cell phones[1] 1

8/3/2019 Cell Phones[1] 1

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A Report

On

Cell Phones


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Table of Contents

Table of Contents .................................................................... 2Cell Phones ............................................................................ 3

1.0 Introduction ................................................................... 32.0 History of Cell Phones ..................................................... 33.0 Cellular Phone Concept .................................................... 54.0 Services Provided by Cell Phone ........................................ 8

4.1 SMS: Short Message Service ......................................... 84.2 Smart Messaging ......................................................... 84.3 EMS: Extended Message Service .................................... 84.4 MMS: Multimedia Messaging Service ............................... 94.5 Email ......................................................................... 94.6 WAP & Internet Access ................................................ 10Setting it up .................................................................... 10WAP Server ..................................................................... 10WAP Gateway .................................................................. 10The Browser .................................................................... 10Two ways to connect......................................................... 10

6.0 Inside a Cell Phone ........................................................ 126.1 Anatomy of a Cell Phone .............................................. 136.2 Mobile phone batteries ................................................. 156.2.1 Nickel Cadmium (NiCd) ............................................. 156.2.2 Nickel Metal Hydride (NiMH) ...................................... 166.2.3 Lithium Ion (Li-Ion) .................................................. 16

7.0 Multiple Band & Multiple Mode Cell Phones ........................ 168.0 Problems with Cell Phones .............................................. 179.0 Cellular Technologies ...................................................... 18

9.1 First-Generation Cellular Technology 1G ........................ 189.2 Second-Generation Cellular Technology 2G .................... 199.3 Advances in 2G Cellular Technology 2.5 G & 2.75 G ......... 269.3.1 General Packet Radio Services (GPRS) ........................ 279.3.2 Enhanced Data rates for GSM Evolution (EDGE) ........... 289.4 Third-Generation Cellular Technology ............................ 299.5 Fourth-generation Cellular Technology 4G ...................... 35

10.0 Key Concerns regarding Cell phone use ........................... 3710.1 Health controversy .................................................... 3710.2 Thermal effects ......................................................... 3710.3 Electromagnetic hypersensitivity syndrome ................... 3810.4 Driving controversy ................................................... 3910.5 Security concerns ...................................................... 3910.6 Claims of Danger at Gas Pumps .................................. 4010.7 Claims of danger on aircraft ........................................ 40

11. Conclusion .................................................................... 41


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Cell Phones

1.0 Introduction

A cell phone is a type of two-way radio which works in a cellularnetwork. A cellular network is a radio network made up of a numberof radio cells (or just cells) each served by a fixed transmitter,known as a cell site or base station. These cells are used to coverdifferent areas in order to provide radio coverage over a wider areathan the area of one cell.

Cellular networks offer a number of advantages over alternativesolutions:

increased capacity reduced power usage better coverage

2.0 History of Cell Phones

The basic concept of cellular phones began in 1947, whenresearchers looked at crude mobile (car) phones and realized thatby using small cells (range of service area) with frequency reusethey could increase the traffic capacity of mobile phones

substantially. However at that time, the technology to do so wasnonexistent.

Dr Martin Cooper, a former general manager for the systemsdivision at Motorola, is considered the inventor of the first modernportable handset. Cooper made the first call on a portable cellphone in April 1973. He made the call to his rival, Joel Engel, BellLabs head of research. Bell Laboratories introduced the idea ofcellular communications in 1947 with the police car technology.However, Motorola was the first to incorporate the technology into

portable device that was designed for outside of an automobile use.

By 1977, AT&T and Bell Labs had constructed a prototype cellularsystem. A year later, public trials of the new system were started inChicago with over 2000 trial customers. In 1979, in a separateventure, the first commercial cellular telephone system beganoperation in Tokyo. In 1981, Motorola and American Radiotelephone started a second U.S. cellular radio-telephone system testin the Washington/Baltimore area. By 1982, the slow-moving FCCfinally authorized commercial cellular service for the USA. A yearlater, the first American commercial analog cellular service or AMPS


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(Advanced Mobile Phone Service) was made available in Chicago byAmeritech.

After the Federal Communications Commission (FCC) declared in1987 that cellular licensees could employ alternative cellulartechnologies in the 800 MHz band, the cellular industry began toresearch new transmission technology as an alternative to AMPS(Advanced Mobile Phone Service) that had been the industrystandard since 1978.

In 1988, the Cellular Technology Industry Association (CTIA) wasestablished to work with the cellular service operators andresearchers to identify new technology requirements and set goals.They wanted the new products and services introduced by 1991, a1000% percent increase in system capacity with both AMPS

(analog) and digital capability during transmission, and new datafeatures such as fax and messaging services.

The Telecommunications Industry Association (TIA) created astandard specification based on the requirements the CTIA hadrecommended. The TDMA Interim Standard 54 or TDMA IS-54 wasreleased in early 1991. The technology was tested that same yearin Dallas and Sweden. In 1994, the FCC announced it was allocatingspectrum specifically for PCS technologies at the 1900 MHz band.Three major standards have been released since 1991

Until the mid to late 1980s, most mobile phones were sufficientlylarge that they were permanently installed in vehicles as carphones. With the advance of miniaturization, currently the vastmajority of mobile phones are handheld. In addition to the standardvoice function of a telephone, a mobile phone can support manyadditional services such as SMS for text messaging, email, packetswitching for access to the Internet, and MMS for sending andreceiving photos and video.

Invented in 1997, the camera phone is now 85% of the market.Mobile phones also often have features beyond sending textmessages and making voice callsincluding Internet browsing,music (MP3) playback, personal organizers, e-mail, built-in camerasand camcorders, ringtones, games, radio, Push-to-Talk (PTT),infrared and Bluetooth connectivity, call registers, ability to watchstreaming video or download video for later viewing, and serving asa wireless modem for a PC.

The world's largest mobile phone manufacturers include Audiovox,BenQ-Siemens, High Tech Computer Corporation, Fujitsu, Kyocera,3G, LG, Motorola, NEC, i-mate, Nokia, Panasonic (Matsushita


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Electric), Pantech Curitel, Philips, Sagem, Samsung, Sanyo, Sharp,Siemens SK Teletech, Sony Ericsson, T&A Alcatel, T-Mobile, andToshiba.

All European nations and most Asian and African nations have

adopted GSM. In other countries, such as the United States,Australia, Japan, and South Korea, legislation does not require anyparticular standard, and GSM coexists with other standards, such asCDMA and iDEN.

3.0 Cellular Phone Concept

A mobile phone sends and receives information (voice messages,fax, computer data, etc) by radio communication. Radio frequencysignals are transmitted from the phone to the nearest base station

and incoming signals (carrying the speech from the person to whomthe phone user is listening) are sent from the base station to thephone at a slightly different frequency. Base stations link mobilephones to the rest of the mobile and fixed phone network.

Figure 1

Once the signal reaches a base station it can be transmitted to themain telephone network, either by telephone cables or by higherfrequency radio links between an antenna (e.g. dish) at the basestation and another at a terminal connected to the main telephonenetwork.


