Achieving energy-efficient “Green” communications requires the cooperation of all blocks in a communication system. This includes the baseband, the transmitter, the receiver, the protocol, and most importantly the signal modulation selected. Optimizing any one of these, which is a common approach, leaves the entire system far from its optimum efficiency. But when the entire system is designed for optimum efficiency in the presence of all throughput requirements, significant energy savings relative to conventional design are likely to be realized. These techniques hold equally for wireless and wireline communication channels.