Capacity Bounds for Dense Massive MIMO in a Line-of-Sight Propagation
Environment
Abstract
The use of large-scale antenna arrays grants considerable benefits in
energy and spectral efficiency to wireless systems due to spatial
resolution and array gain techniques. By assuming a dominant
line-of-sight environment in a massive MIMO scenario, we derive
analytical expressions for the sum-capacity.
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Then, we show that convenient simplifications on the sum-capacity
expressions are possible when working at low and high SNR regimes.
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Furthermore, in the case of a high SNR regime, it is demonstrated that
the Gamma PDF can approximate the PDF of the instantaneous channel
sum-capacity as the number of BS antennas grows. A second important
demonstration presented in this work is that a Gamma PDF can also be
used to approximate the PDF of the summation of the channel’s singular
values as the number of devices increases. Finally, it is important to
highlight that the presented framework is useful for a massive number of
Internet of Things devices as we show that the transmit power of each
device can be made inversely proportional to the number of BS antennas.