D2D communications based scarcity-aware two-stage multicast for video streaming

This paper proposes a device-to-device (D2D) communications based scarcity-aware two-stage multicast mechanism for delivering video streaming, in which the Base Station (BS) and D2D perform cooperative retransmissions to improve the mobile video quality and relieve the load of BS as well. In prior works, after BS's one-round multicast, the clients directly resort to D2D communications to obtain the missing frames by forming social groups. However, after the first-round multicast of BS, it is possible that some frames have not been correctly received by most of the clients, especially when the channel conditions are not good. That is, there are scarce frames in the network and the clients have very limited copies of them. In this case, it is inefficient for the clients to form social groups and directly exchange frames through D2D communications. Instead, this paper proposes an adaptive two-stage multicast mechanism: the BS first multicast video packets to the clients who request the same video services, after which the clients collect the information of missing frames and send it to the BS. Then the BS evaluates the scarcity of frames and re-multicast the scarce frames, if any, to the clients. After the BS's second-round multicast, the clients can then form groups to perform D2D communications so as to obtain the remaining missing packets from each other. Numerical studies show that the proposed simple scarcity-aware two-stage multicast mechanism can achieve about 5% video quality improvement than the existing one-stage multicast mechanism and have the potential to enhance the downlink capacity of the future 5G wireless network.