Resumo:
The emerging mobile communication systems towards an unprecedented evolution in
terms of flexibility, data rate, and latency, enabling wireless networks to support applications
that are typically backed by wired technologies. The next generation of mobile
communication is already being discussed by the scientific community, standardization
institutes, and players in the mobile communication market. The foreseen scenarios are
already beginning to be outlined, anticipating that they might be even harder to achieve
considering the expected increase in flexibility while supporting conflicting requirements
across several applications in different verticals, besides higher data rates, broader coverage,
wider frequency bands, and extreme low latency. It is clear that future mobile
networks cannot rely on a single radio access network to meet all these demands. Different
approaches are needed to address all requirements, but SM (Spatial Multiplexing)-
MIMO (Multiple-Input Multiple-Output) schemes represent a key technology for most
future wireless systems. SM-MIMO can provide the necessary bandwidth, reducing the
frame duration and increasing the robustness for data with a very short life span. Furthermore,
integrating SM-MIMO systems with advanced detection schemes, that leverage
both diversity and multiplexing gains, can substantially boost throughput and extend
coverage area. Usually, MIMO schemes are combined with OFDM (Orthogonal Frequency
Division Multiplexing) to deal with double-dispersive channels, assuming that the channel
coherence time is larger than the duration of the OFDM block and the channel coherence
bandwidth is larger than the subcarrier bandwidth. However, OFDM presents limitations
that could hinder its applications in future mobile systems. High OOB (Out-of-Band)
emissions, low flexibility in terms of parameterization, and low spectral and energy efficiencies
for channels with large delay profiles are some examples of these restrictions.
In this sense, GFDM (Generalized Frequency Division Multiplexing) can be considered a
feasible alternative. However, a challenge arises when considering non-orthogonal MIMOGFDM
since conventional linear detectors exhibit higher complexity and inferior performance
compared to MIMO-OFDM systems. Consequently, there is a compelling need
to explore non-conventional detectors that simultaneously reduce complexity while aiming
for performance enhancement. For this end, this thesis reviews fundamental concepts
in linear estimation and detection techniques, providing a straightforward algorithmic
description that enables complexity comparison and performance simulation. This work
adapts the low complexity and low latency iterative MMSE (Minimum Mean Squared Error)-
PIC (Parallel Interference Cancelation) introduced in [1], designing and simulating
its performance in a practical 6G (Sixth Generation) transceiver for the eRAC (Enhanced
Remote Area Communications) scenario, a challenging task assuming a non-orthogonal
GFDM waveform. The final results, presented in this work, show that MIMO-GFDM is
an interesting approach to deal with very contrasting and challenging requirements in
mobile networks. As a result, the pragmatic assessment of theoretical concepts, validated
through simulations, is interesting to the scientific community, as it demonstrates the
potential improvements that the adoption of a new technology can achieve. Furthermore,
this work provides a versatile computational model, which is an essential tool and also a
reliable reference for hardware development and performance evaluation.