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Each base station provides radio coverage to a geographical areaknown as a cell. Base stations are connected to one another bycentral switching centers, which track calls and transfer them as thecaller moves from one cell to the next. Fig2 below shows the cellstructure of a mobile phone network. An ideal network may beenvisaged as consisting of a mesh of hexagonal cells, each with abase station at its centre. The cells overlap at the edges to ensurethe mobile phone users always remain within range of the basestation. Without sufficient base stations in the right locations,mobile phones will not work.

Figure 2

The size of each cell depends on three factors.

1. The local terrain; radio signals are blocked by trees, hills andbuildings.

2. The frequency band in which the network operates (ingeneral, the higher the radio frequency, the smaller the cell).

3. The capacity (i.e. number of calls) needed in any given area.Base stations are typically spaced about 0.2-0.5 km in townsand 2-5 km apart in the countryside.

If a person with a mobile phone starts to moves out of one cell andinto another, the controlling network hands over communications tothe adjacent base station.

Radio spectrum is a precious natural resource with many differentdemands upon it (for example, radio and TV broadcasting,emergency communication, navigation aids etc). Consequently theamount made available to each mobile phone operator is limitedand this means base stations can only carry a limited number of

calls at any one time.


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To accommodate the steadily increasing volume of users, networkoperators have to use the limited number of radio frequencieslicensed to them to support the maximum number of mobile phoneusers. This is achieved by re-using any given radio frequency manytimes in a network and carefully controlling base station power sothat signals arising in different parts of the network do not interferewith each other. This concept of frequency re-use is illustrated infigure 3. The cells are grouped into clusters, with the frequenciesallocated to a particular cell within a cluster not being re-used untilthe corresponding cell in adjacent clusters. This gives a repeatingpattern of cells and clusters which can be expanded to provide largecoverage.

To increase the capacity of their networks, operators have to buildadditional base stations and thus reduce cell size.

Figure 3 Frequency Reuse

The primary requirement for a network in the cellular concept is away for each distributed station to distinguish the signal from its

own transmitter from the signal from other transmitters. There aretwo common solutions to this, frequency division multiple access(FDMA), and code division multiple access (CDMA). FDMA works byusing a different frequency for each neighboring cell. By tuning tothe frequency of a chosen cell the distributed stations can avoid thesignal from other cells. In CDMA the frequency remains same butsignals are separated by using a pseudonoise code (PN code). Timedivision multiple access is used in combination with either FDMA orCDMA in a number of systems to give multiple channels within thecoverage area of a single cell.


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4.0 Services Provided by Cell Phone

Following are details of some of the main services provided by cellphones.

4.1 SMS: Short Message Service

SMS (Short Message Service) is the simplest and most commontype of text message and is supported by a large number of mobilephones. SMS typically allows for text messages with a maximum of160 characters per message.

4.2 Smart Messaging

Smart Messaging was developed by Nokia and is found only onNokia phones. Smart Messaging allows Nokia phone users to createmessages that have pictures, ring tones, virtual business cards andother types of non-text data, all within a message that is roughlycompatible with the SMS text standard. In other words, althoughthese messages may contain non-text content, they still use SMStext data stream to communicate the data.

The great thing about Smart Messaging is that it allows people to dosimple picture messaging, but with the low cost, quick message

transmission and high simplicity of regular text messages. By "lowcost", we mean that Smart Messages do not cost the mobile phoneuser any more money to send than a regular SMS text message,and they can be sent in roughly the same amount of time as SMStext messages.

4.3 EMS: Extended Message Service

The EMS (Extended Message Service) standard was a collaborativeeffort of Alcatel, Motorola, Siemens and Sony/Ericsson, and this

standard emerged as a response to Nokia's proprietary SmartMessaging standard. The EMS standard allows for pictures,animations, ring tones, and other non-text content similar to SmartMessaging, but in addition, EMS adds the ability to format the textmessages including the font size, font color, font style (bold, italics,etc.) and text and picture placement within a message.

Like Smart Messaging, it uses the SMS text data stream fortransmission, thus providing the low cost, quick messagetransmission, and high simplicity of SMS text messages.


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5.0 Cell Phone Codes

Electronic Serial Number (ESN) - a unique 32-bit numberprogrammed into the phone when it is manufactured

Mobile Identification Number (MIN) - a 10-digit numberderived from your phone's number

System Identification Code (SID) - a unique 5-digitnumber that is assigned to each carrier by the FCC

While the ESN is considered a permanent part of the phone, boththe MIN and SID codes are programmed into the phone when youpurchase a service plan and have the phone activated.

All cell phones have special codes associated with them. These

codes are used to identify the phone, the phone's owner and theservice provider.

Let's say you have a cell phone, you turn it on and someone tries tocall you. Here is what happens to the call:

When you first power up the phone, it listens for an SID onthe control channel. The control channel is a special frequencythat the phone and base station use to talk to one anotherabout things like call set-up and channel changing. If the

phone cannot find any control channels to listen to, it knows itis out of range and displays a "no service" message. When it receives the SID, the phone compares it to the SID

programmed into the phone. If the SIDs match, the phoneknows that the cell it is communicating with is part of itshome system.

Along with the SID, the phone also transmits a registrationrequest, and the MTSO keeps track of your phone's location ina database -- this way, the MTSO knows which cell you are inwhen it wants to ring your phone.

The MTSO gets the call, and it tries to find you. It looks in itsdatabase to see which cell you are in.

The MTSO picks a frequency pair that your phone will use inthat cell to take the call.

The MTSO communicates with your phone over the controlchannel to tell it which frequencies to use, and once yourphone and the tower switch on those frequencies, the call isconnected. Now, you are talking by two-way radio to a friend.

As you move toward the edge of your cell, your cell's basestation notes that your signal strength is diminishing.Meanwhile, the base station in the cell you are moving toward(which is listening and measuring signal strength on allfrequencies, not just its own one-seventh) sees your phone's


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6.1 Anatomy of a Cell Phone

A typical basic cell contains just a few individual parts:

An circuit board containing the brains of the phone An antenna A liquid crystal display (LCD) A keyboard A microphone A speaker A battery

The following figures show theinside of a Nokia cell phone:


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The circuit board is the heart of the system.

The front of the circuit board The back of the circuit board The display and keypad

The analog-to-digital and digital-to-analog conversion chipstranslate the outgoing audio signal from analog to digital and theincoming signal from digital back to analog. The digital signalprocessor (DSP) is a highly customized processor designed toperform signal-manipulation calculations at high speed.

The microprocessor handles allof the housekeeping chores forthe keyboard and display, dealswith command and controlsignaling with the base stationand also coordinates the rest ofthe functions on the board.

The ROM and Flash memorychips provide storage for thephone's operating system andcustomizable features, such as the phone directory. The radiofrequency (RF) and power section handles power managementandrecharging, and also deals with the hundreds of FM channels.Finally, the RF amplifiers handle signals traveling to and from the

antenna.


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The Flash memory card on the circuit board The Flash memory card removed

Most current phones offer built-in phonedirectories, calculators and games. Andmany of the phones incorporate sometype of PDA or

The cell-phone speaker, microphone

6.2 Mobile phone batteries

There are three basic types of rechargeable battery used in mobilephones.

