On the Benefits and Implementation Costs of Multi-Cell Selection in Heterogeneous Networks

We consider a heterogeneous cellular network (HetNet) on the downlink and focus on multi-cell selection (MCS). MCS allows each user to associate with and receive data from multiple base stations (BTSs) at once, potentially boosting the network performance. We formulate a fully coordinated realistic MCS problem that provides an upper-bound on the network performance which is 20% above that of the state-of-the-art single-cell selection (SCS). However, this improvement comes at the cost of inter-BTS coordination which is not so easy to perform in practice. Hence, we focus on how to obtain this performance gain in two practical scenarios; 1) a conventional HetNet with no inter- BTS coordination, and 2) a Centralized Radio Access Network (C-RAN) HetNet. In Scenario 1, we show that SCS with periodic individual opportunities for re-associations along with local Round Robin scheduling (which requires no inter- BTS coordination) can outperform the state-of-the- art SCS by 17% without incurring a huge cost in signaling. In Scenario 2, we show that we can almost reach the upper-bound without paying for the complexity in coordinated scheduling using a simple two-step heuristic.