tailieunhanh - Mobile and wireless communications physical layer development and implementation Part 3

Tham khảo tài liệu 'mobile and wireless communications physical layer development and implementation part 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Wireless Communications and Multitaper Analysis Applications to Channel Modelling and Estimation 31 Proper statistical interpretation of specular component Hsp is much less developed in MIMO literature despite its applications in optics and random surface scattering Beckmann and Spizzichino 1963 . The specular components represent an intermediate case between LoS and a purely diffusive component. Formation of such a component is often caused by mild roughness therefore the phases of different partial waves have either strongly correlated phases or non-uniform phases. In order to model contribution of specular components to the MIMO channel transfer function we consider first a contribution from a single specular component. Such a contribution could be easily written in the following form Ps Hsp a Wa b w H Ị 25 NTNR Here Psp is power of the specular component Ị ỊR jỊI is a random variable drawn according to equation 20 from a complex Gaussian distribution with parameters mi jmQ ơj aQ and independent in-phase and quadrature components. Since specular reflection from a moderately rough or very rough surface allows reflected waves to be radiated from the first Fresnel zone it appears as a signal with some angular spread. This is reflected by the window terms wa and Wb van Trees 2002 Primak and Sejdic 2008 . It is shown in Primak and Sejdic 2008 that it could be well approximated by so called discrete prolate spheroidal sequences DPSS Percival and Walden 1993b or by a Kaiser window van Trees 2002 Percival and Walden 1993b . If there are multiple specular components formed by different reflective rough surfaces such as in an urban canyon in Fig. 1 the resulting specular component is a weighted sum of 25 like terms defined for different angles of arrival and departures Hsp E PẻR a w k bfc Wb k H Ịk 26 It is important to mention that in the mixture 26 unlike the LoS component the absolute value of the mean term is not the same for different elements of the matrix Hsp. .