Implementation of a low complexity structure for MIMO-GFDM receivers based on the interference cancellation technique

Abstract

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.