Capacity Limitation of Small Cell Densification

Abstract

Deployment of small cells is considered as an easy approach for adding capacity to the system. However, it is important to realize that in a non-noise limited system, each additional cell increases the interference in the system. The target of this paper is to show the capacity limitation of the cellular network with an increasing number of small cells in a network. Ultra-dense deployment of small cells implies a high probability of line of sight (LOS) transmission between the transmitter (TX) and receiver (RX). The LOS transmission helps in enhancing the received signal strength, whereas, on the other hand, the interference power significantly grows with small cell densification. This paper presents the analytical analysis of bad cell border area for one-, and two-dimensional grid of small cells. The lamp post solution for the small cell deployment along the street is studied through simulations. The acquired results show that the overall interference in the system and the bad signal to interference plus noise ratio (SINR) cell border area grows with cell densification. System capacity saturates and then starts to collapse as the capacity loss due to the additional cell interference becomes dominant over the gain of cell densification after the saturation point.

Polarization adaptation to improve cell border area bitrates and system capacity in small cells

“…It should be noted that at high frequencies and in the LOS environment, the strength of diffracted paths has lower signal strength compared with LOS and reflected paths. In an LOS environment with cells utilizing the same frequency and polarization, the LOS path is the major contributor to interference between them, as presented in [3]. In the case of utilizing orthogonal polarization in immediate neighbor cells, the interference distance is three times (39) longer for the base station utilizing omnidirectional directional antenna, as shown in Fig.…”

“…Continuously increasing capacity requirements and higher frequencies of new technologies lead to dense base station site grids and small cells. In reference [3], it is shown that the system performance of densely implemented small cell infrastructure is squeezed as a function of site/cell distance. It is observed that the bad SIR area in between neighbor cells inversely increases as a function of site distance when the same frequency and polarization are used in neighbor cells.…”