CDMA stands for Code Division Multiple Access. It is a channel access method which is used by several radio communication technologies. It is a digital cellular technology and an example of multiple access. It is generally used for mobile communication.
Multiple access means that several transmitters can send information simultaneously over a single communication channel. In this system, different CDMA codes are assigned to different users, and the user can access the whole bandwidth for the entire duration. It optimizes the use of available bandwidth as it transmits over the entire frequency range and does not limit the user's frequency range.
Thus, CDMA allows several users to share a band of frequencies without undue interference between the users. It is used as an access method in many mobile phone standards.
It is based on the spread spectrum technology and makes optimal use of the available bandwidth. Since it uses the spread spectrum technology, hence allows each user to transmit the data over the entire frequency spectrum at any time.
The CDMA channel is nominally 1.23 MHz wide. CDMA networks use a design known as soft handoff, which makes smaller signal breakup as a handset develops from one cell to another. The set of digital and spread spectrum modes provides multiple times as few signals per unit of bandwidth as analog modes.
CDMA is appropriate with different cellular technologies. This allows nationwide roaming. The original CDMA standard is also referred to as CDMA One. It provides a transmission speed of only up to 14.4 kilobits per second in its channel form and up to 115 Kbps in an eight-channel form. CDMA2000 and Wideband CDMA (W-CDMA) deliver information several times quicker.
There are various uses of CDMA, which are as follows −
It is used in the Global Positioning System (GPS).
It is used by several mobile phone companies (e.g. Qualcomm standard IS-2000, also known as CDMA2000)
W-CDMA is used in UTMS 3G mobile phone standard.
CDMA has been used in the OmniTRACS satellite system for transportation.
It uses a fixed frequency spectrum in an efficient way.
There is no limit on the number of Users.
It provides a flexible allocation of resources.
It is compatible with other cellular technologies; hence it allows nation-wide roaming.