Trends and challenges in broadband wireless access

This paper gives an overview of broadband wireless access systems, discusses the current trends, and highlights the major technical challenges for future systems. The study covers local multipoint distribution service (LMDS) networks that operate at millimeter wave radio frequencies above 20 GHz, as well as broadband wireless access at microwave frequencies below 11 GHz. We outline the current standardization work in this field by the ETSI in Europe and the IEEE 802.16 Group in the US. We point out that one of the major problems is the intercell interference which limits the frequency reuse factor and the cell capacity. We address the issue of increasing cell capacity using adaptive modulation, code-division multiple access (CDMA), and adaptive antennas. We also discuss the basic transmission technologies for lower frequency bands (below 11 GHz) where a significant amount of multipath propagation must be compensated