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RAM SHANTI VIDYA MANDIR
PANDHURNA
Subject teacher :
Mrs. Tanvi madam
MADE BY PRITAM DIGARSE
CLASS XII
SUBJECT Computer science
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This file contains information about :-
3G
2G
gsm
cdma SIM card
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(Code-Division Multiple Access)
Code division multiple access (CDMA) is achannel access method used by various radiocommunication technologies. It should not be confusedwith themobile phone standards calledcdmaOne,
CDMA2000(the 3G evolution of cdmaOne) andWCDMA (the 3G standard used byGSM carriers),which are often referred to as simply CDMA, and useCDMA as an underlying channel access method.
One of the concepts in data communication is the ideaof allowing several transmitters to send information
simultaneously over a single communication channel.This allows several users to share a band offrequencies (seebandwidth). This concept is calledmultiple access. CDMA employsspread-spectrumtechnology and a special coding scheme (where eachtransmitter is assigned a code) to allow multiple users
to be multiplexed over the same physical channel. Bycontrast, time division multiple access(TDMA) dividesaccess bytime, whilefrequency-division multipleaccess (FDMA) divides it byfrequency. CDMA is aform ofspread-spectrum signalling, since the
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modulated coded signal has a much higherdatabandwidth than the data being communicated.
An analogy to the problem of multiple access is a room(channel) in which people wish to talk to each othersimultaneously. To avoid confusion, people could taketurns speaking (time division), speak at differentpitches (frequency division), or speak in differentlanguages (code division). CDMA is analogous to thelast example where people speaking the same
language can understand each other, but otherlanguages are perceived as noise and rejected.Similarly, in radio CDMA, each group of users is givena shared code. Many codes occupy the same channel,but only users associated with a particular code cancommunicate.
The technology of code division multiple accesschannels has long been known. In the USSR, the first
work devoted to this subject was published in 1935 by
professor Dmitriy V. Ageev.[1]
It was shown that
through the use of linear methods, there are three
types of signal separation: frequency, time and
compensatory. The technology of CDMA was used in1957, when the young military radio engineer Leonid
Kupriyanovich in Moscow, made an experimental
model of a wearable automatic mobile phone, called
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LK-1 by him, with a base station. LK-1 has a weight of
3 kg, 2030 km operating distance, and 2030 hours of
battery life.[2][3]
The base station, as described by the
author, could serve several customers. In 1958,
Kupriyanovich made the new experimental "pocket"
model of mobile phone. This phone weighed 0.5 kg. To
serve more customers, Kupriyanovich proposed the
device, named by him as correllator.[4][5]
In 1958, the
USSR also started the development of the "Altai"national civil mobile phone service for cars, based on
the Soviet MRT-1327 standard. The phone system
weighed 11 kg and was approximately 3 cubic meters
in size[dubious discuss]
. It was placed in the trunk of the
vehicles of high-ranking officials and used a standard
handset in the passenger compartment. The maindevelopers of the Altai system were VNIIS (Voronezh
Science Research Institute of Communications) and
GSPI (State Specialized Project Institute). In 1963 this
service started in Moscow and in 1970 Altai service
was used in 30 USSR cities
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. Individual conversations are
encoded with a pseudo-random digital sequence. CDMA
consistently provides better capacity for voice and data
communications than other commercial mobile technologies,
allowing more subscribers to connect at any given time, and it
is the common platform on which 3G technologies are built.CDMA is a form of spread spectrum, which simply means
that data is sent in small pieces over a number of the discrete
frequencies available for use at any time in the specified
range. All of the users transmit in the same wide-band chunk
of spectrum. Each users signal is spread over entire
bandwidth by a unique spreading code.
CDMA is a military technology first used
during World War II by English allies to foil German
attempts at jamming transmissions. The allies decided to
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transmit over several frequencies, instead of one, making it
difficult for the Germans to pick up the complete signal.
Because Qualcomm created communications chips for
CDMA technology, it was privy to the classified information.
Once the information became public, Qualcomm claimed
patents on the technology and became the first to
commercialize it.
CDMA (Code-Division Multiple Access) refers to any of
several protocols used in so-called second-generation (2G)and third-generation (3G) wireless communications. As the
term implies, CDMA is a form of multiplexing, which allows
numerous signals to occupy a single transmission channel,
optimizing the use of available bandwidth. The technology
isused in ultra-high-frequency (UHF) cellular telephone
systems in the 800-MHz and 1.9-GHz bands.
