Introduction to Ultra-Wideband Communications
The recent rapid growth in technology and the successful commercial deployment of wireless communications are significantly affecting our daily lives. The transition from analog to digital cellular communications, the rise of third-and fourth-generation radio systems, and the replacement of wired connections with Wi-Fi and Bluetooth are enabling consumers to access a wide range of information from anywhere and at any time. As the consumer demand for higher capacity, faster service, and more secure wireless connections increases, new enhanced technologies have to find their place in the overcrowded and scarce radio frequency (RF) spectrum. This is because every radio technology allocates a specific part of the spectrum; for example, the signals for TVs, radios, cell phones, and so on are sent on different frequencies to avoid interference to each other. As a result, the constraints on the availability of the RF spectrum become more and more strict with the introduction of new radio services.
Ultra-wideband (UWB) technology offers a promising solution to the RF spectrum drought by allowing new services to coexist with current radio systems with minimal or no interference. This coexistence brings the advantage of avoiding the expensive spectrum licensing fees that providers of all other radio services must pay. 
This chapter provides a comprehensive overview of ultra-wideband communications, starting with its history and background. Next the discussion turns to the concepts behind UWB technology, as well as its advantages and challenges in wireless communications. The chapter also eliminates the common misconception about UWB and spread spectrum, and it examines the strengths and weaknesses of ultra-wideband compared to narrowband and wideband communications. Further, the single-band and multiband approaches that are two major UWB techniques under consideration for IEEE standardization are explained. Next we discuss the current Federal Communications Commission (FCC) regulations for UWB deployment in the United States and briefly address worldwide regulatory efforts. The chapter ends with a concise overview of UWB applications; we present a detailed discussion of present and future UWB applications and their potential markets in Chapter 5.