6.2.1 Nickel Cadmium (NiCd)

This technology has been around for many years, and rechargeableNiCd batteries are commonplace. They have two major drawbacks,which mean that most quality mobile phones no longer use NiCdbatteries:

Heavy metal: The chemicals in Nickel Cadmium are not

environmentally friendly, and the disposal of cadmium-rich

waste is an increasing problem.

Memory effect: This is sometimes referred to as voltage

depression. If you do not fully discharge a NiCd cell before


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recharging it, after a few cycles, the battery "learns" this

low water mark, and acts as if it is discharged at this point.

The work-around is simple: you have to run the cell down

before recharging it. Unfortunately, it is not alwaysconvenient to do this. In addition, the cells are connected inseries, so although some cells may be discharged, othersmay not be.

6.2.2 Nickel Metal Hydride (NiMH)

Nickel Metal Hydride batteries claim to be superior to NiCd not onlybecause they don't contain cadmium. They also are less prone tothe "memory effect" problem, and a discharge every week or two is

sofficient. They also have a higher capacity in relation to their sizeand weight

The drawback of NiMH is that they don't seem to last as long asNiCd cells. After a few hundred charge cycles, the crystals insideNiMH cells become coarser, and although they are able to providethe power for long standby times, when the extra current to sustaina call is needed, the voltage available drops rapidly, and suddenlyyou're getting Low Battery warnings. End the call, and after a fewminutes rest, the battery is fine for many hours standby.

6.2.3 Lithium Ion (Li-Ion)

This is the current "latest and greatest" technology for mobile phonebatteries. Li-Ion gives exceptional capacity for its size and weight,and does not suffer from the memory effect. The only real drawbackof Li-on is that they are expensive, and so they tend to be suppliedonly in top-of-the-range phones. One should avoid completelydischarging Li-Ion batteries

There are also Lithium Polymer batteries, but these are very similarto Lithium Ion, except that they can be moulded into more variedshapes, and so be squeezed into smaller phone casings.

7.0 Multiple Band & Multiple Mode Cell Phones

If you travel a lot, you will probably want to look for phones thatoffer multiple bands, multiple modes or both. Let's take a look ateach of these options:

Multiple band - A phone that has multiple-band capabilitycan switch frequencies. For example, a dual-band TDMA


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phone could use TDMA services in either an 800-MHz or a1900-MHz system. A quad-band GSM phone could use GSMservice in the 850-MHz, 900-MHz, 1800-MHz or 1900-MHzband.

Multiple mode - In cell phones, "mode" refers to the type oftransmission technology used. So, a phone that supportedAMPS and TDMA could switch back and forth as needed. It'simportant that one of the modes is AMPS -- this gives youanalog service if you are in an area that doesn't have digitalsupport.

Multiple band/Multiple mode - The best of both worldsallows you to switch between frequency bands andtransmission modes as needed.

Changing bands or modes is done automatically by phones that

support these options. Usually the phone will have a defaultoption set, such as 1900-MHz TDMA, and will try to connect at thatfrequency with that technology first. If it supports dual bands, it willswitch to 800 MHz if it cannot connect at 1900 MHz. And if thephone supports more than one mode, it will try the digital mode(s)first, then switch to analog.

You can find both dual-mode and tri-mode phones. The term "tri-mode" can be deceptive. It may mean that the phone supports twodigital technologies, such as CDMA and TDMA, as well as analog. In

that case, it is a true tri-mode phone. But it can also mean that itsupports one digital technology in two bands and also offers analogsupport. A popular version of the tri-mode type of phone for peoplewho do a lot of international traveling has GSM service in the 900-MHz band for Europe and Asia and the 1900-MHz band for theUnited States, in addition to the analog service. Technically, this is adual-mode phone, and one of those modes (GSM) supports twobands.

8.0 Problems with Cell Phones

A cell phone, like any other consumer electronic device, has itsproblems:

Generally, non-repairable internal corrosion of parts results ifyou get the phone wet or use wet hands to push the buttons.Consider a protective case. If the phone does get wet, be sureit is totally dry before you switch it on so you can try to avoiddamaging internal parts.


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Extreme heat in a car can damage the battery or the cell-phone electronics. Extreme cold may cause a momentary lossof the screen display.

Analog cell phones suffer from a problem known as "cloning."A phone is "cloned" when someone steals its ID numbers andis able to make fraudulent calls on the owner's account.

9.0 Cellular Technologies

Table 1 presents a short history of mobile telephone technologies.

Technology 1G 2G 2.5G 3G 4G

Design Began 1970 1980 1985 1990 2000Implementation 1984 1991 1999 2002 2010?Service Analog voice,

synchronousdata to 9.6kbps

Digital voice,

shortmessages

Higher capacity,

packetized data

broadband data

Higher capacity,up to 2 Mbps

Higher capacity, completely

IP- oriented, multimedia,data to hundreds, ofmegabits

Standards AMPS, TACS, TDMA, CDMA, GPRS, EDGE, WCDMA, Single standardNMT, etc. GSM, PDC 1xRTT CDMA2000

Data Bandwidth 1.9 kbps 14.4 kbps 384 kbps 2 Mbps 200 MbpsMultiplexing FDMA TDMA, CDMA TDMA, CDMA CDMA CDMA?Core Network PSTN PSTN PSTN, packet

networkPacket network Internet

9.1 First-Generation Cellular Technology 1G

1G is short for first-generation wireless telephone technology,cellphones. These are the analog cellphone standards that wereintroduced in the 1980s and continued until being replaced by 2Gdigital cellphones. The main difference between two succeedingmobile telephone systems, 1Gand 2G, is that the radio signals that1G networks use are analog, while 2G networks are digital.

One 1G standard is NMT (Nordic Mobile Telephone), used in Nordiccountries, Switzerland, Netherlands, Eastern Europe and Russia.Others include AMPS (Advanced Mobile Phone System) used in the

United States, TACS (Total Access Communications System) in theUnited Kingdom, C-450 in West Germany, Portugal and SouthAfrica, Radiocom 2000 in France, and RTMI in Italy. In Japan therewere multiple systems. Three standards, TZ-801, TZ-802, and TZ-803 were developed by NTT, while a competing system operated byDDI used the JTACS (Japan Total Access Communications System)standard.

AMPS "Analog Mobile Phone Service" or sometimes also known as"Advanced Mobile Phone System" is based on analog technology.AMPS is still in use today for certain high-reliability voiceapplications including GM's On*Star service and certain very-low-


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bandwidth industrial data applications. Although there is a dataelement to AMPS which is used to send the date, time of day, andother low-bandwidth data to mobile phones, AMPS phones cannotdo text or picture messaging.

9.2 Second-Generation Cellular Technology 2G

Second generation (2G) digital cellular systems were first developedat the end of the 1980s. These systems digitized not only thecontrol link but also the voice signal. The new system providedbetter quality and higher capacity at lower cost to consumers.

