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Advanced Antennas for Radio Base Stations 173

be designed to be uncorrelated. In that case, the transmitted intermodu-
lation signal is not directed into a narrow high-gain beam. The suppres-
sion of radiated power for the intermodulation signal with respect to
main beam power for the carrier signal will then be enhanced, and the
requirements on the individual power amplifiers are relaxed.

4.14 Conclusion

Advanced antennas may be deployed network-wide or at select base
station sites to improve capacity and extend coverage of current and
future cellular networks. The discussed advanced antenna technologies
are categorized in Table 4.4 in terms of uplink or downlink, capacity or
coverage, or a combination thereof according to their primary advantage
and usage in macro base station installations.
The use of advanced antennas is a way to achieve higher network
capacity by reducing interference spread in downlink and by utilizing
spatial separation in uplink. Various capacity-oriented antenna concepts
have been evaluated and tested in live cellular networks, proving that
advanced antennas increase the capacity of existing mobile communica-
tion networks. No new additional sites are introduced by a grow-on-site
strategy with site-by-site migration of advanced antennas.
Coverage solutions serve to increase the range of a network. Today,
the use of diversity and modular high-gain antennas already represent
cost-effective coverage solutions. Amplifier integrated antennas offer an
attractive solution, having simple installation with small volume, high
overall power efficiency, and high levels of equivalent radiated power.
These parameters are of great interest, especially in urban areas where
a denser network can be foreseen with increasing capacity and higher
data rate needs.

TABLE 4.4 Summary of Advanced Antenna Technologies
Advanced Antenna Technology Downlink Uplink Capacity Coverage
Three-sector omnidirectional • •
antenna
Higher order receive diversity • •
Transmit diversity • • •
Antenna beamtilt • • • •
Modular high-gain antenna • • •
Higher order sectorization • • •
Fixed multibeam array antenna • • •
Steered beam array antenna • •
Amplifier integrated sector antenna • •
Amplifier integrated multibeam • •
array antenna