04-06-2012, 05:53 PM
CDMA TECHNOLOGY
CDMA TECHNOLOGY.doc (Size: 1.49 MB / Downloads: 7)
INTRODUCTION
We are moving into a new era of communications and information technology. Personal competitiveness in business in relies more and more on increase personal productivity and responsiveness. Today everybody is on the move and mobile is the only way to keep contact with that person. But now a days peoples want multimedia facilities from their mobile handset. But it requires high data rate, hi efficiency and many more technical things, which are available in third generation. (CDMA) so the CDMA TECHNOLOGY makes existing mobile handset more efficient and attractive.
The Cellular Challenge
The world's first cellular networks were introduced in the early 1980s, using analog radio transmission technologies such as AMPS (Advanced Mobile Phone System). Within a few years, cellular systems began to hit a capacity ceiling as millions of new subscribers signed up for service, demanding more and more airtime. Dropped calls and network busy signals became common in
many areas.
To accommodate more traffic within a limited amount of radio spectrum, the industry developed a new set of digital wireless technologies called TDMA (Time Division Multiple Access) and GSM (Global System for Mobile). TDMA and GSM used a time-sharing protocol to provide three to four times more capacity than analog systems. But just as TDMA was being standardized,
an even better solution was found in CDMA.
Commercial Development
The founders of QUALCOMM realized that CDMA technology could be used in commercial cellular communications to make even better use of the radio spectrum than other technologies. They developed the key advances that made CDMA suitable for cellular, then demonstrated a working prototype and began to license the technology to telecom equipment manufacturers.
The first CDMA networks were commercially launched in 1995, and provided roughly 10 times more capacity than analog networks - far more than TDMA or GSM. Since then, CDMA has become the fastest-growing of all wireless technologies, with over 100 million subscribers worldwide. In addition to supporting more traffic, CDMA brings many other benefits to carriers and consumers, including better voice quality, broader coverage and stronger security.
FDMA
FDMA - Frequency Division Multiple Access.
In Frequency Division Multiple Access, the available spectrum is divided into multiple frequency bands or channels. Each user is assigned a channel to make a call. As long as the user has the call established they are using their assigned frequency. No one else can use it.
FDMA is an inefficient use of spectrum.
TDMA
To improve capacity, carriers started looking at a technology called Time Division Multiple Access (TDMA). In TDMA, engineers take the frequency channel and instead of giving it to one person, they divide it up among many users by giving each user their own time slot. The time slots are short, only 30 - 40 milliseconds, and cycle between users there by allowing each user to have access to a common frequency channel.
