Modeling and Analyzing Millimeter Wave Cellular Systems

Abstract

We provide a comprehensive overview of mathematical models and analytical techniques for millimeter wave (mmWave) cellular systems. The two fundamental physical differences from conventional Sub-6GHz cellular systems are (i) vulnerability to blocking, and (ii) the need for significant directionality at the transmitter and/or receiver, which is achieved through the use of large antenna arrays of small individual elements. We overview and compare models for both of these factors, and present a baseline analytical approach based on stochastic geometry that allows the computation of the statistical distributions of the downlink signal-to-interference-plus-noise ratio (SINR) and also the per link data rate, which depends on the SINR as well as the average load. There are many implications of the models and analysis: (a) mmWave systems are significantly more noise-limited than at Sub6GHz for most parameter configurations; (b) initial access is much more difficult in mmWave; (c) self-backhauling is more viable than in Sub-6GHz systems which makes ultra-dense deployments more viable, but this leads to increasingly interference-limited behavior; and (d) in sharp contrast to Sub-6GHz systems cellular operators can mutually benefit by sharing their spectrum licenses despite the uncontrolled interference that results from doing so. We conclude by outlining several important extensions of the baseline model, many of which are promising avenues for future research.

Coverage Analysis for Millimeter Wave Networks: The Impact of Directional Antenna Arrays

“…The complex small-scale fading gain of the l-th cluster is denoted as ρ xl . Due to the poor scattering environment, especially for LOS signals and interference, the Rayleigh fading assumption commonly used in sub-6 GHz systems no longer holds, which has also been noted in recent works [21]. In this paper, we assume, as in [9], that |ρ xl | follows independent Nakagami-M fading for each link.…”

“…Specifically, we define a LOS radius R, which represents the distance between a receiver and its nearby blockages, and the LOS probability of a certain link is one within R and zero outside the radius. Compared with other blockage models adopted in the performance analysis for mm-wave networks, e.g., the 3GPP-like urban microcellular model, the LOS ball model has a better fit with real-world blockage scenarios [21]. The incorporation of the blockages induces different path loss laws for LOS and NLOS links.…”

“…Due to the richer reflections and scattering environment of NLOS propagations, Rayleigh fading is assumed as the small-scale propagation model of the NLOS signals and interference. According to recent measurements, a practical value of the LOS ball radius R should be in the order of hundred meters [21].…”

Over-the-Air Radiated Testing of Millimeter-Wave Beam-Steerable Devices in a Cost-Effective Measurement Setup

“…However, compared to legacy cellular bands (i.e., sub-6 GHz), transmissions at mmWave bands suffer from high transmission loss and are highly susceptible to blockage [1,2]. Furthermore, to achieve the high capacity offered by the large system bandwidth, the signal to interference and noise ratio (SINR) should remain high, indicating that the signal power needs to grow proportionally to bandwidth [1]. MmWave channels are also well-known to be highly sparse and specular, due to high penetration, diffraction, and reflection losses [1][2][3].…”

On the Performance of Spatially Correlated Large Antenna Arrays for Millimeter-Wave Frequencies

“…The S-V style model has been the subject of a number studies (e.g., [34], [35]), and its capacity distribution accuracy has been validated, using MIMO system measurements, for various scenarios [36]- [38]. It thus forms the basis for 3rd Generation Partnership Project (3GPP) sub-6 GHz [39] and above 6 GHz [40] channel models.…”