 for purposes of disaster recovery or to sup- port network diversity, and it even supports mobile services. In addition, in the developing world, BFWA can be deployed more quickly and cost-effectively than traditional wired broadband technologies. IEEE 802.16 (WiMax) The global IEEE 802.16 standard, known as the IEEE WirelessMAN air interface standard, was the first broadband wireless access standard from an accredited Chapter 15 WMANs, WLANs, and WPANs standards body. It is commonly referred to as WiMax (Worldwide Interoperability for Microwave Access). WiMax is designed from the ground up to provide wireless last-mile broadband access in MANs, and it represents an evolution to a standards- based, interoperable, carrier-class solution. Unlike Wi-Fi (discussed later in this chapter), which targets the end user, WiMax has been developed as the basis of a carrier service. The most exciting aspect of WiMax is the evolution to mobility. The main advantages of WiMax include the ability to provision services quickly, the avoidance of costly installations, and the ability to overcome the phys- ical limitations associated with wired infrastructures. By providing a standards- based, cost-effective, and flexible technology, WiMax can fill the existing gaps in broadband coverage and create new forms of wireless broadband services. WiMax channel bandwidth is adjustable from 1.25MHz to 20MHz. The actual transmission rate of the channel is determined by the modulation technique used. Therefore, the bandwidth efficiency of a channel is determined by the bandwidth of the assigned channel and the modulation technique used. This is an important feature for carriers operating in licensed spectrum. The tradeoff is that the more efficiently the transmitter encodes a signal, the more impact noise and interference impairments have on the signal. The WiMax standard defines six modulation techniques that result in varying levels of bandwidth efficiency: BPSK, QPSK, 16-QAM, 64-QAM, OFDM (256- subcarrier OFDM that also conforms to the ETSI