  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.
