Quadrature-division multiple access (QDMA) is a radio protocol. The term combines two standard terms in

telecommunications Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that fe ...

CDMA Code-division multiple access (CDMA) is a channel access method used by various radio communication technologies. CDMA is an example of multiple access, where several transmitters can send information simultaneously over a single communicatio ...

and

QPSK Phase-shift keying (PSK) is a digital modulation process which conveys data by changing (modulating) the phase of a constant frequency reference signal (the carrier wave). The modulation is accomplished by varying the sine and cosine inputs at ...

Applications

QDMA is used for

local area network A local area network (LAN) is a computer network that interconnects computers within a limited area such as a residence, school, laboratory, university campus or office building. By contrast, a wide area network (WAN) not only covers a larger ...

s, usually wireless short-range such as

WiMax Worldwide Interoperability for Microwave Access (WiMAX) is a family of wireless broadband communication standards based on the IEEE 802.16 set of standards, which provide physical layer (PHY) and media access control (MAC) options. The WiMAX ...

. CDMA and QDMA are especially suitable for modern communications, for example, the transmission of short messages such as

SMS Short Message/Messaging Service, commonly abbreviated as SMS, is a text messaging service component of most telephone, Internet and mobile device systems. It uses standardized communication protocols that let mobile devices exchange short text ...

or MMS; communication when in motion (from cars, trains, etc.); the establishment of unplanned links.

Benefits over TDMA and FDMA

The traditional TDMA and

FDMA Frequency-division multiple access (FDMA) is a channel access method used in some multiple-access protocols. FDMA allows multiple users to send data through a single communication channel, such as a coaxial cable or microwave beam, by dividing ...

require a lot of overhead to set a link parameter with a new user, or to detect that a user left and their allocation is free to be allocated to another. In CDMA or QDMA, a new user is simply allocated a new code and is ready to go. It may impose a slight load on the spectrum, but the system is so devised as to absorb a controlled measure of collisions and continue operations at a high level of quality of service.

Applications

Benefits over TDMA and FDMA

References

Further reading