Enhancement: Enhancements In WiMAX

OFDM

OFDM stands for Orthogonal Frequency Division Multiplexing; it’s a technology that provides the operator to beat the challenges of Non-Line-of-Sight (NLOS) transmission in the more efficient manner. OFDM waveform put forward the advantage of functioning with the larger delay spread of the NLOS background. With the excellent quality of OFDM functionality, time and use of a cyclic prefix and its also removes the Inter Symbol Interference (ISI) complications of adaptive equalization. Multiple narrowband orthogonal carriers composed because of OFDM waveform, localizing selective fading to a subset of carriers that are comparatively simple to equalize. A comparison between an OFDM signal and a single carrier signal, with the information being sent in parallel for OFDM and in series for single carrier are shown in Fig: 5. (WiMAX Forum)

The facility to remove delay spread, Inter Symbol Interference (ISI) and multi-path in a proficient manner allows for higher data rate throughput. It is simpler to equalize the individual OFDM carriers than it is to equalize the broader single carrier signal. For these entire reasons modern international standard such as those set by IEEE 802.16, have created OFDM as the ideal technology.  (WiMAX Forum)

Fig 5: Serial datastream renewed to symbols (each symbol = 1 or more data bits)  (WiMAX Forum)

See Also:

WiMAX & IMT-Advanced

Power Control & Error Detection

Sub Channelization & Transmission Diversity

Antennas & Adaptive Modulation