07-11-2012, 05:59 PM
CDMA Techonology
[attachment=38505]
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.
CDMA (3G) mobile devices and services will transform wireless communications into on-line, real-time connectivity. 3G wireless technology will allow an individual to have immediate access to location-specific services that offer information on demand. The first generation of mobile phones consisted of the analog models that emerged in the early 1980s. The second generation of digital mobile phones appeared about ten years later along with the first digital mobile networks. During the second generation, the mobile telecommunications industry experienced exponential growth both in terms of subscribers as well as new types of value-added services. Mobile phones are rapidly becoming the preferred means of personal communication, creating the world's largest consumer electronics industry.
The rapid and efficient deployment of new wireless data and Internet services has emerged as a critical priority for communications equipment manufacturers. Network components that enable wireless data services are fundamental to the next-generation network infrastructure. Wireless data services are expected to see the same explosive growth in demand that Internet service and wireless voice services have seen in recent years.
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.
Multiple Access Wireless Communications
The goals of multiple access communications systems, meaning cellular and PCS, are:
• Near-wireline quality voice service
• Near-universal geographical coverage
• Low equipment cost, both subscriber stations and fixed plant
• Mimimum number of fixed radio sites
Regulatory agencies have allocated limited bandwidth to these services, so that the solutions must achieve high spectral efficiency, measured in Erlangs per unit service area, per MHz. Cellular operators have 25 MHz each, split between the two directions of communications.
When a subscriber moves between cells, over-the-air messaging is used to transfer control from the old cell to the new cell. This transfer of control is termed handoff or handover.
Several hundred channels are available within the spectrum allocation. One channel of one base station is used for each conversation. Upon handoff, the subscriber station is directed via messaging to discontinue use of the old channel and tune to the new one, on which it will find the new cell.
[attachment=38505]
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.
CDMA (3G) mobile devices and services will transform wireless communications into on-line, real-time connectivity. 3G wireless technology will allow an individual to have immediate access to location-specific services that offer information on demand. The first generation of mobile phones consisted of the analog models that emerged in the early 1980s. The second generation of digital mobile phones appeared about ten years later along with the first digital mobile networks. During the second generation, the mobile telecommunications industry experienced exponential growth both in terms of subscribers as well as new types of value-added services. Mobile phones are rapidly becoming the preferred means of personal communication, creating the world's largest consumer electronics industry.
The rapid and efficient deployment of new wireless data and Internet services has emerged as a critical priority for communications equipment manufacturers. Network components that enable wireless data services are fundamental to the next-generation network infrastructure. Wireless data services are expected to see the same explosive growth in demand that Internet service and wireless voice services have seen in recent years.
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.
Multiple Access Wireless Communications
The goals of multiple access communications systems, meaning cellular and PCS, are:
• Near-wireline quality voice service
• Near-universal geographical coverage
• Low equipment cost, both subscriber stations and fixed plant
• Mimimum number of fixed radio sites
Regulatory agencies have allocated limited bandwidth to these services, so that the solutions must achieve high spectral efficiency, measured in Erlangs per unit service area, per MHz. Cellular operators have 25 MHz each, split between the two directions of communications.
When a subscriber moves between cells, over-the-air messaging is used to transfer control from the old cell to the new cell. This transfer of control is termed handoff or handover.
Several hundred channels are available within the spectrum allocation. One channel of one base station is used for each conversation. Upon handoff, the subscriber station is directed via messaging to discontinue use of the old channel and tune to the new one, on which it will find the new cell.