LAUSR

The principle of Cloud Radio Access Network (C-RAN) is the split of traditional base stations into Radio Remote Units (RRU) as low-cost wireless access points, and Base Band Units (BBU) in a centralized location. This new RAN paradigm accepts several choices for a functional split of the protocol stack, with different latency requirements to the front-haul connecting a BBU with those RRUs under its control. In this paper, we focus on the functional split that implements the Medium Access Control layer at the BBU side. Particularly, we analyze the impact of delays on the report of the acknowledgment/negative acknowledgment messages for Hybrid Automatic Repeat reQuest (HARQ). In order to understand the trade-off between the HARQ report delay and user throughput, we define a new metric named as Net Rate. This metric is defined as the throughput that a user can reach after certain HARQ report delay while taking into account the actual channel conditions, the resource scheduling period to that user and the transmission window. The Net Rate metric can be used to determine the maximum HARQ report delay that can be tolerated by a user without throughput degradation. Our simulation results recommend the use for Mobile Edge Computing solutions to minimize the latencies of the front-haul connection and, thus, the impact of the HARQ delay on the throughput.