In this paper, we introduce the concept of a multi-operator mobile relay node (RN) for cellular networks on buses or trains. The installation of RNs improves spectral efficiency because an antenna with a higher gain than that of user equipment (UE) can be installed in an RN. However, installing different RNs for different operators is not efficient because of the large amount of space needed to install multiple RNs in a bus. Thus, sharing one RN among multiple operators is a more practical approach. When we use a multi-operator mobile RN, the required amount of resource for each operator varies independently as the RN moves. Consequently, we propose a system of shared-spectrum allocation among operators for RN-UEs communication. Shared bandwidth can be allocated to operators according to link quality in order to achieve effective utilization of radio resources. However, to introduce shared-spectrum allocation, fairness among the operators and the total efficiency of the system should be taken into consideration. Using computer simulations, we evaluate shared-spectrum allocation based on the Nash bargaining solution (NBS). The results, in terms of both fairness and efficiency, indicate that total throughput can be improved by approximately 20% compared with the situation where multiple operators install different RNs individually.

In this study, we investigate the use of scheduling algorithms to support coordinated multipoint (CoMP) operation for Long Term Evolution (LTE)-Advanced systems studied in the 3rd Generation Partnership Project (3GPP). CoMP, which improves cooperative transmission among network nodes (transmission points: TPs) and reduces or eliminates interTP interference, enabling performance improvements in cell edge throughputs. Although scheduling algorithms in LTE systems have been extensively investigated from the single cell operation perspective, those extension to CoMP where each user equipment (UE) has multiple channel state information (CSI) feedbacks require further consideration on proportional fairness (PF) metric calculation while maintaining PF criteria. To this end, we propose to apply a scaling factor in accordance with the number of CSI feedbacks demanded for the UE. To evaluate the benefits of this scaling factor, multicell system-level simulations that take account of channel estimation errors are performed, and the results confirmed that our improved algorithm enables fairness to be maintained.