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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.

International audienceThe paper considers the use of caching in mobile access networks and seeks to evaluate the optimal memory for band-width tradeoff at base station (BS), packet gateway (PGW) and a possible intermediate mobile cloud node (MCN). Formulas are derived for the hit rate under time varying popularity and for a novel cache insertion policy incorporating a pre-filter. The analytical model is applied first to demonstrate that reactive caching is not efficient for nodes with low demand due to the negative impact of content churn. This means BS or MCN caches must be managed proactively with popular content items pre-fetched under some centralized control. Quantifying the tradeoff at each level leads us to conclude that limited caching at BS and MCN levels brings significant savings while to store the vast majority of the content catalogue at the Internet edge, at the PGW or in some higher level shared facility, is clearly cost effective

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