Presentation on GSM & CDMA N/W


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Presentation on GSM And CDMA Network BY- Aditi Juneja EL/10/348 5 th sem



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A Presentation by ** Bharat Sanchar Nigam Limited (known as BSNL) is a public sector telecommunication company in India. ** It is India's largest telecommunication company with 24% market share as on March 31 , 2009 . ** Currently has a customer base of 90 million as of June 2009. ** It has the status of Mani Ratna , a status assigned to reputed public sector companies in India . INTRODUCTION

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RECENT DEVELOPMENTS ** BSNL have launched blackberry services in India. ** BSNL's has recently launched Wireless Broadband network. ** It has launched the 3G facility in 11 states in India. ** At present, there are nearly 400 million telecom connections in the country and every month 10 million new connections are being added.

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what is it all about????:

what is it all about???? In cellular services there Are two main complementary n/w Technologies-GSM and CDMA.

How is one better than the other ??? Which one is cheaper??? Which one is more reliable??? What is the diff. In tech....if any??:

How is one better than the other ??? Which one is cheaper??? Which one is more reliable??? What is the diff. In tech....if any?? QUESTIONS ???

you can change your gsm sim card to get rid of unwanted calls.... While in cdma there are only tata indicom and reliance communications to provide cdma sim card.... :

you can change your gsm sim card to get rid of unwanted calls.... While in cdma there are only tata indicom and reliance communications to provide cdma sim card.... MARKETING

“MOBILITY”- The Magic Word:

“ MOBILITY”- The Magic Word What is Mobility ? Access the Technology everywhere whether we are work or play, in the office, grounds or at home. To meet this demand the GSM (Global System for Mobile Communication) for mobile telephony was introduced in the mid-1980s. A boom is underway, such that many GSM user find life without their phone practically inconceivable.

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G lobal S ystem for M obile ( G roupe S pecial M obile ) G S M

What is GSM ?:

What is GSM ? Global System for Mobile (GSM) is a second generation cellular standard developed to cater voice services and data delivery using digital modulation Over two billion people use the GSM services across 212 countries & territories in the world. The UTILITY of GSM makes national & international roaming very simple & easy b/w mobile phone operators, which enable USERS to use their cell phone in various parts of the world.


TIME FOR HISTORY…. When ? 1982: GSM created to set standard. 1988: Industrial development started. 1991: First Systems Deployed. Why ? Higher digital voice quality. Low cost alternatives to making calls such as SMS. GSM allows network operators to offer roaming services. Compatibility with integrated services digital network (ISDN) and other telephone company services

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GSM frequency regions in the WORLD

Overview of wireless telephony (cellular concept). :

Overview of wireless telephony (cellular concept). CELLS

A Cell:

1 2 3 4 5 6 7 6 7 2 1 5 Cell 1 Cell 2 A Cell A cell is the geographic zone covered by one radio transmitter and receiver

Representation of Cells :

Representation of Cells Ideal cells Fictitious cells Circular cells

Cell Distribution in a Network:

Highway Town Suburb Rural Cell Distribution in a Network

Advantages of cell structures::

Advantages of cell structures: higher capacity, higher number of users less transmission power needed more robust, decentralized base station deals with interference, transmission area etc. locally

GSM uses paired radio channels:

GSM uses paired radio channels 0 124 0 124 890MHz 915MHz 935MHz 960MHz UPLINK DOWNLINK

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Architecture of a GSM Network

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Cellular System The geographic area is divided into cells Each cell has a Base Station managing the communications A set of cells managed by a single MSC is called Location Area Base Station VLR MSC VLR MSC HLR MSC Mobile Switching Center VLR Visitor Location Register HLR Home Location Register land link land link Radio link

Mobile Station (MS):

Mobile Station (MS) The Mobile Station is made up of two entities: Mobile Equipment (ME) The Mobile Equipment is the hardware used by the subscriber to access the network . Uniquely identified by an IMEI (International Mobile Equipment Identity) Subscriber Identity Module (SIM) Smart card containing the International Mobile Subscriber Identity (IMSI) Allows user to send and receive calls and receive other subscribed services Protected by a password or PIN

Base Station Subsystem:

Base Station Subsystem Base Station Subsystem is composed of two parts : 1) Base Transceiver Station (BTS) 2) Base Station Controller (BSC) Base Transceiver Station (BTS) Houses the radio transceivers that define a cell Handles radio-link protocols with the Mobile Station

