ABSTRACT
One of the most prominent OFDM systems is the IEEE 802.11a WLAN [2]. This OFDM version of the 802.11 standard systems (which are often termed “Wi-Fi”) is primarily used indoors, in the 2.4 and 5 GHz bands, but can also be used outdoors. For indoor systems, mobility is generally limited so that channel dynamics are slow and of little concern. Indoor channel dispersion due to multipath propagation can be significant though, particularly for the wider values of channel bandwidth, so our discussion on this phenomenon applies equally to indoor and outdoor channels. Although in principle OFDM/A could be used in nonterrestrial environments such as aeronautical and satellite systems, our focus here is on the outdoor setting for terrestrial communications, since most current attention is being given to these types of systems. We also limit ourselves to channels for conventional populated areas such as urban, suburban, and some rural environments; hence, we do not consider locations such as wilderness areas or maritime locations. Also worth pointing out is that OFDM/A can and is used in wired applications, for example [3], where it is often termed discrete multitone modulation. We do not consider such wired channels here.
