In urban sensor networks, the diversity of propagation conditions can lead to the simultaneous reception of signals having very different power levels. Given the diversity of wireless technologies used in this area, implementing gateways using a Software-Defined Radio (SDR) approach seems to be a very practical solution. Overcoming the high dynamic range may however require an Analog-to-Digital Converter (ADC) with a resolution fine enough to digitize the weakest signal with a satisfying precision. In order to relax these specifications, an analog processing, such as companding, should be performed before digitization. The companding technique is usually employed on one signal (and not on multiple signals that are only separated on the frequency domain). This report studies three companding laws to test their efficiency in relaxing the digitization constraints with multiple signals. A µ-law, a Piecewise-Linear (PL) law and a Piecewise-Linear, Constant Gain with Offsets (PLCGO) law are tested. It is described how to use a PLCGO approach to reduce ADC's complexity, and two implementations of the compressing law are proposed.