1Scheduling for Cellular Multicast: A Cross-Layer Perspective

Recent years have witnessed the importance of cross-layer design in wireless communication systems. The adoption of simplied on/off models for the wireless channel, in an attempt to reduce it to the traditional wireline case, has been shown to be highly sub-optimal. In this paper, we consider more realistic models for the wireless channel and demonstrate the signicant performance gains that can be leveraged from the wireless medium through intelligent scheduling strategies. We consider a cellular multicast channel, where a central base station transmits the same information stream to all the users within the system. We design scheduling algorithms for this scenario from a cross-layer perspective, which aids us in exploiting the characteristics of the wireless medium. We consider three classes of scheduling algorithms with progressively increasing complexity and study their asymptotic throughput-delay performance with the number of users in the system. The rst class strives for minimum complexity by resorting to static scheduling along with memoryless decoding. Our analysis reveals the existence of a scheduling scheme, within this class, that achieves near-optimal scaling laws of both delay and throughput. The second scheduling policy resorts to a higher complexity incremental redundancy encoding/decoding strategy to achieve a superior throughput-delay tradeoff. The third, and most complex, scheduling strategy benets from the cooperation between the different users and is shown to simultaneously achieve the optimal scaling laws of both delay and throughput. We further study the effect of equipping the base station with multiple transmit antennas on the throughput performance of the proposed low-complexity static schedulers. Finally, we present simulation results that validate our theoretical claims. I