BE 1094 08 Gulshan Prakash

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A Mobile & CellularCommunication Assignment On

• Discuss GSM and CDMA Technology

• Discuss various generations of MobileCommunication (2G, 3G).



Discuss GSM and CDMA

Technology



Code Division Multiple Access (CDMA)

• CDMA is a spread spectrum multiple access technique, that is, it spreads the

bandwidth of the data uniformly for the same transmitted power.

• A spreading code is a pseudo-random code that has a narrow Ambiguity

Function. In CDMA a locally generated code runs at a much higher rate than the

data to be transmitted.

• The data signal with pulse duration of T b is XOR’ed with the code signal with

pulse duration of Tc.

• The ratio T b / Tc is called the spreading factor or processing gain and

determines to a certain extent the upper limit of the total number of users

supported simultaneously by a base station.



Schematic Diagram showing CDMA



Types of CDMA

CDMA is categorized into the following two categories mainly on the basis of the

spreading code used for transmission purposes :

• Synchronous CDMA - Synchronous CDMA exploits mathematical

properties of orthogonality between vectors representing the data strings. Each

user in synchronous CDMA uses a code orthogonal to the others' codes to

modulate their signal.

• Asynchronous CDMA - A unique "pseudo-random" or "pseudo-noise" (PN)

sequences are used in Asynchronous CDMA systems. A PN code is a binary

sequence that appears random but can be reproduced in a deterministic manner by intended receivers. These PN codes are used to encode and decode a user's

signal in Asynchronous CDMA in the same manner as the orthogonal codes in

synchronous CDMA.



Global System for Mobile Communications(GSM)

• GSM is a cellular network, which means that cellular phones connect to it by

searching for cells in the immediate vicinity. • Cell horizontal radius varies depending on antenna height, antenna gain and

propagation conditions from a couple of hundred metres to several tens of

kilometres. The longest distance the GSM specification supports in practical use

is approzimately 35 kilometres or 22 miles.

• The modulation used in GSM is Gaussian Minimum Shift Keying (GMSK), a

kind of continuous-phase Frequency Shift Keying.

• In GMSK, the signal to be modulated onto the carrier is first smoothed with

a Gaussian Low Pass Filter prior to being fed to a frequency modulator, which

greatly reduces the interference to neighboring channels.



The GSM Network Architecture

The GSM Network is structured into a number of discrete sections:

• The Base Station Subsystem (the base stations and their controllers).

• The Network & Switching Subsystem (the part of the network most similar to a fixed

network). This is sometimes also just called the core network.

• The GPRS Core Network (the optional part which allows packet based Internet

connections).

• The Operations Support System (OSS) for maintenance of the network.

GSM has used a variety of voice codecs to squeeze 3.1 kHz audio into between 5.6 and

13 kbit/s. Two codecs, named after the types of data channel they were allocated, were

used, called half Rate(6.5 kbit/s) and Full Rate (13 kbit/s). These used a system based

upon Linear Predictive Coding (LPC). In 1997, GSM was further enhanced with

the Enhanced Full rate (EFR) codec, a 12.2 kbit/s codec that uses a full rate channel.



A Comparison of CDMA and GSM

CDMA GSM

Technology CDMA FDMA and TDMA

Battery Life Lower, due to high demands of

CDMA power control.

Good, due to simple protocol and

power-efficient chipsets.

Voice & data at

the same time

No Yes, GPRS class A onwards.

Patent Issues Exclusively Qualcomm Concentrated among a few

manufacturers.

Global market

share:

18% 82%



Discuss the generations ofMobile Communication

(2G, 3G)



Second Generation Mobile (2G)

• 2G is an abbreviation for second-generation Wireless Telephone technology.

• 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.

• 2G introduced data services for mobile, starting with SMS text messages.

• While radio signals on 1G networks are analog, radio signals on 2G networks

are digital. Both systems use digital signaling to connect the radio towers (which

listen to the handsets) to the rest of the telephone system.



Advantages & Disadvantages of 2G

Advantages of 2G:

• More calls to be packed into the same amount of radio bandwidth, owing to the

use of digital technology.

• The lower power emissions helped address health concerns.

• Going all-digital allowed for the introduction of digital data services, such as

SMS and email.

• Greatly reduced fraud and enhanced privacy owing to better encryption.

Disadvantages of 2G:

• In less populous areas, the weaker digital signal may not be sufficient to reach acell tower.

• The range of sound that digital codecs convey is reduced due to the Lossy

compression.



Evolution of 2G

2.5G (GPRS)

• 2G-systems that have implemented a packet-switched domain in addition to the

circuit-switched domain.

• The first major step in the evolution of GSM networks to 3G occurred with the

introduction of General Packet Radio Service (GPRS). .

• GPRS could provide data rates from 56 kbit/s up to 115 kbit/s. It can be used for services such as Wireless Application Protocol (WAP) access, Multimedia

Messaging Service (MMS), and for Internet Access.

2.75G (EDGE)

• GPRS1 networks evolved to Enhanced Data rates for GSM Evolution

(EDGE) networks with the introduction of 8PSK encoding.

• EDGE is standardized by 3GPP as part of the GSM family and it is an upgrade

that provides a potential three-fold increase in capacity of GSM/GPRS networks.



Third Generation Mobile (3G)

• Application services include wide-area wireless voice telephone, mobile

Internet access, video calls and mobile TV, all in a mobile environment. To meet

the IMT-2000 standards, a system is required to provide peak data rates of at

least 200 kbit/s.

• The tandards typically branded 3G include the Universal MobileTelecommunications System(UMTS) system and the CDMA2000 systems.

• The above systems and radio interfaces are based on kindred spread

spectrum radio transmission technology.

• Applications of 3G include Mobile TV, Video on demand, Videoconferencing,

Telemedicine and other Location-based services.



Features and Evolution of 2G

Features:

• 3G is typically characterised by higher transmission rates: a minimum data rate

of 2 Mbit/s for stationary or walking users, and 384 kbit/s in a moving vehicle.

• 3G networks offer greater security than their 2G predecessors. By allowing the

UE (User Equipment) to authenticate the network it is attaching to, the user can

be sure the network is the intended one and not an impersonator.

Evolution of 3G:

• Extensive research is being done on extensions to 3G standard that are based on

an all-IP network infrastructure and using advanced wireless technologies such

as Multiple-Input and Multiple-Output (MIMO).

• These specifications already display features characteristic for IMT-

Advanced (4G), the successor of 3G. However, falling short of the bandwidth

requirements for 4G (1Gbit/s), these are classified as Pre-4G.



Compiled & Submitted By:

GULSHAN PRAKASH

Roll No – BE/1094/2008

Branch – ECE

Section – A

Session – Monsoon 2011.

BE 1094 08 Gulshan Prakash

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