1. An apparatus comprising: a receiver configured to receive an input signal, wherein the received input signal reflects an encoded and modulated initial source signal, as amplified by a transmit amplifier of a source transmitter and transmitted over one or more channels of a wireless communications network; a demodulator configured to demodulate the received input signal to generate a demodulated input signal; a decoder configured to decode the demodulated input signal to generate a decoded input signal; an encoder and a first modulator respectively configured to encode and modulate the demodulated input signal to generate a received version of the encoded and modulated initial source signal as received by the receiver; a first signal processor configured to generate an estimated signal, that estimates the encoded and modulated initial source signal as amplified by the transmit amplifier, based on a transfer function that models one or more characteristics of the transmit amplifier; a second modulator configured to modulate the estimated signal; and a second signal processor configured to compare the modulated estimated signal and the demodulated input signal to determine a signal error that reflects a correlation between the two, and to determine whether the signal error is within a predetermined threshold; and wherein, when it is determined that the signal error is not within the predetermined threshold, the second signal processor is further configured to determine an update to the transfer function via a non-linear optimization technique to reflect a more accurate model of the transmit amplifier characteristic(s), and to send a corresponding feedback signal to the first signal processor; wherein the first signal processor, the modulator, and the second signal processor are further configured to perform the generation of the estimated signal, the modulation of the estimated signal, and the determination of the signal error and the transfer function update, respectively, as an iterative process, until it is determined that the signal error is within the predetermined threshold, wherein, in view of the feedback signal, for each iteration the first signal processor is configured to generate the estimated signal based on the updated transfer function; and wherein a determination that the signal error is within the predetermined threshold indicates that the transfer function of the respective iteration models the transmit amplifier characteristic(s) to a degree of accuracy associated with the predetermined threshold.