The increasing demand for wireless data services in the recent years has led to traditionally voice and video oriented network architectures such as satellite and cellular systems being adapted for data transmission. Also, since most wireless systems are battery-powered, energy consumption has become an important consideration in the research community.

In this thesis, we first examine the problem of controlling transmission power in order to achieve minimum-energy broadcast packet transmission subject to a minimum QoS requirement. We study the structure of the optimal policy when the transmitter chooses between two power levels, and then extend the results to the continuous-power case.

Subsequently, we examine the effect of network architecture on the downlink performance of the network. Satellite and Cellular systems are compared on the basis of energy, delay and throughput. We then show that having a hybrid network architecture can provide additional throughput benefit, at the cost of energy.