Broadband wireless access (BWA) at frequencies below 11 GHz is an interesting technology, particularly for new operators without an existing wired infrastructure. The frequencies available for this type of networks include the 2.5 GHz microwave multipoint distribution service (MMDS) band in the US, the 3.5 GHz band all across Europe, and the 10 GHz which is available in a number of countries. There are also license-exempt frequency bands at 2.5 GHz and 5 GHz. First-generation BWA systems are today in the field, but their deployment is still very modest compared to DSL and cable modem technologies. To foster the mass deployment of BWA systems, the IEEE 802.16 and ETSI BRAN groups have recently developed technical specifications for interoperable systems.

Unlike BWA systems operating at millimeter-wave frequencies (usually referred to as LMDS systems), BWA systems operating at microwave frequency bands below 11 GHz are non-line-of-sight and require a transmission technique that is very robust to multipath propagation. The IEEE 802.16a specifications for BWA at licensed frequency bands between 2 and 11 GHz include three different transmission and multiple access techniques, namely single-carrier transmission with frequency-domain equalization (SCT/FDE), orthogonal frequency-division multiplexing with time-division multiple access (OFDM/TDMA), and orthogonal frequency-division multiple access (OFDMA). But although the ETSI BRAN group has significantly harmonized its specifications with those of the IEEE 802.16, its specifications are restricted to the OFDM/TDMA mode.

In this talk, we give a general presentation of BWA at frequencies below 11 GHz, describe the technical challenges, highlight the current trends, and discuss the potential technologies. In particular, we highlight the fact that the main issue in these systems is frequency-domain processing vs. time-domain processing rather than OFDM vs. single-carrier transmission, which is the traditionally debated issue.

Hikmet Sari received his engineering degree and his Ph.D. from the ENST, Paris, France, in 1978 and 1980, respectively. He also received the post-doctoral Habilitation degree from the University of Paris XI in January 1992. From 1978 to 1989, he was with the Philips Research Laboratories, first as research engineer and later as group supervisor. He was a Department Head at the SAT Telecommunications Division from 1989 to 1996 and R&D Director for Radio Communications at Alcatel from September 1996 to April 2000. From May 2000 to November 2002, he was Chief Scientist at Pacific Broadband Communications, which was acquired by Juniper Networks in December 2001. He is currently a Professor and Chair of the Telecommunications Department at the Ecole Supérieure d'Electricité (Supélec), near Paris. Over the past 25 years, he has been a major contributor to the field of digital communications and he has published some 140 journal and conference papers. Dr. Sari was Editor for Channel Equalization of the IEEE Transactions on Communications from 1987 to 1991. He served as a Guest Editor of the European Transactions on Telecommunications in 1993 and of the IEEE Journal on Selected Areas in Communications in 1999. He was on the Editorial Board of the Annals of Telecommunications from 1994 to 1997 and an Associate Editor of the IEEE Communications Letters from 1999 to 2002. In 1995, he was elected to the IEEE Fellow Grade and he received the Andre Blondel Medal from the French Electrical & Electronics Engineering Society SEE. He was Technical Program Chair of the 2004 IEEE International Conference on Communications (ICC 2004). He was the recipient of the Edwin H. Armstrong Achievement Award in 2003. He is currently serving as Distinguished Lecturer and Member of the Fellow Evaluation Committee of the IEEE Communications Society and also as Vice-Chair of ICC 2006.