The parameters of channel models are traditionally determined using measurements. Thus, it is critical to understand the connection between channel measurements and channel models. This will address two important questions: (1) How to use the channel measurements in estimating model parameters? Or how to fit the models to the measurements? And (2) what kind of measurements we need to make to measure the various model parameters. Finally, understanding this relationship will also help in propagating the uncertainties in channel parameters obtained from the measurements in the models. This chapter starts with a general physical model which is a specialization of the general model introduced in Chapter 2 to the practical case of uniform linear arrays. A sampled representation of the physical model serves as a starting point for connecting measurements and models, followed by techniques for high-resolution parameter estimation that can improve on the sampled representation.

Device-to-device (D2D) radio channels have fundamentally different properties compared to those of conventional cellular (device-to-infrastructure, D2I) channels. The main reason for this is that most often both the receive antenna and the transmit antenna are located at low heights, and hence there is more interaction with objects in the close neighborhood of the devices. Also, UE mobility, human presence, and finite multipath persistence are the principal factors that degrade link availability. Such models are the focus of this chapter.

Frequencies from 100 GHz to 3 THz are promising bands for the next generation of wireless communication systems because of the wide swaths of unused and unexplored spectrum. Terahertz wireless communications have two key advantages that can be combined to achieve very high data rates. First, the usable frequency band around each frequency is much larger, so each channel can have a much higher data rate. This alone can increase data rates to several hundreds of Gbit/s, but spatial multiplexing is still needed to reach Tbit/s data rates. Fortunately, THz frequencies allow smaller antennas and antenna spacing, which provides for more communication channels within the same array aperture within a chip package. However, to unlock THz wireless communications potential, several challenges in channel measurements and modeling need to be addressed, including antenna design, diffraction, reflection, and scattering. This chapter covers what is known to date in this new area.

Channel sounder verification ensures that participants measure and report channel characteristics that are due to the environment as opposed to measurement artifacts arising from the use of a suboptimal configuration, from nonidealities in the sounder hardware, or from errors in analysis and/or postprocessing. The participants in the 5G mmWave Channel Model Alliance have established a channel sounder verification program. The program allows labs to compare their measured, processed data to theory or to an artifact having known characteristics. Three types of verification are illustrated: “in-situ,” “controlled condition,” and “comparison-to-reference” verification.

The 5G mmWave Channel Model Alliance was formed to take a longer view by addressing issues related to measurement and modeling that impede progress in standards development and hardware optimization. There is a strong link between the modeling and measurement communities. The extent to which the sounder captures the channel’s features will depend on the hardware employed and how well that hardware works, which is why verification is the focus of the first part of this book. The second part of this book describes the main mmWave models that have been presented in the literature, including tapped delay-line stochastic models, geometry-based stochastic channel models, and quasi-deterministic models.

This chapter provides basic knowledge on technologies and circuits for future communication systems. Based on upcoming mm-wave communications, system requirements are derived. E.g. link analysis is used to visualize the need for high-gain antenna systems, which are further investigated in different scenarios such as stationary and mobile use cases. The chapter further gives an overview on different tunable circuits and devices such as phase shifters for antennas systems or tunable filters. The chapter feastures an overview of different technologies available to implement the required fuinctionality. The individual technologies will be described in full detail in later chapters

Chapter 1 aims to give an overview of recent developments in new platforms and technologies and explores their implications in communications, including future mobile traffic, the 5G vision, trends in satellite communication platforms, spectrum allocation, key technology drivers, markets and perspectives.

This chapter describes tunable circuits in CMOS and BiCMOS technologies. First, active and passive basic components are briefly described: MOS and bipolar transistors, and passive components like MOM capacitors, and transmission lines. Slow-wave transmission lines are described and compared to their microstrip lines counterparts, in terms of electrical performance and footprint. Next, tunable components are introduced,varactors and switches, anddigital tunable capacitors. Then, tunable transmission lines are described. Some examples of tunable inductances are also highlighted. Finally, two families of tunable circuits are addressed, phase shifter and VCOs, respectively. Both circuits are used in many systems for beam-forming/steering concerning phase shifters, and transceivers concerning VCOs, respectively. Many design examples are given. Topologies based on the use of lumped components (varactors and inductances) are compared to those based on distributed components (tunable transmission lines). In the middle, hybrid approaches mixing lumped and distributed components can lead to very efficient solutions, both in terms of electrical performance and footprint.