ABSTRACT
This chapter presents an overview of channel modeling for broadband communications. Because broadband communications require a large bandwidth, the channel models have to correctly reproduce the frequency selectivity of the channel; in addition, new techniques like smart antennas may also require knowledge of the directional properties of the channel. This chapter first reviews formal description methods for propagation channels, in particular the WSSUS (wide-sense stationary uncorrelated scattering) model. Next, we discuss various approaches for modeling such channels. Deterministic methods, like stored measurement results and ray tracing, are suitable for site-specific channel modeling and network planning, while stochastic methods, like tapped delay lines and geometry-based stochastic channel models,
are better for the simulation of algorithms and systems. Next, we give an overview of typical values for channel parameters, e.g., delay spread, angular spread, and arrival time statistics. Those values strongly depend on the operating environment; for example, the delay spread typically attains 10 ns in residential buildings, while it can easily reach 10 µs in urban macrocells. A summary of channel models that have been adopted by international standards organizations for systems like GSM (second-generation cellular), W-CDMA (third-generation cellular), IEEE 802.11 (wireless local area networks), and IEEE 802.15.3a (ultrawideband systems) concludes the chapter.
