Feasibility and limitations in relaying broadcast signals

In this paper, we investigate feasibility and limitations in relaying broadcast signals. We find the angle and radius that can be maximally covered by a single relay while not degrading the original data rate achieved without the relay. During a unit-time slot divided into two phases with different lengths, a source and a relay broadcast data in the first and the second phase, respectively. The sum of transmit power at the source and the relay is constrained. We provide and compare two schemes, the optimal time and power allocation and the optimal power and equal-time allocation with maximum ratio combining at destinations. When the relay can access a fraction of transmit time and power without degrading the original data rate, the relay is feasible. Even with the optimal resource allocation, the coverage of relaying broadcast and the possible location for the relay are limited.