The competitive rush to design and implement digital systems ledagain to a variety of different and incompatible standards such asGSM (global system mobile), originally from Europe but usedworldwide; TDMA (time division multiple access) (IS-54/IS-136) inthe U.S.; PDC (personal digital cellular) in Japan; and CDMA (codedivision multiple access) (IS-95), another U.S. system. Thesesystems operate nationwide or internationally and are today'smainstream systems

2G technologies can be divided into TDMA-based and CDMA-basedstandards depending on the type of multiplexing used. The main 2Gstandards are:

GSM (TDMA-based), (Time Division Multiple Access) iDEN (TDMA-based), proprietary network used by Nextel in

the United States and Telus Mobility in Canada IS-136 aka D-AMPS, (TDMA-based, commonly referred as

simply TDMA in the US), used in the Americas IS-95 aka cdmaOne, (CDMA-based, commonly referred as

simply CDMA in the US), used in the Americas and parts ofAsia

PDC (TDMA-based), used exclusively in Japan

2G services are frequently referred as Personal CommunicationsService, or PCS, in the US.

9.2.1 Advantages of Digital System

Using digital signals between the handsets and the towers increasessystem capacity in two key ways:

Digital voice data can be compressed and multiplexed muchmore effectively than analog voice encodings through the use

of various CODECs, allowing more calls to be packed into thesame amount of radio bandwidth.


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The digital systems were designed to emit less radio powerfrom the handsets. This meant that cells could be smaller, somore cells could be placed in the same amount of space. Thiswas also made possible by cell towers and related equipmentgetting less expensive

Digital systems have also following advantages.

The lower powered radio signals require less battery power,so phones last much longer between charges, and batteriescan be smaller.

The digital voice encoding allowed digital error checking whichcould increase sound quality by reducing dynamic andlowering the noise floor.

The lower power emissions helped address health concerns. Going all-digital allowed for the introduction of digital data

services, such as SMS and email. Digital cellular calls are much harder to eavesdrop on by use

of radio scanners. While the security algorithms used haveproved to not be as secure as initially advertised, 2G phonesare immensely more private than 1G phones, which have noprotection whatsoever against eavesdropping

9.2.2 Global System for Mobile Communications, GSM

The GSM (original acronym: Groupe Spcial Mobile) is the mostpopular standard for mobile phones in the world. GSM service isused by over 2 billion people across more than 212 countries andterritories. The ubiquity of the GSM standard makes internationalroaming very common between mobile phone operators, enablingsubscribers to use their phones in many parts of the world.

9.2.2.1 GSM Radio interface

GSM is a cellular network, which means that mobile phones connectto it by searching for cells in the immediate vicinity. GSM networksoperate in four different frequency ranges. Most GSM networksoperate in the 900 MHz or 1800 MHz bands. Some countries in theAmericas (including the United States and Canada) use the 850 MHzand 1900 MHz bands because the 900 and 1800 MHz frequencybands were already allocated.

In the 900 MHz band the uplink frequency band is 890-915 MHz,and the downlink frequency band is 935-960 MHz. This 25 MHzbandwidth is subdivided into 124 carrier frequency channels, eachspaced 200 kHz apart. Time division multiplexing is used to allow

eight full-rate or sixteen half-rate speech channels per radiofrequency channel. There are eight radio timeslots (giving eight


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burst periods) grouped into what is called a TDMA frame. Half ratechannels use alternate frames in the same timeslot. The channeldata rate is 270.833 kbit/s, and the frame duration is 4.615 ms.

The transmission power in the handset is limited to a maximum of 2

watts in GSM850/900 and 1 watt in GSM1800/1900.

GSM has used a variety of voice codecs to squeeze 3.1kHz audiointo between 6 and 13kbps.

9.2.2.2 GSM Network structure

The network behind the GSM system seen by the customer is largeand complicated in order to provide all of the services which arerequired.

The Base Station Subsystem (the base stations and theircontrollers).

The Network and Switching Subsystem (the part of thenetwork most similar to a fixed network). This is sometimesalso just called the core network.

The GPRS Core Network (the optional part which allowspacket based Internet connections).

All of the elements in the system combine to produce manyGSM services such as voice calls and SMS.


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A typical example of a GSM phone working is as follows.

i. When you switch a GSM mobile phone on, it looks in thesim card to find out what phone it is today.

ii. It then looks for a signal on the GSM frequencies. If it can

find its sim card's home network, it logs onto that networkand it then waits for a call.

iii. The cell that it is logged onto is part of a Base TransceiverStation (BTS). Each BTS is connected to a Base StationController (BSC) which is the brains for a group of BTSunits. It does the thinking about what power levels the BTSshould use, controls the handoffs from one BTS to another,controls the frequency hopping, and does the work ofkeeping the phone connections to the right BTS for the

mobiles using them.

iv. Each BSC is under the control of a Mobile Switching Centre(MSC). This controls a group of BSC units, and does theclever stuff involved in keeping tabs on where all themobiles are.

v. In conjunction with the network databases, it connectsthem to the rest of the telephone network, keeps track ofwhat hardware is being used, validates the identity of SIMcards and their associated accounts and phone numbers,keeps track of visiting phones roaming on the network and

similar functions.

9.2.2.3 Subscriber identity module

One of the key features of GSM is the Subscriber Identity Module(SIM), commonly known as a SIM card. The SIM is a detachablesmart card containing the user's subscription information andphonebook. This allows the user to retain his or her information

after switching handsets. Alternatively, the user can also changeoperators while retaining the handset simply by changing the SIM.Some operators will block this by allowing the phone to use only asingle SIM, or only a SIM issued by them; this practice is known asSIM locking, and is illegal in some countries.

In the United States, Europe and Australia, many operators lock themobiles they sell. This is done because the price of the mobilephone is typically subsidized with revenue from subscriptions andoperators want to try to avoid subsidizing competitor's mobiles. Asubscriber can usually contact the provider to remove the lock for afee, utilize private services to remove the lock, or make use of


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ample software and websites available on the Internet to unlock thehandset themselves. While most web sites offer the unlocking for afee, some do it for free. The locking applies to the handset,identified by its International Mobile Equipment Identity (IMEI)number, not to the account (which is identified by the SIM card). Itis always possible to switch to another (non-locked) handset if suchother handset is available.

9.2.2.4 GSM security

GSM was designed with a moderate level of security. The systemwas designed to authenticate the subscriber using shared-secretcryptography. Communications between the subscriber and thebase station can be encrypted.

GSM uses several cryptographic algorithms for security. The A5/1and A5/2 stream ciphers are used for ensuring over-the-air voiceprivacy. A5/1 was developed first and is a stronger algorithm usedwithin Europe and the United States; A5/2 is weaker and used inother countries. A large security advantage of GSM over earliersystems is that the Ki, the crypto variable stored on the SIM cardthat is the key to any GSM ciphering algorithm, is never sent overthe air interface. Serious weaknesses have been found in bothalgorithms, and it is possible to break A5/2 in real-time in aciphertext-only attack. The system supports multiple algorithms so

operators may replace that cipher with a stronger one.

