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Chapter 5 231

yellow and green. All transmitters and receivers in the system communicate with each other to
synchronized signals. The latter signal processing lets increase the maximum number of
identified targets, achieve higher spatial resolution, enhance interference suppression, etc. We
stop here since this topic is far beyond the scope of this book and more related to signal
processing than antenna design. The reader may consult an excellent overview in [3]. Note that
application of MIMO technology in radio link systems like mobile communication increases
their capacity significantly [11]. MIMO systems benefit from complex multipath propagation,
which is demonstrated schematically in Figure 5.3.6. Such multipath systems are more complex
and must be supported by highly sophisticated signal processing. The reader can find more
information about requirements and designs of the antenna for MIMO communication systems
in [4].

18
5.3.6 5G (Fifth-Generation) Wireless Network and “Golden Rush” of MIMO
According to [40], “… The next mobile standard known as 5G is right on the horizon.
Companies are already actively developing and testing designs for this next generation
technology. Achieving the full 5G vision brings significant new challenges for the cellular
industry to solve. With technologies such as massive MIMO, beamforming, network slicing
and virtualization comes unprecedented complexity.” Table 5.3 summarizes shortly the mobile
standard evolution and services provided.

Table 5.3

1 It depends on designated frequency band (in GHz) that might be 27.5 - 28.35, 37 - 37.6, 37.6 - 38.6, 38.6
3
2
- 40, and 64 - 71. FDMA stands for Frequency Division Multiple Access. TDMA stands for Time
Division Multiple Access. CDMA stands for Code Division Multiple Access. IPv4 uses 32 bits for its
5
4
Internet addresses. That means it can support 2 IP addresses — around 4.29 billion. Almost 2 billion
32
6
Web pages are accessible now that is dangerously close to this limit. IPv6 utilizes 128-bit Internet
addresses. Therefore, it can support practically unlimited number of IP addresses - 2 128 of them to be exact.
The significant words in the above citation for us as antenna and microwave professionals are
“massive MIMO and beamforming.” Looking at the footnotes to Table 5.3 we see that 5G
network frequencies are shifted to the range of mm-range wavelengths between 4.22mm (71
GHz) and 10.9mm (27.5 GHz). Note that the highest frequency band in 4G systems is 5.7 GHz
or = 52.6 mm. As we showed in Section 5.2.11 of this chapter (see the equity (5.54)), the

18 Golden rush is a rapid movement of people, i.e. engineers, to a newly discovered goldfield, i.e. 5G
massive MIMO.