Wednesday, October 01, 2008

OFDMA

Orthogonal Frequency Division Multiple Access (OFDMA) is a multiple access scheme for OFDM systems. It works by assigning a subset of subcarriers to individual users.OFDMA featuresOFDMA is the 'multi-user' version of OFDM Functions by partitioning the resources in the time-frequency space, by assigning units along the OFDM signal index and OFDM sub-carrier index Each OFDMA user transmits symbols using sub-carriers that remain orthogonal to those of other users More than one sub-carrier can be assigned to one user to support high rate applications Allows simultaneous transmission from several users ⇒ better spectral efficiency Multiuser interference is introduced if there is frequency synchronization error The term 'OFDMA' is claimed to be a registered trademark by Runcom Technologies Ltd., with various other claimants to the underlying technologies through patents. It is used in the mobility mode of IEEE 802.16 Wireless MAN Air Interface standard, commonly referred to as WiMAX.

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