Spread-spectrum techniques for wireless communication

The primary goal of this paper is to provide a concise introduction to the use of spread spectrum in wireless communications. The symbiotic relationship between wireless communications and digital microelectronics is also developing rapidly. Indeed, mobile and personal communications is now at parity with the computer industry as a major driver in the development of high-speed, low-power integrated circuits. Underlying this is the deep relationship between the theories of signal processing and communication. This is the motivation behind the second objective of this article: to present the concepts and capabilities of spread spectrum so that engineers versed in DSP can quickly grasp its utility and exploit opportunities for further advancing the performance of spread-spectrum systems. To these ends, we first present a simple digital communication system that operates in discrete time. Then we build upon this model to show the basic concepts and resulting benefits of spread spectrum. Then we introduce the two basic spread-spectrum techniques of direct-sequence (DS) and frequency hopping (FH), followed by two methods that have been recently proposed. Next we present simple models for the multipath fading channel, and introduce solutions employing both DS and FH techniques. We then briefly discuss descriptive links to other nonspread modulation techniques and conclude with a brief introduction to the literature for further investigation by the reader.