Background
Wireless broadband data communication is experiencing a rapid expansion, and WiMAX equipment sales are expected to hit US$3 billion by 2009. Mobile data communication revenues, in particular, already account for at least 20-30% of carriers' revenues in many affluent countries. To keep up with this noteworthy growth in the demand for wireless broad-band, new technologies and architectures are needed to greatly improve system performance and network scalability while significantly reducing the cost of equipment and deployment.