Realizing ReMoRa (Reflection of Modulated Radio) Ambient Scatter Communication Links With Perfect Pulses

Abstract

This paper explains how to construct and apply perfect pulses - antipodal binary waveforms with extraordinary dc-nulling properties - to an ambient scatter communications link. Several methods for employing perfect pulses in digital modulation schemes, with particular emphasis on backscatter (and simply scatter) radio modulation, are demonstrated. These waveforms enable a completely new type of RF information exchange by piggy-backing useful information onto ambient wireless signals using low-powered electronics. A mathematical model of perfect pulses is shared as well as an overview of their spectral properties. A signal parameter calculation method is presented for desired backscatter message design and spectral characteristics, later implemented in an experimental set-up. Software simulations of perfect pulse enabled communications depict the creation of the channel waveforms, modulation onto a pseudo-random ambient carrier, and retrieval of the intended message data from the noisy and interference laden received signal. A robust receiver system is described which can be implemented via simple post-processing techniques in a software defined system or as a low-cost, low-power RF circuit using commercial-off-the-shelf components. Experimentally retrieved data is used to create a realistic estimate of bit rate errors compared to more traditional waveforms using an ambient FM radio station signal.