OFDM
OFDM is a digital encoding and modulation technology. It has been used successfully in wire-line access applications, such as DSL modems and cable modems as well as WiFi. Products from WiMAX Forum member companies are using OFDM-based 802.16 systems to overcome the challenges of NLoS propagation. OFDM achieves high data rate and efficiency by using multiple carrier signals instead of just one. All future 4G technologies will be based upon OFDM. Orthogonal Frequency Division Multiple Access (OFDMA) is enhanced OFDM and used in Mobile WiMAX technology and the IEEE 802.16e-2005 standard, and it is the foundation for the next-generations of mobile broadband to come. It is a multi-user version of Orthogonal Frequency-Division Multiplexing (OFDM). The difference between the two technologies is that OFDMA assigns subsets of sub-carriers to individual users allowing simultaneous low data rate transmission from several users.
