Energy efficiency of error correction on wireless systems

We consider the energy efficiency of error correction mechanisms on a system consisting of a generalpurpose processor and a wireless interface. Since high error rates are inevitable to the wireless environment, energy efficient error control is an important issue for mobile computing systems. We will show that it is not sufficient to concentrate on the energy efficiency of error control mechanisms only, but the required extra energy consumed by the wireless interface should be incorporated as well. Although good designed retransmission schemes can be optimal with respect to energy efficiency, they can introduce problems to fulfill the required QoS of an application. We have studied the energy efficiency of two different error correction mechanisms and have implemented these in software. It will be shown that from energy efficiency perspective it is not always profitable to minimize the number of bits transmitted over the air. A general strategy will be provided that can be used to determine an energy efficient error correction scheme of a minimal system consisting of a general-purpose processor and a wireless interface. As an example we have investigated a minimal system with a processor and a WaveLAN card.