This research is on theories and techniques for globally reducing energy consumption at the network level. The following issues are investigated: (1) Techniques for network infrastructure design and deployment of network nodes that can reduce network energy consumption. (2) Scheduling and routing algorithms and protocols that can reduce network energy consumption. The goals of this research include: (1) System models will be formalized to realistically express the characteristics and restrictions of current network technologies. (2) Techniques for network nodes deployment that can reduce network energy consumption will be developed. (3) Energy efficient algorithms and protocols for network message routing and scheduling will be developed. (4) Correctness proof of our protocols and algorithms and theoretical analysis of them will be provided. (5) A platform will be built for the simulation of the algorithms, protocols and for testing the infrastructure design and node deployment schemes.