'Introduction to wireless transmission' (Telecommunications, 2017), 'Introduction to Digital Wireless Communications', Chap. 1, pp. 1-11, DOI: 10.1049/PBTE072E_ch1 IET Digital Library, https://digital-library.theiet.org/;jsessionid=300r7p2gvg0e9.x-iet-live-01content/books/10.1049/pbte072e_ch1