Frame Structure Design and Analysis for Millimeter Wave Cellular Systems

TL;DR

This paper proposes a flexible mmWave MAC frame structure for 5G systems, enabling efficient directional control, reduced overhead, and supporting advanced beamforming architectures, with analytical validation of its benefits.

Contribution

It introduces a novel, adaptable mmWave MAC frame structure with analytical formulas for performance metrics, accommodating various MIMO capabilities and outperforming fixed structures.

Findings

Flexible frame structure reduces control overhead.

Fully digital beamforming lowers overhead compared to analog/hybrid.

Analytical models validate performance improvements.

Abstract

The millimeter-wave (mmWave) frequencies have attracted considerable attention for fifth generation (5G) cellular communication as they offer orders of magnitude greater bandwidth than current cellular systems. However, the medium access control (MAC) layer may need to be significantly redesigned to support the highly directional transmissions, ultra-low latencies and high peak rates expected in mmWave communication. To address these challenges, we present a novel mmWave MAC layer frame structure with a number of enhancements including flexible, highly granular transmission times, dynamic control signal locations, extended messaging and ability to efficiently multiplex directional control signals. Analytic formulae are derived for the utilization and control overhead as a function of control periodicity, number of users, traffic statistics, signal-to-noise ratio and antenna gains. Importantly, the analysis can incorporate various front-end MIMO capability assumptions -- a critical feature of mmWave. Under realistic system and traffic assumptions, the analysis reveals that the proposed flexible frame structure design offers significant benefits over designs with fixed frame structures similar to current 4G long-term evolution (LTE). It is also shown that fully digital beamforming architectures offer significantly lower overhead compared to analog and hybrid beamforming under equivalent power budgets.