YMMV: Multiple Session Multicast with MIMO

Multicast is an important application in cellular networks. The 4G technologies, including WiMAX and LTE, invariably adopt Multiple-Input-Multiple-Output (MIMO) to facilitate spatial multiplexing and fundamentally increase channel capacity. However, state-of-the-art multicast protocols are designed to perform in single-hop mode with a single session, leading to under-utilization of the scarce spectrum resource. In this paper, we propose YMMV, a novel multicast protocol that jointly considers MIMO and cooperative communications in OFDMA networks. The base station transmits data in multiple sessions using multiple antennas on the same channel to exploit spatial multiplexing in MIMO. Further, cooperative transmission on different channels among users is also utilized. We tackle the resulted session scheduling problem in YMMV, where the multi-channel characteristic of OFDMA further aggravates the difficulty of efficient algorithm design. With rigorous analysis and extensive simulations, we show that our multi-session multicast protocol is able to improve throughput performance significantly.