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Base Station Controller (BSC) Manages Resources for BTS Handles call set up Location update Handover for each MS

Network Subsystem:

Network Subsystem Mobile Services Switching Center (MSC) Major MSC Functions : Switching and call routing Charging Service provisioning Communication with HLR Communication with the VLR Communication with other MSCs Control of connected BSCs Direct access to Internet services Home Location Registers (HLR) : Contains administrative information of each subscriber Most important database

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Visitor Location Registers (VLR) - Integrated with MSC tracks which customers have the phone on and ready to receive a call periodically updates the database on which phones are turned on and ready to receive calls Authentication Center (AUC) mainly used for security data storage location and functional part of the network Ki is the primary element Equipment Identity Register (EIR) - Database that is used to track handsets using the IMEI ,Made up of three sub-classes: The White List, The Black List and the Gray List Optional database



Problems with cell structures::

Problems with cell structures: fixed network needed for the base stations handover (changing from one cell to another) necessary interference with other cells

Call Routing:

Call Routing Call Originating from MS Call termination to MS

Outgoing Call:

Outgoing Call MS sends dialled number to BSS BSS sends dialled number to MSC 3. MSC checks VLR if MS is allowed the requested service.If so,MSC asks BSS to allocate resources for call. MSC routes the call to GMSC GMSC routes the call to local exchange of called user 7. Answer back(ring back) tone is routed from called user to MS via GMSC,MSC,BSS

Incoming Call:

Incoming Call Calling a GSM subscribers Forwarding call to GSMC Signal Setup to HLR 5. Request MSRN from VLR Forward responsible MSC to GMSC Forward Call to current MSC Get current status of MS Paging of MS 10. MS answers 11. Security checks 12. Set up connection

layman’s view.... Are all different versions of digital technology... :

layman’s view.... Are all different versions of digital technology... TDMA FDMA CDMA What is the underlying Difference ??

Time multiplex:

f t c k 2 k 3 k 4 k 5 k 6 k 1 Time multiplex A channel gets the whole spectrum for a certain amount of time Advantages: only one carrier in the medium at any time throughput high even for many users Disadvantages: precise synchronization necessary

Frequency multiplex:

Frequency multiplex Separation of the whole spectrum into smaller frequency bands A channel gets a certain band of the spectrum for the whole time Advantages: no dynamic coordination necessary works also for analog signals Disadvantages: waste of bandwidth if the traffic is distributed unevenly inflexible guard spaces k 2 k 3 k 4 k 5 k 6 k 1 f t c

Time and Frequency Multiplex:

f Time and Frequency Multiplex Combination of both methods A channel gets a certain frequency band for a certain amount of time t c k 2 k 3 k 4 k 5 k 6 k 1

Time and Frequency Multiplex:

Time and Frequency Multiplex Example: GSM Advantages: Better protection against tapping Protection against frequency selective interference Higher data rates compared to code multiplex But: precise coordination required

Code Multiplex:

Code Multiplex Each channel has a unique code All channels use the same spectrum at the same time Advantages: Bandwidth efficient No coordination and synchronization necessary Good protection against interference and tapping Disadvantages: Lower user data rates More complex signal regeneration Implemented using spread spectrum technology k 2 k 3 k 4 k 5 k 6 k 1 f t c


WHY CDMA? C ode D ivision M ultiple A ccess CDMA is extremely robust & provides excellent audio quality


HISTORY OF CDMA... Introduced in 1980 IN North America.... Purpose....What else .....but Military usage Used in Cellular Communication System,in the early 90’s

Finally ....What is CDMA?....:

Finally ....What is CDMA?.... A way to transmit bits of information through wideband,spread spectrum radio interface. IS-95 is the transmission protocol that employs CDMA. Evolution from IS-95A to IS-95B to CDMA2000 Better utilisation of radio spectrum by allowing multiple users to access the same physical channel.

What is Multiple Access?:

What is Multiple Access? Since the beginning of telephony and radio,system operators have tried to squeeze the maximum amount of traffic over each circuit Multiple Access: Simultaneous private use of a transmission medium by multiple,independent users. Transmission medium Each pair of users enjoys a dedicated,private circuit through the transmission medium,unaware that the other users exist.

