Modulation schemes in ambient backscatter communication

This thesis presents a study of different modulation schemes in the context of backscatter communication. Backscatter communication is a way of wireless communication where no active signal is transmitted. Instead surrounding signals are modified to transmit data. The goal of this thesis is to explore in how far different modulation schemes in combination with off-the-shelf hardware can be used to tackle the current data rate and distance limitations of backscatter systems. This thesis compares the modulation schemes on-off keying (OOK) and frequency-shift keying (FSK) using a constant carrier signal as well as a digital television signal. For the use of a constant carrier signal it is shown that high ranges of up to 225 meters in a line-of-sight environment and up to 30 meters in a non line-of sight environment are reachable extending the current distance limitations by far and even the use of high data rates lead to a range of 175 meters. Moreover, this thesis shows the feasibility of replacing the constant carrier with a television signal and achieves ranges of over a meter in surroundings of television signals with a signal strength of not more than -70 dBm