19-01-2013, 04:29 PM
WIMAX Physical Layer Implementation
ABSTRACT
WIMAX (World Wide Interoperability for Microwave Access) is a Broad band wireless technology similar to BLUE TOOTH. This technology is using for Mobile Internet access at 75 Mbps, 20MHz. It is based on the IEEE 802.16d Standard. This standard specifies the air interface of fixed broadband wireless access systems supporting multimedia, mobile internet, VOIP and satellite communication. The operation frequency range of WIMAX is 2-11GHz. Three alternative modulation techniques such as BPSK/QPSK/QAM are used for OFDM (Orthogonal Frequency Division Multiplexing) Modulation and De-modulation. This standard uses carrier sense multiple access with a collision avoidance medium access mechanism. WIMAX supports peer to peer, star and point to multipoint topologies.
Physical Layer Implementation: The text is the input to down link conversion. The Scrambling, Turbo coding, Interleaving, QPSK Modulation, Pilot modulation and Frequency to time domain conversion generates Real and Imaginary co-efficients. These co-efficients are the input to Uplink. The reverse operation gives the text as output. The transmission is named as Downlink conversion because inverse FFT is used in modulation. The Real Time output waveforms of Downlink conversion are viewable on CRO.