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GSM Vs CDMA

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GSM Vs CDMA
21
SUBMITTED BY Inderpreet Singh Roll no. 7042
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Page 1: GSM Vs CDMA

SUBMITTED BYInderpreet SinghRoll no. 7042

Page 2: GSM Vs CDMA

It all started like thisIt all started like this First telephone (photophone) – First telephone (photophone) –

Alexander Bell, 1880Alexander Bell, 1880 The first car mounted radio The first car mounted radio telephone – 1921telephone – 1921

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Going furtherGoing further 1946 – First commercial mobile 1946 – First commercial mobile

radio-telephone service by Bell and radio-telephone service by Bell and AT&T in Saint Louis, USA. Half AT&T in Saint Louis, USA. Half duplex(PTT)duplex(PTT)

1973 – First handheld cellular phone 1973 – First handheld cellular phone – Motorola.– Motorola.

First cellular net First cellular net Bahrein 1978Bahrein 1978

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But what’s cellular?But what’s cellular?

HLR, VLR, AC, EIR

MSC

PSTN

BS

Page 5: GSM Vs CDMA

Cellular principlesCellular principles Frequency reuse – Frequency reuse –

same frequency insame frequency in many cell sitesmany cell sites Cellular expansion – Cellular expansion –

easy to add new cells easy to add new cells Handover – moving Handover – moving

between cellsbetween cells Roaming between Roaming between

networksnetworks

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CDMACDMA CDMA = CDMA = ccode ode ddivision ivision

mmultiple ultiple aaccessccess CDMA is a spread-spectrum CDMA is a spread-spectrum

technology that allows technology that allows multiple frequencies to be multiple frequencies to be used simultaneously by used simultaneously by coding every digital packet coding every digital packet it sends with a unique key. it sends with a unique key. A CDMA receiver responds A CDMA receiver responds only to that key and can only to that key and can pick out and demodulate the pick out and demodulate the associated signal. associated signal.

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CDMA cont.CDMA cont. Operates in the 800MHz band and Operates in the 800MHz band and

1.9GHz PCS (Personal Communications 1.9GHz PCS (Personal Communications Services) bandServices) band

Uses a 1.25 MHz bandwidthUses a 1.25 MHz bandwidth CDMA is widely used in N. America and is CDMA is widely used in N. America and is

expected to be the 3G technology for GSMexpected to be the 3G technology for GSM CDMA phones are noted for their CDMA phones are noted for their

excellent call quality and long battery life. excellent call quality and long battery life.

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W-CDMAW-CDMA W-CDMA = W-CDMA = WWideband ideband CCode ode DDivision ivision

MMultiple ultiple AAccessccess Provides a higher capacity for voice and Provides a higher capacity for voice and

data at higher data rates than CDMAdata at higher data rates than CDMA Uses a 5 MHz carrier (4 times that of Uses a 5 MHz carrier (4 times that of

CDMA)CDMA) Higher data rate than both GSM and Higher data rate than both GSM and

GPRS (up to 2 Mbps)GPRS (up to 2 Mbps) W-CDMA is considered a 3G technologyW-CDMA is considered a 3G technology

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GSGSMM•GSM = GSM = gglobal lobal ssystem ystem

for for mmobile obile communicationcommunication•Digital TDMA system Digital TDMA system now (2G), 3G expected now (2G), 3G expected to be W-CDMAto be W-CDMA•Phones use SIM Phones use SIM (System Identity (System Identity Module) cards Module) cards containing user containing user account informationaccount information•provides a short provides a short messaging service messaging service (SMS) that enables (SMS) that enables text messages up to text messages up to 160 characters in 160 characters in lengthlength

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More than 800 million end users in 190 countries and representing over 70% of today's digital wireless market. source: GSM Association

Israel Orange uses GSM Pelephone and Cellcom are about to use

GSM

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GSM OverviewGSM Overview

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Into the architectureInto the architecture Mobile phone is Mobile phone is

identified by SIM identified by SIM card.card.

