Quadrature-division multiple access

Quadrature-division multiple access (QDMA) is a radio protocol.[1] The term combines two standard terms in telecommunications, CDMA and QPSK.

Applications

QDMA is used for local area networks, usually wireless short-range such as WiMax. CDMA and QDMA are especially suitable for modern communications, for example, the transmission of short messages such as SMS 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 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.

References
  1. Held, Gilbert (2005). Wireless mesh networks. CRC Press. p. 44. ISBN 978-0-8493-2960-9.

Further reading
  • John G. Proakis, Digital Communications, Third Edition, McGraw-Hill, ISBN 0-07-051726-6
  • Ulrich L. Rohde, Jerry Whitaker, T. T. N. Bucher, Communications Receivers, Second Edition, McGraw-Hill, ISBN 0-07-053608-2
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