Contents I. Introduction
Broadband wireless link using the upper millimeter-wave (MMW) band has recently been attracting significant interest among a diverse group comprising telecommunications carriers, mobile telephone and data network operators, broadcasters, consumer electronics manufacturers, enterprise users, and others, because of its gigabit-class data transmission capability. For indoor applications, gigabit-class 60-GHz-band wireless standards, such as WirelessHD and IEEE802.15.3c, have been established, and a WirelessHD system has achieved 4.0Gbit/s and already been integrated into television systems [1]. For outdoor applications, TV program relay broadcast and high-speed backhaul services for mobile communications appear to be the most promising applications, because the data rate necessary for these applications is increasing in proportion to the broadband trend in high-definition video or new mobile services. The 60-GHz-band and -band wireless link can achieve a data rate from 1.0 to 2.5 Gbit/s, and they have been actually used in the mobile backhaul services. It is expected that the over-10-Gbit/s data rate will be required for mobile backhaul in the near future.