9.2.3 CDMA

CDMA (code division multiple access) is a mobile digital radiotechnology that transmits streams of bits and whose channels aredivided using codes (PN sequences). CDMA, after digitizing data,spreads it out over the entire available bandwidth. Multiple calls areoverlaid on each other on the channel, with each assigned a uniquesequence code. CDMA is a form of spread spectrum, which simply

means that data is sent in small pieces over a number of thediscrete frequencies available for use at any time in the specifiedrange.

All of the users transmit in the same wide-band chunk of spectrum.Each user's signal is spread over the entire bandwidth by a uniquespreading code. At the receiver, that same unique code is used torecover the signal. Because CDMA systems need to put an accuratetime-stamp on each piece of a signal, it references the GPS systemfor this information. CDMA technology is the basis for InterimStandard 95 (IS-95) and operates in both the 800-MHz and 1900-MHz frequency bands.


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CDMA permits many radios to share the same frequency channel.Unlike TDMA (time division multiple access), all radios can be activeall the time, because network capacity does not directly limit thenumber of active radios. Since larger numbers of phones can beserved by smaller numbers of cell sites, CDMA-based standardshave a significant economic advantage over TDMA-based standards,or the oldest cellular standards that used frequency division multipleaccess (FDMA).

9.2.3 CdmaOneThe Family of IS-95 CDMA Technologies cdmaOne describes acomplete wireless system based on the TIA/EIA IS-95 CDMAstandard, including IS-95A and IS-95B revisions. It represents theend-to-end wireless system and all the necessary specifications thatgovern its operation.

9.2.4 IS-95A

The first CDMA cellular standard TIA/EIA IS-95(Telecommunications Industry Association / Electronic Industries

Association Interim Standard - 95) was first published in July 1993.The IS-95A revision was published in May 1995 and is the basis formany of the commercial 2G CDMA systems around the world. IS-95A describes the structure of the wideband 1.25 MHz CDMAchannels, power control, call processing, hand-offs, and registrationtechniques for system operation. In addition to voice services, manyIS-95A operators provide circuit-switched data connections at 14.4kbps. IS-95A was first deployed in September 1995 by Hutchison(HK).


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CDMA Network Diagram

9.2.4 Comparison of GSM & CDMA

GSM and CDMA are the two most prevalent mobile communicationtechnologies. Both technologies have the same goal: to divide thefinite RF spectrum among multiple users.

TDMA (Time Division Multiple Access - underlying technology usedin GSM) does it by chopping up the channel into sequential timeslices. Each user of the channel takes turns to transmit and receivesignals. In reality, only one person is actually using the channel at aspecific moment. This is analogous to time-sharing on a largecomputer server.

CDMA (Code Division Multiple Access) on the other hand, usesspecial digital modulation Spread Spectrum which spreads thevoice over very wide channel in pseudo random fashion. Thereceiver undoes the randomization to collect the bits together andproduce the sound.

Advantages of GSM

GSM is mature, this maturity means a more stable networkwith robust features.

Less signal deterioration inside buildings. Ability to use repeaters Talktime is generally higher in GSM phones due to pulse

nature of transmission. The availability of Subscriber Identity Modules allows users to

switch networks and handsets at will.

GSM covers virtually all parts of world so internationalroaming is not a problem.


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Disadvantages of GSM

Pulse nature of transmission interferes with some electronics,especially certain audio amplifiers.

Intellectual property is concentrated among a few industryparticipants, creating barriers to entry for new entrants andlimiting competition among phone manufacturers.

GSM has a fixed maximum cell site range of 35 km, which isimposed by technical limitations. [

Advantages of CDMA

Capacity is CDMA's biggest asset. It can accommodate more

users per MHz of bandwidth than any other technology. CDMA has no built-in limit to the number of concurrent users. CDMA uses precise clocks that do not limit the distance a

tower can cover. [2] CDMA consumes less power and covers large areas so cell size

in CDMA is larger. CDMA is able to produce a reasonable call with lower signal

(cell phone reception) levels. CDMA uses Soft Handoff, reducing the likelihood of dropped

calls. CDMA's variable rate voice coders reduce the rate being

transmitted when speaker is not talking, which allows thechannel to be packed more efficiently.

Has a well-defined path to higher data rates.

Disadvantages of CDMA

Most technologies are patented and must be licensed fromQualcomm.

Breathing of base stations, where coverage area shrinksunder load. As the number of subscribers using a particularsite goes up, the range of that site goes down.

Because CDMA towers interfere with themselves, they arenormally installed on much shorter towers. Because of this,CDMA may not perform well in hilly terrain.

Currently CDMA covers a smaller portion of the world ascompared to GSM which has more subcribers and is in morecountries overall worldwide.

9.3 Advances in 2G Cellular Technology 2.5 G & 2.75 G


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The term "second and a half generation" is used to describe 2G-systems that have implemented a packet switched domain inaddition to the circuit switched domain. Thus an interim step isbeing taken between 2G and 3G, the 2.5G. It is basically anenhancement of the two major 2G technologies to provide increasedcapacity on the 2G RF (radio frequency) channels and to introducehigher throughput for data service, up to 384 kbps. It does notnecessarily provide faster services because bundling of timeslots isused for circuit switched data services (HSCSD) as well. A veryimportant aspect of 2.5G is that the data channels are optimized forpacket data, which introduces access to the Internet from mobiledevices, whether telephone, PDA (personal digital assistant), orlaptop. GPRS is a 2.5G technology used by GSM operators.

2.75G is the term which has been decided on for systems whichdon't meet the 3G requirements but are marketed as if they do(e.g. CDMA-2000 without multi-carrier) or which do, just, meet therequirements but aren't strongly marketed as such. (e.g. EDGEsystems).

While the terms "2G" and "3G" are officially defined, "2.5G" &2.75G are not. They were invented for marketing purposes only.

9.3.1 General Packet Radio Services (GPRS)

General Packet Radio Services (GPRS) is a mobile data serviceavailable to users of GSM and IS-136 mobile phones. GPRS can beutilized for services such as WAP access, SMS and MMS, but also forInternet communication services such as email and web access.

GPRS is packet-switched which means that multiple users share thesame transmission channel, only transmitting when they have datato send. This means that the total available bandwidth can beimmediately dedicated to those users who are actually sending atany given moment, providing higher utilization where users onlysend or receive data intermittently. Web browsing, receiving e-mailsas they arrive and instant messaging are examples of uses thatrequire intermittent data transfers, which benefit from sharing theavailable bandwidth.

Usually, GPRS data are billed per kilobytes of informationtransceived.


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9.3.2 Enhanced Data rates for GSM Evolution (EDGE)

Enhanced Data rates for GSM Evolution (EDGE) or Enhanced GPRS(EGPRS), is a digital mobile phone technology that allows forincreased data transmission rate and improved data transmissionreliability. It is generally classified as a 2.75G network technology.EDGE has been introduced into GSM networks around the worldsince 2003, initially in North America.

It can be used for any packet switched applications such as anInternet connection. High-speed data applications such as videoservices and other multimedia benefit from EGPRS' increased datacapacity.

