Spread‐spectrum systems
Nevio Benvenuto, Giovanni Cherubini, Stefano Tomasin · 2021
This chapter considers the two most common spread-spectrum techniques: direct sequence (DS) and frequency hopping. The most common applications of spread-spectrum systems, that are discussed in this chapter, may be enumerated as follow: multiple access, narrowband interference rejection, and robustness against fading. The chapter introduces a structure that is often employed in receivers for DS spread-spectrum signals. It also considers two equalizers for single-user detection: chip equalizer and symbol equalizer. To mitigate the interference in the signal sampled at the chip rate, after the chip matched filter a zero forcing or a mean square error equalizer can be used. Multiuser detection techniques are essential for achieving near-optimum performance in communication systems where signals conveying the desired information are received in the presence of ambient noise plus multiuser interference.