Chia-Hao Yu

Beam Space Selection for High Rank Millimeter Wave Communication

We address beam space reduction method inside which proper analog beamformers are selected for hybrid beamforming millimeter Wave (mmWave) system. We apply insights from spatial multiplexing theory on beam subspace selection and show that computational effort of searching for desired beamformers can be significantly reduced. A simplified channel throughput estimation measure is also devised to further lessen the complexity in the course of beamformer searching. Simulation results demonstrate that near-optimal performance can be achieved with significantly reduced complexity.

Modeling and evaluation of beam tracking in mobile millimeter wave communication

The most critical challenge facing mobile millimeter wave communication is the precise projection of high-gain and narrowly focused radiation toward the multi-paths leading to a device as it moves and rotates in the field. In order to design and evaluate such beam tracking mechanism, an accurate model of the propagation environment is required. Unfortunately, conventional channel models for system operating in carrier frequency lower than 6 GHz are typically statistically based with time-invariant parameters and thus inadequate to simulate the dynamics in spatial characteristics the millimeter wave channel may exhibit. In this paper, such shortcoming is overcome by the introduction of certain time-varying parameters to a widely adopted geometry based stochastic model. With the revised model, we proceed to tune its parameters to fit the statistics extracted from the latest measurement data and subsequently investigate the models capability in evaluating beam tracking performance. The beam tracking algorithms are generic in nature and only assume certain imperfect knowledge of the channels spatial profile. It is found that at 28 GHz carrier frequency, beam tracking can be maintained at a moving speed of 60 kmph and an angular speed of 720°/sec with around 20% loss comparing with the stationary reference if the spatial profile is updated at a rate of 50 Hz.