Bit loading algorithms: Circuit area, energy consumption and theoretical complexity

Portable devices are increasingly running complex applications wireless multimedia while at the same time facing stringent implementation constraints. UWB devices are candidates for a wide range of applications. The potential UWB devices will be of short range, portable and capable of delivering high bit rate. Multi-band orthogonal frequency division multiplexing (MB-OFDM) being a special case of multicarrier transmission is chosen by WiMedia and EMCA International for its high bit rate capability. To meet this high bit rate requirement while keeping the peak transmitted power under the permitted limit, several bit loading algorithms have been presented in technical literature for OFDM. These algorithms are evaluated and compared on the basis of their theoretical complexity and computation efficiency. However, this theoretical complexity analysis is unable to take into account final implementation issues such as energy consumption and required chip area. In this paper, energy consumption and circuit area estimation of two popular bit-loading algorithms are analyzed in a multiobjective approach and put into evidence the need to analyze new proposals in a more global approach.