CDMA is a Spread –Spectrum System:

CDMA is a Spread –Spectrum System Traditional technologies try to squeeze signal Into minimum required bandwidth CDMA uses larger bandwidth But uses resulting processing gain To increase capacity TRADITIONAL COMMUNICATIONS SYSTEM TX RX Slow Information sent Slow Information recovered Narrowband signal SPREAD –SPECTRUM SYSTEM TX RX WIDEBAND SIGNAL Slow Information sent Slow Information recovered Fast spreading sequence Fast spreading sequence Spread Spectrum Payoff: Processing Gain


SPREAD SPECTRUM PRINCIPLES MATH HAMMER MATH HAMMER 30 KHZ 1.25MHZ Power is “spread “over a Larger Bandwidth


SPREAD SPECTRUM PRINCIPLES Many code channels are individually “spread” & then added together to create a “composite signal”

Spreading:What can we do,we can undo:

Spreading:What can we do,we can undo Input data Recovered data ORIGINATING SITE DESTINATION Spread data stream Spreading Sequence Spreading Sequence Sender combines data with a fast spreading sequence, transmits spread data stream Receiver intercepts the stream,uses same spreading sequence to extract original data



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TDMA of GSM. The data transmission in TDMA is actually not continuous.It occurs in bursts..But the time b/w these bursts for a single mobile phone user is very very short ,so that he never knows that the speech of the other person is discontinous ! But the CDMA system has a soft capacity limit. That is increasing the number of users will decreases the system performance.(any comments Reliance users..?..!!).

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CDMA Ad/ Dis Advantages of CDMA include: Increased cellular communications security. Simultaneous conversations. Smaller phones. Low power requirements & little cell-to-cell coordination Needed by the operators. Extended reach- benefical to rural users situated far from cells. Disadvantages of CDMA include: CDMA is relatively new,& the n/w is not as mature as GSM. CDMA cannot offer international roaming,a large GSM advantage

GSM Ad/dis:

GSM Ad/ dis Advantages of GSM: GSM is already used worldwide with over millions of subscribers. International roaming permits subscribers to use one phone throughout Western Europe.CDMA will work in Asia,but not France,Germany ,the U.K. And other popular European destinations. GSM is mature ,having started in the mid -80’s.This maturity means a more stable n/ w.CDMA is still building its n/w. GSM’s maturity means engineers cut their teeth on the technology ,creating an unconsious preference. The availability of Subscriber Identity Modules,which are smart cardsthat provide secure data encryption give GSM advantages. Disadvantages of GSM: Lack of access to burgeoning American market


SOME FACTS GSM is a widely spread standard & CDMA is a patented technology. That is you must pay a royalty for using for using CDMA!.So being a GSM user you have virtually an interntional roaming. You can easily use a GSM phone in any of Available countries while roaming. GSM users are almost 8 times in number than CDMA users worldwide. By being a GSM user you will be part of the largest mobile community. And coming to voice quality GSM is far better than CDMA.


CONCLUSION In general I say both GSM and CDMA are frontier technologies & both have good & bad qualities.And in the case of mobile handsets the fact is That GSM handsets are very popular & many of the new facilities are readily available in GSM phones with lesser price.The reason is simple.... nokia and motorola needs profit.....& they will invest more in GSM because GSM has 8 times more users than CDMA. GSM still holds the upper hand however.There’s the numerical advantage for one thing:456 million GSM users versus CDMA ‘s 82 million.


PRIVACY & SECURITY IN GSM Each subscriber is identified using a cryptographic security mechanism Subscriber security information is stored in the SIM Card The algorithm are stored in the SIM card & in the authentication center .


SECURITY ALGORITHMS FOR GSM 1.Authentication Algorithm (A3) Used by handset to compute a signed response to a random number transmitted by BS 2.Private key generation (A8) Uses the same random number & K( i )to generate a private key (K) That is used for voice and data privacy A3 K(I) on SIM CARD SRES TO BS A8 RAND(from BS) (K) Privacy mask

Services offered by GSM::

Services offered by GSM:


WHAT IS ALL DIS No boundary b/w telephony ,information & entertainment services It will range from voice only to voice ,data, & other multimedia application Wireless users will be able to make video conference calls & surf the internet simultaneously GENERATION 3G….

Questions ?:

Questions ?

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