Abstract
To meet the requirements of beyond 5G networks, the significant amount of unused spectrum in sub-TeraHertz frequencies is contemplated for high-rate wireless communications. Yet, the performance of sub-TeraHertz systems is severely degraded by strong oscillator phase noise. We investigate in this paper the design of digital communications robust to phase noise. This problem is addressed in three steps: the characterization of the phase noise channel, the design of the optimum receiver, and the optimization of the modulation scheme. This paper proposes a joint performance and implementation optimization. First, we address the design of the demodulation scheme for phase noise channels and propose the polar metric, a soft-decision rule for symbol detection. It is shown that performance gains are achieved for coded and uncoded systems with valuable complexity reductions of the receiver. Second, we investigate the optimization of the modulation scheme for phase noise. We demonstrate that using a constellation defined upon a lattice in the amplitude-phase domain leads to significant performance gains and a low-complexity implementation. Thereupon, we propose the Polar-QAM scheme with efficient binary labeling and demodulation. Numerical simulation results show that the proposed modulation and demodulation schemes offer valuable solutions to achieve high-rate communications on systems strongly impaired by phase noise.
Highlights
With a specific demand for wireless connectivity, the current exponential data traffic growth will require within few years data rates above 100+ Gbit/s
The proposed schemes offer a valuable solution to realize high rate communications on practical systems impaired by strong phase noise (PN), and to meet the requirements of future sub-THz wireless communication systems
We have addressed the design of the optimum demodulation scheme for the Gaussian phase noise (GPN) channel
Summary
With a specific demand for wireless connectivity, the current exponential data traffic growth will require within few years data rates above 100+ Gbit/s. An analytical approach is conducted to demonstrate how optimal constellations can be built to maximize performance on the GPN channel Motivated by this theoretical analysis, we propose the polar quadrature amplitude modulation (PQAM or Polar-QAM), a PN robust modulation scheme based on a structured APSK. The constellation and the binary labeling of the Polar-QAM are jointly designed to improve the system performance on PN channels while maintaining a low-complexity implementation It enables to implement the symbol detection with a simple threshold comparison, and the soft-output demapper with piecewise linear functions. The model in Eq (1) can be adapted to include the propagation gain and phase shift of a frequency-flat channel with a single dominant path, the envisaged model for sub-THz scenarios This is achieved by integrating a complex coefficient h as follows r = h · s · e jφ + n, where h varies slowly. This work targets sub-THz applications and focuses on propagation channels with a single dominant path
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