Bit and Power Allocation in QAM Capable Multi-Differential Frequency-Shifted Reference UWB Radio

Auto-correlation receivers, such as frequency shift reference systems, offer a low-complexity alternative to Rake receivers, for low data-rate ultra-wideband applications. In such systems, a data signal and a reference signal are simultaneously transmitted. At the receiver, the received signal corresponding to the data is correlated with the received signal corresponding to the reference signal, thereby accumulating the multi-path channel energies in-phase. For improving bandwidth and energy efficiency, multi- differential schemes have also been proposed where multiple data signals share the same reference signal. With the aim of further boosting the achievable data rates, in this work we propose a multi-differential frequency shift reference receiver that supports higher order modulation formats. We design the corresponding receiver architecture that can exploit both the in-phase and quadrature-phase signal components and analytically characterize the signal and noise components. We also study the problem of optimal bit and power allocation to the multiple data signals, both for uncoded and coded systems, as a function of channel metrics that can be easily tracked at the receiver.