This paper verifies the performance enhancement. that preamble cancellation (PC)-based transmitter identification (TxID) signal detection can attain in repeater-assisted broadcast networks. In order to evaluate the PC gain over the conventional detection scheme, closed-fOrm outage probabilities are derived for each detection scheme, using Cramer-Rao bound (CRB) as a representative of detection error variances. To this end, we additionally derive a useful probability density function that brings the combine-and-forward relay channel tractable. Based on the analytic derivations, PC is shown to be especially beneficial when the network consists of abundant transmitters.