EDGE/EGPRS is implemented as a bolt-on enhancement to 2G and

2.5G GSM and GPRS networks, making it easier for existing GSMcarriers to upgrade to it. EDGE/EGPRS is a superset to GPRS andcan function on any network with GPRS deployed on it, provided thecarrier implements the necessary upgrades.

Although EDGE requires no hardware changes to be made in GSMcore networks, base stations must be modified. EDGE compatibletransceiver units must be installed and the base station subsystem(BSS) needs to be upgraded to support EDGE. New mobile terminalhardware and software is also required to decode/encode the new

modulation and coding schemes and carry the higher user datarates to implement new services.

EDGE can carry data speeds up to 236.8 kbit/s for 4 timeslots(theoretical maximum is 473.6 kbit/s for 8 timeslots) in packetmode and will therefore meet the International TelecommunicationsUnion's requirement for a 3G network.

9.3.3 CDMA IS-95B: 2.5G

The IS-95B revision, also termed TIA/EIA-95, combines IS-95A,ANSI-J-STD-008 and TSB-74 into a single document. The ANSI-J-STD-008 specification, published in 1995, defines a compatibilitystandard for 1.8 to 2.0 GHz CDMA PCS systems. TSB-74 describesinteraction between IS-95A and CDMA PCS systems that conform toANSI-J-STD-008. Many operators that have commercialized IS-95Bsystems offer 64 kbps packet-switched data, in addition to voiceservices. Due to the data speeds IS-95B is capable of reaching, it iscategorized as a 2.5G technology. CdmaOne IS-95B was firstdeployed in September 1999 in Korea and has since been adopted

by operators in Japan and Peru.


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9.4 Third-Generation Cellular Technology

3G is the term used to describe next generation mobile serviceswhich provide better quality voice and high-speed Internet andmultimedia services. Following vision has been envisaged for 3G

Universal global roaming Multimedia (voice, data &video) Increased data rates

o 384 kbps while movingo 2 Mbps when stationary at specific locations

Increased capacity (more spectrally efficient)

IP architecture

Brief summary of some services to be provided by 3G systems aregiven below:

SMS, EMS, MMS Location-based services

o Emergency services E911-Enhanced 911

o Value-added personal services Friend finder, directions

o Commercial services coupons or offers from nearby stores

o Network internal Traffic &coverage measurements

o Lawful intercept extensions law enforcement locates suspect

3G-324M Video VoIP w/o QoS; Push-to-Talk IP Multimedia Services (w/ QoS) Converged All IP networks the Vision

9.4.1 3G Standards

ITU, working with industry bodies from around the world, definesand approves technical requirements and standards as well as theuse of spectrum for 3G systems under the IMT-2000 (InternationalTelecommunication Union-2000) program.

The ITU requires that IMT-2000 (3G) networks, among othercapabilities, deliver improved system capacity and spectrum


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9.4.1.1 UMTS

The 3G standard that has been agreed for Europe and Japan isknown as UMTS. UMTS is an upgrade from GSM via GPRS or EDGE.UMTS is the European vision of 3G,.

The terrestrial part of UMTS is known as UTRA (UMTS TerrestrialRadio Access ) The FDD component of UTRA is based on the W-CDMA standard (a.k.a. UTRA FDD). This offers very high data ratesup to 2Mbit/sec. The TDD component of UTRA is called TD-CDMA(or UTRA TDD).

The standardization work for UMTS is being carried-out under thesupervision of the Third Generation Partnership Project (3GPP). W-

CDMA has recently been renamed 3GSM (to avoid confusion withCDMA2000).

UMTS combines the W-CDMA, TD-CDMA, or TD-SCDMA airinterfaces, GSM's Mobile Application Part (MAP) core, and the GSMfamily of speech codecs. In the most popular, cellular mobiletelephone, variant of UMTS, W-CDMA is currently used. The otherwireless standards use W-CDMA as their air interface, includingFOMA.

Since 2006, UMTS networks in many countries have been or are inthe process of being upgraded with High Speed Downlink PacketAccess (HSDPA), sometimes known as 3.5G. Currently, HSDPAenables downlink transfer speeds of up to 3.6Mbit/s. Work is also

UMTS over W-CDMA uses a pair of 5 MHz channels providing 50times higher data rate than in present GSM networks (and 10 timeshigher data rate than in GPRS networks). In contrast, thecompeting CDMA2000 system uses one or more arbitrary 1.25 MHzchannels for each direction of communication. The specific

frequency bands originally defined by the UMTS standard are 1885-2025 MHz for uplink and 2110-2200 MHz for downlink. In the US,the 1700MHz band will used instead of 1900MHz - which is alreadyin use - for the uplink by many UMTS operators. Additionally, UMTSis commonly run on 850MHz and 1900MHz (independently, for boththe uplink and downlink).

9.4.1.1.2 UMTS Interoperatibility and global roaming

At the air interface level, UMTS itself is incompatible with GSM. WithUMTS/GSM dual-mode phones, one can make and receive calls onregular GSM networks. If a UMTS customer travels to an areawithout UMTS coverage, a UMTS phone will automatically switch to


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GSM. If the customer travels outside of UMTS coverage during acall, the call will be transparently handed off to available GSMcoverage. Regular GSM phones cannot be used on the UMTSnetworks.

Vodafone Japan operates a 3G network based on UMTS compatibleW-CDMA technology, that launched in December 2002. Lack ofinvestment in the network through 2003 meant that coverage wasslow to expand and subscriber numbers remained low. The networkwas publicly relaunched in October 2004 and again in 2005, andVodafone now claims network coverage of 99% of the population,while 15% of their subscribers are 3G users.

9.4.1.2 FOMA

NTT DoCoMo has gone live with 3G in Tokyo. Its service is calledFOMA. This is the world's first IMT-2000 W-CDMA service (there aresmall but significant differences between the Japanese andEuropean versions of W-CDMA). The first W-CDMA version used byNTT DoCoMo was incompatible with the UMTS standard at the radiolevel, however USIM cards used by FOMA phones are compatiblewith GSM phones, so that USIM card based roaming is possible fromJapan to GSM areas without any problem.

9.4.1.3 CDMA2000

The chief competitor to Europe's UMTS standard is San Diego-basedQualcomm's CDMA2000. The standardization work for CDMA2000 isbeing carried-out under the supervision of the Third GenerationPartnership Project 2, (3GPP2). The CDMA Development Groupoffers advice to 3GPP2.

Even though "W-CDMA" and "CDMA2000" both have "CDMA" intheir names, they are completely different systems using differenttechnologies.

CDMA2000 has two phases: phase one is 1XRTT (144 Kbps) (alsoknown as 1X). The next evolutionary step is to the two CDMA20001X EV standards. CDMA2000 1X EV-DO will use separatefrequencies for data and voice. The following step is to CDMA20001X EV-DV which will integrate voice and data on the same

frequency band.


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CDMA2000 represents a family of technologies that includesCDMA2000 1X and CDMA2000 1xEV.

