Interference Management in Small Cells.

摘要

Wireless transmissions at microwave bands are observed with strong multipath components at the receiver, resulting in high-rank channel. This results in high interference independent from directionality of the transmission. Interference cancellation (IC) can provide significant gains in wireless networks with strong interference, that arise, for example, in emerging femto- and picocellular deployments. This work considers the problem of optimal downlink rate selection in networks where each mobile can perform IC on up to one interferer. When mobiles are capable of IC, it is argued that rate selection can play analogous roles as power control by permitting a tradeoff between rates on the desired link with "cancellability" on interfering links. A utility maximizing scheduler based on loopy belief propagation is presented that enables computationally-efficient local processing and low communication overhead. It is shown that the fixed points of the method are provably globally optimal for arbitrary (potentially non-convex) rate and utility functions. In addition, the result applies to an arbitrary network where the interference is determined by a single dominant interferer, for which the IC problem is a special case. Simulations are presented in industry standard femtocellular network models.;Millimeter-wave (mmWave) channels, on the other hand, have low ranks because of the high attenuation and absorption. High attenuation might seem a challenging factor to sustain a link between two stations. However, directional antennas can utilize "the portion that they need" with almost full antenna gain thanks to the low-rank property of the channel. Moreover, the mmWave frequency bands offer orders of magnitude greater spectrum than current cellular microwave frequencies currently deployed below 3 GHz. Therefore, in this work, recent real-world measurements at 28 GHz are used to provide systematic assessment of mmWave picocellular networks. It is found that, even with its limited propagation characteristics, mmWave systems can offer an order of magnitude increase in capacity over current state-of-the-art 4G cellular networks with similar cell density thanks to directional isolation. It is also observed that, under spatial multiple access scheme, intercell interference dominates the intracell interference in mmWave networks.