The unlicensed spectrum has plenty of bandwidth.
For instance, approximately 500 MHz and 7 GHz
bandwidths are available in the 5 GHz and 60 GHz
bands, respectively. In order for the 5G system to utilize
the unlicensed spectrum, regulations imposed
on each frequency band should be carefully reconsidered.
Representative examples of the regulations
are the Transmit Power Control (TPC), Dynamic Frequency
Selection (DFS), and Listen Before Talk (LBT).
To efficiently utilize the unlicensed spectrum, we will
develop the 5G system with the following characteristics.
First, we will design PHY/MAC/network algorithms
suitable for the nature of the unlicensed spectrum.
Since a wide range of frequency bands are included
in the unlicensed spectrum, each frequency band
has its own characteristics. Hence, band-specific
solutions will be provided.
Second, efficient coexistence mechanisms that take
into account other RATs (e.g., WiFi or WiGig) operating
in the unlicensed spectrum will be suggested.
Finally, techniques for interworking and integrating
the 5G system with other RATs will be developed. By
taking advantage of multiple RATs, the 5G system
will be able to take advantage of the unique characteristics
of each RAT and improve the practicality
of the system as a whole. For instance, the 4G system
is used for exchanging the control messages
to maintain the connection, to perform handover,
and to provide real-time services such as VoLTE.
The technology operating in mmWave unlicensed
frequency band would support the gigabit data rate
service. Multiple mmWave cells can be overlaid on
top of the underlying 4G macro cells, as shown in
Figure 18.