How to Migrate From Operational LTE/LTE–A Networks to C–RAN With Minimal Investment?

By leveraging the fully–centralized and virtualized cloud radio access network (C–RAN) architecture over densely deployed small cells, mobile network operators (MNOs) are expected to meet the ever–increasing coverage and capacity demands. Towards this end, finding the optimal numbers, and locations of centralized unit (CU) pools, and centralizing the baseband units of eNBs at the optimal CU pools plays a pivotal role in curtailing the required investments in order to transit from legacy decentralized RAN (D–RAN) to C–RAN. In this paper, we propose an approach for MNOs to adopt the C–RAN architecture with minimal investment by using the available infrastructure (e.g., site locations and transmission links). Specifically, we propose a decentralized unit – CU (DU–CU) mapping algorithm, which effectively selects the quantity and the locations of CU pools and assigns the CU of each DU to the appropriate CU pool. We then compare the traffic aggregation gains of C–RAN and traditional D–RAN. Lastly, in order to quantify the total cost of ownership savings that can be obtained by employing the legacy network infrastructure while migrating to C–RAN, we compare this scenario with the C–RAN migration scenario in which there is no available infrastructure. In both scenarios, the mapping algorithms are formulated as virtual network embedding problems using integer linear programming techniques. The results of the simulations, conducted using data traffic of 26 eNBs (209 cells) of an operational LTE–A mobile network, reveal that significant saving can be obtained by employing the available mobile network infrastructure while migrating to C–RAN.