# Joint Functional Splitting and Content Placement for Green Hybrid CRAN

## TL;DR

This paper proposes an integrated approach combining functional splitting and content caching in hybrid CRANs to optimize power consumption, latency, and bandwidth, revealing trade-offs among these factors.

## Contribution

It introduces a constraint programming model for joint optimization of functional split and content placement in H-CRANs, considering power, delay, and bandwidth constraints.

## Key findings

- Caching reduces content access delay and bandwidth usage.
- Functional splitting with caching increases power consumption.
- Trade-offs exist between power, bandwidth, and latency.

## Abstract

A hybrid cloud radio access network (H-CRAN) architecture has been proposed to alleviate the midhaul capacity limitation in C-RAN. In this architecture, functional splitting is utilized to distribute the processing functions between a central cloud and edge clouds. The flexibility of selecting specific split point enables the H-CRAN designer to reduce midhaul bandwidth, or reduce latency, or save energy, or distribute the computation task depending on equipment availability. Meanwhile, techniques for caching are proposed to reduce content delivery latency and the required bandwidth. However, caching imposes new constraints on functional splitting. In this study, considering H-CRAN, a constraint programming problem is formulated to minimize the overall power consumption by selecting the optimal functional split point and content placement, taking into account the content access delay constraint. We also investigate the trade-off between the overall power consumption and occupied midhaul bandwidth in the network. Our results demonstrate that functional splitting together with enabling caching at edge clouds reduces not only content access delays but also fronthaul bandwidth consumption but at the expense of higher power consumption.