- FQAM
One of key requirements for 5G is enhancement
of cell-edge performance, which means that every
user should be supported with Gigabit experience
anywhere. Conventional approaches to enhance
the cell-edge performance mainly focus on managing
interference (e.g., interference cancellation,
interference avoidance), by dealing with interference
as a Gaussian. However, it is proved that the
worst-case additive noise in wireless networks with
respect to the channel capacity has a Gaussian distribution.
From this observation, one can expect that
the channel capacity can be increased by a non-
Gaussian interference design which makes Inter-
Cell Interference (ICI) non-Gaussian. The distribution
of ICI depends on the modulation schemes of
the interfering BSs. Therefore, an active interference
design for improved cell-edge performance can be
achieved by applying a new type of modulation.
FQAM, a combination of Frequency Shift Keying
(FSK), and Quadrature Amplitude Modulation
(QAM) can be used as an active interference design
scheme. Figure 22 shows the signal constellation of
16-ary FQAM that is a combination of 4-ary FSK and
4-ary QAM.