This paper focuses on spectral lines suppression for non-coherent impulse-radio ultra-wideband (IR-UWB) signalsinthepresenceofpulseattenuationandtimingjitter. Particularattentionisdevotedtoseverelyunbalanced(i.e. non-uniformdistributed)datasourceswhereaunifiedspectralanalysisisconsideredforbothuncorrelatedandcorrelated M-ary biorthogonal data-stream scenarios. Indeed, the specific novelty insights of this paper are as follows: i) Proposal of a new spectral-efficient signal model as a modified version of transmitted-reference (TR) approach, where each transmitted symbol is represented by a preamble Data-based Statistical Reference (DSR) followed by a set of transmitted data pulses and within this context, the preamble signal is designed to eliminate spectral lines viaanadaptivemonitoringofdata-streamstatisticsastheoptimalspectralpolicy; ii)Performanceanalysisinorder to derive optimal signal parameters; iii) Evaluation of the system capabilities over different predefined operational modes.