scalable orthogonal frequency division multiple access (SOFDMA)

Scalable Orthogonal Frequency Division Multiple Access (SOFDMA) and normal OFDMA differ in the scalability of the subcarriers. SOFDMA was developed for Wireless Broadband (Wibro) and later adopted in Mobile-WiMAX.

The radio transmission method operates with constant subcarrier spacing and allocates the subcarriers dynamically. Depending on the bandwidth of the radio channels, such a transmission system operates with more or fewer subcarriers. For mobile WiMAX according to 802.16e, a subcarrier spacing of 10.94 kHz has proven to be optimal. Due to the variable radio channel widths, WiMAX can transmit with 128 to 2,048 subcarriers. With a radio channel width of 10 MHz, the downlink uses 1,024 subcarriers in which the synchronization signals and data are transmitted.

Because SOFDMA uses constant subchannel width, system complexity is simplified and performance data improves at higher channel bandwidths.

SOFDMA technology avoids degradation of radio channels due to Doppler effects or fading during multipath propagation. Therefore, this technology is particularly suitable for mobile radio transmission.