Inter-Numerology Interference Management With Adaptive Guards: A Cross-Layer Approach

Abstract

The next-generation communication technologies are evolving towards increased flexibility in various aspects. Although orthogonal frequency division multiplexing (OFDM) remains as the waveform of the upcoming fifth-generation (5G) standard, the new radio provides flexibility in waveform parametrization (a.k.a. numerology) to address diverse requirements. However, managing the peaceful coexistence of mixed numerologies is challenging due to inter-numerology interference (INI). This paper proposes the utilization of adaptive guards in both time and frequency domains as a solution along with a multi-window operation in the physical (PHY) layer. The adaptive windowing operation needs a guard duration to reduce the unwanted emissions, and a guard band is required to handle the INI level on the adjacent band. The guards in both domains are jointly optimized with respect to the subcarrier spacing, use case (i.e., service requirement), and power offset between the numerologies. Also, the multi-window approach provides managing each side of the spectrum independently in case of an asymmetric interference scenario. Since the allowed interference level depends on the numerologies operating in the adjacent bands, the potential of adaptive guards is further increased and exploited with a medium access control (MAC) layer scheduling technique. The proposed INI-based scheduling algorithm decreases the need for guards by allocating the numerologies to the available bands, considering their subcarrier spacing, power level, and SIR requirements. Therefore, INI management is performed with a cross-layer (PHY and MAC) approach in this study. The results show that the precise design that accommodates such flexibility reduces the guards significantly and improves the spectral efficiency of mixed numerology systems.

Intelligent multi-branch allocation of spectrum slices for inter-numerology interference minimization

“…The authors of [17] and of [18] design an INI mitigation scheduling algorithm based on adaptive guard intervals and on subband power offset reduction between different numerologies, respectively. However, the proposed schemes do not ensure an optimal INI minimization as they do not analytically consider the INI within the problem formulation.…”

Spectrum Allocation for Network Slices with Inter-Numerology Interference using Deep Reinforcement Learning

“…The authors of [9] and of [10] propose a INI-based scheduling scheme to reduce the size of the guard interval between different numerologies and to mitigate the interference power, respectively. However, the designed solutions are based on heuristic approaches, which are not supported by an optimal problem formulation that analytically accounts for the INI.…”

6G vision: An ultra-flexible perspective

“…Two important issues that require lexibility in PHY and MAC would be the "waveform parameter assignment" or "numerology scheduling" paradigm under the context of 5G multi-numerology systems [25,100], where the MAC layer is responsible for assignment of parameters of the PHY signal. Similarly, adaptive guard utilization methods have been developed for the MAC layer [101][102][103] to control the new type of interferences in 5G systems.…”