A fundamental and outstanding question for the design of mmWave networks is to understand the effects of interference and, more specifically, under which circumstances mmWave cellular networks are likely to be limited by interference or by thermal noise. Identifying in which regimes networks operate is important to system design: for example, while interference limited networks can benefit from advanced techniques such as inter-cellular interference coordination, coordinated beamforming and dynamic orthogonalization, these techniques have little value in networks where thermal noise, rather than interference, is dominant.

While for traditional cellular deployments, in particular macrocell-based, the relative power of interference to thermal noise is a function of the distance between cells and of the transmit power spectral density, the results in our study demonstrate that in mmWave systems the relative strength of interference depends on many more factors.

Example of a large-scale mmWave scenario.

Most importantly, mmWave systems rely on highly directional transmissions to overcome the high isotropic path loss. Directional transmissions tend to isolate users, thereby reducing the interference. However, the degree of isolation depends strongly on the size of the antenna arrays, the antenna pattern, and the level of local scattering and spatial multipath. In addition, mmWave signals can be blocked by many common materials, eliminating long distance links. This potentially improves the isolation but may also lead to coverage holes. There are also significant differences in path loss for mobiles in Line-of-Sight (LoS) and Non-Line-of-Sight (NLoS) locations.

To precisely design mmWave systems, it is important to examine mmWave interference under large-scale deployments. For this purpose, we study scenarios that apply both an accurate mmWave channel model, derived from experiments, and accurate beamforming pattern, into an analytical framework based on stochastic geometry. In this way we can obtain metrics of interest in large-scale mmWave cellular networks.

Title  DateArea
M. Rebato, J. Park, P. Popovski, E. de Carvalho, and M. Zorzi, "Stochastic Geometric Coverage Analysis in mmWave Cellular Networks with a Realistic Channel Model," in IEEE Global Communications Conference: Mobile and Wireless Networks (Globecom2017 MWN), Dec. 2017.
M.Rebato, M.Mezzavilla, S.Rangan, F.Boccardi and M.Zorzi, "Understanding Noise and Interference Regimes
in 5G Millimeter-Wave Cellular Networks", in the 22th European Wireless Conference, 2016.
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