6 research outputs found
A WINNER+ Based 3-D Non-Stationary Wideband MIMO Channel Model
In this paper, a three-dimensional (3-D) non-stationary wideband
multiple-input multiple-output (MIMO) channel model based on the WINNER+
channel model is proposed. The angular distributions of clusters in both the
horizontal and vertical planes are jointly considered. The receiver and
clusters can be moving, which makes the model more general. Parameters
including number of clusters, powers, delays, azimuth angles of departure
(AAoDs), azimuth angles of arrival (AAoAs), elevation angles of departure
(EAoDs), and elevation angles of arrival (EAoAs) are time-variant. The cluster
time evolution is modeled using a birth-death process. Statistical properties,
including spatial cross-correlation function (CCF), temporal autocorrelation
function (ACF), Doppler power spectrum density (PSD), level-crossing rate
(LCR), average fading duration (AFD), and stationary interval are investigated
and analyzed. The LCR, AFD, and stationary interval of the proposed channel
model are validated against the measurement data. Numerical and simulation
results show that the proposed channel model has the ability to reproduce the
main properties of real non-stationary channels. Furthermore, the proposed
channel model can be adapted to various communication scenarios by adjusting
different parameter values
Optimizing the Age-of-Information for Mobile Users in Adversarial and Stochastic Environments
We study a multi-user downlink scheduling problem for optimizing the
freshness of information available to users roaming across multiple cells. We
consider both adversarial and stochastic settings and design scheduling
policies that optimize two distinct information freshness metrics, namely the
average age-of-information and the peak age-of-information. We show that a
natural greedy scheduling policy is competitive with the optimal offline policy
in the adversarial setting. We also derive fundamental lower bounds to the
competitive ratio achievable by any online policy. In the stochastic
environment, we show that a Max-Weight scheduling policy that takes into
account the channel statistics achieves an approximation factor of for
minimizing the average age of information in two extreme mobility scenarios. We
conclude the paper by establishing a large-deviation optimality result achieved
by the greedy policy for minimizing the peak age of information for static
users situated at a single cell.Comment: arXiv admin note: text overlap with arXiv:2001.0547