The wireless industry is undergoing a major evolution from narrow-band, circuit-switched legacy systems to broadband, IP-centric platforms. A common theme in this broadband evolution is the use of OFDM modem and open network architectures. This chapter discusses the modern view of packet-based broadband wireless communications and their associated challenges. We will cover some of the latest technological advances in digital broadcasting, wireless local area network (LAN), and beyond 3rd generation mobile networks. The roles of OFDM modem and MAC protocols in an air interface are described. These modules must be synergistically integrated in order for the network to (1) achieve high spectral efficiency per unit area (bit/s/Hz/square-meter), and (2) to meet the anticipated peak throughput requirements for multimedia traffic.
OFDM has become one of the most exciting developments in the area of modern broadband wireless networks. Although the notion of multicarrier transmission or multiplexing (e.g., frequency-division multiplexing - FDM) can be dated back to 1950s, high spectral efficiency and low cost implementation of FDM became possible in the 1970s and 1980s with advances in Digital Fourier Transform (DFT). It is not until the 1990s that we witnessed the first commercial OFDM-based wireless system – the digital audio broadcasting (DAB) standard. A few historical notes are listed below