CDMA: Code Division Multiple Access

Code Division Multiple Access (CDMA) is a cellular technology defined by Qualcomm in IS-95 and IS-2000.Other widely used multiple access techniques for cellular are Time Division Multiple Access (TDMA) and Frequency Division Multiple Access (FDMA).

CDMA is a form of Direct Sequence Spread Spectrum communications. In general, Spread Spectrum communications is distinguished by three key elements: 1) The signal occupies a bandwidth much greater than that which is necessary to send the information, which results in immunity to interference and jamming and multi-user access; 2) The bandwidth is spread by means of a code which is independent of the data; 3) The receiver synchronizes to the code to recover the data. The use of an independent code and synchronous reception allows multiple users to access the same frequency band at the same time.

Due to increasing market demand for a convered network for both voice and data cpmmunications, CDMA technologies are evolving into CDMA2000 to meet the challenges. CDMA2000 is the 3rd Generation solution based on IS-95. Unlike some 3G standards, It is an evolution of an existing CDMA wireless standard. CDMA2000 supports 3G services as defined by the International Telecommunications Union (ITU) for IMT-2000. The goal is access to any service, anywhere, anytime from one terminal - true converged, mobile services.

The term Code Division Multiple Access (CDMA) is also widely used to refer to a key technology in the Universal Mobile Telecommunications System (UMTS). The two different uses of this term can be confusing. Actually, the Qualcomm standard CDMA and UMTS have been competing for adoption in many markets.