CDMA employs analog-
to-digital conversion (ADC) in combination with spread
spectrum technology. Audio input is first digitized into binary
elements. The frequency of the transmitted signal is then
made to vary according to a defined pattern (code), so it canbe intercepted only by a receiver whose frequency response is
programmed with the same code, so it follows exactly along
with the transmitter frequency. There are trillions of possible
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frequency-sequencing codes, which enhance privacy and
makes cloning difficult.
Third Generation
3G or 3rd generation mobile telecommunications is a
generation of standards for mobile phones andmobile
telecommunication services fulfilling the InternationalMobile Telecommunications-2000 (IMT-2000)
specifications by theInternational Telecommunication
Union.[1] Application services include wide-area wireless
voicetelephone,mobile Internetaccess, video calls and
mobile TV, all in a mobile environment.
Several telecommunications companies market wirelessmobile Internet services as 3G, indicating that the advertised
service is provided over a 3G wireless network. Services
advertised as 3G are required to meet IMT-2000 technical
standards, including standards for reliability and speed (data
transfer rates). To meet the IMT-2000 standards, a system is
required to provide peak data rates of at least 200kbit/s
(about 0.2Mbit/s). However, many services advertised as
3G provide higher speed than the minimum technical
requirements for a 3G service. Recent 3G releases, often
denoted3.5Gand3.75G, also providemobile broadband
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access of severalMbit/stosmartphones andmobile modems
in laptop computers.
The following standards are typically branded 3G: theUMTS system, first offered in 2001, standardized by
3GPP, used primarily in Europe, Japan, China (however
with a different radio interface) and other regions
predominated by GSM2Gsystem infrastructure. The
cell phones are typically UMTS and GSM hybrids.
Several radio interfaces are offered, sharing the sameinfrastructure:
o The original and most widespread radio interface is
calledW-CDMA.
o TheTD-SCDMAradio interface was
commercialised in 2009 and is only offered in
China.
o The latest UMTS release,HSPA+, can providepeak data rates up to 56 Mbit/s in the downlink in
theory (28 Mbit/s in existing services) and 22
Mbit/s in the uplink.
theCDMA2000system, first offered in 2002,
standardized by 3GPP2, used especially in North
America and South Korea, sharing infrastructure withtheIS-952G standard. The cell phones are typically
CDMA2000 and IS-95 hybrids. The latest release
EVDORev B offers peak rates of 14.7 Mbit/s
downstream.
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The above systems and radio interfaces are based onspread
spectrum radio transmission technology. While theGSM
EDGE standard ("2.9G"),DECTcordless phones and
Mobile WiMAXstandards formally also fulfill the IMT-2000 requirements and are approved as 3G standards by
ITU, these are typically not branded 3G, and are based on
completely different technologies.
A new generation of cellular standards has appeared
approximately every tenth year since1Gsystems were
introduced in 1981/1982. Each generation is characterizedby new frequency bands, higher data rates and non
backwards compatible transmission technology. The first
release of the3GPP Long Term Evolution(LTE) standard
does not completely fulfill the ITU 4G requirements called
IMT-Advanced. First release LTE is not backwards
compatible with 3G, but is a pre-4G or3.9Gtechnology,
however sometimes branded "4G" by the service providers.
Its evolutionLTE Advanced is a4G technology.WiMAX is
another technology verging on or marketed as4G.
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3G or 3rd generation mobile
telecommunications is a generation of standards for
mobile phones and mobile telecommunication services
fulfilling the International Mobile Telecommunications-
2000 (IMT-2000) specifications by the InternationalTelecommunication Union. 3G promises increased
bandwidth, up to 384 Kbps when a device is stationary of
moving at pedestrian speed.
Several telecommunications
companies market wireless mobile Internet services as 3G,
indicating that the advertised service is provided over a 3Gwireless network. Services advertised as 3G are required to
meet IMT-2000 technical standards, including standards for
reliability and speed (data transfer rates). To meet the IMT-
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2000 standards, a system is required to provide peak data
rates of at least 200 kbit/s (about 0.2 Mbit/s). However, many
services advertised as 3G provide higher speed than the
minimum technical requirements for a 3G service. Recent 3G
releases often denoted 3.5G and 3.75G also provide mobile
broadband access of several Mbit/s to smartphones and
mobile modems in laptop computers.
