Low Complexity Millimeter Wave Point-to-point Communication: Interference Assessment of BPSK vs QPSK Decomposition

Abstract

The Information Age is far from slowing down. Along with the explosion in wire- lessly connected devices, a giant amount of data is being generated at a pace that we never witnessed before. Not only this information can be stored, but also streamed for numerous applications. All these changes in the paradigm demanded new approaches for wireless com- munications. In the recent studies, Massive Multi-Input Multi-Output systems (mMIMO), with hundreds or thousands of communicating antennas, are the most prevalent candidates to the evolution of wireless communications. Despite these systems' advantages, the joint optimization of spectral and energy e±ciencies is only achieved by combining multilevel modulations and e±cient power ampli¯cation. To reach this target, a transmitter employing high order modulations can spread the information into several ampli¯cation branches, which will process only the result of the decomposition of the multilevel constellation symbols into quasi constant envelope signals. The decomposed signals are then sent in parallel, assuming a fully connected architecture, where each Radio Frequency (RF) chain is connected to a single antenna. The original constellation symbol will be re-generated over the ai, so this composition can be adjusted according to the direction in which the antenna array is optimized. The performance of this architecture is studied, comparing the adoption of symbol decomposition using Binary Phase Shift Keying (BPSK) components or Quadrature Phase Shift Keying (QPSK) components. Additionally, the high number of antennas involved in this type of communication causes the channel matrix size to increase, augmenting the complexity of the equalization process, which can increase power consumption and latency. We studied the combination of a multi-layer transmitter with a low complexity receiver based on an Iterative Block Decision Feedback Equalizer (IBDFE). This receiver avoids the matrix inversion operation in the equalizer feed-forward by replacing it with an Equal Gain Combiner (EGC) or a Maximum Ratio Combiner (MRC) module. Results show that this architecture can be used without penalties on performance, provided that the number of communicating antennas is high.