Simple Reduced Feedback Multicast Schemes for Mobile Networks

The rapid growth of video traffic over mobile networks in recent years, including live streaming, prompted 3GPP to define a broadcast/multicast mode for LTE called evolved multimedia broadcast/multicast service (eMBMS). One of the schemes of eMBMS, called single-cell point-to-multipoint (SC-PTM), can flexibly multiplex multicast traffic with unicast traffic. In the current standard, the most robust modulation and coding scheme (MCS) is adopted by the evolved Node B (eNB) when transmitting multicast data to user equipments (UEs) so that most UEs can decode data correctly. In this paper, we present and compare two multicast schemes with limited feedbacks for SC-PTM. In the first scheme, only one channel is allocated for UEs to send NAKs while in the second scheme, two channels are used for UEs to send separately ACKs and NAKs. Results show that by dynamically adjusting the MCS based on feedbacks, the total throughput could increase dramatically. Moreover, the scheme with two feedback channels outperforms the one with only one feedback channel. The radio resource consumed by the two-feedback-channel scheme is less than 1% of the original scheme defined in the standard.