Key feature of the Key feature of the GSMGSM

Has the “secret” Has the “secret” for authenticationfor authentication

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GSM specsGSM specs frequency bandfrequency band—The frequency range specified for GSM —The frequency range specified for GSM

is 1,850 to 1,990 MHz (mobile station to base station). is 1,850 to 1,990 MHz (mobile station to base station). duplex distanceduplex distance—The duplex distance is 80 MHz. Duplex —The duplex distance is 80 MHz. Duplex

distance is the distance between the uplink and downlink distance is the distance between the uplink and downlink frequencies. A channel has two frequencies, 80 MHz apart. frequencies. A channel has two frequencies, 80 MHz apart.

channel separationchannel separation—The separation between adjacent —The separation between adjacent carrier frequencies. In GSM, this is 200 kHz. carrier frequencies. In GSM, this is 200 kHz.

modulationmodulation—Modulation is the process of sending a signal —Modulation is the process of sending a signal by changing the characteristics of a carrier frequency. This by changing the characteristics of a carrier frequency. This is done in GSM via Gaussian minimum shift keying (GMSK). is done in GSM via Gaussian minimum shift keying (GMSK).

transmission ratetransmission rate—GSM is a digital system with an over-—GSM is a digital system with an over-the-air bit rate of 270 kbps. the-air bit rate of 270 kbps.

access methodaccess method—GSM utilizes the time division multiple —GSM utilizes the time division multiple access (TDMA) concept. TDMA is a technique in which access (TDMA) concept. TDMA is a technique in which several different calls may share the same carrier. Each call several different calls may share the same carrier. Each call is assigned a particular time slot. is assigned a particular time slot.

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GPRSGPRS GPRS = GPRS = GGeneral eneral

PPacket acket RRadio adio SService ervice enhancement to the enhancement to the

GSM mobile GSM mobile communications communications system that supports system that supports data packetsdata packets

Allows for continuous Allows for continuous flows of data packets flows of data packets for web browsing and for web browsing and file transferfile transfer

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More GSMMore GSM GSM comes in three GSM comes in three

flavors(frequency bands): 900, flavors(frequency bands): 900, 1800, 1900 MHz. 900 is the Orange 1800, 1900 MHz. 900 is the Orange flavour in Israel.flavour in Israel.

Voice is digitized using Full-Rate Voice is digitized using Full-Rate coding.coding.

20 ms sample => 260 bits . 13 Kbps 20 ms sample => 260 bits . 13 Kbps bitratebitrate

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SharingSharing GSM uses TDMA and FDMA to let GSM uses TDMA and FDMA to let

everybody talk.everybody talk. FDMA: 25MHz freq. is divided into FDMA: 25MHz freq. is divided into

124 carrier frequencies. Each base 124 carrier frequencies. Each base station gets few of those.station gets few of those.

TDMA: Each carrier frequency is TDMA: Each carrier frequency is divided into bursts [0.577 ms]. 8 divided into bursts [0.577 ms]. 8 bursts are a frame. bursts are a frame.

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ChannelsChannels The physical channel in GSM is the The physical channel in GSM is the

timeslot. timeslot. The logical channel is the The logical channel is the

information which goes through the information which goes through the physical ch.physical ch.

Both user data and signaling are Both user data and signaling are logical channels. logical channels.

Page 19: GSM Vs CDMA

Wireless GenerationsWireless Generations 1G: Analog (1970s-1980s)1G: Analog (1970s-1980s)

AMPS, TACS, NMTAMPS, TACS, NMT VoiceVoice

2G: Digital (1990s)2G: Digital (1990s) GSM, TDMA, CDMAGSM, TDMA, CDMA Mostly for voice, although GSM uses SMS text Mostly for voice, although GSM uses SMS text

messagingmessaging 2G+: Digital (ongoing)2G+: Digital (ongoing)

GPRS, EDGE, IS-95B, HDRGPRS, EDGE, IS-95B, HDR Packet data enhancements, improved data ratesPacket data enhancements, improved data rates

3G: now3G: now UMTS, CDMA2000UMTS, CDMA2000 High-speed multimedia data and voiceHigh-speed multimedia data and voice Goals of global roaming and high-quality audio and Goals of global roaming and high-quality audio and

videovideo

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FUTURE POTENTIALFUTURE POTENTIAL

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AcknowledgementsAcknowledgements http://www.iec.org/online/tutorials/ghttp://www.iec.org/online/tutorials/g

sm/sm/ http://www.iec.org/online/tutorials/thttp://www.iec.org/online/tutorials/t

dma/dma/ http://www.techweb.comhttp://www.techweb.com http://www.gsmworld.comhttp://www.gsmworld.com http://www.ericsson.com/technology/http://www.ericsson.com/technology/

tech_articles/WCDMA.shtmltech_articles/WCDMA.shtml


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