The bandwidth and location information
available to 3G devices gives rise to applications notpreviously available to mobile phone users. Some of the
applications are:
Mobile TV
Video on demand
Video Conferencing
Telemedicine
Location-based services
Global Positioning System (GPS)
3G refers to the third generation of mobile telephony (that is,
cellular) technology. The third generation, as the name
suggests, follows two earlier generations.
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2g(Second Generation)
2G (or 2-G) is short for
second-generation wireless telephone technology. Second
generation 2G cellular telecom networks were commercially
launched on the GSM standard in Finland by Radiolinja (now
part of Elisa Oyj) in 1991.[1] Three primary benefits of 2G
networks over their predecessors were that phone
conversations were digitally encrypted; 2G systems were
significantly more efficient on the spectrum allowing for far
greater mobile phone penetration levels; and 2G introduced
data services for mobile, starting with SMS text messages.
While digital calls tend tobe free of static and background noise, the lossy compression
used by the codecs takes a toll; the range of sound that they
convey is reduced. You will hear less of the tonality of
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someone's voice talking on a digital cellphone, but you will
hear it more clearly.
Digital voice data can be compressed and multiplexed much
more effectively than analog voice encodings through the use
of various codecs, allowing more calls to be packed into the
same amount of radio bandwidth.
Disadvantages
In less populous areas, the weaker digital signal may not
be sufficient to reach a cell tower. This tends to be a
particular problem on 2G systems deployed on higher
frequencies, but is mostly not a problem on 2G systems
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deployed on lower frequencies. National regulations
differ greatly among countries which dictate where 2G
can be deployed.
Analog has a smooth decay curve, digital a jaggedsteppy one. This can be both an advantage and a
disadvantage. Under good conditions, digital will sound
better. Under slightly worse conditions, analog will
experience static, while digital has occasionaldropouts.
As conditions worsen, though, digital will start to
completely fail, by dropping calls or being
unintelligible, while analog slowly gets worse, generally
holding a call longer and allowing at least a few words
to get through.
Advantage
While digital calls tend to be free ofstaticand
background noise, thelossy compression used by thecodecs takes a toll; the range of sound that they convey
is reduced. You will hear less of the tonality of
someone's voice talking on a digital cellphone, but you
will hear it more clearly.
Subscriber Identity Module)
A SIM card, also known as a
subscriber identity module, is a smart card that stores data for
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GSM cellular telephone subscribers. Such data includes user
identity, location and phone number, network authorization
data, personal security keys, contact lists and stored text
messages. Security features include authentication andencryption to protect data and prevent eavesdropping.
A Subscriber Identity Module (SIM) card
is a portable memory chip used mostly in cell phones that
operate on the Global System for Mobile Communications
(GSM) network. These cards hold the personal information
of the account holder, including his or her phone number,address book, text messages, and other data. When a user
wants to change phones, he or she can usually easily remove
the card from one handset and insert it into another. SIM
cards are convenient and popular with many users, and are a
key part of developing cell phone technology. A SIM is
actually a tiny computer chip that gives a cellular device itsunique phone number. It has memory, processor and ability
to interact with the user. Current SIMs typically has 16 to 64
kb of memory which helps in storing phone numbers, text
messages and other data.
A subscriber identity module or subscriber identificationmodule (SIM) is anintegrated circuitthat securely stores
theInternational Mobile Subscriber Identity (IMSI) and the
relatedkey used to identify and authenticate subscribers on
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mobiletelephonydevices (such asmobile phonesand
computers).
A SIM is embedded into a removableSIM card
, which canbe transferred between different mobile devices. SIM cards
were first made the same size as a credit card (85.60 mm
53.98 mm 0.76 mm). The development of physically-
smaller mobile devices prompted the development of a
smaller SIM card, the mini-SIM card. Mini-SIM cards have
the same thickness as full-size cards, but their length and
width are reduced to 25 mm 15 mm.
A SIM card contains its unique serial number (ICCID),
international mobile subscriber identity (IMSI), security
authentication and ciphering information, temporary
information related to the local network, a list of the services
the user has access to and two passwords: apersonal
identification number(PIN) for ordinary use and apersonalunblocking code(PUK) for PIN unlocking.
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