What is the basic defference between GSM & CDMA Mobile Technology ?  

The major difference between GSM/TDMA and CDMA is in the way they divide up those signals between multiple users.

GSM/TDMA uses a Time Division method. TDMA, in fact, stands for Time Division Multiple Access. Simply put, this means that each device on the local network is allocated a time slice where it "owns" the bandwidth, and it can send/receive its data.

So lets just pick a number and say there are 30 available time slices in a given cycle. Each phone would then get 1/30th of every cycle that it could send and receive data (aka, voice).

CDMA uses a different method, called Code Division Multiple Access. The specifics of how it breaks the cycle up are beyond me, but how it works out is that the phones only get a slice of the bandwidth cycle when they actually need one. So if you are not talking, and the other person is not talking, nothing is transmitted.

With GSM/TDMA, each phone is transmitting and receiving during its slices of the bandwidth cycle, whether it needs it or not.

Since most coversations are comprised largely of silence, the end result is that CDMA phones have to transmit less data. They don't have to send silence, like GSM/TDMA phones do.

This means a few things. More CDMA calls can be fit into a given amount of frequency spectrum (ie. it is more efficient for the network), less radiation is being created from the phone towards the user (you only get radiation when you are talking, basically), and battery power is conserved since the handset only transmits when it actually has something to send.

There are other differences, too, that I can't get into. For one, it is harder to implement a CDMA network. The tower placement is more difficult. Dealing with hills is more difficult than with GSM/TDMA.

Answered by Ashish Yadav at 4:59 PM on April 08, 2008

27)GSM & CDMA
GSM (Global System for Mobile Communications).

GSM is the "branded" term referring to a particular use of TDMA (Time-Division Multiple Access) technology. GSM is the dominant technology used around the globe and is available in more than 100 countries. It is the standard for communication for most of Asia and Europe.

GSM operates on four separate frequencies: You’ll find the 900MHz and 1,800MHz bands in Europe and Asia and the 850MHz and 1,900MHz (sometimes referred to as 1.9GHz) bands in North America and Latin America. GSM allows for eight simultaneous calls on the same radio frequency and uses “narrowband” TDMA, the technology that enables digital transmissions between a mobile phone and a base station. With TDMA the frequency band is divided into multiple channels which are then stacked together into a single stream, hence the term narrowband. This technology allows several callers to share the same channel at the same time.

CDMA (Code Division Multiple Access).

CDMA takes an entirely different approach from GSM/TDMA. CDMA spreads data out over the channel after the channel is digitized. Multiple calls can then be overlaid on top of one another across the entire channel, with each assigned its own “sequence code” to keep the signal distinct. CDMA offers more efficient use of an analog transmission because it allows greater frequency reuse, as well as increasing battery life, improving the rate of dropped calls, and offering far greater security than GSM/TDMA. For this reason CDMA has strong support from experts who favor widespread development of CDMA networks across the globe. Currently, you will find CDMA mostly in the United States, Canada, and North and South Korea. (As an interesting aside, CDMA was actually invented for the military during World War II for field communications.)

Answered by Bishan Preet at 10:12 PM on April 07, 2008

well godawari GSM (Global System for Mobile communication) is a digital mobile telephony system that is widely used in Europe and other parts of the world. GSM uses a variation of time division multiple access (TDMA) and is the most widely used of the three digital wireless telephony technologies (TDMA, GSM, and CDMA). GSM digitizes and compresses data, then sends it down a channel with two other streams of user data, each in its own time slot. It operates at either the 900 MHz or 1800 MHz frequency band.

Mobile services based on GSM technology were first launched in Finland in 1991. Today, more than 690 mobile networks provide GSM services across 213 countries and GSM represents 82.4% of all global mobile connections. According to GSM World, there are now more than 2 billion GSM mobile phone users worldwide. GSM World references China as "the largest single GSM market, with more than 370 million users, followed by Russia with 145 million, India with 83 million and the USA with 78 million users."

Since many GSM network operators have roaming agreements with foreign operators, users can often continue to use their mobile phones when they travel to other countries. SIM cards (Subscriber Identity Module) holding home network access configurations may be switched to those will metered local access, significantly reducing roaming costs while experiencing no reductions in service.

GSM, together with other technologies, is part of the evolution of wireless mobile telemmunications that includes High-Speed Circuit-Switched Data (HCSD), General Packet Radio System (GPRS), Enhanced Data GSM Environment (EDGE), and Universal Mobile Telecommunications Service (UMTS).

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 is used 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 can be 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 frequency-sequencing codes, which enhances privacy and makes cloning difficult.

The CDMA channel is nominally 1.23 MHz wide. CDMA networks use a scheme called soft handoff, which minimizes signal breakup as a handset passes from one cell to another. The combination of digital and spread-spectrum modes supports several times as many signals per unit bandwidth as analog modes. CDMA is compatible with other cellular technologies; this allows for nationwide roaming.

The original CDMA standard, also known as CDMA One and still common in cellular telephones in the U.S., offers a transmission speed of only up to 14.4 Kbps in its single channel form and up to 115 Kbps in an eight-channel form. CDMA2000 and wideband CDMA deliver data many times faster.

Answered by sujata at 4:04 PM on April 07, 2008

MR.godawari the basic diffrences are Difference between CDMA & GSM-
These are the two different means of mobile communication being presently used world wide. The basic difference lies in the Multiplexing method used in the airial communication i.e. from Mobile Tower to your mobile and vice versa...

CDMA uses Code Division Multiple Assess as the name itself indicates, for example you are in a hall occupied with number of people speaking different language. You will find that the one language you are knowing will be heard by you and the others will be treated like noise. In the same manner each CDMA mobile communication takes place with a "code" communicating between them and the other end if one is knowing that code then only it can listen to the data being transmitted i.e. the communication is in the coded form.

On the other hand GSM uses Frequency Division Multiplexing in which each user is allocated a particular bandwidth till the communication is taking place.

Ans 2. I thing i have covered it in the above Ans1., in case you need it in detail then you can ask me for it.

Ans 3. About the sim card....
CDMA handsets do not use SIM cards. The handset is assigned a number from the telecom operator and get incorporated in itself. CDMA handset have RSN number which gets linked to a specific number assigned by operator.

Ans 4. full form of GSM & CDMA.

GSM - Global System for Mobile communication.
CDMA - Code Division Multiple Access

Answered by varadaraju at 1:11 PM on April 07, 2008