Hierarchical multicast transmission for single cell point-to-multipoint (SC-PTM) in cellular networks

Recently, Single-Cell Point-to-Multipoint (SC-PTM) has been studied in 3GPP as an agile broadcast/multicast mechanism. Due to cell-level support of the multicast service, SC-PTM can adjust the service area dynamically and its scheduling is quite agile. In the conventional SC-PTM, however, a single multicast transmission is set for the worst user and provided for all the users regardless of their channel qualities. Since the transmission is configured with a modulation level and coding rate (MC) so that the user even with the worst channel quality can correctly decode the data, it may be wasteful for most users with better qualities. In this paper, we propose a hierarchical multicast transmission to enhance the SC-PTM. In the proposed scheme where the users are categorized into upper group or lower group according to their channel qualities, two hierarchical multicast transmissions in the Single Cell Point-to-Multipoint (SC-PTM) are provided. In addition to the basic transmission, a supplementary transmission is additionally provided for the users with poor channel qualities, i.e., belonging in lower group. Through mathematical derivation, we evaluate the proposed scheme with various group sizes. Interestingly, the amount of resource required for two multicast transmissions is beneficial compared to that of a conventional single transmission.