  To address the massive growth of data traffic over cellular networks,
increasing spatial reuse of the frequency spectrum by the deployment of small
base stations (SBSs) has been considered. For rapid deployment of SBSs in the
networks, caching popular content along with new coded caching schemes are
proposed. To maximize the cellular network's capacity, densifying it with small
base stations is inevitable. In ultra-dense cellular networks, coverage of SBSs
may overlap. To this aim, the multi-access caching system, where users
potentially can access multiple cache nodes simultaneously, has attracted more
attention in recent years. Most previous works on multi-access coded caching,
only consider specific conditions such as cyclic wrap-around network
topologies. In this paper, we investigate caching in ultra-dense cellular
networks, where different users can access different numbers of caches under
non-uniform content popularity distribution, and propose Multi-Access Hybrid
coded-uncoded Caching (MAHC). We formulate the optimization problem of the
proposed scheme for general network topologies and evaluate it for 2-SBS
network scenarios. The numerical and simulation results show that the proposed
MAHC scheme outperforms optimal conventional uncoded and previous multi-access
coded caching (MACC) schemes.
