Technologies for 3G wireless communications

Discusses and compares three prominent contenders for 3G wireless communication. These are: OFDM (orthogonal frequency division multiplexing), CDMA (code division multiple access) and MC-CDMA (multi-carrier CDMA) - a hybrid of the first two. OFDM has gained increasing acceptance as an alternative to single-carrier modulation for wireless systems. Potential exists for very high bit rates and for reaching the channel capacity even over frequency-selective fading channels. CDMA is the technique being most seriously considered for 3G wireless systems. It uses PN (pseudonoise) sequences to spread the signal spectrum to a wide band, thereby achieving greater robustness to deep fades than a narrowband signal, and the capability for multi-user access. The third technique, MC-CDMA, uses a combination of OFDM and CDMA, and has certain advantages that are pointed out. Finally, this paper touches upon an application, namely wireless video