Conclusions

In this context, this book presented an energy-driven design strategy, focusing on the system-to-circuit design of the physical layer of wireless communication devices. The adopted design strategy overcomes themain drawbacks of the classical (digital) top–down design flow when applied to the design of energy-limited systems. The classical top–down flow is based on the introduction of independent layers of design abstraction, which are traversed during a top–down synthesis, followed by a bottom–up implementation. This approach enables the design of large, complex systems. It is, however, exactly the strict separation of the different abstraction layers which forms a bottleneck for energyaware design. Energy-optimality can only be obtained by carefully weighing high-level performance and low-level implementation aspects at every design step. This requires a cross-layer as well as a cross-disciplinary approach, since the optimization should span all levels of design: from an implementation-aware system study down to circuit level. In the context of wireless communication, this involves the simultaneous consideration of both digital and analog implementation theory, as well as communication theory. Finally, it is very important, to already at design time, consider the introduction of runtime flexibility into a system. This flexibility allows a system to dynamically adapt at any time to the current operating conditions, bringing significant energy savings compared with a conservative worst-case design.