Communication systems play a major role in the modern society. Since the 1990ies especially wireless communications is of increasing interest worldwide. For the definition of such systems lots of aspects need to be taken into consideration. Among others, frequency band allocation, efficient use of radio and network resources, number of sites required to provide radio coverage, targeted user service characteristics like maximum bit rate and quality and last but not least cost of implementation.

After a short presentation of the wireless communications history, the characteristics of the terrestrial mobile radio channel are introduced.

This is followed by a discussion of the key components of wireless communication systems. Specifically, aspects such as the digital tranmsission over the mobile radio channel, multiplexing and multiple access, etc. are covered.

In the next chapter, we discuss and compare the mobile communication standards GSM (Global System for Mobile Communications - 2G), UMTS (Universal Mobile Telecommunications Standard - 3G), LTE (Long Term Evolution - 4G) and NR (New Radio- 5G). A special focus is on the lower layer specifications for these systems. For UMTS we discuss spread spectrum systems and for LTE we give an introduction to OFDM.

Finally we have a brief look to market figures and discuss actual developements of wireless communication systems.