Abstract-This note shows how centralized or distributed power control algorithms in wireless communications can be viewed as S-modular games coupled policy sets (coupling is due to the fact that the set of powers of a mobile that satisfy the signal-to-interference ratio constraints depends on powers used by other mobiles). This sheds a new light on convergence properties of existing synchronous and asynchronous algorithms, and allows us to establish new convergence results of power control algorithms. Furthermore, known properties of power control algorithms allow us to extend the theory of S-modular games and obtain conditions for the uniqueness of the equilibrium and convergence of best response algorithms independently of the initial state.

Three dimensional beamforming (3D) (also elevation beamforming) is now gaining a growing interest among researchers in wireless communication. The reason can be attributed to its potential to enable a variety of strategies like sector or user specific elevation beamforming and cell-splitting. Since these techniques cannot be directly supported by current LTE releases, the 3GPP is now working on defining the required technical specifications. In particular, a large effort is currently made to get accurate 3D channel models that support the elevation dimension. This step is necessary as it will evaluate the potential of 3D and FD(Full Dimensional) beamforming techniques to benefit from the richness of real channels. This work aims at presenting the on-going 3GPP study item "Study on 3D-channel model for Elevation Beamforming and FD-MIMO studies for LTE", and positioning it with respect to previous standardization works.

This article investigates the slicing concept in the 5G Radio Access Network (RAN) with the related challenges and research problems. The objective is to identify the plausible options for implementing the slicing concept at the RAN level by the Mobile Network Operator (MNO) to respond to the needs of verticals. We start by identifying the different slice granularity options, i.e., how to define slices by combining customer and service needs. We then present how the 5G New Radio (NR) features can be used for facilitating slice implementation and provide typical configurations for different slice types from technology and RAN architecture perspectives. The main challenges for RAN slicing are then discussed, with a special attention to the resource allocation problem between slices sharing the same spectrum band. We also investigate the multi-tenant slicing implementation in terms of the openness of the network to third parties which is regarded as a key issue that may encourage vertical players to use operators' networks rather than deploying their own infrastructure.

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