CDMA(Coded-Division-Multiple Access)

CDMA is abbreviated as Code-Division Multiple Access refers to any of numerous protocols used in second-generation (2G) and third-generation (3G) wireless communications. CDMA is a form of multiplexing, which allows frequent signals to occupy a single transmission channel, optimizing the use of available bandwidth. The CDMA channel is supposedly 1.23 MHz wide. CDMA minimizes signal breakup as a handset passes from one cell to another. CDMA is compatible with other cellular technologies, this permit for countrywide roaming.

CDMA utilizes analog-to-digital conversion (ADC) in grouping with spread spectrum technology. Audio input is first converted into binary elements. The frequency of the transmitted signal is then made to differ according to a discrete pattern (code), so it can be intercepted only by a receiver whose frequency response is associated with decoder, so it follows exactly along with the transmitter frequency. There are trillions of possible frequency-sequencing codes, which enhance privacy and makes genetic copy difficult. The technology is used in ultra-high-frequency (UHF) cellular telephone systems in the 800-MHz and 1.9-GHz bands.

CDMA is a "spread spectrum" technology; permits many user to occupy the same time and frequency allocations in a given band/space. CDMA (Code Division Multiple Access) assigns sole codes to each communication to discriminate it from others in the identical spectrum. In a world of fixed spectrum resources, CDMA enables many more people to split the airwaves at the same time than do alternative technologies.

There are two main version of it:

1.   CDMA1: Still in use in USA, has transmission speed of only up to 14.4 Kbps in its single channel appearance and up to 115 Kbps in an eight-channel figure.

2.   CDMA 2000: IMT-CDMA Multi-Carrier, wideband that can support mobile data communications at speeds sorting from 144 Kbps to 2 Mbps.

Application Of Technology:

•     Consumer Oriented: Admired consumer claims include short messaging, instant messaging, picture messaging, mobile TV, music downloads, video downloads, online gaming with luxuriantly caused to be 3D graphics, and location-based services.
•     Business: The business client benefits from having high-speed data connectivity to the Internet and their virtual private network (VPN), and services such as sending and receiving e-mail with bulky attachments, push-to-talk and multimedia (PTT and PTM) functions.
•     Public Help: The over services are also valuable gear for the public sector, including national security, first-responder and public safety users. Providing worldwide access to telephony and Internet services is a key economic priority for most governments. Forward looking governments are taking full benefit of these services by connecting schools, hospitals, medical clinics, police stations and communities to CDMA2000 telecommunication networks........ to be cont...