Device-to-Device Communications Enabled Multicast Scheduling for mmWave Small Cells Using Multi-Level Codebooks

Heterogeneous cellular networks with small cells in the millimeter wave (mmWave) band densely deployed have become one of promising candidates for future wireless networks due to huge bandwidth available in the mmWave band. To overcome high path loss in the mmWave band, the beamforming technique of directional antennas is adopted. Consequently, concurrent transmissions of links can be enabled to improve network capacity. On the other hand, multicast services can support many applications like popular content downloading and broadcast communication services. In user intensive region where multicast services usually happen, device-to-device (D2D) communications in physical proximity provide better channel conditions, and can improve multicast efficiency. In this paper, we develop an efficient multicast scheduling scheme for mmWave small cells, referred to as CONMD2D, where both concurrent transmissions and D2D communications are exploited based on a multi-level antenna codebook to optimize network performance. In CONMD2D, the multicast group is partitioned into subgroups, and D2D transmission paths are established between subgroups. Then, a concurrent scheduling algorithm schedules the multicast links concurrently into the transmission stage. Performance evaluation under various system parameters demonstrates CONMD2D achieves significant improvement in network throughput and energy efficiency compared with other state-of-the-art schemes.