Energy-Aware Cross-Layer Radio Management

Anything, anywhere, anytime: the query is not new. Still, offering ubiquitous wireless connectivity and seamless access to multimedia services is not yet a reality. A major need to realize this vision is Software Defined Radio (SDR): a reconfigurable radio implementation offering support for a large variety of wireless standards on the same hardware resources. Main advantages of such SDR implementations are higher flexibility (multi-purpose multi-standard platform, reprogrammable in the field) at lower cost (product development and manufacturing cost lowered thanks to better time-to-market, higher chipset production volume and lower number of components to integrate). In the coming years, the implementation of wireless standards on such reconfigurable radios is expected to become the only viable option [1, 2] This results from the combination of the increasing need for functional flexibility in communication systems (the variety of wireless standards to be supported is very large, and can be expected to still grow in the future) and the exploding cost of system-on-chip design (newer design technology nodes urge high-volume, multi-purpose and preferably widely programmable devices that can be easily updated) (Fig. 6.1).

The major bottleneck to enable such reconfigurable implementations for handheld devices is energy efficiency. Due to its flexibility requirements, the SDR concept indeed intrinsically suffers from a significant energy penalty compared to dedicated hardware solutions. The major challenge in this context is thus to enable low energy SDRs matching the energy efficiency requirements of battery-powered handheld terminals and competitive with dedicated implementations. This is becoming a key concern: there exists a continuously growing gap between the available energy, resulting from battery technology evolution, and the steeply increasing energy requirements of emerging radio systems (Fig. 6.2). Technology scaling, platform improvements and circuit design progress are not sufficient for bridging this energy gap. There is a clear need for disruptive system-level strategies.