
• Network Switching Subsystem (NSS)
• Network Management Subsystem (NMS)
• 
  

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GSM-

• 
  
• DWDM
  DWDM
  
• (BHOPAL)
  (DELHI)
• DWDM- Dense wavelength division multiplexer

DWDM
DWDM
OFC
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GSM Overview
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GSM Architecture
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GSM Architecture-

• HLR- Home location registers
• The Home Location Register (HLR) contains the
  identities of mobile subscribers (called
  International Mobile Subscriber Identities or
  IMSIs)
• Main customer database
• It is a subscriber data unit and it it is
  responsible
• In summary, the HLR contains-
• Identity of mobile subscriber
• ISDN directory number of mobile station
• Subscription information on teleservices and
  bearer services
• Service restrictions (if any)
• Supplementary services
• Location information for call routing

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GSM Architecture-

• Vlr- visitor location registers
• The Visitor Location Register (VLR) contains the
  subscriber parameters and location
• information for all mobile subscribers currently
  located in the geographical area (i.e., cells)
  controlled by that VLR.
• It is a private secretary of HLR and it define
  the Roaming of mobile
• In summary, the VLR contains-
• Identity of mobile subscriber
• Any temporary mobile subscriber identity
• ISDN directory number of mobile
• A directory number to route calls to a roaming
  station
• Location area where the mobile station is
  registered
• Copy of (part of) the subscriber data from the
  HLR

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GSM Architecture-

• EIR- Equipment identity registers
• The Equipment Identity Register (EIR) is accessed
  during the equipment validation procedure when a
  mobile station accesses the system.
• It contains the identity of mobile station
  equipment (called International Mobile Station
  Equipment Identity or IMEI)
• This contains
• White or Valid list - List of valid MS equipment
  identities
• Grey or Monitored list - List of suspected
  mobiles under observation
• Black or prohibited list - List of mobiles for
  which service is barred.

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GSM Architecture-

• AUC- Authentication centre
• Stores encryption keys necessary for secure
  communications
• Contains subscriber authentication data called
  Authentication Keys (Ki)
• Generates security related parameters needed to
  authorize service using Ki
• Generates unique data pattern called a Cipher Key
  (Kc) needed for encrypting user speech and data

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GSM Architecture-

• At a time 128 BTS can be connected with a BSC
• BSS means Base Station Subsystem
• LINK- When two or more different thing are
  connected with each other is known as link

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BSS-

• BSS- Base station subsystem

BTS BSC
BSS
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BSS-

• The Base Station Subsystem is responsible for
  managing the radio network
• and it is controlled by an MSC
• The BSS consists of the following elements -
• BSC Base Station Controller
• BTS Base Transceiver Station
• TRAU Transcoder and Rate Adaptation Unit (often
  referred to as TC (Transcoder)

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LINK-

• Mobile to BTS
  BTS to Mobile
• FRQ- 824-849 mhz
  FRQ- 869-889 mhz
• Frequency never penetrate any solid body. It
  expand as like baloon.

link
Up link
Dwn link
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GSM Architecture-

• SIM Subscriber Identity Module.
• Allows you to switch phones.
• Stores your phonebook and ringtones.
• ME Mobile Equipment.
• Your cellphone
• UM User Mobile Frequency
• The actual radio frequency you are using.

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GSM Architecture-

• BTS Base Transceiver Stations.
• The radio antennas.
• In GSM, 1 sends and 1 receives.
• Only 2 are necessary.
• BSC Base Station Controller.
• Packages up all the radio signals and sends them
  to the switch.
• Handles handoffs and some other low-level
  functionality.
• Manages up to 50 or so radio antennas
• Provides better network segmentation.
• Abis Typically a T1 SS7 connection using ISUP

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GSM Architecture-
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RF/RT-

• RF/RT- Radio frequencies OR Terminals
• It works as a carrier to carry our
  voice or data.
• Radio frequency is always be in BTS
• The mobile journey is start from the BTS
• One RF have only 8 slot
• 
  

1 2 3 4 5 6 7 8
SLOT
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Radio Frequencies-

• Operates in the 1850 MHz band and from-
• 1850 to 1910 MHz Mobile to Base
• 1930 1990 MHz Base to Mobile
• There are 300 forward/reverse channels in this
  band.
• Each channel is 200 KHz
• GSM uses TDMA to fit 8 conversations on a
  channel.
• So, technically, GSM is TDMA and FDMA based.

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Speech Coding-

• GSM uses LPC Linear Predictive Coding.
• Uses interpolation.
• Basically, previous samples, which dont change
  very quickly, are used to predict current
  samples.
• So, instead of actually sending the voice sample,
  the delta in the voice sample is sent.
• Also, silence is not transmitted.
• This increases throughput by about 40.
• This bits can be used for other conversations.

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Power Requirements-

• Since GSM is purely digital
• It requires a lot less power since it doesnt
  have to transmit an analog wave.
• The maximum output power of a GSM phone is only 2
  watts.
• And this can be notched down by the controlling
  cell phone tower.
• The minimum power is only 20 mW.

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Difference B/W CDMA GSM-
CDMA GSM
More reliable Less reliable
Code division Time Frequency division
More comfortable Less comfortable
Maintenance cost less Maintenance cost more
Reused factor No reused factor


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But whats cellular ?
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MSC
BTS
B S
HLR, VLR, AC, EIR
PSTN

• Public Switched Telephone Network

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Cellular principles-

• Frequency reuse same frequency in
• many cell sites
• Cellular expansion easy to add new cells
• Handover moving between cells
• Roaming between networks

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GSM conclusion-

• Widely used.
• Upwards of 70 of phones.
• Uses SIM cards so customers can use any phone and
  for security.
• Allows more customers than analog.
• Worse voice quality than analog.
• Purely digital.
• Open source, very complex standard.
• Uses TDMA FDMA.

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Presented By

• ABHISHEK SINHA
• THANKS A LOT.