What does B3G Wireless Need?

Beyond 3G (B3G) wireless systems should deliver higher data transmission rates and more diverse
services than current 2- to 3G systems can. The all-IP wireless architecture has emerged as the most
preferred platform for B3G wireless communications. Therefore, the design of a future wireless air
interface has to take into account the fact that the dominant load in B3G wireless channels will be  high-speed burst-type traffic. The necessity to support such high-capacity bursty traffic in extremely
unpredictable wireless channels has already posed a great challenge to all existing air link technologies
based on TDMA or CDMA alike. Many research initiatives have been underway to investigate
the type of multiple access technologies that could be the most suitable for B3G wireless applications.
Some suggested that the current CDMA technologies, all based on direct-sequence (DS) CDMA, are
only suited for slow-speed continuous transmission applications such as voice services, but may not
be a good choice for high-speed burst type traffic in future all-IP B3G wireless systems. Therefore, a
new wave of worldwide research is underway to search for next generation multiple access technologies,
which should effectively address all the constraints and problems existing in current TDMA and
CDMA technologies, such as poor bandwidth efficiency, strictly interference-limited capacity, difficulties
in performing rate-matching algorithms, and complexity in implementing fast adaptive equalizers.
The study of next-generation multiple access technologies involves many cutting-edge research topics,
such as novel CDMA code design, time-frequency adaptive equalization, interference-free CDMA
architecture [781, 782], high-data-rate TDMA, Orthogonal Frequency-Division Multiplexing (OFDM)
techniques, and Multiple-Input Multiple-Output (MIMO) algorithms.