Cooperative Power Allocation for Broadcast/Multicast Services in Cellular OFDM Systems

In this paper, we investigate the transmission power allocation for the support of broadcast/multicast services (BMSs) in multi-cell OFDM systems. We consider a cooperative architecture for distribution of the BMS data where the copies of the same data are transmitted by multiple base stations (BSs) in a synchronized manner and then aggregated at the receiving users. Under this architecture, we develop a power allocation scheme that optimizes the transmission power of the multiple BSs on each sub-channel to maximize the total data rate. The optimal power allocation turns out to take the form of iterative water-filling, particularly when heterogeneous modulation and coding schemes are allowed in each sub-channel. In addition, we study the two special cases where the BMS system has extended or limited capabilities: First, we consider the BMS system that supports a more sophisticated video coding technique,fine granularity scalability (FGS) video coding, which encodes the BMS data into base layer and enhancement layer. Taking the layered structure into account, we propose a power allocation scheme that maximizes the data rate of the enhancement layer while guaranteeing the minimum data rate requirement of the base layer. Second, we consider the BMS system that only allows average channel state information of users to be available at the resource manager. In this case, as it is not possible to guarantee successful transmission of every data due to instant deep fading, we propose a power allocation scheme that minimizes the probability of transmission failure. Simulation results reveal that the cooperative distribution system performs far better than the non-cooperative distribution system and the proposed power allocation schemes outperform the equal power allocation scheme significantly.