11 research outputs found
Impact of Spatially Consistent Channels on Digital Beamforming for Millimeter-Wave Systems
The premise of massive multiple-input multiple-output (MIMO) is based around
coherent transmission and detection. Majority of the vast literature on massive
MIMO presents performance evaluations over simplified statistical propagation
models. All such models are drop-based and do not ensure continuity of channel
parameters. In this paper, we quantify the impact of spatially consistent (SC)
models on beamforming for massive MIMO systems. We focus on the downlink of a
28GHz multiuser urban microcellular scenario. Using the recently standardized
Third Generation Partnership Project 38.901 SC-I procedure, we evaluate the
signal-to-interference-plus-noise ratio of a user equipment and the system
ergodic sum spectral efficiency with zero-forcing, block diagonalization, and
signal-to-leakage-plus-noise ratio beamforming. Our results disclose that at
practical signal-to-noise ratio levels, SC channels yield a significant
performance loss relative to the case without SC due to substantial spatial
correlation across the channel parameters.Comment: Invited Paper in the Proceedings of EuCAP 202
EMR: A New Metric to Assess the Resilience of Directional mmWave Channels to Blockages
Millimeter-wave (mmWave) communication systems require narrow beams to
increase communication range. If the dominant communication direction is
blocked by an obstacle, an alternative and reliable spatial communication path
should be quickly identified to maintain connectivity. In this paper, we
introduce a new metric to quantify the effective multipath richness (EMR) of a
directional communication channel by considering the strength and spatial
diversity of the resolved paths, while also taking into account beamwidth and
blockage characteristics. The metric is defined as a weighted sum of the number
of multipath component (MPC) clusters, where clustering is performed based on
the cosine-distance between the MPCs that have power above a certain threshold.
This process returns a single scalar value for a transmitter (TX)/receiver (RX)
location pair in a given environment. It is also possible to represent the EMR
of the whole environment with a probability distribution function of the metric
by considering a set of TX/RX locations. Using this proposed metric, one can
assess the scattering richness of different communication environments to
achieve a particular quality of service (QoS). This metric is especially
informative and useful at higher frequencies, such as mmWave and terahertz
(THz), where the propagation path loss and penetration loss are high, and
directional non-light-of-sight (NLOS) communication is critical for the success
of the network. We evaluate the proposed metric using our channel measurements
at 28 GHz in a large indoor environment at a library setting for LOS and NLOS
scenarios.Comment: This work has been submitted to the IEEE for possible publicatio