CDMA2000 1X can double the voice capacity of cdmaOnenetworks and delivers peak packet data speeds of 307 kbps in

mobile environments.

CDMA2000 1xEV ("EV" = "Evolution") includes

o CDMA2000 1xEV-DO("Data Only") :

CDMA2000 1xEV-DO in its latest revision, Rev. A,supports downlink (forward link) data rates up to 3.1

Mbit/s and uplink (reverse link) data rates up to 1.8Mbit/s in a radio channel dedicated to carrying high-speed packet data. 1xEV-DO Rev. A was firstdeployed in Japan and will be deployed in NorthAmerica in 2006.. It supports applications such asMP3 transfers and video conferencing.

o CDMA2000 1xEV-DV ("Data and Voice"):

CDMA2000 1xEV-DV supports downlink (forward link)

data rates up to 3.1 Mbit/s and uplink (reverse link)data rates of up to 1.8 Mbit/s. 1xEV-DV can alsosupport concurrent operation oflegacy 1x voice users,1x data users, and high speed 1xEV-DV data userswithin the same radio channel. It provides integratedvoice and simultaneous high-speed packet datamultimedia services at speeds of up to 3.09 Mbps.

1xEV-DO and 1xEV-DV are both backward compatible withCDMA2000 1X and cdmaOne.

The world's first 3G (CDMA2000 1X) commercial system waslaunched by SK Telecom (Korea) in October 2000. Since then,CDMA2000 1X has been deployed in Asia, North and South Americaand Europe.

CDMA2000 1xEV-DO was launched in 2002 by SK Telecom and KTFreetel. The commercial success of CDMA2000 has made the IMT-2000 vision a reality.

9.4.1.4 TD-CDMA/TD-SCDMA


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The UMTS standard also contains another radio transmissionstandard: TD-CDMA (a.k.a. TDD UTRA because it is the TDDcomponent of UTRA). TD-CDMA was developed by Siemens. WhileW-CDMA is an FDD technology (requiring paired spectrum), TD-CDMA is a TDD technology and thus can use unpaired spectrum.TDD is well-suited to the transmission of internet data.

The Chinese national 3G standard is a TDD standard similar to TD-CDMA: TD-SCDMA. TD-SCDMA was developed by the ChinaAcademy of Telecommunications Technology (CATT) in collaborationwith Siemens. TD-SCDMA elimates the uplink/downlink interferencewhich affects other TDD methods by applying "terminalsynchonisation" techniques (the "S" in TD-SCDMA stands for"synchronisation"). Because of this, TD-SCDMA allows full networkcoverage over macro cells, micro cells, and pico cells. Hence, TD-

SCDMA stands alongside W-CDMA and CDMA2000 as a fully-fledged3G standard. The 3GPP have extended the TD-CDMA standard toinclude TD-SCDMA as an official IMT-2000 standard.

Unfortunately, TD-SCDMA has performed poorly in trials, andChinese network operators may prefer W-CDMA over TD-SCDMA.

9.4.2 Migration Path to 3G

The following diagram shows the migration path from oldertechnologies to 3G.

9.4.2 Issues in 3G

Even though 3G has successfully been introduced to European

mobile users, there are some issues that are debated by 3Gproviders and users.


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High input fees for the 3G service licenses; Great differences in the licensing terms; Current high debt of many telecommunication companies,

making it more of a challenge to build the necessaryinfrastructure for 3G;

Member State support to the financially troubled operators; Health aspects of the effects of electromagnetic waves; Expense and bulk of 3G phones; Lack of 2G mobile user buy-in for 3G wireless service; Lack of coverage because it is still new service; High prices of 3G mobile services in some countries, including

Internet access

9.5 Fourth-generation Cellular Technology 4G

This new generation of wireless is intended to complement andreplace the 3G systems, perhaps in 5 to 10 years. Accessinginformation anywhere, anytime, with a seamless connection to awide range of information and services, and receiving a largevolume of information, data, pictures, video, and so on, are thekeys of the 4G infrastructures.

The future 4G infrastructures will consist of a set of variousnetworks using IP (Internet protocol) as a common protocol so thatusers are in control because they will be able to choose every

application and environment. Based on the developing trends ofmobile communication, 4G will have broader bandwidth, higher datarate, and smoother and quicker handoff and will focus on ensuringseamless service across a multitude of wireless systems andnetworks.

The key concept is integrating the 4G capabilities with all of theexisting mobile technologies through advanced technologies. Thesefeatures mean services can be delivered and be available to thepersonal preference of different users and support the users' traffic,

air interfaces, radio environment, environment, and quality ofservice. The dominant methods of access to this pool of informationwill be the mobile telephone, PDA, and laptop to seamlessly accessthe voice communication, high-speed information services, andentertainment broadcast services. The fourth generation willencompass all systems from various networks, public to private;operator-driven broadband networks to personal areas; and ad hocnetworks as depicted in fig below:

The 4G systems will interoperate with 2G and 3G systems, as wellas with digital (broadband) broadcasting systems. In addition, 4Gsystems will be fully IP-based wireless Internet.


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Comparison Of Key Parameters of 4G with 3G

3G (including 2.5G, sub3G) 4GMajor RequirementDriving Architecture

Predominantly voice driven -data was always add on Converged data and voice over IP

Network Architecture Wide area cell-based Hybrid - Integration of WirelessLAN (WiFi, Bluetooth) and widearea

Speeds 384 Kbps to 2 Mbps 20 to 100 Mbps in mobile modeFrequency Band Dependent on country or

continent (1800-2400 MHz) Higher frequency bands (2-8 GHz)Bandwidth

5-20 MHz

100 MHz (or more)

Switching Design Basis Circuit and Packet All digital with packetized voiceAccess Technologies W-CDMA, 1xRTT, Edge OFDM and MC-CDMA (Multi

Carrier CDMA)Forward Error Correction Convolutional rate 1/2, 1/3 Concatenated coding scheme

Component Design Optimized antenna design,multi-band adapters

Smarter Antennas, softwaremultiband and wideband radios

IPA number of air link protocols,

including IP 5.0All IP (IP6.0)

NTT-DoCoMo and Hewlett-Packard have announced that the twocompanies are jointly developing technologies for 4G wireless


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communications. They have named the technology platform: MOTO-Media.

10.0 Key Concerns regarding Cell phone use

10.1 Health controversy

Mobile phone radiation and health concerns have been raised,because mobile phones use electromagnetic waves in themicrowave range. Part of the radio waves emitted by a mobiletelephone handset are absorbed by the human head. The the radiowaves emitted by a digital mobile technologies, such as CDMA andTDMA are under 1 watt. The average radiation rate of cellphones insome countries is regulated and it is mandatory to inform theconsumers about it (usually printed in the battery compartment).

The rate at which radiation is absorbed by the human body ismeasured by the Specific Absorption Rate (SAR), and its maximumlevels for modern handsets have been set by governmentalregulating agencies in many countries. In the USA, the FCC has seta SAR limit of 1.6 W/kg, averaged over a volume of 1 gram of

tissue, for most parts of the body.

