Hover or Perch: Comparing Capacity of Airborne and Landed Millimeter-Wave UAV Cells

On-demand deployments of millimeter-wave (mmWave) access points (APs) carried by unmanned aerial vehicles (UAVs) are considered today as a potential solution to enhance the performance of 5G+ networks. The battery lifetime of modern UAVs, though, limits the flight times in such systems. In this letter, we evaluate a feasible deployment alternative for temporary capacity boost in the areas with highly fluctuating user demands. The approach is to land UAV-based mmWave APs on the nearby buildings instead of hovering over the area. Within the developed mathematical framework, we compare the system-level performance of airborne and landed deployments by taking into account the full operation cycle of the employed drones. Our numerical results demonstrate that the choice of the UAV deployment option is determined by an interplay of the separation distance between the service area and the UAV charging station, drone battery lifetime, and the number of aerial APs in use. The presented methodology and results can support efficient on-demand deployments of UAV-based mmWave APs in prospective 5G+ networks.Comment: Accepted to IEEE Wireless Communications Letters on July 20, 2020. Copyright may be transferred without further notice after which this version may become non-availabl

An Accurate Approximation of Resource Request Distributions in Millimeter Wave 3GPP New Radio Systems

The recently standardized millimeter wave-based 3GPP New Radio technology is expected to become an enabler for both enhanced Mobile Broadband (eMBB) and ultra-reliable low latency communication (URLLC) services specified to future 5G systems. One of the first steps in mathematical modeling of such systems is the characterization of the session resource request probability mass function (pmf) as a function of the channel conditions, cell size, application demands, user location and system parameters including modulation and coding schemes employed at the air interface. Unfortunately, this pmf cannot be expressed via elementary functions. In this paper, we develop an accurate approximation of the sought pmf. First, we show that Normal distribution provides a fairly accurate approximation to the cumulative distribution function (CDF) of the signal-to-noise ratio for communication systems operating in the millimeter frequency band, further allowing evaluating the resource request pmf via error function. We also investigate the impact of shadow fading on the resource request pmf.Comment: The 19th International Conference on Next Generation Wired/Wireless Networks and Systems (New2An 2019

On the Degree of Multi-Connectivity in 5G Millimeter-Wave Cellular Urban Deployments

Outage event caused by dynamic link blockage at millimeter-wave (mmWave) frequencies is a challenging problem for cell-edge users. To address it, 3GPP is currently working on multi-connectivity mechanisms that allow a user to remain connected to several mmWave access points simultaneously as well as switch between them in case its active connection drops. However, the actual number of such simultaneous links -- named the degree of multi-connectivity -- to reach the desired trade-off between the system design simplicity and the outage probability levels remains an open research question. In this work, we characterize the outage probability and spectral efficiency associated with different degrees of multi-connectivity in a typical 5G urban scenario, where the line-of-sight propagation path can be blocked by buildings as well as humans. These results demonstrate that the degrees of multi-connectivity of up to 4 offer higher relative gains. At the same time, performance improvements brought by the multi-connectivity degrees of 5 and higher are much lower. Our analytical framework can be further employed for the performance analysis of multi-connectivity-capable mmWave systems across their different deployment configurations.acceptedVersionPeer reviewe

System-Level Analysis of Blockage Dynamics in Millimeter-Wave Communications

The new generation of wireless technology, termed as the fifth generation (5G), introduces a large amount of novel features. An operation in the millimeter-wave (mmWave) spectrum becomes one of those features unlocking a wide bandwidth. The latter allows for a notable increase in the peak data rate by up to tens of gigabits per second and decreases latency to as low as few milliseconds. These improvements provide an opportunity to support high-rate and low-latency applications, such as augmented and virtual reality, eHealth, and many others. Though mmWave communications have great potential, they suffer from severe attenuation caused by signal blockage. In addition to large-scale blockers (i.e., buildings), small-scale blockers such as human bodies bring new challenges to the operation over mmWave bands. Large attenuation losses, as well as the unpredictable mobility of human body blockers, can significantly decrease a service quality when communicating over a mmWave link. Thereby, there is a need to properly model the blockage process, evaluate its impact on mmWave network performance, and estimate performance gains brought by different blockage mitigation techniques. The thesis proposes a mathematical methodology to characterize and evaluate the effect of blockage dynamics in mmWave networks. With the help of stochastic geometry and probability theory, it delivers mathematical models of static and dynamic small-scale blockage, as well as static large-scale blockage. It then introduces system-level performance evaluation frameworks accounting for the main features of mmWave communications, such as blockage and multipath propagation. The mathematical frameworks can also evaluate the impact of several blockage mitigation techniques in realistic deployment scenarios