QoS priority-based coordinated scheduling and hybrid spectrum access for femtocells in dense cooperative 5G cellular networks

A third-generation partnership project long-term evolution system uses the concept of a 2-tier heterogeneous network, where low-power and short-range femtocells are laid under macrocells to fulfill the quality of service (QoS) requirements of users and to boost overall network throughput. However, cochannel deployment gives rise to the problem of cross-tier interference that significantly deteriorates the performance of the cellular network. The coordinated multipoint (CoMP) transmission scheme is proposed as a promising solution to alleviate cross-tier interference by doing cooperation among the neighbor base stations. In this paper, we propose a QoS priority-based coordinated scheduling and hybrid spectrum access (QoS-CSaHSA) scheme for downlink CoMP transmission in 2-tier networks. The proposed QoS-CSaHSA scheme dynamically reduces the femtocells' power requirements by considering the neighbor cell interference, and it also balances the macrocell load by switching the femtocells to HA mode. Moreover, it can reduce unnecessary muting of the base stations because it only enables the coordinated scheduling CoMP when there is no other possibility to reduce the cross-tier interference. System-level simulation results prove the validity of the proposed QoS-CSaHSA scheme in a heterogeneous network environment. Compared with the existing schemes that operate the femtocells in a closed-subscriber group without considering users' QoS requirements, the proposed scheme almost doubles the cell-edge user throughput and reduces the packet loss rate and call-blocking probability.