The World Health Organization has officially ruled out adversehealth effects from cellular base stations and wireless datanetworks, and expects to make recommendations about mobilephones in 2007-08. In December 2006, a 21-year Danish study with420,000 participants (considered a large, reliable, study of long-term effects) publised in the Journal of the National Cancer Instituteruled out any causal link between cell phones and cancer.

10.2 Thermal effects

One well-understood effect of microwave radiation is dielectricheating, in which any dielectric material (such as living tissue) isheated by rotations of polar molecules induced by theelectromagnetic field. In the case of a person using a cell phone,most of the heating effect may occur in the head surface, causingits temperature to increase by a fraction of a degree. The level oftemperature increase is an order of magnitude less than thatobtained during the exposure of the head to direct sunlight. The

brain's blood circulation easily disposes of excess heat byinstantaneously increasing local blood flow. However, the cornea of


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the eye does not have this temperature regulation mechanism.Premature cataracts are known as an occupational disease ofengineers who work on high power radio transmitters at similarfrequencies. Due to the low power of mobile phones, cataracts havenot been reported to occur in users of these.

It has been claimed that some parts of the human head are moresensitive to damage due to increases in temperature, particularly inanatomical structures with poor vasculature, such as nerve fibers.More recent results from a Swedish scientific team at the KarolinskaInstitute (Lonn, Ahlbom, Hall and Feychting) have suggested thatcontinuous use of a mobile phone for a decade or longer can lead toa small increase in the probability of getting acoustic neuroma, atype of brain tumor. The increase was not noted in those who usedphones for less than 10 years. The study has been criticized for

possible problems in data analysis such as recall bias. However,another study conducted by the Swedish National Institute forWorking Life supported an increased risk of "malignant tumors onthe side of the head the phone is used." Such long term heavy useinvolved phones of older higher power analog designs that were firstintroduced to Sweden in 1984, earlier than many other countries.

No increased cancer risk was found in a larger and more recentstudy, and the hypotheisized link is now generally regarded ashaving been ruled out.

10.3 Electromagnetic hypersensitivity syndrome

Many users of mobile handsets have reported feeling severalunspecific symptoms during and after its use, such as burning andtingling sensations in the skin of the head and extremities, fatigue,sleep disturbances, dizziness, loss of mental attention, reactiontimes and memory retentiveness, headaches, malaise, tachycardia(heart palpitations) and disturbances of the digestive system. Someresearchers, implying a causal relationship, have named this

syndrome as a new diagnostic entity, EHS or ES (electrosensitivity).The World Health Organization prefers to name it "idiopathicenvironmental intolerance", in order to avoid the implication ofcausation. This entity is quite controversial, because albeit identifiedin unmistaken terms by the patients who affirm to suffer from it, insome cases in such a radical way that they avoid using cellphones,it has not been recognized as a separate clinical entity by mostmedical researchers.

Two recent literature reviews, however, one reviewing 13 publishedpapers in 2003 and 2004, and another reviewing 31 paperspublished before 2004, have concluded that there is no scientific


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evidence for a causal relationship between the reported clusters ofsymptoms and exposure to microwave radiation used in cellphones,well below the safety standards. A workshop conducted by the WHOin Prague in 2004 also reached the same conclusions, viz., that 1)reported symptoms are very unspecific and could have othercauses; 2) there is no causal association demonstrated betweenexposure and symptoms, 3) that patients who display thosesymptoms should be medically examined for alternativeexplanations and causes, including psychiatric/psychological ones(since they are typical manifestations of stress, somatization, orpsychosomatic illness), and that the environment where they workor live should be assessed in order to discover other factors at workthat could explain the symptoms; and 4) lowering the safety limitsfor handset radiation (SAR levels) will not affect the situation.

10.4 Driving controversy

Another controversial but potentially more lethal health concern isthe correlation with road traffic accidents. Several studies haveshown that motorists have a much higher risk of collisions andlosing control of the vehicle while talking on the mobile telephonesimultaneously with driving, even when using "hands-free" systems.Other studies have shown that using a mobile phone while drivingposes the same risk as someone operating a vehicle while under theinfluence of alcohol. Four U.S. states and many countries, such as

Australia, have now restricted or prohibited the use of mobilephones while driving. In Israel and nearly all European countries,driving whilst using a hand-held mobile phone is illegal.

10.5 Security concerns

Early mobile phones were limited in their security features. Someproblems with these models were "cloning", a variant of identitytheft, and "scanning" whereby third parties in the local area could

intercept and eavesdrop in on calls. Analogue phones could also belistened to on some radio scanners.

Although more recent digital systems (such as GSM) haveattempted to address these fundamental issues, security problemscontinue to persist. Vulnerabilities (such as SMS spoofing) havebeen found in many current protocols that continue to allow thepossibility of eavesdropping or cloning.

Location tracking using mobile phones is also a concern.


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As mobile phones begin to converge with the Internet, new securityconcerns will exist. Early forms of mobile viruses, spam, adultcontent and socially engineered scams have begun to targetInternet capable mobile phones. Users of mobile phones will bemuch less tolerant of such malicious activities.

Recently, it has been shown that cell phone microphones can beremotely activated for use as "roving bugs". This has been approvedas legal in the U.S. under existing wiretapping laws. This capabilityis confirmed by the Western Region Security Office of the U.S.Department of Commerce (citing a newsletter from the NationalReconnaissance Office), which says that :

A cellular telephone can be turned into a microphone andtransmitter for the purpose of listening to conversations in the

vicinity of the phone. This is done by transmitting to the cell phonea maintenance command on the control channel. This commandplaces the cellular telephone in the "diagnostic mode." When this isdone, conversations in the immediate area of the telephone can be

monitored over the voice channel.

10.6 Claims of Danger at Gas Pumps

Since 1999 there have been many claims that cell phones can cause

electrostatic discharge that ignite fumes in the air due to thebattery, signal, or ringer. These have been proven to be false as thebattery is the same kind as a car battery, the signals are too weakto ever start it, and cell phones don't actually have a ringer. Despitethis many places have banned cell phone use near gas pumpsincluding places in Canada and Belgium.

It has been alleged that the bans are maintained in order to ensurepatrons are not distracted while refueling, which could causepotentially hazardous spills.

10.7 Claims of danger on aircraft

Almost all countries and airlines ban the use of mobile phones ontheir aircraft due to unproven claims that they can interfere withsystems like the radio link to Air Traffic Control and the autopilot.When Corsair Flight 498 crashed early in 2000, many countries thathad previously been reluctant to introduce this legislation adopted itbecause of claims it was downed by passenger cell phone use, butthe official report blames pilot error and makes no mention of

mobile phone use. Besides the possibility of interfering with airplaneequipment, Cellular phones and other mobile devices could be used


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to detonate remote Improvised Explosive Devices (IEDs), which isyet another reason why they are banned.

11. Conclusion

The report presents the operation of cell phone including the insidesof the cell phone. The various technologies have been presented.The main technologies like GSM & CDMA have been discussed ingrater detail as compared to les used ones. The key concerns onuse of cell phone have been listed out & discussed.

cell phones[1] 1

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